WO2020040344A1

WO2020040344A1 - Folding door connector and folding door

Info

Publication number: WO2020040344A1
Application number: PCT/KR2018/011056
Authority: WO
Inventors: 이순우
Original assignee: 동국이엔지
Priority date: 2018-08-22
Filing date: 2018-09-19
Publication date: 2020-02-27
Also published as: KR102018555B1; CN111083929A; JP2020534453A

Abstract

Provided are: a folding door connector capable of precisely and smoothly guiding the folding of a first door and a second door; and a folding door including the folding door connector.

Description

Connector for folding door and folding door

The present invention relates to a folding door connector and a folding door.

In the general folding door, the connector connecting the first door and the second door to guide the folding does not properly guide the folding of the first door and the second door, and the user applies excessive force to the folding door. However, there is a problem that the door is not opened or closed because the connector is easily worn and the operating period is shortened or the connector is damaged.

The problem to be solved by the present invention is to provide a folding door connector that can guide the folding of the first door and the second door precisely and smoothly, and a folding door including the folding door connector.

Problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The folding door connector according to an aspect of the present invention for solving the above problems is a connector for connecting the first door and the second door that rotates with respect to one rotation axis, respectively, the first to support the first door 1 bracket; A second bracket for supporting the second door; A first gear disposed on one side of the first bracket; A second gear disposed on one side of the second bracket and engaged with the first gear; A third gear disposed on the other side of the first bracket; A fourth gear disposed on the other side of the second bracket and engaged with the third gear; A first shaft engaged with the first gear and the third gear; It may include a second shaft coupled to the second gear and the fourth gear.

Rotation of the first gear and the third gear may be linked by the first shaft, and rotation of the second gear and the fourth gear may be linked by the second shaft.

The first gear is disposed on the upper side of the first bracket, the second gear is disposed on the upper side of the second bracket, the third gear is disposed on the lower side of the first bracket, and the fourth gear is It is disposed below the second bracket, the first shaft and the second shaft may have an axis in the vertical direction.

The folding door connector may further include an upper cap member covering the first gear and the second gear, and a lower cap member covering the third gear and the fourth gear.

The folding door connector is disposed on a lower surface of the upper cap member to support the first shaft in an axial direction, and an upper first bearing to be disposed on a lower surface of the upper cap member to support the second shaft in an axial direction. An upper first bearing, a lower first bearing disposed on an upper surface of the lower cap member to support the first shaft in an axial direction, and an upper first bearing disposed on an upper surface of the lower cap member to support the second shaft in an axial direction. It may further include a lower second bearing.

The upper first bearing, the upper second bearing, the lower first bearing, and the lower second bearing may be thrust bearings.

The first bracket includes a first accommodating part for accommodating the first gear and the third gear, a first support part for supporting the first door in combination with the first door, and the second bracket includes: It may include a second accommodating portion for accommodating a second gear and the fourth gear and a second support portion for supporting the second door in combination with the second door.

The first gear includes a first gear portion and a first coupling portion, the second gear includes a second gear portion and a second coupling portion, and the third gear includes a third gear portion and a third coupling portion. The fourth gear may include a fourth gear part and a fourth coupling part, wherein the first gear part and the second gear part are engaged with each other, the third gear part and the fourth gear part are engaged with each other, and the first coupling part is engaged. The third and third coupling parts may be accommodated in the first accommodating part, and the second coupling part and the fourth coupling part may be accommodated in the second accommodating part.

The folding door connector includes an upper first packing member disposed between the first gear part, the second gear part, the first accommodating part, and the second accommodating part, the third gear part, and the fourth gear. And a lower second packing member disposed between the portion and the first accommodation portion and the second accommodation portion.

Folding door according to an aspect of the present invention for solving the above problems is a first door frame; A first door disposed on the first door frame to be rotatable about a first axis of rotation; A second door frame spaced apart from the first door frame; A second door disposed on the first door to be rotatable based on a second axis of rotation and spaced apart from the second door frame; A connector connecting between the first door and the second door and guiding the first door and the second door to rotate about the second rotation axis, wherein the connector includes the first door. Supporting first bracket; A second bracket for supporting the second door; A first gear disposed on one side of the first bracket; A second gear disposed on one side of the second bracket and engaged with the first gear; A third gear disposed on the other side of the first bracket; A fourth gear disposed on the other side of the second bracket and engaged with the third gear; A first shaft engaged with the first gear and the third gear; And a second shaft coupled to the second gear and the fourth gear, wherein the rotation of the first gear and the third gear are linked by the first shaft, and the second gear and the fourth gear Rotation may be linked by the second shaft.

