Note: Descriptions are shown in the official language in which they were submitted.
21 70855
BRAKE DEVICE
FIELD OF THE INVENTION
The present invention relates, in general, to railway
type braking equipment and, more particularly, this invention
relates to a brake device which is mounted on a railroad car
and which produces a braking force by pressing brake shoes
against the tread surfaces of respective wheels.
BACKGROUND OF THE INVENTION
Generally, as is quite well known in the passenger
transit industry, railroad cars consist of both driven cars
and undriven trailer cars. Both types of these cars include
pairs of trucks. When traveling along a railroad track,
these trucks can be effected via the peripheral surfaces
(tread surfaces) of the wheels (4 wheels). Further, since
the wheels provided for each respective car truck are closely
installed to match the spacing between railroad tracks, there
are restrictions, particularly in driving cars, on the space
for installation of equipment that is required to be
installed around the trucks. Specifically, motors, etc.,
constituting the drive sources for driving wheels and brake
devices for braking the wheels.
Because of this, one system employed for current
railroad car brake devices is a direct-acting type system in
which, as described in the disclosure of Japanese Laid-open
Patent Application No. 59-192666 and the disclosure of
Japanese Utility Model Publication No. 4-4936, etc., the
braking force is produced by pushing a brake shoe against the
tread surface of each wheel. A brake device of this type is
one in which the output of a brake cylinder, installed in a
21708.S~
main body, is transmitted via a piston to a cylinder lever
which extends in the main body's upward and downward
direction and, with the output amplified by this cylinder
lever, a sleeve rod and a push rod are caused to move towards
a respective wheel, thereby producing a braking force by
causing a brake shoe which is mounted on the front end of the
push rod to be pressed against the wheel. An air pressure
source is used as the pressure source for actuating the brake
cylinder.
However, with a conventional air pressure type direct-
acting brake device in which a braking force for pushing a
brake shoe against the tread surface of a respective wheel is
produced by an air pressure source in this manner, there is
the problem that many items of equipment such as piping for
supplying air pressure to the brake cylinder, control valves
for operating and controlling the air pressure and a
compressor, etc., are required and the weight of the car is
increased, and for a long time there has been a demand for a
purely electrical brake device.
The brake device described in Japanese Laid-open Patent
Application No. 2-266130 has been disclosed as such a purely
electrical brake device. This brake device can be made to
correspond to the direct-acting type brake device as
described above. This purely electrical brake device is
constituted by an energy storage element (coil spring), an
energy supply unit (control motor) which supplies energy to
the energy storage unit, a force transmission unit, movement
conversion elements (spindle, ball nut) which convert rotary
movement to movement in the axial direction of the force
. , , 2l7o8.s~
transmission unit, a drive sleeve which transmits rotary
movement from the energy storage unit to the movement
conversion elements, and clutch control elements (outer
tightening spring, inner tightening spring) which are
provided between the movement conversion elements.
This brake device is one in which, as the result of
rotation of the energy supply unit, rotary movement (energy)
stored in the energy storage element is transmitted from the
drive sleeve to the movement conversion elements via the
clutch control elements, and the movement conversion elements
convert the rotary movement to axial movement, thereby
causing the force transmission unit to move in a straight
line and causing the brake to be applied.
However, when a conventional purely electrical brake
device is made to correspond to a direct-acting type brake in
a railroad car, certain problems as described hereinafter
arise.
In recent railroad cars, because of demands for
improvement in riding comfort, etc., axle support of the
wheels of trucks is provided with the interposition of a
pliant material, etc., and consequently, in a direct-acting
type brake system in which a braking force is produced by
pressing a brake shoe against the tread surface of a wheel,
when the brake shoe is pressed against the tread surface, the
pliant material, etc. is deformed by the pressing force and
the wheel moves under the force of inertia. Also, at times
of passage over joints of the railroad track, a
reaction force going from the wheel to the brake device is
produced.
` 21 70855
Normally, in a purely electrical brake device, when a
reaction force from a wheel is transmitted, since it goes via
the force transmission unit - clutch control elements - drive
sleeve, there is the problem that a locked state can be
maintained by the clutch. Consequently, when the reaction
force acts in this state, it is not possible to absorb it and
so great force or stress is imposed on the force transmission
unit and the movement conversion elements, etc., and there is
a risk of this ultimately leading to breakage and/or damage
of various parts.
