Title of Invention	METHOD AND SYSTEM OF LUBRICATING CONVEYOR SYSTEM
Abstract	The present invention is directed to a method of lubricating a conveyor system comprising i) diluting a conveyor lubricant concentrate with water to obtain an aqueous conveyor lubricant with the concentration c, ii) irradiating an aqueous conveyor lubricant with light, iii) determining the concentration c of the aqueous conveyor lubricant by measuring the absorption of the light by the aqueous conveyor lubricant with an absorption detector and iv) applying the aqueous conveyor lubricant to the conveyor system. The present invention further relates to a conveyor lubrication system including a measuring device (21) with a light source and with an absorption detector for measuring the absorption of light by an aqueous conveyor lubricant within a conveyor lubrication system.

Title of Invention

METHOD AND SYSTEM OF LUBRICATING CONVEYOR SYSTEM

Abstract

The present invention is directed to a method of lubricating a conveyor system comprising i) diluting a conveyor lubricant concentrate with water to obtain an aqueous conveyor lubricant with the concentration c, ii) irradiating an aqueous conveyor lubricant with light, iii) determining the concentration c of the aqueous conveyor lubricant by measuring the absorption of the light by the aqueous conveyor lubricant with an absorption detector and iv) applying the aqueous conveyor lubricant to the conveyor system. The present invention further relates to a conveyor lubrication system including a measuring device (21) with a light source and with an absorption detector for measuring the absorption of light by an aqueous conveyor lubricant within a conveyor lubrication system.

