WO2017219626A1

WO2017219626A1 - Elastic contact member for intelligent plug board

Info

Publication number: WO2017219626A1
Application number: PCT/CN2016/110387
Authority: WO
Inventors: 何伟; 黎建平
Original assignee: 广东百事泰电子商务股份有限公司
Priority date: 2016-06-22
Filing date: 2016-12-16
Publication date: 2017-12-28
Also published as: CN105932483B; CN105932483A

Abstract

An elastic contact member for an intelligent plug board comprises an electrically-conductive connection member (10) and a socket (20). The electrically-conductive connection member (10) is disposed transversely, and has a front end surface and a rear end surface. The socket (20) comprises: a fixing frame (201) having a top opening and connected with an upper edge of the electrically-conductive connection member (10); and multiple elastic engagement members (202) vertically and securely disposed inside the fixing frame (201). The multiple elastic engagement members (202) form a circular enclosing structure for securing a plug pin. The fixing frame (201) exhibits favorable position-limiting performance. When a plug pin is inserted into the enclosing structure, the multiple elastic engagement members (202) are limited in the fixing frame (201), such that displacement resulting from deformation caused by squeezing does not occur. When the plug pin is inserted into the enclosing structure, the plug pin is in contact with all elastic engagement members. A large contact area ensures favorable contact, reduces current resistance, enhances conductivity, and saves energy.

Description

Contact shrapnel for smart plug

Technical field

The present invention relates to the field of plugging technology, and in particular to a contact spring for smart plugging.

Background technique

In the prior art, a common socket includes a housing, a live contact spring piece with a live wire insertion seat for connecting a live wire, and a neutral wire insertion seat for connecting the neutral wire. The neutral contact spring piece, the ground wire contact spring piece with the ground wire insertion seat for connecting the ground wire, and the socket disposed outside the casing opposite to the corresponding insertion seat.

Although the plugging of such a structure has been widely used, it still has certain defects and deficiencies.

Specifically, on the one hand, the structure of the insertion seat provided on the corresponding contact elastic piece is generally simple and does not have good clamping elasticity, and after inserting and removing the plug pin multiple times in the corresponding insertion seat, correspondingly The insertion seat is easily deformed and displaced, and the locking elasticity is easily lost, so that the plug pins that need to be inserted are not well clamped, so that the inserted plug pins are easily deformed due to the loose deformation of the corresponding insertion seat. Loose, on the other hand, when the plug pins that need to be inserted are not well clamped, there must be a bad contact between the corresponding plug and the corresponding plug pins, so that the corresponding plug pins cannot be very Good power-on, so that it will cause power hazards and other hidden dangers during the power-on process.

Therefore, in view of the above-mentioned status quo, it is very necessary to improve and optimize the existing contact elastic sheets for intelligent row insertion.

Summary of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide a contact spring for smart insertion that overcomes the deficiencies of the prior art described above.

The technical solution adopted by the present invention to solve the prior art problem is: a contact elastic piece for intelligent plugging, characterized in that it comprises a conductive connecting piece and a plug piece integrally formed with the conductive connecting piece for inserting a plug pin Plug-in seat; among them,

The conductive connecting piece is disposed laterally, and the conductive connecting piece has a front end surface and a rear end surface;

The insertion base includes a fixed frame formed to be open at an upper end connected to an upper edge of the conductive connecting piece, and a plurality of cards integrally formed in the fixing frame and integrally formed with the fixing frame The solid elastic piece is surrounded by a plurality of the locking elastic pieces so as to be formed into a surrounding structure for fastening the plug pins.

The above technical solutions are further elaborated below:

Preferably, the upper ends of the plurality of the fastening elastic pieces are inclined inwardly so that the upper port diameter of the formed enclosure structure is smaller than the lower port diameter thereof, and the upper ends of the plurality of the fastening elastic pieces are exposed to the fixing Outside the frame, and folded outward to form Open petals.

Preferably, the fixing frame is formed into a transverse U-shaped structure, and includes a first fixing piece, a second fixing piece and a third fixing piece which are sequentially connected; wherein

a lower edge of the second fixing piece is integrally connected with an upper edge of the conductive connecting piece, a width of the first fixing piece is equal to a width of the third fixing piece, and the first fixing piece is Both the width and the width of the third fixing piece are set to W1.

