US4501192A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Piston for precision dosing instrument
Assignee: WALTER GRAF U CO & Co A CORP OF GERMANY GmbH
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Filing: 1982-09-15
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Granted: 1985-02-26
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Expires: 2002-09-15
Abstract
Abstract A piston for a precision dosing instrument includes a cylindrical core which may be made of glass, ceramic or metal, and a precision ground sleeve of polytetrafluorethylene disposed over the core. One end of the sleeve is closed while the core is open at both ends but the openings may have different diameters.
Inventors
- 👤 Erich Knodel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:31
CPC Classifications
F; F16; F16J; F16J1/00; F16J1/02; F05; F05C; F05C2225/00; F05C2225/04; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49229; Y10T29/49249; Y10T29/49256
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
170 words
A piston for a precision dosing instrument comprising: a cylindrical core and a sleeve of polytetrafluorethylene disposed on said core, said core being of glass, ceramic or metal and being formed as a rigid tube open at both longitudinal ends, said longitudinal end adjacent the working end of the piston is defined by a substantial planar surface extending perpendicularly of the longitudinal axis of the core with at least one relatively small opening therein forming a part of the opening of said tube, said sleeve being one integral piece with a cylindrical first portion extending about the cylindrical walls of said core and having a cylindrical outer surface and a closed end second portion extending over and engaging the longitudinal end of said core adjacent the working end of the piston, said closed end second portion having a greater thickness than said first portion and a planar front working face extending perpendicularly of the longitudinal axis of said core, said sleeve being thermally shrunk onto said core and precision-ground finished.
Claim 2
Dependent Claim
170 words
A piston for a precision dosing instrument comprising: a cylindrical core and a sleeve of polytetrafluorethylene disposed on said core, said core being of glass, ceramic or metal and being formed as a rigid tube open at both longitudinal ends, said longitudinal end adjacent the working end of the piston is defined by a substantial planar surface extending perpendicularly of the longitudinal axis of the core with at least one relatively small opening therein forming a part of the opening of said tube, said sleeve being one integral piece with a cylindrical first portion extending about the cylindrical walls of said core and having a cylindrical outer surface and a closed end second portion extending over and engaging the longitudinal end of said core adjacent the working end of the piston, said closed end second portion having a greater thickness than said first portion and a planar front working face extending perpendicularly of the longitudinal axis of said core, said sleeve being thermally shrunk onto said core and precision-ground finished.
Claim 3
Dependent Claim
20 words
A piston according to claim 1, wherein said second portion is at least five times thicker than said first portion.
Claim 4
Dependent Claim
31 words
A piston according to claim 2, wherein said longitudinal end adjacent the working end of the piston is defined by a closure end part provided with said at least one opening.
Claim 5
Dependent Claim
17 words
A piston according to claim 1, wherein said rigid tube is defined by a uniform thick wall.
Claim 6
Dependent Claim
38 words
A piston according to claim 1, wherein said core has a through passage of two different diameters with the smaller diameter passage being at the working end of the said core and defined by said relatively small opening.
Claim 7
Dependent Claim
16 words
A piston according to claim 5, wherein said through passage is disposed coaxially of said core.
Claim 8
Dependent Claim
126 words
A method for manufacturing a piston according to claim 1 comprising the steps of providing a round rod of polytetrafluorethylene material, forming a longitudinally extending opening in said rod of a diameter smaller than the outer diameter of said core, said longitudinally extending opening extending substantially the longitudinal length of said rod but terminating short of one longitudinal end of said rod to thereby provide a closed end on said rod with said rod thereby defining said sleeve, heating said sleeve to a temperature of from 200° to 250° Centigrade, inserting said core into said heated sleeve while said core is at ambient temperature, allowing said sleeve to cool to thereby obtain a unified piston, and machining the outer sleeve to the desired diameter and finish.
Claim 9
Dependent Claim
21 words
A method according to claim 7 comprising initially cutting said rod to the desired length before forming said longitudinally extending opening.
Claim 10
Dependent Claim
15 words
A method according to claim 8 wherein said longitudinally extending opening is formed by drilling.
References Cited (Backward Citations)
US2315944A
Cited
US2607342A
Cited
US2895773A
Cited
US3237815A
Cited
DE2343687A1
Cited
US4315454A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-02-26 | 1988-08-27 | 1989-02-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-02-26 | 1992-08-27 | 1993-02-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-02-26 | 1996-08-27 | 1997-02-26 | $7700.00 | Window Closed / Lapsed |