1. Field of the Invention
The subject invention relates to thermal recording with thermal recording heads including a plurality of clocked heating elements and, more specifically, to a density control for records so produced.
2. Information Disclosure Statement
The following disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necssarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments which may be subsequent in time or priority.
Also, no preamble of any statement of invention or claim hereof is intended to represent that the content of that preamble is prior art, particularly where one or more recitations in a preamble serve the purpose of providing antecedents for the remainder of a statement of invention or claim.
Efforts to provide operable and efficient recorders with thermal printheads have been of long standing and were to no small part prompted by inadequacies of moving coil galvanometer-type recording apparatus, which have inherent limitations despite various improvements, including those disclosed in U.S. Pat. No. 4,134,062, by Pizzuti et al, issued Jan. 9, 1979 to Atlan-Tol Industries, Inc., for a limited rotation instrument rebalance apparatus employing a wiper having vibration damping, and U.S. Pat. No. 4,211,92, by D. M. Gaskill, Jr., issued July 8, 1980 to Atlan-Tol Industries, Inc., for positioning means for a limited rotation motor.
For an example of a moving coil thermal recorder, reference may be had to U.S. Pat. No. 3,689,937, by Phillips et al, issued Sept. 5, 1972 to Evershed & Vignoles Limited, for thermal recording styli and control circuits therefor.
The development of thermal recorders also has benefited from the development of transverse recorders as disclosed, for instance, in U.S. Pat. No. 3,774,226, by Ballinger et al, issued Nov. 20, 1973 to Honeywell Inc., and disclosing a plurality of recording elements arranged across the recording medium to define a transverse recording line.
Thermal recording media also developed into different forms as may, for instance, be seen from U.S. Pat. No. 3,792,481, by Nagashima et al, issued Feb. 12, 1974 to Canon K.K., for recording by heat sensitive multicolor indication, disclosing suitable heat sensitive materials.
An array of heat producing elements is disclosed in U.S. Pat. No. 3,815,144, by H. H. Aiken, issued June 4, 1974, for Thermal Recorder Having an Analogue to Digital Converter. In this respect, an analog-to-digital converter for a magnetic transverse recorder was disclosed in the above mentioned Ballinger et al U.S. Pat. No. 3,774,226.
A computer controlled chart advance is disclosed in U.S. Pat. No. 3,840,878, by Houston et al, issued Oct. 8, 1974 to Texas Instruments Incorporated, for a dual mode thermal recorder. An event marker for graphic recorders has been disclosed in U.S. Pat. No. 3,877,035, by Miller et al, issued Apr. 8, 1975 to Leeds & Northrup Company, and showing also a print element suspension. Another print element suspension is shown in U.S. Pat. No. 3,980,169, by Decker et al, issued Sept. 14, 1976 to Triumph Werke Nurnberg A.G., for an impact control for a single element printer.
A chart recorder using a fixed thermal printhead is disclosed in U.S. Pat. No. 3,971,041, by C. F. Mason, issued July 20, 1976 to Esterline Corporation, and disclosing a marginal array of heat generating dots in addition to a single row of heat generating dots along the printhead. A recording control or chart lock is disclosed in U.S. Pat. No. 4,038,664, by A. R. Muir, issued July 26, 1977 to The Perkin-Elmer Corporation. A sequential value multi-point recording device with unidirectional scan is disclosed in U.S. Pat. No. 4,074,273, by Dupree et al, issued Feb. 14, 1978 to The Dow Chemical Company.
Even after the development of thermal printheads, resort still was had to the use of mechanical recording stylii as may, for instance, be seen from U.S. Pat. No. 4,085,407, by Stratbucker et al, issued Apr. 18, 1978 to Health Technology Laboratories, Inc., and U.S. Pat. No. 4,096,484, by Ferre et al, issued June 20, 1978 to Edo Western Corporation, for a graphic recording system including a plurality of memories for storing information received over different channels for recording with different recording devices.
The recording apparatus disclosed in U.S. Pat. No. 4,119,974, by Ondis et al, issued Oct. 10, 1978 to Atlan-Tol Industries, Inc., employed both a thermal recording head and a thermal recording stylus.
