AU717032B2 - An improved trailer hitch - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: Actual Inventor: ANTONIO CARTA ANTONIO CARTA Address for Service: CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, Qld. 4000, Australia.

AN IMPROVED TRAILER HITCH V-0 0 .00.

0 Invention Title: Details of Associated Provisional Applications: No. PN6550 filed 13 November 1995 No. P00100 filed 28 May 1996 The following statement is a full description of this invention, including the best method of performing it known to me: 2 THIS INVENTION relates to an articulated connection between a towing vehicle (or prime mover) and a towed vehicle (or trailer) In particular, the invention is directed to a weight transfer hitch for a trailer, particularly a sugar cane transporter, although the invention is not so limited.

BACKGROUND ART During harvesting of sugar cane, the cane stalks are cut into billets by the cane harvester, and dropped into a sugar cane transporter. Typically, the transporter comprises a bin-like structure mounted on a trailer. The trailer is towed by a suitable prime mover, such as a tractor, and the combination is commonly referred to as a "haul-out". Once filled, the transporter is taken to a railway siding where the cane billets are transferred to rail-mounted bins.

Alternatively, the cane may be delivered by the transporter to another transfer station or direct to a sugar cane mill. Typically, two or more haul-outs work 20 in tandem, shuttling between the cane harvester and the siding, other transfer station, or mill.

*--The centre of gravity of the transporter is usually located forward of the trailer axle. Hence, some the weight of the transporter is transferred through the trailer hitch to the tractor.

With such weight transfer hitches, it has been found that if the prime mover turns too sharply, the trailer may overturn. In particular, if the prime mover turns through an angle greater than about 450 at normal S 30 operating speeds, the trailer tends to dip sideways, lifting the inside wheel and making the vehicle unstable.

If the trailer overturns, it may also cause the prime S• mover to overturn, posing a very serious safety risk to the driver.

Known weight transfer hitches generally comprise two degrees of freedom of movement. Namely, the hitches include a pivot joint with a vertical pivot axis to enable the prime mover to turn relative to the trailer, and a rotational joint with a longitudinal horizontal axis to enable the trailer to roll relative to the tractor. Not only does this second degree of freedom of movement allow the trailer to follow undulations in the ground independently of the tractor, but it also provides a safety measure as it allows the trailer to roll in extreme situations without necessarily tipping the prime mover also.

However, it has been found that the arrangement of the joints in weight transfer hitches of conventional design does not permit the trailer to roll freely unless its longitudinal axis is substantially aligned with the longitudinal axis of the prime mover, i.e. when the prime mover is towing the trailer in a substantially straight line. When the prime mover is turning and the longitudinal axis of the trailer is angled to the longitudinal axis of the prime mover, the trailer is no longer able to roll entirely freely. If the inside wheel of the trailer rises to ride over a bump in the ground while the prime mover is turning, the conventional hitch design does not permit the trailer to roll back to a *--stable horizontal position immediately after the bump is cleared. The wheel tends to stay raised until the prime mover and trailer realign. Consequently, the trailer is more likely to roll as it is pulled around the corner in an inclined orientation.

Known hitches are therefore not considered satisfactory, particularly when turning sharply under load, on undulating terrain such as found in cane fields.

It is an object of the present invention to provide an improved trailer hitch.

S: SUMMARY OF THE INVENTION In one broad form, the present invention provides a hitch assembly for connection between a prime mover (or leading) vehicle and a trailer (or following) vehicle, the hitch assembly comprising a first joint having two portions pivotable relative to each other about a vertical axis, one portion being connected, or adapted to be connected in use, to the prime mover, a rotational joint having two portions rotatable relative to each other about a horizontal axis, one portion being connected, or adapted to be connected in use, to the trailer and the other portion being connected to the other portion of the first joint.

The connections to the prime mover and trailer may be direct or indirect connections.

Preferably, the hitch assembly also comprises a second joint having two portions pivotable relative to each other about a vertical axis, one portion being connected, or adapted to be connected in use, to the trailer and the other portion being, or being connected to, the other portion of the rotational joint.

The hitch assembly suitably includes means biasing the second joint against pivotal movement. The biasing means may suitably comprise pneumatic cylinders, springs or other resilient biasing mechanism.

20 Typically, the angular movement of the first joint is limited to about 450 either side of its straightline orientation where the trailer and prime mover are longitudinally aligned).

The hitch assembly of the preferred embodiment permits two pivot actions and a rolling action. When the prime mover is towing the trailer in a substantially straight line, the rotational joint permits the trailer to freely roll about a longitudinal horizontal axis to follow undulations of the ground. During turning, there 30 will be angular movement between the prime mover and the trailer initially about the first pivot joint only (as S• the second joint is biased against pivotal movement) •The joints in the hitch assembly are so arranged that the horizontal (rolling) axis of the rotational joint remains aligned with the longitudinal axis of the trailer.

