US1840800A - Current regulator for electric lamps - Google Patents

Description

Jan. 12, 1932. c, w 1,840,800

CURRENT REGULATOR FOR ELECTRIC LAMPS Filed Aug. 7. 1929 2 Sheets-Sfie et 2 mvzu'roa 4% w PM Patented Jan. 12, 1932 UNITED STATES PATENT 'OFFICE'F CARL L. wmcirEL'r, OF PHILADELP IA, PENNSYLVANIA, AssIGNoR TO winr COMPANY, 1

OF IPHTLAID'ELPHIA, PENNSYLVANIA, A CORPORATION OF 'MAIlYE CURRENT REGULATOR FOR ELECTRIC LAMPS Application filed August 7, 1929. Serial No. 384,106.

The present invention relates to attachments for incandescent lamps, by means of which the flow of current to the filament may be regulated, and the intensity or candle power of the light produced thereby controlled. The invention may be considered as in the nature of an improvement upon the device described in my copending application Serial No. 98,171, filed March 29th, 1926, which issued as Patent No. 1,720,051, July 9, 1929. I

The general object of the invention is to provide a new improved device of the character above mentioned which is simple in construction, efficient in operation and capable of being economically manufactured.

One of the novel features of the invention resides in the new improved means of supporting the rheostatring which forms one of the elements of the device so as to facilitate the radiation of heat therefrom. This rheo stat ring comprises new and improved constructional features, which render it more satisfactory in operation and make it easy and economical to manufacture, and is claimed in divisional application Serial. No. 473,790, filed August 8, 1930' Other novel features of the invention will be apparent from the following description and claims.

The invention will be understood from the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a side view of an assembled device embodying the present invention, and

illustrates its adaptation for attachment between a socket and a lamp; Fig. 2 is a vertical sectional view of the deviceshowing the parts in assembled position; Fig; 3 is a similar view on the planes indicated by the lines 3m3w of Figs. 1 and 2; Fig. 4 is a horizontal sectional view looking downwardly on the plane indicated by the line im-4m of Fig. 3 and illustrates in particular the disposition of the brushes on the rheostat ring relative to the limit positions of said ring; Fig. 5 illustrates the electrical circuit connections between the conducting parts of the device; Figsf6 to 18 inclusive are perspective views of various parts or portions entering into the construction of the device, said parts or portions being shown mainly one above theother for the purpose of clarifying their assembly; Fig. 19 is a-perspective view of oneof the .two resistance units forming. the rheostat ring before coiled into semi-circular shape; Fig. 20 is a schematic illustration of the electrical connections in regard to the conductive support and the two resistance wires wound thereon; it, also illustrates the relative disposition of the two pairs of insulat ing and conducting contacts which serve respectively to'open circuit and to short circuit the resistance of the two wires; Fig. 21 is a partial view in detail of the rheostat ring, showing the means of uniting the ends ofthe two supporting metallic strips on which the resistance wires are respectively wound; Figs. 22 and 23 areviews taken onthe planes indicated by the lines 22m2200 and 23m23w of Fig. 21 respectively.

A lamp reducer or dimmer constructed in I accordance with my invention comprises plug and socket members 1 and 2, respect1vely,adapted to form .a connectlon between anelectric lamp and the terminal socket of an electric fixture. It also embodies a tubular rheostat ring 26, composed of two resistance wires 30, 30 spirallywound respectively on two semi-circular metallic strips, the ends of which are joined together. The rheostat ring 26 is adapted for rotation around the common axis of the plug and socket members and is spaced from the inner parts and from the outer protective casing of the device so as to be substantially completely surrounded by air. The threaded conductive shells 4 and 5 of the plug and socket members are adapted to be permanently electrically connected together; and a pair of conducting wipers 31,

32 in permanent electrical connection, respecenables the current through the lamp to be interrupted.

