Structural design of universal fixture for fire pump body parts for machining center

Abstract

The invention relates to structural design of a fire pump body part universal clamp for a machining center, which comprises a clamp bottom plate and a plurality of supporting mechanisms arranged on the surface of the clamp bottom plate, and the supporting mechanisms are used for bearing flange ends of fire pumps respectively. A pressing mechanism and a locking assembly capable of locking the pressing mechanism to prevent the pressing mechanism from rotating are rotatably arranged on the surface of each supporting mechanism, and the pressing mechanism can press the top of the flange end of the fire pump when in a locking state; a first limiting mechanism used for limiting axial movement of the fire pump is arranged on the side, close to the middle of the clamp bottom plate, of each supporting mechanism, and a second limiting mechanism is arranged on one side of each supporting mechanism. After the fire pump is limited through the clamp, the whole clamp cannot interfere with a tool of a machining center after locking the fire pump, and content machining of a motor mounting hole, an inlet and outlet flange face, a mounting face and a mounting hole in the fire pump can be completed at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of fire pump processing, in particular to a universal fixture structure design for fire pump body parts used in a processing center. Background Art

[0002] The core machining features of fire pump body parts primarily include motor mounting holes, inlet and outlet flange surfaces, assembly reference planes, and various functional mounting hole systems. Traditional machining processes generally employ a multi-device, sequential processing model, with a typical discrete manufacturing process: First, the main machining process of the motor mounting holes is completed on a lathe. This stage requires the use of a dedicated fixture to position the pump body, utilizing turning techniques to achieve high-precision dimensional control of the cylindrical surface within the mounting hole, while also completing axial finishing of the relevant end faces. The semi-finished product is then transferred to a machining center workstation, where multi-axis milling technology is used to perform three-dimensional shaping of the inlet and outlet flange surfaces, simultaneously completing plane milling and surface finishing of the pump body mounting surface.

[0003] The authorization announcement number is CN216179943U, which discloses a fixture for processing fire pump impellers. Combined with its instructions and drawings, its solution is installed on the fixture fixing seat through fixing bolts. The fixture fixing seat is fixedly installed on the fixture adjustment bracket, and the processing position can be adjusted according to different processing tools.

[0004] However, the solution still has the following defects: 1. It is impossible to effectively limit the position of fire pumps in all directions for items such as fire pumps; 2. How to ensure that the fire pump is clamped well so that the subsequent processes can process the fire pump in one go without interfering with the fixture is one of the issues that need to be considered; 3. How to coordinate the fixture itself to have a lower manufacturing cost while being able to clamp fire pumps of various specifications is also one of the issues that need to be considered; 4. How to ensure that the fixture that clamps the fire pump can be easily repaired if a single part is damaged is also one of the issues that need to be considered. Summary of the Invention

[0005] The present invention mainly addresses the problems existing in the design of fire pump fixtures and invents a universal fixture structure design for fire pump body parts for machining centers. After the fixture is used to limit the fire pump, the entire fixture will not interfere with the tool of the machining center after locking the fire pump, and can simultaneously complete the processing of the motor mounting hole, inlet and outlet flange surfaces, mounting surface, and mounting hole on the fire pump.

[0006] The object of the present invention is achieved through the following technical solutions: A universal fixture structure design for fire pump body parts for a machining center, including a fixture base plate, a plurality of supporting mechanisms arranged on the surface of the fixture base plate, the plurality of supporting mechanisms being used to respectively support the flange ends of the fire pumps, the surface of each of the supporting mechanisms being rotatable and being provided with a clamping mechanism and a locking assembly capable of locking the clamping mechanism from rotating, the clamping mechanism being able to clamp the top of the flange end of the fire pump when in a locked state, a first limiting mechanism being provided on one side of each of the supporting mechanisms close to the middle of the fixture base plate for limiting the axial movement of the fire pump, and a second limiting mechanism being provided on one side of at least one of the supporting mechanisms for limiting the axial rotation of the fire pump.

[0007] Preferably, flanges connected to the pipeline are provided on both sides of the fire pump, a mounting surface is provided in the middle of the fire pump, a plurality of mounting through holes are provided on the surface of the mounting surface and a motor mounting hole is provided in the middle of the mounting surface, a plurality of reinforcing ribs are also provided on the surface of the fire pump, and the second limiting mechanism can abut against the side of the reinforcing rib.

