US3434089A - Relay with voltage compensation - Google Patents

Relay with voltage compensation Download PDF

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Publication number
US3434089A
US3434089A US518297A US3434089DA US3434089A US 3434089 A US3434089 A US 3434089A US 518297 A US518297 A US 518297A US 3434089D A US3434089D A US 3434089DA US 3434089 A US3434089 A US 3434089A
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United States
Prior art keywords
blade
heater
relay
bimetal
contacts
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Expired - Lifetime
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US518297A
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English (en)
Inventor
Joseph W Waseleski Jr
Francis P Buiting
Bernard M Kulwicki
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Texas Instruments Inc
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Texas Instruments Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H61/00—Electrothermal relays
    • H01H61/02—Electrothermal relays wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
    • H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
    • H01C7/022—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient mainly consisting of non-metallic substances

Definitions

  • Another embodiment shows a PTC heater pill mounted on a support with an air gap of a predetermined size separated the heater from the bimetallic blade to provide a time delay of a desired amount.
  • Still another embodiment shows a cantilever mounted support for the heater pill so that the air gap will vary as the bimetallic blade flexes due to heat generated by the heater.
  • the use of the PTC material minimizes the effects of voltage variations on temperature and the use of the air gap as thermal barrier results in voltage compensation.
  • This invention relates to electrical relays and more particularly to thermal time delay relays.
  • the present invention while having more general uses, is particularly useful in applications for controlling an auxiliary heater for a heat pump (e.g., a space heater) and as a time delay control for air conditioners or for compressors in refrigeration systems.
  • a heat pump e.g., a space heater
  • a time delay control for air conditioners or for compressors in refrigeration systems.
  • an improved thermal time delay relay adapted to control an electrical circuit; the provision of such an improved thermal relay which includes ambient compensated thermally responsive actuating means as well as being voltage compensated; the provision of a thermal relay having means to prevent overheating and burn out problems; the provision of such a relay with rapid response; the provision of a thermal relay of the class described which includes snap-acting switch means; and the provision of a time delay relay of the class described which is simple in construction, compact in form and economical to assemble and manufacture.
  • the invention accordingly comprises the elements and combination of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described and the scope of which will be indicated in the appended claims.
  • FIG. 1 is a top plan view of a switch according to the present invention.
  • FIG. 2 is an enlarged sectional view taken on line 2--2 of FIG. 1;
  • FIG. 3 is a bottom plan view of the switch shown in FIG. 1;
  • FIG. 4 is a partial top plan view of a second embodiment of the present invention.
  • FIG. 5 is a vertical cross section taken on line 5-5 of FIG. 4;
  • FIG. 6 is a view similar to FIG. 5 but showing a third embodiment of the invention.
  • FIG. 7 shows resistivity v. temperature. curves for several materials useful in our invention.
  • Relay or switch 10 includes a housing 12 formed of a conventional electrically insulating material such as a moldable phenolic resinous material. As best seen in FIG. 2, housing 12 includes a base 14 and a peripherally extending skirt portion 16 on one side thereof, defining a cavity 18 for reception therein of electrically conductive snap-acting switch means generally indicated at numeral 40. Housing 12 also includes a plurality of upstanding wall portions 20, 22, 24 and 26 on the other side of base 14 which define a cavity 30 for reception of thermally responsive actuator means generally indicated at 70 and which will be described in greater detail below. Cover members (not shown) may be connected to the housing 12 to close cavities 18 and 30 after assembly of switch 10 has been completed.
  • snap-acting switch means 40 is received within housing cavity 18 and comprises an electrically conductive flexible blade 42 cantilever mounted adjacent one end 44 thereof, on base 14. End 44 is firmly clamped between, and secured to base 14 and an electrically conductive terminal 46 by means of a rivet 48 which also electrically connects blade 42 to terminal 46.
  • the free end of blade 42 carries a pair of electrical contacts 50 and 52 on opposite sides thereof, as best seen in FIG. 2, for alternate engagement, respectively, with electrical contacts 54 and 56 which are respectively carried by electrical terminals 58 and 60.
  • Housing 12 supports and mounts terminals 58 and 60 on opposite sides of blade 42 and in the path of movement thereof, as best seen in FIGS. 2 and 3.
  • Contacts 50, 52, 54 and 56 are formed of a suitable electrical current-conducting material such as silver or the like.
  • Blade 42 is formed of a suitable highly electrically conductive spring material such as, for example, a beryllium-copper alloy or a Phosphor bronze alloy.
  • a spring member 62 is provided which is flexed into a U-shaped form (as seen in FIG. 2), with one end thereof connected with the blade 42 adjacent the contact-carrying end thereof, and the other end of the spring member connected with a centrally located tongue 64 formed integrally with the blade 42 as by blanking out portions of the center of the blade. Tongue 64 extends from its integral connection with end 44 of the blade toward the free contact-carrying end of the blade. As best seen in FIGS. 2 and 3, tongue 64, ad-
