An Improved Slide Valve Motion.
Year: 1896

page_text: An Improved Slide Valve Motion.
I, VICTOR Pore of 80, Rue Taitbout, Paris, France, Engineer; do hereby declare
the nature of this Invention to be as follows:-
This Invention relates to an improved slide valve motion with reversing gear
and cut off variable by hand.
My Invention has for object to reduce the length of the crank shaft and
to render the engine more compact while retaining the advantages of the ordinary
Meyer's Expansion Valve Gear with three eccentrics and reversing link. The
action within the valve chest is exactly the same as if the main slide valve were
actuated through a link in one or other of its two extreme positions only and the
expansion slides were operated by a special eccentric, these different actions being
however obtained by a single can producing the same effects as the three eccentrics
generally employed.
My improved valve motion is illustrated in the accompanying drawings
as applied to the two cylinder engine of a compressed air tramway loco-
motive, in which Figure 1 is a longitudinal section and Figure 2 a
plan of the valve gearing. Figure 3 is a transverse section of the cylinders
shewing the respective positions of the valve chests. Figure 4 is a detail view
of the cam. The same letters of reference denote like parts in all the Figures.
The driving wheel axle a supports a frame b carrying the bearings c of the
crank shaft actuated by the pistons of the two cylinders e f and geared with
a pinion g with a toothed wheel h keyed on the axle a.
In this example the two motor cylinders are supposed to be coupled chiefly
for working compound, the cut off to the larger cylinder being fixed and the
smaller cylinder only having a variable expansion whereby the speed of the
vehicle is regulated. The distribution valve of each cylinder e f is controlled each
by a special cam ij keyed on the crank shaft d, the two valve motions being
identical except that the large cylinder has no provision for variable expansion
and the description will therefore be confined to the small cylinder (Figure 1)
and its cam i. This cam acts on two bell crank levers pivoted respectively
at 13 and bearing by rollers m³ m² against the cam i, the other arms of the
levers being coupled by means of short links with the rods of pistons n¹ n²
working in cylinders carried by a frame o attached to the rod o¹ of the main
slide valve and guided at its free end by a piston n³, compressed air under pressure
being admitted behind said piston to act as a cushion constantly tending to force
the slide valve inwards. If compressed air he admitted behind the piston n¹
(which is made of sufficiently large area to be pressed constantly against its abut-
ment whatever may be the resistance to be overcome in order to move the valve
rod) the piston n' will be fast with the part o and consequently with the valve rod.
Moreover by the compressed air acting upon the back of the piston ³ the roller m
will be constantly held against cam i in all positions of the latter the compressed
air behind the piston acting as a spring. When therefore shaft d is rotated the

