Abstract:
A reliable, low cost mounting assembly for a tire pressure transducer removably mounts the transducer on a multi-piece automobile wheel to enable the transducer to transmit tire pressure information that will enable the detection of an unsafe tire pressure. The mounting assembly includes a mounting bracket, a valve stem that passes through an air hole in the wheel and secures the mounting racket to the wheel while facilitating the adjustment of tire pressure, and a set of seals that seal both the valve stem and the mounting bracket relative to the air hole in the wheel. The mounting bracket has a generally flat base and a tab that extends radially outward from the base on one side at an oblique angle that assures proper positioning of the transducer within the wheel drop.

Description:
BACKGROUND OF THE INVENTION 
   Tire pressure transducers are mounted on a wheel inside a tire and detect air pressure within the tire. An air pressure transducer includes a radio frequency transponder that responds to received radio frequency signals. A computerized automobile monitoring system for a vehicle on which the tire is mounted transmits a radio frequency poling signal and the pressure transducer responds by communicating the detected pressure back to the automobile monitoring system. A different pressure transducer is located within each tire, thus making the tire pressure for each tire on a vehicle available to the automobile monitoring system. 
   Wheel mounted tire pressure transducers are expected to attain increasing importance as time goes by. Because improperly inflated tires can lead not only to excessive tire wear, but also to tire damage that can cause a high speed blow out, wheel mounted tire pressure transducers are becoming an important safety device on many automobiles. 
   The pressure transducers are presently mounted within a small box or container that is secured to a fastener in the form of a valve stem that controls moving air into and out of the tire in a conventional manner. On a single piece wheel the pressure transducer is mounted inside the tire with the valve stem portion extending through a valve stem hole in the wheel to provide access connection to an air nozzle. The valve stem hole on a one pieces wheel is located at least partially on a side wall of the wheel so that the transducer extends into the wheel drop and tire containment space at an angle relative to the cylindrical center region of the wheel. That is, the pressure transducer extends neither parallel to the central axis of the wheel nor radially outward relative to the central axis. Consequently, the pressure transducer is radially spaced from the wheel center cylinder but does not extend radially outward beyond the rim of the wheel and does not interfere with the mounting of the tire on the wheel or the flexing of the tire when the automobile is being driven. 
   This mounting technique is satisfactory for single piece wheels, but is not adequate for multi-piece wheels. Multi-piece wheels, which are typically high performance alloy wheels, have a modular design with two or three pieces being bolted together to form the complete wheel. Such multi-piece wheels are required to have the valve stem hole located in a central, cylindrical part of the wheel and extend radially through the wheel. Such a radial mounting causes the pressure transducer to extend too far radially outward from the central cylindrical portion of the wheel and beyond the outer radius of the wheel rim, thus interfering with flexure and mounting of the tire and incurring possible damage in the event of a flat tire. 
   Two different mounting techniques have been used to mount a pressure transducer within a multi-piece wheel. Neither technique is fully satisfactory. One technique is to simply weld the pressure transducer to a central portion of the wheel. This technique avoids the radial over extension problem but makes it difficult or impossible to move the relatively expensive pressure transducer from one wheel to another in the event that a wheel is exchanged because of a flat tire, because a new set of wheels have been purchased or for some other reason. Another technique is to secure the transducer to the central cylindrical portion of the wheel by a strap that extends around the circumference of the central portion of the wheel. Such a strap is subject to stretching and slippage under the centrifugal force of high speed wheel rotation and adds unwanted mass to the wheel. 
   A need thus exits for an inexpensive, low mass, reliable pressure transducer mounting assembly that properly secures the pressure transducer to a wheel, but allows the pressure transducer to be easily transferred to a different wheel when appropriate. 
   SUMMARY OF THE INVENTION 
   An inexpensive, low mass, reliable tire pressure transducer mounting assembly securely mounts a tire pressure transducer on a wheel, such as a multi-piece wheel, having a radially extending valve stem hole while allowing the transducer to be readily removed and transferred to a different wheel. The tire pressure transducer includes a container that houses a pressure sensing device and a radio communication device that transmits an indication of sensed tire pressure in response to a received wireless signal. 
