Note: Descriptions are shown in the official language in which they were submitted.
CA 02502129 2012-06-22
=
DASH CONTROL VALVE WITH TWO
STEP FUNCTION FOR PARK RELEASE
Background of Invention
The invention relates to the art of vehicle braking systems and finds
particular application
in heavy trucks, tractors, and buses. The invention will be described in
relation to an air pressure
braking system of a tractor-trailer truck system. It will be appreciated,
however, that the
invention is also amenable to other applications (e.g., other braking systems
such as those of
other kinds of vehicles and those based on other technologies such as
hydraulic or electronic
braking systems).
U.S. Patent No. 4,844,553 to Bliss and U.S. Patent No. 4,330,157, disclose
control valve
arrangements for us in a braking system. The valve arrangements include a pair
of valve
actuators or plungers that are operated by a vehicle operator. One of the
actuators controls
communication between an air pressure source and a tractor parking/emergency
brake system.
The tractor parking/emergency brake system includes spring brakes that are
actuated to resist
wheel rotation. A force of an included spring or set of springs in the spring
brakes urges a
braking member against the wheel. During vehicle operation, air pressure is
applied against a
piston that is associated with the springs. The force applied against the
piston counteracts the
force of the springs thereby releasing the spring brake and allowing the
wheels of the vehicle to
rotate. The other actuator controls communication between the pressure source
and service
brakes of a trailer.
In addition to providing for manual application and release of the
parking/emergency
brakes, the disclosed valve arrangements also provide for the automatic
application of brakes
should the source or actuation pressure fall below a threshold. That is to
say, the first actuator is
forced into a pressure exhaust position by internal springs if the source
pressure drops below a
first threshold. Similarly the other actuator is forced into a pressure
exhaust position if the
pressure drops below a second threshold. This provides for the trailer brakes
and the tractor
1
CA 02502129 2005-03-23
brakes to be applied in an appropriate order should a malfunction or leak
occur in the braking
system.
One feature the prior art valve arrangements do not provide is an assurance
that a vehicle
operator has actuated the service brakes before the parking brakes are
released. As a result, the
vehicle could roll unexpectedly when the operator releases the parking brakes.
Therefore, a braking system interlock arrangement that requires the service
brakes of a
vehicle to be engaged before the parking brakes of the vehicle can be
disengaged is desired.
The present invention provides a new and improved apparatus and method which
addresses the above-referenced problems.
Summary of Invention
In one embodiment, a valve assembly for an air pressure system includes an
inlet valve, a
first control valve, and a second control valve. The inlet valve includes an
inlet port, an outlet
port and a control port. The inlet valve inlet port communicates with the
inlet valve outlet port
when the inlet valve control port is above a threshold pressure. The first
control valve includes
an inlet port, an outlet port, an exhaust port, and a control member. The
first control valve inlet
port communicates with the inlet valve outlet port. The first control valve
outlet port
communicates with one of the first control valve inlet port and the first
control valve exhaust port
as a function of a position of the first control valve control member. The
second control valve
includes an inlet port, an outlet port, an exhaust port, and a control member.
The second control
valve inlet port communicates with the inlet valve outlet port. The second
control valve outlet
port communicates with one of the second control valve inlet port and the
second control valve
exhaust port as a function of a position of the second control valve control
member.
2
CA 02502129 2005-03-23
Brief Description of the Drawings
In the accompanying drawings which are incorporated in and constitute a part
of the
specification, embodiments of the invention are illustrated, which, together
with a general
description of the invention given above, and the detailed description given
below, serve to
exemplify the embodiments of this invention.
FIGURE 1 is a schematic diagram illustrating the control logic of a braking
system
control block operative to require a two-step brake release process.
FIGURES 2A and 2B are a diagram showing a first valve assembly configured as a
braking system control block operative to require a two-step brake release
process, the valve
assembly being in a first operational state.
FIGURES 3A and 3B are a diagram showing the valve assembly of FIGURES 2A and
2B in a second operational state.
FIGURES 4A and 4B are a diagram showing the valve assembly of FIGURES 2A and
2B in a third operational state.
FIGURES 5A and 5B are a diagram showing the valve assembly of FIGURES 2A and
2B in a fourth operational state.
FIGURES 6A and 6B are a diagram showing the valve assembly of FIGURES 2A and
2B in a fifth operational state.
FIGURE 7 is a functional diagram of an inlet valve shown in a first
operational state.
FIGURE 8 is a functional diagram of the inlet valve of FIGURE 7 in a second
operational state.
FIGURE 9 is a functional diagram of a third valve assembly configured as a
braking
system control block operative to require a two-step brake release process.
3
CA 02502129 2005-03-23
=
Detailed Description of Illustrated Embodiment
Referring to FIGURE 1, a valve assembly 104 operative to require an operator
of a
vehicle to apply service brakes 106 of the vehicle before both i) tractor
parking or spring brakes
107 and ii) trailer parking or spring brakes 184 can be released includes a
control double check
valve 108 and an inlet valve 110. The inlet valve 110 and control double check
valve 108 co-
operate to form a sensor, system inlet valve, and an interlock device. As will
be seen below, the
sensor monitors the state of the vehicle braking system. The system inlet
valve directs pressure
to certain parts of the braking system at appropriate times as determined by
the sensor. The
interlock latches the sensor and system inlet valve into a permissive or open
state when
appropriate.
More particularly, the control double check valve 108 includes a service
pressure port
114, a locking pressure port 116, and a control pressure outlet 118. The
control double check
valve 108 operates to direct system status information to the sensor. For
example, the
information is in the form of system pressures. The control double check valve
108 directs a
greater of pressures applied at the service pressure port 114 and the locking
pressure port 116 to
the control pressure outlet 118.
