US2732461A - Bimetallic snap-action switch - Google Patents

Bimetallic snap-action switch Download PDF

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Publication number
US2732461A
US2732461A US2732461DA US2732461A US 2732461 A US2732461 A US 2732461A US 2732461D A US2732461D A US 2732461DA US 2732461 A US2732461 A US 2732461A
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United States
Prior art keywords
disk
bimetallic
contact
casing
switch
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Expired - Lifetime
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English (en)
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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
    • H01H37/5427—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting encapsulated in sealed miniaturised housing
    • 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
    • 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
    • H01H2037/5463—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting the bimetallic snap element forming part of switched circuit

Definitions

  • This invention relates to bimetallic snap-action switches such as employed for the supervision of electrical machines and other apparatus, and more particularly to switches which may be manufactured in ex tremely small sizes to respond to temperature changes at a critical point or zone of the controlled machine or apparatus.
  • Objects of the invention are to provide bimetallic snapaction switches in which domed bimetallic disks are housed in lenticular casings to act as switch blades coopcrating with relatively stationary contacts supported on and axially of one or both of the lenticular walls of the casing.
  • Other objects are to provide switches of the type stated in which the lenticular casing is formed of two plates with dished rims which meet at substantially the median plane of the casing and flare away from each other to provide two opposed seats against which the edge portion of the bimetallic disks rests in alternation according to the ambient temperature, the edge portion of the disk being confined between but not otherwise mechanically connected to the casing plates.
  • a further object is to provide switches of the character above-stated in which the relatively stationary contact or contacts of a switch are slidably mounted in bushings and springpressed towards the center of the bimetallic disk, and in which stops limit the movement of the relatively stationary contacts in different manners according to the desired operating characteristics of the switch.
  • Fig. 1 is a central vertical section through a switch embodying the invention.
  • Fig. 2 is an elevation of the same.
  • the reference numerals 1 and 2 identify two plates which preferably are of metal, as shown, and with dished rims which meet at substantially the median plane of the lenticular casing which is formed by bending the outer edge 3 of the plate 1 over and around the rim of the plate 2.
  • a narrow strip 4 is separated from the edge 3 and reversely bent to form a terminal lug for one branch of the control andalarm circuits, as will be described later.
  • the dished rim of the plate 2 terminates in a shallow radial flange 2 which spaces the adjacent rims apart and constitutes a seat for the edge of an imperforate domed bimetallic disk 5 which is designed and constructed in known manner to reverse curvature at the critical temperature at which the switch is to operate.
  • the disk 5 rests loosely on its flange seat 2' and has two stable end positions at which its outer edge portion bears against one or the other of the annular seats formed by the inner surfaces of the dished rims of the casing plates 1 and 2.
  • the bimetallic disk 5 constitutes a switch blade which moves between and in its alternate end positions engages one or the other of two relatively stationary contacts 7,
  • a metal bushing 9 extends through a central aperture of the plate l and is insulated therefrom by an intermediate washer 10 which fits within the plate aperture, and inner and outer washers 11, 12 of larger diameter.
  • the enlarged inner end 13 of the bushing 9 is clamped against the inner insulation sheet 11 by an outer nut 14 which is slotted radially to receive the insulating covering 15 of a terminal wire 16 which is clamped against the nut 14 by a nut 17 having an inturned flange which seats upon the nut 14 and compresses the insulation 15 to provide a sealed chamber for the terminal connection.
  • the bushing 9 is counterbored from the outer end to receive the contact 7 which has a flange 18 constituting a stop for limiting inward movement of the contact by a spring 19 seated between the flange and a disk or washer 29 which is retained in the bore by spinning over the outer end 21 of the bushing.
  • the terminal wire for the contact 8, and its insulating cover will be designated by primed numerals 16 and 15 respectively.
  • a current source which is shown schematically as a battery 22 is connected to the casing terminal 4 by a lead 23, a visual and/ or audible alarm 24 is connected to contact 7 by the wire 16, the controlled apparatus 25 is connected to the contact 8 by the wire 16, and the return circuits to the battery are completed by leads 26, 26 respectively.
  • a switch 27 will be included in the lead 23 when the controlled apparatus 25 is energized by the source 22, but may not be necessary when the controlled element is a relay for regulating some larger apparatus in accordance with the ambient temperature at the bimetallic switch.
