Abstract:
An open ended wrench incorporating both English (inch) and metric sizes. Two conventional single-size wrenches are replaced by a dual-size hex pattern wrench, reducing the number of wrenches likely to be needed to do a job. One hex pattern is sized to match preferably a metric component and the other hex pattern is sized to match preferably an English component. The two different sized hex patterns are preferably offset by 30 degrees.

Description:
[0001]    This application is a continuation-in-part of U.S. application Ser. No. 12/960,516, filed Dec. 5, 2010, which claims the benefit of U.S. Provisional Application No. 61/349,811, filed May 28, 2010. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates generally to hand tools, and more particularly to open end or combination end wrenches. 
         [0004]    2. Discussion of Prior Art 
         [0005]    Conventional wrenches for turning a hexagonal nut have faces to bear on each of at least the two opposite sides of the nut.  FIG. 1  illustrates a typical prior art combination end wrench  10 , having a handle  13  and open end slots  12  and  14 . The open slots  12  and  14  are typically different sizes. The slots  12  and  14  contact and apply force to the surface around about two-thirds of the periphery of a hexagonal nut. 
         [0006]    Automobiles often are assembled from components that are manufactured in many different countries. Some countries utilize the inch system and others the metric system for measuring bolt sizes. Many machines are assembled with both metric and English sized nuts and bolts. A conventional hand driven inch or metric sized wrench is made to fit only one specific size nut or bolt. This has obliged mechanics, machinists, electricians and consumers to purchase a large number of individual wrenches to make up a tool set that will accommodate different jobs involving inch and metric hardware. 
         [0007]    U.S. Pat. No. 5,048,379 shows double-ended sockets with an internal axially central square drive well, accessible from either open socket end by a conventional extension rod for driving the tools. However, this patent requires the removal, rotation, and replacement of the socket to change from inch to metric size. This patent also requires an extension or a special driving wrench to operate. 
         [0008]    In addition to the large number of wrench sizes needed, mechanics or other persons proceeding to install or remove nuts and bolts are often uncertain of the precise size and, by eyeballing the nut, guess which size wrench to use. Further, when servicing an automobile it is often difficult to determine whether a bolt is inch or metric. Commonly, the mechanic needs to try wrenches until he or she discovers the correct sized wrench for the bolt or nut of interest. It may take a few tries to discover whether the bolt is metric or inch, and the size required. If they choose wrongly and their choice is smaller, the wrench will of course not fit. If their wrong choice is larger but not too much the wrench will fit loosely. If both the wrench and the nut are made of material that is hard enough to withstand the application of applied turning forces then this will turn the nut, but if either material (usually the nut) is not strong enough, then there is an increased chance that the mismatch will round off the vertices of, and ruin, (usually) the nut. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a wrench that accommodates two sizes of nuts and bolts, and thereby reduces the total number of wrenches required for assembly and disassembly of various sizes nuts and bolts. Wrenches configured according to the invention reduce the time required to determine the correct sized wrench for a particular nut or bolt. It does this by combining sizes that, while different, differ by only small amounts. 
         [0010]    Standard English sizes of wrenches considered alone are spaced far apart, or differ, enough to limit opportunities for making an inner hex pattern of the next smaller size than an outer pattern. Standard metric sizes of wrenches are spaced similarly far apart. However, considering the range of English sizes side-by-side with the range of metric sizes, there are numerous couples of English and metric sizes that are only slightly different. This is a very cause of confusion over correct sizes as discussed in the Background section. The present invention takes advantage of the fact that a 12 point wrench could accommodate two slightly different nut sizes. One of the hex patterns could be sized to match a metric component and the other hex pattern sized to match an inch component. These two different sized hex patterns enable the user to use one wrench for the two different sizes of hexagonal nuts. 
         [0011]    The present invention in a preferred embodiment provides a wrench for turning hexagonal nuts and bolts, having a jaw with a center axis and, around the axis, a partial cylindrical opening which has, intersected by a plane perpendicular to the axis, some sides along the perimeter of a first, larger size hexagon, and other sides along the perimeter of a second, smaller size hexagon which is offset around the axis from the first hexagon. 
