Title of Invention

IN-VEHICLE AUTOMATED FALLING WEIGHT DEFLECTOMETER

Abstract

In-vehicle automated falling weight deflectometer to provide non-destructive evaluation of strength of highway and airfield pavements. It is also useful for testing of bridges and other like applications. The in-vehicle falling weight deflectometer comprise a load-deflection measuring unit having a load cell, geophone assembly, loading plate with rubber sole at its lower face such that for deflection measurement said rubber sole extend beyond the vehicle floor and press against the road surface; means to raise the vehicle wheels above ground and lowering of the geophone assembly to rest on the ground with geophones pressed against the road surface ; a releasably secured falling weight adapted to fall on said pad as and when the deflection measurement is required ;means for monitoring the signals from the load cell upon impact of the falling weight ;means for monitoring the signals from the geophones and generating the deflection measurement values based thereon. The above in-vehicle automated falling weight deflectometer would provide for a more precise and effective measure of the strength of road and airport pavement to enable estimation of remaining strength and forecast appropriate strengthening measure using mechanistic approach well ahead of failure condition. Importantly the system would enable identification of deficiency in every layer of pavements more accurately. The deflectometer is easily transported from one place to another and thus favour its application and end use. Moreover, the deflectometer is adapted to use power for running hydraulic pump is derived from the vehicle engine itself thereby avoiding need for a battery operated D.C. Motor and pump. The device is simple and easy to handle/use and also cost effective.

