Note: Descriptions are shown in the official language in which they were submitted.
TIRE DEFLATION SENSOR 2 1 0 5 3 1 9
FIELD OF THE lNv~l~lON
This invention generally relates to tire deflation sensing and
signalling devices able to warn the operator of a vehicle of
impending tire failure. This invention is an improved design
- over previous sensing and warning systems using levers,
switches, and associated fastening methods.
~A~R~.ROUND OF THE lNv~nllON
In 1986 my Tire Deflation Sensor came into being
when I personally felt the need to have a warning prior to
possible trailer tire failure. When I could not locate any
commercial product on the market intended for this purpose I
had to invent my own. Subsequent searches produced similar
products, although none met with my specifications for quality
or performance, nor was I able to locate any that were
available in retail outlets.
I used my invention in the ensuing years and, with
some minor modifications, it has performed flawlessly for me.
Over the years I was encouraged by many people to make it
available to the general public. When I was able to locate
a reasonably priced micro switch I decided to manufacture the
Tire Deflation Sensor and offer it in the marketplace.
DESCRIPTION OF PRIOR ART
Other inventors have designed various types of tire
deflation indicators using mechanical levers and acoustical
signalling devices. Since my invention is not comparable to
acoustical signalling devices, I am confining my attentions
to only that prior art which deals with mechanical levers.
These include: [U.S. Patents] Denhart (1934) #1,947,760;
- A ~
",
2105319
Neiswanger (1954) #2,686,493; Grajeda (1971) #3,602,885;
Mitchell (1980) #4,187,495 [canadian Patent] Clothier (1977)
#1,087,273.
Denhart [U.S. Patent (1934) #1,947,760] used a
lever system attached to guide wires and seems to be limited
to automobiles. The system design makes it impractical for
trailer use since the system is designed to work on four
wheels. Furthermore, guide wires would be difficult to
connect a trailer system to an automobile. The complexity of
a lever and guide wire system with proper tensions and
required fastening would make it difficult for the average
consumer to install and maintain.
Neiswanger [U.S. Patent (1954) # 2,686,493]
operates on the principle of an audio sound produced by a thin
steel lever dragging on the ground when tire pressure
decreases. This audio indication could not be heard when any
extraneous noise was present (i.e. a vehicle sound system,
occupant conversation, gravel road). My invention employs
both visual and audio warning signals which are controlled by
an electrically connected micro switch. Neiswanger's lever
height is not adjustable. The lever would have to be replaced
each time it was worn down, rather than readjusting the lever
downwards for additional use, in the manner that the lever rod
in the Tire Deflation Sensor can be adjusted.
Grajeda's [U.S. Patent (1971) #3,602,885] device
was designed to be attached to the body of an automobile or
trailer, a most inefficient location. The lever would be
affected by load changes and the constant movement of the
spring and shock system. A more efficient location would be
on the axle where the lever would be unaffected by the
suspension system and load changes within the tire
manufacturers specified load and pressure ratings. Grajeda's
-- 2 --
2105319
method of attachment of his device to the underside of the
vehicle body restricts the upper extension of the lever to the
depth of the device. This restriction means the lever cannot
readily accommodate various height differences in vehicle or
- trailer styles nor readily adjust for a fully loaded vehicle
or trailer. The method of attachment of the lever by a small
bolt into a tapped shaft is not of durable quality. The case
` -~ in which the copper electric contact strips are enclosed is
not waterproof. This invention is therefore unsuitable for
use on wet roads. Grajeda's invention would be particularly
dysfunctional when used on a boat trailer which is constantly
immersed in water when unloading a boat. Submersion would
probably cause this device to electrically short circuit.
Water could also become trapped in the horizontally attached
case in which the electric contact strips are enclosed.
Mitchell's [U.S. Patent (1980) #4,187,495] lever
method depends on the Honeywell Switch LSJIA-7A, which at
present costs $129.00 per switch, two of which are required
for a single axle trailer and four of which are required for
a tandem axle trailer. The micro switch used in my invention
is 1/40 of the cost of the switch used by Mitchell, making the
Tire Deflation Sensor much more economical to manufacture.
