Improvements in Apparatus Used in the Manufacture of Paper Pulp.
Year: 1893

page_text: Date of Application, 11th Aug., 1893
Complete Specification Left, 11th June. 1894-Accepted, 11th Aug., 1804
PROVISIONAL SPECIFICATION.
Improvements in Apparatus Used in the Manufacture of Paper Pulp.
I, WILLIAM HAY CALDWELL, of Bilston Lodge, Loauhead, Midlothian,
Gentleman, do hereby declare the nature of this invention to be as follows :-
In an ordinary Hollander or beating engine, the roll carrying the knives is so
arranged that it can be raised or lowered in such a way as to leave any required
space between its own knives and the fixed bed plate.
The roll rests on bearings in which it is free to rise. The weight of the roll is
such that the fibres passing beneath it can together exert a resistance sufficient to
raise the roll. This automatic action results in a large proportion of fibres being
squeezed and not cut. Owing to this construction, only a small bed plate can be
used, for in raising or lowering the roll, the centres of roll and plate do not remain
concentric.
In order to obtain a large beating surface, I make the knives of one by the
grinding surfaces moveable in slots, so that the centres of the wearing circles on both
revolving and fixed knives are concentric.
Further I propose to make the pressure required to move the knives controllable
by means of weights or springs acting on the backs of the knives, or by hydraulic or
other pressure acting behind a flexible wall against which the knives press. One
method of carrying out the above system is as follows. A cylindrical roll with fixed
knives is driven by pulley in either vertical or horizontal position. Surrounding this
is built up a double-walled cylinder containing water. The inner wall is made of
india rubber, corrugated steel, or other suitable flexible material. Inside this
flexible wall and pressing against it, are a number of small bed plates, fitted with
knives, each sliding in a suitable groove or slot. These knives may rest against
the knives of the inner cylinder, thus ensuring their regular wear, or they may be
allowed to rest against an adjustable ring capable of acting as a stop, so as to leave
a fixed distance between the fixed and revolving knives.
Any desired pressure on the flexible wall can be produced by hydraulic means.
In this way the knives can be made to cut or squeeze the fibres as may be
required for any particular quality of paper.
The material may be fed to the machine either by one of the ends, or, across its
breadth in the same direction as in an ordinary Hollander. Similarly the exit
orifice may be at the other end or across the breadth behind the inlet.
Another way of bringing about the same result is to fix the knives on the outer
cylinder, and at the same time to form either a flexible chamber inside the inner
cylinder with water or other pressure, arranging moveable kuives round this in
slots, or to control the pressure of the moveable knives by adjustable springs or
weights. The centrifugal force produces an independent pressure which varies
with the speed of rotation, if the inner cylinder rotates, and in certain circumstances
this centrifugal force may be used to give the necessary pressure without the
addition of hydraulic or other pressure from outside.
Dated this 10th day of August 1893.

