Strain gauge calibration system used for measuring the dynamic forces acting on the rail from railway vehicles

Abstract

The invention relates to a portable, modular assembly for calibrating strain gauges applied to the rail for determining vehicle-induced dynamic loads on rail lines, for both lateral and vertical loads.

Description

[0001] STRAIN GAUGE CALIBRATION SYSTEM USED FOR MEASURING THE DYNAMIC FORCES ACTING ON THE RAIL FROM RAILWAY VEHICLES

[0002] Technical Field of the Invention

[0003] The invention relates to a portable, modular assembly for calibrating strain gauges applied to the rail for determining vehicle-induced dynamic loads on rail lines, for both lateral and vertical loads.

[0004] State of the Art of the Invention

[0005] The contact force resulting from the interaction of the wheels with the rails is a critical factor affecting the dynamic performance, safety and smooth operation of rolling stock. Therefore, direct and indirect measurement methods have been developed to measure wheel-rail contact forces. Direct methods can be divided into vehicle-side and road-side. Direct methods used for measuring wheel-rail contact forces measure contact forces directly, usually through sensors mounted on rails or wheels. These sensors determine the contact forces by measuring the deformation of the wheels or rails.

[0006] To increase the reliability of monitoring results, strain gauge sections and measuring equipment are calibrated under operating conditions. Calibration methods can be static or dynamic, depending on predetermined forces.

[0007] The method of calibrating the strain gauge unit using dynamic force involves a special impact device of known weight dropped from a certain height onto the rail. The dynamic calibration method has issues such as the inability to determine the application point of the dynamic force and the formation of a force moment that causes lateral stresses in the rail bodies in cases of high eccentricity.

[0008] In the study conducted by Milkovic et al. [1], a device for calibrating the system was designed to increase the reliability of the measurements. The hydraulic-mechanical device for the independent application of vertical and lateral forces at predetermined positions on the rail profile is described here. Vertical forces are applied by two manual hydraulic jacks with a capacity of 125 kN and lateral forces are applied by a hydraulic cylinder with a maximum force of 50 kN. However, the application of vertical and lateral forces with separate systems leads to more equipment requirements, increasing the complexity of the design. The design of the calibration device requires taking advantage of the weight of the EMU trailer unit. The device is supported by placing it on the front cross beam of the train unit. The applied calibration forces were measured with HBM U5-100 kN (for vertical forces) and HBM U3-50 kN (for lateral forces) transducers. The pressure knob arrangement on the device allows forces to be applied at predetermined positions. The correlation between force intensities, contact point position, and strain gauge measurements is recorded using the DAQ system SPIDER 8.

[0009] In the study conducted by Bocciolini et al. [2] a system consisting of a hydraulic jack interfacing with a system load cell and a device that allows the application of arbitrary forces at different predefined heights is described. Here, the vertical calibration loads are applied via a standard H-series boxcar using a device consisting of a hydraulic jack and a load cell, while the lateral loads are applied with a separate device that allows force application at different heights with a load cell and another hydraulic jack.

[0010] In the study of Kolomeets and Sych [3] a device designed for the calibration of a strain gauge system is shown. In this system, the loading device is placed on the gripper platform on the rail. Vertical and lateral forces are applied by separate hydraulic cylinders. The system requires the vertical hydraulic cylinder to rest on the cross beam and adjustable support of a flat car loaded from above, while the horizontal hydraulic cylinder at the base rests on the leveling beam. The force point of the horizontal hydraulic cylinder cannot be adjusted. To create pressure in the hydraulic cylinders, two independent manual hydraulic pumps NRG-7010 were used, connected to the hydraulic cylinders via high pressure hoses. The pressure can be monitored by MA100VU63 pressure gauges. The manometers are attached directly to manually operated hydraulic pumps. The force transferred to the rail and the pressure can be read from the gauge.

[0011] The calibration device developed by Zhou et al. [4] is used for vertical loading up to a maximum of 200 kN (accuracy: 0.1 kN) and lateral loading up to a maximum of 150 kN (accuracy: 0.75 kN). For vertical loading, two gripper structures mounted on two traves are used to support the hydraulic cylinder. For lateral loading, the hydraulic cylinder must also be independently supported using adjustable rods. Pressure sensors are placed next to the hydraulic cylinders to digitally read the lateral and vertical loading forces.

