AU8157887A - Trailer hitch assembly - Google Patents

Description

TRAILER HITCH ASSEMBLY

This invention relates in general to trailers and more particularly to a hitch assembly for coupling a trailer to a tow vehicle.

Automobiles and pick-up trucks have long been used _.to tow trailers, and in the typical combination the trailer is connected to the tow vehicle through a ball and socket coup¬ ling located at the rear of the tow vehicle. More specifi¬ cally, the tow vehicle is fitted with a hitch ball which pro¬ jects upwardly in the region of the rear bumper for that vehicle, while the trailer at the end of its tongue has a socket which fits over and closes around the hitch ball, thereby securing the trailer to the tow vehicle such that the trailer may turn relative to the tow vehicle, rock forwardly and rearwardly with respect to the tow vehicle, and also rock left and right with respect to the tow vehicle, or in other words undergo a universal pivoting movement.

The offset of the hitch from the rear axle of the tow vehicle detracts from the overall stability of the combina¬ tion, particularly at higher speeds, for it enables wind in- duced forces to cause a swaying motion known as fishtailing. The wind may amount to nothing more than a simple surface wind of the type often present or it may be gusts of the type experienced during storms.- The wind may also be generated by a large over-the-road truck traveling at high speed, for such a vehicle will displace a considerable amount of air and cre¬ ate turbulence that affects any other vehicle which happens to be alongside of it. Inertial forces created by uneven road surfaces may also produce fishtailing. Typical of this type- of road surface is a shoulder onto which the wheel on one side of a trailer may run. As the trailer wheel climbs back onto the pavement, the trailer experiences a sudden jolt which may induce fishtailing.

Irrespective of its source, fishtailing is dangerous, for it may cause the driver of the tow vehicle to lose control of his vehicle. Moreover, fishtailing imposes severe stresses on the trailer hitch and the frame compon¬ ents to which it is attached, and may bend or fracture them. Fishtailing likewise imposes severe demands on the suspen- sion system of the tow vehicle, and may cause components such as shock absorbers, bushings and springs to experience excessive wear or to fail.

While large over-the-road tractor-trailer combina¬ tions would, because of their size, seem more susceptible to fishtailing, they are not, and this to a large measure derives from the fact that the pivot axis for the trailer is set generally over the rear axle of the tractor (see U. S. Patents Nos. 3,796,443 and 3,955,831). In vehicles with tandem rear axles, the pivot mechanism or fifth wheel as it is called is often located over the space between the two axles. In any event, tractor-trailer combinations do not pivot substantially behind the rear axle or axles of the tractor, and therefore these combinations possess good sta¬ bility at high speeds. Devices are currently available for reducing swaying and fishtailing, but these have the effect of stiffening the pivot joints at which they are used (see U. S. Patents Nos. 3,520,556, 3,645.,560, 3,751,069, 3,814,463, 3,948,544, 4,106,794, 4,312,516 and 4,502,561. They are not very effective, and they impose substantial stresses on the vehicular components to which they are attached, particular¬ ly when turns are negotiated. Heretofore, attempts have been made to stabilize trailers by employing converging linkages in the hitch mechanisms, with these linkages having the effect of displacing the effective pivot axis for the hitch mechanism forwardly, even though the hitch mechanism is not in any sense located in the region to which the axis is displaced. U. S. Patent No. 4,019,754 shows such a link¬ age arrangement. Hitch mechanisms of this type cannot ac¬ commodate sharp turns of the type one may encounter in urban areas or in attempting to park a trailer in a confined parking place.

The principal object of the present invention is to provide a trailer hitch assembly which, although being off¬ set from the rear wheels of the tow vehicle to which it attaches, enables the towed vehicle to be moved without significant swaying or fishtailing, even in the presence of substantial side winds.

Accordingly, the present invention provides a hitch assembly for coupling a trailer to a tow vehicle, said hitch assembly comprising a first pivot member adapted to be attached to the tow vehicle in a fixed position with respect to that vehicle; a second pivot member adapted to be at¬ tached to the trailer and being offset above the first pivot member; a pair of connecting links extended between the first and second members with each link being pivotally connected to the first member and also to the second member such that the ^'second member may swing to a position in which it is lo¬ cated generally over the first member, the pivotal connec¬ tions between the first member and the links being normally located ahead of the pivotal connections between the second member and the links insofar as the normal direction of move¬ ment for the tow vehicle and trailer is concerned, the pivo¬ tal connections between the links and the first member being spaced closer together than the pivotal connections between the links and the second member, whereby the links normally converge forwardly, yet enable the tow vehicle and trailer to negotiate turns .