The present invention has been devised in order to
resolve these problems, and provide a brake device which, by
rapidly absorbing and easing the reaction force which acts on
a brake shoe, makes it possible to prevent breakage of or
damage to various parts.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention
provides a brake device that includes an energy production
unit and a force transmission unit which receives the drive
force of the energy production unit and produces outputs by
advancing and retreating. There is a clutch unit provided
between the energy production unit and the force transmission
unit which maintains the advance and retreat positions of the
force transmission unit when outputs are produced. Such
brake device further includes a brake shoe which produces a
required braking force by being pressed against a wheel tread
surface which is mounted at the front end of the force
transmission unit. There is a guide structure provided,
which permits such brake shoe to move in each of an advance
21 708S5
and a retreat direction relative to the force transmission
unit, between the force transmission unit and the brake shoe.
This brake device further includes a buffer unit disposed in
the guide structure. Such buffer unit urges the force
transmission unit and the brake shoe in the directions of
separation and, also, permits movement of the brake shoe in a
withdrawal direction on transmission of a reaction force
exceeding the maximum output of the force transmission unit.
Additionally, according to a second aspect of the
present invention, there is provided a brake device that
includes an energy production unit, a force transmission unit
which receives the drive force of the energy production unit
and produces outputs by advancing and retreating and a clutch
unit which is disposed between the energy production unit and
the force transmission unit. Such clutch unit maintains both
the advance and retreat positions of the force transmission
unit when outputs are produced. A gap portion is provided
which permits relative advance and retreat movement of the
force transmission unit with respect to the clutch unit.
This gap portion is formed between the force transmission
unit and the clutch unit. A buffer unit is provided in the
gap portion which urges the force transmission unit towards
the relative advance position and which allows movement of
the force transmission unit to the retreat position on
imposition of a reaction force exceeding the maximum output
of the force transmission unit.
In a third aspect, the present invention provides a
brake device having an energy production unit, in which the
force transmission unit produces outputs by converting rotary
21 708~
.
movement to rectilinear movement and moving forwards and
backwards, and the clutch unit transmits the drive force of
the energy production unit in the direction of the rotary
movement of the force transmission unit. An engagement
section, which separates the clutch unit and the force
transmission unit at the force transmission unit's relative
advance position, is provided between the force transmission
unit and the clutch unit.
In a fourth and final aspect, the present invention
provides a brake device possessing an energy production unit,
a force transmission unit, which receives the drive force of
the energy production unit and produces outputs by advancing
and retreating, and a clutch unit disposed between the energy
production unit and the force transmission unit. Such clutch
unit maintains advance and retreat positions of the force
transmission unit when outputs are produced. A brake shoe is
mounted at the front end of the wheel tread surface side of
the transmission unit.
OBJECTS OF THE lNV~NlION
It is, therefore, one of the primary objects of the
present invention to provide a brake device which prevents
breakage and/or damage to parts of the braking device when a
braking force is produced by pushing a brake shoe against the
tread surface of a wheel, if the brake shoe is subjected to a
reaction force that is greater than the value of the maximum
output of a force transmission unit through the use of a
guide structure and a buffer unit installed between the brake
shoe and the force transmission unit.
- 21 70~S~
Another object of the present invention is to provide a
brake device which will absorb a reaction force that is
greater than the maximum output of the force transmission
unit by moving the force transmission unit in a withdrawal
direction in a gap portion by an amount corresponding to the
reaction force to which it had been subjected.
Still another object of the present invention is to
provide a brake device such that if a reaction force greater
than the maximum output of the force transmission unit is
encountered it can be absorbed by a buffer unit as the force
transmission unit is moved in the withdrawal direction in the
gap portion and, after that, since the force transmission
unit can be restored to the maximum output state by the
buffer unit the brake shoe's functions are not adversely
effected and breakage of and/or damage to various parts of
the brake device is prevented, and in case of a reaction
force less than the maximum output value, the reaction force
is not absorbed by the gap portion and buffer unit and thus
an increase in the requisite gap for the brake shoe is
prevented.
