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Description  |
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BACKGROUND OF THE INVENTION
This invention relates generally to pumps and compressors, and more
particularly, to electrically powered pumps and compressors of the
reciprocating type.
Present day pumps and compressors are generally comprised of two basic
types. These two basic types may be divided into rotary and reciprocating
types. The rotary types comprise strictly rotary compressors such as gear
pumps and impeller pumps, and the more common types wherein a crank shaft
is employed to convert the rotary motion into reciprocating motion. The
reciprocating types generally employ a linear motor having a two coil
stator and an armature, and a pair of opposed pistons attached to the
armature. The armature may be fabricated from a magnetic material, or may
be a wire wound type. When a wire wound armature is used, the armature is
engergized with alternating current, and when a magnetic armature is used,
the stator coils ar alternately energized with direct current by means of
a switch mechanically coupled to the armature.
While a large variety of pumps and compressors may be provided utilizing
the conventional rotary and reciprocating techniques, pumps employing
rotary techniques tend to have a large number of moving parts and hence,
tend to be relatively costly and require periodic maintenance. Prior art
pumps and compressors of the reciprocating type, while being less complex
than rotary type pumps, tend to be inefficient in operation and limited in
power.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a new and
improved reciprocating compressor.
A further object of the present invention is to provide an improved
reciprocating compressor that is more efficient and more powerful than
reciprocating compressors of the prior art.
Yet another object of the present invention is to provide a self-contained
compressor useable for refrigeration purposes.
Another object of the present invention is to provide a compact, low cost
reciprocating structure useable as a compressor or a pump.
In accordance with a preferred embodiment of the invention, an elongated
reciprocating armature having a pair of conductive induction rings at
opposite ends thereof is fabricated from laminations of ferromagnetic
material. A pair of opposed pistons or diaphragms are attached to the ends
of the elongated armature by a rod made from nonmagnetic material. A pair
of stator coils are disposed in coaxial relationship about the armature,
and a laminated magnetic structure is employed to complete a magnetic path
between the stator coils and the armature. A two piece housing, split
along a longitudinal axis, is provided for supporting the stator coils and
the magnetic structure. The armature is supported in coaxial relationship
with the stator coils by the pistons or diaphragms which are supported at
opposite ends of the housing.
The stator coils are alternately energized on alternate cycles of an
alternating current wave applied thereto. The energizing current is
applied to the stator coils by means of a pair of oppositely poled half
wave rectifier diodes, each rectifier diode being connected to a source of
alternating current voltage and to one of the stator coils. Alternatively,
a switching circuit such as a flip-flop may be connected to a source of
direct current voltage and to each of the stator coils to alternately
provide energizing current thereto.
When the half wave rectifier diodes are used to energize the stator coils,
each stator coil is provided with two windings, one winding being
connected directly in series with one of the rectifier diodes and the
other winding being connected in series with the same rectifier diode and
a phase shifting capacitor. The phase shifting capacitor shifts the phase
of the current flowing through one of the windings to increase the duty
cycle of the energizing current flowing through each stator coil to
increase the mechanical output power available from the reciprocating
armature. The conductive induction rings disposed about the ends of the
armature further increase the mechanical output power by generating a
magnetic field that reacts with the field produced by the stator coils to
increase the magnetic force available to move the armature.
DESCRIPTION OF THE DRAWING
The invention, and its method of operation, together with further objects
and advantages thereof, will best be understood by reference to the
following specification taken in connection with the accompanying drawing
in which:
FIG. 1 is a side view, partially in cross section, showing a self-contained
opposed piston reciprocating compressor according to the invention;
FIG. 2 is a side view, partially in cross section, of a self-contained
reciprocating opposed diaphragm pump according to the invention;
FIG. 3 is an exploded perspective view of a valve assembly for use with the
compressor of FIG. 1;
FIG. 4 is a perspective view showing the laminated magnetic structure for
use with the compressor or pump of FIGS. 1 and 2;
FIG. 5 is a perspective view of the stator windings for use with the
compressor or pump of FIGS. 1 and 2;
FIG. 6 is a perspective view of the laminated armature for use with the
compressor and pump of FIGS. 1 and 2 showing a pair of conductive
induction rings affixed to the ends of the armature;
FIG. 7 is a simplified diagram of the magnetic structure and armature of
the reciprocating motor used in the compressor and pump of FIGS. 1 and 2;
FIG. 8 is a schematic circuit diagram of the energizing circuit for the
stator coils of FIG. 5 showing a two winding embodiment of the stator
coils and a pair of oppositely poled half wave rectifier diodes for
energizing the stator windings; and
FIG. 9 is a schematic circuit diagram showing an alternative method for
energizing the stator coils from a source of direct current potential and
shows a single winding embodiment of the stator coils of FIG. 5.
