US2375967A - Circuits - Google Patents

Description

y 1945. v. G. VAUGHAN 2,375,967

CIRCUIT Filed Jan. 24, 1941 Patented May 15, 1945 CIRCUITS Victor G. Vaughan, Attleboro, Mass, assignorto Metals & Gontrols Corporation, Attleboro. 'Mass., a corporation of Massachusetts Applicationd'anuary 24, 1941, Serial No. 375,805

(Cl. 3l5--100) 4 Claims.

This invention relates I to thermostatically controlled electric circuitsandrmore particularlyto switch circuits for starting'fiuorescent tubelights.

An object of thisinvention is .to-providea thermostatically controlled starting switch circuit for starting so-called fluorescent ligh tubes or lamps. Another object of .theinvention is-to p'ro vide a circuit wherein only two wires are needed to connect thestarting switchto the circuit in order to accomplish the starting of the lamp. Other objects WilLbeinpart obvious andin part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, and arrangements of parts which will be exemplified in the circuit hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which are illustrated several of the various possibleembodiments of the invention,

Fig. 1 is a diagram of a circuit embodyingthe present invention;

Fig. 2 is a diagram of a similar circuit but employing a different-type of thermostatic element;

Fig. 3 is a diagramoi a similar circuit embodying a still different type of thermostaticelement; and,

Fig. 4 is a diagram of a similar circuit but embodying a still different type ofthermostat'ic element.

Similar reference characters indicate correspending parts throughout'the several views of the two electrodes are customarily placed in series with a choke coil across the power lines. After a given interval of time necessary to heat the electrode the interconnection between the electrodes electrodes can be done in many ways, but it is the purposeof this invention to provide a simple thermostatic switch circuit for that purpose.

The preferred thermostaticswitch for use in this invention is that shown and described inJohn D. Boleskys United States Patents 2,199,387 and 2,199,388. However, any thermostatic switch of similar nature can be used to accomplish the purpose of .the present invention. Briefly described, the preferred switch is as iollowszA base made of electrically insulating material is provided having a circular rim and an upstanding skirt thereon. Mounted on an adjusting screw passing through the center of the baseis a thermostatic snap-acting disc such as is described and shown in John A. Spencer's Patent 1,448,240. Thedisc is mounted on the adjusting post by means of the usualaoutments and shoulders so as to provide a secure, yet not binding, mounting of the disc. Contact buttons are welded or otherwise electrically fastened to thedisc on diametrically opposite points on its periphery, to cooperate with stationary contacts passing through holes in the base and. clamped therein, or otherwise fastened. A third stationary contact is provided and is similarly fastened to the base I. A heater wire is fastened at one end to the third stationary contact and at'it's otherend to one of the other stationary contacts. This switch and its operation are described in detail in John D. Boleskys patents above referred to.

Referring now to Fig. l of the drawing, numeral 3 indicates generally a thermostatic switch comprising asnap-acting disc 5, movable contacts G and] mounted on disc 5, and stationary contacts 8 and 9 cooperating with contacts Sand 1 to open and close the electrical circuit,'and stationary contact H The heater wire I! for the-thermostat is connected between stationary contacts 8 and it. Such a switch is fully described in the aforesaid Patents Nos. 2,199,387 and 2,199,388.

Numeral l2 indicates, in'general, the outer wall of a conventional type fluorescent lamp. Sealed into the ends of this lamp are the two electrodes l3 and I l. Power line It is connected to one side of the electrode iii-through a choke coil'l5. Power line ll is connected to one side of the electrode i l. The other side of electrode 13 is connected to stationary contact It. The other side of electrode it is connected to contact 9. Permanently shunted across stationary contacts 8 and dis'an external resistance 18.

In this circuit, the choke coil I5 is used for two purposes as described .above: First, to provide a momentary high-voltage discharge to ignite the lamp when the thermostatic disc opens, and secondly, to limit the amount of current which flows through the lamp.

