Temperature operated switch of a variable operating temperature

Abstract

A temperature operated switch comprising a reed switch, permanent magnets temperature sensitive ferromagnetic materials and an auxiliary permanent magnet in which permanent magnets and temperature sensitive ferromagnetic materials is so disposed along the reed switch that they make a magnetic closed loop together with reeds of the reed switch and in which the auxiliary permanent magnet is rotatably disposed in the vicinity of a set of the permanent magnet and the temperature sensitive ferromagnetic material. The operating temperature of the switch is generally defined by the Curie point of the temperature sensitive ferromagnetic material, but can be fine controlled by adjusting the orientation of the rotatable auxiliary permanent magnet.

Description

BACKGROUND OF THE INVENTION

This invention relates to temperature operated switches and, in particular, thermo-magnetically operated switch comprising a reed switch, one or more permanent magnets disposed alongside the reed switch and one or more temperature sensitive ferromagnetic materials disposed to make a magnetic closed loop together with the permanent magnets and two reeds of the reed switch.

The operating temperature of the thermo-magnetically operated switch is defined by the Curie point of the temperature sensitive ferromagnetic material. When the peripheral temperature is lower than the Curie point of the temperature sensitive ferromagnetic material, the magnetic flux from the permanent magnet flows through the temperature sensitive ferromagnetic material and two reeds of the reed switch so that both reeds may be closed. When the peripheral temperature is higher than the Curie point of the temperature sensitive ferromagnetic material, both reeds of the reed switch is opened because the temperature sensitive material exhibits not ferromagnetism but paramagnetism to inhibit the magnetic flux from the permanent magnet from flowing over the two reeds of the reed switch.

If it is required to change the operating temperature, the temperature sensitive ferromagnetic material must be replaced by another ferromagnetic material having a different Curie point, or another thermo-magnetically operated switch having a different operating temperature must be used.

SUMMARY OF THE INVENTION

An object of this invention is to provide a thermomagnetically operated switch of which operating temperature can be readily varied.

Another object of this invention is to provide a thermo-magnetically operated switch which is capable of fine-control of the operating temperature.

Still another object of this invention is to realize above objects with a simple and economical structure.

A temperature operated switch of this invention comprises an elongated reed switch, having a pair of needs at least one permanent magnet disposed alongside said reed switch, at least one ferromagnetic body having a predetermined Curie point lower than that of said at least one permanent magnet and which is disposed alongside said reed switch and in the vicinity of said at least one permanent magnet to selectively establish a closed magnetic loop together with said at least one permanent magnet and the two reeds of said reed switch, and an auxiliary permanent magnet rotatably mounted in the vicinity of said at least one permanent magnet and said ferromagnetic body. The auxiliary magnet is notable relative to said at least one permanent magnet and to said ferromagnetic body.

The auxiliary permanent magnet may be, preferably, in the form of a disk which is magnetized in the direction of a diameter thereof. The magnet disk is so disposed that its center axis is perpendicular to the axis of the reed switch, with the disk being rotatable about the center axis thereof.

The auxiliary permanent magnet may be in the form of a rod which is disposed in parallel with the reed switch and rotatable about the center axis, with both halves of the rod sectioned by a plane including the center axis of the rod being magnetized in the axial direction but in opposite directions one another.

Further objects and features of this invention will be understood from descriptions relating to embodiments of this invention referring to the annexed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 diagrammatically shows a sectional view of a known thermo-magnetically operated switch,

FIGS. 2a-2c diagrammatically show sectional views of thermo-magnetically operated switches, of which operating is varied by three different principles, respectively,

FIGS. 3a and 3b show a perspective view of a thermo-magnetically operated switch according to the first principle for varying the operating temperature, and the variation of the operating temperature, respectively,

FIGS. 4a and 4b show a perspective view for explaining the fundamental structure of an embodiment of this invention, and the variation of the operating temperature, respectively,

FIG. 5 diagrammatically shows a perspective view of a fundamental structure of another embodiment of this invention and,

FIG. 6 and FIG. 7 show perspective views of different embodiments of this invention, partially broken away to illustrate the internal structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIG. 1, in which an example of known thermomagnetically operated switch is shown, the switch comprises an elongated reed switch 4, an annular temperature sensitive ferromagnetic body 5, in the bore of which the reed switch is disposed and two annular permanent magnets 6 and 7 which are disposed at opposite sides of the ferromagnetic body 5.

The reed switch 4, as is well known in the art, comprises a glass envelope 3 and a pair of ferromagnetic reeds 1 and 2 hermetically sealed in the envelope 3 with free ends thereof overlapped for opening and closing movements relative to one another.

The annular temperature sensitive ferromagnetic body 5 has a Curie point which is a desired temperature generally equal to the operating temperature of the switch.

The two annular permanent magnets 6 and 7 are magnetized in the axial direction, the Curie points of which are sufficiently higher than the operating temperature of the switch.

