CN86100835B - Brake clearance automatic compensation device for hydraulic brake - Google Patents

Abstract

A retainer is installed between one end of a hydraulically operated brake equipped with an automatic brake clearance compensation device and the brake shoe web. The retainer has a brake shoe web connecting portion, a fixed mounting portion that is approximately at a right angle to the web connecting portion, and a curved portion. The fixed mounting portion of the retainer is mounted on the supporting portion of the brake cylinder by bolts.

Description

Brake gap automatic compensation device for hydraulic brake

The invention relates to a brake gap automatic compensation device for a hydraulic brake.

As is known, drum brakes are designed as a rear circular plate with a pair of curved brake shoes. The expansion of the brake shoe is that one end is a pivot, and the other end is controlled by a hydraulic brake cylinder, so that the friction plate on the brake shoe is pressed against the inner circular surface of the brake drum that is integrally rotated with the wheel, thereby realizing braking. move. When the friction lining is worn due to braking, the braking gap between the friction lining and the inner surface of the brake drum will increase. The brake gap automatic compensation device which is not restricted by the brake cylinder can expand the brake shoe, so that the brake gap remains constant.

The disadvantage of this type of device in the prior art is that the brake gap compensation device installed in the pressure chamber of the brake wheel cylinder has a complex structure, which is troublesome to disassemble and assemble, and makes maintenance more difficult.

The object of the present invention is to provide a hydraulic brake gap automatic compensation device installed in the brake wheel cylinder for the wheel brake. The structure is simple, the number of parts is small, the automatic compensation function can be reliably realized, and the assembly is easy.

Various embodiments of the present invention are represented as follows with accompanying drawing:

Figure 1 is a front view along the section of Figure 2I-I, which shows the automatic brake gap compensation device according to the first embodiment;

Fig. 2 is a top view along the section of Fig. 1Ⅱ-Ⅱ;

Figure 3 is an exploded axonometric view of the plunger and the automatic compensation device installed in the brake cylinder;

Figure 4 is an axonometric view of the cage;

Fig. 5 is a sectional front view of the automatic compensation device according to the second embodiment <&&>;

Figure 6 is Figure 5 <&&>

Figure 7 <&&>

Fig. 8 is a partial sectional top view of a modification of the retainer mounting structure in the first embodiment;

Fig. 9 is an axonometric exploded view of the main parts of the structure shown in Fig. 8;

Fig. 10 is a top view of a further improved partial section of the retainer mounting structure in the first embodiment;

Fig. 11 is a partial cross-sectional top view of the retainer when the brake shoe in the structure shown in Fig. 10 is removed.

Now with reference to the accompanying drawings, the best embodiment of the present invention and its <&&> examples are described as follows. The equivalent parts or components among the various embodiments in the figures are represented by the same numbers and letters.

At first introduce the first embodiment of the present invention, it is applicable to double self-tightening brake shoe type drum brake, can refer to Fig. 1 to 4.

A pair of brake cylinders are mounted up and down on the rear circular plate P fixed on the car body (the lower brake cylinder is not shown in the figure), and a pair of brake shoes 2 and * are installed on the left and right, and the brake shoes are opposite to the rear circular plate The P centers are arranged symmetrically.

The brake wheel cylinder has a cylinder bore *<&&>

The plunger 5 is made up of parts such as <&&> and the small diameter portion 5c. The small diameter portion 5c is connected to the large diameter portion 5h by a shoulder and faces the pressure chamber 4 . The end of the small-diameter portion 5c is integrated with the flange 9, which is in a sliding fit with the pressure chamber 4 in the cylinder bore 3a. When the plunger 5 moves axially, the flange 9 also slides in the cylinder bore 3a together. The plunger cup 11 is mounted on the outer surface of the annular groove 10 close to the small diameter portion 5c to prevent the pressure oil in the pressure chamber 4 from leaking outward.

