U.S. patent number 3,859,966 [Application Number 05/333,069] was granted by the patent office on 1975-01-14 for linear balanced free piston machines.
Invention is credited to Anton Braun.
United States Patent |
3,859,966 |
Braun |
January 14, 1975 |
LINEAR BALANCED FREE PISTON MACHINES
Abstract
The invention provides a novel class of linear balanced free
piston machines which include a first movable assembly supported
for reciprocating movement along an inner axis, at least two
counterbalancing assemblies supported for individual reciprocating
movement along respective separate paths spaced around the inner
axis, and a corresponding plurality of separate synchronizing
mechanisms individually connecting each counterbalancing assembly
to the first movable assembly for simultaneous synchronized
movement of the counterbalancing assemblies along their respective
paths with component vectors of such movement directed at all times
in the opposite direction to the movement of the first assembly. At
least one of the movable assemblies includes a movable member of an
energy absorbing device, such as a compressor, electric generator
or pump. The parts are arranged and interrelated to maintain the
common center of gravity of all moving masses of the apparatus at a
substantially fixed location therein for all operating positions of
the respective assemblies. Preferred arrangements of individual
synchronizing levers and of a cooperating sealing member between
such inner and outer movable assemblies are shown.
Inventors: |
Braun; Anton (Minneapolis,
MN) |
Family
ID: |
23301128 |
Appl.
No.: |
05/333,069 |
Filed: |
February 16, 1973 |
Current U.S.
Class: |
123/46R; 60/910;
123/46B; 123/192.2; 417/343; 123/192.1; 417/313 |
Current CPC
Class: |
F02B
71/00 (20130101); Y10S 60/91 (20130101) |
Current International
Class: |
F02B
71/00 (20060101); F02b 071/00 (); F02d
039/10 () |
Field of
Search: |
;60/DIG.1
;123/192B,192R,46R,46B ;417/343,313 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Antonakas; Manuel A.
Assistant Examiner: O'Connor; Daniel J.
Attorney, Agent or Firm: Dorsey, Marquart, Windhorst, West
& Halladay
Claims
I claim:
1. A balanced linear free piston machine comprising a first movable
assembly having portions substantially all of which move together
as a unit, said first movable assembly being supported for
reciprocating movement with its center of gravity moving along an
inner longitudinal axis of the machine, at least two movable
counterbalancing assemblies each of which has portions
substantially all of which move together as a unit, each
counterbalancing assembly being supported for individual separate
reciprocating movement with the respective centers of gravity of
the counterbalancing assemblies moving along respective separate
outer paths spaced from each other around said inner axis and first
movable assembly, a separate synchronizing means mechanically and
independently interconnecting each movable counterbalancing
assembly with said first movable assembly for simultaneous
synchronized movement of each movable counterbalancing assembly
along its path in a direction having component vectors of such
movement which are moving at all times in the opposite direction to
the movement of the first movable assembly, at least one power
cylinder stationarily mounted on said machine, one of the movable
assemblies having a power piston portion supported for
reciprocating movement in said power cylinder, and at least one of
the other movable assemblies including a movable member of an
energy absorbing device.
2. A balanced linear free piston machine according to claim 1 in
which the paths of movement of the movable counterbalancing
assemblies are angularly oriented and spaced around the inner axis
at positions determined by the relative masses and lengths of
stroke of the respective movable counterbalancing assemblies and of
the first movable assembly, the relative location and orientation
of said plurality of paths and the construction, orientation and
operation of said synchronizing devices positioning all of the
masses included in and associated and moving with each movable
counterbalancing assembly at radial distances and angularly spaced
positions around said inner axis and first movable assembly which
maintain the common center of gravity of all moving masses of the
apparatus in a substantially fixed position in the apparatus at all
possible operating positions of the movable assemblies.
3. A balanced linear free piston machine according to claim 1 in
which at least one, but less than all, of said movable assemblies
is provided with a power piston.
4. A balanced linear free piston machine according to claim 1 in
which at least two of said movable assemblies are each provided
with at least one power piston and in which the power pistons of
different movable assemblies are movable in respectively different
paths.
5. A balanced linear free piston machine according to claim 1 in
which said one power cylinder is coaxial with said inner axis and
said one power piston portion is also coaxial therewith, said power
piston portion being part of said first movable assembly for
movement of said first assembly in response to power strokes of the
power piston portion coaxially along said inner axis in at least
one direction, and with the center of mass of the first assembly
located at all times on said inner axis.
6. A balanced linear free piston machine according to claim 5 in
which the first movable assembly includes two oppositely acting
power piston portions for movement of the first assembly in
response to successive alternating power strokes of the two power
piston portions along said inner axis in both directions.
7. A balanced linear free piston machine according to claim 6 in
which the counterbalancing movable assemblies include at least one
first working member which performs work during movement of the
first movable assembly in one direction and at least one second
working member which performs work during movement of the first
movable assembly in the opposite direction.
8. A balanced linear free piston machine according to claim 5
having two counterbalancing assemblies supported for movement along
respective separate paths each of which is parallel to said inner
axis and spaced 180.degree. around said inner axis and first
movable assembly from the other separate path.
9. A balanced linear free piston machine according to claim 8 in
which the two counterbalancing assemblies are of substantially
equal mass and their respective paths of movement are spaced
radially equal distances from said inner axis and first movable
assembly.
10. A balanced linear free piston machine according to claim 9 in
which only one of the two counterbalancing assemblies includes a
movable energy absorbing device member and the other
counterbalancing assembly operates only as a counterbalancing
mass.
