US1955143A - Electric arc lamp - Google Patents

Description

April 17, 1934.

B. OBRIEN ELECTRIC ARC LAMP Filed April 15, 1930 4 Sheets-Sheet 1 April 17, 1,934. a. @BRIEN 1,955,143

ELECTRIC ARC LAMP Filed April l5, 1930 4 Sheets-Sheet 2 April 17, 1934. Bl QBRlEN 1,955,143

ELECTRIC ARC LAMP Filed April l5, 1930 4 Sheets-Sheet 3 S11/vento April 17, 1934. B. O'BRIEN 1,955,143

ELECTRIC ARC LAMP Filed April 15, 1930 4 Sheets-Sheet 4 :Erika 0:371

Patented YApr. 17, 1934 UNITED STATES PATENT OFFICE 22 Claims.

This invention relates to electric arc lamps and more particularly to improvements in mechanisms for automatically regulating the movement of the controlled electrode. A mechanism for this purpose must function; first, to permit the electrodes to'be moved together to start the arc, second, to separate the electrodes to produce the required length of arc and, third, to feed the controlled electrode at a speed determined by the rate at which the electrodes are consumed, to maintain the required length of the arc. l

One object of the invention is to provide a mechanism of the kind generally described which, upon establishmentof a circuit through the electrodes, separates them to produce the required length of arc, feeds the controlled electrode silently and evenly at a speed determined by the consumption of the electrodes to maintain the required length of arc and which when the arc is extinguished for any reason, for example, as by being blown out or by suspension of current supply, is operative to bring the electrodes together so that the arc circuit may be re-established, whereupon the cycle of operations described-is repeated.

Further objects are: a mechanism in which one of the electrodes may be universally adjusted thereby facilitating their alignment even though one/or both of them may be warped; a mechanism -in which the electrodes are held by their extremities, hence permitting their complete consumption without adjustment of their holding means; a mechanism in which the clutch does not engage the controlled electrode, this object contemplating the use of a holder and having the advantage that the action of the regulating mechanism is not affected by the physical characteristics of the particular electrode in use;' a mechanism which may be set to stop automatically the feeding movement of the controlled electrode after there has been a predetermined electrode consumption; and a mechanism in which the actuating means is damped at all times, thereby insuring a smooth feed of the controlled electrode.

The invention is illustrated in the accompanying drawings, in whichz Y Figure 1 is a front elevation of an electricarc lamp constructed in accordance with the invention.

Figure 2 is a longitudinal section-along line 2-2 of Figure 1.

Figure 3 is an enlarged section of the upper electrode holder taken along line 3-3 of Figure 2.

Figure 4 is a transverse section of the same taken along line .4 4 of Figure 2.

Figure 5 is a detail section of the holder for the upper electrode taken along line 5--5 of Figure 2.

Figure 6 is an enlarged section of the lower 60 electrode holder taken along line 6--6 of Figure 2.

Figure 'l is a detail section of the holder for the lower electrode taken along line 7-7 of Figure 6.

Figure 8 is an enlarged detail section of the clutch mechanism taken along line 8-8 of Fig- 65 ure 2, the clutch being shown in operative position.

Figure 9 is a section of the same taken along line 9-9 of Figure 8.

Figure 10 is an enlarged transverse section 70 taken along line 10-10 of Figure 2.

Figure 11 is a section taken along line 11-11 of Figure 10.

Figure 12 is a detail'view showing thev lower electrode holder locked in its down position.

Figure 13 is a detail view of the lower electrode holder showing means for preventing its further movement after there has been'a predetermined consumption of the electrode.

Figure 14 is a fragmentary section taken along line 14-14 of Figure 1, showing a receptacle in one of the tubular supports for the discarded electrodes.

Figure 15 is a fragmentary section taken along line 15-15 of Figure 1 showing a receptacle in the other tubular support for containing the supply of unused electrodes.

