THE PROCESS OF BEATING
_Introduction._--The process of beating has for its object the complete
breaking down of the bleached pulp to the condition of single fibres,
and the further reduction of the fibres, when necessary, into smaller
pieces. The disintegration of the material is essential for the
production of a close even sheet of paper, and the amount of beating
required varies greatly according to the nature of the raw material,
and the class of paper to be produced.
The textile trade, on the other hand, depends on a raw material
composed of strong fibres, or of filaments characterised by great
length, and any processes of treatment which tend to reduce the length
of such fibres are carefully avoided, and it is therefore obvious that
fibres which are of no value for textile purposes can be appropriated
for paper-making.
_Condition of Fibres._--The great differences in the physical
characteristics and structure of the fibres employed for paper-making
suggest that the possible variations in the final product obtained by
beating are very numerous. This is a well-known fact, and it is further
to be noted that this mechanical operation brings about not merely
alterations of a physical order, but introduces some interesting and
important chemical changes.
Of the better-known materials linen, with an average fibre length of 28
mm., the structure of which lends itself to considerable alteration by
beating, is in marked contrast to esparto, the fibre length of which
is only 1·5 mm. If the process of beating a linen rag merely resulted
in the cutting of all the fibres of 28 mm. long into short fragments of
1·5 mm., there would be nothing remarkable in it, but the changes which
occur in reducing the long linen fibre to 1·5 or 2·0 mm. are of a far
more important character than this.
_Early Methods._--In the early days of paper-making the disintegration
of the half-stuff was effected by a true "beating" process, the rags
being subjected to the action of heavy stampers, which broke up the
mass of tangled fibre into a uniform pulp. The fibres for the most part
retained their maximum length in this operation, which was exceedingly
slow and tedious, though at the same time giving a sheet of paper of
remarkable strength.
The nearest imitation of these old-time rag papers is to be seen in
the well-known Japanese papers, which are extraordinarily strong. Some
of these the writer has examined in order to determine the length of
the fibre. The sheets when held up to the light appear "cloudy" and
"wild" owing to the presence of the long fibres, which have only been
separated or teased out by the primitive methods of beating used, and
not completely disintegrated.
_Conditions of Beating._--About A.D. 1700 there began a great epoch
in the history of paper-making. With the invention of the Hollander
engine about A.D. 1670, the process of disintegration was greatly
hastened, because it was possible to reduce the half-stuff much more
readily. The substitution of the idea of plain "beating" by a principle
which combined the gradual isolation of the individual fibres with a
splitting up of those fibres lengthwise and crosswise was not only an
advantage in point of economy of time and cost, but also a material
advance in the possibilities of greater variations in the finished
paper.
The conditions of the process of beating carried out with a Hollander
permit of considerable alteration, so that these changes in the fibre
are not surprising when properly understood. In fact, it is now
conceded that a close study of the theory and practice of beating
is likely to bring about still more remarkable improvements in this
important department of the paper-maker's work. The quality and
character of the paper made may be varied with--
(1) The origin of the raw material, _e.g._, rags, esparto, or wood;
(2) The condition of the material, _e.g._, old or new rags, green or
mature esparto, mechanical or chemical wood pulp;
(3) The time occupied in beating, _e.g._, four hours for an ordinary
rag printing and twelve hours for a rag parchment;
(4) The state of the beater knives, _e.g._, sharp tackle for blottings
and dull tackle for cartridge papers;
(5) The speed of the beater roll, also its weight;
(6) The rate at which the beater roll is lowered on to the bedplate;
(7) The temperature of the contents of the engine.
_The Beater Roll._--If the beater roll is fitted with sharp knives, and
this is put down close to the bedplate quickly, the fibres are cut up
short, and they do not assimilate the water. If the roll is fitted with
dull knives, or "tackle," as it is sometimes called, and it is lowered
gradually, the fibres are drawn and bruised out without being greatly
shortened. In this condition the stuff becomes very "wet," or "greasy,"
as it is termed. The cellulose enters into association with water when
beaten for many hours, and the pulp in the beating engine changes into
a curious greasy-like mass of a semi-transparent character. Rag pulp
beaten for a long time produces a hard, translucent, dense sheet of
paper. Flax thread beaten 48 to 60 hours is used in practice for the
manufacture of gramophone horns and similar purposes.
Soft porous papers like blottings, filtering papers, heavy chromos,
litho papers, antiques, light printings, are made from pulps which are
beaten quickly with the roll put down close to the bedplate soon after
the stuff has been filled in.
