Abstract:
A system for providing quantitative process control of a finesse polishing based upon feedback to the operator as to whether he/she is meeting the one or more predetermined key control characteristics (KCCs). One or more sensors provide data to a controller, wherein the controller provides the operator feedback regarding his/her operational compliance with respect to the KCCs, and disables operation in the event of operator noncompliance, with the intention to promote proper operator procedure and prevent operator error when polishing a flawed painted surface.

Description:
TECHNICAL FIELD 
     The present invention relates to devices and methods for polishing painted surfaces, and more particularly to a system that provides quantitative process control of the polishing. 
     BACKGROUND OF THE INVENTION 
     In a paint shop, process control is critical in order to insure quality standards are met. This control poses varying levels of difficulty depending on the operation being performed. One particularly challenging operation is finesse sanding and polishing performed by personnel on a painted product, typically using pneumatic hand tools, for the purpose of removal or concealment of small, yet otherwise visible defects. Generally, this operation involves first finesse sanding followed by finesse polishing of the flawed painted surface to achieve a flawless painted surface. 
       FIG. 1  depicts a prior art finesse polishing operation, in which a polishing tool  10  (for nonlimiting example a model 57126 Dynabuffer™ of Dynabrade, Inc. of Clarence, N.Y. 14031) is held in the hand  12  of an operator at the handle  14  of the polishing tool. When the operator presses down on an actuation arm  18  pivotally mounted on the handle  14 , an internally disposed operator actuation device (i.e., an electrical switch or pneumatic valve) actuates the polishing tool, otherwise the polishing tool is not actuated. The polishing tool  10  further includes a head  20  attached to the handle  14 , and a rotary component  22  at which a selected polishing pad  24  is located. As seen at  FIG. 1 , the polishing tool  10  is being used to polish a painted surface  26  so as to thereby impart thereto a flawless finish. 
     In order to obtain a desired flawless paint finish with each polishing procedure, proper finesse polishing technique must be consistently used by the operator. If the proper finesse polishing technique is not used, then small scratches will remain in the surface of the paint, which can present a dull, swirl-like defect that, although difficult to see under shop lighting, might be perfectly visible in day light. Typically, paint shop management relies on personnel training to insure operators are polishing with proper finesse technique. Unfortunately, training is time consuming and often yields inconsistent long term results. 
     In identifying criteria involved with a proper finesse polishing technique, there are four key control characteristics (KCCs) involved: polishing time, applied force, tool (pad) rotational speed, and polishing tool movement. With regard to polishing time, this is typically between 8 and 16 seconds, depending on the substrate temperature of the paint surface being polished, wherein as the substrate temperature increases, polishing time should also increase. With regard to applied force, too much force will flatten the waffle structure of the polishing pad and result in swirl marks in the paint, whereas too little force will not adequately remove sanding marks and also result in swirl marks, wherein a target net applied force is, for example, between about one and two pounds (by net applied force is meant total applied force of the polishing pad on the paint surface less the weight of the polishing tool, and wherein the polishing tool  10  of  FIG. 1  has a typical weight of about 1.1 pounds). Next, with regard to tool (pad) rotational speed, a relationship exists (discussed in detail hereinbelow) between the tool rotation speed and the force applied by the operator to the painted surface at the polishing pad, wherein higher applied forces result in lower tool rotational speeds. Finally, the polishing pad should move across the flaw continuously to ensure full removal of sanding marks, ideally using a series of mutually orthogonal movements (i.e., x-y axes movements), wherein the pattern uses an overlap of about one-quarter of the polishing pad during each movement. 
     Accordingly, what would be useful in the art is if somehow a system could be provided which prevents an operator from polishing a flawed painted surface unless predetermined KCCs are met. 
