Engraving equipment for flexible printed circuit board

Abstract

The invention discloses engraving equipment for a flexible printed circuit board, and belongs to the technical field of flexible printed circuit board machining.The engraving equipment comprises a rack placed above the ground, a collecting tank is fixedly installed at the upper end of the rack, and a conveying frame is fixedly installed above the collecting tank; a support is fixedly installed at the upper end of the conveying frame, movable pipes are evenly and rotationally installed on the support, and spray heads are evenly installed on the movable pipes. A driving assembly for driving the movable pipe to rotate in a reciprocating manner is mounted on the rear side of the bracket; a pressure adjusting assembly used for adjusting the liquid spraying pressure of the spray head is arranged between the support and the pressure adjusting bin. According to the engraving equipment for the flexible printed circuit board, multi-direction swing adjustment of the spray head can be achieved, it is ensured that etching liquid on the board body can flow uniformly and be updated, the board body can be slightly shaken, the phenomenon that the etching rate is reduced due to formation of a water film is avoided, and the etching effect is effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of flexible printed circuit board processing, in particular to engraving equipment for flexible printed circuit boards. Background Art

[0002] Flexible printed circuit board (FPC) is a printed circuit board made of a flexible insulating substrate. During the production and processing of flexible printed circuit boards, it is necessary to engrave circuits on the surface of the board. Since the material of flexible printed circuit boards is relatively soft, etching is generally used for circuit engraving.

[0003] The prior art (application number: 202323626014.8, Chinese patent with application date of 2023-12-28) discloses a flexible circuit board etching device, including a conveying mechanism and a gas-liquid spraying mechanism. The conveying mechanism is used to convey the flexible circuit board substrate from the inlet to the outlet. The gas-liquid spraying mechanism includes a liquid inlet pipe, an air inlet pipe and a spray pipe. The liquid inlet pipe and the air inlet pipe are arranged at intervals, and the spray pipe is used to spray chemicals or release gases. The spray pipe includes a connecting pipe, a control valve and a nozzle. The two ends of the connecting pipe are connected to the liquid inlet pipe and the air inlet pipe. Control valves are arranged at both ends of the connecting pipe. Multiple nozzles are arranged on the connecting pipe at intervals and are located between the two control valves. The control valve is opened or closed to control the connecting pipe to spray liquid or gas. The flexible circuit board etching device of the present application is provided with a gas-liquid integrated spray mechanism, which controls the nozzle to release inert gas during the process of etching the substrate of the flexible circuit board, thereby reducing the contact between the outside air and the substrate being etched or completed, thereby preventing the oxidation of the etched substrate; when in use, the installation position of the nozzle is fixed, so that the uniformity of the agent coverage at the gap between adjacent nozzles is limited, resulting in different etching effects at different positions on the circuit board, thereby affecting the processing quality of the flexible printed circuit board, and there are certain usage defects. Summary of the invention

[0004] The object of the present invention is to provide an engraving device for a flexible printed circuit board to solve the problem raised in the above-mentioned background technology that the nozzle installation position of the engraving device for flexible printed circuit boards on the market is fixed, resulting in limited uniformity of agent coverage at the gap between adjacent nozzles, thereby causing different etching effects at different positions on the circuit board.

[0005] To achieve the above object, the present invention provides the following technical solution: an engraving device for a flexible printed circuit board, comprising a frame placed above the ground, a collecting trough fixedly installed on the upper end of the frame, a conveying frame fixedly installed above the collecting trough, a conveying shaft evenly rotatingly installed on the inner side of the conveying frame, and a conveying wheel evenly fixedly installed on the outer side of the conveying shaft; A bracket is fixedly installed on the upper end of the conveying frame, and a movable pipe is evenly rotated and installed on the bracket, and nozzles are evenly installed on the movable pipe. At the same time, a pressure regulating bin is fixedly installed on the upper part of the bracket, and a shunt pipe is connected to the outer side of the pressure regulating bin, and a hose is connected between the shunt pipe and the end of each movable pipe; A driving assembly for driving the movable tube to reciprocate is installed on the rear side of the bracket, and a connecting plate is provided on the front side of the bracket, and each movable tube is rotatably installed on the connecting plate, and a transmission assembly for controlling the movement and adjustment of the connecting plate is connected between the front end of the movable tube located in the middle position and the bracket, and a gas transmission assembly is also installed on the connecting plate; A pressure regulating assembly for regulating the liquid spraying pressure of the nozzle is arranged between the bracket and the pressure regulating chamber.

