Abstract:
A wrench comprising a handle having a fixed flat anvil surface and a pair of arms movable within the handle, said arms projecting from said handle from opposite sides of the fixed flat anvil surface and movable at an acute angle of substantially 16° 6′ with a centerline of the wrench. The arms have opposed gripping heads arranged so that their respective gripping surfaces form an abutting relationship with the entire one of the sides of the six-sided fastener when said arms are in said gripping positions. A means for moving said arms along said linear paths includes a helical thumbscrew disposed between the arms and configured to engage threaded portions of the arms.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119(e) from co-pending, commonly owned U.S. provisional patent application serial No. 60/392,506, entitled HEXLOCK WRENCH, filed Jun. 28, 2002. 
     
    
     STATEMENT OF GOVERNMENT INTEREST  
       [0002] The U.S. Government has no interest in or to the present invention. 
     
    
     
       FIELD OF THE INVENTION  
         [0003]    The invention relates generally to gripping tools and more particularly to an adjustable wrench suitable for use on six-sided fasteners.  
         BACKGROUND  
         [0004]    Six-sided or “hex-head” fasteners such as screw heads and nuts are in wide use. Many hand-held devices have been developed over the years for use on six-sided fasteners. Principal among these wrenches are the adjustable wrenches which allow the user to utilize the same wrench for different size fasteners. Of the open end adjustable wrenches used on hex-head fasteners, the so-called “crescent” wrench is the best known. The crescent wrench has an open end between a fixed gripping head and another gripping head which is adjustable by a rotatable screw. One disadvantage of the crescent wrench when used on hex-head fasteners is that the gripping heads only bit two of the six sides. Another disadvantage is that the adjusting screw is oriented transversely to the longitudinal axis of the wrench handle, thereby causing the crescent wrench to have a large width adjacent to the gripping heads which may not conveniently fit a fastener because of obstructions located adjacent to the hex-head.  
           [0005]    A number of problems are common to any wrench which only grips two sides of a polygonal fastener. Among these is a relatively “poor grip” which causes the wrench to slip which in turn causes rounding of the corners of the fastener. This problem is particularly troublesome where it is necessary to loosen a very tight or “frozen” fastener.  
           [0006]    U.S. Pat. No. 183,266 to Jordan, U.S. Pat. No. 1,242,097 to Anderson and U.S. Pat. No. 3,358,533 to Wren disclose other mechanical arrangements in which two jaws close in on the fastener in order to grip it. Such arrangements eliminate some problems associated with the standard crescent wrench, but the fastener is still only gripped on two of its six sides. As a result, torque is being exerted on the fastener only at two opposite sides of the six-sided fastener. In Jordan and Wren, two additional sides of the fastener may come in contact with the wrench, however, if such contact is made there is only minimal force exerted by the wrench upon those two sides, and in any event that force is not equal to the force exerted on the fastener by the two jaws. Any such additional unequal force exerted on the fastener will not provide markedly improved grip nor will it alleviate the problem of rounding edges.  
           [0007]    U.S. Pat. No. 3,670,604 to Fronell discloses a wrench which grips the hex-head fastener on three sides. Fronell, however, does not disclose an open end wrench but rather discloses a spanner which must completely surround the fastener. In U.S. Pat. No. 433,358 to McCarthy, a wrench is disclosed that utilizes two extending arms with gripping heads. McCarthy, however, is only concerned with improvements in the strength and adjusting mechanism of a wrench and not with any special gripping configuration which makes the wrench more useful on six-sided fasteners.  
           [0008]    U.S. Pat. No. 4,534,246 discloses an improvement over the foregoing by providing a “hexlock wrench” employing typical cylindrical thumbscrew means for moving the arms (and heads) of hexlock wrench. While this approach is an improvement, the mechanism for moving the gripping means of the wrench is relatively complicated and, depending on the placement of the traditional thumbscrew can be awkward to manipulate when holding the wrench.  
         SUMMARY OF THE INVENTION  
         [0009]    A hexlock wrench in accordance with this invention includes two gripping heads each formed on one of two arms that protrude symmetrically from one end of the handle. Each gripping head has a gripping surface, and each gripping surface grips one of the sides of a six-sided fastener. On the top of the handle between the two arms there is a fixed, flat anvil surface which grips a third side of the six-sided fastener. A hexlock wrench in the gripping position will grip the six-sided fastener on each alternate side.  
