GB1566102A - Thermostat devices - Google Patents

Thermostat devices Download PDF

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Publication number
GB1566102A
GB1566102A GB5257375A GB5257375A GB1566102A GB 1566102 A GB1566102 A GB 1566102A GB 5257375 A GB5257375 A GB 5257375A GB 5257375 A GB5257375 A GB 5257375A GB 1566102 A GB1566102 A GB 1566102A
Authority
GB
United Kingdom
Prior art keywords
arm
thermostat device
support
toaster
thermostat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB5257375A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hotpoint Ltd
Original Assignee
Hotpoint Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hotpoint Ltd filed Critical Hotpoint Ltd
Priority to GB5257375A priority Critical patent/GB1566102A/en
Priority to NL7614137A priority patent/NL7614137A/en
Priority to FI763692A priority patent/FI763692A/fi
Priority to BE173615A priority patent/BE849828A/en
Publication of GB1566102A publication Critical patent/GB1566102A/en
Expired legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K5/00—Measuring temperature based on the expansion or contraction of a material
    • G01K5/48—Measuring temperature based on the expansion or contraction of a material the material being a solid
    • G01K5/50—Measuring temperature based on the expansion or contraction of a material the material being a solid arranged for free expansion or contraction
    • A—HUMAN NECESSITIES
    • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
    • A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
    • A47J37/00—Baking; Roasting; Grilling; Frying
    • A47J37/06—Roasters; Grills; Sandwich grills
    • A47J37/08—Bread-toasters
    • A47J37/0814—Bread-toasters with automatic bread ejection or timing means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
    • G01K1/20—Compensating for effects of temperature changes other than those to be measured, e.g. changes in ambient temperature
    • G01K1/24—Compensating for effects of temperature changes other than those to be measured, e.g. changes in ambient temperature by means of compounded strips or plates, e.g. by bimetallic strips
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/32—Thermally-sensitive members
    • H01H37/46—Thermally-sensitive members actuated due to expansion or contraction of a solid
    • H01H37/50—Thermally-sensitive members actuated due to expansion or contraction of a solid with extensible wires under tension

