Abstract: A constant energy drive circuit comprises two interconnected chopping circuits successively operable to control the current in a coil of an electromagnetic actuator. One chopping circuit operates during the rise time portion of the operating interval, the other operates beginning with the occurrence of a predetermined peak current and for remainder of the operating interval of fixed duration.

Abstract: A heat exchange system for an electromagnetically operated print hammer of a print hammer bank provides internal and external heat transfer for the operating windings. A non-magnetic metal bobbin of the heat exchange system provides conductive transfer of heat from the interior of the operating winding to the magnetic core. Flat parallel plates of magnetic material are attached to the sides of the operating winding for external heat transfer and magnetic flux shielding. The plates may have multiple laminations having different saturation and permeability characteristics.

Abstract: Bank for accommodating adjacent ram units, each of which consists of a flat, narrow frame. An electromagnetic actuator for a ram, which is guided in two bores of the frame, is positioned in a recess of the latter. For accommodating and guiding the individual ram units the bank has a substantially U-shaped cross-section. At least on one of its two ends, the frame of each ram unit is provided with a flexible pin arranged between two frame sections. The frames are detachably mounted between the U-sections of the bank. Both U-sections have recesses for positively and/or non-positively accommodating the front or rear frame part and the pin, respectively.

Abstract: A constant energy drive circuit for an electromagnetic print hammer has a chopping circuit including a comparator which cycles a switch connecting the energizing coil of the print hammer to an unregulated power supply. Changes in the drive voltage of the unregulated source are compensated for by altering the switching rate of the switch by adjusting the amplitude of a reference signal applied to the comparator. The reference signal adjustment is inverse to changes in the drive voltage.

Abstract: The continuous type belt is arranged round two rollers, one of which is driven. One straight section of the type belt contacts over its entire length the support designed as a platen.In order to avoid groove on the platen caused by the rotating type belt, and to achieve a distribution of other kinds of wear of the platen over its circumference, a gear motor causes the platen to rotate very slowly (approximately 1 revolution in 72 hours).The platen can also be rotated without a gear motor. For this purpose, the longitudinal axis of the platen is slightly inclined relative to the edge of the type belt. This inclination effects a small movement component in the direction of the platen circumference while the type belt slides along the lateral surface of the platen, said component causing a slow revolution of the platen.

Abstract: A hammer limit control for an on-the-fly line printer comprises a counter which counts compare signals from a compare circuit which detects coincidences of print data and type position data in synchronism with the motion of an endless type carrier. The counter maintains a running count of the number of compare signals for a control interval having a duration which is a function of the printing interval of a print line cycle. A hammer on storage device stores a plurality of compare counts registered by the counter at the end of each of a plurality of control intervals. An adder adds the running count registered in the counter to the total count stored in the storage means and stores the total sum in a hammer on register. When the total sum in the hammer on register equals a maximum number, a limit comparator generates a control signal which inhibits further comparisons by the compare circuit.

Abstract: An electromagnetic ram actuator, the electromagnet of which consists of two symmetrically designed magnetizable yoke halves. The facing pole ends of the yoke halves are in each case essentially semicircularly recessed, forming two aligned essentially circular operating gaps. Between the operating gaps a ram is arranged which is shiftable in the direction of their line of alignment and whose cross-section is adapted to the area of the operating gaps. The ram comprises two armature disks of magnetizable material and a spacer element arranged therebetween consisting of predominantly non-magnetizable material. One armature disk is associated with each operating gap. The armature disks are geometrically designed in such a manner that their volume is of the order of the operating gap volume. In the starting position of the ram the armature disks are positioned in front of the operating gaps of the electromagnet in its non-excited state.

Abstract: A magnet movable under the influence of magnetic edge forces is arranged between stationary magnets.The magnet is surrounded by a release coil in such a manner that the coil part contributing to the force active in the release direction is located in the space formed by the stationary magnets.

Abstract: A printer control system for a belt printer has an arrangement for checking print hammer operating circuits by comparing a real time actual parity of the circuits with a precalculated expected parity. Prior to printing, a microprocessor calculates expected parity bytes for each subscan for storage in a storage device along with the print position fire data used for selecting the operating circuits to be activated in the related subscans. An actual parity byte is generated on a real time basis by ODD/EVEN parity circuits associated with groups of operating circuits for comparison with a composite parity byte generated each subscan by the microprocessor. The composite parity byte is generated by combining the expected parity bytes from the storage device for several successive subscans. The composite parity byte is updated each subscan by a process of subtracting the initial expected parity byte and adding a new subscan expected parity byte.

Abstract: A method and apparatus for testing print elements of a printer, such as a belt printer, in which the print element operating circuits are energized at an energy level insufficient to cause printing but sufficient to generate feedback signals for checking operativeness by a microprocessor.

Abstract: A printer having an ink ribbon with a bidirectional ribbon drive in which a pair of stepper motors have their windings cross-coupled so that a drag current flows through one stepper motor to apply drag torque to the ribbon when the other stepper motor is operated for driving.

