Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
Case No. 8739-N 2~ r~
LOCK-OUT MECHANISM
FOR EMPTY/LOAD CHANGEOVER VALVE
BACKGROUND OF THE INVENTION
The present invention relates to lock-out mechanisms
for limiting the stroke of actuators or the like and
particularly to such a lock-out mechanism as may be
employed with railroad type empty/load control valves.
In the railroad industry, empty/load control valves
are typically employed on freight cars having high gross to
tare weight ratios, the purpose being to automatically
reduce the car brake pressure under "empty" car load
conditions, in order to prevent the occasion of wheel slide
due to excessive brake force, particularly under heavy
service and emergency braking.
The "empty" or "load" condition of a freight car is
typically determined by sensing the car spring deflection,
which indirectly reflects the weight of car lading, or by
sensing the pressure of lading on a slope sheet on hopper
type cars, which directly reflects the weight of the car
load. Spring deflection may be detected by means of a car-
body-mounted empty/load valve having a sensing arm adapted
to engage the car truck during a brake application.
Alternatively, the empty/load valve may be truck-mounted
with the sensing arm arranged to engage the car body.
Slope sheet pressure may be detected by a sensing rod that
contacts a deflectable membrane forming part of the slope
sheet. The sensing rod measures the deflection of the
membrane in accordance with the weight of the car lading
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and accordingly positions a spool within the empty/load
valve that is mounted on the slope sheet generally in
concentric relationship with the deflectable membrane.
Under certain conditions, it is desirable to disable
the empty/load valve in order to prevent an "empty" car
load condition from being detected, such as in carrying out
brake tests and/or when setting up a slack adjuster, the
desideratum being to achieve normal brake pressure.
Where empty/load valves are employed in a manner to
detect spring deflection indicative of the car weight, the
empty/load valve is typically disabled by strategically
locating a block of wood or the like, between the sensing
arm and car body or truck, as the case may be, so as to
cause a false reading by the sensing arm.
Where empty/load valves are utilized in slope sheet
configurations, a plug is generally removed from an access
hole in the empty/load valve to accommodate insertion of
various devices for jamming the sensing rod to thereby
lockup the valve in its "load" setting.
Such disabling methods are not only laborious and time
consuming, but there is no guarantee that the
operator/tester conducting the brake test or slack adjuster
set-up will remember to restore the disabled valve to its
operative condition. Such an oversight, of course, can
have serious consequences, since full "load" brake pressure
would then be available for braking an "empty" weight car,
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resulting in the likelihood of wheel damage due to sliding
wheels.
Summary of the Invention
It is the object of the present invention, therefore,
to provide a simple, yet reliable lock-out mechanism for
such actuators as empty/load valves or the like;
It is an extension of the foregoing objective to
provide a lock-out mechanism that can be pre-set by an
operator/tester to disable an empty/load valve or the like
upon subsequently effecting operation thereof;
It is another extension of the foregoing objective to
provide a lock-out mechanism that automatically resets, in
order to ensure restoration of the empty/load valve or the
like to a proper operating condition.
In accordance with these objectives, there is provided
a lock-out assembly for limiting axial extension of an
actuator rod from a retracted position comprising a
manually operable plunger having a reset position and a
lock-out position, a lock pin connected to the plunger with
relative axial movement therebetween, the locking pin
projecting a predetermined distance from one end of the
plunger when relative axial movement therebetween is taken
up, detent means for latching the plunger in its lock-out
position in which the distance between the periphery of the
actuator rod and the one end of the plunger is less than
the predetermined distance the lock pin projects from the
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plunger, such that the lock pin is pre-set under
compression for subsequent engagement with stop means
associated with the actuator rod when the actuator rod is
extended from its retracted position, the detent means
being automatically released in response to subsequent
movement of the actuator rod back toward its retracted
position to unlatch the plunger and effect forced return to
its reset position, whereby the locking pin through its
connection with the plunger is withdrawn from locking
engagement with the actuator rod.
