CN216045349U - Reduction gearbox of seat driver - Google Patents

Abstract

The application discloses reduction box of seat driver, its characterized in that: including box, worm wheel, cross ferryboat and worm, the worm wheel rotate along the fore-and-aft direction set up in the box, just the lead screw passes to the screw thread meshes in the worm wheel, cross the ferryboat rotate along the fore-and-aft direction set up in the box just be located the worm wheel top, the worm wheel with cross the ferryboat meshing, the worm rotate along the left and right sides direction set up in the box, the worm is suitable for connecting the motor. The height-increasing type has the advantages of compact structure, safety, reliability and low cost.

Description

Reduction gearbox of seat driver

Technical Field

The application relates to the field of automobile parts, in particular to a seat driver.

Background

A Horizontal Driver (HDM) of a vehicle seat is one of the key moving parts of a vehicle seat position adjustment system. The existing horizontal driver of the automobile seat generally comprises a reduction gearbox, a screw rod and a mounting seat, wherein the screw rod is installed on the mounting seat, a worm gear is arranged in the reduction gearbox, and the reduction gearbox is used for reducing the speed and then is matched with the screw rod to realize displacement. However, the prior horizontal driver of the automobile seat corresponds to one seat, so that the driving efficiency is not high, and in addition, the prior horizontal driver of the automobile seat has the defects and defects of large vibration, large size of installation bodies such as a seat motor and the like, more parts, complex structure, higher manufacturing cost, limited strength and the like.

Therefore, it is an urgent problem for those skilled in the art to improve the existing seat driver to overcome the above problems.

Disclosure of Invention

An object of this application is to provide a can install a plurality of reducing gear boxes, intensity is high, and spatial configuration is reasonable's extension strenghthened type seat driver.

Another object of the present application is to provide a reduction gearbox for a seat actuator that is of an elevated type, compact, safe, reliable and low cost.

In order to achieve the above purposes, the technical scheme adopted by the application is as follows: a lengthened reinforced seat driver comprises a screw rod, a mounting seat and a reduction gearbox, wherein the mounting seat is arranged at two ends of the screw rod, the reduction gearbox is movably arranged on the screw rod, the reduction gearbox comprises a box body, a worm wheel, a transition wheel and a worm, the worm wheel is rotatably arranged in the box body along the front-back direction, the screw rod penetrates through the worm wheel and is in threaded engagement with the worm wheel, the transition wheel is rotatably arranged in the box body along the front-back direction and is positioned above the worm wheel, the worm wheel is engaged with the transition wheel, the worm is rotatably arranged in the box body along the left-right direction, and the worm is suitable for being connected with a motor;

the outer side of the reduction gearbox is coated with an elastic cushion, the elastic cushion is of a U-shaped structure, and the elastic cushion is suitable for being clamped on the reduction gearbox along the vertical direction.

Preferably, the worm wheel and the transition wheel are meshed in a helical tooth fit manner, and the worm and the transition wheel are meshed in a staggered shaft helical gear transmission manner. It is well known in the field of mechanical design that worm gears cannot mesh perfectly; therefore, the worm wheel and the transition wheel are both helical gears in nature, can realize perfect meshing, have the advantages of good meshing performance, stable transmission and low noise, and meet the design requirement of a reduction gearbox; the meshing condition of the helical gears and the worm in the field of mechanical design is met between the transition wheel and the worm, and perfect meshing is achieved in a staggered shaft helical gear transmission mode (the staggered shaft helical gear transmission refers to the gear transmission between staggered shafts formed by two paired helical gears). It is worth mentioning that the working strength of the reduction gearbox in the seat driver is not high, and the matching structure and the engagement mode can completely meet the use requirements.

Aiming at the arrangement of the transition wheel, the box body of the scheme needs to be correspondingly improved and designed, and the scheme is as follows:

the box includes first cavity, second cavity and the third cavity of supreme arranging in proper order down from, the first cavity left and right sides has been seted up and has been run through the first shaft hole of box, the second cavity left and right sides has been seted up and has been located second shaft hole in the box, both sides have been seted up around the third cavity and have been run through the third shaft hole of box.