Hence, the trailer is still able to roll freely about its longitudinal horizontal axis (which is now angled to the longitudinal horizontal axis of the prime mover). This maintains stability while turning, particularly on undulating terrain.

Further, the angular movement of the first joint is limited (to roughly 450). If the prime mover turns to a greater degree, the trailer can also pivot about the second joint against its bias. Sharp turns are effectively divided into two pivot actions by limiting the maximum angular movement of the main joint. Hence, no joint will turn more than about 450, thereby avoiding excessive overturning force on the trailer.

In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side elevational view of a weight transfer trailer hitch according to one embodiment of the invention; Fig. 2 is an exploded side elevational view of 20 the hitch of Fig. 1; and ~Figs. 3A to 3C are plan views of the hitch of Fig. 1 at various orientations.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings, the weight transfer hitch 10 comprises a first clevis joint formed by an inner (or secondary) C-shaped clevis component 11 pivotally mounted, top and bottom, to an outer (or main) C-shaped clevis component 12 along the same vertical pivot axis. The outer clevis 12 is fixed to brackets 13 which are connected to a towing frame 14 by bolts The towing frame 14 is suitably mounted to the rear of a S" prime mover, such as a tractor (not shown) •A transverse plate 16 extends between the brackets 13, adjacent the inner clevis 11, and forms the web for the outer clevis 12. The inner clevis 11 is pivotable relative to the outer clevis 12 about the vertical axis, but the transverse plate 16 limits the angular extent of its rotation (as described in more detail hereafter) The inner clevis 11 is generally C-shaped in vertical section as shown in Figs. 1 and 2. A short horizontal shaft 17 has one end fixed rigidly to the web portion of the inner clevis 11. The shaft 17 forms a stub axle for a collar 18 which is rotatably mounted thereon, and retained axially by end plug 24. The collar 18 and shaft 17 form a rolling joint.

An outer (or "trailer") clevis 19 is pivotally connected to the collar 18, to form a second clevis joint. The trailer clevis 19 is formed by two spaced flanges which are pivotally connected to the top and bottom, respectively, of the collar 18, and which are fixed by bolting or welding) to the leading end of the drawbar 20 of a trailer, as can be seen in Fig. 1.

In its operative orientation, the trailer clevis 19 is pivotable about a vertical axis relative to the collar 18.

A pair of horizontal flanges 21 extend from 20 opposite sides of the ,collar 18 as can be seen in Fig.

3A. A pneumatic cylinder 22 has the end of its ram pivotally connected to a respective flange 21, while the opposite end of the cylinder housing is pivotally connected to a respective bracket 23 fixed to the side of the drawbar 20, as shown in Fig. 1.

The pneumatic cylinders 22 resiliently bias the trailer drawbar 20 to a straight line configuration with the collar 18. That is, the pneumatic rams 22 bias the drawbar to align with the axis of stub shaft 17, and S 30 resist pivotal motion of the second clevis joint.

Although the abovedescribed hitch is "double jointed", the pneumatic cylinders 22 "stiffen" the second joint against pivotal motion.

In use, if the prime mover turns while travelling, it will pivot relative to the trailer about the first clevis joint. That is, the relative pivoting between the prime mover and the trailer will be at the first (or main) clevis joint only, as the second clevis joint is biased against pivot action by pneumatic cylinders 22.

Since the second clevis joint does not pivot, the drawbar 20 connected to the second clevis joint remains aligned with the axis of the collar 18 and shaft 17. Even though the tractor is turning, the shaft 17 of the rolling joint turns relative to the tractor, about the pivot axis of the first clevis joint, to remain aligned with the longitudinal axis of the trailer. The trailer therefore retains its independent rolling ability during the turn, resulting in greater stability during turning manoeuvres.

Additionally, the pivoting action of the first clevis joint is angularly limited to roughly 450 either side of the centreline axis. As can be seen more clearly in Fig. 3B, the inner clevis component 11 is so constructed that it abuts the transverse plate 16 if it turns about 450 either side of the centreline axis. Such physical abutment of the inner clevis component 11 against the transverse plate 16 limits the angular range of the pivot action of the first clevis joint.

i' Due to the limited angular range of the first clevis joint, if the tractor turns sharply more than about 450), the drawbar 20 also pivots about the second clevis joint, against the bias of the pneumatic cylinders 22. Conversely, when the trailer realigns with the direction of motion, the second clevis joint is returned to its rest position under the biasing action of the pneumatic cylinders, before there is any substantial 30 pivotal motion of the first clevis joint.

It will be evident to those skilled in the art •that during normal turning of the prime mover, the trailer will pivot about the first clevis joint only and the trailer will retain freedom of rolling movement.