Figure 16 is a diagrammatic view showing the wiring system.

Figure 17 is a diagrammatic View showing pull curves for the solenoid and spring employed in the feed regulating mechanism.

Figure 18 is an enlarged section of the lower holder assembly showing the mounting of the electrical conductor which leads to the lower electrode. g

In the illustrated/embodiment of the' invention, the mechanism for regulating the movement ofthe controlled electrode is shown in connection with' a lamp suitable for therapeutic or other purposes. It is to be understood, however, that the invention is concerned 'primarily with the feed mechanism per se which, of course, is not dependent upon associated mechanisms which may be utilized in adapting it to meet the .l requirements of different uses.

The lamp,as illustrated, is mounted upon a suitable base or pedestal 20 and is supported thereon by a frame which includes a pair of main tubular supporting members 21 and a pair of auxiliary tubular Supporting members 22. A

-cross member 23 is suitably secured for adjustment upon the main tubular members 21, and.

provides a support for the auxiliary vtubular members 22. The members 22 are mounted in suitable openings formed in the cross member 23 and extend below it to support a second cross member 24. The auxiliary tubular members 22 are preferably secured for adjustment to the cross member 23 and carry at their upper ends a cross head 25, the latter being preferably hollow as best shown in Figure 2.

. The two electrodes 26a and 27a of the arc lamp are arranged for co-operation in the auxiliary -frame provided by the auxiliary tubular members. The upper electrode 26a is secured in a holder 26 which is supported by the cross head 25 for universal adjustment. For this purpose, the holder 26 is formed with a flattened ballshaped head 28 (Figs. 2, 3 and 4) which ts in a socket provided in the cross head. The socket consists of an opening 29 in the rear wall 30 of the cross member,Y the said opening being of a smaller diameter than the ball 28, A second opening 31 is formed opposite the opening -29 in the front wall of the crosshead, the last mentioned opening having mounted therein a cupshaped cap 32. The cap 32 may be adjusted with respect to the ball 28 by means of a plate 33 which is secured at either side of the cap to the cross head. In securing the holder- 26 to the cross head 25 for universal adjustment, the plate 33 is loosened and the head 28 is inserted through an opening 34 in the lower wall of the cross head with its flattenedsides extending lengthwise of the head. vThe head is then rotated through an angle of ninety degrees to thel position shown in Figure 4, whereupon the plate 33 may be tightened.

The holder 26 includes a body 35 (Figs. 3 and 5) to which the upper electrode is' secured and which is insulated from the head 28 as by an insul lating disc 36, the head and body portions of the holder being provided with cup shaped recesses within which the insulating disc fits, thereby preventing its disintegration even though it becomes cracked or otherwise injured in use. The head 28, body 35, and interposed insulating disc 36 are secured together as a unit by a rod 37 which is connected to the body 35 but insulated from the head 28 by the oversize opening 38 through which it extends and by the insulating washer 36. In this connection, it will be understood, of

course, that the rod 37 also functions as a conductor to form part of the arc circuit. The electrode 26a is adapted to be removably secured to the body 35. To this end the said body is formed with a V-shaped slot in which the terminal portion of the electrode may be positioned and secured as by a plate 40 (Fig. 5). A baille plate 41 having a central opening through which the electrode passes is secured in spaced relation with respect to the body35, the said baille plate being designed to prevent overheatingI of the electrode holder. By Virtue of the universal adjustment of the upper holder 26, fresh electrodes may be readily aligned at the outset of their use so that they will co-operate without further adjustment, until one of them is substantially entirely consumed` and this despite the fact that the electrodes, which are supported by the extremities,

. may be warped.

t \As'illustrated, the lower electrode 27a is mountfed for axial movement toward the upper electrode 26a, the fo'ij'men'for.convenience being hereinafter designated as the controlled or lower electrode. 'I'he controlled electrode is carried'by a holder 27 which is substantially similar to the upper holder 26 and is best shown in 'Figure 6. It includes a body 42 to which the lower electrode is clamped as by a plate 43 (Fig. 7) A baffle plate 44 is secured to the upper face of the body but in spaced relation therewith, the said baille plate being designed to prevent overheating of the holder 27.

