Measuring and testing – Tire – tread or roadway – Tire inflation testing installation
Reexamination Certificate
2001-09-25
2003-07-22
Williams, Hezron (Department: 2855)
Measuring and testing
Tire, tread or roadway
Tire inflation testing installation
Reexamination Certificate
active
06595046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the fields of tires and tire pressure gauges. More specifically the present invention relates to an air pressure gauge apparatus which is combined with a tire valve stem to remain on the stem and display the tire pressure accurately and reliably over a wide range of ambient temperatures. The pressure gauge apparatus displays the tire pressure either continuously or momentarily with the application of force to a portion of the apparatus, so that the user can see at a glance whether the tire is properly inflated, and thus know at a glance whether the tire is safe and providing optimum tire wear and fuel efficiency. The gauge apparatus preferably is combined with the valve stem either by screwing it onto existing external cap threads of the valve stem and letting it remain attached until momentary removal during tire inflation, or by integrating it permanently into the structure of the valve stem during stem manufacture.
The essential elements of the continuous reading display version of the apparatus include an apparatus housing, containing a received air chamber for placement in fluid communication with received air from within a vehicle tire and containing a biasing air chamber containing a fixed quantity of biasing air, the chambers being sealingly separated from each other by a pressure equilibration structure which includes a pressure indicator element. The pressure equilibration structure moves within the housing to alter the relative volumes of the two chambers and thus to equalize the pressures of the two chambers. The pressure indicator element moves relative to the apparatus housing as the equilibration structure moves to equalize chamber pressures to display a tire pressure reading. The gauge apparatus operates on the principle of continuous re-establishment of pressure equilibrium, where alteration of received air pressure from outside the apparatus, that is, from within the tire, causes movement of the pressure equilibration structure within the housing against the trapped, fixed quantity of biasing air sealed within the biasing air chamber, thereby moving the indicator structure to reveal the pressure reading. The biasing air functions as a fixed standard against which varying tire pressure is measured.
2. Description of the Prior Art
There have long been gauges for measuring the pressure of air contained within vehicle tires. All of these prior gauges have relied on springs to provide biasing against which a pressure reading is taken. A problem with such prior gauges is that the pressure or air within the tire varies significantly at various ambient temperatures, while the resilience of a spring varies only negligibly. As a result, these prior gauges can show that the air pressure in a tire is correct when the tire is at or close to the temperature at which the gauge was calibrated, but also can show that the same quantity of air in the same tire is incorrect at an ambient temperature substantially different from the gauge calibration temperature. Thus a tire on an airliner, for example, may be filled and checked with a gauge in a geographic location which has an ambient temperature matching the gauge calibration temperature, and then the airliner may fly to a location having a very different ambient temperature so that the gauge shows the correct tire pressure to be incorrect. Furthermore, ambient temperature at high altitudes can be close to freezing, so that upon landing the airliner tires are still at this temperature and the gauge gives a misleading reading. In a worse case, the tire is filled and checked with the gauge at a temperature far from calibration temperature so that the pressure appears to be correct, but is not, and the airliner is endangered upon landing. The same problem exists for tires on ground vehicles, such as trucks and automobiles that are driven long distances north and south. Another problem with such prior gauges is that they become inaccurate at ambient pressures other than the ambient pressure at which they are calibrated. In these gauges, the tire air pressure is counterbalanced by the resilience of the spring plus the ambient pressure of the surrounding atmosphere entering the gauge. Ambient pressure varies with altitude, so that the sum of the spring resilience and ambient pressure varies and the reading is altered for the same tire pressure. Yet another problem with such prior gauges is that springs can lose resiliency, can corrode, and can add cost and complexity to the gauges.
These prior, spring biased gauges include Parker, U.S. Pat. No. 4,310,014, issued on Jan. 12, 1982 for a tire pressure indicator integral with a tire stem; Yabor, U.S. Pat. No. 4,901,747, issued on Feb. 20, 1990 for a tire inflation valve with a pressure indicator; Hunt, et al., U.S. Pat. No. 4,924,697, issued on May 15, 1990 for a tire-mounted air pressure gauge assembly; Huang, U.S. Pat. No. 5,014,643, issued on May 14, 1991 for a tire pressure indicator; Rabizadeh, U.S. Pat. No. 5,503,012, issued on Apr. 12, 1996 for a tire pressure monitoring device; Cummings, U.S. Pat. No. 5,569,849, issued on Oct. 29, 1996 for a visual tire cap pressure gauge; Wang, U.S. Pat. No. 5,856,619, issued on Jan. 5, 1999 for a tire pressure indicator; Halcomb, U.S. Pat. No. 5,979,232, issued on Nov. 9, 1999 for a tire pressure indicator carried aboard a wheel; Chi, U.S. Pat. No. 5,886,254, issued on Mar. 23, 1999 for a tire valve pressure-indicating cover utilizing colors to indicate tire pressure.
On the other hand, Wong, U.S. Pat. No. 4,384,543, issued on May 24, 1983, discloses a air release check valve and indicator device which automatically releases air from an over-inflated tire. A critical problem with Wong is that the device is inoperative, for multiple reasons. First, air from within a tire stem bearing against the piston
19
cannot move piston
19
because its pressure is opposed by equivalent air pressure entering the piston cylinder
16
through port
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. Thus the piston will not move no matter what tire air pressure is introduced into the device housing, and the device cannot function either as a pressure relief valve or as a pressure indicator. Nor can Wong receive air from an air line to fill the tire. Air entering Wong would have no way of moving the piston shaft to place its narrower segment within the partition aperture.
None of the displaceable, pressure measuring structures within the known prior art gauges are at equilibrium and at rest prior to installation on a tire. All have set points above atmospheric, unlike the gauge embodiments of the present application. All can become misleadingly inaccurate at ambient temperatures differing significantly from the gauge calibration temperature.
It is thus an object of the present invention to provide a tire gauge apparatus which relies on pressure equilibration rather than on a mechanical spring to produce a tire pressure reading, and thus gives the same accurate reading over a wide range of ambient temperatures because the pressure of air or other gas retained within a gauge biasing gas chamber changes in precise direct proportion to the pressure of air retained within a tire being tested over widely varying ambient chambers.
It is another object of the present invention to provide such a gauge apparatus which is unaffected by variations in ambient pressure and which gives accurate readings at virtually all ambient pressures, and which remains on the tire and produces an accurate and easily visible tire pressure reading.
It is still another object of the present invention to provide such a gauge apparatus which can be integrated into a valve stem during manufacture.
It is yet another object of the present invention to provide such a gauge apparatus which is initially at equilibrium with the atmosphere, is always active, which measures both under- and over-inflation, which can be constructed with a thin pressure responsive membrane with no elastic force constant, and does not rely on preset valves.
It is finall
Anthony Michael M.
Lemberger Gary
Mack Corey D.
Oltman Flynn & Kubler
Williams Hezron
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