GB2203123A

GB2203123A - Personnel access lift boom

Info

Publication number: GB2203123A
Application number: GB08807596A
Authority: GB
Inventors: Ridley Stokoe
Original assignee: Aerial Access Equipment Ltd
Current assignee: Aerial Access Equipment Ltd
Priority date: 1987-04-04
Filing date: 1988-03-30
Publication date: 1988-10-12
Anticipated expiration: 2008-03-30
Also published as: DE3868962D1; GB8708123D0; GB2203122A; FI881542A0; EP0286301A1; EP0286301B1; GB2203123B; GB2203122B; GB8807596D0; EP0286300A1; FI881542A; GB8807595D0

Description

9 A 1 Personnel Access Lift,Bom 2203123 The present invention is concerned

witli personnel access lifts, that is lifts of the type used to enable an operator to gain access to an elevated location to perform, some task at that location. The invention is an improved bocrq for that purpose.

Personnel access lifts are avaIlable in many forms and a wide range of sizes, ranging fraL large c=nercial units to units which are small enough to be t behind a car and manoeuvred manually. A major requirement is that all such lifts should be stable in use and in general safe in operation.

In such lifts as comprise a bocm having two or more sections articulated together, mutual pivoting of adjacent boom sections is usually achieved by means of hydraul ically-operated rams. However the use of such rams entails the provision of control equipment, both to ensure that no rams, operated individually or together, can move the boom sections into an unstable configuration and also to insure against the cionsequences of hydraulic pressure failure. Each ram anTassociated control equipment adds significantly to both the cost and the weight of the lift overall.

1 It is an object of the present invention to provide a novel form of bocm for a personnel access lift, by means of which at least one operating rain and its associated control equit my be dispensed with.

The personnel access lift bocrn according to the present invention ocinprises a first bocin section, pivotally supported at a first pivot point in the region of a first end thereof, a second bocrn section pivoted at a second pivot point spaced frcm an end of said second bom section upon a pivot in the region of the other end of said first boom section, a link pivotally connecting a first link point in the region of said end of said second bmn section and a second link point fixed relative to but spaced from said first pivot point, such that said link extends at an angle across the length of said first bc)cn section in at least a majority of relative positions of said first and second boom sections, and hydraulic means for reving said first boom section about said first pivot point.

By virtue of the link and in particular the disposition of the two link points between which it extends, pivoting of the first boom section about the first pivot point automatically gives rise to pivoting of the second boom section about the second pivot point in the sam rotational direction. Thus the conventional need for hydraulic m-ms to effect relative movement of the first and second bocm sections no longer arises.

The personnel access lift boom my cise mre than two sections. Thus, foj: example, the two boom sections 1 referred to above ray be directly munted upon a suitable fixed or mobile base or they may comprise the uppe=ost two sections of a bocin consisting of three or four sections.

In one preferred form of the invention, the first bom section is pivoted at the upper end of a generally vertical boom section and the second link point is located upon the generally vertical bom section below the first pivot point. The generally vertical bom section my be retained in that orientation by reans of a parallel motion linkage to the lift base. As an alternative, the first boom section rmy be pivoted at the upper end of a support colurrn on the lift base, the second link point being located on the colunm below the first pivot point. The support colurm nay be extensible vertically, for example telescopically extensiblef to give' further potential is operating height to the access lift.

The first and second boan sections are pivoted together at a point (the second pivot point) 1 spaced from the adjacent end of the second bocm section. In A particularly preferred form of the invention, the second bom section extends at an angle to its length (that is, is cranked) beyond the second pivot point, so that the point of connection of the link (the first link point) is smewhat out of line with the length of the second bocn section.

Preferably the link, by nie-ans of which pivoting of the second boam section is achievdd, is a rigid link, for example in the form of a rod or flat b4r. However the link rray in appropriate forms of the invention be a flexible link such as f a cable. In such latter forms of the invention, it is essential that the second bocin section be so pivoted that it is able to return to its inoperative or stowed position by gravity alone.

The hydraulic means for mving the first bocrn section about the first pivot point ray take the form of a hydraulic ram, which extends between the first boom section and a point upon the support for that section. Thus, for example, when the boam, comprises only two sections, the ram may operate between the first boom section and either the base of the lift or a column upon which that section is pivoted. When the first and second boom sections are parts of a boom having Mre than tyn sections, then the ram my operate between the first boom section and a lower bocm section upon which said first section is pivoted. Advantageously, the hydraulic driving power for operating the access lift way be provided by some form of power take-off from an adjacent vehicle, for exarrple vehicle by ny-ams of which a mbile access lift is towed or vehicle upon which the lift is munted.

The uppermost boom section will carry at its upper end a platform or cage to carry the operator. It is highly desirable that a self-levelling mechanism be provided to maintain the platform level at all positions of the boom assembly. Such self-levelling mechanisms, for example tie-rods linking the platform to another part of the lift structure, are already known per se.

Operation of the lift is preferably effected from controls located on the platform or cage, so that an operator my enter the cage and elevate the latter and adjust its spatial position frcrn within the cage. As a less preferred alternative which requires a second operator, the mvement of the booms and cage my be controlled frcin a position at the base of the lift.

The invention will now be further described by way of example with reference to the accompanying drawings, wherein:

Fig. 1 illustrates, in elevation from the rear, one ent)odiment of personnel access lift incorporating a lift boom according to the present invention, the lift being shown in a stowed condition;'and Fig. 2 illustrates, in elevation frcin the rear and to a smt smaller scale, the lift of Fig. 1 in a fully-extended condition.

