AU687700B2 - Pivotable lifting arm apparatus - Google Patents

Description

PIVOTABLE LIFTING ARM APPARATUS The present invention relates to pivotal lifting arms and, in particular, to an apparatus which assists in the pivotal movement of the lifting arm, the apparatus providing a mechanical advantage to normal pivotal operation and being reliable for extended periods of heavy use thereof.

BACKGROUND TO TEIE INVENTION It has become the practice that loose loads such as coal in coal trucks are covered according to regulations which are presently in force. Such regulations are in place to ensure that the load, such as coal, is nor dislodged and spilled from the truck when in 10 motion on the roads.

S-There are a number of different systems or apparatuses, whethler automatic or manual, which are used to cover such loose loads. One such system includes a roller mounted to the front of the body of an open topped truck with a bowed steel rod connected to one end of the cover material, the bowed steel rod being moved longitudinally along the sides of 15 the body by a wire rope and pulley arrangement which is mounted on both sides of the truck body, This roller is driven by a winch in both the forward and reverse directions to cover and uncover the load respectively.

Such a system has difficulty trying to pass over heaps of coal loaded in the body of the truck by a front end loader, as one example. Such a system works well for loads which are no higher than the sides of the body, for example, high density loads such as sand, gravel and aggregate. However, it is totally unacceptable for loads such as coal due to the nature of the heaped coal loaded in the trucks.

Another system developed by the inventor of the present invention, provides a cover system which moves the cover over the load from side to side different to the front to rear movement of the previously described system. In this system, the cover is on a roller with its free end attached to a cable which extends the length of the body of the truck. The front and rear ends of the cable are both connected to pivotable arms attached and pivotable about the central point of a cross arm which is located across the body and which spans the width of the body. Thus the pivot arm when moved by a drive means draws the bar and hence the cover, in an arc over the top of the body. Therefore, if for example, the width of the body is approximately 2.5 metres wide and the pivot arm is approximately 1.25 metres in length, the cover is able to successfiully pass over a load of coal which is up to at least 1 metre higher than the sides of the body. This means that the system is able to cover coal loads, and other types of similar type loads, without having difficulties such as jamming and the like.

In the system as so described, the drive means is realised by the use of a 1300 Newton gas spring and a winch, the gas spring being held horizontally in the compressed state when the cover is rolled upon the roller in its unused state being connmected between a fixed position on the cross arm and a position on the pivotal arm. The winch is activated by a switch, preferably located in the drivers cabin, which releases the cover from the roller.

The gas spring compression is released and forces the pivot arm to pivot 180 degrees about i: 1 the central position on the cross arm. The gas spring is substantially at its greatest extent a e 15 when the pivot arm is substantially horizontal in the covered position, A limit switch is used to turn offthe winch when the cover is in position and thus be locked in this position.

f It is noted that the gas spring is substantially horizontal when the cover is in the covered position and also when it is unused. This arrangement causes failure in the gas spring as the oil around the seal of the gas spring tends to be allowed to settle on the underside of the seal only and not around it for normal sealing action. Over a short period of time, even though there are a substantial number of operations of the apparatus, the seal of the gas spring fails and hence the apparatus fails and requires replacement parts. This is unsatisfactory, as the truck is out of service for repairs to this apparatus and losses in productivity result therefrom.

Therefore it is seen that it is desirable to have an apparatus and method of using same to increase the reliability of a load covering system, which in turn increases productivity of load transfer.

OBJECT OF THE INVENTION Therefore it is the object of the invention to provide a pivotable lifting arm apparatus which substantially overcoArs or ameliorates the above mentioned problem. At the very least the object of the present invention is to provide an alternative to known lifting arm apparatus.

DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is provided a pivotable lifting arm apparatus comprising a rotable shaft on which a pivotal arm is attached thereto, said S" rotable shaft being rotated by the combined action of a spring means and cable with said 10 cable rotating said shaft when said spring means extends in length, wherein said spring means moves relative to said shaft.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the present invention will now be described with reference to the drawings in which: 15 Fig. 1 is a partial front view of a pivotable lifting arm apparatus of a preferred embodiment; Fig. 2 is a partial plan view of the apparatus of Fig. 1; and Fig. 3 is a transverse cross sectional view along the lines III-Ill of Fig. 2.

BEST MODE OF CARRYING OUT THE INVENTION A pivotable lifting arm apparatus 10 as partially illustrated in the drawings is used preferably in the pivotal motion of a lifting arm which is attached to a cable (not illustrated) which runs along a free edge of a tarpaulin cover (not illustrated) which is used to cover a load being transported by a truck (not illustrated), usually by road. Even though this description refers to the use of the pivotable lifting arm apparatus 10 for this preferred purpose, the present invention is not limited to this use only but can be used where such pivotal motion is required or desirable.

The apparatus 10 includes a cross arm 11 which spans the width of the truck and in the preferred embodiment there are two cross arms 11, one at the front and the other at the rear of the body of the truck adjacent the top opening thereof. In this preferred embodiment the cross arm 11 is an enclosed body in which other components are located, but is not limited thereto and can be an angle section.

