GB2099966A - Refractory plate for sliding gate valve - Google Patents

Abstract

A refractory plate 18 comprises a refractory body 160 having a stepped opening 166 of progressively increasing diameter, in which is received a porous plug 168 having a stepped external diameter, the end steps of the plug and opening being of corresponding diameter and cemented together while an annular gas channel 174 is defined between the intermediate steps. An inclined passageway 176 extends from the top plate surface to the channel 174 to supply inert gas to the channel and porous plug. The plate may be used as a top plate in a sliding gate valve of the type in which refractory gates are sequentially disposed in operative position beneath the top plate, in which a central aperture 112 in the plug is aligned with the pour opening from a teeming vessel to throttle the metal flow stream from the vessel. <IMAGE>

Description

1 GB 2 099 966 A 1

SPECIFICATION

Refractory plate for sliding gate valve The present invention relates to refractory plates for 70 use in a valve for controlling the flow of liquid metal from a teeming vessel.

There are known, e.g. from German Offenlegung schrift No. 2746265 and United States Reissue Patent No. 27,237, sliding gate valve arrangements for use on molten metal teeming vessels, in which refractory slide gates, either blank, imperforate gates or orificed gates, are sequentially positioned with respect to the vessel pour opening in order to initiate or terminate molten metal flow. The rate of flow through the valve is regulated by replacing the operative slide gate with one having an orifice of different diameter, and/or by adjusting the position of the slide gate orifice with respect to vessel pour opening.

In orderto prevent freezing of metal in the vessel pour opening, it is necessary to position a slide gate having a permeable plug beneath the pour opening for the injection of inert gas thus requiring the expenditure of additional slide gates for this purpose. It has been proposed to provide an annular gas supply surrounding the porous plug, as disclosed in British Patent No. 1428644, but hitherto it has been the practice to machine a groove in the plug receiving opening of the refractory body to provide the channel, which contributes significantly to the cost of manufacturing the plate and requires the use of a collapsible or multi-part machine tool.

According to the present invention there is pro- vided a refractory plate for use in a valve for controlling the flow of liquid metal from a teeming vessel, comprising a refractory body having a through opening which has axially spaced steps of progressively greater diameter from one end of said opening to the other, and receives a porous plug which has an exterior surface formed of axially spaced steps of progressively reduced diameter from one end of said plug to the other, the endmost steps on said plug being cemented to the corres- ponding steps in the axial opening in said body, and 110 the step on said plug intermediate said endmost steps having a diameter less than that of the corresponding step in the axial opening so as to define an annular passage.

With the stepped configuration of the opening and the plug the plate can be fabricated by conventional refractory-forming processes without the need for expensive machining.

The porous plug may be provided with a central through aperture, in which case the plate maybe employed as a top plate mounted with the aperture aligned with the pour opening of a teeming vessel, and will enable the effective distribution of inert gas injection into the vessel pour opening when the valve is in its closed condition. The valve may then be closed with plain blank gates and gates with porous plugs are no longer necessary.

The invention is further described, byway of example, with reference to the accompanying draw- ing, in which:- Figure 1 is a vertical sectional view of a sliding gate valve; Figure 2 is a vertical sectional view taken along line 2-2 of Figure 1; Figure 3 is a plan sectional view taken along line 3-3 of Figure 1; Figure 4 is a partially broken perspective representation of the mounting plate embodied in the gate valve illustrating the flow paths for cooling air and inert gas therethrough; Figure 5 is a partially broken perspective representation of a top plate embodying in the present invention; Figure 6 is a plan view of a sliding gate, Figure 7 is a perspective view of the sliding gate of Figure 6; Figure 8 is a perspective view taken from above of the valve frame structure prior to assembly; and Figure 9 is a perspective view taken from below of the valve frame structure of Figure 8.

In Figures 1 and 2 of the drawings there is shown a sliding gate valve organization 10 adapted for installation in operative relation to the pour opening 12 in the lining 14 of a teeming vessel 16, such as a tundish or the like, forteeming molten metal to the mold e.g. of a continuous caster (not shown). Teeming is controlled by the manipulation of refractory slide gates or plates, that may be orificed as shown at 17 in Figures 2,6 and 7 or blank as shown at 17' in Figure 1, with respect to a refractory top plate 18 which constructed in accordance with the invention and described in more detail below. The organization 10 also includes replaceable pour tube assemblies 19 thatform extension of the valve for conducting the teemed molten metal stream to a caster mold. The valve organization 10 is adapted for mounting to the vessel 16 by means of threaded connectors 20 extending through holes 21 in the frame 22 attaching the same to the mounting plate 23 which is, in turn, attached to the vessel by means of bolts (not shown) that connect with a nut plate 24 underlying the vessel lining 14. A heat insulating pad 26 formed of asbestos, or the like, may be interposed between the mounting plate 23 and the vessel 16.

