AU667513B2

AU667513B2 - Lifting tow bar

Info

Publication number: AU667513B2
Application number: AU35307/93A
Authority: AU
Inventors: Kevin John Prater
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-03-17
Filing date: 1993-03-17
Publication date: 1996-03-28
Anticipated expiration: 2013-03-17
Also published as: AU3530793A

Description

6751 3

AUSTRALIA

P/00/011 Regulation 3.2 PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 0 Go0 0 a o e oo 0 a 0 o 0 0 *Q a o oo a a D o 0 Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: 10 Bushby Street Bellevue WA, 6056 Australia Kevin J. Prater GRIFFITH HACK CO, Patent Trade Mark Attorneys 256 Adelaide Terrace PERTH WA, 6000 KEVIN J. PRATER 0 0 0 0 Standard Complete Specification for the invention entitled: LIFTING TOW BAR Details of Associated Provisional Applications: 0 00 00000 Details of Parent Application for Divisional Applications: The following is a full description of this invention, including the best method of performing it known to me:- -2- LIFTING TOW BAR The present invention relates to a lifting tow bar for towing a trailer and relates particularly, though not exclusively, to a lifting tow bar for a mobile field bin.

Throughout the specification particular reference will be made to a mobile field bin for temporarily storing and transporting grain during harvesting. However, it should be understood that the invention can be used for towing many other kinds of trailer, where the term "'trailer" should be understood in the broad sense of a wheeled vehicle drawn by another vehicle.

0.O A field bin is a bin or silo for temporarily O Oostoring grain or lupins, which is mounted on a wheeled S 15 frame or chassis so that it can be transported to selected locations in the field. The field bin is typically located in a field which is being harvested and is used to temporarily store the grain while a truck transports the :Vo. grain to a larger, remotely located silo. The field bin is 20 fitted with an auger and can be emptied to reload the transporting truck when it returns empty from the silo.

The chassis of the field bin is designed to be lowered onto *o the ground so that the bin is supported in a stable position during loading and unloading.

°o 25 Preferably, once the field bin has been located in a field, the vehicle used to tow the field bin is unhitched so that it is not sitting idle in the field and can be used for other purposes. However, even when the field bin is empty it requires considerable strength to manually unhitch the tow bar from the vehicle, and the lifting and lowering operation places considerable strain on the back. When it is necessary to relocate the field bin, the tow bar must be lifted back onto the tow pivot of the towing vehicle and the same difficulties are encountered. Similar problems are encountered with other 3 types of trailers.

The present invention was developed with a view to providing a lifting tow bar that takes some of the strain out of hitching and/or unhitching a trailer to a towing vehicle.

According to the present invention there is provided a lifting tow bar for towing a trailer, the tow bar comprising: a draw bar adapted to couple the trailer to a tow pivot on a towing vehicle, said draw bar being pivotally connected to the trailer at a first pivot point; a lever arm pivotally connected at one end to the trailer at a second pivot point which is spaced apart from said first pivot point, the other end of the lever arm being free to move; a compression arm pivotally connected at one end ist t to the draw bar and pivotally connected to the lever arm at a point intermediate said one end of the lever arm and said free end of the lever arm, wherein said compression arm can I.l 20 act as a fulcrum for the lever arm when a downwards force is applied to the free end of the lever arm whereby, in use, said lever arm can apply a lifting force to the FF44 trailer at said second pivot point.

IPreferably said compression arm is pivotally connected to said lever arm at a point intermediate a mid point of the lever arm and said one end of the lever arm.

F 44 Preferably said one end of the compression arm is pivotally 4 I, connected to the draw bar at a point adjacent the end taisgh is coupled to the tow pivot on the towing vehicle.

