Improved Machinery for the Production of Slabs of Plaster, Cement, or Composition.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improved Machinery for the Production of Slabs of Plaster, Cement,
or Composition.
I, RICHARD WILLIAM HITCHINS, of 16 South Street, Finsbury, London, E.C.
Plasterer, do hereby declare the nature of this invention to be as follows:-
My invention relates to apparatus for producing slabs of plaster, cement, or
composition, suitable for use in the construction of ceilings and walls, from plastic
material which is delivered in a continuous stream to, and compressed between,
endless travelling bands, and then cut off into suitable lengths.
The apparatus comprises a hopper within which works a screw conveyor for the
purpose of consolidating the plastic material and extruding it in a uniform and
continuous stream from a slit-like orifice into the space between the entering ends
of two endless travelling bands formed of canvas, wire netting, or the like. These
bands are of a width not less than that of the slabs to be produced and are so
stretched upon rollers that their adjacent or working faces are maintained parallel
and at a distance from one another approximately equal to the thickness of the
slabs to be produced.
The travelling bands are preferably arranged so that their adjacent or working
faces move horizontally over a series of rollers which serve the double purpose of
exerting pressure upon the material in its passage between the rollers and of
counteracting the tendency of the travelling bands to sag. Either or both of the
series of rollers may be adjustable so as to vary the distance between the faces of
the travelling bands, and the pressure consequently exerted upon the material in its
passage between them.
The slabs may be covered with canvas or other suitable fabric which is fed from
two rollers mounted respectively above and below the hopper orifice, and the
travelling bands are provided with projecting pins adapted to seize the webs of
fabric so that when the travelling bands are set in motion the webs are drawn in
between the bands and thus also carry along between them a layer of the plastic
material. The layer of plastic material on emerging from between the travelling
bands with the woven fabric embedded in each of its faces, is then cut off by méans
of a guillotine knife, into the required lengths.
In some cases, the slabs made in the manner described may, either before or
after they are cut up into lengths, be further consolidated by pressure between
metal plates, one of which may form an ornamental surface so as to produce a
pattern on the slab.
Dated this 10th day of Januar 1005
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.

page_text: Improved Machinery for the Production of Slabs of Plaster, Cement,
or Composition.
I, RICHARD WILLIAM HITCHINS, of 16, South Street, Finsbury, London, E.C.
Plasterer, 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 :—
My invention relates to a method of, and apparatus for, producing slabs of
plaster, cement, or composition, suitable for use in the construction of ceilings and
walls, and consists essentially in providing apparatus whereby the material is
continuously delivered in a plastic state so as to be received and compressed in a
uniform stream or layer between endless travelling bauds stretched upon rollers
which may also serve to spread and attach upon either or both of the surfaces of
the stream a strengthening web of woven fabric; the continuous sheet of plastic
material thus produced being subsequently cut off into predetermined lengths as
required.
The composition of the plastic materials to be used in the formation of the slabs
will vary according to the character and requirements of the work in which such
slabs are to be employed. Thus for example for common ceilings and cheap work
generally, I may use plaster of Paris in which is incorporated loose fibre such as
hair cocoa-nut fibre, wood-dust, wood-pulp, straw, hay, paper, or rags in small
fragments, or any other similar binding medium, and for such work it might not be
necessary to combine with or attach upon the surface of the slabs any special
strengthening material. In the case of better class work, however, it would be
desirable to spread and attach upon one or both surfaces of the slabs a continuous
web of woven fabric, the latter consisting usually of canvas, but, for fireproofing
purposes, preferably of galvanized or other wire netting or gauze. In the latter
case also it would be desirable to substitute for the binding media mentioned above,
an incombustible substance such as slag-wool, asbestos-fibre, or the like. For out-
door work I may use Portland or other cement, with or without the canvas or wire
netting and as a protective covering or remedy for damp walls I may employ as a
basis for the slabs a mixture of oils, varnishes, or the like, with suitable fibrous
material.
The apparatus is illustrated in the accompanying drawings, forming part of this
Specification, wherein
Figure 1 is a longitudinal side elevation and Figure 2 a plan of my improved
slab making machine.
Figures 3 and 4 are enlarged detail views shewing respectively in longitudinal
and transverse section a form of cutting apparatus adapted to divide the sheet of
plastic material into lengths as required.
The same letters of reference denote like parts in all the figures.
