A testing fixture for testing gear end face runout of a crankshaft
By designing a fixture consisting of crankshaft support, positioning, and clamping mechanisms, the problem of controlling the assembly accuracy of gears at both ends of the crankshaft was solved, achieving efficient end face runout detection and meeting the market's technical requirements for small backlash design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- XIANGYANG FUDA DONGKANG CRANKSHAFT
- Filing Date
- 2025-07-28
- Publication Date
- 2026-07-14
AI Technical Summary
Existing technologies are insufficient to effectively control the assembly precision of gears at both ends of the crankshaft, especially under small backlash designs, and cannot meet the detection requirements for gear end face runout.
A gauge was designed, consisting of a crankshaft support mechanism, an axial positioning mechanism, an axial clamping mechanism, and a measuring device. The crankshaft is accurately positioned and measured by sliding contact with the platform via a T-key, and the gear end face runout is detected by a dial indicator.
It achieves high-precision detection of the end face runout of the gears at both ends of the crankshaft. It has a simple structure, is quick to operate, and is suitable for detection in different positions and directions, thus improving the adaptability of the detection.
Smart Images
Figure CN224499304U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of automotive parts manufacturing technology, specifically a tool for inspecting the runout of the end faces of gears at both ends of a crankshaft. Background Technology
[0002] Two gears are mounted at each end of the crankshaft. With market product iteration and optimization, the vibration damping effect of these gears during operation needs to be improved during new product design and development. Therefore, the backlash design value for the mating gears is becoming increasingly smaller. To ensure the normal operation of the crankshaft under the required technical parameters, the assembly accuracy of the gears on the crankshaft must be controlled simultaneously. Product drawings require that the end face runout of the gears at both ends of the crankshaft after assembly must be controlled within a certain range. To meet the inspection requirements for the end face runout of the gears at both ends after assembly during crankshaft mass production, it is particularly important to develop a tool for inspecting the end face runout of the gears at both ends of the crankshaft. Summary of the Invention
[0003] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a tool for inspecting the runout of the gear end faces at both ends of a crankshaft, so as to facilitate and quickly detect the runout of the gear end faces at both ends of the crankshaft.
[0004] To achieve the above-mentioned invention objectives, the inspection fixture consists of a crankshaft support mechanism, an axial positioning mechanism, an axial clamping mechanism, and a measuring device. A guide groove with an inverted T-shaped cross-section is opened on the platform. The crankshaft support mechanism, the axial positioning mechanism, and the axial clamping mechanism are connected to the platform through T-key 1, T-key 2, and T-key 3, respectively. The bottom of the measuring base of the measuring device is in contact with the platform and can move freely on the platform.
[0005] Furthermore, the keyway at the bottom of the roller bracket and the keyway at the top of the guide groove of the crankshaft support mechanism slides with the key at the top of the first T-key; the keyway at the bottom of the axial positioning bracket and the keyway at the top of the guide groove of the axial positioning mechanism slides with the key at the top of the second T-key; the keyway at the bottom of the clamping bracket and the keyway at the top of the guide groove of the axial clamping mechanism slides with the key at the top of the third T-key; the crankshaft support mechanism, the axial positioning mechanism, and the axial clamping mechanism are on a straight line and their center of symmetry is parallel to the axis of the crankshaft.
[0006] Furthermore, the T-key of the crankshaft support mechanism is placed in the guide groove of the platform, and two bolts connect and fix the roller bracket to the T-key. Two bearings are fixed to the roller bracket by pins. The roller bracket and the two bearings together form a roller support. The two roller supports support the main journal of the crankshaft and the second main journal, respectively, providing horizontal support for the crankshaft. The crankshaft can rotate freely on the roller support.
[0007] Furthermore, the T-key 2 of the axial positioning mechanism is placed in the guide groove of the platform, and two bolts 1 connect and fix the axial positioning bracket to the T-key 2. The inner arc diameter of the axial positioning bracket is larger than the diameter of the main journal 3 of the crankshaft. The main journal 3 is placed on the axial positioning bracket in a suspended state. The bearing 2 is vertically connected and fixed to the axial positioning bracket by the pin 2. The center line of the bearing 2 is perpendicular to the axis of the crankshaft. The outer side of the bearing 2 protrudes from the side of the axial positioning bracket and contacts the positioning end face of the main journal 3 of the crankshaft. The outer circle of the bearing 2 is tangent to the positioning end face of the main journal 3 of the crankshaft.
