A device for detecting the protrusion of an angular contact bearing

Abstract

This invention discloses a device for detecting the protrusion of angular contact bearings, comprising a working platform, an upper driving mechanism above the working platform, and a lower driving mechanism below the working platform. The upper driving mechanism is connected to a detection mechanism, which is positioned above the working platform and directly above the lower driving mechanism. The advantages of this invention are: the cooperation of the upper driving mechanism and the detection mechanism enables the detection of the protrusion of face-to-face (DF) mounted angular contact bearings; the cooperation of the lower driving mechanism and the detection mechanism enables the detection of the protrusion of back-to-back (DB) mounted angular contact bearings; the arrangement of a second motor and a rotating block, and a third motor and a reducer, drives the inner ring of the angular contact bearing to rotate, reducing the wobble of the inner ring relative to the outer ring and improving the detection accuracy of the protrusion; this protrusion detection device can detect the protrusion of angular contact bearings with inner rings of different sizes and specifications, and is highly practical.

Description

Technical Field

[0001] This invention relates to the field of bearing testing technology, specifically to a device for detecting the protrusion of angular contact bearings. Background Technology

[0002] Angular contact bearings, also known as angular contact ball bearings, can simultaneously withstand radial and axial loads and operate at high speeds. The overhang of the angular contact ball, also called the grinding allowance, refers to the distance by which the inner ring end face protrudes beyond the outer ring end face at the same end face of the bearing after a preload is applied. A "+" value indicates a convex inner ring, while a "☐" value indicates a concave inner ring. This overhang can affect various aspects of the bearing's performance.

[0003] Angular contact ball bearings are widely used in high-precision, high-speed applications, making their installation crucial. The design of the bearing's protrusion during manufacturing can significantly reduce installation difficulties, allowing even customers unfamiliar with bearing installation to fully utilize its capabilities and ensure optimal performance. Two common installation methods for angular contact bearings are face-to-face (DF) mounting and back-to-back (DB) mounting. In face-to-face (DF) mounting, the load center is within the bearing's centerline. This method is simple in structure and easy to install and disassemble. However, when the shaft expands due to heat, the bearing clearance decreases, potentially causing the bearing to seize. Therefore, careful adjustment of the bearing clearance is essential. In back-to-back (DB) mounting, the load center is outside the bearing's centerline, resulting in a larger force application point span and greater rigidity at the cantilever end. When the shaft expands due to heat, the bearing clearance increases, preventing seizure. Regardless of the mounting method (DF or DB), protrusion testing is necessary to ensure the angular contact bearing's performance. Existing angular contact bearing protrusion detection devices can generally only be used to detect angular contact bearings with a single mounting method, and can only be used to detect angular contact bearings with an inner ring of one specification and size, which makes them relatively impractical. Summary of the Invention

[0004] The purpose of this invention is to provide a device for detecting the protrusion of angular contact bearings, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an angular contact bearing protrusion detection device, comprising a working platform, an upper driving mechanism above the working platform, a lower driving mechanism below the working platform, a detection mechanism connected to the upper driving mechanism, and the detection mechanism being disposed above the working platform and directly above the lower driving mechanism.

[0006] The detection mechanism includes a second connecting plate, which is horizontally mounted on the upper drive mechanism. A counterweight support is fixed above the second connecting plate, and a counterweight is provided above the counterweight support. The counterweight has a circular cross-section, and two support rods with its center as the center of symmetry are provided on the side of the counterweight. The two support rods are vertically fixed on the counterweight support, and a connecting rod is connected to the ends of the two support rods. A vertically arranged linear displacement sensor is installed in the middle of the connecting rod, and the lower end test head of the linear displacement sensor abuts against the upper center of the counterweight. A second top connecting seat is provided at the lower end of the conical block.

[0007] Further preferably, the upper end of the counterweight is cylindrical, and the lower end is provided with a conical block to facilitate the rotation of the counterweight; the diameter of the conical block gradually decreases from top to bottom to facilitate the installation of the counterweight on the counterweight support.

[0008] Further preferably, the counterweight support is a stepped cylindrical structure, with the diameter of its upper end being larger than that of its lower end, which facilitates the installation and fixing of the counterweight support on the second connecting plate; the counterweight support is provided with a tapered hole that matches the tapered block for the installation of the counterweight.

