IMPROVEMENTS IN OR CONNECTED WITH STRAINERS FOR PAPER PULP
Year: 1882

page_text: LETTERS PATENT to Robert Laurie, Manager of the Darley Paper Mills, in the
County of Derby, for an invention of "IMPROVEMENTS IN OR CONNECTED
WITH STRAINERS FOR PAPER PULP,"
"
PROVISIONAL SPECIFICATION left by the said Robert Laurie at the Office
of the Commissioners of Patents on the 13th March 1882.
ROBERT LAURIE, Manager of the Darley Paper Mills, in the County of Derby,
IMPROVEMENTS IN OR CONNECTED WITH STRAINERS FOR PAPER PULP,"
This Invention relates to Improvements in or connected with flat strainers, or
machines for straining and cleaning paper pulp, designed to simplify the con-
struction and mode of operating such machines so that they may be worked with
little expenditure of power, while being more efficient and economical in action.
In the ordinary construction of flat strainer, one of the long sides of the frame
carrying the straining plates, is carried on fixed hinges, and the other long side is
by means of projecting horns brought in contact with ratchet cams fixed on a
revolving shaft, which communicate to it a vertical reciprocating or jogging motion,
and the weight or inertia of the frame having to be overcome at each movement,
power is absorbed, and the action rendered very noisy and violent. But by the
present improvements the strainer frame is suspended by hinges at one end, and
from a spring or springs at the other end which receives motion, so that it hangs
in equilibrium, and a gentle vibratory motion is produced by the simple depression
and consequent recoil of the spring, thereby avoiding the lifting of the dead weight
of the frame and its contents. The strainer frame is connected to the usual outer
box or vat by means of an improved arrangement of flexible diaphragm which is
fitted to produce at each upward motion of the strainer frame, a partial vacuum
below the strainer plates, to facilitate the straining operation. The action of
forcing the pulp through the fine cut slits in the strainer plates is by these means
rendered much less violent than in strainers operated by ratchet cams, and the pulp
passes through very clean.

page_text: In carrying out the Invention the strainer frame is made of wood or other
material of the ordinary oblong form fitted with the usual fine cut strainer plates
fitted near the bottom. This frame is placed within a box or vat of cast-iron or
other material a little larger than the strainer frame, so that there is a space of a
few inches all round between the inner frame or strainer proper and the outer box
or vat. In this space, and on the underside of the strainer frame is fixed a
diaphragm of india-rubber or other flexible material, preferably on three sides of
the frame only, thus forming a lower compartment partially air-tight. The
strainer frame may be placed level, but the plates are by preference placed at a
slight inclination. The bottom or lower end of the frame is hung on fixed pivots
or hinges; and the top or high end is connected to and supported by a spring,
preferably of bow shape, the ends of which spring are carried on the fixed outer box
or vat. This spring is sufficiently strong to carry the weight of the strainer, but
at the same time flexible enough to allow the strainer to vibrate on a very small
power being applied thereto by a crank and connecting rod or other means.
The strainer plates being thus fixed at an angle as described, the pulp to be
strained is made to flow on to the higher end of the strainer; the vibratory action
causes it to pass through the fine cut slits in the plates into the vat or lower
compartment, its flow being facilitated by the partial vacuum formed inter-
mittently in this compartment. Knots or other impurities that are retained
on the upper surface of the strainer plates are gradually shaken down to the lower
end of the strainer, and there dropped into a suitable receiver provided for that
purpose. The clean or strained pulp is taken off by an aperture at a suitable level
in the outer box or vat.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Laurie in the Great Seal Patent Office on the 11th September
1882.
ROBERT LAURIE, Manager of the Darley Paper Mills, in the County of Derby
"IMPROVEMENTS IN OR CONNECTED WITH STRAINERS FOR PAPER PULP."
My said Invention relates to improvements in or connected with flat strainers,
or machines for straining or cleaning paper pulp, designed to simplify the con-
struction and mode of operating such machines, so that they may be worked with
little expenditure of power, while being more efficient and economical in action.
In the ordinary construction of flat strainer, one of the long sides of the frame
carrying the straining plates, is carried on fixed hinges, and the other long side is
by means of projecting horns brought in contact with ratchet cams fixed on a
revolving shaft which communicate to it a vertical reciprocating or jogging motion;
and the weight or inertia of the frame having to be overcome at each movement,
power is absorbed, and the action rendered very noisy and violent. But by the
present improvements, the strainer frame is suspended by binges or similarly
jointed at one end, and from a spring or springs at the other end which receives
motion. The strainer frame thus hangs in equilibrium, and a gentle vibratory
motion is produced by the simple depression and consequent recoil of the spring,
thereby avoiding the lifting of the dead weight of the frame and its contents. The
strainer frame is connected to the usual outer box or vat by means of an improved
arrangement of flexible diaphragm which is fitted to produce at each upward
motion of the strainer frame a partial vacuum below the strainer plates, to facilitate
the straining operation. The action of forcing the pulp through the fine cut slits
in the strainer plates, is by these means rendered much less violent than in
strainers operated by ratchet cams, and the pulp passes through very clean.
My said Invention is illustrated in the accompanying Drawings, of which
figure 1 is a longitudinal vertical section, figure 2 is a transverse vertical section
on the line 1 - - 1, and figure 3 is a plan of a modification of my improved pulp
strainer, Figure 4 is a cross section of the strainer frame at the line 2-2 in
figure 1.
In carrying out the Invention the strainer frame A is made of wood or other
material of the ordinary oblong form, and is fitted with the usual fine cut strainer
plates A¹, forming the bottom, a space or receptacle A³ being left at the lower end
to receive the knots or lumps in the pulp which do not pass through the slits in
the plates a. This frame A is hung within a box or vat B of cast iron or other
material a little larger than the strainer frame A so that there is a space of a few
inches all round between the inner frame or. strainer proper A, and the outer box
or vat B.
In this space, at the under side of the strainer frame is fixed a
diaphragm C of india rubber or other flexible material also attached to the vat B
preferably on three sides of the frame only, thus forming a partially air-tight
lower compartment B¹ between the strainer frame A and the vat B. The
diaphragm C is secured to the underside of the frame A, and to the inside of the
vat B by strips of wood. The strainer frame A may be placed level, but the
plates A¹ are by preference placed at a slight inclination, being carried on edges
formed round the inside of the frame A. The end of the frame towards which the
cut plates a incline downwards, is hung on fixed pivots or hinges, which in the
modification shown in the Drawings, consist of brackets D fixed to the frame H,
having eyes in them by which they are hung on to a transverse shaft D', this
shaft being carried in bearings on the sides of the vat B. The other end of the
frame A is connected to and supported by a spring E, preferably of bow shape, the

