US2398682A - Starting control for electric discharge devices - Google Patents

Description

April 16, 1946- J. R. WHITESIDE ETAL STARTING CONTROL FOR ELECTRIC DISCHARGE DEVICES Filed April 8, 1942 w L Q lnven't'ors: Jack RJWhiteside,

N x p I Mark A. Tow nsend, by 1 Wm/ Their A'ttorneg.

'broken to start the discharge.

Patented Apr. 16,

s PATENT orrlca STARTING CONTROT; FOB ELECTRIC DISCHARGE DEVICES Jack R. Whiteslde, Cambridge, Mass, and Mark A. Townsend, Cleveland Heights, Ohio, assignors to General Electric Company, a corporation of New York.

Application April 8, 1942, Serial No. 438,208

6 Claims.

This invention relates to the control of electric discharge devices, and is especially concerned with the starting: of such devices. The invention is very useful in connection with fluorescent tubes or lamps of the positive column discharge type, and is hereinafter explained with particular reference to lamps of this character and their usual starting arrangements, as exemplified in U. S. Patent 1,951,112, March 13, 1934, to Wels, or,

Patent 2,212,427, August 20, 1940, to Peters, for instance.

Ordinary tubular fluorescent lamps have electrical starting circuits which are energized and Sometimes this has to be done several times before the discharge actually starts. For this purpose, automatic means are commonly provided which will make and break the starting circuit indefinitely until starting is accomplished.

Through deterioration in service or as the resuit of accident, fluorescent lamps and other discharge devices often or eventually become incapableof starting and normal running, so that the only eiIect of the automatic efforts to start I such a lamp is a continual flashing in it that is very annoying to those in the area that receives the light of the flashing lamp, besides uselessly wearing out the starter device. Usually such incapacity for starting is due to loss or electron emission from one or both electrodes of the lamp,

which may result from dissipation or other loss of activating material on which the emission depends. The objectionable flashing of such a lamp goes on indefinitely until the power supply is shut off, or thelamp is removed from the circult.

start as long as there is any reasonable promise of success. This is accomplished by keeping the starting circuit open or rendering the starter ineflective to close the starting circuit alter repeated operation of the starter has failed to start the discharge, thus locking ou the starter, so to speak. We have hereinafter described and, explained this lock-out" as applied to the type of starter disclosed inU. S. Patent No. 2,372,148, granted March 20, 1945, upon an application Serial No. 430,611, flied February 12, 1942, by Mark A. Townsend, in lieu of lock-in provisions there shown. However, our invention is also applicable to other types otstarter, such as that disclosed in application Serial No. 422,416, filed December 10, 1941, by Jack R. Whiteside, or even an ordinary gicw-switch Both of the applications r; mentioned are assigned to the assignee of this application.

Various features and advantages of the invention will become apparent from the description of species and forms of embodiment, and from the drawing, 7

In the drawing, Fig. 1 is a digrammatic view of a fluorescent tube or lamp with circuit connections includin the present invention, a midportion, of the lamp envelope being broken out and omitted; Fig. 2 is a tilted or perspective view of one form of starting switch device; and Fig. 3 is a fragmentary view corresponding to the upper portion of Fig. 2, but showing certain parts in other operating positions,

Fig. 4 is a view similar to Fig. 2 illustrating our lock-out in connection with a glow-switch.

Figs. 5 and 6 are views similar to Fig. 2 illustrating othert forms of embodiment of the invention:

Fig. 1 shows an ordinary fluorescent tube lamp L of the positive column electric discharge type with a tubular envelope "I having spaced apart activated thermionic cathodes II, II in its ends, which may be specially heated cathodes of usual coiled fllament type, and are shown connected across a power-supply circuit P including the usual ballast I, which also serves as a starting inductance, and the manual make-and-break switch I. The envelope ll may contain a lowpressure atmosphere of starting gas, such as argon at a pressure of 2 to 5 mm. of mercury, and also a vaporizable and ionlzable working substance such as mercury. A supply of mercury, which may exceed the amount that will vaporize during operation of the lamp L, is indicated by a drop ll inside the envelope l0, and an internal coating of fluorescent material or phosphor II on the envelope wallsis also indicated. A starting and electrode-heating circuit H is shown connected across the circuit P through the filamentary cathodes l I, II, with a starting switch S included therein, which may be of thermal type. A capac- 0.00'7 mlcrofarad) may be connected across the switch 8, to minimize radio interference as well as arcing when the switch 8 opens and breaks the circuit H.