Advantageously said lever arm pivots about said intermediate point between a first position, in which the weight of the trailer at the first pivot point cannot be transferred to the tow pivot, and a second position in which the weight of the trailer at the first pivot point can be transferred to the tow pivot. In said second position, said lever arm is typically substantially aligned Swith said compression arm, so that part of the weight of c 4 4 the trailer at said first pivot point can be transferred to the tow pivot by said compression arm. Preferably means are provided for locking the lever arm in the second position.

In the preferred embodiment said draw bar is one of a pair of draw bars pivotally connected to the trailer at spaced apart first pivot points; said lever arm is one of a pair of lever arms pivotally connected to the trailer at spaced apart second pivot points; and, said compression arm is one of a pair of compression arms pivotally connected to a respective one of said pair of draw bars and pair of lever arms. Preferably said pair of draw bars are pivotally connected at one end to the trailer at said spaced apart first pivot points, and are rigidly connected to a common coupling plate at the other end.

According to another aspect of the present invention there is provided a mobile field bin comprising: a silo; a wheeled chassis on which the silo is mounted; and, a lifting tow bar for coupling the field bin to a towing vehicle, the tow bar comprising: a draw bar adapted to couple the field bin to a tow pivot on the towing vehicle, said draw bar being

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pivotally connected to a supporting leg of the chassis at a

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first pivot point; a lever arm pivotally connected at one end to the supporting leg at a second pivot point which is spaced apart from said first pivot point, the other end of the lever arm being free to move; a compression arm pivotally connected at one end to the draw bar and pivotally connected to the lever arm at a point intermediate said one end of the lever arm and said .iree end of the lever arm, wherein said compression arm can Xact a. fulcrum for the lever arm when a downwards force i; L is applied to the free end of the lever arm whereby, in use, said lever arm can apply a lifting force to the supporting leg of the chassis at said second pivot point.

In order to facilitate a better understanding of the nature of the invention a preferred embodiment will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a preferred embodiment of the tow bar on a field bin, shown in a first (lowered) position; and, Figure 2 is similar to Figure 1 except the tow bar is shown in a second (lifting) position.

The preferred embodiment of the lifting tow bar illustrated in Figures 1 and 2 is fitted to a mobile field bin 12 comprising a circular silo 14 mounted on a o wheeled chassis 16. The tow bar 10 is designed to allow 4the field bin to be towed behind a towing vehicle 18. The wheeled chassis 16 is provided with a lowering/raising mechanism (not illustrated) for lowering the field bin onto the ground at a required location.

The illustrated embodiment of the lifting tow bar 10 comprises a pair of draw bars 20, each draw bar being pivotally connected at one end to a supporting leg 22 of the wheeled chassis 16 at a first pivot point 24. The 25 other ends of the respective draw bars 20 are rigidly connected to a common coupling plate 26 adapted to couple the field bin to a tow pivot 28 on the towing vehicle 18.

The tow bar 10 further comprises a pair of lever arms each lever arm 30 being pivotally connected at one end to a respective supporting leg 22 of chassis 16 at a second pivot point 32. The other end of each lever arm 30 is free to move.

A pair of compression arms 34 are pivotally connected at one end to a respective one of the draw bars 20, and are pivotally connected at the other end to a respective one of the lever arms 30 at a point 36 intermediate the length of each lever arm 30. Typically, i- r lU; 6 the compression arms 34 are pivotally connected to the respective draw bars 30 at a point 38 adjacent coupling plate 26.

The location of each of the pivot points 24, 32, 36 and 38 can be varied in use to suit the particular application and to obtain the most favourable mechanical action. For example, the nearer intermediate pivot points 36 are located to the second pivot points 32, the greater the mechanical advantage provided by lever arms The lifting tow bar 10 operates as follows.