11. A balanced linear free piston machine according to claim 10 in
which only the first movable assembly is provided with any power
piston.
12. A balanced linear free piston machine according to claim 1 in
which a second power cylinder is stationarily mounted on said
machine, and one of the other movable assemblies has a power piston
portion supported for reciprocating translational movement in said
second power cylinder.
13. A balanced linear free piston machine according to claim 1
having a first housing portion for the first movable assembly and a
second housing portion for one of the other movable assemblies,
said first and second housing portions having wall portions
generally separating said movable assemblies from each other but
providing a limited transverse connecting passageway between them,
the synchronizing device connecting the first movable assembly to
said one other movable assembly including a lever extending through
said passageway generally transversely from said inner axis toward
the outer path of movement of said one other movable assembly, said
lever having a pivotal support on one of the housing portions close
to said passageway for pivotal movement of the lever on a pivotal
axis generally perpendicular to a plane defined by said inner axis
and by said outer path of movement, and a flexible sealing member
extending across and sealing said passageway and having sealing
engagement with said lever close to its pivotal axis.
14. A balanced linear free piston engine according to claim 13 in
which said flexible sealing member has its outer edges clamped in
sealing engagement against at least one of said first and second
housing portions.
Description
BACKGROUND OF THE INVENTION
Free piston engines are known in which power is transmitted from a
suitable power piston to a movable member of an energy absorbing
device by connections within the engine. In some of these machines,
the desired balance is achieved by connecting a power piston and
energy absorbing device member, such as a compressor piston, to
move together as a unit, and by providing a substantially identical
unit movable along the same axis as the first unit and at all times
in opposite directions. In such machines, a member of a particular
function, such as a power piston, moving with one unit is
counterbalanced by a substantially identical member such as another
similar power piston moving in the opposite direction with the
other unit. Thus the balancing is achieved by an arrangement of two
oppositely moving assemblies which are essentially symmetrical,
i.e. which constitute substantially mirror images of each other on
each side of a central axis or plane of symmetry.
As described and claimed in my earlier U.S. Pat. Nos. 3,501,088 and
3,525,102, unsymmetrical free piston engines have been developed in
which two oppositely moving counterbalancing assemblies which are
not symmetrical, for one reason or another, are arranged to balance
each other.
There are problems, however, when one wishes to utilize such prior
free piston engine devices for applications in which it is
necessary or desirable to isolate part or all of one of the movable
assemblies from the other. For example, if the energy absorbing
device in such an apparatus is to operate on food materials for
human or animal consumption, there is a need to insure that the
food product handled by the machine cannot be contaminated by oil
or other impurities from the power section of such an engine.
Similarly in such applications as refrigeration, it may be
important to seal off or isolate an energy absorbing device, such
as a compressor or pump for the refrigerant, from the power section
of the machine or from the atmosphere or other surroundings. In any
case, it is desirable to prevent the escape of oil or other
contaminants from the power section of a free piston engine.
The desired isolation of such movable working or energy absorbing
members from their associated driving engine power sections or
surroundings has been previously achieved in other types of
machines, such as rotary machines by the use of appropriate rotary
seals. In piston machines where reciprocating translational
movement of power and working pistons along the same axis is
involved, it is possible to achieve some isolation by special seals
or packings along an axially movable piston shaft extending between
the power and working pistons. Such arrangements, however, involve
greater axial length for the entire machine and extra expense for
the cost of the packings. The extent and speed of axial movement of
the parts also tends to wear out the seals prematurely.
SUMMARY OF THE INVENTION
The present invention provides a novel class of free piston
machines in which a first movable assembly is mounted for
reciprocating movement with its center of gravity moving along an
inner axis, and in which at least two counterbalancing assemblies
are mounted for individual reciprocating, i.e., back and forth,
movement with the respective centers of gravity of the
counterbalancing asemblies moving along separate individual paths
spaced from each other around such axis. A separate synchronizing
mechanism connects each respective counterbalancing assembly with
the first movable assembly for movement of the counterbalancing
assembly along its path with a component vector of movement which
is at all times opposite to the direction of movement of the first
assembly along the inner axis. The machine further includes at
least one power cylinder stationarily mounted in the engine, and
one of the movable assemblies includes a power piston portion
movable within the power cylinder, while at least one of the other
movable assemblies includes a movable member of an energy absorbing
device. Such device may be partly or entirely driven by
transmission of forces from such a power cylinder to the energy
absorbing device member through the particular synchronizing
mechanism which connects the two assemblies. To further achieve the
desired balance, the respective paths of movement of the
counterbalancing assemblies are angularly oriented and spaced
around the inner axis, and the construction and operation of the
respective synchronizing mechanisms are so arranged, that the
common center of gravity of all moving masses within the machine
remains at a substantially fixed point therein for all operating
positions of the respective assemblies. The outer assemblies are
preferably spaced symmetrically around the inner axis to simplify
the design considerations.
Free piston machines according to the invention may include a
plurality of power piston portions carried by one or more of the
movable assemblies, but preferably by less than all of the
assemblies. Such plural power piston portions may be connected and
operated to provide simultaneous or parallel power strokes for the
assembly or assemblies involved, or to provide successively
alternating power strokes in first one direction and then the
opposite direction.
