IMPROVEMENTS IN STEAM AND OTHER ENGINES, AND IN MECHANISM FOR CONVERTING OR TRANSMITTING MOTION OR TRANSMITTING PRESSURE
Year: 1880

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of "IMPROVEMENTS
IN STEAM AND OTHER ENGINES, AND IN MECHANISM FOR CONVERTING OR
TRANSMITTING MOTION OR TRANSMITTING PRESSURE,” A communication
from abroad by Asa Johnson, of the City, County, and State of New York,
United States of America.
PROVISIONAL SPECIFICATION left by the said Alexander Melville. Clark
at the Office of the Commissioners of Patents on the 1st November 1880.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "IMPROVEMENTS IN STEAM AND OTHER ENGINES, AND IN
MECHANISM FOR CONVERTING OR TRANSMITTING MOTION OR TRANSMITTING
PRESSURE," [A communication from abroad by Asa Johnson, of the City, County,
and State of New York, United States of America.]
This Invention is embodied mainly in an improved form and arrangement of
friction clutches, whereby a reciprocating motion may be converted into a continuous
rotary motion, or whereby a continuous rotary motion may be transmitted from
one shaft to another, as hereinafter fully set forth. The Invention also consists in
an improved form of balanced slide valve, and in several details of construction and
modifications, as hereinafter set forth.
The transmitting mechanism is designed more especially for steam or other
engines as a substitute for the crank and connecting rod, whereby the motion of
the piston may be imparted directly and in a straight line to the driving wheel or
shaft, and in such manner also as will obviate all dead points and admit of
reversing the motion of the shaft without changing the valve of the engine. To
this end a leading feature of the Invention consists in connecting the reciprocating
bar or piston rod with two or more friction clutches, each acting alternately and in
opposite directions on friction rims and hubs on two or more distinct wheels which
are geared together, whereby a continuous rotary motion is imparted to the wheels
by the alternating bite of the clutches. Another feature of the Invention lies in
the special form of these clutches, and also in a means of shifting these clutches,
whereby the direction of their bite on the friction rim becomes reversed, and,
accordingly reverses the direction of rotation.

page_text: The power of the reciprocating piston or other motor is imparted to two shafts
geared together by toothed wheels, one of which shafts may serve as the driving shaft
from which a train of machinery may be driven; both shafts may, however, be so
used if desired. The friction clutches, which are reciprocated by the piston rod or
other reciprocating bar, act on friction rims or purchase wheels which are also fixed
on the shafts, or to the gear wheels, so as to revolve therewith. These wheels are
preferably formed as plate wheels with a thin central web and a projecting rim on
each side of the web at the periphery, and their diameter is nearly as large as the
gear wheels, or as large as practicable, so as to obtain greater leverage. The
friction clutch consists of a radial arm which is mounted loosely on the hub of the
purchase wheels, or on the shafts thereof, and carries at its outer ends two friction
shoes which embrace respectively the inner and outer face of the rims on the
The crosshead
purchase wheels, and are pivoted at or about the centre to the arm.
on the piston rod of the engine connects to a straight reciprocating bar, which is
mounted in guides at its outer end and is connected midway with each of the
clutch arms, the said bar having notches which fit over pins projecting from the
clutch arms, so that the reciprocation of the piston correspondingly reciprocates the
clutches in short circular arcs. In this kind of engine I prefer to have the diameter
of the piston large and its stroke small, so as to be able to transmit a great power
through the clutches, but in short arcs, so that the clutch movement will approximate
closely to straight lines. The inner or pivoted end of the clutch arms which are
mounted on the axis of the purchase wheels are slotted, so that the clutch arms
may be shifted one way or the other to cause the arms to incline slightly in either
way. Now the clutches bite when moved in the direction towards which they
incline, and slip when moved in the opposite direction, and the clutch of each
purchase wheel inclines in opposite directions, so that when the piston rod or
reciprocating bar moves forward one of the clutches bite and the other slips, while
both wheels revolve by the power applied to one, and when the rod or bar moves
backward the second clutch bites upon the other wheel while the first slips, but it
will be observed that as both wheels are geared together these alternate clutchings
on each wheel cause both wheels to revolve continuously and in the same direction
with a uniform and steady motion.
