Improvements in or relating to the Production of Stereotype Plates for Printing Purposes.
Year: 1890

page_text: Date of Application, 9th Sept., 1890-Accepted, 25th Oct., 1890
CUMIN LEIE DIECIFICATIVA.
Improvements in or relating to the Production of Stereotype Plates
for Printing Purposes.
We, JOHN WALTER OSBORNE of 212 Delaware Avenue, Washington in the District
of Columbia, Natural Philosopher and CARL EDELHEIM of 253/259 North Broad
Street, Philadelphia, State of Pennsylvania, Manufacturer, both in the United States
of America, 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 :-
This invention is related to several which have for their object the production of a
mould into or against which type-metal may be cast for the production of a stereotype
plate for printing purposes.
One of these methods, which is now largely employed, is known as the papier-
maché process, and this invention is designed especially to improve the method of
making matrices in accordance with that art. In practising the same it has hitherto
been the custom to take a number of sheets of thin paper of good quality, well covered
with a mixture of paste and whiting, and hacked by one or more sheets of stronger
paper pasted down upon the former, and to lay the whole (it being thoroughly
soaked and softened with moisture) upon the upturned face of the page or pages of
type to be reproduced; and then to beat, by strokes from a brush, this papier-
maché layer into contact with all the interstices and convolutions of the raised
letters, so as to fill every depression. When large forms are stereotyped,
substantially the same result as that got by the brush is reached, by causing a
suitable roller to traverse the wet matrix, while some elastic material is interposed
to stretch and indent the paper between the letters and spaces. The mould so
taken has been dried hitherto in a way which gave rise to no distortion or shrink-
age, by bringing the type, held in a suitable chase, and covered with the moulded
matrix, as described, under the platen, or follower of a screw press of simple
construction. Botween the platen and the wet paper on the type, one or more
thicknesses of woollen blanket or of a soft and open felt are placed, and the effect
of the screw pressure applied to this elastic stratum is to complete the work of the
brush or roller, by establishing the most perfect accommodation of the matrix to the
form. The next operation is to dry tho layer of paper, without removing it from
the form. This is accomplished by applying heat (generally steam heat) to the iron
table on which the form rests, and over which the platen is supported and controlled
by its screws. As the leat from below passes through the mass of type and reaches
the paper mould it heats the water in the paper to the boiling point and forces it
to escape and make its way through the blankets as steam. After a few minutes the
platen pressure may be removed, the form taken from the press and the dry paper
matrix lifted off, in a condition ready for the casting operations of the stereotyper,
which need not be considered in this Specification.
Although the paper matrix thus obtained is very satisfactory as far as its quality
is concerned, the length of time required for its production is sometimes much
longer than is desirable, and one of the objects of this invention is to shorten that
time by hastening materially the drying process. It is often necessary in printing
offices to start printing at a precise hour of the day or night as the case may be,
and also, to continue the setting of type up to the last moment before such start, so
that a gain of four or five minutes in the time required for stereotyping would
frequently have much value.
The drawings forming part of this Specification illustrate certain forms of
apparatus adapted for working this process, and are as follows:-
Figure 1 represents, in side elevation and partly in section, a press like that

page_text: generally used for making matrices, but modified for this procuss; and a form on
its table ready to go under the platen.
Figure 2 is a plan view of the same without the form.
Figure 3 gives a plan view of a different kind of platen with an enclosed
chamber.
Figure 4 is a side elevation of the same.
Figure 5 is a vertical longitudinal section of the same platen.
Figure 6 shows, in plan, the face plate of the platen, and the distribution of its
perforations.
Figure 7 is an inverted plan of the platen, with the face plate removed, showing
ribs within the hollow portion.
Figure 8 exhibits, on an enlarged scale in vertical section and elevation, a
portion of a form with matrix and blankets ready to receive the platen pressure.
Figure 9 illustratos, in section, a supplemental face plate made use of io snit a
small form.
The construction of presses used in making papier-maché matrices is well known.
and is substantially represented in Figures 1 and 2. On the bed 10, which is heated
by a circulation of steam, the pages of type 12 are placed, face up, and properly
locked in a chase, (see also Figure 8). Upon these the pasted paper sheets 11 are
beaten down by the brush and are then covered with two or more thicknesses of
blanket or open felt 16. The whole is then pushed beneath the platen 18, which is
brought down upon the blankets by means of the screw 20. Under the old system,
the form remained in this position till the wet paper was dried, by reason of the
direct steady hent imparted to it from the steam-heated table. The temperature of
the latter may be easily raised considerably above 212 degrees F., and as the mass
of type is a good conductor, the drying was effected by boiling away the water
contained in the several sheets of paper forming the inatrix. The operation of
drying in this way is prosecuted at a disadvantage, because the vapour from the
water in the paper and paste has to overcome much resistance to get away, and to
force itself, in fact, through the blankets by virtue of its own elasticity; while its
generation, in the first instance, is also much impeded by reason of the slow diffusion
of water vapour in an atmosphere like itself, a physical fact that is true of all
gaseous bodies.
