EP0376660A2 - Thermische Schalter - Google Patents

Thermische Schalter Download PDF

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Publication number
EP0376660A2
EP0376660A2 EP89313539A EP89313539A EP0376660A2 EP 0376660 A2 EP0376660 A2 EP 0376660A2 EP 89313539 A EP89313539 A EP 89313539A EP 89313539 A EP89313539 A EP 89313539A EP 0376660 A2 EP0376660 A2 EP 0376660A2
Authority
EP
European Patent Office
Prior art keywords
switch
blade
bimetal
snap
parts
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Withdrawn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
EP89313539A
Other languages
English (en)
French (fr)
Other versions
EP0376660A3 (de
Inventor
Stephen William Harrison
Thomas Wise
Robert O' Neill
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.)
Otter Controls Ltd
Original Assignee
Otter Controls 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 Otter Controls Ltd filed Critical Otter Controls Ltd
Publication of EP0376660A2 publication Critical patent/EP0376660A2/de
Publication of EP0376660A3 publication Critical patent/EP0376660A3/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Withdrawn legal-status Critical Current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
    • H01H37/5418—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
    • H01H2037/525—Details of manufacturing of the bimetals, e.g. connection to non bimetallic elements or insulating coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H69/00—Apparatus or processes for the manufacture of emergency protective devices
    • H01H69/01—Apparatus or processes for the manufacture of emergency protective devices for calibrating or setting of devices to function under predetermined conditions

