Fire-fighting apparatus and elongate cantilever boom assembly therefor

[57] ABSTRACT

An elongate cantilever boom assembly. The assembly is fabricated from identical U-shaped extrusions. The web is thicker than the legs of the extrusion so that when the extrusions are welded together the webs which are positioned at the extreme fiber have the greatest stress resistance to provide a strong, lightweight boom. The legs define tongue and groove means, one leg defining a tongue and the other the groove so that a pair of such extrusions from a single die may be juxtaposed in tongue and groove engagement for welded securement.

Claims, 6 Drawing Figures

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PATENTED FEB 51974

3,789,869

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3,789,869

FIRE-FIGHTING APPARATUS AND ELONGATE CANTILEVER BOOM ASSEMBLY THEREFOR

A wide variety of heavy duty construction equipment and the like utilizes elongate, hollow, load bearing cantilever boom assemblies. In such equipment, a cantilever boom assembly is secured at one end to a support, usually for movement with respect to the support. Such booms are then stressed in use, as by applying vertical loads to the free ends of the boom.

A usual mode of fabricating booms of that character entails the bending or folding of elongate steel plates into desired shapes, such as a box-like shape or Ushaped sections, which are then finished as necessary, as by welding. The use of folded shapes means, of course, that all portions of the folded shapes will have about the same strength or load bearing characteristics. To vary the load bearing characteristics of such booms, thereby to minimize the weight of the boom, it has been necessary to add additional pieces, as additional elongate plates, at particular locations, thereby to strengthen those portions of a boom assembly. Other efforts to adjust the distribution of stresses in cantilever beams have been suggested, as for example in Morton et al U.S. Pat. No. 3,572,528.

It has now been discovered that the complexities and disadvantages of prior art practices may be avoided by the fabrication of elongate hollow booms from appropriately dimensioned aluminum extrusions, which extrusions are integrally formed with a plurality of legs, a continuous portion of at least one of which is greater in thickness across its width than the other legs. Preferably the continuous portion extends across the entire width whereby the leg and the continuous portion thereof are coincident in width. By so forming elongate boom sections, when assembled into a cantilever boom, a larger mass of material is positioned at the extreme fiber of the boom, i.e., at the location where the greatest stresses will be encountered. Not only does that eliminate subsequent strengthening operations, as by the addition of reinforcing plates or the like, but it also makes it possible initially to form a boom section which will be of the lightest possible weight to satisfy design requirements. That is because the alternative to adding reinforcing plates or the like is to fold a boom section from a plate which is thick enough to withstand the anticipated stresses at the extreme fiber.

By fabricating a boom of extruded aluminum sections having legs of different thicknesses, by a difference of at least about 10 percent, other advantages, beyond weight reduction and simplicity of formation, also result. For example, during extrusion it is possible also to form pre-shaped, weld preparation joints. Indeed, it has been determined that pre-shaped weld preparation joints of the tongue and groove type may readily be formed as a boom section is being extruded. When a cantilever boom assembly is to be formed as from two U-shaped sections and tongue and groove formations have been formed at alternate edges of the legs of the U-shaped sections, a pair of such sections may be disposed in tongue and groove engagement with each other to mate and interlock, after which they may be welded together. That arrangement of tongue and groove formation makes it possible to use only one extrusion die to form both of the sections to be used in fabricating a boom. Furthermore, when identical Ushaped sections are used, and the central legs of the “U” are the portions of greatest thickness, the welds will be located at the neutral axis, i.e., at about the center of the boom sides where the tensile and compressive stresses in the cantilever boom in use are at a minimum.

Although booms constructed in accordance with this invention have applicability in a wide variety of heavy duty equipment, they are especially useful where minimum boom weight, dimensional accuracy and appearance are important factors, such as in fire-fighting equipment. Booms in accordance with this invention may be much more accurately dimensioned throughout their entire lengths, than those which are folded from plates, or the like. Further, because tongue and groove formations may be integrally formed, they may be more precisely located, and a minimum number of boom sections may be more easily and precisely juxtaposed and aligned for securement by welds in the assembly of the boom.

