Improvements in Portable Plaster Slabs, Methods of Making the same, and Molds therefor.
Year: 1890

page_text: Date of Application, 16th Dec., 1890-Accepted, 7th Mar., 1851
COMPLETE
SPECIFICATION.
Improvements in Portable Plaster Slabs, Methods of Making the
same, and Molds therefor.
I, THOMAS CURRAN, a citizen of the United States, residing at 135, Broadway,
in the City, County, and State of New York, United States of America, 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:
The first part of my invention relates to an improved mold for forming plaster
slabs or sections of composite material which are adapted to be attached to the
interior or exterior walls or ceilings of buildings; the said mold consisting of a
frame combined with a flexible molding sheet inserted therein or formed in one
therewith as will be hereinafter described, and provided with grooves and ribs so as
to indent the slab when formed, whereby it will be enabled to retain superimposed
layers of plaster or cement.
The second part of my invention relates to the process of utilizing the mold for
the making of portable plaster slabs, and it consists in arranging the frame and
molding sheet in a horizontal position with the longitudinal grooves or ribs before
mentioned exposed, of inserting the plastic material with a trowel or in any other
desired manner, and of then smoothing the surface at a height corresponding with
the frame and finally in removing the frame and the flexible molding sheet, thus
completing the slab.
The third part of my invention relates to the slab itself; to its peculiar con-
struction having as it does the ribs or raised portions and the grooves which have
been formed by the complementary molding sheet, and being of such a nature that
they can be utilized for retaining superimposed coatings of cement or plaster, or
other like substances, as will be described.
The fourth part of my invention consists in the utilization of the plaster slabs as
a foundation for walls, ceilings and floorings of buildings and coating the said slabs
with any suitable plastic substance and to which may be added when desired, while
such superimposed plastic substance is still moist, tile, or other work, for a
finish.
For the purpose of ascertaining the exact nature of my invention I will proceed
to describe it in connection with the accompanying drawings.
In these drawings :
Figure I is a plan view of one of my improved flexible molds.
Figure II is a cross section of the same.
Figure III represents a cross section of a slab.
Figure IV represents a cross section of a slab with superimposed layers of mortar
and hard finish.
Figure V represents a cross section of a slab with a coating of plastic material on
which is placed the tile-work.
Figure VI represents a modification of my mold.
Figure VII represents slabs attached to the studding and the wall completed.
Figures VIII, IX, X and XI are detail views.
In these drawings A, A, represents the sides of my combined flexible molding
sheet and frame and B, B the ends thereof, these four portions constituting the
frame and forming the substitute for the rigid frame shown in Figure VI and
hereinafter described. C represents the longitudinal ribs or raised strips which
extend between and connect the ends B, B. D represents the longitudinal grooves
or depressions in the mold which are parallel with and intermediate to the
longitudinal ribs C.

page_text: These grooves are provided with corrugations d as shown in Figure I so that
when the plaster slab is removed from the mold the outer faces of the slab will
have an additional means for supporting the superimposed mortar.
The
In Figure I, I show the mold in its operative position the plaster E being con-
tained therein. When the plaster has been inserted in the mold as shown it is
smoothed over at the surface so that it will be even with the frame A, A B, B.
When it has hardened sufficiently the frame and its contents are turned over.
frame is then removed from the slab by lifting it at one side A (see left hand side
of the drawing). The mold is so made that by virtue of its elasticity it can be
bent and readily drawn off from the slab in the manner described.
Another feature of this part of my invention is the formation of the sides or edges
of the longitudinal ribs of the flexible molding strip. These sides or edges are
preferably made substantially as shown in Figure II of the accompanying drawings,
one of the edges, as shown at F being considerably inclined after the manner of a
dove-tail joint so that when the plaster cast formed thereby is attached to the wall
or ceiling the outsetting edge G on the slab formed by the aforesaid projection F
will retain the mortar and prevent it from dropping. In other words it constitutes
a permanent lock for the superimposed plaster or mortar. The opposite sides of
the ribs C are made nearly straight as shown at H so that when the mold is with-
drawn it will encounter no opposition. The corrugations d in the grooves of the mold
will create corresponding elevations and depressions on the most exposed part of the
plaster slab, thereby affording additional support for the mortar when applied.
In Figure III I show the slab after it has been removed from the mold.
In Figure IV I show a section of wall employing the slab having the mortar M
and the coating of white finish W.
In Figure V this coating of hard finish is omitted and I apply the tiles T while
the mortar is still plastic.
In Figure VII show a modification.
In this figure A represents a frame which may be of wood, iron or other suitable
material. B' is a flexible molding sheet and it may be formed of cloth or canvas
and it is preferably double as shown, the two parts C, D being sewn together at
points E forming thereby raised or hollow portions between the two sheets into
which may be threaded strips of wood R of various shapes and sizes according to
the pattern desired. The face of the flexible sheet is covered with rubber cloth
and then properly shellaced so that the plaster will not stick to it.
At F is shown
the slab or section of plaster after it has been formed, G representing the longi-
tudinal openings, grooves or recesses corresponding with the raised molding strips on
the flexible molding sheet aforesaid, the cross section and conformation of said
openings, grooves or recesses depending upon the size and nature of the raised strips
on the flexible molding sheet.
The method of carrying this form of my invention into effect is as follows:-
Referring to Figure VI the flexible molding sheet B is spread with its uneven
face upwards on a suitable horizontal table or support A' and the molding frame A
is then placed in position on top of the molding sheet so that the sides of the frame
will be parallel to, and the ends of the frame at right angles with, the raised strips
or ribs of the molding sheet. The plaster is then introduced in the receptacle
formed by the walls of the frame and the molding sheet and after a sufficient
amount has been inserted the plaster is smoothed over on the top of and within the
frame and gently pressed so as to embody the ribs or molding strips in the body of
the plastic material. When the plaster is hardened the frame and its contents are
turned over and one edge B* of the flexible molding sheet B' is raised and if the
molding strips or pieces are of a nature such as hereinafter described the whole
sheet may be removed by simply drawing it in this manner from one side to the
other; after the slab has been subjected to a drying process it is ready for use.
I construct my molding ribs of various sizes in cross section, the purpose being
to form grooves or longitudinal recesses of various shapes according to the demand
of the trade, some being desirable in heavy work and others in lighter, work. For

