Thermo-magnetically operated switches

Abstract

A thermo-magnetically operated switch comprises a reed switch, two ferromagnetic members having predetermined and different Curie points and plural permanent magnets. The switch has two operating or switching points on a temperature axis and provides control over a range of temperatures.

Description

BACKGROUND OF THE INVENTION

This invention relates to temperature-operated switches and more particularly, to thermo-magnetically operated switches which utilize the saturation flux density versus the temperature characteristic of a magnetic substance to control the switching temperature.

A thermo-magnetically operated switch using magnetic materials which is constructed by positioning a permanent magnet and a magnetic substance proximate a reed switch whereby the contacts of the reed switch are opened and closed in response to changes in the temperature, is known in the prior art, as exemplified for example, by in French Pat. No. 1,549,349, U.S. Pat. No. 3,295,081 and other.

Such thermo-magnetically operated switches as above mentioned are conveniently used to control the operation of devices operating in response to a predetermined temperature, because they are mechanically and thermally strong and solid, operatively stable in long use and, therefore, have a long life-time.

Known thermo-magnetically operated switches are of the one point operation type or of the type with which a switching operation is available at one point on a temperature axis. This restricts fields the of use of thermo-magnetically the known operated switches.

In certain automatic controls, it is often required that a device should be operated within a temperature range on a temperature axis and should have its operation stopped at the other temperatures on the temperature axis. In that case, known thermo-magnetically operated switches are not useful. However, the use of two known thermo-magnetically operated switches having different operation temperatures meets such requirement, but it necessarily requires greater area for the location of two switches.

OBJECTS OF THE INVENTION

An object of this invention is to provide a thermo-magnetically operated switch which has two different operating points on a temperature axis so that it may be maintained closed (or open) below the lower operating point and above the higher operating point; and be maintained open (or closed) between the two different operating points.

Another object of this invention is to realize the above object with simple construction, low cost and with a small-size switch.

SUMMARY OF THE INVENTION

According to the present invention a thermo-magnetically operated switch comprises: an elongated reed switch comprising an envelope and a pair of ferromagnetic reeds hermetically sealed in said envelope with free ends thereof overlapped for opening and closing movements relative to one another; two elongated permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different angular positions on the circumference of said reed switch and in reverse polarity with respect to each other, the respective magnetic poles of each permanent magnet being disposed over the respective reeds; and two elongated ferromagnetic bodies having different predetermined Curie points within the operating temperature range of the switch and overlying respective permanent magnets.

According to another aspect of the present invention a thermo-magnetically operated switch comprises: an elongated reed switch comprising an envelope and a pair of ferromagnetic reeds hermetically sealed in said envelope with free ends thereof overlapped for opening and closing movements relative to one another; two permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different axial positions of said reed switch in same polar direction with respective magnets disposed over the respective reeds but short of the overlapped ends of the reeds; a first ferromagnetic body having a predetermined Curie point within the operating temperature range of the switch and disposed over the overlapped ends of the reeds in the axial space between said two magnets in such manner that opposite ends of said first ferromagnetic body may engage with adjacent different pole faces of the two magnets; and second ferromagnetic body means having a predetermined Curie point lower than that of said first ferromagnetic body within the operating temperature range of the switch and overlapped and disposed on the two magnets in such manner that said second ferromagnetic body means is magnetically coupled between the other poles of the magnets opposite the poles thereof engaging said first ferromagnetic body.

Another to another aspect of the present invention a thermomagnetically operated switch comprises: an elongated reed switch comprising an envelope and a pair of ferromagnetic reeds hermetically sealed in said envelope with free ends thereof overlapped for opening and closing movements relative to one another; two elongated permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different axial positions of said reed switch in reverse polar direction relative to each other and with respective magnets disposed over the respective reeds short of the overlapped ends of the reeds; a first ferromagnetic body having a predetermined Curie point within the operating temperature range of the switch and disposed in the axial space between said two magnets with one end thereof engaging with the adjacent pole face of one magnet, the other end thereof being short of the overlapped ends of the reeds; and a second ferromagnetic body having a predetermined Curie point lower than that of said first ferromagnetic body within the operating temperature range of the switch and disposed in the axial space between said first ferromagnetic body and the other magnet with one end thereof engaging with the adjacent pole face of said other magnet, the other end thereof exceeding the overlapped ends of the reeds and engaging with said the other end of said first ferromagnetic body.