In addition to the objects and advantages of the present
invention which have been described above, various other
objects and advantages of the brake device will become more
readily apparent to those persons who are skilled in the
relevant railway braking art from the following more detailed
description of the invention, particularly, when such
description is taken in conjunction with the attached drawing
figures and with the appended claims.
2170855
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side view for the purpose of describing
the dispositional relations of a car and brake devices in
accordance with a presently preferred embodiment of the
invention;
Figure 2 is a side view, partially in section, for the
purpose of describing the structure of the brake device in
such presently preferred embodiment of the invention;
Figure 3 is an enlarged view of principal parts which
illustrates a modification of the brake device of the
invention shown in Figures 1 and 2; and
Figure 4 are drawings for the purpose of describing the
structure of a brake device according to an alternative
embodiment of the invention, (a) is an overall side view
partially in section, and (b) is an enlarged view of the
principal parts.
DETAILED DESCRIPTION OF THE INVENTION
Prior to proceeding with the more detailed description
of the present invention it should be noted that, for the
sake of clarity, identical components which have identical
functions have been designated by identical reference
numerals throughout the several views illustrated in the
drawings.
A brake device, generally designated 10, which
constitutes one presently preferred embodiment of the
invention will now be described with reference to the
drawings. Figure 1 is a side view for the purpose of
describing the dispositional relations of a car 1 and brake
devices 10 and Figure 2 is a side view, partially in section,
21 7~8~S
for the purpose of describing the structure of the brake
device 10.
In Figure 1, there is illustrated a driving car or a
trailer car 1, which includes trucks 3 that travel along the
tracks 2. Wheels 4 (although not shown, 4 wheels) are
axially supported by a truck 3 in a manner permitting
rotation. The peripheral surfaces (referred to below as the
tread surfaces 4a) of these wheels 4 roll while in contact
with the tracks 2. There are axle springs 5 which extend
between a truck 3 and a wheel 4. A brake device 10, in this
embodiment of the invention, produces a requisite braking
force for stopping rotation of the wheel 4. Such braking
device 10 is fixed to and supported by the wheel 4 via a
support bracket 6.
Reference is now made more particularly to Figure 2.
Illustrated therein are the details of the structure of the
brake device 10. Such brake device 10 includes, as the
principal components, a drive motor 11 constituting an energy
production unit, a force transmission unit 12 that receives
the drive force of the drive motor 11 and produces an output,
a clutch unit 13 which, at times when the force transmission
unit 12 produces an output, maintains an advance or retreat
position of the force transmission unit 12, and a brake shoe
14 which is pressed against the tread surface 4a of the wheel
4 and produces a braking force.
The brake unit 10 includes a brake housing 15. Inside
such brake housing 15 there is formed an accommodation space
A and a stepped hole in which a clutch hole B and a motor
hole C are disposed in successive continuation. A strong
, 2170855
coil spring 16 is accommodated and installed in the
accommodation space A of the brake housing 15. The outer
peripheral surface of such coil spring 16 is engaged by a
sleeve 17 which is provided between it and the brake housing
15, while its inner peripheral surface encloses the
accommodation space A and is engaged by a drive sleeve 18
which is held by the main body of the brake device 10. The
sleeve 17 is engaged by a motor 19 attached to the brake
housing 15 and it is allowed to rotate in only one direction
by a tightening spring 20, which is provided between it and
the brake housing 15, and it can tighten the coil spring 16.
A cylindrical shaft portion 18A which extends along the
accommodation hole A and the clutch hole B and a large
diameter portion 18B which extends with its diameter
increased at the motor hole C end are integrally formed in
the drive sleeve 18.
The drive motor 11 is mounted via a structural lid 25 to
the brake housing 15 into which the motor hole C opens. A
gear 26 which is mounted on the front end of its drive shaft
lla engages gear ring 28 that is formed on the outer
peripheral surface of a control sleeve 27 installed inside
the clutch hole B.
