Tire pressure indicator

[0001] Not Applicable

[0002] Not Applicable

[0003] This invention is directed to a tire pressure indicator that can readily be installed on valve stems of vehicle tires to provide a highly visible indication when the tire pressure is above or below a predetermined limit.

[0004] Proper maintenance of tire pressure is important in the operation of a motor vehicle for a number of reasons. First, it is noted that under inflation of vehicular tires is the leading cause of tire failure. Second, the maintenance of proper tire inflation promotes more even tread wear and thus increases the life of the tire. Lastly, a vehicle with properly inflated tires will exhibit greater gas mileage than a vehicle with under inflated tires.

[0005] Tire failure is generally caused by overheating which is typically caused by under inflation of the tire and/or by overloading of the vehicle. More specifically, tire heating is caused by the normal flexure of the tire sidewalls and road friction. If the tires are properly inflated, the sidewalls will be stiff and sidewall flexure is reduced. However, if the tires are under inflated, greater sidewall flexure along with tire heating results. Thus, in the circumstance in which tires are under inflated, overheating and tire failure are more likely to occur.

[0006] Various tire pressure measurement devices have been developed to allow the measurement of tire pressure. For example, hand-held tire pressure gauges are well known. The user typically slides such a pressure gauge over the valve stem of the tire until the gauge seals with the value stem so as to minimize the escape of air during the measurement process. Once the gauge has been appropriately positioned, the user notes the pressure value displayed on the gauge. The user then compares the measured value to the tire pressure value recommended by the tire manufacturer to determine if the tire is under inflated. The user must either refer to a manual or other source for this information or commit this value to memory.

[0007] Mechanical tire pressure gauges of the above-described type typically require a great deal of user intervention or do not provide a constant and instantaneous indication of whether the tire is under inflated. Tire pressure is often not measured due to the inconvenience associated with the use of typical mechanical tire pressure gauges and consequently drivers are often operating their vehicles on under inflated tires.

[0008] It would therefore be desirable to have a tire pressure indicator that may be installed on the valve stem and left in place so as to provide an immediate visual indication upon inspection if a tire is exhibiting a pressure below a predetermined limit.

[0009] A tire pressure indicator for coupling with a valve stem of a tire is disclosed. The tire pressure indicator provides a first visual indication in the event that the tire pressure is below a first threshold limit and a second visual indication if the tire pressure is above a second threshold limit.

[0010] The presently disclosed indicator includes a base having internal threads that is mateable with a valve stem by threading the base onto cooperative threads of the valve stem. The base having first and second ends includes a pin that opens the valve within the valve stem when the first end of the base is threaded onto the valve stem. At least one opening is provided through the base. A diaphragm is disposed over the second end of the base and a collar having first and second ends is mounted to the base so as to capture the diaphragm between the second end of the base and the collar. The center of the diaphragm moves away from the valve stem in response to increased air pressure on the side of the diaphragm in fluid communication with first end of the base. The distance that the center of the diaphragm moves is a function of the air pressure within the pressure range of interest.

[0011] A post or piston is disposed over the diaphragm and a spring is disposed around the post between the second end of the collar and the diaphragm. The spring serves to urge the diaphragm downward as the pressure below the diaphragm decreases.

[0012] A dome shaped indicator is rotatably mounted to the post and moves up and down in response to movement of the center of the diaphragm under varying pressure while permitting rotation of the indicator with respect to the diaphragm. The outer surface of indicator has alternating colored segments that extend from near the top of the dome to the lower periphery of the dome. A plurality of recesses, each having a ramp formed on a surface of the respective recess, is formed in the outer surface of the indicator.

[0013] A dome shaped cover is disposed over the indicator and is mounted to the collar. The cover includes alternating clear and opaque arcuate segments that extend generally from the top center of the cover toward the lower periphery of the cover. A first set of colored segments is visible through the clear segments of the cover when the tire pressure is above a predetermined limit and a second set of colored segments is visible through the clear segments of the cover when the tire pressure is below the predetermined pressure limit. A plurality of projections is provided on the inside surface of the cover, each projection having a ramped surface that is cooperative with the ramped surfaces in the recesses of the indicator to define a first rotational position of the indicator.

[0014] More specifically, in response to air pressure above a predetermined pressure limit at the first end of the body, the diaphragm deforms and the piston moves toward the cover causing the indicator to similarly move toward the cover. The ramps projecting from the cover cooperate with the ramps in the recesses in the outer surface of the indicator to align the first set of alternating colored segments of the indicator with the transparent segments of the cover in the first predetermined position so that the first set of alternating colored segments are plainly visible through the transparent segments of the cover.

