US2516964A - Thermostatic circuit controlling device - Google Patents

Description

g- 1950 J. H. DERBY ETAL 2,516,964

THERMOSTATIC CIRCUIT CONTROLLING DEVICE Filed Nov. 29, 1946* 2 Sheets-Sheet l 3noentors Jm/A/ H QE/PBY THOMAS G was gay,

Gttorncp 1950 J. H. DERBY ETAL 2,516,964

THERMOSTATIC CIRCUIT CONTROLLING DEVICE Fi'l-ed Nov; 29,1346 2 Sheets-Sheet 2 31mm tors 70H /v D595) 7/70/14; 6. 60.4 4 //V65 Gttomeg Patented Aug. 1, 1950 THERMOSTATIC CIRC DEVIC UIT CONTROLLING I John H. Derby, Scarsdale, N. Y., and Thomas G. Collings, North Plainfield, N. J., assignors to American Fire Prevention Bureau, Inc., New York, N. Y., a corporation of New York Application November 29, 1946, Serial No. 713,176

3 Claims.

This invention relates to thermostatic circuit controlling devices, and particularly to thermostatic circuit closers operating upon the broad principle of those shown in U. S. Letters Patent No. 1,274,248, granted July 30, 1918, to John H. Derby and Ernest S. Clayton, assignors to American Fire Prevention Bureau, Inc. of New York.

'Circuit closers of the type shown in the Letters Patent above identified, both in the form shown in said Letters Patent and with slight later modifications and improvements, have been extensively and successfully used for both fire alarm and fire prevention purposes throughout all the years since their invention. The pressure upon the disk of fusible conducting material in the circuit closer of said prior Letters Patent is produced by the preliminary shaping of the two terminal disks which, when clamped into the final circuit closer structure in insulated relation to each other, remain under a stress which maintains a pressure upon the disk of fusible conducting material and thus insures its flow, when fused, through the thin perforated insulating disk into short-circuiting relation to the terminal disks.

Thermostatic circuit closers embodying the invention of said prior Letters Patent and designed to operate when the temperature in the region thereof reaches, say. 152 F., operate with certainty but require a certain amount of time after the temperature of the surrounding air reaches the desired degree before the fusion of the disk of fusible conducting material effects the closure of the circuit. This time element in the operation of the thermostatic circuit closers of said prior Letters Patent, as they have been made and perfected in the years of their extensive use, has varied from 140 to 150 seconds, that is from approximately 2 minutes and 20 seconds to 2 minutes. Although this time element does not constitute a drawback to the use of these circuit of said prior Letters Patent but which is so designed and constructed that the time element is materially reduced.

, Among the objects of the present invention .is

providing a fixed temperature circuit closer that will operate in appreciably less time than those fusible alloy circuit closers now generally employed and yet which will not be so sensitive as to .give false alarms by reason of sudden changes in room temperature having no relation to fire hazards, such, for example, as the opening of a door between a heated room and a cold room, the uncovering of a container containing a heated liquid, etc.

As a result of extensive experiments we have discovered that a thermostatic circuit closer, of much smaller overall dimensions than those made in accordance with the said prior Letters Patent hereinabove identified but so constructed that the pressure exerted upon the disk of fusible conducting material is not a function of the structure of the terminals but is maintained by special pressure producing means, will operate to close the circuit in much less time than will a circuit closer incorporating the general structure of said prior Letters Patent. We have particularly found that, if one circuit terminal be made in the form of a cup, in the bottom of which the disk of conductive alloy fusible at a predetermined temperature is located, and if a perforated piston-like disk of insulation be pressed down upon this disk of conductive alloy by means, for example, of a compressed coil spring located between the cup closure and the disk of insulation, and if the other terminal be mad in the form of a conductive rod insulated from the cup and extending thereinto into immediate proximity to the insulating disk over the perforated part thereof, the whole thermostatic circuit closer can be made of such dimensions that the overall length of the cup and closure may be less than onehalf inch, in fact considerably less than one-half inch, if desired, and its overall diameter also considerably less than one-half inch and that such a circuit closer will operate much more quickly to close the circuit by fusion of the disk of conductive alloy than will a circuit closer embodying the structural principles of said prior Letters Patent.

Not only does the circuit closer of the present invention have important advantages over the circuit closer embodying the structural principles of said prior Letters Patent by reason of the shorter time required for its operation (from seconds to seconds) but it lends itself, by reason of its overall dimensions, to use in an eiiective substitute for the so-called continuous wire systems such, for example, as those in which twisted piano wires are insulated from each other by plastic insulation fusible at predetermined temperatures.