[0012] In the study conducted by Peng et al [5], a calibration device is described. This device is supported with foundation supportjack, pull rod ack support, pressure sensor, pressure head, and rail clamp. A pressure sensor with a range of 200 kN was used. In addition, the elaborate structure of the rail clamp, consisting of three side clamps, is equipped with assemblies created to facilitate the transport of the calibration device to other parts of the rail. The system can only provide calibration for vertical loads.

[0013] The patent document with publication number CN106197811A discloses a railroad vertical and horizontal integrated wheel-rail force calibration device and method. The device comprises a calibration frame body, a hydraulic pump assembly in the calibration frame body, a first connecting rod and a second connecting rod respectively at two ends of the hydraulic pump assembly, two horizontal drive wheel assemblies on two sides of the end of the calibration frame body, two or more vertical drive wheels on the bottom plate of the calibration frame body, a guide wheel assembly and a hook assembly on the side wall of the calibration frame body, two handle assemblies at the two ends of the calibration frame body respectively, a vertical laser range finder on the bottom plate of the calibration frame body, and a horizontal laser range finder at the end of the calibration frame body.

[0014] The utility model document with publication number CN219749818U describes a rail force coefficient calibration device. The vertical calibration system of the calibration device includes multiple groups of first rail head clamping units, and each group of first rail head clamping units includes a connecting plate and two lower clamps clamped opposite, vertical and detachably on two sides of a rail head. The connecting plate is detachably and fixedly connected between the two lower clamps and can adjust the distance between the two lower clamps. The horizontal calibration system of the calibration device includes multiple second rail head clamping units, each second rail head clamping unit includes a main clamping plate and an auxiliary clamping plate which are opposite, horizontal and detachably clamped on two sides of the rail head, and the auxiliary clamping plate is detachably and fixedly connected to the main clamping plate and can adjust the fixing position; the rail force loading units are detachably and fixedly connected between the rail and the first rail head clamping unit and between the rail and the second rail head clamping unit, and maintain pressure contact; and the rail force coefficient calibration unit is connected on the rail.

[0015] The utility model document with publication number CN212988671U discloses the design of a steel rail vertical force measuring device. The design, which can only exert force in the vertical direction, includes a load cell device, a top plate, a rail fixing gripper, a support slot, a vertical pull rod, a pull plate and a top bar, and the force sensor device includes a tail fixing slot, a manual screw jack, a jack front fixing plate, a load cell, a sensor fixing slot, a fully threaded screw, a nut, a bolt, and a guide slot.

[0016] As a result all the above-mentioned problems have made it imperative to make an innovation in the relevant field.

[0017] Objects and Summary of the Invention

[0018] The main object of the invention is to introduce a portable, modular assembly for calibrating strain gauges applied to the rail for determining vehicle-induced dynamic loads on rail lines, for both lateral and vertical loads.

[0019] The object of the invention is, in particular, to introduce a structure of a calibration device which allows working with elements such as a portable hand pump and a computer.

[0020] In order to achieve the present objects, the invention is an assembly for calibrating strain gauges used in track-side test methods for determining vehicle-induced dynamic loads on rail system lines, comprising a hydraulic piston, a load cell disposed at the end of the piston, and a strain gauge to be attached to the rail. It further comprises a top plate including at least one top plate connection aperture, having at least two top plate connection lugs and positioned at the end of the hydraulic piston not facing the load cell. A cell connection part is provided at the end of the load cell, with at least one connection aperture provided at the end not facing the load cell. This structure includes a main gripper configured to be placed on the rail, a cell connection part and first and second connection openings for horizontal and vertical connection of the main gripper. It further comprises at least two support grippers configured to be inserted into the rail on either side of the main gripper, at least two support arms at both ends, one of which connected to the top plate connection opening via a pin, and primary and secondary support lugs provided on the support grippers and enabling the support end and the support arm to be horizontally and vertically connected to each other.

[0021] An embodiment of the invention comprises a vertical arm comprising a pin slot each at its ends, one end extending to the top plate lug, and a horizontal arm comprising a pin slot each at its ends, the other end extending to a pin slot at the end of the vertical arm.

[0022] An embodiment of the invention comprises a support arm extending between a vertical arm pin slot and a horizontal arm pin slot of the support arm.

[0023] An embodiment of the invention comprises at least one primary center arm including a pin slot at each end for connecting the support arms to each other.

[0024] An embodiment of the invention comprises two center arms positioned to receive the pin slot of the support arm therebetween.

