Improvements in or relating to Reciprocating Blowing-engines.
Year: 1899

page_text: Date of Application, 9th Aug., 1899-Accepted, 18th Nov., 1899
COMPLETE SPECIFICATION.
Improvements in or relating to Reciprocating Blowing-engines.
I, ALEXANDER JOHN DUDGEON, of 63, Leadenhall Street, in the City of London,
Engineer, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by Societe Anonyme John Cockerill, of Seraing,
Belgium, Engineers,) and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
This invention relates to reciprocating blowing engines and consists in certain
means for use in combination with the compression cylinder or cylinders by
the use of which the engine can, when necessary, deliver air at a higher pressure
than that used in ordinary work without requiring more power from the motor
or a reduction of speed.
The
The novel apparatus by suitably retarding when required the compressive
action of the blast piston renders it non-effective during the early part of its
stroke. For the remainder of the stroke the pressure of the air expelled may be
higher than the ordinary working limit, but the average pressure on the piston
during the full length of the stroke is maintained constant in all cases.
work performed by the blowing cylinder remains constant and the power developed
by the motor equally so. This last condition supposes a constant speed or
number of reciprocations per minute in the case (now under consideration) of gas
engines in which the power is proportional to the speed.
In fully describing the invention reference is made to the accompanying draw-
ings in which Fig. 1 represents a horizontal blowing-engine having one motor
cylinder and one compression cylinder; the invention however is equally
applicable to engines having more than one cylinder and whether vertically
arranged or otherwise, the particular disposition having no influence upon the
principle of the invention. Fig. 2 is an enlarged elevation of the compression
or blowing cylinder, partly in section, and Fig. 3 an enlarged horizontal section
through the same showing the invention applied thereto.
M is the gas motor and S the blowing cylinder, surrounding each end of
which latter are arranged the valve boxes D D provided with ordinary suction and
delivery valves d d. The arrangement in this respect differs in no way from
the blast part of such machines as usually constructed.
Between the suction and delivery valves the compression chambers E E' are
located, and upon them in suitable position for operation by special valve gear,
hereinafter described, is arranged the device which forms the subject of this
invention.
In the said compression chambers E El are provided valve chambers F F¹
containing slide or piston-valves T T'. which are adapted to move simultaneously
upon seats G G¹ provided with ports L L', opening directly to the atmosphere or
as shown in the drawing communicating with each other by means of the con-
duit C (which forms no essential part of the invention). The valves T T¹ are

page_text: worked by a variable cut-off gear so as to leave the ports L L' open during a
certain variable proportion of the stroke of the blast piston. In the drawings a
link-gear is shown at I operated by the eccentric I on the crankshaft; in the
link works a sliding-block J, connected by side-rods K K' to the valve spindle t.
The position of the sliding-block J in the link I may be controlled by the
governor R or otherwise as hereinafter explained.
In the drawing the distributing motion is shown as being controlled by the
crank-shaft of the machine but if the arrangement of the latter requires it this
distributing motion may also be controlled by an auxiliary shaft or otherwise
conveniently.
The valves T T are so constructed as to ensure an alternate opening and
closing of the ports L L in such a manner that the left hand edges of the
valves T T uncover the ports when the blast piston runs from left to right and
the right-hand edges perform the same functions when the blast piston passes
from right to left; the operation may of course be reversed, this depending
entirely on the adjustment of the valve motion.
The valves T T may obviously be so arranged as to admit air to the ports L L'
by one of their edges only, but in that case it would be necessary for them to
receive alternating motions twice as frequent as those of the blast-piston P.
The valves T T begin to open the ports L L¹ at or preferably a little after the
dead centre.
The operation of the engins is as follows:-
When the pressure of the blast exceeds the ordinary working limit, it becomes
necessary to reduce the quantity of air delivered as above explained. Supposing
the blast piston P to have completed an entire suction stroke and the cylinder S
to be full of air at the atmospheric pressure or thereabouts, the piston now
starts on the return or delivery stroke; at the dead point the valves T T begin
to uncover the ports L L', allowing the air driven outwards by the piston either
to escape into the atmosphere or as shown in the drawing to pass by the con-
duit C to the suction end of the cylinder. As the stroke of the valves is regulated
by a centrifugal governor R or one worked by compressed air (the latter being
derived either from a special pump or from the feed-conduit of the blowing
engine itself, as indicated in dotted lines in Fig. 1 of the drawings), the valve
motion automatically recloses the ports L L' at such a moment as to ensure
during the compression and delivery part of the stroke a mean pressure on the
blast piston corresponding to the power of the driving motor. At this moment
the edges B B of the valves T T reclose the ports Land the piston P begins
to compress and subsequently to deliver the air. The piston P having com-
pleted its stroke stops and returns, but at the second dead point the valves T T¹
having continued their stroke uncover the ports L L' by their edges B2 B3 and in
the return stroke of the piston the cycle of operations already described is repeated
and so on.
"
The valves T T¹ may be worked by any form of variable admission gear, the
"cutting-off" action in this case consisting in the more or less prolonged opening
of the ports L L' during the early portion of the compressive piston stroke.
The slide-valves may be either flat or cylindrical as shown, and they are operated
by link gear or other motion of suitable kind, such as a mechanism of the "Meyer"
adjustable cut off type: Corliss valves may also be substituted this being
immaterial as regards the shortening of the effective compression stroke, which
is the object aimed at and attained in our case by the use of such mechanism.
The point of the stroke where the compression begins is determined by the
centrifugal or air-actuated governor in the following manner; supposing first
the pressure of the air to be normal, the engine then executes its normal number
of revolutions per minute. The ports L L¹ remain closed during the whole
length of the piston stroke and the air delivery attains its maximum. Under
these circumstances the sleeve of the centrifugal governor, if such be used to
control the valves T T¹, will remain constantly at its highest position.

