Method and mechanism for indicating mold friction in a continuous-casting machine

Claim 2

In a continuous-casting operation in which liquid metal is introduced continuously to the top of an open-ended mold, a partially solidified casting of indefinite length emerges from the bottom of the mold, and the mold is oscillated vertically, the movement of said casting through said mold being opposed by friction, and in which the drive means for oscillating the mold includes a motor operatively connected therewith, the magnitude of the armature current to said motor being proportional to the load on the motor, an improved method of determining the magnitude of the mold friction, said method comprising measuring the magnitude of the armature current to said motor with the motor oscillating the mold through a representative number of cycles during a casting operation, and compensating for factors which contribute to the load on the motor other than mold friction.

Claim 3

A method as defined in claim 1 in which the factors for which compensation is made include the varying force required to lift and lower the mold through different portions of its oscillation cycle, motor losses, and mechanical losses in the gearing and other mechanisms.

Claim 4

A method as defined in claim 2 in which the varying force required to lift and lower the mold is compensated for by averaging the current measurement through said cycles.

Claim 5

A method as defined in claim 2 in which the mold losses and mechanical losses are compensated for by running said motor with the mold empty and calibrating the measuring means to read zero with the motor driving the empty mold.

Claim 6

A method as defined in claim 2 in which an additional factor for which compensation is made is the accelerating force on the motor brought about by changes in the speed of mold oscillation, and the accelerating force is compensated for by operating the motor at a constant speed during said cycles.

Claim 7

In a continuous-casting operation in which liquid metal is introduced continuously to the top of an open-ended mold, a partially solidified casting of indefinite length emerges from the bottom of the mold, and the mold is oscillated vertically, the movement of said casting through said mold being opposed by friction and in which the drive means for oscillating the mold includes a variable speed d-c motor operatively connected therewith, and means for producing a master reference sIgnal for controlling the casting speed and maintaining the speed at which the mold oscillates at a predetermined ratio to the casting speed, the magnitude of the armature current being proportional to the load on the motor, an improved method of determining the magnitude of the mold friction, said method comprising measuring the average magnitude of the armature current to said motor with the motor oscillating the mold through a representative number of cycles during a casting operation, calibrating the measuring means to compensate for motor losses and mechanical losses by running said motor with the mold empty and setting the measuring means to zero, and replacing said master reference signal with a steady reference signal while the mold friction determination is made to compensate for accelerating forces.

Claim 8

In a continuous-casting operation in which liquid metal is introduced continuously to the top of an open-ended mold, a partially solidified casting of indefinite length emerges from the bottom of the mold, and the mold is oscillated vertically, the movement of said casting through said mold being opposed by friction and in which the drive means for oscillating the mold includes a variable speed d-c motor operatively connected therewith, and means for producing a master reference sIgnal for controlling the casting speed and maintaining the speed at which the mold oscillates at a predetermined ratio to the casting speed, the magnitude of the armature current being proportional to the load on the motor, an improved method of determining the magnitude of the mold friction, said method comprising measuring the average magnitude of the armature current to said motor with the motor oscillating the mold through a representative number of cycles during a casting operation, calibrating the measuring means to compensate for motor losses and mechanical losses by running said motor with the mold empty and setting the measuring means to zero, and replacing said master reference signal with a steady reference signal while the mold friction determination is made to compensate for accelerating forces.

Claim 9

A method as defined in claim 6 in which said steady reference signal approximately equals the magnitude of said master reference signal at the beginning of the determination.

Claim 10

A method as defined in claim 6 in which the average magnitude of the armature current is obtained by applying said steady reference signal to an integrating amplifier.

Claim 11

A method as defined in claim 6 in which the average magnitude of the armature current is obtained by applying said steady reference signal to a digital computer through a predetermined number of oscillation cycles.

Claim 12

A method as defined in claim 6 in which the mechanical losses are at a maximum at the beginning of a casting operation, but diminish and reach a steady magnitude as casting progresses, and said calibrating step is conducted immediately after the completion of a casting operation.

