JPS6340663Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a sealing device for a show hold down pin in a drum brake.

A drum brake suppresses rotation of the brake drum by pressing the brake shoe held by a disc-shaped bucking plate against the inner peripheral surface of the brake drum using a hydraulic cylinder or mechanical shoe expansion mechanism. Therefore, the brake shoe must be able to move along the bucking plate, but at the same time, it must be designed so that it does not easily separate from the bucking plate even when the brake is vibrated. It is necessary to. For this purpose, a shun hold down device as shown in FIG. 1 is widely used.

In FIG. 1, reference numeral 2 denotes a brake shoe, which includes a lining 4 arranged in an arc shape along the inner surface of the brake drum, a shoe rim 6 fixed to the back surface of the lining 4, and a shoe web 8 fixed at right angles to the back surface of the rim. It consists of. Although not shown, the rim 6 is capable of contacting the bucking plate 10 at three locations in the longitudinal direction, and is pressed toward the bucking plate 10 by the shew hold-down device 12. There is. The show hold down device 12 includes a show hold down pin 14 which is disposed through a pin hole formed in the bucking plate 10 and the show web 8, and two show hold down pins fitted into the show hold down pin 14. Dish-shaped spring seats 16, 18
and a compression coil spring 20 installed between the spring seats 16 and 18 with precompression applied thereto. The hold-down pin 14 has heads 22 and 24 at each end thereof, which engage the edges of holes formed in the spring seat 16 and bucking plate 10, respectively. There are various types of show hold down devices, such as those that use a leaf spring instead of the compression coil spring 20 as described above.
In any case, one end of the hold-down pin 14 penetrates through the bucking plate 10 and projects to the outside, and the head formed at the projecting end engages with the edge of the pin hole in the bucking plate 10. It is common to be

Therefore, water or the like may enter the drum brake through the gap between the bucking plate 10 and the shuhold down pin head 24, lowering the coefficient of friction between the lining 4 and the brake drum, or damaging the internal parts of the drum brake. Problems such as rust may occur. Therefore, conventionally the first
As shown in the figure, a sealer 26 is applied to the backing plate 10 so as to cover the head 24 of the hold-down pin 14 to prevent water from entering. However, the shew hold down pin 14 cannot avoid swinging at a small angle around the head 24 as the drum brake operates, and as a result, the sealer 26 may peel off from the bucking plate 10. There was a risk that the sealing effect would decrease or disappear.

Therefore, as shown in FIG. 2, by fitting the rubber bushing 30 into the pin hole of the bucking plate 28 and inserting the shoe hold down pin 32 into the rubber bushing 30, the bucking plate 28 and the shoe hold down Watertightness between the pin 32 and the pin 32 was also maintained. However, as described above, the head 34 of the hold down pin 32 is biased in the direction toward the bucking plate 28 by the elastic force of the spring, and when the drum brake is operated, the head 34 is biased toward the bucking plate 28. Since the rubber bushing 30 undergoes repeated rocking motions at small angles, the rubber bushing 30 is prone to wear and cracks, making it unsatisfactory in terms of durability.

The present invention was developed against the background of the above-mentioned circumstances, with the purpose of providing a sealing device for a show hold down pin that provides a reliable sealing effect and is highly durable. The reason for this is that a diameter decreasing part is provided between the shaft and the head of the shuhold down pin, and the diameter gradually decreases from the head side to the shaft side, and the diameter decreasing part is connected to the backing plate. An annular groove is formed between the bucking plate and the head when it is engaged with the edge of the pin hole, and an O is inserted into the groove.
The ring is disposed to seal between the head of the hold down pin and the outer surface of the bucking plate.

In this way, the force exerted by the spring on the shew hold down pin is received directly by the bucking plate through the engagement of the reduced diameter portion with the edge of the pin hole, and the O-ring is subjected to excessive compression. Since no force is applied, there is no risk of damage to the O-ring, and the rocking motion of the shuh-hold down pin when the drum brake is activated will cause the O-ring to contact the shuh hold down pin head or bucking plate. Even if a slight relative movement occurs between the O-rings and the There is no risk that the sealing effect will deteriorate. Furthermore, during assembly work, if you insert the O-ring into the shuhold-down pin and insert the shuhold-down pin into the pin hole of the bucking plate, the O-ring will fit between the bucking plate and the shuhold. It is automatically positioned and held between the head of the down pin and produces a shielding effect, and one of the effects of the present invention is that assembly work is extremely easy.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 3, reference numeral 36 denotes a show hold down pin, and a head 40 is formed at one end of a shaft portion 38 of the pin. The head 40 is composed of a ball band part 42 adjacent to the shaft part 38 and a disk part 44 formed continuously with the ball band part 42. In other words, the spherical band portion 42 forms a decreasing diameter portion whose diameter decreases at an accelerating rate from the disk portion 44 side toward the shaft portion 38. On the other hand, a dish-shaped recess 48 is formed in the backing plate 46.
A pin hole 50, which is a circular through hole, is formed in the center. The show hold down pin 36 is the first
It forms part of a shoe hold-down device having the same structure as the shoe hold-down device 12 shown in the figure, and is always pushed inward by the reaction force of a spring to press the shoe against the bucking plate 46. The ball band portion 42 is always engaged with the edge of the pin hole 50 by this urging force. As a result, the head 40 of the hold down pin 36 and the bucking plate 46
An annular groove 52 having a substantially V-shaped cross section is formed between the outer circumferential surface of the spherical band portion 42, the recessed portion 48, and the bottom surface. An O-ring 54 is disposed within this annular groove 52, and this O-ring 54 is pressed against the bottom surface of the concave portion 48 by the ball band portion 42, and at the same time, the inner diameter is slightly reduced. It's being expanded. Therefore, the O-ring 54 has narrow annular surfaces on the bottom surface of the concave portion 48, that is, the outer surface of the bucking plate 46, and on the outer circumferential surface of the spherical band portion 42, that is, the outer circumferential surface of the reduced diameter portion of the head of the shuhold down pin. are in elastic contact with each other.

