Film drawing mechanism and battery processing equipment
By designing a combination of membrane support components, buffer components, and guide components, the problem of membrane breaking during stretching was solved, enabling continuous conveying and precise cutting of the membrane.
Patent Information
- Application Number
- CN202422997980.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-04
- Publication Date
- 2025-11-07
- Estimated Expiration
- 2034-12-04
AI Technical Summary
In the prior art, the membrane is easily torn before it is cut due to the large resistance of the membrane support rod and the high pulling speed.
A membrane stretching mechanism was designed, including a membrane support assembly, a first conveying assembly, a buffer assembly, and a second conveying assembly. The buffer assembly buffers a membrane sheet of a preset length, and together with the guide assembly and the cutter assembly, it achieves uniform and rapid conveying of the membrane sheet, avoiding membrane breakage due to the resistance of the membrane support assembly.
This effectively avoids the problem of the membrane breaking due to the resistance of the membrane support assembly during rapid stretching, ensuring continuous conveying and cutting accuracy of the membrane.
Smart Images
Figure CN223520195U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of battery processing equipment, and particularly relates to a film pulling mechanism and a battery processing equipment. BACKGROUND
[0002] Before the film is cut, the battery film needs to be supported by the film supporting mechanism.
[0003] In the related art, the film is directly stretched after passing through the mold rod. Since the resistance of the film supporting rod to the film is large and the film pulling speed is fast, the film is subjected to a large pulling force, thereby the film may be pulled off. UTILITY MODEL CONTENT
[0004] The application aims to provide a film pulling mechanism and a battery processing equipment.
[0005] According to a first aspect of the application, a film pulling mechanism is provided, comprising:
[0006] a film supporting assembly configured to support the film;
[0007] a first conveying assembly arranged downstream of the film supporting assembly, the first conveying assembly being configured to convey the film;
[0008] a buffer assembly arranged downstream of the first conveying assembly, the buffer assembly being configured to buffer the film of a preset length;
[0009] a second conveying assembly arranged downstream of the buffer assembly, the second conveying assembly being configured to convey the film.
[0010] Optionally, the first conveying assembly comprises a first driving member, a first driving roller and a first driven roller, the driving end of the first driving member is connected with the first driving roller, the first driving member can drive the first driving roller to rotate about the axis thereof, the first driving roller and the first driven roller are arranged in a spaced manner and form a first gap, and the first gap is used for passing the film.
[0011] Optionally, the first conveying assembly further comprises a second driving member, the driving end of the second driving member is connected with the first driven roller, and the second driving member can drive the first driven roller to move towards or away from the first driving roller.
[0012] Optionally, the second conveying assembly comprises a third driving member, a second driving roller and a second driven roller, the driving end of the third driving member is connected with the second driving roller, the third driving member can drive the second driving roller to rotate about the axis thereof, the second driving roller and the second driven roller are arranged in a spaced manner and form a second gap, and the second gap is used for passing the film.
[0013] Optionally, the second conveying assembly further comprises a fourth driving member, a driving end of the fourth driving member is connected with the second driven roller, and the fourth driving member is capable of driving the second driven roller to move towards or away from the second driving roller.
[0014] Optionally, the film stretching mechanism further comprises a guide assembly, and the guide assembly is located between the second driving roller and the second driven roller.
[0015] The guide assembly comprises a guide groove in which the film moves, and the guide assembly is provided with a first avoiding groove and a second avoiding groove, the first avoiding groove and the second avoiding groove are both in communication with the guide groove, the first avoiding groove is close to the second driving roller, the second avoiding groove is close to the second driven roller, and the second driving roller and the second driven roller convey the film at the first avoiding groove and the second avoiding groove.
[0016] Optionally, the film stretching mechanism further comprises a cutter assembly, and the cutter assembly is arranged downstream of the second conveying assembly and is configured to cut the film.
[0017] Optionally, the buffer assembly comprises a sliding member, a first roller set and a fixed roller, the first roller set is in sliding connection with the sliding member, the fixed roller is arranged in a spaced manner with the first roller set, and the first roller set is capable of moving towards or away from the fixed roller along the sliding member.
