Patent Publication Number: US-6981311-B2

Title: Fastening apparatus and method

Description:
FIELD OF THE INVENTION 
   The present invention relates to a fastening system. In particular, the present invention relates to a feedback control for a fastening system. 
   BACKGROUND OF THE INVENTION 
   A typical fastening system includes a motor that drives an output element to rotate a threaded fastener onto a threaded connecting element. Proper connection of the fastener requires exertion of torque on the fastener and proper alignment of the threads. 
   SUMMARY OF THE INVENTION 
   Operators desire a fastening system that indicates when inadequate tightening of the fastener and/or improper alignment of the threaded fastener occurs. Indication lights and/or audio alarms can be difficult to recognize in a fast-paced and noisy industrial environment. 
   In one construction, the invention provides a fastening system that includes a housing defining a chamber, a motor positioned within the chamber and having a rotor, a sensor, and a controller. The sensor is coupled to the rotor and provides a feedback signal of a motor operation. The controller receives the feedback signal, determines an error condition based upon the feedback signal, and oscillates the rotor between a first position and a second position to vibrate the housing in response to the error condition. The vibrating housing provides an indication to the user that the fastener was improperly installed. In one construction, the sensor is a torque transducer and the feedback signal represents a torque force exerted by the motor. In a second construction, the sensor provides a feedback signal that represents a revolution of the rotor. 
   In another construction, the invention provides a method for indicating an error condition of a fastening system that includes detecting a feedback signal from a motor of the fastener system, comparing the feedback signal to a threshold value, determining an error condition based upon the feedback signal, and oscillating a rotor to the motor between a first position and a second position to vibrate a housing to the motor in response to the error condition. 
   As is apparent from the above, it is an aspect of the invention to provide a system and method for providing precision fastening of a fastener. Other features and aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a fastening system of the invention including a control console; 
       FIG. 2  is a schematic view of the control system of  FIG. 1 ; and 
       FIG. 3  is a schematic view of the fastening system of  FIG. 1 . 
   

   DETAILED DESCRIPTION 
   Before any constructions of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other constructions and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     FIG. 1  is a perspective view of a construction of a fastening system  10  according to the present invention for fastening/unfastening a fastener. In one construction of the invention, the fastening system  10  includes a fastening device or tool  20  electrically connected by a communication bus  25  to a control console  27 . The control console  27  includes a controller  30  (See  FIGS. 2 and 3 ) and an interface  32 . In another construction, the fastening tool  20  can be a portable tool in wireless communication (e.g., via a rf signal, etc.) with the control console  27 . In yet another construction, the fastening tool  20  can be a portable tool having a portable controller  30 . The fastener or fastener component (not shown) can be any connector rod, bolt, nut, screw, etc. known those in the art that is operable in fastening an assembly and is not limiting on the invention. 
   An exemplary control console  27  having the controller  30  and the user interface  32  is the INSIGHT™ Model PFS manufactured by the INGERSOLL-RAND™ Company. However, the fastening system  10  of the invention can work with other motor controllers and/or user interfaces known in the art and is not limiting on the invention. 
   One construction of the communication bus  25 , as shown in  FIG. 1 , includes a power line and a communication line. The power line allows the controller  30  (See  FIGS. 2 and 3 ) at the control console  27  to enable/disable the fastening tool  20 . The communication line allows communication to and from the controller  30  with the fastening tool  20 , including control information related to operation of the fastening tool  20  and command signals from the controller  30 . 
   The fastening tool  20  provides the torque for driving a fastener. As shown in  FIG. 1 , one construction of the fastening tool  20  includes a motor  35  (not shown) that drives an output spindle  40 . In general, the motor  35  provides the torque to the output spindle  40  to fasten/unfasten a fastener to an assembly. The exemplary construction of the fastening tool  20  as shown in  FIG. 1  is a Model DEP15NS4TL manufactured by the INGERSOLL-RAND™ Company. Of course, the fastening tool  20  can be any electrically driven tool (angle tool, in-line tool, hand-held tool, etc.) known to those skilled in the art for fastening/unfastening a fastener or fastener component (not shown). The fastening tool  20  also includes a housing  45  that forms a chamber to enclose or retain the motor  35 . The housing  45  can be any suitable size and shape and made from any suitable material (e.g., metal, plastic, etc.) known in the art of fastening systems. 