Full Text	Field of the invention The invention relates to methods and systems for lubricating conveyor systems. More specifically, the invention relates to lubricating conveyor systems, which are moving containers made of metal, glass, paper, cardboard and/or plastic, particularly containers used in the food industry. These are especially containers to be filled up with food including beverages, e.g. glass or plastic bottles, boxes, glasses, vessels, beverage containers, paper and cardboard holders and the like. Background of the invention The application of aqueous conveyor lubricants for lubricating and possibly also cleaning and disinfecting conveyor systems, specifically for lubricating the inter-face between a container and a moving conveyor belt or track surface, is well known in prior art. If a conveyor system is not lubricated sufficiently, this can lead to the falling down of the containers or have the result that the containers do not stop, even though they have reached a filling, cleaning or labelling station. Both kinds of malfunctions can lead to longer standing times of the conveyor system and to a considerable loss of capacity. Aqueous conveyor lubricants are usually applied in very low concentrations e.g. in a range from 0.1 % to 2 %, while the necessary quantity of aqueous conveyor lubricant is high. The exact determination of concentration of the applied lubricants is of a high significance, in order to guarantee an optimal lubrication of the conveyor system. Presently the concentration of aqueous conveyor lubricants is determined by manually retaining a sample of the conveyor lubricant and examining it by titration. This method is very inaccurate, due to the difficult recognition of the equilibrium point during the titration. Furthermore, this analysis technique takes a long time to obtain results and is not adapted for an on-line application. The present invention seeks to avoid these disadvantages by proposing a technique of measuring by a spectro-photometric method, particularly by the absorbance of light, which is simpler, faster and easier to implement than the laboratory method discussed above. Furthermore, this method can be adapted to use on-line. Many molecules absorb ultraviolet or visible light. Lambert-Beer's Law is a mathematical means of expressing how light is absorbed by matter. The Law states that the amount of light emerging from a sample is diminished by three physical phenomena: 1. The amount of absorbing material in its path length (concentration) 2. The distance the light must travel through the sample (optical path length) 3. The probability that the photon of that particular wavelength will be absorbed by the material (absorptivity or extinction coefficient). This relationship may be expressed as: A = ebc were A = absorbance e = molar extinction coefficient b = path length in cm and c = molar concentration. Different molecules absorb radiation of different wavelength. An absorption spectrum will show a number of absorption bands corresponding to structural groups within a molecule. An absorption spectrum shows the absorption of light as a function of a wavelength. The determination of a concentration by measuring the absorption of light is a modern, reliable and competitive method, which is applied especially for industrial waste- water analysis. Examples for the concentration detection of a component of an industrial water system can be found in US 5,419,837 or in US 2004/013221 A. US 4,666,858 teaches the determination of the quantity of anionic material in electrolyte metal plating baths by spectro- photometrical measuring the ultraviolet absorption of the extracted material. DE-A1 42 34 466 is directed to a method for the determination of the concentration of a substance within a solution. This document teaches the use of a tracer, which is a fluorescence dye, the concentration of which is measured by an optical method. An object of the present invention is to provide a method of lubricating a conveyor system, which assures an optimal concentration of the applied lubricant. Another object of the present invention is to make a conveyor system more efficient by avoiding standing times and increasing its transport capacity. Another object of the present invention is to permit the on-line determination of the concentration of an aqueous conveyor lubricant, which is applied to a conveyor system. Summary of the invention These and other objects are achieved by the present invention, which comprises a method of lubricating a conveyor system comprising i) irradiating an aqueous conveyor lubricant having a concentration c with light, ii) determining the concentration c of the aqueous conveyor lubricant by measuring the absorption of the light by the aqueous conveyor lubricant with an absorption detector and iii) applying the aqueous conveyor lubricant to the conveyor system. This automated procedure allows exact dosage of applied lubricants and the concentration measurement to be integrated directly into the lubrication process. The invention provides a secure lubrication process, avoiding unnecessary over-concentration of the lubricant and therefore avoiding high product costs. The concentration of the lubricant has to be observed e.g. if the aqueous conveyor lubricant is not stable or if the conveyor lubricant is diluted prior to application and the diluting process is not constant or reliable. Furthermore, if the tank containing the conveyor lubricant concentrate or the aqueous conveyor lubricant is nearly empty, the attention of an operator has to be called to the resulting drop in concentration. The conveyor lubrication system of the present application can be equipped with an alarm device, which raises an alarm signal if an unwanted concentration of the aqueous conveyor lubricant is determined. If the conveyor lubricant is delivered to the conveyor lubrication system in a concentrated form, the conveyor lubricant concentrate can be diluted with water to obtain an aqueous lubricant with a concentration c, before carrying out steps i) to iii) of the method according to the invention. If the conveyor lubricant is already delivered in the desired concentration c, this diluting step is not necessary. The present invention further refers to a conveyor lubrication system including an application device for applying an aqueous conveyor lubricant to a conveyor system. The conveyor lubrication system further includes a measuring device with a light source and with an absorption detector for measuring the absorption of light by the aqueous conveyor lubricant within the conveyor lubrication system. The present invention further refers to another conveyor lubrication system, including a dosing station and an application device, the dosing station containing at least one dosing pump for pumping a conveyor lubricant concentrate through a dosing pipe into at least one mixing space. The mixing space is attached to a water supply for diluting the conveyor lubricant concentrate with water within the mixing space to obtain an aqueous conveyor lubricant. The mixing space is attached to at least one outlet pipe for transporting the aqueous conveyor lubricant out of the mixing space. The outlet pipe is leading to the application device for applying the aqueous conveyor lubricant to a conveyor system. The conveyor lubrication system further includes a measuring device with a light source and with an absorption detector for measuring the absorption of light by the aqueous conveyor lubricant within the conveyor lubrication system. Brief description of the/drawings Figure 1 shows absorbance spectra of different aqueous solutions containing components of conveyor lubricants, plotting absorbance versus wavelength Figure 2 shows a plot of absorbance versus concentration at one specific wavelength for a first aqueous conveyor lubricant. Figure 3 shows a plot of absorbance versus concentration at one specific wavelength for a second aqueous conveyor lubricant. Figure 4 shows a plot of absorbance versus concentration at one specific wavelength for a third aqueous conveyor lubricant. Figure 5 shows a plot of absorbance versus concentration at one specific wavelength for a fourth aqueous conveyor lubricant. Figure 6 shows an absorbance spectrum of a tracer, plotting absorbance versus wavelength. Figure 7 shows a plot of absorbance versus concentration at one specific wavelength for the first aqueous conveyor lubricant of figure 2, to which a tracer has been added. Figure 8 is a plot of absorbance versus time, being the result of an on-line measurement at a conveyor lubrication system. Figure 9 shows schematically a dosing station, which is part of a conveyor lubrication system according to the present invention. Description of various and preferred embodiments The method of the present invention is concerned with lubricating a conveyor system. Conveyor systems are systems for transporting goods in industrial plants, comprising conveyor belts, conveyor bands, conveyor lines, tracks and the like. According to the proposed method, if the lubricant is available in a concentrated form, the conveyor lubricant concentrate is diluted with water to obtain an aqueous conveyor lubricant. This dilution step of a concentrate is necessary, since the lubricant is applied to the conveyor system with a low concentration. Examples of conveyor lubricant concentrates and aqueous conveyor lubricants can be found in EP 0946 692 B1, the disclosure of which is incorporated herein by reference. This European patent refers to lubricants on the basis of soap, on the basis of fatty amines and on the basis of phosphate esters. The present invention is mainly directed to lubricants on the basis of amines and on the basis of soap and furthermore to lubricants on the basis of ether carboxylic acid. Preferably the conveyor lubricant concentrate is diluted with water to obtain an aqueous conveyor lubricant with a concentration c in a range from 0.05 to 2.5 %, particularly in a range from 0.1 % to 0.3 % referring to lubricants on the basis of amines, ether carboxylic acids or ethoxylate and particularly in a range from 0.5 to 2 % referring to lubricants on the basis of soap. All percentages referred to in this context are percentages by weight. If the aqueous conveyor lubricant is available with the desired concentration c, the diluting step is unnecessary. According to the present invention the aqueous conveyor lubricant is irradiated with light, the absorption of the light by the lubricant being measured with a light detector. For the irradiation a light source is used, preferably a light source selected from the group of a hydrogen lamp, a deuterium lamp, a laser and a tungsten lamp. Preferably the aqueous conveyor lubricant is irradiated with visible or ultraviolet light of one specific wavelength. This wavelength is advantageously the wavelength of an absorption peak of a component of the aqueous conveyor lubricant. If the used light source is a continuous light source, emitting light in a range of wavelength, the desired specific wavelength for irradiating the lubricant can be selected by a wavelength separator, e.g. a prism, a grating or a monochromator. According to one preferred embodiment of the present invention, the absorption of light with a wavelength in a range from 200 to 300 nm is measured. The light from the light source is focused and sent into the aqueous conveyor lubricant within an element of the conveyor lubrication system, e.g. within a pipe or chamber of the dosing station. The emerging light, which has penetrated the aqueous conveyor lubricant is measured on the opposite side of the element by an absorption detector. The absorption detector includes for example a photo-electric