Mitchell's lever is can not be adjusted. Multiple lever
lengths are necessary to accommodate various wheel/rim size
combinations from 8" to 16". The lever rods on the Tire
Deflation Sensor are readily adjusted with an allen set screw.
The fastening method for Mitchell's device is very limited,
dictating that each consumer would have to purchase a specific
model for his individual requirements. Retailers cannot
- 30 profitably stock products with too many variances to meet all
possible combinations and requirements of each consumer. My
invention incorporates a universal fitting fastening bracket,
-- 3 --
A
2105319
thereby supplying the retailer with a product suitable for any
four-sided or round axle. The high price of the switches and
the various combinations of parts in Mitchell's invention
restricts the availability of his product, which is
contradictory to the public good. Consumers need a tire
deflation sensor that is inexpensive, well constructed, and
universally fitted to most axles, in order to attain safer
trailer towing.
- Clothier [Canadian Patent (1977) #1,087,273] has
constructed his lever arm of rigid material; the top is
wrapped around a shaft to form a spring for a spring action.
The construction of the lever with a rigid material does not
allow a trailer so equipped to be backed up over rough terrain
without causing damage to the lever. It is common for
trailers to be backed into an area of uneven rough terrain
comprised of holes, rocks, sticks, and roots. In normal use
boat trailers are backed into a body of water where the shore
and water edge will have large rocks as well as soft and
uneven ground. Obstructions and terrain during the backing
up could bend the lever out of shape or push the lever through
the housing, destroying the spring action and switch feature.
The attachment strap on Clothier's device allows moisture to
enter the case and therefore his device is not of waterproof
construction and would not be suitable for use during
inclement weather nor for boat trailer use. This device is
constructed in such a manner that it does not allow for simple
replacement of parts. The lever will wear out or be ground
down due to bumps and dips in the road. Clothier's assembly
is such that the whole unit would have to be replaced, thereby
making repairs expensive.
. ~
- ,r&
` 2105319
SUMMARY OF THE lN V~n llON
This invention relates to a low tire pressure
warning device and is particularly directed towards a new and
improved mechanical lever and warning switch device. The
device is able to detect a lowering of the height of an axle
which is caused by the deflation of air pressure in a
pneumatic tire. The micro switch is activated by the
mechanical lever rod and dependent cam and is thereby able to
switch on an electrical warning system to alert the driver of
the vehicle to the deflation of air pressure.
Tire manufacturers have stated that under-inflation
of tires creates excessive heat which can cause tire failure.
Tires operated under such conditions generate excessive heat
by flexing, thereby increasing the risk of tire separations
and tire damage.
Operating on tires with low air pressure creates a
potentially dangerous situation particularly on certain
geographical contours of a road or under certain conditions
such as hot weather or high speeds.
Low tire pressure, which can develop while driving,
- may precipitate other serious problems. A puncture acquired
while driving can develop over time into a rapid loss of air
pressure, resulting in complete tire failure. In many similar
situations there may be no detectable indication of a problem
until the driver is abruptly confronted by a sudden loss of
control. In most situations this invention will alert the
driver to the loss of air pressure and allow sufficient time
to slow down and stop the vehicle before loss of control
occurs.
In the past many different tire failure warning
devices have been designed. Most, if not all, prior
inventions had serious limitations such as high cost of
-- 5 --
2105319
components, non-waterproof switches, limited adjustability,
complicated installation, and unreliable points of attachment.
My invention overcomes all of these limitations and
has been in use on my personal trailer since 1986. It is
extremely dependable, of rugged design, and manufactured of
corrosion proof materials. All components and manufacturing
processes a-re of a low cost factor to make the invention
affordable to a broad motoring public. It is manufactured
with high quality materials and work~sn~h;p to ensure
dependability and long life.
Objectives and advantages of the Tire Deflation
Sensor are as follows:
(a) To provide a lever rod of flexible material so
that when a force is applied while backing up a trailer, the
lever rod will bend and thereafter return to its original
shape and the Tire Deflation Sensor will retain its' operative
function. The lever rod is comprised of a resilient material
which is easy to cut to size if necessary and is able to
- contain a protective member on one or both ends to extend the
life of the lever rod.
