Automatic feeding device for thermoplastic SMC material production

Abstract

The present application relates to a kind of automatic feeding device for thermoplastic SMC material production applied to the technical field of pneumatic conveying equipment, including discharging module, receiving module, discharging pipeline, receiving pipeline, group joint pipe, telescopic cylinder, telescopic column, straight-through hole and receiving hole, the present application is communicated with discharging pipeline by receiving pipeline, and it is telescopic movement in telescopic cylinder by telescopic column, when group joint pipe is communicated with straight-through hole, thermoplastic SMC particles in discharging pipeline directly pass through group joint pipe to next receiving pipeline transmission by straight-through hole, when group joint pipe is communicated with receiving hole, thermoplastic SMC particles in discharging pipeline are transmitted into receiving pipeline, to realize that receiving module receives thermoplastic SMC particles, group joint pipe selectively communicates with straight-through hole and receiving hole, to facilitate the thermoplastic SMC particle demand of discharging module supply multiple receiving module, effectively improve the production feeding efficiency of thermoplastic SMC particles.

Description

TECHNICAL FIELD

[0001] The application relates to an automatic feeding device, in particular to an automatic feeding device for thermoplastic SMC material production applied to the technical field of pneumatic conveying equipment. BACKGROUND

[0002] Thermoplastic SMC plastic is in the form of white particles and is formulated into plastic by adding various additives. Under certain temperature conditions, the plastic can be softened or melted into any shape, and the shape does not change after cooling.

[0003] Chinese patent CN217555259U discloses an auxiliary feeding device for thermoplastic polymer material. A driving mechanism is used. A driving motor drives a screw feeding piece through a feeding rod to rotate clockwise. The rotating screw feeding piece can convey the thermoplastic plastic particles in the feeding box upward through the feeding pipe and fall into the inside of the discharging box. Then the particles are conveyed to the inside of the processing box through the discharging pipe, so that the feeding of the inside of the processing box can be completed. The feeding efficiency is high, time and labor are saved, and it is convenient. Chinese patent CN116354117A discloses a pneumatic conveying system. In the process of conveying materials, the materials will hit the expansion pad, and the expansion pad has a certain buffering effect, which can protect the inner wall of the elbow pipe. At the same time, the intermittent air extraction and inflation of the inflation part between the air chambers can prevent the materials from adhering to the expansion pad and causing the elbow pipe to be blocked.

[0004] The existing thermoplastic SMC particles are generally manually fed into the inside of the processing equipment by using a container, which is not only troublesome and laborious but also has low feeding efficiency. Therefore, an automatic feeding device is needed to assist the thermoplastic SMC particles to be added into the processing equipment. The thermoplastic SMC particles are light in quality and have the same size and shape, which are particularly suitable for pneumatic conveying of materials. However, the existing pneumatic conveying pipeline is fixed and can only perform one-to-one transmission. In order to supply materials to multiple processing equipment, the pneumatic conveying pipeline needs to be divided accordingly. The division of the pipeline can easily affect the pneumatic balance, and the flow of thermoplastic SMC particles conveyed by each branch pipe can easily fluctuate, which makes it difficult to uniformly supply materials to the processing equipment, thereby affecting the production feeding efficiency of thermoplastic SMC particles. SUMMARY

[0005] In view of the above prior art, the technical problem to be solved by the present application is that the existing pneumatic conveying feeding device is not convenient for supplying materials to multiple processing equipment, which affects the production feeding efficiency of thermoplastic SMC particles.

[0006] To solve the above problems, the present invention provides an automatic feeding device for the production of thermoplastic SMC materials, including a feeding module and a plurality of receiving modules. The output end of the feeding module is fixedly connected to a feeding pipeline, and the input end of the receiving module is fixedly connected to a receiving pipeline. The feeding pipeline and the receiving pipeline are connected through a selection module.

[0007] The selection module includes a connecting pipe. The end of the discharge pipe away from the discharge module is equidistantly connected to the connecting pipe. A telescopic cylinder is fixedly connected to the middle of the connecting pipe, and the connecting pipe and the telescopic cylinder are internally connected. A telescopic column is fixedly connected to the end of the receiving pipe away from the receiving module. The telescopic column is inserted into the telescopic cylinder, and a straight through hole and a receiving hole are respectively opened at the top and bottom of the telescopic column. One end of the straight through hole and the receiving hole are internally connected to the connecting pipe, and the other end of the receiving hole is connected to the receiving pipe.