The worm wheel set up in the first cavity, the worm wheel includes first tooth portion and first axial region, be provided with the internal thread in the first axial region, the lead screw passes first axial region and threaded connection in the internal thread, first axial region rotate set up in the first axial hole.

The transition wheel is arranged in the second cavity and comprises a second tooth part and a second shaft part, and the second shaft part is rotatably arranged in the second shaft hole.

The worm set up in the third cavity, the worm includes third tooth portion and third axial region, third axial region rotate set up in the third axial region.

The first tooth portion meshes with the second tooth portion, and the second tooth portion meshes with the third tooth portion.

As a conventional arrangement, a shaft sleeve is further arranged in the first shaft hole, the first shaft part is rotatably arranged in the shaft sleeve, a gasket is further arranged on the first shaft part, and the gasket is positioned between the first tooth part and the shaft sleeve; the second shaft part is a cylindrical rotating shaft, and the second shaft part penetrates through and is clamped and fixed at the position of the circle center of the second tooth part. The arrangement of the shaft sleeve and the washer enables the reduction gearbox to operate more stably, the noise is lower, and the service life is longer.

As an improvement, a structural cavity is formed in the front end of the worm, a connecting piece is concentrically and fixedly arranged in the structural cavity, and the connecting piece is suitable for being connected with the motor through a flexible shaft. The arrangement of the structural cavity can ensure that the wall thickness of the worm is uniform, thereby being convenient for injection molding processing; and the arrangement that the structural cavity is filled with the connecting piece can also reduce the material cost.

Preferably, the structural cavity comprises a cylindrical hole and limiting grooves, the cylindrical hole is concentrically arranged on the worm along the front-back direction, the limiting grooves are arranged on the inner wall of the cylindrical hole, the cross sections of the limiting grooves are isosceles right triangles, the number of the limiting grooves is four or a multiple of four, and the limiting grooves are uniformly distributed along the circumferential direction; the connecting piece is the cuboid structure of transversal personally submitting the square, the connecting piece card is established and is fixed in four that are square distribution the spacing inslot, the four sides extrusion of connecting piece the right angle limit of spacing groove. The structure cavity and the connecting piece have the advantages of small processing difficulty, convenient installation and firm fixation; and the structure cavity of the structure can conveniently drive the worm to rotate and demould.

Preferably, the elastic cushion comprises a bottom cushion and side cushions which are integrally formed on the left side and the right side of the bottom cushion and extend upwards, abdicating holes for the screw rod to pass through are formed in the side cushions, and interference fit rings are convexly arranged on the peripheral sides of the abdicating holes; the side pads are also convexly provided with lower interference fit strips extending downwards from the interference fit ring to the two sides of the bottom pad and upper interference fit strips extending upwards from the interference fit ring to the top ends of the side pads; the interference fit ring, the lower interference fit strip and the upper interference fit strip are flush and are suitable for being pressed in the middle support in an interference mode. The protruding setting of interference fit ring, lower interference fit strip and last interference fit strip makes the cushion have the deformation space when receiving well support interference extrusion on the one hand, and on the other hand reduces with the area of contact of well support, and then reduces the frictional resistance that the reducing gear box installed in well support in-process.

As an improvement, a guide arc surface extending to the lower interference fit strip is arranged at the joint of the bottom pad and the side pad. The guide cambered surface has the installation guide effect, and the reduction gearbox coated with the elastic cushion is conveniently installed on the middle support.

The improved structure is characterized in that the front side and the rear side of the side pad are provided with covered edges extending inwards, and the covered edges are suitable for being tightly attached to the front side and the rear side of the reduction gearbox. The arrangement of borduring is used for increasing the parcel nature of cushion, avoids the cushion to break away from the reducing gear box, also further protects the reducing gear box.

Preferably, the screw rod is provided with a plurality of reduction boxes.

As various embodiments, a plurality of transition wheels are arranged between the worm wheel and the worm, and the transition wheels are sequentially arranged and meshed along the vertical direction. The number of transition wheels can be increased to adapt to a longer center distance.