The operation of the circuit is as follows: When line switch 59 is closed, current flows through wire 26, electrode l4, wire 2!, disc 5, heater wire I I, wire 22, electrode 13, wire 23, choke coil l5, and to the power line It. The electrodes l3 and M commence to heat, and heater wire ll commences to heat up disc 5. Within two or three seconds, disc 5 snaps to its upward (circuit opening) position, thus opening the interconnection between the'electrodes through wires 2i and 22. This opening of the circuit causes a momentary, induced, relatively high. voltage to be impressed across the tube from electrode IE to electrode I l and starts the gaseous discharge. This discharge between the electrodes causes the fluorescent coating of the tube to glow and give the light for which the lamp is designed. noted that when the disc 5 is in its closed position, the electrical resistance i8 is shunted out of the circuit since its resistance is relatively very high in comparison to the resistance of the disc 5. However, when disc 5 opens, heater wire I8 is now in the circuit and current now passes through the electrodes, electrical resistance l8, and heater H. However, resistance It is purposely of such value as to reduce the current passing through the electrodes to a very low value. This low current allows heater wire H to generate just enough heat to keep the disc 5 in its switch-open position while the tube is lighted. When the switch is is opened, the gaseous discharge ceases and the tube no longer fluoresces.

Heater l I now has no current flowing through it, so it cools down, and disc 5 likewise cools to snap back to the switch-closed position. The circuit is then ready for relighting the lamp.

Any other form. of simple thermostatic switch may be employed in this invention, as well as ambient compensated types such as shown for example in Harold M. Wilson's United States Patent No. 2,203,558.

A simple strip type composite metal thermostat is shown in Fig. 2. It is mounted at one end in any suitable manner as shown at 26. The opposite end carries a movable contact 2'! which cooperates with a fixed contact 9. The relatively high resistance I8 is as before shunted around the contacts. in this instance, movable contact 21 and stationary contact 9. The heater H is connected to movable contact 21 as shown and is located so as to control the strip type thermostat 25. The circuit operates in a manner similar to that of the Fig. 1 circuit. Movable contact 2'! and stationary contact 9 are held in contact by strip 25 when the device is cold. Upon closing switch is the current passes through the contacts 9 and 21 and through heater H until strip 25 is heated sufficiently to break the circuit. The current thereupon passes through the high resistance iii to movable contact 2? and heater l i at a rate sufficient to cause thermostatic strip 25 to maintain contact 21 away from contact 9.

Fig. 3 illustrates a circuit embodying an am bient compensated type of thermostat such as is shown and described for example in Harold M. Wilsons United States Patent No. 2,203,558. The thermostatic element 28 in this instance is composed of two composite metal snap acting discs 29 and 30. The outer edges of these discs are preferably mounted so as to be relatively immovable as shown at 3| and 32. Such a mounting is,

It is to be together.

however, arranged to be suificiently loose so that the discs can snap back and forth freely. The centers of the discs are held together by any suitable means as shown at 33 so that they move The discs 29 and 30 are operatively associated with arm 43 which is made of spring metal. The connection 33 between the discs is elongated as shown at 4| so as to contact an in sulating sleeve 42 which sets into an opening 43 in the arm All. Insulating member 42 is headed over as shown at M where it contacts portion M of connection 33. The arm carries a contact 45 which cooperates with contact 46 mounted on stationary arm 41. The tension in arm. 40 is arranged so that the arm tends to move contact 4-5 out of engagement with contact 66. When the discs 23 and 3B are in the position shown in Fig. 3.

. however, they, through connecting member 33.

and insulating member 42 force arm 4!? against the tension thereof into position so that contacts and it are in engagement,

When the discs 29 and 30 snap into the opposite position of concavity due to heat from the heater wire H the portion 4| of connecting member 33 no longer keeps the arm 40 in a position such that the contacts 45 and 46 are in contact. The

inherent tension of arm 40 then separates the contacts 15 and 45. The current then passes through resistance l8. Inasmuch as the construction and operation of an ambient compensating device such as indicated is clearly described and explained in the aforesaid Letters Patent, it will not be repeated here.