On the small diameter part 5c of the plunger, there are three circular blind holes 12 uniformly distributed in the circumferential direction, and these holes extend from the connecting surface 14 on one side of the flange 9 through the flange 9 . Because of the three blind holes 12, a crescent-shaped communication hole 13 is also formed. The flange 9 divides the pressure chamber 4 into two left and right chambers, which are communicated with each other by these communication holes 13 .

An adjusting nut 15 is installed on the right side of the flange 9 in the pressure chamber 4 . The nut 15 includes a shaft portion 15b with an axial hole 15c and a flange 15a. The axial hole 15c is made as an internally threaded hole. Engage with the external thread of the adjusting bolt 19 (to be described later). The flange 15a is integrally formed with the shaft portion 15b, is located at one end close to the flange 9, and is bonded to the connection surface 14 of the flange 9. Between the adjusting nut 15 and the flange 9 of the plunger 5, there is no relative rotation due to the effect of the spring holder 16 (described later), and the compression force of the spring 17 between the spring holder 16 and the flange 15a Under the action, the adjusting nut 15 is tightly pressed on the connecting surface 14 of the flange 9 .

Reference numeral 15e denotes a groove which is formed by cutting the peripheral edge of the threaded hole or shaft hole 15e in order to remove burrs when machining the internal thread of the adjusting nut 15.

The flange 15 a of the adjusting nut 15 has three cutouts 18 whose positions correspond to the communicating holes 13 of the flange 9 . <&&> spring retainer 16 is made up of an annular spring <&&> engaged with a * of spring 17 and spring support seat 16a and extends a certain distance from one side <&&>. The ends of the above-mentioned legs are bent radially outwards to form claws 16b.

The plunger 5, the adjusting nut 15, the spring holder 16 and the spring 17 are assembled as follows. First, attach the flange 15a of the adjusting nut 15 to the connection surface 14 of the flange 9 of the plunger 5, and align the communication hole 13 with the cutout 18. Then, put the spring 17 between the adjustment nut 15 and the spring holder 16, the leg 16c of the spring holder 16 is inserted into the cutout 18 of the adjustment nut 15, and its claw 16b is radially outward from the communication hole 13, and the hook Live the back side of the connecting surface 14 of the flange 9. The spring 17 is then compressed between the flange 15 a of the adjusting nut 15 and the spring support seat 16 a of the spring holder 16 .

The installed adjusting nut 15 may compress the spring 17 to leave the connecting surface 14 of the flange 9. At this time, because the legs 16c are engaged with the cutout 18, it is possible to prevent the adjustment nut 15 from happening to the flange 9 of the plunger 5. relative rotation.

What should be noted is that the design of each slit must have enough area to enable the left and right sides of the flange 9 in the cavity to be in a connected state through the hole 13 . Even after the plunger 5 is assembled with the adjusting nut 15, that is to say, when the flange 9 and the flange 15a are tightly pressed together by the legs 16 and <&&> of the spring retainer 16, the form a connected state.

Adjusting bolt 19 is integrated by being processed into <&&>. <&&> rotation and axial sliding in the bore portion 20, and <&&> the conical clutch surface 21 at the bottom of the small bore portion 20 cooperates. The sealing member 22 is installed in the sealing groove 19c of the adjusting bolt 19 to prevent the pressure oil in the pressure chamber 4 from leaking onto the clutch face 2 . In addition, the innermost part of the support portion 31 forms an air chamber r with the clutch surface 21 .

As clearly shown in FIG. 2 , the connecting surface 33 perpendicular to the web 32 a of the respective brake shoe 2 is located at the end of the support portion 31 . A mounting surface 34 for mounting the holder 6 is formed at right angles to the connecting surface 33 on the side of the support portion 31 and is opposed to the rear circular plate P. As shown in FIG. Screw holes 35 are processed on the mounting surface 34 , and the mounting surface 34 and the connecting surface 33 are connected by an angular slope 36 .

