US2501485A - Means for mounting and controlling electric discharge devices - Google Patents

Description

March 21, 1950 E. TUcK 2,501,485

MEANS FOR MOUNTING AND CONTROLLING A ELECTRIC DISCHARGE DEVICES Filed Aug. 29, 1947 3 Sheets-Sheet 1 n Q '2 RF m v R? E l Q n N L. 5 i .1. r i

i i i I i i I l 5 'r i i I i n I N I.- w "'1 N h m k 1-1 1; Elm -|m I I Q I cu Jl l v El l I g L t k E INVENTOR. m W m "R Q i I VB (0 53 3 a g March 21, 1950 E. TUCK 2,501,485

MEANS FOR MOUNTING AND CONTROLLING ELECTRIC DISCHARGE DEVICES 3 Sheets-Sheet 2 Filed Aug. 29, 1947 March 21, 1950 E. TUCK 2,501,485

MEANS FOR MOUNTING AND CONTROLLING ELECTRIC DISCHARGE DEVICES s Sheets-Sheet s Filed Aug. 29, 1947 FIG 12.

INVENTOR- W TM 94 I 94 Ll6 66 m Patented Mar. 21, 1950 MEANS FOR MOUNTING AND CONTROLLING ELECTRIC DISCHARGE DEVICES Edward Tuck, Takoma Park, Md.

. Application August 29, 1947, Serial No. 771,280

This invention relates to means for mounting and controlling electric discharge devices and more particularly to a socket for double ended electric lamps of the fluorescent type constructed and adapted to be mounted upon and supported by a ballast transformer, hereinafter referred to as a ballast, and having switching means therein for interrupting the primary circuit to the ballast when the lamp is removed from the socket.

In devices heretofore employed for mounting double ended tubular fluorescent lamps it has been the usual practice to provide a channel member to which the ballast is secured and extending for a distance substantially equal to the length of the lamp and arranged parallel thereto, the sockets or lamp holders preferably being secured to the channel or to an elongated reflector connected thereto. When an array of such lamps is employed in which the lamps are disposed in end-to-end relationship, it has heretofore been necessary, by reason of the type of lamp holder employed, to arrange within each of the aforesaid channels a plurality of insulated conductors extending substantially throughout the length of the channel. Such arrangements possess the disadvantage of requiring a considerable amount of wire for establishing the necessary electrical connections between the lamp sockets, ballast elements and the source of electrical power when the lamps are arranged in end-to-end relationship.

The present invention provides an arrangement which possesses all of the advantages of the arrangements heretofore devised and none of the foregoing disadvantages. In accordance with the invention herein disclosed and claimed this is accomplished by providing a new and improved lamp holder or socket for the fluorescent lamps in which the high voltage circuit for the lamp and the primary circuit of the ballast are brought into the lamp holder, and in which the primary circuit of the ballast is interrupted by switching means within the socket when a lamp is not inserted therein. By employing a lamp socket in accordance with the present invention mounted directly on a ballast, I am able not only to efiect a substantial reduction in both cost and weight of the lamp mounting but in addition thereto I may change the color of the illumina tion selectively at will by employing a novel and simplified circuit arrangement in which the wiring and external control elements therefor are reduced to a minimum.

One of the objects of the present invention 5 Claims. (Cl. 315-257) is the provision of a new and improved lamp holder for a gaseous discharge tube constructed and arranged to interrupt the primary winding of the lamp ballast when a lamp is not inserted therein and having means within the holder for establishing a high voltage connection to the lamp.

Another object is to provide a new and improved lamp holder for a plurality of fluorescent lamps in which an electrical connection is established within the lamp holder between the filaments of adjacent lamps as the lamps are inserted in the lamp holder.

Another object is the provision of a fluorescent lamp support in which the lamp holders are secured to the ballast and in which no channel member is required.

Another object is the provision of a new and improved arrangement of circuits and instrumentalities for supporting for operation a plurality of fluorescent lamps in which all electrical conductors including the high voltage and ground wires are maintained at a minimum length.

Still another object is the provision of a lamp holder for fluorescent lamps of new and improved design and which is readily interchangeable with lamp holders of existing design.

An'additional object is the provision of a new and improved ballast and lamp holder unit in which a reflector and channel is not required thereby permitting a free circulation of air around the entire ballast.

A further object is the provision of means for establishin a plurality of quick detachable connections between the lampholder and the ballast. 4

A still further object is the provision of a new and improved mounting for a fluorescent lamp which is light in Weight, economical to manufac ture, easily installed with a minimum of wiring,

and which possesses all the advantages of durability and reliability in operation.