[0008] Furthermore, the axial clamping mechanism is installed on the right side of the crankshaft. T-key three is placed in the guide groove of the platform. Two bolts connect and fix the clamping bracket to T-key three. A circular hole is horizontally opened on the clamping bracket along the axis. Wear-resistant sleeves are inlaid on both sides of the circular hole. The clamping shaft with a central groove that matches pin three is installed in the inner ring of the wear-resistant sleeve. The wear-resistant sleeve and the clamping shaft slide together. A circular hole for placing pin three is vertically opened above the clamping bracket. The left end of the clamping shaft is a boss structure. Compression spring one is fixed between the inner side of the boss and the wear-resistant sleeve. The right end of the clamping shaft is a handle structure. Bolt two connects the pad block, thrust bearing and clamping shaft together. The thrust bearing is fixed in the circular countersunk hole in the center of the left end boss of the clamping shaft. The right side boss of the pad block is pressed against the inner hole of the thrust bearing. The inner hole of the pad block is clearance-fitted with bolt two. The pad block can rotate freely on its own under the action of the thrust bearing.
[0009] Furthermore, the measuring base of the measuring device has an L-shaped groove 1 inside its upper end, and a threaded hole 2 is opened on the upper part of the groove 1. A through hole is opened on the side of the measuring base corresponding to the threaded hole 2. The probe of the dial indicator is placed into the through hole, and a bolt 3 is installed in the threaded hole 2. Tightening the bolt 3 fixes the dial indicator on the measuring base. A threaded hole 1 is machined at the position adjacent to the through hole. A compression spring 2 is installed in the threaded hole 1 and extends into the groove 2 of the measuring rod crossbar. A set screw is installed in the threaded hole 1 to hold the compression spring 2. A vertical pin hole is machined at the corner of the groove 1. A pin 4 passes through the pin hole of the measuring rod and the pin hole on the measuring base to fix the measuring rod on the measuring base. The center distance of the pin hole from the center of the through hole is L, and the center distance of the pin hole of the measuring rod from the center of the measuring rod probe is L. When the side rod probe moves, the side rod crossbar moves proportionally. The measuring rod has a T-shaped structure, and the measuring rod crossbar is perpendicular to the measuring rod stop. The measuring rod crossbar has a groove 2 that matches the compression spring 2.
[0010] During inspection, place the crankshaft horizontally on bearing one of the shaft support mechanisms at both ends of the inspection table; loosen pin three of the axial clamping mechanism, allowing the shim to engage with the small end journal of the crankshaft. Simultaneously, the crankshaft moves to the left under the thrust of the shim until the positioning end face of the crankshaft engages with bearing two, completing the clamping and positioning. Move the measuring base to the measuring position of gear one or gear two, and press the measuring rod probe against the end face of gear one or gear two. Simultaneously, press the measuring rod crossbar against the probe of the dial indicator. After pressing the indicator, rotate the crankshaft and observe the dial indicator reading. Identify the fluctuation range of the dial indicator reading to determine the end face runout of the gears at both ends of the crankshaft. After the inspection is completed, remove the base and pull the right handle of the clamping shaft to the right until pin three falls freely into the central groove of the clamping shaft. With the axial clamping mechanism released, remove the crankshaft.
[0011] Compared with the prior art, this utility model has a simple structure and is convenient and quick to inspect. Since the crankshaft support mechanism, axial positioning mechanism and axial clamping mechanism are on a straight line and the center of symmetry is parallel to the axis of the crankshaft, the positioning accuracy of the crankshaft is high. Furthermore, due to the mobility of the measuring base, the end face runout detection of the gears at both ends of the crankshaft at different positions and in different directions can be realized, which has the advantage of high adaptability. Attached Figure Description
[0012] To make the content of this utility model easier to understand, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:
[0013] Figure 1 This is a simplified structural diagram of the present invention.
[0014] Figure 2 for Figure 1 The AA sectional view is a simplified structural diagram of the crankshaft support mechanism.
