MACHINE DRIVE 223
*
The drive takes up very little space, and may conveniently be housed either
alongside the paper machine or outside the machine room in an annexe, with
the driving-in shafts passing through the wall or partition, as shown in Fig. 88.
It is very compact and accessible, and does away with all troubles from belts,
ropes and clutches.
-The drive is very efficient and provides great flexibility of layout both from
the point of view of mechanical arrangement and control. In particular, the
drive to each section of the paper machine can be designed to suit the inertia
and factional loading characteristics to ensure equal accelerative response on
all sections to any common change in speed, thus relieving the paper of tendency
to tighten or slacken between sections .under such conditions. The speed of
the whole paper machine can be maintained so constant as to limit the variation
to a fraction of I per cent, a factor of considerable importance for high-speed
paper machines. All control can readily be arranged at the front of the machine
in the most desirable positions for machine speed as a whole, section motor
inching, crawling, starting and stopping and draw adjustment with local
indication of speed, power requirements and draw settings. Individual sections
of the machine can be shut down, inched or crawled without affecting the
correct interlocked running of the remainder. Heavy sections can be electrically
braked for quick stopping, thus niinirnising delays and tending for safety in
the event of accident.
The ease of control, speed constancy and reliability of this form of drive
combine to give maximum output of highest grade product, and it is not
surprising to find its application being extended to all classes of paper-making
machine, both large and small.
The British Thomson-Houston Company also make a sectional electric
drive which is in use on paper machines, and a recent improvement is the
separate driving of each individual cylinder which has been developed by
Siemens, who were licensees for the Harland system. For certain papas tiiis
system possesses definite advantages.