   The tire pressure transducer mounting assembly includes a fastener in the form of a valve stem that extends radially into the valve stem hole of a multi-piece wheel, a mounting bracket located inside the wheel tire drop and a seal assembly that seals both the valve stem and the mounting bracket against the wheel in the vicinity of the valve stem hole. The bracket includes a base that is secured to the valve stem, and thus to the wheel, and a tab that extends generally radially outward from the base. The tab has a hole there through that receives a fastener that secures the transducer to the tab. Commercially available transducers have a fastener in the form a threaded valve stem that passes through the hole in the tab and is secured to the tab by a nut. 
   The seal assembly includes radially inward and radially outward hat shaped seals for the valve stem and mounting bracket respectively. The valve stem seal seals the valve stem to the wheel on the radially inward side of the wheel and the mounting bracket seal seals the mounting bracket base to the wheel on the radially outward side of the wheel (inside the tire). The mounting bracket base includes a concave seal seat that receives the bracket seal to assure proper placement of the base and proper sealing engagement with the seal. 
   The tab is positioned at an oblique angle relative to the base. The tab preferably deviates from a perpendicular angle relative to the base by an angle in the range of 8–12 degrees and deviates from perpendicular by an angle of 10 degrees in the preferred example. This angle results in the container portion of the tire pressure transducer extending radially inward into the drop for a leaded tire as it extends from the tab, thus assuring that the container portion of the tire pressure transducer is mounted closer to the central cylindrical portion of the wheel that forms the tire drop. This avoids interference with tire mounting and with tire flexure in the event of a flat tire. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the invention may be had from a consideration of the following Detailed Description, taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a simplified top view of a tire pressure transducer mounting assembly and method in accordance with the invention; 
       FIG. 2  is a sectional rear view of the tire pressure transducer mounting assembly and method taken along line  2 — 2  in  FIG. 1  in the direction of the arrows; 
       FIG. 3  is a sectional side view of the tire pressure transducer mounting assembly and method (with the transducer omitted for clarity) taken along line  3 — 3  in  FIG. 2  in the direction of the arrows; 
       FIG. 4  is a top view of a mounting bracket used in the mounting assembly and method sown in  FIGS. 1–3 ; 
       FIG. 5  is a cross sectional side view of a mounting bracket used in the mounting assembly and method shown in  FIGS. 1–3 , taken along line  5 — 5  in  FIG. 4  in the direction of the arrows; 
       FIG. 6  is an end view of a mounting bracket used in the mounting assembly and method shown in  FIGS. 1–3 ; and 
       FIG. 7  is an alternative arrangement of a mounting bracket used in the mounting assembly and method shown in  FIGS. 1–3 . 
   

   DETAILED DESCRIPTION 
   Referring now to  FIG. 1 , an air pressure transducer mounting assembly  10  in accordance with the invention secures an air pressure transducer  12  to the inside piece  14  of a multi-piece automobile wheel  16 . Air pressure transducers may be mounted within each tire of an automobile and sense the pneumatic pressure within the tire. A tire pressure subsystem which forms a portion of the automobile instrumentation transmits radio frequency poling signals to the pressure transducers. The pressure transducers respond to the poling signals by transmitting an indication of the tire pressure back to the tire pressure subsystem. 
   These tire pressure sensing systems improve driving safety by providing a warning to a driver if tire pressure becomes either too high or too low. Improper tire inflation can lead to a high speed blow outs and serious accidents. Even if a blow out does not occur, improper tire pressures can lead to early tire ware or to tire damage that will require early tire replacement. Presently available transducers  12  have a container portion  20  that is secured to a valve stem portion  22  that serves as a fastener for the transducer  12 . The container portion  20  contains the pressure sensor and wireless transmission circuits while the valve stem portion  22  has a threaded rod that passes through the valve stem hole in a single piece wheel and is secured to the wheel by a nut and suitable seals. 
   On a single piece wheel the valve stem hole is located at least partially on the sidewall. This enables the pressure transducer  12  to be oriented more horizontally and to remain within the tire drop so that it does not interfere with mounting and dismounting of tires or with tire flexure in the case of a flat tire. In contrast, the valve stem hole for a multi-piece wheel is located on a flat central portion of the wheel. This results in the transducer extending beyond the outer rim of the wheel and interfering with the mounting, dismounting and flexure of the tire when conventionally mounted by securing the valve stem  22  within the valve stem hole of a multi-piece wheel. 
