Apparatus for the manufacture of thin-walled shaped articles of thermoplastic material

Claim 2

Apparatus for manufacturing thin-walled synthetic plastic articles which comprises extrusion means for forming a continuous hot plastic web of thermoplastic material at a predetermined high temperature, means for substantially immediately stabilizing said web to self supporting condition by cooling opposite surfaces of the web to provide therealong continuous outer supportive layers that are sufficiently deformable for shaping in subsequent shaping tool operation while the hot plastic material between said layers remains sufficiently plastic and fluid for redistribution between said layers during said tool operation, and means for advancing the stabilized web toward and into a thermal forming station in synchronism with shaping tools in said station adapted for forming articles in successive areas of said web during the period that said hot plastic material between the layers remains capable of redistribution between them.

Claim 3

Apparatus as defined in claim 1, wherein means is provided for continuously moving said web through said stabilization means, and said cooling means comprises means in area contact with the continuously moving web surfaces for relatively rapid cooling of the web surfaces.

Claim 4

Apparatus as defined in claim 2, wherein said means for cooling the web surfaces comprises a plurality of cooling rollers over which said hot plastic web is drawn in opposite surface contact, and means is provided for controlling the amount of heat exchange between said rollers and the web surfaces.

Claim 5

Apparatus as defined in claim 3, wherein said means for controlling heat exchange comprises means for adjustably varying the areas of contact between said rollers and said web surfaces.

Claim 6

Apparatus as defined in claim 4, wherein one of said cooling rollers rotates on a fixed axis and another of said rollers is selectively movable in an arc about said axis.

Claim 7

Apparatus as defined in claim 4, wherein a first cooling roller is provided rotating about a fixed axis and second and third cooling rollers are provided at opposite sides of said first cooling roller, said second and third cooling rollers being adjustable in a direction perpendicular to a horizontal plane containing said axis.

Claim 8

Apparatus as defined in claim 3, wherein said cooling rollers are adapted to be cooled by means of fluid cooling medium and wherein said controlling heat exchange comprises means for adjustably varying the temperature of said cooling medium.

Claim 9

The apparatus defined in claim 1, including means defining a treatment station for treating the outer layers of said stabilized web for obtaining uniform temperature distribution across the outer surfaces of successive web areas prior to said tool operation.

Claim 10

The apparatus defined in claim 9, wherein temperature distribution is effected by means providing proportional reflection of radiant heat from the hot plastic web.

Claim 11

The apparatus defined in claim 8, including means whereby air at controlled temperature is circulated over the layer surfaces at said areas for effecting temperature distribution.

Claim 12

Apparatus as defined in claim 8, wherein means is provided for converting continuous advance of said web through said stabilizing means into intermittent advance into and through said web surface treatment station whereby successive web areas are disposed for a predetermined period of said station.

Claim 13

Apparatus as defined in claim 1, including means whereby said areas of said stabilized web are intermittently introduced in succession into said thermal forming station.

Claim 14

Apparatus as defined in claim 12, wherein said shaping tool means comprises at least one contoured forming die surface against which one surface of the web is pressed, and means is provided acting on the other side of said web for forcing said web into contact with said one die surface.

Claim 15

Apparatus as defined in claim 13, wherein said other surface of the web is engaged by a web stretching die element.

Claim 16

Apparatus as defined in claim 13, wherein fluid pressure is applied to the other side of said web to urge the web into contact with said one die surface.

Claim 17

Apparatus as defined in claim 1, characterized in that means synchronized with the shaping operation is provided for precooling the web prior to said shaping.

Claim 18

Apparatus as defined in claim 16, characterized in that said precooling means comprises cooled tools having recessed areas that during precooling do not contact the surface of the web at the areas to be shaped into articles.

Claim 19

Apparatus as defined in claim 16, characterized in that the precooling means comprises tools of coacting form mounted on opposite sides of the web.

