IMPROVED APPLIANCES FOR ASSISTING THE DESIGNING AND SETTING OF SLIDE VALVES FOR ENGINES
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Joseph King at the Office of the
Commissioners of Patents on the 19th August 1879.
JOSEPH KING, of Horslydown, in the County of Surrey. "IMPROVED APPLIANCES
FOR ASSISTING THE DESIGNING AND SETTING OF SLIDE VALVES FOR ENGINES."
According to this Invention I construct a diagram consisting of first a circle, gay,
10 inches in diameter, and nanied path of crank pin, the same being divided into
200 equal parts and numbering from 10 to 100 for each semicircle, a centre line
of engine dividing this circle into two equal parts, and of course the crank will
travel round one of these semicircles for the outward, and one for the inward.
stroke of the engine.
Outside the crank pin circle is drawn another circle divided into 360 degrees,
and this is used for seeing the angle of the crank in any part of the. crank pin
circle, also for setting the forward and backward eccentrics at their proper angle
in advance of the crank due to any given amount of lap and lead of the valve.
This circle can be used as a protractor for setting out angles for a great many
useful purposes in the drawing office or workshop.
Within the crank-pin circle and through the centre of the diagram two lines are
drawn square with each other. The horizontal line is the centre line of the engine,
and is supposed to pass through the centre of the crank shaft, piston rod, and
cylinder. This line also divides the crank pin circle into two halves, and to be
used with each half is a "cylinder stroke line" drawn parallel to the centre line
of the engine and divided into 100 parts, the numbers reading from 10 to 100, the
same as on each half of the crank-pin circle. These two stroke lines are used for
finding the position of the piston in the cylinder in percentages of tlie stroke, both
for the outward and inward stroke, due to any position of the crank pin on the
crank pin circle, and both can be seen at the same time on the diagram.
The two stroke lines are connected by two lines at their ends, and these lines
shew that they are square with and equal in length to the diameter of the crank
pin circle. Within the crank pin circle there are four radial lines.
On one of them the half centre line horizontally three inches are taken, each
inch being divided into eights, and reading from the centre outwards; this is the

page_text: exhaust lap line, and is used for finding the additional amount of expansion and
compression due to any given amount of lap on the exhaust or underneath side of
the valve.
On the upper vertical line is found the travel of the valve. This line is divided
into, t, and inches, each half inch is numbered, and the divisions read from 1
to 10 from the centre outward. A. twofold value is given to the divisions on this
line because each division is a radius of an eccentric circle, and the travel of the
valve will be the diameter or twice the radius of this circle.
From the centre of the diagram, the divisions on the "travel of valve" line
being used as radii, arcs are drawn to the "lap and lead" line which is the other
half centre line horizontally, their use being to find the opening of the steam port
due to any travel and lap of valve.
This line is the "lap and lead" line; this line is 5 inches long, and each inch is
divided into eights, each division being carried up to within of an inch of the
crank pin circle.
The first inch of the "lap and lead" line is used for the exhaust lead; it is
divided into eight parts, and the divisions are drawn at right angles to the division
on the "lap and lead " line, and as before run to within of an inch of the crank
pin circle.
Outside the two main circles of the diagram are drawn six arcs of circles above
and below, each are being divided into 70 divisions and numbered from 20 to 90.
For the sake of greater plainness each prime division contains five instead of ten
sub-divisions, each counting for two. At the commencement of each arc are
the Figures 2, 2, and 3, and they mean that when the length of the crank
connecting rod is 2, 2, or 3 times the stroke of the piston, the are so marked must
be used for finding the point of cut off and the angle of the eccentric in advance of
the crank on the crank shaft for any lap and travel of valve that may be required,
or the cut off can be found for any known lap and travel of valve.
Each of the 70 subdivisions in either arc are angular points for the eccentric in
advance of the crank on the crank shaft for as many corresponding points of cut
off for any desired grade from 20 to 90 per cent.
The diagrain is mounted on millboard and fitted with a hollow stud to receive,
a truly turned compass centre, also a spindle, one end of which is fitted to the
above centre stud, while to the other end of the spindle is fitted a pair of hands,
one of them fixed, the other slotted and adjustable, a jam nut being fitted to hold
the slotted hand in any desired position. In addition to the above, each set is
composed of three cardboard curves about 134 inches long and 21%, wide at the
centré line, each of which is numbered and lettered. The complete set contains in
addition one 6 cardboard square, one edge of which is divided into inches and
eighths, also one piece of cardboard cut taper about 13, inches long, 3 inches wide
at one end and 1 inch wide at the other, a slot is cut at each end into which is
fitted a knotted string, also one cardboard pressure scale containing 7 inches
divided into tenths, this at 10 pounds to the inch would shew 60 pounds pressure"
above the atmosphere and 15 below the same. The atmospheric and perfect vacuum
lines are marked upon this scale.
By these appliances the following particulars are readily found:
:-
1. For any desired cut-off and opening of port the diagram will shew the lap
and travel of valve required to accomplish it.
2. For any desired cut off the diagram will shew the angle in advance of the
crank of the forward and backward eccentrics.
3. Should the alteration of a slide valve be desired by either increasing or
decreasing the outside lap, and the same lead to be maintained, the diagram will
shew the amount that the eccentric must be put forward for the former, and back-
ward for the latter on the crank shaft, and also how the alteration has affected the
distribution of the steam in the cylinder.
4. When the point of cut off is once agreed upon the diagram will shew how far
+

page_text: the piston and crank pin have travelled in percentages of their respective patlis,
together with the angle of the crank and eccentric for the following particulars :-
I. When the port is full open.
II. How much the port has opened.
III. When the port has closed and expansion begins.
IV. The percentage of the stroke done before the steam is cut off.
V. The percentage of the stroke done by expansion.
VI. When exhaust takes place.
VII. The percentage of the stroke to be performed during compression after the
exhaust has closed.
5. If variable expansion is carried on by any fixed amount of lap or valve, and
by varying its stroke such as a link motion, the diagram will shew how the stroke
of the valve and opening of the port will vary for each point in the grade.
6. The diagram will shew the amount of exhaust or inside lap required if it is
desired to keep the steam on the piston beyond what the lap on the steam side
will admit of, and also how much expansion and compression is increased by any
given amount of exhaust lap.
7. Should a slide valve have exhaust lead, so that when it is at half-stroke both
steam ports are somewhat open to the exhaust, the diagram will shew how a given
amount will cause the steam to exhaust earlier and compression to be delayed in
proportion thereto.
8. For any given amount of lap and lead the diagram will shew the difference in
the distribution of the steam for the outward and inward stroke of piston due to
connecting rods of various lengths.
9. When the eccentric centre line is drawn from the centre of the diagram or
crank shaft through the desired grade of cut off, on the same line can be found for
the same grade any travel of valve, any lap of valve, and any opening of port, so
that any required opening of port with its necessary travel and lap of valve can be
selected for that particular point of cut off.
10. Since the stroke line of this diagram is ten inches long and divided into 100
parts, the distribution of the steam in engines of any other stroke can be found
from the points of distribution on this one by simple multiplication.
11. With this instrument the designer or setter of slide valves can learn in a few
moments all he wishes to know as completely as though he had a full sized model
of his engine before him, neither is it necessary that he should possess a knowledge
of mathematics or even common arithmetic.