Note: Descriptions are shown in the official language in which they were submitted.
lil~3Z95
This invention relates to the brake system of
a railroad vehicle.
The standard air brake system on a railroad car
includes a brake cylinder (or cylinders) which, when the
brake is to be applied, receives air from an auxiliary
reservoir. The air so received is released from the auxiliary
reservoir by opening a brake valve which is interposed
between the brake cylinder and auxiliary reservoir. The
brake valve is connected by a branch pipe to a brake pipe
connected to the main air reserve at the locomotive. All
this is well known.
The brake pipe is supported by the car; so are
the combined emergency and auxiliary reservoir, brake valve,
branch pipe and brake cylinders. At each end of the car
there is a hose connected to the end of a like hose on the
next car via a hose coupling.
Each hose on the car has a so-called angle cock
valve which enables the related end of the brake pipe to
be cut in (opened) or cut out (closed). The angle cock
valve is located in a hazardous position near the car couplers
and the primary object of the present invention is to reduce
the probability of injury by eliminating both angle cock
valves and incorporating their functions in a single multi-
function valve assembly so located that it can be easily
operated from either side of the car, at a location remote
from the car couplers.
The aforementioned brake valve is itself associated
with a cut-out valve to enable the brake valve be isolated
if the occasion should arise. This cut-out valve is located
__ __ _ _ _
295
in the branch pipe in a position where it is sometimes
difficult to operate the cut-out valve. Another object
of the present invention is to remove the cut-out valve
and incorporate its function in ~he same combination valve
assembly which replaces the angle cock valves. Another
object of the invention is to so construct the valve assembly
as to accommodate a dirt trap.
As can be imagined, there is a maze of equipment
slung beneath the car from one end to the other, amounting
to considerable impediment to discerning how the objects
of the present invention could be reduced to practice with-
out altering in any material way the standard system which
evolved over a long period of time.
It is therefore another object of the invention
to eliminate the three valves identified above while en-
abling their functions to be realized by a single, combined
valve assembly so located that no material alteration need
otherwise be made in the standard railroad air brake system.
This object can be accomplished by installing a valve assembly
at the "T" junction where the branch pipe meets the brake
pipe in the standard system, replacing the standard "T~
fitting with a valve housing incorporating a valve capable
of performing the functions of the combination dirt collector
and cut-off valve and the two end-of-vehicle angle cock
valves of the standard system.
3Z~5
,,,
The present invention accordingly meets the above
objects by providing a brake system for a railroad vehicle equip-
ped with a brake cylinder which receives fluid under pressure
from an auxiliary reservoir when a fluid operated brake control
valve, interposed between the cylinder and reservoir, is
~: opened by a change in fluid pressure in a brake pipe, the brake
control valve being connected to the brake pipe by a branch
pipe which intersects a sectioned portion of the brake pipe;
a valve housing having three communicating openings of which
one is assigned to the proximal end of the branch pipe and of
which the remaining two are respectively assigned to the
sectioned ends of the brake pipe; a selectively positionable
valve member inside the valve housing; the valve member being
effective in a first position to place all three openings in
communication with each other thereby to communicate the
!' .
: branch pipe with both section ends of the brake pipe in the
: first position of the valve member, the valve member being
effective in a second position to communicate the branch pipe
. opening with only a first one of the other two openings
20 thereby to communicate the branch pipe solely with only one of
the brake pipe section ends in the second position of the
valve member, the valve member being effective in a third
position to communicate the branch pipe opening with only the
second one of the other two openings thereby to communicate
the branch pipe solely with the other brake pipe section ends
in the third position of the valve member, and the valve member
in a fourth position being effective to communicate both brake
pipe openings with one another while closing the branch pipe
opening in the fourth position of the valve member; and
operating means connected to the valve member and extending
outward at the housing for turning the valve member; the
operating means being a rotary shaft extending through the
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"
alve housing and projecting from opposite sides thereof, and
~: the valve member being a plug connected to the shaft for
rotary movement therewith and capable of sealing one of the
openings in each of the second, third, and fourth positions.