The inlet valve 110 includes an actuating pressure port 120, an input or
supply pressure
input port 122, and an output or supply pressure delivery port 124.
Additionally the valve
includes a biasing member 126 for urging the inlet valve toward a closed
position, thereby
blocking air flow to the supply pressure delivery port 124 from the supply
pressure input port
122. The actuating pressure port 120 communicates with the control pressure
outlet 118 of the
control double check valve 108 through a control check valve output channel
130. When air
pressure delivered to the actuating pressure port 120 exceeds that required to
counteract the
urging force of the biasing member 126, the inlet valve is actuated to permit
flow and pressure
equalization between the input port 122 and delivery port 124.
The input port 122 communicates with a supply pressure source through a supply
selector
double check valve 131 and a supply conduit 132. The supply conduit 132
connects to the check
valve 131 at a selected supply delivery port 134. The supply selector double
check valve 131
4
CA 02502129 2005-03-23
=
includes a primary supply port 136 connected to a primary supply reservoir 140
via a primary
supply line 142 and a secondary supply port 138 connected to a secondary
supply reservoir 144
via a secondary supply line 146. The supply selector double check valve 131
directs a higher of
pressures from the primary supply port and the secondary supply port to the
selected supply
delivery port 134.
Typically, the pressurized air is delivered to the supply reservoirs 140, 144
by one or
more pumps or compressors (not shown). The pressurized air is used to actuate
various
components of the vehicle braking system. For example, the pressurized air is
used to drive a
piston and counteract the force of the springs thereby releasing the brake
pads from engagement
with respective wheels (not shown) in the tractor and trailer spring brakes
107, 184.
The control double check valve 108 and the inlet valve 110 work together to
provide
pressurized air for enabling release of the tractor parking brakes 107 and the
trailer parking
brakes 184 at appropriate times. When it is inappropriate to release the
parking brakes the
control double check valve 108 and the inlet valve 110 work together to
prevent the delivery of
pressurized air to the spring brakes 107, 184.
For example, port 114 of the control double check valve 108 communicates with
a
service brake line 152 to receive pressurized air from a service supply double
check valve 153.
The check valve 153 directs, for example, a higher of two pressures delivered
from a
proportional valve 154 to the service brake line. Here, the proportional valve
154 is operatively
associated with a brake pedal (not shown) of the vehicle. The proportional
valve 154 receives
pressurized air from a primary service supply conduit 155 and a secondary
service supply
conduit 156. The proportional valve 154 proportions the pressures delivered to
it. For example,
the proportional valve 154 delivers a proportioned primary supply pressure and
a proportioned
secondary supply pressure to the service supply double check valve 153. The
proportioned
pressures depend on the degree of actuation of the proportional valve 154. For
example, if the
brake pedal is not actuated at all, then the delivery pressure of the
proportional valve 154 is 0 psi.
If the brake pedal is partially depressed then a percentage or fraction of the
primary and
secondary supply pressures are delivered to service supply double check valve
153. Obviously,
various pressures or fractional pressures may be delivered as well. The
service supply double
5
CA 02502129 2005-03-23
=
check valve 153 then directs one of the supplied pressures to the service
brake line 152 to effect
braking. When the pressure in the service brake line 152 is higher than a
pressure at the locking
pressure port 116 the control double check valve operates to deliver the
service brake line
pressure to the actuating pressure port 120 of the inlet valve 110, thereby
indicating that degree
to which the service brakes are applied to the wheels of the vehicle. When the
pressure at the
actuating pressure port 120 exceeds a predetermined threshold, for example 25
psi, the inlet
valve 110 directs supply pressure from the supply conduit 132, to the supply
delivery port 124
where it enables the tractor and trailer spring brakes 107, 184, respectively,
to be released once
the respective plungers are deactuated as will become more apparent below.
For example, the supply delivery port 124 is connected to a parking/emergency
brake
control valve 160 and a trailer parking/emergency brake control valve 180 via
a first control
valve supply conduit 162.
The spring brake control valve 160 includes a tractor spring brake supply port
164, a
tractor spring brake exhaust port 166, and a tractor spring brake delivery
port 168. The spring
brake delivery port 168 communicates with the tractor spring brake system 107
via a spring
brake pressure line 170. Additionally, the spring brake pressure line 170
provides spring brake
pressure to the locking pressure port 116 of the control check valve. A
biasing spring 172 urges
the tractor spring brake control valve toward an exhaust state, wherein any
pressure stored in the
spring brakes 107 is normally vented via the tractor spring brake exhaust port
166.
It is anticipated that in a comparable electrical braking system, energy will
not be stored
in the braking system. Therefore, in an electrical analog to the exhaust
state, the parking brakes
would simply be de-powered. However, some designs, such as, for example
capacitive and
inductive designs may benefit from energy regeneration or dissipation.
Therefore in an electrical
analog to the exhaust state, the parking brakes may be connected to an energy
storage device or a
dummy load.
