A device for purifying silicon nitride powder by acid washing

Abstract

The application discloses a kind of nitride silicon powder's pickling purification device, it is related to nitride silicon powder production technical field, for the screening pretreatment process of nitride silicon powder in pickling purification device, nitride silicon powder is often only vibrated screening treatment along single direction, so that the screening efficiency of nitride silicon powder is not good for the problem of screening effect, including pickling tank and the sieving cylinder being arranged at the top position of pickling tank, one end of the outer circumferential surface of sieving cylinder is fixed with first abutment block, one end of first abutment block is fixed with first abutment seat, the bottom of first abutment seat is fixed with the surface of the top of pickling tank, the other end of the outer circumferential surface of sieving cylinder is fixed with second abutment block;The application can apply multi-directional force to nitride silicon powder placed in the inside of sieving cylinder to realize multi-directional vibrated screening treatment, so as to improve the impurity removal screening efficiency of nitride silicon powder, so as to improve the pickling processing efficiency of nitride silicon powder.

Description

Technical Field

[0001] This invention relates to the field of silicon nitride powder production technology, specifically to an acid washing and purification apparatus for silicon nitride powder. Background Technology

[0002] Silicon nitride powder is an important material with wide applications in various fields. However, during the production process, impurities often adhere to the surface of silicon nitride powder, affecting its performance and quality. In order to remove these impurities and improve the purity and quality of silicon nitride powder, acid washing process is widely used, which requires corresponding acid washing and purification equipment.

[0003] Existing acid pickling and purification devices typically consist of a pretreatment end and an acid pickling end. Pretreatment of silicon nitride powder requires steps such as impurity removal and sieving to remove large particles and impurities. The pretreated silicon nitride powder is then fed into the acid pickling end for further processing. However, existing acid pickling and purification devices often only vibrate and sieve the silicon nitride powder in a single direction during the pretreatment sieving process. This results in poor sieving efficiency and reduces the overall acid pickling efficiency, making the device unsuitable for use.

[0004] Therefore, there is a need for an acid washing and purification device for silicon nitride powder to solve the problem that existing acid washing and purification devices often only vibrate and screen silicon nitride powder in a single direction during the pre-treatment process, resulting in poor screening efficiency. Summary of the Invention

[0005] To solve the above-mentioned technical problems, an acid washing and purification device for silicon nitride powder is provided. This device solves the problem that in the existing acid washing and purification device, the silicon nitride powder is often only vibrated and screened in one direction during the pretreatment process, resulting in poor screening efficiency.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an acid washing and purification device for silicon nitride powder, comprising an acid washing tank and a sieve cylinder disposed at the top of the acid washing tank, wherein a first abutment block is fixed to one end of the outer peripheral surface of the sieve cylinder, a first abutment seat is attached to one end of the first abutment block, the bottom of the first abutment seat is fixed to the surface of the top of the acid washing tank, a second abutment block is fixed to the other end of the outer peripheral surface of the sieve cylinder, a second abutment seat is attached to the end of the second abutment block away from the sieve cylinder, the bottom of the second abutment seat is fixed to the surface of the top of the acid washing tank, and a driving component is disposed on one side of the top surface of the acid washing tank;

[0007] The drive assembly includes a fixed base, the bottom of which is fixed to the surface of the top of the pickling tank. A motor is installed on the side of the fixed base away from the sieve cylinder. Rotary disks are arranged sequentially on the fixed base near the sieve cylinder. The output end of the motor passes through the fixed base and is fixed to the surface of the rotating disks. A connecting frame is fitted against one side of the rotating disks. A limiting shaft is inserted through the surface of the connecting frame. The bottom of the limiting shaft is fixed to the surface of the top of the pickling tank. An abutment groove is formed on the surface of the connecting frame. A movable rod is inserted into one end of the inner cavity of the abutment groove. One side of the movable rod is fixed to the surface of the rotating disks. A support assembly is provided on one side of the connecting frame.

