US 3701063 A
A temperature responsive electric control device has electric contacts, a body of thermo-magnetic material, and a magnet movable between two positions in the first of which it is held by magnetic attraction with the body while this body is at a temperature below its Curie point, and in the second of which it operates by magnetic attraction to actuate the contacts.
Description (OCR text may contain errors)
[ 51 Oct. 24, 1972 United States Patent Clausse [$41 TEMPERATURE RESPONSIVE 3,328,561 6/ 1957 Sakamoto et al.19/495 ELECTRIC CONTROL DEVICE 2.794.100 5/1957 Baader et al...............335/146 Inventor: J Laleham, England  Assignee: The Hoover Company, North Can- FOREIGN PATENTS OR APPLICATIONS 659,822 2/1965 Belgium.....................335/207 ton, Ohio  Filed: Oct. 9, 1970  Appl. No.: 79,568
Primary Examiner-Harold Broome Attorney-Alfred G. Gross and James A. Wanner ABSTRACT A temperature responsive electric control device has  Foreign Application Priority Data Oct. 9, 1969 Great Br ta n..........49,708l69 electric contacts, a body of thermGmaSnetic material, 3:2 gig: and a magnet movable between two positions in the 5 Great first of which it is held by magnetic attraction with the body while this body is at a temperature below its Curie point, and in the second of which it operates by magnetic attraction to actuate the contacts.
'  Int. 51/00 .335/146. 208, 207, 217;
 Field of 219/495; 317/133 8 Claims, 7 Drawing Figures [56} References Cited UNITED STATES PATENTS 2,751,483 6/1956 Keen et al................. 335/l46 ooooaonoo ooocoaonn couanocnn ooaucmnon oowtnro PAIENTEDHBI 24 I 72 3.701. 063
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sum 5 or 6 TEMPERATURE RESPONSIVE ELECTRIC CONTROL DEVICE This invention relates to temperature responsive electric control devices, such as thermostats, cut-outs and the like, which are used to control an electric circuit when the temperature to which the device is exposed reaches a predetermined value. Some known devices of this kind often rely on the use of a bi-metallic element which changes shape as the ambient temperature changes. Such arrangements do not usually operate very precisely at a predetermined temperature and they tend to become unreliable in use.
The present invention utilizes a temperature sensitive ferromagnetic material which is ferromagnetic at temperatures below the Curie point and parramagnetic at temperatures above this point. In consequence such material will be attracted by a magnet when it has a temperature below its Curie point but will cease to be so attracted when it has a temperature above this point. Certain nickel-iron alloys are examples of such temperature sensitive materials.
In the following description of the invention these temperature sensitive ferro-magnetic materials will be termed for convenience thermo-magnetic materials.
The improved temperature responsive electric control device of this invention comprises electric contacts, a body of thermo-magnetic material, and a magnet movable between two positions, in the first of which the magnet is held by magnetic attraction with the body while this body is at a temperature below its Curie point, and in the second of which it operates by magnetic attraction to actuate the contacts.
The movement of the magnet will occur when the temperature of the body reaches or exceeds its Curie point and the body ceases to be of gravity or by the action of a spring. A wide range of alloys having different Curie points are now commercially available so that by the selection of a suitable alloy and control of the design, particularly as regards the manner in which heat is transmitted to the body, it is possible to construct a device operable at almost any desired temperature.
Some examples of a control device in accordance with this invention will now be described by way of example in relation to the control of beverage making apparatus although it is to be understood that the device may be used in any application where it is desired to control an electric circuit at a predetermined temperature.
in the drawings:
FIG. I is a sectional elevation of a beverage making apparatus;
FIG. 2 is a section elevation of a liquid heating apparatus;
FIGS. 3 and 4 are sectional elevations of beverage making apparatus incorporating different forms of the device of this invention;
FIG. 5 is a sectional elevation of a beverage making apparatus incorporating a further form of the device of this invention;
FIG. 6 is a fragmentary sectional view to a larger scale of part of FIG. 5; and,
FIG. 7 is a section on the line VII-VII in FIG. 6.
Referring now to FIG. I there is shown a beverage making apparatus having a water compartment 1, an
electric heating element 2 in the water compartment, and a perforated container 3. A lid 4 includes a compartment 5 the bottom surface of which is formed by a flap 6 which is pivotally mounted about one edge 7. The compartment 5 is provided with a cover 8.
