CN211402994U

CN211402994U - TP (touch pad) adhesion mechanism

Info

Publication number: CN211402994U
Application number: CN201922073812.XU
Authority: CN
Inventors: 王鹏; 刘勇; 贾伟; 徐灿
Original assignee: Shenzhen Jiyin Technology Co ltd
Current assignee: Shenzhen Jiyin Technology Co ltd
Priority date: 2019-11-26
Filing date: 2019-11-26
Publication date: 2020-09-01
Anticipated expiration: 2029-11-26

Abstract

The utility model discloses a TP adhesion mechanism, including at least two sets of adhesion assembly of connecting through the connecting piece and be connected with the connecting piece and go up and down simultaneously with the drive arrangement of all adhesion assembly of drive, adhesion assembly includes the connecting rod and the piece that adheres that is connected through the one end of buffer and connecting rod, and the one end that the connecting rod was kept away from to the piece that adheres is the TP smooth surface that can adhere, and the one end that the piece that adheres was kept away from to the connecting rod of all adhesion assemblies is passed a mounting panel and is fixed in on the mounting panel through sealed mounting. The utility model discloses a drive arrangement drive multiunit adheres to the subassembly and adheres to TP simultaneously, and effort when cavity closure back evacuation can be resisted completely about, compares with traditional vacuum adsorption TP, can avoid TP to produce the skew or drop after the closure cavity evacuation to guarantee TP's laminating precision. And the arrangement of the buffer part can prevent the adhesive block from crushing and damaging the TP.

Description

TP (touch pad) adhesion mechanism

Technical Field

The utility model relates to a liquid crystal display panel assembles technical field, concretely relates to TP adhesion mechanism.

Background

In the production process of the liquid crystal Panel, one of the links is that a Touch Panel (TP) and a Liquid Crystal Display (LCD)/Liquid Crystal Module (LCM) are bonded to a hard substrate in a vacuum environment, an upper cavity Panel vacuum adsorption TP and a lower cavity Panel adsorption LCD/LCM are required, the upper cavity and the lower cavity are closed after alignment by a vision system, and then air in the cavities is removed for bonding.

When the cavity is closed and vacuumized, air in the upper cavity template can be pumped out, and the TP can be deviated or fall off due to the fact that the acting force of vacuum adsorption TP on the upper cavity template is far smaller than the acting force of vacuumization when the cavity is closed, and the attaching precision is affected.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a TP adhesion mechanism can avoid TP to produce the skew or drop during closed cavity evacuation, guarantees TP's laminating precision.

To achieve the purpose, the utility model adopts the following technical proposal:

the TP adhesion mechanism comprises at least two groups of adhesion assemblies connected through connecting pieces and a driving device connected with the connecting pieces to drive all the adhesion assemblies to lift simultaneously, wherein each adhesion assembly comprises a connecting rod and an adhesion block connected with one end of the connecting rod through a buffer part, one end, far away from the connecting rod, of each adhesion block is a TP smooth surface capable of being adhered, and one end, far away from the adhesion block, of each connection rod of all the adhesion assemblies penetrates through a mounting plate and is fixed on the mounting plate in a sealing mode through a sealing fixing piece.

As a preferable scheme of the TP adhesion mechanism, the buffer portion includes a guide cylinder and a spring installed in the guide cylinder, the adhesion block is fixed to one end of a slider, one end of the slider, which is far away from the adhesion block, is inserted into the guide cylinder and connected with the spring, and one end of the guide cylinder, which is far away from the adhesion block, is connected with the connecting rod.

As a preferable scheme of the TP adhesion mechanism, two opposite sides of the guide cylinder are respectively provided with a mounting hole, the mounting hole has a first end surface close to the adhesion block and a second end surface opposite to the first end surface along the axial direction of the guide cylinder, the buffer portion further includes a gasket located in the guide cylinder and connected to the spring, two sides of the gasket extend into the mounting hole, the gasket can move along the length direction of the mounting hole, the spring makes the gasket have a tendency of moving towards the first end surface all the time, and the slider is movably mounted in the guide cylinder.

