CUTTING	313
helps to prevent turned-up edges, particularly at high speeds, when cutting only
one or a few webs, and also in handling light-weight papers.
The automatic hydraulic overlapping layboy enables the high speed of the
cutter to be taken full advantage of. It is actuated by oil under pressure supplied
by a pump driven by the main motor. The speed of the layboy carriage is
first adjusted to suit the thickness of the bundles of paper by means of a hand-
wheel, and thereafter the layboy carriage rises automatically as the height of
the stack increases. When the layboy reaches the top of its run it is lowered
to the starting position in two or three seconds by simply opening a valve.
As the sheets are delivered from the cutter to the layboy they are overlapped
like tiles on a roof, so that they can reach the stack at only a fraction of the speed
at which they have passed through the cutter. The sheets are thus easily
controlled on the layboy and are not liable to be damaged by the stop board.
A system of air nozzles above the layboy conveyor facilitates handling light-
weight papers, and a further series of air nozzles at the end of the layboy float
the sheets gently into position on the stack.
The cutter and layboy are controlled entirely from a central push-button
panel. A number, of extra 'stop' push-buttons are fitted at convenient points
about the machine to enable the operator to stop it from whatever position
he may be in.
There are designs for simplex, duplex, and triplex cuttings, while models are
available for installation at the end of a board machine for which the new slitter
gear with single handwheel adjustment is used so that the width of slit can be
altered while the machine is running.
On the duplex cutters a special coupling is fitted to disengage the duplex
unit when cutting simplex only, and an automatic hydraulic stack equalizing
device is provided to compensate for the unequal height of the stacks when
cutting duplex.
Recently various auxiliaries for these cutters have been developed. Chief
among these is a push-button-operated attachment on the drive to the rotary
knife drum, enabling the length of cut to be varied by small amounts to locate
the water-mark on the cut sheet. Registration of the water-mark is controlled
by an operative as he stands at the layboy and watches the overlapped sheets
passing to the stack. With this equipment water-marked papers are being cut
accurately to register at speeds of nearly 400 ft. a minute.
The ream counter and tabber counts the sheets in reams of 480, 500, 516
sheets as required and inserts a coloured paper strip between each ream. This is
all automatic.
When handling papers which are liable to give trouble due to static elec-
tricity, the electric neutralizer has proved extremely useful. It discharges tke