The clutches bite by an eccentric or cramping action of the friction shoes upon
the rims of the purchase wheels, which occurs only when the clutch is moved in the
direction towards which they incline, and the shoes relax and move loosely over
the rims when moved in the opposite direction. The bite of the shoes is such as
to grip the rim in an instantaneous and positive manner, yet without denting the
rims or being liable to slip when advancing or catch when retiring. By this form
of transmitting mechanism the power of the piston is transmitted in a direct line
to the long end of the lever, and without any dead points in its movement, as is
the case with the crank motion in which the power is applied in a direct line to
the centre of the shaft, and in which also the piston rod has to stop and wait at
the dead points for the crank to be carried a long distance by the momentum alone,
which is not the case with this transmitting mechanism. Moreover, by this
mechanism the rotation of the driven shaft does not react upon the piston, but
the momentum of the driven shaft and its wheels may continue the rotation when
the movement of the piston ceases, thus allowing intervals of rest to the piston if
required to further economise the power.
Another advantage of this mechanism is, that by shifting the clutches by the
movement of a hand lever the rotation of the driving shaft may be instantly
reversed without changing the valve of the engine. The clutches are accordingly
shifted and held in either of their acting positions by forked levers pivoted below
the purchase wheels while their forked ends embrace the slotted pivoted ends of the
clutch arms, and these levers are connected by links to the short arms of a long hand
lever which projects above the bed of the engine in convenient position for operation
by the hand. This lever when shifted to one side or the other catches on either
side of a stop which holds the clutches in the required position, and the effect of

page_text: shifting the clutches to one side or the other is to throw the pivot line of the
friction shoes eccentric to the axis of the purchase wheels, which hence causes the
shoes to grip when moved toward the longer radius of the eccentric and slip in the
opposite direction. Hence, when the clutch is shifted from one side to the other
the eccentricity of the shoes becomes reversed, thus causing them to grip in the
opposite direction, and hence reversing the direction of rotation.
The described form of transmitting mechanism is obviously adapted for many
purposes other than engines where a reciprocating motion is to be converted into a
rotary motion, and the described clutch may also be employed in various kinds of
machinery, either for transmitting or converting a reciprocating motion, or for
transmitting a continuous rotary motion from one shaft to another. It may thus
be employed in treadles, friction pulleys, car starters, &c.
The arrangement of gear wheels and clutches is double, that is, the purchase
wheels are arranged between two gear wheels, which mesh together, and a clutch is
arranged on each side of the purchase wheels, the clutch arms being joined together
by connecting pins, which engage with the reciprocating bar, but only a single set
of gear wheels and clutches may be used when preferred, and the friction rims on
which the clutches act may be formed directly on the gear wheels themselves.
Positive ratchets and pawls may be used in place of the friction clutches, and also
a different form of reversing mechanism, in which case the connecting rod from the
piston of the engine is jointed to swinging arms, which oscillate on the shafts of
the geared driving wheels. Now on the shafts of these wheels are fixed ratchicted
hubs, having a small number of double sided ratchet teeth. The swinging arms
carry double pawls, which engage with the said ratchets in either direction, according
to the position in which they are set for rotation, either forward or backward.
The pawls are pivoted on the swinging arms midwise, and they are thrown into
ongagement with the ratchet hubs in either direction by shifting springs which are
fixed to short pivoted arms connected by toggles with the link and slide, which
slide may be raised or lowered by an elbow lever, so as in one case to straighten
the toggles and shift the pawls into the one position, or on the other hand to bend
the toggles and reverse the engagement of the pawls, so as to reverso their action
on the ratchet wheel.
This reversing mechanism may also be used with the before described friction
clutches if desired.
In the form of steam engine employed I use a peculiar form of valve. In this
valve the valve chest is a little longer than the cylinder, and from its extreme end
the steam ports extend directly into the ends of the cylinder. Close to these steam
ports independent exhaust ports extend on a slight incline to the valve seat opening
between the steam ports. The valve is made in two sections moving in the ends
of the valve chest, and each long enough to cover one exhaust port when the
adjacent steam port is open, and vice versa. Now these valve sections move steam
tight between the valve seat and a fixed overlying plate, over which the steam has
access to the steam ports and valve only at each end, so that by this means only
that part of the valve which projects beyond the overlying plate and covers the
steam port is exposed to the steam pressure, which being partly counteracted by
the pressure froin within the cylinder thus renders the valve nearly balanced.
