# Patent

## Title
Retread tire buffing with multiple response curves

## Abstract

A method and apparatus for buffing tread from a tire carcass, the method comprising the steps of: positioning a sensor at a first lateral location along a width of the tread; receiving a first signal from the sensor, the first signal generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic; selecting a first signal response curve from a plurality of signal response curves based upon the first lateral location of the sensor, the selected signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic; determining from the response curve the distance between the sensor and the belt for the signal response received; buffing tread from the tire until the distance between the sensor and the belt reaches a final distance. The steps are repeated at a second lateral location.

## Background
This application is a continuation-in-part of U.S. patent application Ser. No. 12/593,233, filed Sep. 25, 2009 with the U.S. Patent Office as a national stage application of PCT/US2007/065522, filed Mar. 29, 2007, where the present application claims priority to and the benefit of each such application, and where the disclosure of each application is also incorporated herein by reference.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a machine and process for removing polymeric material, such as tread, from a tire carcass.
2. Description of the Related Art
Tires are known to comprise a tread consisting of an outer layer of rubber-based mixtures, of greater or lesser thickness, in which are molded various grooves and tread patterns intended, inter alia, to improve the vehicle's grip relative to the ground.
In certain cases, it is necessary to machine or remove the outer surface of the tire, for example, the tire tread, for the purpose of preparing a worn tire for retreading. Typically, tire tread removal has been accomplished by various types of abrading devices, such as rasps, grinding wheels, and wire brushes. Another process used for tire tread removal is a cutting process that utilizes a cylindrical cutter called a “peeler.”
During the tread removal process, it may be desirable to monitor the amount of material remaining above the belt so that the removal device does not contact or damage the belt, which, if occurring would destroy the tire. Therefore, removal devices may use various types of sensors to monitor the amount of material remaining above the belt during the tread removal process. Such sensors are well known to those having ordinary skill in the art and an example of one is fully disclosed in U.S. Pat. No. 6,386,024.
SUMMARY OF THE INVENTION
A particular embodiment of the present invention includes a method of buffing tread from a tire carcass, the method comprising the steps of: positioning a sensor at a first lateral location along a width of the tread; receiving a first signal response from the sensor, the first signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic; selecting a first signal response curve from a plurality of signal response curves based upon the first lateral location of the sensor, the selected signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic; determining from the first signal response curve the distance between the sensor and the belt for the signal response received; buffing tread from the tire across a first portion of the tread width until the distance between the sensor and the belt reaches a final distance; positioning a sensor at a second lateral location along a width of the tread; receiving a second signal response from the sensor at the second lateral location, the second signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic; selecting a second signal response curve from a plurality of curves based upon the second lateral location of the sensor along the width of the tread, the second signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic, where the second signal response curve is different than the signal response curve selected in the prior step of selecting; determining from the second signal response curve the distance between the sensor and the belt for the signal response received; and, buffing tread from the tire across a second portion of the tread width until the distance between the sensor and the belt reaches a final distance. Additional embodiments of the invention include a computer program including instructions for performing the steps identified in the method of buffing recited above, the computer program being embodied on a computer readable medium.
A further embodiment of the invention includes a tire buffing machine for buffing at least a portion of the tread from a tire carcass, the machine comprising a sensor that provides a sensor output signal that is a function of a distance between the sensor and a belt of a tire and a controller comprising a processor and a memory storage device that stores instructions readable by the processor, the instructions comprising the instructions for performing the steps in the method of buffing recited above.
These and other advantages will be apparent upon a review of the detailed description of the invention.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a polymeric material removal machine according to an embodiment of the invention.
FIG. 2 is a perspective view of a tire and sensor portion of the machine of FIG. 1.
FIG. 3 is a perspective view of a controller of the machine of FIG. 1.
FIG. 4 is a cross-sectional view of the tire and sensor portion of FIG. 2.
FIG. 5 is a graph showing a plurality of signal response curves according to an embodiment of the invention.
FIG. 5A is a table showing a plurality of signal responses with corresponding distances according to an embodiment of the invention.
FIG. 6 is a flow chart showing a method of removing material from a tire according to an embodiment of the invention.
FIG. 7 is a cross-sectional view of a tire and sensor portion of the machine of FIG. 1 with a second calibration sensor, according to an embodiment of the invention.
FIG. 8 is a flow chart showing a method of calibrating the sensor of the machine in FIG. 1, according to an embodiment of the invention.
FIG. 9 is a cross-sectional view of a tire and sensor portion of the machine of FIG. 1, showing a step in generating a signal response curve in accordance with an embodiment of the invention.
FIG. 10 is a cross-sectional view of a tire and sensor portion as shown in FIG. 9, showing a step in generating a signal response curve in accordance with an embodiment of the invention.
FIG. 11 is a flow chart showing a method of generating a signal response curve in accordance with an embodiment of the present invention.
FIG. 12 is a cross-sectional view of an further embodiment of the tire and sensor portion shown in FIG. 3.
FIG. 13 is a graph showing a plurality of signal response curves for use at different lateral locations along a width of the tread according to an embodiment of the invention;
FIG. 14 is a flow chart showing a method of removing material from a tire according to an embodiment of the invention.
FIG. 15 is a flow chart showing additional steps performed in the method of removing material from a tire as shown in FIG. 14 according to an embodiment of the invention.



