Title of Invention

THE HYDRAULIC DIFFERENTIAL CYLINDER FOR A DEVICE WITH AT LEAST ONE EXTENSION ARM OR SUPPORT ARM FOR MULTI - LINKED CRANE - SHAPED EXTENSION ARMS, CONCRETE SPREADER COLUMNS AND SIMILAR

Abstract

The hydraulic differential cylinder for a device with at least one extension arm or support arm for multi-linked extension arms, concrete spreader columns, lifting platforms, manipulators and similar characterized in that the hydraulic differential cylinder is provided with a hollow piston rod (2) that comprises a tubular segment (4) and two end pieces (5, 6) arranged at the ends of this segment (4) that are either designed as a (single piece or joined to each other in such a way as to obtain material continuity across the joint, wherein with a view to avoiding stress concentrations the cross section of the wall of the tubular segment (4) over the entire length of the tubular segment (4) and the transitions from the tubular segment (4) to the end pieces (5, 6) are made to be substantially smooth and plane or with a radius of curvature that has practically no adverse effects on the strength, wherein, given jointing that establishes material continuity across the joint, at least one of the end pieces is welded to the segment and wherein the welded joint (7) is made to be substantially flush with the segment (4) and the end piece joined to it by the welded joint by means of finishing in the form of material-removing processing, especially material removing machining and the root of the welded joint is eliminated by the finishing, and the region of the welded joint, especially on the internal face of the tubular segment (4), is smoothed and that, in case of a one-piece design and in case of jointing establishing material continuity across the joint, at least one of the end pieces (5, 6), preferably the end piece (6) at the pin-jointed end of the piston rod, is provided with an opening (8) through which a cutting tool can be introduced into (gain access to) the space within the hollow piston rod (2) for performing the said finishing therein.