[0006] Preferably, the driving assembly includes a motor fixedly mounted on the outside of the bracket, and a driving disk is fixedly mounted on the output end of the motor, and a slider is fixedly mounted on the upper surface of the driving disk. At the same time, a rack is also slidably mounted on the outside of the bracket, and a linkage member with a bar-shaped ring structure is fixedly mounted on the outside of the rack. At the same time, during the rotation of the driving disk, the slider slides back and forth along the inner side of the linkage member to drive the rack to slide back and forth.

[0007] Preferably, a sleeve is slidably mounted on the outer side of the rear end of the movable tube through a connecting key, and the sleeve is rotatably mounted on the outer side of the bracket, and a gear is fixedly mounted on the outer side of the sleeve, and at the same time, a plurality of groups of tooth blocks are evenly arranged on the rack, and each group of tooth blocks on the rack is respectively meshed and connected with gears at different positions, and the rack slides back and forth to drive the movable tube to rotate back and forth.

[0008] Preferably, the transmission assembly includes a fixed plate fixedly mounted on the front end of the movable tube located in the middle position, and a push rod is symmetrically fixedly mounted on the rear side of the fixed plate, and a support member with an annular structure is fixedly mounted on the outer side of the bracket, and the end surface of the support member facing one end of the fixed plate is a wavy structure, and when the movable tube drives the fixed plate to rotate, the push rod on the outer side of the fixed plate slides in contact with the wavy end surface of the support member to drive the movable tube to be telescopically adjusted on the bracket, and a spring is connected between the support member and the bracket.

[0009] Preferably, the movable tube performs synchronous reciprocating sliding adjustment during the reciprocating rotation, and the nozzle on the movable tube performs multi-directional reciprocating adjustment for spraying.

[0010] Preferably, the air delivery assembly includes an air delivery bag connected between the bracket and the connecting plate, and the outside of the air delivery bag is connected to an intake pipe and an exhaust pipe, and a filter is provided at the air inlet end of the intake pipe, and both the intake pipe and the exhaust pipe are provided with a one-way valve structure.

[0011] Preferably, the exhaust end of the exhaust pipe is rotatably connected to the end of the conveying shaft located in the middle position, and the interior of the conveying shaft located in the middle position is a hollow structure, and air holes are evenly opened on the conveying wheel connected to the conveying shaft in the middle position, and the exhaust pipe is connected to the air holes through the cavity of the conveying shaft.

[0012] Preferably, the voltage regulating assembly includes two fixed shells symmetrically fixedly installed on the outside of the bracket, and a pressure plate is slidably arranged on the inner side of the fixed shell, and an air storage bag is arranged between the pressure plate and the fixed shell, and the rack pushes the pressure plate during the reciprocating movement.

[0013] Preferably, the pressure regulating assembly also includes an elastic airbag fixedly mounted on the inner side of the pressure regulating chamber, and the elastic airbag is connected to the air storage bag through a ventilation tube, and after the air storage bag is pressurized, air is supplied to the elastic airbag through the ventilation tube.

[0014] Compared with the prior art, the invention has the following beneficial effects: the engraving equipment for flexible printed circuit boards can realize multi-directional swing adjustment of the nozzle, ensure that the etching liquid on the board body can flow and update evenly, and can slightly shake the board body to avoid the formation of water film and reduce the etching rate, thereby effectively improving the etching effect. The specific contents are as follows; 1. A movable tube and a support are provided. By starting the motor, the driving disk can be driven to rotate, and then the rack is driven to move back and forth through the transmission action of the linkage, so that the rack drives the movable tube to rotate back and forth through the meshing with the gear. With the reciprocating rotation of the movable tube, the movable tube located in the middle position can drive the fixed disk to rotate synchronously, and then drive multiple movable tubes to reciprocate and slide through the connecting plate, so that the movable tube can slide back and forth during the reciprocating rotation, realizing multi-directional adjustment spraying, effectively improving the flow uniformity of the liquid on the circuit board, and ensuring the etching uniformity.

