US3051325A

US3051325A - Crane

Info

Publication number: US3051325A
Application number: US713372A
Authority: US
Inventors: William L Risto
Original assignee: Thew Shovel Co
Current assignee: Thew Shovel Co
Priority date: 1958-02-05
Filing date: 1958-02-05
Publication date: 1962-08-28
Anticipated expiration: 1979-08-28

Description

Aug. 28, 1962 W. L. RISTO CRANE Filed Feb. 5, 1958 INVENTOR. WILLIAM L. R 5T0 BY (9600M AT T a (SRNEYS United States Patent 3,051,325 CRANE William L. Risto, Amherst, Ohio, assignor to The Thew Shovel Company, Lorain, Ohio, a corporation of Ohio Filed Feb. 5, 1958, Ser. No. 713,372 Claims. (Cl. 21238) The present invention relates generally as indicated to a crane, and more particularly to a crane of the type that comprises a mobile chassis on the turntable of which the crane structure (the cab and boom) are mounted for swinging about the vertical axis of the turntable.

In the case of a crane that is mounted on a wheeled chassis, the chassis frame usually is of much greater length than width, for instance 13' X 2 /22 with axle support brackets 8' apart, whereby the side-stability of the crane is much less than the end (fore and aft) stability. Stated in other words, the load handling capacity of such mobile crane is much greater when the boom thereof extends either forwardly or rearwardly of the chassis than when the boom extends out to either side of the chassis. Accordingly, there is an element of danger involved in the crane being tipped on its side as when a heavily loaded boom is swung from the rear or front to the side.

Hitherto, the most widely used expedient for increasing the side-stability of a crane has been to provide outriggers or props that may he slid out or swung out from the opposite sides of the frame, such outriggers usually being equipped with screw jacks at their free ends for shifting the shoes thereof to ground-engaging position outward of the wheels. A disadvantage of such Outriggers is that the manipulation thereof is a time-consuming operation; and furthermore, when the Outriggers are in operating position, the crane is immobilized for travel, thereby hampering its use in handling of loads that are to be moved to points beyond the reach of the boom. Aside from the foregoing, a careless or inattentive operator, not wishing to be bothered with the setting up of the outriggers, may lift a heavy load at the front or rear and swing it to the side, only to find that the crane tips over on its side with resulting damage to it and personal injury to himself.

Another expedient that is known in the art is the provision of shiftable weights on the chassis, but this requires weight-shifting mechanism and slideways along which the weights are shifted. In this connection, it also has been proposed to mount the crane structure on the chassis for transverse shifting so as to increase the length of the moment arm of its center of gravity about the wheels that are on the same side of the chassis as the load on the boom. Again, this requires the provision of a transverse slideway on the frame, and of mechanism for transversely shifting the crane structure on the chassis. With the foregoing in mind, it is a main object of this invention to provide a simple form of crane stabilizer that has no moving parts of any kind.

It is another object of this invention to provide a crane stabilizer which does not, in any way, interfere with the mobility of the crane and which does not require any attention on the part of the crane operator.

It is another object of this invention to provide a crane stabilizer that is maintenance-free.

It is yet another object of this invention to provide a mobile crane having a free-stability, i.e. the rated load that may be safely swung in a full circle, which is comparable with, or substantially equal to the fore and aft stability. Otherwise stated, the present crane has a side stability corresponding to the fore and aft stability where by the maximum safe load that can be handled by the crane is the safe load at any and all swing positions of the boom.

It is still another object of this invention to provide 3,051,325 Patented Aug. 28, I962 a crane that has a cruciform chassis frame that utilizes the cross-portions between the wheels as the stabilizers without adding to the overall height, length, or width of the mobile chassis and without adding to the bulk of the crane structure (the cab and boom) that is swingable on the turntable of the chassis.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 is a perspective view of a mobile crane embodying the present improvements;

FIG. 2 is a bottom plan view of the chassis of the crane shown in FIG. 1; and

FIG. 3 is an end elevation wiew of the crane chassis shown in FIG. 2.

Referring now in detail to the drawings, and first more especially to FIG. 1, the crane comprises a mobile chassis 1 which herein is shown, for purpose of illustration only, as a truck chassis which includes a chassis frame 2 supported on propelling wheels 3 at the front and rear of the frame. Mounted on the turntable 4- of said chassis 1 is the crane structure 5 which may comprise a base 6 which carries the crane cab 7 and to which the foot F of the crane boom 8 is pivotally connected for swinging in a vertical plane for raising or lowering the tip of the boom. Suitable cables 9 extend from power-operated drums (not shown) inside the cab 7 to the boom for thus raising and lowering the boom and for raising and lowering and/ or for manipulating the load handling device 10 which is shown here as being a grab bucket but which obviously may be a lifting magnet, a crane hook, lifting tongs, etc.

Also located in the cab 7 is an engine E for operating the drums aforesaid, for driving the wheels 3 and for swinging the crane base 6 on the turntable 4.

Without more, the crane thus far described would have a side-stability less than its fore and aft stability owing to the generally long and narrow proportions of the chassis frame 2 and accordingly, there would be a greater than desired differential between the free stability of the crane and the maximum safe load that can be lifted to the front or to the rear of the crane. This differential would be even more pronounced in the case of a motor crane wherein the wheelbase is still longer in proportion because of the mounting of a drivers cab on the frame forwardly of the crane cab.