In the present invention, the first gear and the third gear disposed on the first bracket (supporting the first door) is interlocked by the first shaft, the second gear and the second gear disposed on the second bracket (supporting the first door) Four gears are interlocked by the second shaft, the first gear and the second gear are meshed with each other, and the third gear and the fourth gear are meshed with each other.

Therefore, in the present invention, the first door and the second door are guided by four gears interlocked with each other. As a result, the present invention provides a connector for a folding door in which the folding of the first door and the second door can be guided precisely and smoothly. Furthermore, the present invention provides a folding door including the folding door connector.

Effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description.

1 is a perspective view showing a state in which the folding door of the present invention is closed.

2 and 3 are perspective views showing an open state of the folding door of the present invention.

Figure 4 is a perspective view showing a connector for a folding door of the present invention.

5 is an exploded perspective view showing a connector for a folding door of the present invention.

6 is a cross-sectional view taken along the line a-a 'of FIG. 4.

Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be embodied in various different forms, only the present embodiments are intended to complete the disclosure of the present invention, and those of ordinary skill in the art to which the present invention belongs. It is provided to fully inform the skilled person of the scope of the invention, which is defined only by the scope of the claims.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” does not exclude the presence or addition of one or more other components in addition to the mentioned components. Like reference numerals refer to like elements throughout, and "and / or" includes each and all combinations of one or more of the mentioned components. Although "first", "second", etc. are used to describe various components, these components are of course not limited by these terms. These terms are only used to distinguish one component from another. Therefore, of course, the first component mentioned below may be the second component within the technical spirit of the present invention.

Unless otherwise defined, all terms used in the present specification (including technical and scientific terms) may be used in a sense that can be commonly understood by those skilled in the art. In addition, terms that are defined in a commonly used dictionary are not ideally or excessively interpreted unless they are specifically defined clearly.

The spatially relative terms "below", "beneath", "lower", "above", "upper" and the like are shown in FIG. It can be used to easily describe a component and its correlation with other components. Spatially relative terms are to be understood as including terms in different directions of components in use or operation in addition to the directions shown in the figures. For example, when flipping a component shown in the drawing, a component described as "below" or "beneath" of another component may be placed "above" the other component. Can be. Thus, the exemplary term "below" can encompass both an orientation of above and below. Components may be oriented in other directions as well, so spatially relative terms may be interpreted according to orientation.

Hereinafter, the folding door 1000 of the present invention will be described with reference to the drawings. 1 is a perspective view showing a closed state of the folding door of the present invention, Figures 2 and 3 is a perspective view showing an open state of the folding door of the present invention, Figure 4 is a perspective view showing a connector for a folding door of the present invention 5 is an exploded perspective view illustrating the folding door connector of the present invention, and FIG. 6 is a cross-sectional view taken along the line a-a 'of FIG. 4.

Folding door 1000 of the present invention is the first door 100, the second door 200, the door grip 300, the first door frame 400, the second door frame 500 and the connector 600 It may include. The folding door 1000 of the present invention may have a closed state and an open state. In the state in which the folding door 1000 of the present invention is closed, the first door 100 and the second door 200 may be released. In the state in which the folding door 1000 of the present invention is opened, the first door 100 may be released. 100 and the second door 200 may be folded. Meanwhile, according to the user's selection, the second door 200 may be pulled to fold the first door 100 and the second door 200 (see FIG. 2), or the second door 200 may be pushed to push the first door 200. The 100 and the second door 200 may be folded (see FIG. 3).

The first door 100 may be rotatably coupled to the first door frame 400. In this case, the first door 100 may be rotated based on the first rotation shaft 1 formed in a substantially vertical direction in a state where the first door frame 400 is fixed.