page_text: Next suppose a higher pressure of air to be required; the engine not being
able to overcome this pressure and at the same time to supply the ordinary
maximum amount of air slackens speed, causing the sleeve of the governor to
descend and impart an increased stroke to the valves T T which
uncover the ports L L', allowing the air to escape at the beginning
of the piston stroke. Compression can only then take place at ધ
later moment of the piston-stroke, when the motion of the valves T T again
closes the ports L and L. While these ports remain open the work performed
by the engine is nil, and the action of the mechanism already described amounts
to a virtual shortening of the blast-piston stroke corresponding to the increase
of blast-pressure required. Within certain limits any extra pressure may be
obtained without an appreciable reduction of the speed or (in the case of a gas-
engine) the power of the motor. The shortening of the effective stroke may
be obtained by other means than the centrifugal governor described. For example
an arrangement such as is shown in dotted lines on Fig. 1 may be substituted.
This consists of a cylinder V wherein a piston V₁ is moved by the compressed
air through pipe , acting on one side against the force of an opposing spring W
on the other side. The piston rod V2 is connected to the sliding block I in the
guide-link J of the eccentric and thus, as above described, the initial compression
point of the blast-piston stroke is retarded proportionately to the increase of
pressure of the blast.
Again we may dispense with the governor and regulate the point of initial
compression by hand, but these two latter means (viz., the air piston and
regulation by hand) are not as efficient as the centrifugal governor for the follow-
ing reasons:-On stopping the engine the centrifugal governor presents the
following advantage which is a useful feature of the invention namely, that at
the moment of stoppage the blast-cylinder governor descends to its lowest
position and moves the valves T T¹ to open the ports L L during nearly the
whole length of the piston stroke, thus getting rid of all compression and reducing
practically the resistance of the blast cylinder to that simply due to friction, so
that the gas motor can easily be started again without the necessity of operating
any valve, slide or other device for relieving the engine of its load.
After starting when the speed of the motor increases and approaches the
normal the blast-cylinder governor acts prior to that of the gas-motor, because
the blast-cylinder governor is already at the top of its stroke when the gas motor
governor commences to act in order to maintain the constant speed; for example
taking the normal speed to be N revolutions per minute, the governor of the
blast cylinder acts at N-n revolutions per minute, that is to say it is at its highest
position corresponding to n revolutions prior to the normal speed of the engine:
thus before arriving at the normal speed of N revolutions per minute, the blast-
cylinder governor rises and the valves T T allow the compression in the blow-
ing cylinder to begin at such a moment on the stroke of the piston that the
engine always discharges the air at the desired pressure.
Having now particularly described and ascertained the nature of my said
invention (as communicated to me from abroad) and in what manner the same
is to be performed I declare that what I claim is:-
1. In a blowing engine the arrangement in combination with the compression
cylinder of means such as above described whereby, when the pressure of the
air-blast exceeds the normal, two air compression chambers situated at the ends
of the cylinder are placed in communication with the atmosphere or with each
other during a certain part of the beginning of the piston stroke, thereby
reducing the effective or compression length of the said stroke, the power
absorbed in blowing at the higher pressure remaining constant and the said
reduction of stroke affording the means of raising the blast pressure, substantially
as herein described.
2. The use in connection with the blast cylinder of a blowing engine of com-

page_text: pression chambers and eduction and admission valves controlling a passage to
the atmosphere or between the opposite ends of the blast-cylinder, the said
valves being automatically operated as required by a governor acting upon the
rod reciprocating or operating them, substantially as herein described.
3. The arrangement of valve-boxes, compression chambers, air passages, valves
and apparatus for working the same, substantially as and for the purposes herein
set forth.
For the Applicant,
J. C. CHAPMAN & Co.,
Chartered Patent Agents, 70, Chancery Lane, London, W.C.