     SUMMARY OF THE INVENTION 
     The present invention is a system for providing quantitative process control of finesse polishing based upon automatic polishing tool stoppage in the event of fault detection and continuous operator feedback as to whether the operator is meeting at least one predetermined key control characteristic (KCC), which informational feedback is intended to promote proper operator procedure and prevent operator error when polishing a flawed painted surface. 
     The system for providing quantitative process control of finesse polishing according to the present invention includes at least one sensor for sensing, and thereby providing data regarding, at least one operational characteristic of the selected polishing tool, a controller (i.e., a microcontroller having appropriate electronic components for data processing and I/O interfacing) which is programmed to recognize the sensed data from the at least one sensor and provide at least one output responsive to the data and the programming, and a feedback indicator providing information regarding operator compliance with the at least one operational characteristic, most preferably at least one predetermined KCC, responsive to the output. The controller monitors operation of the polishing tool and will disable operation of the polishing tool in the event it detects a fault, wherein by “fault” is meant a detected operation of the polishing tool outside an acceptable range of the at least one operational characteristic. The disabling of operation preferably requires a manual reset to re-enable the polishing tool, as for example by manually pressing a reset button. 
     In operation, the data and the programming enable the controller to provide the operator continually updated feedback, via the indicator, as to his/her compliance with one of more selected KCC during a polishing process. For example, a sensor may sense the rotational speed of the polishing tool and, thereby, the data therefrom allows the controller to recognize the operator applied force of the polishing pad on a painted surface (applied force KCC) over a predetermined polishing time duration (polishing time KCC). Accordingly, the operator is enabled to continually assess his/her compliance with the at least one KCC, via the indicator such as for example predetermined visual and/or audible indications, and thereby make real time corrections, if needed, to maintain KCC compliance, as for example adjusting the applied force to the polishing tool. If the controller determines that the operator is not complying with the at least one predetermined KCC, then the controller will output a fault, whereupon the polishing tool becomes disabled and a manual reset would be required to re-enable operation of the polishing tool. 
     Preferably, a log is recorded of the polishing tool operational characteristics during polishing cycles which may be accessed for periodic assessment of operator performance. 
     Accordingly, it is an object of the present invention to provide a system that enables quantitative process control of finesse polishing based upon feedback to the operator of the operator&#39;s meeting of predetermined KCCs so as to promote proper operator procedure and prevent operator error when polishing a flawed painted surface. 
     This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a prior art polishing tool being used by an operator to polish a painted surface. 
         FIG. 2  is a block diagram of an example of apparatus and the interfacing thereof to provide the system according to the present invention. 
         FIG. 3  is a partly sectional view of a polishing tool, showing an internal orbital swing arm and Hall effect sensor for detecting revolutions thereof. 
         FIG. 4  is a graph of applied force versus polishing tool rotation speed, showing a measured plot of the relationship therebetween for a selected polishing tool. 
         FIG. 5  is a perspective view of a polishing tool modified according to the present invention to incorporate selected apparatus of  FIG. 2 . 
         FIG. 6A  is a graph of time versus polishing tool rotation speed, showing a measured plot of a successful finesse polishing cycle. 
         FIG. 6B  is a graph of time versus polishing tool net applied force, per the successful finesse polishing cycle of  FIG. 6A . 
         FIG. 7  is a graph of time versus polishing tool rotation speed, showing a measured plot of a finesse polishing cycle interrupted by fault due to operator timing error. 
         FIG. 8  is a graph of time versus polishing tool rotation speed, showing a measured plot of a finesse polishing cycle interrupted by a fault due to operator applied force error. 
         FIG. 9  is a flow chart for an exemplar programming of the controller of  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning attention now to  FIGS. 2  though  9 ,  FIG. 2  depicts a block diagram overview of the system for providing quantitative process control of finesse polishing  100 . 
