Abstract:
A power driven tool for rotating a mechanical element includes a housing including a base and a head connected to the base. The head has a yoke formed by opposing arms separated by an opening. A selectively operable motor is positioned in the housing having an output shaft that rotates relative to the housing during operation of the motor. A ratchet mechanism is mounted in the housing and includes an output drive at least partially mounted in the opening for rotation relative to the housing to rotate the mechanical element in a selected direction. A cap is positioned on the head of the housing across the opening forming the yoke. The cap reinforces the yoke during operation of the tool to prevent the arms from separating and blocking at least part of the opening between the arms to prevent debris from entering the ratchet mechanism.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to power driven tools, and more particularly, to a power driven tool for tightening or loosening fasteners including a ratchet mechanism and an end cap. Examples of power driven ratchet wrenches are disclosed in co-owned U.S. Pat. Nos. 4,821,611 and 8,261,849, which are incorporated by reference. 
     Although configurations vary, ratchet wrenches usually have a drive element rotatably mounted in a yoke. The drive element is operatively connected to a motor that selectively rotates the drive element to tighten or loosen fasteners. Some of these ratchet wrenches also include an impact mechanism connecting the motor to the drive element that imparts an impact to the drive element under high load conditions such as may occur when a seized fastener is being loosened. The yoke that holds the drive element is formed by a pair of spaced, cantilevered plates or arms. The drive element positioned in the space or opening between the plates usually is exposed around its entire circumferential surface except where the plates connect to the ratchet body. 
     Frequently, when dirt and debris comes in contact with the exposed surface, the drive element pulls the dirt and debris into the interior of the ratchet wrench. Once inside the wrench, the dirt and debris can cause wear between internal moving parts of the wrench. Worse, the dirt and debris can cause the wrench to jam. Further, under high loads forces inside the wrench can act to spread the plates that form the yoke. Spreading is undesirable. Thus, there is a need for a way to prevent yoke spreading, as well as to guard against dirt and debris entering the wrench. 
     SUMMARY OF THE INVENTION 
     In one aspect, a power driven tool for rotating a mechanical element generally comprises a housing including a base and a head connected to the base. The head has a yoke formed by opposing arms separated by an opening. A selectively operable motor is positioned in the housing having an output shaft that rotates relative to the housing during operation of the motor. A ratchet mechanism is mounted in the housing and includes an output drive at least partially mounted in the opening between the opposing arms of the head for rotation relative to the housing to rotate the mechanical element in a selected direction. A cap is positioned on the head of the housing across the opening forming the yoke. The cap reinforces the yoke during operation of the tool to prevent the arms from separating and blocking at least part of the opening between the arms to prevent debris from entering the ratchet mechanism. 
     In another aspect, a power driven tool for tightening and loosening a mechanical fastener generally comprises a housing having front and back ends spaced along a longitudinal axis. A ratchet mechanism is mounted in the housing and includes an output drive rotatably mounted at the front end of the housing for operatively engaging the mechanical fastener. A motor is positioned in the housing and has an output shaft. An impact mechanism is positioned in the housing and operatively connects the motor and the output drive. A cap is positioned on the front end of the housing to reinforce the front end during operation of the tool. 
     In yet another aspect, a pneumatic tool for tightening and loosening a mechanical fastener generally comprises n elongate tubular housing sized for being manually held. A pneumatic motor in the housing has an output shaft adapted for rotation. An impact mechanism within the housing operatively connects to the motor output shaft. A ratchet mechanism operatively connects to the impact mechanism. The ratchet mechanism includes an output drive mounted for rotation relative to the housing for rotating the mechanical fastener in a selected direction. A cap is positioned on the housing. The cap reinforces the housing during operation of the tool. 
