Abstract:
A workbench anchor utilizing counter acting wedges configured to expand laterally as they are drawn together longitudinally in order to lock the anchor in a workbench dog hole or other suitably sized hole by tightening a screw that passes through one wedge and into a threaded hole in a second wedge. Another threaded hole in the anchor can receive a screw or bolt for securing work pieces, jigs, fixtures or other structures to the anchor and, thereby, to the bench in which the anchor or anchors are mounted. An optional O-ring or other friction-increasing structure facilitates securing the anchor in and removing the anchor from the workbench by preventing the anchor from falling through the dog hole or other hole in which it is being positioned or from which it is being removed.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 61/035,219, for a Bench Anchor, filed Mar. 10, 2008, which is incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to woodworking benches and devices attached to or anchored in such benches for holding work pieces, jigs, fixtures and the like that need to be temporarily secured to a bench or other structure. 
       BACKGROUND OF THE INVENTION 
       [0003]    Workbenches have probably been in use for at least thousands of years, and some of the woodworking bench designs in use today date back at least hundreds of years. Benches are used to support and, frequently, hold work pieces, jigs or fixtures during use. A substantial number of work piece, jig or fixture holding accessories are commonly used with woodworking benches, including, vises of several types, bench dogs, hold-downs, surface clamps, and a variety of other such accessories. Generally, such workbench accessories are designed to exhibit great strength and holding power to enable them to resist significant force as a work piece is shaped, sawn or otherwise worked. For applications where the user or the device being held exerts little or no force, such devices are often larger and more expensive than they need be, if they are usable at all. 
         [0004]    Furthermore, many of these conventional accessories have a fixed configuration and are usable only in a limited number of ways. Notwithstanding the substantial number of such accessories, there is frequently a need for a work piece, jig or fixture holding device or structure with a different or more versatile structure than those currently available. Frequently, this need could be filled with relocateable attachment points. Accordingly, there remains a need for a versatile work piece securing device for temporary use with a workbench. 
         [0005]    Most existing woodworking benches have holes penetrating at least the bench top, sometimes one or more of the bench legs and one or more of the cheeks of the vise or vises mounted on the bench. These holes are intended to receive bench dogs, which are metal or wood pins that may be inserted in holes for securing work pieces, such as between a bench dog in a bench top and a second bench dog in the movable cheek of a vise attached to the bench. Most such dog holes in early benches were square or rectangular, but many more recently manufactured benches use round dog holes and round bench dogs because of a number of benefits associated with such devices. 
         [0006]    The availability of dog holes in existing benches makes it attractive to utilize those holes for securing work pieces, jigs and fixtures. 
       SUMMARY OF THE INVENTION 
       [0007]    A threaded opening in a bench is a more appropriate solution than most conventional holding structures for the light duty clamping and fixturing needs that need only resist vibration, gravity or relatively light force. Furthermore, such threaded anchors can be more versatile, easier to use, require smaller tools and are less expensive than many of the alternatives. 
         [0008]    The workbench anchors of this invention are generally cylindrical, square or rectangular structures utilizing two cooperating wedges that can be easily inserted in a woodworking bench dog hole and removably secured therein. A screw or bolt can then be threaded into a threaded hole in the anchor for the purpose of securing work pieces, jigs, fixtures or other structures to the anchor and, thereby, to the bench in which the anchor or anchors are mounted. When no longer needed, the work piece, jig or fixture can be readily detached from the anchor by removal of the screw or bolt that secures it, and rotation of a screw within the anchor quickly and easily permits its removal from the hole in the bench within which its positioned. An O-ring of resilient material encircling the anchor or an alternative structure serving the same friction-increasing function may be used to facilitate installation and removal of the anchor by engaging the wall of the bench dog hole to prevent the anchor from slipping out of position when the anchor locking screw is not tight. 
         [0009]    Other embodiments of the anchor of this invention may use a long screw for actuating the wedging action that rotates inside a threaded tube attached to one of the wedges so that the anchor may be secured in a blind or other hole in a first object by rotating the long screw to actuate the wedging action, and the first object may then be secured to a second object through which the threaded tube passes with a wingnut or other threaded fastener rotated on the threaded tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an exploded perspective view of one embodiment of the bench anchor of this invention. 
           [0011]      FIG. 2  is a side view of the assembled bench anchor shown in  FIG. 1 . 