[0008] Preferably, the support mechanism includes a first support plate and a second support plate, each of the first support plates is connected to the surface of the fixture base plate, a second support plate is placed vertically on the surface of each of the first support plates, and a trapezoidal avoidance groove is provided on the surface of the second support plate, and the trapezoidal avoidance groove can be adapted to flanges of different diameters.

[0009] Preferably, the clamping mechanism includes a clamping support column, a clamping support plate and a clamping block, the clamping support column can be rotatably connected to the top side of the second support plate, the top of the clamping support column is provided with a clamping support plate, the middle part of the clamping support plate is provided with a clamping block that can move up and down, the end of the clamping support plate is provided with a locking groove, and the locking assembly can be connected to the inside of the locking groove.

[0010] Preferably, the middle part of the clamping support plate is threadedly connected to a first screw and slidably connected to a first guide rod, the ends of the first screw and the first guide rod are rotatably connected to the top of the clamping block, and the bottom surface of the clamping block is provided with an arc-shaped groove, which can clamp the top of the flange.

[0011] Preferably, the locking assembly includes a locking support block and a second screw, the bottom of the locking support block can be rotatably connected to the other side of the top of the second support plate, the top of the locking support block is threadedly connected to the second screw, and the top of the second screw is provided with a locking pressure plate, and after the locking groove is stuck on the surface of the second screw, the second screw rotates downward to enable the locking pressure plate to lock the pressure support plate.

[0012] Preferably, each of the first limiting mechanisms includes a first limiting support plate and a first limiting screw, the first limiting support plate is connected to the side wall of the second support plate, the middle part of the first limiting support plate is threadedly connected with the first limiting screw, the axis of the first limiting screw is parallel to the bottom plate of the clamp, and the end of the first limiting screw can press the side of the flange.

[0013] Preferably, the second limiting mechanism includes a second limiting support plate and a second limiting screw, the surface of the second support plate is provided with a plurality of locking through holes, the surface of the second limiting support plate is provided with a first waist-shaped through hole, the external bolt passes through the first waist-shaped through hole and is connected to the inside of the locking through hole, the end of the second limiting support plate is provided with a second limiting screw, the axis of the second limiting screw is perpendicular to the bottom plate of the clamp, and the surface of the second limiting screw can rest against the side of the reinforcing rib.

[0014] The second limiting screw is used to abut against the side surface of the reinforcing rib to limit the rotation of the entire fire pump.

[0015] Preferably, a triangular support plate is provided between the surface of the first support plate and the side wall of the second support plate, and a second waist-shaped through hole is provided on the side surface of the locking support block.

[0016] The provision of the second waist-shaped through hole makes it easy to carry the entire clamp after the clamp has completed clamping the fire pump 3, and can effectively provide a support point and a grasping point.

[0017] Preferably, a positioning pin is further provided on the surface of the first support plate, and the positioning pin can limit the position of the first support plate compared to the surface of the fixture bottom plate.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. After the fire pump is limited by the fixture, the entire fixture will not interfere with the tool after locking the fire pump, so the motor mounting hole, inlet and outlet flange surfaces, mounting surface, and mounting hole can be processed simultaneously. Compared with the traditional pump parts processing process, the lathe process processes the motor mounting hole, and the machining center processes the inlet and outlet flange surfaces, mounting surface, and various mounting holes. This solution only uses one process in the machining center, which greatly improves the efficiency of the production process. 2. The outer contours of the flanges on both sides of the fire pump are placed inside the trapezoidal avoidance groove. This unique geometric configuration of the trapezoidal avoidance groove of the second support plate breaks through the size limitations of traditional tooling. By matching the curvature of the contact surface, it achieves adaptive positioning of flange outer diameters in different intervals. Compared with traditional fixed fixtures, it has improved compatibility and can meet the processing requirements of pump bodies with different flange outer diameters, reducing the investment cost of processing fixtures and improving development efficiency. 3. First, the first limiting screw is used to press against the side of the flange to limit the axial displacement of the fire pump. Then, the compression block and the trapezoidal avoidance groove are used to limit the up and down movement of the fire pump. Finally, the second limiting screw is used to press against the side of the flange to limit the rotation of the fire pump. The entire clamping process is simple and can minimize the labor intensity of workers during the clamping operation. 4. A positioning pin is designed between the first support plate and the second support plate for positioning. When the tooling is installed on the fixture base, the workload of the calibration process when switching tooling can be reduced; 5. In the fixture design of this solution, the fixture base plate, support mechanism, clamping mechanism, first limit mechanism and second limit mechanism are all detachably connected by bolts, so that when a single part is damaged, it can be replaced as needed, reducing the company's production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a three-dimensional diagram of the clamp of the present invention in a loosened state; Figure 2 This is a three-dimensional diagram of the clamp of the present invention clamping the fire pump; Figure 3 is a three-dimensional diagram of the clamp of the present invention in a loosened state; Figure 4 For the present invention Figure 3 A local enlarged view of area A; Figure 5 It is a three-dimensional diagram of the fire pump of the present invention.