           [0010]    In one embodiment, the arms are mounted in the handle in such a way that they will slide in and out of the handle so as to accommodate different size fasteners. For any size fastener within the predetermined range, all three gripping surfaces will be in a flat, abutting, gripping relationship with three alternate sides of the fastener. The path along which the arms slide forms an angle of about 16° 6′ with a central longitudinal axis of the handle which bisects the fixed flat anvil surface. These arms then form an angle of about 133° 54′ with the gripping surfaces of the gripping heads. By utilizing such dimensions, the hexlock wrench will always exert equiangular force upon the fastener and the upper end of the jaws always make contact with the outer corners of the six-sided fastener.  
           [0011]    The arms may each include a threaded portion as part of a means for adjusting and controlling the translation of the arms. Disposed between the threaded portions of the arms is a tapered thumbscrew that is threaded to simultaneously mate therewith. The thumbscrew may include a variable helix thread pattern.  
           [0012]    The handle portion of such a hexlock wrench may be made as a two piece handle using known broaching techniques or using precision casting techniques, or some combination thereof. In other forms the wrench may be made using metal injection molding (MIM) techniques, in which case the handle may take the form of a one piece handle. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The drawing figures depict preferred embodiments by way of example, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements.  
         [0014]    [0014]FIG. 1A is a side view of a hexlock wrench in accordance with the present invention, the hexlock wrench engaging a small sized fastener. And, FIG. 1B illustrates the forces applied to the fastener by the hexlock wrench of FIG. 1A.  
         [0015]    [0015]FIG. 2 is a perspective view of the hexlock wrench of FIG. 1A engaging a medium sized fastener.  
         [0016]    [0016]FIG. 3A, FIG. 3B and FIG. 3C are views showing the interior portion of the hexlock wrench of FIG. 1A.  
         [0017]    [0017]FIG. 4A and FIG. 4B are diagrams showing the tapered helical thumbscrew of the hexlock wrench of FIG. 1A. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    Referring to FIGS.  1 A- 3 C, an embodiment of an adjustable open end hexlock wrench  10  for use on six-sided or hexagonal-shaped fasteners is variously shown. These six-sided shaped fasteners have six sides of equal length. Every fastener side forms a 120° angle with each of its two adjacent sides. The hexlock wrench  10  includes 3 surfaces configured to grip every other side of the fastener, which results in substantially equal forces being applied to the gripped sides of the fastener, as is shown in FIG. 1B (discussed in more detail below).  
         [0019]    In FIG. 1A, an adjustable hexlock wrench  10  according to the present invention has a longitudinally extending handle  12 . On one end of the handle  12  there is a fixed, flat anvil surface  14 , against which one side of the six-sided fastener F 1  is placed, here fastener F 1  is a relatively small sized fastener. Projecting from the same end of the handle  12  as the anvil surface  14  are two arms  16 A,  16 B, movable along linear paths by an adjustment means  30 . The arms  16 A,  16 B and adjustment means  30  are movably disposed within a handle head  12 A. Secured on the end of each arm  16 A,  16 B there is a gripping head  18 A,  18 B, respectively. Preferably these gripping heads  18 A,  18 B and their respective arms  16 A,  16 B are integrally formed out of a high strength hard material, such as forged steel. Each of these gripping heads  18 A,  18 B is configured to “grip” a side of the six-sided fastener F 1  by forming a generally flat, abutting relationship between an associated gripping surface  20 A,  20 B and the corresponding side of fastener F 1 . In the preferred form, the gripping heads  18 A,  18 B are formed on the arms  16 A,  16 B in such a way that the gripping surface  20 A of gripping head  18 A and the gripping surface  20 B of gripping head  18 B form an angle of about 133° 54′ with an arm surface  22 A and  22 B, respectively, that face the central longitudinal axis A, see FIG. 2.  
