Automatic shoe clearance adjustment device for drum brakes

Details Automatic shoe clearance adjustment device for drum brakes Automatic shoe clearance adjustment device for drum brakes

1998-06-09

2001-03-06

Oberleitner, Robert J. (Department: 3613)

Brakes

Wheel

Transversely movable

C188S1960BA

Reexamination Certificate

active

06196360

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to an automatic shoe clearance adjustment device for a drum brake device equipped with an over-adjustment preventive measure which suspends the adjustment operation when the brake temperature rises.
In traditional automatic shoe clearance adjustment devices for a drum brake device, an opening action of the two facing plates of a folded bimetal member provided at the strut restricts the over-adjustment operation in case the brake drum expands as the brake temperature rises. One example is shown in Japanese Patent Publication Number Showa 58-49739.
Yet, in the above-described device, simply, a tube of the strut fits over the screw rod with a gap therebetween. Hence, until the strut is actually placed between the brake shoe and the hand brake lever and until the return spring is fitted, the strut could freely come out in the direction of that axle and could freely rotate.
Then, a rib of the folded bimetal member is structurally apt to come out from a triangle-like concave portion of the tube. For this reason, assembling the strut, in which the concave portion of the rib is interlocked, is said to be difficult.
If the strut is assembled while the rib is dislocated off from the concave portion of the tube, due to a large thrust force on the strut while the hand brake lever is in operation, the rib is deformed and may adversely affect the automatic adjustment operation which requires a delicate adjustment operation. Also, the same type of adverse effect may occur if the folded bimetal member rotates to interfere with other parts such as the shoe return spring. In addition, even if the misassembled parts are fortunately found, a correction of the misassembled parts demands effort and time.
OBJECTS AND SUMMARY OF THE INVENTION
This invention is designed to resolve the problems described above. To that end, an object of the invention is to provide a method to improve the ease of assembly of this bimetal member and to prevent misassembly, where a bimetal member is used as an over-adjustment preventive device which suspends the automatic adjustment operation of a clearance between the brake drum and the brake shoe when the brake temperature rises.
Another object of the invention is to provide an automatic shoe clearance adjustment device, wherein a bimetal member is movable in the direction of the adjuster axis with the stationary parts of the adjuster and is not relatively rotatable, thereby facilitating the assembling process and preventing misassembly.
Another object of the invention is to provide an automatic shoe clearance adjustment device, wherein the bimetal member is placed between the stationary parts of the adjuster, thereby improving the usability of the adjuster, increasing the ease of assembly, and preventing misassembly, if the worst should happen and the stationary parts are separated.
Another object of the invention is to provide an automatic shoe clearance adjustment device, wherein, from the above described advantages, the automatic shoe clearance adjustment operation between the brake drum and the brake shoe is accurately suspended when the brake temperature rises, thereby preventing over-adjustment.
In the first aspect of the invention, an automatic shoe clearance adjustment device for a drum brake device comprises an adjuster equipped with a screw mechanism for an automatic adjustment of the length of the adjuster in response to an excessive opening of brake shoes and a bimetal member provided between the parts constituting the adjuster. The bimetal member is provided to suspend the extension of the adjuster according to the brake temperature increase. In this invention, the bimetal member is connected together with an non-rotating segment which is a part of the adjuster.
In the second aspect of the invention, the bimetal member has a hook thereon and a cavity is formed in the non-rotating segment of the adjuster. The hook fits into the cavity. In this manner, the bimetal member is affixed to the non-rotating segment in the way that the bimetal member does not rotate about and does not come off from the longitudinal axis of the adjuster.
In the third aspect of the invention, the hook has a wider top portion and the cavity is specially shaped to receive the wider top portion. In this manner, the bimetal member is affixed to the non-rotating segment in the way that the bimetal member does not come off from the adjuster longitudinal axis.
In the fourth aspect of the invention, the bimetal member has an elastic hook, with the hook fitting locked with the non-rotating segment in a male-female contact. In this manner, the bimetal member is affixed to the non-rotating segment in the way that the bimetal member does not rotate about and does not come off from the adjuster longitudinal axis.


REFERENCES:
patent: 4148380 (1979-04-01), Haraikawa
patent: 4385681 (1983-05-01), Conrad et al.
patent: 4390086 (1983-06-01), Conrad
patent: 4533024 (1985-08-01), Rath
patent: 4729457 (1988-03-01), Cousin et al.
patent: 4809826 (1989-03-01), Charbonnier
patent: 5295561 (1994-03-01), Le Moigne
patent: 5758750 (1998-06-01), Le Moigne et al.

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