APPARATUS FOR CASTING PLASTIC SHEET

• US 3,694,129 A
• Filed: 08/24/1970
• Issued: 09/26/1972
• Est. Priority Date: 08/24/1970
• Status: Expired due to Term

• Current Assignee: PT Operating Company Incorporated
• Original Assignee: Paul R. Daddona
• Inventors: Daddona, Paul R.
• Primary Examiner(s): Spicer, Jr., Robert L.
• Application Number:
  US05/066,357
• Time in Patent Office: 764 Days
• Field of Search: 18/26R 249/81,82 264/102,219 425/405,436,441
• US Class Current: 425/405.1
• CPC Class Codes: B29C 39/006 Monomers or prepolymers by reaction injection moulding B29C67/246

Abstract

An apparatus for casting sheets of plastic is shown. It includes a casting zone defined by two glass surfaces and a marginal sealing gasket, and an adjacent temperature control cell. The cell is an enclosed chamber comprised of a rigid frame having two extended, semi-rigid sides which may be of sheet metal or glass and which are flexible and responsive to pressures acting upon them. In one embodiment, the cell frame has a rigid brace attached within it, positioned adjacent to the inner surface of its sheet metal or glass side. The brace prevents inward deflection of that side so that the casting zone adjacent to that side is not distorted by the hydrostatic pressure of the liquid charged to it. In this embodiment, there is no need for charge measuring apparatus, the side of the casting zone is free to deflect outwardly and follow the cast sheet as it shrinks during polymerization and higher temperature and higher pressure media can be used in the temperature control cell. In the preferred embodiment the side of the temperature control cell is glass bonded to the sides of the frame at a series of novel bonding zones. The amount of liquid plastic charged to the casting zone is controlled by first adjusting the head of temperature control liquid in the adjacent control cell to a height which just balances the head of liquid plastic in the full casting zone.

Claims

1. In a casting apparatus including a casting zone and an adjacent temperature control zone the improvement which comprises:

an enclosed temperature control cell having a rigid rectangular frame and at least one semi-rigid side in sealable contact with said frame which is deflectible in response to pressures acting upon it, said cell having rigid bracing means consisting of a plurality of horizontal and vertical cross members which are firmly connected at cross-over points affixed to said frame and positioned within said cell adjacent to the inner surface of said semi-rigid side, said bracing means providing a stop against the inward deflection of said side.

2. An apparatus as described in claim 1 wherein the said semi-rigid side of said cell is a casting zone element of said adjacent casting zone.

3. An apparatus as described in claim 1 wherein the outer surface of said semi-rigid side of said cell is in contact with a casting zone element of said adjacent casting zone.

4. In an apparatus for casting flat sheets of plastic including a casting zone defined between glass surfaces and an adjacent temperature control zone, the improvement which comprises:

an enclosed hollow, substantially unobstructed temperature control cell defined by a rigid frame and at least one extended, semi-rigid side connected thereto, said side being deflectible in response to pressUre acting upon it; and

rigid bracing means affixed to said rigid frame and positioned in said cell adjacent to and in contact with the inner surface of said semi-rigid side, said bracing means providing a stop against inward deflection of said side.

5. The apparatus of claim 4 wherein said cell includes two extended semi-rigid sides connected to said rigid frame, each of said semi-rigid sides being braced against inward deflection by rigid bracing means.

6. The apparatus of claim 4 wherein said semi-rigid side is a casting zone element of said adjacent casting zone.

7. The apparatus of claim 4 wherein said semi-rigid side of said cell is in contact with a casting zone element of said adjacent casting zone.

8. The apparatus of claim 4 wherein said semi-rigid side is sheet metal.

9. The apparatus of claim 4 wherein said semi-rigid side is a sheet of glass.

10. In a casting apparatus including a casting zone and an adjacent, temperature control cell, the improved temperature control cell comprising:

a frame describing a closed area, and having at least one flat surface adapted to receive and to have bonded to it a glass sheet;

a plurality of bonding zones comprising continuous recesses in said surface, each of said recesses having an expanded volume beneath the said surface;

means forming an enclosure with said frame including a glass sheet bonded to said frame at said bonding zones; and

means associated with said frame for introducing a temperature control medium into and out of said temperature control cell.

11. The temperature control cell of claim 10 wherein said frame is planar and generally rectangular in area and includes a first hollow structural member having an inlet port for said temperature control medium and a plurality of spaced outlet ports for distributing said medium into the enclosed cell and a second hollow member spaced opposite to said first hollow member having a plurality of spaced inlet ports for receiving said temperature control medium and an outlet port for said medium.

12. The temperature control cell of claim 10 wherein said frame is comprised of hollow members of rectangular cross-section, said hollow members having two flat surfaces on either side thereof having said bonding zones to which two glass sheets are bonded.

13. In a plastic sheet casting apparatus including a casting zone for plastic sheet and an adjacent temperature control cell, the improved temperature control cell comprising:

a planar frame describing a closed rectangular area and consisting essentially of hollow members of rectangular cross-section;

a plurality of continuous, female bonding zones on opposite side surfaces of said hollow members, each of said bonding zones having an expanded volume below the said side surfaces of said hollow members;

two flat sheets of glass positioned on either side of said frame and bonded to said hollow members at said bonding zones thereby forming an enclosed cell; and

means for introducing and distributing a temperature control medium into and out of said enclosed cell.

14. The improved temperature control cell of claim 13 wherein two of said hollow frame members, opposite one another, include an inlet and outlet port respectively on their exterior sides and a plurality of distribution ports on their interior sides.

15. The apparatus of claim 13 wherein said bonding zones are of a truncated triangular cross-section.

16. The apparatus of claim 13 wherein the bonding agent is a two-part silicone adhesive.

17. In an apparatus for casting plastic sheet comprising a plastic casting zone bounded by two parallel glass sheets sealed by a marginal gasket, and a temperature control cell adjacent to said plastic casting zone, said cell having a wall deflectible under pressure, means for controlling the volume of the liquid plastic charge to the said casting zone, including:

introducing a temperature control liquid into said temperature control cell until the height thereof reaches a height predetermined as sufficienT to hydrostatically balance the head of liquid plastic in said casting zone when the latter is fully charged; and

charging said casting zone with liquid plastic until the latter is totally filled.