The hitch assembly of the present invention, although being located to the rear of the tow vehicle, effectively places the pivot axis forwardly of its location. The hitch assembly of this invention will accomodate the conventional sockets used with trailer tongues. The hitch assembly of this invention is suitable for use with 'conventional under car hitch receivers, including the type used with weight- distributing hitches. Further, the hitch assembly is cap¬ able of accommodating sharp turns, so that the tow vehicle and towed vehicle, when connected, may negotiate turns of the type encountered in urban areas or in attempting to position the towed vehicle in a parking place. The hitch assembly of this invention is simple in construction, easy to manufacture, and reliable in service. These and other features and advantages will become apparent hereinafter. In the drawings:

Figure 1 is a perspective view of a trailer connected to a tow vehicle with a hitch assembly constructed in accordance with and embodying the present invention;

Figure 2 is a top plan view of the hitch assembly; Figure 3 is a side elevational view of the hitch assembly taken along line 3-3 of Figure 2;

Figure 4 is a sectional view of the hitch assembly taken along line 4-4 of Figure 2;

Figure -5 is a sectional view taken along line 5-5 of Figure 2 and showing the front pivot mount of the hitch assembly;

Figure 6 is a sectional view taken along line 6-6 of Figure 2 and showing the rear pivot mount of the hitch assembly; Figure 7 is a plan view of the hitch assembly showing the configuration it would assume when the tow vehicle negotiates a relatively wide right turn;

Figure 8 is a plan view of the hitch assembly showing the configuration it would assume when the tow vehicle negotiates a sharper right turn;

Figure 9 is a plan view of the hitch assembly showing the configuration it would assume in a still sharper turn; and

Figure 10 is a fragmentary elevational view showing a modification to the tightening device for the spring bars.

Referring now to the drawings, a trailer A (Figure 1) is coupled to a tow vehicle B at a hitch assembly C, which is for the most part located at the very rear of the tow vehicle B so that it is easily accessible. Thus, the trailer A is easily and quickly connected to and discon¬ nected from the tow vehicle B. Despite the location of the hitch assembly C well aft of the rear axle for the tow vehicle B, the trailer A and tow vehicle B when operated over the road as a combination possess amazing stability and exhibit little if any tendency to sway or fishtail when buffeted by cross winds or when otherwise subjected to lat- eral forces such as may b-e caused through the intertial effects of an uneven road surface. This stability derives from the fact that the effective pivot axis for the hitch assembly C, at least when the trailer A is directly behind and aligned with the tow vehicle B, is projected a consid- erable distance forwardly and may even be in the region of the rear axle for the tow vehicle B.

The tow vehicle B (Figure 1) may be a conventional automobile, a van, or light truck, such as a pickup truck. As such it includes some type of framework 2 on which a ' body 4 is mounted and of course front and rear road wheels 6 on which the framework 2 is supported. At its trailing end the framework 2 supports a rear bumper 8. The rear wheels 6 revolve about an axis x which is essentially common to bot rear wheels 6, even though they may be independently suspend ed, and this axis is located well ahead of the hitch assembl C, or at least the portion of the hitch assembly C at which the connection between the trailer A and tow vehicle B exists.

The trailer A (Figure 1) has a frame 14 which is sup- ported on wheels 16 that revolve about a common axis y, and the frame 14 in turn supports a trailer body 18. The front of the frame 14 forms a so-called tongue or A frame, in that it has side members 20 which converge forwardly and are con¬ nected at their forward ends to a coupler 22 containing a generally spherical socket 24 (Figures 4 &. 6) that opens downwardly and is sized to receive a conventional trailer hitch ball. The coupler 22 also has a locking device 26 which will close upon the hitch ball and retain it in the socket 24.

Turning now to the hitch assembly C, it includes a hitch bar 30 (Figure 1) that is mounted beneath the body 4 of the tow vehicle B along the longitudinal centerline m of the vehicle B. The hitch bar 30 projects rearwardly a short distancebeyond the rear bumper 8, but is secured firmly to the framework 2 of the tow vehicle A by bracing 32 which is located for the most part ahead of the rear bumper 8.