In one operating form of the invention, two or more
counterbalancing assemblies are movable along paths which are
parallel to the inner axis of the machine, are separated therefrom
by equal radial distances and are spaced around said axis at equal
angular spacings, with the masses of the respective
counterbalancing assemblies equal to each other and with the center
of gravity of the first movable assembly moving at all times along
said inner axis. In the preferred form of the invention, the first
movable assembly includes two alternately and oppositely acting
power piston portions movable coaxially along the inner axis, all
power pistons of the machine are included in the first movable
assembly, and two counterbalancing assemblies are located with
their parallel paths of movement spaced 180.degree. apart around
the inner axis and with two alternately and oppositely acting
compressor piston portions on one of these two counterbalancing
movable assemblies and with the other counterbalancing movable
assembly operating essentially only as a counterbalancing mass.
In order to achieve the desired synchronizing action while
maintaining the center of gravity of all moving parts at the
desired common point, the preferred synchronizing mechanism for
each counterbalancing assembly includes a lever having an
intermediate part pivotally supported on the machine for limited
swinging movement on a pivotal axis perpendicular to the common
plane defined by the respective inner path or axis of movement of
the first movable assembly and the path of movement of the
particular outer counterbalancing assembly. This pivotal axis is
thus spaced between the two assemblies, and the lever has ends
projecting toward each assembly and connected thereto by respective
inner and outer links. For maximum elimination or balancing of
components of vibration, the synchronizing lever and its links
should have a Z-shaped configuration as shown in the accompanying
drawings, with the inner and outer connecting links projecting in
opposite parallel directions from the outer ends of the
synchronizing lever to the respective movable assemblies. Moreover,
the length of the synchronizing lever should be selected with
reference to the desired distances through which the inner and
outer assemblies are to reciprocate, so that the synchronizing
lever swings through equal arcs, as small as practically possible,
above and below a reference line passing through the pivotal axis
of the lever and perpendicular to the paths of movement of the
assemblies.
To provide the desired separation of the power sections from the
energy absorbing or working members, all power piston portions are
preferably located on one movable assembly, i.e., the inner or
first movable assembly, and this assembly is enclosed within a
first housing portion. The working members can then be positioned
on one or more of the counterbalancing assemblies, each within its
own outer or second housing portion. These housing portions are
sealed from each other by suitable housing or partition walls,
except for a limited area at which a transverse passageway is
provided to accommodate a synchronizing mechanism lever. Thus,
according to a further feature of the invention, a flexible sealing
partition can be positioned across the limited passageway between
the first movable assembly and the counterbalancing assemblies,
such sealing member being penetrated only by the rocking lever of
its synchronizing mechanism and being sealed around such rocking
lever close to the pivotal axis of the synchronizing lever. In this
construction, sealing surface displacements and velocities can be
much lower than on conventional shaft or similar sealing surfaces
running at the same speeds and distances as the movable assemblies
themselves, and the usual rubbing velocities which wear out such
conventional seals are eliminated and replaced by limited flexing
of a sealing partition.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings which form a part of this application, and in which
like reference characters indicate like parts
FIG. 1 is a schematic elevation view, partly in section, of one
operating form of linear balanced free piston machine according to
the invention, in which a reciprocating inner power assembly is
individually connected to and counterbalanced by two outer
oppositely movable counterbalancing assemblies, each of which
includes a movable member of an energy absorbing device.
FIG. 2 is a schematic top view of a modified form of such a machine
in which a central assembly is connected to three outer
counterbalancing assemblies;
FIG. 3 is a view similar to FIG. 2 of a free piston machine of this
type in which a central assembly is connected to four oppositely
moving outer counterbalancing assemblies spaced at equal angles
around the axis of the inner assembly;
FIG. 4 is a view similar to FIGS. 2 and 3 of a modified free piston
machine in which an inner movable assembly is connected to four
oppositely moving outer counterbalancing assemblies which are not
distributed at equal angles from each other around the inner
assembly, but which are symmetrically spaced around the axis of the
inner assembly in balanced pairs;
FIG. 5 is a view similar to FIG. 2 of a modified free piston
machine in which an inner movable assembly includes at least one
pair of pistons at opposite sides of the axis of movement of the
inner assembly, and in which this assembly is counterbalanced by
two oppositely moving outer counterbalancing assemblies;
FIG. 6 is a view similar to FIG. 1 of a modified linear balanced
free piston machine in which the inner assembly is a power assembly
which is individually connected to two movable outer assemblies,
one of which includes a movable member of an energy absorbing
device, while the other assembly serves primarily as part of the
counterbalancing weight for the inner assembly;
FIG. 7 is a view similar to FIGS. 1 and 6 of a further modification
in which power pistons are mounted on each of two outer
counterbalancing assemblies, while the inner movable assembly
performs only a balancing function;
FIG. 8 is a view similar to FIG. 6 of a preferred free piston
machine in which an inner movable assembly has two coaxial
alternately and oppositely acting power pistons and is individually
connected to two oppositely moving outer counterbalancing
assemblies, and one of which includes a pair of alternately and
oppositely acting compressor piston portions and the other of which
operates only as a part of the counterbalancing mass;
FIG. 9 is an enlarged sectional view on the line 9 -- 9 of FIG. 8
(but with the synchronizing lever in its mid-position), showing
details of a flexible sealing member and synchronizing lever
combination according to the invention; and
FIG. 10 is a sectional view on the line 10 -- 10 of FIG. 9, with
portions broken away for clearness.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 1, a preferred linear balanced free piston machine
according to the invention includes a main housing or frame portion
11 on which a first movable assembly 12 is supported for
reciprocating translational movement along an inner longitudinal
axis of the machine. In this embodiment, the first movable assembly
includes a power piston portion 13 which reciprocates within a
power cylinder 14 stationarily mounted on the housing or frame 11.
