US2322918A - Apparatus for tightening electrode joints - Google Patents

Description

June 29, 1943. F. w. BROOKE l APPARATUS FOR TIGHTENING ELECTRODE JOINTS Filed June 27, 1940 4 Sheets-Sheet l m .7 W WA:

r. K Rm Y m Wm WM am M fi m 4 Sheets-Sheet 2 I HIIHIH H II 1 I I v F. W. BROOKE APPARATUS FOR- TIGHTENING ELECTRODE JOINTS Filed June '27, 1940 June 29, 1943.

ATTORNEY J1me 1943- F. w. BROOKE ,32 ,918

APPARATUS FOR TIGHTENING ELECTRODE JOINTS Filed June 27, 1940 4 Sheets+Sheet 3 INVENTOR F/rmv/r M fi/rooxf gjadfdl ATTORNEY June 29, '1943. 2,322,918

F. W. BROOKE APPARATUS FOR TIGH'IENING ELECTRODE JOINTS Filed June 27, 1940 4 Sheets-Sheet 4 INVENTOR Ffifl/V/f M 5/?00/(6 .0000! BY I I I I I I I I000 2000 3000 4000 5000 6000 F0 OT-POU/ DS OPQUE I @W AT ORNEY Patented June 29, 1943 UNITED STATES PATENT OFFICE Frank W. Brooke, Pittsburgh, Pa., assignor to Swindell-Dressler Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application June 27, 1940, Serial No. 342,657 3 Claims. .(Cl. 29-84) The general object of the present invention is to provide an improved method of and apparatus for tightening the threaded coupling connections between end to end sections of carbon furnace electrodes, so as to eliminate objectionable electrode joint resistance.

The use of electric arc furnaces for iron and steel melting and other metallurgical and chemical purposes, is extensive and continuously increasing. In such furnaces, the electrodes are rod-like bodies, usually circular in cross section,

of' carbon in amorphous, semi-graphitic, or graphitic form. Such electrodes vary in their dimensions with the character of the furnace in which they are used and the conditions of use, from a diameter of about four inches up to a diameter of forty inches. The individual electrode sections customarily vary in length from forty inches to one hundred ten inches. In iron and steel melting furnaces, the electrodes employed are ordinarily of the order of eighteen inches in diameter and six feet in length.

' In most cases, each furnace electrode in use, consists of two or more electrode sections connected end to end. In use, the arcing end of a furnace electrode is constantly wasting away, so that it is necessary from time to time at relatively frequent intervals to add a new section to the outer end of the electrode. The end to end electrode sections are connected, in standard practice, by nipples or plugs formed of the same material as the electrode sections, and having end portions oppositely tapered and externally threaded to screw into internally threaded tapered sockets formed in the ends of the electrode sections. Heretofore, it has been customary to tighten up the threaded connection between the outer electrode section previously in use, and a section being added, by the manual actuation of a wrench or analogous implement attached to the last mentioned section. In practice, the maximum joint tightening torque used in thus tightening an electrode joint customarily amounts to some three or four hundred foot pounds, in the case of an electrode 18" in diameter and of the usual construction.

I'have discovered that it is practically feasible and desirable to employ an electrode joint tightening torque and contact pressure much greater than those heretofore customary, and that it is thus possible to greatly reduce the electrode joint resistance and joint temperatures, and thereby increase the furnace efficiency and materially reduce the tendency tobreakage of the electrode portions Within the furnace. Specifically I have found, for example, that a standard graphite electrode eighteen inches in diameter will have a joint resistance when the joint tightening torque is three hundred foot pounds, which is about four times the joint resistance when the joint tightening torque is three thousand foot pounds.

The importance of joint resistance increases with the amount of current flow through the electrode. There is a constant tendency in the industry to increase the electrode current flow.

