US2133305A - Clamp for electric arc furnace electrodes - Google Patents

Description

Oct. 18, 1938. w. H. PAYNE CLAMP FOR ELECTRIC ARC FURNACE ELECTRODES Patented Oct. 18, 1938 PATENT OFFICE CLAMP FOB, ELECTRIC ABC FURNACE ELECTRODES William Harvey Payne, La Grange, Ill. Application September a, 1936, Serial No. 99,227

Claims.

I An electric arc furnace to which this invention applies is such as may be used for the melting and/or refining of metals, as, for example, steel,

iron, and alloy metals, ferrous and non-ferrous. 5 In such an electric furnace electric heat is applied by arcing to scrap and slag, the current being taken into the furnace through graphite or carbon electrodes which, in turn, are clamp-supported to separate movable electrode arms which, in turn, slide up and down columns or like members fastened to the side of the furnace shell or parts thereof.

In the operation of an electric arc melting furnace, the carbon or graphite electrodes gradually wear away at the bottom end in the furnace. This means that each electrode has to be "slipped" down in its clamp three or more times per day. Once or so a day a new section of electrode must be screwed to the one which has been slipped almost down to the top of the electrode clamp on the arm. At the present stage of the art, the operator has to climb up on top of the hot electric furnace each time the clamps have to be operated, to slip the electrodes. This is extremely hot work and also takes too much valuable time of electric arc furnace operation, because every 'time an electrode is slipped, the power has to be shut off. Y

With these conditions in mind, the objects of this invention are to provide (a) A distantly located (from heat) power means which operates the clamp. This power means has to be located away from the heat to prevent the heat from damaging packings, heating the power fluids, or such as are used.

(b) A power operated electrode clamp. This relieves the furnace operator from climbing up on the furnace to adjust the electrodes, in immediate proximity to heat most of the time so intense that it is very hard on the operator.

(0) A much faster operating clamp, saving dollars of valuable (electric heat) furnace time.

(d) A uniform, correct, constantly applied pressure to clamp the electrode. In the art up 45 to the present time there is usually a fixed (at each setting) screw or wedge gripping of a clamp. Graphite and carbon electrodes have almost a neutral co-efflcient of expansion. Therefore, such electrodes gripped in expansible copper, plus steel screws, and in terrific heat, though partially water cooled, vary in their hold on the electrode. This causes dirty and burning contacts, and occasionally slipping trouble. When holding an electrode, my invention constantly applies correct pressure to the clamp, which gives with the differential thermal expansion and therefore always grips uniformly.

(e) A power mechanism which will exert a force for releasing the wedge clamp substantially greater. than for setting the clamp. When a wedge clamp is first pushed down to clamp-hold the electrode, a certain amount of power is required, but to break the hold a greater wedgewithdrawal power must be used. By the power mechanism herein disclosed, it is possible to use a uniform fluid pressure for both operations, yet with a substantially greater wedge-withdrawal pressure than push-down pressure. The power application may either be constant or intermittent, i. e., it may be delivered in a series of hammer-like blows which will break a wedge lock easier than a steady high pressure.

(I) Use of a fluid blast, located around the electrode, directly on the top of each clamp. In all electric arc furnace operations, dust and grit settle on the electrodes. It is very desirable to blow oil this dust and grit each time immediately before an electrode is slipped. By so mechanically connecting the air valve with the electrode clamp power means, the operator may, with one movement, release the clamp, and also turn on a blast of air into the blast pipe around the electrode, and so clean off the dust and the electrode is slipped down through the clamp.

As will shortly appear, my new electrode clamp utilizes a clamping ring having a wedge block which is actuated by suitable connections, and operable by any source of power, or by hand, distantly located from the heat so that each electrode can he slipped quickly as required. The clamps of this invention are designed for use in mounting and suspending the electrodes which are used in any direct are electric melting furnace. The clamps shown in the attached drawing are adapted to a well known type of electric arc furnace.

Further objects and details will appear from the description of the invention in conjunction with the accompanying drawing, wherein.

Figure 1 is a side elevation of an electric furnace employing the clamping mechanism of the present invention;

Fig. 2 is a top plan view of the clamping mechanism for one electrode, the power operating means therefor being omitted from the view;

Fig. 3 is a central vertical section through the clamping mechanism and power operating means there'or; and

Fig. 4 is a view partly in longitudinal section and partly in elevation of a power mechanism and operating connections of modified construe-j tion.

