Automatic film laminating machine for concrete prefabricated column curing

Abstract

The invention discloses an automatic film laminating machine for concrete prefabricated column maintenance, which comprises a suspension platform used for being supported on the top of a prefabricated column and provided with a positioning hole matched with a reinforcing steel bar extending out of the top of the prefabricated column; the rolling wheels are arranged at the four corners of the suspended table, a traction rope is unwound on the rolling wheels, and the tail end of the traction rope is connected with a balance weight; the sliding sleeve sleeves the traction rope, and the four corners of the lower end of the plastic film are fixedly connected with the sliding sleeve; and the unlocking assembly is used for connecting the suspended table and the sliding sleeve, and when the winding wheel rolls to unwind the traction rope to the maximum length, the unlocking assembly is triggered to enable the sliding sleeve to freely slide down along the traction rope. The four pulling ropes are put downwards from the four corners of the suspended table in advance, then the unlocking assembly is triggered when the winding wheel rolls to unwind the pulling ropes to the maximum length, the sliding sleeves slide down freely along the pulling ropes, the sliding sleeves on the four corners slide down smoothly along the vertical pulling ropes, and the four corners of the plastic film are driven to be unfolded downwards at a certain distance; and the phenomenon of clamping stagnation of the plastic film is greatly avoided.

Description

Technical Field

[0001] This invention relates to the field of prefabricated building technology, specifically to an automatic film covering machine for curing precast concrete columns. Background Technology

[0002] Precast reinforced concrete columns are building support components produced through steps such as erecting a steel reinforcement frame, setting up formwork, pouring concrete, and curing concrete. During the concrete curing process, a plastic film needs to be fixed over the precast column to ensure the curing effect.

[0003] Existing membrane covering operations often involve placing a folded plastic film over a rectangular frame, then using a crane and manual labor to hoist the frame above the precast column and slowly lower it. The inner side of the plastic film then abuts against the top of the precast column, and the folded part of the plastic film slowly unfolds as the frame descends, forming a sleeve that is then placed over the precast column from top to bottom. Next, the plastic film is tightened and tied with ropes to secure it.

[0004] Obviously, the unfolding of the plastic film mainly relies on the gravity of the metal frame fixed at the lower end of the plastic film. In this way, the plastic film is prone to problems such as uneven descent of the four corners and jamming. Therefore, there is an urgent need for an automatic film covering machine for the curing of precast concrete columns to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an automatic film covering machine for the curing of precast concrete columns, so as to overcome the above-mentioned shortcomings in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An automatic film covering machine for curing precast concrete columns includes a suspended platform for supporting the top of the precast column, with positioning holes matching the protruding reinforcing bars at the top of the precast column; reels located at the four corners of the suspended platform, on which traction ropes are wound out, with counterweights connected to the ends of the traction ropes; a sliding sleeve fitted onto the traction ropes, with the lower four corners of the plastic film fixedly connected to the sliding sleeves, the top of the plastic film fixedly connected to the suspended platform, and the remaining parts of the plastic film folded vertically into a U-shape to fit over the outside of the precast column; and an unlocking component for connecting the suspended platform and the sliding sleeves. When the reels roll out the traction ropes to their maximum length, the unlocking component is triggered, allowing the sliding sleeves to slide freely down the traction ropes.

[0008] Preferably, the suspended platform is provided with a hook for connecting lifting equipment.

[0009] Preferably, a support is provided on the suspended platform, the shaft of the reel is hinged to the support, and an electronic control component for limiting the rotation of the reel shaft is provided on the support.

[0010] Preferably, an insert plate is fixedly provided on the sliding sleeve, and a slot matching the insert plate is provided on the suspended platform. The unlocking component includes a limiting rod movably provided inside the suspended platform, a limiting hole matching the limiting rod is provided on the insert plate, a synchronization component for controlling the retraction of the limiting rod is provided on the suspended platform, and a limiting component for restricting the movement of the limiting rod is provided inside the suspended platform. When the reel rolls to unwind the traction rope to its maximum length, the limiting component cancels the limit.

