Abstract:
A reduced arc box end ratchet wrench or ratchet drive wrench utilizes a multiple pawl ratchet assembly comprised of a body having an insert cavity to enclose critical components of an insert that is secured within the ratchet assembly. The insert is set into the wrench body and includes a plurality of pivoting pawls. Each pawl comprises a lever arm with ratchet engaging teeth. The pawl arms are positioned relative to the ratchet wheel to create “pawl swing arcs” and “reduced ratcheting arcs” to alternately or successively engage a portion of the teeth of a ratchet wheel at all times. This configuration allows smaller degrees between ratchet teeth and a smaller wrench rotation that is otherwise required to apply torque.

Description:
This application is a continuation-in-part of U.S. patent application Ser. No. 13/300,494 filed Nov. 18, 2011 now U.S. Pat. No. 8,567,287; which is a continuation-in-part of U.S. patent application Ser. No. 12/419,791 filed Apr. 7, 2009, now abandoned. The subject matter of these applications is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of box end ratchet wrenches and ratchet drive wrenches. More specifically, it relates to a box end ratchet wrench and/or a ratchet drive wrench with a multi-pawl assembly that facilitates a reduced ratcheting arc of 5 degrees, 2.5 degrees, 1.75 degrees, or lower. 
     BACKGROUND OF THE INVENTION 
     A ratchet wrench is a type of wrench having at least one end that surrounds a nut or the head of a bolt. The wrench provides a mechanical advantage by applying torque to turn bolts, nuts or other items designed to interface with a wrench. The ratcheting mechanism allows the nut or bolt to be tightened or loosened with a reciprocating motion of the wrench, without requiring that the wrench be removed, refitted or repositioned after each turn. 
     A ratchet wrench includes ratchet and pawl components known in the mechanical arts to control and secure movement. Ratchets consist of a ratchet wheel, or gear wheel, and may include a spring assembly which applies pressure to a pivoting spring loaded finger called a pawl that engages the teeth. Either the teeth, or the pawl, are slanted at an angle, so that when the teeth are moving in one direction, the pawl slides up and over each tooth in turn, with the spring forcing it back in place with a “click” into the depression before the next tooth. When the teeth are moving in the other direction, the angle of the pawl causes it to catch against a tooth and stop further motion in that direction. 
     More specifically, a pawl is a movable component that operates as a lever. The pawl includes protuberances or other projections that engage the teeth of the ratchet wheel. The pawl is used to control the direction of the ratchet wheel rotation. In various embodiments, bolt engaging components may be used to apply pressure to a pawl (e.g., a spring loaded component) to keep a pawl engaged within the teeth of the ratchet wheel. A pawl may be machined, stamped or molded and constructed of one or more components having singular or multiple protuberances or projections. 
     Generally, a ratchet wheel is similar to other types of gear wheels. The pawl, which is usually spring-loaded to keep it engaged with the teeth of the ratchet wheel, will, when the ratchet wheel is rotated in one direction, slide up or “climb” the one side of a tooth. The pawl will then “jump” down into the bottom of the tooth space after going over the tip of the tooth, and the spring will have pushed it there. It will then ride up the slope of the next tooth as the ratchet wheel moves in the same “forward” direction. If the ratchet wheel is rotated in a “backward” direction, however, the pawl will only allow movement until it comes in contact with the opposite side of the next tooth back and it will jam there. This will limit backward movement of the ratchet wheel to a tooth length and no more, as long as the pawl is acting as intended to check the backward rotation. 
     One problem generally known in the art of box type wrenches using ratchet and pawl systems is that they are limited to a “nominal ratcheting arc,” which is defined by the number of teeth on the ratchet gear divided into 360 degrees. Various attempts are known in the art to create a reduced ratcheting arc ratchet wrench. However, these wrenches require a large rotational degree in order to use the wrench which is not possible in confined spaces. The need for such a large rotational movement lessens the utility of such wrenches. If a large degree of motion is required to rotate the ratchet, the wrench cannot be used in small or tight spaces. Attempts are also known in the art to create more efficient ratcheting mechanisms. 
     Accordingly, and in the view of these inventors, a need exists for a reduced ratcheting arc ratchet wrench assembly that can rotate a ratchet within small degrees. Further, it would be highly desirable to introduce a reduced ratcheting arc box end wrench and ratchet drive wrench using a ratchet and multiple pawl system that can operate at small rotational degrees and can be affordably manufactured and mass produced. 
     SUMMARY OF THE INVENTION 
     The present invention is a reduced arc box end ratchet wrench or a ratchet drive wrench which utilizes a multiple pawl ratchet assembly comprised of a box end wrench and ratchet drive wrench body or housing having an insert cavity to enclose critical components of an insert that is secured within the ratchet assembly. The insert is significant in that it can be press-fit or otherwise set into the wrench body or housing. The insert further includes at least two pivotal pawls. Each pawl comprises a pawl lever arm, the pawl lever arm being an elongated portion of the pawl. Further, each of the pawl lever arms has an outer end within which ratchet engaging teeth are formed. The pawl arms are positioned at critical angles of “pawl swing arc,” which is the location of the axis of rotation of identical pawls from the center axis of a ratchet wheel as it relates to tooth depth. In this way, the ratchet engaging teeth of each of the pawl lever arms alternately or successively engage a portion of the teeth of a ratchet wheel at all times. 
     This configuration allows smaller wrench rotation (or “ratcheting arc”) of down to 2.5, 1.75, or lower, degrees required to apply torque. The present invention further allows for a multiple pawl assembly. In the view of these inventors, a multiple pawl assembly is advantageous because it overcomes the geometrically defined restriction of the number of teeth on a ratcheting gear wheel as a limitation to achieving a reduced ratcheting arc. The advantage is achieved insofar as alternately or successively engaged pawls do not require the gear wheel to travel the complete increment of one gear tooth to engage the gear. Prior art limits the nominal ratcheting arc by dividing the number of teeth on the gear into 360. For example, with a gear having 72 teeth, the nominal ratcheting arc results in a 5 degree ratcheting arc (i.e. 360 degrees÷72 teeth=5 degrees per tooth). 
     The “reduced ratcheting arc” as described and claimed in the present invention defines the nominal ratcheting arc as follows: 360 divided by the number of teeth on the gear divided by the number of alternately or successively engaging pawls. For example, for a two pawl assembly, the equation would be as follows:
 
