Патент USA US2055106

Sept. 22, 1936.
zot-‘35,106
E. E. HEwlTT
~
ELEGTROPNEUMATIC BRAKE
Filed O_Ct. 1'0, 1934
-
INVENTOR`
N
ELLIS EHEwn-T
BY
A
ORN
2,055,106
Patented Sept. 22, 1936
UNITED NSTATES PATENT oFFlcE‘
ELECTROPNEUMATIC BRAKE
Ellis E. Hewitt, Edgewood, Pa., assignor to The
’ Westinghouse Air Brake Company, Wilmer
ding, Pa., a corporation of Pennsylvania
Application October 10„1934, Serial No. ’747,729
17 Claims. (Cl. 303-15)
This invention relates to electropneumatic
brakes, and more particularly to electropneumatic
brakes for high speed trains.
In trains designed for high speed service safety
5A considerations demand that the braking equip
ment employed provide for the highest practical
degree of reliability.
One‘ manner of providing
for this reliability in a fluid pressure brake sys
tem is to arrange the system such that an appli
10 cation of the brakes may be effected either by
straight air operation, by automatic operation,
or by a combination of the two. In systems of
this character a control valve device is generally
l provided on each car in the train, and these valve
1'5 devices are controlled from the head end of the
train through some form of controlling brake
valve device.
'
`
Each control valve device most generally com
prises some form of relay valve for controlling all
flow to the brake cylinder, and an electrically>
20 controlled valve device and an automatic valve
device for controlling operation of the relay valve.
The electrically controlled valve device controls
operation of the relay valve during straight air
operation,
while the automatic valve devicecon
25
trols operation of the relay valve during auto
matic operation. In addition to these valve de
vices, the control valve device usually‘includes
additional electrically actuated valvesA under the
to intermittently release fluid under pressure
from the brake cylinder without at any time re
Vsupplying fluid under pressure thereto.
-
However, while it is desired that the retarda
tion controller device release from the brake cyl- -1
inder whatever fluid under pressure is necessary
to maintain the desired rate of retardation, an
accidental release of total brake cylinder pres
sure should be guarded against.
In the equipments providing for both straight
air and automatic operation as heretofore pro
posed, the retardation controller device has been
effective in controlling only applications effected
by straight air operation. It is of course desir
able that the retardation controller device be ef
fective in controlling applications by either
straight air operation or by automatic operation.
With the above considerations in mind, it is a
principal object of the present invention to pro
vide a brake equipment in which applications 20
may be effected either by straight air operation
or by automatic operation, and in which a re
tardation controller device may be employed to
control applications by either mode of operation.
Another object of the present invention is to
provide means for effecting a more gradual re
lease of the brakes in response to operation of the
retardation controller device, so as to prevent the
needless loss of ñuid under pressure and to main
tain a more nearly constant rate of retardation. 30
30 control of a retardation controller device, which .
A yet further object of the invention is to pro
valves-and retardation controller device function
to control the brake cylinder pressure so as to vide means, in connection with an equipment of
decelerate the train at some predetermined de
sired rate of retardation. The retardation con
35 troller device and electrically actuated valves usu
ally function to first cut off the supply of fluid
under pressure to the brake cylinder and subse
quently to effect a release of fluid under pressure
from the brake cylinder. One of the difficulties
40 heretofore encountered has been that more fluid
under pressure has been released from the brake
cylinder through this operation than necessary to
maintain the desired rate of retardation, with the
result that the rate maintained was not Vmain
45` tained constant within tolerable limits. In ad
dition, there has been an undesired cycling oper
this character, which will prevent a total loss of
brake cylinder pressure in the event of undesired
operation of the electrically actuated valves con- ï
trolled by the retardation controller device.
Yet further and more speciñc objects of the
invention will appear from the following descrip
tion, which is taken in connection with the single
figure of the attached drawing, which shows in ‘ 40
schematic and diagrammatic form one arrange
ment of apparatus which may be employed in car
rying out the invention.
In this drawing, an arrangement for only one
car has been shown, but, as will hereinafter more
fully‘appear, portions of the apparatus may be
ation of the apparatus in alternately supplying
duplicated on other cars in the train, and thus
fluid under pressure to and releasing it from the
brake cylinder, thereby causing unnecessary loss
50 of fluid pressure. It is desirable in practice that
the retardation controller device function first to
cutoff the supply of fluid under pressure to the
brake cylinder, and thereafter, as the speed of the
train diminishes and the coeñìcientof friction
provide for a complete train braking equipment.
between the rubbingparts of the brakes increases,
In the embodiment illustrated, I have shown a
control valve device I0, which operates to control
the supply of fluid under pressure to and its re
lease from a brake cylinder l2, .whether effected
by straight air operation or by automatic opera
tion. One of these control valve devices is lo
cated on each car in the train.
At the head end "Ul
2,055,106
of the train, I provide a controlling brake valve
device, diagrammatically indicated at I4, and this
position, the slide valve 44 uncovers one passage
brake valve device is employed to control opera
54 and a port 51 therein registers with the other
tion of all of the control valve devices through
passage 54, so that fluid pressure may be released
from the slide Valve chamber 48, and the con
out Vthe train.
.
In order to limit the rate of retardation pro
duced by an application of the brakes to some
predetermined maximum value which will not
produce sliding of the wheels, a retardation con
10' troller device I6 has been included, and this de
vice functions to control certain electrically op
erated valve devices, as will more fully appear
hereinafter.
f
Y
Í
Considering now more in detail the control
15
sponding annular portion of a gasket 56. In this
valve device I8, this valve` device comprises a
relay valve section I8, an electrically controlled
self-lapping magnet valve section 28, an auto-V
matic valve section 22, a pneumatic cut-off vvalve
section 24, an inshot Valve section 26, and a mag
20 net valve section 28.
nected brake cylinder I2, to the atmosphere by
way of passages 54 and pipe 55.
When the relay piston 45 is actuated upwardly
to application position, slide valve 44 blanks both
of passages54, to cut oiî communication from the 10
slide valve chamber 48 and the brake cylinder I2
tothe atmosphere, and thereafter the upper end
of the piston stem 41 first engages stem 58 of the
pilot valve 36, to partially unload the main sup
ply valve 32, and then engages and unseats the 15
main supply valve. Unseating of this supply
valve effects a supply of fluid under pressure to
the slide valve chamber 48 and the brake cylinder
I2, through the passages heretofore indicated.
posed within'the supply valve 32 is a pilot valve
Relay piston 45 is actuated to application posi 20
tion by the supply of fluid under pressure to the
volume therebelow. When fluid under pressure
is thus supplied below the piston it acts initially
upon the piston area within the annular ñange
in engagement with the gasket 56, and as soon as 25
the piston is lifted from the gasket, fluid pressure
then acts upon the total piston area and thus
causes the piston to move quickly upwardly to ap
„36, _urged toward a seat 31 by a spring 36.
plication position.
