US3581263A - Thermally responsive switch - Google Patents

Thermally responsive switch Download PDF

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Publication number
US3581263A
US3581263A US743157A US3581263DA US3581263A US 3581263 A US3581263 A US 3581263A US 743157 A US743157 A US 743157A US 3581263D A US3581263D A US 3581263DA US 3581263 A US3581263 A US 3581263A
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US
United States
Prior art keywords
switch
recess
bridge
contact
cap
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Expired - Lifetime
Application number
US743157A
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English (en)
Inventor
Antonio Moro
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.)
Fratelli Borletti SpA
Borletti SpA
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Borletti SpA
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Publication date
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Publication of US3581263A publication Critical patent/US3581263A/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

Definitions

  • a cap of insulating material is secured to the metal body closing the recess.
  • a disc-shaped bimetallic strip is loosely housed in the recess,
  • the fixed contact is carried by a stiff metal bridge which bridges across the recess.
  • the position of the fixed contact is adjustable. Adjustment being made by a tool inserted through an aperture in the cap.
  • the thermally responsive switch according to the invention is particularly designed to be mounted on the radiators of engines of motor vehicles for the purpose of opening and closing the electric circuit of an electromagnetic coupling which produces the connection and disconnection of the cooling fan for the radiator water, in accordance with the temperature of said water.
  • the switch according to the invention is of the type comprising a bimetallic strip which, when the tem perature increases, snaps out of position, at the temperature value predetermined during construction, in accordance with the conformation and precalibration imparted to it before being inserted in the body of the switch, while, when the temperature decreases, the bimetallic strip snaps out of position at a temperature value predetermined by means of a calibration effected from outside the body of the switch when this is fully assembled.
  • thermally responsive switches Fitting of these thermally responsive switches is effected by screwing them into a flange in the wall of the lower tank of the radiator, which generally has a threaded hole with a standard diameter of 20 mm; any thermally responsive switch intended for this type must therefore have a threaded shank of the above-mentioned diameter.
  • the strip is produced with a diameter equal to that of the threaded shank, so as to provide optimum conditions for the transfer of the heat from the shank to the strip itself.
  • the switch according to the invention presents advantageous, but not secondary, improvements which permit simple, reliable and cheap construction thereof and which make it possible to insert it in an electric circuit subjected to higher control currents.
  • a flexible insulating tongue which separates it from a flexible conductive tongue insulated from the housing and carrying a first contact in the center; a second contact, the fixed position of which can be set from outside the body of the switch, is disposed so as to cooperate with the first contact at the instant when the electric circuit is closed.
  • the upper part, or cap, of the body of the switch is produced by injection moulding insulating plastics material and in it 'there are incorporated in the moulding process conductive plates connected to said first and second contacts, respectively; each plate has one end projecting outside the cap and acts as a pin for effecting connection to a conductor of the electric circuit.
  • first plate bears directly on a peripheral zone of said conductive tongue carrying the first contact
  • second plate bears on a peripheral zone of an insulated metal support carrying the second contact.
  • the latter is mounted in the support so that it can be set through the medium of screw means adapted to be actuated from outside by means of a suitable screwdriver passed through a hole in the cap; this hole is then closed so that it is watertight once the operation of setting, or calibrating, said contact has been carried out.
  • This setting in the final calibration stage, is effected so as to position said second contact with respect to the first contact in such manner as to obtain the reverse snap action of the bimetallic strip when the falling temperature reaches the predetermined value.
  • FIGS. I and 2 are vertical sectional views of the switch in planes disposed at with respect to one another;
  • FIG. 2b shows in section a detail of the insulating tongue and of the movable contact
  • FIG. 3 shows the device in plan view
  • FIG. 4 illustrates in detail in plan view the flexible tongue carrying the movable contact
