GB2429001A - Tow arm assembly - Google Patents

Abstract

A tow arm assembly comprises a mounting (10), an elongate arm (17) extending from the mounting (10) and having a hitch (22) at a distal end, and a spring (15) for biasing the arm (17) upwardly. A proximal end of the arm (17) is connected to the mounting (10) such that the distal end of the arm (17) can move in a vertical plane under an applied bias.

Description

Tow Arm Assembly This invention relates to a tow arm assembly for a

vehicle, which enables the vehicle to tow a wheeled article safely and securely.

Wheeled articles such as trolleys, roll cages, refuse bins and hospital beds etc often have to be moved over considerable distances by hand, which is difficult and time consuming, especially if the articles are heavy. Accordingly, it is desirable to be able to tow the articles behind a driven vehicle. However, most wheeled articles do not have any attachments or fittings which enable them to be towed.

It has been proposed to provide towing arms on vehicles which can be coupled to a frame or other point on the wheeled article. However, such arms are complicated to connect and disconnect, and often provid i..t. upiing w1iich can become detached when travelling over uneven ground.

We have now devised a tow arm assembly for a vehicle which alleviates the above-mentioned problems.

In accordance with this invention, there is provided a tow arm assembly for a vehicle, the assembly comprising a mounting, an elongate arm extending outwardly from the mounting and having an upstanding hitch at its outer end for engaging a wheeled article to be towed, and means for biassing the arm upwardly, the inner end of the arm being connected to the mounting by a coupling which permits the outer end of the arm to move in a vertical plane under the applied bias.

In use, the arm of the assembly is moved downwardly against the bias, whereupon the upstanding hitch is located under a portion of the article to be towed. The arm is then released to cause the arm to move upwardly so that the hitch engages the article.

When towing the article over uneven ground, the arm is able to move upwards and downwards in a vertical plane under the applied bias so that the hitch remains securely engaged with the article being towed.

Preferably adjustment means are provided for setting the hitch in a position in which an upwards bias is applied to the arm at all operating conditions of the vehicle when towing.

Preferably the coupling at the end of the arm also permits the arm to move in a horizontal plane so that articulation of the tow vehicle with respect to the wheeled article can occur, for example whilst manoeuvring corners.

Preferably an actuator is provided for moving the arm in the vertical plane when hitching or unhitching the wheeled article.

Preferably means are provided for locking the arm member to the mounting to prevent movement of the arm member relevant to the mounting when the assembly is not in use.

Preferably the coupling is arranged to maintain the aiPiie "f thc movement within said vertical plane.

Preferably the coupling comprises a shaft which is slidably mounted to a bracket of the tow arm assembly for vertical movement, the inner end of the arm being fixed to the shaft.

Preferably the shaft is able to rotate about its vertical longitudinal axis.

Preferably a spring is arranged to bias the shaft upwardly.

An embodiment of this invention will be described by a way of an example only and with reference to the accompanying drawings, in which Figure 1 is a side view of a tow arm assembly in accordance with this invention, when uncoupled from a wheeled article; and Figure 2 is a side view of the tow arm assembly of Figure 1, when coupled to a wheeled article.

Referring to Figures 1 and 2 of the drawings, there is shown a tow arm assembly comprising an upright mounting plate for attaching to the rear of a tow vehicle (not shown).

Upper and lower parallel projections ii, 12 extend outwardly from the rear face of the mounting plate 10 at respective locations, which are spaced apart vertically but which lie in a common vertical plane.

An elongate shaft 13 extends vertically through aligned S apertures formed in the projections 11, 12. The lower end of the shaft 12 extends below the lower projection 12 and comprises an enlargement (not shown) which prevents the shaft from being withdrawn upwardly through the aperture in the lower projection 12.

The upper end of the shaft 12 is externally screw threaded and carries an enlarged adjustment wheel 14, which can be moved axially upwardly and downwardly of the shaft 13 by respectively turning it clockwise or anticlockwise. An elongate helically-wound compression spring 15 is constrained vu Lhe shaft i between the adjustment wheel and the upper surface of the upper arm 11. A disc or cup 16 is located between the spring 15 and the adjustment wheel 14 to facilitate turning of the wheel 14 against the spring 15.

An elongate arm 17 extends radially outwardly from the shaft 13 at a point intermediate the upper and lower projections 11, 12. The shaft 13 is free to rotate about its vertical axis and the arm 17 is rigidly attached to the shaft 13. such that the arm 17 swings freely as the shaft 13 rotates.

A block 18 is mounted on the arms 17 at the point where it meets the shaft 13. The block 18 has a front vertical face 19, lying in a plane which extends normal to the axis of the arm 17.