[0015] 2. An air storage bag and an elastic air bag are provided. As the rack slides back and forth, it pushes the pressure plate on the inner side of the fixed shell to slide, so that the pressure plate can squeeze the air storage bag, so that part of the gas in the air storage bag enters the elastic air bag through the ventilation tube, thereby causing the elastic air bag to expand and deform, thereby causing the internal space of the pressure regulating chamber to change, thereby achieving the spray pressure of the nozzle at different angles, making the pressure impact on the circuit board balanced, and ensuring that the etching liquid can keep flowing and updating on the outside of the board.

[0016] 3. Air holes and air bags are provided. As the connecting plate moves back and forth, it can squeeze and stretch the air bags back and forth, so that the air bags inhale external air through the air suction pipe, and transport it to the cavity inside the conveying shaft in the middle position through the exhaust pipe, and discharge it through the air holes on the conveying wheel on its outside, so as to realize automatic blowing of the flexible circuit board passing above it, so that the flexible circuit board shakes under the action of air pressure, so as to achieve the purpose of removing water film and ensure etching efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the main structure of the present invention; Figure 2 It is a side view structural schematic diagram of the present invention; Figure 3 It is a schematic diagram of the rack and gear connection structure of the present invention; Figure 4 For the present invention Figure 3 The enlarged structural diagram at A in the middle; Figure 5 This is a schematic diagram of the connection plate installation structure of the present invention; Figure 6 It is a schematic diagram of the connection structure between the movable tube and the sleeve of the present invention; Figure 7 This is a schematic diagram of the installation structure of the fixing plate and the supporting member of the present invention; Figure 8 It is a schematic diagram of the connection structure between the air storage bag and the elastic air bag of the present invention; Fig. 9 This is a schematic diagram of the installation structure of the air storage bag of the present invention; Fig.10 It is a schematic diagram of the connection structure between the delivery shaft and the air delivery bag of the present invention.

[0018] In the figure: 1. frame; 2. collecting trough; 3. conveying shaft; 4. conveying wheel; 401, air hole; 5. bracket; 6. movable pipe; 7. nozzle; 8. pressure regulating chamber; 9. shunt pipe; 10. hose; 11. motor; 12. driving plate; 13. slider; 14. rack; 15. linkage; 16. sleeve; 17. gear; 18. fixed plate; 19. push rod; 20. support; 21. connecting plate; 22. air delivery bag; 23. suction pipe; 24. exhaust pipe; 25. fixed shell; 26. pressure plate; 27. air storage bag; 28. ventilation pipe; 29. ​​elastic air bag. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Example 1: Please refer to Figure 1-Figure 9As shown, the existing engraving equipment for flexible printed circuit boards is prone to uneven spraying when spraying etching liquid, and the liquid spray head is placed in a single direction, so that the etching liquid update rate on the surface of the circuit board is different, resulting in poor etching uniformity of the circuit board. In order to solve this technical problem, this embodiment discloses the following technical content; A flexible printed circuit board engraving device comprises a frame 1 placed above the ground, a collecting tank 2 is fixedly installed on the upper end of the frame 1, a conveying frame is fixedly installed above the collecting tank 2, and a conveying shaft 3 is evenly rotated and installed on the inner side of the conveying frame, and a conveying wheel 4 is evenly fixed and installed on the outer side of the conveying shaft 3; A bracket 5 is fixedly installed on the upper end of the conveying frame, and a movable pipe 6 is evenly rotatably installed on the bracket 5, and a nozzle 7 is evenly installed on the movable pipe 6. At the same time, a pressure regulating bin 8 is also fixedly installed above the bracket 5, and a shunt pipe 9 is connected to the outer side of the pressure regulating bin 8, and a hose 10 is connected between the shunt pipe 9 and the end of each movable pipe 6; A driving component for driving the movable tube 6 to reciprocate is installed on the rear side of the bracket 5, and a connecting plate 21 is provided on the front side of the bracket 5, and each movable tube 6 is rotatably installed on the connecting plate 21, and a transmission component for controlling the movement and adjustment of the connecting plate 21 is connected between the front end of the movable tube 6 located in the middle position and the bracket 5, and a pressure regulating component for adjusting the liquid spraying pressure of the nozzle 7 is provided between the bracket 5 and the pressure regulating chamber 8.