`
The Vrelay valve section I8 controls the supply
offluid under pressure from a connected supply
reservoir 38 to the connected brake cylinder I2.
The-flow ,ofV fluid from the reservoir to the brake
25 ’cylinder is V_controlled by a supply valve 32, which
is disposed in a valve chamber 33. The valve 32
iis-urged toward a seat 34 by 'a spring 35. Dis
30. When the pilot valve 36 is seated, the ñuid pres
sure acting upon the valve 32 from the valve
chamber 33, plus the pressure >of spring 35, will
-hold the valve upon its seatV 34. When the pilot
valve 36 is actuated to unseated'position, fluid
under pressure in _the valve chamber 33 is re
.
When the supply of fluid under pressure to the 30
volume below the piston has been cut off, the
pressure of fluid flowing to the space above the
piston, through the choke 53, equalizes with that
below, whereupon the piston moves downwardly
until the supply valve 32 is seated. The supply of 35
leased past'the unseated pilot valve to a slide
iiuid under pressure to the brake cylinder is then
valve chamber 48 at a rate fasterV than it can be
lapped.
vsupplied Vto the valvechamber 33 through a choke
39 from'a'. supply chamber 4I, which is inV com
munication with the supply reservoir 38 by way
of >passage 42 and pipe 43. As a consequence,
the pressure on the upper side of the valveV 32 is
reduced and the'valve can then be unseated by a
relatively small pressure from below. When the
r.4.15 valve 32 is unseated, .fluid under pressure may
-iiow fromr the supply chamber 4I, and the supply
reservoir `38, to the slide valve chamber 48.
Disposed in the slide valve chamber 48 is a
slide valve 44, and for operating the slide valve
50 and for unseating the pilot valve 36 and the main
supply valve 32, there is provided a piston 45 dis
posed'in> a pistonl chamber 46 and having a stem
41. The piston stem 41 is provided with an en
'
- The supp-ly of fluid under pressure to the vol
ume below relay piston 45 is primarily controlled
by the self-lapping magnet valve section 28 dur 40
ing straight air operation, or by the automatic
valve section 22 during automatic operation, and
secondarily by the inshot valve section 26 andthe
cut-olf valve section 24 Yduring either operation.
The self-lapping magnet Vvalve section 28 is
provided with a supply valve 68, which controls
the flow of fluid under pressure from the supply
reservoir 38 to the Volume below relay piston 45,
by way of pipe 43, passages 42 and 6I, past supply
valve 68 when unseated, to passage 62, and from 50
thence through the inshot valve section and the
pneumatic cut-off valve section, as will hereinafter
be more fully described.
larged flanged portion 48 interfitting with a bore
The supply valve 68 is urged toward >seated
Y49, for the purpose of providing a seal between
guiding movement of the stem when the piston
position by a spring 63, and toward unseated 55
position byl action of an electromagnet having
a winding 64, which when- energized actuates
members to be described to unseat the> valve.
When the winding 64 is energized, the magnetic
its movement is coextensive with the movement
effect produced thereby actuates a movable core 60
member 65 downwardly. Secured to the core
member 65 is a stem 66 which engages a pin 61
of the piston 45.
to actuate a sliding` member 68.
`the piston' chamber-46 and the slide valve cham
ber 48 as the piston 45 moves. Also, the stem
41` is provided with a guiding element 58 for
60 45 is moved upwardly and downwardly. The slide
>valve 44 is carried in a recess in the stern 41 and
„
.
.
The slide valve chamberV 48 is in constant com
munication with the brake cylinder I 2 by way. of
pipe and passage 5I , and is also in restricted com
municartion with the piston chamber 46 by Vway
of passage 52, in which is disposed a choke 53. .
-The slide valve 44 controls communication be
l70 tween the slide valvechamberV 48 vand the at
mosphere, by way of passages 54 and pipe 55.
~ In release position of the relay valve section I8,
which is that shown in the drawing, the piston 45
‘_is- in its lowermostposition, where an annular
275 flange» thereon contacts andiseals with a corre
The sliding
member 68 is provided with a valve seat 69
which engages and interñts with the upper end 65
of the stern of the supply valve 68, which end
forms a release valve 18, controlling the vrelease
of fluid pressure from the volume below relay pis
ton 45.
,
'I'he sliding member 6,8 is normally held in an 70
upper or release position by a resilient diaphragm
1I, which is secured thereto and to the casing
embodying the self-lapping valve device in a
manner tov form a chamber 12 therebelow and a
`chamber 13 thereabove.A When the sliding mem 75
s
2,655,106
berï§68 is»in»its upper or‘ »release- positi’om'the re'
lease valveï‘16-is unseated,»vso that ñuid pressure
is »released from the volume belowrelay piston
45 to the atmosphere, past the `unseated release
valve, 4through an orifice 14, passage 15, and
port
162
‘
»
i
v
ì
When the sliding member »68 is actuated down
wardly theV release valve 16 is seated, to cut off
this lcïommunication‘to the atmosphere, and the
'10 supply valve 66 is unseated,‘to eiîect a supply
of fluid under pressure to the under side of the
relay
piston.
~
"
»
*
»
l
l
~
ber 66V is,` as aforesaid, caused by downward
~15 movement of the core member 65. The down
ward movement of the core member- 65 is op
posed by a spring "18 reacting against a Vspring
cup 19 secured to the upper end of stem 66. The
downwardfmov'ement of the core member 65 and
the stem 66‘is governed or limited by aflanged
collar '86,‘which is adapted to engage a» stop
Washer 8|» upon a predetermined downward
movement of the corel and stem.
’
»' >As may be seen from the construction shown
25 in the drawing, the spring cup 19 and the flanged
collar 86 may be Aadjusted'to different positions
on the stem 66. The stem 66 may be also ad
justed with respect to the Acore member 65 by
means of the screw-’thread connection shown.
