Patent Publication Number: US-8973476-B2

Title: Ratcheting torque wrench

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to ratchet wrenches, and more particularly to ratcheting torque wrenches commonly used in the aircraft and automotive industries. 
     BACKGROUND 
     In many industrial applications, the tightening of threaded fasteners to a specific degree or torque is of critical importance. In the assembly of automobiles or aircraft, it is imperative that nuts, bolts, screws, lugs, and the like (which, for brevity, will all be referred to as “bolts”) are sufficiently tightened to ensure that the resulting assembly functions properly not only at initial use, but over the long term. Over-tightening, however, may strip the threads or cause vibrational problems in the assembly. 
     It has long been known to use torque wrenches to tighten bolts. Such wrenches not only enable the user to rotate and tighten bolts, but also provide the user with a visual, audible, or tactile indication of the amount of torque that has been applied. Some known arrangements include slipper type, beam type, deflecting beam type, click type, and electronic strain gauge type indicators. The click type torque indicator is frequently used in wrenches designed for use in automotive applications and often includes a calibrated clutch mechanism disposed in a handle, or lever arm, of the wrench. When a user has applied the pre-selected torque force, the clutch mechanism clicks, providing the user with both an audible sensation and a tactile sensation that the pre-selected torque force has been applied. U.S. Pat. No. 4,655,104 to Blattner describes one type of torque indicator in detail, and that disclosure is incorporated into this disclosure by reference. 
     The head of a torque wrench can be configured as a ratchet wrench. However, the amount of play that is provided in some ratchet wrenches can affect the accuracy of a torque indictor, so not all ratchet assemblies are always appropriate for use in torque wrenches. 
     Ratchet wrenches have a ratchet assembly that engages and drives the bolt when the wrench is rotated in one rotational direction and disengages when the wrench is rotated in the opposite direction, enabling the user to move the wrench without reversing the prior movement, and thus enabling a user to avoid the need to remove and reposition the wrench when further rotation in one direction becomes blocked or inconvenient. The type of slide gear ratchet assembly seen in U.S. Pat. No. 6,341,543 has a ratchet wheel, a slide gear with sets of opposed teeth, and a ball and spring assembly that releasably biases the teeth on the push bar against teeth on the ratchet wheel. A user can selectively switch the wrench so that one or the other of the sets of opposed teeth on the push bar engage the teeth on the ratchet, thus configuring the ratchet assembly so that it either drives when rotated in a clockwise direction and releases when rotated in a counterclockwise direction, or vice versa. 
     To enable a user to readily shift between one mode of operation and the other, the slide gear on the prior ratchet wrench is slidably disposed within a bore that extends laterally through the head. The slide gear is wider than the head, and one lateral end projects out one side of the head in one mode of operation, and the other lateral end projects out the other side of the head in the other mode of operation. The user switches the ratchet assembly between modes of operation by pressing the projecting end of the slide gear into the bore. This motion shifts one part of the slide gear out of engagement with the ratchet wheel and another part of the slide gear into engagement with another part of the ratchet wheel, and pushes the other end of the slide gear out of the other side of the head. 
     While the projection of the ends of the slide gear makes it easy for a user to shift the wrench between the two modes of operation, it also creates problems. First, the arrangement of the lateral bore requires multiple set-ups on a computer-controlled vertical mill, making it more time-consuming to machine the head of the wrench. Second, the projecting end of the slide gear creates a risk of unintentional shifts of the wrench between modes and operations. Because the ratchet wrench creates a single-ended torque couple, workers place the palm of one hand over the head of a wrench to counter the side force, and that hand can apply sufficient force on the projecting end of the slide gear to cause it to shift out of position. Third, the exposure of the bore and the slide gear to the environment creates a risk that dirt, metal dust, or other materials will enter between the two moving parts and ultimately damage the wrench. 
     The slide gear on the prior wrench has a rounded profile that enables an easier fit in the lateral bore and may provide some tolerance for debris in the slideway. However, axial rocking of the slide gear in the bore can lead to point contact between the teeth on the ratchet wheel and the teeth on the slide gear, and such contact significantly increases the stresses on the teeth and can lead to quicker breakage. 
