COMBINATION GRINDER/BALANCER

Abstract: A combination force variation tire grinding and tire balancing machine in which a tire and wheel assembly (TA) is mounted on a single shaft (40) and the tire and wheel assembly is corrected by first force variation grinding thereof and then dynamic balancing same. The tire and wheel assembly is mounted on a spindle assembly (12) and first rotated about its rotational axis (AR) under a prescribed load applied by a loading unit (50). The loaded radial runout of the tire tread is measured, and those portions of the tire tread which exceed a prescribed level are removed by a grinding unit (51) which includes a buffing head (66). The tire and wheel assembly is then rotated about its rotational axis while unloaded at a speed sufficient to measure dynamic imbalance, and the dynamic imbalance is measured and located.

Description: COMBINATION GRINDER/BALANCER BACKGROUND OF THE INVENTION This invention relates generally to the correction of vehicular tires to reduce undue vibration in the tire rotating on a vehicle and more particularly to a machine which combines force variation tire grinding with dynamic balancing in a single machine. Because vehicular tires support the sprung mass of a vehicle on a road surface and such tires are resilient, any irregularities in the dimensions of the tire itself or in its resiliency, and dimensional irregularities in the wheel rim and/or any dynamic imbalance of the tire and wheel rim assembly will cause undue vibrations to be transmitted to the sprung mass of the vehicle, thereby producing undesirable ride characteristics commonly known as "smooth road shake." Dimensional and resilient irregularities have been reduced using a technique known as "force variation tire grinding" while weight imbalance was typically reduced using a technique known as "dynamic balancing." Heretofore, one machine was required to force variation grind the tire while another machine was used to dynamically balance the tire and wheel assembly. A good description of such an arrangement is illustrated in Patent No. 4,139,041, the disclosure of which is incorporated herein by reference. The main problem with this arrangement is that it was necessary to transfer the wheel and tire assembly between the force variation grinding machine and the tire balancer in order to complete the overall correction operation. This was, reletively speaking, time-consuming and also physically demanding on the operator. Therefore, there existed the need for a single machine which could both force variation tire grind and dynamic balance. SUMMARY OF THE INVENTION These and other problems and disadvantages associated with the prior art are overcome by the invention disclosed herein by providing a tire correction machine and a method which is capable of both force variation tire grinding and dynamic balancing while the tire and wheel assembly remains mounted on a common shaft without detrimentally affecting either operation. As a result, the minimum number of components are required to complete both of these tire correction operations and the machine is considerably simpler than the two machines required by the prior art. The method of invention includes mounting a tire and wheel assembly on a support means so that the tire and wheel assembly on a support means so that the tire and wheel assembly is rotatable about an axis corresponding to the rotational axis on the vehicle and, while the tire and wheel assembly is so mounted, first rotating the tire and wheel assembly about its rotational axis under a prescribed load while measuring the loaded radial runout of the tire tread and removing those portions of the tire tread which exceed a prescribed loaded radial runout level; and then rotating the tire and wheel assembly about its rotational axis while unloaded at a speed sufficient to measure dynamic imbalance f and measuring and locating the dynamic imbalance in the tire and wheel assembly while it is so rotated. The method also includes rotating the tire and wheel assembly sufficiently slowly during the loaded radial runout reading and correction to effectively eliminate the effect of dynamic imbalance in the tire and wheel assembly. The method also includes isolating the measurement of a second set of radially directed forces imposed on a rotatable shaft where a first set of radially direct forces imposed on the shaft do- not rotate about the shaft axis while the second set of radially directed forces rotate about the shaft axis. This method may include operatively associating a first transducer means with the shaft to detect the magnitude of the first force loading on the shaft, operatively associating a second transducer means with the shaft so that the first set of forces is not imposed thereon while the magnitude of the second set of forces is detected as the second set of forces rotates thereby. The invention also includes the apparatus for carrying out the