Claim 13

In a continuous-casting machine which comprises an open-ended mold for receiving liquid metal and from the bottom of which a partially solidified casting emerges, a motor operatively connected with said mold for oscillating it vertically, the magnitude of the armature current to said motor being proportional to the load on the motor, one of the factors contributing to said load being the frictional force between the mold and the casting, the combination therewith of a mechanism for determining the magnitude of the mold friction, said mechanism comprising; means for measuring the armature current, and means for compensating for other factors contributing to said load, whereby the armature current measurement affords a direct determination of mold friction.

Claim 14

In a continuous-casting machine which comprises an open-ended mold for receiving liquid metal and from the bottom of which a partially solidified casting emerges, a motor operatively connected with said mold for oscillating it vertically, the magnitude of the armature current to said motor being proportional to the load on the motor, one of the factors contributing to said load being the frictional force between the mold and the casting, the combination therewith of a mechanism for determining the magnitude of the mold friction, said mechanism comprising; means for measuring the armature current, and means for compensating for other factors contributing to said load, whereby the armature current measurement affords a direct determination of mold friction.

Claim 15

A continuous-casting machine as defined in claim 11 in which another factor contributing to said load is the varying force required to lift and lower the mold through different portions of its oscillation cycle, and the means for compensating for variations in the lifting and lowering force includes means for averaging the armature current through a representative number of oscillation cycles.

Claim 16

A machine as defined in claim 12 in which said averaging means is a digital computer.

Claim 17

A machine as defined in claim 11 in which said averaging means is an integrating amplifier.

Claim 18

A continuous-casting machine as defined in claim 11 in which other factors contributing to said load are motor losses and mechanical losses, and the means for compensating for said losses include calibration means which are set to show a zero with said motor driving an empty mold.

Claim 19

A continuous-casting machine as defined in claim 11 in which another factor contributing to said load is acceleration force brought about by changes in the speed at which said mold oscillates, and the means for compensating for acceleration force includes means for producing a steady reference signal for controlling the armature current.

Claim 20

In a continuous-casting machine which comprises an open-ended mold for receiving liquid metal and from the bottom of which a partially solidified casting emerges, a motor operatively connected with said mold for oscillating it vertically, and means for producing a varying master reference signal which controls the speed of said motor, the magnitude oF the armature current to said motor being proportional to the load on said motor, the factors contributing to said load including mold friction, the varying force required to lift and lower the mold through different portions of its oscillation cycle, motor losses, mechanical losses, and accelerating forces brought about by speed changes, the combination therewith of a mechanism for determining the magnitude of the mold friction, said mechanism comprising means for measuring the armature current averaged over a representative number of oscillation cycles to compensate for the varying force required to lift and lower the mold, means connected with said measuring means for compensating for the effect of said losses, and means for replacing said master reference signal with a steady reference signal while the mold friction determination is made to compensate for said accelerating forces.

Claim 21

In a continuous-casting machine which comprises an open-ended mold for receiving liquid metal and from the bottom of which a partially solidified casting emerges, a motor operatively connected with said mold for oscillating it vertically, and means for producing a varying master reference signal which controls the speed of said motor, the magnitude oF the armature current to said motor being proportional to the load on said motor, the factors contributing to said load including mold friction, the varying force required to lift and lower the mold through different portions of its oscillation cycle, motor losses, mechanical losses, and accelerating forces brought about by speed changes, the combination therewith of a mechanism for determining the magnitude of the mold friction, said mechanism comprising means for measuring the armature current averaged over a representative number of oscillation cycles to compensate for the varying force required to lift and lower the mold, means connected with said measuring means for compensating for the effect of said losses, and means for replacing said master reference signal with a steady reference signal while the mold friction determination is made to compensate for said accelerating forces.

Claim 22

A mechanism as defined in claim 17 in which the means for measurng the armature current includes a voltmeter and an integrating amplifier operatively connected with said voltmeter and receiving said steady reference signal.

Claim 23

A mechanism as defined in claim 17 in which the means for measuring the armature current includes a digital computer and a print-out operatively connected with said computer, said computer receiving said steady reference signal.

Claim 24

A mechanism as defined in claim 17 in which the means for replacing said master signal with a steady reference signal includes a blocking rectifier and a potentiometer connected to the circuit which carries said signals, said blocking rectifier normally permitting said master reference signal to pass, but permitting said steady reference signal to pass when its magnitude is greater than said master reference signal.