[0020] Markings in the figure: 1. Clamp base plate; 2. Support mechanism; 21. First support plate; 22. Second support plate; 23. Trapezoidal avoidance groove; 24. Triangular support plate; 221. Locking hole; 3. Fire pump; 31. Flange; 32. Mounting surface; 33. Mounting hole; 34. Motor mounting hole; 35. Reinforcement rib; 4. Clamping mechanism; 41. Clamping support column; 42. Clamping support plate; 43. Clamping block; 44. A screw rod; 45, a first guide rod; 421, a locking groove; 431, an arc-shaped groove; 5, a locking assembly; 51, a locking support block; 52, a second screw rod; 511, a second waist-shaped through hole; 521, a locking pressure plate; 6, a first limiting mechanism; 61, a first limiting support plate; 62, a first limiting screw rod; 7, a second limiting mechanism; 71, a second limiting support plate; 72, a second limiting screw rod; 711, a first waist-shaped through hole. DETAILED DESCRIPTION

[0021] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings: like Figure 1 and Figure 2As shown, a universal fixture structure design for fire pump parts for machining centers includes a fixture base plate 1 and several support mechanisms 2 arranged on the surface of the fixture base plate 1. The support mechanisms 2 include a first support plate 21 and a second support plate 22. Each first support plate 21 is connected to the surface of the fixture base plate 1. A second support plate 22 is placed perpendicular to the surface of each first support plate 21. The surface of the second support plate 22 is provided with a trapezoidal avoidance groove 23. The trapezoidal avoidance groove 23 can adapt to flanges 31 of different diameters. A triangular support plate 24 is provided between the surface of the first support plate 21 and the sidewall of the second support plate 22.

[0022] Please refer to Figure 5 Both sides of the fire pump 3 are provided with flanges 31 connected to the pipeline. The middle part of the fire pump 3 is provided with a mounting surface 32. The surface of the mounting surface 32 is provided with a plurality of mounting through holes 33 and the middle part of the mounting surface 32 is provided with a motor mounting hole 34. The surface of the fire pump 3 is also provided with a plurality of reinforcing ribs 35. The fixture base plate 1 is rectangular in shape, with several threaded holes on its surface, allowing it to be removably mounted on the first support plate 21. Similarly, a second support plate 22 is removably connected to the surface of the first support plate 21 via bolts. To increase the rigidity of the connection between the first and second support plates 21, a triangular support plate 24 is installed at the connection point. The surface of the first support plate 21 is also equipped with a positioning pin 211, which can limit the position of the first support plate 21 relative to the surface of the fixture base plate 1.

[0023] In this embodiment, several support mechanisms 2 are used to respectively support the flange ends of the fire pump 3. During product placement, the outer contours of the flanges 31 on both sides of the fire pump 3 can be placed within the trapezoidal avoidance groove 23. This unique geometric configuration of the trapezoidal avoidance groove 23 of the second support plate 22 overcomes the dimensional limitations of traditional tooling. By matching the curvature of the contact surface, adaptive positioning of flange outer diameters in different ranges is achieved. Compared with traditional fixed fixtures, this improved compatibility can meet the processing requirements of pump bodies with different flange outer diameters, reduce the investment cost of processing fixtures, and improve development efficiency.

