Boom members having stiffener elements for crane boom constructions

Abstract

A multisection crane boom construction is disclosed herein. The various boom sections are each formed of a plurality of members which are interconnected in a unique fashion and are reinforced to provide boom sections that have a high strength-to-weight ratio and provide both vertical and lateral rigidity. Each boom section consists of a pair of elongated channel members having webs and flanges with the flanges being interconnected by connecting members and the webs being reinforced by web stiffeners to increase the buckling resistance of the web portions.

Description

BACKGROUND OF THE INVENTION

For many years now, telescoping crane booms have been common in the art of material handling units. These telescoping crane booms generally consist of a plurality of hollow sections which are telescoped relative to each other by hydraulic rams or cables so that the effective length between the base section attached to a mobile carrier and the outer end can be varied.

As the overall lifting capacity of these units is increased, it is also necessary to effectively increase the strength of the boom with respect to vertical and lateral rigidity. The most ideal type of boom construction would be to form a boom that is rectangular and hollow and is integrally formed to provide the desired rigidity. However, such a boom section construction adds a substantial amount of overall weight to the entire boom.

It will be appreciated that in large multisection crane booms, the overall weight of the boom has a direct bearing on the lifting capacity of the crane. For example, each pound of weight added to the cantilevered boom will decrease the amount of lifting capacity for the crane. Thus, manufacturers are constantly striving to decrease the overall weight of the boom without sacrificing vertical and lateral rigidity.

SUMMARY OF THE INVENTION

The present invention provides a boom design with a high strength-to-weight ratio. The elements forming the boom are rigidified in such a manner that the overall weight of the boom can be substantially reduced without sacrificing lifting capacity.

More specifically, the boom construction of the present invention consists of a pair of elongated channel members that each have a central web portion and a pair of flanges extending substantially perpendicular at opposite edges of the web portions. The channel members are positioned so that the web portions are located in spaced parallel relation to each other and extend substantially vertically with respect to the boom. The respective pair of adjacent flanges of the two channel members are interconnected by plates which define the upper and lower horizontal portions of the substantially rectangular hollow boom. The hollow rectangular boom is reinforced at each of the corners thereof by four elongated angle irons that have their bases located at the respective corners of the rectangular boom and have legs extending from the corners thereof along the respective flanges and webs of the channel members.

The webs of the respective channel members are reinforced between opposite edges thereof in a manner to produce a high strength web portion that has a high strength-to-weight ratio. More specifically, the reinforcing means consists of generally transversely extending stiffeners which provide vertical and lateral rigidity to the boom section.

In one version of the invention, the web stiffeners consist of a plurality of longitudinally spaced stiffener elements for each web portion of the elongated channel members. Each stiffener element includes a central core having a plurality of arms extending therefrom and integral therewith. The central core is located generally along the center line between the pair of flanges that extend from opposite edges of the web portion of the elongated channel and, in the specific embodiment illustrated, the stiffener elements are X-shaped with the respective pairs of arms extending in opposite directions and terminating adjacent the flanges of each web portion. The web portions are further rigidified by substantially circular buttons which have a circumferential dimension greater than that of the central cores for the respective stiffening elements and these buttons are aligned with the central cores and connected to the web portions of the respective elongated channels.

To substantially reduce the overall weight of the boom sections without sacrificing overall strength, the web portions have cutouts that are substantially diamond shaped and extend generally parallel to the adjacent edges of the arms of adjacent pairs of web stiffeners. The result is that the overall structure for the boom sections will substantially decrease the weight of the unit without sacrificing lateral or vertical stability of the unit. This will substantially increase the load capacity that can be lifted with a crane that has a plurality of boom sections.

In one version of the invention, the web stiffeners consist of a plurality of longitudinally spaced reinforcing channel bars that extend substantially vertically or perpendicular with respect to the longitudinal axis of the elongated channel members and the channel bars each have a pair of legs extending from a web portion thereof with the free ends of the legs being connected to the webs of the channel members.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a transport vehicle having a multi-section crane boom supported thereon;

FIG. 2 shows a plan view of one of the outer telescopic boom sections;

FIG. 3 shows a vertical section of the boom section shown in FIG. 2, as viewed along line 3--3 of FIG. 2;

FIG. 4 is a transverse section of the boom section shown in FIG. 3, as viewed along line 4--4 of FIG. 3;

FIG. 5 is an exploded fragmentary perspective view of a portion of the boom section shown in FIG. 2;

FIG. 6 is an enlarged fragmentary view of the base section of the boom shown in FIG. 1;

FIG. 7 is a transverse section of the boom shown in FIG. 6, as viewed along lines 7--7 of FIG. 6; and

FIG. 8 is a horizontal section, as viewed along line 8--8 of FIG. 6.