  • Snap-acting means 40 can be either of the so-called bistable or monostable types, depending upon the spacing between the stationary contacts 54 and 56 relative to the neutral position of the blade 42, movement beyond which in either direction will cause snap-acting or over-centering movement.
  • Switch means 40 as illustrated by way of example in FIG. 2, is of the monostable type and contacts 52 and 56 are normally closed, so that upon removal of a force applied against tongue 64 to cause snap opening of contacts 52 and 56, blade 42 will automatically snap back to the FIG. 2 solid line position to reclose contacts 52 and 56.
  • Thermally responsive actuating means Switch also includes a thermally responsive actuating means generally indicated at numeral 70 for causing snap action of means 40 to effect contact actuation.
  • Means 70 comprises two blade members 72 and 74, each of which are formed of a composite bimetallic thermally responsive material having a relatively high expansion component and a relatively low expansion component, as best seen in FIG. 2.
  • Member 72 as best seen in FIG. 1 is in the form of a frame and provides a substantially rectangular shaped window opening 76 which is defined by four legs 78, 80, 82 and 84.
  • Member 72 can be formed from a sheet by a simple punching or blanking operation.
  • Member 74 is substantially T-shaped and includes a transversely extending end portion 86. As best seen in FIGS.
  • end portion 86 and leg 84, respectively, of bimetal members 74 and 72 are arranged in stacked overlying relationship and mutually separated by a thermally and electrically insulating strip 90 formed, for example, of mica.
  • This stacked assembly is cantilever mounted on an extension 92 of an electrically conductive terminal member 94 by means of a pair of rivets 96.
  • a thermally and electrically insulating strip 98 (formed, for example, of mica) separates bimetal member 74 from terminal portion 92. Rivets 96 not only serve to firmly cantilever mount the bimetal blade-insulator assembly but also serve to electrically connect bimetal member 72 with terminal 94.
  • a lost motion connection for the other ends of bimetal members or blades 72 and 74 is provided by a bifurcated portion on the other end of member 74 as defined by fingers 102, 104 and 106, which receive and sandwich therebetween, leg 80 of member 72.
  • This connection permits relative sliding movement between the free ends of members 72 and 74 in a direction along the plane of these members, to avoid creating undesirable stresses and also confines upward and downward movement (as seen in FIG. 2) of the free ends of these members to movement in unison.
  • Leg 80 is provided with a dimpled portion 110 which is positioned to engage one end of a motion transfer pin 112 which is slidably received in an aperture 114 provided by base 14 of the housing 12.
  • pin 112 is positioned to engage the dimpled portion 66 on the central tongue 64 of the snap-acting blade 40 to cause tongue 64 to move in response to unitary movement of bimetal members 72 and 74 to effect snap-acting motion of blade 40.
  • bimetal blades 72 and 74 are made up as a separate subassembly which is thereafter mounted on the housing by means of a threaded fastener 100.
  • the bimetal members 74 and 72 are arranged and constructed to provide for ambient compensation.
  • the inside bimetal components of the blades as are nearest one another or those which face one another have relatively similar coefficients of thermal expansion, i.e., these components either both have relatively low coefiicients of thermal expansion or both have relatively high coetficients of thermal expansion. It is preferred (but not essential) that blades 72 and 74 be formed of the same or similar bimetal material.
  • member 74 Upon heating of member 74 to a temperature different from that of member 72, member 74 will exert a flexing force against member 72 which is greater than the opposing flexing force exerted by member 72 against member 74, which will cause the free ends of members 72 and 74 to move in unison either downwardly or upwardly depending on whether the inside components of the blades have relatively low or relatively high coeflicients of thermal expansion.
  • the inside components of the blades have relatively low coefiicients of thermal expansion so that upon suitable differential heating of member 74, downward movement (as seen in FIG. 2) in unison of the free ends of members 72 and 74 will take place.
  • Relay 10 includes an electrical heater 119 which, in the FIGURES 1-3 embodiment, comprises a plurality of pieces or pills 120. Three are shown but the number is a matter of choice. Electrically conducting layers 122 and 124, formed of silver, for example, are attached in a conventional manner to opposite faces of each pill 120. Pills 120 are located in close thermal juxtaposition to bimetal member 74, and in the FIGS. l-3 embodiment is electrically separated therefrom by a layer of electrically insulating material 126, which may, for example, be mica. Layers 122 are electrically connected by conductors 125 to an electrically conductive terminal 126 which is located intermediate upstanding portions 24 and 26 of housing 12 and secured to base 14 by means of rivet 127.
  • Layers 124 are electrically connected by conductors 128 to bimetal member 72 which is in turn electrically connected to terminal 94.
  • Pills 120 are electrically connected in parallel. Pills 120 are constructed of material which has a steep-positive-sloped resistivity-temperature curve (hereinafter referred to as PTC material). This will be explained in greater detail below.
  • PTC material steep-positive-sloped resistivity-temperature curve
  • Heater 119 may be mounted, as seen in FIGURES 4 and 5, by mounting pill 120 on layer 132 of an electrical and thermal insulation material such as a polycarbonate, which is separated from bimetal member 74 by portions or bosses 130, 131 to produce an air gap of a predetermined size.
  • an electrical and thermal insulation material such as a polycarbonate
  • the time required for member 74 to flex due to differential heating is dependent upon the thermal conductivity between the heater and member 74.
  • the air gap is, of course, a thermal insulator. It will be obvious that other thermal insulation material can be used to effect the same result.