As best shown in Figure 4, the mounting plate 23 is a generally flat metal plate having a central opening 28 for reception of the lower end 30 of the refractory material forming the vessel pour opening 12. The upper surface of the mounting plate 23 contains, along its side edges, recesses 31 that communicate with bolt holes 32 for reception of the connectors 20 and their associated nuts 34.

The mounting plate 23 is provided with a plurality of internal fluid passages for conducting cooling air and inert gas during periods of valve operation. A first passage 36, concentric with the central opening 28, is defined by a recess formed in the wall of the opening and covered by a ring 38 that is weldedly attached to the plate in order to seal the passage. In addition, the plate is formed with a pair of oppositely extending elongated passages 40 and 42 extending about three sides of the plate and terminating in downwardly discharging ports 44 for supplying cooling air to the valve springs as hereinafter more fully described. An air inlet port 46 is provided atone 2 GB 2 099 966 A 2 side of the plate for delivering cooling air to the fluid passages 36&40, 42 which, as shown by the arrows 48, are connected in series whereby cooling air is first conducted about the annular passage 36 and then in opposite directions through the passages 40, 42 before being discharged through the ports 44.

Also provided in the mounting plate 23 is an elongated passage 50 which, at one end, communicates with an inlet opening 52 atthe side of the plate for connection with a source of inert gas and at the other end, with a downwardly directed discharge opening 54 adapted to communicate with gas supply means in the valve top plate 18 as hereinafter described.

The valve frame 22, formed essentially of a 80 machined metal casting stiffened by members 56 is best illustrated with particular reference to Figures 8 and 9. This frame 22 contains the operating parts of the valve organization and is adapted for attachment to the mounting plate 23, or release therefrom, as an assembled unit through the connectors 20. The frame 22 comprises three principal sections, indicated generally in Figure 3 as plate loading section 58, operating section 60 and plate discharge section 62. Adjacentthe plate loading section 58 the frame 22 attaches, through connectors (not shown) engageable with threaded holes 64 (Figure 8), bracket means 66for mounting feed motor 68. The feed motor 68 comprises a fluid operated cylinder 70 having a reciprocable piston attaching a piston rod 72 and pusher 74. A second set of motors, termed "throttling motors" are attached to the frame 22 adjacent the operating section 60 thereof. These motors 76 are oppositely acting and are operated independently of the feed motor 68. They each comprise an operating cylinder 78 mounted on the frame by bracket 80 which attaches to the frame side wall by connectors engageable with the holes 82. The cylinders 78 each contain a reciprocable piston whose rod 83 attaches a laterally elongate connecting brace 86 which connects slide pins 88 that are guidingly received in openings 90 in the frame side wall and attach throttling rails 84 and 84' that operate to manipulate a slide plate disposed in the operating section 60 of the frame. Rail 84' is of a length shorter than rail 84 in order to accommodate passage of a plate through the loading section 58 of the frame.

The interior of the frame 22 is configured to define communicating paths of travel for slide plates 17 or 115 17'and pourtube assemblies 19 between the respective frame sections 58,60 and 62. The loading section 58 of the frame 22 heredescribed is defined by laterally extending guideways 92 and 94 adapted to pass slide plates 17,17'and pourtube assemblies 19 respectively. The guideway 92 is vertically spaced from guideway 94 by oppositely extending slide rails 96 that serve to support the slide plates that are loaded in the valve. The bottom of guideway 94 is defined by a similar set of slide rails 98 that support pourtubes 19for loading. Rub rails 99 along the roof of the frame in this section serve to vertically position a slide plate 17 as it is moved from the loading section 58 of the valve to the operating section 60 thereof.

