Patent Application
20130048897
The present invention generally relates to exchangeable valve plates for use in slide gate valves for controlling a flow of molten metal, and more specifically relates to an exchangeable valve plate assembly that distributes the sealing force across a sealing surface and minimizes the change in force distribution as the thickness of the plate stack changes.
Slide gate valves are used to control the flow of molten metal in steelmaking and other metallurgical processes. For some slide gate valves where plates are exchanged sequentially during pouring, an upstream stationary plate is used in conjunction with exchangeable downstream plates. Such valves often comprise a main frame, an upstream stationary plate, and a movable exchangeable plate. The upstream stationary plate includes an orifice that is in registry with a metallurgical vessel for conducting the flow of molten metal. The movable exchangeable plate includes a flow conducting orifice that is downstream of the upstream stationary plate and which, when aligned with the orifice of the upstream stationary plate, may provide a pouring orifice. In some processes, the slide gate valve also incorporates a stationary downstream exchangeable plate that has a flow conducting orifice that is substantially aligned with an orifice of the upstream stationary plate, and which may also be part of the pouring orifice. The rate of flow of molten metal during pouring may be dependent upon the position of a stopper upstream of the upstream stationary plate, the orifice size of the moveable exchangeable plate, and/or the misalignment of the orifice of the movable exchangeable plate with the orifice of the upstream stationary plate.
Plates of such sliding gate valves are formed from heat and erosion resistant refractory materials, such as aluminum oxide, magnesium oxide, alumina carbon, magnesia carbon, and zirconium oxide, among others. Despite the heat and erosion resistance properties of such materials, the orifice(s) of the plates of such sliding gates eventually erode, corrode, or become plugged to a point that the plate(s) is/are no longer viable. For example, in steelmaking, each plate can be subjected to temperatures of 1600° C. at the area immediately surrounding the plate's flow-conducting orifice, and exposed to corrosive chemicals such as manganese, calcium, silicon, oxygen and their compounds. The resulting degradation of the flow controlling orifice(s) necessitates the termination of the pouring operation or the exchange of the plate(s) to introduce a new orifice or pouring tube into the system.
For prior slide gate valves in which all dimensions are nominal, the rocker tip of the rocker arm may be positioned to be in contact with a load surface of a plate in the plate stack or other load plate in the valve. Yet dimensional changes can occur during operation as the temperature of the plates increase, or when replacement plates are added to the valve, such as by replacing an existing movable plate. Moreover, even if the plates are manufactured to the exact same size, they often are not the same size during the plate exchange, as the existing plate typically has a higher temperature than a pre-heated replacement plate, and thus existing plate may be dimensionally longer, wider, and thicker or thinner than the incoming plate. Yet, if the dimensional tolerance of the stack up of plates is thicker or thinner than nominal, the location that the rocker arm contacts the plate stack changes, as the line of contact between the rocker arm and the stack of plates is displaced toward or away from the center line of the pouring orifice. Such changes can significantly, and adversely, alter the force distribution at the plate sealing surface. Moreover, such an alteration in the sealing force can allow metal leakage or aspiration of the surrounding atmosphere. And attempts to overcome these challenges through the use of using a swivel tip on the rocker arm that contacts the plate stack increases the cost and maintenance requirements of the system.
An aspect of the invention is an exchangeable plate for use with a sliding gate valve, the sliding gate vale being used to control the flow of, or protect the stream of molten metal. The exchangeable plate assembly includes an exchangeable plate. The exchangeable plate includes an upper portion that has at least one concave cylindrical load surface.
Another aspect of the invention is a cylindrical bar tip rocker arm for a sliding gate valve that controls the flow of, or protects the stream of, molten metal. The cylindrical bar tip rocker arm has a distal end, a proximate end, and a bar slot. The proximate end has a substantially cylindrical bar tip. According to certain embodiments, the cylindrical slot includes a spherical surface that is configured for engagement with a spherical washer.
A further aspect of the present invention is an assembly for use with sliding gate valves that control the flow of molten metal. The assembly includes a rotatable bar tip rocker arm that has a distal end and a proximate end. The proximate end of the bar tip rocker arm has a substantially cylindrical bar tip. The assembly also includes an exchangeable plate that has a concave cylindrical load surface configured for engagement with the substantially cylindrical bar tip.
