Typewriting machines – Including type-set-assemblage mounted on carrier and... – Imprint by movement of record-medium against type-face
Patent
1991-09-26
1994-05-17
Wiecking, David A.
Typewriting machines
Including type-set-assemblage mounted on carrier and...
Imprint by movement of record-medium against type-face
400124, 101 9329, B41J 900
Patent
active
053121953
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention concerns an electromagnetic drive mechanism for a printing pin of a dot matrix print head with an E-shaped magnetic frame whose center limb carries an electric field coil and with a longitudinal cutout blade that is wider than the outer limb and the center limb and is arranged on or near the outer limb of the magnetic frame in a swivelling manner with one end and whose other end protrudes over the other outer limb of the magnetic frame and acts upon the printing pin. Such a drive mechanism of this general type is disclosed in DE-AS 20 56 364.
BACKGROUND ART
Dot matrix print heads are used in electric printers and produce mosaic-like symbols that are compiled from printed dots produced by several printing pins. The quality of the symbols depends on the number of printing pins and/or on the frequency of their activation. The more printing pins are contained in a dot matrix print head, the better the ability of the printing dots to produce a symbol and the better the ability to read the same.
A dot matrix print head should contain the highest possible number of printing pins. In addition to this it should work at high speed and execute the movement of the printing pins with the highest possible impact, so that duplicates in the form of carbon copies can be produced during the printing process. These demands should also be fulfilled during long term use, which means that the dot matrix print head should have a high continuous output.
It has thus far not been possible to fulfill simultaneously the demands set for a dot matrix print head, which are high printing speeds, high impact and high continuous output. The main reason for this fact is the heat produced by the electromagnetic drive mechanisms for the printing pins, because one proceeded from the premise that a high activation frequency of a printing pin and a high impact force can only be obtained with strong energizing currents and/or a high number of ampere turns in large ferromagnetic circuits. A dot matrix print head constructed according to this principle has very high magnetic frame limbs with a large number of drive mechanisms in order to realize the large volume of iron and the large number of ampere turns. This fact was thus far predetermined by a circular arrangement of the drive mechanisms with printing pins that are arranged in the area of the center of the circle.
SUMMARY OF THE INVENTION
The objective of the invention is to create an electromagnetic drive mechanism for a printing pin of a dot matrix print head that fulfills the previously described demands in regard to printing speed, impact and continuous output while only necessitating a small structural space.
A drive mechanism of the initially mentioned kind for the solution of this objective is constructed in such a way that the cutout blade is wider than the magnetic frame limb over its entire length opposing the magnetic frame limbs while the average length of the iron path formed by the center limb and the outer limb is smaller than 30 mm. The inductivity of the magnetic circuit is less than 3 mH and the cutout blade has an effective magnetic cross section that is 10 to 50% smaller compared to the effective magnetic cross section of the outer limb.
The invention is based on the idea that even a small electromagnetic drive mechanism can transfer sufficiently high energy onto the printing pin, if a largely stable magnetic force is produced during the driving movement. It is known that an electromagnetic drive with a cutout blade has a hyperbolic, not a linear, magnetic force characteristic. If the cutout blade is at its largest distance from the magnetic frame and begins its driving movement from its resting position, the magnetic force produced is very small. However, it steadily increases according to the hyperbolic magnetic force characteristic as the distance from the cutout blade to the magnetic frame decreases. The invention makes it possible to produce a magnetic force already in the beginning phase of the movement of the cutout blade that app
REFERENCES:
patent: 4840501 (1989-06-01), Wong
Grandke Dieter
Hoffmann Heinrich
Prahl Detlef
Reinkemeier Ralf
Roeschlein Rolf
Kelley Steven S.
Siemens Nixdorf Informationssysteme AG
Wiecking David A.
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