DETAILED DESCRIPTION

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated.

Referring to the drawings, particularly FIG. 1, there is shown a vehicle 10 having turntable 12 rotatable thereon with boom 14 supported on turntable 12 by horizontal pin 16. Boom 14 is pivoted about pin 16 through fluid ram 18, which is interposed between turntable 12 and boom 14.

Boom 14 consists of a plurality of sections including a base section 20 and a plurality of additional outer sections 22 that are telescoped relative to each other and all outer sections are capable of being retracted into the outer open end of base section 20. The telescoping movement may be accomplished through any suitable means, such as fluid rams (not shown).

The outer boom sections 22 are all substantially identical in construction, except for size, and thus only a single section will be described in detail with the understanding that the remaining sections incorporate the same elements in the same relation. FIGS. 2 through 5 show the details of boom section 22.

Boom section 22 consists of a pair of elongated channel members 24 each of which has web portion 26 and a pair of flanges 28 extending from opposite edges of elongated web portion 26. The two elongated channel members are positioned so that the web portions are in spaced, parallel vertical planes and the flanges of the respective channel members extend towards each other, as shown in FIG. 4. The free edges of adjacent flanges of the respective channel members are spaced from each other and are interconnected by a pair of interconnecting members or plates 30 and plates 30 are preferably welded to flanges 28.

Thus, the plates 30 and channels 24 define a generally hollow rectangular box-like structure in cross-section having a plurality of flat walls. Each of the corners of the hollow rectangular box-like structure is reinforced by reinforcing plates which are located adjacent the intersection between flanges 28 and web portions 26. The pairs of reinforcing plates for each of the corners consists of angle iron 32 which has a pair of legs 34 that respectively extend along flanges 28 and web portions 26 and are secured thereto, as by welding.

The purpose of the reinforcing plates, defined by legs 34, is to add the most efficient mass as far from the neutral axis as possible so as to achieve the greatest possible stiffness for the box-like boom structure. An additional advantage is that angle irons 32 transmit the vertical compressive reaction forces into the web portions 26 to increase the distortion strength thereby greatly decreasing the potential of lateral distortion of the boom section. A further advantage of the angle irons 32 is to provide a fixed corner support at each corner of the boom section, which increases the resistance to buckling stresses that may be developed in the web portions 26.

Another advantage of the location and size of the angle irons 32 is that they may also act as wear plates between adjacent portions of two adjacent boom sections. An inspection of FIG. 4 shows that the thickness of interconnecting plates 30 is slightly less than the thickness of the angle iron legs 34 so that the surfaces of legs 34 extend above the outer surfaces of plates 30.

The elongated boom section 22 also has web stiffeners connected to each web portion for increasing the buckling resistance of the web portion when weight is supported by the boom 14. The web stiffeners for boom section 22 consist of a plurality of stiffener elements 40 which are longitudinally spaced along web portion 26. Each stiffening element 40 has a central core 42 and four arms 44 extending in different directions from central core 42 towards the respective flanges 28 of the associated channel member 24.

In the illustrated embodiment, legs 44 and central core 42 define a generally X-shaped stiffener element, in plan view, with the centers of cores 42 located generally along center line CL of the elongated channel, center line CL being located between flanges 28 and spaced an equal distance therefrom, as shown in FIG. 3. The pairs of aligned arms 44 have a combined vertical height which is substantially equal to the dimension between opposite edges of web portion 26 and the arms extend diagonally, as viewed from the inside of the box structure defining boom section 22. The stiffener elements are located inside the box section and are secured directly to web portions 26, as by welding.

To decrease the overall weight of boom section 22, without sacrificing strength, diamond-shaped openings 50 may be cut from the boundaries defined by an adjacent pair of web stiffener elements. The net effect is that the material cut from the web portions 26 substantially decreases the overall weight of the boom section. This will create a semi-closed lattice boom construction as shown in FIG. 3.

The web stiffener elements increase the buckling strength of the edges of openings 50 and provide substantial resistance to bending and vertical buckling of the web portion which might result from local compressive reaction forces. If further resistance to buckling is required, buttons 52 may be positioned to overlie the respective central cores 42 and be secured directly to the web portions. These buttons have a dimension that is slightly greater than the dimension of the central core 42 and may be secured directly to web portions 26 by welding.

