Stepper motor for data recorder

#The present invention relates to methods of and apparatus for data recording and the like, being more particularly directed to the recording of data such as that produced during measurement, control or production monitoring and similar operations, and documenting the recorded information in a format suitable for direct use in logs and reports and in related usages.

#In many industrial, research and similar processes, it has long been desirable to have a data recording apparatus positioned where the operator can readily view the most recent values of important parameters under monitor, such as, for example, temperatures, pressures, flow rates, motor speeds, and many other quantities. The recorded data, moreover, must be presented in a manner which permits the operator to observe changes in the data, and the recorder apparatus itself must have a physical design which can operate reliably in industrial and similar environments. Among the recording apparatus heretofore used for such purposes have been the multi-point or pen recorder which printed a series of marks or a continuous line on a paper scroll, with the left-to-right location of the marks or lines representing the value of the data being recorded. This type of equipment, however, is subject to disadvantages of limited resolution, interpolation errors, and clogged pens, and the requirement for special recording chart paper. The operator, furthermore, is required to interpret the analog meaning of the record and to convert the same to digital value, where required.

#It is also often necessary, in addition, that the parameters being recorded or logged for display to the operator be summarized in a form suitable for ultimate presentation in a written report or the like. A tabular form is often desirable. In the past, accordingly, the data has been extracted from the recorder charts and summarized or transcribed manually; or, in more elaborate systems, the data has been transmitted to a computer system in a different part of the plant to be summarized for inclusion in a report.

#The invention will now be described with reference to the accompanying drawings,

#FIG. 1 of which is an isometric view, partly broken away to illustrate details of construction, of a preferred embodiment;

#FIG. 2 is a combined block and schematic circuit diagram of the paper drive for the system of FIG. 1;

#Referring to FIG. 1, the invention enables the before-mentioned highly desirable result of positioning the recorder printed page as close to the front face of the apparatus as possible for the most facile viewing by the observer, by positioning the print head 1 at a predetermined location near the bottom and on the opposite face of the paper 2 from the observer, such that it strikes or impacts upon the paper from the rear. The paper 2 is mounted to travel longitudinally vertically, traversing between the print head 1 and a platen 3 such that the impact force of the print head 1 is absorbed by the platen 3 through the paper 2. The print head 1 is transversely horizontally driven from side to side by a single motor 4 running in one direction. The motor 4 drives a chain 5 through a slider-pin mechanism 6, with the print head 1 riding upon a set of guides 7 to maintain constant spacing between the print head 1 and the platen 3. While the terms "vertically", "horizontally" and "bottom" are illustrative of a preferred orientation, they are generically used herein to connote equivalent relative positions, as well. Suitable impact-sensitive chart paper for enabling this reverse printing (ink-impregnated pressure sensitive, or the like) is, for example, type SC White #17 of NCR Corporation.

#A light source and optical sensor 1', mounted rearwardly with the print head 1, detects, as the head transversely traverses the apparatus, alternate transparent and opaque vertical lines on a fixed transverse strip 8, extending beyond the width of the printed page, and serving as an optical fence, with one end completely opaque, and the other end completely transparent. A special electronic circuit detects each transition from transparent to opaque as a potential print position, and the printer logic will cause the appropriate character to be printed. When the print head 1 reaches either end region and does not detect a transition for a pre-determined period of time, an associated control circuit will continue to print the next line of data or turn off the motor if there is no further data to be printed. By sensing whether the strip is completely transparent or completely opaque, the printer logic is informed whether the print head 1 is at the left or right margin of the page so that, unlike other prior printing apparatus, there is no need to have separate sensors to determine when the print head 1 is at a margin, and to determine which margin.

#The control logic is designed such that printing can occur with the print head 1 travelling in either transverse direction, so that it is not necessary to bring the print head 1 back to the left margin each time before starting a new line. The construction of the invention thus eliminates the typical carriage return operation of most printers. If the next line to be printed is already available, the motor 4 driving the print head 1 does not stop when a margin is detected, but it continues to drive the print head 1, and the slider-pin mechanism 6 automatically reverses the direction of the print head 1. With this type of mechanism, the next complete line to be printed is stored in the hereinafter described microprocessor memory before the printing operation of that line is started.