Note: Descriptions are shown in the official language in which they were submitted.
~18'7~i~
IMPROVE~5ENTS I~ COMB IN13D AIR
RESERVOIR/BRAKE; CYLI.NDlE:R DEVICE
BACKGROU~D OF THE lN v~;N~ oN
United States Patent No. Re. 30,408, reissu~d September
30, 1981, to the assignee of the present applicationO dis-
c~oses railway br~ke apparatus including a brake cylinder
device and a control valve de~ice. The usual air reservoirs
associated with conventional pneumatic brake e~uipment are
eliminated in the disclosed apparatus in favor of storing
the compresæed air within the brake cylinder de~ice it~elf~
The brake cylinder device embodi s a pair of tandem,connected
pistons of unequal diameter, the larger piston cooperating
with the brake cylinder body to form on the respective oppo~
site side~ of this piston two chambers that are charged with
compressed air via the train brake pipe, and in w~ich chaD,
bers the air required for use by the brake apparatus, includ-
ing the brake c~linder device, is stored. The aforementioned
control ~alv~ device operates in response to variations in
the train brake pipe pressure to control the trans~er of air
stored in the brake cylinder d~vice, so as to develop dif~er-
ential forces across the respective pistons thereof, and
thereby effect a brak~ application and brake release~
In addition to the typical packing cup type pressure
seals as~ociated with the respective pistons of this brake
c~linder deviceO there are several additional axeas in which
dynamic sealing is required, all of which are critical in
the sense that leakage thereat a~fects the desired operation
of the brake cylinder device~
5~
Fuxther, passageway are required in the body of the
brake cylinder devi~e to conduct pres,sure bekween the con-
trol valve device and brake cylinder operating components.
It is well known that the expense in the manufacture of a
casting increases with the complexity in the configuration
of these passages, as well as in the shape of the casting
itself.
SUMMARY OF THE l~v~ ON
It is an object of the present invention to provide an
improved brake cylinder device of khe combined brake ~ylinder
and air reservoir t~pei in which the construction o the
brake ~ylinder device is such as to reduce the number of
dynamiz seals heretofore required, in order to reduce the
cost o the brake cylinder device and further to attain im~
proved operating reliability and service life with less main-
tenance.
Another objact of the invention i.s to design the brake
cylinder device to employ a sLmplified main body cast~ng to
which the brake cylinder control valve device may be direct-
ly mounted and in which all of ~he passages conducting ~luidpressure between the control valve device and the brake cyl-
inder pres~ure ~h~m~rs are contained.
In accordance with a preferred e~bodiment of the present
invention, the brake cylinder devic~ comprises a main body,
which may be a casting in which is formed a first cylinder
having opposike end walls, each with an opening kherein.
Connected to the main body casting about the opening in the
- 2 -
t~
one end wall of the first cylinder i~ a second smaller cyl~ ¦
indar that i8 closed at one end and is coaxial with the
fir~t cylinder. A larger and a smaller piston abutment is
operatively dispo~ed in the respectiv~e first and second cyl-
inders. The larger piston ab~LI,~el-t includes a hollow piston
rod that extends through the opening in the other end wall
of the ~irst cylinder, thus admitting atmospheric pressure
to the area of the larger pi~ton wi*hin the area of the
hollow piston rod. The first cylinder i~ ~eparated ~y the
larger piston a~u~ nt into first and second chambers in
which fluid under pressure i~ normally stored. The small~r
piston ab~.,c.lt is provided with an elongated body that 2X
tends through the opening in the one end wall o~ the first
cylinder for connection with the larger piston abutment, 80
as to ~r.~m a dual-connected piston assembly. Being ~o con-
nected to the larger piston abutment~ which is guidably sup-
ported in the ~irst cylinderO the smaller piston abutment is
arranged in the ~econd cylinder, ~o that an annular space is
formed between the elongated body of the smaller piston abut-
ment and the ~cond cylinder. The annular space is delimitedat one end by the pressure h ad of the second cylinder and at
the other end by a seal fixed to the main casting at the open-
ing in the one end of the first cylinder. m is seal engages
the elongated body of the smallex piston abu~ent where it
~5 passes through the opening for connection with the larger
piæton~ thus providing a pressure s~al between the ~irst
chamber and the annular space forming a third chamber to
- 3 -
'75~
which air is connected from the first chamber vi.a a contro~
~alve device to effect movement of the dual piston assembly
to brake application position~
The ~ontrol val~e device is mounted to the brake cyl-
inder at a mounting boss formed on t'he main ca~ting. The
fixed location of ~he seal in the main casting, and the
mounting of the control valve to the brakP cylinder at the
main casting makes possible the use of a passa~e ext~n~;ng
directly from the ~rake cylinder/control valve inter~ace to
the third chamber to control pressuri~ation thexeof. In
addition, the other passage~ transmitting pressure to and
from the irst and second ~h- '-crs via the control valv~
device are also contained solely in the main casting~ Con-
sequently, no passage~ are re~uired in the other parts of
the brake cylindar device, which is therefore more econom~
ical to build.