With strong, dense, hard papers, such as parchments, banks,
greaseproofs and the like, the pulp is beaten slowly and the roll
lowered gradually.
The nature of the pulp and the time occupied in beating are also
important factors in producing these different papers, three to four
hours being ample for an ordinary wood pulp printing, whereas a wood
pulp parchment requires seven to eight hours.
_Beating Pulps Separately._--The use of esparto and wood pulp in
conjunction with one another, or blended with rag, has introduced new
problems into the question of beating. Perhaps the most important
of these is the advisability of beating the pulps separately and
eventually passing them through a mixer of some kind before discharging
into a stuff chest. The necessity for differentiating the amount of
beating is already partly recognised when very dissimilar pulps, such
as strong rag and esparto, are blended, but the whole subject ought to
be carefully studied by the paper-maker and investigated on its merits
from the standpoint of "beating effects," apart from questions of cost
and expediency. The former fully understood and exhaustively examined
by practical tests would of course only be developed if proved to be
advantageous.
The field of research in this direction has not yet been seriously
explored. With the enormous consumption of wood pulps of varying
quality made from many different species of wood by several processes,
there is ample room for interesting and profitable enquiry,
particularly as the types of beating engine are so numerous. The
effects produced by the Hollander, the refiner, the edge runner, the
stone beater roll, and other mechanisms, are all of varying kinds.
EFFECT OF PROLONGED BEATING.
The importance of a knowledge of the precise effects produced by the
beating of pulp cannot be emphasised too much, and any contributions to
the subject along the lines of special research will be welcomed by all
students of cellulose.
[Illustration: FIG. 46.--Cotton Pulp beaten 8 hours.]
Some experiments were conducted by the writer in 1906 with cotton rags,
in order to determine the results obtained by beating the pulp for a
prolonged period under exact and specific conditions.
[Illustration: FIG. 47.--Cotton Pulp beaten 37 hours.]
The cotton rags, of good quality, were boiled with caustic soda in
the usual way for six or seven hours, at a pressure of 15 to 20 lbs.,
washed and partially broken down in the rag breaker, and finally
bleached, made into half-stuff, and then transferred to a Hollander
beating engine.
The particular conditions specified for the beating operation were that
the beaterman should manipulate the pulp according to his usual routine
for the manufacture of the paper which he was accustomed to make from
these rags. In this case the routine process meant beating for eight
hours, by which time the pulp was ready for the paper machine. In the
ordinary course the pulp would be discharged into the stuff chest, and
converted into a strong, thin, bank paper.
During the prolonged beating the pulp became very soft and "greasy,"
and when made up into sheets the paper as it dried exhibited remarkable
differences in shrinkage, the dry sheets obtained from pulp beaten
thirty-seven hours being much smaller than those obtained from pulp
beaten only four or six hours. The actual shrinkage is shown in the
following table:--
------+---------------+----------------+--------------+----------
| | | Relative |
Hours.| Area of Sheet.| Loss of Area. | Areas. |Shrinkage
| Sq. mm. | Sq. mm. | Deckle 100 |per cent.
------+---------------+----------------+--------------+----------
0 | 26,384·0 | -- | 100·0 | --
4 | 26,076·0 | 308·0 | 98·9 | 1·1
6 | 25,520·1 | 863·9 | 96·7 | 3·3
8 | 25,160·0 | 1,224·0 | 95·4 | 4·6
10 | 24,794·8 | 1,589·2 | 93·9 | 6·1
13 | 24,467·4 | 1,916·6 | 92·8 | 7·2
15 | 24,215·2 | 2,168·8 | 91·8 | 8·2
17 | 24,024·0 | 2,360·0 | 90·9 | 9·1
19 | 23,616·2 | 2,767·8 | 89·6 | 10·4
21 | 23,616·0 | 2,768·0 | 89·6 | 10·4
23 | 23,535·7 | 2,848·3 | 89·3 | 10·7
25 | 23,329·9 | 3,054·1 | 88·5 | 11·5
27 | 22,920·5 | 3,463·5 | 86·9 | 13·1
29 | 22,831·2 | 3,552·8 | 86·5 | 13·5
31 | 22,492·9 | 3,891·1 | 85·3 | 14·7
33 | 21,917·2 | 4,466·8 | 83·1 | 16·9
35 | 21,226·1 | 5,157·9 | 80·5 | 19·5
37 | 20,778·8 | 5,605·2 | 78·8 | 21·2
------+---------------+----------------+--------------+----------
If these results are plotted in the form of a curve the relation
between the period of beating and the shrinkage in area is clearly
shown. For the first twenty hours the shrinkage is proportional to the
period of beating, after which the curve assumes an irregular shape,
showing a tendency for shrinkage to proceed at a faster rate.
