A fourth axis of a vertical machining center with a servo tailstock

Abstract

The fourth axis of a vertical machining center with a servo tailstock disclosed in the present invention comprises a base plate, a workbench, a fourth axis turntable and a servo tailstock, wherein the base plate is mounted on the workbench, the fourth axis turntable and the servo tailstock are mounted on both sides of the base plate respectively, a rotary cylinder and a chuck are coaxially mounted on both sides of the fourth axis turntable respectively, the servo tailstock comprises a tailstock body, a center and a servo motor, the tailstock body can be mounted on the base plate in a linearly movable manner, the center is mounted on the tailstock body, the center and the chuck are positioned oppositely, the servo motor is used to drive the tailstock body to move linearly, the top force of the top on the workpiece is controlled by the servo motor, and the servo motor is provided with an encoder for feeding back the position information of the tailstock body and the top force of the top on the workpiece to the machine tool control system. The fourth axis can realize highly efficient tailstock auxiliary processing, greatly improve the positioning accuracy and processing efficiency of the workpiece, meet the needs of automated processing, and is particularly suitable for processing shaft parts on a vertical machining center.

Description

Technical Field

[0001] The invention relates to a fourth axis of a vertical machining center, in particular to a fourth axis of a vertical machining center with a servo tailstock. Background Art

[0002] When the existing vertical machining center is equipped with a fourth-axis swivel table and a tailstock, a disc tailstock or an ejector tailstock is commonly used. The disc tailstock is generally only suitable for structures with base plates, L plates and bridge plates. It is highly specialized and not suitable for the processing of shaft parts on the vertical machining center. The ejector tailstock is divided into two types: a manual ejector tailstock and a hydraulic ejector tailstock. The ejector tailstock requires manual operation, is inefficient, and cannot be automated; while the hydraulic ejector tailstock has low control accuracy for the tightening force, and the matching hydraulic station requires maintenance. In addition, if the manual ejector tailstock and the hydraulic ejector tailstock are to be used for workpieces of different lengths, it is necessary to manually adjust the position of the tailstock body and fix it by screwing screws in different screw holes. The operation is cumbersome, time-consuming and labor-intensive. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a fourth axis of a vertical machining center with a servo tailstock in view of the shortcomings of the prior art, which can realize highly efficient tailstock-assisted processing, greatly improve the positioning accuracy and processing efficiency of the workpiece, meet the needs of automated processing, and is particularly suitable for the processing of shaft parts on a vertical machining center.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: a fourth axis of a vertical machining center with a servo tailstock, comprising a base plate, a worktable, a fourth axis turntable and a servo tailstock, wherein the base plate is mounted on the worktable, the fourth axis turntable and the servo tailstock are respectively mounted on both sides of the base plate, and a rotating cylinder and a chuck are coaxially mounted on both sides of the fourth axis turntable, respectively, and the rotating cylinder is used to drive the chuck to clamp or release one end of the workpiece, and the servo tailstock comprises a tailstock body, a center and a servo motor, the tailstock body can be linearly movably mounted on the base plate, the center is mounted on the tailstock body, the center is opposite to the chuck, the chuck and the center are used to clamp and fix the workpiece left and right, and the servo motor is used to drive the tailstock body to move linearly toward or away from the chuck, and the size of the top tightening force of the center on the workpiece is achieved by the servo motor by controlling different output torques, and the servo motor is provided with an encoder, and the encoder is used to feed back the position information of the tailstock body and the size of the top tightening force of the center on the workpiece to the machine tool control system.

[0005] The fourth axis of the vertical machining center of the present invention can realize full-stroke servo positioning and automatic adjustment of the top position through the servo motor, which meets the processing needs of the fourth axis for workpieces of different lengths, and the clamping force on the workpiece is completely realized by the servo motor through controlling different output torques, with high control accuracy. In addition, when replacing workpieces of different lengths, the corresponding tailstock position adjustment can be automatically controlled by the servo motor without manual intervention, and high-efficiency tailstock auxiliary processing can be achieved, which greatly improves the positioning accuracy and processing efficiency of the workpiece, meets the needs of automated processing, and is particularly suitable for the processing of shaft parts on the vertical machining center.

