Improvements connected with the Valve Gear of Steam Engines.
Year: 1893

page_text: Date of Application, 26th May, 1893
Complete Specification Left, 22nd Feb., 1894-Accepted, 24th Mar., 1894
PROVISIONAL SPECIFICATION.
Improvements connected with the Valve Gear of Steam Engines.
A communication by TROPHIME DELVILLE, of Brussels, in the Kingdom of
Belgium, Engineer.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street,
Manchester, both in the County of Lancaster, and 323, High Holborn, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of this
invention to be as follows:-
This invention has for its object to enable the admission of steam to and the
discharge of the same from the cylinders of steam engines having distributing slide
gear, to take place as easily as possible, in order to avoid the resulting over- or
back-pressure which is opposed to the advantageous utilization of the steam, such
back-pressure being an unavoidable drawback in the lead ("Voreilung ") imparted to
a slide valve by means of a suitable connection with the eccentric.
This invention has for its object to provide an arrangement for operating the free
running slide valve in such a way, that thereby firstly a very large opening of the
inlet and outlet passages is brought about, secondly, a large linear lead of the inlet
and outlet, and thirdly, however, only a small angular lead for the inlet and outlet.
In order to graphically represent the course of the slide valves suitable for
producing the desired action, the Zeuner's circular polar diagram must be drawn, as
an extended, flattened or oval curve, as shown in Figure 1 of the accompanying
drawing, and it then appears from the comparison of the figures, that in the case of
the dotted curve the maximum opening of the inlet passages P P is considerably
greater than that produced by means of the circular course P P', that the linear
lead to the inlet AA" is much greater than A A', but that the angular lead A l'
is considerably smaller than A I, from which the conclusion is drawn that in the
dotted oval course of the slide valve the commencement of the inlet, which in the
circular diagram with the same maximum openings takes place too soon, is suitably
delayed.
In order then to carry out this movement of the slide valves theoretically exactly,
that is to say to suitably accelerate or retard towards both sides the stroke of the
valve, and that in a suitable proportion for producing an even piston speed, in
other words to describe the theoretically correct line of curve corresponding to the
desired object, the slide valve operated from the eccentric must be influenced in
such a way that it only has the normal speed at the moment when it is in a middle
position, and from this moment however must be progressively accelerated towards
both sides in order to again resume the middle position with an equal progressive
retardation, so that at each stroke of the piston the slide makes one half of
its course with a progressive retardation, and the other half of its course with
a progressive acceleration. If these alterations of speed are to take place
by means of lever transmission in an exactly correct progression to the even
strokes of the piston there is only one possible mode of connecting the lead lever
with the remaining parts of the engine in order to produce an absolutely correct
maintenance of the proportions, and this is characterised by one end of the lever
making a straight back and forward movement corresponding to the piston stroke,
whilst the other end appears as a longer or shorter lever arm opposite the point of
engagement of the slide rod, according to the position of the slide, for which purpose

page_text: the point of engagement of the eccentric rod which operates the lever, must always
lie between the point of engagement of the slide rod, and the straight end of the
lever.
These indispensable conditions for producing the desired result are obtained in
the simplest manner by the arrangement of lead levers shown as a sketch in
Figures 2 and 3. In these the lower end A. of the lever is compulsorily moved
backwards and forwards in a straight line, like the piston, by being connected with
a crosshead, whilst the lever oscillates on the point of engagement B of the eccentric
rod, and ends above as a suitably formed connecting link (', which embraces the
slide block D attached to the straight slide rod, so that then at each to and fro
movement of the lever arm B, D is shortened or lengthened in alternate progression
in proportion to the movement of the piston, and thus the slide valve undergoes in
its course the above named retardation or acceleration.
These progressive proportions of lead can however only be correctly maintained,
in other words, the pure oval dotted course describing this travel of the slide valve can
only be obtained, by the alterations of the proportions of the lead lever being made
to exactly correspond to the length of stroke of the piston. If in fact the course
of the lower lever were shorter than the stroke of the piston, or even equal to zero,
the acceleration, and consequently also the proportion of lead, would also be less.
whilst the same would also be diminished to the same extent if the duration of the
course were longer, as for instance would be the case if the lower end of the lead
lever moved from one point to another on a curved instead of a straight line, so the
necessary increase of the levers B D in both cases would no longer take place in
correct proportion to the position of the piston, whereby the slide diagram would
then undergo inflections, and thus the theoretic transformation of the circular track
of the Zeuner polar diagram become an extended curve of pure regular course, that
is to say the solution of the problem is excluded.
This extremely simple mode of construction also allows of the further arrange-
ments usual in slide valves for varying the degree of filling etcetera being used.
Thus for instance the point B instead of being directly influenced from the eccentric
rod, may be connected with a rod attached to the slide block of an ordinary
connecting link arrangement, Figures 4 and 5, and it suffices, in order to alter the
degree of filling, to operate the so-called reversing lever by hand, or by means of a
regulator. In non-reversing machines the connecting link only requires to be half
the length, and the suitable oval diagrams shown in Figure are obtained for the
various positions of the distribution or expansion lever, the largest of these ovals
corresponding to the maximum filling and the smaller to the maximum expansion.
Dated this 25th day of May 1893.
WM. P. THOMPSON & Co.,
Agents for the Applicant.
COMPLETE
SPECIFICATION.
Improvements connected with the Valve Gear of Steam Engines.
A communication by TROPHIME DELVILLE, of 53, Rue Dupont, Brussels, in the
Kingdom of Belgium, Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool and 6, Bank Street, Manchester,
both in the County of Lancaster and 323 High Holborn in the County of
Middlesex Civil 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 :-
This invention has for its object to enable the admission of steam to and the
discharge of the same from the cylinders of steam engines having distributing slide

