Abstract: A line printer having a hammerbank with hammers that are held by a permanent magnet and released by electrically driven coils. The temperature of the coils is determined by the relative resistance of the coils to provide an output equivalent to the temperature of said coils. The resistance is determined as a function of the current through the coils or voltage of the coils which is converted from an analog to a digital value. The attendant method of determining temperature of the coils in the hammerbank is by comparing a pre-established current or voltage value based upon a pre-established temperature of the coil with the current passing through the coil during operation of the hammerbank. The comparison of the current passing through the coil during operation with the pre-established current is provided to a controller for controlling the printer in response to the current differential between the currents which is in turn a function of the operating temperature.

Abstract: This disclosure sets forth a dot matrix printer having an improved ribbon drive. The ribbon drive is provided by two respective stepper motors. When one stepper motor is in a take-up mode, the second is in a feed mode. The process is reversed proximate the end of the tape as it is unwound. A re-generative mode for the feed motor is provided and a resistance bank varies amounts of drag on the ribbon as it is fed from the feed motor spool. Both motors when in the take-up mode are driven by full H bridge drivers and amplifiers controlled by a micro controller through an address and decode input and output latch. In order to provide for a uniform velocity of the print ribbon the angular velocity of the take up motor is controlled by counting the zero crossings of the feed motor, and then loading it into the micro controller to compare it with a look-up table for purposes of providing a proper speed to the take-up motor and the proper peak drag through the resistance bank to the feed motor.

Abstract: Each of a pair of spaced apart paper feed mechanisms within the paper feed system of a dot matrix line printer has opposite upper and lower portions thereof slightly angled relative to each other and disposed on opposite sides of and close to an elongated print station having a platen at one side thereof on which the paper feed mechanisms are mounted. Guides within the print station direct a length of paper introduced onto one portion of the paper feed mechanism through the print station and onto the other portion. Each paper feed mechanism is locked in a desired position on the platen using a manually operated lever arm arrangement having a mechanical advantage. Phasing or pitch adjustment between the opposite portions of each paper feed mechanism is accomplished by either of two arrangements which vary the position of a pulley engaging an endless belt between the opposite portions in combination with an opposite spring mounted pulley which bears against the inside of and tensions the endless belt.

Abstract: In a printer in which a shuttle is driven in reciprocating fashion by a rotating cam, a counterbalance assembly disposed on the opposite side of the cam from the shuttle and having a cam follower disposed along a common axis extending through the cam and a cam follower of the shuttle includes a mass in the form of a generally rectangular block mounting the cam follower at one of a pair of opposite ends thereof. Reciprocating movement of the block in response to rotation of the cam is provided by a pair of tapered flex pivots coupled to opposite ends of a base and extending upwardly and coupled to the opposite ends of the block. The end of the block opposite the cam follower receives a spring disposed against a reference surface to bias the cam follower against the cam.

Abstract: In a printer in which a plurality of hammers mounted along the length of an elongated hammerbank are selectively fired as the hammerbank is reciprocated relative to an elongated platen to impact a length of ink ribbon against at least one length of print paper supported by the platen to effect printing in dot matrix fashion, the platen being rotatable about an axis of rotation to vary the size of a platen gap between the plurality of hammers and the platen, a mechanism is provided for positively locking the platen in any one of a succession of different rotational positions to provide locking platen gap adjustment. The Positions are identified in order to facilitate resetting of the platen to a desired gap size. The mechanism includes a rotatable knurled thumbknob having mounted thereon a cam having a succession of eccentric or radially varying detents in an outer surface thereof which receives the end of a pivotally mounted, spring-biased lever.

Abstract: In a dot matrix line printer in which an elongated hammerbank and an opposite conunterbalancing assembly are driven in opposing reciprocating fashion by a motor driven cam, the size of the cam drive motor and the current requirements thereof during startup of the printer are greatly reduced by applying current pulses to the motor in a pattern synchronous with the resonant frequency of the reciprocating cam driven system. The current pulses which are considerably smaller in amplitude than the continuous current conventionally used to produce startup are generated during alternate half cycles of the resonant frequency, causing the cam to rock back and forth until eventually the peak resistance presented by opposite lobes on the cam and the consequent maximum compression of springs within the cam followers coupling the cam to the hammerbank and the counterbalancing assembly is overcome.

Abstract: In a color printer in which a shuttle assembly containing a plurality of impacting print hammers is reciprocated in bidirectional fashion relative to an opposing platen to impact a print paper against the platen through the different color zones of an ink ribbon to print in color, the different color zones of the ribbon are arranged in a repeating pattern along the length thereof enabling the lightest color to be printed first followed by successively darker colors as the ribbon is advanced bidirectionally between the opposite ends thereof. A pair of barrier zones having a blank ribbon zone therebetween are disposed between each adjacent pair of color zones on the ribbon to prevent ribbon contamination due to bleeding of ink between adjacent color zones when the ribbon is wound on a reel. Ribbon contamination is further prevented by the blank ribbon zones which absorb ink that rubs off onto the ribbon guides.