According to still another aspect of the present invention a thermo-magnetically operated switch comprises: an elongated reed switch comprising an envelope and a pair of ferromagnetic reeds hermetically sealed in said envelope with free ends thereof overlapped for opening and closing movements relative to one another; two elongated permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different axial positions of said reed switch in the same polar direction relative to each other and with respective magnets disposed over the respective reeds short of the overlapped ends of the reeds; a first ferromagnetic body having a predetermined Curie point within the operating temperature range of the switch and disposed in the axial distance between said two magnets with one end thereof engaging with the adjacent pole face of one magnet, the other end thereof being just adjacent of the overlapped ends of the reeds; and a second ferromagnetic body having a predetermined Curie point lower than that of said first ferromagnetic body within the operating temperature range of the switch and disposed in the axial distance between said first ferromagnetic body and the other magnet with one end thereof engaging with the adjacent pole face of said other magnet, the other end thereof being just adjacent of the overlapped ends of the reeds and engaging with said other end of said first ferromagnetic body.

The other features and objects of this invention will be understood from the following descriptions taken in conjunction with the annexed drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the saturated flux density vs. temperature characteristic of two ferromagnetic substances,

FIGS. 2A and 2B show front and side views of an embodiment of this invention, respectively, but partially cross-sectioned,

FIGS. 3A-3C show views for schematically explaining the operation of the switch in FIGS. 2A and 2B,

FIGS. 4A-4C show front views at different temperatures of another embodiment,

FIGS. 5, 6, 7A, 7B, 8A and 8B show various modifications of the switch in FIGS. 4A-4C,

FIG. 9 shows a perspective view of another embodiment,

FIG. 10 shows a perspective view of a modification of the switch in FIG. 9,

FIGS. 11A-11C show views for schematically explaining the operating principle of switches in FIGS. 9 and 10,

FIGS. 12A-12B show front views at different temperatures of another embodiment of this invention, and

FIGS. 13-15 show various modifications of the switch in FIG. 10.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This invention intends uses two ferromagnetic substances having different Curie points as shown in FIG. 1 together with plural permanent magnets and a reed switch, all arranged so that the reed switch may be operated at two points on a temperature axis.

Referring to FIG. 1, in which the saturated flux density vs. temperature characteristics of two ferromagnetic substances which are used in this invention for sensing temperature is illustrated, the curve "A" shows the characteristic of one of the two temperature sensitive ferromagnetic substances and the curve "B" shows that of the other substance.

The substance A has a lower Curie point T.sub.c1 than that (T.sub.c2) of the other substance B.

FIGS. 2A and 2B show an embodiment of this invention, which comprises a reed switch 1, two elongated permanent magnets 2 and 3, and two ferromagnetic bodies 4 and 5 having different Curie points, as indicated in FIG. 1.

The reed switch, as well known, comprises an elongated envelope 11, which is preferably made of glass, a pair of reeds 12 and 13 hermetically sealed therein, which are made of ferromagnetic and electro-conductive materials, with ends thereof being overlapped for opening and closing movements relative to one another, and lead wires 14 and 15 connected with respective reeds, sealed to opposite ends of the glass envelope 11 and outwardly extending therefrom.

The permanent magnets 2 and 3 have higher Curie points exceeding the operating temperature range of the switch and are mounted on and secured by adhesive 16 to the outside of the glass envelope 11. The permanent magnets 2 and 3 are so disposed that magnetic poles of one magnet are reversely disposed relative to those of the other magnet and that both of these magnets 2 and 3 are in parallel to one another and stradle the overlapped ends of the reeds 12 and 13.

The ferromagnetic bodies 4 and 5 overlie and are secured on respective permanent magnets 2 and 3.

