IMPROVEMENTS IN THE STRAINING OF PAPER PULP, AND IN THE MACHINERY, MECHANISM, OR APPARATUS THEREFOR OR CONNECTED THEREWITH
Year: 1869

page_text: LETTERS PATENT to Robert Nicholson Slight, Paper Manufacturer,
and William Forrest Denholm, Engineer, both of Chirnside Bridge,
in the County of Berwick, North Britain, for the Invention of
"IMPROVEMENTS IN THE STRAINING OF PAPER PULP, AND IN THE MACHINERY,
MECHANISM, OR APPARATUS THEREFOR OR CONNECTED THEREWITH."
Sealed the 28th January 1870, and dated the 1st December 1869.
PROVISIONAL SPECIFICATION left by the said Robert Nicholson
Slight and William Forrest Denholm at the Office of the Com-
missioners of Patents, with their Petition, on the 1st December
1869.
We, ROBERT NICHOLSON SLIGHT, Paper Manufacturer, and WILLIAM
FORREST DENHOLM, Engineer, both of Chirnside Bridge, in the County
of Berwick, North Britain, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE STRAINING OF PAPER PULP, AND IN THE
MACHINERY, MECHANISM, OR APPARATUS THEREFOR OR CONNECTED THEREWITH,"
to be as follows, that is to say :-
This said Invention consists substantially in a new or improved modé
of straining the crude or unstrained paper pulp from the receiving vats

page_text: placed at the back of and preparatory to leading it on to the paper-
making machine, and by new or improved constructions and arrange-
ments of stationary enclosed strainers with close fitting internal
reciprocating suction and discharge pistons, and arrangements of their
vats and conducting spouts or ducts and sluices, whereby much greater
straining surface is obtained within equal or less space with greater
freedom from "grass" or "pulp knots," which are more effectually
broken up by being thrown back off the straining slits and surfaces
at each stroke, besides giving a cleaner and more regular current of
strained pulp without throwing a strain upon the vats by the action of
the suction and discharge pistons worked within the strainers than has
been the case with the "jogging," shaking, or revolving strainers,
heretofore in use for the like purposes.
One modification and arrangement of the new or improved apparatus
and mode of performing this said Invention consists in drawing the
unstrained pulp fed and filled into the long transverse outer vat or vats
through the slits or "cuts" in the straining surfaces or plates into tho
interior of an otherwise close vessel or strainer, or it may be strainers,
each, by preference, of the long, square, rectangular form, but con-
siderably smaller on all sides than the vat, within the centre of which it
is made fast and stationary, and completely immersed within the paper
pulp, which is drawn into the interior of the strainer by the sucking.
action of a reciprocating piston actuated to and fro within it by a crank,
eccentric, or cam mechanical action upon and from any adjacent prime
moving shaft. While the strained paper pulp thus drawn into the
interior of the strainers through the slits or "cuts" in its straining
surface is discharged from it by the reverse or pressure action of the
piston through valve openings and lids formed and working freely
against the power of a light spring on each, so as to open outwards
through the ends of the strainers, which, by preference, also form the
ends of the vat, so as to discharge the pulp into main ducts or spouts
common to all, and leading to other similar arrangements of strainers.
on a lower level in front having finer "cuts" or slits, or otherwise direct
to the discharge vat containing the revolving "hog." The valve lids,
by preference, are made to work or slide on the actuating and centre
rod of the piston or pistons fixed on it; and the pistons are each, by
preference, formed by a broad rubbing surface or band of india-rubber or
other equivalent elastic packing secured round the body and between the

page_text: two end brass plates of the piston, one piston working within each of
the straining vessels and vats which are placed in the centre line of their
piston rod. Two or more of these first sets or rows of strainers being
arranged on a higher level than the second or finer sets of strainers in
front have their discharge sluices (leading to their common ducts or
spouts) so arranged that any one of the said sets or rows of strainers
may be shut off for cleaning, or stopped in its action by uncoupling the
connecting rod of the piston or pistons for repair, or other purpose when
desired, so that all the other strainers may continue to work, and the
paper-making machine not be required to stop for anything going wrong
with a single row or set of strainers arranged in this new or improved
manner.
The strainer, although described as square, may be made of other
polygonal or round form in cross section, and its straining sides or
surfaces may be made of sheet metal, or of ordinary straining plates
with the long straining slits pierced or formed through them, while
the body of the vats may be made of wood or iron, or of other metal.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Robert Nicholson Slight and William Forrest
Denholm in the Great Seal Patent Office on the 30th May 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, wc, ROBERT
NICHOLSON SLIGHT, Paper Manufacturer, and WILLIAM FORREST
DENHOLM, Engineer, both of Chirnside Bridge, in the County of
Berwick, North Britain, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of December, in the year of
our Lord One thousand eight hundred and sixty-nine, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto us, the said Robert Nicholson Slight and William
Forrest Denholm, Her special licence that we, the said Robert Nicholson
Slight and William Forrest Denholm, our executors, administrators, and
assigns, or such others as we, the said Robert Nicholson Slight and
William Forrest Denholm, our executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and
at all times thereafter during the term therein expressed, should and

