Note: Descriptions are shown in the official language in which they were submitted.
lOSi489
SPECIFICATION
This application is a division of copending Canadian
application Serial No. 221,831 filed March 11, 1975.
This invention relates generally to a pneumatic brake
system and more paricularly to such a system as it relates
to the braking of a tractor-trailor vehicle parked and un-
parked positions.
This invention is particularly applicable to positive
air pressure brake systems used on tractor-trailer rigs and
will be described with particular reference thereto. How-
ever, it will be appreciated by those skilled in the art
that the invention has broader application and may be applied
in negative pressure (vacuun~ brake systems.
Vehicles in interstate commerce have become widely equ-
ipped with spring-set brake actuators to automatically in-
sure in a failsafe manner, braking of the rig if failure
occurs in the air brake system. Recent regulations have
also required that the brakes of both tractor and trailer
be set and released from their set position by a single
valve when the rig is parked and released from its parked
position. Several systems meeting these regulations have
beem promoted and are in use today. One deficiency of at
least one system in use today is that air pressure cannot
be supplied to the -trailer unless the tractor and trailer
brakes are released. Thus, air operated devices such as
tailgate lifts which are actuated by compressed air from
the trailer air brake system cannot be operated. To over-
come this deficiency, certain brake arrangements have been
employed which do permit air to be supplied to the trailer
while the rig remains parked. However, in each of these
installations the trailer brakes must be released while the
tractor spring-set parking brakes remain set for braking the
rig. Such systems have not been acceptable for sorne special
1489
purpose tractor-trailer c~inations which require
that both tractor and trailer b~kes remain set
while air operated devices on the trailer are used.
1.
:`
- la -
:~051~89
It is thus an object of the subject invention to pro-
vide a braking system on tractor-trailer combinations using
spring-set brake actuators on the tractor which permit trac-
tor parking and trailer service brakes to be set while a
source of pressurized fluid is supplied to the trailer.
'I'his object along with other features of the subject
invention is achieved in a braking system which employs
spring-set brake actuators on the tractor, either a conven-
tional trailer brake system utilizing an emergency relay
valve or a newer trailer brake system employing antilock
controlled service brake and spring-set parking brakes. A
conventional source of fluid "supply" and "signal" pressures
is supplied by the tractor and delivered to a unique valve
arrangement within the tractor brake system. The valve
arrangement includes a manually operable park valve having
an,applied or brake position which vents supply line press-
ures to tractor brake actuators and trailer supply line to
set tractor and trailer brakes and restores supply line
pressures to the tractor actuators and trailer system to re-
lease the brakes. Operatively associated with the park
control valve is an air control valve which is optionally
operable to a fill position. Associated with the park valve
and the air control valve are several valves which automati-
cally react in a predetermined sequence to the position of
the air control valve and the park valve. More specifically,
with the park valve in an applied position and the air con-
trol valve in a fill position,the automatic valves provide
certain fluid communication paths with the trailer arrange~
ment whereby supply pressure is directed to the service
line of the trsiler system to maintain the trailer brakes
in an applied position while the trailer system is pressur-
ized.
- ~ - 2 -
,
~0514~9
In accordance with another feature of the subject
invention, the afore-mentioned automatic valve mecha-
nisms cmd air control valve
- 2a -
- ~051~89
automatically react to movement of the park valve from its applied
to released position ~o simultaneously release both tractor and
traller brakes Release of tractor and trailer brakes occurs
even if the air control valve was not previously placed in ~ts
fill posltion. Additionally, the valve structure is sequenced to
provide all normal braking functions heretofore required in
braking systems in a manner which is characterized as being fail-
safe and foolproof.