[0008] In the above-mentioned automatic feeding device for the production of thermoplastic SMC material, the telescopic column moves in and out of the telescopic cylinder, and the assembly pipe selectively connects with the through hole and the receiving hole, so that multiple receiving modules can receive the thermoplastic SMC particles transmitted by wind in an orderly manner.

[0009] As a further improvement of this application, the connecting pipe and the telescopic cylinder are arranged at an inclined angle, and the angle between the connecting pipe and the telescopic cylinder is less than 60°. The smaller angle makes it easier for the receiving hole to bend at a small angle when it is connected to the connecting pipe, which facilitates the pneumatic transmission of thermoplastic SMC granules.

[0010] As a further improvement of this application, an electric push rod is fixedly connected to the bottom end of the telescopic cylinder, and the output end of the electric push rod is fixedly connected to the bottom end of the telescopic column. The telescopic column is adjusted by using the electric push rod to realize the automatic extension and retraction adjustment of the telescopic column inside the telescopic cylinder.

[0011] As a further improvement of this application, a vent is provided at the top of the telescopic cylinder, and a filter plug is inserted inside the vent. The vent allows the telescopic cylinder to communicate with the outside world, facilitating the automatic telescopic movement of the telescopic column inside the telescopic cylinder.

[0012] As a further improvement of this application, an air-assisted module is fixedly connected to the top of the telescopic cylinder, and an air-assisted pipe is fixedly connected to the air outlet of the air-assisted module. The air-assisted pipe passes through the filter plug, which is made of sponge material. The top of the telescopic column is provided with a No. 1 air-assisted hole that communicates with the through hole. The end of the air-assisted pipe away from the air-assisted module is inserted into the No. 1 air-assisted hole. The air-assisted module supplies air to the through hole through the air-assisted pipe, which effectively improves the pneumatic transmission capacity of the discharge pipeline and facilitates the long-distance transmission of thermoplastic SMC granules.

[0013] As a further improvement of the application, the outer sleeve of the telescopic column is provided with a heat expansion sealing sleeve, and the air assisting module comprises a hot air unit and a cold air unit; when the hot air unit of the air assisting module is enabled to supply air to the straight-through hole, the heat expansion sealing sleeve is expanded by heat, thereby effectively improving the sealing effect of the telescopic column in the telescopic cylinder and effectively reducing air leakage; before the telescopic column is about to perform telescopic movement, the air assisting module switches to the cold air unit to supply air, and the heat expansion sealing sleeve is contracted by cold, so that the telescopic column is more easily to perform telescopic movement.

[0014] As a further improvement of the application, the heat expansion sealing sleeve is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber, and the heat expansion sealing sleeve is provided with through holes corresponding to the straight-through hole and the material collecting hole, thereby effectively improving the sealing effect of the straight-through hole and the material collecting hole and the connecting pipe.

[0015] As a further improvement of the application, the heat expansion sealing sleeve is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber, and the heat expansion sealing sleeve is provided with through holes corresponding to the straight-through hole and the material collecting hole, thereby effectively improving the sealing effect of the straight-through hole and the material collecting hole and the connecting pipe.

[0016] As a further improvement of the application, the heat expansion sealing sleeve is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber, and the heat expansion sealing sleeve is provided with through holes corresponding to the straight-through hole and the material collecting hole, thereby effectively improving the sealing effect of the straight-through hole and the material collecting hole and the connecting pipe.

[0017] As a further improvement of the application, the heat expansion sealing sleeve is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber, and the heat expansion sealing sleeve is provided with through holes corresponding to the straight-through hole and the material collecting hole, thereby effectively improving the sealing effect of the straight-through hole and the material collecting hole and the connecting pipe.