     FIG. 2  shows a schematic diagram of the controller  30  in communication with the motor  35 . As shown in  FIG. 2 , in one construction, the motor  35  is a direct current (DC) brushless motor having a stator  50  and a rotor  55 . The stator  50  includes a plurality of stator windings  60  located at a radial distance from the rotor  55 . The rotor  55  includes a plurality of permanent magnets (not shown) located along a periphery of the rotor  55 . When electrically energized, the windings  60  generate a magnetic field. The magnetic interaction between the magnetic field from the windings  60  and the permanent magnets induces rotation of the rotor  55 . The controller  30  provides a control signal that regulates the excitation of the respective windings  60  of the stator  50 . The excitation of the stator windings  60  controls the position and rotational speed of the rotor  55 . 
     FIG. 3  is a schematic diagram of the fastening system  10  of the invention. One construction of the fastening system  10  includes the controller  30  electrically connected to the stator  50  of the motor  35 , a sensor, and the user interface  32 . The controller  30  includes a processor  75  and a memory  80 . The processor  75  obtains, interprets, and executes a plurality of software program instructions stored in the memory  80 . In addition to software instructions, the memory  80  provides storage for pre-programmed control parameters, manually input parameters, and a history of measured parameter information from operation of the fastener tool  20 . Additionally, the controller  30  can include other circuitry or components (e.g., signal conditioners, filters, drivers, analog-to-digital converters, amplifiers, etc.) not shown but that would be apparent to one skilled in the art. 
   Among its functions, the processor  75  is configured by the software to receive signals or input from sensors/transducers, to analyze the received signals and input, and to generate command signals to the stator  50  of the fastening tool  20 . In one construction, the processor  75  is a microprocessor operable in executing a plurality of instructions. An example microprocessor is an Intel Pentium processor of a personal computer. However, other processors (e.g., programmable logic controllers, etc.) known to those skilled in the art can be used. 
   In one construction, the controller  30  includes a servo-drive control device to control operation of the motor  35 . In general, the servo-drive control device receives feedback information from sensors/transducers at the motor  35 , processes the feedback information, and adjusts the control signal to the stator  50  in response to the feedback information. Of course, other types of controllers known to those skilled in the art can be used. 
   Referring to  FIGS. 1 and 3 , a sensor/transducer located at the motor  35  provides feedback signals via the communication bus  25  to the controller  30 . The feedback signal includes control information or parameters detected at the motor  35 . As shown in  FIG. 3 , one construction of a sensor/transducer includes a torque transducer  85  to provide a feedback signal that represents a value of the torque force exerted by the motor  35 . The controller  30  includes a converter that translates the feedback signal into a torque value. The controller  30  can also include a comparator that determines if the torque value is outside a predetermined threshold range stored in the memory  80  of the controller  30 . In another construction, the torque transducer  85  may include the comparator that enables the transducer  85  to provide a feedback signal if the exerted torque is below a threshold value. A high torque value is indicative that the fastener component is too tight. A low torque value is indicative of an error condition that the operator did not adequately tighten the fastener component with the fastening tool  20 . In another embodiment, the sensor can provide signals representative of values of other parameters (e.g., heat, slippage, etc.) of interest in the fastening process. 
   Referring to  FIG. 3 , another construction of a sensor/transducer is a resolver  105  to provide a feedback signal to determine the angular rotation traveled by the rotor  55 . The resolver  105  is positioned in the vicinity of the rotor  55  and stator  50 . The resolver  105  converts the angular position of the rotor  55  relative to the stator  50  into an analog or digital signal. In general, as the stator  50  induces the rotor  55  to rotate, the resolver  105  generates voltage waveforms (e.g., sine and cosine waveforms) of different magnitude depending on the position of the rotor  55  relative to the stator. The resolver  105  translates the voltage waveforms into a feedback signal indicative of the rotor  55  position. One construction of the resolver  105  provides this feedback signal via the communication bus  25  to the controller  30 . 