Still other objects, advantages and improvements will be apparent from the following specification, taken in connection with the accompanying drawings, of which:

Fig. 1 is a diagrammatic view of a plurality of fluorescent lamps employing the present invention;

Fig. 2 is a fragmentary enlarged plan view of a plurality of lamps supported by the lamp holders secured to one of the ballast members of Fig. 1;

Fig. 3 is a side elevational view of the device of Fig. 2;

Fig. 4 is an end view of the lamp supporting means of Fig. 2 with the lamps removed;

Fig. 5 is an enlarged detailed elevational View 01' a lamp holder of the present invention;

Fig. 6 is a view similar to Fig. 5 and showing the lamp in the assembled position;

Fig. 7 is a circuit showing in diagrammatic form a plurality of fluorescent lamps connected for operation in which the devices of Figs. 1 to 6 are employed;

Fig. 8 is a view of a ballast having a plurality of lamp holders secured thereto in accordance with an alternative form of the invention;

Fig. 9 is a view of a plurality of lamp holders secured to a ballast in accordance with still another form of the invention;

Fig. 10 is a circuit diagram suitable for use with the device of Fig. 9;

Fig. 11 is a circuit diagram similar to Fig. 10 and including switching means for selectively operating at will two groups of lamps;

Fig. 12 is a diagrammatic view of another lamp holder arrangement for mounting the lamps;

Fig. 13 is an enlarged fragmentary view of one of the lamp holders of Fig. 12;

Fig. 14 is a greatly enlarged central longitudinal sectional view of the device taken along the line M|4 of Fig. 13;

Fig. 15 is an enlarged view taken alon the line i5-i5 of Fig. 13;

Fig. 16 is a view taken along the line l6-i6 of Fig. 14; and

Fig. 17 is a circuit arrangement suitable for use with the lamp arrangement of Fig. 12.

Referring now to the drawings on which like numerals of reference are employed to designate like parts throughout the several views, and more particularly to Fig. 1 thereof, there is shown thereon an array generally designated by the numeral Ill comprising a plurality of fluorescent lamps H sup orted by the lamp holders l2 and 13 of which the lamp holder I2 is provided with three external circuit connections and the lamp holder [3 is provided with a single grounded electrical connection. With the exce tion of the lam holders l3 shown at the left hand portion of Fi 1, the pairs of lam holders l2i3 are mounted in abutt ng back-to-back relation on a plurality of ballasts [4.

As more clearly shown on Fig. 5, the lamp holder 12, which I prefer to call a Minimax lamp holder, comprises a casing is composed of insu ating material suitable for the purpose and having a shoulder l6 formed thereon and adapted to enga e the inner surface of the ballast casing and. secure the lamp holder thereto. the lamp holders preferably bein interfittingly received within suitable apertures provided therefor in the ballast casing. The lamp holder casing is constructed and arran ed to receive a pair of prongs IT on the lamp H in such a manner that the prongs cause a pair of resilient contact elements 18 and I9 to be operated as the lamp is rotated 90 degrees within the socket, each of the contact elements is and is being formed inwardly as at 2| and 22 respectively to efiect a locking engagement with the prongs I1 sufficient to prevent premature disconnection of the lamp from the socket.

With the contact element !8 in engagement with a prong l1, Fig. 6, a circuit is established from the high voltage conductor 23 to one end of the filament disposed in the adjacent end of the fluorescent tube.

The contact element l9, it will be noted, is provided with an insulating sleeve or member 24 formed thereabout and adapted to prevent an electrical contact between the element l9 and the prong ll associated therewith. The insulating member 24 may be composed. if desired, of an insulating compound applied thereto in liquid form and adapted to harden thereafter, or by placing a tube of plastic insulating material over the member 19. or in any other desired manner.

As the lamp is rotated into the locked position thereof, the contact member I9 is forced outwardly into engagement with the contact member 25 thereby closing a switch to complete a circuit between conductors 26 and 2'! included in the operating circuit to the primary winding of the ballast. The casing 15 is preferably provided with a pair of shoulders '28 and 29 against which the contact elements l8 and I9 are normally tensioned thereby to establish a secure contact with the prongs {T when the lamp H is in the locked position within the lamp holder.

