US4067939A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Casting of articles containing calcined gypsum
Assignee: Individual
•
Filing: 1975-06-27
•
Granted: 1978-01-10
•
Expires: 1995-06-27
Abstract
Abstract A method of making a cast article from a composition which contains a hydraulic binding agent comprising by weight from 90% to 10% calcined gypsum and from 10% to 90% Portland cement comprises mixing the composition with water to produce a fluid mixture, either the water or some at least of the components of the composition or both being heated so that the mixture has a temperature of from 70° to 130° F, and pouring the fluid mixture into a mould or other supporting device where the reaction of the calcined gypsum with the water causes the mixture to set and the heat of this reaction causes the temperature of the mixture to begin to rise. As soon as the mixture has set sufficiently to be self supporting, the set mixture, which forms the cast article, is removed from the mould or other supporting device and then the dissipation of both heat and moisture from the cast article is controlled so that the temperature of the article continues to rise to from 90° to 180° F. This temperature is maintained for a period of at least two hours to allow the moisture in the article to cure the cement. Preferably the dissipation of heat and moisture from the cast article is controlled by confining the cast article in a heat and moisture insulating jacket which maintains an atmosphere of 100% relative humidity around the article. After the temperature and moisture content has been maintained to cure the cement, the cast article is dried either by the application of a vacuum to a part at least of its surface or by causing air to flow over its surface while the article is still hot.
Inventors
- 👤 James N. Lowe
- 👤 Byron C. Grebe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:52
CPC Classifications
B; B28; B28B; B28B1/00; B28B1/14; Y; Y10; Y10S; Y10S264/00; Y10S264/43
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
192 words
A method of making a cast article comprising the steps of: a. mixing water with a composition comprising a binding agent containing, by weight, from 90% to 10% calcined gypsum and from 10 to 90% Portland cement, to produce a fluid mixture, at least one of said composition and said water being heated whereby said mixture has a temperature of from 70° to 130° F; b. pouring said fluid mixture into a supporting device; c. allowing a reaction between said calcined gypsum and said water in said mixture to cause said mixture to set in said supporting device, said reaction producing heat which causes the temperature of said mixture to begin to rise; d. removing said mixture from said supporting device after said mixture has set sufficiently to be self supporting and thus form said cast article; e. controlling the dissipation of both heat and moisture from said set mixture forming said cast article whereby the temperature of said set mixture rises to from 90° to 180° F; and, f. maintaining the temperature and moisture content of said set mixture for a period of at least two hours to cure said cement.
Claim 2
Independent Claim
192 words
A method of making a cast article comprising the steps of: a. mixing water with a composition comprising a binding agent containing, by weight, from 90% to 10% calcined gypsum and from 10 to 90% Portland cement, to produce a fluid mixture, at least one of said composition and said water being heated whereby said mixture has a temperature of from 70° to 130° F; b. pouring said fluid mixture into a supporting device; c. allowing a reaction between said calcined gypsum and said water in said mixture to cause said mixture to set in said supporting device, said reaction producing heat which causes the temperature of said mixture to begin to rise; d. removing said mixture from said supporting device after said mixture has set sufficiently to be self supporting and thus form said cast article; e. controlling the dissipation of both heat and moisture from said set mixture forming said cast article whereby the temperature of said set mixture rises to from 90° to 180° F; and, f. maintaining the temperature and moisture content of said set mixture for a period of at least two hours to cure said cement.
Claim 3
Dependent Claim
38 words
A method as claimed in claim 1, further comprising the step of drying said set mixture forming said cast article after said dissipation of heat and moisture has been controlled for said period of at least two hours.
Claim 4
Dependent Claim
42 words
A method as claimed in claim 2, wherein said step of drying said set mixture forming said cast article includes the step of applying a vacuum to at least a part of the surface of said cast article to suck moisture therefrom.
Claim 5
Dependent Claim
55 words
A method as claimed in claim 2, wherein said step of drying said set mixture forming said cast article includes the step of causing air to flow over at least a part of the surface of said cast article while the temperature of said cast article is still at least as high as 90° F.
Claim 6
Dependent Claim
21 words
A method as claimed in claim 1, wherein said dissipation of heat and moisture is controlled for at least three hours.
Claim 7
Dependent Claim
24 words
A method as claimed in claim 1, wherein said binding agent contains from about 40 to about 50% by weight of said calcined gypsum.
Claim 8
Dependent Claim
21 words
A method as claimed in claim 1, wherein said binding agent further comprises up to 15% by weight of Pozzolana cement.