methods. These and other features and advantages of the invention will become more apparent upon consideration of the following detailed description and accompanying drawings wherein like characters of reference designte corresponding parts through the several views and in which: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front view of the apparatus embodying the invention; Fig. 2 is a left end view thereof; Fig. 3 is an enlarged end view with the covers removed; Fig. 4 is an enlarged cross-sectional view taken generally along line 4-4 in Fig. 1; Fig. 5 is an enlarged cross-sectional view taken generally along line 5-5 in Fig. 1; Fig. 6 is a schematic illustrating the control circuit used in the invention. & These features and the following detailed description disclose specific embodiments of the invention, however, it is to be understood that the inventive concept is not limited thereto since it may be embodied in other forms. DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS The apparatus embodying the invention was designed to test and correct "smooth road shake" problems associated with a tire and wheel assembly TA, that is, an inflated pneumatic vehicular tire T mounted on a vehicular wheel rim WE. The pneumatic tire T has a peripheral road engaging tread TT thereon while the wheel rim WR has a central disc CD that defines both lug holes therein and a central axle opening therethrough so that the wheel lugs on the vehilce can mount the tire and wheel assembly TA on that vehicle. The tire correction machine 10 embodying the invention includes a frame assembly 11 which mounts thereon a spindle assembly 12 on which the tire and wheel assembly TA is mounted with a mounting assembly 14 so that the effective rotational axis AR of the tire and wheel assembly on the vehicle coincides with the rotational axis of the spindle assembly 12. The machine 10 also includes a drive assembly 15 for driving the spindle assembly 12 in both it force variation grinding mode and dynamic balance mode. The correction machine 10 also includes a force variation grinding subsystem 16 which serv 7es to correct loaded radial runout in the tire and wheel assembly and a dynamic balancer subsystem 18 which serves to detect and locate dynamic imbalance in the tire and wheel assembly so that it can be corrected. In operation, the tire and wheel assembly TA is mounted on the spindle assembly 12 using mounting assembly 14. A control system 19 is then activated which causes the force variation grinding subsystem 16 to be first activated as well as the drive assembly 15 to rotate the spindle assembly 12 at the appropriate low speed for force variation grinding. After the force variation grinding subsystem 16 has completed the force variation grinding mode, the control system 19 activates the dynamic balance subsystem 18 while deactivating the force variation grinding subsystem 16. This causes the drive assembly 15 to rotate the spindle assembly 12 at a higher rotational speed sufficient for dynamic balancing. The dynamic balance subsystem 18 then determines the amount of imbalance and the location thereof so that weights can be added to the vehicular wheel rim WR after the dynamic balancing mode is completed. When the dynamic balancing mode is completed, the control system stops the drive assembly 15 while leaving the dynamic balancing system 18 connected to the spindle assembly 12 so that the tire assembly TZ can be rotated to the proper location for mounting the weights on the wheel rim WR. Frame The frame assembly 11 includes an L-shaped base 20 which sits on the floor to support the machine. The base 20 has a first leg 21 and a second leg 22 connected to leg 21, both of which have an open rectilinear configuration. The force variation subsystem 16 is mounted on the first leg 21 of the base 20. The spindle assembly 12, the drive assembly 15 and the dynamic balance subsystem 18 are mounted on the second leg 22 of the base 20. This locates the force variation subsystem 16 in operative association with the tire and wheel assembly TA- on spindle assembly 12. As will become more apparent, the central axis of the leg 21 is normal to that of leg 22. Spindle Assembly The spindle assembly 12 is mounted on the second leg 22 of the base 20 and projects upwardly therefrom. The spindle assembly 12 includes an upright box beam 25 whose lower end is mounted on the leg 22 with appropriate access opening on opposite sides thereof. A cast support base 26 is mounted in the uppper end of the box beam 25 on cross supports 28. The support base 26 defines a forwardly projecting bearing support 29 on the front end thereof which projects forwardly of the box beam 25 as will become more apparent. A pair of balancer type bearing blocks 30 nad 31 are mounted on the bottom of the support base 26 and depend therebelow. The front bearing block 30 is mounted on the bearing support 29 while the rear bearing block 31 is mounted a prescribed