     A conventional polishing tool  102 , as for example an orbital polishing tool such as for nonlimiting example a model 57126 Dynabuffer™ of Dynabrade, Inc. of Clarence, N.Y. 14031, wherein other polishing tools of other companies may also be used, is modified to include at least one sensor  104 . The at least one sensor  104  is, by way of preferred example, a rotational speed sensor  104 ′ affixed to the head  102   a  of the polishing tool  102  which senses the rotational speed of the polishing tool  102 . By way of exemplification, the speed sensor  104 ′ is a Hall effect sensor  104 ″, affixed to the head  102   a  of the polishing tool  102  as indicated at  FIG. 3 , wherein the Hall effect sensor senses the revolutions of the internal orbital swing arm  102   b  of the polishing tool  102 . The at least one sensor  104  is connected by a data line  106  to a controller  108 . 
     The intendment is to monitor applied force of the polishing tool upon the painted surface by the operator vis-a-vis a range of acceptable applied forces (applied force KCC), which information is indirectly obtained by knowing in advance the relationship between tool rotational speed and the applied force. It will be understood that the sensor  104  may also be an applied force sensor (i.e., a commercially available pressure sensor) to directly provide applied force data to the controller, as for example located at the handle of the polishing tool or elsewhere. 
     With regard to using a rotational speed sensor to obtain applied force data,  FIG. 4  is a graph  110  of applied force versus polishing tool rotational speed, wherein a plot  112  shows a measured relationship between tool rotational speed and net applied force (net applied force equals the total applied force of the polishing pad  102   c  (for example Finesse-it™ buffing pad 02648 of Minnesota Mining &amp; Manufacturing Co. of St. Paul, Minn. 55144) on the painted surface less the weight of the polishing tool, which is for example about 1.1 pounds, or a little more depending on the weight of the indicator, if present, see below) for a Dynabuffer™ type polishing tool. To perform the test, a 4″ by 12″ painted surface was placed upon a scale. Prior to each measurement, a dime-size dollop of polish (for example Finesse-it™ polish of Minnesota Mining &amp; Manufacturing Co. of St. Paul, Minn. 55144) was applied to a cleaned area of the painted surface. The polishing tool was then operated normally to polish the painted surface (as for example in a manner depicted at  FIG. 1 ), wherein for each measured rotational speed, the corresponding applied force was read from the scale and recorded. It will be seen that there is a generally linear relationship between tool rotational speed and applied force. This relationship is empirically determined for each selected polishing tool and then programmed into the controller so that the controller is enabled to infer applied force from tool rotational speed data from the speed sensor  104 ′,  104 ″. By way of example as shown by plot  112 , a target tool net applied force range is between one pound (see plot point  112   a ) and two pounds (see plot point  112   b ), wherein the corresponding tool rotational speeds are, respectively, 9,012 RPM and 8,568 RPM when a 10,000 RPM pneumatic polishing tool (and polishing pad) as indicated above is operated at 90 PSI. 
     The controller  108  is any suitable electronic computational device, as for example a microcontroller such as for nonlimiting example a Basic Stamp 2 microcontroller of Parallax, Inc. of Rocklin, Calif. 95765, wherein other microcontollers of other companies may also be used. The controller  108  has a preferably integrated timer device  114 , and has various peripheral or integrated devices, including by way of example a data logging device  116 , a programming interface  118  and an operator reset device  120 . The controller  108  is programmed, for example as detailed hereinbelow with respect to  FIG. 9 . 
     An operator feedback indicator  122  is provided, preferably located at the polishing tool by a modification thereof as shown at  FIG. 5  wherein the feedback indicator is affixed to the head  102   a  of the polishing tool  102 , or located elsewhere, such as for example (see phantom  122 ) at the panel  108   a  for housing of the controller  108 . By way of exemplification the feedback indicator may inform the operator by means of lights (preferably LEDs) and/or sounds (preferably a siren). Where lights are used, it is preferred to include a normal operation indicator light (preferably green)  122   a  to indicate polishing tool operation is within the at least one KCC, a high indicator light (preferably red, but possibly orange or yellow)  122   b  to indicate polishing tool operation is above the at least one KCC, a low indicator light (preferably red, but possibly orange or yellow)  122   c  to indicate polishing tool operation is below the at least one KCC, and a fault indicator light (preferably red)  122   d  to indicate fault has been detected by the controller  108  pursuant to data from the at least one sensor  104  and the programming (see  FIG. 9 ). Where sound is used, preferably a sound is made when fault has been detected by the controller  108 . 