It has also been determined that when matching extruded U-shaped boom sections are joined, the resulting boom is straighter and freer of twists than booms which are assembled from folded material or from a multiplicity of component parts. Furthermore, booms constructed in accordance with this invention present a more uniform and neater appearance, a factor which is of great importance in some applications, such as in fire-fighting equipment.

These and further objects, advantages and features of this invention will become apparent from the following description and drawings, of which:

FIG. 1 illustrates a typical fire-fighting truck, with which a boom assembly of this invention is adapted for use;

FIG. 2 is an enlarged fragmentary view of the boom assembly of FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along line 3—3 of FIG. 2;

FIG. 4 is an enlarged view of a portion of FIG. 3;

FIG. 5 is an enlarged fragmentary exploded view of a joint assembly of FIG. 3; and

FIG. 6 is an enlarged fragmentary view of a portion of FIG. 3.

Referring now to the drawings, a telescopic, cantilever boom incorporating the present invention is illustrated in its entirety at 10 in FIG. 1. In FIG. 1, the cantilever boom 10 is depicted in a retracted position on a mobile support which is illustrated as being a pumper truck 12. Pumper truck 12 may be of a conventional design, and desirably includes suitable control means (not shown) by which a fireman may remotely control the boom 10 for discharge of a controlled spray of water onto a fire. The support includes a turntable 14 mounted at the rearward end of the truck 12. Turntable 14 mountingly supports the boom assembly 10 at one end for rotational movement about a vertical axis. The turntable 14 may be of the type disclosed in U.S. Pat. Nos. 3,346,052 and 3,599,722.

As is explained in those patents, turntable 14 may also mount the boom for oscillatory movement about a horizontal axis 16. Movement about axis 16 is provided by a suitable hydraulic cylinder means 18 which is connected at one end to the turntable 14 and at the other end to anchor plate means 20 suitably secured to the boom 10.

The outer free end of boom 10 provides a suitable monitor assembly 22 which includes a discharge nozzle 24 through which water may be discharged in desired

3,789,869 volumes and patterns, as in the ways disclosed in the aforementioned patents.

The boom 10 may be constructed and assembled in a manner similar to that boom assembly which is described in commonly assigned, copending U.S. Pat. Application Ser. No. 83,925 filed on Oct. 26, 1970, now U.S. Pat. No. 3,675,721, issued July 11, 1972, and desirably includes suitable water supply or conduit means 26 which are supplied with water from adjacent turntable 14. At their other ends, conduit means 26 communicate with monitor assembly 22 so that water may be discharged through nozzle 24. The disclosure of said application Ser. No. 83,925 is here incorporated by reference.

Boom 10, as stated, may be constructed and may be operated generally in accordance with application Ser. No. 83,925, except that the boom members themselves, and particularly the outer or lower boom member, are made and assembled in accordance with the invention herein disclosed.

Referring now to FIGS. 2 to 6, boom assembly 10 comprises an elongate lower outer boom member 30 and an elongate upper inner boom member 32, each of which is generally rectangular in transverse crosssection and each of which is hollow. Each is very substantially longer than any dimension in transverse cross-section. Boom member 32 is mounted for telescopic movement in boom member 30.

Boom member 30, as best seen in FIGS. 3 and 4 comprises a pair of identical elongate outer boom sections 34, 34', each of which is generally U-shaped in crosssectional configuration, and each of which comprises a central web 36 and a pair of integral flanges 38 extending substantially at right angles . to central web 36. Flanges 38 are disposed at the transverse edges of the central web 36.