page_text: ends of which spring are carried on the fixed outer box or vat B, or on brackets
carried on it. This spring E is sufficiently strong to carry the weight of the
strainer A, but at the same time flexible enough to allow the strainer to vibrate
on a very small power being applied thereto by a crank and connecting rod or
other means.
In the Drawings, the strainer frame A is shown fitted with a strong hoop or
bow F, which is connected to the spring E by a screwed pin G so that the length
may be easily adjusted and jointed to a connecting rod G¹ attached to a crank
disc H, on a rotating shaft I. This shaft I is carried in bearings on standards J
over the vat B, and driven by a belt passing over a pulley K fitted on the shaft I,
a fly wheel L being also provided. The spring E and hoop F are secured by nuts g
on the screwed pin G. The crank pin of the disc H is made adjustable so as to
give a variable stroke of the connecting-rod, and corresponding vibration of the
strainer frame A. The spring E though shown of bow shape may be of any other
form. The strainer plates A¹ a being fixed at an angle as shown, the pulp to be
strained is made to flow on to the higher end of the strainer A through a box or
spout placed under the bow, when the vibratory action causes it to pass through
the fine cut slits in the plates into the vat or lower compartment B', its flow being
facilitated by the partial vacuum formed intermittently in this compartment, by the
vibratory motion of the frame A, and the action of the rubber diaphragm C.
Knots or other impurities that are retained on the upper surface of the strainer
plates A', are gradually shaken down to the lower end of the strainer and there
dropped into the box or receptacle A². The clean or strained pulp is taken off by
an aperture m at a suitable level in the outer box or vat B, the level of the
outflowing pulp being just under the strainer plates A' at their lowest end, and
over the diaphragm C, so that a partial vacuum may be formed as described when
the frame A is vibrated. The vat or box B, is carried on brackets or standards B',
with the bottom at a slight inclination, and a sluice or valve M is fitted at the
lower end, so that the contents of the vat may be entirely withdrawn, by simply
raising the sluice.
Having thus described my said Invention, and the manner of performing the
same, I have to state that I do not restrict myself to the precise details of the
apparatus herein described and delineated, but what I consider to be novel
and original and claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,-
First. The arranging and combining of the parts of machines or apparatus
for straining paper pulp, substantially in the improved manner berein described
and delineated.
Second. The combination with a pulp strainer, of a spring interposed or fitted
between the vibrating strainer frame, and the connecting rod or driving gear, by
which the vibratory motion is imparted to such frame, substantially as and for the
purposes herein set forth, in reference to the accompanying Drawings.
In witness whereof, I the said Robert Laurie, have hereunto set my hand
and Seal this Fourth day of September, in the year of our Lord One
thousand eight hundred and eighty-two.