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'Jan. 4, 1949.
K. c. COOPER’
2,458,147
A CONTROL FOR FREE-PISTO‘N UNITS
Filed April 15, 1944
INVENTORY
mm
M
w
ATTORNEY
.4,
Patented Jan. .4, 1949
2,458,147
UNITED STATES PATENT OFFICE
2,458,147
CONTROL FOR FREE-PISTON UNITS
Kenneth C. Cooper, Portland, Conn., assignor to
United Aircraft Corporation, East Hartford,
Conn., a corporation of Delaware
Application April 15, 1944, Serial No. 531,301
3 Claims. (Cl. 230-56)
1
2
This invention relates to a free-piston unit
center of the engine cylinder by a linkage, not
shown.
Intake manifold 42 which extends around the
compressor and engine cylinders, conducts air to
adapted for operation at varying intake pres~
sures.
I
A free-piston engine-and-compressor unit de
signed for compressing one density of gas is im
properly dimensioned for compressing gas at
other densities. A feature of this invention is
a unit that will operate properly at varying gas
densities.
intake valves 44 in the heads of the compressor
cylinders through which air alternately enters
opposite ends of the cylinders. .The compressed
air leaves the cylinders through discharge valves
46, also at opposite ends of the compressor cylin
The change in density may affect the length of 10 ders, and passes into a central scavenge cham
ber 48 and end chambers 50 and 52. These
piston stroke and may shorten it so that the
chambers may be interconnected by a scavenge
scavenge and exhaust ports in the engine cylin
manifold, not shown.
der will not be completely uncovered. A fea
Compressed gas from the scavenge chambers
ture of the invention is a unit in which the eifec
tive volume of the compressor may be adjusted 15 enters engine ports 54 and 56 which are uncovered
to compensate for varying densities of gas.
These units may be used in aircraft power
plants. The compressor, which pumps in air at
by pistons l2 and it at the end of the power
stroke, thereby permitting air to be blown through
the engine cylinder. ' Gas in the engine cylinders
is discharged through exhaust ports 58 into ex
the surrounding pressure if designed for high al~
manifold 60.
i
titudes, will not be properly dimensioned for other 20 haust
For the purpose of maintaining a substantially
altitudes. Another feature of the invention is a
constant stroke, the amount of work done by the
provision for controlling the volume of air com
compressor on each stroke is controlled by adjust
pressed on each stroke of the engine to compen
ing the effective volume of the compressor. To
sate for changes in altitude or gas density.
25 this end, each compressor cylinder has a number
Another feature is the control of the effective
of axially spaced vents 62, each in the form of
volume of the compressor, by which to compen
a row of spill ports in the cylinders to permit
sate for altitude changes, without seriously affect
air to discharge from the cylinder without com
ing the length of the piston stroke.
'
pression. Each vent maybe individually con
A feature of the invention is a number of axial
30 trolled by a poppet valve 64, the stem 66 of which
ly spaced vents, each of which may comprise
may be guided in manifold 42. Any well-known
a circumferential row of openings in the com
structure may control these valves; for example.
pressor cylinder. The vents may be individually
as
shown, the valve stem 66 may have a piston 68
opened or closed to vary the volume of air com
sliding in a cylinder ‘I0. A spring 12 acts on the
pressed on each piston stroke.
to open the valve, and ?uid under pressure
Other objects and advantages will be apparent 36 piston
through a conduit 14 may be admitted to the
from the speci?cation and claims, and from the
cylinder to close the valves. All the valves of
accompanying drawings, which illustrate an em
any one row may be controlled by springs of the
bodiment of the invention.
same strength so that all the valves in one row
The single figure is a sectional view through a 40 will open or close simultaneously.
free-piston unit.
‘
The intake manifold includes a housing 82
The unit shown includes an engine cylinder
which may extend around the compressor cylin
i0 having reciprocating pistons I2 and It to
ders, and end caps 83 and 84 on the housing.
which compressor pistons l6 and [8 in cylinders
forming passages to the intake valves at the outer
20 and 22 are integrally connected. Sleeves 24 and 45 ends of the compressors. The vents 62 open into
25 attached to the compressor pistons complete
the intake manifold.
the reciprocating piston assemblies. The sleeves
in combination with stationary pistons 28 and 30
When the air being pumped by the compressor
has a high density, as at sea level atmosphere,
all the rows of ports are open and only a small
form air spring cylinders.