[0011] Preferably, the synchronization component includes extrusion chambers arranged at the four corners of the positioning holes on the suspended platform. A connecting rod is elastically and movably arranged between two adjacent extrusion chambers. A first extrusion block and a second extrusion block are fixedly arranged at both ends of the connecting rod, respectively. The adjacent first extrusion block and second extrusion block are movably arranged in the same extrusion chamber and are wedge-shaped. The first extrusion block is linked with the adjacent limiting rod.

[0012] Preferably, a linkage frame is movably arranged inside the suspended platform, and a linkage pin that is movably connected to the linkage frame is fixedly arranged at the lower end of the second extrusion block, and the end of the limiting rod away from the slot is fixedly connected to the linkage frame.

[0013] Preferably, the limiting component includes a sliding groove provided in the suspended platform, a locking rod elastically and movably provided in the sliding groove, a locking groove matching the locking rod on the limiting rod, a column provided in the suspended platform, a lifting block movably provided in the column and linked to the rotation of the roller, a lever provided in the locking rod, and the lower end of the lifting block wedge-shapedly engaging with the lever.

[0014] Preferably, a vortex track is provided on one end face of the roller near the column, and a sliding column that is slidably connected to the vortex track is fixedly provided on the lifting block.

[0015] Preferably, it also includes a base sleeved on the lower end of the precast column, and the base is provided with a clamp assembly for connecting the traction rope.

[0016] Preferably, the clamp assembly includes a spring seat fixedly mounted on a base, a pressure rod movably mounted on the spring seat, and a pad fixed to the base below the pressure rod. Under elastic force, the pressure rod automatically maintains a minimum gap with the pad.

[0017] In the above technical solution, the beneficial effects of the present invention are:

[0018] This automatic film covering machine for precast concrete column curing is equipped with a roller, traction ropes, and counterweights. It can release four traction ropes from the four corners of the suspended platform in advance. Then, the unlocking component is triggered when the roller rolls out the traction ropes to their maximum length, causing the sliding sleeves to slide freely down the traction ropes. The sliding sleeves at the four corners then slide smoothly down the vertical traction ropes, causing the plastic film to unfold downwards at a distance from the four corners, greatly avoiding the phenomenon of the plastic film getting stuck.

[0019] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit this disclosure.

[0020] This application provides an overview of various implementations or examples of the technology described in this disclosure, and is not a full disclosure of the entire scope or all features of the disclosed technology. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 For the present invention Figure 1 Enlarged structural diagram at point A;

[0024] Figure 3 For the present invention Figure 1 Enlarged structural diagram at point B;

[0025] Figure 4 This is a schematic diagram of the internal structure of the suspended platform of the present invention;

[0026] Figure 5 For the present invention Figure 4 Enlarged structural diagram at point C;

[0027] Figure 6 This is a front cross-sectional view of the winding wheel structure of the present invention;

[0028] Figure 7 For the present invention Figure 6 Enlarged structural diagram at point D;

[0029] Figure 8 This is a side cross-sectional view of the winding wheel structure of the present invention;

[0030] Figure 9 For the present invention Figure 8Enlarged structural diagram at point E;

[0031] Figure 10 This is a top view cross-sectional structural diagram of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Suspended platform; 2. Positioning hole; 3. Roller; 4. Traction rope; 5. Counterweight; 6. Sliding sleeve; 7. Hook; 8. Support; 9. Insert plate; 10. Slot; 11. Limiting rod; 12. Limiting hole; 13. Extrusion chamber; 14. Connecting rod; 15. First extrusion block; 16. Second extrusion block; 17. Linkage frame; 18. Linkage pin; 19. Sliding groove; 20. Locking rod; 21. Locking slot; 22. Column; 23. Lifting block; 24. Pulley block; 25. Scroll rail; 26. Sliding column; 27. Base; 28. Elastic seat; 29. ​​Pressure rod; 30. Pad block. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0035] Please see Figure 1-10 This invention provides an automatic film covering machine for curing precast concrete columns, comprising a suspended platform 1 for supporting the top of the precast column, having positioning holes 2 on it that match the protruding reinforcing bars at the top of the precast column; a roller 3 located at the four corners of the suspended platform 1, on which a traction rope 4 is wound out, with a counterweight 5 connected to the end of the traction rope 4; a sliding sleeve 6 fitted onto the traction rope 4, with the lower four corners of the plastic film fixedly connected to the sliding sleeve 6, the top of the plastic film fixedly connected to the suspended platform 1, and the other parts of the plastic film folded vertically into a U-shape to fit over the outside of the precast column; and an unlocking component for connecting the suspended platform 1 and the sliding sleeve 6, wherein when the roller 3 rolls out the traction rope 4 to its maximum length, the unlocking component is triggered to allow the sliding sleeve 6 to slide freely down the traction rope 4.