[0008] Preferably, the support assembly includes a support frame, one side of the connecting frame is fixed to the surface of the support frame, and symmetrically distributed storage slots are provided on both sides of the surface of the support frame. An embedded shaft is fixed inside the storage slot, and limiting sleeves are slidably fitted on both ends of the outer peripheral surface of the embedded shaft. The top of the limiting sleeve is fixed to the surface of the bottom of the sieve cylinder. A spring is fitted on the outer peripheral surface of the embedded shaft near the outer peripheral surface of the adjacent limiting sleeve. One end of the spring is fixed to the surface of the adjacent limiting sleeve, and the other end of the spring is fixed to one end of the inner wall of the adjacent storage slot. A through-hole is provided in the middle of the support frame.

[0009] Preferably, an inlet is provided at the middle position of the top surface of the pickling tank, a filter layer is fixed on the inner circumferential surface of the sieve cylinder, a discharge pipe is fixedly connected to the bottom of the sieve cylinder, the bottom of the discharge pipe passes through the connecting port and the inlet in sequence and extends to the inner cavity of the pickling tank, abutment ports are provided at both ends of the inlet on the top surface of the pickling tank, shaft brackets are fixed at both sides of the abutment ports on the top surface of the pickling tank, and a stirring assembly is provided at the middle position of the two shaft brackets.

[0010] Preferably, the stirring assembly includes a threaded rod, one side of which is rotatably connected to the surface of an adjacent shaft bracket, the other side of which passes through another shaft bracket and extends to one side of the shaft bracket, a threaded sleeve is threadedly connected to the middle position of the outer circumference of the threaded rod, a movable shaft is rotatably connected to the bottom surface of the threaded sleeve, the bottom of the movable shaft extends to the inner cavity of the pickling tank, and multiple stirring rods are evenly fixed at both ends of the outer circumference of the movable shaft located inside the pickling tank.

[0011] Preferably, a gear is fixedly fitted on the outer circumferential surface of the movable shaft at the bottom position of the threaded sleeve, one end of the gear is engaged with a rack, and the bottom of the rack is fixed to the surface of the top of the pickling tank.

[0012] Preferably, the outer peripheral surface of the threaded sleeve is rotatably fitted with a limiting sleeve located on the outer peripheral surface at the bottom of the gear, and the surfaces at both ends of the limiting sleeve are in contact with the inner walls of the adjacent positions.

[0013] Preferably, a first pulley is fixedly sleeved on one side of the outer circumferential surface of the threaded rod, and two second pulleys are fixedly sleeved on the outer circumferential surface of the motor output end. A connecting belt is provided at the middle position between the first pulley and the adjacent second pulley.

[0014] Compared with the prior art, the advantages of the present invention are as follows:

[0015] 1. By setting up the drive component and the support component, when the silicon nitride powder is placed inside the sieve cylinder, the rotating disk is driven by the motor to rotate, so that the support component drives the sieve cylinder to reciprocate in the vertical direction. During this process, under the contact action between the first contact seat and the first contact block and the contact action between the second contact block and the second contact seat, the sieve cylinder can reciprocate in the horizontal direction. This can apply multi-directional force to the silicon nitride powder placed inside the sieve cylinder to achieve multi-directional vibration sieving, thereby improving the impurity removal and sieving efficiency of silicon nitride powder, and thus improving the acid washing efficiency of silicon nitride powder.

[0016] 2. By setting up the stirring assembly, when the motor starts, the threaded sleeve drives the movable shaft to rotate horizontally, causing the gear to mesh with the adjacent rack. This allows the movable shaft to rotate while rotating horizontally, thus enabling a large-scale stirring effect inside the pickling tank with a relatively small movable shaft. This avoids the movable shaft and stirring rod occupying too much space inside the pickling tank, allowing for full utilization of the internal space and improving the practicality of the device. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of the present invention viewed from the front.

[0018] Figure 2 In this invention Figure 1 Enlarged structural diagram at point A;

[0019] Figure 3 This is a top-view perspective three-dimensional structural diagram of the driving component and the supporting component of the present invention;

[0020] Figure 4 This is a partial three-dimensional structural diagram of the driving component of the present invention;

[0021] Figure 5 This is a three-dimensional cross-sectional view of the sieve cylinder and support assembly of the present invention;

[0022] Figure 6 This is a three-dimensional structural diagram of the stirring assembly of the present invention.

