Patent Publication Number: US-8109181-B2

Title: Ratchet screwdriver and construction method

Description:
This invention relates to ratchet screwdrivers and their construction methods. 
     BACKGROUND OF THE INVENTION 
     Ratchet screwdrivers are already known in the art of applying a ratchet tool for rotating a threaded fastener such as a screw. Those prior tools can be applied in both the tightening and removing processes of the threaded fastener, including use in the medical arts. 
     The present invention improves upon the prior screwdrivers in that it provides a ratchet screwdriver that has pivotal pawls and that provides for optimum control and operating confinement of the pawl or pawls, and the drive direction selector, and the driven gear. That produces greater precision in operation. 
     The pivotal pawl or pawls are snugly mounted and cooperate with the adjacent parts of the screwdriver to be accurate and secure in both the operative and inoperative positions. The selector, which operates the pawl or pawls, cooperates to lend support in both the pawl operative and inoperative positions, and it is releasably lockable in all its two or three selectable positions of operations, and it thereby secures the pawls in their selected operative and inoperative positions. 
     In achieving the foregoing, the screwdriver is structured and made in a manner that provides for the aforementioned features. It is constructed such that it can be assembled from its back end, rather then from the front end as with the prior art structures. The assembly imposes an axial force on the mechanism for snug containment of the ratchet. Also, it is secured by an axially movable rotation locking member and by fasteners. In that arrangement, the fasteners apply axial force on the assembly and on the drive gear for stabilizing the gear and avoiding the play of the prior art assemblies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a screwdriver of this invention. 
         FIG. 2  is a front end perspective view of a fragment of  FIG. 1 . 
         FIG. 3  is a back end exploded perspective view of a fragment of  FIG. 1 . 
         FIG. 4  is an enlarged section view taken on a plane designated by the line  4 - 4  of  FIG. 2 . 
         FIG. 5  is an enlarged view of the circled portion designated “B” in  FIG. 4 . 
         FIG. 6  is a section view taken on a plane designated by the line  6 - 6  of  FIG. 4 . 
         FIG. 7  is an enlarged perspective view of a part shown in  FIG. 3 . 
         FIG. 8  is an enlarged end elevation view of a part shown in  FIG. 3 . 
         FIG. 9  is a perspective of a part shown in  FIG. 3 . 
         FIG. 10  is a slightly enlarged end elevation view of a part shown in  FIG. 3 . 
         FIG. 11  is a section view similar to  FIG. 6  but showing another embodiment of this invention. 
         FIG. 12  is a perspective view similar to  FIG. 7  but with parts added thereto. 
         FIG. 13  is a section view similar to  FIG. 4  but with a different part, namely, the selector lock. 
         FIG. 14  is an enlarged view of the portion of  FIG. 13  in the circle designated G on  FIG. 13 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS AND METHOD 
       FIG. 1  shows a screwdriver of this invention, and it is rotatable about the longitudinal axis A. There is a handle  10  for gripping by the operator, and there is and adapter  11  rotatable by the handle, and it will be understood that the adapter attaches with the handle by having a suitable adapter shank  12  securely threaded into a threaded opening  13  in a ratchet mechanism at  14  which is supported by the handle  10 . Likewise, the ratchet  14  has a threaded shank  16  which is suitably conventionally secured in the handle  10 . The adapter is conventional in that it receives and drives replaceable tools which are interchangeably releasably held in the adapter. The ratchet  14  determines the direction of rotation of the adapter and its tool about the axis A. 
     The ratchet mechanism  14  in  FIG. 3  is viewed from its front end, that is, from opposite the handle end which is the end from which it is assembled, and the assembly achieves a desired no-play axial condition. 
