Year: 1895

page_text: Date of Application, 29th Mar., 1895
Complete Specification Left, 27th Dec., 1895-Accepted, 14th Mar., 1896
I WILSON HARTNELL of Bensons Buildings Park Row Leeds in the County of
York Consulting Engineer do hereby declare the nature of this invention to be
as follows:-
My invention consists in improvements in dashpots and their connections so that
they may be used in connection with governors or controlling agents, not merely as
passive retarding mechanisms, but to give active assistance to move, or to hold
securely the gear attached.
The dashpot is made with two or more passages communicating with opposite
sides of the piston furnished with check valves opening opposite ways.
These passages may be either in the dashpot piston or in its surrounding cylinder,
and may be opened or closed as required.
The governor is so connected to the piston as to be able to close or open one or
both these passages before it attempts to move the dashpot piston.
In order to give active assistance the fluid in the dashpot is reciprocated, say by
a reciprocating piston or plunger (which may be at any convenient distance) or by
reciprocating the dashpot.
To hold securely the gear attached the fluid is not reciprocated.
In order to explain this invention more definitely I will give examples.
Suppose the governor of a steam engine acts against a passive resistance, such as
in twisting an expansion valve rod, or in moving a throttle valve, let the dashpot
be vertical and the passages and check valves be in the piston of the dashpot.
In which also let there be a piston valve which can close either passage when
the governor begins to act.
Let the dashpot piston be coupled to the valve rod or throttle valve. Let the
governor also be connected but with a small amount of play, so that the governor
can work freely through a small space.
The fluid in the dashpot must be reciprocated, but as both passages are open
when the governor is not acting, the fluid reciprocates through the dashpot piston
without moving it.
If now the governor tries to depress the dashpot, it first moves the piston valve
and closes the passage from the top to the bottom of the dashpot piston.
The piston will therefore be pushed down by the reciprocating fluid, with or
without the assistance of the governor until the governor by resting in a new
position re-opens the passage. Thus no effort on the part of the governor to
overcome the resistance of the gear is required. The gear takes the exact position
due to the speed, and in this case avoids cyclic variations of speed due to the
resistance of the gear.
Next suppose the governor of a steam engine controls the expansion of the steam
through the medium of a vibrating link, which unless prevented would shake the
governor.
The arrangements may be the same as above except that the fluid is not
reciprocated and the piston valve is made to cover both passages when the governor
is not acting.
The dashpot piston cannot move and the expansion gear is held rigidly.
If now the governor tries to depress the piston it first opens the passage allowing
the fluid to pass from below to above the piston. The dashpot can now move

page_text: downwards freely. If at the same time the link gear tries to pull the piston down,
it will go down, with or without direct pressure from the governor. But when the
governor has taken up a new position the passages will be closed and the dashpot
securely held. If however, at the same time that the governor opens the upward
passage the link gear tries to push the dashpot piston upwards it cannot do so
because the check valve opening the wrong way closes the passage. Thus with
this arrangement of dashpot the governor can use its opportunities to move the
expansion gear and hold it in its position undisturbed.
In either arrangement of dashpot the reverse actions may be similar and the
movement may or may not be by successive stages. When the passive resistance
is comparatively small and uniform and the fluid reciprocating the valves may
sometimes be omitted, the passage or passages being so regulated that the
reciprocating pressure on the dashpot approximately balances the resistance of the
valve gear, thus making opportunities for the governor to act freely.
The dashpots may be closed at each end and placed horizontally or in any
convenient position.
When more convenient the dashpot piston may be fixed or reciprocated and the
dashpot cylinder moved to control the gear.
Air may sometimes be used in place of a fluid.
In some cases the dashpot may form virtually a part of the governor itself. The
improved dashpots may be used for almost any controlling mechanism where a
continuous movement is not necessary.
The valve which closes the dashpot passages need not be a piston valve, any
suitable valve may be substituted. Or in some cases the check valves themselves
may be secured as desired, instead of using a separate valve.
The dashpot itself may be controlled by almost any form of governor, by electric
magnets or solanoids, or by hand.
Any force capable of opening and closing the dashpot passages can secure an
accurately controlled assistance of any desired power.
The dashpot may therefore be used as an auxiliary for a variety of purposes,
such as the control of prime movers, or of electrical appliances, for reversing large
engines etc.
When the gear to be controlled requires both to be moved or held fast two
dashpots may be used with differently controlled passages.
Dated this 28th day of March 1895.
WILSON HARTNELL.
Improvements in Dash-pots.
1, WILSON HARTNELL, late of Bensons Buildings, Park Row, in the City of
Leeds, but now of Volt Works, Kirkstall Road Leeds aforesaid, Consulting
Engineer do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :-
My invention consists in improvements in dashpots and their connections, so that
they may be used in conjunction with governors or controlling agents, not merely
as passive retarding mechanisms but to give active assistance to move or to hold
securely the gear attached.
The dashpot is made with two or more passages communicating with opposite
sides of the piston furnished with check valves opening opposite ways.
These passages may be either in the dashpot piston or in its surrounding cylinder,
and may be opened or closed as required.
The governor is so connected to the piston as to be able to close or open one or
both these passages before it attempts to move the dashpot piston.

