WO1981000710A1

WO1981000710A1 - Electric melter needle and drive

Info

Publication number: WO1981000710A1
Application number: PCT/US1980/001287
Authority: WO
Inventors: C Fineo
Original assignee: Johns Manville Corp; Johns Manville
Current assignee: Johns Manville Corp; Johns Manville
Priority date: 1979-09-04
Filing date: 1980-09-04
Publication date: 1981-03-19
Anticipated expiration: 1982-03-04
Also published as: JPS56501243A; CA1168686A; EP0036013A4; EP0036013A1; AU6335080A

Abstract

A melter needle position control mechanism and motorized incremental drive for controlling the position of a needle relative to an orifice in a furnace. Conventional melter needle control mechanisms are cumbersome, inaccurate and do not facilitate servicing of the needle. The present mechanism has a support (36) for a fluid operated piston (49) which allows a boom or an 1-beam (76) to be rotatably mounted and to extend over the orifice (32) of a melter (10). A movable mount (144), providing a support for a needle (30), is vertically translatable by a vertical adjustment shaft (184) that is driven by a miter gear (156). The gear (156) is coupled to a rotatable command shaft (164) which is controllably rotated by a motorized incremental drive (26). A rotary actuator (58) rotates the I-beam (76) and the needle (30) to a retracted position after the I-beam (76) is sufficiently moved vertically whereby the needle (30) may be serviced. Radial, lateral and initial vertical adjustments are also possible with the present invention.

Description

ELECTRIC MELTER NEEDLE AND DRIVE

Technical Field This invention relates to electrical melting furnaces and more particularly to an apparatus for controlling the mass flow rate of molten material through the furnace. Background of the Invention Electrical open-top melting furnaces having primary electrodes that are shaped and mounted in such a manner that they enter the furnace through the furnace top are known in the art as evidenced by U.S. Patent Nos. 3,983,309 and 2,978,526. Generally, these furnaces utilize several electrodes spaced around an outlet member that also acts as an electrical conducting member operating with the electrodes to form a current flow pattern. These furnaces also utilize a melter needle, usually made of molybdenum, in order to control the mass flow or the pull rate of the molten material flowing from the furnace. Conventionally, the position of the melter needle tip relative to an orifice in the outlet member is controlled by hand or by utilizing a suitable motorized drive mechanism. However, these prior melter needle control mechanisms were cumbersome, inaccurate in that they could not provide a linear displacement of the melter needle in incremental amounts, e.g., of about .010 inches, and could not provide a means for rapidly retracting the melter needle from its operational position in the furnace during emergency or routine servicing of the melter needle.

Brief Summary of Invention Accordingly, it is an object of the present invention to provide a melter needle assembly, for controlling the position of the melter needle relative to the outlet orifice in an electric melting, furnace.

It is another object of the present invention to provide a melter needle mount and drive capable of producing an incremental and relatively small linear displacement of the melter needle with respect to the orifice in an electric melting furnace. A further object of the present invention is the provision of a melter needle assembly which allows quick and ready servicing of the melter needle.

Still another object of the present invention is the provision of an incremental drive for controlling the position of the melter needle relative to the outlet orifice of an electric melting furnace.

These and other objects are attained in the present invention by means of an apparatus for controlling the position of a flow obturator or needle relative to the outlet orifice of an electric melting furnace, comprising a support and an I-beam mounted at one end on and extending from the support to a proximate position above the orifice. An incremental motor drive is mounted on the I-beam at the proximity of the support and drives a command shaft either incrementally when the needle is in its operational position or very rapidly when the needle requires routine or emergency servicing. rotary to linear motion converter mounted on the other end of the I- beam causes a movable needle mount to vertically translate either toward or away from the outlet orifice. The needle, which is mounted on the movable mount, is provided with a radial and lateral adjustment, which ensures colinearity of the center lines of the needle and orifice, and a vertical adjustment that is capable of initially positioning a needle relative to the orifice after the needle has either been replaced or otherwise serviced.

