US3387246A - Helical thermal switch - Google Patents

Helical thermal switch Download PDF

Info

Publication number
US3387246A
US3387246A US489220A US48922065A US3387246A US 3387246 A US3387246 A US 3387246A US 489220 A US489220 A US 489220A US 48922065 A US48922065 A US 48922065A US 3387246 A US3387246 A US 3387246A
Authority
US
United States
Prior art keywords
tube
rod
temperature
helical
contact
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
US489220A
Other languages
English (en)
Inventor
Richard D Grayson
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.)
TDK Micronas GmbH
ITT Inc
Original Assignee
Deutsche ITT Industries GmbH
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Deutsche ITT Industries GmbH filed Critical Deutsche ITT Industries GmbH
Priority to US489220A priority Critical patent/US3387246A/en
Priority to NL6613293A priority patent/NL6613293A/xx
Application granted granted Critical
Publication of US3387246A publication Critical patent/US3387246A/en
Assigned to ITT CORPORATION reassignment ITT CORPORATION CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: INTERNATIONAL TELEPHONE AND TELEGRAPH CORPORATION
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
    • H01H37/56—Thermally-sensitive members actuated due to deflection of bimetallic element having spirally wound or helically wound bimetallic element
    • 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
    • H01H37/46—Thermally-sensitive members actuated due to expansion or contraction of a solid
    • H01H37/48—Thermally-sensitive members actuated due to expansion or contraction of a solid with extensible rigid rods or tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/002—Thermally-actuated switches combined with protective means