In addition, a second pressure seal is provided between
the hollow piston rod and the op~n~ ng in the other end of
the first cylinder. The first and second pressure seals
have equal sea~ing diameters, such that the atmospheric
area o~ the larger piston within the hollow piston gulde
is egual to the effective pres~ure area of the smaller
piston within the third chamber. This arrangem~nt opti-
mizes the sealing requirement and brak.ing force capability.
Furthermore, the elongated body of the smaller piston
abutment may be tubular, with one end dosed~ pen end
i3 connected to the laxger piston abu~nent to provide a
-- 4 --
'7~
~ourth pres~ure chamber within the elongated tubular body
and is in fluid pressure commllnlcation with the irst pres-
sure ch~mber. This pr~sur~ effectlve in the fourth rhamber
acts on opposite and equal pressure areas of the ~maller and
larger piston abubme~ts and thus exerts no net directional
force on the dual piston asse~bly. Conseguently, an addi~
tional volume i~ gained for the storage of air supplied to
the first chamber without any pressure force beiny developed
on the dual piston a~embly in opposition to the pre~sure in
th~ third chamber urging piston ~.lo~e...ent in the brake appli-
cation direction.
It is also noteworthy that this internal pressure tPnds
to force the two piston abutments apart and this tension
tends to ~lo...oLe favorable aligr--~ts of the dual piston
axis with the c~linder axis.
33RIEF DESCRIPTIO~ OF ~E DRl~WING
~ hese and other o~ects and attendant advantages will
appear in the following more detailed ,p~rl~n~tion of the
~ single figure drawing showing a cross-section assembly view
0 of the brake cylinder de~ice of the present invention.
n~ TpTIo~ AND OPERATION
~ he pre~erred embodiment comprising an i.~ o~ed brake
cylinder device la of the present i~vention includes a main
body memher 1, which may be a ca~ting :Eorming a power cylin-
der 2 with a pressure head 3 ha~iny a central opening 4formed therein, and a positioning cylilldex 5 ha~ing an in~
tegral pressure head 6 conne~ted, as by cap scr~ws, to
pressure head 3 of the power cylinder~ so as to enclose the
opening 4. Power cylinder 2 and posilioning cylinder 5 are
coaxially axranged to receive a dual piston assembly compris
ing a power piston 7 operatively disposed in power cylinder
2, and a positioning piston 8 operatively disposed in posi-
tioning cylinder 5. An end cover 9 is co~nected, as by cap
scxews 10 to the left~hand end of main casting 1, ~o aæ to
surround posi~ in~ cylinder 5 and fo~m a pressure chamb~r
11 therebetween. Sealingly connected to the righ~hand end
of main ca~tlng 1 by cap ~crews 12a is an end cover 12 having
a central opening 13 through which a hollow rod 14 of power
piston 7 projects. The connectior. of hollow rod 14 with
p~wer piston 7 may ba ~y screw threads, as shown. Disposed
within hollow rod 14 i~ a piston push rod 15 haviny one end
lS pivotably engaged with an arcuately-shaped end piece 15a of
power piston 7, and the opposite end projecting beyond the
extremity of hollow rod 14 for connection with conventional
brake apparatus.