DETAILED DESCRIPTION OF THE DRAWINGS
FIGS. 1-4 disclose a tire buffing machine 10 that is adapted to more accurately remove tread 42 from a variety of tires 40 by using information specific to each tire variety.
Buffing machine 10 generally includes a tread removal tool 11, a belt sensor 12, a sensor mount 15, a sensor output 14, a programmable logic controller 16 or other device having a processor that can execute programmed instructions, such as, for example, a personal computer or main frame computer, and a user interface 26. Removal tool 11 removes tread 42 from tire 40, and may comprise any device capable of removing tread 42 from tire 40, including, without limitation, abrading devices, such as rasps, grinding wheels, and wire brushes, and cylindrical cutters or “peelers.” It is contemplated that removal tool 11 may be used to remove material other than tread 42, for example, undertread.
Sensor 12 is generally used to monitor the amount of tread 42 being removed (or buffed) from tire 40, and to prevent any damage to belt 44. More specifically, sensor 12 measures the distance 37 between the sensor 12 and the belt 44 of tire 40. Sensor 12 is generally located radially above tread 42 and belt 44 of tire 40. In one embodiment, sensor 12 is located an offset distance 32 above tread 42 to prevent tread contact with sensor 12, and any damage resulting therefrom during the tread removal process. Sensor 12 may comprise an ultrasonic, magnetic, or inductive proximity sensor for measuring the distance between sensor 12 and belt 44. However, it is contemplated that any other sensor type may be used, including those capable of locating non-ferrous cord material. In operation, sensor 12 generates a signal response as a function of the distance 37 between the sensor 12 and the tire belt 44. The signal response may be represented by a value, which may represent current, voltage, resistance, or any other characteristic of the signal response. Ultimately, the signal is sent to the programmable logic controller 16 by way of input/output (I/O) cable 14 for evaluation and processing. Without limitation, the signal may also be sent by infrared signal, by radio frequency, by one or more cables, including fiber optics, or any other method known to those having ordinary skill in the art.
Programmable logic controller 16 generally receives signal responses from sensor 12 to monitor and help control the amount of tread 42 being removed from tire 40. More specifically, controller 16 may utilize signal-distance functions or tables (i.e., signal response curves 38) to convert a signal response into a corresponding distance. Further, controller 16 may also be used to calibrate the sensor position and generate signal response curves, and/or instruct the machine 10 to perform an operation. Controller 16 includes a logic processor 18, which may be a microprocessor, a memory storage device 19, such as RAM (random access memory), ROM (read-only memory), PROM (programmable read-only memory), and at least one input/output (I/O) cable 14 for communicating with buffing machine 10. Further, controller may include an I/O slot 20 for housing an I/O card having I/O cable connector 22.
An operator may utilize a user-interface 26 to monitor the sensor measurements and to program, or otherwise control or instruct, the operation of controller 16 and buffing machine 10. User-interface 26 and controller 16 may communicate by way of I/O cable 24. It is also contemplated that wireless communications may exist between controller 16, user-interface 26, and machine 10. Generally, controller 16 may be programmed by any known graphical or text language. Programmed instructions, data, input, and output may be stored in a memory storage device 19, which is accessible to processor 18. Memory device 19 may comprise any commercially known storage device, such as such as hard disk drives, optical storage devices, flash memory, and the like. Processor 18 executes programmed instructions and may perform the distance calculations and measurements, as wells as other operations, discussed herein. Memory storage device 19 also stores inputs, outputs, and other information, such as, for example, functions and tables 39 representing signal response curves 38, for use by processor 19 in performing its operations. In addition to performing distance conversions and measurements, controller 16 may also be programmed to generate signal response curves 38, including tables 39, based upon received input.
With reference to FIGS. 5 and 5A, signal response curves 38 are used by controller 16 to convert signal responses into distances. Signal response curves 38 are generally functions of the distance 37 between sensor 12 and belt 44, and relate a signal response to a distance. Signal response curves 38 may, for example, be stored in a memory storage device 19 as one or more equations or as a table 39, which provides a plurality of signal responses and corresponding distances 37. The one or more equations are mathematical expressions of the function. Since the function is typically not linear over the entire range of the signal response signal, a series of equations may be used that are linear over a given range of the sensor response signals.
