Abstract:
An electronic torque wrench for driving a workpiece includes a wrench body having a handle end and a wrench head receiving end. A wrench head a workpiece receiving end and a mounting end, and the mounting end is removably received by wrench head receiving end. A user interface having a processor and a display is mounted on the wrench body. A wrench head sensing device is carried by the wrench head receiving end and includes an electrical connection between the wrench head sensing device and the processor. The wrench head sensing device sends an electrical signal to the processor indicating the presence of the wrench head on the wrench head receiving end.

Description:
CLAIM OF PRIORITY 
   This application claims priority to U.S. Provisional Application 60/700,131 filed Jul. 18, 2005. 

   FIELD OF THE INVENTION 
   The present invention relates generally to electronic torque wrenches and extensions for use therewith. More particularly, the present invention relates to a device for use with torque wrenches that identifies an extension being used with the wrench and compensates displayed torque values accordingly. 
   BACKGROUND OF THE INVENTION 
   Often, fasteners used to assemble performance critical components require tightening to a specified torque level. A popular method of tightening such fasteners is through the use of a torque wrench. The accuracy and reliability of these wrenches is important to insuring that the fasteners are properly tightened the specified torque levels. 
   Torque wrenches vary from simple mechanical types to sophisticated electronic types. Mechanical type torque wrenches are generally less expensive than electronic ones. There are two common types of mechanical torque wrenches, beam and clicker types. With beam type torque wrenches, a beam bends relative to a non-deflecting beam in response to the torque applied. The amount of deflection of the bending beam relative to the stationary beam is indicative of the torque applied. Clicker type torque wrenches work by pre-loading a snap mechanism with a spring to release at a specified torque, thereby generating a click noise. 
   Electronic torque wrenches (ETW) tend to be more expensive than mechanical torque wrenches, and more accurate as well. Often, ETWs allow a user to preset a torque limit, store data for later retrieval by the user, and alert the user when the torque limit is reached. ETW models range from relatively low-cost basic models to expensive models with multiple features. 
   Regardless of which type ETW is used, torque extensions may be required to tighten fasteners that are in locations that the torque wrench will not reach. One of the most common methods of attaching a torque extension to an ETW is to replace the original drive head with an extension that has its own drive head. Once the extension is inserted, the readings of the ETW must usually be corrected for any change in lever arm length due to the extension. With the extension in place, the actual torque experienced by the fastener will be either higher or lower than what is actually displayed on the ETW, depending on whether the extension extends outwardly or inwardly from the end of the ETW, respectively. 
   For each different length extension, a different correction factor must be calculated. Typically, the end user calculates a correction factor and either divides or multiplies the desired final actual torque value to be applied to the fastener by this correction factor to determine the final compensated set torque value (as displayed by the ETW) that is to be input into the ETW. Whether the actual torque value is divided by or multiplied by the correction factor is dependent upon the method of determining the correction factor. The final compensated set torque value is the value at which, when displayed, the user ceases to apply torque to the fastener. Typically, the user will only know the final compensated set torque value accurately and is not able to accurately determine the intermediate torque values. In other words, the user only calculates the final compensated set torque value for the set torque and will not be able to continuously monitor the actual torque values during torquing operations as only “compensated” values are displayed by the ETW. This situation can lead to over and under-torquing, possibly resulting in loss of performance of the fasteners. 
   The present invention recognizes and addresses the foregoing considerations, and others, of prior art constructions and methods. 
   SUMMARY OF THE INVENTION 
   One embodiment of the present invention provides an electronic torque wrench for driving a workpiece, the torque wrench including a wrench body having a handle end and a wrench head receiving end. A wrench head includes a workpiece receiving end and a mounting end that is removably received by the wrench head receiving end of the wrench body. A user interface including a processor and a display is routed on the wrench body. A wrench head sensing device is carried by the wrench head receiving end and includes an electrical connection between the wrench head sensing device and the processor so that the wrench head sensing device can send an electrical signal to the processor indicating the presence of the wrench head on the wrench head receiving end. 
   The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended drawings, in which: 
       FIG. 1  is a partially cut-away top view of an electronic torque wrench including a torque compensation device in accordance with an embodiment of the present invention; 
       FIGS. 2A through 2C  are partially cut-away top views of the electronic torque wrench as shown in  FIG. 1 , including a variety of different extensions; 
       FIG. 3  is a perspective view of a spanner head extension for use with the electronic torque wrench as shown in  FIG. 1 ; 
       FIG. 4  is a partial cross-sectional side view of the socket of the electronic torque wrench as shown in  FIG. 1 , taken along line  4 - 4 ; 
       FIG. 5  is a schematic of an electronic circuit of the torque compensation device as shown in  FIG. 1 ; 
       FIG. 6  is a schematic diagram of an electronic circuit of the torque compensation device as shown in  FIG. 1 ; and 
       FIG. 7  is a schematic diagram of the electronic circuit of the torque compensation device integrated with the electronic circuit of the electronic torque wrench as shown in  FIG. 1 . 
   

   Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention according to the disclosure. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation, not limitation, of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope and spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
   Referring now to  FIG. 1 , an electronic torque wrench including a torque compensation device in accordance with the present invention is shown. The electronic torque wrench  10  includes a wrench body  12 , a ratchet/wrench head  14 , an extension sensor probe  16 , and an electronic unit  18 . Preferably, the wrench body  12  is of tubular construction, made of steel or other rigid material, and houses a strain tensor for measuring torque applied by torque wrench  10  to a fastener. As shown, a socket  20 , typically of rectangular or square cross-section, accepts a correspondingly shaped projection, or mounting boss  22 , on wrench head  14 , or alternatively, a torque extension. 
   Various configurations of torque extensions, such as extension  24  ( FIG. 2A ), extension  26  ( FIG. 2B ), and extension  28  ( FIG. 2C ) can be used with the torque compensation device of the invention. Extensions  24  and  26  shown in  FIGS. 2A and 2B , respectively, include spanner wrench ends  30  for engaging a fastener  31 , whereas extension  28  shown in  FIG. 2C  includes a ratchet head  32  for engaging a fastener. Other extensions that can be used can include a ratcheting square drive head, a box-end wrench head, a hex drive head, a square drive head, a socket, etc. As well, the rectangular cross-section of socket  20  is only a preferred embodiment and sockets with other cross-sectional shapes are within the scope of this invention. 
   As shown in  FIG. 2A , extension  24  includes mounting boss  22  that is rectangular in cross-section and wrench body  12  includes a correspondingly shaped socket  20 . To connect extension  24  to wrench  10 , mounting boss  22  is inserted into socket  20  of wrench body  12  until a spring loaded detent pin  34  on the projection snaps into a corresponding aperture  36  ( FIG. 4 ) formed in the wall of socket  20 . Wrench body  12  includes a hand gripper  38  at its distal end for allowing the user to comfortably grasp and operate wrench  10 . Electronic unit  18  is mounted to wrench body  12  between hand gripper  38  and the drive end. Electronic unit  18  includes electronic circuits ( FIGS. 5 through 7 ) to receive signals from the strain tensor and convert them to equivalent torque values being applied by torque wrench  10  at wrench head  14 . Electronic unit  18  includes the electronic circuitry of the torque compensation device as well as a printed circuit board (not shown) with electronic components, a liquid crystal display (LCD)  39 , batteries (not shown), and a switch bank  40 . 
   The torque extensions shown in  FIGS. 2A through 2C  are all extensions that are inserted after removing the standard wrench head  14  with which electronic torque wrench  10  is designed to provide torque measurements with. Alternately, embodiments of electronic torque wrenches can have integrated ratchet heads as part of the strain tensor which are not removable. As such, embodiments of the invention can be configured to work with a torque wrench having an integrated ratchet head. For example, various embodiments include contact switches mounted on the drive boss of the wrench head that are switched on or off when an extension having a socket with a unique pattern of projections is mounted on the drive boss. 
   Referring now to  FIGS. 2A and 3 , torque extension  24  including a spanner head  30  is shown. Torque extension  24  includes mounting boss  22  with a spring loaded pin  34  for engaging aperture  36  ( FIG. 4 ) formed in the wall of socket  20  on wrench body  12 . As shown, the extension&#39;s mounting boss  22  has a rectangular cross-section including up to four detent projections  44  extending outwardly therefrom that correspond to four contact switches  46   a,    46   b,    46   c  and  46   d  on extension sensor probe  16  ( FIG. 4 ) mounted in socket  20  of wrench body  12 . 
   Mounting projection  22  of spanner extension  24  includes one of the four possible detent projections  44   a  extending therefrom that identifies the torque extension to the torque compensation device as Extension-1000, or Extension-8 (see Table 1). Since there are four contact switches in the preferred embodiment, it is possible to uniquely identify up to 16 torque extensions (2 to the power of 4) that can be automatically detected so that the displayed torque values may be compensated for. An example list of possible extensions is shown in Table 1. Of the sixteen extensions, the first one (Extension-0/Extension-0000) is reserved for the standard ratchet head  14  shown in  FIG. 1 , leaving a total of fifteen extensions that can be uniquely identified by the torque compensation device. The number of extensions that can be automatically detected can be increased by increasing both the number of contact switches  46  and detent projections  44 . For example, the number of extensions that can be automatically detected can be increased to 32 if the number of contact switches  46  and detent projections  44  is increased to five each (2 to the power of 5). 