distance rearwardly of the breaing block 30 so that the bearing blocks align along a common axis A R which will be the rotational axis of the tire and wheel assembly TA when mounted on the machine. The bearing blocks 30 and 31 each have an enlarged hub 32 at the lower end thereof which receivest the shaft bearing 38 therein. A reduced cross-sectional area connector 34 connects the hub 32 with the base flange 35 attached to the support base 26. One of the projecting ends of the base flange 35 on each of the bearing blocks 30 and 31 defines a depending support flange 36 spaced from connector 34 a prescribed distance. Each of the support flanges 36 is designed to accept a piezoelectric transducer as will become more apparent. Each of the bearings blocks 30 and 31 mount the shaft bearing 38 therein with the inner races of the bearings mounting a drive spindle 40 therein which extends through both of the bearing blocks 30 and 31 as rotatable about the axis A . The working end of the drive spindle 40 projects out over the second leg 22 of the base 20 to mount the tire and wheel assembly TA as will become more apparent. The working end of the spindle 40 mounts the mounting assembly 14 thereon in a manner described in earlier Patent No. 4,139,041, which description is incorporated herein by reference. Thus, it will be seen that any type tire and wheel assembly can be mounted using the mounting assembly 14 so that the tire and wheel assembly TA rotates about its rotational axis A R coinciding with the axis A R of the spindle 40. The rear end of the spindle 40 mounts at a one¬ way freewheeling clutch 41 thereon with its output portion 42 connected to the drive spindle 40. -Its input portion 44 is connected to a transfer shaft 45 through a universal joint 46. The opposite end of the transfer shaft 45 is connected to the ooutput shaft 48 of a grinding drive unit 49 in the drive assembly 15 through another universal joint 50. A grinding drive unit 49 is attached to the support base 26 and includes a drive motor 51 with a speed reducing gear box 52. Typically, the output shaft 48 of the drive unit 49 is rotated at about 12-15 RPM. The drive assembly 15 also includes a balancer drive // drive spindle 40 therein which extends through both of the bearing blocks 30 and 31 as rotatable about the axis A~ . The working end of the drive spindle 40 projects out over the second leg 22 of the base 20 to mount the tire and wheel assembly TA as will become more apparent. The working end of the spindle 40 mounts the mounting assembly 14 thereon in a manner described in earlier Patent No. 4,139,041, which description is incorporated herein by reference. Thus, it will be seen that any type tire and wheel assembly can be mounted using the mounting assembly 14 so that the tire and wheel assembly TA rotates about its rotational axis A R coinciding with the axis A R of the spindle 40. DRIVE ASSEMBLY The drive assembly 15 is connected to the spindle 40 between the bearing blocks 30 and 31 and drives the spindle 40 during both the force variation grinding mode and the dynamic balancing mode. The spindle 40 is typically rotated at about 12-15 RPM during the grinding mode and about 500- 1500 RPM during the balancing mode. The drive assembly 15 includes a motor support 45 mounted on the support base 26 by spaces 46 so that the /2 support 45 is located directly below the spindle 40. The support 45 mounts drive motor 48 so that its output shaft is located parallel to and in vertical alignment with the spindle 40. A belt and pulley arrangement 49 drivingly connects the motor 48 to a spindle 40 to drive same. The motor 48 is a variable speed motor of known construction so that both the lower rotational speed for grinding and higher rotational speed for balancing can be achieved. The motor 48 will act as a brake when the polarity is reversed. It will also be appreciated that separate motors may be used to drive the spindle 40 during the grinding and balancing modes. Such an arrangement is illustrated in Dutch Application No. 8603022, filed November 27, 1986, which is incorporated herein by reference. When the two separate motors are used, it is necessary to isolate the motor not used in balancing while balancing is taking place. FORCE VARIATION GRINDING SUBSYSTEM The force variation grinding subsystem 16 is similar to that of U.S. Patent No. 4,139,041 and incorporated herein by reference. Subsystem 16 includes a loading unit 50 and a grinding unit 57. The loading unit 50 serves to radially load the tire and wheel assembly TA to determine the reactive force variations circumferentially about the tire. The grinding unit 51 serves to grind away small portions of the tread at the shoulders to reduce the loaded radial runout of the tire and wheel assembly TA. The loading unit 50 includes a loading arm assembly 54 pivoted on the leg 22 of base 20 about an axis parallel to the spindle axis A R . The arm assembly 54 pivotally mounts a