cell, a photo-diode or a photo- multiplier. The detector is usually connected with an amplifier and a data processing unit. The measured absorbance is compared to a calibration curve (e.g. by the data processing unit) to determine the concentration of the lubricant. The calibration curve shows the absorbance as a function of the concentration for this aqueous lubricant (according to the Lambert-Beer- Law) at the chosen wave length and with the used set-up. The calibration curve has been determined by measuring the absorbance of the same lubricant of known concentrations with the same set-up. According to a preferred embodiment of the present invention, the absorption of the light is measured on-line during operation of the conveyor system. Preferably the measured concentration values are used to control the application quantity of the aqueous conveyor lubricant. The on-line measurement of the concentration permits a fast response to unwanted concentration variations by varying the application quantity of lubricant to the conveyor system. Another possibility would be controlling the amount of water mixed with the conveyor lubricant concentrate or the amount of conveyor lubricant concentrate mixed with the water in the diluting step, depending on the determined concentration of the aqueous conveyor lubricant. According to the present invention, the aqueous lubricant is applied to the conveyor system. The conveyor system is automatically and continuously lubricated by a conveyor lubrication system according to the present invention. Preferably the aqueous conveyor lubricant is applied to the conveyor system by spraying, brushing or dipping. The spraying can be carried out by spraying nozzles, the brushing by brushes and the dipping by leading the conveyor band through dip trays, which contain the aqueous conveyor lubricant. The conveyor lubrication system preferably includes a dosing station and an application device. The dosing station doses the amount of conveyor lubricant concentrate and the amount of water, which are mixed in order to obtain the aqueous conveyor lubricant with a concentration c. The application device serves to apply the lubricant to the conveyor system, including for example spraying nozzles for a spray application. For measuring the absorption of light as described above, the conveyor lubrication system further contains a measuring device. According to a preferred embodiment of the present invention, the measuring device of the conveyor lubrication system includes a flow cell, which is equipped with the light source and the absorption detector and which is connected to an element of the dosing station or the application device, the element containing the aqueous conveyor lubricant. The flow cell can be connected for example to a pipe or a mixing chamber of the dosing station or the application device, through which the aqueous conveyor lubricant is flowing during the operation of the conveyor lubrication system. Figure 1 represents absorbance spectra of different aqueous solutions containing components of conveyor lubricants, plotting absorbance A versus wavelength X. The absorbance spectra were measured by scanning a wavelength separator over the wavelength range from 200 nm to 300 nm. A first aqueous solution contained the component 1, which was an alkyl (C16-18) ether (9 EO) carboxylic acid, with a concentration of 10 %. The absorbance spectrum of this aqueous solution with the component 1 shows an absorption maximum at about λ = 234 nm. A second aqueous solution contained the component 2, which was N-oleyl-1,3- diamino propane, with a concentration of 10 %. The absorbance spectrum of this aqueous solution with component 2 shows an absorption maximum at about λ = 220 nm. A third aqueous solution contained the component 3, which was oleylamine ethoxylate (12 EO), with a concentration of 2 %. The absorbance spectrum of this aqueous solution with the component 3 shows an absorption maximum at about λ = 234 nm. A fourth aqueous solution contained the component 4, which was N-coco-1,3-diamino propane, with a concentration of 10 %. The absorbance spectrum of this aqueous solution with the component 4 shows an absorption maximum at about λ = 220 nm. The four components 1 to 4 are typical components of aqueous conveyor lubricants. An optimum wavelength for an ultraviolet absorption detection using lubricants containing at least one of these components is the wavelength of the absorption peaks in Figure 1, i.e. 220 nm or 234 nm. According to a preferred embodiment of the present invention the concentration c of the aqueous conveyor lubricant is determined my measuring the absorption of ultraviolet light of a specific wavelength, the ultraviolet light being primarily absorbed by at least one lubricant component of the aqueous conveyor lubricant, the lubricant component being a component selected from the group of an amine, an ether carboxylic acid and an sulfonate. The amine is preferably used in the form of an acetate. Preferred amines which could be a lubricant component according to the invention are those corresponding to the general formula I, as well as salts thereof, wherein R6, R7, R8 and R9 independently from each other are the same or different and indicate: hydrogen a substituted or unsubstituted, linear or branched alkyl rest with 1 to 22 C-atoms or a mono or polyunsaturated alkenyl rest with 2 to 22 C-atoms, which could display as substituents one or more hydroxyl, amine, imine, halogen and / or carboxyl rests, a substituted or unsubstituted phenyl rest, which could display as substituents one or more amine, imine, hydroxyl, halogen, carboxyl and /or possibly again substituted, linear or branched, saturated or mono or polyunsaturated alkyl rest with 1 to 22 C-atoms, A2 indicates a linear or branched alkylene group with 1 to 8 carbon atoms, and n is a positive integer number in the range of 1 to 30. Preferred amines are of the general formula I, wherein R7,R8 and R9= hydrogen A2= -(CH2)3-,and n= 1. Also the salts of those compounds which belong to the following general formulas (II) and (III) can be preferably applied, wherein R6 has the meaning as mentioned for the formula I and wherein the anion X- is chosen from all the customary rests, which are familiar to the professional, which originate from inorganic acids, organic acids and which do not influence the lubricant concentrate according to the invention in a detrimental manner, for example do not result in undesired turbidity or standstills, can be applied. In the sense of the present invention such acids are preferred of which the anion X- is chosen from the group: amidosulphonate, nitrate, halide, hydrogensulphate, sulphate, hydrogencarbonate, carbonate, phosphate or R5-COO- whereby the rest R5 indicates hydrogen, a substituted or unsubstituted, linear or branched alkyl rest with 1 to 20 C-atoms, whereby the substituents are chosen from one or more hydroxyl, amine, imine and/or carboxyl rests. Especially mentioned as examples for the organic anions X- of the type R5-COO- are: formate, acetate, glycolate, oleate, lactate, gluconate, citrate and glutamate. In another embodiment of the present invention, preferred amines can also be obtained according to the general formula I, wherein R6 is a saturated or unsaturated, branched or linear alkyl group with 8 to 22 carbon atoms, R7 is hydrogen, an alkyl group of hydroxyl-alkyl group with 1 to 4 carbon atoms or A2-NH2, n = 1 and R8 and R9 indicate hydrogen. Some individual examples of amines which could be applied according to the invention are among others ethylene diamine, diethylene triamine, triethylene tetra-amine, propylene diamine, dipropylene triamine, tripropylene tetra-amine, butylene diamine, aminoethyl propylene diamine, aminoethyl butylene diamine, tetramethylene diamine, hexamethylene diamine, N-coco- 1,3-diamonopropane, (N-cocos fatty-alkyl-1,3-diaminopropane) N-tallow fatty-alkyl-1,3- diaminopropane (N-oleyl-1,3-diaminopropane), N-lauryl-1,3-diaminopropane, each time in the form of the free amine or in the form of the salt like formate, acetate, oleate, glycolate, lactate, gluconate, citrate, glutamate, benzoate or salicylate. More preferred polyamines are N-coco-1,3-diaminopropane and N-oleyl-1,3- diaminopropane, the most preferred polyamine is N-oleyl-1,3-diaminopropane. Compounds according to the general formulas IV and V can also be applied as an amine component: wherein R19 is a linear or branched, saturated or unsaturated, alkylene rest with 8 to 22 carbon atoms, A12 is a linear or branched alkylene group with 8 to 22 carbon atoms, A9, A10, A11 are the same or different ethoxy or propoxy groups, whereby the total of the groups A9, A10, A11 is between 2 and 200. Useful compounds among others are: Cocos-bis(2-hydroxylethyl)amine, polyoxyethylene (5) cocos-amine, polyoxyethylene (15) cocos- amine, tallow-bis(2-hydroxylethyl)amine, polyoxyethylene(5) tallow-amine, tallow/oleyl-bis(2- hydroxylethyl)amine, oleyl-bis (2-hydroxylethyl)amine, polyoxyethylene (5) oleylamine, polyethylene (15) oleylamine, tallow-bis(2-hydroxylethyl) amine (hydrated), polyoxyethylene (5) tallow-amine (hydrated), polyoxyethylene (15) tallow-amine (hydrated), polyoxyethylene (50) tallow-amine, N,N1N'-tris(2-hydroxylethyl)N- tallow - 1,3-diaminopropane, N,N',N,-polyoxy- ethylene (10) -N-tallow -1,3-diamlno-propane, N,N',N'-polyoxyethylene (15)-N-tallow-1,3- diaminopropane and poly oxyethylene (15)-tallow-amine Preferred ether carboxylic acids which could be a lubricant component according to the invention are those corresponding to the general formula VI, wherein R20 is a saturated, linear or branched alkyl rest with 1 to 22 carbon atoms or a mono or polyunsaturated linear or branched alkaryl or alkinyl rest with 2 to 22 carbon atoms or a possibly mono or poly C1-C22 alkyl or C2-C22 alkenyl or C2-C22-alkinyl substituted aryl rest n is a positive number between 0 and 30, and m is 2 or 3, M is hydrogen or an alkali metal. As ether carboxylic acids with the general formula VI , which can be applied advantageously, can be mentioned among others: Preferred sufonates which could be a lubricant component according to the invention are those corresponding to the general formula VII: wherein R1 is a C1 to C14 alkyl rest and if n > 1, each R1 can independently be a different C1 to C14 alkyl rest and n = 1 to 5. As sulfonates with the general formula VII, which can be applied advantageously, can be mentioned among others: sodium xylenesulfonate or an alkyl benzenesulfonate. The numbered components are the same as referred to in the description of figure 1. The absorption spectra of a plurality of aqueous conveyor lubricants containing at least one of these lubricant components have been measured. The compositions of various aqueous conveyor lubricants A to K under examination can bee seen in Table 1: The lubricant G contains for example component 1 with a concentration of 5 % and component 4 with a concentration of 5 %. All of the aqueous conveyor lubricants under examination showed an absorption maximum within the wavelength range from 200 nm to 300 nm, mostly in the region of 220 nm or 234 nm. The total absorption of each wavelength can be the result of the absorption by one component of the lubricant or by several components of the lubricant. Figure 2 shows a plot of absorbance A versus concentration c at one specific wavelength for a first aqueous conveyor lubricant. This plot is a calibration curve, which can be used to determine the concentration of the lubricant after measuring the absorption of light at this specific wavelength by the lubricant. In this case the aqueous conveyor lubricant was lubricant G of table 1. The absorbance A was measured at a wavelength