Definitions

  • a thermally responsive over-temperature switch includes an elongated helical bimetallic element which surrounds one end of a low thermally responsive rod within a high thermally responsive tube forming a probe unit to be positioned within a water heater.
  • a free end of the element carries a movable contact which cooperates with a fixed contact mounted on a tube which surrounds the other end of the rod and is insulated from the probe tube.
  • This invention relates in general to thermal switches for use in storage water heaters and in particular to helical thermal switches in which a bimetal element coils and uncoils in response to temperature variations to make and break electrical contacts.
  • a switch unit of the above character which consists of a helical bimetal element which has a plurality of turns to provide an accurate and precise switching point; which is readily adjustable; and which is constructed to fit inside of the normal thermostatic sensing element or probe wherein it is insulated from external ambient temperature and heat losses, in addition to being relatively tamper-proof by virtue of its location.
  • FIGS. 1 through 5
  • FIG. 1 shows a diagrammatic view of a conventional storage water heater incorporating the inventive helical thermal switch
  • FIG. 2 shows a partly sectionalized view of the helical thermal switch of the system of FIG. 1;
  • FIGS. 3 to 5 show various cross-sectional and enlarged views of the thermal switch of FIG. 2.
  • a conventional storage water heater has a gas control unit 2 mounted thereon for controlling the passage of fuel from inlet pipe 3 to the pilot burner 4 and to the main burner 5 in accordance with demand conditions determined jointly by the setting of a temperature dial 6 and the temperature of the water as sensed by the water heater temperature sensing probe 7.
  • a pilot generator or thermocouple 8 is positioned immediately adjacent the pilot burner 4 and is subjected to the pilot burner flame. In response to heat from the pilot flame, the thermocouple 8 generates a voltage which is electrically connected to a holding eletcromagnet 9 in the gas control unit 2 over a circuit which includes normally closed contacts 13-28 of probe 7.
  • Contacts 13-28 form a part of the inventive thermal switch and are adjusted to open at a predetermined temperature above the normal temperature range of the water to release electromagnet 9 and terminate all fuel flow. This arrangement, thus, provides a safety feature in the event of failure of the usual thermostatic control and a consequent over-temperature condition in the water heater.
  • the control unit 2 is of the well-known manual reset type gas control unit and includes a gas cock having OFF, PILOT, and ON positions; a thermomagnetic safety valve, a main line automatic valve, and an adjustable water temperature control element.
  • the pilot valve (not shown) operates and fuel flows from the main line 3 to the pilot burner 4 over pilot line 10.
  • the pilot valve is mechanically coupled to armature 12 of electromagnet 9 and the above described operation of the pilot valve moves armature 12 into mechanical association with the pole pieces of electromagnet 9.
  • the pilot burner 4 may be ignited causing the voltage generated by the thermocouple 8 to energize electromagnet 9 and maintain armature 12 in its attracted position. Thereafter, knob 9 may be released, with armature 12 now holding the pilot valve open as long as the pilot flame remains.
  • the main line 3 is connected to the main burner line 11 through a main gas valve (not shown).
  • the main gas valve is operated by the thermal expansion portion of probe 7 as determined by adjustable linkage associated with the temperature setting knob 6.
  • the main gas valve is open and the main burner 5 is ignited by the pilot flame.
  • the main valve closes.
  • the invention herein relates to a helical thermal switch unit rather than a concentric switch as shown in the above noted patent, and is of a construction suitable for positioning it inside the confines of probe 7 rather than being mounted external thereto.
  • the probe 7 or sensing element is inserted into the water heater, is held in position by shank 19 threadedly engaging a threaded opening in the water heater housing 15.
  • the control unit 2 is secured to probe 7, as by bolts 20, for example.
  • the probe 7 consists generally of a copper tube 16 having one end threadedly secured to shank 19 and the other end secured, as by welding, to an Invar rod 17 which is encompassed by the copper tube 16 and which extends coaxially therewith. The free end of rod 17 extends within the confines of control unit 2 and engages element 18 of control 2.
  • the copper tube 16 expands and contracts in response to changes in water temperature and the non-expanding rod 17 transmits such movement to element 18 which activates a snap action thermostatic mechanism (not shown) which in turn controls the noted main gas valve of control unit 2.
  • a snap action thermostatic mechanism (not shown) which in turn controls the noted main gas valve of control unit 2.
  • the above described structure is well known in the art and is one variation of the thermal bulb thermostatic element of the noted United States Patent No. 2,409,387. For purposes of clarity, it has been chosen to omit a showing of the normal sealing and insulating material and components for connecting the copper tube 16 to shank 19 and for connecting shank 19 to the housing of control unit 2.
  • the helical thermal unit shown generally at 21 consists of an inner cylinder or tube 22 having an inner diameter slightly in excess of the diameter of rod 17 to permit free movement of the rod 17 therethrough.
  • the rearward end 24 of the inner cylinder 22 may be formed into hexagonal shape to enhance gripping thereof by an adjusting tool or having a screwdriver slot for adjustment functions as will be described hereinafter.
