Apparatus for forming a bend in sheet material

Claim 2

Apparatus for use in conjunction with a vacuum system for forming a plastic sheet to a final configuration in which the sheet has a reverse bend formed therein, which apparatus comprises: a base; stationary mold means secured to said base for defining at least a portion of the reverse bend to which the sheet of plastic is to be formed; a movable mold means for defining at least another portion of the reverse bend to which the sheet of plastic is to be formed and mounted for movement with respect to said base from a first position to a second position; said movable mold means being remote from said stationary mold means when in its said first position and being in juxtaposition to said stationary mold means when in its second position so that said two mold means define therebetween the reverse bend to which the plastic sheet is to be formed; biasing means for moving said movable mold means normally to its said first position; gripping means formed on said movable mold means for holding the plastic sheet on said movable mold means as that means is moved relative to said stationary mold means whereby the plastic sheet is formed into the reverse bend shape as said movable mold means is moved to its second position; and clamping means cooperable with said base and said two mold means for clamping the plastic sheet in sealing association therewith so that a vacuum may be drawn on the interior of the plastic sheet and said movable mold means be moved to its second position against the action of said biasing means thereby forming the reverse bend in the plastic sheet.

Claim 3

The apparatus for forming a reverse bend in a plastic sheet as defined in claim 1 wherein: said gripping means formed on said movable mold means is in the form of a roughened surface defining at least a portion of the surface of said movable mold means which defines the reverse bend to which the plastic is to be formed.

Claim 4

The apparatus for forming a reverse bend in a plastic sheet as defined in claim 2 wherein: said roughened surface forming said gripping means has a surface finish with a roughness of at least 250 microinches.

Claim 5

Apparatus for use in conjunction with a vacuum system for forming a plastic sheet to a final configuration in which the sheet has a reverse bend formed therein, which apparatus comprises: a base; a stationary mold member secured to said base and defining at least a portion of the reverse bend to which the sheet of plastic is to be formed; a movable mold member defining at least another portion of the reverse bend to which the sheet of plastic is to be formed and mounted for movement with respect to said base from a first position to a second position, said movable mold member being remote from said stationary mold member when in its said first position and being in juxtaposition to said stationary mold member when in its second position so that said two mold members define therebetween the reverse bend to which the plaStic sheet is to be formed; spring means acting between said two mold members for moving said movable mold member normally to its said first position; said spring means being compressed to move said movable mold member to its second position; a roughened surface formed on at least a portion of the surface of said movable mold member defining the reverse bend to which the plastic is to be formed, said surface being sufficiently rough to grip a hot plastic sheet when such a sheet is placed thereon; and a clamping member cooperable with said base and said two mold members for clamping a plastic sheet in sealing association therewith so that a vacuum may be drawn on the interior of plastic sheet whereby exterior pressure acts against said spring means to compress the same and move said movable mold member to its second position thereby to form the reverse bend in the plastic sheet.

Claim 6

Apparatus for use in conjunction with a vacuum system for forming a plastic sheet to a final configuration in which the sheet has a reverse bend formed therein, which apparatus comprises: a base; a stationary mold member secured to said base and defining at least a portion of the reverse bend to which the sheet of plastic is to be formed; a movable mold member defining at least another portion of the reverse bend to which the sheet of plastic is to be formed and mounted for movement with respect to said base from a first position to a second position, said movable mold member being remote from said stationary mold member when in its said first position and being in juxtaposition to said stationary mold member when in its second position so that said two mold members define therebetween the reverse bend to which the plaStic sheet is to be formed; spring means acting between said two mold members for moving said movable mold member normally to its said first position; said spring means being compressed to move said movable mold member to its second position; a roughened surface formed on at least a portion of the surface of said movable mold member defining the reverse bend to which the plastic is to be formed, said surface being sufficiently rough to grip a hot plastic sheet when such a sheet is placed thereon; and a clamping member cooperable with said base and said two mold members for clamping a plastic sheet in sealing association therewith so that a vacuum may be drawn on the interior of plastic sheet whereby exterior pressure acts against said spring means to compress the same and move said movable mold member to its second position thereby to form the reverse bend in the plastic sheet.

Claim 7

The apparatus for forming the reverse bend in a plastic sheet as defined in claim 4 wherein: said roughened surface has a surface finish with a roughness of at least 250 microinches.