A fuel injector or spark plug 16, and appropriate inlet and outlet
ports, provide for compression ignition or spark ignition of an
appropriate combustible mixture within the combustion chamber 17
between the piston portion 13 and the head of cylinder 14 in known
manner.
Piston 13 is secured to a longitudinally movable shaft 18, which in
this case is co-axial with piston 13 and cylinder 14 and defines an
inner axis or path of longitudinal movement of the first movable
assembly.
At the lower end of shaft 18 is secured a connecting member 19 for
the synchronizing mechanisms to be described below, together with a
further piston portion 21 designed to reciprocate along the axis 18
within a lower cylinder 22. The space between piston portion 21 and
the head of the cylinder portion 22 may serve as any desired
portion of a free piston engine power section, and may, as in FIG.
8, constitute another combustion chamber to provide power during
successive power strokes in opposite directions for inner assembly
12. Alternatively, chamber 23 may serve as a bounce compressor
chamber to provide return energy for upward movement of the inner
assembly 12, or it may serve as a scavenging chamber to provide air
for scavenging the combustion chamber 17. Chamber 23 may also serve
as a part of an energy absorbing device such as a compression
chamber in which the piston 21 serves as the movable member of such
a device to provide desired pressures or pumping actions within
chamber 23.
As described, the first movable assembly 12 includes a plurality of
portions or members, all of which move essentially as a unit during
the reciprocating translational movement of this assembly.
According to the present invention, at least two counterbalancing
assemblies are supported for reciprocating translational movement
along paths which are spaced outwardly from and around the inner
axis of the first movable assembly 12. In this embodiment, two such
counterbalancing assemblies are shown, as indicated generally at 24
and 26 respectively. Counterbalancing assembly 24 includes a
movable member 27 of an energy absorbing device, which is
illustrated as a compressor piston working in a compressor cylinder
28 provided with appropriate inlet and outlet ports 29 and 31. In
this embodiment the second counterbalancing assembly 26 also
comprises a movable energy absorbing device member and is shown as
a compressor piston 32 operating in compressor cylinder 33 with an
inlet 34 and outlet 36. Other forms of energy absorbing devices,
such as generators, pumps, or the like could also be advantageously
incorporated or substituted for these particular counterbalancing
members. Compressors 28 and 33 may be independent, or connected in
parallel as parts of a single stage compressor, or connected in
series for two stage compression.
According to a further feature of the invention, each outer
counterbalancing assembly is individually connected by a separate
synchronizing device to the first movable inner assembly 12. The
respective counterbalancing assemblies are symmetrically positioned
around the axis 18 in a manner which is determined by the relative
masses of the moving parts incorporated in or moving with the
various movable assemblies, and the paths of movement of the
counterbalancing assemblies and their relative angular spacings
around the inner axis 18 are selected in such a manner that the
common center of gravity of all moving masses of the machine
remains at a substantially fixed location in the engine for all
operating positions of the respective assemblies. In this
particular case, the paths of movement of the outer
counterbalancing assemblies are parallel to the inner axis 18, the
masses of the respective counterbalancing asemblies are equal to
each other, and their paths of movement are spaced at equal radial
distances from the inner axis 18 and at equal angular distances
around that axis, i.e., 180.degree. apart from each other as
measured around the axis 18.
The individual synchronizing mechanisms are constructed and
oriented to provide movement of each counterbalancing assembly in
directions having component vectors of such movement which move at
all times in the opposite direction to the direction of movement of
the inner assembly 12.
A preferred synchronizing mechanism is shown in FIG. 1, in which a
swinging or oscillating lever 37 is pivoted on a transverse axis at
38 fixed in housing 11 and extending in a direction perpendicular
to the common plane defined by the axis of movement of shaft 18 and
the axis of movement of piston 27. The pivotal axis 38 of lever 37
is thus located, as shown, at an intermediate position between the
paths of movement of the respective assemblies which are connected
by the lever.
Lever 37 has its outer lever end arm 39 pivotally connected at 41
to a connecting link 42, which is pivoted in turn at 43 to the
compressor piston 27. The opposite or inner end 44 of the lever 37
is pivoted at 46 to another connecting link 47, the lower end of
which is pivoted at 48 to the member 19 of the first movable
assembly 12. The axes of rotation of all of these pivots are
parallel to each other in this embodiment.
A similar synchronizing lever 49 is pivoted at 51 to connect the
other counterbalancing assembly 26 to the first assembly 12. Lever
49 has its outer end pivoted to a connecting link 53, which is
pivoted to compressor piston 32, while the inner end of the lever
49 is similarly pivoted to a connecting link 52 pivoted to member
19 of the first movable assembly 12.
To achieve the desired balance, and to minimize or eliminate
lateral or rotary unbalanced forces, the two synchronizing
mechanisms are constructed in similar fashion and are symmetrically
oriented, so that rotation or swinging movement of one element of
one synchronizing mechanism is symmetrically balanced by an
opposite rotation or swinging movement of a corresponding element
of the other synchronizing mechanism. It will be understood that if
more than two counterbalancing assemblies and individual
synchronizing devices are used according to the invention, they
would be arranged symmetrically with respect to axis 18 in such a
way that the desired condition of balance would be achieved. Also,
as illustrated in FIG. 1, the respective arms of levers 37 and 49
are equal, i.e., the counterbalancing assemblies move along their
paths over the same total distances as the inner or first movable
assembly 12. The lever arms could in some cases be unequal for
special design needs, e.g., to achieve the proper compatibility
between the power piston speed and the speed of a pump piston or
other working member. The desired balance is achieved in each case
by making sure that the absolute values of the product of the
masses moving in one direction times the lengths of their
respective strokes are equal at all times to the absolute values of
the masses moving in the opposite direction times the lengths of
their strokes.
