US2173948A - Resistance unit for spot and flood lamps - Google Patents

Description

Sept. 26, 1939. P. MOLE ET AL 2,173,948

RESISTANCE UNIT FOR SPOT AND FLOOD LAMPS Filed NOV. 29, 1957 2 Sheets-Sheet l E at Sept. 26, 1939. P. MOLE ET AL RESISTANCE UNIT FOR SPOT AND FLOOD LAMPS Filed NOV. 29, 1957 2 Sheets-sheaf. 2

V/llll/I/ld 7 who my? Patented Sept. 26, 1939 UNITED STATES PATENT OFFICE RESISTANCE UNIT FOR SPOT AND FLOOD LAMPS Application November 29, 1937, Serial No. 176,993

6 Claims.

My invention relates to spot and flood lamps and has particular reference to a resistance unit which may be employed in connection therewith.

In spot lighting and flood lighting, particularly in the motion picture industry, it is the common practice to employ a lamp, usually an arc lamp, adapted to be supported upon a supporting yoke permitting the lamp to be readily moved about to direct the illumination therefrom upon a particular portion of a motion picture set desired to be illuminated. The yokes of these lamps are adapted to be mounted upon a portable stand having rollers or casters thereon permitting the same to be readily shifted about the fioor upon which the stand rests, while frequently it is necessary to mount the lamps upon overhead structures, known as parallels, comprising balconies upon which lamps are mounted so as to cast their illumination downwardly upon the sets from overhead, in which case, the stands are dispensed with, the lamps being mounted directly on the overhead structure or other yokes are mounted upon the overhead structure.

In order to control the illumination of the lamps and particularly to provide the necessary resistance in series with the electrodes of are lamps employed for this purpose, it is necessary to provide a bank of resistance elements, the resistance characteristics of which must be carefully selected for the particular lamp with which they are associated. When the lamps are to be employed upon the portable stands, the resistance bank is preferably also mounted upon the stand so as to provide relatively close electrical coupling between the resistance elements and the electrodes of the lamp, so that the voltage drop in the conductors extending between the electrodes and the resistance elements may be maintained at a minimum and for this purpose it has been the common practice to mount the resistance elements directly upon the portable stand. When, however, it is necessary to place the lamps in the parallels, the lamps are removed from the portable stands and mounted in the parallels, requiring the coupling of the resistance elements which remain upon the floor to the lamps which are now spaced a considerable distance away from the stands by means of relatively long conductors. Since the amount of resistance employed with each lamp is carefully selected to conform with the desired operating characteristics of the lamp, it will be apparent that the employment of the long conductors necessary to extend from the floor to the overhead mounting of the lamps introduces additional resistance in circuit with the electrodes, altering the operating characteristics of the lamp and usually diminishing the intensity or brilliance of the illumination produced thereby.

It is therefore an object of our invention to provide a resistance unit which may be selected and adapted to any particular lamp and to so construct the resistance unit that it may be removably mounted upon the portable stand when the lamp is to be used upon the stand, the unit being so constructed as to permit its disassembly from the stand and ready mounting in the parallels close to the lamp for which the unit is designed, thus enabling the same coupling conductors to be employed either when the lamp is mounted upon the portable stand or when the lamp is placed in the parallels or any other location remote from the portable stand.

Another object of our invention is to provide a resistance unit which may be readily placed upon or removed from the portable stand with a minimum of efiort.

Another object of our invention is to provide a resistance unit for lamps of the character described, wherein the resistance elements are contained within a housing adapted to be placed about the central stem or support of a portable stand or removed therefrom without requiring the disassembly of any of the resistance elements or the housing.

Another object of our invention is to provide a resistance unit of the character set forth, wherein each of the resistance elements employed to make up the resistance unit associated with any particular lamp may be so supported within a housing as to permit ready expansion and contraction thereof without producing strains upon the housing.

Other objects of our invention will be apparent from a study of the following specification read in connection with the accompanying drawings, wherein:

Fig. l is a perspective view of a lamp, stand and resistance unit constructed in accordance with our invention.

Fig. 2 is a perspective view of the resistance unit shown in Fig. I removed from the portable stand.

Fig. 3 is a top plan view of the resistance unit shown in Fig. 2.

Fig. 4 is a vertical sectional view taken along line IV-IV of Fig. 3 and illustrating the interior construction of the housing and the manner of mounting the resistance elements therein.

Fig. 5 is a detail vertical sectional view of a portion of the housing, the section being taken along line V-V of Fig. 4.

Fig. 6 is a detail sectional view taken through one of the brackets employed upon the housing to support the resistance elements, the section being taken along line VI-VI of Fig. 4.

