Ballast Circuit And Switch Therefor

Abstract

A pair of fluorescent lamps operated from a single tow-lamp ballast. The ballast circuit includes a switch for operation of each lamp individually and both together. In some embodiments, the switch has a pair of electrically insulated rotors, one of which makes and breaks an electrical connection to the ballast primary and to the other of which makes and breaks electrical contact between a common lead to one end of each lamp and alternatively a lead to the first lamp and a lead to the second lamp, thereby shorting leads to these lamps. The switch thus causes the second lamp and the first lamp respectively to operate singly and together in a predetermined sequence.

Description

BACKGROUND OF THE INVENTION

This invention relates to electrical circuits for controlling a fluorescent lamp ballast, and in particular to such a circuit for controlling more than one fluorescent lamp from a single ballast.

In numerous applications it is desirable to provide a fluorescent luminaire having more than one lamp, in which the lamps may selectively be operated individually or together. These applications include two-lamp desk luminaires and the like in which selective operation of either lamp or both, to obtain different lighting levels similar to those obtained with familiar three-way incandescent bulbs, is desirable. They also include wall-mounted fixtures such as those sometimes used over hospital beds, in which one fluorescent lamp provides direct lighting and another provides indirect lighting. Heretofore, such fixtures have required two single-lamp ballasts. The use of two ballasts in such luminaires substantially increases their cost and the quantity of wiring needed between the ballast and the lamps.

Although fluorescent lamps made in the form of tubes coated with a phosphor are presently the only type of discharge lamp for which the circuit and switch of this invention have a practical use, it will be appreciated that they are potentially useful in many types of discharge lamps having a pair of electrodes, and the term "fluorescent" lamp is therefore used to indicate any such discharge lamp.

One of the objects of this invention is to provide a ballast circuit and switch which allow selective individual operation of more than one fluorescent lamp with a single multilamp ballast.

Another object is to provide such a circuit and switch which are simple to manufacture and to operate.

Other objects will occur to those skilled in the art in the light of the following description and accompanying drawing.

SUMMARY OF THE INVENTION

In accordance with this invention, generally stated, a ballast circuit is provided in which a switch is provided for selectively introducing and disconnecting a short circuit between ballast secondary leads to opposite ends of a first fluorescent lamp and between ballast secondary leads to opposite ends of a second fluorescent lamp. The same switch controls current from a power source to the ballast primary. The switch has two sides, electrically insulated from each other but mechanically connected. The first side of the switch connects and disconnects the source of electricity to the primary and the second side connects and disconnects the shorting leads in the secondary.

In the illustrative embodiments a two-lamp ballast with a series rapid-start circuit is used. This type of ballast is particularly well adapted for satisfactory operation with only one lamp operating by introducing a short circuit between ballast wires leading to opposite sides of the other lamp. In two illustrative embodiments the sides of the switch comprise eight-position rotors joined mechanically to turn together, so that the first position of the first ("primary") rotor is associated with the first position of the second ("secondary") rotor, the second position of the primary rotor is associated with the second position of the secondary rotor, and so on. These embodiments differ in the sequence in which the first lamp, second lamp and both are turned on and off.

In another illustrative embodiment the rotors have four positions and are operated by a knob.

In still another embodiment the switch is a pushbutton type and the lamp or lamps desired can be lighted and turned off without the need for going through a sequence of lighting patterns.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, FIG. 1 is a diagrammatic view of the ballast circuit and switch of this invention;

FIG. 2 is a diagrammatic view of a first illustrative embodiment of switch of this invention;

FIG. 3 is a view in side elevation of a primary rotor of the switch shown in FIG. 2;

FIG. 4 is a view in side elevation of a secondary rotor of the switch shown in FIGS. 2 and 3;

FIG. 5 is a diagrammatic view of another illustrative embodiment of switch of this invention;

FIG. 6 is a diagrammatic view of another illustrative embodiment of switch of the invention; and

