IM- PROVEMENTS IN VALVE GEAR, APPLICABLE TO LOCOMOTIVE, MARINE, AND OTHER ENGINES
Year: 1876

page_text: LETTERS PATENT to John Wesley Hack worth and Albert Hackworth, both of
Darlington, in the County of Durham, Engineers, for the Invention of "IM-
PROVEMENTS IN VALVE GEAR, APPLICABLE TO LOCOMOTIVE, MARINE, AND OTHER
ENGINES."
Sealed the 13th February 1877, and dated the 2nd November 1876.
PROVISIONAL SPECIFICATION left by the said John Wesley Hackworth and
Albert Hackworth at the Office of the Commissioners of Patents on the 2nd
November 1876.
JOHN WESLEY HACKWORTH and ALBERT HACKWORTH, both of Darlington, in the
County of Durham, Engineers. "IMPROVEMENTS IN VALVE GEAR, APPLICABLE TO
LOCOMOTIVE, MARINE, AND OTHER ENGINES."
The movement of the valve, both head and back way, is obtained from one fast
eccentric, the rod of which has straps to embrace the eccentric pulley at one end,
whilst the other clasps the joint pin of the valve rod, which is attached at right
angles. The eccentric rod hinges on a fulcrum pin about two-thirds of its length
from the centre of the straps and one third from the valve-rod joint.
The fulcrum pin has a slide block at each end for working in a parallel guide
plane. The said plane is provided with a reverse lever and trunnions resting in
carriages, whereby the guide plane may be moved round angularly seventy degrees
of a circle. At thirty-five degrees from each extreme, that being the centre of its
range, if the engine is put in motion the fulcrum pin will move to and fro in the
guide plane in a direct line with the centre of the main shaft, meantime the
eccentric rod performs the functions of a lever, imparting about one-half of the
throw of the eccentric to the valve, being "lap" and "lead." This is designated
"lead" motion; which movement may be less or more, as designed, the extent being
fixed by the disposal of the fulcrum pin and the throw of the eccentric, but once
determined it remains invariable.
As the extremes occur when the engine is "on the centre" it gives the "lead"
for either way round, and determines the relative positions of crank and eccentric.
This action is reversed by throwing the guide plane to the opposite extremes of its
range with the reverse lever, or in large engines a sector and worm, one angle
giving the greatest charge of steam one way round and the other the opposite (this

page_text: is designated "traverse motion "), the charge of steam being reduced as the guide
plane approaches its central or normal position, thereby increasing expansion.
When the guide plane is set in mid gear the engine will go either way round,
the valve opening the "lead" only. When the "lead" and "traverse" are both in
action the valve has a compound movement; one action is at its extreme when the
other is in the middle; or, in other words, they act at right angles. This reverse
and variable expansion valve motion possesses the following advantages over the
"link motion":-
1st. It is much nearer mathematical correctness.
2nd. It has a greater range of variation.
3rd. The "lead" never varies.
4th. There is much less machinery, the parts being more durable and more easily
kept oiled.
5th. The combination of two right-angle movements causes the valve to open
quickly on turning the centre, which is immediately succeeded with partial
suspension of motion, the two actions neutralizing each other; in this way both
ingress and egress of steam are facilitated and increased useful effect obtained.
6th. Double the expansion is secured when cutting off short by retaining the
steam in the cylinder so much longer before the exhaust opens. The "theoretical
loss" consequent on the use of the "link motion" by too early exhaust is well known
to all intelligent engineers; hence, to remedy the evil, various complicated devices
have been resorted to, such as auxiliary and special cut-off valves, tappet and cam
actions, &c., but hitherto nothing simple or sufficiently practical for the quick-
moving engine of the present day has been devised. However, by combining two
right-angle movements, as in the simple machinery above described, an intermittent
action is produced adapted to obtaining all the possible advantages of expanding
steam in the cylinder. Moreover, the reverse plane being provided with steel gibs
for taking up lost motion, the fulcrum pin and side blocks being well hardened and
extra wearing surface allotted to all the details by requiring room for only one
eccentric; a valve motion is furnished of the most simple, durable, economical, and
efficient kind, calculated fully to meet the requirements of the present day.
7th. Less power is required for performing the various manipulations. We may
remark that the reverse plane will be carried on the axle on axle boxes or special
bearings in locomotives to prevent variation in the distance between the trunnion
and axle centres through the action of the springs.
Sometimes it may be desirable to use the following arrangements :-The eccentric
rod is extended beyond a pin or part which reciprocates in the changeable path,
and the valve rod is attached to such overhanging end. By this means we can obtain
when the reciprocating path is adjusted to be exactly radial with the shaft the
required motion, thereby giving the proper amount of motion to allow for the "lap"
and "lead," and on changing the position of the reciprocating path by inclining it
in one direction or the other can induce an increase in the travel of the valve, with
the proper motion for either forward or backward working, and with the advantage
of giving a greater travel of the valve with a less amount of inclination of the
reciprocating path.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Wesley Hackworth and Albert Hackworth in the Great Seal
Patent Office on the 2nd May 1877.
JOHN WESLEY HACKWORTH and ALBERT HACKWORTH, both of Darlington, in the
County of Durham, Engineers. "IMPROVEMENTS IN VALVE GEAR,, APPLICABLE TO
LOCOMOTIVE, MARINE, AND OTHER ENGINES."
In said Drawings Figure 1 is side view (partly in section) of one form of our
improved valve gear; Figure 2, plain view.

