FIELD OF INVENTION
This invention relates to an improved over hoist safety system for crane. The system is used to warn the operator against over-hoisting the hook block, which might result damage to crane, hook block or the wire rope.
PRIOR ART
The known system comprises of a spring-loaded drum with Teflon coated cable for conducting current from vehicle i.e. telescopic connection to a battery operated horn (audio), thru a mechanical switching device. Further, it comprises of a hanging weight over the lifting hook block of the crane. However, the known art is not provided with a warning system so as to warn the operator against over-hoisting the hook block.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide an improved over hoist safety system for crane which warns the operator, when hook block approaches close to crane boom while lifting load.
Another object of the present invention is to provide an improved over hoist safety system for crane which is simple in construction.
Further object of the present invention is to provide an improved over hoist safety system for crane which is cost effective and reliable.

Yet further object of the present invention is to provide an improved over hoist safety system for crane which does not limit the distance between operator cabin & hook block unlike the prior art.
SUMMARY OF THE INVENTION
According to this invention, there is provided an improved over hoist safety system for crane wherein spring loaded drum is replaced with cable and switch without use of wires based on radio frequency to give signal to operator in crane cabin when hook block approaches closer to boom while lifting load. Thus, the operator is warned against over-hoisting the hook block, which may cause damage to crane, hook block or the wire rope.
The present invention comprises a transmitter, a receiver & a hanging weight with a switching device operated by the hook block when the block moves up (close to boom) while lifting load.
The present invention does not require any wiring i.e. the cable drum and cable as the operation is through a transmitter on crane boom extension and a receiver in operator cabin for providing audio and video warning signal to the operator against further lift of the hook.
When hook block approaches closer to boom-extension during load lifting the hanging weight also moves up, activates the transmitter, through a magnetic plunger (part of hanging weight). The transmitter installed on boom-extension of crane & signals receiver installed in operator cabin. This gives audio 8B visual warning through buzzer & LED to operator, against further lift of hook block. When hook block is lowered the buzzer stops.

The unit is powered by a battery housed in the transmitter on the crane boom-extension. The unit also provides low battery indication through a LED on the receiver unit. Both transmitter & receiver units are matched pairs, having unique ID.
During lifting of load through winch, the hook block approaches close to boom-extension. The hanging weight assy, is also carried out vertically, resulting in the operation of mechanical switch which activates the transmitter fitted on it. This sends signal through antenna to receiver. The receiver activates LED & buzzer giving audio warning to operator not to lift hook block (H) further. Then the hook block is moved down a little to stop the buzzer warning operation & vice-versa.
STATEMENT OF INVENTION
According to this invention, there is provided an improved over hoist safety system for crane comprising of a transmitter, a receiver and a winch assembly mounted on a crane boom having a plurality of extensions, in which wire rope is connected to hook block, a hanging weight and a switch.
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 to 4 shows: the schematic of present system fitted with the spring loaded drum with cable, mechanical switching device and hanging weight.

Fig. 5 shows: the schematic arrangement of transmitter, magnetic plunger and handing weight.
Fig. 6 to 10 shows: the schematic of the system of the present invention.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
Referring to fig. 1, the buzzer (1) is fitted in operator cabin (A), Teflon coated cable (2) is wound up on spring loaded drum (3) 8B connected to mechanical switch (HS) which is further connected to hanging weight (5) thru, wire rope (WR).
Referring to fig. 2 to 4 that shows complete schematic of the current system in which winch assay (F) is mounted on the crane boom (B) having atleast three extensions (C, D 8B E). The wire rope (G) is connected to hook-block (H), hanging weight (5), mechanical Switch (4) hinged to extension plate (3). It also comprises atleast three pulleys (P).
Referring to fig. 5, wherein the transmitter assembly (4) is hinged to boom extension plate (E) at print (P1) in which an antenna (1.1) is provided in connection with a transmitter assembly (4.2) accommodating a battery compartment (4.1). Said transmitter assembly (4.2) is connected to plunger (4.4) through a magnetic plunger (4.3) in which the plunger (4.4) is connected to a plunger spring (4.5). The assembly thus obtained is connected to guard spring for wire-ripe (4.6) and fork assembly (4.7 and 4.8). The fork assembly is attached for hanging weight (5) at point (P2).

Reference may be made to fig. 6-9 in which the operator cabin (A) is provided with a receiver (1). The system of the present invention comprises of winch assembly (F), telescopic sliding extensions (C, D, & E) fitted on boom (B) and a hanging weight (5) placed loosely over hook-block (H) through the wire rope (4.7, fig. 5). In fig. 8, wire rope (G) is connected to hook block (H) through pulleys (P).
Reference may be made to fig. 7, in which the receiver (1) is installed in the operator cabin (A) connected to each other by means of an antenna (1.1). Further, the receiver comprises of LED (1.2) indicating battery status and LED (1.3), which gives indication regarding buzzer (1.4).
Referring to fig. 10, wherein the transmitter system with battery is mounted on mechanical switch (4). The switch is connected to the hanging weight (5) through a wire (4.7). The weight is placed above hook block (H).
In the present invention, horn gets connected through the switching device as the hook approaches close to the crane boom extension, while lifting the load.
OPERATION
During lifting of load (Fig. 8) as the hook block (H) approaches close to the boom extension plate (3), the hanging weight assy. (5) is also carried over-vertically resulting in upward-movement of magnetic plunger (4.4) by the spring (4.5) (fig. 5) close to transmitter (4.2). This transmits signal thru antenna (1.1) to receiver (1) (Fig. 7). The receiver activates LED (1.3) 8B buzzer (1.4) giving audio/visual warning signal to operator for not to lift hook block (H) further up. The hook block is required to be moved down to a little to stop buzzer operation & vice versa.

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. An improved over hoist safety system for crane comprising of a transmitter, a receiver and a winch assembly mounted on a crane boom having a plurality of extensions, in which wire rope is connected to hook block, a hanging weight and a switch.
2. An improved over hoist safety system as claimed in claim 1, wherein the transmitter assembly is hinged to boom extension plate in which an antenna is provided in connection with a transmitter assembly accommodating a battery compartment.
3. An improved over hoist safety system as claimed in claim 1 or 2, wherein said transmitter assembly is connected to plunger through a magnetic plunger in which the plunger is connected to a plunger spring.
4. An improved over hoist safety system as claimed in any of the
preceding claims, wherein the receiver is installed in the
operator cabin connected to each other by means of an
antenna, in which the receiver comprises of LED indicating
battery status and another LED gives indication regarding
buzzer.
5. An improved over hoist safety system as claimed in any of the
preceding claims, wherein the transmitter system with battery
is mounted on mechanical switch, which is connected to the
hanging weight through a wire.

6. An improved over hoist safety system for crane substantially as herein described with reference to the accompanying drawings.