US445217A - Thermal cut-out - Google Patents

Description

(No Mode1.)

A. BARRETT. THERMAL GUT-OUT.

No. 445,217. Patented Jan. 27,1891.

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UNITED STATES AL SERT BARRETT, OF KANSAS CITY, MISS@ PATENT OFFICE.

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THERMAL CUT-OUT.

SPECIFCAT-ION forming part of Letters Patent No. 445,217, dated January 27, 1891.

Application tiled December 5, 1890. Serial No. 373,670. (No modelf! To all whom it may concern,.-

Be it known that I, ALBERT BARRETT, residing at Kansas City, in the countyof Jackson and State of Missouri, haveinvented certain Improvements in. Thermal Protecting Devices, of which the following` is a specification.

The apparatus of telephonie, telegraphic, and other electric circuits 'in which circulate relatively feeble electrical currents includes, necessarily, instruments of comparatively delicate character having` helices of line insulated wire. i

Since the general introduction of electric illumination and power distribution the above apparatus has becomccxposed to great. danger otA damage and destruction, because, since the major part of the wires of both classes of ci rcuits is suspended in the air upon poles or other supports, they are liable to become crossed. or to come into contact with each other, especially during stormy weather, and the result ot' such contacts is most disastrous to the apparatus of the circuits first mentioned. It has therefore been demonstrated by practical experience that telegraphic, telephonie, and similar classes of circuits-such as electric-clock,burglar and fire alarm, and the instruments included in or connected wit n them-m ust be provided, preferably, at both termini with appliances of a protective character which shall guard against lightning, and more particularly which shall effectively secure immunity against the destructive heating effects of electric currents utilized industrially, but which are unduly strong with respect to the more delicate applications of the science.

In the practical operation of telephonie exchanges, especially where by reason of the nature of the business insulated wires are at central stations massed in great numbers, it has been fully demonstrated that foreign currents of extraordinary volume or underhigh pressures are not necessarily more dangerous than are those of medium strength, which, however, arc of much greater volume than currents which are intended to traverse the helices of most forms of signaling appliances. The dangerous character of such medium currents lies in the fact that they often can innocuously pass the line-conductors and many forms of protector without exciting an undue degree of heat or causing the said protective devices to become operative, but that, reaching the said masses of office-wires the insulation of which is often very combustible) and instrument-helices, they tend there to develop a degree ot' heat which, though frequently low at first, soon causes the insulation to smoulder and ultimately is most destructive, in some cases deteriorating the insulation and in others finally breaking ont into flame, the amount of damage, of course, in each individual case being, @retort partons, dependent uponthe size of the plant.

The invention described and claimed in this specification is a thermal protecting appliance, which I have found most efficient in p rotecti ng electrica-l circuits and instruments from the deleterious results of the passage of the undesirable sneak currents, so called, described above,and also to be a satisfactory lightning-arrester, and inasmuch as it is capable of affording protection against the said lesser dangerous currents it is needless to remark that it is likewise effective with respect to greater ones.

rlhcinvention comprises an attenuated and relatively fragile portion ot the circuit, a strong spring or an equivalent device capable under certain conditions of exerting a strong and sudden force upon the said fragile portion and of breaking the same, and thus causing a wide gap in the continuity of said circuit, a normal support for the said spring, whereby the said fragile section is ordinarily freed from the tension thereof, and means, comprising a ball or mass of matter, solid and hard, ordinarily, but capable of fusing, softening, or fracture undera moderate degree of heat when closely applied, which I term a heat-responsive mass,77 and a heat-concen-V trating coil of the said attenuated conductor closely associated therewith (being, in fact` embedded therein) for enabling the said spring to come promptly and forcibly into action and to break or tear away the said fragile conducting-section to open the circuit.

It also consists in the specific details` wherein the above-recited elements are embodied, comprising a suitable length of tine wire of relatively high resistance, agstrong` larger than said ring, aiixed to its end, the said loop being caused to support the free end of the said spring in tension, but ac ting also to prevent the said tension of said spring from being exerted upon the fine-wire section under ordinary conditions and in coiling a portion of the fine-wire section round the shank of thc loop within the fusible material, so that the heat developed in thelsaid fine wire by the passage of an unduly strong` current may be concentrated in said coil, and, acting upon the said heat-responsive material, may release the loop and permit the spring to suddenly exercise its full force upon the iine wire andV to break or otherwise destroy the same. Of course a weight, being the obvious equivalent of a spring, can readily be substituted therefor, and I have hereinafter described a moditication in which a weight is employed.