FIG. 7 is a diagrammatic view of another illustrative embodiment of switch of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and in particular to FIGS. 1-4, reference numeral 1 indicates one illustrative embodiment of ballast circuit of this invention. The ballast circuit 1 is illustratively a 2/40-watt ballast circuit of the standard series rapid-start type, and includes a two-lamp ballast 3. The ballast circuit 1 controls a hospital light 5, which includes a first fluorescent lamp 51 for direct lighting and a second fluorescent lamp 53 for indirect lighting. The lamps 51 and 53 are held in a housing 55 which is mounted on a wall by support brackets 57.

As is common practice in two-lamp rapid-start circuits, the ballast 3 includes a primary winding 31, a secondary winding 33, and three cathode heating windings 35, 37 and 39.

The primary winding 31 is connected to a source of alternating current, not shown, by a pair of leads 11 and 12.

An electrode 61 of the first lamp 51 and an electrode 63 of the second lamp 53 are connected in parallel to the first cathode heating winding 35 to form a common electrode circuit 15. The second cathode heating winding 37 is electrically connected to the second electrode 65 of the first lamp 51, to form a first lamp electrode circuit 17. The third cathode heating winding 39 is electrically connected to the second electrode 67 of the second lamp 53, to form a second lamp electrode circuit 19. The secondary winding 33 is electrically connected to the first lamp electrode circuit 17 through a capacitor 71 by a conductor 73. The first electrode circuit 17 is also connected to the common electrode circuit 15 through a capacitor 75. The second lamp electrode circuit 19 is electrically connected to one of the leads 11 to the primary 31 by a conductor 77.

The circuit described thus far is a standard one, used, with minor variations, in most two-lamp rapid-start ballast systems.

The ballast circuit 1 also includes a switch 8. In this illustrative embodiment, the switch 8 is in the form of a lever-actuated switch 81, in which a chain pull 83 moves a lever actuator 85, which in turn rotates a rotor assembly 87. A pawl 89 at the free end of the lever 85 engages a ratchet 91 on the rotor assembly 87, thereby converting reciprocal motion of the chain pull 83 to unidirectional rotation of the rotor assembly 87 in the commonly known manner of the standard pull chain switch.

The rotor assembly 87 includes a pair of rotors 93 and 95 attached to opposite faces of the ratchet 91. The rotors 93 and 95 and the ratchet 91 are all made of an electrically nonconductive material, and are mounted for rotation in an electrically nonconductive housing 97. The ratchet 91 is provided with eight teeth and is adapted to turn the rotor assembly 87 45.degree. with each pull of the pull chain.

The first ("primary") rotor 93 is in the form of a regular octagon having flat edges 101a-101h. A pair of fixed electrical contacts 103a and 103b are secured to the housing 97. The free ends of the fixed contacts 103 are biased into engagement with opposing edges 101 of the primary rotor 93. Two opposed edges 101a-101e are electrically nonconducting, and the other six edges 101 are electrically connected by a piece 105 of electrically conductive material. Therefore, if the rotor assembly 87 is taken as being initially in the position shown in FIGS. 3 and 4, the fixed contacts 103 are electrically disconnected in the first operative position of the rotor assembly 87. When the chain pull 83 is pulled the primary rotor 93 is turned clockwise, as viewed in FIG. 3, to a position in which a second pair of edges 101h-101d are engaged by the fixed contacts 103. Electrical contact is therefore made between the fixed contacts 103. It will be seen that the next two pulls on the chain 83 will rotate the primary rotor 93 to positions in which electrical contact is also made between the fixed contacts 103. The remaining four operative positions of the primary rotor 93, to which it is moved by subsequent pulls on the chain 83, repeat the sequence of breaking and making electrical contact between the fixed contacts 103.

