Claims:We Claim:

1. A centralized control system for movement of furnace roofs through uniform movement of hydraulic cylinders for avoiding misbalance comprising:

each said hydraulic cylinder provided with corresponding proportional valves for precise control of operation of individual cylinders;

position transducer means at the top of each cylinder providing for positional feed back of each cylinder at any given time;

a centralized control means for receiving all online positional feedback from respective hydraulic cylinders and enabling controlled synchronizing of all the operative cylinders together through a cooperative PLC.

2. A centralized control system for movement of furnace roofs as claimed in claim 1 wherein a LVDT (Linear variable differential transducer) is fixed in each hydraulic cylinders for having exact piston position in the individual cylinders.

3. A centralized control system for movement of furnace roofs as claimed in anyone of claims 1 or 2 comprising HNC (Hydraulic numeric controller) fixed between the proportional valves and PLC for synchronization of all cylinders resulting in auto balancing of the roof
4. A centralized control system for movement of furnace roofs as claimed in anyone of claims 1 to 3 generating position of individual cylinder feedback at all time to the operator.
5. A centralized control system for movement of furnace roofs as claimed in anyone of claims 1 to 4 wherein any incident of internal leakage in hydraulic cylinder is also visible in PLC.
6. A centralized control system for movement of furnace roofs as claimed in anyone of claims 1 to 5 which is fully automatized and free of any manual intervention for roof balancing.

Dated this the 21st day of May, 2019
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199

, Description:FIELD OF THE INVENTION
The present invention relates to a centralized control system for movement of furnace roofs involving hydraulic controlled auto balancing of furnace roof. More particularly, the present invention is directed to provide a system for auto balancing of furnace roof as applicable in case of Electric Arc Furnace (EAF) or Electric Arc Type Ladle Heating Furnace (LHF) where lifting and lowering of the furnace roof is actuated by a number of hydraulic cylinders wherein each said hydraulic cylinder is individually controlled using individual proportional valves based on the feedback received from LVDT (Linear variable differential transducer) attached to each cylinder. Additionally, a HNC (Hydraulic numeric controller) has been introduced for synchronization of all cylinders resulting in auto balancing of the roof. This system has completely eliminated the manual intervention for roof balancing and can be applied to any number of cylinders.

BACKGROUND OF THE INVENTION
Metallurgical industry uses many type of furnaces such as Electric Arc Furnace (EAF), Electric Arc Type Ladle Heating Furnace (LHF) etc for heating, melting and mixing operations. Such furnaces inevitably have water cooled roofs designed with openings to have electrode insertion, fume extraction and additions. These heavy roof are hydraulically moved up and down using DC valves during the operations and regularly have misbalancing and breakdowns affecting the production process.

All the metallurgical furnaces designed for heating, melting and mixing operations have movable roofs most of which are water cooled. The roof is provided for covering the mouth of the furnace such that there is no spillage of metal while arcing and during addition of alloy/fluxes. The roof is normally operated using multiple hydraulic cylinders with the help of a common Direction Control(DC) Valve. At normal position, the roof is at the top position, when the furnace is ready for treatment and before the start of operation, this roof is lowered onto the furnace, by giving command to the DC Valve. Once the treatment is over the roof is lifted to the top. The movement of roof is accomplished normally with multiple hydraulic cylinders (without any kind of position feedback), in which pressurised oil is filled and drained for up and down movement respectively. The cylinders are connected in series through a common DC valve.

Over a period of time with frequent up/down operations the roof, on or other arbitrary cylinder lags behind thereby causing roof misbalance. With multiple cylinders in operation, low fluid level, low accumulator pressure, system leaks, fluid degradation due to over-heating, solids build-up in valves or in hydraulic lines or wear in one cylinder causes misbalance of the roof. This leads to damage of electrodes (if used) or the cooling water tubes during up/down movement. This many times also causes water leakage from cooling circuit. Both the above situations are very dangerous and requires shut down of the furnace and production loss. As the hydraulic system is in series, manual adjustment is required to physically equalize all cylinders to balance the roof. This is a regular problem in all furnaces having DC valve controlled hydraulic roofs.

The present invention thus attempts to provide an auto balancing system which can adjust the cylinders individually in order to resolving the issue.

OBJECTS OF THE INVENTION

The basic object of the present invention is directed to providing a centralized control system for movement of furnace roofs involving hydraulic controlled auto balance of furnace roof to achieve uniform movement of furnace roof through auto correction of piston position in hydraulic cylinders to avoid imbalance.

A further object of the present invention is directed to a system for hydraulic controlled auto balance of furnace roof wherein each of multiple hydraulic cylinders are actuated by individual proportional valve replacing common Direction Control(DC) valve.

