JPH0135071Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a relatively small diameter drum brake that employs a U-shaped return spring.

(Prior Art) The structure of a general drum brake is as shown in FIGS. 5A and 5B, as shown in FIG.
A pair of brake show arms 103, 103 are arranged in the space between 01 and the outer peripheral part 102, and a brake panel 104 is attached to the boss part 101 to close the outside of these brake show arms 103, 103. Brake show arm 103, 10
3 is pivotally supported by an anchor pin 105, and a return spring 1 is attached to each arm 103, 103.
06 is stretched, and the arms 103,
103 is expanded, the brake shoe 107 is brought into pressure contact with the inner peripheral surface of the hub to perform braking, and the tensile force of the return spring 106 causes the arms 103, 1
03 is closed, the brake shoe 107 is separated from the inner peripheral surface of the hub, and the braking is released.

Incidentally, there are cases where the diameter of the brake shoe arms 103, 103 must be made small in relation to the diameter of the entire wheel. In this case, if a coil spring is used as the return spring 106, the coil spring and the boss portion 101 of the hub will interfere with each other, so a U-shaped return spring 108 is used as shown in FIGS. 6A and B. There is.

(Problems to be Solved by the Invention) As mentioned above, a U-shaped return spring 108 is used in a small-diameter drum brake, but when using this return spring 108, reliability of operation and In order to prevent it from coming off,
The tip of the return spring 108 is bent at a bend 1 perpendicular to the opening/closing direction of the brake show arm 103.
09, and this bent portion 109 is locked in a locking hole 110 of the brake shoe arm 103.

By the way, if the brake shoe 107 is worn out, it is necessary to remove the return spring 108 when replacing it. As shown in FIG. 6C, this removal work involves inserting a jig such as a screwdriver 111 between the return spring 108 and the arm 103 to remove the return spring 108 from the anchor pin 105. Bent portion 109 of return spring 108
It is necessary to widen the angle θ of the hole 11, which requires a large force.
There is a problem that it is difficult to pull out from zero, and furthermore, it cannot be removed successfully unless both bent portions are pulled out at the same time.

(Means for solving the problem) In order to solve the above problem, the present invention provides a drum brake using a U-shaped return spring, in which the tip of the return spring is moved in the closing direction of the brake shoe arm. On the other hand, the brake shoe arm is formed with a locking portion that is locked by the bent portion and a projecting portion that positions the return spring from the outside.

(Function) When the return spring is removed from the anchor pin, no great force is required because it rotates around the bent portion, and when the return spring is set, it can be accurately attached using the overhang.

(Example) An example of the present invention will be described below based on the accompanying drawings.

FIG. 1 is an overall view of the drum brake according to the present invention.
A pair of cast brake show arms 3, 3 are housed in the space between the outer part 2b and the outer part 2b, and the bases of these brake show arms 3, 3 are pivotally supported by anchor pins 4 so as to be freely openable and closable. Each brake shoe arm 3, 3 is
is biased in the closing direction.

As a result, the brake shoe arms 3, 3 expand against the return spring 5 due to the operation of a cam mechanism (not shown), and the brake shoe arms 6, which are fixed to the outer circumferential surface of the arms, touch the inner circumferential surface of the outer hub portion 2b. Braking is performed by the pressure contact, and the brake shoe arms 3, 3 are closed by the tensile force of the return spring 5, and the brake shoe 6 is separated from the inner circumferential surface of the hub outer portion 2b, and the braking is released.

Here, as shown in FIG. 2, the tip of the return spring 5 is bent into the closing direction of the brake show arms 3, 3, and these bent parts 5a, 5a , 3, and the base of the return spring 5 is locked to the anchor pin 4.

As shown in FIG. 3, the locking part 7 is formed by forming a through hole 11 in the opening/closing direction of the arm in the rim 3a of the brake show arm 3 using a convex part 9 and a concave part 10 at the center position of the brake show arm 3. The bent portion 5a is rotatably inserted into the through hole 11 from the outside. Further, the locking portion 8 is composed of a through hole 12 formed with a concave and convex portion in the same manner as described above, into which the tip of the bent portion 5a is inserted, and a stopper boss 13 against which a corner portion of the bent portion 5a comes into contact. and,
When the return spring 5 is assembled to the locking parts 7 and 8, the distance A between the center of the cam and the center of the locking part 7 is smaller than the distance B between the center of the cam and the center of the locking part 8. Also, the distance C between the left and right bent portions 5a, 5a and the cam center,
D is set to be equal.

Furthermore, the locking portion 7 of the brake show arm 3,
Inwardly extending projecting portions 14, 14 are integrally formed in the vicinity of 8. The amount of inward protrusion of these projecting portions 14 is such that they come into contact with the return spring 5 from the outside, or that a slight gap is formed between them and the return spring 5.

In the above, the return spring 5 is attached and detached as shown in FIG.

That is, when setting the return spring 5, first the tip bent portion 5 of the return spring 5 is set.
a, 5a to the locking parts 7, 8, and then arrow A
The return spring 5 is bent in the direction of the bent portions 5a, 5a.
The return spring 5 is rotated around the center to lock the base of the return spring 5 to the anchor pin 4. In addition, when removing the return spring 5, insert the screwdriver 15 between the return spring 5 of the anchor pin 4 portion and the brake show arm 3, release the engagement between the return spring 5 and the anchor pin 4, and remove the return spring 5. is rotated about the bent portions 5a, 5a in the direction of arrow B, and then the return spring 5 is expanded to release the locked state between the bent portions 5a, 5a and the locking portions 7, 8.

(Effect of the invention) As explained above, according to the invention, in a drum brake using a U-shaped return spring, the tip of the return spring is bent in the closing direction of the brake shoe arm, and this bent part is bent in the closing direction of the brake shoe arm. Since the return spring is locked to the locking part of the brake shoe arm so that it can be the center of rotation, removing the return spring does not require a large amount of force as in the conventional case, and the return spring can be attached and detached in a short time with a simple operation.

In addition, since the brake shoe arm has an overhang, this overhang serves as a guide when setting the return spring.In other words, if the return spring is not set correctly, the overhang will get in the way, and the return spring cannot be attached to the anchor pin. Since it cannot be locked, the return spring can be reliably installed at an accurate position.
Moreover, since the return spring has a bent portion as small as possible and is configured in a flat shape, it is easy to manufacture and can be obtained at low cost.

[Brief explanation of drawings]

Figure 1 is an overall view of the drum brake according to the present invention, Figure 2 is a perspective view of the return spring, and Figure 3 is a perspective view of the return spring.
Figure 4 is a perspective view of the brake shoe arm, Figure 4 is a diagram explaining how to attach and remove the return spring, Figure 5 A and B are diagrams showing a conventional drum brake using a coil spring, and Figures 6 A to C. 1 is a diagram showing a conventional drum brake using a U-shaped spring. In the drawings, 2 is a hub, 3 is a brake shoe arm, 4 is an anchor pin, 5 is a return spring, 5a is a bent portion, 7 and 8 are locking portions, and 14 is a projecting portion.

Claims (1)

[Scope of utility model registration request] A drum brake includes a pair of brake show arms whose bases are pivotally supported by an anchor pin so as to be freely openable and closable, and a return spring that biases these brake show arms in the closing direction. The brake show arm has a U-shape that locks onto the anchor pin, and both ends thereof are bent portions in the closing direction of the brake show arm, and the brake show arm has a locking portion where the bent portion of the return spring locks. A drum brake characterized in that an overhang is formed to position the return spring from the outside.