The chinese utility model patent publication No. CN209650095U, a linear car seat horizontal driver, and the chinese utility model patent publication No. CN203211125U, a compact car seat horizontal driver, all disclose car seat horizontal drivers of similar structures, which are common seat horizontal driver structures on present fuel cars. With the market scale of new energy vehicles becoming larger and larger, certain changes need to be made to traditional vehicle parts for being more adaptive to part of unique structures of new energy vehicles. One of them structure difference of traditional fuel vehicle and new energy automobile lies in: in the traditional fuel vehicle, because of the existence of a structure such as a tail gas emission system and the like which needs to be arranged on a chassis, the floor of the chassis is difficult to be leveled, and more or less height drop exists; and the new energy automobile can be connected into a flat floor by only installing a storage battery in the chassis.

To the vehicle chassis floor of leveling the structure, this application has designed extension strenghthened type seat driver, can install a plurality of reducing gear boxes on a lead screw, is connected with solitary motor and seat on every reducing gear box, realizes a plurality of seats of mountable on the driver. In order to realize the above functions, the driver is mainly modified by the following two points:

(1) the screw rod is lengthened and thickened (the length is lengthened to 0.5-1.8 m, the diameter is thickened to 10-12 mm from the original 8mm or so) so as to meet the requirements of translation amount and strength.

(2) The reduction box is heightened to meet the requirement of space design. Specifically, because the front and rear seat structures are not identical, the installation positions and the installation modes of the motors have different possibilities, and enough installation space needs to be reserved for the motors; therefore, the reduction gearbox of the driver adopts the design of increasing the center distance (the center distance refers to the distance from the center of the worm wheel to the center of the worm) so as to meet the space design requirement (the center distance is more than 30mm in the design of the driver).

In the field of drive design, the center-to-center distance is generally increased by increasing the pitch circle diameter of the worm wheel and worm. However, the increase in diameter directly increases the overall size of the reduction gearbox, which on the one hand reduces the space utilization and on the other hand increases the manufacturing cost of the drive considerably. Therefore, the transition wheel is arranged between the worm wheel and the worm, the center distance is directly increased on the premise that the transmission ratio is not changed, the reduction gearbox is made to be high and thin, and the space design requirement is met.

It should be noted that, the present application only limits the specific structure of the driver, and does not limit the application scenario thereof. The driver is preferably applied to a new energy commercial vehicle with front, middle and rear seats, and is used for driving the horizontal displacement of the front seat and the middle seat. However, the structure that the screw rod of the driver is shortened and a single seat is installed is not excluded, and the driver with the structure is not excluded from being applied to any vehicle type except for a new energy commercial vehicle.

In addition, as can be seen from the two publications, the existing elastic cushion mostly adopts a split structure, and the elastic cushion with the structure has the problems of inconvenient installation and high cost; in addition, the in-process of installing the reducing gear box to well support, well support can interference extrusion cushion, can make the cushion produce the dislocation along upper and lower direction, and lead to cushion and lead screw to take place to interfere, influence driver normal use.

In order to overcome the problems, the elastic cushion of the integrated wrapping structure is adopted, so that the elastic cushion can be installed in place at one time, and the manufacturing cost is lower than that of a split type elastic cushion; in addition, the bottom of the elastic cushion (namely the bottom cushion) with the U-shaped structure can pull two side faces (namely the side cushions) of the elastic cushion, so that the elastic cushion is prevented from being misplaced in the vertical direction in the process of installing the reduction gearbox on the middle support, and the installation precision is improved.

To sum up, compare with prior art, the beneficial effect of this application lies in: the seat driver can be provided with a plurality of reduction boxes, and adopts a heightened reduction box to meet the increasingly changing automobile design requirements. In addition, the integral elastic cushion has the advantages of low cost, convenience in installation and high installation precision.

Drawings

FIG. 1 is a schematic perspective view of a preferred embodiment according to the present application;

FIG. 2 is a schematic view of the structure of the elastic pad separated according to a preferred embodiment of the present application;

FIG. 3 is an exploded view of a preferred embodiment according to the present application;

FIG. 4 is an exploded view of the reduction gearbox according to a preferred embodiment of the present application;

FIG. 5 is a top plan view of the reduction gearbox according to a preferred embodiment of the present application;

FIG. 6 is a cross-sectional view taken along the line A-A in FIG. 5, in accordance with a preferred embodiment of the present application;

FIG. 7 is a cross-sectional view taken along the line B-B in FIG. 5, in accordance with a preferred embodiment of the present application;

FIG. 8 is a front view of a worm according to a preferred embodiment of the present application;

FIG. 9 is a cross-sectional view taken along the direction C-C of FIG. 8 in accordance with a preferred embodiment of the present application;

FIG. 10 is a schematic perspective view of an elastic pad according to a preferred embodiment of the present application;

FIG. 11 is a schematic view of a fit with a mid-mount according to a preferred embodiment of the present application;

fig. 12 is a schematic structural view when a double reduction gearbox is installed according to a preferred embodiment of the present application.

