AU623485B2

AU623485B2 - Fork lift truck

Info

Publication number: AU623485B2
Application number: AU48947/90A
Authority: AU
Inventors: Phillip Jules Arnold
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-01-31
Filing date: 1990-01-31
Publication date: 1992-05-14
Anticipated expiration: 2010-01-31
Also published as: AU4894790A

Description

1 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 Forra COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE 1L~L~) k'V~A' 7 348~ Short Title: Int. Cl: Application Number: Lodged: PJ2475 31 January 1989 0U t 0 4 Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art; 0 1 TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service:

PHIL

T IP JULES ARNOLD 4 Buckman Close, Toormina, New South Wales, 2452, Australia PHILLIP JULES ARNOLD GRIFFITH HACK CO.

71 YORK STREET SYDNEY NSW 2000

AUSTRALIA

Complete Specification for the invention entitled: FORK LIFT TRUCK The following statement is a full descriptic., of this invention, including the best method of performing it known to me/us:- 127.

I '9r 9~ 5854A/KLH i .ILi.i i 2- This invention relates to a fork lift truck and has been devised particularly though not solely for use as a heavy duty fork lift truck on rough terrain.

There are many instances where it is necessary to utilise a fork lift truck for the loading, unloading or Lransportation of goods over comparatively rough terrain, e.g. in builders' yards or at site works. Conventional fork lift trucks have the problem that they are prone to pitching in rough terrain which may cause the forward ends of the tynes to dig-in to the ground or which may cause the load to become dislodged from the tynes of the fork lift truck. This can be overcome by providing the fork lift truck with a lifting mast which is slidable in a fore and aft direction so that the mast may be moved 15 rearwardly after lifting of the load and before S" transportation to contain the load within the wheelbase o of the fork lift truck. Such configurations are known in lightweight fork lift vehicles often used in warehouse .p situations. The Vuse of a movable mast of this type however results in a fork lift truck which is comparatively long overall and therefore difficult to manoeuvre or to transport to a required site on the back of a truck.

In one aspect the present invention therefore provides a fork lift truck having a imain chassis, a mast and tynes for lifting a load at the front of the main chassis, front support wheels at the front of the main chassis, and a drive motor, characterised by the provision of rear support wheels mounted on a sub-chassis slidably connected to the main chassis in such a manner that the rear support wheels may be moved toward and away from the front sivport wheels.

Preferably the rear wheels, as a set, are rotatable about a central vertical axis to provide oteering for the fork lift truck.

Preferably the rear wheel set is rotatable through at least 1800 and arranged such the rear wheel set may be ¢a turned to a position 900 from the normal direction of 18264D -3 forward travel when in the fully extended position (away from the front wheels). Preferably the mast and tynes of the fork lift truck are slidable toward and away from the front of the chassis between a first position in which the tynes protrude forwardly in front of the front wheels, and a rearward position in which the tynes are located above or rearwardly of the front wheels.

Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described by way of example only with reference to the accompanying drawings, in which:- Fig. 1 is a diagrammatic perspective view of the chassis of a fork lift truck invention; Fig. 2 is a diagrammatic plan view of the rear part 15 of the chassis of a second form of fork lift truck Jo o according to the invention; Fig. 3 is a diagrammatic side view of the configuration shown in Fig. 2, and o° Fig. 4 is a diagrammatic rear view of the 20 configuration shown in Fig. 2.

In the preferred form of the .nvention a fork lift truck is provided having a chassis k: sup)orted by a set of front wheels and a set of rear wheels The fork i i 0 6 a 18264D lift truck may conventionally be driven by an engine (not shown) which in turn drives a hydraulic pump connected by way of hydraulic hoses to hydraulic drive motors located either within the hubs of the rear wheels or within the hubs of all four wheels.

The fork lift truck is provided with a vertical mast on which is mounted a set of tynes for lifting a load in a manner well known for fork lift trucks.