     SUMMARY 
     A new ratcheting torque wrench has been developed. It is easier to manufacture (requiring only a single set-up on a vertical mill), less prone to accidental changes in mode, and better protected against conditions that lead to premature breakage. 
     Like the wrench disclosed in the U.S. Pat. No. 6,341,543, the new wrench has a head with a working face and an opposed rear face. A slide gear slides laterally in a slide channel in the head, and has a first (upper) side that faces a ratchet. A biasing element is arranged to urge the slide gear laterally into operative engagement with the ratchet in one of either of two ratcheting positions. In those positions, ratcheting occurs when rotation of the wrench causes part of the slide gear to engage an engaged tooth on the ratchet and push the slide gear toward a centerline of the wrench until the engaged part of the slide gear disengages from that engaged tooth. The biasing element then urges the slide gear away from the centerline of the wrench, where the slide gear engages a new engaged tooth. 
     Unlike in the prior wrench, the slide gear in the new wrench fits in a channel that is cut solely from the working face of the wrench. Enclosed ends on the head cover and seal the ends of the slide gear from the environment. 
     To move the wrench between the two ratcheting positions, a pin is used to selectively slide the slide gear laterally within the slide channel. The pin protrudes from a slot in the rear face of the wrench, and can be protected from inadvertent movement by recessing it within the rear face. 
     The slide gear has a generally rectangular configuration with rounded shoulders that engage teeth on the ratchet. Preferably, each shoulder is curved and outwardly flanked by a single recess, the radial distance from the top of the shoulder to the base of the recess being no more than half the difference between the outside diameter and the root diameter of the teeth on the ratchet. The teeth on the ratchet preferably have essentially planar faces, top lands that traverse at least one quarter of the pitch, and bottom lands that extend continuously from the faces, have essentially constant radius, and traverse at least one quarter of the pitch. 
     The ratchet sits in a ratchet recess that can be machined in the same machining operation used to cut the slide channel. The ratchet is preferably journaled over a centering journal in the ratchet recess. The centering journal may have a gapped wall that leaves a small gap between the ratchet and the journal. 
     Other aspects and forms of the invention will become apparent when reviewing the accompanying drawings, the following detailed description, and the claims that follow that. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of one example of a ratcheting torque wrench that utilizes the new invention. 
         FIGS. 2-4  are front, side, and rear views of the head of the wrench seen in  FIG. 1 . 
         FIG. 5  is an exploded partial isometric view of the head of the ratchet wrench. 
         FIG. 6  is an enlarged axial cross-sectional view of the head along the lines  6 - 6  in  FIG. 2 . 
         FIGS. 7 and 8  are enlarged views of the teeth and shoulders in two different embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrated ratcheting torque wrench  10  has a lever arm  12 , a grip  14  at a first end of the lever arm  12 , and a head  16  at a second end of the lever arm  12 . A ratchet assembly  20  is carried in the head  16 . 
     As best seen in  FIGS. 2-4 , the head  16  of the wrench  10  has a front or working face  22  opposite a rear face  24 , a left lateral side  26 , a right lateral side  28 , a distal side  30 , and a shank  32 . (All directional descriptors, such as top, bottom, left, right, etc., are used solely for ease of reference with respect to the drawings and are not meant as limitations.) The left and right lateral sides  26 ,  28  and the distal side  30  are formed by one or more side wall sections that extend along and connect the outer peripheries of the working face  22  and the rear face  24 . The shank  32  projects outwardly from the body opposite the distal side  30  and is operatively connected to the lever arm  12 . 
     As best seen in  FIG. 6 , a ratchet cavity  34  is disposed in the head  16  adjacent one side of a slide channel  36 , and a spring cavity  38  is disposed adjacent an opposite side of the slide channel  36 . The ratchet cavity  34 , the slide channel  36 , and the spring cavity  38  are all recessed into the working face  22  of the head  16  in an arrangement that enables each cavity/channel to be cut or formed in a single set-up on a computer controlled vertical mill. 
     The ratchet assembly  20  includes a double-acting pawl or slide gear  40 , a ratchet, such as a ratchet wheel  42 , and a biasing element, such as a spring  44  and ball  46  assembly, that resiliently and operatively engages the slide gear  40  against the ratchet. 