[0015] Figure 3 for Figure 1 The BB sectional view is a simplified structural diagram of the axial positioning mechanism.
[0016] Figure 4 for Figure 1 A simplified structural diagram of the axial clamping mechanism.
[0017] Figure 5 for Figure 1 A simplified structural diagram of the measuring rod of the measuring device.
[0018] Figure 6 yes Figure 5 Side view.
[0019] Figure 7 for Figure 1 The CC cross-sectional view, i.e., the schematic diagram of gear two inspection.
[0020] Figure 8 for Figure 1 The CC cross-sectional view, i.e., the gear inspection schematic diagram.
[0021] Figure 9 for Figure 1 Left view of the measuring base.
[0022] In the diagram: 1. Platform; 2. Guide groove; 3. Crankshaft; 4. Main journal one; 5. Main journal two; 6. Main journal three; 7. Positioning end face; 8. Small end journal; 9. Gear one; 10. Gear two; 11. Roller bracket; 12. Bearing one; 13. Pin one; 14. Bolt one; 15. T-key one; 16. T-key two; 17. Axial positioning bracket; 18. Bearing two; 19. Pin two; 20. Tightening shaft; 21. Tightening bracket; 22. T-key three; 23. Pin three; 24. Wear-resistant sleeve; 25. Compression spring one; 26. Thrust bearing; 27. Pad; 28. Bolt 2; 29. Measuring base; 30. Dial indicator; 31. Bolt 3; 32. Measuring rod; 33. Pin 4; 34. Compression spring 2; 35. Measuring rod probe; 36. Measuring rod stop; 37. Measuring rod crossbar; 38. Set screw; 39. Pin hole; 40. Threaded hole 1; 41. Through hole; 42. Threaded hole 2; 43. Center groove; 44. Groove 1; 45. Measuring rod pin hole; 46. Groove 2. Detailed Implementation
[0023] To make the invention's objectives, technical solutions, and advantages clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of protection of the present invention.
[0024] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 As shown, the inspection requirement of this utility model for inspecting the end face runout of the gears at both ends of the crankshaft is to measure the right end face runout of gear 9 and the left end face runout of gear 10 on both sides of the crankshaft 3, with the outer circles of main journal 4 and main journal 5 as references.
[0025] This utility model mainly consists of a crankshaft support mechanism, an axial positioning mechanism, an axial clamping mechanism, and a measuring device. A guide groove 2 with an inverted T-shaped cross-section is opened on the platform 1. The crankshaft support mechanism, axial positioning mechanism, and axial clamping mechanism are connected to the platform 1 via T-key 15, T-key 16, and T-key 22, respectively. The bottom of the measuring base 29 of the measuring device is in contact with the platform 1 and can move freely on the platform 1.
[0026] The keyway at the bottom of the roller bracket 11 of the crankshaft support mechanism and the keyway at the top of the guide groove 2 slide in engagement with the key at the top of the T-key 15; the keyway at the bottom of the axial positioning bracket 17 of the axial positioning mechanism and the keyway at the top of the guide groove 2 slide in engagement with the key at the top of the T-key 16; the keyway at the bottom of the clamping bracket 21 of the axial clamping mechanism and the keyway at the top of the guide groove 2 slide in engagement with the key at the top of the T-key 22; the crankshaft support mechanism, the axial positioning mechanism, and the axial clamping mechanism are on a straight line and their center of symmetry is parallel to the axis of the crankshaft 3.
[0027] The T-key 15 of the crankshaft support mechanism is placed in the guide groove 2 of the platform 1. Two bolts 14 connect and fix the roller bracket 11 to the T-key 15. Two bearings 12 are fixed to the roller bracket 11 by pins 13. The roller bracket 11 and the two bearings 12 together form a roller support. The two roller supports support the main journal 4 and main journal 5 of the crankshaft 3 respectively, providing horizontal support for the crankshaft 3. The crankshaft 3 can rotate freely on the roller support.
