Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a rapid tire deflation system
for emergency vehicles such as ambulances, fire trucks,
rescue vehicles and the like particularly those existing at
airports and used to fight fires and rescue victims of air
crashes located on or nearby the airport. Such emergency
vehicles must have the capability of traveling as quickly as
possible over paved runways, roads and the like and the
capability of traveling as quickly as possible over soft
terrain such as mud, sand, snow and the like.
It is well ~nown that the traction of vehicles on soft
terrain may greatly improve by decreased inflation pressure
within the tires and thus increased contact area between the
tires and terrain. Central tire inflation/deflation systems
are also known, particularly for military vehicles as may be
seen by reference to U.S. Patent Nos. 4,690,331, 2,634,781
and 3,361,180. Such systems are known as central tire
inflation systems tCTIS) which allow the operator to remote-
ly, manually and/or automatically vary and/or maintain the
inflation pressure of one or more of the vehicle tires
utilizing an on board source of pressurized fluid (usually
compressed air from the vehicle air brake compressor and/or a
compressed air reservoir) and are quite satisfactory for
vehicles such as military vehicles which may utilize the CTIS
over varying conditions of terrain.
However, these prior art systems are not satisfactory
for the aforesaid emergency vehicles since they include an
inflation system as well as a deflation system for the tires,
are relatively slow in inflating or deflating the tires and
are relatively expensive to install and maintain.
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U.S. Patent No. 3,361,180 discloses a tire deflating
system for military aircraft, including an electrically
actuated tire valve, which will enable the aircraft to take
off fully loaded with the tires fully inflated and which will
S allow the tires to be partially deflated in flight to a
predeter~ined lower pressure to enable the aircraft to land
on an unprepared field or sandy desert. The electrically
actuated tire valve requires three sets of brushes and
commutator rings to energize the tire valve. The system is
likewise slow acting, relatively expensive and difficult to
maintain.
Accordingly, it is an object of this invention to
provide a tire deflation system wherein the pressures in all
of the tires of an emergency vehicle may be readily and
quickly deflated to a predetermined minimum pressure while
nearing the end of a hard surfaced, road or runway so that
the "footprint" of the tires is increased at or about the
time the vehicle reaches soft terrain to enable the vehicle
to reach the site of a crash as quickly as possible.
Another object of the invention is to provide a novel
tire deflation system for emergency vehicles whereby a
minimum pressure of the deflated tirés is obtained by
controlling the duration of time that the tires are being
deflated.
~ccording to a feature of the invention, a rapid tire
deflation system for emergency vehicle tires comprises a
plurality of wheels each provided with a pressurized tire.
An air actuated two position wheel valve is mounted on each
wheel. Each valve is normally closed and when opened,
exhaust the pressurized air in the associated tire to
atmosphere. An air circuit for actuating each wheel valve
includes conduits for communicating air between each wheel
valve and a single solenoid valve connecting the air circuit
to a source of pressurized air on the Yehicle. The solenoid
valve is mounted on the vehicle and is energized by a
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manually activated switch which when actuated, energizes the
solenoid valve to pressurize the air circuit to open the
wheel valves to deflate the tires. An electrical control
circuit and timer control the duration of time ~he solenoid
is energized. The duration of time the solenoid valve is
energized is also the duration of time the wheel valves are
opened so that the tires are depressurized to a predetermined
lower pressure.
This and other objects and advantages of the present
invention will becomes apparent from a reading of the
following description of the preferred embodiment taken in
connection with the attached drawings.
Figure 1 is a schematic illustration of the pneumatic
components of the present invention as utilized to control
the deflation of the tires of an emergency vehicle.
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Fig. 2 is a sectional view of the normally closed
wheel valve.
In accordance with this invention all of the tires
12 of emergency vehicles as described above are deflated
5 substantially, simultaneously and rapidly by the
deflation system 10 shown in Fig. 1. The inflatable
tires 12 are each mounted on a tire rim 14 which is
fixed to a wheel hub assembly 16 rotatably supported on
the outer end of an axle housing 18 by means of bearings
10 20. An annular sleeve 24 is pressed fitted to the axle
at a location inboard of the bearings 20. The wheel hub
is provided with an inwardly extending sleeve type
annular flange 26 telescopically surrounding sleeve 24.
A pair of rotary seals 28 and 30 extend radially between
15 the outer periphery of sleeve 24 and the inner periphery
of sleeve type flange 26 to define an annular seal
chamber 32 therebetween, as may be seen in greater
detail by reference to U.S. Patent No. 4,434,834,
assigned to the assignee of this invention. Sleeve 24
20 is provided with an inlet 34 and a passage 36 opening to
the chamber 32. The sleeve type flange 26 is provided
with a generally radially extending passage 38 extending
from the sealed chamber 32 to the exterior outer
diameter surface thereof. A single passage 40 may be
25 provided in the radial flange portion 42 of the wheel
hub 16 for passage of a pressure conduit 44.
The pressure conduit 44 is connected to the inlet 46
of the tire control valve 48 mounted on the wheel hub
16. The valve 48 has a port 50 connected by a pressure
30 conduit 52 to the interior chamber 54 of the tire 12. A
manual inflate and check valve 56 may be connected to
the conduit 52 or directly through the rim 14 to the
tire chamber 54.