In the figure: 100. a middle bracket; 1. a screw rod; 2. a mounting seat; 3. a reduction gearbox; 4. an elastic pad; 31. a box body; 32. a worm gear; 33. a transition wheel; 34. a worm; 310. a pin shaft; 311. a first chamber; 312. a second chamber; 313. a third chamber; 314. a first shaft hole; 315. a second shaft hole; 316. a third shaft hole; 317. a shaft sleeve; 318. a gasket; 321. a first tooth portion; 322. a first shaft portion; 323. an internal thread; 331. a second tooth portion; 332. a second shaft portion; 341. a third tooth portion; 342. a third shaft portion; 340. a structural cavity; 35. a connecting member; 3401. a cylindrical bore; 3402. a limiting groove; 41. a bottom pad; 42. a side pad; 43. a guiding cambered surface; 421. a hole of abdication; 422. interference fit ring; 423. a lower interference fit strip; 424. an upper interference fit strip; 425. and (6) edge covering.

Detailed Description

The present application is further described below with reference to specific embodiments, and it should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment.

In the description of the present application, it should be noted that, for the terms of orientation, such as "central", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., it indicates that the orientation and positional relationship shown in the drawings are based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, but does not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be construed as limiting the specific scope of protection of the present application.

It is noted that the terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

The terms "comprises," "comprising," and "having," and any variations thereof, in the description and claims of this application, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

As shown in fig. 1 and 2, a preferred embodiment of the present application includes a screw rod 1, a mounting seat 2 and a reduction gearbox 3, the mounting seat 2 is disposed at two ends of the screw rod 1, the reduction gearbox 3 is movably disposed on the screw rod 1, an elastic pad 4 is coated outside the reduction gearbox 3, the elastic pad 4 is in a U-shaped structure, and the elastic pad 4 is suitable for being clamped on the reduction gearbox 3 along the up-down direction. The concrete structure is as follows:

as shown in fig. 3, the reduction gearbox 3 in this embodiment includes a box 31, a worm wheel 32, a transition wheel 33 and a worm 34, the worm wheel 32 is rotatably disposed in the box 31 along the front-back direction, the lead screw 1 passes through and is engaged with the worm wheel 32 in a threaded manner, the transition wheel 33 is rotatably disposed in the box 31 along the front-back direction and is located above the worm wheel 32, the worm wheel 32 is engaged with the transition wheel 33, the worm 34 is rotatably disposed in the box 31 along the left-right direction, and the worm 34 is suitable for being connected with a motor; the box 31 is divided into a front and a rear halves and is fixedly connected by a pin 310. It should be mentioned that the worm wheel 32 and the transition wheel 33 are engaged in a helical tooth matching manner, the worm 34 and the transition wheel 33 are engaged in a staggered shaft helical gear transmission manner, in this embodiment, the worm wheel 32 and the transition wheel 33 are both helical gears in nature, perfect engagement can be realized, and the worm gear has the advantages of good engagement performance, stable transmission and low noise, and meets the design requirements of the reduction gearbox 3; and the transition wheel 33 and the worm 34 meet the meshing condition of the helical gear and the worm in the field of mechanical design, and perfect meshing can be realized. It should be noted that the parameters of the helical tooth matching are designed based on the common knowledge in the art, and therefore are not specifically described in the present embodiment, but this does not prevent the technical features from being implied in the present application.