Definitions

  • This invention generally concerns improvements relating to thermal switches and more particularly concerns switches employing bimetallic elements as thermal actuators.
  • bimetallic actuators Many kinds of electrical switches employing bimetallic actuators are known and likewise many different forms of bimetallic switch actuators are known.
  • Early bimetallic switches simply employed a plain bimetal blade arranged to open a pair of switching contacts via a push-rod arrangement with the bimetal simply exposed to heat developed in an appliance or other apparatus controlled by the switch so as to effect an overtemperature control function.
  • Development of the snap-acting bimetallic actuator provided a major advance in the art and there are various known forms of snap-acting bimetallic actuators, such as those disclosed in British Patent Specifications Nos. 600055, 657434, 1064643 and 1542252 for example, and various known forms of electric switches employing such snap-acting actuators.
  • bimetallic actuator such as the pear-shaped blade of our British Patent Specification No. 2124429 for example, have been developed for the provision of operating characteristics to suit particular applications and in this regard the amount of blade movement and the force that the blade can develop have been of particular interest as indeed has the current carrying capability of the blade, the latter being an important parameter in those applications where the blade is required to be current carrying in use and where the heat developed in the blade by current flow therein at least contributes to switching of the blade.
  • the bimetallic blade of our British Patent Specification No. 2124429 is particularly well suited to utilization in the electric motor protection switch that is described in our British Patent Specification No. 2133931.
  • the subject motor protection switch has the principal characteristic of being relatively insensitive to high currents of short duration but being sensitive to lower values of current flowing for relatively long time periods, this being the characteristic required for example of a motor protection switch adapted for use with an automotive window lift motor where the initial operating current of the motor is high and then reduces as the heating of the motor windings causes an increase in the resistance of the winding.
  • this characteristic is achieved by judicious combination of selected bimetal characteristics with selected characteristics of terminal, contact, and/or bimetal mounting parts of the switch, so that at relatively high overload current levels the bimetallic heating predominates in determining the operation of the switch and resistance heating in other switch parts has a substantially negligible effect, whereas at current levels barely of an overload level the resistance heating of such other switch parts contributes significantly to the switch operation.
  • a blade having a generally rectangular outer form and with a tapering (rhomboidal) aperture cut in the centre when mounted by a weld on the short side, at the narrow end of the aperture, gives forces and movement comparable to the three-legged blade of Specification No. 2124429 and has similar current carrying capability.
  • the tapered blade aperture has been found to optimize the stiffness of the blade and enhances the useful movement of a rectangular blade.
  • the invention in one of its aspects, thus resides in a snap-acting bimetal blade as aforesaid having a generally rectangular outer shape and having a generally rhomboidal cut-out defining two spaced-­apart and tapering legs connected together at their opposite ends.
  • the present invention provides a thermally responsive switch incorporating a bimetal blade as above defined.
  • the switch comprises first and second spaced-apart metal parts one of which is formed of rigid, electrically resistive material and the other of which is a spring member, first and second contacts provided on said first and second parts, a bimetal blade as above defined welded or otherwise affixed to one of the first and second parts, and an insulating push rod arranged for transferring switch-operating movement of the bimetal to the spring member for operating the switch.
  • the moving contact of the switching contacts set is carried by the bimetal itself and both of the first and second metal parts of the switch are of rigid construction.
  • the kind of switch shown therein is a current-sensitive switch wherein the operation of the switch is dependent upon the current flowing through the switch and, more particularly, through the bimetallic actuator incorporated into the switch.
  • the switch 1 comprises a moulded plastics body portion 2 supporting first and second rigid metal parts 3 and 4, and a snap-acting bimetal 5 as outlined in the foregoing and as will be more particularly described hereinafter welded or otherwise conductively affixed to the upper metal part 3, the bimetal carrying at its free end a contact 6 constituting the moving contact of the switch and cooperating with a fixed switch contact 7 provided on the lower metal part 4.
  • a moulded plastics body portion 2 supporting first and second rigid metal parts 3 and 4
  • a snap-acting bimetal 5 as outlined in the foregoing and as will be more particularly described hereinafter welded or otherwise conductively affixed to the upper metal part 3, the bimetal carrying at its free end a contact 6 constituting the moving contact of the switch and cooperating with a fixed
  • the bimetal 5 holds the moving contact 6 spaced-apart from the fixed contact 7, whereas in the cold condition of the switch, as shown in Fig. 1B, the bimetal adopts its oppositely dished configuration and maintains the contacts 6, 7 in closed condition.
  • the switch of Figs. 1A and 1B is adapted for use with the load current of the switch flowing through the bimetal 5 and can be constructed in accordance with the teachings of our British Patent No. 2133931 aforementioned such that the nature of the non-bimetal switch parts has an influence upon the operation of the switch.
  • FIG. 2A and 2B An alternative form of switch in accordance with the present invention is shown in Figs. 2A and 2B and, as with the switch of Figs. 1A and 1B, this alternative switch 10 comprises first and second metal parts 11 and 12 supported in a moulded plastics body portion 13, a snap-acting bimetal 14, and fixed and moving contacts 15 and 16 respectively.
  • this alternative switch 10 comprises first and second metal parts 11 and 12 supported in a moulded plastics body portion 13, a snap-acting bimetal 14, and fixed and moving contacts 15 and 16 respectively.
  • the upper switch part 11 is of rigid metal and carries the fixed contact 15 of the switch at its cantilevered end
  • the lower part 12 is formed of spring metal and carries the moving contact 16 of the switch
  • the bimetal 14 is welded or otherwise affixed to the upper metal part 11 and operates through the intermediacy of an insulating push-rod 17 affixed to the spring metal switch part 12 for effecting switching operations.
  • the bimetal 14 is separate from the current path through the switch and is heated indirectly, for example by provision of a separate heater (not shown) or by heat transfer from the main current carrying parts of the switch.
  • FIG. 2A and 2B may thus be formed of a material which is designed to self-heat in current-­carrying operation of the switch so that heat conduction from the part 11 into the bimetal 14 influences the operation of the switch.
  • FIGs. 2A and 2B the hot or open condition of the switch is shown in Fig. 2A wherein the bimetal 14 is shown depressing spring metal part 12 via push-rod 17, and the cold or closed condition of the switch is shown in Fig. 2B.
  • Figs. 3A to 3F an exemplary switch of the kind described above with reference to Figs. 2A and 2B is shown therein with corresponding parts bearing the same reference numerals as were used in the description of Figs. 2A and 2B.
  • the form of the bimetal 14 can be seen clearly from Figs. 3A, 3B and 3F and exemplary dimensions are given in Fig. 3F.
  • the bimetal as shown, comprises a generally rectangular blade 20 provided with curved, stress-­relieving corners and with a tapering, rhomboidal aperture 21 cut in the centre of the blade so as to define two tapering outer legs 22, 23 bridged at their opposite ends by thin-end bridging portion 24 and thich-end bridging portion 25.
  • the blade 20 is dished so as to be movable with snap-action between two oppositely dished configurations as is well known in the art, and the dishing of the blade may as is also well known be achieved by press-forming the blade during its manufacture for example or alternatively may be achieved by impressing a crimp deformation in the thin-end bridging portion 24.
  • the tags 26 shown projecting outwardly from the bridging portions 24 and 25 merely result from the formation of the blade 20 as one of a plurality of such blades by a continuous manufacturing process wherein the blades are stamped from a continuous strip of suitable bimetal material.
  • the bimetal blade 20 is mounted on to the upper metal part 11 of the switch by means of a weld at its thick-end bridging portion 25 and as thus mounted has been found to provide forces and movement comparable to those obtainable with a three-legged blade of the kind described in our British Patent No. 2133931 and with similar current-carrying capability, but in a substantially smaller blade.
  • the provision of a tapered aperture 21 in a generally rectangular bimetal blade has been found to optimise the stiffness of the blade and to enhance the useful movement of a rectangular blade of such size.
  • the operation of the switch of Figs. 3A to 3F is substantially as above described with reference to the switch of Figs. 2A and 2B.
  • the bimetal 14 is separate from the current path through the switch and is heated by the heat developed in the main current-carrying members of the switch, particularly the upper metal part 11 which may be formed of a resistive material so as to be self-heating in use.
  • the illustrated switch configuration is characterized by being insensitive to high values of initial current, but being sensitive to lower values of current applied for relatively long periods of time, and having a high ratio of "off" time to "on” time. Both of these features are desirable in the protection of short term rated DC motors used in automobiles (window lift motors for example).
  • Figs. 4A, 4B and 4C show a further exemplary embodiment of the kind of switch that is illustrated in Figs. 2A and 2B, Figs 4A and 4B being exploded perspective views of the switch taken from different positions, and Fig 4C being a series of plan and elevation views showing stages in the assembly of the switch.
  • the switch of Figs. 4A to 4C is similar to that of Figs. 3A to 3F and differs therefrom only in regard to the different shapes of its constituent parts and the provision of a moulded plastics cover for the switch, the bimetal being identical to that previously described with reference particularly to Fig. 3F. Accordingly, the same reference numerals are used in Figs. 4A, 4B and 4C as were used to describe like parts of the switch of Figs. 3A to 3F.
  • the switch comprises moulded plastics cover parts 30 and 31 with the part 30 incorporating an integral boss 32 shaped to receive thereupon the switch component parts 12, 13 and 11 in the order shown in Figs. 4C(ii), 4C(iii) and 4C(iv) and then to be received in a complementarily shaped aperture 33 formed in cover part 31, the tip of the boss 32 being arranged to project through and beyond the aperture 33 so as to be thermally deformable to secure the two cover parts 30 and 31 together.

