US3971687A
Expired / Lapsed
US
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Method for forming double-walled units
Assignee: Imperial Chemical Industries Ltd
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Filing: 1974-08-28
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Granted: 1976-07-27
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Expires: 1994-08-28
Abstract
Abstract A method of forming a double-walled unit from thermoplastic materials, preferably polymethyl methacrylate, in which two sheets, one of which is provided with an aperture to allow the passage of air between the sheets, are stretched apart under thermoforming conditions by imposed pressure differences, the desired spatial relationship between the sheets being obtained by adjustment of the pressure differences, and in which the sheets are simultaneously bonded about their perimeters.
Inventors
- 👤 Kent Reaney Greer
- 👤 William Rodney Hampson
- 👤 Benjamin James Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 07:02
CPC Classifications
B; B29; B29C; B29C51/00; B29C51/008; E; E06; E06B; E06B3/00; E06B3/66; E06B3/6608; E06B3/673; Y; Y10; Y10T; Y10T156/00; Y10T156/10; Y10T156/1002; Y10T156/1043; Y10T156/1044; Y10T156/1048
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
171 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each sheet can be shaped independently of the other after they have been bonded together about their perimeter, (3) providing means for bonding the two sheets together about their perimeters and heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) stretching the unapertured sheet relative to the other bonded sheet by means of different pressures acting on each of the sheets to give a desired shape, the control of the shape being effected by the different pressures applied so that the use of moulds is avoided, and (5) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 2
Independent Claim
171 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each sheet can be shaped independently of the other after they have been bonded together about their perimeter, (3) providing means for bonding the two sheets together about their perimeters and heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) stretching the unapertured sheet relative to the other bonded sheet by means of different pressures acting on each of the sheets to give a desired shape, the control of the shape being effected by the different pressures applied so that the use of moulds is avoided, and (5) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 3
Independent Claim
191 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each of the sheets can be shaped independently of the other after they have been bonded together about their perimeter, (3) heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) applying a clamping means to the perimeter of the sheets thereby bonding them together by the application of pressure over the area of the sheets contacted by the clamping means, (5) stretching the unapertured sheet relative to the other sheet by means of different pressures acting on each of the sheets to give a desired shape, the control of the shape being effected by the different pressures applied so that the use of moulds is avoided, and (6) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 4
Independent Claim
191 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each of the sheets can be shaped independently of the other after they have been bonded together about their perimeter, (3) heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) applying a clamping means to the perimeter of the sheets thereby bonding them together by the application of pressure over the area of the sheets contacted by the clamping means, (5) stretching the unapertured sheet relative to the other sheet by means of different pressures acting on each of the sheets to give a desired shape, the control of the shape being effected by the different pressures applied so that the use of moulds is avoided, and (6) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 5
Dependent Claim
50 words
A method according to claim 1 in which the bonding means is in the form of a solution of a low molecular polymer of the polymer forming the sheet which forms a non-tacky film when applied to the sheet and dried and is reactivated to provide an adhesive when heated.
Claim 6
Dependent Claim
183 words
A method of forming a double walled article according to claim 1 comprising heating a pair of organic thermoplastic sheets above the softening point of the thermoplastic, clamping the pair of sheets between a pair of cooperable members with complementary sloping surfaces to bond them together and to provide a sloping flange on the bonded sheets, stretching a first sheet away from the second sheet by the application of different pressures acting on the two sheets, until the first sheet contacts a supporting rim spaced apart from the first sheet and enclosing a major proportion of the area of the stretched sheet, maintaining a pressure on the band of the first sheet lying outside the supporting rim to form a shoulder around the sheet between the rim and the clamped portion of the sheet, applying a pressure to the second sheet over an area of said second sheet not containing an aperture to stretch it towards the first sheet until the two sheets have a desired spatial relationship, before the unit is allowed to cool below the softening point of the thermoplastic sheet.
Claim 7
Dependent Claim
43 words
A method of forming a double-walled unit according to claim 4 in which pressure is applied to the second sheet by means of a cup member making sealing engagement with the sheet over an area of said second sheet not containing an aperture.