Furthermore, the above objects are further met by
the present invention which may be seen as providing a brake
: system for a railroad vehicle equipped with a brake cylinder
which receives fluid under pressure from an auxiliary reservoir
when a fluid operated brake control valve, interposed between
the cylinder and reservoir, is opened by a change in fluid
pressure in a brake pipe, the brake control valve being
connected to the brake pipe by a branch pipe which intersects
a sectioned portion of the brake pipe; a valve housing having
j three communicating openings of which the first one is
; assigned to the proximal end of the branch pipe and of which
the second and third are respectively assigned to the sectioned
ends of the brake pipe; a selectively positionable seal carrier
member supporting a seal inside the valve housing; the seal
carrier member being effective in a first position to place
all three openings in communication with each other thereby to
communicate the branch pipe with both section ends of the brake
pipe in the first position of the seal carrier member, the
seal carrier member being effective in a second position to
seal only the second opening thereby to communicate the branch
- pipe solely with only one of the brake pipe section ends in
the second position of the seal carrier member, the seal
carrier member being effective in a third position to seal only
the third opening thereby to communicate the branch pipe solely
with the other one of the brake pipe section ends in the third
position of the seal carrier member and the seal carrier member
in a fourth position being effective to communicate both brake
pipe openings with one another while sealing the branch pipe
, . .
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PZ~5
. -
opening in the fourth position; an operating shaft supported
on the valve housing for both axial displacement and rotary
movement once displaced; ~he seal carrier member being con-
nected by a toggle link to the shaft so as to be displaced
radially from one of its positions upon axial displacement
; of the shaft and orbited to a new position when the shaft
: is rotated; spring means resisting axial shaft displacement;
and lock means to hold the shaft ayainst rotary displacement.
:- .
, .
:
'~
''
.
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2~5
~ IN TI~E DRAWING:
:,
Fig. l is an end view of the valve structure on the
line l-l of Fig 2;
Fig 2 is a sectional view on the line 2-2 of Fig. 3;
Fig 3, appearing on the same sheet as Fig, l, is a
sectional view taken on the line 3-3 of Fig 2;
Fig. 4 is a detail view, partly in section of the
valve element and its operating shaft, taken at line 4-4 of Fig. 2;
Fig~ 5 is a sectional view on the line 5-5 of Fig. 2;
Fig. 6 is a plan view of an air brake system at the
underside of a railroad car;
Fig. 7 is a sectional view, similar to Fig. 2, showing
a modified form of valve assembly in accordance with the present
invention;
Fig. 8 is an end view of the valve assembly shown in
-~ Fig. 7, partly broken away;
Fig. 9 is a detail view of a preferred form of seal
carrier, partly in section;
Fig. lO, appearing on the same sheet as Fig. 6, is an
assembly view showing the manner in which the valve assembly may
be suspended beneath the vehicle ! and operated from either side
thereof;
Fig. ll is a sectional view, similar to Fig. 7, showing
a modified form of lock, bearing and seal for the operating shaft;
Fig 12 is a fragmentary detail view on an enlarged
scale, showing the groove in which the lock pin rotates, taken
substantially on the line 12-12 of Fig. 11.
i ~..
sd/~ ~, -3-
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'' . .
Except for the valve installation 10, the air
brake system shown in Fig. 6 is a standard one for rail-
road cars, installed beneath the car frame.
The brake system comprises a brake pipe 14, a
brake valve 16, an auxiliary air reservoir 18, an emergency
air reservoir 20 and a brake cylinder 22.
The brake pipe has couplers 24 and 26 for coupling
to the brake pipe on the car ahead and the car behind.
The brake pipe receives air indirectly from the main locomotive
reservoir (not shown).
A brake cylinder pipe 28 is connected at its
opposite ends to the brake valve 16 and brake cylinder 22.
An auxiliary reservoir pipe 30 is connected at its opposite
ends to the auxiliary reservoir 18 and valve 16. An emer-
gency reservoir pipe 32 is connected at its opposite ends
to the emergency reservoir 20 and the brake valve.
In accordance with the present invention, the
brake pipe for each car is sectioned in effect so there
are two end sections 14A and 14B, flange-mounted in respec-
tive fittings 36 and 38 attached to the valve housing 40
which is part of the valve installation or assembly 10.
A branch pipe 42 is flange-mounted at one end
in a third fitting 43 which is attached to the top of the
valve housing. The opposite end of the branch pipe 42 is
connected to the brake valve 16.
When the brake is to be applied, in the standard
air brake, air under pressure in the brake pipe 14 is re-
duced; reduced pressure is also established in the branch
pipe 42, opening the brake valve 16. Since the brake valve
. _ _ .. , . . _ _ . . . . . ..