   Making further reference to  FIGS. 2 and 3 , the multi-piece wheel  16  is shown as a two piece wheel in the present example with an inner piece or portion  14  and an outer piece or portion  18 . The two inner and outer wheel pieces  14 ,  18  are conventionally bolted together at blot flanges  26 ,  28  (the bolts not being shown) to form a complete wheel  16 . A ring or bead of silicon sealer  24  extends around the circumference of wheel  16  to seal the joint between bolt flanges  26 ,  28  and prevent leakage of air there through. 
   Wheel  16  has a tire drop  30  in the space between the inner and outer rims  32 ,  34  of wheel  16 . An extended tire drop or circumferential groove  36 , which provides a further drop for a loaded tire, is provided in the inner wheel piece  14  adjacent inner rim  32  to form an even deeper groove within tire drop  30  that extends around the circumference of wheel  16 . The mounting assembly  10  positions the transducer  12  within the tire drop  30  and the deeper tire drop for a loaded tire  36 . The transducer  12  is thus located radially inward of the outer edges of rims  32 ,  34  to enable mounting and dismounting of a tire on wheel  16  without damage to transducer  12  and to protect transducer  12  from damage in the event of a flat tire. 
   In the preferred embodiment, the air pressure transducer mounting assembly  10  includes a mounting bracket  40 , an L-shaped valve stem  42  having a cap  44  or an axially digital end of valve stem  42 , a threaded screw  46  that threadedly engages the radially outward end of valve stem  42  to secure the mounting bracket to the valve stem  42  and to the inner piece  14  of wheel  16 , and a set or assembly of seals  50  which include a radially inward hat shaped seal  52  and a radially outward hat shaped seal  54 . The L-shaped valve stem  42  has a shorter leg that extends radially outward through the valve stem hole and a longer axially extending leg that extends axially outward toward an outward side of the wheel and receives the valve stem cap  44  at the distal end there of. 
   Mounting bracket  40  is shown in greater detail in  FIGS. 4–6 , to which further reference is now made. Mounting bracket  40  includes a generally flat or planar base  60  and a tab  62  that extends radially outward from a radially outward or top side  66  of base  60  along a longitudinal adjacent one end  64  of base  60 . Tab  60  extends at an oblique angle from top or radially outward surface  66  of base  60 . The oblique angle is preferably in the range of 8–12 degrees from perpendicular (98–112 degrees relative to base  60 ) and is 10 degrees relative to perpendicular (100 degrees relative to base  60 ) in the preferred embodiment. This oblique angle is selected to enable the transducer container portion  20  to extend deeper into groove  36  and reduce the radially outward extremity of transducer  12 . The container portion  20  of transducer  12  is mounted at an angle relative to the valve stem portion  22  and the oblique angle of tab  62  further tilts the pressure transducer radially inward, causing transducer  12  to extend deeper into the groove of extended tire drop  36 . The angle relative to perpendicular should be small enough that the bottom of groove  36  does not interfere with transducer  12  and large enough to place transducer sufficiently radially inward that transducer  12  does not prevent tire mounting and removal and is not damaged in the event of a flat tire. 
   Tab  62  has a hole  70  there through which, in the preferred embodiment, is perpendicular to front and back surfaces  72 ,  74  of table  62  and thus at an angle of 10 degrees (radially inward) relative to top surface  66  of base  60 . A hole  80  passes through base  60  adjacent a rounded end  82  opposite end  64  of base  60 . A concave, cylindrical seal seat  84  is formed in bottom or radially inward surface  86  of base  60  opposite top surface  66 . Seal seat  84  is concentric with hole  80 . In the example of the mounting bracket  40  illustrated in  FIGS. 4–6 , base  60  has a width of 0.818 inch, and a length of approximately 1.220 inch. Base  60  has a thickness of 0.110 inch and tab  62  has a height of 0.700 inch from the bottom surface  86  of base  60  to the top of tab  62 . Tab  62  has a thickness of 0.200 inch and a width of 0.570 along the longitudinal dimension of base  60 . The hole  70  through tab  62  has a diameter of 0.406 inch and the hole  870  through base  60  has a diameter of 0.406 inch. The seal seat  84  has a diameter of 0.687 inch and a thickness of 0.050 inch. 
