Abstract:
A torque indicating wrench has a resilient beam with a handle end and a work-engaging end carrying a ratchet mechanism. The resilient beam is generally channel-shaped in transverse cross section and is tapered in thickness from the work-engaging end to the handle end. A reference beam is disposed in the channel and has first and second ends respectively pivotally coupled to the work-engaging and handle ends of the resilient beam. The reference beam has openings adjacent to its first and second ends to facilitate pivotal coupling to the resilient beam while substantially eliminating non-pivotal relative movement in use. A handle housing encloses the beams along substantially their entire lengths and is fixed to the resilient beam only adjacent to its handle end. The reference beam carries a Hall-effect sensor disposed between magnets on the resilient beam and coupled to electronic indicating circuitry including a display viewable through a window in the housing and push-button switches operable through apertures in the housing.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to torque-measuring and torque-indicating wrenches and has particular application to such wrenches of the bending-beam type. 
     Bending beam torque wrenches typically include a resilient beam and a rigid reference beam fixedly secured together at a work-engaging end of the tool. When torque is applied to a workpiece by application of force at a handle end of the resilient beam, the resilient beam deflects an amount which varies as a function of the torque applied. This deflection results in a relative movement between the resilient beam and the reference beam, the distal end of which is free, this relative movement being visually observable with the use of suitable scale indicia, or being detected by suitable sensors. 
     Another type of torque wrench disclosed, for example, in copending U.S. application Ser. No. 09/118,873, filed Jul. 20, 1998, utilizes two rigid beams with a spring coupling between the ends thereof remote from the workpiece, the torque being coupled from one beam to the other through the spring mechanism, which also accommodates relative displacement of the beams to indicate the magnitude of the torque. 
     These prior types of torque wrenches have been relatively costly and/or have required that the beams be relatively large and bulky in order to provide the requisite deflection while, at the same time, accommodating transmission of the desired range of torque. 
     SUMMARY OF THE INVENTION 
     It is a general object of the invention to provide an improved torque wrench which avoids the disadvantages of prior wrenches while affording additional structural and operating advantages. 
     An important feature of the invention is the provision of a bending beam-type torque wrench which is of relatively small size and weight and of relatively simple and economical construction. 
     In connection with the foregoing feature, another feature of the invention is the provision of a torque wrench of the type set forth, which produces a torque measurement substantially unaffected by a user&#39;s hand-hold position on the wrench. 
     Certain ones of these and other features of the invention may be attained by providing a torque wrench comprising: a resilient beam having a work-engaging end and a handle end, a reference beam having first and second ends coupled to the resilient beam respectively adjacent to the work-engaging and handle ends, and measurement apparatus disposed between the first and second ends and responsive to deflection of the resilient beam relative to the reference beam for providing an indication of the amount of torque causing the deflection. 
     Other features of the invention may be attained by providing a torque wrench of the character described, which includes a handle housing enclosing the beams along substantially their entire lengths and fixed to the resilient beam only adjacent to the handle end. 
     The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawings a preferred embodiment thereof, from an inspection of which, when considered in connection with the following description, the invention, its construction and operation, and many of its advantages should be readily understood and appreciated. 
     FIG. 1 is a perspective view of the torque wrench in accordance with the present invention; 
     FIG. 2 is a reduced, exploded, perspective view of the torque wrench of FIG. 1 with portions broken away; 
     FIG. 3 is an enlarged bottom plan view of the upper handle housing of the wrench of FIG. 2; 
     FIG. 4 is an enlarged view in vertical section taken generally along the line  4 - 4  in FIG. 1; 
     FIG. 5 is a top plan view of the wrench of FIG. 1 with the cover portion of the handle housing removed and in an at-rest condition; 
     FIG. 6 is a view similar to FIG. 5, illustrating the wrench in a torque-applying condition; 
     FIG. 7 is an enlarged, fragmentary, top plan view of the rear end portion of FIG. 5; 
     FIG. 8 is an enlarged, fragmentary, top plan view of the front end portion of FIG. 5; and 
     FIG. 9 is a view similar to FIG. 5, but including the PC board and other electronic components. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, there is illustrated a bending beam-type torque wrench, generally designated by the numeral  10 , in accordance with the present invention. The wrench  10  includes an elongated resilient beam  11  having an enlarged, generally circular head or work-engaging end  12  which carries a ratchet assembly  13  of known construction, and a handle end  14 . The resilient beam  11  is generally channel-shaped in transverse cross section, having a rectangular base wall  15  unitary at its opposite side edges with upstanding side walls  16  and  17 . The resilient beam  11  is tapered in thickness from the head end  12  to the handle end  14 . More specifically, the base wall  15  tapers from a relatively thick portion adjacent to the head end  12  to a relatively thin portion adjacent to the handle end  14  (see FIG.  4 ), while each of the side walls  16  and  17  has a height which tapers from a maximum height at the head end  12  to a negligible height at the handle end  14 . Upstanding from each of the side walls  16  and  17 , substantially midway along its length, is a pair of axially spaced posts  18 , for a purpose to be explained more fully below. 
