Improvements in Direct Acting Electric Generators and in Directly Driven Electric Compressors for Air or other Gases.
Year: 1899

page_text: Date of Application, 4th Sept., 1899
Complete Specification Left, 3rd July, 1900-Accepted, 11th Aug., 1900
Improvements in Direct Acting Electric Generators and in Directly
Driven Electric Compressors for Air or other Gases.
I, JAMES ATKINSON, of The Woodlands, Marple, Engineer, do hereby declare
the nature of this invention to be as follows:-
:-
This invention relates to machines for the direct production of electric current
by means of steam (or other gases under pressure) and also for somewhat similar
machines having a reverse action suitable for directly compressing air or other
gases and using electric current as the motive power.
The electric generator consists of a double acting steam cylinder, the piston
of which by means of a piston rod and suitable connections causes the rapid
reciprocations of such parts as may be necessary to cause the production of
clictric currents through their movement in rilation to other fixed parts. There
is no rotary motion or movement of any portion of the machine excepting the
piston, piston rod and its electrical connections.
The piston has a very rapid reciprocating motion which may be at the rate
of some thousand double strokes per minute in a small machine and one or two
thousand in a large machine. The regulation of the steam admission and
exhaust is performed by the piston movement by means of ports in the piston
and cylinder, opened and closed at suitable times as will be explained.
In one arrangement of ports there are two in the cylinder and three in the
piston. The lower port in the cylinder is the steam admission port for both
sides of the piston and the upper port is the exhaust port also for both sides of
the piston. In the piston the lowest port is the steam admission port to the upper
side of the piston, suitable passages in the piston itself forming the communica-
tion, the middle port is the steam admission and the exhaust port for the under
side of the piston and the highest port provides for the exhaust from the upper
side of the piston. These ports may consist of circular grooves turned out of
the outer cylindrical surface of the piston body and the inner cylindrical surface
of the cylinder in connection with suitable passages or drilled holes spaced
equally round the circumference.
In another arrangement of ports there are three ports in the cylinder and two
in the piston each of the latter providing for the exhaust and admission to one
side of the piston; in the cylinder the upper and lower ports are steam admission
ports and the middle port is an exhaust port common to both sides of the piston.
To make the machine more or less self governing it is necessary to make the
piston of such a length that it never uncovers any of the ports in the cylinder
with its ends and each end of the cylinder forms a cushioning chamber.
I also provide outside the cylinder chambers of considerable capacity for the
steam supply and for the exhaust these being necessary if the best results are
to be obtained owing to the extremely short intervals of time during which supply
and exhaust take place: to assist in self governing I may however provide short
passages between the ports in the cylinder and these chambers.
The action in the cylinder, is as follows:-
Assume that the piston is near the lower part of its stroke, moving unwards

page_text: and the port which supplies steam to the under side of the piston is open to the
steam supply port in the cylinder, at about the same time the exhaust port in
the piston to the upper side is open to the exhaust port of the cylinder, steam
is thus admitted below the piston and exhausted from the upper side. As the
piston moves upwards these ports are closed and the steam below the pistoa
expands driving it upwards against the pressure of the steam above it, the mean
ressure below being greater than the mean pressure above. The cushioning
chamber at the top of the cylinder is so proportioned that although the steam
above the piston is compressed by the upward movement its pressure does not
ise above the steam supply pressure at the time the steam port in the piston
opens to the supply port in the cylinder consequently a little steam enters to
the upper side of the piston. At about the same time the ports for the exhaust
from the lower side of the piston open and the lower cushioning chamber being
also suitably proportioned there is also a pressure below the piston in excess of
the pressure in the exhaust chamber and a little steam is exhausted from below
the piston. This steam admission and exhaust may be sufficient to check the
piston movement or even reverse it if moving slowly in which case the ports
remain open a comparatively long period giving opportunity for an ample steam
supply and for a copious exhaust which would give a vigorous downwards
stroke. If however owing to less resestance during the upstroke the piston is
not thus reversed, it is brought up and reversed by the cushioning chamber
which practically without loss converts any excess upwards energy into down-
wards energy, the greater this cushioning effect the more rapidly the ports flash
past each other in both directions and the less the steam admitted and exhausted
as the ports open in both directions. The short passages to the ports above
referred to increase this governing effect by initially, but only initially, restrain-
ing fluid motion. A similar action takes place when the piston is at the bottoni
and the downwards motion reversed to upwards motion.