Po~itioning piston 8 is in the form of an elongated, tu-
bular body, one end being closed by a head 16 and the opposite
end open. Head 16 forms on the right-hand side thereof a posi-
tioning pressure area. The open end of tubular positioning
piston 8 fits over a flange 17 that projects coA~;~lly from
the left-hand face of power piston 7. Flange 17 and the open
end of the positioning piston are fo~oed with aligned holes
18 in which roll pins 19 are pressed to connect th~ power
piston and positioning piston together or movement as an
6 --
integral unit. The tubular shape of positionir,g pis~on 8,
being closed at one end~ forms a holl~w interior which, when
connected with power piston 7, forms a pressure chamber 20
therabetween. In addition, positioning piston 8 is disposed
within positioning cylinder 5 in spaced-apart relationship
therew.ith, the space between the piston and cylinder form.ing
a pressure chamber 21. A pressure type seal 22 i5 fixed to
pxessure head 3 of main casting 1 by means of an annular
clamp ring 23 and screws 24, so as to surround openin~ 4 and
sealingly engage the periphery of the tubular bod~ comprising
po~itioning piston 8. In the extreme leftward or brake re-
lease position, as shown, seal ~2 engages the periphery o~
piskon 8 near its open end and maintains constant ~ealing
engagement therewith during rightward l-.o~ .Pnt of the piston
ass~mbly t~ward br~ke application position. The continuou~
sealing efect of seal 22, therefore, establishes and main-
tains a fluid pressure seal between pre~sure ~h~e~ 20 and
another pressure chamber 25 formed between pressure head 3
and the left-hand side of p~wer piston 7 to thereby delimit
an application pressure area of power piston 7. Pressure
chamber 25, on the other hand, is in constant fluid pressure
c~mm~lnication with pressure chamber 20, by way of the through
openings of the respective roll pins 13.
Formed between the right hand side of power piston 7
and end co~er 12 is still another pressure chamber 26, which
delimits a release pressure area of powsr piston 7O A retu.rn
~pring 27 is disposed in chamber 26 with one end supported by
-- 7 ~
~Lt~ 75~
end cover 12 and the other end acting on power piston 7 to
urge ~he power piston toward its extreme leftward or brake
release position. A pressure type packing cup seal 27a is
arranged on piston 7 to engage power c~linder 2 and effect
a fluid pressure seal between pressure chambers 25 and 26.
An annular element 27b, preferably made of a rubber or
plastic material, lockingly engages piston 7 and seal 27a
to secure the seal in place and to further serve as a cushion
stop to esta~lish t,he ~xtreme leftward or release position of
the piston asse~bly by engagement with pr~ssure head 3. In
order to establish fluid pre~sure across the entire applica-
tion pressure area of piston 7, the stop abutting portion of
element 27b is fluted, as shown. An annular gu.ide ring 28~
preferably of a long wearing plastic material is arranged in
the periphery of power piston 7 to also engage power cylinder
2 and therehy support the pswer pi~ton concentrically within
the cylinder bore.
End cover 12 is furthQr formed with an inwardly extend-
ing annular guide flange 29 in surrounding relationship with
central opening 13 in end cover 12. Power piston 7 i~ pro-
vided with an inwardly extending annular projection 30 that
lies concentrically within the annulus of guide flange 29.
The end o projection 30 cooperates with an annular end plate
31 to support a pressure type packing cup seal 32 r as well as
an annular guide ring 33, each of which engages the inner
peri.phery of guide flange 29. Pac~ing cup 32 establishes a
fluid pressure ~eal between pressure cha~ber 26 and an
- 8 -
~ 77 ~7~
atmospheric chi~mber.3~ fo~med within the annuli of the annu-
lar guide flanga 29 and projection 3n. Chambar 34 delimits
a return pressure area on power piston 7. Guide ring 33 aids
guide ring 28 in supporting the piston assembly and maintain-
ing concentricity of pistons 7 and 8 within their respectivecylinders 2 and 5 during i~xial movement of the piston asse~bly.
Within the annulus of opening 13 in pressure head 12 i~
a scraper ring 35 that engages the periphery of hollow rod 14.
