Controlling an extrusion blowing process
AssigneeKrupp Kautex Maschinenbau GmbH
InventorsWerner Daubenbuchel, Dieter Hess
Life of this patent
Estimating the term…
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.
Claims18
Apparatus for maintaining substantially constant the final weight of a hollow member which is made from a thermoplastic material by an extrusion blowing process wherein a preform is continuously extruded through a discharge opening of an extrusion pressing head connected to an extrusion press and blown in a mold means, comprising means for determining the final weight of a said hollow member after leaving the mold means and comparing said final weight to a reference value representing desired weight, means for increasing or decreasing the size of said discharge opening in response to the comparison operation such that the volume and therefore the weight of the preform increases when said final weight is less than said reference value and decreases when said final weight is greater than said reference value, means for detecting when the length of the preform has reached a preselected length, said detecting means being operable to initiate closure of the mold means about the preform, and control means for maintaining substantially constant the time to extrude said preform to said preselected length.
A system for producing a hollow member from thermoplastic material by extrusion blowing, comprising:
- (a) an extrusion press;
- (b) an extrusion means connected to the output of the extrusion press and providing a variable size discharge opening for producing a preform;
- (c) mold means for receiving the preform and means for inflating the preform therewithin to form a said hollow member;
- (d) means for determining the final weight of the hollow member after leaving the mold means and comparing said final weight to a reference value representing desired weight;
- (e) means for increasing or decreasing the size of the discharge opening in response to said comparison operation such that the volume and therefore the weight of the preform increases when said final weight is below said reference value and decreases when said final weight is above said reference value;
- (f) means for detecting when the length of the preform has reached a preselected length, said detecting means being operable in response thereto to initiate closure of the mold means about the preform;
- and
- (g) control means for maintaining substantially constant the time to extrude said preform to said preselected length.
A system for producing hollow members from thermoplastic material by extrusion blowing, comprising:
- (a) an extrusion press;
- (b) an extrusion means connected to the output of the extrusion press and providing a variable size discharge opening for producing performs;
- (c) mold means for receiving the performs and means for inflating the preforms therewithin to form said hollow members;
- (d) means for determining the mean weight of a plurality of successive hollow members after leaving the mold means and comparing said mean weight to said reference value representing desired weight;
- (e) means for increasing or decreasing the size of the discharge opening in response to said comparison operation such that the volume and therefore the weight of the performs increases when said mean weight is below said reference value and decreases when said mean weight is above said reference value;
- (f) means for detecting when the length of the performs has reached a preselected length, said detecting means being operable in response thereto to initiate closure of the mold means about the performs;
- and
- (g) control means for maintaining substantially constant the time to extrude said performs to said preselected length.
Dependencies are inferred from the claim text.