Fitted over the rearwardly projecting portion of the hitch bar 30, that is the portion which extends beyond the rear bumper 8, is a hitch box 34 (Figures 2 & 3) to which a pivot member or mount 36 is fastened securely such as by welding. The hitch box 34 has a forwardly opening socket 38 that is large enough to receive the hitch bar 30 without ex¬ cessive free motion. Indeed to facilitate installation of the hitch box 34 over the hitch bar 30, the end of the hitch bar 30 and likewise the socket 38 of the hitch box 34 are tapered slightly on their upper and lower surfaces and on their side surfaces as well (Figure 4) . Thus the hitch bar 30 and hitch box 34 constitute connecting members for secur¬ ing the pivot mount 36 in a fixed position with respect to the framework 2 of the tow vehicle B. The hitch box 34 is held securely on the end of the hitch bar 30 by two overcenter latches 39 (Figures 2 & 3) , there being a latch 39 at each side of the hitch box 30. Each latch 39 includes a long toggle link 40 and a short toggle link 41 which are joined together at a pivot pin 42 that is fixed rigidly in one end of the short link 41, but has a hexagonal head exposed above the long link 40. Thus, the long link 40 at its one end turns relative to the pin 42 and in so doing pivots relative to the short link 41. The other end of the long link.40.mo_m±ed on a tab 43 which pro- jects laterally from the hitch bar 30 ahead of the hitch box 34, and indeed pivots relative to that tab. The short link 41 at its end remote from the pivot pin 42 is curved to en¬ gage a concave recess in another tab 44 which projects outwardly from the side of the hitch box 34. Indeed, when the two links 40 and 41 are alongside and against the hitch box 34 with the curved end of the latter in the recess of the tab 44, the latch 39 is in its overcenter condition - the condition in which it secures the hitch box 34 firmly to the hitch bar 30 (Figure 2 - right side of bar 30). When the links 40 and 41 are in this condition, the tab 44 on the hitch box 34 projects beyond the two links 40 and 41 and to insure that they remain overcenter or more specifi- cally in the condition in which the short link 41 is en¬ gaged with the tab 44, a safety pin 45 is inserted through the tab 44 adjacent to the side of the long link 40. The short links 41 may have threaded end portions so that^' their lengths may be varied to accommodate the tabs 44 which they engage.

To release each of the overcenter latches 39, the safety pin 45 for that latch 39 is withdrawn from its tab 44. Then a wrench w is placed over the hex head on the pivot pin 42 that connects the two links 40 and 41. The wrench w is turned in the direction that moves the connec¬ ted ends of the two links 40 and 41 away from the side of the hitch box 34, and as it is turned the opposite end of the short link 41 rotates in the concave recess of the tab 44. After a few degrees of rotation, the short link passes overcenter, that is it passes beyond a condition in which it is parallel to the hitch bar 30. The two links 40 and 41 then swing freely away from the side of the hitch box 34, allowing the short link 41 to be totally disengaged from the tab 44 (Figure 2 - left side) . To couple the hitch box 34 with the hitch bar 30, the hitch bar 30 is inserted as far as possible into the socket 38 of the hitch box 34, and when so fitted, little if any, free motion exists either vertically or laterally by reason of the tapered configuration of the bar ^'30 and socket 38. Then the curved end of the short link 41 for one of the latches 39 is engaged with the concave recess in the tab 44 at that link 41. Next the wrench w is placed over the head of the pivot pin 42 which joins .the short link 41 to its long link 40, and a torque is applied to the pin 42, causing the short link 41 to pivot toward the hitch box 34. Indeed, the two links 40 and 41 move overcenter and lodge against the side of the hitch box 34, thus, securing the hitch box 34 to the hitch bar 30. The safety pin 45 is then inserted through the outwardly projecting portion of the tab 44. The latch 39 on the other side of the hitch bar 30 is engaged with the hitch box 34 in a like manner. The pivot mount 36 may consist of nothing more than two steel plates (Figures 4 & 5) , each welded firmly to the hitch box 34 with the one being located about 7.62 cm. (about 3 inches) above the other. Indeed, the plates may form op¬ posite walls of square steel tubing. In any event, the pivot mount 36 extends horizontally across the rear end of the hitch box 34 to which it is securely fastened, and car¬ ries two spaced apart bushings 46 which are set into it and function as bearings. The bushings 46 are closed at their lower ends, but open -upwardly and have their axes parallel. Moreover, they are spaced equidistantly from the common centerline of the hitch box 34 and hitch bar 30, which is of course the longitudinal centerline m of the tow vehicle B. They are likewise spaced equidistantly from the rear bumper 8 and the axis x of the rear wheels 6 for the tow vehicle B, or in other words they are located along a line that is perpen¬ dicular to the centerline m. Where the mount 36 consists of spaced apart plates, the bushings 46 extend between the plates. The typical spacing between the axes of the two bushings 46 may be about 18^".1 cm. (about 7-1/8 inches). In each bushing 46 is a pivot pin 48 (Figures 2 & 5) , which as its name implies rotates freely in its bushing 46, its lower end being against the closed lower end of the bush¬ ing 46. Yet the clearance between the pin 48 and bushing 46 is quite small, if any, so that side play is minimal. The pins 48 project upwardly out of their respective bushings 46, and each at its upper end is joined rigidly to a connecting link 50. The two connecting links 50 are equal in length and are directed rearwardly from their respective bushings 46 (Figure 5). Each at its trailing end is fitted with another pivot pin 52 (Figure 6) which is likewise rigidly joined to the link 50. The front and rear pins 48 and 52 for each link _*_ 50 are parallel, that is they have parallel axes which are oriented in the vertical direction. Since the two links 50 are equal in length, the spacing between the axes of the front and rear pins 48 and 52 of the one link 50 equals the spacing between axes of the front and rear pins 48 and 52 for the other link 50. That spacing should be about 11.43 cm. (about 4-1/2 inches).