[0009] In a further preferred embodiment, the second mandrel connecting seat is provided with a second mandrel, which can be inserted into the inner ring of the angular contact bearing to achieve positioning of the angular contact bearing.

[0010] Further preferably, the upper drive mechanism includes a first mounting plate, which is vertically fixed to the work platform. A vertically arranged first motor is mounted on the upper end of the first mounting plate, and a vertically arranged ball screw is connected to the lower output shaft of the first motor. The first motor can drive the screw of the ball screw to rotate, thereby causing the nut of the ball screw to move up and down linearly, thus driving the detection mechanism to move up and down. The nut of the ball screw is connected to a first connecting plate, and the first connecting plate is connected to a horizontally arranged second mounting plate for mounting the detection mechanism. A second motor is mounted on the upper part of the second mounting plate near the first connecting plate. The second motor is vertically arranged, and a rotating block is connected to its lower output shaft. The second motor can drive the rotating block to rotate, thereby driving the counterweight to rotate.

[0011] In a further preferred embodiment, the end of the second mounting plate away from the first connecting plate is provided with a circular hole for cooperating with the counterweight, which facilitates the lifting and lowering of the counterweight and can guide the lifting and lowering of the counterweight; the second connecting plate is fixed below the second mounting plate.

[0012] Further preferably, two linear guide rails are connected between the first connecting plate and the first mounting plate to ensure that the lifting and lowering of the first connecting plate is stable and smooth.

[0013] Further preferably, the rotating block has an waist-shaped structure and its outer side is covered with a flexible material to ensure that the rotating block pushes the counterweight block flexibly and prevents the rotating block from generating a large impact force on the counterweight block, which would cause the rotating block or the counterweight block to be damaged.

[0014] Further preferably, the lower drive mechanism includes a base, with a vertically arranged cylinder above the base. The upper piston rod end of the cylinder is connected to a horizontally arranged lifting plate. The cylinder can drive the lifting plate to rise and fall, thereby raising and lowering the angular contact bearing to be tested. A vertically arranged third motor is fixed below the lifting plate and is located on the side of the cylinder. The upper output shaft end of the third motor is connected to a reducer installed above the lifting plate. A first mandrel connecting seat is connected above the reducer, and a first mandrel is installed on the upper end of the first mandrel connecting seat. The third motor and the reducer can drive the first mandrel connecting seat and the first mandrel to rotate. The first mandrel is inserted into the inner ring of the angular contact bearing. The rotation of the first mandrel drives the inner ring of the angular contact bearing to rotate, which can reduce the runout amplitude between the inner and outer rings of the angular contact bearing and improve the detection accuracy.

[0015] Further preferably, four guide members are connected between the lifting plate and the base to ensure that the lifting plate rises and falls smoothly and steadily; the guide members are composed of linear bearings and guide rods, and the four guide members are symmetrically arranged on both sides of the cylinder. A limiting plate is connected to the top of the two guide members located on the same side of the cylinder to limit the lifting height of the lifting plate.

[0016] Beneficial effects: The angular contact bearing protrusion detection device of the present invention, through the cooperation of the upper drive mechanism and the detection mechanism, realizes the protrusion detection of face-to-face DF-mounted angular contact bearings; through the cooperation of the lower drive mechanism and the detection mechanism, it realizes the protrusion detection of back-to-back DB-mounted angular contact bearings; through the setting of the second motor and the rotating block, and the setting of the third motor and the reducer, it realizes the rotation of the inner ring of the angular contact bearing, which can reduce the runout of the inner ring of the angular contact bearing relative to the outer ring, and improve the detection accuracy of the angular contact bearing protrusion; through the setting of the first mandrel connecting seat and the first mandrel, and the second mandrel connecting seat and the second mandrel, it realizes the detection of the protrusion of angular contact bearings with inner rings of different sizes and specifications, with a wide detection range and high practicality. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the isometric structure of the angular contact bearing protrusion detection device disclosed in the embodiment of the present invention;

[0018] Figure 2 This is a schematic front view of the angular contact bearing protrusion detection device disclosed in an embodiment of the present invention.