The difficulty of drying the matrix is overcome in great part at least and the time
required therefor lossened by modifying the apparatus as shown in Figures 1 and 2.
In those views of the press used, the platen 16 is perforated over the most of its
surfaco by small round holes 22, at equal distances apart. These facilitate the
drying of the paper under the influence of steady heat applied as already described,
because the provision so made for the escape of the elastic steam shortens the
journey the water has to make from the paper to the external air. But the time
required may be still further lossoned, by directing currents of air from a fan or
other blower, down upon the upper surface of the platen, as from the tubes 24, which
are connected with some source of air at low pressure. By such additional means,
the escaping vapour is swept away as fast as it is formed and its diffusion
promoted.
In Figures 3, 4, 5, 6 and 7, apparatus is shown which puts the practice of this
method into still more practical shape. Theso figures represent different views of a
peculiarly constructed platen, which, substituted for that of an ordinary drying press,
accomplishes all that the old platen accomplished, as far as the efficient and positive
application of pressure is concerned, and much moro in other respects. This platen
consists of a hollow box of metal, made (as here designed) in two parts and bolted
together. The upper part 26, with which the screw 20 is connected, may be
described as a rectangular bell-shaped vessel, strengthened by ribs 27, inside; while
the lower part 28, which forins the face of the platen, is a plate screwed to the flange
on 26, by the tap-bolts 30. The face-plate 28 is perforated with numerous holes 42,
and the completed structure has at 31 an opening through which the flexible tube 36
connects the chamber within the closed box with an air-pump or other suitable

page_text: blower. The hose 36 may have either a current of air sent through it to the
platen; or, an exhaust in the latter may be maintained by continuously drawing the
air out in the contrary direction through the same tube. Each of these methods of
using the apparatus shown, will shorten very materially the time required to dry the
matrix, but the former adapts itself well to other improvements on the established
practice, and will be first considered.
When the type 12, with its coverings, is in place under a platen like that described,
and subjected to the necessary pressure, the matrix would dry spontaneously without
beat, if sufficient time were allowed. This is in fact (using the old platen) the
recognized course which should be followed when a paper mould from a wood-cut
is required. Whatever the time may be in such a case (and it will vary greatly
according to the size of the form) it will be much shortened if ordinary dry air be
blown into the platen through the tube 36. This result is due to the fact that the
evaporation of water (or any other fluid) is very much more rapid, at any given
temperature, when it takes place into an atmosphere differing from itself in
constitution, than when the water is enveloped in its own vapour. When air is blown
into the hollow platen, the holes 32, being closed only by the porous blanket 16,
the air, under very little pressure, permeates the blankets and finds its way rapidly
to their edges. In doing so it constantly renews over the wet matrix a foreign
atmosphere for the water vapour to diffuse into, according to the well-known law,
and sweeps away all such water vapour as it is formed. Under such circumstances,
the cold paper process may be well applied to wood-cuts without injuring them, and
without excessive loss of time; for the rate of evaporation will depend essentially
upon the quantity of air at low pressure which passes over the matrix, and that is
thoroughly under control. As will be seen from an examination of Figures 5
and 6, the face-plate, 28, is abundantly supplied with holes ihrough which the air
escapes into the porous blankets, and through them till it reaches the moist paper,
where it is necessarily deflected towards the edges of the form. In this way the
continuous movement of a stratum of air upon and parallel to the back of the
matrix is maintained till all its moisture is removed, the currents through the plate
reaching all parts of the same.
If now the table on which the masses of type rest is made hot by steam under
pressure, the heat passing through the type-metal will boil the water in the matrix
and drive it off in the form of steam, which as before, is instantly taken up and
removed by the air currents with a great acceleration in the rate of drying as the
result. In the method which is now common, the steam so formed is allowed to
accumulate and force its way, and the dissipation of the water is, therefore, much
slower.
To still further hasten the drying of the matrix while it is under the platen pressure,
the air which is blown through the tube 36 is heated and so the maximum of rapidity
gained. To whatever extent the injected air may be heated, its avidity for moisture
will be increased, so that air, which in cold weather would be regarded as very damp
and unfitted for drying purposes, may, by simply raising it in any way to a summer
warmth, become relatively, and for all practical purposes, exceedingly dry. But when
the hot air used in this process at low pressure is raised to 212 degrees, or above that
temperature, and is driven at the same time rapidly over the wet surface of the
matrix, already made hot from below, the best possible conditions for drying are
established.
