Wheel mounted electronic tire pressure gauge
This invention relates in general to tire pressure gauges, and more particularly, to a wheel mounted electronic tire pressure gauge system using valve stem mounted strain gauge transducers circuit connected to a hub mounted display device for a wheel or dual wheel unit. 
     Proper inflation of tires is important and air pressure indication as to whether a tire is over inflated or whether the air pressure has dropped below safe operating levels is useful in knowing when to bleed air or increase tire pressure. Normal practice is to check tires infrequently by removing a valve cap and applying a pressure gauge to the valve stem. While a visual check of the tire and wheel may visually indicate under inflation this is not too reliable with present day low pressure and radial type tires. Improper tire inflation pressures is a major contributor to excessive tire wear and tire failure blowouts so great savings are realized, through increased tire life by maintaining proper tire pressures, along with enhanced safety. Proper tire inflation also enhances vehicle ride and handling characteristics so, if a vehicle is provided with an easy to use reliable tire pressure gauge system mounted on each wheel unit tire pressure will be checked more frequently and proper tire pressures will be more closely maintained. 
     It is therefore a principal object of this invention to provide a conveniently useable wheel mounted electronic tire pressure gauge system. 
     Another object is, through use of such a tire pressure gauge system, to increase tire wear life. 
     A further object is to improve vehicle ride and handling through proper tire inflation and to enhance vehicle safety with fewer tire blow out failures. 
     Still another object is to provide such an electronic tire pressure gauge system that draws low power for pressure display only when manually actuated for tire pressure indication at each respective wheel unit. 
     Features of the invention useful in accomplishing the above objects include, in a wheel mounted electronic tire pressure gauge system, valve stem mounted strain gauge transducers, one in each valve stem, connected to a wheel hub mounted display device that includes a small battery power supply. The strain gauge transducers used are small and light and light circuit wires are used with quick disconnect connectors and the hub mounted display device altogether are sufficiently small and light so as to not impose materially adverse unbalance problems on a rotating wheel while the using vehicle is moving down the road. Manual control switching is used to connect battery power to the strain gauge(s) of the wheel unit and to the display device mounted on the hub of that wheel unit. Wheel units are single wheel units and dual wheel units with, in the case of dual units, two strain gauges, one in the valve stem of each wheel tire controllably connected through manual switches to the hub mounted display device of that wheel unit. 
     Specific embodiments representing what are presently regarded as the best modes of carrying out the invention are illustrated in the accompanying drawings. 
    
    
     In the drawings: 
     FIG. 1 represents a side elevation of a vehicle wheel with a valve stem mounted strain gauge wire circuit connected to a wheel hub end mounted display device; 
     FIG. 2, a partial enlarged cut away and sectioned view taken along line 2--2 of FIG. 1 showing wheel, wheel mounting and tire pressure indicating system detail; 
     FIG. 3, an enlarged partially cut away and sectioned view taken along line 3--3 of FIG. 2 of a valve stem mounting; 
     FIG. 4, a partial cut away and sectioned view like FIG. 2 however of a dual wheel unit in place of a single wheel with both tires and wheels of the dual wheel unit included with the tire pressure indicating system; 
     FIG. 5, a partial end view of the wheel hub of the dual wheel unit of FIG. 4; and 
     FIG. 6, a block schematic of a tire pressure indicating system. 
    
    
     Referring to the drawings: 
     The vehicle wheel 10 of FIGS. 1 and 2 is shown to be generally a wheel unit of standard construction mounted by roller bearings 11 for rotation of wheel hub 12 and wheel 10 about wheel spindle 13. The wheel disk 14 that mounts wheel rim 15 via a welded interconnection 16 is mounted on wheel hub 12 by a plurality of nut and stud assemblies 17 in a conventional manner. A grease cup 18 is inserted in and mounted in hub bearing opening 19 to enclose the bearing opening 19 and the threaded nut 20 end of wheel spindle 13. 