[0019] Figure 3This is an exploded structural diagram of the detection mechanism disclosed in the embodiments of the present invention;

[0020] Figure 4 This is a schematic diagram of the right-side structure of the detection mechanism disclosed in the embodiment of the present invention;

[0021] Figure 5 This is an isometric structural diagram of the upper drive mechanism disclosed in the embodiment of the present invention;

[0022] Figure 6 This is an isometric structural diagram of the lower drive mechanism disclosed in an embodiment of the present invention.

[0023] Reference numerals: 1-Working platform, 2-Upper drive mechanism, 21-First mounting plate, 22-First motor, 23-Ball screw, 24-First connecting plate, 25-Second mounting plate, 251-Round hole, 26-Second motor, 27-Rotating block, 28-Linear guide rail, 3-Lower drive mechanism, 31-Base, 32-Cylinder, 33-Lifting plate, 34-Third motor, 35-Reducer, 36-First top head connecting seat, 37-First top head, 38-Guide component, 39-Limiting plate, 4-Detection mechanism, 41-Second connecting plate, 42-Counterweight support seat, 421-Conical hole, 43-Counterweight, 431-Conical block, 44-Support rod, 45-Connecting rod, 46-Linear displacement sensor, 47-Second top head connecting seat, 48-Second top head. Detailed Implementation

[0024] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0025] like Figure 1-6 As shown, a protrusion detection device for angular contact bearings is used to detect the protrusion of face-to-face (DF) mounted angular contact bearings and back-to-back (DB) mounted angular contact bearings. The device includes a working platform 1, an upper drive mechanism 2 above the working platform 1, and a lower drive mechanism 3 below the working platform 1. The upper drive mechanism 2 is connected to a detection mechanism 4, which is positioned above the working platform 1 and directly above the lower drive mechanism 3. The cooperation between the upper drive mechanism 2 and the detection mechanism 4 is used to detect the protrusion of face-to-face (DF) mounted angular contact bearings, while the cooperation between the lower drive mechanism 3 and the detection mechanism 4 is used to detect the protrusion of back-to-back (DB) mounted angular contact bearings.

[0026] The detection mechanism 4 includes a second connecting plate 41, which is horizontally mounted on the upper drive mechanism 2. A counterweight support base 42 is fixed above the second connecting plate 41, and a counterweight 43 is mounted above the counterweight support base 42. The counterweight 43 is supported and mounted by the counterweight support base 42. The counterweight 43 has a circular cross-section, and two support rods 44 with their center as the center of symmetry are provided on the side of the counterweight 43. The two support rods 44 are vertically fixed on the counterweight support base 42, and a connecting rod 45 is connected to the end of the two support rods 44. A vertically arranged linear displacement sensor 46 is installed in the middle of the connecting rod 45. The lower end test head of the linear displacement sensor 46 abuts against the upper center of the counterweight 43. A second top connecting seat 47 is provided at the lower end of the conical block 431. The support rod 44 is installed via the counterweight support seat 42, which also serves to abut against the outer ring of the angular contact bearing, thereby supporting and installing the connecting rod 45. The linear displacement sensor 46 is installed via the connecting rod 45. The second top connecting seat 47 is used to press against the inner ring of the angular contact bearing. The counterweight 43 applies pressure to the second top connecting seat 47, thereby applying a specified axial force to the upper end face of the inner ring of the angular contact bearing, i.e., applying a measuring load to the angular contact bearing, causing the inner ring of the angular contact bearing to move vertically, which in turn moves the counterweight in the vertical direction. At the same time, the counterweight support seat 42 abuts against the outer ring of the angular contact bearing to prevent the outer ring of the angular contact bearing from moving vertically. The linear displacement sensor 46 detects the displacement of the counterweight 43, thereby detecting the relative height difference between the inner and outer rings of the angular contact bearing, and thus detecting the protrusion of the angular contact bearing.

[0027] In this application, the upper end of the counterweight 43 is cylindrical, and the lower end is provided with a conical block 431. The diameter of the conical block 431 gradually decreases from top to bottom, which facilitates the rotation of the counterweight 43. By rotating the counterweight 43, the runout of the inner ring of the angular contact bearing is controlled, ensuring that the runout of the inner ring of the angular contact bearing relative to the outer ring is small and stable, improving the detection accuracy of the protrusion of the angular contact bearing, and reducing the measurement error caused by runout.