When routine or emergency servicing of the needle is demanded, a motive fluid operates on a piston to cause the I-beam to vertically translate so that the needle may clear the uppermost surface of the furnace. A release mechanism allows the I-beam to be rotated by a rotary device to its retracted position.

The incremental needle drive of the present invention comprises a motor whose torque is reduced and transmitted via couplings to a shaft which effects an upward movement of the needle and to a shaft which effects a downward movement of the needle. An electromechanical clutch brake and an electromagnetic clutch coupling are mounted on both the up shaft and the down shaft to ensure that the angular rotation of the coirmand shaft is incremental. Brief Description of Drawings

FIG. 1 is a schematic view, in side elevation, of the melter needle assembly of the present invention

FIG. 2 is a schematic plan view illustrating the needle orientation in its operational and retracted positons.

FIG. 3 is an enlarged cross sectional view taken along the line 3-3 in FIG. 1.

FIG. 4 is an enlarged view of a portion of the embodiment shown in FIG. 1 and better showing the needle radial adjustment means. FIG. 5 is an isolated view of the mounting bracket shown in cross section in FIG. 3.

FIG. 6 is a plan view of the mounting bracket illustrated in FIG. 5.

FIG. 7 is a schematic side elevational view of the needle head subassembly.

FIG. 8 is a frontal view of the needle head subassembly.

FIG. 9 is a cross sectional view, with parts broken away, of the gear box shown in block form in FIG. 7.

FIG. 10 is an enlarged view of the cross section taken along the line 10-10 in FIG. 8.

FIG. 11 is a plan view of the motorized incremental needle drive. FIG. 12 is a side view of the motor drive illustrated in

FIG. 11. Detailed Description of the Preferred Embodiment

Referring now to the drawings wherein the same numerals refer to like elements, FIG. 1 shows the melter . needle assembly of the present invention installed beside a conventional electric melting furnace or melter 10. Typical of an electric melter furnace which may utilize the present invention is shown in U.S. Patent No. 3,983,309 issued September 28, 1976 to Faulkner et al and U.S. Patent No.

4,159,392 issued June 26, 1979 to Fineo et al.

The furnace 10, partially shown in FIG. 1, is comprised of a container for molten material 12 having a top crust level or melt line 14, a plurality of primary electrodes (not shown) and a central electrically conducting outlet member 16. The container for the molten material comprises an outer metal shell 18 which can be water cooled by any conventional means, particularly when melting materials at a temperature above 2000ºF. The metal shell 18 may be lined with a layer of suitable refractory material (not shown) compatible with the material being melted in the furnace 10. The electrically conducting outlet member 16 is supported in the proper position by a metallic cone 20 preferably made of a refractory metal like molybdenum, tungsten, or tantalum. This metallic cone is in turn supported by a water cooled metallic lower cone (not shown) usually made of a high heat conductive material such as copper. The melter 10 also comprises a number of rings, the upper surface of which is represented by line 21 in FIG. 1. The melter needle assembly is partially disposed outside of the melter 10 and partially disposed above the outlet member 16 and comprises a ram subassembly 22, a boom subassembly 24 mounted on the ram subassembly 22, a motorized incremental needle drive 26 mounted at one end of the boom subassembly 24, a needle head subassembly 28 mounted at the other end of the boom subassembly and vertically disposed above the outlet member 16, and a flow obturator or needle 30. The needle 30 cooperates with an orifice 32 formed in the outlet member 16 to control the mass flow rate or pull rate of the molten material flowing out of the melter 10 through the outlet member 16. The pull rate of the melter Ϊ0 is controlled by translating the needle point 34 within the orifice 32 whereby the effective flow passage defined between the needle point 34 and the orifice 32 is adjusted. Subtle differences in the positioning of the needle point 34 relative to the orifice 32 have a profound effect on the pull rate of the melter 10. Therefore, it is a goal of the present invention to provide an incremental translation of the needle point 34 relative to the orifice 32.

It is also a goal of the present invention to provide a means for raising the needle 30 above the upper surface 21 of the rings forming part of the melter 10 and rotating the needle out of the melter so that the needle 30, which may be made of a highly oxidizable material such as molybdenum, may be serviced. In routine as well as emergency situations, the present invention also provides a means for rapidly moving the needle 30 out of the melter 10 such that the molybdenum needle material is not rapidly oxidized in the oxidizing atmosphere present proximate the melt line 14. Such a means is provided, in part, by the ram subassembly 22.

