Abstract:
A low profile substantially flat head power ratchet comprising a pair of spaced shells joined together to for a housing which is tubular at one end for attachment to a pneumatic motor and flat at the other end for operating use in confined areas, said ratchet comprising a gear journaled on a post in the upper shell and a boss on the lower shell, a yoke disposed about the gear and pivotally journaled about the boss, a pair of spaced pawls confined primarily in the yoke but projecting slightly upwards therefrom, and a reversing plate pivotally disposed about the post and lying on the yoke between the pawls, said reversing plate being shaped and sized such that only one of the two pawls may be selectively engaged with the gear at any one given time.

Description:
This invention relates to pneumatically operated ratchet tools. 
     BACKGROUND 
     There is a need for a low profile flat end pneumatically operated ratchet tool adapted for use in small areas where the conventionally sized ratchets cannot provide ready access. U.S. Pat. No. 5,736,192 was issued to me for a through hole ratchet containing a drive mechanism, which I have adapted to an anvil driven ratchet in such manner that power sufficient to drive smaller ratchet anvils in confirmed spaces is achieved, while the benefits of reduced wear and tool longevity is realized. This tool capability is achieved by utilizing the housing in conjunction with the moving parts as an operating part of the tool. 
     It is the object of this invention to provide a low profile flat head ratchet which utilizes its housing as an operating part of its mechanism and thereby enables ratchet to operate in confirmed areas which were previously inaccessible. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is a top plan view of a preferred embodiment of my invention; 
     FIG. 2 is a plan view of the interior of the lower shell of my housing; 
     FIG. 3 is a sectional view taken along lines  3 — 3  of FIG. 2; 
     FIG. 4 is a plan view of the interior of the upper shell of my housing; 
     FIG. 5 is a sectional view taken along lines  5 — 5  of FIG.  4 : 
     FIG. 6 is an enlarged fragmentary sectional view taken along lines  6 — 6  of FIG. 1; 
     FIG. 7 is an upper plan view of a preferred embodiment of my invention with the upper shell removed; 
     FIG. 8 is an enlarged sectional view taken along lines  8 — 8  of FIG. 7; 
     FIG. 9 is an enlarged fragmentary sectional view taken along lines  9 — 9  of FIG.  6 ; 
    
    
     DESCRIPTION 
     Referring now in more detail by reference character to the drawings, which illustrate a preferred embodiment of my invention, A designates a ratchet assembly comprising a housing  20  formed by an upper shell  22  and a lower shell  24  secured together by four screws  26 ,  28 ,  30  and  32 , which extend through bores  36 ,  38 ,  40  and  42  in the upper shell  22  and are attached to threaded bores  46 , 48 ,  50  and  52  respectively in the lower shell  24 . At one end, the housing  20  is provided with a threaded aperture  54  formed by complementary threaded sections  56 ,  58 , in the shells  22  and  24  respectively, which aperture  54  is sized and shaped for conventional attachment to a conventional pneumatic motor B. At its other end, the housing  20  is substantially rectangular in cross section with preferably though not necessarily the height being less than half the width. 
     The lower shell  24  includes an arcuate recess  60  immediately adjacent the threaded section  56  defining a shoulder  62 , an elongated arcuate channel  64 , a rectangular recess  66 , an arcuate shoulder  68 , a bearing retaining channel  70 , a second arcuate shoulder  72 , and an enlarged chamber  74 . Near the flat end  76 , the shell  24  is provided with a raised annular boss  78  having an axial bore  80 , all for purposes presently more fully to appear. Intermediate the shoulder  72  and the boss  78 , the lower shell  24  is provided with an downwardly extending clearance relief  82 , also for purposes presently more fully to appear. 