It will be noted that the current path is through the wire 2i, arm at, contact 46, contact &5, arm id, heater H, and wire 22 when the device is in the Fig. 3 position. When the discs 29 and 39 snap to the opposite position the current path is from wire 2! through resistance l3, arm 49, heater H, wire 22. The heater II is located so to affect disc 3Q more than disc 29. The passage of current through heater H causes disc 38 to over balance disc 29 and open contacts 35 and 46. When the contacts are open, a small amount of curent is carried by resistance iii to heater I i and keeps the disc 30 at a relatively higher tempera ture than disc 29.

A still further embodiment of the invention is illustrated in Fig. 4. This likewise employs an ambient compensated thermostatic switch. The thermostatic switch in this instance comprises two composite metal strips of thermostatic material 3&- and 35. They may be mounted in any suitable manner at one end as indicated at is and 3?. Cooperating contacts 38 and 33 are attached to the opposite ends, that is, the movable ends of the thermostatic strips. Strips 3d and 35 are constructed so that they will maintain the contacts 38 and til together during variations in ambient temperature, since they have the same relative response to changes in ambient temperature. I-Ieatcr ll however, is positioned so as to affect one of the strips. in this instance to a greater extent than the other strip. Accordingly, when current passes through the circuit when contacts 38 and 39 are together. it passes through the heater ll likewise, thereby imparting a relatively greater movement to strip 35 than to strip 36. Strip 35 therefore moves a greater distance than strip 34 and separates the contacts 3f! and 39. The current is then shunted around the contacts 353 and 39 and passes through resistance Hi. It will be noted how ever, that the current still passes through heater H so that strip 35 is kept at a relatively higher temperature than strip 34 and contacts 38 and 39 are maintained apart.

Similarly other forms of thermostatic switches may be employed in this invention with only relatively minor changes in the circuit,

Among the advantages of the invention are (1) the need of only two wires (2! and 22) to connect thestarting switch to the lamp, which makes for ease of wiring and installation; and (2) the fact that when the lamp is lighted the heat holding disc 5, strip 25, or the like in circuit-open position is just enough for this purpose; this means that when the main line switch I9 is opened to shut off the lamp, disc 5 immediately.

cools to circuit-closed position. Thus, the delay necessary before the lamp can be reignited by means of switch I9 is reduced to a minimum.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A circuit comprising a fluorescent light source, a thermostatic switch characterized by having only two lead wires, said switch being connected across the electrodes of said light source, an electrical heating resistance connected in series with said thermostatic switch and adapted to heat said switch, and a relatively high resistance connected across the contacts of said switch, said switch comprising a snap-acting thermostatic element.

2. A circuit comprising a fluorescent light source, a thermostatic switch characterized by I having only two lead wires, said switch being connected across the electrodes of said light source, an electrical heating resistance connected in series with said thermostatic switch and adapted to heat said switch, and a relatively high resistance connected across the contacts of said switch, said switch comprising a thermostatic element.

3. A circuit comprising a fluorescent light source, a thermostatic switch characterized by having only two lead wires, said switch being connected across the electrodes of said light source, an electrical heating resistance connected in series with said thermostatic switch and adapted to heat said switch, and a relatively high resistance connected across the contacts of said switch, said switch comprising a creep-type thermostatic element.

4. A circuit comprising a fluorescent light source, a thermostatic switch characterized by having only two lead wires, said switch being connected across the electrodes of said light source, an electrical heating resistance connected in series with said thermostatic switch and adapted to heat said switch, and a relatively high resistance connected across the contacts of said switch, said switch comprising an ambient compensated thermostatic element.

VICTOR G. VAUGHAN.

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