The general mode of operation in starting the lamp L with this circuit arrangement is that when the switch ll is closed to turn on the lamp L, the

switch device 8 permits flow of current through the circuit H and the cathode filaments H, H in series therein for a suiflcient length 0! time to preheat the cathodes to an adequate emissive tem- Odes ii, ii suiiices to initiate discharge between them, or, in other words, starts the lamp,

As shown in Figs. i end 2, the switch device S is a thermal switch co. prising switch members it that are connected to opposite sides oi the starting circuit H and cooct in making and breaking this circuit. The switch members 2t, 22 may consist of slender, straight, approximately up right thermostatic etal strips coacting as both temperatureo'esponsive elements and currentcarrying contact members. Contact pieces it, (as of coin silver wire) shown welded to the upper free ends oi the members El, 22, and extending at right angles to one another, The members ll are preieroioly hem; semicircuiorlv near their anchored lower ends, these bends it, it being both turned th right in Fig. 2. Ad

jacent the thermostat :sieinher ill, 22, about concentric with their hendc it, it, there are resistance heaters iii, heating these members. The circuit connections oi these heater will he more fully described hereiriaiter; for the present it suffices to say that the heater it for the mom" ber M is connected across the circuits H end P in parallel wi h the members ii, 22, so as to respond essentially to the energizatlon and voltage of the main discharge circuit P during starting, while the heater 20 for the member 22 is connected in the circuit H in series with the members 2|, 22, so as to respond to the energizatlon of this starting circuit H and to the current flow therein. The thermostatic switch members 2|, 22 may be arranged to flex in the same direction (toward the right in ,2) when heated, and vice versa.

The switch 8 may have as its lease an insole" tive disc end roev also hiclude an upright insulative frame structure ti, somewhat resemhllnr; an E with the short horizontal mid-stroke omitted. Underneath the lease disc 30 are shown binding post connector 3d, M to which the Wires oi circuit H are co "'ected, and their reduced shanks are iastenecl "ouch the disc 30 and have attached extension, o. up through the lower por tion of the :irsrne ti, ore headed over or expanded. into rial-ices hearing on the frame iii 33, 33 to secure it to t. A sheet metol cover, casino", or ooh not" J an, insulotive lin inc may enclose the r l device i'rom the lease 3t up. The flower is or twitch memloers ii, iii ore shown "i ored at opposite sides oi the lower meniher iii, lacing attached by Welding to staple- litre iootenero 35, 35 whose shanks are suitoioly fliiiiil in tliic frame member. The heater to, which is preicrahh; or high re sistance, hos one end connected by a lead It to one or the conoectors while its other end is connected by a lead iii to the fastener 35 that car-- ries the switch member 2|, and is also normally connected (icy means hereinafter described) to the other connector 31'. One end 01' the heater 26 is connected by a lead '38 to the same connector 32 to which the lead 36 or heater 25 is connected, while its other end is connected by a lead 39 to the fastener 35 that carries the switch member 22, and is thus also connected through the switch 8 (when closed) to the other connector 32. The heater 2!, which is subject and responsive to the high ballast output voltage when the switch 8 opens, 18 preferably of very high resistance, such as 100,000 ohms, for example, in order to prevent it from seriously lowering the voltage available for starting the discharge. It may also be found advantazeoua to ill) make the heating resistance 25 ct a type having a negative temperance-resistance coeiiiicient, so that it may heat more rapidly and cause the switch member ii to close more quickly, though not moving enough to close under the normal operating voitoge or the lamp. The heater it, through which flows the cathode preheating current in the sterling circuit H when the switch S is closed, is preferably of low resistance, such as 3 ohms, in order to s its energy consumption. Airy suitehle p1 ovlsio may he made to cause the heater the thermostat 22 ly, such as enclosin Ziass sleeve til, so