The foregoing summary, as well as the following detailed description of certain embodiments, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentalities shown in the attached drawings.
The following reference characters are used in the specification and figures:
The present invention will now be described more fully with reference to the accompanying drawings, in which several embodiments are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth here. Rather, these certain embodiments are examples of the invention, which has the full scope indicated by the language of the claims. Like numbers refer to like elements throughout.
The vessel shell 1 may be configured to contain molten metal. Further, the vessel shell 1 may include a vessel lining 2 and a well nozzle 3, the well nozzle 3 containing a well nozzle flow channel 54. The well nozzle flow channel 54 is configured to be in open communication with other pouring orifices when a moving plate orifice 56 is in an open position. More specifically, when the moving plate 16 is in an open position, pouring orifices, such as, for example, an upstream stationary plate orifice 55, a moving plate orifice 56, a downstream stationary plate orifice 57, and a pouring tube bore 58, are in open communication to provide a flow path that allows molten metal to flow from the vessel shell 1. A pouring orifice centerline 10 defines the centerline of these pouring orifices 54, 55, 56, 57.
The moving plate 16 is movable between an open position and a closed position so as to at least assist in controlling the flow of molten metal from the vessel shell 1. Moreover, the moving plate 16 is driven between the opened and closed position by a moving plate drive frame 14. More specifically, when the moving plate 16 is in the open position, molten metal is free to flow through the stationary pouring orifices 54, 55, 56, 57 at the full capacity of the system. When the moving plate 16 is in the partially closed position, as shown in
The moving plate 16 is mechanically held firmly between the upstream stationary plate 15 and the downstream stationary plate 17. The upstream stationary plate 15 is prevented from moving upstream by its contact with the mounting plate 5. Additionally, the upstream stationary plate 15 is prevented from moving with the moving plate 16 as the moving plate 16 moves between open and closed positions, as the upstream stationary plate 15 is stroked open and closed by a separate mechanical structure (not illustrated). Further, the downstream stationary plate 17 is prevented from moving with moving plate 16 as the downstream stationary plate 17 is stroked open and closed by a seal plate 13.
The nominal dimension three plate reciprocating valve shown in
The pivot slot 64 is configured to receive a stud or rocker bolt 11, the rocker bolt 11 being mechanically secured to the three plate reciprocating valve 67, such as, for example, by a bolted, pinned, or welded connection, among others, to the main frame 6. As shown in
A spherical washer 12 is seated in the pivot slot 64 and/or on the rocker bolt 11, and is configured to assist with the ability of the bar tip rocker arm 26 to be rotated about the intersection of the parallel rotational centerline 29 (which is generally parallel to the pouring orifice centerline 10) and the perpendicular rotational centerline 30 (which is generally perpendicular to the pouring orifice centerline 10). As shown in
Besides being configured to receive the insertion of the rocker bolt 11, according to certain embodiments, the pivot slot 64 may also be sized to allow for some lateral displacement, or float, of the bar tip rocker arm 26 so that the bar tip rocker arm 26 may move toward and away from the pouring orifice centerline 10. For example, for a bolt mounted bar tip rocker arm 26, providing the pivot slot 64 with sufficient clearance for the rocker bolt 11, such as, for example, by making the pivot slot 70 1.0 to 3.0 mm larger than the rocker bolt 11 may allow the bar tip rocker arm 26 to move towards and away from the pouring orifice centerline 10. Such float may assist in maintaining proper alignment between the engagement of the cylindrical bar tip 27 and the concave cylindrical load surface 32 as the thickness of the stack of plates 15, 16, 17, and/or 28 changes.