Electrode joint resistance necessarily results in an electrode temperature higher at the electrode joints than in the body of the electrode and the difference in many cases is sufiicient to significantly increase the rate of electrode oxidation and thereby decrease the electrode cross sectional area at the joint. The evil effectsof the oxidation due to high joint resistance. are thus cumulative. Electrode joints not only increase electrode resistance and thereby reduce furnace efficiency, but they ordinarily reduce the'lectrode strength, and in particular they reduce the capacity of the electrodes to withstand the enormous electromagnetically produced, vibratory stresses to which they are subjected as a result of the constantly occurring load condition changes. Those stresses tend to loosen the joints and thus increase the joint temperatures. and thereby further impair the joints, so that from time to time an electrode section below a joint within the furnace chamber breaks away from the electrode. This not only involves objectionable electrode wastage, but disturbs the furnace operation and in some metallurgical operations, the addition of the carbon electrode section to. the

molten bath may disastrously effect the value" of the furnace charge. i v

A major object of the invention is to provide a practical method of and means for subjecting electrodes to joint tightening forces much higher than have been customary heretofore.

A more specific but practically important object of the invention is to provide a method of and means for adding an electrode section to .an electrode installed in a furnace and to subject the connecting joint to a tightening force of the relatively great magnitude characteristic of the present invention which will require no modification of, or addition to existing furnace structures and which will not subject the furnace structures to objectionable stresses or operating conditions. My invention is characterized by the simple provisions made whereby in tightening the joint between the outer end section of an electrode mounted in a furnace and a section to be added thereto, each of the two sections is subjected. to a torque opposite in direction and substantially equal in magnitude to the frictional resistance torque with which each of said sections opposes turning movement relative to the other section.

Furnace dust or other dirt in an electrode joint tends to a great increasein joint resistance and a materialreduction in the strength of the joint and in its capacity to stay tight. A specific object of the present invention is to provide the joint tightening device which I have devised. with, simple and effective means for cleaning joint forming surfaces, and particularly the upper end of the furnace electrode to which a section is tobe added, by compressed air jets. My improved joint tightening device may include power multiplying provisions enabling a man to subject. the. electrode sections to joint tightening torques as high as are required, but where conditions make this desirable, my jointtightening device may include a suitable motor supplying the joint tightening power.

The various features of novelty which. charact'erize. myinventionare pointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the-invention, however, its advantages, andspecific objects attained. with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustratedv and described a preferred embodiment of the invention.

Of the drawings:

Fig. 1 is a diagrammatic representation of a plant comprising an electric furnace, and associated apparatus for adding sectionsto the fur nace electrodes as the latter waste away:

I Fig. 2 is an elevation on an enlarged scale of. a portion of the electric furnace shown in Fig. 1 and also shows a preferred. form of my electrode joint tightening device;

Fig. 3 is an elevation, partly in section,.of an electrode section and asupport on which the section. is mounted preparatory to its connection to my electrode joint tightening device;

Fig; 4 is a view showing my electrode joint tightening device in operative relation with the electrode section and'support shown in Fig. 3;;

Fig; 5 is a somewhat diagrammatic representationof screwthread relations of an electrode section coupling parts and of the joint tightening device,,in an intermediate stage of an electrode section coupling operation; Fig. 6 illustrates the screw thread relations 0 the electrode section coupling parts in a final stage of an electrode section coupling operation;

Fig. '7 is a large scale reproduction, with parts broken away and in section, of aportion of Fig. 2;

Fig. 8 is a sectionon theline 8.8 of Fig. '7;

Fig. 9 is a section on the line 9-9 of Fig, '7;

Fig. 10- is an elevation'of a motor actuating torque tightening device; and

Fig. 11 is a curve illustrating the reduction in electrode joint resistance effected by increasing the joint tightening force.

In the drawings'I'have illustrated the use of the present invention in connection with a conventionally illustrated electrical arc furnace A of well known type, comprising three electrodes B extending into the furnace chamber through openings in its roof, and each supported for longitudinal adjustment by an individual gallows element 0. Each of the latter comprises ahorizontal arm with a clamp C at one end for encircling and gripping the corresponding electrode B, and having its other end connected to a vertically movable plunger C The latter, which is mounted in a vertical guideway, is customarily supported and given vertical adjustments by a winch operated by a reversible electric motor automatically controlled by means responsive to the voltage drop in the are between the electrode and the charge, to raise or lower the electrode as required to maintain the arc voltage drop approximately constant. The current carrying connection D to each electrode is mechanically supported by the corresponding gallows member C. The construction details of the members C and the mechanism by which said members C are guided and vertically adjusted, need not be illustrated, or further referred to herein, as they form no part of the present invention and may be of well known form.