A real breakthrough is apparent from U.S. Pat. No. 4,145,698, by R. D. Wysong, issued Mar. 20, 1979 to Shakespeare Marine Electronics, Inc., and subsequently assigned to Holly Springs of Florida Incorporated, and by them to the common assignee of the entire interest hereof. In particular, that Wysong patent shows a thermal printhead biasing arrangement using, in its own words, a helical compression spring for biasing at least one thermal printhead into tangential contact with the thermal printing paper. That Wysong patent also discloses an arrangement of two thermal printheads in substantially aligned, substantially abutting end-to-end relation with each other so that the longitudinal dimensions of these printheads are in substantially transverse relation to the chart at the printing station and so that the printheads engage that chart on the opposite side thereof from the chart advancing means. That Wysong patent also discloses mounting means independently mounting the first and second printheads so that they are independently movable toward the chart. The helical compression springs are also arranged in this Wysong patent for independently biasing the first and second printheads towards the chart. Independent biasing of several thermal printheads with helical compression springs has also been disclosed in U.S. Pat. No. 4,151,397, by Boor, Jr. et al, issued Apr. 24, 1979 to E-Systems, Inc.
A thermal recording stylus usable in the above mentioned Ondis et al U.S. Pat. No. 4,119,974 was subsequently disclosed in U.S. Pat. No. 4,168,505, by Gaskill, Jr. et al, issued Sept. 18, 1979 to Atlan-Tol Industries, Inc.
Microprocessor-controlled multiple-head thermal recorders have been disclosed by Markson et al, in an illustrated article entitled Thermal Printer with In-Memory Scan-Line Composition in the IBM Technical Disclosure Bulletin, Vol. 22, No. 5 (October 1979), p. 2022, and in U.S. Pat. No. 4,205,395, by E. J. Shortridge, issued May 27, 1980 to Shakespeare Marine Electronics, Inc.
U.S. Pat. No. 4,262,336, by E. K. Pritchard, issued Apr. 14, 1981 for a Multi-Axis Contouring Control System in which a host computer and multi-processor system is shared with a master controller, and a slave controller controlled by part of the master controller.
A thermal line printer with a plurality of printheads has also been disclosed in U.S. Pat. No. 4,332,193, by B. P. Noyes, issued June 1, 1982. A thermal recording head and a drive therefor have been disclosed in U.S. Pat. No. 4,369,452, by Anno et al, issued Jan. 18, 1983 to Tokyo Shibaura Denki K.K.
U.S. Pat. No. 4,393,386, by P. C. Di Giulio, issued July 12, 1983 to Pitney Bowes, Inc., for Ink Jet Printing Apparatus also discloses application of the above mentioned host computer, multi-processor, master and slave controller system to printing apparatus.
U.S. Pat. No. 4,425,571, by Mueller et al, issued Jan. 10, 1984 and U.S. Pat. No. 4,426,651, by Muellner et al, issued Jan. 17, 1984, both to The Perkin-Elmer Corporation, also show control of the chart advance from a microprocessor. A data synchronization system for graphic recording apparatus has been disclosed in U.S. Pat. No. 4,442,442, by G. B. O'Dell, issued Apr. 10, 1984 to Tektronix, Inc.
U.S. Pat. No. 4,447,819, by Moriguchi et al, issued May 8, 1984 to Fuji Xerox Co., Ltd., discloses thermal recording apparatus including a control for determining a number of blocks to be simultaneously driven to perform recording without exceeding the capacity of the power source.
U.S Pat. No. 4,455,578, by W. T. Fearnside, issued June 19, 1984 to Eastman Kodak Company, for Electronics for Arrayed Photosources discloses controlled circuitry in which each sub-array of LED recording devices was controlled by its own control assembly governed by a sequence controller with the aid of clock generator circuits. That patent also discloses replacement of a prior-art print enable signal by binary weighted pulses derived from clock generator circuits, which also supply a shift frequency pulse train instead of the prior-art weighted frequency clock. This could easily be implemented as a master/slave control arrangement of the type employed for millions of years. In particular, it became known some time ago that the so-called "second brain" of the kind of dinosaur called "Stegosaurus" actually was an enlargement of the spinal chord in the hip region which, in turn, was controlled from the actual brain in the head through the spinal chord. In other words, the enlargement of the spinal chord in the hip region actually was a slave of the master controller in the head brain that also included the host computer which processed the sensory signals received from the eyes, ears and other sensors and which applied corresponding signals to the "master controller" for energizing the fore part of the animal and for actuating the "slave controller" in the hip region to energize the hind portion of the animal. Reference may in this respect be had to COLLIER'S ENCYCLOPEDIA (The Crowell-Collier Publishing Company, 1962), Vol. 8, pp. 226 and 232.