The clamps of the present invention are applicable to an electric furnace of standard, construction having a cover 6 from which depend a group of three electrodes 1 arranged in triangular relation. Since the electrodes and clamping mechanism are substantially identical in each case, a description of one will suffice for all.

The clamping mechanism for each electrode comprises a circular collar it having a lateral extension H wherein is formed a cam-way l2, beyond which lies an open space here shown as a slot 63. Connected to the collar extension upon opposite sides thereof are spaced arms M which in unison support the electrode. Preferably these arms are formed of copper, thereby constituting a conductor for'supplying current through the collar to the electrode. Within the cam-way is fitted a wedge block i5 in engagement with the electrode surface and adapted to exert a variable pressure thereagainst according as the block is shifted vertically within the collar. The inner face l6 of the wedge blockis rounded to conform to the curvature of the electrode, and the inner curvature of the. clamping collar is such as to afford a direct bearing surface I! with a cut-away 'area l8 on each side in the region adjacent its lateral extension to afford a clearance so that on the inner side a clamping contact will be afforded solely by the wedge block I5.

Mounted upon the collar extension are a pair of blocks 20 in which is supported a pin 28 forming a fulcrum mounting for a bell crank having a weight arm 22 and a power arm 23. As shown,

the end of the weight arm is rounded to fit within a socket 2 3 in the wedge block adjacent its upper end. The power arm of the bell crank depends into the open space rearwardly of the camway and at its lower end connects as at 25 with a thrust rod 26 which extends to a relatively remote point where a power device may be located away from the heat.- As shown, this power device comprises a cylinder 30 in which is reciprocally fitted a piston 3! to the forward side of which is connected a plunger 32 which passes out through a cylinder head 33 having a stuffing box 35 which may be of conventional construction. The plunger connects with the thrust rod, integrally or otherwise, and, by reason of its cross sectional area, considerably reduces the working face of the piston upon its side which is proximate to a port 35 through a fluid medium, hydraulic, gaseous, or otherwise, is admitted under pressure.

The opposite end of the cylinder is provided with a port 36, also having a connection which leads to a source of fluid pressure which may be the same as that supplied to the port 35.

By the operation of appropriate valves (not shown) the piston may be caused to reciprocate either wa within the cylinder, thereby rocking the bell crank with a consequent transmission of motion to the wedge block. Inasmuch as a greater force is required for the .release of pressure between the wedge block and the electrode than for the application of such pressure, I have so arranged the cylinder mechanism that the sur- Hace area of the piston on the side proximate to the port 36 will be considerably greater, perhaps twice, than on the opposite side of the piston; accordingly, the same pressure admitted through the port 36 will transmit through the cylinder mechanism a much greater power on the outstroke, which releases the wedge block, than on the in-stroke, which advances the block.

In the furnace shown, each pair of arms I4 is connected with a ring-shaped mounting III which rides upon a standard 4|, and may be raised or lowered by means of a counterweighted cable 42 actuated by a motor driven winch drum 43 around which the cable is coiled.-

The clamping collar ID is preferably cored or piped to provide channels 45 which are connected to a source of water supply for cooling purposes. In order to remove any accumulation of dust or dirt upon the electrode, each clamping collar may be provided with a blast pipe 66 of ring shaped formation which closely encircles the electrode and is perforated at recurrent intervals to provide discharging jet openings 47. Each blast pipe is preferably provided with a valve 68 which, as shown may be tripped by a finger 69 on the thrust rod 26, so that as. the rod is advanced to release the clamp and permit the electrode to slide downwardly the pipe valve will be opened and a blast of air or other fluid discharged upon the surface of the electrode to remove any coating of dust or other foreign material.

In use, the electrode will be properly adjusted to depend into the furnace to the intended position, after which the thrust rod 26 will be actuated to set the clamp and the current will then be turned on in the usual manner for operation of the furnace. Each of the electrodes can be individually lifted by its winch drum 43, but in addition to the regulation thus afforded it becomes necessary at intervals to provide for the down slipping of the electrodes themselves, and

this may be accomplished by actuating the clutch mechanism in the manner described and from a distant point, so that the operator will not be compelled to approach the region of extreme heat in making the necessary adjustment.