Ram subassembly 22 is comprised of a weldment or ram base 36 which is mounted on the floor or melter platform 38 by means of a ram mounting plate 40 and vibration mounts 42 which are juxtaposed between a ram base plate 44 and the ram mounting plate 40. A stabilizing trunnion mount 46 is fixedly attached to the base plate 44 and suitably supports a cylinder 48 which slidingly supports a piston 49. The piston 49 provides a means for rapidly moving the boom subassembly 24 in a vertical direction away from the outlet member 16. A motive fluid capable of causing the piston within the cylinder 48 to rise, thereby causing the boom assembly 24 to also rise, is supplied to the piston by a source of fluid under pressure (not shown) via a conduit 47. The pressure may be regulated to control the ram force supplied by the motive fluid operating on the piston 49 so that in the event that the molten material freezes caused by, e.g., a malfunction of an electrode, the melter needle assembly will not be damaged. Attached to the upper portion of the piston 49 is a head plate 50 to which is attached by means of lock nuts 52 an alignment shaft 54 which is slidingly supported by an alignment shaft cylinder or bushing 56. The bushing 56 is fixed to the ram base 36 by means of a bracket (not shown) and a fastener 58. The bush.ing 56 allows the shaft 54 to stabilize the vertical movement of the boom subassembly 24 as it is translated by the piston 49 within the cylinder 48. Suitable sensors (not shown) are mounted on the ram base to detect the fully up and fully down position of the shaft 54.

Fastened on the upper surface of the head plate 50 is a rotary actuator 58, a pair of shock absorbers £0 (only one of which is shown in FIG. 1) and a pilot mounting bracket 62. The rotary actuator 58 cooperates by means of a shaft (not shown) with a boom top plate 64 mounted underneath the boom subassembly 24.

The rotary actuator 58 is capable of moving the boom subassembly 24 and consequently the needle head subassembly 28 and needle 30 from an operational position shown in solid lines in FIG. 2 to a retracted position shown in phantom in that same figure via a bearing plate 65 and a rotary air bearing 66. The shock absorbers 60 decelerate the rotational movement of the boom subassembly 24 as it rotates either from the operational position to the retracted position or from the retracted position to the operational position.

When in the operational position, a solenoid operated pilot 67, mounted on the bracket 62, is activated and a pilot plunger 68 translates upwardly in order to engage a bushing (not shown) fixed in the top plate 64 thereby locking the boom subassembly 24 in its operational position. Of course, when it is desired to rotate the boom subassembly 24 to its retracted position, the plunger 68 would be moved downwardly to a position where it no longer engages the bushing fixed in the top plate 64. Attached to the boom subassembly 24 is a bracket 70 which mounts conventional proximity switches (not shown) which detect the up and downward movement of the plunger 68.

As was noted, the boom subassembly 24 is mounted on the top plate 64 and comprises an elongated member or I-beam 76, an adjustable counterweight 78, a needle head subassembly-boom subassembly coupling means 80 and a needle radial adjustment means 82» The center of gravity of the melter needle assembly of the present invention is adjustably controlled utilizing the counterweight 78 which is affixed on the bottom flange of one end of the I-beam 76. The counterweight 78 is made adjustable by means of a threaded counterweight adjusting shaft 84 which is suitably rotatably supported by means of a shaft bracket 86 and a block 88. As the shaft 84 is rotated the position of the weight 78 may be varied in order to shift the center of gravity of the entire assembly. The coupling means 80 is disposed at the other end of the