Numerical machine tool controls also employ several processors and monitoring circuits as may, for instance, be seen from U.S. Pat. 4,456,951, by Henneberger et al, issued June 26, 1984 to Siemens Aktiengesellschaft.
U.S. Pat. No. 4,462,704, by Kurata et al, issued July 31, 1984 to Fuji Xerox Co., Ltd., discloses a thermal head driving system with selective energization of printheads in parallel relation, including prior-art systems (FIGS. 1-3) and a pulse generator for producing drive pulses having a width determined in accordance with a ratio of a resistance value of each thermal head (FIGS. 4 and 5) .
U.S. Pat. No. 4,504,906, by Itaya et al, issued Mar. 12, 1985 to Anritsu Electric Company Limited, discloses a multiprocessor system comprising a plurality of central processing units periodically and cyclically enabled to access a bus for data transfer from one unit to another.
U.S. Pat. No. 4,536,778, by De Schamphelaere et al, issued Aug. 20, 1985 to AGFA-Gevaert N.V., discloses recording apparatus with modular LED arrays of higher production yield.
Appropriate control of the heat of thermal heads can be an important factor, as may be seen from U.S. Pat. No. 4,574,293, by Inui et al, issued Mar. 4, 1986 to Fuji Xerox Co., Ltd., for a compensation for heat accumulation in a thermal head. Electric energy to be applied to each heating element of the thermal head is controlled by taking into account the energy applied to the heating element up to two scan periods before, as well as the effect of heat accumulated in heating elements surrounding the heating element, and then the energy thus controlled is recorrected taking into consideration the temperature change in a thermal head base plate or the change in printing time between lines.
U.S. Pat. No. 4,590,488, by M. J. Sullivan, issued May 20, 1986 to Astro-Med, Inc., discloses a circuit for controlling energization of a thermal print head, by varying the pulse width of head energization depending on the head temperature which is fed back to the circuitry.
An example of different controls for printing apparatus may also be seen from U.S. Pat. No. 4,595,303, by Kuzuya et al, issued June 17, 1986 to Brother Kogyo K.K., for printing apparatus with two print heads. A system for detecting defective thermal printhead elements has been disclosed in U.S. Pat. No. 4,595,935, by Brooks et al, issued June 17, 1986 to NCR Canada Ltd.
U.S. Pat. No. 4,607,262, by Moriguchi et al, issued Aug. 19, 1986 to Fuji Xerox Co., Ltd.&lt;discloses a thermal head drive circuit and describes a transfer-type heat sensitive recording medium responsive to selective energization of the thermal printhead for selectively producing markings on a chart or an ordinary sheet of paper. That patent also discloses prior-art thermal head drive circuits (FIGS. 1-3) and head drive circuits with a heat accumulation calculating unit for calculating the heat residual from prior recording steps and from data recorded on neighboring recording elements (FIGS. 4-11).
U.S Pat. No. 4,613,872, by Naito et al, issued Sept. 23, 1986, discloses a recorder which records analog input waveforms and converts analog input data into digital data at regular intervals and at selected times records the digital data in the form of a list of data alongside of the analog input waveforms together with the time and other information. When analog waveforms and characters are recorded in side-by-side relation, the speed at which the paper is fed is changed from that employed when only analog waveforms are recorded, whereby the list of data can be quickly recorded.
U.S. Pat. No. 4,660,052, by Kaiya et al, issued Apr. 21, 1987, for heat sensitive recording apparatus discloses a plurality of elongate thermal printheads mounted so that the longitudinal dimension thereof are in substantially transverse relation to the recording chart at the printing station and at fixed positions in the transverse extent of the chart. As disclosed in that patent, the printheads are disposed adjacent different longitudinally extending sections of the chart and cooperate to define a substantially continuous printing width which extends substantially across the width of the chart at the printing station.
U.S Pat. No. 4,748,454, by Ikeda et al, issued May 31, 1988 to Nihon Kohden Corporation, discloses a dot array recorder having an LED level meter arranged to correspond position array to a dot array head, to indicate printed dot position.