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus Used in the Manufacture of Paper Pulp..
I, WILLIAM Hay Caldwell, of Bilston Lodge, Loanhead, Midlothian,
Gentleman, do hereby declare the nature of this invention and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement :-
In treating fibres so as to render them capable of making paper, there are two
distinct processes involved.
The first is the making of a uniform mixture, and this implies with most
materials, a shortening of the longer fibres.
The second process has to do with the relations of the fibres to the fluid in which
they are carried, and controls the speed and manner of separation of the fibres from
their fluid vehicle.
Such control is possible owing to the fact that fibres when submitted to pressure
in one direction become flattened. This flattening enables the pulp when passed
on to the wire of the paper machine, to retain water for a longer time.
The ease with which a mass of small needle crystals compared to a similar
quantity of small flat plates drain in a filter, is a good illustration of the difference
between the two states of a fibre.
In order to obtain pressure on the fibres while between beating or grinding
surfaces, and without at the same time destroying a large proportion by cutting
them into too short lengths, it is necessary that a pressure, beyond that which a
fibre can resist without being divided, shall at once move the beating or grinding
surfaces apart. Such separation of these surfaces results in the required flattening.
In an ordinary Hollander this automatic action is obtained when the roll is free
to rise in its bearings and its weight and distance from the bed plate adjusted to
the particular fibres being treated.
Previous attempts to increase the capacity of the ordinary Hollander by
multiplying the size and number of fixed bed plates, have failed, for the reason
that the above action takes place only over a small area directly below the roll
bearings, and when the number of fixed bed plates is increased so as to surround a
cylindrical roll with fixed knives, it is obvious that automatic squeezing movement
is impossible.
If the roll be made conical, a new set of conditions depending on the greater
wear of the knives at the larger end together with a greater number of fibres
accumulating at the smaller end, serves to reduce the working surface, and
similarly in machines when the grinding takes place on surfaces at right angles to
the axis of rotation.
In order to carry out the above principle I make the bars or knives of one or
both of the grinding surfaces between which the fibres are treated, moveable, and
press the knives of the one set towards the knives of the other set-either
separately or in assemblages of two or more together-by means of weights,
springs, hydraulic or other fluid pressure, the pressure being regulated to suit the
particular fibre being treated.
In the drawings annexed I have shewn one form of beating engine constructed
to act in the above manner.
Figure 1 is a longitudinal section, Figure 1 an elevation of the left hand end
of the driving gear, and Figure 2 a cross section.
A is a fixed cylindrical casing. B a shaft passing through the centre of the
casing and carrying a drum C having knives C' on its circumference extending
from one end of the drum to the other. D are knives ranged radially around the
drum C they pass through slots in a cylinder E which may extend from one end to
the other of the cylinder A or in slots in shorter cylinders one at each end of the
interior of cylinder A.

page_text: Fis a flexible cylinder preferably of india rubber surrounding the exterior of
the knives D. G is a pipe by which water or other fluid under pressure can be
admitted to the space between the flexible cylinder F and outer casing A. The
knives D are in the construction shewn by the drawing broader than the knives C¹
so that they are always bearing against one or other of them.
Water mixed with fibre is supplied to one end of the casing A through a pipe H
and is allowed to pass off from the other end of the casing by a pipe I. The acting
faces of the knives D have inclined corrugations across them this tends to force
the water towards the outlet I when the shaft B is rotated.
Another way of bringing about the same result is to fix the knives on the outer
cylinder and at the same time to form either a flexible chamber inside the inner
cylinder with water or other pressure, arranging movable knives round this in slots,
or to control the pressure of the moveable knives by adjustable springs or weights.
The centrifugal force produces an independent pressure which varies with the
speed of rotation, if the inner cylinder rotates, and in certain circumstances this
centrifugal force may be used to give the necessary pressure without the addition
of hydraulic or other pressure from outside. It is evident also that the outer
cylinder may if desired he revolved in place of the inner one.
Again the adoption of this method of controlling pressure gets over the difficulty
of the uneven action mentioned above in refining engines when the surfaces are
cones or discs, because the greater wear of the more rapidly moving parts is taken
up as it occurs.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, 1 declare that what I
claim is :-
1. The use in a rotary beating engine of adjustable weights, springs or other
pressure acting on three or more independently moveable beating or grinding
surfaces free to move independently of each other in such a way that these surfaces
shall at once move apart, whenever any required pressure is exceeded, substantially
as described.
2. A rotary beating engine in which one set of knives or bars ranged in a circle
are revolved around an axis and are thereby caused to move past and in close
proximity to other knives or bars concentrically arranged and in which the knives
or bars of one set are pressed towards the knives or bars of the other set either
separately or in two or more assemblages substantially as described.
3. A beating engine in which a roll carrying knives on its circumference is
revolved within a surrounding casing and has other knives pressed radially inwards.
by fluid pressure towards the knives of the revolving roll substantially as described.
4. The construction of rotary beating engines substantially as hereinbefore
described.
Dated this 7th day of June 1894.
W. H. CALDWELL,