The present invention relates to Extensible Boom with Self Load Leveling on a
Mobile Crane Machine and more particularly an efficient Extensible Boom with
Self Load Leveling for application on Pick and Cany type of Hydraulic mobile
cranes.
BACKGROUND OF THE INVENTION:
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 an outer main boom attached to the crane at
rear end and at least one or more extension members which are disposed inside
the outer main boom fi'om its front end. Hydraulic cylinder is connected
between outer main boom and first extension boom. Hydraulic cylinder
facilitates for telescopic driving in and out the first extension boom. In the
event of two or more extension booms from the outer main bOOlR a multiple of
hydraulic Ram means or a combination of hydraulic ram and synchronized
extension using Chains or Cables are operated over a set of pulley or rollers.
Hook means are provided on the telescopic boom assembly for lifting the loads.
Some prior art cites the usage of the said hooks main at the base of the outer
main boom, while some other citations have a slotted outer main boom base,
where hooks can also be mounted on to the first extension boom base and these
hooks can travel along in the slotted outer main boom base for handling a
variety of loads. A separate hook block is mounted at the end of First Extension
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boom connected through winch driven wire rope to the Outer main boom which
is movable and is used for lifting loads. The main hooks secured at the base of
boom members are also used to lift and handle load.
In the known prior m1 as mentioned in US 3,889,818; for Load leveling in crane
boom with one extension member; this alTangement employs one compensation
pul1ey not main but is free to move fOlward and backward with respect to the
outer main boom. The compensating pul1ey is moved by rope with two
additional Idler pul1eys. The one end of this rope is attached to compensating
pul1ey and other end of the rope is routed through idler pul1eys and main to
outer main boom. The hook block is attached to extendable boom with rope
from winch and routed from compensating pul1ey.
When the first extendable member moves, this compensating pul1ey also moves
prop0l1ioned to first extendable boom, thereby compensating the hook block by
looping in and looping out the rope from winch to hook block. This
alTangement automatical1y keeps the hook block at a constant distance from the
front end or nose on Extensible extension when the winch is not in operation.
This keeps load in level condition when extension is operated and winch is not
required to be operated.
A disadvantage of the said alTangement is that the automatic hook height
adjustment or for load leveling on hook block with respect to boom extension or
retraction, is not a exact prop0l1ionate compensation for rope length with
respect to the travel of single extendible boom member.
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As for a gIven boom extension or retraction amount, compensation pulley
rotating at a slower rate will only ensure hook height getting adjusted
automatically, but not by the same amount as of the boom travel.
Another disadvantage of this said alTangement is that an additional rope is
required for moving the compensation pulley with respect to extensible boom.
Yet another disadvantage of this system IS two additional idler pulleys are
required in this load leveling.
Franna Cranes Pty. Ltd. Patent AU-8-89180/82 cites Load leveling on Crane
boom but with two extensible Extensions that one extendable extension. TIlis
involves a compensation pulley mounted in horizontal manner on the proximal
end of first extension. The rope from winch routes through this horizontal pulley
and then to veItical pulley on second extension then to hook block and finally
back to front nose of main second extension in order to achieve rope
compensation or automatic leveling of hook block.
Also some pnor aIt mentions this alTangement as compensation pulleys
mounted on to the front and rear ends of the single extendible boom member
itself. This alTangement uses one compensating horizontally mount pulley
mounted on rear of first extendable member and veltical idler pulleys mounted
at the fi'ont of first extendable member to achieve the automatic hook height
adjustment or rope compensation mechanism. The rope from winch is routed to
idler pulley then to hook block back to another idler pulley on extendable
member then to horizontal compensating pulley and then main to side of outer
main boom.
The disadvantage of the use of horizontally mounted pulley on the rear end side
of extendible boom member is not a fail safe operation. as the pulley is not
secured or supp0l1ed from both sides and thus eventually it may come out in the
event of bearing or guide bushing failure.
Another disadvantage of this is routing of rope is in various horizontal and
ve11ical plains thus creating unbalance of force distribution in booms when load
are lifted.
Yet another disadvantage of this is misalignment of booms with unbalanced
force distribution.
