US3917773A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for fabricating a shaped dielectric antenna lens
Assignee: United States Department of the Navy
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Filing: 1974-10-03
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Granted: 1975-11-04
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Expires: 1994-10-03
Abstract
Abstract A light-weight, temperature-resistant spherical antenna lens is formed of an homogeneous ceramic material to provide a uniformlydistributed dielectric constant. The ceramic material formulation can be varied to adjust the dielectric constant for various wavelengths. A protective sealant coating is applied to the exterior surface and, because of the very high porosity of the lens, the sealant is applied over an under coating having essentially the same dielectric and temperature characteristics as the lens matrix material. The shaped spherical body of the lens is provided by press-forming and fusing together a quantity of highly-porous ceramic granules each being the same in composition and each having essentially the same pore size. Pore size is controlled by first preparing a ceramic slip, mixing the slip with an organic ''burn-out'' material, such as stearic acid powder, and then subjecting the mix to a wet granulation process to provide granules of a particular size. A burn-out produces granules having the desired pore size which then are mixed with a mechanical binder, pressed to form the sphere and subsequently sintered to provide a rigid spherical structure capable of being machined and coated with the sealant glaze.
Inventors
- 👤 Jr Louis E Gates
- 👤 William E Lent
- 👤 Jose A Flores
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 20:45
CPC Classifications
H; H01; H01Q; H01Q15/00; H01Q15/02; H01Q15/08
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
178 words
A PROCESS FOR FABRICATING A RIGIDLY-SHAPED DIELECTRIC STRUCTURE FOR TRANSMITTING HIGH-FREQUENCY ELECTROMAGNETIC ENERGY, SAID STRUCTURE HAVING A PREDETERMINED AND UNIFORM DIELECTRIC CONSTANT AND SAID PROCESS COMPRISING THE CONSECUTIVE STEPS OF: PROVIDING A QUANTITY OF POROUS CERAMIC GRANULES HAVING A SUBSTANTIALLY UNIFORM PORE SIZE NO LARGER THAN THE MINIMUM WAVELENGTH OF SAID ELECTROMAGNETIC ENERGY SAID PORE SIZE AS WELL AS THE COMPOSITION OF THE GRANULES BEING A DETERMINABLE FUNCTION OF SAID PREDETERMINED DIELECTRIC CONSTANT, INTIMATELY MIXING SAID QUANTITY OF POROUS GRANULES INITIALLY WITH A COHESIVE ORGANIC BINDER MATERIAL CAPABLE OF COHESIVELY BINDING ONE GRANULE TO ANOTHER AND THEN WITH A FLUX MATERIAL SAID INITIAL INTIMATE MIXING APPLYING SAID BINDER MATERIAL TO THE EXTERIOR SURFACES OF EACH OF SAID GRANULES FOR INHIBITING PENETRATION OF SAID GRANULE PORES BY SAID FLUX MATERIAL, CONTROLLABLY PRESSING SAID GRANULAR MIXTURE TO BINDABLY FORM THE MIXTURE IN TO SAID SHAPED STRUCTURE THE APPLICATION OF THE PRESSURE BEING CONTROLLED TO PROVIDE A DESIRED STRUCTURAL DENSITY, CONTROLLABLY HEATING SAID SHAPED STRUCTURE SUFFICIENTLY TO REMOVE SAID ORGANIC BINDER MATERIAL AND, SINTERING SAID SHAPED STRUCTURE FOR PROVIDING SAID RIGIDITY-.
Claim 2
Dependent Claim
178 words
A PROCESS FOR FABRICATING A RIGIDLY-SHAPED DIELECTRIC STRUCTURE FOR TRANSMITTING HIGH-FREQUENCY ELECTROMAGNETIC ENERGY, SAID STRUCTURE HAVING A PREDETERMINED AND UNIFORM DIELECTRIC CONSTANT AND SAID PROCESS COMPRISING THE CONSECUTIVE STEPS OF: PROVIDING A QUANTITY OF POROUS CERAMIC GRANULES HAVING A SUBSTANTIALLY UNIFORM PORE SIZE NO LARGER THAN THE MINIMUM WAVELENGTH OF SAID ELECTROMAGNETIC ENERGY SAID PORE SIZE AS WELL AS THE COMPOSITION OF THE GRANULES BEING A DETERMINABLE FUNCTION OF SAID PREDETERMINED DIELECTRIC CONSTANT, INTIMATELY MIXING SAID QUANTITY OF POROUS GRANULES INITIALLY WITH A COHESIVE ORGANIC BINDER MATERIAL CAPABLE OF COHESIVELY BINDING ONE GRANULE TO ANOTHER AND THEN WITH A FLUX MATERIAL SAID INITIAL INTIMATE MIXING APPLYING SAID BINDER MATERIAL TO THE EXTERIOR SURFACES OF EACH OF SAID GRANULES FOR INHIBITING PENETRATION OF SAID GRANULE PORES BY SAID FLUX MATERIAL, CONTROLLABLY PRESSING SAID GRANULAR MIXTURE TO BINDABLY FORM THE MIXTURE IN TO SAID SHAPED STRUCTURE THE APPLICATION OF THE PRESSURE BEING CONTROLLED TO PROVIDE A DESIRED STRUCTURAL DENSITY, CONTROLLABLY HEATING SAID SHAPED STRUCTURE SUFFICIENTLY TO REMOVE SAID ORGANIC BINDER MATERIAL AND, SINTERING SAID SHAPED STRUCTURE FOR PROVIDING SAID RIGIDITY-.