As more fully pointed out hereinafter, the novel thermostatic circuit closer of the present invention, by reason of its small dimensions, may be so installed at intervals in a fire detection cable comprising two wires adapted to constitute the two sides of a signal or other fire control circuit, said wires being each covered with heatresisting insulation and being twisted together except at intervals suitably spaced for fire de tection purposes, that one of these circuit closers, located at each of such intervals and connected to the respective wires, will serve effectively to detect any fire within the spaces to be protected by the detection circuit. Moreover, its operation can quickly be determined by suitable indicatin means, such, for example, as that disclosed in U. S. Letters Patent No. 1,938,583, granted December 12, 1933, to John H. Derby, and the circuit closer, thus easily detected, can be as easily and quickly replaced,

An important feature of the present invention is the arrangement of the means for exerting constant pressure on the perforated disk of insulation and thereby upon the disk of fusible conductive alloy, for example a coil spring compressed between the cup closure and the perforated disk of insulation, so that it exerts its pressure upon the margin of said disk, thereby insuring fiow of the fused alloy up through the perforation in the disk into circuit closing contact with the said rod, while preventing flow about the periphery of said insulating disk.

Another important feature of the invention is the effective insulation, in a structure of such small overall dimensions, of one terminal from the other, both electrically and thermally. Still another feature of the invention is the effective sealing of all operative parts of the structure from corrosive gases, dust, moisture and everything else that might interfere with their functioning,

Other features, advantages and objects of the invention, to which references has not specifically been made hereinabove, will appear hereinafter when the following description and claims are considered in connection with the accompanying drawings, in which Figure 1 is a, section on the line 1-4 of Figure 2 showing particularly the details of construction of the novel thermostatic circuit'closer of the present invention and also one way of mounting this thermostatic circuit closer for connection to a circuit including outlet boxes. This figure shows the parts drawn to an enlarged scale;

Figure 2 is a bottom plan view, substantially to scale, of the thermostatic circuit closer of the present invention and of the insulating support therefor through which connection is made to an outlet box in an alarm or other control circuit;

Figure 3 is a section on the line 33 of Figure 2 showing the circuit connections at the back of the insulating disk or outlet box cover through which connection is made to the circuit wires in the outlet box;

Figure 4 is a broken view showing fire detecting cable comprising twisted wires, each covered with fire resisting insulation, in which thermostatic circuit closers, embodying the present invention, are inserted at untwisted intervals along the line of said cable;

Figure 5 is an end View, substantially to the scale of Figure 1, of one of the thermostaticcir- 4 cuit closers shown in Figure 4, this view being taken from the closure end and having for its purpose to show the location of the indicator which indicates the one of the circuit closers which has operated;

Figure 6 is a section on the line 6-6 of Figure 7 of a slightly modified form of the circuit closer and of the mounting therefor, and

Figure '7 is a plan view of the inside of the outlet box cover shown in Figure 6 and of the circuit connections.

The thermostatic circuit closer of the present invention, shown in section in Figure 1, comprises a cylindrical cup 2 of good conductive material for both heat and electricity, such, for example, as brass, this cup having thereon, preferably integral with its bottom, connective jaws 4 to receive between them a stripped portion of a wire constituting one side of a fire alarm or other control circuit. These jaws 4 are shown projecting from a shoulder 6, also integral with the bottom of the cup, the purpose. of the shoulder 6 being to form a spacer and terminal contact portion for the cup bottom when the connection to the circuit is to be made in the manner shown in Figures 1 to 3. The jaws l may be pinched together to grip the wire inserted between them, thus making a good conductive connection, as shown in Figure 5.

Located in the bottom of the cup 2 is a disk 8 of a conductive alloy, fusible at a predetermined temperature, such, for example, as the alloy disclosed in U. S. LettersPatent to John H. Derby, No. 1,982,645 granted December 4, 1934, which is designed to fuse at a temperature from to 152 F. The disk 8 preferably fits snugly within the side walls of the cup 2 and, as above suggested, rests upon the bottom of the cup. Bearing upon the otherwise exposed face of the alloy disk 8 is a piston-like disk In of insulating material, such, for example, as Bakelite, this disk III, as shown, also fitting closely but slidably within the'inner cup wall and having a central perforation i2 through which the alloy of the disk 8, when fused, may flow into circuit-closing contact with a conductive rod M, of brass or other suitable electrically conductive material, which constitutes the other terminal of the circuit closer and which has on its outer end connective jaws l6, similar to the jaws 4 on the cup 2, these jaws being adapted to receive between them a stripped portion of a wire constituting the other side of the fire alarm or other control circuit and to be pinched into tight clamping relation thereto. The rod 14 is also preferably provided with a shoulder I8 for the same purpose as the shoulder 6 on the cup 2. a i

