US3771090A - Temperature responsive switch - Google Patents

Temperature responsive switch Download PDF

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Publication number
US3771090A
US3771090A US00261491A US3771090DA US3771090A US 3771090 A US3771090 A US 3771090A US 00261491 A US00261491 A US 00261491A US 3771090D A US3771090D A US 3771090DA US 3771090 A US3771090 A US 3771090A
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United States
Prior art keywords
lever
spring
working element
casing
force
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Expired - Lifetime
Application number
US00261491A
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English (en)
Inventor
J Andresen
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Danfoss AS
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Danfoss AS
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Publication date
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Publication of US3771090A publication Critical patent/US3771090A/en
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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
    • H01H37/36—Thermally-sensitive members actuated due to expansion or contraction of a fluid with or without vaporisation

Definitions

  • the invention relates to a temperature responsive switch assembly of the type having a pivotally mounted lever attached to a snap action spring with the lever being pivotally movable in response to opposing forces provided by a rated spring and a vapor containing working element, The moving contact of the switch is attached to the lever.
  • the vapor pressure curve of the working element is not linear, the temperature differentials between the switch on and off temperatures are kept substantially constant for the whole range of nominal temperature'settings for the system.
  • This object is achieved by an arrangement in which the line of force of the rated spring forms an acute angle with the lever which angle is of a selected magnitude that compensates for the nonlinearity of the vapor pressure curve of the working element is provided.
  • the invention relates to a temperature responsive assembly of the snap action type.
  • the assembly comprises a rigid lever, a snap action spring, a vapor containing working element and an adjustable rated-value spring which counteracts the working element.
  • the snap action spring in particular a spring having the shape of the Greek letter omega, has a negative spring characteristic in the working direction.
  • the snap over action therefore takes place when the difference between the forces applied by the working element and the ratedvalue spring exceed the force of the snap action spring in the rest position.
  • These switches are therefore called force-proportional springs in contrast to distanceproportional springs in which at least one lever of the snap action system must be moved through a dead-cent position before the snap-over action takes place.
  • the temperature difference i.e., the difference between the switch-on temperature and the switch-off temperature varies with each nominal temperature to which the system is set. It is however desirable to keep this difference approximately constant over the entire working range. It is therefore known practice in the case of temperature responsive actuating devices comprising a vapor containing working element and a rated value spring, so to design this spring that the steepness of the spring characteristic curve increases as the spring force rises, so that the spring characteristic curve resembles the vapour pressure curve. In the case of force proportional temperature responsive switches, compensation cannot be achieved in this way.
  • a force proportional temperature responsive switch in which use is made of a double-armed lever.
  • the working element and the rated value spring are arranged side-by-side, one on each side of the point of rotation, and act on the lever over an angle of 90.
  • the working el-' ement and the rated-value spring are arranged coaxially with each other. They engage a common rod. The rod transmits the difference in force to the lever.
  • the object of the present invention is to provide a force proportional temperature responsive switch which is at least partially compensated.
  • this object is achieved by an arrangement in which the line along which the rated value spring applies force forms with the lever an angle that deviates from 90 to an extent such that the effect of the bend in the vapour pressure curve on the difference in the switching temperatures is at least partially compensated.
  • the angle between the line along which the force of the rated value spring is applied and the lever is 60 80, and preferably 65- 75.
  • a particularly space saving construction is obtained if the lever consists of two arms which form an obtuse angle with each other, and if the rated value spring engages that arm remote from the snap action spring and extends substantially parallel with the arm presented to the snap action spring.
  • the switch can then be formed as a very compact unit by fitting the working element and the contact system side-by-side on that side of the arm presented to the snap action spring that is opposite thev rated value spring.
  • FIG. 1 is a diagrammatic illustration of a form of construction in accordance with the invention.
  • FIG. 2 is a graph of the vapour pressure curve and the forces occurring at the springs
  • FIG. 3 is a longitudinal section through a temperature responsive switch in accordance with the invention.
  • FIG. 4 is a cross section on the line A-A of FIG. 3.
  • the temperature responsive switch comprises a snapaction system which consists of a double-armed lever l and a spring 2 of the shape of the Greek letter omega.