  • FIG. 5 is an axial section of the bimetallic strip
  • FIG. 6 shows in detail the bridge-shaped support carrying the fixed contact
  • FIG. 7 and 8 show in vertical section two modified constructional forms of the switch according to the invention.
  • FIG. 9 shows in detail in perspective view of the plate carrying the fixed contact in the constructional form of FIG. 8;
  • FIGS. I0a and 10b are two axial sections of two modified constructional forms of the threaded shank of the switch.
  • a metal housing body 1 has a hollow cylindrical zone 2 with a recess 3 in which is freely housed the bimetallic strip 4 in the form of a bent disc and having, in the case in question, its diameter 5 approximately equal to the diameter of the threaded shank 6.
  • the dimensions of the housing I and the diameter of the bimetallic strip 4 may be different, within certain limits, but is preferable to keep the diameter of the bimetallic strip substantially equal to that of the threaded shank so that the transmission of heat from the latter may be as uniform as possible over the entire extent of the strip.
  • the strip is preferably shaped with a diametral section such as appears in FIG. 5, that is with a central portion 4' formed with a slight curvature opposite to the main curvature, or even like a very open truncated cone, and with a diameter about one third of the total diameter.
  • the ring 9 which is made of material which is a good conductor and from which a flexible radial tongue 10 projects toward the center.
  • a hole 11 in which is inserted a stud 12 made of metal suitable for electric contacts and having a head which is preferably spherical; the stud 12 is fixed with the interposition of the washer 13 by flanging its tip over in the form of a spherical head 14.
  • the three rings 7, 9, 15 and the bridge 16 are held oriented angularly and radially by two pins 17 formed in one piece with the cap 18, said pins being engaged in holes or notches 19, 19'
  • the pins 17 are positioned in such manner that on assembly the rings 7, 9, 15 cannot be fitted upside-down or turned with respect to the prescribed position.
  • the four parts 7, 9, 15 and 16 aforesaid are held in position in the seat 2 under pressure from the cap 18 of insulating material, which is held in the seat in turn by means of the flanged over portion 20 of the housing 1 with the interposition of the metal ring 2
  • the cap 18 is preferably made by injection moulding suitable plastics material (for example Dcln'n) and the plates 23 and 24 areincorporated in said plastics material in the same moulding stage; that part of the plates which extends outside the cap 18 has the function of a pin for connection to the conductors of the electric circuit.
  • suitable plastics material for example Dcln'n
  • the internal portion of the plate 24 presses by means of its end 25 on a peripheral zone of the bridge 16, thereby producing electrical continuity; the internal portion of the plate 23, on the other hand, presses by means of its end 26 on a peripheral zone 27 of the surface of the metal ring 9, thereby establishing electrical continuity with the latter and therefore with the contact 12.
  • the bridge 16 is formed centrally in the shape of a bridge (see FIG. 6) in which a threaded hole 28 is provided in a position coinciding with the axis of the switch; said threaded hole is widened into a longitudinal slot 29, which enables the hole 28 to be pinched and restricted, due to the flexibility of the two parts separated by the slot, in order to make it possible to produce a certain pressure on the thread of the screw 30 and thus avoid the latter unscrewing as a result of vibration.
  • the screw 30 carries the electrical contact 31 at its lower end; said electrical contact is therefore electrically connected to the plate 24 through the metal bridge 16, while it is insulated from all the other metal parts of the switch.
  • the fixed contact 31 is coaxial with the movable contact 12 and is spaced therefrom in the inoperative position, as can be seen from the drawing.
  • a hole 32 through which it is possible to obtain access with a suitable tool, such as a screwdriver, a spanner or the like, for the purpose of screwing in and unscrewing the screw 30 during the stage of calibration of the device for adjusting the reverse snap action of the bimetallic strip 4, that is the snap action at the value predetermined for the temperature as it falls, in substantially known manner.
  • a suitable tool such as a screwdriver, a spanner or the like
  • watertightness may be ensured by covering the head of the screw with suitable sealing material.
  • the bimetallic strip snaps or trips in the direction opposite to the previous direction at the predetermined value: the contact 12 moves away from the contact 31 and the electric circuit is broken again.