Full Text

FORM 2 THE PATENTS ACT 1970 [39 OF 1970] RIGINTAR "THE MYDORAULIC DIFFERENTIAL CYLINDER FOR A DEVICE WITH AT LEAST ONE EXTENSION ARM OR SUPPORT ARM FOR MULTI-LINKED CRANE-SHAPED EXTENSION ARMS, CONCRETE SPREADER COLUMNS AND SIMILAR" ORIGINAL 601/MUMNP/2003 13/6/03 COMPLETE SPECIFICATION [See Section 10; rule 13] SCHWING GMBH, of Heerstrasse 11, 44647 Heme, Germany, GRANTED 24/11/2004 The following specification particularly describes the nature of the invention and the manner in which it is to be performed;- The present invention concerns a device with at least one extension arm or support arm for crane-shaped extension arms, concrete spreader columns, lifting platforms, manipulators and similar multi-linked working systems. The invention fur-ther concerns a method for the production of such a device, especially a hydraulic differential cylinder used for the de¬vice. More particularly, the invention concerns the construc¬tion of a concrete spreader column for a concrete pump, be it mobile or in a fixed position, said column (mast) consisting of several sections that can be folded and possibly also telescoped, and where the operation of the column arms is ef¬fected especially by means of hydraulic differential cylin¬ders. Concrete spreader columns made up of column arms that are linked together by means of articulated joints and, with a view to saving space, are capable of being folded and subse-quently being swung out or extended for actual operating pur-poses, make use, especially for the lowest extension and/or support arm or arms, of relatively large differential hydrau-lic cylinders, which are employed as drive for the lifting and lowering and, where appropriate, also for the telescoping of an extension arm. The hydraulic cylinders used for this purpose have stroke lengths of up to 2.5 m and over. It is practically self-evident that these hydraulic cylinders have to be designed to be sufficiently large and dimensionally stable to render them capable of coping with the forces that come into play when the whole of the column is operated and, more particularly, of reliably extending and/or moving the arms as desired. It is no more than logical that such multi-1inked column structures involve considerable weights, so that particular attention has to be paid to minimizing the masses that have to be moved, not least, by means of the low¬est hydraulic cylinder. It is therefore desirable for exten¬sion arms of this type to be made as light as possible. It is thus the task of the invention to further develop a device of the described kind in such a manner as to render possible, given skilful design, a reduction of the weight of the device "via the differential hydraulic cylinders that are to be used as drives for the extension arms or support arms of multi-linked crane-shaped extension arms, concrete spreader columns and similar and have therefore to be de¬signed with a view to saving weight. According to the invention, this task is absolved by means of the features of the device set out in the characterizing part of Claim 1, whereas the process engineering aspects of a solution for the fabrication of such a device are determined by the characteristics of the independent Claim 6. In accordance with the invention, the hydraulic differen¬tial cylinders are already turned into lightweight structures by virtue of the fact that the piston rod is designed as a hollow component. The hollow piston rod comprises a tubular segment and end pieces arranged at the ends of the tubular segment, especially an end piece on the piston side, prefera¬bly closed on its front face, and an end piece on the side of the pin joint of the piston rod. A piston is arranged on the end piece on the piston side and may be attached thereto by means of either screw connections or a thread. Where appro¬priate, the piston may also be attached by welding. According to the invention, the tubular segment and the end pieces may either constitute a single component or be joined to each other in such a way as to assure continuity of material. In case of such material continuity it will be advantageous if the end piece on at least one side is welded on. The opposite terminal part of the tube can be appropriately designed if another end piece is either welded on or attached in some other way, possibly by means of a thread or screws. But the opposite terminal part may also be designed as a single piece with the tubular segment. It is also within the scope of the invention for both ends of the piston rod constituted as a tubular segment or a tube to be welded to appropriate end pieces. When the piston rod is constituted by a single piece, it is produced from a cast blank by means of subsequent mate¬rial-removing machining from one end of the piston rod to form the hollow within it. In this connection use is made of a material having a tensile strength of more than 700 N/mm2, so that the piston rod made therefrom will be capable of be ing very heavily loaded. The inventors realized that it is advantageous for the di mensioning of this hydraulic cylinder, which all said and done has to move all the masses of a concrete spreader column that lie above it, if the coming into being of stress con¬centrations in such operating hydraulic differential cylin¬ders can be reduced to a minimum. When the design has to take account also of possible concentrations, this has the gen¬eral effect that the walls of the components of the hydraulic differential cylinders have to be made appropriately thicker. This thickening goes hand in hand with a corresponding weight increase. But if one reduces the stress concentrations that can occur during operation, it becomes possible to design the wall of the components of the hydraulic differential cylin- ders with appropriately smaller thicknesses. This can lead to considerable weight advantages, especially when one bears in mind that it is very often necessary to use hydraulic differ¬ential cylinders with stroke lengths of 2.5 metres and over. In accordance with the invention this result can be obtained by subjecting the regions of the welded joints, especially on the inside of the tubular segment, to finishing processing in the form of material-removing machining and smoothing. Acces¬sibility for the machining tool is assured by the fact that at least one of the end pieces is provided with an opening by means of which the cutting tool and possible a smoothing tool can be introduced into the interior of the piston rod to carry out the necessary work there. Of course, the invention can also be applied quite generally to hydraulic