  • FIGURE 6 shows a similar mounting but utilizes only one mounting portion or boss 131 so that the air gap between heater 119 and bimetal 74 will vary as bimetal 74 flexes due to heat generated by heater 119.
  • great flexibility can be effected in the opening and closing characteristic of the switch by the mounting of the heater elements as described.
  • relay 10 Operation of relay 10 is as follows: Contacts 52 and 56 are normally closed, as shown in the FIG. 2 solid line position of the parts. Upon a change in ambient temperature (e.g., an increase) bimetal blades 72 and 74 will tend to flex in directions opposite to each other to produce substantially equal opposing forces with the result that little or no motion of the bimetal members takes place. However, when heater 119 is electrically energized (by the circuit in which terminals 94 and 126 are connected),
  • member 74 becomes heated to a temperature different from that of member 72. This results in a downward flexure force (as seen in FIG. 2) exerted by member 74 which is greater than the opposing upward flexure force exerted by bimetal member 72 causing downward movement in unison of the free ends of members 74 and 72 from the solid line to the broken line position shown in FIG. 2.
  • the U-shaped portion of frame 72 defined by legs 78, 80 and 82 which projects from the cantilever mounted end leg 84 advantageously is relatively thermally isolated from heater 119 by the spacing between legs 78 and 82 from blade 74 which is positioned therebetween in the window opening 76, as best seen in FIG. 1.
  • blade 72 does not become heated to any substantial extent by heater 119.
  • Insulators 90 and 98 further serve to minimize heat transfer between blades 72 and 74 and between heater 119 and blade 72 so that the heat generated by heater 119 is directed primarily to the blade 74 to raise the temperature of the latter above that of the ambient compensating blade 72 to produce desired contact actuating motion of the free ends of these members.
  • Locating member 74 in the window opening 76 intermediate legs 78 and 82 in addition to providing for a compact construction also permits a substantial portion of the length of blade member 74 to lie substantially in the same plane as or at least very close to the plane of legs 78 and 82, which avoids or at least minimizes creation of undesirable stresses upon temperature change which might tend to twist or rotate the free end of blade 72. This also simplifies the construction and assembly of parts, and provides for compact construction.
  • leg 84 of blade 72 and portion 86 of blade 74 can be omitted and the unjoined ends of legs 78, 82 and of blade 74 can be cantilever mounted in the same plane on terminal 94 so that a greater portion of member 74 will lie substantially in the same plane with legs 78 and 82 to further minimize creation of undesirable twisting stresses and moments at the free ends of these members 72 and 74, when the latte'r flex in response to temperature change.
  • a heater which electrical resistance increases rapidly in region of the control temperature.
  • Such material include the semiconducting barium titanate ceramics and certain plastics such as carbon-black loaded, cross-linked polyethylene.
  • FIGURE 7 shows typical resistivity temperature curves. Curve A is for Ba- 997La 003TiO3; curve B is for carbon black filled, cross-linked polyethylene; and C is for soa nss ooa s- Heaters constructed from such PTC materials cannot overheat due to the tremendous increase in resistance over a very narrow temperature range.
  • Such heaters selfheat to the control temperature (located in the near vertical portion of the curves in FIG. 7). A change in voltage causes very little shifting of the curves in FIG. 7 so that the temperature is more or less independent of the applied voltage.
  • the present invention provides for a thermal time delay relay (the time delay resulting from the time interval required for transferring heat from heater 120 to blade 74 and raising its temperature sufiiciently to overcome the opposing fiex-ure force of blade 72), which is essentially independent of voltage, has a rapid response time due to the initial low resistance of the PTC element yet has a very high resistance at elevated temperature preventing burning out with higher voltage.
  • a voltage compensated electrical switch comprising a base; contacts mounted on the base; thermostatic means including an elongated thermostatic element mounted on the base to provide contact actuation motion for the contacts; an elongated generally fiat support having two ends composed of electrical insulating material; a plurality of bosses of thermal insulation mounting the support to and spacing the support from the thermostatic element; and a heater composed of a steep-sloped PTC material located on the support and separated from the thermostatic element by the support and the spacing whereby the transfer of heat from the heater to the thermostatic element is impeded.
  • PTC material is selected from the group consisting of carbon black filled, cross-linked polyethylene and doped barium titanate.
  • a voltage compensated electrical switch comprising a base; contacts mounted on the base; thermostatic means including an elongated thermostatic element mounted on the base to provide contact actuation motion for the contacts; an elongated generally flat support having two ends composed of thermal and electrical insulating material; a mounting boss located on one end of the support and cantilever connecting the support to the thermostatic element; and a heater located on the support intermediate the boss and the other end and spaced from said bimetal, the heater comprising a steep-sloped PTC element selected fi'om the group consisting of carbon black filled, polyethylene and doped barium titanate, whereby the space between the PTC heater and the thermostatic element will vary with flexing of the thenmostatic element.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Ceramic Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermally Actuated Switches (AREA)
US518297A 1966-01-03 1966-01-03 Relay with voltage compensation Expired - Lifetime US3434089A (en)

