Machine tool cutting indication and control

Claim 2

In combination with a machine tool which includes a workpiece holder and a cutting tool, an electric motor for moving the workpiece holder in relation to the cutting tool, and means for advancing the workpiece holder in relation to the cutting tool to bring a workpiece attached to the workpiece holder into engagement with the cutting tool for performing a machining operation on the workpiece, apparatus for providing an indication of engagement of the tool with the workpiece comprising a first signal means connected to said electrical motor for sensing the no-load power input to said electrical motor and deriving a first unidirectional electrical signal the amplitUde of which corresponds to said no-load power input, a storage means connected to said first signal means for storing said first unidirectional signal, a second signal means connected to said storage means for sensing the power input to said electrical motor in response to loading of said motor and for providing a second unidirectional signal, the amplitude of which varies with and corresponds to the loading of said motor, no-load means connected to said storage means and to said second signal means for combining said stored first unidirectional signal and said second unidirectional electrical signal to develop a third unidirectional signal the amplitude of which varies in accordance with the amplitude of the difference of said first and second electrical signals corresponding to the difference in said no-load and load power input respectively to said motor, whereby an indication of the engagement of said tool with said workpiece is obtained.

Claim 3

The combination of claim 1 including means connected to said combining means responsive to a predetermined level of said third signal corresponding to a predetermined loading of said motor by the engagement of said tool with said workpiece to provide an indication of the engagement of said tool with said workpiece.

Claim 4

The combination of claim 1 in which the factor of proportionality in said first signal means between no-load power input to the amplitude of said first unidirectional signal is greater than the factor of proportionality in said second signal means between the load power input to the amplitude of second unidirectional signal, whereby zero amplitude of said third unidirectional signal corresponds to a threshold level of loading of said motor, said threshold level being determined by the difference in said factors of proportionality.

Claim 5

The combination of claim 2 in which said means responsive to said third unidirectional signal is a timer.

Claim 6

In combination with a machine tool which includes a workpiece holder and a cutting tool, an electric motor for rotating the workpiece holder in relation to the cutting tool, and means for advancing the workpiece holder in relation to the cutting tool to bring a workpiece attached to the workpiece holder into engagement with the cutting tool for performing a machining operation on the workpiece, apparatus for providing an indication of engagement of the tool with the workpiece comprising means connected to a source of electrical energy for electrically energizing said motor, means coupled to the input circuit of said electric motor for sensing power flowing thereto and providing a first unidirectional signal corresponding to the power flowing to said motor, a pair of channels, each having an input circuit and an output circuit, means for applying said first unidirectional signal to the input circuits of said channels, one of said channels including an amplifier for developing a second unidirectional signal in response to said first unidirectional being applied thereto and being capable of providing said second unidirectional signal at the output thereof for a long period of time when said first predetermined input is no longer being applied thereto, means connected to the input circuit of said one channel for disconnecting the input circuit of said one channel a short time after the energization of said motor and before loading is applied thereto whereby said first signal is applied solely to the input circuit of said other channel, said other channel providing a third electrical signal at the output thereof in response to said first electrical signal, the amplitude of which varies with and corresponds to the loading of said motor, means connected to the output circuits of said channels for differentially combining the outputs of said channels and for deriving a fourth unidirectional signal the amplitude of which varies in accordance with the amplitude of the difference of said second and third electrical signals correspondiNg to the difference in said no-load and load power input respectively to said motor, whereby an indication of the engagement of said tool with said workpiece is obtained.

Claim 7

In combination with a machine tool which includes a workpiece holder and a cutting tool, an electric motor for rotating the workpiece holder in relation to the cutting tool, and means for advancing the workpiece holder in relation to the cutting tool to bring a workpiece attached to the workpiece holder into engagement with the cutting tool for performing a machining operation on the workpiece, apparatus for providing an indication of engagement of the tool with the workpiece comprising means connected to a source of electrical energy for electrically energizing said motor, means coupled to the input circuit of said electric motor for sensing power flowing thereto and providing a first unidirectional signal corresponding to the power flowing to said motor, a pair of channels, each having an input circuit and an output circuit, means for applying said first unidirectional signal to the input circuits of said channels, one of said channels including an amplifier for developing a second unidirectional signal in response to said first unidirectional being applied thereto and being capable of providing said second unidirectional signal at the output thereof for a long period of time when said first predetermined input is no longer being applied thereto, means connected to the input circuit of said one channel for disconnecting the input circuit of said one channel a short time after the energization of said motor and before loading is applied thereto whereby said first signal is applied solely to the input circuit of said other channel, said other channel providing a third electrical signal at the output thereof in response to said first electrical signal, the amplitude of which varies with and corresponds to the loading of said motor, means connected to the output circuits of said channels for differentially combining the outputs of said channels and for deriving a fourth unidirectional signal the amplitude of which varies in accordance with the amplitude of the difference of said second and third electrical signals correspondiNg to the difference in said no-load and load power input respectively to said motor, whereby an indication of the engagement of said tool with said workpiece is obtained.

Claim 8

The combination of claim 5 in which said amplifier includes a capacitance of high internal impedance connected between the output and input circuits of said amplifier, and said amplifier also includes a high input impedance whereby said capacitance retains electrical charge over a long period of time and provides a constant unidirectional electrical output corresponding to no-load power input to said motor when said first signal is disconnected from said amplifier.

Claim 9

The combination of claim 5 in which said electric motor is an induction motor.