As a preferable scheme of the TP adhesion mechanism, the floating block includes a first floating column and a second floating column which are coaxially connected, an outer diameter of the first floating column is smaller than an outer diameter of the second floating column, a connecting flange fixedly connected with one end of the guide cylinder close to the adhesion block is sleeved outside the first floating column, the second floating column is inserted into the guide cylinder and fixedly connected with the gasket, and one end of the first floating column, which is far away from the second floating column, is fixedly connected with the adhesion block through an intermediate connecting member.

As a preferable scheme of the TP adhesion mechanism, an installation groove in inserting fit with the connecting rod and a connection hole coaxial with the installation groove are formed in one end of the guide cylinder, which is far away from the adhesion block, the connection hole is located in the installation groove, and the connecting rod is screwed with a screw thread inserted into the connection hole.

As a preferred scheme of the TP adhesion mechanism, the sealing fixing member includes a first fixing member, a second fixing member, and a sealing member, the first fixing member, the second fixing member, and the sealing member are sleeved on the connecting rod, the sealing member includes an O-ring and a Y-ring, the first fixing member is fixed on the mounting plate by a screw, an annular groove is formed at one end of the first fixing member close to the adhesion block, the O-ring is installed in the groove, and part of the O-ring protrudes out of the surface of the first fixing member, and the Y-ring is fixed between the first fixing member and the second fixing member.

As a preferable scheme of the TP adhesion mechanism, the number of the Y-shaped sealing rings is two, and the sealing member further includes an annular supporting portion, and the supporting portion is sleeved on the connecting rod and located between the two Y-shaped sealing rings.

As a preferred scheme of the TP adhesion mechanism, the connecting member includes an i-shaped connecting plate and locking portions for locking the connecting rod, the number of the adhesion assemblies is four, the four adhesion assemblies are respectively fixed to four ends of the connecting plate through one of the locking portions, the driving device includes two jacking cylinders, and the two jacking cylinders are respectively connected to two sides of the connecting plate.

As a preferable scheme of the TP adhesion mechanism, the locking portion includes a fixing ring sleeved on the connecting rod and fixedly connected to a surface of the connecting plate away from the adhesion block, a screw passing through the fixing ring and screwed to the connecting rod, and a nut engaged with the screw, and the nut is located on a surface of the fixing ring away from the connecting plate;

the fixing ring is provided with an expansion notch along the thickness direction, the expansion notch is connected with the fixing ring through a through hole of the connecting rod in an inserting mode, the opening of the expansion notch is located on the outer side wall of the fixing ring, the fixing ring is provided with two locking holes communicated with the expansion notch, and the locking holes are connected through bolts.

As a preferred scheme of TP adhesion mechanism, the locking portion is still including being fixed in on the solid fixed ring and being located door type support and the locking cap of screw rod top, door type support has the upper end plate and is located the both sides board at upper end plate both ends, the nut has back of the body and parallel two sides, and two distance between the side equals two distance between the inside wall of curb plate, the locking cap includes that connecting portion, interval are fixed in support tight portion and locking cap body on the connecting portion, connecting portion with the screw rod screw thread connects soon, support tight portion with the lower surface butt of upper end plate, support tight portion with distance between the locking cap body is not less than the upper end plate thickness.

The utility model has the advantages that: the utility model discloses in, the upper and lower cavity after the closure has good leakproofness all the time when sealing fixed part can guarantee that drive arrangement drive adhesion subassembly goes up and down, the surface of adhesion piece is the smooth surface, both adhere together after it and the contact of same glossy TP surface, adhere the subassembly through drive arrangement drive multiunit and adhere TP simultaneously, the effort of evacuation after the cavity closure about can resisting completely, compare with traditional vacuum adsorption TP, can avoid TP to produce the skew or drop during the closure cavity evacuation, thereby guarantee TP's laminating precision. And the arrangement of the buffer part can prevent the adhesive block from crushing and damaging the TP.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be obtained from these drawings without inventive effort.

Fig. 1 is a schematic structural diagram of a TP bonding mechanism according to an embodiment of the present invention.

Fig. 2 is a partially exploded view of an adhesion assembly and a connection plate according to an embodiment of the present invention.

