This invention is concerned with the provision of assistance to vehicle drivers in aligning a towing or tractor vehicle with a trailer to be attached thereto.

There are many forms of attachments for connecting trailers to towing vehicles, but one for which the invention is particularly, though not exclusively, intended is that in which an upwardly directed ball is mounted at the rear of the towing vehicle and a downwardly directed socket is mounted at the front of the trailer. The socket is usually at the forward end of a towbar projecting from the trailer and the ball is usually projecting behind the rear bumper of the towing vehicle. In the case of a lightweight trailer with one axle, it is possible to lift the front of the trailer b the towbar and manoeuvre the trailer until the socket is over the ball and can be lowered onto it and attached thereto. However, in the case of close-coupled twin axle tr lers, this is not so easy and a jockey wheel of adjustable height is often provided on the towbar, by which the height of the towbar can be adjusted so that the socket clears the ball for detachment and attachment. The jockey wheel can also be used to lift the front of the trailer, so that one of the pairs of wheels is lifted clear of the ground to make manoeuvring easier. Nevertheless, with heavy loads in the trailer, such as horses, boεtr or the contents of a caravan, it is much easier to leave the trailer at the point of detachment and to reverse the towing vehicle into position w h the ball under the socket when attachment is again required.

However, it is still not easy to reverse the towing vehicle exactly into the position required to

within a few centimetres. This is particularly the case when the driver of the towing vehicle is trying to attempt the manoeuvre alone. It may not be so difficult to align the towing vehicle in the lateral direction, though experience suggests that even this may require several attempts. But in order to place the ball exactly under the socket, it is necessary to align the vehicle with the trailer in the fore-and-aft direction. Without being able to see the ball or socket, as they are too low in most cases, this is very difficult.

By the invention, the alignment of a towing vehicle with a trailer in the lateral and/or fore-and-aft direction is rendered much easier.

According to the invention, a vehicle alignment device for a towing vehicle and trailer, comprises a visible target located on the trailer in predetermined relationship with a socket to be attached to a ball on the towing vehicle, and a sighting mark on a rear window of the towing vehicle in a corresponding predetermined relationship with the ball. The predetermined relation¬ ships may be such as to enable the target to come into contact with the rear window when the ball is under the socket.

Whilst the target could be fixed on the trailer, it is preferred that the target be so mounted on the trailer as to be locatable at will in its predetermined relation¬ ship with the socket. This is in order that there be no forwardly projecting member on the trailer liable to damage.

In a convenient arrangement, the target is at the forward end of a telescopic member or a folding member. Because the rear windows of towing vehicles may

be at different angles to the vertical, the target may be angularly adjustable on the carrying member. For manoeuvres which occur in conditions of poor visibility, it may be advantagec us to make the target of fluorescent material, or to coat its forward face with fluorescent material.

For the convenience of users, the target and its carrying member could be permanently mounted on the front of the trailer within a waterproof box secured thereto. In this case, with a telescopic arm as the carrying member, the arm may conveniently be pivotally mounted in the box and stored in an upright position. For use, the arm would be pivoted down to a horizontal position and drawn out to its full extent to place the target in its predetermined relationship with the socket. The length of the fully extended carrying arm would need to be pre-set to suit the particular trailer and towing vehicle rear window position. This would be done with the socket clear of the ball and above it to allow the towing vehicle to move away freely from the trailer.

The sighting mark on the rear window of the towing vehicle is preferably a circle and the target a similar circular disc, so that the approach of the target to the rear window could be observed by the enlargement of the target within the sighting mark. However, to allow for towing vehicle drivers of different heights, it may be convenient to have a pair of parallel vertical lines as well .

The scope of the present invention is defined by the appended claims; and how it can be carried into effect is hereinafter particularly described with reference to the accompanying drawings in which:-

Figure 1 is a diagrrammatic ^" sidevv.iβw, "partly broken away, of portions of a towing vehicle and trailer with a device according to the present invention in position prior to reversal of the towing vehicle to attach the trailer thereto;

Figure 2 is a similar view to Figure 1, with more parts broken away, but with the towing vehicle in the position for attachment, though detached;

Figure 3 is a diagrammatic view from the rear of the rear portion of the towing vehicle with the sighting mark in position; and

Figure 4 is a diagrammatic view of the front end of the trailer with the target and its carrying member within the box secured to the trailer.

In a preferred embodiment of the present invention, a vehicle alignment assistance device is mounted on a towing vehicle 10 and a trailer 12 (Figure 11. The device includes a target in the form of a circular disc 14 mounted at the forward end of a telescopic carrying arm 16. The carrying arm 16 is pivotally mounted in a box 1B mounted on the front wall of the trailer 12, so as to be movable between a horizontal position ^' in which it can be extended telescopically or retracted likewise, and a vertical position with the target end uppermost within the box 18. The box 1B has a hinged door 20 by which it may be closed with the target and carrying member therewithin, against water, dust and debris.

