US3683062A
Expired / Lapsed
US
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Rotational casting method
Assignee: Essex International Inc
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Filing: 1970-08-20
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Granted: 1972-08-08
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Expires: 1990-08-20
Abstract
Abstract A method for rotationally molding or casting thermoplastic or thermosetting resinous compositions. The machine includes a rotatable turret on which at least one mold-rotating spindle and a pair of motor drives therefor are mounted as a removable unit with the spindle projecting radially outwardly from the turret. The spindle includes means for removably mounting a pair of perpendicular axes at the same or different speeds as determined by the speeds of the motor drives, which are independently variable. The turret has provision for mounting additional spindle and motor drive units thereon with equi-angular spacing of the spindles about the turret to satisfy varying output and/or process requirements. The machine further includes treating stations through which the molds on the spindle or spindles are successively indexed. The number, type, and location of the treating stations may be varied to suit a number of different molding processes. Inert gas may be fed into each mold cavity, and maintained therein at a predetermined positive pressure during any predetermined portion of the mold processing cycle after loading and closing the molds and until they are to be opened for removal of the molded or cast article. Separate ovens with independent temperature controls may be provided at successive stations. Cooling at a cooling station is two stage, first with a wet steam spray and second with a liquid coolant spray.
Inventors
- 👤 Elmer J Von Der Heide
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 18:21
CPC Classifications
B; B29; B29C; B29C33/00; B29C33/34; B29C33/36; B29C41/00; B29C41/02; B29C41/04; B29C41/06
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
223 words
In the method of rotational molding of resinous material to form a hollow article by heating the material in a substantially closed mold while rotating the mold about a plurality of angularly related axes until the resin has taken the shape of the interior of the mold and then cooling the mold and the material therein to produce the molded article in a handleable solid condition, the improvement comprising the following combination of steps: a. simultaneously rotating the mold about the axis of an elongated, rotating, mold-supporting spindle and about an axis transverse thereto adjacent one end of the spindle during the heating and cooling steps while supporting the spindle at a point adjacent the opposite end thereof, b. maintaining a gas passageway from inside the mold to and along said spindle axis to a point adjacent said point of spindle support with one end of said passageway opening inside the mold and inside the article being molded therein and the opposite end of said passageway opening adjacent said point of spindle support for gas flow through saiD passageway between the inside of said article being molded and the passageway opening adjacent said point of spindle support, and c. at least throughout the mold cooling step, sealing said mold against flow of gas into the article being molded other than through said passageway.
Claim 2
Dependent Claim
223 words
In the method of rotational molding of resinous material to form a hollow article by heating the material in a substantially closed mold while rotating the mold about a plurality of angularly related axes until the resin has taken the shape of the interior of the mold and then cooling the mold and the material therein to produce the molded article in a handleable solid condition, the improvement comprising the following combination of steps: a. simultaneously rotating the mold about the axis of an elongated, rotating, mold-supporting spindle and about an axis transverse thereto adjacent one end of the spindle during the heating and cooling steps while supporting the spindle at a point adjacent the opposite end thereof, b. maintaining a gas passageway from inside the mold to and along said spindle axis to a point adjacent said point of spindle support with one end of said passageway opening inside the mold and inside the article being molded therein and the opposite end of said passageway opening adjacent said point of spindle support for gas flow through saiD passageway between the inside of said article being molded and the passageway opening adjacent said point of spindle support, and c. at least throughout the mold cooling step, sealing said mold against flow of gas into the article being molded other than through said passageway.
Claim 3
Dependent Claim
29 words
The method improvement of claim 1 in which the passageway opening adjacent said point of spindle support is maintained open to the atmosphere during the heating of the mold.
Claim 4
Dependent Claim
30 words
The method improvement of claim 1 in which the passageway opening adjacent said point of spindle support is maintained open to the atmosphere during heating and cooling of the mold.
Claim 5
Dependent Claim
31 words
The method improvement of claim 1 in which the mold is cooled in a cooling chamber with the passageway opening adjacent said point of spindle support remaining outside of said chamber.
