JPS5937625A - Heat sensitive circuit breaker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] M distortion difference A The present invention relates to heat sensitive circuit breakers.

BACKGROUND OF THE INVENTION There are many applications in which highly reliable heat sensitive circuit breakers can be used advantageously. For example, a circuit breaker that operates to interrupt a circuit when exposed to a predetermined critical temperature or above can be used to issue an alarm or any other appropriate response. One use of circuit breakers is to monitor the temperature of components of a device and shut down the device if a critical temperature is detected.

A common type of thermostat can function as a circuit breaker. However, a thermostat has a limitation in that although it can detect the temperature in its immediate vicinity, it cannot detect overheating in areas far from its vicinity. That is, in many cases thermostats can only be used if the cost of installing them in large numbers is acceptable. For example, it would be highly desirable to be able to detect overheating of a cable, whether used for heating purposes or simply carrying power or information signals. Thermostats cannot be used to detect localized overheating of cables at an acceptable cost.

For example, the heating cable used to protect Suzuland from frost is commonly referred to as heating tape. Such heating tape is wrapped around the construction piping and provided with an insulating cover. Hot spots in the tape cannot be reliably detected by monitoring the applied current or tape resistance, and therefore heating tapes or systems incorporating them cannot be used in hazardous areas if they are used in hazardous areas. must be designed to be “fail safe”. A fail-safe design is one in which no foreseeable failure can result in overheating. Fail-safe designs are expensive because they require higher complexity and higher nominal capacity than if the straddle does not have to accommodate a variety of possible failure conditions.

It has been known for many years to detect heating of an electrical circuit above a critical temperature by incorporating into the circuit a wire-shaped circuit breaker that melts at the critical temperature. For example, British Patent No. 336,270 of 1929 proposes a heating element energized by a wire which melts and breaks the supply circuit if the heating element becomes overheated. However, such configurations generally require an insulating cover for the wire, which insulating cover maintains the molten metal in electrical continuity in its initial position at least temporarily when the wire melts. Since it is often held, uke is not accepted.

This molten metal retention effect is described in British Patent No. 1,164,238, which defines a fusible wire without insulation with sufficient space within it for the molten metal to easily flow away from its initial position. It is proposed to overcome this problem by supporting the inside of a strong tube. One way to provide this space is to fill the interior of the tough tube with an insulating material that is non-combustible and melts at a temperature lower than that at which the wire melts. Examples of such filling materials include silicone grease and paste flux.

GB 1 141 234 also refers to the retention of molten metal and proposes to overcome the above-mentioned problems by providing a device capable of absorbing molten metal.

Both of the above proposed solutions to the problem of molten metal retention are undesirable because they require non-standard extra features that cannot be included in the cable at low cost.

More recently, proposals have been made to provide monitoring cables in which a fusible electrical conductor is separated from another electrical conductor by a transparent insulator, as described in PCT Publication No. WO 33101138. In the event of overheating, the molten conductor diffuses through the insulator and the resulting droplet resistance between the two conductors is detected by suitable monitoring equipment. The device therefore relies on the molten portion of the fusible electrical conductor being maintained in electrical contact with the unfused portion of the fusible electrical conductor leading to the monitoring device.

Fluxes are used in conventional fusible alloys, such as solders, to help the molten metal wet the surface to which it is attached; therefore, incorporating flux into sheathed fusible wires It is reasonable to assume that this would increase the probability that the fused portion of the wire would retain electrical continuity.

However, surprisingly we found that this is not the case.

OBJECTS OF THE INVENTION It is an object of the invention to provide an improved circuit breaker.

SUMMARY OF THE INVENTION According to the present invention, in a heat-sensitive circuit breaker comprising an electrical conductor made of a material of a predetermined melting temperature and supported by an electrically insulating member capable of withstanding temperatures above said melting temperature, the electrical conductor When the conductor melts, the contact angle between the molten conductor and the insulating material becomes smudged, causing the molten conductor to flow and separate into droplets. A heat sensitive circuit breaker is provided that is of a material that is thick enough to break continuity.

DETAILED DESCRIPTION OF THE CONFIGURATION AND EFFECTS OF THE INVENTION The electrical conductor is preferably manufactured from flux-containing solder. . A solder consisting of 60 inches of tin and 40 inches of lead and incorporating a vertical core of flux has been shown to be particularly useful. Such solders are commonly used to make electrical connections. The solder can be rolled into a flat strip.