The conductive rod it passes through a closure 20 of insulating material, such as Bakelite, which fits closely the inner wallof the cup 2 and serves to close and to seal'the otherwise open end of said cup, this closure 20 also having a flange 22 which overlaps and fits tightly against the lip of the cup 2. The conductive rod 14 ispreferably located at the center of the closure 20 and is sealed into the Bakelite or other insulating material of which the closure 20 ismade, as, for example, by being molded thereinto when the closure is molded, and extends, as shown, into immediately proximity to or contact with-the insulation disk H3 over the opening l2 therein.

Between the closure 20 and the insulation disk ID' a coil spring 24,01" any suitable material, such, forexample, as stainless steel, is located and is compressed to-a predetermined extent to exert upon the insulation disk H! the pressure desired or required to insure flow ofthe' alloy of the disk 8, when fused, through the perforation l2 in the disk l0. To maintain this spring 24 in its compressed condition. and to prevent any chance that the closure 20 might moveout of its closing and sealing relation to the mouth of the cup-2, the closure 20 is preferably provided, on that part of its periphery which lies within and tightly fits the inner wall of the cup 2, with a groove 26 which may be, as shown, V-shaped in section and into which, after assembling the parts, is rolled a correspondingly shaped rib of the cup 2, as shown-at 28.

In order that the movement of the insulation disk l toward the bottom of thecup 2 under the action of the spring 24, when the alloy disk 8 fuses, may not open a passagebetween the end of the conductive rod M and the insulation disk 10 through which the fused alloy might flow into the chamber in which the spring 24 is located, and thus out of circuit closing contact with the rod i l, the insulation disk 10 is made of a thickness, at least around the lower or inner end of the rod it, to provide a well around the opening 12 in the disk into which the inner end of the conductive rod [4 projects and closely but slidably fits, this well being sufliciently deep so thatimovement of the insulation disk In under the action of the spring 24 completely to the bottom of the cup 2 would not open a passage for the fused alloy between the rod 14 and the insulation disk Hi. It will be seen, therefore, that, at all times, even if the fusion be so complete and continue so long that the insulation disk i0 is moved completely to the bottom of the cup 2 by action of the spring 24, there will still be a conductive or circuit-closing contact made by the fused alloy 8 through the opening I2 between the bottom of the cup 2 and the bottom of the conductive rod 14, the fused alloy being confined in the opening l2 and in the well 30 at all times.

From the foregoing description it will be seen that the circuit closer of the present invention, which, as above pointed out, is shown in Fig. 1 of the drawings drawn to an enlarged scale, is so constructed that its action is positive and that any expansion of the metal parts thereof incident to the rise in temperature necessary for its operation will in no way affect the positive nature of its operation. By reason of the fact that the cup 2, of a good heat conducting as well as electrically conductive material, such, for example, as brass, is of a comparatively rigid construction and is of such overall contour and dimensions that the heat received by it from the surrounding air is concentrated principally in the region where it is needed for effecting the fusion of the alloy disk '8, a fusion of the disk 8, sufiicient to effect circuit closing by how of the fused material into contact with the conductive rod I4, takes place, as above stated, in much less time (from 70 second to 90 seconds) than in circuit closers of the prior art which operate on the same general principle. the fact that, in the much larger circuit closers of the prior art, there is liability to too great diffusion of the heat imparted to the structure from the surrounding air. Moreover, the pressure brought to bear upon the solder in the earlier circuit closers, although fully effective for its purpose, is probably not proportionately so great. In the structure of the present invention it will be seen that the spring 24 is confined between the rigid cup closure 20 and the insulation disk One reason for this is believed to be H] which presses the fusible alloy disk 8 against the fixed and unyielding bottom of the cup 2. It will further be seen that the pressure thus exerted by the spring 24 on the disk Ii] may be so predetermined that any lengthwise expansion of the cup '2, incident to the rise in temperature necessary to fuse the disk 8 and make the circuit closer operate, will not materially or even appreciably reduce this pressure of the spring 24- on the disk to and, therefore, will not in any way affect or slow up the operation of the circuit closer as a whole.