The rear pins 52 of the two links 50 project into bushings 54 (Figure 6) that are set into another pivot mem¬ ber or mount 56 which is located slightly to the rear of the pivot mount 36 and likewise slightly above that mount.

The bushings 54 of the rear pivot mount 56 are closed at their upper ends and likewise serve as bearings, with the pins 52 projecting downwardly from them. The bushings 54, while being parallel to each other like the bushings 46 of the pivot mount 36, are spaced somewhat farther apart than the bushings 46, typically being about 20 cm. (about 7-7/8 inches) apart.

Thus, when the rear pivot mount 56 is centered behind the front pivot mount 36, that is when its bushings 54 are spaced equidistantly from the centerline m, the connecting •links 50 converge forwardly. Indeed, the convergence is such •that the links 50 if extended forwardly beyond the front pins 46 will meet along the centerline m, perhaps. 91 to 122 cm. (three to four feet) ahead of the rear bumper 8, or more aσ- curately lines extended forwardly through and perpendicular to .the axes of the pins 52 and 46 for each link 50 will in¬ tersect along the centerline m of the vehicle at a point that is between the rear bumper 8 and the axis of the rear wheels 6 (Figure 2) . This symmetical positioning of the links 50 only exists when the rear pivot mount 56 is directly behind the front mount 36 and hitch bar 30, for when the rear mount 56 is shifted to one side or the other, the intersection of the lines transfers to points which are located closer to the bumper 8 and offset from the centerline m (Figure 7) .

Indeed, the geometry of the arrangement is such that the rear pivot member 56 may move to a position in which it lies directly over and parallel to one of the links 50 (Figure 8) and even beyond that position into a position where one of the links 50 projects straight forwardly, while the other projects generally rearwardly (Figure 9) . In the latter position, the angle between the rear pivot mount 56 and the front pivot mount 36 is quite large and, of course, the angle a between the centerline m of the trailer A and the centerline m of the tow vehicle B is of a corresponding magnitude. Projecting upwardly from the upper surface of the hitch box 34 is a stop 57 which lies in the arcs of ro¬ tation for the links 50 and prevents either link 50 from passing completely over the hitch box 34.

To prevent the pivot pins 48 and 52 from moving axi- ally in their respective bushings 46 and 54, the pins 48 and 52 are provided midway between their ends with annular grooves, while the bushings 46 and 54 are fitted with retain- ing pins that project radially into the grooves. These re¬ taining pins do not prevent the pivot pins 48 and 52 from bearing against the closed ends of their respective bushings 48 and 52, and indeed those ends like the cylindrical walls serve as bearing surfaces. Midway between its bushings 54, the rear pivot mount 56 carries a conventional hitch ball 58 which is attached firmly to the mount 56 and projects upwardly from it. Thus, when the rear mount 56 is centered with respect to the front mount 36 and the hitch box 34, which is the condition in which the links 50 lie symmetrical on each side of the centerline m, the hitch ball 58 will be located along the centerline m (Figure 2) .