[0018] Optionally, the film stretching mechanism further comprises a buffer assembly.
[0019] The buffer assembly comprises a second roller set, the second roller set is formed with a third gap.
[0020] The buffer assembly further comprises a third roller set, the third roller set is arranged in a spaced manner with the second roller set, and the third roller set is formed with a fourth gap.
[0021] The buffer assembly further comprises a supporting rod, the supporting rod comprises a first part, a second part and a third part connected in sequence, one end of the first part away from the second part is located in the third gap, and one end of the third part away from the second part is located in the fourth gap.
[0022] According to a second aspect of the embodiments of the present application, a battery processing device is provided, characterized by comprising the film stretching mechanism.
[0023] One technical effect of the embodiments of the present application is that the film stretched at a constant speed by the first conveying assembly from the film forming assembly is stretched by the second conveying assembly, and the buffer assembly is arranged to avoid the film from being broken due to the resistance of the film stretching mechanism.
[0024] Other features and advantages of the present application will become apparent from the following detailed description of illustrative embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0025] The accompanying drawings incorporated in and forming a part of the specification, illustrate embodiments of the present application and, together with the description, serve to explain the principles of the application.
[0026] Figure 1 is a structural schematic view of a film pulling mechanism in an embodiment of the present application;
[0027] Figure 2 is a structural schematic view of a film pulling mechanism in an embodiment of the present application;
[0028] Figure 3 is a structural schematic view of a film pulling mechanism in an embodiment of the present application;
[0029] Figure 4 is a structural schematic view of a film pulling mechanism in an embodiment of the present application.
[0030] BRIEF DESCRIPTION OF DRAWINGS: film pulling assembly 1; second roller set 11; third roller set 12; supporting rod 13; first portion 131; first end portion 1311; second portion 132; third portion 133; sixth end portion 1331; first conveying assembly 2; first driving member 21; first driving roller 22; first driven roller 23; second driving member 24; first gap 25; second conveying assembly 3; third driving member 31; second driving roller 32; second driven roller 33; fourth driving member 34; second gap 35; guiding assembly 4; guiding groove 41; first avoiding groove 42; second avoiding groove 43; first mounting plate 44; second mounting plate 45; buffer assembly 5; sliding member 51; first roller set 52; sliding block 521; first passing roller 522; second passing roller 523; fixed roller 53; cutter assembly 6. DETAILED DESCRIPTION
[0031] Various illustrative embodiments of the present application will now be described in detail with reference to the accompanying figures. It should be noted that the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated.
[0032] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the scope of the application or its application or uses.
[0033] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as part of the specification, where appropriate.
[0034] In all the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.
[0035] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.
[0036] First, it should be noted that the X and Z directions mentioned in the embodiments of this application are referred to in the appendix. Figure 2 The marked directions. Among them, the X direction intersects the Z direction.
[0037] In this application, the downstream mentioned in the embodiments refers to the component through which the diaphragm passes along the conveying direction of the diaphragm.
[0038] like Figures 1-4 As shown, according to a first aspect of the embodiments of this application, a film stretching mechanism is provided, including a film stretching assembly 1, a first conveying assembly 2, a buffer assembly 5, and a second conveying assembly 3; the film stretching assembly 1 is configured to stretch a film; the first conveying assembly 2 is located downstream of the film stretching assembly 1 and is configured to convey the film; the buffer assembly 5 is located downstream of the first conveying assembly 2 and is configured to buffer a film of a preset length; the second conveying assembly 3 is located downstream of the buffer assembly 5 and is configured to convey the film.
[0039] The film-pulling mechanism in this embodiment of the application is used to transport a heat-shrinkable film, which is used to cover the battery casing. Before feeding, the film is a roll, and the film-pulling mechanism is used to stretch the roll wound with the film. Before covering the casing, the film needs to be stretched open so that it can be covered on the battery casing in subsequent processes.
