US2906981A - Variable resistance device - Google Patents

Variable resistance device Download PDF

Info

Publication number
US2906981A
US2906981A US716705A US71670558A US2906981A US 2906981 A US2906981 A US 2906981A US 716705 A US716705 A US 716705A US 71670558 A US71670558 A US 71670558A US 2906981 A US2906981 A US 2906981A
Authority
US
United States
Prior art keywords
bore
coating
resistance
expansion
mercury
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
US716705A
Other languages
English (en)
Inventor
Benjamin F Freeberg
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.)
Vapor Heating Corp
Original Assignee
Vapor Heating Corp
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 Vapor Heating Corp filed Critical Vapor Heating Corp
Priority to US716705A priority Critical patent/US2906981A/en
Priority to BE574665A priority patent/BE574665A/fr
Priority to FI30359A priority patent/FI40183C/fi
Application granted granted Critical
Publication of US2906981A publication Critical patent/US2906981A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K1/00—Details of thermometers not specially adapted for particular types of thermometer
    • G01K1/14—Supports; Fastening devices; Arrangements for mounting thermometers in particular locations
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0091—Transmitting or indicating the displacement of liquid mediums by electrical, electromechanical, magnetic or electromagnetic means
    • G01L9/0092—Transmitting or indicating the displacement of liquid mediums by electrical, electromechanical, magnetic or electromagnetic means using variations in ohmic resistance