An annular filter element 36 is carried in the i~nnular spac~
of chamber 34 between projection 30 and hv110~7 rod 14, with
one end abutting a plurality of reinforcing ribs 37 of pro-
jection 30. The ~ilter element 36 is held in place against
ribs 37 by the end plate 31, which is provided with passages
39 tharein. A lock ring 40 abuts end plate 31 and is welded
or otllexwi~e cli~mped to holl~w rod 14 to secure the filter
and end plate for movement with power piston 7 and hollow rod
14. On the left_hand side of filter element 36 i6 provid~d a
plurality of holes 41 in hollow rod 14. Surrounding the ex~
~ernal end of holl~w rod 14 in spaced-apaxt relat;o~.~hip with
end cover 12 i~ a collar 42 that is he:Ld in place by scr~w
pins 43 that are scr~w-threaded in col:Lax 42~ Screw pins 43
are formed with a pin-like end adapted to enter conforming
holes in the end of the hollow rod 14 to lock the collar in
place.
Main casting 1 further includes mounting bo~s 44, one
face 44a of which is adapted to receive the corresponding
face of a control valv~ 45 or the like~ ~ich may be of the
5~
type similar to the control valve device 6 shown and dis-
closed in U.S. Patent Re. 30,40~ or similar to the control
valve device disclosed in U.S. Paten-t NoO 4,339,155, both of
which are assigned to the assignee of the present invention.
S In so arranging the brake cylin~er and control vaLve devices
as a unit assembly, external pipin~ heretofore required be-
tween the brake cylinder and control valve devices is elimi-
nated. A plurality of passages 46, 47, 48, and 49 extend
from face 44a of mounting boss 44 directly into -the respect
ive pressure chambers 11, 21, 25, and 2~. Another face 44b
oE boss ~4 is arranged to receive a branch pipe 51 of the
train brake pipe, which may be mollnted to face 44b in a con-
ventiGnaL manner. A passage 50 in boss 44 extends between
the brake pipe mounting face 44b and the control valve
mounting face 44aO Finally a cavity 52 is formed in boss 44
at the control valve mounting Eace ~a. When connected in
place, control valve device 45 closes cavity 52 to for~ a
pressure chamber to which air may be supplied via a passage
53 in control valve 45.
A train equipped with brake apparatus includins a brake
cylinder device in accordance with the present invention re-
quires no externaL reservoirs for the storage of compressed
air, thereby further eliminating a need Eor external piping~
except a branch pipe between the train bxake pipe and the car
control valve device. When the train is charged, air is con-
nected from the brake pipe and the branch pipe 51 at each car
to passage 50, from where it is connected to the control vaLve
~ 10-
45 mounted on the brake cylinder at mounting boss 44. Con-
txol ~alve 45 is conditioned by the increase of brake pipe
pressure to charge via passages 46, 48) and 49 the various
chambers 11, 25, and 26 of the brake cylind~r device, which
cha~bers are utilized for the storage of air, as well as or
providiny pneumatic braking power.
The effective area of power piston 7 subject to the
pneumatic pressure in chamber 26 is e~lal to the effective
area o~ piston 7 subject to the pneumatic pressur~ in chamber
25. With both cha~bers 25 and 26 being charged to the same
pressure~ that is, the pxe sure of the brake pipe, there is
conse~uently no net pneumatic pressure force exerted on the
brake cylinder piston a~sembly in either direction due to the
charging of chambers 25 and 26. Ch~mber 20 provides an addi-
tional volume into which the air stored in cha~ber 25 can flow
via the co~--nication provided by the conventional throu~h
passages in the several roll pins 19~ This pneumatic pres~
sure in chamber 23 likewise exerts no nPt force on the piston
aæsembly, due to the opposing effec~ive pressure areas of the
respective positioning piston 8 and power piston 7 subject to
the pnaumatic pressure in chamber 20 being equal, so that the
forces counteract. Accordingly, return spring 27 is ef~ective
to force the piston assembly to its laftward-most position in
which cll~h;on stop 27a engages pressure head 3, ther~by as-
tablishing brake release position of the respective positioning and power plstons comprising the dual piston assembly.
5~
At this point, it should ~e noted that the arrangement
of the present invention eliminates the need for a dynamic
seal to isolate the pneumatic pressure in chamber 25 from
the righ-t-hand side of the positioning piston, as required
in the arrangement disclosed in the aforementioned Reissue
Pa-tent No. ~e. 30,408 and U. S. Patent No. 4,339,155. This
is accomplished by connecting the power piston so that the
leftward-acting force of pressure in chamber 20 acting
on the positioning piston is balanced by a counteracting
force of pressure in chamber 20 acting on the power
piston.