         [0012]    Among its advantages the dual function open wrench reduces the number of times a user has to change tools and thereby allows faster repairs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0013]      FIG. 1  is an isometric view of a prior art open end wrench; 
           [0014]      FIG. 2  is an isometric view of an open end dual-size double hex wrench according to an embodiment of the present invention; 
           [0015]      FIG. 3  is an end view of the  FIG. 2  wrench identifying features of two different size outer and inner hex patterns; 
           [0016]      FIG. 4  is another end view of the  FIG. 2  wrench identifying dimensions of the two different size large and small hex patterns; 
           [0017]      FIG. 5  is a table listing, in Column A English sizes in fractions of an inch for an outer hex pattern, in Column D metric sizes under consideration for an inner hex pattern, and in Column J indicating with a check mark if the combination is preferred; 
           [0018]      FIG. 6  is a table listing, in Column A metric sizes for an outer hex pattern, in Column D English sizes under consideration for an inner hex pattern, and in Column J indicating with a check mark if the combination is preferred; 
           [0019]      FIG. 7  is a table similar to  FIG. 5  but evaluating maximum and minimum size English sizes for an inner hex pattern; 
           [0020]      FIG. 8  is a table similar to  FIG. 6  but evaluating maximum and minimum size metric sizes for an inner hex pattern; 
           [0021]      FIG. 9  is an end view of a dual-size double hex open end wrench according an embodiment having an outer hex size H 1 = 11/16″ and an inner hex size H 2 =17 mm, used with the 11/16″ hex size mismatched to a 17 mm nut with surface contact area increased over an all 11/16″ prior art wrench; and 
           [0022]      FIG. 10  is a diagram showing the theoretical limit for the reduction in size for an inner hex pattern. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 2  is an isometric view of an open end wrench  20  according to an embodiment of the invention. Wrench  20  comprises a handle  24  having an outside surface with a preferably generally oval cross-section, although other shapes are possible. The handle  24  at its left end  25  has a nut opening  26 . Handle  24  delivers torque to the outer hex pockets  31  and the inner hex pockets  32 . Other types and shapes of drive pockets could be used. 
         [0024]    As shown in  FIG. 3  the nut opening  26  is centered around a rotational axis X and bounded by an inside surface  32  having preferably 18 facets F in planes parallel to the axis. Adjacent facets intersect in alternately positive (CW 60°) and negative (CCW 30°) angles. Each positive angle vertex V and its adjacent facets form a pocket P. A first set of pockets Pouter including every other pocket defines the boundaries of a first hexagonal pattern H 1  (pockets connected by dashes). A second set Pinner of the alternate pockets defines the boundaries of a second hexagonal pattern H 2  (pockets connected by dots). In a conventional single-size wrench the two hexagonal patterns are of equal sizes and offset by 30° around axis X; in a wrench according to the invention the two hexagonal patterns H 1  and H 2  are of different sizes to accommodate different sized nuts. 
         [0025]      FIG. 4  identifies dimensions of a larger, outer, first hex size HSL and a smaller, inner, second hex size HSs in a wrench  20  according to an embodiment of the invention. The two hex patterns are preferably offset by ø=30° around axis X. 
         [0026]    Large Hex Pattern 
         [0027]    Hex Size Large=HSL 
         [0028]    Hex Radius Large=HRL 
         [0029]    Hex Diagonal Large=HDL 
         [0030]    Point Hex Distance Large=PHDL (not shown) 
         [0031]    Small Hex Pattern 
         [0032]    Hex Size Small=HSs 
         [0033]    Hex Radius Small=HRs 
         [0034]    Hex Diagonal Small=HDs 
         [0035]    Point Hex Distance Small=PHDs 
         [0036]    The nominal sizes of the accommodated hex nuts, larger hex size HSL and smaller hex size HSs, yield further dimensions as follows: 
         [0037]    The Hex Radius HR is half the overall Hex Size HS (i.e., face-to-face diameter). 
         [0038]    HR=½*HS 
         [0039]    For each pattern the Point-to-Hex Distance PHD is that pattern&#39;s Hex Diagonal HD minus the alternate pattern&#39;s Hex Radius HR: 
         [0040]    For the larger, outer hex pattern H 1 ; 
         [0041]    HDL=HRL/cos 30° 
         [0042]    PHDL=HDL−HRs 
         [0043]    For the smaller, inner hex pattern H 2 ; 
         [0044]    HDs=HRs/cos 30° 
         [0045]    PHDs=HDs−HRL 
         [0046]    The Surface Contact lengths for the large and small hex sizes are: 
         [0047]    SCL=PHDL/sin 30° 
         [0048]    SCs=PHDs/sin 30° 
         [0049]    The above dimensions determine what different wrench sizes can be advantageously combined in dual sized wrenches according to the invention. The surface contact areas of facets F of a dual hex wrench need to be large enough to adequately grip and turn a hex nut, and the pockets deep enough not to round the nut vertices. Reducing the hex size HSs of an inner hex pattern reduces its point-to-hex distance PHDs and correspondingly its surface contact length and hence, surface contact area. (Conversely, reducing the hex size HSs of an inner hex pattern increases the outer hex pattern&#39;s point-to-hex distance PHDL and correspondingly its surface contact area, as discussed below with reference to  FIG. 9 .) Preferably, an inner hex pattern H 2  preserves at least 80% of the surface contact area of an equal size hex pattern in a standard one size dual hex wrench. In other words, the reduction in point-to-hex distance shown in Column I of  FIGS. 5 ,  6 ,  7  and  8  preferably does not exceed 20%. An alternate calculation for the minimum preferred practical size HSs of an inner hex pattern is that it preferably use at least 97% of the outer hex size HSL as shown in Column F of  FIGS. 5 ,  6 ,  7  and  8 . 