Brief Description of the Drawings
These and other objects and attendant advantages of
the invention will become apparent from the following
explanation of the invention when considered in conjunction
with the accompanying drawings in which:
Fig. 1 is an assembly view partially in outline and
partially in section showing an empty/load brake control
valve, with which the lock-out assembly of the present
invention is incorporated, mounted to a slope sheet of a
railroad hopper car;
Fig. 2 is an enlarged sectional view of the lock-out
assembly of Fig. 1 shown in its normal reset position;
Fig. 3 is an enlarged sectional view of the lock-out
assembly of Fig. 1 shown in its pre-set position; and
Fig. 4 is an enlarged sectional view of the lock-out
assembly of Fig. 1 shown in its lock-out position.
Description and Operation
Referring to Fig. 1 of the drawings, a lock-out assembly 1
comprising the present invention is shown housed in the cover 3
of an empty/load type valve device 5. Such an empty/load valve
device is know from U.S. Patent Nos. 5,005,915; 5,100,207; and
5,106,168. Whereas applicants'empty/load valve device embodying
lock-out assembly 1 is arranged to sense the weight of freight
car lading by deflection of a slope sheet membrane, as will be
hereinafter explained, the aforementioned Patents employ a
sensing arm to detect car spring deflection and thus car
weight. It will be understood however, that the basic
empty/load valve device operates essentially the same in either
case, the only difference being in how the car load condition
is detected.
In sensing the load weight acting on a hopper car slope
sheet 13, empty/load valve device 5 is connected, as by bolts
(not shown) to a volume reservoir 11, which is in turn
connected to the car slope sheet 13. Reservoir 11 comprises a
cup-shaped body 15 and a base plate 17, each having a central
aperature into which is placed a sleeve member 19. Reservoir
11 is secured to slope sheet 13 by bolting the rim 21 of base
plate 17 around an opening 23 provided in the slope sheet.
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n 7
~his opening 23 is covered by an elastomeric diaphragm member
25 that is clamped between base plate 17 and slope sheet 13.
5A
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An actuator rod 27 of empty/load valve device 5 passes
through a locking chamber 29 of lock-out mechanism 5 formed
in cover 3, extends into sleeve 19, and through a guide
bushing 31 in sleeve 19, the projecting end of rod 27 being
adapted to engage a metal insert 33 that reinforces
diaphragm 25.
It will be appreciated that as the weight of the
commodity carried by the hopper car increases, so does the
degree of deflection of diaphragm member 25. This in turn
determines the maximum distance that actuator rod 27 is
capable of extending to thereby establish the load setting
that the empty/load valve device 5 assumes when activated
in response to a brake application, as will hereinafter be
explained.
A relatively light spring 35, such as a wave spring or
Belleville spring is arranged between metal insert 33 of
diaphragm member 25 and either the end of sleeve 19, as
shown, or alternatively base plate 17, the purpose being to
maintain diaphragm member 25 in engagement with the
commodity at the slope sheet opening, particularly during
cold temperatures when the diaphragm elastomer tends to
stiffen.
As shown in Figs. 2, 3 and 4, actuator rod 27 is
screw-threaded to the empty/load valve actuator piston 37,
which in turn positions a spool valve 39 through a lost-
motion connection 40 to effect either load or empty brake
control. Until the brake pressure effective in an
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actuating chamber 41 formed on the left-hand side of piston
37 develops sufficient force to overcome the force of a
spring 43 acting on the opposite side, piston 37 is
maintained in its release position, as shown in Fig. 2.
Accordingly, actuator rod 27 is maintained in its leftward-
most release position in which the end thereof is spaced-
apart from diaphragm member 25 regardless of the car load
condition. In this position, an annular recess 45 in
actuating rod 27 is located on the left-hand side of a lock
pin 47 of lock-out assembly 1 comprising the present
invention.