Fig. 3 is a schematic structural diagram of a locking portion according to an embodiment of the present invention.

Fig. 4 is a side view of a locking portion according to an embodiment of the present invention.

In the figure:

1. a connecting member; 11. a connecting plate; 12. a fixing ring; 121. an expansion gap; 122. a locking hole; 13. a screw; 14. a nut; 15. a gantry support; 16. a connecting portion; 17. a tightening part; 18. a locking cap body;

2. an adhesive component; 21. a connecting rod; 22. a buffer section; 221. a guide cylinder; 222. a spring; 223. mounting holes; 224. a gasket; 23. an adhesive block; 24. sealing the fixing member; 241. a first fixing member; 242. a second fixing member; 243. an O-shaped sealing ring; 244. a Y-shaped seal ring; 245. a bearing part; 25. a slider; 251. a first floating column; 252. a second floating column; 253. a connecting flange; 254. an intermediate connecting member;

3. a drive device.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments with reference to the accompanying drawings.

Wherein the showings are for the purpose of illustration only and are shown by way of illustration only and not in actual form, and are not to be construed as limiting the present patent; for a better understanding of the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "inner", "outer", etc. are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not indicated or implied that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are used only for illustrative purposes and are not to be construed as limiting the present patent, and the specific meaning of the terms will be understood by those skilled in the art according to the specific circumstances.

In the description of the present invention, unless otherwise explicitly specified or limited, the term "connected" or the like, if appearing to indicate a connection relationship between the components, is to be understood broadly, for example, as being either a fixed connection, a detachable connection, or an integral part; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or may be connected through one or more other components or may be in an interactive relationship with one another. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.

As shown in fig. 1 and 2, the present embodiment provides a TP adhesion mechanism, which includes at least two sets of adhesion assemblies 2 connected by a connecting member 1 and a driving device 3 connected to the connecting member 1 to drive all the adhesion assemblies 2 to ascend and descend simultaneously, wherein each adhesion assembly 2 includes a connecting rod 21 and an adhesion block 23 connected to one end of the connecting rod 21 by a buffer portion 22, one end of the adhesion block 23 away from the connecting rod 21 is a TP smooth surface capable of being adhered, and one end of the connecting rod 21 away from the adhesion block 23 of all the adhesion assemblies 2 passes through a mounting plate and is fixed on the mounting plate in a sealing manner by a sealing fixing member 24.

In this embodiment, sealed mounting 24 can guarantee that the upper and lower cavity after the closed when drive arrangement 3 drive adhesion subassembly 2 goes up and down has good leakproofness all the time, the surface of adhesion piece 23 is the smooth surface, it is in the same place with both adhesions after the contact of same glossy TP surface face, it adheres to TP simultaneously through drive arrangement 3 drive multiunit adhesion subassembly 2, the effort of evacuation after the cavity closure about can resisting completely, compare with traditional vacuum adsorption TP, can avoid TP to produce the skew or drop during the closed cavity evacuation, thereby guarantee TP's laminating precision. And the buffer part 22 can prevent the adhesive block 23 from crushing and damaging the TP.

Specifically, the buffer part 22 includes a guide cylinder 221 and a spring 222 installed in the guide cylinder 221, the slider 23 is fixed to one end of a slider 25, one end of the slider 25 remote from the slider 23 is inserted into the guide cylinder 221 and connected to the spring 222, and one end of the guide cylinder 221 remote from the slider 23 is connected to the connecting rod 21.

The guide cylinder 221 guides the extension direction of the spring 222, so as to prevent the spring 222 from bending during extension and contraction to affect the adhesion of the adhesion assembly 2 to the TP, when the driving device 3 drives the adhesion assembly 2 to move downwards until the adhesion block 23 contacts the TP, the adhesion block 23 is subjected to resistance of the TP, so that the floating block 25 pushes the spring 222 upwards, and the spring 222 contracts, thereby realizing the buffer effect when the adhesion block 23 adheres to the TP. Similarly, the driving device 3 drives the adhesive block 23 to adhere to the TP and then to descend to adhere to the LCD/LCM, and the buffer portion 22 also provides a certain buffer force for the adhesion process.