Plates, such as, for example, a downstream stationary plate 17 and/or a moveable plate 16, are loaded by the rocker arm 26. Moreover, force is applied to the distal end 69 of the bar tip rocker arm 26 by a load element 7, which may result in the pivoting or rotational movement of the bar tip rocker arm 26 about the rocker bolt 11 to a loaded position so that the cylindrical bar tip 27 engages and/or transmits a force against the exchangeable plate 28. The cylindrical bar tip 27 is configured to complement the concave cylindrical load surface 32 of the exchangeable plate 28. According to certain embodiments, the cylindrical bar tip 27 and mating concave cylindrical load surface 32 may be sized to maximize the contact surface between the cylindrical bar tip 27 and concave cylindrical load surface 32, while still allowing operability and structural integrity of the rocker arm 26 and/or exchangeable plate 28, so as to lower unit pressure and avoid friction welding. For example, according to an embodiment, the concave cylindrical load surface 32 may have a concave cylindrical radius of about 4 mm to about 15 mm, while the cylindrical bar tip 27 may have a diameter of about 8.0 mm to about 30.0 mm
When the bar tip rocker arm 26 is moved to the loaded position, the cylindrical bar tip 27 may transmit a force against the exchangeable plate 28 that is sufficient to hold the exchangeable plate 28 in a metal tight, sealable relationship with the downstream surface 9 of the downstream stationary plate 17. The contact between the concave cylindrical load surface 32 of the exchangeable plate 28 and a cylindrical portion of the cylindrical bar tip 27 of the rocker arm 26 provides an array of force vectors 31 into the exchangeable plate 28 emanating from the center line of the cylindrical bar tip 27. This array of force vectors 31 spreads the sealing load across the sealing surface 33, 35 (shown in
The bar tip rocker arm 26 is configured to maintain intimate contact between a concave cylindrical load surface(s) 32 and a cylindrical bar tip(s) 27 such that the force distribution on the exchangeable plate 28 surface generally will not change, or not change significantly, as the thickness and/or width of the stack of plates 15, 16, 17, and/or 28 individually or collectively changes due to, for example, manufacturing specifications, tolerances, or production, or thermal expansion. As the thickness of the stack of plate 15, 16, 17, and/or 28, or plate stack, changes, the bar tip rocker arm 26 may rotate about its pivot point to accommodate those changes. For example, during operation of a three plate reciprocating valve 67, the exchangeable plates may become worn, damaged, or otherwise compromised. Therefore, replacement plates are typically placed in position to replace existing plates without interruption of the operation of the system. Moreover, when a new plate is to be inserted into the operating position, a drive mechanism, such as a motorized or electric screw, for example, may push or pull the replacement plate into the operating position, and thereby push the existing plate out of operation. However, due to a number of different factors, such as a difference in the temperatures and/or manufactured sizes of the new and replaced plate 28, among others, the thickness of the plate stack may change, thereby changing the position of the rocker arm 26 and/or the position the rocker arm 26 contacts the exchangeable plate 28. The inability of a system to accommodate for such changes may adversely impact the load vectors from the force exerted by the rocker arm 26 on the exchangeable plate 28. The present invention however accommodates for such changes in plate stack thickness. The system may be designed to place the perpendicular rotational center line 30 tangent to the upstream quadrant of the cylindrical bar tip 27. Such a configuration may minimize the change in dimension between the centerline of the cylindrical bar tip 27 and the pouring orifice centerline 10 as the thickness of the stack of plates 15, 16, 17, and/or 28 changes. Additionally, such changes in plate thickness may also be accommodated by the ability of the bar tip rocker arm 26 to float toward or away from the pouring orifice centerline 10, as previously discussed. Failure to account for such dimensional changes in the design of the bar tip rocker arm 26 typically will cause a change in force distribution at the plate sealing surface 33 that can be detrimental to the performance of the three plate reciprocating valve 67.
The rocker shaft 45 is sized for insertion into, and is tangent to the upstream quadrant of, the shaft hole 46. The shaft hole 46 may be oversized in relation to the size of the rocker shaft 45 so that the bar tip rocker arm 44 may move towards and away from the pouring orifice centerline 10 to accommodate the arc generated when the bar tip rocker arm 44 rotates. Such movement may allow the cylindrical bar tip 27 to be moved in a straight line parallel to the pouring orifice centerline 10 and maintain intimate contact with the concave cylindrical load surface 32 of the exchangeable plate 28.