When a brake application is desired, brake pipe pressure
is reduced in a well-known manner, in response to which the
car control valve device 45 operates to transfer air stored
in chan~er 26 to chamber 21 via passages 49 and 47. It will
be appreciated that the tubular-shaped positioning piston 8,
in addition to providing an annular space between it and the
positioning cylinder to form chamber 21, aLso permits pres-
sure seal 22 to be mounted on the main casting 1 for contin-
uous engagement with the tubular positioning piston through-
out the length of its stroke. This, in turn, permits passage
47 in main casting 1 to enter the annular space comprising
chamber 21 at a location just adjacent seal 22, in order to
effect pressurization of chamber 21. Accordingly, passage
47 may be formed antirely within main casting 1, so as to
enter chamber 21 directly from the face 44a of boss ~4~ This
represen-ts a significant improvement over the aforementioned
` r3` ';
~ - 12 -
758
arrangem~nt disclo~ed in U. S. Patent No. Re. 30~408, wh~rein
the design of the positioning piston and locakion of the
piston ~eal require~ a complex design and additional sealirlg
to provide a pa~sage to the positioning cylinder in order to
pressurize the face of positioning piston 8.
Pressuriæa~ion of chamber 21 with the pne~unatic pressure
stored in chamber 26 develops sufficient force on positicning
plston 8 to overcome the opposing ~orcs of return spring 27
and force the dual piston asse~bly to move in a rightward
direction to brake application position, In order to ac om~
modate this ~ v~r..ent of the piston assembly, the control valve
operates to allow the air in ~e reduc:lng volume of chamd~er 26
to equali~a into the ~ n~ing volume of cha~er~ 25 and 21
via passageæ 49 and 48.
In brake àpplication po~ition of the dual piston assembly,
the volume of chamber 26 is m;n~m; ~e~ and the control valve
operat~ to ter~in~te the transfer of air from ~ m~r 26 to
chamber 21, whila concurrently venting the aix from chamber
26 in proportion to the reduction of brake pipe pr~sure.
Accordingly, a pres~ure dif~erential is establi~hed across
power pi~ton 7 to exert an increased force on the dual piston
assembly, in addition to the force already exerted by the
pre~sure on posit;on; n~ piston 8, to obkain the desired
braking force. The m~;mllm pressure reduction in chamber
2~ 26 is limited to a predetermined value by the control valve
during a service brake application, thereby establishing a
m~ximllm brake orce during a ~ull service brake application.
_ 13 ;
s~
During an emergency brake ap~lication, the brake pipe
reduct7on occur~ at a rate that is greater than the rate of
reduction during a æervice application. ~hi3 emerg2ncy rate
of brake pipe reduction is sensed by the control valve,
which operates ~o completely vent the air in ch~mber 26 of
the brake cyl;n~er device and to concurrently connect the air
in ch~mber 11 to chamber 21 ~ia passages 46 and 47, whereby
the pressure in chambers 11 and 21 essentially equalize.
Accordingly, th~ pres~ure in chamber l:L acting on position-
ing piston 8 increases during an emergency application con-
currently with an increasad pressure d:ifferential created
acros~ power piston 7 to thereby cause the dual piston as~em~
bly ouL~u~ force during an emergency brake applicàtion to
~ee~ the m~imllm ~u~ orce capable o~ being ganerated
during a ~ull service brake application.
In a~plying the brakes during either a service or emer~
gancy brake application, it will be appreciated that the
volume of the posit;oni ng cylinder is increased to a nominal
value of only 140 cu. inO, due to the relatively small area
of positioning piston 8, so that only a small am~unt of air
is required to take up the brake rigging slack during move~
ment of the dual piston as~embly ~o braXe ap~lication posi-
tion.