The invention is based on the known principle of the behavior of a liquid when placed on a solid planar surface, whose behavior depends on the contact angle. Contact angle is defined as the angle made by a planar surface and a tangent drawn from the edge of the liquid to the liquid surface at a surface perpendicular to the planar surface and the edge of the liquid. If this contact angle is small, the liquid will wet a flat surface. A large contact angle will result in the formation of droplets or bubbles.

The contact angle is the result of three thermodynamic forces F, , F2 and F3 acting on each interface of the liquid/solid/surrounding vapor system, and these forces are related as follows.

Fl ”' F2 + F5 CmC where C = contact angle F, = surface free energy of solid/vapor interface F2 = surface free energy of solid/liquid interface p, = surface free energy of liquid/vapor interface (surface tension ) The thermodynamic forces and thus the contact angles are influenced by the presence of 7 lux in the molten solder.The flux-free molten solder remains as a liquid film and contracts into discrete droplets. Although this is not the case, we have discovered that when solder containing flux is melted, it shrinks into bubbles.

In common solder, 7lux is used to help the liquid wet the surface.

In the present invention, in contrast, a flux is used to separate the liquid solder into individual droplets or bubbles. This contrast can be explained by considering three possible effects of flux.

l) Chemically remove (or attack) flat surface oxides or defects that tend to impart high surface energies to the surface.

2) Remove lead and tin oxides formed on the solder surface (
or corrosion).

3) The excess 7 lux provides a thinner energy film, which allows the liquid solder to move more easily.

In general solder, the dominant effect is the removal of deposits on the solid surface, which causes the solder to wet the surface. In contrast, in the present invention, the removal of the oxide film of the solder is the dominant influence, whereby the surface tension of the liquid solder causes the liquid solder to flow into a low-energy shape, i.e., in the form of droplets or bubbles. be.

EXAMPLES Two embodiments of the present invention will be illustrated below with reference to the accompanying drawings.

The accompanying drawing is an end view of a heating tape incorporating a heat-sensitive circuit breaker according to the invention, the exemplary heating tape consisting of a sheath 1 internally surrounding two copper foils 2, 3. . The heating textile element 4 is located below the foil but is electrically insulated therefrom by a web 5 of insulating material. A pair of solder foils 6, 7 are supported on a support film 8 on the copper foils 2, 3, separated from the copper foil by a web 9 of insulating material. The support film can be fiberglass or glasstic, commercially available as Kapton®, the connections between the copper foil 2.3 and the heating element 4 being spaced along the length of the tape. This is done by inserting rivets through the copper foil and a heating element located in the same direction.For example, rivets can be placed 1 meter apart along each foil, with the rivets in one seedling connecting to the copper foil in the other. 50 for rivets
It can be shifted by crn. A heating tape having a cylindrical heating element and a current-dissipating conductor structure is described in GB 1523129.

The exemplary heating tape is made by forming a core consisting of foil conductors 2, 3 embedded in an insulating pod containing webs 5 and 9. The outer shell of the core is glued to the film 8 by a bonded foil 6.7, which is indicated by dotted lines 10 in the drawing. The heating element 4 is pressed onto one side of the core and riveted to the foils 2, 3, and the film 8 is pressed onto the opposite side. The resulting assembly is then enclosed in a sheath 1 by an extrusion process.

The tape can be of any convenient size, such as 20 mesh width and 4 tone thickness. The solder foils 6, 7 can be formed by rolling out strips approximately 4 mm wide from thin multi-core lead/tin solder wire, a typical thin multi-core lead/tin solder wire used to connect electronic components. By using such a solder foil, when it is heated to its melting point, a break with a width of about 10wn occurs in the foil, and the molten solder flows away from the broken part (melted part), causing a break in either part of the broken part. The edges of the foil are thicker on the side.

Solders that melt at defined temperatures over a wide range of temperatures, for example from 1006C to 3000C, can be easily prepared. That is, the tape of Example 1 can be used for a wide variety of purposes.