_Weight and Substance of the Paper._--The shrinkage of the paper after
prolonged beating indicates a closer and denser sheet, so that for
papers of equal thickness the weight per unit area was much greater in
the case of the pulp beaten for the full period. The results obtained
are very interesting, and the following summary for a few of the
readings obtained will serve to show the alteration effected.
----------+--------------+--------------+------------+---------------
| Weight of | Thickness of | Grams per | Lbs. per ream
Hours. |20,000 sq. mm.| Sheet. | sq. metre. | 480 sheets,
| Grams. | mm. | | 20" × 30".
----------+--------------+--------------+------------+---------------
Class A | | | |
8-10 hrs. | 1·875 | ·183 | 93·75 | 38·23
| | | |
Class B | | | |
19-21 hrs.| 2·043 | ·189 | 102·15 | 41·65
| | | |
Class C | | | |
33-35 hrs.| 2·203 | ·189 | 110·15 | 44·93
----------+--------------+--------------+------------+--------------
_Sizing and Glazing Effects._--The behaviour of the waterleaf paper
after sizing and glazing gave some interesting results. In the first
place, the effect of the altered density of the paper is strikingly
shown by the amount of the size absorbed. Certain selected sheets
were passed through a solution of ordinary gelatine in the usual way,
and subsequently dried. The amount of gelatine absorbed differs in a
remarkable degree, as shown in table.
_Tensile Strength of the Paper._--It is interesting to note that the
tensile strength of the waterleaf papers appears to remain fairly
constant throughout the whole period of beating. But this uniformity is
greatly altered by the operations of sizing and glazing.
PERCENTAGE OF AIR-DRY GELATINE ABSORBED BY THE WATERLEAF SHEETS.
----------+-----------------------------------+---------
| Percentage of Size absorbed. |
Hours. +-----------+-----------+-----------+ Mean.
| 1st Trial.| 2nd Trial.| 3rd Trial.|
----------+-----------+-----------+-----------+---------
8 | 5·5 | 6·0 | 6·2 | 5·9
10 | 5·4 | 6·8 | 6·5 | 6·2
19 | 3·8 | 5·0 | 4·5 | 4·4
21 | 4·8 | 3·9 | 4·6 | 4·4
33 | 2·7 | 1·7 | 2·4 | 2·3
35 | 2·4 | 1·9 | 1·7 | 2·0
----------+-----------+-----------+-----------+---------
These results are rather remarkable. The prolonged beating does not
seem to have affected the tensile strength of the waterleaf, and the
practical loss of strength which actually occurs in the more completely
finished paper does not manifest itself until after the sizing process.
The importance of the gelatine as a factor in the ultimate strength is
thus clearly and strikingly demonstrated.
TESTS FOR STRENGTH ON ORIGINAL WATERLEAF PAPER.
--------------+--------------+--------------
|Mean result of|Mean Strength
Hours. | Readings. |of the Paper.
| Lbs. | Lbs.
--------------+--------------+--------------
8 | a 14·1 | 12·1
| b 10·1 |
10 | a 15·4 | 13·2
| b 10·9 |
19 | a 16·5 | 14·0
| b 11·4 |
21 | a 15·2 | 14·0
| b 12·8 |
33 | a 13·4 | 12·4
| b 11·4 |
35 | a 14·5 | 13·6
| b 12·7 |
--------------+--------------+--------------
TESTS FOR STRENGTH ON PAPERS, SIZED ONLY.
--------------+--------------+--------------
|Mean result of|Mean Strength
Hours. | Readings. |of the Paper.
| Lbs. | Lbs.
--------------+--------------+--------------
8 | a 22·7 | 20·0
| b 17·3 |
10 | a 28·5 | 23·2
| b 18·0 |
19 | a 22·5 | 21·0
| b 19·5 |
21 | a 26·0 | 21·7
| b 17·5 |
33 | a 15·0 | 15·0
| b 15·0 |
35 | a 14·2 | 15·3
| b 16·5 |
--------------+--------------+--------------
TESTS FOR STRENGTH ON PAPER SIZED AND GLAZED.