         [0050]      FIG. 5  Column A lists English sizes considered for use as the larger hex pattern with a Column D metric size for the smaller hex pattern in a dual size wrench, and Column J indicates with check marks the combinations of sizes that are suitable. For example, the two similar wrench sizes 11/16 inch and 17 mm are considered in  FIG. 5 , row  8 . The English size 11/16″ (Col. A) is equal to 0.688″ (Col. B) while the metric size 17 mm (Col. D) is equal to 0.669″ (Col. E). 11/16″ is larger so it becomes the outer hex size HSL (Col. A) while 17 mm becomes the inner hex size HSS (Col. D). Applying the above formulas, Inner size HSs uses 97.4% (Col. F) of Outer size HSL, satisfying the 97% preferred minimum and meaning that the Row  8  sizes 11/16 inch and 17 mm are suitable to be combined in a dual sized wrench according to an embodiment of the invention, as indicated by the check mark in Row  8  Column J. 
         [0051]      FIG. 6  Column A lists metric sizes considered for use as the larger hex pattern with a Column D English size for the smaller hex pattern in a dual size wrench, while Column J indicates with check marks which combinations of sizes are suitable. For example, referring to  FIG. 6  row  7 , an outer, first hex pattern H 1  may have a width HSL of 13 mm (Col. A) while an inner, second hex pocket H 2  has a width HSs of ½″ (Col. E). 13 mm equals 0.512″ (Col. B) so a ½ inch hexagon is only slightly, 0.012″, smaller. The first set of hex pockets is used to turn a 13 mm bolt or nut. The second set of hex pockets is used to turn a ½″ bolt or nut. 
         [0052]    Further, as shown in the tables of  FIGS. 7 and 8 , two sets of hex pockets could be of two closely spaced English (inch) sizes or two closely spaced metric sizes.  FIGS. 7 and 8  do not indicate any possible combinations of English/English or metric/metric sizes yielding at least 97% in Column F or at most 20% in Column P. The difference between 1 1/16 inch and 1⅛ inch wrenches is slight. English/English and metric/metric combinations become more practical on larger wrenches. 
         [0053]    As mentioned above, as the inner hex pattern size HSs decreases, the outer hex pattern&#39;s point-to-hex distance PHDL, and correspondingly its surface contact length SCL and area, increases beyond the standard first point-to-hex distance HRL. Therefore, as the inner hex H 2  gets smaller the gripping ability of the wrench&#39;s outer hex H 1  gets stronger. Consequently, as shown by  FIG. 9 , in the  FIG. 5  row  8  wrench the increased Surface Contact (SC) area of the outer pattern H 1  is better even for a mismatched Nut Size NS=17 mm than is a conventional single sized ( 11/16″) wrench for a mismatch. The strength of the hex pockets is maximized if the two sets of pockets are offset by 30° around axis X, but other offsets are possible. 
         [0054]    If harder materials were used to fabricate nuts, bolts and wrenches, then the preferred limits of no more than 20% reduction in point-to-hex distance, or that the inner hex size HSs be at least 97% if the outer hex size HSL, might be exceeded to consider dual sizes such as those listed in  FIG. 7  rows  7 ,  9  and  10 , and in  FIG. 8  rows  8 - 18 . Referring to  FIG. 10 , the maximum theoretical difference between outer and inner sizes, or the minimum theoretical size of the inner hex pattern, is for the inner hex pattern diagonal HDs to be at least the outer hex pattern radius HRL. HRL is equal to HDL times sine 60°. This extreme of (HDL)*(86.6%) is only approached when the offset between the two hex patterns is 30° around axis X. 
         [0055]    While the present invention is described in terms of preferred embodiments, it will be appreciated by those skilled in the art that these embodiments may be modified without departing from the essence of the invention. For example, the principles of the invention could be applied to square-headed nuts and bolts by using offset outer and inner sets of square patterns. It is therefore intended that the following claims be interpreted as covering any modifications falling within the true spirit and scope of the invention.