  • the bimetallic disk 5 Under normal temperature conditions, the bimetallic disk 5 is domed toward the left, as shown, and in engagement with contact 8, thereby energizing the controlled apparatus 25 when the switch 27 is closed. Assuming that the apparatus 25 is to be tie-energized upon a rise .in ambient temperature to a preselected value, the concavity of the bimetallic disk 5 will decrease progressively with the temperature rise and it will eventually be planar and in unstable equilibrium at the critical value of the ambient temperature. The apparatus 25 remains energized during this period since the contact 8 is moved axially by the spring 19 to maintain engagement with the disk 5.
  • the bimetallic disk engages the contact 7 before reaching its unstable midposition, and the alarm 24 is thus energized to warn the operator or attendant that the ambient temperature is approaching the critical value at which the apparatus 25 will be de-energized by a reversal of the curvature of the disk 5. If corrective action is not taken or is not effective, a further temperature rise will reverse the curvature of the bimetallic disk 5 and it will snap over quickly to separate from the contact 8 and seat against the rim of the plate 1 and the contact 7.
  • the ambient temperature varies at a relatively slow rate and a time lag between the ambient temperature and the temperature of the bimetallic disk 5 is of no significance.
  • the casing plates 1, 2 and insulating sheets 11, E2 may be provided with openings 28 by which radiant heat may act directly upon the bimetallic disk 5, thus increasing the sensitivity of the thermal switch by reducing or eliminating a time lag of temperature response.
  • the shape and the number of the openings 28 must of course be so selected that the strength of the casing is not adversely atfected.
  • the stop collars 18 of the contacts 7 and 8 may be so postioned that the bimetallic disk 5 separates from one contact before it engages the other contact, the cit contact 7 may be a fixed contact rigidly mounted on the plate 1, or the contact 7 may be omitted from switches for certain applications. In the latter case, the casing plate 1 will be a simple curved plate.
  • Another modification comprises movable contacts mounted on the bimetallic disk and cooperating with contacts rigidly mounted upon the casing.
  • the unstable neutral position of the disk usually will be its planar or mid-position
  • the disk With this construction, the disk will flex slowly with changing temperature over 40% of its movement from one end position, and then snap suddenly to its other end position as it passes through its unstable neutral position.
  • the advantage of this asymmetrical characteristic is that it provides a relatively wide separation of the disk from the contact which it left in spite of the follow-up movement of that contact by its spring 19.
  • the invention is not limited to switches of any one size or range of sizes but is of particular utility in that it permits manufacture in small or so-called miniature sizes.
  • the small size is of advantage for a number of reasons in addition to the initial advantage of low manufacturing costs.
  • a small and light weight switch may be supported by the switch leads, and it responds to temperature changes at a point or small zone.
  • the thermal switch of small size When employed to shut down a motor or generator upon an abnormal temperature rise, the thermal switch of small size may be installed within the motor or generator casing at or adjacent a point of maximum temperature and thus eliminate the time lag which is characteristic of large size thermal switches which are positioned at the exterior of the motor or generator casing and which have an inherent time lag in view of their mass even when so dimensioned that they could be located within the casing of the apparatus to be protected.
  • the casing plates 1, 2 and the bushings 9 will be of metal for adequate strength and small thermal lag in the smaller size embodiments of the invention but they may be of a molded plastic material in larger size embodiments when small size and minimum time lag are not essential design requirements.
  • a bimetallic snap-action switch comprising a lenticular casing formed of two sheet metal plates with dished rims meeting at substantially the median plane of the casing, an imperforate domed bimetallic disk constituting a movable switch blade, one of said metal plates having an outer edge extending over the other plate to hold the same in assembled position and said other plate having a shallow radial flange constituting a circumferential seat for said disk, the outer edge of said disk resting loosely on said seat and having two end positions according to the existing temperature at which its outer edge portion bears against the inner surface of the dished rim of one or the other of said casing plates, a contact mounted axially on one of said plates, and terminal means for said bimetallic disk and said contact; the terminal means for said bimetallic disk including said lenticular casing.
  • a bimetallic snap-action switch as recited in claim 2 in combination with metallic bushings mounted on and insulated from the respective casing plates to support said contacts for axial movement, springs urging said contacts towards said bimetallic disk, and cooperating stop means on each bushing and its associated contact limiting movement of a contact to space the same from said disk in that end position thereof at which the concave disk face is towards that contact.
  • a bimetallic snap-action switch as recited in claim 1, wherein a metallic bushing is mounted axially of and insulated from one of said plates, said contact is slidably mounted in said bushing, and a spring yieldingly urges said contact towards said disk.

