AU687230B2

AU687230B2 - Control method and apparatus for lifting equipment

Info

Publication number: AU687230B2
Application number: AU31722/95A
Authority: AU
Inventors: Graeme Haggar
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-09-19
Filing date: 1995-09-19
Publication date: 1998-02-19
Anticipated expiration: 2015-09-19
Also published as: AU3172295A

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIF I CATION FOR A STANDARD PATENT

ORIGINAL

TO BE COMPLETED BY APPLICANT 0* o e o o e Name of Applicant(s): Actual Inventor(s): Address for Service: Invention title: iJQIIH GARDNER CONTROL METHOD AND LIFTING EQUIPMENT p127c= S CPo 6ox Ps 6sbanc QCenslandl APPARATUS FOR Details of Associated Provisional Applications Nos: PM 8272 The following statement is a full description of this invention, including the best method of performing it know to me:-

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This invention relates to a control method and apparatus particularly but not exclusively applicable for use with lifting equipment of the type used on vehicles for transferring loads to and from the vehicle. The control method and apparatus of the invention however may be applied to lifting equipment in other mobile or non-mobile applications.

Vehicles for carrying shipping containers normally include a trailer having leading and trailing load transfer devices which are adapted to lift containers onto the trailer chassis or lift containers from the chassis.

Such load transferring devices include lifting arms which may be raised or lowered usually under the control of hydraulic rams. Fluid is normally supplied to the hydraulic rams from a hydraulic pump by an operator utilising control valves normally proportional valves which are either directly manually operable or which are operable °;through joystick controllers. Operation of the valves controls the flow of fluid to the rams and thus the speed erIIr S° 20 of movement of the lifting arms and the load carried by the S" lifting arms. Manipulation of the lifting arms and the load carried by the lifting arms is therefore subject to operator skill. For unskilled operators, moving of the "lifting arm under high speed when the arms are carrying a 25 load can prove difficult and dangerous and can result in damage, either to the container being lifted or to the vehicle onto which the container is to be loaded.

Furthermore in these systems, the pumps which supply the rams which are commonly swash plate or variable piston pumps provide varying flow output depending upon the size of the load. If the load is reduced flow increaE3f which, when supplied to the rams of the load transfer mechanisms, tend to cause a rapid increase of speed of movement. In such load transfer devices, the load on the rams tend to vary as the arm is brought towards and away from the vehicle and the varying nature of the load is accompanied by increases and decreases in fluid flow to the rams and therefore results in difficulties in controlling the rams.

I R Sometimes this results in the vehicle tipping and therefore provides considerable danger to the operator and also persons in the vicinity of the vehicle.

The present invention aims to overcome or alleviate the above disadvantages by providing a method and apparatus for controlling the operation of lifting equipment such as that used as load transfer devices on vehicles in such a manner as to minimise or reduce the risks of damage to the vehicle or equipment and possible injury or death to the operators of the equipment or persons in the vicinity. In a first preferred aspect, the present invention aims to provide a method and apparatus whereby the maximum speed of operation of the rams of the lifting devices may be controlled to limit maximum speed of operation of the lifting devices. In a further preferred aspect, the present invention aims to provide a method and apparatus in which the possible maximum speed of operation of the lifting equipment is automatically reduced or limited if the load being lifted by the equipment exceeds a predetermined level. Other objects and advantages of the invention will become apparent from the following description.

:The present invention thus provides in a first preferred aspect, a method for controlling the operation of lifting equipment of the type having a fluid operable lifting ram and fluid supply means for supplying fluid to said ram, said method including the steps of selectively limiting the pressure of said fluid supplied from said fluid supply means to said ram whereby to prevent said 30 equipment lifting a load which exceeds a predetermined limit determined by said pressure of said fluid supply means.

Preferably, the equipment is further selectively controllable such that the lifting equipment can function to lift a load which exceeds the predetermined limit by limiting the flow of fluid to said lifting ram to thereby limit the speed of operation of the lifting ram and thus said lifting equipment.