There is a clutch unit 13 provided which extends over
the inner surface and outer surface of this control sleeve
27. This clutch unit 13 includes, as principal components
thereof, an outer tightening spring 30 (coil spring) which is
disposed between the large diameter portion 18B of the drive
sleeve 18 and the outer peripheral surface of the control
sleeve 27 and an inner tightening spring 31 (coil spring)
217085~
which is disposed between the cylindrical shaft portion 18A
of the drive sleeve 18 and the inner peripheral surface of
the control sleeve 27. One end of the outer tightening
spring 30 is fixed to the control sleeve 27, and the outer
peripheral surface of its other end portion is disposed such
that it contacts the drive sleeve 18 and the inner peripheral
surface of such brake housing 15 on the same axis. The inner
peripheral surface of the inner tightening spring 31 is
engaged by the outer peripheral surfaces of the cylindrical
shaft portion 18A of the drive sleeve 18 and a drive ring 32
which is disposed on the same axis, and one end of this inner
tightening spring 31 is fixed to the drive ring 32. A
projecting end portion 3lA which extends radially outward is
formed at the other end of the inner tightening spring 31.
This projecting end portion 31A is provided such that it acts
cooperatively with a projection portion 27A formed at the
accommodation space A end of the control sleeve 27. As a
result, the clutch unit 13 possesses clutch functions with
which rotation of the drive sleeve 18 in one certain
direction is prevented by the outer tightening spring 30, and
rotary movement in one direction is transmitted between the
drive sleeve 18 and the drive ring 32 by the inner tightening
spring 31.
In this embodiment of the invention, the force
transmission unit 12 is disposed in a manner such that it
will project from the accommodation space A side of such
brake housing 15, and it is connected to a force transmission
sleeve 35 which slidably penetrates the interior of the drive
sleeve 18. The force transmission sleeve 35 is fixed to a
21 708.~
ball nut 36, provided inside it, and is supported by a ball
bearing 37. A spindle 38 is disposed inside the force
transmission sleeve 35. The spindle 38 extends from the end
of the force transmission unit 12 to a point below the drive
ring 32 and is rotatably supported by the ball bearing 37 and
by a ball bearing 39 provided inside the clutch hole ~. A
screw shaft portion 38A of such spindle 38 penetrates the
ball nut 36 and is engaged with it by the interposition of
plural balls (not shown). Further, the spindle 38 and the
drive ring 32 are in a state of connection through a spline
engagement of the drive ring 32 by a spindle ring 40 provided
on the end of the spindle 38.
A cup element 41 fixedly supports the ball bearings 39,
42. There is a resilient disk 42 disposed between the cup
element 41 and the brake housing 15. There is a pressure
converter 43 provided inside the brake housing 15 that is in
contact with the resilient disk 42. Additionally, a fixed
yoke 44 is fixed to the drive motor 11. A disk 45, which
functions cooperatively with the fixed yoke 44, is provided
on the drive shaft lla of the drive motor 11, and it has
plural holes formed therein. Such disk 45 constitutes an
encoder which controls rotation of the drive motor 11 as the
result of these holes being counted by the fixed yoke 44.
The brake shoe 14 is mounted on such force transmission
unit 12 via a guide structure, generally designated 50, and a
buffer unit, generally designated 60, and is positioned at a
set interval from the wheel 4. The guide structure 50 has as
its main components a bearing block 51 which is fixed to the
force transmission unit 12, a bearing block 52 which is fixed
12
21 708S~
to the shoe head 14A of the brake shoe 14, and a guide plate
section 53. Connection shafts 54 and 55, which project
radially outward, are respectively provided on the bearing
block 51 and the bearing block 52. The guide plate section
53 is suspended between these two connection shafts 54 and
55. One end of the guide plate section 53 is fixed to the
connection shaft 55, a long hole 53A formed at its other end
fits in a manner permitting play on the connection shaft 54,
and the guide plate section 53 is installed with a set gap D
which is formed between it and the connection shaft 54 and
which permits movement of such brake shoe 14 in the direction
of an advance and a retreat of the force transmission unit
12.
The buffer unit 60, of the present invention, is
constituted by stacking plural dish springs 61 having a
generally V-shaped cross-section. Further, the buffer unit
60 is externally fitted via a washer 62 on a support shaft
51A which is provided on the bearing block 51 and projects
towards the bearing block 52. Such buffer unit 60 is
positioned such that it will extend between the bearing block
51 and the bearing block 52 and it imposes a spring force
which acts in the directions of mutual separation of the
brake shoe 14 and the force transmission unit 12 and which,
when the brake shoe 14 is subjected to a reaction force
exceeding the maximum output of the force transmission unit
12, allows the brake shoe 14 to move in a withdrawal
direction. There is a guide link section 65 which consists
of a pair of links 66 and 67. The link 66 is rotatably
21708.~
mounted on such connection shaft 55 of the bearing block 52
and the link 67 is fixed to the brake housing 15.
