US2303153A - Carrier current controller - Google Patents

Description

Nov. 24, 1942. J L, WOODWORTH 2,303,153

CARR I ER CURRENT CONTROLLER Filed March 26, 1941 z a ///5 E0 6 //v.s'l/. .Arr/o,v-

r0 ELECTRICAL APPAHA n s TO BE CONTROLLED 8 TEMPERATURE MJUMT/Old I ITIVYTtOT:

John L. Woodwcrth,

Y Att or e y Patented Nov. 24, 1942 CARRIER CURRENT CON-mm m John L. Woodworth, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application March 20, 1941, Serial No. new a Claim, c1; zoo-12:)

My invention relates to carrier current systems for controlling the connection of electrical apparatus to a circuit from a remote point.

The invention is directed particularly to thermal switch means employed. selectively to connect the remotely controlled apparatus, to a circuit and subsequently to disconnect the apparatus therefrom.

It is the general object of the invention to provide a simple, low cost, and dependable switch means of this character, and so arranged that upon sending a carrier current impulse from the remote point to the switch means for a predetermined, preferably short time interval the electrical apparatus is caused to be connected through the switch means to the circuit, and upon sending a similar carrier current impulse to the switch means from the remote point but for a different, preferably long time interval, the electrical apparatus is caused to be disconnected from the circuit.

In accordance with my invention a thermal switch is provided comprising a thermostatic bar for operating the switch contacts including two sections connected end to end, one of the sections being adapted to be heated by conduction from the other section and having a temperature-deflection characteristic increasing through a temperature range, and the other section being associated with a'heating winding and having a temperature-deflection characteristic firstincreasing and later decreasing perature range.

In a modification oi the invention the two sections 01 the thermostatic bar have substantially the same temperature-deflection character-'- through the temlstic, increasing through the temperature range,

' in heating relationship respectively with'onc and f the other of the thermostatic bar section's, oneof the heater portion; having a constant resist ance with temperature rise and the other portion having an increasing resistance with term perature rise.

Means are preferably provided, comprising a contact or contacts of magnet material'or comprising a resilient member operatively associated with the thermostatic bar, for ensuring quick or snap-action operation oi the contacts in opening and closing the circuit. Means in the form of auxiliarycontacts are also preferably provided, I especially in case main contacts comprising magnet material are employed, to protect the main contacts from the effects of burning or arcing and thereby to ensure the maintenance of proper .but the heating means comprises two portions calibration o1 theswitch means. Means in the form of an auxiliary thermostatic bar associated with one of the contact members is further prei- I erably provided so arranged as to aid in com pensating forchange in operation of the switch means due to variation of ambient temperature.

The novel features which are considered to be characteristic of myinvention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing wherein Fig. l is a semi-diagrammatic representation of a carrier current system employing a thermal switch embodying the lnvention and which is shown in side elevation; Fig. 2 is a side elevational view or the reverse side of the thermal switch; Fig. 3 shows temperaturedeflection characteristics of the two sections of the thermostatic bar; Fig. 4 shows time deflection characteristics of the thermostatic bar; Figs;

5 to 7 are end elevational views illustrating positions of the contacts employed in the thermal switch; Fig. 8 illustrates a modified form-of thermostatic bar and heating means; Figs. 9 and 10 are respectively trout and side elevational views oi a modification o1. the invention-shown in Figs. 1 and 2; and E12. 10a illustrates an alternative arrangement to thetshow'n in' IPlg. l0.

- Referring to the embodiment illustrated in Fig. 1, for remotely controlling the. supplyin or an electrical apparatuslnot shown) from a power line I, I a thermal switch 8 is provided the energization of which is controlled by a relay means 8 or other suitable controlmeans. The relay means 4 may comprise a coupling capacitor and a reactor I having-a core 1 and a winding 8 or:

ranged to operate'a mercury switch 0 having an i armature member it for moving a switch memflinto engagement with a mercury contact 1' II. The capacitor 5 and reactor winding I are- 1 connected across the power line and are in series resonance for carrier current frequency. I

1 The thermal switch 3 comprises a thermostatic bar or strip ll mounted at one end by; terminal screw ll on a preferably insulating support ll and carrying at its free end one member ll of a pair or cooperating main contacts the other member H of which-igpreferably mounted'ion the free end of a compensating thermostatic bar or strip ll secured adjustably to a base member.