I-beam 76 and is shown in FIG. 3 as comprising a sliding plate 92, attachment screws 94, guides 96, a mounting bracket 98, and clamp screws 100. The sliding plate 92 is affixed to the upper flange of the I-beam 76 by means of a suitable attachment means such as the attachment screws 94. The sliding plate 92 is capable of a sliding movement within the guides 96 which are disposed at opposite ends of the plate 92. The guides 96 are suitably fixed within the mounting bracket 98 by means of the clamp screws 100 that are passed through bores 102 formed in gussets 104 (see FIG. 5) and are locked in place by means of lock nuts 106. The gussets 104 are fixedly attached to a mounting bracket back plate 108 and an upper plate 110. Threadingly passing through the I-beam 76 and adjustably fixed at its ends between gussets 104 is a lateral adjustment screw 112. The lateral adjustment screw 112, which passes through holes 113 formed in each of the gussets 104, allows an adjustment in the lateral orientation of the mounting bracket 98 relative to the I-beam 76 so that the needle 30 may be properly laterally oriented within the outlet member 16. A suitable head 114 facilitates the rotation of the adjustment screw 112 and lock nuts 116 fix the adjustment screw in the desired position.

Affixed atop the upper flange of the I-beam 76 is a block 118 (see FIG. 4) which rotatably supports one end of a radial adjustment shaft 120. The radial adjustment shaft 120 is fixed at its one end by means of a pair of clamping collars 121. The other end of the radial adjustment shaft 120 is rotatably supported by a nut 122 which slidingly bears down on the upper surface of the slide plate 92. The nut 122 fits within a transverse portion 124 of a cross shaped slot 126 formed in the upper plate 110 of the mounting bracket 98 (see FIG. 6). A dust cover 128 is suitably attached to the upper plate 110 by means of a plurality of bolts 130 which fit in bores 132 in the plate 110.

As FIG. 4 shows, when the radial adjustment shaft 120 is rotated about its axis the distance between the block 118 and the sliding bearing nut 122 may be varied. Therefore, since the nut 122 travels within the tranverse portion 124, the mounting bracket 98 may be moved relative to the I-beam 76. This movement allows a radial adjustment on the orientation of the melter needle 30 relative to the orifice 32 so that the center line of the melter needle 30 and the center line of the orifice 32 may be aligned radially.

Referring now to FIGS. 4 and 9, the plate 108 of the mounting bracket 98 is illustrated as being fixedly attached to a vertical plate 134 of a stationary needle drive mount 136, forming part of the needle head subassembly 28 , by means of bolts 138 which pass through mounting holes formed in the plate 134 and in the back up plate 108. An electrical insulator 140 is juxtaposed between the plate 134 and the plate 108 and serves to electrically isolate the boom subassembly 24 from the needle head subassembly 28 which is illustrated more clearly in FIGS. 7 and 8.

The needle head subassembly comprises a miter gear box 142, the stationary needle drive mount 136, a movable needle support and vertical adjustment means or moveable mount 144 and a needle vertical adjustment means 146. As FIG.. 7 shows, the needle drive mount 136, comprises an upper and lower plate 148 and 150 fixedly attached to the vertical plate 134. The lower plate 150 is shown in FIG. 10 as a generally T-shaped plate having a fillet 149 in order to reduce stress concentrations. The upper plate 148, which is substantially similar to the plate 150, is provided with a bearing boss 152 to allow free passage of a rotatable vertical adjustment shaft 184 while the lower plate 150 is provided with a clearance 212 which allows for the free passage of the shaft 184. Both the upper and lower plates 148 and 150 are provided with bushings 182 which allow free movement of a pair of guide shafts 208. A pair of gussets 151 are fastened perpendicular to both of the plates 148, 150 and to the vertical plate 134. The miter gear box 142 sits atop the upper surface of the upper plate 148.

FIG. 9 shows the miter gear box 142 in cross section with parts broken away and comprises the bearing boss 152 which is fixed in a hole 154 formed in the upper plate 148. The bearing boss 152 rotatably supports a first miter gear 156 by means of thrust bearings 158. The miter gear 156 intergages a second miter gear 160 which is rotatably fixed on a command shaft extension 162 by means of a roll pin 163. The extension 162 is coupled by means of a flange 166 to a flange 168 formed on a command shaft 164 (see FIG. 4) which is driven by the motorized incremental needle drive 26. An electrical insulator 170 is juxtaposed between the flanges 166 and 168 and is clamped in place by means of bolts 172. The command shaft extension 162 is rotatably supported by means of bearings 174 which are clamped in place by means of a bearing housing 176. The housing 176 is clamped to a block 178 that is fixed on the plate 148 by means of bolts 180.