Also, the paths of movement of the counterbalancing assemblies need
not be parallel to the path of movement of the first movable
assembly 12, provided that the angular orientation of the various
paths of movement of the two or more outer counterbalancing
assemblies according to the invention are so arranged, and the
relative masses moving along the different paths, the lengths of
their moving strokes, and the construction and orientation of the
individual synchronizing connections between such outer assemblies
and the inner or first movable assembly all cooperate and are
interrelated to maintain the common center of gravity of all moving
masses of the machine at a fixed location in the engine for all
operating positions of the engine assemblies. In the example of
FIG. 1, the center of gravity of the moving parts of the first
assembly 12 are symmetrically located with respect to the shaft
axis 18, so that the common center of gravity of all members of the
first movable assembly 12 remains at all times somewhere along the
shaft axis 18. The various masses of the counterbalancing
assemblies and synchronizing mechanism parts are similarly arranged
in this case to have their common center of gravity likewise
located along the shaft axis 18 in such a manner that they
substantially completely counterbalance the first movable assembly,
a condition which is defined when the common center of mass of all
the movable masses which form a part of or move with the various
assemblies and synchronizing connections of the machine remains at
a substantially fixed location within the machine, i.e., in this
case at a particular fixed point along the shaft axis 18.
FIGS. 2 to 4 are schematic top views of modified forms of linear
balanced free piston machines according to the invention in which
the relative number or arrangement of counterbalancing assemblies
may be varied within the principles already set forth. Thus FIG. 2
is a schematic top view of a modification in which a first movable
assembly, indicated generally at 71, is movable along an axis 72 in
a direction which would be perpendicular to the plane of the
drawing as viewed in FIG. 2. In this case, three counterbalancing
assemblies 73, 74 and 76 are spaced around the axis 72 at equal
angular distances from each other and at equal radial distances
from the axis 72 itself. Each of the counterbalancing assemblies
73, 74 and 76 is individually movable on its own axis parallel to
the axis 72 of the first movable assembly. Each of these
counterbalancing assemblies is also individually and separately
connected to the first movable assembly by appropriate
synchronizing linkages essentially similar to those shown in the
device of FIG. 1. The main levers 77, 78 and 79 of the respective
individual synchronizers are shown in FIG. 2 as oscillating on
fixed pivots 81, 82 and 83 suitably fixed within a main housing or
frame 84 of the machine. These main levers are connected by
appropriate intermediate links (not shown) to the respective
pivotal connections 86, 87 and 88 of the respective
counterbalancing assemblies, as well as to the parallel pivotal
axes 89, 91 and 92 on the first movable assembly. In this case, as
well as in the modifications of FIGS. 3, 4 and 5, the synchronizing
levers are pivoted at their mid-points so that the relative lengths
of reciprocating movement of the first movable assembly and of each
counterbalancing assembly are essentially the same.
In the particular configuration shown in the modification of FIG.
2, the total mass of each counterbalancing assembly 73, 74 and 76
is equal to one-third of the total mass of the first movable
assembly 71. It would be possible to provide synchronizing levers
which have arms of unequal length, and to space the counterblancing
assemblies angularly at other relatively symmetrical positions
around the first movable assembly, for example with two of the
three counterbalancing assemblies relatively close to each other
and with the third counterbalancing assembly located at the
opposite side of the first movable assembly at an angular location
half way between the first two counterbalancing assemblies, in
which case the masses of the respective counterbalancing assemblies
would be adjusted with respect to each other to achieve the
balancing condition previously described, i.e., in which the common
center of gravity of all moving masses of the apparatus remains at
a substantially fixed position within the machine at all operating
positions of the various assemblies.
FIG. 3 illustrates another modification in which a first movable
inner assembly 93 is individually connected to four outer movable
counterbalancing assemblies 94, 96, 97 and 98, by means of
individual synchronizing levers 99, 101, 102 and 103 respectively.
Here again, the various assemblies are individually movable with
respect to a main housing or frame 104, and the individual paths of
movement of the outer counterbalancing assemblies, as well as their
lengths of stroke and relative masses are so chosen as to position
the common center of gravity of all movable masses of the machine
at a fixed location in the machine for all operating positions. In
this case, the outer counterbalancing assemblies are spaced at
equal angles around the axis of the inner assembly 93, i.e.,
90.degree. apart, the main synchronizing levers have arms of equal
lengths, so that the relative lengths of travel of the respective
assemblies are equal, and to achieve the desired balancing
condition, each of the counterbalancing assemblies has a total mass
equal to one quarter of the mass of the inner movable assembly,
with each counterbalancing mass at the same radial distance
outwardly from the axis of movement of the inner movable assembly
93.