The piston assemblies are moved apart by the 50 volume of air is compressed. As the density
burning of fuel injected into engine cylinder In
decreases, as when the compressor operates at
through one or more nozzles 32.
Air compressed.
in the air spring cylinders on the power stroke re
turns the piston assemblies. The assemblies are
altitude, one or more of the rows of ports may be
closed, beginmng with the end rows, thus increas
ing the eifective volume of the compressor. The
always maintained at equal distances from the 55 several rows of ports permit adaptation of the
2,408,147
3
4
\
compressor to substantially any altitude or to any
inlet and discharge valves, said pistons being con
density of air being pumped. In this way sub
nected together and having a variable length
stroke,. and means for adjusting the e?'ective
volume of the compressor cylinder, said means
including axially spaced vents in the compressor
cylinder, each vent including a number of radially
stantially the same mass of air may be pumped
on each stroke of the compressor, and by main
taining the same mass ?ow, the compressor does
substantially the same amount of work and the
stroke remains substantially constant, assuring
the uncovering of scavenge and exhaust ports on
each stroke.
‘
extending openings circumferentially arranged
around the cylinder and means for controlling‘
all oi’ the openings of each vent_‘.,_simultaneously.
‘
It is to be understood that the invention is 10
3. A free-piston engine-and-compressor unit
not limited to the speci?c embodiment herein
including an engine cylinder. opposed pistons in
illustrated and described, but may be used in
said cylinder, compressor pistons moving with
other ways without departure from its spirit
said engine pistons and compressor cylinder for
as de?ned by the following claims.
the compressor pistons, said compressor cylinder
I claim:
'
15 having inlet and discharge valves for the ?uid
1. A free-piston engine and compressor unit
being pumped, in combination with means for
including an engine cylinder and piston, said cyl
adJusting the e?'ective volume of each compressor
cylinder independently of the lengthot piston
inder having scavenge ports therein adapted to
stroke, said means including axially spaced vents
be uncovered by the piston on each stroke for
the admission of air to the cylinder, va compressor 20 in the compressor cylinders, each vent including
a number of radial openings arranged clrcum.
cylinder and piston, said compressor cylinder
ferentially of the cylinder, and means for closing
having inlet and discharge valves, said pistons
all the openings of each vent simultaneously.
being connected together and having a variable
KENNETH C. COOPER.
length stroke, the length of stroke being a func
tion of the pressures in said cylinders and the
REFERENCES- CITED ’
work done in the compressor cylinder, and means
for maintaining a length of stroke such that the
The following references are of record _in the
engine piston will move far enough to uncover
v?le of this patent:
the scavenge ports on each stroke, said means
UNITED STATES PATENTS
including a number of vents axially spaced from 80
each other in the wall of the compressor cylinder,
Number
Name
Date
each vent including a number of radially extend
ing openings extending through the cylinder wall
and arranged circumferentially. of the cylinder
and means for closing all of the openings for each
vent simultaneously thereby providing for adjust
ment of the work done on each stroke in the event
of pressure changes in the compressor intake
pressure.
'
'
-
'2. A free-piston engine-and-compressor unit 40
including an engine cylinder and piston, ‘a com
pressor cylinder and piston, said cylinder having
0
877,492
1,481,358
Doelling ______ --,___ Jan. 28, 1908
Dwyer _________ _-.. Jan. 22, 1924
1,869,787
2,064,976
2,076,258
2,086,162
2,108,890
2,134,920
2,189,497
2,282,562
Trumble __ _______ -- Aug. 2,
Janicke _________ __ Dec. 22,
Wltkiewicz ________ _.. Apr. 6,
Janicke __________ _.. June 6,
Janicke __________ __ Feb. 22,
Kadenacy _________ _.- Nov. 1,
Pescara ___________ _- Feb. 6,
Cole ____________ __ May 12,
‘2,319,566
Sunderman et al. _-.‘- May 18, 1943
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