     The Ratchet Cavity and the Ratchet Wheel 
     The ratchet cavity  34  is a circular disc-shaped recess that is sized to accept the ratchet wheel  42 . It has a centering journal  44  on which the ratchet wheel  42  is mounted. The ratchet wheel  42  has a generally disc-shaped body with a blind bore  46  ( FIG. 6 ) disposed centrally in its rear face. This blind bore fits onto the centering journal  46  in the ratchet cavity  34 , enabling the ratchet wheel to be mounted for rotation within the ratchet cavity  34 . In a precision torque wrench, a tight fit is required. To accommodate this, it is preferred that at least a portion of the centering journal  44  has a slightly smaller radius than the blind bore of the ratchet wheel  42 , forming a spaced wall that leaves a vent  48  ( FIG. 6 ) between an inner diameter of the ratchet wheel  42  and the centering journal  44 . This vent accommodates lubricant, such as oil. 
     A drive stem  50  is disposed centrally on the front face of the ratchet wheel  42  and projects outwardly from the working face  22  of the head  16 . The drive stem could be a screwdriver or a wrench head such as a socket, but preferably is a conventional fitting with a spring-loaded ball detent mechanism that can be used to hold interchangeable sockets. 
     The ratchet wheel  42  has teeth  52  on a peripheral wall that extends around the outer circumferential periphery of the ratchet wheel between the front face and a rear face. As explained in more detail below, these teeth provide ratcheting engagement with the slide gear  40 . Because the teeth cooperate with the elements of on the slide gear, the configuration of the teeth may affect the configuration of the shoulders, and vice versa. As best seen in the examples illustrated in  FIGS. 7 and 8 , the teeth preferably have essentially planar faces  53 , top lands  54  that traverse at least one quarter of the pitch P, and bottom lands  55  that extend continuously from the faces, have essentially constant radius, and traverse at least one quarter of the pitch. Other arrangements may be suitable in these or other embodiments. 
     The Slide Channel and the Slide Gear 
     The slide channel  36  slidably receives the slide gear  40 . The slide channel  36  is an elongate rectangular recess immediately adjacent and substantially tangent to the ratchet cavity  34 . The slide channel  36  is aligned laterally, preferably perpendicularly, to the radius of the ratchet cavity  34 . As best seen in  FIG. 6 , the slide channel  36  has a first (upper) side  56  that faces the ratchet cavity  34 , a second side  58  that is opposite the first side  56 , a left end  60 , and a right end  62 . A central portion of the first side  56  of the slide channel  36  intersects with an arc section of the ratchet cavity  34 , forming an opening, such as a window  66 , that connects the slide channel  36  and the ratchet cavity  34 . The left end  60  of the slide channel  36  is closed by the left lateral side  26  of the head  16  and the right end  62  of the slide channel  38  is closed by the right lateral side  28  of the head  16 . In use, the left lateral side  26  and the right lateral side  28  of the head prevent lateral access to the left and right ends  60 ,  62  of the slide channel  36  from outside of the head  16 . 
     The slide gear  40  is preferably formed from a straight elongate rectangular bar that has a top side  72 , a bottom side  74 , a front side  76 , a rear side  78 , and generally rectangular left and right ends  80 ,  82 . The slide gear is sized and shaped to fit closely within the slide channel  22 , and should slide laterally relative to a radius of the ratchet wheel  42 . The illustrated slide gear  40  is arranged to slide laterally left and right in the slide channel  36 , and thus also slides laterally relative to an axis of the lever arm  12 . In other arrangements, the path of the slide gear could be rotated clockwise or counterclockwise about the ratchet wheel  42 , leaving it angularly offset from the shank  32 . 
     To minimize rocking of the slide gear  40  within the slide channel  22 , the intersections of the bottom side  74  with each of front side  76  and the rear side  78  define angular or sharp edges  75  rather than rounded edges. This helps to reduce rocking of the slide gear within the slide channel  44 , and thus helps to reduce wear and limit fatigue on the teeth  52  by helping to maintain line contact with the teeth  52  on the ratchet wheel  42 , rather than point contact. 