     Other objects and features will be in part apparent and in part pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective of a hand-held pneumatic ratchet wrench of the invention incorporating an impact drive and pneumatic motor; 
         FIG. 2  is an elevation of the wrench of  FIG. 1  in partial section to show internal construction; 
         FIG. 3  is a perspective of an impact drive of the wrench; 
         FIG. 4  is a separated perspective of the impact drive; 
         FIG. 5  is a separated perspective of a ratchet mechanism of the wrench; 
         FIG. 6  is an enlarged fragmentary rear perspective of a head of the wrench with an end cap mounted on the head; 
         FIG. 7  is a front perspective of the head and end cap of  FIG. 6   
         FIG. 8  is a side view of the head and end cap of  FIG. 6 ; 
         FIG. 9  is a perspective of the end cap; 
         FIG. 10  is a front view of the end cap; 
         FIG. 11  is a right side view of the end cap; 
         FIG. 12  is a left side view of the end cap; 
         FIG. 13  is a back view of the end cap; 
         FIG. 14  is a top view of the end cap; 
         FIG. 15  is a bottom view of the end cap; 
         FIG. 16  is a section of the end cap taken through line  16 - 16  in  FIG. 15 ; and 
         FIG. 17  is an enlarged fragmentary perspective of a wrench having an end cap of a second embodiment mounted on a head of the wrench. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and particularly to  FIGS. 1 and 2 , a hand held, pneumatically-driven, ratchet wrench is indicated in its entirety by reference numeral  10 . The wrench  10  includes a tubular grip or base, generally designated  12 , and a head, generally designated  14 . An end cap (or, more precisely, a U-shaped cap)  15  is positioned on the head  14 . As shown in  FIG. 2 , the grip  12  and head  14  are connected by a tubular threaded coupling, generally designated  16 , so the grip, coupling, head, and end cap  15  form a housing that houses the functional components of the wrench  10 . The grip  12  houses a motor, generally designated  18 . An impact drive, generally designated  20 , is positioned inside the coupling  16 , and a ratchet mechanism, generally designated  22  ( FIG. 5 ), is provided in the head  14  and end cap  15 . Each of these components will be described in greater detail below. For convenience of description, when describing orientations of components, forward will be understood to be toward an end of the wrench  10  having the head  14  and end cap  15 . 
     Referring to  FIG. 1 , an air inlet fitting  30  provided at a rearward end of the grip  12  is capable of connecting the wrench  10  to a conventional external pressurized air source (not shown). A lever  32  provided adjacent the grip  12  controls fluid flow to the motor  18 . The lever  32  is pivotally mounted on the grip  12  and is spring biased toward a position in which a free end of the lever is laterally displaced away from the grip as shown so that it can be squeezed toward the grip to open a valve  34  to selectively permit pressurized air to flow through the air inlet fitting  30  to the motor  18 . As shown in  FIG. 2 , the motor  18  includes a rotor  36  rotatably mounted on the grip  12  for rotation about a centerline  38 . The rotor  36  rotates in response to air passing through the motor  18  when the valve  34  is open. The rotor  36  includes an output shaft  40  centered on the centerline  38 . Although the output shaft  40  may has other shapes without departing from the scope of the present, in one embodiment the shaft has a generally cylindrical, splined (i.e., ridged) exterior for connecting the shaft to the impact drive. The motor  18  illustrated and described is a standard, air-driven motor of the type commonly used in pneumatic tools. Because the motor  18  is conventional, it will not be described in further detail. 