Coupled to the first miter gear 156 is the vertical adjustment shaft 184 which forms part of the movable needle support and vertical adjustment means 144. The vertical adjustment shaft 184 is suitably threaded (e.g., an Acme thread) so as to fit within an internally threaded bore 186 of the miter gear 156.

A purge housing 188 is fitted about the miter gear box 142 and provides a means of preventing furnace dust from entering the mechanical workings of the miter gear box. Purge housing 188 comprises sheet metal which is attached to the plate 148 and to the bearing housing 176. An enlarged hole 190 allows free passage of the vertical adjustment shaft 184 and a port 192 conducts the flow of purge air into the housing 188 by means of a flexible hose 194 which is coupled to a source of air under pressure (not shown). The flexible hose 194 is appropriately attached to the I-Beam 76. The air entering the housing 188 pressurizes the housing and flows through the hole 190 and through passageways 196 and 198 which are formed in the bearing boss 152. The passage of the pressurized air through the housing 188 ensures that any dust possibly interfering with the mechanical operations of the miter gear box 142 will be carried out of the housing 188.

The movable needle support and vertical adjustment means 144 comprises the vertical adjustment shaft 184, an upper tube bracket

200, a lower tube bracket 202, a left hand angle support bracket 204, a right hand angle support bracket 206, the guide shafts 208 and a support tube 210.

The drawings illustrate, in FIGS. 7 and 8, a clamping block 214 being rotatably fixed to one end of the vertical adjustment shaft 184 and to one of the ends of each of the guide shafts 208. As more appropriately shown in FIG. 10, the lower tube bracket 202 and thus the equivalent upper tube bracket 200 are generally U-shaped and are provided with two ears 213 which are fixedly attached to the guide shafts 208 using an appropriate fastening means such as bolts 215. Each of the brackets 200, 202 are provided with a tube mounting cut-out 216 which allows the insertion of the support tube 210. In abutting contact with the support tube 210 and adjustably mounted on each of the brackets 200, 202 is a non-metallic tube mounting block or isolator 218 which electrically isolates the support tube 210 from the brackets 200, 202.

The left hand angle support bracket 204 and the right hand angle support bracket 206 are fixedly attached to the upper and lower tube brackets 200, 202 by means of bolts 220. The support brackets 204, 206 provide the support for a means for removably fixing the support tube 210 against the tube brackets 200, 202 and the electrical isolator blocks 218. Support tube 210 is removably fixed by means of a clamping plate 222 which is pivotably fixed at one end by means of a bolt 224 which passes through a bushing 226 that is fixed in the plate 222 and a nut 228 fixed on the left hand support bracket 204. The other end of the clamping plate 222 is removably fixed to the right hand ,support bracket 206 by means of a clamping knob 230 that is threadingly fitted within a flange of the right hand support bracket 206. An insulating pad 232 electrically isolates the clamping plate 222 from the support tube 210. During servicing, an access door 231 allows the clamping plate 222 to be released by an appropriate rotation of the clamping knob 230. The plate 222 pivots downwardly about the bolt 224 to a vertical position under the influence of gravity whereby the tube housing 210 may be removed. In order to prevent dust from contaminating the sliding parts of the movable needle support and vertical adjustment means 144, sheet metal 234 is provided. Bottom cover 236 protects the workings of the guide shafts and the lower portion of the vertical adjustment shaft 184, as shown in FIG. 7. Both the sheet metal housing 234 and the bottom cover 236 are pressurized with air in a manner not shown in order to purge these compartments of any dust which may migrate from the furnace environment.

