Abstract:
An adjustable width chuck assembly for a tire testing machine including upper and lower relatively movable rims by which a tire is clamped and held during a testing cycle. A pilot or nose cone forming part of one of the rims is gas pressure biased towards engagement with complementally formed structure on the other rim. The gas pressure bias is provided by a gas spring which can be replaced with gas springs of differing pressures in order to adjust the biasing force or, alternately, the gas spring can be removed from the chuck assembly and re-pressurized to a different level in order to change its biasing force. The use of a gas spring for providing the necessary biasing force expands the range of motion for the nose cone, thus allowing a given chuck assembly to accommodate tires having a wide range of bead widths.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority from U.S. Provisional Application No. 61/312,432, filed Mar. 10, 2010, the entirety of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to tire testing. More particularly, the invention relates to an apparatus and method for chucking tires of differing bead widths in a test machine such as a tire uniformity-testing machine. 
       BACKGROUND ART 
       [0003]    While the present invention may find application in a wide variety of tire testing apparatus wherein it is necessary to rapidly chuck tires it is applicable to great advantage in tire uniformity testing machines. Tire uniformity testing machines commonly include an upper rim, a vertically-movable lower rim, and a conveyor to bring a tire between the upper and lower rims. A mechanism is provided to raise the lower rim through an opening in the conveyor, carrying a tire with it, to the upper rim where the tire is inflated. The lower rim carries a center cone that is engagable with a center recess in the upper rim, the cone precisely positioning the upper rim with respect to the lower rim so that the two rims are concentric when a tire is clamped between them. A motor is connected to the upper rim to rotate it at a predetermined test speed. A load wheel or road wheel, rotatable on an axis parallel to the axis of the tire, is movable into engagement with the tire tread so as to load the tire as it rotates in a manner simulating a road condition. 
         [0004]    A hydraulic actuator is connected to the lower rim to raise and lower it. This actuator must be capable of applying a force sufficient to overcome the separation force of tens of thousands of pounds acting on the rims when the tire is inflated. The force applied by the actuator must also be sufficiently great to hold the cone against the recess of the upper rim with sufficient pressure to driveably couple the upper and lower rims so that the rotational force applied to the upper rim is transmitted to the lower rim through the center cone rather than through the tire substantially without slip which might otherwise distort the tire and possibly affect test results. 
         [0005]    A prior art apparatus and mechanism is described in U.S. Pat. No. 4,852,398. 
       DISCLOSURE OF INVENTION 
       [0006]    The present invention provides a new and improved tire testing apparatus. In particular, the present invention provides a new and improved chuck assembly, which improves upon the chuck assembly disclosed in U.S. Pat. No. 4,852,398 which is hereby incorporated by reference. 
         [0007]    According to a preferred embodiment, the chuck assembly is capable of chucking tires of various bead widths and the variation of bead widths may be substantial. The chuck includes first and second rims, each rim engageable with a bead of a tire. An actuator is connected to at least one of the rims and is operated to move the rim towards and away from the other rim. The actuator moves the associated rim towards the other rim in order to engage a tire between the rims. After the completion of a test cycle, the rims separate in order to release the tested tire. According to the invention, at least one of the rims forms part of an assembly that includes a telescoping pilot element or nose cone that is biased towards the other rim by gas pressure. In the preferred and illustrated embodiment, the nose cone is biased by a gas spring, which urges the nose cone towards engagement with a receiving structure i.e., recess, forming part of the other rim assembly. 
         [0008]    In the illustrated embodiment of the invention, when the rims are brought together into a tire holding position, the nose cone tightly engages an associated recess of the other rim. The force of the now compressed gas spring rotatably couples the rims together so that rotating one rim produces attendant rotation in the other rim. 
         [0009]    According to a feature of the invention, the gas spring is removably mounted within a shank of the nose cone. If a different biasing force for the nose cone is desired, the gas spring may be removed and replaced with one of different pressurization, or alternately, the gas spring may be pressurized to a different level and then reinstalled into the shank of the nose cone. 
         [0010]    With the disclosed invention, the biasing force exerted by the nose cone (or pilot) can be easily adjusted. Moreover, the construction and operation of the chuck apparatus is simplified. The elimination of a mechanical spring, as used in the prior art, allows the limits of travel of the nose cone to be substantially extended, thus allowing the chuck assembly to accommodate a wider range of tire bead widths. 