Figure 1 illustrates the tow bar in a first, lowered position in which the front end of the field bin 12 is resting on the ground. In this position, the weight of the field bin 12 at the first and second pivot points 24, 32 1 15 cannot be transferred to the tow pivot since there is no rigid connection between the coupling plate 26 and the field bin 12. Each draw bar 20, lever arm 30, compression arm 34 and supporting leg 22 form a quadrilateral shape, and two of the pivot points 36, 38 are free to move relative to the first and second pivot points 24, 32. If V- an upwards force is applied to the free ends 40 of lever t" A arms 30 the respective draw bars 20 can be lifted, via the compression arms 34, so that the coupling plate 26 can be pivotally connected to tow pivot 28 of the towing vehicle 25 18. The only weight that is lifted is the combined weight of the draw bars 20 and compression arms 34, and therefore I, there is very little strain on the operator's back. The position of the intermediate pivot points 36 on lever arm also provides a degree of mechanical advantage during lifting.

Once the coupling plate 26 has been pivotally connected to the towing pivot 28 the operator applies a downwards force to the free ends 40 of lever arms 30 in order to lift the front end of field bin 12 to a suitable height for towing. As can be seen most clearly in Figure 1, when a downwards force is applied to the free ends 40 of lever arms 30, each pivotal connection of the compression I I 7 arms 34 at intermediate pivot points 32 provides a fulcrum for the lever arms 30 whereby the lever arms 30 apply a lifting force to the front end of the field bin 12 at the second pivot points 32. As the free ends 40 of lever arms 30 pivot downwards the weight of the front end of field bin 12 is transferred to the tow pivot 28 via compression arms 34 and draw bars 20, until both lever arms 30 are substantially aligned with the respective compression arms 34 as illustrated in Figure 2.

In the position of the lifting tow bar illustrated in Figure 2, the respective lever arms compression arms 34, draw bars 20 and supporting legs 22 form a rigid triangle shape, which can be locked in this position by a locking pin (not illustrated) which passes through a pair of apertures 42 in the free end of each lever arm 30 and a matching bore 44 in each compression arm 34. In this second, lifting position of the tow bar Ill t substantially all of the weight of the front end of the field bin 12 on the respective supporting legs 22 is transferred to the towing pivot 28 on the towing vehicle.

Because of the mechanical advantage provided by lever arms the downward force required at the free ends 40 of lever arms 30 is much less than the actual force required to lift the front end of the field bin. Furthermore, as only a downwards force is required to lift the field bin the risk of operator back injury is substantially eliminated. In order to lower the field bin substantially the reverse of the lifting procedure described above is followed.

The draw bars 20, lever arms 30 and compression arms 34 of the tow bar 10 can be manufactured from any suitably rigid material. In the illustrated embodiment the draw bars 20 and compression arms 34 are manufactured from hollow, galvanised steel tubing, crimped at the ends to form the pivotal connections. The lever arms 30 are manufactured from hollow, U-shaped section galvanised steel members sized to receive the compression arms 34 within the 8 open end of the U-shaped section, as illustrated in Figure 2.

Now that a preferred embodiment of the lifting tow bar 10 has been described in detail, numerous variations and modifications, in addition to those already described, will suggest themselves to persons skilled in the mechanical arts without departing from the basic concepts of the invention. For example, each lever arm may be provided with a handle or grip mounted adjacent the respective free ends 40 to enable the lever arms 30 to be more easily gripped by the operator. It will be apparent that the relative lengths of the draw bars 20, lever arms and compression arms 34 may be varied to suit th.

particular application, as can the relative positions of 15 the pivot points 24, 32, 36 and 38. Obviously the first i o and second pivot points 24 and 32 need not be on a common 3osupport leg 22, or even located one above the other as in a. 0 r the illustrated embodiment. Furthermore, although in the described embodiment it is advantageous to have a pair of draw bars 20, a pair of compression arms 34 and a pair of j lever arms 30, exactly the same principal can be applied using a single draw bar, a single lever arm and a single compression arm. All si.ch variations and modifications are to be considered within the scope of the present invention, 25 the nature of which is to be determined from the foregoing description and the appended claims.