[0028] In this application, the counterweight support base 42 is a stepped cylindrical structure, with the diameter of its upper end being larger than that of its lower end. It is secured to the second connecting plate 41 by means of the stepped structure, which facilitates the installation and fixation of the counterweight support base 42 on the second connecting plate 41. The counterweight support base 42 is provided with a conical hole 421 for the installation and placement of the conical block 431, ensuring that the counterweight support base 42 provides uniform support for the counterweight block 43, and at the same time facilitating the rotation of the counterweight block 43.

[0029] In this application, the second mandrel connecting seat 47 is provided with a second mandrel 48, which facilitates the insertion of the second mandrel 48 into the angular contact bearing for positioning and fixing the angular contact bearing. This also facilitates the detection of the protrusion of the angular contact bearing when it is mounted face-to-face with the drive mechanism 2. Furthermore, the second mandrel connecting seat 47 allows for the installation of second mandrels 48 of different specifications, facilitating the detection of the protrusion of angular contact bearings with inner rings of different sizes.

[0030] In this application, the upper drive mechanism 2 includes a first mounting plate 21, which is vertically fixed on the work platform 1. A vertically arranged first motor 22 is mounted on the upper end of the first mounting plate 21. A vertically arranged ball screw 23 is connected to the lower output shaft end of the first motor 22. The first motor 22 can drive the screw of the ball screw 23 to rotate, and the rotation of the screw is converted into the linear motion of the nut through the nut of the ball screw 23. A first connecting plate 24 is connected to the nut of the ball screw 23. A horizontally arranged second mounting plate 25 is connected to the first connecting plate 24. A second motor 26 is mounted above the end of the second mounting plate 25 near the end of the first connecting plate 24. The second motor 26 is vertically arranged and a rotating block 27 is connected to the lower output shaft end of its motor. The first motor 22 drives the screw of the ball screw 23 to rotate, causing the nut of the ball screw 23 to move the first connecting plate 24 up and down, which in turn drives the second mounting plate 25 to move up and down, thus driving the detection mechanism 4 to move up and down. This causes the counterweight 43 to move downward, applying a measuring load to the inner ring of the angular contact bearing, thereby detecting the protrusion of the angular contact bearing. The second motor 26 drives the rotating block 27 to rotate, which in turn drives the counterweight 43 to rotate, thereby controlling the runout of the inner ring of the angular contact bearing relative to the outer ring. This ensures that the runout of the inner and outer rings of the angular contact bearing is small and stable, improving the accuracy of the protrusion detection, reducing measurement errors caused by runout, and achieving accurate detection of the protrusion of the DF-mounted angular contact bearings.

[0031] In this application, the end of the second mounting plate 25 away from the first connecting plate 24 is provided with a circular hole 251. The second connecting plate 41 is fixed below the second mounting plate 25. The circular hole 251 guides the up and down movement of the counterweight 43, ensuring the stability of the counterweight 43 and ensuring that the counterweight 43 can move up and down.

[0032] In this application, two linear guide rails 28 are connected between the first connecting plate 24 and the first mounting plate 21 to ensure that the second mounting plate 25 can be raised and lowered smoothly and steadily.

[0033] In this application, the rotating block 27 has an waist-shaped structure and its outer side is covered with a flexible material to ensure that the rotating block 27 can flexibly push the counterweight 43, drive the counterweight 43 to rotate, and prevent the rotating block 27 from generating a large impact force on the counterweight 43, which would cause the rotating block 27 or the counterweight 43 to be damaged.