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3521138A (en) * 1967-04-05 1970-07-21 Danfoss As Thermal starting device for a singlephase asynchronous motor
US3696611A (en) * 1969-09-17 1972-10-10 Scovill Manufacturing Co Thermal motors
US3944787A (en) * 1973-12-26 1976-03-16 Texas Instruments Incorporated Heater on metal composites
US4042860A (en) * 1975-10-21 1977-08-16 General Electric Company Combination starter-protector device
US4084202A (en) * 1974-09-23 1978-04-11 General Electric Company Combination starter-protector device, method of protecting a dynamoelectric machine, and circuit
US4174511A (en) * 1977-03-24 1979-11-13 Robert Bosch Gmbh Bimetal device with an electrical heating element
US4237508A (en) * 1978-09-08 1980-12-02 General Electric Company Electrical control
US4355458A (en) * 1978-09-08 1982-10-26 General Electric Company Method of making an electrical control
US4450496A (en) * 1979-08-16 1984-05-22 Raychem Corporation Protection of certain electrical systems by use of PTC device
US5214310A (en) * 1990-11-29 1993-05-25 Emerson Electric Co. Timing mechanism with a PTC thermistor
US5844465A (en) * 1995-12-18 1998-12-01 Texas Instruments Incorporated Temperature compensated time-delay switch
US20090224864A1 (en) * 2008-03-05 2009-09-10 Moeller Gebaudeautomation Gmbh Switching device

