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US3775843A Expired / Lapsed US ⏱️ 0.0 years remaining

Method of making temperature responsive apparatus

Assignee: Individual
•
Filing: 1972-09-06
•
Granted: 1973-12-04
•
Expires: 1992-09-06
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Abstract

Abstract There is disclosed a method of making thermistors included in apparatus for measuring precisely, to 0.01* C., difference in temperature; the thermistors are subjected to the temperatures whose difference is being measured. The logarithm of electrical resistance of each thermistor is proportional to its temperature and the thermistors are connected in a ratiometric circuit for measuring their relative resistances. Each thermistor is a ceramic of ferroelectric material (for example, barium-strontium titanate) formed by mixing powders of different compositions, each composition having a different ferroelectric resistance anomaly, and then firing and oxidizing bodies pressed from the mixture of powders. The powders are derived by reducing separate slurries, each containing a composition, to powder. The mixture of powders is heterogeneous so that the grains of the ceramic include a plurality of particles of powder which microscopically would manifest distinct ferroelectric resistance anomalies if fired along but the macroscopic response of the ceramic is loglinear over a substantial temperature range.

Inventors

  • 👤 R Wendt

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-01 21:24
CPC Classifications
G; G01; G01K; G01K3/00; G01K3/08; G01K3/14; H; H01; H01C; H01C7/00; H01C7/04; H01C7/042; H01C7/043; H01C7/045; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49085

Claims Analysis

Total Claims: 9
Claim 1
Independent Claim 119 words
The method of making thermistors having a predetermined temperature-resistance characteristic which comprises: a. producing a plurality of separate powders, each powder including a plurality of chemical components which react to produce ferroelectric thermistor material, each powder having a different relationship of said chemical components, so that each said material respectively derived from a powder has a different relationship of its components; b. mixing together predetermined quantities of each said powder to produce a composite intermediate powder; c. pressing said intermediate powder into thermistor shapes; d. firing said shapes at a high temperature to produce ceramic structures of said shapes; and e. thermo-chemically treating the components of the shapes, fired as aforesaid, to prOduce electrical conductivity in the ceramic shapes.
Claim 2
Dependent Claim 17 words
The method of claim 2 wherein at least some of the powders include an electron donor material.
Claim 3
Dependent Claim 35 words
The method of claim 2 wherein each powder is conditioned to be pressed by adding a small quantity of a binder of a material that does not deleteriously affect the ferroelectric properties of the thermistor.
Claim 4
Dependent Claim 99 words
The method of claim 2 for producing a barium-strontium titanate thermistor wherein each powder includes barium carbonate, strontium carbonate and titanium dioxide and a small quantity of yttrium oxide as an electron donor, at least the barium carbonate and the strontium carbonate being present in the different powders in different relative quantities, and wherein the binder is polyvinyl alcohol, and wherein the powder is pressed into shapes at a pressure of about 10,000 pounds per square inch, and wherein the pressed shapes are fired in an inert atmosphere at about 1,400* C. and are oxidized at about 1,000* C.
Claim 5
Dependent Claim 63 words
The method of claim 2 wherein the mixture of intermediate powders are processed into thermistors each made up of grains, each grain including components of different powders, and the different powders being heterogeneously mixed so that the ferroelectric resistance anomaly of different grains of the thermistor are at different temperatures, each anomaly corresponding to a different relationship of components in said last-named grain.
Claim 6
Dependent Claim 44 words
The method of claim 2 wherein equal quantities of six separate powders having the following compositions in weight percent are mixed: Powder Strontium Titanate Barium Titanate 1 3 97 2 10 90 3 17 83 4 23 77 5 30 70 6 37 63
Claim 7
Dependent Claim 41 words
The method of claim 2 wherein equal quantities of five separate powders having the following compositions in weight percent are mixed: Powder Strontium Titanate Barium Titanate 1 15 85 2 23 77 3 32 68 4 40 60 5 47 53
Claim 8
Dependent Claim 18 words
The method of claim 7 wherein the shapes produced from the powders are fired at about 1,398* C.
Claim 9
Dependent Claim 18 words
The method of claim 8 wherein the shapes produced from the powders are fired at about 1,377* C.

References Cited (Backward Citations)

US2976505A Cited
US3295087A Cited
US3644864A Cited
US3673538A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1976-12-03 1977-06-04 1977-12-04 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1980-12-03 1981-06-04 1981-12-04 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1984-12-03 1985-06-04 1985-12-04 $7700.00 Window Closed / Lapsed

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