US3323660A

US3323660A - Lattice boom construction

Info

Publication number: US3323660A
Application number: US488872A
Authority: US
Inventors: Sr George S Allin
Original assignee: NORTHWEST ENGINEERING CORP
Current assignee: NORTHWEST ENGINEERING Co
Priority date: 1965-09-21
Filing date: 1965-09-21
Publication date: 1967-06-06
Anticipated expiration: 1984-06-06

Description

June 6, 1967 G. s. ALLEN, SR

LATTICE BOOM CONSTRUCTION 4 Sheets-Sheet 1 Filed Sept. 21, 1965 I NVENTOR. @z'ORGE S. ALL/M31 2. BY

June 1957 G. s. ALLIN, SR 3,323,650

LATTICE BOOM CONSTRUCTION Filed Sept. 21, 1965 4 Sheets-Sheet 2 a l INVENTOR. Kg GEORGE S. ALLIN, SR.

14%RNE Y5 June 6, 1967 G. s. ALLIN, SR 3,323,660

LATTICE BOOM CONSTRUCTION Filed Sept. 21, 1965 :11; ll l i1--""' l In 1' 2 ,A vi

INVENTOR. GEORGE S. mum, rm.

4 Sheets-Sheet 5 June 6, 1967 G. s. ALLIN, an

LATTICE BOOM CONSTRUCTION 4 Sheets-Sheet 4 Filed Sept. 21, 1965 m a NU m E MM f E 57 6 Wm m d EYW 6 United States Patent 6 3,323,660 LATTIQE 1390M CONSTRUCTION George S. Allin, Sn, Green Bay, Wis., assignor to Northwest Engineering Corporation, Green Bay, Wis, a corporation of Wisconsin Filed Sept. 21, 1965, Ser. No. 488,872 8 Claims. (Cl. 212144) This invention relates to lattice boom construction and includes both novel structural features and a novel method of construction for lattice booms employed in large cranes, shovels and the like.

In the past it has been customary to individually weld the ends of the lattice members directly to the correspond ing chords. This had a tendency to introduce stresses in the chords that could not be relieved and which often produced distortion of the entire boom. Where several lattice members were welded to a chord in close proximity the stress concentrations were aggravated and frequently resulted in cracks in the chord, thus weakening the entire boom.

. The danger of booms breaking under load and falling is becoming more of a concern with the use of long lightweight booms on erection cranes for modern tall buildings.

The present invention provides a boom construction that strengthens the chords instead of weakening them and that facilitates securing of the lattice members to the chords while introducing a minimum of weld stresses into the chords.

The invention is applicable to booms having angle iron chords with flanges or legs at right angles to each other and also to booms having tubular chords. When angle iron chords are employed the invention employs a connector that fits into the bosom of the chord and is welded to both legs, thus adding support to the legs and strengthening the chords. When tubular chords are employed the invention employs a partial sleeve-like connector that fits approximately a 180 circumferential portion of the chord and strengthens the same.

The connectors are welded to the chords and the latter may then be stress relieved to assure freedom from undesirable locked in welding stress. Thereafter the lattice members are welded to the connectors of spaced chords to complete the boom assembly. The welds for the lattice members are desirably spaced from the chords so as not to directly stress the latter. Thus the predetermined relation and position of the chords can be maintained without distortion.

Where it is desired to reduce the weight of the boom by the employment of heat treated chords and lattice members, the construction provides a type of welded joint that makes possible the joining of the members without losing the effect of the heat treatment therein.

The accompanying drawings illustrate the best mode presently contemplated for carrying out the invention.