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2628597C3 (de) * 1976-06-25 1979-07-19 Ellenberger & Poensgen Gmbh, 8503 Altdorf Verriegelungsvorrichtung für Türen u.dgl. an elektrisch betriebenen Geräten
GB9418221D0 (en) * 1994-09-09 1994-10-26 Strix Ltd Energy regulators

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1569804A (en) * 1923-03-10 1926-01-12 Trumbull Electric Mfg Co Relay construction
US2172189A (en) * 1937-03-13 1939-09-05 Westinghouse Electric & Mfg Co Control for range heat
US2758175A (en) * 1952-04-12 1956-08-07 Gen Controls Co Voltage compensated thermal timer switch
US3064103A (en) * 1958-05-22 1962-11-13 Controls Co Of America Variable thermostat anticipator
US3205327A (en) * 1963-02-11 1965-09-07 Texas Instruments Inc Time delay relay having ambient compensated thermally responsive actuating means
US3243753A (en) * 1962-11-13 1966-03-29 Kohler Fred Resistance element
US3338476A (en) * 1965-10-24 1967-08-29 Texas Instruments Inc Heating device for use with aerosol containers

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1569804A (en) * 1923-03-10 1926-01-12 Trumbull Electric Mfg Co Relay construction
US2172189A (en) * 1937-03-13 1939-09-05 Westinghouse Electric & Mfg Co Control for range heat
US2758175A (en) * 1952-04-12 1956-08-07 Gen Controls Co Voltage compensated thermal timer switch
US3064103A (en) * 1958-05-22 1962-11-13 Controls Co Of America Variable thermostat anticipator
US3243753A (en) * 1962-11-13 1966-03-29 Kohler Fred Resistance element
US3205327A (en) * 1963-02-11 1965-09-07 Texas Instruments Inc Time delay relay having ambient compensated thermally responsive actuating means
US3338476A (en) * 1965-10-24 1967-08-29 Texas Instruments Inc Heating device for use with aerosol containers

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3521138A (en) * 1967-04-05 1970-07-21 Danfoss As Thermal starting device for a singlephase asynchronous motor
US3696611A (en) * 1969-09-17 1972-10-10 Scovill Manufacturing Co Thermal motors
US3944787A (en) * 1973-12-26 1976-03-16 Texas Instruments Incorporated Heater on metal composites
US4084202A (en) * 1974-09-23 1978-04-11 General Electric Company Combination starter-protector device, method of protecting a dynamoelectric machine, and circuit
US4042860A (en) * 1975-10-21 1977-08-16 General Electric Company Combination starter-protector device
US4174511A (en) * 1977-03-24 1979-11-13 Robert Bosch Gmbh Bimetal device with an electrical heating element
US4237508A (en) * 1978-09-08 1980-12-02 General Electric Company Electrical control
US4355458A (en) * 1978-09-08 1982-10-26 General Electric Company Method of making an electrical control
US4450496A (en) * 1979-08-16 1984-05-22 Raychem Corporation Protection of certain electrical systems by use of PTC device
US5214310A (en) * 1990-11-29 1993-05-25 Emerson Electric Co. Timing mechanism with a PTC thermistor
US5844465A (en) * 1995-12-18 1998-12-01 Texas Instruments Incorporated Temperature compensated time-delay switch
US20090224864A1 (en) * 2008-03-05 2009-09-10 Moeller Gebaudeautomation Gmbh Switching device
US8026785B2 (en) * 2008-03-05 2011-09-27 Moeller Gebäudeautomation GmbH Switching device

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FR1509244A (fr) 1968-01-12
GB1156810A (en) 1969-07-02

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