It will be appreciated that frame 22, as depicted in Figures 8 and 9, is adapted for slide plate or pour tube insertion from either the right or left hand side by the provision of identical guideways 92' and 94' on the opposite side of the frame. When the guideways 92 and 94 are selected for use, those guideways indicated as 92' and 94' on the opposite side of the frame are closed by a stuffer member 100 comprising a backing plate 102 threadedly connect- able to the frame 22 at holes 104 (Figure 8) and vertically spaced stop plates 106 and 108 that fill the guideways 92' and 94' effectively preventing movement of a pour tube beyond its desired position adjacent the pusher 74. Obviously, loading from the opposite side of the frame can be readily effected by simply moving the stuffer member 100 from passageways 92' and 94' to the opposite side of the frame where it will fill the passageways 92 and 94.

The operating section 60 of the frame 22 contains a rectangular opening 110 in the upper surface thereof for reception of a stationary refractory top plate 18 whose central orifice 112 aligns with the pour opening 12 from the vessel and defines the inlet to the valve 10. Vertically spaced below the opening 110 the frame 22 is provided with oppositely spaced bases 114 that cooperate with the upper wall of the frameto define a cavity 115. The bases 114 are provided with laterally spaced threaded holes 116 which receive connectors 118 for mount- ing a series of spring biased levers 120 that operate to retain the pour tube assembly 19, slide plate 17 or 17' and top plate 18 in surface-to- surface sealed relation. The levers 120 pivot upon rockers 122 retained by the connectors 118 and are spring biased by headed push pins 124 movably mounted in holes 126 in the frame. The holes 126 are counter bored at their upper ends at 127 to provide seats for the push pin heads 128 and for springs 130 that bear between the push pin heads and the facing surface of mounting plate 23.

As shown in Figure 2 the holes 126 in the frame 22 are caused to communicate with the ports 44 in the mounting plate 23 whereby cooling air is supplied to prevent overheating of the springs 130. Desirably, the ports 44 contain discharge orifices 132 in order to effectively distribute cooling air to the respective spring assemblies.

Opposite walls of the valve frame 22, adjacentthe operating section 60, are provided with vertically spaced pairs of aligned holes, indicated as 196 and 198 respectively. Each pair of aligned holes is adapted to receive a selectively positionable stop pin 200 that traverses the respective paths of travel of the slide plate or pourtube assembly and is operative during plate changing procedures to obstruct movement of either the slide plate 17 or pour tube assembly 19 when it is desired to replace the other. Similar holes 196' are provided in rails 84 and 84'to accommodate passage of the stop pin 200 through these members. When the simultaneous replacement of both the slide plate 17 and the pour tube assembly is desired the stop pin 200 is withdrawn from the frame completely leaving both paths of travel free of obstruction. Under normal operation conditions the stop pin 200 is retained in the lower 3 GB 2 099 966 A 3 pair of holes 198 to leave the slide plate travel path free of obstruction in order to permit rapid termina tin of molten metal flow as hereinafter described.

The discharge section 62 of the frame 22 is formed by vertically spaced guideways 134 and 136 opening at th end of the frame. The guideways 134 and 136 are defined by stepped shoulders 138 and 140 formed in the longitudinal extensions of the bases 114 and are adapted to sliclably guide the slide plates 17 or 17'and pour tube assemblies 19 respectively from their positions in the operating section 60 of the valve to a point of discharge as hereinafter de scribed.

As shown best in Figure 3, the throttling rails 84 and 84'are disposed in the frame 22 at substantially the same elevation as slide plate loading guideway 92. Rail 84 is longer than rail 84'extending substan tially the full length of the frame interior. Rail 84', on the other hand, is shorter than rail 84 by an amount to permit passage of a slide plate 17 from the guideway 92 into position with respect to pusher 74 upon loading of these members. Rail 84 is further provided along that portion of its length that faces the guideway 92 with a plurality of longitudinally spaced magnets 142 here shown as being six four-pole permanent magnets, thefunction of which is to prevent dislodgement of a slide plate 17 or 17' in the loaded "ready" position, hereinafer described, from the rail 84 as it is moved during the perform ance of the throttling function of the valve.