     The top (or upper) side  72  of the slide gear  40  has opposed first and second shoulders  84  that engage the teeth  52  on the ratchet wheel  42 . One shoulder  84  is disposed at or adjacent the left end  80  of the slide gear and the second shoulder  84  is disposed at or adjacent the right end  82  of the slide gear. Each of the illustrated shoulders is outwardly flanked by a recess  85 , such as those seen in the example arrangements seen in  FIGS. 7 and 8 . The base  83  of the recess is laterally spaced from the top of the shoulder by a distance of approximately ½ the pitch of the teeth on the ratchet wheel. Preferably, each shoulder is curved, and the radial distance R from the top of the shoulder to the base of the recess is no more than half the difference between the outside diameter OD and the root diameter RD of the teeth  52  on the ratchet wheel  42 . The recess serves to accommodate a tooth on the ratchet wheel. 
     The slide gear  40  also has an engagement member, such as a pin  86 , that projects outwardly from the rear side  78  of the slide gear. The pin  86  is located centrally on the rear side  78 , and is accessible to a user through a slot  88  on a rear face  24  of the head  16 . The pin  86  and the slot  88  enable the slide gear  40  to be selectively shifted between a clockwise ratcheting position and a counterclockwise ratcheting position without exposing the lateral ends  80 ,  82  of the slide gear to the environment. The area of the slot is smaller than the cross section of the end of the slide gear, and the perimeter of the slot (which forms the boundary where dirt or debris might enter the head) is not significantly larger than the perimeter of either lateral end of the slide gear. Thus, this arrangement not only reduces the risk of unintended switching of the slide gear between the two positions, but also exposes to the environment less moving perimeter than would be exposed in a comparable arrangement in which the ends of the slide gear would project out the sides of the head. 
     The Spring Cavity and the Spring and Ball Assembly 
     Although other biasing arrangements are possible, the illustrated wrench  10  uses a conventional spring  44  and ball  46  assembly to bias the slide gear  40 . The illustrated spring cavity  38  is an elongate recess that opens into the second (lower) side  58  of the slide channel  36 , opposite the window  66 , and is preferably aligned radially with the ratchet cavity  34  and perpendicular to the slide channel  36 . The illustrated spring cavity is also aligned axially with the shank  32 , though this may not always be the case. The spring cavity receives the spring  44  and ball  46  assembly. The spring urges the ball up into the slide channel  39 , where the ball cooperates with ramped recesses  89 ,  90  on the bottom side of the slide gear. The inner portions of the recesses are modestly sloped so that the pressure of the ball biases the slide gear away from a centered position within the slide channel, but can be overcome by sufficient force so that the slide gear can be moved far enough laterally to cause the ball to leave one recess and enter the other. The outer portions of the recesses are steep, and thus provide an effective outer limit on the range of travel of the slide gear. 
     An optional spring cover  92  ( FIG. 5 ) covers the spring cavity  38  on the side toward the working face  22 , holding the spring  44  and the ball  46  within the spring cavity  38 . The spring cover  92  may be press-fit or loosely fit into a recess  94  adjacent the spring cavity  38  and the slide channel  36 . 
     Other Elements 
     The illustrated wrench has a face plate  96  that is disposed on the working face  22  of the head  16 , covering the ratchet cavity  34 , the slide channel  36 , and the spring cover  92 , and holding the ratchet assembly  20  inside the head  16 . The illustrated face place  96  is locked in place by a locking clip  98  that resiliently engages an undercut, such as one or more grooves  100 , that extends about portions of an inner periphery of the sidewall of the head  16  adjacent the working face  22 . 
     The illustrated ratchet wrench  10  may have a torque indicator assembly (not shown) in the lever arm  12 . For example, a click-type indicator that provides a clicking tactile and/or audible sensation when a pre-set torque force is achieved when tightening a bolt could be used. In many cases, any type of torque indicator that is presently known in the art or may be developed in the future could be used. 
     In the illustrated wrench, the shank  32  extends from the head  16  into the lever arm  12 . The shank  36  is pivotably connected to the second end of the lever arm  12  with a pivot pin  104  in an arrangement that causes the ratchet head  16  to pivot about the pivot pin  104  when the pre-set torque force is reached. Further details are omitted here but can be found, for example, in U.S. Pat. No. 4,655,104. Other arrangements for operatively connecting the ratchet head  16  to the lever arm  12  can also or alternatively be used. 
