FIELD OF INVENTION
This invention relates to a boom with automatic rope adjusting means for use in a crane.
PRIOR ART
Cranes presently known in the art have normally a boom of a fixed length. Due to such a fixed length of the boom, hooks are provided along different lengths of the boom depending upon the weight of the load to be lifted by the crane. A rope adapted to be operated by the operator is provided to adjust the height of the hook block with respect to the distal end of the first extension of the boom.
The main disadvantage of the boom known in the art is that the operator has to operate a plurality of levers to adjust the length of the rope during the operation of the crane. In such an operation, or the hook block can be damaged, and often the rope is broken due to mis operation of the levers by the operator unknowingly.
OBJECTS OF THE INVENTION
Therefore the main object of this invention is to propose an improved construction of a boom for use with a crane.
Another object of this invention is to propose an improved boom provided with automatic rope adjusting means.

Still another object of this invention is to propose an improved boom which is efficient.
A further object of this invention is to propose an improved boom which obviates the disadvantages of the known art.
DESCRIPTION OF THE INVENTION
According to this invention there is provided a boom with automatic rope adjusting means for use in a crane comprising a retractable boom disposed in the mother boom or main jib, a hook block being secured to the distal end of the retractable boom, characterized by automatic rope adjusting means being provided to adjust the height of the hook block said rope means comprising a pulley provided on the retractable boom for facilitating the passing of said rope with respect to the distal end of said retractable boom.
In accordance with this invention a boom for use with a crane comprises a retractable boom disposed in the mother boom of the crane operated by the hydraulic means provided therefore. A hook block is secured to the distal end of the retractable boom. A rope means is provided for adjusting the height of the hook block with respect to the distal end of the extendable member.
Specifically according to this invention a pulley is provided on the retractable boom for passing the rope there through and such that to adjust the height of the hook block with respect to the distal end of the retractable boom automatically.

DESCRIPTION WITH REFERENCE TO DRAWING
A boom for use in a crane according to a preferred embodiment is herein described and illustrated in the accompanying drawing wherein:-
Fig. 1 shows thee exploded plan view of the boom;
Referring to the drawing, Fig 1 shows fixed boom (1) on which a winch (4) is mounted at the rear end. The telescopic retractable boom (2) is housed in the fixed boom (1) and is extended or retracted through a hydraulic cylinder (7). Rope (5) is fixed at one end to the winch and passes through hook block (3), horizontal pulley (6) and fixed at the other end on the front end of fixed boom (1).
The fixed boom (1) is attached to a crane structure. Hook block (3) is provided on the front end of the telescopic boom (2) which can be lifted/lowered by winding/unwinding of rope (5) through winch (4) mounted on the rear end of the fixed boom (1). During the operation of extension/retraction of telescopic boom, the distance between the lower edge of the telescopic boom and the hook block is decreased/increased due to construction of the rope routing. In the present invention, a horizontal pulley (6) is provided on the telescopic boom (2) the rope from winch (4) passing through the hook block also passes through the horizontal pulley (6) and then is fixed onto the front end of the fixed boom.

WE CLAIM:
1. A boom with automatic rope adjusting means for use in a crane comprising a retractable boom (2) disposed in the mother boom (1) or main jib, a hook block (3) being secured to the distal end of the retractable boom (2), characterized by automatic rope adjusting means (5) being provided to adjust the height of the hook block (3) said rope means (5) comprising a pulley (6) provided on the retractable boom (3) for facilitating the passing of said rope (5) with respect to the distal end of said retractable boom (2).
2. A boom with automatic rope adjusting means for use in a crane as claimed in claim 1 wherein said pulley (6) is horizontally disposed on the retractable.
3. A boom with automatic rope adjusting means for use in a crane as claimed in claim 1 wherein said retractable boom (2) is telescopically disposed within said fixed boom (1).
4. A boom with automatic rope adjusting means for use in a crane as claimed in claim 1 wherein said rope (5) has one end held to the front end of the fixed boom (1) and the other end to the winch (4).
5. A boom with automatic rope adjusting means for use in a crane as claimed in claim 1 wherein said pulley (6) is provided in the proximity of the proximal end of the retractable boom (2).

6. A boom with automatic rope adjusting means for use in a crane substantially as herein described and illustrated.