The slide plates 17,17', top plate 18 and pour tube assemblies 19 of the valve organization 10 each essentially comprise a refractory material encased in a metal frame. The pour tube assembly 19 contem plated for use in the described organization is of essentially conventional construction consisting of an elongated cylindrical tube 144 having an axial opening 145. The tube 144 can be of a length to permit its lower end to extend into a caster mold, or the like. (not shown). The upper end of the tube 144 105 is adapted for reception into a recess 146 in the lower surface of a generally flat, rectangular refrac tory plate, termed the tube holder plate 148. The plate 148 contains a through-opening 149 coaxial with tube opening 145 and is enclosed about the exposed portion of its bottom and about its peripher al sides by a metal casing 150. As shown in the drawing, a mortar cement is employed to sea[ the joint between the upper end of the tube 144 and the holder plate 148 and to attach the holder plate within 115 the metal enclosure. The metal enclosure may be provided with a depending skirt 152 which serves to protect the mortared joint and to stiffen the enclosure bottom surface. A heat resistant material such as asbestos rope (not shown) can be used to fill the space 153 between the skirt and the tube. A secondary attachment between the tube 144 and the holder plate can be effected by provision of a collar 154 defining a shoulder 156 adjacent the upper end of the tube for engagement by a retention ring 158 125 which is releasably secured to the metal casing 150 by threaded fasteners, or the like (not shown). The openings 145 in the pour tube 144 and 149 in plate 148 are preferably formed of a diameter slightly greater than that of the slide plate orifice in order to 130 permit metal drainage from the passage upon throttling the valve to a fully closed condition.

The top plate assembly 18 of the present organization is shown in Figures 1, 2 and 5. The assembly 18 comprises a rectangular refractory plate 160 set by mortar in a metallic casing 162 of generally L-shaped cross section that extends aboutthe peripheral sides of the plate. The upper surface 164 of the plate 160 extends above the upper edge of the casing and is provided with a polished finish to provide a smooth surface-to-surface contact with the lower surface of mounting plate 23 and the vessel refractory lining 14 when the assembly is in its operative position in the valve organization. Plate 160 is provided with a centrally disposed stepped through opening 166 in order to receive a permeable refractory insert 168 having an axial opening defining the molten metal flow passage 112 through the plate. The insert 168 has an exterior surface 172 that is stepped in a fashion complimentary to that of the plate opening 166 with the outermost steps being adapted for cemented engagement with the mating steps of the opening but with the intermediate step of a significantly smaller diameter than that of the intermediate step of the opening. In this way there is defined an annular passage 174 about the circumference of the insert 168 for the supply of inert gas through the insert into the metal flow passage 112. The refractory plate is provided with an oblique channel 176 that opens at the top of the plate at 178 and being positioned to communicate with the opening 54 in the lower surface of the mounting plate 23 when the valve is assembled. There is thus provided a convenient means for supplying inert gas into the metal flow passage 112 during periods when the valve is closed thereby to stir the metal in flow passage and thus prevent its freezing. By forming the annulus in this fashion, so-formed refractory top plates can be fabricated by conventional refractory forming methods without the need for expensive machining with collapsible or multi-part machine tooling.

The slide plate assemblies utilized in the valve organization may be blank or imperforate as the type shown at 17' in Figure 1 or may contain a through opening 180 as the type shown at 17 in Figures 2,6 and 7. Blank plates 17' are employed, as shown in Figure 1, to prevent metal flow through the valve while orificed plates 17 are employed when it is desired to controllably pass molten metal through the valve as hereinafter described. Both slide plate assemblies 17 and 17' are fabricated in an identical manner comprising a generally rectangular refractory plate 182 which is slightly shorter in the feed direction indicated as F in Figures6 and 7 than in the throttling direction indicated as T. The plate 182 is cemented within a metal casing 184 that encloses the peripheral sides of the plate. The casing 184 is provided with a shoulder 186 intermediate its upper and lower edges for seating engagement on the throttling rails 84 and 84' and for sliding engagement upon the slide rails 96 in the loading section 58 of the valve and the shoulders 138 in the discharge section 62 thereof. The refractory plate 182 is formed at 188 with a mating shoulder conforming to that in the casing.

4 GB 2 099 966 A 4 The lower portion of the casing, indicated as 190, is formed with an enlarged radius curvature provid ing a guide cam surface to enable the respective slide plate assemblies when being moved by pusher 64 into the operating section 60 of the valve to be guidingly urged up and over the upper edge of the pour tube holder assembly without causing damage to either member.

The lower portion of the plate 182 adjacent the enlarged radius portion 190 of the casing is tapered as shown thus to provide an enlarged receptacle 192 for mortar between the plate and the metal casing.

The enlarged mortar bed in this region of the assembly operates to cushion the plate during movement of the plate across the tube holder 80 assembly 19 and when the plate is manipulated by the movable rails 84,84' during periods of throttling.

