Title:
Vapor compression system including a swiveling compressor
Kind Code:
A1


Abstract:
A refrigeration system includes a fluid circuit circulating a refrigerant in a closed loop. The fluid circuit has operably disposed therein, in serial order, a compressor, a first heat exchanger, an expansion device and a second heat exchanger. The compressor is pivotable about an axis. The compressor has a first part and a second part slidably coupled to the first part. A linkage includes a cyclically movable element. A linking element is attached to the second part of the compressor and is pivotably coupled to the cyclically movable element such that the linking element follows movement of the cyclically movable element to thereby slide the second part of the compressor relative to the first part of the compressor and pivot the compressor about the axis.



Inventors:
Manole, Dan M. (Tecumseh, MI, US)
Application Number:
11/250806
Publication Date:
04/20/2006
Filing Date:
10/13/2005
Primary Class:
Other Classes:
417/244
International Classes:
F04B3/00; F04B5/00
View Patent Images:



Primary Examiner:
BAYOU, AMENE SETEGNE
Attorney, Agent or Firm:
FAEGRE DRINKER BIDDLE & REATH LLP (FORT WAYNE, IN, US)
Claims:
What is claimed is:

1. A refrigeration system comprising: a fluid circuit circulating a refrigerant in a closed loop, the fluid circuit having operably disposed therein, in serial order, a compressor, a first heat exchanger, an expansion device and a second heat exchanger, the compressor being pivotable about an axis, the compressor having a first part and a second part slidably coupled to the first part; and a linkage including: a cyclically movable element; and a linking element attached to the second part of the compressor and pivotably coupled to the cyclically movable element such that the linking element follows movement of the cyclically movable element to thereby slide the second part of the compressor relative to the first part of the compressor and pivot the compressor about the axis.

2. The system of claim 1 wherein the axis about which the compressor is pivotable comprises a first axis, the linking element being pivotable about a second axis relative to the cyclically movable element, the second axis being substantially parallel to the first axis.

3. The system of claim 2 wherein the movement of the cyclically movable element is in a direction substantially perpendicular to the second axis.

4. The system of claim 2 wherein the compressor comprises a first compressor, the fluid circuit having a second compressor, the linking element comprising a first linking element, the linkage including a second linking element attached to the second compressor and pivotably coupled to the cyclically movable element such that the second linking element follows movement of the cyclically movable element to thereby slide a second part of the second compressor relative to a first part of the second compressor and pivot the second compressor about a third axis.

5. The system of claim 4 wherein the third axis is substantially parallel to each of the first axis and the second axis.

6. The system of claim 1 wherein the first part of the compressor comprises a cylinder, and the second part of the compressor comprises a piston.

7. The system of claim 1 wherein the linking element comprises a connecting arm, and the cyclically movable element comprises a rod.

8. The system of claim 1 further comprising a motor drivingly coupled to the cyclically movable element.

9. The system of claim 8 wherein the motor comprises a linear motor.

10. The system of claim 8 wherein the motor comprises a rotary motor.

11. The system of claim 1 wherein the linking element is fixedly attached to the second part of the compressor.

12. A vapor compression apparatus comprising: a compressor having a first part and a second part slidably coupled to the first part, the compressor being pivotable about an axis; a linkage including: a cyclically movable element; and a linking element attached to the second part of the compressor and pivotably coupled to the cyclically movable element such that the linking element follows movement of the cyclically movable element to thereby slide the second part of the compressor relative to the first part of the compressor and pivot the compressor about the axis; and a motor drivingly coupled to the cyclically movable element.

13. The apparatus of claim 12 wherein the axis about which the compressor is pivotable comprises a first axis, the linking element being pivotable about a second axis relative to the cyclically movable element, the second axis being substantially parallel to the first axis.

14. The apparatus of claim 13 wherein the movement of the cyclically movable element is in a direction substantially perpendicular to the second axis.

15. The apparatus of claim 14 wherein the compressor comprises a first compressor, the fluid circuit having a second compressor, the linking element comprising a first linking element, the linkage including a second linking element attached to the second compressor and pivotably coupled to the cyclically movable element such that the second linking element follows movement of the cyclically movable element to thereby slide a second part of the second compressor relative to a first part of the second compressor and pivot the second compressor about a third axis.

16. The apparatus of claim 15 wherein the third axis is substantially parallel to each of the first axis and the second axis.