[0028] The T-key 16 of the axial positioning mechanism is placed in the guide groove 2 of the platform 1. Two bolts 14 connect and fix the axial positioning bracket 17 to the T-key 16. The inner arc diameter of the axial positioning bracket 17 is larger than the diameter of the main journal 6 of the crankshaft 3. During inspection, the main journal 6 of the crankshaft 3 falls into the arc area of the axial positioning bracket 17, and the main journal 6 is suspended, which can effectively prevent the axial positioning bracket 17 from scratching the crankshaft 3 during inspection. The bearing 18 is perpendicularly connected and fixed to the axial positioning bracket 17 by the pin 19. The centerline of the bearing 18 is aligned with the centerline of the bearing 18. The axis of crankshaft 3 is perpendicular. The outer side of bearing 2 18 protrudes from the side of axial positioning bracket 17 and contacts the positioning end face 7 of main journal 3 6 of crankshaft 3. The outer circle of bearing 2 18 is tangent to the positioning end face 7 of main journal 3 6 of crankshaft 3. During testing, after crankshaft 3 rotates, the positioning end face 7 of crankshaft 3 rolls along the outer circle of bearing 2 18. Since the center of bearing 2 18 is fixed, this structure can ensure the axial positioning of crankshaft 3 during rotation. At this time, rotating crankshaft 3 can ensure that crankshaft 3 does not move axially and will not affect the measurement of gear end face runout.
[0029] An axial clamping mechanism is installed on the right side of crankshaft 3. T-key 3 22 is placed in guide groove 2 of platform 1. Two bolts 14 connect and fix clamping bracket 21 to T-key 3 22. A circular hole is horizontally opened on clamping bracket 21 along the axis. Wear-resistant sleeves 24 are respectively inlaid on both sides of the circular hole. Clamping shaft 20 with a central groove 43 that matches pin 3 23 is installed on the inner ring of wear-resistant sleeve 24. Wear-resistant sleeve 24 and clamping shaft 20 slide fit. A circular hole for placing pin 3 23 is vertically opened above clamping bracket 21. The left end of clamping shaft 20 is a boss structure. Compression spring 1 25 is fixed between the inner side of the boss and wear-resistant sleeve 24. Bolt 28 connects pad 27 and thrust bearing. 26 is connected to the tightening shaft 20. The thrust bearing 26 is fixed in the circular countersunk hole in the center of the left end boss of the tightening shaft 20. The right end boss of the pad 27 is pressed against the inner hole of the thrust bearing 26. The inner hole of the pad 27 is clearance-fitted with the bolt 28. The pad 27 can rotate freely on its own under the action of the thrust bearing 26. The right end of the tightening shaft 20 is a handle structure, which is used by the operator to tighten and loosen the axial tightening mechanism. When loosening is required, the operator pulls the right end handle of the tightening shaft 20 to the right. The pin 3 23 falls and gets stuck in the central groove 43 of the tightening shaft 20. At this time, the compression spring 1 25 is in the compressed state. When tightening is required, the operator lifts the pin 3 23. The tightening shaft 20 moves to the left under the force of the compression spring 1 25 until the pad 27 fits against the end face of the small end journal 8, completing the axial tightening of the crankshaft 3 by the axial tightening mechanism.
[0030] The measuring base 29 of the measuring device has an L-shaped groove 44 inside its upper end. A threaded hole 42 is located on the upper part of the groove 44. A through hole 41 is located on the side of the measuring base 29 corresponding to the threaded hole 42. The probe of the dial indicator 30 is inserted into the through hole 41, and a bolt 31 is installed in the threaded hole 42. Tightening the bolt 31 fixes the dial indicator 30 to the measuring base 29. A threaded hole 40 is machined adjacent to the through hole 41. A compression spring 34 is inserted into the threaded hole 40 and extends into the groove 46 of the measuring rod crossbar 37. A set screw 38 is inserted into the threaded hole 40 to hold the compression spring 34 in place. At the corner of the groove 44... A vertical pin hole 39 is machined, and pin 33 passes through the pin hole 45 of the measuring rod and the pin hole 39 on the measuring base 29 to fix the measuring rod 32 on the measuring base 29. The center distance of the pin hole 39 from the center of the through hole 41 is L (that is, the center distance of the pin hole 39 from the center of the probe A of the dial indicator 30 is L). The center distance of the pin hole 45 of the measuring rod from the center of the probe 35 of the measuring rod is also L. This ensures that when the probe 35 of the measuring rod is displaced, the crossbar 37 of the measuring rod is displaced proportionally. The measuring rod 32 has a T-shaped structure, and the crossbar 37 of the measuring rod is perpendicular to the stop bar 36 of the measuring rod. The crossbar 37 of the measuring rod has a groove 46 that matches the compression spring 34. In the free state, under the combined force of the set screw 38 and the second compression spring 34, the measuring rod crossbar 37 is lifted. At this time, it does not press the dial indicator 30 probe. The measuring rod stop bar 36 rotates to the side of the groove of the measuring base 29 and is blocked. At this time, the measuring rod probe 35 is in the extended state. In the measuring state, the measuring base 29 is moved to the gear 10 or gear 9 of the object being measured. The measuring rod probe 35 is pressed onto the left end face of gear 10 or the right end face of gear 9. When the measuring rod probe 35 is pressed into a certain position, the measuring rod crossbar 37 simultaneously presses onto the dial indicator 30 probe, and the pressure on the gauge is completed.
