FIELD OF THE INVENTION
The present invention relates to an electrical control device to restrict movement
of an EOT crane entering into an unsafe zone.
BACKGROUND OF THE INVENTION
The accidents caused by improper handling of EOT cranes are common in
industry. Especially handling cranes under tall machineries and furnaces is very
critical operation, where an operator has consider the load, distance and other
related parameters substantially accurately, so as to avoid accidents. For
example, the LPG fired furnaces have the LPG pipelines running throughout the
furnace shell; any improper handling of the EOT crane under such positions
entails higher possibility of hitting or damaging the LPG pipelines by the crane
leading to a major accident. A need, therefore, exists to provide a safe and full
proof environment in industries for EOT-crane handling particularly under such
unsafe zones.
OBJECT OF THE INVENTION
It is therefore an object of the invention to propose an electrical control device
for controlling EOT-crane operation.
SUMMARY OF THE INVENTION
EOT cranes installed in Bays with tall machineries and LPG fired furnaces are
prone to cause damage to the top portions of the machines while carrying loads
above them. To avoid such possibility, an electrical device is provided such that
further movement of LT (long travel) of the EOT crane is restricted when CT
(cross travel) is inside an unsafe zone (where tall machines and furnaces exists.)
Similarly, the device ensures that the CT will not move further when LT is above
said unsafe zone. The device comprises a plurality of micro switches and relays,
incorporated with a logic rule to restrict the operation of the crane in insafe
zones and shall enable normal operation of the crane when the crane moves
away from the unsafe zone.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 : Shows a circuit means to restrict EOT crane operation in unsafe zones
accordingly to the invention.
Figure 2 : Shows a circuitry means to allow EOT Crane cross travel and long
travel movements.
Figure 3 : Shows a block diagram of the electrical device of the invention
specifying the limit switches and cam arrangement.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION.
Figure 1 shows a circuitry means for restricting EOT crane operation according to
the invention.
i
Figure 2 shows a circuiting means for control of a typical EOT crane movement.
Figure 3 shows the electrical device incorporating the circuitry means of figure
1, emphasizing the limit switches installed in the EOT-crane including the
corresponding actuating cams incorporated in the device according to the
invention.
As shown in figure 1, Si is the by-pass switch which is used to energize the
circuit with 110V power supply. This is also used to temporarily by-pass the
circuit during maintenance or for testing. The limit switches LSI, LS2, LS3, LS4
are mechanically actuated with fork style lever and 'maintained operation' type;
since this task needs the actuator lever and electrical contacts to remain in their
operated state after the actuator is no longer in contact with the target (cam).
CI and C2 are the electronic relays with multiple NO and NC contacts used to
perform the logical operation.
Figure 2 shows that CT FWD, LT FWD & LT REV are the manual switches to
operate their respective functions like cross travel forward movement, long travel
forward movement and long travel reverse movement respectively. The limit
switches LSS LS6 and LS7 which are normally in closed state represent several
other conditions to be satisfied for the crane to function.
The contacts CI & C2 are the contacts of the relays mentioned in figure 1.
The principal object of the invention is to prevent a cross travel (CT) and
entering into an unsafe zone. This is achieved by the various combinations of the
limit switches under the four conditions.

The conditions IN and OUT mean the physical presence of the CT and LT in the
unsafe zone which are sensed by the limit switches.
Case 1: CT out and LT out
In this case the crane operator is free to operate the crane and the circuit will be
exactly what is shown in figure 1 and figure 2.
Case II: CT out and LT in
Though LT is inside the zone CT is under safe area and therefore the crane
operator is free to operate. In this case only the LSI which is normally open will
close and since LS3 is still open the relay CI will not send signal for stopping the
LT or CT.
Case III: CT in and LT out
This is the same as above wherein LT is away from unsafe zone and therefore
the crane operator is free to operate. Here though LS3 is closed, since LT is out
LSI will be open and hence the relay CI will not send signal for stopping the LT
orCT.
Case IV: CT in and LT in
This condition will arise when LT is moving forward to the unsafe zone with CT
inside. Since CT is IN LS3 will be in closed condition and when LT is about move
inside the zone LSI will be hit by the target and LSI will transit to closed state;
since LSI and LS3 are closed the normally closed contact CI of relay CI will be
open and send a signal to C4 to stop further movement of LT and CT in forward
direction. Once LT made to move in the reverse direction the LSI will open and
crane operates freely.
Case V: LT in and CT in
This is a secondary case arising out of case II wherein the LT is already inside
unsafe zone with LSI closed. When the CT is operated in the forward direction
i.e. moving towards unsafe zone, when CT is about move inside the zone LS3 will
be hit by the target and LS3 will transit to closed state; since LSI and LS3 are
closed the normally closed contact CI of relay CI will be open and send a signal
to C4 to stop further movement of LT and CT in forward direction. Once CT
made to move in the reverse direction the LS3 will open and crane operates
freely.
Symmetrical Operation
The same cases are applicable when the crane move from the opposite side of
the unsafe zone i.e. movement from left to right, this is the symmetry of the
previous case. To achieve this, switches LS2 and LS4 are used.
WE CLAIM :
1. An electrical control device for restricting EOT crane operation
comprising an electrical power source means for providing an output
voltage proportional to the input voltage with a switch means for
making and breaking the supply to the circuit, a plurality of operation
limit switch means actuable in the occurrence of the crane traveling
inside an unsafe zone, and an electronic relay means connected in
series to said plurality of limit switches to transfer signal for stopping
the travel of the EOT crane, characterized jn that the normally closed
contacts of said electronic relay means is disposed in series enabling
operating the travel motor drives of the EOT crane.
2. An electrical control device for restricting EOT crane operation as
substantially described and illustrated herein with reference to the
accompanying drawings.

The invention relates an electrical control device for restricting EOT crane
operation comprising an electrical power source means for providing an
output voltage proportional to the input voltage with a switch means for
making and breaking the supply to the circuit, a plurality of operation limit
switch means actuable in the occurrence of the crane traveling inside an
unsafe zone, and an electronic relay means connected in series to said
plurality of limit switches to transfer signal for stopping the travel of the EOT
crane, characterized in that the normally closed contacts of said electronic
relay means is disposed in series enabling operating the travel motor drives
of the EOT crane.