CN211353154U

CN211353154U - Grass pushing machine

Info

Publication number: CN211353154U
Application number: CN201922141001.9U
Authority: CN
Inventors: 张薇; 关小东
Original assignee: Globe Jiangsu Co Ltd
Current assignee: Globe Jiangsu Co Ltd
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2020-08-28
Anticipated expiration: 2029-12-04

Abstract

The utility model provides a grass pusher, including drive assembly, striking protection subassembly, drive assembly and cutting assembly, striking protection subassembly includes transition fit's primary shaft bearing and secondary shaft bearing and is located elastic component and ball between primary shaft bearing and the secondary shaft bearing, be equipped with the jut on the primary shaft bearing, when drive assembly normal drive, the ball pushed by the elastic component to with the jut contact of primary shaft bearing, in order to drive assembly and cutting assembly rotate in step, work as when the resistance that cutting assembly received is greater than a definite value, the elastic component is passed on compression, ball and is crossed the jut, drive assembly with produce relative rotation between the drive assembly. Compared with the prior art, the utility model discloses a mower has striking protect function, protection drive assembly that can be better.

Description

Grass pushing machine

Technical Field

The utility model relates to a grass pusher belongs to garden instrument technical field.

Background

The cutters of the grass pushers on the market are basically single cutters. With the development of the market, in order to meet the requirements of consumers on the width of the mowing width, the blade of the grass pushing machine is changed from a single blade to a double blade, so that the width of the mowing width of the grass pushing machine is greatly increased, and the higher requirements of the consumers are met.

For the double-blade grass pushers, in order to avoid excessive noise in the gear transmission process, plastic gears are generally adopted to replace common metal gears. However, in the process of mowing, obstacles such as stones often appear on the lawn, when the cutter bar rotates at a high speed and collides with the obstacles, the cutter bar is stopped due to the reverse acting force of the obstacles, the reverse acting force is transmitted to the plastic gear through the cutter bar connecting shaft, the motor still runs at the moment, the moment is very large, the gears collide with each other, and the gear breaking and the whole machine cannot work normally.

In view of the above, there is a need for an improved conventional lawnmower to solve the above problems.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a grass mower, this grass mower have the striking protect function.

In order to realize the above object, the utility model provides a grass pusher, including drive assembly, striking protection subassembly, drive assembly and cutting assembly, striking protection subassembly includes transition fit's primary shaft bearing and secondary shaft bearing and is located elastic component and the ball between primary shaft bearing and the secondary shaft bearing, be equipped with the jut on the primary shaft bearing, when drive assembly normal drive, the ball push by the elastic component to with the jut contact of primary shaft bearing, in order to drive assembly and cutting assembly rotate in step, work as when the resistance that cutting assembly received is greater than a definite value, the elastic component is continued compression, the ball is crossed the jut, drive assembly with produce relative rotation between the drive assembly.

As a further improvement of the present invention, the first bearing seat is further provided with a sliding groove for the ball to slide, the sliding groove is annularly disposed and passes over the protrusion.

As a further improvement of the present invention, the driving assembly includes a motor and a motor shaft, the one end of the motor shaft is inserted into the first bearing seat, and a flat key is received in the first bearing seat, so that the motor shaft and the first bearing seat pass through the flat key to transmit the torque.

As a further improvement, the second bearing seat is provided with a boss, the elastic part and the ball are both accommodated in the boss, when the second bearing seat is sleeved on the first bearing seat, the ball contacts with the first bearing seat, the elastic part is limited to be accommodated between the boss and the ball.

As a further improvement, the striking protection subassembly is still including connecting drive assembly and cutting assembly's drive shaft and cover are established drive epaxial one-way bearing, when drive assembly normal drive, drive assembly drives drive shaft, one-way bearing and cutting assembly rotate in step, work as when the resistance that cutting assembly received is greater than a definite value, one-way bearing will the drive shaft lock is died.

As a further improvement of the present invention, the transmission assembly includes a first gear connected to the second bearing seat and a second gear engaged with the first gear, the cutting assembly includes a first blade connected to the second gear, the second gear and the first blade are connected to each other through a driving shaft and a one-way bearing.