[0036] Specifically, the precast column is set on the foundation, shaped like a quadrangular prism, with rectangularly arranged reinforcing bars extending from its upper end; the suspended platform 1 is horizontally set, with straight edges at its four corners and rings, through which the traction rope 4 passes to prevent deviation; the positioning hole 2 is rectangular, matching the overall size of the reinforcing bars extending from the upper end of the precast column, and is fitted onto the outside of the reinforcing bars to limit the stability of the suspended platform 1 relative to the precast column; the axis of the reel 3 is parallel to the straight edges at the four corners of the suspended platform 1; the length of the traction rope 4 is adapted to the height of the precast column, and after the traction rope 4 is unwound to its maximum length, it is vertically positioned on the outside of the precast column; the counterweight 5 ensures that the reel 3... In the free-rotation state, the counterweight 5 can drive the end of the traction rope 4 to descend so that the traction rope 4 can be unwound; the sliding sleeve 6 is fitted on the traction rope 4, and the friction between the sliding sleeve 6 and the traction rope 4 is small. The sliding sleeve 6 itself has a certain weight, which is sufficient to drive the four corners of the plastic film to slide down; the plastic film is sleeve-shaped, and the closed end of the plastic film is connected to the bottom surface of the suspended platform 1 by a detachable adhesive method such as double-sided tape or glue. The open end of the plastic film faces downward and the four corners are connected to the outside of the sliding sleeve 6 respectively. The connection method is to use detachable adhesive or detachable fasteners. The middle part of the plastic film is neatly stacked together; the connection between the sliding sleeve 6 and the suspended platform 1 can be disconnected under the control of the unlocking component. In practical use, the roller 3 works in conjunction with the counterweight 5 to unwind the traction rope 4 downwards, forming four vertical traction ropes 4 at the four corners of the suspended platform 1. When the traction rope 4 is unwound to its maximum length, the unlocking component is triggered, causing the sliding sleeve 6 to separate from the suspended platform 1. The sliding sleeve 6 falls under the action of gravity, and the four corner sliding sleeves 6 slide smoothly down along the vertical traction rope 4, causing the four corners of the plastic film to unfold downwards at a distance so as to smoothly fit onto the entire precast column, greatly avoiding the phenomenon of the plastic film getting stuck.

[0037] Compared with the prior art, the automatic film covering machine for curing precast concrete columns proposed in this embodiment of the invention, by setting up a roller 3, traction ropes 4 and counterweights 5, can release four traction ropes 4 downward from the four corners of the suspended platform 1 in advance. Then, the unlocking component is triggered when the roller 3 rolls the traction ropes 4 to the maximum length, so that the sliding sleeves 6 slide freely down along the traction ropes 4. The sliding sleeves 6 at the four corners slide smoothly down along the vertical traction ropes 4, driving the plastic film to unfold downward at a distance from the four corners, which greatly avoids the phenomenon of plastic film jamming.

[0038] As a preferred technical solution in this embodiment, the suspended platform 1 is provided with hooks 7 for connecting lifting equipment. Specifically, multiple hooks 7 are provided and arranged symmetrically to ensure stable lifting.