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
EP19890313539 1988-12-28 1989-12-22 Thermische Schalter Withdrawn EP0376660A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8830299A GB2227884A (en) 1988-12-28 1988-12-28 Snap-acting bimetal blade
GB8830299 1988-12-28

Publications (2)

Publication Number Publication Date
EP0376660A2 true EP0376660A2 (de) 1990-07-04
EP0376660A3 EP0376660A3 (de) 1991-09-25

Family

ID=10649219

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890313539 Withdrawn EP0376660A3 (de) 1988-12-28 1989-12-22 Thermische Schalter

Country Status (2)

Country Link
EP (1) EP0376660A3 (de)
GB (1) GB2227884A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992012524A1 (en) * 1991-01-04 1992-07-23 Otter Controls Limited Thermally responsive electric switch
DE19545998A1 (de) * 1995-12-09 1997-06-12 Hofsaes Marcel Schalter mit einem bei Übertemperatur schaltenden Schaltwerk
EP1296344A2 (de) * 2001-09-24 2003-03-26 Texas Instruments Incorporated Leistungschalter

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2286053A (en) * 1940-09-10 1942-06-09 Westinghouse Electric & Mfg Co Thermostat
US2834853A (en) * 1957-04-12 1958-05-13 Essex Wire Corp Snap-acting bimetal device
DE2300333A1 (de) * 1972-01-04 1973-07-12 Buxton Elektrische schaltervorrichtung
FR2330068A1 (fr) * 1975-10-30 1977-05-27 Taylor John Procede et appareil pour former des organes d'actionnement bimetalliques thermosensibles a action brusque
GB2124429A (en) * 1982-07-29 1984-02-15 Otter Controls Ltd Bimetallic actuators

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2286053A (en) * 1940-09-10 1942-06-09 Westinghouse Electric & Mfg Co Thermostat
US2834853A (en) * 1957-04-12 1958-05-13 Essex Wire Corp Snap-acting bimetal device
DE2300333A1 (de) * 1972-01-04 1973-07-12 Buxton Elektrische schaltervorrichtung
FR2330068A1 (fr) * 1975-10-30 1977-05-27 Taylor John Procede et appareil pour former des organes d'actionnement bimetalliques thermosensibles a action brusque
GB2124429A (en) * 1982-07-29 1984-02-15 Otter Controls Ltd Bimetallic actuators

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992012524A1 (en) * 1991-01-04 1992-07-23 Otter Controls Limited Thermally responsive electric switch
DE19545998A1 (de) * 1995-12-09 1997-06-12 Hofsaes Marcel Schalter mit einem bei Übertemperatur schaltenden Schaltwerk
DE19545998C2 (de) * 1995-12-09 1998-05-20 Hofsaes Marcel Schalter mit einem bei Übertemperatur schaltenden Schaltwerk
US5835001A (en) * 1995-12-09 1998-11-10 Hofsaess; Marcel Temperature-dependent switch having a movable contact carrying a heating resistor
EP1296344A2 (de) * 2001-09-24 2003-03-26 Texas Instruments Incorporated Leistungschalter
EP1296344A3 (de) * 2001-09-24 2004-06-16 Texas Instruments Incorporated Leistungschalter

Also Published As

Publication number Publication date
EP0376660A3 (de) 1991-09-25
GB2227884A (en) 1990-08-08
GB8830299D0 (en) 1989-02-22

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