CERTAIN IMPROVEMENTS IN METALLIC PISTONS, PUMP BUCKETS, AND BOILERS OF STEAM ENGINES
Year: 1834

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, Jonn
MCDOWALL, of Johnstone, near Paisley, in the County of Renfrew, Scotland,
Mechanist and Engineer, send greeting.
WHEREAS His present most Excellent Majesty King William the Fourth,
by His Letters Patent, under the Great Seal of Great Britain, bearing date at
Westminster, the Twelfth day of May, in the fourth year of His reign, did,
for Himself, His heirs and successors, give and grant unto me, the said John
McDowall, His especial licence, full power, sole privilege and authority, that
I, the said John McDowall, my exors, admiors, and assigns, or such others
as I, the said John McDowall, my exors, admors, 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, my Invention of "CERTAIN IMPROVEMENTS IN METALLIC PISTONS, PUMP
BUCKETS, AND BOILERS OF STEAM ENGINES;" in which said Letters Patent is con-
tained a proviso that I, the said John McDowall, shall cause a particular
description of the said Invention, and in what manner the same is to be
performed, to be inrolled in His Majesty's High Court of Chancery within
four calendar months next and immediately after the date of the said in

page_text: 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 snid
John McDowall, do hereby declare that the nature of the said Invention,
and in what manner the same is to be performed, is described and ascertained
in the manner following, and by the Drawings hereunto annexed.
In the annexed Sheet of Drawings, Figures 1, 2, 3, 4, 5, are designed to
elucidate the construction of my improved pistons. Figure 1 is an external
elevation; Figure 2 is a plan of the same, but having the cap plate taken off
to show the internal arrangement of tlic principal parts. Figure 3 is a vertical
and diametrical section of the whole piston represented in Figure 1; and
Figures 4 and 5 are detached portions, which will be better explained
hereafter. The same letters of reference that occur in the different figures
are indicative of corresponding parts in each; thus a indicates the piston
rod; b, a solid block of cast iron, through which it passes, as well as
through the bottom plate c, and these three parts are firmly united together
by any adequate means. The cap plate d, for the convenience of removal
at pleasure, is fastened to the central block b by screws, as shewn at e, c.
Between the cap and bottom plates, and around the periphery of the
central block, an annular cavity is formed, wherein are fitted an expanding
ring of segments; f.ff.f. the lines of separation or spaces between these
segments, through which the steam might pass, are stopped by the moveable
pieces 9, 9, 9.9, which I term slides, and these slides are made continually to
press upon the segments by the agency of springs h, h, h, h, the middle parts of
which bear against the central block, and their extremities fit into notches in
the slides. The form of these slides is further shown by the separate Figure 4
in perspective, and the back of one in elevation by Figuro 5, which has added
to it one of the aforesaid springs h, to show the form of the latter and the
manner in which they are fitted into the notches of the slides. The divisions
between the segments ff, are inclined, as represented, to prevent an irregular
abrasion against the interior of the working cylinder, and the slides and the
grooves in which they work I construct with similarly inclined surfaces, to
accommodate the increasing openings between the segments, as these latter or
the cylinder wear away, and in order to make the slides as perfect stops as
possible to the passage of the steam, I duely face and grind those surfaces of
them with the opposing surfaces against which they press or slide.
My experience in the working of cast iron pistons in steam engines has led
me to observe that the surfaces of the metal between the segments and the
plates against which they slide rapidly corrode, and become converted into a

page_text: substance resembling plumbago, by which the effectiveness of the piston is
seriously impaired. As a remedy for this defect in cast iron pistons, I line or
cover the aforesaid surfaces with brass, gun metal, or other alloy of copper,
which I connect by screws, pins, or other means known to workmen. These
linings are distinguished in the Drawings by the letter k. My claims to improve-
ment in metallic pistons relate in particular to the slides described, and all
imitations of them, and likewise to the lining of cast iron pistons in the parts
described with brass or other alloy of copper.
My improvements in pump buckets are represented by Figures 8, 9, and 10.
Figure 8 is a vertical and diametrical section; Figure 9, a plan of the upper-
most side; and Figure 10, an elevation; in each of the Figures the same letters
of reference where they occur indicate corresponding parts. a is the bucket
rod fixed to the body b, b, the darkly tinted parts of which, b, b, in the section,
are intended to represent the arms or bars which connect the central with the
circumferential portion, and between which bars the water freely passes; c, c,
is a gun metal collar, on which the circular plate valve d, d, slides up upon the
descent of the bucket, and slides down upon the ascent of the same, at which
time the brass-lined periphery of the valve on the underside comes in contact
with an annular seat e, e, and prevents the return of the water in the up stroke
of the bucket. Owing to the rapidity with which the air pump buckets of
steam engines usually work, the valves in the down stroke of the buckets (from
the resistance of the water) strike violently against the guards or checks which
limit the range of their action. The collision of these parts I have found to
be very injurious and destructive, and I have in consequence devised a hollow
cover or cap ff, which I denominate my "water guard," as the reaction of
the water which occupies the hollow space g prevents an instantaneous contact
between it and the valve, thereby causes the mechanism of these parts to work
without noise or collision, and to become.in consequence far more effective and
durable. The manner of fixing this water guard to the bucket, as shown in
the Drawings, is by the intervening little pillars h, h, the lower extremities of
which are screwed into the bucket, and the upper are secured to the water
guard by screws and nuts. In the example delineated of my improved pump
bucket I have shown attached thereto another modification of my improve-
ments in metallic pistons. The segments in Figures 8, 9, and 10, being made
entirely of brass or gun metal, require no linings, and the segments are in this
case divided straight or vertically, instead of inclined; the direction of these
divisions being immaterial in the bucket, while the straight cut and slide to it
are more easily manufactured than the inclined; at i, i, are four brass screwed
pins, which pass through slots made in the segments, and thus limit the range