The parent application, of which this is a division,
relates to an invention incorporating the first feature and thus
defines a vehicle brake system for braking a tractor coupled to
a towed trailer by means of a source of fluid supplied to the
system under supply and variable signal pressures, the trailer
adapted to be equlpped with associated, fluid-operated devices,
the system comprising: a plurality of spring-set brake actuators
on the tractor and trailer, each actuator having a first chamber
operable by the source under signal pressure to normally brake
the tractor and trailer, spring means operable in a release
position to brake the vehicle in an emergency condition and a
second chamber operable by the source under supply pressure to
, maintain the spring means in a compressed inoperable manner under
; normal operating conditions; trailer valve means on the trailer
including first and second brake lines and a relay valve, the
trailer valve means operable in a normal position by fluid under
supply pressure in the first line to communicate fluid in the
second line under signal pressure to the trailer brake actuators
and automatically shifted to an emergency position upon sensing a
drop in pres6ure of the fluid in the first line to actuate the
trailer brake actuators; a manually operable park valve on the
mb l~ap ~ 3
. .
.
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... . . . ~ .
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... : . . . .:: . .
.. .. ... . . . . ....
1051489
tractor having an inlet connected to the source under supply
pressure, an outlet and a vent, the park valve having a released
position communicating its inlet with its outlet and an applied
posit:ion communicating its outlet with its vent effective to
actuate the spring means; control valve means including a control
valve on the tractor having a first inlet in communication with
the source under supply pressure, a second inlet in communication
with the outlet of the park valve, and at least a first outlet,
the control valve means manually operable to a fill position when
the park valve is in its applied position to communicate the
first inlet with the first outlet of the control valve; automatic
valve means on the tractor in fluid communication with the outlet
of the control valve and in fluid communication with the trailer
valve means, the automatic valve means operable when the park
valve i8 in its applied position and the control valve means is in
its fill position to port fluid under supply pressure to both the
first and second brake lines of the trailer valve means whereby
the trailer brake actuators are actuated while the first line may
be adapted to simultaneously operate the associated devices; and
the trailer valve means includes a first reservoir, the relay
valve associated with the first reservoir and in communication with
the second chamber of the actuator and the first brake line, a
second reservoir and an antilock valve associated with the second
reservoir and in fluid communication with the second brake line
and the first chamber of the actuator, the trailer valve means
further operable with the control valve means in the fill position
and the park valve in the applied position to maintain the trailer
brake aetuators in a fully actuated position while the trailer
reservoirs are being pressurized with fluid at supply pressure.
b/~,J~ ~ - 3a -
.
. j . ~ .
.
.
' - '
iO514~39
The present application relates to an lnvention
incorporating the second feature and thus defines a vehicle
brake system for braking a tractor coupled to a towed trailer
by means of a source of fluid supplied to the system under supply
and variable signal pressures, the trailer adapted to be equlpped
with associated, fluid-operated devices, the system comprising:
a plurality of spring-set brake actuators on ~he tractor, each
actuator having a first chamber operable by the source under
signal pressure to normally brake the tractor and trailer, spring
means operable in a release position to brake the vehicle in an
emergency condition and a second chamber operable by the source
ùnder supply pressure to maintain ,he spring means in a compressed
inoperable manner under normal operating conditions; a plurality
of brake actuators on the trailer, each trailer actuator having
a service brake chamber effective to actuate the trailer actuator
when supplied with the source of fluid; traller valve means on
the trailer including first and second brake lines and a relay
valve, the trailer valve means operable in a normal position by
fluid under supply pressure in the first line to communicate
fluid in the second line under signal pressure to the trailer
brake actuators and automatically shifted to an emergency position
upon sensing a drop in pressure of the fluid in the first line to
actuate the trailer brake actuators; a manually operable park
valve on the tractor having an inlet connected to the source under
supply pressure, an outlet and a vent, the park valve having a
released position communicating its inlet with its outlet and an
applied position communicating its outlet with its vent effective
to actuate the spring means and shift the trailer valve means to
its emergency position; control valve means including a control
mb/~ 3b -
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.: .... : : . .. . ... . .