A pair of electrical connectors 107a and 107b are provided at the anchored ends of the fixed contacts 103a and 103b respectively. The line 11 from the source of alternating current to the primary winding 31 of the ballast 3 is broken and the side 11a to the source of current is attached to the electrical connector 107a and the side 11b to the ballast primary is connected to the electrical connector 107b. Therefore, as the chain 83 is pulled repetitively, the primary rotor 93 of the switch 81 activates the ballast primary 31 in the repetitive sequence off-on-on-on.

The other ("secondary") rotor 95 of the rotor assembly 87 is in the form of an eight-pointed star the clockwisely forward edges 111a-111h of which are adapted to be engageable by the free ends of three fixed contacts 113a, 113b and 113c. The opposite ends of the fixed contacts 113 are anchored in the housing 97 and are provided with electrical connectors 117a, 117b, and 117c respectively. The fixed contacts 113 are arranged to engage alternate leading edges 111 of the secondary rotor 95. Thus, in the position shown in FIG. 4, the first fixed contact 113a engages leading edge 111a of the secondary rotor 95, the second fixed contact 113b engages leading edge 111c, and the third fixed contact 113c engages leading edge 111e. Two pairs of alternate leading edges 111b-111d and 111f-111h are electrically connected by electrically conductive strips 115a and 115b respectively.

It will be seen that the fixed contacts 113 are electrically insulated from each other when the secondary rotor 95 is in the position shown in FIG. 4. In the next operative position of the rotor assembly 87 the first conductive strip 115a electrically connects fixed contacts 113b and 113c. In the next operative position of the rotor assembly 87 the fixed contacts 113 are again electrically separated, and in the fourth operative position of the rotor assembly 87 the second conductive strip 115b electrically connects the fixed contact 113a and 113b. Continued movement of the secondary rotor 95 causes repetition of this same sequence of electrically connecting and separating the fixed contacts 113.

The electrical connector 117a on the fixed contact 113a is electrically connected by a lead 119a to the first lamp electrode circuit 17. The electrical connector 117b on the fixed contact 113b is electrically connected by lead 119b to the common electrode circuit 15. The electrical connector 117c on fixed contact 113c is electrically connected by lead 119c to the second lamp electrode circuit 19. Thus, opposite ends of the second lamp are shorted through the switch 81 when the rotor assembly 87 is in its second position, and opposite ends of the first lamp 51 are shorted when the secondary rotor 95 is in its fourth position.

When power is supplied to the ballast 3 and opposite ends of one lamp are shorted, only the other lamp lights. Therefore, when the rotor assembly 87 is in the position shown in FIGS. 3 and 4, no current is supplied to the ballast 3 and the lamps 51 and 53 are off. The first pull on the chain causes the primary rotor 93 to activate the ballast primary 31 and the secondary rotor 95 to short the second (indirect lighting) lamp 53. Therefore, only the first (direct lighting) lamp 51 lights. The second pull on the chain 83 causes the secondary rotor to remove the short and therefore causes both lamps to light. The third pull on the chain 83 causes the secondary rotor 95 to short the ends of the first lamp 51, thereby turning it off and leaving only the second lamp 53 lighted. As the chain 83 is pulled repetitively, the rotor assembly 87 of the switch 81 activates the lamps 51 and 53 in the repetitive sequence both off-first lamp on-both on-second lamp on.

It will be seen that the rotors of the switch 81, although being mechanically secured to form a single unit, are electrically completely separate, and in fact control current which may be completely out of phase and of entirely different voltages.

A second illustrative embodiment of switch 8 of this invention is shown in FIG 5. This switch 281 differs from the switch 81 of the first illustrative embodiment only in the secondary rotor and its associated fixed contacts. In this embodiment, a secondary rotor 295 of the same shape as the secondary rotor 95 of the first embodiment is provided having eight clockwisely leading edges 211a-211h. Two pairs of adjacent leading edges 211a-211b and 211e-211f are electrically connected by electrically conductive strips 215a and 215b respectively.