[0039] As a preferred technical solution in this embodiment, a support 8 is provided on the suspended platform 1, and the shaft of the reel 3 is hinged to the support 8. An electronic control component for limiting the rotation of the shaft of the reel 3 is provided on the support 8. Specifically, the support 8 is located on one side of the reel 3 and supports the reel 3. The electronic control component includes a pressure telescopic unit provided inside the support 8. A damping block is provided at the output end of the pressure telescopic unit. The pressure telescopic unit integrates a power supply and signal module, which can realize remote start and stop, and is used to control the free rotation or damped stationary state of the reel 3. A rocker arm is provided at one end of the shaft of the reel 3 connected to the support 8, which is used to actively control the rotation of the reel 3.

[0040] As a preferred embodiment, a sliding sleeve 6 is fixedly provided with an insert plate 9, and a suspended platform 1 is provided with a slot 10 that matches the insert plate 9. The unlocking component includes a limiting rod 11 that is movably disposed within the suspended platform 1, a limiting hole 12 that matches the limiting rod 11 on the insert plate 9, a synchronization component for controlling the retraction of the limiting rod 11 on the suspended platform 1, and a limiting component for restricting the movement of the limiting rod 11 within the suspended platform 1. When the winding wheel 3 rolls and unwinds the traction rope 4 to its maximum length, the limiting component cancels the limiting. Specifically, the insert plate 9 is vertically arranged and is thin; the slot 10 is disposed at the edge of the suspended platform 1, close to the unwound traction rope 4; the insert plate 9 inserts... When the sliding sleeve 6 is positioned in the slot 10, it corresponds exactly to the vertical unwinding position of the traction rope 4; the extension direction of the limiting rod 11 is set perpendicular to the insert plate 9; the synchronization component controls the four corner limiting rods 11 to move synchronously, thereby ensuring that the four corner limiting rods 11 simultaneously cancel the restriction on the insert plate 9, and thus the four corner sliding sleeves 6 fall freely at the same time; the limiting component limits the limiting rod 11 to the position of inserting into the limiting hole 12, that is, it prevents the limiting rod 11 from retracting. When the winding wheel 3 rolls and unwinds the traction rope 4 to the maximum length, the limiting component cancels the restriction, and the limiting rod 11 retracts under the drive of the synchronization component to leave the limiting hole 12, canceling the restriction on the insert plate 9, and the sliding sleeve 6 can fall freely.

[0041] As a preferred embodiment, the synchronization component includes extrusion chambers 13 arranged at the four corners of the positioning holes 2 on the suspended platform 1. A connecting rod 14 is elastically movably arranged between two adjacent extrusion chambers 13. A first extrusion block 15 and a second extrusion block 16 are fixedly arranged at both ends of the connecting rod 14. The adjacent first extrusion block 15 and second extrusion block 16 are movably arranged within the same extrusion chamber 13 and wedge-shaped. The first extrusion block 15 is linked with an adjacent limiting rod 11. Specifically, the extrusion chamber 13 is L-shaped. The connecting rod 14 is parallel to the edge of the positioning hole 2 and moves in the direction of its two ends. A protruding ring is provided on the connecting rod 14, and a spring is connected between one side of the protruding ring and an adjacent extrusion chamber 13. The elastic force on the connecting rod 14 causes it to push the first extrusion block 15. The first extrusion block 15 actively extrudes towards the second extrusion block 16; the surfaces of the first extrusion block 15 and the second extrusion block 16 that abut against each other are both set as bevels, and the end of the first extrusion block 15 is missing a corner; the first extrusion blocks 15 and the second extrusion blocks 16 at both ends of each connecting rod 14 are connected end to end in the extrusion chamber 13 to move in tandem, that is, each first extrusion block 15 must move synchronously to extrude the second extrusion block 16 that it cooperates with; a linkage frame 17 is movably set in the suspended platform 1, and a linkage pin 18 is fixedly set at the lower end of the second extrusion block 16 and movably connected to the linkage frame 17; the end of the limiting rod 11 away from the slot 10 is fixedly connected to the linkage frame 17; the setting of the linkage frame 17 and the linkage pin 18 makes the movement of the second extrusion block 16 linked with the movement of the limiting rod 11 without interference. In actual use, through the setting of the synchronization component, each limiting rod 11 must move synchronously, thereby realizing the synchronous retraction of each limiting rod 11 to cancel the limitation on the sliding sleeve 6, and the four corner sliding sleeves 6 can fall simultaneously.