     As illustrated in  FIGS. 3 and 4 , the impact drive  20  of the wrench  10  generally comprises a clutch base  50 , a hammer  52 , and an anvil shaft  54 . As further illustrated in  FIG. 4 , the base  50  includes forward and rearward bushing plates  60 ,  62 , respectfully, separated by integral spacers  64  creating a space  66  between the plates for receiving the hammer  52 . Each of the bushing plates  60 ,  62  includes a respective machined central opening  68 ,  70  for receiving the shaft  54 . Holes  72  are provided on opposite sides of the openings  68 ,  70  for receiving pins  74 ,  76  that capture the hammer  52  in the space  66  formed between the plates  60 ,  62 . A portion  78  of the rearward central opening is  68  splined for receiving the splined output shaft  40  of the motor  18 . Thus, the base  50  turns with the motor rotor  36 . The hammer  52  includes a lobed central opening  80 , a semi-circular slot  82  on one side and a broad slot  84  on an opposite side. The slots  82 ,  84  receive the pins  74 ,  76  so they extend between the plates  60 ,  62  for retaining the hammer  52  in the space  66 . As will be appreciated by those skilled in the art, the semi-circular slot  82  and the pin  74  permit the hammer  52  to pivot. The broad slot  84  and pin  76  limit rotation of the hammer  52  as it pivots on pin  74 . The anvil shaft  54  extends through the central openings  68 ,  70  of the bushing plates  60 ,  62  and the lobed central opening  80  of the hammer  52 . The shaft  54  also has spaced journals  88 ,  90  corresponding to the central openings  68 ,  70  in the plates  60 ,  62 . The journals  88 ,  90  engage the central openings  68 ,  70  for supporting the shaft  54  and permitting the shaft to rotate in the base  50 . An anvil  92  is provided on the shaft  54  between the journals  86 ,  88  so lands  94 ,  96  in the lobed opening  80  of the hammer  52  can intermittently engage the anvil to provide increased torque as will be explained in greater detail below. In addition, the shaft  54  includes a crank  98  at its forward end for driving the ratchet mechanism  22 . 
       FIG. 5  illustrates the ratchet mechanism  22  of the wrench  10  which converts orbital motion of the crank  98  to rotational motion in a selected direction. The crank  98  drives an internal ring gear or oscillatory member  100  to oscillate back and forth in a yoke  102  of the head  14 . The ring gear  100  is positioned between opposing sides  103 ,  105  of the yoke  102 . The crank  98  and ring gear  100  are operationally connected by a bushing  104  that is received in a generally cylindrical opening  106  of an arm  108  extending from the ring gear. A drive body  110  is rotatably mounted inside the ring gear  100 . The drive body  110  includes square output drive  112  and a dog carrier  114 . A pivotal ratchet dog or ratchet pawl  120  is pivotally captured in the dog carrier  114  by a pin  122 . The dog  120  is biased to pivot in one selected direction by a selector knob  124 . The selector knob  124  includes a shaft  126  that extends inside the dog carrier  114 . The shaft  126  has a recess  128  that holds a spring  130  for biasing a pusher  132  against the dog  120 . The pusher  132  pushes the dog  120  in a selected direction so the ring gear  100  drives the drive body  110  in one direction but not in the other direction as the ring gear oscillates back and forth. An axial bushing pad  140  is positioned between the shaft  126  of the selector knob  124  and the drive body  110 , and a keeper  142  is positioned between the drive body and the yoke  102  of the head  14 . Spring biased bearings  144  and a race  146  allow the drive body  110  to spin freely in the head  14 . A snap ring  148  retains the race  146  in position in the head  14 . The illustrated ratchet mechanism  22  is similar to that shown in U.S. Pat. No. 4,346,630, generally including an output drive  112  rotatably mounted on the head  14  for engaging a mechanical fastener or other mechanical element. 
     The ratchet mechanism  22  selectively limits rotation of the output drive  112  in one direction. It may be seen that by manually rotating the selector knob  124 , the shaft  126  can be rotated, which rotates the pusher  132  within a channel  150  of the dog  120 . In a first position, the dog  120  is positioned to be rotated by the ring gear  100  in one direction (e.g., clockwise). In a second position, the dog  120  is positioned to be rotated by the ring gear  100  in the opposite direction (e.g., counterclockwise). Each end of the dog  120  operates only in one direction, and is free to move in a direction opposite that direction. Because the ratchet mechanism  22  is conventional, it will not be described in further detail. It is envisioned that the ratchet mechanism  22  may have a dual or double pawl configuration. For convenience of description, when describing orientations of components, a bottom of the wrench  10  will be understood to be a direction in which the drive body  110  extends from the head  14 . 