As a further improvement of the present invention, the transmission assembly further includes a third gear and a fourth gear, the third gear respectively engages with the first gear and the fourth gear, the cutting assembly further includes a second blade connected to the fourth gear, the fourth gear and the second blade are also connected to the drive shaft and the one-way bearing.

As a further improvement, the circle centers of the first gear, the second gear, the third gear and the fourth gear are located the same straight line, the first blade with the second blade mutually perpendicular just rotates towards opposite direction in the coplanar.

As a further improvement, the transmission assembly is still including the gear box that is formed with accommodation space and being used for coveing the apron at accommodation space top, the gear box includes the diapire, upwards convex annular lateral wall and two bulges of stretching downwards from the double-phase opposite end of diapire from the diapire periphery, accommodation space forms between diapire and annular lateral wall, drive assembly fixes on the apron, two drive shafts are respectively to stretching downwards the bulge surpass the correspondence the bulge.

As a further improvement of the present invention, the first gear, the second gear, the third gear and the fourth gear are accommodated in the accommodating space, the second gear and the third gear are separately disposed on two opposite sides of the first gear, and the fourth gear is disposed on the first gear.

The utility model has the advantages that: the utility model discloses a grass pusher is through setting up elastic component and ball between primary shaft bearing and secondary shaft bearing, set up the jut simultaneously on primary shaft bearing, thereby when drive assembly normal drive, the ball is pushed to the jut contact with primary shaft bearing by the elastic component, can drive assembly and cutting assembly synchronous rotation, and when cutting assembly received the reaction force of external barrier and is greater than a definite value, the elastic component is continued the compression, the jut is crossed to the ball, make and produce relative rotation between drive assembly and the drive assembly, then can reach the purpose of protection drive assembly.

Drawings

Fig. 1 is a partial perspective view of the grass mower of the present invention.

Fig. 2 is a partially exploded view of fig. 1.

Fig. 3 is an exploded view of the impact protection assembly of fig. 2.

Fig. 4 is an exploded view of the transmission assembly of fig. 2.

Fig. 5 is another angular schematic of fig. 4.

Fig. 6 is an exploded view of the first blade bar of fig. 2.

Fig. 7 is an exploded view of the second blade bar of fig. 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

The utility model discloses a grass pusher (not shown), including the main part, from the push rod of backward extension on the main part rear direction and locate the walking wheel of main part bottom, the walking wheel is including dividing two preceding travelling wheels of establishing in main part front end both sides and dividing two back travelling wheels of establishing in main part rear end both sides to support the main part jointly and drive the walking of grass pusher. Because the push rod and the walking wheel can be designed according to the existing scheme, the structures of the push rod and the walking wheel are not described any more.

As shown in fig. 1 and 2, the main body is provided with a driving assembly 10, an impact protection assembly 20, a transmission assembly 30 and a cutting assembly 40, the driving assembly 10 is used for driving the transmission assembly 30 to rotate, and the transmission assembly 30 is connected with the cutting assembly 40, so that the transmission assembly 30 can drive the cutting assembly 40 to rotate when rotating, thereby realizing the cutting function.

The driving assembly 10 includes a motor 11 and a motor shaft 12, the motor shaft 12 protrudes beyond the bottom of the motor 11, and one end of the motor shaft 12 extends into the transmission assembly 30, so that when the motor 11 is started, the motor shaft 12 rotates and drives the transmission assembly 30 to rotate.

As shown in fig. 4 and 5, the transmission assembly 30 includes a first gear 31, a second gear 32, a third gear 33 and a fourth gear 34, which are horizontally disposed, centers of circles of the first gear 31, the second gear 32, the third gear 33 and the fourth gear 34 are located on the same straight line, and the first gear 31 is connected to the motor shaft 12 so as to rotate synchronously with the motor shaft 12 under the driving of the motor shaft 12.

The second gear 32 meshes with the first gear 31, and the third gear 33 meshes with the first gear 31 and the fourth gear 34, respectively, in other words, the second gear 32 and the third gear 33 are respectively arranged at two opposite sides of the first gear 31, and the fourth gear 34 is arranged away from the first gear 31. When the first gear 31 is driven by the motor shaft 12 to rotate, the second gear 32 and the third gear 33 can be driven to rotate synchronously, the fourth gear 34 is driven by the third gear 33 to rotate synchronously, but the rotation directions of the second gear 32 and the fourth gear 34 are opposite, that is, when the first gear 31 rotates clockwise, the second gear 32 rotates counterclockwise, and the fourth gear 34 rotates clockwise.