In view of the foregoing, and for illustrative purposes, according to one example, a bolt or stud mounted rocker arm 26 having a rotational centerline 30 perpendicular to the pouring orifice centerline 10 tangent to the upstream quadrant of the cylindrical bar tip 27 may include a cylindrical bar tip 27 having a radius of 221.944 mm from the pivot point to the upstream quadrant of the cylindrical bar tip 27. With such a bar tip rocker arm 26, a 1.0 mm change in the thickness of the plate stack 15, 16, 17, and/or 28 may result in a change in the distance from the upstream quadrant of the cylindrical bar tip 27 to the pouring orifice centerline 10 of 0.00225 mm. Moving the upstream quadrant of the load 0.00225 mm away from the pouring orifice centerline 10 may result in a line contact between the cylindrical bar tip 27 and the concave cylindrical load surface 32, and a single force vector at 0.129° away from the pouring orifice centerline 10. Conversely moving the upstream quadrant of the cylindrical bar tip 27 0.00225 mm toward the pouring orifice centerline 10 may result in a line contact between the cylindrical bar tip 27 and the concave cylindrical load surface 32, and a single force vector at 0.129° toward the pouring orifice centerline 10. For a stud mounted rocker arm 26 with the rotational centerline 30 perpendicular to the pouring orifice centerline 10 mm upstream of the tangency with the upstream quadrant of the cylindrical bar tip 27, with a 222.17 mm radius from the centerline 30 of rotation to the upstream quadrant of the cylindrical bar tip 27, a 1.0 mm increase in the stack height of the plates may result in a change in the distance from the upstream quadrant of the cylindrical bar tip 27 to the pouring orifice centerline 10 of 0.04732 mm. This is 18.93 times the change that results from the previous example with optimum geometry.
According to another example, a shaft mounted bar tip rocker arm 44 may have a 10 mm diameter rocker shaft 45, a 12.0 mm diameter hole 46 in the bar tip rocker arm 44, and a rotational centerline 30 perpendicular to the pouring orifice centerline 10 tangent to the upstream quadrant of the cylindrical bar tip 27, with a radius of 221.944 mm from the pivot point to the upstream quadrant of the cylindrical bar tip 27. A 1.0 mm change in plate stack thickness will result in a change in the distance from the upstream quadrant of the cylindrical bar tip 27 to the pouring orifice centerline 10 of 0.00225 mm. Maintaining the centerline of the cylindrical bar tip 27 at a fixed distance from the pouring orifice centerline 10 and changing the plate stack thickness by 1.0 mm may cause the bar tip rocker arm 44 to move 0.0000033 mm upstream at the pivot due to climbing over the rocker shaft 45. Moving the upstream quadrant of the cylindrical bar tip 27 0.00225 mm away from the pouring orifice centerline 10 results in a line contact between the cylindrical bar tip 27 and the concave cylindrical load surface 32, and a single force vector of 0.129° away from the pouring orifice centerline 10. Conversely moving the upstream quadrant of the cylindrical bar tip 27 0.00225 mm toward from the pouring orifice centerline 10 results in a line contact between the cylindrical bar tip 27 and the concave cylindrical load surface 32, and a single force vector of 0.129° toward from the pouring orifice centerline 10. For a shaft mounted rocker arm 44 with the rotational centerline 30 perpendicular to the pouring orifice centerline 10 mm upstream of the tangency with the upstream quadrant of the cylindrical bar tip 27, a 10.0 mm diameter rocker shaft 45 and a 12.0 mm diameter hole 46 in the rocker arm 44, with a 222.755 mm radius from the centerline 30 of rotation to the upstream quadrant of the cylindrical bar tip 27, a 1 mm increase in the stack height of the plates will result in a change in the distance from the upstream quadrant of the load to the pouring orifice centerline 10 of 0.087789 mm. This is 35.11 times the change that results from the previous example with optimum geometry. Maintaining the centerline of the cylindrical bar tip 27 at a fixed distance from the pouring orifice centerline 10 and changing the plate stack thickness by 1.0 mm may cause the rocker arm 44 to move 0.005777 mm upstream at the pivot due to climbing over the rocker shaft 45. Moving the upstream quadrant of the cylindrical bar tip 27 0.087789 mm away from the pouring orifice centerline 10 results in a line contact between the cylindrical bar tip 27 and the concave cylindrical load surface 32, and a single force vector of 5.017° away from the pouring orifice centerline 10. Losing the intimate contact between the cylindrical bar tip 27 and the concave cylindrical load surface 32 of the plate results in the loss of the force vector array, and the formation of a single force vector that can vary from 37.5° toward the pouring orifice centerline 10 to 37.5° away from the pouring orifice centerline 10.
