Abstract:
This is a device where one component is a member which, without recourse to any tools, can be attached to or removed from a tow-ball that is anchored to or integral with a tow-bar. The member is rigidly located and unable to move in any plane or about any axis when it is engaged with the tow-ball and the remainder of the device. The member has an integral platform that can be used to support and or tow any desired object e.g. bicycles on a rack attached to the platform.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Australian Provisional Patent number 2007905231 filed 25 Sep. 2007 Australian Provisional Patent number 2008901713 filed 9 Apr. 2008 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The field of endeavor generally relates to means of mounting a carrier rack on a vehicle and particularly concerns mounting on a tow-ball that is securely attached to or integral with a tow-bar.
         A variety of mechanisms have been adopted to fulfill the objective of providing a rigidly located member on a tow-bar that has the tow-ball attached. The previously adopted mechanisms fall into one of two categories:   1) Category 1. The tow-ball is only used to bolt the member or the base-plate for a member to the tow-bar. In the case of it being a base-plate the member is then rigidly linked to the base-plate by a variety of methods that would be obvious to anyone skilled in the art. With this category the stability of the member is not dependent on any direct engagement between the member and the head of the tow-ball.   2) Category 2. The head of the tow-ball is critical to establishing a rigidly located member. Thus far this approach has involved surrounding the head of the tow-ball to a varying degree and using friction to grip the head of the tow-ball. Various means have been described to establish a sufficient compression force to create adequate friction between the member and the tow-ball head to avoid the member slipping from its desired position when subjected to a displacing force. In many instances generating the gripping (compression) force requires a specific tool. U.S. Pat. No. 5,228,607 and New Zealand Patent number 226926 are relevant to the concept of using friction between a tow-ball head and a member to retain the member in a desired position.       

     Both of the above categories of attachment suffer from the possibility of the member moving substantially, relative to the tow-bar, if the securing-nut on the stem of the tow-ball is not sufficiently tight. In both categories the member can separate completely from the tow-bar if the securing-nut on the stem of the tow-ball comes completely off. An object separating from a tow-bar represents a significant hazard to other road users. 
     Category 1 mechanisms that are bolted directly to the tow-bar also suffer from the disadvantage of having to unbolt then re-attach the tow-ball each time the device is to be removed or attached. 
     Category 1 mechanisms that use a base-plate have the advantage of convenience of removal or attachment of the remainder of the member without having to unbolt the tow-ball. Previously disclosed base-plate designs however present certain shortcomings that relate to their type of configuration. There have been two broad types of configuration adopted: 
     a) a vertical component that extends upwards in close proximity to the tow-ball wherein the vertical component obstructs a ball-coupling articulating with the tow-ball. The obstruction occurs because there is generally insufficient space to locate such a vertical component between the tow-ball and the rear of the vehicle where it would not hinder the articulation of a ball-coupling. 
     b) a horizontal component that extends for quite a distance to one or both sides of the tow-bar so that vertical elements arising from it cause minimal interference with the range of articulation available to a ball-coupling linked to the tow-ball that secures the base-plate. These bulky horizontal plates represent an impediment to standing behind the vehicle to access the boot (trunk). Such sideways extensions from the tow-bar are also unsightly and a potential hazard to pedestrians. 
     Category 2 devices invite the risk of the member slipping on the tow-ball if the friction between the tow-ball and the device is inadequate. The friction may be inadequate because the compression force exerted on the tow-ball is inadequate at the outset or declines during use. Friction between the tow-ball and the member is also lowered if the tow-ball is lubricated, as is often the case following use of the tow-ball for towing. 
     BRIEF SUMMARY OF THE INVENTION 
     The primary object of this invention is to provide a new and improved device for mounting a readily removable member, which is capable of securely supporting a desired object(s), on a tow-bar that has either an integral or a fitted tow-ball. The improvements are directed at improved safety and overcoming the above listed shortcomings of earlier devices. 