[0021] The driving assembly includes a motor 11 fixedly mounted on the outside of the bracket 5, and a driving disk 12 is fixedly mounted on the output end of the motor 11, and a slider 13 is fixedly mounted on the upper surface of the driving disk 12. At the same time, a rack 14 is also slidably mounted on the outside of the bracket 5, and a linkage member 15 with a bar-shaped ring structure is fixedly mounted on the outside of the rack 14. At the same time, during the rotation of the driving disk 12, the slider 13 slides back and forth along the inner side of the linkage member 15 to drive the rack 14 to slide back and forth.

[0022] A sleeve 16 is slidably sleeved on the outer side of the rear end of the movable tube 6 through a connecting key, and the sleeve 16 is rotatably installed on the outer side of the bracket 5, and a gear 17 is fixedly installed on the outer side of the sleeve 16. At the same time, multiple groups of tooth blocks are evenly arranged on the rack 14, and each group of tooth blocks on the rack 14 is respectively meshed and connected with the gears 17 at different positions. The rack 14 slides back and forth to drive the movable tube 6 to rotate back and forth.

[0023] The transmission assembly includes a fixed plate 18 fixedly installed at the front end of the movable tube 6 located in the middle position, and a push rod 19 is symmetrically fixedly installed on the rear side of the fixed plate 18, and a support member 20 with an annular structure is fixedly installed on the outer side of the bracket 5, and the end surface of the support member 20 facing the fixed plate 18 is a wavy structure. At the same time, when the movable tube 6 drives the fixed plate 18 to rotate, the push rod 19 on the outer side of the fixed plate 18 slides in contact with the wavy end surface of the support member 20 to drive the movable tube 6 to be telescopically adjusted on the bracket 5, and a spring is connected between the support member 20 and the bracket 5.

[0024] The movable tube 6 performs synchronous reciprocating sliding adjustment during the reciprocating rotation, and the nozzle 7 on the movable tube 6 performs multi-directional reciprocating spraying adjustment.

[0025] The voltage regulating assembly includes two fixed shells 25 symmetrically fixedly mounted on the outside of the bracket 5, and a pressure plate 26 is slidably arranged on the inner side of the fixed shell 25, and an air storage bag 27 is arranged between the pressure plate 26 and the fixed shell 25, and the rack 14 pushes the pressure plate 26 during the reciprocating movement.

[0026] The pressure regulating assembly also includes an elastic airbag 29 fixedly mounted on the inner side of the pressure regulating chamber 8 , and the elastic airbag 29 is connected to the air storage bag 27 through a ventilation tube 28 , and the air storage bag 27 transmits air to the elastic airbag 29 through the ventilation tube 28 after being pressurized.

[0027] Through the above technical scheme, the flexible printed circuit board is placed above the conveying wheel 4 for conveying, and at the same time, the external conveying pump is controlled to convey the etching liquid to the pressure regulating chamber 8, and enters the movable tube 6 through the shunt pipe 9 and the hose 10, so as to spray to the surface of the circuit board through the nozzle 7 to achieve etching, and at the same time, the motor 11 is started, so that the motor 11 drives the driving disk 12 at its output end to rotate, so that the slider 13 on the upper surface of the driving disk 12 slides back and forth along the groove body of the linkage 15, and then drives the rack 14 to slide back and forth through the linkage 15. At this time, the rack 14 will be meshed and connected with the gear 17 on the outside of each sleeve 16, so as to drive the movable tube 6 to reciprocate through the sleeve 16 to achieve swing spraying, and at the same time, when the movable tube 6 in the middle position rotates, the fixed disk 18 fixed at its front end will rotate synchronously, so that the push rod 19 on the outside of the fixed disk 18 slides against the wavy arc surface of the linkage 15. At the same time, the movable tube 6 in the middle position will drive other movable tubes 6 to slide synchronously through the connecting plate 21, so that the movable tube 6 can slide reciprocatingly while rotating back and forth, realizing multi-angle adjustment of spraying, effectively improving the uniformity of spraying, and at the same time, with the reciprocating movement of the rack 14, its end will push the pressure plate 26 on the inner side of the fixed shell 25 to move synchronously, so that the pressure plate 26 can squeeze the air storage bag 27 on the inner side of the fixed shell 25, so that part of the gas exchange tube 28 in the air storage bag 27 enters the elastic air bag 29, realizing the expansion adjustment of the elastic air bag 29, so that the accommodating liquid space inside the pressure regulating chamber 8 can be adjusted, so as to achieve real-time automatic adjustment of the spraying pressure of the nozzle 7, and ensure that the impact force of the circuit board is close when sprayed at different angles, so that the etching liquid on the surface of the circuit board can flow and update evenly, ensuring the uniformity of etching.