           [0012]      FIG. 3  is a section view taken along line  3 - 3  in  FIG. 2 . 
           [0013]      FIG. 4  is an end view of the assembled bench anchor shown in  FIG. 1 . 
           [0014]      FIG. 5  is an enlarged detail taken at circle  5  in  FIG. 3 . 
           [0015]      FIG. 6  depicts an alternative embodiment of the anchor of this invention that has a rectangular (specifically a rectangle that is square) cross section. 
           [0016]      FIG. 7  is a perspective view of another alternative embodiment of the anchor of this invention. 
           [0017]      FIG. 8  is another side view, partially in section of the anchor of this invention depicted in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    As will be appreciated by reference to the figures, particularly including  FIG. 1 , the first embodiment  10  of the bench anchor of this invention is a counter wedge structure that may be locked within a hole or tube of appropriate depth and diameter. Anchor  10  is intended for use in a round dog hole (which may be a blind hole) and incorporates a pair of cylindrical members—a base  12  and a head  14 . A screw  16  passes through a recessed, oversize hole  18  in the head  14  and into a threaded hole  20  in base  12 . Contacting surfaces  22  (of head  14 ) and  24  (of base  12 ) are tilted by approximately 45 degrees relative to the longitudinal axis  15  of the head  14  and base  12 . The oversized hole  18  in head  14  through which screw  16  passes allows head  14  to move laterally relative to screw  16 . As a result, when screw  16  is tightened into threaded hole  20  of base  12 , thereby drawing head  14  and base  12  together, head  14  slides laterally relative to base  12  until such movement is stopped by contact between the wall of hole  18  and the shank  24  of screw  16  and or between other structure of head  14  and screw head  26 . Objects like work pieces, jigs or fixtures may be secured to the bench or other device within which the anchor  10  is secured with a screw  29  that is threaded onto threads  40  in head  14 . 
         [0019]    When the screw  16  is tightened, this structure allows the two counter wedge members, base  12  and head  14 , to slide against each other while maintaining contact between the tilted surfaces  22  and  24 . The screw  16  thereby converts coaxial motion associated with rotating the screw into lateral separation of the two wedge members head  14  and base  12 . The geometry of the screw  16  and head  14  also limits the amount of lateral movement possible. A O-ring  30  of neoprene or other resilient, relative high-friction material is captured within an angular groove formed by groove  32  in base  12  and groove  34  in base  14 . 
         [0020]    Groove  32  in base  12  is as wide as the diameter of O-ring  30  but not quite as deep so that O-ring  30  protrudes by a nominal amount “x” easily seen in  FIG. 5  and therefore projects beyond the cylindrical surface  36  of base  12 . Groove  34  in head  14  is as deep as the diameter of O-ring  34  and is wider than O-ring  34  by the amount of vertical travel that head  14  can achieve relative to base  12 . With this structure, when screw  16  is tightened and the counter wedges base  12  and head  14  move laterally relative to each other, the outer diameter of the O-ring is increased at roughly the same rate and remains larger than the overall “cylindrical” structure by about the same nominal amount. This permits the user to set or adjust the desired friction between the anchor  10  and the hole into which it is placed. At the same time, this allows the O-ring  30  to provide friction in a larger range of diameters than would normally be possible with an O-ring  30  installed within a groove of fixed dimensions. The additional width of the groove  34  in head  14  keeps the O-ring  30  from being pinched between the sliding members  12  and  14  as they move longitudinally relative to each other. 
         [0021]    At least a portion of the recess  38  in head  14  is machined with threads  40 . This permits a screw or bolt to be threaded into the head  14  of anchor  10  after it has been positioned in a dog hole in a workbench or another appropriate structure. 
         [0022]    The anchor  10  can be dropped into a dog hole from the top of the workbench and locked in placed using a hex recess or Allen wrench if screw  16  is an Allen head cap screw as shown in  FIGS. 1 ,  3  and  4  or with an appropriate screwdriver if a different screw head is utilized. This provides a nonpermanent, reusable anchor that can be attached to a workbench or other structure if only one side of a hole in the workbench or other structure is accessible or if it is a blind hole. Incorporation of the O-ring  30  in the structure of the anchor  10  significantly improves the utility of the anchor  10 . A similar anchor without the O-ring is prone to fall through a dog hole in a bench or other structure if the anchor  10  is not held in place from below, which is often difficult or impossible. 