     Referring also to FIG. 3 valve stem 21, for tire 22 mounted on wheel rim 15, is mounted in opening 23 in wheel rim 15 in a conventional manner with the groove 24 of stem mounting base 25 fitting the rim of opening 23. The valve stem 21 has an extension 26 terminating in an externally threaded 27 and internally threaded 28 end into which valve insert 29 would be threaded if valve stem extension adapter 30 were not used with the valve insert 29 instead threaded into internal threads 31 of the adapter 30 and valve cap 32 threaded 33 on the outer end thereof. The stem extension adapter 30 is provided with a flat portion 34 for the mounting of a strain gauge pressure transducer 35 having a tubular extension 36 extended into opening 37 of valve stem extension adapter 30. This provides for free fluid air communication from the interior of the strain guage pressure transducer 35 through tubular extension 36, the center opening 38 of valve stem extension adapter 30, and the opening 39 through valve stem 21 to the interior of the tire 22 mounted on wheel rim 15. 
     The air strain gauge pressure transducer 35 is of a four wire or six wire type such as produced and made available in the market place by companies, for example, Celesco Transducer Products, Inc.; Entran Devices, Inc.; The Foxboro Co.; Kavlico Corp.; Motorola, Inc. Semiconductor prod and others. A quick disconnect connection 40 connects the wire package 41 of light fine wires to the wire connections 42 of the strain gauge pressure transducer 35. Quick disconnect connection 43 connects the other end of wire package 41 to the signal converter, battery, display driver and display unit 44 mounted on the outer end of grease cup 18. 
     With the dual wheel unit 45 of FIGS. 4 and 5 dual tires 46 and 47 are mounted on outer rim 48 and inner rim 49 respectively and a valve stem extension adapter 30 is mounted on a valve stem 21 on outer rim 48 just like with the single wheel of FIGS. 1, 2 and 3. With inner rim 49 an extra long valve stem 21&#39; extends from inner rim 49 through openings 50 and 51 in wheel disk webs 52 and 53 that mount rims 48 and 49 from the wheel center 54 fastened by nuts 55 on wheel hub 56 at the end of axle 57. An additional valve stem extension adapter 30 is mounted on valve stem 21&#39; in order that both valve stem extension adapters 30 are accessable from the outside of the dual wheel unit 45 and for connection of both valve stem extension adapters 30 via their respective strain gauge pressure transducers 35 and wire packages 41 respectively to the signal converter, battery, display driver and display unit 66. The unit 66 is is mounted on the middle of a bracket 58 that is mounted by nuts 55 on two opposite side studs of wheel studs 59 for ease of viewing and operation of manual switches 60 and 61 included therewith. In the single wheel embodiment of FIGS. 1 and 2 the manual switch 60 is used. 
     Referring also to FIG. 6 the strain gauge air pressure transducer 35 is connected through small multi-wire wire package 41 to signal converter and battery circuit section 62 that is operationally connected through display driver 63 to the display section 64 that may be a liquid crystal type display. Manual switch 60 is included to connect one of the lines of wire package 41 for power feed from the battery (which may be a small watch type battery) to and through the transducer 35 and thereby also power flow for the signal converter of section 62, the display driver 63 and the display 64. With the dual wheel embodiment of FIGS. 4 and 5 the additional transducer 35&#39; therefore is connected through its multi-wire wire package 41&#39; to the signal converter and battery circuit section 62 for pressure checking of the air pressure in tire 47 when manual switch 61 is depressed for pressure indication display. Such momentary drain of battery power insures long battery life even though it is a small low power battery. A single display could be used as shown with the single wheel embodiment of FIGS. 1 and 2 or a two display unit 66 with two liquid crystal displays 67 and 68 could be used for the dual wheel unit as indicated in FIG. 5. 
     Whereas this invention has been described with respect to several embodiments thereof, it should be realized that various changes may be made without departure from the essential contributions to the art made by the teachings hereof.