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Backspace Interlock of Escapement Pawl Interposer

IP.com Disclosure Number: IPCOM000049601D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Robinson, CW: AUTHOR [+2]

Abstract

When a rotary ratchet and pawl arrangement is used to control the escapement motion of a typewriter carriage or carrier, it is desirable to incorporate a means for holding the escapement pawl clear of the ratchet when the carriage or carrier is moving in the carriage return direction. This prevents the pawl from dragging across the ratchet teeth and producing noise. A frictional type interposer driven from the ratchet is commonly used to drive the escapement pawl clear of the ratchet. In order for the interposer to allow the escapement pawl to reengage the ratchet, the carriage or carrier must move slightly in the escapement direction. This requirement creates a problem for the backspace mechanism.

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Backspace Interlock of Escapement Pawl Interposer

When a rotary ratchet and pawl arrangement is used to control the escapement motion of a typewriter carriage or carrier, it is desirable to incorporate a means for holding the escapement pawl clear of the ratchet when the carriage or carrier is moving in the carriage return direction. This prevents the pawl from dragging across the ratchet teeth and producing noise. A frictional type interposer driven from the ratchet is commonly used to drive the escapement pawl clear of the ratchet. In order for the interposer to allow the escapement pawl to reengage the ratchet, the carriage or carrier must move slightly in the escapement direction. This requirement creates a problem for the backspace mechanism. Since the backspace moves the carriage in the carriage return direction, the carriage must be displaced greater than one space to allow the escapement pawl to engage the proper tooth in the ratchet. This excess backspace motion causes the backspace function to appear jerky. Also, variations in the amount of motion necessary to reengage the escapement pawl with the ratchet cause the backspace function to be unreliable.

The solution is to interlock the interposer to keep it from functioning during a backspace operation.

The backspace cam (not shown) drives link 10 to the left which rotates backspace bellcrank 12 clockwise. The backspace bellcrank 12 simultaneously drives backspace pawl 14 and interlock link 16. The backsp...