EP0165731A2 - Elektrische Schalter - Google Patents

Elektrische Schalter Download PDF

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Publication number
EP0165731A2
EP0165731A2 EP85303808A EP85303808A EP0165731A2 EP 0165731 A2 EP0165731 A2 EP 0165731A2 EP 85303808 A EP85303808 A EP 85303808A EP 85303808 A EP85303808 A EP 85303808A EP 0165731 A2 EP0165731 A2 EP 0165731A2
Authority
EP
European Patent Office
Prior art keywords
contact member
configuration
movement
centre
over
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.)
Withdrawn
Application number
EP85303808A
Other languages
English (en)
French (fr)
Other versions
EP0165731A3 (de
Inventor
Alan Murray
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.)
Elmwood Sensors Ltd
Elmwood Sensors Inc
Original Assignee
Elmwood Sensors Ltd
Elmwood Sensors 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 Elmwood Sensors Ltd, Elmwood Sensors Inc filed Critical Elmwood Sensors Ltd
Publication of EP0165731A2 publication Critical patent/EP0165731A2/de
Publication of EP0165731A3 publication Critical patent/EP0165731A3/de
Withdrawn legal-status Critical Current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
    • H01H37/5409—Bistable switches; Resetting means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/02—Details
    • H01H13/26—Snap-action arrangements depending upon deformation of elastic members
    • H01H13/36—Snap-action arrangements depending upon deformation of elastic members using flexing of blade springs
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/64—Contacts
    • H01H37/70—Resetting means
    • H01H2037/705—Resetting means wherein the switch cannot be closed when the temperature is above a certain value
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/02—Details
    • H01H37/60—Means for producing snap action