DETAILED DESCRIPTION
A. General
Referring now to the drawing, with particular reference to FIG. 1, there is
shown a compressor unit generally designated as 10 constructed in
accordance with the principles of the present invention. The compressor 10
includes a two piece housing having a base portion 12 and an upper portion
14. A channel 13 is provided in the base portion 12 for supporting a lower
member 16 of a laminated magnetic structure 17 (FIG. 4). An upper member
18 of the magnetic structure 17 is supported in a similar channel 15 in
the upper portion 14 of the housing. Two stator coils 20 and 22 are
supported by the magnetic structure members 16 and 18. A pair of cylinder
liners 24 and 26 are supported by the housing portions 12 and 14 and serve
to support a pair of opposed pistons 28 and 30. The opposed pistons 28 and
30 are connected together by a nonmagnetic shaft 32. The pistons 28 and 30
may be attached to the shaft 32 by means of threads 34 and 36 (FIG. 6) or
any other suitable mounting method. If threads are employed to secure the
pistons 28 and 30 to the shaft 32, a pair of flats 38 and 40 (FIG. 1) may
be relieved in the skirts of the pistons 28 and 30 to provide gripping
surfaces for tightening the pistons onto the shaft 32.
A laminated armature 42 is attached to the shaft 32. The armature 42 is
supported in coaxial relationship with the stator coils 20 and 22 by the
pistons 28 and 30, and requires no bearings or other supporting structure.
Two armature travel limiting washers 44 and 46 are supported by the two
housing portions 12 and 14, and serve to limit the maximum travel of the
armature 42. A pair of shock absorbing springs 48 and 50 are attached to
the ends of the armature 42 and serve to cushion the impact between the
armature 42 and the limiting washers 44 and 46. A pair of conductive
induction rings 52 and 54 (FIG. 6), fabricated from a conductive
nonmagnetic material such as copper, are affixed to opposite ends of the
armature 42. The function of the induction rings will be described in a
subsequent portion of the specification.
Two cylinder heads 56 and 58 are disposed at opposite ends of the
compressor unit 10. A valve mechanism 60 is interposed between the
cylinder head 58 and the housing portions 12 and 14. A similar valve
mechanism 62 is interposed between the head 56 and the opposite ends of
the housing portions 12 and 14. Each of the heads 56 and 58 is affixed to
the housing portions 12 and 14 by means of four bolts 64. Inlet 66 and 68
and outlets 70 and 72 are attached to the heads 56 and 58, respectively.
A more detailed drawing of the valve mechanism 60 is shown in FIG. 3. The
valve mechanism 60 comprises a pair of reed valves 74 and 76. A spacer
plate 78 is interposed between the reed valves 74 and 76. The reed valves
74 and 76 and the spacer plate 78 each have four holes 80 for receiving
the four bolts 64. The spacer 78 also has a pair of inlet holes 82 and a
pair of outlet holes 84. A reed 86 is formed in the valve 74 and a reed 88
is formed in the valve 76. A pair of apertures 90 are formed in the valve
74 in alignment with the outlet holes 84. Similarly, a pair of apertures
92 are formed in the valve 76 in alignment with the inlet holes 82.
In operation, as the piston 30 (FIG. 1) is moved away from the cylinder
head 58, the vacuum created in the cylinder deflects the reed 86 away from
the inlet holes 82 to allow fluid in the form of liquid or a gas from the
inlet 68 to enter the cylinder through the apertures 82 and 92 in the
valve mechanism 60. Simultaneously, the reed 88 is drawn against the
spacer 78 and covers the holes 84 to prevent fluid from leaking into the
cylinder from the outlet 72. As the piston is moved toward the cylinder
head during the following stroke, the pressure build up in the cylinder
causes the reed 86 to be pressed against the plate 78 to seal the holes
82, while simultaneously the reed 88 is deflected away from the spacer 78
to allow the fluid to pass through the holes 90 and 84 and into the outlet
72. Because of the high pressure generated during the compression stroke
of the piston 30, a travel limiting member 94 is provided adjacent the
reed 88 to prevent excessive travel and possible damage to the reed 88.
