JPH04474Y2 - - Google Patents

Description

[Detailed description of the invention] This invention applies a deforming force to plastically deform the plate-like shape memory alloy, which returns to the shape before deformation by heating, and a spring material. A reed switch that is fixed to the inner surface of a partition wall of a duct, has a rod-shaped permanent magnet fixed to the other end, and further has the direction of the magnetic pole closely aligned with the direction of the reed contact at a position corresponding to the position of the permanent magnet. This is a fire alarm temperature sensor attached to the outer wall of the bulkhead.

Conventionally, in temperature sensors for fire alarms, a current is constantly passed through an easily melted metal that melts at a specified temperature, and when the temperature rises due to a fire, the alloy melts, the current is cut off, and an alarm is issued. Those that emit are used. In this type of sensor, the constantly flowing current is cut off in the event of a fire, so even if there is no abnormality in the sensor, it may be caused by a break in the alarm circuit or the wiring between the sensor and the alarm. There was also a problem with the alarm being activated, which could be mistaken for a sensor activation. Furthermore, since the easily melted metal is melted, it cannot be reused, and since it has no reusability, it has the disadvantage that individual operation tests cannot be performed.

The present invention eliminates such drawbacks of the conventional method and uses a permanent magnet that is fixed to a plate-like body in which a shape memory alloy and a spring material are brought into close contact with each other, and a permanent magnet that is placed in close proximity to lead the shape memory alloy to return to its original shape by heating. This is a temperature sensor that closes the contact piece of the switch.It can be reused and allows testing of operation and characteristics.

FIG. 1 shows one embodiment of the present invention. As shown in the figure, one end of a rectangular plate-like body 6 in which a shape-memory alloy 1 that has been plastically deformed into a flat plate shape and a bias leaf spring 2 are overlapped in the thickness direction and brought into close contact with each other is connected to a duct, etc. A reed switch is fixed to the inner wall surface of the non-magnetic partition wall 4, a permanent magnet 3 is fixed to the other end, and contact pieces 7, 7' are positioned on the outer wall surface of the partition wall 4 in the direction of the magnetic pole of the permanent magnet 3. 8.

The shape memory alloy 1 is made of a nickel-titanium alloy, a nickel-aluminum alloy, a copper-based alloy, or the like, and has a shape memory effect in which the shape returns to its original shape before plastic deformation when it is heated after being plastically deformed by applying a deforming force. When gradually cooled from a high temperature, martensitic transformation occurs from an austenite phase to a martensitic phase at a certain temperature transformation point, and conversely, when heated, a reverse transformation occurs from a martensite phase to an austenite phase at a certain temperature reverse transformation point. Usually, the reverse transformation point is 20°C to 50°C higher than the transformation point.

In the present invention, a rectangular plate-shaped shape memory alloy 1 which has been plastically deformed by applying a deforming force is stacked with a bias plate spring 2 curved in an arc shape, and this plate-shaped body 6 is formed in a martensitic phase. The deformation force is set to be larger than the yield force and smaller than the yield force in the austenite phase. A permanent magnet 3 is fixed to one end of the arc-shaped joining plate 6 with the surface of the plate 6 facing the partition wall 4' and with the magnetic poles oriented in the longitudinal direction of the plate 6. The other end of the plate member 6 is fixed to the inner wall surface of the partition wall 4' via a spacer 5 having approximately the same thickness as the magnet 3. Further, a reed switch 8 is fixed to the outer wall surface of the partition wall 4' at a position facing the permanent magnet 3 and such that the internal reed contact pieces 7, 7' coincide with the direction of the magnetic poles.

In normal times, the plate-like body 6 is bent inside the duct 4 by the force of the leaf spring 2 and the weight of the permanent magnet 3, as shown in Fig. 1, and the magnet 3 is connected to the reed switch 8 as shown in the figure.
It is assumed that the contact pieces 7, 7' are in a separated state. In the case of FIG. 1, the deforming force applied to the plate-shaped body 6 is the sum of the deforming force of the leaf spring 2 and the weight of the magnet 3.

When a fire breaks out near the duct 4 and the temperature rises abnormally, the shape memory alloy 1 reaches its reverse transformation point.
The martensite phase reversely transforms into the austenite phase, and the plate-shaped body 6 overcomes the combined deformation force of the deformation force of the leaf spring 2 and the weight of the magnet 3, and becomes the flat plate before plastic deformation as shown in FIG. Return to state. The magnet 3 therefore approaches the reed switch 8 and closes its contacts 7, 7'. When the external connection leads 9, 9' of the reed switch 8 are connected to an alarm circuit, it is possible to notify that there is an abnormal temperature rise in the vicinity of the duct due to a fire or the like.

When the fire is extinguished and the temperature inside the duct 4 decreases and reaches the transformation point, the shape memory alloy transforms from the austenite phase to the martensite phase, and the plate-shaped body 6 again assumes the arc-like shape as shown in FIG. 1. Permanent magnet 3
is separated from the reed switch 8, and its contact pieces 7, 7'
is released.

Unless this shape memory alloy 1 is directly exposed to flame for a long period of time, the alloy will not be oxidized and can repeat the transformation between the austenite phase and the martensite phase.

In the above embodiment, the plate-shaped body 6 is provided on the partition wall of the duct 4, but the bias plate spring 2
By setting both the sum or the difference between the deformation force of Reliable operation can be achieved no matter which partition wall of the duct 4 the plate-like body 6 to which 3 is attached is placed. In addition, the normal shape of the shape memory alloy 1 is curved, the leaf spring 2 is made into a flat plate, and the state shown in FIG. Of course, it is also possible to take the normal shape and, when operating at high temperatures, take a curved state as shown in FIG. 1 and open the contacts.

As explained above, the present invention can quickly detect an abnormal rise in temperature, such as the occurrence of a fire near a duct, and issue an alarm. Additionally, since the sensor is capable of self-recovery, it has the advantage of being able to be tested as a single component. The sensor of the present invention can be used not only to detect fires in ducts, but also to detect temperatures in liquid tanks and air tanks.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of the embodiment of the present invention installed in a duct in normal operation, and FIG. 2 is a vertical cross-sectional view of FIG. 1 when a sensing operation is performed. The symbols shown in the drawings are 1...shape memory alloy, 2...plate spring, 3...permanent magnet, 4...duct, 4'...partition wall, 6...plate-like body, 7, 7'... . . . Reed switch contact piece, 8 . . . Reed switch is shown.

Claims (1)

[Scope of utility model registration request] In a temperature sensor for duct fire alarm, a rectangular plate-shaped body made by closely bonding one side of a plate-shaped shape memory alloy and a plate spring that have been plastically deformed by applying a deforming force is attached to the inner wall surface of the duct partition with one end. A reed switch is provided on the outer wall of the duct, with a permanent magnet fixed to the other end, and a reed switch facing the permanent magnet so that the direction of the magnetic pole and the direction of the contact piece closely match. Temperature sensor.