Definitions

  • This invention relates to electrical switches and in one particular example to temperature sensitive switches for use in protecting electrical equipment from the damaging and possibly dangerous effects of over-heating.
  • Switches have been produced which satisfy this criterion but they are often complex in structure and expensive to manufacture.
  • a mechanism is suggested in which movement of a reset button imparts sufficient kinetic energy to a steel ball to enable the ball to reset the thermostat. If the reset button is permanently depressed, the weight of the steel ball is not itself sufficient to reset the mechanism.
  • An alternative approach is shown in GB 1 527 567 in which a reset mechanism is shown acting through a spring chosen to be "weaker" than the bimetallic disc at high temperatures. Only when temperatures have dropped is the power in the spring sufficient to restore the bimetallic disc to the normal configuration. This requires, however, that the spring forces are very accurately controlled in manufacture and this can increase production costs.
  • the safety criterion is satisfied in a manner which is not directly visible and confirmable.
  • the present invention consists in an electrical switch comprising fixed and movable contacts; a bistable contact member associated with said movable contact such that in a first stable configuration of the contact member the said contacts are in engagement whilst in a second stable configuration the said contacts are disengaged; actuating means serving to move the contact member from the first to the second configuration to disengage the contacts and a resetting member actuable ' manually to restore the contact member to the first configuration; characterised in that movement of the resetting member in one sense displaces the contact member from the second configuration to an unstable configuration in which the -contacts remain disengaged, movement of the resetting member in an opposite sense then serving to restore the contact member from the unstable configuration to said first configuration.
  • said bistable member takes the form of over-centre spring means.
  • said over-centre spring means is mounted for movement over centre between said first and second stable configurations and also for displacement, the resetting member being adapted on said movement in one sense to move the spring means over-centre and to displace the spring means, return movement of the resetting member being accompanied by a return displacement of the contact member.
  • said actuating means comprises temperature responsive means serving at a selected temperature to move the contact member to said second configuration.
  • the thermostat shown in Figure 1 comprises an electrically insulating housing 10 defining an internal contact cavity 12.
  • a circular recess 14 in which is located a bimetallic disc 16.
  • the disc is held in position by means of a metallic cap 18 serving also as a heat collector.
  • the cap is formed with a circular ridge 20 which supports the disc close to its perimeter.
  • the disc cooperates with a transfer pin 21 which is slidable in a bore extending through the housing, between the recess 14 and the contact cavity 12.
  • the first terminal carries on the limb 30 a contact member 24 formed of thin metal sheet.
  • the contact member comprises a hollow rectangular frame 26 formed integrally with an inwardly directed tongue 28.
  • the tongue 28 is secured at its free end to the limb 30 of the first terminal with the frame 26 passing behind the terminal and being located in a groove 31 formed in the second limb 32.
  • the contact member carries a movable contact 34.
  • the secured end of the tongue 28 lies beneath the plane of the frame 26 and the length of the tongue is such that in the normal position shown in Figure 1, the tongue is under significant stress.
  • a second L-shaped terminal 36 has an internal limb 38 positioned to form a fixed contact cooperable with the movable contact 34.
  • a reset button 40 is mounted for sliding movement relative to the housing into and out of the contact cavity.
  • the reset button is biased to the position shown in Figure 1 by means of a leaf spring 42 having one end passing through an aperture 44 in the reset button and the other end trapped in the housing.
  • Figures 3a), b) and c) which are similar to Figure 1 but which show the thermostat at different stages of operation.
  • the bimetallic disc 16 In the normal position shown in Figure 1, the bimetallic disc 16 is concave with respect to the transfer pin 21 which then engages - but exerts no significant force upon - the contact member.
  • the movable contact 34 is urged into engagement with the fixed contact 36 by means of the resilient energy in the tongue 28. In this position, current may pass from the first terminal, through the contact member and movable contact to the second terminal. If the working temperature should exceed a predetermined safe threshold, the bimetallic disc will snap over from the concave position shown in Figure 1 to the convex position shown in Figure 3a).
  • the consequent upward movement of the transfer pin 21 will push the tongue 28 over-centre to a position in which the bowed portion of the tongue is on the opposite side of the plane of frame 26.
  • the movable contact is in this action forced downward and electrical continuity is broken.
  • the thermostat In conformity with safety standards, the thermostat will remain in the open circuit position even if the bimetallic disc should thermally reset since, as shown in Figure 3b), downward movement of the transfer pin will leave the contact member in the over-centre position.
  • the reset button In order to reset the thermostat, it is necessary for the reset button to be depressed against the action of leaf spring 42 to the position shown in Figure 3c) in which the tongue 28 has been forced, over-centre, through the plane of the frame 26.
  • the reset button As the reset button is released and moves upwardly under the action of the leaf spring, the movable contact will move upwardly into re-engagement with the fixed contact. It is important to note that the initial movement of the reset button causes the contact member to adopt an intermediate configuration in which the contacts remain disengaged.
  • the desired safety features are provided in a construction having a minimal number of parts. Reliability of the device can therefore be expected to be good and manufacturing costs will be relatively low.
  • a mounting portion 50 is riveted to a support block 52 and includes oppositely directed wings 54 each formed with a deformable tab 56. Centrally of the wings, a tongue 58 extends from the mounting portion to a generally semi-circular end piece 60.
  • Parallel tensioning members 62 extend from this end piece to the mounting portion 50 and have, at their ends, stirrups 64 which respectively engage the tabs 56.
  • the end piece 60 carries a moving contact 66 cooperable with a fixed contact 68.
  • a force is applied along line A, for example by a bimetallic disc acting on a tranfer pin, in order to force the tongue over-centre and displace the movable contact upwardly.
  • a resetting force applied along line B will return the tongue over-centre, removal of the force then permitting re-engagement of the contacts.
  • the resetting force is preferably applied through a reciprocally mounted reset button but other arrangements are possible.
  • the frame 26 of the first described. embodiment and the tensioning members 62 of the second described embodiment perform the similar function of tensioning the contact member tongue so defining two stable configurations.
  • this function can be performed not by elements of the contact member itself but through engagement of the free end of the contact member tongue with, for example, guide slots in the housing.
  • the contact member 100 takes the form of a disc which can be snapped between stable convex and concave states.
  • the disc is not bimetallic and does not respond to temperature.
  • the disc carries an integral tab (not seen in the drawings) through, which it is secured to the terminal 22.
  • the disc carries on its upper surface a movable contact 102.
  • the bistable disc 100 is convex with respect to the transfer pin and biases the movable contact 102 into engagment with the fixed contact.
  • the lines of action of the reset button 40 and transfer pin 21 are parallel and approximately equally spaced on opposite sides of the disc centre.
  • the bimetallic disc snaps upwardly and the consequential movement of the tranfer pin causes the bistable disc to snap over to the concave position shown in Figure 5b). Electrically continuity is then broken and will not be restored on thermal relaxation of the bimetallic disc.
  • the reset button is depressed so returning the bistable disc to the convex configuration as shown in Figure 5c). At this point, however, the contacts are still disengaged. Only on release of the reset button is electrical continuity re-established.
  • thermoly responsive means could be employed in place of the described bimetallic disc and axially displaced transfer pin.
  • the movable contact could be associated with, but not directly carried on, the contact member which would then not necessarily form part of the electrical circuit.
  • the movable contact might comprise a bridge establishing continuity between two fixed contacts.