The trailer air supply valve 180 includes a trailer air supply port 181, a
trailer air exhaust
port 182, and a trailer air delivery port 183. The delivery port 183 is
connected to the trailer air
system 184 via a trailer air line 185. A biasing member or spring 186 urges
the trailer air supply
6
CA 02502129 2005-03-23
=
valve 180 to an exhaust state position where pressure in the trailer air
system 184 is vented to
atmosphere 178. In order to supply air to the trailer systems 184, the
operator must deactuate
(e.g., push) a plunger button 187 associated with the trailer air supply valve
180. Deactuating the
plunger directs whatever pressurized air that is present at the trailer air
supply port 181 to the
trailer air delivery port 183. Additionally, pressurized air at the trailer
air delivery port 183 is
applied to a trailer air supply valve pilot or control port 188. Pressure at
the pilot port 188 holds
the trailer air supply valve plunger (not shown) and button 187 in position
after the operator
releases the plunger button 187, thereby holding the trailer air supply valve
180 in the trailer
system pressurization state. The trailer air supply valve 180 directs
pressurized air for releasing
brakes of a trailer. Additionally, trailer air pressure is made available to
power trailer accessories
such as conveyer belts, ramps and lifts. In one embodiment, pressurized air
from the trailer air
supply valve is delivered to the trailer system through a tractor protection
valve. The tractor
protection valve serves to isolate the tractor systems from the trailer in the
event of an
unintentional disconnection.
As described above, in order to release the tractor parking or spring brakes
107 or the
trailer parking or spring brakes 184, the operator must first apply the
service brakes.
Additionally, the operator must also deactuate plunger buttons or control
switches 174, 187
associated with the tractor spring brake control valve 160 and the trailer air
supply valve 180,
respectively. Deactuating the plunger buttons 174, 187 positions the control
valve 160 in a
tractor spring brake pressurization state and the trailer air supply valve 180
in a trailer spring
brake pressurization state.
While in the tractor spring brake pressurization state, the tractor control
valve 160 directs
pressurized air at the supply port 164 to the delivery port 168. Additionally,
pressurized air at
the spring brake delivery port 168 is applied to a tractor spring brake
control valve pilot or
control port 176. Pressurized air at the pilot port 176 latches or holds the
tractor spring brake
control valve in position after the operator releases the plunger button 174,
thereby latching the
tractor spring brake control valve 160 in the spring brake pressurization
state. Furthermore,
system status information, in the form of spring brake pressure, delivered to
the locking pressure
port 116 of the control double check valve 108 is directed to the actuation
port 120 of the inlet
7
CA 02502129 2005-03-23
valve 110, thereby locking or latching the inlet valve in a supply pressure
delivery state in
response to the secondary or spring brakes being in a released state. The
control double check
valve 108 also operates to isolate the service brake line 152 from the spring
brake system.
While in the trailer spring brake pressurization state, the control valve 180
directs
pressurized air at the supply port 181 to the delivery port 183. Additionally,
pressurized air at
the spring brake delivery port 183 is applied to a trailer spring brake
control valve pilot or
control port 188. Supply pressure at the pilot port 188 latches or holds the
trailer spring brake
control valve in position after the operator releases the plunger button 187,
thereby latching the
trailer spring brake control valve 180 in the spring brake pressurization
state.
When the operator desires to again park the vehicle and apply the tractor
parking/spring
brakes 107 and/or the trailer parking/spring brakes 184, the operator actuates
the plunger buttons
174, 187 to overcome forces associated with the spring brake pressure applied
to the tractor
spring brake control valve pilot port 176 and the spring brake pressure
applied to the trailer brake
control valve pilot port 188. This returns the tractor and trailer spring
brake control valves 160,
180 to their exhaust states. Pressures at the tractor and trailer spring brake
delivery ports 168,
183 are vented to exhaust ports 166, 182 and the spring brakes engage the
wheels of the vehicle
tractor and trailer. Additionally, pressure at the locking pressure port 116
is relieved. Therefore,
pressure is relieved from the actuating pressure port 120 of the inlet valve
110. The spring 126
then urges the inlet valve into a closed position, thereby preventing the
release of the tractor
parking brakes 107 and the trailer parking brakes 184 without a prior
application of the service
brakes 106.
When the tractor and trailer spring brake control valves 160, 180 are placed
in an exhaust
state in order to vent or relieve pressure in the tractor and trailer spring
brakes 107, 184,
pressurized air flows from the tractor spring brake exhaust port 166 and the
trailer spring brake
exhaust port 182 to atmosphere 178. An exhaust conduit 190 carries the exhaust
flow from the
tractor spring brake exhaust port 166 to atmosphere 178.
Having described the invention in general terms, details of an exemplary
embodiment are
now discussed. Referring to FIGURES 2A and 2B, a valve assembly 604 requires
an operator
8
CA 02502129 2005-03-23
=
of a vehicle to apply service brakes 606 of the vehicle before parking spring
brakes 607 of the
vehicle tractor and parking spring brakes 609 of the vehicle trailer are
released. The valve
assembly comprises a control double check valve 608 and an inlet valve 610.
The control double
check valve 608 and inlet valve 610 reside in a common housing 612. The
housing 612 includes
a check valve chamber 614 and an inlet valve chamber 616.
The control double check valve 608 includes a spacer 618, a biasing spring
620, and
check valve member 622. The spacer includes grooves 624 that carry seals such
as o-rings 626.
The seals 626 divide the check valve chamber 614 into a first region 628 and a
second region
630. The spacer 618 includes a passage 632 that provides communication between
the first
region 628 and the second region 630. Additionally, the spacer includes a
first valve seat 634
operative to receive the check valve member 622. As will be further described
in reference to
FIGURES 3A and 3B, a second region end 636 of the passage 632 is closed when
the first valve
seat 634 receives the check valve member 622.
The spring 620 is located between the spacer 618 and the check valve member
622,
urging the check valve member 622 toward a second valve seat 638. When seated
on the second
valve seat 638, the check valve member 622 isolates the second region 630 from
a service
pressure port 640.