To prevent breakage of glass envelope 11 at its end portions caused by treatment of lead wires 14 and 15 sealed thereat, such as a bending treatment in practical use of the switch, non-conductive and non-magnetic jackets 6 and 7 are, preferably, provided so that they may enclose end portions of the glass envelope 11 and small lengths of lead wires 14 and 15 extending from their sealed portions. Thus, small lengths of the lead wires extending immediately from the glass envelope cannot be bent so that breakage of the glass envelope may be prevented.

A heat-conductive cylindrical part 8 is, advantageously, provided to enclose the permanent magnets (2, 3), the ferromagnetic bodies (4, 5) and the reed switch 1.

The operation of the switch illustrated in FIGS. 2A and 2B will be explained in conjunction with FIGS. 3A-3C in which only the permanent magnets 2 and 3, the temperature sensitive ferromagnetic bodies 4 and 5 and the pair of reeds 12 and 13 are shown for simplicity of the drawings.

When the environment or observed object is at a lower temperature than the Curie point of either of the temperature sensitive ferromagnetic bodies 4 and 5, magnetic fluxes from the magnets 2 and 3 flow through respective ferromagnetic bodies 4 and 5 as indicated by broken lines in FIG. 3A. The two reeds 12 and 13 are thereby maintained open.

Elevating the temperature, the saturated magnetic flux density is reduced as shown in FIG. 1.

When the temperature is elevated to a temperature between different Curie points of the two temperature sensitive ferromagnetic bodies 4 and 5, or in the drawing, higher than the Curie point of the body 4 and lower than the Curie point of the body 5, magnetic fluxes from the magnet 2 flow through the reeds 12 and 13 as illustrated in FIG. 3B, because the ferromagnetic body 4 turns to the non-magnetic characteristic. The magnetic strength between overlapped ends of the reeds 12 and 13 overcomes the elasticity of the reeds to permit the overlapped ends to close.

When the temperature is further elevated and is at a temperature higher than the Curie point of the other temperature sensitive body 5, magnetic fluxes from each of the magnets 2 and 3 flow through the other, and do not flow through reeds 12 and 13 because they are cancelled in the reeds by the flux from the other temperature sensitive body. The overlapped ends of reeds 12 and 13 are thus opened.

The above described operation is clearly reversible.

It will be understood that the switch illustrated in FIGS. 2A and 2B may be advantageously used to observe the inner temperature of a heating box to be maintained at a temperature between two different temperatures.

FIGS. 4A, 4B and 4C show another embodiment of this invention, which comprises a reed switch 1, two permanent magnets 2 and 3 and two temperature sensitive ferromagnetic bodies 4 and 5.

The permanent magnets 2 and 3 are mounted on and secured to the glass envelope 11 of the reed switch in such fashion that they are disposed in similar polar directions alongside the reed switch 1 at different axial positions and in parallel with the respective reeds 12 and 13, but short of the overlapped ends of the reeds.

The temperature sensitive ferromagnetic body 4 having a predetermined Curie point overlies both of the two permanent magnets 2 and 3 over the axial lengths of both magnets.

The other temperature sensitive ferromagnetic body 5 has a predetermined Curie point higher than the body 4 and is disposed in the space between the two permanent magnets 2 and 3 and beneath the ferromagnetic body 4, with axial opposite ends thereof engaging with adjacent pole faces of the magnets.

When the temperature of an observed object (or of the environment) is lower than the Curie point of either of temperature sensitive ferromagnetic bodies 4 and 5, magnetic fluxes from both of the permanent magnets 2 and 3 flow through both of the ferromagnetic bodies 4 and 5. Thus, the overlapped ends of reeds 12 and 13 are maintained open, as illustrated in FIG. 4A.

When the temperature is elevated higher than the Curie point of the ferromagnetic body 4 and lower than the Curie point of the other temperature sensitive body 5, magnetic fluxes flow through the body 5 and reeds 12 and 13, because the temperature sensitive body 4 turns non-magnetic. The magnetic strength between overlapped ends of reeds 12 and 13 then overcomes the elasticity of each reed to permit the overlapped ends to close.