lOSl~9
valve on the tractor having a first inlet in communication with
the source under supply pressure, a second inlet in communication
with the outlet of the park valve, and at least a first outlet,
the c:ontrol valve means manually operable to a fill position when
the park valve is in its applied position to communicate the
first: inlet with the first outlet of the control valve; automatic
valve means on the tractor in fluid communication with the outlet
of the control valve and in fluid communication with the trailer
valve means, the automatic valve means operable when the park
valve i8 in its applied position and the control valve means is
in its fill position to port fluid under supply pressure to both
the first and second brake lines of the trailer valve means where-
by the trailer brake actuators are actuated while the first line
may be adapted to simultaneously operate the associated devices;
and the control valve means automatically disengages from the
fill posltion when the park valve is manually operated to the
release position, and the automatic valve means responds to the
movement~ of the park valve and the control valve means to vent
fluid at supply pressure from the second brake line.
2~ The invention may take physical form in certain parts
and arrangement of parts, a preferred embodiment of which will
be de~cribed in detail herein and illustrated in the accompanying
drawings which form a part hereof and wherein:
Figure 1 is a schematic diagram of the brake system of
the sub~ect invention;
Figure 2 is a schematic illu~tration of an alternative,
but conventional, trailer brake system;
Figure 3 is a sectioned elevation view of the air
control vslve employed in the sub~ect inventlon, and
mb/~yJ ~ - 3c -
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105~489
Figures 4 and 5 are section views of two different
- valve~ employed in the brake sys~em.
Referring now to the dra~71ngs wherein the showings
are for the purpose of illustrating a preferred embodiment
of the invention only and
mb/ ~ ~ - 3d -
1051489
not for the purpose of limiting same, FIGURE 1 illustrates generally a
brake arrangement for a tractor-trailer vehicle including a tractor brake
system and a trailer brake system as designated, which are adapted to
be coupled to one another. Shown within dot-dash envelope 10 in the
tractor brake system is the specific valve arrangement of the subject
invention.
The rear brakes of the tractor are shown to be spring-set
actuators 12 of a known dual diaphragm type and will not be described in
detail herein. Briefly, each spring-set actuator 12 comprises a first
diaphragm 13 defining a service brake chamber 14 and a second dia-
phragm 16 defining an emergency brake chamber 17. Biased against
second diaphragm 16 is a compression spring 18 stored at one end of the
actuator. A push rod 19 extends from each actuator and in an extended
position applies the brakes of a vehicle (not shown) by a known slack ad-
~uster mechanism 20. Spring-set actuators 12 are operated during nor-
mal use of the tractor-trailer by admitting air at signal pressure into
service brake chamber 14 which acts against first diaphragm 13 to ex-
tend puah rod 19. Also durlng normal operation, air is admitted at sup-
ply pressure into emergency brake chamber 17 which forces second dia-
phrsgm 16 against spring 18 to maintain that spring in a compressed
position. When air is vented from emergency brake chamber 17, such
as when the vehicle is parked or when an air failure occurs, spring 18
extends push rod 19 to set the brakes.
A source of compressed air for activating the brake actuators is
supplied by the components shown within dotted envelope 21. Such com-
ponents include, generally speaking, a compressor 23 driven by the
tractor engine to supply air at a given pressure, controlled by governor
24, into a reservoir arrangement indicated generally at 25. Reservoir 25
_4-
lOS1489
is capable of maintaining air supplies at "supply" or "emer-
gency" pressure for brake system purposes which are associ-
ated with such terms as known in the art. An outlet line
26 form reservoir 25 communicates air at supply pressure to
a known treadle valve 27 which is turn communicates air at
"signal" or "control" pressure to serive brake chambers 14
of the spring-set actuators at the rear of the tractor by
line 28 and similarly communicates control pressure by line
29 to the tractor's front brake actuators 30 which are of
the normal air operated, single diaphragm type ("Signal"
or "control" pressures are terms known in the art for apply-
ing varying pressures to effect braking of~the vehicle dur-
ing normal operation and are used in that sense herein.)