Landscapes

  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
EP85303808A 1984-05-31 1985-05-30 Elektrische Schalter Withdrawn EP0165731A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB848413912A GB8413912D0 (en) 1984-05-31 1984-05-31 Electrical switches
GB8413912 1984-05-31

Publications (2)

Publication Number Publication Date
EP0165731A2 true EP0165731A2 (de) 1985-12-27
EP0165731A3 EP0165731A3 (de) 1988-05-18

Family

ID=10561747

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85303808A Withdrawn EP0165731A3 (de) 1984-05-31 1985-05-30 Elektrische Schalter

Country Status (2)

Country Link
EP (1) EP0165731A3 (de)
GB (1) GB8413912D0 (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2675965A1 (fr) * 1991-04-26 1992-10-30 Secap Dispositif de protection thermique dans un domaine limite de temperatures, notamment pour appareil a enregistrement de donnees entretenues par piles et en particulier machine a affranchir.
EP0656610A1 (de) * 1993-12-01 1995-06-07 Neopost Industrie Thermische Schutzvorrichtung für einen gesicherten elektronischen Apparat, insbesondere eine Frankiermaschine
GB2347271A (en) * 1999-02-25 2000-08-30 Otter Controls Ltd Thermal controls
CN109119272A (zh) * 2018-09-25 2019-01-01 深圳马太亚科技有限公司 静音微动开关及鼠标

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE6608907U (de) * 1967-09-07 1971-12-09 Dreefs E Elektro Fab Temperaturbegrenzer fuer elektrische geraete.
US3924213A (en) * 1974-09-30 1975-12-02 Ranco Inc Thermostat
CH629623A5 (en) * 1978-05-24 1982-04-30 Landis & Gyr Ag Intrinsically safe temperature limiter
US4480246A (en) * 1982-10-18 1984-10-30 Therm-O-Disc, Incorporated Trip-free manual reset thermostat

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2675965A1 (fr) * 1991-04-26 1992-10-30 Secap Dispositif de protection thermique dans un domaine limite de temperatures, notamment pour appareil a enregistrement de donnees entretenues par piles et en particulier machine a affranchir.
WO1992020085A1 (fr) * 1991-04-26 1992-11-12 Secap Dispositif de protection thermique dans un domaine limite de temperatures
US5274525A (en) * 1991-04-26 1993-12-28 Secap Device for thermal protection within a limited range of temperatures, especially for an apparatus for recording battery-backed data and in particular a franking machine
EP0656610A1 (de) * 1993-12-01 1995-06-07 Neopost Industrie Thermische Schutzvorrichtung für einen gesicherten elektronischen Apparat, insbesondere eine Frankiermaschine
FR2713372A1 (fr) * 1993-12-01 1995-06-09 Neopost Ind Dispositif de protection thermique pour appareil électronique sécurisé, notamment machine à affranchir.
US5659454A (en) * 1993-12-01 1997-08-19 Neopost Industrie Thermal protection apparatus for a secure electronic appliance, in particular a postage meter
GB2347271A (en) * 1999-02-25 2000-08-30 Otter Controls Ltd Thermal controls
GB2347271B (en) * 1999-02-25 2003-05-07 Otter Controls Ltd Improvements relating to thermal controls
CN109119272A (zh) * 2018-09-25 2019-01-01 深圳马太亚科技有限公司 静音微动开关及鼠标

Also Published As

Publication number Publication date
EP0165731A3 (de) 1988-05-18
GB8413912D0 (en) 1984-07-04

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Effective date: 19881118

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Inventor name: MURRAY, ALAN