When actuating rod 27 is shifted rightwardly out of
release position by actuator piston 37, the end of rod 27
engages the metal insert 33 of diaphragm member 33, which
limits the axial distance actuating rod 27 is extended, in
accordance with the weight of the commodity carried by the
hopper car and acting on slope sheet 13 at opening 23
therein. Accordingly, piston 37 through its lost-motion
connection 40 engages and shifts spool valve 39 in a
rightward direction to either a load setting or an empty
setting, as determined by the extended position of
actuating rod 27. In this manner, annular recess 45 in
actuating rod 27 may be shifted axially through a range of
travel extending from its leftward-most position on the
left hand side of lock pin 47, as shown in Figs. 1 and 2,
corresponding to release position, to a position on the
right hand side of lock pin 47 corresponding to the empty
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setting of spool valve 39. The load setting of spool valve
39 corresponds to a position of actuator rod 27 in which
annular recess 45 lies between its leftward-most location
and a location on the left-hand side of lock pin 47, as
viewed in the drawings.
Lock-out assembly 1 includes, in addition to lock pin
47, a plunger 49 comprising a cylindrical sleeve 51 having
an end plug 53 that closes sleeve 51 at one end and a push
button cap 55 that encloses sleeve 51 at its opposite end
which projects from body 3. End plug 53 is provided with
a bore 57 in which lock pin 47 is reciprocably disposed.
A retaining ring 59 on lock pin 47 supports one end of a
spring 61 that is captured within sleeve 51 by engagement
with push button cap 55 at its other end. Retaining ring
59 is adapted to engage end plug 53 in a caged position of
spring 61, in which position the active end of lock pin 47
projects a predetermined distance from end plug 53 toward
abutment with actuating rod 27.
Plunger 49 is pivotally supported in a bore 63 in
empty/load valve body 3 by a guide member 65, which is
assembled on sleeve 51 and held in place against a
retaining ring 67 under the force of a reset spring 69. In
the reset position of plunger 49, as shown in Fig. 2, guide
member 65 engages a stop provided by a retaining ring 71 in
body 3 adjacent the open end of bore 63 to limit upward
movement of the plunger by spring 69. The outer periphery
73 of guide member 65 is spherical in shape such that
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engagement of the outer periphery of guide member 65 with
bore 63 accommodates the above-mentioned pivotal support of
plunger 49 for a purpose hereinafter explained.
A latching mechanism 66 is provided between plunger 49
and body 3 to provide a means of presetting the plunger in
a lock-out position. The latching mechanism 66 includes
an outturned flange 73 of end plug 53 that overlaps an
inturned lip 75 in bore 63 that projects into the path of
travel of plunger 49. The underside 77 of flange 73 is
chamfered, as is the upper surface 79 of lip 75, while the
underside of lip 75 is formed by an undercut surface 81
that lies in a plane generally normal to the axis of bore
63. This lip 75 is crescent-shaped so as to extend only
over a circumferential portion of bore 63, the maximum
dimension of crescent-shaped lip 75 being generally in line
with and on the side of bore 63 corresponding to the
direction of movement of actuator rod 27 during extension
thereof. In addition, the maximum diameter of flange 77 is
less than the minimum diameter of bore 63 at lip 75 thereof
to accommodate passage of flange 77.
When it is desired to disable empty/load valve device
5, in order to perform certain brake tests requiring
unmodulated brake pressure, for example, lock-out assembly
is activated prior to brake cylinder pressure being
supplied via empty/load valve device 5. Activating lock-
out assembly 1 is accomplished by manually depressing
plunger 49 against the force of reset spring 69
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sufficiently to engage latching mechanism 66. Engagement
of latching mechanism 66 occurs when outturned flange 73
overrides inturned lip 75 and latches with the undercut
surface 81, as shown in Fig. 3. This overriding action is
brought about by initial engagement of the chamfered
surface 79 of lip 75 with the correspondingly chamfered
surface 77 of flange 73, as plunger 49 is moved axially in
a downward direction. In that lip 75 is crescent-shaped so
as to extend circumferentially about only a portion of bore
63, plunger end plug 53 is deflected laterally out of the
axial path of travel of plunger 49 sufficient to allow
flange 73 to pass crescent-shaped lip 75. This lateral
deflection of plunger 49 at end plug 53 is provided for by
guide member 65 about which the plunger is pivotally
supported in bore 63. In that depression of plunger 49
concurrently compresses reset spring 69, it will be
appreciated that this spring exerts a centering force on
plunger 49 so that when flange 73 is depressed sufficiently
to override lip 75, axial alignment of plunger 49 is
restored so that the upper surface of flange 73 becomes
engaged with undercut surface 81 of lip 75 to latch and
maintain plunger 49 in its latching position without any
further manual effort.
