Abstract:
A torque wrench for engaging a workpiece includes a wrench body having a first end and a second end. A wrench head is disposed on the first end of the wrench body and is configured to engage the workpiece. A display device is carried by the wrench body and includes a housing, a display, and an input device for inputting a preset torque value. A torque sensor is carried by the wrench head and is electrically connected to the display device. A detent extends outwardly from one of the wrench body, the wrench head, and the user interface and a plurality of recesses is formed in another of the wrench body, the wrench head, and the user interface, each of the recesses being configured to releasably receive the detent. The display device is rotatable relative to the wrench head so that the detent is received by one of the recesses for retaining the display device in a desired angular position with regard to the wrench head.

Description:
CLAIM OF PRIORITY 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/487,251, filed Jul. 14, 2006, which claims priority to U.S. Provisional Application 60/700,130 filed Jul. 18, 2005, the entire disclosures of which are incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to torque application and measurement devices. More particularly, the present invention relates to a display device for an electronic torque wrench. 
       BACKGROUND OF THE INVENTION 
       [0003]    Often, fasteners used to assemble performance critical components are tightened to a specified torque level to introduce a “pretension” in the fastener. As torque is applied to the head of the fastener, beyond a certain level of torque the fastener begins to stretch. This stretch results in the pretension in the fastener which then holds the components together. A popular method of tightening these fasteners is to use a torque wrench. Accurate and reliable torque wrenches help insure the fasteners are tightened to the proper torque specifications. 
         [0004]    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 a beam type torque wrench, a beam bends relative to a non-deflecting beam in response to the torque being applied with the wrench. The amount of deflection of the bending beam relative to the non-deflecting beam indicates the amount of torque applied to the fastener. Clicker type torque wrenches work by preloading a snap mechanism with a spring to release at a specified torque, thereby generating a click noise. 
         [0005]    Electronic torque wrenches (ETWs) tend to be more expensive than mechanical torque wrenches, and more accurate as well. When applying torque to a fastener with an electronic torque wrench, the torque readings indicated on the display device of the electronic torque wrench are proportional to the pretension in the fastener due to the applied torque. However, the readings also depend on, among other factors, the under head friction between the head of the fastener and the adjacent surface of the component and the friction between the mating threads. Static friction is greater than dynamic friction. Therefore, when torquing operations are initiated, increased amounts of torque may be required to overcome static friction forces and initiate rotation of the fastener. Therefore, it follows that torque is preferably applied to the fastener in a slow and continuous manner to allow friction forces to stabilize, to help insure accuracy and to help prevent over-torquing. 
         [0006]    Existing electronic torque wrenches typically have an electronic interface unit that includes a digital torque display, alarm signals, and operating switches, the unit being rotationally fixed with respect to the wrench body. These electronic interface units of fixed orientation are suited for tightening fasteners whose axes are vertical since the user can view the electronic interface unit. However, often these units are not convenient when the user has to tighten fasteners whose axes cause the wrench to be situated such that the electronic interface unit is not readily visible. Although the sound alarm, if present, can be heard in most cases, it is only one of several indicators that the user can utilize to prepare to stop applying torque at the proper time, so as not to over-torque the fastener. When applying torque, the user may use the numerical display to adjust the speed of rotation of the wrench so that he is prepared to stop as soon as he hears an alarm sound and/or sees a light signal. Without the continuous numerical display feedback available, and using only the alarm signals, the probability of over-torquing may increase. In summary, not only is it difficult to apply torque to a fastener while trying to simultaneously view a display at an odd angle, it may also increase the chances of over or under-torquing the fasteners. 
         [0007]    Drawbacks present in prior art electronic torque wrenches may lead to the over or under-torquing of fasteners, which can contribute to reduced performance, and eventual failure, of the fasteners. 
         [0008]    The present invention recognizes and addresses the foregoing considerations, and others, of prior art constructions and methods. 
       SUMMARY OF THE INVENTION 
       [0009]    One embodiment of the present invention provides an electronic torque wrench for engaging a workpiece, the wrench including a wrench body having a first end and a second end. A wrench head is disposed on the first end of the wrench body and the wrench is head configured to engage the workpiece. A grip handle is disposed on the second end of the wrench head and a user interface is carried by the wrench body. The user interface includes a housing, a digital display, and an input device for inputting a preset torque value. A torque sensing element is carried by the wrench head and there is an electrical connection between the torque sensing element and the display device. A detent extends outwardly from one of the wrench body, the wrench head, and the user interface. A plurality of recesses is formed in another of the wrench body, the wrench head, and the user interface, each of the recesses being configured to releasably receive the detent. The display device is rotatable relative to the wrench head about a longitudinal center axis of the wrench body so that the detent is received by one of the recesses for retaining the display device in a desired angular position with regard to the wrench head. 