In the preferred form of the invention the mast is slidably mounted in the chassis so that it is movable between a rearward or retracted position shown in solid outline at in Fig. 1, and a forward or extended position shown in broken outline. In this manner the mast and tynes may be moved to the extended position for picking up and lifting a load, and then retracted to the rearward position for manoeuvring and transport so that the load is located within the wheel base of the chassis, and above the front wh-,ls A configuration as thus far described would normally result in a fork lift truck having a longer than normal chassis in order to accommodate the lengthwise movement of the mast This is necessary in order to provide a counterweight, located sufficiently far behind the rear wheels to counterbalance the lifting of a load when the mast is in the extended position To obviate the necessity for a long chassis, the fork lift truck according to the invention is provided with a counterweight at the rear of the chassis movable between a retracted position (9) So o° shown in solid outline in Fig. 1 and an extended position (10) shown in broken outline. The counterweight may typically be mounted on retractable rams actuated by a hydraulic mechanism to move the counterweight between the extended and retracted positions.

When using the fork lift truck according to the invention, the counterweight may be extended to the extended position (10) to counterbalance the lifting of a load with the mast in the forward or extended position and the counterweight may then be retracted to the 0460U/KLH 4 retracted positicn when the mast has be,:ln moved to the rearward position to give a "close coupled" configuration to the fork lift chassis for manoevuring in confined spaces. The fork lift truck also has the advaatage that with both the mast and the counterweight in the retracted positions and respectively) the fork lift truck is short and compact and suitable for transL ortation, e.g. on the bacok of a truck.

In an alternative form of the invention as shown in Figs. 2-4, the extendable counterwieight is eliminated and the same effect is achieved by providing the rear wheel set (11) mounted on a sub-chassis (12) which in turn is slidably mounted to the main chassis The sub-chassis may, for K example, have an upper support plate (13) which is slidably mounted within channels (14) to enable the forward and rearward movement of the rear wheel set. Movement of the sub-chassis relative to the main chassis may be achieved by a hydraulic piston and cylinder assembly powered by the main hydraulic pump driven by the drive engine In this manner the rear wheels may be moved to a rearward or extended position to counterbalance the liftirag of a load on the tynes when the mast is in the forward or extended position, and the rear wheels retracted to a close coupled position for transportation of the foik lift truck on the back of a transport vehicle. It has been found, that with this form of the invention, a fork lift truck may be manufactured which with all components retracted will fit transversely on the tray of a 2 conventional truck.

It is Preferred that the sub-chas~'is and the rear wheel set are rotatable about r vertical axis (16) through at least 180 0, to provide the steering movement for the fork lift truck. To this end the sub-chassis (12) is mounted on a slewing bearing (17) to allow the rotational movement Once again the drive to the fork lift truck is provided by way of hyeiraulic motors located within the hubs of the rear wheels (arid optionally also within the hubs of the 0460S/KLH front wheels In either form of the invention it is possible to provide a fork lift truck which is suitable for lifting heavy loads and manoevuring over rough terrain, while yet being compact enough (in the retracted configuration) to be readily transportable on a conventional truck to an intended site of operation.

i 2 1 22 (f22 2 222.

0460s/KLH 6

Claims

1. A fork lift truck having a main chassis, a mast and tynes for lifting a load at the front of the main chassis, front support wheels at the front of the main chassis, and a drive motor, characterised by the provision of rear support wheels mounted on a sub-chassis slidably connected to the main chassis in such a manner that the rear support wheels may be moved toward and away from the front support wheels.

2. A fork lift truck as claimed in claim 1, wherein the rear support wheels, as a set, are rotatable about a substantially vertical axis to provide steering for the o° fork lift truck. 0 o

3. A fork lift truck as claimed in claim 2, wherein the 15 rear support wheel set is rotatable through at least 1800 and arranged such that the rear wheel set may be turned :oa^ to a position 90° from the normal direction of forward travel when in a fully extended position away from the 00 front wheels. o 0 0 20

4. A fork lift truck substantially as described herein I with reference to figures 2 to 4 of the accompanying drawings. i DATED this 20th February, 1992 PHILLIP JULES ARNOLD By their Patent Attorneys GRIFFITH HACK CO 18264D "0a0