With respect to the brake device 10, of this embodiment
the invention as described above, the action of easing of a
reaction force from the wheel 4 in control and operation of
the brake device 10 will now be described. For the
convenience of such description, it is assumed that when the
coil spring 16 is in a state in which it is pulled by the
action of the motor 19 the motor 19 is prevented from turning
in reverse by the tightening spring 20 and the drive sleeve
18 is subjected to a relatively large torque in one
direction. It is also assumed that at normal times the drive
sleeve 18 is fixed by such outer tightening spring 30 in a
manner such that it cannot turn in one direction.
At the time the drive motor 11 is actuated and the
control sleeve 27 is rotated, in order to apply the brake
shoe 14 to the surface 4a on the wheel 4, the outer
tightening spring 30 becomes tightened on the control sleeve
27, so that the inner diameter of such outer tightening
spring 30 becomes smaller and it becomes possible to release
the engagement of such outer tightening spring 30 and the
drive sleeve 18, i.e., it becomes possible to rotate the
outer tightening spring 30 in the direction opposite to the
fixing direction. As a result, up until the time when the
drive sleeve 18 is fixed to the brake housing 15 again by the
outer tightening spring 30, the drive sleeve 18 can be freely
rotated by the action of such coil spring 16.
Thus, the rotary movement of the drive sleeve 18
corresponds to the rotary movement of the control sleeve 27.
14
21 7085~
Also, during this rotary movement, the projection portion 27A
of the control sleeve 27 engages the projecting end portion
3lA of the inner tightening spring 31, and the inner
tightening spring 31 is turned in the direction in which its
inner diameter is made smaller. Since, as a result, the
inner tightening spring 31 is fixed and clamps the drive
sleeve 18 and the drive ring 32, rotary movement, or torque,
is transmitted to the drive ring 32 via the inner tightening
spring 31.
The turning force being transmitted to the drive ring 32
is transmitted to the spindle 38 via the spindle ring 40 in
spline engagement with the drive ring 32 as the spindle 38
rotates and since this turning force is converted to
rectilinear force, because of the relationship between the
spindle 38 and the ball nut 36 with which it is in screw
engagement via plural balls, the ball nut 36, while guided by
the spindle 38, is moved together with the force transmission
sleeve 35 towards the wheel 4.
As a result, the brake shoe 14 mounted on the force
transmission unit 12 via the guide structure 50 is moved and
the gap located between it and the wheel 4 is gradually
narrowed and, eventually, the brake shoe 14 is pressed
against the tread surface 4a of the wheel 4, so as to produce
a braking force and apply a brake onto such wheel 4. Then,
when the pressure converter 43 detects that a set braking
force has been reached, i.e., when it is detected that the
resistance force in the spindle 38 which is transmitted to
the pressure converter 43 via the cup element 41, the
resilient disk 42, ball bearing 39, and spindle ring 40 has
21 708~5~
reached a set value, the drive motor 11 is stopped, and the
braking force of the brake shoe 14 is held at a set value.
If, at this time, a reaction force resulting from the
brake shoe 14 being pushed against the tread surface 4a of
the wheel 4, particularly an impulsive reaction force which
is greater than the maximum output of the force transmission
unit 12 acts on the brake shoe 14, the brake shoe 14 is moved
towards the brake housing 15, or, more specifically, towards
the brake housing 15 in the direction of such brake shoe 14
advance and retreat. Such movement is by an amount which
corresponds to the gap D located between the connection shaft
54 of the bearing block 51 of the guide structure 50 and the
long hole 53A of the guide plate section 53 and since, during
this movement, the buffer unit 60 (plural dish springs 61),
which is installed so as to extend between the bearing block
51 and the bearing block 52 of the guide structure 50, is
elastically deformed to a state in which it is compressed.
In this manner, the impulsive reaction force is absorbed by
this elastic deformation and the reaction force that is
transmitted directly to the brake device 10 is eased.