Claim 3
Dependent Claim
28 words
The process of claim 1 wherein controlled pressing of the granular mixture is accomplished by isostatically pressing the mixture at between 100-1,000 psi to attain said desired density.
Claim 4
Dependent Claim
42 words
The process of claim 1 wherein said controlled heating is accomplished by increasing the temperature of the structure to about 400*C at a rate sufficiently gradual to minimize spalling due to temperature differential between the inner and outer portions of the structure.
Claim 5
Dependent Claim
158 words
The process of claim 1 wherein the step of providing said quantity of porous granules includes the steps of: intimately mixing a ceramic slurry formed of a liquid dispersion of ceramic material and a binder material, combinably mixing said slurry with an organic burn-out material of a particular particle size determined by the desired pore size of the porous granules to be formed, partially drying said combined materials to produce a moist granular mass, screening said mass to produce a quantity of granules having a grain size range of about 20-48 mesh, drying said sized grains, and exposing said dried grains to a hot flame for a limited period of time sufficient to burn out said organic materials from the ceramic grains without destructively melting the ceramic material comprising the grains, said burn out operation producing said quantity of porous granules each of which has a pore size approximating said particle size of the removed burn out material.
Claim 6
Dependent Claim
15 words
The process of claim 4 wherein said organic burn out material is stearic acid powder.
Claim 7
Dependent Claim
29 words
The process of claim 5 wherein said stearic acid powder is approximately 38 percent by weight, the balance of said combined mixture being essentially provided by said ceramic slurry.
Claim 8
Dependent Claim
18 words
The process of claim 4 wherein said ceramic slurry is formed in accordance with the following general formula:
Claim 9
Dependent Claim
13 words
The process of claim 7 wherein said ceramic slurry is formed as follows:
Claim 10
Dependent Claim
13 words
The process of claim 4 wherein said ceramic slurry is formed as follows:
Claim 11
Dependent Claim
13 words
The process of claim 7 wherein said ceramic slurry is formed as follows:
Claim 12
Dependent Claim
64 words
The process of claim 7 wherein said organic burn out material is stearic acid powder, and said step of exposing the grains to a hot flame includes: supporting said grains thinly on a flat screen, igniting said stearic acid powder by exposing said grains to a vented flame, and stopping said flame exposure when said stearic acid powder is charred and ceases to flame.
Claim 13
Dependent Claim
30 words
The process of claim 7 wherein the intimate mixture of the porous and sized granules with the organic binder material and the flux material has the following composition by weight:
Claim 14
Dependent Claim
42 words
The process of claim 4 further including the step of adhering a continuous protective thin-film sealant coating on the porous surface of said sintered structure, said coating having a thickness no greater than the wavelength of said electromagnetic energy to be transmitted.
Claim 15
Dependent Claim
48 words
The process of claim 13 wherein said ceramic slurry composition is selected to provide a temperature-resistant shaped structure, said sealant coating being formed of a material having thermal characteristics approximating those of said shaped structure whereby said sealed structure has a temperature resistance comparable to said shaped structure.
Claim 16
Dependent Claim
74 words
The process of claim 14 wherein said sealant coating is applied over a base coating, said base coating being applied directly to said shaped ceramic structure, and being formed by: preparing a thin slurry composed essentially of a quantity of material having the same composition as the porous ceramic granules of said shaped structure, a binder and a flux material, coating said shaped ceramic structure with said thin slurry, and sintering said slurry-coated structure.
Claim 17
Dependent Claim
39 words
The process of claim 15 wherein said sealant coating is formed of an aqueous mixture of glass frit and a binder material, the coating being applied by: spraying the mixture over said binder coating, and sintering said applied mixture.
References Cited (Backward Citations)
US3829403A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-03 | 1979-05-05 | 1979-11-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-03 | 1983-05-05 | 1983-11-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-03 | 1987-05-05 | 1987-11-04 | $7700.00 | Window Closed / Lapsed |