The plug 1 comprises an insulating body surrounded at one end by a threaded metal casing 1 of a length suitable to engage a standard threaded lamp socket, and a pin 6' forming the center contact of the plug and tapped to receive a center screw 8 extending through the body. To prevent a rotation of the pin 6, relative to the insulating body, the pin is provided with two diametrically opposite extensions 9 (Fig. 6) fitting within cor responding grooves formed at the upper end of the central aperture in the insulating body. For reasons to be discussed later, the insulating body of; the plug is preferably formed in two parts 9 and 10, held together by the screw 8 threaded into the pin 6. To prevent rotation of the parts 9 and 10 relative to one another, the upper part 9 is provided with a non-circular projection 11, whichfits into a similarly shaped depression 12 in the lower member 10. s

The threaded shell 4: is held in fixed position on the plug by providingan aperture in its bottom which fits over the projection 11.

. The lower end of part 10 is formed with a non-circular projection 15 of substantial height and two washers 80 and 81 having apertures conforming to the shape of the projection 15 are seated on the shoulders 18 and 19' formed on the insulating part 10 at opposite sides of the projection 15; the purpose of said projection 15 and said washers 80 and 81 will be made apparent in the later description. The upper end of the socket shell 5 is formed with an aperture shaped similarly to said projection 15 and is adapted to be held adjacent the lower end of the latter by means of the spacing brackets 16 and '17.engaging the sides of the projection 15.

The lower ends of said brackets 16 and 17 are formed with outwardly projecting flanges 16a and 17a which are riveted to the upper end portions of the shell 5 engaging the sides of the projection 15 at its lower end; and the upper ends of said brackets 16 and 17 are likewise formed with outwardly projecting flanges 165 and 177) which engage the lower washer 81 seated with the washer 80 against the shoulders 18 and 19. Said upper flanges 16-?) and 17?) are formed with tapped openings 20 and 21 and screws 22 and 23, passing through vertically alined apertures formed through the washers 80 and 81,

the insulating part 10 and through the lower end portions of the plug shell 1 engaging the sides of the projection 11, cooperate with said tapped openings 20 and 21 in securing the two shells 4 and 5 and the washers 80 and 81 to the insulating part 10, the screws 22 and 23 and the brackets 16 and 17 aifordin means for permanent electrical connection between the two shells 4 and 5. The shoulders 13 and 14 on the insulating part 9 are formed with diametrically disposed depressions 24 and 25 to accommodate the heads of the screws 22 and 23..

The desired current reduction is produced by a rotatable tubular rheostat ring 26 which comprises an inner shell 27 having an inturned flange 27a formed with ventilation openings 28. The upper washer 80 is formed atits edge with an upwardly depressed shoulder 80a and the lower washer 81 is formed at its edgewith a downwardly depressed shoulder 81-a, the inner edge of said rheostat flange 27 a being looselyheld and rotatable between said shoulders 80a and 81 a. 'Diametrically disposed contact wipers 31 and 32 are adapted to cooperate with the upper end of the rheostat coil in a sliding engagement respectively with dia metrically opposite points of the convolutions of the two resistance wires 30, 30. Said wipers 31 and 32 are arcuate in shape, extend around the insulating part 10 and comprise inwardly directed arms 31a and 32-a which engage the alined grooves 33 and 34 formed in the same plane of and on the lower surface of the depression 12 in the insulating part 10. In order to restrict movement of the wipers 31 and 32 from their proper positions on the resistance coil, their arms 31-a and 32 a are seated within channel pieces 35 and 36, the inner width of which is made to correspond to the width of said arms, said channel pieces being-in turn seated on the bottom surfaces of the grooves 33 and 34; the screws and 38, passing through vertical apertures formed through the insulating part 10 and extending from the lower end of the projection '15 into said grooves, cooperate with the nuts 39 and 4:0 in rigidly securing the arms 3-1a and 32a and channel pieces 35 and 36 to the insulating part 10. i