The inlet valve 610 includes a valve frame 642, a piston 644, a piston spring
646, a valve
guide 648, an inlet valve member 650, and an inlet valve member return spring
652. The valve
frame 642 includes a set of grooves 654 carrying associated seals 656 that
divide the inlet valve
chamber 616 into a third region 660, fourth region 661, and fifth region 662.
The valve frame
642 also includes a piston guide region 664 and an inlet valve seat 666. The
inlet valve seat 666
is located at a boundary between the fourth 661 and fifth 662 regions of the
inlet valve chamber.
During inlet valve 610 operation, the inlet valve member is occasionally
seated on the
inlet valve seat 666. During those times, the inlet valve member 650 and the
inlet valve seat 666
form a seal separating the fourth 661 and fifth 662 inlet valve regions. When
the inlet valve
member 650 is not seated on the inlet valve seat 666, there is free
communication between the
fourth 661 and fifth regions 662. As will be explained in greater detail
below, the valve frame
9
CA 02502129 2005-03-23
=
642 also includes various grooves, cutouts and passages that, either alone, or
in cooperation with
various inlet valve components, form passages or conduits for air flow.
The piston 644 has a piston head 668 and a shaft portion 669. The piston head
668 and
the shaft 669 each include grooves carrying seals 670 to maintain isolation
between the third and
fourth inlet valve regions 660, 661. The shaft 669 is slidably received in the
piston guide region
664 of the frame 642. The piston is urged toward the third region 660 by
piston spring 646. The
piston spring 646 is mounted between an overhang portion of the piston head
668 and a piston
spring support 674 portion of the inlet valve frame 642. The piston shaft 669
includes a valve
guide bore 676. The valve guide bore 676 is located axially with respect to
the piston shaft 669.
The valve guide 648 is, for example, a pin. The valve guide 648 is received
within the
valve guide bore 676. A portion of the valve guide 648 projects outwardly from
the valve guide
bore into the fifth region 662 of the inlet valve chamber 616.
In one embodiment, the inlet valve member 650 is made of a resilient material
such as
rubber. The inlet valve 650 member includes a valve guide bore 677 axially
located with respect
to the inlet valve member 650. The guide bore 677 receives a tip of the
projecting portion of the
valve guide 648 to axially locate the inlet valve member 650 within the fifth
region 662 of the
inlet valve chamber 616.
The second region 630 of the control double check valve 608 communicates with
the
third region 660 of the inlet valve 610 through a second passage 679. In
addition to the control
double check valve 608 and the inlet valve 610, the first embodiment 604
further comprises a
primary pressurized air source 680, a secondary pressurized air source 681, a
source selection
valve 682, a service brake actuator or pedal 683, a tractor spring brake
control valve 684, and a
trailer air supply valve 685.
The primary and secondary pressure sources 680, 681, respectively, are each
connected
to the source selection valve 682 which directs air from one of the pressure
sources to an inlet
port 686 of the inlet valve 610 through a supply conduit 687. The primary and
secondary
CA 02502129 2005-03-23
=
pressure sources are also each connected to the service brake actuator 683
through first and
second service supply lines 689, 690, respectively.
The service brake actuator 683 delivers proportioned pressure outputs to a
second source
selection valve 691 through first 689' and second 690' respective service
actuator output lines.
The pressures delivered in output lines 689', 690' are related to both their
respective supplies
680, 681 and the position of the service brake actuator 683. The second source
selection valve
691 connects one of the output lines 689', 690' to a service brake line 692
based on the relative
pressures of the airs contained within the output lines 689', 690'. For
example, the output line
containing air at a higher pressure is directed to the service brake line 692.
The service brake line delivers the selected output pressure to the service
brakes 606 of
the vehicle. Additionally a branch of the service brake line delivers the
selected output pressure
to a control inlet 693 of the control double check valve 608. When the check
valve member is
not seated on the second valve seat 638, the control inlet 693 communicates
with the second
region 630 of the control double check valve 608.
An inlet valve outlet port 694 is connected to a tractor spring brake valve
inlet port 695 of
the tractor spring brake control valve 684 and a trailer valve inlet 688 of
the trailer air supply
valve 685 through an inlet valve output conduit 696. The inlet valve outlet
port 694
communicates with the fourth region 661 of the inlet valve 610.
A tractor valve delivery port 697 is connected to a spring brake line 698. A
branch of the
spring brake line 698 is connected to a lockout port 699 of the control double
check valve. The
lockout port 699 communicates with the first region 628 of the control double
check valve 608.
As depicted in FIGURES 2A and 2B, the first embodiment 604 of a valve assembly
is in
a brake release prevention state. Supply pressure is available in the supply
conduit 687.
Additionally, plunger buttons of the tractor spring brake control valve 684
and the trailer air
supply valve 685 have been deactuated. Therefore, the tractor spring brake
control valve 684
and the trailer air supply valve 685 are configured to deliver air to the
tractor spring brakes 607
and the trailer spring brakes 609 for causing the spring brakes to release the
wheels (not shown).
11
CA 02502129 2005-03-23
However, the service brake actuator 683 has not been actuated and, therefore,
no pressure is
applied to the control input 693 of the control double check valve and no
pressure is applied to
the piston 644 to counteract the force of the spring 646. Therefore, the
piston is positioned
toward the third region 660 and the inlet valve member 650 is seated on the
inlet valve seat 666.
Although supply pressure is available at the inlet valve inlet 686 and
therefore in the fifth
region, there is no communication between the fifth and fourth regions.
Therefore, supply
pressure is not available at the inlet valve outlet port 694 and no supply
pressure is available at
the tractor spring brake valve inlet 695 or the trailer valve inlet 688.