Care should be taken to proportion the cushioning spaces to suit the steam
and exhaust pressures so as to ensure ample expansion and I prefer to make them
easily adjustable so as to get the best results. They may be readily calculated
on the assumption that the compression and expansion lines for the portions of
the strokes when the ports are closed are similar to such lines when no heat 19
absorbed or given out excepting that due to work done, the rapidity of the strokes
being so great as to make this assumption practically correct.
The electrical parts may be attached to the upper cover of the steam cylinder
and consist of a fixed electro magnet and a moving coil attached to and recipro-
cating with the steam piston by means of a suitable piston rod and attachments.
The coil may be flattened at the sides and wound on two pillars fixed in a
crosshead attached to the head of the piston rod. One pole of the field magnet
is inserted downwards into the coil and two opposite poles are placed outside
one on each side of the coil there is thus, say, a north pole inside the coil and
two south poles outside. The field coils may be placed on the upper end of the
middle pole and the two outer poles attached to the middle pole above the field
coils, being levelled outwards to make room for the coils and then brought
inwards at their lower ends so as to limit the air gaps in which the inductor coi!
riciprocates.
Two vertical metalic insulated rods are arranged in suitable grooves attached
to the cross head in such a manner that they have a very slight vertical up and
down movement given to them by the first movement of the cross head at each
reversal, one end of the inductor coil is in electrical contact with one rod and
the other end of the coil with the other rod. The slight endwise movement
brings the rods into contact with one pair of contact makers during the up
strokes and another pair of contacts during the down strokes. These contacts
are so connected to the outer curcuit that though an alternate current is generated
in the inductor coil a pulsating current, but always in one direction, is delivered
to the outer circuit. The field coils consist of shunt and series coils supplied

page_text: with the one direction current so that the field pole faces are always of the same
polarity, the pulsations being so rapid that they retain their magnetism during
the intervals between the pulsations.
The shunt and series coifs are so proportioned that a constant voltage or any
desired variation in voltage at full and lighter loads is automatically maintained.
The self governing arrangements of the motor tend to maintain a more or less
constant rate of reciprocations but would not give a steady voltage without
suitable compounding of the field coils, moderate varations in the frequency of
the pulsations in the current would have no material prejudicial effect in using
such current for lighting, driving motors or many purposes for which electricity
is used.
Two or more similar machines could be driven in parallel and if of different
sizes care must be taken to make their natural periods of reciprocations the
same. The weight of the reciprocating parts has largely to do with the rate of
speed and these should be kept as light as possible if the maximum result is to be
obtained from a certain size of machine. To assist in keeping this weight low
the piston which has to be of considerable length may be in vertical section
somewhat of the form of the letter H.
Electric currents can be economically produced by these machines which are
of very moderate dimensions for the results obtained. The piston moves almost
frictionless in the cylinder care being taken to prevent any unbalanced side
strains. The steam can be very economically utilized with a very high rate of
expansion and owing to the high rate of the reciprocations the loss from heating
and cooling may be extremely small. The economical use of the steam also will
extend to very much lighter loads than in steam engines as usually constructed.
I wish it to be understood that I do not confine myself to the exact arrange-
ments of ports described so long as the provisions for self governing are
retained.
The electrical arrangements may also be modified to suit varying conditions.
as for instance, alternating currents can be delivered in an outer curcuit whilst
still making provision for the excitation of the field magnets by a one direction
current.
For the purpose of preventing any objectionable vibration the cylinder and
its base may be made of considerable weight it may also rest on or be suspended
by springs.
The machine for compressing air or other gases by using electric current as
the motive power may be constructed in just the same manner as the machine
for generating electric current, a continuous current being delivered to the
electric portion.
A slight modification however may be required in the contacts which transmit
the current to the contact rods for the purpose of preventing sparking at the
reversals of the current through the moving coil. I attach springs having short
restrained movements to keep the coil in contact a very short interval after
each reversal, before being placed in contact with the reversing contacts, the
sudden reversal of the motion of the coil between the pole faces reverses the
direction of the current through the coil or at any rate checks it so as to prevent
a spark when the contact is broken. In these machines also I do not confine
myself to the electrical arrangements described as these may be modified to suit
circumstances. In another arrangement I have no moving coil on the piston
rod but a suitable soft iron cylinder which is drawn in one direction by and into
a coil and in the other direction by a second coil, the current being directed
through these two coils atternately.
Dated this 2nd dor of Sentember 1800.

page_text: Improvements in Direct Acting Electric Generators and in Directly
Driven Electric Compressors for Air or other Gases.
I, JAMES ATKINSON, of Station Road, late of The Woodlands, Marple, Cheshire,
England, Engineer, do hereby declare the nature of this invention and in what
imanner the same is to be performed, to be particularly described and ascertained
in and by the following statement* -
This invention relates to machines for the direct production of electric current
by means of steam (or other gases under pressure) and also for similar machines
having a reverse action suitable for directly compressing air or other gases and
using electric current as the motive power.
