GB2062258A

GB2062258A - Safe Load Indicator

Info

Publication number: GB2062258A
Application number: GB8034229A
Authority: GB
Original assignee: Simon Engineering Dudley Ltd
Current assignee: Simon Engineering Dudley Ltd
Priority date: 1979-11-01
Filing date: 1980-10-23
Publication date: 1981-05-20
Also published as: GB2062258B

Abstract

In hydraulic platform apparatus comprising a boom assembly (12, 13) or other lifting mechanism such as a scissor lift or telescopic mast, and a working platform (14) attached to the outermost end of the lifting mechanism, such that the platform may be elevated to a working position, the platform or a part thereof is mounted for uniform vertical movement relative to its attachments to the lifting mechanism when a load is placed on the platform or part, irrespective of the position of application of said load. Means such as a load cell is provided to respond to the movement and the load is shown by an indicator 22. The vertical movement may be achieved by means of pivoted links (17) or vertical slides, having low friction bearings. <IMAGE>

Description

SPECIFICATION Safe Load Indicator This invention relates to hydraulic platform apparatus of the kind generally comprising a supporting structure mounted, for example, on a vehicle and carrying a boom assembly or other lifting mechanism and a working platform attached to the outermost end thereof whereby upon movement of the lifting mechanism the platform may be elevated to a working position.

In such apparatus the working platform is usually intended to carry one or more workmen and their tools, and is sometimes used for carrying equipment and other loads to elevated positions. As a safety measure, particularly when the platform is intended for carrying personnel, it is desirable to measure the load in the platform.

One difficulty experienced with this kind of apparatus has been that in many cases there is no position on the machine where the loading is accurately and constantly proportional to the load applied.

The object of the present invention is to provide means for measuring the load applied to the platform irrespective of whether the load is concentrated at any point or is evenly distributed over the platform floor area.

According to the present invention there is provided hydraulic platform apparatus comprising a boom assembly or other lifting mechanism and a working platform attached to the outermost end thereof, means for driving the lifting mechanism so that the platform may be elevated to a working position, characterised in that at least a part of the platform is mounted with respect to the lifting mechanism for uniform vertical movement relative thereto when a load is placed on the platform or said part thereof, irrespective of the position of application of said load, and means is provided to measure such movement and thus the weight of the load.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is an elevation of hydraulic platform apparatus embodying the invention; Fig. 2 is an enlarged view of a working platform being part of the apparatus illustrated in Fig. 1; Fig. 3 is a view taken on line Ill-Ill of Fig. 2; and Fig. 4 is a schematic perspective view of an alternative assembly embodying the invention.

Referring now to Figs. 1 to 3 of the drawings, the apparatus generally comprises a vehicle 10 having mounted on its chassis a supporting structure 11 to which is pivotally attached about a horizontal axis a boom assembly comprising a pair of booms 12 and 13. Pivotally connected to the outermost end of the boom 13 is a working platform 14.

Means (not shown in detail) is provided for elevating the booms 12 and 13 with respect to the supporting structure 11, and additionally for maintaining the working platform 14 level for all configurations of the boom assembly.

Referring now more particularly to Figs. 2 and 3, it will be seen that the working platform 14 comprises a first part 1 spa which is attached at 1 6 to the boom 13, and a second part 1 sub which constitutes the cage or personnel-carrying unit itself. As will be seen, the part 1 sub is connected to the part 1 spa by means of a number of pivotal links 1 7 having low friction bearings such as ball races and having shafts 1 8 extending between complementary pairs of the links 1 7 to provide rigidity. Attached to one of the shafts 1 8 on the part 1 Sb of the working platform is a pressure pad 1 9 which is adapted to bear upon the ram of a hydraulic cylinder 20.The cylinder 20 is connected via a pipe 21 to an indicator 22 visible from within the platform part 1 sub.

Thus when the part 1 sub tends to move downwardly by a small distance with respect to the part 1 spa as a result of a load applied to the former, the indicator 22 provides a reading and is calibrated in terms of the weight applied.

A cushioning device 23 determines an upper limit of movement of the platform part 1 Sb with respect to the part 1 spa. The device 23 also serves as a damper to prevent the part 1 5b from oscillating in a vertical mode when the vehicle travels on rough roads. In an alternative arrangement the shafts and links can be replaced by vertical slides with linear low friction bearings such as recirculating ball linear bearings. A single such bearing can be positioned beneath the platform permitting same to swivel about a vertical axis and simultaneously allowing vertical movement for measurement of the load.

Means in accordance with the invention for measuring a load applied to a working platform, can similarly be provided in cases where the platform is mounted vertically above the lifting mechanism, for example, where the lifting mechanism is a scissor assembly or telescopic mast.

Referring now to Fig. 4, in an alternative system for measuring the load applied to a platform, the load carrying part thereof is illustrated as having a base 50 on pairs of fixed supporting members 51 and 52 carrying shafts 53 which also carry four bell crank members 54 having connecting rods 55. This arrangement provides parallel movement in a vertical direction of all parts of the base 50 relative to the lifting mechanism and supporting members 51 and 52.

A load cell 56 is provided beneath the base 50 to be responsive to vertical movements thereof, and is accordingly connected to means such as the indicator 22 in Figs. 1 to 3 for providing a reading of the load applied.

It will be appreciated that whilst the dotted line has been used to illustrate the base of a working platform or cage, the whole unit assembly illustrated in Fig. 4 can, as an alternative, be in the form of a seperate unit which can be placed on the existing floor of a working platform so that the line 50 represents a false floor therein movable vertically with respect to the existing floor.

The means used for detecting and measuring the load applied to the working platform may take many forms. For example, the indicator may be a mechanical device such as a spring balance, or it may be electrically operated using a force transducer. In addition to providing an indication as an alternative, the signal from the hydraulic cylinder 20, or load cell 56 can be used to produce an alarm signal and/or to arrest operation of the apparatus as a whole in or approaching an over-load condition.

Claims

1. Hydraulic platform apparatus comprising a boom assembly or other lifting machanism and a working platform attached to the outermost end thereof, means for driving the lifting mechanism so that the platform may be elevated to a working position, characterised in that at least a part of the platform is mounted with respect to the lifting mechanism for uniform vertical movement relative thereto when a load is placed on the platform or said part therof, irrespective of the position of application of said load, and means is provided to measure such movement and thus the weight of the load.

2. Apparatus according to Claim 1, wherein said working platform comprises a first part attached to a lifting mechanism, and a second part attached to said first part for vertical movement relative thereto when a load is placed on the second part, said measuring means being so disposed as to detect the relative movement of said platform parts.

3. Apparatus according to Claim 2, wherein said second part is connected to said first part by pairs of pivoted links.

4. Apparatus according to Claim 2, wherein said second part is connected to said first part by means of vertical slides.

5. Apparatus according to any one of the preceding claims, wherein said movable part of said platform comprises the floor thereof which is capable of uniform vertical movement relative to other parts of the platform.

6. Apparatus according to Claim 5, wherein a load cell is provided below said movable floor thus to detect the degree of movement thereof.

7. Hydraulic platform apparatus substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 3 or Fig. 4 of the accompanying drawings.