The lower end of the core member 65 is pref
erably of a bevelled configuration, as shown` in
30
as will hereinafter be more fully referred to;
The slide valve chamber 85 is connected to an
ber 891s reduced at a service rate, the over
balancing pressure beneath the piston in th-e slide
valve chamber actuates theV piston upwardly to
service position. In service position, the main
slide valve 86 blanks the two passages 95 and |64,
and brings port> | |2 therein in registration with
the passage 91, the graduating valve 81- having 40
uncovered the port | | 2 at this time. Fluid under
'
"
valve'16 is ñrst seated and the supply valve 66
the downward movement ofthe stem 66 and
movable‘core 65. This movement is opposed by
the spring 18 and the unseating‘of the supply
45 valve 60A is thus determined by the degree of en
ergization of the winding 64; _
diaphragm overbalances> >that acting downwardly
on the ‘diaphragm due to the magnetic pull on
the. core member65,l the sliding member 68 is
actuated‘upwardly to» permit‘s’upply valve 60 to
be͑seated'by spring 63. ,The supplyY of iiuid under
pressure tothe volume belowV relay piston 45 will
`
,
‘
,
`
’ivIf the- pressure >below diaphragm 1| is great
enough, release valve 16 may be unseated to re
lease pressure from below the relay piston. If,
on the other hand, after supply valve 66 is seated
the pressure below >the diaphragm should di~
minism, ,due to leakage or for other reasons, the
diaphragm will be actuated downwardly'by the
magnetic force above, to unseat ,the supply valve
and thus readmit ñuid underfpressure to the
volume 'below4 the` relay piston. VThe self-lapping
magnet ’valve portion >thus operates to supply and
maintain a pressureto the relay valve'section
iníac'cordance with'the current -supplied to the
winding
64.`
`
e
'
'
chamber 85', and the auxiliary reservoir H6, to
both the volume reservoir 99 and to the double
of reduction in brake pipe pressure.
andi when the >fluid pressure acting Vbelow the
then be lapped.
pressure then flows from the main slidev valve
check valve chamber |6|, according to the degree 45
¿When the supply valve 66 is unseatedA ñuid
under pressure also flows to the'chamber> `12 be
low the diaphragm 1|, by way of passage 83,
65
charge valve |06 controls communication between
the passage |04 and the brake pipe passage 93,
what decreased reluctance. The casing embody
ing the `valve device provides the return path for
innext unseated an‘amount in accordance with
60
disposed a fast recharge valve |66, urged toward
a seated position by’a spring |01. This fast re
so as to provide an air gap-therebetween of some
Í_ ¿When the winding 64 is energized, the release
55
also has a port |63 in registration with a passage
|64 leading to a valve chamber |65, in which is 25
auxiliary reservoir ||0 by way of pipe and pas
sage | | I; When the pressure in the piston cham
the magnetic flux1established by the energized
50
as shown inlthe drawing, which is also the re
lease position. In this release position, a cavity V15
94 in the main slide valve 86 connects a passage
95', which leads tothe atmosphere by way of pipe
96, with a passage 91, which has two branches,
one branch leading by way of pipe 98 to a volume
reservoir 99, and the other branch leading by way -20
of passage |66 to a double check valve chamber
I 0| in which is disposed a double check valve |02.
In release position, the main slide valve 86
the drawing, and interñts with a corresponding
recessed portion ina stationary core member 82,
winding 64.
40
ber 89.'V The piston 88 is provided with a stem
96 adapted to move the'graduating valve 81 co
extensive therewith, and' to move" the main slide
valve 86 with a delayed or lost motion.
The piston chamber 89 is in communication
with a brake pipe 92 by way of pipe and passage 10
93. When the pressure in the brake pipe is nor
mal, that is, maintained at a lpredetermined
value, the piston, 88 is in its lowermost position,
“f The'downwar'dïmovement of the sliding mem
20
valve chamber 85 in which is disposed a main
slide valve 86 andïa graduating valve 81. For
operating themain and graduating valvesthere
is provided a piston 88, disposed in a piston cham
'
As before indicated, „the supply of‘ ñuid under
pressure nto the volume below relay piston 45
may be ‘also controlled’by'the automatic valve
75 section’
221' This section is providedwith a‘slide
`
The pressure of fluid supplied to the double
check valve chamber |0|, above the double check
valve |02, will actuate the >double check valve to
lower position, and thereafter fluid under pres 50
sure willflow to the volume below relay piston 45,
through the inshot valve section, as will more
fully appear presently.
When the pressure in piston chamber 89> is
reduced at an emergency rate, th-e piston 88 55
moves upwardly andseals against gasket I I4, and
the main slide valve 86 uncovers passage 91 while
blanking passages 95 and |04. Fluid under pres
sure then ñows from the slide valve chamber 85,
and the auxiliary reservoir | I0, to both the volume
reservoir 99 and the volume below relay piston
45 until equalization takes place.
As before stated, ñuid under pressure supplied
to the volume below relay piston 45 by operation
of the self-lapping magnet valve section 20`also 65
flows through the inshot valve section 26, now
ing ñrst to the double check valve chamber |0|,
Where the pressure of the fluid actuates the dou
ble checkV valve |02 to its upper position. From
the double check valve chamber |0|, the ñow is
initially through two branches, one branch be
ing by way of passage ||5 and the other branch
being by way of a‘ball valve chamber ||6- Dis
posed in this chamber is a ball valve ||1, which
is urged toward an unseated position by action
4
.2,055,106
of. a spring -I I8 actingv upon a piston` II9 having
a stem |20 lengagingthe ball valve. An adjust
ing member |2| is provided for adjusting the ten
sion onthe spring I I8, and upward movement of
the piston II9, and consequently the unseating
of the ball valve II_1, maybe controlled by ad-_justing nuts |22 >threadablyV disposed on an ad
justing stem |23 associated with the piston.
When the ball valve I I1 is in unseated position,
10 ñuid under Ypressure may iiow from the cham
When in upper seated position, the double beat
valve |42 opens communication between the pis
ton chamber |28 and the brake cylinder I2, and
when in lower seated position this communica
tion i's cut oif and the pressure in the piston
chamber |28 is released to the atmosphere
through an exhaust port and passage |45.
The releasevalve |43 is urged toward seated
position by a spring |46 and toward unseated -10
ber |I6 past the unseated ball valve to a passage
position b_y action of another electromagnet in
|24 >leading to the volume below the relay pis
the upper part of the casing, which when ener
gized actuates the valve downwardly. In un
seated position, this valve opens a communica
tion between a passage |41, leading to the volume v15
below the relay piston 45, and a passage |48 lead
ing to the seat of a limiting valve |49.
toni45.