Referring to the drawings, we have illustrated in Fig. 1 a lamp 5 which may be of any suitable size, shape and construction such as those commonly employed in the motion picture industry for flood lighting and spot lighting of motion picture sets, the particular lamp illustrated herein being one of a type employing an electric are as a source of illumination, the electrodes (not shown) being controlled by suitable adjacent handles 2 and 3 projecting from the rear of the lamp i. The lamp l is adapted to be supported upon a yoke or bracket member l, the connection of the lamp with the yoke or bracket 4 being usually pivotal to permit the lamp to be swung about a horizontal axis to elevate or lower the position of the beam of light projected from the lamp, while the bracket 4 is pivotally mounted upon the upper end of a supporting stem 5 of a portable stand 6 for pivotal movement about a vertical axis to divert the beam of light in the desired direction. The portable stand 5 comprises a plurality of legs, usually three in number, indicated as l, 8 and 9, upon the outer ends of which are mounted suitable casters it by which the stand 63 and the lamp i may be readily shifted over a floor or other suitable supporting surface to any desired location. In the particular form of stand illustrated herein, the legs '8, 8 and 9 comprise suitable lengths of pipe (see Fig. l) the inner ends of which are received between a pair of clamping castings ii and i? to which is also secured the vertical stem or supporting pipe 5 upon the upper end of which the yoke or bracket i is mounted.

Associated with the lamp contained within the housing 1 is a resistance unit it which, as is illustrated particularly in Fig. 4, contains a plurality of resistance elements, two of which are illustrated at it and i5, though it will be understood bythose skilled in the art that any desired number of resistance elements may be employed, the resistance characteristics of which are selected to produce the desired operating characteristics of the arc lamp with which they are associated. The resistance unit it comprises a housing constructed of a top plate l5 and a bottom plate Ill secured in spaced relation to each other by means of a plurality of tie rods M5,. one end of which is threaded as indicated at is into a suitable threaded boss 28 formed upon the upper or top plate it, the rods being held in desired position within the bosses 20 by means of suitable lock nuts 2i engaging the lower faces of the bosses 2H. As will be understood by reference to Fig. 3, four or more of these tie rods may be em ployed distributed at desired intervals about the circle described by the top bottom plates l6 and il the rods it being connected to the bottom plate as by passing the threaded lower ends of the rods i8 through suitable openings 22 in the lower plate ll aligned with the threaded bosses 20 of the upper plate, lock nuts 23 and 2 3 being provided above and below the plate ll to hold the rods securely in place thereon (see Fig. 4). The remainder of the housing containing the resistance elements it and i5 is constructed of two sheets of perforated sheet material. One of these sheets being indicated at 25 comprises a substantially cylindrical sheet adapted to extendabout the periphery of the top and bottom plates, suitable recesses 26 and 27 being provided at the periphery on each of the plates i6 and H to form shoulders receiving the upper and lower edges of the sheet 25, the sheet 25 being secured to the upper and lower plates H5 and H as by means of screws 28 or other suitable securing devices. The other of the sheets, indicated at 29, is preferably U-shaped in cross-section, adapted to follow the outline of a U-shaped slot 30 extending into both the upper and lower plates [6 and I! from the circumference of the circle described by these plates to the center of the circle so described, the upper and lower plates being provided with vertically extending grooved bosses 3| and 32 (see Fig. 4) for receiving the upper and lower edges of the sheet 29, the sheet 29 defining a longitudinally extending recess or passage disposed along the entire length of the resistance unit H to provide a passageway for the supporting post 5 or any other support upon which the unit i3 is to be mounted.

By providing the slot 38 in the upper and lower plates and arranging the sheet 29 as described, it will be apparent that the housing is provided with a slot which permits the reception therein of the vertical support 5 of the portable stand 6, the width of the slot being somewhat in excess of the external diameter of the supporting pipe and the circle 33 described by the inner end of the slot 36 being of suflicient radius to substantially fit the pipe ii when the housing is mounted upon the stand ii with the pipe 5 substantially concentric with the housing of the resistance unit it. sistance unit may be readily placed upon or removed from the portable stand t by merely sliding the same laterally relative to the pipe 5.

The unit it may be held in place upon the stand 6 by providing a plurality of downwardly depending legs 3%, 35, 33 and Si (see Figs. 1 and 4), the legs and 31 being so spaced about the circle described by the lower plate i! as to enage the forward surfaces of the legs 'i and 9 as viewed in Fig. 1 when the housing I3 is in the location upon the stand as shown in that figure, while the legs 35 and 36 are adapted to engage upon opposite sides of the third leg 8 of the stand. The upper plate it is preferably provided with an upwardly and inwardly tapered boss 38, surrounding the inner end of the slot 35] and projecting upwardly above the surface of the plate [6 to receive thereon a cone-shaped collar 39 surrounding the supporting post 5 and slidable vertically thereon so that when the unit it is in place upon the stand, as shown in Fig. 1, the collar 35 may be drawn downwardly upon a seating relation upon the boss 38 to securely hold the upper end of the unit it against displacement. A thumb screw or hand screw 49 is preferably provided on the collar 39 adapted to be tightened against the post 5 to hold the collar against Vertical displacement when the collar is employed to secure the unit it on the stand.

It will therefore be apparent that by merely loosening the screw it) and sliding the collar 39 upwardly, the unit is may be detached from the stand 5 and may be removed therefrom by merely sliding the same laterally away from the .post, suitable handles ii being provided upon the upper plate It for convenience in handling the unit it.

