US2345638A - Enclosed arc device and controlling means for service at varying intensities - Google Patents

Description

ENCLOSED ARC DEVICE AND CONTROLLING MEANS FOR SERVICE AT VARYING INTENSITIES Filed May 3. 1941 April 4, 1944. G. s. SPERTI 2,345,638

11 14%; 22 P 12 15 29 l 19 a 13 J0 LIL I26 INVENTOR. Games: 5. SPEETI.

M I-M ATTORNEYS.

Patented Apr. 4, 1944 UNITED STATES PATENT OFFICE SITIES George S. Sperti, Covington,

Ky., assignor to The Institutum Divl Thomae Foundation, Cincinnati, Ohio, a corporation of Ohio Application May 3, 1941, Serial No. 391,680

6 Claims.

" distinct field of utility for enclosed are devices to be operated at a plurality of different intensities; and such devices should be so arranged as to be instantly responsive to variations in the exciting current. By way of a single example, devices of this character are useful in electrical refrigerators or in refrigerated storage spaces of any kind. For such use the enclosed arc device is made in the form of a fluorescent tube with an envelope pervious to ultraviolet radiation, said envelope being wholly or partially coated with a fluorescent coating. The control circuits are so arranged that the arc is operated at low intensity when the refrigerated space is closed, the intensity of the ultra violet'radiation under these circumstances however, being sufiicient to keep the refrigerated space sterile. I have found that with a pervious envelope, a useful quantity of ultra violet energy will pass through a fluorescent coating of useful thickness; but as indicated. a portion of the envelope may be left uncoated if desired. When the refrigerated space is opened, the circuit arrangement is such that the arc operates at a very much higher intensity. This not only gives a bright illumination sufficient for visual purposes, but also increases the emanation of ultra violet light for an additional sterilizing effect during the period of interchange of air in the refrigerated space. This is exemplary only of one type of utility for a lamp and system of the kind herein described and claimed.

The principal object of my invention is the provision of a new type of starting means and consequently a new lamp structure, and the provision of a new circuit and control means for such a lamp, with the attainment of a number of advantages such as will hereinafter be set forth. This object and others which will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain structure and arrangement of parts of which I shall now describe an exemplary embodiment in the aforementioned use, it being understood that neither the structures nor the utility of my invention are so limited.

Reference is made to the drawing wherein:

Figure 1 is a diagrammatic view showing a lamp and the attendant circuit arrangement.

Fig. 2 is an elevational view of a lamp.

Fig. 3 is a cross sectional view of the envelope thereof taken along the lines 33 of Fig. 2.

I have illustrated in Fig. 2 an enclosed are lamp having an envelope l of elongated form terminating at each end in bases 2. These bases have contact members 4 in appropriate number. The type of arc device of the exemplary embodiment is that comprising an envelope containing a suitable rarefied ionizable atmosphere, and electrodes for an arc discharge, together with starting means comprising means for ionizing the atmosphere. The envelope contains a quantity of mercury adapted to be vaporized during the operation of the are for the purpose of increasing the ultra violet radiation of the arc. My invention is applicable to the operation of enclosed arc lamps as fluorescent tubes, in which event it is not necessary that the envelope be pervious to ultra violet radiation, and the interior of the envelope will usually be coated with fluorescent substances. My invention is also applicable to enclosed arc lamps, the primary or sole function of which is to give off ultra violet radiation, and in which the envelope, or a portion of it at least, will be pervious to ultra violet radiation. For many uses, the envelope may advantageously have a filtering action, diminishing theradiation of the shorter wave lengths in the ultra violet spectrum, say, wave lengths of about 2700 angstrom units and shorter. Or as illustrated in Fig. 3, the envelope I may be of a character pervious to ultra violet light, and may be coated within with a fluorescent substance 5, the coating, however, being absent over a portion of the area of the envelope. In the particular embodiment a longitudinal area 6 of the envelope is left uncoated.