I. oi omdnctive material having a terminal screw 20 attached thereto. One of the contact members, as H, is preierably a magnet and the other contact member i8 is of such material, as iron, as to operate as an armature for the magnet. The thermostatic bar i2 is constituted by two sections 2| and 22 welded or otherwise connected end to end in heat conductive relation, and the material of the sections is so arranged that for-small or ambient temperature changes the outer ends 23 and 24 of the sections tend to deflect at a certain rate in opposite directions. The deflection of the sections 2| and 22 for larger temperature changesextending over a considerable range will be explained hereinafter.

.A pair of auxiliary contacts 25 and 2|, better shown in Fig. 2, are provided in parallel relation with the main contacts II and I1. The auxiliary contacts are carried respectively by the free ends of the thermostatic bars l2 and il, and one oi the auxiliary contacts, as 2|, is resiliently mounted on its supporting bar by a flexible strip or plate 21 or other suitable means.

For actuating the thermostatic bar l2 a heating means or winding 2| is provided wound insulatingly on or in heating relation with, preterably, that one of the sections of the bar l2, in the present case the section 22; which carries the movable contact or contacts. The winding 2| is arranged to be connected across the power line i, 2 by the mercury switch 0, and the switch 2 is so arranged that the power line connections to the apparatus which is to be cont olled from the remote point include terminal l4. thermostatic bar l2, the pairs of contacts M, n and 2|, 2|, the compensating bar mounting member ll, terminal 2|, and the circuit including the apparatus to be controlled. To avoid the conducting of current through the thermostatic bars l2 and il, shunt conductors (not shown) may be provided for these bars.

A metal plate 2| or like member may be mounted between the thermostatic bars l2 andto shield the bar l2 from heat radiated from winding 2|. n

In Fig. 3 the curve 2| shows the deflection of the thermostatic bar section 22 of Fig. 1 with change of temperature over a considerable range.

,the deflection of this bar flrst increasing and flection characteristic of free end 24 of bar l2.

One 0! the two constituent strips of section 2| is composed preferably of a material known commercially as Invar comprising 36 per cent nickel and 64 per cent iron, and the other strip of section 2| of a material known commercially as 22 per cent nickel steel" comprising 22 per cent nickel, three per cent chromium, and '75 per cent iron. One of the constituent strips of section 22 is composed preferably of Invar, and the other strip of section 22 of a material commercially known as "60 per cent nickel steel" comprising 60 per cent nickel and 40 per cent iron.

In operation, assuming that thermal switch 2 and relay 4 are in their open positions as illustrated in Fig. l, a carrier voltage of the frequency to which the series circuit 5 and is tuned is impressed on the power line I, 2 01 usual commercial frequency from a remote point on the line. The relay winding 8 being energized by the resulting carrier current actuates the armature iii of mercury switch 9 to close the contacts ii and i2, which in turn control the energization of the heater winding 28 oitherrnal switch 2.

Assuming first that the heater winding 2| is energized for a predetermined short time interval only, for example the time interval ii in Fig. 4, then during this short time interval the deflection of bar section 22, as illustrated by curve 22, tends to rise to a relatively high point as 25. But the oppositely directed deflection of section 2| shown by curve 22 tends to remain at a low value since heat is transferred to section 2| from section 22 by conduction and convection after an appreciable time delay only. The resultant deflection point of free end 24 of bar I2 for the short time interval i1 is shown on curve 24 as point 26. It is assumed that at this point in the deflection curve of the free end 24 the movable contact member H is carried so close to the magnet contact member that the contacts are drawn or snapped suddenly into engagement magnectically thereby connecting the power line I, 2 to the apparatus which is to be controlled and which is connected between terminal 2| 0! switch 2 and conductor 2 of the power line.

At the end of the predetermined short time interval the operator cuts oil the carrier current and the heating of thermostatic bar section 22 consequently ceases. The free end 24 tends to deflect back to its original position with contact out of engagement with contact i! as the bar 2 cools oil, but because of the high magnetic attraction between the closed contact members i2 and I1 these contacts remain closed. The power line I, 2 thus remains connected to the controlled apparatus indeflnitely after the above described closing of contacts l2 and i1 due to the supplying of carrier current to the switch control means for the predetermined short time interval.

Assuming next that the heater winding 2| is energized for a relatively long time interval, for example, the time interval t: of Fig. 4, then as illustrated by the resultant curve 24 a force is first exerted tending to maintain the contacts in their. closed position. Later this force reverses as the deflection of section 22 shown by curve 22 decreases and the oppositely directed deflection 01 section 2| shown by curve 22 increases. At some point as t: the force in the reverse direction overcomes the magnetic pull of contact i! oncontact I8 and snaps the contacts open. Bections 2| and 22 0| bar l2 then cool simultaneously, the resultant cooling curve 21 being such that during the cooling period no force is exerted by the bar H to reclose the contacts l8 and H. The power line I, 2 thus will remain disconnected after the opening of contacts II and H due to the supplying of carrier current to the switch means for the predetermined relatively long time interval.