         [0023]    The O-ring  30  also facilities locking the anchor  10  by resisting the tendency that anchor  10  might have to rotate within the dog hole as screw  16  is tightened. 
         [0024]    Because of the configuration of the O-ring, it is effectively made larger by turning screw  26  to draw head and base  12  together. This enables the user to place the O-ring portion of the anchor within a dog hole while holding the head  14 , as illustrated in  FIG. 6 . The screw  16  is then rotated to increase friction until the anchor  10  will no longer fall freely into or through the dog hole, but screw  16  is not rotated so much that it cannot be pushed down by the user to a position flushed with the surface of the workbench, as is illustrated in  FIG. 7 . Anchor  10  can then be locked in place by further tightening screw  16 , as is illustrated in  FIG. 8 . 
         [0025]    While the anchor  10  and other embodiments of this invention can be produced in a wide variety of sizes and configurations and of a wide variety of materials, a desirable diameter for the base  12  and head  14  of the cylindrical embodiment  10  illustrated in the figures (and intended for use in a round dog hole) is 0.740 inches. This provides 0.010 inches of clearance within a ¾ inch dog hole. Among other materials useable for the base  12  and head  14  are low malleability materials such as steel, iron, brass or engineering plastics. In a well-functioning nominally ¾ inch diameter anchor  10 , the O-ring  30  can protrude from groove  32  by an amount “x” (see  FIG. 5 ) of approximately 0.015 inches. For instance, the diameter of the O-ring  30  material may be 0.103 inches, and the depth of groove  32  can be 0.088 inches. Different amounts of protrusion may be desirable depending on the nominal diameter and weight of the anchor  10  and depending on the properties of the O-ring  30  and possibly other considerations such as the material and finish of the structure in which the anchor  10  is used. 
         [0026]    While brass, bronze and other materials can be used, the screw  16  should typically be made of steel to provide enough strength to avoid breaking during use in an anchor structure of the size described immediately above. A desirable diameter for the screw  16  is ¼ inch, and it may, for instance, be a ¼-20 UNC screw. 
         [0027]    The O-ring  30  should preferably be made of a medium durometer EPDM (ethylene propylene diene monomer) rubber. Utilizing an anchor  10  of the above described dimensions, nominally ¾ inch in diameter, the recess  38  having threads  40  should desirably be nominally a ½ inch threaded opening such as a ½-13 UNC. 
         [0028]    In the embodiment  10  of the anchor of this invention described above and depicted in the drawings, the O-ring  30  projects from the base  12  and is fully recessed within the head  14 . This configuration appears to function better than the reverse with the O-ring  30  projecting from head  14  and recessed within base  12 . However, this alternative achieves the same basic function and can be used. As is described above and shown in the figures, the groove  34  in head  14  is wider than the O-ring  30 . This provides space for the O-ring  30  to move when the base  12  and head  14  wedges slide against each other and the grooves  32  and  34  no longer line up. Similar function could be achieved with equal-width grooves but with the lead-in at the mating wedge surface  22  and  24  heavily rounded to prevent severing of the O-ring  30 . Alternatively, both grooves  32  and  34  could wider than the O-ring  30 , thus providing space for it to move about. 
         [0029]    In the embodiment  10  described and depicted herein, the O-ring  30  encircles the entire structure. This provides and anchor  10  that can accommodate greater variations in dog hole sizes. However, the O-ring  30  can be placed within a groove that is entirely contained within one of the base  12  or head  14 , provided that dog hole diameter is tightly controlled. 
         [0030]    The sloped surfaces  22  and  24  may be at a 45° angle with respect to the longitudinal axis  15 , as illustrated in the figures. This angle is somewhat arbitrary. Angles between approximately 45° and 60° would be equally functional, although some angles may be more prone to jamming. Angles less than 45° would also be usable, but would necessitate greater vertical travel and thus longer parts. 
         [0031]    In the described embodiment  10 , the thread  40  in the head  14  is illustrated as ½-13. Smaller diameter threads would be possible, particularly if the head  14  is made in two components so that the head of screw  16  can be captured between those two components. 