   Making more specific reference to  FIG. 3 , seal set  50  includes a hat shaped top seal  54  having a cylindrical central portion  90  which engages a radially outward portion of valve stem hole  92 . Seal  54  has a cylindrical center hole  94  that receives and sealingly engages the radially outward end of valve stem  42 . A flange  96  seats within seal seat  84  and provides a seal between base  60  of mounting bracket  40  and the radially outward periphery of inner piece  14  of wheel  16 . 
   Seal  52  of seal set  50  has a cylindrical central portion  100  which engages a radially inward portion of valve stem hole  92 . Seal  52  has a cylindrical central hole  104  that receives and sealingly engages the radially outward portion of valve stem  42 . A flange  106  of seal  52  engages a flange  108  of valve stem  42  and provides a seal between the radially inward periphery of inner piece  14  of wheel  16  and the flange  108  of valve stem  42 . 
   Screw  46  has a central aperture  114  that allows the passage of air there through and an externally threaded end  116  that engages mating internal threads in the radially outward end of valve stem  42 . The fine detail of the conventional threaded engagement between screw  46  and the radially outward end of valve stem  42  has not been shown in the interest of clarity. When screw  46  is tightened, the base  60  of mounting bracket  40  is drawn toward valve stem  42  and particularly flange  108 , enabling the seal set  50  to seal base  60 , valve stem hole  92  and valve stem  42  against unwanted leakage. 
   In an alternative arrangement shown in  FIG. 7 , the mounting bracket of the air pressure transducer mounting assembly  10  is implemented as an L-shaped bracket  120  having a base  122  formed by a longer leg  124  and a shorter leg  126 . Base  122  has a radially outward or upper surface  128  and a radially inward or lower surface  130  (hidden on the bottom side as shown in  FIG. 7 ). A tab  132 , which is similar to tab  62 , has a hole  134  there through and extends radially outward from the upper surface  128  at an angle of 10 degrees relative to upper surface  128  at the distal end  136  of long leg  124 . 
   The distal end  138  of shorter leg  126  is rounded and a screw hole  140  passes through the base  122  approximately half way along the length of shorter leg  126 . A cylindrical seal seat  142  is formed as a concavity in the lower surface  130  of base  122  concentric with screw hole  140 . Screw hole  140  and seal seat  142  are the same in size and shape as the hole  82  and seal seat  84  except that they are longitudinally offset from tab  132  by the longer leg  124 . In one example, longer leg  124  has a length of 2.828 inches and in another example longer leg  124  has a length of 1.818 inches. In each case the shorter leg  126  has a length of 1.330 inches. The implementation of longer leg  124  facilitates mounting a transducer on a wheel having a valve stem hole farther from the extended tire drop than in the arrangement shown in  FIGS. 1–6 . 
   As used in this specification, the word “or” is intended to mean an inclusive or covering either alternative or both alternatives unless the context explicitly indicates otherwise. 
   In the following claims, it is intended that a claim element be interpreted as a means plus function or step plus function claim element that is to be interpreted to cover the corresponding structure, material or acts described in the specification and equivalents thereof as specified by 35 USC § 112, paragraph 6, when, and only when, the claim element recites the express language “means for” or “step” for performing a function. 
   While there has been shown and described a pressure transducer mounting assembly and method for the purpose of enabling a person of ordinary skill in the art to make and use the invention, it will be appreciated that the invention is not limited thereto. For example, specific features or dimensions may be disclosed as implemented in a preferred or alternative embodiment of the invention. However, the disclosure of a specific feature or dimension does not mean that the feature or dimension is required for all implementations of the invention or that an alternative feature or dimension (whether or not specifically disclosed) could not be used in place of the disclosed feature or dimension. The embodiment or embodiments described herein are intended to exemplify, but not limit the claimed invention. The subject matter which applicants regards as the invention is defined by the attached claims. Accordingly, any modifications variations or equivalent arrangements within the scope of the attached claims should be considered to be within the scope of the invention.