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
US2732461D 1951-04-10 Bimetallic snap-action switch Expired - Lifetime US2732461A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH703963X 1951-04-10

Publications (1)

Publication Number Publication Date
US2732461A true US2732461A (en) 1956-01-24

Family

ID=4530235

Family Applications (1)

Application Number Title Priority Date Filing Date
US2732461D Expired - Lifetime US2732461A (en) 1951-04-10 Bimetallic snap-action switch

Country Status (8)

Country Link
US (1) US2732461A (nl)
BE (1) BE510570A (nl)
CH (2) CH294737A (nl)
DE (1) DE1058606B (nl)
FR (1) FR1053598A (nl)
GB (1) GB703963A (nl)
LU (1) LU31325A1 (nl)
NL (2) NL168156B (nl)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2811611A (en) * 1956-04-17 1957-10-29 Odenwald Alfred Small-type thermostat for preventing overheating in electrical apparatus
US2819367A (en) * 1956-10-29 1958-01-07 Maxime E Ouellette Fire detector
US2839635A (en) * 1956-11-01 1958-06-17 Cook Electric Co Lightning arresters
US2873328A (en) * 1955-08-29 1959-02-10 Baso Inc Thermostat for low power circuits
US2889430A (en) * 1957-01-11 1959-06-02 Smith Webster Deroyce Thermostats
US3038978A (en) * 1959-01-16 1962-06-12 Penn Controls Flame detector
US3096418A (en) * 1958-05-16 1963-07-02 Odenwald Alfred Small-type thermostat for preventing overheating, provided with a bimetal disk in a lenticular casing and with beam-like profiled bracing means on said casing
US3529272A (en) * 1968-05-21 1970-09-15 Fasco Industries Temperature switch

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE553414A (nl) * 1956-03-15
US3083309A (en) * 1960-05-27 1963-03-26 Texas Instruments Inc Thermal motor protective means
CH400297A (de) * 1963-03-22 1965-10-15 Huber & Cie Ag J Elektrischer, temperaturabhängiger Kleinstschalter
DE2744963C2 (de) * 1977-10-06 1982-04-08 Fa. Leopold Kostal, 5880 Lüdenscheid Schnappvorrichtung für elektrische Schalter
US4325047A (en) * 1980-04-09 1982-04-13 Aisin Seiki Kabushiki Kaisha Temperature responsive switch
US5043690A (en) * 1990-07-12 1991-08-27 Sundstrand Data Control, Inc. Balanced snap action thermal actuator
DE19527254C2 (de) * 1995-07-26 2000-01-20 Thermik Geraetebau Gmbh Temperaturwächter
DE19704563B4 (de) * 1997-02-07 2005-07-21 Thermik Gerätebau GmbH Vorrichtung zum Schützen eines Gerätes

