IMPROVEMENTS IN THE CONSTRUCTION OF ARTICLES OF EARTHENWARE
Year: 1867

page_text: LETTERS PATENT to James Richard Pratt, of Fenton, Stoke-on-Trent,
in the County of. Stafford, Earthenware Manufacturer, for the Invention
of "IMPROVEMENTS IN THE CONSTRUCTION OF ARTICLES OF EARTHENWARE."
Sealed the 19th May 1868, and dated the 28th November 1867.
PROVISIONAL SPECIFICATION left by the said James Richard Pratt
at the Office of the Commissioners of Patents, with his Petition, on the
28th November 1867.
I, JAMES RICHARD PRATT, of Fenton, Stoke-on-Trent, in the County of
Stafford, Earthenware Manufacturer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE CONSTRUCTION OF ARTICLES OF EARTHEN-
WARE," to be as follows:-
The Invention relates to an improved method of joining together the separate
portions of articles of earthenware by forming upon them male and female
screw threads or worms while the clay or plastic material of or from which the
articles are made is in a soft or unbaked state.
By one method the screw thread or worm is cut into the earthenware article
immediately after it has been shaped or moulded upon the potter's jigger or
lathe, having a vertical spindle, and before it has been removed therefrom. A
suitable cutting tool is brought into contact with the earthenware article while
in a plastic state, and at the same time a motion is communicated to the tool
by suitable mechanism attached to the jigger so as to form a screw thread or
worm on the article.

page_text: By another method the clay is forced into dies or around mandrils which
have threads cut upon their surfaces. The clay while under pressure finds its
way into and fills up the interstices formed by the thread or worm which is
cut on the die or mandril. The dies or mandrils are afterwards withdrawn or
unscrewed from the pressed clay and the thread or worm is impressed upon
the clay. The articles having the thread or worm thus formed upon them are
afterwards baked, hardened, fired, or glazed in the usual way. It will be
seen that by these means male and female screw threads can be constructed
so as to join together any articles of earthenware which require to be connected.
I am aware that screw threads have been formed upon articles of earthenware
aforetime by suitable mechanism applied to a lathe having a horizontal spindle.
This I do not claim as part of my Invention.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said James Richard Pratt in the Great Seal Patent Office on the
27th May 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
RICHARD PRATT, of Fenton, Stoke-on-Trent, in the County of Stafford,
Earthenware Manufacturer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-eighth day of November, in the year of our
Lord One thousand eight hundred and sixty-seven, in the thirty-first year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said James Richard Pratt, Her special license that I, the said James
Richard Pratt, my executors, administrators, and assigns, or such others as I,
the said James Richard Pratt, my executors, administrators, and assigns, should
at any time agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and 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 "IMPROVE-
MENTS IN THE CONSTRUCTION OF ARTICLES OF EARTHENWARE," upon the condition
(amongst others) that I, the said James Richard Pratt, by an instrument in
writing under my hand and seal, 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.

page_text: NOW KNOW YE, that I, the said James Richard Pratt, do hereby
declare the nature of my said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the
following statement, reference being had to the accompanying Drawings, that
is to say:-
The Invention relates to an improved method of joining together the
separate parts of articles of earthenware by forming on them male and
female screw threads while the clay or plastic material from which the articles
are made is in a soft state..
By one method the screw is formed on the article immediately' after it has
been shaped on the lathe, having a vertical spindle such as the "jigger™"
or "throwers" or "potter's wheel," and before it has been removed there
from. A suitable tool is brought into contact with the earthenware-article
while in a soft state, and a motion being communicated to the tool by suitable
mechanism a thread is formed on the surface of the article.
By another modification the clay is pressed or forced into dies or moulds
having threads cut in them, the clay being pressed into the spaces formed by
the thread or worm fills up the spaces, and when the tool or die is removed
the thread' or worm is left formed upon the clay. The articles are afterwards®
baked, fired, and glazed, as is usual in manufacturing earthenware.
In order to explain some of the methods of carrying out the Invention
more clearly, reference must be made to the Sheets of Drawings hereunto'
appended.
In Sheet 1, Figs. 1 and 2 are elevations, and Fig. 3 is a plan of an ordinary
potter's "jigger" with the apparatus for cutting or forming the screw threads
attached to it.
A is the frame of the "jigger;" B, the pulley for driving the spindle C;
D, shows the block on which the loose mould E is placed; on which the soft
earthenware article F is moulded by means of the." rib " G. The "rib" G is.
held by the hand of the workman, and has grooves and recesses in it so that
when the spindle C with the mould E and soft article F revolve, the clay of.
which it is composed takes the shape of the recesses in the "rib” G.
Figs. 6 and 7 are enlarged views of the "rib." G, with one description of
tool attached for forming the screw.
Figs. 1, 2, 3, 4, and 5 show a method of moving the tool so as to form the
thread. On the spindle C is fixed a hoop having a thread on its surface, the
same pitch as the thread to be formed on the article of earthenware, a 'die H
having a similar thread is attached to the lever I by links, so that when the
workman's foot is pressed upon the end of the lever I the die H engages