Claim 9
Dependent Claim
14 words
A method as claimed in claim 1, wherein said Portland cement is sulphate resistant.
Claim 10
Dependent Claim
21 words
A method as claimed in claim 1, wherein said Portland cement has a specific surface of above 450 m 2 /Kg.
Claim 11
Dependent Claim
28 words
A method as claimed in claim 1, further comprising the step of entraining air in said fluid mixture before said fluid mixture is poured into said supporting device.
Claim 12
Dependent Claim
35 words
A method as claimed in claim 10, wherein said composition further comprises an air entraining agent including sodium lauryl sulphonate in an amount not less than 0.01% by weight of said water in said mixture.
Claim 13
Dependent Claim
24 words
A method as claimed in claim 1, in which said calcined gypsum consists at least partly of high strength autoclaved α or α+ gypsum.
Claim 14
Dependent Claim
43 words
A method as claimed in claim 1, wherein said step of mixing said composition and said water is performed in a rotary paddle mixer and includes the step of rotating a paddle of said mixer at a speed of at least 40 r.p.m.
Claim 15
Dependent Claim
14 words
A method as claimed in claim 1, wherein said composition further comprises reinforcing fibers.
Claim 16
Dependent Claim
29 words
A method as claimed in claim 14, wherein said fibers are of sisal and are present in an amount of up to 2% by weight of said binding agent.
Claim 17
Dependent Claim
20 words
A method as claimed in claim 1, further comprising the step of incorporating a fluidising agent in said fluid mixture.
Claim 18
Dependent Claim
42 words
A method as claimed in claim 16, wherein said fluidising agent is selected from the group consisting of sulphonated melamine formaldehyde resin and Gum Arabic and is present in an amount of from 0.1% to 2% by weight of said binding agent.
Claim 19
Dependent Claim
27 words
A method as claimed in claim 1, further comprising the step of incorporating in said fluid mixture a retarding agent for retarding the setting of said mixture.
Claim 20
Dependent Claim
30 words
A method as claimed in claim 18, wherein said retarding agent is sodium citrate and is present in an amount of up to 0.1% by weight of said binding agent.
Claim 21
Dependent Claim
26 words
A method as claimed in claim 1, further comprising the step of incorporating in said fluid mixture an accelerator for accelerating the setting of said mixture.
Claim 22
Dependent Claim
29 words
A method as claimed in claim 20, wherein said accelerator is potassium sulphate and is present in an amount of up to 0.1% by weight of said binding agent.
Claim 23
Dependent Claim
99 words
A method as claimed in claim 1, further comprising the step of sealing at least part of the surface of said cast article while said cast article is still moist and has a temperature of from 90° to 180° F by applying to said at least part of said surface a moisture curing liquid synthetic resin, allowing said liquid synthetic resin to be sucked by capillary action into said at least part of said surface and allowing said resin to be cured by moisture in said cast article and to be hardened by heat contained in said cast article.
Claim 24
Dependent Claim
15 words
A method as claimed in claim 22, wherein said liquid curing synthetic resin is polyurethane.
Claim 25
Dependent Claim
35 words
A method as claimed in claim 21, further comprising applying to a remaining part of said surface of said article which has not been sealed with said liquid curing synthetic resin, an acrylic resin emulsion.
Claim 26
Dependent Claim
34 words
A method as claimed in claim 1, further comprising the step of incorporating in said fluid mixture a wax resin emulsion in an amount of up to 2% by weight of said binding agent.
Claim 27
Dependent Claim
46 words
A method as claimed in claim 1, wherein said step of controlling said dissipation of heat and moisture includes the step of confining said cast article in a heat and moisture insulating jacket and thereby maintaining an atmosphere of 100% relative humidity around said cast article.
Claim 28
Dependent Claim
34 words
A method as claimed in claim 1 further comprising the step of incorporating an acrylic resin emulsion in said fluid mixture in an amount of up to 2% by weight of said binding agent.
References Cited (Backward Citations)
US2310023A
Cited
US2533263A
Cited
US2681863A
Cited
US2753608A
Cited
US2882175A
Cited
US2921862A
Cited
US3427374A
Cited
US3770859A
Cited
US3808299A
Cited
US3873332A
Cited
US3957522A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-01-09 | 1981-07-11 | 1982-01-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-01-09 | 1985-07-11 | 1986-01-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-01-09 | 1989-07-11 | 1990-01-10 | $7700.00 | Window Closed / Lapsed |