In order to overcome the above disadvantages, one of the objectives of the
present invention is to -
Improve the pul1ey anangement for a single extensible extension boom for use
in crane by having two compensation pulleys mounted on different boom
members such that one compensation pulley mounted to the front end of the
outer main boom and the other compensation pulley mounted at the rear end of
the first extension boom.
Another objective of the present invention is to have the compensation pul1ey
mounted in inclined manner on front end of the outer main boom to keep lower
height. While other compensation pul1ey on rear of first extension boom which
is mounted ve11ical1yand also supp0l1ed on either side.
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Yet another objective is to fix winch rope centrally on mid of front end of main
boom. These all improvements ensure smooth, trouble-free and improved roperouting
in the system. The frontal and rear end of the single extendible member
can be suitably designed to facilitate the smooth and trouble-fi'ee rope-routing
and front pulleys installation layout.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
We shall now describe the invention with reference to accompanymg
drawings which are given for the sake of illustration, but do not restrict the
scope of present invention.
RefelTing to drawings:-
Figure I shows Schematic view of the new two part assembly of the present
invention.
Figure 2-A shows the fi'ontal view of pulley layout;
Figure 2-B shows the rear view of pulley layout;
Figure 3 shows rope routing alTangement through pulley for auto leveling of
hook block;
Figure 4 shows frontal view of pulley layout on first extension and rope fixing
on outer boom; and
Figure 5 shows fi"ontal plan view of first extension profile change from wide to
nanow at front.
DESCRIPTION OF THE INVENTION
According to present invention there is provided Extensible Boom with Self
Load Leveling on a Mobile Crane Machine provided at front end of the
extension boom member wherein the hook block is suspended with pulley and
rope statting fi"om winch dmm and then being routed to a tilt compensation
pulley fixed on outer main boom front end and then routed to another
compensation pulley vertically fixed within reat" end of first extension boom
member and then fmther routed to idler pulleys fixed vettically to front end of
first extension boom then fmther routed to hook block and then back to front
face of outer main boom through another set of idler pulleys fixed to front end
of first extension boom.
The said outer main boom front top face has a suitable provision to lock the
rope end.
The said compensation pulley on the said outer mam boom and the
compensation pulley on the said first extension telescopic boom being aligned
to allow smooth passage of the rope.
The said first telescopic extension has a natTOw fi'ont section in comparison to
its rear body.
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At the outset of the description which follows, it is to be understood that the
ensuring description only illustrates a pat1icular fonn of its invention. However.
such a pat1icular fonn is only an exemplaty embodiment and without intending
to be understood as an exemplaty embodiment and teaching of the invention
and not intended to be taken restrictively.
The nature of the invention, its objective and further advantages residing in the
same will be apparent fi'om the following description made with reference to the
non-limiting exemplaty embodiment of the invention represented in the
accompanying drawing, which is given by way of illustration, but does not
restrict the scope of present invention.
Refening to shown in Fig.l: It is apparent that crane boom assembly in general
consist of an outer main boom 1, disposed therein first extension boom 2. The
first extension boom 2 is connected through a hydraulic cylinder 3 which drives
the first extension boom 2 in & out from the outer main boom 1. A hydraulic
winch 4 is used to raise or lower the lifting load through a hook block 6. This
hook block 6 is connected through a wire rope 5 & set of pulleys 7, 8, 9 to the
boom assembly.
Fut1her as shown in Fig. 2(a), the fixing of compensation pulley 9 mounted in
ve111cal orientation on rear end of the single extension boom 2 and front
compensation pulley 7 mounted at 45deg angle to the ve11ical on fi'ont end of
outer main boom 1.
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The Figure 2(a) also shows the installation layout scheme for idler pulleys 8
mounted on the front top side and front bottom side of single extension boom 2
with respect to compensation pulley 9 and fI-ont compensation pulley 7.
Figure 2(b) shows the fixing of compensation pulley 9 mounted in veliical
orientation on rear end of the single extension boom 2 fi'om rear side of boom.
Such an installation layout of the said pulley is aimed to achieve the smooth,
trouble fi'ee and safe wire rope 5 routing and subsequent wire rope
compensation or automatic hook height adjustment or self load leveling in crane
boom assembly.
