EP0028462A1

EP0028462A1 - Apparatus for lifting or lowering a load

Info

Publication number: EP0028462A1
Application number: EP80303511A
Authority: EP
Inventors: Melville James
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-10-08
Filing date: 1980-10-06
Publication date: 1981-05-13
Also published as: GB2060554B; ZA806154B; GB2060554A

Abstract

A boom comprises:

a longitudinally extensible arm (1) having first and second opposite ends, said first end being adapted to support load (2), said second end being adapted to pivot about an axis (3) of rotation so that said arm can pivot upwards or downwards;
at least one displacement means (7,8) for adjustably displacing said arm so that said arm will undergo said pivoting; and
at least one sensor (12) for providing at least one signal in response to position of centre of gravity (10) of said arm. The arm can be mounted to e.g. a vehicle, especially a fork lift truck. Preferably, at least one of the displacement means (7,8) is hydraulic.

Description

It is known that at least one load can be lifted or lowered by means of a longitudinally extensible boom having first and second end portions, said first end portion being adapted to support at least one said load, said second end portion being adapted to be pivotally mounted about an axis of rotation constituted by a spindle so that said boen can pivot upwards or downwards. In one example of such a boom, said pivotal mouvting can be provided on a fork lift truck.
A problem present with the vertical stability of a said fork lift truck is that the position of the cantre of gravity of the loaded boom will change with change in length of said boon. Thus, depending on the position of the centre of gravity of the boom, and the load applied to the first end portion of the boom, there may be risk of the fork lift truck overturning during change in the length of the boom while said load is applied.
It has now been found in accordance with the present invention that said prcblen can be overcome or mitigated by utilising at least one signal in response to position of said centre of gravity. This utilisation can find many applications, for example when the fork lift truck is another vehicle, as will be described later herein.
According to a first aspect of the present invention, there is provided a longitufinally extensible boon suitable for lifting or lowering at least one load, said boom comprising: longitudinally extensible arm means constituting said boon, said arm means having first and second end portions, said first end portion being adapted to support said at least the load, said second end portion being adapted tc be ivotally mounted about on axis of rotation so that said arm means can pivot at least upwards or downwards; at least one displacement means for adjustably displacing said arm means so that said arm means will undegro a said pivoting; and at least one censor means for providing at least one signal in response to position of the centre of gravity of said arm means when said arm means supports or dces not support said at least one load.
According to a second aspect of the present invention, there is provided sensor means adapted for use as a said sensor means of said boom according to said first aspect of the present invention.
According to a third aspect of the present invention, there is provided at least one control means responsive to at least one said signal so as to provide control of at least one function of at least said boom according to said first aspect of the present invention.
According to a fourth aspect of the present invention, there is provided apparatus for lifting or lowering at least one load, said apparatus comprising: at least one said boom according to said first aspect of the present invention; and at least one support means for supporting said at least one boom, said pivotal mounting of the or each said boom being to at least one said support neans.
It will be appreciated that said apparatus of said fourth aspect of the present invention can be e.g. in accordance with said second and third aspects of the present invention.
Said apparatus according to said fourth aspect of the present invention can be statically located. For example, that apparatus can be a statically located crane. However, said apparatus of said fourth aspect of the present invention can be movably located. For example, that apparatus can be a vehicle. It will be appreciated that the present invention can be applied to any suitable vehicle, for example a vehicle that is a land vehicle, for instance a fork lift truck, a lorry, or a train. Said vehicle can be a water vehicle vehicle, for instance a barge or other kind of boat. Said vehicle can be an air vehicle, for instance a helicopter or a bovercraft.
In carrying out the present invention, said longitudinally extensible arm means is preferably telescopic. However, it should be noted that any other other suitable way of providing longitudinal extension can be used. For example, said longitudinally extensible arm means can be constituted by nembers placed placed side by side for movement relative to each other, for instance in the case of a ladder constituted by one exanple of a said boom according to the first aspect of the present invention. Said longitudinally extensible arm means can be articulated, so as to be articulateble in at least one direction.
Said first end portion of a boom according to the first aspect of the present invention can support in any suitable way at least one load. For example, in the case of a fork lift truck constituting one embodiment of the fourth aspect of the present invention, a work platform can be permanently or removably mounted to said first end portion. It will be appreciated that said first end portion may comprise pulley or other suitable guide means for guiding line means ( for exanple a chain having at one end a hook for lifting a load) for fastening to at least one load.
Said pivotal meurting of the second end portion of a boom according to the first aspect of the present invention can be provided in any suitable way. For example, that second end portion can pivot about an axis of rotation constituted by for instance spindle means. That axis can be statically or adjustable oriented.
Preferably, said at least one displacenent means means is arranged to provide at at least one location between said axis of rotation and said centre of gravity, force for enabling said adjustable displacement of said arm means.
Preferably, said at least one displacement means is connected to an upper portion of said arm means.
A respective said displacement means can be provided for each of the opposite sides of said arm means.