[0024] Please continue to refer to Figure 2 and Figure 3 The surface of each supporting mechanism 2 is rotatably provided with a clamping mechanism 4 and a locking assembly 5 that can lock the clamping mechanism 4 and prevent it from rotating. When the clamping mechanism 4 is in a locked state, it can clamp the top of the flange end of the fire pump 3.

[0025] Specifically, the clamping mechanism 4 includes a clamping support column 41, a clamping support plate 42, and a clamping block 43. The clamping support column 41 is rotatably connected to one side of the top of the second support plate 22. The top of the clamping support column 41 is provided with a clamping support plate 42. The middle of the clamping support plate 42 is provided with a clamping block 43 that can move up and down. The end of the clamping support plate 42 is provided with a locking groove 421, and the locking assembly 5 can be connected to the inside of the locking groove 421. The middle of the clamping support plate 42 is threadedly connected to a first screw 44 and slidably connected to a first guide rod 45. The ends of the first screw 44 and the first guide rod 45 are both rotatably connected to the top of the clamping block 43. The bottom surface of the clamping block 43 is provided with an arc-shaped groove 431, and the arc-shaped groove 431 can clamp the top of the flange 31.

[0026] When it is necessary to tighten the tops of the flanges 31 on both sides of the fire pump 3, the tightening support column 41 is rotated, thereby simultaneously driving the tightening support plate 42 to change position until the tightening block 43 is located directly above the trapezoidal avoidance groove 23. At this time, the locking assembly 5 is first used to lock the tightening support plate 42, so that the entire tightening mechanism 4 is in a fixed state.

[0027] Next, the first screw 44 is rotated downward relative to the surface of the compression support plate 42. Since the end of the first screw 44 is hingedly connected to the interior of the compression block 43, the rotation of the first screw 44 does not simultaneously drive the compression block 43. Instead, the first screw 44 hinges and rotates within the compression block 43, continuously pushing the compression block 43 downward to press the top of the flange 31. After compression, the arcuate groove 431 firmly presses the top of the flange 31. Similarly, the arcuate groove 431 can adapt to the outer contour of the compression flange 31 of different diameters.

[0028] In this embodiment, the locking assembly 5 includes a locking support block 51 and a second screw 52. The bottom of the locking support block 51 is rotatably connected to the other side of the top of the second support plate 22. The top of the locking support block 51 is threadedly connected to the second screw 52. A locking pressure plate 521 is provided on the top of the second screw 52. After the locking groove 421 is engaged with the surface of the second screw 52, the second screw 52 rotates downward, allowing the locking pressure plate 521 to lock and compress the support plate 42.

[0029] When the pressing block 43 is located directly above the trapezoidal avoidance groove 23, the locking support block 51 is moved upward, so that the locking groove 421 at the end of the pressing support plate 42 is exactly engaged with the surface of the second screw 52. The second screw 52 is then rotated, so that the locking pressure plate 521 can press against the surface of the pressing support plate 42, thus locking the entire pressing mechanism 4.

[0030] The side of the locking support block 51 is provided with a second waist-shaped through hole 511. The second waist-shaped through hole 511 makes it easy to carry the entire clamp after the clamp completes the clamping of the fire pump 3, and can effectively provide a support point and a gripping point for easy transportation.

[0031] After the locking pressure plate 521 locks and presses the support plate 42, the arc-shaped groove 431 of the pressing block 43 firmly presses the top of the flange 31, thereby limiting the entire fire pump 3 from moving up and down along the Z-axis direction.

[0032] Please continue to refer to Figure 3 and Figure 4 Each of the support mechanisms 2 is provided with a first limiting mechanism 6 on one side close to the middle of the fixture base plate 1 for limiting the axial movement of the fire pump 3, and at least one side of the support mechanism 2 is provided with a second limiting mechanism 7 on one side for limiting the axial rotation of the fire pump 3, and the second limiting mechanism 7 can abut against the side of the reinforcing rib 35.

[0033] Specifically, each of the first limiting mechanisms 6 includes a first limiting support plate 61 and a first limiting screw 62. The first limiting support plate 61 is connected to the side wall of the second support plate 22. The middle part of the first limiting support plate 61 is threadedly connected with the first limiting screw 62. The axis of the first limiting screw 62 is parallel to the clamp base plate 1, and the end of the first limiting screw 62 can press the side of the flange 31.