[0018] As a further improvement of the application, the heat expansion sealing sleeve is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber, and the heat expansion sealing sleeve is provided with through holes corresponding to the straight-through hole and the material collecting hole, thereby effectively improving the sealing effect of the straight-through hole and the material collecting hole and the connecting pipe. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1Figure 1 is a perspective view of the first embodiment of the application;

[0020] Figure 2 Figure 2 is a sectional perspective view of the first embodiment of the application;

[0021] Figure 3 Figure 3 is a perspective view of the first embodiment of the application;

[0022] Figure 4 Figure 4 is a perspective view of the first embodiment of the application;

[0023] Figure 5 Figure 5 is a perspective view of the second embodiment of the application;

[0024] Figure 6 Figure 6 is a sectional perspective view of the second embodiment of the application;

[0025] Figure 7 Figure 7 is a perspective view of the second embodiment of the application;

[0026] Figure 8 Figure 8 is an enlarged view of the second air hole and the closing sleeve of the third embodiment of the application;

[0027] Figure 9 Figure 9 is a bottom view of the clamping sheet of the third embodiment of the application;

[0028] Figure 10 Figure 10 is a perspective view of the air pipe inserted into the second air hole of the third embodiment of the application.

[0029] Figure 1 is a perspective view of the first embodiment of the application;

[0030] 1, material discharging module; 101, material collecting module; 102, material discharging pipeline; 103, material collecting pipeline; 2, connecting pipe; 201, telescopic cylinder; 202, telescopic column; 203, straight-through hole; 204, material collecting hole; 205, electric push rod; 206, air vent; 207, filter plug; 3, air assisting module; 301, air pipe; 302, first air hole; 303, thermal expansion sealing sleeve; 304, through hole; 305, second air hole; 306, closing sleeve; 307, clamping sheet. DETAILED DESCRIPTION

[0031] The three embodiments of the application will be described in detail below with reference to the accompanying drawings.

[0032] First embodiment:

[0033] Figure 1The utility model discloses an automatic feeding device for thermoplastic SMC material production, including the material discharge module 1 and a plurality of quantity's material receiving module 101, the output of material discharge module 1 is fixedly connected with the material discharge pipeline 102, the input of material receiving module 101 is fixedly connected with the material receiving pipeline 103, and the material discharge pipeline 102 is communicated with the material receiving pipeline 103 through the gating module, and the gating module includes the group interface pipe 2, and the one end of material discharge pipeline 102 away from material discharge module 1 is connected with the group interface pipe 2 equidistantly;

[0034] The material discharge module 1 carries out the pneumatic transmission of thermoplastic SMC particles through the material discharge pipeline 102, and the material receiving module 101 is communicated with the material discharge pipeline 102 through the material receiving pipeline 103, the communication of the material receiving pipeline 103 and the material discharge pipeline 102 is controlled through the gating module, the thermoplastic SMC particle demand of multiple material receiving modules 101 is supplied by the material discharge module 1, and the production feeding efficiency of thermoplastic SMC particles is effectively improved;

[0035] The specific communication control mode of the gating module can be judged according to the inventory of thermoplastic SMC particles in the material receiving module 101 (specifically, a weighing sensor can be used for monitoring, and the weighing sensor is not given in the drawing);

[0036] In order to avoid the shutdown of the material discharge module 1, the inventories of multiple material receiving modules 101 are compared, the gating module controls the communication of the material receiving pipeline 103 and the material discharge pipeline 102 of the material receiving module 101 with the lowest inventory, and in the process of conveying thermoplastic SMC particles to the material receiving module 101, the material discharge module 1 always maintains the pneumatic transmission state of thermoplastic SMC particles, and the influence of the shutdown of the material discharge module 1 on the transmission efficiency of thermoplastic SMC particles is minimized;

[0037] The thermoplastic SMC particles in multiple material receiving modules 101 can be simultaneously produced, and the production and processing efficiency of thermoplastic SMC particles is effectively improved.

