NZ299808A - Tow ball; detail of flanged portion between ball and fastening means - Google Patents

Description

98 08 Patents Form 5 Priority Date(s):.

Complete Specification fiie-J: Glass: (8) ...SMo.Q.iP.J.j.QQ.j.-Q.k Publication Data: ll.mM O. Wo: <!+>2r N.Z. No.

NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION TOW BALL I, LEO LIVICK ROBINSON, a New Zealand citizen, of 37 Tui Road, Te Aroha, New Zealand, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- -1 - (Followed by page 1A) J 1 A 299508 TOW BALL This invention relates to a tow ball, particularly although by no means exclusively, to a tow ball for trailer couplings.

A conventional tow ball comprises a post, one end of which is formed in the shape of a ball and the other end being threaded to receive a lock nut. There is usually a flanged portion between the ball and threaded end of the post.

This type of tow ball is mounted to a tow bar attachment mounted on the towing vehicle. The threaded end of the tow ball post extends through a recess in the tow bar wherein the flanged portion of the tow ball abuts against the upper surface of the tow bar to thereby sit on top of the tow bar. The tow ball is then securely fastened to the tow bar by a lock nut threaded onto the threaded end of the tow ball post to abut against the lower surface of the tow bar. Plain washers and/or spring washers may also be used in the lock nut/threaded post arrangement to secure the fastening.

One disadvantage of this type of tow ball is that it can sometimes break at a point just below the flanged portion where the post is at its narrowest and, therefore, weakest point.

The present invention provides a tow ball which overcomes, at least to some extent, the aforesaid problem.

According to the present invention there is provided a tow ball comprising a post member, one end of which is formed in the shape of a ball and the other end comprising a fastening means, and having a flanged portion therebetween, wherein the flanged portion comprises two or more steps when viewed in longitudinal section.

In a second embodiment the flanged portion may comprise three steps when viewed in longitudinal section. 9 8 08 2 The first step of the flanged portion, located closest to the ball member, is preferably circular in axial cross-section and the diameter is larger than the second step which is also circular in axial cross-section and, the diameter of which in turn is larger than the next step.

The fastening means expediently comprise a threaded section of post located at said other end and associated lock nut.

Plain washers and/or spring washers may be used in the fastening arrangement.

A rotatable plate may be located in between the tow bar and uppermost step of the flange portion to support an arched safety device of the type disclosed in New Zealand Patent Specification No. 243843 or New Zealand Patent Specification No. 270661. One or more steps of the flanged portion may sit on top and/or within, the rotatable plate depending on the size of the recess of the rotatable plate.

The flanged portion comprising two or more steps when viewed in longitudinal section of the present invention provides increased post cross-sectional area thereby increasing the strength of the tow ball to avoid the problem of prior art tow balls breaking at a single weak point below a single stepped flange.

The invention will be further described with reference to the figures of the accompanying drawings in which: Figure 1 shows a conventional prior art tow ball; Figure 2a shows a tow ball of the present invention comprising a flange portion having two steps; Figures 2b-2d show the tow ball of Figure 2a coupled in differing ways to a tow bar; Figure 3a shows a tow ball of the present invention comprising a flanged portion having three steps; and Figures 3b and 3c show the tow ball of Figure 3a coupled in differing ways to a tow bar. 2$9808 3 Referring to Figure 1 it will be seen that a conventional tow ball comprises a post 12 having a ball shaped member 13 at one end of the post and fastening means comprising a threaded section of post 14, lock nut 17 and washer 16 at the opposite end of the post, and having a flanged portion 15 located between ball member 13 and bolt 14.

Figure 2a shows a tow ball 111 according to the present invention comprising a post 112 having a ball shaped member 113 at one end of the post 112 and fastening means 114 located at the opposite end of the post. Fastening means 114 comprises a threaded section of post 115, lock nut 116 and washer 117 arrangement. The tow ball 111 has a flanged portion comprising two steps 118 and 119 of circular axial cross-section wherein the diameter of step 118 (nearest the tow ball 113) is larger than step 119. The cross-section of steps 118 and 119 may be hexagonal or any other suitable shape.