     As further shown at  FIG. 2 , the polishing tool is powered by a tool power source  130 , as for example electrical power if the polishing tool is electrically powered, or a pressurized air source if the polishing tool is pneumatically operated. A commercially available controlled switch  132  (i.e., an electrical or pneumatic valve wherein the enabled/disabled states thereof being controlled by a signal from the controller, for example Series 8210 solenoid valve of Asco Valve, Inc. of Florham Park, N.J. 07932) is connected through a data line  134  to the controller  108 , wherein the controller is able to disable operation of the polishing tool in the event of fault detection. As shown at  FIG. 5 , the polishing tool  102  may have an actuator arm  138  which when depressed by the operator, closes an internally disposed operator actuation device  140  (i.e., an electrical switch or pneumatic valve) to thereby effect operation of the polishing tool, provided the controller  108  has enabled the controlled switch  132  to deliver power to the polishing tool via power line  142 . 
     Aspects of operation of a preferred form of the present invention can be understood by reference to  FIGS. 6A through 8 , wherein the selected KCCs are applied force KCC (as inferred from sensed tool rotational speed) and polishing time KCC. It is to be understood, that other KCCs may be selected, such as for example tool movement in relation to the painted surface (tool movement KCC) wherein a conventional motion sensor is interfaced with the controller  108 . 
       FIGS. 6A and 6B  depict a situation in which the operator complies with the predetermined KCCs during operation of the polishing tool.  FIG. 6A  is a graph of time versus rotational speed of the polishing tool  150  having an acceptable range R of the rotational speed as it relates to the applied force KCC which is inferred from the acceptable range of rotational speed of the polishing tool (as for example per an empirically obtained relation therebetween as shown at  FIG. 4 ), defined by a maximum rotational speed R MAX  and minimum rotational speed R MIN . The relationship between tool rotational speed and the applied force is explicitly shown by comparison between  FIGS. 6A and 6B , where  FIG. 6B  is a graph of time versus net applied force (total applied force less tool weight)  150 ′ having an acceptable range R′ of the net applied force as it relates directly to the applied force KCC, defined by a maximum net applied force R′ MAX  and minimum net applied force R′ MIN . In the example of  FIGS. 6A and 6B , R MAX  is 9,012 RPM which corresponds to R′ MIN  of one pound, and R MIN  is 8,568 RPM which corresponds to R′ MAX  of two pounds. 
     Plot  152  is indicative of polishing tool applied force as correlated to rotational speed as a function of time, and plot  152 ′ is indicative of polishing tool net applied force. When power is supplied to the polishing tool by both the operator actuation device  140  and the controlled switch  132  being enabled (or closed), operational rotational speed of the polishing tool is obtained and tool rotational speed is monitored via the sensor  104 ,  104 ′,  104 ″ and an indicator of the operator compliance with the applied force KCC is output by the controller, which for plot portions  152   a ,  152   a ′ is in the form of illumination of the normal operation indicator light  122   a . It will be seen that plot portion  152   a , lies between R MAX  and R MIN , and plot portion  152   a ′ lies between R′ MAX  and R′ MIN ) so that therefore the controller will find no fault because the operator always complies with the applied force KCC by keeping the net applied force between one and two pounds. 