in at Dice to give hand, the her-1till} may he mix, to lower its heat "JJhen the switch line voltage is an "iii and the her it is haste tact at with S and fully 8318103211155 the Closing of the switc" it, which is thus de-eo off, as well as thermost J The current flow through the cathode cells I! i, ii and the heater it preheots the cat" also heats up the thermostat member .2, out of contact with i i, breaking the circuit H. opening of starting circuit H is a quick, sharo action, giving a maximum voltage Erich which the dischorge in the 1 When the switch o heater closed for a cold start, glee the circuits P,

i, inostat memut into conosing the switch PT the heater t-circuits heater e rnenlh the mp L shunts or the heoter (i T or more times,

.ilo thus for described, the device end its op eration correspond in main principles to the disclosed in the above--cited Townsend application, though the arrangement and conotructlorl are somewhat diilerent.

in ace i nee with the present invention, means oi co o1 provided for determining the condi i or. the as to continuity in such a we r that reasonable eiforts oi. the starter to start the main discharge, on open-circuit condition oi circuit that prevents flashing oi the lomo L is established and main 'talried, indepenc'ient regardless 03. any lurther action or operation oi starter 5, indeed, the ordinary operetion or starter B may he suspended. For this purpose, automatic control means may be employed whose period of operation (as ilxed by design. and adjustment) is long enough to include whatever number or attempts by starter-S may he considered reasonably worthwhile, e. s, a period of about a minute under iavoralole voltage conditions, embracing some rlve to ten attempts, say. The action or this automatic control need not he an arbitrary matter of fixed adjustment, however, but can be made responsive to the actual attempts of starter, 8 to start the main disci'ccrge,

A simple control Ior this purpose is shown in Figs. 1 and 2- as reflected by cumulative or progressive action involving the starter S, and more particularly its heating means. As it is the circuit H that is to be opened and kept open, en-

ergy from another source than this circuit H is needed. Rather than provides. relay by connections' from the main circuit P, we may employ-an independent mechanical motor or source of energy, such as a spring brought into action in response to the energization and voltage of this circuit during starting.

For this purpose, there is shown in Fig. 2 a selfopening switch X connected in series with the automatic starter S, and comprising as switch members a slender, straight approximately upright thermostatic bimetal strip 4| and a somewhat similar spring strip 42. These members 4|, 42 are arranged to flex and move at a substantial angle to one another, and preferably in planes at right angles to one another but both parallel to the axis of the can 3|. As shown the lower end of the member 4| is anchored by welded attachment to the same' fastener 35 as the member-2|, while the lower end of the member 42 is anchored on the bottom member of frame 3| (and thus to the disc 30) by being welded or otherwise attached to the head 33 of the shank of one of the binding posts 32. Accordingly, the lower end of the member 4| lies in close proximity to the heater 25 and the member 2|, so as to be heated by radiation, convection, and conduction from them. This member 4| is arranged to flex back to the left away from the members 2| and 42 when heated. To retard the action of the switch X as compared with the switch S, the thermostatic member 4| is shown lagged with a thermoinsulative wrapping of sheet asbestos 43, which slows the transfer of heat to it, and also gives it somewhat greater heat capacity. The free upper ends of the members 4|, 42 coact as switch contacts and otherwise as hereinafter explained, and for this purpose the thermostat member 4| is shown provided with a wire latch and contact 44 welded thereto. The wire 44 extends diagonally to the right in Fig.- 2 on a bevel, is then bent back at 45, and is again bent to the right at 48 to afford a reentrant angle presenting shoulders that engage against the corresponding edge of the spring member 42 when the latter is resiliently flexed back to the right as in Fig. 2, and the thermostat member 4| is cold, thus holding the member 42 stressed until released by the thermal fiexure of the member When the switch X is thus "set in closed'condition, it completes the circuit from one conne'ctor 32 and one side of starting circuit H through heater 2! to the other connector 32 and the other side of circuit H, independently of switch 8; when the switch X opens, this circuit is broken, and heater 2! and thermostats 2| and 4| are allowed to cool off. The spring switch Thus the condenser I9 is connected across the or open as in Fig. 3. When the pin 50 is pushed inward by hand after the switch X has opened,