Therefore, the O-ring 54 seals between the bucking plate 46 and the shuhold down pin head 40, and water and mud are prevented from entering the inside of the bucking plate 46 through the gap between the two. is prevented. Moreover, in this embodiment, since the reduced diameter portion is formed by the ball band portion 42, even if the shuhold down pin 36 swings about the head 40 when the drum brake is activated, Only a slight relative movement occurs between the ball band portion 42 and the O-ring 54, and the O-ring 5
The inner diameter of the O-ring 54 is not significantly increased, and the O-ring 54 is not forcibly compressed.
Breakage of the ring 54 and reduction in durability can be effectively avoided. Further, in this embodiment, the head 40 of the shew hold down pin 36 and the O-ring 54 fit into the recess 48 formed in the bucking plate 46.
The head 40 of the shuhold down pin 36 protrudes largely from the general outer surface of the bucking plate 46 and gets in the way, and the O-ring 54
There is no risk of damage to the O-ring 54 due to collision with flying stones or the like. Although it is desirable to provide the concave portion 48 in this sense, it is of course possible to omit the formation of the concave portion 48.

FIG. 4 shows another embodiment of the present invention. In this embodiment, the head 58 of the hold-down pin 56 includes a tapered portion 62 formed adjacent to the shaft portion 60, a cylindrical portion 64 formed adjacent to the tapered portion 62, and a cylindrical portion 64 formed on the distal end side thereof. It consists of a disk portion 66. The tapered portion 62 forms a decreasing diameter portion whose diameter decreases linearly from the cylindrical portion 64 side toward the shaft portion 60 side, and is engaged with the edge of a pin hole 70 formed in the bucking plate 68. There is. As a result, an annular groove 72 having a substantially rectangular cross section is formed between the outer surface of the bucking plate 68, the opposing surface of the disc portion 66, and the outer circumferential surface of the cylindrical portion 64. An O-ring 74 is disposed within the groove 72. The dimensions of the O-ring 74 are determined so that when the tapered portion 62 is engaged with the edge of the pin hole 70, it is slightly compressed by the bucking plate 68 and the disk portion 66.
A narrow annular surface is brought into close contact with the outer surface of the bucking plate 68 and the opposing surface of the disk portion 66 to provide a sealing effect.
In this embodiment, O
Although there is a problem that the compression amount of the ring 74 varies somewhat in some parts, by setting the precompression amount of the O-ring 74 to a large value, it is possible to avoid the sealing effect becoming incomplete due to the above-mentioned rocking motion. It is possible.

Two embodiments of the present invention have been described above based on the drawings, but the present invention can be modified and improved in various ways based on the knowledge of those skilled in the art without departing from the scope of the claims for utility model registration. Of course, it can be implemented in the manner described above.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing an example of a show hold-down device equipped with a sealing device in a conventional drum brake. FIG. 2 is a front sectional view showing another example of a conventional sealing device. Third
4 and 4 are front sectional views showing the sealing device according to the present invention, respectively. 36, 56: Shu hold down pin, 3
8, 60: Shaft, 40, 58: Head, 42: Ball zone (reduced diameter part), 46, 68: Bucking plate, 48: Recess, 50, 70: Pin hole, 5
2, 72: Annular groove, 54, 74: O ring, 6
2: Tapered part (diameter decreasing part), 64: Cylindrical part, 6
6: Disc part.

Claims (1)

[Claims for Utility Model Registration] A shoe hold down pin of a shoe hold down device for pressing a brake shoe against a bucking plate is inserted into a pin hole formed in the bucking plate, In a drum brake of the type in which a head formed at one end of the shaft is engaged with an edge of the pin hole, the head of the shuhold down pin is provided with a diameter decreasing part whose diameter gradually decreases toward the shaft. and an annular groove is formed between the outer surface of the bucking plate and the head with the reduced diameter portion engaged with the edge of the pin hole, and an O-ring is provided in the groove. 1. A sealing device for a shhold-down pin in a drum brake, characterized in that a sealing device for a shhold-down pin in a drum brake is provided to seal between the head and the outer surface.