[0040] like Figures 1-4 As shown, the membrane stretching mechanism includes a membrane support assembly 1, a first conveying assembly 2, a buffer assembly 5, and a second conveying assembly 3; wherein, the membrane support assembly 1 is configured to stretch the membrane sheet, specifically, the membrane support assembly 1 stretches the membrane sheet, and when the membrane sheet passes through the membrane support assembly 1, the membrane support assembly 1 has resistance to the membrane sheet, which will affect the conveying of the membrane sheet.
[0041] Further, the first conveying assembly 2 is arranged downstream of the film supporting assembly 1, the buffer assembly 5 is arranged downstream of the first conveying assembly 2, and the second conveying assembly 3 is arranged downstream of the buffer assembly 5. The first conveying assembly 2 is used to convey the film at a constant speed, the second conveying assembly 3 is used to convey the film at a high speed in an interval manner, and the buffer assembly 5 is used to buffer the film of a preset length. Specifically, the film is stretched by the film supporting assembly 1, the first conveying assembly 2 conveys the film at a constant speed, the second conveying assembly 3 conveys the film at a high speed when the film needs to be cut, the buffer assembly 5 is arranged between the first conveying assembly 2 and the second conveying assembly 3, and the buffer assembly 5 buffers the film of a preset length so as to facilitate the second conveying assembly 3 to stretch the film at a high speed. Since the film supporting assembly 1 has a resistance to the film, the buffer assembly 5 is arranged so as to avoid the film from being broken due to the resistance of the film supporting assembly 1 when the second conveying assembly 3 stretches the film at a high speed.
[0042] In an optional embodiment, the first conveying assembly 2 comprises a first driving member 21, a first driving roller 22, and a first driven roller 23. The driving end of the first driving member 21 is connected with the first driving roller 22, the first driving member 21 can drive the first driving roller 22 to rotate around the axis thereof, and the first driving roller 22 is arranged in a spaced manner with the first driven roller 23 and forms a first gap 25 for the film to pass through.
[0043] As shown in Figures 1-4 , the first conveying assembly 2 comprises a first driving member 21, a first driving roller 22, and a first driven roller 23. Specifically, the first driving roller 22 is arranged in a spaced manner with the first driven roller 23, and the first gap 25 is formed between the first driving roller 22 and the first driven roller 23 for the film to pass through. The driving end of the first driving member 21 is connected with the first driving roller 22, and the first driving member 21 can drive the first driving roller 22 to rotate around the axis thereof. Therefore, the first driving member 21 drives the first driving roller 22 to rotate, and the film is conveyed to the buffer assembly 5 under the action of the first driving roller 22 and the first driven roller 23.
[0044] In the embodiment, the first driving member 21 can be a motor or a rotary cylinder.
[0045] In an optional embodiment, the first conveying assembly 2 further comprises a second driving member 24. The driving end of the second driving member 24 is connected with the first driven roller 23, and the second driving member 24 can drive the first driven roller 23 to move towards or away from the first driving roller 22.
[0046] As shown in Figures 1-3As shown, the first conveying assembly 2 also includes a second driving member 24. The driving end of the second driving member 24 is connected to the first driven roller 23. The second driving member 24 drives the first driven roller 23 to move closer to the first driving roller 22 to reduce the first gap 25, so as to prevent the first driving roller 22 and the first driven roller 23 from being unable to convey the film if the first gap 25 is too large. Before the film pulling mechanism starts working, the second driving member 24 drives the first driven roller 23 to move away from the first driving roller 22 to increase the first gap 25, so that the end of the film can pass through the first gap 25.
[0047] The second driving component 24 can be a linear motor, a pneumatic cylinder, or a hydraulic cylinder.
[0048] In one optional embodiment, the second conveying assembly 3 includes a third driving member 31, a second active roller 32, and a second driven roller 33. The driving end of the third driving member 31 is connected to the second active roller 32. The third driving member 31 can drive the second active roller 32 to rotate around its own axis. The second active roller 32 and the second driven roller 33 are spaced apart to form a second gap 35, which is used for the passage of a diaphragm.