The transmission assembly 30 further includes a gear box 35 formed with an accommodating space 301, and a cover plate 36 for covering the top of the accommodating space 301, and the first gear 31, the second gear 32, the third gear 33, and the fourth gear 34 are all accommodated in the accommodating space 301. The gear box 35 includes a bottom wall 351, an annular side wall 352 protruding upwards from the periphery of the bottom wall 351, and two protruding portions 353 protruding downwards from two opposite ends of the bottom wall 351, the accommodating space 301 is formed between the bottom wall 351 and the annular side wall 352, the two protruding portions 353 are respectively provided with accommodating spaces 302 communicated with the accommodating space 301, and the accommodating spaces 302 penetrate through the corresponding protruding portions 353 downwards.

The bottom wall 351 of the gear box 35 is further provided with a convex column 303 and a through hole 304, wherein the convex column 303 is arranged in a blind hole shape and is used for being matched with the impact protection component 20 so as to limit the first gear 31 in the up-down direction; the through hole 304 is correspondingly arranged at the bottom of the third gear 33, the fixed shaft 37 is accommodated in the through hole 304 and locked with the bottom wall 351 of the gear box 35 through the screw 50, and the third gear 33 is rotationally fixed on the fixed shaft 37, so that the third gear 33 is ensured not to move freely in the gear box 35 and not to be separated from the gear box 35.

The periphery of the cover plate 36 and the annular side wall 352 of the gear case 35 are fixed by screws to seal the accommodating space 301, so that the first gear 31, the second gear 32, the third gear 33 and the fourth gear 34 can stably rotate in a certain space. The cover plate 36 is configured as a horizontal plate structure and is provided with a mounting hole 361 penetrating up and down, and the driving assembly 10 is fixed on the cover plate 36 and is fixedly connected with the cover plate 36 through the mounting hole 361. The motor shaft 12 passes downward through the mounting hole 361 and enters the inside of the accommodating space 301, and is connected to the first gear 31 to rotate the first gear 31.

As shown in fig. 3 in combination with fig. 2, the impact protection assembly 20 includes a first bearing seat 21 and a second bearing seat 22 that are in transition fit, and an elastic member 23 and a spherical ball 24 that are located between the first bearing seat 21 and the second bearing seat 22, where the first bearing seat 21 is provided with at least one protrusion 211, and when the driving assembly 10 is normally driven, the spherical ball 24 is pushed by the elastic member 23 to contact with the protrusion 211 of the first bearing seat 21, so as to drive the transmission assembly 30 and the cutting assembly 40 to rotate synchronously; when the cutting assembly 40 is subjected to a resistance greater than a certain value, the elastic member 23 is compressed continuously, the spherical ball 24 passes over the protrusion 211, and the transmission assembly 30 and the driving assembly 10 rotate relatively.

Specifically, the first bearing housing 21 includes a cylindrical body 210 and an extension 212 extending outward from an outer side wall of the body 210, and the extension 212 is annularly disposed and has a diameter larger than that of the body 210. The protrusion 211 is provided with three sliding grooves 213 uniformly distributed on the upper surface of the extension 212, the extension 212 is further provided with a sliding groove 213 for the ball 24 to slide, the sliding groove 213 is annularly disposed and passes over the protrusion 211, that is, the protrusion 211 is also provided with the sliding groove 213, so that the ball 24 can slide between two adjacent protrusions 211 along the sliding groove 213, and can also directly pass over the protrusion 211 along the sliding groove 213.

The body 210 has an inner cavity 214 and two grooves 215 formed by outwardly recessing the inner wall of the body 210, each groove 215 accommodates a flat key 216 therein, and one end of the motor shaft 12 is inserted into the inner cavity 214 and abuts against the two flat keys 216, so that torque can be transmitted between the motor shaft 12 and the first bearing housing 21 through the flat keys 216.

