Method for manufacturing containers from blanks, with detection of defective opening of solenoid valves

Method for manufacturing containers (23) by blow molding in a mold of blanks (2) of plastic material, comprising, during the manufacture of a container:

• a step for inserting a blank (2) into a mold (26);
• at least one step for putting the interior of the blank (2) in communication with at least one fluid circuit (34;
• 40;
• 46;
• 52) by means of a solenoid valve (EV1;
• EV2;
• EV3;
• EV4) comprising a fluid valve associated with said fluid circuit (34;
• 40;
• 46;
• 52) and an actuator (R1, R2, R3, R4) driven by a solenoid driver, the fluid valve comprising:
• a valve body including a stop which is stationary with respect to the fluid circuit, and
• a moveable valve element being moved by the actuator between (i) a closed position wherein the moveable valve element prevents the fluid from passing through the fluid valve and (ii) a fully opened position wherein the mobile valve element is stopped by contacting the stop and allows the fluid to pass through the fluid valve;
• at a specific time, referred to as solenoid valve opening trigger pulse (TEV1;
• . . . ;
• TEV4), sending an opening order to said solenoid driver, the solenoid valve (EV1;
• EV2;
• EV3;
• EV4) having a theoretical delay (Dt1;
• . . . ;
• Dt4) of opening, i.e., a time that theoretically must pass between the opening trigger pulse and a time when the valve element actually reaches the fully opened position;
• wherein the method further comprises steps consisting in:
• receiving, continuously from a pressure sensor 32, a measured pressure within a nozzle (30) positioned at the mold (26);
• receiving the theoretical delay (Dt1;
• . . . ;
• Dt4) from a memory (64) of a control unit (58);
• determining an actual delay (Del;
• . . . ;
• De4) of opening of said solenoid valve (EV1;
• EV2;
• EV3;
• EV4), i.e., a time passed between the opening trigger pulse and an actual time (Tel;
• . . . ;
• Te4) when the valve element reaches the fully opened position;
• calculating a difference (Δt1;
• . . . ;
• Δt4) between the actual delay (De1;
• . . . ;
• De4) of opening and the theoretical delay (Dt1;
• . . . ;
• Dt4) of opening;
• if the difference calculated is greater than a maximum allowable difference, transmitting, from the control unit (58), a notification of exceeding the maximum allowable difference to a notification device.