The width of the second door 200 may be longer than the width of the first door 100. The second door 200 may be spaced apart from the second door frame 400. The second door 200 may be a door that is foldable to the first door 100. In this case, the first door 100 and the second door 200 may respectively rotate based on the second rotation shaft 2 formed in the vertical direction. As a result, the angle between the first door 100 and the second door 200 may be changed.

The first rotating shaft 1 and the second rotating shaft 2 may be perpendicular to the width of the first door 100 and may be spaced apart from each other in the width direction of the first door 100. In addition, the first rotation shaft 1 and the second rotation shaft 2 may be approximately positioned at one end portion in the width direction of the first door 100 and the other end portion in the width direction of the first door 200, respectively.

Meanwhile, the door grip 300 may be disposed in the second door 200, and the user may hold the second door while holding the door grip 300 in order to open or close the folding door 1000 of the present invention. An external force (eg, a rotation moment) may be applied to the 200.

As described above, in the folding door 1000 of the present invention, the first door 100 rotates with respect to the first rotating shaft 1, and the first door 100 and the second door 200 rotate with the second rotating shaft ( Each of the first door 100 and the second door 200 may be folded by rotating based on 2). In this case, the second door 200 may be spaced apart from the second door frame 500, and as a result, an open space may be formed between the second door 200 and the second door frame 500. On the other hand, in the modified example (not shown) of the present invention, the second door frame is omitted, and the third door is added, so that the second door may rotate based on the third door and the third rotation axis.

The connector 600 may be a member connecting the first door 100 and the second door 200. The connector 600 may guide rotation of the first door 100 and the second door 200 based on the second rotation shaft 2, respectively. Thus, connector 600 may be referred to as a "hinge."

The connector 600 includes a first bracket 610, a second bracket 620, a first gear 630, a second gear 640, a third gear 650, a fourth gear 660, and a first shaft. 670, a second shaft 680, an upper cap member 700, and a lower cap member 800 may be included.

The first bracket 610 and the second bracket 620 may be disposed adjacent to each other, the first bracket 610 may be coupled to the first door 100 to support the first door 100, The second bracket 620 may be coupled to the second door 200 to support the second door 200. As a result, the first bracket 610 may rotate with respect to the second rotation shaft 2 together with the first door 100, and the second bracket 620 may be rotated together with the second door 200. It can rotate based on (2).

The first bracket 610 may include a first accommodating part 611 and a first support part 612, and the first gear 630 and the first accommodating part 611 of the first bracket 610 are formed. The three gears 650 may be accommodated, and an upper cap 710 may be disposed above the first accommodating part 611 of the first bracket 610, and the first accommodating part of the first bracket 610 may be disposed. The lower cap 750 may be disposed below the 611. The first door 100 may be coupled to the first support part 612 of the first bracket 610. As a result, the first bracket 610 may support the first door 100.

The second bracket 620 may include a second accommodating part 621 and a second support part 622, and the second gear 640 and the second accommodating part 621 of the second bracket 620 are formed on the second bracket 620. Four gears 660 may be accommodated, and an upper cap 710 may be disposed above the second accommodating portion 621 of the second bracket 620, and the second accommodating portion of the second bracket 620 may be disposed. The lower cap 750 may be disposed below the 621. The first door 100 may be coupled to the second support part 622 of the second bracket 620, and as a result, the second bracket 620 may support the first door 100.

The first gear 630, the second gear 640, the third gear 650, and the fourth gear 660 may be spur gears. The first gear 630 and the third gear 650 may be disposed on the first bracket 610, the second gear 640 and the fourth gear 660 may be disposed on the second bracket 620. have. The first gear 630 and the third gear 650 may be combined with the first shaft 670, and the rotation of the first gear 630 and the third gear 650 may be performed by the first shaft 670. It can be interlocked. The rotation of the second gear 640 and the fourth gear 660 may be linked by the second shaft 680. In addition, the first gear 630 and the second gear 640 may be engaged in a gear ratio of 1: 1, and the third gear 650 and the fourth gear 660 may be engaged in a gear ratio of 1: 1. have.