Description

(54) IMPROVEMENTS IN OR RELATING TO THERMOSTAT DEVICES (71) We, HOTPOINT LIMITED, of Peterborough, England, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the foUowing statement: This invention relates to thermostat devices, more especially, though not exclusively, for controlling the operation of electric heating appliances, such as electric toasters.
According to the invention a thermostat device comprises a support, a substantially rigid arm carried by, and capable of a degree of rotational movement relative to, the support spring biassing means tending to rotate the arm relative to the support, and a relatively thin elongate element held in a tensioned condition between regions of the arm and support which are spaced from the axis of rotational movement, so as to restrain the arm against said rotation, the element being formed of a material having a coefficient of linear thermal expansion greater than that of the material of the arm such that, when the assembly is heated, the resultant differential expansion of the element and arm permits the arm to rotate a limited amount under the action of the biassing means.
The thermostat device may have associated with it a control mechanism, arranged to be actuated in response to a predetermined movement of the arm. The control mechanism may comprise for example, an electric switch controlling the operation of a heating circuit, and/or a mechanical latching arrangement.
Thus where the device forms part of an electric toaster of the kind incorporating a bread carriage capable of being lowered against spring means into a toasting position in which a slice of bread supported thereby is located adjacent the heating elements, the latching arrangement may be arranged to hold the carriage in the toasting position, movement of the rod when the tensioned element is heated a predetermined amount being arranged to actuate the latching arrangement to cause it to release the carriage and permit the latter to rise under the action of the spring means; a switch can also be actuated to deenergise the heating elements In such a toaster means may be provided for selectively adjusting the position of the support so as to vary the distance between the arm and a co-operating part of the latching means prior to a toasting operation, this controlling the time taken for the arm to engage and actuate the latching means and thereby enabling different degrees of browning of the toast to be obtained.
The support, together with the arm and tensioned element, can conveniently be formed as a unit capable of being readily fitted into and removed from the remainder of the toaster thereby enabling the operation of the device to be tested prior to assembly, and also enabling it to be replaced without difficulty when this proves to be necessary during servicing.
The use of a thin tensioned element has the advantage that the element possesses a small thermal capacity, this enabling the thermostat device to reset itself for re-use very rapidly.
The rigid arm can be of any convenient material and cross-section providing the required degree of rigidity and low thermal expansion, and is conveniently in the form of a circular section rod of Invar (Registered Trade Mark). The tensioned element is preferably in the form of a thin tape of a nickel-chrome alloy such as Nichrome (Registered Trade Mark), although it can be in the form of wire.
The tensioned element is preferably secured as by welding to the end of the arm remote from the support, the opposite end of the arm projecting beyond the pivot point on the support, and the arm being biassed by means of a tension spring extending between said opposite end of the arm and an appropriate part of the support.
One thermostat device in accordance with the invention, for use in an electric toaster of the kind having a movable bread carriage, will now be described by way of example with reference to Figures 1 to 4 of the accompanying schematic drawing, in which: Figure 1 shows a side view, in part, of the thermostat device as arranged between the end frames of the toaster, Figure 2 shows an end view of the device, in the direction indicated by the arrow 'X' of Figure 1, Figure 3 shows a transverse sectional view of the toaster, and Figure 4 shows an end view of the toaster with part of its outer cover removed and illustrating a latching mechanism for the bread carriage.
The thermostat device comprises a rod 1 formed of a material having a low coefficient of linear thermal expansion, for example between 3 X 10-6 and 4.5x10-6 per degree centigrade, to which is secured at one end 2 by welding a thin nickel-chrome alloy tape 3 having a high coefficient of thermal expansion for example of the order of 17 x 10-s perdegree centigrade, the other end of which tape is fixed, also by welding, to a projection 4 forming part of a bracket 5 through a hole 80 in which the opposite end of the rod 1 extends.
A roller 9 is rigidly attached to the rod 1 near to this latter end with its axis extending transverse to that of the rod, and is rotatably held between a pair of upturned projections 11, forming part of the bracket 5, and the main face of the bracket, as shown, so as to provide a pivot point for the rod 1. A tension spring 12 is held between the adjacent end 13 of the rod 1 and a lug 14 projecting downwards near to the lower end of the bracket 5.