Depressing treadle 27 varying degrees admits air at corres-
ponding pressures into ~er~ice brake chambers 14 of rear
tractor actuators 12 and front tractor actuators 30 via lires
28, 29 respectively and release of the treadle permits air
flow to reverse its direction and ~ent through treadle val~
27. In communication with line 29, as by a suitable T-conn-
ection, is a signal line 32 and upstream of treadle valve 27
is communication with line 26 is a supply line 33. Signal
and supply lines 32, 33 lead into valve system envelope lG
~ of the subject invention and extend out therefrom to the
i trailer system through suitable connections 34, 35 which com-
prise coupling means for coupling the trailer system to the
, tractor system.
¦ The trailer brake system shown in FIGURES l and 2 are
representative of typical systems. In FIGURE 1, an antiskid
trailer brake system utilizing spring-set, dual diaphragm
actuators 12 is illustrated. More particularly, trailer
supply line communicates with a primary reservoir 37 associ-
ated with the service brake chamber of the spring-set actua-
tor 12. Air at supply pressure is also communicated to a -
secondary reservoir 38 through line 44; secondary reservoir
~i 38 being
.,
-
1051489
associated with t~e emergency brake chamber of trailer
spring-set actuators 12. Air at signal pressure in signal
line 32 is in fluid communication with a known antilock
valve 39. Antilock valve 39 functions in a known manner in
accordance with signals generated from a wheel speed skid
indicator system (not shown) to port air at modulated or
unmodulated signal pressure through line 40 to the service
brake chambers of spring set actuktor l2. Air at supply
pressure in line 33 is communicated to a known relay-type
valve 41 which in its normal operating position permits air
at supply pressure from secondary reservoir 38 to be in
fluid communication through lines 42 to emergency brake cham-
bers of the spring-set actuators 12 and thus maintain actu-
ator springs in a compressed position. When a drop in pre-
ssure occurs in supply line 33, relay valve 41 will vent air
in lines 42 and the emergency brake chamber of the spring
set actuators. This will permit the springs to set the
brakes on the trailer vehicle. Upon restoration of supply
pressure in line 33, relay valve 41 delivers air from reser-
voir 38 to the emergency brake chambers of the spring-set
actuators, releasing same. In FIGURE 2, a second type of
conventional trailer brake system is illustrated. In the
system shown in FIGURE 2, the trailer brake actuators 203
illustrated are of the known single diaphragm~ air apply type~
The system more particularly includes an emergency relay
valve 200 which is connected to signal and supply lines 32,
33, a reservoir 201 and trailer brake actuators 203 connec-
ted to relay valve 200 through suitable line 204. Emergency
relay valve 200 functions in the usual manner to admit res-
ervoir air at ~ignal pressures to brake actuators 203 when
treadle valve 27 is depressed and vent same when the treadle
is released. Similarly, in the eve~t of a predetermined pre-
ssure drop in supply line 33, emergency relay valve 200 is
~ - 6 -
1(~5~4b~9
actuated to supply air at supply pressure from reservoir
.
- 6a -
1051~9
201 to trailer brake actuators 203 to set the brakes. When
supply pressure is restored in line 33, emergency relay
valve 200 vents the air at trailer brake actuators 203 to
re-establish normal operating mode of the trailer brake
system.
The valve arrangement shown within dotted envelope 10
controls the air supplied from source 21 and treadle valve
27 and admits same to the trailer brake system while also
controlling air at supply pressure to emergency chambers 17
of the tractor brake actuators 12. This arrangement inclu~es
a park control valve 46, an air control va~ve 47 and automa-
tically reacting valve means associated with park valve 46
and air control valve 47. The automatic valve means includes
a normally open/pilot closed valve 48, a two-way check valve
49 and a pilot operated, tractor protector valve 50. All
valves designated, with the exception of air control valve
47, are known in the art and thus will not be described or
explained in detail herein. Air control valve 47 by itself
and in a conventional tractor brake system comprises the
subject matter of a copending application identified by
Canadian Serial No. 221,232, filing date March 4, 1975 by
H. Durling and assigned to the assignee herein. Reference
may be had to that application for a detailed description of
the operation and structure of air control valve 47.