The coupler 22 on the front end of the trailer A attaches to the hitch ball 58 on the rear pivot mount 56, or in other words the hitch ball 58 fits into the socket 24 of the coupler 22, the locking device 26 holding the two together (Figures 4 & 6) . Ordinarily, the typical ball-and socket trailer hitch accommodates univeral movement, but in the hitch assembly C the trailer A is prevented from turning relative to the hitch ball 58, that is rotating about a ver¬ tical axis, by a pair of struts 60 (Figures 2 & 3) which ex- 5 tend between the ends of the mount 56 and the converging side members 20 that form part of the trailer frame 14. More specifically, the rear pivot mount 56 at its ends is provided with upwardly directed tabs 62 (Figure 6) which at their upper ends turn over and close the tops of the rear

10 bushings 54. Indeed, each bushing 54 is attached at both of its ends to the rear mount 56. Being at the ends of the rear mount 56, the tabs 62 are located to the sides of the hitch ball 58 and the coupler 22 which fits over that ball. The trailer A, on the other hand, along each of side members

15 20 is fitted with frame brackets 64 which are clamped firmly in place by U-bolts 66. The struts 60 extend between the tabs 62 on the rear mount 56 and the brackets 64 of the trailer frame 14, each being connected to its tab 62 and bracket 64 through swivel fittings 68 to enable a limited 0 amount of rocking movement between the trailer frame 14 and the cross bar 56 of the hitch assembly C. The swivel fit¬ tings at the tabs 62 should be at the same elevation as the center of the hitch ball 58, so if the ball 58 is raised, the front swivel fittings 68 should likewise be raised. 5 In this connection, the struts 60 prevent the trailer frame from rotating relative to the hitch ball 58 about a vertical axis , and as a result of this movement is accommo¬ dated by the connecting links 50. Nevertheless, the trailer A may tilt one way or the other with respect to the tow ve- 0 hicle B as might be expected on uneven road surfaces. When this occurs, the coupler 22 merely turns slightly on hitch ball 58 about an axis of rotation that extends longitudinally through the trailer A. Likewise the trailer A may rock for¬ wardly or backwardly relative to the tow vehicle B, and when 5 this occurs, the coupler 22 rotates on the hitch ball 58 about an axis that extends transversely through the ball 58. Since the swivel fittings 68 do not lock the struts 60 rig¬ idly to either the rear mount 56 or the trailer frame 14, they do not inhibit the rocking motion about the longitudi¬ nal or transverse axes.

Preferably each strut 60 includes a pair of eye bolts 70 at which the strut 60 is connected to the swivel fittings 68 and a tube 72 which extends between the eye bolts 70. Indeed, the tube 72 is threaded at its ends and the eye bolts 70 thread into the tube 72, so that the strut 60 functions much like a turnbuckle. Thus when the tube 72 is turned relative to the eye bolt 70, the length of the strut 60 changes, and this facilitates installing the hitch as- sembly C on the trailer A and enables the rear mount 56 to be adjusted to a position in which a line passing through the axes of its bushings 54 is parallel to the axis y of the trailer wheels 18, as it should be for proper operation of the hitch assembly C.

Where the so-called tongue weight of the trailer A is quite heavy, it is desirable to redistribute the weight of the trailer A somewhat, so that more of it is carried by the wheels of the trailer A and the front wheels of the tow vehicle B and less of it by the rear wheels 6 of the tow vehicle B. To this end the hitch assembly C may be fitted with spring bars 80 (Figures 2 & 3) that extend between the front pivot mount 36 and the trailer frame 14 and are stressed such that the rear of the tow vehicle B is urged upwardly. This increases the force at the hitch ball 58 significantly above that of the normal tongue weight for the trailer A. Spring bars have long been used in conjunction with trailer hitches to achieve better v/eight distribution, and the principle by which they operate will therefore not be described.

The spring bars 80 for the most part extend gener¬ ally horizontally, but each at its forward end turns upwardl where it is received in more bushings 82 (Figure 5) which ar located in the front pivot mount 36, much the same as and parallel to the bushings 46 for the links 50. However, the bushings 82 are set inwardly from the bushings 46 and are closed at their upper ends by the upper plate of the mount 36 The upwardly turned forward ends of the spring bars 80 pro¬ ject through the bushings 82 and bear against the under- surface of the top plate for the mount 36. The spring bars 80 are prevented from dropping downwardly and working out of the bushings 46 by small pins which extend from the bushings 82 radially into grooves that open out of the upwardly turned portions of the spring bars 80.