After receiving the signal and its value, a corresponding distance may be determined from a signal response curve 38 by processor 18. More specifically, in one embodiment, the distance is determined from a function that represents signal response curve 38, which may be linear or non-linear. In another embodiment, the distance is determined from a table 39, by locating from the table the two signal responses closest in value to the signal response received and then obtaining a linear relationship between the two signal responses and their corresponding distances. From the linear relationship, a distance is determined for the signal response received. The linear relationship may comprise a linear function or may be based upon a percentage or ratio relating the signal received to range between the two points selected from the table. If, by chance, the signal response received is substantially equivalent to a signal response within a table 39, the corresponding distance may also represent the distance of the received signal response. Because signal responses may vary from tire to tire, a plurality of signal response curves 38 are provided, where each response curve 38 represents a tire or a plurality of tires sharing a common tire characteristic, such as, for example, a tire size, shape, construction, manufacturer or brand, or a tread profile. Consequently, to more accurately control tread measurement and removal, processor 18 selects a signal response curve 38 based upon a known tire characteristic, or based upon certain information or instructions received from an operator. Signal response curves 38, as functions or as tables 39, are generally stored in a memory storage device 19 and used by the processor 18 to determine the distances according to programmed instructions reflecting the above stated methods.
In operation, sensor 12 is aligned above the tread 42 and belt 44 (i.e., radially outward of tire), and may be placed at any location across the belt width 46 to monitor the tread thickness (i.e., depth or gauge) 34 in conjunction with tread removal, as described in FIG. 6. More specifically, sensor 12 generates a signal corresponding to the distance 37 between sensor 12 and belt 44. The signal is converted to a distance from a selected signal response curve 38. If the sensor is not offset from the tread, the signal response is equivalent to the tread thickness 34. If the sensor is located an offset distance 32 radially away from tread 42, the signal response is equivalent to the offset distance 32 and the tread thickness 34. The sensor 12 may be located away from the tread 42 to protect the sensor from becoming damaged during the tread removal process.
A target final tread thickness, or set point, (i.e., gauge) 36 may be provided to protect belt 44 from being inadvertently damaged by removal tool 11. Because the tread thickness 34 is generally unknown, tread thickness 34 is determined by subtracting the offset distance 32 from the distance 37 between sensor 12 and belt 44 (i.e., the distance corresponding to the signal response). Once determining the tread thickness 34, the amount of tread to be removed can be determined by subtracting the target final distance 36 from the tread thickness 34. The amount to be removed is then subtracted from the distance between the sensor and belt to provide a final sensor distance 39, which provides a tire tread 42 having a target final thickness 36. It is contemplated the sensor may monitor tread removal continuously or intermittently throughout the tread removal process, at one or more locations across the tread. Once the final thickness 36 is reached, the tread removal operation terminates. Because the characteristics of the belt vary across its width, especially at the outermost portions of the belt width, it may be desirous to limit the use of sensor 12 to certain portions of belt width 46. In one embodiment, sensor 12 is only used to monitor tread removal within the inner most 80% of belt width 46.
Because buffing machine 10 is exposed to vibrations and other dynamic loads, buffing machine 10 is susceptible to wear and misalignment. If sensor 12 is maintained an offset distance 32 from the tire, any wear or misalignment may cause the offset distance 32 to change. As a result, the accuracy of tread removal may be reduced since the offset distance 32 may be used to determine the tread thickness 34, and consequently, the amount of tread to remove. Further, if removal tool 11 over-travels the tread and reaches the belt, the belt becomes damaged and the tire discarded. Therefore, the machine 10 may be calibrated periodically to determine the present offset distance 32 to better maintain accuracy and control of tread removal.
In one embodiment, as shown in FIGS. 7-8, a first calibration signal response is generated from sensor 12 at the present offset distance 32 from the tire tread outer surface 48, the first calibration signal response being generated as a function of a distance between the sensor and the tire belt. A second calibration signal response is also generated from a second sensor 28 at a zero distance from the tread 42 (i.e., at the tread outer surface 48), the second calibration signal response being generated as a function of a distance between the second sensor and the tire belt. The second sensor 28 may be located at or near the location along the tire tread from which the first calibration signal was generated, in an effort to obtain the tread thickness corresponding to the first calibration signal and location. For example, the second sensor 28 may be adjacent to sensor 12, such as laterally (as shown in FIG. 7) or circumferentially. Both the first calibration distance and the second calibration distance are converted to a first calibration distance and a second calibration distance, respectively, by using the signal response curve applicable to the present tire. The present offset distance 32 is then determined by subtracting the second calibration distance from the first calibration distance. This process, in whole or in part, may be performed manually by an operator, by machine 10, and/or controller 16.
Referring to FIG. 5, as mentioned above, signal response curves 38 are functions of the distance 37 between sensor 12 and belt 44. Further, each curve 38 is also a function of a particular tire characteristic. With reference to FIGS. 9-11, each signal response curve 38 or table 39 may be generated by obtaining response signals, typically 3 or more, at different known distances from belt 44 of a tire 40, the tire 40 having a known tire characteristic. Obtaining at least three different response signals at known distances (or three data points) facilitates generation of a non-linear function (i.e., a signal response curve 38), assuming the data points provide for a non-linear curve.