Deprived of supply
pressure, neither the tractor spring brake control valve 684 nor the trailer
spring brake control
valve 685 can deliver pressurized air to the spring brake line even though the
valve is configured
to do so. Therefore, the tractor spring brakes remain engaged and the vehicle
is prevented from
rolling unexpectedly.
Referring to FIGURES 3A and 3B, the valve assembly 704 illustrates a second
operational state of the FIGURES 2A and 2B embodiment. In the second
operational state, a
tractor spring brake control valve 708 and a trailer spring brake control
valve 707 are in
respective spring brake exhaust configurations. A tractor valve button 710 and
associated
plunger 712 is actuated (lifted upwardly as shown), thereby directing
pressurized air in spring
brake line 714 connected at a spring brake delivery port 716 to an exhaust
port (not shown). The
tractor spring brakes 718 thus engage the wheels of a vehicle, thereby
preventing the vehicle
from rolling. Similarly, a trailer valve button 711 and associated plunger 713
is actuated (lifted
upwardly as shown), thereby directing pressurized air in spring brake line 715
connected at a
spring brake delivery port to an exhaust port (not shown). The trailer spring
brakes 709 thus
engage the wheels of the vehicle, thereby preventing the vehicle from rolling.
Additionally, in the second operational state, service brake actuator/brake
pedal 720 is
actuated so that air in service brake line 722 is above a threshold pressure
and the service brakes
724 engage the wheels (not shown) of the vehicle. The threshold pressure is
selected so that the
vehicle will not roll unexpectedly if the tractor spring brakes or the trailer
spring brakes 718,
709, respectively, are released. Service pressure is also delivered to an
input 726 of a control
double check valve 728. With the check valve member 730 unseated from valve
seat 734, the
12
CA 02502129 2012-06-22
pressurized air at the control input 726 communicates with the second check
valve region 742
and with a passage 744 between the second check valve region 742 and a third
region 746 of an
inlet valve 748. A force arising from pressure applied to the piston overcomes
a force of a piston
spring 752 so that the piston moves toward a fourth region 754 of the inlet
valve. Valve guide
756 moves with the piston 750 and an inlet valve member 757 associated with
the valve guide.
Both the valve guide 756 and inlet valve member 757 are moved further into a
fifth region 758
that communicates with an inlet valve supply port 759. The fourth region 754
communicates
with an inlet valve outlet port 760. As a result of movement of the inlet
valve member from an
inlet valve seat 762, a communication path is opened between the fourth and
fifth inlet valve
regions. Pressurized air delivered to the inlet valve inlet port 759 is
communicated to the fourth
region 754 by the communication path that was opened when the inlet valve
member 757 was
lifted off the inlet valve seat 762. As described above, the inlet valve
outlet port 760
communicates with the fourth region 754. Therefore, the inlet valve outlet
port 760 also receives
pressurized air which is made available to a tractor spring brake control
valve inlet port 770 and
a trailer spring brake control valve inlet port through an inlet valve output
conduit 771. If the
tractor valve button 710 (and associated plunger 712) or the trailer valve
button 711 (and
associated plunger 713) were deactuated (e.g., pushed down), the tractor
spring brake control
valve 708 and the trailer spring brake control valve would deliver pressurized
air for releasing
the spring brakes 718, 709, respectively.
Referring to FIGURES 4A and 4B, the valve assembly (now referenced as numeral
804)
is shown in a third operational state. In the third operational state, the
service brake pedal 808
has been actuated beyond a threshold degree so that supply pressure is
available at a tractor valve
inlet port 810 of a tractor spring brake control valve 812. However, in the
third state, tractor
valve button 814 and a tractor valve plunger 816 are deactuated while trailer
valve button 811
and a trailer valve plunger 813 are actuated. As is explained in greater
detail in the U.S. Patent
4,844,553 to Bliss, depressing the valve button 814 and plunger 816 directs
pressurized air
available at the inlet port 810 to a tractor spring brake control valve
delivery port 818 and to
tractor spring brakes 820 through a spring brake line 822, thereby releasing
the tractor spring
brakes. Since the trailer valve button 811 and plunger 813 are actuated, the
trailer spring brakes
809 are engaged. A branch of the spring brake line also
13
CA 02502129 2005-03-23
delivers pressurized air to a lockout port 824 of a control double check valve
826. The lockout
port 824 communicates with a first region 828 of the control double check
valve 826. A passage
829 in spacer 830 conducts pressurized air in the first region 828 to a second
region 834 of the
passage 828, urging check valve member 836 away from a first check valve seat
838 and against
a second check valve seat 840.
The pressurized air in the passage 829 acting downwardly (relative to the
FIGURE) on
the check valve member 836 is higher than or equal to a pressure of
pressurized air acting
upwardly (relative to the FIGURE) on the check valve member 836 and,
therefore, the check
valve member is pressed against the second seating surface 840 thereby sealing
off the control
input. The check valve member 836 is moved away from the first seating surface
and
pressurized air flows through the passage into a third region 842 of the
control double check
valve and into a second passage 848 that communicates with a fourth region 850
of an inlet valve
852. This provides a force acting on piston 856 of the inlet valve 852 and, in
this way, spring
brake line pressure 822 delivered to the lockout port 824 latches the inlet
valve 852 in an open
position independent of the degree of actuation of the service brake actuator
808. This allows
the tractor spring brakes to be maintained in their released state after a
vehicle operator, for
example, removes his foot from a service brake pedal 808.