yoke assembly 55 therein also about an axis parallel to spindle axis A R . The yoke assembly 55 rotatably mounts a loading drum 56 thereon so that drum 56 rotates about an axis- parallel to spindle axis A R which is also about vertically aligned with the spindle 40 to press against the tire tread TT to radially load the tire and wheel assembly TA. The loading arm assembly 54 is positioned by load cylinder 58 which presses the drum 56 against the tire as its piston is extended. Typically, an incompressible fluid is used in cylinder 58 so that the position of arm assembly 54 is fixed after the assembly TA is loaded. The load on the tire tread is maintained by a spring assembly.between the arm assembly 54 and the yoke assembly 55. A transducer 60 measures the relative positions between the arm assembly 54 and the yoke assembly 55 which is a function of the variation in the loaded radial runout of the tire and wheel assembly TA. Thus transducer 60 detects the N amount of loaded radial runout. The grinding unit 51 includes a buffer arm assembly 65 also pivoted on the leg 22 of base 20 so that its axis of rotation is parallel to spindle 40. The upper end of arm assembly 65 mounts a buffing head 66 about horizontally level with spindle 40. The buffing head 66 has a pair of tapered rasps 68 on shaft 69. The. shaft 69 is driven by a motor 70 through a belt drive. The rasps 68 are bheld adjacent the tire tread TT by a spring loaded positioner 72. The buffer arm assembly 65 is connected to the loading arm assembly 54 by preload springs 74 that maintain the positioner 72 in contact with the tire thread TT. A buffing cylinder 75 also connects the arm assemblies 54 and 65 to move the rasps 68 against the tread TT during grinding. DYNAMIC BALANCE SUBSYSTEM The dynamic balance subsystem 18 includes a shaft encoder assembly 76 to measure the rotation angle of spindle 40 and a force transducer assembly 78 to measure the dynamic loading on the tire and wheel assembly TA. The shaft encoder assembly 76 is of typical construction with a apertured encoder disc 79 fixed to the rear end of spindle 40 and rotatable therewith. Appropriate photoelectric pickups 80 are provided at the edge of disc / 79 to read the angular position of the spindle 40 for the measured dynamic loading to be related to the angular position around the tire and wheel assembly TA. The force transducer assembly 78 includes a pair of piezoelectric transducers 81, one being mounted on the support flange 36 of each bearing 30 and 31. The operating end of the transducer 81 bears against that portion of bearing 30 oβ 31 subject to movement due to dynamic imbalance in the tire and wheel assembly TA. The line of action LA of the transducers 81 is generally normal to the load imposed on the spindle 40 by the loading unit 50 and by the belt tension to the motor 48. This isolates the transducers 81 from these forces so that only dynamic unbalance is detected. It will be understood that different types of transducers which can withstand higher loads may be substituted for transducers 81. This would allow the radial loading and belt loading to be aligned with the line of action of the transducers, however, appropriate circuity would be used to correct the transducer readouts for the extraneous loads. COVER ASSEMBLIES To protect the operator, a tire cover assembly 84 is provided which must be lowered over the tire assembly TA as seen in Fig. 1 at least when the machine is in its dynamic balancing mode. In the particular machine illustrated, it is necessary to lower the cover assembly 84 over the tire assembly TA before the machine will operate. This is controlled by the tire cover switch SW-1 which is closed when the cover assembly 84 is lowered. To also protect the operator while the machine is operating, a rasp cover assembly 85 is provided over the buffing head 66 which must be closed at least while the machine is in its force variation grinding mode. In the particular machine illustrated, a rasp switch SW-2 is provided which disables the machine until the cover assembly 85 is closed. CONTROL SYSTEM The control system 19 includes a set of manually operated input switches SW-3 - SW-6. Switch SW-3 is the cycle start switch when force variation tire grinding is desired, while switch SW-4 initializes the machine if it is desirable to buff to a finer value than standard or to overbuff . Switch SW-5 enables the dynamic balancing mode to operate and switch SW-6 is the stop switch. The switches SW-3 - SW-6 are mounted on the control panel 88. Also mounted on the control panel 88 are a set of potentiometers P-7 - P-9. These potentiometers are used to set up the machine for the balancing operation. Potentiometer P-7 is used to input rim width, potentiometer P-8 is used to input the distance between the rim edge and a known reference plane and potentiometer P-9 is used to input rim diameter. The output of the load transducer 60 also serves as another input to