Furthermore, the two opposite sides of the guide cylinder 221 are respectively provided with a mounting hole 223, the mounting hole 223 has a first end surface close to the adhesion block 23 and a second end surface opposite to the first end surface along the axial direction of the guide cylinder 221, the buffer part 22 further comprises a gasket 224 located in the guide cylinder 221 and connected with the spring 222, two sides of the gasket 224 extend into the mounting hole 223, the gasket 224 can move along the length direction of the mounting hole 223, the spring 222 enables the gasket 224 to have a tendency of moving towards the first end surface all the time, and the slider 25 is movably mounted in the guide cylinder 221.

In the embodiment, the mounting holes 223 are formed in the two opposite sides of the guide cylinder 221, so that the mounting of the gasket 224 and the fixing of the spring 222 in the guide cylinder 221 are facilitated, meanwhile, the two sides of the gasket 224 extend to the mounting holes 223 and are flush with the periphery of the guide cylinder 221, the gasket 224 can further provide guidance for the expansion and contraction direction of the spring 222, the expansion and contraction limit of the spring 222 is limited, and the spring 222 is prevented from being excessively contracted or excessively stretched and deformed and cannot be recovered.

In this embodiment, the floating block 25 includes a first floating column 251 and a second floating column 252 coaxially connected, an outer diameter of the first floating column 251 is smaller than an outer diameter of the second floating column 252, a connecting flange 253 fixedly connected to one end of the guide cylinder 221 near the adhesive block 23 is sleeved outside the first floating column 251, the second floating column 252 is inserted into the guide cylinder 221 and fixedly connected to the gasket 224, and one end of the first floating column 251 far from the second floating column 252 is fixedly connected to the adhesive block 23 through an intermediate connecting member 254.

Specifically, the first floating post 251 is clearance-fitted to the connecting flange 253, and the second floating post 252 is clearance-fitted to the inner wall of the guide cylinder 221, so that the slider 25 is smoothly moved in the axial direction of the guide cylinder 221. The connecting flange 253 in this embodiment serves as a stopper plate for preventing the slider 25 from coming off the guide cylinder 221.

The one end of guide cylinder 221 far away from adhesion block 23 is seted up with connecting rod 21 grafting complex mounting groove and with the coaxial connecting hole of mounting groove, the connecting hole is located the mounting groove, connecting rod 21 and the screw thread that inserts in the connecting hole connect soon to make connecting rod 21 and guide cylinder 221 fixed connection, the design of mounting hole 223 on the guide cylinder 221 also is favorable to the quick connection between connecting rod 21 and the guide cylinder 221.

In this embodiment, the sealing fastener 24 includes a first fastener 241, a second fastener 242 and a sealing element sleeved on the connecting rod 21, the sealing element includes an O-ring 243 and a Y-ring 244, the first fastener 241 is fixed on the mounting plate by a screw, an annular groove is formed at one end of the first fastener 241 close to the adhesion block 23, the O-ring 243 is installed in the groove and partially protrudes out of the surface of the first fastener 241, and the Y-ring 244 is fixed between the first fastener 241 and the second fastener 242.

The O-ring 243 seals between the first fixing member 241 fixed to the mounting plate and the mounting plate, and the Y-ring 244 is fixed between the first fixing member 241 and the connecting rod 21 through the second fixing member 242, thereby providing a good seal between the first fixing member 241 and the connecting rod 21.

Further, the number of the Y-shaped sealing rings 244 is two, and the sealing member further includes an annular supporting portion 245, and the supporting portion 245 is sleeved on the connecting rod 21 and located between the two Y-shaped sealing rings 244.

In this embodiment, in order to further enhance the sealing function between the first fixing member 241, the second fixing member 242 and the connecting rod 21, two Y-shaped sealing rings 244 are required, and the supporting portion 245 plays a role of supporting the two Y-shaped sealing rings 244.