     A rigidly located member extending from a tow-bar can be put to numerous uses. For example someone skilled in the art could use such an extension to support a rack for carrying bicycles. Additional devices attached to the rigidly located member can be made integral to the member or can be articulated with the member. 
     The specific aims are that the device provides a means of attaching a member to a tow-bar in a manner that:
         a) Allows, without recourse to any tools, the member to be readily attached to or to be removed from the remainder of the device which is permanently attached to the tow-bar.   b) Precludes significant movement, relative to the tow-bar, of the attached member.   c) Requires contact between the member and the tow-ball for its stability and rattle free performance.   d) Maintains the desired position of the attached member without frictional engagement between the member and the tow-ball which is integral to or mounted on the tow-bar.   e) Leaves the tow-ball accessible for normal articulation with a ball-coupling when the member is not attached to the permanently attached component of the device.   f) The permanently attached component of the device does not impede access to the boot (trunk) of the vehicle.   g) The permanently attached component of the device does not constitute a hazard to pedestrians beyond that posed by a tow-bar with no attachments.   h) Is secure and amenable to locking to discourage theft.   i) Is suitable for low cost manufacture.   j) Is reliable under demanding conditions over extended periods of time.   k) Avoids significant movement of the member relative to the tow-bar if the securing-nut on the stem of the tow-ball is loose.   l) Precludes the tow-ball and the device separating from the tow-bar if the securing-nut on the stem of the tow-ball comes completely off.       

    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a schematic exploded view of the components that are employed in the device when it is configured to fit to tow-bars of a predetermined width and to tow-balls whose dimensions may vary slightly from the size claimed by the manufacturer. 
         FIG. 2  is a schematic side view of the assembled elements depicted in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIG. 1  the tow-bar  1  has a hole  2 . The part of the tow-bar  1  that joins to the back of the associated vehicle (not depicted) is drawn as ragged to distinguish it from the free end which is furthest from the back of the vehicle and has a rounded outline. 
     In the following description the term “front” applies to being nearer to the vehicle and the term “rear” applies to being further away from the vehicle to which the tow-bar  1  is attached. 
     The tow ball  3  has a seating flange  4  and a stem  5 . The tow-ball  3  is secured with a spring washer  6  and securing-nut  7  that fit the stem  5  after it has passed through the hole  8  in the anchoring-plate  9  and the hole  2  in the tow-bar  1 . 
     The bottom face of the anchoring-plate  9  is flat to engage the flat upper face of the tow-bar  1 . The rear of the anchoring-plate  9  is shaped to lie within the outline of the rear of the tow-bar  1 . The top face of the anchoring-plate  9  is flat. 
     Some tow-bars  1  are angled upwards forward of the tow-ball  3  (refer  FIG. 2 ). The dimensions of anchoring-plate  9  are therefore set to ensure that when holes  8  and  2  align the front edge of anchoring-plate  9  does not extend forward of the place, if any, where the tow-bar  1  starts to bend upward. If this requirement is not met the flat anchoring-plate  9  is distorted when the securing-nut  7  is tightened and the flange  4  acts to bend the anchoring-plate  9  into a contour that matches the angled section of the tow-bar  1 . 
     The anchoring-plate  9  has lugs  10  and  11  that extend down and fit snuggly alongside opposite sides of the tow-bar  1 . The lugs  10  and  11  have holes  12  and  13  respectively. The diameter of the hitching-pin  14  is matched to the diameter of the holes  12  and  13 . The lugs  10  and  11  are long enough to ensure that a hitching-pin  14  passing between the holes  12  and  13  will clear the underside of the tow-bar  1 . 
     The shape of the lugs  10  and  11  is such that they do not interfere with a spanner tightening the securing-nut  7  on the stem  5  after it has passed through the hole  8  and the hole  2 . In addition the holes  12  and  13  are positioned in a manner that allows the hitching-pin  14  to pass between them without fouling the securing-nut  7  or the stem  5 . 