The second bearing housing 22 is disposed outside the main body 210 of the first bearing housing 21 and is engaged with the extension 212. The second bearing seat 22 is provided with a boss 221, the elastic member 23 and the spherical ball 24 are both accommodated in the boss 221, that is, when the second bearing seat 22 is sleeved on the first bearing seat 21, the spherical ball 24 contacts the sliding groove 213 on the first bearing seat 21 and at least part of the spherical ball 24 is accommodated in the boss 221, and the elastic member 23 is compressed and limited to be accommodated between the boss 221 and the spherical ball 24. In this embodiment, three bosses 221, three elastic members 23 and three round balls 24 are provided to correspond to the three protrusions 211, but the invention is not limited thereto.

The second bearing seat 22 and the first gear 31 are fixed by screw locking, and the first bearing seat 21 and the motor shaft 12 are fixed by two flat keys 216, so that the whole impact protection assembly 20 cannot fall down, and the stability is good.

As shown in fig. 2 and 4, in order to further protect the transmission assembly 30, a locking structure (as part of the impact protection assembly 20) is further added between the transmission assembly 30 and the cutting assembly 40, and the locking structure rotates in the opposite direction to the cutting assembly 40, so that when the cutting assembly 40 impacts a hard object, the locking structure is directly locked, and part of the instant impact force is transferred to the gear box 35, so that the impact on the transmission assembly 30 is reduced.

Specifically, the impact protection assembly 20 further includes a driving shaft 25 connecting the transmission assembly 30 and the cutting assembly 40, and a one-way bearing 26 sleeved on the driving shaft 25, when the driving assembly 10 is normally driven, the transmission assembly 30 drives the driving shaft 25, the one-way bearing 26 and the cutting assembly 40 to synchronously rotate, and when the resistance applied to the cutting assembly 40 is greater than a certain value, the one-way bearing 26 locks the driving shaft 25, so as to prevent the transmission assembly 30 from being affected by the instant impact force.

As shown in fig. 4 to 7 in combination with fig. 2, the cutting assembly 40 includes a first blade bar 41 connected to the second gear 32 and a second blade bar 42 connected to the fourth gear 34, and since the second gear 32 and the fourth gear 34 rotate in opposite directions, the first blade bar 41 and the second blade bar 42 rotate in opposite directions perpendicular to each other and in the same plane.

The first blade bar 41 comprises a first blade 411, a first fixed seat 412 located above the first blade 411 for limiting the first blade 411, a first gasket 413 located below the first blade 411, and a first nut 414 for locking and fixing the first gasket 413, the first blade 411 and the first fixed seat 412. The second blade bar 42 includes a second blade 421, a second fixing seat 422 located above the second blade 421 for limiting the second blade 421, a second gasket 423 located below the second blade 421, and a second nut 424 for locking and fixing the second gasket 423, the second blade 421, and the second fixing seat 422. The first blade 411 and the second blade 421 are both used for cutting grass blades, and the rotation speed of the first blade and the rotation speed of the second blade are the same, and the rotation directions of the first blade and the second blade are opposite.

Since the cutting assembly 40 includes the first blade bar 41 and the second blade bar 42, the two driving shafts 25 are correspondingly provided, namely a first driving shaft 251 connected between the second gear 32 and the first blade 411 and a second driving shaft 252 connected between the fourth gear 34 and the second blade 421; the two one-way bearings 26 are correspondingly provided, namely a first one-way bearing 261 sleeved on the first driving shaft 251 and a second one-way bearing 262 sleeved on the second driving shaft 252.

The first driving shaft 251 is accommodated in the accommodating space 302 of one of the protrusions 353 of the gear housing 35, and the top end thereof is fixedly connected with the second gear 32 through the bearing seat 271 and the end cover 272, and the bottom end thereof protrudes downwards beyond the protrusion 353 and passes through the first fixing seat 412 to be connected with the first blade 411, and finally passes through the first gasket 413 to be locked and fixed with the first nut 414, so as to lock and fix the first blade 411 and the first driving shaft 251. The first one-way bearing 261 is located at the lower end of the first driving shaft 251 and is disposed near the first fixing seat 412, and when the first driving shaft 251 is driven by the second gear 32 to rotate, the first blade bar 41 is driven to rotate integrally, so that the first blade 411 performs a cutting action.

