IMPROVEMENTS IN APPARATUS FOR INDICATING THE ACTION OF SLIDE VALVES
Year: 1878

page_text: LETTERS PATENT to George Low, of Ipswich, in the County of Suffolk, for
the Invention of "IMPROVEMENTS IN APPARATUS FOR INDICATING THE ACTION
OF SLIDE VALVES."
Sealed the 13th June 1878, and dated the 1st January 1878.
PROVISIONAL SPECIFICATION left by the said George Low at the Office of
the Commissioners of Patents on the 1st January 1878.
GEORGE Low, of Ipswich, in the County of Suffolk.
APPARATUS FOR INDICATING THE ACTION OF SLIDE VALVES."
" IMPROVEMENTS IN
This Invention has for its object improvements in apparatus for indicating the
action of slide valves.
The apparatus is for the purpose of quickly finding out the proper proportions of
slide valves, main and cut-off of various kinds; also of valves worked by link
motion, and of their ports, lap and stroke; also the correct centre of the eccentrics,
the range of cut-off eccentrics; the proper width of gridiron valve bars, together
with the times of cut-off or suppression, the grades of expansion, amount of com-
pression, time and duration of exhaust, with or without inside lap, and so on.
The apparatus is composed of 2 boards or plates, one over the other, and secured
together at a slight distance apart at their four corners. Through the upper
plate is a large central circular opening, and around the edge of the opening is
marked a scale to show the position of the crank relatively to the position of the
piston through all parts of its stroke. There may be 2, 3, or more lines at each
division for connecting rods 2, 2¹, or other times, the length of the stroke of the
piston.
Across the centre of the lower board is a divided scale to show the corresponding
position of the piston. There is also a corresponding scale along the top and
bottom edges of the upper board. Four fine wires are stretched across the face of
the lower board to represent the edges of the ports in the cylinder. They are set
in position by the straight scales above mentioned, and are retained by spring clips
which bear against the top and bottom edges of both boards. They are set two on

page_text: either side of a central line passing down across the centre of the lower board.
The distance between the wires of each pair represent the width of the ports, and
the distance between the central line and the nearest wire represents the lap.
At the centre of the lower board is a spindle, from which an arm extends to the
edge of the opening in the upper board; this arm represents the crank. Passing
down through the centre of the spindle is another spindle with a head at the top,
through which slides an arm, which represents the radial line of the main eccentric ;
it carries at its end a small pin, on to which can be suspended a plate to represent
the port in back of main valve. A number of such plates are provided to allow
for different widths of ports.
The opposite end of the arm comes over a quadrant scale on the crank arm, so
that the angle at which the arm is set to the crank arm can be read off upon
the scale.
The eccentric and crank arms are held together by. friction elastic washers, so
that when they have been adjusted to any desired angle to one another, they
remain in the same relative positions.
To represent the action of the cut-off valve another arm is used, which can be
slid through a socket on an axis concentric with the axis of the crank arm, such
axis being carried by a bracket which stands up from the crank arm. On the
bracket is a quadrant scale to allow of the arm being set to any desired angle to
the crank arm. The end of the arm carries a disc which represents the centre of
the cut-off eccentric; also the port in cut-off valve.
The arm has a scale marked along its face, and there is a hole through the top
of the socket through which the arm slides, through which the figures on the scale
can be seen. Any figure on the arm can be brought below the hole, and the disc
thus set at any required distance from the crank axis.
When the crank and eccentric arm have been adjusted to their proper relative
positions, the crank arm is turned to its different positions for each portion of the
stroke of the piston, and the plate and disc at the end of the eccentric arms as they
are carried to and fro over the wires before mentioned, which represent the cylinder
ports and laps, and to and fro one over the other, will show the action of the main
and cut-off valves.
To be able to show the correct action of a slide valve when a link motion is
used, a bar, having a sliding pointer upon it, is jointed to the two eccentric arms,
which are then set at equal angles to the crank arm. By moving the pointer to
different positions on the bar, and turning the crank arm, the action of the valve
for different parts of the stroke can be seen for different positions of the link
slide.

page_text: SPECIFICATION in pursuance of the conditions of the Letters ratent nied by
the said George Low in the Great Seal Patent Office on the 29th June
1878.
GEORGE LOW, of Ipswich, in the County of Suffolk.
APPARATUS FOR INDICATING THE ACTION OF SLIDE VALVES."