The arrangement of parts described, with particular reference to the inturned apertured flange 27-a which supports the rheostat ring in place and spaces the latter from the inner parts, makes possible an effective ventilation of said rheostat, the latter being substantially completely surrounded by air, the inner spacing of the rheostat and the openings formed in said flange providing vertical circulation of air within the rheostat, which. serves both to keep the latter from overheating and to keep the inner parts cool. In this connection, the non-cylindrical projection 15 on the insulating part 10 provides a greater "air space within the rheostat in the vicinity of the apertured flange 27a and spaces the heat conductive shell from the upper part of the rheostat. It is also noted that the flange 27-a in cooperation with the space provided by the shoulders 80-a and 81-a on the washers 80 and 81 produces a perfect sliding contact arrangement and a positive engagement between the moving coil and stationary wipers, the coil being perfectly free to rotate, but movement of the coil in an axial direction in that-plane in which positive engagement of the wipers by the coil is obtained being restricted to a minimum.

The lower end of the projection is formed with an inward slot 41 for a purpose to be presently described, the central aperture for the center screw 8 and" the apertures for the screws 37 and 38 extending from the base of said slot. The center contact which is commonly associated with an electrical socket shell is represented herein in the form of a spring contact 42 having a finger portion extending into the slot 41at'one'side' thereof and secured therein by means of the screw 3'7, and a depending portion extending through the aperture in the bottom of the shell 5 for contact with the center or end terminalof an incandescent lamp base. ,The other screw 38 holds a flat metallic strip 43 on the bottom of the slot 41, said strip 43 extending inwardly and being also held by the center screw 8. Thus the wiper 31 is in-permanent electrical connection with the socket center contact 42 through the medium of the screw 37' and the other wiper 32 is in permanent electrical connection with the plug center contact '6 through the medium of the screw 38, metallic strip 43 and center screw 6. It is noted that the side walls of the slot 41 restrict the center contact 42 from lateral movement, thus effectively insulating said contact from the socket shell 5. f V

t will be understood by the later description that a rotation of the rheostat ring 26 produces a variation of the resistance measured between the wipers 31 and 32in contact with the resistance wires 30, respectively. Thus, with the arrangement of parts de scribed, a series circuit is established which includes the center contact 6, the spring wiper 32, the resistance circuit between the two wipers, thespring wiper 31, the center contact 42, a lamp filament, the socket shell5 and the plug shell 4; and a rotation of the rheostat unit 26 correspondingly enables a variation of the current through said lamp filament.

The outer casing of the device consists of two members 44 and 45 having a telescoping connection and joined at their free ends by locking devices whichmay be readily detachable, the upper member 44 being formed with outwardly struck shoulders on its side Wall, which interlock with apertures formed'in the side wall of the lower member 45. The insulating part 10 is formed with diametrically'opposite outwardly extending flanges 46 and 47, located on the sides of the grooves 33 and 34, the uppershoulders provided by said flanges affording a seat for the inner edge of the inturned flange 44a formed at the upper end of the casing member 44. Aring 70 having'a diametrically extending inner portion 7 0-a integral'therewith and fitted bei tween the insulating parts 9 and 10 in theslot 12'formed at the upper end of the-insulating part 10, is seated over the inner edge of the inturned flange 44a, said ring 70 being centrally apertured for thepassage of the center screw 8 and serving in cooperation with the insulating part 9, center screw '8 and pin 6to clamp the outer casing on the insulating part 10. Thiscring 70 will be referred to in the later description as serving 5 another purpose. It is noted that the arcuate portions of the wipers 31 and 32 are positioned below the bottom surfaces of the flanges 46and 47 which thus also serve to protect said wipers and insulate the latter from'the casing 44. r i