»
Y
As the pressurel of the iiuid supplied to the
15 volume below relay piston 45 increases and
reaches a predetermined value, it acts upon the
,upper-sideof the inshotpiston II9 and actuates
the piston downwardly against resistance of
spring IIB, to seat the ball valve II1. After the
ball valve is seated, the flow of fluid to the volume
below relay piston'45 takes place only through
the passage II5, which leads through the pneu
,matic cut-olf valve’section 24.
The pneumatic cut-off valve section 24 is pro
25 vided with a slide valve |25, disposedin a slide
valve chamber |26, and a piston |21 disposed in
a piston chamber |28. The piston |21 has a stem
|29 adapted to actuate the slide valve |25 co
exte'nsive with movement of the piston |21. A
spring .|30 urges theA pistonV |21 upwardly to a
vnormal or biased position.Y In this position a
cavity I3| in the slide valve |25 connects the
aforementioned passage II5 with a passage `|32
joiningrwith the passage I24-leading to the vol
-35 ume below relay piston 45.
, lAt the same time, al port |33 in the slide valve
|2_5 is in registration with a passage |34 leading
lto a control reservoir |35, so that the slide valve
chamber I 26 is connected to this control reser
.40 voir.
Theslide valvechamber |26 isV in con
-stant communication with the brake cylinder I2
by way of passages |31 and |38, and hence when
_the piston |21 is in its upper position, the control
reservoir r|35 and brake cylinder I2 are con
nected.
The piston chamber |28 is at Vtimes* also in
50
whenV energized actuates the valve downwardly.
As shown, the limiting valve |49 is urged toward
its seat by a spring |50, and is adapted to be ac
tuated to unseated position by a chosen pressure 20
in the passage |48. In unseated position, the
valve |49 permits the release of fluid pressure
from passage |48 and the volume below relay pis
ton 45 to the atmosphere, by way of an exhaust
passage |5I.
The brake valve device I4, which controls the
major operations of the control valve device I0,
may be one of a large number of types and in the
type illustrated comprises a drum controller por
tion having a drum |54, adapted to engage and 30
connect together a pair of contact fingers |55
and to thereafter sequentially engage a plurality
of contact fingers |56, to electropneumatically
control brake applications by. straight air opera
tion.
35
'I'he brake valve device also includes a valve
portion for effecting and controlling applications
by automatic operation. This portion is prefer
ably provided with a rotary valve diagrammati
cally shown at |51, which is adapted to control
communication between a branch pipe |58, con
necting with the brake pipe 92, and a feed valve
pipe I 59,.and with an exhaust pipe I 60 leading
to the atmosphere.
.
The feed valve pipe |59 connects with a feed 45
valve device IGI, which in turn is connected to
communication vwith the brake cylinder I2,
a source of fluid under pressure, as for example
¿through a passage-|39 which runs through the
magnet valve section 28 to connect with the
a main reservoir |62. The feed valve device I6|
may be of one of a large number of types, and as
aforementionedrpassage y|31 leading to theV brake
is well known in the art, is provided for the pur 50
pose of maintaining a substantially uniform
pressure of the fluid supplied from the main res
cylinder. When the pressure in the piston cham
lberw|28 substantially equals the pressure in the
slide valve chamber |26, the piston I 21 will re
main in its upperposition. When the pressure
55 in the piston chamber |28 is reduced below that
ervoir |62.
Y
The drum controller and rotary valve portions
are preferably combined in a manner such that
in chamber |26, the overbalancing pressure in both- may be operated by manipulation of a sin
the chamber |26 actuates the piston downwardly - gle control element, as for example the familiar
to'where it engages gasket |40. In this position brake valve handle. This control element, or
of the piston |21, the slide valve |25 blanks pas
handle, is movable to diiîerent positions, as indi
A60 sage I|5 and connects passage |32 to passage cated inthe diagrammatic representation shown 60
|34, for a purpose which will appear later.
The pressure in the piston chamber .|28 is con
trolled by the magnet valve section 28. This
valve section comprises a double beat valve |42,
65 which controls the supply of fluid under pressure
.to and its release from the aforementioned pis
in the drawing, and as will hereinafter be re
ferred to.
In order that the supply reservoirs 30 through
out the train shall be charged at all times, a sup
ply pipe |6l|_isY provided which extends through
controls the release of Víiuid Ypressure from the
out the train. Each of the supply reservoirs 30
is then connected to this pipe, so that the supply
reservoirs are at all times charged to main reser
volume below relay piston 45. These two valves
voir pressure.
ton chamber |28, and a release valve |43, which
70 lare under the control of the retardation
troller device I6.
con
Y
The retardation controller device I6 may also 70
upper seated position by a spring |44, and is
be of one of a large number of types and for that
reason I have shown in more or less diagrammatic
form a pendulum type which may be employed.
urged toward a lower seated position by an elec
In this type a pendulum |66 is freely suspended
_. . The double beat valve |42 is urged toward an
Vtromagnet in the upper part of the casing, which
65
from a frictionless pivot |61 and carries there 75
5
with-and»insulatedtherefrom contacts |68 andr the relay piston will be in >its lowermost` Vor re
|69.
l
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Y
1
>
,
The retardation controller device is‘positioned
on the vehicle so that the pendulum |66 is swung
, to the right or left according to the rate of speed
change of the vehicle. As the pendulum |66
swings to the left, its contact |68 will ñrst engage
a stationary and resiliently supported contact
|10, and thereafter another and similar stationary
10 contact |1|. As the pendulum swings to the right,
it‘engages in'a similar manner similar stationary
contacts |12 and |13.
Y
»Considering -ñrst the contacts to the left, the
contact |10 is connected to the electromagnet in
the magnet valve section 28 controlling the double
beat valve |42, and the contact |1| is connected
to the electromagnet controlling the release valve
|43. `The other terminalof each of these elec
tromagnets -is connected to a ground `connection
2.0 |14.A 'I'he movable contact |68 of the retarda
tion controller device is connected to one terminal
of a battery |15, andthe other terminal of the
battery is also connected to a ground connection,
so'that as the movable contact |68 engages the
l25 stationary contacts> `_|10 and |1l| the electromag
nets in the magnet valve section 28 will be ener
gized.
l
'
Now if when the train is decelerating the pen
dulum |66 swings to the left, it will be obvious
30 that contacts |68 and |10 will be brought into en
gagement at one rate of retardation, and that
contacts |68 and |1‘I will be brought into engage
ment at a higher rate of retardation. The double
beat valve |42 will then be actuated downwardly
35 when ‘the iirst two of these. contacts engage,
and the release valve |43 will be unseated when
the second of these contacts engage. When it
is desired that the same result be Yaccomplished
for either direction of swing of the pendulum |66,
40 then contact |12 is connected to Contact |10, con
tact |13 is connected to contact I1|, and contact
|69 is connected to contact |68.