Referring to Figures 1 and 2, A is a hopper into which is thrown the plaster,
cement, or other material forming the basis of the slabs to be produced, such
material containing the requisite proportions of fibrous binding medium, the whole
being in a plastic condition, although the thorough incorporation of the various
ingredients may be completed, and the mass brought to the proper consistency,
within the hopper itself. In this hopper work a set or sets of agitating arms a,
these arms or certain of them being so shaped and mounted as to fulfil also the
function of a screw-conveyor for the purpose of forcing the material in a continuous
and uniform stream through a narrow horizontal or slit-like orifice a', extending
across the width of and just above the surface of the bed or table B of the
machine, at the feeding end of the latter. Means may be provided for the purpose
of regulating the extent of opening of the orifice a'. The plastic material when

page_text: delivered as described is received between a pair of cylindrical rollers C, C¹
extending horizontally across the the width of the table B and mounted the one
vertically above the other so that the top of the lower roller C, is level with the
upper surface of the table B, whilst the bottom of the upper roller C is maintained
at the requisite distance above the same, such distance being approximately equal
to the thickness of the slabs to be produced whilst the rollers are of a length not
less than the width of the slabs. The rollers C, C', are continuously rotated at the
same surface speed and in the same surface direction, so as to draw in between
them the plastic material and spread it out in a layer of uniform thickness. The
rollers C, C, form the first of a series of pairs whereof two other pairs D, D',
and E, E. are shewn in the drawing, all mounted and working similarly to the
first pair C, C, the table B being continued at the same surface level between the
lower rollers C¹, D', and E', whilst the distance between the upper and lower
members of the pairs is variable and may be reduced in successive pairs from the
entering towards the finishing pair, so as, if desired, to gradually compress and
consolidate the layer of plastic material during its passage through the machine.
All the rollers are geared together as indicated in Figure 2, so as to rotate at
the same surface speed and in the proper direction, the action of the rollers being
assisted and maintained between adjacent pairs by means of two endless travelling
bands F, F, of wire gauze, strong canvas, or similar material of the same width as
the rollers and stretched the one over the upper series and the other over the lower
series of rollers so as to be continuously actuated thereby. These bands may be kept
tightly stretched by means of jockey-rollers f, f1, Figure 1, or the end pair of
niain rollers might be forced apart from the adjacent pair by means of spring or
other pressure.
The upper rollers C, D, and E, have flanges c, d, e, at both ends, these flanges
being preferably provided with knife-edges for the purpose of trimming up the
margins of the sheet of plastic material; but it might be preferable in some
cases to affix the trimming flanges to the lower instead of to the upper
rollers.
Figure 1 shews clearly the means whereby the strengthening web of woven
fabric, of whatever kind, is stretched upon and attached to the surface of the slabs.
The fabric G, G', in continuous roll form, is mounted upon axles g, gl, running in
fixed bearings under the control of brakes 92, one roll G being carried above and
the other G¹, beneath the entering rollers C, C', so as to permit of the fabric from
the rolls being led over guide rollers H, H, on to the surfaces of the corresponding
rollers and C. The fabric thus directed is carried by the bands F, F¹, through
the machine along with the layer of plastic material, with whose surface or
surfaces it is united by the pressure of the rollers CC, D D, E E', the
friction of the bands F, F1, upon the fabric being, if desirable, supplemented
by their edges, or their entire surfaces, being furnished with projecting pins.
The cutting mechanism shewn in Figures 3 and 4 comprises a straight knife
blade I whose length is equal to the width of the sheet or layer of material to
be cut, mounted upon and parallel to the axis of a roller J extending across and
carried in bearings above the table B at any convenient distance beyond the last
pair of rollers E, E, at the delivery end of the machine. The axis of the roller J is
parallel to that of these other rollers, and its height is so adjusted as to permit of the
sheet of material to be cut passing clear beneath it whilst the knife blade I projects
from its surface so as to cut completely through the sheet of material during the
passage of the latter, the line of division produced being at right angles to the
edges of the sheet, which is thus subdivided into rectangular slabs. The roller J
is continuously rotated by gearing from the adjacent roller E', tbe speed of its
rotation and consequently the length of sheet allowed to pass between the adjacent
cuts (cr in other words the length of the slabs produced) being variable and
determined by the diameter of a change wheel K interpse! in the train of
driving wheels, this wheel K being carried in a bearing mounted on an adjustable
arm k in the manner usual in change gear.