[0049] like Figures 1-4 As shown, the second conveying assembly 3 includes a third driving member 31, a second active roller 32, and a second driven roller 33. Specifically, the second active roller 32 and the second driven roller 33 are spaced apart, and a second gap 35 is formed between the second active roller 32 and the second driven roller 33. The film will pass through the second gap 35. The driving end of the third driving member 31 is connected to the second active roller 32, and the third driving member 31 can drive the second active roller 32 to rotate around its own axis. Therefore, the third driving member 31 drives the second active roller 32 to rotate, and the film is conveyed to the cutter assembly 6 under the action of the second active roller 32 and the second driven roller 33.
[0050] The third drive component 31 can be a motor or a rotary cylinder.
[0051] In one alternative embodiment, the second conveying assembly 3 further includes a fourth driving member 34, the driving end of which is connected to the second driven roller 33, and the fourth driving member 34 is capable of driving the second driven roller 33 to move toward or away from the second driving roller 32.
[0052] like Figures 1-4As shown, the second conveying assembly 3 further comprises a fourth driving member 34, a driving end of the fourth driving member 34 is connected with the second driven roller 33, the fourth driving member 34 drives the second driven roller 33 to move, the fourth driving member 34 drives the second driven roller 33 to move towards the second driving roller 32 to reduce the second gap 35, so as to prevent the second gap 35 from being too large, and the second driving roller 32 and the second driven roller 33 cannot convey the diaphragm; before the diaphragm pulling mechanism starts to work, the fourth driving member 34 drives the second driven roller 33 to move away from the second driving roller 32 to increase the second gap 35, so as to facilitate the end of the diaphragm to pass through the second gap 35.
[0053] The fourth driving member 34 can be a linear motor, a pneumatic cylinder or a hydraulic cylinder.
[0054] In an alternative embodiment, the diaphragm pulling mechanism further comprises a guide assembly 4, the guide assembly 4 is located between the second driving roller 32 and the second driven roller 33; the guide assembly 4 comprises a guide groove 41, the diaphragm moves along the guide groove 41, the guide assembly 4 is provided with a first avoiding groove 42 and a second avoiding groove 43, the first avoiding groove 42 and the second avoiding groove 43 are both communicated with the guide groove 41, the first avoiding groove 42 is close to the second driving roller 32, the second avoiding groove 43 is close to the second driven roller 33, and the second driving roller 32 and the second driven roller 33 convey the diaphragm at the first avoiding groove 42 and the second avoiding groove 43.
[0055] As shown in the drawings, Figures 1-3 The diaphragm pulling mechanism further comprises a guide assembly 4, the guide assembly 4 is located between the second driving roller 32 and the second driven roller 33, and the guide assembly 4 is used to provide a guiding effect for the diaphragm.
[0056] Specifically, the guide assembly 4 comprises a guide groove 41, the diaphragm moves along the length direction of the guide groove 41, and the guide groove 41 provides a guiding effect for the diaphragm; the guide assembly 4 is provided with a first avoiding groove 42 and a second avoiding groove 43, and specifically, the guide assembly 4 is located between the second driving roller 32 and the second driven roller 33, the guide assembly 4 is provided with the first avoiding groove 42 on the side facing the second driving roller 32, the first avoiding groove 42 is communicated with the guide groove 41, that is, at the first avoiding groove 42, the second driving roller 32 can contact the diaphragm; the guide assembly 4 is provided with the second avoiding groove 43 on the side facing the second driven roller 33, and the second avoiding groove 43 is communicated with the guide groove 41, that is, at the second avoiding groove 43, the second driven roller 33 can contact the diaphragm; therefore, at the first avoiding groove 42 and the second avoiding groove 43, the second driving roller 32 and the second driven roller 33 jointly act to convey the diaphragm.
[0057] The guiding assembly 4 is arranged to provide a guiding effect for the film conveying, so that the second conveying assembly 3 can quickly stretch the film and avoid the film from being skewed.
[0058] In one specific embodiment, the guiding assembly 4 comprises a first mounting plate 44 and a second mounting plate 45, the first mounting plate 44 is arranged to be spaced apart from the second mounting plate 45, a guiding groove 41 is formed between the first mounting plate 44 and the second mounting plate 45, the first mounting plate 44 is provided with a first avoiding groove 42, the second mounting plate 45 is provided with a second avoiding groove 43, and the first avoiding groove 42 is arranged to be opposite to the second avoiding groove 43.