The flap 6 has an extension 9 on the edge remote from the pivoted edge 7 which is made of a thermomagnetic material which is ferromagnetic at room temperatures but at higher temperatures is non-magnetic, or at least very much less magnetic.
A magnet 10 is mounted in the lid 4 on a light spring 11. When the extension 9 is in the position shown and at room temperature the magnet 10 attracts the extension 9 thus holding the flap 6 in the horizontal position. When the extension 9 is heated by steam it becomes less magnetic and is no longer held by the magnet 10. Consequently the flap 6 falls emptying the contents of the compartment 5 into the water.
In addition the magnet 10 being no longer attracted by the extension 9 moves upwards under the action of the spring 11. The top 12 of the magnet 10 engages in an aperture 13 in the lid and is arranged to attract a steel plate 14 and pull the latter downwards. Downward movement of the plate 14 breaks contacts 15 thus disconnecting the heater element 2 from the supply.
The contacts 15 are housed in the handle 16 of the apparatus, which may be made of a plastics material. The plate 14 is bent at the top as seen in the figure and when attracted by the magnet 10 the bent portion of the plate comes in front of a transparent window 17 to indicate that the beverage making cycle has finished.
To restart the apparatus, a slider 18 is moved forward to engage the plate 14 and retain the contacts 15 open. The lid 4 is then removed and the flap 6 is pushed back into its horizontal position while at the same time magnet 10 is depressed against the spring 1]. The magnet 10 then supports the extension 9 again. The hopper 5 is then refilled with tea, teabags or other infusible matter and the water compartment is filled with fresh water. The lid 4 is then replaced, the magnet 10 being repositioned under the plate 14. When the slider 18 is moved back the heating element 2 is reconnected and heating begins again.
The sudden upwards movement of the magnet 10 ensures positive action in opening the contacts 15, which is necessary in view of the large current flowing through the contacts.
In view of the sudden temperature rise of the extension 2 when the water boils the decrease in magnetic attraction between the magnet 10 and extension 9 is sudden and marked, causing positive action and also meaning that extreme accuracy in assembly is not essential. The size of the magnet 10 also need not be large.
FIG. 2 shows a similar device applied to control an ordinary electric kettle. A part 19 of the lid 4 exposed to steam is made of thermo-magnetic material which is ferromagnetic at room temperatures and not so magnetic at higher temperatures. The magnet 12 is held against the part 19 when the latter is cold, but when the part is heated by steam the magnet is released and opens the contacts to a heater element (not shown) in the manner described with reference to FIG. I.
As shown in FIG. 2, supplementary contacts may be provided for connection to a pilot light or to a keep-warm" heater element of low power. Such an additional heater element may be desirable in a coffeemaker. The supplementary contacts are closed when the main contacts are opened.
An important feature of the apparatus of FIG. 2 is that the operative members are entirely sealed from the steam within the kettle without the need for special sealing rings or the like.
The beverage making apparatus shown in FIG. 3 includes a water receptacle in which there is a heating element 21 which is connected to electrical power input terminals 22 by leads and by contacts 23.
A circular lid 27 includes a tea compartment 28 which is closed on its lower side by a flap 29 pivoted at 30. A compartment 31 also formed in the lid covers a magnet 32 which is fixed to the flap 29 on the side of the pivot remote from the tea compartment 28. A vent 33 is formed in the roof of the compartment 31.
When the magnet is in the position shown in full lines with the tea compartment 28 closed by the flap 29, the magnet 32 rests against a plate 34 which is made of thermo-magnetic material having a Curie point slightly lower than the boiling point of water.
The attraction between the plate 34 and the magnet 32 is sufficient when the plate is below its Curie temperature to hold the flap 29 in a horizontal position under the weight of tea or tea bags within the tea compartment 28.
A screening plate 35 is positioned under the plate 34 in such a position as to substantially screen the plate from direct heat radiation from water in the receptacle and thus forms a heat-insulating air gap.
When the lid is in the position shown, the magnet 32 in the lid attracts a soft iron block 39 mounted on one end of an arm 40 pivoted at 41 in a housing 25. The other end of the arm 40 carries a contact bridge 42 which connects contact points 43 and thus completes the circuit through the contacts 23.