[0023] The numbers on the map are:

[0024] 1. Pickling tank; 2. Sieving cylinder; 3. Filter layer; 4. Discharge pipe; 5. Drive assembly; 51. Fixed base; 52. Motor; 53. Rotating disk; 54. Connecting frame; 55. Limiting shaft; 56. Abutment groove; 57. Movable rod; 6. Support assembly; 61. Support frame body; 62. Storage groove; 63. Embedded shaft; 64. Limiting sleeve; 65. Spring; 66. Connecting port; 7. Shaft frame; 8. Stirring assembly; 81. Threaded rod; 82. Threaded sleeve; 83. Rack; 84. Movable shaft; 85. Gear; 86. Limiting sleeve; 87. Stirring rod; 9. Connecting belt; 10. First abutment seat; 11. First abutment block; 12. Second abutment seat; 13. Second abutment block; 14. Abutment port; 15. Insertion port; 16. First pulley; 17. Second pulley. Detailed Implementation

[0025] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0026] Reference Figure 1 , Figure 2 and Figure 3 As shown, a heat sink riveting mold for a silicon nitride powder pickling and purification device includes a pickling tank 1 and a sieve cylinder 2 disposed at the top of the pickling tank 1. A first abutment block 11 is fixed to one end of the outer peripheral surface of the sieve cylinder 2, and a first abutment seat 10 is attached to one end of the first abutment block 11. The bottom of the first abutment seat 10 is fixed to the top surface of the pickling tank 1. A second abutment block 13 is fixed to the other end of the outer peripheral surface of the sieve cylinder 2. A second abutment seat 12 is attached to the end of the second abutment block 13 away from the sieve cylinder 2. The bottom of the second abutment seat 12 is fixed to the top surface of the pickling tank 1. A drive assembly 5 is disposed on one side of the top surface of the pickling tank 1.

[0027] A motor 52 is installed on the side of the fixed base 51 away from the sieve cylinder 2. A rotating disk 53 is arranged in sequence on the fixed base 51 near the sieve cylinder 2. The output end of the motor 52 passes through the fixed base 51 and is fixed to the surface of the rotating disk 53. A connecting frame 54 is attached to one side of the rotating disk 53. A limiting shaft 55 is inserted through the surface of the connecting frame 54. The bottom of the limiting shaft 55 is fixed to the surface of the top of the pickling tank 1. A contact groove 56 is opened on the surface of the connecting frame 54. A movable rod 57 is inserted into one end of the inner cavity of the contact groove 56. One side of the movable rod 57 is fixed to the surface of the rotating disk 53. A support assembly 6 is provided on one side of the connecting frame 54.

[0028] By setting the drive component 5, the rotating disk 53 is rotated when the motor 52 is started, so that the movable rod 57 makes a circular motion and can abut against the connecting frame 54. During this process, due to the abutment of the limiting shaft 55 against the connecting frame 54, the connecting frame 54 can reciprocate in the vertical direction, so that the sieve cylinder 2 can reciprocate in the vertical direction. When the sieve cylinder 2 moves vertically downward, the first abutting block 11 will abut against the first abutting seat 10, so that the sieve cylinder 2 can move in the front end direction. When the sieve cylinder 2 moves vertically upward, the second abutting block 13 will abut against the second abutting seat 12, so that the sieve cylinder 2 can move in the rear end direction.

[0029] Further as Figure 1 , Figure 3 as well as Figure 5 As shown, it is worth noting that the support assembly 6 includes a support frame 61. One side of the connecting frame 54 is fixed to the surface of the support frame 61. The two sides of the surface of the support frame 61 are provided with symmetrically distributed storage slots 62. An embedded shaft 63 is fixed inside the storage slot 62. Limiting sleeves 64 are slidably sleeved at both ends of the outer peripheral surface of the embedded shaft 63. The top of the limiting sleeve 64 is fixed to the bottom surface of the sieve cylinder 2. A spring 65 is sleeved on the outer peripheral surface of the embedded shaft 63 near the outer peripheral surface of the adjacent limiting sleeve 64. One end of the spring 65 is fixed to the surface of the adjacent limiting sleeve 64, and the other end of the spring 65 is fixed to one end of the inner wall of the adjacent storage slot 62. A connecting port 66 is provided through the middle of the support frame 61.

