IMPROVEMENTS IN EXPANSION VALVE GEAR FOR HIGH-PRESSURE STEAM ENGINES
Year: 1878

page_text: LETTERS PATENT to Franz Joseph Hoster, of Manchester, in the County of
Lancaster, Engineer, for the Invention of "IMPROVEMENTS IN EXPANSION
VALVE GEAR FOR HIGH-PRESSURE STEAM ENGINES."
Sealed the 18th June 1878, and dated the 12th January 1878.
PROVISIONAL SPECIFICATION left by the said Franz Joseph Hoster at the
Office of the Commissioners of Patents on the 12th January 1878.
FRANZ JOSEPH HOSTER, of Manchester, in the County of Lancaster, Engineer.
"IMPROVEMENTS
IN EXPANSION VALVE GEAR FOR HIGH-PRESSURE STEAM
ENGINES."
This Invention, which relates to certain new and useful improvements in or con-
nected with high-pressure steam engines, has special reference to improved
expansion valve gear, by the use of which the well-known practical objects aimed
at in carrying out expansion in steam engines are attained in a more efficient
manner than hitherto. The said objects being the admitting of steam into the
cylinder at full boiler pressure, the sharp or rapid cutting off of the steam, the
allowing of the steam pressure in expansion to act to the end of the stroke, and the
discharging of the steam with the least loss from back pressure; the special utility
of the expansion valve gear being to regulate the speed of the engine, and to get
uniformity of driving power throughout each revolution by automatically varying
the degree of expansion, so that according as the boiler pressure or the load on the
engine varies, the supply of steam to the cylinder is cut off at a varying period of
each stroke; and this the said expansion valve gear is enabled to do, being con-
nected to the governor and effected by the varying motion thereof as in the manner
herein-after described.
The improved expansion valve gear is applicable to existing high-pressure
steam engines as it does not necessitate any special arrangement of the parts
thereof.
The main slide or D valve has the usual invariable motion, and is worked as

page_text: usually from an excentric on the crank shaft; it may be of the usual form, but I
prefer (though it is not material) that it should be longer than generally made, so
that the cylinder ports may be correspondingly shortened. The expansion slide
valves (of which there are two) are also worked as regards their usual continuous
reciprocating or cutting off movements from an excentric on the crank shaft (these
excentrics being properly set in relation to each other) by means of a rod which is
connected to and reciprocates a guide rod carried by bearings on the bed plate and
steam chest, and which guide rod is bent to rise above the steam chest, and carries a
collar or fork which embraces a journal on a right and left hand quick threaded
screwed bar, and gives similar reciprocating movements thereto in the direction of
the length of the cylinder and steam chest. The threaded portions of the bar are
encircled by nuts connected to short guide rods carried by bearings on. the steam
chest, and bent down to the level of the expansion valve rods to which they are
suitably connected, the reciprocating movements of the bar are thus further
transmitted to the expansion valves, which thus receive the said usual reciprocating
or cutting off movements from the excentric on the crank shaft as above referred to.
I also provide the bridge by which the governor is supported with a bearing for
carrying a bell-crank lever, one arm of which engages in a collar rotating, and
rising, and falling with the governor, and the other arm of which is connected to
a rod which is also connected at its other end to one arm of a lever, the axis of
which is carried by a bearing on the steam chest, and the other arm of which lever
is connected to an arm fastened on the said screwed bar. By this connection from
the governor the proper supply of steam and degree of expansion applicable to the
load on the engine is regulated as the action of the governor causes (by means of
the said levers and their connecting rod) a rotary motion of the said screwed bar
(independent of its said usual continuous reciprocating movements caused as above-
described) which effects the nuts thereon in such a manner as to cause the expansion
valves (which are connected thereto as above described) to rapidly recede from or
approach each other, and to automatically vary the cut-off of steam and degree of
expansion, according to the power required to be developed.
The arrangement of the screwed bar and the bent down rods is such that the
steam is quickly cut off, and that there is a corresponding motion to each expansion
valve, giving the same results for each end of the cylinder, the point of cut-off being
the same in each stroke of the piston.