     Formed through the base wall  15  adjacent to the handle end  14  is a circular aperture  20  surrounded by a cylindrical hub  21 , which projects upwardly from the upper surface of the base wall  15 . Formed through the base wall  15  adjacent to the head end  12  is a circular aperture  22  surrounded by an upstanding cylindrical hub  23  which projects upwardly from the upper surface of the base wall  15 . Fixedly secured in the hub  23  is a cylindrical sleeve  25 , the lower end of which is spaced from the bottom surface of the base wall  15  and the upper end of which projects upwardly above the hub  23  and slightly above the upper edges of the side walls  16  and  17 . Preferably, the resilient beam  11  is formed of a suitable moldable plastic material, while the cylindrical sleeve  25  may be formed of metal and may be secured in the hub  23  with a suitable bonding material. 
     The torque wrench  10  also includes an elongated reference beam  30 , preferably formed of a suitable plastic material and of unitary, one-piece molded construction. The reference beam  20  has an elongated, flat, substantially rectangular body  31  dimensioned to fit in the channel defined by the resilient beam  11  and having a width substantially less than the distance between the side walls  16  and  17  of the resilient beam  11 . The body  31  is provided at one end with a clevis  32 , including a pair of forwardly projecting legs  33  terminating at their distal ends with laterally inturned, generally triangular feet  34  having arcuate inner surfaces  35 . Projecting forwardly from the body  31  between the clevis legs  33  is a short rectangular bearing tab  36 , provided at its distal end with a thin, upwardly curved lip  37 . The lip  37  cooperates with the legs  33  and the feet  34  to define an opening  38  through the body  31 . The body  31  is provided with an enlarged rectangular handle end  40  having an oblong aperture  41  formed therethrough. Projecting into the aperture  41  from one side thereof is a short, rectangular side tab  42  provided at its distal end with a thin, upwardly curved lip  43 . 
     The aperture  41  has a front-to-back dimension substantially greater than the outer diameter of the hub  21  of the resilient beam  11 , and a dimension from the lip  43  to the opposite side of the aperture  31  substantially the same as or very slightly larger than the outer diameter of the hub  21 . Thus, in assembly, the hub  21  is fitted through the aperture  41 , while the hub  23  is fitted through the opening  38  in the reference beam  30 , the length of the aperture  41  facilitating this assembly. The width of the aperture  41  substantially inhibits lateral movement of the reference beam  30  relative to the resilient beam  11 , while accommodating relative pivotal movement thereof about the axis of the hub  21 . Similarly, the opening  38  is so dimensioned that the arcuate inner surfaces  35  of the feet  34  define a common circle which, in use, is substantially coaxial with the hub  23  and has a diameter substantially the same as or very slightly greater than that of the hub  23 . Thus, once assembled, in the configuration illustrated in FIGS. 4-6, the legs  33  and the feet  34  cooperate with one another and with the lip  37 , substantially to inhibit lateral and axial movement of the reference beam  30  relative to the resilient beam  11 , while accommodating relative pivotal movement therebetween about the axis of the hub  23 . 
     Integral with the beam body  31  and projecting upwardly therefrom substantially midway between its ends are two pairs of axially and laterally spaced bracket posts  45 , which cooperate to resiliently retain therebetween a thin, rectangular Hall-effect sensor plate  46 . A magnet bracket  47 , preferably formed of a suitable plastic material, spans the side walls  16  and  17  of the resilient beam  11  above the sensor plate  46 , the opposite ends of the bracket  47  being retained between the posts  18 . The bracket  47  carries a pair of laterally spaced permanent magnets  48 . The parts are arranged so that, in the at-rest condition illustrated in FIG. 5, the sensor plate  46  is disposed substantially midway between the magnets  48 . 