Referring to FIGURES 5A and 5B, the valve assembly 904 is in a fourth
operational
state. The fourth operational state is similar to the third operational state
of FIGURES 4A and
4B; however, the service brake pedal 908 is not actuated. Nevertheless,
pressure in spring brake
line 910 is delivered to a lockout port 912 and serves to hold an inlet valve
914 in an open
position. Therefore supply pressure continues to be delivered to a tractor
spring brake control
valve inlet 916 of a tractor spring brake control valve 918 and a trailer
spring brake control valve
inlet 942 of a trailer spring brake control valve 940. A plunger 920 (and
button 922) of the
tractor spring brake control valve 918 and a plunger 913 (and button 911) of
the trailer spring
brake control valve 940 are maintained in a deactuated (depressed) position
(relative to the
FIGURE). For example, internal to the tractor spring brake control valve 918
the pressure of the
air applied to the inlet 916 overcomes the force generated by a tractor valve
return spring 924
and holds the plunger 920 in the depressed position. Therefore, supply
pressure continues to be
14
CA 02502129 2005-03-23
=
delivered to the spring brake line 910, spring brakes 926 and the lockout port
912. Additionally,
supply pressure at the inlet 916 is also delivered to an inlet 942 of the
trailer supply valve inlet
942. The pressure at the inlet 942 holds a plunger 944 of the trailer supply
valve 940 in the
depressed position. The trailer supply valve 940 delivers supply pressure to
trailer systems,
including, for example, trailer spring brakes (not shown). In one embodiment,
a tractor
protection valve 946 is included between the trailer supply valve 940 and the
trailer. With
pressure supplied to the trailer, parking brakes of the trailer are released
and the combination
vehicle (tractor and trailer) can be driven to its destination.
Referring to FIGURES 6A and 6B, the valve assembly is shown in a fifth
operational
state which is actually a transition from the fourth operational state to the
first operational state.
In the fifth operational state plunger buttons 1006, 1008 and plungers 1010,
1012 of the tractor
spring brake control valve 1014 and a trailer supply valve 1016 have been
actuated (i.e., lifted).
Therefore the valves 1014, 1016 are in an exhaust position where pressurized
air from spring
brakes 1018 and spring brake line 1020 is vented through a tractor spring
brake control valve
exhaust port 1022. Likewise, pressurized air from a trailer system (not shown)
and trailer supply
line 1024 is vented through a trailer supply valve exhaust port 1026.
Additionally, in the fifth operational state, a service brake actuator 1028 is
not actuated so
that air pressure in service brake line 1030 is zero. For example, the
pressure of air in the service
brake line is below a threshold thereby indicating that the service brakes are
not engaged
sufficiently to prevent the vehicle from rolling unexpectedly. As the spring
brakes 1018 and
spring brake line 1020 are vented, pressurized air in a first region 1032 of a
control double check
valve 1034 flows from a lockout port 1036 of the control double check valve
1034 and into the
spring brake line 1020 to be vented to atmosphere. As air leaves the first
region 1032, air in a
second region 1038 of the control double check valve 1034 flows through a
first passage 1040
into the first region 1032 and out the lockout port 1036. Therefore, a
pressure in the second
region 1038 is reduced. Similarly, air in a third region 1042 of an inlet
valve assembly 1044
flows through a second passage 1046 into the second region 1038 and eventually
out the lockout
port 1036. As pressurized air leaves the third region 1042, a piston spring or
resilient member
1048 is able to urge a piston 1050 of the inlet valve assembly 1044 toward the
third region 1042.
CA 02502129 2005-03-23
As the piston 1050 moves toward the third region 1042, forces from an inlet
valve member
return spring 1052 and/or pressurized air supplied from an inlet port 1054 of
the inlet valve
assembly 1044 urge an inlet valve member 1056 and an associated valve 1058
guide toward and
further into a fourth region 1060 of the inlet valve assembly 1044,
respectively. Ultimately, the
inlet valve member 1056 is seated on an inlet valve seat 1062 thereby
preventing communication
between the fifth region 1064 and the fourth region 1060. Therefore, no
significant amount of
pressurized air is available to the tractor spring brake valve inlet port 1070
or the trailer spring
brake valve inlet port. When substantially all the pressurized air has been
vented or returned to a
low pressure tank or reservoir, the transition is complete and the fifth valve
assembly 1004 is in
the first operational state.
Referring to FIGURE 7, a closed inlet valve assembly 1304 preferably includes
a
venting means 1308 operative to vent air from a fourth region 1312 of the
closed inlet valve
assembly 1304. A piston 1314 is positioned in a right-most piston position so
that a third region
1316 of the inlet valve assembly 1304 is at a minimum size. An inlet valve
member return
spring 1320 urges an inlet valve member 1322 and a valve guide 1324 into a
right-most position.
The inlet valve member 1322 is seated on valve seat 1330. Therefore,
communication between a
fifth region 1334 and the fourth region 1312 of the inlet valve assembly 1304
is prevented.
Typically, the inlet valve assembly 1304 assumes the closed state when an
operator of a vehicle
switches the tractor spring brake control valve 160, 684, 1216 from a spring
brake release state
into a spring brake exhaust state. This operation tends to trap pressurized
air in the fourth region
1312 of the inlet valve assembly 1304 and in an inlet valve output conduit or
passage 162, 696
(see FIGURES 1, 2A, and 2B).
This trapped air can affect the operation, sound and feel of the tractor
spring brake
control valve when the operator next attempts to release the spring brakes.
For example, as the
tractor spring brake control valve is moved from the exhaust state to the
spring brake release
state, trapped air would flow from the fourth region 1312 and associated
passages into the spring
brake line. As the air is delivered, an audible sound is emitted even if the
primary and secondary
pressure reservoirs are empty. In this case, the sound may confuse the
operator into believing the
spring brakes are released, when, in fact, they are still engaged.