         [0020]    The arms  16 A,  16 B are mounted within the handle  12  in such a way so as to allow for sliding movement into and out of the handle  12 , without compromising the abutting relationships of the gripping surfaces  18 A,  18 B and anvil  14  with whatever sized fastener that may be gripped, and the equal forces that are applied to every other side of the fastener. The arms  16 A,  16 B slide between a gripping position and a releasing position. Preferably, the arms  16 A,  16 B slide along a linear path that forms an angle of about 16° 6′ with the central longitudinal axis A of handle  12 , see FIG. 3B. The central longitudinal axis A bisects the fixed flat anvil surface  14 . The angle formed by the linear paths and the central longitudinal axis A remain the same regardless of the size of the fastener the wrench is gripping, i.e., and the extension of arms  16 A,  16 B. The surfaces  22 A,  22 B are parallel to their associated linear paths. Stated more generally, the gripping surface  20 A,  20 B of each head  18 A,  18 B forms an angle of about 133° 54′ with the linear path of motion of the associated arm  16 A,  16 B.  
         [0021]    In use, the ability to extend the arms  16 A,  16 B allows the wrench to accommodate any size fastener within a predetermined dimensional range. For example, FIG. 2 shows the hexlock wrench  10  of FIG. 1A gripping a medium sized fastener F 2 . The precise angular dimensions of the mounting of the gripping heads on the arms and of the paths along which the arms slide assure that there will always be a perfect “bite” on three alternate sides of the six-sided fastener. This perfect bite results in an equiangular application of three gripping forces upon the fastener, as is shown by force vectors f 1 , f 2 , and f 3  in FIG. 1B. Also, each gripping surface of the wrench, the anvil surface  14 , and the flat gripping surfaces  20 ,  20  of the heads  18 ,  18  will each be in a face-abutting relationship with one side of the fastener.  
         [0022]    [0022]FIG. 3A through FIG. 3C show a cross section of an upper portion, including a handle head  12 A, of wrench  10  of FIG. 1A. In FIG. 3A wrench  10  is shown gripping a large sized fastener F 3 . In this embodiment, arms  16 A and  16 B each travels in its own linear path in response to actuation of adjustment means  30 . As is shown in FIG. 3A, arm  16 A travels in a path defined by double arrow Y and arm  16 B travels in a path defined by double arrow X. To ensure travel along these paths, channels are formed within the handle head  12 A, for example channel  24 A for arm  16 A and  24 B for arm  16 B (see FIG. 3B). Here, handle head  12 A includes a cover  12 B and a body portion  12 C formed within handle  12 . When assembled, cover  12 B and body portion  12 C encase the arms  16 A,  16 B and adjustment means  30 . In FIG. 3A and 3C cover  12 B is not shown.  
         [0023]    In the embodiment of FIG. 3A through 3C, handle  12  may be formed by precision casting, requiring no second machining. Traditional broaching methods are not preferred, since they would require boring channels throughout the length of handle  12 . Those holes would then need to be broached the full length of handle and plugging the end of the channel with a handle extension, rather than just covering handle head  12 A with cover  12 B. Therefore, the broaching approach would require more complex handle parts and longer machined channels, which would be far less desirable in terms of manufacturing costs and overall durability and strength of wrench  10 . In this embodiment, cover  12 B need not be formed any longer then required to encase arms  16 A,  16 B.  
         [0024]    Tests have shown that the highest areas of stress experienced by handle head  12 A during typical use of wrench  10  occur at high stress areas S 1 -S 4 , shown in FIG. 3B. Accordingly, handle  12  is preferably formed to avoid seams at the high stress areas, since these would be vulnerable to cracking. Therefore, the height h of cover  12 B is chosen such that the seam formed with handle body portion  12 C is proximate to a midline  12 D of handle head  12 A. Handle cover  12 B can be made from forged steel and welded to body portion  12 C at the midline  12 D. Other processes of coupling cover  12 B to body portion  12 C can be used, but it is preferred that such couplings avoid seams at the high stress areas S 1 -S 4 . In embodiments where broaching is used to form channels  24 A and  24 B, similarly, seams should avoid high stress areas S 1 -S 4 .  
         [0025]    Another process for making a hexlock wrench in accordance with the present invention is metal injection molding (MIM). Using MIM, handle  12  can be formed as a single unit having channels  24 A,  24 B formed therein and accommodating encasement of the adjustment means, without the need for a separate cover, e.g., cover  12 B. In such a case arms  16 A,  16 B would be slid into channels  24 A,  24 B, then a thumbscrew  32  (discussed below) could be inserted though the side of the handle head  12 A to engages threaded portions  26 A,  26 B of arms  16 A,  16 B, and then a thumbscrew shaft  34  could be installed via an opening in anvil  14  to maintain the thumbscrew  32 , which in turn maintain the arms  16 A,  16 B within handle  12 .  