[0015] The lower peripheral edge of the indicator includes a serrated profile that includes ramped surfaces. The ramps in the serrated edge along the lower periphery of the indicator cooperate with ramps formed on the outside surface of the collar to define a second rotational position of the indicator when the tire pressure is below the predetermined pressure limit. More specifically, when the tire pressure is below the specified pressure limit, the spring urges the diaphragm and the post downward causing the indicator to also move downward. The ramps on the lower periphery of the indicator slide downward along the ramps of the collar causing the indicator to rotate into the second predetermined position in which the second set of colored segments are plainly visible through the transparent segments of the cover. In the foregoing manner, a visible indication is provided as to whether the tire pressure is above or below the predetermined pressure limit.

[0016] Other features, aspects and advantages will be apparent to those of ordinary skill in the art from the Detailed Description of the Invention and Drawing that follow.

[0033] In accordance with the present invention, a tire pressure indicator is disclosed. The tire pressure indicator is coupled to the valve stem of a tire and provides a visual indication of whether the tire pressure is above or below a predetermined pressure limit. A determination may thus be made by visual inspection of the indicator as to whether the tire pressure is below a tire pressure value recommended for safe operation of the vehicle. Referring to FIGS. 1-8, the tire pressure indicator 10 includes a base 12, a diaphragm 14, a post 16, a spring 18, a collar 20, an indicator 22 and a cover 24. The tire pressure indicator includes first and second camming mechanisms that define first and second rotational orientations of the indicator with respect to the cover as subsequently described. The first camming mechanism is operative during axial movement of the indicator in a first direction when the air pressure is above a specified pressure limit to cause rotation of the indicator into a first rotational orientiation with respect to the cover and the second camming mechanism is operative during axial movement of the indicator in a second direction opposite to the first direction when the air pressure is below the specified pressure limit to cause rotation of the indicator into a second rotational orientiation with respect to the cover.

[0034] More specifically, female threads 26 are provided at a first end 28 of the base 12 and the second end 32 of the base 12 includes a cylindrical end portion 30. The female threads 26 are typically sized to permit threaded engagement with the male threads of a conventional tire valve (not shown). First and second cavities 34, 36 are formed within the first and second ends 28, 32 of the base 12 respectively and at least one opening 38 is provided between the first and second cavities 34, 36 through a divider 40 to permit pressure equalization therebetween.

[0035] The diaphragm 14 is disposed over the second end 32 of the base 12 and includes a first surface 42 facing the second cavity 36 when the diaphragm 14 is disposed on the second end 32 of the base 12. The diaphragm 14 further includes a second surface 44 on the opposing side of the diaphragm 14. The diaphragm 14 comprises a generally circular flexible member that is fabricated out of rubber or any other suitable material and includes a peripheral edge 46 around the circumference of the diaphragm 14. The peripheral edge 46 is captured between the second end 32 of the base and the collar 20 as subsequently discussed. A nib 48 extends generally from the center of the second surface 44 of the diaphragm 14 and serves as a locator for the post 16. The thickness of the diaphragm 14 is determined such that the center of the diaphragm 14 will move a specified distance in the direction away from the base in response to increased air pressure on the first surface 42 of the diaphragm 14 and in the direction toward the base 12 in response to decreased air pressure at the first surface 42 within a defined pressure range.

[0036] The post 16 includes a flange 50 at a first end and a generally conical head 52 at a second end. A shaft 54 couples the flange 50 and the head 52. The underside of the flange 50 includes a recess 56 that is sized to receive the nib 48 projecting from the second surface 44 of the diaphragm 14. In the assembled pressure indicator 10, the post 16 is positioned with the flange 50 abutting the second surface 44 of the diaphragm 14 with the nib 48 extending into the recess 56 within the flange 50 to locate the post 15 on the center of the diaphragm 14.

[0037] The spring 18 is disposed coaxially over the post 16 and serves to urge the post 16 and the diaphragm 14 toward the base 12.

