Abstract:
An adapter operable to connect a hook or chain double clevis to a tubular trailer hitch receiver. Certain embodiments are double-ended to permit either attachment of a larger D-ring to one end, or a hook or clevis to the opposite end.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the benefit under 35 U.S.C. 119(e) of the filing date of Provisional Application Serial No. 60/282,947, filed Apr. 2, 2001, for “TRAILER HITCH ADAPTER”. 
     
    
     
       BACKGROUND  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates generally to equipment and apparatus for towing vehicles. It particularly relates to adapters suitable to connect a chain or tow-strap to a commercially available tubular trailer hitch receiver.  
           [0004]    2. State of the Art  
           [0005]    Circumstances may arise, during the course of operating a vehicle, in which it may be desired to attach a towing member to the vehicle. Vehicles may slide off of a road and lose traction as a result of driving too fast in low visibility, icy, or other slippery conditions. Traction may also be lost while still on the road or desired path of travel. In one example, a vehicle may simply get stuck while attempting to drive in snowy conditions. In another example, driving off-road, a vehicle may get stuck in any number of terrain traps, including deep snow, muddy spots, water crossings, and loose sand. In the event a vehicle becomes stuck, a helper vehicle often-times can extract the stuck vehicle by way of a short towing operation using a towing member. Alternatively, a winch, or even a jack (such as a High-Lift™ jack), sometimes can be used to extract a stuck vehicle by providing tension on a towing member.  
           [0006]    Typical towing members include lengths of chain, strong ropes, and resilient tow-straps. Chains can be attached to a vehicle with either a double clevis, or more commonly, with a grab hook. A chain with a grab hook at an end conveniently can be formed into a loop to attach to structure carried on either of the stuck or helper vehicle, such as a slip hook, or even bumper attach structure. Sometimes a chain&#39;s hook can be inserted into a hole in a frame member to form an attachment. A chain without end hooks sometimes can be attached using a double clevis to form an end loop. Some ropes, fashioned as dedicated automotive tow-ropes, have a hook on each end to permit attachment to a helper vehicle. Tow straps typically have either a slip hook or a loop at opposite ends of the strap. An end-loop commonly is formed in a tow strap by stitching a folded distal end portion of the strap onto a proximal portion of the strap. In any case, an end of the towing member is attached in some way to structure carried by the stuck vehicle, and tension is then applied to the towing member to extract the stuck vehicle.  
           [0007]    While it sometimes is possible to attach a towing member to frame or bumper attach structure, such attachment may inconveniently entail crawling under the vehicle. In many cases, the person crawling under the vehicle to attach the towing member unavoidably will become wet or muddy. It is certainly preferred to accomplish attachment of the towing member without requiring such undue effort.  
           [0008]    Attach structure for towing members is known, including solid hooks which can be mounted to a frame member, or bumper. Such hooks typically are permanently mounted to the vehicle, and lack any pivoting capability to align a hook with a direction of pull on the towing member.  
           [0009]    A tubular trailer hitch, such as illustrated in FIG. 1, could serve as a convenient foundation for towing member attach structure. However, the size of the trailer ball opening is too large for fasteners of optimally sized hooks. The hook fasteners unavoidably would rattle around, and could improperly load or bind. Furthermore, desirable hooks are optimally sized to have adequate-strength and a small-size to facilitate their storage in a small volume. Commercially available such hooks have too small of a fastener reach (compared to the distance from the edge of a ball-mounting plate to a ball mounting hole) to permit passing the hook&#39;s fastener through an opening for a trailer ball. Furthermore, the ball mounting plate typically is too thick for receipt in the clevis gap provided by the desirable hooks. Even if the fastener could be received in the ball mounting hole, the mismatch between the diameter of the fastener and hole could contribute to a bearing or bending failure of the fastener.  
           [0010]    An adapter for a large D-ring, illustrated in FIG. 2, is commercially available. However, due to both the large diameter of the hole in which the threaded D-ring stem is received and the thickness of the mounting plate, such an adapter is essentially specialized to receive only the large D-ring. Smaller D-rings, if capable of fitting on the plate, unavoidably wobble and rattle in the mounting hole, potentially being loaded in improper orientations. As with the trailer ball adapter, the mounting hole and plate thickness preclude mounting of optimally sized and commercially available slip and grab hooks to the commercially available D-ring adapter.  
           [0011]    One commercially available tow hook, illustrated in FIG. 3, is removably installable in a tubular trailer hitch. While offering a measure of convenience for removable attachment, this hook arrangement lacks any swiveling capabilities to align with a load direction. Furthermore, the hook is welded to the adapter tube, forming a unitary assembly which requires a certain length for storage.  