A still further object of the present invention is directed a system for hydraulic controlled auto balance of furnace roof wherein uniform movement of each cylinder can be achieved and can also have auto correction of the position if there is any deviation.

A still further object of the present invention is directed a system for hydraulic controlled auto balance of furnace roof which would completely eliminate the manual intervention for roof balancing.

A still further object of the present invention is directed a system for hydraulic controlled auto balance of furnace roof which can be applied to any number of cylinders.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to a centralized control system for movement of furnace roofs through uniform movement of hydraulic cylinders for avoiding misbalance comprising:

each said hydraulic cylinder provided with corresponding proportional valves for precise control of operation of individual cylinders;

position transducer means at the top of each cylinder providing for positional feed back of each cylinder at any given time;

a centralized control means for receiving all online positional feedback from respective hydraulic cylinders and enabling controlled synchronizing of all the operative cylinders together through a cooperative PLC.

A further aspect of the present invention is directed to said centralized control system for movement of furnace roofs wherein a LVDT (Linear variable differential transducer) is fixed in each hydraulic cylinders for having exact piston position in the individual cylinders.

A still further aspect of the present invention is directed to said centralized control system for movement of furnace roofs comprising HNC (Hydraulic numeric controller) fixed between the proportional valves and PLC for synchronization of all cylinders resulting in auto balancing of the roof
A still further aspect of the present invention is directed to said centralized control system for movement of furnace roofs generating position of individual cylinder feedback at all time to the operator.

A still further aspect of the present invention is directed to said centralized control system for movement of furnace roofs wherein any incident of internal leakage in hydraulic cylinder is also visible in PLC.

A still further aspect of the present invention is directed to said centralized control system for movement of furnace roofs which is fully automatized and free of any manual intervention for roof balancing.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1: is the schematic line diagram showing conventional DC Valve based hydraulic control system for furnace roof.

Figure 2: is the schematic line diagram for auto balancing system of furnace roof involving Proportional Valve based hydraulic control for synchronized operation of hydraulic cylinders according to present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention relates to a centralized control system for movement of furnace roofs involving hydraulic controlled auto balancing of furnace roof applicable for EAF or LHF etc to achieve uniform movement of furnace roof through auto correction of piston position in hydraulic cylinders to avoid misbalance.

In the proposed system, the multiple cylinders responsible for the roof movement are operated with corresponding dedicated proportional valves as against common DC Valve. Each cylinder is connected to its own proportional valve and the common DC valve is removed from the circuit. This allows the precise control of the speed at which the individual cylinders are operated. A LVDT (Linear variable differential transducer) which is a position transducer is fixed at the top of each cylinder which provides the position feedback or exact piston position in the individual cylinders. An HNC (Hydraulic numeric controller) is also connected for synchronization of all cylinders. HNC collects the position feedback from LVDT and commands the proportional valve. By following the logic of master slave operation with respect to the cylinder position uniform movement of each cylinder can be achieved and can also have auto correction of the position if there is any deviation. With this new system having a combination of individual proportional valves, LVDT and HNC, position of individual cylinder feedback is now available at all time to the operator. Any incident of internal leakage in hydraulic cylinder is also visible in PLC. Manual intervention for roof balancing is completely eliminated. This new developed system can be applied to any number of cylinders.

Accompanying Figure 1 shows the general schematic of the conventional DC Valve based hydraulic control in a 3-cylinder system. Here the cylinders (1) are controlled using a common DC valve (2). The control is through a PLC (3). The cylinders are connected in series through a common DC valve. Over a period of time with frequent up/down operations the roof, the individual pressure of cylinders is disturbed and results in non-uniform movement leading to roof misbalance.

Accompanying Figure 2 shows the schematic of new developed the Proportional Valve based hydraulic control according to present invention. Here each cylinder is connected to its individual Proportional valve (4) replacing common DC valve for individual cylinder position control. A LVDT (5) which is a position transducer is fixed at the top of each cylinder (1) which provides the position feedback or exact piston position in the individual cylinders. An HNC (6) is also connected for synchronization of all cylinders. HNC collects the position feedback from LVDT and commands the proportional valve through the PLC (3).This new developed system can be applied to any number of cylinders.

It is thus possible by way of the present invention to provide a centralized control system for movement of furnace roofs involving hydraulic controlled auto balancing of furnace roof through uniform movement of hydraulic cylinders for avoiding misbalance. The system introduced individual proportional valves for individual cylinder position control and PLC based control system enable synchronization of all cylinders based on feedback of exact piston position in the individual cylinders resulting in auto balancing of the roof, whereby manual intervention for roof balancing is completely eliminated and the developed system can be applied to any number of cylinders. Furnace operating life is thus enhanced without breakdown due to roof imbalance and hence improving furnace productivity.