Claim 20

Apparatus as defined in claim 17, characterized in that said precooling means is provided with surfaces at those parts that touch the surface of the web for forming into the web a framelike structure outside the areas to be shaped.

Claim 21

Apparatus as defined in claim 16, characterized in that precooling is effected in a plurality of correlated successive stages in each of which a web section of predetermined length is successively disposed.

Claim 22

Apparatus as defined in claim 20, characterized in that recessed areas of different size are provided in the consecutive precooling stages such that the non-cooled areas are smaller in the successive stages.

Claim 23

Apparatus as defined in claim 16, where means is provided whereby a thermal die is moved to and from the web by a support and means is provided whereby the web is moved at right angles to the direction of motion of the thermal die through the latter's operating range and intermittently in steps adapted to the movement of the thermal die, characterized in that at least one precooling means correlated with respect to size and recessed areas in the thermal die is mounted on the support in the path of the web upstream of the thermal die and for simultaneous motion with said thermal die.

Claim 24

Apparatus as defined in claim 22, where accessories such as forming elements and counter dies relating to the thermal die are mounted on a second support moved out of phase with respect to said first support, characterized in that at least one second precooling means is mounted on the second support, the structure of which corresponds essentially to that of the first precooling means, and in that the second precooling means and the first precooling means are constructed and arranged for clamping the web with firm bilateral pressure when the thermal die is closed.

Claim 25

Apparatus as defined in claim 22, characterized in that means is provided whereby the first precooling means and/or the second precooling means may be retracted against the action of compression springs in the direction of said supports.

Claim 26

Apparatus as defined in claim 16, characterized in that pneumatic or hydraulic cylinders are provided for supporting both of said precooling means under predetermined pressure.

Claim 27

Apparatus as defined in claim 23, characterized in that positive and negative shaping elements are provided on at least one cooperating pair of precooling means for the formation of a framelike structure in the cooled stabilized web.

Claim 28

Apparatus as defined in claim 1, wherein means is provided for subsequently stamping the formed articles out of said web.

Claim 29

Apparatus for manufacturing thin-walled synthetic plastic articles which comprises means including extrusion means for forming a continuous plastic web of thermoplastic material at a selected high temperature and means for substantially immediately stabilizing said web to self supporting condition by cooling opposite surfaces of the web to provide therealong continuous outer supportive layers that are sufficiently deformable for shaping in subsequent shaping tool operation while the hot plastic material between said layers remains sufficiently plastic and fluid for redistribution between said layers during said tool operation, and means for advancing the stabilized web toward and into a thermal forming station wherein successive areas of the web are subjected to the action of shaping tool means, said web advance being effected at such speed and in such timed relation to operation of the shaping tool means and in such correspondence with the web extrusion temperature that said stabilized web arrives at said thermal forming station while it retains sufficient heat in its inner core portion to partially reheat its cooled surface layers by heat conduction from the inner core portion outwardly during transport from said stabilizing means to said thermal forming station so that said layers are elastically deformable for improved shaping.

Claim 30

Apparatus for manufacturing thin-walled synthetic plastic articles which comprises means including extrusion means for forming a continuous plastic web of thermoplastic material at a selected high temperature and means for substantially immediately stabilizing said web to self supporting condition by cooling opposite surfaces of the web to provide therealong continuous outer supportive layers that are sufficiently deformable for shaping in subsequent shaping tool operation while the hot plastic material between said layers remains sufficiently plastic and fluid for redistribution between said layers during said tool operation, and means for advancing the stabilized web toward and into a thermal forming station wherein successive areas of the web are subjected to the action of shaping tool means, said web advance being effected at such speed and in such timed relation to operation of the shaping tool means and in such correspondence with the web extrusion temperature that said stabilized web arrives at said thermal forming station while it retains sufficient heat in its inner core portion to partially reheat its cooled surface layers by heat conduction from the inner core portion outwardly during transport from said stabilizing means to said thermal forming station so that said layers are elastically deformable for improved shaping.