Patent ID: 8221673

Claim:
A method for manufacturing a load bearing panel member having a first portion, a second portion, and an appearance surface portion, said method comprising: inserting the appearance surface portion of the panel member into a mold cavity having a first chamber, a second chamber, and a mold feature configured to separate the first chamber and the second chamber such that the appearance surface portion spans the first and second chambers and the mold feature; wherein said first and second chambers and said mold feature are configured to produce an integral hinge between the first portion and the second portion of the panel member; sequentially opening a plurality of valve gates configured to control the transfer of molten plastic into the first and second chambers of the mold; transferring molten plastic into the first and second chambers of the mold according to the sequence dictated by the valve gates, wherein said transferring occurs without expelling plastic from one of said first and second chambers into the other of said first and second chambers; transferring said molten plastic into said first chamber in a manner to form: a first plurality of horizontally disposed ribs; a second plurality of vertically disposed ribs orthogonal to and bisecting the first plurality of horizontally disposed ribs; a third plurality of ribs generally located around the periphery of the first portion; a fourth plurality of ribs originating in an X-shape and extending to the periphery of the first portion, wherein each of the fourth plurality of ribs is non-orthogonal to another of the fourth plurality of ribs and non-orthogonal to the third plurality of ribs; injecting pressurized gas into said first chamber of the mold cavity through a single gas pin in fluid communication with each of the fourth plurality of ribs in a manner to form a tubular cavity inside each of the fourth plurality of ribs; injecting said pressurized gas into said first chamber of the mold cavity through a plurality of peripheral gas pins in fluid communication with said third plurality of ribs in a manner to form a tubular cavity inside each of the third plurality of ribs; cooling the molten plastic in the first and second chambers; and venting the pressurized gas from the first chamber of the mold cavity.