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is opened, air under pressure in the auxiliary reservoir
flows through pipe 30, flows through passages in the brake
valve, and is delivered from thence through pipe 28 to
operate the brake cylinder 22; the brake apply piston 44
extends to actuate the supports for the brake shoes (or
brake discs) to apply brake forces to the car wheels.
Valve assembly 10 is installed in the standard
system at (and takes the place of) the standard, special
"T" fitting normally installed where the branch pipe 42
communicates with the brake pipe. This can be readily seen
in Fig. 6 and it will also be recognized by those skilled
in the art that there are no angle cocks in the brake pipe
ad]acent the couplers 24 and 26; nor is the branch pipe
42 equipped with the usual combination dirt collector and
cut-out cock. Rather, valve assembly 10 is constructed
to enable either one of the brake pipe sections 14A or 14B
to be closed or cut out, and the brake valve 16 as well,
by merely positioning a valve element inside its valve
housing 46, Fig. 2, as will now be described.
The valve housing 46 is generally rectangular
in appearance. The aforementioned fittings to which the
pipe ends are connected are appropriately secured to the
exterior sides of the valve housing. The interior or chamber
. . .
of the valve housing is of sufficient dimension to enable
a valve member 50 of plug form to be moved radially therein,
to one of four positions, by an operating shaft 51, Figs.
2 and 3. The preferred shaft motion is rotary and in this
connection it will be noted from Fig. 2 that opposed walls
of the valve chamber closely confine the valve plug 50 so
that it is guided by the valve chamber side walls when orbited
from one position to another.
2~5
The valve housing has three openings A, B and
P, Fig. 3, each of which may be lined with a bronze sleeve
54 having an interiorly-located annular seat 55 to be sealed
selectively by the valve member. Each sleeve 54 is press-
fitted in place.
Shaft 51 which carries valve member 50 is located
at the intersection of the three valve housing openings.
Member 50 has a seal 50S supported thereon to engage selec-
tively one of the three seats 55. By turning member 50,
its seal may be presented in the normal position (dashed
line, Fig. 3) to communicate the brake pipe section openings
A and B to one another and to the branch pipe opening P
as well, Fig. 3. This may be viewed as the first or "valve
in" position where air flows through the brake pipe from
one end of the car to the other and flows to the brake valve
as well.
The valve or seal support member 50 may be turned
clockwise from the dashed-line position as viewed in Fig. 3
to a second position shown by solid line where the seal
50S blocks the brake pipe section 14B or it may be positioned
in the third position so that seal 50S blocks the other
brake pipe section end. In the fourth position, the branch
pipe is cut ~out", disabling the brakes on the car, but
the brake pipe is "in" on both sides of valve member 50.
.
The valve member 50 may be easily turned from
a safe position at either side of the railroad vehicle.
This is accomplished by extending ends 51A and 51B of shaft
51 outward of opposite sides of the valve assembly and
equipping the extended end portions with handle attachments
of whatever length and configuration may be necessary as
will be described below.
2~5
The valve assembly may be suspended in a fixed
position beneath the car frame as by a bracket; also indicia
may be provided adjacent the valve operating handles (not
shown) for showing the valve position. A locking means
is employed to hold the valve in the position to which the
operating rod is turned. Details of the valve lock and
its operation will now be described.
The shaft 51 is supported and guided in part by
a first boss 56 projecting from one side of the valve hous-
ing as shown in Fig. 2.
A lock mechanism including a sleeve 58 is secured
to the opposite side of the valve housing, interposed be-
tween the valve housing and a second support boss 60 which
is secured thereto.
Each guide boss 56 and 60 has an enlarged internal
chamber 61 in which is positioned a centering coil spring
62, as shown in Fig. 2. A washer 66 is located at the outer
end of each chamber 61, serving as a seat for the corres-
ponding end of the coil spring. The opposite end of each
coil spring bears against a second washer 68 which in turn
engages a stop shoulder 70 formed on the operating shaft
51. An O-ring 72 surrounds the portion of shaft 51 outward
of each washer 66 to afford an air-tight seal.
The two springs 62 operate normally to bias shaft
51 with the valve member 50 centered so that its seal 50S
seals the periphery of whichever insert 55 it may be aligned
with when in the second, third or fourth position. The
seal 50S is an approved AAR seal member and is retained
in an annular recess 71 formed in the head 72 of the valve
member 50, as shown in Fig. 3.
. _ .. . . . .. . . ... .. .. . . . .