The present aspect provides in a further preferred aspect, control apparatus for controlling the operation of lifting equipment of the type having a lifting ram, said apparatus including selectively operable control means, said control means being operable to prevent said equipment lifting a load which exceeds a predetermined limit.

Preferably the control means is further operable to limit the maximum flow of fluid to the lifting ram juch as to permit said equipment to lift the load at a range of speeds up to a maximum which is less than that achievable at no load.

Preferably, the control apparatus includes a selectively operable control means which in a first attitude permits a first maximum flow of fluid to the ram of said equipment and a second attitude which permits a second reduced maximum flow of fluid to the ram at a higher pressure to permit the lifting equipment to lift the load.

The control means further may include a third attitude 20 permitting a third maximum flow of fluid to the ram. The first and third attitudes of the control means suitably correspond to possible operation of the ram at a sr~w rate and fast rate respectively but do not allow lifting of the *.to load at those rates.

The present invention in yet a further preferred •aspect provides a method for controlling the operation of lifting equipment, said method including the steps of sensing the load lifted by said lifting equipment and "preventing said lifting equipment operating beyond a 30 predetermined maximum speed when said sensed load exceeds a predetermined limit.

Preferably, the lifting equipment includes a lifting ram and the method of the invention controls the maximum flow of fluid to the ram if the load exceeds said predetermined limit.

The present invention in yet a further preferred aspect provides control apparatus for controlling the operation of lifting equipment of the type having a lifting i, ram, said apparatus including load sensing means for sensing the load being lifted by said lifting equipment and means for preventing said ram and thus said equipment operating beyond a predetermined maximum speed when said load sensing means senses a load beyond a predetermined limit.

Preferably, the control apparatus is such as to limit the maximum flow rate of fluid to the ram when the load exceeds the predetermined limit. The equipment may thus be operated as normal in a range of speeds however the maximum speed is limited to prevent the load being lifted by the equipment being moved beyond a set speed limit.

Preferably the load sensing means comprises a pressure sensor associated with the ram or with a fluid line connected to the ram to sense system pressure which varies in accordance with the size of the load being lifted. Fluid is selectively supplied to the ram via a selectively operable control valve and from a controllable io" pump. Preferably the pump is a variable piston pump, such 20 as a swash plate pump.

If the load exceeds the predetermined limit, the control apparatus reduces the maximum possible flow from the pump to thereby reduce the maximum speed of operation *goa.

of the ram. The control apparatus may serve to reduce the S 25 maximum flow output from the pump in a number of steps in "accordance with the load sensed. For this purpose, the pressure sensor may includes a series of pressure switches which are set to operate at different pressures which correspond to different loads being lifted. Operation of the respective pressure switches will set the pump to operate at respective flow rates. Thus if a high load is sensed, the maximum speed of operation is reduced to a first limit. If a lower load is sensed, the maximum speed of operation is reduced but not to the same extent as with a higher load.

Optionally, the arrangement is such that after the control apparatus reduces the maximum flow from the pump, the flow output from the pump cannot be increased unless the load is substantially reduced or is removed.

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:- Fig. 1 illustrates a vehicle employing lifting equipment with which the control apparatus of the invention may be used; and Fig. 2 illustrates schematically the control apparatus according to the invention.

Referring to the drawings and firstly to Fig. 1 there is illustrated a typical vehicle trailer 10 on which is supported a load transfer device 11 which incorporates a lifting arm 12 which is controlled by an hydraulic ram 13.

A pair of load transfer devices 11 are located at spaced apart positions along the trailer 10 and both devices 11

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are adapted to be connected to opposite ends of a container 14 shown in dotted outline normally via a pair of chains to lift a container 14 from the ground up onto the trailer 20 or from the trailer 10 onto the ground by means of Sactuation of the respective hydraulic rams 13 associated with each device 11. Each load transfer device 11 may be provided with an associated stabilising assembly 15 to es..

stabilise the trailer 10 during the lifting or lowering 25 operation.