360 degrees÷72 teeth=5 degrees.
 
     The 5 degrees is then divided as follows:
 
5 degrees÷2 pawls=2.5 degrees ratcheting arc.
 
     For a three pawl assembly, the 5 degrees is divided as follows:
 
5 degrees÷3 pawls=1.75 degrees ratcheting arc.
 
     For a four pawl assembly, the 5 degrees is divided as follows:
 
5 degrees÷4 pawls=1.25 ratcheting arc; and so on.
 
     The foregoing and other features of the box end wrench and ratchet drive wrench of the present invention will be apparent from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an assembled perspective view of the wrench head of one embodiment of a box end wrench that is constructed in accordance with the present invention. 
         FIG. 2  is an unassembled and exploded perspective view of the wrench head assembly illustrating the components within the wrench head of the box end wrench shown in  FIG. 1 . 
         FIG. 3  is a top plan view of portions of the wrench head assembly as they would be positioned when captured within the insert used in the wrench head body or housing. 
         FIG. 4  is a top plan view similar to  FIG. 3  but showing the gear wheel and pawls only. 
         FIG. 5  is a top and side perspective view of the wrench head body or housing shown in  FIG. 3 . 
         FIG. 6  an enlarged top and side perspective view of a pawl used in the wrench head body or housing. 
         FIG. 7  is an enlarged bottom plan view of the insert used in the wrench head body or housing. 
         FIG. 8  is a top and side perspective view of the insert shown in  FIG. 7 . 
         FIG. 9  is an enlarged top and side perspective view of the gear wheel used in the wrench head body or housing. 
         FIG. 10  is a top plan view of the gear wheel shown in  FIG. 9 . 
         FIG. 11  is an enlarged top and side perspective view of the gear wheel used with the ratchet drive, which is an alternative embodiment of the present invention. 
         FIG. 12  is a top plan view of the alternative gear wheel shown in  FIG. 11 . 
         FIG. 13  is an assembled perspective view of an alternative embodiment of a reversible box end wrench constructed in accordance with the present invention. 
         FIG. 14  is an unassembled and exploded perspective view of the wrench head assembly illustrating the components within the wrench head of the reversible box end wrench shown in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings in detail, wherein like numbered elements refer to like elements throughout,  FIG. 1  illustrates a perspective view of an exemplary embodiment of a box ended ratchet wrench, generally identified  100 , that is constructed in accordance with the present invention. The box ended ratchet wrench  100  may be used to apply torque force in a clockwise or counter-clockwise direction. In the embodiment shown, box ended ratchet wrench  100  comprises an ergonomic handle  102  and a box ended wrench head, generally identified  110 . The box ended wrench head  110  comprises a ratchet wrench head assembly, generally identified  10 . 
     Referring now to  FIG. 2 , it shows an exploded view of the various components used in the ratchet wrench head assembly  10  of the box ended ratchet wrench head  110  of the present invention. In the exemplary embodiment that is illustrated, the box ended ratchet wrench head assembly  10  comprises a wrench head body (or housing)  20 , a body insert  40  and a ratchet gear wheel  70 . Significantly, the box ended ratchet wrench head  10  further comprises a plurality of pawls  90  and a multiplicity of force components  60 . Lastly, the box ended ratchet wrench head comprises a gear retaining ring  30  and a cover  50 . 
       FIG. 3  illustrates a top plan view of the wrench head body  20  of the exemplary embodiment ratchet wrench head assembly  10 . The body  20  comprises an insert cavity  22 . The insert cavity  22  is contoured to receive and secure the ratchet wrench insert  40  within it.  FIG. 7  illustrates a bottom plan view of the insert  40  and  FIG. 8  illustrates a perspective view of the insert  40 . Likewise, the insert  40  is contoured and configured to receive pawls  90  of the assembly  10 . The body  20  further comprises a circular ratchet gear aperture  24 . 