[0028] Embodiment 2: The technical content disclosed in this embodiment is a further improvement on the above embodiment 1. When the existing flexible printed circuit board engraving equipment is spraying the liquid, a water film is easily formed on the surface of the circuit board, thereby affecting the subsequent contact between the liquid and the board body, thereby reducing the etching efficiency. In order to further solve this technical problem, this embodiment discloses the following technical content, such as Figure 7 and Fig.10 As shown; an air delivery component is also installed on the connecting plate 21; the air delivery component includes an air delivery bag 22 connected between the bracket 5 and the connecting plate 21, and the outer side of the air delivery bag 22 is connected to an intake pipe 23 and an exhaust pipe 24, and a filter is provided at the air inlet end of the intake pipe 23, and both the intake pipe 23 and the exhaust pipe 24 are provided with a one-way valve structure.

[0029] The exhaust end of the exhaust pipe 24 is rotatably connected to the end of the conveying shaft 3 located in the middle position, and the interior of the conveying shaft 3 located in the middle position is a hollow structure, and the conveying wheel 4 connected to the conveying shaft 3 in the middle position is evenly provided with air holes 401, and the exhaust pipe 24 is connected to the air holes 401 through the cavity of the conveying shaft 3.

[0030] Through the above technical solution, as the elastic movement of the connecting plate 21 is adjusted, it will cooperate with the bracket 5 to reciprocately stretch and squeeze the air delivery bag 22, so that the air delivery bag 22 inhales the purified clean air through the suction pipe 23, and delivers it to the inner side of the delivery shaft 3 at the middle position through the exhaust pipe 24, and sprays it out through the air hole 401 opened on the delivery wheel 4, so as to blow the circuit board passing above it, so that the circuit board shakes under the action of air pressure, and the water film on its surface is automatically removed, ensuring that the subsequent chemical solution can fully contact the circuit board, thereby ensuring the etching efficiency.

[0031] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0032] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An engraving device for a flexible printed circuit board, comprising a frame (1) placed above the ground, a collecting trough (2) being fixedly mounted on the upper end of the frame (1), a conveying frame being fixedly mounted above the collecting trough (2), a conveying shaft (3) being evenly rotatably mounted on the inner side of the conveying frame, and a conveying wheel (4) being evenly fixedly mounted on the outer side of the conveying shaft (3); It is characterized in that A bracket (5) is fixedly mounted on the upper end of the conveying frame, and a movable tube (6) is evenly mounted on the bracket (5) for rotation, and a nozzle (7) is evenly mounted on the movable tube (6). A pressure regulating chamber (8) is also fixedly mounted above the bracket (5), and a shunt tube (9) is connected to the outer side of the pressure regulating chamber (8), and a hose (10) is connected between the shunt tube (9) and the end of each movable tube (6); A driving assembly for driving the movable tube (6) to reciprocate is installed on the rear side of the bracket (5), and a connecting plate (21) is provided on the front side of the bracket (5), and each movable tube (6) is rotatably installed on the connecting plate (21), and a transmission assembly for controlling the movement and adjustment of the connecting plate (21) is connected between the front end of the movable tube (6) located in the middle and the bracket (5), and a gas transmission assembly is also installed on the connecting plate (21); A pressure regulating assembly for regulating the liquid spraying pressure of the spray head (7) is provided between the support (5) and the pressure regulating chamber (8).