[0006] Preferably, a tailstock sleeve is installed on the inner side of the tailstock body, and a tapered hole, a threaded hole and a light hole are transversely opened in the tailstock sleeve, which are connected in sequence. The main body of the top tip is a cone that matches the tapered hole, and the main body of the top tip is installed in the tapered hole. The first bolt passes through the light hole and is threadedly connected to the threaded hole. The first bolt is used to push the top tip out of the tapered hole. The main body of the top tip is self-locked in the tapered hole by its own taper, and the positioning is firm and reliable. The design of the above-mentioned first bolt makes it easy to push the top tip out of the tapered hole, so as to realize the rapid disassembly or replacement of the top tip.

[0007] Preferably, parallel linear rails and lead screws are installed on the bottom plate, a slider is installed on the linear rail, the slider is fixed to the bottom of the tailstock body, the output end of the servo motor is connected to the lead screw via a coupling, a nut is installed on the lead screw, and the nut is connected to the tailstock body. Driven by the servo motor, the rotation of the lead screw is converted into the linear motion of the tailstock body through the nut, and as the tailstock body moves, the top moves synchronously with the tailstock body, so as to realize the positioning and tightening needs of workpieces of different lengths, and the whole action process is reliable and high-precision.

[0008] Preferably, the rotary oil cylinder comprises a coaxially arranged rotating part and an oil cylinder, the rotating part comprises a pull rod, a plane bearing, a bearing seat and a mounting seat, the bearing seat can be linearly mounted in the mounting seat, the plane bearing is mounted in the bearing seat, one end of the pull rod is used to connect the chuck, and the other end of the pull rod extends into the mounting seat and is connected with the plane bearing, the oil cylinder comprises a piston and a cylinder body, one end of the cylinder body is fixedly connected to the mounting seat, the piston can be linearly mounted on the cylinder body, one end of the piston extends out of the cylinder body and is fixedly connected to the bearing seat by a second bolt, the second bolt passes through the bearing seat and is threadedly connected to the piston, a radial convex ring is integrally provided at the middle part of the piston, a first oil chamber and a second oil chamber are provided in the cylinder body, the first oil chamber and the second oil chamber are respectively arranged on both sides of the axial direction of the radial convex ring, and a first oil port and a second oil port are provided on the side wall of the cylinder body, the first oil port is communicated with the first oil chamber, and the second oil port is communicated with the second oil chamber. The working principle of the above-mentioned rotary cylinder is as follows: the hydraulic oil enters the first oil chamber through the first oil port, pushing the piston to move to the extreme position away from the mounting seat. At this time, the piston exerts a pulling force on the pull rod, and the pull rod pulls the chuck to clamp. After the top moves into place and the chuck and the top clamp the workpiece left and right, the vertical machining center can process the workpiece. During the machining process, the pull rod and the bearing seat can rotate synchronously with the chuck; when the workpiece needs to be released, the first oil port returns oil and the second oil port enters oil, pushing the piston to move to the extreme position close to the mounting seat. At this time, the piston exerts a pushing force on the pull rod, and the pull rod pushes the chuck to release the workpiece. At this time, the vertical machining center can perform unloading operations on the workpiece. The above-mentioned rotary cylinder has a compact structure and a large pulling force. Its pull rod can rotate independently by 0~360°, and the pull rod can move linearly synchronously with the piston.

[0009] Preferably, a spacer is fixed to the other end of the pull rod, the number of the plane bearings is two, the two plane bearings are respectively mounted on the spacer, the other end of the pull rod is integrally provided with a radial positioning ring and threadedly connected with a pressure ring, and the spacer is clamped by the radial positioning ring and the pressure ring. The installation of the two plane bearings is achieved through the spacer, which is convenient for assembly. The design of the two plane bearings can improve the reliability of the rotation of the pull rod. The spacer is fixed by the radial positioning ring and the pressure ring, which has a simple structure and is easy to assemble.

[0010] Preferably, a cylinder cover is installed at the other end of the cylinder body, the other end of the piston extends from the cylinder cover, a signal plate is fixed at the other end of the piston, and the cylinder cover is connected with a first signal switch and a second signal switch matching the signal plate, the first signal switch and the second signal switch are respectively arranged at the two extreme positions of the linear motion of the piston, and the first signal switch and the second signal switch are used to feedback the position information of the piston to the machine tool control system. When the signal plate is activated, the first signal switch and the second signal switch feed back the position information of the piston to the machine tool control system, and can activate the robot or manipulator to perform corresponding loading and unloading actions. The design of the signal plate and the first signal switch and the second signal switch can realize the detection of the piston in place and meet the needs of automated processing.