Operation of the valve mechanism 62 is similar to that of the mechanism 60
and need not be discussed in detail.
The reciprocating compressor unit 10 has been designed for ease of
assembly. In order to assemble the unit, the lower magnetic structure
member 16 is first placed in the channel 13 of the base portion 12 of the
housing. The spring 48 and 50, the limiting washers 44 and 46, and the
stator coils 20 and 22 are then placed over the armature 42 and the shaft
32. The pistons 28 and 30 are affixed to the shaft 32 and the cylinder
liners 24 and 26 are placed over the pistons 28 and 30, respectively. The
assembly thus prepared is then placed into the base portion 12 of the
housing, and the coils, cylinder liners and limiting washers are aligned
with recesses in the base portion 12 provided to receive these components.
The upper magnetic structure member 18 is then placed in the upper portion
14 of the housing and the two housing portions 12 and 14 are secured by
means of four bolts 96 which pass through the upper portion of the housing
15 and into threaded holes (not shown) in the base portion 12. Finally,
the valve assemblies 60 and 62, and the heads 56 and 58 are secured to the
two halves of the housing by the bolts 64.
The assembled unit is completely self-contained and has no surfaces moving
with respect to each other except for the pistons 28 and 30 moving within
the cylinder liners 24 and 26. To reduce friction and provide an adequate
seal between the pistons and the cylinder liners, two pairs of piston
rings 98 and 100 are carried by the pistons 28 and 30, respectively. The
piston rings 98 and 100 may be made of a self-lubricating material such as
carbon or an oil impregnated metallic substance, to eliminate the need for
any lubrication during the life of the compressor unit.
The compressor unit 10 described in the foregoing utilizes opposed pistons
to pump high pressure fluids such as Freon and other substances used in
air conditioning applications. The same priniciples may be employed to
pump fluids at low pressure, and when low pressure fluids are being
pumped, the pistons 28 and 30 of FIG. 1 may be replaced by a pair of
diaphragms 102 and 104 (FIG. 2). FIG. 2 shows a typical low pressure pump
10a employing the same driving mechanism used to drive the compressor unit
10 of FIG. 1. Accordingly, for purposes of clarity, whenever the same
components are used in the apparatus of FIG. 1 and FIG. 2, they will be
designated by the same reference numeral, and similar components serving
an analagous function will be designated by the same reference numeral
followed by the suffix a. Thus, the housing portions 12a and 14a (FIG. 2)
are analagous to the housing portions 12 and 14 (FIG. 1), but have been
modified to accept a pair of diaphragms 102 and 104 rather than the
cylinder liners 24 and 26. The heads 56a and 58a are analagous to the
heads 56 and 58, respectively, the main difference being the use of low
pressure valves 106, 108, 110 and 112 in place of the reed valve
mechanisms 60 and 62.
The intake valves 106 and 108 are pivotally mounted over a pair of inlets
66a and 68a in the heads 56a and 58a, respectively. Each of the intake
valves 106 and 108 is pivoted such that it is opened by the decrease in
pressure occurring when the respective one of the diaphragms 102 and 104
is moved away from the head, and closed by the increase in pressure
occuring when the diaphragm is moved toward the head. A pair of outlet
valves 110 and 112 is mounted in the heads 56a and 58a and hinged in the
opposite direction in order to open when the pressure in the diaphragm
chamber increases and close when the pressure in the diaphragm chamber
decreases. Although the valves 106, 108, 110 and 112 are self-actuating,
due to the high speed of operation of the pump 10a, in a preferred
embodiment, a set of springs 114 is employed to bias the valves in a
closed position to assure that the valves are properly closed after each
stroke.
B. Reciprocating Motor
FIG. 4 shows the magnetic structure members 16 and 18 in greater detail.
The members 16 and 18 are fabricated from E-shaped laminations of magnetic
material. The E-shaped laminations are insulated from each other to reduce
eddy currents and the three pole pieces extending from the E have curved
surfaces to conform to the curvature of the armature 42. The curved
surfaces are formed by varying the lengths of the laminations forming the
pole pieces.
