Brakes – Wheel – Transversely movable
Reexamination Certificate
2002-02-19
2002-09-24
Rodriguez, Pam (Department: 3683)
Brakes
Wheel
Transversely movable
C188S328000, C188S341000, C301S006700
Reexamination Certificate
active
06454062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a drum brake preferable for an industrial vehicle such as a fork lift truck. Specifically, the present invention relates to an improvement in achieving a light-weighted structure for reducing production cost and achieving promotion of maintenance performance.
2. Description of the Related Art
FIG.
5
and
FIG. 6
show a conventional example of a drum brake for braking a front wheel of a fork lift truck.
The drum brake
1
is disclosed in JP-A-11-201203 and is constituted by providing a drum
5
formed in a headed cylindrical shape and integrally rotated with a front wheel tire
3
; a pair of brake shoes
7
and
8
arranged to be opposed to each other at the inside of the drum
5
; a shoe drive mechanism
9
for expanding the brake shoes
7
and
8
toward an inner peripheral face of the drum
5
; an anchor pin
11
applied with brake torque by being brought into contact with end portions of the brake shoes
7
and
8
; a backing plate
13
having a circular disc portion
13
a
on which side edges
7
a
and
8
a
of the respective brake shoes
7
and
8
slidingly move and a cover portion
13
b
extended from an outer periphery of the circular disc portion
13
a
in an axial direction for covering an outer peripheral portion of the drum
5
; and a mount bracket
15
having a portion thereof attached with the backing plate
13
and fixed to a vehicle body.
As shown in
FIG. 5
, the mount bracket
15
is integrally formed with a first flange portion
15
a
fastened to a frame
17
on the vehicle side by a screw
19
; a second flange portion
15
c
formed with a shaft inserting hole
15
b
inserted with a drive shaft
21
of the front wheel tire
3
at its center; and a sleeve
15
d
formed in a cylindrical shape concentric with the shaft inserting hole
15
b
. The mount bracket
15
is formed by casting or the like.
The illustrated shoe drive mechanism
9
is a wheel cylinder
9
a
arranged between opposed ends of the pair of brake shoes
7
and
8
on one side and operated by hydraulic pressure. The pair of brake shoes are expanded by urging the end portions of the pair of brake shoes in directions separating from each other.
The wheel cylinder
9
a
is fixed to the circular disc portion
13
a
of the backing plate
13
.
The pair of brake shoes
7
and
8
are supported by the circular disc portion
13
a
of the backing plate
13
operable to expand by shoe hold-down pins, not illustrated.
As shown in
FIG. 6
, the backing plate
13
, attached with the pair of brake shoes
7
and
8
and the shoe drive mechanism
9
, is fixed to the second flange portion
15
c
of the mount bracket
15
via a stud bolt
23
.
The cover portion
13
b
of the backing plate
13
functions as a dust cover for preventing foreign matter from invading from the outside into the drum
5
.
The anchor pin
11
is fixedly fastened by a screw member
25
in a state of being inserted to both of the circular disc portion
13
a
of the backing plate
13
and the second flange portion
15
c
of the mount bracket
15
.
In the case of the above-described conventional drum brake
1
, the backing plate
13
is formed by pressing. On the other hand, since the mount bracket
15
is constructed by a three-dimensional structure in which the sleeve
15
d
is projected relative to the first flange portion
15
a
and the second flange portion
15
c
, casting or forging is needed as a method of producing the mount bracket
15
. Therefore, there poses a problem that production cost is increased highly since there are needed not only a pressing facility but also a facility for precision casting or the like in a production line. Furthermore, according to the mount bracket
15
produced in this way, its weight is increased.
Moreover, the circular disc portion
13
a
of the backing plate
13
, on which the side edges
7
a
and
8
a
of the brake shoes
7
and
8
slidingly move in braking, is worn by repeating braking operation and needs to be replaced. However, according to the above-described conventional drum brake
1
, the backing plate
13
is attached with the brake shoes
7
and
8
, the shoe drive mechanism
9
and the anchor pin
11
; therefore, when the backing plate
13
is replaced due to wear thereof, an article to be replaced is obliged to reassemble again after temporarily removing all of attached parts. This poses a problem that maintenance performance is poor in replacing the backing plate or the like.
SUMMARY OF THE INVENTION
The present invention has been carried out in view of the above-described situation and it is an object thereof to provide a drum brake capable of forming a mount bracket by pressing and capable of reducing production cost by omitting a facility for precision casting or the like in a production line. At the same time, it is an object of the present invention to provide a drum brake capable of achieving a light-weighted structure of a product, further, excellent in maintenance performance by dispensing with removal or reattachment of a brake shoe, a shoe drive mechanism and the like when a backing plate is replaced in accordance with wear of a sliding portion thereof.
In order to achieve the above-described object, according to the invention, there is provided a drum brake comprising: a pair of brake shoes arranged opposedly to each other in a drum; a shoe drive mechanism for expanding the brake shoes toward an inner peripheral face of the drum; an anchor pin applied with a brake torque by being brought into contact with end portions of the brake shoes in braking; a backing plate having a circular disc portion on which side edges of the respective brake shoes slidingly move and a cover portion extended from an outer periphery of the circular disc portion in an axial direction for covering an outer peripheral portion of the drum; and a mount bracket having a portion for attaching the backing plate and fixed to a vehicle body,
wherein the mount bracket is constructed by a structure substantially in a shape of a flat plate having a circular plate portion overlapping the circular disc portion of the backing plate and a flange portion extended from an outer periphery of the circular plate portion to constitute a portion for attaching the vehicle body, and
wherein the pair of brake shoes, the shoe drive mechanism and the anchor pin are directly attached to the circular plate portion of the mount bracket without interposing the backing plate.
Further, according to the above-described constitution, the mount bracket is constructed by the structure substantially in the shape of the flat plate which is a simple two-dimensional structure; therefore, the mount bracket can be formed by pressing similar to the backing plate or the like.
Further, there is constructed a constitution in which the pair of brake shoes, the shoe drive mechanism and the anchor pin are directly attached to the circular plate portion of the mount bracket without interposing the backing plate; therefore, when the backing plate is replaced in accordance with wear of a sliding portion (edge face) thereof, it is not necessary to remove or reattach the brake shoes, the shoe drive mechanism or the like. That is, only the backing plate may be removed by itself, and a part to be replaced may newly be attached thereto.
Further, according to the present invention, the drum brake may be characterized in that the mount bracket is formed by pressing a metal plate.
Further, by constructing the above-described constitution, in comparison with the conventional cast product or forged product, a considerable light-weighted structure can be realized.
REFERENCES:
patent: 4219923 (1980-09-01), Marti
patent: 5269396 (1993-12-01), Jones
patent: 10-148230 (1998-06-01), None
patent: 11-201203 (1999-07-01), None
Arita Masatoshi
Yokokura Hisanori
Akebono Brake Industry Co. Ltd.
Morgan & Lewis & Bockius, LLP
Rodriguez Pam
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