           [0012]    In many off-road vehicles, such as Jeeps, and small SUVs, limited space is available for storage. It therefore is desirable to provide a towing member attach structure in a removable and compact arrangement for storage in a tool box, or other container. A device permitting a hook to align in the direction of load from a towing member is desirable. An operable, convenient, and small device removably to mount an optimally sized slip or grab hook, or other towing member fastening structure, onto a vehicle is desired, and would be an improvement over available devices.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention provides an apparatus for mounting a towing implement in engagement with a tubular trailer hitch receiver. The invention includes a body having a first passageway in which to receive a commercially available hitch retaining pin to attach the body to the receiver. A first plate element protrudes from the body, a midplane of the first plate being oriented approximately parallel to a plane passing through the first passageway. The first plate carries a second passageway oriented approximately orthogonal to the first passageway. Typically, a centerline of the second passageway is spaced from an edge of the first plate element by a distance of about three-quarters of an inch. The adapter is generally constructed and arranged such that a towing implement carried by the first plate is rotatably positionable for connection to, and in at least partial alignment with, a towing member when the adapter is installed in the receiver. Towing members can include chains, ropes, and straps.  
           [0014]    An exemplary embodiment of the invention has a body fashioned as a cylinder with its axis oriented generally parallel to the first passageway. Usually, the first plate element has a thickness of about one-half inch to receive commercially available hooks. Some embodiments of the invention include a second plate element, oriented approximately orthogonal to the first plate element, and disposed to protrude from an opposite side of the body from the first plate element, to permit reversible mounting of the adapter in the receiver. The second plate carries a third passageway oriented approximately orthogonal to the second passageway, and usually has a larger diameter hole to hold a D-ring of sufficient strength for pulling a vehicle. In reversible embodiments with two plates, the second passageway typically has a diameter of about one-half of an inch, and the third passageway has a diameter of about three-quarters of an inch.  
           [0015]    An adapter according to the invention can be used in combination with a towing implement such as: a grab hook, a slip hook, a D-ring, or a chain double clevis. The implements are desirably rotatably connectable to the adapter by an easily removable fastener. Preferred adapters are structured in harmony with a mounting tube of the trailer hitch receiver to permit a hook to rotate, about a hook fastener axis, through an angle of approximately 90 degrees when the adapter is engaged in the mounting tube.  
           [0016]    A currently preferred embodiment of the invention is fashioned as an adapter for mounting a towing implement in engagement with a tubular trailer hitch receiver. Typical such receivers are made from 2-inch square tubing. The currently preferred adapter has a cylindrical body with an axially oriented passageway sized to receive an adapter retaining pin to hold the body inside the receiver tube. A plate, having a thickness of about one-half inch, is affixed at one end to the body, a midplane of the plate being oriented approximately parallel to a plane passing through the first passageway. The plate includes a second passageway oriented approximately orthogonal to the first passageway, a centerline of the second passageway being spaced from an edge of the plate by a distance of about three-quarters of an inch to accommodate commercially available towing implements. The currently preferred adapter is constructed and arranged such that a towing implement attached to the plate is rotatably positionable for connection in at least partial alignment with a direction of pull from a towing member when the adapter is engaged in the receiver. Towing implements typically used with the preferred adapter include grab hooks, slip hooks, and chain double clevises.  