differential cylinders that are used independently of the application cases mentioned hereinabove, though the preferred field of application is constituted by crane-shaped extension arms, concrete spreader columns and similar manipulators. It is essential for the purposes of the invention, and this also and specifically in connection with the cases where the piston rod is constituted by a single piece, that espe¬cially the length of the tubular segment and the transitions between the segment and the end pieces should remain even as far as wall thickness is concerned and/or that, in the case of changes of the cross section or transitions from the tubu¬lar segment to the end pieces, there is provided a radius of curvature that avoids stress concentration effects and that the surface as a whole should be smooth. This makes sure that stress concentration effects will be substantially avoided. The stress concentration factor is thus appropriately mini¬mized and/or eliminated, so that it becomes possible to re¬duce the wall thickness of the tube by this factor and obtain a corresponding weight minimization and/or weight reduction. This weight minimization of the hydraulic differential cylin¬ders naturally also has effects on the other components of the structure. If the interior surface of the hollow piston road is to be machined and/or smoothed with a view to reducing the loads due to possible stress concentrations or producing the inte¬rior space of the piston rod from a previously produced solid casting, it will be advantageous to provide at least one of the end pieces of the hollow piston rod with an opening by means of which a machining tool can gain access to the inte¬rior cavity of the piston rod. As regards this opening neces¬sary for machining tool guidance purposes, it will be advan¬tageous to provide this opening at the pin-jointed end of the hollow piston rod, because this implies constructional advan¬tages as compared with an opening situated at the end on the piston side, and this particularly when the piston is at¬tached to the closed end of the piston rod on the piston side in a mechanically safe manner by prestressing the screws or by means of a threaded joint. Because the lighter the exten¬sion arm, the greater will be its useful reach in both the horizontal and the vertical direction. Although the require¬ment of a light construction applies basically to all the components of the structure, it applies particularly and above all to the hydraulic cylinder. A particularly simple method of obtaining material conti¬nuity across a joint is represented by welding, especially front-face welding of the end pieces to the tubular segment. If in this case a smooth finish of the hollow piston rod is to be obtained also in the region of the welded joints, where smooth means smooth as regards the surface and plane as re¬gards the cross section of the wall, it will be advantageous, especially at least in these regions, to subject the interior and/or the exterior wall of the hollow piston rod to mate- rial-removing processing, especially material-removing ma¬chining, where care has to be taken to ensure that this proc¬essing will not only eliminate abrupt changes in wall thick¬ness, but also to remove the welding seams to such an extent as to eliminate the root of the welded seem. Because welding seams will produce stress concentrations even when, notwith¬standing the complete absence of abrupt changes in wall thickness, the root of the welding seam is still present. In the manner described hereinabove it is thus possible by smoothing the surface, avoiding abrupt changes in wall thickness and eliminating the roots of the welding seams to avoid stress concentrations and therefore to design the components of the hydraulic differential cylinder with a smaller weight, while yet obtaining the same stability. In the case of single-piece hollow piston rods in which the hollow within the piston rod is produced by subjecting a solid blank to material-removing machining, it will be advan-tageous to produce the blank by means of known shaping proc-esses, for example forging, casting or rolling or similar, because this will render possible a simple fabrication, Some preferred embodiments of the invention will now be described with reference to the drawing, of which Figure 1 shows a cross section through a hydraulic differen¬tial cylinder suitable for moving an extension arm or a carrier arm, Figure 2 shows a detail of the welded joint of Figure 1, again as a cross section, Figure 3 shows the cross section of another embodiment of such a hydraulic differential cylinder, and Figures 4 and 5 show cross sections with piston rods designed as a single piece. Figure 1 shows a cross section through an embodiment of a hydraulic differential cylinder 1 in accordance with the in¬vention. The hydraulic cylinder 1 consists of the cylinder tube 3 and the piston rod 2, which is displaceably arranged within the cylinder tube 3 and is designed as a hollow piston rod. The hollow piston rod 2 comprises a tubular segment 4 that at its ends is provided with the end piece 5 on the side of the piston and the end piece 6 on the other side, the piston 11 being attached to the end piece 5 on the piston side by means of screw connections 10. The end piece 6 on the pin-jointed end of the piston rod is provided with two laterally cantilevered tubular stubs 13, 14 for connecting the piston rod to a column arm or similar and an opening 8 by means of which it is possible to access the hollow within the piston rod 2 from outside. The cross section of the piston wall 9 remains uniformly smooth and plane over the entire region of the tubular segment 4, and even the transition to the end pieces 5, 6 is shaped in such a manner as to avoid any stress concentration effects. In particular, the transition from the tubular segment 4 to the piston-side end piece 5, which here consists of solid mate¬rial, is provided with a sufficiently large radius of curva¬ture to assure that no inadmissible stress concentration ef¬fects will occur. The hollow piston rod is fabricated from the end pieces 5 and 6 and the tubular segment 4 by means of welded joints 7. The welded joints 7, which in the illustrated embodiment as¬sume the form of V-joints, are shaped by means of material-removing finishing processing in such a manner as to obtain a smooth and plane and also flush transition at the position of the joint between the parts that are to be joined. In this way one avoids the possibility of projecting parts of the welded joint as illustrated in Figure 2 contributing to the