  • the lever is adapted to rotate about a pivot 3 solid with the casing. It forms a link 4 with the spring 2.
  • This spring is secured on a backing element 5 which is solid with the casing and which may be adjustable.
  • the lever consists of two arms 6 and 7.
  • the force Pd of a working element is applied perpendicularly to the arm 6.
  • the force P of the rated value spring is applied at an angle a of 60 80 and preferably
  • the rated value spring is a tension spring which can be elongated in the direction of its force line.
  • Mounted on the lever arm 6 is an electric contact 8 which cooperates with a fixed contact 9. In this arrangement this latter contact also acts as a mechanical stop.
  • the at-rest position is determined by a stop 10 solid with the casing. Consequently, when the snap-over action occurs, the lever 1 can swing through an angle 3,
  • the vapour pressure P,, of the working element is plotted against temperature; on the right are illustrated the forces occurring in the snapaction system at different positions and for different settings of the rated value spring.
  • the force curve is shown against the angle of swing B.
  • the range of swing is limited to the angle 3,.
  • the omega spring 2 has a negative characteristic curve c in this range. For a first setting of the rated value spring giving a small force P, a force having the characteristic curve c and acting on the lever l is obtained in the range of swing, and for a greater force P the characteristic curve c, is obtained.
  • the characteristic curve c results.
  • the forces determined by these characteristic curves counteract the force of the vapor pressure curve P,. If, for the first setting, the vapour pressure moves up past to the point a the system snaps over and the working .point moves from b to 0. Only when the vapour pressure has dropped below the point d does the system snap back into the initial position. Similar conditions are obtained with the second setting. When the point e is exceeded, the system snaps from f to g. It only snaps back again when the vapour pressure falls below point h.
  • the effective spring characteristic curve (steepness decreasing as force increases), here of interest, is obtained by causing the rated value spring to apply force to the lever 1 along a line that is at an angle of a to the lever.
  • the force of the rated value spring which counteracts the force P varies in proportion to its elongation, the rise in the characteristic curve that takes place in the angle of swing B surprisingly does not remain constant, but decreases as the force increases.
  • FIGS. 3 and 4 illustrate a practical form of construction of the temperature responsive switch of the invention.
  • the lever 1 having two arms 6 and 7 is fitted in a casing 11.
  • the lever 1 simply rests on the bearing 3 solid with the casing, and is drawn towards the fixed bearing 3 with the aid of the rated value springs which take the form of tension springs 26.
  • the rated value springs 26 are held at their other, ends by backing elements 12.
  • backing elements 12 are mounted on screw threaded members 13.
  • the latter members are secured to a slide 14 which can be displaced by means of a cammed disc 15 on an adjusting spindle 16 for the purpose of setting to the required value.
  • a working element 17 is formed by a tubular bellows 18 and a part 19 of the casing.
  • a capillary tube 20 communicates with a sensor, not illustrated. The temperature of the sensor determines the vapour pressure in the working element 17.
  • the end face of the tubular bellows l8 acts on a raised portion 21 on the lever arm 6.
  • the first step is not formed by a fixed contact 9 but by a part 22 of the casing, which part surrounds a contact system 23.
  • the lever arm 6 acts on a plunger 24 which in turn acts on a spring 25 carrying the movable contact of the system 23.
  • FIG. 4 parallel shows that two rated-value springs are arranged side-by-side and aprallel with each other, and that the stops 10 are disposed symmetrically, one on each side of a line of symmetry.
  • omega spring another type of snap action spring may be used that has a negative characteristic curve in the working range.
  • the idea underlying the invention may also be applied to snap action systems having a single anned lever, and to such levers in which the lines along which the forces of the working element and the rated value spring run to the same point on the lever.
  • a temperature responsive switch assembly comprising a casing, a rigid lever in said casing, pivot means for mounting said lever for pivotal movement relative to a fixed part of said casing, a snap action spring between said lever and said casing, a working element positioned between and connected to said casing and said lever, said working element having a moving part for applying forces to said lever on one side of said pivot means, said working element having a nonlinear vapor pressure curve, spring means attached to said casing and said lever for applying forces to said lever which oppose said working element applied forces to said lever, said spring means forces being applied to said lever on the side of said pivot means opposite said one side,
  • said spring means having a line force forming an angle with said lever so that the reaction response of said I spring means parallels said working element nonlinear vapor pressure curve.
  • a temperature responsive switch assembly in which said lever has two arms forming an obtuse angle with the apex thereof concident with said pivot means, said working element being in contact with one of said lever arms, said spring means being attached to the other of said lever arms with said I other of said arms.