The lamp holder i3 is of the conventional type adapted to receive the tube H and permit rotav tion thereof to a locking position in which two contact elements therein are in electrical and locking engagement with the pair of prongs on the end of the lamp adjacent thereto. The ballast, it should be noted, is provided with a pair of tabs 31 extending therefrom and having apertures 32 therein adapted to receive the screws 33 by means of which the ballast may be readily mounted on a ceiling, wall, or other desired surface. The lamp holders is shown at the extreme left of Fig. l are mounted upon any suitable support such, for example, as the support 34 illustrated which may be grounded or otherwise adapted to permit a ground connection to be made to the lamp holders 13 mounted thereon. The support 34 is also adapted to be secured to a surface in any suitable manner as by the tabs 35, a pair of screws 33 being preferably employed for this purpose.

On Fig. 7 is shown in diagrammatic form a circuit diagram suitable for operating the lamp array of Fig, 1. For the purpose of description of the operation of the circuit. the lamps I! will hereinafter be referred to by the letter designations LI through L6 and the ballasts associated with each pair of lamps Ll--L2, L3-Lfl, and LEE-L8 will be referred to as Bl, B2 and B3, respectively.

Let it be assumed, for the purpose of description, that conductor 36 is connected to ground, and that conductor 31 is connected to the usual source of alternating current and that all of the lamps L|-L6 have been inserted and locked. within their respective lamp holders. The primary circuit for ballast BI may be traced from a source of electrical power on conductor 31 through primary winding 38 of transformer BI. conductor 39, contact elements l9 and 25 of lamp holder l2 associated with lamp Ll, conductor M, contact elements 25 and [9 of lamp holder 62 associated with lamp L2, conductor 42 and thence to ground on conductor 36 thereby energizin the transformer of ballast Bl. ihe transformer secondary winding 43 is connected by the conductor 44 to contact spring 18 of the lamp holder l2 of lamp L2, from whence the circuit is continued to the filament 45 of lamp L2. The opposite end of this filament, it will be noted, is not connected to the contact member 25 by reason of the insulating sleeve 24 thereon. In like manner, the secondary winding 46 is connected by way of conductor 41 to contact spring I8 of lamp holder I2 associated with lamp LI, the circuit including the center tap connection from the junction of secondary windings 43 and 46 to one side of the primary winding 38 and the phase shifting capacitor 48 to reduce the stroboscopic effect of the lamps LI and L2, from whence the circuit is continued to the filament 45 of lamp LI. Conductor 36 is connected by way of lamp holders I3 to the filament 49 of lamps LI and L2 respectively and, if desired, the filaments 49 may be short circuited by a shunt wire across the terminals of lamp holder I3.

It will be noted that in the arrangement of Fig. '7, the lamps are lighted without the use of a conventional type starter in which a glow discharge tube having a bi-metallic element therein is employed to preheat the filament as the bimetallic element closes a contact. The operation of the tubes of Fig. 7, therefore, is of the type known to the art as' starterless operation in which the voltage generated by the secondary windings of the ballast transformers is sufiicient to break down the tube and initiate a gaseous discharge therein when voltage is applied to conductor 31. The circuits for the operation of the pairs of lamps L3-L4 and L5'L6 are similar to the circuit for operating the lamps LI--L2 and, therefore, will not be described in detail, it being sufiicient to note that the application of electrical power to the conductor 31 causes all of the lamps LI-L5'to be illuminated.

In the arrangement of Fig. '7 it should also be noted that the primary transformer circuit includes contact elements I92-5 of the lamp holders l2 associated with lamps LI and L2 respectively and the removal of either of these lamps from the associated lamp holder I2, therefore, causes the primary circuit to ballast BI to be interrupted. It should also be noted that conductor 36 is connected to lamp holder I3 associated with lamps L3 and L4 and in abutting relation with lamp holders I2 associated with lamps LI and L2 respectively whereby the only wires extending between or along the pairs of lamps L3--L4 and L5-L6 are the conductors 36 and 31 and, in the case of the pair of lamps LIL2 only a single conductor 36 extends alon the lamps t the lamp holders I3. It will be .clearly apparent, therefore, that this arrangement employs a minimum of wiring.

On Fig. 8 is shown. a lamp mounting unit having a plurality of tabs 52 thereon for securing the unit to a surface and a pair of ballast units B4 and B therein connected to a plurality of lamp holders I2, the lamp holders I2 and I3 secured thereto being adapted to receive, support, and apply electrical control connections to the ends of eight fluorescent lamps disposed in aligned spaced relation in four parallel rows.

On Fig. 9 is shown an arrangement in which four lamp holders are secured to one end of the ballast B, the lamp holders comprising two lamp holders I 3 and two lamp holders I 2.