The retainer 6 is made by bending a metal plate. The brake shoe web connection portion 6a and the fixed installation portion 6b approximately at right angles to the brake shoe connection portion 6a are integrally connected through the middle bending portion 6c. The arched and elastically curved portion 6c is raised towards the brake shoe web 32a. A mounting hole 6d is opened on the fixed mounting portion 6b. The mounting portion 6 b of the holder 6 is fixed to the mounting surface 34 of the supporting portion 31 with bolts 37 . Due to the elastic action of the curved portion 6c, the connecting portion 6a directly presses against the connecting surface 33 of the supporting portion 31 with a biasing force, and is clamped by the supporting end 32b of the brake shoe web 32a and the supporting portion 31 . Reference numeral 33 denotes a gasket.

Due to the arch 6c, the supporting end 32b of the brake shoe web 32 is in close contact with the curved portion 6c and the web connecting portion 6a, so as to prevent the brake shoe 2 from floating during braking, that is, to prevent the brake shoe <&&> <&&> moving hoof web connection part 6a leans against <&&>, then align the top of bolt 37 with the opening of screw hole 35, and then screw bolt 37 into screw hole 35, at this time, retainer 6 faces the rear circular plate P direction, and guide the brake shoe abdomen connection part 6a with pressing force, so that it is tightly pressed against the predetermined position of the connection surface 33, at this time, due to the elastic force of the bending part 6c, the connection part 5a is subjected to an outward force. expansion force. The mounting portion 6 b is fixed between the bolt head 37 and the mounting surface 34 of the supporting portion 31 .

Through the above-mentioned arrangement of the retainer 6, especially because the bending part between the brake shoe web connection part and the fixed installation part is made into a bow shape, the pressure is effectively distributed and the strength of the bending part is enhanced. Moreover, since there is no gap between the connecting part of the brake shoe web and the connecting surface of the support part, the brake shoe web and the brake wheel cylinder are rigidly joined. Furthermore, since the dimensional error can be absorbed by the spring effect of the bent portion, the processing error in manufacturing the retainer can be increased. Due to the use of the curved portion, the floating phenomenon of the brake shoe during braking is also avoided.

The operation of the embodiment is described below.

When not braking, the elastic force of the return spring (not shown in the figure) is applied to the plunger 5 in the direction of returning the plunger through the brake shoe 2, and this force is transmitted to the adjustment nut 15 and the adjustment bolt 19, and then acts on the clutch portion 19b and clutch face 21, and generates an engaging torque. Since the adjusting nut 16 and the adjusting bolt 19 are engaged with multiple threads at this time, a rotational torque is also generated in the adjusting bolt 19 . But the above-mentioned engagement torque is greater than the rotation torque of the adjusting bolt, so the adjusting screw <&&> cannot rotate, and the plunger remains in its original position.

When the brake main pump (not shown in the figure) enters the pressure oil into the pressure chamber 4 for braking by entering <&&>, the plunger <&&> pushes the brake shoe to the inner surface of the brake drum, <&&> Integral connection, thus producing a braking action.

At the <&&> of the friction plate, the adjusting nut 15 moves simultaneously with the plunger b; and due to the action of the spring 17 in the spring holder 16, the two still maintain an engaged state. Because the amount of movement of the adjusting nut 15 corresponds to the amount of idle travel in the threaded portion, no rotational torque is produced in the adjusting bolt engaged with the adjusting nut 15, and the bolt 19 is still attached to the clutch surface 21 without compensation. After the brake is released, the plunger 5 and the adjusting nut 15 get back to their original positions together.

Under normal braking conditions, the oil pressure in the pressure chamber 4 is relatively low. Therefore, the frictional adhesion force between the clutch part 19b of the adjusting bolt 19 and the clutch surface 21 in the small bore part 20 is also relatively small. If because the friction plate of brake shoe 2 and 2 wears away, plunger 5 continues to move outwards, and adjusting nut 15 is due to the effect of spring 17 in spring retainer 16, also moves accordingly for keeping interconnected state.

