Abstract: In a process and apparatus for producing hollow bodies from thermoplastic material by blow molding of preforms using a closing support structure having at least first and second blow molding molds, a common drive means engages a drive plate and a first carrier plate which carries a mold portion. The drive plate is connected to a second carrier plate carrying another mold portion. At least one further carrier plate is arranged displaceably in the opening and closing direction between the first and second carrier plates. At each of its two sides the further carrier plate carries a respective mold portion, each thereof with a mold portion carried by an adjacent carrier plate forming a respective blow molding mold. Each of the two blow molding molds afforded thereby is provided with a means for locking the respective mold in the closed condition thereof.

Abstract: In a process for the production of a hollow body of thermoplastic material which is to include an additional portion, by expansion of a preform in a blow molding mold, the additional portion is connected to the hollow body upon expansion of the preform to form the hollow body. To form the connection between the hollow body and the additional portion, the latter is heated by a heating element which is brought into contact with at least the surface of the additional portion that is to involve the welded connection to the hollow body, prior to expansion of the preform. The heating element is brought into contact with the additional portion when already disposed in the blow molding mold in order in that way to heat at least the appropriate surface of the additional portion to a temperature which premotes the production of an adhesive join to the hollow body. The region of the additional portion that is to be heated is at least substantially covered relative to the outside atmosphere by the heating element.

Abstract: In a process and apparatus for the discontinuous production of preforms for producing hollow bodies from thermoplastic material, the wall of which is a laminate having at least first and second layers, by extrusion blow molding, the flow of material for forming the laminate is guided within the extrusion head which serves to produce the preforms, by suitable dimensioning of the volume of the duct system accommodating the laminate, such that regions of disturbed laminate occur in the end portions of the preform which are squeezed off the extruded preform by the blow molding mold as a waste portion.

Abstract: In a process and apparatus for the production of hollow bodies from thermoplastic material, having a wall of a laminate formed by at least first and second layers, by means of extrusion blow molding, a preform having a wall structure with a suitable number of layers is first produced in a batch-wise procedure using an extrusion head. The material required to produce the preform is guided in the extrusion head in such a way that disturbed portions of the laminate pass into the waste flash portions at the ends of the hollow body produced from the preform, so that the wall of the finished hollow body is devoid of disturbed laminate portions of that kind.

Abstract: In a process and apparatus for the production of hollow bodies from thermoplastic material, the walls of the hollow bodies are of a laminate structure having at least first and second layers, by means of extrusion blow molding, the pressure within the extrusion head and more particularly at the location at which the laminate is formed by the discharge of flows of material from a storage chamber in the head is maintained within limits such as to avoid disturbing the laminate to such an extent as to have an adverse effect on its function. The pressure at the time of a transition between filling and emptying of the storage chamber and between emptying and filling of the storage chamber is maintained substantially at a pressure level which approximately corresponds to the storage chamber emptying pressure.

Abstract: A barrel of thermoplastic material has at least one connecting portion having an emptying opening and arranged in a trough-like depression in the upper end part of the barrel. In the region of the connecting portion the barrel has at least one inclined surface which extends between the upper end part of the barrel and the side wall of the barrel. The inclined surface is of such a configuration that in a barrel emptying position the emptying opening forms the lowest part of the interior of the barrel to permit at least almost complete emptying of the barrel.

Abstract: In a process for producing a hollow body with a wall which partially comprises foamed thermoplastic material by an extrusion blow molding procedure, a preform which comprises at least first and second layers of which at least one comprises foamable plastics material is first extruded, the layer of foamable material is foamed, and then the preform is expanded in a blow molding mold by the application of an internal pressure. The hollow body may have a welded seam at a region of the hollow body at which an operation of squeezing off excess material has been carried out, the seam being in the form of an outwardly projecting flange web portion and the thickness thereof being such that the layer of foamable material is compressed at least to such an extent that it is not thicker than in the unfoamed condition.

Abstract: In extrusion blowing a hollow member, a preform is extruded and then blown in a mold to produce the final member. The weight of the hollow member is determined after its removal from the mold and compared to a reference value, thereby to adjust the size of the extrusion discharge opening to control the amount of material in the preform. The length of the preform is detected to control the movement of the mold thereby to keep a substantially constant length of extruded preform, while the time required to produce a preform is also maintained at a substantially constant value.

Abstract: In extrusion blowing a hollow member, a preform is extruded and then blown in a mold to produce the final member. The weight of the hollow member is determined after its removal from the mold and compared to a reference value, thereby to adjust the size of the extrusion discharge opening to control the amount of material in the preform. The length of the preform is detected to control the movement of the mold thereby to keep a substantially constant length of extruded preform, while the time required to produce a preform is also maintained at a substantially constant value.

Abstract: Blow-moulding apparatus for the manufacture of hollow bodies from a thermoplastic in which a screw extruder extrudes the thermoplastic into an accumulating chamber, and a piston forces the thermoplastic through a gap-like outlet orifice of the accumulator chamber to form a parison. A blow-mould consisting of at least two parts which can be opened is positioned so that the blow-mould encompasses the parison. Control means are provided for adjusting the width of the gap-like outlet orifice of the accummulator chamber as a function of the length of the parison extruded, which length can be detected e.g. by a light beam and a photo-cell.

Abstract: Multiple extrusion head extrusion-blow moulding apparatus, preferably using a common continuously operating extrusion conveyor, in which apparatus the various extrusion heads have their accumulator pistons driven for identical and simultaneous movement during the extrusion strokes either by means of a common drive means or by separate drive means each controlled from a common control means. Common control may also be exercised over the charging stroke of the accumulator piston.Closed loop control over the wall thickness in dependence upon the final length of the parison, as well as open loop control over the wall thickness in response to a desired program may be imposed simultaneously on the extrusion orifice gap width.