page_text: example, the construction shown in Figure VII represents a plaster slab formed in
the manner above described and according to my invention attached to a wall of
a room or building, the grooves or longitudinal receptacles being shown in cross-
section. These grooves, it will be seen, are so constructed as to support the
ordinary rough brown mortar M inasmuch as the grooves or longitudinal receptacles
will form pockets or supports for the plastic mortar and will serve the same purpose
as the open laths heretofore employed and by this means the said mortar will be
fully supported by the plaster slab as shown. After the rough mortar M has been
applied the coating or finish W may be put on.
As above stated I may vary the form of the grooves or longitudinal receptacles
according to the nature of the work for which the slabs are intended.
In Figure VIII I show a section of slab having grooves or longitudinal openings
of which one series of sides are dove-tailed and the other nearly or approximately
at right angles to the face of the slab. I depart slightly from the right angle so
as to make the flexible molding sheet the more easily removable.
In making these slabs and withdrawing the flexible molding sheet provided with
the ribs hereinbefore described the said sheet when raised will come off easily
without the separate removal of the ribs. The same may be said of the form of
plaster slab shown in Figure IX. Both of these forms of slabs are of value in the
construction of walls as I may use them in the manner shown in Figure VII with
the angle of the dove-tailed portion pointing downwardly, and it will be seen that
two of these grooves taken together form a lock and that the mortar after being
once inserted and thoroughly dried will be as firmly held by means of these grooves
and their overhanging corners as in the case of the ordinary wooden lath and even
in some cases much better as what are known as the keys of the plaster will not, in
the case of my invention, be liable to break off.
In Figures X and XI I show modifications where the dove-tail extends to both
sides of the groove or longitudinal receptacle and in manufacturing these forms it
is necessary to withdraw the wooden strips or ribs R from the flexible molding
sheet after the slab has been formed and before the said sheet is removed. The
ribs or strips of wood R can be withdrawn endwise by drawing them out of the
pockets in the molding sheet and after they all have been removed the flexible
molding sheet can be drawn off leaving the slab with the dove-tail grooves or
openings as shown.
It will be seen by referring to Figure VII that the slabs or sections are attached
to the wall and that the after coatings of brown mortar M and superimposed white
hard finish W obliterate the dividing lines.
In the composition of these slabs I use plaster lime alum, and fibre, the fibre
being saturated with "pyrodine' or other well known liquid adapted to render it
fire and water proof. The fibre renders it elastic so that the slabs can be readily
bent to any shape desired. It also toughens them thereby permitting nails to be
driven through without damage. The length of the fibre is immaterial so long
as it is adapted to carry out the purposes of this part of my invention as above
set forth.
CLAIMS.
Having thus described my invention, the following is what I claim as new

page_text: 3: The method of making grooved portable plaster slabs which consists in
introducing the plaster while in a plastic form into a moulding frame having at
the bottom thereof a flexible molding sheet provided with raised ribs and after said
plaster is hardened of removing the said flexible molding sheet, as set forth.
4 A portable plaster slab formed with longitudinal grooves or receptacles as
set forth.
5: A plaster slab formed with longitudinal grooves or receptacles having one or
more dove-tailed edges as and for the purposes set forth.
6 The plaster slabs formed with grooves and ribs in combination with the
superimposed mortar, hard finish or tiling as shown and described.
Dated this 16th day of December 1890.
WHITE & WOODINGTON,
27, Southampton Buildings, London, Agents.