The second driving shaft 252 is accommodated in the accommodating space 302 of the other protrusion 353 of the gear box 35, the top end of the second driving shaft is also fixedly connected with the fourth gear 34 through the bearing seat 271 and the end cover 272, the bottom end of the second driving shaft protrudes downwards to exceed the protrusion 353, the second driving shaft passes through the second fixing seat 422 to be connected with the second blade 421, and finally the second driving shaft is locked and fixed with the second nut 424 through the second gasket 423, so that the second blade 421 and the second driving shaft 252 are locked and fixed. The second one-way bearing 262 is located at the lower end of the second driving shaft 252 and disposed near the second fixing seat 422, and when the second driving shaft 252 is driven by the fourth gear 34 to rotate, the second driving shaft can drive the second blade 42 to rotate integrally, so that the second blade 421 performs a cutting operation.

When the driving assembly 10 is normally driven, firstly, the motor shaft 12 drives the first bearing seat 21 to rotate, when the first bearing seat 21 rotates until the spherical ball 24 contacts with the protrusion 211, the elastic member 23 is compressed, the axial force applied to the first gear 31 cannot continuously compress the elastic member 23, so that the spherical ball 24 cannot pass through the protrusion 211 on the first bearing seat 21, and at this time, the second bearing seat 22 and the first gear 31 rotate along with the first bearing seat 21; then, under the driving of the first gear 31, the second gear 32, the third gear 33 and the fourth gear 34 rotate synchronously; finally, the second gear 32 drives the first driving shaft 251 and the first one-way bearing 261 to rotate, the first blade 411 rotates smoothly, the fourth gear 34 drives the second driving shaft 252 and the second one-way bearing 262 to rotate, and the second blade 421 rotates smoothly, so that the first blade 411 and the second blade 421 can perform mowing actions simultaneously.

When the first blade 411 rotates at a high speed, if the first blade 411 collides with a hard object instantaneously, the first blade 411 may rapidly transmit the reverse axial force to the second gear 32, and the first gear 31 is simultaneously subjected to a large axial force, and instantaneously compresses the elastic element 23 continuously, and the spherical ball 24 passes over the protrusion 211 on the first bearing seat 21, so that no torque can be transmitted between the first bearing seat 21 and the second bearing seat 22, and the first gear 31 slips, i.e., the first bearing seat 21 and the second bearing seat 22 are unloaded, thereby protecting the first gear 31, the second gear 32, the third gear 33, and the fourth gear 34. In addition, the first blade 411 also transmits the received reverse axial force to the first driving shaft 251 and the first one-way bearing 261, and because the first one-way bearing 261 can only rotate in one direction, the first one-way bearing 261 locks the first driving shaft 251 under the action of a large axial force, and at the moment, part of the axial force is dispersed to the gear box 35, so that the instant impact force on the first gear 31, the second gear 32, the third gear 33 and the fourth gear 34 is small, and the first gear 31, the second gear 32, the third gear 33 and the fourth gear 34 are protected.

Similarly, when the second blade 421 rotates at a high speed, if it collides with a hard object instantaneously, the elastic member 23 and the spherical ball 24 can be used to unload the first bearing seat 21 and the second bearing seat 22; meanwhile, the second one-way bearing 262 may also be used to lock the second driving shaft 252, so that part of the instant impact force is dispersed to the gear box 35, and the instant impact force applied to the first gear 31, the second gear 32, the third gear 33 and the fourth gear 34 is small.

To sum up, the utility model, on one hand, arranges the elastic part 23 and the round ball 24 between the first bearing seat 21 and the second bearing seat 22, and at the same time arranges the protrusion 211 on the first bearing seat 21, so that when the driving component 10 is normally driven, the round ball 24 is pushed by the elastic part 23 to contact with the protrusion 211 of the first bearing seat 21, and then drives the transmission component 30 and the cutting component 40 to synchronously rotate; when the reacting force of the cutting assembly 40 by the external obstacle is larger than a certain value, the elastic member 23 is continuously compressed, and the round ball 24 passes over the protrusion 211, so that the transmission assembly 30 and the driving assembly 10 rotate relatively, unloading is realized, and the purpose of protecting the transmission assembly 30 is achieved.