Definitions

  • the present invention relates to variable resistance devices of the liquid column type. More particularly, the present invention is concerned with an electrical resistance element coated on the interior bore of a capillary tube containing the liquid column. Portions of the resistance element are shorted out by the liquid column the level of which varies within the capillary in response to a change in a physical condition such as pressure, temperature or momentum.
  • the resistance coating is a chemically-deposited solid solution of a metallic carbide in a metal the coeicient of expansion of which may be varied to correspond to the coecient of expansion of the material of the capillary tube, for example, glass tubes having different coeicients of expansion.
  • Such devices have uses as accelerometers, pressure sensors, thermostats and a variety of other uses.
  • the device is shown herein as a conventional and relatively small thermostat of the type shown in the patent of William M. Smith et al., No. 2,596,825, issued May 13, 1952.
  • One contemplated use of the device as illustrated is in association with a control device for varying the delivery of heated or unheated air into an enclosure.
  • the present invention improves upon the prior devices by providing a chemically-deposited coacting or resistive element which is strong and dense; bonds well with the glass capillary tube which carries it; has a thermal coefcient of expansion corresponding to that of the glass of the capillary tube; and, has a thickness not in excess of two millionths (.000002) of one inch when applied.
  • the coating is chemically stable in the presence of the liquid column and of the inert, pressurizing gas also contained within the capillary tube which gas cooperates with the small bore diameter to prevent splitting of the liquid column as discussed above. Another feature of the coating is that its thickness may be varied to vary the ohmic resistance per unit length.
  • coelhcient of expansion of the coating may be varied, within certain adequate limits, to correspond to the coefcient of expansion of the particular material, glass, upon which it is being coated. This is accomplished by varying the proportion of the metallic carbide to the metal in the solid solution comprising the coating. The desired result is attainable, it is theorized, because the metals used have a lower coeficient of expansion than does the glass while the metallic carbide has a higher coefficient of expansion than the glass. A solid solution of the two may be made to match, in terms of thermal expansion, the particular composition of glass to which it is bonded. Thermal cycling of the coated tube between F. and +300 F. with no evidence of cracking or separation from the tube wall serves to substantiate the theory.
  • the improved device has suiicient current-carrying capacity that it may be connected directly into an appropriate system thereby eliminating the need for relays or electrical amplifying means to bolster its signal.
  • variable resistance device of the character described, having the characteristics discussed above.
  • Fig. 1 is a full view of a variable resistance thermostat, partly in section, constructed in accordance with the present invention
  • Fig. 2 is an enlarged longitudinal sectional view of the device shown in Fig. l;
  • Fig. 3 is a sectional view taken substantially on the line 3-3 of Fig. 2.
  • variable resistance thermostat shown is constructed to respond to temperature changes, therefore it is intended to be exemplary only, since the principles of the invention can be embodied in other similar devices constructed to respond to inertia or pressure.
  • Said thermostat includes, in its general organization, a capillary tube 10 having a central capillary bore 11 formed therein.
  • the bore is hermetically closed or sealed, as at 12, at its upper end and communicates with an interior chamber 13.0f a reservoir 14 located at its lower end.
  • the tube and reservoir are preferably formed of lglass of a character selected to fulfill the thermal requirements of the device.
  • the chamber 13 is lled with an electrically conductive liquid 15 such as mercury or a mercury thallium alloy which liquid extends from the chamberv into the bore 11V of the capillary tube.
  • the height of the mercury within the tube is dependent upon the extent of expansion of the overall volume of mercury.
  • the upper portion ofthe tube is pressurized with an inert gas such as argon, helium, krypton, neon or zenon.
  • the inner cylindrical surfaceV of a limited portion of the bore 11 is coated with an electrically conductive coating 16.
  • the coating is chemically-deposited upon the Wall of the bore and is a solid solution o f a metallic carbide in a metal selected and applied so as to have a coecient of expansion corresponding to that of the glass of the tube.
  • the coating in effect, provides an internal conductive sleeve or liner within the bore of the capillary tube throughout the expected range of movement of the mercury column.
  • Preferred solid solutions of metallic carbides in metals for coating the bore include tungsten carbide in tungsten and molybdenum carbide in molybdenum. These preferred materials, in solid solution, have the desired thermal characteristics; are chemically stable in the presence of mercury 0r a mercury thallium alloy and of ⁇ an inert, pressurizing gas; and, have sufficient current-carrying capacity. In addition they may be chemically deposited along pre-determined portions of the bore with relative ease.
  • Two lead-in wires 17 and 18 are illustrated making electrical contact with upper and lower portions respectively of the electrically conductive coating 16, However, additional leads may be provided if, for example, it is desired to vary resistance to more than one electrical load or for other purposes.
  • Various means may be employed for establishing the electrical connection between the llead-in wires and the coating.
  • the coating 156 makes physical and electrical contact at its upper portion with a transverse'metallic conductor 19 which is embedded in and passes through the glass material of the tube substantially tangential to the bore 11. The medial regions of the conductor 19 engage the coating as at 20 to establish the electrical connection.
  • the ends of the conductor 19 make electrical Contact with a terminal .or attachment ring 2,1 which surrounds the tube 10.
  • the terminal may be secured to conductor 19 by solder.
  • the lead wire 17 may be soldered to the ring 21 completing the upper lead-in connection to the coating.
  • the lower lead-in yconnection is the same as the upper connection, and, for descriptive purposes, it is deemed suificient to apply the reference numerals 22 and 23 to the conductor ⁇ and ring, respectively, employed in making the electrical connection.
  • a variable electrical resistance device of the liquid column type including a glass capillary tube having a central bore hermetically sealed at opposite ends; a resistance element comprising a tubular lining having a wall thickness 0f approximately .000002 inch bonded to the wall of the bore of said capillary tube and composed of a solid solution of a metallic carbide in a metal selected from a group of carbide in metal solutions consisting of molybdenum carbide in molybdenumrand tungsten carbide in tungsten which solid solution has a coeicient of expansion substantially identical to the coeicient of expansion of said capillary tube; electrodes sealed through the wall of said capillary tube at spaced locations lengthwise thereof for establishing electrical Vcommunication with said resistance element; and an electrically conductive liquid contained within said tube and movable as a column within said resistance element in response to changing physical conditions to short out portions of the resistance element.
  • variable resistance device as deiined in claim l characterized in that the overall ohmic value of said resistance element is relatively high by comparison to the ohmic value of a portion of the liquid column equal in length and diameter to the length and diameter respectively of the central bore of said resistance element.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermistors And Varistors (AREA)
US716705A 1958-02-21 1958-02-21 Variable resistance device Expired - Lifetime US2906981A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US716705A US2906981A (en) 1958-02-21 1958-02-21 Variable resistance device
BE574665A BE574665A (fr) 1958-02-21 1959-01-12 Dispositif à résistance électrique variable du type à colonne de liquide.
FI30359A FI40183C (fi) 1958-02-21 1959-02-20 Reglerbar motståndsanordning