As a result, when the first door 100 and the second door 200 rotate with respect to the second rotation shaft 2, respectively, the first gear 630 and the second gear 640 mesh with each other to rotate. The gear 650 and the fourth gear 660 mesh with each other to rotate, the first gear 630 and the third gear 650 interlock with each other, and the second gear 640 and the fourth gear 660 interlock with each other. Rotation of the door 100 and the second door 200 can be accurately guided (four gears interlocked). In addition, the first door 100 and the second door 200 may rotate at the same rotation angle (gear ratio).

The first gear 630 may include a first gear portion 631 and the first coupling portion 632, the first gear portion 631 of the first gear 630 is a portion where the gear teeth are formed. The first coupling part 632 of the first gear 630 may be a part accommodated in the first accommodating part 611 of the first bracket 610.

The second gear 640 may include a second gear part 641 and a second coupling part 642, and the second gear part 641 of the second gear 640 is a part where the gear teeth are formed. The second coupling portion 642 of the second gear 640 may be a portion accommodated in the second accommodation portion 621 of the second bracket 620.

The third gear 650 may include a third gear part 651 and a third coupling part 652, and the third gear part 651 of the third gear 650 is a part where the gear teeth are formed. The third coupling part 652 of the third gear 650 may be a part accommodated in the first accommodating part 611 of the first bracket 610.

The fourth gear 660 may include a fourth gear part 661 and a fourth coupling part 662, and the fourth gear part 661 of the fourth gear 660 is a part where the gear teeth are formed. The fourth coupling part 662 of the fourth gear 660 may be a portion accommodated in the second accommodation part 621 of the second bracket 620.

In order to accommodate the first coupling part 632 of the first gear 630 and the third coupling part 652 of the third gear 650 in the first accommodating part 611 of the first bracket 610. The hollow space may be formed in the vertical direction. In this case, the first coupling part 632 of the first gear 630 may be located above the space inside the first accommodation part 611 of the first bracket 610, the third gear 650 The third coupling part 652 of the first bracket 610 may be located in the lower portion of the space inside.

Similarly, the second coupling part 642 of the second gear 640 and the fourth coupling part 662 of the fourth gear 660 are accommodated in the second accommodation part 621 of the first bracket 620. To this end, hollow spaces may be formed in the vertical direction. In this case, the second coupling portion 642 of the second gear 640 may be located in the upper portion of the space inside the second accommodation portion 621 of the second bracket 620, the fourth gear 660 The fourth coupling part 662 of the second bracket 620 may be located in the lower portion of the space inside the second bracket 620.

The first shaft 670 extends in the vertical direction (up and down direction) (having an axis in the vertical direction) so that the upper portion may be coupled to the first gear 630 and the lower portion may be coupled to the third gear 650. Can be. In addition, the upper end of the first shaft 670 may be supported by the upper first bearing 720, and the lower end of the first shaft 670 may be supported by the lower first bearing 820.

The second shaft 680 may extend in the vertical direction (up and down direction) (having an axis in the vertical direction) such that an upper portion may be coupled to the second gear 640, and a lower portion may be coupled to the fourth gear 660. Can be. In addition, the upper end of the second shaft 680 may be supported by the upper second bearing 730, and the lower end of the second shaft 680 may be supported by the lower second bearing 830.

The upper cap member 700 may be disposed above the first bracket 610 and the second bracket 620. The upper cap member 700 may cover the first gear 630 and the second gear 640, like the case of the gear box. In addition, a bearing is provided on the upper cap member 700 to support the upper ends of the first shaft 670 and the second shaft 680 to be rotatable.

The upper cap member 700 includes an upper cover 710, an upper first bearing 720, an upper second bearing 730, an upper first packing member 740, an upper 2-1 packing member 750, and an upper side. The second-second packing member 760 may be included.

The upper cover 710 may cover the first gear 630 and the second gear 640. In addition, an upper first bearing 720 and an upper second bearing 730 may be fixedly disposed on a lower surface of the upper cover 710.

The upper first bearing 720 may be a thrust bearing in which a load is applied in the axial direction of the first shaft 670 (supporting the first shaft in the axial direction). The outer ring of the upper first bearing 720 may be fixed to the lower surface of the upper cover 710, and the inner ring of the upper first bearing 720 may be combined with the upper end of the first shaft 670.