In the drawings:

FIGURE 1 is a top plan view of a boom segment employing angle iron chords and incorporating the connector of the invention;

FIG. 2 is a side elevation of the boom segment of FIG. 1;

FIG. 3 is an enlarged transverse section taken on line 3-3 of FIG. 1;

FIG. 4 is a detail section taken transversely of a chord on line 4--4 of FIG. 2;

FIG. 5 is a detail section taken on line 5-5 of FIG. 4 and showing a connector with its attachment to the chord and to the ends of a plurality of lattice members;

FIG. 6 is a perspective view of a portion of a chord with a connector secured thereto and adapted to receive the ends of three lattice members;

FIG. 7 is a view similar to FIG. 6 and showing a connector adapted to receive the ends of six lattice members; FIG. 8 is a detail section showing an end connector;

FIG. 9 is a detail plan view of an end connection at one corner of two beam sections;

FIG. 10 is a detail enlarged transverse section of one type of end connection taken on line 1010 of FIG. 1;

FIG. 11 is a detail enlarged transverse section of the other type of end connection taken on line 1111 of FIG. 1; and

FIG. 12 is a perspective view of a portion of a boom segment made up of tubular chords.

The boom illustrated is constructed of sections joined end to end and which may vary in dimensions according to their position in the boom. Sections disposed near the base or in the central body region of the boom may have their chords substantially parallel. Sections disposed near the outer end of the boom will generally be tapered to a smaller cross sectional dimension toward the outer end, by disposing the chords at a predetermined angle to each other.

In the embodiment illustrated in FIGS. 1-9, the boom section 1 is made up of four generally parallel

angle iron chords

2, 3, 4 and 5, respectively, and a plurality of cross lattice or lac ng members and diagonal or lacing members more specifically identified hereinafter.

The lattice members converge adjacent the chords to form a series of planular transverse strengthening zones, generally indicated in FIGURE 1 as zones A, B, C, D, E, F and G, respectively.

At each of these strengthening zones a connector is employed to secure the lattice members to a corresponding chord. Thus, at the end zones A and G, two types of connectors 6 and 7 are employed as individually illustrated respectively in FIGS. 10 and 11. Similarly, at each of zones B, C, D, E and F, two types of

intermediate connectors

8 and 9 are employed as individually illustrated in FIGS. 6 and 7.

More specifically chords 2 and 4 have the following connectors secured thereto in the order named starting with zone A and ending with zone G:

connectors

6, 9, 8, 9, 8, 9 and 6. Similarly

chords

3 and 5 have the following connectors secured thereto in the order named starting with zone A and ending with zone G: connectors '7, 8, 9, 8, 9, 8, and 7.

Each intermediate connector as illustrated in FIGS. 47, inclusive, is a casting adapted to fit in the bosom of a chord at a selected zone. The connector is a convex member having its opposite edges welded as at 10 and 11 to the

corresponding legs

12 and 13 of the chord. The connectors bridge the angle of the chord and support the legs relative to each other, thereby strengthening the chord at each zone.

Each connector 6 and 7 is adapted to receive the end of two

lattice members

14 and 15 disposed at right angles to each other and in the transverse plane of the zone. Lattice member 14 extends from connector 6 on chord 5. Lattice member 15 extends at right angles to the corresponding lattice member 14 and from connector 6 on chord 2 to connector 7 on chord 5 and a similar lattice member 15 extends from connector 6 on chord 4 to connector 7 on chord 3. Thus the two lattice members 14 and the two lattice members 15 at each end of section 1 form a rectangular outline corresponding to the rectangular cross section of the boom section 1.

Associated witheach connector '7 is an angular connector 16 which receives and secures two

diagonal lattice members

17 and 18 extending at an angle toward a corresponding connector 9 on an adjacent chord, i.e., the member 17 extending from connector 16 on chord 3 to connector 9 on chord 2 and member 18? extending from connector 16 on chord 3 to connector 9 on chord 4.

Similar lattice members

17 and 18 join a connector 16 associated with connector 7 on chord to the respective connectors 9 on chords 4 and 2.

The connectors 6 and 7 at each end of the boom section 1 have means for securing the section to the end of an adjacent similar section. Various means may be employed for this purpose, that shown comprising one or more cars 19 on the connectors and disposed to fit adjacent corresponding ears on the next adjacent section. The connectors at one end of boom section 1 have one ear 19 while the connectors at the opposite end of boom section 1 have two ears 19 spaced apart to receive the single ear of a corresponding end connector of an aligned boom section, as shown in FIG. 9. Each ear 19 has a bore 20 therethrough for receiving a pin 21 and which passes through the aligned bores of adjacent ears when two similar sections are aligned for securing the same together.