[0034] In this application, the lower drive mechanism 3 includes a base 31, a vertically arranged cylinder 32 is provided above the base 31, a horizontally arranged lifting plate 33 is connected to the upper piston rod end of the cylinder 32, a vertically arranged third motor 34 is fixed below the lifting plate 33, the third motor 34 is located on the side of the cylinder 32, a reducer 35 is connected to the upper output shaft end of the third motor 34 and installed above the lifting plate 33, a first top head connecting seat 36 is connected above the reducer 35, and a first top head 37 is installed at the upper end of the first top head connecting seat 36. The cylinder 32 drives the lifting plate 33 to rise and fall, which in turn drives the third motor 34, reducer 35, first top head connecting seat 36, and first top head 37 to rise and fall synchronously. This lifts the angular contact bearing placed on the working platform 1, so that the outer ring of the angular contact bearing abuts against the counterweight support seat 42, and the inner ring of the angular contact bearing abuts against the second top head connecting seat 47 below the counterweight 43. Under the action of the cylinder 32, it can continue to rise. The third motor 34 and reducer 35 drive the first top head connecting seat 36 to rotate, which drives the first top head 37 to rotate synchronously. The first top head 37 can be inserted into the inner ring of the angular contact bearing, realizing the positioning of the angular contact bearing and lifting the angular contact bearing. It also drives the inner ring of the angular contact bearing to rotate synchronously, realizing the detection of the protrusion of the back-to-back DB-mounted angular contact bearing and improving the detection accuracy of the protrusion of the back-to-back DB-mounted angular contact bearing.

[0035] In this application, four guide members 38 are connected between the lifting plate 33 and the base 31 for guiding the lifting plate 33 to rise and fall, ensuring that the lifting plate 33 rises and falls smoothly and steadily. The guide member 38 is composed of a linear bearing and a guide rod. The four guide members 38 are symmetrically arranged on both sides of the cylinder 32. The top of the two guide members 38 located on the same side of the cylinder 32 is connected to a limiting plate 39 for limiting the rising height of the lifting plate 33, ensuring that the lifting plate 33 rises to the set height.

[0036] In this application, the protrusion detection device can detect the protrusion of both face-to-face DF-mounted angular contact bearings and back-to-back DB-mounted angular contact bearings, enabling the detection of protrusion of angular contact bearings with two different mounting methods. It has multiple detection functions and wide applicability. At the same time, by setting the second motor 26 and rotating block 27 of the upper drive mechanism 2, as well as the third motor 34 and reducer 35, the inner ring of the angular contact bearing is driven to rotate, which can reduce the runout amplitude of the inner ring of the angular contact bearing relative to the outer ring and improve the detection accuracy of the protrusion of the angular contact bearing.

[0037] When the angular contact bearing being tested is a face-to-face DF mounting angular contact bearing, the upper drive mechanism 2 is activated, driving the screw of the ball screw 23 to rotate via the first motor 22, which in turn drives the first connecting plate 24 to descend. This causes the second mounting plate 25, the second motor 26, the rotating block 27, and the testing mechanism 4 to descend synchronously. The counterweight support 42, counterweight 43, second top connecting seat 47, and second top 48 on the testing mechanism 4 descend synchronously. The second top 48 inserts into the inner ring of the angular contact bearing on the working platform 1. The counterweight support 42 and the angular contact bearing... When the outer ring of the angular contact bearing abuts, the second top connecting seat 47 and the counterweight 43 are displaced upward relative to the counterweight support seat 42 under the action of the inner ring of the angular contact bearing. This causes the detection head of the linear displacement sensor 46 to be compressed, thereby detecting the protrusion of the angular contact bearing. At the same time, the second motor 26 drives the rotating block 27 to rotate, which in turn drives the counterweight 43 to rotate synchronously, thereby driving the inner ring of the angular contact bearing to rotate. This reduces the sway amplitude of the inner ring of the angular contact bearing relative to the outer ring and improves the detection accuracy of the protrusion of the angular contact bearing.

[0038] When the detected angular contact bearing is a back-to-back DB-mounted angular contact bearing, the lower drive mechanism 3 actuates, extending the piston rod of cylinder 32 to lift the lifting plate 33 upward. This drives the third motor 34, reducer 35, first jack connecting seat 36, and first jack 37 to move upward synchronously. The first jack 37 inserts into the inner ring of the angular contact bearing, causing the angular contact bearing to move upward synchronously, so that the outer ring of the angular contact bearing abuts against the counterweight support seat 42, and the inner ring of the angular contact bearing abuts against the second jack connecting seat 47. As the air... The piston rod of cylinder 32 continues to push out, causing the inner ring of the angular contact bearing to continue to rise and push up the second mandrel connecting seat 47 and the counterweight 43, thereby compressing the test head of the linear displacement sensor 46 and realizing the detection of the protrusion of the angular contact bearing. At the same time, the third motor 34 and the reducer 35 are activated, driving the first mandrel connecting seat 36 and the first mandrel 37 to rotate, thereby driving the inner ring of the angular contact bearing to rotate synchronously, reducing the sway amplitude of the inner ring of the angular contact bearing relative to the outer ring, and improving the detection accuracy of the protrusion of the angular contact bearing.