On the other hand, the driving shaft 25 and the one-way bearing 26 sleeved on the driving shaft 25 are arranged between the transmission assembly 30 and the cutting assembly 40, so that when the driving assembly 10 is normally driven, the transmission assembly 30 drives the driving shaft 25, the one-way bearing 26 and the cutting assembly 40 to synchronously rotate; when the reaction force of the cutting assembly 40 from an external obstacle is greater than a certain value, the one-way bearing 26 locks the driving shaft 25, so that the transmission assembly 30 is prevented from being influenced by the instant impact force, and the purpose of protecting the transmission assembly 30 is achieved.

The above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. The utility model provides a grass pusher, includes drive assembly, striking protection component, drive assembly and cutting assembly, its characterized in that: the impact protection assembly comprises a first bearing seat and a second bearing seat in transition fit, and an elastic part and a round ball which are positioned between the first bearing seat and the second bearing seat, wherein a protruding part is arranged on the first bearing seat, and when the driving assembly is driven normally, the round ball is pushed by the elastic part to be in contact with the protruding part of the first bearing seat so as to drive the transmission assembly and the cutting assembly to rotate synchronously, when the resistance received by the cutting assembly is greater than a certain value, the elastic part is continuously compressed, and the round ball passes over the protruding part, and the transmission assembly and the driving assembly rotate relatively.

2. A lawnmower according to claim 1, wherein: the first bearing seat is further provided with a sliding groove for the ball to slide, and the sliding groove is annularly arranged and passes over the protruding portion.

3. A lawnmower according to claim 1, wherein: the driving assembly comprises a motor and a motor shaft, one end of the motor shaft is inserted into the first bearing seat, and a flat key is accommodated in the first bearing seat, so that the motor shaft and the first bearing seat can transmit torque through the flat key.

4. A lawnmower according to claim 1, wherein: the ball bearing is characterized in that a boss is arranged on the second bearing seat, the elastic piece and the ball are contained in the boss, when the second bearing seat is sleeved on the first bearing seat, the ball is in contact with the first bearing seat, and the elastic piece is contained between the boss and the ball in a limiting mode.

5. A lawnmower according to claim 1, wherein: the impact protection assembly further comprises a driving shaft and a one-way bearing, wherein the driving shaft is connected with the transmission assembly and the cutting assembly, the one-way bearing is arranged on the driving shaft in a sleeved mode, when the driving assembly is driven normally, the transmission assembly drives the driving shaft, the one-way bearing and the cutting assembly to rotate synchronously, and when resistance borne by the cutting assembly is larger than a certain value, the one-way bearing locks the driving shaft.

6. A lawnmower according to claim 5, wherein: the transmission assembly comprises a first gear connected with the second bearing seat and a second gear meshed with the first gear, the cutting assembly comprises a first cutter bar connected with the second gear, and the driving shaft and the one-way bearing are connected between the second gear and the first cutter bar.

7. A lawnmower according to claim 6, wherein: the transmission assembly further comprises a third gear and a fourth gear, the third gear is meshed with the first gear and the fourth gear respectively, the cutting assembly further comprises a second cutter bar connected with the fourth gear, and the driving shaft and the one-way bearing are also connected between the fourth gear and the second cutter bar.

8. A lawnmower according to claim 7, wherein: the circle centers of the first gear, the second gear, the third gear and the fourth gear are located on the same straight line, and the first cutter bar and the second cutter bar are perpendicular to each other and rotate in opposite directions in the same plane.

9. A lawnmower according to claim 7, wherein: the transmission assembly further comprises a gear box and a cover plate, wherein an accommodating space is formed in the gear box, the cover plate is used for covering the top of the accommodating space, the gear box comprises a bottom wall, an annular side wall protruding upwards from the periphery of the bottom wall and two protruding portions protruding downwards from two opposite ends of the bottom wall, the accommodating space is formed between the bottom wall and the annular side wall, the driving assembly is fixed on the cover plate, and two driving shafts respectively protrude downwards to exceed the corresponding protruding portions.

10. A lawnmower according to claim 9, wherein: the first gear, the second gear, the third gear and the fourth gear are accommodated in the accommodating space, the second gear and the third gear are respectively arranged on two opposite sides of the first gear, and the fourth gear is far away from the first gear.