In order to provide for a maximum free-stability which approaches or equals the maximum safe fore and aft load at the tip of the boom 8, the frame 2 herein, is cruciform as shown, including longitudinally extending portions 11 to which the wheel supporting differential axle housings 12 are secured adjacent the ends of said frame portions 11 and transversely extending portions 14 between the front and rear wheels 3. Said transversely extending frame portions 14 are preferably made up of welded steel plates P forming box-like structures that are filled with pig iron embedded in concrete or filled with other heavy material.

The front and rear wheels 3 are rotatably supported by the respective axle housings 12 and are secured on axles (not shown), power being transmitted from the engine E in the cab 7, through

shafts

15, 16, and 17 and intervening universal joints 18. (See FIG. 2..)

The turntable 4 is mounted on the top of the cruciform frame 2 and includes the usual bull gear 19 which meshes with a power driven pinion gear journalled in the crane base 6 for elfecting swinging of the crane structure 5 about the vertical center axis of the turntable 4.

his now clear, especially from FIG. 3, that the side stability of the crane is greatly increased owing to the stabilizing influence of the transversely extending frame portions 14.- When the boom load is to the left of the chassis 1, the right portion 14 will produce the predominating stabilizing influence because its moment arm about the left wheels 3 is much greater than that of the left portion 14. On the other hand, when the boom load is to the right of the chassis 1, the left portion 14 will produce the predominating stabilizing influence because its moment arm about the right wheels 3 is much greater than that of the right portion 14. In any event, the portions 14 although of equal weight serve alternately to produce substantial stabilizing influence as to loads lifted by the boom 8 on opposite sides of the chassis 1.

When lifting fore and aft loads, the weights of the portions 14 may be nicely figured, without substantial side overhang, so that the side and the fore and aft stabilities are approximately equal. In that way, the free stability of the crane, that is, the rated load that may be safely swung around a full circle, is maximum. Therefore, the crane operator need not fear tipping of the crane since any load that can be safely lifted at the front or rear can be safely swung over to either side.

While the weight of the cross-portions 14 would appear to add to the total weight of the crane, it should be observed that for a specified rated load of the crane, the counterweight on the base 6 may be eliminated or reduced to merely counterbalance the boom 8.

As an example, the chassis frame 2 (excluding the portions 14) may be of hollow structure, approximately 2 /2 wide and 13' long, end to end with axle mounting brackets 21 spaced apart about 8. The cross-portions 14 may be roughly about 2 /2 square while just barely projecting beyond the wheels 3 as viewed in FIG. 2 and about l /2-2' in thickness as viewed in FIG. 3. Each portion 14, therefore, may accommodate between about 9 to 12.5 cu. ft. of heavy material such as pig iron embedded in concrete. Thus, insofar as fore and aft stabilizing influence is concerned, both portions 14 will have a moment arm of 4', and insofar as side stabilizing influence is concerned, one portion 14 will have a moment arm of about 7 while the other portion will have a moment arm of about 1' whereby they will have the same side stabilizing effect as both portions 14 have about the fore and aft 4' moment arms.

Considered from another standpoint, the present invention may be utilized in the increasing of the free-stability of existing sizes and ratings of cranes to the value of the present end stability. In other words, by providing the cruciform chassis frame 2 in place of the usual chassis frame the existing rated end stability of a specified size and type of crane becomes its free-stability. Actually, in that case, the cruciform frame 2 would increase the end stability also, but the operator, being familiar with existing equipment, would be handling loads within the previously existing end load limits which now can be swung safely through a full circle.

, In summa y, therefore, the present crane stabilizer is of simple, maintenance-free form, and has no moving 7 parts that need to be manipulated from inoperative to operative position or vice versa. Contrast this with existing outrigging techniques which temporarily immobilize the crane for travel and with existing weight-shifting techniques that require slideways and mechanisms for shifting the weights. In addition, the present invention makes use of otherwise wasted space between the wheels 3 without requiring modifications in the chassis frame 2 in or about the area of the turntable 4.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a swinging crane, the combination of a mobile chassis having a chassis frame and ground-engaging propelling means, a turntable on said chassis frame between the ends and sides thereof, a crane base swingably mounted on said turntable about a vertical axis, a crane cab mounted on said base, drive means for said ground-engaging propelling means in said crane cab, a boom having its foot pivotally connected to said base whereby the tip of said boom may be raised or lowered, and fixed counterweights carried on said chassis frame and spaced above the ground with their centers of gravity inward of said propelling means to substantially increase the side stability of said crane with reference to swinging of a load on said boom to either side of said crane.

2. The swinging crane of claim 1 wherein said chassis frame is cruciform with said propelling means mounted adjacent the ends of the longitudinally extending portions and with the laterally extending portions constituting said fixed counterweights.

3. The swinging crane of claim 2 wherein said laterally extending portions are of hollow box-like form arranged to be filled with a heavy material.

4. The swinging crane of claim 2 wherein said propelling means comprises spaced apart front and rear wheels between which the laterally extending portions of said chassis frame are disposed, and power transmission means from said drive means.

5. A chassis for cranes and the like having a cruciform chassis frame, ground-engaging propelling means mounted adjacent the ends of the longitudinally extending portions of said chassis frame, a turntable on said chassis frame between the ends and sides thereof adapted to support a crane and the like, power transmission means leading from said turntable to the ends of said longitudinally extending portions of said chassis frame adapted to drive said propelling means from a prime mover in such crane, the laterally extending portions of said cruciform frame constituting plates forming hollow box-like structures arranged to be filled with a heavy material such as concrete and thus constituting fixed counterweights carried on said chassis frame within the confines of said ground-engaging propelling means and spaced above the ground substantially to increase the side stability of such crane with reference to swinging of a load on either side of said chassis.

References Cited in the file of this patent UNITED STATES PATENTS