Arrangement for adjusting the mass of thermoplastic gobs for a molding machine

An arrangement for adjusting the mass of gobs of thermoplastic material, especially molten glass, which are severed one after the other off a cord of the material issuing from a feeder, fed into the mold of a molding machine and by means of a pressing member which penetrates into the gobs deformed in a positive manner, with the maximum penetration depth achieved by the pressing member during each operating cycle being mechanically detected by a distance transducer, the distance transducer being connected to a metallic actuating element for a differential transformer at whose output is produced an electrical signal which is proportional to such respective maximum penetration depth and which is applied to a regulating circuit for control of a dosing structure which adjusts the mass of the gobs, characterized in that,

• in the regulating circuit an output of the differential transformer is connected to a measurement transducer whose output is connected to a maximum-value storage, the output of the latter being connected to a sample-and-hold circuit whose output is connected via a summing junction to a PI- or PID-regulator, the output of the latter being connected to an adjusting motor which adjusts the dosing structure, furthermore including a drive train between the adjusting motor and an adjusting member for the dosing structure, the drive train being connected to a feedback transducer to which there is connected a rotary-angle-to-voltage transducer whose output is connected to the PI- or PID-regulator, the arrangement furthermore including a control and display panel connected to transmit signals to and receive signals from a control logic circuit, the control logic circuit having outputs connected to the maximum-value storage and to the sample-and-hold circuit, the control logic circuit having an input for receipt of a synchronizing signal derived from the operating cycles of a molding machine, the control and display panel being connected to means providing a desired-value voltage representing the optimum penetration depth for the pressing member, the desired-value voltage being applied to the summing junction.