the edge of the switch spring 42 engages thesioping bevel of the wire 44 and forces the springy thermostat 4| back to the left, Fig. 3, until the spring finally slips or latches past the latch angle 45 into the reentrant angle 44, and the thermostat 4| springs forward again. Thus the switch X is reclosed, relatched, and reset, and the spring 42 is returned to restraint by the thermostat 4| and its latch, and the starting circuit is restored to the control of the starter S. During such resetting of the switch X, as well as at other times, the upper end of the contact member 42 is sustained against lateral thrust by the operator and indicator 50 sliding in its bore in the frame 3|.

The thermostat 4| is preferably so adjusted as to press resiliently against the edge of the sprin 42 when the switch is closed as in Fig. 2 with a certain elastic tension; in other words, the thermostat 4| is prefiexed or pretensioned. As the thermostat 4| heats up from the heater 2!, this pretension is taken up On relaxed before the thermostat actually begins to move. After this, the

thermostat 4| moves to the left (Fig. 2) a short condenser IQ may be mounted on the back of f the frame 3| with its leads 56,, 58 extending through the frame down to the heads 33, 33 of the connectors 32, 32 and welded to said heads.

circuit H, H in parallel with'the switches S and X, to obviate or minimize radio interference as well as arcing at the switch contacts. In the case of a normal good lamp, starting is effected by the action of the switch S as above described, unaffected by the switch X and without brin ing this switch X into operation. In other words, one or more operating cycles of the switch 8 and its thermostats 2|, 22 start the discharge in the lamp L, after which the heater 25, 28 cool off and the starting circuit H remains open. If repeated eflorts of the starter S are required to start the lamp L, the thermostat 4| may heat up quite appreciably, but'it does not flex enough to release the spring 42, and may not even relax its own pretension; and when the thermostat 2| cools oi! after the discharge has started, the

v thermostat 4| also cools off.

member 42 is released to spring forward beyond and away from the wire 44 by the movement of the thermostat switch member 4| to the left in Fig. 2 as it heats up. For resetting the switch X in closed position, there is shown a push-pin type of operator 50 sliding in a bore in the upper end of the frame 3|, with its inner'end in position to push against the spring 42. A wire stirrup 5| attached to the inner end of the pin it engages around the upper end of the spring. This pin 44 extends out and operates through an opening in the side of the enclosing casing or can 34 and by its degree of projection indicates the condi- ,In the case of a defective lamp, however, or of one that has so nearly lost its activation as'to be within a few hours of its end, and hence abnormally difficult to start, the repeated futile starting efforts of switch 8 result in a gradual accumulation of heat in heater 2! and in thermostat members 2| and 4|, until eventually the member 4| flexes back to the left sufllciently to release the spring 42, which unilexes to the left and breaks the starting circuit H at 48, at the same time pushing out the pin 50 to afford a visual indication of a bad orabnormal lamp. This may happen with the switch S closed so as to short-circuit the heater 2!, and under this condition the high-voltage kick due to opening of the switch Xmay start the discharge in an ab normally dimcult lamp L, which will thus be'operated to the very end of its possible life. Being connected across the switch X as well as across the switch S, the condenser l functions to prevent arcing or radio interference at the switch X in such a case, just as in the ordinary operation of the switch S.

When the lamp L refuses to start on this action of the switch X, or to run any longer, its darkness and the indication at 50 show that renewal is necessary. When the lamp L i replaced with a new one, the pin 50 is pushed in to reset the switch X as shown in Fig. 2, so that the starter S can start the new lamp in the normal way.