Located at the centre of the cross arm 11 is an pin 12 which passes through holes 13 on the sides 14 of the cross arm 11 and which is held in place by bearings 15 bolted to the sides 14. The pin 12 is free to rotate within the bearings 15 and protrudes from the bearing in the fcrm of a protruding portion 12a. A pivotal arm 16 is connected at one end 17 to a 15 key 18 in the pin 12a with the other end (not illustrated) connected to the cove; via the cable.

A bush 19 and cam 20 are fitted onto the pin 12. The cam 20 has a lug 21 with a hole 22 therein in which a wire cable 23 of a pulley device 24 is attached to the cam 20 The lug 21 acts as the cam arrangement of the cam 20. The bush 19 and hence the cam 20 are friction 20 fitted to the pin 12 and therefore the cam 20 rotates with the pin 12.

The wire cable 23 of the pulley device 24 is fixed at its other end to a further pin 25 which spans between the sides 14 of the cross arm 11 and which is fixed into position. The pulley device 24 further includes two pulley wheels 26 which are free to move within the cross arm 11 during operation of the apparatus 10. One of the pulley wheels 26a moves along the bottom side 27 of the cross arm 11 while the other pulley wheel 26b moves in relatively to the peripheral side of the cam 20. These wheels 26 a,b have pins 28 a,b acting as axles.

The pulley device 24 also includes a pair of parallel gas springs 30 extending between the pins 28 a,b. This is the preferred configuration but the present invention is not limited to such a configuration. It is seen that the length of the gas springs 30 are less than half the length of the prior art gas springs as previously described and therefore two have been used to provide enogh stored energy.

The apparatus 10 as illustrated in Fig. 1 shows the pair of gas springs 30 in bold when extended, and in phantom when compressed, therefore the pivotal arm 16 is shown in the covered position in Fig. 2.

The apparatus 10 operates in a similar manner to the previously described prior art in that o ;'10 the cover roller is rotated by a winch mechanism. In the operation to cover a load, the winch is activated by a switch located in the cabin of the truck, which releases the 9l. 99 9 compression of the gas springs 30 via the pivotal arm 16 and hence the pulley device 24.

As the gas springs 30 decompress the wheel 26a moves along the bottom side 27 while the 9@• wheel 26d moves relative to the cam 20. The extension of the gas springs 30 pulls the 15 wire cable 23 which in turn rotates the cam 20 and thus the pin 12 which in turn pivots the pivotal arm lthrough 180 degrees to the covered position. During this pivotal movement the cover is held above the open top of the truck and the load which may be heaped therein 99o .9 i is cleared.

04 Once this covering operation is completed, limit switches (not illustrated) stop power to the winch and therefore the winch stops and the cover is held in place by the force of the gas springs and pulley arrangement. The reverse operation of removing the cover requires for the winch to be operated to roll the cover onto the roller while at the same time pulling the pivotal anrm in an arc over the truck body, and compressing the gas springs 30 into the position as shown in phantom in Fig. 1.

It is seen from the drawings that the gas springs 30 are kept out of horizontal alignment and thus the aforesaid difficulty with the gas spring in the prior art is negated. The configuration of the apparatus, eg the cross arm 11 and pivotal arm 16 prevent any other configuration to be used. It is also seen that the pulley device 24 provides an improved pivotal arm lifting device to known devices in this particular use.

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

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Claims (7)

1. A pivotable lifting arm apparatus comprising a rotatable shaft on which a pivotal arm is attached thereto, said rotatable shaft being rotated by the combined action of a spring means and cable with said cable rotating said shaft when said spring means extends in length, wherein said spring means moves relative to said shaft.

2. The apparatus as claimed in claim 1 wherein said spring means is held in compression by said cable.

3. The apparatus as claimed in claim 2 wherein said cable is fixed at one end to said rotatable shaft and at its other end to a preselected location adjacent said rotatable shaft 10 with said cable forming a pulley arrangement with said spring means.

4. The apparatus as claimed in claim 3 wherein said cable is received within a pair of opposed pulley wheel means which are able to move within a frame and about said rotatable shaft respectively under the action of said cable and said spring means.

The apparatus as claimed in claim 4 wherein said spring means are gas springs.

6. The apparatus as claimed in claim 5 wherein frame is adapted to prevent said gas r, *springs from a horizontal alignment.

7. A pivotable lifting arm apparatus substantially as described with reference to the accompanying drawings. DATED this SEVENTEENTH day of MARCH 1997 COLT INDUSTRIES PTY LTD Patent Attorneys for the Applicant sWILSON YOUNG ABSTRACT PIVOTABLE LIFTING ARM APPARATUS A pivotable lifting arm apparatus (10) comprising a rotatable shaft (12) on which a pivotal arm (16) is attached thereto is disclosed. The rotatable shaft (12) is rotated by the combined action of a spring means (30) and cable (24) with the cable (24) rotating the shaft (12) when the spring means (30) extends in length. The spring means (30) moves relative to the shaft (12) when activated. Fig. 1 *e