Fixed at the lower portion of the support tube 210 is a plug 238 which is fixedly attached to an upper block 240. The upper block 240 is adjustably fixed to a intermediate block 242 by means of a key fitting (not shown) and adjustable screws 244. The adjustable screws 244 are utilized to force the intermediate block 242 to translate left or right as shown in FIG. 8 with respect to the upper block 240 in order to ensure that the center line of the support tube 210 is laterally aligned with the center line of the needle 30. These screws 244 are locked in their final position using fasteners 245. The needle vertical adjustment means 146 comprises a needle holder or weldment 246 which is fixedly attached to a lower portion of the intermediate block 242 and provides a support for an upper cooling tube clamping block 248 and a lower cooling tube clamping block 250. Cooling tubes 252 and 254 are clamped to and pass through clamping blocks 248 and 250. Adjustably clamped about the cooling tubes 252, 254 is an adjustable bar or needle vertical adjustment block 256. The upper portion of the needle 30 is fixedly attached to the adjustment bar 256 by any suitable means such as a collar (not shown). The adjustment bar 256 is removably fixed to the tubes 252, 254 by means of set screws 258. When set screws 258 are released the adjustment bar 256 may slide on the tubes 252, 254 and thus the needle 30 may be adjusted vertically relative to the needle holder 246. This adjustment facilitates the vertical positioning of the needle point 34 relative to. the orifice 32 when a needle 30 is first installed in the furnace 10 either after replacement of a former needle 30 or servicing of the needle.

A cooling can 259, fixed by means of a lock nut 260 on the needle 30, is nominally disposed at the melt line 14 of the furnace 10 and is supplied with a coolant such as water by means of the cooling tube 252. The cooling can 259 protects the molybdenum needle 30 from the harmful critical oxidation temperatures experienced at the melt line 14. The cooling tube 254 provides a means of returning the spent and now hot coolant to a suitable heat exchanger (not shown). As is shown in FIGS. 1 and 3, the cooling tubes 252, 254 are suitably affixed on the I-beam 76.

Turning now to FIGS. 10 and 11, the motorized needle drive 26 is illustrated. As shown in the figures, a bi-directional, constant torque DC motor 262 is mounted on a drive mounting plate 264 which is fixed to the upper flange of I-beam 76 by means of a fixture 266 and a stand off support 268. The motor 262 is capable of operating at a relatively low rotational speed, e.g., 150 RPM and at a relatively high rotational speed, e.g., 700 RPM. There is a need in the present invention for these two speeds because at the relatively low rotational speed, an incremental displacement of the needle 30 may be effected. It is necessary at times, e.g., during routine or emergency servicing for the melter needle to be rapidly removed from the environs of the furnace because the molybdenum, consituting the highly oxidizable material of the needle 30, must be removed very rapidly from the highly oxidative atmosphere present proximate the melt line 14 of the furnace 10. At these times the motor must be capable of the relatively high rotational speed. The motor output shaft 270 is fixed to a torque limiting coupling 272 whose output shaft 273 is rotatably supported on pillow block bearings 274. The torque limiting coupling 272 is included as a safety device in the drive train of the melter needle assembly. Should, for example, the needle so jam or molten material freeze, this coupling would slip avoiding serious damage. Fixed on the shaft 273 is a small up mode pulley 276 and a small down mode pulley 278.

Small up mode pulley 276 is coupled via belt 280 with a large up mode pulley 282 which is fixed upon an up mode shaft 284. The shaft 284 is rotatably fixed on two pillow block bearings 286 and is provided intermediate the two bearings 286 with a conventional electromechanical clutch brake 288. The end of the shaft 284 is provided with a conventional electromagnetic clutch coupling 290 whose output shaft is coupled with the command or output shaft 164 by means of a pulley 292, a belt 294 passing through an opening 295 in the plate 264 and a pulley 296 which is fixed about the command shaft or output shaft 164. The command shaft 164 is rotatably supported upon the drive mounting plate 264 by means of pillow block bearings 298. An electromechanical clutch brake found suitable for use in the present invention is sold by the Warner Electric Company, PSI Division under the trade name of Incremental Clutch, Model # CB-5. An appropriate electromagnetic clutch coupling suitable for use in the present invention is sold by the Warner Electric Company under the trade name of Warner Clutch, Model # SF-400. Rotational torque provided by the shaft 273 is simultaneously transmitted via a belt 300 to a large down mode pulley 302. The large pulley 302 is fixed about a down mode shaft 304 which is rotatably supported by means of pillow blocks 306 fixed on the mounting plate 264. A conventional electromechanical clutch brake 308, which is equivalent to the brake 288, is affixed about the shaft 304 and a conventional electromagnetic clutch coupling 310, equivalent to the coupling 290, is affixed about the shaft 304 at its distal end. The output of the coupling 310 is provided with a pulley 312 which transmits torque via a belt 314 to a pulley 316 which is mounted upon the command shaft 164.