         [0026]    Regardless of the process for making the handle  12  of hexlock wrench  10 , the adjustment means  30  preferably includes a helical thumbscrew  32 . Accordingly, as is shown in FIG. 3A, arm  16 A includes threaded portion (or teeth)  26 A and arm  16 B includes threaded portion  26 B. Helical thumbscrew  32  is disposed within handle head  12 A such that it simultaneously and operatively engages the threaded portion  26 A of arm  16 A and the threaded portion  26 B of arm  16 B.  
         [0027]    In this embodiment, helical thumbscrew  32  includes or is positioned on thumbscrew shaft  34 , about which the thumbscrew is rotatable. Thumbscrew shaft  34  is disposed along central longitudinal axis A. A shaft first end  34 A is coupled to anvil  14  and an opposite, second end  34 B is coupled to shaft pocket  38  formed within handle head  12 A, as is shown in FIG. 3B. As can be seen from FIG. 3C, a spring  40  is also included on thumbscrew shaft  34 , and provides a manner of loading the helical thumbscrew  32 , thereby preventing undesirable rotation of thumbscrew  32 . Thumbscrew  32  and shaft  34  act to allow rotation of the thumbscrew  32  relative to the handle  12  and about the central longitudinal axis A. Rotation of thumbscrew  32  causes linear displacement of each of arms  16 A,  16 B with in their respective channels  24 A,  24 B. The linear displacement of the arms  16 A,  16 B allows for engaging and disengaging grip heads  18 A,  18 B, while also maintaining the 16° 6′ angles of arms with respect to the central longitudinal axis A and the 133° 54′ angles of the grip heads  18 A,  18 B with respect to the arms  16 A,  16 B.  
         [0028]    In the preferred form, the threaded portions  26 A,  26 B of arms  16 A,  16 B are threaded at 6 threads per inch, with uniform spacing between the threads. Theoretically, it follows that to properly mate with the threaded portions  26 A,  26 B, the helical thumbscrew  32  should also be threaded at about 6 threads per inch, measured perpendicular to the tapered surface  42  of the thumbscrew  32 , see FIGS. 4A and 4B. In order for the tapered thumbscrew to mate properly with the threaded portions  26 A and  26 B, the helix angle of the thumbscrew will vary around an average value (e.g., 5° 45′). However, rather than 6 threads per inch (or 1 thread every 0.1666667 inches), experimentation showed that iterating the pitch on the thumbscrew  32  from 1 thread every 0.1666667 inches (i.e., 6 threads per inch) to about 1 thread every 0.160 inches results in a better match with the teeth of threaded portions  26 A,  26 B of arms  16 A,  16 B.  
         [0029]    [0029]FIG. 4A shows a portion of thumbscrew  32  and FIG. 4B shows thumbscrew  32  within handle  12  and engaged with arm threaded portions  26 A,  26 B. The thumbscrew threads  44  are formed at constant speed with a cut angle of substantially equal to an average helix angle, the average helix angle chosen to be about 5° 45′ in this embodiment to accommodate the angles of threaded portions  26 A,  26 B of arms  16 A,  16 B. Using the 5° 45′ cut angle, rather than a straight cut angle, and using a constant cut speed causes the tapered thumbscrew to have a helical thread with a variable thread angle. By variable helical thread angle it is meant that the angle of the teeth  44  of the thread of thumbscrew  32  with respect to the central longitudinal axis A gets larger as the thread works toward the smaller diameter end of the taper. As a result, the angle of 16° 6′ of the arms is preserved, as is the angle of about 133° 54′ of the head grips  18 A,  18 B. Consequently, the grip heads  18 A,  18 B and anvil  14  apply substantially equal forces against 3 different sides (120° apart) of a fastener being rotating in direction of arrow R, as shown in FIG. 1B.  
         [0030]    While the foregoing has described what are considered to be the best mode and/or other preferred embodiments, it is understood that various modifications may be made therein and that the invention or inventions may be implemented in various forms and embodiments, and that they may be applied in numerous applications, only some of which have been described herein. As used herein, the terms “includes” and “including” mean without limitation. It is intended by the following claims to claim any and all modifications and variations that fall within the true scope of the inventive concepts.