λ of 234 nm and with a path length d through the lubricant of 1 cm. The calibration curve shows a nice linearity of the absorbance as a function of the concentration. Therefore, a linear equation can be given (y = 0.7615x - 0.0019). With the help of this equation the concentration c (x) can be calculated from a measured absorbance A (y) for this lubricant, at this wavelength with the absorbance measured with the same set-up. Figure 3 shows a plot of absorbance A versus concentration c at a wavelength λ of 234 nm and with a path length d of 1 cm for a second aqueous conveyor lubricant. In this case, the lubricant was lubricant E from table 1. Figures 4 and 5 show a plot of absorbance A versus concentration c at a wavelength λ of 220 nm and with a path length d of 1 cm for a third an fourth aqueous conveyor lubricant, which were lubricants A and J respectively, according to table 1. All of the lubricants listed in table 1 showed a similar linear correlation of the absorbance and the concentration, all of the calibration curves being measured at 220 nm or 234 nm. Furthermore, the influence of different water qualities (used for diluting the conveyor lubricant concentrates) and of product aging on the calibration curves was tested. Some of the calibration curves showed a minor dependency on these factors, which can be rated as being neglectable. According to one embodiment of the present invention, the conveyor lubricant concentrate contains a tracer with a known concentration, the concentration of the aqueous conveyor lubricant being determined by measuring the absorption of light with a specific wavelength being absorbed primarily by the tracer. When the conveyor lubricant concentrate is diluted, the tracer (with a known starting concentration) is diluted to the same degree. The tracer shows an absorption peak at a known wavelength. By measuring the absorbance of the aqueous conveyor lubricant with the diluted tracer at this wavelength, the concentration of the tracer and consequently the concentration of the conveyor lubricant can be determined. The tracer to be used in this context must be homogeneously distributable within the aqueous conveyor lubricant. Figure 6 shows an absorbance spectrum of a tracer, plotting the absorbance A versus the wavelength λ. The tracer (0.5 mg/L) shows a maximum of absorption at a wavelength of about 228 nm (path length d = 1 cm). The tracer used was a naphtaline sulphone acid derivate, which is commercially available. Figure 7 shows a plot of absorbance versus concentration at a wavelength of 228 nm for the lubricant G (Table 1), to which the tracer (0.1% referring to the conveyor lubricant concentrate) has been added. Figure 8 is a plot of the absorbance A versus the time t, being the result of an on-line measurement at a conveyor lubrication system. The absorbance of the aqueous conveyor lubricant varies with time, which means, that the concentration of the lubricant also varies. By controlling the application quantity of lubricant applied to the conveyor system by the conveyor lubrication system depending upon the determined concentration, a constant lubrication can be assured, counteracting the variations of concentrations of the aqueous lubricant. Figure 9 shows schematically one embodiment of a dosing station, which is part of a conveyor lubrication system according to the present invention. The dosing station 20 comprises dosing pumps 1 (attached to a power socket 7), which are connected to a suction pipe 11 via a pipe system 18. The suction pipe 11 is mounted within a tank (not shown) which contains a conveyor lubricant concentrate. The concentrate is pumped by the dosing pumps 1 through the suction pipe 11 via dosing pipes 12 into four different mixing spaces 13. The mixing spaces 13 are each attached to a water supply (not shown) the water being led through water pipes 14. The water pipes 14 are connected to a main water pipe 15. The main water pipe 15 further contains a main regulating valve 17, a water filter 10 and a disconnecting part 9. The main water pipe 15 meets the four water pipes 14 at the branching 16. Next to each branching 16 each water pipe 14 contains a regulating valve 5 and a pressure measuring device 8 with a pressure reducing regulator 4. Within each water pipe 14 a water meter 2 is installed. The water pipes 14 meet the dosing pipes 12 at dosing valves 3, which control the amount of conveyor lubricant concentrate to be added to the water. The lubricant concentrate and the water are mixed within the mixing spaces 13, obtaining an aqueous conveyor lubricant, which flows through outlet pipes 19 to the application device (not shown) for the application to a conveyor system. The electronical parts of the dosing station 20 are placed in housings 6. With the four different water pipes 14 and the four different dosing pipes 12, four different concentrations of the aqueous conveyor lubricant can be mixed and led to four different conveyor systems or alternately to one conveyor system. The conveyor lubrication system further includes a measuring device 21, which is shown schematically in Figure 9. The measuring device includes a light source and an absorption detector for measuring the absorption of light by the aqueous conveyor lubricant. The measuring device 21 can be positioned anywhere within the conveyor lubrication system, where the system contains the readily mixed aqueous conveyor lubricant (starting from the mixing spaces 13 and previous to the location where the lubricant is applied to the conveyor). The measuring device can be installed in such a way, that the aqueous conveyor lubricant flowing through the pipes of the system is measured directly within these pipes or that part of the aqueous conveyor lubricant is lead through a bypass, the lubricant being analyzed by the measuring device 21 within this bypass. By way of example the measuring device 21 is shown schematically in figure 9, attached to one outlet pipe 19, the aqueous conveyor lubricant being analyzed by the measuring device 21 within the outlet pipe 19 through light transmitting windows (e.g. of a flow cell), or attached to a bypass 22, the aqueous conveyor lubricant being analyzed by the measuring device 21 within the bypass 22 through light transmitting windows (e.g. of a flow cell). WE CLAIM: 1. A method of lubricating a conveyor system comprising i. irradiating an aqueous conveyor lubricant having a concentration with light from a light source, ii. determining the concentration of the aqueous conveyor lubricant, wherein a measuring device (21) is used, and iii. applying the aqueous conveyor lubricant to the conveyor system, with an application device; wherein the conveyor system includes the measuring device including a flow cell equipped with the light source and with an absorption detector and wherein the flow cell is connected to an element of a dosing station (20) or the application device, the element containing the aqueous lubricant, and further wherein the concentration of the aqueous conveyor lubricant is determined by measuring the molecular absorption of the light by the aqueous conveyor lubricant with the absorption detector of the measuring device. 2. The method as claimed in claim 1 containing the step of diluting a conveyor lubricant concentrate with water to obtain the aqueous conveyor lubricant with the concentration. 3. The method as claimed in claim 2, wherein the conveyor lubricant concentrate is diluted with water to obtain an aqueous conveyor lubricant with a concentration in a range from 0.05 % to 2.5 %. 4. The method as claimed in claim 1, wherein the concentration of the aqueous conveyor lubricant is determined by measuring the molecular absorption of ultraviolet light of a specific wavelength, the ultraviolet light being primarily absorbed by at least one lubricant component of the aqueous conveyor lubricant, the lubricant component being a component selected from the group of an amine, an ether carboxylic acid and a sulfonate. 5. The method as claimed in claim 1, wherein the molecular absorption of light with a wavelength in a range from 200 nm to 300 nm is measured. 6. The method as claimed in claim 1, wherein the molecular absorption of the light is measured on- line during operation of the conveyor system. 7. The method as claimed in claim 1, comprising controlling the application quantity of the aqueous conveyor lubricant depending on the determined concentration. 8. The method as claimed in claim 2, wherein the conveyor lubricant concentrate contains a tracer with a known concentration, the concentration of the aqueous conveyor lubricant being determined by measuring the molecular absorption of light with a specific wavelength being absorbed primarily by the tracer. 9. The method as claimed in claim 1, wherein the aqueous conveyor lubricant is applied to the conveyor system by spraying, brushing or dipping. 10. A conveyor lubrication system, including i. an application device for applying an aqueous conveyor lubricant to a conveyor system, ii. a measuring device (21) including a light source and an absorption detector for measuring the molecular absorption of light by the aqueous conveyor lubricant within the conveyor lubrication system, and iii. a data processing unit for determining a concentration of the aqueous conveyor lubricant from the measured molecular absorption, wherein the measuring device (21) includes a flow cell, which is equipped with the light source and the absorption detector and which is connected to an element of a dosing station (20) or the application device, the element containing the aqueous conveyor lubricant. 11. The conveyor lubrication system of claim 10, including a dosing station (20), the dosing station (20) containing at least one dosing pump (1) for pumping a conveyor lubricant concentrate through a dosing pipe (12) into at least one mixing space (13), the mixing space (13) being attached to a water supply for diluting the conveyor lubricant concentrate with water within the mixing space (13) to obtain the aqueous conveyor lubricant and the mixing space (13) being attached to at least one outlet pipe for transporting the aqueous conveyor lubricant out of the mixing space (13), the outlet pipe (19) leading to the application device for applying the aqueous conveyor lubricant to the conveyor system. 12. The conveyor lubrication system as claimed in claim 10, wherein the flow cell is connected to a pipe or a mixing chamber of the application device or of the dosing station (20), through which the aqueous conveyor lubricant is flowing during the operation of the conveyor lubrication system. 13. The method as claimed in claim 1, wherein the flow cell is connected to a pipe or a mixing chamber of the application device or of the dosing station (2), through which the aqueous conveyor lubricant is flowing during the operation of the conveyor lubrication system. ABSTRACT METHOD AND SYSTEM OF LUBRICATING CONVEYOR SYSTEM The present invention is directed to a method of lubricating a conveyor system comprising i) diluting a conveyor lubricant concentrate with water to obtain an aqueous conveyor lubricant with the concentration c, ii) irradiating an aqueous conveyor lubricant with light, iii) determining the concentration c of the aqueous conveyor lubricant by measuring the absorption of the light by the aqueous conveyor lubricant with an absorption detector and iv) applying the aqueous conveyor lubricant to the conveyor system. The present invention further relates to a conveyor lubrication system including a measuring device (21) with a light source and with an absorption detector for measuring the absorption of light by an aqueous conveyor lubricant within a conveyor lubrication system.