[0038] Figures 2 to 4It is shown that the middle part of the group connecting pipe 2 is fixedly connected with the telescopic cylinder 201, and the group connecting pipe 2 is in internal communication with the telescopic cylinder 201. The group connecting pipe 2 and the telescopic cylinder 201 are arranged in an inclined intersection, and the intersection angle of the group connecting pipe 2 and the telescopic cylinder 201 is less than 60°. When the collection hole 204 is in communication with the group connecting pipe 2, the setting bending angle of the collection hole 204 is also less than 60°, which facilitates the smooth entry of the thermoplastic SMC particles and the transmission air into the collection hole 204, facilitates the pneumatic conveying of the thermoplastic SMC particles, and the end of the collection pipeline 103 away from the collection module 101 is fixedly connected with the telescopic column 202. The telescopic column 202 is inserted with the telescopic cylinder 201, and the top and bottom of the telescopic column 202 are respectively provided with a straight-through hole 203 and a collection hole 204. One end of the straight-through hole 203 and the collection hole 204 is in internal communication with the group connecting pipe 2. The other end of the collection hole 204 is in communication with the collection pipeline 103. The bottom end of the telescopic cylinder 201 is fixedly connected with the electric push rod 205. The output end of the electric push rod 205 is fixedly connected with the bottom end of the telescopic column 202. The telescopic column 202 is adjusted by the electric push rod 205 to realize the automatic telescopic adjustment of the telescopic column 202 in the telescopic cylinder 201. The top end of the telescopic cylinder 201 is provided with an air vent 206. The air vent 206 is inserted with a filter plug 207. The telescopic cylinder 201 is in communication with the outside through the air vent 206, which facilitates the automatic telescopic movement of the telescopic column 202 in the telescopic cylinder 201.

[0039] When the gating module controls the communication condition of the collection pipeline 103 and the discharge pipeline 102, the telescopic column 202 is driven by the electric push rod 205 to move telescopically in the telescopic cylinder 201. When the group connecting pipe 2 is in communication with the straight-through hole 203, the thermoplastic SMC particles in the discharge pipeline 102 directly pass through the group connecting pipe 2 through the straight-through hole 203 and are conveyed to the next collection pipeline 103. When the group connecting pipe 2 is in communication with the collection hole 204, the thermoplastic SMC particles in the discharge pipeline 102 are sent into the collection pipeline 103, so as to realize the reception of the thermoplastic SMC particles by the collection module 101.

[0040] Since only one collection pipeline 103 is in communication with the discharge pipeline 102 during the pneumatic conveying of the thermoplastic SMC particles, the conveying force of the thermoplastic SMC particles is more concentrated, and compared with the traditional separate-pipe pneumatic conveying, the air force in the pipeline is concentrated, which effectively improves the pneumatic conveying distance of the thermoplastic SMC particles.

[0041] Second embodiment:

[0042] Compared with the first embodiment, the main addition is the air assisting module 3, and the specific added structure is as follows, and the remaining structure is the same as that of the first embodiment.

[0043] Figures 5 to 7It is shown that the top end of the telescopic cylinder 201 is externally fixedly connected with the air assisting module 3, the air outlet end of the air assisting module 3 is fixedly connected with the air assisting pipe 301, the air assisting pipe 301 penetrates through the filter plug 207, the filter plug 207 is made of sponge material, the top end of the telescopic column 202 is provided with a first air assisting hole 302 which is in communication with the straight-through hole 203, and the end of the air assisting pipe 301 away from the air assisting module 3 is inserted into the first air assisting hole 302 (in the embodiment, the air assisting pipe 301 is made of a corrugated flexible pipe, and the air assisting pipe 301 is telescoped into or out of the air permeable hole 206 according to the telescopic change of the telescopic column 202), the air assisting module 3 supplies air into the straight-through hole 203 through the air assisting pipe 301, effectively improves the pneumatic conveying wind power of the discharging pipe 102, facilitates the long-distance transmission of the thermoplastic SMC particles, the outer portion of the telescopic column 202 is provided with a thermal expansion sealing sleeve 303, the air assisting module 3 includes a hot air unit and a cold air unit, when the air assisting module 3 supplies air into the straight-through hole 203 by using the hot air unit, the thermal expansion sealing sleeve 303 is heated and expanded, thereby effectively improving the sealing effect of the telescopic column 202 in the telescopic cylinder 201, and effectively reducing the air leakage, and before the telescopic column 202 is about to perform the telescopic movement, the air assisting module 3 switches to supply air by using the cold air unit, the thermal expansion sealing sleeve 303 is cooled and contracted, and the telescopic column 202 is more easily to perform the telescopic movement, the thermal expansion sealing sleeve 303 is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber, and the thermal expansion sealing sleeve 303 is provided with through holes 304 corresponding to the straight-through hole 203 and the material collecting hole 204, thereby realizing that the thermal expansion sealing sleeve 303 is provided at the positions of the straight-through hole 203 and the material collecting hole 204, and effectively improving the sealing effect of the straight-through hole 203 and the material collecting hole 204 and the connecting pipe 2;