page_text: In order to give active resistance the fluid in the dashpot is reciprocated, say by
a reciprocating piston or plunger (which may be at any convenient position) or by
reciprocating the dashpot.
To hold securely the gear attached the fluid is not reciprocated.
In order to explain this invention more definitely I will give examples.
Suppose that the governor of a steam engine acts against a passive resistance,
such as in twisting an expansion valve rod or in moving a throttle valve. Let the
dashpot D be vertical as shown by Figure 1 and let the piston P be furnished with
passages p1, p2, and check valves, the one 1, allowing the fluid to flow upward
through the piston D, the other v2, allowing it to flow downwards. Let the
governor open or close either of the passages p1 p2 by the piston valve g.
Let the dashpot piston he coupled to the valve gear by the rods and let the
governor also be connected to the dashpot piston by the rod G but with a small
amount of play at a, so that the governor can close either of the passages p 1, p 2,
by means of the piston valve before it presses on the dashpot.
Let the fluid in the dashpot be reciprocated say in this example, by raising and
lowering the dashpot. If the governor now presses the dash-pot piston P, down-
wards at the point a it must first have moved the piston valve g & have closed the
passage p2 which allows the fluid to flow from the top to bottoin side of the piston.
When the dashpot rises the fluid will pass freely upwards through the piston by
the passage p 1, but when the dashpot falls the fluid cannot now return by either
passage. The piston P is therefore pushed down by the reciprocated fluid (with a
force not less than atmospheric pressure) with or without the assistance of the
governor and will continue to move downwards until the governor by resting
10 a new position allows the downward movement of dashpot to open the
passage p 2.
Thus no effort on the part of the governor to overcome the resistance of the gear
is required.
Thus the governor and controlled gear take the exact position due to the speed
of the engine unchecked by friction. In this case those cyclic variations of speed
due to the retarded action of the governor by friction are eliminated.
In a steam engine the reciprocating movement of the dashpot may be conveniently
obtained from the reciprocating valve rods.
The dashpot piston may be balanced or connected to the governor by a supporting
spring, so as to keep the passages always open when the governor is not acting and
avoid an otherwise slight continuous reciprocation of the piston to alternately open
the closed port.
Next suppose the governor of a steam engine controls the expansion of the steam
through the medium of a vibrating link which vibration unless prevented would
shake the governor.
The arrangement of the dashpot to hold the gear securely may be precisely
There
the same as in Figure 1, except that the fluid is not reciprocated.
would however be a slight reciprocation of the piston which might be
undesirable.
If the piston is to be held still the piston valve must now cover both passages as
at g Figure 2.
The dashpot piston cannot then move and the expansion gear will be held
rigidly.
If now the governor presses the dashpot piston P at the point a, Figure 1, it
must first have moved the piston valve g Figure 2, and opened the passages_pl
which allows this fluid to pass from the bottom to the top of the piston. The
dashpot can now move downwards freely, but if at the same time the liuk gear tries
to pull the piston down it will go down with or without direct pressure from the
governor, but when the governor has taken up a new position the continued
descent of the piston will close the passage p1 & the dashpot is again
securely held.
If however at the same time that the governor opens the upward passage p1,

