When hitching a trailer to a vehicle, a person will normally reverse the vehicle, which is equipped with a tow bar, until the tow bar of the vehicle is very close to the hitch of the trailer. If the person succeeds in stopping the vehicle so that the tow bar is immediately beneath the hitch, it may simply be lowered onto the tow bar of the vehicle. However, it is more usual to have to move the trailer a short distance in order to align the tow hitch with the tow bar of the vehicle. The distance which the trailer must be moved depends on the skill of the person driving the vehicle in placing the tow bar near to the hitch of the trailer. It requires much skill and practice to achieve this manoeuvre accurately, although it is made easier if there is second person to direct the driver of the vehicle. If the vehicle is not positioned close to the trailer, then much effort is required in manoeuvring the trailer so it can be attached to the vehicle. In addition, once the trailer begins to move, it can be difficult to control, and often results in damage to the vehicle as a result of it overrunning.

One of the main problems with hitching a trailer to a vehicle is that the tow bar of the vehicle, and the hitch of the trailer are invisible to the person while he is positioning the vehicle.

The present invention may be used to assist a person in the hitching of a trailer to a vehicle, and in particular to bringing the tow bar into close proximity with the hitch of the trailer.

The present invention is a device for assisting in hitching a trailer hitch to a vehicle tow bar comprising means for determining the relative positions of the hitch and the tow bar, and an indicator for indicating the relative positions.

The trailer may be a simple box trailer, a caravan, heavy machinery on wheels such as a portable generator, or other similar article which is suitable for towing by a vehicle.

The trailer may even be of an articulated type having more than one axle, one of which is pivotally movable with respect to the body of the trailer.

In particular, the device assists a person hitching the trailer to know the distance between the tow bar and the hitch and/or whether the hitch of the trailer is to the left or to the right of the tow bar as the vehicle reverses. It is preferred that the device includes means for determining the distance between the tow bar of the vehicle and the hitch of the trailer. According to one embodiment, this is a device which, once the tow bar of the vehicle is less than a set distance from the trailer, indicates this to the person hitching the trailer. This minimises the risk of the person reversing the vehicle into the trailer and causing damage to either of them.

The device preferably includes means for determining the angle of the hitch relative to the longitudinal axis of the vehicle, ie how far to the left or right of the car the hitch is positioned. This enables the person hitching the trailer to put the tow bar as close as possible to the hitch.

An embodiment of the present invention will now be described by way of example only, and with reference to the accompanying drawings in which: Figure 1 shows a device according to the present invention being used connected between the tow bar of a vehicle, and a tow hitch of a trailer; Figure 2 is a plan view showing the device in use between a vehicle and a trailer.

Referring to the drawings, a vehicle 1 and a trailer 2 are shown, the vehicle having a tow bar 3 attached thereto for connection of a tow hitch 4 of the trailer 2. A device for assisting and hitching the trailer is shown, and includes several components, namely a vehicle unit 5, a trailer unit 6 and an indicator 7 (shown only in Figure 1).

The vehicle unit 5 includes a mounting 8 by which the vehicle unit 5 is mounted on a tow bar 3 of the vehicle 1. The mounting 8 includes a socket arrangement into which the ball of tow bar 3 fits, together with a clamp to hold the vehicle unit 5 in position and still. This may be achieved by the use of a two-part clamp, or by a manually operated screw which tightens against the tow bar 3 to hold the vehicle unit 5 still. The unit 5 also includes an upright portion 9 which extends upwardly from the mounting 8, and above which is carried a detector portion 10.

A guide line 11 is extendable from the detector portion 10, and at its distal end includes a hook 12 for attachment to the trailer unit 6. The detector portion 10 includes a housing 15 from which the guide line 11 is extendable. Preferably, the guide line 11 is carried on a reel within the housing 15 which releases the guide line 11 resiliently as it

is pulled out. Alternatively, the guide line 11 can be arranged like a steel tape measure such that it seeks to become coiled itself.

In order to indicate the distance between the vehicle unit 5 and the trailer 6, the guide line 11 includes a finger 13 which, as the guide line 11 is received into the housing 15 of the detector portion 10 contacts a switch 14 in order that the device is able to indicate that the tow hitch 4 is less than a certain distance away from the tow bar 3. The finger 13 may be fixed at any of a number of positions along the guide line 11 such that the person hitching the trailer to the vehicle can decide how close he is happy to move the vehicle 1 to the trailer 2.

The housing 15 of the detector portion 10 is mounted such that it is angularly displaceable about a vertical axis with respect to the rest of the vehicle unit 5. Thus, referring to Figure 2, the housing 15 may be angularly displaced as is shown where the trailer 2 is offset from the axis of the vehicle 1. The housing 15 is mounted on a turntable (not shown) having a shaft which is connected to a rotary potentiometer. As the housing 15 is angularly displaced, the potentiometer is turned and, when connected to a suitable electric circuit, the angle of the housing relative to the vehicle unit 5 can be detected.

The indicator 7 includes a dial 16 which indicates the angle of the housing 15 relative to the vehicle unit 5. When the guide line 11 extends axially rearwards from the vehicle 1, a needle 17 on the dial 16 will point to zero in the centre, but when the housing 15 is angularly displaced to one side or the other, this is indicated by the needle 17 moving to one side or the other of the zero in order to indicate whether or not the person must steer to the left or to the right, and how tightly to turn.

The indicator 7 also includes a portion, which may be audible or visual, for example a buzzer, which indicates to the driver of the vehicle when the finger 13 has come into contact with the switch 14.