Then, since this elastic deformation of the buffer unit
60 is terminated after easing of the reaction force by the
buffer unit 60, the brake shoe 14 will be pressed against the
tread surface 4a of the wheel 4 in a manner such that it has
a set braking force. If the brake shoe 14 is subjected to a
reaction force that is less than the maximum output of the
force transmission unit 12, then, as described in connection
with the prior art, the force goes via the force transmission
12 - clutch unit 13 - drive sleeve 18, etc., and finally is
16
21 70~55
absorbed through wind-up counter to the turning force of the
coil spring 16.
To release the brake shoe 14 from the wheel 4, the drive
motor 11 is rotated in the direction opposite to that
described above, and as a result of the spindle 38 being
rotated in reverse, via the control sleeve 27, inner
tightening spring 31 and drive ring 32, the ball nut 36 is
moved in a straight line towards the cup element 41, and the
brake shoe 14 is withdrawn until it is at a set interval from
the tread surface 4a of the wheel 4.
Although a unit constituted by plural dish springs 61
was described as the buffer unit 60 in the brake device 10 in
this embodiment of the invention, it is not to be limited
thereto or thereby. For example, this buffer unit 60 may
also be a unit in which, as shown in Fig. 3, a cylindrical
body produced from hard urethane rubber is interposed between
the bearing block 51 and the bearing block 52, or it could be
a unit which makes use of a normally employed hydraulic
damper.
Thus, with the brake device 10 of embodiment, if, when a
braking force is produced by pressing the brake shoe 14
against the tread surface 4a of the wheel 4, the brake shoe
14 is subjected to a reaction force that exceeds the value of
the maximum output of the force transmission unit 12, then,
due to the provision of the guide structure 50 and the buffer
unit 60, which are easily installed between the brake shoe 14
and the force transmission unit 12, the brake shoe 14 is
moved by the guide structure 50 so that it is withdrawn in
- 21 708~iS
the advance and retreat direction and the reaction force is
absorbed by elastic deformation of the buffer unit 60.
Consequently, since direct transmission of the reaction
force to the brake device 10 is eased, damage to and/or
breakage of the various parts of the brake device 10 are
prevented. While in the case of a reaction force which is
less than the maximum output value, since there is no
absorption by such guide structure 50 and the buffer unit 60,
but absorption is effected by the coil spring 16, it is
possible to prevent an increase of the requisite brake shoe
14 gap.
A brake device 100, which constitutes an alternative
embodiment of the invention, will now be described with
reference to the drawings. Fig. 4(a) is an overall side
view, partially in section, for the purpose of describing the
structure of the brake device 100 in this embodiment and Fig.
4(b) is an enlarged view of principal components of the brake
device 100 in this embodiment. Components in Fig. 4 which
are the same as corresponding components illustrated in Figs.
1 and 2, as mentioned above, are given the same reference
symbols, and a detailed description thereof has been omitted
for the sake of brevity.
The brake device 100, in this embodiment of the
invention, includes a function by which the wheel 4 reaction
force is eased inside the brake housing 15 and it represents
a modification of the above described embodiment.
In Fig. 4(a) and Fig. 4(b), a preset gap E is formed
between the spindle ring 40 and the ball bearing 39. There
is a buffer unit 160 provided in this gap E. This buffer
18
21 708S~
unit 160 combines two dish springs 161 which have a V-shaped
cross-section and it is formed to a rhombus cross-section.
Each dish spring 161 is installed in the gap E in engagement
with the spindle ring 40 and with the ball bearing 39. In
this manner, this buffer unit 160 will impose on the spindle
ring 40 (spindle 38) and such ball bearing 39 a spring force
which acts in the directions of their mutual separation and
which will allow the brake shoe 14 to move in the advance and
retreat direction when it is subjected to a reaction force
exceeding the r~; rllm output of the force transmission unit
12.
The sloped surfaces 40A and 32A, constituting an
engagement section 164, are respectively formed on the
spindle ring 40 and the drive ring 32 and it is possible for
the spindle ring 40 to come into contact with the drive ring
32 from the cup element 42 side, bringing its sloped surface
40A into engagement with the sloped surface 32A of the drive
ring 32 and to move away. The brake shoe 14 is mounted
directly onto the force transmission unit 12 via a mounting
element 165.