This amount of movement is equal to the amount of idle travel plus the amount of wear of the friction plate, which is certainly greater than the amount of idle travel. Therefore, the adjustment bolt 19 moves integrally with the adjustment nut 15 , and the clutch portion 19 b on the adjustment bolt 19 is also disengaged from the clutch surface 21 in the small bore portion 20 . Due to the effect of the spring 17, the adjustment nut 15 is always in the state of being pressed to the connecting surface 14 of the flange 9, and because of the effect of the leg 16c of the spring holder 16, it cannot be opposed to the plunger 5. turn. Since the pressure direction of the pressure oil on the adjusting bolt is rightward along its axial direction, a rotational torque is generated at the thread engagement portion of the adjusting nut 15 and the adjusting bolt 19 . Along with the rotation of adjusting bolt 19 relative to adjusting nut 15, <&&> reengages. In this way, the automatic compensation function of the wear amount of the friction linings on the brake shoes 2 and 2 is realized. If the pressure chamber 4 depressurizes and releases the brake, the brake shoes 2 and 2 will be drawn in by the reset force of the return spring. This restoring force acts like a thrust force on the plunger 5 via the clutch surface 21 . The clutch portion 19b is pushed toward the clutch face 21 by <&&>, and is in frictional contact with it, thereby blocking the adjustment bolt <&&>. So the plunger 5 and the adjusting nut 15 can only return with the empty travel distance equivalent to the adjusting nut and the bolt <&&> spiral portion. As a result, a new suitable braking gap is formed between the friction plate on the brake shoe 2, 2 and the inner surface of the brake drum, and this gap is just in time equivalent to the idle travel of the spiral portion.

Once emergency braking is required, the pressure in the <&&> cavity 4 is realized before reaching a predetermined value. This predetermined value corresponds to the value at which the brake shoes 2 and 2 and the brake drum etc. start to elastically deform. When the oil pressure exceeds the predetermined value, the <&&> acting on the clutch part 19b of the adjusting bolt 19, the thrust direction is towards the clutch surface 21, forcing the clutch 19 to maintain frictional engagement with the * clutch surface 31, so that the adjusting bolt 19 cannot be rotated. The adjustment nut 15 cannot rotate because of the effect of the legs 16e of the spring retainer 16, and still maintains a relatively immobile state with the adjustment bolt*. However, the plunger 5 continues to move to * due to the deformation of the brake drum, etc., the <&&> adjusting nut 15 and the adjusting bolt 19 maintain their original positions, and the connecting surface 14 of the flange 9 of the plunger 5 is separated from the adjusting nut 15, In this case, the automatic compensation function stops.

As mentioned above, the brake gap automatic compensation device among the present invention is contained in the wheel brake wheel cylinder, which forms the adjustment <&&> of the device, and the relative transmission does not take place with the plunger, <&&>. Therefore, according to the <&&> situation of the friction plate, when the <&&><&&> force chamber brakes, some air sometimes remains in the groove due to the engagement between the <&&> adjusting nut and the plunger flange. The residual air is harmful to the normal operation of the brake cylinder and the automatic compensation device for the brake clearance, and needs to be removed. However, it is very difficult to get rid of this air.

The embodiment shown in FIGS. 5 and 6 includes a structure which prevents the above-mentioned air from remaining while retaining the advantages obtained by the first embodiment, thus exhibiting better braking performance.

In the second embodiment shown in FIG. 6 , the flange 9 of the plunger 5 has a groove 42 extending outward from the center of the flange 9 in a radial trident shape. The slots 42 form three communication holes 43 approximately in the shape of an arc on the flange 9 . The connecting surface 14 of the adjusting nut flange 15a and the plunger flange 9 is assembled into a detachable connection.

The spring retainer 16 is designed to fit its three legs 16c with the slits 18 on the adjusting nut during assembly, and the claws 16b pass through the communication hole 48 of the flange 9 and engage with the back of the flange 9 . On the other hand, the end of the adjustment bolt 19 adjacent to the plunger 5 is formed as a hemispherical end surface 19a whose diameter is smaller than that of the multi-threaded portion 19a. The taper part 19f is connected between the multi-start thread part 19a and the hemispherical end 19d, and its diameter gradually becomes smaller toward the hemispherical end 19a. The groove 15e set a position in the axial direction, that is, the initial position before the brake backlash compensation is realized.