--------------+--------------+--------------
|Mean result of|Mean Strength
Hours. | Readings. |of the Paper.
| Lbs. | Lbs.
--------------+--------------+--------------
8 | a 25·8 | 23·6
| b 21·4 |
10 | a 28·4 | 23·6
| b 18·9 |
19 | a 27·0 | 22·9
| b 18·9 |
21 | a 24·9 | 22·7
| b 20·6 |
33 | a 16·1 | 15·2
| b 14·4 |
35 | a 17·5 | 16·2
| b 15·0 |
--------------+--------------+--------------
It may also be noticed that the strength of the finished paper after
twenty hours' beating, as in class B, is equal to that of the paper
after nine hours' beating, as in class A. This is curious, especially
in view of the fact that the percentage of gelatine in the papers of
class B. is only 4·4 per cent. as against 6·0 per cent. in class A.
The relation of the percentage of gelatine to the period of beating
thus becomes a matter of interest, and well worth investigation. The
figures are suggestive of further experimental research along definite
lines.
[Illustration: FIG. 48.--Plan and Sectional Elevation of a "Hollander."]
_Developments in Beating Engines._--Since the introduction of the
Hollander beating engine, about A.D. 1670, other types of beater almost
too numerous to mention have been devised to supersede it, but the fact
remains that the principle of the original Hollander and its general
design are still adhered to in the engines used by paper-makers for
high-class work.
The alterations and improvements which have taken place during the
last fifty years relate chiefly to the modifications naturally arising
from the introduction of fibres not requiring such drastic treatment as
rags.
The machines now in use for reducing half-stuff to beaten pulp ready
for the paper machine may be classified as follows:--
(1) Beaters of the Hollander type, in which the circulation of the pulp
in the engine and the actual beating process are both effected by the
beater roll.
(2) Beaters of the circulator type, in which the movement of the pulp
is maintained by a special contrivance, and the beater roll used only
for beating.
(3) Beaters of the stone roll type in which the roll and bedplate are
either or both composed of stone, granite, or similar non-metallic
substance.
(4) Refiners, containing conical shaped beater rolls working in a
conical shell fitted with stationary knives.
[Illustration: FIG. 49.--Beating Engine with Four Beater Rolls.]
_The Hollander._--This beating engine in its simplest form consists of
an oval shaped trough, divided into two channels by a "midfeather,"
which does not, however, reach completely from one end to the other.
In one of the channels the bed of the trough slopes up slightly to the
place where the "bedplate" is fixed. The bedplate consists of a number
of stout metal bars or knives firmly fastened into an iron frame, which
lies across this channel. The beater roll, a heavy cast-iron roll
provided with projecting knives or blades arranged in clumps of three
around the circumference, and supported on bearings at each side of the
engine, revolves above the bedplate with the knives adjusted to any
required distance from it, the raising or lowering of the beater roll
for this purpose being effected by the use of adjustable bearings.
The bed of the trough behind the beater roll rises sharply up from the
bedplate and then falls away suddenly, as shown in the diagram, forming
the "backfall."
When the engine is in operation the mixture of water and pulp is drawn
between the knives and circulated round the trough. The material is
disintegrated into fibres of the required condition, discharged over
the backfall, and kept in a state of continual circulation, and the
beating maintained until the stuff has been sufficiently treated.
The dimensions of the engine vary according to the capacity, which is
usually expressed in terms of the amount of dry pulp the beater will
hold, and the following figures may be taken as giving the average
sizes:--
-----------------+----------------+----------------
-- | 2 cwt. Engine. | 5 cwt. Engine.
-----------------+----------------|----------------
Length | 11 ft. 0 in. | 16 ft. 0 in.
Width | 5 ft. 6 in. | 8 ft. 0 in.
Depth (average) | 2 ft. 3 in. | 2 ft. 9 in.
Diameter of roll | 3 ft. 6 in. | 3 ft. 6 in.
-----------------+----------------+----------------
Sundry modifications in the form and arrangement of the beater
have been tried from time to time. In 1869 Granville patented the
substitution of a second beater roll in place of the stationary
bedplate for the purpose of hastening the operation. Repeated attempts
have been made to construct a beating engine with two or more rolls,
but it is evident that such a device could hardly succeed, since it
would be impossible to ensure proper adjustment of the rolls, and in
that case one roll might be doing all the work.