With respect to the brake device 100, of this embodiment
of the invention as described above, the action of easing of
a reaction force from the wheel 4 in control and operation of
the brake device 100 will now be described. Since control
and operation of the brake device 100 in this embodiment are
performed by the same procedure as for the brake device 10 of
the embodiment described above, a detailed description
thereof will be omitted.
19
- 21 708~5
As a result of actuation of the drive motor 11 to apply
the brake shoe 14 onto the tread surface 4a of the wheel 4,
the control sleeve 27 is rotated and as the result of
transmission by the spring force of the buffer element 160 of
a turning force, or torque, to the spindle, via the spindle
ring 40 connected to the drive ring 32, and rotation thereof,
the ball nut 36, while guided by the spindle 38, will move
together with the force transmission sleeve 35 towards the
wheel 14. As a result, the brake shoe 14 mounted on the
force transmission unit 12 via the guide structure 50 is
moved and the gap between it and the tread surface 4a of the
wheel 4 gradually becomes narrower and, eventually, the brake
shoe 14 is pressed against the tread surface 4a of the wheel
4 so as to produce a braking force, and after the brake has
been applied on the wheel 4, the motor 11 is stopped and the
braking force of the brake shoe 14 is kept at a set value.
If, at this point in time, a reaction force resulting
from the brake shoe 14 being pushed against the tread surface
4a of the wheel 4, particularly, a reaction force which is
greater than the maximum output of such force transmission
unit 12 acts on such brake shoe 14, then, on transmission of
this reaction force to the ball nut 36 via the force
transmission unit 12 and force transmission sleeve 35, the
ball nut 36, together with the spindle 38 in screw engagement
therewith, moves very slightly in its withdrawal direction
(towards the cup element 41), counter to the spring force of
the dish springs 161 of the buffer unit 160.
As a result of this, the sloped surface 40A of the
spindle ring 40 will move away from the sloped surface 32A of
~1 7085~
the drive ring 32 and the connection between the spindle ring
40 and the drive ring 32 ends, and, after this, as the ball
nut 36, while rotating the spindle 38, moves in the
withdrawal direction in the gap portion E, and the reaction
force is absorbed by the buffer unit 160 provided in the gap
portion E, so as to ease the reaction force that is being
transmitted directly to the brake device 100. Then, after
easing of the reaction force by the buffer unit 160, since
the elastic deformation of such buffer unit 160 is ended, a
spring force resulting from ending of this deformation acts
on the spindle ring 40, and this spring force causes the
sloped surface 40A of the spindle ring 40 to come into
engagement with the sloped surface 32A of the drive ring 32,
so as to connect the spindle ring 40 to the drive ring 32.
This makes it possible to perform an output
action/output cancellation process for the brake shoe 14. If
the brake shoe 14 is subjected to a reaction force that is
less than the max;mllm output of the force transmission unit
12, as described in connection with the prior art, the force
goes via the force transmission unit 12 - clutch unit 13 -
drive sleeve 18, etc., and finally is absorbed through wind-
up counter to the turning force of the coil spring 16.
Thus, with the brake device 100 according to this
embodiment of the invention, if the brake shoe 14 is
subjected to a reaction force that is greater than the
maximum output of the force transmission unit 12 when a
braking force is produced by pushing the brake shoe 14
against the tread surface 4a of the wheel 4, damage to and/or
breakage of various components of the brake device 100 can be
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prevented. This is possible because the ball nut 36,
together with the spindle 38 in screw engagement therewith,
will move in its withdrawal direction (towards the cup
element 41), counter to the spring force of the dish springs
161 of the buffer unit 160.
Additionally, the sloped surface 40A of the spindle ring
40 moves away from the sloped surface 32A of the drive ring
32 and the connection between the spindle ring 40 and the
drive ring 32 ends and, after this, as the ball nut 36, while
rotating the spindle 38, moves in the withdrawal direction in
the gap portion E, the reaction force is absorbed by such
buffer unit 160 provided in the gap portion E, so as to ease
the reaction force that is being transmitted directly to the
brake device 100. While in the case of a reaction force
that is less than the ~x;~um output value, an increase in
the requisite gap for the brake shoe 14 can be prevented,
since there is no absorption by the gap portion E and the
buffer unit 160, but absorption is effected by the coil
spring 16.