Abstract: A moving element is held without contacts in a relatively stable holding position, out of which it is released by the application of an external force. The relatively stable holding position is obtained by superimposing a potential field of magnet edges by a further potential field based on a mechanical bias of the moving element or a magnet in such a manner that the curve of the total potential has a trough corresponding to the holding position. By applying an external force, the moving element is moved to a peak position of the total potential curve, whence it is subject to accelerating forces. Preferably rare earth magnets are used to form the potential field of magnet edges. In a print hammer actuator the moving element includes a moving coil.

Abstract: Printing apparatus, in particular for performing multi-color printing operations, has a ribbon shift mechanism for selectively interposing different transversely spaced portions of a print ribbon between a print head and platen. The print head is of the impact type and probably, although not necessarily, of the type which moves along the platen to define a print row. When color printing is required, a ribbon having a plurality of longitudinally extending stripes of different colors transversely spaced across its width is used. Selection of required portions or colors of the ribbon is performed by moving the head to pre-selected positions along the print row to engage, for example, a camming mechanism (including a cam and follower) which moves the shift mechanism the required amount to make the selection. Selection of the ribbon portion or color is by program control and in the case of color printing, the range of colors is increased by superimposed printing of the available colors on the print ribbon.

Abstract: An all-points addressable dot printer has rows of sloped parallel anvils on a rotating drum. Alternate rows slope in opposite directions for bi-directional printing with a single row of hammer blades. The blades which are spaced apart, are shifted bi-directionally in synchronism with the scanning motion of the anvils to print dots at all dot line points. A second embodiment has a reciprocating comb bar located between the blades and a print medium. Spring fingers on the comb bar have dot forming protrusions. The spring fingers are uniformly spaced with center spacing equal to the center distances between the blades. Comb bar motion is linear with time along the line segments. Blade motion is simple harmonic.

Abstract: A control system for the carriage drive of a line printer includes a microprocessor which controls a carriage drive stepper motor through programmable timers and interface adapter along with other non-print units of a printer mechanism. A control counter in the carriage drive responsive to feedback pulses from the stepper motor coacts with the timers to control various operation of the stepper motor during line feeding of a print medium and is used by the microprocessor for preventing loss of control of the carriage drive due to interrupts from other devices.

Abstract: A printer system comprising a belt printer mechanism controlled by a stored program digital microprocessor to print lines of data on a print medium. Selective operation of a linear array of print hammers, paper feeding, data conversion and arranging in scan/subscan order are performed by the microprocessor. The fire data for operating hammers is precalculated and arranged in scan/subscan order during the print medium feeding interval with printing occurring immediately at the first print scan after print medium motion in which one or more desired characters become aligned with print hammers. An indirect addressing technique which eliminates sorting is used to arrange the print position fire data in scan/subscan order.

Abstract: A belt printer control system for attachment to a host system has a first microprocessor connected by a dedicated bus to the host system and control elements operable to perform carriage control, belt drive, and ribbon drive operations of the printer mechanism. A second microprocessor is connected by a dedicated bus structure to controls for operating the print hammers. A common RAM is accessed by the two microprocessors through a common bus structure. The first microprocessor passes control and print information to the RAM for use by the second microprocessor in building print algorithm tables in the RAM for use by the second microprocessor to operate the print hammers. Communication between the microprocessors is done through control information stored by the microprocessors in the common RAM. Storing printing information and building of tables and controlling printing and nonprinting operations of the print mechanism are done concurrently.

Abstract: An electro-magnetic print hammer comprises a single magnetic hammer element in which an impact mass is coupled to a pivotted armature by flexible stem. The hammer-stem has (N+1/2) periods of oscillation at its resonant frequency during the free flight time of the hammer mass. A permanent magnet with a strong magnetic force which decays rapidly with distance holds the hammer element fixed upon motion of the armature until the armature torque exceeds the magnet holding force to cause the hammer mass to break loose with a snap action. Stop means prevents armature impacts with the operating pole piece of a stator core. The visco-elasticity of the armature stop matches the rebound characteristics of the print medium when impacted by the hammer mass.

Abstract: From the variables print hammer magnet voltage, print hammer magnet temperature, impact force, and a value derivable from the actual print time, a control voltage, which correspondingly delays an early trigger pulse by means of a variable delay element, is determined in an "open" control loop. The variables are analogously combined by adding, subtracting, and multiplying the analogue values, and by subsequently forming a weighted sum.

Abstract: A pulse width modulated DC motor control system is designed to operate a DC motor at constant velocity. Feedback pulses generated at a rate proportional to the rotational velocity of the motor are converted to control pulses having a fixed on-time period which is independent of changes in the velocity of the motor. The control pulses are used to modulate a constant current source whose output is integrated to generate a sawtooth voltage signal whose average DC value is used as the basis of or pulse width modulating a DC voltage applied to the motor drive circuits of a DC motor.