For the convenience of those wishing to use the invention, particulars of a starter such as shown in Figs. 2 and 3 suitable for 30-40 watt fluorescent lamps of the usual positive column type are given:

The thermostatic members 2|, 22 may be strips of the bimetal commercially known as "Chace #2400 bimetal, composed of laminae of Invar, an alloy of 64 per cent iron and 36 per cent nickel, and of chrome iron, an alloy of 75 per cent iron, 22 per cent nickel, and 3 per cent chromium, in equal thicknesses, Welded together. Each of the strips 2|, 22 may be 0.004 inch thick, and /8 inch wide, and they may have lengths of 17 /2 mm. and 19 /2 mm., respectively, before being bent, while the lengths of their lower straight portions to which the fasteners 35, 35 are welded may be 3 mm. and mm, and the horizontal distance apart of these portions may be about 5 mm. The diameters of their semicircular bends 24, 24 may be about 2 mm. The contacts 23, 23 may be of 40 mil coin silver wire, and the gap between them when the switch is cold may be about 0.04 inch. The heater 26 may be a helical coil of about turns of 5 mil resistance wire such as is commercially known as Nichrome V," wound on a 40 mil mandrel, with end legs about 3 mm. long each, giving a. total resistance of about 4 ohms, and its surrounding sleeve 36 may consist of a 5 mm. length of gauge Nonex glass tubing. The Nichrome above referred to is an alloy of nickel 75 per cent, iron 12 per cent, chromium 11 per cent, and manganese 2 per cent. The heater 26 may be a solid rod of high resistance material of 66 inch diameter. inch long, showing a resistance of 100,000 ohms under a voltage of 100 volts D. C., and characterized by a negative temperatureresistance coefficient, such a the material commercially known a Globar BNR. The thermostatic member 4| may be a strip of the abovementioned Chace #2400 bimetal," 0.005 inch thick, inch wide, and 23 mm. long, while the spring contact member 42 may be a strip of phosphor bronze 0.005 inch thick, 27 mm. long.

The device illustrated in Fig. 4 differs from that in Figs. 1 and 2 principally in the substitution of another type of thermal switch for the two-bimetal thermal switch, such as a glow-switch W of ordinary time, and in the provision of a special heater 60 for heating the thermostat member 4|, here shown as connected in series with the glow-switch W and with the switch X, and as consisting of fine wire coiled around the member 4| over its thermoinsulative covering 43, near its anchorage at 35. One of the glow switch leads 6| is connected directly to the lead 38 and thus to one connector 32, while the other glow switch lead 82 is connected through the heater 60 to the switch member 4| and through its latch and 0.07 inch wide, and

I that contact 44a and the spring member 42 to the other connector 32. The part 44a. differs from the part 44 in Figs. 2 and 3 in being stamped out of sheet metal such as nickel and welded to the upper end of the member 4|, instead of being bent up out of wire; but its essential features and operation are the same.

Except as indicated above, the device shown in Fig. 4 is essentially like that in Figs. 2 and 3. and

its homologous parts and features are marked with the same reference characters as are used in Figs. 1-3, in order to dispense with repetitive descripiton, a distinctive letter being added where such distinction appears necessary.

Fig. 5 illustrates a device similar in principle to that of Fig. 4, but considerably simplified. The frame 30 of Figs. 2-4 is dispensed with, and the thermostatic member 4|b is mounted directly on the base disc 30, being secured thereto by a rivet 63 through its laterally bent foot 64. The latch 44b consists of the bent over upper end of the strip 4|b, which is beveled in correspondence to the bevels on the latches 44 and 44a. The spring member 42b consists of a phosphor bronze wire anchored at one end directly to the connector 32, and having its upper end provided with an insulative handle 66 which extends and moves sidewise through an opening or guide slot 81' in the top or end wall of the casing 34.

The open or closed condition of the switch X is indicated by the position of the handle 66 at one end or the other of the slot 61. When the thermostat 4|b and latch 44b move rearward and release the spring member 421), this member and its handle 66 fly over to the right-hand end 01'- the slot 61., which thus limits movement of the handle or operator 66. Thereafter, the latch 44b and the switch X can be reset by pushing the handle 66 to the left in the slot 61 until the latch 44b automatically re-engages the member 4217 as shown in Fig. 5. The condenser I9 is shown connected only across the the glow switch S, instead of across both the switches. Except as indicated above, the device shown in Fig. 5 is essentially like that in Fig. 4, and its homologous parts, features, and connections that appear in Fig. 5 are marked with same reference characters as are used in Fig. 4, in order to dispense with repetitive description, a distinctive letter being added where such distinction appears necessary.