Slide plate assembly 17 differs from assembly 17' in that the latter is imperforate while the former contains the molten metal flow opening 180. The position of the opening 180 in the refractory plate is critically located along the longitudinal centerline of the plate but offsetfrom the center point of the plate toward the left in Figure 2 by an amount equal to one-half the length of stroke of the throttling pins 88 thereby permitting the opening 180 to be vertically aligned with the top plate opening 112 for full flow of metal through the pour passage with the plate fully stroked to the right as viewed in Figure 2 with the rail 84'in abutment with the wall 194of the cavity 115.

With the plate 17 being fully stroked to the left and the rail 84 abutting wall 196 the opening 180 is moved completely out of registry with the opening 112 thereby effecting termination of molten metal flow through the valve. By operation of the throttling motors 76 the position of the opening 180 in the plate 17 can be adjusted to any desired location with respectto the top plate opening 112 intermediate these full stroke positions thereby to alterthe effective size of the molten metal flow passage through the valve for regulating molten metal flow therethrough.

A typical commercial embodiment of the slide plate assembly 17 is approximately 10.9 inches along in the feed direction F and 12.9 inches long in the throttling direction T with the center of the opening 180 having a three inch diameter being offset from the plate center point approximately 1.75 inches thereby providing about one-half inch of refractory material between the holes 112 and 180 115 with the plate 17 in the shutoff position.

The operation of the hereindescribed valve organi zation 10 is as.follows:

The valveframe 22 is attached to the mounting plate 23 atthe bottom of the teeming vessel 16 as shown in Figure 1 with the top plate 18, a blank slide plate 17' and a pour tube assembly 19 preassembled in the operating section 60 of the valve frame. The flow passage 112 through the top plate 18 is thus vertically aligned with the pour passage 12 through the vessel lining 14. When molten metal is deposited in the vessel its flow through the valve is prevented due to the obstruction in the flow passage presented by the flow-impervious blank slide plate 17'. During 65 such metal holding periods an inert gas, such as argon or nitrogen, is admitted to the pour passage 112 of the top plate through passages 52 in the mounting plate 23 and 176 in the top plate into the annulus 174 about insert 168 from whence it perme- ates the porous wall of the insert to enter the passage 112. Entry of inert gas in this fashion serves to stir the molten metal in the obstructed flow passage and thereby prevents its freezing therein. Also, cooling air is admitted to the valve through inlet 46 in the mounting plate 23 from whence it flows seriatim through annular passage 36 about the lower region of the vessel lining 14 to cool the refractory material in this region and thence through passages 40,42 to discharge from ports 44 to cool the springs 130.

With the throttling mechanism disposed to place the rails 84 and 84' in the position shown in Figure 2 with rail 84 in abutment with cavity wall 196, an orificed slide plate 17 is inserted manually into the valve loading section 58. The slide plate 17 is inserted through the guideway 92 with the plate shoulders 186 in sliding engagement upon the slide rails 96. The slide plate 17 is moved until its leading edge surface abuts the rail 84, being retained thereagainst by the magnets 142, thus placing the slide plate 17 in its "ready" position adjacent the pusher 74 of the feed motor 68. Thereafter, the feed motor 68 is actuated to cause the pusher 74 to move the slide plate 17 from its---ready-position into the operating section 60 of the valve frame 22 between the top plate 18 and pour tube assembly 19 by displacing the blank plate 17 which slides along the shoulders 138 to the discharge section 162 from whence it exits the frame. An effective surface-to- surface seal between the respective plates is provided by the spring- biased levers 120 which urge the tube holder plate 148 upwardly against the slide plate 17 and that, in turn, upwardly againstthe top plate 18. Due to the presence of the enlarged radius 190 on the casing 184 of the slide plate 17 the moving plate is guided across the facing edge of the spring biased pour tube holder plate 148 without damaging that plate. The feed motor 68 is then actuated in the reverse direction to retract the pusher 74 to the position shown in Figure 1 whereupon, for safety reasons, a blank slide plate 17', as shown in Figure 3, is inserted into its "ready" position in the valve frame 22 in the same manner as described above in connection with the insertion of the slide plate 17.

