GB2300136A - Spray apparatus - Google Patents

Abstract

An array of valves and associated nozzle holders 5 is arranged along a header 1, fastened to a manifold plate 2. Each valve has a body 6 with a central valve spool bore 7. A valve spool 11 has a spigot 12 and a closure member 13. A spring 17 is carried on the spigot 12 and acts between the manifold and the closure member 13 to assist the spool towards its normally closed position, in which the closure member 13 sits against the step between the end section 9 and the central section 8 of the bore 7, thereby closing the passage downstream of the port drillings 4. A control air port 20 is in communication via drillings 21 with the end section 10 of the spool bore. Air pressure at the port 20 acts to drive the spool 11 towards the header, opening a passage for the liquid into the central section 8 from whence it is discharged via nozzles 26.

Description

SPRAY APPARATUS The present invention relates to spray apparatus, particularly though not exclusively for spraying rolls in a rolling mill.

In a rolling mill, as rolling progresses, the rolls progressively heat up. This is a phenomenon not only of hot rolling, where the metal being rolled is at high temperature and can quickly heat the rolls, but also of cold rolling where the working of the metal heats it and the rolls.

Where rolling is being carried out to close tolerances, as in production of strip, thin strip and foil, uneven heating of the rolls causes their diameter to change over their length. To alleviate this problem, it is known to spray the rolls with jets of cooling liquid. Depending on the type of mill and product rolled, different cooling liquids can be employed. These range from water, via water/oil emulsions, to oil and kerosene. The latter in particular is used for cold rolling.

Conventionally, the cooling jets are supplied via valves, which can be individually controlled by air pressure, so that the camber of the rolls can be controlled by supplying more less coolant to different zones of the rolls. The conventional pneumatically operated spray valves used, mounted on or in front of spray headers, are of the Normally Open (NO) type. They are controllably closable against the coolant pressure in the header with the application of compressed air, usually from a remotely installed directional control valve. This arrangement has the following disadvantage.

In the event of compressed air failure, any valves being held shut by the air will immediately open. Thus on air failure all the valves in the mill will allow coolant to discharge at full pressure, resulting in uncontrolled coolant flow to the mill until the coolant pumps are shut down. Where kerosene or other flammable coolant is used, uncontrolled flow represents a severe fire risk. This can, in the event of a fire in the mill, increase the damage suffered.

The object of the present invention is to provide improved spray apparatus, in which normally open valves are not used.

According to the invention there is provided spray apparatus comprising: a spray liquid header, to which the liquid is supplied under pressure in use; an array of valves arranged along the header, each valve being a normally closed valve and being arranged to allow passage of liquid from the header when open; and an array of nozzles, each being connected to a respective valve for providing a jet of liquid when its valve is open.

To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional side view through a spray liquid header, valve and nozzle of the invention; Figure 2 is a plan view of the header, valve and nozzle of Figure 1; Figure 3 is a diagrammatic side view of four spray apparatuses of the invention installed to cool a set of rolls.

The spray apparatus shown in Figures 1 and 2 comprises a spray liquid header 1, of square section tube, to which the coolant, typically kerosene under a pressure in the region of 4 to 10 bar is supplied in use. To one side of the header, a manifold - or spray valve mounting - plate 2 is welded. It has an array of pilot drillings 3, of which one only can be seen in Figure 1, and of coolant feed port drillings 4.

An array of valves and associated nozzle holders 5 is arranged along the header, screw fastened to the manifold plate 2. Each valve has a body 6 with a central valve spool bore 7. This has a small diameter central section 8 and larger diameter end sections 9,10. In sequence from the manifold side, the valve spool 11 has a pilot spigot 12, a closure member 13, a central stem 14, a liquid seal seat 15 and an air seal seat 16. A spring 17 is carried on the spigot 12 and acts between the manifold and the closure member 13 to assist the spool towards its normally closed position, in which the closure member 13 sits against the step between the end section 9 and the central section 8 of the bore 7, thereby closing the passage downstream of the port drillings 4. In this position of the spool, the pressure in the header 1 acts to hold the spool and the valve positively closed.This results in instantaneous on/off operation.

The manifold plate 2 also has for each valve a control air port 20 in communication via drillings 21 with the end section 10 of the spool bore. Here the air seal seat 16 on the spool carries an outwardly directed lip seal 22, whereby air pressure, typically at 5 to 7 bar, at the port 20 can act to drive the spool towards the header (against the higher pressure of the liquid which acts on a smaller area), opening a passage for the liquid into the central section 8 of the bore, namely the annular space around the central stem 14. The liquid is prevented from reaching the end section 10 by another lip seal 23, arranged to face it on the seat 15.

From the central section 8 of the bore, a series of drillings 24 lead coolant out of the valve body 6 via a nozzle holder 25 to an nozzle 26 for directing a liquid jet when the valve is open. In the event of intentional or unintentional removal of air pressure, the combination of the liquid pressure and the spring's 17 force instantly closes the valve.

As shown in Figure 2, the header has a plurality of valves arranged on it, in zones along it, with one or more valves arranged vertically on the header at each zone.

Figure 3 shows a foil F being rolled in the bite B between top and bottom work rolls 30, respectively backed up by top and bottom back-up rolls 31. In the arrangement shown in Figure 3, coolant headers 32 are arranged on both the up- and down-stream side of both the work rolls. As shown, at each zone along the headers, the headers each have three valves 33. Of these one has its associated nozzle 34 directed at the bite B; the second has its nozzle directed towards the roll per se; and the third has its nozzle directed towards the nip N between the work roll and the back-up roll. In alternative arrangements, differing numbers of headers and valves per zone may be employed.

Further the nozzles may be arranged, by suitable drilling and threading of the nozzle holders, to concentrate all the jets from one header in an individual zone onto the same roll or part of it. This gives the facility to provide a variable flow rate to the roll by switching on or off the individual valves of the zone.

All the valves both at the zone shown in Figure 3 and along the headers 32 are individually controllable for control of the temperature of the rolls and hence their camber. It is of course possible to gang the valves of a zone and/or of a row in the header to operate together if desired.

Claims (5)

Claims:

1. Spray apparatus comprising: a spray liquid header, to which the liquid is supplied under pressure in use; an array of valves arranged along the header, each valve being a normally closed valve and being arranged to allow passage of liquid from the header when open; and an array of nozzles, each being connected to a respective valve for providing a jet of liquid when its valve is open.

2. Spray apparatus as claimed in claim 1, wherein each valve includes a valve spool and a spring biasing the valve spool towards its closed position.

3. Spray apparatus as claimed in claim 1 or claim 2, wherein each valve spool carries a closure member and has a seat coaxial with the spool, the upstream side of the seat being in communication with the liquid header and the downstream side being in communication with the respective nozzle, the arrangement being such that both the spring and any pressure difference across the closure member due to the liquid being under pressure act to bias the spool towards its closed position.

4. Spray apparatus as claimed in claim 1, claim 2 or claim 3, wherein each valve spool includes a piston and cylinder arrangement at its downstream end for displacement of the spool to its open position on application of pressure air to the cylinder.

5. Spray apparatus substantially as hereinbefore described with reference to the accompanying drawings.