When the temperature is further elevated higher than the Curie point of the temperature sensitive body 5, magnetic fluxes from the magnet 2 flow only through the adjacent reed 12 while fluxes from the other magnet 3 flow only through the other reed 13, because the body 5 turns non-magnetic. Thus, no magnetic strength overcoming elasticity of the reeds present between the overlapped ends of reeds 12 and 13, and the overlapped ends are opened.

Additional combinations of the two permanent magnets and the two temperature sensitive bodies may be provided at different angular positions in circumference of the reed switch as shown in FIG. 5, in which additional members are referred by primed numbers.

In FIGS. 4A-4C and 5, the temperature sensitive ferromagnetic body 5 (and/or 5') are of same thickness as the permanent magnets 2 and 3 (or 2' and 3') at the thickest. But this is not important. For example, the other temperature sensitive means 4 (and/or 4') may be formed of two parts of ferromagnetic materials 4A and 4B (4'A-4'B) having the same Curie point, as illustrated in FIG. 6. Clearly from FIG. 6, the temperature sensitive bodies 5 and 5' are thicker than the permanent magnets, each of ferromagnetic materials 4A, 4B, 4'A and 4'B engaging with the adjacent end of each of the bodies 5 and 5'.

The switch shown in FIG. 6 operates, as clearly and readily understood, similarly as the switch described in connection with FIGS. 4A-4C. Broken lines shown in FIG. 6 show how magnetic flux passes under a condition when the environmental temperature is lower than the Curie point of either temperature sensitive means (4A, 4B, 4'A, 4'B, 5 and 5').

It will be understood from FIG. 5 that a similarly functioning switch may be constructed by employing a reed switch 1, two cylindrical permanent magnets 2 and 3, and two temperature sensitive cylindrical bodies 4 and 5, as shown in FIGS. 7A and 7B.

FIGS. 8A and 8B show a modification of the switch in FIG. 6, in which two cylindrical permanent magnets 2 and 3, a temperature sensitive ferromagnetic cylindrical body 5, and two temperature sensitive ferromagnetic cylindrical pieces 4A and 4B are employed as shown in the drawings.

Operation of the switches in FIGS. 7A-8B are similar as the switch in FIGS. 4A-4C and, therefore, are not descirbed for simplification of the description.

In FIGS. 7A-8B, an axial groove 9 may be provided on the outer surface of the temperature sensitive cylindrical body 4 (FIGS. 7A and 7B) or surfaces of the temperature sensitive cylindrical pieces 4A and 4B and cylindrical body 5 (FIGS. 8A and 8B) to introduce one of lead wires, for example, 15 at same side as the other lead wire 14. Thus, the lead wire 15 is bent adjacent the sealed portion of the glass envelope 11 and, therefrom, is introduced along the cylindrical body 4 (FIG. 7A) or the cylindrical pieces 4A-4B and body 5 (FIG. 8A) in the groove 9. Accordingly, the resulting switches may be conveniently used in such applications where electric leads must be introduced from one direction.

Similar jackets and cylindrical members as members 6, 7 and 8 illustrated in FIGS. 2A and 2B may be provided for the switches shown in FIGS. 4A-8B. Such members are not shown in FIGS. 4A-8B for simplicity of the drawings.

Referring to FIGS. 9 and 10, in which are shown other embodiments of this invention, each of which comprises a well known reed switch 1, two permanent magnets 2 and 3 having Curie points higher than the operating temperature range of the switch, a temperature sensitive ferromagnetic member 4 having a predetermined Curie point and another temperature sensitive ferromagnetic member 5 having a predetermined Curie point higher than that of the temperature sensitive member 4.

The embodiments in FIGS. 9 and 10 are similar in principle but have differently shaped permanent magnets 2 and 3 and temperature sensitive members 4 and 5, which block shaped in FIG. 9, cylindrically shaped in FIG. 10.

The positional relation between the permanent magnets 2 and 3 and the temperature sensitive members 4 and 5, as well as the reeds of the reed switch 1, are shown in FIGS. 11A-11C, in which the operation of the switches in FIGS. 9 and 10 is schematically illustrated.