The first machine of this type was patented in 1872 by Salt. Similar
beaters were devised by Forbes in 1880, Macfarlane in 1886, Pickles in
1894, who proposed to use three rolls, and Partington in 1901. Hoffman
describes a beating engine which was working in America containing four
rolls, as shown in the diagram.
_The Umpherston._--A notable modification of the Hollander, having
an arrangement by which the two channels of the engines are placed
under one another, and one which is largely used for fibres, is the
Umpherston. Several engines differing in detail, but embodying the same
principle, have been built in imitation of this one.
[Illustration: FIG. 50.--Umpherston Beater.]
Bedplates of large working surface were first tried in England by Cooke
and Hibbert, in 1878, but in practice it has been found that no serious
deviations from the narrow type of plate are of much value. As a matter
of fact it is held by some paper-makers that one or two knives would
be sufficient if they could be relied on to keep true and in proper
adjustment.
_The Circulating Type of Beater._--The addition of some device for
keeping the pulp in circulation apart from the action of the roll
has received considerable attention. The early experiments in this
direction with the Hollander led ultimately to the construction of the
engine of the circulator type mentioned in class 2.
[Illustration: FIG. 51.--Section of Umpherston Beating Engine.]
Thus, in 1872, Nugent patented a special paddle to be used in the
Hollander, by which the pulp in the trough of the beater was impelled
towards the roll. Many other plans were tried for this purpose, and
details can be seen in the List of Patents (see page 192).
The introduction of the beaters with special means of circulating the
pulp was found to be of the greatest service in the treatment of stuff
like esparto and wood pulp, since these materials did not require the
drastic measures necessary with rag pulp. In 1890 several engines of
this class were being adopted, amongst which may be mentioned Hemmer's,
Reed's and Taylor's. The pulp discharged from the beater roll was drawn
through an independent pipe or channel by means of an Archimedean
screw, or a centrifugal pump.
_Stone Beater Rolls._--The substitution of stone for metal in the roll
and bedplate of the engine brings about some remarkable changes in the
nature of the beaten stuff. The fibre is submitted to the action of
rough surfaces rather than that due to the contact of sharp edges, with
the result that the disintegration is much more rapid, and produces
a "wet" working pulp suitable for imitation parchments and similar
papers. The latest materials used for this purpose are basalt lava
stone in Germany, and carborundum in America.
[Illustration: FIG. 52.--Nugent's Beating Engine with Paddles for
Circulating the Pulp.]
Care is necessary in the manipulation of these beaters to prevent
fracture of the stone parts. In the Wagg Jordan engine this danger is
materially reduced by the construction of the working parts.
_Refiners._--In these engines the beater roll is a conical shaped drum
carrying the knives, which revolve inside a conical shell completely
lined with fixed knives. The fibres are thus cut up to the desired
length, but before discharge from the engine they pass between two
circular discs, one stationary and the other revolving in a vertical
position. The effect of the discs is to tear or bruise the fibres
rather than to cut them.
The refiner is best employed to clear or brush out the mass of pulp
after a certain amount of preliminary treatment in the beater, as the
refiner cannot produce the effects obtained by actual beating as in the
Hollander.
[Illustration: FIG. 53.--A "Tower" Beating Engine with Centrifugal Pump
for Circulating Pulp.]
_Power Consumption._--The long treatment required to thoroughly pulp
a strong material demands a great amount of power. Engines differ
considerably in their power consumption, and comparisons are frequently
made in terms of the power required to beat a given weight of pulp.
But this is not always a true criterion of efficient work. Some types
of beater are suitable for producing certain results, and the mere
substitution of a beater consuming less power is worse than useless
unless it can be shown that the same effects are being obtained. The
efficiency of the Hollander for the beating of rag pulp, in spite of
the high power consumption, is a case in point.
[Illustration: FIG. 54.--Working Parts of a Modern Refining Engine.]
With this factor properly considered, the power required for beating
becomes an interesting study. Many detailed experiments have been
published from time to time, the most recent being those described by
Beadle.
PATENTS TAKEN OUT IN CONNECTION WITH BEATING ENGINES.
1855. PARK (1170).--A small steam engine was attached to the shaft of
the beater roll, so that it could be driven direct.
1856. KINGSLAND (2828).--A form of refiner in which the pulp was beaten
by a vertical disc rotating in an enclosed case.
1860. JORDAN (792).--A machine devised for mixing size with pulp, made
like a conical refining engine, the rubbing surface being provided with
teeth or cutters.