         [0010]    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 
         [0011]    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: 
           [0012]      FIG. 1  is a perspective view of a preferred embodiment of an electronic torque wrench in accordance with the present invention; 
           [0013]      FIG. 2  is an exploded perspective view of the electronic torque wrench as shown in  FIG. 1 ; 
           [0014]      FIG. 3  is a top view of a display device of the electronic torque wrench as shown in  FIG. 1 ; 
           [0015]      FIGS. 4A through 4C  are cross-sectional views of the electronic torque wrench as shown in  FIG. 1 , taken along line  4 - 4 ; and 
           [0016]      FIGS. 5A through 5C  are cross-sectional views of the electronic torque wrench as shown in  FIG. 1 , taken along line  5 - 5 . 
       
    
    
       [0017]    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 
       [0018]    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. 
         [0019]    Referring now to  FIGS. 1 and 2 , an electronic torque wrench  10  including a rotary indexable display device  20  in accordance with the present invention is shown. The electronic torque wrench  10  includes a wrench body  12 , a ratchet/wrench head  14 , a grip handle  16 , a housing  18 , a battery assembly  19 , and display device  20  with a user interface  22 . Preferably, wrench body  12  is of tubular construction, made of steel or other rigid material, and receives wrench head  14  at a first end and battery assembly  19  at a second end, secured therein by an end cap  17 . Housing  18  is mounted therebetween and carries display device  20 . 
         [0020]    As shown, a front end  26  of wrench head  14  includes a ratcheting mechanism with a lever  28  that allows a user to select whether torque is applied to a fastener in either a clockwise or counterclockwise direction. The ratcheting mechanism includes a boss  30  for receiving variously sized sockets, extensions, etc. (not shown). A rear end  32  of wrench head  14  is slidably received in wrench body  12  and rigidly secured therein. Wrench head  14  includes a flat portion  34  formed between front and rear ends  26  and  32  for receiving a strain gage assembly (now shown). In the preferred embodiment, the strain gage assembly is a full-bridge assembly including four separate strain gages on a single film that is secured to flat portion  34  of wrench head  14 . An example of one such full-bridge strain gage assembly is Model No. N2A-S1449-1KB manufactured by Vishay Micromeasurement. Together, the full-bridge strain gage assembly mounted on the flat portion of wrench head  14  is referred to as a strain tensor. 
         [0021]    Housing  18  includes a bottom portion  36  and a top portion  37  defining an aperture  38  for receiving display device  20 . Display device  20  provides a user interface  22  for the operation of the electronic torque wrench. Display device  20  includes a printed circuit board  42  including a digital display  44  and an annunciator  46  mounted thereon. Printed circuit board  42  and a user input device  48  are secured to a housing cover  40  that is received in aperture  38  defined by top portion  37  of the housing. As best seen in  FIG. 3 , input device  48  includes a power button  50 , a unit selection button  52 , increment/decrement buttons  54   a  and  54   b , and three light emitting diodes (LEDs)  56   a ,  56   b  and  56   c . Light emitting diodes  56   a ,  56   b  and  56   c  are green, yellow and red, respectively, when activated. 
         [0022]      FIG. 3  shows a detailed view of an embodiment of digital display  44  of the present invention. Preferably, digital display  44  is a liquid crystal display (LCD) including a current torque level indicator  70  (a four digit numeric display), an indication of units selected  74  (foot-pound, inch-pound, and Newton-meter), a torque direction indicator  76  (clockwise (CW) by default and counterclockwise (CCW) if selected), a battery level indicator  78 , a peak hold indicator  80 , and an error (Err) indicator  82 . 
         [0023]    As noted, display device  20  is rotatable with request to wrench head  14 . Preferably, display device  20  is selectively rotatable, or indexable, between a discrete number of desired angular positions. As best seen in  FIG. 4A , the indexing of display device  20  relative to wrench head  14  is provided by a spring-loaded detent  60  that is received in any one of a plurality of recesses  62 . As shown, recesses  62  for receiving detent  60  are formed on an exterior surface of wrench body  12  and detent  60  is received in a bore  64  formed in top portion  37  of housing  18 . Detent  60  includes a ball  66  that is urged outwardly by a spring  68 . Ball  66  is retained in bore  64  by insuring that the front edge  64   a  of bore  64  has a diameter that is less than that of the ball. 