The lower casing member 45 is formed with an inturned flange 45a at its lower end,

both, of the flanges 44a and 45.a being prg vided with vertically apertured ventilation openings, 48 and 49, respectively, to facilitate the circulation of air within the easing; The outer diameter of both casing members 44 and 45 is such as to provide ample spacing between the rheostat ring 26 and the outer casing, the rheostat ring being thus substantially completely surrounded by air and the spacingbetween the rheostat ring and the casing serving to prevent the latter frombecoming .heated byr'adiation and to 2 permit a proper circulation of air in contact a with said rheo-stat ring. Y An extension 50 of smaller diameter. than the outer casing is provided at the lower end of the casing member 45 which may be threaded to receive the threads of a lamp shade holder (not shown in the drawings). Preferably outwardly struckportions 51 in the shape of a single thread are formed on the extension 50 as a means to retain said 3 1 shade holder. Within the extension 50, an annular band of insulating material 52 is fitted, the lattersurrounding the lower end of the socket shell 5. for the purpose of protecting it and for the purpose of insulating 56, 56 formed in the side wall of the lower casing member 45 at its upper end. These eyes give a proper lead for the cords or chains 53, 53 and transform the vertical pull upon the latter to the necessary tension to rotate the rheostat unit. Slots 57, 57 are formed on the lower end of the upper casing member 44,

said slots corresponding to the openings 56, 56.

and likewise providing passage for the'cords 53, 53. In the general form of the device to which the present invention relates, the rotational movement of the rheostat ring 26 will be limited to approximately one-half of a revolution, the two limit positions of the rheostat unit serving in cooperation with the wipers 31 and 32 to open circuit and short circuit the resistance respectively. In this respect, the eyes 56, 56 and corresponding slots 57, 57 are disposed diametrically opposite to'one another and the desired limitation of the rotational movement of the rheostat ring is accomplished by stops 58, 58 exteriorly attached to the chains 53, 53 and cooperating with the eyes 56, 56. Thus the point of attachment of the staple 54 should bear such a relation to the rheostat unit and the location of the eyes 56, 56 should hear such a relation to the wipers 31 and 32 that the rheostat unit is permitted to cooperate with the wipers in a sliding engagement therewith between its limit positions described above. In the embodiment of the invention shown in the drawings, the position of the staple 54 on the rheostat ring is such that it is situated in an axial plane approximately at right angles to the plane of the engaging portions of the wipers 31 and 32'when the rheostat is in either of its limit positions and the eyes 56, 56 are disposed in a plane at right angles to the plane of said engaging portions. 1

It is obvious from the arrangement of parts described that the upper casing member 44 should have a certain fixed position relative to the insulating part 10 which holds the wipers 31 and 32, and this position should be permanently insured against any possible rotational movement of the casing. This object is accomplished in the present embodi ment of the invention by the ring 7 which is provided with a depending tooth 72 (Fig. 9) at its rim engaging the inner edge of a ventilation opening 73 (Fig. 10) formed on the upper casing flange 44-a, said opening 73 extending inwardly a greater distance than the remaining openings 48 so as to distinguish said opening 73 from said openings 48. Thus the inner portion 7 0-a of the ring 70 cooperating with the slot 12 on the upper end of the insulating part 10 and the tooth 72 cooperating with the opening 73 insure a proper positioning of the casing part 44 and prevent a displacement of the latter relative to said insulating part.

A brief description of the assembly of the various parts will now be given, this description further assisting the demonstration of the simplicity of the parts and their ease of assembly. The spring wipers 31 and 32, the channel pieces 35 and 36, thecenter contact 42 and the metallic strip 43 are connected in place on the insulating part 10 by means of the screws 37 and 38 and nuts 39 and 40. The washer 80, the rheostat flange 27--a,and the washer 81 are positioned on the lower end of the insulating part 10, and the socket shell 5, holding the brackets 16 and 17, is inserted into place within the rheostat ring 26 to which is attachedthe chains 53, 53, passing through the lowercasing member the upper casing 44, the ring 70 and the plug shell 4 are then positioned on the upper end of the insulating part 10 and all of said parts positioned on the lower, and upper ends of the insulating part 10 are secured thereto by the screws 22 and 23 cooperating with the tapped openings 20 and 21 on the brackets 16 and 17. The insulating part 9 is positioned within the plug 4 and the center screw 8 passing through the metallic strip 43 and insulating parts 9 and 10 rigidly secures the latter parts together in cooperation with the center contact 6. The lower casing member 4:5'l10ldlIlQ' the insulating band 52 is then fitted to the upper casing member 44.

