Abstract:
A tire test apparatus, comprising a base, a support, a force applicator, a tire contact member in contact with a tire, a travel indicator mechanism, and a force indicator mechanism. The support extends upwardly from the base and holds a tire a predetermined distance above the base. The force applicator applies a force to cause pressure between the tire and the tire contact member. The travel indicator mechanism quantifies a change in relative positions between the tire and the tire contact member. The force indicator mechanism quantifies the force applied by the force applicator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS, IF ANY 
     This application claims the benefit under 35 U.S.C. §119(e) of provisional application Ser. No. 60/067,542, filed Dec. 4, 1997. 
    
    
       37  C.F.R. §1.71(E) AUTHORIZATION 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO A MICROFICHE APPENDIX, IF ANY 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, generally, to testing apparatus and methods. More particularly, the invention relates to electromechanical testing apparatus for measuring the spring rate of automobile or kart tires. 
     2. Background Information 
     Balancing a car optimizes performance, particularly the cornering characteristics of a racing class automobile. The traction, adherence or grip between the tires and the track at each end of a car is proportional to the percentage of the weight at that end of the car. A car&#39;s grip is optimized when both the front tires and the rear tires begin to slide at the same time and at the same rate, resulting in the car having responsive, near-neutral handling characteristics. However, if the front tires slide first, the car tends to understeer and slide off of the track, and if the rear tires slide first, the car tends to oversteer and spin. 
     Numerous factors contribute to the near-neutral handling characteristics of a balanced car, including tires, wheel alignment, suspension, weight distribution, center of gravity and aerodynamics. A properly suspended car has more braking and acceleration control when the car is moving in a straight line and more steering control when the car is maneuvering around corners. 
     The spring rate of tires produced with current manufacturing practices vary considerably. For example, a tire produced earlier in the day using a particular tire molding machine will have considerably different characteristics than a tire produced later in the day using the same machine. Additionally, different portions of the same tire may have different characteristics. For example, a particular tire may have soft spots. It is therefore desirable to be able to accurately rate the tires, including the different portions of the tires, in order to balance the car and ultimately improve the handling characteristics of the car. 
     Applicant&#39;s invention provides an apparatus and method for testing and measuring the spring rate of tires which is believed to constitute an improvement over existing technology. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method for testing the spring rate of tires. The tire test apparatus generally comprises a base, a support, a force applicator, a tire contact member in contact with a tire, a travel indicator mechanism, and a force indicator mechanism. The support extends upwardly from the base and holds a tire a predetermined distance above the base. The force applicator causes the tire and the tire contact member to apply pressure against each other. The force applicator is preferably a hydraulic jack. The travel indicator mechanism quantifies the change in the relative position of the tire contact member with respect to the tire upon application of a force. The force indicator mechanism quantifies the force applied by the force indicator mechanism. The travel indicator mechanism and the force indicator mechanism preferably have digital displays that allow the user to accurately rate the tire. The tire tester of the preferred embodiment has a capacity of 2500 lb. or 1250 kg. 
     The features, benefits and objects of this invention will become clear to those skilled in the art by reference to the following description, claim and drawings. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     FIG. 1 is perspective view of one embodiment of the apparatus of the present invention. 
     FIG. 2 is a perspective view of another embodiment of the apparatus of the present invention. 
     FIG. 3 is a top view of the apparatus of FIG.  1 . 
     FIG. 4 is a side view of the apparatus of FIG.  1 . 
     FIG. 5 is a front view of the apparatus of FIG.  1 . 
     FIG. 6 is a top view of the platform for the apparatus of FIG.  1 . 
     FIG. 7 is a side view of the platform of FIG.  6 . 
     FIG. 8 is a top view of the base for the apparatus of FIG.  1 . 
     FIG. 9 is a side view of the base of FIG.  8 . 
     FIG. 10 is a front view of the base of FIG.  8 . 
     FIG. 11 is a top view of the mast for the apparatus of FIG.  1 . 
     FIG. 12 is a side view of the mast of FIG.  11 . 
     FIG. 13 is a top view of the stiffening spline for the apparatus of FIG.  1 . 
     FIG. 14 is a side view of the stiffening spline of FIG.  13 . 
     FIG. 15 is a side view of a gusset for the apparatus of FIG.  1 . 