A circuit suitable for the arrangement of Fig. 9 is shown on Fig. 10 in which a pair of ballasts designated for the purpose of description B6 and B! respectively are employed to control the operation of the lamps L1, L8, L9, LII]. The primary windings of ballasts B6 and B1 are connected by conductor 53 to a source of electrical power and the conductor 54 is connected to ground. Ballast B1 controls the operation of lamps LL-LB and, in like manner, ballast B6 controls the operation of lamps L9 and LIO. Removal of either lamp L1 or L8 from the associated lamp holder I2 interrupts the circuit to the primary winding of the transformer of ballast B! thereby removing high potential from the contact elements I8 of lamp holders I2 associated with lamps L1 and L8. In like manner, the removal of either lamp L9 or LII) from its lamp holder I2 causes the primary circuit to ballast B6 to be interrupted and thereby remove th high voltage from contact elements I8 of lamp holders I2 associated with lamps L9 and LII).

On Fig. 11 is shown a circuit arrangement for lighting the lamps LII, LI2, LI3 and LI4 of which the lamps LI I--LI2, for example, are white and the lamps LI3--LI4 are colored, the circuit arrangement including a switch S adapted to be moved selectively into engagement with a pair of switch contacts I and 2. The switch blade is connected by way of conductors 55 to ground, contact I thereof is connected by way of conductor 55 to lamp holders I 3 of lamps LII and of LI2,-and contact 2 is connected by way of conductor 5'! to the lamp holders I3 of lamps LI 3 and LIL The primary winding of the transformer ofballast B is connected at one end thereof to the source of electrical power by conductor 58 and at the other end thereof to ground on conductor 55, the circuit including the contacts 25 and IQ of each of the lamp holders I2 associated with the lamps LII to Lld. With the switch S in engagement with its contact I, white lamps LII and LI2 are lighted. As the switch is moved from terminal I to terminal 2 the white lamps are extinguished and the colored lamps LI3LI4 are lighted, it being merely necessary to operate the switch to either of its two positions to change the color of the light emanating from th lamps of Fig. 11. It will be understood, however, that any number of the aforesaid units may be employed and operated by the switch S.

On Fig. 12 is shown a plurality of lamps LI5, LIS, LH and LI8 connected to form an array in which the lamps are supported by a plurality of lamp holders 59, the lamp holder 59 shown at the extreme left of the figure being secured in any convenient manner to a support BI and the remaining two lamp holders 59 shown in the figure being secured to ballasts B8 and B9, respectively. The lamp holder 59 comprises a casing 62 having a pair of blocks of insulating material 63 and 64 secured thereto. Secured to the block 63 as by a bolt or rivet 65 is a spring contact member 66, Fig. 14, adapted to be engaged by. one of the prongs of a lamp as the lamp is inserted within the socket. There is also provided a flexible contact member 61 secured by the bolt 68 to the block 63, a slip connector 69 being in electrical circuit with the spring contact member 66 and a slip connector TI being in electrical connection with the contact member 6?. The contact member 61 is provided with an insulating strip 12 secured thereto by the bolt 68 and adapted to prevent an electrical connection between the prong of the lamp and the member 61 as the lamp is inserted in the socket of the lamp holder 59. ,There is also provided a contact member 13 generally similar to the contact member 66 and secured by a bolt or rivet l' lto the slip connector 15. A contact member 1'6 generally similar to the contact member 61 is provided and in abutting relation with an insulating member 11 generally similar to .the' member 1'2 to prevent electrical contact between the member 16 and'the prong of the lamp. The contact members 61 and 16 are adapted to be moved into electrical engagement with a flexible metal connector 18, secured to the block 63. as by the rivets '19 whereby the members 6'! and it are short circuited in response to the insertion of a pair of lamps within the lamp holder 59 such, for example, as the pair of lamps Ll Ll5, Fig. 12. When this occurs a circuit is closed from the slip connector H to conductor 8|, the circuit including a strap member 82 to which the-member 16 is secured.

Each of the slip connectors 59, ii and is recessed to receive a complementary plug 83 secured to the casing of the ballast B by a nut 84 and insulated therefrom as by the insulating washers 85, a plurality of external electrical connections thereto being provided by the conductors clamped in electrical contact with the plugs by the nuts 84. The clamping of the plugs 83 to the casing of the ballast B is facilitated by a shoulder 86 formed on each of the plugs and adapted to engage a strip of insulating material 81 disposed between the casing of the ballast and the shoulder. The casing 62, it will be noted, is provided with a plurality of apertures 88 of greater diameter than the maximum diameter of the plugs to facilitate the insertion of the plugs into the associated slip connectors without any possibility of short circuiting the plugs by the casing.