Full Text

Field of the invention
The invention relates to methods and systems for lubricating conveyor systems. More
specifically, the invention relates to lubricating conveyor systems, which are moving
containers made of metal, glass, paper, cardboard and/or plastic, particularly containers used
in the food industry. These are especially containers to be filled up with food including
beverages, e.g. glass or plastic bottles, boxes, glasses, vessels, beverage containers, paper and
cardboard holders and the like.
Background of the invention
The application of aqueous conveyor lubricants for lubricating and possibly also
cleaning and disinfecting conveyor systems, specifically for lubricating the inter-face
between a container and a moving conveyor belt or track surface, is well known in prior art.
If a conveyor system is not lubricated sufficiently, this can lead to the falling down of the
containers or have the result that the containers do not stop, even though they have reached a
filling, cleaning or labelling station. Both kinds of malfunctions can lead to longer standing
times of the conveyor system and to a considerable loss of capacity.
Aqueous conveyor lubricants are usually applied in very low concentrations e.g. in a
range from 0.1 % to 2 %, while the necessary quantity of aqueous conveyor lubricant is high.
The exact determination of concentration of the applied lubricants is of a high significance, in
order to guarantee an optimal lubrication of the conveyor system.
Presently the concentration of aqueous conveyor lubricants is determined by manually
retaining a sample of the conveyor lubricant and examining it by titration. This method is
very inaccurate, due to the difficult recognition of the equilibrium point during the titration.
Furthermore, this analysis technique takes a long time to obtain results and is not adapted for
an on-line application.
The present invention seeks to avoid these disadvantages by proposing a technique of
measuring by a spectro-photometric method, particularly by the absorbance of light, which is
simpler, faster and easier to implement than the laboratory method discussed above.
Furthermore, this method can be adapted to use on-line.
Many molecules absorb ultraviolet or visible light. Lambert-Beer's Law is a
mathematical means of expressing how light is absorbed by matter. The Law states that the
amount of light emerging from a sample is diminished by three physical phenomena:

1. The amount of absorbing material in its path length (concentration)
2. The distance the light must travel through the sample (optical path length)
3. The probability that the photon of that particular wavelength will be absorbed
by the material (absorptivity or extinction coefficient).
This relationship may be expressed as:
A = ebc
were
A = absorbance
e = molar extinction coefficient
b = path length in cm and
c = molar concentration.
Different molecules absorb radiation of different wavelength. An absorption spectrum
will show a number of absorption bands corresponding to structural groups within a
molecule. An absorption spectrum shows the absorption of light as a function of a
wavelength.
The determination of a concentration by measuring the absorption of light is a
modern, reliable and competitive method, which is applied especially for industrial waste-
water analysis.
Examples for the concentration detection of a component of an industrial water
system can be found in US 5,419,837 or in US 2004/013221 A. US 4,666,858 teaches the
determination of the quantity of anionic material in electrolyte metal plating baths by spectro-
photometrical measuring the ultraviolet absorption of the extracted material.

DE-A1 42 34 466 is directed to a method for the determination of the concentration of
a substance within a solution. This document teaches the use of a tracer, which is a
fluorescence dye, the concentration of which is measured by an optical method.
An object of the present invention is to provide a method of lubricating a conveyor
system, which assures an optimal concentration of the applied lubricant.
Another object of the present invention is to make a conveyor system more efficient
by avoiding standing times and increasing its transport capacity. Another object of the present
invention is to permit the on-line determination of the concentration of an aqueous conveyor
lubricant, which is applied to a conveyor system.
Summary of the invention
These and other objects are achieved by the present invention, which comprises a
method of lubricating a conveyor system comprising
i) irradiating an aqueous conveyor lubricant having a concentration c with
light,
ii) determining the concentration c of the aqueous conveyor lubricant by
measuring the absorption of the light by the aqueous conveyor lubricant with an
absorption detector and
iii) applying the aqueous conveyor lubricant to the conveyor system.
This automated procedure allows exact dosage of applied lubricants and the
concentration measurement to be integrated directly into the lubrication process. The
invention provides a secure lubrication process, avoiding unnecessary over-concentration of
the lubricant and therefore avoiding high product costs. The concentration of the lubricant has
to be observed e.g. if the aqueous conveyor lubricant is not stable or if the conveyor lubricant
is diluted prior to application and the diluting process is not constant or reliable. Furthermore,
if the tank containing the conveyor lubricant concentrate or the aqueous conveyor lubricant is
nearly empty, the attention of an operator has to be called to the resulting drop in
concentration. The conveyor lubrication system of the present application can be equipped
with an alarm device, which raises an alarm signal if an unwanted concentration of the
aqueous conveyor lubricant is determined.
If the conveyor lubricant is delivered to the conveyor lubrication system in a
concentrated form, the conveyor lubricant concentrate can be diluted with water to obtain an

aqueous lubricant with a concentration c, before carrying out steps i) to iii) of the method
according to the invention. If the conveyor lubricant is already delivered in the desired
concentration c, this diluting step is not necessary.
The present invention further refers to a conveyor lubrication system including an
application device for applying an aqueous conveyor lubricant to a conveyor system. The
conveyor lubrication system further includes a measuring device with a light source and with
an absorption detector for measuring the absorption of light by the aqueous conveyor
lubricant within the conveyor lubrication system.
The present invention further refers to another conveyor lubrication system, including
a dosing station and an application device, the dosing station containing at least one dosing
pump for pumping a conveyor lubricant concentrate through a dosing pipe into at least one
mixing space. The mixing space is attached to a water supply for diluting the conveyor
lubricant concentrate with water within the mixing space to obtain an aqueous conveyor
lubricant. The mixing space is attached to at least one outlet pipe for transporting the aqueous
conveyor lubricant out of the mixing space. The outlet pipe is leading to the application
device for applying the aqueous conveyor lubricant to a conveyor system. The conveyor
lubrication system further includes a measuring device with a light source and with an
absorption detector for measuring the absorption of light by the aqueous conveyor lubricant
within the conveyor lubrication system.
Brief description of the/drawings
Figure 1 shows absorbance spectra of different aqueous solutions containing
components of conveyor lubricants, plotting absorbance versus wavelength
Figure 2 shows a plot of absorbance versus concentration at one specific wavelength
for a first aqueous conveyor lubricant.
Figure 3 shows a plot of absorbance versus concentration at one specific wavelength
for a second aqueous conveyor lubricant.
Figure 4 shows a plot of absorbance versus concentration at one specific wavelength
for a third aqueous conveyor lubricant.
Figure 5 shows a plot of absorbance versus concentration at one specific wavelength
for a fourth aqueous conveyor lubricant.
Figure 6 shows an absorbance spectrum of a tracer, plotting absorbance versus
wavelength.