Preferably, the fastening elastic piece is provided with 2N, wherein N is a positive integer greater than 1, and the width of each of the fastening elastic pieces is set to W2.

Preferably, the lower ends of the inner side walls of the N fastening elastic pieces are sequentially connected so that the N fastening elastic pieces are formed as the first surrounding parts; and the lower ends of the inner side walls of the N fastening pieces are sequentially connected to make another The N locking elastic pieces are formed as a second surrounding portion; the position of the first surrounding portion is opposite to the position of the second surrounding portion to form the surrounding structure.

Preferably, the contact elastic piece for intelligent row insertion according to claim 5 is characterized in that:

In the N pieces of the elastic sheets in which the first surrounding portion is formed, the lower end of the outer side wall of the one of the first surrounding portions is connected to the outer side wall of the first fixing piece;

In the other N pieces of the elastic pieces forming the second surrounding portion, the lower end of the outer side wall of the reinforcing elastic piece on one side of the second surrounding portion is connected to the outer side wall of the third fixing piece;

An outer side wall of the elastic elastic piece on the other side of the first surrounding portion abuts against an outer side wall of the elastic elastic piece on the other side of the second surrounding portion.

Preferably, the insertion seat is provided with a plurality of the insertion seats uniformly fixed to the upper edge of the conductive connecting piece.

Preferably, the width of the conductive connecting piece between two adjacent insertion seats is set to W3;

Among them, W3 ≥ 2W1 + 4W2.

Preferably, the conductive connecting piece is uniformly bent and formed into a square wave type structure or an approximately square wave type structure so that the conductive connecting piece is composed of a plurality of sections of the front connecting piece and the rear connecting piece which are staggeredly connected. One of the insertion seats is respectively fixed in a middle portion of the upper edge of each of the rear connecting pieces, and the open ends of the fixing frames of the U-shaped structure of each of the insertion seats are respectively directed toward the front of the corresponding rear connecting piece .

Preferably, the vertical distance between any one of the front connecting pieces and the rear connecting piece adjacent thereto is equal to W1.

The beneficial effects of the invention are:

A contact spring piece for intelligent plugging provided by the present invention, in the specific implementation, because the insertion seat includes An upper end connected to the upper edge of the conductive connecting piece is formed as an open fixing frame and a plurality of locking elastic pieces vertically formed in the fixing frame and integrally formed with the fixing frame, and a plurality of The fastening elastic piece is encased so as to be formed into a surrounding structure for fastening the plug pin. Thus, on the one hand, when the invention is fixed to the corresponding row of the inserted casing, the added fixing frame is just right. It is placed in the slot on the corresponding plug-in housing, and is fixed by the corresponding slot, so that it can play a good limit function, and the enclosing of a plurality of the said elastic shrapnel When the plug pins are inserted into the structure, the plurality of the latching elastic pieces are always restrained in the fixed frame regardless of how they are squeezed, so that they are not displaced by the deformation, and the corresponding plug pins are on the other hand. When the plurality of the locking elastic members are inserted into the surrounding structure, the corresponding plug pins are in contact with the plurality of the locking elastic pieces, and the contact area is large, so that the contact is good, and the contact can be reduced. Current resistance and good electrical conductivity make Better energy saving, therefore, the present invention is practical, and good results.

Secondly, in the technical solution of the present invention, since the upper ends of the plurality of the fastening elastic pieces are inclined inwardly, the upper port diameter of the formed surrounding structure is smaller than the lower port diameter thereof, and the plurality of the fastenings are The upper ends of the elastic sheets are exposed outside the fixing frame, and are respectively folded outward to form an open petal shape. Thus, on the one hand, the upper port diameter of the formed surrounding structure is smaller than the diameter of the lower port, so that the corresponding clamping can be increased. The elasticity of the elastic piece, when the plug pin is inserted into the enclosed enclosure structure, the upper end of the plurality of the fastening elastic pieces can be strengthened in the outward pressing force, and then the plurality of the fastening elastic pieces are caused Both of them can give a corresponding reaction force to the corresponding plug pins, so that the interference performance with the corresponding plug pins is good. On the other hand, the upper ends of the plurality of the latching elastic pieces are respectively folded outward to form an open petal shape, which also makes The insertion and extraction of the plug pins are facilitated, so that the use effect of the present invention can be effectively improved.