[0039] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for detecting the protrusion of an angular contact bearing, comprising a working platform (1), characterized in that: The upper drive mechanism (2) is provided above the working platform (1), and the lower drive mechanism (3) is provided below the working platform (1). The upper drive mechanism (2) is connected to a detection mechanism (4). The detection mechanism (4) is located above the working platform (1) and directly above the lower drive mechanism (3). The detection mechanism (4) includes a second connecting plate (41), which is horizontally mounted on the upper drive mechanism (2). A counterweight support seat (42) is fixed above the second connecting plate (41), and a counterweight (43) is provided above the counterweight support seat (42). The counterweight (43) has a circular cross-section, and two support rods (44) with its center as the center of symmetry are provided on the side of the counterweight (43). The two support rods (44) are vertically fixed. On the counterweight support base (42), the ends of the two support rods (44) are connected to a connecting rod (45). A vertically arranged linear displacement sensor (46) is installed in the middle of the connecting rod (45). The lower end test head of the linear displacement sensor (46) abuts against the upper end center of the counterweight (43). The upper end of the counterweight (43) is cylindrical, and its lower end is provided with a conical block (431). The lower end of the conical block (431) is provided with a second top connecting seat (47). The upper drive mechanism (2) includes a first mounting plate (21), which is vertically fixed on the work platform (1). A vertically arranged first motor (22) is mounted on the upper end of the first mounting plate (21). A vertically arranged ball screw (23) is connected to the lower output shaft of the first motor (22). The nut of the ball screw (23) is connected to a first connecting plate (24). A horizontally arranged second mounting plate (25) is connected to the first connecting plate (24). A second motor (26) is mounted above the end of the second mounting plate (25) near the first connecting plate (24). The second motor (26) is vertically arranged and its lower output shaft is connected to a rotating block (27). A round hole (251) for a counterweight block (43) is provided on the end of the second mounting plate (25) away from the first connecting plate (24). The second connecting plate (41) is fixed below the second mounting plate (25). Two linear guide rails (28) are connected between the first connecting plate (24) and the first mounting plate (21). The lower drive mechanism (3) includes a base (31), a vertically arranged cylinder (32) is provided above the base (31), the upper piston rod end of the cylinder (32) is connected to a horizontally arranged lifting plate (33), a vertically arranged third motor (34) is fixed below the lifting plate (33), the third motor (34) is located on the side of the cylinder (32), the upper output shaft end of the third motor (34) is connected to a reducer (35) installed above the lifting plate (33), a first top head connecting seat (36) is connected above the reducer (35), and a first top head (37) is installed at the upper end of the first top head connecting seat (36).

2. The angular contact bearing protrusion detection device according to claim 1, characterized in that: The diameter of the conical block (431) gradually decreases from top to bottom.

3. The angular contact bearing protrusion detection device according to claim 2, characterized in that: The counterweight support (42) is a stepped cylindrical structure with a larger diameter at the upper end than at the lower end. The counterweight support (42) is provided with a tapered hole (421) that matches the tapered block (431).

4. The angular contact bearing protrusion detection device according to claim 1, characterized in that: The second top head (48) is provided inside the second top head connecting seat (47).

5. The angular contact bearing protrusion detection device according to claim 1, characterized in that: The rotating block (27) has a waist-shaped structure and its outer side is covered with a flexible material.

6. The angular contact bearing protrusion detection device according to claim 1, characterized in that: Four guide members (38) are connected between the lifting plate (33) and the base (31). The guide members (38) are composed of linear bearings and guide rods. The four guide members (38) are symmetrically arranged on both sides of the cylinder (32). A limiting plate (39) is connected to the top of the two guide members (38) located on the same side of the cylinder (32).

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