However, if the prime mover turns too sharply, the hitch will pivot about the second clevis joint also. This provides better weight transfer during sharp turning, and minimises the risk of overturning.

8 Further, as the second joint is pivotable about the horizontal stub axle 17, the trailer may tip without overturning the prime mover. This ensures that even if the trailer does overturn, the driver of the prime mover is not put in danger.

The foregoing describes only one embodiment of the invention, and modifications which are obvious to those skilled in the art may be made thereto without departing from the scope of the invention.

For example, the pneumatic cylinders 22 may be replaced by springs or any other resilient biasing means.

Further, although the trailer hitch has been described with particular reference to its use on a sugar cane transporter, it can also be used in other applications, such as semi-trailers, multiple trailer arrangements.

etc.

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Claims (20)

1. A hitch assembly for connecting a trailer to a prime mover, the hitch assembly comprising a first pivot joint having two portions pivotable relative to each other about a vertical axis, one portion being connected, or adapted to be connected in use, to the prime mover, a rotational joint having two portions rotatable relative to each other about a horizontal axis, one portion being connected to the other portion of the first joint, a second pivot joint having two portions pivotable relative to each other about a vertical axis, one portion being connected, or adapted to be connected 15 in use, to the trailer, and the other portion being, or being connected to, the other portion of the rotational joint. o o

2. A hitch assembly as claimed in claim i, further -comprising means for biasing the second joint against pivoting out of a straightline configuration.

3. A hitch assembly as claimed in claim 2, wherein the biasing means comprises at least one pneumatic cylinder.

4. A hitch assembly as claimed in claim 2, wherein 25 the biasing means comprises at least one coil spring.

A hitch assembly as claimed in any preceding claim, wherein the pivot axes of the first and second pivot joints are substantially coaxial.

6. A hitch assembly as claimed in claim 5, wherein the horizontal rotational axis of the rotational joint is substantially coplanar with the pivot axes of the first and second pivot joints.

7. A hitch assembly as claimed in any preceding claim, wherein the second pivot joint is a clevis joint.

8. A hitch assembly as claimed in any preceding claim, wherein the first pivot joint is a clevis joint.

9. A hitch assembly as claimed in any preceding claim, further comprising means for limiting pivotal claim, further comprising means for limiting pivotal movement of the first pivot joint to about 450 from its straightline orientation.

A hitch assembly as claimed in any preceding claim, wherein the rotational joint comprises a stub axle connected at one end thereof to said other portion of the first pivot joint, and a collar member rotatably mounted to the stub axle and rotatable about the longitudinal axis of the stub axle.

11. A hitch assembly as claimed in claim wherein the other portion of the first pivot joint is a C-shaped member having a central web portion, the stub axle being connected perpendicularly to the web portion.

12. A trailer having a weight transfer hitch assembly for connection to a towing vehicle, the hitch 15 assembly comprising a first clevis joint having an inner C-shaped member pivotally mounted within an outer C-shaped member, the two members being relatively pivotable about a first vertical pivot axis, 20 a rotational joint comprising a stub axle having one end fixed to a central portion of the inner C- shaped member and extending substantially horizontally therefrom, and a collar rotatably mounted on the stub axle and rotatable about a horizontal axis, and 25 a second clevis joint comprising a pair of spaced connector members respectively connected to the top and bottom of the collar, the connector members being pivotable relative to the collar about a second vertical pivot axis, the connector members being connected to the leading end of the trailer.

13. A trailer as claimed in claim 12, further comprising means for resiliently biasing the second clevis joint to an orientation wherein the rotational axis of the rotational joint is parallel to the longitudinal axis of the trailer.

14. A trailer as claimed in claim 13, wherein the biasing means comprises at least one pneumatic cylinder.

A trailer as claimed in claim 13, wherein the 11 biasing means comprises at least one coil spring.

16. A trailer as claimed in any one of claims 12 to further comprising means for limiting the pivotal movement of the first clevis joint to about 450 either side of a straightline orientation.

17. A trailer as claimed in any one of claims 12 to 16, wherein the limiting means comprises a central portion of the outer C-shaped member adapted to abut the inner C-shaped member when the outer C-shaped member pivots about 450 relative to the inner C-shaped member.

18. A trailer hitch having first and second pivot joint assemblies each having two portions pivotable relative to each about the same vertical axis, the second pivot joint assembly being rotatable relative to the 15 first pivot joint assembly about a horizontal axis.

19. A trailer hitch as claimed in claim 18, wherein the pivotal movement of the first pivot joint assembly is limited to a predetermined angular displacement, and the second pivot joint assembly is biased against pivotal movement.

20. A trailer hitch substantially as hereinbefore described with reference to the accompanying drawings. 4*