US3577111A - Miniaturized snap acting thermostatic switch - Google Patents

Miniaturized snap acting thermostatic switch Download PDF

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Publication number
US3577111A
US3577111A US812699A US81269969A US3577111A US 3577111 A US3577111 A US 3577111A US 812699 A US812699 A US 812699A US 81269969 A US81269969 A US 81269969A US 3577111 A US3577111 A US 3577111A
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US
United States
Prior art keywords
housing
thermostatic element
nondevelopable
leg
cover
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 - Lifetime
Application number
US812699A
Other languages
English (en)
Inventor
Antonio Nardulli
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.)
Texas Instruments Inc
Original Assignee
Texas Instruments Inc
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 Texas Instruments Inc filed Critical Texas Instruments Inc
Application granted granted Critical
Publication of US3577111A publication Critical patent/US3577111A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H37/54—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting
    • H01H37/5418—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting using cantilevered bimetallic snap elements
    • 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
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H37/54—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting
    • H01H37/5427—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting encapsulated in sealed miniaturised housing
    • 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
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H37/54—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting
    • H01H2037/5445—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting with measures for avoiding slow break of contacts during the creep phase of the snap bimetal
    • 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
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H37/54—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting
    • H01H2037/5463—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting the bimetallic snap element forming part of switched circuit

Definitions

  • thermoelectric switch A miniature thermostatic switch in which a snap acting thermostatic element having a nondevelopable portion responsible for its snap action is cantilever mounted in a metallic shell.
  • a second mating shell is of electrically insulating material and clamped thereto is an adjustable stationary contact member.
  • the operating temperature of the snap acting thermostatic element is controlled by eliminating creep action prior to snapping of the element by means of a dimple in the metallic shell which applies a bias to the nondevelopable portion of the thermostatic element.
  • the creep action is avoided by forming the entire thermostatic element in the nondevelopable shape.
  • the present invention relates to a miniaturized thermostatic switch device particularly suitable for the protection of the windings of electric motors.
  • the devices are inserted -directly in contact with the windings of the motor and, consequently, it is important that they be of minimal dimensions and that their sensitivity to overcurrents and overtemperatures be as high aspossible.
  • the devices are generally composed of a bimetallic member which deforms itself as a result of the combined joule-radiated temperature effect of the apparatus to be protected causing two contacts to open, interrupting the power supply to the motor.
  • the bimetallic member is generally disposed in the vicinity of the metallic case which also contains all the other parts making up the motor protector, as the snap-action member, contacts, terminals and the insulating body.
  • a device which contains in combination a preformed thermostatic element such as a bimetal having a nondevelopable surface, fastened directly on the metallic case of the motor protector to obtain maximum sensitivity to the ambient temperature, and a contact terminal mounted along with a calibrating member on the insulating base, the bimetal and the contact terminal being disposed in parallel relationship to form a small magnetic field to allow the suppression of arcs by blasting which form during the opening of the contacts to extend the life of the contacts.
  • a preformed thermostatic element such as a bimetal having a nondevelopable surface
  • the device has a cup shaped cover or shell which is provided with dimple extending into the switch cavity.
  • the dimple is arranged to physically contact the central part of the nondevelopable portion of the thermostatic element when the contacts are in engagement. This facilitates the calibration of the switch and improves the accuracy of the operating tem perature at which it snaps as well as avoids creep opening of the contacts prior to snapping of the thermostatic element to. the contacts disengaged position.
  • the thermostatic protection device contains a housing or shell 1 of electrically insulating material which has a closed end portion with side walls depending therefrom. An aperture is provided in the closed end for reception of a first terminal member 2, clasped by the bicornuous portion 3 of member 2 to the closed end of housing I and ending in a stationary contact support arm 4 on which is mounted stationary contact 2a.
  • the position of the fixed contact 2a can be regulated by means of a calibration screw 5 mounted in the closed end of housing I.
  • Arm 4 is cantilever mounted and formed with the distal portion bent out of the general plane of the arm. Calibration screw 5 engages the bent distal portion or arm 4 near the bent line.
  • a metallic shell 6 is clamped by a flange 7 to an annular flange of housing 1.
  • An extension 12 is provided on shell 6 which forms a second terminal of the device.
  • the metallic shell 6 is also provided with a dimple 8 turned inwardly into the switch cavity as shown in FIGS. 1 and 2 for a purpose specified below.
  • thermostatic element such as bimetallic member 9 is cantilever mounted and carries a movable contact 10 on its distal end.
  • Bimetallic member 9 is formed with a nondevelopable portion 11, making member 9 a snap acting element in a manner conventional in the art.
  • movable contact member 2a in the at rest position is moved into physical and electrical contact with stationary contact 10 by calibration screw 5.
  • arm 4 is forced toward the open end of housing 1 and force is transmitted through stationary contact 2a to movable contact 10 and in turn, thermostatic element 9 is biased against the dimple 8 to establish a desired prestress to effect calibration of the device.
  • the position of screw 5 can be locked into place by a conventional potting compound.
  • the bimetallic member 9 While in operation, the bimetallic member 9 will execute a small rotation about dimple 8 opening the contacts 2a, 10 with a sudden snap movement and without any prior creep due to the prestress of dimple 8 on portion 11.
  • Forming the switch cavity with electrically insulating material permits closer spacing of the housing sidewalls while still satisfying the international standards.
  • mounting the thermostatic element directly on a metallic cover enhances the heat transfer from the windings of the protected apparatus to the element. This is further enhanced by the physical contact of dimple 8 directly with the nondevelopable portion 11.
  • the device is mounted so that the outer surface of shell 6 is in physical contact with a surface whose temperature is to be sensed or moni- Such a themtostatic element does not tend to creep in the open contacts direction prior to snap action since the entire switch element comprises the nondevelopable portion and therefore dimple 8 in shell 6 can be omitted.
  • the rest of the structure is identical to the FlG. l and 2 embodiment, therefore the detailed description will not be repeated.
  • a thermostatic switch comprising:
  • a relatively stiff, generally bicomuous member located in the aperture and having two legs in clamping engagement with the end wall, one leg of the member being elongated and extending substantially across the cavity;
  • a second aperture provided in the end wall and receiving therein an adjustable member adapted to engage the elongated leg and bias the leg toward the open end of the housing;
  • a snap acting thermostatic element having two ends and a nondevelopable portion, the element cantilever mounted by interposing one end between the housing and the cover;
  • a switch according to claim 1 in which a third leg extends from the bicomuous member outside the housing generally parallel but in an opposite direction to that of the one leg.
  • a switch according to claim 1 in which the one leg of the bicomuous member is formed with a section intermediate the portion in clamping engagement with the housing end wall and the distal end of the one leg, which section is bent out of the general plane of the one leg, the adjustable member aligned to contact the leg section.
  • a switch according to claim 1 in which a dimple is formed in the cover and aligned with the nondevelopable portion of the thermostatic element and in physical contact with the nondevelopable portion only when the contacts are in engagement.
  • a switch according to claim 1 in which the entire area of the thermostatic element extending from the mounting forms the nondevelopable portion.
  • a thennostatic switch comprising:
  • a. a housing of electrically insulating material and formed with a cavity therein;
  • a snap acting thermostatic element having a nondevelopable portion responsible for its snap action cantilever mounted in the housing by interposing an end of the element between the housing and the cover with a free end of the element extending into the cavity;
  • a dimple formed in the cover aligned generally with the center of the nondevelopable portion of the thermostatic element and in physical connection therewith when the contacts are in engagement whereby the thermostatic element pivots about the dimple when the thermostatic element snaps to the open contacts position.
  • a switch according to claim 6 including an adjustable member mounted in the housing and adapted to bias the stationary contact to vary the amount of force exerted on the thermostatic element by the dimple when the thermostatic element is in the contacts closed position.