[0042] As a preferred embodiment, the limiting component includes a sliding groove 19 disposed within the suspended platform 1, a locking rod 20 elastically movably disposed within the sliding groove 19, a locking groove 21 matching the locking rod 20 disposed on the limiting rod 11, a column 22 disposed on the suspended platform 1, a lifting block 23 movably disposed within the column 22 and linked to the rotation of the roller 3, a lever 24 disposed on the locking rod 20, and a wedge-shaped engagement between the lower end of the lifting block 23 and the lever 24. Specifically, the extension direction of the locking rod 20 is perpendicular to the extension direction of the limiting rod 11, and another spring is disposed at the end of the locking rod 20 away from the locking groove 21, the spring abutting against the inner wall of the sliding groove 19. The lever 20 tends to approach the slot 21, and when the lever 20 corresponds to the slot 21, the lever 20 automatically remains embedded in the slot 21; the column 22 is set on the opposite side of the support 8; the end face of the reel 3 near the column 22 is provided with a vortex track 25, and the lifting block 23 is fixedly provided with a sliding column 26 that is slidably connected to the vortex track 25; when the reel 3 rotates to unwind, the interaction between the vortex track 25 and the sliding column 26 causes the lifting block 23 to descend, and vice versa; the lower end of the lifting block 23 is provided with an inclined surface, which faces away from the sliding column 26; when the lifting block 23 descends to near the lowest height, it is wedge-shaped squeezed with the lever 24. In actual use, when the reel 3 unwinds the traction rope 4 to its maximum length, the interaction between the vortex track 25 and the sliding column 26 causes the lifting block 23 to descend to its lowest height. As a result, the lower end of the lifting block 23 wedges against the push block 24, and the push block 24 is forced to move the locking rod 20 away from the locking groove 21. Then, one limit rod 11 is released from its limit. When all four corner reels 3 unwind the traction rope 4 to their maximum length, all limit rods 11 are released from their limits. Then, the synchronization component is triggered, so that all limit rods 11 retract simultaneously to release the limit on the sliding sleeve 6, and all sliding sleeves 6 can fall simultaneously.

[0043] In another embodiment of the present invention, a base 27 is further included, which is sleeved on the lower end of the precast column. The base 27 is provided with a clamping assembly for connecting the traction rope 4. Specifically, the base 27 is composed of two symmetrical panels, which are easy to install and disassemble on the outside of the precast column. The connection part can be fastened with fasteners. The clamping assembly includes an elastic seat 28 fixedly installed on the base 27. A pressure rod 29 is elastically movably installed on the elastic seat 28. A pad 30 fixed on the base 27 is provided below the pressure rod 29. The pressure rod 29 automatically maintains a minimum gap with the pad 30 under the elastic force. An inclined groove is provided on the elastic seat 28 to guide the movement of the pressure rod 29. The outer surfaces of the pressure rod 29 and the pad 30 are both roughened to hinder the movement of the traction rope 4 when clamping it. In actual use, the traction rope 4, which is unwound and falls onto the base 27, is embedded between the pressure bar 29 and the pad 30, and the traction rope 4 is pulled taut in the direction outward from the base 27. This causes the winding wheel 3 to reach the maximum unwinding length, thereby triggering the corresponding limit component to cancel the limit. When the traction rope 4 is released after being taut, it undergoes a certain backward movement, thereby forcing the pressure bar 29 to move closer to the pad 30 through frictional resistance. At the same time, the pressure bar 29 descends, thereby automatically clamping the traction rope 4.