The outer end of the arm 17 is cranked downwardly and is provided with a hitch 22 at its outermost end. The hitch 22 comprises inner and outer upstanding plates 20, 21 lying in respective parallel planes which extend normal to the axis of the arm 17, and which define a horizontal channel extending transversely of the arm 17.

Any elongate upright handle 23 is pivoted intermediate its opposite end, at point P, to the outer end of the upper projection 11 for rotation about a horizontal axis which extends perpenthcular to the projection ii. The upper end of the handle 23 is provided with an ergonomic hand grip 24. The lower end of the handle 23, below the pivot point P, is bifurcated and carries an elongate roller 25 mounted on an axle which extends between the lower ends of the bifurcated sectjog of the handle 23.

Referring to Figure 2 of the drawings, in use, the arm 17 can be connected to a wheeled article such as a roll cage 26, by Pivoting the handle 23 rearwardly in direction L: this brings the roller 25 down onto the arm 17 and urges the arm 17 downwardly against the spring bias.

Once lowered, the hitch 22 at the end of the arm 17 is positioned under a lower cross-member of the roll cage 26. The l lia1 23 is then pivoted forwardly in direction R, allowing the arm 17 to move upwardly under the spring bias until the cross member of the roll cage 26 is received in the channel of the hitch 22 at the end of the arm 17.

In this position, the arm 17 is securely engaged with the roll cage 26. The outer end of the arm 17 is adjustable in the vertical plane at point 27, to bring the hitch 22 into engagement with the roll cage 26. The outer end of the arm is set such that, on level ground the arm 17 is positioned at a point midway in the travel of the spring. These adjustments only need to be made prior to first use of the tow arm or when towing articles which are engaged at a different height.

As the vehicle and roll cage 26 travel over uneven ground, the arm 17 moves upwardly and downwardly under the applied spring bias, keeping the hitch 22 in constant secure engagement with the roll cage 26.

The attitude of the arm 17 is maintained because the cross-member of the roll cage 26 is a close fit within the channel of the hitch 22. During cornering, the shaft 13 rotates about its longitudinal vertical axis, thereby allowing the tow vehicle to freely articulate.

In order to decouple the roll cage 26 from the tow vehicle, the handle 23 is pulled rearwardly in direction L, thereby urging the arm 17 downwardly against the spring bias and disengaging the roll cage 26 from the channel of the hitch 22.

When not in use, the handle 23 is pulled further rearwardly, bringing the lower end of the handle 23 past its vertical position, whereupon the arm 17 begins to rise until the roller 25 abuts the rear face 19 of the block 18. The upwards bias of the Spring 15 on the arm 17 urges the roller upwardly against the rear flat face 19 of the block 18, causing the arm 17 to be held securely in its central outward position and preventing it from moving in both vertical and horizontal planes.

A t asi sembiy in accordance with this invention is simple in construction, yet provides a secure coupling between a tow vehicle and a wheeled article such as a roll cage.

Claims (10)

1. Claims 1. A tow arm assembly for a vehicle, the assembly comprising a

   mounting, an elongate arm extending outwardly from the mounting and having an upstanding hitch at its outer end for engaging a wheeled article to be towed, and means for biassing the arm upwardly, the inner end of the arm being connected to the mounting by a coupling which permits the outer end of the arm to move in a vertical plane under the applied bias.
2. 2. A tow arm assembly as claimed in claim 1, in which adjustment means are provided for setting the hitch in a position in which an upwards bias is applied to the arm at all operating conditions of the vehicle when towinc.
3. 3. A tow arm assembly as claimed in claims 1 or 2, in which the coupling at the end of the arm also permits the arm to move in a horizontal plane so that articulation of the tow vehicle with respect to the wheeled article can occur.
4. 4. A tow arm assembly as claimed in any preceding claim, in which an actuator is provided for moving the arm in the vertical plane when hitching or unhitching the wheeled article.
5. 5. A tow arm assembly as claimed in any preceding claim, in which means are provided for locking the arm member to the mounting to prevent movement of the arm member relevant to the mounting when the assembly is not in use.
6. 6. A tow arm assembly as claimed in any preceding claim, in which the coupling is arranged to maintain the attitude of the arm during movement within said vertical plane.
7. 7. A tow arm assembly as claimed in any preceding claim, in which the coupling comprises a shaft which is slidably mounted to a bracket of the tow arm assembly for vertical movement, the inner end of the arm being fixed to the shaft.
8. 8. A tow arm assembly as claimed in claim 7, in which the shaft is able to rotate about its vertical longitudinal axis.
9. 9. A tow arm assembly as claimed in claim 7 or claim 8, in which a Spring is arranged to bias the shaft upwardly.
10. 10. A tow arm assembly substantially as herein described with reference to the accompanying drawings.