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Claims

2. A lifting tow bar as claimed in claim i, wherein said compression arm is pivotally connected to said lever arm at a point intermedi.ate a mid point of the lever arm and said one end of the lever arm.
3. A lifting tow bar as claimed in claim 2, wherein '4 said one end of the compression arm is pivotally connected to the draw bar at a point adjacent the end which is coupled to the tow pivot on the towing vehicle and the other end of the compression arm is pivotally connected to the lever arm at said intermediate point.
4. A lifting tow bar as claimed in claim 3, wherein said lever arm pivots about said intermediate point between a first position, in which the weight of the trailer at the first pivot point cannot be transferred to the tow pivot, and a second position in which the weight of the trailer at -i t -i i I 10 the first pivot point can be transferred to the tow pivot. A lifting tow bar as claimed in claim 4, wherein in said second position, said lever arm is substantially aligned with said compression arm, so that part of the weight of the trailer at said first pivot point can be transferred to the tow pivot by said compression arm.
6. A lifting tow bar as claimed in claims 3 or 4, wherein means are provided for lolking the lever arm in the second position.
7. A lifting tow bar as claimed in claim 6, wherein said locking means comprises a locking pin removably received through a pair of apertures provided in the free end of the lever arm and a matching bore in the compression arm.
8. A lifting tow bar as claimed in any one of the preceding claims, wherein said draw bar i. one of a pair of draw bars pivotally connected to the trailer at spaced apart first pivot points; said lever arm is one of a pair of lever arms pivotally connected to the trailer at spaced apart second pivot points; and, said compression arm is one of a pair of (i compression arms pivotally connected to a respective one of said pair of draw bars and pair of lever arms.
9. A lifting tow bar as claimed in claim 8, wherein said pair of draw bars are pivotally connected at one end to the trailer at said spaced apart first pivot points, and are rigidly connected to a common coupling plate at the other end.
110. A mobile field bin comprising: /z Ra silo; 11 a wheeled chassis on which the silo is mounted; and, a lifting tow bar for coupling the field bin to a towing vehicle, the tow bar comprising: a draw bar adapted to couple the field bin to a tow pivot on the towing vehicle, said draw bar being pivotally connected to a supporting leg of the chassis at a first pivot point; a lever arm pivotally connected at one end to the supporting leg at a second pivot point which is spaced apart from said first pivot point, the other end of the lever arm being free to move; a compression arm pivotally connected at one end to the draw bar and pivotally connected to the lever arm at a point intermediate said one end of the lever arm and said free end of the lever arm, wherein said compression arm can Ott. t, act as a fulcrum for the lever arm when a downwards force is applied to the free end of the lever arm whereby, in use, said lever arm can apply a lifting force to the supporting leg of the chassis at said second pivot point. 11. A lifting tow bar substantially as herein described with reference to and as illustrated in the accompanying drawings. Dated this 22nd day of January 1996. KEVIN J. PRATER By His Patent Attorneys GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. ABSTRACT A lifting tow bar (10) for towing a trailer such as, for example, a mobile field bin The tow bar comprises a pair of draw bars pivotally connected to a supporting leg (22) of the wheeled chassis (16) of the field bin at a first pivot point A pair of lever arms (30) are pivotally connected to a respective supporting leg (22) of the chassis (16) at a second pivot point The other ends of the lever arms (30) are free to move. A pair of compression arms (34) are pivotally connected to a respective one of the pair of draw bars and pair of lever arms Each compression arm is pivotally connected to a lever arm (30) at a point (36) intermediate the length of the lever arm so that the compression arm (34) can act as a fulcrum for the lever arm when a downwards force is applied to the free end of the lever arm In this way, the lever arms can be used to apply a lifting force to the front end of the field bin The mechanical advantage afforded by the lever arms (30) substantially reduces the force required to lift the front end of the field bin The lifting tow bar (10) of the invention greatly simplifies r hitching and unhitching of the field bin (12) to a tow pivot (28) of a towing vehicle (18). r6