17. The apparatus of claim 12 wherein the first part of the compressor comprises a cylinder, and the second part of the compressor comprises a piston.

18. The apparatus of claim 12 wherein the linking element comprises a connecting arm, and the cyclically movable element comprises a rod.

19. The apparatus of claim 12 wherein the motor comprises a linear motor.

20. The apparatus of claim 12 wherein the motor comprises a rotary motor.

21. The apparatus of claim 12 wherein the linking element is fixedly attached to the second part of the compressor.

22. A vapor compression apparatus comprising: a plurality of compressors, each of the compressors having a respective piston slidably coupled to a respective cylinder, each of the compressors being pivotable about a respective swivel axis; and a linkage including: a rod defining a longitudinal axis; and a plurality of connecting arms, each of the connecting arms being attached to a respective one of the pistons and being pivotably coupled to the rod such that each of the connecting arms follows movement of the rod along the longitudinal axis to thereby slide each respective piston relative to each respective cylinder and pivot each respective compressor about each respective swivel axis.

23. The apparatus of claim 22 wherein the compressors are in fluid communication with each other.

24. The apparatus of claim 22 further comprising a linear motor coupled to the rod and configured to reciprocate the rod along the longitudinal axis.

25. The apparatus of claim 22 wherein each of the connecting arms is pivotable about a respective pivot axis relative to the rod, each of the pivot axes being substantially parallel to a respective one of the swivel axes.

26. The apparatus of claim 25 wherein the longitudinal axis is substantially perpendicular to each of the pivot axes.

27. The apparatus of claim 22 wherein each of the connecting arms is fixedly attached to a respective one of the pistons.

Description:

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to vapor compression apparatus and, more particularly, to vapor compression apparatus that may be used in refrigeration systems.

2. Description of the Related Art

Vapor compression apparatus are used in a variety of applications including heat pump, air conditioning, and refrigeration systems. Such systems may include either rotary compressors or linear compressors. In a rotary compressor, refrigerant may be compressed in a chamber defined between a fixed outer housing and a rotating inner core. In a linear compressor, refrigerant may be compressed in a cylinder that slidingly receives a piston that reciprocates with a linear motion in and out of the cylinder.

One problem with linear compressors is that it may be difficult to control the position of the moving part, e.g., the piston, which may result in the piston hitting a stationary part, e.g., hitting the bottom of the cylinder at the bottom dead center of the piston stroke. Such collisions may result in damage to the piston, the cylinder, and/or the rod that drives the piston. It is known to provide a linear compressor with a stopper in order to prevent the piston from hitting a stationary part. The stopper may be in the form of a spring in the piston cup or electronics for sensing the position of the piston and controlling the movement of the piston, for example. A stopper adds to the cost and complexity of the compression system, however.

Another problem with linear compressors is that reducing the cooling capacity may result in lower efficiency. For example, the cooling capacity may be reduced by shortening the stroke of the piston. When the stroke is shortened, the piston still reaches the outermost position of the stator. Thus, in order to shorten the stroke, one must eliminate a portion of the stroke in which the piston is near the middle of the motor and in which the motor is most efficient. p Yet another problem with linear compressors is that a pivoting joint that may be provided between the piston and a rod that drives the piston is subject to high levels of stress and is thus susceptible to failure. More particularly, one end of the rod may be rotated by a rotary motor, while the opposite end of the rod is pivotably attached to the piston. Operation of the rotary motor results in the piston being reciprocated, i.e., moved linearly, in and out of the cylinder. The forces required to both push the piston into the cylinder and pull the piston out of the cylinder are transferred from the rod to the piston via the pivoting joint. In some applications, such as when carbon dioxide is used as the refrigerant, the piston diameter tends to be small. Thus, the pivoting joint between the rod and the piston must be correspondingly small. A small pivoting joint is even less able to withstand the stresses that are imposed upon the joint during operation.

A further problem particular to the pivoting joint between the piston and the rod is that the mass of the pivoting joint adds to the reciprocating motion inertia of the oscillating piston. Thus, the added mass of the pivoting joint adds to the stresses placed on the motor, on the rod, and on any other linking elements associated therewith.

A still further problem particular to the pivoting joint between the piston and the rod is that the pivoting joint is difficult for maintenance personnel to access. That is, the position of the pivoting joint between the rod and the piston may be such that it is difficult for maintenance personnel to lubricate or replace the pivoting joint.

