Brakes – Wheel – Transversely movable
Reexamination Certificate
2000-09-11
2001-07-17
Oberleitner, Robert J. (Department: 3613)
Brakes
Wheel
Transversely movable
C188S259000
Reexamination Certificate
active
06260671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a brake band apparatus for use in the automatic transmission of a vehicle, a construction machine, an agricultural machine or the like.
2. Related Background Art
A one-wrap brake band has heretofore been used in a brake band apparatus for fastening with a self-engaging force exerted on the rotation of a drum (inner ring) in both directions.
FIG. 8
of the accompanying drawings is a side view showing a brake band apparatus
51
according to the prior art.
The brake band apparatus
51
is comprised of a rotatable drum
52
, a substantially C-shaped brake band
61
disposed on the outer periphery of the drum
52
, and two actuators
71
and
81
for giving a load to the brake band
61
.
The brake band
61
is comprised of a band
62
, a frictional material
63
secured to the inner peripheral surface of the band
62
, and brackets
66
and
67
fixed to the opposite end portions of the band
62
which are free ends.
The two actuators
71
and
81
are identical and therefore, only the construction of one actuator
71
will be described. The actuator
71
is comprised of a substantially cylindrical case
75
, an oil chamber
73
provided in the case
75
, an oil supply hole
77
leading to the oil chamber
73
, a hole
78
for letting pneumatic pressure created in a void
72
escape outwardly, a piston
74
sliding on the inner wall of the case
75
, and a rod
79
provided integrally with the piston
74
. Further, in the void
72
, a return spring
80
is mounted around the rod
79
.
The operation of this brake band apparatus is such that oil pressure is supplied to the oil chamber
73
through the oil supply hole
77
to thereby create a load to the brake band
61
, and fasten the drum
52
. On the other hand, to liberate the fastening state of the brake band
61
, the oil pressure in the oil chamber
73
is drawn, and the piston
74
and the rod
79
are retracted by the biasing force of the return spring
80
, and the band
62
is restored.
The operating state of the apparatus at this time is shown in
FIG. 9
of the accompanying drawings. In
FIG. 9
, the rotational direction of the drum
52
is a counter-clockwise direction (indicated by arrow in drawings) and therefore, oil pressure is supplied to the oil chamber
73
of the actuator
71
, the piston
74
is moved rightwardly as viewed in
FIG. 9
, and the rod
79
mounted on the piston
74
biases the bracket. The bracket
67
provided on the other end of the band
61
cannot be moved because a rod
89
abuts against it in a fixed state. By this construction, the brake band
61
fastens the drum
52
.
The rod
89
supporting the bracket
67
may be completely fixed, but it has also been practised to support the bracket so that the rod
89
may deviate somewhat rightwardly as viewed in the figure so as to alleviate the shock to the band
62
during fastening in conformity with the coefficient of friction of the frictional material
63
which is fluctuated by the environment such as the temperature of lubricating oil.
On the other hand, when the rotational direction of the drum
52
is clockwise, the operations of the actuators
71
and
81
become opposite to what has been described above, as shown in FIG.
10
. Also, the function of alleviating the above-mentioned shock occurring during fastening is likewise performed by the operation of the other actuator
71
when the rotation of the drum
52
is opposite in direction (the direction of arrow).
The direction of the above-described load to the brake band
61
is the direction in which the drum
52
is rotated (hereinafter referred to as the rotational direction side), and by the direction being made identical, the self-engaging force of the brake band
62
works and the drum
52
is fastened. The torque capacity of the brake band by this self-engaging force is represented by the following expression:
T=F·R
·(
e
&mgr;B
−1)
where T: torque, F: load (apply), R: the outer diameter of the drum, e: natural logarithm, &mgr;: coefficient of friction, &bgr;: angle of contact.
However, the above-described brake band apparatus according to the prior art is complicated in mechanism and control because two actuators need be provided. Also, the frictional material secured to the inner peripheral surface of the brake band must receive rotations in two directions and is high in frequency of use, and this has led to the problem that the life thereof becomes short.
SUMMARY OF THE INVENTION
So, the present invention has as its task to provide a brake band apparatus which is simple in mechanism and improved in the life of a frictional material.
In order to solve the above task, a first aspect of the invention is a double-wrap brake band apparatus provided with outer bands having a frictional material secured to the inner peripheral surfaces thereof, an intermediate band interposed between the outer band and having a frictional material secured to the inner peripheral surface thereof, a coupling portion for coupling one end portion of each of the outer bands and one end portion of the intermediate band in the circumferential direction thereof, an apply bracket provided integrally with or discretely from the coupling portion, a first anchor bracket provided on the free ends of the outer bands in the circumferential direction thereof, a second anchor bracket provided on the free end of the intermediate band in the circumferential direction thereof, and an actuator for giving a load in two directions to the apply bracket.
A second aspect of the invention is a double-wrap brake band apparatus according to the first aspect of the invention, wherein the direction of the load is the rotational direction side of the drum.
A third aspect of the invention is a double-wrap brake band apparatus according to the first aspect of the invention, wherein the actuator is single.
A fourth aspect of the invention is a double-wrap brake band apparatus wherein the actuator is provided with a connecting portion for a rod mounted integrally on a piston operated in response to fluid pressure and the apply bracket, and the portion of contact between the connecting portion and the apply bracket is arcuate.
A fifth aspect of the invention is a double-wrap brake band apparatus wherein the characteristics of the frictional material secured to the intermediate band and the frictional material secured to the outer bands differ from each other.
The anchor bracket refers to a receiving member used to fix, and the apply bracket refers to a receiving member for receiving the load.
REFERENCES:
patent: 4602706 (1986-07-01), Blinks et al.
patent: 4757880 (1988-07-01), Grzesiak
patent: 5012905 (1991-05-01), Tanaka
patent: 5083642 (1992-01-01), Stefanutti et al.
patent: 5588928 (1996-12-01), Koivunen
Miles & Stockbridge P.C.
NSK-Warner K.K.
Oberleitner Robert J.
Torres Melanie
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