[0030] By setting the support component 6, the limiting sleeve 64 can only slide along the outer circumferential surface of the adjacent embedded shaft 63 in the inner cavity of the adjacent placement slot 62, thereby limiting the movement trajectory of the sieve cylinder 2. During this process, when the limiting sleeve 64 moves, it will abut against the adjacent spring 65, causing the spring 65 to deform. Thus, under the action of the spring 65's rebound force, a corresponding force can be applied to the sieve cylinder 2, allowing the sieve cylinder 2 to move in the reset direction. Thus, when the first abutting seat 10 and the first abutting block 11 and the second abutting seat 12 and the second abutting block 13 do not abut, the sieve cylinder 2 is in the middle position at the top of the support frame 61.

[0031] Further as Figure 2 , Figure 3 as well as Figure 5 As shown, it is worth noting that an inlet 15 is provided at the middle position of the top surface of the pickling tank 1, a filter layer 3 is fixed on the inner circumferential surface of the sieve cylinder 2, and a discharge pipe 4 is fixedly connected to the bottom of the sieve cylinder 2. The bottom of the discharge pipe 4 passes through the connecting port 66 and the inlet 15 in sequence and extends to the inner cavity of the pickling tank 1. Abutment ports 14 are provided at both ends of the inlet 15 on the top surface of the pickling tank 1. Shaft brackets 7 are fixed at both sides of the abutment ports 14 on the top surface of the pickling tank 1. A stirring assembly 8 is provided at the middle position of the two shaft brackets 7.

[0032] The sieve cylinder 2, with its filter layer 3 inside, allows silicon nitride powder to be placed inside. The sieve cylinder 2 reciprocates vertically to vibrate and screen the silicon nitride powder. The powder is then discharged into the pickling tank 1 through the discharge pipe 4, the connecting port 66, and the inlet 15.

[0033] Further as Figure 1 , Figure 2 and Figure 6 As shown, it is worth noting that the stirring assembly 8 includes a threaded rod 81. One side of the threaded rod 81 is rotatably connected to the surface of the adjacent shaft bracket 7. The other side of the threaded rod 81 passes through another shaft bracket 7 and extends to one side of the shaft bracket 7. A threaded sleeve 82 is threadedly connected to the middle position of the outer circumference of the threaded rod 81. A movable shaft 84 is rotatably connected to the bottom surface of the threaded sleeve 82. The bottom of the movable shaft 84 extends to the inner cavity of the pickling tank 1. Multiple stirring rods 87 are evenly fixed at both ends of the outer circumference of the movable shaft 84 located inside the pickling tank 1. A gear 85 is fixedly sleeved on the outer circumference of the movable shaft 84 located at the bottom position of the threaded sleeve 82. A rack 83 is meshed at one end of the gear 85. The bottom of the rack 83 is fixed to the top surface of the pickling tank 1.

[0034] When the threaded rod 81 is in a rotating state, it moves horizontally due to the interaction between the internal thread of the threaded sleeve 82 and the external thread of the outer circumference of the threaded rod 81. This allows the threaded sleeve 82 to drive the gear 85 and the movable shaft 84 to move horizontally. During this process, the meshing action between the gear 85 and the rack 83 causes the movable shaft 84 to rotate, thereby driving a set of stirring rods 87 in adjacent positions to reciprocate, thus fully mixing the solution and silicon nitride powder placed inside the pickling tank 1.

[0035] Further as Figure 1 , Figure 2 and Figure 6 As shown, it is worth noting that the outer peripheral surface of the threaded sleeve 82 is rotatably fitted with a limiting sleeve 86 on the outer peripheral surface of the bottom of the gear 85, and the surfaces at both ends of the limiting sleeve 86 are in contact with the two ends of the inner wall of the adjacent contact port 14.

[0036] Because the two ends of the limiting sleeve 86 abut against the inner wall of the contact port 14, the movement trajectory of the limiting sleeve 86 can be limited, thereby allowing the threaded sleeve 82 to move in the horizontal direction. This ensures that the threaded sleeve 82 can only move in the horizontal direction under the force between it and the threaded rod 81.