At least one said displacement means can comprise first and second end portions thereof, the first end portion being connected to said arm means, the second end portion being connected to support means ( for example part of said apparatus according to said fourth aspect of the present invention), relative movement between those first and second end portions enabling said adjustable displacement of said arm means. It will be appreciated from the above description, that the second end portion of a said displacenent means can be connected to said support means at a location thereof between both of said axis of rotation and said centre of gravity. Preferably, said connections of the first and second end portions of a said displacement means are pivotal connections, but those connections can be provided in any other suitable way. Preferably, said relative movement between the first and second end portions of a said displacement means is provided by moving that first end portion. For example, the first end portion of a said displacement means can be comprised by a piston or ram, or any other suitable means. Preferably, the second end portion of at least one said displacement means is pivotally mounted to support means. Preferably, this pivotal mounting is provided by means of an axis of rotation constituted by for example spindle means. That axis can be statically or adjustably oriented. It will be appreciated that the above description refers to two different axes of rotation, i.e. said axis of rotation about which said second end portion of the longitudinally extensible arm means is to pivot, and said axis of rotation for said second end portion of a said displacement means. These axes can be statically or adjustably oriented with respect to each other. Preferably, those axes will be kept parallel with respect to each other. For example, this parallel condition can be a fixed constant or enabled by any suitable means, for instance at least one said control means or other control means.
Said at least one sensor means can be provided in any suitable way. For example, any said sensor means can comprise or be constituted by at least one transducer means and/or at least one switch means. Like or unlike kinds of sensor means can be used. Preferably, at least one said sensor means comprises a strain gauge, for example transducer means for converting pressure changes into electrical signals. When a said displacement means has a said second end portion thereof pivotally mounted by using spindle means, that spindle means can have at least one said sensor means, for example inserted thereinto. Preferably, when such a spindle means passes through opposite supports therefor ( for example opposite walls of a trunnion ) corresponding to one end of the boon, this spindle means can have first and second said sensor means corresponding respectively to those supports; and these sensor means are preferably symmetrically located relative to a mid-point between those supports.
It will be appreciated that at least one said sensor means can be operatively connected to at least one control means so as to prcvide control of at least one function of said boon according to the first aspect of the present invention. in general, at least one said control means or any other ccntrol means can control at least one function of said apparatus according to the fourth aspect of the present invention.
Any control means used in the present invention can be provided in any suitable way. For example, at least one said control means can be adapted to respond to at least one predetermined value of at least one said signal. This response can be instantaneous or comprise at least one predetermined delay. Any said control means can be adapted to enable or dis-enable at least a portion of at least one said function. Preferably, at least one said control means is adjustable, so as to provide for example different predetermined conditions thereof. Preferably, at least one said control means is potentiometric, for example comprise at least one potentiometric bridge, for instance a Wheatstone bridge. Electrical circuity of any said control means can be provided in any suitable way, for example comprise printed circuitry and/or at least one microprocessor.
It is not essential for at least one said signal to be an electrical signal. For example, at least one said signal can be constituted by information comprised by gas, liquid, solid, or radiation ( for instance light of any colour). However, it is convenient that said at least one signal be electrical, and that said at least one control means therefor also be electrical.
At least one said control means can comprise at least one indicator means so as to indicate at least one state of that control means, for example indicate when a said control means is at a particular state in a predetermined programme of control states, for instance a first said indicator means can be activated when a safe working load for the boom is applied, approached, or reached, and a second said indicator means can be activated when a predetermined maximum safe working load for the boom is reached. Similarly, at least one said control means can comprise at least one indicator means so as to indicate at least one state of apparatus according to said fourth aspect of the present invention. Thus, what has just been said about first and second indicator means can apply to the safe working load and maximum safe working load of such apparatus, regarding activation of indicator means. Different colored lights can be used to provide different said indicator means. These lights can be constituted in any suitable way, for example be incandescent lamps and/or light emitting diodes. It will be appreciated that it is not necessary for any said indicator means to provide a visual response or only a visual response. For example, it is possible for indicator means to provide visual and/or non-visual responses ( for instance warning sound). When there is a plurality of said indicator means, at least two thereof can be like or unlike indicator means. If desired, fibre optics can be utilised with at least one said indicator means.
It is not essential for at least one said control means to comprise at least one said indicator means. For example, at least one said indicator means can be directly associated with at least one said sensor means and not be part of at least one said control means.
If desired, at least one display means can comprise at least one said indicator means. For example, a said display means can be an instrument having any suitable cursor ( for instance a pivoted needle) and/or counter. If desired, a said display means can be electronic, for instance a cathode ray tube display, or display utilising liquid crystal display means.
One preferred embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic view of one fork lift truck embodying the present invention; and
Fig. 2 is a view of a spindle fitted with two strain gauges, the spindle constituting an axis of rotation for one of two identical hydraulic pistons for displacing a longitudinally extensible boom fitted to the fork lift truck of Fig. 1.