page_text: lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle
of Man, an Invention for "IMPROVEMENTS IN THE STRAINING OF PAPER PULP,
AND IN THE MACHINERY, MECHANISM, OR APPARATUS THEREFOR OR CONNECTED
THEREWITH," upon the condition (amongst others) that we, the said
Robert Nicholson Slight and William Forrest Denholm, our executors
or administrators, by an instrument in writing under our, or their, or
one of their hands and seals, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to
be performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date
of the said Letters Patent.
NOW KNOW YE, that we, the said Robert Nicholson Slight and
William Forrest Denholm, do hereby declare the nature of our said
Invention, and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement
in writing, reference being had to the accompanying Sheet of Drawings,
and to the letters and figures marked thereon, that is to say:-
Our said Invention consists substantially in a new or improved mode
of straining the crude or unstained paper pulp from the receiving vats,
placed at the back of and preparatory to leading it on to the paper-
making machine, and in and by new or improved constructions and
arrangements of stationary parallel closed in strainers having close easy
fitting suction and discharge pistons reciprocating within them, their
outer shells or surface being closely perforated with "cuts" or slits
which are wholly immersed some depth within the pulp and vat, also in
improved arrangements of the said vats and their conducting spouts,
ducts, or channels, and sluices suitable for working with one set of
strainers while the other is thrown out of gear and action, or any single
or double strainer is so stopped for cleaning or repairs.
And in order that the nature of our said Invention as so far. stated,
and the best modes and means we are at present aware of for performing
or carrying it into effect or practice, may be properly and fully under-
stood, we shall now proceed to describe the several illustrative Figures on
the Sheet of Drawings which we have hereunto appended for the purpose,
the same reference letters and numerals indicating the same or like parts
in all the Figures.

page_text: Figure 1 is a transverse vertical section taken on the irregular line
1-1, in Figure 2, and Figure 2 is a plan corresponding to Figure 1 of
an arrangement of paper pulp strainers and their vats, constructed in
accordance with and illustrative of one modification of our said Invention
and a means of carrying it into practice, as applicable to and for any
ordinary paper-making machine.
Figures 3 and 4 are respectively a transverse and partial longitudinal
section of one of the strainers and vats (shown in Figures 1 and 2) to a
large scale to show the construction of the parts more clearly, and
Figure 5 is a plan of the same corresponding to Figure 4.
Figure 6 is an end view of one of the strainers; and Figure 7 is a side
elevation of part of the strainer both to double the large scale corre-
sponding to Figures 3 to 5, or half the full size.
Referring to these Figures 1 to 7 inclusive, and particularly to the
large detailed Figures 3 to 7, each strainer is constructed in the form of a
long hollow parallel chamber or vessel, by preference square in transverse
section (Figure 3); but it may be made rectangular, polygonal, or round
in cross section when preferred.
The vertical side plates A are made in one piece and the horizontal
top and bottom plates A° are made in three lengths or pieces for removal
and ease of getting at the inside for repair or cleaning, both formed of
the ordinary brass metal used for straining plates, and having the usual
straining "cuts" or slits formed transversely across and through them
with the flat smooth sides of all the plates placed or turned to the inside;
the upper and lower plates A° are jointed at their adjacent ends A³ to
each other and along their sides to the side plates A* by groove and
feather joints A³, and secured laterally by screw bolts B at their sides
passing through snugs in the upper and lower plates A, and screw
pins B at the extreme ends to flanges on the end plate C of the
strainer A, all so as to make and maintain it in a true square and
parallel form of a portable or detachable construction, so as to be placed
in working position in the centre of its vat a secured by the broad
flanges C¹ of its end plates C to the ends of the vat in which the whole is
immersed and covered to a considerable depth with the paper pulp z.
A square plunger or piston D made of wood (or having wood, india-
rubber, or other suitable elastic packing or soft rubbing surface) is made,
to fit and work or reciprocate freely within and from end to end of each
strainer A. A valve E is fitted on each outer end plate C so as to open