As shown in Fig. 3, The wire rope 5 rolled over winch drum 4 is routed through
inclined compensation pulley 7 mounted on the top of the outer main boom I.
and then traveling to the inside of the outer main boom 1. The wire rope 5 is
then guided through the vertical compensation pulley 9 mounted on single
extension boom 2. Wire rope 5, then travels fi'om inside of hollow body of the
single extension boom 2 towards the set of idler pulleys 8 mounted on the front
top side and fi'ont bottom side of single extension boom 2.
Frontal section of single extension boom 2 is so designed for mounting idler
pulleys 8 for fUliher guiding wire rope to hook block 6. The frontal section of
the single extension boom 2 has a nalTOWfront from wider main body as shown
in Fig 4 and Fig 5.
Wire rope 5 fi·om the set of idler pulleys mounted on Hook block 6 moves
fUliher to the set of idler pulleys 8 mounted on the front top and front bottom
side of the single extension boom 2. FUl1her, the wire rope 5 is finally anchored
on the top side of the outer main boom 1 in the frontal p0l1ion 10 as shown in
figure 4. The wire rope eye end is mounted on to the anchor bracket 17 and
locked through a hexagonal bolt 16 and with lock nut 17 on the outer main
boom I.
Compared to known prior m1, the said anchoring does not utilise any special
spacer, profiled bushings with grooved profile or similar alTangements to anchor
the wire rope 5. To ease the assembly and rope anchoring, the rope eye end is
simply held secured with the help of hexagonal bolt or a Pin 16 and lock nut 17.
The improvement is aimed at rope anchOling on the outer boom 1 fi'ontal
section with suitable design of anchor brackets.
As the hydraulic cylinder 3 dlives in and out the single extension boom 2 from
the outer main boom 1, there will be a relative travel of compensation pulley 7
on outer main boom 1 and compensation pulley 9 on single extension boom 2.
which results in looping and un-looping of wire rope 5. The wire rope 5 p0l1ion
between compensation pulleys 7 and 9 and also between compensation pulley 9
and idler pulleys 8 get automatically compensated. This will heIp in keeping the
position of the hook block 6 leveled with respect to the fi'ont of single extension
boom 2 in the event of telescopic in and out action of single extension boom
with respect to the outer main boom 1.
The invention as described above characterizes the following novel features:
( I) Incorporation of improved and better load leveling mechanism such as the
automatic hook-height adjustment with placement of a vel1ical compensation
pulley 9 at the rear end of single extension boom in vel1ical orientation.
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(2) Incorporation of relative placement of compensation pulley 7 mounted
inclined on the outer main boom I with respect to compensation pulley 9 and
also the set of idler pulleys 8 mounted on the single extension boom 2.
(3) Incorporation of a unique single extension boom 2 nalTOWfi'ontal section for
mounting fi'ont idler pulleys 8 to facilitate smooth and trouble-free wire rope 5
routing.
(4) Incorporation of wire rope 5 anchoring on the top the outer main boom 2
frontal top side 10 as shown in figure 4 and figure 3.

WE CLAIM
I. Extensible Boom with Self Load Leveling on a Mobile Crane Machine
provided at front end of the extension boom member wherein the hook block is
suspended with pulley and rope starting from winch dlUm and then being routed
to a tilt compensation pulley fixed on outer main boom front end and then
routed to another compensation pulley ve11ically fixed within rear end of first
extension boom member and then further routed to idler pulleys fixed ve11ically
to front end of first extension boom then fi1l1her routed to hook block and then
back to front face of outer main boom through another set of idler pulleys fixed
to fi'ont end of first extension boom.
2. Extensible Boom with Self Load Leveling on a Mobile Crane Machine
as claimed in I wherein the said outer main boom front top face has a suitable
provision to lock the rope end.
3. Extensible Boom with Self Load Leveling on a Mobile Crane Machine
as claimed in claim I wherein the said compensation pulley on the said outer
main boom and the compensation pulley on the said first extension telescopic
boom being aligned to allow smooth passage of the rope.
4. Extensible Boom with Self Load Leveling on a Mobile Crane Machine
as claimed in claim I wherein the said first telescopic extension has a nalTOW
front section in comparison to its rear body.