Patent Application
20070286253
Referring now the drawings wherein the showings are for the purposes of showing one or more exemplary embodiments only and not for limiting the scope of the appended claims,
The frame 16, also referred to herein as the furnace body, can include a frame plate 18, which can be a heavy structural steel plate, upon which a bottom portion 12b of the crucible 12 can rest and be supported. The frame 16 can further include an annular flange portion 20 connected to the frame plate 18 by a frame bottom portion 22. Alternatively, the bottom portion 22 can be considered to include the frame plate 18 and/or the flange portion 20. A tilting support 24 defining a recess 26 is disposed within a sleeve 28 of the frame bottom portion 22 and immediately below the frame plate 18. A support 30 can also be disposed within the sleeve 28 for snuggly holding the tilting support 24 in position. The frame 16, and specifically the frame bottom portion 22, holds a heat insulating member 32 annularly about the crucible base portion 12b. More particularly, the heat insulating member 32 resides between the sleeve 28 and wall 34 of the frame bottom portion 22. In one embodiment, the heat insulating member 32 can be pre-cast prior to installation on the frame 16.
As shown, a plurality of vertical frame members 40, also referred to herein as support columns or supports, extends upward from the frame flange portion 20 to a support plate 42, which can be a heavy structural steel plate, upon which a top flange portion 12c of the crucible rests and/or is supported. A skirt 44 can depend downwardly from a peripheral edge 42a of the support plate 42 and radially outside the supports 40 to limit radially movement of the plate 42 with respect to the supports 40. As will be described in more detail below, a plurality of clamping assemblies 46 and intermediate yoke assemblies 48 can be mounted to and supported by the supports 40, which themselves can be considered as included by the frame 16.
The crucible 12, which can alternately be referred to as a refractory, is radially surrounded by the induction coil 14, which is comprised of a plurality of windings. More particularly, an active current-receiving coil or coil portion 14a is helically wound to radially surround a cylindrical wall portion 12d of the crucible 12 and is axially flanked by cooling coils or coil portions 14b,14c which radially surround the crucible 12 and are usually not provided with current. The induction coil 14 can be radially separated or spaced from the crucible by layer 52, such as a layer of mica. Intermediate yokes 56 of the intermediate yoke assemblies 48 can similarly be radially separated or spaced from the induction coil 14 by a layer 58, such as a layer of grout material. As illustrated, grout material 60, which can be integrally provided with the layer 58, can also be used to axially insulate between the coil portions 14a,14b,14c and between the individual windings of each coil portion 14a,14b,14c.
As shown in the illustrated embodiment, insulating rings 62,64 can be provided at respective ends of the induction coil 14. The lower insulating ring 62 separates the induction coil 14 from a lower annular support 66, which is received within a groove 68 defined in the insulating member 32, that can be a heavy structural ring that resists any forces or movements imported from the induction coil assembly 14. Wedged between the lower support 66, the insulating member 32, the layer 52 (separating the crucible sleeve portion 12d from the induction coil 14), and the crucible 12 is an insulating member 70, which can be formed of a pre-cast grouting material into the illustrated wedge shape. An upper insulating member 72 is disposed annularly about the crucible 12 adjacent the support plate 42. The upper insulating member 72 is held in the illustrated position by frame members 74,76 of the frame 16. As shown, the upper insulating member 72 and the frame members 74,76 can be appropriately shaped (at 72a, 74a and 76a) to permit passage by the crucible spout 12a. A suitable angle member or members 78 (
With additional reference to
With still additional reference to
With further reference to
Additional threaded members 108 (such as the nuts illustrated), can be threadedly secured on an opposite or second threaded end 92b of the rod. Like nuts 96, nuts 108 can be provided in pairs so as to be disposed in locking relation. To provide the urging force on the lever lower leg 90a, a compression spring 110 is annularly disposed about the rod 92 between the nuts 108 and the outer wall 40b. In one embodiment, the compression spring 110 can exert a spring force of about 750 pounds, which is applied to the lower lever leg 90a. Optionally, washers 112 can be provided about the rod 92 so as to axially flank the spring 110. The compression spring 110 acts against the fixedly provided column wall 40b and the nuts 108 so as to urge the rod 92 and thereby the lever lower leg 90a in a radially outward direction relative to the axis 80 (i.e., to the left in
With reference now to
Mounting arm support structures 140, which include base wall 140a and spaced apart angularly disposed walls 140b,40c, are secured to respective side walls 40c,40d of each support column 40. In the illustrated embodiment, each support structure 140 is secured to a respective side wall 40c,40d by a suitable fastener, such as bolt 142, and a mounting plate 144 is provided between the base wall 140a and the respective side wall 40c or 40d. Each intermediate yoke assembly 48, which can include the mounting arm support structure 140, includes a corresponding intermediate yoke 56 secured to an adjacent mounting arm structure 140 so as to urge the yoke 56 radially inwardly into the induction coil 14 and toward the crucible 12.