Four fixed contacts 213a-213d are arranged to engage four consecutive leading edges 211 of the secondary rotor 95. Thus, in the position of the secondary rotor 295 shown in FIG. 5, the first fixed contact 213a engages leading edge 211b of the secondary rotor 295, the second fixed contact 213b engages leading edge 211c, the third fixed contact 213c engages leading edge 211d and the fourth fixed contact 213d engages leading edge 211e. Electrical connectors 217a-217d are provided at the anchored ends of the fixed contacts 213a-213d respectively.

The principal advantage of this embodiment over the first illustrative embodiment is that it allows the installer of the switch to select any sequence of lighting patterns which he may consider desirable. Thus, if the lead 119c to the second lamp electrode circuit 19 is attached to the first electrical connector 217a, the lead 119b to the common electrode circuit 15 is attached to the second and third electrical connectors 217b and 217c, and the lead 119a to the first lamp electrode circuit 17 is attached to the fourth electrical connector 217d, the switch provides the same repetitive lighting sequence provided by the first illustrative embodiment of switch of this invention: both off-first lamp on-both on-second lamp on.

If the lead 119c to the second lamp electrode circuit 19 is attached to the first electrical connector 217a, the lead 119b to the common electrode circuit 15 is attached to the second electrical connector 217b and the lead 119a to the first lamp electrode circuit 17 is attached to the third electrical connector 217c, the switch provides the repetitive sequence both off-first lamp on-second lamp on-both on.

If leads 119c, 119b, and 119a are attached to electrical connectors 217b, 217c and 217d respectively the repetitive sequence is both off-both on-first lamp on-second lamp on.

It will be seen that in any of the above combinations the sequence in which the first lamp and second lamp are lighted may be reversed simply by attaching the leads 119a and 119c to the opposite electrical connectors 217. Other lighting sequences, in which one or more of the foregoing lighting patterns are not used, can also be achieved. For example, attaching lead 119c to connector 217b and lead 119b to connector 217c gives the sequence both off-both on-first lamp on-both on, while attaching lead 119b to connectors 217a and 217c, lead 119c to connector 217b and lead 119a to connector 217c gives the sequence both off-first lamp on-first lamp on-second lamp on.

Another embodiment of switch 8 of this invention is shown in FIG. 6. In this illustrative embodiment, each side of a switch 381 is a slightly modified knob-actuated switch of the type commonly used for three-way incandescent bulbs. A "primary" modified switch 383 controls current to the ballast primary 31, and a "secondary" modified switch 384 connects and disconnects the shorting leads. The modified switches 383 and 384 are of conventional construction in each having a knob 385 connected to a rotor 387 which is rotatably mounted in a housing 389. The rotors 387 are of the conventional four-position construction, and the conventional three fixed-spring contacts 313a, 313b and 313c are mounted in the housings 389 and arranged to contact edges 311 of the rotors 387. Each fixed contact 313a is provided with the conventional electrical connector 317a at its anchored end. A second electrical connector 318 is conventionally supplied on each housing 389, but is not in any way electrically connected with the rotor 387. A conventional lost-motion device, not shown, is provided between the knob 385 and the rotor 387 to provide a snap-action movement of the rotor from one of its operative positions to the next. The lost-motion device is conventionally a spring attached to both the rotor 387 and a stem 386 on the knob 385. The spring performs the additional function of preventing excessive backward rotation of the knob 385 and the rotor 387.

The principal differences between the switch assemblies 383 and 384 and conventional three-way bulb switches are that the switch assemblies 383 and 384 lack a conventional threaded socket on their upper faces and that they are provided with screw-type electrical connectors 317b and 317c connected to the fixed contacts 313b and 313c respectively, rather than having the conventional bulb-engaging contacts.