In the embodiment of the present invention, the fixing frame of the insertion seat and the elastic elastic piece and the conductive connecting piece are integrally formed, and there is no solder joint between them, so that the manufacturing process is excellent, and The width of the first fixing piece and the width of the third fixing piece are both set to W1, and the width of each of the locking elastic pieces is set to W2, between the two adjacent insertion seats. The width of the conductive connecting piece is set to W3, and W3≥2W1+4W2, so that the requirements of the fixing frame, the locking elastic piece and the conductive connecting piece are integrally formed, and at the same time, the conductive connecting piece passes through the front and rear. Multiple times of uniform bending and shaping into a square wave structure or an approximately square wave structure, which in turn makes it possible to greatly reduce the distance between two adjacent insertion seats, making the structure of the present invention more compact, which in turn It can satisfy the layout of more plug insertion and placement positions on the same row of plugs, so that the use effect of the present invention can be optimized.

DRAWINGS

Figure 1 is a front elevational view of a contact elastic piece for intelligent insertion of the present invention;

2 is a schematic view 1 of the overall structure of the contact elastic piece for intelligent insertion and insertion of the present invention;

3 is a second schematic structural view of the contact elastic piece for intelligent insertion and insertion of the present invention;

4 is a top plan view of a contact elastic piece for intelligent power strip insertion according to the present invention;

The implementation, functional features, and advantages of the present invention will be further described in conjunction with the embodiments.

Reference number:

Conductive connecting piece 10;

Front connecting piece 101; rear connecting piece 102;

Inserting seat 20;

The fixing frame 201; the first fixing piece 2011; the second fixing piece 2012; the third fixing piece 2013; the locking elastic piece 202; the first surrounding part 2021; and the second surrounding part 2022.

detailed description

The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments in order to understand the invention.

1 , 2, 3 and 4;

The contact elastic piece for the intelligent insertion and removal of the present invention comprises a conductive connecting piece 10 and a socket 20 integrally formed with the conductive connecting piece 10 for inserting the plug pin;

The conductive connecting piece 10 is disposed laterally, and the conductive connecting piece 10 has a front end surface and a rear end surface;

The insertion base 20 includes a fixed frame 201 formed to be open at an upper end connected to an upper edge of the conductive connecting piece 10, and a fixing frame 201 vertically fixed in the fixing frame 201 and formed in the fixed frame 201 The plurality of fastening elastic pieces 202 are integrally surrounded by the plurality of fastening elastic pieces 202 so as to be formed into an enclosed structure for fastening the plug pins.

Based on the above, it can be understood that the contact elastic piece for intelligent row insertion provided by the present invention, in a specific implementation, on the one hand, when fixing the invention to the corresponding row of the housing, The additional fixed frame 201 is just received in the slot on the corresponding plug-in housing, and is fixed and fixed by the corresponding slot, so that a good limit function can be achieved, in the plurality of the said elastic shrapnel When the plug pins are inserted into the enclosed structure of the 202, the plurality of the fastening elastic pieces 202 are always restrained in the fixing frame 201 regardless of how they are squeezed, so that they are not displaced by the deformation. .

On the other hand, when the corresponding plug pins are inserted into the surrounding structure enclosed by the plurality of the locking elastic pieces 202, the corresponding plug pins are in contact with the plurality of the locking elastic pieces 202, and the contact area is large. The good contactability also makes it possible to reduce the current resistance and make the electrical conductivity better, which makes the energy saving better. Therefore, the invention has good practicability and good use effect.

Further, in a preferred technical solution, the upper ends of the plurality of the fastening elastic pieces 202 of the present invention are inclined inwardly so that the upper port diameter of the formed surrounding structure is smaller than the lower port diameter thereof, and the plurality of the cards are The upper ends of the solid elastic sheets 202 are exposed outside the fixing frame 201, and are respectively folded outward to form an open petal shape.

Thus, on the one hand, the upper port diameter of the formed enclosure structure is smaller than the diameter of the lower port, which also enables corresponding increase The elasticity of the locking elastic piece 202 can insert the plug pins in the enclosed enclosure structure, so that the upper ends of the plurality of the fastening elastic pieces 202 can be strengthened in the outward pressing force, and then the plurality of The card-shaped elastic pieces 202 can give a good reaction force to the corresponding plug pins, so that the interference performance with the corresponding plug pins is good.