Y
If ‘howeverfit is desired that contacts |12 and
|13 be employed in connection withcontrolling
45 the acceleration of the train, then these contacts
may be connected to an> acceleration control ap
paratus, as described and claimed in the >co
pending application of *Clyde C.i.lï‘armer,` Serial
No. 707,918, ñled January 23, 1934.V >
50
l
The operation of this embodiment of my inven
tion is as follows:
v Running condition
lease position.
~ ‘
The other Vparts of the apparatus shown will
be substantially in the positions indicated.
Service application
When it is desired to effect a service applica
tion of the brakes, the~ brake valve device is
operated through the zone indicated as “Electric
service zone.” When the drum |54 thus engages
and connects together the fingers |55, current
will be supplied from a battery |18 to each self
lapping magnet valve winding 64, through a re
sistance |16. As the drum |54 rotates,»it se
quentially engages the contact lingers |56 to pro
gressively out out portions of the, resistance |19,
and thereby energize each winding .64 according
to~ operation of the brake valve devicethrough
the. “Electric service zone.”
,
1%
1.5.
’
In each control valve device, with the winding
64 energized, the core member 65 is actuated
downwardly to first effect seating of release valve
10 and subsequently unseating of the supply valve
60. Fluid under pressure then iiows from the
supply reservoir 30 to the volume below relay 25
piston 45, through a communication including
pipe 43, passages 42 and 6|, past the unseated
supply Valve 60, passage 62,. double check valve
chamber |0| (where double check Valve |02 is
actuated to upper position), and from thence 30
to the volume below relay piston 45 by way of
two paths. The first_of these two paths includes
passage H5, slide valve cavity |3|, and passages
|32 and |24. The second of these paths includes
ball valvechamberA | I6, past unseated ball valve 35
||1, and passage |24.
,
,
Y
Fluid pressure beneath the relay piston 45 `ac
tuates the piston and slide valve 44 upwardly
to cut oiî the communication between the‘slid'e
valve chamber 40 and the atmosphere, and to 40
effect unseating of the main supply valve 32.
Fluid underpressure then ñows from the Vsup
ply reservoir 30 to the slide valve chamber 40
and from thence to the brake cylinder |21>
As the pressure on the under side of relay 45
piston 45 builds up, a value will be reached at
which the inshot piston ||9 .will be actuated
downwardly far enough to seatthe ball valve
||1. Thereafter the ñow of fluid to the under
side of the> relay` piston will be by way of» the 50
other path only. The pressure at which the
ball valve ||1 closes is selected as- that corre
sponding to a brake cylinder pressure’which
Y When the train is running, the brake valve
55 device I4 at the head end of the train is main
tained .in “Release” position, in which the `active
parts of the brake vvalve device are in the posi
will insure that> the train will be brought to a
stop in case the path leading through the cut 55.
oiî valve section 24 should be closed. This brake
tion shown in the drawing.Y As will be observed,
in thisposition the _drum |54 isout of engage
60 ment with the contact fingers, and the rotary
generally obtaining in normal full service ap
plications, in which the retardation controller
valve |51 connects the feed valve pipe |59 with
the Íbrake pipe branch pipe |58, by way of port
|16.
»
The brake pipe pressure is thus maintained uni
form by thev feed valve device |6|, and each aux
iliary reservoir | I0 is charged from the brake pipe
92 by Way of charging groove |11 in the auto
matic valve section 22. With the brake pipe pres
sure maintained at normal, each automatic Valve
piston 88 will be in its lower position, as shown.
y At the same time, in each self-lapping mag
net valve section 20, the supply valve 60 will be
seated and the release valve 10 unseated, so
that the Volume below the relay piston 45 `will
be in communication with the atmosphere and.
cylinder pressure is preferablywell `below that
device iseffective.
¿
.
ì
_
60
The supply of fluid under pressure to the >re
lay valve section will be lapped by the self-lap
ping valve section when the pressure reaches a
value corresponding to the brake valve move
ment, and when the supply thereto has been 65
lapped, the relay piston 45 will move to lap
position.
,
In the train, each self-lapping section 20. of
each control valve device will operate `inde
pendently of every other self-lapping section,
so that the brake cylinder pressures eiîected will
be substantially uniform throughout the‘train,
and according to the position of the brake valve
handle, regardless of diiîerences in `piston travel,
leakage, etc.
,
6
2,055,106
`~ ' v’When fluid'underípressureis supplied to theV in the rate of retardation of the train will be
brake cylinder. I2, it also iiows to the piston small and a more uniform rate of retardation
chamber |28 in the pneumatic cut-oiî valve sec
tion 24, by way of passage |31, past the un
‘ seated double beatvalve |42, and through pas
sage |39, and to slide valve chamber I26, by way
of passages |31 and |38.
jAs pressure builds up in the brake cylinders,
the train begins to decelerate. If the rate of
10" retardation produced by application of the brakes
is suflicient >to cause the pendulum |66, of the
retardation controller device I6, to swing far
enough to the left to causeV engagement of con
, tact |68 with contact |10, Ythen each electro
magnet controlling a double beat valve |42 Vwill
be energized, and the double beat valve will
be actuated to lower seated position, to cut oil
communication between the Abrake cylinder I2
, and the piston chamber |28 in each pneumatic
cut-off valve section -24. At the same time, the
double beat valve' opens communication between
the piston chamber .|28 and the atmosphere,
through the exhaust port passage |45.
1 As the pressure in piston chamber |28 reduces,
the overbalancing pressure above the piston ac
tuates it downwardly, and cavity I3I in slide
valve '|25 connects the two passages |32 and
|34. Connection of these two passages brings
25
. into communication the volume below relay p-is
30 ton 45 andthe control reservoirV |35, The con
trol Vreservoir |35 is lat this time' substantially
at Vthe same pressure as the volume below re
lay. piston 45, because as fluid is supplied to the
brake cylinder I2 it also ñows to this reservoir,
35 through passages |31 and |38, slide valve cham
ber |26, port |33, and pipe and passage |34.