When it is desired to initiate molten metal flow through the valve the flow of inert gas to the passage 112 is terminated and the throttling motors 76, which operate in unison, are actuated to move the rails 84, 84' and the retained slide plate 17 laterally of the cavity 115. Normally, the motors 76 will be actuated to move the rails 84, 84'to place rail 84' into abutment with wall 194 of cavity 115 thereby placing the orifice 180 of slide plate 17 in axial alignment with the opening 112 in the top plate 18. This defines the -full-open- position of the valve. Alternatively, however, it will be appreciated that, where molten metal flow is desired at a rate less than full flow, the throttling motors can be controlled to locate the slide plate 17 at any intermediate position betweeen "full GB 2 099 966 A 5 open" and "full close" to produce the desired intermediate flow rate. Furthermore, during the course of teeming the position of the slide plate can be altered, either to increase or decrease the rate of molten metal flow through the valve as desired by controlling the operation of the throttling motors 76 which impart throttling movementto the slide plate 17 and its orifice 180 with respect to the top plate pour opening 112.

0 The invention permits ready repIcement of both the slide plate 17 and the pour tube assembly 19, either singly or jointly. When it is desired to replace a spent slide plate 17 the stop pin 200 is inserted through holes 198 in the valve frame 23 to prevent movement of the pour tube assembly. The blank plate 17' is withdrawn from the "ready" position adjacent the pusher 74 and a replacement slide plate 17 inserted in its stead. The feed motor 70 is then actuated to move the replacement plate into the operating section 60 of the valve while discharging the spent plate through the discharge opening 62.

This procedure can be accomplished with the throttling rails 84, 84' disposed in any lateral position across the operating section 60 since the replace- ment plate 17 is retained on the rail 84 by means of the magnets 142. Thus, when intalled in the operat ing section 60, the replacement plate 17 will assume the same throttling position of the spent plate it replaced.

When it is desired to replace a pour tube assembly 95 19, the throttling rails 84, 84' are operated by the throttling motors 76 to move the slide plate 17 to the fully closed position shown in Figure 2 and the safety blank 17'withdrawn from the valve frame. The stop pin 200 is next removed from holes 198 and inerted in holes 196,196'to prevent movement of the operative slide plate 17. The replacement pour tube assembly 19 is then manually inserted through guideway 94 of the loading section 58 of the valve frame 23 to a position adjacent the pusher 74 whereupon the feed motor 70 is actuated to move the replacement pour tube assembly 19 into its operative position beneath the slide plate 17 in the section 60 while expelling the spent pour tube assembly through the guideway 136 of the discharge section 62.

When, alternatively, it is desired to change both a slide plate 17 and a pour tube assembly 19, the throttling motors 76 are actuated to move rails 84, 84' and the operative slide plate 17 to the fully closed position and the stop pin 200 is withdrawn from the valve frame. The replacement slide plate 17 and pour tube assembly 19 are inserted through guideways 92 and 94 respectively in the loading section 58 to their "ready" positions adjacent the pusher 74. Upon actuation of the feed motor 68, thereplacement slide plate and pour tube assembly are simultaneously moved into position into the operating section 60 while expelling their spent counterparts through guideways 134 and 136 of the discharge section 62.

An important characteristic of the herindescribed valve organization is the ability to rapidly terminate molten metal flow through the valve and independently of its throttling function. This characteristic is achieved by virtue of the fact that the operation of the feed motor 68 which effects plate replacement in the valve is totally independent from that of the throttling motors 76 and that slide plate 17 can be changed regardless of the throttling position of the operative slide plate located in valve section 60. Thus, during the course of normal valve operation a blank slide plate 17' is preferably retained in the 11 ready" position adjacent pusher 74. This plate, like all plates in the "ready" position, is secured to the rail 84 by the magnets 142 and thus is caused to move laterally back and forth with the operative slide plate 17 thereby insuring thatthe former is always longitudinally aligned with the latter. If for any reason it becomes necessary to rapidly terminate the flow of molten metal, as for example, due to malfunction of the casting process, the feed motor 68 need only be actuated to replace the operative orificed slide gate 17 with the blank gate 17'. The advantage of this feature can be appreciated when it is considered that a plate change can be effected by the feed motor in less than.2 second as contrasted with a period of approximately 2 seconds duration that is required to move the operative slide plate from its fully open position to its fully closed position by the throttling motors 76.

The sliding gate valve described above is also described and claimed in our copending applications Nos. 7932972 and 8201454 (Serial Nos. 2031567 and

Claims (20)

1. A ref - ractory plate for use in a valve for controlling the flow of liquid metal from a teeming vessel, comprising a refractory body having a through opening which has axially spaced steps of progressively greater diameter from one end of said opening to the other, and receives a porous plug which has an exterior surface formed of axially spaced steps of progressively reduced diameter from one end of said plug to the other, the endmost steps on said plug being cemented to the corresponding steps in the axial opening in said body, and the step on said plug intermediate said endmost steps having a diameter less than that of the corresponding step in the axial opening so as to define an annular passage.