1860. JORDAN (2019).--An engine of the refiner type, constructed with a
conical drum rotating in a conical casing. The knives at the larger end
of the drum are placed closer together than those on the smaller end.
1863. PARK (1138).--Two beaters placed side by side are driven by one
steam engine placed between them, the operations being so timed that
one rag engine is used for breaking while the other is finishing.
1864. IBOTSON (2913).--The pulp is passed continuously from one engine
roll to another, or from one part of a beater roll to another part of
the same roll through slotted plates.
1866. ROECKNER (140).--A beating engine of the refiner type with
conical drum and casing.
1866. BERHAM (3299).--A beating engine of the conical type with the
beater roll rotating vertically instead of horizontally.
1867. CROMPTON (482).--Device for raising the bars in the beater roll
as the edge of the plate wears away.
1867. WOOD (914).--Modification in the form of the beater bars (of
little importance).
1867. EDGE (3673).--The knives of the beater roll distributed at equal
distances apart all round the roll, alternated with strips of wood.
1869. GRANVILLE (1041).--Substitution of a second beater roll for the
stationary bed-plate, the knives being set spirally round the roller.
1869. NEWELL (2905).--Weight of the beater roll counterpoised to allow
of the exact regulation of the pressure on the stuff in the beating
engine.
1870. ROSE (997).--An intercepting plate fixed to the cover of the
beating engine which causes that part of the stuff which was usually
carried right round by the roll to fall back behind the backfall.
1870. BENTLEY AND JACKSON (1633).--A beater roll having the same width
as the engine, and provided with a cover fitted with a pipe which
conducted the material back to the front of the roll.
1871. PATTON (1336).--Bottom of beating engine curved in order to
prevent the stuff settling or accumulating at any portion of the
machine.
1872. SALT (1901).--A beating engine of usual type, but having two
beater rolls and two drum washers, one pair in each of the two channels.
1873. GOULD (769).--A curious engine with horizontal shaft having
a circular disc at the lower end, fitted with knives on the
under-surface, which are in contact with fixed knives lying at the
bottom of the vessel. The circulation of the pulp is effected by the
centrifugal force generated.
1873. MARTIN (3751).--A beating engine with two rolls in the same
trough, the first roll working in conjunction with a smooth surfaced
beating roll, the other being in contact with a bedplate of the usual
type, the object of the first roll being to partially disintegrate the
material without danger of choking.
1874. JOHNSTONE (3708).--A pulping engine in which the rubbing action
of two grindstones one upon the other is utilised as a means of beating.
1876. GARDNER (307).--A beating engine in which the beater roll is
conical in shape, working vertically in contact with the bottom of the
beating engine, which is also conical in shape, the engine itself being
circular.
1878. COOKE AND HIBBERT (4068).--The bedplate constructed in the form
of a circular segment with a much larger face than usual, and capable
of adjustment, the beater roll itself being fixed in the bearings.
1880. FORBES (692).--A long oval shaped beating engine divided into
three channels instead of two. In the two outer channels are placed
beater rolls and drum washers. The stuff discharged over the backfalls
from the two beating engines flows down the central channel and is
circulated by a special paddle constructed in such a manner as to
deliver the pulp in two equal streams into the outer channels to each
of the beater rolls.
1880. UMPHERSTON (1150).--An engine constructed with a passage below
the backfall so that the stuff circulates in a trough underneath the
beater roll, the object being to ensure more effective treatment and to
save floor space.
1883. AITCHISON (5381).--A beating engine of usual form, but with
the beater roll made conical in shape with the larger circumference
outwards, and the bedplate placed on an incline parallel with the
knives on the beater roll.
1884. MAYFIELD (2028).--The backfall of the beating engine is of
entirely different construction to the ordinary machine, for the
purpose of improving the circulation.
1884. HOYT (11177).--An engine resembling the Umpherston, but with a
larger roll, the diameter of which is equal to the full depth of the
engine, the backfall being in a line with the axis of the beater roll.
1885. JORDAN (7156).--Additions to the Jordan engine for admitting
water and steam to the engine as required.
1885. KORSCHILGEN (9433).--The beater roll made of stone or of metal
with a stone casing furnished with ribs or knives placed close together.
1886. HIBBERT (4237).--A beating engine fitted with an ordinary beater
roll, and having in addition a heavy disc rotating vertically, the
disc being fitted with knives on one surface which rotate in contact
with knives fixed on a stationary disc.
