US3547278A - Mobile cranes - Google Patents

Description

United States Patent Frederick H. Tayler 201 Chartridge Lane, Chesham, England [2!] Appl. No. 767,350

[72} Inventor [22] Filed Oct. 14, I968 [45] Patented Dec. 15, 1970 [3 2] Priority May 3, 1968 [3 3 1 Great Britain [31 No. 20994/68 [54] MOBILE CRANES 2,891,681 6/1959 Greivell 212/49 Primary Examiner-Harvey C. Hornsby Attorney-Shoemaker & Mattare ABSTRACT: A mobile crane provided with a counterweight having a support member extending away from the center of gravity of the counterweight and including first and second pivot points, with the first pivot point located further from the center of gravity of the counterweight than the second, first and second link means pivotally connected to a lower point and a higher point, respectively, on the crane and to the second pivot point and the first pivot point, respectively, on the support member, and a hydraulic jack connected to said links for controlling the angular positions of the links so that the counterweight is caused to be moved away from the crane in such a manner that the line joining the first and second pivot points on the support member is rotated to increase the angle of the inclination of this line to the vertical.

MOBILE CRANES This invention relates to mobile cranes and is particularly concerned with side-boom mobile cranes of the kind used for pipe laying. Such cranes may have a derricking jib at one side of the crane and a counterweight on the other side of the crane to balance the load lifted by the crane. The axis of derricking movement of the .jib is normally parallel to the longitudinal axis of the crane and the counterweight may be arranged to be swung outwardly from the crane about a further axis parallel to the longitudinal axis of the crane-The crane will normally be a tractor-mounted, but may also be a tractordrawn, crane.

It is an object of the invention to provide a novel system of mounting the counterweight on the crane in order to increase its effectiveness in balancing the load lifted by the crane.

The term counterweight" is used'herein to describe not only the weights themselves, which may 'be, for example, blocks of metal or concrete, but also any framework provided to carry these weights. Further, the term crane" is used herein to include the vehicle on which the jib and other parts of the crane proper are mounted.

The invention consists in a mobile crane provided with a counterweight mounted on first and second links pivotally connected to the crane and to the counterweight, and a hydraulic jack controlling the angular positions of said links, wherein the pivot points are so located and the links are so dimensioned that, as the pivot points onthe counterweight are moved away from the crane by operation of the hydraulic jack, the line joining these pivot points is'rotated in such a direction as to increase the distance between the centre of gravity of the counterweight and the crane.

It will normally be desirable to use two counterweights on a mobile crane in accordance with the invention, and in the case of a side-boom mobile crane, for example; the two counterweights will be mounted side-by-side with corresponding pivots coaxial and parallel to the fore-and-aft axis of the crane.

It will be seen from FIG. 2 that each of the links8is'in the form of a solid bar, whereas each of the links 14 is channelshaped in cross section. The two links 14 are interconnected by means of a framework consisting of two horizontalmembers 16 and 17 and two diagonal members 18 and I9.

The positions of the counterweights are controlled by means of two hydraulic jacks, one of which is shown at 20. The cylinder of each jack is pivotally secured to the respective bracket 11 by means of an extension of the shaft which constitutes the pivot point for the link 8. The lower end of the piston rod of each of the hydraulic jacks is pivotally connected to an intermediate point 21 on the respective link I4. The lefthand link 14 is shown broken away in FIG. 2 to show the bearing 22 and the shaft 23 constituting the pivotal connection for one of the piston rods. When the pistons of the two hydraulic jacks are drawn as far as possible into their respective cylinders, the weights are fully retracted so that the links 14 are substantially vertical. Under these conditions each hydraulic jack 20 is located substantially within the cross section of its associated link 14. One advantage of this arrangement is that each jack acts in a more direct line with its associated link and the excessive bending moments which occur on the cylinder anchorage points in some known systems are eliminated.

When hydraulic fluid is admitted to the cylinders to extend the two hydraulic jacks, the two pairs of links 8 and 14 will be rotated clockwise as seen in FIG. 1, and the counterweights l and 2 will be swung outwardly from the tractor. It will be seen that the counterweights will be not only displaced laterally but also rotated about the pivot points 5 and, when the jacks are fully extended, the lines joining the pairs of pivot points 4 and 5 will become substantially horizontal. In this position the centre of gravity of each counterweight is displaced outwardly A separate hydraulic jack will normally be provided with each counterweight but the two first links will be interconnected by means of a bracing framework.