For the convenience of those wishing to use the invention, particulars of the switch X shown in Fig. 5 suitable for ordinary 30-40 watt fluorescent lamps are given:

The thermostatic switch member 4|b may be made of the "Chaos #2400 bimetal" mentioned above. It may be a strip 0.030 inch thick 1; inch wide, and 1 inch long from its foot that is riveted to the base 30 to its end that carries the laterally projecting latch 44b. The insulative wrapping 43 may be of asbestos paper 0.007 inch thick and extending 10 mm. lengthwise of the bimetal, while its leng h wrapped around the bimetal may be 13 mm. The heating winding may be of the above mentioned Nichrome V" resistance wire,

.of 0.0063 inch diameter, found 5% turns around the wrapped strip 4| b, giving an active length of 72 mm., while the total length may be mm. including the lead ends. The spring member 42b may be of brass-plated piano wire of 0.018 inch diameter, 1% inch long.

Fig. 8 illustrates a device somewhat resembling subject matter of a sole application of Mark A.

Townsend, Serial No. 490,048, filed June 8, 1943,

' member like those in Figs. 2-5, there is a fixed longitudinal support and guide rod HI upstanding alongside the starters from one of the connectors 32 that is attached to the base 30, with a. contact and latching head ll mounted to slide thereon and coacting with the latch c. The head II has a conical downward bevel I2 surmounted by I an annular latch-engaging shoulder I3, and also has an insulative shouldered handle or operator 88c which works or moves inward and outward through a hole GIc in the top or end wall of the casing 34. Around the upright guide rod there is a switch-opening helical compression spring that acts against the head II to yieldingly urge the head upward along the rod.

Normally, when the lamp controlled by the starter S is a good one, the contact head H is held down or retained as shown by the latch 440 of the thermostat fllc, that extends along adja-- cent the rod 10 and has its other end ultimately anchored or attached to the base 30, as at 63. and the handle 61c protrudes only slightly through the top of the casing 34, as shown in Fig. 6. But when the thermostat Me bends back away from the head H as a. result of repeated eiiorts to start a bad lamp, the head ll and handle 16c iiy up until stopped by engagement oi the shoulder on the handle 660 with the top of the casing, through which the handle then protrudes very conspicuously. The switch X is reclosed and relatched by simply pushing down on the handle or button 610, causing the bevel 12 of the head H to force backthe thermostat member He and latch under it at I3.

- To dispense with repetitive description, parts and features in Fig. 6 are marked with the same reference characters as their homologues in other figures, a distinctive letter being added where such distinction appears necessary.

What we claim as new and desire to secure by Letters Patent 01 the United States is:

1. Starting means for a discharge device having a starting circuit comprising, in combination, a casing-can open at one end and having an opening in its wall; a base disc closing the open end of the can; connectors for connection to the starting circuit fastened through said disc; 'an

' insulative frame structure upstanding from said disc in said can; fa thermal starting switch in said can mounted on said frame structure and connected to one of said connectors; a lock-out switch in said can connected between said starting switch and the other connector and comprising resilient means with a latching contact urged in one direction thereby, with an operator extending through said can wall opening and operable therethrough to shift said latching contact' against the action of said resilient means. and thus stress the latter, a thermostatic laterally resilient switch member, having one end anchored substantially at said disc, responsive to heat accumulated during repeated operation of said starting switch and thereby thermally flexed away from said latching contact, and a beveled latch on the free end of said thermostatic :nemher for latching past said latching contact and holding said resilient means stressed as aforesaid until released by the thsrmal flexure ofthe thermostatic member.