Thus, whenever the lamp l is to be disassembled from the stand 6, the associated resistance unit 113 may also be disassembled from the stand It will therefore be apparent that the re-,

and located in the parallels or at any other location immediately adjacent the new location of the lamp, the unit I3 being merely set up upon the floor in an upright position, as shown in Fig. 2, with the depending legs 34, 35, 36, 31 acting to hold the lower plate in spaced relation to the floor and permitting ample ventilation thereunder or if desired, the unit may be hung upon the rail of the parallels by merely sliding the same along the rails, the rails entering the slots 30 in the same manner as the pipe 5 was received within the slots.

It will therefore be apparent that whether the lamp is mounted upon the stand 6 or is mounted on any other support or in any other location, the unit I3 may be disposed sufiiciently close to the lamp I that the conductors 42 employed to connect the unit I 3 with the lamp when it is mounted upon the stand may also be employed to connect the lamp and the unit in its new location, thus avoiding the necessity of extension or alteration of the length of these conductors and thus avoiding any alteration in the operating characteristics of the lamp.

By referring particularly to Figs. 3 and 4, it will be noted that the upper plate I6 is provided with a plurality of downwardly depending lugs 43 disposed in substantially equally spaced relation about the plate Hi, the lugs having slots 44 extending upwardly from their lower ends to receive therein a bolt 45 passing through the slotted end 46 of a bar 41 upon which the insulating core 48 of the resistance element I4 is mounted. The bolt 45 rigidly connects the upper end of the bar 41 to the plate I6. The lower plate I! is likewise provided with a plurality of upwardly projecting lugs 49 aligned with the lugs 43 on the upper plate IS, the lugs 49 having vertical slots 50 extending from their upper ends, through which a bolt 5| may pass, the bolts 5| also extending through the slotted lower end 52 of the bar 41.

By referring particularly to Fig. 6, it will be observed that the lower end 52 has welded thereto a nut 53 into which the bolt 5| is adapted to be threaded, a suitable lock nut 54 being provided upon the outwardly extending end of the bolt 5| so that the bolt may be held in any suitable locked position relative to the end 52 of the bar 41. Thus, the bolt 5| may be screwed into the nut 53 until the head thereof or a washer 55 interposed between the head and the lug 49 just snugly engages but does not bind upon the lug 49 and the bolt 5| may be locked in this position by means of the lock nut 54.

Thus, it will be apparent that while the resistance element I4 is held against displacement within the housing, expansion and contraction of the bar 41 under varying conditions of heat in the resistance element I4 will be readily permitted by the sliding movement permitted between the bolt 5| and the lug 49.

It will therefore be apparent that we have provided a resistance unit which may be associated with a selected lamp to produce the desired operating characteristics in the lamp and which may be readily mounted upon a stand employed to support the lamp or may be dismounted from the stand and transported to any other location to which the lamp may be carried apart from the stand, in either location the resistance element being readily adapted to be so closely coupled with the lamp as to permit the employment of the same conductors between the unit and the lamp at all times.

While we have shown and described the preferred embodiment of our invention, we do not desire to be limited to any of the details illustrated or described herein except as described in the appended claims.

We claim:

1. In combination with a lamp and a portable stand therefor having a lamp supporting post, a resistance unit for association with the lamp, comprising a housing having a recess disposed along its length and extending inwardly from the exterior of the housing to provide a passageway for removably receiving said post.

2. In combination with a lamp and a portable stand therefor, having a lamp supporting post, a resistance unit including a housing having a recess disposed along its length and extending in-- wardly from the exterior of the housing to the longitudinal center of the housing to provide a passageway for removably receiving the post.

3. In combination with a lamp and a portable stand therefor, having a lamp supporting post and a plurality of legs radiating from said post, a resistance unit for association with said lamp comprising a housing having a recess disposed along the length of said housing and extending inwardly thereof from the exterior of said housing to provide a passageway for removably receiving the supporting post, and feet formed upon the lower end of said housing for engaging the legs of said stand when said housing is in position upon said post.

4. In combination with a lamp and a portable stand therefor, having a lamp supporting post, a resistance unit for association with said lamp including a cylindrical housing, a recess disposed along the length of said housing and extending radially inwardly from the exterior of said housing to provide an unobstructed passageway for removably receiving the supporting post and means on said post for engaging said housing to lock said housing about said post.

5. In combination with a lamp and a portable stand therefor, having a lamp supporting post, a resistance unit for association with said lamp including a housing having a top and bottom, a recess disposed along the length of said housing and through the top and bottom thereof, said recess extending inwardiy from the exterior of said housing to provide a passageway for removably receiving the supporting post, a boss extending upwardly from the top of said housing and a lock collar on said post for engaging said boss to lock said housing in position on said post.

6. In a resistance unit for detachably mounting upon a support which includes a vertical post and horizontal base members, a housing having a recess disposed along its length and extending from the exterior of the housing toward the 1ongitudinal center thereof for removably receiving said post for supporting said housing, and feet formed upon said housing for engaging said horizontal members to maintain said post in said recess and for supporting said housing when removed from said support.

PETER MOLE. ELMER C. RICHARDSON.

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