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1725296A (en) * 1925-08-31 1929-08-20 Arthur E Paige Burner-lighting mechanism
US2199388A (en) * 1938-02-07 1940-05-07 Metals & Controls Corp Thermostatic device
US2207601A (en) * 1936-11-06 1940-07-09 Shakespeare Products Co Igniter
US2239541A (en) * 1938-11-23 1941-04-22 Metals & Controls Corp Temperature responsive apparatus
US2239540A (en) * 1936-01-27 1941-04-22 Metals & Controis Corp Thermostatic control
FR924492A (fr) * 1946-03-27 1947-08-06 J M Dard & Cie Ets Relais à lame bimétallique sans dispositif d'accrochage
US2477801A (en) * 1945-05-19 1949-08-02 Claude M Hathaway Air pressure switch
US2514807A (en) * 1948-04-05 1950-07-11 Walter M Shaw Portable electric fire alarm device
US2596171A (en) * 1949-08-03 1952-05-13 Us Army Pressure switch for fuses

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE510270C (de) * 1926-09-11 1930-10-17 Radio Patents Corp Inc In Lampenfassungen nutzbarer Thermoschalter
DE690573C (de) * 1935-10-23 1940-04-29 Walther Burstyn Dr Selbsttaetiger Feuermelder
GB491390A (en) * 1936-01-27 1938-08-29 Metals & Controls Corp Thermostatic electric controls
US2461903A (en) * 1945-06-16 1949-02-15 Metals & Controls Corp Thermostatic control
NL66547C (nl) * 1945-12-17
US2469217A (en) * 1946-04-17 1949-05-03 Gen Electric Snap-action thermostatic switch
US2543040A (en) * 1946-09-24 1951-02-27 Charles S Mertler Snap-action thermostatic switch

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1725296A (en) * 1925-08-31 1929-08-20 Arthur E Paige Burner-lighting mechanism
US2239540A (en) * 1936-01-27 1941-04-22 Metals & Controis Corp Thermostatic control
US2207601A (en) * 1936-11-06 1940-07-09 Shakespeare Products Co Igniter
US2199388A (en) * 1938-02-07 1940-05-07 Metals & Controls Corp Thermostatic device
US2239541A (en) * 1938-11-23 1941-04-22 Metals & Controls Corp Temperature responsive apparatus
US2477801A (en) * 1945-05-19 1949-08-02 Claude M Hathaway Air pressure switch
FR924492A (fr) * 1946-03-27 1947-08-06 J M Dard & Cie Ets Relais à lame bimétallique sans dispositif d'accrochage
US2514807A (en) * 1948-04-05 1950-07-11 Walter M Shaw Portable electric fire alarm device
US2596171A (en) * 1949-08-03 1952-05-13 Us Army Pressure switch for fuses

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2873328A (en) * 1955-08-29 1959-02-10 Baso Inc Thermostat for low power circuits
US2811611A (en) * 1956-04-17 1957-10-29 Odenwald Alfred Small-type thermostat for preventing overheating in electrical apparatus
US2819367A (en) * 1956-10-29 1958-01-07 Maxime E Ouellette Fire detector
US2839635A (en) * 1956-11-01 1958-06-17 Cook Electric Co Lightning arresters
US2889430A (en) * 1957-01-11 1959-06-02 Smith Webster Deroyce Thermostats
US3096418A (en) * 1958-05-16 1963-07-02 Odenwald Alfred Small-type thermostat for preventing overheating, provided with a bimetal disk in a lenticular casing and with beam-like profiled bracing means on said casing
US3038978A (en) * 1959-01-16 1962-06-12 Penn Controls Flame detector
US3529272A (en) * 1968-05-21 1970-09-15 Fasco Industries Temperature switch

Also Published As

Publication number Publication date
NL79469C (nl)
FR1053598A (fr) 1954-02-03
DE1058606B (de) 1959-06-04
BE510570A (nl)
CH301665A (de) 1954-09-15
LU31325A1 (nl)
CH294737A (de) 1953-11-30
GB703963A (en) 1954-02-10
NL168156B (nl)

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