"IMPROVEMENTS IN
This Invention has for its object improvements in apparatus for indicating the
action of slide valves.
The apparatus is for the purpose of quickly finding out the proper proportions
of slide valves, main and cut-off of various kinds; also of valves worked by link
motion, and of their ports, lap and stroke; also the correct centre of the eccentrics,
the range of cut-off eccentrics; the proper width of gridiron valve bars, together
with the times of cut-off or suppression, the grades of expansion, amount of com-
pression, time and duration of exhaust, with or without inside lap, and so on.
Figure 1 of the Drawings hereunto annexed shows a plan view; Figures 2 and 3,
transverse sections; and Figure 4, an edge view of the improved apparatus.
It is composed of two boards or plates X, Y, one over the other, and secured
together at a slight distance apart at their four corners. Through the upper plate X
is a large central circular opening, and around the edge of the opening is marked a
scale to show the position of the crank relatively to the position of the piston
through all parts of its stroke. There may be 2, 3, or more lines at each division
for connecting rods 2, 21, or other times, the length of the stroke of the piston.
Across the centre of the lower board is a divided scale to show the corresponding
position of the piston. There is also a corresponding scale along the top and
bottom edges of the upper board. Four fine wires E, E, E¹, E¹, are stretched
across the face of the lower board to represent the edges of the ports in the cylinder.
They are set in position by the straight scales above mentioned, and are retained
by spring clips which bear against the top and bottom edges of both boards. I
form the spring clips in the manner shown in the Drawings. One end of each wire
is gripped as shown in a block V, which rests against one edge of the boards X, Y.
The other end of the wire is secured to the end of a screw, on the opposite end of
which is a nut. Around the screw is a coiled spring, and this is enclosed in a
telescopic casing. One part of the casing is pressed by the spring against the edge
of the boards X, Y, the other against the nut on the screw; the wire is thus kept
taut and prevented from shifting its position. When it is required to shift the wire
from one position to another, it can be done by drawing back that portion of the
telescopic case which bears against the edges of the boards, or by pressing in the
nut, so setting free one or other end of the wire, and allowing that end of the wire
to be shifted sidewise in either direction. The wires are set two on either side
of a central line A, A, passing down across the centre of the lower board. The
distance D, D, between the wires of each pair represents the width of the ports,
and the distance C, C, between the central line and the nearest wire represents
the lap.
At the centre of the lower board is a spindle from which an arm B extends to
the edge of the opening in the upper board; this arm represents the crank.
Passing down through the centre of the spindle is another spindle with a head at
the top, through which slides an arm J, which represents the radial line of the
main eccentric; it carries at its end a small pin F, on to which can be suspended a
plate G to represent the port in back of main valve. A number of such plates are
provided to allow for different widths of ports.
The opposite end of the arm comes over a quadrant scale on the crank arm, so
that the angle at which the arm is set to the crank arm can be read off upon
the scale.
The eccentric and crank arms are held together by friction elastic washers, as
shown, so that when they have been adjusted to any desired angle to one another,
they remain in the same relative positions.

page_text: To represent the action of the cut-off valve another arm J¹ is used, which can be
slid through a socket on an axis concentric with the axis of the crank arm, such
axis being carried by a bracket, which stands up from the crank arm B. On the
bracket is a quadrant scale to allow of the arm J¹ being set to any desired angle to
the crank arm. The end of the arm J¹ carries a disc H, which represents the centre
of the cut-off eccentric, also the port in cut-off valve.
The arm has a scale marked along its face, and there is a hole through the top
of the socket, through which the arm slides, through which the figures on the scale
can be seen. Any figure on the arm can be brought below the hole, and the disc
thus set at any required distance from the crank axis.
When the crank and eccentric arm have been adjusted to their proper relative
positions, the crank arm is turned to its different positions for each portion of the
stroke of the piston, and the plate and disc at the end of the eccentric arms as they
are carried to and fro over the wires before mentioned, which represent the cylinder
ports and laps, and to and fro one over the other, will show the action of the main
and cut-off valves.
To be able to show the correct action of a slide valve when a link motion is used,
a bar, having a sliding pointer upon it, is jointed to the two eccentric arms, which
are then set at equal angles to the crank arm. The arms, sliding pointer, and bar
are shown at Figures 5 and 6. By moving the pointer to different positions on the
bar, and turning the crank arm, the action of the valve for different parts of the
stroke can be seen for different positions of the link slide.
