DESC:FIELD OF INVENTION

The present invention relates to an electromechanical hoist transfer system operated in the shop floor of an automobile plant. In particular, the present invention relates to an electromechanical auto-hoist trolley system for performing safe hoisting operations. More particularly, the present invention relates to a stopover mechanism for an electromechanical auto-hoist system provided for monitoring, detecting and controlling its malfunctions, which are considered unsafe to the personnel working in the vicinity thereof.

BACKGROUND OF THE INVENTION

In automobile industry material handling with hoisting equipment plays a vital for transferring raw /semi-finished and final products between various production processes. Human and equipment safety has gained great importance in the modern day manufacturing processes. Safety has become an uncompromised feature of the manufacturing process. Use of material handling equipment is an integral part of manufacturing process. Many such equipment are used like- forklift, stacker, pallets etc. One such important equipment is electromechanical hoist. It is used to move large sized, weight, quantities of load from one place to another. In any organization, electromechanical hoists from many manufacturers are used for this purpose.

The purpose of the hoist is for lifting and moving the desired load from one place to another place depending upon the application of process load. The capacity and speed of the hoist and traverse operations thereof are chosen based on load application. Hoisting equipment are classified in 3 varieties based on the method of operation viz. manually operated, semi-automated and fully automated control. These hoists have Traverse, Longitudinal and Up /Down Operations based on the application. Manual hoist (Fig. 1a) is fully operated by human beings, whereas Auto-hoist (Fig. 1b) is controlled by PLC (Programmable logic controller) as well as relay logic for all movements except loading and unloading of the components. The hoists are configured to be operated with lowest effort and without any strain or fatigue to the operator.
PRIOR ART

The publication US 3735221 A discloses an electrical control system for raising and lowering a drum-and-cable supported load. A reversible shunt wound drive motor which is connected to the drum is operable under the control of a continuously driven shunt wound generator. By measuring the amount of current flowing in the armature coil of the drive motor and varying the flow of current in the field coil thereof in relation to such armature current, the speed of the drive motor will become a direct function of the load which is placed on the latter. By reversing the polarity of the voltage which is supplied to the field coil of the generator, the direction of rotation of the drive motor may be reversed without disturbing the relationship between the load and the motor speed. Thus, whether the load is rising or descending, the greater its magnitude, the slower its speed. An electromechanical brake arrangement becomes automatically effective to lock the cable drum in a fixed position when load speed drops substantially to zero.

However, there are following main disadvantages with the electrical circuit of the above-mentioned electrical control systems:

a) Logic having various synchronous parts.

b) High probability of failure due to presence of many parts.

c) Difficult to understand because of complex design.

d) Difficulty in troubleshooting of circuit.

e) High-cost due to motors and generators.

f) Resistance varies due to climatic conditions.

g) Malfunctioning during use of semiconductor (amplifier) at high temperatures.

h) Requires special circuits (supply and rectifier) for limit switch functioning.

i) Risk of short-circuiting of open contacts of limit switch due to the presence of dust and dirt at location.

j) High response time due to series of parts.
DISADVANTAGES WITH THE CONVENTIONAL AUTO-HOIST SYSTEMS

The disadvantage with the conventional auto hoists manufactured by OEMs and equipped in mass production units like automobile manufacturing plants is that the trolley system comprising multiple auto-hoists moves forward to load the component by a predefined distance and returns empty by covering the same distance to complete the loop and vice-versa. There is no interlock provided by OEMs in the forward motion of the hoist from the point of view of the safety of the operator/shop floor personnel. A predefined group of hoists is controlled by a master PL C located on the shop floor in coordination with a respective slave PLC in each of such auto hoists. Both the master and slave PLCs are coordinated by using a wireless module.

Another major disadvantage with such auto-hoist trolley system is that while the auto-hoist moves forward with or without load, there is a safety hazard on an inadvertent entry of any personnel in such path of electromechanical hoist travel and it may hit such personnel/s and lead to an accident (Fig. 1c).

A further disadvantage with the conventional auto-hoist system equipped with mechanical limit switches are frequent breakdowns occurring due to load wheel and chains, because the hoist is used to lift and transfer loads at a specific working height. Such breakdowns occur due to the following conditions:

a) Plunger damage due to continuous hitting during upward movement.

b) Disturbance in the alignment of the plunger assembly.

c) Entanglement issues with various components.

d) Failure of the limit switch due to its complicated design.