It is possible to supply energy to the heating element using a copper foil 2,3 dispense and a solder foil 6,7. However, if the power is supplied through the solder, it is not advantageous because sparks are emitted when the solder melts and breaks. In contrast, in the exemplary arrangement, the low potential monitoring circuit can be connected between the foils 6, 7 at one end of the tape, and the other ends of the foils 6, 7 can be connected together.

There is no risk of sparks when using a low potential monitoring circuit.

It goes without saying that one of the solder foils 6, 7 could be replaced by a non-fusible electrical conductor, such as copper, for example.

The invention may also have uses not related to heating tapes.
Needless to say. For example, surveillance tapes are the only
Or it can be made with two solder conductors and without a heating element or separate supply conductor. This monitoring tape is then easily adapted to be placed in areas where it is desirable to detect overtemperatures, such as electrical cable ducts or warehouse ceilings, to generate an alarm in the event of a rupture of a solder conductor. Can be connected to various circuits. Monitoring tapes can also be used to place on the windings of devices, for example electric motors, to automatically shut down the device in case of overheating.

The exemplary embodiment shows a thin foil solder conductor.

However, it will be appreciated that the solder Ol may have other shapes suitable for the particular application, as long as it is able to flow and form a break once melted.

Experimental results show that both single and multi-core 7-lux solder work satisfactorily, with multi-core solder in particular free-flowing better to form independent spheres of molten metal, and especially It was good. Plain un-fluxed solder will generally not work because it will melt but will not flow easily to form a break. Unfluxed solder present in the 7 lux powder also does not work effectively if the flux powder is oxidized.

The above embodiment of the present invention utilizes a solder containing flux in the form of a core, but the solder may also be coated on the outside with flux.

As used herein, the term "solder" refers to any electrically conductive fusible substance or material. Generally speaking, solder takes the form of a low melting point fusible alloy. The flux may be of any suitable type, but care must be taken that the flux is stable at the normal temperatures of the dew atmosphere in which it is used.

[Brief explanation of the drawing]

The accompanying drawing is an end view of a heating tape incorporating a heat sensitive circuit breaker in accordance with the present invention. DESCRIPTION OF SYMBOLS 1...Sheath, 2,3...Copper foil, 4...Heating textile element, 5,9...Weso, 6,7...Solder foil, 8...Support film. Engraving of the following margin drawings (no changes to the content) Procedural amendment c method) % formula % 1. Indication of the case 1982 Patent application No. 89298 2. Name of the invention Heat sensitive circuit breaker 3. Case of the person making the amendment Relationship with Patent applicant name Heat Trace Limited 4, agent (3 others) 5. Date of amendment order August 30, 1980 (shipment date) 6. Subject of amendment (1) Description (2) Figures Page 7, Contents of amendment (1) Cleaning of the specification (no change in content) (2) Cleaning of page 4 (no change in content) (2) 8. List of attached documents

Claims (1)

[Claims] 1. A heat-sensitive circuit breaker consisting of an electrical conductor made of a material with a predetermined melting temperature and supported by an electrically insulating member capable of withstanding temperatures higher than the melting temperature, the electrical conductor material When the conductor melts, the contact angle between the molten conductor and the insulating material is such that the molten conductor flows and separates into droplets with a force of 9.
A heat-sensitive circuit breaker is a material that is large enough to interrupt the electrical continuity of an electrical conductor. 2. The circuit breaker according to claim 1, wherein the conductor is made of a solder containing 7 lux. 3. The circuit breaker according to claim 1 or 2, wherein the conductor is in the form of a flat strip. 4. The circuit breaker according to claim 2, wherein the conductor is a flat strip formed by flattening and rolling a circular solder wire containing a plurality of flux cores. 5. Consisting of two electrical conductors arranged in parallel, at least one of which is said electrical conductor made of a material of a predetermined melting temperature, whose electrical continuity at one end is monitored from the other end. 5. A circuit breaker according to claim 1, wherein the circuit breaker is connected together in such a way that the circuit breaker can be connected together in such a way that the circuit breaker can 6. The circuit breaker according to any one of claims 1 to 5, which is introduced as an electric heating tape. 7. The circuit breaker of claim 6, wherein said electrical conductor made of a material of a predetermined melting temperature constitutes a heating element of a heating tape. 8. The circuit breaker according to any one of claims 1 to 7, wherein the support member is in the form of a sheath surrounding the or each conductor.