AN IMPROVED PISTON
Year: 1857

page_text: LETTERS PATENT to Theophilus Marsh, of the Firm of Marsh Brothers
and Company, of Ponds Works, Sheffield, in the County of York,
Manufacturers, for the Invention of "AN IMPROVED PISTON."- A com-
munication.
Sealed the 12th March 1858, and dated the 14th September 1857.
PROVISIONAL SPECIFICATION left by the said Theophilus Marsh at
the Office of the Commissioners of Patents, with his Petition, on the
14th September 1857.
I, THEOPHILUS MARSH, of the Firm of Marsh Brothers and Company, of
Ponds Works, Sheffield, in the County of York, Manufacturers, do hereby.
declare the nature of the said Invention for "AN IMPROVED PISTON," (a
communication from a foreigner residing abroad,) to be as follows:-
The object of this Invention is to facilitate the adjustment, from time to
time as it wears, of the packing of engine pistons. It embraces a combination
to form the piston head of a skeleton frame, through which the piston rod
passes, with plates and moveable stems acting on springs to thrust out the
steel and brass rings or packing. The skeleton frame is made with four or.
more arms, according to the size of the piston, and formed with a hole
diminishing in diameter towards the piston end, to admit the end of the
piston rod, enlarged and tapered, to pass through and fit it; this is secured
by a screw collar. The end of the piston rod is drilled in the centre, in a

page_text: direction parallel with its length, of such size as may be necessary to admit
a mandril to pass in some distance below the piston head; the mandril is
made tapering, increasing in size towards the end of the piston rod, where it
is acted upon by turning a screw. Between each arm of the skeleton frame
a hole radiates from the centre of the piston rod; in these are fixed stems, one
end of which reaching the mandril, and to the other end are attached strong
segmental springs, with the concave side turned outwards towards a steel
ring, which with brass rings or packing surround the skeleton frame, and
bear upon the ends of the springs. When the mandril is pressed inwards by
turning the screw, it forces out the stems, which acting upon the springs
force out the packing. This operation occupies only a few minutes.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Theophilus Marsh in the Great Seal Patent Office on the
18th March 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THEOPHILUS
MARSH, of the Firm of Marsh Brothers and Company, of Ponds Works,
Sheffield, in the County of York, Manufacturers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of September, in the year of our
Lord One thousand eight hundred and fifty-seven, in the twenty-first year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Theophilus Marsh, Her special licence that I, the said Theophilus
Marsh, my executors, administrators, and assigns, or such others as I, the
said Theophilus Marsh, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times
thereafter 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 "AN
IMPROVED PISTON" (a communication from a foreigner residing abroad), upon
the condition (amongst others) that I, the said Theophilus Marsh, my exe-
cutors or administrators, by an instrument in writing under my, or their,
or one of their hands and seals, 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 Theophilus Marsh, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement (that is to say) :-
The object of this Invention is to facilitate the adjustment, from time to
time as it wears, of the packing of engine pistons. It embraces a combination,
to form the piston head, of a skeleton frame, through which the piston rod
passes, with plates and moveable stems acting on springs to thrust out the
steel and brass rings or packing. The skeleton frame is made with four or
more arms, according to the size of the piston, and formed with a hole
diminishing in diameter towards the piston end, to admit the end of the piston.
rod, enlarged and tapered, to pass through and fit it; this is secured by a
screw collar. The end of the piston rod is drilled in the centre in a direction
parallel with its length, of such size as may be necessary to admit a mandril
to pass in some distance below the piston head; this mandril is made tapering,
increasing in size towards the end of the piston rod, where it is acted upon
by turning a screw. Between each arm of the skeleton frame a hole radiates
from the centre of the piston rod; in these are fixed stems, one end of each
reaching the mandril, and to the other end are attached strong segmental
springs, with the concave side turned outwards towards a steel ring, which
with brass rings or packing surround the skeleton frame, and bear upon the
ends of the springs. When the mandril is pressed inwards by turning the
screw, it forces out the stems, which acting upon the springs force out the
packing. This occupation occupies only a few minutes.
In order that this Invention may be better understood, and more readily
carried into effect, I will now proceed to describe the same, reference being
had to the accompanying Sheet of Drawings, and to the letters and figures
marked thereon, the same parts in each Figure being indicated by the same
letters of reference.
Fig. 1 is a view of the end of the piston; Fig. 2 is a horizontal section.
at a, b, (see Fig. 3); Fig. 3 is a vertical section through c, d, (see Fig. 2),.
embracing also a portion of the cylinder; Fig. 4 is a side view of the piston
complete, and a portion of the piston rod; and Fig. 5 is an elevation of the
end of the cylinder.
The piston head consists of a skeleton or spider frame A (see Figs. 2 & 3),
which fits on the enlarged tapered end of the piston rod B, to which it is
secured by a screw collar C; this spider frame may be cast in connection
with the sole plate D, or the sole plate may, with the cap plate E, be fixed to
the frame by the screw bolts F. There are four stenis G, G, G, G, (or more,