[0011] Preferably, a first U-shaped sealing ring is arranged between one end of the piston and the cylinder body, and the first U-shaped sealing ring is fixed on the cylinder body; a rotary pressure seal and an O-shaped sealing ring are arranged between the radial convex ring and the cylinder body, and the rotary pressure seal and the O-shaped sealing ring are respectively fixed on the radial convex ring; a second U-shaped sealing ring is arranged between the other end of the piston and the cylinder cover, and the second U-shaped sealing ring is installed on the cylinder cover. The above sealing structures can have a good contact sealing effect on the oil cylinder to prevent oil leakage.

[0012] Preferably, one end of the pull rod is provided with an internal threaded hole, a connecting rod is fixed on the chuck, the pull rod is threadedly connected with the connecting rod, a plug hole is provided on the side wall of the mounting seat, and a positioning hole matched with the plug hole is provided on the pull rod. When the bearing seat drives the pull rod to move to a position where the positioning hole is opposite to the plug hole, a metal rod is inserted into the plug hole and the positioning hole to fix the pull rod, and the connecting rod can be threadedly connected with the pull rod. The cooperation of the above-mentioned plug hole and the positioning hole can play a good anti-rotation role for the pull rod, and prevent the rotation of the pull rod during the threaded connection between the connecting rod and the pull rod from affecting the assembly efficiency.

[0013] Preferably, the side wall of the mounting seat is provided with an oil hole for filling grease; the outer peripheral wall of the bearing seat is provided with a plurality of annular oil grooves for storing grease. The grease lubricates the rotation of the rotating part.

[0014] Preferably, the workbench is provided with a plurality of T-slots, the base plate is fixed to the workbench by a plurality of T-bolts, and the plurality of T-bolts are respectively installed in the plurality of T-slots.

[0015] Compared with the prior art, the present invention has the following advantages: the fourth axis of the vertical machining center of the present invention can realize full-stroke servo positioning and automatic adjustment of the top position through the servo motor, which meets the processing needs of the fourth axis for workpieces of different lengths, and the clamping force on the workpiece is completely realized by the servo motor through controlling different output torques, and the control accuracy is high. In addition, when replacing workpieces of different lengths, the corresponding tailstock position adjustment can be automatically controlled by the servo motor without manual intervention, and high-efficiency tailstock auxiliary processing can be achieved, which greatly improves the positioning accuracy and processing efficiency of the workpiece, meets the needs of automated processing, and is particularly suitable for the processing of shaft parts on the vertical machining center. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an appearance diagram of the fourth axis of the vertical machining center in the embodiment;

[0017] Figure 2 It is a schematic diagram of the internal structure of the fourth axis of the vertical machining center in the embodiment;

[0018] Figure 3 This is an appearance diagram of the fourth axis turntable side in the embodiment;

[0019] Figure 4 Schematic diagram of the internal structure of the fourth axis turntable side in the embodiment;

[0020] Figure 5 Schematic diagram of the internal structure of the servo tailstock side in the embodiment;

[0021] Figure 6 It is a schematic cross-sectional view of the structure when the rotary oil cylinder is at the left limit position in the embodiment;

[0022] Figure 7 It is a schematic cross-sectional view of the structure when the rotary cylinder is in the right limit position in the embodiment. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings.