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As may be seen by reference to Fig. 2, the wheel
valve 48 is an air actuated normally closed valve. The
valve 48 defines three ports, port 50 connected by
conduit 52 to the tire chamber 54, port 46 connected to
5 the sealed chamber 32 and port 58 connected to the
exhaust conduit 60 which is vented to atmosphere. Valve
48 includes a tubular body 62 sealed by end plugs 64 and
65. An annular valve seat 68 is positioned between the
ports 50 and 58. A valve member 70 having a valve seat
10 72 is urged by compression spring 74 into sealing
engagement against the seat 68. The plug 64 includes a
projection 76 partially extending into a blind hole in
the valve member 70 forming a cavity 78 to retain the
spring 74. Accordingly, the valve 48 is normally held
15 in closed position to prevent air from escaping from the
conduit 52 to the exhaust conduit 60.
The valve 48 is opened by pressurized air entering
port 46 to actuate the piston 80 to thereby move the
piston and the projection 82 toward the valve member 70
so that the valve seat 72 thereof is moved off of the
valve seat 68 against the bias of spring 74. The valve
seats 72 and 68 are thus unsealed and moved apart far
enough to permit free flow and rapid exhaust of air from
the tire 12 to the conduit 60. While the structure of
valve 48 has been described with a certain degree of
detail, it is understood that air actuated valves
performing the same function, but of different
construction, may be substituted therefor.
Each of the wheel assemblies 16 of the emergency
30 vehicle is provided with a wheel valve 48 each supplied
with actuating pressurized air from a common source 84
which is typically a pressurized air reservoir supplied
by a compressor. The pressurizing air source 84 is
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connected to inlet 86 of a dual shut-off and exhaust
valve 88 by a conduit 90. The outlet 92 of valve 88 is
connected to a manifold 94 and is normally connected to
the port 100 of the exhaust conduit 102. A plurality of
5conduits 104 connect the manifold 94 to each of the
inlets 34, sealed chamber 32, conduits 44 and hence to
the wheel valves 48 on each wheel of the vehicle.
The shut-off and exhaust valve 88 has a first or
normal position, as shown in Fig. 1, blocking the flow
oOf air between the inlet 86 and outlet 92 thereof, and a
second or open position permitting air flow between the
inlet 86 and outlet 92 thereof. The valve 88 is
electrically operated and preferrably a solenoid
controlled valve of conventional design spring biased to
15the normal position shown in Fig. 1. In the normal
closed position outlet 100 is open to exhaust air to the
exhaust 102 from the manifold 94 and the air circuit to
each wheel valve 48.
The solenoid 106 of the valve 88 is connected to a
20"deflate" push button switch 108 mounted on the control
panel 110 located in the cab of the vehicle. An on/off
switch 112 and a timer 114 with a screw operated
adjusting means 116 are also mounted on the control
panel 110 and connected to a battery 118. The timer
2sadjusting means 116 is initially manually adjusted so
that the timer clock therein is set to run for a
predetermined period of time necessary to deflate the
tires 12 from a normal over the road operating pressure
of, for example 60 psi, to a lower pressure, for example
3020 psi, for operation over soft terrain such as mud,
sand, snow or the like. The duration of time that the
timer clock is set to run depends on the initial tire
pressure, the tire size and the size of the passages and
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ports in the conduit 52 and wheel valve 48 mounted on
each wheel 16. Generally, the timer adjusting means 116
is manually set so that the timer 114 operates for a
duration of between a few seconds and 30 seconds
5 corresponding to the time necessary to lower the tire
pressure from its normal operating pressure to a minimum
pressure for most efficiently operating over soft
terrain.
Assuming that an emergency vehicle, equipped with
10 the tire deflation system of this invention, is
stationed at an airport and an air crash occurs nearby
in soft terrain some distance from the end of the
runway. The vehicle can travel at top speed down the
runway with the tires inflated at normal pressure. As
15 the vehicle approaches the end of the runway the
operator turns the switch 112 to the "on" position. As
the vehicle approaches soft terrain, the operator pushes
the "deflate" push button lG8 energizing the solenoid
106 of the valve 88 and starts the timer 114. The
20 solenoid 106 moves the valve 88 to open the inlet 86 and
outlet 92 so that pressurized air from the air source 84
flows into the manifold 94 and the air circuit to open
the normally closed wheel valves 48. At the same time,
the outlet port 100 of the solenoid valve 88 is closed.
25 The wheel valves 48 are all kept open so long as the air
circuit to the valves 48 is pressurized. After the
timer 114 has operated for the predetermined period of
time, the solenoid 106 of the solenoid valve is
deenergized and the valve 88 is moved to its normal
30 deactivated position shown in Fig. 1. The air circuit
to the wheel valve 48 is depressurized and each of the
wheel valves move to the closed position shown in Fig. 2
with the pressure of each tire lowered to a predetermined
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minimum pressure for traveling over soft terrain which
occurs at or about the same time the vehicle reaches
soft terrain.
Accordingly, this invention provides a tire
5 deflation system for rapidly deflating all of the tires
of an emergency vehicle which is operator initiated by
simply pushing the push button switch 108 as the vehicle
approaches soft terrain so that all of the tires are
deflated for a predetermined period of time to enable
10 the vehicle to proceed over soft terrain with a larger
tire "footprint" and increased traction so that the
vehicle can proceed to the site of a crash, or the like,
as quickly as possible.