Each boom section 34, 34', in the embodiment illustrated, is extruded from a high strength aluminum alloy through a single appropriate extrusion die and the finished cross-section is integrally formed at the time the sections are extruded. By extruding sections 34, 34', a multiplicity of conventionally necessary fabrication steps are eliminated. Most importantly, however, by extruding sections 34, 34' properly proportioned integral leg and flange portions are provided, thereby to position the greatest mass of material at the zones which are subject to the most severe stresses, i.e., the boom section portions at the extreme fiber. In the embodiment illustrated the zones subjected to the greatest stresses in use are the upper and lower webs 36 of the rectangular boom member 30.

As such, as best illustrated by FIG. 4, the thicknesses A of central webs 36 are greater across their entire widths than are the thicknesses B of the flanges 38 save only at the free longitudinal edges of the flanges. At those edges, the flanges 38 provide appropriately configured joint members. The joint members desirably comprise a first tongue joint member 40 and a second groove joint member 42 which are complementary in configuration. When the U-shaped sections 34, 34' are provided with a tongue joint member 40 adjacent one flange edge and a complementary groove joint member 42 adjacent the other flange edge, a pair of identical boom sections 34, 34' with opposite joint members in engagement with each other may be juxtaposed for securance to each other. As such, only a single extrusion die to form both of the sections necessary to the formation of a rectangular boom member 30 is required.

When sections 34, 34' are juxtaposed with each other, i.e., are positioned in the interlocking tongue and groove engagement illustrated in the drawings, they are in alignment for securance to each other, as by welding. When so juxtaposed, the flange ends define an appropriately sized and configured weld preparation joint or fillet 44 which is adapted to receive weld material 46. FIG. 5 illustrates an exploded view of the joint members 40, 42 and FIG. 6, at the left, illustrates the interlocked, aligned and welded joint, with the weld material 46 filling fillet 44, thereby permanently securing sections 34, 34' to each other. It is to be noted that welds 46 are located at the neutral axes of boom member 30 so that they do not adversely affect the designed strength characteristics at the extreme fibers, i.e., the central webs 36 which are subjected to the greatest tensile and compressive stresses.

Although the individual U-shaped sections 34, 34' are quite flexible and easily twisted when separate, when held in true alignment at the time they are juxtaposed and welded together, they provide boom members which are much straighter, truer and freer of twists than conventionally fabricated booms.

A boom member of the character of boom member 30 has been fabricated from identical extruded Ushaped sections. Each section was approximately 9.2 inches wide and about 6 inches high. The central web was about 0.31 inch thick and the flanges were about 0.28 inch thick. As such, the central web was at least about 10 percent thicker than the flanges. When assembled, the hollow boom member 30 was substantially rectangular and was about 9.2 by 12 inches in transverse cross-section and was about 23 feet in length. Such boom sections have been formed of aluminum alloys designated as 5086-H111 and 5083-H111.

The other boom member 32 may be formed of sections 50, 50' which are made and assembled in a manner similar to boom member 30. However, because the stresses and loads which boom member 32 must withstand are less than those which the lower boom member 30 must withstand, the thickness of central webs 52 and the flanges 54 may be the same. A first tongue joint member 56 is disposed at one flange edge and a second complementary groove joint member 58 is provided at the other flange edge, for juxtaposed interlocking engagement and securance by a longitudinal weld 60. As such, identical U-shaped sections 50, 50' may be formed in a single extrusion die, as were sections 34, 34'.

Boom members fabricated in accordance with this invention are truer, straighter, freer of twists, and more dimensionally accurate than conventionally formed booms. They are neat in appearance. The sections from which they are fabricated are easily and relatively inexpensively made, and, when made by an extrusion process with a plurality of integral elongate webs, place the welds remote from the extreme fibers and provide a greater mass of material at the extreme fibers and across substantially all without the necessity of adding separate pieces to strengthen particular webs or zones.

Although this invention is susceptible of embodiment in different forms, only a presently preferred embodiment has been illustrated and described. That embodiment exemplifies the principles of the invention and is

3,789,869 not intended to limit the invention. The scipe of the invention will be pointed out in the claims.