In this latching position of plunger 49, lock pin 47
is retracted into end plug 53, by engagement of its
projecting end with the outer periphery of actuator rod 27,
it being understood that in the absence of brake cylinder
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pressure, empty/load valve device 5 is set in its release
position by spring 43, such that annular recess 45 of
actuator rod 27 is offset from lock pin 47. In this
manner, the locking assembly is conditioned to disable
empty/load valve device 5 when brake cylinder pressure is
subsequently supplied thereto.
With the lock-out assembly plunger pre-set as
explained, the brake test may be safely initiated, in
consequence of which compressed air is supplied to the car
brake cylinder via empty/load valve device 5. This brake
cylinder pressure is effective in actuating chamber 41 of
empty/load valve device 5, forcing actuator piston 37 and
actuator rod 27 in a right-hand direction from their normal
release position shown in Fig. 3. In response to this
rightward movement of actuator rod 27, annular recess 45 is
moved toward alignment with the locking pin 47, which is
maintained in engagement with the periphery of actuating
rod 27 by spring 61. When recess 45 is aligned with lock
pin 47, the lock pin is forced by spring 61 into locking
engagement therewith, as shown in Fig. 4. Consequently,
the actuating piston force acting on actuator rod 27 is
transferred to the body 3 of empty/load valve device 5 via
the left-hand side of recess 45, lock pin 47, end plug 53
and the periphery of flange 73, thereby preventing further
rightward movement of actuator rod 27. This position of
actuator rod 27, as determined by the axial location of
recess 45 relative to locking pin 47, occurs prior to
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actuator piston 37 pulling spool valve member 39, through
lost-motion-connection 40, a distance sufficient to effect
transition of empty/load valve device 5 from its normal
load setting to empty setting, thus preserving the
integrity of the brake cylinder pressure for test purposes,
even on a car that is in an "empty" load condition.
Following completion of the brake test, as evidenced
by release of brake cylinder pressure, compressed air
effective in actuating chamber 41 is released, allowing
spring 43 to urge actuator rod 27 and piston 37 in a left-
hand direction. In that lip 75 is crescent-shaped, so as
to extend into bore 63 around only a portion of the bore,
and the dimension of lip 75 in the axial direction of
movement of actuator rod 27 is greater than the
corresponding dimension of flange 73, leftward movement of
the actuator rod, through engagement of the right-hand side
of recess 45 with lock pin 47, shifts end plug 53
leftwardly to allow flange 73 to slide out from under lip
75. Accordingly, plunger 49 is unlatched, allowing reset
spring 69 to move plunger 49 through guide member 65 to its
upper-most reset position in which guide member 65 is
stopped against retaining ring 71. As plunger 49 moves
upwardly toward its reset position, end plug 53 picks up
lock pin 47 through engagement with retaining ring 59 to
lift the lock pin 47 out of locking engagement with recess
45 in actuator rod 27. In this manner, plunger 49 is
automatically reset from its latching position in response
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to movement of actuator rod 27 toward release position,
thereby assuring retraction of lock pin 47 from actuator
rod 27 without any initiative on the part of the
operator/tester to enable the empty/load valve device
following completion of the brake test.
While the foregoing explanation of the invention has
been given in terms of a slope sheet sensing arrangement
for achieving the appropriate setting of empty/load valve
device 5, the invention is also applicable to other sensing
arrangements, such as a sensing arm configuration for
monitoring the spring distance between a railroad car body
and truck as a means of setting an empty/load valve
according to the car load condition. Moreover, application
of the invention is not intended to be limited to
empty/load valve related operation, but may be employed
with other actuators, where it is desirable to temporarily
disable the actuator operation.