(b) To provide a warning device that is
universally adaptable to fasten on the majority of trailer or
vehicle axles. (Note: "Universal" here means a device
equipped with one bracket which is able to fit most four-sided
or round axles.
(c) To provide a lever rod which is adjustable to
fit all trailer axle height requirements. The lever rod can
be readjusted vertically to extend the life of the lever rod
after some wear to the lower end has occurred.
(d) To provide a lever rod with a protective
member of a highly wear resistant material on each end to
allow for the lever rod to be reversed when it has become worn
- 6
2105319
on one end and thereby double the life of the lever rod.
(e) To provide a device that is waterproof in both
saltwater and fresh water so that it is submersible without
any damage to the operative function of the tire deflation
warning device.
(f) To provide a device made from highly durable
materials to ensure long life and dependability.
(g) To provide a product in which the two main
replacement components, namely the lever rod and the centring
device are readily available in hardware or plastic stores,
thereby making replacement parts easily accessible.
(h) To provide the consumer with a reliable,
durable, long lasting, and well constructed product which is
simple and fully functional for the purposes for which it was
designed.
BRIEF DESCRIPTION OP DRAWINGS
The invention known as the Tire Deflation Sensor is
illustrated in drawings designated as: FIG 1, FIG 2, FIG 3,
FIG 4, FIG 5, and FIG 6.
FIG 1 is a view of a single device as seen from the
driver's side of the vehicle
FIG 2 is a view of a single device as seen from the
rear of the vehicle.
FIG 3 is a view similar to FIG 1 but showing
modifications thereof.
FIG 4 is a view similar to FIG 2 but showing
modifications thereof.
FIG 5 is a sectional view of a round axle and the
orientation of the universal clamping bracket against the
round axle.
FIG 6 is a three dimensional view of the clamping
bracket.
-- 7 --
- 2105319
,~
DT~rATT~T~n D~ rT~rIoN OF THE ~rr~dK~ ~MBODINENTS
The device known as the Tire Deflation Sensor is
attached to an axle adjacent to a tire, there being one device
for each tire. When a tire loses air pressure the axle height
is lowered, causing lever arm 6 to come into contact with the
ground surface. This ground surface contact causes dependent
cam 3 to tilt on hinge pins 4 in a forward motion, pressing
the normally open single pole single throw micro switch 20,
located in switch cavity 5, against the inside portion of body
1, the normally open SPST micro switch 20 will be closed,
thereby completing a closed electrical circuit when it is
connected to the vehicle~s electrical system.
The device illustrated in FIG 1, FIG 2, FIG 3, and
FIG 4 is comprised of body 1, described as a channel cut to
the designated shape. Square holes 2, located at the upper
and lower position on the web of the channel, are to
accommodate carriage bolts 55 used in fastening the Tire
Deflation Sensor to a trailer axle.
The method used to fasten the Tire Deflation Sensor
to most types of standard trailer axles is universal bracket
50 (see FIG 5 and FIG 6). Universal bracket 50 is also of a
channel construction. The channel, with V-type cutouts on
each flange, facilitates the gripping of various round axle
diameters; the flat web of the channel is used to accommodate
flat axle surfaces. The mounting bracket with round holes 60
on the web surface, matching in distance the square holes 2
on body 1, enables two carriage bolts 55 to line up to fasten
the Tire Deflation Sensor to the backside of most standard
trailer axles.
In this embodiment, a cylindrically shaped com-
ponent [cam 3] of a non-conductive corrosion-proof material
is a section of round stock, sized to a slightly shorter
-- 8 --
rJ 2 1 0 5 3 1 9length, than the inside width of the flanges of body 1. A
hole of a specific diameter and depth is prepared in each end
of said round stock directly opposite each other, but on an
axis offset from the true centre line of the said round stock.