In one embodiment, a portion of the tread 42 is removed to expose the top of belt 44, and the sensor 12 is placed atop the belt 44 to generate a signal response at a zero distance above belt 44 (i.e, the tread outer surface 48). Other signal responses may be generated at other distances from the belt 44, or, if the belt 44 is not exposed, the tread 42. These other distances may be generated at certain intervals, such as, for example, one millimeter intervals, or at any independent and arbitrary known distance. Because the resulting signal response curve 38 or table 39 may be used to convert response signals from a range of distances (the expected distance range), signal responses may be measured at distances located at or near the upper and lower limits of the expected distance range. For example, the thickest tread 42 expected to be removed from a tire may be 10 millimeters (mm) thick (i.e., the tread gauge) with the sensor 12 offset by 5 mm. The expected final thickness of the material remaining above the belt (i.e., the tread) 36 may be 1 mm. Therefore, the upper limit of the signal response curve 38 for the exemplary tire would be 17 mm (tread thickness 34 plus offset distance 32), while the lower limit would be 6 mm (the final thickness 36 plus the offset distance 32, assuming sensor 12 remains at the offset distance 32 throughout the tread removal process). Because the characteristics of belt 44 generally change with the width of the belt 46, and because signals may respond differently with belt variations, a signal response curve 38 may only be applicable to certain portions of the belt width 46, such as, for example, the inner most 80% of the belt width 50. Variation at the outer limits of belt 44 (i.e., approaching the full belt width) is generally the result of tire design and curing, including, for example, the specific belt and cap designs and the cured tread profiles (i.e., the amount of crowning or arcing across the tread width) and any changes in the mold profile for forming the lateral path or shape of belt 44 and/or of outer tread surface 48. Therefore, due to such variations, it is understood that one or more different signal response curves may be employed to buff different lateral locations along a width of a tire tread, where the different lateral locations may arise at any location along the tread width.
For example, a first signal response curve may be employed to buff a first central portion of the tread width, while one or more different signal response curves may be employed to buff one or more other portions of the tread width. With reference to an exemplary embodiment shown in FIG. 12, the different lateral portions 50, 52, 54 of the tread width are shown, where different signal response curves 38 (exemplarily shown in FIG. 13 for different lateral locations of the tread or belt) may be employed to buff such tread portions as generally taught herein. In particular, a first portion 50 is shown to be a central portion of the tread width while second and third portions 52, 54 are shown arranged laterally outward the first portion. It can also be said that the different portions 50, 52, 54 are associated with different lateral portions of the belt 44, where such portions are first, second, and third portions 50, 52, 54 of the belt width 46. Specifically, at least in the present embodiment, the different portions 50, 52, 54 are associated with variations in the construction of belt 44, where the second and third portions 52, 54 are associated with a third belt layer 44a extending partially across the belt width 46. With regard to each portion, it is understood that each portion may comprise any percentage of the tread or belt width. For example, the first portion may comprise the innermost 40% or 50% and upwards of the innermost 70% or 80% of the tread or belt width, while the second and third portions may each comprise approximately 50% of the remaining tread or belt width. As mentioned above, the different portions may be associated with any other variation in the belt construction, or more generally based upon variations in the tire construction, the curing process, or the mold shape. For example, variations in the belt or tire construction include variations in the location and/or quantity of belt layers, termination of layer endings, and the presence or location of any cap material arranged overtop of the belt. Cap material is a reinforced layer of natural or synthetic rubber, or the like, similar to the reinforcement layers forming the belt, which is well known in the art. By further example, changes in the mold may include changes in the widthwise profile of the mold used to form the outer, exposed surface of the tread and to control the lateral shape of the belt.