Often, these auto-hoists are equipped with a slip clutch mechanism to prevent the load from lifting on exceeding the safe working load limit. In some other types of auto-hoists, thermal contact type safety feature is provided, which draws additional current on lifting the excess load.
This causes an increase in the temperature of the contact strip beyond a safe limit and thus the contact strip being opened due to its thermal expansion to stop hoist operation for protecting the equipment. However, the auto-hoists with such slip clutch mechanism also have a very high response time in the range of about 10-20 seconds and during this time the chain already gets damaged.

Thus, the unsafe working condition because of hoist chain breakage due to overloading (lifting of the load exceeding the safe working load limit) causes a free fall of the load from the height to which it was lifted. This may prove fatal to the shop floor personnel operating the hoist and also to those walking alongside the load. It is also a major operational hazard to the equipment (e.g. hoist) carrying the load.

After damage to the mechanical limit switch, first the chain box bolt is loosened and the chain is taken out from the hoist wheel and through the limit switch assembly. Then, the damper spring of the plunger is opened by loosening the Allen Bolts.

Subsequently, the plunger dowel is taken out and the lever assembly is opened to replace the damaged plunger and pusher plate, if it is bent and finally the lever assembly is refitted. Now, the plunger assembly is completed with a new dowel pin and the damper spring is tightened with Allen Bolts.

Thereafter, the chain of hoist is rerouted through the hoist wheel and mechanical limit switch assembly. However, this process requires minimum 60 minutes.

Therefore, there is an existing need for avoiding such potentially unsafe movements of the auto-hoists in automotive and other production facilities to protect hoist operator/s and personnel working on shop floors equipped with electromechanical auto-hoists.

There is also another existing need for developing a solution with a faster response time to fully protect the equipment and the shop floor personnel.
OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide an improved electromechanical auto-hoist system to substantially reduce the response time thereof in milliseconds.

Another object of the present invention is to provide an electromechanical hoist system which identifies limit switch failures.

Still another object of the present invention is to provide an electromechanical hoist system which eliminates minor stoppages / breakdowns possible due to limit switch malfunctions.

Yet another object of the present invention is to provide an electromechanical hoist system which obviates any blind operation thereof.

A further object of the present invention is to provide an electromechanical hoist system which reduces Mean time to repair (MTTR) of the limit switch thereof.

A still further object of the present invention is to provide an electromechanical hoist system which simplifies the working mechanism of the limit switch thereof.

A yet further object of the present invention is to provide an electromechanical hoist system to eliminate the safety concerns for personnel in the vicinity thereof and thereby to improve their moral.

An additional object of the present invention is to provide an electromechanical hoist system which prevents damages during movement or lifting excess loads.

One more object of the present invention is to provide an electromechanical hoist system to reduce the operator’s fatigue and to improve their operational efficiency.
Still more object of the present invention is to provide an electromechanical hoist system with a faster response time to fully protect the equipment and the shop floor personnel.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.

DESCRIPTION OF THE INVENTION

In order to avoid any potential safety hazard to the operator/s and/or shop floor personnel present in the travel path of the electromechanical auto-hoists, a smart stopover mechanism (Fig. 2a) for electromechanical auto-hoists is developed in accordance with the present invention by introducing additional stiffness rod and limit switch incorporated in the existing trolley system of the electromechanical auto-hoists used in production facilities, such as automobile manufacturing plants.

According to this configuration, the metallic stiffness rod first comes in contact with personnel in the event of any such fouling. This stopover mechanism includes a circuit, which enables the metallic stiffness rod to touch the body of the personnel and to simultaneously activate a limit switch by signaling the forward motor of the respective auto-hoist to immediately stop the forward motion of auto-hoists to ensure the safety of shop floor personnel (Fig. 2b, 2c).

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a stopover interlocking mechanism for electromechanical auto-hoist trolley system. The mechanism comprises:

• a protection means;

• a hoist frame structure equipped with a forward motor suspended on gantry;

• the protection means, and the hoist frame structure connected via a mechanical linkage disposed therebetween;

• at least one electrical limit switch fitted on the electromechanical auto-hoist trolley system; and

• a current control device fitted on the electromechanical auto-hoist trolley system;

wherein the limit switch issues electrical signals to the forward motor via a cable for starting or stopping the forward motion of the forward motor.

In an embodiment of the present invention, the electrical limit switch comprises a housing having a microswitch fixed thereon by means of a plurality of fasteners, the microswitch connected to an octagonal block via a nylon thread.