I also provide the engines with a cut-off indicator which I actuate from the axis
of the second of the above-mentioned levers, the axis carrying a toothed wheel
gearing with and actuating a small pinion on the centre pin of a pointer travelling
over a quadrant dial marked in inches or other convenient measurement, and
carried by the bearing of the said lever's axis, and which pointer is thus caused to
indicate the exact period of the stroke at which the steam is cut off.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Franz Joseph Hoster in the Great Seal Patent Office on the 12th
July 1878.
FRANZ JOSEPH HOSTER, of Manchester, in the County of Lancaster, Engineer.
"IMPROVEMENTS IN EXPANSION VALVE GEAR FOR HIGH-PRESSURE STEAM
ENGINES."
This Invention, which relates to certain new and useful improvements in or
connected with high-pressure steam engines has special reference to improved
expansion valve gear, by the use of which the well-known practical objects aimed
at in carrying out expansion in steam engines are attained in a more efficient
manner than hitherto; the said objects being the admitting of steam into the
cylinder at full boiler pressure; the sharp or rapid cutting-off of the steam; the
allowing of the steam pressure in expansion to act to the end of the stroke and the
discharging of the steam with the least loss from back pressure; the special utility
of the expansion valve gear being to regulate the speed of the engine and to get
uniformity of driving power throughout each revolution by automatically varying
the degree of expansion, so that according as the boiler pressure or the load on the
engine varies, the supply of steam to the cylinder is cut off at a varying period of
each stroke, and this the said gear is enabled to do, being connected to the
governor, and affected by the varying motion thereof as in the manner herein-after
described.
Such being the nature and object of my said Invention, I will now proceed to
describe the manner in which the same is to be or may be performed or carried into
practical effect, and in order that such description may be properly understood
I have annexed hereunto one Sheet of Drawings, and have marked the same with
figures of reference corresponding with those in the following explanation :-
On the annexed Drawings Figure 1 represents in front elevation so much of a
steam engine as is necessary to illustrate the application of my improvements
thereto; Figure 2 is a plan view of the same, the governor being removed; Figure 3
illustrates the action of the governor, and its connection with the expansion valve
gear; Figure 4 is a sectional plan view of the steam cylinder and its valvular
mechanism; and Figure 5 is an elevation of the slide box, the cover being
removed.
1 represents the main slide or D valve which has the usual invariable motion, and is
worked as usually from an excentric on the crank shaft; it may be of the usual form,
but I prefer (though it is not material) that it should be longer than generally made,
so that the cylinder ports 2 may be correspondingly shortened, both as shown most
clearly in Figure 4.
The expansion slide valves 3, of which there are two, are also worked as regards
their usual continuous reciprocating or cutting-off movements from an eccentric on
the crank shaft (these excentrics being properly set in relation to each other) by
means of a rod which is connected to and reciprocates a guide rod 4 carried by
bearings 5 on the bed plate 6 and steam chest 8, and which guide rod is bent to
rise above the steam chest, and carries a collar or fork 9 which embraces a journal 10
on a right and left hand quick threaded screwed bar 11, and gives similar recipro-
cating movements thereto in the direction of the length of the cylinder 7 and steam
chest.
The threaded portions of the bar 11 are encircled by nuts 12, connected to guide
rods 13, carried by the bearings 5 on the steam chest, and bent down to the level
of the expansion valve rods 14, as shown in Figures 1 and 5, to which they are
suitably connected by nuts 15; the reciprocating movements of the bar 11 are
thus further transmitted to the expansion valves 3, which thus receive their usual
reciprocating or cutting-off movements from the excentric on the crank shaft,
as above referred to.

page_text: 16 represents the governor which receives motion from the crank shaft by
a cord 17 and pulley 18 (or other convenient gear), which is connected to a disc
or faced pulley 19, carried by a shaft 20, supported by a pillar 21, by which the
governor is also supported; the disc or pulley 19 imparts its motion by friction to
a pulley 22, which is suitably fastened on a tubular shaft 23, and rises and falls with
the governor.
