Field of invention:
The present inventio.n relates to an improved telescopic boom assembly for pick and carry
type cranes and more particularly an improved crane telescopic boom assembly with an
extendable telescopic boom having fixed hooks moving inside the efficient slot in the main
outer boom. The fixed hooks are attached to the bottom plate member of first extendable
boom which is disposed inside the main outer boom. In the said improved crane telescopic
boom there is provided a provision of wear liner supports provided inside on the bottom plate
of main outer boom and at the both ends of the slot to enable first extendable boom with fixed
hooks to travel efficiently inside the slot.
Background oflovention
It is a common that in the known art pick and carry types of mobile hydraulic cranes have a
telescopic boom assembly for lifting and handling the load. The boom assembly comprises of
a main outer boom attached to the crane at one of its end and disposed inside the main outer
boom on its other end are at least one or more extendable boom members known as extension
booms.
Hydraulic cylinder is connected between main outer boom and first extension boom.
Hydraulic cylinder facilitates for telescopic moving in and out the first extension boom. In
the event of two or more extension booms from the main outer boom, a multiple of hydraulic
ram means as present in the teachings a/patents such as US Patent 3315821 and US Patent
3620579 or a combination of hydraulic ram and synchronized extension using Chains or
Cables being operated over a set of pulleys or rollers for extension of 2nd and forth boom
extension members as taught in the Australian patent AU00580947B2.
Hook shackles are provided on the cranes at bottom plate member of main outer boom for
lifting the loads. These hooks shackles are mounted on steel plates having at-least one or
more pivot holes and fixed to the bottom plate of both main outer boom and in some case on
first extension boom at its end also. In the later case fixed hooks attached to the end of first
extension boom, the fixed hook stay outside the main outer boom.
2
One of the prior arts also consists of the main outer boom in a crane, with bottom plate
having at. least one or more individual hook mounting pivots instead of steel plates with
multiple pivot holes. These pivots are mounted at different locations· depending upon the
rated loads to be lifted by the crane.
A separate hook block is also connected through winch mounted on main outer boom and
wire rope is routed through first and subsequent extension booms till the end of last extension
boom end point. This hook block is movable with the wire rope that connects hook block and
winch and is also used for lifting loads besides the fixed hooks secured at the base of main
outer boom and first extension boom members as present in the teachings of patents such as
US Patent 2919036 and US Patent 3752327.
In one of yet another known art of the pick and carry crane function, load lifting capacity
depends on position and height of the fixed hook points with respect to the front wheels of
the crane. The crane boom assembly can move to a raised inclined position or lowered
horizontal position as shown in figure I (a), I (b) and I (c) ofthe accomI?anying drawings.
During working of a crane boom assembly can be raised and held at inclined position as
shown in figure I (c) while at least one or more extension booms (101), (102) and (103) can
have telescopic extension or retraction. When such a boom assembly is raised and inclined as
shown in figure 1, the fixed hooks come nearer to the crane and the height is increased from
ground. When the boom assembly is in raised and at inclined position, the fixed hook can
only get to a particular height and position depending on the angle of inclination of boom
assembly and distance of placement of fixed hook from the front wheels of crane.
In such a boom assembly, load carrying capacity of every fixed hook placed at bottom plate
member of main outer boom decreases and the height from the ground of these fixed hooks
increases with increase in distance of placement of these fixed hooks from the front wheels of
the crane.
3
The disadvantage of such a method is that the individual fixed hook mounting pivots have
limited distance of hook from center of front wheels, height and load lifting capacity that is
possible during working of the crane.
In other known prior art, main outer boom bottom plate is provide with a slot. This slot is
open from the end where first or more extension members are placed inside the boom
assembly. In such a boom with a slot the fixed hooks are placed at the bottom of first
extension boom. When the first extension boom is telescopically extended or retracted, the
hooks fixed on first extension boom travel inside the slot of main outer boom.
With provision of such fixed hooks capable of sliding is that the when the boom assembly is
raised, the fixed hooks on first extension boom come near the crane and then these can be
moved with telescopic extension of first extension to a greater height. So that the hooks can
lift load and shift the same load to a greater height than that is possible with a hook that is
fixed on main outer boom and cannot be moved.
In other prior art as disclosed in Indian patent application number 1469/DEL/2005, there is
provision of slot at the bottom plate of the main outer boom of a crane and this slot can be
open and of closed type and hooks can be either placed on the end or at the bottom of first
extension boom.
The disadvantage of above is that in case of closed type of slot the hooks on first extension
boom have limited movement and the load lifting and positioning is also limited. In the event
of open type of slot and hook fixed at the end of first extension boom, the hook can not slide
in the slot to its length.
Yet another disadvantage of slot is that this weakens the bottom plate of main outer boom
that has to carry all extension booms and load that is lifted with crane. Tnsuch a boom with
slot, reinforcement is provided surrounding the slot to give it some strength during working.