Even though the brake device 100, in this embodiment of
the invention, is simply one in which a gap portion E is
provided between such spindle ring 40 and the ball bearing 39
and the spindle ring 40 is brought into spline engagement
with the drive ring 32, if the brake shoe 14 is subjected to
a reaction force that is greater than the maximum output of
the force transmission unit 12, this reaction force can be
easily absorbed, since the ball nut 36 and spindle 38, etc.
can move in the withdrawal direction.
21 70855
It should therefore be readily apparent that the present
invention provides a brake device which when a reaction force
greater than the max;mllr output of the force transmission
unit acts on the brake shoe which is pressed against a wheel
tread surface and produces a braking force, the brake shoe is
moved by the guide structure in the withdrawal direction and
the reaction force is absorbed by the buffer unit. In the
case of a reaction force that is less than the m~x; mllr output
value, there is no absorption by the buffer unit and an
increase in the brake shoe's requisite gap can be prevented.
Also, when a reaction force greater than the m~x;rllm
output of the force transmission unit acts, the force
transmission unit is moved in the withdrawal direction inside
the gap portion and the reaction force is absorbed by the
buffer unit and, after that, the force transmission unit can
be restored to the maximum output state by the buffer unit.
In the case of a reaction force that is less than the maximum
output value, there is no absorption by the buffer unit and
an increase in the force transmission unit's requisite gap
can be prevented.
Further, since the force transmission unit produces
outputs through conversion of rotary movement to rectilinear
movement and advance and retreat movements, the clutch unit
transmits the drive force of the energy production in the
direction of rotation of the force transmission unit and an
engagement section which separates the clutch unit and the
force transmission unit at the position of relative advance
of the force transmission unit is provided between the force
transmission unit and the clutch unit, when a reaction force
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21 70855
is imposed, the clutch unit is disengaged, and the force
transmission unit is allowed to move a necessary amount in
the withdrawal direction without being restrained by the
clutch.
Thus, according to the brake device of the invention,
when a braking force is produced by pushing a brake shoe
against the tread surface of a wheel, if the brake shoe is
subjected to a reaction force that is greater than the value
of the m~x;mllm output of a force transmission unit, the brake
shoe's functions are not harmed and breakage of and/or damage
to various parts of the brake device can be prevented due to
the provision of a guide structure and a buffer unit which
are easily installed between the brake shoe and the force
transmission unit, the brake shoe is moved away in a
withdrawal direction, the reaction force is absorbed through
elastic deformation of the buffer unit and direct
transmission of the reaction force to the cylinder device is
prevented and, after that, force resulting from ending of the
elastic deformation of the buffer unit presses the brake shoe
against the wheel's tread surface with a set braking force
and in the case of a reaction force that is less than the
maximum output value, there is no absorption by the guide
structure and buffer unit, and an increase in the requisite
gap for the brake shoe is prevented.
Also, when a reaction force greater than the maximum
output of the force transmission unit acts, breakage of
and/or damage to various parts of the brake device can be
prevented, since the reaction force can be absorbed by moving
the force transmission unit in a withdrawal direction in a
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21 708~5~
gap portion by an amount corresponding to the reaction force
to which it has been subjected.
Further, if a reaction force greater than the maximum
output of the force transmission unit acts, it can be
absorbed by a buffer unit as the force transmission unit is
moved in the withdrawal direction in the gap portion and,
after that, since the force transmission unit can be restored
to a ~-~;mllm output state by the buffer unit, the brake
shoe's functions are not harmed and breakage of and/or damage
to various parts of the brake device is prevented and in the
case of a reaction force that is less than the maximum output
value, the reaction force is not absorbed by the gap portion
and buffer unit and an increase in the requisite gap for the
brake shoe is prevented.
It will be understood that various alterations and
changes may be made by those skilled in the art without
departing from the spirit and scope of the subject invention.
Therefore, it will be appreciated that certain modifications,
ramifications, and equivalents will be readily apparent to
persons skilled in the art, and accordingly, it is understood
that the present invention should not be limited to the exact
embodiments shown and described, but should be accorded the
full scope and protection of the appended claims.