The disc 19 is caused to revolve in accordance with the speed of the engine,
but the pulley 22, as soon as the engine starts to run any other than the desired
speed, by reason of any change of the boiler pressure or of the load, is caused by
the rising or lowering of the governors to come to a higher or lower diameter of
the disc 19, and is thereby caused to make more or less revolutions independent of
the speed of the engine, and is thus caused to act with the greatest rapidity and
accuracy, regulating the expansion in the most efficient manner, and decreasing the
deviation from the proper speed of the engine to the utmost regularity. In order
to render the governor more sensitive to the fluctuations of the speed of the engine,
and to make it act more promptly in regulating the admission of steam to the
cylinder I mount the balls 37 upon links 38, centred at 39, at the upper part of
the shaft 23, and suspended or held at the points 40 by links 41, centred at 42, at
the upper part of the governor rod 43, the counterpoise 44 surmounting and being
carried by the shaft 23. With this method of mounting the balls 37, in lieu of
suspending them as hitherto, they are far more sensitive to the fluctuations of the
speed of the engine, and rise about 2 or 3 per cent. increase of speed, an equal
distance to what they would do if suspended as usually with about 15 per cent.
increase of speed, and are consequently much more sensitive; and in order to allow
of the governor being rendered more or less sensitive as desired, I make suitable
provision for placing one or more thin washers or collars 45 between the balls and
the joints 40, by which the balls can be raised and lowered to a certain degree.
On one side of the pillar 21 is a bearing 24, which carries a lever 25 which
engages with a rod 26, connected to a collar or fork 27, and which collar embraces
the lower part of the shaft 23, and thus rises and falls with the governor; the lever
25 is connected at its free end by a link 28 to an arm 29, fastened to the bar 11.
By this connection from the governor the proper supply of steam and degree of
expansion applicable to the load on the engine is regulated, as the action of the
governor causes (by means of the rod 26, lever 25, link 28, and arm 29) a rotary
motion of the screwed bar 11 (independent of its said usual continuous reciprocating
movements caused, as above-described) which effects the nuts 12 thereon in such a
manner as to cause the expansion valves 3 (which are connected thereto as above
described) to rapidly recede from or approach each other, and to automatically
vary the cut-off of steam and degree of expansion, according to the power required
to be developed.
The arrangement of the bar 11 and the bent down rods 13 is such that the
steam is quickly cut off, and that there is a corresponding motion to each expansion
valve, giving the same results to each end of the cylinder, the point of cut-off being
the same in each stroke of the piston. It is thus not possible to make the engine
run a higher or lower speed by opening or closing the valve between the boiler and
engine, and so should it be desired to work the engine at any other required
number of revolutions per minute, the friction pulley 22 has first to be set and
fastened upon the tubular shaft 23 of the governor, the setting being facilitated by
a pointer 30, which indicates on a scale 31 at what point the pulley should be set
and fastened for the required velocity, and so the engine will work at any required
speed with the same regularity, no matter if there is the most sudden or greatest
change in the load on the engine.
I also provide the engine with a cut-off or expansion indicator 32, which I
actuate from the axis 33 of the lever 25, the axis carrying a toothed segment 34,
gearing with and actuating a small pinion 35, on the centre pin of a pointer 32,
travelling over a quadrant dial 36 marked in inches (or other convenient measure-
ment), according to the length of the stroke, and carried by the bearing 24 of the

page_text: said lever's axis, and which pointer is thus caused to indicate the exact period of
the stroke at which the steam is cut off.
The above-described improved expansion valve gear is applicable to existing high-
pressure steam engines, as it does not necessitate any special arrangements of the
usual parts thereof.
Having now described the nature and object of my said Invention, together with
the manner in which the same is to be or may be performed or carried into practical
effect; I would remark in conclusion that I claim as my Invention, the novel and
peculiar construction of expansion valve gear for high-pressure steam engines, with
a right and left hand quick threaded screwed bar operated from the governor, and
operating the expansion valves, substantially in the manners herein-above described,
and as illustrated on the accompanying Drawings, together with the above-described
improved construction of governor, and the position of the above-described
expansion or cut-off indicator, for the rendering of the action of such gear more
perfect and under better control, and for the more efficiently attaining the well-
known practical objects sought to be obtained in carrying out expansion in steam
engines.
In witness whereof, I, the said Franz Joseph Hoster, have hereunto set my
hand and seal, this Eleventh day of July, in the year of our Lord One
thousand eight hundred and seventy-eight.