For the purpose of more clearly explaining my invention I append three
sheets of drawings in which Fig. 1 Sheet 1 is a vertical elevation in section of a
direct acting electric generator, Fig. 2 Sheet 2 is a vertical elevation at right
angles to Fig. 1 Sheet 1 partly in section, Fig. 3 Sheet 3 is a plan of the electrical
portion in section. Figs. 4 and 5 Sheet 3 are diagrams showing the action of
the steam in the motor portion and Figs., 6 and 7 Sheet 3 are a vertical section
and a plan view of the modified electrical contact makers of the machine when
it is operated in a reverse manner and used for compressing air.
The electric generator consists of a double acting steam cylinder a, the
piston of which by means of a piston rod causes the rapid reciprocations of
such parts as may be necessary to cause the production of electric currents
through their movement in relation to other fixed parts. There is no rotary
motion or motion of any part excepting the rapid reciprocating motion of the
piston b, piston rod c and its electrical connections.
The piston has an extremely rapid reciprocating motion which may be at the
rate of many thousand double strokes per minute in a small machine and one or
more thousand in a large machine. The regulation of the steam admission and
exhaust is performed by the piston movement by means of ports in the piston
and cylinder opened and closed at suitable times as will be explained.
The arrangement of these ports may vary, but a suitable arrangement is shown
in Fig. 1 Sheet 1 there being two ports in the cylinder and three in the piston.
The lower port d in the cylinder is the steam admission port for both sides of
the piston and the upper port e is the exhaust port also for both sides of the
piston. In the piston the lowest port f is the steam admission port to the
upper side of the piston, suitable passages in the piston b itself forming the
communication as shown, the middle port is the steam admission and the
exhaust port for the under side of the piston also communicating with the under
side by means of suitable passages in the piston and the highest port provides
for the exhaust from the upper side.
These ports d, e, f and g may consist of circular grooves turned out of the
outer cylindrical surface of the piston body and the inner cylindrical surface
of the cylinder in connection with suitable passages or drilled holes spaced
equally round the circumference. The port in the upper part of the piston b
may be similarly constructed or it may consist of a number of equally spaced
holes circumferentially drilled at the same level as shown in Fig. 1 Sheet 1.
To make the machine more or less self governing the piston is of such a
length that it never uncovers any of the ports in the cylinder a with its ends
and each end forms a cushioning chamber, also the manner in which the ports
are opened is a matter of material importance as will be hereinafter explained.
I also provide outside the cylinder chambers of considerable capacity, for the
steam supply and for the exhaust, these being necessary if good results are

page_text: to be obtained owing to the extremely short intervals of time during which
supply and exhaust can take place. The chambers i and k should be large
enough to prevent any material rise or fall of pressure as the steam is drawn
from or delivered into so that the supply pipe which is not shewn on the
drawings and exhaust pipe m, are not depended on for the sudden and rapid
movements of the steam which otherwise would set up wave actions in these pipes
As well as interfere with free and unristricted movement. I may however pro-
vide short passages between the ports and in the cylinder and the chambers i
and for the purpose of initially restraining fluid motion but only initially and
such passages will have a material effect in assisting self governing as will be
hereinafter understood. In Fig. 1 Sheet 1 one of these passages is shown on
the steam admission side as being the more important and in many instances the
only one required.
The action in the cylinder is as follows:-
Assume that the piston is near the lower part of its stroke moving upwards
and the port.g which supplies steam to the under side of the piston 6 is open to
the steam supply port in the cylinder a, at about the same time the exhaust
port in the piston opens the upper side of the piston b to the exhaust port e
in the cylinder, steam is thus admitted to the under side of the piston b and
exhausted from the upper side.
As the piston moves upwards these ports are closed and the steam shut in below
the piston expands driving it upwards against the steam pressure above it, the
mean pressure below being greater than the mean pressure above. The cushion-
ing space at the top of the cylinder a is so proportioned that although the steam
shut in above the piston is compressed by the upward movement its pressure
is lower than, or does not rise above, the steam pressure in the chamber i at the
time the steam port f in the piston communicating with its upper side opens
to the steam supply port consequently a little steam enters to the upperside.