page_text: of the latter and prevent their falling away when the bucket is not in use.
(A similar contrivance is adopted in the pistons, but not shown in the Draw-
ings of them). My claims to improvements in the pump buckets consist in
the lining of the cast iron surfaces as mentioned with regard to the pistons,
the form and adaptation of the slides, whether vertical or inclined, and the
form of construction and application of my "water guard" to valves.
My improvements in the construction of the boilers of steam engines I now
proceed to describe with reference to Figures 6 and 7 in the Drawings.
Figure 6 is an elevation partly in section; and Figure 7 a plan, also partly in
section. I place a series of two, three, or more rows of metallic tubes a, a',
vertically, and arrange the rows with respect to each other in the manner
shown in the plan at a, in order that the heated air and flames directed hori-
zontally may be made to impinge upon and around their surfaces as much as
possible. I connect these tubes at their lower ends to a water chamber b, b',
and at their upper ends to a steam chamber c, c', by passing their ends
through suitable countersunk holes made in stout plates d, d', of wrought iron,
and thereto rivetting them down; around the edges of those plates 1 place a
rectangular frame of malleable bar iron c, d, which frame forms the sides or
depth of the chamber over or covering this frame. I place another plate of
stout wrought iron ff', and then throughout these plates and the intermediate
frame of bar iron 1 drill a series of holes g. 9, (see plan), through which are
passed a series of screw bolts h, h, by which those parts are brought firmly in
contact, taking previously the usual precautions of cement or packing (well
known to workmen) for making steam and water-tight joints. At i is the fuel
chamber between the two congeries of tubes; the water chambers are connected
by the pipe, and to the latter are joined branches k, k, for the supply and
discharge of tho water. The steam chambers are in like manner connected by
a pipe, which is surmounted with a safety valve m; and at n is the branch for
conveying the steam to the engine. To cause the current of heated matters
from the fire to take a horizontal direction amongst the tubes, the upper part
of the fire-place is covered in by an iron plate or plates, the edges of which are
seen at o, o, and the outside of tho tubes are provided with similar plates at p, p,
fastened in their places by screw bolts q, q, or any other convenient means.
The currents from the fire are directed equally on both siles by means of corre-
sponding flues r, r, on each side, which unite at the crown of the arch and
enter the common chimney & above. When the tubes require cleaning out the
operation is easily effected by taking off the external plates of the water and
steam chambers, and it is this convenient arrangement and mode of construc-
tion of the water and steam chambers to tubular boilers, which constitute the

page_text: eading feature of my improvements; but I claim in addition as of my Invention
he general arrangement of the parts of the apparatus considered as a whole.
In witness whereof, I, the said John McDowall, have hereunto set my
hand and seal, this Sixth day of September, in the year of Our Lord
One thousand eight hundred and thirty-four.
This is the Specification referred to in the affidavit of Luke Hebert, sworn
before me this Twelfth day of September 1834.
HENLEY.
Luke Hebert, of Highgate, in the County of Middlesex, Gentleman, maketh
oath and saith that he is acquainted with the manner and character of the
handwriting of William Houston, Esquire, a Justice of the Peace, residing at
Johnstone, in the County of Renfrew, within that part of the United Kingdom
of Great Britain and Ireland called Scotland. And this deponent further
saith that the name or signature "William Houstoun," with the addition
"J. P." set, subscribed, and written upon or indorsed in the margin of the
Specification marked A. hereunto annexed, and dated the Sixth day of Sep-
tember instant, and executed by John McDowall, of Johnstone aforesaid,
Machinist and Engineer, whereby it is stated that the said Specification was
acknowledged by the said John McDowall before the said William Houstoun,
on the said Sixth day of September, at Johnstone aforesaid, are of the proper
respective handswriting of the said William Houstoun and John McDowall.
And that the said William Houstoun at the time of setting and subscribing bis
name on the said Specification in manner above stated was and now is one of
the Justices of the Peace acting in and for that of the United Kingdom called
Scotland.
Sworn at the Public Office, Southampton)

page_text: AND BE IT REMEMBERED, that on the oath of Luke Hebert the
Specification aforesaid was inrolled, word for word, as above written. And also
the Specification aforesaid was stamped according to the tenor of the.Statute
made for that purpose.
Inrolled the Twelfth day of September, in the year of our Lord Ono
thousand eight hundred and thirty-four.