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US716705A US2906981A (en) 1958-02-21 1958-02-21 Variable resistance device

Publications (1)

Publication Number Publication Date
US2906981A true US2906981A (en) 1959-09-29

Family

ID=24879104

Family Applications (1)

Application Number Title Priority Date Filing Date
US716705A Expired - Lifetime US2906981A (en) 1958-02-21 1958-02-21 Variable resistance device

Country Status (3)

Country Link
US (1) US2906981A (bg)
BE (1) BE574665A (bg)
FI (1) FI40183C (bg)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3087811A (en) * 1960-11-03 1963-04-30 Vapor Corp Alloys of mercury

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2023740A (en) * 1934-05-16 1935-12-10 Honeywell Regulator Co Electrical resistance apparatus
US2566369A (en) * 1946-01-23 1951-09-04 Henry M Putman Pressure gauge
US2735881A (en) * 1956-02-21 Metal-impregnated heating rods for electric
US2743340A (en) * 1952-05-28 1956-04-24 Honeywell Regulator Co Electrical resistor device
US2748231A (en) * 1954-09-30 1956-05-29 Honeywell Regulator Co Electrical indicator

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2735881A (en) * 1956-02-21 Metal-impregnated heating rods for electric
US2023740A (en) * 1934-05-16 1935-12-10 Honeywell Regulator Co Electrical resistance apparatus
US2566369A (en) * 1946-01-23 1951-09-04 Henry M Putman Pressure gauge
US2743340A (en) * 1952-05-28 1956-04-24 Honeywell Regulator Co Electrical resistor device
US2748231A (en) * 1954-09-30 1956-05-29 Honeywell Regulator Co Electrical indicator

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3087811A (en) * 1960-11-03 1963-04-30 Vapor Corp Alloys of mercury

Also Published As

Publication number Publication date
FI40183B (bg) 1968-07-31
BE574665A (fr) 1959-05-02
FI40183C (fi) 1968-11-11

Similar Documents

Publication Publication Date Title
US4103135A (en) Gas operated switches
GB2098012A (en) Thermal fuse and the method of manufacturing the same
US3959696A (en) Over voltage arrester
US2685015A (en) Resistance thermometer element
NO130887B (bg)
US2906981A (en) Variable resistance device
US3436713A (en) Cryogenic resistance temperature detector
US2914637A (en) System and device for prolonging the life of current energized filamentary elements
US2743340A (en) Electrical resistor device
US2783341A (en) Probe for liquid level indicator
US2974531A (en) Accelerometer
US3136973A (en) Sealed resistor
US2332392A (en) Current regulator tube
US2749754A (en) Electrical apparatus for measuring pressure
US3068459A (en) Apparatus for indicating the liquid or gaseous state of a fluid
US2389915A (en) Resistor device
US4419652A (en) Temperature sensor
US3102179A (en) Liquid contact switch
US2300882A (en) Vacuum tube
US2611057A (en) Thermally actuated mercury switch
US3023389A (en) Electrical resistor unit
US2391506A (en) Resistance device
US3315517A (en) Thermal conductivity detector cell
US2308459A (en) Electrical heating element
US2878355A (en) Electrical temperature sensing element