Full Text

2 FIELD OF THE INVENTION The present invention relates to in-vehicle automated falling weight deflectometer The system is directed to provide non-destructive evaluation of strength of highway and airfield pavements. It is also useful for testing of bridges and other like applications. It is presently known to have systems/falling weight deflectometers which are usually mounted on trolley and towed by a motor vehicle for transporting to different places for testing. Such systems involve circuitry and other gadgets which require electrical cables and circuits which are subject to damage in areas having high rainfall maneuvering of a motor vehicle with FWD on a trolley becomes difficult because of its length on a busy road. Moreover, such equipments are expensive and too costly for common use. The maintenance of such devices and their operation is also difficult as the same involves sophisticated gadgets / machinery and operation / maintenance is thus essentially required to be done through trained hands/experts. OBJECT OF THE INVENTION it is thus the basic object of the present invention to provide (for) in-vehicle automated falling weight deflectometer which would avoid the above-disclosed problems/shortcomings of the existing device. Another object of the present invention is directed to provide for a more precise and effective measure of the strength of road and airport pavement to enable estimation of remaining strength and forecast appropriate strengthening measure using mechanistic approach well ahead of failure condition. Another object of the present invention is directed to provide for in-vehicle automated falling weight deflectometer, which would enable identification of deficiency in every layer of pavements more accurately. Yet another object of the present invention is to provide for an automated falling weight deflectometer which can be easily transported from one place to another and thus favour its application and end use. 3 Yet another object of the present invention is to provide for a automated falling weight deflectometer wherein power for running hydraulic pump is derived from the vehicle engine itself thereby avoiding need for a battery operated D.C. Motor and pump. Yet another object is directed to provide for a automated falling weight deflectometer which would be simple and easy to handle/use. Yet another object is directed to provide in-vehicle automated falling weight deflectometer which would be simple to manufacture and cost effective to obtain and can cost much less as compared to the presently available systems/devices. SUMMARY OF THE INVENTION Thus according to the present invention there is provided an in-vehicle falling weight deflectometer comprising a movable cylinder adapted to move a connecting pad to support a falling weight on top thereof and a load-deflection measuring unit comprising a load cell, geophone assembly, loading plate with rubber sole at its lower face such that for deflection measurement said rubber sole extend beyond the vehicle floor and press against the road surface thereby raising the rear wheels of the vehicle above the ground; and means for lowering of the geophone assembly to rest on the ground with geophones pressed against the road surface ; a releasably secured falling weight adapted to fall on said pad as and when the deflection measurement is required ; means adapted to retract said deflection measuring unit within said vehicle and said falling weight in its releasably secured position as and when the deflection measurement is over/not required ; means, for monitoring the signals from the load cell upon impact of the falling weight; means for monitoring the signals from the geophones and generating the deflection measurement values based thereon. 4 In accordance with a preferred aspect of the present invention, the said movement of the movable cylinder and the movement of the geophone assembly are achieved by hydraulic means. In accordance with a more preferred aspect of the present invention the in- vehicle automated falling weight deflectometer comprises: a support structure installed with respect to the vehicle floor having two vertical members supporting a horizontal member; a piston means secured to said horizontal member and extending into a movable cylinder, said cylinder having an oil inlet at the top and an oil outlet at the bottom to favour hydraulic movement of said cylinder with said rubber pad and the deflection measuring unit; a further hydraulic unit operatively connected to said geophone assembly and adapted for lowering the geophone frame on ground with said geophone probes touching the ground for measuring the deflection parameters ; and computer based system for measuring the load cell signals and said geophone signals. The falling weight mass is adapted to releasably secure with respect to a fixture such that as and where required for measuring the deflection, the falling weight means is released from the fixture to fall on the rubber pad at the top of said cylinder. After the measurement is over the deflection unit is retracted into the vehicle and simultaneously the load is relocated back to its position supported by the fixture. The load cell is comprised of resistance strain gauge. The signals from the load cell is amplified by instrumentation amplifier before being fed into the computer. Both the load cells and geophones are calibrated before use. Signals from the geophones are integrated by an electronic circuit before being recorded in the computer. It is thus possible by way of the above disclosed system of the invention to provide for a simple to operate and cost-effective falling