| 摘要 |
The free platen has a weight inside to produce inertia against movement by typing, as well as extensible end pieces for extension to correspond to lateral extension of a paper guide. An adjustable end plate at each end of the typewriter frame carries a lower supporting and positioning roller which engages the platen at a point forwardly of the vertical centerline thereof and a rear supporting and positioning roller which is essentially opposite the point of impact of the typing element and engages the platen at a point below its horizontal centerline. The platen has a pair of ring gears having an outer diameter less than the thickness of the elastomer covering the platen between the gears, with a short section of elastomer beyond each ring gear. The ring gears are engaged by a gear of a pivoted indexing device, which gear engages the platen ring gear when the respective indexing device is in down position. The ratcheted indexing device is actuated by conventional levers, arms, etc. The rollers of a special bail engage the paper just above the printing line, the rollers being mounted on a rod supported by a forwardly extending bar at each end. A spring acting on each end bar provides a thrust force directed at an acute angle to a tangent to the platen at the point of engagement by the rollers. Conventional paper feed rollers are disposed underneath the platen but are pressed upwardly against the platen with sufficient force to hold the paper against the platen, but insufficient to lift the platen from its supporting rollers.
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