Abstract:
A motion mechanism in a type printer, wherein the axial displacement of a type drum relative to a printing hammer for setting the required type in position opposite the hammer, and the axial movement of both hammer and type drum for obtaining a new printing position on the sheet, is effected by means of a cord system which consists of a single cord, a type of endless chain. The cord runs over pulleys arranged at each end of the line to be printed, such that the cord is divided into four cord parts extending substantially parallel to the line on the sheet, one cord part supporting the hammer, and one supporting the type drum. At one side, two pulleys are arranged in spaced relationship on a plate which is mounted pivotally about an axis lying intermediate the rotational axes for the two pulleys. Furthermore the cord co-operates with a driving motor operating on that part of the cord which leads to the hammer. Setting of the hammer to a new printing position on the sheet is then effected by displacing the whole cord in its length direcion by means of the driving motor, whereby the hammer and the type drum will move equal distances. Setting of the type drum to a posion with a new type opposite the hammer is made by pivoting the mounting plate for the pulleys, whereby the type drum only is moved, while the hammer is held fixed.
Description:
The invention relates to a device in a printer comprising a type drum with types arranged around the periphery. The drum is mounted in two ways rotatably, and; axially displaceable for setting required type opposite a hammer unit. The hammer which is pressed against the drum with an interposed printing sheet produces printing on the sheet displacement of the drum and the hammer unit for setting the hammer in desired printing position along the line on the sheet to be printed, and displacement of the drum relative to the hammer for the axial setting of the drum are achieved by means of a cord system comprising a first cord part supporting the hammer unit, and a second cord part supporting the drum and cooperating with pulleys and driving means, which cord parts extend along the line to be printed.
Known devices of this kind have a complicated cord system with separate cords for the type drum and the hammer unit, respectively. The cords for changing the printing position are driven in parallel, while for the axial displacement of the type drum only one of the cords is actuated.
The invention has for its object, in such a device, to produce a simplification of the cord system and a decrease of the required inertia of the movable parts, thereby enabling higher printing speed. The characteristic for the invention consists in that one end of the first cord part is, via a return cord, directly connected with the opposite end of the second cord part. This part in corresponding manner, is via a return cord directly connected with the opposite end of the first cord part. This forms a continuous cord system a type of endless chain, which supports both the hammer unit and the type drum. At one end of this system, the pulleys, where the respective cord part is continuous in the return cord, are arranged at a distance from each other on a mounting plate which is swingable about an axis extending substantially parallel to the rotational axes for the pulleys, and is situated half-way between the rotational axes for the pulleys. A change of printing position is produced by displacement of the whole cord system in the length direction of the cord which conforms both the hammer unit and the type drum to follow this motion, while axial displacement of the drum relative to the hammer, is produced by pivoting the mounting plate while locking the cord part which supports the hammer unit.
In a device according to the invention, the cord system consists of one single continuous cord, a type of endless chain, comprising only four cord parts extending parallel with the line to be printed, two of the cord parts serving to support the hammer unit and the type drum, respectively, and two return cords. Change of the printing position is produced simply by moving the cord in its length direction, whereby both the hammer unit and the drum will be forced to move an equal distance. Change of the position of the type drum relative to the hammer unit, is produced by influencing the mounting plate for the two pivotably mounted pulleys. These pulleys can be arranged relatively close to each other, and the mounting plate with pulleys will then have small dimensions resulting in a small inertia mass and short setting time. Suitable stepping motors can be used for both motions, which will give exactly adapted driving steps and automatic locking of the respective driving wheel during intervals between the stepping operation.
The invention is illustrated in the accompanying drawings, in which;
FIGS. 1 and 2 show two schematic views of the cord system in a device according to the invention, and
FIG. 3 shows a perspective view of a complete type printer provided with a device according to the invention.
The principle for driving the hammer unit and the type drum in a driving system according to the invention is evident from FIG. 1, in which the hammer unit is designated 10 and the type drum is designated 11. A printing sheet is schematically indicated at 12. The hammer unit is fastened to a first cord part 13 extending between a driving wheel 14 situated on one side of the printing sheet, and a pulley 15 situated at the opposite side of the printing sheet. From the pulley 15, the cord runs via a cord part 16, to a pulley 17 situated on the same side of the printing sheet as the driving wheel 14. From the last pulley 17, the cord continues via cord part 18, to a further pulley 19 situated at the opposite side of the printing sheet. This cord part 18 supports the type drum 11. From the pulley 19, the cord finally runs through a cord part 20 back to the driving wheel 14. The end portions of the cord are wound a number of turns upon the wheel 14 and frictionally engage to the wheel, whereby the cord will follow the wheel when it is rotated. The driving wheel 14 and the pulley 17 are mounted on fixed shafts, while the pulleys 15, 19 situated at the opposite side of the sheet are mounted on a mounting plate 21, which is pivotable about an axis "O." The axis O is located half-way between the rotational axes for the two pulleys 15, and 19. When the plate is swung about O, one of the pulleys will approach the printing position a distance equal to the distance the second pulley will move away from the position pivoting of the plate about O while clamping those cord parts which run to the driving wheel 14, will hereby be possible. The motion of the plate 21 is controlled by a driving wheel 22 cooperating with a toothed segment 23 situated at one side of the plate.