     The torque wrench  10  also includes a rigid handle housing, generally designated by the numeral  50 , which is of two-part construction, including a base  60  and a cover  70 , secured together by suitable fasteners so as to substantially completely enclose the resilient beam  11  and the reference beam  30 , except for the work-engaging end  12 . The handle housing  50  has an elongated main body  51  rectangular in transverse cross section and provided at one end with an enlarged handle grip  52  and being open at the opposite head end  53 . The handle grip  52  defines an end wall  58 , in which is disposed a recharge jack  54  and an RS 232  port  55 . Formed in the top wall of the main body  51  is a rectangular window opening  56  closed by a transparent window  56   a  formed of suitable glass or plastic. Also formed through the top wall of the main body  51  are four rectangular, countersunk apertures  57 , for a purpose to be explained more fully below. 
     Referring to FIGS. 2,  4  and  6 , the base  60  is generally channel-shaped, having a rectangular bottom wall  61  and upstanding side walls  62 . Formed through the bottom wall  61  adjacent to the forward or head end is a small circular hole  63  (FIG.  4 ). Formed through the bottom wall  61  in the handle grip  52 , adjacent to the end wall  58  is a circular hole  64  which is encircled with a cylindrical hub  65 , unitary with and projecting upwardly from the inner surface of the bottom wall  61 . The hub  65  has a reduced outer diameter tip portion  66 . Projecting laterally inwardly from the side walls  62  at the junction between the main body  51  and the handle grip  52  are cylindrical screw embossments  67  which have screw holes  68  therethrough. 
     Referring to FIGS. 2-4, the cover  70  is similar in shape to the base  60 , having a substantially rectangular top wall  71  and depending side walls  72 . Depending from the top wall  71  adjacent to the front or head end of the cover  70  is a cylindrical hub  73 , dimensioned to receive therein the upper end of the cylindrical sleeve  25  of the resilient beam  11 . Also depending from the top wall  71  at axially spaced locations adjacent to the side walls  72  are a plurality of screw lugs  74  for a purpose to be described below. Depending from the top wall  71  adjacent to the handle grip end wall  58  is a cylindrical hub  75  provided with equiangularly spaced, generally triangular reinforcing webs or gussets  76 . Integral with the side walls  72  at the junction between the main body  51  and the handle grip  52  are cylindrical screw embossments  77 , which may be internally threaded. It will be appreciated that the window aperture  56  and the rectangular apertures  57  are formed in the top wall  71  of the cover  70 . Also formed through the top wall  71  are two small circular holes  78  and  79 , for a purpose to be explained below. 
     The torque wrench  10  also includes a rectangular printed (“PC”) circuit board  80  (FIGS. 2,  4  and  9 ), on which are mounted a processor chip  81 , an LCD display  82 , four rectangular push-button keys  83  with cylindrical touch pads  84 , and other associated circuitry (not shown). The PC board  80  is mounted on the cover  70 , being screwed to the lugs  74  by screws  90 , with the LCD display  82  disposed immediately beneath the window  56   a  and the keys  83  being respectively aligned with the rectangular apertures  57 , so that the touch pads  84  respectively project up into the countersinks of the apertures  57 , but do not project above the top wall  71  of the cover  70  (see FIG.  4 ). The circuitry of the torque wrench  10  is powered by a pair of batteries  85 , preferably 1.5 volt batteries, such as “AAA”-size batteries. The wrench  10  also includes an 9-volt battery  86  for powering a vibrator motor  87 , the batteries  85  and  86  being secured by suitable brackets (not shown) to the cover  70  and/or the base  60 . The batteries may be of a rechargeable type, in which case they are suitably connected to the recharge jack  54 . It will be appreciated that the batteries  85  and  86  and the vibrator motor  87  are also suitably connected to the processor chip  81  and associated circuitry, which is also suitably connected to the RS 232  port  55  by connections not shown. Also mounted on the PC board  80  are an LED  88  and an audible annunciator  89 , such as a buzzer or beeper, which are also suitably connected to the processor chip  81 . The LED  88  and the annunciator  89  are, respectively, disposed so as, in assembly, to be respectively positioned immediately beneath the cover holes  78  and  79 . 