Ifrnowthe rate of retardation is great enough
40
tocau'se engagement of contact |68 with con
tact I1I, each Aelectromagnet controlling a 're
lease valve |43 will be energized, and the re
lease valve `will be unseated. Unseating of this
release valve releases iiuid under pressure from
the volume below relay piston 45, and from the
now _connected control reservoir |35, to the at
mosphere, through'passages |48 and |5|, the
limiting valve |49 being unseated by the pres
sure in the passage |48.
Y Since theY control reservoir |35 is connected to
Volume belowj the relay piston 45, the effect
to the
of this release of pressure upon the operation
r55
of the Vrelay valve section I8 is more gradual
than were the vadditional volume of the control
reservoir not present. As a result, the relay
valve'section functions to release pressureirom
the lbrake cylinder more gradually, because the
piston 45 moves slowly downwardly to only par
tially, or crack, open the exhaust passages 54.
' -As the rate of retardation diminishes due to
60
this release of pressure from the brake cylinders,
the pendulumV |66 swings back to the right until
contact |68 disengages from contact |1I. Each
release valve |43 will then be seated and theY parts
65
of each control valve device will again assume lap
position, .with the cut-off valve piston |21 re
maining in lower position.
'
_ 7 vAs the speed of the vehicle diminishes, the co
will be maintained.
Y
YIf when the retardation controller contact |68
disengages from the contact I1 I, the release valve
|43 should fail to be seated, then a total release
of the brakes would result were it not for the
limiting valve |49. When the pressure acting
on valve |49 from passage |48 falls below a pre
determined value, corresponding to the upward 10
force exerted by spring |50, the limiting valve |49
will be seated, and sufficient pressure is thereby
maintained in the volume below relay piston 45
to insure that the train will be brought to a
stop.
15
When it is desired to effect a release of the
brakes following a service application, the brake
valve device is operated to “Release” position,
whereupon the self-lapping magnet Valve wind
ing 4Gillis deenergized and a total release of fluid 20
pressure from the brake cylinder is effected.
If at the time the brake valve handle is moved
to release position, the pneumatic cut-off valve
piston |21 should be in its lowermost position, the
operator may open switch |65 in the circuit to the 25
retardation controller device and full control of
the brakes will then be transferred to the brake
Vvalve device I4.
Auxiliary service application
30
In case of failure of the electropneumatic con
trol in effecting an application by straight air
operation, a service application by automatic op
eration may be effected by movement of the
brake valve handle to “Automatic service” posi 35
tion. In this position, rotary valve |51 discon
nects the brake pipe from the feed valve device
I6I, and connects the brake pipe to the atmos
phere through a port having a restriction |88
therein. The brake pipe is thus vented to the at 40
mosphere at a service rate.
Y
As before explained, a service rate of brake
pipe reduction causes the automatic valve piston
88 in each control valve device to move to service
position, to effect a supply of iiuid under pres 45
sure from the connected auxiliary reservoir IIO
to the volume below relay piston 45, in accordance
with the degree of brake pipe reduction. The
flow from the auxiliary reservoir II!) is through
pipe and passage I II, slide valve chamber 85, 50
slide valve port II2, and from thence to both
the volume reservoir 99 and the double check
valve chamber I8 I. From the double check valve
chamber I0 I, the flow is to the under side of relay
piston 45 through the same passages as previously 55
described for a straight airservice application.
After a predetermined pressure has been es
tablished in the volume below the relay piston 45,
_the inshot valve piston II9 operates as before to
60
seat the ball valve II1.
n The volume reservoir 99 is provided to permit
a more ñexible control of the pressure of fluid
supplied to the volume below relay piston 45
through operation of the automatic valve section
22. If the volume reservoir 99 were not provided,
the pressure effected below relay piston 45 would
eiìcient ofA friction between the rubbing parts of
bear a relation to brake pipe pressure reduction
the brakes increases, so that the rate of retarda
much higher than in present standard equip
ments, and light applications of the brakes could
not be effected. By introducing additional vol 70
70 tion tends to increase.
When this takes place,
the pendulum |66 willagain swing to the left
toreffect a further release of iluid pressure from
thebrake cylinders. Since for each release ef
fected by theretardation controller device, the vol
of the control reservoir |35 is added to the
76 ume
volume below the relay piston 45, the variations
ume a given reduction in brake pipe pressure will
effect a pressure below relay piston 45 more nearly
in accordance with the ratio in standard auto
matic brake systems.
„
Now since the flow of fluid under pressure to 75
2,055,106
the'under side of relay piston 45 passes through
the pneumatic cut-off valve section 24 for either
straight air operation or automatic operation, it
where, as' before described, each winding 64 ‘is de
energized and each automatic valvepiston 88 is
follows that the retardation controller device I6
will function to control brake cylinder pressure
for both modes of operation, and as described in
While the' operation of the embodiment illus
connection with service `applications by straight
' air operation,
Therefore, if the rate of retarda
tion during automatic operation becomes great
enough, the retardation controller device I6 will
take control to limit the rate as already described.
When it is desired to effect a release of the
brakes following an automatic application, the
brake valve handle is moved to “Releaseï’ position,
15 where the brake pipe is again connected to the
feed valve device and brake pipe pressure restored.
The automatic valve piston 88 is then actuated
to lower position and slide valve cavity-94 con
nects the volume below relay piston 45 and‘vol
ume reservoir 99 to passage 95 and pipe 96 lead
ing to the atmosphere.
`
At the same time, port |03 in slide valve 86
registers with passage |04, so that the now high
er brake pipe pressure unseats the fast recharge
25 valve |06, and fluid under pressure flows past 'this
unseated valve through passage |04 and port |63
to slide valve chamber 85, from whence it flows
to the auxiliary reservoir |-|0. The auxiliary res
ervoir is thus recharged at a rapid rate, and
30 when the pressure in the reservoir reaches a pre
determined value, the fast recharge valve |06
seats, and further charging of the auxiliary reser
voir takes place through the charging groove
|11.
35
Emergency application
When it is desired to effect an emergency appli
cation of the brakes, the lbrake valve handle is
moved to the position indicated as “Emergency”.
40 In this position, full strength current will bersup
plied to each self-lapping magnet valve winding
64, and the brake pipe will be vented to the at
mosphere through an unrestricted port |82 in the
rotary'valve |16.
