Browse Prior Art Database

Printer Hammer Coil Firing Control

IP.com Disclosure Number: IPCOM000049381D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Bohg, A: AUTHOR [+2]

Abstract

The firing of the hammer coils of belt printers can be controlled by a microprocessor defining the start of the firing pulse. The total hammer on-time, i.e., the length of the firing pulse, defines the hammer flight time and thus the moment of hammer impact. The flight time, however, depends on parameters, such as hammer coil supply voltage and temperature.

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Printer Hammer Coil Firing Control

The firing of the hammer coils of belt printers can be controlled by a microprocessor defining the start of the firing pulse. The total hammer on-time,
i.e., the length of the firing pulse, defines the hammer flight time and thus the moment of hammer impact. The flight time, however, depends on parameters, such as hammer coil supply voltage and temperature.

The arrangement of Fig. 1 measures these two parameters by measuring the time between the leading edge of hammer firing pulse H(on) (Fig. 2) and the time at which current I(HC) through hammer coil HC reaches a predefined level. This time is referred to as current rise time T(CR) in Fig. 2 and entered into the microprocessor of the printer to define the trailing edge of the hammer-firing pulse. According to Fig. 1, firing pulse H(on) from microprocessor uP is applied to transistor T1 by driver 1 and AND gate 2. T1, when on, switches on transistor T2, and hammer coil current I(HC) starts flowing through hammer coil HC. When this current reaches the predefined level I(H) (Fig. 2), the voltage drop across measuring resistor R1 exceeds the value of part of reference voltage U(REF) obtained from resistor divider R2-R3 and applied to the inverting input of comparator 3. As a result, the potential at node A goes up, closing AND gate 2. T1 and T2 are switched off, and the current through the hammer coil decreases to a value I(L) defined by the hysteresis characteristics determined by...