[0024] The fourth axis of the vertical machining center with a servo tailstock of the embodiment, as shown in the figure, includes a base plate 11, a worktable 1, a fourth axis turntable 12 and a servo tailstock 2, a plurality of T-slots 13 are provided on the worktable 1, the base plate 11 is fixed to the worktable 1 by a plurality of T-bolts (not shown in the figure), the plurality of T-bolts are respectively installed in the plurality of T-slots 13, the fourth axis turntable 12 and the servo tailstock 2 are respectively installed on both sides of the base plate 11, a rotating cylinder 3 and a chuck 14 are respectively coaxially installed on both sides of the fourth axis turntable 12, the rotating cylinder 3 is used to drive the chuck 14 to clamp or release one end of the workpiece (not shown in the figure), and the servo tailstock 2 includes a tailstock 11. The tailstock body 21, the top 22 and the servo motor 23, the tailstock body 21 is linearly movably mounted on the base plate 11, the top 22 is mounted on the tailstock body 21, the top 22 is opposite to the chuck 14, the chuck 14 and the top 22 are used to clamp and fix the workpiece left and right, the servo motor 23 is used to drive the tailstock body 21 to move linearly toward or away from the chuck 14, the size of the clamping force of the top 22 on the workpiece is achieved by the servo motor 23 by controlling different output torques, the servo motor 23 is equipped with an encoder (not shown in the figure), the encoder is used to feedback the position information of the tailstock body 21 and the size of the clamping force of the top 22 on the workpiece to the machine tool control system.

[0025] In this embodiment, a tailstock sleeve 24 is installed on the inner side of the tailstock body 21, and a tapered hole 25, a threaded hole 26 and a light hole 27 are transversely opened in the tailstock sleeve 24, which are connected in sequence. The main part of the top 22 is a cone that matches the tapered hole 25, and the main part of the top 22 is installed in the tapered hole 25. The first bolt 28 passes through the light hole 27 and is threadedly connected to the threaded hole 26. The first bolt 28 is used to push the top 22 out of the tapered hole 25.

[0026] In this embodiment, a parallel linear rail 15 and a lead screw 16 are installed on the base plate 11, a slider 17 is installed on the linear rail 15, the slider 17 is fixed to the bottom of the tailstock body 21, the output end of the servo motor 23 is connected to the lead screw 16 via a coupling 18, and a nut 19 is installed on the lead screw 16, and the nut 19 is connected to the tailstock body 21.

[0027] In this embodiment, the rotary cylinder 3 includes a coaxially arranged rotating part and a cylinder, the rotating part includes a pull rod 31, a plane bearing 32, a bearing seat 33 and a mounting seat 34, the bearing seat 33 can be installed in the mounting seat 34 for linear motion, the plane bearing 32 is installed in the bearing seat 33, one end of the pull rod 31 is used to connect the chuck 14, the other end of the pull rod 31 extends into the mounting seat 34 and is connected to the plane bearing 32, the cylinder includes a piston 41 and a cylinder body 42, one end of the cylinder body 42 is fixedly connected to the mounting seat 34, the piston 41 can be installed in the cylinder body 4 for linear motion 2. One end of the piston 41 extends out of the cylinder body 42 and is fixedly connected to the bearing seat 33 by a second bolt 43. The second bolt 43 passes through the bearing seat 33 and is threadedly connected to the piston 41. A radial convex ring 44 is integrally provided at the middle of the piston 41. A first oil chamber 45 and a second oil chamber 46 are provided in the cylinder body 42. The first oil chamber 45 and the second oil chamber 46 are respectively provided on both sides of the axial direction of the radial convex ring 44. A first oil port 47 and a second oil port 48 are provided on the side wall of the cylinder body 42. The first oil port 47 communicates with the first oil chamber 45, and the second oil port 48 communicates with the second oil chamber 46.

[0028] In this embodiment, a spacer sleeve 35 is fixed to the other end of the pull rod 31. There are two plane bearings 32, which are respectively mounted on the spacer sleeve 35. A radial positioning ring 36 is integrally provided at the other end of the pull rod 31 and is threadedly connected with a pressure ring 37. The spacer sleeve 35 is clamped by the radial positioning ring 36 and the pressure ring 37.

[0029] In this embodiment, a cylinder cover 5 is installed at the other end of the cylinder body 42, and the other end of the piston 41 extends from the cylinder cover 5. A signal transmitting plate 51 is fixed to the other end of the piston 41. The cylinder cover 5 is connected with a first signal switch 52 and a second signal switch 53 matching the signal transmitting plate 51. The first signal switch 52 and the second signal switch 53 are respectively arranged at the two extreme positions of the linear motion of the piston 41. The first signal switch 52 and the second signal switch 53 are used to feed back the position information of the piston 41 to the machine tool control system.