FIG. 4 shows a modified arranngement in which an inner movable
assembly 106 reciprocates on an axis 107 relative to a machine
frame or housing 108, and in which the movement of the first
assembly is balanced by four outer counterbalancing assemblies 109,
111, 112 and 113. These outer counterbalancing assemblies are
individually connected by separate synchronizing levers 114, 116,
117 and 118 respectively to the inner movable assembly 106 in such
a manner that the outer assemblies have the desired component
vectors of movement at all times in the opposite direction to the
movement of the inner assembly 106. In this case, the four outer
counterbalancing assemblies are symmetrically spaced with respect
to axis 107, but are not spaced at equal angles from each other
around that axis. Instead, the four outer counterbalancing
assemblies are located in symmetrical pairs, so that assemblies 109
and 111 are angularly close to each other and are symmetrically
balanced by diametrically opposite assemblies 112 and 113 which are
also relatively close to each other on the opposite side of axis
107. Here again the respective arms of the synchronizing levers
114, etc. are equal, so that the respective inner and outer
assemblies travel along parallel paths for equal distances in
opposite directions to achieve the desired condition of
balance.
FIG. 5 shows another modification of the invention in which the
inner assembly indicated generally at 119 is movable along an inner
axis 121 and includes two piston members 123 and 124 which are
rigidly connected as parts of the first movable assembly 119 and
are symmetrically positioned so that the center of mass of the
first assembly remains at some point along axis 121, while all
parts of the first assembly move together as a unit with respect to
the machine housing or frame 122.
In this case two counterbalancing assemblies 127 and 128 are
located 180.degree. apart around axis 121 and are supported for
individual movement along paths parallel to axis 121. Each
counterbalancing assembly is individually connected by a separate
synchronizing member, such as synchronizing levers 129 and 131
respectively, to the inner movable assembly 119, so that each of
the outer assemblies always moves in the opposite direction to the
direction of movement of the inner assembly. Here again the
synchronizing levers are supported for limited oscillation on fixed
rotary axes 132 and 133 respectively.
In each of the arrangements shown in FIGS. 2 to 5, there will be at
least one power piston on one of the movable assemblies and at
least one movable member of an energy absorbing device on another
of the movable assemblies. For example, each of the inner movable
assemblies of FIGS. 2 to 5 could involve a power piston for driving
each respective machine, while at least one, or even all of the
outer counterbalancing assemblies could include a movable
compressor piston or other movable energy absorbing device member.
Alternately, such an energy absorbing device member can be included
in at least one, but less than all of the outer counterbalancing
assemblies, and the remaining counterbalancing assembly or
assemblies may constitute merely a counterbalancing weight, or may
perform some other function which does not necessarily classify it
as an energy absorbing device.
FIG. 6 shows another modification of this latter type. In this
modification the first movable assembly 136 includes a power piston
138 reciprocating in a stationary power cylinder 139 fixed with
respect to the housing or frame portion 137. A connecting shaft 141
rigidly connects the power piston 138 to a second piston 142 which
moves as a unit with the other parts of assembly 136 and operates
within a second cylinder 143 to provide any desired operating
function. In this case cylinder 143 preferably serves to provide a
bounce chamber or scavenging chamber for cooperation with the power
cylinder 139.
All of the parts of this first assembly move together as a unit
along the longitudinal axis 144 of the machine which preferably
constitutes an axis of symmetry of this first assembly, so that the
center of mass of all movable elements of the first assembly is
located at all times somewhere along axis 144.
In the device of FIG. 6 two outer counterbalancing assemblies are
provided. The first counterbalancing assembly 146 includes an
energy absorbing device member which is illustrated as a compressor
piston 147 operating within a compressor cylinder 148. In this
example, the compressor piston 147 is connected by a shaft 149 to a
longitudinally movable cross-head 151 which slides within guide 152
to insure the desired path of movement of this outer
counterbalancing assembly. The assembly 146 is individually
connected to the first inner movable assembly 136 by a
synchronizing lever 153 pivoted at 154 for limited swinging
movement on a fixed axis on housing 137 at a point intermediately
spaced between the inner and outer movable assemblies. Lever 153 in
this case has two equal arms, one of which is pivoted at 156 to a
connecting link 157, the other end of which is pivoted at 158 to
crosshead 151. Similarly, the inner end of lever 153 is pivoted at
159 to a symmetrical connecting link 161, the other end of which is
pivoted at 162 to a portion 163 secured to the inner movable
assembly 136 and moving as a unit therewith. Thus the synchronizing
linkage just described insures movement of counterbalancing
assembly 146 at all times with a major component vector of such
movement (and in this case with the entire direction of such
movement) extending always in the opposite direction to the
movement of the first assembly 136.
The second counterbalancing assembly 164 in the modification of
FIG. 6 is illustrated as one which performs only a counterbalancing
function and which includes no movable energy absorbing device
member. In this case the assembly has a shaft portion 166 fixed to
a crosshead 167 vertically movable in guide 168 on portion 169 of
the main housing 137. At the upper end of shaft 166 a further
crosshead member 171 moves within guide member 172, with all parts
of the counterbalancing assembly 164 moving as a unit along a path
parallel to axis 144 and spaced from that axis a radial distance
equal to the spacing of counterbalancing assembly 146. Here the
elements 166, 167 and 171 of the counterbalancing assembly move as
a unit, and are individually connected by the separate
synchronizing lever 173 and the intermediate links 174 and 176 to
the portion 163 of the inner assembly to obtain the desired
balancing movement of assembly 164 at all times in the opposite
direction to the movement of the inner assembly 136.