1886. KRON (9885).--A device for securing better circulation of the
pulp, the stuff leaving the beater roll being divided into two streams
which are brought together again in front of the roll.
1886. HORNE (10237).--A long rectangular vessel with a large beater
roll at one end, contrived so as to force the pulp leaving the beater
roll to pass down a partition separating it from the pulp going towards
the beater roll.
1886. MACFARLANE (11084).--An engine fitted with two beater rolls which
rotate in opposite directions, the stuff being mixed between them.
1887. NACKE (746).--A centrifugal circulating wheel rotating
horizontally in the centre of the beating engine is used in combination
with a parallel cutting disc.
1887. MARSHALL (1808).--A conical refiner having in addition at its
large end a pair of grinding discs fitted with knives and rotating
vertically.
1887. VOITH (6174).--An alteration to the covers of the beater rolls
which prevent stuff from being carried round the cylinder, and cause it
to pass over the backfall freely.
1890. HEMMER (17483).--A beating engine provided with a separate
return channel for the pulp, the circulation through the channel being
effected by a small centrifugal pump.
1890. A. E. REED (19107).--A beating engine in which the pulp
discharged over the backfall is delivered to the front of the beater
roll by a screw propeller.
1891. KARGER (11564).--A beater similar to the Umpherston, but provided
with a circulating roll fitted with radial projections which delivers
the stuff to the front of the beater roll.
1892. TAYLOR (7397).--A beating engine in which the beater roll
operates in a closed chamber above the vat full of pulp, the stuff
being continually circulated by a centrifugal pump which draws the
stock from the bottom of the vat and delivers it to the beater roll.
1892. ANNANDALE (9173).--A conical-shaped beating engine with the
beater roll rotating in a vertical position; the larger end of the cone
being downwards.
1892. UMPHERSTON (15766).--An addition to the beating engine arranged
so that two fixed bedplates are used instead of one.
1892. MILLER (15947).--A machine in which two fixed bedplates are used,
one below the beater roll and one above, the engine being fitted with
suitable baffle plates to ensure proper circulation.
1893. PEARSON AND BERTRAM (11956).--A special form of refining engine
in which the pulp is subjected to the action of discs rotating
vertically, the knives being arranged radially on the disc.
1893. CALDWELL (15332).--A rotary beating engine in which the beating
surfaces admit of accurate adjustment.
1894. CORNETT (945).--An outlet is fixed to the beater roll casing
close to the discharge from the bedplate, so that the roll is not
impeded by the weight of the pulp, which is subsequently pumped to the
front of the beater roll.
1894. SHAND AND BERTRAM (4136).--A beating engine similar to the
Umpherston beater in which the beater roll is raised up out of the pulp
and the circulation effected by means of a worm which delivers the pulp
to the front of the beater roll.
1894. PICKLES (20255).--A beating engine somewhat similar to an
Umpherston, but fitted with three beater rolls and bedplates.
1894. HIBBERT (25040).--A beating engine in which the pulp is beaten
between two discs rotating vertically, the pulp being brought between
the discs through the hollow shaft of one of the discs.
1895. BROWN (1615).--An engine in which the beater roll and bedplate
both revolve, but in opposite directions, and at different speeds in
order to draw out the fibres.
1895. SCHMIDT (24730).--A device by means of which the pulp discharged
from the beater roll is diverted into supplementary channels on either
side which come together again in front of the beater roll.
1900. HADFIELD (2468).--An adjustable baffle board passing through the
cover of the beater roll which prevents the pulp being carried round by
the roll, more or less.
1900. MASSON AND SCOTT (5367).--An improved form of Taylor beating
engine in which the chest of the engine is vertical instead of
horizontal.
1901. PARTINGTON (24654).--A continuous elliptical trough provided with
two beater rolls.
1902. PICARD (19635).--Improvements in the form of the propellers used
for circulating the material.
1902. POPE AND MULLEN (22089).--Improvements in propellers for
circulating the pulp.
1903. ANNANDALE (26012).--A new form of beating engine somewhat on the
principle of a steam turbine.
1905. BERTRAM (1727).--A beater similar to Masson's tower beater, but
in which a pair of reciprocating wheels fitted with projecting knives
are used instead of a centrifugal pump.
1907. WAGG'S JORDAN ENGINE (6788).--A conical refiner fitted with
specially arranged metal or stone knives.