The invention consists, also, iny so formin g and assembling the various elements of the appliance that it can be readily and speedily attached to any circuit, and in combining it with spring-jaws forming a part of said cir-l cuit, and into which it isadapted to be introduced. The entire appliance, together with the said spring-jaws, can be. and preferably is, made to occupy very little lateral space, so that a large number can without diiculty be mounted in a comparatively narrow space.

In the drawings which illustrate and form a part of this specification, Figure l is a perspective View of an appliance mounted in circuit which embodies my invention and which exemplifies a construction which I have found in practice to be extremely serviceable. Fig. 2 is an end elevation of the same appliance. Fig. 3 isa side elevation of the appliance detached from its circuit-terminals. Fig. 4 shows the same, the spring having` been released by the disruption of the fine wire. Fig. 5 indicates one form of the spring-supporting` loop, the iine wire coiled round one end thereof, and thefusible block surrounding the same. Fig. (i is a diagram of an elect ric circuit extending between stations each of which is protected by one of my appliances.

ranged to protect an equal number of circuits.

I will describe these instru mentalities, referring in the first place to Figs. 1 to 5.- A foundation-plate d, of non-conducting material, such as vulcanized fiber, is conveniently made of rectangular form, and in size about the same as, or slightly narrower and thinner than, that shown in the drawings. This forms the foundation of the detachable appliance A, considered as a Whole. A thin Fig. 7 shows several of the thermal protectors mounted on a base and arand narrow ribbon b, of metal, (brass answers perfectly,) is lapped over one end, and the two overlapping ends thereof may be tightly fixed bythe screw-bolt z', which passes through them and the intervening substance of the foundation-plate d, and is secured at the other side by the nut 3, which is screwed on the end i2. The nut is then preferably soldered to themetal strip. The overlapping f ends of said strip may, if desired, be secured by solder in the irst place; but, since a binding-screw is required for the heat-concentrating wire, itis preferable to cause the said screw also to aid in holding` the ends of the strip. The other end of the plate d is likewise armored by a similar metal strip c, secured in like manner, and also provided with a binding-screw t'. The attenuated conductor and concentrating device is formed as follows: A fine insulated wire j, preferably of low specific conductivity, such as German silver, is wound with a sufficient number of turns, as especially shown in Fig. 5, round the shank or ixed end ot' a loop or hook l, made of some tough and preferably fibrous and non-conducting material, and the said Winding is then surrounded with, or embedded in, a small block of easily-fusible substance or material which easily softens orbecomes friable under the application of a modcrate degree of heat. This may be of any desired form, but is conveniently either sphere passes through the plate d at the hole f, is

brought back to the original side through a slit h in the edge of said plate d, and is finally bent into a ring or perforated bracket e2. The arm g at its free end g is slightly curved to constitute a hook. The purpose of the pear-shaped block of heat-responding material will now appear. The two ends of the tine wire j are att-ached, respectively, to the two binding-screws z', and are thus brought into electrical connection with the metal armorstrips c and h and adapted thereby to be connected with the circuit to be protected. The cord loop lis then put through the ring e2, formed of the fixed end of the spring e, and the ball or pear shaped mass m will then rest on the upper side of said ring, which constitutes a rigid support therefor, its superior size preventing lit from falling through. The free hook-shaped end of the spring is then hooked into the loop Z, and the detachable appliance A is complete, and is accurately represented IIO by Fig. 3.A These may be made in large` quantities, as they can, as hereinafter eX- plained, be attached or detached in a moment of time.

