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Circuit for the Prevention of Errors Due to the Contamination of the Timing Holes in the Dot Element Band in a Dot Element Band Printer

IP.com Disclosure Number: IPCOM000061474D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Johnson, SD: AUTHOR [+4]

Abstract

A dot element band printer includes a transducer for sensing timing holes in the dot element band and generating corresponding timing signals. In order to avoid errors in the operation of the printer due to the absence of a timing signal from a blocked timing hole, the printer also includes an error-prevention circuit which allows the printer to continue to operate even though one or more of the timing holes is blocked by paper dust or pieces of ink ribbon. Fig. 1 illustrates a portion of the dot print element band 1 of a printer. The band 1 is formed with a plurality of chevron-shaped fingers 2 by forming holes 3 in the band 1. To the apex 4 of each finger is attached a dot printing element 5. Extending along the length of the band 1 are two rows of timing holes 7 and 8.

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Circuit for the Prevention of Errors Due to the Contamination of the Timing Holes in the Dot Element Band in a Dot Element Band Printer

A dot element band printer includes a transducer for sensing timing holes in the dot element band and generating corresponding timing signals. In order to avoid errors in the operation of the printer due to the absence of a timing signal from a blocked timing hole, the printer also includes an error-prevention circuit which allows the printer to continue to operate even though one or more of the timing holes is blocked by paper dust or pieces of ink ribbon. Fig. 1 illustrates a portion of the dot print element band 1 of a printer. The band 1 is formed with a plurality of chevron-shaped fingers 2 by forming holes 3 in the band 1. To the apex 4 of each finger is attached a dot printing element 5. Extending along the length of the band 1 are two rows of timing holes 7 and 8. The upper row 7 is called the Home row and consists of one hole for each of the fingers 2. These holes are spaced apart equally by the distance between adjacent fingers 2 and therefore correspond in position to the fingers 2. The lower row 8 is called the Print row and consists of a set of equally spaced holes between the holes of the Home row. The number of holes so spaced is equal to the dots to be printed in the distance between leading edges of two consecutive Home holes. These rows of holes are sensed by an optical sensor which generates a corresponding timing pulse for each hole detected. If any hole is blocked, the sensor will not generate a corresponding timing pulse. Fig. 2 illustrates the two sets of timing pulses which will be generated by sensing the two rows 7, 8 of timing holes. Fig. 2a illustrates the two sets of timing pulses which will be generated when all the Home and Print rows of holes are sensed. It will be seen that there is a set of 18 Print timing pulses generated by sensing the lower Print row of timing holes for each Home timing pulse generated by sensing the upper Home row of timing holes. Missing Print Timing Pulse Fig. 2b illustrates what happens when one of the lower Print row of timing holes is blocked and no corresponding Print timing pulse is generated. As illustrated, the Print timing pulse corresponding to timing hole #5 of one set of holes in the lower Print row 8 associated with one of the Home holes of the upper row 7 of holes is missing and without the error- prevention circuit the rest of that set of Print timing pulses and the next Home timing pulse would be generated and there would be printing errors. The fact that a Print timing pulse is missing is detected by measuring the length of time from each Print timing pulse rising edge to the next Print timing pulse rising edge. If the next Print timing pulse does not occur within a set length of time, then one Print timing pulse is considered to be missing. Fig. 2c illustrates how the error- prevention circuit ignores this missing Print timi...