The rotor 387 of the "primary" switch assembly 383 is provided with a conventional conductive spider 315, which electrically connects three edges 311b, 311c and 311d of the rotor 387 to each other. An electrically conductive spider 316 on the rotor 387 of the "secondary" switch assembly 384 is modified by removal of one of its arms, and therefore electrically connects only two adjacent edges 311a and 311d of this rotor 387.

The switch 381 is completed by mounting the switch assemblies 383 and 384 in fixed relationship to each other in a frame 391. A gear 393 is mounted in the frame 391 between the switch assemblies 383 and 384 and engages their toothed knobs 385. An actuating knob 395 is attached to the gear 393 by a shaft 397. The rotors 387 and the switch assemblies 383 and 384 are turned to the relative positions shown in FIG. 6 before the gear 393 is inserted between them. In this position the electrically nonconductive rotor edge 311a of the primary switch assembly 383 is contacted by the fixed contact 313a and the two electrically nonconductive rotor edges 311b and 311c of the secondary switch assembly 384 are contacted by fixed contacts 313b and 313c respectively.

The lead 11a to the source of alternating current is attached to the first electrical connector 317a of the primary switch assembly 383, and the lead 11b to the ballast primary 31 is attached to the second and third connectors 317b and 317c of the primary switch assembly 383. If desired, the fourth connector 318 may form a junction terminal for the lead 12. It will be seen that the primary switch assembly 383 disconnects power to the ballast 3 in its first position, shown in FIG. 6, and supplies power to the ballast 3 in its other three positions.

The second lamp electrode circuit lead 119c is attached to the first electrical connector 317a of the secondary switch assembly 384. The common electrode circuit lead 119b is attached to the second connector 317b of the assembly 384. The first lamp electrode circuit lead 119a is attached to the third connector 317c of the assembly 384. It will be seen that in the first position of this rotor, shown in FIG. 6, the leads are all disconnected, in the next position the second lamp electrode circuit 19 and common electrode circuit 15 are connected, in the third position the first lamp electrode circuit 17 and the common electrode circuit 15 are connected, and in the fourth position the leads are again electrically disconnected.

It will therefore be seen that as the actuator knob 395 is turned the lamps 51 and 53 are lighted in the sequence both off-first lamp on-second lamp on-both on.

Another embodiment of switch 8 of this invention is shown in FIG. 7. This illustrative embodiment 481 is a pushbutton switch of the type in which the depression of any button releases the others, one and only one button always being depressed. Four push buttons 483a, 483b, 483c, and 483d are mechanically linked by a swingable rod 485 biased into contact with cams 487a-487d on the pushbuttons 483a-483d respectively. Each of the pushbuttons 483 is spring biased upwardly. As each button 483 is pushed down, its cam 487 pushes the rod 485 away from the cam 487 of the previously depressed button 483 sufficiently to release that button. The upper surface of the cam 487 of the depressed button is held by the rod 485.

Depression of the first button 483a separates a normally closed pair of contacts 411 and 413, which are respectively connected to the lead 11a to a source of alternating current and to the lead 11b to the ballast primary 31. Depression of the second button 483b simply releases the other buttons. Depression of the third button 483c connects a pair of normally separated contacts 415 and 417. The contact 415 is electrically connected to the second lamp electrode circuit lead 119c, and the contact 417 is electrically connected to the common electrode circuit lead 119b. Depression of the fourth button 483d connects a pair of normally separated contacts 419 and 421. The contact 419 is electrically connected to the common electrode circuit lead 119b, and the contact 421 is electrically connected to the first lamp electrode circuit 119a.

It will be seen that depression of the first pushbutton 483a disconnects the ballast primary and turns off both lamps; depression of the second button 483b connects only the contacts 411 and 413 and therefore lights both lamps; depression of the third button 483c connects the second lamp electrode circuit 19 and the common electrode circuit 15 and therefore lights the first lamp only; and depression of the fourth button 483d connects the first lamp electrode circuit 17 and the common electrode circuit 15 and therefore lights the second lamp only.

