Apparatus for indicating tire pressure

An apparatus for indicating tire pressure is disclosed which indicates whether the tire pressure in a pair of pneumatic tires is low, normal or excessive. The apparatus includes a valve body which is operatively connected to each of the tires and comprises a valve which longitudinally moves in the apparatus responsive to air pressure. The valve is operatively connected to a scale pan having an arcuate display portion at one end thereof. The display portion on the scale pan includes colored rectangular segments which are visible through a sight window in the apparatus. The scale pan pivots in response to valve movement and the colored segment visible in the sight window indicates whether the tire pressure is low, normal or excessive.

BACKGROUND OF THE INVENTION 
This invention relates to an apparatus for indicating tire pressure and 
more particularly to an apparatus for indicating tire pressure in a pair 
of pneumatic tires. 
Prior art devices are available which are designed to equalize the pressure 
between a pair of pneumatic tires. Devices are also available which 
indicate to the driver that a low pressure condition exists in one or both 
of the tires. Disadvantages of certain of the prior art devices which 
equalize air between the dual tires are that they are not sufficiently 
sensitive to changes in tire pressure. Some of the prior art devices 
permit the air in both tires to be lost if one of the tires experiences a 
sudden drop in pressure. A further disadvantage of some of the prior art 
devices is that they are not durable and frequently malfunction. A still 
further disadvantage of certain of the prior art devices is that they 
become contaminated with moisture and will freeze during periods of cold 
weather. Still another disadvantage in the prior art is that if the 
pressure sensing means thereof ruptures or fails due to leak or poor seal, 
the device will sometimes permit complete loss of air from one tire. 
A disadvantage in a vast majority of the prior art devices is that they are 
electronic in nature and due experience some malfunctions. Additionally, 
the electronic devices are extremely expensive. 
In applicant's earlier patent, a device was disclosed which was believed to 
represent a significant advance in the art. Applicant also filed a 
continuation-in-part application, Ser. No. 344,211 on Jan. 29, 1982 which 
also was believed to represent a significant advance in the art. 
Although applicant's earlier devices were satisfactory, applicant's earlier 
devices did not indicate if excessive pressure was present. Therefore, it 
is a principal object of the invention to provide an apparatus for 
indicating tire pressure which does indicate low pressure, normal pressure 
or excessive pressure. 
In applicant's earlier devices, it was necessary to disassemble the devices 
to change the calibration thereof. Accordingly, an object of this 
invention is to provide an apparatus for indicating tire pressure which 
may be calibrated without disssembling the apparatus. 
Still another object of the invention is to provide an apparatus for 
indicating tire pressure which has fewer parts than the prior art devices. 
A further object of the invention is to provide an apparatus for indicating 
tire pressure which includes a visual display in the form of a scale pan. 
Still another object of the invention is to provide an apparatus for 
indicating tire pressure which is durable in use. 
These and other objects will be apparatus to those skilled in the art.