the control system 19 for use during the force variation tire grinding operation. The shaft encoder 76 as well as the two piezoelectric transducers 81 p and 81 R provide inputs to the control system 19 during the dynamic balancing operation. The enabling switches SW-1 for the tire cover and SW-2 for the rasp cover are also providing inputs to the control system 19. The control system 19 includes a programmable controller 89 which controls the operation of the unit. The programmable controller 89 includes a central processing unit as is known in the art and Is programmed with an externally produced program, illustrated as an insertable magnetic media 90. The programming of the controller 89 is within the capability of those skilled in the art and will not be described in detail herein. The controller 89 controls the operation of the rasp drive motor 70 through an appropriate motor controller 91. The controller 89 also controls the operation of the spindle drive motor 48 through a variable speed controller 92 so that the motor 48 can be operated at the lower speed required for force variation grinding and at the higher speed required for dynamic balancing. While any of a number of different speed controllers may be used, the motor "48 illustrated is a d-c motor with the controller 92 being a AC converter which has an output frequency to the motor 48 which can be varied. Also, the controller 89 can be used to selectively position the motor 48 in different angular positions using the phase controller 94 as is known in the art. It will also be appreciated that the controller 89 can be used to operate the motor 48 as a brake by appropriately reversing the polarity on the motor 48. This allows the rotation of the tire and wheel assembly TA to be quickly ή stopped at the end of the balancing mode and also allow the motor 48 to be stopped at the various positions required when the motor is being used to rotationally position the tire and wheel assembly TA. The controller 89 also controls the valve network 95 that controls the operation of the load cylinder 58 and buffing cylinder 75. The cylinders 58 and 75 are enabled by a run valve V-R whose solenoid is connected to the controller 89. The run valve V-R supplies air to a pneumatic hydraulic reservoir 96 so as to pressurize the hydraulic portion of the reservoir. The hydraulic portion of the reservoir is connected to the loading cylinder 58 through a locking valve V-L whose operating solenoid is connected to the controller 89. The air outlet from the run valve V-R is also connected to a buff value V-B which can power the buff cylinder 75 while the run solenoid V-R is in its run position. The solenoid of the buff valve V-B is also controlled from the controller 89. The controller 89 also powers the display DP. The display DP includes a first light array labelled L1-L6 that indicates the particular state of the force variation grinding mode as labelled on Fig. 6. Also, a loaded radial runout gauge DL may be driven by the controller 89 to visually indicate the radial runout in the tire and wheel ° assembly TA . The display DP also includes a pair of imbalance displays labelled ID for the left side of the rim and IDn for the right side of the rim. The displays ID may be any conventional displays used in the balancing art and are illustrated as liquid crystal displays. Appropriate arrow arrays AA, and AA R may likewise be powered from the controller 89 to indicate the location of the imbalance so that wheel weights can be applied to the rim after the tire is balanced. OPERATION In operation, it will be seen that the operator mounts the tire and wheel assembly on the drive spindle 40 using the mounting assembly 14. This locks the tire and wheel assembly TA both axially along the spindle 40 and rotationally about the spindle 40 so that rotating the spindle 40 rotates the tire and wheel assembly TA therewith. The operator then inputs the rim width, measured distance between the inside wheel rim and a fixed reference point on the machine and inputs the rim diameter using the potentiometers P7-P9. Typically, the machine is initialized and the start switch SW-3 as well as the balance switch SW-5 depressed while at least the tire cover assembly 84 is raised. If the fine buff or overbuff mode is desired, the switch SW-4 is also manipulated. After the tire cover assembly 84 is lowered to close switch SW-1, and provided that the rasp cover assembly 85 is also closed to close switch SW-2, the automatic operation of the machine proceeds. First, the controller 89 energizes the run valve V-R to pressurize the pneumatic hydraulic reservoir 96 and extend the load cylinder 58 to raise the drum 56 against the tire tread to load same. When the prescribed loading of the tire tread by the drum 56 is achieved, the locking valve V-L is operated by the controller 89 to lock the hydraulic fluid in the cylinder 58 and fix it in that position. The controller 89 then operates