The end connectors 7 provide an additional diagonal socket 22 for receiving a diagonal lattice member 23 which extends laterally in a transverse plane normal to boom section 1 and between the connector 7 on chord 3 in zone A and the connector 7 on chord 5 in the same zone. At the opposite end of boom section 1, in zone G the lattice member 23 may extend between the connectors 7 on the same chords 2 and 4.

Referring to zone B, as illustrated in FIGS. 1 and 2, a connector 9 is welded to each of chords 2 and 4, and a connector 8 is welded to each of

chords

3 and 5. The same is true at zones D and F, zone D being additionally illustrated in FIG. 3.

Referring to zone C, as illustrated in FIGS. 1 and 2, a connector 9 is welded to each of

chords

3 and 5, and a connector 8 is welded to each of chords 2 and 4. The same is true at zone E.

Connector 9 is specifically shown in FIG. 7 and has six holes or fittings for receiving the ends of tubular lattice members. As shown there are three circular openings or fittings on a side, the central socket or fitting 24 being generally perpendicular or normal to the opposite leg of the chord, and the two end sockets or

fittings

25 and 26 on each side being disposed at suitable angles to receive diagonal lattice members as shown in FIGS. 4 and 5.

As shown in FIG. 1, one of the fittings 25 of connector 9 on chord 2 receives diagonal lattice member 17 from the connector 16 on chord 3, and as shown in FIG. 2, one of the fittings 25 of connector 8 on chord 4 receives diagonal lattice member 18 from the connector 16 on chord 3. Similarly, the other fitting 25 of connector 9 on chord 2 receives a diagonal lattice member 18 from the connector 16 on chord 5 and the other fiitting 25 of connector 9 on chord 4 receives diagonal lattice member 17 from the connector 16 on chord 5.

The fittings 26 of each connector 9 on chords 2 and 4 at zone B secure diagonal lattice members 27 and 28, respectively, which extend to the corresponding fittings 25 of connectors 9 on

chords

3 and 5 at zone C. Similarly the fittings 26 of each connector 9 at each of the zones secure diagonal lattice members 27 and 28, respectively, extending to the fittings 25 of corresponding connectors 9 at the next succeeding zone.

The central fittings 24 of each conector 9

secure lattice members

29 and 30 which extend at right angles to each other to corresponding fittings 31 in connectors 8 on adjacent chords.

Connectors 8 are illustrated in FIG. 6 and each has the two sockets or fittings 31 disposed at right angles to each other and generally perpendicular to the opposite leg of the chord. In addition to fittings 31, each connector 8 has an intermediate diagonal fitting 32, as shown in FIGS. 3 and 6 and which secures a strut 33 that extends diagonally of the section, i.e. from one chord to the chord diagonally opposite thereto,

More specifically, as shown in FIG. 3, at zone D 4 the connector 8 on chord 3 has a fitting 32 which secures one end of the diagonal strut 33, and the similar connector 8 on chord 5 has a fitting 32 which secures the other end of the diagonal strut 33. Since

chords

3 and 5 are diagonally opposite in the boom structure struts 33 serve to brace the structure diagonally. Similar struts 33 join the diagonally opposite connectors 8 at zones B and F. At zones C and E struts 34 join the corresponding connectors 8 and extend diagonally between chords 2 and 4.

In assembling the boom section, after the connectors are welded to the individual chords and the latter properly stress relieved, the four chords are generally positioned in a fixture and the lattice members and struts are individually positioned and welded in place. In positioning lattice members and struts one end is first inserted into a socket or fitting far enough to permit the member or strut to be aligned with the opposite fitting, whereupon a slight retraction of the member or strut will result in both ends of the same being confined in the corresponding fittings. Thereafter a fillet Weld 35 around the tubular member or strut will secure it to the fitting at each end.

It will be noted that welds 35 are generally spaced from

welds

10 and 11 and from the chords so that stresses resulting from welds 35 are not concentrated in the chords and do not weaken them.

If a lattice member or strut becomes damaged in service of a boom, it is possible to cut the member or strut out and replace it with a new one without injury to or stressing the adjacent chords.