SUMMARY OF THE INVENTION 
An apparatus for indicating tire pressure is described including a valve 
body operatively connected to a pair of pneumatic tires. A diaphragm valve 
means is mounted in the apparatus and is movable in response to the air 
pressure in the tires. A scale pan is pivotally mounted in the apparatus 
and is operatively connected to the diaphragm valve so that movement of 
the diaphragm valve causes the scale pan to pivot. The scale pan includes 
a display portion having generally rectangular, colored segments appearing 
thereon in a side-by-side relationship. A generally rectangular sight 
window is provided on the apparatus through which can be seen the colored 
segments. As the diaphragm valve moves, the scale pan pivots to display 
the colored segments. When one of the colored segments is visible in the 
sight window, the operator will be able to visually determine that a 
condition of low air pressure exists in the tires. When another of the 
colored segments is visible in the sight window, the operator will be able 
to determine that the air pressure in the tires is normal. When the third 
colored segment is visible in the sight window, the operator will know 
that the air pressure in the tires is excessive. The apparatus may be 
calibrated by rotating the sight window assembly. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
The apparatus of this invention is referred to generally by the reference 
numeral 10 while the reference numerals 12 and 14 refer to a pair of 
pneumatic tires such as commonly found on a truck 16 or the like. A 
mounting bracket 18 is provided for mounting the apparatus 10 on the wheel 
20 as seen in FIG. 2. 
Apparatus 10 comprises a valve body 22 having an internally threaded inner 
end 24 and an annular groove 26 provided inwardly thereof. Air passageway 
28 extends inwardly from one side of the valve body 22 and is adapted to 
receive one end of an air hose 30. Air hose 30 is maintained on the valve 
body 22 by bracket 32 and bolts 34. Hose 30 is operatively connected to 
the valve stem 36 of tire 14. 
Valve body 22 is also provided with an air passageway 38 extending inwardly 
from one side thereof and which communicates with chamber portion 40 in 
valve body 22. Air passageway 38 is internally threaded and is adapted to 
receive the valve 42 therein. Valve 42 is conventional in construction and 
is designed to permit air under pressure to be supplied to the chamber 
portion 40 as will be described in more detail hereinafter. 
Valve body 22 is also provided with an air passageway 44 extending inwardly 
from one side thereof and which communicates with chamber portion 40 as 
illustrated in FIG. 4. Air passageway 44 is adapted to receive one end of 
the air hose 46. Air hose 46 is maintained in air passageway 44 by the 
brackets 48 and bolts 50. Air hose 46 is connected to the valve stem 52 of 
tire 12. As seen in FIG. 4, air passageway 28 includes a port 54 which 
extends therefrom to chamber portion 40. 
Diaphragm valve 56 is received in the groove 26 and has a washer 58 mounted 
at one side thereof. Spring tube 60 is provided with an externally 
threaded surface and is threadably recevied by valve body 22 as 
illustrated in FIG. 4. The end of spring tube 60 engages the washer 58 to 
aid in maintaining the diaphragm valve 56 in position. As seen in FIG. 4, 
a display ring or cap 62 is threadably received on the other end of spring 
tube 60. 
Spring guide 64 is slidably mounted in the interior of spring tube 60 and 
has one end in engagement with the diaphragm valve 56 as seen in FIG. 4. 
Compression spring 66 is mounted in the interior of spring guide 64 so 
that one end thereof engages the spring guide 64 and so that its other end 
is in engagement with spring adjustment screw 68 threadably mounted in the 
spring tube 60. Adjustment screw 68 is provided with a central opening 70 
which slidably receives display rod 72. One end of display rod 72 is 
mounted in bore 74 formed in spring guide 64. As seen in FIG. 5, the other 
end of display rod 72 is provided with a notch 76 positioned between end 
portions 78 and 80. As seen in FIG. 5, end portion 78 extends outwardly 
beyond the end portion 80. 
Display adjustment screw 82 is threadably mounted at one end of spring tube 
60 and has shaft 84 secured thereto. Barrel 86 is pivotally or rotatably 
mounted on shaft 84 and has a spring 88 mounted thereon. Scale pan 90 is 
operatively secured to the barrel 86 for rotation therewith. Scale pan 90 
includes an arcuate display portion 92 having generally rectangular, 
colored segments 94, 96 and 98 provided thereon arranged in a side-by-side 
relationship. It is recommended that segment 94 be red, segment 96 be 
yellow and that segment 98 be black. O-ring 100 is mounted on the end of 
spring tube 60 and sealably engages the interior of cap 62 and the 
exterior of spring tube 60. Cap 62 is provided with an air passageway or 
vent opening 102 extending from the interior thereof to annual groove 104. 
O-ring 106 is mounted in grooves 104 and normally seals port or opening 
102. However, when pressure builds up within cap 62, the O-ring 106 will 
unseat to permit air to be vented from the interior of cap 62. The outer 
end of cap 62 is provided with a disc-shaped member 108 having a generally 
rectangular sight window 110 formed therein. Member 108 is maintained in 
cap 62 by any convenient means. The sight window 110 is offset 1/64th of 
an inch from the center of the member 108 so that the member 108 may be 
selectively rotated 180.degree. to permit calibration of the scale pan or 
the valve with respect to the sight window 110. 
In operation, air may be introduced to the interior of the tires through 
the valve 42. In its normal operation, the valve 56 will be in the 
position illustrated in FIG. 4 so that the interiors of the two tires will 
be in air communication with each other through passageway 44, chamber 
portion 40, port 54 and passageway 28. If excessive pressure builds up in 
the tires, the valve 56 will move to the right as viewed in FIG. 4 and 
will cause the spring guide 64 to also move to the right. As spring guide 
64 moves to the right, display rod 72 also moves to the right and the 
engagement of the end portion 78 with the barrel 86 causes the barrel 86 
to rotate which in turn causes the scale pan to also rotate. As the scale 
pan 90 rotates or pivots, the red colored segment 94 will appear or will 
be visible in the sight window 110 which will indicate to the operator 
that excessive pressure exists in the tires. When the tire pressure within 
the tires is normal, the yellow colored segment 96 will be visible in the 
sight window. Should one of the tires lose pressure, the valve member 56 
will move to the left as viewed in FIG. 4 to seal the port 54 thereby 
preventing air communication between the two tires. Movement of the valve 
56 to the left as viewed in FIG. 4 will cause the scale pan 90 to pivot so 
that the black colored segment 98 will be visible in the sight window 110 
to indicate to the driver or operator that a low pressure exists. 
Thus it can be seen that the apparatus of this invention accomplishes at 
least all of its stated objectives.