As shown in fig. 4 to 7, for the addition of the transition wheel 33, the box 31 of the present embodiment needs to be designed correspondingly, specifically as follows:

the box 31 includes first cavity 311, second cavity 312 and third cavity 313 that from the bottom up arranges in proper order, and the first axle hole 314 that runs through box 31 is seted up to first cavity 311 left and right sides, and the second axle hole 315 that is located box 31 is seted up to the second cavity 312 left and right sides, and third axle hole 316 that runs through box 31 is seted up to both sides around the third cavity 313. The worm wheel 32 is disposed in the first cavity 311, the worm wheel 32 includes a first tooth portion 321 and a first shaft portion 322, an internal thread 323 is disposed in the first shaft portion 322, the lead screw 1 passes through the first shaft portion 322 and is screwed to the internal thread 323, and the first shaft portion 322 is rotatably disposed in the first shaft hole 314. The transition wheel 33 is disposed in the second chamber 312, the transition wheel 33 includes a second tooth portion 331 and a second shaft portion 332, and the second shaft portion 332 is rotatably disposed in the second shaft hole 315. The worm 34 is disposed in the third chamber 313, the worm 34 includes a third tooth portion 341 and a third shaft portion 342, and the third shaft portion 342 is rotatably disposed in the third shaft hole 316. The first tooth 321 meshes with the second tooth 331, and the second tooth 331 meshes with the third tooth 341. A shaft sleeve 317 is further arranged in the first shaft hole 314, the first shaft portion 322 is rotatably arranged in the shaft sleeve 317, a washer 318 is further arranged on the first shaft portion 322, and the washer 318 is located between the first tooth portion 321 and the shaft sleeve 317; the second shaft portion 332 is a cylindrical rotating shaft, and the second shaft portion 332 penetrates through and is clamped and fixed at the center of the second tooth portion 331.

In order to reduce the manufacturing cost while ensuring the strength, in the embodiment, the worm wheel 32 is made of a metal material (preferably, free cutting steel), the transition wheel 33 is made of plastic, and the worm 34 is also made of plastic. The worm 34 is relatively stressed, and the worm 34 of the embodiment is made of engineering plastics, namely Polyetheretherketone (PEEK); however, the cost of the polyetheretherketone material is high, so in this example, the front end of the worm 34 is provided with a structural cavity 340, a connecting member 35 made of a polyoxymethylene material is concentrically and fixedly arranged in the structural cavity 340, and the connecting member 35 is connected with the motor through a flexible shaft. As shown in fig. 8 and 9, in order to more conveniently and firmly mount the connecting member 35, the structural cavity 340 is provided with a cylindrical hole 3401 and limiting grooves 3402, the cylindrical hole 3401 is concentrically arranged on the worm 34 along the front-back direction, the limiting grooves 3402 are arranged on the inner wall of the cylindrical hole 3401, the cross section of each limiting groove 3402 is in the shape of an isosceles right triangle, and the number of the limiting grooves 3402 is eight and is uniformly distributed along the circumferential direction; the connecting piece 35 is a cuboid structure with a square cross section, the connecting piece 35 is clamped and fixed in four limiting grooves 3402 which are distributed in a square shape, and the four sides of the connecting piece 35 extrude the right-angle sides of the limiting grooves 3402.

As shown in fig. 10, the present embodiment further performs an optimized modification on the elastic pad 4, specifically as follows:

the elastic cushion 4 comprises a bottom cushion 41 and side cushions 42 which are integrally formed at the left side and the right side of the bottom cushion 41 and extend upwards, the side cushions 42 are provided with abdicating holes 421 for the screw rods 1 to pass through, and interference fit rings 422 are convexly arranged on the peripheral sides of the abdicating holes 421; the side pad 42 is also convexly provided with a lower interference fit strip 423 which extends downwards from the interference fit ring 422 to two sides of the bottom pad 41, and an upper interference fit strip 424 which extends upwards from the interference fit ring 422 to the top end of the side pad 42; the interference fit ring 422, the lower interference fit strip 423 and the upper interference fit strip 424 are flush and adapted to be interference compressed within the mid-support 100. In addition, a guide arc surface 43 extending to the lower interference-fit strip 423 is provided at a junction of the bottom pad 41 and the side pad 42. The front and rear sides of the side pad 42 are provided with covered edges 425 extending inwards, and the covered edges 425 are suitable for being tightly attached to the front and rear sides of the reduction gearbox 3. As shown in fig. 11, a structure diagram of the reduction box 3 when being mounted on the middle bracket 100 through the elastic pad 4 is shown, wherein the bottom pad 41 is arranged to prevent the side pad 42 from moving upwards and shifting when being mounted, and ensure that the abdicating hole 421 is aligned with the first shaft hole 314.