The valve stem is made in two parts, a solid and tubular part, each connected to a
distinct section of the valve, and movable within or on the other, so that by
extending or contracting the stems the valve sections will be set further from
or closer to each, thus regulating the cut off action of the valve to any required
degree. The valve stems are connected together at the required point by a pin
passing through both, or by a screw connection. A number of pin holes may be
formed through the stems to admit of holding the valves at different adjustments,
but I prefer to accomplish this adjustment by a screw movement by threading the
ends of the valve stems, and screwing them into the valve sections.
The valve stems of the engine may be operated by an ordinary eccentric on a
secondary shaft, which may be driven by a pinion gearing into one of the gear

page_text: wheels. The valve stem may also be operated by a lever, one arm of which projects
over the reciprocating bar, and is struck by adjustable stops thereon at each end of
the stroke, so as to actuate the valve in the proper manner. This lever is slotted,
and is mounted on an ordinary fulcrum, by adjusting which the stroke of the
valve may be lengthened or shortened, thus giving it more or less lap or lead,
and thus enabling the cut off to be regulated as desired in a simple manner.
To regulate the stroke of the valve to correspond to the spreading or contracting
of the sections the fulcrum of the lever or the stops on the bar may be adjusted so
as to give the valve the proper stroke. The overlying valve plate is ordinarily
fixed to the valve seat or chest by bolts, but by detaching it from the valve seat
and screwing it to each of the valve sections the valve will then be converted into
a common slide valve.
Where the valve stem is driven by the eccentric I prefer to have a slot in the
connection between the valve stem and the eccentric rod, so that the valve will
move only at the necessary times for opening and closing the ports, and will then
move quickly.
The Invention also comprises another form of balanced slide valve for the said
engine or for engines in general. In this case the valve chest is considerebly longer
than the cylinder, the valve being of about the same length as tho cylinder, and
the ports opening in a straight line from the valve chest into the extreme ends of
the cylinder. The valve has a central cavity for exhaust, and its ends alternately
cover and uncover the steam ports for admitting and exhausting the steam in
about the usual manner of a common slide valve. The valve chest however is of
curved or arched form in cross section, and is cast with angular or radial flanges to
meet with similar flanges on the cylinder casting. The valve seat is curved
concentric with the cylinder, or nearly so, and the valve is of crescent shape in
cross section, and moves in a crescent-shaped archway in the steam chest, the valve
filling this archway like a piston, having heads with packing rings at each end in
the manner of a piston. Hence by this construction the ends of the valve only are
exposed to the steam pressure, and as this is equalized at each end of the valve,
and as the steam cannot enter to press the valve to its seat a superior form of
balanced slide valve is thus produced. The actuating stem to operate the valve of
course extends therefrom through a gland on the front of the valve chest, and an
idle stem of similar diameter also extends through a gland on the opposite end to
render the area exposed to steam pressure equal at each end of the valve. It may
be observed that the curved form of the valve, its sent and archway in cross section,
renders the construction of those parts by the ordinary process of casting and
turning a simple and inexpensive matter, and forms an important advantage of this
construction. I prefer to operate the stem of the improved valve by a projecting
pin on the crosshead, striking the short curved arm of a lever at either end of the
stroke, which levers are connected with the valve stem.
I prefer to have a positive driving connection between the reciprocating piston
rod and the rotary clutch or ratchet wheels, so that while the clutch wheels will
ordinarily lead in the rotation, yet should the clutches become momentarily inactive
by any accident, the said positive connection, while ordinarily lagging, will then
lead and continue the rotation in a positive manner, thus ensuring a certain motion
of the mechanism under all circumstances. This is effected by a slotted link or
short connecting rod connected respectively to the piston rod or bar, and to a crank
pin on the small wheel gearing with the larger wheels, as above mentioned. A
similar device may also be employed, except that a common form of connecting
rod is used to make the connection between the piston rod and the crank gear
wheel. The crauk pin is fixed in the end of the rod, and the crank is slotted with
a short slot extending inwardly from the end of the crank's throw to allow the
clutch wheels to lead in the rotation, as before described.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the
30th April 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "IMPROVEMENTS IN STEAM AND OTHER ENGINES, AND IN
MECHANISM FOR CONVERTING OR TRANSMITTING MOTION OR TRANSMITTING
PRESSURE." A communication from abroad by Asa Johnson, of the City, County,
and State of New York, United States of America.