     In assembly, after the reference beam  30  is mounted in the resilient beam  11  and the magnet bracket  47  is mounted thereon, the beam assembly is seated in the handle housing base  60 , with the reduced tip portion  66  of the cylindrical hub  65  received in the cylindrical hub  21  (see FIG.  4 ), and with the beam aperture  22  coaxially aligned with the base hole  63 . Then the cover  70  of the handle housing  50  is positioned over the base  60 , with the lower end of the cylindrical hub  75  received in the cylindrical hub  21  of the resilient beam  11  and abutting the upper end of the reduced tip  66  of the base cylindrical hub  65 . The cylindrical hub  73  coaxially aligns with the cylindrical hub  23  and receives the upper end of the cylindrical sleeve  25 . The screw embossments  77  respectively coaxially abut the screw embossments  67 . Then the cover  70  is secured to the base  60  by a screw  91  received through the base hole  64  and threadedly engaged in the cover hub  73 , thereby securely to clamp the resilient beam hub  21  between the base hub  65  and the cover hub  73 . A screw  92  is received through the base hole  63  and the cylindrical sleeve  25  and threadedly engaged in the cover hub  73 . Preferably, the parts are so dimensioned that the cylindrical sleeve  25  bottoms on the cover hub  23  to provide a slight space between the ends of the base and cover hubs  23  and  73 , so that when the screw  92  is tightened, the resilient beam hub  21  will not be clamped against the cover hub  73 . Thus, while the base  60  is fixed to the cover  70  by the screw  92 , the resilient  11  remains free to pivot about the axis of the screw  92 . Screws  93  are received through the base screw embossments  67  and threadedly engaged in the cover screw embossments  77 , the screw heads preferably being received in recesses in the handle grip  52 . 
     It is a significant aspect of the invention that, when thus assembled, the handle housing  50  is fixedly secured to the resilient beam  11  only at the handle end  14 . Thus, torque-applying force will be applied to the resilient beam  11  only at that location, irrespective of the user&#39;s hand-hold position along the handle housing  50 , thereby effectively preventing the user&#39;s hand-hold position from affecting the measurements and readings of the torque-detecting and indicating circuitry. 
     Another significant aspect of the invention is that the reference beam  30  is coupled to the resilient beam  11  for only relative pivotal movement about the axes of the cylindrical hubs  21  and  23 . Accordingly, in use, when the ratchet assembly  13  is coupled to an associated workpiece for applying torque thereto, torquing force applied to the handle housing  50  is transmitted to the resilient beam  11  at the cylindrical hub  21 . This torquing force tends to deflect or bend the resilient beam  11  from the at-rest position illustrated in FIG. 5 to a deflected position, as illustrated, for example, in FIG.  6 . However, since the reference beam  30  is free to pivot relative to the resilient beam  11  about the axes of the cylindrical hubs  21  and  23 , the torquing force is not transmitted to the reference beam  30 . Thus, the reference beam  30  does not deflect or bend. 
     By reason of the bending movement of the resilient beam  11  relative to the reference beam  30 , one or the other of the magnets  48  is moved closer to the sensor plate  46 , as illustrated in FIG. 6, depending upon the direction of rotation. This change in distance between the magnets  48  and the sensor plate  46  is proportional to the torque applied and is sensed by the Hall-effect sensor plate  46 , which outputs a suitable signal to the processor chip  81  which, in a known manner, converts the signal to a torque output displayed on the LCD display  82 . It will be appreciated that the circuitry can be operated as a direct-reading, torque-indicating wrench or as a torque limit wrench which presents a visible indication on the LCD display  82  and/or by the LED  78 , as well as an audible indication by the annunciator  89  and/or a tactile indication by the vibrator motor  87  when a predetermined torque level is reached. It will further be appreciated that the setting of the predetermined torque level and the selection of the mode of operation of the torque wrench  10  is user-selectable by means of the keys  83 . 
     The tapered construction of the resilient beam  11  results in a substantially constant-strength beam which affords sufficient deflection at the midpoint of the beam where the sensor plate  46  is located. This construction permits sufficient deflection of the resilient beam  11  in relatively small-size wrenches. Furthermore, the unique construction and inter-relationship of the resilient beam  11  and the reference beam  30  afford a small, light-weight and economical construction. Thus, it will be appreciated that the channel-shaped construction of the resilient beam  11  makes it easier to mold and permits achievement of the required strength and flexibility while keeping the overall size of the tool relatively small and minimizing material costs. In larger size wrenches it may not be necessary that the resilient beam  11  be of tapered construction. 
     While the torque wrench  10  is shown with a ratchet assembly  13  at the work-engaging end  11 , which may a reversible ratchet assembly, it will be appreciated that other workpiece-engaging arrangements could be utilized. 
     From the foregoing, it can be seen that there has been provided an improved torque-indicating and torque-measuring wrench which is of relatively small size and inexpensive and light-weight construction, while providing torque measurements which are substantially immune to the user&#39;s hand-hold position. 
     While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.