FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION: Assembly for Energy Saving Endurance Testing For Hydraulic Cylinder
2. APPLICANT:

(a) NAME: Larsen&Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. 0. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Assembly for Energy Saving Endurance Testing For Hydraulic Cylinder
Field of the invention
The present invention relates to testing setup for hydraulic cylinders which are used on construction/earth moving equipment, and more particularly, to an assembly for endurance testing of the hydraulic cylinder.
Background of the invention
Conventionally, endurance testing setups are widely used by hydraulic cylinder manufacturers to test the hydraulic cylinders. The endurance testing setup for the hydraufic cyfinders are used to determine life of tHe hydraun'c cylinder and its internal components. Determining life of the hydraulic cylinder is very essential as reliability of the hydraulic cylinder becomes more important when the hydraulic cylinders are subjected to field application.
Normally, the endurance testing setup consists of a test hydraulic cylinder with load or mass attached at the end of a piston rod of the test hydraulic cylinder. This mass is defined depending on the size of the test hydraulic cylinder and required working pressure inside the test hydraulic cylinder. The test hydraulic cylinder is extended and retracted with the help of a single prime mover, for example, a pump which feds oil flow in to a barrel side and a rod side of the test hydraulic cylinder respectively. The test hydraulic cylinders speed is controlled or varied by controlling the pump displacement or flow.
The pump size required for the abovementioned endurance testing of the hydraulic cylinder is big as required for directly running the test hydraulic cylinder of different sizes at the required speed. The pump used here have to generate required pressure at required flow which demands for high power consumption which in turn increases size of the electric motor size and overall cost of the power pack in the testing set up.

Specifically, US Patent No. 5331842 discloses a cyclical pressure testing apparatus utilizing a first fluid to pressurize test hydraulic cylinder and a second fluid to pressurize the first fluid.
However, in the abovementioned patent, and in general electrical power consumption is more as the single pump works for the highest pressure and highest flow demand from the test hydraulic cylinder. Also, more power consumption increases running cost of the test setup. Moreover, the prime mover i.e. the electric motor, and the hydraulic pump sizes required are big which in turn increases capital cost the overall setup for testing hydraulic cylinder.
Accordingly, there exists a need to provide an assembly for endurance testing of . the hydraulic cylinder which overcomes drawbacks of the prior art.
Objects of the invention
An object of the present invention is to reduce cost of testing setup of the hydraulic cylinder.
Another object of the present invention is to reduce power consumption required for testing setup of the hydraulic cylinder.
Summary of the invention
Accordingly, the present invention provides an assembly for energy saving endurance testing for a hydraulic cylinder. The assembly comprises a test hydraulic cylinder, a load hydraulic cylinder having a second piston rod end coupled to a first piston rod of the test hydraulic cylinder thereby forming a linkage therebetween, and a drive hydraulic cylinder having a third piston rod end linked to the linkage of the test hydraulic cylinder and the load hydraulic cylinder.
Further, the assembly includes a load circuit having first variable displacement pump capable of feeding oil to a barrel side of the test hydraulic cylinder and the

load hydraulic cylinder, and a drive circuit having a second variable displacement pump capable of feeding oil to a barrel side of the drive hydraulic cylinder. The drive hydraulic cylinder extends and moves along the direction of load hydraulic cylinder when oil is supplied to a barrel side of the drive hydraulic cylinder.
Furthermore, the assembly includes a electro-proportional pressure relief valve capable of releasing excess supply of oil to the barrel side of the test hydraulic cylinder and the load hydraulic cylinder during testing of the test hydraulic cylinder, wherein the drive cylinder is small in size to move the linkage which requires less pressure and flow to generate required force and speed for testing the test hydraulic cylinder thereby reducing power consumption required for the drive circuit.
Brief description of the drawings
Figure 1 a schematic diagram of an assembly for endurance testing of a hydraulic
cylinder.
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred
embodiments.
The present invention provides an assembly for energy saving endurance testing for a hydraulic cylinder. The assembly for energy saving endurance testing for a hydraulic cylinder requires less power thereby reducing the cost of the assembly.
Referring now to figure 1, a schematic drawing of an assembly (100) for endurance testing for a hydraulic cylinder, is shown.

The assembly [100] includes a test hydraulic cylinder (10), a load hydraulic cylinder [20], a drive hydraulic cylinder (30), a load circuit (40), a drive circuit (50) and an electro-proportional pressure relief valve (60).
The test hydraulic cylinder (10) includes a first piston rod (12). The first piston rod (12) of the test hydraulic cylinder (10) is coupled to a second piston rod (22) of the load hydraulic cylinder (20), thereby forming a linkage ((14) therebetween. In an embodiment, the linkage (14) is formed by fixing means known in the art. The test hydraulic cylinder (10) and the load hydraulic cylinder (20) are positioned parallel to each other such that the first piston rod (12) and the second piston rod (22) linked together in a straight line. Specifically, size and strokes of the test hydraulic cylinder (10) is equal to the load hydraulic cylinder (20).
Further, the drive hydraulic cylinder (30) includes a third piston rod (32) linked to the linkage (14) formed by the first piston rod (12) and the second piston rod (22). Furthermore, the load circuit (40) includes a first variable displacement pump (42) which is capable of feeding oil to a barrel side (16) of the test hydraulic cylinder (10) and a barrel side (24) the load hydraulic cylinder (20). Typically, the first variable displacement pump (42) feeds oil to the barrel side (16) of the test hydraulic cylinder (10) and to the barrel side (24) of the load hydraulic cylinder (20) through a first directional control valve (44) when the first variable displacement pump (42) is activated by electrical means.
As both the first piston rod (12) and the second piston rod (22) are physically linked and constrained, movement of the test hydraulic cylinder (10) and the load hydraulic cylinder (20) due to oil flow is blocked. Accordingly, closed and fixed volume in the barrel side (16) of the test hydraulic cylinder (10) and the barrel side (24) of the load hydraulic cylinder (20) gets pressurized up to a circuit relief pressure setting in the electro-proportional pressure relief valve (60). During the course of testing of the test hydraulic cylinder (10), the fixed volume of oil inside the barrel side (16) of the test hydraulic cylinder (10) and the barrel side (24) of the load hydraulic cylinder (20) may get exhausted due to leakages in oil seals. To compensate this loss of the oil, the first variable displacement pump (42) supply

