vacuum forming machine
A vacuum forming machine has a machine frame and a forming station which includes a tensioning device for clamping a thermoplastic sheet blank to be deformed into an article, a bridge and a positive mold carried thereby. The bridge is vertically displaceable together with the positive mold between an inoperative position in which the positive mold is spaced from a location where the blank is clamped by the tensioning device and an operative position in which the positive mold is in an operative, contacting relationship with the blank. The positive mold is vertically displaceable with respect to the bridge between the operative position and a transfer position in which the article formed on the positive mold is transferred therefrom.
In a vacuum forming machine including a machine frame; a forming station having tensioning means for clamping a thermoplastic sheet blank to be deformed into an article, abridge and a positive mold carried by said bridge; the improvement comprising in combination:(a) first guide means for vertically displaceably supporting said bridge in said machine frame;(b) first drive means for vertically displacing said bridge and said positive mold as a unit between an inoperative position in which said positive mold is spaced from a location where the blank is clamped by said tensioning means and anoperative position in which said positive mold is in an operative, contacting relationship with the blank clamped by said tensioning means;(c) second guide means for vertically displaceably supporting said positive mold on and relative to said bridge; and(d) second drive means for vertically displacing said positive mold with respect to said bridge between said operative position and a transfer position in which the article formed on said positive mold is transferred therefrom.
In German Utility Model (Gebrauchsmuster) No. 7,328,626 there is disclosed a vacuum forming machine which cooperates with a foaming apparatus. The negative deep-drawing molds are arranged for orbital motion, thus during operation they swing insequence into the forming station. Such a known vacuum forming machine has been found to be disadvantageous in that a positive deformation of the blanks is not possible. Such a machine, however, has particular advantages in the deformation of grainedsheets including grained foam sheets as well as the manufacture of relatively deep (large-height) components.
It is a further disadvantage of the vacuum forming machine disclosed in German Utility Model No. 7,328,626 that a relatively large number of negative deep-drawing molds has to be circulated. It is difficult to maintain all these molds at apredetermined temperature which is required for the deformation.It is further known to deform the sheet blanks directly by the foam pressure; that is, the sheet blank is positioned in a cold state into the foaming mold. The pressure generated during foaming causes the sheet blank to conform to the mold wall. Such a method is feasible, however, only in case of flat and simple shapes. Otherwise, in case of grained sheets, the upper surface structure is distorted excessively and the resetting stresses in relatively deep articles having abrupt configurationslead to a warping of the article.
A vacuum forming machine as defined in claim 1, wherein said operative position is at a lower level than said inoperative position and said transfer position is at a lower level than said operative position.A vacuum forming machine as defined in claim 1, wherein said tensioning means comprises a stationary clamping frame and a movable clamping frame being in substantial alignment and cooperating with said stationary clamping frame; eachclamping frame having an inner diameter; the inner diameter of said movable clamping frame being greater than the inner diameter of said stationary clamping frame.A vacuum forming machine as defined in claim 1, further comprising rolling elements carried by said machine frame and supporting the machine on the ground, whereby said machine is displaceable.
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