Figure 7 shows a plot of absorbance versus concentration at one specific wavelength
for the first aqueous conveyor lubricant of figure 2, to which a tracer has been added.
Figure 8 is a plot of absorbance versus time, being the result of an on-line
measurement at a conveyor lubrication system.
Figure 9 shows schematically a dosing station, which is part of a conveyor lubrication
system according to the present invention.
Description of various and preferred embodiments
The method of the present invention is concerned with lubricating a conveyor system.
Conveyor systems are systems for transporting goods in industrial plants, comprising
conveyor belts, conveyor bands, conveyor lines, tracks and the like.
According to the proposed method, if the lubricant is available in a concentrated form,
the conveyor lubricant concentrate is diluted with water to obtain an aqueous conveyor
lubricant. This dilution step of a concentrate is necessary, since the lubricant is applied to the
conveyor system with a low concentration.
Examples of conveyor lubricant concentrates and aqueous conveyor lubricants can be
found in EP 0946 692 B1, the disclosure of which is incorporated herein by reference. This
European patent refers to lubricants on the basis of soap, on the basis of fatty amines and on
the basis of phosphate esters. The present invention is mainly directed to lubricants on the
basis of amines and on the basis of soap and furthermore to lubricants on the basis of ether
carboxylic acid.
Preferably the conveyor lubricant concentrate is diluted with water to obtain an
aqueous conveyor lubricant with a concentration c in a range from 0.05 to 2.5 %, particularly
in a range from 0.1 % to 0.3 % referring to lubricants on the basis of amines, ether carboxylic
acids or ethoxylate and particularly in a range from 0.5 to 2 % referring to lubricants on the
basis of soap. All percentages referred to in this context are percentages by weight.
If the aqueous conveyor lubricant is available with the desired concentration c, the
diluting step is unnecessary.
According to the present invention the aqueous conveyor lubricant is irradiated with
light, the absorption of the light by the lubricant being measured with a light detector. For the
irradiation a light source is used, preferably a light source selected from the group of a
hydrogen lamp, a deuterium lamp, a laser and a tungsten lamp. Preferably the aqueous
conveyor lubricant is irradiated with visible or ultraviolet light of one specific wavelength.

This wavelength is advantageously the wavelength of an absorption peak of a component of
the aqueous conveyor lubricant. If the used light source is a continuous light source, emitting
light in a range of wavelength, the desired specific wavelength for irradiating the lubricant
can be selected by a wavelength separator, e.g. a prism, a grating or a monochromator.
According to one preferred embodiment of the present invention, the absorption of
light with a wavelength in a range from 200 to 300 nm is measured.
The light from the light source is focused and sent into the aqueous conveyor
lubricant within an element of the conveyor lubrication system, e.g. within a pipe or chamber
of the dosing station. The emerging light, which has penetrated the aqueous conveyor
lubricant is measured on the opposite side of the element by an absorption detector. The
absorption detector includes for example a photo-electric cell, a photo-diode or a photo-
multiplier. The detector is usually connected with an amplifier and a data processing unit.
The measured absorbance is compared to a calibration curve (e.g. by the data processing unit)
to determine the concentration of the lubricant. The calibration curve shows the absorbance
as a function of the concentration for this aqueous lubricant (according to the Lambert-Beer-
Law) at the chosen wave length and with the used set-up. The calibration curve has been
determined by measuring the absorbance of the same lubricant of known concentrations with
the same set-up.
According to a preferred embodiment of the present invention, the absorption of the
light is measured on-line during operation of the conveyor system. Preferably the measured
concentration values are used to control the application quantity of the aqueous conveyor
lubricant. The on-line measurement of the concentration permits a fast response to unwanted
concentration variations by varying the application quantity of lubricant to the conveyor
system. Another possibility would be controlling the amount of water mixed with the
conveyor lubricant concentrate or the amount of conveyor lubricant concentrate mixed with
the water in the diluting step, depending on the determined concentration of the aqueous
conveyor lubricant.
According to the present invention, the aqueous lubricant is applied to the conveyor
system. The conveyor system is automatically and continuously lubricated by a conveyor
lubrication system according to the present invention.
Preferably the aqueous conveyor lubricant is applied to the conveyor system by
spraying, brushing or dipping. The spraying can be carried out by spraying nozzles, the

brushing by brushes and the dipping by leading the conveyor band through dip trays, which
contain the aqueous conveyor lubricant.
The conveyor lubrication system preferably includes a dosing station and an
application device. The dosing station doses the amount of conveyor lubricant concentrate
and the amount of water, which are mixed in order to obtain the aqueous conveyor lubricant
with a concentration c. The application device serves to apply the lubricant to the conveyor
system, including for example spraying nozzles for a spray application. For measuring the
absorption of light as described above, the conveyor lubrication system further contains a
measuring device.
According to a preferred embodiment of the present invention, the measuring device
of the conveyor lubrication system includes a flow cell, which is equipped with the light
source and the absorption detector and which is connected to an element of the dosing station
or the application device, the element containing the aqueous conveyor lubricant. The flow
cell can be connected for example to a pipe or a mixing chamber of the dosing station or the
application device, through which the aqueous conveyor lubricant is flowing during the
operation of the conveyor lubrication system.
Figure 1 represents absorbance spectra of different aqueous solutions containing
components of conveyor lubricants, plotting absorbance A versus wavelength X.
The absorbance spectra were measured by scanning a wavelength separator over the
wavelength range from 200 nm to 300 nm. A first aqueous solution contained the component
1, which was an alkyl (C16-18) ether (9 EO) carboxylic acid, with a concentration of 10 %.
The absorbance spectrum of this aqueous solution with the component 1 shows an absorption
maximum at about λ = 234 nm.
A second aqueous solution contained the component 2, which was N-oleyl-1,3-
diamino propane, with a concentration of 10 %. The absorbance spectrum of this aqueous
solution with component 2 shows an absorption maximum at about λ = 220 nm.
A third aqueous solution contained the component 3, which was oleylamine
ethoxylate (12 EO), with a concentration of 2 %. The absorbance spectrum of this aqueous
solution with the component 3 shows an absorption maximum at about λ = 234 nm.
A fourth aqueous solution contained the component 4, which was N-coco-1,3-diamino
propane, with a concentration of 10 %. The absorbance spectrum of this aqueous solution
with the component 4 shows an absorption maximum at about λ = 220 nm.

The four components 1 to 4 are typical components of aqueous conveyor lubricants.
An optimum wavelength for an ultraviolet absorption detection using lubricants containing at
least one of these components is the wavelength of the absorption peaks in Figure 1, i.e. 220
nm or 234 nm.
According to a preferred embodiment of the present invention the concentration c of
the aqueous conveyor lubricant is determined my measuring the absorption of ultraviolet light
of a specific wavelength, the ultraviolet light being primarily absorbed by at least one
lubricant component of the aqueous conveyor lubricant, the lubricant component being a
component selected from the group of an amine, an ether carboxylic acid and an sulfonate.
The amine is preferably used in the form of an acetate.
Preferred amines which could be a lubricant component according to the invention are
those corresponding to the general formula I, as well as salts thereof,

wherein R6, R7, R8 and R9 independently from each other are the same or different and indicate:
hydrogen
a substituted or unsubstituted, linear or branched alkyl rest with 1 to 22 C-atoms or a
mono or polyunsaturated alkenyl rest with 2 to 22 C-atoms, which could display as
substituents one or more hydroxyl, amine, imine, halogen and / or carboxyl rests,
a substituted or unsubstituted phenyl rest, which could display as substituents one or
more amine, imine, hydroxyl, halogen, carboxyl and /or possibly again substituted, linear
or branched, saturated or mono or polyunsaturated alkyl rest with 1 to 22 C-atoms,
A2 indicates a linear or branched alkylene group with 1 to 8 carbon atoms, and
n is a positive integer number in the range of 1 to 30.
Preferred amines are of the general formula I, wherein
R7,R8 and R9= hydrogen
A2= -(CH2)3-,and

n= 1.
Also the salts of those compounds which belong to the following general formulas (II) and (III)
can be preferably applied,