The connecting piece 1 comprises an I-shaped connecting plate 11 and locking parts for locking the connecting rod 21 on the connecting plate 11, the number of the adhesion assemblies 2 is four, the four adhesion assemblies 2 are fixed at four ends of the connecting plate 11 through one locking part respectively, the driving device 3 comprises two jacking cylinders, and the two jacking cylinders are connected with two sides of the connecting plate 11 respectively.

In this embodiment, the i-shaped connecting plate 11 is provided with one adhesion assembly 2 near its four ends, so as to further improve the adhesion stability and the bonding flatness of the TP adhesion mechanism to the TP, and the two sides of the i-shaped connecting plate 11 are connected with one jacking cylinder, so as to improve the stress uniformity of the four adhesion assemblies 2, and enable the four adhesion blocks 23 to stably float and adhere to the TP.

Specifically, as shown in fig. 3 and 4, the locking portion includes a fixing ring 12 sleeved on the connecting rod 21 and fixedly connected to a surface of the connecting plate 11 away from the adhesion block 23, a screw 13 threaded with the connecting rod 21 through the fixing ring 12, and a nut 14 engaged with the screw 13, the nut 14 being located on a surface of the fixing ring 12 away from the connecting plate 11;

an expansion notch 121 is formed in the fixing ring 12 along the thickness direction of the fixing ring, the expansion notch 121 is communicated with a through hole of the fixing ring 12 for being connected with the connecting rod 21 in an inserting mode, an opening of the expansion notch 121 is located on the outer side wall of the fixing ring 12, two locking holes 122 communicated with the expansion notch 121 are formed in the fixing ring 12, and the two locking holes 122 are connected through bolts.

The expansion notch 121 is designed to allow the fixing ring 12 to adapt to a range of floating connecting rods 21 and to be fastened to the connecting rods 21 and the fixing ring 12 by bolts passing through the two fastening holes 122. The nut 14 is designed on the upper surface of the fixing ring 12 to facilitate screwing.

Locking portion is still including being fixed in on solid fixed ring 12 and being located door type support 15 and the locking cap of screw rod 13 top, door type support 15 has the upper end plate and is located the both sides board at upper end plate both ends, nut 14 has two sides that back to back and parallel, and the distance between two sides equals the distance between the inside wall of two curb plates, the locking cap includes connecting portion 16, the interval is fixed in supporting portion 17 and locking cap body 18 on connecting portion 16, connecting portion 16 and screw rod 13 screw thread revolve and connect, support the lower surface butt of tight portion 17 and upper end plate, support the distance between tight portion 17 and the locking cap body 18 and be not less than the upper end plate thickness.

The two side plates of the door-shaped support 15 are attached to the two sides of the nut 14, so that the nut 14 can be prevented from rotating and loosening, the fixing ring 12 is stably arranged on the connecting plate 11, the problem that the stability of the fixing ring is affected due to loosening of the bolt is avoided, the problem that the adhesion block 23 is affected to stably adhere to the TP is avoided, and the inconsistency of the attaching force of the four groups of adhesion assemblies 2 after adhering to the TP is prevented.

Further, the door-shaped bracket 15 further includes two connecting transverse plates respectively connected to the lower end of one of the side plates, the connecting transverse plates are located outside the side plates, circular arc notches are respectively formed in one side of the connecting transverse plates and one side of the upper end plate, and the connecting transverse plates are fixedly connected to the fixing ring 12 through screws inserted into the circular arc notches. The design of circular arc breach can be convenient for the dismouting of door type support 15 and locking cap.

It should be understood that the above-described embodiments are merely illustrative of the preferred embodiments of the present invention and the technical principles thereof. It will be understood by those skilled in the art that various modifications, equivalents, changes, and the like can be made to the present invention. However, these modifications are within the scope of the present invention as long as they do not depart from the spirit of the present invention. In addition, certain terms used in the specification and claims of the present application are not limiting, but are used merely for convenience of description.

Claims

1. A TP adhesion mechanism is characterized by comprising at least two groups of adhesion assemblies connected through connecting pieces and a driving device connected with the connecting pieces to drive all the adhesion assemblies to ascend and descend simultaneously, wherein each adhesion assembly comprises a connecting rod and an adhesion block connected with one end of the connecting rod through a buffering part, one end, far away from the connecting rod, of each adhesion block is a TP smooth surface capable of being adhered, and one end, far away from the adhesion block, of each connection rod of all the adhesion assemblies penetrates through a mounting plate and is fixed on the mounting plate in a sealing mode through a sealing fixing piece.