In this and other cases, the outer arm portions of the
synchronizing levers, such as 153 and 173, can not only differ in
length from the inner portions, but may even differ in length from
each other, provided the relative outer lever arm lengths and the
masses of the outer assemblies connected to them are selected to
maintain the desired condition of balance, with the common center
of gravity of all movable masses of the complete machine remaining
at a substantially fixed location for all operating positions of
the parts.
FIG. 7 schematically illustrates another modification in which the
inner movable assembly 181 constitutes essentially a counterweight
which is movable similarly to a crosshead within guide 182 of the
main frame or housing of the apparatus. The outer counterbalancing
assemblies 183 and 184 in this configuration each include piston
members. For example assembly 183 includes a power piston 186 and
the compressor piston 187, while assembly 184 similarly includes a
power piston 188 and a compressor piston 189. In each of these
outer assemblies, there is essentially a complete free piston
engine portion, all parts of which move together as a unit in one
direction. The individually movable outer assemblies are connected
by separate synchronizing levers 191 and 192, and the intermediate
linkage connections previously described, to the inner movable
assembly 181, which then moves in the opposite direction as a
counterbalancing weight to provide the specified condition of
balance for the entire machine. Alternately, the inner movable
assembly 181 could include a pump piston, compressor piston or
other working member.
Another modification of the invention is shown in FIGS. 8, 9 and
10. In FIG. 8, the inner movable assembly 221 includes upper and
lower power pistons 222 and 223 which move along a common axis
within coaxial upper and lower power cylinders 224 and 226. A
connecting shaft 227 rigidly interconnects the power pistons for
movement of this inner assembly as a unit.
An outer housing portion 228 is provided at one side of the main
housing of the inner power unit, and this outer housing encloses
one of the outer movable assemblies 229, which consists of upper
and lower compressor pistons 231 and 232. Piston 231 reciprocates
within a compressor cylinder 233 and the compressor includes inlet
and outlet valves 234 and 236. The lower compressor piston 232
operates within its own lower compressor cylinder portion 237,
which also has appropriate inlet and outlet valves 238 and 239. A
rigid connecting shaft 240 connects the upper and lower power
pistons for movement of all parts of this outer assembly as a unit.
The main housing portion 241 has a projecting flange area 242 which
is adapted to engage one surface of an intermediate member 243,
which is secured between portion 242 and a cooperating flange
portion 244 on the outer housing 228 to provide appropriate lines
of separation between the inner and outer housings and member 243.
Thus the respecting housing portions 241 and 228 effectively
separate the inner and outer movable assemblies from each other,
but provide a transverse passageway 246 extending transversely
between the two housings. The synchronizing mechanism for
separately interconnecting the outer assembly 229 with the inner
assembly 221 includes a transversely extending lever 247 which
projects through passageway 246 and which is provided with a
pivotal support in at least one of the housing members 242, 243 and
244. In this case, as shown in detail in FIG. 9, lever 247 includes
an inner end 248 with a bearing 249 for pivotal connection with a
link 251. The other end of link 251 is connected at 252 to a cross
member 253 rigidly secured to shaft 227.
Lever 247 has a main lever portion 254 extending to a pivotal
bearing 256 at its other end for a pivotal connection to a link
257, the other end of which is pivoted at 258 to the outer movable
assembly 229.
In this case the pivotal support for lever 247 is provided by two
angularly projecting arms 261 and 262 which terminate in shaft
portions 263 and 264 pivotally supported in bearings 266 and 267.
These bearing portions are secured between the respective inner and
intermediate members 242 and 243 so that the pivotal axis is
generally along the plane of separation 245 between these two
members.
The remaining removable outer assembly shown in FIG. 8 is the
counterbalancing assembly 268 which is illustrated as having upper
and lower counterweight members 269 and 271 movable vertically
within guides 272 and 273 along an outer path essentially parallel
to the path of inner shaft 227. A connecting shaft 274 rigidly
interconnects counter-weights 269 and 271 for movement of the parts
of this counterbalancing assembly as a unit.
The desired counterbalancing movement is provided by a separate
synchronizing lever 275, pivoted at 276 in one of the housing
portions for pivotal movement on an axis essentially perpendicular
to the common plane defined by shafts 227 and 274. Thus, similarly
to lever 247, the outer end of lever 275 is secured through a
connecting link 277 to the outer movable assembly 268, while the
inner end of lever 275 is similarly secured by a connecting link
278 to the rigid portion 253 of the inner movable assembly. Thus
all movements of the inner assembly 221 are counterbalanced at all
times by opposite movements of the respective outer assemblies 229
and 268. In this case only one of the outer assemblies involves any
working or energy-absorbing device, while the other outer
counterbalancing assembly performs merely a part of the
counterbalancing function without any corresponding work function.
The embodiment of FIG. 8, however, has the distinct advantage that
the free piston machine is provided with positive power strokes in
both directions of operation, and these power strokes occur in this
particular example along the common axis of movement of the two
power pistons on the inner movable assembly. This device therefore
does not depend on the return energy of a bounce compressor for its
return strokes, and there is no need to adjust any such bounce
return energy during starting, for example during the transition
from an initial starting stroke to normal operation.
Moreover, work is performed by one energy-absorbing device member
in one direction of movement and by another such member in the
opposite direction of movement. Instead of two separate oppositely
acting working members, a single member which is double-acting can
be provided, such as a compressor piston with two oppositely acting
faces. Also, where maximum speed of operation is desired, the FIG.
