FIELD OF THE INVENTION
The present invention relates to a cantilever type jib crane for galvanizing pots or hot
pits with space constraints at its top. More particularly, the present invention is directed
to providing a cantilever type jib crane for handling 1 ton pay load over galvanizing pots
or hot pits wherein the jib crane is having self supporting column, rotating cantilever
type jib arm and a movable trolley pulled in forward and reverse direction, for hoisting
and cross travel operation to carry out charging operation above the hot pit.
Advantageously, drive motors and gear boxes are mounted above the crane column to
reduce bending moment due to the traveling motor block and to protect the motors and
cable from heat and zinc dust. An electrical control circuit enables faster lowering of the
ingot till it touches the molten zinc in the pot and then very slowly till it is completely
submerged, avoiding on one hand longer exposure of the hoist equipments to high
temperature of pot and on the other hand prevents drastic fall in bath temperature. The
pot change operation is performed by rotating the jib arm thus needing no permanent
super structure over the hot pit. The cantilever jib crane of the present invention is thus
suitable for application in hot dip galvanizing industry, ensuring efficient charging of
zinc ingot and handling of pot change over, where over head space is a constraint.
BACKGROUND ART
In hot dip galvanizing lines in many industries, 25 kg zinc ingots are used in the pot as
input material. These plants have now started using 1 ton zinc ingots with mechanized
feeding for operational advantages. Jib cranes of around 2 ton capacity can be used to
feed these ingots. However, the galvanizing pot operates at around 460°C. The crane
motor and gear box have to operate above this pot with exposure to heat and zinc dust.
Moreover, the bending moment of this equipment on cantilever type jib arm need to be
reduced from crane structure point of view. Further a permanent structure above such
baths is not permissible considering requirement of pot change over. In similar
applications like hot furnace pits, such equipment can be used.
A monorail type zinc hoisting system is known in the existing art behind the snout of a
galvanizing line over the zinc pot to insert the 1 ton zinc ingots. In this system the
motor block wheels travel on a monorail while carrying the payload. The motorized
drives are there for both travel and hoisting operation. After charging the ingot in the
pot, the motor block retracts back to a safer position outside the pot. It is feasible in a
galvanizing line where the top area of the zinc pot is comparatively larger and the zinc
pot is not changed often. In electrically heated steel pots, pot changing takes place
around once in six months depending on production. At this time any fixed monorail
system needs to be dismantled. Moreover, there is limited space available over the zinc
pot.
In some cases, overhead EOT cranes are used to charge such heavy zinc ingots. In this
case also, the top surface area should be large and hoist motors should not be kept
over the hot zinc pot for a long time.
There has been thus a need in the art to develop a cantilever type jib crane for charging
of zinc ingot of higher weight in galvanizing pots which would favour avoiding long
exposure of motor and hoist equipments including electrical cables to high temperature
bath, do not over load the jib arm, carry out faster charging of zinc ingot as well as not
to cause drastic fall of bath temperature. The equipment would facilitate pot change
over as well as material handling where overhead space is a constraint without needing
any permanent superstructure.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to providing a cantilever type
jib crane for charging of zinc ingot in galvanizing pots or for handling materials over hot
pits in a controlled and efficient manner without undesired longer exposure of motor
and the hoist to the heat and dust of the bath.
A further object of the present invention is directed to providing said cantilever type jib
crane for galvanizing pot or hot pits wherein the loading/bending of the jib arm is
reduced by selectively locating the motor and gearbox on top of the column.
A still further object of the present invention is directed to providing said cantilever type
jib crane for galvanizing pot or hot pits wherein no permanent structure is required over
the hot pot/pit.
A still further object of the present invention is directed to providing said cantilever type
jib crane for galvanizing pot or hot pits wherein the equipment is capable of working
satisfactorily even with space constraint at its top.
