Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
294 words
A sealing composition for joining ceramic or cermet parts, the sealing composition comprising, as starting materials, a mixture of alumina (Al₂O₃), silica (SiO₂) and magnesia (MgO), the mixture comprising in the ranges of from 22% to 24.5% by weight of Al₂O₃, from 45.5% to 49.5% by weight of SiO₂, and from 26.0% to 32.5% by weight of MgO; the sealing composition containing less than 40% by weight (expressed as the percentage of the total weight of the mixture) of the crystalline phase α-Cordierite when subjected to a test procedure comprising the following steps: (i) thoroughly mixing the constituents of the sealing composition and sintering the mixture at 1200 o C for 10 hours to produce a friable lump which is crushed, transferred to a platinum (10% Rhodium) crucible, and heated in a muffle furnace at 1550 o C for 2 hours while the glass is in a molten condition; (ii) pouring the contents of the crucible into distilled water to form a brittle frit or cullet and, after drying at 160 o C, grinding the glass in an Agate Cone Grinder to form a powder of particle size less than 180µm; (iii) mixing the powdered glass with 4% by weight of a binder comprising a solution in toluene of methyl/butyl methacrylate, and pressing the mixture in a 16 mm diameter die at 100 MPa to produce 1g samples; (iv) sintering a sample continuously for 6 hours at a sintering tempterature equal to or greater than the temperature a seal made from the sealing composition is intended to withstand; and (v) evaluating, by X-ray Diffractometry, the proportion by weight (expressed as a percentage of the total weight of alumina, silica and magnesia) of the crystalline phase α-Cordierite in the sample sintered at the sintering temperature.
Claim 2
Dependent Claim
294 words
A sealing composition for joining ceramic or cermet parts, the sealing composition comprising, as starting materials, a mixture of alumina (Al₂O₃), silica (SiO₂) and magnesia (MgO), the mixture comprising in the ranges of from 22% to 24.5% by weight of Al₂O₃, from 45.5% to 49.5% by weight of SiO₂, and from 26.0% to 32.5% by weight of MgO; the sealing composition containing less than 40% by weight (expressed as the percentage of the total weight of the mixture) of the crystalline phase α-Cordierite when subjected to a test procedure comprising the following steps: (i) thoroughly mixing the constituents of the sealing composition and sintering the mixture at 1200 o C for 10 hours to produce a friable lump which is crushed, transferred to a platinum (10% Rhodium) crucible, and heated in a muffle furnace at 1550 o C for 2 hours while the glass is in a molten condition; (ii) pouring the contents of the crucible into distilled water to form a brittle frit or cullet and, after drying at 160 o C, grinding the glass in an Agate Cone Grinder to form a powder of particle size less than 180µm; (iii) mixing the powdered glass with 4% by weight of a binder comprising a solution in toluene of methyl/butyl methacrylate, and pressing the mixture in a 16 mm diameter die at 100 MPa to produce 1g samples; (iv) sintering a sample continuously for 6 hours at a sintering tempterature equal to or greater than the temperature a seal made from the sealing composition is intended to withstand; and (v) evaluating, by X-ray Diffractometry, the proportion by weight (expressed as a percentage of the total weight of alumina, silica and magnesia) of the crystalline phase α-Cordierite in the sample sintered at the sintering temperature.
Claim 3
Dependent Claim
19 words
A sealing composition according to Claim 1 wherein the sintering temperature in the test procedure is 1000 o C.
Claim 4
Dependent Claim
45 words
A sealing composition according to Claims 1 or 2 wherein the mixture comprises silica, alumina and magnesia in proportions such that the mixture falls within the region enclosed by broken line E in the ternary phase diagram shown in Figure 2 of the accompanying drawings.
Claim 5
Dependent Claim
32 words
A sealing composition according to any one of the preceding Claims wherein the mixture consists of 22.9% by weight of Al₂O₃, 46.3% by weight of SiO₂ and 30.8% by weight of MgO.
Claim 6
Dependent Claim
33 words
A sealing composition according to any one of Claims 1 to 3 wherein the mixture consists of 24% by weight of Al₂O₃, 49.0% by weight of SiO₂ and 27.0% by weight of MgO.
Claim 7
Dependent Claim
33 words
A sealing composition according to any one of Claims 1 to 3 wherein the mixture consists of 23.0% by weight of Al₂O₃, 48.0% by weight of SiO₂ and 29.0% by weight of MgO.
Claim 8
Dependent Claim
24 words
A sealing composition according to any one of the preceding claims, the sealing composition consisting only of the mixture of Al₂O₃, SiO₂ and MgO.
Claim 9
Dependent Claim
25 words
A sealing composition according to any one of Claims 1 to 6, the sealing composition consisting of the mixture and up to 5% of additive.
Claim 10
Dependent Claim
13 words
A sealing composition according to Claim 8 wherein the additive comprises titania (TiO₂).
Claim 11
Dependent Claim
39 words
An arc tube for a discharge lamp, the arc tube comprising an envelope of ceramic material and one or more end closures hermetically sealed to the envelope by a sealing composition according to any one of the preceding Claims.
Claim 12
Dependent Claim
59 words
An arc tube for a discharge lamp, the arc tube comprising an envelope of ceramic material and one or more end closures hermetically sealed to the envelope by a seal formed from a sealing composition comprising, as starting materials, a mixture of Al₂O₃, SiO₂ and MgO, the seal containing less than 40% by weight of the crystalline phase α-Cordierite.
Claim 13
Dependent Claim
59 words
An arc tube for a discharge lamp, the arc tube comprising an envelope of ceramic material and one or more end closures hermetically sealed to the envelope by a seal formed from a sealing composition comprising, as starting materials, a mixture of Al₂O₃, SiO₂ and MgO, the seal containing less than 40% by weight of the crystalline phase α-Cordierite.
Claim 14
Dependent Claim
28 words
An arc tube according to Claims 10 or 11 wherein the envelope is made of a material selected from the group comprising polycrystalline alumina, sapphire and a spinel.