Abstract: In a printer in which a shuttle and a counterbalancing mass are driven in opposing reciprocating fashion by a rotating, generally oval-shaped cam, the cam followers which couple the shuttle and the counterbalancing mass to the cam are castered to prevent skewing of the cam followers relative to the cam. Each of the cam followers is disposed between and rotatably mounted on a pair of opposite arms extending outwardly from a generally planar base of a castered yoke assembly, the planar base being pivotally coupled to a supporting member therefor which is either coupled to the shuttle or forms a part of the counterbalancing mass. In a first embodiment the pair of opposite arms extend from the planar base toward the cam so as to dispose the cam follower between the pivotal mount of the yoke assembly and the cam.

Abstract: An arrangement for bidirectionally driving a hammer bank shuttle assembly along a linear path in a line printer includes an opposite pair of circular, rotatable elements having an elongated shuttle assembly mounting element and an elongated counterbalancing element extending between the pair of rotatable elements on the opposite sides thereof. Pole pieces and a magnet disposed between and adjacent the shuttle assembly mounting element and the counterbalancing element provide magnetic flux which flows through portions of the opposite elements to attract and maintain the elements in contact with the opposite rotatable elements.

Abstract: In a dot matrix line printer in which selected ones of a plurality of hammers mounted on a reciprocating hammer bank are released in response to successive sets of serial data to print dots on a paper, the changing hammer release characteristics which are caused by different numbers of hammers being released with each new set of serial data are compensated for by an arrangement providing a varying hammer release signal in accordance with the number of hammers being released. The variable release signal is provided in the form of a variation in the time interval during which the drive amplifiers associated with hammer release coils are turned on, thereby effectively varying the length of a current pulse provided to each coil in direct proportion to the number of hammers to be released. A counter is preset, then counted down from the preset value in accordance with the number of hammers to be released as represented by a set of serial data being provided to a shift register.

Abstract: In a print hammer mechanism in which an elongated, resilient hammer element mounted at a fixed end thereof has an opposite free end thereof selectively released from a retract position for impact of a dot imprinting element carried by the free end of the element, an improved magnetic circuit is provided for use in release and retraction of the hammer element. The improved magnetic circuit includes a pair of elongated pole pieces of like configuration having back ends thereof mounted on opposite sides of a rare earth magnet and tips at the opposite front ends thereof disposed adjacent the free end of the hammer element to form a pair of gaps therewith.

Abstract: A counterbalanced bidirectional drive for a hammer bank shuttle assembly within a line printer utilizes a band formed into an endless loop extending around and between an opposite pair of rotatable pulleys on opposite sides of the pulleys. A hammer bank-carrying shuttle assembly is coupled to a portion of the band between the pulleys on one side of the pulleys and is counterbalanced by an elongated bar of similar mass coupled to a portion of the band between the pulleys on the opposite side of the pulleys from the shuttle assembly. A DC motor coupled to one of the pulleys is alternately energized in opposite senses so as to bidirectionally drive the shuttle assembly along a linear path between opposite limits defined by resilient members impacted by an element mounted on the counterbalancing bar.

Abstract: A print hammer mechanism which forms a magnetic path between the opposite fixed and free ends of an elongated resilient hammer element using a permanent magnet, a first pole piece terminating in a pole tip adjacent the free end of the hammer element and electromagnetic means for cancelling the effects of the permanent magnet employs a second pole piece having a pole tip disposed adjacent the free end of the hammer element between the first pole piece and the fixed end of the hammer element. The relatively short magnetic path of low reluctance along the hammer element between the pole pieces combines with the effect of flux flowing in two gaps perpendicular to the flat surface of the hammer element to significantly improve the magnetic properties of the print hammer mechanism including the ability to quickly release and then retract the hammer element and the ability to increase the resonant frequency and/or the amount of energy stored in the hammer element for a given amount of magnetic flux available.

Abstract: A dot matrix printer system utilizes a reciprocating shuttle having a plurality of hammer elements and externally energized hammer controls mounted with the hammers on the shuttle. Each hammer scans a number of dot printing positions within a dot matrix line, and is energized at a high repetition rate during movement to imprint serially the dot patterns in that line for several successive characters. The paper is then advanced and the next dot matrix line is printed in the reverse direction. The shuttle mechanism forms a part of a dynamically balanced system, being in one example driven in a trapezoidal motion from a cam system that also engages an oppositely moving counterweight system. A highly reliable fast acting hammer bank comprises an array of individual spring hammer elements and associated magnetic actuators, the hammer elements normally being magnetically biased to a retract position by a permanent magnet.