[0037] Further as Figure 1 , Figure 2 and Figure 6 As shown, it is worth noting that a first pulley 16 is fixedly sleeved on one side of the outer circumference of the threaded rod 81, and two second pulleys 17 are fixedly sleeved on the outer circumference of the output end of the motor 52. A connecting belt 9 is provided at the middle position between the first pulley 16 and the adjacent second pulley 17. When the motor 52 rotates, the two second pulleys 17 can be rotated, so that the first pulley 16 can drive the two threaded rods 81 to rotate synchronously under the connection of the adjacent connecting belt 9.

[0038] Working Principle: In actual use, when the user needs to pre-treat and sieve silicon nitride powder, the silicon nitride powder is placed inside the sieve cylinder 2, and then the top of the sieve cylinder 2 is sealed with an external sealing cover. Then, the motor 52 is started, causing its output end to rotate, thus rotating the rotating disk 53. This causes the movable rod 57 to move in a circular motion. Through the contact action of the movable rod 57 against the connecting frame 54 and the limiting action of the limiting shaft 55 on the connecting frame 54, the connecting frame 54 can reciprocate vertically, thereby causing the support assembly 6 to reciprocate vertically. During this process, the sieve cylinder 2, connected by the limiting sleeve 64, can reciprocate vertically with the support assembly 6. When the sieve cylinder 2 can reciprocate vertically, when the sieve cylinder 2 is vertically downward... During movement, the first contact block 11 abuts against the first contact seat 10, causing the sieve cylinder 2 to move along the front end direction, and the second contact block 13 abuts against the second contact seat 12, causing the sieve cylinder 2 to move along the rear end direction, and the sliding of the limit sleeve 64 causes the adjacent spring 65 to deform. Under the action of the spring 65's rebound force, the sieve cylinder 2 can be reset. When the first contact seat 10 and the first contact block 11 and the second contact seat 12 and the second contact block 13 do not abut, the sieve cylinder 2 is in the middle position at the top of the support frame 61. Thus, two forces can be applied to the sieve cylinder 2, so that the sieve cylinder 2 can perform multi-directional vibration sieving of silicon nitride powder, improving the vibration sieving effect of silicon nitride powder.