[0038] The collar 20 includes a first end 58 having a generally cylindrical bore 60 sized for a close fit with the cylindrical end portion 30 of the base 12. An opening 62 is provided in the second end 64 of the collar 20 to allow the second end of the post 16 and the head 52 of the post 16 to extend therethrough. Additionally, the second end 64 of the collar 20 includes an interior shoulder 66 that provides an abutment for the spring 18. A lip 68 is provided within the collar 20 that serves to engage the diaphragm 14 and capture the diaphragm 14 in its mounting position between the second end 32 of the base 12 and the lip 68 of the collar 20 when the collar 20 is mounted on the cylindrical end portion 30 of the base 12. A plurality of integrally formed ramps 70 and stops 71 are provided on the exterior surface of the collar 20. The function of the ramps 70 is subsequently discussed in connection with the positioning of the indicator 22. The stops 71 limit the rotational movement of the indicator so as to cause the indicator to assume a defined rotational orientation when the air pressure in a tire to which the tire pressure indicator 10 is coupled, is below a specified threshold pressure value.

[0039] The indicator 22 is generally dome shaped and includes a wall 72 defining an interior cavity 74. The indicator 22 has a recess 76 within the interior cavity that is sized to receive and retain the head 52 of the post 16 while permitting free rotatable movement of the indicator 22 around the head 52 of the post 16. While the illustrated post 16 includes generally conical head 52 any suitably shaped head may be employed with a cooperative recess that captively engages the head while permitting rotation of the indicator 22 around the head 52. The indicator 22 is mounted to the post 16 by urging the head 52 of the post 16 into the recess 76. The indicator 22 includes a lower peripheral edge 78 and a plurality of ramps 80 formed within the interior cavity that mate with and are slidable along the ramps 70 of the collar 20. The rotation of the indicator 22 in one direction is limited by the stops 71.

[0040] Colored arcuate segments 82 are provided on the outer surface 84 of the wall 72. The segments 82 extend from near the peak of the dome shaped indicator 22 toward the lower peripheral edge 78. In the illustrated embodiment, alternating segments are of the same color; e.g. a first set of segments 82a may be black and a second set of segments 82b located between the first set of segments may be red. The colors specified are purely for illustrative purposes and different colors or visual patterns may be used. Of significance is that the alternating sets of segments be visually distinguishable, one from the other.

[0041] A plurality of angled recesses 86 is provided in the outer surface of the indicator 22 that extend radially outward from near the peak of the dome. The angled recesses each include a sloped surface 88 that cooperates with a cooperative projection on the cover 24 to define the rotational orientation of the indicator 22 with respect to the cover 24 when the pressure within a tire to which the pressure indicator 10 is coupled is above a specified threshold limit.

[0042] The dome shaped cover 24 is disposed over the indicator 22 and is secured to the collar 20 by ultrasonic welding, an adhesive, or any other suitable means. The cover 24 includes alternating arcuate segments 92 that extend generally from the near the peak of the dome shaped cover 24 to the lower peripheral edge 90 of the cover 24. A first set of the segments 92a that includes every other segment is opaque while the second set of segments 92b, that includes those segments between adjacent segments 92a is transparent. Thus, the segments 82 of the indicator 22 are visible through the clear segments 92b of the cover 24. The cover 24 may be produced via a two-part molding process to produce the transparent and opaque segments 92b, 92a respectively or alternatively, a clear cover may be provided and selected areas may be painted or coated to provide the first set of segments 92a that are opaque.

[0043] The cover 24 further includes a plurality of projections 96 that are located inside the cover 24 near the peak of the dome shaped structure. The projections 96 extend outward generally radially from near the peak of the dome shaped structure and are oriented such that the projections 96 are receivable in the angled recesses 86 in the indicator 22. More specifically, the projections 96 each include a ramped surface 97 that is cooperative with the ramped surface 88 of the angled recesses 86 of the indicator 22 to cause the indicator 22 to rotate into a first rotational position in which the segments 82a of the indicator 22 are visible through the clear segments 92b of the cover 24. The indicator 22 rotates into the first position when urged upward as a result of tire pressure in excess of the specified pressure limit as a result of slidable movement of the sloped surfaces 97 of the projections 96 on the sloped surfaces 88 of the recesses 86 of the indicator 22. The viewing of the segments 82a through the segments 92b of the cover indicates that the tire pressure is above the specified threshold limit.

[0044] When the tire pressure is below the predetermined threshold limit, the spring 18 urges the post 16 and the diaphragm 14 downward causing the ramps 80 within the interior cavity 74 of the indicator 22 to slide with respect to the ramps 70 on the collar 20 into a second rotational position in which the segments 82b of the indicator 22 are visible through the clear segments 92b of the cover 24. In the foregoing manner a visual indication is provided that the tire pressure is below the specified threshold limit.

[0045] It will be appreciated by those of ordinary skill in the art that variations to and modification of the above-described tire pressure indicator may be made without departing from the inventive concepts disclosed herein. Accordingly, the invention should not be viewed as limited except by the scope and spirit of the appended claims.