page_text: the link gear tries to push the dashpot piston upwards it cannot do so because
the check valve 1, prevents the fluid flowing downward and thus hold the
piston.
21
In either arrangement of dashpot the reverse (or upward) movement will be
similar to the downward above described.
The movement of the piston from one position to another may be during one or
more reciprocations.
When the passive resistance of the gear to be controlled is comparatively small
and uniform and the fluid is reciprocating then in some cases the valves v1, v2,
and g may be omitted and the passage or passages through the piston P' Figure 3
being so regulated that the reciprocating pressure on the dashpot approximately
balances the resistance to be. overcome, thus making opportunities for the governor
to act freely.
The dashpots may be closed at each end as in Figures 4 and 6 and placed
horizontally or in any other convenient position.
The valve by which the governor controls the passages in the dashpot piston
need not be a piston valve but of any convenient form, as also may be the valves in
the passages.
The governor valve may sometimes be unbalanced as at 91, 92, Figure 4.
The piston P is fixed to the rod v attached to the part to be controlled. The
governor attachment G on pressing the piston must close one of the passages pl
or p 2.
In some cases the governor may secure the check valves themselves as in
Figure 5 by means of the stops g 1. 92. acting on the valves 1. v2.
The passages may be placed in the cylinder instead of the dashpot piston as
shown in Figure 6 where p1 p 2 are the passages, 1, 2 the valves, and g the
governing valve.
The fluid in the dashpot Figure 6 may be reciprocated without reciprocating the
dashpot by means of a reciprocating piston c Figure 7 placed at any convenient
position and connected to the dashpot by means of pipes, d, e, or instead of the
piston a plunger f, Figure 8 may be used communicating by the pipe d, to the
dashpot but in this case there must be sufficient space beyond the valve v1 v2 to
allow for the alternating displacement of fluid by the plunger without uncovering
the valves.
Experience has shown that in governing prime movers it is generally advantageous
that the position of their governing gear should be dependant upon the position of
the governor.
This involves the use of a differential gear. When the valve 9 connected to the
governor gear is in the piston as in Figure 1 or 4 it constitutes a differential gear
since the opening of the passages by the valve a depends upon the difference of
position between the governor connection G and the controlled gear V.
When the valve g is in a fixed chamber as in Figure 6 the differential motion
must be obtained in some other way. Many well known forms of differential gear
may be adopted. Two arrangements are shown by Figures 9 and 10. In Figure 9
there is a radius bar h for the purpose of carrying the pin k on which is pivoted the
lever attached to the governor at a where there is a certain play before the
governor can press the rod v, the other end of the lever is connected to this piston
valve g (see Figure 6).
It is obvious that in whatever position the radius bar / may be, the governor by
pressing the end of the lever will open the valve g, and that when the governor
ceases to press the lever the continued movement of the rod V in the same
direction will by moving the radius bar h and its pivot k close the valve and stop
further motion.
In the differential gear Figure 10 the governor connection G is attached near
the middle on the lever and when the rod G has moved the valve the latter will
be returned to its mean position when the rod G ceases to move, by the further
movement of the rod V acting on the pivot k. The valve G to suit this gear must

page_text: be cut off on the two inner edges and not on the two outer edges as in Figures 1, 2
and 6.
In some cases the dashpot may form virtually a part of the governor itself as in
the crank shaft governor shown in outline in Figure 11 where the dashpot D forms
part of a direct connection between the governor levers and the eccentric m
through the rod G and the rod V. The dashpot may be secured to the frame of
the governor-any pressure on the eccentric due to its moving the valves of the
engine will be transmitted direct to the frame instead of to the governor and is
there held securely. The eccentric will be moved by the governor when in that
position which assists or offers least resistance to being moved. The dashpot
itself may be controlled by any form of governor by electric magnets or solenoids
or by hand.
The improved dashpots may be used for almost any mechanism to be controlled
where a continuous movement is not a necessity such as for governing engines
turbines, water wheels or any other prime mover, or for reversing gear, or for
steering gear, for opening locks and sluices or sometimes raising weights, for
moving electrical resistance &c. But in all cases where active assistance is
required a pulsating fluid conveyed to the dash-pot by a pipe or pipes or a
reciprocating motion acting on the dash-pot or its piston must be provided.
When the available power of the governing apparatus is very small as is usually
the case when an electric solenoid is used, it is desirable to couple the plunger
direct to the valve as in Figures 12 and 13, where the plunger O of the solenoid p
coupled direct to the valve g. In each of these Figures 12 and 13 the travel of the
dashpot piston P is greater than that of the solenoid core. The differential motion
shown will be obvious from inspection of the diagram, in Figure 12 the dashpot
moves, in Figure 13 the solenoid moves. The fluid is reciprocated in Figure 12
by means of a plunger not shown and a flexible pipe.
Owing to this differential arrangement the controlled apparatus attached to V
will rise and fall in proportion to the movement of the solenoid core as already
explained.
If no differential actions be provided the piston will continue to move until the
current ceases to act (or until the piston reaches the end of its travel).
This independant action of the dashpot may be necessary for some purposes.
Obviously if required the small dashpot might control a larger one which latter
acted direct on the controlled gear.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what 1
claim is-
1. Improvements in dashpots and their connections by the addition of valves and
passages by means of which the flow of fluid from one side of the piston to the
other may be regulated by a controlling agents with the objects and for the
purposes set forth which improvements are shewn carried into effect in and by
the arrangements described herein and shown in the drawings.
2. The method of actively assisting the governor or controlling agent by
reciprocating the dashpot or its piston, or otherwise reciprocating the fluid therein
substantially as described herein and shown on the drawings.
3. The combination of the improved dashpots (with or without a reciprocating
fluid) with governors of prime movers or with electro magnets substantially as
described herein for the purpose set forth and as shown on the drawings.
Dated this Twenty-fourth day of December 1895.
WILSON HARTNELL.