On the other hand, the upper ends of the plurality of the fastening elastic pieces 202 are respectively folded outward to form an open petal-like structure, which also facilitates the insertion of the plug pins, so that a good insertion guiding function can be achieved, and thus, the present invention The use effect can be effectively improved.

Further, in the embodiment of the present invention, the fixing frame 201 is formed into a horizontal U-shaped structure, and includes a first fixing piece 2011, a second fixing piece 2012 and a third fixing piece 2013 which are sequentially connected;

The lower edge of the second fixing piece 2012 is integrally connected with the upper edge of the conductive connecting piece 10, the width of the first fixing piece 2011 is equal to the width of the third fixing piece 2013, and the The width of one of the fixing pieces 2011 and the width of the third fixing piece 2013 are both set to W1.

Moreover, in the present technical solution, the fastening elastic piece 202 is provided with 2N, wherein N is a positive integer greater than 1, and the width of each of the fastening elastic pieces 202 is set to W2.

In other words, in the embodiment of the present invention, the fastening elastic piece 202 is provided with at least four pieces.

Preferably, the N is 2 or 3, that is, in a preferred embodiment, the carding elastic piece 202 of the present invention is set to four or six pieces.

In a specific technical solution, the lower ends of the inner side walls of the N fastening elastic pieces 202 are sequentially connected, so that the N fastening elastic pieces 202 are formed as the first surrounding portion 2021; and the inner side walls of the N fastening elastic pieces 202 The lower ends of the two ends are connected in order to form the other N-shaped elastic pieces 202 as the second surrounding part 2022; the position of the first surrounding part 2021 is opposite to the position of the second surrounding part 2022, so as to form a Said enclosure structure.

Based on this, in the N of the N-shaped elastic pieces 202 of the first surrounding portion 2021, the lower end of the outer side wall of the locking elastic piece 202 on one side of the first surrounding portion 2021 is opposite to the first fixing The outer side walls of the sheet 2011 are connected; in the other N pieces of the elastic pieces 202 forming the second surrounding portion 2022, the lower end of the outer side wall of the locking elastic piece 202 on one side of the second surrounding portion 2022 is The outer sidewalls of the third fixing piece 2013 are connected;

An outer side wall of the elastic elastic piece 202 on the other side of the first surrounding portion 2021 abuts against an outer side wall of the elastic elastic piece 202 on the other side of the second surrounding portion 2022.

In this manner, the first enclosure portion 2021 is enclosed with the second enclosure portion 2022, that is, the enclosure structure for inserting the plug pins.

Preferably, in the technical solution, the insertion seat 20 is provided in plurality, and the plurality of insertion seats 20 are uniformly fixed on the upper edge of the conductive connecting piece 10.

Moreover, the width of the conductive connecting piece 10 between the two adjacent insertion seats 20 is set to W3;

Among them, W3 ≥ 2W1 + 4W2.

With reference to the above, it can be understood that, in the embodiment of the present invention, the fixing frame 201 and the locking elastic piece 202 of the insertion seat 20 and the conductive connecting piece 10 are integrally formed without any relationship between them. The solder joints make the production process excellent.

Moreover, since the width of the first fixing piece 2011 and the width of the third fixing piece 2013 are both set to W1, the width of each of the fastening elastic pieces 202 is set to W2, and the two adjacent ones are The width of the conductive connecting piece 10 between the insertion seats 20 is set to W3, and W3 ≥ 2W1 + 4W2, so that the fixing frame 201, the locking elastic piece 202 and the conductive connecting piece 10 are integrally formed. need.

It should be emphasized that, in order to meet the needs, in the technical solution, the conductive connecting piece 10 is uniformly bent multiple times before and after and formed into a square wave structure or an approximately square wave structure, so that the conductive connecting piece 10 is composed of a plurality of segments of the front connecting piece 101 and the rear connecting piece 102; the middle portion of the upper edge of each of the rear connecting pieces 102 is respectively fixed with the insertion seat 20, and each of the insertion seats 20 The open ends of the fixed frame 201 of the U-shaped structure are respectively directed forward of the respective rear connecting pieces 102.