There is also provided within the casing 62 a pair of contact members 88 and 89, Fig. 15, adapted to be engaged by the prongs electrically connected to one end of the filament of each of a pair of adjacent lamps respectively such, for example, as the pair of lamps LIT-Lit. The contact member 88 is in electrical connection with the contact member 11 by the conductor 8| aforesaid. There is also provided within the lamp holder at flexible bridging contact member 9| adapted to be engaged by the contact members 88 and 89 thereby closing a circuit from one end of the filament of one of the lamps by way of contact members 89, 9 and 88 to the filament of the other one of the adjacent lamps and to conductor 8!. The contact members 88 and 89 are secured to the insulating block 69 in any suitable manner such, for example, as by the supports 92 and rivets 93, a pair of rivets 93 Sufi-icing to secure member 9| to the block 64. A pair of resilient members 94 are also secured to the block 64 as by the supports 95 and rivets 96. The members 94 are not necessarily employed for establishing external electrical connections to the filaments of the adjacent pair of lamps but merely apply an endwise thrust to the prongs of the lam s to effect securement of the lamps within the lamp holders although, if desired, the contact members 88 and 89 may be electrically connected to the members 94 respectively adjacent thereto. Conductor I04. it will be noted, is connected to a sli connector adapted to be engaged by the plug 9'! for establishing an external electrical connection thereto when the lamp holder is connected to the ballast. The various plugs 83 and 91 are constructed and arranged to be gripped tightly by the slip connectors respectively associated therewith whereby the lamp holder 59 is adapted to be plugged into the ballast and removed at will, a pair of brackets 98 secured to the ballast B in any convenient manner, as by welding the parts together, being provided for engagement with the casing 62 when the casing. is in the assembled position with respect to the ballast thereby to additionally support and secure the casing to the ballast.

While the casing 62 may be constructed in any desired manner, I have found it convenient to employ a pair of plates 99 and I91, Fig. 16, of suitable insulating material and connected by a plurality of studs I92 as by the screws Hi3.

On Fig. 17 is shown a circuit arrangement suitable for use with the lamp array of Fig. 12 in which the lamps U5 and US are controlled by ballast B8 and thelamps LI! and Lit by the ballast B9, the primary circuit of ballast B8 including contact members 61, 1'8 and 75 of lamp holder 59 supported by ballast B8 and the primary circuit for ballast B9 including the correspending elements of lamp holder 59 mounted thereon. The conductor 82 is, of course, connected to ground, and conductor I04! is connected to the source of electrical power. From the foregoing, it will be apparent that removal of either one of the lamps 1J5 or LIE interrupts the primary circuit to ballast B8 and, in like manner, the removal of either one of the lamps Ll! or L58 interrupts the primary circuit to ballast B9.

It will be apparent from the foregoing that there has been described a lighting device embodying novel features of construction and operaticn which gives satisfactory results in attaining the objects of the invention.

I claim:

1. In a system of the character disclosed for controlling a pair of fluorescent lamps having filaments at each end thereof, a ballast transformer having a casing, a pair of lamp holders supported On said casing for receiving and supporting said lamps respectively at one end thereof, a'pair of normally open switches respectively arranged within the lamp holders, means including said switches and a plurality of electrical circuit connections for establishing a series control primary circuit to said ballast transformer, means within said holders for closing said switches thereby to render said primary circuit effective as the lamps are inserted within the holders, and means including a pair of contact devices respectively disposed within said holders for establishing a pair of high voltage connections between the ballast transformer secondary circuit and the filaments of said lamps, said last named means including a center tap connection from the secondary winding of the transformer to one side of the primary winding thereof and a condenser interconnected between one of said filaments and one end of the secondary winding whereby a shift in phase is produced in the secondary voltages at said filaments thereby to prevent stroboscopic effects in the lighting of the lamps.

