Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to truck-mounted
brakes for a railroad vehicle and more particularly to
an improved single actuator for truck mounted brakes.
The accepted truck mounted brakes throughout the
railroad industry approved by AAR is a double actuator
system known as NYCOPAC* sold by New York Air Brake
Corporation and its equivalent WABCOPAC* sold by
Westinghouse Air Brake Corporation. Two actuators are
used, one connected to each brake beam on opposite
sides of the center axis: An example of the structure
is illustrated in U.S. Patent 3,499,507. The next
generation of truck mounted brake includes a single
actuator, truck mounted brake assembly known as
NYCOPAC II* and WABCOPAC II*. This structure includes
a single actuator with a pair of force transmitting
arms and a lever connected to the opposite brake beam.
A typical example of this structure is illustrated in
U.S. Patent 4,793,446.
As illustrated in U.S. Patent 3,499,507, the
slack adjuster is provided on the opposite end of the
force transmitting device from the actuator and in the
opposing brake beam. The NYCOPAC and WABCOPAC have no
slack adjuster. In the single actuator system
illustrated in U.S. Patent 4,793,446 the slack
adjuster is on the return force transmitting device:
It is important that the force transmitting elements
and the slack adjuster do not intersect the openings
in the bolster for the various angular positions of
the force transmitting elements.
The single actuator, truck mounted brake provides
a force generated by the brake cylinder multiplied by
a factor of four. This system is very effective as a
force generated by the brake cylinder is transferred
to the center of the arc of each of the shoes equally.
The center of the force in the middle of each of the
* Trade-mark
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shoes eliminates wasted torsional components that
exist in other systems.
The NYCOPAC II including a double acting slack
adjuster brake cylinder having air on one side of the
piston to apply the brakes and a spring return. The
hand brake is connected to the piston directly by a
series of cables, rods and chains. Since the hand
brake worked directly on the piston, the slack
adjuster operated the same when actuated by air as
well as the hand operated brakes. In a single
actuator system illustrated in U.S. patent 4,793,446,
wherein the slack adjuster is in the return force
transmitting element or device, the hand brake has
been applied at the output of the actuator prior to
the slack adjuster. This structure, as illustrated in
U.S. Patents 4,771,686 and 5,069,312, applies a single
force in a common direction to the slack adjuster and
thus is similar to operation to the NYCOPAC II without
the use of cables or connection to the piston itself,
internal the brake cylinder.
When one attempts to incorporate a hand brake
connected to the output of the actuator where the
actuator includes the slack adjuster thereby
eliminating the cables from the NYCOPAC II, dangerous
situations may be produced. The pulling forces
produced by the hand brake are substantially larger
than the pushing force produced by the pneumatic
actuated piston. This could detrimentally affect and
possibly destroy the slack adjuster. Also, if the
actuator is not operated by air after replacement of
brakes, the elements within the slack adjustor are not
in their appropriate position and an application of
the hand brake would not produce a slack adjusting
operation. Thus, either the hand brake will not apply
the brakes in one situation or the hand brake will
produce a force which could destroy or severely damage
the slack adjuster in the other extreme.
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Thus, it is an object of the present disclosurzto
provide an improved single actuator and slack adjuster
for use with hand brakes.
Another object is to
provide a single actuator and slack adjustor for truck
mounted brake systems which will operate the same for
pneumatic as well as hand brake actuation.
These and other objects are attained by a slack
adjuster for use in combination with a pneumatic brake
actuator cylinder wherein the slack adjuster includes
a friction clutch which prevents rotation of the screw
for a first relative position of the screw and piston,
while allowing rotation of the screw for excess force
on the ram pulling the screw to relative position
beyond the first relative position. A second clutch,
which is a standard toothed clutch, prevents rotation
of the screw for second relative position of the
piston and screw when pressure is applied. The screw
rotates when clutches are disengaged. A spring biases
the piston in opposition to the fluid pressure which
actuates the cylinder. In response to fluid
actuation, the piston and screw are in the first
relative position with the friction clutch engaged at
the beginning of the extension of the ram and in
second relative position, with the toothed clutch
engaged, at the end of the ram extension. In response
to the pulling force on the ram, the piston and screw
are in the first relative position with the friction
clutch engaged at the beginning and the end of the
extension of the ram with correct cylinder slack.. The
hand brake is connected to the ram extending from the
combined actuator slack adjuster. The hand brake may
operate on the ram directly or through the brake
beams.
