Patent US3960995A successfully refreshed from Google Patents.
US3960995A
Expired / Lapsed
US
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Method for prestressing a body of ceramic material
Assignee: Individual
•
Filing: 1972-04-17
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Granted: 1976-06-01
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Expires: 1992-04-17
Abstract
Abstract Thermal prestressing methods using unit and selective heating of tendons incorporated in a ceramic or cermet body to selectively elongate the tendon with respect to the body and soften the latter. Upon cooling an anchorage bond is formed between the body and the ends of the tendons, which bond develops a tension in the tendon and prestress in the body upon further cooling. Bodies are also prestressed by forming a bond between the tendon and the body and then heating the body in use so as to elongate the tendon relative to the body, the tendon having a greater coefficient of expansion than the material of the body.
Inventors
- 👤 Jacques P. Kourkene
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:39
CPC Classifications
B; B28; B28B; B28B23/00; B28B23/02; B28B23/04; B28B23/043; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49826; Y10T29/49863; Y10T29/49865; Y10T29/49874; Y10T29/49906
Claims Analysis
Total Claims: 46
Claim 1
Independent Claim
179 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon having a greater coefficient of linear thermal expansion than the material of said body, b. elevating the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 2
Independent Claim
179 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon having a greater coefficient of linear thermal expansion than the material of said body, b. elevating the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 3
Dependent Claim
24 words
The method of claim 1 wherein said step of elevating the temperature is carried out by selectively heating said elongate tendon within the body.
Claim 4
Dependent Claim
26 words
The method of claim 1 wherein said step of elevating the temperature is carried out by heating said elongate tendon and said body as a unit.
Claim 5
Dependent Claim
23 words
The method of claim 1 wherein said step of elevating the temperature is carried out before said ceramic body is formed and fired.
Claim 6
Dependent Claim
23 words
The method of claim 1 wherein said step of elevating the temperature is carried out after said ceramic body is formed and fired.
Claim 7
Independent Claim
205 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon and said body each having a positive coefficient of linear thermal expansion, the coefficient of linear thermal expansion of said body being greater than that of said tendon, b. elevating the temperature of said tendon and region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to unsoftened portions of said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said unsoftened portions of the body to prestress said ceramic body, said tendon seeking to contract with respect to said unsoftened portions of the body as a result of its linear thermal expansion with respect to said unsoftened portions of said body, said bond stress anchorage developing the entire tensile force of said tendon.
Claim 8
Independent Claim
205 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon and said body each having a positive coefficient of linear thermal expansion, the coefficient of linear thermal expansion of said body being greater than that of said tendon, b. elevating the temperature of said tendon and region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to unsoftened portions of said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said unsoftened portions of the body to prestress said ceramic body, said tendon seeking to contract with respect to said unsoftened portions of the body as a result of its linear thermal expansion with respect to said unsoftened portions of said body, said bond stress anchorage developing the entire tensile force of said tendon.
Claim 9
Dependent Claim
24 words
The method of claim 6 wherein said step of elevating the temperature is carried out by selectively heating said elongate tendon within the body.
Claim 10
Independent Claim
234 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon and said body each having a positive coefficient of linear thermal expansion, the coefficient of linear thermal expansion of said tendon being comparable and not greater than the coefficient of linear thermal expansion of said body, b. elevating the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to unsoftened portions of said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to unsoftened portions of said body as a result of the positive linear thermal expansion of the tendon with respect to said unsoftened portions of said body as a result of the positive linear thermal expansion of the tendon with respect to said unsoftened portions of the body, said bond stress anchorage developing the entire tensile force of said tendon.
Claim 11
Independent Claim
234 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon and said body each having a positive coefficient of linear thermal expansion, the coefficient of linear thermal expansion of said tendon being comparable and not greater than the coefficient of linear thermal expansion of said body, b. elevating the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to unsoftened portions of said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to unsoftened portions of said body as a result of the positive linear thermal expansion of the tendon with respect to said unsoftened portions of said body as a result of the positive linear thermal expansion of the tendon with respect to said unsoftened portions of the body, said bond stress anchorage developing the entire tensile force of said tendon.