[0030] In this embodiment, a first U-shaped sealing ring 61 is arranged between one end of the piston 41 and the cylinder body 42, and the first U-shaped sealing ring 61 is fixed on the cylinder body 42. A rotating pressure seal 62 and an O-shaped sealing ring 63 are arranged between the radial convex ring 44 and the cylinder body 42, and the rotating pressure seal 62 and the O-shaped sealing ring 63 are respectively fixed on the radial convex ring 44. A second U-shaped sealing ring 64 is arranged between the other end of the piston 41 and the cylinder head 5, and the second U-shaped sealing ring 64 is installed on the cylinder head 5.

[0031] In this embodiment, an internal threaded hole 38 is provided at one end of the pull rod 31, a connecting rod 10 is fixed on the chuck 14, the pull rod 31 is threadedly connected to the connecting rod 10, a socket 39 and an oil hole 30 are provided on the side wall of the mounting seat 34, and a positioning hole 71 matched with the socket 39 is provided on the pull rod 31. When the bearing seat 33 drives the pull rod 31 to move to a position where the positioning hole 71 is opposite to the socket 39, a metal rod is inserted into the socket 39 and the positioning hole to fix the pull rod 31. At this time, the connecting rod 10 can be threadedly connected to the pull rod 31; the oil hole 30 is used to add grease; a plurality of annular oil grooves 72 are provided on the outer peripheral wall of the bearing seat 33, and the oil grooves 72 are used to store grease.

[0032] When the fourth axis of the vertical machining center with servo tailstock is working, under the drive of the servo motor 23, the rotation of the lead screw 16 is converted into the linear motion of the tailstock body 21 through the nut 19. As the tailstock body 21 moves, the center 22 moves synchronously with the tailstock body 21 to achieve the positioning and tightening needs of workpieces of different lengths. The entire action process is reliable and high-precision.

[0033] During operation, the hydraulic oil enters the first oil chamber 45 through the first oil port 47, pushing the piston 41 to move to the extreme position away from the mounting seat 34 (i.e. Figure 7 The piston 41 exerts a pulling force on the pull rod 31, and the pull rod 31 pulls the chuck 14 to clamp it. After the center 22 moves into place and the chuck 14 and the center 22 clamp the workpiece left and right, the vertical machining center can process the workpiece. During the machining process, the pull rod 31 and the bearing seat 33 can rotate synchronously with the chuck 14. When the workpiece needs to be released, the first oil port 47 returns oil and the second oil port 48 allows oil to enter, pushing the piston 41 to move to the limit position close to the mounting seat 34 (i.e. Figure 6 The left limit position is shown in the figure), at this time, the piston 41 exerts a pushing force on the pull rod 31, and the pull rod 31 pushes the chuck 14 to release the workpiece. At this time, the vertical machining center can perform unloading operations on the workpiece.

[0034] The fourth axis of the vertical machining center with a servo tailstock can achieve full-stroke servo positioning and automatic adjustment of the position of the center 22 through the servo motor 23, which meets the processing needs of the fourth axis for workpieces of different lengths, and the clamping force on the workpiece is completely achieved by the servo motor 23 by controlling different output torques, with high control accuracy. In addition, when replacing workpieces of different lengths, the corresponding position adjustment of the tailstock body 21 can be automatically controlled by the servo motor 23.