         [0011]    Additional features of the invention will become apparent and a fuller understanding obtained by reading the following detailed description made with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a diagrammatic side elevational view of a tire testing machine incorporating a preferred embodiment of the present invention and 
           [0013]      FIGS. 2A and 2B  illustrate the construction of an automatic adjustable width chuck constructed in accordance with a preferred embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1  illustrates a tire uniformity inspection machine  10  that incorporates a tire chucking/clamping apparatus constructed in accordance with the invention. The machine  10  also includes a frame  11 , which supports a conveyor  12  having a plurality of rollers  13  for delivering a tire  14  to be inspected to a test station  15 . Conveyor  12 , is described in detail in commonly, assigned U.S. Pat. No. 4,846,334, expressly incorporated by reference herein in its entirety. Conveyor  12  includes an opening  16 , which is small enough to prevent a tire from falling through, but large enough to pass a lower rim  17 , which is rotatably mounted upon a vertically retractable, lower rim assembly  18 . An upper rim  20  is rotatably mounted by means of an upper rim spindle  21  to the upper portion of frame  11 . Upper rim  20  is disposed opposite lower rim  17  so that upper and lower rims  20  and  17  cooperate to function as a rim to support a tire  14  under test when lower rim  17  is in its extended position as shown in  FIG. 1  and in phantom view in  FIG. 2 . Upper rim spindle  21  includes an axial air passage  22  which communicates with an orifice  23  in upper rim  20  to permit inflation of tire  14 . The rims and associated components described above form part of an adjustable width tire chuck assembly constructed in accordance with the invention. 
         [0015]    In order to rotate a tire under test, upper rim spindle  21  is fitted with a drive pulley  24  connected to a drive motor  25  by way of a timing belt  26 . 
         [0016]    A loadwheel  27  having a circumferential surface  28  is supported by loadwheel spindles  30  for free rotation about an axis parallel to that of the tire  14  under test. Loadwheel spindles  30  are in turn supported by a carriage  31  which is slidably secured to frame  11  by one or more ways  32  so as to be movable in the radial direction, toward and away from tire  14 . As carriage  31  urges loadwheel  27  radially inward (to the left in  FIG. 1 ) against tire  14 , the radial load on tire  14  increases, Likewise, movement of carriage  31  radially outward (to the right in  FIG. 1 ) reduces the radial force on tire  14 . Carriage  31  is moved back and forth by a reversible D.C. motor  33  secured to frame  11 . Motor  33  drives a gear box  34  whose output drives a chain and sprocket linkage  35  to rotate a ball screw rotation only female screw  36 . A screw shaft  37  fixed to carriage  31  is received within female screw  36  in order to translate carriage  31  in the radial direction as female screw  36  rotates. 
         [0017]    Referring to  FIGS. 2A and 2B , the upper rim  20  is mounted on an adaptor  40  that is secured to the drive pulley  24  ( FIG. 1 ). The air passage or central bore  22  provides a conical recess or seat  41  to receive a slidable pilot or nose cone  42  ( FIG. 2B ) on the lower half rim or chuck  17 . Cone  42  includes an axial bore  43 , which mates with air passage bore  22  when nose cone  42  engages seat  41  to provide a path for tire inflation air, which is supplied to the interior of tire  14  by way of radial ports  44  which intersect, bore  43 . The cone  42  is vertically slidable in a lower spindle  45  along a path indicated by the line  100 . 
         [0018]    The spindle  45  is rotatably supported by a spindle housing  58 . In particular, the spindle  45  is supported by upper and lower bearings  210 ,  212 . Associated bearing seals  214 ,  216  seal the interface between the housing  58  and the spindle  45  in the vicinity of the bearings  210 ,  212 , respectively. According to the invention, the nose cone  42  is reciprocally movable towards and away from the conical seat  41  formed in the adaptor  40  (see  FIG. 2A ) by a gas spring  220  (shown in elevation in  FIG. 2B ). The air spring  220  biases the nose cone  42  towards its extended position shown in  FIG. 2B  and is attached to the nose cone by one or more bolts  219 . 
         [0019]    As seen best in  FIG. 2B , the nose cone  42  is mounted to or forms an integral part of a hollow shank  222  that is slidable within a bore  226  defined by the spindle  45 . At least one, but preferably two longitudinal slots  228  are formed in shank  222  to form keyways. Internally threaded keys  230  are secured within keyways  228  by associated bolts/screws  231  counterbored within lower spindle  45 . Keys  230  and keyways  228  permit cone  42  to slide or reciprocate axially with respect to spindle  45  but preclude rotation of cone  42  with respect to spindle  45 . Thus, the rotary force imparted to the upper rim  20  is transmitted to cone  42  and through the keys  230  and keyways  228  to the spindle  45 . Keys  230  further serve to limit the axial travel of shank  222  to retain it within spindle  45 . The extremes of motion for the shank  222  are determined by the extent of the longitudinal slots  228 . 