[0044] When the connecting pipe 2 is in communication with the straight-through hole 203, the thermoplastic SMC particles in the discharging pipe 102 directly pass through the connecting pipe 2 to the next material collecting pipe 103 through the straight-through hole 203, in this process, the air assisting module 3 supplies air into the straight-through hole 203 through the air assisting pipe 301, effectively enhances the pneumatic conveying wind power of the discharging pipe 102, and further effectively prolongs the transmission distance of the thermoplastic SMC particles, and facilitates the thermoplastic SMC particles to be transmitted to the next material collecting pipe 103 while maintaining sufficient pneumatic force;

[0045] After the telescopic column 202 finishes the telescopic position adjustment, the air-assisted module 3 starts the hot air unit to realize the hot air delivery to the straight-through hole 203, and the delivered hot air realizes the thermal expansion of the thermal expansion sealing sleeve 303, and the expanded thermal expansion sealing sleeve 303 tightly fills the space between the telescopic column 202 and the telescopic cylinder 201, effectively improving the sealing effect of the telescopic column 202 and the telescopic cylinder 201, thereby effectively reducing the air leakage. Before the telescopic column 202 is about to perform the telescopic movement, the air-assisted module 3 switches to the cold air unit to deliver the cold air, and the delivered cold air realizes the thermal contraction of the thermal expansion sealing sleeve 303, effectively reducing the tightness between the telescopic column 202 and the telescopic cylinder 201 (the process time is short, and the air leakage between the telescopic column 202 and the telescopic cylinder 201 is small), and the telescopic column 202 is more easily telescopic, effectively improving the telescopic adjustment efficiency of the telescopic column 202.

[0046] Third embodiment:

[0047] Compared with the second embodiment, the second air-assisted hole 305 is mainly added, and the specific added structure is as follows, and the remaining structures are the same as those of the second embodiment.

[0048] Figures 8 to 10 As shown, the second air-assisted hole 305 is arranged between the straight-through hole 203 and the material collecting hole 204, and the end of the air-assisted pipe 301 away from the air-assisted module 3 is inserted into the second air-assisted hole 305. When the connecting pipe 2 is connected to the material collecting hole 204, the air-assisted pipe 301 is inserted into the second air-assisted hole 305 (in this embodiment, the air-assisted pipe 301 is made of stainless steel pipe, and the air-assisted pipe 301 is fixed in the telescopic cylinder 201, and when the telescopic column 202 performs the telescopic movement, the air-assisted pipe 301 can pass through the first air-assisted hole 302 and be inserted into the second air-assisted hole 305), which realizes the air delivery to the material collecting hole 204 and effectively improves the air transmission effect of the material collecting pipeline 103. The inside of the second air-assisted hole 305 is fixedly connected with the sealing sleeve 306, which is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber. After the air-assisted pipe 301 is separated from the second air-assisted hole 305, the sealing sleeve 306 seals the second air-assisted hole 305 by using the elasticity of the sealing sleeve 306, thereby effectively reducing the influence of the second air-assisted hole 305 on the straight-through hole 203. The top inner wall of the material collecting hole 204 is fixedly connected with the clamping sheet 307, which is arranged in a V shape and is fixedly connected with the conical end of the sealing sleeve 306. The clamping sheet 307 is made of spring steel sheet, and the clamping sheet 307 clamps the conical end of the sealing sleeve 306, thereby further improving the sealing effect of the sealing sleeve 306.