This Invention is embodied mainly in an improved form and arrangement of
friction clutches, whereby a reciprocating motion may be converted into a continuous
rotary motion, or whereby a continuous rotary motion may be transmitted from
one shaft to another, as hereinafter fully set forth. The Invention also consists in
an improved form of balanced slide valve, and in several details of construction and
modifications, as hereinafter set forth.
In the accompanying Drawings, Figure 1 represents a sectional side elevation of
the improved mechanism applied to a steam engine for changing tho reciprocating
motion of its piston into a continuous rotary motion of the driving shaft. Figure 2
is a plan view of the same, and Figure 3 is a transvorse section thereof; Figure 4
is a fragmentary transverse section of the valve chest of Figure 2; Figure 5 is a
sectional side elevation of a modified system of transmitting mechanism, employing
positive ratchets and pawls in place of friction clutches; Figure 6 represents a
longitudinal section of a cylinder and valve chest, showing the improved and
preferred form of slide valve; and Figure 7 is an end elevation thereof with the
head of cylinder and valve chest removed; Figure 8 is a plan view of a portion of
an engine, illustrating the form of valve operating mechanism I prefer to use with
the said valve.
The transmitting mechanism is designed more especially for steam or other
engines as a substitute for the crank and connecting rod, whereby the motion of
the piston may be imparted directly and in a straight line to the driving wheel or
shaft, and in such manner also as will obviate all dead points, and admit of
reversing the motion of the shaft without changing the valve of the engine. To
this end a leading feature of the Invention consists in connecting the reciprocating
bar or piston rod with two or more clutches, each acting alternately and in
opposite directions on friction rims or hubs on two or more distinct wheels which
are geared together, whereby a continuous rotary motion is imparted to the wheels
by the alternating bite of the clutches. Another feature of the Invention lies in
the special form of these clutches, and also in a means of shifting these clutches,
whereby the direction of their bite on the friction rim becomes reversed, and
accordingly reverses the direction of rotation.
In the Drawings a, a, indicate the shafts to which the power of the reciprocating
piston or other motor is imparted, one of which may serve as the driving shaft,
from which a train of machinery may be driven, but both shafts may be so used if
desired. These shafts are geared together by the toothed wheels b, b, which are
fixed on the shafts. The friction clutches, which are reciprocated by the piston rod
or other reciprocating bar, act on friction rims or purchase wheels c, c, which are
also fixed on the shafts a, a', or to the gear wheels b, so as to revolve therewith.
These wheels are preferably formed as plate wheels with a thin central web, and a
projecting rim on each side of the web at the periphery, as seen best in Figure 3,
and their diameter is nearly as large as the gear wheels, or as large as practicable,
so as to obtain greater leverage. The friction clutch consists of a radial arm d
which is mounted loosely on the hub of the purchase wheels, or on the shafts.

page_text: thereof, and carries at its outer ends two friction shoes e, e, which embrace
respectively the inner and outer faces of the rims on the purchase wheels. and are
pivoted at or about the centre to the arm d, as seen best in Figure 1. The cross-
head on the piston rod of the engine connects to a straight reciprocating bar f,
which is guided at its outer end in the guide g, and is connected midway with each
of the clutch arms d, d, the said bar having notches which fit over pins h projecting
from the clutch arms, as shown in Figure 1, so that the reciprocation of the piston
correspondingly reciprocates the clutches in short circular arcs. In this kind of
engine I prefer to have the diameter of the piston large, and its stroke small, so as
to be able to transmit a great power through the clutches, but in short arcs, so that
the clutch movement will approximate closely to straight lines, as will be readily
understood. It will be observed from Figure 1 that the inner or pivoted ends of
the clutch arms which are mounted on the axis of the purchase wheels, are slotted
so that the clutch arms may be shifted one way or the other, to cause the arms to
incline slightly in either way. Now the clutches bite when moved in the direction
towards which they incline, and slip when moved in the opposite direction; and it
will be seen from Figure 1 that the clutch of each purchase wheel inclines in
opposite directions, so that when the piston rod or reciprocating bar moves forward,
one of the clutches bites and the other slips, while both wheels revolve by the
power applied to one, and when the rod or bar moves backward, the second clutch
bites upon the other wheel while the first slips; but it will be observed that as
both wheels are geared together, these alternate clutchings on each wheel cause
both wheels to revolve continuously and in the same direction with a uniform and
steady motion. The clutches, as may be perceived from Figure 1, bite by an
eccentric or cramping action of the friction shoes upon the rims of the purchase
wheels, which occurs only when the clutch is moved in the direction towards which
they incline, and the shoes relax and move loosely over the rims when moved in the
opposite direction. The bite of the shoes is such as to grip the rim in an instan-
taneous and positive manner, yet without denting the rims, or being liable to slip
when advancing or catch when retiring.
