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Method for Calculating Realtime Escapement Velocity for Printers

IP.com Disclosure Number: IPCOM000060876D
Original Publication Date: 1986-May-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 4 page(s) / 19K

Publishing Venue

IBM

Related People

Albaugh, VA: AUTHOR [+2]

Abstract

A method is described for calculating in realtime the velocity of the print head carrier of a printer to obtain optimum carrier velocity. When printing on the fly, that is not stopping the escapement mechanism at each print position, all subsystems of the printer must be synchronized. For a daisywheel-type printer, this means that the carrier cannot pass over the print point until wheel and ribbon advancement have completed. It also means that the hammer must be actuated prior to the print point to account for its flight time such that impact is synchronized with the carrier passing over the print point. The time taken for escapement to traverse between print points must allow for completion of tasks for the other subsystems. Between impacts, the following tasks must occur: The hammer must recover to the starting point.

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Method for Calculating Realtime Escapement Velocity for Printers

A method is described for calculating in realtime the velocity of the print head carrier of a printer to obtain optimum carrier velocity. When printing on the fly, that is not stopping the escapement mechanism at each print position, all subsystems of the printer must be synchronized. For a daisywheel-type printer, this means that the carrier cannot pass over the print point until wheel and ribbon advancement have completed. It also means that the hammer must be actuated prior to the print point to account for its flight time such that impact is synchronized with the carrier passing over the print point. The time taken for escapement to traverse between print points must allow for completion of tasks for the other subsystems. Between impacts, the following tasks must occur: The hammer must recover to the starting point. The wheel must be moved to the new location. The ribbon must be advanced. The hammer must move forward and strike the wheel into the platen. Portions of these tasks may be overlapped to a degree. Ribbon advancement is physically independent of the other tasks. However, the print hammer cannot be in the plane of the wheel during the selection time (the time taken to rotate the wheel to the new location and settle). Note that the out-of-plane time of the hammer after the hit and the in-plane time of the hammer prior to the hit are different from the recovery time of the hammer and the flight time of the hammer. When overlapped to the greatest extent, the minimum time required between print points will be the greatest of the following three times: Tmin = Time1: Hammer out-of-plane time (the time from impact until the hammer exits the plane of the wheel a function of the impression level used for the previous character). plus Selection time (the time to advance and settle the printwheel) and in-plane time prior to impact (a function of the impression level of the current character). or Time2: 1/(Maximum hammer rep rate) In this case, the minimum time is set by the performance capability of the hammer. This is typically the situation for a zero selection (same character). or Time3: Time required to advance the ribbon. For a given execution cycle, this time is easily calculated and determines the minimum time that escapement must take to traverse the print points. Occasionally for large selection moves and short escapement moves, the escapement will be required to stop at the print point. More typically, escapement times can be matched to the desired times by speeding up or slowing down. To implement escapement velocity modifications on prior-art printers, three parameters were used to search a table for the most appropriate escapement velocity algorithm. These parameters are the desired time (Tmin), the existing escapement velocity, and the distance. The requirement for the lookup was to find a stored algorithm for the initial velocity and distance that to...