Landscapes

  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
US812699A 1968-04-03 1969-04-02 Miniaturized snap acting thermostatic switch Expired - Lifetime US3577111A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT3603268 1968-04-03

Publications (1)

Publication Number Publication Date
US3577111A true US3577111A (en) 1971-05-04

Family

ID=33017927

Family Applications (1)

Application Number Title Priority Date Filing Date
US812699A Expired - Lifetime US3577111A (en) 1968-04-03 1969-04-02 Miniaturized snap acting thermostatic switch

Country Status (5)

Country Link
US (1) US3577111A (de)
DE (1) DE1915721B2 (de)
FR (1) FR2005424A1 (de)
GB (1) GB1237634A (de)
NL (1) NL161610C (de)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3818404A (en) * 1972-10-30 1974-06-18 Texas Instruments Inc Circuit breaker apparatus
US3936792A (en) * 1972-10-30 1976-02-03 Texas Instruments Incorporated Circuit breaker apparatus
US3996547A (en) * 1974-09-05 1976-12-07 Texas Instruments Incorporated Motor protector apparatus
US4039992A (en) * 1976-02-19 1977-08-02 Portage Electric Products, Inc. Non-creep thermostat construction
US4103271A (en) * 1976-04-08 1978-07-25 Taylor John C Thermostats
US4220939A (en) * 1979-02-12 1980-09-02 Emerson Electric Co. Thermal responsive electrical switching device and calibration method therefor
US4317098A (en) * 1980-01-28 1982-02-23 Elmwood Sensors, Inc. Grounded thermostat switch
US4367452A (en) * 1982-02-11 1983-01-04 Elmwood Sensors, Inc. Thermostatic switch construction
US4445105A (en) * 1982-06-28 1984-04-24 Portage Electric Products, Inc. Thermostat
US4517541A (en) * 1982-11-24 1985-05-14 Susumu Ubukata Snap type thermally responsive switch device
US4567458A (en) * 1984-08-15 1986-01-28 Index Industries, Inc. Thermostatic switch
US5014034A (en) * 1989-12-04 1991-05-07 Portage Electric Products, Inc. Thermostatic switch with insulated calibration dimple
US6559752B1 (en) * 1999-05-24 2003-05-06 Frank J. Sienkiewicz Creepless snap acting bimetallic switch having flexible contact members