Claim 6
Dependent Claim
64 words
The method improvement of claim 1 in which the mold is cooled in a cooling chamber with the passageway opening adjacent said point of spindle support remaining outside of said chamber, the cooling being effected first by enveloping the mold with wet steam directed toward the mold from a plurality of directions and then by directing sprays of a liquid coolant against the mold.
Claim 7
Dependent Claim
27 words
The method improvement of claim 1 in which the mold is cooled in a cooling chamber while maintaining a substantially constant positive gas pressure in said passageway.
Claim 8
Dependent Claim
45 words
The method improvement of claim 1 in which said spindle is moved to position the mold in a heating chamber and again to position the mold in a cooling chamber with the passageway opening adjacent said point of spindle support remaining outside of said chambers.
Claim 9
Dependent Claim
67 words
The method improvement of claim 1 in which said spindle is moved to position the mold in a heating chamber and again to position the mold in a cooling chamber with the passageway opening adjacent said point of spindle support remaining outside of said chambers, the method including the step of maintaining a substantially constant positive pressure of gas in said passageway during both heating and cooling.
Claim 10
Dependent Claim
29 words
The method improvement of claim 9 in which said gas is inert to the material being molded at the highest temperature of said material produced by heating the mold.
Claim 11
Dependent Claim
68 words
The method improvement of claim 9 in which said gas is inert to the material being molded at the highest temperature of said material produced by heating the mold, the mold having a parting plane between mold sections, and said sections being joined to permit gas leakage at said parting plane until blocked by distribution of said material over the interior mold surface during heating and mold rotation.
Claim 12
Dependent Claim
266 words
In the method of rotational molding of resinous material to form a hollow article by heating the material in a substantially closed mold while rotating the mold about a plurality of angularly related axes until the resin has taken the shape of the interior of the mold and then cooling the mold and the material therein to produce the molded article in a handleable solid condition, the improvement comprising the following combination of steps: 9 a. repeatedly moving a series of four molds along a continuous closed path in a stepwise manner from one to the next of four stations along said path with a constant dwell of all molds at all stations, the four molds and the four stations being equally spaced along said path with a mold at each station during each dwell; and b. charging each mold at a first station and heating each mold at the second station, followed by cooling each mold at the fourth station, and finally unloading and recharging each mold at the first station, the third station being devoted to a continuation of the heating step begun at the second station, the heating of the molds at the second station being effected by subjecting the molds to a high temperature atmosphere to bring them to a temperature substantially below said high temperature during the dwells of the molds, and the heating at the third station being effecTed by subjecting the molds to an atmosphere at a final temperature also substantially below said high temperature to bring the molds to said final temperature during the dwells of the molds.
Claim 13
Dependent Claim
266 words
In the method of rotational molding of resinous material to form a hollow article by heating the material in a substantially closed mold while rotating the mold about a plurality of angularly related axes until the resin has taken the shape of the interior of the mold and then cooling the mold and the material therein to produce the molded article in a handleable solid condition, the improvement comprising the following combination of steps: 9 a. repeatedly moving a series of four molds along a continuous closed path in a stepwise manner from one to the next of four stations along said path with a constant dwell of all molds at all stations, the four molds and the four stations being equally spaced along said path with a mold at each station during each dwell; and b. charging each mold at a first station and heating each mold at the second station, followed by cooling each mold at the fourth station, and finally unloading and recharging each mold at the first station, the third station being devoted to a continuation of the heating step begun at the second station, the heating of the molds at the second station being effected by subjecting the molds to a high temperature atmosphere to bring them to a temperature substantially below said high temperature during the dwells of the molds, and the heating at the third station being effecTed by subjecting the molds to an atmosphere at a final temperature also substantially below said high temperature to bring the molds to said final temperature during the dwells of the molds.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-08-08 | 1976-02-07 | 1976-08-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-08 | 1980-02-07 | 1980-08-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-08 | 1984-02-07 | 1984-08-08 | $7700.00 | Window Closed / Lapsed |