     FIG. 16 is a front view of the gusset of FIG.  15 . 
     FIG. 17 is a side view of the load cell for the apparatus of FIG.  1 . 
     FIG. 18 is a bottom view of the load cell of FIG.  17 . 
     FIG. 19 is an opposite side view of the load cell of FIG.  17 . 
     FIG. 20 is a side view of shaft bolt for the apparatus of FIG.  1 . 
     FIG. 21 is a side view of the hex jam nut for the apparatus of FIG.  1 . 
     FIG. 22 is a front view of the hex jam nut of FIG.  21 . 
     FIG. 23 is a side view of the offset backing ring for the apparatus of FIG.  1 . 
     FIG. 24 is a front view of the offset backing ring of FIG.  23 . 
     FIG. 25 is a side view of the tightening cone for the apparatus of FIG.  1 . 
     FIG. 26 is a front view of the tightening cone of FIG.  25 . 
     FIG. 27 is an unbent, planar view of the indicator mounting bracket for the apparatus of FIG.  1 . 
     FIG. 28 is a side view of the indicator mounting bracket of FIG.  27 . 
     FIG. 29 is a top view of the indicator support for the apparatus of FIG.  1 . 
     FIG. 30 is a side view of the indicator support of FIG.  29 . 
     FIG. 31 is a side view of the displacement measurement gauge for the apparatus of FIG.  1 . 
     FIG. 32 is a front view of the displacement measurement gauge of FIG.  31 . 
     FIG. 33 a side view of the displacement indicator arm for that apparatus of FIG.  1 . 
     FIG. 34 a bottom view of the displacement indicator arm of FIG.  33 . 
     FIG. 35 is a schematic of the electronic circuitry for the apparatus of FIG.  1   
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1 and 2, examples of the preferred embodiments of the present invention are illustrated. FIG. 1 shows a tire tester  10  used to measure the spring rate of smaller kart tires T. FIG. 2 shows a tire tester  10  used to measure the spring rate of larger automobile tires T. The remaining figures further illustrate the tire tester  10  of FIG. 1, but may be modified to form the embodiment shown in FIG.  2 . 
     Referring to FIGS. 1-5, preferred embodiments of the tire test apparatus  10  generally comprise a base  12 , a support  14  extending upwardly from the base  12  for adjustably holding a tire T a predetermined distance above the base  12 , a force applicator  16 , preferably a hydraulic jack, having a tire contact member  18  for contacting the tire T and applying force thereto, a travel indicator mechanism  20 , preferably digital, connected to the base  12  and contacting the tire contact member  18 , and a force indicator mechanism  22 , preferably digital, connected to the force applicator  16 . 
     The base  12 , shown in more detail in FIGS. 8-10, is preferably rigid and includes an inverted u-shaped plate  24  and a pair of perpendicular base supports  26  positioned within a cavity beneath the plate  24 . The base supports  26  provide the apparatus with structural strength. 
     The support  14  is preferably rigid and extends upwardly perpendicular to the base  12 . The support  14  includes a mast  28 , shown in FIGS. 11 and 12, and a shaft, preferably a shoulder bolt  30 , shown in FIG.  20 . The mast  28  has at least one aperture  30  through which the shoulder bolt  30  may extend. The bolt  30  extends through the hub of the tire T and suspends the tire T a predetermined distance above the base  12 . Multiple apertures  30  spaced along the mast  28  would accommodate tires of varying diameters. A jam nut  32 , shown in FIGS. 21 and 22, may be screwed onto the threads  34  of the bolt  30  and an offset backing ring  34 , shown in FIGS. 23 and 24, may be slid onto the bolt  30 . The suspended tire T is secured onto the bolt  30  by screwing a tightening cone  35 , shown in FIGS. 25 and 26, onto the threads. 
     The force applicator  16  of the preferred embodiments preferably includes a hydraulic jack  36 , although other jacks or means to apply force may be used. The jack  36  has a mount  38  attached to the base  12  and has a piston  40  attached to the tire contact member  18 . The jack  36  is manually pumped to raise the tire contact member  18  and apply pressure to a suspended tire T on the shoulder bolt  30 . The tire contact member  18  of the preferred embodiments is shown in greater detail in FIGS. 6 and 7. The tire contact member  18  is generally a plate that has two screw apertures used to attach a load cell, which is discussed below with respect to the force indicator mechanism. The tire contact member  18  also has a slot  37  through which a spline  39 , shown in FIGS. 13 and 14, can extend to stiffen the plate when it is being raised and lowered by the jack  36 . The stiffening spline  39  extends, and is preferably welded, along the side of the mast  28  up to the aperture. Gussets  41 , such as those shown in FIGS. 15 and 16, may be used to secure the spline  39  to the bolt  30 , or to secure the spline  39  and mast  28  to the base  12 . 
