Abstract: The invention relates to a method in printheads (1) with a plurality of print elements (4) arranged movable in relation to each other and a moving mechanism (7, 9, 11, 12, 14) with magnetic field-responsive forces for moving selectable print elements to print or inactive positions. With utilization of the method the forces with which selected print elements are moved in appropriate cases to their print positions can be changed in coordination for a plurality of print elements. In accordance with the invention this is achieved by a magnetic field change coordinated for several print elements. The invention also relates to a printhead (1) with a plurality of first electromagnet means (9, L1 L24) for moving selectable print elements (4) and also a second electromagnet means (LB) common to a plurality of print elements, for coordinated change of the forces for a plurality of print elements with which the print elements can be moved to their print positions.

Abstract: In an arrangement for feeding carbon ribbons and the like a dog (3) is arranged inside a feed reel (1) for the carbon ribbon (2) of a typewriter. The dog (3) has the form of a cylinder with two projecting flanges (4,5) extending in two slots (11,12) of the feed reel. The lower part of the dog has a slot (9) in which the drive shaft pin (7) of the typewriter engages. Power transmission thus takes place from the drive shaft (8) via the dog (3) to the feed reel (1).

Abstract: A method of measuring of backlash arising in a drive mechanism comprising a screw and a nut device co-operating with the screw, the nut device being connected to a movable unit which is displaceable in opposite directions along the screw. The drive mechanism comprises a pulse generating system of which the number of pulses emitted for each displacement corresponds to the distance traveled in accordance with the method the movable unit is operated to move away from an end position adjacent one end of the screw, and when a predetermined position has been reached the pulse counter is reset while the movement continues. The movement is maintained a distance beyond the position in which the pulse counter was reset, the distance being greater than the possible maximum backlash. The drive mechanism is then stopped and operated to move the movable unit back to the end position, during which movement the pulse counter is counting backwards.

Abstract: In a printing device for printers or typewriters a hammer (11) is axially movable between a print position and a rest position. At one end the hammer has an impact surface (12) which acts upon a selected one of a number of type characters disposed along the periphery of a type disc. Preferably at its front end the hammer (11) is connected to a long guide pin (26) which extends mainly perpendicular to the length direction of the hammer and cooperates with a guide slot (27) that extends in the length direction of the hammer. The guide slot is situated at a distance from the hammer which is considerably greater than the diameter of the hammer in its connection point with the guide pin (26). Preferably, the distance is at least four times the diameter.

Abstract: A paper alignment device for a printer, typewriter or like office machine comprising a friction drive for advancing a sheet of paper in opposite directions past a printing head wherein an alignment mechanism is adapted to co-act with the friction drive to align the sheet of paper from the time when it is about to be released from the friction drive until it has been released and also for generating a force to return the sheet to renewed engagement with the friction drive when the latter has been stopped in preparation for drive of the sheet in the opposite direction.

Abstract: A print hammer for printers and typewriters comprises a hammer rod (11) which is axially movable in a housing (17, 18). The hammer rod is biassed towards a rest position by a spring and can be moved to a print position by a drive means, for example a solenoid coil (19). The hammer rod delimits a room (31) in the housing the size of which increases during the movement of the hammer rod towards the print position. The room (31) is connected to the surrounding atmosphere via a narrow channel (33) and also via a valve means (25, 28) which is open during the movement to the print position but closed during the return movement to the rest position. The valve means (25, 28) also forms a stop member for the hammer rod (11) in the rest position.

Abstract: Printing apparatus for electric office machines a print unit having a motor (14) and a disk-shaped type element (17) connectable with the motor shaft (16). The print unit is pivotably mounted for movement between a printing position, in which the type element is fixed for movement with the motor shaft, and an upwardly pivoted position in which the type element is disengaged from the motor shaft to allow replacement. A locking system permits upward pivoting of the print unit only when the type element has assumed a predetermined angle. The locking system comprises a lock collar (23) rigidly connected to the motor shaft (16) and having an end wall in which there are at least two axially directed recesses (24), or alternatively having at least two axially directed pins, the recesses or pins coacting with complementary parts (39) arranged on a disengagement systems (33, 34, 36, 37), axially displaceable during the pivoting movement.

Abstract: A drive mechanism comprising a power driven screw (16) and a nut means (17) co-operating with the screw includes a device for the correction of backlash prevailing between the screw and the nut means. The correction takes place electronically by modification of two pulse trains (A, B) which are generated by a pulse generator (19) which is synchronized with the movement of the screw. From the two pulse trains information as to position and direction of movement is derived for a movable unit (11), which is connected to the nut means and which, for instance, can be a printing unit in a printer or a typewriter. A measured or estimated value of the backlash is digitally stored with a resolution of one quarter of the period of the pulse trains. This resolution is four times the smallest distance through which the movable unit can be moved.