What is needed in the art is a linear compressor system that overcomes the problems of known linear compressors. More particularly, what is needed is a linear compressor system that does not require expensive components to prevent the moving parts from hitting the stationary parts, that can operate at high efficiency when capacity has been reduced, and that is not subject to the problems associated with pivoting joints between rods and pistons.

SUMMARY OF THE INVENTION

The present invention provides a linear vapor compression system that may include a compressor that is pivotable relative to a fixed structure. A connecting arm that drives the piston of the compressor may be pivotably connected to a cyclically movable element that drives the connecting arm. The connecting arm may follow the cyclical movement to thereby reciprocate the piston in a cylinder of the compressor while causing the compressor to pivot relative to the fixed structure.

The invention comprises, in one form thereof, a refrigeration system including a fluid circuit circulating a refrigerant in a closed loop. The fluid circuit has operably disposed therein, in serial order, a compressor, a first heat exchanger, an expansion device and a second heat exchanger. The compressor is pivotable about an axis. The compressor has a first part and a second part slidably coupled to the first part. A linkage includes a cyclically movable element. A linking element is attached to the second part of the compressor and is pivotably coupled to the cyclically movable element such that the linking element follows movement of the cyclically movable element to thereby slide the second part of the compressor relative to the first part of the compressor and pivot the compressor about the axis.

The present invention comprises, in another form thereof, a vapor compression apparatus including a compressor having a first part and a second part slidably coupled to the first part. The compressor is pivotable about an axis. A linkage includes a cyclically movable element. A linking element is attached to the second part of the compressor and is pivotably coupled to the cyclically movable element such that the linking element follows movement of the cyclically movable element to thereby slide the second part of the compressor relative to the first part of the compressor and pivot the compressor about the axis. A motor is drivingly coupled to the cyclically movable element.

The present invention comprises, in yet another form thereof, a vapor compression apparatus including a plurality of compressors. Each of the compressors has a respective piston slidably coupled to a respective cylinder. Each of the compressors is pivotable about a respective swivel axis. A linkage includes a rod defining a longitudinal axis. Each of a plurality of connecting arms is attached to a respective one of the pistons and is pivotably coupled to the rod such that each of the connecting arms follows movement of the rod along the longitudinal axis to thereby slide each respective piston relative to each respective cylinder and pivot each respective compressor about each respective swivel axis.

An advantage of the present invention is that expensive components are not required to prevent the moving parts of the compressor from hitting the stationary parts.

Another advantage is that the compressor can operate at high efficiency even when the capacity of the compressor has been reduced.

Yet another advantage is that a pivoting joint between the rod and the piston is not required. Rather, a pivoting joint is provided between the cylinder and a fixed structure. Such a pivoting joint between the cylinder and a fixed structure is not reciprocated along with the piston, and is not subject to the forces required to push the piston into the cylinder and pull the piston out of the cylinder. Further, the pivoting joint does not add to the reciprocating motion inertia of the oscillating piston, and thus does not add to the stresses placed on the motor, on the rod, and on any other linking elements associated therewith. Moreover, since the pivoting joint is not disposed on the piston, the size of the joint is not limited, and the joint can be provided with a more sturdy construction. Yet another advantage of the pivoting joint is that it is relatively easy for maintenance personnel to access.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of one embodiment of a refrigeration system of the present invention;

FIG. 2a is a schematic side view of one embodiment of the vapor compression apparatus of the refrigeration system of FIG. 1 in a first position;

FIG. 2b is a schematic side view of the vapor compression apparatus of FIG. 2a in a second position;

FIG. 2c is a schematic side view of the vapor compression apparatus of FIG. 2a in a third position;

FIG. 3a is a schematic view of a first stage of a compression cycle of the vapor compression apparatus of FIG. 1;

FIG. 3b is a schematic view of a second stage of a compression cycle of the vapor compression apparatus of FIG. 1;

FIG. 3c is a schematic view of a third stage of a compression cycle of the vapor compression apparatus of FIG. 1;

FIG. 3d is a schematic view of a fourth stage of a compression cycle of the vapor compression apparatus of FIG. 1;

FIG. 4a is an schematic overhead view of another embodiment of a vapor compression apparatus of the present invention;

FIG. 4b is a schematic overhead view of yet another embodiment of a vapor compression apparatus of the present invention; and

FIG. 5 is a schematic side view of another embodiment of a vapor compression apparatus of the present invention.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed.