The lower holder also includes a hollow stem 45 which is insulated from the body 42 of the holder as by an insulating disc 46, the latter being positioned in cup shaped recesses formed in the lower face of the body and the upper end of a flanged member 47 which is secured to the stem 45. A lower cross head 48 is included in the lower holder assembly and is formed with a pair of laterally extending arms 49. The various parts of the assembly are secured together as a unit by a longitudinally extending rod 50 which is connected tc the body 42 of the holder but is insulated from the stem 45. To this end, therefore, the said rodis smaller in diameter than the opening through the stem, this construction providing an insulating space between the rod and the stem. An insulating bushing 51 (Fig. 18) is mounted in the lower -end of thestemto extend beyond said end so that the nut 52 upon the lower end of the rod may be tightened to draw the elements of the assembly together. In this connection, it is to be noted that during such tightening the rod 50 is tensioned and hence avoids possibility of its contacting withthe inner wall of the stem. However, if desired, an insulated spacer 53 may be mountedupon the rod 50 to insure this.

The lower holder 27 is mounted for movement in the frame of the lamp by means of its stem 45. For this purpose, opposed bosses 54 which carry upper and lower bushings 55 and 56 respectively are formed in the cross member 23. The bore of the upper bushing 55 is enlarged at its upper end to provide a chamber to receive a packing ring 57 which is held therein in any suitable manner, the said ring being adapted to wipe the stem 45 during movement of the holder.

Means is provided which normally tends to lift the lower holder 27 toward the companion holder 26. This means includes a pair of weights 58 which are connected to the laterally extending arms 49 of the lower cross head 48 as by strands 59 (Fig. 2). In order that the weights 58 act in the manner described; the strands 59 pass over pulleys 60 which are secured to the cross member 1 23. As stated, the weights 58 normally urge the stem 45 and the holder 27 carried thereby toward the upper holder 26. In order to prevent sudden movements, either up or down, of the lower holder, means is provided for damping all y f may be filled by any suitable fluid 62 which is i utilized to prevent` sudden movement of theweights 58 in either direction. The relative diameters of the receptacles 61 and the enlarged `portions of the weights 58 may be varied to meet.

different requirements.

The upward movement of the lower holder 27 I resulting from the action of the weights 58 is, of course, faster than the rate of consumption of the electrodes. yIt is, therefore, necessary to provide means which will function to counteract the action of the weights 58, either. entirely or in part, so that the movement of the lower electrode 27a may be controlled to establish and'maintain a substantially uniform arc. To this end, a clutch 63 is employed which is operative to engage and release the stem 45 as required. The said clutch is mounted upon the stem 45 within the cross member 23. It includes a pivoted member 64 (Fig. 8) which is provided With a gripping ring 65, the latter having a central opening relatively greater in diameter than the outer diameter of the stem 45, and being tapered from its upper edge toward the said., stem. In this connection it is to be noted that the stem 45 is fitted in upper and lower'bushings 66 and 67 respectively, and that while the bushings 66 and 67 are concentric with the stem 45 the gripping ring is mounted in eccentric relation with respect to the said stem. The gripping ring 65 is normally urged upwardly about its pivot by a spring 68, which is compressed between the free end of the pivoted member 64 and a shoulder 69 formed on thebody of the clutch, to engage the stem 45 and urge it against the opposite side of the bushing 66. With the gripping ring functioning -in this manner, the clutch and stem 45 'are tightly secured against relative longitudinal movement. The clutch is released by the depression of the pivoted member 64 against the action of its operating spring 68. This is accomplished by a pivoted operating elementv 70 which is rforked at its free end to embrace the stem 45 'and extend beneath the bushing 55. The operating element 70 normally extends angularly toward the bushing 55v with respect to the pivoted member 64 of the clutch by virtue of a pin 71 carried by the said element and resting upon the pivoted member. From this it will be apparent that by depressing the operating element 70 movement is transmitted through the pin 71 to the pivoted member 64 to move it downwardly against the action of the spring 68. The downward movement of thesaid pivoted member, of course, results in the gripping ring 65 moving toward a concentric position with'respect to the stem 45 and results inthe release of the same.v