The degree of adjustment can be regulated to a large extent by permitting the electrode to slip downwardly through the interval of time necessary to afiord the desired slipping movement, at which point the clamp can be instantly set to arrest any further movement. In case, however, the electrode is overfed by the release of the clamp, it can be elevated by the winch drum to the desired degree to bring the end of the electrode to the intended position.

A power mechanism differing somewhat in type is illustrated in Fig. 4. Here I have shown a cylinder 50 wherein is reciprocally mounted a plunger 5i having connection with a thrust rod 52 which is joined to a bell crank 53 whose rocking movements impart an up or down motion to a wedge block in the 'manner already described. The inner end of the plunger is provided with a head 55 forming a limit stop for a piston-hammer 55 which is slidably mounted on the plunger. A second limit stop spaced from the first is provided in a collar 56 having a fixed mounting on the plunger. The piston-hammer is urged toward and against the plunger head 54 as by a spring 51 which may compress, however, in response to an overbalancing counterforce to permit advance of the piston-hammer against the collar 56. A valved pipe 58 leading from a source of fluid pressure connects with the cylinder at its rear end adjacent the plunger head. Upon release of pressure into the cylinder the pistonhammer will be driven forwardly against the tension of the spring until it hits the collar with percussive effect, thereby transmitting through the thrust rod 52 to the wedge block a sharp hammer-like blow. A vent 59 may be employed, if desired, to prevent back pressure on the. forward side of the piston-hammer. In operation, pressure may be momentarily applied through movement of the valve so that the piston will advance with percussive effect against the collar 56 giving a single hammer blow for the withdrawal of the wedge, and thereafter the valve may be turned to a position to exhaust through the port 60 which allows the spring to restore the piston for succeeding withdrawal operations. Some such power device as this, capable of delivering a succession of hard blows may be employed to break the wedge lock, which experience has demonstrated to be necessary. The spring pressure may be suflicient, without other power, to maintain the wedge in clamping position, although the same source of constant pressure only may with appropriate connections be used to set the wedge and maintain it in clamping position.

Although the invention has been described with full detail, it is not the intention to limit the claims to the mechanisms shown, since modifications thereof can be made without materially departing from the spirit of the invention; and it will be understood that the particular means shown for actuating the thrust rod serve merely for purposes of illustration, and that other mechanisms or appliances can be employed for a like purpose, and that the thrust rods can be operated by hand from a distant point where it is inconvenient to employ power mechanism.

I claim:

1. In a clamp for furnace electrodes, the combination of a clamping collar adapted for fitting around an electrode, the collar having a lateral extension providing a longitudinal cam-way, a wedge extending between the electrode and the cam-way adapted when moved longitudinally of the collar to exert a variable clamping pressure against the electrode, an operating means for the wedge including a bell crank mechanism connected therewith, and a pressure operated double acting piston connected with the bell crank and positioned remote therefrom, and arranged to exert a lesser force in the wedge setting direction and a greater force in the wedge releasing direction.

2. In a clamp for furnace electrodes, the combination of a clamping collar adapted for fitting around an electrode, the collar having a lateral extension providing a longitudinal cam-way. a wedge extending between the electrode and the cam-way adapted when moved longitudinally of the collar to exert a variable clamping pressure against the electrode, and power transmission means connected to the wedge for operation thereof adapted to translate a horizontal motion into a vertical motion and power applying means adapted to exert a steady force in the wedge setting direction and a percussive force in the wedge releasing direction.

3. In a clamp for furnace electrodes, the combination of a rigid clamping collar having an opening and adapted for fitting around an electrode, a wedge shaped pressure block positioned in the collar opening movable vertically therein to eifect a wedging action and adapted to cooperate with the collar in engaging the electrode with a variable clamping pressure at spaced points upon the surface thereof, reciprocable power transmission means remote from the pressure block and connected thereto for operation thereof, and a pressure operated double acting piston mechanism connected to the transmission means and arranged to exert in the releasing direction a force in excess of that exerted in the clamping direction.

4. In combination with a furnace electrode, a wedge clamp therefor, and power-operated means for setting and releasing the clamp comprising a pressure operated piston and connections adapted to exert in the wedge setting direction a steady force and in the wedge releasing direction a percussive force.

5. In combination with a furnace electrode, a wedge clamp therefor, and power-operated means for setting and releasing the clamp comprising a pressure ,operated piston and connections adapted to set the wedge clamp when moved in one direction and to deliver a percussive force to release the wedge clamp when moved in the reverse direction.

WIILIAM HARVEY PAYNE.

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