     A mechanism body, in the form of a pawl cylindrical cage member  17 , has a central opening  18  and a cutout  19  which extends to the opening  18  and which pivotally receives two pawls  21  and  22 . Pivot posts  23  are secured in the cage  17  and pivotally support the pawls  21  and  22 . The cage  17  rotates with the handle rotation and thusly carries the two pawls with it for orbiting about the axis A. A compression spring  24  abuts each pawl  21  and  22  for pivotally positioning the respective pawl. 
     The cage  17  has a circular exterior  26 , and an annulus or ring  27  is rotatably supported on the surface  26 . The annulus  27  is in a complete circle extending around the cage surface  26  and is rotatable thereon. Thus the annulus  27  has interior arcuate surfaces  28  and  29  snug on and guided by the cage surface  26 . The annulus also has two radially facing cutouts  31  and  32  which constantly receive the respective projecting pawl ends  33  and  34 . It will be understood that the rotation of the annulus will cause engagement of the retilinear. or planar projecting pawl end  33  or  34  and thus pivot the pawl for ratchet selection. The springs  24  can sit in holes  39  on respective tangentially facing surfaces  36  of the cage  17 , and the springs  24  urge the pawls into the ratchet engaged mode. It will also be seen in  FIG. 6  that the surfaces  36  serve as abutments or stops for the pawls in their disengaged or non-ratcheting mode. Additionally, the annulus  27  has two pockets  35  on its arcuate surface  29  and they can be mated with a matching arcuate surface  37  on the pawls, and the released pawl is thusly confined between the surfaces defining the pockets  35  and the pawl surface  37  in the disengaged mode. Still further, the disengaged pawl is further trapped by the corner  38  of the ring  27 , and that can serve as a stop for the rotation of the ring  27  in that direction. 
     The ring  27  has user-grippable projections  41  for both rotation and axial movement of the ring on the cage  17 . In the rotation, the ring  27  can be selectively set in either right hand or left hand, or both, drive direction positions, as with ratchets. In all three positions, the ring  27  can be locked in the selected position and will remain locked until it is axially moved on the cage  17  for unlocking and then moved to another selected position. There is a releasable lock pin  42  that is pressed into the ring hole  43 , so the pin  42  moves with the ring  27 . Without retraction of the ring  27  and its pin  42 , the ring  27  cannot rotate on the cage  17 , thus it is locked in one of three selectable positions for the respective ratchet action mentioned. In doing so, the ring is adjacent to and surrounds a circular member  44  which presents three holes  46  for sequential reception of the pin  42 . 
     The member  44  serves as an end locking and axial compression plate for enclosing the rear end of the ratchet mechanism  14  and it presents a circular surface  47  which, along with a circular surface  48  on the cage  17 , provides further rotation and axial sliding support, as well as foreign matter rejection, for the ring  27  at two interior circular surfaces  49  on the ring. There is axial space at  51  for the ring  17  to slide axially between the cage  17  and the member  44 . The cage  17  is also flanged at  52  for closing off the front end of the ratchet mechanism  14  and providing axial support for three springs  53  which respectively sit in three blind holes  54  in the ring  27  for axially urging the ring  27  into the described pin-locked positions. In operation, the springs  53  slide on the surface  55  of the flange  52  and they extend from the three openings  54  in the ring  27  for axially urging the ring  27 , such as rightward as viewed in  FIG. 4 , and into the selected locked position by pin  42 . 
     A saw tooth gear  56  is rotatably supported, as part of the mechanism  14 , on two bearings  57  supported in cage opening  18 , and there are radially extending teeth  58  for engagment with the pawls  21  and  22  through the teeth  59  on the pawls. A wave washer  61 , along with a plain washer  62 , axially presses between a circular wall  60 , on an interior flange  63  on the cage  17 , and the bearing  57 . With a further arrangement, axial movement of the gear  56  in the assembly is eliminated. The annulus  27  has an axial extent along axis A, and the gear  56  and bearings  57  lie within that extent, as seen in  FIG. 4 . 