the motor 48 through the controller 92 so that the motor 48 rotates the tire and wheel assembly TA in the force variation grinding mode, usually about 12-15 RPM. The tire and wheel assembly TA is rotated one complete revolution while the output of the load transducer 60 produces inputs to the controller 89. After the initial rotation of the tire and wheel assembly TA, the controller 89 shifts the machine into the grinding mode if the loaded radial runout is within a correctable range. If the loaded radial runout is below the correctable range, the "good" lamp L6 is illuminated and the machine shifts into the balancing mode. If the loaded radial runout is within the correcting range, the controller 89 continues to rotate the tire and wheel assembly TA and to selectively energize the buff valve V-B at the appropriate locations to energize cylinder 75 and pull the buffing rasps 68 against the tire tread to buff away the portions of the tire tread exceeding the matching range. This process continues until the entire tire tread reads in the acceptable radial runout range. At this time, the controller 89 deactivates the run valve V-R to disable the circuit 95. The controller 89 then shifts the machine into the dynamic balance mode by causing the controller 92 to shift the motor 48 into the higher RPM mode to spin the tire and wheel assembly TA at a sufficient RPM for balancing, usually 500-1500 RPM. At the same time, the shaft encoder 76 output is monitored as well as the two piezoelectric transducers 81n and 81 R so that the amount of imbalance can be located at the two sides of the rim. The controller 89 calculates this imbalance using a typical imbalance calculation equation and operates the imbalance displays IDτ and ID R to display the amount of weight to be added to the sides of the rim. The arrow arrays AAr and AA R are also illuminated to indicate the direction of the imbalance. The controller 89 applies a braking force to the motor 48 to stop the rotation of the tire and wheel assembly TA and then shifts the motor 48 through the position controller 94 until the rotational position of the wheel rim at which the imbalance is located is in a prescribed rotational position on the machine. .The operator then applies the indicated wheel weight and energizes the machine either using a switch such as switch SW-5 or an additional switch and the controller 89 then moves the motor 48 until the position of the imbalance on the other side of the wheel rim is located at the first mentioned position. The operator then applies the weight to that side of the wheel rim and the tire and wheel assembly ^ TA is ready to be removed from the machine,

Claims: 2£T WE CLAIM: 1. A method of correcting loaded radial runout and dynamic imbalance in a tire and wheel assembly including the steps of: (a) mounting the tire and wheel assembly on a support means so that the tire and wheel assembly is rotatable about its rotational axis on the vehicle; (b) rotating the tire and wheel assembly about its rotational axis on said support means while peripherally loading the tire tread with a prescribed load; (c) measuring the loaded radial runout of the tire tread under load; (d) removing any portions of the tire tread required to reduce the loaded radial runout variation around the tire tread to a prescribed range; (e) rotating the tire and wheel assembly about its rotational axis on said support means at a speed sufficient to measure dynamic imbalance; and ^ (f) measuring and locating the dynamic imbalance in the tire and wheel assembly. 2. The method of Claim 1 wherein step (b) includes rotating the tire and wheel assembly at a first speed during steps (c) and (d) and wherein step O) includes rotating the tire and wheel assembly at a second speed during step (d) . 3. The method of Claim 1 further including the following step: (g) attaching weights to the tire and wheel assembly to correct the measured and located dynamic imbalance. A method of mounting a shaft adapted to be loaded with a first set of radially directed forces that do not rotate about the shaft axis and a second set of radially directed forces that rotate about the shaft axis comprising the steps of: operatively associating first transducer means with the shaft for detecting the force loading on the shaft in a direction such that the magnitude of the first set of forces is detected by said first transducer means; and operatively associating second transducer means with the shaft for detecting the force load on the shaft isolated from the first set of forces and such that the magnitude of the second set of forces is detected as the second set of forces rotates thereby.

Inventors: BOELE HENRIK ARIE, NEWTON ROBERT PARK III, BOELE, HENRIK, ARIE, NEWTON, ROBERT, PARK, III
Applicants: BOELE HENRIK ARIE, NEWTON ROBERT PARK, BOELE, HENRIK, ARIE, NEWTON, ROBERT, PARK, III
Application year: 1987
Main classification: B29D30
IPC codes: B24B5, B24B49, G01M1, G01M17