A still further object of the present invention is directed to providing said cantilever type
jib crane for galvanizing pot or hot pits wherein change over of the zinc pot can be
easily implemented without the need of dismantling any permanent structure like the
monorail etc.
A still further object of the present invention is directed to providing said cantilever type
jib crane for galvanizing pot or hot pits wherein selective controlled motion can be
provided to the zinc ingot to favour faster charging yet avoiding drastic fall in bath
temperature.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to a cantilever type jib crane for
galvanizing pots or hot pits for controlled charging of ingots, comprising
a self-supporting column;
a rotating cantilever type jib arm supported on said column;
a movable trolley pulled in forward and reverse direction on said jib arm, for hoisting
and cross travel operation.
an electric control circuit adapted to ensure controlled hoisting/charging operation.
A further aspect of the present invention is directed to a cantilever type jib crane for
galvanizing pots or hot pits, wherein gear system for the rotational or swing motion of
the jib arm is mounted on said column.
A still further aspect of the present invention is directed to said cantilever type jib crane
for galvanizing pots or hot pits, wherein the drive motors and gear boxes for said
movable wheel mounted trolley, mounted above said crane column are provided to
reduce bending moment on said jib arm and to protect the motors and cable from heat
and dust.
According to yet another aspect of the present invention is directed to said cantilever
type jib crane for galvanizing pots or hot pits , wherein the jib arm is rotatable with no
fixed structure over the pot adapted for favoring pot change operation..
A still further aspect of the present invention is directed to said cantilever type jib crane
for galvanizing pots or hot pits comprising providing for only limited pot surface area
based on the access of the jib arm and the zinc ingot shape.
According to a further aspect of the present invention directed to said cantilever type jib
crane for galvanizing pots or hot pits, wherein an electrical control circuit enable
controlled lowering of zinc ingot for charging in galvanizing pot involves a dual speed
option at a suitable change over height.
According to an advantageous aspect of the present invention directed to said cantilever
type jib crane for galvanizing pots or hot pits, wherein said dual speed option enable
faster downward movement before the payload touches the molten zinc and a very slow
motion thereafter till complete submersion.
A still further aspect of the present invention is directed to said cantilever type jib crane
for galvanizing pots or hot pits, wherein said slow motion provided by VVF controlled
motor during zinc ingot charging to ensure heat balance in the bath and prevent drastic
fall in bath temperature.
The objects and advantages of the present invention are described in greater details
with reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic illustration of the structure/assembly of the jib crane
according to the present invention showing its all main components.
Figure 2: is the schematic electrical diagram showing the VVF control drive, hoist motor
and switch controlled actuators for speed changeover for hoist drive mechanism for
controlled charging of zinc ingot.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to a cantilever type jib crane for galvanizing pots or hot
pits with space constraints at its top, adapted to handle 1 ton pay load over galvanizing
pots or hot pits, particularly for charging of zinc ingot.
Reference is first invited to the accompanying Figure 1 that schematically illustrates
the jib crane according to the present invention showing its different
subassemblies/components. It is seen from the figure that the jib crane is rotatable
around self supporting column (1), rotating cantilever type jib arm (2) and a movable
trolley (6) pulled in forward and reverse direction by wire ropes (7), for hoisting and
cross travel operation. Advantageously, a gear system for the rotational or swing
motion of the jib arm (5) is mounted on its column to favour on one hand maintain
distance from heat and dust while in operation and on the other hand reduce the pay
load on cantilever beam thereby reducing the tendency of bending. Contrary to
conventional jib cranes, the drive motors and gear boxes(4,3) for trolley traveling along
arm and hoisting operation are also mounted above the crane column to reduce
bending moment due to the traveling motor block and to protect the motors and cable
from heat and zinc dust. The wheel mounted trolley instead of a traveling motor block
reduces the load and moment on jib arm.
There is no fixed structure over the pot as the space above the galvanizing pot can be
cleared by rotating the jib arm at any side, enabling the pot change operation to be
carried out by EOT crane or any alternative means without any obstruction. Only limited
pot surface area is required considering the access of the jib arm end and zinc ingot
shape.