page_text: with the thread on the spindle C and causes the cross bar J with the lifter
rods K to move upwards with a relative velocity depending upon the pitch of
the screw on the hoop on the spindle C and the die H. The lifter rods K
are caused to move perpendicularly by the guides M in the clay trough N,
and the guides O fastened to the frame A. The height of the lifter rods K
can be varied to suit the mould E and the "rib" G by means of screws, as
delineated.
Fig. 6 shows one description of tool P attached to the "rib" G. The
tool is made of steel, iron, brass, or any other suitable material, and slides
in the case Q. When the thread is to be formed, the workman at the same
"moment as he places his foot on the lever I presses the tool P inwards, so
that when the "rib" is raised by the lifter rods K the tool P is projected into
the recess of the "rib" G and upon the article F and cuts the clay, thus
forming the thread. The tool P is brought back from the article F by a spiral
spring in the case Q.
Another form of tool is shown in Figs. 8 and 9. A ring R, shown partly
in section, is placed upon the soft clay article F.when partially formed, and
the clay is pressed into the grooves forming the thread on the ring R by a
"rib" of suitable shape, to which the apparatus shown in Figs. 8 and 9 is
attached. The clay is pressed into the grooves of the ring R while it revolves
with the article; the workman at the same moment as he presses foot on
the lever I withdraws the catch T, which enables the spring S to draw in the
wedges U, U, which seize the ring R and prevent it from revolving, and the
"rib" carried upwards at a proper velocity by the lifter rods K raises the
ring R from the article and leaves the thread impressed upon it. It is obvious
that the tools and rings can be made for forming the female thread by
altering the position of them.
Another method of forming screw threads is by forcing the clay into dies
or around mandrills which have threads cut on their surfaces. The clay
while under pressure finds its way into the interstices formed by the thread
or worm cut upon the die or mandrill. These are withdrawn from the clay
articles, and leave the impression of the threads upon them. The articles are
afterwards baked, fired, aud glazed, and manufactured like any other piece-of
earthenware.
In Sheet 2, Figs. 10 and 11 are elevations of a suitable press for the
purposes described.
A is the frame; B, the screw; C, the fly arms with weights at their
extremities; D is the top die, and E is the bottom die, which are shown
enlarged in section in Figs. 12 and 13. The dies are shown closed in

page_text: Figs. 10 and 11, 12 and 18. When the fly arms C are made to turn round,
the slide L with the top die rises; a piece of clay is placed on the bottom
die E, and when the direction of motion of the fly arms is reversed the top
die is brought down upon the clay with considerable force, and the clay is
pressed into and fills the spaces F, F, left between the dies. The direction of
motion of the fly arms C is again reversed raising the top die, & foot lever G
is pressed down, which lifts up an internal portion of the die with the clay
article out of the bottom die. The handle H is then turned while the clay
article is held stationary; this unscrews and liberates the clay article from
the die, and leaves the impression of the thread or worm upon it.
"
D, E, Fig. 12, show a pair of dies for making the lids of "patch boxes;"
and D, E, Fig. 13, show a pair for forming the patch box itself. The
parts I, M, Fig. 18, are contrivances for liberating the air while the clay is
being pressed and for admitting it afterwards while the article is withdrawn
as is usual in forming such objects. The clay articles thus formed by pressure
with screws or worms upon them are afterwards dried, baked, glazed, and
finished in the ordinary manner. When the diameters and pitches of the
screws are properly proportioned the different parts of articles of earthenware
may be screwed together and form a convenient method of so securing them.
Having now by means of the Drawings, and otherwise described the nature
of my Invention, and the manner of carrying it into practice, I wish it to
be clearly understood that I do not confine myself to the precise details
described herein as they may be varied considerably to suit the requirements
of manufacture; what constitutes the new features of my Invention and
what I claim are,-
"
First. The forming screw threads or worms on articles of earthenware
while upon the lathe with a vertical spindle such as the "jigger' or
"thrower's" "wheel."
•
Secondly. The forming screw threads or worms on articles of earthenware"
by pressure, as described.
In witness whereof, I, the said James Richard Pratt, have hereunto
set my hand and seal, the Twenty-fifth day of May, One thousand
eight hundred and sixty-eight.
JAMES RICHARD PRATT. (L.B.)