More particularly, each yoke assembly 48 includes a threaded rod or bolt 146 received through aligned apertures 148,150 defined in the walls 140b,140c of the yoke assembly's mounting structure 140. A distal bolt end 146a (opposite bolt head 146b) is received in a support structure or shoe 152, which can be fixedly secured, such as by welding, to intermediate yoke base plate 154. Angle members 156,158 can be fixedly secured, such as by welding, to the base plate 154 to as to capture the intermediate yoke 56 against the induction coil 14 (though the yoke 56 is spaced from the induction coil 14 by the layer 58). With brief reference to
In the illustrated embodiment, a clamping assembly 46 is provided with each of the six (6) support columns such that there are a total of six (6) clamping assemblies 46. In one embodiment, each clamping assembly 46 can exert about 1,300 pounds of downward directed force to the induction coil 14 and where six (6) clamping assemblies 46 are used a total of 7,800 pounds of downward force can be applied to the induction coil 14, having the effect of firmly retaining the induction coil 14 and increasing the life of the induction coil 14, crucible 12 and other components of the furnace 10 (e.g., the liner 12f and layers 58,60). Of course, the number of clamping assemblies 46 can vary, as can the number of support columns 40 (and a clamping assembly need not be provided on every provided support column). For example, the induction furnace 10 can include eight (8) support columns 40 and six (6) or eight (8) clamping assemblies 46 could be distributed about the eight (8) support columns 40. In any case, unlike conventional methods of applying a clamping load to a lower end of an induction coil, the clamping assemblies 46 of the illustrated embodiment apply a clamping load on an upper end of the induction coil 14, which eliminates the disadvantage of prior art clamping assemblies tending to lift the crucible up and out of the furnace in which it was employed.
The spring-loaded rod 92 of each clamping assembly 46 applies an input load to the clamping assembly's lower lever leg 90a which, due to the pivotal mounting of the lever 90, causes the upper lever leg 90b to induce a leveraged constant positive downward loading or force onto the top or upper end of the induction coil 14. Thus, a much larger force can be exerted to clamp the induction coil 14 which advantageously maintains the coil in compression at all times (i.e., the compression force on the induction coil 14 does not go negative or to tension, or even to zero). This has been found to greatly reduce fatigue in the components of the furnace 10.
As illustrated, a lower end of the induction coil 14 is captured (i.e., axially fixed) and mechanically supported by the plate 18, which has the effect of eliminating or at least substantially reducing the likelihood of crucible deformation. Stated alternatively, the induction coil 14 is pressed against the bottom of the furnace, i.e., the lower frame portion 22, which is a welded integral part of the frame 16, to retain the coil 14 in a fixed position with respect to the crucible lining 12f, the frame 16 and the upper furnace structure. This removes the need for constant torque adjustments to be made with respect to the plurality of clamp assemblies provided for applying a constant force on the induction coil 14. Additionally, by maintaining a constant positive force on the induction coil 14, the life of the mechanical components of the furnace 10 are significantly extended. Still further advantages of the presently disclosed clamping arrangement include allowing the furnace 10 to run at higher power levels (for example 10-11 MW) with reduced likelihood of mechanical failure at such higher power levels and quieter operation of the furnace 10.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