Park vale 46 has an inlet line 52 "T'd" to supply line
33 and an outlet in fluid communication with line 53 and a
vent 54. Park valve 46 is manually operable in the usual
push-pull manner between an applied position which vents
line 53 to atmosphere through vent 54 and a released posi-
tion which communicates line 53 with line 52 to provide air
at supply pressure in line 53. In communication with line
53 is a line 55 which leads to normally open/pilot closed
valve 48 and "T'd" to line 55 is a line 56 which communicates
with emergency brake chamber 17 of truck
- 7 -
brake actuators 12. 10~1489
As shown in FIGURE 4, normally open~pilot closed valve48 has a pilot inlet port in fluid communication with line
55, a main inlet port in fluid communication with a line 57,
an outlet port in commun~cation with a line 58 and a vent 59
When air at supply pressure is applied to the pilot inlet
port of valve 48 through line 55, valve plunger 60 therein
seals main inlet ~line 57) and vents line 58 to atmosphere
via communication with vent 59. If pressure in line 55 is
reduced to atmosphere and pressure above atmosphere exists
in line 57, plunger 60 will move in the opposite direction
to provide fluid communication between line 57 and line 58.
Outline line 58 from ~ormally open/pilot closed va~ve
48 communicates with one of the inlets in two-way check
valve 49. The other inlet in two-way check valve 49 is in
fluid communication with signal line 32. Two-way check
functions in its normal expected manner and will communicate
it outlet 32a with whichever of inlet lines 58, 32 is at
highest pressure. Outlet line 32a of check valve 49 commun-
icates with signal inlet port 65 of tractor protector valve
50.
Tractor protector valve 50 (FIGURE 5) has a supply in-
let port 66 in fluid communication with supply line 33 and
a signal inlet port 65 in fluid communication with line 32a.
Tractor protector valve likewise has a signal outlet port 65'
connected to signal line 32 leading to the trailer system
and a supply outlet port 66' connected to supply line 33
leading to the trailer brake system. The valve shown is
basically a spool-sleeve valve with a spring 70 biasing a
spool 71 out of communication with inlet-outlet ports 65, 66,
65', 66' to vent trailer supply line 33 on the downstream
side of the valve to atmosphere. Spool 71 is normally posi-
tioned to provide f`luid communication between its inlet andoutlet ports by supply
-- 8
l(~S14~39
pressure which normally exists in a line 74 which communi-
cates with a pilot inlet port 75 on tractor protector valve
50. Line 74 is shown in fluid communication with line 57
and leads to a second port 77 on the outlet side of air
control valve 47.
Air control valve 47 as shown in FI&URES 1 and 3 more
specifically includes:
(1) a first port 76 on the inlet side of the valve in
fluid communication with a line 80 in turn in communication
with supply line 33;
(2) a second port 77 on the outlet side of the valve
and in fluid communication with line 74 as previously men-
tioned;
13) a third port 78 on the inlet side of the valve in
; fluid communication with line 53 and being on the downst~am
side of park valve 46 is at supply pressure when park
valve 46 is in its released position; and
(4) a fourth port 79 on the outlet side of the valve
vented to atmosphere.
Air control valve 47 is either manually or automaticall~ -
operated to establish several different operating modes
which are either necessary or desirable to tractor-trailer
brake systems. These modes may be defined as "normal oper-
ation", "failsafe", "park", "fill", and "bobtail". Fluid
communication paths between valve ports 76-79 and each of
these valve modes may best be set forth in tabulated form
as shown below:
g
10514~9
TABLE I
~ratin~ Mode 1st Port_ 2nd Port ~d Port 4th Port
Normal Highway
~ith trailer) Sealed X X Sealed
~hsatfra~aluetr~atic) Sealed X Sealed X
l'ark Sealed X Sealed X
(with trailer)
~ill
(with trailer) X X Sealed Sealed
Bobtail (manual lock) Sealed X Sealed X
(without trailer)
"X" indicates fluid communication therebetween.