production of a stress concentration effect. The letter A in Figure 2 designates the stress-concentration-free remainder of the welded joint after the finishing processing, so that the outer surfaces in the region of the joint remain flush with the adjacent tube surfaces. Over and above this, Figure 3 shows a further embodiment of a hydraulic cylinder 1 in accordance with the invention in which the hollow piston rod 2 is provided with a welded-on end piece 6, the welded joint being indicated by the refer-ence number 7. As far as the remainder of the hollow piston rod 2 is concerned, it may be made of solid material and therefore as a single piece incorporating the end piece 5, which in the illustrated embodiment is provided with a thick-ened wall. The area of the thickening is indicated by 12. The reference number 13 indicates a thread applied to the outer jacket surface of the end piece 5. A corresponding thread 11 is provided on the piston 11, which can therefore be screwed onto the end piece 5. The opening for tool access, which is indicated by 8 and makes it possible to gain access to the cavity within the hollow piston rod 2, is here provided in the end piece 5 on the piston side. Figures 4 and 5 show embodiments of a hydraulic differen-tial cylinder 1 in which the hollow piston rod is constituted by a single piece. To this end use is preferably made of a cast blank, which in the embodiment illustrated by Figure 4 is machined from the upper end in order to form the hollow within it. In this case the internal wall 15 of the end piece 6 at the pin-jointed end and the tubular segment 4 is smoothed by means of material-removing machining in order to avoid the coming into being of stress concentration effects. The transition to the front face at the end of the hollow space 16 assumes the form of roundings 17 that avoid stress concentration effects. The same remarks apply as regards the embodiment illus-trated by Figure 5, with the sole difference that in this case the material-removing processing is effected from the other side, that is to say, from the bottom end of the piston rod as shown in Figure 5. Roundings 18 and 19 are provided in the transition region. This is intended to avoid the coming into being of stress concentration effects. The internal wall 15 is once again smoothed by means of material-removing ma¬chining in order to avoid the coming into being of stress concentration effects. WE CLAIM: 1. The hydraulic differential cylinder for a device with at least one extension arm or support arm for multi-linked extension arms, concrete spreader columns, lifting platforms, manipulators and similar characterized in that the hydraulic differential cylinder is provided with a hollow piston rod (2) that comprises a tubular segment (4) and two end pieces (5, 6) arranged at the ends of this segment (4) that are either designed as a (single piece or joined to each other in such a way as to obtain material continuity across the joint, wherein with a view to avoiding stress concentrations the cross section of the wall of the tubular segment (4) over the entire length of the tubular segment (4) and the transitions from the tubular segment (4) to the end pieces (5, 6) are made to be substantially smooth and plane or with a radius of curvature that has practically no adverse effects on the strength, wherein, given jointing that establishes material continuity across the joint, at least one of the end pieces is welded to the segment and wherein the welded joint (7) is made to be substantially flush with the segment (4) and the end piece joined to it by the welded joint by means of finishing in the form of material-removing processing, especially material removing machining and the root of the welded joint is eliminated by the finishing, and the region of the welded joint, especially on the internal face of the tubular segment (4), is smoothed and that, in case of a one-piece design and in case of jointing establishing material continuity across the joint, at least one of the end pieces (5, 6), preferably the end piece (6) at the pin-jointed end of the piston rod, is provided with an opening (8) through which a cutting tool can be introduced into (gain access to) the space within the hollow piston rod (2) for performing the said finishing therein. 2. The hydraulic differential cylinder for a device as claimed in claim 1, wherein the internal and/or the external wall of the hollow piston rod (2) is processed and smoothed by means of material-removing processing, especially material-removing machining in order to minimize stress concentrations. 3. The hydraulic differential cylinder for a device as claimed in anyone of claims 1 or 2, wherein at least one joint between the tubular segment (4) and the end pieces (5, 6) is a welded joint (7), especially a welded joint (7) on the front face. 4. The klydraulic differential cylinder for a device as claimed in anyone of claims 1 to 3, wherein the joint between the hollow piston rod (2) and the piston (11) is constituted by a thread or a screw connection, where in the case of a thread connection the wall thickness of the end piece (5) is increased in its terminal part. 5. A method for the production of a nydraulic differential cylinder as claimed in anyone of claims 1 to 4, characterized in that in a first step there is formed a blank with a tubular segment (4) and at least one end piece (5, 6) arranged at one end of this segment, that the internal face of this blank is rendered accessible for a cutting tool by means of an opening (8) provided in at least one of the end pieces (5, 6), and that in a further step at least the region of the welded joint between the end piece and the tubular segment, especially inside the tubular segment, is processed and smoothed by means of material-removing machining. 6. A method as claimed in claim 5, wherein in a first step and by means of any desired material-shaping process there is formed a blank with a rod-like segment and two end pieces (5, 6) provided at the ends of this segment and that in a second step, by means of material-removing processing, especially material-removing machining, there is formed an opening in at least one of the end pieces (5, 6) and a hollow space within the rod-like element to produce a hollow piston rod (2). 7. A multi-linked, mast-like support arm for concrete spreader columns or similar, having a support arm whenever provided with one or more hydraulic differential cylinders (1) as claimed in anyone of claims 1 to 4. Dated this June 13, 2003. (RANJANA MEHTA DUTT) OF REMFRY AND SAGAR ATTORNEY FOR THE APPLICANTS