Each of the electrodes B comprises a plurality of similar sections 1) connected end to end. Each section b is formed at each. end with a tapered internally threaded socket b; and the two adjacent sections b of each electrode are connected by a nipple or pin 11 having its two. end portions oppositely tapered and externally threaded to screw into the adjacent end sockets b of two adjacent electrode sections 1). As previously indicated, the electrode sections 1) are ordinarily formed of carbonin amorphous, semi-amorphous or graphitical form, and may widely vary in diameter and length, to adapt them for use in furnaces of different sizes and for different furnace conditions of use. Ordinarily the nipples or pins 1) are formed of the same material as the electrode sections b which they connect.

In use, each electrode B is constantly wasting away at its lower end, and from time to time a new section I) must be added to the upper end of the electrode. Preparatory to the addition to an electrode of an electrode section b, the first step, ordinarily, is to thread a tapered lifting or suspension plug E into the socket b at one end of the section, and to thread a nipple or connecting pin b into the socket b at the opposite end. of the section. The member E is provided with an eye E adapted for engagement by the hook F of a crane or hoist, which after being entered in the eye E, is operated to upend the section b and lift it off such a stock pile as is shown at the left hand side of Fig. 1, and to then move the section b into'a position above and into engagement with the support G as shown in Fig. 3.

The support G, as shown, comprises a base portion and a central portion G cylindrical in outline and extending up from the base portion. The portion G is formed with a cylindrical cavityopen at its upper end and adapted to receive a nipple or pin b threaded in the socket of the lower end of a section b, standing on the horizontal upper end surface of the portion G of the support G. As shown, a tubular metal sleeve or thimble G surrounds the support portion G, and extends upwardly above the upper end of the latter to provide a socket or guide which assists in ensuring that each section b supported by the support G, is properly centered thereon. While the section b is resting on the support G, as shown in Fig. 3, the suspension plug E is removed, and the joint tightening device H is moved into operative relation with the electrode section and is clamped to the latter.

The device H, as shown in detail in Figs. 7, 8 and 9, comprises a body portion beneath an upper suspension section HA, and above upper andlower electrode clamping sections HB and HC. In the. preferred form shown, the device H is U shaped orarc shaped inv cross section, so that it may be laterally moved into the position in which its clamps are in position to engage an electrode, or electrode section, at points of the electrode surface extending around the electrode axis for considerably more than 180, so that when the clamps are tightened on an electrode section, the latter and the tightening device are positively centered, relative to one another. The suspension section HA comprises an upper internally threaded tubular part or nut H coaxial with an electrode section engaged by the device H. An externally threaded suspension bolt H is threaded into the nut H, and is provided at its upper end with an eye H for engagement by the hook F of the crane or hoist employed to move and support the device H. The suspension part HA includes three depending arms H each bolt-connected at its lower end to a corresponding uprising arm H The body portion of the tightening device in the preferred construction shown is a metallic tank, U shaped in horizontal cross section and adapted to hold in its reservoir space h air under pressure for use in cleaning electrode joint surfaces, and provided with a valved inlet H and valved outlet H". The arms H are connected'to the upper end of the tank structure, and arms H secured to and depending from the lower end of the tank structure, are bolted or otherwise detachably connected to corresponding uprising arms H of the upper clamping section HB.