Accordingly, further embodiments of the methods of buffing tread from a tire carcass comprise repeating the method more generally discussed above at different lateral locations across the tread using one or more sensors and different signal response curves. In particular embodiments, with reference to the flow chart in FIG. 14, a method of buffing tread from a tire carcass comprises the steps of: positioning a sensor at a first lateral location along a width of the tread; receiving a first signal response from a sensor, the first signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic; selecting a first signal response curve from a plurality of signal response curves based upon the first lateral location of the sensor, the selected signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic; determining from the first signal response curve the distance between the sensor and the belt for the signal response received; and buffing tread from the tire across a first portion of the tread width until the distance between the sensor and the belt reaches a final distance. Further steps of such methods further includes repeating these steps at one or more lateral locations to buff different portions of the tread using a different signal response curve. For example, with reference to FIG. 15, further steps of such methods comprise: positioning a sensor, which may comprise the same sensor or a second sensor, at a second lateral location along a width of the tread; receiving a second signal response from the sensor at the second lateral location, the second signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic; selecting a second signal response curve from a plurality of curves based upon the second lateral location of the sensor along the width of the tread, the second signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic, where the second signal response curve is different than the signal response curve selected in the prior step of selecting; determining from the second signal response curve the distance between the sensor and the belt for the signal response received; and, buffing tread from the tire across a second portion of the tread width until the distance between the sensor and the belt reaches a final distance. These steps may be again repeated at one or more additional lateral locations using any same or different sensor and any same or different signal response curve to buff a different lateral area or portion of the tread. It is understood that the first and second signal response curves may be different, while any signal response curve employed at any third or subsequent location may be the same as either the first or second signal response curve or may comprise any other signal response curve. In performing these methods and those discussed in association with FIG. 12, just as employed in association with other methods herein and those discussed in association with the embodiments of FIGS. 1-11, signal response curves 38 may be represented as functions or tables 39, as referenced by example in FIGS. 5 and 5A, whereby functions and tables representing signal response curves, such as those discussed in association with FIG. 13, may be employed. Instructions for performing each of these steps may form a computer program embodied on a computer readable medium or on a memory storage device in operable communication with a controller of a tire buffing machine.
It is understood that a signal response at any first, second, or any other lateral location along a width of the tread may be received by the same sensor as the sensor translates relative the tread width, or by employing a plurality of sensors, where two or more different sensors receive signal responses any one or more different lateral locations. Therefore, further steps of such methods may further include determining the first lateral location of the sensor along a width of the tread before the step of selecting a first signal response curve; and, determining the second lateral location of the sensor along a width of the tread before the step of selecting a second signal response curve. As noted above, the sensor at each of the first and second lateral locations may be the same sensor or different sensors (that is, a first and second sensor, respectively). Each step of determining the lateral location of the sensor may be achieved by any known method using any known apparatus, whether presently known or that may be known in the future. For example, the use of a servo, other sensors, and the like, in conjunction with a controller, the buffing machine is able to determine and control the location and movement of the sensor 12 relative tire 40, and in particular, with the tread 42 or belt 44 while each translates and/or rotates with respect to the other. Therefore, the lateral location may be know before the sensor is arranged, meaning that a lateral location may be pre-selected or pre-determined prior to positioning any sensor at a lateral location where the signal response is received. Alternatively, the lateral location may be determined as the sensor is translating at an arbitrary location.
The process of obtaining signal responses to generate a signal response curve 38 may be improved by using spacers 30. A spacer or spacers 30 may be placed between the sensor 12 and the belt 44 or tread 42, for the purpose of more accurately locating the sensor 12 a known distance away from the belt 44 or tread 42. This may also improve the overall efficiency of the process over manual techniques. Spacers 30 may generally be of any thickness to place the sensor at any desired distance from the belt 44 or tread 42. In one embodiment, spacers 30 are 1 mm thick, and may be stacked to obtain distances that are integer multiples of 1 mm. It is also contemplated that a plurality of spacers 30 having different thicknesses may be used, which may also provide distances at desired intervals or increments. Spacers 30 may be made of any non-ferrous material, such as rubber, plastic/polymer, or paper, so not to interfere with the response signals of certain types of sensors 12 (e.g., magnetic or inductive sensors). In one embodiment, spacers 30 are made of ceramic material. In lieu of using spacers 30 and any manual technique, it is contemplated that the machine 10 may be programmed to step sensor 12 away from the belt or tire at known distances to obtain signal responses to generate curve 38.
While this invention has been described with reference to particular embodiments thereof, it shall be understood that such description is by way of illustration and not by way of limitation. Accordingly, the scope and content of the invention are to be defined only by the terms of the appended claims.