8 arrangement can be modified by moving piston 232 and its cylinder
from assembly 229 to replace weight member 271 of assembly 268 and
eliminating weight 269. In this case the masses of power pistons
222 and 223 can be made lighter, thus reducing the total weight of
the moving parts and increasing the speed and, by this, the power
output of the engine. Also, as seen by comparison with FIG. 6, only
a small increase in size and cost is necessary to provide the
increased power output of such a FIG. 8 type of machine, which is
more than double the output of a FIG. 6 machine with the same power
stroke and bore.
In all these cases, the masses are so balanced that the common
center of gravity of all movable masses of the entire unit remains
at a substantially fixed location in the machine for all operating
positions of the respective assemblies. Furthermore, in this FIG. 8
type of machine, all of the power functions are concentrated in the
inner or main housing portion as part of the inner or first movable
assembly.
According to a further feature of the invention, it is desirable in
many cases to provide a positive seal or separation between the
operating mechanisms of the inner assembly and one or more of the
outer assemblies. The present invention provides an improved
arrangement for such a seal in combination with the particular
orientation and relative arrangement of the parts of this type of
free piston machine. Such a sealing arrangement is shown at the
left portion of FIG. 8 between the inner assembly 221 and the outer
assembly 229, and further details of an appropriate sealing member
and arrangement are further shown in FIGS. 9 and 10. Thus a
flexible sealing member or diaphragm 281 is provided which has an
inner edge secured in sealing engagement to lever member 247, and
specifically to a suitable seat 282 located on the central portion
254 of lever 247 at a point essentially along the axis of pivotal
movement provided by bearing shafts 263 and 264. The outer edge of
flexible diaphragm member 281 is secured at 284 to any appropriate
housing portion, and is shown herein between the housing portion
243 and an outer retaining member 286 secured to the housing
portion 243 by screws 287.
It will be understood that the specific design of a flexible
sealing member such as 281 may be varied to fit the particular
application involved. Also, the manner of securing the inner and
outer edges of such a sealing member can be modified by those
skilled in the art. In any case, however, this invention positions
the sealing engagement between such a sealing member 281 and the
movable rocker arm or lever of the synchronizing mechanism in a
plane which either intersects or is close to the pivotal axis of
the lever member. Thus both the physical displacement of the
sealing member and the degree of flexing imparted to it by movement
of the lever can be reduced to a minimum and the life of such a
sealing member correspondingly increased. In effect, the sealing
member is secured to the lever arm at a point where the sealing
surface displacements and velocities are much lower than on any of
the conventional shaft or similar surfaces in prior art devices,
where such sealing surfaces must be running at the same speed or
moving along the same axial distances as the pistons of a prior art
engine configuration. The particular lever arrangement shown in
FIGS. 9 and 10, with the Y-shaped portions 261 and 262 extending
outwardly to bearing shafts 263 and 264 makes it possible in this
particular case to anchor the inner edge of the sealing member 281
at exactly the location of the pivotal axis of the lever, by means
of the retaining clamp 283 and associated bolts. Thus a novel and
advantageous sealing arrangement is provided in the particular
combination of the present invention in which an inner movable
assembly and an outer movable assembly move in essentially parallel
paths and in opposite directions, and in which the motion is
transmitted between these assemblies in the desired manner by means
of a rocking lever extending generally transversely from the inner
assembly to the outer assembly and pivoted for rocking movement on
a pivotal axis which is essentially perpendicular to the common
plane defined by the paths of movement of the inner and outer
assemblies. In this way, a sealing member associated with such a
rocking lever close to its pivotal axis is subjected to minimum
flexing and displacement, in terms of both distance and velocity
and allows hermetic sealing.
As shown in the devices of FIGS. 7 and 8, a plurality of power
pistons are located on one or more, but less than all, of the inner
and outer movable assemblies. In the example of FIG. 7, one power
piston portion is carried by each of the outer movable assemblies,
and the inner movable assembly has no power piston. The two power
pistons are arranged to provide simultaneous power strokes in only
one direction of movement of the respective assemblies.
In the FIG. 8 embodiment, the free piston machine is provided with
plural power piston portions which are arranged for alternating and
successive power strokes and resulting driving movement of the
assemblies successively in opposite directions. Thus work may be
performed by one or more energy absorbing device members in one
direction of movement and by one or more other such members in the
opposite direction of movement. This type of arrangement provides a
machine in which the working and power functions may be
substantially equally balanced. The machine also has its masses
balanced so that the common center of gravity of all movable masses
of the entire unit remains at a substantially fixed location in the
machine for all operating positions of the respective
assemblies.
The balanced linear free piston machines described in the foregoing
specification are believed to offer significant advantages in both
flexibility of design and construction, and in minimizing
production costs for a line of such machines in which standardized
individual elements such as power pistons, power cylinders,
synchronizing linkages, compressor cylinders and pistons and the
like can be assembled in various configurations to meet the
requirements of different applications.
Such machines have a design flexibility which can be adapted to a
wide range of different applications and functions, including not
only pumps, generators and compressors broadly, but also including
operation with different products or fluids, such as air,
refrigeration gases or other gases. The preferred combination of a
specific synchronizing lever arrangement and flexible sealing
member as arranged in this novel class of free piston machines also
provides for hermetic sealing between the respective movable
assemblies and their housings to meet the requirements for relative
isolation of any materials or any parts of the machine, either with
respect to each other or the surrounding environment. The
specifications set forth some of the ways in which the invention
may be practiced, including the best mode presently contemplated
for carrying out the invention. Other modifications and variations
may be apparent to those skilled in the art, in the light of the
foregoing description and the following claims.
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