Each ram 13, as shown in Fig. 2, may be supplied oo ~with fluid from a variable flow pump 16, which in this case comprises a swash plate pump whose flow and pressure output can be varied. Control valves 17 are provided to control the supply of fluid from the pump 16 to the rams 13.

Pressure sensors 18 are connected to the rams 13 or one of the fluid supply lines to the rams 13 so as to sense the operating pressures of the rams 13 and thus the load taken by the rams 13 and being lifted by the load transfer devices 11.

The control apparatus 19 according to the first embodiment of the invention includes a pair of joystick controllers 20 each of which may be selectively operated to -i Icontrol the operation of the respective control valves 17 which control the supply of hydraulic fluid from the pump 16 to the respective hydraulic rams 13 for controlling the speed and the direction of operation of the rams 13. The apparatus 19 includes a control knob 21 which has in this embodiment, three modes a fast mode, a slow mode and a slow/high force mode. In the fast and slow modes as selected by the control knob 21, the control apparatus 19 permits high and low flow outputs from the pump 16 respectively to allow for normal control by the joystick controllers 20 of the rams 13 and the load transfer devices 11 up to a maximum high speed and low speeds respectively.

In both of these modes however, the pressure output of the pump 16 is limited by the apparatus 19 such that the load transfer devices 11 will not lift loads which exceed a predetermined limit. For lifting such loads, the knob 21 is placed in the slow/high force mode. In this mode, the control apparatus 19 will limit the flow output from the pump 16 but permit it to generate a higher pressure. The 20 load transfer devices 11 thus become capable of lifting the loads but only at a slow speed. Where the load transfer devices 11 are required again to operated at a higher speed or where no load is to be lifted, the control knob 21 is simply set at the required poition, for example at a fast 25 or slow rate.

The control apparatus 19 according to the second embodiment of the invention functions automatically to control the output from the pump 16. In this embodiment the pressure sensors 18 sense the size of the load being lifted by the lifting device 11 by sensing the system pressure for example pressure in the hydraulic rams 13.

The control apparatus 19 in this embodiment operates to control the maximum output flow and pressure of the pump 16 in accordance with pressure sensed by the sensors 18.

In use, the load transfer devices 11 will be operable under the control of the respective joystick controllers 20 up to a maximum high speed during no load or small load conditions. If the load transfer devices 11 g, Bglsaaaarrsl--~~- l IP are connected to a load such as a container for lifting of same, the load intended to be lifted causes an increase in system pressure in the fluid lines through the load exerted on the fluid through the rams 13 which will be sensed by the pressure sensors 18. When this pressure exceeds a predetermined limit, the control apparatus 19, upon sensing the increased pressure will cause the pump 16 to be set such as to have a decreased maximum flow output. Thus operation of the joystick controllers will only permit the rams 13 of the load transfer devices 11 to operate at a reduced maximum speed. The pressure supplied by the pump 16 however is sufficient however to enable the load transfer devices 11 to lift the load.

As an optional safety feature, the control apparatus 19 operates such as to prevent the pump 16 again operating at a maximum flow rate until the load is removed.

This prevents the potential maximum speed of operation of the load transfer devices being increased until no load or low load conditions are sensed at which stage the apparatus 20 may be reset.

The control apparatus 19 when used with a pair of load transfer devices 11 preferably functions to reduce :maximum pump output when pressure limits in the ram 13 of e -h device 11 as sensed by either pressure sensor 18 are 25 exceeded. For this purpose, the rams 13 may be connected to a common fluid manifold and a single pressure sensor 18 eo is provided being connected to the manifold to sense excessive pressures therein which will correspond to increased pressure in either ram 13.

Whilst the control apparatus 19 is described in connection with a pair of load lifting devices 11 it may be applied to only one load lifting device 11 or more than two devices 11. Additionally, the control apparatus 19 may incorporate both an automatic load sensing feature to control pump output and a manual feature as embodied in the control knob 21. Alternatively, the control apparatus 19 may include only one of thos, features.