It will be observed that by this form of transmitting mechanism, the power of
the piston is transmitted in a direct line to the long end of the lever, and without
any dead points in its movement, as is the case with the crank motion in which
the power is applied in a direct line to the centre of the shaft, and in which also
the piston rod has to stop and wait at the dead points for the crank to be carried a
long distance by the momentum alone, which is not the case with this transmitting
mechanism. Moreover, by this mechanism, the rotation of the driven shaft does
not react upon the piston, but the momentum of the driven shaft and its wheels
may continue the rotation when the movement of the piston ceases, thus allowing
intervals of rest to the piston if required to further economise the power. Another
advantage of this mechanism is, that by shifting the clutches by the movement of
a hand lever, the rotation of the driving shaft may be instantly reversed without
changing the valve of the engine. The clutches are accordingly shifted and held in
either of their acting positions by forked levers i, i, pivoted below the purchase
wheels, while their forked ends embrace the slotted pivotal ends of the clutch
arms d, as seen best in Figure 1, and these levers are connected by links h, k, to
the short arms of a long hand lever Z which projects above the bed of the engine in
convenient position for operation by the hand. This lever when shifted to one
side or the other, catches on either side of a stop m, Figure 2, which holds the
clutches in the required position, and it will be observed that the effect of shifting
the clutches to one side or the other, is to throw the pivot line of the friction shoes
eccentric to the axis of the purchase wheels, as seen in Figure 1, which hence causes
the shoes to grip when moved toward the longer radius of the eccentric, and slip in
the opposite direction. Hence, when the clutch is shifted from one side to the
other, the eccentricity of the shoes becomes reversed, thus causing them to grip in
the opposite direction, and hence reversing the direction of rotation, as will be
readily understood,

page_text: The described form of transmitting mechanism is obviously adapted for many
purposes other than engines, where a reciprocating motion is to be converted into
a rotary motion, and the described clutch may also be employed in various kinds
of machinery, either for transmitting or converting a reciprocating motion, or for
transmitting a continuous rotary motion from one shaft to another; it may thus be
employed in treadles, friction pulleys, car starters, &c. It will be observed that
the arrangement of gear wheels and clutches is double, as seen best in Figures 2
and 3, that is, the purchase wheels are arranged between two gear wheels, which
mesh together, and a clutch is arranged on each side of the purchase wheels, tho
clutch arms d, d, being joined together by the connecting pins h which engage
with the reciprocating bar, but only a single set of gear wheels and clutches may
be used when preferred, and the friction rims on which the latches act may be
formed directly on the gear wheels themselves.
In Figure 5 a similar system of transmitting mechanism is shown, except that
positive ratchets and pawls are used in place of the friction clutches, and also a
different form of reversing mechanism. In this case the connecting rod f¹ from
the piston of the engine is jointed to the swinging arms d¹ which oscillate on the
shafts of the geared driving wheels b'.
On the shafts of these wheels are fixed the ratcheted hubs c¹, c', having a small
number of double sided ratchet teeth as shown. The swinging arms d¹ carry
double pawls e', which engage with the said ratchets in either direction according
to the position in which they are set for rotation either forward or backward. The
pawls, as may be observed, are pivotted on the swinging arms midwise, and they
are thrown into engagement with the ratchet hubs in either direction by shifting
their springs g¹, which are fixed to short pivoted arms h², connected by the
toggles with the link and slide m', which slide may be raised or lowered
by the elbow lever n', so as in one caso to straighten the toggles and shift the
pawls into the position shown, or on the other hand to bend the toggles and reverse
the engagement of the pawls so as to reverse their action on the ratchet wheel, as
will be readily understood from the Drawing.
This reversing. mechanism may also be used with the friction clutches shown in
Figure 1 if desired.