Having thus described the nature and construction of the apparatus, I will
proceed to give examples in illustration of its mode of working.
In working with the apparatus the valves must be considered as inverted,
their outside lap edges working toward centre instead of from, as indicated in
diagram 7. In this diagram Z, Z, are the inlet ports in cylinder, and Y, Y, are the
two halves of main valve.
Example No. 1. To Find Out the Times of Cut-off, &c. of Main Valve only.―
The lap stroke and size of ports being given, move the two inside shifting wires
E, E, E, E, the distance of the intended lap from lap line measured by scale at
top and bottom of apparatus; then move the two outside shifting wires E¹, E¹, E', E¹,
the distance of the intended width of ports of cylinder measured by the same
scale from the inside wires, adjust the pointer F to the intended radius or half the
stroke of eccentric (which is of course the lap and width of port added together;
or when it is not intended to open the port fully, the width of intended opening
only must be added to the lap); then move it (the pointer) round to a point as
much as the intended lead outside the inner wires, as shown at S, diagram 8; this
is the position for commencement of stroke of piston. Next turn the crank B
round till the pointer F comes opposite the same inside wire, and whatever division
or circle the crank B then points to, represents the moment of cut-off or suppression
by main valve on the stroke of piston. The same operation may be repeated for
the return stroke on other side of dial.
Example No. 2. The Time and Duration of Exhaust.-Turn the crank round a
little further, till the pointer F comes opposite the lap line; the exhaust then begins
in valves that have no inside or exhaust lap; now turn the crank round a half
circle, till the pointer again comes opposite the lap line on the top side of dial. This
represents the duration of exhaust. When there is an inside or exhaust lap it is
only necessary to bring the pointer the depth of lap past the lap line. The crank B
in both cases indicates on circle the parts of stroke the exhaust begins and ends.
Example No. 3. Commencement of Suppression, Range, and Grades of Expansion,
&c., with a Cut-off Valve (on back of Main Valve), when the Stroke is Varied by
Slotted Eccentric (cut-off) moving towards Centre of Crank Shaft, by Hand or by
Governor. The pointer F being properly adjusted for the main valve, select a slip G
of the intended width of cut-off ports in back of main valve, and hang it on centre
behind the pointer F (being the centre of main eccentric; adjust the other or cut-
off eccentric arm J' to the same radius as the other (representing the maximum

page_text: stroke), select a disc H of the diameter of the intended width of ports in cut-off
valve, place it on the end of the arm J¹, and move it round to a position a little in
advance (usually about the width of port in cylinder) of the pointer F, but the exact
position is best found out by trial, and also in proportioning the width of both the
ports in main and cut-off valves, so as to give the desired range of cut-off from the
earliest to the latest. Care should be taken however that there is a lead represented
by the overlap of the disc H (when adjusted for maximum stroke) over the slip G,
as shown at X, diagram 9. When this lead is as small as practicable, say, to", the
slip G and disc H determines the narrowest width of both ports, but wider can be
used if preferred. Now turn the crank B round till the edge of disc H is flush with
the inside edge of slip G, or to express it in an eclipse term, the ." last contact.".
This represents the latest cut-off of cut-off valve on the stroke of piston, as indicated
in diagram 10, by crank B on circle, and by moving the disc (representing the
lessening of the stroke of cut-off eccentric by governor or by hand) effected by sliding
the arm J through the centre axle, as shown by arrow in diagram 11, the suppression
will be earlier and vary to the earliest cut-off, see diagram 12, as the centre of disc
approaches its limit of range near centre of axle.
Example No. 4. Moments of Suppression, Angular Range, Grades of Expansion,
&c., &c., with a Cut-off Valve (on back of Main Valve) when Worked by Cut-off.
Eccentric of Full Stroke always, but Varying its Centre by being Turned Round on
the Shaft by Hand.-When the ports on back of main valve are single, it is usual
to make them the same width as the ports in cylinder, see diagram 13, but should a
gridiron or many-ported valve be used (which are the best, as it avoids wire drawing
of the steam) on this system of cut-off, the ports cannot be as narrow as in the No. 3
or slotted eccentric system; but the least width of ports that can be used with the
turning cut-off eccentric is ascertained simply by placing the cut-off eccentric arm J¹
in a line with the crank B (both arms having been adjusted to the intended radius.
previously) and put on a slip G and disc H of such width and diameter that the
latter will just overlap the former a slight lead at V, see diagram 14; next bring
the arm J with circular piece round and up to the right position in advance of the
pointer F (as before described for slotted eccentric system), which is the position for
latest cut-off, and by moving the same round the centre downwards (representing
the shifting of cut-off eccentric round the shaft) will indicate earlier suppression,.
varying to the earliest cut-off as the limit of angular range is reached, as shown by
dotted lines in diagram 15; the limits of the angular range can also be determined
at the same time.