lt is to be understood that the sensitiveness of such appliances can easily be regulated in their manufacture by Varying the size ot the wire 1y' and by increasing or decreasing the number et convolutions thereof round the loop within the heat-responsive block m. l prefer to regulate by the latter mode, however, and to keep thc size of the wire constantly small, as by so doing the size ot the entire appliance can be kept down. Many ot the appliances which are in actual use and which have given satisfaction are designed especially as a guard against the sneak currents to which reference has been made, and which have also answered well as lightningarrcsters,and are made of No. 36 insulated German-silver wire, about four inches ot" which is wound round the end of the loop, while a suitable i'naterial for surrounding the coil so made is ordinary fruit-canning wax, which l have Vfound to successfully withstand sun-heator the gradual application of ordinary rising temperatures, but to soften, break into pieces, or melt as soon as a dangerous current begins to traverse the coil ot' wire within it. ln making the loop, after winding the wire round its end, l tirst dip it into melted resin and then into the melted wax. l ani not, however, restricted to this mate'- rial, and can readily employ others. Easilyfusible alloys, lor example, maybe employed, care being taken that thcirfusion-point must be below the peint at which the insulation ol' the wire would be damaged.

As shown in VFigs. l and 2, d is a block ot` wood or like material, on which are springjaws f2 and il. 'lhc jaws are of spring metal and may be cheaply made ot' one. piece, the

two sides of each jaw being electrically continuous, and the whole fastened to the baseboard by the screws l, which by the intermediation ot suitable washers may likewise serve as ameans of attachment for the circuit-wires n.' and n". rlhe jaws are in fact spring-jacks. 'lhe detachable part A of the protector. which l call the slide,7 is simply slid into the said spring-jacks, so thatV its two-armed ends, respectively, are in rubbing contact with the two sides ot` the said jacks l and The protector is thus introduced into the circuit, and the tine wire thus becomes a link between two other portions of said circuit.

In Fig. (l is delineated a complete telephone or signaling circuit, the apparatus D at both terminal stations being guarded by my protectors A and A. In the diagram, p is a cable; te, one ot' the conducting-lines thereof; l), the apparatus to be protected; A and A', the protectors, and C the usual fuse at the line end of the cable, acting as an additional security therefor. The said fuse is, however, not a necessary concomitant of mydevice, and it is to be understood that it` an extra protector be required at that point a less sensitive appliance ot' the character described herein may usefully be employed.

ln the operation o my device when a dangerous or unduly strong current from any tween the binding-screws 1'.

reason comes on the circuit, or when an energetic discharge of eleetricity-such asalightning-dischargeMpasses thereover, the section oftinewire,beingot high resistancein compari son with any other equally long section et' the circuit, tends to concentratie in itselt a large portion ot' the heat developed in said circuit.. This is further concentrated by the portion ol such fine wire which is closely coiled round the loop, tirst, because in virtue ot. the windings a large amount et the heat developed in the tine conductor is condensed into a very small space, the heat et" the several convolutions of said wire being therefore enabled to act upon its immediately-surrounding matter with great energy, and, second, because, being perfectly inclosed in the t'usible block, it is preserved from the cooling intluence ot the air. The heat of the circuit, being' concentrated by the em bedded con velutions, sottens, breaks, or fuses the wax, and the spring which exerts a constant pull on the loop held thereby acts promptly to pull out the end loop to break the tine wire and consequently the circuit, and thus to remove the danger. The spring itsell', released by the softening ot the wax, tlics back with great torce to the position indicated in Fig. i. ln fact, so promptly does it tly back that the wireis not merely broken, but usually is also torn completely away from its tastenings, leaving a gap in the circuit as wide as the distance be` l have made these appliances sullieientlysensitive to break the circuit under a current developed on short circuit by a single .lleclanehe cell, and with greater currents they act so promptly that the wax ball scents rather to explode than to soften.

Fig. 7 shows a uuml, r ol eircnitsn: and apparatns 5 included therein, each being protected by one ot' a series ot protectors A2, all mounted together on a single base-board E In a series ot' earth-completed circuits, as shown, the several circuits after passing' through the protector continue by wire tu to the call-receiving instrument, and thence by wire to2 to the common earth terminal w3.

In Fig. S I have shown that a weight may in some circumstances be substituted Vlor the spring e. rlthe slide would require little alteration; but since the spring e would be absent the ring e?, holding the fusible block m, has to be made independently, and may be secured to the plate d by a screw or in any well-known way. A weight lV, of any heavy metal, as lead, having a hook in one end, is then attached to the loop, and in action the potential energy ot said weight will pull out the loop, as hereinbetore described.

It will be understood Ylrom what has been statedthat this appliance is capable of being used not only as a protector ot electrical apparatus from destruction attributable to currents of medium streugtl1,but that itis also adapted to serre as a protector from the et'- fects ot lightning-discharge, and, in brief, to

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exercise the functions of an automatic thermal circuit-breaker, regardless of circumstances.