It is evident that, if the driving wheel 14 is rotated, the hammer unit 10 and the type drum 11 will be displaced equal distances. The hammer unit 10 determines the printing position and setting of the wheel 14 and changes the printing position on the printing sheet. Because rotation of the wheel 14 displaces the type drum an equal distance as that of the hammer unit, the mutual position between the hammer and the type drum will not be changed. On the contrary, if the wheel 14 is kept fixed, and the mounting plate 21 is pivoted about axis O, the hammer unit 10 will remain in its position because it is directly connected with the locked driving wheel 14, while the type drum 11 is displaced relative to the hammer unit. Pivoting the plate 21 is therefore made for setting the desired type column on the drum 11 opposite the hammer 10.
In FIG. 2, where corresponding parts have been provided with the same reference numerals as in FIG. 1, an alternative embodiment of the device according to FIG. 1 is shown. The device according to FIG. 2 is different from that of FIG. 1 only in a slightly different cord arrangement, and in the replacement of pulley 17 (FIG. 1) with two pulleys 24, 25. The arrangement according to FIG. 2 is better in achieving a desired mutual placing of the type drum and the hammer unit. The hammer unit in FIG. 2 is as in FIG. 1 arranged on a cord part leading directly to the drive wheel 14. This wheel determines the position of the hammer unit, and thereby controls the printing position, while the position of the drum relative to the hammer unit is determined by the setting angle of the mounting plate 21.
FIG. 3 shows a perspective view of a complete printer constructed in accordance with the principle shown in FIG. 2. In FIG. 3 the following parts can be recognized: the hammer unit 10, the type drum 11, the cord parts 13, 16, 18, and 20, the driving wheel 14 and the pulleys 24, and 25 and 15 and 19. Pulleys 15 and 19 are arranged on the pivotable mounting plate 21. The driving wheel 14 is arranged on the output shaft of a first stepping motor 30, and the driving wheel 22, which is in engagement with the toothed segment 23 on the mounting plate 21, is connected to the output shaft of a second stepping motor 31. The stepping motor 30 determines the position of the printing hammer, and thereby the printing position, while the stepping motor 31 determines the axial position of the type drum relative to the hammer. The type drum 11 is displaceably arranged on a shaft 32 to which it is angularly locked. The shaft 32 is coupled to a third stepping motor 33, which determines the angular setting of the drum about its rotational axis. By means of the stepping motors 31 and 33, the desired type is set opposite the printing hammer.
The motion of the hammer for effecting printing is derived from a continuously rotating motor 35, on the output shaft of which a cam disk 36 is fixedly mounted. The cam disk 36 cooperates with a cam follower roll 37 mounted on an actuation arm 39, which arm projects from an actuating bar 38.
The actuating bar 38 is pivotally mounted and provided with an actuating shoulder 40, which cooperates with the movably mounted hammer 41. Under the influence of the motor 35, the bar 38 is acted upon in such manner that the shoulder 40 moves back and forth in a direction (shown by the arrows) axial to the hammer unit. In a rest position of the hammer unit, the hammer 41 is free from the shoulder 40 and no printing is effected. When order for printing is obtained, a magnet 42 is excited which influences an armature 43. This armature is connected by a bar 44 to the hammer unit. Upon excitation of the magnet 42, the hammer unit is rotated in such manner that the hammer 41 comes into engagement with the shoulder 40 on the actuating bar 38. When the said shoulder next time moves in a direction to the hammer, this hammer will be pressed against the drum 11, and printing will be effected. Finally there is also a stepping motor 46 for driving the paper sheet 12, which is unwound from a storing roll 47.
In operation the stepping motor 30 is first stepped forward a step to the next printing position. Thereafter, or simultaneously therewith the required type is set in position opposite the hammer by suitable excitation of the stepping motors 31 and 33. After the setting order is accomplished, magnet 42 is excited, and in described manner causes printing to take place.