Process and apparatus for thermoforming a thermoplastic carton having an aperture therein for latching the cover
AssigneeMobil Oil Corporation
InventorRaj K. Mangla
Life of this patent
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Abstract
Apertures are formed in plastic resin sheet material during a thermoforming process by shearing the heated plastic sheet between shear members which have cooperating shear faces extending in two dimensions in a plane perpendicular to the direction of movement of the thermoforming dies. The resulting apertures have a three dimensional configuration.
Claims18
In a method for forming an aperture in a sheet of plastic resin material during a thermoforming moulding process by moulding the sheet at an elevated temperature between male and female die members which are capable of being moved from an open position to a closed, moulding position, the improvement which comprises forming the aperture in a three-dimensional configuration in the material by shearing the sheet at an elevated temperature by means of cooperating shear members on the die members, the shear members having three cooperating shear faces which extend in the relative direction of movement of the die members and in two dimensions in a plane extending perpendicular to the direction of die movement.
A process for the production of a thermoformed thermoplastic carton comprising:
- (i) providing a relatively flat sheet of polystyrene foam;
- (ii) preheating said sheet to a forming temperature;
- (iii) thermoforming the preheated sheet by bringing together a male mould member and female mould member to form the carton including a cover having an offset surface which is inwardly offset with respect to the front wall of the cover;
- (iv) shearing an aperture in the offset surface while thermoforming by relative movement between a male key mounted on the female mould member, each key having three cooperating shear faces, the movement being parallel to the closing motion between the male and female members;
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- (v) shearing the sheet between the offset surface and the front wall of the cover to extend the aperture to the front wall.
A mould for forming apertures in a thermoformed plastic resin article by moulding a sheet of plastic resin material by thermoforming, comprising:
- (i) male and female die members between which a preheated sheet of the plastic resin material may be positioned when the members are in an open position from which they are capable of being moved to a closed position in which they form the sheet into the desired configuration,
- (ii) first and second shear members attached to the male and female die members, respectively, the shear members having three shear faces which extend outwardly from moulding faces of their respective die members to form mating cooperating shear faces which extend in the relative direction of movement of the die members and in two dimensions in a plane extending perpendicular to the direction of die movement.
Dependencies are inferred from the claim text.