Automatic purging and shutdown for plastic injection machines

Claim 2

An automatic purging and shutdown system for a reciprocating type of plastic injection machine having a reciprocating member received in a barrel for ejecting such plastic material for cooling down the barrel of such machine to prevent degradation of plastic material remaining in the barrel after shutdown, comprising circuit means which operates in a cycle of operation and causes said member to initiate an ejection cycle including first timer circuit means connected to delay retraction of said member for a predetermined short time interval to assure the emptying of said barrel of plasticized plastic material and thereafter to causE the return of said member inwardly of said barrel to receive an additional quantity of plasticized material therein, second timer circuit means connected to initiate a subsequent ejection cycle after a predetermined time delay of a duration longer than that provided by said first timer circuit means providing for absorption of heat from said barrel by the new charge of unplasticized material and providing for plasticizing of said material, and means automatically terminating further ejection cycles when said barrel has cooled sufficiently to prevent degradation of plastic material remaining therein.

Claim 3

The system of claim 1, in which said last-named means includes a counter connected to operate on each cycle of operation and which, after a predetermined number of such cycles, disables further operation.

Claim 4

The system of claim 1 further including means providing an audible warning signal for each cycle of operation.

Claim 5

An automatic purging and shutdown system for a reciprocating screw type of plastic ejection machine in which a hydraulic drive motor is connected to rotate the screw and a hydraulic piston is connected to thrust the screw forwardly in the barrel, including a source of fluid under pressure and first valve means connected to said source and said motor to control the hydraulic motor and cause rotation of the screw for receiving and plasticizing a charge of plastic material in the barrel and second valve means is connected to said source and to said piston to control the application of such fluid pressure thereto for effecting ejecting movement of such charge from the barrel, the improvement in automatic purge and shutdown system for such machine including control means connected to said first valve means to cause a charge of plastic material to be formed in said barrel, timer means connected to control said second valve means for ejecting said charge after a predetermined time interval sufficient to permit plasticizing resulting in removal of a quantity of heat from said barrel, and switch means for repeating in sequence the operation of said control means and said timer means until said barrel has cooled sufficiently to permit shut down of said machine without degradation of plastic material remaining in said barrel and thereafter automatically shutting down said machine.

Claim 6

An automatic purging and shutdown system for a reciprocating screw type of plastic ejection machine in which a hydraulic drive motor is connected to rotate the screw and a hydraulic piston is connected to thrust the screw forwardly in the barrel, including a source of fluid under pressure and first valve means connected to said source and said motor to control the hydraulic motor and cause rotation of the screw for receiving and plasticizing a charge of plastic material in the barrel and second valve means is connected to said source and to said piston to control the application of such fluid pressure thereto for effecting ejecting movement of such charge from the barrel, the improvement in automatic purge and shutdown system for such machine including control means connected to said first valve means to cause a charge of plastic material to be formed in said barrel, timer means connected to control said second valve means for ejecting said charge after a predetermined time interval sufficient to permit plasticizing resulting in removal of a quantity of heat from said barrel, and switch means for repeating in sequence the operation of said control means and said timer means until said barrel has cooled sufficiently to permit shut down of said machine without degradation of plastic material remaining in said barrel and thereafter automatically shutting down said machine.

Claim 7

The system of claim 4 in which said control means includes a controllable timer for delaying for a variable but short time period the operation of said first valve means subsequent to the operation of said second valve means to assure complete ejection of plastic material from said barrel.

Claim 8

The system of claim 4 in which said repeating means includes a counter which causes said control means to operate through a preset number of cycles of operation and thereafter disables said control means.

Claim 9

The system of claim 4 further includes an audible signal operable in each cycle of operation to warn that automatic purging is in progress.

Claim 10

The system of claim 1 in which each said first and second timer circuit means includes a variable timer.