DESCRIPTION OF THE PRESENT INVENTION

FIG. 1 illustrates one embodiment of a refrigeration system 10 of the present invention including a fluid circuit circulating refrigerant in a closed loop. In the illustrated example, a two stage vapor compression apparatus 11 is employed having a first compressor 12 and a second compressor 14 that are in fluid communication with each other. The first compressor 12 receives the refrigerant on an inlet port 13a and compresses the refrigerant from a suction pressure to an intermediate pressure before expelling the refrigerant on an outlet port 15a. An intercooler 16 is positioned between the first and second compressors and cools the intermediate pressure refrigerant. The second compressor 14 then receives the refrigerant on an inlet port 13b and compresses the refrigerant from the intermediate pressure to a discharge pressure before expelling the refrigerant on an outlet port 15b. Inlet ports 13a, 13b and outlet ports 15a, 15b may each include a respective one-way valve (not shown), sometimes referred to as a “check valve”, that allows the refrigerant to flow through the port in only one direction, i.e., in the direction indicated in FIG. 1. The refrigerant is then cooled in a gas cooler 18 before having its pressure reduced by expansion device 22. The refrigerant then enters evaporator 24 where it is boiled and cools a secondary medium, such as air, that may be used, for example, to cool a refrigerated cabinet. The refrigerant discharged from the evaporator 24 enters the first compressor 12 to repeat the cycle.

As shown in FIG. 2a, compressors 12, 14 include respective cylinders 26a, 26b slidably coupled to respective pistons 28a, 28b. Pistons 28a, 28b are slidable within cylinders 26a, 26b in directions indicated by respective double arrows 29a, 29b. By sliding into cylinders 26a, 26b, pistons 28a, 28b compress the refrigerant that is in respective chambers 30a, 30b that are defined between the pistons and cylinders.

Each of cylinders 26a, 26b is pivotably coupled to a respective fixed structure 31a, 31b by a respective pivoting joint 32a, 32b. Pivoting joints 32a, 32b define respective swivel axes 34a, 34b extending into the page of FIG. 2a. Compressors 12, 14 are pivotable about respective axes 34a, 34b in directions indicated by double arrows 36a, 36b, respectively.

In addition to compressors 12, 14, vapor compression apparatus 11 includes a motor 38 and a linkage 40 for driving compressors 28a, 28b in and out of cylinders 26a, 26b. In the embodiment of FIG. 2a, motor 38 is shown in the form of a linear motor that is configured to drive a shaft along a longitudinal axis 42. More particularly, linear motor 38 is drivingly coupled to a rod 44 of linkage 40 such that motor 38 may reciprocate rod 44 along the longitudinal axis 42 in opposite directions indicated by arrows 46, 48. Rod 44 may be at least partially formed of a magnetic or magnetizable material such that the changing magnetic field produced by magnets 50a, 50b of motor 38 can selectively cause rod 44 to move in one of directions 46, 48. Magnets 50a, 50b may be electromagnets or permanent magnets. In order for a force to be exerted on rod 44 in one of directions 46, 48 rather than in the other of directions 46, 48 at a given point in time, rod 44 may have sections of different magnetic polarity along its length. Thus, rod 44 may be moved in one of directions 46, 48. Alternatively, rod 44 may have different amounts of magnetic or magnetizable material along its length. As another possibility, the upper end of rod 44 may be disposed between magnets 50a, 50b, such that most of rod 44 is disposed below magnets 50a, 50a, thus enabling magnets 50a, 50b to selectively attract rod 44 in direction 48 or repel rod 44 in direction 46. The force of gravity on rod 44 may be negligible in comparison to the magnetic force exerted on rod 44 by magnets 50a, 50b.

Linkage 40 also includes two linking elements in the form of connecting arms 52a, 52b having respective ends that are pivotably and independently coupled to rod 44 via a pivoting joint 54. Pivoting joint 54 defines a pivot axis 56 oriented into the page of FIG. 2a about which connecting arms 52a, 52b are pivotable relative to rod 44 in the directions indicated by double arrow 58. Axis 56 may be perpendicular to directions 46, 48. Opposite ends of connecting arms 52a, 52b may be fixedly attached to respective pistons 28a, 28b. For example, connecting arms 52a, 52b may be welded, bonded, attached with fasteners, or integrally formed with pistons 28a, 28b.

