US3562690A - Snap-acting thermostatic element and method for making same - Google Patents

Snap-acting thermostatic element and method for making same Download PDF

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Publication number
US3562690A
US3562690A US819868A US3562690DA US3562690A US 3562690 A US3562690 A US 3562690A US 819868 A US819868 A US 819868A US 3562690D A US3562690D A US 3562690DA US 3562690 A US3562690 A US 3562690A
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United States
Prior art keywords
snap
strip
pair
deformations
acting
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Expired - Lifetime
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US819868A
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English (en)
Inventor
Hamlet D Vezza
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Texas Instruments Inc
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Texas Instruments Inc
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Publication date
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    • 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
    • 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

Definitions

  • a thermally responsive multimetallic element formed with a dished area to make it snap-acting is provided with a plurality of deformations formed in pairs in the dished portion of the strip with each pair comprising two points and ridge connecting each point in a pair with a corresponding point in the adjacent pair. These deformations enhance the snap characteristics of the element and reduce creep prior to snap action of the element from one configuration to another at a critical temperature.
  • This invention relates to improvements in snap-acting thermostatic elements and the like.
  • FIG. 1 is a perspective view of a thermostatic element before forming in accordance with the invention
  • FIG. 2 shows the same element after it has been formed in accordance with the invention and showing means to accomplish this formation
  • FIG. 3 is a side elevation partly in section of a switch made in accordance with the invention.
  • thermostatic element 10 which is in the form of an elongated strip having at one end a generally rectangular mounting portion 12 with an aperture 13 provided therein and at the opposite end, a portion 14 which mounts an electrical contact 17 by conventional means such as welding.
  • a typical size for the element shown is in the order of long by wide.
  • This thermostatic element 10 may, for example, be formed of bimetallic material having a layer of metal of a comparatively high thermal coeflicient 3,562,690 Patented Feb. 9, 1971 of expansion on its lower side as viewed in FIG. 3, and a layer of metal with a lower coefficient of expansion on its upper side. Because of the thinness of the element 10, the two layers are not indicated on the drawings.
  • element 10 is formed with a curved portion, that is, it is dished upwardly as indicated in FIG. 3 to cause the element to snap between the solid and dotted line configurations shown in FIG. 3.
  • Reference numeral 10' indicates a strip formed as a snap-acting element. When the element is cool, it is in the position shown by the solid line. Upon heating it to a predetermined critical temperature, the greater expansion of the lower layer of metal relative to the upper layer of metal causes the element to snap upward to the FIG- 3 dotted line position. Thereafter, on cooling of the strip to another predetermined critical temperature, the strip will snap back to the solid line position.
  • Element 10 can be cantilever mounted on a support such as electrical insulating base 15, by conventional securing means, such as screw 16, which is inserted through aperture 13 into base member 15.
  • Movable contact 17 mounted on portion 14 of element 10 is adapted to engage and disengage with stationary contact 18 mounted on base 15 as indicated by the .solid and dotted line positions in FIG. 3, and hence, with terminals (not shown) connected to stationary contact '18 and portion 12 of element 10, controls the opening and closing of an electrical circuit.
  • Other types of thermally responsive sheet materials may be employed such as other multimetallic structures as well as elements of other shapes.
  • Forming die 20 and die punch 22 are used to form the dished portion of the strip. Included in the forming die 20 are a plurality of interconnected recesses such as bores 24, 26, 28. The intersections of these recesses are shown at 25a, 25b, 27a and 2712. Forming die 20 and forming punch 22 are movable relative to one another as by plunger 23 attached to punch 22. The bottom surface of punch 22 which is concave and the top surface of die 20 which is convex have the same contour except for the recesses formed in die 20.
  • the surface is made up of two radii, one causing curvature along the length of the die and punch (arcs 31 and 30 of die 20 and punch 22 respectively), and the second causing curvature along the width of the die and punch (arcs 33, 32 of die 20 and punch 22 respectively).
  • the points are located in pairs, each point in a pair preferably equidistant from longitudinal axis 2 and" each pair equidistant from a chosen latitudinal axis 4.
  • the location of axis 4 controls the effective center of snapping of the strip along longitudinal axis 2 as can be seen in FIG. 3. It will be understood that more than two pairs of points can be provided if desired. While in some cases, one pair can be employed to achieve the objects of the invention, it is necessary to use a plurality of deformations. While in the description the deformations are formed in the element in the same operation as the forming of the dished area, it will be appreciated that a separate forming action to impart the deformations could be employed if desired. Further, it is within the purview of the invention to provide a greater number of recesses or to employ shapes other than circular, although it is preferable that they be smooth curves.
  • Snap acting elements made in accordance with the invention have many advantages, inter alia, they are more dependable, more predictable, have longer life, are easier to calibrate and have a greatly improved yield rate, improved by as much as 95 percent in some cases.
  • snapacting elements are made to snap at a selected temperature, e.g., 250 F.; however, there is necessarily some variation in the temperature at which the element snaps from one time to another.
  • This variation of range is typically in the order of to F. for elements not having deformations; however, it has been found that elements made in accordance with the invention having a temperature range nearly half that, approximately a 13 F. range. Further, the particular range is maintained for a longer period of time; that is, for more cycles, giving it a longer useful life than prior art elements.
  • Yet another advantage is that elements having the deformations are easier to calibrate.
  • One way to calibrate an element after it has been formed is to apply pressure to the element by a calibrating pin through the' movable contact.
  • the pin is moved a certain distance to effect the desired calibration. Without the deformations, this distance is very short and critical making it difficult to obtain accurate calibration.
  • an operator moves the pin approximately twice the distance. This makes it possible for a less skilled operator to calibrate an element even more accurately and in less time than a prior art element since there is less criticality involved in the movement of the pin per unit of distance.
  • Still another advantage is achieved since the deformations tend to prevent snap action for a longer period of time until the forces built up in the element concomitant with the temperature rise finally cause the element to snap, resulting in a greater amount of force exerted by the element.
  • This could be utilized, for instance, to transfer motion by a motion transfer member from the snapacting element to some other element to effect actuation or deactuation of a circuit isolated therefrom.
  • a snap acting thermostatic element comprising:
  • thermostatic strip formed with a dished surface portion responsible for the snapping of the element and plurality of deformations formed in pairs in the dished portion of the strip, each pair comprising two points and a ridge connecting each point in a pair with a corresponding point in an adjacent pair whereby the snap acting characteristics of the element are improved and creep movement prior to snap action is reduced.
  • An element as defined in claim 1 having a longitudinal axis in which each deformation of a pair is located on opposite sides of the longitudinal axis and equidistant therefrom.
  • a method of making a snap acting thermostatic element comprising the steps of (a) providing a multimetallic sheet of material,
  • An electrical switch comprising a base of electrically insulating material
  • thermally responsive bimetallic element having two ends formed with a dished portion causing it to snap act at a critical temperature from one configuration to an opposite configuration

