IMPROVEMENTS IN VARIABLE EXPANSION-GEAR " FOR ENGINES WORKED BY STEAM OR OTHER ELASTIC FLUID
Year: 1883

page_text: LETTERS PATENT to Thomas English of Hawley near Dartford in the County
of Kent for an Invention of IMPROVEMENTS IN VARIABLE EXPANSION-GEAR
"
FOR ENGINES WORKED BY STEAM OR OTHER ELASTIC FLUID "
PROVISIONAL SPECIFICATION left by the said Thomas English at the Office
of the Commissioners of Patents on the 1st February 1883.
THOMAS ENGLISH of Hawley near Dartford in the County of Kent
"IMPROVE-
MENTS IN VARIABLE EXPANSION GEAR FOR ENGINES WORKED BY STEAM OR OTHER
ELASTIC FLUID
"
My invention relates to gear for varying the cut off of the expansion slide of an
engine worked by steam or other elastic fluid. For this purpose I mount on the
engine shaft the eccentric which works the cut off or expansion slide so that it is
free to revolve thereon but not to move longitudinally, and in the body of this
eccentric I mount a conical wheel without teeth-the axis of-which wheel is
geared to a worm also mounted in the eccentric, this worm engaging with a
worm wheel fixed on the shaft. On each side of the eccentric is a conical wheel
which is prevented from revolving but is free to slide along the shaft, and both
these wheels are connected to a lever worked by any known governor, so that,
according as the speed of the engine increases or diminishes, the one or the other
of the two conical wheels is moved up towards, so as to press against the conical
wheel in the eccentric. When this conical wheel is so pressed against, it is caused
by the friction to revolve on its axis and, working the worm geared to it, it causes
the eccentric to turn partly round on the shaft. The expansion slide worked by
the eccentric is thus timed in its movement relatively to the piston in such a way
as to cut off the supply of working fluid sooner or later according as the governor
moves at greater or less than its normal speed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Thomas English in the Great Seal Patent Office on the 27th July
1883.
THOMAS ENGLISH of Hawley near Dartford in the County of Kent
"IMPROVE-
MENTS IN VARIABLE EXPANSION GEAR FOR ENGINES WORKED BY STEAM OR OTHER
ELASTIC FLUID
33
My invention relates to gear for varying the cut off of the expansion slide of an
engine worked by steam or other elastic Huid. For this purpose, I mount on the
engine shaft the eccentric which works the cut off or expansion slide so that it is
free to revolve thereon but not to move longitudinally, and in the body of this
eccentric or of a sleeve on the shaft constituting an extension of the eccentric
boss I mount a conical wheel without teeth the axis of which wheel is geared to
a worn also mounted in the eccentric or its sleeve this worm engaging with a
worm wheel fixed on the shaft. On each side of the worm geared conical wheel is
a conical wheel which is prevented from revolving but is free to slide along the
shaft, and both these wheels are connected to a lever worked by any known
governor, so that, according as the speed of the engine increases or diminishes, the
one or the other of the two conical wheels is moved up towards, so as to press
against the worm conical wheel in the eccentric or its sleeve. When this latter
conical wheel is so pressed against-by one of the other conical wheels while the
shaft is revolving, the worm geared conical wheel is caused by the friction to
revolve on its axis and, working the worm geared to it, it causes the eccentric to
turn partly round on the shaft. The expansion slide worked by the eccentric is
thus timed in its movement relatively to the piston in such a way as to cut off
the supply of working fluid sooner or later according as the governor moves at
greater or less than its normal speed.
Fig. 1 of the accompanying Drawings is a side view, Fig. 2 is a longitudinal
section, and Fig. 3 is a plan of variable expansion gear according to my invention.
A is the engine shaft on which the eccentric B which works the cut off or expansion
slide of the engine shaft is fitted free to revolve, but is prevented from moving
longitudinally along the shafts by being held between a collar a and a worm wheel Č
which is keyed on the shaft and revolves with it. In the body of the eccentric B
is mounted in bearings a worm spindle D, the worm of which gears with the worm
wheel C. A pinion d on this spindle gears with a toothed wheel e attached to a
conical wheel E without teeth, the axis of E and e being fitted to revolve in
bearings formed in the eccentric B. On each side of the eccentric is a conical
wheel F and F which is free to slide along the shaft A but is prevented from
revolving, being held by a pair of fork arms g g and g g engaging with studs
projecting from the sides of the wheels F and F respectively. The fork arms g gl
are respectively fixed on rocking shafts G G either of which can be partly turned
by hand or by the action of any known governor so as to press either of the
wheels F F against the conical wheel E. When both the wheels F F¹ are out of
contact with the wheel E, the eccentric B turns with the shaft A working the cut
off or expansion slide in the usual way. When one of the conical wheels such
as F is pressed against E, the frictional contact causes E to revolve and the worm D
being thus made to turn causes the eccentric B to turn partly round the shaft A,
while it still continues to revolve with it, thus giving more or less lead to the cut
off or expansion valve. When the other wheel F¹ is pressed against E by a corre-
sponding action, the eccentric B is caused to turn in the opposite direction, thus
reversing the alteration of lead given to the valve by the advance of the wheel F.

page_text: In this manner, while the engine shaft and expansion eccentric revolve, the set or
augular position of the eccentric relatively to the shaft can be varied either by
hand or by the governor working one or other of the rocking shafts G or G¹, and
thus the lead of the expansion can be altered either manually, or automatically by
the action of the governor.
Having thus described the nature of my invention and in what manner the
same is to be performed, I claim in respect of expansion gear for engines worked
by steam or other elastic fluid :-
In combination with the eccentric which works the expansion slide, worm gearing
worked by a conical wheel which can be turned in either direction by frictional
contact with one or other of two conical wheels so as to alter the set or angular
position of the eccentric on the shaft and so to vary the lead of the expansion
slide while the shaft is revolving, substantially as herein described.
In Witness whereof I the said Thomas English have hereunto set my hand and
seal this Twenty Seventh day of July in the year of our Lord One thousand eight
hundred and eighty-three.
THO. ENGLISH (L.S.)