         [0020]    In the preferred embodiment, O-rings (not shown) are used to seal the screws  231  to their respective bores. The O-rings inhibit air leakage from an inflated tire held between the upper and lower rim  20 ,  17 . In the preferred and illustrated embodiment, the slots  228  are not through slots for most of their lengths. In other words, the slots  228  do not extend through the body of the shank  222 . However, in the preferred and illustrated embodiment, the lower ends of the slots  228  (as viewed in  FIG. 2B ), include through portions  228   a , which enable the installation of the keys  230 . To assemble the chuck assembly, the shank  222  is suitably positioned within the bore  226  such that the through slots  228   a  are aligned with the mounting positions for the keys  230 . While held in position, the set screws  231 , with associated seals, are threaded into the keys in order to lock them to the wall of the housing  45 . The gas spring  220  would then be installed into the cylindrical recess  222   a  defined by the shank  222 . 
         [0021]    A piston rod  220   a  extends from the cylinder  220   b  and acts between the cylinder and a removable plate  234  secured to the bottom of the spindle  45  by suitable bolts  236 . As is known, an inside region of the gas spring is pressurized with a suitable gas such as nitrogen. The pressure acting on the upper and lower sides of an internal piston produce a net force acting on the piston tending to extend the piston rod  220   a . Since the piston rod  220   a  is fixed, the cylinder  220   b  moves or is urged upwardly (as viewed in  FIG. 2B ) due to the forces exerted on the piston by the pressurized gas within the gas spring. A gas spring suitable for this application is available from Kaller Gas Springs of Frazer Michigan. It has been found that for a chuck assembly constructed in accordance with the preferred embodiment of the invention, a Kaller gas spring Part No. TU 750-160 will provide a 5″ range of motion for the nose cone  42  (as compared to a range of motion of 2.5″ for a prior art chuck assembly that utilizes a mechanical spring. A 5″ range of motion for the nose cone enables the chuck assembly to accommodate a wide variation in tire bead widths. 
         [0022]    As seen in  FIG. 2B , a lubricating fitting  140  is provided to lubricate the outside of the shank wall to facilitate axial movement of the nose cone shank  222  within the spindle bore  226 . 
         [0023]    The spindle housing  58  is suitably mounted to an adaptor plate  70  by a plurality of fasteners  152  which are threadedly received in the housing  58  and are spaced 120° apart. A plurality of springs  156  provide a resilient mounting between the adaptor plate  150  and the spindle housing  58  to allow slight relative movement between the adaptor plate  70  and the housing which can compensate for slight misalignments between the nose cone  42  and the conical seat  41  (shown in  FIG. 2A ). A plurality of lubricating fittings  160  are provided by which lubricant is injected into the region  162  between the rotatable spindle  45  and an internal recess in the housing  58  which receives the spindle. O-rings such as O-ring  166  are used in various locations to seal interfaces between components. A nut  168  acts as a bearing retainer for the lower bearing  116 . An upper cap  170  is secured by bolts  172  to the main housing  58  and serves to retain the bearing  110  in position. 
         [0024]    The base plate or adapter  70  is suitably coupled to the hydraulic actuator  73  (see  FIG. 1 ) which includes a piston  75  and which reciprocates within a cylinder  72 . The operation of the actuator  73  raises and lowers the spindle housing (and associated spindle) along the path  100  in order to engage a tire between the upper rim  20  and the lower rim  17 . 
         [0025]    Matched sets of concave and convex washers or spacers  176   a ,  176   b  are also provided between the base plate  70  and the housing  58 . The washers/spacers  176   a ,  176   b  serve as a spherical bearing  176  which facilitates the alignment of the nose cone  42  with its associated recess  41  located in the upper rim assembly. During clamping of the tire between the upper and lower rims, the actuator  73  moves the lower spindle housing towards the upper rim in order to engage the nose cone  42  with its recess  43 . After the nose cone  42  enters the recess, the actuator  73  continues to raise the lower spindle, thus causing compression of the gas spring  120 . The force exerted by this gas spring on the spindle housing  58  causes the springs  156  to compress until the spindle housing  58  contacts the spherical bearing  176  tightly capturing it between the housing  58  and the base plate  70 . The spherical bearing  176  allows slight movement in the spindle housing  58  during this clamping phase to ensure tight and full engagement between the nose cone  42  and the recess  41 . 