Claim 8
Independent Claim
212 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each sheet can be shaped independently of the other after they have been bonded together about their perimeter, (3) providing means for bonding the two sheets together about their perimeters and heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) stretching away the unapertured sheet from the other sheet by means of the application of different pressures to the two sheets until the stretched sheet makes contact with a supporting rim spaced apart from the organic thermoplastic sheet and enclosing a major proportion of the area of the stretched sheet, (5) rapidly equalizing the atmospheric pressure on either side of the stretched sheet contained within the rim to bring the spaced apart sheets into substantially parallel relationship while maintaining contact between the rim and the stretched sheet, and (6) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 9
Independent Claim
212 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each sheet can be shaped independently of the other after they have been bonded together about their perimeter, (3) providing means for bonding the two sheets together about their perimeters and heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) stretching away the unapertured sheet from the other sheet by means of the application of different pressures to the two sheets until the stretched sheet makes contact with a supporting rim spaced apart from the organic thermoplastic sheet and enclosing a major proportion of the area of the stretched sheet, (5) rapidly equalizing the atmospheric pressure on either side of the stretched sheet contained within the rim to bring the spaced apart sheets into substantially parallel relationship while maintaining contact between the rim and the stretched sheet, and (6) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 10
Independent Claim
233 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each of the sheets can be shaped independently of the other after they have been bonded together about their perimeter, (3) heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) applying a clamping means to the perimeter of the sheets thereby bonding them together by the application of pressure over the area of the sheets contacted by the clamping means, (5) stretching the unapertured sheet away from the other sheet by means of the application of different pressures to the two sheets until the stretched sheet makes contact with a supporting rim spaced apart from the organic thermplastic sheet and enclosing a major proportion of the area of the strecthed sheet, (6) rapidly equalizing the atmospheric pressure on either side of the stretched sheet contained within the rim to bring the spaced apart sheets into substantially parallel relationship while maintaining contact between the rim and the stretched sheet, and (7) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 11
Independent Claim
233 words
A method of forming a double-walled unit comprising the steps of (1) selecting two sheets of an organic thermoplastic material, a first sheet having a perimeter fitting wholly within or matching the perimeter of the second sheet, (2) providing one of the sheets with at least one aperture to allow the passage of air into the space between the sheets so that each of the sheets can be shaped independently of the other after they have been bonded together about their perimeter, (3) heating at least the unapertured sheet to a temperature above the softening point of the thermoplastic, (4) applying a clamping means to the perimeter of the sheets thereby bonding them together by the application of pressure over the area of the sheets contacted by the clamping means, (5) stretching the unapertured sheet away from the other sheet by means of the application of different pressures to the two sheets until the stretched sheet makes contact with a supporting rim spaced apart from the organic thermplastic sheet and enclosing a major proportion of the area of the strecthed sheet, (6) rapidly equalizing the atmospheric pressure on either side of the stretched sheet contained within the rim to bring the spaced apart sheets into substantially parallel relationship while maintaining contact between the rim and the stretched sheet, and (7) allowing the unit to cool below the softening point of the thermoplastic material.
Claim 12
Independent Claim
100 words
An apparatus for forming a double-walled unit from a pair of thermoplastic sheets comprising: means for clamping the pair of sheets together at their peripheries, means for heating at least one of the sheets to above the softening point of the thermoplastic, means for applying different fluid pressures to each of the sheets to stretch a heat-softened sheet relative to the other sheet, to give a desired separation of sheets, and upstanding rim for receiving a first stretched sheet, and means for independently varying the pressures acting on the areas of the stretched sheet inside and outside the contacted rim.
Claim 13
Independent Claim
100 words
An apparatus for forming a double-walled unit from a pair of thermoplastic sheets comprising: means for clamping the pair of sheets together at their peripheries, means for heating at least one of the sheets to above the softening point of the thermoplastic, means for applying different fluid pressures to each of the sheets to stretch a heat-softened sheet relative to the other sheet, to give a desired separation of sheets, and upstanding rim for receiving a first stretched sheet, and means for independently varying the pressures acting on the areas of the stretched sheet inside and outside the contacted rim.
Claim 14
Dependent Claim
64 words
An apparatus according to claim 8 which includes a cup member for supplying pressure to the second of the pair of sheets whereby the second sheet can be stretched into the space formed after stretching the first sheet towards the rim by contacting the cup member with an area of the second of the pair of sheets not containing an aperture and applying pressure.
References Cited (Backward Citations)
US1310439A
Cited
US2142445A
Cited
US2448173A
Cited
US2564656A
Cited
US2599554A
Cited
US3140325A
Cited
US3281301A
Cited
US3390482A
Cited
US3616197A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-07-27 | 1980-01-26 | 1980-07-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-07-27 | 1984-01-26 | 1984-07-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-07-27 | 1988-01-26 | 1988-07-27 | $7700.00 | Window Closed / Lapsed |