       FIG. 7  depicts a situation in which the operator complies with the predetermined KCCs during a first portion of operation of the polishing tool, but then prematurely releases the operator actuation device  140 . As in  FIG. 6A , a graph of time versus rotational speed of the polishing tool  160  shows the acceptable range R of the applied force KCC inferred from the acceptable range of rotational speed of the polishing tool (as for example per an empirically obtained relation therebetween as shown at  FIG. 4 ), defined by a maximum rotational speed R MAX  of 9,012 RPM corresponding to a minimum net applied force of the pad of the polishing tool against the painted surface of one pound, and minimum rotational speed R MIN  of 8,568 RPM corresponding to a maximum net applied force of the pad of the polishing tool against the painted surface of two pounds. Plot  162  is indicative of polishing tool applied force as correlated to rotational speed as a function of time. Tool rotational speed is monitored via the sensor  104 ,  104 ′,  104 ″ and an indicator of the operator compliance with the applied force KCC is output by the controller, which for plot portion  162   a  is in the form of illumination of the normal operation indicator light  122   a , in that the applied force KCC is being met. However, at point  162   b  the operator actuation device is prematurely released by the operator, as indicated by plot portion  162   c . In this situation, the controller  108  determines a fault because the polishing time KCC has not been fulfilled, turns off the normal operation indicator light  122   a , illuminates the fault indicator light  122   d , and disables the controlled switch  132 , preventing polishing tool operation until the system fault is remedied by manually pressing the operator reset device  120 . 
     With regard further to the polishing time KCC, the operator is expected to operate the polishing tool until the controller has determined that the polishing time KCC duration has been fulfilled, whereupon the controller momentarily disables the controlled switch to inform the operator of the polishing time KCC fulfillment and to immediately cease polishing. In this manner the operator learns the polishing time KCC duration, which may be, for example between 8 and 16 seconds, 15 seconds being shown by way of exemplification in  FIGS. 6A through 8 . 
       FIG. 8  depicts a situation in which the operator complies with the predetermined KCCs during a first portion of operation of the polishing tool, but then fails to comply during a second portion of the operation. As in  FIG. 6A , a graph of time versus rotational speed of the polishing tool  170  shows the acceptable range R of the applied force KCC inferred from the acceptable range of rotational speed of the polishing tool (as for example per an empirically obtained relation therebetween as shown at  FIG. 4 ), defined by a maximum rotational speed R MAX  of 9,012 RPM corresponding to a minimum net applied force of the pad of the polishing tool against the painted surface of one pound, and minimum rotational speed R MIN  of 8,568 RPM corresponding to a maximum net applied force of the pad of the polishing tool against the painted surface of two pounds. Plot  172  is indicative of polishing tool applied force as correlated to rotational speed as a function of time. When power is supplied to the polishing tool by both the operator actuation device  140  and the controlled switch  132  being enabled (or closed), the tool rotation speed increases and tool rotational speed is monitored via the sensor  104 ,  104 ′,  104 ″ and an indicator of the operator compliance with the applied force KCC is output by the controller, which for plot portion  172   a  is in the form of illumination of the normal operation indicator light  122   a . It will be seen that plot portion  172   c  lies between R MAX  and R MIN , even if momentarily above R MAX  at plot portion  172   b , so that therefore the controller will find no fault due to applied force KCC. However, the operator begins noncompliance to the applied force KCC at point  172   c  when he/she presses too hard, corresponding to the rotational speed falling below R MIN . The controller  108  detects this event and times its duration, as for example for about 1.5 seconds of noncompliance time by the operator during plot portion  172   e , where during the controller turns off the normal operation indicator light  122   a , illuminates the high indicator light  122   b  (note that the high indicator light is illuminated because the applied force is too high and is the KCC of concern is applied force, not tool rotational speed). At the end of a permitted noncompliance time (as for example 1.5 seconds), the controller  108  finds a system fault at point  172   d , whereupon the controller turns off the high operation indicator light  122   b , illuminates the fault indicator light  122   d , and disables the controlled switch so that power to the polishing tool is terminated. In this situation, the controller  108  prevents polishing tool operation until the system fault is remedied by manually pressing the operator reset  120 . 