In the form of steam engine illustrated in Figure 2, I employ a peculiar form of
valve, as shown in Figures 2 and 4. In this valve the valve chest is a little longer
than the cylinder, and from its extreme end the steam ports extend directly into
the ends of the cylinder. Close to these steam ports independent exhaust ports
extend on a slight incline to the valve seat opening between the steam ports as
shown. The valve is made in two sections moving in the ends of the valve chest,
and each long enough to cover one exhaust port when the adjacent steam port is
open, and vice versa, as illustrated. Now these valve sections move steam tight
between the valve seat and a fixed overlying plate, over which the steam has access
to the steam ports and valve only at each end, so that by this means only that
part of the valve which projects beyond the overlying plate and covers the steam
port is exposed to the steam pressure, which being partly counteracted by the
pressure from within the cylinder, thus renders the valve nearly balanced. The
valve stem is made in two parts, a solid and tubular part, each connected to a
distinct section of the valve, and movable within or on the other, so that by
extending or contracting the stems the valve sections will be set further from or
closer to each, thus regulating the cut off action of the valve to any required degree.
The valve stems are connected together at the required point by a pin passing
through both, or by a screw connection. A number of pins holes may be formed
through the stems to admit of holding the valves at different adjustments, but I
prefer to accomplish this adjustment by a screw movement by threading the ends
of the valve stems and screwing them into the valve sections as illustrated. The
valve stems of the engine may be operated by an ordinary eccentric on a secondary

page_text: To
shaft, which may be driven by a pinion n gearing into one of the gear wheels b.
The valve stem may also be operated by a lever o, one arm of which projects over
the reciprocating bar fand is struck by adjustable stops c, d, thereon at each end
of the stroke, so as to actuate the valve in the proper manner. This lever o is
slotted and is mounted on an adjustable fulcrum r, by adjusting which the stroke
of the valve may be lengthened or shortened, thus giving it more or less lap or lead,
and thus enabling the cut off to be regulated as desired in a simple manner.
regulate the stroke of the valve to correspond to the spreading or contracting of the
sections, the fulcrum of the lever or the stops d' on the bar fmay be adjusted so as
to give the valve the proper stroke. The overlying valve plate is ordinarily fixed to
the valve seat or chest by bolts, as seen best in Figure 4, but by detaching it from
the valve seat and screwing it to each of the valve sections the valve will then be
converted into a common slide valve. Where the valve stem is driven by the
eccentric, I prefer to have a slot in the connection between the valve stem and the
eccentric rod, as shown at in Figure 2, so that the valve will move only at the
necessary times for opening and closing the ports, and will then move quickly, as
will be readily understood.
In Figures 6 and 7 I show a novel form of balanced slide valve, which I
prefer and specially recommend for the said engine or for engines in general,
In this case the valve chest is considerably longer than the cylinder as shown, the
valve being of about the same length as the cylinder and the ports opening in a
straight line from the valve chest into the extreme ends of the cylinder. The
valve a has a central cavity for exhaust, and its ends alternately cover and
uncover the steam ports for admitting and exhausting the steam in about the usual
manner of a common slide valve. The valve chest, however, is of curved or arched
form in cross section, and is cast with angular or radial flanges to meet with similar
flanges on the cylinder casting, as shown best in Figure 7." It will be also seen
that the valve seat is curved concentric with the cylinder or nearly so, and that the
valve is of crescent shape in cross section, and moves in a crescent shaped archway
in the steam chest, the valve filling this archway like a piston, having heads with
packing rings at each end in the manner of a piston, as illustrated in Figures
6 and 7. Hence, by this construction, the ends of the valve only are exposed to the
steain pressure, and as this is equalised at each end of the valve, and as the steam
cannot enter to press the valve to its sent, a superior form of balanced slide valve is
thus produced. The actuating stem to operate the valve of course extends therefrom
through a gland on the front of the valve chest, and an idle stem of similar diameter
also extends through a gland from the opposite end, as seen in Figure 6, to render the
area exposed to steam pressure equal at each end of the valve. It may be observed
that the curved form of the valve, its seat and archway in cross section, render the
construction of those parts by the ordinary process of casting and turning a simple
and inexpensive matter, and forms an important advantage of this construction.
