BACKGROUND ART A trailer is usually connected to a towing vehic via a single pivotal connection located rearwardly a centrally of the towing vehicle.

In smaller vehicles the connection is usually via tow ball located at the rear of the towing vehicle and co-operating tow hitch on a draw bar extending forwardly the trailer. »

In larger vehicles the connection is usually via turntable located at the rear of for example, a prime move In this case the turntable is engageable with a co-operati hitch on the trailer such that forces generated durin motion, are distributed over the surface of the turntabl However, the turntable usually includes a relatively narr eck section which can shear in conditions of excessi force.

In each case uncontrolled pivotal motion of t trailer relative to the towing vehicle can have dangero consequences.

One form of common uncontrolled pivotal motion i known as "jack-knifing". Damage to the vehicle and traile following a jack-knifing can be substantial. The turntabl may be sheared. The driver of the vehicle may be injured. In smaller vehicles jack-knifing is not as commo

However, uncontrolled pivotal motion of small trailers, suc as caravans, can result in substantial damage to the rear the towing vehicle and the caravan. The drawbar can buckled and the tow bar can be sheared. Another particularly dangerous form of uncontroll pivotal motion is known as "sway" and this is the tendency a towed trailer to sway from side-to-side, to rock and ev roll over under certain conditions . Such action may initiated by sudden turns, by cross winds or by air draf produced by passing vehicles. While swaying is usual manifested by a side-to-side motion the forces involved a complex having both horizontal and vertical component Certain combinations of various parameters, such as length the trailer draw bar, the height of the trailer, the weig v of the load and the surface of the road contribute increase the tendency of a trailer to sway and even increas the intensity or amplitude of the swaying action once it h started. Under these conditions, it is difficult, if n impossible, for the driver to maintain control of the ^• towi vehicle.

The effects of uncontrolled pivotal motion of

trailer are unpredictable and can be sudden, in the case "jack-knifing" or progressive in case of swaying.

It has been proposed to provide trailers and/or t towing vehicles with means to resist and inhibit uncontroll pivotal motion.

In the case of larger vehicles such as articulat vehicles it has been proposed to provide complex hydrauli responsive to monitored values of sway in order to provi forces to counter the sway when it exceeds predetermin limits. These hydraulic systems have proved comple expensive and have been of limited success.

In the case smaller trailers such as domestic b trailers, caravans etc., a number of proposals have arise

One proposal described in Australian Patent No. 483,172 us a flexible cord connected between the towing _^ vehicle and t trailer. The cord is arranged substantially horizontally a is made to travel through a guide on the trailer and as t trailer pivots about its pivot connection the fricti between the cord and the guide resists swaying. The tensi of the cord can be increased to increase the fricti generated between the cord and the guide. While th arrangement can resist the horizontal component in the ear stages of sway there is no resistance to rocking or to a vertical components of sway. In short this arrangement h very limited application to only very light and sma trailers.

Whilst little has been done to alleviate th abovementioned problems of vehicles travelling in the forwar direction attempts have been made to control the pivota motion of a trailer in order to facilitate reversing. One reversing aid for use in conjunction with conventionally hitched trailer consists of parallel bar which, when operatively positioned, form a rigi interconnection between the towing vehicle and the trailer thus rendering the single pivotal connection redundant. A problem with this aid is that it prevents pivota movement of the trailer and is only effective for reversin movemen .

Another reversing aid is described in U.S. Paten No. 4,429,894. This aid dispenses with the conventiona single pivotal connection and provides two crossed arms o end of each being attached to the trailer and the other e of each being attachable at spaced transverse locations o the towing vehicle. The crossed arms are relatively movabl for normal pivotal movement of the trailer and can be lock together to facilitate reversing.

This aid has gained little acceptance partl because of its unconventional form. In addition, it is n readily -adaptable to the vast majority of existing traile and towing vehicles. Furthermore, it has no application larger vehicles.

DISCLOSURE OF THE INVENTION With the abovementioned deficiencies of the prio art in mind it is therefore, a principal object of th present invention to provide an apparatus for controlling th pivotal movement of a trailer relative to a towing vehicl which alleviates or at least minimises some of th disadvantages referred to above.

