US3572238A - Print-head drive - Google Patents

Abstract

A PRINT HEAD DRIVE FOR TRANSFORMING A CABLE OR BAND TRANSMISSION TO A STEP-BY-STEP MOTION. THE CABLE OR BAND TRANSMISSION IMPARTS AN OSCILLATORY MOTION TO A SLIDE ELEMENT ON WHICH A PRINT HEAD IS PIVOTALLY MOUNTED. THE

MOVEMENT OF THE PRINT HEAD IS LIMITED TO STEP-BY-STEP INCREMENTS BY RESTRAINING SPRINGS.

Description

March 23,1971 ANDEgggN 3,572,238

PRINT-HEAD DRIVE 7 Filed Nov. 12, 1968 INVENTOR.

ADOLF' ANDERSEN.

iwwz 1 GENT United States Patent U.S. Cl. 101-93 1 Claim ABSTRACT OF THE DISCLOSURE A print head drive for transforming a cable or band transmission to a step-by-step motion. The cable or band transmission imparts an oscillatory motion to a slide element on which a print head is pivotally mounted. The movement of the print head is limited to step-by-step increments by restraining springs.

The invention relates to a step-by-step drive of a print head, for example, print heads and drive means such as those shown in U.S. Pat. Nos. 3,236,351 and 3,292,530.

As a print-head advances step by step with the aid of a cable or band transmission (such as shown in the abovementioned patents) difficulty occurs in that the transmission elements (cable or band) are resilient due to their great length. When combined with the mass of the print head a low-frequency oscillatory system is produced. As a result there is no time-independent relation between the movement of the drive mechanism such as a band drum, and the movement of the print head, in other words, rotation of the drum and movement of the print head are not synchronized.

Desired synchronization (with allowable error) may be obtained by causing the fundamental frequency of the oscillatory system to be considerably higher than the step frequency of the print head.

Another problem encountered with the prior art devices (not related to the resilience of the transmission members) is the fact that of large mass inertia forces determined by the step-by-step motion requires high power output from the driving motor.

Reduction of the moving masses of the print head would result in a reduction of the required driving power and an increase in the fundamental frequency of the oscillatory system. The severity of the above-mentioned disadvantages would thereby be considerably reduced.

According to the invention the print-head drive is characterized in that the print-head (which is driven by a band or cable transmission such as known from the referred to patents) guided along the printing surface with the aid of a slide is pivotally connected to said slide by a shaft which is arranged at right angles to the plane in which the slide is guided and extends parallel to the end face of the print head. The print head is connected to the slide by means of springs which are active both in the direction of movement of the slide when the printhead is operating to print on the paper and in the direction opposite thereto.

In order that the invention may be readily carried into effect it will now be described in detail, by way of exam- 3,572,238 Patented Mar. 23, 1971 ple, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view showing an embodiment of the print-head drive elements according to the present invention; FIG. 2 is a diagrammatic representation of print-head displacement versus time; and FIG. 3 is a diagrammatic representation of slide displacement versus time.

The part of a mosaic type print head 3 which is closest to the paper 2 to be written on is driven by a steel cable 4 on a cable drum 1. The relief print head 3 is rotatable about a shaft 5 which extends parallel to the paper and is at right angles to the direction of movement. The shaft 5 is secured to a slide 6 which is arranged on a guide 7. The relief print head 3 is connected to the arm 9 of slide 6 not only by pivots 8 but also by springs 10. The point of fixation 11 of cable 4 and the centre of gravity of the print head 3 are determined. The distance between the pivot 8 and point of fixation 11 of cable 4 determines the magntiude of the maximum forces occurring. All this can be proportioned in such manner that a minimum of forces is achieved.

In the diagrams x represents the coordinate of displacement of the endface of the print head and x represents the coordinate of displacement of slide 6, while 1' indicates the time. These diagrams show that the print head performs a real step-by-step movement while on the other hand the slide performs an oscillatory movement which, however, has no influence on the picture being printed.

What is claimed is:

1. A step-by-step drive for a print-head in a printing device comprising a print-head for contact with the media to be printed, a cable attached to said print head for moving said print-head, means connected to said cable for same, a guide member arranged parallel to said cable, a slide movably mounted on said guide member for movement in a direction parallel to said cable, an arm attached to said slide, said print-head being pivotally attached to said arm, and a pair of springs, each of said springs attached at one end thereof to said arm and at the other end thereof to opposite sides of said print-head, whereby as said cable is driven said slide will be caused to move in oscillating motion and said print-head will be caused to move in step-by-step motion as a result of the interaction of the connecting elements between said print-head and said slide.

References Cited UNITED STATES PATENTS 2,911,085 11/1959 Leathers 197-1 3,135,195 6/1964 Potter 10193 3,167,166 1/1965 Schiebeler 197-1 3,236,351 2/1966 Fitch et al. 197-1 3,292,530 12/1966 Martin 101-93 3,300,017 1/1967 Yazejian et al. 1971 3,322,253 5/1967 Burns et al. 1971 WILLIAM B. PENN, Primary Examiner U.S. Cl. X.R. 197-1

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