           [0017]    These features, advantages, and alternative aspects of the present invention will be apparent to those skilled in the art from a consideration of the following detailed description taken in combination with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    In the drawings, which illustrate what is/are currently considered to be the best mode(s) for carrying out the invention:  
         [0019]    [0019]FIG. 1 is an exploded view in perspective of a prior art tubular trailer hitch receiver mounted under a vehicle bumper and including a trailer hitch adapter to hold a trailer ball;  
         [0020]    [0020]FIG. 2 is a view in perspective of a prior art D-ring and hitch adapter;  
         [0021]    [0021]FIG. 3 is a view in perspective of a prior art removable fixed hook;  
         [0022]    [0022]FIG. 4 is a view in perspective of a currently preferred embodiment of an adapter in combination with a slip hook;  
         [0023]    [0023]FIG. 5 is a view in perspective of a first alternate adapter;  
         [0024]    [0024]FIG. 6 is a view in perspective of a second alternate adapter;  
         [0025]    [0025]FIG. 7 is a view in perspective of a third alternate adapter in combination with a grab hook;  
         [0026]    [0026]FIG. 8 is a side view of a fourth alternate adapter that is reversibly mountable in a tubular receiver and in combination with a chain double clevis;  
         [0027]    [0027]FIG. 9 is a view in perspective of a fifth alternate adapter; and  
         [0028]    [0028]FIG. 10 is a view in perspective of a sixth alternate adapter that is reversibly mountable in a tubular trailer hitch receiver.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    As illustrated in FIG. 1, a prior art tubular trailer hitch receiver, generally indicated at  21 , can be mounted on a vehicle. The receiver  21  can be mounted in both front and rear vehicle locations. A prior art adapter  23  releasably holds a trailer ball  25  in registration with the receiver  21 . Commonly available trailer balls  25  have threaded stems  27  of ¾ or 1 inch in diameter, which are received in ball mounting hole  29 . The adapter  23  is generally affixed in the receiver  21  by one or more fasteners, such as pin  31 . Illustrated pin  31  is retained for safety by a self-biased clip  32 . Fasteners such as pin  31  generally have a ⅝ inch shaft diameter, and are received in correspondingly like-sized holes for safe load transfer between components of the hitch assembly. The shaft of pin  31  fits through receiver hole  35  and one of adapter retaining holes  37 . Removal of the adapter is easily accomplished without tools by removing pin  31  and then sliding adapter  23  from engagement within the tubular receiver  39 .  
         [0030]    In certain situations, such as when a vehicle is stuck or attempting to retrieve a stuck vehicle, it is desirable to attach a towing member to each vehicle. Towing members typically include strong ropes, chains, and dedicated towing straps. An advantage of dedicated towing straps is their tendency to stretch under load and reduce shock loading as a vehicle first tightens the towing member. Towing members can have various end connection options, such as attached hooks, or formed to have end loops. A commercially available D-ring can make a suitable connector for a strap loop end.  
         [0031]    D-rings are commercially available having sufficient strength for forming a safe connection between an adapter  23  and a towing strap member. Such a D-ring can be installed in replacement of the ball  25 . D-rings suitably sized for such purpose have a retaining pin sized at least in approximate agreement with the diameter of the ball retaining hole  29 . Furthermore, such size D-rings have a span between open ends sufficient to accommodate the thickness of a ball mounting plate  41 .  
         [0032]    A commercially available adapter, generally indicated at  44 , to attach a D-ring  46  to a receiver  21  is illustrated in FIG. 2. A special purpose adapter such as adapter  44  can save storage room in a vehicle, since the adapter length can be shorter than for adapter  23 . However, the adapter  44  cannot receive hooks of an optimum space-saving, and sufficiently-strong, size. Such hooks typically have a retaining pin of about ⅜ to ½ inch in diameter. Furthermore, the clevis portion of optimum sized hooks is too narrow to accommodate the thickness of the mounting plate  48 .  
         [0033]    One commercially available solution for removably attaching a hook to a receiver  21  is generally indicated at  50  in FIG. 3. Removable hook adapter  50  has a hook portion  52  welded to a square tube portion  54 . The hook portion  52  is therefore fixed in one single orientation after the tube portion  54  is installed in a tubular receiver  39 . This fixed orientation detrimentally can cause the hook  52  to be bent or distorted if a load from a towing member is applied at an angle to the hook shaft  56 . Such off-axis loads are inevitable in retrieving vehicles that are stuck off of a road.  
         [0034]    A preferred embodiment of the invention, generally indicated at  60  in FIG. 4, addresses the deficiencies of the prior art devices. Adapter  60  has an approximately 2 inch long cylindrical body  62  from which protrudes a plate  64 . Bodies may be made having other lengths to fit into other sized tubular receivers  39 . Plate  64  has a hole in which to receive a fastener of a towing implement, such as bolt  67  of slip hook  69 . The implement fastening arrangement of the invention permits an implement, such as a hook  69 , to rotate and align with a load direction from a towing member. Furthermore, the plate  64  has a thickness to provide sufficient strength for towing loads, but thin enough to fit into a hook clevis, such as clevis area  71  of hook  69 . Hook  69  is a slip hook, and it has been determined that a ⅜ inch slip hook is about an optimal size, accounting for hook strength and size.  
         [0035]    The invention is typically made from steel, although other metals and materials having sufficient strength and durability may be used. Illustrated plate  64 , in FIG. 4, is attached to body  62  by welding the components together. Workable manufacturing techniques to form the invention include casting, forging, and welding separate components together. Alternative embodiments of an adapter are illustrated in FIGS.  5 - 10 .  