' .The clamping section HB comprises an arcshaped body portion or clamp frame, having ratchet-like teeth H distributed along a central innerside portion and adapted to bite into and grip the electrode section engaged by the device H. To each end of the body portion of the clamping section HB, a corresponding clamping lever I is pivotally connected by a pivot 1'. Each lever I comprises an outer handle portion by which ratchetelike teeth I at the inner end of the lever may be brought into gripping engagement with the electrode section. As shown, the toothed inner end of each lever I is cam. shaped so as to engage and bite into the electrode section with increasing pressure as the lever isturned in the clockwise direction as seen in Fig. 8. As shown, the ratchet-like teeth I and H are each inclined in the direction required for biting movement of its end edge into the electrode section b, when the clamping section HE is subjectedto a torque tending to give it a clockwise rotation about the axis. of the electrode section. As will be understood, the teeth Hand H are inclined and the inner ends of the lever I are shaped as described on the assumption that the screw threads on the parts b, b; H and H are all right hand threads.

--'I-'he clamping section'I-IB comprises depending arms H having ishouldersH at their ends,

which extend beneath and support arc-shaped flanges H on an uprising portion H of the lower clamping section H0. The sections HB and HC are releasably secured against radial displacement, by a part H bolted to the section H0 and overlapping the central arm H The section HC includes teeth H and clamping levers J, respectively similar to the teeth H and levers I of the section HB, except that the inner cam ends of the levers J are shaped, and their teeth J and the teeth H are inclined to bite into and grip an electrode section, when the clamping section HC is subjected to a torque tending to give it acounterclockwise rotation about the electrode axis.

The support G and the tightening device H are formed and proportioned to position the tightening device in, predetermined longitudinal relation to an electrode section I) supported on the portion G of the support G. To this end, the support G is formed with a horizontal annular surface G surrounding the lower. end of the portion G, and forming a seat engaged by the bottom of the clamping section HC, and thereby supporting the device H in the proper longitudinal relation with the electrode section supported on the support portion G. In that relation the clamping section HC is suitably below the electrode section b, and the clamping teeth H and I engagethe electrode section at a level slightly below the upper end of its lower end cavity b, where suitably heavy tightening stresses may be applied to the electrode without risk of injury to the latter.

After the tightening device H is properly positioned with respect to the electrode section b resting on the support G, and the levers I are adjusted'to positively clamp said section in the device H, the crane or hoist is manipulated to move the tightening device H and the electrode section b clamped therein, ofi the support G, and into the position shown in Fig. 2, in which said section b is in alignment with and above the upper end of the electrode B; to which the section b is to be added. The crane is then lowered far enough to enter the tapered lower end portion ofthe pin or nipple b of the section b' held by the device H, in the socket b' in the upper end of the electrodeB, but not low enough to bring the threads of said pin and socket into crushing engagement.

The tightening deviceH is then rotated clockwise about the electrode axis, as by manual force applied to the handles of the levers I. This results in a relative rotation of the nut H and bolt H which lowers the device H and the elec trode section b which it supports. As this rotative and lowering .movement of the device H progresses, the thread onthe tapered lower end portion of the pinor-nipple b of the section b held in the device H, comes into operative engagement with the Wall thread of the socket b" at the upper end of the corresponding electrode B as shown in Fig. '7. The rotative movement ofthe device H is normally continued until the lower end of the electrode section b held in the device H, abuts directly against the upper end of the subjacent section of the electrode B. 1 In ordinary practice, after the initial torque applied to the device H has started the latter into rotation, the rotation is continued by the momentum of the device and the electrode section b which it supports, until arrested by the frictional en-' gagement ofthe end surface of said section with the upper end of the electrode B.

, In the preferred form of the invention, the thread pitch of the similar threads on the inner wall of the sockets b and on the pins or nipples 12 is coarser than the-thread pitch of the nut H and suspension bolt H by apredet'ermined amount of pitch difference is that required to raise the outer edge of the thread rib on the pin b relative to the bottom of the thread groove in the wall of the socket b, from its position shown in Fig. 5 to its position shown in Fig. 6, as the device H is rotated to move the lower end of the section I) held by the device H into engagement with the upper end of the upper section of the electrode B. The thread pitch difference required for the purpose, depends upon, and can be readily calculated, or predetermined, as will be apparent, from the thread pitch and thread angle "of the electrode section and pin threads.