Additionally, the trapped air
16
CA 02502129 2005-03-23
resists the operator's actuation of the tractor spring brake control valve.
For example, the
operator must compress the trapped air in order to move the tractor spring
brake control valve
into the spring brake release state. For the forgoing reasons, the inlet valve
assembly 1304
preferably includes the venting means 1308.
For example, the venting means includes a vent seat 1340. The vent seat 1340
is
operative to receive the inlet valve member 1322 when the inlet valve is in an
open state.
However, in the illustrated closed state, the inlet valve member 1322 is not
seated on the vent
seat 1340. When the piston 1314 is in the illustrated right-most position, the
inlet valve seat
1330 serves to separate the inlet valve member 1322 from the vent seat 1340.
The vent seat
1340 is at an inlet valve member end of an axial bore 1342 in a shaft portion
1344 of the piston
1314. The bore 1342 is operative to slidably receive the valve guide 1324.
Additionally, a gap
1346 between the valve guide 1324 and a wall 1348 of the bore is operative as
a first portion of a
piston vent passage 1350 in the piston 1314. When the inlet valve assembly
1304 is in the
illustrated closed state, the vent seat 1340 is positioned in the fourth
region 1312. The piston
vent passage 1350 is in communication with a frame vent passage 1352. The
frame vent passage
1352 communicates with a vent region 1353, e.g., atmosphere.
When the inlet valve member 1322 is not seated on the vent seat, as shown in
FIGURE
7, the fourth region 1312 is in communication with the piston vent passage
1342 through the
open vent seat 1340, the piston vent passage 1350, and in turn with the frame
vent passage 1354
and the vent region 1353. When the inlet valve assembly 1304 is in the closed
state, the venting
means 1308 is in an open state. Therefore, air that would otherwise be trapped
in the fourth
region 1312 and associated passages when the inlet valve is closed is instead
vented. Of course,
the venting means 1308 must be sealed or closed when the inlet valve assembly
1304 is in an
opened state.
Referring to FIGURE 8, an open inlet valve assembly 1404 includes a sealed
venting
means 1408. A piston 1414 is positioned so that a third region 1416 of the
inlet valve assembly
1404 is at a maximum size. Inlet valve member 1422 is unseated from inlet
valve seat 1430 to
form a communication path 1432 between fourth region 1436 and fifth region
1434. Typically,
the inlet valve assembly 1404 is urged toward an open state when an operator
of a vehicle
17
CA 02502129 2005-03-23
actuates a service brake actuator 154, 683 in preparation to release parking
spring brakes of a
vehicle. This delivers pressurized air to the third region 1416 of the inlet
valve assembly 1404
and drives the piston 1414 to the illustrated left-most position. As a result,
the inlet valve
member is urged against a vent seat 1444 portion of the piston 1414.
Additionally, pressurized
air in the fifth region 1434 also urges the inlet valve member against the
vent seat 1444.
Therefore, pressurized air is prevented from leaking out through the venting
means 1408 while
the inlet valve assembly 1404 is in the open state.
Referring to FIGURE 9, the inlet valve assembly 1304, 1404 of FIGURES 7 and 8
may
be included in any of the valve assembly embodiments described herein. The
third valve
assembly 1504 includes in a single housing 1508, a tractor spring brake
control valve 1510, a
trailer supply valve 1512, a supply selector 1514, a control double check
valve 1516, and an inlet
valve 1518.
As described previously, the supply selector 1514 communicates with primary
and
secondary supply input ports 1521, 1522. Typically the primary and secondary
supply ports are
connected to primary and secondary pressurized air reservoirs (not shown). A
selector check
valve member 1524 of the supply selector 1514 moves to direct one of the
primary and
secondary supplies to a supply passage 1525. For example, the supply
delivering pressurized air
at the highest pressure is directed to the supply passage 1525.
The supply passage 1525 delivers pressurized air to an inlet or fifth region
1526 of the
inlet valve 1518.
The control double check valve 1516 communicates with a control input port
1530, a
control check valve output passage 1531 and a lockout passage 1532. As
previously described,
in a first mode of operation, a control check valve member 1533 within the
control double check
valve 1516 moves to direct one of pressurized air delivered to the control
input port 1530 and
pressurized air delivered to the lockout passage 1532 to the control check
valve output passage
1531. For example, the port 1530 or passage 1532 carrying pressurized air at
the highest
pressure is directed to the control check valve output passage 1531. In a
second mode of
operation, pressurized air in the control check valve output passage 1531 is
vented through the
18
CA 02502129 2005-03-23
=
lockout passage 1532. The control check valve output passage 1531 merges into
a third, or
actuation region or piston, or control port 1534 of the inlet valve 1518. The
lockout passage
1532 is in communication with a seventh region 1536 of the tractor spring
brake control valve
1510.
The tractor and trailer spring brake control valves 1510, 1512, respectively,
communicate
with other devices through tractor and trailer valve input ports 1538, 1528,
respectively, a spring
brake delivery port 1540, and a first exhaust passage 1542. The tractor and
trailer valve input
ports 1538, 1528 receive pressurized air from a fourth inlet valve region 1544
through an inlet
valve output passage 1546. Of course, the tractor and trailer valve input
ports 1538, 1528 only
receive pressurized air when the inlet valve 1518 is open. Of course, as
previously described in
reference to other figures, the inlet valve 1518 is only open when pressurized
air directed to the
third region or piston port 1534 by the control double check valve 1516 from
the control port
1530 or the lockout passage 1532 are of sufficient pressure to hold the inlet
valve 1518 open.