The upper second bearing 730 may be a thrust bearing, in which a load is applied in the axial direction of the second shaft 680 (supporting the second shaft in the axial direction). The outer ring of the upper second bearing 730 may be fixed to the lower surface of the upper cover 710, and the inner ring of the upper second bearing 730 may be combined with the upper end of the second shaft 680.

The upper first packing member 740 may be disposed between the first gear 630 and the first bracket 610 and between the second gear 640 and the second bracket 620. More specifically, the upper first packing member 740 is the first coupling portion 632 of the first gear 630 and the second coupling portion 642 and the first bracket 610 of the second gear 640. It may be disposed between the first accommodating portion 611 and the second accommodating portion 621 of the second bracket 620. In addition, a first opening and a second opening may be formed adjacent to the upper first packing member 740. When assembling the connector 600 of the present invention, the first coupling part 632 of the first gear 630 passes through the first opening of the upper first packing member 740 to allow the first bracket 610 to be first. The second coupling part 642 of the second gear 640 may pass through the second opening of the upper first packing member 740 and may be positioned at an upper portion of the space inside the accommodating part 611. It may be located in the upper portion of the interior of the second accommodating portion 621 of 620. Therefore, the upper first packing member 740 may prevent the first bracket 610 and the second bracket 620 from being worn by the rotation of the first gear 630 and the second gear 640.

The upper 2-1 packing member 750 may be disposed between the first gear 630 and the first shaft 670. The upper 2-1 packing member 750 may perform a function of strengthening the coupling force by bringing the first gear 630 into close contact with the first shaft 670.

The upper second-second packing member 760 may be disposed between the second gear 640 and the second shaft 680. The upper second-two packing member 760 may perform a function of strengthening the coupling force by bringing the second gear 640 and the second shaft 680 into close contact with each other.

The lower cap member 800 may be disposed below the first bracket 610 and the second bracket 620. The lower cap member 800 may cover the third gear 650 and the fourth gear 660, like the case of the gear box. In addition, a bearing is provided in the lower cap member 800 to support the lower ends of the first shaft 670 and the second shaft 680 so as to be rotatable.

The lower cap member 800 includes a lower cover 810, a lower first bearing 820, a lower second bearing 830, a lower first packing member 840, a lower 2-1 packing member 850, and a lower side. The second-second packing member 860 may be included.

The lower cover 810 may cover the third gear 650 and the fourth gear 660. In addition, a lower first bearing 820 and a lower second bearing 830 may be fixedly disposed on an upper surface of the lower cover 810.

The lower first bearing 820 may be a thrust bearing in which a load is applied in the axial direction of the first shaft 670 (supporting the first shaft in the axial direction). The outer ring of the lower first bearing 820 may be fixed to the upper surface of the lower cover 810, and the inner ring of the lower first bearing 820 may be combined with the lower end of the first shaft 670.

The lower second bearing 830 may be a thrust bearing, in which a load is applied in the axial direction of the second shaft 680 (supporting the second shaft in the axial direction). The outer ring of the lower second bearing 830 may be fixed to the upper surface of the lower cover 710, and the inner ring of the lower second bearing 830 may be combined with the lower end of the second shaft 680.

The lower first packing member 840 may be disposed between the third gear 650 and the first bracket 610 and between the fourth gear 660 and the second bracket 620. More specifically, the lower first packing member 840 includes the third coupling part 652 of the third gear 650 and the fourth coupling part 662 and the first bracket 610 of the fourth gear 660. It may be disposed between the first accommodating portion 611 and the second accommodating portion 621 of the second bracket 620. In addition, a third opening and a fourth opening may be formed adjacent to the lower first packing member 840. When assembling the connector 600 of the present invention, the third coupling part 652 of the third gear 650 passes through the third opening of the lower first packing member 840 to allow the first bracket 610 to be first. The fourth coupling part 662 of the fourth gear 660 may pass through the fourth opening of the lower first packing member 740 to be positioned at a lower portion of the space inside the accommodating part 611. It may be located in the lower portion of the interior of the second accommodating portion 621 of 620. Therefore, the lower first packing member 840 may prevent the first bracket 610 and the second bracket 620 from being worn by the rotation of the third gear 650 and the fourth gear 660.

