US3794811A - Automatic safety switch member - Google Patents

Automatic safety switch member Download PDF

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Publication number
US3794811A
US3794811A US00273032A US3794811DA US3794811A US 3794811 A US3794811 A US 3794811A US 00273032 A US00273032 A US 00273032A US 3794811D A US3794811D A US 3794811DA US 3794811 A US3794811 A US 3794811A
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US
United States
Prior art keywords
circuit
main current
heatable
load
switching element
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00273032A
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English (en)
Inventor
K Hehl
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Individual
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Individual
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Filing date
Publication date
Priority claimed from DE2017422A external-priority patent/DE2017422C3/de
Application filed by Individual filed Critical Individual
Application granted granted Critical
Publication of US3794811A publication Critical patent/US3794811A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B18/00—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body
    • A61B18/04—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating
    • A61B18/08—Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body by heating by means of electrically-heated probes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
    • H01H47/002—Monitoring or fail-safe circuits
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H61/00—Electrothermal relays
    • H01H61/01—Details
    • H01H61/013—Heating arrangements for operating relays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H71/00—Details of the protective switches or relays covered by groups H01H73/00 - H01H83/00
    • H01H71/10—Operating or release mechanisms
    • H01H71/12—Automatic release mechanisms with or without manual release
    • H01H71/14—Electrothermal mechanisms
    • H01H71/20—Electrothermal mechanisms with fusible mass