The groove 42 of the plunger flange 9 has a central portion 42a (its diameter is equal to or greater than the diameter of the groove 15e on the adjusting nut 15) and three extensions 42b, which extend radially outward from the central portion 42a to form a trident. Groove 42 should be made to have at least one extension 42b to be in substantially the same direction as the engagement groove 5a of plunger 5, like this, after installing plunger, one extension 42b must <&&> position upward. Therefore, even the residual air in the flange 15a of the adjusting nut <&&> and the groove 16a on the <&&> adjusting nut 15 will move rapidly to the middle <&&>, especially the air in the lower groove 15e of the adjusting bolt 19, The flow is guided by the cone portion 19f of the adjusting bolt 19 into the central portion 42a, and introduced into the pressure chamber 4 through the extension portion 42b, and then discharged from the exhaust hole not shown in the figure.

Fig. 7 is a third embodiment of the present invention. In the above-mentioned second embodiment, the flange 9 of the plunger 5 has a groove 42, so that the groove 15e on the adjusting nut communicates with the pressure chamber 4; An annular groove 15g is formed on the joint surface 15f of the adjusting nut 15 to which the plug 5 is connected, and the groove is used to communicate the groove 15e with the notch 18 . Therefore, it is only necessary to make three communication holes 53 on the plunger flange 9, so that the left and right pressure chambers separated by the flange 9 are connected, and the three legs of the spring cage 16 pass through these three holes. . The communication hole 52 can be made into any shape, as long as it can meet the requirements of the above-mentioned communication function. In addition, in this embodiment, the end portion of the adjusting bolt 19 engaged with the plunger flange engaging surface 19 is also formed like the end portion of the multi-start thread portion 19a. It should be noted that the above-mentioned end can also be made into a shape similar to that in the second embodiment shown in FIGS. 5 and 6 .

Fig. 8 and Fig. 9 are a partial modification of the supporting part 31 and the mounting structure of the retainer 6 on the supporting part 31 shown in Figs. 1 to 4 in the first embodiment.

In this modified embodiment, a hole 61 communicating with the outside is drilled from one side of the bolt hole 35 in the support portion 31, so that the innermost airtight chamber r in the clutch surface 21 is connected with the bolt hole 35 screwed with the mounting bolt 37. The bottom is connected. The communication hole 61 is beneficial to the engagement operation of the brake gap automatic compensation device A, and makes the compensation device A work smoothly.

Mounting bolt 37 is made up of bolt head and <&&>. There is a flange 37a at the lower end of the bolt head, and an annular groove 37b is separated from the flange <&&> on the shaft. The above-mentioned distance is approximately equal to the thickness of the fixed mounting part 6* of the retainer 6 , the threaded portion 37c extends to the annular groove 37b. At the opening end of the bolt hole 35 on the mounting surface 34 of the support portion 31, <&&>

In this embodiment, the retainer * is installed on the support part * in such a way that the threaded part 37 * of the mounting bolt 37 is passed into the mounting hole 6a of the retainer 6, and the flange 37a is fixed to the mounting part. After <&&>, the collar 62 is inserted into the annular groove 37b below the fixed installation part 6b, so that the retainer 6 and the mounting bolt 37 are assembled together and can rotate relatively. Tighten the bolt 39 in the screw hole 35, so that the assembled retainer 6 and the mounting bolt <&&> are on the support part 31; at the same time, the brake shoe web connection part 6a of the retainer 6 is inserted into the connection surface of the support part 31 33 and the end 32b of the brake shoe web, and make the fixed installation part 6b closely engage with the installation surface 34, so as to seal the periphery of the bolt hole 36.

Reference numeral 63 denotes a retainer limiting flange mounted on one end of the support portion 31 .