[0034] Before the clamping block 43 presses the flange 31 of the fire pump 3, the flange 31 is placed inside the trapezoidal avoidance groove 23. Then the first limiting screw 62 is rotated so that the end of the first limiting screw 62 can continuously move toward the inside of the trapezoidal avoidance groove 23.

[0035] When both left and right first limiting screws 62 are firmly against the sides of the flange 31, the fire pump 3 is unable to move axially. The compression block 43 then compresses the flange 31 of the fire pump 3. This effectively limits the displacement of the fire pump 3 along the X, Y, and Z axes. However, the fire pump 3 still has the problem of rotating along the X axis.

[0036] In order to solve this problem, in this embodiment, the second limiting mechanism 7 includes a second limiting support plate 71 and a second limiting screw 72. The surface of the second support plate 22 is provided with a plurality of locking through holes 221. The surface of the second limiting support plate 71 is provided with a first waist-shaped through hole 711. The external bolt passes through the first waist-shaped through hole 711 and is connected to the inside of the locking through hole 221. The end of the second limiting support plate 71 is provided with a second limiting screw 72. The axis of the second limiting screw 72 is perpendicular to the clamp base plate 1.

[0037] With this arrangement, after the first limiting screw 62 limits the axial displacement of the fire pump 3, the position of the second limiting support plate 71 relative to the first support plate 21 is adjusted until the surface of the second limiting screw 72 can abut against the side of the reinforcing rib 35. An external bolt is passed through the first waist-shaped through hole 711 and connected to the interior of the locking through hole 221, so that the second limiting support plate 71 is firmly fixed to the surface of the first support plate 21.

[0038] After the axial displacement and rotation of the fire pump 3 in the X-axis direction are limited, the flange 31 of the fire pump 3 is compressed by the compression block 43. Thus, the displacement limitation of the fire pump 3 in the X-axis, Y-axis and Z-axis is completed.

[0039] Working principle and usage of the present invention: like Figure 3 As shown, when the clamping support plate 42 and the second screw 52 are not locked, the clamp is in a loose state. At this time, the outer contour of the inlet and outlet flanges 31 of the fire pump 3 is placed on the second support plate 22; then the clamping support plate 42 is rotated to lock it with the second screw 52; the first limiting screw 62 is rotated so that the end of the first limiting screw 62 can continuously move toward the inside of the trapezoidal avoidance groove 23 until the first limiting screws 62 on both sides firmly abut the side of the flange 31, thereby limiting the product's X-axis movement and rotational freedom. Next, the first screw 44 is rotated downward relative to the surface of the pressing support plate 42. Since the end of the first screw 44 is hingedly connected to the interior of the pressing block 43, the first screw 44 does not simultaneously rotate the pressing block 43 during its rotation. Instead, the first screw 44 hinges and rotates within the pressing block 43, continuously pushing the pressing block 43 downward to press the top of the flange 31. After compression, the arcuate groove 431 firmly presses the top of the flange 31, securing the product to the fixture and limiting the product's freedom of movement in the Z-axis and rotation in the Y-axis, thus locking and securing the product.

[0040] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A universal fixture structure design for fire pump parts for a machining center, comprising a fixture base plate (1), and a plurality of support mechanisms (2) arranged on the surface of the fixture base plate (1), characterized in that: A plurality of support mechanisms (2) are used to respectively support the flange ends of the fire pumps (3); a surface of each of the support mechanisms (2) is provided with a rotatable pressing mechanism (4) and a locking assembly (5) capable of locking the pressing mechanism (4) from rotating; the pressing mechanism (4) is capable of pressing the top of the flange end of the fire pump (3) when in a locked state; a first limiting mechanism (6) for limiting the axial movement of the fire pump (3) is provided on one side of each of the support mechanisms (2) close to the middle of the fixture base plate (1); and a second limiting mechanism (7) for limiting the axial rotation of the fire pump (3) is provided on one side of at least one of the support mechanisms (2).