The structure of air control valve 47 which permits
these various flow paths to be obtained is shown in FI&U~E
3 with the valve position illustrated being its normal
highway operating mode. Briefly, this valve structure
includes a valve body having a first valve cavity 82 in fluid
communication with third and fourth ports 78, 79 and also in
fluid communication with a second valve cavity 83; second
valve cavity 83 being in fluid communication with first and
second ports 76, 77. Disposed within first cavity 82is a first
plunger 86 and disposed within second cavity 83 is a second plunger 87.
First plunger 86 has a first slider-piston 88 and is norma~y
biased as by springs 90 into its first position whereby
first slider-piston 88 seals third port 78 from communicat-
ing with fourth port 79 or second cavity 83. At the opposite
end of first plunger 86 is a second slider-piston 89 which,
in the second position of first plunger 86, seals fourth
port 79 when third port 78 is pressurized. First and second
slider pistons 83, 89 are connected by a connecting member
91 to define a gap 92 th~rebetween.
Second cavity 83 is especially configured-to have a
stop defined by
.
= 10 --
~051489
a bottom shelf 101 formed as a segmented ring and a top stop
defined by an annular shoulder 107. In between sbops 101,
107 is a plurality of circumferentially spaced flutes 108
cut into second cavity 83 and communicating at their open
upper end with second port 77. As clearly shown in FIGURE
3, the bottom portion of second cavity 83 is larger than top
portion and second plunger 87 which is received within seccnd
cavity 83 is cylindrically stepped in configuration to be
received therein. More particularly, second plunger 87 is
recessed as at 113 to define an area 114 in fluid communica-
tion with first port 76 and sealed therefrom by appropriate
seals as shown. The bottom larger diameter portion of seccnd
plunger 87 has a frusto-conical surface 118 adapted to con-
tact second stop 107 and a generally flat bottom surface 120
adapted to seat on first stop 101 when second plunger 87 is
manually moved downwardly to its fill mode position. Depend-
ing from bottom surface 120 is a semicircular boss 121
which is positioned at one side of second plunger's center-
line 102 and depending from boss 121 is an eccentrically
mounted actuating lever 123 which extends into gap 92. When
the valve is rotated to its bobtail mode, the bottom of boss
121 rests on shelf 101 and eccentric actuating lever 123
locks first slider-piston 88 into contact with port 78 there-
by locking first plunger 86 in its first position. It
should also be noted that whenever second plunger 87 contacts
second stop 107, fluid communication is provided between
second port 77 and one of the third or fourth ports 78, 79
When second plunger is displaced axially downward to rest
against shelf 101, seal 125 on second plunger 87 acts to pre-
vent fluid communication between first and second cavities
82, 83.
In opera-tion, the brake sytem disclosed will operate
in accordQnce with the operating modes listed in above Table I.
-- 11 --
10514~g
More specifically, the normal operating highway mode
occurs with the trailer coupled to the tractor and park
valve 46 in its released position to supply air at supply
pressure in line 53. Supply pressure is thus communicated
from :Line 53 through lines 55 and 56 to emergency brake
chambers 17 maintaining actuator spring 18 compressed.
Supply pressure in line 53 simultaneously enters third port
78 of air control valve 47 to move first plunger 86 into
its second position and bias second plunger 87 upwardly
into the position shown in FIGURE 3. This seals first port
76 and fourth port 79, and communicates third port 78 with
second port 77.. Supply pressure is thus communicated to
pilot line 74 raising spool 71 in tractor protector valve 50
to provide fluid communication between inlet and outlets
65, 66, 65', 66'. Normally open/pilot closed valve 48 re-
ceives supply pressure in line 55 at its pilot inlet port to
move plunger 60 rearward thus venting line 58 to atmosphere.