## Claims

1. A method of buffing tread from a tire carcass, the method comprising the steps of:
positioning a sensor at a first lateral location along a width of the tread;
receiving a first signal response from the sensor, the first signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic;
selecting a first signal response curve from a plurality of signal response curves based upon the first lateral location of the sensor, the selected signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic;
determining from the first signal response curve the distance between the sensor and the belt for the signal response received;
buffing tread from the tire across a first portion of the tread width until the distance between the sensor and the belt reaches a final distance;
positioning a sensor at a second lateral location along a width of the tread;
receiving a second signal response from the sensor at the second lateral location, the second signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic;
selecting a second signal response curve from a plurality of curves based upon the second lateral location of the sensor along the width of the tread, the second signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic, where the second signal response curve is different than the signal response curve selected in the prior step of selecting;
determining from the second signal response curve the distance between the sensor and the belt for the signal response received; and,
buffing tread from the tire across a second portion of the tread width until the distance between the sensor and the belt reaches a final distance.

2. The buffing method of claim 1, further comprising:
determining the first lateral location of the sensor along a width of the tread before the step of selecting a first signal response curve; and,
determining the second lateral location of the sensor along a width of the tread before the step of selecting a second signal response curve.

3. The buffing method of claim 1, further comprising:
receiving a tire characteristic input identifying the tire characteristic;
using the tire characteristic input to select the signal response curve from the plurality of signal response curves.

4. The buffing method of claim 1, further comprising:
receiving an instruction to select a signal response curve from the plurality of signal response curves.

5. The buffing method of claim 1, wherein the tire characteristic is selected from a tire manufacturer, a tire construction, a tire brand, a tire size, a tire shape, a tread profile or combinations thereof.

6. The buffing method of claim 1, wherein the signal response curve is in the form of a table, the table containing a plurality of signal responses with corresponding distances.

7. The buffing method of claim 5, the step of determining the distance between the sensor and the belt for a signal response received comprises determining the distance from a linear relationship between two response signals selected from the plurality of response signals in the table that are closest in value to the signal response received.

8. The buffing method of claim 1, wherein the sensor is located an offset distance outward the tread outer surface, the final distance being approximately equivalent to a final amount of material remaining above the tire belt and the offset distance.