I claim as my inventionl. A thermal protector for an electric circuit and apparatus included therein, comprisingaball or mass of material solid and hard at a normal temperature, but capable of fusing or softening when heated, a loop or hook having one end embedded in the said mass, a fixed ring or bracket support for the said mass and its dependent hook, an attenuated and relatively fragile section of circuitconductor extending between terminals and having a portion of its length coiled within thesubstauce of said heat-responsive mass and adapted to serve as a heat-concentrator therefor, and a power device, such as a spring or weight, normally engaged and su pported by thesaid loop and held in tension thereby and adapted to break the attenuated conductor when freed by the developmentof heat in the embedded coil-section of said conductor, slibstantially as described.

L In a thermal' protector for electric circuits, an attenuated and relatively fragile Section of circuit-conductor, a portion of which is coiled round the' shank of a loop-support and embedded within a mass or ball of matci-ial adapted to become plastic when warmed,

combined with a rigid support for said mass,A

and a spring engaged by said loop and normally held in tension thereby, but adapted to overcome the same and to tear the said loop and the coils secured thereto from the heat-responsive mass on the passage of an unduly strong current through the said coils.

3. The combination, in a thermal-protector cut-out, of asection ot' attenuated and relatively fragile circuit conductor having a portion of its length coiled within a ball or mass of material ordinarily solid and liard,but capable of becoming plastic when warmed, a loop or hook having one end attached to the fragile conductor-coils within the heat-,responsive mass and depending therefrom, and a strong spring engaged by said loop and adapted to pull the same away and to exercise its power on the fragile conductor when the said heat-responsive mass is softened, substantially as described.

4. 'lhe combination, with a mass or ball of easily-fusible material and alink of fine wire forming a portion of an electriccircuit,a porlion of the length of said fine wire being coiled within said mass, of a strong spring or its equivalent attached to the said fine wire, but normally held in tension away therefrom by a support sustained by said fusible mass and adapted when released by the softening of said mass to exercise its full power on said fine wire and todisrupt the saine.

5. The combination, in atherinal protector substantially as herenbefore described, of a iion-conducting foundation or base plate,

metal armor-stri ps therefor secured round the two ends, respectively, binding-screw terminals, one for each metal end strip, a strong spring secured to the base-plate by one arm' terminating in an annular bracket, the other arm being terminated by a hook and adapted when unconstrained to separate itself widely from the first, a ball or mass of wax-like material sufficiently large to rest on the said annular bracket, a loop depending from said ball through said bracket adapted to engage the spring-arm-hook terminal and to support the same in tension, and a section of fine wire of relatively high resistance uniting the two binding-screw terminals and having a portion of its length coiled round the shank of said loop and embedded within the said wax-like mass, substantially as and for the purpose specied.

G. In a thermal protecting device or circuit-breaker, a detachable slide comprising in a single compound attachment a non-conducting foundation-plate armed at each end with metal strips supporting wire-terminals,

a tine and fragile section of insulated wire uniting said terminals, a portion of said wire being coiled within a mass of Wax or like material, a spring-supporting loop attached within said mass to said coils, and a spring engaged by said loop and tending to pull the same away from said mass and to thereby break the said fragile wire, combined with spring jack or jaws suitably mounted, forming associated terminals of the circuit to be protected, and adapted, respectively, to rey ceive and to maintain frictional contact with the metal strips of the said detachable slide for the purpose of including the said fragile section of conductor in the circuit to be protected, substantially as hereinbefore -described.

7. The combination, in a thermal protecting device, of a section of line insulated Wire of relatively high resistance, forming part of the circuit to be protected, and having part of its'length coiled up within a mass of wax or like material becoming plastic when warmed,astrongspring device attached to aud tending to exercise when in tension a breaking strain ou said fine wire, and a loopsupportengaging the said spring, having its fixed end also embedded in said wax-like mass, and thereby taking the tension of said spring normally from said tine Wire, substantially as described.

In testimony whereof I have signed my naine to this specification, in the presence of two subscribing witnesses, this 1st day of December, 1890.

ALBERT BARRETT.

Witnesses:

M. D. RAY, W."W. SMITH.

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