         [0026]    In a preferred method of operating the machine, the spindle housing  58  is driven upwardly to a “0” position at which the upper and lower rims are spaced apart less than the actual bead width of the tire held between the rims. The spindle housing  58  is then lowered by the actuator  71  to the proper bead width for the tire being tested. Further details of the operation of the overall machine with a prior art spindle assembly can be found in U.S. Pat. No. 4,852,398, which is hereby incorporated by reference. 
         [0027]    Referring to  FIG. 1 , an LVDT  88  is mechanically connected between the base plate/adaptor  70  and the frame  11 . Its function is to produce an electrical signal that is the measure of the vertical distance between the lower rim  17  and the upper rim  20 . As previously noted, hydraulic actuator  73  ( FIG. 1 ) includes a piston  75 , which reciprocates within a cylinder  72 . The top side  90  of piston  75  and the bottom side  91  of piston  75  are connected to a hydraulic servo-control system  92  which will now be described in further detail. 
         [0028]    Control system  92  includes a high pressure fluid supply  93  and a low pressure, high volume fluid supply  94 . High pressure supply  93  is at a nominal pressure of 2000 psi, while low pressure supply  94  is at a nominal pressure of 1000 psi and is capable of supplying fluid at a rate of about 25 gpm. A valve  96  has a first input port  97  connected to low pressure high volume supply  94  and a second input port  100  connected to a hydraulic return  101 . Valve  96  is a double acting  4  way, 3 position solenoid valve with spring return to center. Valve  96  further includes a first output port  102  connected by way of a flow control  103  to the top side  90  of piston  75 . Valve  96  has a second output port  104  connected by way of a flow control  105  to the bottom side  91  of piston  75 . A line incorporating a check valve  110  shunts the input  97  of valve  96  and the output of flow control  103  to provide regenerative action when piston  75  is raised. 
         [0029]    High pressure supply  93  is connected to a 3 way, 2 position single acting solenoid valve  106  at a first input port  107  thereof. A second input port  108  of valve  106  is connected to a return  109 . Valve  106  has a first output port  112 , which is also connected to return  109  and a second output  113  which is connected by way of a check valve  114  and a 3 micron filter  115  to the pressure input of servo-valve  116  which is preferably a Part No. BD-15-25-N manufactured by Parker Hannifin. The input to filter  115  is further connected to low pressure supply  94  through a check valve  117  which prevents high pressure fluid from flowing into the low pressure system. Servo-valve  116  includes a return connection  118 , a first output  119  connected to the bottom side  91  of actuator  73  and a second output  120  connected to the top side  90  of actuator  73 . Servo-valve  116  is connected electrically by way of a control line  122  to a conventional servo-amplifier  123  having a set point input  124  and a control input  125  the latter of which receives a distance indication signal from a comparator board  127 . The comparator board  127  takes a distance indication signal from the LVDT  88  and compares it to the signal corresponding from the main control computer  130 . It calculates a bead set location, which is input to the servo amplifier  123 . Set point input  124  is shown connected to a set point control potentiometer  126  whereby a desired bead width set point may be determined. Alternatively, a set point input  124  could receive approximate set point control signals from which signal may be varied according to the bead widths of individual tires being tested. The main control computer  130  of machine  10  includes, inter alia an input  131  from the comparator board/circuit  127  from which it receives distance information as well as appropriate outputs  132  and  133  for actuating valve  96  to the right and left respectively and an output  134  for actuating valve  106 . 
         [0030]    In operation, piston  75  and rod  71  are initially in a fully retracted or home position. When a tire  14  to be tested is in position for mounting, the main control computer  130  actuates valve  96  by way of output  132  to shift its spool to the right in the  FIG. 1  to connect low pressure, high volume supply  94  to the underside  91  of piston  75  through flow control  105 . This results in rapid upward movement of piston  75 , the velocity of which is controlled by the setting of flow controls  103 . 