In a typical system and assuming that the pump LC Ipss -qBAp 9 provides a variable flow output to cause a variable speed of operation of the rams 13 of between 0 and 100%, the control apparatus 19 may serve either manually using the control knob 21 or automatically to reduce the flow output to 0 to 25% to reduce the maximum speed or opeLrtion of the ram. Where the apparatus 19 includes a series of pressure switches which respond to different pressures, the pump output may be reduced to variable outputs of 0-25%,0-50% and 0-75% to provide for differing possible maximum speeds of operation according to the load.

The present invention thus provides control apparatus which permits lifting equipment such as load transfer devices on vehicles to be operated by unskilled personnel whilst reduciig or minimising the risk of damage or injury by preventing the lifting equipment operating at a high speed when subject to predetermined loads.

"Whilst the above has been given by way of illustrative embodiment of the invention, all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein defined in the appended claims.

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Claims

2. Control apparatus as defined in Claim 1 wherein said control means in a first position permits a first maximum flow of fluid to said ram and a second position permits a second reduced maximum flow of fluid to said ram at a higher pressure to permit said lifting equipment to lift said load. *e 4
3. Control apparatus as defined ±n Claim 2 wherein said control means in a third position permits a °'third maximum flow of fluid to said ram.
4. Control apparatus as defined in Claim 2 wherein ft said first position of said control means corresponds to possible operation of said ram at a S•slow rate but does not allow lifting of said load at said slow rate. Control apparatus as defined in Claim 3 wherein said first and third positions of said control means correspond to possible operation of said ram at a slow rate and fast rate respectively but do not allow lifting of said load at said slow and fast rates.
6. Control apparatus for controlling operation of lifting equipment of the type having a lifting ram, said apparatus comprising: II I-- 11 a load sensing means for sensing a load being lifted by said lifting equipment which includes a pressure sensor associated with said ram or with a fluid line connected to said ram to sense system pressure which varies in accordance with the size of said load; and means for preventing said ram and thus said equipment operating beyond a predetermined maximum speed when said load sensing means senses said load to be beyond a predetermined limit; wherein said control apparatus is adapted to limi-T the maximum flow rate of fluid to said ram when said load exceeds said predetermined limit, said "fluid oeing selectively supplied to said ram via a p p.p control valve.
7. Control apparatus as defined in Claim 6 wherein said pump comprises a variable piston pump.
8. A method for controlling operation of lifting equipment of the type having a lifting ram, said method comprising: sensing a load being lifted by said lifting equipment with a load sensing means which includes a pressure sensor associated with said ram or with a fluid line connected to said ram to sense system pressure which varies in accordance with the size of said load; and limiting the maximum flow rate of fluid to said ram when said load exceeds a predetermined limit thus preventing said ram and thus said equipment from oerating beyond a predetermined maximum speed. A V'T I I I I-IR 6 1' 12
9. A method as defined in Claim 8 wherein pressure of said fluid to said lifting ram is limited to prevent said equipment from lifting said load when said load exceeds said predetermined limit. A method for controlling operation of lifting equipment substantially as hereinbefore described with reference to the accompanying drawings.
11. Control apparatus for controlling operation of lifting equipment substantially as hereinbefore described with reference to the accompanying .4 drawings. DATED THIS twenty-first DAY OF November 1997. S* GRAEME HAGGAR By r Patent Attorneys *P PIZZEYS PATENT AND TRADE MARK ATTORNEYS 4 e o ABSTRACT A method and apparatus for controlling lifting equipment of the type having at least one lifting ram (13) by controlling supply of fluid to the ram (13) to prevent the lifting equipment lifting a load which exceeds a predetermined limit. In a further aspect of the method and apparatus of the invention, the pressure of fluid in the system supply to the ram (13) is sensed and the fluid volume supply to the ram (13) is reduced if the load exceeds a predetermined limit as sensed by the pressure of fluid so as to control the speed of operation of the lifting equipment under load. too 0 *0 0 so *500* 6 S o*oo *r 0 1111