wherein R6 has the meaning as mentioned for the formula I and
wherein the anion X- is chosen from all the customary rests, which are familiar to the
professional, which originate from inorganic acids, organic acids and which do not
influence the lubricant concentrate according to the invention in a detrimental
manner, for example do not result in undesired turbidity or standstills, can be
applied.
In the sense of the present invention such acids are preferred of which the anion
X- is chosen from the group: amidosulphonate, nitrate, halide, hydrogensulphate,
sulphate, hydrogencarbonate, carbonate, phosphate or R5-COO- whereby the rest R5
indicates hydrogen, a substituted or unsubstituted, linear or branched alkyl rest with 1 to
20 C-atoms, whereby the substituents are chosen from one or more hydroxyl, amine,
imine and/or carboxyl rests. Especially mentioned as examples for the organic anions X-
of the type R5-COO- are: formate, acetate, glycolate, oleate, lactate, gluconate, citrate
and glutamate.
In another embodiment of the present invention, preferred amines can also be obtained according
to the general formula I, wherein
R6 is a saturated or unsaturated, branched or linear alkyl group with 8 to 22 carbon atoms,
R7 is hydrogen, an alkyl group of hydroxyl-alkyl group with 1 to 4 carbon atoms or A2-NH2,
n = 1 and R8 and R9 indicate hydrogen.
Some individual examples of amines which could be applied according to the invention
are among others ethylene diamine, diethylene triamine, triethylene tetra-amine, propylene

diamine, dipropylene triamine, tripropylene tetra-amine, butylene diamine, aminoethyl propylene
diamine, aminoethyl butylene diamine, tetramethylene diamine, hexamethylene diamine, N-coco-
1,3-diamonopropane, (N-cocos fatty-alkyl-1,3-diaminopropane) N-tallow fatty-alkyl-1,3-
diaminopropane (N-oleyl-1,3-diaminopropane), N-lauryl-1,3-diaminopropane, each time in the
form of the free amine or in the form of the salt like formate, acetate, oleate, glycolate, lactate,
gluconate, citrate, glutamate, benzoate or salicylate.
More preferred polyamines are N-coco-1,3-diaminopropane and N-oleyl-1,3-
diaminopropane, the most preferred polyamine is N-oleyl-1,3-diaminopropane.
Compounds according to the general formulas IV and V can also be applied as an amine
component:

wherein
R19 is a linear or branched, saturated or unsaturated, alkylene rest with 8 to 22
carbon atoms,
A12 is a linear or branched alkylene group with 8 to 22 carbon atoms,
A9, A10, A11 are the same or different ethoxy or propoxy groups, whereby the total of
the groups A9, A10, A11 is between 2 and 200.
Useful compounds among others are:
Cocos-bis(2-hydroxylethyl)amine, polyoxyethylene (5) cocos-amine, polyoxyethylene (15) cocos-
amine, tallow-bis(2-hydroxylethyl)amine, polyoxyethylene(5) tallow-amine, tallow/oleyl-bis(2-
hydroxylethyl)amine, oleyl-bis (2-hydroxylethyl)amine, polyoxyethylene (5) oleylamine,

polyethylene (15) oleylamine, tallow-bis(2-hydroxylethyl) amine (hydrated), polyoxyethylene (5)
tallow-amine (hydrated), polyoxyethylene (15) tallow-amine (hydrated), polyoxyethylene (50)
tallow-amine, N,N1N'-tris(2-hydroxylethyl)N- tallow - 1,3-diaminopropane, N,N',N,-polyoxy-
ethylene (10) -N-tallow -1,3-diamlno-propane, N,N',N'-polyoxyethylene (15)-N-tallow-1,3-
diaminopropane and poly oxyethylene (15)-tallow-amine
Preferred ether carboxylic acids which could be a lubricant component according to the
invention are those corresponding to the general formula VI,

wherein
R20 is a saturated, linear or branched alkyl rest with 1 to 22 carbon atoms or a mono or
polyunsaturated linear or branched alkaryl or alkinyl rest with 2 to 22 carbon atoms or a possibly
mono or poly C1-C22 alkyl or C2-C22 alkenyl or C2-C22-alkinyl substituted aryl rest
n is a positive number between 0 and 30, and m is 2 or 3,
M is hydrogen or an alkali metal.
As ether carboxylic acids with the general formula VI , which can be applied
advantageously, can be mentioned among others:

Preferred sufonates which could be a lubricant component according to the invention are those
corresponding to the general formula VII:

wherein
R1 is a C1 to C14 alkyl rest and if n > 1, each R1 can independently be a different C1 to C14
alkyl rest and
n = 1 to 5.
As sulfonates with the general formula VII, which can be applied advantageously, can be
mentioned among others: sodium xylenesulfonate or an alkyl benzenesulfonate.
The numbered components are the same as referred to in the description of figure 1.
The absorption spectra of a plurality of aqueous conveyor lubricants containing at
least one of these lubricant components have been measured. The compositions of various
aqueous conveyor lubricants A to K under examination can bee seen in Table 1:

The lubricant G contains for example component 1 with a concentration of 5 % and
component 4 with a concentration of 5 %.
All of the aqueous conveyor lubricants under examination showed an absorption
maximum within the wavelength range from 200 nm to 300 nm, mostly in the region of 220
nm or 234 nm. The total absorption of each wavelength can be the result of the absorption by
one component of the lubricant or by several components of the lubricant.
Figure 2 shows a plot of absorbance A versus concentration c at one specific
wavelength for a first aqueous conveyor lubricant. This plot is a calibration curve, which can
be used to determine the concentration of the lubricant after measuring the absorption of light
at this specific wavelength by the lubricant.
In this case the aqueous conveyor lubricant was lubricant G of table 1. The
absorbance A was measured at a wavelength λ of 234 nm and with a path length d through
the lubricant of 1 cm. The calibration curve shows a nice linearity of the absorbance as a
function of the concentration. Therefore, a linear equation can be given (y = 0.7615x -
0.0019). With the help of this equation the concentration c (x) can be calculated from a
measured absorbance A (y) for this lubricant, at this wavelength with the absorbance
measured with the same set-up.
Figure 3 shows a plot of absorbance A versus concentration c at a wavelength λ of
234 nm and with a path length d of 1 cm for a second aqueous conveyor lubricant. In this
case, the lubricant was lubricant E from table 1.
Figures 4 and 5 show a plot of absorbance A versus concentration c at a wavelength λ
of 220 nm and with a path length d of 1 cm for a third an fourth aqueous conveyor lubricant,
which were lubricants A and J respectively, according to table 1. All of the lubricants listed in
table 1 showed a similar linear correlation of the absorbance and the concentration, all of the
calibration curves being measured at 220 nm or 234 nm.
Furthermore, the influence of different water qualities (used for diluting the conveyor
lubricant concentrates) and of product aging on the calibration curves was tested. Some of the
calibration curves showed a minor dependency on these factors, which can be rated as being
neglectable.
According to one embodiment of the present invention, the conveyor lubricant
concentrate contains a tracer with a known concentration, the concentration of the aqueous
conveyor lubricant being determined by measuring the absorption of light with a specific
wavelength being absorbed primarily by the tracer. When the conveyor lubricant concentrate