     In the exemplary embodiment shown, the pawls  90  are preferably like-configured components as illustrated in  FIG. 6 . Each pawl  90  comprises a lever arm  92  having a first end  91  and a second end  92 . The first end  91  of the pawl  90  comprises a cylindrically-shaped portion and the second end  93  comprises a toothed portion having ratchet engaging teeth  94 . The ratchet engaging teeth  94  may be of varying sizes and configurations. The pawls  90  are configured to be positioned within pawl apertures  42  defined within the body insert  40 . The pawl apertures  42  are openings in the body insert  40  that accept the pawls  90  and limit and define movement of the pawls  90  therein. In other embodiments, the ratchet engaging teeth  94  of the second pawl end  93  may vary in size, shape and length designed to interact with ratchet teeth  78 . See  FIGS. 9 through 12 . The scope of the present invention is not so limited. 
     Again referring to the illustrated embodiment in  FIGS. 3, 4, 7 and 8 , the first end  91  of the pawl  90  is disposed within a first portion  41  of each pawl aperture  42 . A force component  60  is disposed within a second portion  43  of each pawl aperture  42 . As illustrated in  FIGS. 2 and 3 , the force component  60  is shown to be a flex spring band. The force component  60  is not limited to the particular shape as shown. It is within the scope of the present invention that the force component  60  be alternatively configured and fabricated of various materials having “memory” such that the force component  60  continuously urges the pawl  90  into a forced default position. The force component  60  could also be comprised of magnets imbedded within the insert  40 . 
     The second, or toothed, end  93  of each pawl  90  extends slightly beyond the curved edge  44  of the insert  40 . In this position, the pawl ends  93  and ratchet engaging teeth  94  can engage teeth  78  of the ratchet gear  70 . The ratchet gear  70  is disposed within a circular ratchet gear aperture  24  of the body  20 . Again, see  FIG. 3 . It is to be understood that the pawls  90  are capable of slight pivotal movement about the first end  91  of the pawl  90 , the first end  91  effectively being “captured” within first portion  41  of the pawl aperture  42 . The second end  92  of the pawl  90  is biased in a first position by means of the force components  60 . 
     As shown in the exemplary embodiment of  FIGS. 9 and 10 , the ratchet gear  70  is a ratchet wheel gear with an inner contour  71  to accept standard bolt heads. The ratchet gear  70  has a plurality of protuberances or ratchet teeth  78  on its outer ratchet edge  77 . It is to be understood that various embodiments of ratchet gears  70  may include more, fewer or differently proportioned ratchet teeth  78 . In the embodiment shown, the inner contour  71  of the ratchet gear  70  is designed to match or correspond to a standard six-sided or hexagonal shaped nut, bolt head, or other hardware. In other embodiments, the inner contour  71  of the ratchet gear  70  may be designed to accommodate or engage other shaped mechanical pieces or hardware. That is, the precise shape of the inner contour  71  is not a limitation of the present invention. 
     Further, as shown in  FIGS. 11 and 12 , the ratchet gear  170  could also comprise a structure that does not include an aperture, but instead comprises a ratchet drive  171  extending outwardly from one side of the gear  170 . In all other respects, the structural components of the ratchet gear  170  are substantially similar to the ratchet gear  70  described in the embodiment discussed above. 
     Unique to the box end ratchet wrench that is configured with the “reduced ratcheting arc” of the present invention is placement of the pawl  90 . As discussed at the outset of this disclosure, the “reduced ratcheting arc” can be calculated, as can the “pawl swing arc.” 
     Fundamental to the present invention is the claim that, with a given gear  70  and a given number of pawls  90 , the ratcheting arc of the gear  70  can be reduced in proportion to the number of pawls  90 , i.e. the “reduced ratcheting arc.” To achieve this, the present invention employs a unique system of placement of the pawls  90  around the circumference of the gear  70  in accordance with the following equations: 
     