Referring to FIGS. 11A-11C, the two permanent magnets 2 and 3 are disposed at different axial positions in parallel with respective reeds 12 and 13 of the reed switch, but are short of the overlapped ends of the reeds. The magnets 2 and 3 are disposed reversely in their polar directions, or in such manner that similar poles may face one another. The temperature sensitive members 4 and 5 are disposed in the axial space between the two magnets 2 and 3 and in series with one another. One end of the member 4 engages with adjacent pole of the magnet 2 with the other end being short of the overlapped ends of the reeds 12 and 13. On the other hand, one end of the member 5 having a higher Curie point engages with the adjacent pole of the magnet 3 and the other end thereof overlies the overlapped ends of the reeds 12 and 13 to engage with the other end of the member 4.

In case the environmental temperature is lower than the Curie point of the member 4, the members 4 and 5 presents a ferromagnetic characteristic. But magnetic fluxes from the magnets 2 and 3 do not flow through the members 4 and 5 because similar poles (S poles in the drawing) face each other with the members 4 and 5 therebetween. Magnetic flux from the magnet 2 flows through the reed 12 and magnetic flux from the other magnet 3 flows through the other reed 13, as shown by broken lines in FIG. 11A. Thus, the overlapped ends of reeds 12 and 13 are maintained opened.

When the temperature is elevated to a temperature higher than the Curie point of the member 4 and lower than the Curie point of the other member 5, the member 4 presents a non-magnetic characteristic. Accordingly, magnetic flux from the magnet 3 flows through reeds 12 and 13 and the ferromagnetic member 5, while magnetic flux from the other magnet 2 flows through the reed 12, as shown by broken lines in FIG. 11B. As a result, magnetic strength between overlapped ends of reeds 12 and 13 overcomes the elasticity of each reed so that the overlapped ends of reeds are closed.

When the temperature is further elevated to a temperature higher than the Curie point of the temperature sensitive member 5, both of the members 4 and 5 present a non-magnetic characteristic, so that magnetic flux of each of the magnets flows through only one reed, as shown by broken lines in FIG. 11C.

As a result the, overlapped ends of reeds 12 and 13 are opened.

Switches shown in FIGS. 9 and 10 have two operating points on a temperature axis, as is clearly understood from the above descriptions.

FIGS. 12A-12C show another embodiment of this invention, which comprises a well known reed switch 1, two permanent magnets 2 and 3 and two temperature sensitive ferromagnetic members 4 and 5.

The two magnets 2 and 3 have Curie points higher than the operating temperature range of the switch and are disposed alongside the reed switch 1 at different axial positions in such manner that they are similarly oriented in their polar directions (different poles face one another) and that they are in parallel with respective reeds 12 and 13 but short of the overlapped ends thereof.

The two temperature sensitive ferromagnetic members 4 and 5 have different Curie points within the operating temperature range of the switch and are disposed, in series with one another and with the magnets 2 and 3, in the axial space between the magnets 2 and 3. Both of these members 4 and 5 engage with one another at a position adjacent to the overlapped ends of the reeds 12 and 13, with the opposite end of each member engaging with an adjacent pole of respective magnets.

When the environmental temperature is lower than the Curie point of either of ferromagnetic members 4 and 5, magnetic flux from magnets 2 and 3 flows through the members 4 and 5 and reeds 12 and 13 as shown by the broken line in FIG. 12A, so that the overlapped ends of the reeds are maintained closed.

When the temperature is elevated higher than the Curie point of one temperature sensitive member 4 but lower than the Curie point of the other member 5, the member 4 becomes non-magnetic, so that the magnetic flux from the magnets 2 and 3 flows as shown by broken lines in FIG. 12B. The magnetic strength between overlapped ends of reeds 12 and 13 is, therefore, reduced to be overcome by the elasticity of each reed, so that the overlapped ends of the reeds are maintained opened.

At a temperature higher than the Curie point of either of members 4 and 5, both members present a non-magnetic characteristic, so that magnetic flux from the magnets 2 and 3 flows through the gap between overlapped ends of reeds 12 and 13 as shown by broken lines in FIG. 12C. As a result the, overlapped ends of reeds are closed.

The switch shown in FIGS. 12A-12C operates reversely by variation of temperature in relation to predescribed switches, and, therefore, may be utilized in a different temperature control system.

