Means for monitoring product quality in a plastics injection-molding machine

Claim 2

A plastics injection-molding machine, comprising plasticizing means for the accumulation of plasticized melt, a cavity mold having a sprue opening, means connected to said plasticizing means and including a discharge nozzle engageable with the sprue opening and reciprocable hydraulic feed mechanism for the periodic discharge of plasticized melt into said mold, variable pressure hydraulic supply means for said feed mechanism, pressure-sensitive transducer means positioned for exposure to plasticized melt generated by said plasticizing means, and feedback-control means connecting said transducer means with said variable pressure hydraulic-supply means, said feedback-control means sensing the peak plasticized melt pressure during an injection-molding cycle and controlling the variable pressure hydraulic-supply means as a function of said peak pressure during the next injection-molding cycle.

Claim 3

A machine according to claim 1, in which said transducer means is carried by said mold and is exposed for response to mold-cavity pressure.

Claim 4

A machine according to claim 1, in which said transducer means is carried by said discharge nozzle and is exposed for response to nozzle-injection pressure.

Claim 5

A machine according to claim 1, in which said feedback-control means includes reference-level means and polarity-sensitive comparator means responsive both to said reference-level means and to the output of said transducer means, said comparator means having an output connected in pressure-controlling relation with said variable pressure hydraulic-supply means.

Claim 6

A machine according to claim 4, in which said reference-level means is manually adjustable.

Claim 7

A machine according to claim 4, and including indicating means responsive to indicate whether or not the pressure detected by said transducer means differs more than a predetermined amount from the level determined by said reference-level means.

Claim 8

A machine according to claim 6, in which said indicating means is polarity-sensitive and includes separate means for indicating whether the transducer-detected pressure exceeds or is less than said level.

Claim 9

A machine according to claim 1, in which said feedback-control means includes peak-signal storage means responsive to the output of said transducer means to develop a signal reflecting peak pressure of plasticized melt, and means tracking the peak-signal output of said storage means and in pressure-controlling relation with said variable pressure hydraulic-supply means.

Claim 10

A machine according to claim 1, in which said hydraulic-supply means includes a source of hydraulic fluid at elevated pressure, and means including a relief valve in the connection of said source to said feed mechanism, said relief valve including means for adjustably varying the relief-pressure setting thereof, said feedback-control means being operatively connected to said adjustably variable means.

Claim 11

A machine according to claim 4, in which said hydraulic-supply means includes a source of hydraulic fluid at elevated pressure, and means including a relief valve in the connection of said source to said feed mechanism, said relief valve including means for adjustably varying the relief-pressure setting thereof, said feedback-control means being operatively connected to said adjustably variable means, said operative connection to said adjustably variable means including reversibly actuable position-stepping means.

Claim 12

A machine according to claim 4, in which said hydraulic-supply means includes a source of hyDraulic fluid at elevated pressure, and means including a relief valve in the connection of said source to said feed mechanism, said relief valve including means for adjustably varying the relief-pressure setting thereof, said feedback-control means being operatively connected to said adjustably variable means, said operative connection to said adjustably variable means including reversible stalled-torque drive means.

Claim 13

A plastics injection-molding machine, comprising plasticizing means for the accumulation of plasticized melt, a cavity mold having a sprue opening, injection means connected to said plasticizing means and including a discharge nozzle engageable with the sprue opening and reciprocable feed mechanism for the periodic discharge of plasticized melt into said mold, said feed mechanism including control means for varying the force with which said injection means is operative upon discharge of plasticized melt, pressure-sensitive means positioned for exposure to plasticized melt generated by said plasticizing means, and feedback-control means connecting said pressure-sensitive means with said control means, said feedback-control means being responsive to the peak pressure signal from said pressure-sensitive means during an injection-molding cycle and actuating said control means during the next injection-molding cycle as a function of said peak pressure signal.

Claim 14

A plastics injection-molding machine, comprising plasticizing means for the accumulation of plasticized melt, a cavity mold having a sprue opening, injection means connected to said plasticizing means and including a discharge nozzle engageable with the sprue opening and reciprocable feed mechanism for the periodic discharge of plasticized melt into said mold, said feed mechanism including control means for varying the force with which said injection means is operative upon discharge of plasticized melt, pressure-sensitive means positioned for exposure to plasticized melt generated by said plasticizing means, and feedback-control means connecting said pressure-sensitive means with said control means, said feedback-control means being responsive to the peak pressure signal from said pressure-sensitive means during an injection-molding cycle and actuating said control means during the next injection-molding cycle as a function of said peak pressure signal.