[0025] An embodiment of the invention comprises said piston selected as a hydraulic piston.

[0026] An embodiment of the invention comprises a piston inlet of the hydraulic piston for connection to an external pump.

[0027] An embodiment of the invention comprises a horizontal support platform comprising a planar plate, carriers provided perpendicular to the plate, and a slot formed on the carriers for accommodating a piston side surface.

[0028] An embodiment of the invention comprises a locking element which prevents the pins from disengaging after passing through the pin slots.

[0029] An embodiment of the invention comprises a hole at the end portion of the pins, a lock pin of the locking element to pass through said hole, and a ring rotatably provided in the end portion of this lock pin.

[0030] An embodiment of the invention comprises a top plate having two top plate connection lugs positioned to receive a pin slot of each support arm. An embodiment of the invention comprises a support gripper comprising two primary support lugs and a secondary support lug each positioned so that each support arm receives a pin slot therebetween.

[0031] An embodiment of the invention comprises a strain gauge and a data processing unit for processing data provided from the load cell.

[0032] Descriptions of the Drawings Describing the Invention

[0033] The figures and the related descriptions used in order to better describe the device designed with this invention are as follows.

[0034] Fig- 1- Isometric representation showing the vertical force application of the test assembly subject to the invention.

[0035] Fig. 1A. Isometric representation showing the horizontal force application of the test assembly subject to the invention.

[0036] Fig. IB. Exploded representation for Fig. 1.

[0037] Fig. 1C. Exploded representation for Fig. 1 A.

[0038] Fig- 2. Isometric representation for the support gripper.

[0039] Fig. 2A. Isometric representation for the cell connection part.

[0040] Fig- 3. Isometric representation for the main gripper.

[0041] Fig. 4. Isometric representation for the horizontal support platform.

[0042] Definitions of the Elements / Features / Parts of the Invention

[0043] In order to better describe the device developed with this invention, the features and parts in the figures are numbered and the equivalent of each number is given below.

[0044] 10. Support arms

[0045] 11. Vertical arm

[0046] 12. Horizontal arm

[0047] 13. Intermediate arm

[0048] 14. Pin slot

[0049] 15. Primary center arm 16. Secondary center arm

[0050] 17. Lock element

[0051] 20. Pin

[0052] 30. Top plate

[0053] 31. Top plate lug

[0054] 32. Top plate connection opening

[0055] 40. Piston

[0056] 41. Piston inlet

[0057] 50. Load cell

[0058] 60. Cell connection part

[0059] 61. Cell connection end

[0060] 62. Cell connection base

[0061] 70. Support gripper

[0062] 71. Primary support lug

[0063] 72. Primary opening

[0064] 73. Secondary support lug

[0065] 74. Secondary opening

[0066] 75. Primary support wall

[0067] 76. Secondary support wall

[0068] 77. Support extension

[0069] 80. Main gripper

[0070] 81. Primary connection opening

[0071] 82. Secondary connection opening

[0072] 83. Primary wall

[0073] 84. Secondary wall

[0074] 85. Main extension

[0075] 86. Fastener

[0076] 90. Horizontal support platform

[0077] 91. Plate

[0078] 92. Carrier

[0079] 93. Slot

[0080] 94. Foot

[0081] R. Rail

[0082] Rl. Primary axis R2. Secondary axis

[0083] L. Lamella

[0084] T. Wedge

[0085] Detailed Description of the Invention

[0086] The invention relates to a portable, modular calibration system that can be used in both lateral and vertical directions for determining vehicle-induced dynamic loads on rail system lines.

[0087] The test assembly subject to the present invention comprises multiple grippers positioned on a rail (R). The data required for said test is provided by data obtained from a load cell (60) while pressure is applied to the rail via a piston (40) and by a strain gauge (not shown in the figures) placed on the rail (R). Said test assembly is arranged to allow the piston (40) to press the rail (R) both vertically and horizontally.

[0088] Fig. 1 and IB show the arrangement where the piston (40) exerts a vertical force on the rail (R). Three grippers, two being support grippers (70) and one being main gripper (80), are placed on the rail (R) with the said main gripper (80) between the support grippers (70). A cell connection part (60) is placed on said main gripper (80) and a load cell (50) is placed on top of the cell connection part (60). The load cell (50) is connected to the piston (40) and measures the force exerted by the piston (40) against the rail (R).

[0089] Preferably the load cell (50) has a capacity of 10 tons. It has a measurement accuracy of C3 level (0.0230%) and features an M36x2 threaded connection.