The operational modes of the motorized needle drive 26, i.e., the up and down modes effectuated by the up and down mode shafts 284, 304, are identical. Thus, the up mode will only be described for the sake of economy and will be equivalent to the down mode. In use, the motor 262, upon activation by a controller (not shown), continuously rotates its output shaft 270. The torque produced by the motor 262 is limited by means of the coupling 272 for the safety of the equipment and its output shaft 273 rotates the pulley 276 and the pulley 278. Pulley .276 causes a rotation of the pulley 282 by means of the belt 280. The shaft 284 is moved at an appropriate speed by means of the pulley 282 such that when an appropriate electrical signal is received from the controller the clutch coupling 290 is activated. Almost simultaneously the brake 288 receives a signal from the controller and causes its pawl 318 to move out of an engaging contact with its ratchet 320 thereby causing a certain incremental angular rotation of the shaft 284. The pawl 318 is caused to almost immediately return to its engaging relationship with the ratchet 320 by deenergizing the brake 288 thereby ensuring an incremental rotation of the shaft 284. Because the coupling 290 has connected the shaft 284 with its output shaft upon receipt of the signal from the controller the pulley 292 allows an incremental rotation of the command shaft 164 via the belt 294 and the pulley 296 and then is deenergized.

The command shaft 164, connected via universal joints 322 with the command shaft extension 162, causes an incremental rotation of the second miter gear 160 which correspondingly causes an incremental rotation of the first miter gear 156. The first miter gear then effects an incremental translation of the vertical adjustment shaft 184. Since the adjustment shaft 184 is fixedly attached to the clamping block 214 the movable needle support and vertical adjustment means 146 translates upwardly. The phantom lines in FIGS. 7 and 8 illustrate the means 146 in its most upward position. Concomitantly the needle 30 is also translated upwardly an incremental distance proportional to the angular rotation of the command shaft 164. Appropriate sensors (not shown) denote the position of the needle relative to the outlet orifice. In the event of failure of the motorized needle drive, a hand wheel can be used to incrementally move the needle 30.

During servicing of the melter needle assembly or during an emergency condition, the motor 262 rotates at its relatively high rotational speed, i.e., 700 RPM and the clutch coupling 295 is activated. Almost simultaneously, the pawl 318 is held in a disengaged position from the ratchet 320 and the command shaft is forced to rotate at a high rotational speed. Consequently, the needle 30 is driven linearly at a relatively high rate of speed, e.g., 6 feet per second. As should be understood, this quick motion of the needle is necessary in order to prevent oxidation of the molybdenum needle.

When the needle is in its full up position as indicated by the needle position sensors, the piston 49 may be forced upwardly by the motive fluid that may be controllably admitted via conduit 47. As a result, the boom subassembly 24 is forced to rise vertically to such an extent that the needle 30 may clear the upper surface 21. Conventional sensors may detect this condition so that the boom subassembly may be released by the solenoid operated pilot 67 and rotated by the rotary actuator 58 to its retracted position. Where in the retracted position, shown in phantom in FIG. 2, the needle 30 may be serviced.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for controlling the position of a flow obturator relative to the outlet orifice of a melting furnace, comprising: a support, an elongated member extending from said support to a proximate position above said orifice, said elongated member being mounted on said support; a torque transmitting member; means mounted on said elongated member proximate said support for producing an incremental rotation of said transmitting member, means mounted on said elongated member distant from said support for converting said incremental rotation to an incremental linear movement, and a flow obturator attached to said conversion means, whereby when said producing means causes said transmitting member to rotate, said conversion means effects an incremental linear movement of said obturator.