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The valve member 50 is so linked to shaft 51 that
it may be displaced along its axis, coaxial with respect
to the associated insert 54, when shaft 51 is moved axially.
In accomplishing this, the valve member 50 is provided with
a slot 74, Fig. 3, in which one end of a toggle link 76
may be located. A pin 78 extends through slot 74 and through
an opening in link 76 as shown in Fig. 3. Link 76 is loose
on the pin so that it may swing with respect thereto. The
opposite end of link 76 extends into a slot 82, Fig. 2,
formed in shaft 51; link 76 is connected to shaft 51 by
a pin 84, Fig. 3, so that the link is normally at right
angles to the axis of the shaft; again the pin connection
is a loose one so that link 76 may swing with respect to
pin 84.
The lock mechanism, as mentioned above, includes
a sleeve or collar 58 interposed between the valve housing
and the guide boss 60. The preferred lock is a pin-in-slot
and to this end the interior of collar 58 is machined to
afford a bore for shaft 51 (as will be apparent from Fig.
2) and also to provide four slots as SL, Figs. 2 and 5,
of cruciform array at 90 displacements corresponding to
the four positions of the valve member. A fixed lock pin
86 is press fitted in shaft 51 so that the opposed ends
thereof will fit a pair of opposed lock slots SL to hold
and maintain the valve member position.
By applying an axial force in either direction,
to either end 51A or 51B of shaft 51, the lock pin 86 may
be displaced from its detent slot as will be evident from
the clearances provided at the ends of the slots as shown
in Fig. 2.
_ . _ . . . .
2~5
As long as the lock pin 86 is disposed in a detent
slot, only axial displacement of shaft 51 is possible.
As axial displacement occurs, link 76 swings (see Fig. 4)
and at the same time displaces valve plug 50 laterally off
the valve seat co-axial with the axis of the opening with
respect to which it is aligned. When pin 86 is displaced
entirely from the locking slot, then it is possible to
rotate shaft 51, and valve member 50 revolves therewith.
The operator can "feel" for the new detent position and
when alignment is achieved the axial displacement force
applied to shaft 51 is relaxed allowing the compressed
spring 62 to return the shaft to its normal position with
the lock pin 86 disposed in a new slot. In connection with
movement of valve member 50, it will be noted in Fig. 2
that the inside of the valve housing narrowly confines valve
member 50 in a guiding relationship.
A strong manual force is required to displace
shaft 51. This coupled with the lock discourages tampering.
The spring force tending to center shaft 51 in
the second, third or fourth position of the valve member
is sufficient, combined with the dimensioning of link 76,
to compress the seal member by approximately ten percent
of its thickness. Also, the pressure of compressed air
in the brake pipe, released to the inside of the valve
housing, is sufficient to apply additional compressive
forces to the seal carrier assembly 50, further compressing
the seal against its seat 55. The force of the air, how-
ever, does not prevent manual displacement.
. .
1~ 2~5
. ,
.
In the event of failure properly to present the
seal to its seat, failure will be in the safe condition,
i.e., the air will leak, diminishing the pressure in the
branch pipe, and allowing the brake to be set automatically
in the actuated condition. In this same connection it will
be noted that vent passages 85 and 87 are drilled in the
extended ends 51A and 51B of the operating shaft, communi-
cable with the spring chambers 61, and hence with the inside
of the valve housing, in the displaced position of the operat-
ing shaft. Hence an audible hiss of air is perceived when
the valve is being displaced and moved into a new position.
When the valve member is repositioned and the displacement
force relaxed, allowing the seal to re-seat, this audible
signal will terminate if the seal is correctly re-seated,
signifying an operative state.
The valve assembly of the present invention incor-
porates a dirt trap collector which serves to confine dirt
to a chamber at the bottom of the housing 46. In this con-
nection it will be noted from Fig. 3 that shaft 51 is located
within the upper half of the interior of the valve housing.
When there is air flow, any dirt particles impinging on
shaft 51 tend to be slowed, swirled and settled on the
bottom wall 90 of the housing, Fig. 3. Accumulated deposits
may be removed by removing a drain plug 92 threadedly mounted
in the bottom wall 90.
Since the valve assembly of the present invention
may be mounted on a hopper car, a dirt trap or retainer
means 100 is incorporated inside the valve housing to prevent
dirt from being dumped into the upper half of the valve
housing when the hopper car is tipped.
