CA1090301A - Arrangement for increasing crane capacity - Google Patents

Abstract

Abstract A conventional crane is given added lifting capacity by adding additional counterweight to the normal counterweight while maintaining stability by adding a pair of auxiliary carbody weights on the front and rear of the carbody between the crawler assemblies. The carbody weights have arms with lugs that cooperate with bracket lugs on the carbody so that the weights can be simply lowered into position. There is no interference with normal operation of the crane.

Description

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This invention relates generally to heavy lift cranes and more particularly concerns an arrangement for increasing the capacity of a heavy lift crane.
Modern heavy lift cranes embody many desicn trade-offs.
While high lifting capacity is obviously desirable, that requires increased crane size and weight, and that affects cost and manue-verability. Since a crane is seldom called upon to work at or near capacity, there is a degree of inefficiency in a design scaled for high capacities but working well beneath capacity.
It would be highly desirable to have a crane scaled for the bulk of the work to be done on a given job, and then have available some means of increasing the capacity of that crane --when increased capacity is called for. Although it was not sound procedure, this objective was often sought in practice by ~-crane users through such expedience as simply hanging additional counterweight, such as a bulldozer, on the rear of a crane. Under modern safety regulations, the addition of a meaningful amount of counterweight above that for which the crane is designed cannot be done because it would change the rearward tipping equations.
That is, when the crane is not under load, the extra counter-weight would tend to tip the crane rearwardly.
According to the present invention an arrangement is provided for increasing the capacity of a crane having a carbody supported by a pair of crawler as~emblies which permit movement of the crane under both heavily loaded and unloaded conditions and an upper deck on the carbody supports a boom at one end and a normal counterweight at the other end, with an additional item of counterweight secured to and becoming part of the normal counterweight, and a pair of auxiliary carbody weights in sub--stantially box-like form attached to the front and rear of the , carbody between the ends of the crawler assemblies so as to con-stitute weighted extensions of the carbody to supplement the additional counterweight and prevent forward tipping of the crane during heavy lifting and to counteract rearward tipping due to :`
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the additional counterweight when a load is not being lifted by the crane, wherein at least one of the carbody weights includes walking treads on the upper surface thereof and a plurality of open steps are fixed between spaced risers attached to the outer side of the carbody weights to permit easy access to the upper deck.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:
Figure 1 is a frasmentary perspective of a crane embodying the present invention;
Fig. 2 is an enlarged plan of the lower works portion of the crane shown in Fig. l;
Fig. 3 is a fragmentary section taken approximately along the line 3-3 in Fig. 2;
Fig. 4 is a fragmentary plan of a portion of the structure shown in Fig. 3; and Fig. 5 is a fragmentary elevation taken approximately along the line 5-5 in Fig. 3.
Turning now to the drawings, there is shown in Fig. 1 a conventional crawler crane 10 modified in accordance with the arrangement of the invention. The crane 10 includes a carbody 11, supported by a pair of crawler assemblies 12 and 13, and an upper deck 14 on the carbody mounting a boom 15, a gantry or mast 16, and a normal counterweight 17 at the end of the deck 14 opposite the mast 15.

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-Pursuant to the invention, an additional item of counterweight 21 is secured to, so as to become part of, the normal counterweight 17 and a pair of auxiliary carbody weights 22 and 23 in substantially box-like form are attached to the front and rear of the carbody so as to constitute weighted extensions of the carbody 11. In the illustrated embodiment, the counterweight 21 consists of a plurality of mPtal slabs tacked together and mounted on the normal counterweight 17 (see Fig.l).
Preferably, the auxiliary carbody weights 22, 23 are plates welded into boxes containing, as weight, sand, concrete or scrap metal.
For ease of handling, the carbody weights 22, 23 are formed with pairs of arms 25 carrying lugs 26 adapted to mate with lugs 27 formed on brackets 28 welded to the carbody 11. Blocks 29 on the weights 22, 23, abut the ends of the carbody 11 when the lugs 26, 27 are mated. The arms 25 are also drilled to form holes 31 above the center of gravity line so that an auxiliary crane can be conveniently attached at the holes 31 to the counterweights 22, 23, allowing the weights to be simply lowered into mounted position. The brackets 28 are formed with cam surfaces 32 to guide the lugs 26 directly into engagement with the lugs 27.
In order to reliably lock the carbody weights 22, 23 in position, the arms 25 and the brackets 28 are formed with holes which are alined when the weights are in position, and locking pins 33 are fitted into the holes preventing inadvertent dislodgement of the carbody weights.
In the illustrated embodiment, non-skid walking treads 34 are mounted on the tops of the weights 22, 23 and a plurality of steps 35 are fixed on the outer sides of the weights, thus providing convenient access to the upper deck 14. Preferably~
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lQ90301 each of the carbody weights 22, 23 is slightly heavier than the added counterweight 21. This insures that the stabilizing effect of the carbody weights more than offsets the added tipping load imposed by the added counterweight.
The effect of the arrangement can now be readily appreciated. The added counterweight 21 becomes part of the basic crane counterweight, thus increasing the capacity of the crane.
The carbody weights 22, 23 stabilize the crane and, at maximum capacity ranges, also tend to increase the crane counterbalancing mass. Less obviously, the carbody weights 22, 23 have the effect of lowering the center of gravity of the entire crane, thus increasing the arc that the center of gravity must traverse if the crane is overloaded and starts to tilt. The increased arc means increased time in such a situation, and this gives the crane operator more opportunity to sense the condition and correct it.
Those skilled in the art will also readily appreciate that the increase in crane capacity has been achieved at little cost and, primarily because of the positioning of the carbody weights, there is no interference with otherwise normal operation of the crane.

Claims (2)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An arrangement for increasing the capacity of a crane having a carbody supported by a pair of crawler assem-blies which permit movement of the crane under both heavily loaded and unloaded conditions and an upper deck on the carbody mounting a boom at one end and normal counterweight at the other end, the combination comprising, an additional item of counter-weight secured to and becoming part of said normal counterweight, and a pair of auxiliary carbody weights in substantially box-like form attached in forwardly and rearwardly projecting canti-lever fashion respectively to the front and rear of said carbody between the ends of said crawler assemblies so as to constitute weighted extensions of the carbody to supplement said additional counterweight and prevent forward tipping of said crane during heavy lifting and to counteract rearward tipping due to said additional counterweight when a load is not being lifted by said crane, at least one of said carbody weights including walking treads on the upper surface thereof and having a plural-ity of open steps fixed between spaced risers attached to the outer side of said carbody weights to permit easy access to said upper deck.

2. The combination of claim 1 in which said carbody weights are formed with a pair of attachment arms carrying lugs adapted to mate with lugs on brackets mounted on said carbody so that the carbody weights can be lowered and hung in mounted position, said brackets being formed with a cam-ming surface to guide said arm lugs and said bracket lugs into mating position and said arms and said brackets having alined holes when said lugs are mated for receiving locking pins.