     Referring to  FIGS. 6-16 , the end cap  15  comprises an arcuate body  200  including a bottom  202 , a top  204 , a front  206 , and opposite sides  208 . The arcuate body  200  has a plurality of integrally-formed, arcuate segments extending between the opposite sides  208  of the body. A first or bottom arcuate segment  210  is positioned generally at the bottom  202  of the body  200  in use. A second arcuate segment  212  extends forward and upward from a forward edge of the first arcuate segment  210  in use. A third, middle, or front arcuate segment  214  extends upward from an upper edge of the second arcuate segment  212 . The third arcuate segment  214  is positioned generally at the front  206  of the body  200  in use. A fourth arcuate segment  216  extends upward and rearward from an upper edge of the third arcuate segment  214  in use. A fifth or top arcuate segment  218  extends rearward from an upper edge of the fourth arcuate segment  216 . The fifth arcuate segment  218  is positioned generally at the top  204  of the body  200  in use. As shown in  FIG. 6 , the bottom segment  210  is frustoconic so a rearward edge of the segment extends inward toward the snap ring  148 . As shown in  FIG. 9 , the top segment  218  is planar to provide clearance for accessing the selector knob  124 . 
     Referring to  FIGS. 1 ,  2 , and  6 - 8 , the end cap  15  is positioned on the head  14  of the wrench  10  such that it extends between the opposing sides  103 ,  105  of the yoke  102  and works to prevent the sides from spreading. Thus, under high load situations, when the ring gear  100  may apply forces to the sides  103 ,  105  in a way that tends to spread the yoke, the cap  15  reinforces the yoke and prevents the sides from spreading. The end cap  15  also covers the front end of the yoke  102  of the head  14  where part of the ring gear  100  would otherwise be exposed. When the wrench  10  is set down, the front end of the wrench sometimes contacts the shop floor or ground first. Without the end cap  15 , the ring gear  100  would contact the floor or ground in these situations, collecting dirt and debris. The collected dirt and debris can be pulling inside the head  14  as the ring gear  100  subsequently rotates, causing wear between parts within the housing. Because the cap  15  covers the forward end of the yoke, the ring gear  100  is less likely to collect dirt and debris. Thus, the cap  15  reduces potential wear within the wrench  10 . In one embodiment, the end cap  15  may be formed from steel sheet and press fit onto the head  14  of the wrench  10 . The end cap  15  is mounted on the head  14  of the wrench  10  such that it covers generally a front half of the head. It is envisioned that in an alternative embodiment, the end cap  15 ′ could extend rearward along the sides of the ring gear  100  to cover substantially all of the ring gear ( FIG. 17 ). 
     During operation of the wrench  10 , air enters through the air inlet fitting  30  at the rearward end of the grip  12  when the lever  32  is squeezed toward the grip. The air enters the motor  18  where it rotates the rotor  36  including the output shaft  40 . The motor shaft  36  rotates the clutch base  50 . When required torque is low, the clutch base  50  turns the hammer  52  which engages the anvil  92  to turn the shaft  54 . The crank  98  orbits the wrench centerline  38 , oscillating the ring gear  100 . As the ring gear  100  oscillates in one direction, the dog  120  pivots into the dog carrier  114  so the output drive  112  does not turn. As the gear  100  oscillates in another direction, the dog  120  engages the gear so the output drive  112  turns with the gear. When the required torque exceeds some preselected value, the hammer  52  pivots on the pin  74 , disengaging the engaged hammer land  94  or  96  from the anvil  92  on the shaft  54  and temporarily preventing the crank  98  from driving the ratchet mechanism  22 . After the anvil  92  passes the hammer land  94  or  96 , the hammer  62  pivots back to a position in which the land engages the anvil  92  on the next revolution. When the combined spinning mass of the motor rotor  36 , base  60 , and hammer  52  acts through the hammer to impact the anvil  92  on the next revolution, an instantaneous torque increase occurs. The torque increase acts to overcome the friction in the mechanical fastener. If the torque exceeds the preselected value on the next revolution the sequence repeats. Otherwise, the impact drive  20  delivers continuous torque. 
     Components of the wrench of this invention may be made of a suitable material, such as metal (e.g., cold-forged steel). 
     When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 
     As various changes could be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.