2. Starting means for a discharge device having a starting circuit comprising, in combination,

a casing-can open at one end and havin an opening in its wall; a base disc closing the open end of the can; connectors for connection to the starting circuit fastened through said disc; an insulative frame structure upstanding from said disc in said can, with means attached to said connectors for'securing said frame structure to the disc; 9. thermal starting switch in said can connected to one of said connectors; a lock-out switch in said can connected between said starting'switch and the other connector and comprising a flexible and resilient switch member anchored at one end to said frame structure, with an operator extending through said can, wail opening and operable therethrough to flex and stress said resilient member, a thermostatic switch member also anchored at one end to said frame structure, responsive to heat accumulated during repeated operation of said starting switch and thereby thermally flexed away from said resilient member, and a beveled latch on the free end of i said thermostatic member for latching past and holding said resilient member, when flexed as aforesaid, until released by the thermal flexure of the thermostatic member.

3. Starting means for a discharge device having a starting circuit comprising, in combination, a casing-can open at one end and having an opening in its wall; a base disc closing the open end of the can; connectors for connection t the starting circuit fastened through said disc; a thermal starting switch in said can connected to one of said connectors; a lookout switch in said can connected between said starting switch and the other connector and comprising a laterally flexible and resilient switch member anchored at one end to said disc and extending substantially at least to the can end remote from said disc, with an operator extending through said can wall opening and operable therethrough to flex and stress said resilient member in a plane substantially parallel to the can axis, a thermostatic switch member anchored adjacent the anchored end of said resilient member, responsive to heat accumulated during repeated operation of said starting switch and thereby thermally flexed in a plane substantially parallel to the casing-can axis and substantially at right angles to the plane of fiexure of the resilient member as aforesaid,

and a beveled latch on the free end of said therin thestarting circuit for producing movement mostatic member for latching past and holding said resilient member, when flexed as aforesaid,

1 until released by thethermal flexure of the thermostatic member.

4. The combination with a discharge device having discharge and starting circuits, and starting switch means comprising coacting switch members for making and breaking the starting circuit to start the discharge, of means including a heater responsive to energization of one of said circuits for producing movement of one 01' said switch members toward the other, means including a second heater responsive to current flow of the said other switch member away from that first mentioned, and thus opening said starting circuit to start the discharge in said device, and

other circuit-opening switch means connected in the starting circuit in series with the aforesaid starting switch means and comprising a thermostat; responsive to heat accumulation in one of said heaters for opening the starting circuit after repeated operation of said starting switch means fails to start the discharge.

5. Starting means for a discharge device having a starting circuit comprising, in combination, a casing-can open at one end and having a slot in its opposite end wall; a base disc closing the open end of the can; connectors for connection to the starting circuit fastened through said disc; a thermal starting switch in said can connected to one of said connectors; a lock-out switch in said can connected between saidstarting switch and the other connector and comprising a, laterally flexible and resilient switch member anchored at one end to said disc and extending substantially at least to the can end remote from said disc, with an operating handle on the i'ree end of said resilient member extending out through said slot and guided therein for sidewise movement to flex and stress said resilient member in a plan substantially parallel to the can axis, a thermostatic switch strip anchored to said disc, responsive to heat accumulated during repeated operation of said starting switch and thereby thermally flexed in a plane substantially parallel to the casing-can axis and substantially at right angles to the plane of fiexure of the resilient member as aforesaid,

iii

the free end of said thermostatic strip being bent and beveled into a latch for latching past and holding said resilient member, when flexed as aforesaid, until released by the thermal ilexure of the thermostatic member.

6. The combination with a discharge device having discharge and starting circuits, and starting switch means comprising coacting switch members for making and breaking the starting circuit to start the discharge, of means including a heater connected in shunt with said switch members and responsive to energization of one of said circuits for producing movement of one of said switch members toward the other, means including another heater connected in series with said switch members within the shunt connection of the first-mentioned heater and responsive to current flow in the starting circuit for produc-E ing movement of the said other switch member away from that first mentioned, and thus opening said starting circuit to start the discharge in said device, and other circuit-opening switch means connected in the starting circuit in series with the aforesaid starting switch means and comprising a thermostat responsive to heat accumulation in the first-mentioned heater for opening the starting circuit after repeated operation of said starting switch means fails to start the discharge.

JACK R. WHITESIDE. MARK A. TOWNSEND.

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