[0049] When the group adapter 2 is communicated with the receiving hole 204, the discharging pipeline 102 is communicated with the receiving pipeline 103 to perform the pneumatic transmission of the thermoplastic SMC particles, the air assisting pipeline 301 passes through the first air assisting hole 302, and then is inserted with the second air assisting hole 305 to realize the air input into the receiving hole 204, effectively improving the pneumatic transmission effect of the receiving pipeline 103, after the air assisting pipeline 301 is separated from the second air assisting hole 305, the closing sleeve 306 utilizes the elasticity thereof to close the second air assisting hole 305, and utilizes the clamping sheet 307 to clamp the tapered end of the closing sleeve 306, further effectively improving the closing effect of the closing sleeve 306 on the second air assisting hole 305.

[0050] In combination with the current actual demand, the above-mentioned embodiments adopted by the present application are not limited to the above, various changes made within the knowledge range of the skilled in the art without departing from the concept of the present application still fall within the protection scope of the present application.

Claims

1. An automatic feeding device for thermoplastic SMC material production, characterized in that: Including the discharge module (1) and multiple number of material receiving module (101), the output end of the discharge module (1) is fixedly connected with the discharge pipeline (102), the input end of the material receiving module (101) is fixedly connected with the material receiving pipeline (103), the discharge pipeline (102) and the material receiving pipeline (103) are communicated through the gating module; The gating module includes a group connection pipe (2), one end of the discharge pipeline (102) away from the discharge module (1) is connected with the group connection pipe (2) at equal distance, the middle part of the group connection pipe (2) is fixedly connected with the telescopic cylinder (201), and the group connection pipe (2) and the telescopic cylinder (201) are communicated, one end of the material receiving pipeline (103) away from the material receiving module (101) is fixedly connected with the telescopic column (202), the telescopic column (202) is inserted with the telescopic cylinder (201), and the top and bottom of the telescopic column (202) are respectively provided with straight-through holes (203) and material receiving holes (204), one end of the straight-through holes (203) and the material receiving holes (204) are communicated with the inside of the group connection pipe (2), and the other end of the material receiving holes (204) is communicated with the material receiving pipeline (103); The bottom end of the telescopic cylinder (201) is fixedly connected with the electric push rod (205), the output end of the electric push rod (205) is fixedly connected with the bottom end of the telescopic column (202), the top end of the telescopic cylinder (201) is provided with the air vent (206), the air vent (206) is inserted with the filter plug (207), the top end of the telescopic cylinder (201) is fixedly connected with the air assisting module (3) outside, the air outlet end of the air assisting module (3) is fixedly connected with the air assisting pipe (301), the air assisting pipe (301) penetrates through the filter plug (207), the filter plug (207) is made of sponge material, the top end of the telescopic column (202) is provided with a first air assisting hole (302) communicated with the straight-through hole (203), one end of the air assisting pipe (301) away from the air assisting module (3) is inserted with the first air assisting hole (302); The second air assisting hole (305) is arranged between the straight-through hole (203) and the material receiving hole (204), one end of the air assisting pipe (301) away from the air assisting module (3) is inserted with the second air assisting hole (305), the inside of the second air assisting hole (305) is fixedly connected with the closed sleeve (306), the closed sleeve (306) is funnel-shaped, the inner wall of the top of the material receiving hole (204) is fixedly connected with the clamping sheet (307), the clamping sheet (307) is V-shaped, and the clamping sheet (307) is fixedly connected with the tapered end of the closed sleeve (306) outside, and the clamping sheet (307) is made of spring sheet.

2. The automatic feeding device for producing thermoplastic SMC material according to claim 1, characterized in that: The group connection pipe (2) and the telescopic cylinder (201) are arranged in inclined intersection, and the intersection angle of the group connection pipe (2) and the telescopic cylinder (201) is less than 60°.

3. The automatic feeding device for producing thermoplastic SMC material according to claim 1, characterized in that: The outside of the telescopic column (202) is sleeved with the thermal expansion sealing sleeve (303), and the air assisting module (3) includes a hot air unit and a cold air unit.

4. The automatic feeding device for producing thermoplastic SMC material according to claim 3, characterized in that: The heat expansion sealing sleeve (303) is provided with a through hole (304) corresponding to the straight through hole (203) and the material collecting hole (204), and the heat expansion sealing sleeve (303) is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber.

5. The automatic feeding device for producing thermoplastic SMC material according to claim 1, characterized in that: The closing sleeve (306) is made of one of silicon rubber, fluorine rubber, butyl rubber and polyurethane rubber.

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