Brakes – Operators – Multiple
Reexamination Certificate
2001-12-28
2003-09-09
Schwartz, Christopher P. (Department: 3683)
Brakes
Operators
Multiple
C188S10600P
Reexamination Certificate
active
06615957
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to improvements in a dual-mode drum brake assembly which functions as the service brake in the form of a leading/trailing type brake during running of an automotive vehicle, and as the parking brake in the form of a duo-servo type brake.
2. Discussion of the Related Art
There is widely known a dual-mode drum brake assembly for a vehicle, including: (a) a backing plate which is fixed to a body of the vehicle; (b) first and second arcuate brake shoes which are disposed, substantially symmetrically with each other, on the backing plate such that the first and second arcuate brake shoes are movable toward and away from each other, the first and second arcuate brake shoes having a first pair of adjacent end portions each of which is provided by one of opposite end portions of a corresponding one of the first and second arcuate brake shoes and each of which is held by an anchor disposed on the backing plate, the first and second arcuate brake shoes further having a second pair of adjacent end portions each of which is provided by the other of the opposite end portions of a corresponding one of the first and second arcuate brake shoes; (c) an actuator which is disposed on the backing plate such that the actuator is positioned between the second pair of adjacent end portions of the first and second arcuate brake shoes, and which is operable to move the second pair of adjacent end portions away from each other so as to force the arcuate brake shoes against a brake drum rotatable with a wheel of the vehicle so that the dual-mode drum brake assembly acts as a leading/trailing drum brake for generating a braking force for braking the wheel; (d) an intermediate lever which has an intermediate portion connected to an intermediate portion of a web such that the intermediate lever is pivotable relative to the web about a pivot axis that is substantially perpendicular to the backing plate, the web being provided by a flat plate portion of the first arcuate brake shoe which portion is substantially parallel to the backing plate; (e) a second strut which is associated at opposite end portions thereof with a first end portion of the intermediate lever and the second arcuate brake shoe; (f) a positioning spring which positions the intermediate lever and the second strut in respective predetermined positions in which the intermediate lever and the second strut are held in engagement at respective engaging portions thereof with each other with the engaging portions lying on a plane that is tangent to the web, the engaging portions being provided by the first end portion of the intermediate lever and one of the opposite end portions of the second strut; (g) a first strut which is engaged with one of the second arcuate brake shoe and a second end portion of the intermediate lever, the second end portion being located on one of opposite sides of the pivot axis which one is remote from the first end portion of the intermediate lever; and (h) a parking lever which is engaged with the other of the second arcuate brake shoe and the second end portion of the intermediate lever, the parking lever being operable to be pivoted so as to be brought into engagement with the first strut whereby the first and second arcuate brake shoes are moved away from each other by a link mechanism constituted by the first and second struts and the intermediate lever, so that the dual-mode drum brake assembly acts as a duo-servo brake for generating a braking force for braking the wheel. An example of the dual-mode drum brake assembly is disclosed in JP-A-2000-170802 (publication of Japanese Patent application laid open in 2000).
The above-described dual-mode drum brake assembly is illustrated in
FIGS. 7A and 7B
, by way of example.
FIG. 7A
is a front elevational view of the dual-mode drum brake assembly.
FIG. 7B
is a cross sectional view which is taken along line
7
B—
7
B of FIG.
7
A and in which some components such as an anchor are not shown. This illustrated dual-mode drum brake assembly is to be provided in an automotive vehicle, for braking a rear right wheel of the vehicle. As shown in
FIG. 7A
, the drum brake assembly includes a backing plate
10
in the form of a generally circular disc which is fixed to a body of the vehicle. A pair of arcuate brake shoes
12
,
14
are supported by the backing plate
10
such that the two arcuate brake shoes
12
,
14
extend substantially in the vertical direction as seen in FIG.
7
A and are movable toward and away from a periphery of the backing plate
10
, namely, toward and away from each other in the right and left directions as seen in FIG.
7
A. The brake shoes
12
,
14
have respective webs
12
a
,
14
a
each provided by a flat plate portion of the corresponding one of the arcuate brake shoes
12
,
14
which portion is substantially parallel to the backing plate
10
. The brake shoes
12
,
14
further have: respective rims
12
b
,
14
b
which are fixed to the arcuate outer periphery of the webs
12
a
,
14
a
and each of which cooperates with the corresponding web
12
a
,
14
a
to constitute a structure that is T-shaped in cross section; and respective linings
12
c
,
14
c
secured to the arcuate outer surfaces of the rims
12
b
,
14
b
. The brake shoes
12
,
14
are provided with respective hold-down devices
16
,
18
at their intermediate portions, and are forced onto the backing plate
10
by the hold-down devices
16
,
18
such that the brake shoes
12
,
14
are movable in the above-described right and left directions. The brake shoes
12
,
14
are positioned relative to the backing plate
10
such that the brake shoes
12
,
14
substantially lie on a single plane which is spaced apart from the backing plate
10
by a predetermined distance in an axial direction of the backing plate
10
. It is noted that the brake shoe
12
serves as the above-described second arcuate brake shoe while the brake shoe
14
serves as the above-described first arcuate brake shoe.
The webs
12
a
,
14
a
of the brake shoes
12
,
14
have a first pair of adjacent portions each of which is provided by a lower end portion (as seen in
FIG. 7A
) of the corresponding web
12
a
,
14
a
, and a second pair of adjacent portions each of which is provided by an upper end portion (as seen in
FIG. 7A
) of the corresponding web
12
a
,
14
a
. The first pair of adjacent portions of the webs
12
a
,
14
a
are held in contact with opposite ends of an anchor
20
which is fixed to the backing plate
10
. On the other hand, the second pair of adjacent portions of the webs
12
a
,
14
a
are held in engagement with respective opposite end portions of a wheel brake cylinder
22
which is also fixed to the backing plate
10
. The anchor
20
is a floating-type abutment block adapted to hold the webs
12
a
,
14
a
of the two brake shoes
12
,
14
such that the webs
12
a
,
14
a
are movable away from the anchor
20
. Normally, the first pair of adjacent portions of the webs
12
a
,
14
a
are held in contact with respective opposite end faces of the anchor
20
under a biasing action of a tension coil spring
24
interposed between the webs
12
a
,
14
a
. The wheel brake cylinder
22
serving as actuator is a generally cylindrical member, and has a pair of pistons which are movable outwardly from respective opposite ends of a main body of the wheel brake cylinder
22
in an axial direction of the cylinder
22
. When the wheel brake cylinder
22
is activated with a hydraulic pressure applied thereto by operation of a brake pedal or other service brake operating member, the pair of pistons are outwardly moved in directions away from each other, whereby the second pair of adjacent portions of the two brake shoes
12
,
14
are moved in the right and left directions (as seen in
FIG. 7A
) away from each other. Consequently, the two brake shoes
12
,
14
are outwardly moved pivotally about respective pivot axes, namely, about the points of contact with the anchor
20
, so that the linings
12
c
,
1
Asai Kazuhiro
Mizuno Mitsuyasu
Hosei Brake Ind. Co., Ltd.
Schwartz Christopher P.
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