Thus check valve 49 is sensitive to control line pressure
in line 32 downstream thereof and control line pressure is
thus communicated through tractor protector valve 50 to the
trailer brake system. Similarly, supply pressure in line 33
is communicated to the trailer brake system and the trailer
brake system is thus placed in its normal operating mode as
defined he~einbef~re.
The brake system 10 automatically shifts to a failsafe
mode if a loss of pressure should occur in the trailer air
system as, for example, if the trailer or towed vehicle
should break away or if any other serious leak should deve-
lop. Such leakage would drop supply line pressure in line
33 which would similarly drop pressure in line 53. This
pressure drop would automatically shift control valve 47
into its failsafe mode when the pressure is reduced to a
value below that of the compression of springs 90. In such
instance, first plunger 86 will shift to its first
- 12 -
. ;: . , : . ~ ,
10S~9
position to seal port 78 and provide communication betweenits second port 77 with atmosphere via fourth port 79. This
will vent line 74 causing spool 71 in tractor protector
valve 50 to drop, thus preventing fluid communication bet-
ween spool inlets and outlets 65, 66, 65' ,66' and venting
66' to the atmosphere. Normally open/pilot closed valve 48
and double check valve 49 have no influence on this reac-
tion.
When the tractor is to be driven not coupled to atrailer, the air control valve is manually placed in its
bobtail operating mode. This mode occurs when the second
plunger 87 is rotated to force the first plunger 86 into
its first position to provide identical fluid flow paths as
if the valve were in its failsafe position. As described
above, this will place the inlet and outlet lines of tractor
protector valve 50 out of communication with one another.
Reverting back now to tractor-trailer operation, the
rig is parked in compliance with safety regulations by
simply placing park valve 46 in its applied position. When
this occurs, supply line pressure is ttill communicated in
line 33 to supply inlet 66 of tractor protector valve 50.
However, line 53 downstream of park valve 46 is vented to
atmosphere through park valve vent 54. This also vents
supply pressure in lines 55 and 56; venting of line 56
allowing expansion of tractor actuator springs 18 to set the
rear axle brakes on the tractor. As in the failsafe mode
described above, decrease in pressure in line 53 bblow a
predetermined value will automatically result in movement
of first plunger 86 to its first position to vent line 74
through second port 77 to atmosphere via port 79. This
will cause spool 71 in tractor protector valve 50 to drop
to prevent fluid communication between inlets and outlets
thereof and vent 66' to atmosphere. When the trailer brake
~ - 13 -
lOSi4~ii9
systems illustrated sense a drop in supply line
pressure, the systems will automatically cycle to their
emergency
'
.
, 1
~,
',:
. ~
- 13a -
~.
lOS~
or park position to set the brakes of the trailer as pre-
viously described.
With the tractor-trailer rig thus parked, the tractor~
trailer actuators may be released simply by moving park
valve 46 to its released position. This will automatically
reposition air control valve 47 into its normal highway
operating position once the force on springs 90 is over-
come by pressure in third port 78 and the system will f`unc-
tion with fluid communication as defined above in the normal
operating hlghway mode. This will, of course, recycle the
trailer brake systems into their normal operating position.
Importantly, this method of releasing the park brakes on the
tractor-trailer vehicle does not permit the trailer air
reservoir to fill priot to releasing the tractor and trailer
brake actuators.
If it is desired to ~upply air to the trailer reser-
voir~s~ with tractor and trailer brakes set so that auxili-
ary air operated equipment on the trailer such as material
handling equipment, tailgate lifts, etc. may be used, then
control valve 47 must be placed in its fill position. That
is, with park valve 46 in its applied position and lines 53
55 and 56 vented, the second plunger 87 on air control
valve 47 is moved downwardly until its base surface 120 con-
tacts first stop 101. In this fill position of the valve,
air at supply pressure in line 33 is communicated to first
port 76 via line 80 and thence through the valve to second
port 77.Supply pressure thus exists in line 75 and line 57 and
spool 71 of tractor protector valve 50 is placed in normal
communication with its inlets and outlets 65, 66, 65', 66'.