With the described difierence between the thread pitch of. the parts H and H 'and the thread. pitch of the partsb and'b the rotation of the device H to lower the new section pin 1) from its position shown in Fig. 5 to that shown in Fig. 6, will not increase the pressure between the thread on the pin. 17 and the wall thread of the socket b in the upper end of the electrode B, thus avoiding the tendency to crush or shear off the edge portions of the threads which would result from the described change in relative electrode and section positions, if there were no such pitch difference. It is readily possible to arrest the crane lowering movement'of the device H with the electrode parts-in the positions shown in Fig. 5, and without creating a contact pressure between the pin and socket threads which is objectionablylarge.

As the member H is being rotated to bring the parts into their positions shown in Fig. 7, air under pressure is discharged through the valved outlet H then open for the purpose, into the narrowing joint spacebetween' the lower end of the section I) held by the device H and the upper end of the electrode B. In the arrangement shown, the air is thus discharged into the joint space through nozzles K and K widely displaced from one another about the axis of the device H, and connected to the valve outlet H' by separate horizontally disposed branch pipes K and K respectively; As shown, the nozzles K and K are arranged to discharge jets directed radially inward toward the axis of the device H and electrode section b held by it, at approximately the level of the annular lower end surface of said section b. With the nozzles located 'as described, the annular lower end surface of the electrode section b and the opposing upper end surface of the electrode B, are very effectually cleaned by the cleaning jets which revolve about the electrode axis as the joint space is being closed.

After the parts are brought into the position shown: in Fig. 7, the levers J of the lower clamping section HC are given counterclockwise adjustments about their pivots J to thereby clamp the electrode section HC firmly to the upper end of the electrode B. Advantageously and as shown, the device H is so proportioned that the levers J grip the upper end of the electrode B at a distance below the upper end of the electrode, which is equal to the distance above the lower end of section b in the device H, engaged by the levers I.

With the upper end of the electrode B gripped by the clamping device HC and with the lower end of the electrode section b gripped by the clamping device HlB, the clamping device HE is given a small clockwise angular adjustment relative to the clamping device 'HC to thereby establish the desired contact pressure between the engaging ends of the electrode B and said section b. As previously stated in the preferred form of the present invention, this relative angular movement of the two clamping devices is effected without the transmission of any significant stress from th clamping device HC through the electrode B to which it is clamped to the supporting gallows C for the latter. To avoid such stress transmission, opposing torques are directly impressed on the clamping devices HB and HG. To

this end, in the construction illustrated, the devices HB and HC are connected by a sort of planetary gear connection.

Asshown in Figs. 1-9, the gear connection comprises a spur gear sector L coaxial with the device H and carried by the portion H of the device HC, and comprises a spur gear L, which is'in mesh with the gear sector L, and is carried by a. vertical shaft L journalled in the clamping frame of the device HB. The shaft L is provided at its upper end with a head L of polygonal outline in cross section, for engagement by a manually actuated wrench. The latter need not be illustrated or described, as it may be of any known or suitable form, and in particular, may well be a wrench of known type, including provisions for indicating its operating torque. By means of a wrench having a lever handle of suitable length, and with gears L and L of suitable pitch, a workman may readily subject the devices HB and HC to the opposing torques needed to establish the electrod joint pressure required for the purposes of the present invention.

Obviously other gear connections between the sections HB and HC may be employed. For example, each section supports a coaxial bevel gear and each of those bevel gears may be in mesh in a known manner with an interposed bevel gear having its axis radial to the axis of the first mentioned bevel gears.

When conditions make it desirable, the tightening connection between the upper and lower clamping devices may b motor actuated. Thus, in the modified form of tightening device I-ID shown in Fig. 10, an electric motor M carried at one side ofthe device, rotates a vertical shaft having a lower portion journalled in the upper clamping device hb, and carrying a spur gear L in mesh with a spur gear sector L carried by the lower clamping section he. Each of the sections hb and he is shown as a complete annulus, but this is not essential to the use of the motor, and otherwise sections hb and he are generally similar in construction and operation with the previously described sections HC and HB. As shown, the device HD includes another gear sector L and gear L the latter being carried by a short shaft L with its upper end shaped for engagement by a wrench, whereby the device HD has the same capacity for manual operation as does the previously described device H.