I prefer to operate the stem of the improved valve by the means shown in
Figure 8, where a projecting pin on the crosshead strikes the short curved arm of a
lever at either end of the stroke, which levers are connected with the valve
stem as illustrated. I prefer to have a positive driving connection between the
reciprocating piston rod and the rotary clutch or ratchet wheels, so that while the
clutch wheels will ordinarily lead in the rotation, yet should the clutches become
momentarily inactive by any accident, the said positive connection while ordinarily
lagging will then lead and continue the rotation in a positive manner, thus ensuring
a certain motion of the mechanism under all circumstances. In Figure 1 this is
effected by the slotted link or short connecting rod n connected respectively to the
piston rod or bar f, and to a crank pin n¹ on the small wheel n gearing with the
larger wheels as illustrated. In Figure 5 a similar device is employed as indicated
by dotted lines, except that a common form of connecting rod is used to make
the connection between the piston rod and the crank gear wheel. The crank pin 5
is fixed in the end of the rod, and the crank is slotted with a short slot extending

page_text: inwardly from the end of the crank's throw to allow the clutch wheels to lead in.
the rotation as before described.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
hereinbefore in part recited Letters Patent is,-
1st. A reversible friction clutch for transmitting motion or pressure, consisting
of a frictional purchase wheel or rim, in combination with a radial arm movable
freely from the axis of the wheel, and shiftable at its pivotal end so as to incline
in either direction, together with a friction shoe or shoes mounted on the outer
ends of said arm and engaging with the said friction rim, substantially as herein
shown and described.
2nd. Mechanism for transmitting or converting motion, consisting of two or
more frictional purchase wheels or rims geared together, in combination with two
or more friction clutches connected with the reciprocating bar or motor, and cach
engaging with one of the wheels, and arranged to bite alternately in opposite
directions on each wheel, whereby a continuous rotary motion is imparted to the
two wheels, substantially as herein shown and described.
3rd. A friction clutch for transmitting motion or pressure consisting of a
frictional purchase wheel or rim in combination with a radial arm moving freely
from the axis of the wheel, and provided with two cramping friction shoes at its
outer end, each embracing respectively the concave and convex faces of the friction
rims, substantially as herein shown and described.
4th. A reversible friction clutch consisting of a frictional purchase wheel or rim,
with a friction shoe or shoes engaging therewith, and radial arm carrying said shoe
or shoes, at its outer end, and having its inner pivotal end slotted and capable of
being shifted from one side to the other, together with a means of thus shifting the
said arm, substantially as herein shown and described.
5th. In transmitting mechanism for engines or other purposes, two or more
friction or ratchet clutches impelled by the reciprocating piston or other driver, and
each acting alternately and oppositely on two purchase wheels, geared or positivoly
connected together, whereby both wheels become revolved continuously in combi-
nation with a crank wheel geared positively with said purchase wheel, and having
its crank connected positively to the said reciprocating driving bar by a connecting
rod or equivalent connection, substantially as and for the purpose herein set forth.
6th. The combination with reciprocating reversible friction or ratchet clutches,
substantially such as described of the reversing toggles k¹ connected at opposite ends
with the clutches, and at the middle joint with a device for straightening or
bending the toggles, and thus reversing the action of the toggles substantially as
herein set forth.
7th. In a reciprocating engine, a valve operating lever mounted on an adjustable
fulcrum whereby the stroke of the valve may be regulated as required, substantially
as herein set forth.
8th. The combination with a valve operated by a crank or eccentric of a slotted
connection between the eccentric rod and valve stem whereby a quick motion is
imparted to the valve at the times for admitting the steam, and the valve allowed
to remain stationary during the intervening time, substantially as herein shown
and described.
9th. A steam or other engine having the steam chest of its cylinder constructed
with a covered arched valve way over the ports in which a piston slide valve moves
steam tight, admitting and exhausting the steam through the ports in the usual
manner but exposed to the steam pressure at opposite ends only, substantially as
and for the purpose set forth.
10th. A steam or other engine having its cylinder formed with an arched valve
seat concentric with the cylinder bore or nearly so, a steam chest formed with an
arched valve way within the same over the said seat, and a cresent shaped piston
slide valve moving steain tight in said valve way and over the said seat, sub-
stantially as and for the purpose herein shown and described.

page_text: 11th. A steam or other engine constructed with an arched steam chest, in com-
bination with a cylinder having radial flanges to meet with similar flanges on the
arched steam chest, substantially as herein shown and described.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Thirtieth day of April, A.D. 1881.
A. M. CLARK. (L.S.)