2. The engraving device for a flexible printed circuit board according to claim 1, characterized in that: The driving assembly comprises a motor (11) fixedly mounted on the outside of a bracket (5), a driving disk (12) fixedly mounted on the output end of the motor (11), and a slider (13) fixedly mounted on the upper surface of the driving disk (12), a rack (14) slidably mounted on the outside of the bracket (5), and a linkage member (15) with a strip-shaped ring structure fixedly mounted on the outside of the rack (14), and during the rotation of the driving disk (12), the slider (13) slides back and forth along the inside of the linkage member (15) to drive the rack (14) to slide back and forth.

3. The engraving device for a flexible printed circuit board according to claim 2, characterized in that: A sleeve (16) is slidably sleeved on the outer side of the rear end of the movable tube (6) via a connecting key, and the sleeve (16) is rotatably mounted on the outer side of the bracket (5), and a gear (17) is fixedly mounted on the outer side of the sleeve (16), and a plurality of groups of tooth blocks are evenly arranged on the rack (14), and each group of tooth blocks on the rack (14) is meshed and connected with a gear (17) at a different position, respectively, and the rack (14) slides back and forth to drive the movable tube (6) to rotate back and forth.

4. The engraving device for a flexible printed circuit board according to claim 1, characterized in that: The transmission assembly comprises a fixed plate (18) fixedly mounted on the front end of a movable tube (6) located in the middle position, a push rod (19) is symmetrically fixedly mounted on the rear side of the fixed plate (18), and a support member (20) with an annular structure is fixedly mounted on the outer side of the bracket (5), and the end surface of the support member (20) facing the fixed plate (18) is a wavy structure, and when the movable tube (6) drives the fixed plate (18) to rotate, the push rod (19) on the outer side of the fixed plate (18) slides in contact with the wavy end surface of the support member (20) to drive the movable tube (6) to be telescopically adjusted on the bracket (5), and a spring is connected between the support member (20) and the bracket (5).

5. The engraving device for a flexible printed circuit board according to claim 4, characterized in that: The movable tube (6) performs synchronous reciprocating sliding adjustment during the reciprocating rotation, and the spray head (7) on the movable tube (6) performs multi-directional reciprocating spraying adjustment.

6. The engraving device for a flexible printed circuit board according to claim 1, characterized in that: The air delivery assembly comprises an air delivery bag (22) connected between the bracket (5) and the connecting plate (21), and an air intake pipe (23) and an air exhaust pipe (24) are connected to the outside of the air delivery bag (22), and a filter is provided at the air intake end of the air intake pipe (23), and both the air intake pipe (23) and the air exhaust pipe (24) are provided with a one-way valve structure.

7. The engraving device for a flexible printed circuit board according to claim 6, characterized in that: The exhaust end of the exhaust pipe (24) is rotatably connected to the end of the conveying shaft (3) located in the middle position, the interior of the conveying shaft (3) located in the middle position is a hollow structure, and air holes (401) are evenly opened on the conveying wheel (4) connected to the conveying shaft (3) in the middle position, and the exhaust pipe (24) is connected to the air holes (401) through the cavity of the conveying shaft (3).

8. The engraving device for a flexible printed circuit board according to claim 1, characterized in that: The voltage regulating assembly comprises two fixed shells (25) symmetrically fixedly mounted on the outside of the bracket (5), a pressure plate (26) is slidably arranged on the inside of the fixed shell (25), and an air storage bag (27) is arranged between the pressure plate (26) and the fixed shell (25), and the rack (14) pushes the pressure plate (26) during the reciprocating movement.

9. The engraving device for a flexible printed circuit board according to claim 1, characterized in that: The pressure regulating assembly further comprises an elastic airbag (29) fixedly mounted on the inner side of the pressure regulating chamber (8), and the elastic airbag (29) is connected to the air storage bag (27) via a ventilation tube (28), and after the air storage bag (27) is pressurized, air is supplied to the elastic airbag (29) via the ventilation tube (28).

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