page_text: In order to enable the knife I to make a drawing cut transversely of the sheet,
which is necessary in cases where the plastic material has woven fabric attached to
one or both of its surfaces, the ends of the roller J are formed with cam surfaces
adapted to bear against friction rollers j', mounted on the framework at each side
of the table, the throw of the cams being equal to the length of draw given to the
knife which, after each cut, is returned by the cams to its original position
transversely of the machine.
In order that the knife may make a clean cut, it projects sufficiently from the
roller to allow of its edge penetrating slightly into the table, the consequent
jamming of the knife in the action of cutting being obviated by that portion of
the table B upon which the cutting is performed being made to slide horizontally
at the same rate of speed as that of the peripheral movement of the knife-edge
about the axis j, during the contact of the knife with the material.
For this
purpose a gap is cut in the table B across its whole width and immediately beneath
the roller J, a frame L of the same width as but shorter than the length of this
gap and with its upper surface level with that of the table B, being arranged to
move longitudinally within the gap, said frame which may be a metal casting being
carried in horizontal guides on the side frames or supports of the table. Into
the upper surface of the frame L, and flush therewith, is inserted a transverse
bar L, of wood, for the purpose of receiving the pressure of the edge of the knife.
A striker M projecting at one end, and from the face, of the roller J is so
arranged relatively to the knife I as to engage with a tooth M', attached to
the frame L, at the moment when the knife enters the material, so as to cause the
frame L and bar L¹, to slide horizontally in time with the movement of the knife,
the cam M extending so far in the circumferential direction as to ensure the
longitudinal movement of the frame and har being continued until the knife
again clears the material after completing the cut, after which the frame is
returned to its normal position of rest against the entering side of the gap in the
table, by the action of a spring or of a weight N suspended by a cord or chain
passing over a guide pulley n and attached to the frame. The tooth M', is made
of sufficient width to remain in contact with the striker M during the transverse
movement of the roller J and knife I in making the drawing cut. In order to
prevent the frame L jamming in its guides, the striker and tooth and also the
weight or spring above described are preferably fitted in duplicate at both sides of
the machine.
In consequence of the repeated penetration of the surface of the wooden bar L',
by the edge of the knife L, said surface gradually becomes worn away and in time
requires renewal. Provision may be made for readily effecting such renewal of
the surface of the bar, without the necessity of completely renewing the bar
itself, by mounting the frame L not directly upon the guides l'in the framework of
the table B but upon a pair of intermediate carriers, adapted to slide in the said
guides. These carriers project at the entering end of the frame L in all positions
of the latter so as to always rest against the corresponding end of the gap in the
table when the knife I is not in action and thus form an abutment whereby to
regulate the position of the frame L and bar L', the position of these latter being
adjusted relatively to the carriers by set screws (2, whilst as the teeth M', are
not on the frame L but on the carriers l, the point in the bar L', struck by the
edge of the knite may be altered at will by varying the position of the frame L
upon the carriers 1. The bar L', is preferably made square in section so as to
present four successively renewable surfaces.
In place of the cutting mechanism above described, a guillotine knife may be
employed for the purpose of dividing the sheet of plastic material into slabs.
In order to free the surfaces of the endless travelling bands F, F, from any
particles of the plastic material which might adhere to them, scrapers or brushes
(not shewn) either fixed or rotary, may be arranged in contact with the said
surfaces.
In cases where the plastic material after being mixed and brought to the proper

page_text: consistency can be delivered to the rollers C, C', from a sufficient height, as for
instance from the upper storey of a building, by means of a shoot, the machine
being situated at the ground level, the mixing hopper A need not form part of the
machine but may be placed at the higher level, or even (when the nature and
composition of the plastic materials used admits thereof) may be dispensed with
altogether.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I dclare that what I
I claim is
1. The herein described machine for continuously producing slabs of plaster,
cement, and the like, from materials in a plastic state, consisting essentially of a
pair of endless travelling bands and consolidating rollers whereon the bands are
stretched, both bands and rollers being actuated at the same speed and so arranged
relatively to one another as to receive between them and distribute the plastic
material in a sheet of uniform thickness; a cutter for dividing the sheet of
material transversely into slabs of equal lengths; and means for feeding the
plastic material to the endless travelling bands, substantially as specified.
2. In a machine constructed substantially as specified in Claim 1, the herein
described cutting mechanism adapted to transversely divide the sheet of plastic
material into slabs of predetermined length, substantially as specified.
3. A machine for the continuous production of slabs of plaster, cement, and the
like, constructed substantially as specified.
Dated this 18th day of October 1895.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.