When the lid is turned away from the position shown, attraction between the magnet 32 and block 39 ceases, and by virtue of a spring 44 the arm 40 is biased clockwise opening the contacts 23.
In use, the lid 27 is removed. With the lid inverted the tea compartment 28 is filled and the flap 29 moved to close the compartment 28 in which position it will remain due to attraction between the magnet 32 and plate 34. The water receptacle 20 is filled with water to a suitable level and the lid replaced.
The lid is then turned to the position shown whereupon, as described above, the magnet 32 attracts the block 39 and the contacts are closed causing electric current to flow through the heating element 21. It should be noted that the contacts will not be closed if the flap 29 should not be in its horizontal position. After a time the water boils and the plate 34, due to the screening plate 35, experiences a sudden temperature rise due to stream release which, due to the slight pressure thus created in the container, enters the compartment 31 in the lid and escapes through the vent 33. The attraction between the magnet 32 and the plate 34 then ceases, allowing the flap 29 to fall to the position shown in dashed lines in FIG. 2, whereupon the matter within the tea compartment 28 is dispensed into the boiling water.
Due to the movement of the magnet 32, there is no longer an attractive force on the block 29, and the contacts 23 are opened by the spring 44, disconnecting the heating element 21 from the supply.
The block 39 may be replaced by another magnet or may form part of a reed switch. It will be appreciated that auxiliary contacts may be provided to operate a pilot light.
FIG. 4 illustrates a modification of the tea maker of FIG. 3 in which the lid includes a compartment 61 the lower surface of which is constituted by a flap 62 pivoted at 63. The flap is normally retained in the horizontal position shown by a resiliently biased latch 64 A magnet 65 is pivotally mounted in a compartment 66 in the lid and is movable between position A shown in full lines and position B indicated in dashed lines. The magnet is retained in position A by attraction between itself and a plate 67 of thermo-magnetic material positioned near an exit vent 68 of the compartment 66. An inlet vent 69 is provided adjacent the latch 64.
When in position A the magnet further attracts a soft iron member 70 as in the tea maker of FIG. 3. Also as in the tea maker of FIG. 3, the lid 60 is rotatably between an ON position and an OFF position.
When the tea compartment has been filled and the lid positioned so that current flows to the heating element, all as described with reference to FIG. 3, water in the container will be caused to boil. Due to the slight pressure thus created, steam enters the vent 69 and thus reaches the plate 57. When the plate reaches its Curie temperature, the magnet 65 is no longer attracted to it and rotates about its pivot point due to gravity. As it descends, the magnet 65 strikes one end of the latch member 64 which then rotates counter clockwise about its mid-point to release the flap 62. The rotation of the magnet 65 also opens the contacts as described with reference to FIG. 2.
When the lid is inverted to fill the tea compartment 61 the magnet 65 is automatically returned to position A in readiness for the next cycle.
The apparatus illustrated in FIG. 5 to 7, which is primarily intended for use in making tea, comprises a water receptacle in the bottom of which there is an immersion heater, not shown, of conventional type. The receptacle has a spout 111 and a handle 112 formed of a suitable plastics.
The receptacle is closable by a lid 113, and the mouth of the receptacle and the mating surface of the lid are circular so that the lid may be rotated on the receptacle for a purpose to be described below.
The lid 113 is formed on its underside with a compartment 114 for tea or other soluble or infusible matter, which is closable by a pivoted flap 115, and with a compartment 116 through which, when water in the receptacle boils, steam may flow to a vent 1 17.
The compartment 1 16 houses a plate 1 18 of thermomagnetic material, a magnet 119 carried by arms 120 extending from a spindle 121 journalled in the side walls of the compartment, and a spring biased latch 122 which normally acts to hold the flap in closed position.
The magnet 119 is normally held in the position shown in full lines by magnetic attraction with the plate 118. When the water in the receptacle boils, steam passing into the compartment 116 and leaving through the vent 117 heats the plate to a temperature above its Curie point so that it becomes non-magnetic. The magnet 119 then drops away to the position shown in dotted lines and the rotation of spindle 121 causes a projection thereon to move the latch 122 against spring 123 so as to release the flap 115.
The plate 1 18 is formed with one or more projections 124 which serve to prevent direct face to face contact between the plate and magnet 119. This has two advantages. Firstly, the small air gap so formed acts to compensate for changes in magnetic strength as may occur between different samples or as the result of ageing and thus ensures reliable operation at the required temperature. Secondly, water present between the faces does not act to stick them together as may occur if face to face contact is permitted.