:
Z95
The dirt trap, Fig. 3, comprises a hinged, swing-
ing baffle hinged at 104, and having downwardly sloped side
plates 106 and 108 which normally direct dirt downward to
the bottom wall 90.
To trap the dirt when the car is tipped or tilted,
there are a pair of stop plates 110 and 112 over-hanging
the respective side plates 106 and 108. The stops are
spaced above the side plates in the normal attitude of the
railroad vehicle, allowing space for the dirt to slide there-
past but if the car is tipped the baffle swings toward and
into contact with one or the other of the stops thereby
to trap the dirt.
A modified valve assembly is shown in Fig. 7,
incorporating several preferred changes compared to the
above described modification. Only the essential changes
will be described.
! The projecting bosses 111 and 113 on the valve
- housing which serve to afford supports for valve positioning
shaft 114 are provided with bores having bronze sleeve
bearings 116 and 118 which support shaft 114. The ends
of the bores in the bosses, outward of the sleeve bearings,
are enlarged to accommodate compound seals, each of which
includes an O-ring 120 retained by an annular member having
a lip 121 for wiping the shaft during axial movement.
The position of shaft 114, as in the foregoing
embodiment, is held by a lock. The lock includes a lock
pin 122 extending through an opening in shaft 114, just
as in the foregoing embodiment, held in place by a set screw
124.
Z95
The lock, as in the foregoing embodiment, includes
a collar 126 inserted into one of the housing bosses; collar
126 is secured in place by a dowel 128, Fig. 8. The collar
126 has four lock slots SL for the projecting ends of the
lock pin, the lock slots being diametrically opposed in
pairs as in the foregoing embodiment so that there are four
90 displaced positions for shaft 114, corresponding again
to four different positions for the valve member.
The valve member 130, as in the foregoing embodi-
ment, while it may be conveniently termed a plug, carries
a seal 132 adapted, in one of three positions, to seal off
one of the three openings in the housing to which a pipe
end is communicated; only one opening is shown in Fig. 7,
opening P, lined with a bronze bushing 134.
The valve member 130, Fig. 7, is in the position
corresponding to the dashed line position of Fig. 3 where
all three openings are disclosed.
As in the foregoing embodiment, valve member 130
is pivotally, loosely joined by a pin 135 to a supporting
toggle link 136 in turn pivotally mounted on a pin 138
carried by shaft 114. Shaft 114 is slotted at 140 to enable
the upper end of link 136 to be fitted freely therein and
after being so fitted the pivot pin 138 is pressed through
openings in the shaft, and through the corresponding (aligned)
opening in the upper end of link 136 thereby to support
the valve member on shaft 114.
To limit the chance of the seal 132 being dis-
located, it is in effect locked positively to the valve
member or seal carrier plug 130. Thus, member 130, Fig. 9,
2g5
is provided at its seal end with an annular recessed shoulder
142. The seal 132 has an annular collar 144 fitting the
shoulder 142 and has an annular free end 146 constituting
the effective seal element.
The seal 132 is clamped in the recess 142 by a
seal retaining ring 148 in turn secured to the carrier 130
by cap screws 150.
To stabilize the valve member when in the position
shown in Fig. 7, which may be deemed the at-rest position,
a support plate 154 is located therebeneath.
The support plate 154 may be used as part of the
dirt collector, Fig. 8. Thus, and again, the operating
shaft 114 is located in the upper half of the valve housing,
allowing room for dirt to settle and collect on the bottom
wall of the valve housing.
Dirt may be guided to the bottom of the housing
,
and retained there (in cooperation with the support plate
154) by two dirt collector guide and trap plates 156 and
158. The dirt collector plates are hinged to the inside
vertical walls of the valve housing by hinge pins 160 and
162. The dirt collector guide plates are normally positioned
in the attitude shown in Fig. 8, inclined downward, by stops
164 which rest against the inside vertical walls of the
valve housing.
If the valve assembly is on a hopper car, the
hinged dirt collector guide plates may swing by gravity
into bridging contact with the support plate 154 when the
car is tipped, trapping the dirt against movement into the
portion of the valve housing where the valve member and
the pipe openings are located.
295
In the embodiment shown in Fig. 2, the return
springs for centering the valve member and coupling the
actuator shaft to the lock are located inside the valve
housing. In the preferred embodiment, the return springs
are located outside the valve housing as will now be described
together with the support for the mechanism and the preferred
means for operating the actuator shaft.