FIG. 12 illustrates an embodiment of the invention employing tubular chords 36 and in which the connectors 37 are half sleeves thereon having the desired projecting sockets or fittings 38 for securing the lattice members and struts. In this construction the half sleeves 37 greatly strengthen and support the chords at the junction zone for the lattice members.

Half sleeves 37 are welded to the chords by fillet welds 29 along the peripheral edges of the half sleeves.

The detail description given above is illustrative only, and various modifications and embodiments may be employed. The principle involved is to keep the welds for the various lattice members and struts away from the chords and to provide an intermediate connector that both strengthens the chords and cushions or relieves the stress under working loads.

By employing fillet welds with the chord or lattice member extending beyond the weld in both directions, it is possible to keep the heat input low enough during the welding process to effect a quenching of the weld by the mass of metal adjacent to it without removing the desired high strength of a previously heat treated chord or lattice member.

Various modes of carrying out the invention are contemplated as being within the scope of the following clalms particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. For use in connecting lacing members to angle iron chords in a boom framework, a connector comprising a unitary body shaped to closely fit in the bosom of a chord and to be welded thereto, said unitary body having a plurality of openings therein remote from the chord welds and adapted to receive and secure the ends of boom lacing members.

2. In a boom having a plurality of longitudinally extending angle iron chords, a plurality of connectors fixedly secured in the bosom of each of said chords, each of said connectors having a plurality of openings therein, and lacing members disposed with their ends secured in said openings and extending between connectors on different chords.

3. In a boom having a plurality of longitudinally extending angle iron chords, a plurality of connectors fixedly secured in the bosom of each of said chords, each of said connectors having a plurality of openings therein which are disposed in the same plane, at least some of said connectors having an additional plurality of openings disposed in a plane which intersects said first-named plane, each said opening being aligned with a corresponding opening in a connector on a different chord, and lacing members disposed with their ends secured in corresponding aligned openings and extending between connectors on different chords.

4. A boom made up of sections, each comprising a plurality of longitudinally extending chords, a plurality of connectors spaced longitudinally of each chord and secured thereto by welds, each said chord and the connectors welded thereto being stress relieved as a unit, a plurality of lattice members joining connectors on adjacent chords to space the chords from each other, and welds securing said lattice members to said connectors and generally remote from said first named welds to facilitate replacement of a lattice member without effecting the characteristics of the chords to which it is secured.

5. The construction of claim 4 in which the welds are of a fillet type with the corresponding chord or lacing member extending both directions therefrom.

6. A boom made up of sections, each comprising a plurality of longitudinally extending angle iron chords, a plurality of connectors spaced longitudinally of each chord and secured in the bosom thereof by welds to the adjacent legs of the chord, each said chord and the connectors Welded thereto being stress relieved as a unit, a plurality of lattice members joining connectors on adjacent chords to space the chords from each other, and welds securing said lattice members to said connectors and generally remote from said first named Welds to facilitate replacement of a lattice member Without effecting the characteristics of the chords to which it is secured.

7. A boom made up of sections, each comprising a plurality of longitudinally extending tubular chords, a plurality of partial sleeve-like connectors spaced longitudinally of each chord and secured thereto by welds along the periphery of the connectors, each said chord and the connectors welded thereto being stress relieved as a unit, a plurality of lattice members joining said connectors on adjacent chords to space the chords from each other, and welds securing said lattice members to said connectors and generally remote from said first named welds to facilitate replacement of a lattice member without effecting the characteristics of the chords to which it is secured.

8. In the manufacture of boom sections from longitudinal chords and transverse and diagonal lattice members, positioning a series of connectors in longitudinally spaced relation along each chord, welding said connectors to the corresponding chord, stress relieving the chord and connectors after said welding, assembling the chords for each section, individually positioning lattice members between connectors on different chords and welding said members to said connectors at positions generally remote from said first named stress relieved welds.

References Cited UNITED STATES PATENTS 1,760,955 6/1930 Moss. 2,149,844 3/ 1939 George. 2,219,599 10/ 1940 Penote. 3,021,014 2/1962 Korensky 212-144 ANDRES H. NIELSEN, Primary Examiner.