With the foregoing and other objects in view in on broad form, the present invention resides in an apparatus fo controlling the pivotal movement of a trailer coupled to vehicle about a pivot connection, said apparatus including a arcuate guide mountable to extend between the vehicle and th trailer and having two free ends each of said free ends bein detachably mountable to the vehicle at spaced transvers locations and adjacent opposite sides of the pivot connectio and a guideway mountable to the trailer and being co-operabl with and movable relative to said arcuate guide when th trailer pivots about the pivot connection to control th pivotal movement of the trailer about the pivot connection. The arcuate guide is preferably semi-circular i shape with the free ends being located at a diameter of tha shape. The guide is substantially rigid in construction an may be made of tubular or solid material. Preferably, th guide comprises a tubular semi-circular rail. Preferre material of the rail is metal although fibreglass or rigi plastics or other suitable materials may also be used. I

one advantageous form, the free ends of the guide ar pivotally connectable to the towing vehicle at locatio equi-distant from the pivot connection of the trailer. I another form the free ends of the guide are mountable to towing vehicle via motion dampers such as conventional sho absorbers. Advantageously the motion dampers are vertical acting conventional shock absorbers or hydraulically driv vertically acting shock absorbers actuable in response uncontrolled pivoting of the trailer. The guide may additionally include motion dampe located between the trailer and the towing vehicle on ea side of the pivotal connection and which act to damp t pivotal motion of the trailer toward the towing vehicl Preferably the motion dampers are formed about or as part the arcuate guide and extend from the free ends of the gui toward the trailer to operatively damp the pivotal motion the trailer when the angle between the trailer and the towi vehicle exceeds a predetermined limit.

The guideway preferably extends along at least portion of the arcuate guide and is preferably made up of plurality of discrete guideway elements spaced along t guide through which the guide travels. Preferably t guideway permits limited movement of the guide transverse of its direction of travel through the guideway. One or mo of the guideway elements may comprise roller assemblies which the guide travels. Advantageously the roll

assemblies include roller pairs and the guide is hel captive between the roller pairs . Biasing means may employed to bias the rollers against the guide. Preferabl the roller pairs are adapted to move against the biasi means in the direction of their axes of rotation. Th biasing means can comprise one or more coil springs biasin the rollers against the guide. Each roller can b independently biased.

Preferably at least one of the discrete guidewa elements can selectively inhibit motion of the guide. Th element may be in the form of a releasable lock whic selectively locks the guide relative to the guideway at selected position to facilitate reversing. Preferably, th lock comprises a brake shoe and means for selectivel biassing the brake shoe and the guide toward each other. Th brake shoe may be curved. Advantageously, the brake shoe i hydraulically or electrically driven under control from th towing vehicle. For safety it is preferable for the lock t be inoperable when the vehicle is travelling in a forwar direction.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention can be more readil understood and be put into practical effect reference wil now be made to the accompanying drawings wherein: - FIG 1 is a perspective view illustrating preferred embodiment of an apparatus constructed i

accordance with the invention operatively mounted to a ca and trailer;

FIG 2, 3 and 4 are perspective views illustratin in greater detail portions of the apparatus of FIG 1. BEST MODE FOR CARRYING OUT THE INVENTION

The following embodiment relates to the applicatio of the invention to a relatively small domestic trailer However, it will be appreciated that by suitable scaling u the dimensions of the apparatus described the invention ma be employed with larger trailers and articulated vehicle such as semi-trailers and the like.

Referring to the drawings and initially to FIG 1 there is illustrated an apparatus 10 operatively mounted fo controlling the pivotal movement of a trailer such as bo trailer 11 relative to a towing vehicle such as a car 12 The apparatus 10 includes a guideway, which is preferably i the form of discrete guideway elements and in this case, i in the form of roller assemblies 13 and 14 and a lock elemen 15 which are mounted to the trailer's drawbars 16 via mounting plate 17. An arcuate guide in the form of a semi circular tubular member 18 is slidable within the guidewa elements 13, 14 and 15 in response to pivotal movement of th trailer about its pivotal axis which is defined by tow hitc 19. The guide element 15 is tubular a,nd is of greate internal diameter than the guide 18 and the roller assemblie 13 and 14 are roller pairs which are biased in the vertica

direction to permit limited vertical motion of the gui (see Figs. 2 and 3)

Preferably at least one of the discrete guide elements, in this case element 15 and the guide 18, relatively movable toward each other to inhibit motion the guide 18 relative to the element 15. The element preferably is adapted to selectively lock the guide relati to the guideway and thereby the trailer relative to t towing vehicle to facilitate reversing. The operation element 15 will be described below with respect to FIG 2 the drawings. The element 15 can include means to indica when the trailer is aligned with the car. The indicati means is preferably indicia on the guide 18 and the guidew which can be aligned at selected positions. The guide 18 has two free ends 20 and 21 which a detachably mountable to the car at spaced transver locations 22 and 23. In the embodiment illustrated t spaced locations 22 and 23 are equi-distant from the t hitch 19 and the free ends 20 and 21 are pivotally mounted the car U-brackets 24 and 25. The free ends 20 and 21 a secured in the U-brackets by removable pins 26 and respectively. The U-brackets 24 and 25 are .attached curved bars 28 and 29 respectively. The bars 28 and 29 a preferably made from spring steel to provide resilience the connection.

