Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
2003-01-15
2004-02-24
Schwartz, Christopher P. (Department: 3683)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S07000R, C188S071100, C188S072300, C188S072400
Reexamination Certificate
active
06695099
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to applying a braking force to a rotor, and more particularly to a disc brake caliper of the type used in vehicles.
BACKGROUND OF THE INVENTION
In a typical disc brake apparatus for a vehicle having wheels, such as an automobile a truck, or a motorcycle, a disc brake caliper apparatus attached to a frame of the vehicle is used for applying braking force to the sides of a rotor attached to one or more of the wheels of a vehicle. The calipers used presently, however, do not fully disengage from the sides of the rotor between applications of braking force. Brake linings of the caliper remain in contact with the sides of the rotor creating a drag force on the rotor that reduces fuel economy of the vehicle.
As shown in
FIG. 1
, a typical disc brake apparatus
10
includes a rotor
12
and a brake caliper
14
attached to a common support
16
, such as a steering knuckle, or the chassis of a vehicle. The rotor
12
is mounted for rotation with a wheel of the vehicle, about a rotor axis
18
coincident with the axis of the axle about which the wheel rotates.
The caliper
14
includes a caliper housing
20
that is slidably mounted on a pair of mounting pins
22
to the support
16
, in a manner that allows the caliper
14
to move a short distance toward or away from the support
16
, during operation of the brake
10
. A flexible dust boot
24
is provided around the pins
22
in the space between the housing
14
and the support
16
.
The housing
20
includes a circumferential shaped slot
26
that fits over a portion of the periphery of the rotor
12
, and to provide clearance for a pair of brake shoes
28
,
29
having linings
30
positioned to be clamped against an inboard and an outboard side
32
,
34
of the rotor
12
. The brake shoes
28
,
29
are suspended on the pins
22
in a manner that lets the shoes
28
,
29
slide on the pins
22
. Tabs
46
,
48
, and
50
on the brake shoes
28
,
29
transfer the braking loads to the housing
20
during vehicle braking.
The caliper
14
also includes a piston
36
mounted in a cylinder bore
38
to be movable along a bore axis
40
for moving the inboard brake shoe
28
into contact with the inboard side
32
of the rotor
12
, for applying a braking force against the inboard side
32
of the rotor
12
, when pressurized fluid is introduced into the cylinder bore
38
in a space
42
behind the piston
36
.
As the piston
36
applies braking force to clamp the inboard brake shoe
28
against the inboard side
32
of the rotor
12
, the pressurized fluid in the space
42
in the cylinder bore
38
behind the piston
36
causes the housing
20
to move in an opposite direction along the bore axis
40
. This movement of the housing
20
pulls the outboard lining
30
of the outboard brake shoe
29
into contact with the outboard side
34
of the rotor
12
, creating a clamping effect, so that the motion of the piston
36
toward the inboard side
34
of the rotor
12
applies braking force to both the inboard and outboard sides
32
,
34
of the rotor
12
.
When fluid pressure is released in the space
42
behind the piston
36
, the piston
36
is retracted a few thousandths of an inch by the action of a specially designed seal
44
, between the cylinder bore
38
and the piston
36
, in a manner known in the art. With the piston
36
retracted, the inboard brake shoe
28
is free to move away from the inboard surface
32
of the rotor
12
.
There is no mechanism provided, however, for moving the outboard brake shoe
29
away from the outboard side
34
of the rotor
12
. This results in undesirable drag between the lining
30
on the outboard shoe
29
and the outboard side
34
of the rotor
12
, thereby reducing fuel economy of the vehicle to which the brake
10
is attached.
In addition, because the caliper
14
and the brake shoes
28
,
29
must slide on the pins
22
, and yet still be capable of withstanding braking loads transferred to the caliper housing
20
by the tabs
46
,
48
, and
50
on the brake shoes
28
,
29
, for proper operation of the brake
10
, the caliper housing
20
is a complex shape, and is typically produced by an expensive process such as casting the housing from iron or steel, and carrying out complex machining operations to bring the housing to its final shape. Caliper housings
20
of the type used in the past are also heavy.
What is needed, therefore, is an improved disc brake apparatus providing a solution to one or more of the problems and disadvantages described above.
SUMMARY OF THE INVENTION
The invention provides an improved braking apparatus for applying a braking force to the inboard and outboard sides of a brake rotor, through the use of a pair of pistons disposed in a back-to-back relationship in a cylinder bore of a housing, and defining a space between them in the cylinder bore for receipt of a pressurized fluid.
In one form of the invention, the rotor is rotatable about a rotor axis, and the cylinder bore defines a bore axis extending parallel to the rotor axis. A first piston of the pair of pistons is slidably disposed in the cylinder bore for movement in a first direction along the bore axis toward the inboard side of the rotor for applying a braking force to the inboard side of the rotor, and the second piston of the pair of pistons is slidably disposed in the cylinder bore for movement in a second direction opposite the first direction along the bore axis for applying a braking force to the outboard side of the rotor.
A braking apparatus, according to the invention, may further include a movable bridge element slidingly attached to the housing for transmitting a braking force from the second piston to the outboard side of the rotor.
The invention may also take the form of a method for applying a braking force to the inboard and outboard sides of a brake rotor by connecting a first piston and a second piston disposed in a back-to-back relationship in the cylinder bore and defining a space between them in a cylinder bore for receipt of a pressurized fluid, to the inboard and outboard sides of the rotor, and introducing a pressurized fluid into the space between the first and second pistons, so that the first and second pistons generate a braking force applied to the first and second sides of the rotor.
REFERENCES:
patent: 3245500 (1966-04-01), Hambling et al.
patent: 3402790 (1968-09-01), Rath
patent: 3421603 (1969-01-01), Schuchmann et al.
patent: 3428152 (1969-02-01), Hoenick
patent: 3448831 (1969-06-01), Newstead
patent: 3470984 (1969-10-01), Goddard
patent: 3493084 (1970-02-01), Maurice
patent: 3712422 (1973-01-01), Haraikawa et al.
patent: 3912051 (1975-10-01), Yokoi et al.
patent: 4611691 (1986-09-01), Gornall
patent: 4715479 (1987-12-01), Buckley
patent: 5253736 (1993-10-01), Kohler
Delphi Technologies Inc.
Kramer Devon
McBain Scott A.
Schwartz Christopher P.
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