Documents:

601-mumnp-2003-cancelled pages(24-11-2004).pdf

601-mumnp-2003-claims(13-6-2003).pdf

601-mumnp-2003-claims(amended)-(24-11-2004).pdf

601-mumnp-2003-claims(granted)-(24-11-2004).doc

601-mumnp-2003-claims(granted)-(24-11-2004).pdf

601-mumnp-2003-claims(granted)-(31-8-2007).pdf

601-mumnp-2003-correspondence(22-03-2006).pdf

601-mumnp-2003-correspondence(ipo)-(05-04-2006).pdf

601-mumnp-2003-correspondence(ipo)-(25-9-2007).pdf

601-mumnp-2003-description(complete)-(13-6-2003).pdf

601-mumnp-2003-description(granted)-(31-8-2007).pdf

601-mumnp-2003-drawing(03-06-2003).pdf

601-mumnp-2003-drawing(13-6-2003).pdf

601-mumnp-2003-drawing(amended)-(24-11-2004).pdf

601-mumnp-2003-drawing(granted)-(31-8-2007).pdf

601-MUMNP-2003-FORM 1(28-8-2008).pdf

601-mumnp-2003-form 19(07-07-2003).pdf

601-mumnp-2003-form 1a(13-06-2003).pdf

601-mumnp-2003-form 2(complete)-(13-6-2003).pdf

601-mumnp-2003-form 2(granted)-(24-11-2004).doc

601-mumnp-2003-form 2(granted)-(24-11-2004).pdf

601-mumnp-2003-form 2(granted)-(31-8-2007).pdf

601-mumnp-2003-form 2(title page)-(13-6-2003).pdf

601-mumnp-2003-form 2(title page)-(granted)-(31-8-2007).pdf

601-mumnp-2003-form 3(07-10-2003).pdf

601-mumnp-2003-form 3(11-09-2003).pdf

601-mumnp-2003-form 3(13-06-2003).pdf

601-mumnp-2003-form 3(23-9-2003).pdf

601-mumnp-2003-form 3(24-11-2004).pdf

601-mumnp-2003-form 3(9-10-2003).pdf

601-mumnp-2003-form 5(13-06-2003).pdf

601-mumnp-2003-form-pct-ipea-409(24-11-2004).pdf

601-mumnp-2003-petition under rule 137(24-11-2004).pdf

601-mumnp-2003-petition under rule 138(08-12-2004).pdf

601-mumnp-2003-power of authority(11-07-2003).pdf

601-mumnp-2003-power of authority(23-11-2004).pdf

601-mumnp-2003-power of authority(24-11-2004).pdf

601-mumnp-2003-power of authority(24-9-2003).pdf

601-mumnp-2003-wo international publication report(13-6-2003).pdf

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