[0090] With reference to Fig. 2 and 2A, the present main gripper (80) comprises two secondary walls (84) arranged parallel to each other for holding the rail (R) and a primary wall (83) connecting these walls at opposite ends. At the other end of these secondary walls (84) are the main extensions (85), which extend towards each other and do not contact each other. There is a primary connection opening (81) provided above said primary wall (83) herein. The cell connection base (62) of the cell connection part (60) sits on the primary wall and is connected to the main gripper (80) through the primary connection opening (81), allowing the power applied by the piston (40) to be transferred vertically to the main gripper (80) and the rail (R). Here, the primary connection opening (81) and a screw-like fastener (86) threaded through a hole provided in the cell connection base (62) are provided for connection.

[0091] Referring to Fig. 1 and IB; a top plate (30) is used to fix the piston (40) to the assembly. The top plate (30) is positioned at the end of the hydraulic piston (40) not facing the load cell (50). At both ends of the top plate (30), at least one, preferably two opposite connecting lugs (31) extend, and a top plate connection opening (32) is provided above the connecting lug (31). Here, the top plate connection openings (32) provide the connection between the top plate (30) and the support grippers (70) by means of the support arms (10).

[0092] Preferably, the connection between the top plate (30) and the piston (40) is provided with 8XM20 bolts.

[0093] The support arms (10) comprise at least one arm including a pin slot (14) at its both ends, and one of said pin slots (14) is positioned so as to fit concentrically into one of the top plate connection openings (32), while the other end extends into the support gripper (70). Here, a pin (20) extending along the first axis (Rl) passes through both the top plate connection openings (32) and said pin slot (14). Here the first axis (Rl) is provided perpendicular to the piston's power transmission axis. After the pin (20) is inserted, a lock element (17) is placed at the end of the pin (20). In order to accommodate said lock element (17), there is a hole provided at the end of the pin (20) extending perpendicular to the primary axis (Rl) and the lock element (17) is inserted into this hole. There is a rotatable ring at the end of the lock element (17), and after the lock element (17) is inserted, this ring is rotated and seated on the pin (20). The pin slots (14) are provided in the form of a cylindrical shell and allow the passage of the pin (20) therethrough.

[0094] Another pin slot (14) is provided at the end of the support arm (10) extending to the support gripper (70).

[0095] With reference to Fig. 3, the present support gripper (70) comprises two secondary support walls (76) arranged parallel to each other for holding the rail (R) and a primary support wall

[0096] (75) connecting these walls at opposite ends. At the other end of these secondary support walls

[0097] (76) are the support extensions (77), which extend towards each other and do not contact each other. There are two primary support lugs (71) extending perpendicular to the wall on said primary wall (83) herein. A primary opening (72) is arranged on the primary support lug (71). The pin slot (14) at the end of the support arm (10) extending to the support gripper (70) is positioned to be concentric with the primary opening (72), and wherein a pin (20) extending in the direction of the primary axis (Rl) provides the connection by passing through the pin slot

[0098] (14) and the primary opening (72). The previously described lock element (17) can be used here.

[0099] In the preferred embodiment, the support arm (10) comprises a vertical arm (11), a horizontal arm (12), and an intermediate arm (13). The vertical arm (11) and horizontal arm (12) are perpendicular to each other and the intermediate arm (13) extends therebetween. This creates a monolithic and triangular structure with a pin slot (14) on each side. One of the pin slots (14) at the ends of the intermediate arm (13) extends to the top plate (30) and the other to the support gripper (70).

[0100] The pin slots (14) at the ends of the two support arms (10) not extending toward the support grippers (70) of the horizontal arms (12) are connected to each other via a primary center arm

[0101] (15) There is a pin slot (14) provided at each end of the primary center arm (15), and these pin slots (14) are positioned concentrically with the pin slots (14) of the horizontal arms (12), and wherein a pin (20) passing through the primary axis provides the connection. The previously described lock element (17) can be used here.

[0102] In a preferred embodiment, two primary center arms (15) are used and these primary center arms (15) are connected to the horizontal arm (12) via the same pin slot (14), and wherein the pin (20) passes through all three concentric pin slots (14). To accommodate the length of the pin (20) also mentioned herein, secondary center arms (16) may be positioned on the pin (20) perpendicular to the horizontal arm, with the pin slots (14) placed therebetween.