   The controller  30  translates the signal provided by the resolver  105  into an angular rotation turned by the rotor  55  and/or interconnected output spindle  40  in driving the fastener. The controller  30  can include a comparator that determines if the measured value for the angular rotation of the rotor  55  and/or spindle  40  is outside a threshold range stored in the memory  80  of the controller  30 . Using a factor associated with a gear ratio of the motor  35 , the controller  30  can convert the angle of rotation or number of revolutions turned by the rotor  55  into an angle of rotation traveled by the output spindle  40 . An angular rotation of the rotor  55  and/or spindle  40  outside the threshold range can indicate that a threaded fastener was installed with the threads out of alignment, and/or the fastener is improperly tightened. The controller  30  can also use the feedback signal from the resolver  105  to regulate the speed and/or position of the rotor  55 , as described later. 
   In another construction of the invention, the resolver  105  can include a comparator that enables the resolver  105  to signal the controller  30  if the rotational angle traveled by the rotor  55  is outside a predetermined threshold range. In yet another construction of the invention, one or more Hall effect sensors can be used to provide a feedback signal to the controller  30  indicative of the rotor  55  position. 
   The controller  30  can also determine an error condition using various combinations of torque information and angle of rotation information, etc. provided by the various sensors/transducers located at the motor  35 . For example, the controller  30  can monitor a yield of the fastening operation based upon the slope of the measured torque versus angle of rotation. In another example, the controller  30  can monitor the angle of rotation information or the number of revolutions once the controller  30  detects a threshold torque force. 
   As noted above, the controller  30  includes a memory  80  for storage of control feedback information from the sensors/transducers described above. In one construction, the controller  30  sets the predetermined threshold ranges for an error condition (e.g., torque, angle of rotation, number of revolutions, etc.) based upon the feedback information from the sensors/transducers. In one construction, the threshold range for an error condition can be determined from the most recent twenty-five measured samples of fastening parameters collected from fastening operations. In another construction, the threshold range for an error condition can be determined from the first twenty-five measured samples of fastening parameters collected from fastening operations. Of course, the selection or number of samples can vary and is not limiting on the invention. In yet another construction, the controller  30  can use different threshold ranges for detecting an error condition for different stages of fastening operations (e.g., start, end, etc.). 
   Upon detecting an error condition, the controller  30  provides an alarm indication to the operator. As described above, the controller  30  can detect error conditions based upon the torque and angle of rotation feedback from the torque transucer  85  and/or resolver  105  at the motor  35 . The controller  30  alerts the operator of the error condition by vibrating the housing  45 . To vibrate the housing  45  ( FIG. 1 ), the controller  30  oscillates the rotor  55  of the motor  35  ( FIG. 2 ). The oscillating motor causes vibration of the housing  45  in the hand of the operator, indicating an error condition in the fastening operation of the fastener. In one construction and as shown in  FIG. 2 , the controller  30  oscillates the rotor  55  between a first  110  position and a second  115  position. To oscillate the rotor  55 , the controller  30  can use feedback information from the resolver  105  representative of the rotor  55  position with respect to the stator  50 . In response to feedback information of the rotor  55  position, the controller  30  adjusts the control signal that regulates the electrical excitation of the pairs of stator windings  60  ( FIG. 2 ). The electrical excitation of the stator windings  60  controls the rotation of the rotor  55  between the first position  110  and the second position  115  and back, thereby vibrating the housing  45 . As shown in  FIG. 2 , the first and second positions of the rotor  55  are ninety degrees apart. Of course, the first and second positions  110 ,  115  of the rotor  55  can vary depending on the desired vibration of the housing. In addition, the controller  30  can set the frequency or speed of oscillation of the rotor  55 . In one construction, the controller  30  sets the frequency of the oscillation to 10 hertz. Of course, the frequency can vary and is not limiting on the invention. 