         [0032]    Furthermore, the described anchor embodiment  10  is designed in such a way as to locate the clamping force-applying mechanism (the screw  16 ) and the hardware-receiving thread  40  in the same component (head  14 ) to facilitate use of the anchor  10  blind applications and with single-sided installation. The anchor of this invention could be made to work equally well with the screw  16  passing through base  12  and threaded into head  14 . Such a configuration would achieve the same function with the only difference being the location of the screw  16  (and, therefore, with the need to access screw  16  from the side opposite than into which a fixture-mounting screw is fastened in hole  38 . 
         [0033]    In another alternative to the embodiment  10  of this invention described above and depicted in the figures, a screw for securing a work piece, jig or fixture to the anchor  10  could be threaded into the other end of the same threaded hole  20  that receives the anchor securing screw  16  if base  12  is long enough to fully receive screw  16  without filling hole  20 . With a suitably long base  12 , the hole  20  could be a stepped opening with a larger threaded hole proximate the flat end  40  of base  12 , and a smaller threaded hole for receiving screw  16  proximate the sloping surface  24 . 
         [0034]    The illustrated embodiment  10  of the anchor of this invention uses counter-wedges to lock the anchor  10  within the dog hole. Alternatively a large compressible O-ring or rubber tube could be clamped between two anchor members having square ends so that such compression expands the O-ring or rubber tube diametrically, thereby fixing it within the dog hole. 
         [0035]    As is described above, the embodiment  10  of this anchor is typically designed to operate within a ¾″ round dog hole. However, appropriately sized, otherwise comparable anchors could be used in round dog holes of other diameters. Furthermore, another alternative embodiment would be made using square or rectangular cross section counter-wedges for use in square or rectangular dog holes, a hole shape found on many older benches and some benches still being manufactured. Such a square cross section embodiment  100  of the anchor of this invention is illustrated in  FIG. 18 , where the base  120  is attached to a head  120  with a screw  16 , and an O-ring  30  encircles these components and seats in a groove  340  in head  140  and a groove  320  in base  120 . 
         [0036]    The present embodiment calls for the O-ring to project from the lower wedge and to be recessed within the upper wedge. However, the same function could be achieved it the O-ring projected from both wedges. The drawback to this configuration is a limitation on the smallest compatible dog hole size. 
         [0037]    The O-ring  30  is used to prevent the anchor  10  from falling too deeply into or though a dog hole. Alternatively head  14  could be formed with a shoulder of greater diameter than the dog hole, or a washer or other structure could be attached to the top of the head  14 . In yet another alternative, a wire or leaf spring could be used as they are on some conventional bench dogs to prevent them from falling through a dog hole. Such a spring could also be incorporated into the anchors of this invention. 
         [0038]    The anchor  10  of this invention can be used to attach to a woodworking bench a wide variety of structures, including, for instance, a work piece support, drying rack, a miter box, a sling jig, a carving mount, a shooting board, a sanding down-draft cabinet, and a spring-dampened motor mount. 
         [0039]    An embodiment of this invention particularly useful for securely attaching large objects like carving work pieces to workbenches is depicted in  FIGS. 7 and 8 . 
         [0040]    Anchor  110  is intended for use in a round hole such as a hole in the bottom of a work piece. Anchor  110  incorporates a pair of cylindrical members—a base  112  and a head  114 . An externally threaded tube screw  116  is attached to head  114 . A rod  117  having a handle  119  on one end passes through tube screw  116 , and the other end of rod  117 , which is threaded, is received in a threaded hole  120  in base  112 . 
         [0041]    As will be appreciated by reference to the descriptions of other embodiments above, rotation of rod  117 —drawing base  112  toward head  114 —causes head  114  and base  112  to slide laterally relative to each other, thereby locking them in a work piece or other hole-containing object within which the head  114  and base  112  are positioned. 
         [0042]    With the anchor  110  base  112  and head  114  secured within a work piece or other object on one side of a workbench top or other structure, and with threaded tube  116  passing through the workbench top, rotation of wingnut  130  on threaded tube  116  against washer  132  will secure the anchor  110  and the object to which it is attached to the workbench. 
         [0043]    As will be appreciated from these descriptions and the accompanying drawings of alternative embodiments of the anchors and attached structures of this invention, numerous variations and modifications can be incorporated in the anchors and anchor-utilizing structures of this invention without departing from the spirit of this invention or the scope of the following claims.