The clutch`63 is connected by a pair of links 72 (Fig. 11) to a horizontal member 73 which is pivotally mounted upon a transverse pin 74 supported by upstanding lugs 75 preferaby formed integral with the cross member 23. The pivotally mounted member 73 includes a pair of arms 76 which are spaced to straddle the sleeve 77 of the clutch at a sufcient distance therefrom so that they may overlie and be connected to the lower ends of the links 72. vAt one end, the arms 76`are connected to an armature 80 which is mounted for movement in a solenoid 81. lThe solenoid is supported upon'a suitable base 82 which carries a pair of opposed pulleys 83, the latter engaging the armature along its margins to prevent vibration.

In this connection it isto be noted that the solenoid 81 is, as shown in Figure 16,l connected in series with the arc of the lamp, hence as the electrodesy are consumed and the arc`becomes longer thetotal impedance in the arc circuit increases correspondingly. As the arc circuit is connected to a source of supply of a constant potential, an increase in^the arc length results in a decrease in the current. Thus as the arc increases or decreases in` length, the solenoid being in series with the said arc pulls more or less upon the armature with av corresponding pull upon the clutch 63. At" this pointit 'should be noted that each time the electrodes are brought together to start the arc the clutch is adapted to Withdraw the lower electrode to establish the required length of arc. In this movement, of course, the clutch is moved away from the bushing 55 against which it abuts to effect its release from the stem of the holder. It is, therefore,

y necessary that the actuating or regulating mechanism be designed so that the lower electrode will be fed at a rate determined by the consumption of the electrodes until the operating member of the clutch has engaged the bushing 55 to effect its release, from this point on the feeding of the electrode. being effected by the slipping of the clutch. In other words, after the required arc has been established the clutch moves through a determined range while it is engaging the stem of the electrode before it permits slippage of the holder. 'Ihis being the case, it is at once obvious that as the movement of the clutch while it-is engaged with the stem 45 is regulated by the solenoid 81, that the armature of the said solenoid must also have a range of vmovement determined by the range of movement of the clutch. As it is intended that an arc of a substantially uniform length be maintained at'all times, the current must remain constant. However, the current being constant, the pull upon the armature 80 varies depending upon the position in its range of movement, as is graphicaly shown in Figure 17. In order to` counteract the action of the solenoid to such an extent that the resultant force acting upon the pivoted member 73 is substantially the. same anywhere within the' range of movement of the clutch 63 I employ a spring 79 in conjunction with the solenoid 81. This spring isIconnected to the opposite end of the pivoted member 73 which is formed into a solid extension, lthe said extension projecting around and in front of a main tubular support 21 tol form a handle 78.

The range of movement of the armature 80 represents only a part of the total effective range of the solenoid. A graphic representation of the .pull of the spring 79 is shown in Figure 17 in connection with the illustration of the pull curve of the solenoid 81. It will be noted that that portion 83 ofthe solenoid pull curve which represents the pull of the solenoid in the range of movement utilized is substantially the same as that portion 83a of the straight line representing the spring pull, it being understoodof course, that the-spring pull is opposite to that of the solenoid pull. The weights 58, as stated, tend to lift the holder 27 and this force is, of course, added to that of the spring 79. Thus it is evident that for a fixed value of current, the pull of the spring 79 plus the unbalanced weight of the weights 58 is equal to tne pull of the solenoid 81 at any point between a and b.

With this arrangement, assuming the arc has just been started, the lower 4electrode is retracted to establish the required arc, in which movement the clutch is withdrawn out of contact with the bushing 55. As the electrodes are consumed with an increase in voltage and decrease in current, the solenoid is correspondingly affected, that is to say, its pull is weakened and it permits the spring 79 and weights 58 to feed the electrode and keep the are uniform. In a like manner, when the electrodes are initially brought together and there is a large amount of current flowing through them, the solenoid is effective, against the spring 79 and weights 58, to lengthen the arc.

In other words, this neutral equilibrium for a constant current becomes a stable equilibrium,

since the solenoid opens the arc to such a length.

that the current equals that for which the spring and solenoid pull curves become equal. This enables the production of the required arc at a normal current value and insures its maintenance even after the electrodes have been consumed to such an extent as to require clutch slipping.

In connecting the lamp to a source of supply, a Wire A (Fig. 16) leading to one side of the power line is connected to the solenoid 81 and from the solenoid is connected to the end of the rod 50, there being a loose lead or pigtail interposed between the latter two connections to permit movement of the stem 45. The circuit continues from the rod 50 to the body 42 of the lower holder 27. From the lower holder, that path of current is through the electrodes 27a and 26a to the upper holder 26. Two wires 84 and 85, in parallel, are connected to a wire B which leads to the other side of the power line, one of these wires being returned through each of the auxiliary tubular members 22. The current is divided i'n this manner so that the arc will be equally repelled by both of the magnetic fields set up bythe current passing through the wires 84 and 85 and hence remain straight, thus facilitating the uniform emission of light in all directions. However, if it is desired that the light be emitted more in the direction of one of the tubes 22 .than the other all of the current may be passed through one of the wires depending upon the direction in which the light is to be emitted.

In order to indicate whether the power is off or on when the electrodes are separated and no current is flowing, a pilot light 86 may be connected across the two electrodes. The power being on and the electrodes separated with no current flowing the light will glow brightly.

- When the arc is established, the light will still be illuminated but less brightly since the voltage across the electrodes is lessened, whenthe arc is established, by the amount `of the voltage drop.

in the ballast resistance or inductance in the arc circuit. I

Suitable means is provided whereby the feeding movement of the ylower electrode 27a may be automatically stopped after there has been a predetermined consumption of the electrodes, said means, as illustrated, including an eye 87 and companionhook 88 which' are formed respectively upon the lower holder 27 and cross member 23. As best shown in Figure 13, the

ysaid hook and eye are adapted to co-operate' with a chain 89 or other suitable means whereby when there has been a predetermined upward movement of the holder 27 the chain will become eiective to prevent its further movement.' By virtue of this arrangement, accidental operation of the'lamp beyond the time required is pre,- vented and allowance is thereby automatically made for intervals during which the lamp is not in operation, that is to say, during such periods as the `arc may be blown out or the power shut 01T. When the lamp is not in operation the holder 27, which will always move to the limit of its upward movement, may bel held` in its down position by a link 92.

The space within the main tubular supporting members 21 may befutilized to storeused and fresh electrodes. For this purpose, receptacles 90and 91, illustrated in Figures 14 and 15 respectively,'r`n`ay be removably supported in the Aupperends of the said members, the receptacle 90 being available yfor used or discarded elec- Lsama I trodes while the receptacle l91 is available for containing a supply of fresh electrodes.

In the use of the lamp, the electrodes being connected to a source of power, the pilot light 86 glows brightly. Upon removal of the latching link 92, the holder 27 is released and with the clutch 63 is moved upwardly, the clutch releasing the stem 45 as it moves against the bushing 55 to permit continued upward movement of the holder until the electrode '27a carried thereby touches the companion electrode 26a. A path of current is thereupon established through the electrodes and the solenoid 81. The solenoid acting upon the armature retracts the clutch 63. During its initial downward movement, While it is engaging the bushing 55,

the clutch has no eiect upon the stem 45 ofthe holder. However, upon continued downward movement the clutch 63 first engages the stem 45 and upon further downward movement pulls with it the holder 27 to a distance determined by the required arc. When this arc has been established, the pivoted operating element 70 of the clutch is spaced from the bushing 55 which effects the operation of the same as shown in Fig. 8. As the electrodes are consumed, the solenoid 8l functions, in the manner described to move the clutch and hence the holder carried thereby to compensate for such consumption. This feeding movement of the clutch continues until the pivoted operating element 70 engages the bushing 55 whereupon continued movement of the clutch effects release of the stem thereby permitting the weights 58 to effect a further upward movement of the holder 27. The clutch permits this movement until the current in the circuit has again reached the required value whereupon it again engages the stem 45. Thus, as the electrodes are consumed, th'e clutch permits slippage of the holder 2 7 under the influence of the weights 58 at a rate commensurate with Ktheir consumption.

It is to be noted that the inertia of the feed mechanism is large as compared to the Weight which produces its motion. Further, by damping the feed mechanism instead of the solenoid or cross member which have a much less effective inertia, the acceleration of the mechanism is small when the clutch is released. This permits .a smooth feed as the progress of the mechanism is by small-increments.

Having fully described my invention I claim:

1. In an electrode feed mechanism, an electrode holder, means for moving said holder in the. direction of feed, means for engaging, said holder within a range of its movement, means for regulating the movement of said holder within said range so as to maintain a substantially uniform arc, means operative upon said holder reaching the limit of said range to render said engaging means inoperative and thereby permit said holder to be moved further in the direction of feed and means for stopping the feeding movement of the holder after a predetermined consumption of the electrode carried'by it, said last named means being adjustable whereby the amont'of such consumption may be varied at will.

.2. In an electrode feed mechanism, an electrode holder, means normally tending to move said holder in the direction of feed, means for engaging said holder within a range of its movement, means for regulating the movement of .said holder within said range so as to maintain a substantially uniform arc, means operative upon said holder reaching the limit of said range to render said engaging means inoperative and thereby permit said holder to be moved further in the direction of feed and means for stopping the feeding movement of the holder after a predetermined consumption of the electrode carried by it, said last named means being adjustable whereby the amount of such consumption may be varied at will.

3. In an electrode feed mechanism, an electrode holder, means normally tending to move said holder in the direction of feed, means for engaging said holder within a range of its movement, means for regulating the movement of said holder Within said range so as to maintain a substantially uniform arc, said regulating means adapted to overcome said means normally tending to move the holder in the direction of feed should the arc become too short, means operative upon said holder reaching the limit of said range to render said engaging means inoperative and thereby permit saidholder to be moved further in the direction of feed and means for stoppingthe feeding movement of the holder after a predetermined consumption of the eleotrode carried by it, said last named means being adjustable whereby the amount of such consumption may be varied at will.

4. In an electrode feed mechanism, an electrode holder, means for moving said holder in the direction of feed, means for engaging said holder within a range of its movement, means for regulating @the movement of said holder within said range so as to maintain a substantially uniform are, means operative upon said holder reaching the limit of said range to render said engaging means inoperative and thereby permit said holdfor stopping the feeding movement of said holderl after a predetermined consumption of the electrode carried by lt.

5. In an electrode feed mechanism, an elec-l trode holder, means for lifting said holder to feed the electrode carried thereby, means for engaging said holder within va range of Aits movement, means for regulating the movement of said holder within said range so as to maintain a substantially uniform arc and means operative upon said holder reaching the upper limit of said range to render said engaging means inoperative and thereby permit said electrode to be lifted further to compensate for its further consumption and thereby prevent increase in the arc length.

6. In an electrode feed mechanism, an electrode holder, means normally tending to lift said holder to feed the electrode carried thereby, means for engaging said holder within a range of its movement, means for regulating the movement of said holder within said range against the "action of said lifting means ,if the arc is too short so as to maintain a substantially uniform arc and means operative upon said holder reaching the upper limit 'of said range to render said engaging means inopeative to thereby permit said lifting means to feed said electrode further and compensate for its further consumption.

7. In an electrode feed mechanism, an electrode holder, a weight for lifting said holder to feed the electrode carried thereby, `means' for engaging said holder within a range of its movement, means for regulating the movement of said holder within said range so as to maintain a lsubstantially uniform arc and means operative upon said holder reaching the upper limit of operative and thereby permit said weight to lift said holder and feed said electrode.

8. In an electrode feed mechanism, an electrode holder, means for moving said holder in the direction of feed, a clutch engaging said holder in a range of its movement, said clutch including a pivoted gripping member, resilient means for forcing said gripping member into engagement with said holder and a pivotally mounted operating element for compressing said resilient means to release said gripping member, means for regulating the movement of said holder in said range to maintain substantially uniform arc and means operable upon said holder reaching the limit of movement in said range for operating said operating element -to release said gripping member and permit said moving means to move said holder further in the direction of feed.

9. In an electric arc lamp, a movable electrode, a holder for said electrode, means for moving said holder to feed said electrode toward the companion electrode, means for engaging said holder within a range of its movement, means tending to move said engaging means and the holder carried thereby toward the companion electrode, means responsive to current changes in the are circuit .resulting from changes in distance between the electrodes as they are consumed for counteracting both of said moving means more or less and thereby maintain a substantially uniform arc and means for rendering said engaging means inoperative upon said holder reaching the limit of its range of` movement and thereby permit said moving means first mentioned to move said holder further and feed said electrode.

10. In an electric arc lamp, a movable electrode, a holder for said electrode, means for moving said holder to feed said electrode toward the companion electrode, means for engaging said holder within a range of its movementbresilient means tending to move said engaging means and the engaged holder toward the companion electrode, means responsive to current changes in the arc circuit resulting from changes in the distance between the electrodes as they are consumed for counteracting both of said moving means more or less and thereby maintain a substantially uniform arc and means for rendering said engaging means inoperative upon said holder reaching the limit of said range and thereby permit said means first mentioned to move said holder further and feed said electrode further.

l1. In lan electric are lamp, means for maintaining a substantially uniform arccomprising a movable electrode, an electrode holder, means for moving said holder to feed said electrode, means engaging said holder Within a range of its movement, means for regulating the feed of said electrode within said range, means operative upon said holder reaching the limitv of said range and there being a further consumption of the electrode to render said engaging means inoperative and permit said electrode to be moved further by said first named means Yto maintain a uniform arc,

said engaging means being again rendered operative upon further movement of the electrode to a suitable extent.

12. In an electric arc lamp, means for maintaining a substantially uniform arc comprising a. movable electrode, an electrode holder, vmeans normally tending to move said holder to feed said electrode, means engaging said holder within a range of itsmovement, means for regulating the feed of said electrode within said range, means operative upon said holder reaching the limit of said range and there being a further consumption of electrode to render said engaging means inoperative and permit said electrode to be moved further by said rst named means so as to maintain a uniform are, said engaging means being again rendered operative upon movement of said electrode to a suitable extent.

13. In an electric arc lamp, means for maintaining a uniform arc comprising a movable electrode, an electrode holder, means for moving said holder to feed said electrode, a clutch normally engaging said holder within a range of its movement, means for regulating the feed of said electrode within said range, means operative upon said holder reaching the limit of said range and there being further electrode consumption to release said clutch and permit further movement of the electrode by said 'first named means thereby to maintain a uniform arc.

14. In an electric arc lamp, means for maintaining a substantially uniform arc comprising a movable electrode, an electrode holder, means acting on said holder to feed said electrode, a clutch normally engaging said holder within a range of its movement, means acting on said clutch to move it in the direction of feed, means responsive to current changes in the arc circuit resulting from changes in distance between the electrodes as they are consumed for counteracting in 'said range, said means acting on said holder and said means acting on said clutch more or less and means for releasing said clutch when said holder reaches the limit of said range and there being av further consumption of i the electrode whereby said means acting on said holder moves it and said electrode further to a suitable extent.

15. In an electric are lamp, means for maintaining a substantially uniform arc comprising a movable electrode, an electrode holder, means acting on said holder to feed said electrode, a clutch normally engaging said holder within a range of its movement',means acting on said clutch to move it in the direction of feed, means responsive to current changes in the arc circuit lresulting from changes in distance between the electrodes as they are consumed for counteracting Within said range, said means acting on said holder and said means acting on said clutch and thereby maintain a substantially uniform arc and means for releasing said clutch when said holder reaches the limit of said range and there being a further consumption of the electrode whereby said means acting on said holder moves itand its electrode further to a suitable extent, said clutch being again rendered operative upon such occurrence.

16.In an electric arc lamp, means for maintaining a substantially uniform arc comprising a movable electrode, an electrode holder, means acting on said holder to feed said electrode, a clutch normally engaging said holder within a range of its movement, resilient means acting on said clutch tending to move itin the direction of feed, means responsive to changes in current in the arc circuit resulting from changes in the distance between the electrodes as they are consumed for counteracting within said range, said means acting on said holder and said resilient means acting on said clutch, the said counteracting means being( adapted to balance at any point in said range both said means acting to move said holder and said resilient means acting on said Clutch thereby maintaining a substantially constantl arc and means for releasing said clutch when said holder reaches the limit of said range and there being a further consumption of the electrode whereby said means acting on said holder moves it further to feed said electrode to compensate for such consumption.

17. In an electric arc lamp, an electrode holder comprising a body to which an electrode is secured, a hollow stem connected to but insulated from' said body, an electrical conductor in said stem connected to said body but insulated from said stem, means for moving said holder and means engaging said stem for regulating the movement of said holder.

18. In an electric arc lamp,an electrode holder comprising a body towhich an electrode is secured, a hollow stem connected to but insulated from said body, an/ electrical conductor held in said stem under tension and connected tosaid body but insulated from said stem, means for moving said holder and means engaging said steml for regulating the movement of said holder. 19. In an electric arc lamp, an electrode holder comprising a body to which an electrode is secured, a hollow stem connected to but insulated from said body, an electrical conductor in said stem connected to said body but insulated from sad stem, means for moving said holder in the direction of feed, means engaging said stem within a range of movement of said holder, means for regulating the movement of said holder-Within said range so as to maintain a substantially uniformare and means operative upon said holder reaching the limit of said range to render said engaging means inoperative andthereby permit said holder to be moved further in the direction of feed.

20. In an electric arc lamp having companion electrodes, a support for one of said electrodes, a holder for said electrode comprising a body to which the electrode is secured, a hollow member securedto but insulated froml said body and adapted to be secured to said support, an electrical conductor in said hollow member connected to said body but insulated from said member and adapted to carry current to said electrode, a holder for the other electrode, means for moving said holder and means for regulating the movement of said latter holder for maintaining a substantially uniform are between said electrodes.

21. In an electrode feed mechanism, an electrode holder, means for moving said holder in the direction of feed, means for damping the action of said means, means for engaging said holder within a range of its movement, means for regulating the movement of said holder within said range so as to maintain a substantially uniform arcand means operative upon said holder reaching the limit of said range to render said engaging means inoperative and thereby permit said holder to be moved further in the direction of feed, said damping means controlling said means first mentioned so that it moves said electrode holder relatively-slowly in the direction of feed when said engaging means is inoperative.

22. In an electric arc lamp, an electrode holder comprising a body to which an electrode is secured, a hollow stem connected to but insulated from said Ebody and adapted to house the conjf

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