       
         
           
             θ 
             = 
             
               
                 ( 
                 
                   360 
                   T 
                 
                 ) 
               
               × 
               
                 ( 
                 
                   n 
                   + 
                   
                     1 
                     P 
                   
                 
                 ) 
               
             
           
         
       
       
         
           
             α 
             = 
             
               360 
               
                 ( 
                 
                   P 
                   × 
                   T 
                 
                 ) 
               
             
           
         
       
     
     In the above equations,
         θ: The “pawl swing arc” which is the angle subtended at the center axis  79  of the gear  70  by the center axes  99  of two adjacent pawls  90 , measured in degrees.   α: The effective achievable lock-to-lock ratcheting arc, or “reduced ratcheting arc,” also measured in degrees.   n: Any non-zero integer.   T: The number of teeth  78  on the gear  70 .   P: The number of pawls  90  utilized in the assembly  10 .       

     For an assembly  10  utilizing two pawls  90 , another way to consider the foregoing is to consider that the tooth  94  of one pawl  90  will be nearly perpendicular to a tooth  78  of the gear wheel  70 . See  FIG. 4 . The tooth  94  of the other pawl  90  will be at a position nearly one-half the length or depth of another tooth  78  of the gear wheel  70 . This configuration allows for alternate engagement of the pawls  90 . As used herein, the term “alternate engagement” means to engage at alternate positions during a series of rotational movements in either direction. 
     For a wrench  100  utilizing three pawls  90 , the tooth  94  of one pawl  90  will be nearly perpendicular to a tooth  78  of the gear wheel  70 . The teeth  94  of the other pawls  90  will be at a position nearly one-third or two-thirds the length or depth of another tooth  78  of the gear wheel  70 . Significantly, this allows for alternate or successive engagement of the pawls  90 . As used herein, the term “successive engagement” means to engage more than two pawls  90  at successive positions on the ratchet gear  70  during a series of rotational movements in one direction. For a wrench  100  utilizing four pawls  90 , the tooth  94  of one pawl  90  will be nearly perpendicular to a tooth  78  of the gear wheel  70 . The teeth  94  of the other pawls  90  will be at a position nearly one-fourth, one-half or three-fourths the length or depth of another tooth  78  of the gear wheel  70 . Similarly, for a wrench utilizing five pawls  90 , the same concept will apply and any of the multiple pawl configurations will allow for alternate or successive engagement of the pawls  90  in accordance with the present invention. 
     For the purpose of promoting an understanding of the present invention, the aforementioned references made to exemplary embodiments of a box ended ratchet wrench and the ratchet drive are made to demonstrate that the multiple pawl assembly is not limited to only two, three, four or five pawls  90 . In addition, it is within the scope of the present invention that the pawls of the present invention could be collectively and alternatively configured as a brush-like structure having many bristles or “teeth” such that their engagement with the ratchet gear  70  is effected by substantially more contact with the teeth of the ratchet gear  70  and almost infinitesimal incremental movement of the ratchet gear  70  thereby. Further, the invention is not limited to the material used to fabricate the bristles or teeth that would engage the ratchet gear  70 . The surface of the ratchet gear  70  at its outer circular perimeter could be configured with structures other than teeth as well. 
       FIGS. 13 and 14  illustrate an embodiment of a reversing box end wrench, generally identified  200 , that is constructed in accordance with the present invention and partially in accordance with the application that this application continues in part from. Significantly,  FIG. 13  shows an exploded view of the various components used in the reversing ratchet wrench head assembly  210  of the box ended ratchet wrench head  201  of the present invention. In the exemplary embodiment that is illustrated, the reversing box ended ratchet wrench head assembly  210  comprises a wrench head body (or housing)  220 , a ratchet gear wheel  270 , a plurality of pawls  290  and a force component  260 . 
     It should also be understood that no limitations on the scope of the invention are intended by describing these exemplary embodiments. One of ordinary skill in the art will readily appreciate that alternate but functionally equivalent box ended ratchet wrenches and ratchet drives with multiple pawl assemblies may be used. The inclusion of additional elements may be deemed readily apparent and obvious to one of ordinary skill in the art. Specific elements disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present invention. 
     It should also be understood that the drawings are not necessarily to scale. Instead, emphasis has been placed upon illustrating the principles of the invention.