2. The universal fixture structure design for fire pump parts for machining centers according to claim 1 is characterized in that: Both sides of the fire pump (3) are provided with flanges (31) connected to the pipeline. A mounting surface (32) is provided in the middle of the fire pump (3). The surface of the mounting surface (32) is provided with a plurality of mounting through holes (33), and a motor mounting hole (34) is provided in the middle of the mounting surface (32). The surface of the fire pump (3) is also provided with a plurality of reinforcing ribs (35), and the second limiting mechanism (7) can abut against the side of the reinforcing rib (35).

3. The universal fixture structure design for fire pump parts for machining centers according to claim 2 is characterized in that: The support mechanism (2) comprises a first support plate (21) and a second support plate (22), each of the first support plates (21) being connected to the surface of the fixture base plate (1), a second support plate (22) being vertically placed on the surface of each of the first support plates (21), and a trapezoidal avoidance groove (23) being provided on the surface of the second support plate (22), and the trapezoidal avoidance groove (23) being adaptable to flanges (31) of different diameters.

4. The universal fixture structure design for fire pump parts for machining centers according to claim 3 is characterized in that: The clamping mechanism (4) includes a clamping support column (41), a clamping support plate (42) and a clamping block (43), wherein the clamping support column (41) is rotatably connected to one side of the top of the second support plate (22), a clamping support plate (42) is provided on the top of the clamping support column (41), a clamping block (43) is provided in the middle of the clamping support plate (42) and can move up and down, a locking groove (421) is provided at the end of the clamping support plate (42), and the locking assembly (5) can be connected to the inside of the locking groove (421).

5. The universal fixture structure design for fire pump parts for machining centers according to claim 4 is characterized in that: The middle part of the clamping support plate (42) is threadedly connected to a first screw rod (44) and slidably connected to a first guide rod (45), and the ends of the first screw rod (44) and the first guide rod (45) are rotatably connected to the top of the clamping block (43), and the bottom surface of the clamping block (43) is provided with an arc-shaped groove (431), and the arc-shaped groove (431) can clamp the top of the flange (31).

6. The universal fixture structure design for fire pump parts for machining centers according to claim 4 is characterized in that: The locking assembly (5) includes a locking support block (51) and a second screw rod (52), the bottom of the locking support block (51) can be rotatably connected to the other side of the top of the second support plate (22), the top of the locking support block (51) is threadedly connected to the second screw rod (52), and the top of the second screw rod (52) is provided with a locking pressure plate (521), and after the locking groove (421) is stuck on the surface of the second screw rod (52), the second screw rod (52) rotates downward to enable the locking pressure plate (521) to lock and compress the support plate (42).

7. The universal fixture structure design for fire pump parts for machining centers according to claim 6 is characterized in that: Each of the first limiting mechanisms (6) includes a first limiting support plate (61) and a first limiting screw (62), wherein the first limiting support plate (61) is connected to the side wall of the second support plate (22), the middle portion of the first limiting support plate (61) is threadedly connected to the first limiting screw (62), the axis of the first limiting screw (62) is parallel to the clamp base plate (1), and the end of the first limiting screw (62) can press the side of the flange (31).

8. The universal fixture structure design for fire pump parts for machining centers according to claim 7 is characterized in that: The second limiting mechanism (7) includes a second limiting support plate (71) and a second limiting screw (72), the surface of the second supporting plate (22) is provided with a plurality of locking through holes (221), the surface of the second limiting support plate (71) is provided with a first waist-shaped through hole (711), the external bolt passes through the first waist-shaped through hole (711) and is connected to the inside of the locking through hole (221), the end of the second limiting support plate (71) is provided with a second limiting screw (72), the axis of the second limiting screw (72) is perpendicular to the clamp bottom plate (1), and the surface of the second limiting screw (72) can abut against the side of the reinforcing rib (35).

9. The universal fixture structure design for fire pump parts for machining centers according to claim 6 is characterized in that: A triangular support plate (24) is provided between the surface of the first support plate (21) and the side wall of the second support plate (22), and a second waist-shaped through hole (511) is provided on the side surface of the locking support block (51).

10. The universal fixture structure design for fire pump parts for machining centers according to claim 9 is characterized in that: The surface of the first support plate (21) is further provided with a positioning pin (211), and the positioning pin (211) is capable of limiting the position of the first support plate (21) relative to the surface of the fixture bottom plate (1).

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