The tightening device HD may also include suspension portions.correspondingportion of the device H. A shown, however, the device I-ID does not include the air reservoir tank portion of the device H, but is-formed' by vertically disposed bars or frame members H, which have inclined upper end portions included in the suspension section of the device 1-11). In lieu of such a tank portion, the device HD includes a blower N mounted above and driven by the motor M, and through a pipe N supplying air under pressure to one or more cleaning nozzles K which may be similar in form and disposition to the nozzles K and K of the construction first described.

As will be apparent from the. foregoing, the general operation of the apparatus shown in Figs; 1-9, comprises the following steps: The initial insertion of the threaded suspension device E in one end of an electrode section b, usually while the latter i horizontally disposed in such a stock pile of such electrode sections as is shown in Fig;

' 1. Usually at the same time at whichthe mem-- ber E is threaded into one end of a section b, a connecting pin or nipple b is threaded into the other end of the section. The device E is then engaged by the crane or hoist hook F which moves the electrode section into position upon the support G as shown in Fig. 3. The member E i then screwed out of the upper end of the section b and the latter is clamped to device If by suitable adjustment of the clamping-levers I.

The device H is then moved by the hook F into the position to bring section b above the electrodeB of the furnace A to which said section b is to be added. The device H is then lowered to enter the pin 1) of the section b into the socket b in the upper end of the electrode B, generally as shown in Fig. 5. The member H is then rotated to lower the nut part H relative to the suspension bolt H and thu moves the section 17 into the position relative to the electrode B in which the abutting ends of the section and electrodes are in engagement as shown in Fig. 6. The levers J are then turned counterclockwise to clamp the clamping section HC to the upper end of the electrode B. The gear shaft L is then rotated in the clockwise direction, as seen in Figs. 8 and 9,

to establish the desired contact pressure between the electrode sections respectively clampedto the clampingsections HB and HC of the clamping device.

The foregoing operation complete the operation of connecting an electrode section to a furnace electrode, and is followed by the rotation of thelevers I and J counterclockwise and clockwise, respectively, to release the clamping devices HB and HC of the device H which is then moved away p;

from the furnace. In the ordinary use of the invention, the supply of current to the furnace electrodes will be interrupted during the period in which the electrode section engaged by the tightening device is being lowered into engagement with the furnace electrode and during the subsequent joint tightening operation.

As the section held by the tightening device is being lowered into engagement with the furnace electrode, compressed air is discharged into the joint space to blow dirt off the electrod surfaces which are to be brought into engagement. When the compressed air is supplied from a reservoir It included in the tightening device a shown in Figs. l-9, the plant station at which the support G is located, preferably includes a compressor for other source of compressed air with a discharge hose 0 conveniently disposed to permit the reservoir space to be recharged each time the device H is moved into the position shown in Fig. 4. With such frequent recharging, the volumetric capacity of the reservoir h, does not need to be great enough to involve objectionable increase in the bulk of the tightening device H, or to require the safety provisions and attention needed with compressed air reservoirs of greater volume. In the actual operation of coupling an electrode section B held by the device H to a furnace electrode, the joint cleaning operation requires no attention from the attendant other than the mere opening and closing of th valved outlet H.

With the form of the invention shown in Fig. 10, the joint cleaning operation requires that the motor M driving the blower N be operated during the period in which an electrode section b is being moved from the general position relative to the furnace electrode shown in Fig. into the position shown in Fig. 6. As those skilled in the art will understand, the shaft M normally will be connected to the armature shaft of the motor M through a suitable speed reduction gear M Advantageously, the motor M may be of a known commercial type, adapted to automatically stall when the motor torque increases to the value corresponding to the predetermined contact pressure desirably established between the electrode sections clamped to the upper and lower clamping sections hb and hc.