The spring bars 80 extend rearwardly from the front pivot mount 36 and at their rear ends are connected to the frame brackets 64 through chains 86 and a chain tightening device 88 (Figures 2 & 3) which controls the tension in the chains 86 and likewise the stress in the spring bars 80. The tightening device 88 includes a torque tube 90 which is mounted in bearings attached to the two brackets 64 and thus extends between those brackets 64. At one end it is pro¬ vided with a torque arm 92 that extends forwardly and indeed the chain 86 at that end is connected to that torque arm 92. At its other end the. or.que.tube 90_is fitted with. nother .torque arm 92 that forms part of a bell crank 94. The other arm 92 likewise extends forwardly and indeed corresponds in angle and position to the single torque arm 92. The forwardly di¬ rected torque arm 92 of the bell crank 94 has the chain 86 for the other spring bar 80 connected to it. The other arm of the bell crank 94 projects upwardly and is attached to a screw jack 96 which is mounted by means of a bracket 98 on the frame bracket 74 at which the bell crank 94 is located.

When the screw jack 96 is turned, the torque tube 90 rotates and moves the forward ends of the torque arms 92 up¬ wardly or downwardly and the chains 86 as well. This of course alters the stress in the spring bars 80. Thus, the jack 96 controls the amount of weight that is redistributed to the front wheel 6 of the tow vehicle B and the wheels 16 of the trailer A.

Since the forward ends of the spring bars 80 are free to turn in the bushings 82, the spring bars 80 accommo¬ date any turning of the tow vehicle B relative to the trailer A. _The connecting chains 86, inasmuch as they are free to pivot relative to the frame brackets 64 and the rear ends of the spring bars 80, permit the rear ends of the spring bars 80 to shift relative to the trailer frame 14 during turns and other relative movement between the trailer A and tow vehicle B.

In use, the hitch assembly C couples the trailer A to the tow vehicle B such that the combination of the two is extremely stable at high speeds, even in the presence of gusty side winds or on uneven road surfaces. This derives from the fact that the effective pivot axis for the trailer, at least when it is aligned directly behind the tow vehicle B, is between the rear bumper 8 and the axis x for the rear wheels 6 of the vehicle B (Figure 2) , and not at the rear bumper 8 where the actual pivoting is accommodated. In this regard, the towing force is transmitted through the hitch bar 30 to the hitch box 34 and front pivot mount.36 and thence through the connecting links 50 to the rear pivot mount 56 to which the trailer A is connected at the hitch ball 58. Since the struts 60 prevent the trailer A from turning with respect to the rear pivot mount 56, that is ro¬ tating about a vertical axis at the hitch ball 58, the turn¬ ing must be accommodated through the connecting links 50, the pins 40 and 52 of those links, and the bushings 46 and 54 in which the pins 40 and 52 fit. The bushings 46 and 52 are spaced such that the connecting links 50 converge and indeed if projected forwardly would meet along the center¬ line m of the- tow vehicle B somewhat ahead of the rear bum¬ per 8, but most likely behind the axis x for the rear wheels 6, assuming of course that the trailer A is aligned with the tow vehicle B, that is directly behind the tow vehicle B, as would occur while driving straight segments of highway. By replacing the pivot point forwardly, the tendency to sway or fishtail is significantly reduced. Actual tests of appli¬ cant's hitch assembly C have demonstrated a marked reduction in fishtailing.

When the tow vehicle B and trailer A negotiate a curved segment of road, the links 50 rotate slightly with respect to both the front pivot mount 36 and the pivot mount ^• 56 which they connect (Figure 7) , this occurring upon enter¬ ing the curve as well as upon leaving it. While in the curve, the links 50 are no longer disposed at equal angles with respect to the centerline m of the tow vehicle B, and indeed one link 50 could be at a substantially greater angle than the other. This displaces the effective pivot point rearwardly and to one side or the other, but curves which require a major displacement of the effective pivot point can only be negotiated at slow speeds - speeds at which side winds are not likely to induce fishtailing. In the case of gentle curves which may be taken at high speeds , the connect¬ ing links 50 may be at slightly different angles with re¬ spect to the centerline m of the tow vehicle B, but the change in angles is not enough to displace the effective pivot point much and it remains close to the centerline m well ahead of the rear bumper B. Thus, the combination of the tow vehicle B and trailer A likewise possesses good sta¬ bility in high speed curves. ^' Since the front pivot mount 36 lies beneath the links 50 and the rear pivot mount 56 lies above the links 50, the latter never comes against the former as it moves with the trailing ends of the links 50 which of course occurs when the tow vehicle B and trailer A negotiate a turn. This arrangement of the pivot mounts 36 and 56 and links 50 en¬ ables the hitch assembly C to accommodate extremely sharp turns, that is turns in which the centerline m of the trailer A is at a substantial angle a with respect to the centerline of the tow vehicle B (Figures 8 and 9). Indeed, when such curves are encountered, the rear mount 56 merely passes over the front mount 36, and in so doing carries one of the links 50 to a position in which it lies directly below and parallel to the rear mount 56 (Figure 8) . In this position the rear mount 56 is presented at a relatively large angle with re- spect to the front mount 36, but that angle may be increased even more, for the links 50 are free to swing forwardly, and when, one link 50 is projected straight forwardly and the - IB - other generally rearwardly, the rear mount 56 is at a sub¬ stantial angle a with respect to the front mount 36 (Figure 9) , the position it would assume in an extremely sharp turn. The stop 57 prevents the forwardly projected link 50 from passing much beyond the straight forward position. Thus, the hitch assembly C permits the tow vehicle B and trailer A to negotate the sharp turns one would expect to encounter in urban areas, and further enables the tow ve¬ hicle B to back the trailer A into an extremely confined parking area - a maneuver which often requires the tow vehicle B to be jacked sharply with respect to the trailer A.