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
  • Mechanical Control Devices (AREA)
US00261491A 1971-06-08 1972-06-08 Temperature responsive switch Expired - Lifetime US3771090A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2128415A DE2128415C3 (de) 1971-06-08 1971-06-08 Thermostat Schalter

Publications (1)

Publication Number Publication Date
US3771090A true US3771090A (en) 1973-11-06

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ID=5810178

Family Applications (1)

Application Number Title Priority Date Filing Date
US00261491A Expired - Lifetime US3771090A (en) 1971-06-08 1972-06-08 Temperature responsive switch

Country Status (13)

Country Link
US (1) US3771090A (ja)
JP (1) JPS519912B1 (ja)
AR (1) AR192454A1 (ja)
BR (1) BR7203663D0 (ja)
CH (1) CH535489A (ja)
DD (1) DD96802A5 (ja)
DE (1) DE2128415C3 (ja)
DK (1) DK137415C (ja)
ES (1) ES403579A1 (ja)
FR (1) FR2140505B1 (ja)
GB (1) GB1399714A (ja)
IT (1) IT959064B (ja)
PL (1) PL82677B1 (ja)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2705545A1 (de) * 1976-02-10 1977-08-11 Ranco Inc Temperatur- oder druckabhaengige schaltvorrichtung

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
YU43548B (en) * 1983-07-08 1989-08-31 Eta Cerkno Thermostat for refrigerators with constant engaging and resetable disengaging temperature

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1915265A (en) * 1928-12-29 1933-06-20 Frigidaire Corp Thermostat for refrigerating apparatus
US1976843A (en) * 1932-07-09 1934-10-16 Edison General Elec Appliance Electrical switch
US2184339A (en) * 1937-11-12 1939-12-26 Edison General Elec Appliance Temperature control device
US3412357A (en) * 1967-01-24 1968-11-19 Kk Condition responsive switch

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1915265A (en) * 1928-12-29 1933-06-20 Frigidaire Corp Thermostat for refrigerating apparatus
US1976843A (en) * 1932-07-09 1934-10-16 Edison General Elec Appliance Electrical switch
US2184339A (en) * 1937-11-12 1939-12-26 Edison General Elec Appliance Temperature control device
US3412357A (en) * 1967-01-24 1968-11-19 Kk Condition responsive switch

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2705545A1 (de) * 1976-02-10 1977-08-11 Ranco Inc Temperatur- oder druckabhaengige schaltvorrichtung
FR2341193A1 (fr) * 1976-02-10 1977-09-09 Ranco Inc Groupe commutateur sensible a la temperature ou a la pression

Also Published As

Publication number Publication date
DK137415C (da) 1978-07-31
GB1399714A (en) 1975-07-02
DK137415B (da) 1978-02-27
FR2140505A1 (ja) 1973-01-19
DE2128415C3 (de) 1973-12-13
DE2128415A1 (de) 1972-12-14
AR192454A1 (es) 1973-02-21
PL82677B1 (ja) 1975-10-31
DD96802A5 (ja) 1973-04-05
ES403579A1 (es) 1975-05-01
CH535489A (de) 1973-03-31
BR7203663D0 (pt) 1973-06-28
DE2128415B2 (de) 1973-05-30
FR2140505B1 (ja) 1977-12-23
IT959064B (it) 1973-11-10
JPS519912B1 (ja) 1976-03-31

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