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
  • Manufacture Of Switches (AREA)
US819868A 1969-04-28 1969-04-28 Snap-acting thermostatic element and method for making same Expired - Lifetime US3562690A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US81986869A 1969-04-28 1969-04-28

Publications (1)

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US3562690A true US3562690A (en) 1971-02-09

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US819868A Expired - Lifetime US3562690A (en) 1969-04-28 1969-04-28 Snap-acting thermostatic element and method for making same

Country Status (6)

Country Link
US (1) US3562690A (enrdf_load_stackoverflow)
JP (1) JPS5012788B1 (enrdf_load_stackoverflow)
CA (1) CA933903A (enrdf_load_stackoverflow)
FR (1) FR2040291A1 (enrdf_load_stackoverflow)
GB (1) GB1288160A (enrdf_load_stackoverflow)
NL (1) NL161611C (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4220938A (en) * 1979-02-12 1980-09-02 Emerson Electric Co. Thermostatic electrical switch
EP3073506A4 (en) * 2013-10-28 2017-06-07 Ubukata Industries Co., Ltd. Thermally actuated switch and molding die

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8322830D0 (en) * 1983-08-25 1983-09-28 Howard Butler Ltd Temperature sensitive switch
DE3709660C2 (de) * 1987-03-24 1994-11-24 Ymos Ag Ind Produkte Verschluß für ein Haushaltsgerät

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4220938A (en) * 1979-02-12 1980-09-02 Emerson Electric Co. Thermostatic electrical switch
EP3073506A4 (en) * 2013-10-28 2017-06-07 Ubukata Industries Co., Ltd. Thermally actuated switch and molding die
US10347450B2 (en) 2013-10-28 2019-07-09 Ubukata Industries Co., Ltd Thermally actuated switch and forming dies

Also Published As

Publication number Publication date
DE2020025B2 (enrdf_load_stackoverflow) 1972-11-16
CA933903A (en) 1973-09-18
DE2020025A1 (de) 1971-01-21
NL161611C (nl) 1980-02-15
NL7005890A (enrdf_load_stackoverflow) 1970-10-30
FR2040291A1 (enrdf_load_stackoverflow) 1971-01-22
JPS5012788B1 (enrdf_load_stackoverflow) 1975-05-14
GB1288160A (enrdf_load_stackoverflow) 1972-09-06

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