In the switch shown in FIGS. 12A-12C, two magnets 2 and 3 and two temperature sensitive members 4 and 5 may be formed cylindrically. In such case the reed switch 1 is contained in a bore of the cylindrical body, similarly as the switch shown in FIG. 10.

FIG. 13 shows a device in which a switch 10 is contained in an enclosure 20. The switch 10 may be a switch such as shown in FIG. 10 which operates according to the operating principle described in conjunction with FIGS. 11A-11C, or may be another switch which is of a type shown in FIG. 10 but operates according to the principle described in connection with FIGS. 12A-12C.

The enclosure 20 comprises opposite end portions 21, 22 made of non-magnetic and non-electrically-conductive material, similar to the jackets 6 and 7 in FIG. 2A, and a cylindrical portion 23 made of non-magnetic and heat-conductive material which corresponds to the part 8 in FIG. 2A.

The opposite end portions 21 and 22, also, serve to prevent the breakage of the sealed portion of the glass envelope 11 of the reed switch 1.

The switch shown in FIG. 10 may be modified as shown in FIG. 14, in which two temperature sensitive members 4 and 5 are formed in imperfect rings and the imperfectness is filled up by non-magnetic material 41. As a result, the temperature sensitive members 4 and 5 are reduced in their heat capacities so that the switch operates more sensitively.

Similarly arrangements may be applied to the switch based on the operating principle illustrated in FIGS. 12A-12C.

FIG. 15 shows a switch shown in FIG. 10 which is further provided with a groove 9 on outer surfaces of the cylindrical bodies 2, 3, 4 and 5. One lead wire 15 is bent and introduced in the groove 9 and is led to the side where the other lead wire 14 extends. Thus, the switch may be conveniently used in applications where lead wires must be taken out in one direction in practical use of the switch.

Similar arrangements would be applicable to the switch operating according to the principle illustrated in FIGS. 12A-12C.

The present invention has been described in connection with specific embodiments, but is not restricted to the specific illustrated and described embodiments. Various and other modifications and alterations are clearly possible within the scope of the invention as defined in the appended claims.

The temperature sensitive ferromagnetic body or member may be made of ferrite or other ferromagnetic material having a desired Curie point.

The permanent magnet may be selected from various known types of magnets.

Claims

We claim:

1. A thermo-magnetically operated switch comprising:

an elongated reed switch including: an envelope,

a pair of ferromagnetic reeds hermetically sealed in said envelope with the free ends thereof overlapped for opening and closing movements relative to one another, and

two lead wires which are connected with respective reeds, the lead wires being secured and sealed to opposite ends of the envelope and extending therefrom in opposite directions,

two elongated permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different angular positions about the circumference of said reed switch and in reverse polarity with respect to each other, the respective magnetic poles of each permanent magnet being disposed over the respective reeds,

two elongated ferromagnetic bodies having different predetermined Curie points within the operating temperature range of the switch and overlying respective permanent magnets, the permanent magnets being interposed between the reed switch and the respective ferromagnetic bodies,

and an enclosure means containing the reed switch, the two permanent magnets and the two ferromagnetic bodies, opposite end portions of the enclosure means being made of non-conductive and non-magnetic material and securing and supporting the respective lead wires, and the intermediate portion of the enclosure means between the opposite end portions thereof being made of heat-conductive material.

2. The thermo-magnetically operated switch as claimed in claim 1 wherein said elongated ferromagnetic bodies are magnetic below their respective Curie points, and are non-magnetic above their respective Curie points.

3. A thermo-magnetically operated switch comprising:

an elongated reed switch comprising an envelope and a pair of ferromagnetic reeds hermetically sealed in said envelope with free ends thereof overlapped for opening and closing movements relative to one another,

two permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different axial positions of said reed switch in similar polar directions, with respective magnets disposed over the respective reeds but short of the overlapped ends of the reeds,

a first ferromagnetic body having a predetermined Curie point within the operating temperature range of the switch and disposed over the overlapped ends of the reeds in the axial space between said two magnets such that opposite ends of said first ferromagnetic body engage with adjacent different pole faces of the two magnets,

and second ferromagnetic body means having a predetermined Curie point lower than that of said first ferromagnetic body within the operating temperature range and overlapped and disposed on the two magnets such that said second ferromagnetic body means may be magnetically coupled between the other poles of the magnets opposite the poles thereof engaging said first ferromagnetic body.