The stator coils 20 and 22 (FIG. 5) are wound around a pair of bobbins
having radially extending flanges. The magnetic structure 17 is provided
with a series of notches adjacent to the pole pieces to receive the
flanges of the bobbins to secure the stator coils 20 and 22 in place. Each
of the stator coils 20 and 22 may contain a single winding or a plurality
of windings. The considerations for determining whether one or a plurality
of windings will be used will be discussed in a subsequent portion of the
specification.
FIG. 6 shows the armature 42 in greater detail. The armature is fabricated
from laminations of ferromagnetic material which may be held together by a
set of rivets 120. The conductive induction rings 52 and 54 are affixed to
the ends of the armature 42 by means of a press fit. Alternatively, rivets
or other methods may be employed to affix the induction rings to the
armature. Two collars 122 and 124 extend from opposite ends of the
armature 42 and serve to retain the springs 48 and 50 (FIG. 4) in place.
The collars 122 and 124 may be separately fabricated from tube stock as
shown in FIGS. 6 and 7, or may be formed by extensions of the laminations
forming the armature 42 as shown in FIGS. 1 and 2. The threaded portions
34 and 36 of the shaft 32 are used to secure the pistons or diaphragms in
place, however, other securing methods may be used.
Referring now to FIG. 8 in conjunction with FIG. 7, two half wave rectifier
diodes 126 and 128 are connected in series with the stator coils 20 and
22, respectively, and a source of alternating current potential. In a
preferred embodiment, solid state rectifier diodes such as silicon diodes
are used, however, any suitable diodes having a sufficient current
carrying capacity to energize the stator coils 20 and and 22 may be
employed.
In the embodiment shown in FIG. 8, each of the stator coils 20 and 22
includes two windings 20a and 20b, and 22a and 22b, respectively. A phase
shifting capacitor 130 is connected in series with the windings 20b and
22b for shifting the phase of the current through the windings 20b and 22b
with respect to the respective windings 20a and 22a. The aforementioned
phase shift serves to increase the duty cycle of the current flowing
through the stator coils 20 and 22 to thereby increase the power output of
the reciprocating armature. Generally, the windings 20b and 22b will have
fewer turns than the windings 20a and 22a, but the number of turns in each
winding may be selected in accordance with the increase in power desired.
Operation is as follows. When a positive potential is applied to the
junction of the diodes 126 and 128, the diode 128 is rendered conductive
to cause current to flow through the stator coil 22. Due to the inductance
of the winding 22a, the current through the winding 22a lags the voltage
applied thereto. The capacitor 130 is connected in series with the winding
22b, and the capacitive reactance of the capacitor 130 tends to cancel the
effects of the inductive reactance of the winding 22b. As a result,
current begins to flow through the winding 22b sooner than through the
winding 22a. Depending on the value of the capacitor 130, the current
through the winding 22b can be made to lead or lag the alternating current
voltage applied to the input terminals.
As the instantaneous voltage across the input terminals continues to build
up during the first half cycle of the alternating current wave, the
current through the stator coil 22 will also continue to build up, the
build up of the current through the winding 22b following the voltage of
the alternating current source more closely than the current through the
winding 22a. As the instantaneous voltage of the alternating current
source begins to decrease, the current through the winding 22b will begin
to decrease. However, due to the inductive reactance of the winding 22a,
the current through the winding 22a will continue to flow after the
current flow through the winding 22b has ceased. As a result, a magnetic
field is maintained within the coil 22 for a longer period of time than
would be achieved with a single winding coil, the winding 22b providing
the magnetic field at the beginning of the half cycle of the alternating
current wave, and the winding 22a providing the magnetic field near the
end of the half cycle.
After the first half of the alternating current cycle has been completed,
the junction of the diodes 126 and 128 is rendered negative, thereby
rendering the diode 128 nonconductive and the diode 126 conductive. When
the diode 126 is rendered conductive on negative half cycles of the
alternating current wave, the coil 20 is energized in a manner similar to
the energization of the coil 22. When the coil 20 is energized, current
flows initially through the winding 20b connected in series with the
capacitor 130, and subsequently through the winding 20a, in a manner
similar to the operation of the windings 22a and 22b. On positive half
cycles the coil 22 is again energized, and the diodes 126 and 128 serve to
alternately energize the coils 20 and 22 to cause the armature 42 to
reciprocate at the alternating current rate.