Numerous variations in the ballast circuit and switch of this invention, within the scope of the appended claims, will occur to those skilled in the art in the light of the foregoing description.

Claims

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. A switch adapted for use in a fluorescent luminaire having a multiple-lamp ballast and at least a first and a second fluorescent lamp, each of said lamps having a pair of electrodes electrically connected to said ballast, said switch having at least four stable operative positions adapted for selectively lighting neither of said lamps in a first position of said switch, both said lamps in a second position of said switch, only said second lamp in a third position of said switch and only said first lamp in a fourth position of said switch, said switch comprising

a. a first set of contacts, at least a first contact of said first set of contacts being adapted to be electrically connected to a lead connected to a source of electricity and at least a second contact of said first set of contacts being adapted to be electrically connected to said ballast;

b. a first movable means, having at least two stable operative positions, for electrically connecting, in at least one of its stable operative positions, said first contact of said first set of contacts and for electrically separating, in at least one other of its stable operative positions, said first contact of said first set of contacts from said second contact of said first set of contacts;

c. a second set of contacts, at least a first contact of said second set of contacts being adapted to be electrically connected to one of said pair of electrodes of said first fluorescent lamp, at least a second contact of said second set of contacts being adapted to be electrically connected to the other of said pair of electrodes of said first fluorescent lamp and to one of said pair of electrodes of said second fluorescent lamp, and at least a third contact of said second set of contacts being adapted to be electrically connected to the other of said pair of electrodes of said second fluorescent lamp;

d. a second movable means, having at least three stable operative positions, for electrically separating said second contact of said second set of contacts from said first and said third contact of said second set of contacts in a first operative position, for electrically connecting said second contact of said second set of contacts with said first contact of said second set of contacts and electrically separating said second contact of said second set of contacts from said third contact of said second set of contacts in a second operative position, and for electrically connecting said second contact of said second set of contacts with said third contact of said second set of contacts and electrically separating said second contact of said second set of contacts from said first contact of said second set of contacts in at least a third operative position, said second set of contacts and said second movable means being electrically isolated within said switch from said first set of contacts and said first movable means in all operative positions of said first and second movable means; and

e. means mechanically connecting said first movable means with said second movable means for providing simultaneous movement of said first and second movable means to said first, second, third, and fourth positions of said switch;

said first movable means electrically separating said first contact of said first set of contacts from said second contact of said first set of contacts in said first operative position of said switch;

said first movable means electrically connecting said first contact of said first set of contacts with said second contact of said first set of contacts and said second movable means being in its first operative position for electrically separating said second contact of said second set of contacts from said first and third contacts of said second set of contacts in said second operative position of said switch;

said first movable means electrically connecting said first contact of said first set of contacts with said second contact of said first set of contacts and said second movable means being in its second operative position for electrically connecting said second contact of said second set of contacts with said first contact of said second set of contacts and electrically separating said second contacts of said second set of contacts from said third contact of said second set of contacts in said third operative position of said switch; and

said first movable means electrically connecting said first contact of said first set of contacts with said second contact of said first set of contacts and said second movable means being in its third operative position for electrically connecting said first contact of said second set of contacts with said third contact of said second set of contacts and electrically separating said first contact of said second set of contacts from said second contact of said second set of contacts in said fourth operative position of said switch.

2. The switch of claim 1 wherein said first movable means and said second movable means comprise manually depressible pushbuttons, and said means mechanically connecting said first movable means with said second movable means comprise means for raising a previously depressed button whenever one of said buttons is depressed.

3. The switch of claim 1 wherein said first movable means comprises a first rotor and first movable contact means carried by said first rotor and said second movable means comprises a second rotor and second movable contact means carried by said second rotor, said first rotor and said second rotor being connected to each other for simultaneous rotation to each of said four operative positions of said switch.