This limits the length of slot to an extent limited by physical capability of boom strength by
virtue of slot and extent of reinforcement possible.
4
Yet another disadvantage of such a system is that the welding is used to fix reinforcement
with boom on both inside and outside edge of reinforcement. This welding gives residual
stresses and disturbs flatness of the boom bottom plate over which the first extension has to
move resulting in rough extension.
Yet another disadvantage of such a system is that the first extension has fixed hooks for
lifting load and the support to first extension is only at the front and at the end inside the
bottom of main outer boom. Since the size of first extension limited and has to be smaller
than the main outer boom, this causes excess bending of first extension system.
The above disadvantages of the known prior art are overcome by the proposed improved
system of the present invention wherein there is provided an improved telescopic boom
assembly for pick and carry type cranes.
Object of Invention
The object of this invention is a Crane boom assembly with an improved slot achieved by
providing a slot on the bottom plate and another slot on additional plate. These two plates are
joined together and the slot is welded from inner side only to reduce the weld stresses and
achieve better flatness. With virtue of two plates at the bottom of the main outer boom, the
slot length can be increased as the strength of bottom member of main outer boom increases.
Also the length of slot on main outer boom is such that the fixed hook on the bottom of first
extension rest near the closed end of slot when the main outer boom and the first extension
are fitted together. Another objective of this invention is that the slot can be of much longer
length so by changing the height and distance of these hooks placed on first extension boom
from the center of front wheels of the crane variety of load capacity can be positioned to
much greater height by only one or two of these fixed hook points.
Another objective of this invention is to provide the efficient support to the first extension
boom with fixed hooks while the first extension boom is having the telescopic extension or
5
retraction and the load is suspended from the fixed hooks which are dropping out of the
efficient slot which is longer and has higher strength on main outer boom.
To achieve this, a wear liner is provided to support the first extension boom positioned inside
the main outer boom but at the end of the slot. So that the first extension boom with fixed
hooks at the bottom has additional middle support when fitted inside the main outer boom.
The boom assembly of the present invention with outer main boom has a slot at the bottom
plate and has an additional plate placed outside the bottom plate with a slot bigger in size of
the slot in bottom plate. Both the slots in bottom plate and additional plate are held together
along the inner edge with welding. While the additional plate is also welded to side edges of
bottom plate and side walls of main outer boom.
Further an efficient support wear liner is arranged at both sides of the slot but at the inner end
to support the first extension boom.
Summary of the Invention
According to the present invention there is provided an improved telescopic boom assembly
for pick and carry type cranes comprising of a fixed outer boom and with at least one or
more extension booms, wherein the first extension boom being extended
telescopically by means of a hydraulic cylinder and second extension boom being
extended with the means of ropes or with another hydraulic cylinder, the said fixed
outer boom having a bottom plate consisting of an open slot from its free end and
placed in a central location with respect to the width of the said main boom wherein
an additional plate is placed at the outside of the bottom plate with another slot
bigger in size than that of the slot in the bottom plate, the said slot in the additional
plate starting from its free end being placed in the central location, disposed within
the main boom is a first extension boom with at least one or more hook pivots fixed
at a central location in the bottom plate of the said first extension boom, the position
of the hooks on the first extension boom being such that upon telescopic retraction
6
of the extension boom in the main outer boom, the fixed hooks being made capable
of traveling till the end of the slot provided in the bottom and the additional plate of
main outer boom.
The boom bottom plate and additional plate being placed outside the bottom plate of
the main boom, both the bottom plate and the additional plates being fixed together
by a process of welding at inner edges and also on the side end of the bottom plate
and to the side walls of the main outer boom.
The boom bottom plate and additional plate being provided with holes placed at the
end of the slot and at the start of the slot placed centrally with respect to the width of
the slot being provided with fixing slider pads on both sides of the slot for supporting
the extendable boom and the hooks being fixed to the central location of extendable
boom.
Being mounted on a crane generally capable of pick and carry type of work but not
limited in its application to other type of cranes.
Referring to drawings:-
Fig. 1 (a) shows Crane with Boom assembly with multiple boom extensions
Fig. 1 (b) shows view of crane with telescopic boom assembly in horizontal and Faised
inclined positions
Fig. 1 (c) shows view of crane with telescopic boom assembly in raised inclined positions
Fig. 2 shows vide and bottom views of outer main boom
Fig. 3 shows isometric view of outer main boom
Fig. 4 shows isometric view of outer main boom front side
7
Fig. 5 shows isometric view of first extendable boom with hooks fixed at bottom
Fig. 6 shows isometric view of boom assembly with outer main boom and first extendable
boom
Brief description of the preferred embodiments
A crane boom assembly with main outer boom member and at-least one or more extension
boom members placed inside the main outer boom. The boom assembly can be raised and
lowered and also the extendable boom members can extend and retract both in boom down
and boom raised conditions while function of crane.