The electrical circuit which forms part of the device is powered either by internal batteries or from the car's own battery. In the latter case, the device may include a plug for insertion into a cigarette lighter in the vehicle 1 in order to power the electrical circuit, or may be connected directly to the battery of the vehicle.

The indicator 7 is connected by a long lead to the vehicle unit 5 so that the indicator 7 may be used by the driver in the front of the vehicle, while the vehicle unit 5 is at the

rear of the vehicle. Alternatively, the indicator 7 maybe permanently wired into the vehicle and a wiring socket fitted in a convenient position in the vehicle, for example, in the dashboard or the boot.

The trailer unit 6 attaches to the tow hitch 4 of the trailer 2, and includes means for attaching the unit 6 to the tow hitch 4 which, in this case, includes an element (not shown) which is inserted into the socket of the tow hitch 4. The trailer unit 6 includes an upright portion 18 upon which is mounted a connector 19 to which the hook 12 of the guide line 11 may be attached. In this case, the connector 19 is generally spherical, and the hook 12 is in the form of a cup which is placed over the connector 19 in order to engage with it.

In use, when it is desired to connect a trailer 2 to a vehicle 1, the vehicle 1 is put into the general proximity of the trailer 2, and the vehicle unit 5 is attached to the tow bar 3 of the vehicle 1 securely with the mounting 8. The trailer unit 6 is attached to the tow hitch 4 as shown in Figure 1.

The guide line 11 is then pulled from the housing 15 of the vehicle unit 5, and the hook 12 is connected to the connector 19 of the trailer unit 6. The indicator 7 is placed with the driver of the vehicle 1 in order that he may be able to view it. A power source is also connected, and as indicated above, this may be in the form of a plug which is pushed into a cigarette lighter of the vehicle 1. The driver of the vehicle 1 then reverses it towards the trailer 2 as shown in Figure 2.

When the guide line 11 moves away from the axis of the vehicle 1, the housing 15 is angularly displaced, and the potentiometer drives the indicator 7 to indicate that the vehicle 1 is not approaching the tow hitch 4 straight. It indicates that the tow hitch 4 is out of alignment relative to the vehicle 1. This is indicated on the dial 16 by the needle 17 moving away from the zero. The driver can then make steering adjustments to bring the needle 17 back towards the zero. Once the finger 13 comes into contact with the switch 14, a buzzer or other element in the indicator 7 operates to tell the driver that he is a predetermined distance from the tow hitch 4 and should stop. The trailer 2 may then be hitched to the tow bar 3 of the vehicle 1 with the minimum of difficulty.

A number of fingers 13 may be affixed to the guide line 11 at intervals and, when contact is made with the switch 14 by successive fingers, the volume or tone of the buzzer is increased or varied as an additional warning to the driver.

Of course, some modifications may be made to the embodiment shown. For example, the potentiometer could be replaced by a double acting pneumatically or hydraulically controlled piston/cylinder combination.

Also, instead of using a guide line 11, one or more laser or light beams could be used to determine the angle of the tow hitch 4 relative to the axis of the vehicle 1. One example of such an arrangement is to mount an optical device on the vehicle unit 5 of a type which includes an optical source which transmits a conical beam of light to the rear of the vehicle 1, and an optical detector integral with the source or separate therefrom for detecting light reflected from the tow hitch 4. A reflector on the tow hitch 4 of the trailer 2 reflects part of the beam of light from the source, and the optical detector is of a type which can detect the direction from which the light is received, and the distance of the tow bar 3 of the vehicle 1 from the tow hitch 4 of the trailer 2. The distance can be calculated in the same way that parking sensors fitted to cars determine the spacing from a parked car in front or to the rear of it.

Another arrangement is to employ two optical source/detectors, each mounted on the rear of the vehicle 1 towards it's near and off sides. Again, a reflector is mounted on the tow hitch 4 of the trailer 2. As the tow bar 3 approaches the tow hitch 4, the hitch's position relative to the vehicle 1 can be determined by analysis of the directions of the reflected light beams as they enter the detectors. Alternatively, if fixed direction sensors and sources are used, the beams can be arranged to cross at the point at which the tow bar 3 should be positioned near to the hitch 4. As the vehicle 1 is positioned, when the reflector mounted on the tow hitch 4 crosses the two beams, the detectors will detect this and the driver will be alerted.

Experienced users of this device might prefer that the ball at the end of the tow bar 3 and the tow hitch 4 are unobstructed by the device so that the vehicle 1 may be reversed such that the tow bar 3 is immediately below the tow hitch 4 whereby no movement of the trailer 2 is required, merely the lowering of the tow hitch 4 onto the tow bar 3. In such a case, the mounting of the vehicle unit 5 and the trailer unit 6 would have to be modified accordingly.

It would also be possible to mount the detector housing 15 and the guide line 11 on the tow hitch 4 instead of on the tow bar 3 of the vehicle. Clearly, besides the mounting of the device, this would require relatively little alteration. However, the preferred embodiment described above requires a shorter lead between the detector portion 10

and the indicator 7, and it is believed that the angle detected is more useful than if the detector was mounted on the tow hitch 4.

Various modifications can be made to indicate the distance between the tow bar 3 and the tow hitch 4. For example, the exact distance can be measured. To achieve this, the guide line might be calibrated, and the detector portion 10 include a counter for identifying how much of the guideline 11 has been extended from the housing 15. In such an instance, a further display can be included in the indicator 7 which shows the amount of guideline 11 which is extended from the housing 15.