The temperature sensitive ferromagnetic body 5, the two permanent magnets 6 and 7 and a pair of reeds 1 and 2 make a magnetic closed loop.

When the peripheral temperature (i.e., the ambient temperature around the switch) is lower than the Curie point of the ferromagnetic body 5, the magnetic flux flows in the magnetic closed loop so that a pair of reeds are closed. On the other hand, a pair of reeds are opened when the peripheral temperature is higher than the Curie point of the ferromagnetic body 5, because the ferromagnetism of the body 5 disappears so that the magnetic closed loop including a pass over both reeds 1 and 2 may not be established.

The operating temperature of this switch is defined by the Curie point of the temperature sensitive ferromagnetic body 5.

It is desired that the operating temperature of the switch can be readily varied, from the view point of the enlarged applications of the thermo-magnetically operated switch.

In order to vary the operating temperature of the switch, three different principles can be employed alternatively.

The first principal is to control the magnetic flux density which is used for opening and closing movement of the reeds by the addition of a ferromagnetic substance 10 which is movable toward near and away from the thermo-magnetically operated switch 8, as shown in FIG. 2a.

This invention is based on the first principle.

The second principle, illustrated in FIG. 2b, is the addition of the magnetic field by a coil 11, the strengh of which may be varied by the variation of the D.C. current fed to the coil 11 so that the operating temperature may be varied. Since it is required to maintain the selected value of the D.C. current fed to the coil 11 during the use of the switch, the device becomes expensive.

The third principle is to control of the permeability of the temperature sensitive ferromagnetic body by the addition of a heater 12 in the vicinity of the switch 8, as shown in FIG. 2c. The accurate control of the permeability by the heater is very difficult so that it may be impossible to establish and maintain a desired operating temperature.

FIG. 3a shows an embodiment based on the first principle as shown in FIG. 2a. This device comprises such a thermo-magnetically operated switch 8 as shown in FIG. 1, and a soft magnetic rod 20 slidably disposed in a hole which is perforated over the annular permanent magnets 6 and 7 and the annular temperature sensitive ferromagnetic body 5 in the axial direction of the reed switch 4. The operating temperature of the switch 8 is controlled by the length of the rod 20 inserted into the hole. FIG. 3b diagrammatically shows the variation of the operating temperature (.DELTA.T) to the length of the rod (l) inserted in the hole.

The more the rod 20 is inserted in the hole, the more the operating temperature drops down.

According to this embodiment, it is impossible to shift the operating temperature of the switch 8 to the higher temperature.

According to the present invention an auxiliary permanent magnet is disposed in the vicinity of a thermo-magnetically operated switch to shift the operating temperature of the switch up and down on the temperature axis by rotating the auxiliary permanent magnet.

Referring to FIG. 4a, in which a fundamental structure of the present invention is shown, an auxiliary permanent magnet 30 is disposed in the vicinity of the thermo-magnetically operated switch 8 as shown in FIG. 1. The auxiliary permanent magnet 30 is rotatable on a middle point between opposite poles of the magnet 30 and about an axis which is perpendicular to the axis of the switch 8.

When the rotatable auxiliary permanent magnet 30 is in an angular position at which the magnet 30 is perpendicular to the switch 8, magnetic flux from the auxiliary magnet 30 does not affect to the operation of the switch 8.

Upon the angular position of the auxiliary magnet 30 being shifted, the magnetic flux from the magnet 30 has a component in the axial direction of the switch 8, which component affects the magnetic flux flowing in a pair of reeds of the switch 8, so that the operating temperature may be shifted.

FIG. 4b shows the variation (.DELTA.T) of the operating temperature of the switch 8 as a function of the angular position of the rotatable auxiliary permanent magnet 30. In the drawing, the angle .theta. represents the angle between the actual position of the auxiliary magnet 30 and the axis which is perpendicular to the central axis of the switch 8. The angle .theta. is negative when the magnetic flux of the auxiliary permanent magnet 30 is opposite to the magnetic flux from the permanent magnets 6 and 7, and, the angle .theta. is positive when the magnetic flux of the auxiliary magnet 30 is in parallel to the magnetic flux of the permanent magnets 6 and 7.

When .theta. is positive, the magnetic flux density flowing through a pair of reeds 1 and 2 is increased so that the operating temperature of the switch 8 is shifted to the higher temperature. When .theta. is negative, the magnetic flux density flowing through a pair of reeds 1 and 2 is decreased so that the operating temperature is shifted to the lower temperature.

Thus the operating temperature of the switch 8 is controlled by the adjustment of the angular position of the rotatable auxiliary permanent magnet 30.

The auxiliary permanent magnet 30 may be, preferably, in the form of a disk, so that the variation of the operating temperature may be linear.