Reference is now invited to the accompanying Figure 2 that illustrates the schematic
electrical diagram comprising power supply lines (12), special switches and actuators
(10,11) to enable faster downward movement before the payload touches the molten
zinc and a very slow motion thereafter till complete submersion. A slow motion, by VVF
control drive (9), of hoist motor (8) during zinc ingot charging ensures heat balance in
the bath and prevents drastic fall in bath temperature.
It is thus possible by way of the present invention to provide a self supporting column
based cantilever type jib crane, wherein the motor and gearbox for the rotation, trolley
travel as well as hoisting is mounted on column top so as to reduce the normal load on
cantilever beam causing bending, while handling zinc ingot of higher weight in the
range of 1 ton. The motor, gearbox, cables etc are kept away from heat and dust to
ensure longer life. The controlled lowering of the ingot on one hand reduces total time
of charging and on the other hand maintains heat balance of molten zinc bath avoiding
drastic fall in bath temperature.
We Claim:
1. A cantilever type jib crane for galvanizing pots or hot pits for controlled charging of
ingots, comprising
a self-supporting column;
a rotating cantilever type jib arm supported on said column;
a movable trolley pulled in forward and reverse direction on said jib arm, for hoisting
and cross travel operation.
an electric control circuit adapted to ensure controlled hoisting/charging operation.
2. A cantilever type jib crane for galvanizing pots or hot pits as claimed in claim 1,
wherein gear system for the rotational or swing motion of the jib arm is mounted on
said column.
3. A cantilever type jib crane for galvanizing pots or hot pits as claimed in anyone of
claims 1 or 2, wherein the drive motors and gear boxes for said movable wheel
mounted trolley, mounted above said crane column are provided to reduce bending
moment on said jib arm and to protect the motors and cable from heat and dust.
4. A cantilever type jib crane for galvanizing pots or hot pits as claimed in anyone of
claims 1 to 3, wherein the jib arm is rotatable with no fixed structure over the pot
adapted for favouring pot change operation.
5. A cantilever type jib crane for galvanizing pots or hot pits as claimed in anyone of
claims 1 to 4 comprising providing for only limited pot surface area based on the access
of the jib arm and the zinc ingot shape.
6. A cantilever type jib crane for galvanizing pots or hot pits as claimed in anyone of
claims 1 to 5, wherein an electrical control circuit enable controlled lowering of zinc
ingot for charging in galvanizing pot involves a dual speed option at a suitable change
over height.
7. A cantilever type jib crane for galvanizing pots or hot pits as claimed in anyone of
claims 1 to 6, wherein said dual speed option enable faster downward movement before
the payload touches the molten zinc and a very slow motion thereafter till complete
submersion.
8. A cantilever type jib crane for galvanizing pots or hot pits as claimed in anyone of
claims 1 to 7, wherein said slow motion provided by VVF controlled motor during zinc
ingot charging to ensure heat balance in the bath and prevent drastic fall in bath
temperature.
9. A cantilever type jib crane for galvanizing pots or hot pits substantially as here in
described with reference to the accompanying drawings.

The present invention relates to a cantilever type jib crane for galvanizing pots or hot
pits with space constraints at its top suitable for handling 1 ton pay load, having a self
supporting column, rotating cantilever type jib arm and a movable trolley pulled in
forward and reverse direction, for hoisting and cross travel operation to carry out
charging operation above the hot pit. Advantageously, drive motors and gear boxes are
mounted above the crane column to reduce bending moment due to the traveling motor
block and to protect the motors and cable from heat and zinc dust. An electrical control
circuit enable faster lowering of the ingot till it touches the molten zinc in the pot and
then very slowly till it is completely submerged, avoiding on one hand longer exposure
of the hoist equipments to high temperature of pot and on the other hand prevents
drastic fall in bath temperature.