[0031] During inspection, the crankshaft 3 is placed horizontally on the bearing 12 of the shaft support mechanism at both ends of the inspection table; the pin 23 of the axial clamping mechanism is loosened, and the pad 27 is in contact with the small end journal 8 of the crankshaft 3. Simultaneously, the crankshaft 3 moves to the left under the thrust of the pad 27 until the positioning end face 7 of the crankshaft 3 is in contact with the bearing 18 to complete the clamping and positioning; the measuring base 29 is moved to the measuring position of gear 9 or gear 10, and the measuring rod probe 35 is pressed against the end face of gear 9 or gear 10. Simultaneously, the measuring rod crossbar 37 is pressed against the probe of the dial indicator 30. After pressing the gauge, the crankshaft 3 is rotated, and the reading of the dial indicator 30 is observed. The fluctuation range of the dial indicator 30 reading can be identified to determine the end face runout of the gears at both ends of the crankshaft. After the test is completed, remove the measuring base 29, pull the right handle of the clamping shaft 20 to the right until pin 3 23 falls freely into the central groove 43 of the clamping shaft 20, and remove the crankshaft 3 with the axial clamping mechanism released. Due to the mobility of the measuring base 29, the end face runout of the gears at both ends of the crankshaft 3 at different positions and in different directions can be detected, thus having the advantage of high adaptability.
Claims
1. A gauge for inspecting the runout of the end faces of gears at both ends of a crankshaft, characterized in that: The fixture consists of a crankshaft support mechanism, an axial positioning mechanism, an axial clamping mechanism, and a measuring device. A guide groove (2) with an inverted T-shaped cross section is opened on the platform (1). The crankshaft support mechanism, the axial positioning mechanism, and the axial clamping mechanism are connected to the platform (1) through T-key 1 (15), T-key 2 (16), and T-key 3 (22), respectively. The bottom of the measuring base (29) of the measuring device is in contact with the platform (1) and can move freely on the platform (1).
2. The inspection tool for testing the runout of the gear end faces at both ends of a crankshaft according to claim 1, characterized in that: The keyway at the bottom of the roller bracket (11) of the crankshaft support mechanism and the keyway at the top of the guide groove (2) slide in fit with the key at the top end of the T-key one (15); the keyway at the bottom of the axial positioning bracket (17) of the axial positioning mechanism and the keyway at the top of the guide groove (2) slide in fit with the key at the top end of the T-key two (16); the keyway at the bottom of the clamping bracket (21) of the axial clamping mechanism and the keyway at the top of the guide groove (2) slide in fit with the key at the top end of the T-key three (22); the crankshaft support mechanism, the axial positioning mechanism, and the axial clamping mechanism are on a straight line and their center of symmetry is parallel to the axis of the crankshaft (3).
3. The inspection tool for testing the runout of the gear end faces at both ends of a crankshaft according to claim 1, characterized in that: The T-key 1 (15) of the crankshaft support mechanism is placed in the guide groove (2) of the platform (1). Two bolts 1 (14) connect and fix the roller bracket (11) to the T-key 1 (15). Two bearings 1 (12) are fixed to the roller bracket (11) by pins 1 (13). The roller bracket (11) and the two bearings 1 (12) together form a roller support. The two roller supports support the main journal 1 (4) and main journal 2 (5) of the crankshaft (3) respectively, providing horizontal support for the crankshaft (3). The crankshaft (3) can rotate freely on the roller support.