         [0024]    As shown in  FIG. 4A , the range of rotation of display device  20  with respect to wrench body  12  is 180 degrees in either a clockwise (arrow  70 ) or a counterclockwise (arrow  72 ) direction when viewing the wrench from the handle end. Recess  62   a  is symmetric about a plane that bisects wrench  10  into identical halves. As such, when detent  60  engages recess  62   a  display device  20  points directly upward when viewing the top of the wrench. To place display device  20  in a desired angular position relative to the top of wrench body  12 , a user rotates housing  18  in the desired direction with a predetermined amount of rotational force. Upon application of the required force, ball  66  will be cammed inwardly against the outward biasing force of spring  68  until the ball rides over the ridge between adjacent recesses  62   a ,  62   b . Ball  66  then engages adjacent recess  62   b  and will remain there unless the user continues to rotate housing  18 . As shown, adjacent recesses  62  are offset in 10° increments (meaning there are 36 recesses  62 ), however, other increments (15°, 20°, etc.) are possible. The predetermined amount of force required to cause detent  60  to move from one recess to the next is affected by a number of factors, such as the shape of the recesses, shape of the detent, biasing force of the spring, etc., that can be varied as desired. Note, the electrical connection (not shown) between the display device  20  and the strain gage assembly (not shown) on flat portion  34  of wrench head  14  provides enough length to remain connected during the rotation of display device  20  relative to wrench body  12 . 
         [0025]    The total amount with which housing  18 , and therefore display device  20 , is rotatable with regard to wrench body  12  can be limited by a pin and slot configuration between the housing and the wrench body. As shown in  FIG. 2 , a slot  80  formed in wrench body  12  is engaged by a pin (not shown) extending inwardly from housing  18 . As housing  18  is rotated about wrench body  12 , the pin will eventually abut either end wall of slot  80 , thereby preventing further rotation of housing  18 . In this instance, it is only necessary to provide recesses  62  over that outer portion of the wrench body that detent  60  is rotatable over. As shown in  FIGS. 1 and 2 , grip handle  16  is rotatably fixed to wrench body  12 . However, embodiments are envisioned wherein grip handle  16  is rotatably fixed to housing  18 . As such, in those embodiments, display device  20  is rotatable by grasping and rotating grip handle  16  relative to the wrench body. 
         [0026]    Referring now to  FIG. 4C , an alternate embodiment includes a detent  60   a  including a plunger  67  that is biased outwardly from bore  64  by spring  68 . Preferably, the portion of plunger  67  extending outwardly from bore  64  includes a substantially cylindrical sidewall  67   a . As such, the end walls  63  of end recesses  62   c  and  62   d  can be configured to limit the rotation of housing  18  relative to wrench body  14 . More specifically, endwalls  63  are extended outwardly toward the inner surface of housing  18  so that sidewall  67   a  will abut them rather than being cammed outwardly by them. As such, the engagement of plunger  67  with either end wall  63  prevents the rotation of plunger  67  beyond end recesses  62   c  and  62   d.    
         [0027]    Referring now to  FIGS. 5A and 5B , the housing, and therefore display device  20 , is rotatably fixed to the wrench body, that is rotatable relative to wrench head  14 . The embodiments as shown in  FIGS. 5A and 5B  function in a similar manner to those embodiments shown in  FIGS. 4A and 4B , with the following exceptions. As shown in  FIG. 5A , a plurality of recesses  62  is provided at 15° increments on an inner surface of wrench body  12  and a spring-loaded detent  60  is received in a bore  64  formed in the strain tensor end of wrench head  14 . As shown in  FIG. 5B , a plurality of recesses  62  is formed on the outer surface of the strain tensor and a spring-loaded detent  60  is received in a bore formed in wrench body  14 . Similar to earlier discussed embodiments, a pin and slot configuration between wrench body  12  and wrench head  14  can be used to limit the amount of rotation between the two. Also, as shown in  FIG. 5C , a plunger  67  style detent and recess combination can be utilized to limit the amount of rotation, as discussed above. 
         [0028]    While applying torque to a fastener, green  56   a , yellow  56   b , and red  56   c  LEDs turn on or off depending on the peak torque value applied to the fastener up until that time. Preferably, green LED  56   a  comes on as long as the peak torque value is below 75% of the preset torque value and is switched off once the peak torque reaches 75% of the preset torque value. Yellow LED  56   b  comes on for peak torque values greater than 75% but less than 99% of the preset torque value. Red LED  56   c  comes on once the peak torque value reaches 99% of the preset torque value and stays on thereafter. The selection of percentage ranges for each color may be programmed, and the percentages at which the LEDs are switched on or off can be changed to suit the specific application. Embodiments are envisioned that include a liquid crystal display device that is capable of displaying multiple colors. This permits the warning LEDs to be replaced by appropriately colored symbols on the LCD. 
         [0029]    Once the peak torque reaches the preset torque value, or is within a user selected range, a microcontroller generates electrical signals to generate an alarm sound on annunciator  46 . A red color backlight (not shown) coincides with the audible alarm signal, indicating that the preset torque value has been reached. More colors, such as yellow and green, can be added as backlights to further assist the user when approaching the preset torque value. The user is also alerted if the mechanically safe torque value (elastic limit of the strain tensor) has been exceeded, possibly causing the torque wrench to lose proper calibration. This is determined by comparing the peak torque value to the elastic limit torque of the torque wrench. If the safe torque value is exceeded, an “Err” message is displayed on error indicator  82  and the unit stops, thus indicating that the electronic torque wrench unit needs calibration before it can be used again. 
         [0030]    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.