In order to balance out the lateral resistive force of compressors 12, 14 on rod 44, and thereby inhibit rod 44 from becoming misaligned in motor 38, connecting arms 52a, 52b may be disposed 180 degrees apart from each other relative to longitudinal axis 42. That is, connecting arms 52a, 52b may be arranged axi-symmetrically about axis 42. The pivot axis 56 may be parallel to both pivot axes 34a, 34b. Thus, pivot axes 34a, 34b may also be oriented parallel to each other.

FIG. 2a may represent the uppermost position of rod 44 and pivoting joint 54 in direction 48. Chambers 30a, 30b may have a maximum volume when vapor compression apparatus 11 is in the position of FIG. 2a.

FIG. 2b illustrates the bottom dead center position of vapor compression apparatus 11 wherein pivoting joint 54 may be aligned with and/or in its position that is closest to pivoting joints 32a, 32b. The volumes of chambers 30a, 30b may be at a minimum in the position of FIG. 2b.

FIG. 2c may represent the lowermost position of rod 44 and pivoting joint 54 in direction 46. Chambers 30a, 30b may have a maximum volume when vapor compression apparatus 11 is in the position of FIG. 2c. It is to be understood, however, that the volume of chambers 30a, 30b in the position of FIG. 2c may be less than, equal to, or greater than the volume of chambers 30a, 30b in the position of FIG. 2a.

An advantage of the invention is that if motor 38 overshoots, thereby causing rod 44 to move in direction 48 past the position shown in FIG. 2a, or causing rod 44 to move in direction 46 past the position shown in FIG. 2c, pistons 28a, 28b will merely be pulled farther out of cylinders 26a, 26b. That is, pistons 28a, 28b will not hit or collide with any stationary parts.

Another advantage of the invention is that magnets 50a, 50b may hold rod 44 in the bottom dead center position when power is not applied to motor 38. Thus, when power is first applied to motor 38 at start up, pistons 28a, 28b will first be pulled out of cylinders 26a, 26b to thereby draw refrigerant into chambers 30a, 30b. The suction of refrigerant into chambers 30a, 30b requires less work than the compression of refrigerant in chambers 30a, 30b. The reduced load at start up enables the use of a less expensive motor having a smaller start force. Moreover, the efficiency of motor 38 in actuating rod 44 may be greater in the bottom dead center position.

Another advantage of vapor compression apparatus 11 starting in the bottom dead center position is that if chambers 30a, 30b become flooded with liquid refrigerant or liquid lubricant while motor 38 is not powered, the liquid will not be compressed by pistons 28a, 28b upon start up. Rather, pistons 28a, 28b will be pulled out of cylinders 26a, 26b at start up. Compressing a liquid can cause damage to a compressor mechanism, as is well known.

In operation, motor 38 may cyclically and alternatingly move rod 44 in directions 46, 48 in order to cyclically and alternatingly push and pull pistons 28a, 28b into and out of cylinders 26a, 26b. As demonstrated in FIGS. 2a and 2c, connecting arms 52a, 52b may be alternatingly oriented at acute and obtuse angle relative to rod 44 during the cyclical movement of rod 44. As demonstrated in FIG. 2b, pivoting joint 54 passes through a point on longitudinal axis 42 that is closest to cylinder 26a and that is closest to cylinder 26b.

FIGS. 3a through 3d illustrate the different stages in a cycle of vapor compression apparatus 11. There may be two compressions of refrigerant in chambers 30a, 30b per cycle.

FIG. 3a illustrates the first of the four stages, i.e., at the start of a cycle, where rod 44 has come to a rest after moving in direction 48 and is beginning to move in direction 46. Suction of refrigerant into chambers 30a, 30b has been completed, and compression of the refrigerant within chambers 30a, 30b is about to start. Pistons 28a, 28b are fully withdrawn from cylinders 26a, 26b to thereby maximize the volume of chambers 30a, 30b. The movement of rod 44 in direction 46 causes connecting arms 52a, 52b to rotate about pivoting joint 54. As pivoting joint 54 moves in direction 46, pistons 28a, 28b move farther into cylinders 26a, 26b to thereby compress the refrigerant in chambers 30a, 30b. As the pressure in chambers 30a, 30b increases past a threshold value, one-way valves (not shown) that are fluidly connected to outlets 15a, 15b are forced open, and the compressed refrigerant vapor is expelled from chambers 30a, 30b. Cylinders 26a, 26b may rotate about respective swivel axes 34a, 34b in order to accommodate the changing orientation of connecting arms 52a, 52b. More particularly, from the viewpoint of FIG. 2a, cylinder 26a may rotate clockwise, and cylinder 26b may rotate counterclockwise.

