Browse Prior Art Database

Hammer Rattling in a Line Printer

IP.com Disclosure Number: IPCOM000060481D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Davis, GW: AUTHOR [+3]

Abstract

In a high speed line printer, printing often occurs in set print patterns such as the listings of inventory with several columns of the page being used very often, whereas other columns such as a total or subtotal may be set up to print in a column that has not been used for the entire page. Other jobs may use the first eighty columns of print for several hours until the job is changed, with the new job printing many of the unused columns of the previous job. In both these examples the problem is similar; the first time a print position is used the resultant hammer impact against the print band is late because the pivots, backstop, and push rods of the print mechanism have relaxed from their dynamic to static conditions. The printed character in the worst case can be unreadable.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Hammer Rattling in a Line Printer

In a high speed line printer, printing often occurs in set print patterns such as the listings of inventory with several columns of the page being used very often, whereas other columns such as a total or subtotal may be set up to print in a column that has not been used for the entire page. Other jobs may use the first eighty columns of print for several hours until the job is changed, with the new job printing many of the unused columns of the previous job. In both these examples the problem is similar; the first time a print position is used the resultant hammer impact against the print band is late because the pivots, backstop, and push rods of the print mechanism have relaxed from their dynamic to static conditions. The printed character in the worst case can be unreadable. This article describes a method of rattling the hammers more frequently, specifically when there is a need to free a previously unused and possibly sticky print position. It may be accomplished quite simply by arbitrarily rattling all the hammers at preset intervals during printing to prevent any hammer positions from remaining in their static condition for sufficient time to become sticky. However, there is a finite amount of time required to execute a hammer rattle cycle, and rattling at arbitrary intervals may unnecessarily degrade throughput of the printer. A much better solution is to perform a hammer rattle just prior to the printing of a line that will use a previously idle column, with a preset minimum time delay between rattle cycles to insure that printer throughput is not excessively degraded. Referring to the printer block diagram of Fig. 1, the Microprocessor Unit controls all print operations in the following manner: 1) Carriage move data and print data will be stored in the associated hardware electronic buffers as the Adapter Go signal is activated. This begins the firing of electromagnetic print hammers as the correct characters are moved in position by a rotating print band containing the character impressions. 2) When all print hammers have fired, the Carriage Go signal will be issued to the Carriage Control hardware 10 by Print Control Hardware 11 and the Print Complete Interrupt Request (IRQ) will be issued to the Microprocessor Unit 12. This will begin the movement of the paper forms to position the paper for the next print line. The Carriage Complete Interrupt Request (IRQ) indicates to the Microprocessor Unit 12 that all operations are done. 3) The method used currently during bring-up of the print band fire...