Claim 12
Independent Claim
194 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon having a greater coefficient of linear thermal expansion than the material of said body, b. applying heat to said tendon and the entire body as a unit, the coefficient of liner thermal expansion of said tendon being greater than that of said body, to thereby elevate the temperature of said tendon and said body to at least the softening temperature of the material of the body, so that said tendon elongates and undergoes differential thermal expansion with respect to said body; c. lowering the temperature of said tendon and said body so that said tendon contracts with a minimum degree of slippage with respect to said body during and after resolidification of said body to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 13
Independent Claim
194 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon having a greater coefficient of linear thermal expansion than the material of said body, b. applying heat to said tendon and the entire body as a unit, the coefficient of liner thermal expansion of said tendon being greater than that of said body, to thereby elevate the temperature of said tendon and said body to at least the softening temperature of the material of the body, so that said tendon elongates and undergoes differential thermal expansion with respect to said body; c. lowering the temperature of said tendon and said body so that said tendon contracts with a minimum degree of slippage with respect to said body during and after resolidification of said body to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 14
Independent Claim
190 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon having a greater coefficient of linear thermal expansion than the material of said body, b. applying heat to said tendon and the region of said body immediately surrounding said tendon selectively, to thereby elevate the temperature of said tendon and said region to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 15
Independent Claim
190 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body, said tendon having a greater coefficient of linear thermal expansion than the material of said body, b. applying heat to said tendon and the region of said body immediately surrounding said tendon selectively, to thereby elevate the temperature of said tendon and said region to at least the softening temperature of the material of the body so that said tendon elongates and undergoes differential thermal expansion with respect to said body, c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 16
Independent Claim
177 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body; b. positioning said tendon and the entire body in an oven, the coefficient of linear thermal expansion of said tendon being greater than that of said body to thereby elevate the temperature of said tendon and said body to at least the softening temperature of the material of the body, so that said tendon elongates and undergoes differential thermal expansion with respect to said body; c. lowering the temperature of said tendon and said body so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said body to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 17
Independent Claim
177 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body; b. positioning said tendon and the entire body in an oven, the coefficient of linear thermal expansion of said tendon being greater than that of said body to thereby elevate the temperature of said tendon and said body to at least the softening temperature of the material of the body, so that said tendon elongates and undergoes differential thermal expansion with respect to said body; c. lowering the temperature of said tendon and said body so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said body to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to said body as a result of its greater coefficient of linear thermal expansion as respects said body, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 18
Independent Claim
187 words
A method for producing a prestressed body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body; b. passing electric current through said tendon, to thereby elevate the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of said body, said tendon having a positive coefficient of linear thermal expansion as respects unsoftened portions of said body, and so that said tendon elongates and undergoes differential thermal expansion with respect to said body c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to unsoftened portions of said body as a result of its positive coefficient of linear thermal expansion, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 19
Independent Claim
187 words
A method for producing a prestressed body with an elongate tendon, comprising the steps of: a. positioning said tendon in said body; b. passing electric current through said tendon, to thereby elevate the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of said body, said tendon having a positive coefficient of linear thermal expansion as respects unsoftened portions of said body, and so that said tendon elongates and undergoes differential thermal expansion with respect to said body c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to unsoftened portions of said body as a result of its positive coefficient of linear thermal expansion, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 20
Independent Claim
16 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of:
Claim 21
Independent Claim
16 words
A method for producing a prestressed ceramic body with an elongate tendon, comprising the steps of:
Claim 22
Dependent Claim
219 words
a. positoning said tendon in said body; b. positioning said tendon and the entire body in an oven, applying heat to said tendon and said body in said oven and causing electric current to flow through said tendon, then discontinuing applying heat to said tendon and said body in said oven and simultaneously maintaining said electric current flowing through said tendon, to thereby elevate the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body, said tendon having a positive coefficient of linear thermal expansion as respects unsoftened portions of said body, and so that said tendon elongates and undergoes differential thermal expansion with respect to said body; c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to unsoftened portions of said body as a result of its positive coefficient of linear thermal expansion, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 23
Dependent Claim
219 words
a. positoning said tendon in said body; b. positioning said tendon and the entire body in an oven, applying heat to said tendon and said body in said oven and causing electric current to flow through said tendon, then discontinuing applying heat to said tendon and said body in said oven and simultaneously maintaining said electric current flowing through said tendon, to thereby elevate the temperature of said tendon and the region of said body immediately surrounding said tendon to at least the softening temperature of the material of the body, said tendon having a positive coefficient of linear thermal expansion as respects unsoftened portions of said body, and so that said tendon elongates and undergoes differential thermal expansion with respect to said body; c. lowering the temperature of said tendon and the region of said body immediately surrounding said tendon so that said tendon contracts with a minimum degree of slippage with respect to said body during and after the resolidification of said region to thereby generate a bond stress anchorage between said tendon and said body to prestress said ceramic body, said tendon seeking to contract with respect to unsoftened portions of said body as a result of its positive coefficient of linear thermal expansion, said bond stress anchorage developing the entire tensile force in said tendon.