[0059] In an alternative embodiment, the film stretching mechanism further comprises a cutter assembly 6, the cutter assembly 6 is arranged downstream of the second conveying assembly 3, and the cutter assembly 6 is configured to cut the film.
[0060] As Figure 2 shown, the film stretching mechanism further comprises a cutter assembly 6, the cutter assembly 6 is arranged downstream of the second conveying assembly 3, that is, the second conveying assembly 3 conveys the film to the cutter assembly 6, so that the cutter assembly 6 cuts the film, and cuts the continuous film into film segments.
[0061] Specifically, along the conveying direction of the film, the cutter assembly 6 is arranged at the tail end of the guiding groove 41 of the guiding assembly 4, at the tail end of the guiding groove 41, the continuous film is cut into film segments by the cutter assembly 6.
[0062] In an alternative embodiment, the buffer assembly 5 comprises a sliding member 51, a first roller set 52 and a fixed roller 53, the first roller set 52 is in sliding connection with the sliding member 51, the fixed roller 53 is arranged to be spaced apart from the first roller set 52, and the first roller set 52 can move along the sliding member 51 to the direction of approaching or moving away from the fixed roller 53.
[0063] As Figure 1 and Figure 2As shown, the buffering assembly 5 comprises a sliding member 51, a first roller set 52 and a fixed roller 53; the first roller set 52 and the fixed roller 53 are arranged at intervals, the first roller set 52 is in sliding connection with the sliding member 51, and the first roller set 52 can move along the length direction of the sliding member 51; specifically, the film passes through the first roller set 52 and the fixed roller 53, when the first roller set 52 moves away from the fixed roller 53, the buffering assembly 5 can buffer the film of a preset size, so as to facilitate the second conveying assembly 3 to quickly stretch the film, when the second conveying assembly 3 quickly stretches the film, the first roller set 52 moves towards the fixed roller 53, so that the second conveying assembly 3 stretches the film buffered by the buffering assembly 5, which can avoid stretching the film located at the supporting rod assembly 1, thereby avoiding the impact when quickly stretching the film and avoiding breaking the film, thereby ensuring the film stretching precision.
[0064] In one specific embodiment, as Figure 2 As shown, the first roller set 52 comprises a first roller 522, a second roller 523 and a sliding block 521, the first roller 522 and the second roller 523 are arranged at intervals in the X direction on the sliding block 521, the sliding block 521 is in sliding connection with the sliding member 51, and the sliding block 521 can move in the Z direction relative to the sliding member 51; the fixed roller 53 is arranged above the first roller set 52 in the Z direction, and the fixed roller 53 is located between the first roller 522 and the second roller 523 in the X direction; the film passes through the first roller 522, the fixed roller 53 and the second roller 523 in the buffering assembly 5 in turn, so that when the first roller set 52 moves towards the fixed roller 53, the buffered film can be released; when the first roller set 52 moves away from the fixed roller 53, the film of a preset length can be buffered between the first conveying assembly 2 and the second conveying assembly 3, so as to facilitate the second conveying assembly 3 to quickly stretch the film.
[0065] In an alternative embodiment, the film supporting assembly 1 comprises a second roller set 11, a third roller set 12 and a supporting rod 13; the second roller set 11 forms a third gap; the third roller set 12 is arranged at intervals with the second roller set 11, and the third roller set 12 forms a fourth gap; the supporting rod 13 comprises a first portion 131, a second portion 132 and a third portion 133 connected in sequence, one end of the first portion 131 away from the second portion 132 is located in the third gap, and one end of the third portion 133 away from the second portion 132 is located in the fourth gap.
