CERTAIN IMPROVE- MENTS IN STEAM ENGINES
Year: 1852

page_text: LETTERS PATENT to George Holcroft, of Manchester, in the County
of Lancaster, Engineer, for the Invention of "CERTAIN IMPROVE-
MENTS IN STEAM ENGINES."
Scaled the 8th December 1852, and dated the 1st October 1852.
PROVISIONAL, SPECIFICATION left by the said George Holcroft.
at the Office of the Commissioners of Patents, with his Petition,
on the 1st October 1852.
I, GEORGE HOLCROFT, of Manchester, in the County of Lancaster,
Engineer, do hereby declare the nature of the said Invention for
"CERTAIN IMPROVEMENTS IN STEAM ENGINES" to be as follows, that is
to say-
My Invention relates, firstly, to a new mode of working direct acting
double cylinder engines, commonly called Wolff's engines, in such a
manner that while the piston of one cylinder is at the highest part of
its stroke the piston of the other is at its lowest, and vice versà; the
object in this method of construction being to allow the steam from
the smaller or high pressure cylinder to expand into that part of the low
pressure cylinder which is next adjacent to its point of exit, namely,
from the lower side of the piston of one cylinder to the lower side of
that of the other, and from the higher to the higher. By this means

page_text: the passages between the two cylinders are rendered comparatively
short, and considerable saving of steam is the result. Now I effect
the purpose above described by arranging the engines in such a manner
that the piston and connecting rods from the two cylinders may work
on two separate cranks, and proceeding from the cylinders at opposite
ends thereof, gearing together the two crank shafts in whatever manner
may be most conveniently suited to the situation. This arrangement
is peculiarly applicable to the horizontal construction of steam engine,
and it may be applied also to the vertical, and in either case it is
moreover adapted to double cylinder oscillating engines, where, on
account of the short compass which such engines occupy in length, the
connecting gearing may be considerably simplified. One of the cranks
may in some cases be a little in advance of the other; and in case of
two double cylinder engines coupled, two cranks may be placed at
right angles to the other two, or one set of cranks may have any lead
of the other set.
My Invention relates, secondly, to another arrangement of double
cylinder, or Wolff's engine, whereby the cylinders are placed upon two
standards side by side, but apart from each other, the connecting rods
working downwards, and the cranks being fixed on the shaft at 180 de-
grees from each other, or nearly so. The strokes may take place, as
before mentioned, simultaneously in opposite directions, or in the same
direction, or in either case the one may have a slight start of the other.
My Invention consists, thirdly, in an improved slide expansion valve.
It has two openings through its face, through which steam is admitted
to the ports; the valve spindle having fixed upon it-two small slides,
capable of adjustment by a right and left handed screw, and fitting
loosely through a hole in the main slide.

page_text: WHEREAS Her present most Excellent Majesty Queen Victoria,
by Her Letters Patent under the Great Seal of Great Britain, bearing
date at Westminster, the First day of October, in the year of our
Lord One thousand eight hundred and fifty-two, in the sixteenth
year of Her reign, and in the year of our Lord One thousand eight
hundred and fifty-two, did, for Herself, Her heirs and successors, give
and grant unto me, the said George Holcroft, Her especial licence, full
power, sole privilege and authority, that I the said George Holcroft,
my executors, administrators, and assigns, and such others as I, the said
George Holcroft, my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times here-
after during the term of years 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 CERTAIN IMPROVEMENTS IN STEAM ENGINES; " in which
said Letters Patent is contained a proviso, that I, the said George
Holcroft, shall cause a particular description of the nature of my
said Invention, and in what manner the same is to be performed, to be
filed in the Great Seal Patent Office within six calendar months
next and immediately after the date 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 George Holcroft, do hereby declare that the nature of the said
Invention, and the manner in which the same is to be performed, is
particularly described and ascertained in and by the Drawings hereto
annexed, and the following explanation thereof, that is to say, reference
being made to the Drawings hereto annexed, and to the letters and
figures marked thereon, that is to say:
My Invention relates to those kinds of steam engines commonly
Known as Wolff's engines, the distinctive feature of which, as is well
understood, is the employment of two working cylinders in such a
manner that the steam, after having actuated the piston of one, is
admitted to the other, so as to act upon it expansively previous to its
condensation. In those engines of this class which work by direct
action, that is to say, without the intervention of a beam, the usual