2. The TP adhesion mechanism of claim 1, wherein the buffer portion comprises a guide cylinder and a spring mounted in the guide cylinder, the adhesion block is fixed to an end of a slider, an end of the slider remote from the adhesion block is inserted into the guide cylinder and connected to the spring, and an end of the guide cylinder remote from the adhesion block is connected to the connection rod.

3. The TP sticking mechanism according to claim 2, wherein mounting holes are respectively formed in two opposite sides of the guide cylinder, the mounting holes are provided with a first end face close to the sticking block and a second end face opposite to the first end face in the axial direction of the guide cylinder, the buffer part further comprises a gasket located in the guide cylinder and connected with the spring, two sides of the gasket extend into the mounting holes, the gasket can move in the length direction of the mounting holes, the spring enables the gasket to always have a tendency of moving towards the first end face, and the floating block is movably mounted in the guide cylinder.

4. The TP attachment mechanism of claim 3, wherein the floating block comprises a first floating column and a second floating column which are coaxially connected, the outer diameter of the first floating column is smaller than that of the second floating column, a connecting flange is sleeved outside the first floating column and fixedly connected with one end of the guide cylinder close to the attachment block, the second floating column is inserted into the guide cylinder and fixedly connected with the gasket, and one end of the first floating column far away from the second floating column is fixedly connected with the attachment block through an intermediate connecting piece.

5. The TP attachment mechanism of claim 2, wherein an end of the guide cylinder remote from the attachment block is formed with an attachment groove for mating with the connection rod and a connection hole coaxial with the attachment groove, the connection hole is located in the attachment groove, and the connection rod is threadedly engaged with a screw inserted into the connection hole.

6. The TP attachment mechanism of claim 1, wherein the sealing fastener includes a first fastener, a second fastener, and a sealing element sleeved on the connecting rod, the sealing element includes an O-ring and a Y-ring, the first fastener is fixed on the mounting plate by a screw, an annular groove is formed at one end of the first fastener near the attachment block, the O-ring is installed in the groove and partially protrudes out of the surface of the first fastener, and the Y-ring is fixed between the first fastener and the second fastener.

7. The TP attachment mechanism of claim 6, wherein the number of the Y-shaped sealing rings is two, and the sealing member further comprises an annular supporting portion, and the supporting portion is sleeved on the connecting rod and located between the two Y-shaped sealing rings.

8. The TP attachment mechanism of claim 1, wherein the connection member comprises an I-shaped connection plate and four sets of attachment assemblies, and locking portions for locking the connection rod, the four sets of attachment assemblies are fixed to four ends of the connection plate through one of the locking portions, respectively, and the driving device comprises two jacking cylinders, and the two jacking cylinders are connected to two sides of the connection plate, respectively.

9. The TP attachment mechanism of claim 8, wherein the locking portion comprises a retaining ring disposed around the connection rod and fixedly connected to a surface of the connection plate away from the attachment block, a threaded rod threaded to the connection rod through the retaining ring, and a nut engaged with the threaded rod, the nut being disposed on a surface of the retaining ring away from the connection plate;

10. The TP bonding mechanism according to claim 9, wherein the locking portion further comprises a door-shaped support and a locking cap, the door-shaped support is fixed on the fixing ring and located above the screw, the door-shaped support is provided with an upper end plate and two side plates located at two ends of the upper end plate, the nut is provided with two opposite and parallel side edges, the distance between the two side edges is equal to the distance between the inner side walls of the two side plates, the locking cap comprises a connecting portion, a tightening portion and a locking cap body, the tightening portion and the locking cap body are fixed on the connecting portion at intervals, the connecting portion is screwed with the screw, the tightening portion is abutted against the lower surface of the upper end plate, and the distance between the tightening portion and the locking cap body is not smaller than the thickness of the upper end plate.