FIG. 3b illustrates the second of the four stages where vapor compression apparatus 11 is at bottom dead center. The compression of refrigerant within chambers 30a, 30b has been completed, the compressed refrigerant has been expelled, and suction of additional refrigerant into chambers 30a, 30b is about to start. Pistons 28a, 28b are fully inserted into cylinders 26a, 26b to thereby minimize the volume of chambers 30a, 30b. The refrigerant within cylinders 26a, 26b has been fully compressed and expelled from chambers 30a, 30b. Further movement of rod 44 and pivoting joint 54 in direction 46 causes pistons 28a, 28b to be pulled out of cylinders 26a, 26b to thereby draw refrigerant vapor into chambers 30a, 30b through inlets 13a, 13b. As the vacuum pressure in chambers 30a, 30b decreases past a threshold value, one-way valves (not shown) that are fluidly connected to inlets 13a, 13b are forced open, and refrigerant vapor at near atmospheric pressure may be drawn into chambers 30a, 30b. Cylinders 26a, 26b may continue to rotate about respective swivel axes 34a, 34b in order to accommodate the changing orientation of connecting arms 52a, 52b.

FIG. 3c illustrates the third of the four stages, where rod 44 has come to a rest after moving in direction 46 and is beginning to move in direction 48. Suction of refrigerant into chambers 30a, 30b has been completed, and compression of the refrigerant within chambers 30a, 30b is about to start. Pistons 28a, 28b are fully withdrawn from cylinders 26a, 26b to thereby maximize the volume of chambers 30a, 30b. The movement of rod 44 in direction 48 causes connecting arms 52a, 52b to rotate about pivoting joint 54. As pivoting joint 54 moves in direction 48, pistons 28a, 28b move farther into cylinders 26a, 26b to thereby compress the refrigerant in chambers 30a, 30b. As the pressure in chambers 30a, 30b increases past a threshold value, one-way valves (not shown) that are fluidly connected to outlets 15a, 15b are forced open, and the compressed refrigerant vapor is expelled from chambers 30a, 30b. Cylinders 26a, 26b may rotate about respective swivel axes 34a, 34b in directions opposite to their directions in the first two stages in order to accommodate the changing orientation of connecting arms 52a, 52b. More particularly, from the viewpoint of FIG. 2c, cylinder 26a may rotate counterclockwise, and cylinder 26b may rotate clockwise.

FIG. 3d illustrates the fourth of the four stages where vapor compression apparatus 11 is again at bottom dead center. In contrast to the second stage illustrated in FIG. 3b, the movement of rod 44 is in direction 48. The compression of refrigerant within chambers 30a, 30b has been completed, the compressed refrigerant has been expelled, and suction of additional refrigerant into chambers 30a, 30b is about to start. Pistons 28a, 28b are fully inserted into cylinders 26a, 26b to thereby minimize the volume of chambers 30a, 30b. The refrigerant within cylinders 26a, 26b has been fully compressed and expelled from chambers 30a, 30b. Further movement of rod 44 and pivoting joint 54 in direction 48 causes pistons 28a, 28b to be pulled out of cylinders 26a, 26b to thereby draw refrigerant vapor into chambers 30a, 30b through inlets 13a, 13b. As the vacuum pressure in chambers 30a, 30b decreases past a threshold value, one-way valves (not shown) that are fluidly connected to inlets 13a, 13b are forced open, and refrigerant vapor at near atmospheric pressure may be drawn into chambers 30a, 30b. Cylinders 26a, 26b may continue to rotate about respective swivel axes 34a, 34b in order to accommodate the changing orientation of connecting arms 52a, 52b. At the end of the fourth stage, vapor compression apparatus 11 is again in the position of FIG. 3a, and the first stage of a subsequent cycle may begin.

As described above, refrigerant in chambers 30a, 30b may be compressed twice per cycle. However, in other embodiments, refrigerant in chambers 30a, 30b may be compressed only once per cycle. In one embodiment, vapor compression apparatus 11 may oscillate between the position of FIG. 2a and the position of FIG. 2b. That is, as soon as rod 44 has moved far enough in direction 46 to reach the bottom dead center position of FIG. 2b, rod 44 begins to move back in direction 48. Thus, vapor compression apparatus 11 undergoes a two stage cycle in which refrigerant compression occurs as rod 44 moves in direction 46, and refrigerant suction occurs as rod 44 moves in direction 48.