     The upper shell  22  includes an arcuate recess  90  immediately adjacent the threaded section  54  defining a shoulder  92 , an elongated arcuate channel  94 , a rectangular recess  96 , an arcuate shoulder  98 , a bearing retaining channel  100 , a second arcuate shoulder  102 , and an enlarged chamber  104 . Near its end  106 , the shell  22  is provided with an inwardly extending cylindrical post  108 , and intermediate the shoulder  102  and the post  108 , the upper shell  22  is provided with an outwardly projecting clearance relief  112 . Intermediate the post  108  and the end  106 , there is provided an arcuate slot  110 . It should be here noted that the annular post  108  and the annular boss  78  are coaxial. 
     Referring in detail to FIG. 6, mounted in the housing  20  in the space defined by the channels  70 ,  100 , and retained therein between shoulders  68 ,  98 , and  72 ,  102 , is a crank bearing  120  in which is journaled a bell crank  122 . Disposed in the space defined by the lower chamber  74  and the upper chamber  104  is a yoke  124  having a bore  126  sized for pivotal disposition about the cylindrical element  78 . 
     Referring now to FIG. 7, the end  128  of the yoke  124  opposite the bore  126  is U-shaped and sized for accepting the bell crank ball  130  of the bell crank  122 . On opposing sides of the bore  126 , the yoke  124  is provided with a pair of complementary pawl chambers  132 ,  134 , each respectively adapted to house a pawl  136 ,  138 . Immediately adjacent to and in communication with the pawl chamber  136  is a spring chamber  140  in which is disposed a curved spring plate  142 . The spring chamber  140  descends downwardly into the yoke  124 , however, the spring chamber  140  is not as deep as the pawl chamber  132  creating a lower shoulder  144  which prevents the pawl  136  from entering the spring chamber  140 . It should also be noted that the spring plate  142  and the spring chamber  140  are each longer that the pawl chamber  132  whereby the spring plate  142  is retained in the spring chamber  140  during movement of the pawl  136 . Similarly, immediately adjacent to and in communication with the pawl chamber  134  is a spring chamber  150  in which is disposed a curved spring plate  152 . The spring chamber  150  also descends downwardly into the yoke  124  to a lesser depth than the pawl chamber  134  creating a lower shoulder  154  which prevents the pawl  138  from entering the spring chamber  150 . It should also be noted that the spring plate  152  and the spring chamber  150  are each longer that the pawl chamber  134  whereby the spring plate  152  is retained in the spring chamber  150  during movement of the pawl  138 . As can best be seen in FIG. 8, it should also be noted that the pawls  136 ,  138 , each extend above the upper surface of the yoke  124 . 
     Rotatably disposed in the housing  20  between the post  108  and the element  78  is a drive gear  160  provided at one end with an axially extending annular recess  162  and at the other end with a square socket attachment post  164 . Disposed between the end of the post  108  and the base  166  of the recess  162  is a washer sandwich  168  comprising a wave washer  170  disposed between an upper friction washer  172  and a lower friction washer  174 . The drive gear  160  also includes a diametrically reduced intermediate segment  176  which is sized for close fitting but freely movable disposition in the bore  80  of the element  78 . It should be here noted that the gear  160  is provided with gear teeth constructed at angles which will enable efficient engagement with the pawls  136 ,  138 , (similar to the teeth on the gear described in U.S. Pat. No. 5,738,192 issued to me on Apr. 14, 1998 for Power Tool Drives), and similarly the teeth on each of my pawls  136 ,  138 , are constructed of differing size and height as described in said patent. It should also be here noted that the axial length of the bore in my yoke  124  is longer than the axial length of my drive gear  160  such that the pawls  136 ,  138 , will extend above the upper surface of the drive gear  160  as it is rotated between the post  108  and boss  78 . It should be also noted that the orientation of the pawl chambers  132 ,  134 , and the pawls  136 ,  138 , respectively is similar to the orientation of the pawls and pawl chambers described in U.S. Pat. No. 5,738,192 such that once contact is made between either pawl and the teeth in drive gear  160 , the teeth of the pawl will slip into full engagement with the teeth in the drive gear  160  and the pawl will backload itself snugly against the yoke  124 , whereby to maximize torque while minimizing friction. 