One embodiment of the invention willnow be described with reference to the accompanying diagrammatic drawings in which g FIG. 1 is a rear view of a part of a side-boom mobile crane in accordance with the invention havingthe counterweights partially extended, and

FIG. 2 is a side view of the embodiment shown-in FIG. 1 with the counterweight retracted. v

. In the arrangement illustrated in the drawings, the crane is provided with two counterweights generally indicated by the reference numerals l and 2. Each counterweight includes a support member 3 which extends away from the centre of gravity of the respective counterweight and is provided with a first pivot point 4 and a second pivot point 5, the pivot 4 being, in each case, located further from the centre of gravity of the respective counterweight than the pivot point 5. As can be seen from the left-hand side of FIG. 2 the pivot point 4 includes a bearing 6 and a shaft 7 rotatable in this bearing. The shaft 7 is secured to a link 8 by means of a nut 9. The other end of the link 8 is pivotally connected to a pivot point 10 secured to the crane, for example, by means'of a bracket 11 fitted to a winch frame 12.

The pivot point 5 includes a bearing-l2 in which a shaft 13 is rotatable. The shaft 13 is secured to a link 14, the other end of which is pivotally connected to the crane at 15. It will be seen that the pivot point I0 is almost directly vertically above the pivot point 15 and that, when the counterweightis retracted, the two links 8 and 14 are substantially vertical, the pivot point 4 being above the pivot point 10 and the pivot point 5 being above the pivot point 15. Further undertheseconditions, the centre of gravity of the counterweight l is below the two pivots points 4 and 5 and the support member 3 is so shaped that the centre of gravity of the counterweight is in-' board of the links 8 and 14.

from the crane but remains in substantially the same horizontal plane as when the counterweights were retracted. In the particular arrangement illustrated, when the counterweights are fully extended, the two pivot points '10, the two pivot points 4 and the two pivot points 5 are all contained substantially in the same horizontal plane. Rotation of each counterweight causes its centre of gravity to be displaced not merely by the length of the respective link 14 but also by the distance between the pivot point 5 and the said centre of gravity.

The increased leverage produced by the linkage system illustrated enables a substantially lower weight of counterweight to be used than is necessary in known balancing systems. Furthermore, the arrangement illustrated enables the centre of gravity of each counterweight, when it is retracted, to be lower and nearer to the centre line of the tractor than in conventional counterweight systems.

Since a system in accordance with the invention enables the counterweights to be extended further from the crane than in known systems the total weight required to balance a given load is lower than in known systems. Hence, the overall weight distribution of the crane is substantially improved in comparison with existing designs. Mobile cranes are usually employed under the most arduous conditions, and therefore weight and applied ground pressure must be kept to a minimum. Furthermore, on a side-boom mobile crane, it is inevitable that the machine will be unbalanced when travelling light, and the lower the weight of the counterweights the better will be the weight distribution and overall balance of the crane. Similarly the better balance and lower overall weight of a crane in accordance with the invention facilitates the transportation of the crane from site to site and it will normally no longer be necessary for counterweights to be moved for transportation purposes.

Iclaim:

l. A mobile crane provided with a counterweight including a support member extending away from the centre of gravity of the'counterweight and provided with first and second pivot to the second pivot point on the support member; a second :1 link one end of which is pivotally connected to a higher pivot point on the crane and the other end of which is pivotally consnected to the first pivot point on the support member; and, a ahydraulic jack connected to said links controlling the angular positions of said links in such a way that, as the counterweight is moved awaytfrom the crane by operation of the hydraulic jack, the line joining the first and second pivot points on the r'support member is rotated in such a direction as to increase "the angle of inclination of this line to the vertical.

" 2. A mobile crane as in claiml, wherein a pair of counterweights are provided, each mounted on first and second links 'pivotally connected to the crane and to the respective counterweight; a pair of hydraulic jacks, each extending between "the crane and a respective one of said links; and a bracing framework interconnecting said two first links.

3. A crane as claimed in claim 1, wherein, when the counterweight is retracted, the two links are substantially vertical, the counterweight pivot point being in each case above the corresponding crane pivot point and the two pivot points on the counterweight being located substantially vertically one above the other 7 4. The crane as claimed in claim 3, wherein the centre of

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