Typewriting machines – Including adjustment for optimum printing plane – Responsive to thickness of record-medium
Patent
1999-01-11
2000-05-09
Bennett, Christopher A.
Typewriting machines
Including adjustment for optimum printing plane
Responsive to thickness of record-medium
40012016, 347197, B41J 1120
Patent
active
060594683
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention comprises a printing mechanism with a print head, especially for incorporation into machines which are suitable for applying printed images to objects of different dimensions.
2. Description of the Related Art
Printing mechanisms which produce an imprint on an object by means of a stamper have been known for a long time. Printing mechanisms of this type served especially to produce postage stamps on envelopes, postcards, and similar postal items. As printing technology advanced, and especially with the arrival of thermal transfer printing technology, the demand increased for transferring the advantages of this so-called thermal printing process to the printing of postage stamps.
SUMMARY OF THE INVENTION
The task was therefore to design a printing mechanism with a print head, e.g., a thermal print head, which contacts the surface of the object to be printed, which mechanism can either be retrofitted into machines already on hand with, for example, an ink pad printing mechanism, or used in the design of a completely new machine equipped with a printer. In the latter case, it is conceivable that it will be possible for certain parts of the printing mechanism, e.g., the printing mechanism housing, to be integrated into the machine (e.g., a postage machine) which holds the printing mechanism. It is also to be understood as a condition of this task, of course, that the new printing mechanism will be able to print on objects of different geometric dimensions, which is to say, letters of different thicknesses, with equal or better results than those obtained with the previously known printing mechanisms based on the known printing technology.
This task is accomplished by the print head which produces the imprint being mounted in such a way on a lever that, when in the printing position, it acts with a constant applied force on an object situated between it and a counterpressure roll, regardless of the distance which separates it from the counterpressure roller, which is also supported by a lever, and by the printing mechanism having a main shaft, on which two cams are mounted, each of which acts positively on a lever. A postage machine which contains the printing mechanism designed in accordance with the invention is also a component of the invention.
The print head and the counterpressure roll are each mounted on levers which are free to pivot and each of which has its own force-exerting element. The two levers have a common center of rotation. The lever carrying the counterpressure roll is connected to another lever by way of the force-exerting element, which can be designed e.g. as a spring. The additional lever is pulled by the other force-exerting element, which can also be designed e.g. as a spring, against a stop on the lever carrying the counterpressure roll, this stop thus acting to limit the counterpressure. A stationary roll, with respect to the printing mechanism housing, serves as a fixed stop for the object and/or limits the distance over which the counterpressure roll can pivot. A transport motor is positively connected by way of force-transmitting means to the counterpressure roll. It has means for detecting the rotational angle of at least one of the rolls and/or the instantaneous position of the object to be printed in the area of the print head. A control unit is present which, at beginning of the printing process, turns the main shaft by a part of a complete revolution, preferably by about 120.degree.. The transport motor is then turned on, and a position sensor in the form of, for example, a photo cell, allows the main shaft to rotate again after the sensor has detected the object to be printed.
The invention offers the advantage that, with little technical effort and in an extremely reliable way, the print head can be set down on objects of different thicknesses (ranging from nearly 0 to, for example, several centimeters or more) and the imprint transferred by means of the transfer ribbon under an applied pressure
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Patent Abstracts of Japan, vol. 012, No. 448 (M-768), Nov. 24, 1988 & JP 63 178056 A (Matsushita Electric Ind Co Ltd), Jul. 22, 1988.
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Patent Abstracts of Japan, vol. 014, No. 140 (M-0950), Mar. 16, 1990 & JP 02 006169 A (NEC Data Terminal Ltd), Jan. 10, 1990.
Bennett Christopher A.
Kueffner Friedrich
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