[0103] Up to this point in the detailed description, the arrangement in which a vertical force is applied to the rail (R) has been described. As explained earlier, this test assembly can also apply a horizontal force to the rail (R).

[0104] Fig. 1 A and 1C show the arrangement where the piston (40) exerts a horizontal force on the rail (R). For this arrangement, the support arms (10), top plate (30), and center arms, if any, are separated from each other by first removing all pins (20) and lock elements (17). The connection element (86) passed through a hole provided in the primary connection opening (81) and the cell connection base (62) is disconnected, separating the piston (40), load cell (50), and cell connection part (60) from the assembly.

[0105] Then the pins (20) connecting the top plate (30) and the center connection arms, if any, are replaced.

[0106] With reference to Fig. IB, 2 and 2A, the previously described main gripper (80) has a secondary connection opening (82) on the secondary walls (84). The secondary connection opening (82) extends perpendicular to the primary connection opening (81). The cell connection part (60), which is separated from the primary connection opening (81), is connected to the main gripper (80) by a screw-like fastener (86), which is threaded through a hole provided in the secondary connection opening (82) and the cell connection base (62), allowing to apply force through the secondary wall (84).

[0107] With reference to Fig. 3, in the horizontal force application, the pin slot (14) at the end of the support arm (10) extending to the support gripper (70) is connected via the secondary support lug (73) instead of the primary support lug (71). The support gripper (70) comprises two secondary support lugs (73). The secondary support lug (73) extends perpendicular to the secondary support wall (76) of the support gripper (70) and includes a secondary opening (74) thereon. Said pin slot (14) is positioned concentrically with the secondary opening (74) and is connected by a pin (20) passing through the pin slot (14) and the secondary opening (74). The previously described lock element (17) can be used here.

[0108] Thus, the horizontal positioning shown in Fig. 1A is easily realized without changing the positions of the grippers.

[0109] With reference to Fig. 3, in the present support grippers (70) preferably a wedge (T) is attached to said support extensions and a lamella (L) is attached to the inner surface of the primary support wall (75).

[0110] With reference to Fig. 1C and Fig. 4; the piston (40) may need support when horizontal positioning is achieved. For this reason, the horizontal support platform (90) is used. The horizontal support platform (90) comprises a planar plate (91), at least one, preferably two, carriers (92) provided perpendicular to the plate (91) and a slot (93), preferably formed in the form of a curved recess, on said carriers (92) for accommodating the side surface of the piston (40). The bottom of the planar plate (91) is provided with height-adjustable feet (94) to sit on the floor.

[0111] In the present invention, the piston (40) is preferably a hydraulic piston and is driven by a hand pump. For the connection of said hand pump, the piston (40) comprises a piston inlet (41) in the body.

[0112] The system includes 4 meters long and 10 mm diameter hoses. The cylinder port connection includes a ball quick coupling and the pump port connection includes a screw quick coupling. There is no safety valve on the hand pump, so the safety valve is activated by means of a T- connection connected to the manometer line. Thanks to the manometer line on the pressure port, pressure safety can be ensured in the system regardless of the diverted side. The pressure required for 10000 kgF load is calculated as 125 bar. The pressure setting of the safety valve is fixed at 140 bar and then sealed. Manual pressure setting of 125 bar is set under operator control. The Werner ® brand hydraulic hand pump is the equipment that provides the system pressure and has a maximum pressure value of 700 bar. It has a dual-effect feature, and the flow direction is provided by a manually controlled 4 / 3 directional valve. Equipment inlet and outlet ports are 3 / 8 NPT.

[0113] Preferably, the piston (40) THS 100 / 56-50 OFB single-shaft cylinder has a working pressure of 160 bar. There are 8 bolt holes with a diameter of 23 mm for mounting the cylinder. Inlet and outlet ports are manufactured as 3 / 4 BSP (British Standard Pipe).

[0114] In an embodiment of the invention, the piston (40) provides pressure, while data from the strain gauge and load cell (50) is transferred to a data processing unit, preferably a computer. Here we ensure the accuracy of the calibration process by recording and analyzing data. REFERENCES

[0115] [1] D. Milkovic, G. Simic, Z. Jakovljevic, J. Tanaskovic, V. Lucanin, Wayside system for wheel-rail contact forces measurements, Measurement, Volume 46, Issue 9, pp. 3308-3318, 2013. [2] L. Bocciolini, A. Bracciali, L. Di Benedetto, R. Mastandrea and F. Piccioli “Wayside

[0116] Measurement of Lateral and Vertical Wheel / Rail Forces for Rolling Stock Homologation,” Civil-Comp Press, Proceedings of the Second International Conference on Railway Technology: Research, Development and MaintenanceCivil-Comp Press, Stirlingshire, Scotland, 2014. [3]A. Kolomeets and T. Sych, "Calibration method for a strain-gauge measurement system based on bidirectional rail loading," MATEC Web of Conferences, vol. 216, p. 03005, 2018, doi : 10.105 l / matecconf / 201821603005.