The blankets used in this method should be such as not to impede the transit of the
air too much, and this can be easily prevented by using suitably woven or felted
material; for the lower the pressure is on the air blown into the hollow platen, the
greater its avidity will be for water in the gaseous form; according to a well-known
physical law.
The means best adapted for heating air, and so rendering it serviceable for the purpose,
need not be discussed in this specification, as they are very well understood; but when
the circumstances are especially favourable for reaching a high temperature (say 300
degrees, or upwards); it will be sometimes found advantageous to depend upon the

page_text: hot blast alone, and either not to heat the form at all, or to do so slightly, and sufficient
only to prevent condensation of water on the face of the type.
In connection with the foregoing it may he said, that a very important advantage
which this invention secures, independently of the saving in time, is the reduction to
a minimum of the injury done the type upon which the matrix is moulded. This
injury is well known and need not be discussed at length; it is generally regarded
as inseparable from the papier-maché process. It is Juo to the effect of frequent
heatings and coolings in altering the length of the type locked in the chase, and to
the conjoined results of high temperature, and pressure applied to the faces of the
same. At present, the only way of hastening the drying of the matrix when it is
in situ on the type, and forced into contact therewith by the screw and platen, is to
raise the temperature. This expands and softens the type-metal and cannot be safely
carried beyond a certain limit, probably about 300 degrees Fahrenheit. But in
following this invention, the operator may warm the type only high enough to prevent
condensation of evaporaled water upon it to an injurions extent, and then apply a hot
blast far above that named, indeed of any temperature that will not scorch the blankets.
The effect of the latter is to remove the water from the matrix with great rapidity,
but in doing so it cannot raise the temperature of the type above 212 degrees Fahren-
heit till all the water in the matrix is gone. As soon as that is accomplished, the
work is done and the form should be removed from the drying press before the hot
air has affected its temperature, which is then low. As a consequence, the injury to
type will he found small in amount.
As has been hereinhefore stated, this process may be successfully worked whether
the air be forced through the tube 36, into the platen, or drawn from the latter through
the same tube. In the latter case, the effect produced is identical in kind, that is, the
exhaust in the platen draws the air through the perforations 32, in the face-plate, and
to supply the deficiency the external air is forced by atmospheric pressure to enter the
pervious blankets at their edges and move in currents converging towards the middle
of the plate. In doing this, the air as before, presents to the back of the matrix,
whether the same bo hented or not, a constantly changing stratum of dry air into
which the vapour of water can readily diffuse, to be then immediately removed by the
exhaust blower or pump. This method has moreover the advantage that the reduction
of atmospheric pressure over the wet matrix promotes very efficiently the generation
of water vapour, causing the water to boil in fact at a temperature very much below
the usual boiling point if the attenuation be considerable. In gaining this advantage,
however, that of using very hot air has to be in part sacrificed, as it would not be easy,
though of course quite feasible, to give the air entering at the edges of the form a
temperature much above that of the warm room in which the work is carried on.
In Figure 6, the parforations in the face-plate through which the air is blown (or
drawn) into the blankets is shown. These perforations may be managed so as to give
practically the same rate of evaporation from all parts of the matrix at once. It is
evident that if the holes were equally distributed, this end would not be gained, for
there would be a reaction towards the centre of the form from all sides, and a
consequent stagnation of the air there. Accordingly, as shown in the drawing, the
closeness and size of the holes about that region are increased and thereby the quantity
of air passing through them is increased, whereby the reaction of air pressure from
the edges is overcome, and radial currents established. Were the plate perforated
about the centre only, then the corresponding part of the matrix under that region
would dry first, and there would be loss of time waiting for the edges which would
lag behind in consequence of the relatively moist atmosphere reaching them. It will
be seen that this evil is counteracted by the sparse distribution of smaller holes about
the outer edges of the form.
It is plain that if the plato 28 were perforated over its whole surface, it would have
to be removed and another one substituted for it, if a papier-mache matrix from a
small form were required, as the blankets would not close all the holes. In many
cases this trouble can be avoided by employing the loose supplemental face-plate
shown in Figure 9. This is the snuo size as the other and is pierced with holes 32,

page_text: to suit the form required. It is provided with a depression at the back which covers
all the holes in the attached face-plate 28, and has also the projections 38 standing up
at intervals. These are level with the edges. When in use, this plate is simply laid
upon blankets, with the side containing the depression upwards, and the platen is then
brought down upon the whole.
All that has been said relative to the distribution and size of the holes and the use
of supplemental face-plates applies equally well to those cases in which the lateral flow
of air over the matrix is determined by an exhaust as by a plenum within the hollow
platen.