     Ratcheting and Driving 
       FIG. 6  shows the slide gear  40  in the clockwise ratcheting position, in which the slide gear  40  is positioned toward the right end  62  of the slide channel  36 , with the right end  68  of the slide gear  40  disposed near the right end  62  of the slide channel  36  and a gap or space between the left end  66  of the slide gear  40  and the left end  60  of the slide channel  36 . The ball  46  is engaged in the ramped recess  89  on the left side of the slide gear. The shoulder  84  on the left side of the slide gear is disposed near the left end of the window  66  to the ratchet cavity  34  and engages between two teeth  52  on the ratchet wheel  42  that are to the left of the centerline of the wrench. The top of the tooth to the left is accommodated by the recess  85 . 
     When the head is rotated in a clockwise direction CW, the shoulder  84  engages the adjacent tooth  52  to its left, away from the centerline of the wrench. Movement of the slide gear to the right within the slide channel is ultimately limited by the engagement of the ball  46  with a relatively perpendicular outer lateral wall on the ramped recess  89 , and, in some embodiments, by bottoming of the shoulder in the bottom land  55  between adjacent teeth on the ratchet wheel  42 . The rotational force will subsequently be transmitted through the engaged tooth and shoulder to the ratchet wheel and the drive stem  50 , enabling the user to drive a bolt. 
     When the head  16  is rotated in a counterclockwise direction CCW, the shoulder  84  on the left side of the slide gear  40  engages the adjacent tooth  52  to its right, toward the centerline of the wrench. Movement of the slide gear to the left is only moderately resisted by engagement of the ball  46  with a sloped inner wall on the ramped recess  82 , permitting the slide gear to move to the left within the slide channel  20  (as seen in the figure) as the wrench rotates about the ratchet wheel  42  until the shoulder clears the tooth. After the shoulder clears the tooth, the force of the spring  44  pressing the ball  46  against the sloped inner wall of the ramped recess  89  will urges the slide gear back to the right within the slide channel, where the slide gear will engage another (preferably the next) tooth on the ratchet wheel  42 . Thus, the head  16  of the wrench rotates about the drive stem  50 , providing a ratcheting action that enables the drive stem  50  to remain in place as the rest of the wrench rotates about it. 
     When the slide gear  40  is pushed to the left to a position where the ball  46  is engaged in the ramped recess  90  on the right, the wrench is set for driving when rotated in the counterclockwise direction CCW and for ratcheting when rotated in a clockwise direction CW. The shoulder  84  on the right side of the slide gear engages teeth  52  on the ratchet wheel  42  that are on right side of the centerline of the wrench as described above, but in the opposite directions. The shoulder  84  on the left remains out of contact with the ratchet wheel. 
     Changing Modes of Operation 
     As described above, the pin  86  projects outwardly through the lateral slot  88  in the rear face  24  of the head  16 , and can be engaged by a user&#39;s thumb or finger to selectively slide the slide gear  40  laterally left and/or right within the slide channel  36  between the clockwise ratcheting position and the counterclockwise ratcheting position. 
     As best seen in  FIG. 4 , a recess  110  surrounding the slot  88  forms a depression or recessed bowl in the rear face  24  of the head  16 . The outer or distal end of the pin  86  is preferably located at or below the outermost surface of the rear face  24  so that the distal end of the pin  86  does not extend beyond the exterior surface of the rear face  24 . The recess  110  enables access to the side of the pin  86 , such as by a user&#39;s thumb or finger, to facilitate pushing the pin  86  laterally along the slot  88 . Having the distal end of the pin  86  flush with or below the outermost surface of the rear face  24 , rather than extending outwardly beyond the outermost surface, can help prevent accidental switching of the slide gear  40  between the clockwise ratcheting position and the counterclockwise ratcheting position during use. 
     Additional modifications to the systems, apparatuses, and methods disclosed here will be apparent to those skilled in the art. Accordingly, this description should be construed as illustrative only, and is presented for the purpose of enabling those skilled in the art to make and use the invention. The exclusive rights to all modifications that come within the scope of the following claims are reserved.