     The travel indicator mechanism  20 , shown in more detail in FIGS. 31 and 32, includes a digital indicator device  42  and a slide  44 . The digital indicator device  42  cooperates with and slides over the slide  44  in a measured fashion to quantify the position of the tire contact member  18 . The digital indicator device  42  is preferably a magnetic ravel indicator that has a display readout for reporting the vertical position of the tire contact member  18  in either English or metric units. The digital indicator device  42  may be reset or initialized to 0.000 inches and can display the tire compression length to the nearest 0.001 inches or 0.01 millimeter. The slide  44  is preferably connected to the tire contact member  18  using the displacement indicator arm  45 , shown in FIGS. 33 and 34 and the digital indicator device  42  is mounted a predetermined distance above the base  12  through an aperture within an angled indicator support  46 , shown in FIGS. 29 and 30. 
     The force indicator mechanism  22  includes a load cell  50 , shown in FIGS. 17,  18  and  19  electrically connected to a force indicator display  52 , which is mounted onto the base using the mounting bracket  54  shown in FIGS. 27 and 28. The force indicator display  52  is preferably a ½ inch, four digit LCD display. The load cell  50  is attached and positioned between the piston  40  and the tire contact member  18 . 
     FIG. 35 is a schematic diagram of the electronic controls for the present invention. The circuitry contains a power supply, which is in this case a  9  volt alkaline or rechargeable nickel-cadmium battery  70 , an EEPROM  72  for holding a program and calibration data, a microcontroller  74  for performing the operations of the program and for performing analog/digital conversions, a load cell input  76  for sensing or reading the strain gauges of the load cell  50 , a signal amplifier  78  for amplifying and conditioning the signals form the load cell input  76 , a LCD display output connector  80  for electrically interfacing with and driving the force indicator display  52 , and a keypad input connector  82  for electrically interfacing with a keypad or other input device. The microcontroller  74  delivers over 4,000 internal counts with its 12 bit analog/digital conversions and allows the tire tester  10  to automatically zero off errors found during zero-load. 
     The tire tester contains an on/off control, a zero control for zeroing the weight of he scale, a pound/kilogram toggle control, and a peak hold control wherein the unit will display only the highest weight applied to the pad. The tire tester also includes an Auto Zero Tracking feature which corrects for slight zero changes during normal operation. 
     Other embodiments of the tire tester are anticipated. For example, rather than pumping the jack to raise the tire contact member into contact with the tire, it is anticipated that the jack could be mounted in such a manner as to lower the tire into contact with a stationary tire contact member. Additionally, the design of the tire tester, particularly the support and the contact member, maybe modified to accommodate various tire types and sizes or various testing procedures. 
     There are a number of procedures for testing or rating a tire, or for finding soft spots on portions of the tire. The tire tester may be used in a variety of these procedures. A method for using the tire tester to rate a tire may include the following steps: 
     (1) Mount the tire to be rated on a support next to a tire contact member. 
     (2) Zero both the travel indicator mechanism and the force indicator mechanism. 
     (3) Pump the jack to apply pressure between the tire and the tire contact member. 
     (4) Read a change in the relative position between the tire and the tire contact member as measured by the travel indicator mechanism. 
     (5) Read the compression weight as measured by the force indicator mechanism. 
     The result of this design is that the tire tester is accurate to within plus or minus 0.5% of the applied load. 
     The descriptions above and the accompanying drawings should be interpreted in the illustrative and not the limited sense. While the invention has been disclosed in connection with the preferred embodiment or embodiments thereof, it should be understood that there may be other embodiments which fall within the scope of the invention as defined by the following claims. Where a claim, if any, is expressed as a means or step for performing a specified function it is intended that such claim be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof, including both structural equivalents and equivalent structures, material-based equivalents and equivalent materials, and act-based equivalents and equivalent acts.