In this way, the conductive connecting piece 10 is uniformly bent and formed into a square wave structure or an approximately square wave structure multiple times before and after, so that the distance between the adjacent two insertion seats 20 can be greatly reduced. The structure of the present invention is made more compact, which in turn makes it possible to arrange more plug insertion and placement positions on the same row of plugs, so that the use effect of the present invention can be optimized.

It should be noted that, in a specific implementation, the vertical distance between any of the front connecting pieces 101 described above and the rear connecting piece 102 adjacent thereto is equal to W1.

Thus, the overall structure of the present invention is made more aesthetically pleasing and more preferably symmetrical.

It should be noted that, in a specific implementation, one or both ends of the conductive connecting piece 10 are provided with wiring holes, and the conductive connecting piece 10 and the insertion seat 20 are preferably made of copper material. And the height H of the fastening elastic piece 202 is preferably 12 mm.

Other embodiments and the like are not described here by way of example.

In summary, the present invention provides a contact elastic piece for intelligent insertion, in which the upper end of the insertion base 20 including the upper edge of the conductive connecting piece 10 is formed as An open fixing frame 201 and a plurality of fastening elastic pieces 202 vertically formed in the fixing frame 201 and integrally formed with the fixing frame 201, and a plurality of the locking elastic pieces 202 are enclosed to Formed as a surrounding structure for securing the plug pins, such that, on the one hand, when the invention is fixed to the corresponding row of housings, the additional fixed frame 201 is just received in the corresponding row of housings On The slot is fixed in the slot and is fixed by the corresponding slot, so that a good limit function can be achieved, and when the plug pins are inserted into the enclosed structure surrounded by the plurality of the latching elastic pieces 202, multiple Regardless of how the snap-on elastic piece 202 is squeezed, it is always confined within the fixed frame 201 so as not to be displaced by the deformation, and on the other hand, the corresponding plug pin is inserted into the plurality of the card. When the solid elastic piece 202 is enclosed in the enclosed structure, the corresponding plug pins are in contact with the plurality of the locking elastic pieces 202, and the contact area is large, so that the contact resistance is good, and the current resistance is reduced and the conductive is made. The performance is good, which makes the energy saving better. Therefore, the invention has good practicability and good use effect.

In addition, in the technical solution of the present invention, the upper ends of the plurality of the fastening elastic pieces 202 are inclined inwardly so that the upper port diameter of the formed surrounding structure is smaller than the lower port diameter thereof, and the plurality of the fastenings are The upper ends of the elastic piece 202 are exposed outside the fixing frame 201, and are respectively folded outward to form an open petal shape. Thus, on the one hand, the upper port diameter of the formed surrounding structure is smaller than the diameter of the lower port, so that the corresponding increase can be made. The elasticity of the locking elastic piece 202 can insert the plug pins in the enclosed enclosure structure, so that the upper ends of the plurality of the fastening elastic pieces 202 can be strengthened in the outward pressing force, and then the plurality of The card-shaped elastic pieces 202 can give a good reaction force to the corresponding plug pins, so that the interference performance with the corresponding plug pins is good. On the other hand, the upper ends of the plurality of the locking elastic pieces 202 are respectively folded outward to form an open. The petal shape also facilitates the insertion of the plug pins, so that a good insertion guiding effect can be achieved, and therefore, the use effect of the present invention can be effectively improved.

In the embodiment of the present invention, the fixing frame 201 and the locking elastic piece 202 of the insertion seat 20 and the conductive connecting piece 10 are integrally formed, and there is no solder joint between them, so that the manufacturing process is excellent. And the width of the first fixing piece 2011 and the width of the third fixing piece 2013 are both set to W1, and the width of each of the fastening elastic pieces 202 is set to W2, and the two adjacent ones are The width of the conductive connecting piece 10 between the insertion seats 20 is set to W3, and W3 ≥ 2W1 + 4W2, so that the fixing frame 201, the locking elastic piece 202 and the conductive connecting piece 10 are integrally formed. It is required that, at the same time, the conductive connecting piece 10 is uniformly bent and formed into a square wave structure or an approximately square wave structure multiple times before and after, so that the adjacent two insertion seats 20 can be greatly reduced. The distance of the present invention makes the structure of the present invention more compact, which in turn enables more plug insertion and placement on the same row of plugs, so that the use effect of the present invention can be optimized.