  • the forward end 23 of cylinder 22 is slightly expanded to match the inner diameter of a helical bimetal element 25 which has a portion near one end suitably secured, as by welding, to the expanded end 23 of inner cylinder 22. As seen most clearly in FIG. 5, the forward free end of the bimetal element 25 is uncurled sufliciently to make electrical and mechanical contact with the inner periphery of the copper tube 16.
  • the remainder of the bimetal element 25 freely passes over the inner cylinder 22 and freely inside of the copper tube 16 to permit frictionless coiling and uncoiling in response to ambient temperature variations.
  • the rearward and free end 27 of the bimetal element 25 includes a contact element 28 suitably secured thereto.
  • the thermal switch unit 21 also includes an outer cylinder or tube 29 having one end terminating in a flange 3t) and the other end terminating in :a forward projecting tab which has a contact 13 suitably secured thereto.
  • the outer diameter of the outer cylinder 29 is less than the inner diameter of copper tube 16 in order to preclude electrical contact therebetween.
  • the outer cylinder 29 is placed over an insulating cylindrical element 31, preferably of Teflon which in turn is placed over the inner cylinder 22, the thickness of the insulating element 31 being selected so as to provide a press fit relationship between the outer cylinder 29 and inner cylinder 22.
  • insulating element 31 includes a plurality of elongated serrations which are deformed slightly to provide the noted press fit.
  • the outer cylinder 29 is positioned longitudinally on inner cylinder 22 so that contact 13 is in alignment with contact 28.
  • An insulating washer 32 of L-shaped cross-section is provided on outer cylinder 29 to prevent its electrical contact with the copper tube 16 and/ or shank 19. Washer 32 also permits easy insertion and removal of helical switch unit while providing an alignment function in maintaining inner cylinder 22 frictionally independent of the rod 17.
  • FIG. 3 shows the position of contacts 13 and 28 prior to the noted over-temperature condition.
  • contact 28 is connected to ground potential. This is accomplished by conductor 33 being suitably connected between the hexagonally shaped, or slotted end 24 of inner cylinder 22 and the shank 19. A parallel connection also exists between the copper tube 16 and the free end 26 of bimetal element 25.
  • the outer cylinder 29, carrying contact 13 is insulated from ground potential and a conductor 34 is suitably secured thereto for series connection with the electromagnet 9 winding as hereinbefore described.
  • the helical thermal switch unit 21 is arranged to fit inside of the copper tube 16 and over the Invar rod 17 so as not to interfere with the normal thermostatic functions thereof. Also, the switch unit 21 is readily adjustable, yet arranged to preclude misadjustment by normal thermal conditions. Still further, switch unit 21 is readily removable for repairs, cleaning and/ or replacement. By virtue of being physically located within the confines of the normal sensing probe 7, an over-temperature condition can be sensed by the control unit 2 without external wiring and the switch is physically located to prevent unaulhorized adjustment or tampering.
  • a thermal switch including a tube-like body having a high thermal coeflicient of expansion, a support for said body, and a rod having one end fixed to one end of said body, said rod having a cross section smaller than that of said body, said rod extending through said body in spaced relation to the internal surface thereof
  • the combination comprising: a bimetallic helix in the said space between said rod and said body, said helix having an axis extending along the lengths of said rod and said body inside of said body, said helix being spaced both from said rod and said body from one end of said helix to a portion thereof near the other end thereof, said helix including a first metal layer at its outside diameter and a second metal layer at its inside diameter, said first and second metals having different thermal coeflicients of expansion; first means to hold only said portion of said helix near said other end in a fixed position in the space between said rod and said body, said one end of said helix being free to move relative to said rod and said body
  • a thermally responsive control device including an elongated main tube of high thermal expansive characteristics adapted to be mounted in a support adjacent the wall of a chamber to be heated, with the forward end of the tube extending into the chamber, and an elongated rod of low thermal expansive characteristics positioned within the tube with its forward end attached to the forward end of the tube, and the remainder of the rod spaced from the surrounding tube, an elongated temperature responsive switch unit positioned within the space between the tube and the rod, the unit comprising: an elongated conductive inner tube surrounding a portion of the rod extending through the wall of the chamber and surrounding a major portion of the rod extending into the chamber, the inner tube having a considerable portion of its length contiguous to but movable with respect to the rod; an elongated bimetallic helical element surrounding a forward portion of the inner tube with a forward portion of the element being attached to a forward portion of the inner tube, and with the portions of the element extending rearwardly from the attachment point loosely surrounding the inner tube, a contact
  • the control device of claim 2 wherein the outer tube has its forward end terminating in a forwardly extending projection carrying the fixed contact and the rear end of the tube terminates in an outwardly extending flange; and including an insulator with an L-shaped crosssection surrounding the rear end of the outer tube for insulating the outer tube with respect to the main tube and for properly aligning the inner and outer tubes within the main tube.