     Turning attention now to  FIG. 9 , an example of an algorithm  200  for programming the controller  108  will be detailed. 
     At Decision Block  202 , inquiry is made whether the system is in operation, waiting until the answer to the inquiry is yes, whereupon the program advances to Block  204 , whereat the controlled switch  132  is enabled. At Decision Block  206  inquiry is made whether the operator actuation switch  140  is enabled (i.e., whether the polishing tool is triggered). If the answer to the inquiry is no, then the program advances to Decision Block  208 , whereat inquiry is made whether a predetermined time duration has passed without tool triggering. If the answer to the inquiry is no then the program loops back to Block  204 ; however, if the answer to the inquiry is yes, then the program advances to Block  210  whereat power is put into a conservation mode and the polishing tool disabled at Block  212  due to disablement of the controlled switch  132 . At Decision Bock  214 , inquiry is made whether the operator reset device  120  has been manually reset (i.e., pressed), and if the answer to the inquiry is yes, then the event is stored in a log at Block  216  and the program returns to Block  204 . 
     Considering again Decision Block  206 , if the answer to the inquiry is yes, then the program advances to Decision Block  218 , whereat inquiry is made, per data from the speed sensor, whether the operational tool rotational speed of the polishing tool has been achieved. If the answer to the inquiry is no, then at Decision Block  220  inquiry is further made whether a tool start fault has occurred, wherein if the answer to the inquiry is yes, then the program advances to Block  222 , whereat the fault indicator light is illuminated and then advances to Block  212  and thereafter as described hereinabove. 
     Considering again Decision Block  218 , if the answer to the inquiry thereat is yes, then at Block  224  the polishing cycle begins to be timed according to the polishing time KCC. At Block  226  the operational condition of the polishing tool is indicated at the feedback indicator  122 , vis-à-vis the applied force and polishing time KCCs. The speed sensor data is converted into applied force data per the empirically determined relationship therebetween, and as long as the applied force is within the acceptable range of the applied force KCC, normal operation indicator light is illuminated at Block  226 , otherwise either the high or the low indicator light is illuminated at Block  226 . 
     The program then advances to Decision Block  228 , whereat inquiry is made whether the operator is complying with the applied force KCC, per data from a speed sensor per correlation with the empirically determined rotational speed relationship. If the answer to the inquiry is no, that is, if the operator has operated the polishing tool outside the predetermined range of the applied force KCC for a predetermined noncompliance time, then the program advances to Block  222 , whereat only the fault indicator light is illuminated and thereupon further advances to Block  212  and further as described hereinabove. However, if the inquiry at Decision Block  228  is yes, then the program advances to Decision Block  230 . 
     At Decision Block  230 , inquiry is made whether the operator is complying with the polishing time KCC. If the answer to the inquiry is no, as for example if the operator disabled the operator actuation device  140  prematurely (see  FIG. 7 ), then the program advances to Decision Block  222  and further as described hereinabove. However, if the answer to the inquiry is yes, then the program advances to Decision Block  232 , whereat inquiry is made whether the polish cycle has completed on time, as for example completed by a predetermined elapsed time since Block  224 , for example 15 seconds, wherein if the answer to the inquiry is no, then the program returns to Decision Block  226 ; however, if the answer to the inquiry is yes, then the program advances to Block  234 , whereat a momentary disablement of the tool via the controlled switch  132  occurs which is intended to inform an operator who is still polishing that the polishing time KCC has been fulfilled, and that polishing must cease. The program then advances to Block  216  and further as described hereinabove. 
     Pursuant to the above detailed description with respect to a hand held polishing tool, it is to be understood that any power hand tool may be quantitatively process controlled by identifying operational characteristics of the tool (as for example key control characteristics), sensing at least of the operational characteristics, and providing operational control of the tool and operator feedback of operator compliance with a predetermined range of the operational characteristics per a controller. 
     To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.