214

MODERN PAPER-MAKING

From our own experience we can say definitely that these 'Happer'
rollers are by far the best method yet introduced for the satisfactory conditioning
of dry felts, and for ensuring evenness of drying across the full width of the
web.

The Heimbach system works on the opposite principle and blows dry air
through the felt into the machine house. This air becomes saturated by taking
up moisture from the felt, and has to be extracted from the room by means
of fans.

Smoothing Rolls.—These are two steel rolls, steam-heated, and are inserted

FIG. 86.—VICKERY FLEXKBIE DOCTOR APHJBD TO A PRESS ROLL

[VtckerysLtd.

before the last section of drying cylinders. Their purpose is to smooth or flatten
tifae web of paper while it is still in a slightly damp condition. They reduce
bulk a good deal, but, if rightly used, are very effective in eliminating felt
marks, and, by dosing up the under side of the sheet, produce a very equal-
wJecl papa. Tbey should be run fairly hot, but not excessively so.
* Gocd doctor blades are necessary for both rolls, as any particle of stuff or
dfot may stick wry firmly to their surfaces owing to the heat used,
Tbe flexible doctor (fig. 86) lias revolutionised 'doctoring' of all rolls on
fche paper maflfeme, 3od it is rapidly displacing the older forms of rigid iron