[0117] [4] Zhou, W., Abdulhakeem, S., Fang, C., Han, T., Li, G., Wu, Y., & Faisal, Y. “A new wayside method for measuring and evaluating wheel-rail contact forces and positions,” Measurement, 166, 108244, 2020.

[0118] [5] X. Peng, J. Zeng, J. Wang, Q. Wang, D. Li, and S. Liang, "Wayside wheel-rail vertical contact force continuous detecting method and its application," Measurement, vol. 193, no. 110975, pp. 1-12, Mar. 2022.

Claims

CLAIMS1. A strain gauge calibration assembly that can be used to determine vehicle-induced lateral and vertical dynamic loads on rail (R) system lines, characterized in that it comprises:■ a hydraulic piston (40), a load cell (50) positioned at the end of said piston (40), and a strain gauge to be attached to the rail (R);■ a top plate (30) having two pairs of top plate connection lugs (31) positioned opposite each other, including at least one top plate connection opening (32), and mounted on the end of the hydraulic piston (40) not facing the load cell (50);■ a cell connection piece (60) placed at the end of said load cell (50), provided at the end not facing the load cell (50), comprising at least one connection opening;■ a main gripper (80) configured to be placed on a rail (R);■ the first connection opening (81) and second connection opening (82) provided in the main gripper (80) and extending perpendicular to each other, which enable the cell connection part (60) and the main gripper (80) to be connected to each other horizontally and vertically through the connection opening;■ at least two support grippers (70) configured to be placed on the same rail (R) on either side of said main gripper (80);■ at least two support arms (10), having at least one arm comprising a pin slot (14) each at both ends, one of which allowing connection to the top plate connection openings (32) by connection part between the top plate connection lugs (31) positioned opposite each other via a pin (20);■ said support gripper (70) having two primary support lugs (71) and secondary support lugs (73) each positioned so that each support arm (10) receives one pin hole (14) therebetween, enabling the support end and the support arm (10) to be horizontally and vertically connected to each other by means of a pin (20); and■ a locking element (17) which prevents the pins (20) from coming out after passing through the pin slots (14).

2. The calibration assembly according to claim 1 , characterized in that said support arm (10) comprises a vertical arm (11) comprising a pin slot (14) each at its ends, one end extending to the top plate lug (31), a horizontal arm (12) comprising a pin slot (14) each at its ends, one end extending to a pin slot (14) at the end of said vertical arm (11) and the other extending to a primary support lug (71) or a secondary support lug (72).

3. The calibration assembly according to claim 1, characterized in that said support arm (10) comprises a support arm extending between the pin slot (14) of the vertical arm (11) and the pin slot (14) of the horizontal arm (12).

4. The calibration assembly according to claim 2 or 3, characterized in that it comprises at least one primary center arm (15) comprising a pin slot (14) each at both ends for connecting the support arms (10) to each other.

5. The calibration assembly according to any one of the preceding claims, characterized in that said support arm (10) comprises two center arms (15) positioned so as to receive the pin slot (14) therebetween.

6. The calibration assembly according to claim 1, characterized in that it comprises said piston (40) selected as a hydraulic piston.

7. The calibration assembly according to claim 6, characterized in that said hydraulic piston (40) comprises a piston inlet (41) for connection to an external pump.

8. The calibration assembly according to claim 1, characterized in that it comprises a horizontal support platform (90) comprising a planar plate (91), carriers (92) provided perpendicular to the plate (91), and a slot (93) formed on said carriers (92) to receive a side surface of the piston (40).

9. The calibration assembly according to claim 1, characterized in that said pins (20) comprise a hole in the end portion thereof, the lock member (17) comprising a lock pin to pass through said hole and a ring rotatably provided in the end portion of said lock pin.

10. The calibration assembly according to claim 1, characterized in that it comprises a data processing unit for processing data provided from the strain gauge and the load cell (50).

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