It will be further appreciated, that in effectins move-
ment of the pi~ton assembly to brake application position,the volume of air in chamber 26 is decrea ed to a no~i n~ 1
value of 350 cu. in.~ ~o that in s~sequently providing
~ 1~ ...
output brake orce ~y venting chamber 26, the 108~ 0~ air i~
ml";m~
Thus, the m~x;m~m~l air loss duriny.a service brake appli-
cation i~ limited to the co~bined volwme of air in cllambers
11 and 26 in applicat.ion pos~tion of the dual brake assembly,
and i~ only slightly more during emerglancy. The pnaumatlc
afficiency of thls type braXe cylindex d~vice requires such
a small amount of air, therefore, that the brake cylinder
device itself can ~e used to ~tore the necessary compre~d
air without increasing the overall 9ize of the bxake c~llnder
relative to conventional single piston brake cylinders or
adding ~eparate reservoir volumes. In accordance with the
present invention, the design of this highly efficlent hrake
cylinder device is urther improved by min;m;7ing ~he re~uired
nu~ber of dynamic pres~ure seal~ and s.implifying the con~truc-
tion, particularly as to the main cast:ing which contains all
the pa~age~ 46, 47, 48O 49, and 50.
During a relaase of elther a service or emergency appli-
catlon, braXe pipe pressure i~ increased, such increase being
~ensed ~y the control valve, w~ich operates to exhaust the
pres~ure in ch~mber 21 via passag~ 47 while rechar~ing cham~
bers 11~ 25, and 26, as previously exp:Lained, to rees~ablish
a forc~ balance acros~ the piston assel~bly and thereby allow
return sp.ring ~7 to move the pi~ton asse~bly lef~ward to
brake release positiun.
During the a~orementioned applical:ion and release brak-
ing cycle, ~;o~e~.ent o~` the power piston projection 30 and
15 -
pressure seal 32 within guide flange 29, and l.-o~e-..ent of the
power piston hollow rod 14 within opening 13 of end cover 12
produces a pumping ~tion, ~y which means the air in atmos
pheric chamber 34 is expelled and drawn in alternately via
holes 41 and the open end of hollow rod 14 leading to atmos
phere. Air within atmospheric cha~ber 34 is conseguently
forced ~hrough filter element 36 to y~event the accu~ulation
of dirt on thê area o guide fl~nge 29 with which s~al 32 is
engageable, ther3by im~roving the reliability and extending
the service lifa of seal 32. Scrap~r ring 35 further acts in
a well-kn~wn m~nner to clean the surface of hollow rod 14 of
any dirt accumulated thereon when the hollow xod is extended
during brake applications, thereby furt:her preventing the
entry of dirt and foreign material into cha~ber 34.
~hen maint~n~n~e or rapair service is required, the dual
piston assembly may ba removed from main casting ~ with end
cover 12, as an integral unit by removi.ng cap screws 12a. As
the cap screws ~re unscrewed, end cover 12 is forced b~ æpring
27 apart from its sealed connection with main casting 1 ~mtil
the end cover at opening 13 engages the hollow rod collar 42,
thareb~ caging spring 27. ~he dual piston assPmbly is then
~ble to be ~ d with end cover 12 to facilitate servicingO
Although the foregoing preferred embodiment has been
described as employing ~wo intercormected pistonæ of differ-
ent sized cylinders, it is readily apparent that the twopistons may take the shape of a single piston having differ~
ent pressure areas constituting the two pistons 7 and 8.
16 -
For example ~ an alterna~e e~:~odiment of the invention
contemplates an actuator assembl~ in which three dynam.ic
pressure seals are arranged between the body of a ~ingle
cylinder and a sinyle piston of the brake cyllnder device.
~he first seal separat~s the cylinder into an application .
portion and a release portion on opposite sides of the piston.
~he second seal acts between the ~ylinder and a sleeve-like
projection on one side of the piston to separate the appli
cation portion into an application cha~ber and a positioning
chamber. Th~ application chamber delimits a first pressure
area on the one side of the piston and the posi tioning chamber
delimits a second pressure area al60 0~ the one side of the
piston. The sleeve-like projection may be closed at its and,
in w~ich case the area of the closed end constitutes the
second pressure area and the chamber within the sleeve_like
projection is ~omml-n;~ted with the application chamber. The
third seal acts between the cylinder and a push rod of the
piston to form a r~lease cha~ber that delimits a third pres~
sure area on the other side of the piston that is preferably
e~ual to the first pressure area on the one side of the piston,
in order to maintain the piston pressure balanced by 1uid
normally stored in the application and release chambers in
release portion of the piston. The push rod may be hollow to
orm a retuxn chamber on the same side of th~ piston as the
release chamber. This return chamber clelimits a fourth pres-
sure area on this same side of the piston that is preferabl~
equal to the second pxessure area on the one side of th~
piston O
-- 17 -
