Self-timing and self-compensating print wire actuator driver

Claim 3

The method of claim 1 including the additional step of inhibiting switching of the second switchable device until the first switchable device has been switched.

Claim 4

A drive circuit for controlling current flow from a source of potential through an actuator coil, said circuit including: a first current path from said source through said actuator coil; a low potential return path; a first device switchable between conducting and nonconducting modes for enabling the first current path; a second device switchable between conducting and nonconducting modes for connecting said actuator coil to the low potential return path; sensing means operable while the second device is in its conducting mode for sensing current level through the actuator coil; first means responsive to the sensing means for switching the first device to its nonconducting mode when the current level is substantially equal to a first predetermined level; second means responsive to the sensing means for switching the second device to its nonconducting mode when the current level is less than a second, lower predetermined level; and a return conduction path from the actuator coil to the source of potential.

Claim 5

A drive circuit for controlling current flow from a source of potential through an actuator coil, said circuit including: a first current path from said source through said actuator coil; a low potential return path; a first device switchable between conducting and nonconducting modes for enabling the first current path; a second device switchable between conducting and nonconducting modes for connecting said actuator coil to the low potential return path; sensing means operable while the second device is in its conducting mode for sensing current level through the actuator coil; first means responsive to the sensing means for switching the first device to its nonconducting mode when the current level is substantially equal to a first predetermined level; second means responsive to the sensing means for switching the second device to its nonconducting mode when the current level is less than a second, lower predetermined level; and a return conduction path from the actuator coil to the source of potential.

Claim 6

The circuit of claim 3 additionally comprising means for preventing the second switch means from being operable prior to the first switching means completing its operation.

Claim 7

The circuit of claims 3 or 4 wherein said first and second devices switchable to conducting or nonconducting modes are transistors.

Claim 8

The circuit of claim 4 wherein said first and second switch means comprise latching means operable in response to an input trigger signal.

Claim 9

The circuit of claims 3, 4 or 6 wherein the actuator coil actuates a print wire in a wire matrix printer.

Claim 10

Circuit apparatus for driving an actuator coil connected in series between two switches at their ends, the first switch being connected also to a source of positive potential; and the second switch being connected also to a source of negative potential with respect to the source of positive potential; a latch means associated with each switch, responsive to an input trigger pulse for latching its associated switch into its conducting state; means responsive to the current level at the second switch for resetting the latch associated with the first switch when the current level reaches a first predetermined value; and second means responsive to the current level at said second switch for resetting the latch associated with the second switch when the current level reaches a second, lower predetermined value and the first latch has been reset.

Claim 11

Circuit apparatus for driving an actuator coil connected in series between two switches at their ends, the first switch being connected also to a source of positive potential; and the second switch being connected also to a source of negative potential with respect to the source of positive potential; a latch means associated with each switch, responsive to an input trigger pulse for latching its associated switch into its conducting state; means responsive to the current level at the second switch for resetting the latch associated with the first switch when the current level reaches a first predetermined value; and second means responsive to the current level at said second switch for resetting the latch associated with the second switch when the current level reaches a second, lower predetermined value and the first latch has been reset.

Claim 12

The circuit apparatus of claim 8 wherein the first and second switches are transistors.

Claim 13

Apparatus for driving a print wire actuator in a wire matrix printer comprising: a power supply means; a first switch connected between the power supply and the actuator; a second switch connected between the actuator and ground; means for inducing current flow from said power supply through the actuator, for monitoring current through the second switch; means responsive to the current level in the second switch for turning off the first switch; and means responsive to the current level in the second switch for turning off the second switch only after the first switch is turned off.

Claim 14

Apparatus for driving a print wire actuator in a wire matrix printer comprising: a power supply means; a first switch connected between the power supply and the actuator; a second switch connected between the actuator and ground; means for inducing current flow from said power supply through the actuator, for monitoring current through the second switch; means responsive to the current level in the second switch for turning off the first switch; and means responsive to the current level in the second switch for turning off the second switch only after the first switch is turned off.