Definitions

  • ABSTRACT 174 52 as a coil which concentrically encloses the heatable switching element and an electrically insulating sup- 5 References Cited porting sleeve which supports the coil and is disposed UNITED STATES PATENTS coaxial to the heatable switching element.
  • the present invention relates to an improvement in the automatic safety switch disclosed in my above mentioned U.S. Patent Application.
  • the prior application relates to an automatic safety switch for monitoring the power switching member of an electric current load, such as, for example, an electric heater, an electric motor, or the like, in order to prevent damage which might occur from a malfunction of the power switching member controlling the main current circuit during cutoff.
  • an electric current load such as, for example, an electric heater, an electric motor, or the like
  • the safety switch contains a relay serving as an auxiliary switching member which is electrically or mechanically connected with the power switching member, an electrical connection between the main current line leading to the electric load and, in one embodiment, an opening contact of the relay, or in another embodiment, an opening contact of the relay which is in turn connected to the power switching member, and a device which is electrically connected with the opening contact and which includes at least one resistance heating element and a heatable switching element in thermal contact with the heating element for disconnectng the load from the main current circuit when a certain temperature is exceeded.
  • the heatable switching element is usually provided in the form of a fuse body and is flanked by two diametrically disposed resistance heating elements. With such a design it mayhappen, particularly upon the occurrence of malfunctions that the resistance heating element comes into electrical contact with the switching element, so that the resistance circuit is connected to the main or operating current circuit. Such a short-circuit generally results in destruction of the amplifier of the safety circuit and damage to the circuit board on which the resisance heating element and the switching element are disposed. In order to overome this danger it has become the practice to additionally insulate the switching element, i.e., the fuse body, with a coating layer of plastic. Such an additional insulation has the drawback, however, that the limit temperature at which electrical cutoff of the load occurs can no longer be reproduced as accurately as when no insulation is used.
  • an object of the present invention to improve the safety circuit discribed above in such a manner that a short-circuit of the heatable switching element is effectively eliminated and the predetermined limit temperature at which safety switch cutoff occurs can be accurately reproduced.
  • the resistance heating element as a coil of resistance wire which concentrically surrounds the switching element and by providing a supporting sleeve which is disposed coaxial with the switching element.
  • the switching element is a radially symmetrical fuse body having at least a central cylindrical section.
  • the body is fully enclosed by the cylindrical inner wall of the supporting sleeve.
  • FIG. 1 is a longitudinal cross-sectional view of a resistance heating element according to the present invention.
  • FIG. 2 is a front view of the heating element of FIG. 1.
  • FIG. 3 is a longitudinal, partially cross-sectional view of the resistance heating element of FIG. I mounted on a circuit board in combination with terminal columns for a fuse body to be inserted within the heating element.
  • FIG. 4 is a front view of the mounted heating element of FIG. 3 without the connecting columns.
  • FIG. 5 is a top plan view, partially in longitudinal section, of the arrangement according to FIGS. 3 and 4 and including a fuse body connected to the terminal columns.
  • FIG. 6 is a schematic top plan layout of a safety circuit utilizing the element according to the present invention and having an electronic power switching member.
  • FIG. 7 is a schematic circuit diagram of the safety circuit of FIG. 6.
  • a load 9 is held at a predetermined rated temperature by an electronic temperature control device.
  • the temperature regulating device has a suitable amplifier 8 which moniters the rated temperature at the heated load 9.
  • the amplifier 8 controls an auxiliary relay 7 which together with the amplifier 8 forms an amplifier current circuit.
  • the relay 7 with the aid of its switch contact 12 switches a power switching member 6 on or off.
  • the power switching member 6 controls a main current circuit 11 which is provided with a suitable fuse 1.
  • the power switching member 6 may be an electronic power switching member, such as a thyristor.
  • the power switching member 6 which is controlled by the relay 7 via a suitable resistor 5, is disposed directly in the main current circuit 11.
  • One significant component of the safety circuit is an electrical connection 14 which is situated between the main current circuit 11 and the opening contact 12 of the relay 7.
  • Another significant component is a device 2, 3, 21, 29, 25, 90, which is disposed in the main current circuit 1 l and is electrically connected with the opening contact 12 of the relay 7 via a line 15.
  • the device includes a resistance heating element 3, 21 and a heatable switching element or radially symmetrical fuse body 2 which is in thermal contact with the resistance heating element 3, 21 and which operates, for example, on a chemical basis to become nonconductive upon being heated to a certain temperature.
  • the resistance heating element 3, 21 is formed by an electrically insulating 18" extending outwardly from the cylindrical section, V
  • the fuse body is enclosed by the cylindrical inner wall of the supporting sleeve 21.
  • the sleeve is formed preferably of a ceramic body and is disposed coaxially to the radially symmetrical switching element 2.
  • the supporting sleeve 21 is provided with a recess in its outer surface.
  • the coil 3 is formed by a single winding and is disposed in the recess in the supporting sleeve.
  • a ceramic protective sleeve 29 is connected with a printed circuit type circuit board 27 by means of slide fittings 25.
  • the circuit board 27 carries part of the current circuit of the resistance heating element 3, 21 as well as of the main or operating current circuit 11.
  • the protective sleeve 2? concentrically mounts the assembled switching element 2 and the supporting sleeve 21 'via the fittings 25 to the circuit board 27.
  • the fittings 25 are secured to the circuit board 27.
  • the fittings 25 are secured to the circuit board 27 by rivet-like portions including a stem 25' and a head 26.
  • Axial grooves are formed in the supporting sleeve 21.
  • the input section 3 and the output section 3", respectively, of the coil 3 pass through the grooves 20 and are electrically and mechanically connected with the circuit board 27 by means of the fittings 25.
  • a pair of terminal columns 90 and 100 are mounted to the circuit board 27 in a manner similar to the fittings 25.
  • the one terminal 100 is disposed in a plane A-A, which intersects the axis of the fuse body 2.
  • the other terminal 90 is disposed outside of this plane in order to facilitate mounting or dismounting of the fuse body in the supporting sleeve 21.
  • the terminals 18, 18" are received within the columns 100, 90, respectively, and are retained therein by clamping connections 111, 112 in each column. As a result of the mounting of the terminals 18', 18 to the columns 100, 90, the fuse body 2 is electrically connected to the circuit board 27.
  • one phase, Mp, of the main current circuit 11 is connected to the resistance heating element 3, 21 via the line 14, the opening contact 12, of the relay 7 and the line 15.
  • the resistance heating element 3, 21 heats the switching element 2 until it exceeds a predetermined limit temperature.
  • the main current circuit 11 is cut off and thus the current flow for the electric load 9 is interrupted.
  • the placement of the resistance heating wire 3 concentric with the fuse body 2 offers absolute protection against a short circuit. Furthermore the fuse body 2 no longer needs to be soldered.
  • the fuse body 2 is constituted by a thermolabile substance disposed in the conductive path.
  • the fuse body is well-known and can be obtained on the market.
  • a circuit arrangement for supplying current to an electric power load as for example, an electric heater, an electric motor and the like, said circuit arrangement comprising, in combination:
  • a main current circuit having said load and a power switching means for controlling the current to said.
  • an automatic safety circuit means for monitoring said power switching means controlling said main current circuit to prevent damage to said load which might occur as a result of a malfunction of said power switching member causing it to remain closed when the main current to the load is to be cut off said automatic safety circuit means includ rent to said load out off, to cause said second means to disrupt said main current circuit in the event said power switching means has not opened, said second means including a heatable switching element, an electrical resistance heating element formed as a coil which encloses said heatable switching element, and an electrically insulating supporting sleeve which supports said coil and is disposed around said heatable switching element.
  • said supporting sleeve has an outer surface with a recess therein, and said coil is formed by a single winding and is disposed in said recess.
  • circuit arrangement as defined in claim 1, further comprising a circuit board carrying a printed circuit, a protective sleeve which encloses said supporting sleeve, and means for fitting said protective sleeve to said circuit board, said circuit board being a component of the current circuit of said resistance heatingelement and the main current circuit.
  • circuit arrangement as defined in claim 4, further comprising terminal columns and means for connecting said columns to said circuit board so that said columns serve as electrical conductors, and clamping means, wherein said heatable switching element is a radially symmetrical fuse body having a central cylindrical section and a pair of terminals which are connected to a respective terminal column by said clamping means, said terminals being disposed, when connected to a respective terminal column, in a plane which intersects the axis of the fuse body.