  • the bimetallic strip is constantly maintained at the temperature of the element with which the device is in contact due to the transfer of heat effected by the metal mass of the threaded shank 6 which, as has been said, is always in direct contact with said element; in effect, the temperature of the latter always varies gradually and not instantaneously, so that, in prac tice, the mass 6 is never subjected to substantial temperature gradients and it can be considered that the bimetallic strip is practically speaking always at the same temperature as said element.
  • FIG. 7 A modified constructional form is shown in FIG. 7.
  • the bridge 16 is dispensed with and its function is performed by the plate 24', the internal end 34 of which, bent at right angles at 35, has a threaded hole 28 into which the screw 30 carrying the contact 31 is screwed directly. All the other elements remain the same as those which have already been described in the case of the first constructional form.
  • a second modified constructional form is shown in FlG.-8.
  • the bridge 16 is also eliminated in this embodiment and is replaced by the plate 24".
  • This plate is bent at right angles at 35' and extends in the form of a uniplanar spiral 36, preferably as shown in FIG. 9.
  • the central terminal end of the spiral 36 is able to undergo small elastic displacements without being permanently deformed.
  • Fixed to said end is the contact 31', on the bottom of which the movable contact 12 presses on the tripping of the bimetallic strip 4.
  • the adjusting or calibrating screw 37 bears on the upper face of the contact 31 this screw is screwed into the threaded hole 32' provided directly in the insulating cap 18 and the position of the contact 31' is set by means of said screw in the calibration stage.
  • the screw 37 is sealed with a suitable lacquer or cement, so as to ensure watertightness and at the same time lock the screw 37 itself against any possible unscrewing due to vibration.
  • the bimetallic strip is constantly kept at the temperature of the element with which the device is in contact, due to the transfer of heat effected by the metal mass of the threaded shank 6, which is always in direct contact with said element; in effect, the temperature of the latter always varies gradually and not instantaneously, so that, in practice, the mass 6 is never subjected to substantial temperature gradients and it can be considered that the bimetallic strip is practically speaking always at the same temperature as said element.
  • a cylindrical chamber 38 (see FIG. l0a) is formed in the shank 6, leaving a wall 39 of small thickness below the bimetallic strip, and a number of radial holes 40 are made at the root of the thread to prevent the formation of cushions of air.
  • the chamber 38' may be made in the form ofa truncated cone without any radial holes.
  • the liquid of which it is desired to control the temperature is separated from the bimetallic strip by a thickness of metal which is reduced to the minimum.
  • a thermally responsive switch having a housing including a metal body with a threaded shank for anchorage to a member whose temperature is to control the switch, themetal body having a recess therein, a cap of insulating material secured to said body and closing the recess, a disc-shaped bimetallic'strip loosely housed in said recess, a movable contact and a fixed contact, terminal means connected to said contacts and extending exteriorly of said housing, said strip changing position at a given temperature to apply the movable contact against the fixed contact to complete an electric circuit, astiff metal bridge that bridges across said recess and carries said fixed contact, calibrating means accessible from outside the switch to move the fixed contact relative to the bridge to adjust the temperature at which the contacts move apart from each other to open said circuit, said body having shoulders in said recess which support the ends of said bridge, and electrical insulation means between said bridge and said body.
  • a switch as claimed in claim 1 said cap having an internal cavity that opens toward said recess, said fixed contact being disposed in said cavity.
  • a switch as in claim 1 the ends of said bridge on opposite sides of said recess being gripped between said cap and said body.
  • a switch as in claim I said bridge having a central portion that is concave and that opens in the direction of the bottom of said recess.
  • Switch as in claim I wherein said movable contact is fixed to the free end of a flexible arm projecting radially towards the center from a peripheral ring supported by said shoulders.
  • said insulation means comprises an insulating ring from which there projects radially a tab forming said flexible insulating tongue interposed between the movable contact and the bimetallic strip.
  • a second metal plate in said insulating cap has its lower end disposed inside the chamber bearing under pressure on a peripheral zone of the surface of said bridge carrying the fixed contact, so as to establish continuity of electrical connection between the latter and said plate.