page_text: arrangement is such that the two pistons are caused to move simulta-
neously or nearly so in the same direction, a method which it will be
perceived incurs the necessity in expanding from one cylinder to the
other for the steam to move from one side of the first piston to the
other side of the second. It is evident, therefore, that the passages
communicating between the cylinders must be the entire length thereof;
and that the steam contained in these passages, which is a considerable
amount, will be much reduced in pressure at the termination of each
stroke. Now by the methods of arrangement which are the subject
of my Invention, the before stated action of the pistons is reversed,
that is to say, I cause the pistons to move simultaneously, or nearly
simultaneously, in opposite directions, by which means the steam,
after having done duty in one cylinder, is immediately transferred.to
the same side of the piston in the other cylinder. The passages are
thus considerably shortened, and a corresponding saving of steam is the
result.
The first of these arrangements is shewn in Sheet 1, which repre-
sents a horizontal double cylinder engine; Fig. 1, being a side cleva-
tion; and Fig. 2, a plan. A, is the small or high pressure cylinder;
and B, the larger or expanding cylinder; the two being connected by
the short passages or nozzles a, b. The steam valves are worked in
the ordinary way by the eccentric c, and I prefer to employ a separate
exhaust valve d, worked by another eccentric, or by any of the well
known methods. The steam, after having done its duty in both
cylinders, is admitted to the condenser C, D, being the air pump,
which may be worked in any convenient manner. It will be perceived
that there are two crank shafts E, and F, at contrary sides of the
cylinders, so that the piston rods also emerge from opposite ends thereof,
so that while the two cylinders are intimately connected, the action is
divided into two separate parts moving in contrary directions; and in
order to connect the one with the other, the two crank shafts are
geared together by an intermediate shaft G, with suitable gearing as
represented. The cranks are placed, as will be seen, at 180° from
each other, although in some cases I prefer to allow one to have a
slight lead of the other; but this does not affect the leading feature of
the Invention of the pistons moving in opposite directions, which has

page_text: the effect of causing the expansion to take place always on the same
side of the pistons, and the passages of intercommunication to be thereby
shortened as before stated. In applying the power of this engine to
driving purposes, the motion may be communicated indiscriminately
from any of the shafts E, F, or G.
The second arrangement of engine, whereby I effect the same object
as before described, is represented in Sheet 2; Fig. 1, being a side
elevation; & Fig. 2, a front elevation. In this case I fix the two
cylinders A, and B, each on suitable standards C, and D, and I
connect them by the nozzles a, and b. The two cranks are keyed
ou to the same shaft E, which has a spur fly wheel F, acting as a
prime mover to the mill gearing, which has to be driven. The piston
rods both proceed from the same ends of the cylinders, but the cranks
are fixed at 180° to each other, or a little less, so that one may have
lead of the other as in the former case. By this means the same
condition which applied to the former engine will also be here clearly
fulfilled, namely, that the pistons may move in opposite directions, and
the steam expand from the lower side of one cylinder to the lower
side of the other, and vice versa. The steam and exhaust valves c,
and d, I have shewn to be worked by one rocking shaft e, and have
placed the condenser and air pump so that the latter may be worked
by a lever connected by a link to one of the cross heads f; but these
and other details may be varied in many ways, into an explanation of
which it will not be here necessary to enter, as they are well understood,
and do not form a part of the general features of my Invention.
Having now fully described and ascertained the nature of my
Invention, and the manner of carrying out the same, I wish it to be
understood that I do not confine myself in all respects to the arrange-
ments exhibited in the Drawings; but the same may be modified in
several ways, at the same time preserving the essential characteristics of
the Invention. For instance, in Sheet 1, the engine is shewn to work
horizontally, which is a convenient construction, but it may be also
made to work vertically; and in either case the cylinders may be made
to oscillate, so as to form a compound oscillating engine, a form which
gives the advantage of shortening the distance between the crank

page_text: may
shaft, and thus simplifying and diminishing the weight of the connecting
gearing. Moreover, with regard to Sheet 2, I have shewn a vertical
construction, but it is clear that if a horizontal one should be preferred,
it be resorted to with great facility; in the latter case also I place
the fly wheel sometimes as shewn between the two cranks, and some-
times outside the framing, according to circumstances, employing such
gearing as may be best adapted to the situation. I sometimes also
place the cylinders at the bottom, and the crank shaft at the top, thus
reversing the vertical construction described. What I claim therefore
as new and of my Invention is, the arrangements described and set
forth in the annexed Drawings of compound or Wolff's engines,
whereby the steam is caused to expand from one cylinder to another,
always on the same side of the piston; and I claim those modifications
thereof not affecting the distinctive features which I have pointed out,
namely, the vertical and the oscillating construction of that shewn in
Sheet 1, also the horizontal construction of that shewn in Sheet 2,
irrespective of the position of the fly wheel, as well as the reversed
vertical construction of the same, the whole as described.
-
In witness whereof, I, the said George Holcroft, have hereunto
set my hand and seal, this Twenty-ninth day of March, in
the year of our Lord One thousand eight hundred and fifty-
three
Signed, sealed, and delivered
by the said George Holcroft
(being first duly stamped) in
the presence of
GEO. HOLCROFT. (L.S.)
Signed, sealed, and delivered
by the said George Holcroft
(being first duly stamped) in
the presence of
CHA COOPER, Sol',
Manchester.
GEO. HOLCROFT. (L.S.)