As hereinabove suggested, the connection of the thermostatic circuit closer of the present invention to the fire alarm or other control circuit in which it is to be used may be effected in various ways, two of which are illustrated in the drawings. In Figures 1 to 3 inclusive are shown convenient means for connecting the circuit closer or the present invention to the two sides of an alarm or other circuit, the wires of which are concealed except at outlet boxes. As herein shown, a cover 32 for a circular outlet box is preferably formed of insulating material such as Bakelite and is provided with two depending contact arms 34 and 35 which extend through openings 33 and so in said cover. The vertical arms 3 and 35? are respectively provided with right-angled or horizontal extensions 42 and M on the inside of the cover 32, into conductive engagement with which binding post brackets 46 and 53 may be clamped by means of screws 50 tapped into the cover 32 itself. Each binding post bracket 46 and 48 may be provided with one or two clamp screws 52 for making connections with the respective sides of the fire alarm or other control circuit.

Each of the depending or vertical arms 34 and 36 is provided with an opening 54 to receive the clamping jaws 4 and I6, the jaws It being shown in Figure 1 as received in the opening 54 of the depending arm 35 and the jaws 4 as received in the opening 54 of the depending arm 34. As also shown, the arms 34 and 3-8 are so spaced that, when the clamping jaws have been inserted in the openings therein and the screws 5% have been screwed down to clamp the binding post brackets 46 and 48 to the horizontal extensions 42 and 44 and to secure these parts tightly to the inner wall of the cover 32, the thermostatic circuit closer will be held tightly clamped between the arms 34 and 36 with the inner faces of these arms in tight conductive relation to the shoulders 6 and 18.

In Figures 4 and 5 thermostatic circuit closers embodying the present invention are shown as constituting the fire detecting parts of a fire detecting cable. These cables are not usually concealed but may be strung along the ceilings of any rooms or other spaces to be protected.

As hereinabove suggested, this fire detecting cable may comprise two wires 55 and 58, constituting respectively the two sides of a fire alarm or other circuit to be rendered operative by the circuit closer of the present invention, each of these wires being covered with flexible fire re sisting insulation 60, preferably of one of the modern insulating plastics, such, for example, as one of the vinyl plastics. In order that, as above suggested, the fire detecting cable need not be concealed but may be exposed along the ceiling of any space to be protected, in preparing the novel fire detecting cable of the present invention the insulated wires 5t and 58 will prefanaaee erably be twisted together except at intervals :properly spaced for fire detecting purposes, wh ch may be, for example, when using the novel onportions thereof may be inserted between the jaws 4 and between the jaws [6, respectively, after which the jaws may be clamped together as .shown in Figure 5, thus effecting a good electrically conductive connection between the cire cuit closers and the two sides of the circuit.

As also pointed out hereinabove, it is important, in any fire prevention system using thermostatic circuit closing means, that the point at which the circuit has been closed shall be readily discernible. The difficulty of locating the point of operation has been one of the objections to the use. of those fire detecting cables which are so constructed that the circuit may be thermostatically closed at any point along their lengths. In order that the point at which the temperature rise has occurred and at which the thermostatic circuit closer has operated may readily be determined we provide each circuit closer, preferably in the closure end (which, for example, may be formed of a black Bakelite), whiclr indicating means E32, such, for example, as that disclosed in U. S. Letters Patent to John H. Derby, No. 1,938,583, granted December 12, 1933, and which comprises a piece of fusible material, for example a wax or similar material, which dis plays a color in contrast to that of the material in which the cavity that contains the detecting material is formed. In this case, if a black Bakelite be used the wax or other fusible material employed might be impregnated with powdered aluminum which upon fusion of the wax would give a white indication on the closure end of the thermostatic circuit closer that had operated.

From the foregoing description or" fire detecting cable incorporating therein thermostatic circuit closers of the present invention it will be seen that, not only can this cable be easily manufactured and installed, but whenever any one of the thermostatic circuit closers has operated to close the circuit it can readily be located and easily replaced without cutting the cable or otherwise disturbing its installation.

The embodiment of the invention shown in Figures 1 to 3 of the drawings and the means there shown for supporting the circuit closer upon the cover of an outlet box and effecting a connection to the circuit in the box are suitable for fire alarm and other control circuits operating at low voltages, for example, voltages of from 14 to 40 volts. However, in some modern installations standard house voltages are used, in the neighborhood of 120 volts. In such cases it is not desirable to have both terminals exposed, as in the embodiment shown in Figures 1 to 3, since someone might accidentally take hold of or contact one terminal with one hand and the other with the other and thus get an unpleasant shock. In Figures 6 and 7, therefore, is shown a slight modification both of the circuit closer construction and of the support therefor whereby only one terminal is exposed in the space to be protected.