page_text: outwards against the power of a light spiral spring E, and either slide on
the piston rod D' or on the spindle E" at the end where the piston rod
does not pass out through it, the pressure on the back of each spring and
valve E', E, is sustained and regulated by the supported cross head E
and its supporting screw studs and nuts Es. The bearing surfaces of these
valves E or their seats are by preference covered with india-rubber or
other equivalent soft substance. A small air pipe. F is fitted and jointed
to each end of each strainer A having a valve F¹ opening inwards to the
strainer against the power of a small spiral spring, which together with a
tightening nut regulates the pressure at which the air will enter the
strainer and consequently the maximum suction pressure desired to be
allowed within the strainer A and on the back of the piston D, but
any other equivalent regulating valve may be used when preferred, or a
fixed hand cock or valve may be used by itself or along with the said
regulating valve, in each of these air pipes F and set at starting the
strainer to suit the suction and speed of piston and particular pulp being
strained for the time being. Four small cleaning pipes G are ranged
and fixed longitudinally in the centre between the two rows of straining
"cuts" or slits 6 along each side of the strainers A with a row of short
slits G¹ exactly opposite the slits 6 in the strainer; the pipes G being all
connected at their ends, by the pipes G2 of each strainer, and arc con-
nected and supplied by the branch pipes Gu from any convenient
main pipe leading from a steam boiler or from a pressure supply or flow
of water, all so that by opening a hand cock or valve on the said branches
or main pipe when required jets of steam or of water (as the case may
be) are made to flow out of the slits G' of the pipe G on to and along the
outside of the straining slits 6 so as to clean off any "knots" or dirt
which may have stuck or collected in the straining slits by suction of
the piston.
Referring to the general arrangement shown in Figures 1 and 2, two
of these strainers A. (described and shown in reference to Figures 3 to 7,)
are mounted and fixed in their respective vats a, in the same axial line, so
as to be worked by the same plunger or piston rod D', the piston D of the
inner strainer being fixed to the body or centre of the rod D¹ by a screw
nut on each side, while that of the outer one is fixed on the extreme end
of the rod D', and fixed by a single screw nut to it. Two of these duplex
constructions of strainers A, A', and their vats a, a, are arranged at such
a level that the pulp will flow from the bottom of their conducting
spouts and channels into the top of a second or front set of vats a", a²,

page_text: and their strainers A", A³, ranged essentially the same as the first set
but on the lower level, as indicated in Figure 1. The two piston rods D¹.
of each of these sets of strainers are actuated by their duplex crank
shafts d, d', placed at their respective levels of the rods and to one side at
right angles to them, each crank d", d, being connected to its respective
piston rod D' by a connecting rod and parallel guide not shown in the
Drawings, but indicated by a red centre line at d. Each vat a is fitted
with a discharge valve c in the bottom at one end opened inwards by a
hand rod when desired for drawing off the thick pulp, "knots," and
dirt which does not pass through the strainer but being heavy falls.
to the bottom of the vat. Instead of this arrangement of discharge valve.
shown in Figures 3 and 5, any other equivalent arrangement of hand.
cock or sluice may be employed. The two sets of strainers A, A', and
A", A, ranged in their vats a, a¹, and a", a³, have three main con-
ducting channels or spouts c, e', ff, which conduct the strained pulp
down the centre from the discharge valves E of the adjacent ends of the
strainers A and from the outer end valves E of the strainers down each
side direct into the delivery "hog" vat j in front from which the strained
pulp is delivered over the open spout or mouth in the usual manner
on to the paper-making machine from a revolving shaft of which a
motion is taken in the usual manner to actuate the hog for agitating
the pulp.
The action and mode of straining paper pulp by this new or improved
apparatus herein so far described, consists in feeding the crude prepared
pulp ready for straining into either of the first vats a or a" of each set
at the different levels or into both, according as desired, regulating the
stream of pulp by a cock, valve, or sluice on the inlet ducts, so as to
keep the strainers A all well covered over (as indicated in Figures 1
and 3,) and to suit the rate of suction and motion of the pistons D as
they recede from either end of the vat, so as to draw or strain the pulp
in through all the slits 6 in the four sides A°, A³, of the strainer behind
the piston D throughout its "stroke" by the revolution of their crank
shafts and cranks d, d, d", d², driven by any ordinary motor or driving
gearing or mechanism. The unstrained pulp z fed into the long trans-
versely ranged outer open vats a or a" is drawn through the straining
slits into the strainers A or A", while the piston D is receding from
the one end to the other, and on its return stroke forces the strained
pulp through the end valves E, which are but slightly loaded behind by
their springs E¹ into the ducts g and main channels e, f, which conduct
2