The lower 2-1 packing member 850 may be disposed between the third gear 650 and the first shaft 670. The lower 2-1 packing member 850 may perform a function of strengthening the coupling force by bringing the third gear 650 into close contact with the first shaft 670.

The lower second-second packing member 860 may be disposed between the fourth gear 660 and the second shaft 680. The lower second-second packing member 860 may function to close the fourth gear 660 and the second shaft 680 to strengthen the coupling force.

In the above, embodiments of the present invention have been described with reference to the accompanying drawings, but those skilled in the art to which the present invention pertains may realize the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims

In the connector for connecting the first door and the second door rotated on the basis of one rotation axis,

A first bracket supporting the first door;

A second bracket for supporting the second door;

A first gear disposed on one side of the first bracket;

A second gear disposed on one side of the second bracket and engaged with the first gear;

A third gear disposed on the other side of the first bracket;

A fourth gear disposed on the other side of the second bracket and engaged with the third gear;

A first shaft engaged with the first gear and the third gear; And

And a second shaft coupled to the second gear and the fourth gear.
The method of claim 1,

The rotation of the first gear and the third gear is interlocked by the first shaft, the rotation of the second gear and the fourth gear is interlocked by the second shaft.
The method of claim 1,

The first gear is disposed on the upper side of the first bracket, the second gear is disposed on the upper side of the second bracket, the third gear is disposed on the lower side of the first bracket, and the fourth gear is A connector for a folding door disposed below the second bracket, wherein the first shaft and the second shaft have an axis in a vertical direction.
The method of claim 3,

The folding door connector further includes an upper cap member covering the first gear and the second gear, and a lower cap member covering the third gear and the fourth gear. .
The method of claim 4, wherein

The folding door connector is disposed on a lower surface of the upper cap member to support the first shaft in an axial direction, and an upper first bearing to be disposed on a lower surface of the upper cap member to support the second shaft in an axial direction. An upper first bearing, a lower first bearing disposed on an upper surface of the lower cap member to support the first shaft in an axial direction, and an upper first bearing disposed on an upper surface of the lower cap member to support the second shaft in an axial direction. A connector for a folding door further comprising a lower second bearing.
The method of claim 5,

The upper first bearing, the upper second bearing, the lower first bearing and the lower second bearing are thrust bearings.
The method of claim 1,

The first bracket includes a first accommodating part for accommodating the first gear and the third gear, and a first support part for supporting the first door in combination with the first door.

The second bracket includes a second accommodating part for accommodating the second gear and the fourth gear and a second support part for engaging with the second door to support the second door.
The method of claim 7, wherein

The first gear includes a first gear portion and a first coupling portion, the second gear includes a second gear portion and a second coupling portion, and the third gear includes a third gear portion and a third coupling portion. The fourth gear includes a fourth gear portion and a fourth coupling portion.

The first gear portion and the second gear portion mesh with each other, the third gear portion and the fourth gear portion mesh with each other,

And the first coupling part and the third coupling part are accommodated in the first accommodating part, and the second coupling part and the fourth coupling part are accommodated in the second accommodating part.
The method of claim 8,

The folding door connector includes an upper first packing member disposed between the first gear part, the second gear part, the first accommodating part, and the second accommodating part, the third gear part, and the fourth gear. And a lower second packing member disposed between the portion and the first accommodation portion and the second accommodation portion.
A first door frame;

A first door disposed on the first door frame to be rotatable about a first axis of rotation;

A second door frame spaced apart from the first door frame;

A second door disposed on the first door to be rotatable based on a second axis of rotation and spaced apart from the second door frame; And

A connector connecting between the first door and the second door and guiding the first door and the second door to rotate with respect to the second rotation axis,

The connector,

A first bracket supporting the first door;

A second bracket for supporting the second door;

A first gear disposed on one side of the first bracket;

A second gear disposed on one side of the second bracket and engaged with the first gear;

A third gear disposed on the other side of the first bracket;

A fourth gear disposed on the other side of the second bracket and engaged with the third gear;

A first shaft engaged with the first gear and the third gear; And

A second shaft coupled to the second gear and the fourth gear,

The rotation of the first gear and the third gear is interlocked by the first shaft, the rotation of the second gear and the fourth gear is interlocked by the second shaft.