The above described cycle of flrst closing and later reopening the circuit contacts by heating the thermostatic bar II for a short time interval and subsequently heating the bar for a long time interval may be repeated indefinitely.

II for any reason relay 4 should fail to open its contacts at the end of a transmitted carrier impulse, heat would continue to be generated conture the solder melts and the tacts 25 and tinuously by the heater winding 28, causing an excessive temperature rise inside a casing (not shown) which may enclose the thermal switch. To prevent damage from this cause a temperature responsive fuse device may be connected in the heater circuit, of the type, for example, comprising a movable member M1 held against a stationary member M2 by a low melting point solder M3. Upon occurrence of unduly high temperamovable member is released thereby opening the fuse may be reset, after the normal condition, by holding her against the stationary member and applying heat to the solder.

Referring to Figs. 5 to 7 which are end-elevational views of the main and auxiliary contacts .and supporting members therefor shown in Fig. 2, looking to the left in the upper portion of the latter figures, in operation of the auxiliary con- 26, in off position of the thermal switch as shown in Fig. 5 both the main and the auxiliary contacts are open. The flexible strip or plate 21 upon the free end of which one of the auxiliary contacts, 25, is mounted is so arranged that in this open or off position the gap between the auxiliary contacts is less than the gap between the main contacts. Therefore, in pass ng to closed position of the main and auxiliary. contacts shown in Fig. 7 the auxiliary contacts 25 and 26 close first, and in passing from. clos d switch position of Fig. 7 to the Fig. 5 these auxiliary contacts auxiliary contacts therefore receive any arcing or pitting which may develop in energizing and deenergizing the controllled apparatus but in the open position of heater circuit. The relay is restored to the movable mem-' open last. The.

normal closed position the current Ldivides be-' tween the two pairs of contacts which are then in parallel.

In cases particularly where the thermal switch 3 is employed for the control of loads, such as a tungsten filament lamp load, characterized by a big inrush current tending to cause welding of the contacts, a suitable l miting resistance may be provided in series with the contacts. This resistance may take the form of a separate resistor R, or may be provided by forming of suit able resistance material the small flexible plate or strip 21 upon which one 01 the auxiliary coni 6U.

tacts is mounted.

The compensating thermostatic, bar II is so arranged that for ambient temperatures its free end,.carrying the contact l1, moves in substantially the same direction as the free end of the main thermostatic bar l3. bar I I improves the operation of the switch means by makingthe operating time to open and close the contacts more nearly'constant at different ambient temperatures.

-The compensating thermostatic bar I! may be constituted by two sections 38 and 39 connected end to end and deflecting in opposite directions with ambient temperature, similarly to the sections 2| and 22 of main thermostatic bar I 3. By suitably proportioning the lengths of the sections 38 and 39 of bar l8, change in ambient temperature will cause a slight variation in the separation of the contacts [8 and I! and will also cause a slight longitudinal to match a similar longitudinal tilting of contact it due to the effect of ambient temperature change on the sections of bar l3. Thus at all ambient temperatures the faces of contacts I and I! tend to remain parallel in the open positicn and to meet reasonablyflat in the closed This movement of 4 tilting of contact l1 tending means of Fig.

position. The forming of bar- I! in two sections also assists in making the operating time more nearly constant with ambient temperature changes.

The shield 29 interposed between the main opposite directions with temperature change. In

Fig. 8, however, the sections 4| and 42 are alike as to material, similarly-characterized as'to deflection for all temperatures throughout the tem- Further,- instead of a single the portions 48, one of the bar sections as 42, having a constant resistance with temperature and the other portion, 44, associated with the other bar section 4!, having an increasing resistance with tempera- The winding is so arranged that in the cold condition the portion 43 is of higher reportion 44 and in prising 60 per cent nickel, 12 per cent chromium and 28 percen may be formed of ly comprising tungsten. i

In operation of switch'means such as l of Fig. 1 but employing the thermostatic bar'an heater 7 8, when the two winding portions 43 and 44 are In the modification illustrated in Figs. 9 and 10. the thermal switch may comprise a main thermostatic bar having two sections 40 and 47 and of the section which carries at its free end a movable contact member 40, all similarly to the thermal switch I of corresponding elements of The movable contact 44 cooperates with Fig. 1. a fixed contact I6 adiustably mountedin a suita screw I2.

bar 4! and the other end I! of which same direction as the free end of main thermostatic bar 45. It will be understood that, as illustrated m Fig. a, contact 50 instead of spring 53 may be mounted on a compensating thermostatic bar such as bar 51.