Referring to Fig. 10, the entire mechanism may
be suspended beneath the railroad vehicle by a pair of support
plates 170 and 172 fastened to the frame of the vehicle
in dependent relation at each side. These plates may be
marked with indicia showing the four positions of the valve:
"Air through each end; Air this end only; Air this end
only; Brake cut out - Air through".
The actuator shaft in each embodiment extends
outward of the sides of the valve housing. To enable rotary
motion to be imparted to the actuator shaft, a universal
joint is preferrably employed. One fork 174 of the universal
joint is keyed to the free end of the actuator shaft as
by a bolt 176 keyed through a slot, Fig. 7, in the actuator
shaft. The other fork 178 is coupled in the usual fashion
to the joint pin 180. The fork 178 is welded to a shaft
182 having an outboard extension 184 journalled in the re-
lated support plate (170 and 172) and thereby the entire
assembly is suspended beneath the vehicle; the valve housing
may be braced to the underside of the vehicle.
Each shaft extension 184 extends outboard of the
related support plate and terminates in a handle 186 having
an outwardly bent lower portion to afford a good mechanical
advantage. The handle has an upper pointer 188 related
to the indicia mentioned above.
14
295
:'
A centering coil spring 190 is interposed between
each handle and the opposed surface of the related support plate.
The two coil springs 190 oppose each other, applying an
outward thrust against the related handle, thereby serving
normally to center the valve member with the lock engaged.
By applying an outwardly directed force to the operating
handle, which results in compression of the opposed spring,
the lock may be disengaged, the shaft turned to re-position
the valve member and the force then relaxed to re-engage
the lock to hold the valve member in its new position.
The mechanical advantage incorporated in the operat-
ing handle aids in gradual displacement of the seal from the
bushing seat when air pressure is being contained as in
cutting through the brake pipe supply under pressure to
an added car or group of cars. Gradual displacement avoids
a sudden release of air pressure likely to result in the
brake equipment going into an emergency mode.
The dirt collector will trap water as well and
the location of the opening as P to the branch pipe is at
an elevated, uppermost position, above the axis of the brake
pipe further supplementing the principle of having the dirt
collector chamber well beneath the axis of the brake pipe.
~ It will be noted in Fig. 7 there is another opening
- E in the valve housing, normally plugged in the instance
of a conventional railroad car. The purpose of this additional
connection is to allow the present valve assembly to be
connected to one or more remotely, manually operated valves
(not shown) to rapidly exhaust brake pipe air to atmosphere
in an emergency as commonly used with caboose cars and loco-
motives. Such manually operated valve is installed in the
caboose cupolo, at each end of the caboose and on the fireman's
side of the locomotive cab.
'
- 15
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Z95
Fig. 11 shows another form of pin-in-slot lock
to hold the position of the operating shaft. One of the
interior walls of the valve housing, as shown in Fig. 12,
is provided with an annular groove 192 and four slots SL-l,
SL-2, SL-3 and SL-4 at 90 displacement. Two of the slots
::
are shown at SL-l and SL-3 in Fig. 11, displaced by 180.
The seal carrier or valve plug member has a laterally pro-
jecting pin 130-P in position to fit into the slots, Fig. 11,
in each home position of the seal carrying member.
As shown in Fig. 11, two sleeve bearings which
support the operating shaft may be outermost and the two
shaft seals for preventing escape of air along the axis
of the shaft may be inward of the sleeve bearings rather
than outward as shown in Fig. 7.
The operating shaft 194 and seal carrier member
196, Fig. 11, are similar to those of Fig. 7. In all instances
it is preferred that the link connection between the operating
shaft and seal carrier member be slightly loose by a few
thousandths of an inch (e.g. elongated opening for one of
the pins) so that the seal is forced into sealing engagement
by air pressure inside the valve housing.
Also, as shown in Fig. 11, it is preferred the
shaft being drilled have a passage 198, opening to the atmosphere,
and communicable (cross drill at 198A) with the interior
of the valve housing when the operating shaft is displaced
longitudinally so that there may be an audible perception
of escaping air in the event a proper valve position is
not attained after the shaft is turned and released to the
return action of the spring. This loss of air may also
16
Z~S
be detected in the locomotive cab and the brakeman can be
alerted to look for the car with the leak. The degree of
air loss is purposely designed to be appreciably greater
. than that required for the brake pipe leak test required
- by statute at the point of departure of the train.