[0039] When the motor 52 rotates, the two second pulleys 17 are in a rotating state. This allows the first pulley 16 to drive the two threaded rods 81 to rotate synchronously under the connection of the adjacent belts 9. Because the contact port 14 can limit the movement trajectory of the threaded sleeve 82 by contacting the limiting sleeve 86, the threaded rod 81 rotates horizontally under the engagement of its internal thread and external thread structure. This causes the gear 85 and the movable shaft 84 to move horizontally. During this process, the gear 85 meshes with the adjacent rack 83, allowing the movable shaft 84 to rotate, thus driving... The adjacent stirring rod 87 rotates, allowing it to move horizontally with the threaded sleeve 82 while simultaneously making its own circular motion. This provides a wide-range stirring of the silicon nitride powder and pickling solution inside the pickling tank 1. The relatively small movable shaft 84 also contributes to the wide-range stirring within the pickling tank 1, preventing excessive space occupation by the movable shaft 84 and stirring rod 87 and ensuring full utilization of the tank's interior space. When the threaded sleeve 82 moves close to the adjacent shaft bracket 7, the output of the control motor 52 rotates in the opposite direction, causing the threaded sleeve 82 to move away from the adjacent shaft bracket 7, thus preventing collisions.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. An acid washing and purification device for silicon nitride powder, comprising an acid washing tank (1) and a sieve cylinder (2) disposed at the top of the acid washing tank (1), characterized in that: A first abutment block (11) is fixed at one end of the outer peripheral surface of the sieve cylinder (2). A first abutment seat (10) is attached to one end of the first abutment block (11). The bottom of the first abutment seat (10) is fixed to the top surface of the pickling tank (1). A second abutment block (13) is fixed at the other end of the outer peripheral surface of the sieve cylinder (2). A second abutment seat (12) is attached to the end of the second abutment block (13) away from the sieve cylinder (2). The bottom of the second abutment seat (12) is fixed to the top surface of the pickling tank (1). A drive assembly (5) is provided on one side of the top surface of the pickling tank (1). The drive assembly (5) includes a fixed base (51), the bottom of which is fixed to the surface of the top of the pickling tank (1). A motor (52) is installed on the side of the fixed base (51) away from the sieve cylinder (2). A rotating disk (53) is arranged sequentially on the side of the fixed base (51) close to the sieve cylinder (2). The output end of the motor (52) passes through the fixed base (51) and is fixed to the surface of the rotating disk (53). A connecting frame (54) is attached to one side of the rotating disk (53). A limiting shaft (55) is inserted through the surface of the connecting frame (54). The bottom of the limiting shaft (55) is fixed to the surface of the top of the pickling tank (1). An abutment groove (56) is opened on the surface of the connecting frame (54). A movable rod (57) is inserted into one end of the cavity of the abutment groove (56). One side of the movable rod (57) is fixed to the surface of the rotating disk (53). A support assembly (6) is provided on one side of the connecting frame (54). The support assembly (6) includes a support frame (61), one side of the connecting frame (54) is fixed to the surface of the support frame (61), and symmetrically distributed storage slots (62) are provided on both sides of the surface of the support frame (61). An embedded shaft (63) is fixed inside the storage slot (62), and a limiting sleeve (64) is slidably sleeved on both ends of the outer peripheral surface of the embedded shaft (63). The top of the limiting sleeve (64) is fixed to the bottom surface of the sieve cylinder (2). A spring (65) is sleeved on the outer peripheral surface of the embedded shaft (63) near the outer peripheral surface of the adjacent limiting sleeve (64). One end of the spring (65) is fixed to the surface of the adjacent limiting sleeve (64), and the other end of the spring (65) is fixed to one end of the inner wall of the adjacent storage slot (62). A connecting port (66) is provided through the middle position of the support frame (61). An inlet (15) is provided at the middle position of the top surface of the pickling tank (1). A filter layer (3) is fixed on the inner circumferential surface of the sieve cylinder (2). A discharge pipe (4) is fixedly connected to the bottom of the sieve cylinder (2). The bottom of the discharge pipe (4) passes through the connecting port (66) and the inlet (15) in sequence and extends to the inner cavity of the pickling tank (1). A contact port (14) is provided at both ends of the inlet (15) on the top surface of the pickling tank (1). A shaft frame (7) is fixed at both sides of the contact port (14) on the top surface of the pickling tank (1). A stirring assembly (8) is provided at the middle position of the two shaft frames (7).

2. The acid washing and purification apparatus for silicon nitride powder according to claim 1, characterized in that, The stirring assembly (8) includes a threaded rod (81). One side of the threaded rod (81) is rotatably connected to the surface of an adjacent shaft bracket (7). The other side of the threaded rod (81) passes through another shaft bracket (7) and extends to one side of the shaft bracket (7). A threaded sleeve (82) is threadedly connected to the middle position of the outer circumference of the threaded rod (81). A movable shaft (84) is rotatably connected to the bottom surface of the threaded sleeve (82). The bottom of the movable shaft (84) extends to the inner cavity of the pickling tank (1). Multiple stirring rods (87) are evenly fixed at both ends of the outer circumference of the movable shaft (84) located inside the pickling tank (1).

3. The acid washing and purification apparatus for silicon nitride powder according to claim 2, characterized in that, A gear (85) is fixedly fitted on the outer circumferential surface of the movable shaft (84) at the bottom position of the threaded sleeve (82). A rack (83) is meshed at one end of the gear (85), and the bottom of the rack (83) is fixed to the surface of the top of the pickling tank (1).

4. The acid washing and purification apparatus for silicon nitride powder according to claim 3, characterized in that, The outer peripheral surface of the threaded sleeve (82) is rotatably fitted with a limiting sleeve (86) on the outer peripheral surface of the bottom of the gear (85). The surfaces at both ends of the limiting sleeve (86) are in contact with the inner walls of the adjacent contact opening (14).

5. The acid washing and purification apparatus for silicon nitride powder according to claim 4, characterized in that, A first pulley (16) is fixedly sleeved on one side of the outer circumference of the threaded rod (81), and two second pulleys (17) are fixedly sleeved on the outer circumference of the output end of the motor (52). A connecting belt (9) is provided at the middle position between the first pulley (16) and the adjacent second pulley (17).

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