4. The thermo-magnetically operated switch as claimed in claim 3 in which the reed switch includes:

lead wires which are connected with respective reeds, the lead wires being secured and sealed to opposite ends of the envelope and extending therefrom in opposite directions,

and an enclosure means containing the reed switch, the two permanent magnets and the two ferromagnetic bodies, opposite end portions of the enclosure means being made of non-conductive and non-magnetic material and securing and supporting the respective lead wires, and the intermediate portion of the enclosure means between the opposite end portions thereof being made of heat conductive material.

5. The thermo-magnetically operated switch as claimed in claim 3, in which the outer surface of said first ferromagnetic body in the radial direction of the reed switch is flush with the outer surfaces of said two magnets at the highest, said second ferromagnetic body means comprising a ferromagnetic piece which overlies the outer surfaces of both magnets while straddling the first ferromagnetic body.

6. The thermo-magnetically operated switch as claimed in claim 3, in which the outer surface of said first ferromagnetic body in the radial direction of the reed switch is beyond the outer surfaces of said two magnets, said second ferromagnetic means comprising first and second ferromagnetic pieces which overlie the respective surfaces of both magnets with an axial end of each of said first and second ferromagnetic pieces engaging with an adjacent axial end of said first ferromagnetic body.

7. The thermo-magnetically operated switch as claimed in claim 5, in which the permanent magnets and the first ferromagnetic body comprise respective cylindrical bodies and are coaxially disposed about the circumference of the reed switch, the ferromagnetic piece of said second ferromagnetic body means comprising a cylindrical body disposed concentric with and outside the cylindrical magnets and first ferromagnetic body.

8. The thermo-magnetically operated switch as claimed in claim 6, in which the permanent magnets and the first ferromagnetic body comprise respective cylindrical bodies and are coaxially disposed about the circumference of the reed switch, the first and second ferromagnetic pieces of said second ferromagnetic body means comprising cylindrical bodies disposed concentric with and outside the cylindrical magnets.

9. The thermo-magnetically operated switch as claimed in claim 7, in which:

the reed switch includes two lead wires connected with respective reeds,

and said cylindrical ferromagnetic piece of said second ferromagnetic body means has a groove on the outer surface thereof, which groove axially extends across the axial length of said cylindrical ferromagnetic piece, one of two lead wires of the reed switch being bent and introduced along said cylindrical ferromagnetic piece in said groove to the side where the other lead wire is led out.

10. The thermo-magnetically operated switch as claimed in claim 8, in which:

the reed switch includes two lead wires connected with respective reeds,

and a groove is provided on the outer surfaces of the first cylindrical ferromagnetic body and the two cylindrical ferromagnetic pieces, the groove axially extending over the axial lengths of the first cylindrical ferromagnetic body and the two cylindrical ferromagnetic pieces, one of two lead wires of the reed switch being bent and introduced along the first cylindrical ferromagnetic body and the two cylindrical ferromagnetic pieces in said groove to the side where the other lead wire is led out.

11. A thermo-magnetically operated switch comprising:

an elongated reed switch comprising an envelope and a pair of ferromagnetic reeds hermetically sealed in said envelope with free ends thereof overlapped for opening and closing movements relative to one another,

two elongated permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different axial positions of said reed switch in reverse polar directions, with respective magnets disposed over the respective reeds but short of the overlapped ends of the reeds,

a first ferromagnetic body having a predetermined Curie point within the operating temperature range of the switch and disposed in the axial space between said two magnets with one end thereof engaging with the adjacent pole face of one magnet, and the other end thereof being short of the overlapped ends of the reeds,

and a second ferromagnetic body having a predetermined Curie point lower than that of said first ferromagnetic body within the operating temperature range and disposed in the axial space between said first ferromagnetic body and the other magnet with one end thereof engaging with the adjacent pole face of said other magnet, and the other end thereof overlying the overlapped ends of the reed and engaging with the other end of said first ferromagnetic body.