The trailer 12 is supported upon four wheels 22 on close-coupled twin axles, and has a forwardly proj¬ ecting towbar 24 with a socket 25 at its forward end and an adjustable height jockey wheel 25 by which the towbar 24 may be lifted. The towing vehicle 10 has a rear window 2B and a ball 30, complementary to the socket and

mounted on a rearwardly projecting arm 32. The sighting mark is in the form of a circular or annular mark 34 on the rear window 2B, for example on a transparency stuck to the inside of the window.

The device is mounted on the vehicle 10 and trailer 12 when they are in the detached position ready for attachment, as shown in Figure 2. This may be achieved by halting and braking the attached vehicle and trailer on flat ground 36, releasing the ball and socket and lifting the towbar 24 by means of the adjustable jockey wheel 26 until the socket 25 is clear of the ball 30 by a small and predetermined distance sufficient to allow the vehicle 10 to be driven away. The expected driver remains in the vehicle and adopts the most comfort- able position for reversing the vehicle, which may involve the driver looking in a mirror or turning to look over the shoulder. Whether reflected or direct vision is used, the line of sight should be horizontal or substantially so. The mark 34 is placed on the rear window 2B and secured thereto, preferably by self-adhesion, at the same height as the eyes of the driver or at mirror height. Then the box 18 is held against the front wall of the trailer 12 with the door 20 open and the telescopic arm 16 partially extended horizontally. The arm 16 is then extended until the target disc 14 comes ir. 3 contact with the rear window 2B and its length in that position is measured. The arm 16 is then swung away from the horizon¬ tal position and its fully extended length is reduced to the measured lehgth, for example by cutting the end section and re-attaching the target disc 14. As an alternative, a mark may be made on one of the sections, preferably the end section, of the arm 16 to indicate the extent to which the arm 16 is to be telescopically extended to reach the measured length. The box 18 is then secured to

the front wall of the trailer 12 at the same, or substantially the same, height as the mark 34 on the rear window 28.

In use, the coupled vehicle and trailer with the device retracted within the box, are driven to a selected site and braked there. The socket and ball are released and the jockey wheel adjusted to lift the towbar to bring the socket clear of the ball by the predetermined and small distance. The vehicle is then driven away. Upon return, the vehicle is halted and braked some distance in front of the trailer, and the box on the front wall of the trailer is opened and the carrying arm pivoted down and extended either to its full extent or to the mark thereon. The target disc is then in position for observation by the vehicle driver through the rear window of the vehicle. The driver then reverses the vehicle, using the mark on the rear window and the target disc to reverse the vehicle accurately towards the trailer until the disc comes into contact with the rear window. By stopping the vehicle when this occurs, the driver can be sure that the ball on the vehicle is under the socket on the trailer ready to receive the socket when the jockey wheel is adjusted to lower the towbar. If the driver reverses too far, the resilience of the carrying arm and its telescopic nature allow the disc to rise up the rear window away from the mark thereon and the driver can then move forward the short distance necessary to allow the disc to drop back again without leaving the rear window.

It may not be possible to ensure that the carrying arm is horizontal or that the line of sight is horizontal. In such case, it is convenient to have two vertical lines, one on each side of the circular mark on

the rear window. The mark on the rear window is best positioned at the centre of the window in the lateral direction, as also is the box on the front wall of the trailer. Some adjustment of the position of the target- carrying arm box and the sighting mark may be needed to suit the particular combination of towing vehicle, trailer driver, but they should be as close as possible to the centreline of the combination at eye or mirror level.

To help ensure that the carrying arm is substantially horizontal when extended, there may be resilient means in the form of a flat spring, for example, engaging the arm in the lowered position in the box to held it against accidental displacement. As oε: rear windows are sloping, but often at different angles to the vertical, the target disc could be secured to the end section of the telescopic arm by a pivoted connection tightened by means of a butterfly nut, for example, so that the disc can be adjusted to the same angle to the vertical as the portion of the rear window, with which it is arranged to come into contact.

The surface of the target disc is preferably of a colour or texture to enable it to be discerned easily, and for the purpose in conditions of poor visibility, the front surface may be coated with fluorescent material. The disc is preferably of a material which will not damage the surface of the rear window. Although the carrying arm may telescope in a contracting direction when the rear window strikes the target disc, it is preferred to rely upon resilient means to displace the disc upwards so that a clear indication of striking is given. For this purpose, the resilisr.oε ⁴ - t e extended telescopic arm may be relied upon, or there may be a spring in the box holding the arm horizontal resiliently.

It will be appreciated that in the preferred embodiment, the device comprises a target disc on the for*-, ward end of a telescopic carrying arm and an annular sighting mark on the rear window of the vehicle. The carrying arm is pivotally mounted in a box on the front of the trailer and, after contraction, can be stowed within the box in an upright position. The arm can be pivoted to an operative position and extended in a substant¬ ially horizontal direction at a height approximately equal to the eye level or mirror level height of the driver.

The sighting mark is also at t is height. The length of the extended carrying arm is so chosen that the distance between the socket and ball in the horizontal direction is equal to the distance in the same direction between the target disc and the rear window surface with the annular mark. Thus, during reversal of the vehicle towards the trailer, the rear window comes into contact with the disc when the socket is above the ball.