page_text: The movement of the valve, both head and backway, is obtained from one fast
eccentric, the rod of which has straps A to embrace the eccentric pulley B at one
end, whilst the other clasps the joint pin C of the valve rod D which is attached at
right angles. The eccentric rod hinges on a fulcrum pin E about two-thirds of its
length from the centre of the straps A and one-third from the valve-rod joint C..
The fulcrum pin has a slide block at each end for working in a parallel guide
plane or changeable path F. The said plane or path is provided with a reverse
lever (H, Figure 1) and trunnions (G, G, Figure 2) resting in carriages, whereby the
guide plane may be moved round angularly seventy degrees of a circle. At thirty-
five degrees from each extreme (that being the centre of its range), if the engine
is put in motion the fulcrum pin will move to and fro in the guide plane or path in
a direct line with the centre of the main shaft; meantime the eccentric rod performs
the functions of a lever, imparting about one-half of the throw of the eccentric to
the valve, being "lap" and "lead." This is designated "lead motion," which move-
ment may be less or more, as designed, the extent being fixed by the disposal of
the fulcrum pin and the throw of the eccentric, but once determined it remains
invariable.
As the extremes occur when the engine is "on the centre" it gives the "lead"
for either way round, and determines the relative position of crank and eccentric.
The action is reversed by throwing the guide plane to the opposite extremes of its
range (as indicated in Figure 1 by the lines x, x, and y, y,) with the reverse lever,
or in large engines a sector and worm, one angle giving the greatest charge of steam-
one way round and the other the opposite (this is designated "traverse motion"),
the charge of steam being reduced as the guide plane manipulated by the engineer
approaches its central or normal position, thereby increasing expansion at pleasure.
When the guide plane is set in mid gear (as shewn in Figure 1) the engine will
go either way round the valve, opening the "lead" only. When the "lead" and
traverse" are both in action the valve has a compound movement; one action is
at its extreme when the other is in the middle; or, in other words, they act at right
angles.
Figures 1 and 2 shew the improved valve gear applied horizontally and reversed
by hand lever.
Figures 3 and 4, a vertical arrangement reversed by hand wheel, worm, and sector.
In the last-named modification the reverse guide plane or changeable path is
represented by a solid parallel forked yoke truly fitted for the fulcrum pin to slide
upon, the latter having suitable jaws at each end for the purpose. The said yoke is
also provided with trunions and a sector gearing with a worm for turning it to the
various degrees of angularity. The eccentric rod is extended beyond the fulcrum
pin which reciprocates on the changeable path or yoke, and the valve rod is attached
to such overhanging end. By this means (when the changeable path reversing
plane or yoke is adjusted to be exactly radial with the main shaft centre) the
required motion is obtained for giving the proper amount of "lap" and "lead,"
and on changing the position of angularity of the reverse plane, changeable path, or
yoke, by the hand wheel, and inclining it more or less in one direction or the other,
can induce an increase or diminution in the travel of the valve, with the proper
motion for either forward or backward working, and with the advantage of giving
a greater travel of the valve with either a smaller eccentric or less amount of
inclination of the reverse plane, changeable path, or forked yoke. Of this form of
gear Figure 3 shews a side view partly in section, and Figure 4 shews a plan view
partly in section.
In these Figures (3 and 4) A is a portion of the stationary frame; B, the main
shaft; b, the single eccentric required; C, an eccentric strap; and C¹, rod; m, the
pin to which the valve rod (M) is connected. The valve rod is marked M and
leads to the slide valve, to communicate the variable motion thereto, as will be
readily understood. D is the fulcrum pin at an intermediate point in the eccentric
rod C, and which is caused to reciprocate backward and forward' in a changeable
path.