It will also be understood that the shape of the envelope and the particular placement of main arc electrodes therein, as well as the form and placement of the bases andelectrical connecting members, do not constitute limitations upon my invention.

In the exemplary embodiment shown, the envelope I is provided with a press at each end. Terminal members 1 and 8 at one end, and 9 and H] at the other, enter the envelope through the presses respectively. The ends of the conductive members I and 8 within the envelope are bent over to form electrode members I l and I2; andthe elements 1 and 8 are connected within the envelope by a filament I3. I have shown a similar structure at the other end of the lamp where the elements 9 and ID are bent over to provide electrode elements l4 and I5 and are connected by a filament Hi. In the lamp of my invention, however, I do not require such an elaborate structure at both ends, since the lonization of the gas may be caused to proceed from a starting means at one end of the envelope only, in which event, I may substitute for the members 9, l0, l4, I5 and iii, a single electrode member if desired. The structure shown, however, is a standard structure with me, and I find that it is as inexpensive to produce and employ these structures as it would be to provide special structures. Moreover, the presence of the filament l6, though it is not used in the circuit arrangement of Fig. 1, permits the use of the lamp in the ordinary circuit if anything should happen to the special starting means hereinafter described. On the other hand, however, the structures at both ends of the tube may be exactly the same, in cluding the special starting means hereinafter described which either may be employed in the lampas a spare starting means or by a re-arrangement of the circuit which will be clear to the skilled worker in the art, may be employed concurrently with a special starting device at the opposite end of the tube.

The special starting device comprises a filament I! located effectively out of the path of the arc and having leads l8 and IS. The filament II will be coated with an electron-emissive substance such as a refractory oxide, so that when the filament becomes heated the giving off of ions from the refractory oxide will ionize the adjacent gas. The filaments I3 and I6 are also preferably coated with an'electron-emissive substance.

Before describing the operation of the lamp structure'thus far set forth, I will describe the exemplary electrical circuit in which it is used. A source of power will be understood to be across the power application points 20 and 2i. The point 20 is connected by a lead 22, through an impedance, preferably in the nature of a choke 23, to the lead 8 of the electrode assembly at one end of the lamp. The other power application point 2! is shown as connected by a lead 24 through an impedance, preferably in the nature of a resistance 25, to lead ID of the electrode assembly at the other end of the lamp. The impedance 25 will be sufficient to ballast the arc at a high operating intensity. When the impedance 231i is in the circuit along with impedance 25, the arc will operate at a lower intensity. I provide means for short-circuiting the impedance 23, which means comprises a short-circuiting lead 26 in which is included one part 21 of a single throw, double pole switch.

The lead [9 of the starting filament I1 is shown connected by a lead 28 through the other half 29 of the single throw, double pole switch and through a high resistance 30 to lead ID of the lamp and to the power lead 2|. The lead I8 of the starting filament I1 is shown as connected through a high resistance 3| to the lead I of the electrode assembly at the left hand end of the lamp.

The filament I! is a relatively small filament adapted to be highly heated under the application of a relatively small current. This makes for more rapid starting of the arc as will be seen hereinafter.

Considering the double pole, single throw switch 21, 29 to be closed, it will be seen first that the impedance 23 is short-circuited, and the higher operating potential is applied across the arc electrodes. Current flows through lead 8, through th filament 13, through the resistance 3|, through the starting filament I1, through resistance 39 and resistance 25 to the opposite one of the power leads. The small filament l! is highly heated and rapidly ioniz'es the adjacent gas. The filament I3 is at a diflerent potential from the filament I! because of the interposition of resistance 3 l, and a trigger arc flashes between filaments l3 and H. The supplementary arc heats the filament l3, and causes the electron-emissive substance thereon to give off electrons. This ionizes the surrounding gas further. Likewise electrode portions II and I2 will be at a different potential as respects each other because of the resistance of filament l3 and a supplementary arc will be formed between them. These supplementary arcs rapidly ionize the entire body of the gas in the envelope to the point where the main arc will flash between electrode elements H and l4, [5. The electrode elements l4, 15 are at a different potential from electrode elements I I, [2 by reason of the interposition of resistances 30, 3 I.