4. The inspection tool for testing the runout of the gear end faces at both ends of a crankshaft according to claim 1, characterized in that: The T-key 2 (16) of the axial positioning mechanism is placed in the guide groove (2) of the platform (1). Two bolts 1 (14) connect and fix the axial positioning bracket (17) and the T-key 2 (16). The inner arc diameter of the axial positioning bracket (17) is larger than the diameter of the main shaft journal 3 (6) of the crankshaft (3). The main shaft journal 3 (6) is placed on the axial positioning bracket (17) in a suspended state. The bearing 2 (18) is vertically connected and fixed to the axial positioning bracket (17) through the pin 2 (19). The center line of the bearing 2 (18) is perpendicular to the axis of the crankshaft (3). The outer side of the bearing 2 (18) protrudes from the side of the axial positioning bracket (17) and contacts the positioning end face (7) of the main shaft journal 3 (6) of the crankshaft (3). The outer circle of the bearing 2 (18) is tangent to the positioning end face (7) of the main shaft journal 3 (6) of the crankshaft (3).
5. The inspection tool for testing the runout of the gear end faces at both ends of a crankshaft according to claim 1, characterized in that: The axial clamping mechanism is installed on the right side of the crankshaft (3). The T-key three (22) is placed in the guide groove (2) of the platform (1). Two bolts one (14) connect and fix the clamping bracket (21) and the T-key three (22). A circular hole is opened horizontally along the axis on the clamping bracket (21). Wear-resistant sleeves (24) are respectively inlaid on both sides of the circular hole. The clamping shaft (20) with a central groove (43) that matches the pin three (23) is installed in the inner ring of the wear-resistant sleeve (24). The wear-resistant sleeve (24) and the clamping shaft (20) slide together. A vertical opening for placing the pin three (23) is opened above the clamping bracket (21). The left end of the top-tightening shaft (20) is a boss structure. The compression spring (25) is fixed between the inner side of the boss and the wear-resistant sleeve (24). The right end of the top-tightening shaft (20) is a handle structure. The bolt (28) connects the pad (27), the thrust bearing (26) and the top-tightening shaft (20) together. The thrust bearing (26) is fixed in the circular countersunk hole in the center of the left end boss of the top-tightening shaft (20). The right side boss of the pad (27) is pressed against the inner hole of the thrust bearing (26). The inner hole of the pad (27) is clearance-fitted with the bolt (28). The pad (27) can rotate freely on its own under the action of the thrust bearing (26).
6. The inspection tool for testing the runout of the gear end faces at both ends of a crankshaft according to claim 1, characterized in that: The measuring base (29) of the measuring device has an L-shaped groove (44) inside its upper end. A threaded hole (42) is opened on the upper part of the groove (44). A through hole (41) is opened on the side of the measuring base (29) corresponding to the threaded hole (42). The probe of the dial indicator (30) is placed into the through hole (41), and the bolt (31) is installed in the threaded hole (42). The bolt (31) is tightened to fix the dial indicator (30) on the measuring base (29). A threaded hole (40) is machined at the position adjacent to the through hole (41). The compression spring (34) is installed in the threaded hole (40) and extends into the groove (46) of the measuring rod crossbar (37). The set screw (38) is installed in the threaded hole (40). To hold the second spring (34) in place, a vertical pin hole (39) is machined at the corner of the first groove (44). The fourth pin (33) passes through the pin hole (45) of the measuring rod and the pin hole (39) on the measuring base (29) to fix the measuring rod (32) on the measuring base (29). The center distance of the pin hole (39) to the center distance of the through hole (41) is L, and the center distance of the pin hole (45) of the measuring rod to the center distance of the measuring rod probe (35) is L. When the side rod probe (35) is displaced, the side rod crossbar (37) is displaced proportionally. The measuring rod (32) is a T-shaped structure. The measuring rod crossbar (37) is perpendicular to the measuring rod stop bar (36). The measuring rod crossbar (37) has a second groove (46) that is compatible with the second spring (34).