'
actuated to lower position.
'
trated has been described in connection with op
eration from one end only, it will be quite appar
ent that another brake valve device |4`may be>
provided at the rear end of the train and similar
connections made as for the brake valve device
at the >head end of the train, so that if ‘it is de 10
sired to operate the train in either direction, con
trol from either end may be effected.
- <
«
.
While I have illustrated and described one par
ticular embodiment of my invention, Vit will be
quite apparent to those skilled in the art that 155
many changes therein and modifications thereof
may be made, and I do not wish to be limited to
the speciñc embodiment shown, or otherwise than
by the spirit and scope of the appended claims.
I-Iaving now described my invention, what I 20
claim as new and desire to secure by Letters `Pat
ent, is:
1. In ‘a vehicle or train braking system, th
combination with a brake <cylinder and a reservoir,
of a valve device operated upon an increase in
pressure for effecting a supply of fluid under
pressure from said reservoir to said brake cylin
der, an electrically operated valve device for con
trolling a communication through whichlñuid
under pressure is supplied to operate said first 30
valve device, an automatic'valve device for con
trolling a second communication through which
fluid under pressure is also supplied to effect
operation of said first valve device, a fluid pres
sure operated cut-off valve device'for controlling 35
the supply of fluid under vpressure through both of
saidV communications, a retardation controller
device, and means controlled by said retardation
controller device for controlling'said cut-off valve
device.
`
f
device for controlling the -supply of fluid under
pressure to said brake cylinder, a reservoir, means
Each self-lapping magnet valve device will op
erate to supply fluid under pressure to the under
side of each relay piston 45 to a maximum degree.
`At the same time, the emergency reduction in
brake pipe pressure will cause each automatic
450 valve piston 88 to move to emergency position, to
also supply fluid under pressure from each auxil
iary reservoir | IS to the under side of each relay
piston 45 to a maximum degree. Since the flow
from the self-lapping valve section and from the
Vestablishing a communication`~ having'parallel
automatic Valve section are both to the double
check valve chamber lill, it will be obvious that
r3. In a vehicle brake system, the combination
with a brake cylinder, of a pressure operated valve
device for _controlling the supply of fluid under
only the supply which dominates in pressure will
reach the relay valve section.
>
Thus during an emergency application,
a
60 double supply of fluid under pressure to operate
each relay valve section is available, thereby en
suring that fluid under pressure will be supplied
to the brake cylinders to a maximum degree. ' It
will be noted however, that in both straight air
65 and automatic applications fluid under pressure
is supplied to the brake cylinders from the sup
ply reservoirs 3B only.
‘
During an emergency application, each inshot
valve section will function as Vheretofore de
scribed, and likewise, the retardation controller
device I6 will also function to limit the maximum
rate of retardation.
À
40
2. In a train braking system,'the `combination
with a brake cylinder, of a pressure operated valve
45
branch` paths between said reservoir and said
pressure operated valve device, an electrically
controlled valve device for controlling the supply
of fluid under pressure through said communica
tion, al valve device in‘one of said branch paths 50
operated upon af predetermined pressurefor clos
ing- said path, and Va second valve device in said
other branch> path operable by brake cylinder
pressure for closing said other branch path,
d
55
pressure to said brake cylinder, means establish
ing a communication havingv parallel branch 60
paths to said pressure operatedvalve device, an
electricallyV controlled valve device Vfor controlling
'the supply of iluid'under pressure through said
communication, a normally open valve device in
one of said paths and operated at a predetermined 65
pressure toclose said path, >a reservoir, and a
second valve device in the other of said branch
paths and operable to close said path and to con
nect said reservoir to said pressure operated valve
device.
f
d
‘
‘ '
4. In a train brake system, the combination
with a brake cylinder, of a relay valvedevice
for controlling the supply of ñuid under pressure
70
to and its release -from said brake cylindenmeans
When it is desired to effect a release of the
brakes following an emergency application, the
for effecting a supply of fluid >under pressureV to
brake valve device is moved to “Release” position,
said relay device to effect operation thereof, an
75
8
2,055,106l
electrically operated release valve device oper
able to effect a release of iiuid pressure from said
relay valve device, a control reservoir, and means
normally isolating said reservoir and operable to
connect said reservoir to said relay valve device
` before said release valve device is operated to re
lease iiuid pressure therefrom.
5. In 'a train brake system, in combination,
a brake cylinder, a valve device operated by the
10 supply of ñuid under pressure thereto for con
trolling the supply of fluid under pressure to and
its release from said brake cylinder, means for
establishing a communication throughv which
fluid under pressure is,` supplied to operate said
115 valve device, a second valve device controlling
said communication, said second valve device
having a piston subject on both sides to brake
cylinder pressure, an electrically operated valve
device lfor reducing the pressure on one side of
20 said piston, and a retardation controller device
for controlling said electrically operated valve
device.
6. In a train brake system, in combination, a
_brake cylinder, a relay valve device operated ac
25 cording to the supply of liuid under pressure
thereto for controlling the supply of iiuid under
pressure to and its> release from said brake cyl
inder, means for establishing a communication
through which iiuid under pressure is supplied to
30 operate said relay valve device, a cut-olf valve
device having a piston normally subject on both
sides to brake cylinder pressure and operable
when the pressure on one side of said piston is
reduced to close said communication, an elec
trically operated valve device operableto reduce
the pressure on one sideof said piston, an elec
device is operated to release ñuid pressure from
.said relay valve device.
9. In a train brake system, in combination, a
brake cylinder, a relay valve device for control
ling the supply of fluid under pressure to and
its release from said brake cylinder, means for
effecting a supply of fluid under pressure to op
erate said relay valve device, a valve device hav
ing a piston normally subject on both sides to
brake cylinder pressure for controlling said last
supply, electroresponsive means for diminishing
the pressure on one side of said piston to cause
said valve device to cut ofi said supply, a second
electroresponsive means operable to reduce the
pressure of said supply to said relay valve device,
a. retardation controller device Vcontrolling said
two electroresponsive means, and a limiting valve
device operable to limit said reduction of pres
sure.
10. In a train brake system, the combination 20
with a brake cylinder, of a relay valve device
having a piston operated upon an increase of
pressure on one side thereof to effect a supply
of fiuid under pressure to said brake cylinder
and operated upon a reduction in pressure on 25
said side for effecting a release of pressure from
said brake cylinder, means for eiîecting a sup
ply of fluid under pressure to one side of said
piston, means for reducing the pressure of fluid
supplied to said side of said piston, a reservoir 30
normally charged to brake cylinder pressure, and
means operable to connect said reservoir to said
side of said piston when said releasing means
is operated to reduce the pressure on that side.