     In the desired assembly from the rear, the parts are brought together along the axis A to the  FIG. 4  assembly, and the screws  64  are tightened through the holes  65  in the member  47  and into the cage threaded holes  66 . The ring  27  is positioned over the member  17 , and the two circular surfaces at  67  and the two at  68  abut each other to achieve snug axial positioning. Likewise, the gear  56  is confined axially through its bearings  57  by the wall  69  on the member  44  and, as mentioned, by the wave washer  61 , all by the tightening of the screws  64 . 
       FIGS. 11 and 12  show another embodiment of this invention, and here only one pivotal pawl  71  is employed. The gear  56  is the same, but the body is now a cage  72 , and the ring is different from the previous embodiment, and it is now ring or selector  73 . Otherwise, the arrangement and the assembly, including the assembly method, are basically unchanged. 
     The cage  72  has its exterior circular surface  74  for rotational and axial sliding support of the ring  73 , and the cage supports a single pivot pin  76  for support of the pawl  71  which extends through the shown cage radial opening  75 . Also, there is a rotation stop  77  protruding from the surface  74  for engagement with the ring  73  such as in the recess  78  on the ring where two circularly spaced-apart stop walls  80  are presented to the pin  77 . 
     The pawl  71  has two spaced-apart sets of pawl teeth  79  for alternate engagement with the gear  56 . The ring  73  carries a pawl contractor in the form of a ball  81 , and a back-up spring  82  is in outer radial restriction on the ring  73  and provides radial inward force on the ball and thus on the pawl. There is sliding engagement of the pawl  71  by the ball for pivoting the pawl between right and left drive engagement with the gear  56  upon rotation of the ring  73 . Left hand engagement is shown, and the ring  73  was rotated counterclockwise from that rear handle end to achieve that mode. The pawl  71  has two arcuate and contiguous exterior surfaces  83  which have the same curvature as that of the circular surface  84  of the ring, thus they have the same radius from axis A. Thus the ring lends support for the pawl in both its engaged positions. Also, the ball  81  precisely and easily slides on the arcuate pawl surfaces  83  for its radial movement in and out upon rotation of the ring. Again, the lock pin  42  could be employed and be carried by the ring  73  for the purposes previously mentioned. 
       FIG. 11  shows that the ball  81  and spring  82  are disposed on a radial line R, and the location of the engaged pawl teeth and the engaged gear teeth is also on that line. That feature occurs in both driving directional modes for the pawl  71 , thus there is secure teeth driving arrangement. 
       FIGS. 13 and 14  show a modification with regard to the locking of the selectors  27  and  73 , and the selector is now slightly changed in its axial length to be selector  86 . Thus, the selector  86 , which is also termed annulus  86 , can be as seen in  FIGS. 13 and 14  and has circular surfaces  87  and  88  which are axially guided by and which can be in rotation contact with the adjacent circular surfaces  89  and  91  respectively on the body  17  and the member  44 . That is, the selector  86  need not move axially in the assembly. Still, the selector  86  presents a lock pin  92  to the member  44 , but the pin  92  itself is axially movably in its mounting hole  93  on the selector  86  for releasable rotation locking with the member  44 . A spring  94  urges the pin  92  into the selected one of three holds now  96  in the member  44  for the rotation releasable locking engagement. For the locking action, the pine  92  will ride into and out of the selected hole  96  upon rotation of the annulus  86 . 
     It should be understood that the variations shown in these embodiments are arranged to have each embodiment constructed and operate as intended and indicated. Such as, the three springs  53  are not employed in the embodiment of  FIG. 13 , and thus the three holes  54  in annulus  27  are not needed. All the embodiments can employ either one or two pawls, as disclosed, and the selector and body can be as appropriate in either  FIG. 6  or  FIG. 11 . The annulus lock pin  42  or  92  and its mounting can be in any embodiment. 
     The embodiments are described in their construction, and it will be understood that changes can be made therein and still be within the scope of this invention. Further, the showings and the description both disclose the methods for constructing and assembling these screwdrivers.