Two hinge pins 4 are inserted into these holes, one on each
side, which can freely rotate in associated holes in the side
flanges of body 1. Due to the offset of these hinge pins 4
from the true centre of the cyclindrical component [cam 3~ a
cam-like motion is achieved when component [cam 3] is pivoted
on the hinge pins 4. Hence the description `cam 3'.
Switch cavity 5 is located within cam 3. Switch
cavity 5 accc -~ates a single pole single throw (SPST)
normally open micro switch 20, such as the waterproof version
TP33W003050 which carries a manufacturer's specification of
60,000 cycles at full electrical load. This micro switch can
be obtained from InTELaTECH inc. Mississauga, Ontario, Canada.
In this embodiment, the micro switch 20 is secured and
protected in switch cavity 5 with an epoxy-like substance.
Lever rod 6 is constructed of flexible material
which is able to bend beyond so and subsequently recover its'
original state without being distorted or damaged.
Lever rod 6 and the associated cam 3 are yieldably
restrained from unacceptable horizontal movement above cam 3
by the resilient means of centring component 7.
Centring component 7 is a loop made of resilient
material such as an `O-ring' which encircles lever rod 6 and
is stretched to hook over slightly outwardly bent ears on each
side flange on the upper portion of body 1. Centring
- component 7 maintains lever rod 6 in a vertical position. An
elastic band could also be used in emergency situations if an
`o-ring' is unavailable to maintain the operative state of the
device.
_ g _
2105319
Lever rod 6 is fitted with a protective member to
provide extra protection against wear during trailer use
caused ~y intermittent ground contact and from rocks and
irregular road surfaces. Protective member 8 is of a highly
wear resistant material with better wear resistance to
friction than the flexible material used in lever rod 6 and
may be in the form of a cap or insert.
The fastening method for lever rod 6 provides for
secure and positive gripping. The lever rod 6 is inserted
lo through the full perpendicular diameter of cam 3, extending
upwards through the centre of centring component 7. Lever rod
6 is then secured by allen set screw 9 which is firmly
enclosed in cam 3.
Allen set screw 9 and vertical hole within the
- diameter of cam 3 provide the means for liberal vertical
movement and height adjustment of lever rod 6. Lever rod 6
can be cut to length or allowed to extend above body 1, thus
providing for various wheel/rim combination height variations
for most trailer models.
After the tires are filled to the correct air
pressure lever rod 6 is adjusted to approximately 25 mm above
the ground and locked in place by allen set screw 9, which is
tightened to prevent lever rod 6 from further vertical
movement.
All components are manufactured from corrosion
proof material to ensure that the operative mechanical
components will not corrode and seize up due to moisture or
chemical elements (i.e. salt).
The waterproof properties of micro switch 20 and
' 30 the epoxy mounting method into cam 3 combine to enable this
device to be submersible. The waterproof construction also
prevents corrosion to electrical contact points, thus ensuring
-- 10 --
A
2 1 053 1 q
long life of the total unit.
The invention claimed is not limited to the
embodiments described. Particularly it may differ due to the
electrical switch location or how the combination of elements
are arranged to turn the electrical warning system on, but the
various tire deflation sensor embodiments will operate using
the same basic mechanical principles and/or various
arrangements of stated features.
It will be necessary to replace lever rod 6 and
lo centring component 7 periodically due to normal wear.
Replacement parts can be obtained from the manufacturer,
dealer, or sùbstituted with common objects available at local
hardware or plastic stores. Availability of replacement parts
at local outlets ensures that the Tire Deflation Sensor can
be maintained in an operative state with little effort.
Previous lever-type warning devices appear to be equipped with
levers and spring devices specifically designed for the
particular invention and not readily available. This would
make the devices non-functioning until replacement parts could
be obtained from the manufacturer.
During some of the previous eight years of road
testing and prototype designs, a plastic-type lever rod
without a protective member on the end was used. This was
done ~o prove that a plastic-type lever rod without a
protective member will work correctly providing the user
occasionally checks the lever rod for correct height settings
before he/she operates the vehicle on a road. A lever rod
with a protective member is a manufacturer's option and is
available to ensure longer durability of the lever rod and
allow less frequent visual inspections of the lever rod height
setting.
-- 11--
