IMPROVEMENTS IN STEAM AND OTHER ENGINES
Year: 1876

page_text: LETTERS PATENT to Alexander Craig, of Mountpottinger, in the County of
Down, in Ireland, Engineer, for the Invention of "IMPROVEMENTS IN STEAM
AND OTHER ENGINES."
Sealed the 28th July 1876, and dated the 29th May 1876.
PROVISIONAL SPECIFICATION left by the said Alexander Craig at the
Office of the Commissioners of Patents on the 29th May 1876.
ALEXANDER CRAIG, of Mountpottinger, in the County of Down, in Ireland,
Engineer. "IMPROVEMENTS IN STEAM AND OTHER ENGINES."
The said Invention relates to the operation of the valves of steam, air, and other
engines in order to obtain a punctual lead and a quick cut-off of the motive power
at any desired point and with the least possible loss, or to keep up such power
during the entire length of the stroke if required.
For this purpose I employ an eccentric or crank and lever strap having a cam
which acts upon the valve lifter, rod, or spindle, and I regulate the length of carry
of the motive power by the adjustment of the cam, which is actuated by the
governor through the lever strap in the ordinary way.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said Alexander Craig in the Great Seal Patent Office on the 27th November
1876.
ALEXANDER CRAIG, lately of Mountpottinger, in the County of Down, but now of
the City of Londonderry, within the County of Londonderry, in Ireland, Engineer.
"IMPROVEMENTS IN STEAM AND OTHER ENGINES."
The said Invention relates to the operation of the valves of steam, air, and other
engines in order to obtain a punctual lead and a quick cut-off of the motive power
at any desired point and with the least possible loss, or to keep up such power
during substantially or almost the entire length of the stroke.
For this purpose I employ an eccentric placed upon the valve shaft. To the
eccentric a lever strap is attached, and the strap is provided with a cam or tappet,

page_text: which is constructed and adjusted so as to act upon the valve lifter, rod, or spindle,
and to lift and carry the valve at and during the time the motive power is required
or desired to actuate the piston, and to permit the valve lifter, rod, or spindle to
drop into its seat and close the valve, thereby suddenly cutting of the motive power.
The lead and length of carry of the motive power are determined by the relative
positions of the cam or tappet and the valve lifter, rod, or spindle, and I regulate
the position of the cam or tappet by the aid of a rod connecting the outer or
opposite end of the lever strap with the corresponding end of an arm placed upon
the shaft actuated by the governor of the engine, which thereby adjusts the cam or
tappet by elevating or depressing such outer or opposite end of the lever strap and
exposing more or less of the face of the cam or tappet to contact with the valve
lifter, rod, or spindle. The prime position of the cam or tappet is set according to
the desired speed by means of the screwed coupling upon the governor rod or
otherwise in the usual way. The eccentric and arm herein-before mentioned are
keyed or otherwise fastened upon the valve shaft and governor shaft respectively,
and the lever strap is kept in position by a tongue fitted into a groove cut in the
eccentric.
By various modifications of the attachments and contrivances I have described
I can apply my said Invention to various engines, and I do not confine myself,
therefore, to the parts and arrangements above referred to.
In order that the said Invention may be more fully understood I shall now
proceed to refer to the Drawings upon the Sheet hereunto annexed, the same
letters of reference indicating the same or corresponding parts throughout all the
Figures.
Fig. I. is a front elevation of part of a horizontal engine, shewing the upper
portion of the valve chest, the valve shaft, the governor shaft, and the governor rod
with its screwed coupling, and the attachments and contrivances herein-before
described. Fig. II. is an end or transverse view of the same.
A is the valve shaft carrying the eccentric B, upon which C the lever strap is
placed. D is the cam or tappet coming into contact with and lifting and carrying E,
the valve lifter, rod, or spindle, at every revolution of the eccentric B. F is the rod
connecting the outer end of the lever strap C with the corresponding end of the
arm G fastened upon the governor shaft H. K is the governor rod with a screwed
coupling, and connected with the governor shaft by a graduated bar or arm to aid
in the setting of the cam or tappet for the desired speed. L is a tongue fitted into a
groove in the eccentric B in order to keep the lever strap C in position.
Having now described the nature of the said Invention and in what manner the
same is to be performed, I would have it to be understood that I do not claim the
exclusive use of a cam or tappet, lever strap, and eccentric, except when the same
are constructed specially and employed as herein-before described; nor do I claim
the use of valves, valve lifters, rods, or spindles, arins and connecting rods, nor of
any of the separate mechanical parts which form the compound automatic apparatus
employed by me; but I claim-
First. The use in steam and other engines of an eccentric arranged with a lever
strap and cam or tappet, substantially as herein-before described and shewn in
the Drawings hereunto annexed.
Secondly. The use in steam and other engines of a cam or tappet to act upon the
valve lifter, rod, or spindle, and constructed and employed substantially as herein-
before described and shewn in the Drawings hereunto annexed.
Thirdly. The actuation of the valve in steam and other engines by the aid of a
cam or tappet, constructed and employed substantially as herein-before described
and shewn in the Drawings hereunto annexed.
Fourthly. The adjustment of the cam or tappet acting upon the valve lifter, rod,
or spindle in steam and other engines by the governor, substantially in the manner
and for the purposes herein-before described and shewn in the Drawings hereunto 5
annexed.
Fifthly. The combination and arrangement of parts constituting the compound

page_text: automatic apparatus herein-before mentioned, constructed and applied substantially
in the manner and for the purposes hercin-before described.
In witness whereof, I, the said Alexander Craig, have hereunto set my hand
and seal, this Twenty-third day of November, in the year of our Lord One
thousand eight hundred and seventy-six.
ALEXANDER CRAIG. (L.S.)