In the embodiment of the invention shown in Figures 6 and 7 the cup part 2 of the circuit closer is constructed without the clamping arms 4 shown in Figure 1 of the drawings. Instead, it iszprovided at its upper end with anqintegral flange 66 which serves both to support it on a countersunk ledge 61 surrounding an opening 68 in the outlet box cover 10, formed of insulating material, and ,to provide a shoulder against which a contact ring 12 may be pressed. The ring 72, which may be stamped out of a thin sheet of suitable electrically conductive metal, has integral with it a strap 14 which extends beneath the binding post bracket 46. The body of the cup part 2 of the circuit closer of Figure 6 extends through the opening 68 into the space to be protected.

- The connection to the otherside of the circuit,in the modified form of the invention shown in Figures 6 and 7, is made bysubstitutingfor theclamping arms H5 at the upper end of the rod l4 of the Figure 1 form a split threaded end '15, above the shoulder l8, upon which may be screwed a clamping nut 16 for clamping against the shoulder l8 a ring 18 of a construction similar to the ring 12, the ring 18 having a strap extension which extends beneath the binding post bracket 43. By spreading the two parts of the split part 75 of rod M the nut 16 may be locked in clamping relation to the contact ring 18. As in the form of the invention shown in Figure l, clamp screws 50, tapped into the outlet box cover l0, serve to clamp the binding post brackets 46 and 48 into good conductive relation respectively to the straps l4 and 80 and thus to connect the cup 2 to one side of the alarm or other control circuit and the rod l4 to the other side of said circuit.

Except for the substitution of the means shown in Figure 6 for connecting the cup 2 and conduc- .tive rod M to the two sides of the alarm or other control circuit the construction of the thermostatic circuit closer shown in Figures 6 and '7 is substantially the same as that shown in Figure l. The only additional change shown in Figure 6 is the substitution of a separate disk 82 of insulating material, having formed therein the well 30-, for the boss integrally molded with the disk H] in which the well 30 is shown as formed in Figure 1 of the drawings, this change being made for convenience and economy in manufacturing the thermostatic circuit closers.

The cover TI) is preferably provided with the usual integrally molded ridge or ridges 8G for further insuring the insulation of the two sides of the alarm or other circuit from each other. A like ridge indicated by the same reference numeral will also be seen as constituting a part of the outlet box cover 32 in Figures 1 and 3 of the drawings.

What is claimed as new is:

1. In a thermostatic circuit closer, a thinwalled-cylindrical electrically and thermally conductive cup having its-bottom connectible to one side of a circuit-and having an insulating closure for its mouth, a relatively thin disk of conductive alloy, fusible at a predetermined temperature, covering the inside bottom of said cup, a piston-like disk of insulation, spring-pressed against and coextensive with the exposed face of the alloy disk and having a central opening therethrough into which the fused alloy may be forced by the pressure of said insulation piston, a conductive rod having its exposed end connectible to the other side ofsaid circuit, said rod extending coaxially through said cup closure into said cup and into the upper end of the central opening in said insulation-piston in fixed spaced relation to the unfused alloy disk and in substantially liquid- -tight relation. to the: upper. end of said opening in all positions of relative movement of said insulation piston and said rod.

2. A thermostatic circuit closer according to claim 1 in which the part of the opening adjacent to the fusible disk is of a diameter less than that of the rod and the insulating disk is provided with a well into which the conductive rod is telescopable to an extent sufiicient to insure confinement of the fused alloy between said rod end and the cup bottom at all stages of the relative movement of said disk and said rod.

3. A thermostatic circuit closer according to claim 1 having a flange about its closure end, an outlet box cover of insulating material having a countersunk opening therethrough for supporting said circuit closer by its flange, with the cup part thereof projecting into the space to be protected, and means carried respectively by the cup and REFERENCES CITED The following references are of record in the 10 file of this patent:

UNITED STATES PATENTS Number Name Date 794,497 Gould July 11, 1905 796,904 Fiske Aug. 8, 1905 875,810 Hall Jan. 7, 1908 1,274,248 Derby et a1 July 30, 1918 1,935,611 Bourbon Nov. 21, 1933

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