         [0031]    As lower rim  17  passes upward through the opening in conveyor  12 , rim  17  engages the lower bead of tire  14  carrying tire  14  upward with it. The lower rim assembly  18  rises until nose cone  42  engages tapered seat  41  to center and insure parallelism of rims  17  and  20 . This alignment is further assisted by spherical washers  176   a ,  176   b  which can pivot slightly about their mated spherical surfaces at  178  as well as shift laterally slightly if required in the seat in housing  58 . At this point the lower rim  17  is indicated at A in  FIG. 2A . It should be noted here that in  FIG. 2A , the lower rim  17 , in position A, is shown in contact with the upper rim  20 . This is usually termed the “bead set’ position. For tires having a large bead width, the “bead set” position may be a position at which the rim  20  and rim  17  are spaced apart but not touching. In any event, during clamping of the tire, the upper and lower rims  20 ,  17  are brought to a “bead set” position at which the rims are spaced apart less than the bead width of the tire so that seating, inflation and clamping of the tire is facilitated. The rims  20 ,  17  are then moved apart to the appropriate bead width for the tire at which point the tire is then tested, balanced and/or inspected depending on the type of equipment the rims are used on. 
         [0032]    In this location, the spacing between rims  17  and  20  as sensed by LVDT  88  (and processed by the comparator circuit  127 ) and indicated by the signal appearing at input  125  of amplifier  123  is narrower than the desired bead width as indicated by the set point signal applied at input  124  of servo amp  123  as determined by the setting of potentiometer  126 . Accordingly, a large position error signal is generated by amp  123  on line  122 . Servovalve  116  then assumes control and, in response to the error signal on line  122 , supplies fluid from port  120  to the top side  90  of piston  75  and receives fluid into port  119  from the underside  91  of piston  75  to begin to move lower rim  17  downward. About the same time, while lower rim  17  is still at or near position A, the main unit controller  120  initiates inflation of tire  14  by flowing air through passage  22  and outward from ports  44  into the area between rims  17  and  20 . Because the upper bead of tire  14  is seating on or at least a reduced distance from upper rim  20 , pressurization of tire  14  while lower rim  17  is so located provides more reliable seating of the upper bead of tire  14  upon rim  20 . 
         [0033]    Lower rim  17  continues to move downward as tire  14  is inflated. As rim  17  approaches the desired bead width set by potentiometer  126 , as indicated by position B in  FIG. 2A , controller  130  energizes valve  106  by way of line  134  to connect high pressure supply  93  to the pressure input of servovalve  116  through filter  115  and deenergizes valve  96  which reassumes its center, blocked position. Lower rim  17  reaches position B which corresponds to a desired bead width appropriate for tire  14  and is maintained there under the continuous closed loop control of system  92  while tire testing proceeds. 
         [0034]    As is well known in the art, testing includes driving carriage  31  radially inward until the surface  28  of loadwheel  27  engages the tread surface of tire  14  which is rotatably driven by motive force supplied by motor  25  through belt  26  to upper rim spindle  21  and through adapter  40  to upper rim  20 . Due to the force applied by spring  53 , tapered seat  41  is securely frictionally coupled to nose cone  42  to drive lower rim  17  with upper rim  20  without significant rotational slip between the two rims. During testing, forces transmitted by the rotating tire  14  to loadwheel are picked up by sensors (not shown) and analyzed by computing means (also not shown) to characterize the uniformity of construction of tire  14 . 
         [0035]    At the conclusion of testing, tire  14  is deflated and high pressure is removed from actuator  73  and controller  130  deactivates valve  106  allowing its spring to return its spool to its normal, recirculating position. Valve  96  is then energized via line  133  to move its spool to the left as shown in  FIG. 1 , thereby connecting the top side  90  of piston  75  to low pressure high volume supply  94  through flow control  103  and connecting the bottom side  91  of piston  75  to return  101  through flow control  105 . This effects a rapid downward movement of piston  75  to its initial or home position at a velocity which be adjusted by way of flow controls  103  and  105 . 
         [0036]    With the disclosed invention, the spring rate for the nose cone assembly can be easily modified by either replacing the installed gas spring with a gas spring having a different gas pressure, or, alternatively, by removing the gas spring  220  and changing its pressurization with an apparatus designed to add or remove pressurized gas from the cylinder  220   b  of the gas spring. This apparatus for adding or removing pressurized gas from the gas spring  220  is known to those skilled in the art. 
         [0037]    While the invention has been described as applied to a tire uniformity inspection machine it is to be understood that the invention is not limited to use in such equipment. To the contrary, the invention may be applied to great advantage in other applications wherein it is necessary to chuck a tire. It is to be further understood that the invention is not limited to the exact form shown and described above which are illustrative of a preferred embodiment of the invention. In view of the present disclosure those having skill in this art will be able to imagine various changes and modifications which can be made without departing from the spirit and scope of the invention as particularly pointed out and distinctly claimed in the appended claims.