A construction of the rheostat unit per se which has been found to be especially satisfactory is the one shown and described herein. The rheostatcoil comprises a tubular conductive support preferably formed in two separate metallic strips 60, 6O coiled into semi-circular shape and joined at their ends. Each strip is covered with a suitable protective insulation, such as a wrapping thereon of several layers of an asbestos sheet 61, the ends a and 60b of the strip 60 being left bare, and a resistance wire 30 is wound spirally on the asbestos covering 61, one end 30a of said wire being attached around two outwardly struck lugs 62 formed on the bare end 60a of the strip, which serves to electrically connect said end of the wire to the strip, while the other end 30b of said wire is left electrically unconnected with relation to end 60-?) of the strip. The upper edge of the latter end. is formed with an angular recess 69 for a purpose which will be made apparent presently and both endsof the strip are outwardly plicated. The strips 60. 60 may be coiled into semi-circular shape before or after positioning of the asbestos covering and wire thereon, and the two resistance units 59, 59 formed in this way are assembled on the inner shell 27 in such a way that the recesses 69, 69 are disposed at the upper end of the rheostat and diametrically opposite to one another. This assembly of the resistance units 59, 59 on the inner shell 27 positions the electricall connected ends 30a, 30a of the resistance wires diametrically oppositely to one another, and the free ends 30?), 3O,?) also diametrically oppositely to one another.- The resistance wires 30, 30 are suitably insulated from the shell 27 as by a coil of mica 63 placed intermediate said wires and shell, the free ends 30-1), 30-?) of the resistance wires being inwardly positioned between said mica insulation 63 and said asbestos insulation 61. C-shaped conductive clamping members 64, 64 cooperate with adj acent plicated ends of the strips 60,60 in holding the two resistance units 59, 59 together and ,in establishing an electrical connection between same. The upper edges of said members 64, 64 are formed with recesses corresponding to, the recesses 69, 69. Insulating mica contacts 65, 65 are inserted longitudinally within the folds connecting the recessed ends Z), 60b of the strips and are made to project above the recesses in alinement with the upper end of the coil. Conducting contacts 66, 66 are placed within the folds connecting the other ends 60a, 60-a. Washers 67, 67 extending through the connected ends of the resistance units serve to prevent a vertical displacement of the connecting members 641, 64 and of the insulating and conducting contacts 65, and 66, 66. The assembled resistance units are protected by the outer shell 55 consisting of a strip of metal buckled at its ends. This shell 55 encircles the outer, surface of the resistance unitsand thus holds the washers 67,67 in place and is insulated from the resistance units by suitable insulating means such as astrip of mica 68. The washers 67, 67 are formed with an inner central recess into which the inner shell 27 is outwardly punched as a means to prevent a vertical displacement of said inner shell.

Thus, the diametrically disposed ends 30 a, 30a of the resistance wires are in electrical connection with one another through the conductive support 60, 60, the resistance wires being placed in; series. The wipers 31 and 32 are adapted to operate respectively on the two resistance wires 30, 30 between their ends, and hence. a continued displacement of the rheostat unit relative to said wipers, in electrical contact with the convolutions of said resistance wires at the upper end of the rheostat, produces a cone tinuous variation of the resistance measured between said wipers,rthe totalresistance be- 7 tween the free ends V3Ob, 30b of theresistance wires being such as to produce a glow or dim light from an electric lamp. Upon rotation of the rheostat unit, such as by pulling either of the chains 53, 53, any desired degree of light intensity from said lamp may beestablished A limit position of the rheostat unit places the wipers in engagement with the insulating contacts65, 65, whereby the current through the device is interrupted,