Abstract: A feed mechanism for sheets of material or continuous webs in a printer or typewriter, comprising a pin wheel feed mechanism for the feeding of continuous webs and a friction feed mechanism for the feeding of sheets of paper as well as the webs. The pin wheel feed mechanism and the friction feed mechanism are coupled together in at least two separate units for the feeding of the webs. During feeding of the webs the frictional feed pressure is reduced compared to that prevailing during friction feed of the sheets when the pin wheel feed mechanism is inactive.

Abstract: A character generator for generating characters which are transferred to a recording medium by a dot-matrix print head. In the character generator there is stored for each character the information required for the activation of the printing needles of the print head. The information comprises two parts, one of which contains a length description, i.a. indicating the total length of the character, and an address to the memory area in which the second part of the information is stored, the said second part constituting the graphic representation of the character. The first part of the information for all characters comprises four bytes while the second part of the information occupies a memory area adapted to the length of the character.

Abstract: A drive means comprising a movable part and a fixed part provided with a stator winding and a magnet yoke with a magnetic gap. A soft-iron magnetic portion is arranged in the magnetic gap. A current generator generates a first current for a stator winding and a second current for another stator winding, the sum of the magnitudes of the two currents being constant. The reluctance effect causes each of two soft-iron magnetic portions to be pulled into an individual magnetic gap driven by one of the two currents. The two reluctance forces vary quadraticly with the two currents, but due to the fact that the net force is the difference between them, this net force will be linearly dependent on the currents. It is suitable to allow the two currents to come from the same amplifier stage, which is push-pull coupled.

Abstract: A printing office machine in which a movable print head is driven by a device comprising a fixed, mounted lead screw and a cooperating nut member connected to an electric motor. The nut member is rotatably mounted in a carrier frame and comprises an inner tubular member which is journalled on the lead screw. An outer tubular member is journalled on the inner tubular member. An end part of the outer tubular member bears against a flange on the inner tubular member under friction. The two members are turnably interconnected by spring means, and the free ends of the members support rotatable bearings which bear on flanks of grooves cut in the lead screw. Each bearing cooperates with the groove flank which faces the respective end of the tubular member. The drive device has a very great freedom from play, and at the same time the friction prevailing between the nut member and the lead screw is minimized.

Abstract: The invention relates to a printing unit in an electric office printing machine, and more exactly the invention has for its object to provide an arrangement which makes it possible with a minimum of manual operations to change print elements of circular disc type. This is achieved by moving the printing unit away from the carriage at the same time as the print element by the action of a special coupling is detached from the motor shaft on which the print element is supported, this being possible only when the attachment device for the print element is in such a position that it can receive a new print element.

Abstract: A stepping motor having at least one stator with circularly disposed and equally interspaced poles. A rotor is provided which coacts with the stator and is rigidly connected to a rotatable shaft. The rotor has a number of teeth which corresponds to the number of stator poles, however the pole faces of the rotor teeth are of a different form and size than the pole faces of the stator poles whereby the torque generating intersecting line between the pole faces of the stator poles and the rotor teeth is lengthened when the rotor moves in over a stator pole and shortened when the rotor teeth leaves the stator pole.

Abstract: A device for marking an information carrying medium has an arm with a pointed tip adapted to engage the medium. The arm is spring biased for movement in one direction, and a solenoid structure is provided for moving the arm in the other direction. A land surface cooperates with the arm to form an air pressure damping arrangement to damp movements of the arm in a direction away from the information carrying medium.

Abstract: A device for producing imprints on a recording medium having a member acting on the medium which strikes or presss against a surface of the medium in its forward position. The member is in the form of an elongated arm being resiliently connected to a frame or other support. The arm is also provided with means to prevent ink from adhering to the member as a result of the latter striking the printing ribbon and the ink moving between the arm and the impact surface when said arm is in its rear position.

Abstract: A high speed printing device having a printing head provided with printing needles. The printing device is mounted on a movable carriage which is adapted to move adjacent to a recording medium. The printing head is pneumatically operated and also is movable relative to the carriage so that the distance between the printing needles and the recording medium is variable.

Abstract: A method of reproducing characters or symbols in place of orthodox typing or printing comprises applying ink to successive points on the paper or other surface by means of a transducer forming a typehead, and building up each character by steering the transducer under the control of digitally stored information which may be selected from the store by a keyboard. The characters can be built up as a series of overlapping dots and each character may have a number of key points, the transducer moving along one of a limited number of pre-set paths from each key point to the next.

Abstract: A protective dust cover for the needles of a mosaic printing head which eliminates the need for precision matching of segments that fit together to form holes for accepting printing needles passing therethrough. There is no precise arrangement of the parts of a dust cover to furnish an effective printing needle dust cover.