weight deflectometer which can be easily transported from one place to another. Importantly, the 5 system provides for very simple but accurate measurement of deflection and its effects which is not known in the art. Importantly, it is possible by way of the system of the invention to have a single hydraulic cylinder to raise the weight as well as the lowering the loading plate which is directed to save power. The details of the invention, its objects and advantages are explained hereunder in greater detail in relation to the non-limiting exemplary embodiments of the system as per the accompanying figures wherein - Figure 1 illustrates a schematic diagram of a known conventional system of deflectometer. Figure 2 illustrates the working principle of a deflectometer. Figure 3 illustrates schematically the falling weight deflectometer system in accordance with the present invention. Figure 4 illustrates the mounting of the geophone system of the invention in vehicle. Figure 5 shows vehicle mounted FWD system. Figure 6 is a circuit diagram of the load ceil instrumentation amplifier. Figure 7 is an integration circuit for the geophone; Figure 8 an illustration of the data acquisition system. Reference is first invited to Fig. 1 which illustrates a schematic diagram of a conventional deflection measurement system. Exact drawing and dimensions are not known. As illustrated in said figure a loading plate (3) is provided with a rubber disc at the bottom. The hydraulic cylinders (1 and 2) lower the entire assembly on the road pavement and the wheel of the trolley get lifted up so that the loading plate (3) is partially loaded. The part (5) is lowered till part (11) gets engaged to (5). The mass (10) is lifted by hydraulic cylinder (4) until the limiting switch on the top. When (5) is released by a hydraulic signal, the mass (10) falls on the rubber pad of specific hardness. 6 Reference is invited to Fig. 2 which schematically illustrates the working principle of falling load deflectometer. As represented in said figure failing weight deflectometers (FWDs) are systems for performing non-destructive testing of pavement and other foundation structures. The system develops forces from the acceleration caused by the arrest of a falling weight and these forces are transmitted onto the surface of a structure causing it to deflect much as it would due to the weight of a passing wheel load. The deformation of the structure is referred to as a "deflection basin" and the FWD uses a series of user positioned sensors to automatically determine the amplitude and shape of this deflected basin. The deflection response, when related to the applied loading, can provide information about the strength and condition of the various elements of the test structure. There are several back calculation programs available that can be used to evaluate pavement and foundation structures from the data produced by the FWD. Reference is now invited to Fig. 3 which illustrates the falling weight deflectometer in accordance with the present invention. As illustrated in said Fig. 3, the system of the invention having a frame of steel joists (SJ) which supports the entire assembly. A piston (P) is firmly fixed at right angled to the horizontal steel joist. Cylinder (C) is movable and when oil is pumped in through the upper inlet (UI) of the cylinder, the cylinder with rubber pad (RP), load cell (LC) geophone (GP), loading plate (LP) with rubber sole (RS) presses against the road surface. The rear wheels of the vehicle are slightly lifted up. Geophone assembly which is touching the lower part of the floor of the vehicle is lowered down by another hydraulic cylinder to rest on the road with geophone pressed against the road surface due to the weight of the frame. The catch is pulled back hydraulically and the mass falls on the synthetic rubber pad of shore hardness 35. The impact generated is measured by the load cell and it is found that the impact duration (the pulse width of the impulse) is about 25 milliseconds as required for a pavement. The load cell consists of four number of 350 ohm resistance strain gauge with gauge factor of two. The signal from the load cell is amplified by an instrumentation amplifier IC 524 of analog Devices before the signal goes to the 7 computer. The geophones have a natural frequency of 4.5 Hz and displacement of amplitude ± 1.25 mm. Both load cells and the geophones are required to be calibrated before use and frequent calibration (once in six months) is necessary. Signals from the geophones are integrated by an electronic circuits before they are recorded in the computer, A data acquisition card PCL-208 is fitted in the computer. The card can accomplish 100 KHz sampling rate in DMA mode the input to the card can be Bipolar, the maximum range being ± 10 V. Any known functional software can be used for data acquisition, There is provision of external pulse trigger. Seven data, six from the geophone and one from load cell are acquired at a rate of 2000Hz per channel (14000 Hz rate for all the signals). Fig. 5 shows a general view of the van/vehicle mounted with the deflection measuring system in accordance with the present invention. As also illustrated in said figure, the vehicle floor supports the frame structure holding the movable cylinder with the deflection measuring unit. The load is also supported by the said frame structure which can preferably be a steel joist. Therebetween the vertical columns of the steel Joist, the vehicle floor is cut out to favour movement of the deflection measuring unit especially the geophone member therethrough to touch the ground. The vehicle also accommodates the required electronic circuitry and the composition for data generation based on signals received from the load cell and the geophone. Fig. 6 shows the circuit for the instrumentation amplifier. Integration circuit for the geophone is given in Fig. 7, Organisation of the data acquisition system with LVDT is shown in Fig. 8. LVDT is used for calibration of geophones. Typical calibration factors for geophone and reproducibility of test data are shown in Tables 1 and 2. 