9. The buffing method of claim 7, further comprising:
comparing a second sensor response with the sensor signal response;
calibrating the sensor signal response with the second sensor response

10. A computer program including instructions embodied on a computer readable medium, the instructions comprising:
positioning instructions for positioning a sensor at a first lateral location along a width of the tread;
receiving instructions for receiving a first signal response from the sensor, the first signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic;
selecting instructions for selecting a first signal response curve from a plurality of signal response curves based upon the first lateral location of the sensor, the selected signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic;
determining instructions for determining from the first signal response curve the distance between the sensor and the belt for the signal response received;
buffing instructions for buffing tread from the tire across a first portion of the tread width until the distance between the sensor and the belt reaches a final distance;
positioning instructions for positioning the sensor at a second lateral location along a width of the tread;
receiving instructions for receiving a second signal response from the sensor at the second lateral location, the second signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic;
selecting instructions for selecting a second signal response curve from a plurality of curves based upon the second lateral location of the sensor along the width of the tread, the second signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic, where the second signal response curve is different than the signal response curve selected in the prior step of selecting;
determining instructions for determining from the second signal response curve the distance between the sensor and the belt for the signal response received; and,
buffing instructions for buffing tread from the tire across a second portion of the tread width until the distance between the sensor and the belt reaches a final distance.

11. The computer program of claim 10, further comprising:
determining instructions for determining the first lateral location of the sensor along a width of the tread before the step of selecting a first signal response curve; and,
determining instructions for determining the second lateral location of the sensor along a width of the tread before the step of selecting a second signal response curve.

12. The computer program of claim 10, wherein the tire characteristic is selected from a tire manufacturer, a tire construction, a tire brand, a tire size, a tire shape, a tread profile.

13. The computer program of claim 10, wherein the signal response curve is in the form of a table, the table containing a plurality of signal responses with corresponding distances.

14. The computer program of claim 10 further comprising:
receiving instructions for receiving a tire characteristic input identifying the tire characteristic; and
using instructions for using the tire characteristic input to select the signal response curve from the plurality of signal response curves.

15. A tire buffing machine for buffing at least a portion of the tread from a tire carcass, the machine comprising:
a sensor that provides a sensor output signal that is a function of a distance between the sensor and a belt of a tire;
a controller comprising a processor and a memory storage device that stores instructions readable by the processor, the instructions comprising:
positioning instructions for positioning a sensor at a first lateral location along a width of the tread;
receiving instructions for receiving a first signal response from the sensor, the first signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic;
selecting instructions for selecting a first signal response curve from a plurality of signal response curves based upon the first lateral location of the sensor, the selected signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic;
determining instructions for determining from the first response curve the distance between the sensor and the belt for the signal response received;
buffing instructions for buffing tread from the tire across a first portion of the tread width until the distance between the sensor and the belt reaches a final distance;
positioning instructions for positioning the sensor at a second lateral location along a width of the tread;
determining instructions to determine the location of the sensor along the width of the tread;
receiving instructions for receiving a second signal response from the sensor at the second lateral location, the second signal response generated as a function of a distance between the sensor and a belt in the tire and a tire characteristic;
selecting instructions for selecting a second signal response curve from a plurality of curves based upon the second lateral location of the sensor along the width of the tread, the second signal response curve representing the function of the distance between the sensor and the tire belt and the tire characteristic, where the second signal response curve is different than the signal response curve selected in the prior step of selecting;
determining instructions for determining from the second signal response curve the distance between the sensor and the belt for the signal response received; and,
buffing instructions for buffing tread from the tire across a second portion of the tread width until the distance between the sensor and the belt reaches a final distance.

16. The tire buffing machine of claim 15, the sensor being a magnetic proximity sensor.

17. The tire buffing machine of claim 15, further comprising:
determining instructions for determining the first lateral location of the sensor along a width of the tread before the step of selecting a first signal response curve; and,
determining instructions for determining the second lateral location of the sensor along a width of the tread before the step of selecting a second signal response curve.

18. The tire buffing machine of claim 15, wherein the tire characteristic is selected from a tire manufacturer, a tire construction, a tire brand, a tire size, a tire shape, a tread profile.

19. The tire buffing machine of claim 15, wherein the signal response curve is in the form of a table, the table containing a plurality of signal responses with corresponding distances.

20. The tire buffing machine of claim 15, the instructions of the memory storage device further comprising:
receiving instructions for receiving a tire characteristic input identifying the tire characteristic; and
using instructions for using the tire characteristic input to select the signal response curve from the plurality of signal response curves.

21. The buffing method of claim 1, wherein the sensor at a first lateral location and the sensor at the second location are the same sensor.