GB2134072A

GB2134072A - Booms

Info

Publication number: GB2134072A
Application number: GB08400309A
Authority: GB
Inventors: Neville Muse
Original assignee: Coles Cranes Ltd
Current assignee: Coles Cranes Ltd
Priority date: 1983-01-24
Filing date: 1984-01-06
Publication date: 1984-08-08
Also published as: GB2134072B; GB8400309D0

Abstract

A boom section (14) for a crane or the like comprises four longitudinal stiffening members (16), shown as rectangular hollow sections, interconnected with four substantially flat longitudinal plates (17) embossed at various intervals (see 20), the arrangement being such that the boom has a substantially diamond shaped cross-section. As shown the boom section (14) telescopes within a boom section (12), bearing means (22) being provided on the inner face of the members (16) of the section (12) to bear against the outer face of the members (16) of the section (14) and comprising pads (24) to take up horizontal forces and pads (26) to take up vertical forces. <IMAGE>

Description

SPECIFICATION Improvements in and relating to embossed booms The present invention relates to booms for cranes or the like particularly those having a box construction.

Box type booms, that is booms constructed from plate as distinguished from lattice type booms, are well known and are used for telescoping booms where the boom sections are comparatively short. The box construction is normally rectilinear in cross-section although our British Patent No. 1,564,509 shows an octagonal construction which has certain advantages over the normal rectilinear shape. Certain disadvantages of the rectilinear shape are set out in our British Patent No. 1,564,509. A particular disadvantage of both rectilinear and octagonal boom construction is evident when the boom is lengthened. In this case, additional stiffening in the form of internal stiffening members has to be provided. But then the assembly of boom components by welding standards require welds to run uninterrupted from end to end.

A boom which mitigates or overcomes one or more of the above problems is described in our copending G.B. Application No. 8223792. In this boom, stiffness and strength is the primary design criterion. Another major criterion however, is the weight of the boom.

It is an object of the invention to provide an extremely light boom construction which is both stiff and strong and hence especially useful for elevating work platforms.

A boom for a crane or the like according to the invention comprises four longitudinal stiffening members spaced apart and four substantially flat longitudinal embossed plates each welded between adjacent such stiffening members to form a boom with a substantially diamond shaped cross-section.

The use of embossed plates means that the plates may be reduced in thickness to a minimum which clearly reduces weight of the boom. The plates are preferably embossed with a pattern which extends along their full length which enhances the stiffness of the plate and tends to eliminate any tendancy for the boom to buckle.

Preferably the boom is telescopic, bearing means being provided between adjacent sections of the boom.

The stiffening members are preferably of rectangular hollow section.

The abutment between the embossed longitudinal plates and the edges of the stiffening members enables a simple external butt weld to be run along the whole length of the boom without interruption which is simple to set up even with boom lengths of 20 m or more.

Advantages of the present invention over rectangular unembossed section booms include the reduction of stress at the corners, elimination of internal fillets, reduction of distortion, easier and better welding during assembly and the reduction of weight of the boom.

Whilst the boom is suitable for cranes and mobile cranes, it is particularly suitable for use with access platforms (aerial lifts) or on other apparatus using similar booms and the expression cranes and the like" is to be interpreted accordingly.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a side elevation of an example of a boom of the invention; Figure 2 is a cross-section of the boom of Figure 1 along lines 2-2; Figure 3 is a cross-section of an embodiment of boom in accordance with the invention, and Figure 4 is a cross-section of a further embodiment of boom in accordance with the invention.

In Figures 1 and 2, a boom 10 is shown having an inner section 1 2 and an outer section 1 4 telescopically movable within the section 12.

The boom construction which can be seen in Figure 2 is extremely simple and comprises four rectangular hollow section stiffening members 1 6 interconnected by embossed plates 1 7 which are butt welded, by welds 1 8 on the outside of the boom, to the members 16.

In Figure 2, it will be noted that the plates 1 7 conform to a diamond shaped parallelogram, the base or end angle being 650 and the side angle being 1150 to 1200 but these can be varied dependent on the loading conditions, the minimum base angle being 600 but the normal base angle being between 620 and 690.

The stress distribution in the boom is shown in Figure 4 of our copending G.B. Application 8223792 where it will be seen to be substantially symmetrical both for stresses caused by boom whip, that is lateral stress and stresses caused by normal boom loading, that is stresses due to the boom weight and boom load.

The plates 1 7 are embossed (see 20) at various intervals substantially along the whole length of the boom 10 in order to reduce weight of the boom while retaining stiffness and strength. The plates are embossed preferably between 25 and 80% of the surface area of the plates. The embossing of the plates eliminates the tendancy of the boom to fail due to local buckling.

Between the sections 12 and 14, bearing means 22 are provided on the inner face of the members 1 6 of the section 12 to bear against the outer face of the members 1 6 of the section 14.

The bearing means comprise a pair of "lateral" bearing pads 24 for taking the horizontal forces which tend to bring the sections 1 2 and 1 4 together and a pair of "vertical" bearing pads 26 for taking the vertical forces which tend to bring the sections 12 and 14 together, so that the outer section 14 is capable of telescoping within the inner section 12.

Different arrangements of lateral and vertical bearing pads are shown in Figures 1,3 and 4. In the arrangements shown in Figures 1 and 3, either a lateral or vertical bearing pad is provided on each side or end stiffening member 16, while in contrast the arrangement in Figure 4 shows both a lateral and vertical bearing pad provided on each of the two side stiffening members 16 of the outer section 12.

In Figures 3 and 4, the stiffening members 16 are of open U-shaped configuration such that the member 16 of the inner section 14 may nest within the member 1 6 of the outer section 12.

This enables a larger inner section to be used as compared with the arrangement shown in Figures 1 and 2.

The bearing pads 24 or 26 may be adjustable (for examplesee 24 in Figures 1 and 4) so that a pad may be made to bear upon the stiffening member 16 after wear of the pad has occurred.

Preferably the bearing pads are of hard-wearing plastics material, however, any hard-wearing material would clearly suffice.

The contents of our co-pending G.B.

Application No. 8223792 are incorporated herein.

Claims

1. A boom for a crane or the like comprising four longitudinal stiffening members spaced apart and four substantially flat longitudinal embossed plates each welded between adjacent stiffening members to form a boom with a substantially diamond shaped cross-section.

2. A boom as claimed in Claim 1 in which the stiffening members are of rectangular hollow section.

3. A boom as claimed in either Claim 1 or Claim 2 in which the welds connecting each longitudinal plate to adjacent stiffening members, are external butt weld running along the length of the boom.

4. A boom as claimed in any preceding claim having two or more sections telescopically movable relative one another.

5. A boom as claimed in Claim 4 wherein bearing means are provided between the stiffening members of adjacent sections.

6. A boom as claimed in Claim 5 wherein the bearing means comprise a pair of lateral bearing pads and a pair of vertical bearing pads.

7. A boom as claimed in any preceding claim wherein the plates are embossed substantially along the whole length of the boom.

8. A boom as claimed in any preceding claim wherein the plates are embossed between 25 and 80% of the surface area of the plates.

9. A crane or the like provided with a boom as claimed in any one of the preceding claims.

10. A boom for a crane or the like substantially as hereinbefore described with reference to the accompanying drawings.