page_text: cam moves lever backwards and through it the valve rod, the relative
movements being similar to those produced by an eccentric suitably arranged.
Supposing the engine to be in backward gear as indicated by the arrow and the
slide valve to be moving by the action of the can and that it is desired to reverse
the direction of motion. According to the ordinary theory of reversing it is
only necessary to shift the eccentric, that is to say to give the cam i another
position on shaft d, but I have found that it is simpler to change the position
of the roller which amounts to the same thing, in other words in order to change
from backward to the forward gear I disconnect the lever from the valve rod
and connect the lever thereto by allowing the compressed air behind the piston n¹
to escape and admitting compressed air behind the piston n whereby piston n²
will be held against its abutment and roller m³ be constantly pressed against
the cam whatever may be its position. Thus by the mere operation of a four-
way cock controlling the pipes pp reversal of motion can be effected at will
by bringing the slide valve under the action of the one or other lever.
The cam i also controls the rod which operates the variable expansion valve;
in an ordinary Meyer Expansion Gear, the eccentric which operates the expansion
valve is keyed exactly at 180 degrees to the crank and in order to obtain the same result
a lever is pivoted to a fixed point and bears by a roller m³ at a suitable point
against cam i. The lever is coupled by rod q to a lever k pivoted at and
terminating in a fork coupled by two short links with a collar in which the
expansion valve rod s is free to turn. The rods receives longitudinal motion
from lever and slides through a bevel pinion tactuated through a train of
gearing suitably arranged whereby the expansion may be varied at will. The
sectional area of the rod s is such that the air pressure in the valve chest which
tends to force said rod outwards will suffice to constantly maintain the roller m³
against cam i. Thus by suitably arranging the three rollers m¹ m³ m³ the cam
alone will operate the main slide valve both in forward and backward gear and
also the Meyer Expansion Valve and thus fulfil the functions of the three
eccentrics generally used.
The valve gear of the large cylinder would be similarly operated and the same
four-way cock may serve to reverse the motion for both cylinders.
It has been stated that the cam i produces movements similar to those of an
ordinary eccentric but geometrical considerations will shew that if the cam is
circular the valve diagram will not be the same as with an ordinary eccentric
and in order to obtain a diagram as good as, or even better than, that of an
ordinary eccentric I make the cam i of the following form, that is to say as shewn
in Figure 4, of two symmetrical parts each slightly greater than a semi-circle
the centres from which they are described being a very slight distance apart
whereby an excellent diagram is obtained which even allows for the disturbance
due to the small radius of the driving crank.
My improved valve motion may be easily adjusted for wear of the rollers, the
abutments of pistons n¹ na being formed by screw stops against which the pistons
bear.
To adjust the gear the crank is placed at the dead point (Figure 1) the slide
valve is brought opposite à mark inside the valve chest and the rollers then
brought against the cam by means of the adjusting screws. The rod q and the
slide valve rod may also be provided with screw couplings for exactly regulating
their length.
My improved valve gear may be applied to all kinds of engines of which the
foregoing is only given as an example, the dimensions and details of arrangement
being variable to suit the case.
Dated December 18th 1896.

page_text: I, VICTOR Porr of 80, Rue Taitbout, Paris, France, 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 relates to an improved slide valve motion with reversing gear
and cut off variable by hand.
My Invention has for its object to reduce the length of the crank shaft and
to render the engine more compact while retaining the advantages of the ordinary,
Meyer's Expansion Valve Gear with three eccentrics and reversing link. The
action within the valve chest is exactly the same as if the main slide valve were
actuated through a link in one or other of its two extreme positions only and the
expansion slides were operated by a special eccentric, these different actions being
however obtained by a single cam producing the same effects as the three eccentrics
generally employed.
My improved valve motion is illustrated in the drawings accompanying the Pro-
visional Specification as applied to the two cylinder engine of a compressed air
tramway locomotive, in which Figure 1 is a longitudinal section and Figure 2 a
plan of the valve gearing. Figure 3 is a transverse section of the cylinders
shewing the respective positions of the valve chests. Figure 4 is a detail view
of the cam. The same letters of reference denote like parts in all the Figures.
The driving wheel axle a supports a frame & carrying the bearings c of a
crank shaft actuated by the pistons of the two cylinders e f and geared by
a pinion g with a toothed wheel 'h keyed on the axle a.
In this example the two motor cylinders are supposed to be coupled chiefly,
for working compound, the cut off to the larger cylinder being fixed and the
smaller cylinder only having a variable expansion whereby the speed of the
vehicle is regulated. The distribution valve of each cylinder e f is controlled each
by a special cam i j keyed on the crank shaft d, the two valve motions being
identical except that the large cylinder has no provision for variable expansion
and the description will therefore be confined to the small cylinder (Figure 1)
and its cam i. This cam acts on two bell crank levers pivoted respectively
at and bearing by rollers m¹ m² against the cam i, the other arms of the
levers being coupled by means of short links with the rods of pistons n' n²
working in cylinders carried by a frame o attached to the rod o of the main
slide valve and guided at its free end by a piston n³, compressed air under pressure
being admitted behind said piston to act as a cushion constantly tending to force
the slide valve inwards. If compressed air be admitted behind the piston n¹
(which is made of sufficiently large area to be pressed constantly against its abut-
ment whatever may be the resistance to be overcome in order to move the valve
rod) the piston n' will be fast with the part o and consequently with the valve rod.
Moreover by the compressed air acting upon the back of the piston n³ the roller m¹
will be constantly held against cam i in all positions of the latter the compressed
air behind the piston acting as a spring. When therefore shaft d is rotated the
cam i moves lever backwards and through it the valve rod, the relative
movements being similar to those produced by an eccentric suitably arranged.
Supposing the engine to be in backward gear as indicated by the arrow and the
slide valve to be moving by the action of the cam and that it is desired to reverse
the direction of motion. According to the ordinary theory of reversing it is
only necessary to shift the eccentric, that is to say to give the cam i another
position on shaft d, but I have found that it is simpler to change the position