The outer main boom made of steel plates has a box type hollow construction. By the virtue
of box type construction the boom has four sides as shown in Figure 2. As the extension
boom are placed inside the space in the outer main boom, these extension boom members rest
on wear liners on the bottom plate inside of main outer boom (201).
The main outer boom (301) with bottom plate (303) has a slot cut (302) at the central location
with respect to the width of the main outer boom. This slot starts from free end of boom and
till inside of boom as shown in figure 3. The length of slot can change from one crane to the
other crane depending on load capacity and the angle boom can be raised.
Further the main outer boom bottom plate (401) has an additional plate with a slot placed
centrally across the width of the additional plate (402). This slot in the additional plate is of
bigger size than the slot on the main outer boom bottom plate. The width of this additional
plate is equal to the width of main outer boom bottom plate so that the additional plate can be
placed at the outside bottom of the main outer boom bottom plate as shown in Figure 4.
Both the outer main boom bottom plate and the additional plate are fixed together by process
of welding (403). The edge of bigger slot on the additional plate is welded to surface and
8
edge of smaller width slot on outer main boom bottom plate. While the outside edges of
additional plates are welded on the edges of bottom plate and side wall of main outer boom.
The First extension boom (501) has at least one or more fixed hooks (502) (503) welded at
the bottom plate of this first extendable boom. These fixed hooks are placed at the central
location on the width of first extendable boom bottom plate width. Further the width of the
fixed hooks is less than the width of the slot on bottom plate of main outer boom bottom
plate. The distance of placement of first hook on the bottom plate from the front edge of first
extendable boom is less than the length of the slot on bottom plate of the outer main boom as
shown in Figure 5.
When this first extendable boom (601) is placed inside the main outer boom (602), the fixed
hooks on the first extendable boom drop out of slot (603) in main outer boom bottom plate
and the additional plate fixed onto the bottom plate. During working of crane the first
extension boom extends with telescopic extension, the fixed hook can travel out but inside
the slot on bottom plate of main outer boom and can come out of the slot as well. While
telescopic retraction of the first extendable boom, these hooks travel back inside the slot of
bottom plate of main outer boom as shown in Figure 6.
When such a boom assembly as described above is raised, the fixed hooks dropping out of
bottom plate of main outer boom come near to the crane front wheels as in the figure 1.
[n the event of the telescopic extension, these fixed hooks travel out in the slot to the more
height as the boom assembly is in raised condition and telescopic extension of first extension
boom will be in vertical so the height of hooks is increased as these travel outside in the slot.
The outer boom has holes at both end of the slot to fix wear liners to support the first
extendable boom. These holes are placed across the slot in a symmetric fashion and at the
both ends of the slot as well. These holes pass through bottom plate and additional plate fixed
to the bottom plate (404) of the main outer boom as shown in Figure 4.

WE CLAIM:
1. An improved telescopic boom assembly for pick and carry type cranes comprising of
a fixed outer boom and with at least one or more extension booms, wherein the first
extension boom being extended telescopically by means of a hydraulic cylinder and
second extension boom being extended with the means of ropes or with another
hydraulic cylinder, the said fixed outer boom having a bottom plate consisting of an
open slot from its free end and placed in a central location with respect to the width
of the said main boom wherein an additional plate is placed at the outside of the
bottom plate with another slot bigger in size than that of the slot in the bottom plate,
the said slot in the additional plate starting from its free end being placed in the
central location, disposed within the main boom is a first extension boom with at
least one or more hook pivots fixed at a central location in the bottom plate of the
said first extension boom, the position of the hooks on the first extension boom being
such that upon telescopic retraction of the extension boom in the main outer boom,
the fixed hooks being made capable of traveling till the end of the slot provided in
the bottom and the additional plate of main outer boom.
2. An improved telescopic boom assembly for pick and carry type cranes as claimed in
claim 1, wherein the boom bottom plate and additional plate being placed outside the
bottom plate of the main boom, both the bottom plate and the additional plates being
fixed together by a process of welding at inner edges and also on the side end of the
bottom plate and to the side walls of the main outer boom.
3. An improved telescopic boom assembly for pick and carry type cranes as claimed in
claim 1, wherein the boom bottom plate and additional plate being provided with
holes placed at the end of the slot and at the start of the slot placed centrally with
respect to the width of the slot being provided with fixing slider pads on both sides of
the slot for supporting the extendable boom and the hooks being fixed to the central
location of extendable boom.
10
4. An improved telescopic boom assembly for pick and carry type cranes as claimed in
claim 1, being mounted on a crane generally capable of pick and carry type of work
but not limited in its application to other type of cranes.