When the tractor spring brake control valve 1510 is pulled upward (actuated)
(relative to
the figure) into an exhaust state, as depicted in FIGURE 9, any pressurized
air delivered to the
tractor valve input port 1538 will pressurize a tractor valve plunger passage
1548. However, the
pressurized air from the tractor valve input port 1538 can travel no further,
since distal ends 1550
of the plunger passage 1548 are isolated by plunger seals 1551 from any other
region or passage.
Additionally, when the tractor spring brake control valve 1510 is in the
illustrated exhaust state,
air in the lockout passage 1532 and the spring brake delivery port 1540 are
placed in
communication with, and flow out through, the first exhaust passage 1542
through an eighth
region 1552 of the tractor spring brake control valve 1510.
When the tractor spring brake control valve 1510 is pushed downward
(deactuated)
(relative to the figure) into a delivery state, the distal ends 1550 of the
plunger passage are placed
in communication with the seventh region 1536 of the tractor spring brake
control valve 1510.
Therefore, pressurized air delivered to the tractor valve input port 1538 is
placed in
communication with the lockout passage 1532 and with the spring brake delivery
port 1540.
Pressurized air in the seventh region 1536 works on a tractor valve seal 1556.
The pressurized
air provides a force that overcomes a spring force of a tractor valve spring
1554. Therefore,
19
CA 02502129 2005-03-23
when the tractor spring brake control valve 1510 is placed in the delivery
state and the seventh
region is filled with pressurized air, the pressurized air serves to hold or
latch the tractor spring
brake control valve 1510 in the delivery state. In the depressed position (not
shown), or deliver
state, the tractor valve seal 1556 is seated on a tractor valve seat 1557. In
this position the tractor
valve seal 1556 prevents communication between the first exhaust passage 1542
and the seventh
1536 or eighth 1552 tractor valve regions.
The trailer supply valve 1512 operates in a similar manner. The trailer supply
valve 1512
communicates with other devices through the trailer valve input port 1528, a
trailer delivery port
1562, a reset passage 1564 or sampling point and, through the reset passage
with an exhaust port
1565. As mentioned above, the trailer valve input port 1528 receives
pressurized air from the
inlet valve output passage 1546.
When the trailer supply valve 1512 is pulled upward (actuated) (relative to
the figure),
into an exhaust state, as depicted in FIGURE 9, any pressurized air delivered
to the trailer valve
input port 1528 pressurizes a trailer valve plunger passage 1566. However, the
pressurized air
from the trailer valve input port 1560 can travel no further since distal ends
1567 of the plunger
passage 1566 are isolated by plunger seals 1568 from any other region or
passage. Additionally,
when the trailer supply 1512 is in the illustrated exhaust state, air in the
trailer delivery port 1562
passes through a tenth region 1570 of the trailer supply valve 1512, through
the trailer supply
valve reset passage 1564 and is vented or exhausted through the exhaust port
1565.
When the trailer supply valve 1512 is pushed downward (relative to the figure)
into a
delivery state, the distal ends 1567 of the plunger passage 1566 are placed in
communication
with a ninth region 1572 of the trailer supply valve 1512. Therefore,
pressurized air delivered to
the trailer valve input port 1528 is placed in communication with the trailer
delivery port 1562.
Pressurized air in the ninth region 1572 works on trailer valve seal 1576,
providing a force that
overcomes a spring force of a trailer valve spring 1575. Therefore the trailer
supply valve 1512
is held or latched in a depressed or delivery state. In the delivery state
(not shown) a trailer valve
seal 1576 is seated on a trailer valve seat 1577. In this position the trailer
valve seal 1576
prevents communication between the trailer supply valve reset passage 1564 and
the ninth 1572
or tenth 1570 tractor valve regions.
CA 02502129 2012-06-22
Of course, pressurized air delivered to the trailer delivery port 1562 flows
out of the valve
assembly. Typically the trailer system (not shown) is connected to the trailer
delivery port 1562.
Therefore, when the trailer valve plunger is in the depressed position,
pressurized air flows from
the supply selector 1514, through the inlet valve 1518, the inlet valve output
passage 1546, and
the trailer plunger passage 1566 into the ninth region 1572, out the trailer
delivery port 1562 and
into the trailer system.
Of course, at low system pressures, the force working on the trailer valve
seal 1576 falls
below a threshold and the trailer valve spring forces the trailer supply valve
1512 into the
exhaust state, thereby applying the brakes of any attached trailer.
In addition to the low pressure auto exhaust feature just described, the
trailer supply valve
1512 can also be automatically driven into the exhaust state by exhaust air
from the tractor spring
brake control valve 1510. When the tractor spring brake control valve 1510 is
switched or
moved into the exhaust state, pressurized air from a spring brake line (not
shown) attached to the
spring brake delivery port 1540 is directed to the first exhaust passage 1542
through the tractor
spring brake control valve 1510. As the air flows toward the exhaust port
1565, reset port 1564
is also pressurized. If the trailer supply valve 1512 is in the delivery state
when tractor spring
brake control valve 1510 exhaust air pressurizes the reset port, then a force
generated by the
pressure in the reset port is added to a force delivered by the trailer valve
spring 1575. The
combined forces overcome the force generated by pressurized air in the tenth
region 1570
applied to the trailer valve seal 1576. Therefore, the trailer supply valve
1512 is automatically
switched into the exhaust state.
The scope of the claims should not be limited by the preferred embodiments set
forth in
the examples, but should be given the broadest interpretation consistent with
the description as a
whole.
21