page_text: rear, to take place as easily as possible, in order to avoid the resulting over- or
back-pressure which is opposed to the advantageous utilisation of the steam, such
back-pressure being an unavoidable drawback in the lead ("Voreilung ") imparted
to a slide valve by means of a suitable connection with the eccentric.
This invention has for its object to provide an arrangement for operating the free
running slide valve in such a way, that thereby firstly a very large opening of the
inlet and outlet passages is brought about, secondly, a large linear lead of the inlet
and outlet, and thirdly. however, only a small angular lead for the inlet and
outlet.
In order to graphically represent the course of the slide valves suitable for pro-
ducing the desired action, the Zeuner's circular polar diagram must be drawn, as an
extended, flattened or oval curve, as shown in Figure 1 of the accompanying
drawing, and it then appears from the comparison of the figures, that in the case of
the dotted curve the maximum opening of the inlet passages P P" is considerably
greater than that produced by means of the circular course P P, that the linear
lead to the inlet A. A" is much greater than A A', but that the angular lead A I'
is considerably smaller than A I, from which the conclusion is drawn that in the
dotted oval course of the slide valve the commencement of the inlet, which in the
circular diagram with the saine maximum openings takes place too soon, is suitably
delayed.
In order then to carry out this movement of the slide valves theoretically exactly,
that is to say to suitably accelerate or retard towards both sides the stroke of the
valve, and that in a suitable proportion for producing an even piston speed, in
other words to describe the theoretically correct line of curve corresponding to the
desired object, the slide valve operated from the eccentric must be influenced in such
a way that it only has the normal speed at the moment when it is in a middle
position, and from this moment however must be progressively accelerated towards
both sides in order to again resume the middle position with an equal progressive
retardation, so that at each stroke of the piston the slide makes one half of its course
with a progressive retardation, and the other half of its course with a progressive
acceleration. If these alterations of speed are to take place by means of lever
transmission in an exactly correct progression to the even strokes of the piston there
is only one possible node of connecting the lead lever with the remaining parts of
the engine in order to produce an absolutely correct maintenance of the proportions,
and this is characterised by one end of the lever making a straight back and forward
movement corresponding to the piston stroke, whilst the other end appears as a
longer or shorter lever arm opposite the point of engagement of the slide rod,
according to the position of the slide, for which purpose the point of engagement of
the eccentric rod which operates the lever, must always lie between the point of
engagement of the slide rods and the straight end of the lever.
These indispensable conditions for producing the desired result are obtained in
the simplest manner by the arrangement of lead levers shown as a sketch in
Figures 2 and 3. In these the lower end A of the lever is compulsorily moved
backwards and forwards in a straight line, like the piston, by being connected with
a crosshead, whilst the lever oscillates on the point of engagement B of the eccentric
rod, and ends above as a suitably formed connecting link C, which embraces the
slide block D attached to the straight slide rod, so that then at each to and fro
movement of the lever arm B, D is shortened or lengthened in alternate progression
in proportion to the movement of the piston, and thus the slide valve undergoes in
its course the above named retardation or acceleration.
These progressive proportions of lead can however only be correctly maintained,
in other words, the pure oval dotted course describing this travel of the slide valve
can only be obtained, by the alterations of the proportions of the lead lever being
made to exactly correspond to the length of stroke of the piston. If in fact the
course of the lower lever were shorter than the stroke of the piston, or even equal
to zero, the acceleration, and consequently also the proportion of lead, would also
be less, whilst the same would also be diminished to the same extent if the duration

page_text: of the course were longer, as for instance would be the case if the lower end of the
lead lever moved from one point to another on a curved instead of a straight line, so
the necessary increase of the levers B D in both cases would no longer take place in
correct proportion to the position of the piston, whereby the slide diagram would
then undergo inflections, and thus the theoretic transformation of the circular track
of the Zeuner polar diagram become an extended curve of pure regular course, that
is to say the solution of the problem is excluded.
This extremely simple mode of construction also allows of the further arrange-
ments usual in slide valves for varying the degree of filling etcetera being used.
Thus for instance the point B instead of being directly influenced from the eccentric
1od, may be connected with a rod attached to the slide block of an ordinary
connecting link arrangement, Figures 4 and 5, and it suffices, in order to alter the
degree of filling, to operate the so-called reversing lever by hand, or by means of a
regulator. In non-reversing machines the connecting link only requires to be half
the length, and the suitable oval diagram shown in Figure 6 are obtained for the
various positions of the distribution or expansion lever, the largest of these
ovals corresponding to the maximum filling and the smaller to the maximum
expansion.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is-
In distributing slide valve gear the arrangement of a lead lever oscillating on the
point of engagement B of the eccentric or expansion rod in such a way that its
lower end A compulsorily shares in the to and fro movement in a straight line of
the piston and thereby the upper lever arm C which influences the slide rod at D
is lengthened or shortened in a proportion which progressively alternately
accelerates or retards the travel of the slide valve at each stroke of the piston
substantially as and for the purposes described.
Dated this 21st day of February 1894.