2. In an apparatus of the character disclosed for controlling a plurality of double prong ended filament type tubular fluorescent lamps, the combination of a ballast transformer, a lamp holder secured to said transformer and adapted to receive and support two pairs of said lamps in endto-end relationship, a pair of flexible members Within said lamp holder adapted to be moved by one of the prongs of each lamp of one of said pairs of lamps from an initial position to a moved position as the lamps are inserted within the holder without making electrical contact with said prongs, a flexible contactor within said holder adapted to be engaged by and to establish an electrical connection between said flexible member as the members are moved to said moved position, means including said electrical connection for establishing a primary circuit to said transformer, means including a pair of flexible contact members respectively arranged in adjacent spaced relationship with said pair of flexible members and adapted to be engaged by another one of the prongs of each lamp for establishing a high voltage connection between the filaments of the lamp and said transformer, a

second pair of flexible members within the lamp holder adapted to be moved by one of the prongs of each lamp of a second pair of lamps from an initial position to a moved position asthe second pair of lamps is inserted within the lamp holder, a second flexible contactor within the holder adapted to be engaged by and to establish an electrical connection between said second pair of flexible members as the members are moved to said moved position thereby, and means for applying a ground connection to one of said second pair of flexible members.

3. In an array of filament type gaseous discharge tubular lamps, the combination of a plurality of ballast transformers, a plurality of lamp holders respectively secured to said ballast transformers, a plurality of covers for respectively enclosing said transformers, each of said covers having apertures therein through which the lamp holders respectively extend, a plurality of terminals on said lamp holders disposed within the covers when the lamp holders are supported on the transformers, means within the covers for establishing a plurality of connections between said transformers and said terminals, means including a plurality of switches respectively arranged within said lamp holders for interrupting the primary circuit to the ballast transformer on which the associated lamp holder is mounted as a lamp is removed from the lamp holder, means within each of said lamp holders for establishing from the secondary circuit of the transformer individual thereto a high voltage connection to the filaments of the lamps adjacent thereto, a plurality of additional lamp holders respectively arranged in back-to-back abutting relationship with said first named lamp holders and secured to said ballast transformers, means within said additional lamp holders for making electrical contact with the filaments of the lamps adjacent thereto, a single grounded conductor extending along the length of said array and connected to said last named contact means, and a single power conductor extending along the length of said array and connected to the primary circuit of each of said ballast transformers whereby the only wiring extending along the length of the array consists of said grounded and power con ductors.

4. In a lighting system of the character disclosed, the combination of a plurality of pairs of double prong ended filament type fluorescent lamps arranged in end to end relation with respect to each other, a plurality of ballast transformers for lighting and supporting said lamps, said plurality of transformers being arranged adjacent the ends of adjacent pairs of said lamps respectively, each of said transformers having a casing, means on said casing for attaching the transformer to a supporting surface, each said casing having two groups of lamp holders interfittingly secured thereto, there being one lamp holder for each lamp end adjacent the transformer, each said lamp holder having a pair of flexible contact members adapted to be engaged and flexed by the prongs of the lamp inserted into the holder, each lamp holder of one of said two groups of holders having a switch therein including one of said contact members and arranged to be closed thereby as said one of the members i flexed upon insertion of a lamp into the holder, each of said one of the contact members having insulation means thereon to prevent electrical contacting with the prong engaged thereby, a primary circuit for each of said transformers including said switches of the holders individual thereto connected in series in the circuit, each lamp being supported on one end thereof by a holder of said one'of said groups of holders and on the other end thereof by a holder of the other of said groups, and a plurality of circuit means individual to the lamps and including at least one contact member of each holder of said other of the groups of holders and the other contact member of each holder of said one of the groups of holders for individually lighting the lamps from the secondary circuits of the transformers individual to said last named group of holders.

5. In lighting apparatus of the character disclosed for double prong ended tubular fluorescent lamps, the combination of a ballast transformer having a casing and means for attaching the casing to a supporting surface, two groups of lamp holders each holder of which is removably secured to said casing interfittingly therewith,

each of said holders having a pair of flexible contact members arranged to be engaged and flexed by the prongs of a lamp upon insertion of one end of the lamp into the holder, a third flexible contact member in each holder of one of said two groups of holders and adapted to be engaged by one of said pair of contact members as the pair of contact members are flexed by the lamp prongs, insulation means carried by said one of the contact members for preventing electrical contacting thereof with the prong engaged thereby, and terminal means for said contact members carried by the holders individual thereto and extended into said transformer casing, said terminals being adapted to receive electrical connections for establishing a power circuit to the primary winding of the transformer and individual lighting circuits from the secondary winding thereof to the lamps carried by said holders upon actuation of said contact members as the lamps are inserted in the holders.

EDWARD TUCK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,295,757 Russell Sept. 15, 1942 2,313,036 Burt Mar. 9, 1943 2,401,555 De Reamer et a1. June 4, 1946 2,457,780 Levenson Dec. 28, 1948

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