FIELD OF INVENTION
This invention relates to a boom assembly used in a crane having at least one extendable boom section. The members move synchronously together by means of hydraulic cylinders and ropes actuated by means of single lever provided in the operator cabin.
BACKGROUND OF INVENTION
In a pick-n-carry crane, boom is an important part which is used to lift load from one position and place it to another position. Normally, these booms have one or two members which move in and out through hydraulic cylinders providing motion to each individually. However, this configuration is associated with the following disadvantages:-
1. Each member moves individually.
2. The member which moves first is also not known as the one having less frictional resistance will move first. To overcome this problem, sequence valve is required to be installed.
3. For every member, cylinder is required making the assembly bulky. Further, more hydraulic hoses and pipes are required. Due to size and space constraint, it is not possible to accommodate more than two cylinders.
4. Incase of more than two extendable members, outer most member is moved manually making it more cumbersome exercise. Also matching of hole in two sections and inserting locking pin is left to operator skill, sometimes resulting rope breakage.
5. To provide sufficient overlaps among extendable members, hollow cylinders are used which are susptible to failures and costly. Another alternative is longer boom and hence more travel length of the crane.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide a boom assembly used in a crane having at least one extendable boom section which overcomes above said limitations.
Another object of the present invention is to provide a boom assembly used in a crane having at least one extendable boom section which is cleaner and compact.
Further object of the present invention is to provide a boom assembly used in a crane having at least one extendable boom section which automatically actuates through single lever and no manual intervention is required.
Yet another object of the present invention is to provide a boom assembly used in a crane having at least one extendable boom section wherein the jib head is narrower in depth to make full utilization of working height.
STATEMENT OF INVENTION
According to this invention, there is provided a boom assembly used in a crane comprising of a main boom housing extendable members and a hydraulic cylinder known as extension cylinder accommodated inside cylinder housing.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig. 1 shows : boom assembly. Fig. 2 shows: jib head profile.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
This invention discloses a boom assembly used in a crane having at least one extendable boom section comprising of additional housing known as cylinder housing, which houses the extension cylinder inside the second extension and hence boom length can be reduced to minimum value. The first extension is connected to this housing and as a result moves while actuating the cylinder. Second extension is connected through rope and pulleys to first extension which makes it move in or out depending upon cylinder movement.
Reference may be made to fig. 1, wherein a main boom is provided housing extendable members, namely first extension (2), second extension (3) and hydraulic cylinder commonly known as extension cylinder (4).
The first extension is connected to main boom (1) through hydraulic cylinder. To make the boom length compact and all boom sections fully powered, said extension cylinder is accommodated inside another member known as Cylinder housing. One end of cylinder is pinned to this housing at the far end point from boom pivot (5). Another end of Extension cylinder is fixed to main boom which is not movable. Since cylinder is the most inner member, hence all hydraulic metal pipes are attached to cylinder and have openings at boom pivot point.
Now, to extend the first extension it is connected to extension cylinder through cylinder housing (6) at the rear end of the extension. Hence, when cylinder is actuated it moves along with housing which in turn moves the first extension and hence boom members move out or move in.
Second extension is connected to first extension through ropes laid on pulleys with bearings, which either moves the second extension out or in depending upon the extension cylinder movement; hence all sections move synchronously and also equal length while actuating the extension cylinder.
When extension cylinder is fully extended, Cylinder housing comes out of second extension. To guide its path of movement, the rollers are provided at the end of it. This ensures that it moves straight, is always guided and comes inside second extension smoothly when extension cylinder is closed.
Reference may be made to fig. 2 indicating jib head with special profile, rope laying, pulley arrangement on hook block and ropes on hook block are parallel when viewed from front of the boom. This configuration has the following advantages-
1. Hook block does not enter jib head during full retraction.
2. Hook block due to special boom design and rope layout ensure its movement always parallel to ground at any angular position of boom.
3. Jib head profile ensures the highest pin height and maximum vertical clearance of hook block.
4. Special geometry ensures that the no. of falls per pulleys can be changed as per requirement.
ADVANTAGEOUS FEATURES
1. Multiple (two or three) extendable boom.
2. Simultaneous and equal movement of each extendable section.
3. All sections move with the single lever, which actuates the hydraulic cylinder and hence no manual intervention making it more user friendly and accident free with ease of operation.
4. Less travel order length of the boom as compared to conventional design and more overlap between extendable members giving more strength to sections.
5. Normal extension cylinder in place of hollow cylinder or telescopic cylinder leading to less wear and tear and simple & easy piping arrangement.
6. Special profile jib head resulting in maximum pin height.

It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM:
1. A boom assembly used in a crane comprising of a main boom housing extendable members and a hydraulic cylinder known as extension cylinder accommodated inside cylinder housing.
2. A boom assembly used in a crane as claimed in claim 1, wherein said extendable members are such as first and second extension.
3. A boom assembly used in a crane as claimed in claim 1 or 2, wherein the first extension is connected to the main boom through the extension cylinder.
4. A boom assembly used in a crane as claimed in any of the preceding claims, wherein one end of the cylinder is pinned to the housing at the far end point from boom pivot.
5. A boom assembly used in a crane as claimed in any of the preceding claims, wherein other end of the cylinder is fixed to main boom.
6. A boom assembly used in a crane as claimed in any of the preceding claims, wherein the first extension is connected to the cylinder through cylinder housing at the rear end of the extension.
7. A boom assembly used in a crane as claimed in any of the
preceding claims, wherein the second extension is connected
through rope and pulleys to first extension, which makes it move
in or out according to cylinder movement.
8. A boom assembly used in a crane substantially as herein described with reference to the accompanying drawings.