IMPROVEMENTS IN ENGINES TO BE WORKED BY STEAM, AIR, OR GAS
Year: 1849

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CROFTON MOAT, of Upper Berkeley Street, Middlesex, Surgeon, send
greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Fourth day of January,
One thousand eight hundred and forty-nine, in the twelfth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
William Crofton Moat, my exors, adññors, and assigns, Her especial licence,
full power, sole privilege and authority, that I, the said William Crofton Moat,
my exors, adiñors, and assigns, and such others as I, the said William Crofton
Moat, my exors, adñiors, or assigns, should at any time agree with, and no
others, from time to time and at all times during the term of years therein
expressed, should and lawfully might make, use, exercise, and vend, within
England, Wales, and the Town of Berwick-upon-Tweed, and in the Islands
of Guernsey, Jersey, Alderney, Sark, and Man, and in all Her said Majesty's
Colonics and Plantations abroad, my Invention of "IMPROVEMENTS IN ENGINES
TO BE WORKED BY STEAM, AIR, OR GAS;" in which said Letters Patent is con-
tained a proviso that I, the said William Crofton Moat, should cause a par-
ticular description of the nature of my said Invention, and the manner
in which the same is to be performed, by an instrument in writing under
my hand and seal, to be inrolled in Her said Majesty's High Court of
Chancery within six calendar months next and immediately after the date

page_text: of the said in part recited Letters Patent, as in and by the same, reference
being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
William Crofton Moat, do. hereby declare that the nature of the said Inven-
tion, and in what manner the same is to be performed, are fully described and
ascertained in and by the present Specification thereof, reference being had
to the Drawings hereunto annexed, that is to say :---
My said Invention has for its object to construct the pistons and stuffing
boxes of engines worked by steam, air, or gas, in such manner or with such
appliances that they shall fit more exactly and be less subject to change of
form and consequent leakage than heretofore; and the manner in which the
said object is carried into effect is exemplified in the Drawings hereunto
annexed, and in the following description thereof :-
Figure 1 is a sectional elevation of so much of a steam engine as is neces-
sary to show how I propose to effect the better fitting or packing of pistons.
A, A, is the cylinder with its covers and stuffing box; B, the piston rod; F,
a solid metal ring, which is turned to fit the inside of the cylinder, and forms
the exterior of the piston B'; C is the lower plate of the piston; D, the
central portion of the upper plate, or, as it is commonly called, the junk ring,
and E, the outer or peripheral portion of the latter; G is a hollow ring;
which is made of some soft or yielding material, as lead or vulcanized
caoutchouc, and fits into a recess made for it in the body of the piston, and
abuts outwardly against the metal ring F. The ring is in its original state
of a circular form, but when pressed into the recess it takes the triangular
shape, or nearly so, represented in the Drawing. L. is a passage which is
bored down through the centre of the piston rod, and terminates in another
passage L', which diverges from it at a right angle, and is connected by a
union joint I to a third pipe J, which leads into the heart of the hollow ring
G; M is a valve box, which covers in the passage L. at top; P, a piece of
cork with a crutch or stool Q, (see detached view of these parts in Figure 1ª,)
which fits into. M, and O a cap .to M; Y is a coil of tubing (of indefinite
length) which is attached, when required, by union joints, z, to the top of
the valve box M at one end, and at the other to an air forcing pump placed
by the side of the engine, or in any other convenient position.. The use of
the hollow yielding ring Ġ is to keep the metal ring F pressed out against
the sides of the cylinder, and this is effected by charging it.at intervals with
air from the pump, and to any amount of pressure which may be found
requisite. When the ring is to be charged, the cap O of the valve box M is
removed, and the coil of pipe Y attached by its inner joints z, z, to the valve