At about the same time the port in the piston opens to the exhaust port e in
the cylinder a making a communication from below the piston 6 to the exhaust
chamber k, the lower cushioning chamber being also suitably proportioned there
is a pressure below the piston in excess of the pressure in the chamber k and a
little steam is exhausted from below the piston b. This steam admission and
exhaust may be sufficient to check the piston movement or even reverse it if
moving slowly in which case the ports remain open a comparatively long period
giving opportunity for an ample steam supply and for a copious exhaust giving
a vigorous downward stroke during which a similar fluid action takes place.
This fluid action is clearly shown in Fig. 4 Sheet 3 which is a diagramatical
illustration of the fluid action assuming that the pressure of the steam in the
steam supply chamber is about four atmospheres above atmospheric pressure
and the motor is working noncondensing and exhausting into the atmosphere.
the diagram showing the fluid action for both sides of the piston, as will be
readily understood.
If however owing to less resistance during the up stroke the piston b is not
thus reversed it is arrested and reversed by the cushioning space above the
piston b which practically without loss converts any excess upwards energy into
downwards energy, the greater this cushioning effect the more rapidly the ports
flash past each other in both directions and the less the steam admitted and
exhausted as the ports open. The short passage to the steam port above
referred to increases this governing effect by initially, but only initially restrain-
ing fluid motion. A similar action takes place when the piston bis at the
bottom and the downwards motion reversed to upwards motion. Fig. 5, Sheet 3
clearly shows this self governing action and the reduced power thus automatically
regulated.
Care should be taken to proportion the cushioning spaces to suit the steam
and exhaust pressures so as to ensure ample expansion and I prefer to make
them easily adjustable so as to get the best results. They may be readily

page_text: calculated on the assumption that the compression and expansion lines for the
portions of the strokes when the ports are closed are similar to what such lines
would be when no heat is absorbed or given out excepting that due to work
done, the rapidity of the strokes being so great as to make this assumption
practically correct. This will also be clearly understood by an inspection of
Figs. 4 and 5 Sheet 3.
The electrical parts may be attached to the upper cover of the steam cylinder
and consist of a fixed electro magnet and a moving coil m attached to and
reciprocating with the steam piston by means of a suitable piston rod and
attachments. The coil m may be flattened at the sides where it passes between
the poles of the magnet and wound on two pillars fixed to or cast in one with a
crosshead as shown. One pole n, of the field magnet 7 is inserted downwards
into the coil m and two opposite poles o are placed outside, one on each side of
the coil m, there is thus, say, a north pole n, inside the coil m and two south
poles o outside.
The field coils p and may be placed on the upper end of the middle pole n
and the two outer poles attached to the middle pole n₁ above the field coils p
and being swelled outwards to make room for the coils and then brought
inwards at their lower ends so as to limit the air gaps in which the coil m
reciprocates. There is a very great advantage in thus constructing the field
magnets as the magnetic lines of force have only got to be driven across one air
gap instead of across two as in an ordinary dynamo, the field magnet coils are
thus considerably reduced and the dead loss of magnetizing current is materially
less.
Two vertical insulated metalic rods are arranged in suitable guides attached
to the cross head in such a manner that they have a very slight vertical up
and down movement given to them by the first movements of the cross head at
each reversal of stroke. One of the ends of the inductor coil m is in electrical
contact with one rod and the other end of the coil m with the other rod. The
slight endwise movement brings the rods s into contact with one pair of contact
makers during the upstrokes and another pair of contact makers during the
down strokes. The arrangement of these contacts is shown in Fig. 2 Sheet 2
which also shows the connections to the outer circuit.
It will be readily understood that the coil m being very rapidly reciprocated
between the poles n, and oo of the field magnet will have an alternating electric
current generated in it and that by means of the reversable contacts this alter-
nating current will be converted into a pulsating current always in the same
direction in the outer circuit. The field coils consist of a shunt coil P and a series
coil and are supplied with the one direction current so that the field poles are
always of the same polarity, the pulsations being so rapid that they retain
their magnetism during the intervals between the pulsations.
The shunt coil and the series coil rare so proportioned that a constant voltage
or any desired variation in voltage at full and light loads may be automatically
maintained. The self governing arrangements of the motor tend to maintain
a more or less constant rate of reciprocation but would not give a steady voltage
without suitable compounding of the field coils p and r. As the load in the
outer circuit decreases the lengths of the strokes and the speed of the coil m
between the field poles n, and oo increases, at the same time the magnetic lines
of force in the field magnets decreases owing to there being less current through
the series coil r and if properly proportioned the desired result in voltage can
be maintained. Should there be slight variations in the frequency of the pulsa-
tions in the current these variations would have no material prejudicial effect in
using such current for lighting, driving motors or many purposes for which
electricity is used. The steam cushions however have a very desirable effect in
preventing variations in frequency.