     Rotation of the anchoring-plate  9 , about the axis of the stem  5 , is limited by the lugs  10  and  11  embracing the sides of the tow-bar  1 . The inability of the anchoring-plate  9  to rotate on the axis of the stem  5  is retained even if the securing-nut  7  is not tight enough to generate sufficient friction between the anchoring-plate  9  and the tow-bar  1  to prevent one turning on the other. 
     The foot-plate  15  has downward extending lugs  16  and  17  that have holes  18  and  19  respectively. The diameter of the holes  18  and  19  are matched to the diameter of the holes  12  and  13  and are positioned so that the hitching-pin  14  can pass through holes  19 ,  13 ,  12  and  18  when the underside of the foot-plate  15  is uniformly separated from the topside of the anchoring-plate  9  by a distance of 0.5 to 1 millimeter. 
     The 0.5 to 1 mm tolerance between the foot-plate  15  and the anchoring-plate  9  allows subtle tilting of the foot-plate  15  about the axis of the hitching-pin  14 . The relevance of this tolerance and possible tilting relates to fitting the device to tow-balls  1  which have dimensions which vary slightly from that nominated by the manufacturer. See below for further details. 
     The lugs  16  and  17  fit snuggly alongside the lugs  10  and  11  when the foot-plate  15  is linked to the anchoring-plate  9  by passing the hitching-pin  14  through the aligned holes  19 ,  13 ,  12  and  18 . 
     The foot-plate  15  has a hole  20  that is centered over the hole  8  in anchoring-plate  9  when the holes  19 ,  13 ,  12  and  18  are aligned. Hole  20  is sufficiently large to ensure that the foot-plate  15  can pass over the tow-ball  3  and the flange  4 . The hole  20  is also large enough to ensure that its edge cannot contact the flange  4  after the hitching-pin  14  has located in the holes  19 ,  13 ,  12  and  18 . 
     Tow-balls generally have dimensions that are specified by a government authority. Some governments have safety design rules for tow-balls which mandate that the flange  4  has a larger diameter than the head of the tow-ball  3 . The government mandated dimensions generally have a manufacturing tolerance which is typically about 1 mm. The hole  20  is therefore made large enough to satisfy the size criteria listed in the immediately preceding paragraph, for the largest tow-ball dimension likely to be encountered for the nominated tow-ball size being used. 
     Permanently attached to the upper surface of the foot-plate  15  is a tube  21 . The walls of the tube  21  are located outside the perimeter of the hole  20 . In  FIG. 1  tube  21  has a square cross-section but a circular or other cross-section is satisfactory provided the walls do not encroach on the hole  20 . 
     The top of the tube  21  has a platform  22  permanently attached to it. The platform  22  thus caps the top of the tube  21 . Any desired attachment  26  can be rigidly linked to or articulated with the platform  22  by means that would be obvious to those skilled in the art.
         Tube  21  is set to a length that ensures, that even if the locking-nut  7  is not attached, the tow-ball  3  can only pass up the tube  21  to a point where the stem  5  still protrudes sufficiently through the hole  8  to engage the hole  2  while the foot-plate  15  remains attached to the anchoring-plate  9  by the hitching-pin  14  being located across the holes  19 ,  13 ,  12  and  18 .       

     After passing through holes  19 ,  13 ,  12  and  18  the hitching-pin  14  is secured in position with a retaining-pin  23  through a hole  24  in its end. The hitching-pin  14  can have a further suitably located hole  25  that accepts a padlock to deter removal of the hitching-pin  14  and theft of any of the illustrated components of the device. Specific hitching-pin locks, which have been described by others, can also be deployed to deter theft. 