In the'diagram shown in Fig. 11, the curve P illustrates the variations in the resistance of an electrode joint between two end to'end sections b of an electrode coupled, as hereinbeforedescribed, as the contact pressure between the'two sections is increased. In Fig. 11, the abscissae unit is a torque foot pound, and the ordinates unit is an ohm. The curve P shown in Fig. 11 is based upon and corresponds to data obtained in tests made on graphite furnace electrode sections 18 in diameter in which use was made of a joint tightening device constructed and operated in accordance with the present invention, to establish high contact pressures between the elec-' trode sections. As the curve P shows, a great reduction in the joint resistance is obtained by increasing the maximum joint tightening torque in the case of a graphite electrode of standard construction and 18 in diameterfrom the limit of about 300 foot pounds, heretofore customary, up to about'3000 foot pounds.

The general advantages of the present invention may be attained with an electrode contact pressure varying froma minimum appreciably above that heretofore customary, to a maximum but little below the safe'crushing strength of the electrode material. While the joint resistance continues to diminish as the joint tightening force increases, the curve P is asymptotic, and the decrease in joint resistance as the torque is increased substantially above 3000 foot pounds, is relatively small and ordinarily will not justify the increase in the power of the tightening device required, and the resultant increase in the risk of injuring the electrode sections.

The general operation of the apparatus shown in Fig. 10 is the same as that of the apparatus shown in Figs. l-9, except in respect to the joint cleaning action, and except as a result of the fact that each of the members hb and be is a complete annulus. While the formation of each of the clamping sections hb and he shown in Fig. 10 as a complete annulus, permits of some reduction in the weight of metal required to give adequate strength to said sections, a tightening device including such annular clamping sections has the practical disadvantage that it must be moved longitudinally relative to the electrodes and electrode sections, into and out of operating relation with the latter. A tightening device open at one side as in the form first described, can be moved laterally into and out of engagement with furnace electrodes and sections, and hence has the advantage of requiring appreciably less crane elevation and head room than are required with the construction shown in Fig. 10.

While in accordance with the provisions of the statutes, I have illustrated and described the best forms of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

, 1. A device for connecting anelectrode section to the upper and outer end of a furnace elec trode having a tapered, internally threaded, axial socket at said end, said electrode section having at its lower end a tapered, externally threaded, axially disposed pin portion adapted to be threaded into said socket, said device comprising clamping means for engaging and gripping said electrode section and comprising suspension means including a nut portion coaxial with. and above an electrode section engaged and gripped by said clamping means and comprising a bolt threaded into said nut, said bolt and nut portion having a thread pitch finer than the thread pitch of said socket and pin, by such a predeterminable amount, that when said section and clamping element are suspended with said pin entered in said socket and the nutand bolt elements are rotated relative to one another to lower said pin into said socket, the pin thread surface may engage and slide along the thread surface of the socket, without transferring any substantial portion of the weight of said device and electrode section to the electrode.

2. Apparatus for establishing a threaded connection between end to end sections of an electrode comprising a gauging element having a seat adapted to be engaged by the lower end of an electrode section and to support the latter, and formed with device supporting means in predetermined relation to said seat, and a device adapted to engage and .be supported by said means :and comprising clamping means adapted for'gripping engagement-with an electrode section supported by said seatsurface and comprising other clamping meansspaced from the first mentioned clamping means and rotatable relative to the first mentioned clamping means and adaptedto engage andtclamp a second electrode section in end to end relation with the first mentioned section.

3. A device adapted for use in establishing a threaded connection betweensections of a cylindrical carbon electrode and comprising a clamping section including clamping means adapted to engage an electrode section at points displaced about its axis, a second clamping section connected to and supported by thefirst mentioned clamping section, and adjustable relative to the latter angularlyabout'the axis of .an electrode section gripped by the :upper *clamping section and including clamping means adapted to engage at points displaced about the electrode axis an electrode section in end :to end relation with the" electrode section engaged by the first mentioned clamping section, means acting between said clamping sections and subjecting the latter to opposing torques about their common axis and a compressed air supply tank carried byone of said clamping sections along side the position of an electrode section engaged by the last mentioned clamping section, and a joint cleaning air nozzle connected to and adapted to receive air under pressure from said tank and operable to discharge a cleaning jet of air into the'joint space between the ends .of the two electrode sections.

FRANK W. BROOKE.

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