         [0036]    In certain preferred embodiments of the invention, a fastener attaching a towing implement, such as bolt  67  in FIG. 4, is sized having a length small enough to slide into reception inside a receiver tube  39  to permit a reduction in a length of adapter  60 . Such configuration permits adapter  60  to be stored in a smaller volume. In certain such embodiments, the hook portion  69  may still swivel a certain amount to align hook  69  with a load direction from a towing member. Typically and desirably, the invention can rotate a hook  69  through a 90 degree arc, or more.  
         [0037]    Adapter  75  in FIG. 5 is formed from a single sheet of material, folded to form passageway  76  in which to receive a retainer, such as pin  3   1 . Adapter  77 , in FIG. 6  10  is formed by bending one end of a plate  79  into an approximate circle to form passageway  80 . The bent end is then desirably affixed by weld  82 . Each of adapters  75  and  77  have a passageway  84  in which to receive a fastener for a towing implement, such as slip hook  69 . Passageways  84  are typically between about ⅜ and about ½ inch in diameter to receive fasteners for various hooks or double clevises.  
         [0038]    [0038]FIG. 7 illustrates another alternative embodiment of an adapter, generally indicated at  90 , to hold a towing implement in registration with a tubular trailer hitch receiver. Adapter  90  is formed from a tubular section  92 , and a plate section  94 . Plate section  94  typically has a thickness of about ⅜ to ½ inch, and is welded to the inside of tubular section  92 . Plate  94  carries a passageway in which to receive fastener  96  of grab hook  98 . The passageway carried by plate  94  desirably is sized in agreement with passageway  99  in hook  98 . Pin  98  permits hook  98  to rotate to align with a load from a towing member. Tool-free assembly and disassembly can be accomplished by use of a safety retainer, such as self-biased clip  101 . A similar retainer, such as pin  31  in FIG. 1, is installed through passageway  105  to hold the adapter  90  in registration with a receiver tube  39 . A workable sized hook  98  includes a {fraction (7/16)} inch grab hook, although other sizes also are acceptable.  
         [0039]    A double-ended adapter, generally indicated at  10 , is shown in FIG. 8. Adapter  110  permits use of a hook or double clevis  112  on one end, and a larger D-ring, such as D-ring  46  in FIG. 2, on the other end. Adapter  110  is essentially a stretched version of adapter  90 , having a plate  114  corresponding to a plate  94 . Additionally, a plate  116  carries a passageway  118  sized to receive a D-ring  46 . Plates  114 ,  116  are both typically welded to the inside of tubular section  120 , which is sized to fit into a tubular receiver  39 . Adapter  110  may be retained in registration with a receiver  21  by a fastener  31  placed into reception in one of passageways  122  and passageway  35 .  
         [0040]    Plate  116  desirably is oriented 90 degrees from plate  114  to orient the D-ring  46  in a preferred orientation. A horizontal D-ring  46  is best able to maintain registration with a hook until tension can be applied to the towing member carrying the hook, which then maintains engagement between the towing member and the D-ring. As with plates  64  and  94 , plate  114  desirably is oriented on installation in a receiver tube  39  to maintain a hook in a vertical orientation so a towing member, such as a strap, will be maintained captive in the hook until tension is applied to the strap.  
         [0041]    Double clevis  112  is typically sized in correspondence with a section of chain of sufficient strength to withstand towing loads. Typical chain sizes range from ¼ inch to about ½ inch, with about ⅜ inch chain generally being preferred. Clevis  112  typically has a pair of fastener pins  125  that are held in position by safety retainers, such as cotter pins  127 .  
         [0042]    Adapters, such as embodiments generally indicated at  130  and  132  in FIGS. 9 and 10, may be manufactured by welding together strap component elements. Adapter  130  has a plate  135  affixed to plates  137  and  138  by welds, such as weld  139 . Plate  135  carries a passageway  140 , sized and oriented to receive a fastener for a hook or double chain clevis. It is preferred to chamfer or radius the corners, generally indicated at  142 , to reduce rattling of the adapter in a receiver tube  39 . Plates  137 ,  138  forming sides of adapter  132  are bent at one end to form a plate carrying passageway  145  to optionally hold a D-ring. Adapter  132  therefore can reversibly be inserted into a receiver tube  39  to provide an anchor for a hook, clevis, or suitably sized D-ring.  
         [0043]    While the invention has been described in particular with reference to certain illustrated embodiments, such is not intended to limit the scope of the invention. The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.