Example No. 5. When the Cut-off Valve is Driven from Eccentric through a
Rocking Link, by which the Stroke is Varied according to the Position of Sliding
Block in Link (to which the Valve Spindle is attached), placed by Governor or by
Hand. This can be indicated in the same manner as described for the Example
No. 3, or slotted eccentric system, and the results will be the same.
Example No. 6.-Smaller gridiron ports, with shorter, stroke of cut-off eccentric,
can also be indicated in the same manner as described for Example, No. 3, by
shortening the radius of cut-off eccentric arm J to suit the shorter stroke of
eccentric and use narrower slip G and disc H.
Example No. 7. To Indicate, &c., &c., for the Meyer System of Cut-off.-Adjust
the arms, pointer, slip, and disc, in the same manner as described for Example
No. 4, or turning eccentric system for the latest cut-off, and the results of earlier
cut-off is ascertained by turning the crank back till the disc H overlaps the inside
edge of slip G as much as the valves are brought together by right and left hand
screw, and every" additional lap of disc over slip corresponds and represents to
the same distance the valves are brought together.
Other examples of cut-off, &c., &c., can be indicated besides those already given,
and the same method of indicating cam be used for proportioning the valves,
ports, &c., &c.
Example No. 8. To Determine the Least Width of Bars in Gridiron Valves on
the Slotted Eccentric System.-Measure from pointer F to the centre of disc when

page_text: placed for shortest stroke for the earliest cut-off, and add a little to result (say, from
" to ") for a lap. On the turning eccentric system.-Measure from the pointer F
to the centre of disc when the latter is placed at the lowest angular range for the
earliest cut-off, and add a little (say, from 1 to +") for a lap. This proportion will
ensure that the steam will not be admitted into cylinder twice over during the
same stroke when working with the earliest cut-off.
Example No. 9.-In order that the engineer can readily find out the proper angles
to key the eccentrics on the crank shaft, the crank is furnished with a protractor
behind each arm J and J', by which the angle from crank can be read off at once
when the proper centres of both eccentrics (represented by the pointer F and disc H)
are determined.
Example No. 10. To Indicate Time of Suppression and Exhaust Amount of
Compression, &c., &c., when one Valve (Main) only is Worked from a Shifting
Eccentric, Varying the Stroke by Moving in a Slot placed at Right Angles to the
Crank. First place the wires in right positions for the lap and cylinder ports,
adjust the two arms to the radius of half stroke of eccentric, place the pointer F in
position, as described before (in No. 1, example for main valve), and the centre of
cut-off arm J' in the same position on opposite side, as shewn in diagram 16 (the
latter being the centre of eccentric if the engine is to run the opposite direction),
connect the two arms by the graduated bar (supplied for link motion), the pointer F
indicates the latest cut-off, as described before, and by moving the sliding pointer
on link or bar down to the centre line of crank, and turn the crank till it (the
sliding pointer) comes opposite the inner wire indicating the earliest cut-off, the port
opening the lead only, the results from intermediate position of sliding point being
found out in the same manner, and by bringing the sliding pointer round to the lap
line will indicate the varying commencement of exhaust for each position and the
amount of compression, which increases as the cnt-off is earlier on this system.
Example No. 11. Reversing Link Motion (Approximate).—This is indicated in the
same manner as last described, but the pointer F represents the centre of fore
eccentric, and the centre for disc the centre of back eccentric; both represents the
latest cut-off or full gear, whichever direction the engine runs, while the sliding
pointer will indicate for any intermediate gears, and represents the sliding block in
link.
Having thus described the nature of my Invention, and the manner of performing
the same, I would have it understood that I claim the construction of apparatus,
substantially in the manner herein-before described, for indicating the action of
slide valves.
In witness whereof, I, the said George Low, have hereunto set my hand and
seal, this 28th day of June, in the year of our Lord One thousand eight
hundred and seventy-eight.