page_text: of the roller which amounts to the same thing, in other words in order to change
from backward to the forward gear I disconnect the lever k¹ from the valve rod
and connect the lever thereto by allowing the compressed air behind the piston n
to escape and admitting compressed air behind the piston n2, whereby said piston n²
will be held against the abutment and roller m² be constantly pressed against
the cam whatever may be its position. Thus by the mere operation of a four-
way cock controlling the pipes p reversal of motion can be effected at will
by bringing the slide valve under the action of the one or other lever.
The cam i also controls the rod which operates the variable expansion valve;
in an ordinary Meyer Expansion Gear, the eccentric which operates the expansion
valve is keyed exactly at 180° to the crank and in order to obtain the same result
a lever is pivoted on a fixed point and bears by a roller m³ at a suitable point
against cam i. The lever is coupled by rod q to a lever k pivoted at and
terminating in a fork coupled by two short links with a collar r in which the
expansion valve rods is free to turn. The rod s receives longitudinal motion
from lever and slides through a bevel pinion actuated through a train of
gearing suitably arranged whereby the expansion may be varied at will. The
sectional area of the rod s is such that the air pressure in the valve chest which
tends to force said rod outwards will suffice to constantly maintain the roller m³
against cam i. Thus by suitably arranging the three rollers m¹ m² m³ the cam i
alone will operate the main slide valve both in forward and backward gear and
also the Meyer Expansion Valve and thus fulfil the functions of the three
eccentrics generally used.
The valve gear of the large cylinder would be similarly operated and the same
four-way cock may serve to reverse the motion for both cylinders.
It has been stated that the. cam i produces movements similar to those of an
ordinary eccentric but geometrical considerations will shew that if the cam is
circular the valve diagram will not be the same as with an ordinary eccentric
and in order to obtain a diagram as good as, or even better than, that of an
ordinary eccentric I make the cam i of the following form, that is to say as shewn
in Figure 4, of two symmetrical parts each slightly greater than a semi-circle
the centres from which they are described being a very slight distance apart
whereby an excellent diagram is obtained which even allows for the disturbance
due to the small radius of the driving crank.
My improved valve motion may be easily adjusted for wear of the rollers, the
abutments of pistons 3 being formed by screw stops against which the pistons
hear.
To adjust the gear the crank is placed at the dead point (Figure 1) the slide
valve is brought opposite a mark inside the valve chest and the rollers then
brought against the cam by means of the adjusting screws. The rod q and the
slide valve rod may also be provided with screw couplings for exactly regulating
their length.
My improved valve gear may be applied to all kinds of engines of which the
foregoing is only given as an example, the dimensions and details of arrangement
being variable to suit the case.
Having now particularly described and ascertained the nature of the said In-
vention and in what manner the same is to be performed I declare that what I
claim is:
1st. The herein described reversing and variable expansion slide valve gear
consisting in the combination with a single cam on the crank shaft of three
levers of which two operate the one in forward and the other in
backward running, and of pistons n respectively connected to said levers
and movable within cylinders attached to the slide valve rod but capable of being
fixed therein by fluid. pressure admitted to the one or other cylinder according
-as the one. or other lever or is to be connected with the slide valve rod for

page_text: forward or backward gear and the lever being connected to the expansion
slides, all substantially as specified and illustrated in the accompanying drawings.
2nd. In a slide valve gear herein described the combination with the pistons
and cylinders for coupling the valve operating levers with the valve rod, of
adjustable stops for regulating the position of the pistons n' n and levers k
upon which the valve operating cani acts as described.
Dated this 7th day of August 1897.
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.