12. The thermo-magnetically operated switch as claimed in claim 11, in which the reed switch includes:

two lead wires which are connected with respective reeds, the lead wires being secured and sealed to opposite ends of the envelope and extending therefrom in opposite directions,

and an enclosure means containing the reed switch, the two permanent magnets and the two ferromagnetic bodies, opposite end portions of the enclosure means being made of non-conductive and non-magnetic material and securing and supporting the respective lead wires, and the intermediate portion of the enclosure means between the opposite end portions thereof being made of heat-conductive material.

13. The thermo-magnetically operated switch as claimed in claim 11, in which the two permanent magnets, the first ferromagnetic body and the second ferromagnetic body are cylindrical and are disposed on a common axis.

14. The thermo-magnetically operated switch as claimed in claim 13, in which:

the reed switch includes two lead wires connected with respective reeds,

and a groove is provided on the outer surfaces of the two cylindrical permanent magnets and the first and second cylindrical ferromagnetic bodies, the groove axially extending over the axial lengths of the two cylindrical magnets and the first and second cylindrical ferromagnetic bodies, one of two lead wires of the reed switch being bent and introduced along the cylindrical bodies in said groove to the side where the other lead wire is led out.

15. The thermo-magnetically operated switch as claimed in claim 11, in which the two permanent magnets are cylindrical, and including a non-magnetic member mounted between said cylindrical magnets to form a cylindrical body in cooperation with the first and second ferromagnetic bodies.

16. A thermo-magnetically operated switch comprising:

an elongated reed switch comprising an envelope and a pair of ferromagnetic reeds hermetically sealed in said envelope with free ends thereof overlapped for opening and closing movements relative to one another,

two elongated permanent magnets having Curie points higher than an operating temperature range of the switch and being disposed alongside said reed switch at different axial positions of said reed switch in similar polar directions, with respective magnets disposed over the respective reeds but short of the overlapped ends of the reeds,

a first ferromagnetic body having a predetermined Curie point within the operating temperature range of the switch and disposed in the axial space between said two magnets with one end thereof engaging with the adjacent pole face of one magnet, and the other end thereof being just adjacent the overlapped ends of the reeds,

and a second ferromagnetic body having a predetermined Curie point lower than that of said first ferromagnetic body within the operating temperature range and disposed in the axial space between said first ferromagnetic body and the other magnet with one end thereof engaging with the adjacent pole face of said other magnet, and the other end thereof being adjacent the overlapped ends of the reeds and engaging with the other end of said first ferromagnetic body.

17. The thermo-magnetically operated switch as claimed in claim 16, in which the reed switch includes:

two lead wires which are connected with respective reeds, the lead wires being secured and sealed to opposite ends of the envelope and extending therefrom in opposite directions,

and an enclosure means containing the reed switch, the two permanent magnets and the two ferromagnetic bodies, opposite end portions of the enclosure means being made of non-conductive and non-magnetic material and securing and supporting the respective lead wires, and the intermediate portion of enclosure means between the opposite end portions thereof being made of heat-conductive material.

18. The thermo-magnetically operated switch as claimed in claim 16, in which the two permanent magnets, the first ferromagnetic body and the second ferromagnetic body are cylindrical and are disposed on a common axis.

19. The thermo-magnetically operated switch as claimed in claim 18, in which:

the reed switch includes two lead wires connected with respective reeds,

and a groove is provided on the outer surfaces of the two cylindrical magnets and the first and second cylindrical ferromagnetic bodies, the groove axially extending over the axial lengths of the two cylindrical magnets and the first and second cylindrical ferromagnetic bodies, one of the two lead wires of the reed switch being bent and introduced along the cylindrical bodies in said groove to the side where the other lead wire is led out of the reed switch.

20. The thermo-magnetically operated switch as claimed in claim 16, in which the two permanent magnets are cylindrical, and including a non-magnetic member mounted said cylindrical magnets to form a cylindrical body in cooperation with the first and second ferromagnetic bodies.