A projection 6 formed at the upper end of the bracket extends through, and is pivoted on the lower edge of, a rectangular hole 7 located in an end frame 8 of the toaster, a spring strip 15, secured to the end frame 8 by a screw 16, serving to retain the upper end of the bracket 5 in pivotal relationship with the end frame 8.
Extending downwards from, and attached to, the bracket 5 is a strip 17 having an aperture 81 through which passes the shank 18 of an adjusting screw 19. A compression spring 20 is arranged between the strip 17 and the end frame of the toaster so that the strip is always held against a shoulder 21 of the screw, thus ensuring that the strip moves with the screw when adjustment takes place. Such movement is such as to pivot the whole thermostat assembly about the end frame 8 so as to provide a change in the normal position of the operating end 2 of the thermostat which is free to move upwards or downwards within an aperture 22 provided in the other end frame 23 of the toaster.
The operative parts of the toaster are enclosed in an outer casing 30 having a pair of elongate slots 31 in its top wall into which slices of bread to be toasted can be inserted. A pair of bread supports 32 are disposed beneath the respective slots 31 for supporting the bread slices so inserted, these supports forming part of a bread carriage 26 which is movable from an upper inoperative position, in which the slices of bread project from the slots, to a lower operative position in which the slices of bread lie between electric heating elements 24. At one end the bread supports 32 are provided with lugs 33 which project through vertical slots 36 in the end frame 23 and are connected outside the end frame 23 to a plate 34.
The end frame 23 carries on its - outer surface a pivoted latching member 35, and when the bread carriage 26 is lowered into its operative position the latching member 35 is moved to a latching position in which it engages a surface of a cooperating member carried by the plate 34. The surface of the cooperating member -(which has not been illustrated in the interests of clarity) is represented by the broken line 38. The latching member 35 is retained in the latching position by a locking member 25, also pivotably mounted on the external surface of the end frame 23, and holds the carriage 26 in its operative position, with the bread slices adjacent the heating elements 24.
In operation, after the bread carriage has been lowered and the heating elements 24 have been energised thermal emission from the heating elements will cause the tape 3 to increase in length to a greater extent than the Invar rod, and, in consequence, the end 2 of the thermostat rod 1 will move upwards because of the energy imparted to the system by the spring 12. This movement is used to actuate the pivoted locking member 25 and when the end 2 of the thermostat rod 1 has moved a sufficient distance, the locking member 25 releases the latching member 35, which is then rotated by a spring 37 away from the latching position, so that it disengages from the surface 38 of the cooperating member on the plate 34, thus allowing the bread carriage 26 to move upwards under the control of a spring 27; at the same time the heating elements 24 are switched off.
Adjustment of the screw 19 has the effect of raising or lowering the free end of the rod and tape assembly relative to the locking member 25, thereby controlling the toasting time, and hence the degree of brownness of the toast.
Because of the relatively low thermal capacity of the tape 3 the thermostat device re-sets itself rapidly, thereby enabling the toaster to be re-used within a very short period.
It will; however, be appreciated that if the toaster is used again very quickly, the remainder of the toaster structure will not have time to cool, so that subsequent slices of bread will tend to reach the required degree of browning in a shorter time than the first. The thermal capacities in a shorter time than the first. The thermal capacities of the rod l and tape 3 can be chosen to provide the required degree of compensation, but if necessary additional compensation may be provided by forming the strip 17, at the lower end of the bracket 5, of a suitable bimetal, such that the bracket is pivoted by a small amount relative to the end frame as the temperature of the toaster rises, thereby deflecting the free end of the rod and tape assembly slightly in relation to the latch mechanism 25.
It will also be appreciated that alternative methods of tensioning the arrangement can be adopted, for example, by use of a torsion spring to provide the pivotal movement for the thermostat rod 1. Likewise alternative methods of pivoting the rod 1 about the end bracket may be adopted.
A toasting operation may be terminated manually if desired, before the completion of a toasting operation, by moving the cooperating member carried by the plate 34 out of engagement with the latching member 35. For this purpose the cooperating member may be pivotably mounted on the plate 34, and the toaster provided with manually operable means for displacing the cooperating member from its operative position.