   As shown in  FIGS. 1 and 3 , the user interface  32  allows an operator to view and to manually input control information (e.g., measured torque and angle of rotation, threshold torque and angle of rotation ranges, etc.) related to the operation of the fastening tool  20 . As shown in  FIG. 1 , one construction of the user interface  32  includes a visual display  120  (e.g., light-emitting diodes, liquid crystal display, monitor, etc.) and a keyboard  125 . In addition, the user interface  32  can further include audio indicators (e.g., buzzers, speakers, etc.) known in the art. The user interface  32  can provide visual and/or audio indications in combination with vibrating the housing  45  to alert the operator of the error condition. Regarding the error or alarm condition, the user interface  32  can indicate the location of the fastening tool  20  in error, and a description of the alarm condition (e.g., threshold value, measured value, past error conditions, etc.). One construction of the interface  32  is located at the control console  27  and/or at a remote control center. The controller  30  and user interface  32  can be used to control and monitor one or more fastening tools  20 . In another construction, the controller  30  can include a modem, common interface gateway, and web browser to allow communication between the controller  30  and a remote workstation via an intranet or internet communication line. 
   Having described the basic architecture of the fastening system  10 , the operation of the fastening system  10  will now be described. 
   In operation, the operator or user activates the fastening system  10  of the invention. Upon activation, the controller  30  uploads stored threshold ranges for torque, angle of rotation, number of revolutions, etc. respective to the sensors and transducers of the fastening tool  20 . The values of the threshold ranges can depend upon the particular fastening tool  20 , output spindle  40 , and fastener being used. This information can be entered by manual computer entry or scanned by an infrared scanner. In one construction, the controller  30  is connected to a fastening tool  20  having a type of output spindle  40  to drive a fastener. In another construction, the controller  30  can be used to simultaneously control more than one fastening tool  20  having a plurality of output spindles for driving various types of fasteners. Upon selecting the type of control for the respective fastening operation, the operator engages the fastening tool  20  to install the fastener to the assembly. The torque transducer  85  and resolver  105  at the motor  35  provide feedback information to the controller  30 . Using the threshold values, the controller  30  determines from the feedback information whether the fastener has been properly installed. If the controller  30  determines from the measured control information that an error condition exists (e.g., sub-threshold torque, inadequate rotation of rotor, excessive torque, excessive rotation of rotor, etc.), the controller  30  causes the rotor  55  of the motor  35  to oscillate between the first  110  and the second  115  position. In controlling the oscillation of the rotor  55 , the controller  30  uses the feedback information of the rotor position provided by the resolver  105 . Based upon the feedback information of the rotor position, the controller  30  provides the control signal that energizes the plurality of stator windings  60  to cause the rotor  55  to oscillate. The oscillation of the rotor  55  causes the housing  45  to vibrate. The vibrating housing  45  provides a tactile indication to the operator that an error condition exists. In one construction, the controller  30  can vibrate the housing  45  at the same frequency to signify an error condition. In another construction, the controller  30  can vibrate the housing  45  at a different frequency depending upon the type of error condition (e.g., torque, angle, etc.). The controller  30  can also provide other indications of the error condition via other visual and/or audio indicators at the user interface  32 . 
   In another construction, an operator can elect to drive the fastener, then backout or reverse the fastener before driving the fastener again. An operator can elect this method of fastening based upon the type of fastener or to correct an error condition. The controller  30  can monitor torque, angle, etc. of the fastener tool  20  during both forward and reverse modes of operation. For example, to correct an error condition, the operator can elect to reverse the fastening operation, called fault backout. In one construction of the invention, the controller  30  can automatically deactivate the error detecting sensors (e.g., torque, angle of rotation, number of revolutions, etc.) and indicators (e.g., vibrating the housing  45 ) when the operator selects to fault backout the fastener. Upon retrying or driving forward the fastener, the controller  30  can automatically re-activate the error condition detecting sensors and indicators. In another construction, the controller  30  can monitor for an error condition during both forward and reverse modes of operation. 
   Thus, the invention provides, among other things, a feedback control for a fastening system. Various features and advantages of the invention are set forth in the following claims.