The illustrated.personnel access lift s designed for munting upon a vehicle chassis and is formed upon a base frame rising tyn cross-nerbers 3, together.carrying a lifting jack 4 at each end. The cross-manbers 3 are intended to be munted transverse to the length of a vehicle chassis, such that the jacks 4 ray be extended downwardly into-contact with the ground on opposite sides of the chassis when the lift is to be brought into use. Projecting vertically from the cross-members 3, at one side, preferably the nearside, of the vehicle is a column 5, which is telescopically extensible under hydraulic pressure. The upper end 6 of the column 5 is at a level, when the column is contracted, which would be a little above the top of a cab of the vehicle. The bom assembly j is carried upon that column end 6.

The bocrn assembly is in four sections 7f 8, 9 and 10 and carries at its uppermost end C4ien extended) a personnel cage The lowermost bocra section 7 is pivoted at one end at a pivot point 12 on the column end 6 and carries at its other end the vertical bocn section 8. Parallel to the boom section 7 and also linking the coiumn end 6 and the bom section 8 is a rigid link 13, which holds the bom section 8 vertical whatever the position of the bom section 7. In the stowed position of the bom assembly, as illustrated in Fig. 1, the vertical boom. section 8 is located above the cross-members 3 at the opposite end of th cross-members to the column 5 and the lowermost bocm section 7 lies across the vehicle at an angle of the order of 45o to the horizontal.

Pivoted at 14 (the "first pivot point" of the foregoing general description) on the upper end of the vertical boom section 8 is the bom section 9 (the "irst boam section" of the foregoing general description). On the other end of the bom section 9, the uppermost boam. section 10 (the "second hom section") is Pivoted at 15 (the "second pivot point"). The pivot 15 is spaced a short distance from the extrem end of the bom section 10, which latter section'is bent at a small angle frcin the straight in the region of the pivot 15. A rigid link 16 connects the end of the boom section 10 to a point 17 on the vertical bocn section 8 slightly below the

1 1 is pivot 14. A self-levelling mechanism (not s) is provided to ensure that the cage 11 remains level in all positions of the boam asly.

Pivoting of the bocin section 7 about the pivot point 12 is effected by a hydraulic ram 18; pivoting of the boan section 9 about the pivot point 14 is effected by a hydraulic ram 19 (crnitted frcm Fig. 2). As is explained hereinafter, no rarn is required to operate the uppermost bom section 10, as this is achieved by reans of the link 16.

In extending the assembly from the stowed position of Fig. 1 to the extended position of Fig. 2, the operator enters the personnel cage 11 at vehicle level and then first extends the column 5 to a desired upward extent, for example until the.

column head 6 is clear of the vehicle cab.- The head 6 is able to rotate relative to the inner shaft 20 of the column if desired. Next the ram 18 is operated to swing the boom section 7 upwards and thereby to raise the vertical boom section 8 to a higher operating position. Operation of the ram 19 now swings the boam section 9 upwards. By virtue of the link 16, this action also causes the uppermost bocxn sectlon 10 to pivot in a clockwise direction as illustrated about the pivot 15,, thus raising the personnel cage 11 to its desired operating height. It will be apparent that the link 16 replaces a hydraulic ram whichwDuld otherwise be required to swing the bocrn section 10 into its upwardly-extending operating position. The opportunity to cniit a hydraulic ram and its associated control equipment frcin the design represents a significant potential saving of Ynight and of cost as compared with a comparable conventional f personnel access lift.

It is a further advantage 6f the access lift bown according to the invention that it is possible to achieve an increase in.operating height relative to a cmparable conventional bom, without any significant increase in the lateral out-reach required to achieve that height.

L 1

Claims

CLAIM

1. A bom for a personnel access lift, xql-dch bom cises a first bocin section, pivotally rted at a first pivot point in the region of a first end thereof, a second boom section pivoted at a second pivot point spaced frem an end of said second boom section upon a pivot in the region of the other end of said first bom section, a link pivotally connecting a first link point in the region of said end of said second boom section and a second link point fixed relative to but spaced frcin said first pivot point, such that said link extends at an angle across the length of said first boom section in at least a majority of relative positions of said first and second boom sections, and hydraulic means for moving said first boom section about said first piv. bt point.

is

2. An access lift bocrn as claimed in claim 1, ccrnprising only said tvQo boom sections, said first bocm section being directly mounted upon a fixed or mobil e base.

3. An access lift as claimed in claim'l, =rprising only said two bom sections, said first bmn..section being pivoted at the upper end of a support colurm on a fixed or mobile base.

4. An access lift boam as claimed in'.claim 3, wherein said support colum is extensible vertically.

5. An access lift boam as clain-ed in claim 1, rising three or four bom sections, wherein said first and second bocn sections are the uppermost thereof.

1 -10

6. An access lift boom as claimed in any of the preceding clalm, wflerein said second bmu section extends at an angle to its length beyond the second pivot point.

-0

7. An access lift boom as claimed in any of the preceding clainis, wherein said link is a rigid rod or a flat bar.

8. An access lift bom as claimed in any of the preceding claim, ein said hydraulic means is a hydraulic ram.

9. An access lift boan substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

10. A personnel access lift camprising a boom as claimed in any of the preceding claims.

Published 1988 at The Patent Office, State House, 66f71 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent Offtce, Sales Branch, St Cray, Orpington, Kent BRS 3P.D. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1187.