page_text: it, as before referred to, into the delivery vat; containing the agitating
"hog". Instead of the cranks d", d, on the crank shafts d, d, for work-
ing the plunger or pistons rods D'; eccentrics or cams may be used, or the
piston rods D' may be actuated direct from the pistons of reciprocating
motive-power engines. The conducting ducts e, e', and channels g, f,
are so arranged that any one of the strainers A may be shut off from these
main channels e, f, by closing the supply and discharge sluices e¹¹, e²,
h, h,, g, and then stopping its action by uncoupling the connecting
rod between its piston rod D¹ and crank d", d³, or removing a piston
from its rod for the purpose of cleaning or repairing a strainer or any of
its parts when desired, and yet allow all the other strainers to continue
to work and supply the paper machine, so that it may not require to
stop in consequence of anything going wrong at one or two of the single
or double arrangements of these new or improved strainers and arrange-
ments of their vats and conducting channels. The valves E at the
adjacent ends of the strainers A (Figures 1 and 2) discharge the strained
pulp into the main channel e, e¹, and the valves E at the outer ends
discharge it into the close ducts g, fitted with sluices g' leading into the
main side channels f, f', which sluices g' are either opened or shut
according as their strainer is at work or stopped, and the three main
conducting channels e and f, f, lead into a main channel h between the
first and second set of vats and strainers A, A', a, a, and A", A², a", a³,
respectively fitted with sluices h', opened when required to feed the pulp
from the first set of strainers to the second for a second straining, when
the sluices e" and " in the channels e, f, would be closed and the
sluices opened; and when the front strainers and vats A', a', and
A', a³, of both sets are at work, they are either fed with the crude pulp
from the vats behind them a and a respectively through the ducts i
and their sluices , ", or with crude prepared pulp direct as into the
first vats from the same source of supply as desired; and when the front
set of strainers only is at work the sluices e", f", and "; are closed and
the crude prepared pulp to be strained is fed in over the top of the
vat a". Thus the strained pulp from either or both of the highest set
of strainers A, A', which may be at work, can be led direct forward to
the delivery vat j, either independently or in conjunction with that from
either or both of the front strainers A", A, or the strained pulp from the
first set of strainers may be passed and strained through the second set
of strainers, all as described, in which latter case the straining slits or
cuts in the back set of strainers would be made wider than those in

page_text: the second or front set of strainers, so as to form a preparing and "knot":
destroying strainer, or set of strainers to the front set as finishing
strainers, or any of these new or improved strainers might be fitted up
in this manner with wider slits as a preparing and "knot" destroying
strainer to the sets of strainers heretofore and usually employed. More
strainers A may be arranged in the same axial line than two, as
described, and have their plungers or pistons D actuated by the same
piston rod and with shorter strokes, when preferred. The straining
plates forming the sides or surfaces of these improved strainers may, in
some cases, be made of sheet metal, which would not corrode or injure
the pulp (instead of solid cast straining plates, as described, and as
usually employed,) and have the straining "cuts" or slits punched in
them in the sheet or web transversely at right angles to the motion of
the plunger or piston working within them, turned or formed in the
shape of a close long chamber or cylinder, strengthened on the outside
with surrounding and longitudinal feathers as a sustaining framework.
The vats and conducting channels may be made of wood in the usual
manner, or of wood lined with varnishes or thin plates of metal, which
would not corrode or strain the pulp, or formed of iron coated with tin
or other good metal which would not act on the pulp.
By these improvements a greater straining surface is obtained within
equal or less space, and a clearer and more uniform consistency and
stream of the strained pulp with greater freedom from " grass or pulp
"knots," which are more effectually broken up by the action of the
plungers or pistons crossing the straining slits at every return stroke,
and either breaking up the knots and drawing the broken fibres
through or forcing them back off the straining slits, all without throwing
a strain on the sides of the vats (as heretofore) from the suction and
discharge action of the piston, being all within the fixed and closed
strainer, which is more simple in construction and noiseless in its action
and less liable to derangement, and more easy of access for. repair all
generally than has been the case with most of the "jogging," shaking,
or revolving strainers heretofore in use for the like purpose.
Having thus particularly described the nature of our said Invention,
and the manner in which the same is or may be performed, we have
to state that we do not restrict ourselves to the precise details herein
described or delineated; but what we believe to be novel and original,

page_text: and therefore claim as the Invention secured to us by the herein-before
in part recited Letters Patent is,―
First. The construction, arrangement, and use of fixed strainers and
of their vats and channels, substantially in the new or improved manner,
and for the purposes herein described and shown in the accompanying
Drawings.
Second. The construction and use of a fixed strainer with a recipro-
cating double-acting plunger or piston working within it for the straining
of paper pulp, substantially as herein described and shown in the accom-
panying Drawings.
Third. The construction and use of this new or improved strainer, as
a first or coarse preparatory straining and "knot" breaking machine, for
other ordinary constructions of strainers heretofore in use, substantially
as herein-before described.
Fourth. The construction and arrangement of the vats and their
conducting channels, so that any number of the strainers may be used
while the others are shut off or out of action, to keep the paper-making
machine going with a supply of pulp, all substantially as herein described
and shown in the accompanying Drawings.
In witness whereof, we, the said Robert Nicholson Slight and
William Forrest Denholm, have hereunto set our hands and scals,
this Twenty-seventh day of May, in the year of our Lord One
thousand eight hundred and seventy.
ROBT. N. SLIGHT. (L.S.)
WM. F. DENHOLM. (L.S.)