In accordance with a first aspect of the
invention there is provided, a brake actuator for a.
brake of a rail vehicle comprising:
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a piston in a housing responsive to fluid
pressure for actuating a brake;
a ram extending from said housing for connecting
said actuator to said brake; and
a slack adjuster for adjustably interconnecting
said piston and said ram as a function of the length
of travel of the ram between ,a brake released and a
brake applied position for said ram;
said slack adjuster including
a screw threadably connected to and
rotatable with respect to said ram,
a first clutch for preventing rotation of
said screw for a first relative position of said
piston to said screw, a second clutch for preventing
rotation of said screw for a second relative position
of said piston to said screw, and said screw being
rotatable for relative positions of said piston to
said screw between said first and second relative
positions,
said f first clutch being a friction clutch to
allow rotation of said screw for excess force on said
ram pulling said screw toward a relative position with
respect to said piston beyond said first relative
position and out of relative positions between said
first and second relative positions and
wherein said second clutch is a toothed
clutch.
In accordance with a second aspect of the invention
there is provided, a brake system for a railway vehicle
comprising:
first and second brake beams;
a transfer lever pivotally connected at a point
intermediate the ends thereof to said second brake
beam;
first and second force transmitting means each
having a second end connected to opposite arms of said
transfer lever and a force transmitting axis, and a
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first end of said second force transmitting means
being connected to said first brake beam;
actuator means mounted to said first beam and
connected to a first end of said first force
transmitting means for controlling the position of
said force transmitting means along a force
application axis in response to fluid pressure;
first and second hand brake levers pivotally
connected at a point intermediate the ends thereof to
said first and second brake beam, respectively;
a first end of said first hand brake lever being
connected to a hand brake actuator and a first end of
said second hand brake lever being connected to the
vehicle;
third force transmitting means interconnecting
second ends of said hand brake levers;
said actuator means including a piston responsive
to said fluid pressure, a ram connected to said first
force transmitting means and a slack adjuster. for
adjustably interconnecting said piston and said ram as
a function of the length of travel of the. ram between
a brake released and a brake applied position for said
ram;
said slack adjuster including
a screw threadably connected to and
rotatable with respect to said ram,
a first clutch for preventing rotation of
said screw for a first relative position of said
piston to said screw, a second clutch for preventing
rotation of said screw for a second relative position
of said piston to said screw, and said screw being
rotatable for relative positions of said piston to
said screw between said first and second relative
positions,
said first clutch being a friction clutch to
allow rotation of said screw for excess pulling force
on said ram produced by said hand brake and wherein
said second clutch is a toothed clutch.
~
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Embodiments of the invention will now be
described with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a plan view of a brake system
embodying the present invention.
Figure 2 is a cross sectional view of the
mounting of the actuator to the brake beam taken along
lines II-II of Figure 1.
Figure 3 is a cross sectional view of the
actuator with slack adjuster taken along lines III-III
of Figure 1.
Figure 4 is a partial. perspective view of a hand
brake linkage embodying the present invention.
1ESCRIPTION OF THE PREFERRED~EMBODIMENTS
A brake system for a railroad vehicle is
illustrated in Figure 1. Although the description of
the system will be provided with respect to conversion
of existing dual actuator, truck mounted brake
systems, the present mounting structure of the single
actuator is also applicable to any other truck mounted
brake system or any other brake system. The existing ___-
structure of the dual actuator, brake mounted system -
will be described first and will be followed by the
specific elements of the present system which is -
mounted thereto. Two pairs of wheels 10/12 and 14/16
are secured to opposites ends of a respective axle,
not shown for sake of clarity, of a two-axle, four
wheel railroad car truck. A pair of brake beams 18
and 20 extend crosswise of the car truck and parallel
to each other and to a truck bolster 22. Brake shoes
24 are mounted to the brake head 26 at each end of the
brake beams 18 and 20. The brake beams 18 and 20 have
a generally U-shaped cross section. Beams have casted
passage holes 30, 34 and mounting surfaces with holes
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32. A pair of opposed mounting holes 36 on the top
and bottom portion of the beams are used to mount the
push rod 90 or the rod 106. The bolster 22 has a pair
of channels 38 on each side of the center axis.
Double acting brake cylinder is mounted on one of
the beams with a force transmitting element or push
rod 90 extending through channels 38 in the bolster 22
and connected to opposed beam through transfer lever
94. The present brake system includes a brake
actuator or cylinder 40 mounted to the brake beam 18
by a bracket 42 and an intermediate gimbal or cage 50.
Bolts 44 extend through the elongated openings 43
(Figure 2) in the bracket 42 and the mounting holes 32
in the brake beam 18 and is secured thereto by nuts
46. The cylinder 40 has double acting internal slack
adjuster 48 increasing or decreasing cylinder length
automatically. The slack adjuster will be discussed
in detail with respect to Figure 3.
