Tray-like container and a method of and an apparatus for manufacturing the container

A molding press adapted to fold a flat paper blank into a tray-like container, the blank having a polygonal base panel with an even number of sides and corners, a continuous border around the base panel, a peripheral band around the continuous border, and respective sets of three fold lines radiating from each corner of the polygonal base panel across the border to the peripheral band to divide the border into side wall portions, contiguous with the respective sides of the base panel, and corner portions consisting of pairs of contiguous identical triangular panels that form respective gussets connecting adjacent side wall portions of the tray blank, the molding press comprising:

• a female mold member having an open mouthed molding cavity formed with an even number of side walls and corners corresponding to side walls and corners of a polygonal tray-like container to be formed in said molding cavity, a marginal surface portion surrounding the open mouth of the molding cavity, a stepped surface extending along the inside of the molding cavity parallel to the plane of the marginal surface portion, and seating means located adjacent to respective corners of the open mouth of the molding cavity and adapted to support a flat paper tray blank prior to folding, each seating means having an abutment spaced above the marginal surface and adapted to contact a corresponding corner portion of such a tray blank at approximately the fold line between the respective pair of triangular panels;
• a male mold member having an outer shape complementary to the side walls of the molding cavity of the female mold member;
• a holding plate;
• means connecting the male mold member to the holding plate for limited relative movement therebetween;
• means for moving the holding plate toward and away from the female mold member between a first position at which the male mold member is spaced from the female member and a second position in which the male mold member is fully engaged with the molding cavity of the female mold member;
• pressing means adapted to exert a force against only alternate ones of the side wall portions of a tray blank when the blank is supported on the seating means, to press such alternate side wall portions against said marginal surface portion while leaving the other side wall portions adjacent to said alternate ones of the side wall portions unrestrained when the blank is forced into the molding cavity by movement of the holding plate from the first position toward the second position, whereby each contiguous pair of corner panels will be folded inwardly on the common fold line between the panels by contact with the corresponding abutment, and said other side wall portions will be folded upwardly as the blank enters the molding cavity so as to fold the contiguous triangular panels against the adjacent alternate ones of the side wall portions when the mold members are fully engaged at the second position of the holding plate;
• and
• means on said holding plate cooperating with said stepped surface of the molding cavity of the female mold member when the holding plate in said second position for forming the peripheral band of the tray blank into a lip-like flange around the periphery of the side wall portions of the folded tray-like container.

A molding press adapted to fold a flat paper blank into a tray-like container, the blank having a polygonal base panel with an even number of sides and corners, a continuous border around the base panel, a peripheral band around the continuous border, and respective sets of three fold lines radiating from each corner of the polygonal base panel across the border to the band to divide the border into side wall portions, contiguous with the respective sides of the base panel, and corner portions consisting of pairs of contiguous identical triangular panels that form respective gussets connecting adjacent side wall portions of the tray blank, the molding press comprising:

• a female mold member having an open mouthed molding cavity formed with an even number of side walls and corners corresponding to side walls and corners of a polygonal tray-like container to be formed in said molding cavity, a lip, upwardly convex in cross section, extending along the edge of the open mouth of the molding cavity, a flat marginal surface portion surrounding the lip, and seating means located adjacent to respective corners of the open mouth of the molding cavity and adapted to support a flat paper tray blank prior to folding, each seating means having an abutment spaced above the marginal surface and adapted to contact a corresponding corner portion of such a tray blank at approximately the fold line between the respective pair of triangular panels;
• a male mold member having an outer shape complementary to the side walls of the molding cavity of the female mold member;
• a holding plate;
• means connecting the male mold member to the holding plate for limited relative movement therebetween;
• means for moving the holding plate toward and away from the female mold member between a first position at which the male mold member is spaced from the female mold member and a second position at which the male mold member is fully engaged with the molding cavity of the female mold member;
• pressing means adapted to exert a force against only alternate ones of the side wall portions of a tray blank when the blank is supported on the seating means, to press such alternate side wall portions against said marginal surface portion while leaving the other side wall portions adjacent to said alternate ones of the side wall portions unrestrained when the blank is forced into the molding cavity by movement of the holding plate from the first position toward the second position, whereby each contiguous pair of corner panels will be folded inwardly on the common fold line between the panels by contact with the corresponding abutment, and said other side wall portions will be folded upwardly as the blank enters the molding cavity so as to fold the contiguous triangular panels against the adjacent alternate ones of the side wall portions when the mold members are fully engaged at the second position of the holding plate;
• and
• an upwardly concave recess on said holding plate cooperating with the lip around the mouth of the molding cavity of the female mold member when the holding plate is in said second position for forming the peripheral band of the tray blank into a lip-like flange around the periphery of the side wall portions of the folded tray-like container, the cross-sectional shape of the flange corresponding to the cross section of the lip on the female mold member.