Claim 24
Independent Claim
161 words
A method for prestressing a body of ceramic or cermet material and the like using an elongate tendon extending therethrough, said tendon having a greater coefficient of linear thermal expansion than the material of said body, comprising: a. positioning the tendon in the body; b. heating the tendon and the region of the body immediately surrounding the tendon until the softening temperature of the body material is reached, and thereby causing the tendon to elongate with respect to the body; c. cooling the tendon and the region of the body immediately surrounding the tendon to resolidify such region; d. forming a bond stress anchorage directly between the body and the tendon during said step of cooling, said bond transmitting by means of anchorage bond stress the entire prestressing force between the body and the tendon; and e. further cooling the tendon to thereby tension the tendon and transmit the compressive force through said bond stress anchorage, whereby the body is prestressed.
Claim 25
Independent Claim
161 words
A method for prestressing a body of ceramic or cermet material and the like using an elongate tendon extending therethrough, said tendon having a greater coefficient of linear thermal expansion than the material of said body, comprising: a. positioning the tendon in the body; b. heating the tendon and the region of the body immediately surrounding the tendon until the softening temperature of the body material is reached, and thereby causing the tendon to elongate with respect to the body; c. cooling the tendon and the region of the body immediately surrounding the tendon to resolidify such region; d. forming a bond stress anchorage directly between the body and the tendon during said step of cooling, said bond transmitting by means of anchorage bond stress the entire prestressing force between the body and the tendon; and e. further cooling the tendon to thereby tension the tendon and transmit the compressive force through said bond stress anchorage, whereby the body is prestressed.
Claim 26
Dependent Claim
40 words
The method of claim 14 wherein said step of heating comprises: a. positioning the body in an oven; and b. heating the tendon and the entire body in the oven until the softening temperature of the body material is reached.
Claim 27
Dependent Claim
17 words
The method of claim 15 wherein the step of heating in an oven comprises firing the body.
Claim 28
Dependent Claim
12 words
The method of claim 14 wherein said step of heating comprises sintering.
Claim 29
Dependent Claim
12 words
The method of claim 14 wherein said step of heating comprises hot-pressing.
Claim 30
Dependent Claim
25 words
The method of claim 14 wherein said step of heating comprises applying heat to the tendon by causing electric current to flow through the tendon.
Claim 31
Dependent Claim
20 words
The method of claim 14 wherein said step of heating comprises applying heat to the tendon by an induction current.
Claim 32
Dependent Claim
72 words
The method of claim 14 further including: a. positioning of the body and tendon in an oven subsequent to positioning the tendon in the body; and b. raising the temperature of the body and the tendon within the oven prior to the step of heating the tendon and the region of the body immediately surrounding the tendon, thereby reducing the risk of cracking or breakage of the body during said heating step.
Claim 33
Dependent Claim
32 words
The method of claim 21 further including: a. allowing the body to cool to a lower temperature while maintaining the tendon at a high temperature by the step of heating the tendon.
Claim 34
Dependent Claim
20 words
The method as set forth in claim 14 including preforming a passageway through the body for positioning the tendon therein.
Claim 35
Dependent Claim
224 words
The method of claim 23 further including the steps of: a. preforming a plurality of segments of ceramic material; b. preforming a first plurality of aligned continuous passageways extending through each of said assembled segments; c. preforming a second plurality of passageways, each of said second passageways extending through said assembled segments in a direction transverse to the direction of said first plurality of passageways; d. assembling the segments into a desired configuration; e. positioning one of a plurality of tendons longitudinally through one of each of said first plurality of passageways; f. positioning one of a plurality of tendons extending longitudinally through one of each of said second plurality of passageways; g. heating each of the tendons and the region of the body immediately surrounding the tendons until the softening temperature of the body material is reached; h. cooling the region of the body immediately surrounding each of the tendons to resolidify such region and thereby establish an anchorage bond between the tendon and the body; and i. cooling each of the tendons to thereby contract the tendons and transmit a compressive force through the anchorage bond to apply therethrough the compressive prestressing force to the body, so that the application of compressive prestressing force to the body forms the plural assembled segments into an integrated monolithic prestressed ceramic body of desired configuration.
Claim 36
Dependent Claim
37 words
The method of claim 23 further including: a. forcing a fusible material into gaps in the passageway between the tendon and the body, thereby closing said gaps as the fusible material solidifies during cooling of the tendon.