page_text: if necessary, according to the size of the piston,) radiating from the centre of
the piston rod; which is drilled or bored at the end, as shewn, for the reception
of the tapered mandril H. The outer ends of the radiating stems are
shouldered, and to them are affixed strong springs I, I, I, I, which press
against the inner steel packing K, and the outer brass packing L, which is
formed, as shewn, in two depths, in order to break the abutting joints on the
circumference, and secure a continuous periphery. The screw bolt M, which
regulates the position of the mandril, is tapped into the collar C; N is a
binding nut, which holds it firm. The mandril H is made of steel, and
tapered so as to act as a wedge; it may be a cone, or it will be equally
efficacious if in section it be square or polygonal. The adjusting bolt M is
formed with a projection e, to fit into a hole bored in the top of the mandril,
which on being turned in the proper direction in the collar C it impels
(without turning it round) into the end of the piston rod; the diminished
guide hole, into which the end of the mandril fits in the piston rod, secures
its true action. The ends of the radiating stems in contact with the mandril
are formed to fit snugly the bevel of the sides. The introduction of the cap O
(see Figs. 3 & 5) is all the alteration needed to adapt any cylinder to this
improved piston.
In putting this piston together, the face and sole plates are placed on the
spider frame, and the piston rod passed through them; the radiating
stems G, G, with the springs I, I, attached, are then introduced, and the
inner and outer packings placed in position. The mandril is then put in,
the screws F tightened up, and the collar C screwed on; the bolt M is passed
through the nut N, and screwed into the collar C, until the mandril be pressed
home sufficiently to thrust out the packing rings as far as may be required,
whereupon the binding nut N is set tight,
When, after continued use, the packing becomes partially worn, and it is
desired to expand it, the cap O is removed and the bolt M screwed down so
as to force the mandril further into the end of the piston rod, the increased
sectional area of the tapered mandril drives the radiating stems further from
the centre, and these acting upon the springs I, which bear against the
packing at regular intervals, distend the packing to the full bore of the
cylinder; this secures perfect equality in setting out the packing. By
the old modes equality of pressure is not attainable; but this system, acting
from a centre, is certain in its operations, and admits at any time of the
accomplishment of all that may be desired in a few minutes.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or 'may be performed, I

page_text: would observe, that what I claim and desire to have secured to me by the
above in part recited Letters Patent is, the mode of producing a perfec ly
equal action upon the packing rings by the central mandril, radiating stems
and springs, substantially as herein-before set forth and described, and
illustrated by the accompanying Drawing.
In witness thereof, I, the said Theophilus Marsh, have hereunto set my
hand and seal, this Twelfth day of March, in the year of our Lord
One thousand eight hundred and fifty-eight.
0 Witness,
T. F. CASKIN,
16, Bank Street, Sheffield.
THEOPHILUS MARSH. (L.S:)