In another embodiment of the present invention, the current control device (CCD) comprises a mounting space; preferably a 7-segment digital display; a control relay contact, preferably a non-potential contact; and a current transformer for reading the current of the electromechanical auto-hoist trolley system during operation thereof.

Typically, the control device or CCD is connected to the microswitch via a control relay contact having NO (normally open), NC (normally closed), and P (440 V power) terminals, and also connected to an AC / DC power supply and the current transformer to continuously read the current of the electromechanical auto-hoist trolley system during the operation thereof.

In accordance with the present invention, there is also provided a method of operation of the aforesaid stopover interlocking mechanism, comprising the steps of:

• setting the safe working load for operating the mechanism;

• starting the electromechanical auto-hoist trolley system;
• reading the current of the trolley system continuously during the operation thereof; and

• stopping the upward movement of the trolley system on detecting an unsafe load being lifted thereby.

Typically, the bottom hook of the trolley system is raised to the topmost position thereof by means of the limit switch and the trolley system is lowered for lifting another load by continuing the current reading step.

Typically, the overload limit (OLL) is shown on the display of the CCD and the limit switch is reset by the trolley system operator to continue the current reading step.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings.

Figure 1a shows a manual hoist fully operated by the shop floor personnel or operator (not shown).

Figure 1b shows an auto-hoist controlled by a PLC as well as relay logic for all movements except loading and unloading of the components by the shop floor personnel or operator.

Figure 1c shows the common safety hazard due to movement / operation of an electromechanical auto-hoist.

Figure 2a shows a conventional auto-hoist system provided with a mechanical limit switch disposed within the encircled region.

Figure 2b-2d show a perspective view of the mechanical limit switch of Fig. 2a.

Figure 3a shows a stopover mechanism configured in accordance with the present invention and equipped in electromechanical auto-hoist trolley system.

Figure 3b shows the operation of the stopover mechanism of Fig. 2a when fitted on the frame structure of the electromechanical auto-hoist trolley system.

Figure 3c shows an actual operational situation of the stopover mechanism of Fig. 2b.

Figure 4a shows a schematic perspective view of the stopover human interlocking mechanism configured in accordance with the present invention.

Figure 4b shows the electrical limit switch fitted on the electromechanical auto-hoist trolley system.

Figure 5 shows a flow chart of operating the stopover interlocking mechanism fitted on the electromechanical auto-hoist trolley system shown in Fig.4a.

DETALED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1a shows a manual hoist 10 fully operated by the shop floor personnel or operator (not shown). The hoist 10 is moveable on gantry 12 both in forward (F) or reverse (R) movements and for raising or lowering the load (not shown) suspended on the load hook LH and by performing up (U) or down (D) movements by using an electromechanical control EC.

Figure 1b shows an auto-hoist 20 disposed on gantry 22 and controlled by a PLC (Programmable logic controller) as well as relay logic for all movements except the loading and unloading of the components (load/s) by the shop floor personnel or operator. It includes a switch gear SG and a control panel CP for performing the forward (F) or reverse (R) movements and for raising (U) or lowering (D) the load suspended on the load hook (not shown).

Figure 1c shows the common safety hazard due to movement / operation of an electromechanical auto-hoist, whereby any personnel Op unknowingly entering the travel path of the electromechanical hoist 20 suspended from a gantry 22, may get injured and this may cause a serious accident. This is a major personnel safety concern during forward motion of the conventional auto-hoist trolley system 20.

Figure 2a shows a conventional auto-hoist system 20 provided with a mechanical limit switch 30 disposed within the encircled region. The load hook LH is used for moving the load up or down by an electromechanical control EC.

Figure 2b shows a front view of the mechanical limit switch 30 of Fig. 2a which includes a plunger dowel 22, a housing 24, a damper spring 26 and Allen bolts 28. The plunger dowel 22 is connected to damper spring 26 by Allen bolts 28 and suspended from housing 24 to accommodate limit switch 30 of Fig. 2a.

Figure 2c shows switch pusher plate 32, one end of which is on the round pin 36 by means of Allen bolts 46 after placing two compression springs 48 for switch axle and provided for tightening the washer 50 with nuts 52.

Figure 2d shows another detailed view of the limit switch 30 of Fig. 2a. The plunger dowel 22 is suspended from the housing 30 and attached to a switch lever 34 by a round dowel pin 36 (e.g. 24 mm diameter). The switch lever 34 is mounted on the round pin 36 by means of Allen bolts 38 (M4 x 40 mm). One end of the round pin 36 is locked by means of a circlip 40 (A-22) and the other end is switch pusher plate 32 assembly (Fig. 2c) with setting spacers 44 mounted on the round pin 36. The pusher plate 32 operates the mechanical limit switch 30 by rotating the round pin 36 due to load acting on plunger 22.