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  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
  • Temperature-Responsive Valves (AREA)
US743157A 1967-07-08 1968-07-08 Thermally responsive switch Expired - Lifetime US3581263A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT1817267 1967-07-08
US74315768A 1968-07-08 1968-07-08

Publications (1)

Publication Number Publication Date
US3581263A true US3581263A (en) 1971-05-25

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Family Applications (1)

Application Number Title Priority Date Filing Date
US743157A Expired - Lifetime US3581263A (en) 1967-07-08 1968-07-08 Thermally responsive switch

Country Status (5)

Country Link
US (1) US3581263A (enrdf_load_stackoverflow)
DE (1) DE1765713A1 (enrdf_load_stackoverflow)
ES (1) ES139319Y (enrdf_load_stackoverflow)
FR (1) FR1579109A (enrdf_load_stackoverflow)
GB (1) GB1230123A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4127838A (en) * 1975-11-10 1978-11-28 Societe Anonyme Francaise Du Ferodo Fitting of a heat-sensitive capsule in a wall of a water chamber or the like
US4413247A (en) * 1982-02-12 1983-11-01 Hi-Stat Manufacturing Co., Inc. Thermally responsive electrical switch means and method of manufacture
US4446451A (en) * 1982-12-15 1984-05-01 Texas Instruments Incorporated Thermostat device having improved mounting means
US4446450A (en) * 1982-12-15 1984-05-01 Texas Instruments Incorporated Thermostat device having improved mounting means
CN113464782A (zh) * 2021-05-26 2021-10-01 贵州电网有限责任公司 基于实时检测变压器桩头温升预警器安装接头

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10226082B4 (de) * 2002-06-12 2006-08-31 Infineon Technologies Ag Schaltungsanordnung zur Strombegrenzung

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2333291A (en) * 1940-06-19 1943-11-02 Herbert E Brannon Temperature responsive device
US2863024A (en) * 1957-04-18 1958-12-02 Lee W Romine Signal connecting bolt
FR1342493A (fr) * 1962-02-24 1963-11-08 Borletti Spa Contacteur thermique à lame bimétallique pour circuit de signalisation de température limite
US3223806A (en) * 1962-05-29 1965-12-14 Moro Antonio Thermally controlled electrical switch having motion-amplifying lever means
US3248503A (en) * 1963-03-22 1966-04-26 Huber & Cie A G J Bimetallic thermostatic snap switch having adjustable contact bolt
US3255331A (en) * 1960-07-05 1966-06-07 Ulanet Herman Immersion thermostatic switch
US3329788A (en) * 1964-05-15 1967-07-04 Borletti Spa Thermally controlled switch

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2333291A (en) * 1940-06-19 1943-11-02 Herbert E Brannon Temperature responsive device
US2863024A (en) * 1957-04-18 1958-12-02 Lee W Romine Signal connecting bolt
US3255331A (en) * 1960-07-05 1966-06-07 Ulanet Herman Immersion thermostatic switch
FR1342493A (fr) * 1962-02-24 1963-11-08 Borletti Spa Contacteur thermique à lame bimétallique pour circuit de signalisation de température limite
US3223806A (en) * 1962-05-29 1965-12-14 Moro Antonio Thermally controlled electrical switch having motion-amplifying lever means
US3248503A (en) * 1963-03-22 1966-04-26 Huber & Cie A G J Bimetallic thermostatic snap switch having adjustable contact bolt
US3329788A (en) * 1964-05-15 1967-07-04 Borletti Spa Thermally controlled switch

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4127838A (en) * 1975-11-10 1978-11-28 Societe Anonyme Francaise Du Ferodo Fitting of a heat-sensitive capsule in a wall of a water chamber or the like
US4413247A (en) * 1982-02-12 1983-11-01 Hi-Stat Manufacturing Co., Inc. Thermally responsive electrical switch means and method of manufacture
US4446451A (en) * 1982-12-15 1984-05-01 Texas Instruments Incorporated Thermostat device having improved mounting means
US4446450A (en) * 1982-12-15 1984-05-01 Texas Instruments Incorporated Thermostat device having improved mounting means
CN113464782A (zh) * 2021-05-26 2021-10-01 贵州电网有限责任公司 基于实时检测变压器桩头温升预警器安装接头
CN113464782B (zh) * 2021-05-26 2022-11-25 贵州电网有限责任公司 基于实时检测变压器桩头温升预警器安装接头

Also Published As

Publication number Publication date
FR1579109A (enrdf_load_stackoverflow) 1969-08-22
GB1230123A (enrdf_load_stackoverflow) 1971-04-28
DE1765713A1 (de) 1971-09-09
ES139319Y (es) 1969-06-16
ES139319U (es) 1968-11-16

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