is diluted, the tracer (with a known starting concentration) is diluted to the same degree. The
tracer shows an absorption peak at a known wavelength. By measuring the absorbance of the
aqueous conveyor lubricant with the diluted tracer at this wavelength, the concentration of the
tracer and consequently the concentration of the conveyor lubricant can be determined. The
tracer to be used in this context must be homogeneously distributable within the aqueous
conveyor lubricant.
Figure 6 shows an absorbance spectrum of a tracer, plotting the absorbance A versus
the wavelength λ. The tracer (0.5 mg/L) shows a maximum of absorption at a wavelength of
about 228 nm (path length d = 1 cm). The tracer used was a naphtaline sulphone acid
derivate, which is commercially available.
Figure 7 shows a plot of absorbance versus concentration at a wavelength of 228 nm
for the lubricant G (Table 1), to which the tracer (0.1% referring to the conveyor lubricant
concentrate) has been added.
Figure 8 is a plot of the absorbance A versus the time t, being the result of an on-line
measurement at a conveyor lubrication system. The absorbance of the aqueous conveyor
lubricant varies with time, which means, that the concentration of the lubricant also varies.
By controlling the application quantity of lubricant applied to the conveyor system by the
conveyor lubrication system depending upon the determined concentration, a constant
lubrication can be assured, counteracting the variations of concentrations of the aqueous
lubricant.
Figure 9 shows schematically one embodiment of a dosing station, which is part of a
conveyor lubrication system according to the present invention.
The dosing station 20 comprises dosing pumps 1 (attached to a power socket 7),
which are connected to a suction pipe 11 via a pipe system 18. The suction pipe 11 is
mounted within a tank (not shown) which contains a conveyor lubricant concentrate. The
concentrate is pumped by the dosing pumps 1 through the suction pipe 11 via dosing pipes 12
into four different mixing spaces 13. The mixing spaces 13 are each attached to a water
supply (not shown) the water being led through water pipes 14. The water pipes 14 are
connected to a main water pipe 15. The main water pipe 15 further contains a main regulating
valve 17, a water filter 10 and a disconnecting part 9. The main water pipe 15 meets the four
water pipes 14 at the branching 16. Next to each branching 16 each water pipe 14 contains a
regulating valve 5 and a pressure measuring device 8 with a pressure reducing regulator 4.
Within each water pipe 14 a water meter 2 is installed. The water pipes 14 meet the dosing

pipes 12 at dosing valves 3, which control the amount of conveyor lubricant concentrate to be
added to the water. The lubricant concentrate and the water are mixed within the mixing
spaces 13, obtaining an aqueous conveyor lubricant, which flows through outlet pipes 19 to
the application device (not shown) for the application to a conveyor system. The electronical
parts of the dosing station 20 are placed in housings 6. With the four different water pipes 14
and the four different dosing pipes 12, four different concentrations of the aqueous conveyor
lubricant can be mixed and led to four different conveyor systems or alternately to one
conveyor system.
The conveyor lubrication system further includes a measuring device 21, which is
shown schematically in Figure 9. The measuring device includes a light source and an
absorption detector for measuring the absorption of light by the aqueous conveyor lubricant.
The measuring device 21 can be positioned anywhere within the conveyor lubrication system,
where the system contains the readily mixed aqueous conveyor lubricant (starting from the
mixing spaces 13 and previous to the location where the lubricant is applied to the conveyor).
The measuring device can be installed in such a way, that the aqueous conveyor lubricant
flowing through the pipes of the system is measured directly within these pipes or that part of
the aqueous conveyor lubricant is lead through a bypass, the lubricant being analyzed by the
measuring device 21 within this bypass. By way of example the measuring device 21 is shown
schematically in figure 9, attached to one outlet pipe 19, the aqueous conveyor lubricant
being analyzed by the measuring device 21 within the outlet pipe 19 through light
transmitting windows (e.g. of a flow cell), or attached to a bypass 22, the aqueous conveyor
lubricant being analyzed by the measuring device 21 within the bypass 22 through light
transmitting windows (e.g. of a flow cell).

WE CLAIM:
1. A method of lubricating a conveyor system comprising
i. irradiating an aqueous conveyor lubricant having a concentration with light from a light
source,
ii. determining the concentration of the aqueous conveyor lubricant, wherein a measuring
device (21) is used, and
iii. applying the aqueous conveyor lubricant to the conveyor system, with an application
device;
wherein the conveyor system includes the measuring device including a flow cell equipped with the
light source and with an absorption detector and wherein the flow cell is connected to an element
of a dosing station (20) or the application device, the element containing the aqueous lubricant,
and
further wherein the concentration of the aqueous conveyor lubricant is determined by measuring
the molecular absorption of the light by the aqueous conveyor lubricant with the absorption
detector of the measuring device.
2. The method as claimed in claim 1 containing the step of diluting a conveyor lubricant concentrate
with water to obtain the aqueous conveyor lubricant with the concentration.
3. The method as claimed in claim 2, wherein the conveyor lubricant concentrate is diluted with water
to obtain an aqueous conveyor lubricant with a concentration in a range from 0.05 % to 2.5 %.
4. The method as claimed in claim 1, wherein the concentration of the aqueous conveyor lubricant is
determined by measuring the molecular absorption of ultraviolet light of a specific wavelength, the
ultraviolet light being primarily absorbed by at least one lubricant component of the aqueous
conveyor lubricant, the lubricant component being a component selected from the group of an
amine, an ether carboxylic acid and a sulfonate.
5. The method as claimed in claim 1, wherein the molecular absorption of light with a wavelength in a
range from 200 nm to 300 nm is measured.

6. The method as claimed in claim 1, wherein the molecular absorption of the light is measured on-
line during operation of the conveyor system.
7. The method as claimed in claim 1, comprising controlling the application quantity of the aqueous
conveyor lubricant depending on the determined concentration.
8. The method as claimed in claim 2, wherein the conveyor lubricant concentrate contains a tracer
with a known concentration, the concentration of the aqueous conveyor lubricant being determined
by measuring the molecular absorption of light with a specific wavelength being absorbed primarily
by the tracer.
9. The method as claimed in claim 1, wherein the aqueous conveyor lubricant is applied to the
conveyor system by spraying, brushing or dipping.
10. A conveyor lubrication system, including
i. an application device for applying an aqueous conveyor lubricant to a conveyor system,
ii. a measuring device (21) including a light source and an absorption detector for
measuring the molecular absorption of light by the aqueous conveyor lubricant within the
conveyor lubrication system, and
iii. a data processing unit for determining a concentration of the aqueous conveyor lubricant
from the measured molecular absorption,
wherein the measuring device (21) includes a flow cell, which is equipped with the light source
and the absorption detector and which is connected to an element of a dosing station (20) or the
application device, the element containing the aqueous conveyor lubricant.
11. The conveyor lubrication system of claim 10, including a dosing station (20), the dosing station
(20) containing at least one dosing pump (1) for pumping a conveyor lubricant concentrate
through a dosing pipe (12) into at least one mixing space (13), the mixing space (13) being
attached to a water supply for diluting the conveyor lubricant concentrate with water within the
mixing space (13) to obtain the aqueous conveyor lubricant and the mixing space (13) being
attached to at least one outlet pipe for transporting the aqueous conveyor lubricant out of the
mixing space (13), the outlet pipe (19) leading to the application device for applying the aqueous
conveyor lubricant to the conveyor system.

12. The conveyor lubrication system as claimed in claim 10, wherein the flow cell is connected to a
pipe or a mixing chamber of the application device or of the dosing station (20), through which
the aqueous conveyor lubricant is flowing during the operation of the conveyor lubrication
system.
13. The method as claimed in claim 1, wherein the flow cell is connected to a pipe or a mixing
chamber of the application device or of the dosing station (2), through which the aqueous
conveyor lubricant is flowing during the operation of the conveyor lubrication system.

ABSTRACT

METHOD AND SYSTEM OF LUBRICATING CONVEYOR SYSTEM
The present invention is directed to a method of lubricating a conveyor system
comprising
i) diluting a conveyor lubricant concentrate with water to obtain an
aqueous conveyor lubricant with the concentration c,
ii) irradiating an aqueous conveyor lubricant with light,
iii) determining the concentration c of the aqueous conveyor lubricant by
measuring the absorption of the light by the aqueous conveyor
lubricant with an absorption detector and
iv) applying the aqueous conveyor lubricant to the conveyor system.
The present invention further relates to a conveyor lubrication system
including a measuring device (21) with a light source and with an absorption detector
for measuring the absorption of light by an aqueous conveyor lubricant within a
conveyor lubrication system.

METHOD AND SYSTEM OF LUBRICATING CONVEYOR SYSTEM

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