In the foregoing it has been shown, that the substitution of a foreign atmosphere
of dry or warm air, for that more or less fully charged with moisture, which is in
contact with the damp matrix, is effected within the substance of the blankets and
after the same have been compressed by the pressure of the platen. It is important,
therefore, to employ blankets or their equivalents, such as mats of fibre, or of twisted
horse-hair, which are sufficiently elastic, not only on account of the capacity possessed
by such material to follow the damp sheet of stratified paper into the interstices of the
form and keep it there (which is an essential part of this process); but also to enable
it to maintain, under the mechanical platen pressure, that perviousness which is
requisite to admit of the transit of considerable quantities of air through its interstices,
without undue increase of pneumatic pressure. The conditions which affect this
matter are many and variable, the size of the form being one of the chief; but it is
evident that the perviousness of the elastic stratum can be increased or decreased by
proper selection of the substance employed, and by modifying the manner in which it
is wover or felted; or the number of layers laid one upon the other. It is also easy
to effect changes in this regard to suit particular cases by the interposition of non-
elastic substances pervious to air, such as pieces of wire gauze, or of thin closely
perforated sheets. By the judicious omployment of such, it is possible to use large
sized holes in the face-plate 28, without thereby releasing the necessary mechanical
pressure on any part of the form, or forcing the blanket up into such openings.
From the foregoing, it will be seen that many changes in the form and construction
of the apparatus described may be made without departing from the principles
involved in the improved method, or affecting its nature essentially. Also that
this invention retains all the advantages possessed by the old process as it is still
commonly practised; this being especially true of the flat and undistorted condition
of the matrix after it is dried. For, the contractive force which buckles and strains
a heavy sheet of paper or card-board while it is being rapidly, and therefore unequally,
dried, is exceedingly great, and can only be resisted by an opposing force which is
sufficient, if need be, to rupture the fibres of the paper. The pressure exerted by the
screw and platen on the papier-maché sheet is enough for this purpose, but it should
not be relaxed till the drying is completed.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what
we claim is:
1. The improvement in the art of making papier-maché matrices, which consists
in beating or otherwise forcing the wet sheet of stratified paper into the interstices
of the form; then pressing and holding it in intimate contact therewith by the
mechanical pressure of a platen, and then drying the matrix while so held, by passing
a current of air over the matrix, substantially as described.
2. The improvement in the art of making papier-maché matrices, which consists
in beating or otherwise forcing the wet sheet of stratified paper into the interstices
of the form; then pressing and holding it in intimate contact therewith by the
mechanical pressure of a platen; then heating said form from its under side; and
then drying the matrix while so held and heated by passing a current of air over the
matrix, substantially as described.
3. The improvement in the art of making papier-maché matricos, wbich consists in
beating or otherwise forcing the wet sheet of stratified paper into the interstices of

page_text: the form; then pressing and holding it in intimate contact therewith by the mechanical
pressure of a platen; then heating said form from its under side, and then drying the
inatrix while so held on the heated form, by passing a current of heated air over the
matrix, substantially as described.
4. The improvement in the art of making papier-maché matrices, which consists in
beating or otherwise forcing the wet sheet of stratified paper into the interstices of
the form; then pressing and holding it in intimate contact therewith by the mechanical
pressure of a platen; then heating said form from its under side, and then drying the
inatrix while so hold on the heated form by currents of hot air blown down against
its upper surface, substantially as described.
5. The improvement in the art of making papier-maché matrices, which consist in
benting or otherwise forcing the wet sheet of stratified paper into the interstices of
the form; then pressing and holding it in intimate contact therewith by the mechanien!
pressure of a platen; and then drying the matrix by currents of air urged against
the same in quantities gradually decreasing from the centro towards its edges,
substantially as described.
6. The improvement in the art of making papier-maché matrices, which consists in
beating or otherwise forcing the wet sheet of stratified paper into the interstices of
the form; then pressing and holding it in intimate contact therewith by the mechanical
pressure of a platen; and then drying the matrix while so held by deflected currents
of air impelled along its upper surface, substantially as described.
7. The improvement in the art of making papier-mnché matrices, which consists in
beating or otherwise forcing the wet sheet of stratified paper into the interstices of
the form; then pressing and holding it in intimate contact therewith by the elastic
pressure of a pervious elastic stratum compressed thereon by the pressure of a platen,
and then drying the matrix while 30 held and pressed, by passing dry air through said
siruium, substantially as described.
8. The improvement in the art of making papier-maché matrices, which consists in
beating or otherwise forcing the wet sheet of stratified paper into the interstices of
the form; then pressing and holding it in intimate contact therewith by the elastic
pressure of a pervious elastic stratum compressed thereon by the pressure of a platen;
ihen henting the form from its under side to about 212 degrees F., and then forcing,
against and along the upper surface of the matrix so held and heated and through
the compressed elastic stratum, a current of air heated to above 212 degrees F.
whereby the water in the matrix is speedily evaporated and removed, substantially as
described.
Dated thin 8th Jan of Santamber 1800
"