     Disposed about the post  108  above the yoke  124  is a reverser  200  comprising a plate  202  provided with an aperture  204  sized for disposition about the post  108 , an upwardly control lever  206 , and a pair of complementary straight sides  208 ,  210 . The end  212  opposite the lever  206  is arcuate and sized for movable disposition in the bore  126  as the lever  206  is moved about the post  108 . The lever  206  projects upwardly through the slot  110  and the slot  110  is sized to limit the rotational movement of the lever  206  about the post  108  in the manner hereafter described. The reverser is sized and shaped such that when the lever  206  is at one end of the slot  110 , the end  212  of the reverser  200  urges the pawl  138  away from teeth in the drive gear  160  and back against the spring  152  while the pawl  136  engages the teeth in the drive gear  160 , and when the lever  206  is at the opposite end of the slot  110 , the end  212  of the reverser  200  urges the pawl  136  away from teeth in the drive gear  160  and back against the spring  142  while the pawl  138  engages the teeth in the drive gear  160 . Disposed between the upper surface of the reverser  200  and the top of the chamber  20  is a sheet  220  of durable low-friction material which is provided with a bore  222  which surrounds the post  108  and a shroud  224  which surrounds the lever  206 . 
     OPERATION 
     When the tool A is threadedly attached to a conventional air motor at aperture  54 , as the motor is actuated the bell crank  122  is rotated in the bearing  120  causing the yoke  124  to pivot alternately back and forth about the drive gear  160 . With the lever  206  in its full counterclockwise position, the pawl  136  engages the teeth in the drive gear  160  while the end  212  of the reverser  202  urges the pawl  138  away from the teeth of the drive gear  160 , causing the gear  160  to be driven in one rotational direction. Conversely, with the lever  206  in its full clockwise position, the pawl  138  engages the teeth in the drive gear  160  while the end  212  of the reverser  202  urges the pawl  136  away from the teeth of the drive gear  160 , causing the gear  160  to be driven in the opposite rotational direction. Axial movement of the drive gear  160  during rotation is eliminated by the washer sandwich B which continuously provides a slight bias between the drive gear  160  and the boss  78 , even during vibration. 
     The reverser  200  is movably disposed about the post  108  and is held in position by the pressure exerted on its end  212  by either the spring biased pawl  138  or the spring biased pawl  136 , depending on the rotational direction selected for the drive gear  160 . The sheet  220  of non-friction material allows the operator to move the lever  206  with his thumb and enables simple rotational direction changes without having to put the tool down. It should be here noted that each of the springs  142 ,  152 , are sized in length such that spring bias is presented to the respective pawls  136 ,  138 , as they are urged toward engagement with the teeth of the gear  160  and that upon a tooth of the selected pawl engaging a gear tooth, the bias provided by the spring  142 ,  152 , is removed from the respective pawl and the shape of the tooth leads the respective pawl into complete engagement with the gear teeth. This unique and novel feature eliminates most of the wear on the pawl teeth and gear teeth caused by the return stroke of the yoke and greatly enhances the life of the tool. The combination of the pawls having different sized teeth, and the gear teeth being constructed at the angles as described in my U.S. Pat. No. 5,738,192 together with the removal of spring bias during the major portion of the forward and return strokes of the yoke, greatly increases the life expectancy of the tool by a factor of at least four. 
     It should further be noted that my invention is by its construction protected from exposure to outside elements such as debris and moisture in that the upper and lower shells are secured snugly together, the tubular end is attached to the pneumatic motor, and the only remaining place that outside contamination could enter is through the bore in the post which is protected by the lower part of the ear which fully convers the top of the boss as best seen in FIG.  6 . 
     It should be apparent that changes and substitutions in the unique and novel arrangement, combination, assembly and interaction of the various parts and components shown and described herein may be made without departing from the nature and principle of my invention.