Brakes – Wheel – Axially movable brake element or housing therefor
Reexamination Certificate
2000-02-10
2002-06-18
Dickson, Paul N. (Department: 3613)
Brakes
Wheel
Axially movable brake element or housing therefor
C188S071500, C188S170000, C192S090000
Reexamination Certificate
active
06405837
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to hydraulic brakes. More particularly, the present invention relates to hydraulic brakes that provide both parking brake and service brake functions.
BACKGROUND OF THE INVENTION
Braking devices having combined service brakes and parking brakes are commonly used on vehicles such as mobile booms, pallet loaders, etc.
FIGS. 1 and 2
illustrate one type of prior art braking device
20
capable of functioning as both a parking brake and a service brake. The braking device
20
includes a rotational shaft
26
that extends through a plurality of co-axially aligned rotor and stator plates
22
and
24
. A first end
28
of the shaft is adapted for connection to a wheel, while a second end
30
of the shaft is adapted for connection to a drive source such as a hydraulic motor. The rotor plates
22
are adapted to rotate in concert with the shaft
26
, while the stator plate
24
are prevented from rotating in concert with the shaft
26
. The plates
22
,
24
are enclosed within a housing
23
.
The plates
22
,
24
of the braking device
20
are arranged in a stack
21
having a first axial end
32
positioned opposite from a second axial end
34
. A spring assembly
36
is positioned at the first axial end
32
of the stack
21
. The spring assembly
36
provides a spring load for biasing the rotor and stator plates
22
,
24
together to provide the parking brake. When the parking brake is engaged, the plates
22
,
24
are compressed between the spring assembly
36
and the housing
23
such that friction between the plates
22
,
24
prevents the shaft
26
from freely rotating.
The parking brake is disengaged by a first piston
38
positioned at the second axial end
34
of the stack
21
. An axial extension
40
is provided for transferring force from the first piston
38
to a parking brake release plate
39
engaged by the spring assembly
36
. When hydraulic pressure is applied to the first piston
38
, the first piston
38
provides a force that overcomes the bias of the spring assembly
36
and moves the parking brake release plate
39
away from the remainder of the plates
22
,
24
. With the spring load removed from the plate stack
21
, the plates
22
,
24
are no longer compressed together and the parking brake is released.
The braking device
20
also includes a second piston
42
for actuating the service brake of the braking device
20
. The second piston
42
is mounted at the first axial end
32
of the stack
21
. When the service brake is actuated as shown in
FIG. 2
, hydraulic pressure applied to the second piston
42
causes the second piston
42
to compress the plate stack
21
. To engage the plate stack
21
, the second piston
42
travels through an opening
37
defined by the parking brake release plate
29
. With the stack
21
compressed as shown in
FIG. 2
, friction between the plates
22
,
24
provides a frictional braking action to the shaft
26
.
The hydraulic brake industry is very competitive and cost is an important factor relating to the success or failure of any given product. As shown by the braking device of
FIGS. 1 and 2
, conventional combined parking and service brakes typically are fairly complicated. Therefore, such brakes are typically fairly expensive to manufacture. What is needed is a simplified and cost effective braking device that functions as both a parking brake and a service brake.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a braking device having a service brake and a parking brake. The braking device includes a housing and a shaft that extends at least partially through the housing. The shaft is rotatable relative to the housing about a longitudinal axis. The braking device also includes a stack of plates spaced axially along the shaft. At least one of the plates is adapted to rotate in concert with the shaft. The stack of plates includes a first axial end positioned opposite from a second axial end. A spring structure is provided for compressing the stack of plates together to provide the parking brake. The spring structure is mounted at the first axial end of the stack of plates. The braking device further includes a first piston for releasing the parking brake, and a second piston for actuating the service brake. The second piston is mounted at the second axial end of the stack of plates. In use, the second piston forces the plates axially toward the spring assembly to actuate the service brake.
Another aspect of the present invention relates to a method for actuating a service brake of a braking device that also includes a parking brake. The braking device includes a shaft that is rotatable about a longitudinal axis and is adapted for connection to a wheel. The braking device also includes a stack of plates spaced axially along the shaft with at least one of the plates being adapted to rotate in concert with the shaft. The braking device further includes a spring structure for biasing the plates together to provide the parking brake. The service brake of the braking device is actuated by forcing the stack of plates axially toward the spring structure thereby causing the plates to be compressed together to provide the service brake.
REFERENCES:
patent: 3680666 (1972-08-01), Sommer
patent: 3770085 (1973-11-01), Cottingham
patent: 3863038 (1975-01-01), Kreitner et al.
patent: 3927737 (1975-12-01), Prillinger et al.
patent: 3941219 (1976-03-01), Myers
patent: 4024932 (1977-05-01), Fay
patent: 4024936 (1977-05-01), Crabb
patent: 4078637 (1978-03-01), Hanks
patent: 4128145 (1978-12-01), Euler
patent: 4184573 (1980-01-01), Bricker et al.
patent: 4245724 (1981-01-01), Beck
patent: 4263991 (1981-04-01), Morgan et al.
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patent: 4615418 (1986-10-01), Atwell
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patent: 4645039 (1987-02-01), Lewis et al.
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patent: 5050710 (1991-09-01), Bargfrede
patent: 5052532 (1991-10-01), Plate
patent: 5469950 (1995-11-01), Lundstrom
patent: 5495927 (1996-03-01), Samie et al.
patent: 5921356 (1999-07-01), Stringer, III et al.
patent: 6073731 (2000-06-01), Ieda
patent: 6145635 (2000-11-01), White
patent: 6170616 (2001-01-01), White
“AUSCO®—A Complete Guide to Selecting Failsafe Brakes” (Catalog F31145),Auto Specialties Manufacturing Co., 48 pgs. (May 1987).
“Modular Multiple Disc Brake (Pressure Override—SAE B Size) Service Instructions”,MICO, Incorporated, 4 pgs., (Jan. 1998).
Drawings of prior art brake shown at Figs. 1 and 2 of this application.
Dickson Paul N.
Mico Incorporated
Pezzlo Benjamin A
LandOfFree
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