oil during testing and excess supply of oil, if any is relieved over electro-proportional pressure relief valve (60).
The first variable displacement pump (42) is able to supply varying oil flow as per the leakage rates in the test hydraulic cylinder (10) and the load hydraulic cylinder (20). The first variable displacement pump (42) only consumes minimum power required to pressurize the oil chamber and to supply minimum oil for leakage compensation.
The drive circuit (50) includes a second variable displacement pump (52) which feeds oil to the drive hydraulic cylinder (30). Typically, the second variable displacement pump (52) feeds oil to the drive hydraulic cylinder (50) through a second directional control valve (54) when the second variable displacement pump (52) is activated by electrical means.
Specifically, the drive hydraulic cylinder (30) extends and moves along the direction of the load hydraulic cylinder (20) when oil is supplied to a barrel side (34) of the drive hydraulic cylinder (30). Further, the load on the test hydraulic cylinder (10) is automatically balanced while extension or retraction thereof due to use of separate load hydraulic cylinder (20) and the drive hydraulic cylinder (30). This permits use of small force using a smaller load hydraulic cylinder (10) to move the test hydraulic cylinder (10) under desired loads.
Further, the testing speed for the test hydraulic cylinder (10) is capable of being altered as desired by setting the second variable displacement pump (52) output flow to required levels. This is achieved by adjusting an electrical knob which in turn gives signal to electrical solenoid (electrical means) of the second variable displacement pump (52), thereby adjusting an internal swash plate of the second variable displacement pump (52) and output flow is varied.
Furthermore, the test hydraulic cylinder (10) extension and retraction speeds and the test pressure in the test hydraulic cylinder (10) can be programmed as a function of the position of first piston rod (12) in the test hydraulic cylinder (10).

The first piston rod (12) position can be sensed by a position sensor or proximity sensor which can give signal to second variable displacement pump (52) and electro-proportional pressure relief valve (60) which in turn varies its output flow and pressure setting respectively for the drive hydraulic cylinder (30).
Specifically, the assembly (100) simulates exactly as per field data, by feeding in the field data on pressure and speed Vs first piston (12) position.
The drive hydraulic cylinder (30) is small in size and moves the linkage (14) formed by the first piston rod (12) and the second piston rod [22) which requires less pressure and flow to generate required force and speed for testing the test hydraulic cylinder (10) thereby reducing power consumption required for the drive circuit (50).
Further, the load circuit (40) for the load hydraulic cylinder (20) and the drive circuit (50) for the drive hydraulic cylinder (30) for driving the test hydraulic cylinder (10), requires less power and thus the energy saved.
Advantages of the invention
1. The assembly (100) requires less power consumption, for example 90% of power is saved when compared to the existing setup for testing hydraulic cylinder.
2. The assembly (100) requires lower running cost.
3. The assembly (100) requires small sizes of the electric motor and hydraulic pump sizes which minimizes the capital cost of power pack system and overall test setup.
4. Using the assembly (100), different sizes and strokes of cylinder can be tested with different velocities.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above

teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We Claim:
1. An assembly for energy saving endurance testing for a hydraulic cylinder, the assembly comprising:
a test hydraulic cylinder having a first piston rod;
a load hydraulic cylinder having a second piston rod coupled to the first piston rod of the test hydraulic cylinder thereby forming a linkage therebetween;
a drive hydraulic cylinder having a third piston rod linked to the linkage of the test hydraulic cylinder and the load hydraulic cylinder;
a load circuit having first variable displacement pump capable of feeding oil to a barrel side of the test hydraulic cylinder and the load hydraulic cylinder;
a drive circuit having a second variable displacement pump capable of feeding oil to the drive hydraulic cylinder, wherein the drive hydraulic cylinder extends and moves along the direction of load hydraulic cylinder when oil is supplied to a barrel side of the drive hydraulic cylinder;
a electro-proportional pressure relief valve capable of releasing excess supply of oil to the barrel side of the test hydraulic cylinder and the load hydraulic cylinder during testing of the test hydraulic cylinder,
wherein the drive cylinder is small in size to move the linkage which requires less pressure and flow to generate required force and speed for testing the test hydraulic cylinder thereby reducing power consumption required for the drive circuit.
2. An assembly as claimed in claim 1, wherein the first variable displacement pump feeds oil to the barrel side of the test hydraulic cylinder and load cylinder hydraulic through a directional control valve when it is activated.
3. An assembly as claimed in claim 1, wherein the second variable displacement pump feeds oil to the drive hydraulic cylinder through directional control valve when it is activated.