Due to repeated braking actions, brake shoe wear grooves are produced on the braking surface of the brake drum. At this time, a new brake shoe needs to be replaced. Out, the loosening of the bolt 37 <&&> and the collar 62 on the lower surface of the retainer 6 pushes the retainer 6* (<&&> in Figure 6) to move, thereby gradually connecting the brake shoe web connection <&&> from between the support portion 31 and the brake shoe web 324 . Insert a tool into the gap between the bottom surface of the fixed installation part <&&> and the fixed surface *4, and pull out the brake shoe web connection part 6a completely. Because the brake shoe web connecting portion 6a itself has a thickness, when it is pulled out, the extent to which the brake shoe 2 is embedded in the brake shoe wear groove on the braking surface of the brake drum is reduced, thus making it easier to replace the brake shoe. Do not accept any hindrance.

Between the replacement of the brake shoes <&&> and the web connection of the retainer 6 <&&>, seal the screw holes with the mounting bolts <&&>*

At this time, the retainer 6 and the mounting bolt 37 have been assembled together by the collar 62, so these parts will not be lost, and the fastening work of the retainer 6 can be easily performed.

As mentioned above, in the present embodiment, the retainer 6 is installed on the supporting part 31 with the mounting bolt 37 and the collar 62, so the beginning of the screw hole can be completely covered by the bolt 37 and the collar 62, thereby improving the The tightness at the position can effectively prevent water and other liquids from intruding into the clutch part of the brake gap automatic compensation device from the side of the bolt hole through the through hole.

10 and 11 show an updated structure in which the holder 6 is mounted on the support portion 31. As shown in FIG.

In this modified embodiment, the support portion 31 includes a connection surface 70 which engages with the web 32a of the brake shoe 2 through the brake shoe web connection portion 6a of the retainer 6; Attach shoulder 71 . The connecting shoulder is recessed to form a plane lower than the connecting surface 70 and connected to the bolt mounting surface 34 at approximately right angles.

The upper end of the mounting bolt 80 has a screw head 80a, a threaded portion 80c extends downward, and a guide shaft portion 80b is provided between the threaded portion 80c and the screw head 80a. Screwing the threaded part 80c into the screw hole 35 can make the bolt 80 vertically mounted on the connecting part 31; the mounting bolt 80 is loosely inserted into the hole 6e opened on the fixed mounting part 6b of the retainer 6, and the hole 6e The diameter is larger than the diameter of the guide shaft portion 80 b of the mounting bolt 80 . The retainer plate 6 is placed in its normal state by the action of the conical coil spring 81, which is wound around the mounting bolt 80 and compressed between the lower surface of the screw head 80a of the mounting bolt 80 and the fixed mounting portion 6b of the retainer 6. Between the outer surfaces, the retainer 6 is in pressure contact with the retainer mounting surface 34 of the support portion 31 . The conical spring 81 is an example of a large-diameter end at the fixed mounting portion 6b. The retainer 6 is bent obliquely upward to form an upturn 6f, so as to prevent the spring 81 from coming off.

There is a tool hole 82 on the rear circular plate for dismounting the retainer 6, and a tool 83 such as a screwdriver can be passed through the hole to complete the above work. The hole 32 is located on the rear circular plate corresponding to the lower end of the web joint portion 6a of the holder 6, that is, corresponding to the end of 6a on the side close to the rear circular plate.

Reference numerals 84 and 84 denote flanges on the support portion 31 which serve to prevent lateral misalignment of the retainer 6 and floating of the brake shoe 2 .