2. A refractory plate according to claim 1, wherein the refractory body includes a passageway for supplying gas to the channel to permeate through the porous plug.

3. A refractory plate according to claim 2, where in the passageway is an oblique channel opening at a main surface of the refractory body.

4. A refractory plate according to claim 1, 2 or3, wherein a metal casing is cemented about the periphery of the refractory body.

5. A refractory plate according to claim 4, where in the metal casing is L-shaped in cross-section and the refractory body protrudes beyond the upper edge of the casing.

6. A refractory plate according to anyone of claims 1 to 5, wherein the porous plug has a central aperture extending therethrough.

7. A valve for controlling the flow of liquid metal 6 GB 2 099 966 A 6 from the pour opening of a teeming vessel, compris ing a refractory top plate according to claim 6, a frame for connection to said vessel and having a hollow interior, the top plate being fixedly mounted in said frame for the aperture to communicate with 70 the vessel pour opening, opposed gate supporting rails mounted in said frame for slidably supporting refractory gates for sequential movement through said frame along a path of travel having gate loading, operating and discharge sections, at least one refractory gate slidably mounted on said rails, said gate comprising a generally rectangular refrac tory body having a lontitudinal axis aligned with said rails and a lateral axis transverse thereto, and an opening through said body which defines a metal flow orifice for registry with said top plate aperture, first moving means attached to said frame and operative to move refractory gates sequentially along said rails, and second moving means operably independent of said first moving means and opera tively connected to said rails to move said gate along a second path of travel transversely of said frame to vary the degree of registry of the gate orifice with said top plate aperture.

8. A valve as claimed in claim 7, wherein said gate includes a metal casing encircling the sides of said refactory body, and shoulders formed in said casing about all sides of said body and defining surfaces for guided movement of said gate in a direction parallel to both the longitudinal and lateral axes thereof.

9. A valve as claimed in claim 8, in which said casing includes a portion forming a convexly arcuate cam surface subjacent said shoulders at least along the lateral sides of said body.

10. Avalve as claimed in claim 9, in which the arcuate cam surface of said casing is spaced from said refractory body, and a cushion of mortar fills the space therebetween.

11. Avalve as claimed in anyone of claims7to 10, in which the frame has a lateral opening communicating with the gate loading section for lateral insertion of the gates, the rail adjacent to said lateral opening being interrupted by said opening and the rail opposite to said lateral opening being substantially coextensive with all three of said frame sections and including means for retaining a gate thereon in the loading section of said frame.

12. Avalve as claimed in claim 11, in which the retaining means comprises at least one magnet.

13. Avalve as claimed in anyone of claims 7to 12, including pour tube supporting rails disposed in said frame subjacentto and substantially coextensive with said gate supporting rails, and a pour tube assembly having a tube support plate engageable with the rails for sliding movement therealong.

14. A valve as claimed in claim 13 in which said first moving means includes means operative to move said pour tube assembly along its rails.

15. A valve as claimed in claim 14, including means for selectively obstructing movement of the gates and the pour tube assembly to enable said first gate moving means to move said gates and pour tube assemblies singly or jointly.

16. A valve as claimed in claim 15 in which said obstructing means comprises a stop pin selectively positionable either in a position traversing the path of travel of the gates or in a position traversing the path of travel of the pourtube assembly.

17. Avalve as claimed in anyone of claims 13to 16, in which the pourtube rails each include a series of levers pivotally attached to said frame and having one end engageable with said pour tube support plate, and springs in said frame providing an upward bias to said one end of each of said levers.

18. A valve as claimed in claim 17, including a valve mounting plate for interposition between said frame and said vessel for effecting a connection therebetween, the mounting plate having means for supplying cooling fluid to ports in said frame in overlying relation to said springs.

19. A valve as claimed in claim 18 said top plate including a gas supply channel communicating with the annular passage and opening on the top surface of the plate in alignment with an opening in the mounting plate connected to an inert gas source for supplying inert gas to said annular passage.

20. A refractory plate for use in a valve for controlling the flow of liquid metal from a teeming vessel, constructed substantially as hereinbefore described with reference to and as illustrated in Figure 5 of the accompanying drawings.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1982. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.

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