Normally open/pilot closed valve 48 automatically responds
to supply pressure in line 57 and atmosphere pressure in
line 55 to move plunger 60 and provide fluid communication
between lines 57 and 58. Line 58 is thus at full supply
pressure and forces two-way check valve 49 to shift, independent
~ - 14 -
lOS1489
of treadle valve 27 position, and communicates .
supply line pressure in line 32a to the trailer brake
system
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105~9
thro~lgh tractor protector valve 50. As noted above, supply
line pressure always exists in supply line 33 and is thus
communicated with the trailer brake system when tractor pro-
tector valve 50 is open. In either trailer brake system,
introduction of supply pressure in supply line 33 will
cause the trailer system to automatically shift from its
emergency or parlc position to its normal operating position
In the conventional trailer brake system illustrated
in FIGURE 2, emergency relay valve 200 will vent air pressure
from trailer brake actuators 203 when air control valve 47
is placed in its fill position. This would normally release
the brakes in single diaphragm actuator 203. However, since
the signal line pressure builds to supply pressure (i.e.,
90 to 110 psi), trailer actuators 203 will be accordingly
reapplied. When reservoir 201 is at supply pressure, trailer
actuator 203 will be fully extended to lock the trailer
brakes while the air within the trailer brake system can be
utilized to actuate air operated devices on the trailer.
When it is desired to release the brakes, actuation of
park valve 46 to its released position vents supply pressure
in control lines 32, 32a through normally open/pilot closed
valve 48.
The trailer brake system sl~own in FIGURE 1 operates in
a similar manner with the added advantage that the use of
,:
dual diaphragm, spring-set actuators 12 thereon permit the
trailer brakes always to remain applied when air control
valve 47 is placed in its fill position. When this occurs
air begins to charge reservoirs 37, 38 via supply line 33
while air at the same pressure enters actuator service brake
chambers 14 via signal line 32, antilock valve 39 and line
40. As supply line pressure builds to its system pressure
(i.e., 90 to 110 psi) to accordingly charger reservoirs
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10514~9
37, 38, the compression spring force of the trailer
actuators 12 are simultaneously diminised as the
pressure builds in
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~0~14~39
actuator emergency chambers 17. This lessening of the
spring force is exactly compensated for by the buildup of
pressure in the actuator service chambers 14. The net re-
sult is that the trailer brake actuators remain in an applied
position and when full supply pressure is reached at the
trailer system, the brakes will be set by full extension of
the service brake diaphragms 13 on the trailer actuators.
When it is desired to release the brakes, all that is re-
quired, in accordance with safety regulations, is to manu-
ally place park valve 46 in its released position. When
this occurs, lines 53, 55, 56 will be pressurized, releasing
the tractor parking brakes, and control valve 47 will auto-
matically shift, because of unequal pressure areas acting
on the second plunger, to its normal highway operating mode.
Pressurization of line 55 likewise causes normal open/pilot
closed valve 48 to vent line 58 to atmosphere through vent
59~ Because tractor protector valve 50 remains in its
open position communicating inlets with outlets, the supply
pressure in control lines 32, 32a is vented through two-way
check valve 49 and line 58 to atmosphere via normally open/
pilot closed valve 48 releasing the trailer service brakes.
The invention has been described with reference to a
preferred embodiment. Obviously, modlflcations and alter-
ations will occur to others upon reading and understanding
the specification. It is my intention to include all such
modifications and alterations insofar as they come within
the scope of the present invention.
It is thus the essence of the invention to provide a
pneumatic vehicle brake system f~`r a tractor-trailer combin-
ation which sets and releases tractor and trailer brakes by
means of a single park valve while a second control valve
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1051489
and automatic valve mechanisms responding to the -
position of the control valve enable the trailer
air supply to fill while tractor and trailer brakes
remai~ applied.
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