The respective web stiffeners including stiffener elements 40 and stiffener buttons 52 provide increased vertical buckling strength for the web and permit greater shear transfer for the web portion without adding a substantial amount of weight to the overall boom section. In fact, the amounts of material removed from the web portions to define openings 50 is greater than the weight of the web stiffeners added to the boom. The effect is that the overall weight of the boom section is decreased while the strength thereof is increased.

Another type of boom section is shown in FIGS. 6 through 8 and this boom section is particularly adapted to use as the base section 20 which is attached to the turntable. Base section 20 is in many respects similar to each of boom sections 22 and differs primarily in the reinforcement for the web portions of the channel members.

As shown in FIGS. 6-8, boom section 20 again consists of a pair of elongated channel members 60 each having a web portion 62 and flanges 64 extending from opposite edges of the web portion. Channel members 60 are positioned so that web portions 62 extend parallel to each other and are horizontally spaced by a distance so that the free edges of adjacent flanges 64 are spaced from each other. Flanges 64 are interconnected by a pair of interconnecting members 66, which may be secured thereto, by welding.

Each corner of each channel member is reinforced by an angle iron 68 with two legs 70 of angle iron 68 defining reinforcing plates or bars extending from each corner of the box-like structure along a portion of web portions 62 and a portion of flanges 64. Again, angle irons 68 produce the most efficient mass as far as possible from the center neutral axis of the box-like structure defining boom section 20. This will achieve the greatest possible stiffness with a minimum amount of weight.

Each of the web portions 62 is again reinforced by web stiffeners 71 and in boom section 20, web stiffeners 71 consist of elongated reinforcing channel bars, each of which has a web 72 and a pair of legs 74 extending from the web. The free edges of legs 74 are secured directly to the web portions 62 of channel member 60 to provide the desired reinforcement. The longitudinal spacing of the web stiffeners 71 is a function of the overall length of the boom section, as well as the shear stress in the web.

As in the previous embodiment, bars or plates 70 at the respective corners of the box-like structure and web stiffeners 71 will substantially increase the transfer of vertical compressive reaction forces directly into web portions 62 to produce a greater resistance to buckling stresses that may be developed on web portions 62. Again, as in the previous embodiment, the web stiffeners are designed so as to produce a minimum amount of weight with a maximum amount of resistance to local compressive reaction forces and buckling stresses that may be developed in the boom section. Since this boom section is specifically designed for use as the base section, the overall weight of the boom section is not quite as critical as the weight of the remaining telescoping boom sections 22, and thus there is no need for producing cutouts in web portions.

To further rigidify the base end of boom section and provide increased resistance to react against compressive forces along the lower portions of base section 20, additional longitudinally extending reinforcing channel bars 80 which are positioned between adjacent pairs of vertical channel bars 71. These channel bars have a first leg 82 secured to web portion 62 and a second leg 84 connected to angle iron 68.

As can be appreciated from the above description, the present invention provides an improved boom construction which produces greatest resistance to buckling stresses of the vertical portions of the boom with a minimum amount of overall weight.

Claims

What is claimed is:

1. A boom for a crane or the like comprising an elongated hollow member having a plurality of flat walls, at least one of said walls having a plurality of openings spaced from each other, a stiffening element located between each adjacent pair of openings, each stiffening element having a central core generally aligned with a longitudinal center line for said at least one wall and a plurality of arms extending from said central core to the outer edges of said at least one member, said stiffening elements being secured to a surface of said at least one wall between said openings and reinforcing the edges of said openings, and a plurality of buttons each having a dimension greater than the dimension of said cores, said buttons overlying respective central cores and being secured to said surface.

2. A boom as defined in claim 1, in which said hollow member is defined by a pair of elongated channel members, each having a web portion and flanges at opposite edges of said web portion, said channel members being positioned so that said web portions define a pair of said flat walls and said flanges of respective channels extend towards each other with free edges spaced from each other, and a pair of interconnecting members connecting adjacent pairs of flanges to define a further pair of said flat walls.

3. A boom as defined in claim 2, in which both of said web portions have openings, stiffening elements and buttons as defined in claim 7.

4. A boom as defined in claim 3, further including elongated reinforcing plates located adjacent the intersection of each flange with its adjacent web portion.

5. A boom as defined in claim 4, in which said elongated reinforcing plates include an angle iron at each intersection.

6. A boom as defined in claim 3, in which said stiffener elements are generally X-shaped in plan view and said openings diamond shaped to produce a semi-closed lattice boom construction.

7. A boom as defined in claim 1, in which said surface is an inside surface of at least one of said walls of said hollow member.