Claim 37
Dependent Claim
24 words
The method of claim 14 further including a. applying an oxidation inhibiting coating to the tendon prior to positioning said tendon in said body.
Claim 38
Dependent Claim
17 words
The method of claim 14 further including: a. forming said tendon by twisting multiple wires into strands.
Claim 39
Independent Claim
89 words
A method for forming a prestressed body of ceramic material for use in an elevated service temperature, comprising: a. selecting a body and a tendon such that the tendon is constructed of a material having a coefficient of linear thermal expansion smaller than that of the material of the body; b. positioning the tendon in the body; c. bonding the tendon to the body; and d. elevating the body to a service temperature, thereby causing the body to expand relative to the tendon and become compressed by the tendon.
Claim 40
Independent Claim
89 words
A method for forming a prestressed body of ceramic material for use in an elevated service temperature, comprising: a. selecting a body and a tendon such that the tendon is constructed of a material having a coefficient of linear thermal expansion smaller than that of the material of the body; b. positioning the tendon in the body; c. bonding the tendon to the body; and d. elevating the body to a service temperature, thereby causing the body to expand relative to the tendon and become compressed by the tendon.
Claim 41
Independent Claim
237 words
A method for prestressing a body of ceramic or cermet material and the like with an elongate tendon extending therethrough, said material and tendon being selected so that when said material is softened under heat it will fuse to the tendon on resolidifying, comprising the steps of: a. positioning said tendon in said body; b. heating said tendon and at least the region of said body immediately surrounding said tendon as a unit in an oven; c. selectively heating said tendon by causing electric current to flow through the tendon until said region softens; d. subsequently discontinuing heating the tendon and at least the region of said body immediately surrounding the tendon as a unit; e. simultaneously with said step of discontinuing, maintaining said tendon and the region of said body immediately surrounding said tendon selectively heated, thereby expanding said tendon with respect to said body; f. subsequently cooling said tendon and said region until material in said region resolidifies and fuses directly to said tendon; g. forming a bond stress anchorage to the outer wall of said tendon at least at each end thereof, said anchorage being capable of transmitting the entire prestressing force between the body and the tendon through bond stress; and h. subsequently further cooling said tendon and region to thereby tension the tendon through said bond stress anchorage at each end thereof and apply a corresponding compressive prestressing force to said body.
Claim 42
Independent Claim
237 words
A method for prestressing a body of ceramic or cermet material and the like with an elongate tendon extending therethrough, said material and tendon being selected so that when said material is softened under heat it will fuse to the tendon on resolidifying, comprising the steps of: a. positioning said tendon in said body; b. heating said tendon and at least the region of said body immediately surrounding said tendon as a unit in an oven; c. selectively heating said tendon by causing electric current to flow through the tendon until said region softens; d. subsequently discontinuing heating the tendon and at least the region of said body immediately surrounding the tendon as a unit; e. simultaneously with said step of discontinuing, maintaining said tendon and the region of said body immediately surrounding said tendon selectively heated, thereby expanding said tendon with respect to said body; f. subsequently cooling said tendon and said region until material in said region resolidifies and fuses directly to said tendon; g. forming a bond stress anchorage to the outer wall of said tendon at least at each end thereof, said anchorage being capable of transmitting the entire prestressing force between the body and the tendon through bond stress; and h. subsequently further cooling said tendon and region to thereby tension the tendon through said bond stress anchorage at each end thereof and apply a corresponding compressive prestressing force to said body.
Claim 43
Dependent Claim
27 words
The method of claim 29 wherein said step of heating said tendon and said region as a unit is carried out before the firing of said body.
Claim 44
Dependent Claim
27 words
The method of claim 29 wherein said step of heating said tendon and said region as a unit is carried out after the firing of said body.
Claim 45
Dependent Claim
24 words
The method of claim 29 further including: a. applying an oxidation inhibiting coating to the tendon prior to positioning said tendon in said body.
Claim 46
Dependent Claim
17 words
The method of claim 29 further including: a. forming the tendon by twisting multiple wires into strands.
References Cited (Backward Citations)
US1960120A
Cited
US2061105A
Cited
US2325469A
Cited
US2319105A
Cited
GB666712A
Cited
US2609586A
Cited
US2727293A
Cited
US2794481A
Cited
US3290197A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-06-01 | 1979-12-01 | 1980-06-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-06-01 | 1983-12-01 | 1984-06-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-06-01 | 1987-12-01 | 1988-06-01 | $7700.00 | Window Closed / Lapsed |