     FIG. 4  shows a close up view of socket  20  formed in wrench body  12  with extension sensor probe  16  mounted therein. As noted, socket  20  is of rectangular cross-section with aperture  36  configured to receive spring-loaded detent pin  34  on the standard ratchet head and extensions. Sensor probe  16  includes a printed circuit board (PCB)  48  with contact switches  46  mounted thereon. The entire unit is preferably encapsulated in a soft polymer material (not shown for ease of description) that is sealed to prevent entry of foreign material, yet allows each contact switch to operate independently of the remaining switches. The four contact switches on PCB  48  are normally inactive. When the mounting boss of standard ratchet head  14  ( FIG. 1 ) (Extension-0 of Table 1) is inserted into socket  20 , none of contact switches  46   a  through  46   d  are activated. For all other extensions, (Extension-1 through Extension-15) at least one of contact switches  46   a  through  46   d  ( 46   b  and  46   c  are not shown) will be activated. Any signals produced by the four switches are carried to the printed circuit board (not shown) of electronic unit  18  by a bundle of wires  50  routed through a hole  52  and a slot  54  formed in wrench body  12 . Note, depending on the configuration of wrench body  12 , wires  50  may be routed through an internal cavity of the body, thereby negating the need for slot  54 . 
   Referring now to  FIGS. 5 through 7 ,  FIG. 5  shows an electronic circuit of the torque compensation device. When a torque extension is inserted into socket  20 , at least one contact switches  46   a  through  46   d  is activated and an electrical signal is generated. In the preferred embodiment, each switch is active-low (i.e., normally closed with a high signal and opens when activated with a low signal). There are other possible types of circuits, for example, an active-high type, that fall within the scope of this invention. Also, a debouncing circuit  47  can be added to the contact switches to eliminate multiple signals when an extension is first inserted, as shown in  FIG. 6 . The debouncing feature adds a low-pass filter that filters out rapidly alternating voltage levels caused by multiple unintended contacts with a switch. Simply put, the low pass filter filters out high frequency changes in voltage levels. For example, when inserting an extension into the socket of the wrench, it is possible that the user could inadvertently depress an improper switch temporarily. When a switch is pressed, for example, for one tenth of a second, the processor may actually sample this signal many thousands of times. This feature is used to avoid getting false readings as to which switches are actually depressed by insertion of the extension, thereby insuring proper identification of the extension. The four contact switch signals are connected to a digital interface circuit  60  that provides power and buffers the input signals. The digital signals are then input to a microcontroller unit  62 .  FIG. 7  is a schematic diagram of the electronic circuit of the torque compensation device incorporated into the electronic circuit of the electronic torque wrench shown in  FIG. 1 . 
   The combination of detent projections  44  on mounting boss  22  of the extension and contact switches  46  on extension sensor probe  16  mounted in socket  20  of wrench body  12  is used in the preferred embodiment of this invention for illustration purposes. It will be understood by those skilled in the art that the basic function of sensing the torque extension can be done with other types of combinations, such as inserts having varying material properties from one to the next can be mounted on the mounting boss of the extension and optical, magnetic, hall-effect, inductance, capacitance, etc., sensors can be included in the socket of the wrench body for identifying the various materials based on their properties, therefore identifying the extension. 
   After the signal has reached the microcontroller unit, the torque compensation device determines the extension number of the extension that has been inserted in the torque wrench and displays the extension number on LCD  39  ( FIG. 1 ) for the user to see and verify. The microcontroller unit then calculates the compensated actual torque value using the following equation:
 