The other ,limit position of i-the; rheostat places the wipers in engagement with the conducting contacts 66, 66, andsince the latterv are in electrical connection through the metallic strips 60,60, the rheostatwillbe short circuited and an electric lamp will correspondingly burn with full brilliancy. It is notedthat'the limit position of the rheostat interrupting the current through thedevice is adjacent those positions which estab lish minimum light intensities from the lamp, whereas the limit position of the rheostat short circuiting the latter is adjacent those positions which. establish maximum light intensities from the lamp. 7 I It is noted that the strips 60, 60 need not be connected electrically at both of their ends, but lnay be connected only at one pair of adjacent ends, the two resistance wires being then connected in series through one of the strips, r From the arrangement of parts described, it will be seen that the device, including the rheostat proper, comprises a simple'construction which may be easily assembled, in which an efficient. ventilation; of the parts is provided, in which "the various members are maintained in rigid mechanical and electrical contact with each other, in which the rheostat ring may be easily rotated to produce between limits any desired degree of light intensity from an electric lamp, and a firm, positive engagementof the stationary contacts with the moving coil, and in which all electrically conducting members are protected; from possible injury by contact with extraneous articles.

. What is claimed is:

1 1. In an electric lamp attachment, an in-. sulating body, a lamp socket shell adapted to ring adapted for rotation around the axis of the body and the shell, said ring having an inturned supporting flange formed with ventilation openings and. spacing the. ringfrom the aforesaid part-s,said flan e being loosely f held atitsinner edge to sai body whereby said rheostat and flange are substantially completely surrounded by air, 7 p

i 2. In an electric lamp attachment, an insulating body, a lamp soclretadapted to be held adjacent the lower. endof said body, an outer rheostat ring having an inturned flange formed withoventilation openings and spacing the ringfrom the aforesaid parts, andfa pair. of washers carried by the body and loosely carrying the inner edge of said flange between their outer edges whereby the ring 18 adapted for rotation around the common axis of the parts. I V

3; In an electric sulating body,an extension of reduced crosssectional area at the lower end of said body, a lamp socket shell the inner end of which lamp attachmentpan in:

105 be held to saidbody, and an outer rheostat s: te to, b h el e the t r r r en. i

stat ring for rotation around the common axis of the parts.

4. In an electric lamp attachment, an 1nsulating body and a conducting shell adapt-ed to form a plug for attachment to a lamp socket, a non-cylindrical extension at the lower end of said body, a pair of brackets electricallyl and mechanically secured to a lamp socket s ell and engaging the sides of said extension so as to space the inner end of said lamp socket shell from the base of said extension, an outer rotatable rheostat ring having an inturned annular supporting flange at its upper end formed with ventilation openings and spacing the ring from the aforesaid parts, means loosely holding the inner edge of said flange substantially in the plane of the base of said extension, and further means securing said last mentioned means and the brackets to the insulating body and electrically connecting the plug shell to the brackets. 5. In an electric lamp attachment, a plug member for attachment to a lamp socket comprising an inner insulating body and a conducting outer shell positioned on the upper end of said body, a non-cylindrical extension at the lower end of said body, a pair of brackets electrically and mechanically secured to the inner end of a lamp socket shell and engaging the sides of said extension so as to position the inner end of the socket shell at the outer portion of said extension, an outer rotatable rheostat ring having an inturned annular supporting flange at its upper end spacin the ring from the aforesaid parts, a

'4 pair 0 apertured washers positioned on the base of said extension and adapted to loose- 1yl hold theinner edge ofsaid flange between t eir outer edges, and securing means passing longitudinally through the insulating body servingto hold the plug shell and the washers and the brackets in place' on the insulating body and to electrically connect the plug shell to the brackets.

6. In an electric lamp attachment, a plug member for attachment to a lamp socket comprising an insulating body, an outer conductive shell and a center contact, a non-cylindrical extension at the lower end of said M. body, a lamp center contact secured to the "to rheostat ring having an inturned annular supporting flange at its upper end spacing t e ring from the aforesaid parts, means loosely holding the inner edge of said flange substantially' in the plane of the base of said extension whereby said rheostat and flange are substantially separated from metallic parts and substantially completely surrounded by air, further meansserving to hold the last mentioned means, the brackets and the plug shell in place on the insulating body and to electrically connect the plug shell to the brackets, a pair of spring wipers attached to the insulating body above the plane of the base of said extension and adapted to cooperate with the rheostat ring in a sliding engagement therewith at its upper end, and means to electrically connect said wipers respectively to the plug center contact and to the socket center contact.