To affix the tow ball 111 to a tow bar 121, the threaded section 115 of post 112 is placed through a recess 120 in tow bar 121. Depending upon the size of the recess 120, the step 119 of the flanged portion either sits above the tow bar 121, as shown in Figure 2b, or sits within tow bar 121 as shown in figure 2c. In the later case, the step 118 of the flanged portion is larger than recess 120 and sits above tow bar 121. The thickness of each step may vary to accommodate differing tow bar thicknesses.

In both cases the increased post cross-sectional area of the tow ball of the present invention provided by the flange portion comprising steps 118 and 119 increases the ball holding area and therefore the overall strength of the tow ball over the prior art devices.

The tow ball 111 is secured to a tow bar 121 by the nut 116 and threaded section 115 of post 112 arrangement. The nut 116 being threaded onto threaded section 115 of post 112 to abut the underside of tow bar 121 and fasten the tow ball 111 to the tow bar 121. A single plain washer 117 may be present, as shown in Figure 2b, located between the underside of tow bar 121 and the nut 116. Alternatively, both a spring washer 117a and plain washer 117 may be employed for extra securing of the tow ball 111 to the tow bar 121, as shown in Figure 2c.

In a further embodiment, as shown in Figure 2d, a rotatable plate 122 may be inserted between the tow bar 121 and step 118 of the flanged portion. The rotatable plate 122 may support a 29 9 8 0 § 4 safety arch locking device as disclosed in New Zealand Patent Specification Nos 243843 or 270661, or any other suitable locking device to prevent the tow ball 111 from becoming uncoupled from a trailer. The rotatable plate 122 comprises a recess 123 through which step 119 of the flanged portion is inserted. Step 118 of the flanged portion is larger than recess 123 and sits on the upper surface of the rotatable plate 122. A washer 124 is located under step 119 and between the underside of rotatable plate 122 and upper surface of tow bar 121 to ensure easy rotation of plate 122. The tow ball 111 is then secured to the tow bar 121 as described above with a washer 117, threaded section 115 of post 112 and lock nut 116 arrangement.

A further embodiment is shown in figures 3a-3c wherein the flanged portions of the tow ball 111 has three steps 118, 119 and 119a which decrease in size from 118, which is located nearest the ball member 113, to 119a, which is located nearest the threaded section 115 of post 112.

To fix the tow ball 111 to a tow bar 121 the threaded section 115 of post 112 is placed through a recess 120 in tow bar 121, said recess 120 being of a size to accommodate step 119a of the flanged portion whilst step U9 of the portion abuts the upper surface of tow bar 121. The tow ball 111 is secured to the tow bar 121 as previously described.

Figure 3c shows the tow ball 111 of figures 3a and 3b with an additional rotatable plate 122. The rotatable plate 122 is inserted between the tow bar 121 and step 118 of the flanged portion as described for figure 2d.

In all embodiments described herein, the tow ball may be made from known materials and may be produced by known methods. The tow ball may be integral or composed of individual parts and may be made in any suitable size or shape and fitted to a vehicle in any suitable way.

The presence of additional steps of the flanged portion provides extra post cross-sectional area on the tow ball which provides extra holding area and strength when in use for towing a trailer.

The tow ball may be used for any other type of coupling, for example, for use in towing boats, caravans etc.

It will be appreciated that it is not intended to limit the invention to the above examples only, many variations, such as might readily occur to a person skilled in the art being possible, without departing from the scope of the accompanying claims.

Claims (7)

299808 WHAT I CLAIM IS:

1. A tow ball comprising a post member, one end of which is formed in the shape of a ball and the other end comprising a fastening means, and having a flanged portion therebetween, wherein the flanged portion comprises two or more steps when viewed in longitudinal section.

2. A tow ball according to claim 1 wherein the flanged portion comprises three steps when viewed in longitudinal section.

3. A tow ball according to claim 1 or 2, wherein the steps of the flanged portion are circular in axial cross section.

4. A tow ball according to any one of claims 1-3, wherein the diameter of the first step is larger than the next step(s).

5. A tow ball according to any one of claims 1-4, wherein the fastening means comprises a threaded section of post and an associated lock nut.

6. A tow ball according to claim 5, wherein the fastening means further comprises plain washers and/or spring washers.

7. A tow ball according to any one of claims 1-6, further comprising a rotatable plate for supporting an arched safety device.