A molding press adapted to fold a flat paper blank into a tray-like container, the blank having a polygonal base panel with an even number of sides and corners, a continuous border around the base panel, and respective sets of three fold lines radiating from each corner of the polygonal base panel across the border, the fold lines dividing the border into side wall portions contiguous with the respective sides of the base panel, and corner portions consisting of pairs of contiguous identical triangular panels that form respective gussets connecting adjacent side wall portions of the tray blank, the molding press comprising:

• a female mold member having an open-mouthed molding cavity having an even number of side walls and corners corresponding to sidewalls and corners of a tray-like container to be formed in the molding cavity, a marginal surface portion surrounding the open mouth of the molding cavity, and seating means formed integrally on said marginal surface portion adjacent to respective corners of the open mouth of the molding cavity and adapted to support a flat paper tray blank prior to folding, each seating means having an abutment spaced above the marginal surface portion and adapted to contact a corresponding corner of such a tray blank at approximately the fold line between the respective pair of triangular panels;
• a male mold member having an outer shape complementary to the molding cavity of the female mold member;
• means for moving said male member into and away from said female mold member;
• and
• pressing means adapted to exert a force against only alternate ones of the side wall portions of such a tray blank when the blank is supported on the seating means, to press such alternate side wall portions against said marginal surface portion while leaving the other side wall portions adjacent to said alternate ones of the side wall portions unrestrained when the blank is forced into the molding cavity by moving the male mold member into the female mold members, whereby each contiguous pair of corner panels is folded inwardly on the common fold line between the panels by contact with the corresponding abutment, and said other side wall portions are folded upwardly as the blank enters the molding cavity so as to fold the contiguous triangular panels against the adjacent ones of the side wall portions when the mold members are fully engaged.

A method of forming a tray-like container from a flat container blank which is provided with a central base panel having four or more even numbers of side edges, the corresponding numbers of side walls, each contiguous with the adjacent side edge, and the corresponding numbers of corner portions, each corner portion consisting of two equal triangular corner panels, by molding the container blank through engagement of an upper movable male and lower stationary female mould complementary to each other, wherein at the commencement of the engagement of said upper and lower complementary moulds, the container blank is subject to successive folding steps of:

• advancing the container blank positioned above the lower female mould toward an upper surface of said lower mould until said side walls of said container blank rest on the upper surface;
• pressing a selected one of respective adjoining side walls of said container blank against the upper surface of said lower female mould by appropriate weight means while permitting the other of said respective adjoining side walls of the container blank to freely rest on said upper surface of the lower female mould, and;
• forcing the base panel of said container blank into the lower female mould by the upper male mould thereby causing said other of said respective adjoining side walls to upwardly stand from said upper surface of said lower female mould so that the two equal triangular corner panels of each corner portion are urged to be inwardly bent and folded upon themselves and toward said selected one of said respective adjoining side walls, by the help of appropriate abutting means against which each corner portion abuts.