page_text: box M at one end, and to the pump at the other. The requisite injection of air
is effected by working the air pump, and the degree of pressure produced on the
interior of the hollow ring is indicated by a pressure guage. When the ring
has been pressed tightly against the cylinder sides, the pressure should be
reduced about one half by unscrewing the top of the valve box until the guage
indicates that the desired degree of reduction has been obtained (which the coils
in the pipe allow of being done without disturbance to the union joints). The
top of the valve box should then be re-screwed down tight against its seat, the
pipe Y removed, and the cap O.put on to prevent any air escaping past the valve.
The arrangements which have been thus described will, it is obvious, answer
equally well whether the ring in immediate contact with the cylinder sides is
solid, as represented in the Drawing, or split, or composed of a number of
segments. It will be obvious also, that instead of forcing in the air through
a passage bored in the piston rod, it may be introduced through a pipe passed
down through the cylinder alongside the piston rod into the body of the piston,
and which pipe.may be either rigid or flexible; or the air may be injected
directly into the piston by introducing a hand condensing syringe through a
door, in the cylinder cover, and inserting the nozzle of it into an opening in
the body of the piston.
An arrangement suitable to both these plans is represented in Figure 2.
A is the cylinder, and a a door in the cylinder cover for the introduction of the
pipe or syringe, as the case may be; B, the piston; D, the upper plate or
"junk ring;" Ġ, the hollow yielding ring, and E the opening in the piston, which,
in the case of the hand syringe being used, should be covered by a valve of the
same kind as that before described as being used for covering the passage in the
body of the piston rod. Again, instead of a constant command being main-
tained by the means aforesaid over the pressure, so that it may be supplied
only when wanted, and to the exact amount wanted, the hollow ring G may
be charged in the first instance with compressed air to such an extent in
excess of the average pressure required as to obviate any necessity for renewal,
in which case the air pump and air passages and their respective appendages
would be dispensed with; but as such an arrangement would leave the
engineer without any ready means of assuring himself of the soundness of the
piston, or of repairing it in the possible event of damage from violence, I do
not consider, it as-preferable or equal to the mode of packing herein-before
described. The objections to the preceding arrangements do not, however,
apply to the stuffing boxes of cylinder covers, especially in the case of engines
worked at a low pressure, and with respect to these, therefore, I do recommend
the employment (in place of the ordinary modes of packing) of air-tight

page_text: hollow rings of some yielding substance, charged at once, with compressed
air to such an extent that this air shall have a constant tendency to press
them outwards on all sides. A mode of charging a piston different from
that before described is shown in Figure 2. B' is a section of a piston in
a partially finished state, and B2 a section of it as ready for working. The
bollow yielding ring G is dropped loosely into a place made for it between
the under and upper plates of the piston, and close to their respective
peripheries, and the plates are then drawn together by means of the screw
bolts d, d, until the ring G is compressed into a much smaller space than
it originally occupied, and the air within it is also proportionally compressed.
Figure 3 is a sectional elevation of a piston rod and stuffing box packed in
the same manner as just described in its complete state. A is the cylinder
cover; B, the piston rod; C, the stuffing box; and G, the yielding hollow
ring. Figure 4 is a plan of the ring G. Sometimes I make this hollow
ring in semicircles or other sections of a circle, as indicated by the dotted
lines in Figure 4. Instead of employing yielding hollow rings applied in a
horizontal position to pack pistons and stuffing boxes, as before described,
I sometimes effect the same object by means of short lengths of tubing of lead
or other yielding material applied spirally in the manner exemplified at A³ in
Figure 2, which is a section of a stuffing box on this plan. The pipe is first
tapered off and closed at the two ends, as shewn in Figure 5, and then coiled
round the piston rod with the bottom end resting on the under plate of the
stuffing box. The upper plate is then screwed down upon the pipe till.it
is not only pressed out at both sides, (that is, against the piston at one side
and the cylinder cover at the other,) but is altogether compressed into a much
narrower space than it originally occupied, accompanied with a corresponding
compression of the air in the inside of it.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that what I claim as of my
Invention is, the employment of yielding hollow rings and yielding tubing, of
whatever material the same may be composed, filled with air more or less
compressed, for the better packing of the pistons and stuffing boxes of engines
worked by steam, air, or gas, as before exemplified and described.
In witness whereof, I, the said William Crofton Moat, have hereunto
set my hand and seal, this Fourth day of July, in the year of our
Lord One thousand eight hundred and forty-nine.
WILLIAM CROFTON (L.s.) MOAT.

page_text: AND BE IT REMEMBERED, that on the Fourth day of July, in the year
of our Lord 1849, the aforesaid William Crofton Moat came before our
said Lady the Queen in Her Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form
above written. And also the Specification aforesaid was stamped according to
the tenor of the Statute made for that purpose.
Enrolled the Fourth day of July in the year of our Lord One thousand.