[0044] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. An automatic film covering machine for curing precast concrete columns, characterized in that, include: A suspended platform (1) is used to support the top of a precast column, and a positioning hole (2) is provided on it to match the protruding steel bar at the top of the precast column. A reel (3) is set at the four corners of the suspended platform (1), and a traction rope (4) is wound out on it. The end of the traction rope (4) is connected to a counterweight (5). The sliding sleeve (6) is fitted onto the traction rope (4). The lower four corners of the plastic film are fixedly connected to the sliding sleeve (6). The top of the plastic film is fixedly connected to the suspended platform (1). The other parts of the plastic film are folded up and down into a square shape to fit on the outside of the precast column. The unlocking component, which connects the suspended platform (1) and the sliding sleeve (6), is triggered when the reel (3) rolls to unwind the traction rope (4) to its maximum length, so that the sliding sleeve (6) slides freely down the traction rope (4).

2. The automatic film covering machine for curing precast concrete columns according to claim 1, characterized in that, The suspended platform (1) is equipped with a hook (7) for connecting lifting equipment.

3. The automatic film covering machine for curing precast concrete columns according to claim 1, characterized in that, A support (8) is provided on the suspended platform (1), and the shaft of the reel (3) is hinged to the support (8). An electronic control component for limiting the rotation of the shaft of the reel (3) is provided on the support (8).

4. The automatic film covering machine for curing precast concrete columns according to claim 1, characterized in that, A plate (9) is fixedly installed on the sliding sleeve (6), and a slot (10) matching the plate (9) is provided on the suspended platform (1). The unlocking component includes a limiting rod (11) movably installed inside the suspended platform (1). A limiting hole (12) matching the limiting rod (11) is provided on the plate (9). A synchronization component for controlling the retraction of the limiting rod (11) is provided on the suspended platform (1). A limiting component for restricting the movement of the limiting rod (11) is provided inside the suspended platform (1). When the reel (3) rolls and unwinds the traction rope (4) to its maximum length, the limiting component cancels the limit.

5. The automatic film covering machine for curing precast concrete columns according to claim 4, characterized in that, The synchronization component includes extrusion chambers (13) arranged at the four corners of the positioning hole (2) on the suspended platform (1). A connecting rod (14) is elastically and movably arranged between two adjacent extrusion chambers (13). A first extrusion block (15) and a second extrusion block (16) are fixedly arranged at both ends of the connecting rod (14). The adjacent first extrusion block (15) and second extrusion block (16) are movably arranged in the same extrusion chamber (13) and wedge-shaped. The first extrusion block (15) is linked with the adjacent limiting rod (11).

6. The automatic film covering machine for curing precast concrete columns according to claim 5, characterized in that, The suspended platform (1) is movably provided with a linkage frame (17), and the lower end of the second extrusion block (16) is fixedly provided with a linkage pin (18) that is movably connected to the linkage frame (17). The end of the limiting rod (11) away from the slot (10) is fixedly connected to the linkage frame (17).

7. The automatic film covering machine for curing precast concrete columns according to claim 4, characterized in that, The limiting component includes a sliding groove (19) provided in the suspended platform (1), a locking rod (20) is elastically and movably provided in the sliding groove (19), a locking groove (21) matching the locking rod (20) is provided on the limiting rod (11), a column (22) is provided on the suspended platform (1), a lifting block (23) that is linked to the rotation of the roller (3) is movably provided in the column (22), a lever (24) is provided on the locking rod (20), and the lower end of the lifting block (23) is wedge-shapedly engaged with the lever (24).

8. The automatic film covering machine for curing precast concrete columns according to claim 7, characterized in that, The roller (3) is provided with a vortex track (25) on one end face near the column (22), and a sliding column (26) is fixedly provided on the lifting block (23) and slidably connected to the vortex track (25).

9. The automatic film covering machine for curing precast concrete columns according to claim 1, characterized in that, It also includes a base (27) fitted on the lower end of the precast column, and a clamp assembly for connecting the traction rope (4) is provided on the base (27).

10. The automatic film covering machine for curing precast concrete columns according to claim 9, characterized in that, The clamp assembly includes a spring seat (28) fixedly mounted on a base (27), a pressure rod (29) elastically mounted on the spring seat (28), and a pad (30) fixed on the base (27) below the pressure rod (29). The pressure rod (29) automatically maintains a minimum gap with the pad (30) under the elastic force.

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