Irrespective of the type of curve no turning occurs between the trailer coupler 22 and the hitch ball 58 that is rotation about a vertical axis. Thie struts 60 prevent such rotation. Even so, the coupler 22 and hitch ball 58 d enable the trailer A to rock left or right and forwardly an backwardly with respect to the tow vehicle B. In other words, the trailer coupler 22 and hitch ball 58 accommodate ^' rotation of the trailer A relative to the tow vehicle B about the longitudinal axis of the trailer A and also about a tranverse axis extending through the hitch ball 58.

The spring bars 80, if used, redistribute the tong load of the trailer A so not as much of it is carried by th rear wheels 6 of the tow vehicle B, yet they do not restric the previously described rotational movements. In this re¬ gard, the spring bars 80 at their forward ends pivot in the bushings 82 of the forward pivot mount 36 and thus accommo¬ date turns. The left and right rocking as well as the up a down rocking are, on the other hand, accommodated through flexure of the bars 80. While the spring bars 80 do increa the reaction force at the hitch ball 58, the hitch ball 58 and the coupler socket 24 in which it fits experience less wear than in conventional hitch arrangements, because in th hitch assembly C turning motion about the vertical axis is eliminated. While it is possible to in effect connect and dis¬ connect the tow vehicle B and trailer A at the hitch ball 58, it is much simpler to connect and disconnect at the hitch bar 30. This procedure begins with the coupler 22 already locked to the hitch ball 58, the struts 60 in place, and likewise the spring bars 80 in place if they are em¬ ployed. In that case the hitch bar 30 on the tow vehicle B is merely aligned with the socket 38 in the hitch box 34, whereupon the tow vehicle B is backed slowly, causing the hitch bar 30 to enter the socket 38. When the hitch bar 30 is fully inserted, the overcenter latches 39 are engaged with their respective tabs 44 on the hitch box 34, and with the wrench w the latches 39 are moved overcenter to securely connect the hitch bar 30 and hitch box 34 (Fig. 3) . The The safety pins 45 are then installed. The spring bars 80, if used, are at their trailing ends drawn upwardly with the jack 96 of the tightening device 88. The trailer A may be disconnected from the tow vehicle B in reverse sequence.

To avoid relaxing the chains 86 when the trailer A is disconnected from the tow vehicle B and again tightening them when it is reconnected, a link assembly 100 (Figure 10) may be substituted for the chains 86. The link assembly 100 includes a rod 102, a sleeve 104 through which the rod 102 passes, and a bracket 106 which is welded to the side of the sleeve 104 and projects obliquely from it. At its lower end the rod 102 possesses a clevis by which it is connected to the trailing end of one of the spring bars 80. The rod 102 fits into the sleeve 104 loosely enough to slide and turn relatively easily in the sleeve 104 when not otherwise con- nected, and near its upper end the rod 102 has a succession of holes 108. The sleeve 104, on the other hand, has an elongated hole 110, which extends circumferentially. Thus, by moving the rod 102 axially in the sleeve 104, the rod 102 can be brought to a position in which one of the holes 108 in it aligns with the elongaged hole 110 in the sleeve 104, so that a pin 112 may be inserted through the two to join the" rod 102 and sleeve 104 together. By reason of the - 18 - elongation in the hole 110, the rod 102 can turn somewhat in the sleeve 104. The bracket 106, on the other hand, is connected to one of the torque arms 92 at another pin 114.

In lieu of forming the front pivot mount 36 from spaced apart plates or the rear pivot mount 56 from a plate with ends turned up and over, each mount may be formed from a heavy tube stock of square cross-sectional configuration. In that case the bushings 46, 54 and 82 would extend between opposite walls of their respective tubular pivot mounts 36 and 56.