Landscapes

  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thermally Actuated Switches (AREA)
US489220A 1965-09-22 1965-09-22 Helical thermal switch Expired - Lifetime US3387246A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US489220A US3387246A (en) 1965-09-22 1965-09-22 Helical thermal switch
NL6613293A NL6613293A (enrdf_load_html_response) 1965-09-22 1966-09-21

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US489220A US3387246A (en) 1965-09-22 1965-09-22 Helical thermal switch

Publications (1)

Publication Number Publication Date
US3387246A true US3387246A (en) 1968-06-04

Family

ID=23942908

Family Applications (1)

Application Number Title Priority Date Filing Date
US489220A Expired - Lifetime US3387246A (en) 1965-09-22 1965-09-22 Helical thermal switch

Country Status (2)

Country Link
US (1) US3387246A (enrdf_load_html_response)
NL (1) NL6613293A (enrdf_load_html_response)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3670807A (en) * 1968-09-04 1972-06-20 Leslie Co Storage type hot water heating system
US5312036A (en) * 1991-09-13 1994-05-17 Ursus Trotter Instantaneous water heater which includes safety devices separately or in combination to prevent the explosion of the heat exchanger in the event of an excessive heating of the water in the heating coil and to shut-off the flow of gas to the burner

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1574508A (en) * 1922-04-28 1926-02-23 Condit Electrical Mfg Corp Thermal electric-circuit controller
US2321852A (en) * 1941-06-25 1943-06-15 William A Ray Control device
US2575481A (en) * 1946-03-30 1951-11-20 Stanley W Anderson Wire fastener
US3093887A (en) * 1958-07-11 1963-06-18 Belling & Lee Ltd Securing inserts in sheet material
US3291390A (en) * 1965-02-26 1966-12-13 Deutsch Controls Corp Thermally operated switch

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1574508A (en) * 1922-04-28 1926-02-23 Condit Electrical Mfg Corp Thermal electric-circuit controller
US2321852A (en) * 1941-06-25 1943-06-15 William A Ray Control device
US2575481A (en) * 1946-03-30 1951-11-20 Stanley W Anderson Wire fastener
US3093887A (en) * 1958-07-11 1963-06-18 Belling & Lee Ltd Securing inserts in sheet material
US3291390A (en) * 1965-02-26 1966-12-13 Deutsch Controls Corp Thermally operated switch

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3670807A (en) * 1968-09-04 1972-06-20 Leslie Co Storage type hot water heating system
US5312036A (en) * 1991-09-13 1994-05-17 Ursus Trotter Instantaneous water heater which includes safety devices separately or in combination to prevent the explosion of the heat exchanger in the event of an excessive heating of the water in the heating coil and to shut-off the flow of gas to the burner

Also Published As

Publication number Publication date
NL6613293A (enrdf_load_html_response) 1967-03-23

Similar Documents

Publication Publication Date Title
US3447746A (en) Burner control device for a water heater
US2353042A (en) Temperature control system
US3387246A (en) Helical thermal switch
US4207053A (en) Igniter and flame sensor assembly for gas burning appliance
US3691501A (en) Thermostat assemblies utilizing a heat expansive and contractive elastomeric material
US3291390A (en) Thermally operated switch
US2165555A (en) Control device
US3090560A (en) Gas regulator apparatus
US3286923A (en) Thermostatic control device for normal and abnormal conditions
US1612246A (en) Thermal cut-out device
US4056348A (en) Glow coil ignition system with flame sensing
US3568123A (en) Electrical thermostat and parts therefor or the like
US3433411A (en) Unitary thermostatic control device with dual temperature sensors
US2902221A (en) Burner control system
US3495925A (en) Combination igniter and temperature sensor
US3092323A (en) Burner fuel control system
US3402886A (en) Thermostatic control device with high limit switch
US2836640A (en) Unitary thermoelectric generator
US3402887A (en) Burner control device for a water heater
US1725296A (en) Burner-lighting mechanism
US3532269A (en) Dual sensing thermostatic control device
US3412934A (en) Thermostatic control device
US3289935A (en) Thermostatic control device
US2717381A (en) matthews
US3908898A (en) Thermostat mounting assembly

Legal Events

Date Code Title Description
AS Assignment

Owner name: ITT CORPORATION

Free format text: CHANGE OF NAME;ASSIGNOR:INTERNATIONAL TELEPHONE AND TELEGRAPH CORPORATION;REEL/FRAME:004389/0606

Effective date: 19831122