The gimbal 50 mounts the actuator brake cylinder
40 to the brake beam 18 through bracket 42 so that it
freely rotates horizontally and vertically which
results in high and consistent efficiency. As
illustrated in -Figure 2, the gimbal 50 is mounted to
the bracket 42 by fasteners 52 which are threadably
received in aperture 41 of the bracket 42 and extend
into a sleeve bearing 54 in the gimbal 50. A non-
pressurized cylinder portion 58 is mounted to the
gimbal 50 by a fastener 55 threadably received in a
bore 56 of the gimbal 50 and having an end extending
into bearing sleeve 57 in the cylinder portion 58.
As illustrated in Figure 3, the brake cylinder
actuator 40 includes a body 60 and non-pressure head
to form a housing. Piston 62 divides the interior of
body 60 into a pressurized and unpressurized volumes.
A port 64 admits the fluid pressure into the volume
between the body 60 and the piston 62 to move the
piston 62 to the left in brake applied position.
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Spring return 66 resting at one of its ends on the
cylinder portion 58 and biases the piston 62 to the
right.
The cylinder slack adjuster portion 48 includes
a back female clutch face 70 and a front female clutch
face 72 both mounted to the piston 62 cooperating with
a corresponding back head clutch face 71 and front
head clutch face 73 both part of the compensator screw
78. To address the problem of pulling force applied
to the output of the slack adjuster by a hand brake
application, as will be explained below, the front
clutch faces 72,73 form a friction clutch while the
back clutch faces 70,71 form a toothed clutch.
A bearing 74 rotationally mounts the screw 78 to
a bearing cup 76. A cup spring 80 rests between the
piston 62 and the bearing cup 76 and biases the front
clutch faces 72,73 into engagement to prevent rotation
of the screw 78. A spring 82 rest between the
actuator internal housing portion 58 and a ring 61
slidable on sleeve 59 mounted to the housing portion
58 and retaining ring 63 on sleeve 59. The spring 82
is stronger than cup spring 80 so as to cause bearing
cup 76 and the screw 78 and clutch faces 72,73 to stop
moving to the left in Figure 3 for continued leftward
movent of the piston 62. This will cause clutch faces -
72, 73 to disengage and allow rotation of the screw 78
until further travel to the left of the piston 62
relative to the cup 76 is terminated by the engagement
of back clutch faces 70, 71.
A ram 84 is guided inside of the tube (sleeve) 59
and is threadably connected to the compensation screw
78 at threads 83. A ram spring 86 extends between the
ram 84 and a flange 87 on sleeve 88 which engages the
piston by follower 89 extending through bearing cup 76
holes. Spring 86 pushes ram 84 leftward when screw 78
rotates during the excessive slack. The slack
adjuster 48 is a double acting slack adjuster integral
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with the actuator 40 or brake cylinder. The operation
of the slack adjuster and the improvement will be
described after the full description of the braking
system.
A first force transmission element or push rod 90
extends from the cylinder slack adjuster 48 at ram
portion 84 through the channel 38 in the bolster 22
and the passage hole 34 in the second brake beam 20.
The rod 90 is connected at its other end by pin 92 to
the left side of transfer levers 94. A pin 98
pivotally mounts the transfer levers 94 to a bracket
96 which is connected to the brake beam 20 by
fasteners 100 extending through the mounting holes 32
and nuts 102. The bracket 96 has the passage hole
104, not shown, which aligns with the actuator passage
30 in the beam 20. A second force transmitting
element or rod 106 has its first end connected to the
right side of the transfer levers 94 by a pin 108.
The force transmitting rod 106 extends through the
aligned passage 104 in bracket 96 and the passage 30
in brake beam 20, through channel 38 in the bolster 22
and into the passage hole 34 of the first brake beam
18. A pin 110 extends through the pre-existing
mounting hole 36 in the beam 18 to connect the other
end of rod 106 to the first brake beam 18.
The gimbal 50 and its connection to the first
brake beam 18 allows the actuator 40 to freely
maintain its axis of force application coaxial with ,
the axis of the first force transmitting element or
rod 90. This prevents twisting and bending of the ram
84 during the arc movement of levers 94 (horizontal
movement) and brake beams (18, 20) movement in the
side frame pockets up and down (vertical movement).
Although the bracket 42 has been shown to be mounted
to the preexisting mounting holes for a dual actuator
beam system, it can be mounted to any brake beam as
well as to brake beams which are not truck mounted.
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The hand brake illustrated in Figures 1 and 4
includes a fulcrum bracket 112 mounted to each of the
brake beams 18 and 20 by beam pin 114. Lever 118 and
120 are mounted to the fulcrum bracket 112 of beams
18 and 20 respectfully by fulcrum pin 116. A push rod
122 is interconnected to the lower end of the levers
118 and 120 by push rod pins 124. Cotter pin 126
retains the push rod pins 124 and the fulcrum pins 116
in place. A hand brake chain 128 through clevis 131
is connected to the upper end of lever 118 by pin 130.