This invention is intended to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure.

Claims (16)

1. A hitch assembly for coupling a trailer to a tow vehicle, said hitch assembly characterized by a first pivot member adapted to be attached to the tow vehicle in a fixed position with respect to that vehicle; a second pivot member adapted to be attached to the trailer and being offset above the first pivot member; a pair of connnecting links extended between the first and second members with each link being pivotally connected to the first member and also to the second member such that the second member may swing to a position in which it is located generally over the first member, the pivotal connections between the first member and the links being normally located ahead of the pivotal connections between the second member and the links insofar as the normal direction of movement for the tow vehicle and trailer is con¬ cerned, the pivotal connections between the links and the first member being spaced closer together than the pivotal connections between the links and the second member whereby the links normally converge forwardly, yet enable the tow vehicle and trailer to negotiate turns.

2. A hitch assembly according to claim 1, characterized by either one of the links when on the inside of a turn being capable of swinging with the second member to a position in which it is substan¬ tially reversed from its normal position so that the pivotal connection between that link and the second member is located substantially ahead of the pivotal connection between that link and the first member, all while the pivotal connection between the other link and the first member remains generally ahead of the pivotal connection be¬ tween that other link and the second member, whereby the angular position of the second member rela- tive to the first member can be varied substantially to enable the tow vehicle and trailer to negotiate sharp turns.

3. The hitch assembly according to claim 1 or 2, characterized in that the first and second members have bearings with the axes of the bearings being paral¬ lel and the links have pins which extend into the bear¬ ings, thus providing the pivotal connections between the links and the first and second pivot members.

4. The hitch assembly according to claim 3, characterized in that the bearings for the first member are the same distance from the axis for the rear wheels of the tow vehicle and the bearings for the second member - are the same distance from the axis for the wheels of the trailer.

5. The hitch assembly according to claim 4, characterized in that the trailer has a longitudinal centerline and the bearings for the second member are also spaced generally equidistantly from the longitudi¬ nal centerline of the trailer, there being one bearing on one side of that centerline and another on the other side.

6. The hitch assembly according to any of claims 1 to 5, characterized in that straight lines passing through and perpendicular to the pivot axes of the two connecting links will intersect in the region behind the axis for the rear wheels of the tow vehicle and ahead of the rear of the body of the tow vehicle.

7. The hitch assembly according to any of claims 1 to 6, characterized in that the trailer also includes at the forward end of its frame a coupler that contains a socket; and further comprising a hitch ball on the second member between the loca¬ tions at which the connecting links are pivotally connected to the second member.

S. The hitch assembly according to claim 7, characterized in that the hitch ball is mounted mid¬ way between the locations at which the connecting links are pivotally connected to the second member.

9. The hitch assembly according to claim 7 or 8, characterized by struts connected to the second member remote from the hitch ball and also to the trailer frame remote from the socket which receives the hitch ball to prevent the second member from ro¬ tating relative to the frame about a vertical axis.

10. The hitch assembly according to any of claims 1 to 9, characterized by a hitch bar mounted firmly with respect to the body of the tow vehicle gen¬ erally parallel to the longitudinal axis of the vehicle and a hitch box fitted over the end of the hitch bar yet being detachable from the bar; the first member being mounted in a fixed position on the hitch box.

11. The hitch assembly according to claim 10, characterized by over-center clamps connecting the hitch bar and hitch box one to the other.

12. The hitch assembly according to claim 11, characterized in that the hitch box has a socket which receives the hitch bar, the socket being defined at least in part by tapered surfaces, and the hitch bar has tapered surfaces which seat against the tapered surfaces of the socket when the hitch box and hitch bar are connected together by the over-center clamps.

13. The hitch assembly according to any of claims 1 to 12, characterized by spring bars pivo¬ tally connected to the first member and to the trailer frame and being stressed so as to lessen the load on the rear wheels of the tow vehicle.

14. The hitch assembly according to claim 13, characterized in that each spring bar is connected to the trailer frame through a link assembly which in use has a fixed length but accommodates some rotation. - λλ -

15. The hitch assembly according to claim 13 or

14, characterized by a torque tube extended across the trailer frame at the rear ends of the spring bars, torque arms attached to the torque tube, flexible means for con¬ necting the rear ends of the spring bars with the torque arms , and means for turning the torque tube, whereby the stress in the spring bars may be altered.

16. The hitch assembly according to any of claims 1 to 15, characterized in that the distance be¬ tween two pivotal connections for the one link is equal to the distance between the two pivotal connections for the other link.