4. The switch of claim 3 wherein each of said rotors is provided with four operative faces, each of said faces on said first rotor being adapted to be engaged by each of said first set of contacts in one operative position of said first rotor, and each of said faces on said second rotor being adapted to be engaged by each of said second set of contacts in one operative position of said second rotor; and wherein, numbering the operative faces of the rotors consecutively, a second, third, and fourth face of said first rotor are electrically connected to each other by said first movable contact means, said first contact of said first set of contacts engaging a first face of said first rotor, said second contact of said first set of contacts engaging said second face of said first rotor and a third contact of said first set of contacts engaging said third face of said first rotor in said first position of said switch, and a first and fourth operative face of said second rotor are electrically connected to each other by said second movable contact means, said first contact of said second set of contacts engaging said first face of said second rotor, said second contact of said second set of contacts engaging a second face of said second rotor and said third contact of said second set of contacts engaging a third face of said second rotor in said first operative position of said switch.

5. The switch of claim 3 wherein said first rotor and said second rotor are secured to each other for simultaneous rotation about a common axis, said first rotor and said second rotor comprising a rotor assembly.

6. The switch of claim 5 wherein each of said rotors is provided with eight operative faces, each of said faces on said first rotor being adapted to be engaged by each of said first set of contacts in one operative position of said rotor assembly, and each of said faces on said second rotor being adapted to be engaged by each of said second set of contacts in one operative position of said rotor assembly.

7. The switch of claim 6 wherein, numbering the operative faces of the rotors consecutively, a second, third, fourth, sixth, seventh, and eighth face of said first rotor are electrically connected to each other by said first movable contact means, said first contact of said first set of contacts engaging a first face of said first rotor and said second contact of said first set of contacts engaging a fifth face of said first rotor in said first operative position of said switch, and a second and fourth face of said second rotor are electrically connected to each other and a sixth and eighth face of said second rotor are electrically connected to each other by said second movable contact means, said first contact of said second set of contacts engaging a first face of said second rotor, said second contact of said second set of contacts engaging a third face of said second rotor and said third contact of said second set of contacts engaging a fifth face of said second rotor in said first operative position of said switch.

8. The switch of claim 6 wherein, numbering operative faces of the rotors consecutively, a second, third, fourth, sixth, seventh, and eighth operative face of said first rotor are electrically connected to each other by said first movable contact means, and a first and second face of said second rotor are electrically connected to each other and a fifth and sixth face of said second rotor are electrically connected to each other by said second movable contact means.

9. A ballast circuit for a fluorescent luminaire comprising a multiple-lamp ballast, a first fluorescent lamp having a pair of electrodes electrically connected to said ballast, a second fluorescent lamp having a pair of electrodes electrically connected to said ballast, and switch means for selectively lighting neither of said lamps in a first stable position of said switch means, both said lamps in a second stable position of said switch means, and only said second lamp in a third stable position of said switch means, said switch means comprising

first contact means for connecting said ballast to a source of electricity and separating said ballast from the source of electricity,

second contact means for introducing and removing a short circuit between said pair of electrodes of said first lamp, and

manually operable means mechanically linking said first contact means and said second contact means for disconnecting said ballast from said source of electricity in the first position of said switch means, for connecting said ballast to said source of electricity and removing said short circuit between said pair of electrodes of said first lamp in the second position of said switch means, and for connecting said ballast to said source of electricity and introducing said short circuit between said pair of electrodes of said first lamp in the third position of said switch means, said switch means introducing no short circuit between said pair of electrodes of said second lamp in at least said second position and said third position of said switch means.

10. The ballast circuit of claim 9 wherein said switch means has a fourth position for selectively lighting only said first lamp, said second contact means further introducing and removing a short circuit between said pair of electrodes of said second lamp, said manually operable means linking said first and second contact means for connecting said ballast to said source of electricity, removing said short circuit between said pair of electrodes of said first lamp, and introducing said short circuit between said pair of electrodes of said second lamp in the fourth position of said switch means.