11. In a train brake system, the combination 35
With a brake cylinder, of a relay valve device
trically operated release Valve device operable
controlling the supply of fluid under pressure
to diminish the pressure of fluid supplied to op
to and its release from said brake cylinder, said
relay valve device being operated upon a supply
of iluid under pressure thereto to eiîect a supply 40
of iiuid under pressure to said brake cylinder
and being operated upon a reduction of the pres
erate said relay valve device, and a retardation
controller device for controlling operation of said
electrically operated valve device.
7. In a train brake system, in combination, a
brake cylinder, a relay valve device operated ac
cording to the supply of fluid under pressure
45 thereto for controlling the supply of fluid under
pressure to and its release from said brake cyl
inder, means for establishing a communication
through which fluid under pressure is supplied
to operate said relay valve device, a reservoir, a
second valve device controlling said communica
tion to said relay valve device and having a pis
ton normally subject on both sides to brake cyl
inder pressure, a magnet valve device operable
when energized to reduce the pressure on one
55 side of said piston, said second valve device be
ing operable thereupon to cut oiî said commu
nication to said relay valve device and to connect
said reservoir to said relay valve device, and a
retardation controller device for controlling said
60 magnet valve device.
Y
8. In a train brake system, in combination, a
brake cylinder, a relay valve device operated ac
cording to the supply of fluid under pressure
thereto for controlling the supply of fluid under
pressure to and its release Vfrom said brake cyl
inder, means for eiïecting a supplyV of fluid under
pressure to said relay valve device, a release
valve device operable to release fluid pressure
from said relay valve device, a control reser
70 voir normally charged to brake cylinder pres
sure, a retardation controller device for con
trolling said release valve device, and means con
trolled Vby said retardation controller device for
connecting said control reservoir to said relay
75 valve device before said release magnet valve
sure of the supply to effect a release of pressure
from said brake cylinder, a retardation controller
device, means operated by said retardation con 45
troller device at one rate of retardation for re
ducing the pressure of fluid supplied to said re
lay valve device, and means operated by said re
tardation controller device at a lower rate of
retardation for controlling the rate at which 50
pressure is reduced in said relay valve device.
12. In a train brake system, the combination
With a brake cylinder, of a relay valve device op
erable to control supply of fluid under pressure
to and its release from said brake cylinder, said 55
relay valve device being operated upon a supply
of fluid under pressure thereto to effect a supply
of liuid under pressure to said brake cylinder and
operated upon a reduction in the pressure of iiuid
supplied thereto for eiîecting a release of pres 60
sure from said brake cylinder, a reservoir nor
mally charged to brake cylinder pressure, a re
tardation controller device having two normally
open contacts, means operated upon closing of
one of said contacts for cutting off the supply 65
to said relay valve device and for connecting said
reservoir thereto, and means operated upon clos
ing of said other contact for reducing the pres
sure of fluid supplied to said relay valve device.
13. In a train braking system, in combination,
a brake cylinder, a relay valve device controlling
the supply of fluid under pressure to and its re
lease from said brake cylinder, means for estab
lishing Ya communication having parallel branch
paths through which ñuid under pressure is sup
9
2,055,106
plied to operate said relay valve device, an inshot
valve device controlling one of said branch paths
and operated upon a predetermined pressure to
close said path, a cut-01T valve device having a
piston normally subject on both sides to equalized
pressures and operated upon a reduction in pres
sure on one side for closing said other branch
path, a selective valve device controlling the sup
ply of fluid under pressure through said com
10 munication, said selective valve device having a
chamber to which fluid under pressure may be
under pressure supplied to effect an application
of the brakes, said self-lapping and triple valve
sections being operable to eiïect separably or con
currently a different supply of fluid under pres
sure to said relay valve section through a com
munication having parallel branch paths, said
double check valve being operable to select be
tween said two supplies, said inshot valve sec
tion controlling one of said branch paths, and
said ñuid pressure operated cut-oir valve section 10
controlling the other of said branch paths.
supplied from a plurality of sources, means for
16. A control valve device having an electrical
electro-pneumatically eiïecting a supply of fluid
under pressure to said chamber, a brake pipe,
ly controlled self-lapping section, a relay valve
15 means operated upon a reduction in brake pipe
pressure for effecting a supply of fluid under
pressure to said chamber, and a brake valve de
section, an automatic valve section, an inshot
valve section, a cut-off valve section, a magnet 15
valve section, and a limiting valve, said control
valve device having a communication with two
vice operable to control said electropneumatic
branch paths leading from said self-lapping and
means and operable to elîect reductions in brake
trically controlled self-lapping section, a relay
automatic valve sections to said relay valve sec
tion, said inshot valve section controlling one of 20
said branch paths and said cut-01T valve section
controlling the other of said branch paths, said
valve section, an automatic valve section, an in
shot valve section and a iluid pressure operated
magnet valve section controlling operation of said
cut-off valve section and being also operable to
20 pipe pressure.
14. A control valve device having an elec
25 cut-off valve section, said relay valve section be
ing operable to control a ilow of fluid under pres
sure supplied to eiïect an application of the
brakes,Y said self-lapping and automatic valve
sections being operable to control a communi
30 cation having branch paths leading from said
two- sections to said relay valve section, said in
shot valve section being operable to control one
of said branch paths, and said fluid pressure op
erated cut-off valve section being operable to con
35 trol the other of said branch paths.
15. A control Valve device having an electri
cally controlled self-lapping section, a relay valve
section, a triple valve section, an inshot valve
section, a fluid pressure operated cut-off valve
40 section, and a double check valve, said relay valve
section being operable to control the ñow of iluid
release fluid pressure from said relay valve sec
25
tion, and said limiting valve being operable to
prevent release of pressure from said relay valve
section by said magnet valve section below a pre
determined value.
17. In a vehicle brake system, in combination, 30
a brake cylinder, means for eiîecting a supply
of ñuid under pressure to said brake cylinder,
means operated according to the rate of retarda
tion of the vehicle, and means responsive to op
eration of said last means at a chosen rate of 35
retardation for eiîecting a release of fluid under
pressure from said brake cylinder and for con
trolling the rate of release according to the exist
ing brake cylinder pressure.
ELLIS E. HEWITT.
40