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  • Health & Medical Sciences (AREA)
  • Surgery (AREA)
  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biomedical Technology (AREA)
  • Molecular Biology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Plasma & Fusion (AREA)
  • Physics & Mathematics (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Medical Informatics (AREA)
  • Otolaryngology (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Fuses (AREA)
  • Control Of Resistance Heating (AREA)
US00273032A 1970-04-11 1972-07-19 Automatic safety switch member Expired - Lifetime US3794811A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2017422A DE2017422C3 (de) 1970-04-11 1970-04-11 Selbsttätige Sicherheitsschaltung zur Überwachung des Leistungsschaltgliedes eines elektrischen Stromverbrauchers
DE2137285A DE2137285C3 (de) 1970-04-11 1971-07-26 Selbsttätige Sicherheitsschaltung zur Überwachung des Leistungsschaltgliedes eines elektrischen Stromverbrauchers

Publications (1)

Publication Number Publication Date
US3794811A true US3794811A (en) 1974-02-26

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
US00273032A Expired - Lifetime US3794811A (en) 1970-04-11 1972-07-19 Automatic safety switch member

Country Status (5)

Country Link
US (1) US3794811A (de)
CH (1) CH551708A (de)
DE (1) DE2137285C3 (de)
FR (1) FR2147233B2 (de)
NL (1) NL7209719A (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4096370A (en) * 1977-06-15 1978-06-20 Litton Systems, Inc. Microwave oven door interlock switch system
US4222087A (en) * 1978-08-21 1980-09-09 Hawthorne Industries, Inc. Passive triac output asymmetry detector
US4242713A (en) * 1979-10-25 1980-12-30 Goodrich Edward W Triac output asymmetry detector
US5726850A (en) * 1996-07-24 1998-03-10 Rowe, Jr.; William M. Fail safe protection circuit for PTC comfort devices

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4328387A (en) * 1980-03-19 1982-05-04 Nordson Corporation Fail-safe thermostatically controlled circuit for use in apparatus for melting and dispensing thermoplastic material
FR2521344A1 (fr) * 1982-02-09 1983-08-12 Valeo Dispositif de protection thermique d'un moteur electrique

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1279020A (en) * 1913-04-21 1918-09-17 Edmund O Schweitzer Fuse device.
US1966466A (en) * 1930-12-23 1934-07-17 Hevi Duty Electric Co Electrically heated electric fuse circuit
US2425032A (en) * 1944-08-24 1947-08-05 Du Pont Enamel for resistors
US3383496A (en) * 1965-08-27 1968-05-14 Ginsburg Leon High temperature vacuum firing porcelain furnace
US3581062A (en) * 1968-02-19 1971-05-25 Pavelle Corp Electronic thermostat
US3616533A (en) * 1969-10-28 1971-11-02 North American Rockwell Method of protecting articles in high temperature environment
US3697812A (en) * 1970-04-11 1972-10-10 Karl Hehl Automatic safety switch for electric current load

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1279020A (en) * 1913-04-21 1918-09-17 Edmund O Schweitzer Fuse device.
US1966466A (en) * 1930-12-23 1934-07-17 Hevi Duty Electric Co Electrically heated electric fuse circuit
US2425032A (en) * 1944-08-24 1947-08-05 Du Pont Enamel for resistors
US3383496A (en) * 1965-08-27 1968-05-14 Ginsburg Leon High temperature vacuum firing porcelain furnace
US3581062A (en) * 1968-02-19 1971-05-25 Pavelle Corp Electronic thermostat
US3616533A (en) * 1969-10-28 1971-11-02 North American Rockwell Method of protecting articles in high temperature environment
US3697812A (en) * 1970-04-11 1972-10-10 Karl Hehl Automatic safety switch for electric current load

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4096370A (en) * 1977-06-15 1978-06-20 Litton Systems, Inc. Microwave oven door interlock switch system
US4222087A (en) * 1978-08-21 1980-09-09 Hawthorne Industries, Inc. Passive triac output asymmetry detector
US4242713A (en) * 1979-10-25 1980-12-30 Goodrich Edward W Triac output asymmetry detector
US5726850A (en) * 1996-07-24 1998-03-10 Rowe, Jr.; William M. Fail safe protection circuit for PTC comfort devices

Also Published As

Publication number Publication date
FR2147233A2 (de) 1973-03-09
NL7209719A (de) 1973-01-30
DE2137285C3 (de) 1980-04-24
DE2137285B2 (de) 1979-08-16
FR2147233B2 (de) 1977-04-01
CH551708A (de) 1974-07-15
DE2137285A1 (de) 1973-02-15

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