The handle 112 encloses a further magnet 125 which is carried on a pivoted arm 125' so that it is movable towards and away from the lid 113.
When the lid is in position on the receptacle and in the ON position the two magnets 119 and 125 are adjacent and the magnet 125 is held in the position shown in full lines by magnetic attraction. With the lid in any other position or removed from the receptacle the magnet 125 falls away, to the left in FIG. 5, and in this position it acts to separate a pair of contacts 126, the contact carrying spring adjacent the magnet being for this purpose formed from or provided with a piece of magnetic material.
The contacts 126 are included in the circuit of the immersion heater by connections, not shown, extending within the handle and a conventional neon indicator lamp may also be arranged in the handle.
To ensure that the magnet 125 moves so that the contacts may close when the lid is in position the magnet is provided with a pin 127 that projects through a slot in the handle and is engaged by a cam surface formed on the underside of a projecting part 129 on the lid.
Accordingly when the lid is in position on the receptacle and rotated clockwise to the ON position shown in FIG. 5, the pin 127 will be engaged by the cam surface and will be moved towards the lid so as positively to bring the magnet 125 into position where it will be held in place by magnetic attraction with magnet 119. The contacts 126 will then be able to close.
In use the lid 113 is removed from the receptacle 110 and while in inverted position the compartment 114 is filled with tea. In this position of the lid the magnet 119 will fall down onto the plate 118 and will be retained in this position by magnetic attraction. The flap 115 is now closed and is held in this position by the latch 122. The receptacle is now filled with the required amount of water and the lid placed thereon.
When it is desired to commence operations the lid is rotated clockwise to the ON position. In this position of the lid the magnet 125 has been moved forward and is held by magnetic attraction with the magnet 119 and the contacts 126 can now close.
When the water in the receptacle boils the steam heats the plate 118 and when this becomes non-magnetic the magnet 119 will fall. This on the one hand moves the latch 122 to allow the flap 115 to fall to 6 $2 22228 t '2 133532? iii Qilifiiihiffi? ir niiile llfl and acts to open the contacts 126 thereby opening the circuit of the immersion heater.
1. A temperature responsive electric control device comprising electric contacts, said contacts having an open position and a closed position, a ferro-magnetic material associated with said electric contacts, a body of thermal-rnagnetic material, and a magnet movable between first and second spacially separated positions, said magnet in said first position being held by magnetic attraction with said body of thennal-magnetic material while said body of thermal-magnetic material is at a temperature below its Curie point, said magnet being biased to said second position when said body of thermal-magnetic material is at a temperature above its Curie point, said magnet actuating said electric contacts by magnetic attraction with said ferro-magnetic material when said magnet is in one of said magnet position.
2. A temperature responsive electric control device of claim 1 including seal means positioned between said ferro-magnetic material associated with said electric contacts and said magnet.
3. A temperature responsive electric control device of claim 1 wherein said electric contacts are in said closed position when said magnet is in said first position.
4. A temperature responsive electric control device of claim 1 wherein said second position of said magnet is spacially separated from said first position, and said electric contacts being in said open position when said magnet is in said second position.
5. A temperature responsive electric control device of claim 1 including an additional magnet positioned to be attracted by said first mentioned magnet when said first mentioned magnet is in said magnet second position and said additional magnet is arranged to magnetically attract said electric contacts by movement of said additional magnet.
6. A temperature responsive electric control device of claim 5 including a ferro-magnetic block associated with said electric contacts, wherein said additional magnet is movable between an attracted position and a released position, said additional magnet when in said attracted position being held by magnetic attraction with said first mentioned magnet and said additional magnet in said released position magnetically attracts said ferro-magnetic block, said additional magnet moving from said attracted position to said released position when said first mentioned magnet is moved to said magnet second position.
7. A temperature responsive electric control device of claim 6 including means for effecting relative displacement between said first mentioned magnet and said additional magnet to inhibit actuation of said electric contacts regardless of the position of said first mentioned magnet.
8. A temperature responsive electric control device of claim 1 including means for effecting relative displacement between said magnet and said ferro-magnetic block to inhibit actuation of said electric contacts regardless of the position of said magnet.
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