 T   ACT   =T   ORIG *( L   E   /L   O )
 
where (T ACT ) is the actual torque applied to the fastener with the torque extension; (Torig) is the torque that would have been applied to the fastener if the standard ratchet head  14  ( FIG. 1 ) were being used; L E  is the distance between the center point of hand gripper  38  and the center of the fastener to be torqued with the torque extension (Extension-1 through Extension-15 in the present case); and L O  is the distance between the center of hand gripper  38  and the center of the fastener if standard ratchet head  14  (also called Extension-0 in the present case) were being used.
 
   The compensated torque value actually applied to the fastener with the torque extension is then output to electronic unit  18  that displays the current compensated actual torque value on LCD  39 . Also, if selected, a peak hold feature records the maximum actual torque value reached during the torquing of the fastener and displays the value on LCD  39 . 
   While one or more preferred embodiments of the invention are described above, it should be appreciated by those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit thereof. It is intended that the present invention cover such modifications and variations as come within the scope and spirit of the appended claims and their equivalents. 
   
     
       
             
             
             
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
               Name 
               A 
               B 
               C 
               D 
             
             
                 
                 
             
           
           
             
                 
               Extension-0/Extension-0000 
               0 
               0 
               0 
               0 
             
             
                 
               Extension-1/Extension-0001 
               0 
               0 
               0 
               1 
             
             
                 
               Extension-2/Extension-0010 
               0 
               0 
               1 
               0 
             
             
                 
               Extension-3/Extension-0011 
               0 
               0 
               1 
               1 
             
             
                 
               Extension-4/Extension-0100 
               0 
               1 
               0 
               0 
             
             
                 
               Extension-5/Extension-0101 
               0 
               1 
               0 
               1 
             
             
                 
               Extension-6/Extension-0110 
               0 
               1 
               1 
               0 
             
             
                 
               Extension-7/Extension-0111 
               0 
               1 
               1 
               1 
             
             
                 
               Extension-8/Extension-1000 
               1 
               0 
               0 
               0 
             
             
                 
               Extension-9/Extension-1001 
               1 
               0 
               0 
               1 
             
             
                 
               Extension-10/Extension-1010 
               1 
               0 
               1 
               0 
             
             
                 
               Extension-11/Extension-1011 
               1 
               0 
               1 
               1 
             
             
                 
               Extension-12/Extension-1100 
               1 
               1 
               0 
               0 
             
             
                 
               Extension-13/Extension-1101 
               1 
               1 
               0 
               1 
             
             
                 
               Extension-14/Extension-1110 
               1 
               1 
               1 
               0 
             
             
                 
               Extension-15/Extension-1111 
               1 
               1 
               1 
               1