The following describes the steps for removing the brake drum (not shown) when the brake drum and the brake shoe 2 interfere with each other and the brake drum is difficult to remove. Insert the tool 83 into the tool hole 82 of the rear circular plate, and push the tip of the tool 83 against the web connection portion 6a of the retainer 6 clamped between the connection surface 70 of the support portion 31 and the end of the brake shoe web 32e When the tool 83 is pressed down toward the direction away from the rear circular plate P, the retainer passes through the guide shaft portion 80b of the mounting bolt 80 and overcomes the elastic force of the spring 81 to move to the side in the direction away from the rear circular plate, thus The web connecting portion 6a is disengaged from between the brake shoe web 32a and the connecting surface 70 and falls on the connecting shoulder 71 connected with the connecting surface 70, and its lower end abuts against the shoulder at the position shown in FIG. 11 . In this way, the end of the brake shoe web 32a is moved to a position in direct contact with the connecting surface 70 of the support portion 31, so that the brake shoe 2 is retracted, thereby avoiding the friction between the brake shoe 2 and the brake drum. Interfere with each other; after that the brake drum can be removed, which also removes the brake shoes and things like that. In the process of replacing the brake shoe, after removing the brake shoe and the worn friction lining, press the upper wing end 6f of the fixed installation part 6b, so that the web connecting part of the retainer 6 that is engaged at the connecting shoulder 71 6a turns to engage with the connection surface 71 of the support portion 31 . Due to the action of the spring 81, the retainer 6 automatically returns to the normal position, that is, the web connecting portion 6a is forced to straddle the connecting surface 70 of the supporting portion 31, thereby entering a predetermined connecting position. The new brake shoe is now installed.

Although in the present embodiment, the connection shoulder 71 connected to the connection surface 70 is in a state of being engaged with the end of the web joint portion 6a of the retainer 6 on the side close to the rear circular plate P, it should be noted that , even if there is no shoulder 71, the result of this embodiment can be received completely. <&&>

Claims (4)

1. An automatic brake gap compensation device used in hydraulic storage brakes, which includes an adjusting nut and an adjusting bolt that engage with each other through non-self-locking multi-threaded threads. The adjusting nut and the adjusting bolt are put into a pressure chamber, and the pressure chamber Consisting of one end of a plunger slidingly fitted in the brake sub-cylinder and an end wall of the cylinder, said end wall serving as a support which engages the web of a brake shoe, In the pressure chamber, the adjusting bolt has a clutch portion which is usually in contact with a clutch surface formed on one end wall of the cylinder, and the adjusting nut is connected to the plunger by the action of a spring. so that when the brake gap exceeds a predetermined limit, the adjusting bolt moves axially relative to the adjusting nut to push the plunger to restore the brake gap to its original state. The web joint, the support portion includes a brake shoe web connection surface and a retainer mounting surface, the installation surface is approximately at right angles to the web connection surface, and the retainer includes a brake shoe web connection surface part, a fixed installation part approximately at right angles to the web connection part, characterized in that the retainer also includes a curved part, which connects the brake shoe web connection part and the fixed installation part, and is directed to the Brake shoe web protrudes. 2. A device as claimed in claim 1, wherein the shoe web connecting surface and the retainer mounting surface of said support portion are connected to each other by an inclined surface. 3. The device according to claim 1 or 2, characterized in that there is a bolt hole on the support part, and the bolt hole is threadedly engaged with a mounting bolt, and the bolt is used to install the fixed mounting part of the retainer on the On the installation surface of the retainer, the support part also has an air communication hole, which communicates with the bolt hole and the clutch surface, and in the annular groove of <&&> of the bolt hole, the installation The bolt has a journal with an annular groove, and a collar can be installed in the annular groove to assemble the mounting bolt and the retainer together, and the mounting bolt is matched with the collar and then screwed into the The retainer can be fixedly installed on the support part through the bolt holes. 4. The device as claimed in claim 1 or 2, wherein said support portion has a bolt hole threadedly engaged with a mounting bolt for mounting the fixed mounting portion of said retainer on the mounting surface of said retainer In addition, the fixed mounting part of the retainer also has a hole, the diameter of which is larger than the diameter of a journal of the mounting bolt, the journal of the mounting bolt can protrude through the hole, and pass through a The retainer is mounted in place by the action of the spring means, which is contained in compression between the upper surface of the mounting portion and the lower surface of the mounting bolt head, engages and supports the retainer mounting surface of the support portion on that surface.

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