As soon, however, as the main arc strikes, the arc itself effectively short-circuits that circuit branch which comprises filament I3, resistance 3|, filament I1 and resistance 30. It will be noted that this circuit branch lies on the are side of the ballast impedance 25. As a consequence, as soon as the main arc is struck the current applied across the small filament I'I falls approximately to zero. This substantially deenergizes the filament l1, and also extinguishes any are which may be passing between filament l1 and any other element of the apparatus. Thus the life of filament I! is greatly prolonged. If the double pole, single throw switch 21, 29 be opened it will be noted that one effect is to destroy the short-circuit by-passing impedance 23. The effect of this impedance will be to cause the arc to operate at a very much lower intensity. Another efiect of the opening of the switch is to break the circuit branch which includes the small filament ll. Thu the starting apparatus is protected from any of the effects of the arc. The are, however, continues to function between electrodes l2 and I5, but at lower intensity. The switch 21, 29 may be thought of as operated by the door of-the refrigerated cabinet in the exemplary embodiment, so as to be closed. when the door is open.

In this system, while the arc is operating at low intensity, if it should become extinguished, it will not be re-ignited unless and until switch 21, 29 is closed, as by the opening of the door of the refrigerated space. For certain uses this is advantageous. Moreover, it assures that the arc shall always be started at a time when the circuit arrangement is such as to cause the arc to operate at high intensity. However, the shortcircuiting of the circuit branch of filament I! by the arc is so effective at both high and low intensities that it is possible to omit the portion 29 of the double pole, single throw switch so as to leave the filament I! always in circuit.

Modification may be made in my invention without departing from the spirit of it.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In an enclosed arc lamp an envelope, an electrode assembly in said envelope comprising a pair of leads passing through a press in said envelope with their ends juxtaposed to form electrodes, said leads being connected by a filament coated with electron-emissive substance, a second filament in said envelope also coated with electron-emissive substance in juxtaposition to said first filament, a separate pair of leads passing through said press for applying power to said ascaess second filament, and at least one other electrode acting as a main arc electrode in said envelope.

2. The structure claimed in claim 1 in which said envelope is pervious to ultra-violet radiation, and contains a small quantity of mercury, and is coated in part at least with a fluorescent substance.

3. The structure claimed in claim 1 in which said other electrode comprises a pair oi leads with their ends bent over and juxtaposed to form electrodes, and a filament coated with electronemissive substance connecting said leads.

4. The structure claimed in claim 1 in combination with means for applying power to said electrodes for the operation of an arc, said means including a ballasting impedance, and a circuit for said second mentioned filament to apply power thereto, said circuit including said first mentioned filament and a resistance whereby said filaments are maintained at different electrical potentials as respects each other.

5. The structure claimed in claim 1 in combination with means for applying power to said electrodes for the operation of an arc, said means including a ballasting impedance, and a circuit for said second mentioned filament to apply power thereto, said circuit including said first mentioned filament and a resistance whereby said filaments are maintained at different electrical potentials as respects each other, said last mentioned circuit being a circuit in shunt to said arc, and located on the lamp side of said ballasting resistance, whereby said are is caused to short circuit said last mentioned filament.

6. The structure claimed in claim 1 in combination with means for applying power to said electrodes for the operation of an arc, said means including a ballasting impedance, and a circuit for said second mentioned filament to apply power thereto, said circuit including said first mentioned filament and a resistance whereby said filaments are maintained at difierent electrical potentials as respects each other. said power applying means containing a second impedance to limit still further the application of power to said arc, means for short circuiting said second impedance, and switch means concurrently breaking said short circuit, and breaking said circuit for said second filament.

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