JPS6231693Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a drum brake equipped with a device for regulating the backward position of a brake lever.

<Prior art> In the case of a drum brake equipped with an adjustment device, which includes a strut with a telescopic function arranged between one brake shoe and the brake lever, the gap between the brake drum and the brake shoe is determined. Therefore, it is necessary to provide a regulating device to regulate the backward position of the brake lever.

This regulating device retracts the brake lever's regulating position to reduce the diameter of the brake shoe when the brake is over-adjusted or when the sliding surface of the drum has uneven scratches and the brake shoe engages. This is a device designed to

Conventionally, as a drum brake equipped with a regulating device having such a function, for example, the Utility Model 105993
The type shown in the publication is widely known.

In this conventional drum brake, a pair of brake shoes are disposed inside the brake drum so that they can expand freely relative to each other with their lower ends serving as fulcrums by the operation of a hydraulic cylinder device arranged between their upper ends. A brake lever is attached to the upper end of the brake shoe, and an adjustable strut is mounted between the intermediate portion of the brake lever and the other brake shoe.

The strut and the adjustment member cooperate during parking braking, in which the free end of the brake lever is pulled to suppress rotation of the brake drum, or during service braking, in which the hydraulic cylinder device is actuated to suppress rotation of the brake drum. The brake shoe is configured to adjust the gap between the brake shoe and the brake drum.

Regarding the regulating device that regulates the backward position of the brake lever, as shown in Fig. 6, a removable pin member b is attached to the web a of one brake shoe, and the pin member b protrudes from the web a. The back edge d of the brake lever c is brought into contact with the head of the brake lever c to restrict the backward movement of the brake lever c, and when reducing the diameter of the brake shoe, insert a screwdriver etc. into the tool insertion hole f drilled in the back plate e. The structure is such that a tool is inserted, the tip of the tool is applied to the bottom surface of the pin b, and a pressing force is applied to remove the tool, allowing the brake lever c to move backward.

<Problems to be Solved by the Present Invention> The conventional drum brake described above has the following problems.

(a) The work of pushing out pin material b to reduce the diameter of the brake shoe must be done inside the drum brake in a dark environment.

Therefore, it is very difficult to reduce the diameter of the brake shoe since it takes time to push out the pin material b.

(b) When reducing the diameter of the brake shoe, pin material b must be completely removed from web a.

Therefore, when removing the brake drum, the sliding surface of the drum may be damaged, or the pin material b
I'm worried about losing it or forgetting to put it back together.

(c) If the tool insertion hole f drilled in the back plate e is left open, foreign matter such as mud and water will enter the drum brake through the tool insertion hole f.

Therefore, in order to close the tool insertion hole f,
Separate sealing material such as a rubber cap is required, increasing the number of components.

(d) When the tool insertion hole f is drilled in the back plate e, a decrease in the strength of the back plate e is unavoidable.

<Purpose of the present invention> The present invention was devised to solve the above-mentioned problems.The diameter reduction operation of the brake shoe can be performed easily and reliably, and there is no need to worry about losing or forgetting to assemble components. Moreover, it is an object of the present invention to provide a drum brake that does not adversely affect the strength of the back plate.

<Configuration of the present invention> The drum brake according to the present invention will be described below with reference to the drawings.

<A> Overall configuration of drum brake Figure 1 shows an example of a drum brake equipped with a device for regulating the backward position of the brake lever.

In the figure, reference numerals 1 and 2 are brake shoes, and an anchor 4 fixed to a back plate 3 and a cylinder 5 are disposed in contact with each other between the upper and lower ends of the brake shoes.

Furthermore, a brake lever 7 is pivotally supported near the upper side of one brake shoe 2 with a pin 6.

An intermediate portion of the brake lever 7 is engaged with one end of a strut 8 having a function of adjusting the gap between the brake shoes 1, 2 and a brake drum (not shown).

A bell crank lever 82 is pivotally supported at the other end of the strut 8 and is screwed into a toothed element 81 fixed to the intermediate portion thereof.
The brake shoe 1 is engaged with the other brake shoe 1 via the brake shoe 2.

Reference numeral 9 denotes a return spring stretched between the upper and lower parts of the pair of brake shoes 1 and 2, and the spring force in the contraction direction of the return spring 9 causes one end of the strut 8 to teeth,
It is always engaged with the inner edge of the brake lever 7.

One end of a cable 71 sheathed with a coil spring (not shown) is connected to the lower free end of the brake lever 7, and the other end of the cable 71 is connected to the back plate 3.
It passes through and connects to the operating lever.

When applying the parking brake, the brake lever 7 is rotated by pulling the cable 71 in the direction of arrow P, thereby expanding the diameter of the brake shoes 1 and 2.

Further, during service braking, when the cylinder 5 is actuated, the diameters of the brake shoes 1 and 2 are expanded.

At this time, if the linings of the brake shoes 1 and 2 are worn and the amount of expansion is large, the bell crank lever 82 rotates counterclockwise in FIG. The gaps 1 and 2 are automatically corrected to predetermined values.

The configuration described above is the same as that of a known drum brake.

<B> Means for regulating the backward position of the brake lever In the present invention, a bolt 10 is screwed into the back plate 3 so as to be able to go in and out, and the rear edge 72 of the brake lever 7 is brought into contact with the circumferential surface of the shaft portion of the bolt 10, so that the brake lever can be adjusted. This is a method that restricts the retreat position of 7.