page_text: As the mechanism is here represented the guide or path for this fulcrum pin D is
changed in position and inclined in one direction or the other by means of the hand,
wheel which operates through bevel gear and a worm wheel on the segment of the
forked yoke, but the mechanism for thus changing the position of the path for the.
reciprocation of the fulcrum pin D is susceptible of various changes, which may be
effected by any mechanic. It is only important that the path be capable of being
changed to a considerable inclination in either direction, and may be held firmly at
the extremes, or any intermediate position. As the provisions for guiding the
fulcrum pin D and inclining the path are illustrated in the Drawing, E is a forked
yoke capable of turning to a certain extent on trunnions e, e, and finished on its
sides to form guides for the jaws formed on the ends of the fulcrum pin D. On the
yoke E is a segment El, which is controlled by the worm H receiving motion at
will (through the bevil gear represented) from the hand wheel H². The tru-
nions e, e, being mounted on fixed bearings as the wheel H¹ is turned in one
direction or the other the yoke E is changed in its inclination, and consequently the
fulcrum pin D is caused to reciprocate in a different path, and to have a greater or
less amount of vertical movement. Whatever its amount of vertical or up-and-down
motion may be the pin m (and consequently the valve rod. M) has a greater amount
of motion. This arrangement allows a moderately large eccentric to give a large
amount of travel to the valve.
In practice a crank or radial pin may be used in place of an eccentric, and any of
the well-known guide bar forms, or parallel motion arrangements, such as are
commonly used for guiding piston rods, &c., may be used for the reverse plane or.
changeable path.
In applying the gear to locomotives the reverse guide plane or changeable path
may be carried on the main axle, on the axle boxes, or special bearings, to prevent
variation in the distance between the trunion and axle centres through the action.
of the bearing springs. This reverse and variable expansion motion possesses the.
following advantages over the "link motion":-
1st. It is much nearer mathematical correctness.
2nd. It has a greater range of variation.
3rd. The "lead" never varies.
4th. There is much less machinery, the parts being more durable and more easily
kept oiled.
5th. The combination of two right-angle movements causes the valve to open
quickly on turning the centre, which is immediately succeeded with partial suspension
of motion, the two actions neutralizing each other; in this way both ingress and
egress of steam are facilitated and increased useful effect obtained.
6th. Double the expansion is secured when cutting off short by retaining the
steam in the cylinder so much longer before the exhaust opens. The theoretical
loss consequent on the use of the "link motion" by too early exhaust is well known
to all intelligent engineers; hence, to remedy the evil, various complicated devices
have been resorted to, such as auxiliary and special cut-off valves, tappet and cam
actions, &c., but hitherto nothing simple or sufficiently practical for the quick-
moving engines of the present day has been devised. However, by combining two
right-angle movements, as in the simple machinery above described, an intermittent
action is produced adapted to obtaining all the possible advantages of expanding
steam in the cylinder.
7th. Less power is required for performing the various manipulations.
Having now particularly described and ascertained the nature of the said
Invention, and in what manner the same is to be performed, we claim the
before-described improvements in valve gear substantially as herein-before set forth
and described, wherein the following are important points or features:-
(1st.) Increased expansion of steam is obtained through connecting the valve to
the extreme end of the eccentric rod.
(2nd.) Admittion of a more equal charge of steam at both ends of the cylinder
(at all grades of expansion) through being able to proportion the length of the

page_text: eccentric rod and throw of the eccentric to the length of the connecting rod and
range of the main crank, thus correcting the irregularity of the piston's movement
in the cylinder (through the angularity of the connecting rod at half stroke) by a
proportionate irregularity in the movement of the valve.
3rd. Procuring superior ingress and egress of steam by the intermittent move-
ment of the machinery above described.
In witness whereof, we, the said John Wesley Hackworth and Albert Hackworth,
have hereunto set our hands and seals, this Thirtieth day of April, in the
year of our Lord One thousand eight hundred and seventy-seven.
Witness,
J. H. CLOUGH,
Yarn Road,
Stockton-on-Tees.
JUILN W. HAVA
ALBERT HACKWORTH.
(L.S.)
(L.S.)