The spring 53 and bar 45 may be so arranged that the end 54 of the spring engages the bar at a point thereof at or closely adjacent the extreme end 58. It is preferable, however, that the end 54 of the spring engage the bar not it the end but at an intermediate point of the bar as shown. This arrangement of the spnirg end 54 with relation to the bar 45 has been found to provide faster tripping of the spring in opening of the contacts.

In operation of the thermal switch illustrated in Figs. 9 and i0, assuming the contacts 49 and 50 to be in open position as shown, if the bar 45 is heated for a short time interval the bar section 41 deflects in a direction to move the contact 49 against the pressure of the spring until the latter is in position to close the contacts with asnap action. Upon cooling of the bar 45 the contacts remain closed by the spring pressure. It, later, the bar is heated for a long time interval, the-bar sections 41 and 48 tend to deflect in directions such that the free end of the bar tends to move contact 49 out of engagement with contact 50. When the resultant deflecting force in bar 45 overcomes the spring pressure the contacts reopen with a snap action. Upon cooling of the bar 45 the contacts remain in open position.

My invention has been described herein in particular embodiments for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

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

l. A thermal Switch for controlling the en ergizing of a circuit comprising a thermostatic bar having two portions in thermally conductive relation end to end, and heating means associated with said bar to bend one of said portions to close said circuit after a predetermined short time interval and to bend the other of said portions to open said circuit after a predetermined long time interval.

2. A thermal switch for controlling the energizing of a circuit comprising a thermostatic element constituted by two metallic strips connecked in thermally conductive relation end to end, one of said strips having a temperaturedeflection characteristic increasing throughout a temperature range, the other of said strips having temperature-deflection characteristic first ii'icreesing and later decreasing throughout said and heating means associated with said neri strip for bending said last-named as said circuit after a short time infor bending said first-named strip -i from said last-named strip switch for controlling the enernit comprising a thermostatic bar having'two sections connected end to end, a second thermostatic bar for compensating the movement or said first-named bar, the free ends 0! said bars moving in the same direction with.

ambient temperature changes, a pair of contacts in said circuit connected respectively to said free ends of said bars, and heating means for bending one of said sections to close said circuit at said contacts after a short time interval and for bending the other of said sections to reopen said circuit at said contacts after a long time interval.

4. A thermal switch for controlling the energizing of a circuit comprising a thermostatic bar having two sections connected end to end, a second thermostatic bar for compensating the movement of said first-named bar due to ambient temperature changes, a pair of contacts in said circuit connected respectively to the free ends of said bars, one of said contacts being a magnet and the other being an armature for said magnet. a pair of auxiliary contacts in said circuit arranged to close before and to open after said firstnamed contacts, one auxiliary contact being connected resiliently to the free end of one bar and the other auxiliary contact being connected to the free end of the other bar, and heating means for bending one of said sections to close said circuit at said pairs of contacts after a short time interval and for bending the other of said sections to open said circuit at said contacts after a long time interval.

5. A thermal switch for controlling the energizing of a circuit comprising a thermostatic bar having two sections connected end to end, a second thermostatic bar for compensating the movementof said first-named bar due to ambient temperature changes, a pair of cooperating contacts in said circuit, one of said contacts being fixed and the other being connected to the free end of said bar, a resilient member connected between the free end of said second bar and a point of said first bar for biasing said other contact into and out of engagement with said one contact, and heating means for bending one of said sections to cause said resilient member after a short time interval to close and maintain closed said contacts and for bending the other of said sections to cause said resilient member after a long time interval to open and maintain open said contacts.

6. A thermal switch for controlling the energizing of a circuit comprising a thermostatic bar including two sections having substantially the same temperature-deflection characteristic throughout a temperature range, and a heating means for bending one of said sections alter a short time interval to close said circuit and for bending the other or said sections after a long time interval to open said circuit, said heating means having two portions, one of we portion: being in heating relationship with said one section and having a substantially constant resistance with rise of temperature, the other of said portions being in heating relationship with said other section and having an increasing reattance with rise of temperature.

JOHN L WOODWORTB.

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