In an alternative embodiment (not shown) , t

connection of the free ends to the vehicle is via respectiv motion dampers which preferably inhibit vertical motion o the free ends . Any conventional motion damper such a conventional shock absorbers can be used. In this embodimen a pivotal connection can also be employed.

In a further modification, one form of which i illustrated in FIG 1, motion dampers are located between th trailer 11 and the car 12 on each side of the tow hitch 19 In the embodiment illustrated, coil springs 30 restric pivotal movement of the trailer to a predetermined angula range determined by their length at maximum compression. Th ends 31 and 32 of the springs 30 are free and hence they ar not placed under tension at any time. They may of course b connected to the trailer and/or the car. In a modified for sway may be resisted using controlled hydraulic cylinder which extend between the towing vehicle - and the trailer i planar parallel relationship with the guide 18.

Referring now to FIG 2 there is illustrated detai the guide element 15 of Fig. 1. The arcuate guide 18 i illustrated slidably disposed within guide element 15. T v element 15 comprises a curved brake housing 33 shown part cut-away from which extends a solenoid housing 34. Dispos between the brake housing 31 and the guide 18 is a releasab lock which in this case, is a curved brake shoe 35 having i curved surface conforming to the surface of guide 18. T brake shoe 35 can be selectively biased toward the guide by

solenoid located within solenoid housing 34 in response to electrical control signal emanating from a driver activat switch inside the towing vehicle. Many other alternati locks can be employed to lock the guideway relative to t guide, including hydraulically or pneumatically driven loc or even a single pin inserted through one of a series spaced holes in the guideway. Preferably an enable signal provided to ensure that the brake or lock is operable on when the vehicle has its reverse gears engaged. Such enable signal can be taken directly from the rear reversi lights of the towing vehicle.

Referring to Fig. 3 there is illustrated in greate detail the pivotal connection by which a free end of guide 1 of Fig. 1 can connected to the towing vehicle. As can seen a the U-bracket 25 is fitted to the spring steel bar 2 which in turn is connected to a mild steel bracket 36. Hole 37 and 38 are provide so the bracket 36 can be secured to th towing vehicle chassis.

Referring to Figs. 1 and 4 there is illustrated i detail the roller assembly 13. The roller assembly 14 is o the same construction. As can be seen each roller assembl comprises a roller pair where each roller 39 is suspende

> between plates 40 and 41 on respective shafts 42 and ar biased against the plate 40 by a coil spring 43. Althoug the illustrated embodiment shows a single spring below eac roller a spring may also or alternatively be employed betwee

the respective roller and the plate 40. In any event t rollers are operative to move vertically when positioned in Fig. 1 in respect to twisting or other relative vertic movement of guide 18. In use, the apparatus according to the inventi provides a pivot connection between the towing vehicle a the trailer which has a higher moment of inertia than t conventional centrally located connection. Thus, rotation the trailer about its longitudinal axis is inhibited. In long wheel base vehicles where the relative si of the vehicle to the apparatus is greater than in small vehicles, motion dampers as described above are preferab employed. It will be realised however that motion dampe are not essential to the invention. Furthermore, the apparatus can be activated to lo the trailer at any one of a plurality of selected angl relative to the towing vehicle. In the embodime illustrated the operator initially positions the trailer at predetermined angle relative to the towing vehicle. T operator then activates the solenoid and the guide is lock relative to the guideway thus preventing pivotal movement the trailer about the tow hitch. The operator can th reverse the trailer with ease.

It will be apparent that the lock is not essenti to the invention and while the lock is useful to facilita reversing the lock does not contribute to the stabilisi

effect afforded by the guide and guideway. The guide and t guideway as configured in the present invention provide greater resistance to rotation of the trailer about i longitudinal axis than was the case where the pivota connection alone was employed.

As a consequence, it will be appreciated tha although the invention has been described in one embodime applied to a small vehicle that the invention has equ application to larger vehicles such as long wheel bas vehicles including semi-trailers or the like. In the cas where the pivotal connection between trailer and towi vehicle is a turntable the arcuate guide and the pivo connection have the same relative positioning as for th smaller vehicle. Of course, the dimensions of the guide an the guideway will vary depending on the application as wil the material from which they are manufactured and it will b clear to those skilled in the art that such variation falls within the scope of the present invention as defined in the appended claims.