U.S. Pat. No. 4,748,455, by Masaaki Mori, issued May 31, 1988 to Ricoh Company, Ltd., discloses systems for driving a thermal print head including a plurality of heat-producing elements which are activated selectively in accordance with digital image data obtained from an analog image signal is provided. In one aspect, the driving system is so structured to insert additional data between any two adjacent image data whenever the space between the two exceeds a predetermined level thereby allowing to maintain the dot density at constant when printed. In another aspect, that driving system controls the time period of activation of each of the heat-producing elements in accordance with preheat control data obtained by carrying out inverting and AND processing between each of the digital image data of one print line and the corresponding each of the digital image data of the next following print line (FIGS. 11 to 13). In a further aspect, that driving system has a structure such that a reference point in a print line may be set at a desired location along the print line.
Japanese Utility Model Publication 54-159928, by Motoo Kuroiwa et al, Hokuso Kaihatsu Tetsudo K.K., published Nov. 8, 1979, discloses a thermal dot printer in which heads are alternatively energized.
Japanese Patent Publication 55-97976, by Wakabayashi et al, Japanese National Railways and Nihon Singo K.K., published July 25, 1980 discloses a thermal printer wherein several printheads are mounted side by side and are independently biased from each other. In one embodiment, the thermal printheads are mounted on a crankshaft having a crank so that the thermal heads are collectively moved up and down when the crankshaft is driven by an electric motor. Another embodiment provides a slight play or gap in a junction between each of the thermal heads and the crankshaft, and pressure is exerted on the thermal head by use of compression springs. However, freedom of each thermal head at its supporting portion is excessively limited, since there is only a slight play or gap in the junction between each thermal head and the crankshaft.
Japanese Patent Publication 55-156080, by Shinshu Seiki Co., Ltd. et al, published Dec. 4, 1980, discloses a different approach in which one or two thermal heads are reciprocated transversely of the recording paper. That Patent Publication also shows circuitry for effecting and controlling the energization of the two thermal printheads.
Japanese Patent Publication 58-31022, by T. Dobashi, Nippon Denshin Denwa Kosha, published Feb. 24, 1983, discloses a processor controlling system having a common memory of a main control processor and a processor to be controlled, and a control circuit for sending out control signals to the processor to be controlled, in accordance with a control order from the main control processor.
Japanese Pat. No. 60-29990, issued from Japanese Patent Publication 58-112170, by H. Takatsudo, Casio Keisanki K.K., published July 4, 1983, discloses an electronic register with automatic load control circuitry.
For a summary of the prior art, reference may be had to the recently issued U.S. Pat. No. 4,739,344, by Sullivan et al, issued Apr. 19, 1988 to Astro-Med, Inc., for a chart recorder having multiple thermal printheads mounted so that the longitudinal dimensions thereof are in substantially transverse relation to the chart at the printing station and at fixed positions in the transverse extent of the chart. That Sullivan et al patent also claims, but does not otherwise disclose, the printheads being disposed adjacent different longitudinally extending sections of the chart and cooperating to define a substantially continuous printing width which extends substantially across the width of the chart at the printing station, as disclosed in the above mentioned Kaiya et al U.S. Pat. No. 4,660,052.
That Sullivan et al patent, also shows and describes the mounting of elongate printheads in substantially aligned, substantially abutting end-to-end relation with each other so that the longitudinal dimensions of the elongate printheads are in substantially transverse relation to the chart, as disclosed, for instance, in the above mentioned Wysong U.S. Pat. No. 4,145,698 and in the above mentioned IBM Technical Disclosure Bulletin Publication by Markson et al. That Sullivan et al patent also describes and shows the kind of independent biasing of each recording head disclosed in the above mentioned Wysong U.S. Pat. No. 4,145,698, Boor et al U.S. Pat. No. 4,151,397, and Wakabayashi et al Japanese Patent Publication 55-97976. That Sullivan et al patent also describes and shows microprocessor control systems including a master/slave control of the above mentioned kind applied to energization of two thermal printheads.
That Sullivan et al U.S. Pat. No. 4,739,344 also describes master and slave history circuits shown at 40 and 60 in FIGS. 2 and 2a and disclosed by reference to the above mentioned Inui et al U.S. Pat. No. 4,574,293, Moriguchi et al U.S. Pat. No. 4,607,262, and Sullivan U.S. Pat. No. 4,590,488.
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