FIG. 5 shows another structure in which the auxiliary permanent magnet is in the form of a rod as shown by 31, both halves of the rod 31 sectioned by a plane including a central axis of the rod being magnetized in the axial direction thereof but in opposite directions to one another. The rod magnet 31 is disposed in parallel with and in the vicinity of the switch 8, and is rotatable about the central axis thereof. By the rotation of the rod magnet 31, similar variation of the operating temperature of the switch as shown in FIG. 4a may be achieved.

Referring to FIG. 6, in which an embodiment of this invention is shown, the thermo-magnetically operated switch 8 and the auxiliary permanent magnet 32 are contained in a case 43 of a non-magnetic material. The auxiliary permanent magnet 32 is magnetized in the axial direction thereof, and is suspended by a holder 40. The holder 40 is connected to a shaft 41 which is rotatably mounted on the case 43, so that the auxiliary permanent magnet 32 may be rotated by the rotation of the shaft 41. To the shaft 41 an indicator 42 is secured which indicates the angular position of the auxiliary permanent magnet 32. The indicator 42 also defines the rotatable angular range of the shaft in cooperation with the two stoppers 46 mounted on the case 43.

The device of FIG. 6 has an aluminum fin plate 45 for receiving a peripheral temperature and an electrical terminal 44 for connecting the reed switch with a peripheral device.

Referring to FIG. 7, in which another embodiment of this invention is shown, the switch 8 and the auxiliary magnet 33 are accomodated in the case 43 similarly in the embodiment of FIG. 6. However, the auxiliary magnet 33 is in the form of a disk which is magnetized in the direction of a diameter thereof. The disk magnet 33 is exposed outside the case 43. The exposed surface of the magnet 33 has a groove by formed therein by means of which the magnet 33 may be readily rotated.

The device of FIG. 7 is capable of fine control of the operating temperature and, therefore, provides a highly accurate switch.

The present invention has been described in detail relating to thermo-magnetically operated switches of specific arrangements, but it will be understood by those skilled in the art that the invention is readily applicable to thermo-magnetically operated switches of other arrangements, regardless of the numbers, the positions and the forms of the permanent magnet and the temperature sensitive ferromagnetic material.

Claims

What we claim is:

1. A temperature operated switch comprising

an elongated reed switch including a pair of reeds,

at least one permanent magnet disposed alongside said reed switch,

at least one ferromagnetic boyd having a predetermined Curie point lower than that of said at least one permanent magnet, and which is disposed alongside said reed switch and in the vicinity of said at least one permanent magnet to selectively establish a closed magnetic loop together with said at least one permanent magnet and the two reeds of said reed switch, and

an auxiliary permanent magnet rotatably mounted in the vicinity of said at least one permanent magnet and said ferromagnetic body, said auxiliary permanent magnet being rotatable relative to said at least one permanent magnet and to said ferromagnetic body.

2. The switch as claimed in claim 1 wherein said auxiliary permanent magnet is rotatably mounted substantially at the mid-point between opposite poles thereof and about an axis which is perpendicular to the longitudinal axis of said reed switch.

3. The switch as claimed in claim 2 wherein said auxiliary permanent magnet is in the form of a disk which is magnetized in the direction of a diameter thereof.

4. The switch as claimed in claim 2 wherein said auxiliary permanent magnet is an elongated permanent magnet.

5. The switch as claimed in claim 2 wherein the axis about which said auxiliary permanent magnet is rotatable is located substantially at the mid-point of said reed switch, said mid-point being taken in the longitudinal direction of said reed switch.

6. The switch as claimed in claim 1 wherein said auxiliary permanent magnet is an elongated magnet having a longitudinal axis, and is rotatably mounted so as to be rotatable about said longitudinal axis thereof.

7. The switch as claimed in claim 6 wherein said elongated auxiliary permanent magnet is disposed in parallel with said elongated reed switch.

8. The switch as claimed in claim 6 wherein said elongated permanent magnet is in the form of a rod, both halves of the rod which are sectioned by a plane including a central axis thereof being magnetized in the axial direction of the rod but in opposite directions relative to one another.

9. The switch as claimed in claim 1 comprising a pair of permanent magnets disposed alongside said reed switch, said at least one ferromagnetic body being interposed therebetween.

10. The switch as claimed in claim 9 wherein said two permanent magnets are disposed with their poles in series-aiding.

11. The switch as claimed in claim 1 wherein said at least one permanent magnet and at least one ferromagnetic body are annular members, the elongated reed switch being disposed within the central openings of said at least one permanent magnet and said at least one ferromagnetic body.

12. The switch as claimed in claim 1 wherein said at least one ferromagnetic body has a Curie point whereby when the temperature of said body is below said Curie point, magnetic flux flows in the closed magnetic loop, and when the temperature is higher than said Curie point, said ferromagnetic body becomes non-ferromagnetic so as to prevent said closed magnetic loop from being established.