     The lugs  10  and  11  on anchoring-plate  9  are made short enough to preclude the stem  5  from disengaging with the hole  2  whenever the hitching-pin  14  is engaged, below the tow-bar  1 , with the holes  19 ,  13 ,  12  and  18 . This arrangement ensures that it is impossible for the assembled device to separate from the tow-bar  1  even if the securing-nut  7  is absent. This arrangement also means that when the hitching-pin  14  is locked in position it is not possible to steal the device by undoing the securing-nut  7 . 
     The rear of the tube  21  has a threaded hole  27  that accepts a setting-screw  28  that in turn carries a locking-nut  29 . The setting-screw  28  is critical to controlling rotation of the foot-plate  15  about the axis of the hitching-pin  14 . Controlling this rotation stabilizes the position of the tube  21  relative to the tow-bar  1 . The setting-screw  28  is also critical to avoiding rattles between the foot-plate  15  and the anchoring-plate  9  and also rattles between the tube  21  and the tow-ball  3 . 
     The integrity of the connection between the anchoring-plate  9  and the foot-plate  15  is assured whenever the hitching-pin  14  is permanently engaged in the holes  19 ,  13 ,  12  and  18 . The setting-screw  28  is only necessary to avoid undue rotation of the foot-plate  15  around the axis of the hitching-pin  14 . The setting-screw  28  is tightened just up to the point where no rotation of the foot-plate  15 , about the hitching-pin  14 , is possible. Over tightening setting-screw  28  results in a constant compression force on the tow-ball  3  and this makes it impractical to readily insert and remove the hitching-pin  14  through the holes  19 ,  13 ,  12  and  18 . 
     The setting-screw  28  is made only finger tight to eliminate rattles and is then locked in position with the locking-nut  29 . The setting-screw  28  may need readjustment at a later time if significant wear or distortion of the engaged components occurs with prolonged use. 
     The setting-screw  28  does not perform the same function as the “T” locks (parts  17 ) disclosed in New Zealand Patent number 226926. Those “T” locks generate constant compression forces against a tow-ball and thereby friction between the tow-ball and the “T” locks as well as friction between the tow-ball and the cylinder supporting the “T” locks. The stability of the device disclosed in the current application is not dependent upon friction between the tow-ball  3  and the setting-screw  28 . 
     In addition the properly adjusted setting-screw  28  does not need to be tightened or loosened every time the tube  21  is engaged with or removed from the tow-ball  3 . This is totally different to the mechanism disclosed in New Zealand Patent number 226926 where the “T” locks have to be released and tightened each time that mechanism is attached to or removed from a tow-ball. 
     When the tow-ball  3  has known dimensions, which do not vary between batches, there is no need for a setting screw  28  if the internal dimensions of the tube  21 , at the level of the head of the tow-ball  3 , is matched to the diameter of the equator of the head of the tow-ball  3   
     Referring now to  FIG. 2 , this is a side view of the device fitted to a tow-bar  1  that has an angulated segment between the tow-ball  3  and the vehicle (not illustrated). The various components are numbered as for  FIG. 1 . The part of the tow-ball  3  and the setting-screw  28  that are inside the tube  21  are depicted with broken lines. 
       FIG. 2  clarifies how, with the hitching-pin  14  in place, the device cannot release from the tow-bar  1 , even if the securing-nut  7  is absent.  FIG. 2  also demonstrates how the setting-screw  28  can avoid rattles by tilting the tube  21 , about the axis of the hitching-pin  14 , and thereby simultaneously taking up any slack between the rear of the tow-ball  3  and the neighboring face of the inside of the tube  21  as well as between the underside of the foot-plate  15  and the topside of the anchoring-plate  9 . Point A indicates the location where the underside of the tilted foot-plate  15  contacts the topside of the anchoring-plate  9 . 
     It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, any alternative means, such as welding, of securely attaching anchoring-plate  9  to the tow-bar  1  may be adapted. Alternative means of attaching anchoring-plate  9  to the tow-bar  1  would be essential if the tow-ball  3  was manufactured as an integral part of the tow-bar  1 .