7 In an electric lamp attachment, a plug member for attachment to an electric lamp comprising an insulating body, an outer conductive shell and a center pin extending through the insulating body and adapted to form the center contact of said plug, said body being formed with an extension of reduced cross-sectional area at its lower end, a socket shell having an inner apertured end adapted to be held at the outer portion of the extension, a rotatable rheostat ring having an inturned annular supporting flange at its upper end formed with ventilation openin and loosely held by the insulating bod su stantially in the plane of the base of t e extension, a pair of spring wiperscarried by the insulating body above the plane of the base of the extension and adapted to slidingly engage the upper end of the rheostat, a spring contact for the socket shell positioned on the lower end of the extension, a conductive strip also positioned on the lower end of the extension and in electrical contact with said center pin, securing means for electrically connecting the plug and socket shells and further securing means extending through the insulating body for electrically connecting the wipers respectively to the socket center contact and'to the conductive strip.

8. In a current reducer for electric lamps, two insulating bodies adapted to be joined end to end, 'a conductive shell surrounding the upper body and adapted to form the outer terminal of a plug for attachment to a lamp socket, a center pin extending through said bodies and adaptedto form a center contact for said plug, the lower body being formed with a pair of recesses at its upper end and with an extension of reduced cross-- sectional area at its lower end, a lamp socket shell having an apertured inner-end adapted to be held at the outer portion end of said extension, a rotatable, rheostat ring having the conductive strip.

substantially in the plane of the base of the extension, 21 pair of springvwipers secured to the lower insulating body within said recesses and adapted to slidingly engage the upper end of said rheostat, a center contact for the lamp socket shell positioned on the lower end of the extension, a conductive strip also positioned on the lower end of the extension and in electrical connection with the center pin, securing devices holding the plug and socket shells and the 'rheostat flange to the lower insulating body and further securing devices passing through the lower insulating body electrically connecting the wipers respectively to the socket center contact and 9. In an electric lamp fixture, an insulating body having on its upper surface an extension provided with a slot, a rotatable rheostat ring loosely held by said body at its lower end, a cylindrical casing having at its upper end an inturned flange formed with ventilation openings and seated on the shoulder formed by said extension, said casing cooperating wit-h means for limiting the rotary movement of the ring, and a ring ostat, means securing said brackets to said body and electrically connecting them to one of said terminals, means securing said center contact to said body and electrically connecting it to one of said wipers, and means electrically connecting the other of said wipers to the other of said terminals.

In testimony whereof, I have afiixed my signature to this specification.

CARL L. WEICHELT.

seated above said shoulder on the inner edge 7 of said flange, said ring being formed with an inner diametricallyextending portion integral therewith engaging said slot and with a depending tooth'engaging one of said ventilation openings.

10. In an electric lamp attachment, an insulating body carrying switching means and terminals for connection to a source of current, said body being formed with an extension at its inner end, a pair of conducting brackets engaging sides of said extension, a lamp socket shell held by said brackets at a distance from the base of said extension, an outer rotatable rheostat ring cooperating with said switching means and having an inturned annular supporting flange spacing the ring from said body and said shell, said flange being loosely held at its inner edge to the base of said extension, and means securing said brackets to said body and electrically connecting them to one of said terminals.

11 In an electric lamp attachment, an insulating body carrying terminals for con nection to a source of current, said body being formed with an inner extension, a pair of conducting brackets engaging sides of said extension, a lamp socket shell held by said brackets at a distance from the base of said extension, a lamp socket center contact positioned at the inner end of said extension, an outer rotatable rheostat ring having an i11 turned annular supporting flange. spacing the ring from said body and said shell,'said flange being loosely held at its'inner edge to the base of said extension, a pair of wipers carried by said body above the plane of said extension and cooperating with said rhe- V

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