In a preferred embodiment, when a source of alternating current is used to
energize the stator coils 20 and 22, the coils are wound in opposite
directions to maintain the direction of the magnetic field through the
magnetic structure in the same direction. The maintenance of a
unidirectional magnetic field reduces the hysteresis losses in the
magnetic path and increases the output power of the motor for the reasons
explained below. Referring to FIG. 7, the three pole pieces extending from
the magnetic structure member 18 will be designated as 18a, 18b and 18c,
and the three pole pieces extending from the magnetic pole member 16 will
be designated as 16a, 16b and 16c. The coils 20 and 22 are wound such that
the pole pieces 16a and 18a become south magnetic poles, and the pole
pieces 16b and 18b become north magnetic poles when the coil 20 is
energized. Similarly, the coil 22 is wound such that the pole pieces 16b
and 18b become south magnetic poles and the pole pieces 16c and 18c become
north magnetic poles when the coil 22 is enenrgized. As a result, the
magnetic flux flowing through the magnetic structure 17 will always flow
in the same direction.
As the coils are alternately energized, the armature 42 will be moved
toward the energized coil as the magnetic field generated applies force to
the armature in an effort to close the magnetic path around the energized
coil. For example, when the coil 20 is energized, the armature 42 will be
moved toward the pole pieces 16a and 18a in an effort to complete the
magnetic path between the pole pieces 16a and 16b, and 18a and 18b.
Conversely, as the coil 22 is energized, the armature 42 will be moved
toward the pole pieces 16c and 18c. Accordingly, as the coils 20 and 22
are alternately energized, the armature 42 will reciprocate in synchronism
with the energization of the coils.
In addition to the magnetic effects described above, the changing magnetic
field flowing through the armature 42 causes current to be induced in the
conductive induction rings 52 and 54. The current thus induced generates
magnetic poles at opposing ends of the armature 42 in a direction opposite
to the direction of the magnetic field produced by the coils 20 and 22.
The magnetic poles thus generated at the opposing ends of the armature are
alternately attracted to the poles 16a and 18a and 16c and 18c to further
increase the output power of the reciprocating motor.
For example, when the armature is positioned as shown in FIG. 7 and the
coil 22 is energized, the induced current flowing through the conductive
induction ring 54 produces a south magnetic pole at the end of the
armature positioned between the pole pieces 16b, 18b and 16c, 18c. The
south pole thus generated is repelled away from the south pole generated
at the pole pieces 16b and 18b and attracted toward the north pole at the
pole pieces 16c and 18c. This action reinforces the magnetic forces
attracting the armature 42 toward the pole pieces 16c and 18c. Similarly,
when the coil 20 is energized, the current induced in the conductive
induction ring 52 aids the forces attracting the armature 42 toward the
pole pieces 16a and 18a.
The embodiments discussed in the foregoing have all utilized a source of
alternating current potential to energize the reciprocating motor. The
system may also be energized from a source of direct current potential if
an appropriate switching arrangement for alternately energizing the coils
20 and 22 is provided. One such system is shown in FIG. 9. In the
embodiment of FIG. 9, the coils 20 and 22 are energized by a battery 132
or other source of direct current potential. A flip-flop 134 is used to
alternately connect one of the coils 20 and 22 to the battery 132 in
response to a signal from an oscillator circuit 136. The flip-flop 134 may
comprise a standard solid state flip-flop or a switching relay or the
like. Any oscillator or astable multivibrator suitable for driving the
flip-flop 134 may be used in the oscillator circuit 136. The frequency at
which the flip-flop 134 is switched may be set at any desired frequency,
depending on the desired frequency of reciprocation of the reciprocating
motor. Because the pulse from the flip-flop 134 may be tailored to suit
the particular reciprocating motor used, single winding coils may be used
for the coils 20 and 22 if desired. However, due to the unidirectional
voltage provided by the flip-flop, the coils 20 and 22 should be wound in
the same direction if a unidirectional flux is desired in the magnetic
structure.
Although particular embodiments of the invention have been illustrated, it
should be noted that the illustrated embodiments are not intended to limit
the scope of the invention, and that other embodiments and modifications
occurring to those skilled in the art still fall within the scope and
spirit of the invention as defined in the appended claims.
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