2. The apparatus of Claim 1, further comprising means for causing said elongated member to rotate between positions radially aligned with said orifice and outside the confines of said furnace, said rotation means being mounted on said support.

3. The apparatus of Claim 2, wherein said elongated member is mounted on said rotation means.

4. The apparatus of Claim 3, further comprising a fluid damper for decelerating the rotational motion of said elongated member .

5. The apparatus of Claims 1 or 3, further comprising means for translating said elongated member vertically.

6. The apparatus of Claim 5, wherein said translation means comprises a fluid operated piston.

7. The apparatus of Claim 5, wherein said conversion means comprises a first rotatable miter gear attached to said transmitting member, a second rotatable miter gear interengaged with said first miter gear, said second miter gear having an internal thread and screw means engaging said internal thread, whereby when said first miter gear rotates and causes said second miter gear to rotate, said screwmeans moves linearly incrementally.

8. The apparatus of Claim 7, wherein said conversion means is enclosed in a housing, said housing being supplied with a pressurized fluid.

9. The apparatus of Claim 7, wherein said conversion means is supported by a stationary obturator mount, said stationary mount being fixedly attached to said elongated member distant from said support.

10. The apparatus of Claim 9, wherein said screw means is a threaded vertical shaft, a shaft clamping means being rotatably fixed at the end of said shaft distant from said conversion means, at least one stabilizing bar, said bar being fixed on said clamping means, said bar being slidingly supported within said stationary mount, whereby when said shaft is moved linearly, said bar stabilizes its motion.

11. The apparatus of Claim 10, wherein said stabilizer bar is fixedly attached to a movable obturator mount, an obturator support tube removably mounted on said movable mount and an obturator lateral adjustment for aligning the center line of said tube with the center line of said obturator, means, said lateral adjustment means beingsupported by said tube.

12. The apparatus of Claim 11, further comprising means for cooling said obturator, said cooling means being supplied with a coolant by an inlet pipe and discharging spent coolant by means of an outlet pipe.

13. The apparatus of Claim 12, wherein a weldment is affixed to said lateral adjustment means, said weldment also being fixedly supported on said inlet and outlet pipes.

14. The apparatus of Claim 13, further comprising an obturator vertical adjustment means for initially fixing said obturator relative to said orifice.

15. The apparatus of Claim 14, wherein said vertical adjustment means comprises an obturator mounting clamp, said obturator being fixedly attached to said obturator mounting clamp, said obturator mounting clamp being removably fixed to said pipes, whereby when said obturator mounting clamp is removed from said pipes, said obturator may be initially positioned relative to said orifice.

16. The apparatus of Claim 11, further comprising means for adjusting the radial position of said obturator relative to said orifice.

17. The apparatus of Claim 1, wherein said producing means comprises a motor, a torque reducing coupling being fixed to the output shaft of said motor, said torque coupling having an output shaft, an intermediate rotatable shaft, means for rotatably coupling said torque coupling output shaft to said intermediate shaft, an electromechanical clutch brake attached to one end of said intermediate shaft, an electromagnetic clutch coupling attached to the other end of said intermediate shaft, said electromagnetic clutch coupling being rotatably attached to said transmitting member.

18. An incremental drive mechanism for producing small angular rotations of a rotatable member, comprising: a high torque motor, said motor, when activated, continuously drives its output shaft; a torque limiting coupling attached to said motor shaft, said limiting coupling having an output shaft; a rotatable intermediate shaft, said intermediate shaft being rotatably coupled to said limiting coupling shaft; an electromechanical clutch brake being connected at one end of said intermediate shaft, an electromagnetic clutch coupling attached at the other end of said intermediate shaft, said electromagnetic clutch coupling having an output shaft, means connecting said clutch coupling output shaft to said rotatable member, and means for sequentially activating first said clutch coupling and then said clutch brake, whereby when said clutch coupling is activated its output shaft may be driven and when said clutch brake is activated said intermediate shaft is momentarily rotated through an incremental angle such that said clutch coupling output shaft is rotated incrementally and consequently said rotatable member.