Claims

1. A fourth axis of a vertical machining center with a servo tailstock, characterized in that: The invention comprises a base plate, a workbench, a fourth-axis turntable and a servo tailstock, wherein the base plate is mounted on the workbench, the fourth-axis turntable and the servo tailstock are respectively mounted on both sides of the base plate, a rotating oil cylinder and a chuck are respectively coaxially mounted on both sides of the fourth-axis turntable, the rotating oil cylinder is used to drive the chuck to clamp or release one end of the workpiece, the servo tailstock comprises a tailstock body, a center and a servo motor, the tailstock body can be linearly movably mounted on the base plate, the center is mounted on the tailstock body, the center is opposite to the chuck, the chuck and the center are used to clamp and fix the workpiece left and right, the servo motor is used to drive the tailstock body to move linearly toward or away from the chuck, the clamping force of the center on the workpiece is realized by the servo motor by controlling different output torques, the servo motor is provided with an encoder, and the encoder is used to feed back the position information of the tailstock body and the clamping force of the center on the workpiece to the machine tool control system; The rotary oil cylinder comprises a coaxially arranged rotating part and an oil cylinder, the rotating part comprises a pull rod, a plane bearing, a bearing seat and a mounting seat, the bearing seat can be linearly mounted in the mounting seat, the plane bearing is mounted in the bearing seat, one end of the pull rod is used to connect the chuck, the other end of the pull rod extends into the mounting seat and is connected with the plane bearing, the oil cylinder comprises a piston and a cylinder body, one end of the cylinder body is fixedly connected with the mounting seat, the piston can be linearly mounted on the cylinder body, one end of the piston extends out of the cylinder body and is fixedly connected with the bearing seat by a second bolt, the second bolt passes through the bearing seat and is threadedly connected with the piston, a radial convex ring is integrally provided at the middle part of the piston, a first oil chamber and a second oil chamber are provided in the cylinder body, the first oil chamber and the second oil chamber are respectively arranged on both sides of the axial direction of the radial convex ring, a first oil port and a second oil port are provided on the side wall of the cylinder body, the first oil port is communicated with the first oil chamber, and the second oil port is communicated with the second oil chamber; A spacer is fixed to the other end of the pull rod, there are two plane bearings, and the two plane bearings are respectively mounted on the spacer. A radial positioning ring is integrally provided at the other end of the pull rod and is threadedly connected to a pressure ring, and the spacer is clamped by the radial positioning ring and the pressure ring; a cylinder cover is installed at the other end of the cylinder body, and the other end of the piston extends from the cylinder cover, and a signal plate is fixed to the other end of the piston, and a first signal switch and a second signal switch matching the signal plate are connected to the cylinder cover, and the first signal switch and the second signal switch are respectively arranged at the two extreme positions of the linear motion of the piston, and the first signal switch and the second signal switch are used to feed back the position information of the piston to the machine tool control system; one end of the piston is aligned with the cylinder body A first U-shaped sealing ring is arranged between the piston and the cylinder body, and the first U-shaped sealing ring is fixed on the cylinder body. A rotary pressure seal and an O-shaped sealing ring are arranged between the radial convex ring and the cylinder body, and the rotary pressure seal and the O-shaped sealing ring are respectively fixed on the radial convex ring. A second U-shaped sealing ring is arranged between the other end of the piston and the cylinder cover, and the second U-shaped sealing ring is installed on the cylinder cover; an internal threaded hole is provided at one end of the pull rod, a connecting rod is fixed on the chuck, the pull rod is threadedly connected with the connecting rod, a socket is provided on the side wall of the mounting seat, and a positioning hole matched with the socket is provided on the pull rod. When the bearing seat drives the pull rod to move to a position where the positioning hole is relative to the socket, a metal rod is inserted into the socket and the positioning hole to fix the pull rod, and the connecting rod can be threadedly connected with the pull rod at this time.

2. The fourth axis of a vertical machining center with a servo tailstock according to claim 1, characterized in that: A tailstock sleeve is installed on the inner side of the tailstock body, and a tapered hole, a threaded hole and a light hole are transversely opened in the tailstock sleeve, which are connected in sequence. The main body of the top tip is a cone that matches the tapered hole. The main body of the top tip is installed in the tapered hole. A first bolt passes through the light hole and is threadedly connected to the threaded hole. The first bolt is used to push the top tip out of the tapered hole.

3. The fourth axis of a vertical machining center with a servo tailstock according to claim 1 or 2, characterized in that: The bottom plate is provided with parallel linear rails and lead screws, the linear rails are provided with sliders, the sliders are fixed to the bottom of the tailstock body, the output end of the servo motor is connected to the lead screw via a coupling, the lead screw is provided with a nut, and the nut is connected to the tailstock body.

4. The fourth axis of a vertical machining center with a servo tailstock according to claim 1, characterized in that: An oil hole is provided on the side wall of the mounting seat, and the oil hole is used for filling grease; a plurality of annular oil grooves are provided on the outer peripheral wall of the bearing seat, and the oil grooves are used for storing grease.

5. The fourth axis of a vertical machining center with a servo tailstock according to claim 1, characterized in that: The workbench is provided with a plurality of T-shaped slots, and the bottom plate is fixed to the workbench through a plurality of T-shaped bolts, and the plurality of T-shaped bolts are respectively installed in the plurality of T-shaped slots.

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