Correspondingly, the overall structure of the invention is simple, easy to implement, easy to operate, strong in practicability, strong in specificity, low in manufacturing cost, and does not need to add too much cost in structural improvement and technical improvement, so that the present invention Inevitably has a good marketing value, the invention will be very popular and can be effectively popularized.

The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the invention, and the equivalent structure or equivalent process transformations made by the description of the invention and the drawings are directly or indirectly applied to other related The technical field is equally included in the scope of patent protection of the present invention.

Claims

A contact elastic piece for intelligently inserting, characterized in that it comprises a conductive connecting piece and a socket for integrally inserting the conductive connecting piece for inserting a plug pin; wherein

The conductive connecting piece is disposed laterally, and the conductive connecting piece has a front end surface and a rear end surface;

The insertion base includes a fixed frame formed to be open at an upper end connected to an upper edge of the conductive connecting piece, and a plurality of cards integrally formed in the fixing frame and integrally formed with the fixing frame The solid elastic piece is surrounded by a plurality of the locking elastic pieces so as to be formed into a surrounding structure for fastening the plug pins.
The contact elastic piece for intelligent row insertion according to claim 1, wherein the upper ends of the plurality of the fastening elastic pieces are inclined inwardly so that the upper port diameter of the formed surrounding structure is smaller than the lower port diameter thereof. And the upper ends of the plurality of the fastening elastic pieces are exposed outside the fixing frame, and are respectively folded outward to form an open petal shape.
The contact elastic piece for intelligent row insertion according to claim 1 or 2, wherein the fixing frame is formed into a transverse U-shaped structure, and includes a first fixing piece and a second fixing piece which are sequentially connected and a third fixing piece; wherein a lower edge of the second fixing piece is integrally connected with an upper edge of the conductive connecting piece, and a width of the first fixing piece is equal to a width of the third fixing piece, and The width of the first fixing piece and the width of the third fixing piece are both set to W1.
The contact elastic piece for intelligent row insertion according to claim 3, wherein the fastening elastic piece is provided with 2N pieces, wherein N is a positive integer greater than 1, and the width of each of the fastening elastic pieces is Set to W2.
The contact elastic piece for intelligent power strip insertion according to claim 4, wherein the lower ends of the inner side walls of the N fastening elastic pieces are sequentially connected, so that N of the fastening elastic pieces are formed as the first surrounding portion; The lower ends of the inner side walls of the N fastening pieces are sequentially connected so that the other N pieces of the elastic pieces are formed as the second surrounding portion; the position of the first surrounding part is opposite to the position of the second surrounding part So that the enclosed structure is formed.
The contact elastic piece for intelligent row insertion according to claim 5, wherein:

In the N pieces of the elastic sheets in which the first surrounding portion is formed, the lower end of the outer side wall of the one of the first surrounding portions is connected to the outer side wall of the first fixing piece;

In the other N pieces of the elastic pieces forming the second surrounding portion, the lower end of the outer side wall of the reinforcing elastic piece on one side of the second surrounding portion is connected to the outer side wall of the third fixing piece;

An outer side wall of the elastic elastic piece on the other side of the first surrounding portion abuts against an outer side wall of the elastic elastic piece on the other side of the second surrounding portion.
The contact elastic piece for intelligent row insertion according to claim 6, wherein the insertion seat is provided with a plurality of the insertion seats uniformly fixed on the upper edge of the conductive connecting piece .
The contact elastic piece for intelligent row insertion according to claim 7, wherein two adjacent insertion seats are The width of the conductive connecting piece is set to W3;

Among them, W3 ≥ 2W1 + 4W2.
The contact elastic piece for intelligent row insertion according to claim 8, wherein the conductive connecting piece is uniformly bent a plurality of times before and after, and is formed into a square wave type structure or an approximate square wave type structure, so as to The conductive connecting piece is composed of a plurality of segments of the front connecting piece and the rear connecting piece which are staggered; each of the upper edges of the rear connecting piece has a fixing seat, and a U of each of the insertion seats The open ends of the fixed frame of the type structure are respectively directed forward of the respective rear connecting pieces.
The contact elastic piece for intelligent row insertion according to claim 9, wherein a vertical distance between any one of the front connecting pieces and the rear connecting piece adjacent thereto is equal to W1.