8 Table -1: Calibration factors for geophones SENSOR R2 STD-ERR (mm) CALIBRATION FACTOR Geophone-1 0.99 0.009 0.0906 mm/volt Geophone-2 0.99 0.006 0.0904 mm/volt Geophone-3 0.99 0.009 0.087 mm/volt Geophone-4 0.99 0.006 0.0864 mm/volt Geophone-5 0.99 0.008 0.0842 mm/volt Table - 2 : Reproducibility of FWD Deflection data (Height of Fall = 500 mm) SI. No. Deflections recorded by six geophones kept at different radial distances (mm) 0 300 600 900 1200 1500 1 0.883 0.670 0.399 0.305 0.190 0.178 2 0.848 0.670 0.401 0.303 0.191 0.164 3 0.894 0.636 0.386 0.300 0.183 0.170 4 0.840 0.630 0.392 0.309 0.185 0.175 5 0.880 0.674 0.404 0.306 0.197 0.175 6 0.840 0.665 0.399 0.300 0.195 0.176 Power for running the hydraulic pump can be derived from battery also using a DC motor. Advantageously, on the above system of the invention the same cylinder and piston combination lifts the load as well as presses the pavement. The entire system is inside a van which gives protection against rain to all components. The geophone frame also is foldable type so that during transportation no part is protruding out side the vehicle to avoid accidents. It is thus possible by way of the above disclosed system of deflection measurement in accordance with the invention to achieve the following advantages/benefits: i) it is in-vehicle mounted, hence no additional vehicle is required for transportation. ii) Power for running the hydraulic pump is derived from the vehicle engine itself where as in others, the power is derived from battery which are to be charged continuously because of heavy drain of current. iii) A single hydraulic cylinder is used to raise the weight as well as lowering the loading plate whereas it appears that two hydraulic cylinders are used for lowering and raising the loading plate and another hydraulic cylinder is used for raising the weights. iv) Geophone frame is foldable so that the entire frame is inside the vehicle and there is no protrusion outside the vehicle during long travel to testing places. v) Cost is low (total cost of fabrication in a 2nd hand Matador van was about Rs. 8.50 lakhs including a computer, data acquisition cards, geophones and electrical circuits whereas imported ones cost about Rs. 90 lakhs or higher without computer and towing vehicles) vi) Repair and maintenance will be easy because of local know-how. 10 WE CLAIM: 1. An in-vehicle falling weight deflectometer comprising a movable cylinder (C) adapted to move a connecting pad to support a falling weight on top thereof and a measuring unit comprising of a load cell (LC), geophone assembly (GP), loading plate (LP) at its lower face such that for deflection measurement said loading plate (LP) extend beyond the vehicle floor and press against the road surface thereby raising the rear wheels of the vehicle above the ground; and means for lowering of the geophone assembly (GP) to rest on the ground with geophones pressed against the road surface ; a releasably secured falling weight adapted to fall on said pad (RP) as and when the deflection measurement is required ; means adapted to retract said deflection measuring unit within said vehicle and said falling weight in its releasably secured position as and when the deflection measurement is over/not required ; means for monitoring the signals from the load cell (LC) upon impact of the falling weight; means for monitoring the signals from the geophones (GP) and generating the deflection measurement values based thereon. 2. An in-vehicle falling weight deflectometer as claimed in claim 1 wherein said loading plate (LP) under surface is provided with a rubber sole (RS). 3. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 or 2 comprising hydraulic means for said movement of the movable cylinder (C) and the movement of the geophone (GP) assembly. 4. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 3 comprising : a support structure installed with respect to the vehicle floor having two vertical members supporting a horizontal member; a piston means secured to said horizontal member and extending into a movable cylinder (C), said cylinder having an oil inlet at the top and an oil outlet at the bottom to favour hydraulic movement of said cylinder with said rubber pad (RP) and the deflection measuring unit; 11 a further hydraulic unit operatively connected to said geophone assembly and adapted for lowering the geophone frame on ground with said geophone probes touching the ground for measuring the deflection parameters ; and computer based system for measuring the load cell (LC) signals and said geophone (GP) signals. 5. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 4 wherein the falling mass (FM) is adapted to releasably secure with respect to a fixture such that as and where required for measuring the deflection, the falling weight means release from the fixture to fall on the rubber pad (RP) at the top of said cylinder (C), after the measurement is over the deflection unit is adapted to retract inside the vehicle and simultaneously the load is relocated back to its position supported by the fixture. 6. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 5 wherein the load cell (LC) is comprised of resistance strain gauges. 7. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 6 comprising amplifier means to amplify the signals from the load cell (LC) before being fed into the computer. 8. An in-vehicle falling weight deflectometer as claimed in claim 7 comprising an electronic circuitry wherein signals from the geophones (GP) are integrated before being recorded in the computer. 9. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 8 wherein said support structure comprises of a frame of steel joists, which support the entire assembly. 5. 12 10. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 9 comprises means for lifting of the rear wheels after which the said geophone (GP) assembly is laid on ground for measurement. 11. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 10 comprising catch means adapted to be pulled back hydraulically to allow the mass to fall on the synthetic rubber pad (RP), said load cell (LC) providing for measurement of the impact generated. 12. An in-vehicle falling weight deflectometer as claimed in claim 11 wherein the load cell (LC) consists of four number of 350 ohm resistance strain gauge with gauge factor of two, the signal from the load cell (LC) is amplified by an instrumentation amplifier of analog Devices before the signal is fed to the computer, said geophones having a natural frequency of 4.5 Hz and displacement of amplitude + 1.25 mm ; said signals from the geophones (GP) are integrated by an electronic circuits before they are recorded in the computer, a data acquisition card is fitted in the computer. 13. An in-vehicle falling weight deflectometer as claimed in claim 12 wherein said card is adapted to accomplish 100 KHz sampling rate in DMA mode the input to the card being bipolar, the maximum range being ± 10 V. 14. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 13 wherein the vehicle floor supports the frame structure holding the movable cylinder (C) with the deflection measuring unit, the load is also supported by the said frame structure there between the vertical columns of the support structure, the vehicle floor is cut out to favour movement of the load plate (LP) with rubber sole (RS) there through to touch the ground, said vehicle also accommodating the required electronic circuitry and the composition for data generation based on signals received from the load cell (LC) and the geophones (GP). 14. 13 15. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 14 wherein the instrumentation amplifier is provided for the load cell (LC) and the operator circuitry is shown Fig. 6. 16. An in-vehicle failing weight deflectometer as claimed in anyone of claims 1 to 15 wherein said geophone means is provided with integration circuit as illustrated in Fig. 7. 17. An in-vehicle falling weight deflectometer as claimed in anyone of claims 1 to 16 wherein power for running the hydraulic pump can be derived from battery also using a DC motor. 18. An in-vehicle falling weight deflectometer is substantially as herein described and illustrated with reference to the accompanying figures. In-vehicle automated falling weight deflectometer to provide non-destructive evaluation of strength of highway and airfield pavements. It is also useful for testing of bridges and other like applications. The in-vehicle falling weight deflectometer comprise a load-deflection measuring unit having a load cell, geophone assembly, loading plate with rubber sole at its lower face such that for deflection measurement said rubber sole extend beyond the vehicle floor and press against the road surface; means to raise the vehicle wheels above ground and lowering of the geophone assembly to rest on the ground with geophones pressed against the road surface ; a releasably secured falling weight adapted to fall on said pad as and when the deflection measurement is required ;means for monitoring the signals from the load cell upon impact of the falling weight ;means for monitoring the signals from the geophones and generating the deflection measurement values based thereon. The above in-vehicle automated falling weight deflectometer would provide for a more precise and effective measure of the strength of road and airport pavement to enable estimation of remaining strength and forecast appropriate strengthening measure using mechanistic approach well ahead of failure condition. Importantly the system would enable identification of deficiency in every layer of pavements more accurately. The deflectometer is easily transported from one place to another and thus favour its application and end use. Moreover, the deflectometer is adapted to use power for running hydraulic pump is derived from the vehicle engine itself thereby avoiding need for a battery operated D.C. Motor and pump. The device is simple and easy to handle/use and also cost effective.

Documents:

00551-cal-2001-abstract.pdf

00551-cal-2001-claims.pdf

00551-cal-2001-correspondence.pdf

00551-cal-2001-description(complete).pdf

00551-cal-2001-drawings.pdf

00551-cal-2001-form-1.pdf

00551-cal-2001-form-19.pdf

00551-cal-2001-form-2.pdf

00551-cal-2001-form-3.pdf

00551-cal-2001-p.a.pdf

551-CAL-2001-FORM-27.pdf

551-cal-2001-granted-abstract.pdf

551-cal-2001-granted-claims.pdf

551-cal-2001-granted-correspondence.pdf

551-cal-2001-granted-description (complete).pdf

551-cal-2001-granted-drawings.pdf

551-cal-2001-granted-form 1.pdf

551-cal-2001-granted-form 19.pdf

551-cal-2001-granted-form 2.pdf

551-cal-2001-granted-form 3.pdf

551-cal-2001-granted-letter patent.pdf

551-cal-2001-granted-pa.pdf

551-cal-2001-granted-reply to examination report.pdf

551-cal-2001-granted-specification.pdf