WHAT WE CLAIM IS: 1. A thermostat device comprising a support, a substantially rigid arm carried by and capable of a degree of rotational movement relative to the support, spring biassing means tending to rotate the arm relative to the support, and a relatively thin elongate element held in a tensioned condition between regions of the arm and support which are spaced from the axis of rotational movement so as to restrain the arm against said rotation, the element being formed of a material having a coefficient of linear thermal expansion greater than that of the material of the arm such that, when the assembly is heated, the resultant differential expansion of the element and arm permits the arm to rotate a limited amount under the action of the biassing means.
2. A thermostat device according to Claim 1 having associated with it a control mechanism arranged to be actuated in response to a predetermined movement of the arm under the action of the biassing means.
3. A thermostat device according to Claim 2 wherein said control mechanism incorporates an electric switch controlling the operation of a heating circuit.
4. A thermostat device according to Claim 2 or 3 wherein said control mechanism incorporates a mechanical latching arrangement.
5. A thermostat device according to Claim 4 incorporated in an electric toaster of the kind incorporating a bread carriage capable of being lowered against spring means into a toasting position in which a slice of bread supported thereby is located adjacent heating elements, wherein said latching arrangement is arranged to hold the carriage in the toasting position, and wherein the movement of the arm when the tensioned element is heated a predetermined amount is arranged to actuate the latching arrangement to cause it to release the carriage and permit the latter to rise under the action of the spring means.
6. A thermostat device according to Claim 5 having means for adjusting the position of the support so as to vary the distance between the arm and a co-operating part of the latching arrangement prior to a toasting operation so as to control the time taken for the arm to engage and actuate the latching arrangement in use of the toaster for enabling different degrees of browning of the toast to be obtained.
7. A thermostat device according to Claim wherein the support is pivotably carried by a co-operating part of the toaster and means are provided for adjusting the angular position of the support relative to said part of the toaster.
8. A thermostat device according to Claim 6 or 7 incorporating a temperature compensator capable of altering the adjusted position of the support to a limited degree in dependence upon the temperature of the adjacent part of the toaster.
9. A thermostat device according to Claim 8 wherein the temperature compensator comprises a bimetallic strip between the support and the adjustment means.
10. A thermostat device according to any one of Claims 5 to 9 wherein the support, together with the arm and tensioned element, are formed as a unit capable of being fitted into and removed from the remainder of the toaster as a complete assembly.
11. A thermostat device according to any preceding claim wherein the arm is in the form of a circular section rod.
12. A thermostat device according to any preceding claim wherein the arm is formed of a material having a co-efficient of linear thermal expansion of between 3 x 10-6 and 4.5 x 10-6 per degree centigrade.
13. A thermostat device according to any preceding claim wherein the tensioned element is formed of a material having a coefficient of thermal expansion of at least 17 x 10-6 per degree centigrade.
14. A thermostat device according to any preceding claim wherein the tensioned element is secured to the arm at or near the end of the latter remote from the support, the
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. remainder of the toaster structure will not have time to cool, so that subsequent slices of bread will tend to reach the required degree of browning in a shorter time than the first. The thermal capacities in a shorter time than the first. The thermal capacities of the rod l and tape 3 can be chosen to provide the required degree of compensation, but if necessary additional compensation may be provided by forming the strip 17, at the lower end of the bracket 5, of a suitable bimetal, such that the bracket is pivoted by a small amount relative to the end frame as the temperature of the toaster rises, thereby deflecting the free end of the rod and tape assembly slightly in relation to the latch mechanism 25. It will also be appreciated that alternative methods of tensioning the arrangement can be adopted, for example, by use of a torsion spring to provide the pivotal movement for the thermostat rod 1. Likewise alternative methods of pivoting the rod 1 about the end bracket may be adopted. A toasting operation may be terminated manually if desired, before the completion of a toasting operation, by moving the cooperating member carried by the plate 34 out of engagement with the latching member 35. For this purpose the cooperating member may be pivotably mounted on the plate 34, and the toaster provided with manually operable means for displacing the cooperating member from its operative position. WHAT WE CLAIM IS:
1. A thermostat device comprising a support, a substantially rigid arm carried by and capable of a degree of rotational movement relative to the support, spring biassing means tending to rotate the arm relative to the support, and a relatively thin elongate element held in a tensioned condition between regions of the arm and support which are spaced from the axis of rotational movement so as to restrain the arm against said rotation, the element being formed of a material having a coefficient of linear thermal expansion greater than that of the material of the arm such that, when the assembly is heated, the resultant differential expansion of the element and arm permits the arm to rotate a limited amount under the action of the biassing means.
2. A thermostat device according to Claim 1 having associated with it a control mechanism arranged to be actuated in response to a predetermined movement of the arm under the action of the biassing means.
3. A thermostat device according to Claim 2 wherein said control mechanism incorporates an electric switch controlling the operation of a heating circuit.
4. A thermostat device according to Claim 2 or 3 wherein said control mechanism incorporates a mechanical latching arrangement.
5. A thermostat device according to Claim 4 incorporated in an electric toaster of the kind incorporating a bread carriage capable of being lowered against spring means into a toasting position in which a slice of bread supported thereby is located adjacent heating elements, wherein said latching arrangement is arranged to hold the carriage in the toasting position, and wherein the movement of the arm when the tensioned element is heated a predetermined amount is arranged to actuate the latching arrangement to cause it to release the carriage and permit the latter to rise under the action of the spring means.
6. A thermostat device according to Claim 5 having means for adjusting the position of the support so as to vary the distance between the arm and a co-operating part of the latching arrangement prior to a toasting operation so as to control the time taken for the arm to engage and actuate the latching arrangement in use of the toaster for enabling different degrees of browning of the toast to be obtained.
7. A thermostat device according to Claim wherein the support is pivotably carried by a co-operating part of the toaster and means are provided for adjusting the angular position of the support relative to said part of the toaster.
8. A thermostat device according to Claim 6 or 7 incorporating a temperature compensator capable of altering the adjusted position of the support to a limited degree in dependence upon the temperature of the adjacent part of the toaster.
9. A thermostat device according to Claim 8 wherein the temperature compensator comprises a bimetallic strip between the support and the adjustment means.
10. A thermostat device according to any one of Claims 5 to 9 wherein the support, together with the arm and tensioned element, are formed as a unit capable of being fitted into and removed from the remainder of the toaster as a complete assembly.
11. A thermostat device according to any preceding claim wherein the arm is in the form of a circular section rod.
12. A thermostat device according to any preceding claim wherein the arm is formed of a material having a co-efficient of linear thermal expansion of between 3 x 10-6 and 4.5 x 10-6 per degree centigrade.
13. A thermostat device according to any preceding claim wherein the tensioned element is formed of a material having a coefficient of thermal expansion of at least 17 x 10-6 per degree centigrade.
14. A thermostat device according to any preceding claim wherein the tensioned element is secured to the arm at or near the end of the latter remote from the support, the
opposite end region of the arm projects beyond the pivot point on the support, and the arm is biassed by means of a tension spring extending between said projecting end region of the arm and an appropriate part of the support.
15. A thermostat device substantially as shown in and as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.
16. An electric toaster incorporating a thermostat device according to any preceding claim.
GB5257375A 1975-12-23 1975-12-23 Thermostat devices Expired GB1566102A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
GB5257375A GB1566102A (en) 1975-12-23 1975-12-23 Thermostat devices
NL7614137A NL7614137A (en) 1975-12-23 1976-12-20 THERMOSTAT ASSEMBLY.
FI763692A FI763692A (en) 1975-12-23 1976-12-22
BE173615A BE849828A (en) 1975-12-23 1976-12-23 IMPROVEMENTS TO THERMOSTAT DEVICES

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB5257375A GB1566102A (en) 1975-12-23 1975-12-23 Thermostat devices

Publications (1)

Publication Number Publication Date
GB1566102A true GB1566102A (en) 1980-04-30

Family

ID=10464445

Family Applications (1)

Application Number Title Priority Date Filing Date
GB5257375A Expired GB1566102A (en) 1975-12-23 1975-12-23 Thermostat devices

Country Status (4)

Country Link
BE (1) BE849828A (en)
FI (1) FI763692A (en)
GB (1) GB1566102A (en)
NL (1) NL7614137A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2574611A1 (en) * 1984-12-12 1986-06-13 Rowenta Werke Gmbh TIMEPINE IN BILAME

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2574611A1 (en) * 1984-12-12 1986-06-13 Rowenta Werke Gmbh TIMEPINE IN BILAME
GB2169493A (en) * 1984-12-12 1986-07-16 Rowenta Werke Gmbh Bimetallic timing mechanism

Also Published As

Publication number Publication date
FI763692A (en) 1977-06-24
NL7614137A (en) 1977-06-27
BE849828A (en) 1977-04-15

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CSNS Application of which complete specification have been accepted and published, but patent is not sealed