That is, as shown in FIG. 3, a screw hole 31 is provided in the back plate 3, and the bolt 10 is firmly screwed into the screw hole 31 from the outside of the back plate 3 toward the inside of the drum brake.

The entire length of the bolt 10 is at least the length from the back plate 3 to the rear edge 72 of the brake lever 7.

In addition to using an existing bolt with only a male thread formed on the circumference as the bolt 10,
If a stopper 11 is provided in the middle of the shaft,
It is possible to reliably prevent the bolt 10 from falling off or being lost.

This stopper 11 can be formed by crushing the threads of the bolt 10 by caulking or the like, or by using a snap ring 11a as shown in FIG.

Further, the shape of the shaft portion of the bolt 10 that is scheduled to come into contact with the back edge 72 of the brake lever 7 may be formed into a smooth shape by removing the threads, as shown in FIG.

If the back plate 3 is a thin plate, the nut 12 is fixed to the inner or outer surface of the back plate 3 by welding or the like.

In particular, this bolt 10 not only functions as a locking member for regulating the backward position of the brake lever 7, but also functions as a closing member and a reinforcing member for the screw hole 31 formed in the back plate 3.

<C> Operation [When the brake is not in operation] (Figs. 1 and 3) When the parking brake is not in operation and the service brake is not in operation, the gap between the brake drum and the pair of brake shoes 1 and 2 is as follows: This is determined by the effective length of the strut 8 and when the back edge 72 of the brake lever 7 is in contact with the circumferential surface of the bolt 10 to restrict the backward position of the brake lever 7.

[When reducing the diameter of the shoe] (Figures 1 and 4) When reducing the diameter of brake shoes 1 and 2 and removing the brake drum for repair and inspection of the drum brake, perform the following operations.

Bolts 10 exposed on the outer surface of the back plate 3
Loosen the head of the bolt 10 and retract the bolt 10 to the outside of the back plate 3.

When the bolt 10 is further loosened, the circumferential surface of the bolt 10 comes off from the back edge 72 of the brake lever 7.

The circumferential surface of the bolt 10 is the back edge 7 of the brake lever 7
2, the brake lever 7 receives the contraction force of the return spring 9 and rotates counterclockwise in FIG. 1, and as a result, the diameter of the brake shoes 1 and 2 is reduced.

After the diameter of the brake shoes 1 and 2 has been reduced, the brake drum is removed and the parts are inspected and replaced.

When the bolt 10 comes off the back edge 72 of the brake lever 7, the loosening operation of the bolt 10 is stopped and the bolt 10 is screwed into the back plate 3 as it is.

Further, when a stopper 11 is provided on the circumferential surface of the bolt 10, the retreating position of the bolt 10 is regulated by the stopper 11.

In order to determine whether the circumferential surface of the bolt 10 has come off the rear edge 72 of the brake lever 7, the change in rotational resistance when loosening the bolt 10 or the sound of the brake shoes 1 and 2 contracting in diameter is used as a guide.

<Effects of the present invention> Since the present invention is as explained above, the following effects can be obtained.

(a) The diameter of the brake shoe can be reduced by simply loosening the bolt exposed on the outside of the back plate from the outside.

Therefore, the diameter reduction operation of the brake shoe can be easily performed without any trouble.

(b) When reducing the diameter of the brake shoe, it is not necessary to completely remove the bolt that is the locking member of the brake lever, and it is sufficient to leave it screwed into the back plate.

Therefore, the sliding surface of the brake drum will not be damaged or the bolts will not get caught between the drum and the brake shoe due to falling into the brake, and there is no need to worry about losing or forgetting to assemble the bolts.

(c) Since the screw holes made in the back plate are completely closed with bolts, it is possible to reliably prevent foreign substances such as mud and water from entering the drum brake.

Moreover, since the screw holes are closed with bolts, which are rigid bodies, the strength of the back plate can be maintained at the same level as before the holes were opened.

(d) In addition to being a member for regulating the backward position of the brake lever, the bolt also serves as a member for closing the screw hole provided in the back plate, so the number of component parts does not increase.

[Brief explanation of the drawing]

Figure 1: Plan view of drum brake, Figure 2: Cross-sectional view of - in Figure 1, Figure 3: - in Figure 1.
Figure 4: Explanatory diagram when the bolt is loosened and the brake lever is moved backward, Figure 5: Cross-sectional diagram when another bolt is screwed onto the back plate, Figure 6: Conventional FIG. 2 is a cross-sectional explanatory diagram of a regulating device that regulates the backward movement of a brake lever.

Claims (1)

[Scope of Claim for Utility Model Registration] A pair of brake shoes are disposed on the back plate so as to be freely expandable, and one of the brake levers is rotatably supported on the expansion side of the other brake shoe. A traction member is connected to the other free end, and a strut with an adjustment function is installed between the intermediate portion of this brake lever and the other brake shoe, and by regulating the backward movement of the brake lever, the brake drum In a drum brake that determines the gap between the back plate and a pair of brake shoes, a bolt is screwed from the outside of the back plate, and when the bolt is screwed in, the circumferential surface of the bolt comes into contact with the back edge of the brake lever. A drum brake configured to allow the brake lever to move backward when the bolt is loosened and the circumferential surface of the bolt is removed from the rear edge of the brake lever.