Fig. 12 shows a structure diagram of two reduction boxes 3 mounted on a single screw rod 1 in this embodiment, so as to show an expanded embodiment of this example.

It should also be noted that in the present embodiment, a plurality of transition wheels 34 are disposed between the worm wheel 32 and the worm 35, and the transition wheels 34 are sequentially meshed in an up-down direction. The number of transition wheels 34 is increased, so that the longer center distance can be adapted.

The foregoing has described the general principles, essential features, and advantages of the application. It will be understood by those skilled in the art that the present application is not limited to the embodiments described above, which are merely illustrative of the principles of the application, but that various changes and modifications may be made without departing from the spirit and scope of the application, and these changes and modifications are intended to be within the scope of the application as claimed. The scope of protection claimed by this application is defined by the following claims and their equivalents.

Claims (6)

1. A reduction box of a seat driver is characterized in that: including box, worm wheel, cross ferryboat and worm, the worm wheel along the fore-and-aft direction rotate set up in the box, and the lead screw passes to the screw thread meshes in the worm wheel, cross the ferryboat along the fore-and-aft direction rotate set up in the box and be located the worm wheel top, the worm wheel with cross the ferryboat meshing, the worm along the left and right sides direction rotate set up in the box, the worm is suitable for connecting the motor.

2. A reduction gearbox for a seat driver according to claim 1, characterised in that: the worm wheel is meshed with the transition wheel in a helical tooth matching mode, and the worm is meshed with the transition wheel in a staggered shaft helical gear transmission mode.

3. A reduction gearbox for a seat driver according to claim 2, characterised in that: the box body comprises a first cavity, a second cavity and a third cavity which are sequentially arranged from bottom to top, wherein the left side and the right side of the first cavity are provided with first shaft holes penetrating through the box body, the left side and the right side of the second cavity are provided with second shaft holes positioned in the box body, and the front side and the rear side of the third cavity are provided with third shaft holes penetrating through the box body;

the worm wheel is arranged in the first cavity and comprises a first tooth part and a first shaft part, an internal thread is arranged in the first shaft part, the screw rod penetrates through the first shaft part and is in threaded connection with the internal thread, and the first shaft part is rotatably arranged in the first shaft hole;

the transition wheel is arranged in the second cavity and comprises a second tooth part and a second shaft part, and the second shaft part is rotatably arranged in the second shaft hole;

the worm is arranged in the third chamber and comprises a third tooth part and a third shaft part, and the third shaft part is rotatably arranged in the third shaft hole;

the first tooth portion meshes with the second tooth portion, and the second tooth portion meshes with the third tooth portion.

4. A reduction gearbox for a seat driver according to claim 3, characterised in that: a shaft sleeve is further arranged in the first shaft hole, the first shaft part is rotatably arranged in the shaft sleeve, a gasket is further arranged on the first shaft part, and the gasket is located between the first tooth part and the shaft sleeve;

the second shaft part is a cylindrical rotating shaft, and the second shaft part penetrates through and is clamped and fixed at the position of the circle center of the second tooth part.

5. A reduction gearbox for a seat driver according to claim 1, characterised in that: the front end of the worm is provided with a structural cavity, a connecting piece is concentrically and fixedly arranged in the structural cavity, and the connecting piece is suitable for being connected with the motor through a flexible shaft.

6. A reduction gearbox for a seat driver according to claim 5, characterised in that: the structure cavity comprises a cylindrical hole and limiting grooves, the cylindrical hole is concentrically arranged on the worm along the front-back direction, the limiting grooves are arranged on the inner wall of the cylindrical hole, the cross sections of the limiting grooves are isosceles right triangle-shaped, the number of the limiting grooves is four or a multiple of four, and the limiting grooves are uniformly distributed along the circumferential direction;

the connecting piece is the cuboid structure of transversal personally submitting the square, the connecting piece card is established and is fixed in four that are square distribution the spacing inslot, the four sides extrusion of connecting piece the right angle limit of spacing groove.

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