RU1795492C - Thermosensitive fire detector - Google Patents

Abstract

The invention relates to thermal fire detectors of maximum differential action on the basis of a thermobimetallic sensing element and allows to increase the sensitivity and vibration resistance of the detector when controlling temperature in aggressive and explosive atmospheres. The detector contains a thin-walled hermetically-sealed thermosensor case of square cross-section and a removable two-channel thermosensitive element, consisting of two cases-sliders hinged to each other. A heat-sensitive unit with a flat cover is located in the slider body, which can be made of two copper-plated bimetallic plates bending in opposite directions. The removable element is inserted into the thermocouple housing along its flat guide walls and secured by a collapsible joint. In this case, the heat-sensitive flat covers / slider bodies are 90 ° rotated relative to each other, are spring-loaded and are in movable thermal contact with the shell of the probe. 4 ill. (L

Description

The invention relates to maximum fire detectors based on a thermo-bimetallic sensing element for fire alarm and automation systems.

The aim of the invention is to increase the functional reliability of the detector.

In FIG. 1 shows a diagram of a thermal fire detector; in FIG. 2 and 3 - design of the heat-sensitive detector unit; in FIG. 4 is a construction of a bimetallic base of a heat-sensitive assembly.

The detector consists of a sealed thin-walled metal case of a probe 1 of square cross section and a removable two-channel thermosensitive element 2. The thermosensitive element 2 contains a cover 3 in the form of a bushing, two bimetallic heat-sensitive nodes 4 of a rectangular shape, interconnected by wires 5 using hinges 6 A removable heat-sensitive element 2 is inserted into the internal cavity of the housing - the probe 1 along the guiding walls 7 and is tightly fixed by fasteners 8. When this Ohm, the heat-receiving surfaces of the base 9 of the heat-sensitive units 4 are rotated 90 ° relative to each other, are pressed by the springs 10 and are in thermal contact with the shell of the probe 1.

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in FIG. Figure 2 shows the construction of the heat-sensitive assembly 4 in the form of a housing 11 with a heat-receiving base 9. A bimetallic plate 12 mounted on it with the possibility of acting on the elastic plates 13 and the electrical contact group 14. The heat-sensitive assembly 4 can be maximally differential. For this, one of the elastic plates 13 is made of thermo-bimetallic, and the housing 11 is in the form of a case of heat-insulating material to ensure the directivity of the heat flux from the heat-receiving base 9 to the bimetallic plates 12, 13. The maximum differential sensor works as if the temperature rises to some threshold value, and when a certain rate of increase is reached. Maximally differential heat detectors are more sensitive than maximally effective detectors and are able to detect significantly smaller (in terms of burning area) fire sources.

In order to improve the conductive heat transfer and, therefore, to increase the sensitivity of the detector, it is necessary to ensure good thermal contact of the bimetallic plate 12 with the flat wall 7 of the casing - the probe 1. For this purpose, the heat-receiving base 9 is made bimetallic.

In FIG. 3 shows the construction of a thermosensitive unit 4 with a base of a bimetallic plate 15, which is in a state of temperature deformation. The external bending of the bimetallic plate 15 causes the heat-sensitive unit 4 to move in the longitudinal ((5i) and transverse (&) directions due to the action of the rod 5 and the hinge 6.

In FIG. 4 shows a split bimetallic plate 15 with peripheral sections 16, 17, the functional deflections of which have opposite signs. The middle section 16 is firmly mechanically bonded to the plate 15 in such a way that its active layer 18 passes into the passive layer 19 of the plate 15 and, conversely, the passive layer of section 16 passes into the active layer of the plate 15. The bimetallic plate 15 is coated on both sides with a thin layer of copper 20 to increase the heating rate of the peripheral sections 17. J

On the bimetallic base 15, in addition to the internal temperature stresses, external forces and moments, depending on the method of its fastening and caused by

the action of the spring 10. When unilaterally fastening a conventional bimetallic plate to the body 11 with the possibility of bending outward, its free end will be tightly pressed against the guide wall 7, the bending radius will be minimal, and the heat-sensitive unit 4 will experience angular displacement relative to the plate insert. When both ends of the plate 15 are firmly fixed, it can instantly change its position even at low temperature strains. In each case, the heat-receiving bimetallic base 15 deforms 5 s so. so that the balance of external and internal forces comes. In this case, the detector design allows the heat-sensitive nodes 4 to move along their guides and provides effective movable thermal contact of the heat-receiving surfaces 15 with the heated walls 7 of the probe 1. A soft spring suspension reduces the influence of mechanical stresses on the electric

5 contact group 14. The orthogonal arrangement of the elastic contact plates 13 also increases the vibration resistance of the detector. In addition, the detector design allows safe production

0 replacement of the sensing element 2 on pressure vessels.

The detector operates as follows. At normal temperature, the contact5 groups 14 are in a closed state. When the temperature of the controlled medium rises above the permissible temperature, the thin-walled case-probe 1 is heated and heat is transferred from it

0 of the guide walls 7 to the heat-receiving bases 9, 15. Under the influence of temperature, the bimetallic plates 12, (15 bend and act on the contact group 14, which opens and

5 generates an electrical signal about the operation of the corresponding channel of the detector tuned to a specific temperature. The information coming from the two-channel detector circuitry to the receiving device allows one to obtain data on the rate of rise in temperature, to increase the reliability of data on fire, false alarms and failure of the detector in the event of tinkling or flooding of contacts.

Thus, the design of thermosensitive units in the form of thermo-bimetallic sensors-sliders and the mechanism of their movement in orthogonal planes allows to improve the speed and vibration resistance of the detector and to use it effectively in automatic fire protection installations of objects with explosion-proof and aggressive environments.

Claims (1)

The claims A heat detector containing a sealed housing in the form of a straight cylinder with a lid and fasteners installed at one end, a spring-loaded heat-sensitive unit containing a base, on which a bimetallic plate with a contact group is placed, characterized in that, in order to increase functional reliability of the detector, the cross-section of the housing is square, additional heat-sensitive nodes are introduced, moreover, a heat-sensitive node, additional heat-sensitive The knots and the cover are hinged together, the heat-sensitive knots are oriented on the sides of the case, the base of each heat-sensitive knot is bimetallic, the functional bending of the base is opposite to the functional bending of the bimetallic plate, the bimetallic plate and the base are copper-plated.