Two or more similar machines could be driven in parallel and if of different
sizes care must be taken to make there natural periods of reciprocations the

page_text: same. The weight of the reciprocating parts has largly to do with the rate of
speed and these should be kept as light as possible if the maximum result is to
be obtained from a certain size of machine. To assist in keeping this weight
low the piston b which has to be of considerable length may be in vertical
section somewhat of the form of the letter H, as shown.
Electric currents can be economically produced by these machines which are
of very moderate dimensions for the results obtained. The piston 6 moves almost
frictionless in the cylinder a care being taken to prevent any unbalanced side
strains. The steam can be very economically utilized with a very high rate of
expansion and owing to the high rate of the reciprocations the loss from heating
and cooling may be extremely small. The economical use of the steam also
will extend to very much lighter loads than in steam engines as usually
constructed.
I wish it to be understood that I do not confine myself to the exact arrange-
ments of ports described so long as the provisions for self governing are retained.
The electrical arrangements may also be modified to suit varying conditions,
as for instance, alternating currents can be delivered in an outer circuit whilst
still making provision for the excitation of the field magnets by a one direction
current.
For the purpose of preventing any objectionable vibration the cylinder a and
its base may be made of considerable weight, it may also rest on or be suspended
by springs.
The machine for compressing air or other gases by using electric current as
the motive power may be constructed in just the same manner as the machine for
generating electric current, a continuous current being delivered to the electric
portion. A slight modification however may be required in the contacts which
Transmit the current to the contact rods for the purpose of preventing sparking
at the reversals of the current through the moving coil. I attach springs having
short restrained movements to keep the coil in contact a very short interval
after each reversal before being placed in contact with the reversing contacts,
the sudden reversal of the motion of the coil between the pole faces reverses
the direction of the current through the coil or at any rate checks it so as to
prevent a spark when the contact is broken. This modification in the contacts
is shown in Figs 6 and 7 Sheets 3.
In these machines also I do not confine myself to the electrical arrangements
described, as these may be modified to suit circumstances.
In another arrangement I have no moving coil on the piston rod but a suitable
soft iron cylinder which is drawn in one direction by and into a coil and in the
other direction by a second coil, the current being directed through these two
coils alternately.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that
what I claim is:-
1. In a direct acting reciprocating, steam driven, electric generator of the
type described in this specification, the use of steam cushions and the arrange-
ments of ports with steam and exhaust chambers, giving the self governing
effect, as described and illustrated.
2. In a direct acting, reciprocating, steam driven, electric generator of the
type described in this specification, the use of steam cushions, the arrangement
of supply and exhaust ports, combined with steam and exhaust chambers and
short passages between the ports and the steam and exhaust chambers, giving
the self governing effect, as described and illustrated.
3. In a direct acting, reciprocating, steam driven. electric generator of the
type described in this specification, the use of a generating coil in which an
alternating electric current is generated by its reciprocations between an inner
pole face if one polarity and two outer pole faces of an opposite polarity, sub-
stantially as described and illustrated.

page_text: 4. In a direct acting, reciprocating, steam driven, electric generator of the
type described in this specification, the use of alternating contacts which rectify
the alternating electric current generated in the coil into one direction current
for the purpose of exciting the field magnet, in such a manner that the pole
faces always have the same polarity, substantially as described and illustrated.
3. In a direct acting, reciprocating, steam driven, electric generator of the
type described in this specification, the suitable proportioning of the shunt coil
and series coil which excite the field magnet, so that as the strokes of the piston
vary their range, the strength of the magnetic iines of force in the field magnet
vary in an inverse manner, so as to give & constant voltage or any desired
variation in voltage in the current generated, substantially as described and
illustrated.
6. In a direct acting, reciprocating air or gas compressor driven by a continuous
electric current, the use of a double acting compressor cylinder, the piston of
which is reciprocated by the electric current by any suitable electric arrange-
ments, the fluid action being entirely controlled by ports in the piston and
cylinder, substantially as described and illustrated.
7. In a direct acting, reciprocating air or gas compressor driven by a continuous
electric current, the use of a double acting compressor cylinder the piston of
which is reciprocated by the electric current by any suitable electric arrange-
ments, the fluid action being entirely controlled by ports in the piston and
cylinder and having large chambers for the supply of the air to be compressed
and to receive the compressed air, substantially as described and illustrated.
8. The general arrangement and construction if reciprocating electric genera-
tors, substantially as described and illustrated.
9. The general arrangement and construction of electrically driven, recipro-
cating, air compressors, substantially as described and illustrated.
Dated this 2nd day of July 1900.
JAMES ATKINSON.