Figure 3a shows a schematic perspective view of the stopover human interlocking mechanism 150 configured in accordance with the present invention and fitted on the electromechanical auto-hoist trolley system 100 to avoid any potential major hazard to the shop floor personnel. It includes an additional metallic stiffness rod 110 attached to the hoist frame structure 120 via a mechanical linkage 115 (not shown) between this rod 110 and the limit switch 130 for making smart stopover human interlocking mechanism 150 (encircled).

Figure 3b shows the electromechanical auto-hoist trolley system 100 equipped with the smart stopover human interlocking mechanism 150 having a metallic stiffness rod 110 attached to the hoist frame structure 120 via a mechanical linkage disposed between rod 110 and limit switch 130.

Figure 3c shows the smart stopover human interlocking mechanism 150 for carrying a load or cargo is running on gantry 122 and operated by a forward motor 102 (Fig. 4a) and including an additional stiffness rod 110 mechanically linked to limit switch 130 and fitted on frame structure 120. The limit switch 130 issues electrical signal for starting or stopping the forward motion of forward motor (102) which is transmitted via an electrical cable 104 (Fig. 4a).

Figure 4a shows an actual operational situation of the stopover mechanism 150 during a forward (F) motion of the improved auto-hoist trolley system 100. During the forward movement, the auto-hoist trolley system 100 carrying a load or cargo runs on gantry 122 and the stopover mechanism 150 facilitates to avoid hitting the operator/personnel Op present in the vicinity thereof. This is achieved by metallic stiffening rod 110 first contacting the personnel Op and limit switch 130 stops the forward (F) motion of the trolley system 100. Therefore, the electrical signal issued by the limit switch 130 is directly transferred to the forward motor 102 to cut the power supply to forward motor 102 for stopping the forward movement of the electromechanical auto-hoist trolley system to ensure human safety by preventing accident due to any further forward motion thereof.

Figure 4b shows the electrical limit switch 130 fitted on the electromechanical auto-hoist trolley system 100 and including a housing 124 containing a micro switch 132 (e.g. Elcom M-222), an octagonal block 134 (e.g. made of Nylon-66), a Nylon thread 136 (e.g. 4 mm thickness) and flat-headed screw (M3 x 30 mm).
Figure 4c shows a schematic line diagram of the current control device or CCD 140 of the novel stopover human interlocking mechanism 150 fitted on the electromechanical auto-hoist trolley system 100, as shown in Figure 4a. CCD located on control circuit of hoist includes a mounting space 142 (e.g. 200 mm x 200 mm x 75 mm). It has a response time of 250 milliseconds and operates with 24 V AC supply using a 7-segment display 144 and non-potential (control relay) contact 146 for control. Here, NO (Normally open), NC (Normally closed), P (Phase 440 V), AC (Alternating current supply) and DC (Direct current supply) are also marked. The housing 124 containing micro switch 132 suspends the octagonal block 134 by means of a Nylon thread 136. The switch 132 is connected to CCD 140 via non-potential (control relay) contact 146.

Figure 5 shows a flow chart of the operation of the stopover human interlocking mechanism 150 and fitted on the electromechanical auto-hoist trolley system 100 shown in Figure 4a. After setting the safe working load, the current to CCD 140 shows zero reading and the hoist 100 is started at 200. At step 210, CT (Current Transformer – an instrument to measure current) 148 continuously reads the current of the hoist 100 during the operation thereof.

If at step 220, an unsafe load lifting by the hoist 100 is detected, the upward movement of the hoist 100 is stopped at step 230. Otherwise, on reading the load lifted by the hoist 100 being within safe working limits, the process step 225 leads back to step 210 to read the current further.