A chain 132 is similarly connected to the upper end of
lever 120 by a pin 134. The other side of the chain
132 is connected to the car body 135. The pulling
force on chain 128 rotates the lever 118 transmitting
force by rod 122 to separate the brake beams 18 and
20. This force separating the brake beams 18 and 20
is transmitted back through the brake actuation system
as a pulling input through bracket 96, rod 106, levers
94 and rod 90. Although the hand brake directly
applies the brakes through the brake beams, the
pulling force on the cylinder slack adjuster
determines the ram extension 84 relative to the
actuator 40 as needed.
The slack adjuster in its release or non-brake
position is illustrated in Figure 3 with the front
clutch 72, 73 engaged and back clutch 70, 71
disengaged. When air is applied to the cylinder
through port 64, the piston 62 and the whole internal
mechanism moves to the left. The front clutch 72, 73
remains locked by the force of cup spring 80.
Movement of the screw 78 is stopped by the bearing cup
76, ring 61 and spring 82. If excess slack remains or
exists, piston 62 continues to move to the left
against spring 82, causing front clutch 72 and 73 to
disengage and allowing the screw 78 to rotate. This
allows spring 86 to move the ram 84 forward until the
brake shoes 24 contact the wheels. Piston 62
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continues moving to the left until the back clutch 70
and 71 is locked. The cylinder starts to buildup
braking force with the back clutch 70, 71 locked.
When the brakes are to be released, fluid at port
64 is evacuated and the return spring 66 moves the
piston 62 to the right with the whole internal
mechanism. The back clutch 70, 71 disengaged when
bearing cup 76 moves right and the force of the spring
80 overcomes force of the spring 82. Piston 62 still
moves to the right increasing the clearance between
the cup bearing 76 and ring 61. The force of the
spring 80 moves the screw 78 and ram 84 to the left-
locking the front frictional clutch 72, 73 and
preventing the screw 78 from rotating.
For a hand brake application, the pulling forces
are applied to the ram 84. When the slack is smaller
than the maximum piston stroke defined by the distance
between piston 62 and front of the non-pressure head
58, clutch 72, 73 remains locked and in contact. When
the slack is greater than the maximum piston stroke,
ram 84 with locked clutch 72, 73 move to the left
until cup 76 intersects the ring 61. The force of
spring 82 through ring 61 overcomes the cup spring 80'.
Ram 84 continues to move left until the hand brake
force overcomes the friction torque between the front
clutch faces 72, 73. Screw 78 then begins to rotate
and force of spring 86 moves ram 84 forward. This
increases the length of the ram 84 as needed. The
friction clutch 72, 73 guarantees the full contact
between the shoes 24 and all wheels. The friction
clutch 72, 73 guarantees the extension of the cylinder
length and takes up the slack if needed when the hand
brake forces apply to the beams. When brake shoes are
changed out, retraction of the cylinder ram 84 is
normally necessary. Thus, if the piston is not
actuated by air prior to a hand brake application, a
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substantial amount of excess slack must be taken up
during the first initial hand brake application.
During the release of the hand brake, the springs
82 and 66 return the actuator s piston to the release
position.
In review, the front clutch 72 and 73 is engaged
at the beginning of the air applied brakes and
disengages when the control distance defined between
ring 61 and cup 76 is exceeded. At this point,
clutches 72, 73 and 70, 71 are disengaged and allow
rotation of the screw 78. Once the brake shoes have
engaged the wheel, the back clutch 70 and 71 engage
for the remainder of the travel or force application
of the brakes. In a hand brake application, the front
clutch 72 and 73 are engaged at the beginning and
through a substantial portion of the travel of the
actuator and remain engaged but not locked for slack
adjusting and to the end of the travel. Any excess
force overcomes the frictional forces of the clutch to
allow relative movement even though they are not
disengaged. Back clutch 70 and 71 are always
disengaged during the hand brake application.
Although the present invention has been described
and illustrated in detail, it is to be clearly
understood that the same is by way of illustration
and example only, and is not to be taken by way of
limitation. The hand brake may be applied directly to
any of the elements or rods 90, 106 or levers 94
directly instead of just through the brake beam 18 and
20. Also, the specific adjuster and the two clutches
including faces 70, 71 and 72, 73 are by way of
example. The important element being the relation
that the front clutch 72, 73 or the clutch related to
preventing rotation of the screw during the initial
application or extension of the ram be a clutch which
is capable of being disengaged for excessive pulling
forces on the ram 84. Similarly, the present
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invention may be used with a spring applied, air
release brake cylinder. The spirit and scope of the
present invention are to be limited only by the terms
of the appended claims.
