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Hammer Firing Circuit

IP.com Disclosure Number: IPCOM000073483D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 3 page(s) / 37K

Publishing Venue

IBM

Related People

Walewski, LG: AUTHOR

Abstract

In earlier hammer firing circuits for printers, it was necessary to provide large and costly regulated power supplies to keep the power applied to the hammer constant despite varying AC line voltages. A circuit for regulating the power supplied to a hammer operating circuit will enable the use of an unregulated supply with substantial cost savings.

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Hammer Firing Circuit

In earlier hammer firing circuits for printers, it was necessary to provide large and costly regulated power supplies to keep the power applied to the hammer constant despite varying AC line voltages. A circuit for regulating the power supplied to a hammer operating circuit will enable the use of an unregulated supply with substantial cost savings.

In the drawing, hammer driving circuits 1 are connected in parallel between two supply leads 4 and 5 and are each comprised of a solenoid coil 2 connected to supply lead 4 and the anode of an SCR 3 whose cathode is connected to the other supply lead 5. Coil 2 is shunted by a diode with its anode connected to the junction of coil 2 and SCR 3. The hammer to be operated is selected by applying a trigger pulse to the gate of SCR 3 of the desired circuit and then applying a supply voltage to the supply leads.

The power supplied to a coil 2 is passed through a transformer 6 having its secondary 7 connected to the supply leads 4 and 5 and a primary having two parts 8 and 9 in series. The transformer core has no air gap and must, therefore, be driven between magnetic states. Power to drive the core for energizing the hammer coil 2 is provided by an unregulated DC supply on leads 11 and 12 with lead 12 connected to the junction of primaries 8 and 9. The other end of each primary 8 and 9 is connected to line 12 through diodes 13 and 14 and SCR's 15 and 16, respectively. Each SCR 15 or 16 is shunted by an oppositely poled diode 17 or 18 and a series circuit of a saturable core coil 19 or 20 and a capacitor 21 or 22. Additionally, the junction of reactor 20 and capacitor s connected to lead 11 by a resistor 23 and a diode 24 in series to conduct current to lead 11.

In operation, reactor 20 may be considered as set, reactor 19 as reset and capacitors 21 and 22 are charged to the voltage of lead 1...