[0066] As Figure 2As shown, the film supporting assembly 1 comprises a second roller set 11, a third roller set 12 and a supporting rod 13; wherein the second roller set 11 and the third roller set 12 are arranged along the Z direction with a spacing, the second roller set 11 forms a third gap, the third roller set 12 forms a fourth gap, the third gap and the fourth gap coincide in the Z direction, and the supporting rod 13 is located between the second roller set 11 and the third roller set 12; specifically, the supporting rod 13 comprises a first part 131, a second part 132 and a third part 133 connected in sequence, the first part 131 comprises a first end 1311 and a second end, the second part 132 comprises a third end and a fourth end, the third part 133 comprises a fifth end and a sixth end 1331, the first end 1311 is flat, the first end 1311 is located in the third gap, the second end is connected with the third end, the fourth end is connected with the fifth end, the sixth end 1331 is flat, and the sixth end 1331 is located in the fourth gap.
[0067] Further, the supporting rod 13 penetrates into the inside of the film sheet at the first end 1311, and the film sheet is expanded by the second part 132, and then the sixth end 1331 penetrates out, so as to expand the film sheet, thereby facilitating the subsequent process of sleeving the cut film sheet on the shell of the battery.
[0068] According to a second aspect of the embodiments of the present application, a battery processing equipment is provided, comprising the film pulling mechanism.
[0069] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, and are not intended to limit the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.
Claims
1. A film pulling mechanism characterized by comprising: The film pulling mechanism comprises: a film supporting assembly configured to support a film sheet; a first conveying assembly arranged downstream of the film supporting assembly, the first conveying assembly being configured to convey the film sheet; a buffer assembly arranged downstream of the first conveying assembly, the buffer assembly being configured to buffer a film sheet of a preset length; a second conveying assembly arranged downstream of the buffer assembly, the second conveying assembly being configured to convey the film sheet.
2. The film pulling mechanism according to claim 1, wherein The first conveying assembly comprises a first driving member, a first driving roller and a first driven roller, the driving end of the first driving member is connected with the first driving roller, the first driving member can drive the first driving roller to rotate about its axis, the first driving roller is arranged in space with the first driven roller and forms a first gap for passing the film sheet.
3. The film pulling mechanism according to claim 2, wherein The first conveying assembly further comprises a second driving member, the driving end of the second driving member is connected with the first driven roller, the second driving member can drive the first driven roller to move towards or away from the first driving roller.
4. The film pulling mechanism according to claim 1, wherein The second conveying assembly comprises a third driving member, a second driving roller and a second driven roller, the driving end of the third driving member is connected with the second driving roller, the third driving member can drive the second driving roller to rotate about its axis, the second driving roller is arranged in space with the second driven roller and forms a second gap for passing the film sheet.
5. The film pulling mechanism according to claim 4, wherein The second conveying assembly further comprises a fourth driving member, the driving end of the fourth driving member is connected with the second driven roller, the fourth driving member can drive the second driven roller to move towards or away from the second driving roller.
6. The film pulling mechanism according to claim 4, wherein The film pulling mechanism further comprises a guide assembly between the second driving roller and the second driven roller. The guide assembly comprises a guide groove along which the film sheet moves, the guide assembly is provided with a first avoiding groove and a second avoiding groove, the first avoiding groove and the second avoiding groove are in communication with the guide groove, the first avoiding groove is close to the second driving roller, the second avoiding groove is close to the second driven roller, the second driving roller and the second driven roller convey the film sheet at the first avoiding groove and the second avoiding groove.
7. The film pulling mechanism according to claim 1, wherein The film pulling mechanism further comprises a cutter assembly arranged downstream of the second conveying assembly, the cutter assembly is configured to cut the film sheet.
8. The film pulling mechanism according to claim 1, wherein The buffer assembly comprises a sliding member, a first roller set and a fixed roller, the first roller set is in sliding connection with the sliding member, the fixed roller is arranged in space with the first roller set, the first roller set can move towards or away from the fixed roller along the sliding member.
9. The film pulling mechanism according to claim 1, wherein The film supporting assembly comprises: a second roller set forming a third gap; a third roller set arranged in space with the second roller set, the third roller set forming a fourth gap; A strut comprising a first portion, a second portion, and a third portion connected in sequence, one end of the first portion away from the second portion being located in the third gap, one end of the third portion away from the second portion being located in the fourth gap.
10. A battery processing apparatus, characterized by, The film pulling mechanism comprises the strut as claimed in any one of claims 1-9.