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2481240B (en) * 2010-06-17 2017-04-12 Otter Controls Ltd Thermally responsive electric switches

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2222291A (en) * 1938-10-19 1940-11-19 Freeman Maurice Electric circuit breaker
US3021405A (en) * 1959-02-26 1962-02-13 Texas Instruments Inc Thermostatic switch
US3054871A (en) * 1958-12-16 1962-09-18 Ford Motor Co Pressure actuated switch
US3139500A (en) * 1960-03-02 1964-06-30 Wilcolator Co Thermally actuated double throw switch mechanism
CA694717A (en) * 1964-09-22 Texas Instruments Incorporated Thermostatic switch
US3171925A (en) * 1961-05-01 1965-03-02 Mechanical Products Inc Snap-acting thermo-responsive member that minimizes creep action
US3361883A (en) * 1966-11-01 1968-01-02 Theodore Brassard Jr. Calibrated thermostatic switch and method for calibrating the same including welded lug and recess means
US3416116A (en) * 1960-12-19 1968-12-10 Texas Instruments Inc Thermostatic switches
US3430177A (en) * 1966-12-30 1969-02-25 Texas Instruments Inc Miniature thermostatic switch
US3431527A (en) * 1966-12-30 1969-03-04 Texas Instruments Inc Thermostatic snap-acting switch

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA694717A (en) * 1964-09-22 Texas Instruments Incorporated Thermostatic switch
US2222291A (en) * 1938-10-19 1940-11-19 Freeman Maurice Electric circuit breaker
US3054871A (en) * 1958-12-16 1962-09-18 Ford Motor Co Pressure actuated switch
US3021405A (en) * 1959-02-26 1962-02-13 Texas Instruments Inc Thermostatic switch
US3139500A (en) * 1960-03-02 1964-06-30 Wilcolator Co Thermally actuated double throw switch mechanism
US3416116A (en) * 1960-12-19 1968-12-10 Texas Instruments Inc Thermostatic switches
US3171925A (en) * 1961-05-01 1965-03-02 Mechanical Products Inc Snap-acting thermo-responsive member that minimizes creep action
US3361883A (en) * 1966-11-01 1968-01-02 Theodore Brassard Jr. Calibrated thermostatic switch and method for calibrating the same including welded lug and recess means
US3430177A (en) * 1966-12-30 1969-02-25 Texas Instruments Inc Miniature thermostatic switch
US3431527A (en) * 1966-12-30 1969-03-04 Texas Instruments Inc Thermostatic snap-acting switch

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3818404A (en) * 1972-10-30 1974-06-18 Texas Instruments Inc Circuit breaker apparatus
US3936792A (en) * 1972-10-30 1976-02-03 Texas Instruments Incorporated Circuit breaker apparatus
US3996547A (en) * 1974-09-05 1976-12-07 Texas Instruments Incorporated Motor protector apparatus
US4039992A (en) * 1976-02-19 1977-08-02 Portage Electric Products, Inc. Non-creep thermostat construction
US4103271A (en) * 1976-04-08 1978-07-25 Taylor John C Thermostats
US4220939A (en) * 1979-02-12 1980-09-02 Emerson Electric Co. Thermal responsive electrical switching device and calibration method therefor
US4317098A (en) * 1980-01-28 1982-02-23 Elmwood Sensors, Inc. Grounded thermostat switch
US4367452A (en) * 1982-02-11 1983-01-04 Elmwood Sensors, Inc. Thermostatic switch construction
US4445105A (en) * 1982-06-28 1984-04-24 Portage Electric Products, Inc. Thermostat
US4517541A (en) * 1982-11-24 1985-05-14 Susumu Ubukata Snap type thermally responsive switch device
US4567458A (en) * 1984-08-15 1986-01-28 Index Industries, Inc. Thermostatic switch
US5014034A (en) * 1989-12-04 1991-05-07 Portage Electric Products, Inc. Thermostatic switch with insulated calibration dimple
US6559752B1 (en) * 1999-05-24 2003-05-06 Frank J. Sienkiewicz Creepless snap acting bimetallic switch having flexible contact members

Also Published As

Publication number Publication date
DE1915721B2 (de) 1972-02-17
NL6904899A (de) 1969-10-07
DE1915721A1 (de) 1969-10-16
GB1237634A (en) 1971-06-30
FR2005424A1 (de) 1969-12-12
NL161610B (nl) 1979-09-17
NL161610C (nl) 1980-02-15

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