If the hoist’s upward movement is stopped at step 230, via process step 235, the bottom hook of the hoist 100 is brought to its topmost position at step 240 by electromechanically operating the limit switch 130 and the hoist 100 is lowered at step 260 and thereafter process step 265 returns it back to step 210 to read the current further. On the other hand, from the hoist’s stopped upward movement at step 230, the process step 245 brings the CCD 140 to show OLL (Overload Limit) on the display 144 at step 250. At subsequent step 270, the limit switch 130 is reset by the team members of the hoisting operation and finally the process step 275 returns it back to step 210 to read the current further.
WORKING OF THE INVENTION

The Current Control Device or CCD 140 is a small, compact unit which can be installed on any existing electromechanical auto-hoist as an add-on unit. This CCD 140 can be set to a current value which is drawn by the hoist 100 working under a predefined safe load. It also monitors the current (step 210) continuously for hoist operation in safe working (loaded or unloaded) conditions. If the actual current drawn by the hoist during operation thereof, exceeds the preset safe working load limit (at step 220), the CCD 140 immediately opens the ‘UP’ movement contact at step 230 for the hoist to stop the upward movement thereof. Then, to restart the hoist operation, CCD needs to be reset at step 270 by the hoist maintenance team. Thus, unsafe working condition is acknowledged. This way, the CCD unit 140 eliminates any unsafe working condition for the shop floor personnel and thus achieves overload protection.

Therefore, the present invention provides a low-cost solution, which is easy to install and simple to use with wide scope of deployment to eliminate major hazard to equipment (e.g. electromechanical hoist) carrying heavy loads and to prevent hoist operators from lifting load exceeding predefined safe working load.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The electromechanical auto-hoist trolley system configured with a stopover mechanism in accordance with the present invention has the following technical and economic advantages:

• Reduced fatigue and enhanced operational efficiency.

• Safer working environment for the operator/shop floor personnel.

• Eliminates safety hazards caused to operator/personnel inadvertently entering the travel path of the auto-hoists.

• Substantial cost-savings as being maintenance free.

• No external power source is required.

• Operation is very simple and easy to understand by the operator.

• Universally deployable having no load value limits.

• Operable in any climatic conditions due to absence of semiconductors.

• This inventive concept is also deployable in elevators.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention.

The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, the skilled person will recognize that the embodiments herein can be practiced with modification within the spirit and scope of embodiments described herein.

Therefore, the skilled person can easily make innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies, assemblies and in terms of the size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention. ,CLAIMS:We claim:

1. A stopover interlocking mechanism (150) for electromechanical auto-hoist trolley system (100), said mechanism (150) comprising:

• a protection means (110);

• a hoist frame structure (120) equipped with a forward motor (102) suspended on gantry (122);

• said protection means (110) and said hoist frame structure (120) connected via a mechanical linkage (115) disposed therebetween;

• at least one electrical limit switch (130) fitted on said electromechanical auto-hoist trolley system (100); and

• a current control device (140) fitted on said electromechanical auto-hoist trolley system (100);

wherein said limit switch (130) issues electrical signals to said forward motor (102) via a cable (104) for starting or stopping the forward motion of said forward motor (102).

2. Stopover interlocking mechanism as claimed in claim 1, wherein said electrical limit switch (130) comprises a housing (124) having a microswitch (132) fixed thereon by means of a plurality of fasteners, said microswitch (132) connected to an octagonal block (134) via a nylon thread (136).

3. Stopover interlocking mechanism as claimed in claim 1, wherein said current control device or CCD (140) comprises a mounting space (142); preferably a 7-segment digital display (144); a control relay (146) contact, preferably a non-potential contact; and a current transformer (148) for reading the current of said electromechanical auto-hoist trolley system (100) during operation thereof.

4. Stopover interlocking mechanism as claimed in claim 3, wherein said current control device or CCD (140) is connected to said microswitch (132) via a control relay (146) contact having NO (normally open), NC (normally closed), and P (440 V power) terminals, and also connected to an AC / DC power supply and said current transformer (148) to continuously read the current of said electromechanical auto-hoist trolley system (100) during the operation thereof.

5. A method of operation of said stopover interlocking mechanism as claimed in anyone of claims 1 to 4, wherein said method comprises steps of:

• setting the safe working load for operating said mechanism;

• starting (200) said electromechanical auto-hoist trolley system (100);

• reading (210) the current of said trolley system (100) continuously during the operation thereof; and

• stopping (230) the upward movement of said trolley system (100) on detecting (220) an unsafe load being lifted thereby.

6. Method as claimed in claim 5, wherein raising (240) the bottom hook of said trolley system (100) to the topmost position thereof by means of said limit switch (130) and lowering (260) said trolley system (100) for lifting another load by continuing the current reading step (210).

7. Method as claimed in claim 5, wherein showing (250) the overload limit (OLL) on said display (144) of said CCD (140) and resetting (270) said limit switch (130) by said trolley system (100) operator to continue the current reading step (210).

Digitally Signed.

Dated: this day of 01st August 2017. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT