US2641729A - Carbon holder for arc lamps - Google Patents

Description

June 9, 1953 H. 1.. CRONKHITE 2,641,729

CARBON HOLDER FOR ARC LAMPS Filed June 16, 1951 2 Sheets-Sheet l June 9, 1953 H. L. CRONKHITE 2,641,729

CARBON HOLDER FOR ARC LAMPS Filed June 16, 1951 2 Sheets-Sheet 2 ATTOKNEJS Patented June 9, 1953 UNITED STATES PATENT OFFICE 16 Claims.

This invention relates to a device for positioning and holding a carbon in an arc lamp, which device preferably includes an auxiliary holder for positioning a carbon to be first burned and which operates to automatically replace such carbon by a new carbon without noticeable interruption of the flame of the arc.

The carbon holder of the invention is particu larly designed for application to types of arc lamps used in professional models of motion picture projectors, for in this field the operation of the device is especially useful in solving a prob-- lem of high carbon wastage.

The following discussion of the nature of the invention and its place in the art will be confined to the motion picture type of lamp, it being understood, however, that many of the operating problems of such lamps and features of the in vention which overcome these problems, are applicable to are lamps generally.

High wastage of carbon on motion picture are lamps is due to the fact that here a carbon can not be replaced if consumed during the performance as it necessitates stopping the projector. Since running times of reels of films are by no means uniform so as to permit the length of a carbon to be designed for the running time of a standard reel, a large quantity of partially used stubs are daily accumulated, all having a burning time so short as to render them normally unusable. A partial solution of carbon wastage problem is disclosed in U. S. Letters Patent No. 2,362,281, but that device has not proved satisfactory for the following principal reasons: Any carbon-changing device designed to overcome this wastage must be capable of replacing one carbon with another without interrupting the arc, must be capable of taking used carbons of varying lengths, must be capable of automatically initiating the change to a new carbon when the used one is consumed without possible malfunctioning due to seizure between parts from heat or electric arcing, and, in general, must completely satisfy the rigid safety requirements prescribed for arc lamps in this field. Parts which comprise the holder for the stub carbon should be readily movable to an inoperative position where they offer no interference with the functioning of the parts comprising the main carbon holder.

Features which overcome these disadvantages are included in the device of the present invention which also provides a unit, including main and auxiliary or stub carbon holders, that can be substituted for the existing carbon holder in various present designs of commercial lamp house by the use of simple adapters or mounting brackets. This unit includes provision for vertical and lateral adjustment of the parts so that any carbon carried thereby can readily be brought into proper alignment and registered with the arc of the lamp and with the other carbon carried by the device.

The accompanying drawings illustrate a preferred embodiment of the invention as applied to the positive carbons of a lamp house, and comprise the following views:

Fig. l, a side elevation of the device in representative association with a feed screw of the lamp house, with the carbons being indicated in broken line, and showing the relative position of the parts at the instant the first burned or stub carbon is replaced by the main or successive carbon. The parts which comprise the auxiliary carbon holder for the stub carbon are shown in their inoperative position in dotted lines;

Fig. 2, a plan view of the device shown in Fig. 1;

Fig. 3, an enlarged sectional detail taken along the line 33 of Fig. 1 and showing the connection of the arm carrying the auxiliary carbon holder to the main carbon holder assembly;

Fig. 4, a perspective View of the clamp for the stub carbon;

Fig. 5, an end elevation of the device shown in Fig. 1 with a portion of the structure thereof being shown in section to bring out the interrelationship between the parts of the carbon holder assembly and the mounting bracket for supporting the same;

Fig. 6, a section taken along the line 6-6 of Fig. 1 and indicating the lateral adjustment and pivotal movement of the parts about a vertical axis.

Fig. 7, an elevation showing a pair of alternate style mounting brackets for the various parts of the device;

Fig. 8, a side elevation showing the relationship between a negative carbon, a stub carbon being first burned, and a main carbon which will shortly automatically replace the stub carbon after the latter is consumed;

Fig. 9, an end elevation taken along the line 99 of Fig. 8 to show the relationship between main and auxiliary carbons and the guide post which supports the latter and its carbon holder; and

Fig. 10, a sectional view taken along the line l0|ll of Fig. 8 showing the construction of the auxiliary carbon holder.

Referring to Fig. 1, a feed screw II is shown engaged by a carriage l2 so that rotation of the former will cause lineal movement of the latter. These parts are common to various types of arc lamps, though their particular design and relative location varies considerably in present types of lamp houses for commercial projectors, thereby presenting a problem in 'pIOViGlIlg a standardized carbon holder unit which can be substituted for the particular unit now employed in any one of these various types.

The present carbon holder unit has been designed to be supported by an adaptor or base member I3, whose construction will be described in detail hereafter, but which may be said to be generally comprised of a standardized portion for receiving and supporting the parts of the unit and a variable portion whose design can be accommodated to fit existing parts in presen lamp house constructions.

The member i3 is provided with an internal bore I4 (Fig. 5), and carries a U-shaped retainer [5 provided with an arcuate slot N: (Fig. 6). Bolt l1 passes through this slot into a threaded hole formed in a boss is of the adapter I3 to hold the retainer in place. Aset screw IE! (Fig. 1) projects through the boss l8 and into the bore [4, for a purpose which will presently be described.

The foregoing parts comprise the standardized portion of the adapter. The remaining portion comprises an attaching flange and bolts 2| for securing the adapter to the carriage l2 or equivalent moving part of a lamp house assembly.

The parts of the carbon holding unit consist first of a cylindrical bushing 22, provided with an eccentric hole 23 which is threaded and adapted to receive the threaded portion 24 of a pivot pin 25. ceived within the bore M of the adapter l3 and is machined with an upper groove 26 and a lower groove 21. When the bushing is assembled to the adapter the upper groove 26 is engaged by the retainer l5 and the lower groove 21 is engaged by the set screw I9. When the pivot pin is assembled to the bushing, it is held in position against rotation by a second set screw 33 carried by the bushing and engaging an intermediate cylindrical portion 28 of the threaded portion of the pivot pin.

An arm 29 is pivotally carried by the pin 25, being supported by a collar 3% formed on the pin, and held in position by a nut 3| engaging the threaded upper portion of the pin 25. After this nut 3| is assembled it is held in position against rotation by some suitable means such as a dowel 32 engaging a hole in the nut and the upper portion of the pin.

The arm 29 supports a bracket 34 (Fig. 5) which is secured thereto by bolts 35, an insulating pad 36 being placed between the arm and bracket and insulating collars 3'! being used between the bracket 34 and bolts so that the arm 29 and bracket 34 are electrically independent. The bracket 34 is formed with a forked upper end or clevis 38, and adjacent the clevis has a projecting shoulder 39 (Fig. 1) provided with a recess 40 to receive one end of a positioning spring 4|.

A main carbon supporting bracket 42 is pivotally carried by the bracket 34, for movement about a substantially horizontal axis defined by a pivot pin 43 extending across the clevis 38, and has a tongue 45 which is engaged by the other end of the positioning spring All. This bracket 32 also carries the carbon holder for the main carbon 46, which consists of an upper notched clamping block 41 against which the carbon 46 can be frictionally secured by the clamping action of a lower clamping block 48, movable towards or The bushing 22 is rotatably re- 7 4 away from the upper clamping block 41 by the rotation of a clamping screw 49.

The carbon to be first burned, which will be referred to for convenience as the stub carbon, 53, is held by a clamping head 5| secured to the outer end of an arm 52, the inner end of which is pivotally attached to the bracket 52 by the connection shown in detail in Fig. 3. This connection comprises a pivot pin 53 having a circular face 54 to which the arm 52 is eccentrically attached by ascrew 55. The pin is held in place by a retainer 58, and a piece of bonding wire 51, having one terminal 58 secured to the pin 53 and the other terminal 59 secured to the bracket 42,

is preferably employed to insure a good electrical I contact between the bracket 32 and arm 52 and minimize any arcing between the pin 53 and bracket which would tend to pit the mating surfaces and interfere withfree rotational movement of the pivot pin.

This pivoted connection of the arm 52 permits the arm to be rotated to an inoperative position where it projects in a direction substantially the reverse of the direction of burning travel of the device, as indicated by the dotted-line showing in Fi l.

Referring to Figs. 4 and 10, the stub carbon clamping head 5! is connected to theouter end of the arm 52 by a screw 6|, a spacer block 62 being positioned between these two parts and engaging a slot 63 in the arm 52 and a similar slot 64 in the clamping head, the angular relationship between the clamping head 5| and arm '52 being precisely defined and maintained by this connection.

A single block of material is preferably employed for the clamping head. It is formed with a slot 65 to provide a pair of clamping jaws 65 and 67, the jaw 61 being separated from the base 38 of the head by a section 33 of reduced thickness formed by the cutting of a vertical slot Hi. This increases the flexibility of the jaw 6'! and makes it more easily movable relative to jaw 66 by the rotation of a clamping screw H which joins the two jaws. This clamping screw threadedly engages a hole 12 in the jaw 66 and a collar 13 mounted in a hole M in the jaw 67 so that either'clamping or separating action is positively obtained by rotating the clamping screw H in the appropriate direction.

The lower portions of the jaws 66 and 6'5 are formed with tapered bottom faces 55 and 15 respectively (Fig. 9), these faces being formed to lie substantially tangent to the diameter, of the stub carbon 50, which is engaged by a circular recess H formed in the opposed faces of each of the jaws. The faces '55 and it meet to form an apex along the base portion 58 of the head, and this apex lies substantially flush with the lower surface 19 of the stub carbon 50, as can be clearly seen from the side elevation of Fig. 1.

An improved form of guide rest assembly is employed to successively support the stub and main carbons at a fixed point somewhat proximate to the location of the arc struck between the positive and the negative carbon. In addition to supporting the carbon as the carbon head assembly is gradually advanced by the rotation of the feed screw ll, this guide rest assembly also performs a function of contributing to proper alignment between the positive and negative carbons.

The construction of this guide rest assembly is similar to the construction of the carbon holder assembly in the sense that the main portion of the assembly is comprised of a number of standard parts having an interrelationship which permits them to be used in a number of designs of lamp house by employing a suitable base member or adapter. The base member consists of a suitable bracket 80 provided with a drilled boss 8|, adapted to be positioned so that the axis of the hole in the boss Bl extends substantially horizontally. This bracket 88 is designed to be attached to the particular supporting structure employed in any given design of lamp house and herein indicated by the member 82 in Fig. 1.

The main portion of the guide rest assembly consists of a clamping bracket 83 having a bore adapted to engage a guide post 8 clamping action being obtained by employing a split construction in the bracket 83 in conjunction with a clamping screw 85. Bracket 83 is also adapted to receive the end of an attaching bolt 85 which secures the main portion of the guide rest as- I sembly to the adapter bracket an. A pair of insulating washers 81, in combination with an internal insulating collar, electrically separate the clamping bracket 83 and bolt 85 from the adapter bracket 88, this construction being somewhat similar to the form of attachment between the arm 29 and bracket 34 illustrated in Fig. 5, and hence is not shown in detail.

The guide post 84 is formed with an upper notched surface 83 generally corresponding in configuration to the V undersurface of the clamping head 5|, and the upper side portion of the post 84, facing in the direction of movement of the carbons, is undercut as at 89. An auxiliary supporting pin 55 projects from one side of the post 84 and is adapted to support the arm 52 after the device hasoperated to replace the stub carbon 55) by the main carbon 48.

The operation of placing main and stub carbons in their respective clamps is facilitated by the fact that the main carbon holder assembly can be rotated about the pivot pin to a loading position. With the parts shown as in Fig. 6, this rotation occurs in a counterclockwise direction, the loading position of the main carbon holder assembly being indicated in broken lines and designated by the reference 92. Loading position is defined by the abutment of face 93 on the arm 29 against a stop 94 formed on the U-shaped retainer ring I 5. Operative position of l the main carbon holder assembly is defined by an engagement between the arm 29 and retainer ring [5 along a surface 85 of the latter. A detent 86, of resilient material, is secured to the arm 29 and operates to define the operative position of the assembly by the engagement between its outer end S? and the stop surface 94 an retainer ring l5.

A number of adjustments in the relative position of the parts are provided in order that the main and stub carbons carried by the carbon holder assembly can be positioned in proper alignment with the negative carbon. Proper alignment, in. an ideal sense, means that the axes of the negative carbon and main or stub positive carbons lie along the same line during burning. These adjustments, in the parts of the main carbon holder assembly, comprise, first, an adjustment of the operative position of the arm 29 ra dially about the pivot pin 25, this adjustment being effected by loosening the screw l1 and moving the retainer member l5 until the surface 95 thereof properly defines the operative position of the arm 29.

The lateral position of the axis of the pivot pin 25, eccentrically carried by the bushing 22, can be adjusted by loosening the set screw 19 and rotating the bushing 22; and in Fig. 6 the effect of such lateral adjustment is evident by comparison of the full-line position of the parts shown and the dotted-line position of the arm 29 indicated by the reference 290..

The vertical position of the arm 29 can be varied by loosening the set screw 33 and turning the nut 3| to screw the threaded base 24 of the pivot pin 25 into or out of the bushing 22.

An independent adjustment of the axial position of the stub carbon 59 is provided in the form of the connection between the stub carbon carrying arm 52 and the bracket 42, shown in Fig. 3. By loosening the screw 55 the position of the pivoted end of the arm 52 can be varied with relation to the axis of the pivot pin 53 supporting it.

At, the guide post assembly, vertical adjustment of the position of the notched supporting surface 88 is accomplished by loosening the clamping screw 85 and sliding the guide post 84 in the clamp 83. Lateral adjustment is accomplished by loosening bolt 86 and rotating the clamp 83 relative to its supporting bracket 80.

In the operation of the device, as the carriage 52 carrying the stub and main carbons is advanced by the rotation of the feed screw H, the stub carbon 58 is gradually consumed and progressively advanced over the notched surface 88 of the guide post 8 3. This movement continues until the clamping head 5!, which carries the stub carbon, is also advanced over the surface of the guide post, and culminates when the lower surface 78 of the clamping head 5| passes beyond the support of the notched surface 88 of the guide post, at which time the clamping head falls freely, carrying the remains of the stub carbon. An instant after this occurrence, the parts occupy a relationship such as shown in Fig. 1, with the stub carbon still falling and having been replaced by the main carbon which is now seated in the notched surface 88 of the guide post.

During the burning of the stub carbon 58 the main carbon 46 rests on the top of the clamping head 5: in a small notch 98 provided thereon (see Fig. 8). As long as the carbons are in this relationship the carbon supporting bracket 42 will be tipped in a clockwise direction about the pivot pin 43, compressing the spring 41. When the stub carbon head 5! advances beyond the guide post 84 and falls by gravity into the position shown in Fig. 1, the support given by the clamping head for the main carbon 45 will be simultaneously removed, and the main carbon will fall on to the notched portion 88 of the guide post 84 with a counterclockwise pivoting of the bracket 42 about the pivot pin d3 as urged by the force of the spring 4%, and the stub carbon will be immediately replaced by the main carbon.

Just prior to this occurrence, as shown by the relationship of the parts in Fig. 8, the main carbon 45 is adjacent to and above the arc struck between the stub carbon 58 and a negative carbon 99 and the main carbon is thereby preheated by the from this are so that when it falls into place it is in such a condition that an are between the main carbon and the negative car con 99 will immediately be struck, provided, of course, that its position with relation to the stub carbon has been properly adjusted before the device was put in operation. With proper adjustment, the interruption of the arc is so slight as to be not discernible by eye.

In setting the stub and main carbons up in the device in proper relationship for successive burning, the stub carbon 50 is first clamped in place by tightening the clamp screw H, and then the main carbon 46 is slid along the top of the stub carbon carrying head 5| until its tip I projects beyond the head a distance substantially equal to the consumed length of the stub carbon. In other words, at the time the stub carbon is replaced by the main carbon, the latter should fall into the exact position vacated by the former. One convenient way of adjusting the main carbon is to place its tip H30 the.

same, distance from the rear face ll of the clamping head 5| as will be the tip of the stub carbon 50 from that rear face llll when it is consumed and at the instant of its replacement. This distance is, of course, determined by the location of the guide post relative to the location of the arc.

This application is a continuation in part of my prior co-pending application Serial Number 108,369, filed August 3, 1949.

I claim:

1. A device for movably supporting a carbon to be first burned and a main carbon, of the type wherein said main carbon is retained in an assembly carried by a support for pivotal movement about an axis transverse to the path of movement of said device, said carbon to be first burned is retained in a projecting holder carried by said assembly for pivotal movement about an axis transverse to the path of movement of said device, and said carbons are successively positioned in the arc of a lamp by a stationary supporting member located in the path of movement of said device; characterized by said projecting holder including a supporting arm, a carbon clamping element positioned laterally thereon, said supporting arm being pivotally connected to said main carbon retaining assembly in lateral relationship to said stationary supporting member for noninterfering movement relative thereto.

2. The invention set forth in claim 1 further characterized by said device including means for adjusting the relative position between said main and said carbon to be first burned, occupied during the burning of the latter carbon, with respect to the longitudinal centerlines thereof.

3. The invention set forth in claim 1 further characterized by said holder for retaining a carbon to be first burned comprising a clamping element adapted to engage said carbon laterally, the lower surface of said clamping element being substantially contiguous to the lower surface of the carbon engaged thereby, the lower surface of said carbon and said clamping element presenting a substantially continuous line for contact with said stationary supporting member.

4. The invention set forth in claim 1 further characterized by said holder for retaining a carbon to be first burned being formed with a lower surface extending substantially contiguous to the lower surface of the carbon to be first burned retained thereby, said lower surfaces presenting a continuous line for contact between said carbon holder assembly and said stationary supporting element, the supporting surface of said supporting member extending in said direction of movement of said device beyond that portion of the body of said member below said supporting surface thereof.

8 5. The invention set forth in claim 1 further characterized by said projecting holder of said carbon holder assembly being also positioned laterally with respect to said main carbon and being pivotally carried by said main carbon retaining assembly for movement from an operative position extending in said direction of movement of said device to an inoperative position extending substantially opposite to said direction of movement.

6. A device of the type described including a carbon holder assembly, a base portion, means for mounting said base portion in a lamp house for movement toward the arc of a lamp, a stationary supporting element comprising a pedestal member and means for mounting said pedestal member in a fixed position in said path of movement; characterized by said carbon holder assembly being mounted for pivotal movement laterally of said path of movement from an operating position to a loading position, and means carried by said base portion for adjustably defining said operating position of said carbon holder assembly.

7. The invention set forth in claim 6 further characterized by means for adjusting the position of said supporting member laterally and vertically relative to said path of movement.

8. The invention set forth in claim 6 further including means for adjusting the location of the axis of said pivotal movement of said carbon holder assembly laterally with respect to said path of movement.

9. The invention set forth in claim 6 further including means for adjusting the position of said carbon holder assembly vertically with respect to the said mountingmeans therefor.

10. The invention set forth in claim 6 wherein the mounting means for said carbon holder assembly comprises a mounting bracket having a portion of standard design adapted. to engage said base portion and a portion of variable design adapted to engage the supporting structure of a lamp house, and wherein the means for mounting said fixed supporting member similarly comprises a mounting bracket having a portion of fixed design adapted to carry said supporting member and a portion of variable design adapted to engage the fixed structure of the lamp house.

11. The invention set forth in claim 6 wherein said base portion of said device includes a vertically disposed pivot pin, a bracket pivotally carried by said pin and adapted to support said carbon holder assembly, means electrically insulating said carbon holder assembly from said pivot pin, and means for adjusting said pivot pin vertically and laterally relative to the mounting means for said base portion.

12. The invention set forth in claim 6 wherein said base portion of said device includes a vertically disposed pivot pin, a bracket pivotally carried by said pin and adapted to support said carbon holder assembly, means electrically insulating said carbon holder assembly from said pivot pin, means for adjusting said pivot pin vertically and laterally relative to the mounting means for said base portion, said means for adjusting said pivot pin comprising a bushing adapted to engage said mounting means and rotatable with respect thereto, said pivot pin threadedly engaging said bushing, the axis of said threaded engagement being displaced from the center of said bushing.

13. In combination, means for mounting a carbon in an arc lamp, including a carbon holder assembly adapted to retain a carbon and a fixed supporting member adapted to guide said carbon, an adapter bracket for mounting said carbon holder assembly to the movable carriage of a lamp house, means for connecting said carbon holder assembly to said adapter bracket to permit relative movement therebetween in directions perpendicular and transverse of the path of movement of said carbon holder assembly, an adapter bracket for mounting said supporting member to the fixed structure of a lamp house, and means for connecting said supporting member to said latter adapter bracket to permit relative movement between the supporting surface of said member and said adapter bracket in directions perpendicular to and transverse of the path of travel of said carbon holder assembly.

14. The invention set forth in claim 13 wherein said means for connecting said carbon holder assembly to the adapter bracket therefor further includes means for permitting pivotal movement of said carbon holder assembly relative to said bracket from an operative position to a loading position.

15. The invention set forth in claim 13 wherein said means for connecting said carbon holder assembly to the adapter bracket therefor further includes a pivotal connection about an axis transverse to the path of travel thereof and said carbon holder assembly further includes means for retaining a main carbon, a projecting element pivotally carried by said assembly and including means for retaining a carbon to be first burned, said projecting element being positioned laterally with respect to said retaining means for said carbon to be first burned and the position of said main carbon.

16. The invention set forth in claim 13 wherein said means for connecting said carbon holder assembly to the adapter bracket therefor further includes a pivotal connection about an axis transverse to the path of travel thereof and said carbon holder assembly further includes means for retaining a main carbon, a projecting element pivotally carried by said assembly and including means for retaining a carbon to be first burned, said projecting element being positioned laterally with respect to said retaining means for said carbon to be first burned and the position of said main carbon, and means for adjusting the point of pivotal connection between said projecting element and said carbon holder assembly.

HARRISON L. CRONKHITE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,269,771 Klamm Jan. 13, 1942 2,362,281 Kuehl Nov. 7, 1944 2,375,476 Hunt May 8, 1945 2,584,579 Hanover Feb. 5, 1952

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