In Fig. 1, a longitudinally extensible telescopic arm 1 constitutes an extensible boom for lifting or lowering at least one load. At a first end portion of the arm 1 is mounted a removable work platform 2. At the other end portion of the arm 1, the arm 1 is pivotally mounted about an axis of rotation constituted by a spindle 3 of trunnion means mounted on an elevatable support platform 4 carried by the forks 5 of the fork lift truck 6. There are two forks 5 side by side and inserted into respective pockets in the support platform 4. At each side of the arm 1 is a respective hydraulic cylinder 7. The first end portion of each cylinder 7 comprises a respective piston 8 pivotally connected to a respective upper portion 9 of the arm 1, at location between the spindle 3 and a variably positionable centre of gravity 10 of arm 1. The other end portions of each cylinder 7 are pivotally mounted each about a respective axis of rotation ccnstituted by a spindle 11, there being respective spindles 11 for each cylinder 7. The spindles 11 are parts of respective trunnion means mounted on the elevatable support platform 4. The locations of the spindles 11 are between the variable centre of gravity 10 and the spindle 3.
Each spindle 11 ( Fig. 2) has inserted therein two respective strain gauges 12 symmetrically located so as to correspond to opposite sides of the cylinder 7 comprising that spindle 11. The strain gauges 12 will provide output signals to a control means 13 mounted on the elevatable support platform 4 or elsewhere on the fork lift truck, one instance of such alternative mounting being shown by the reference numeral 14 in Fig. 1.
The control means 13 comprises a Wheatstone bridge responsive to the output signals from the strain gauges 12, those signals passing to the control means 13 via a line 15 ( Fig. 2). When the output signals change in response to change in location of the centre of gravity 10 of the arm 1, the control means 13 will respond in at least one predetermined manner, for exanple trigger predetermined safety operations. For instance, the control means 13 can activate a yellow light when the safe working load of the boom and/or fork lift truck is approached, and when such a safe working load is reached activate a red light. As soon as an unsafe working load for the boom and/or the fork lift truck is reached, the control means 13 can isolate in a predetermined safe manner at least one function of the boom and/or of the fork lift truck.
It will be appreciated that the elevatable support platform 4 can be regarded as part of the boom. The arm 1 can be articulatable or non-articulatable.
The present invention extends to equivalents of the above description of the accompanying drawings. In general, the present invention can be embodied in any suitable way, and includes equivalents of the various possibilities disclosed by the above description given before the description of the accompanying drawings.

Claims

1. A longitudinally extensible boon suitable for lifting or lowering at least one load, said boom characterised by:

longitudinally extensible arm means (1) constituting said boom, said arm means having first and second end portions, said first end portion being adapted to support said at least one load, said second end portion being adapted to be pivotally mounted about an axis of rotation (3) so that said arm means can pivot at least upwards or downwards;

at least one displacenent means (7,8) for adjustably displacing said arm means so that said arm means will undergo at least one said pivoting; and

at least one sensor means (12) for providing at least one signal in response to position of the centre of gravity (10) of said arm means when said arm means supports or does not support said at least one load.

2. A boom as claimed in claim 1, characterised by that said arm means (1) is telescopic.

3. A boom as claimed in claim 1 or 2, characterised by that said first end portion of said arm means (1) comprises work platform means (4) mourted to said first end portion.

4. A boom as claimed in any one of claims 1 to 3, characterised by that said pivotal mounting comprises spindle means (3) constituting a said axis of rotation.

5. A boom as claimed in claim 4, characterised by that said spindle means (3) comprises at least one said sensor means (12).

6. A boom as claimed in any one of claims 1 to 5, characterised by that at least one said displacement means (7,8) is arranged to provide, at at least one location between said axis of rotation (3) and said centre of gravity (10), at least a portion of force for enabling said adjustable displacement of said arm means (1).

7. A boom as claimed in any one of claims 1 to 6, characterised by at least one control means (13) to provide control in response to at least one said signal.

8. A boom as claimed in any one of claims 1 to 7, characterised by at least one indicator means to indicate at least one state of at least one said sensor means (12) and/or at least one state of at least one said control means (13).

9. A boom as claimed in any one of claims 1 to 8, characterized by a vehicle (6) supporting at least one said boom.

10. A boom as claimed in claim 9, characterised by that said vehicle (6) is a fork lift truck.