In another embodiment in which refrigerant is compressed only once per cycle, vapor compression apparatus 11 may oscillate between the position of FIG. 2b and the position of FIG. 2c. That is, as soon as rod 44 has moved far enough in direction 48 to reach the bottom dead center position of FIG. 2b, rod 44 begins to move back in direction 46. Thus, vapor compression apparatus 11 undergoes a two stage cycle in which refrigerant compression occurs as rod 44 moves in direction 48, and refrigerant suction occurs as rod 44 moves in direction 46.

The one-compression-per-cycle embodiments described above have the same advantage as the two compression per cycle embodiments in that if motor 38 overshoots, thereby causing rod 44 to move in direction 48 past the position shown in FIG. 2a, or causing rod 44 to move in direction 46 past the position shown in FIG. 2c, pistons 28a, 28b will merely be pulled farther out of cylinders 26a, 26b. That is, pistons 28a, 28b will not hit or collide with any stationary parts.

In other embodiments, there may be more than two compressors and corresponding connecting arms pivotably coupled to the rod. FIG. 4a illustrates an embodiment of a vapor compression apparatus 111 in which three compressors 112a, 112b and 112c are axi-symmetrically arranged around a longitudinal axis 142 of a rod 144 driven by a linear motor 138. Each piston 128a, 128b, 128c may be fixedly attached to a respective connecting arm 152a, 152b, 152c that is pivotably coupled to rod 144. Angles θ1, θ2 and θ3 between the connecting arms may each be approximately 120 degrees. Other aspects of vapor compression apparatus 111 may be substantially similar to those of vapor compression apparatus 11, and thus are not discussed in detail herein.

FIG. 4b illustrates an embodiment of a vapor compression apparatus 211 in which four compressors 212a, 212b, 212c and 212d are axi-symmetrically arranged around a longitudinal axis 242 of a rod 244 driven by a linear motor 238. Each piston 228a, 228b, 228c, 228d may be fixedly attached to a respective connecting arm 252a, 252b, 252c, 252d that is pivotably coupled to rod 244. Angles θ1, θ2, θ3 and θ4 between the connecting arms may each be approximately 90 degrees. Alternatively, angles θ1, θ2, θ3 and θ4 may have some other axi-symmetrical set of values, such as 30 degrees, 120 degrees, 30 degrees, and 120 degrees, respectively, for example. Other aspects of vapor compression apparatus 211 may be substantially similar to those of vapor compression apparatus 11, and thus are not discussed in detail herein.

Another embodiment of a vapor compression apparatus 311 is illustrated in FIG. 5. In contrast to previously discussed vapor compression apparatus that include linear motors, vapor compression apparatus 311 includes a rotary motor 338. Motor 338 is drivingly coupled to a cyclically movable element in the form of a rotating disc 344 that may be rotated about a rotational axis 342 in either of the directions indicated by double arrow 347. Rotating disc 344 may include a pivoting joint 354 that is pivotably and independently coupled to each of connecting arms 352a, 352b. Connecting arms 352a, 352b may be fixedly attached to respective pistons 328a, 328b. As disc 344 rotates, pistons 328a, 328b are cyclically pushed into and pulled out of respective cylinders 326a, 326b. Cylinders 326a, 326b are attached to respective pivoting joints 332a, 332b such that cylinders 326a, 326b may swivel in directions indicated by respective double arrows 336a, 336b in order to accommodate the changing orientations of connecting arms 352a, 352b. Other aspects of vapor compression apparatus 311 may be substantially similar to those of vapor compression apparatus 11, and thus are not discussed in detail herein.

When multiple compressors are used in conjunction with a linear motor, the compressors have been shown herein as being disposed at approximately the same locations along the longitudinal axis of the rod. However, it is also possible for the compressors to be placed at different positions along the rod's longitudinal axis.

The pivoting joints on which the compressor cylinders swivel have been shown herein as being attached near the middle of the end walls of the cylinders. However, it is to be understood that the pivoting joints can be attached at any point on the cylinders, including on the annular side wall. Further, the swivel axes defined by the pivoting joints need not be closely adjacent the cylinders. Rather, the swivel axes may be farther from the cylinders than as shown in the drawings.

The inlet ports and outlet ports of the cylinders have been shown herein, for ease of illustration, as being disposed on the annular side walls of the cylinders. However, the inlet ports and outlet ports could also be located on the end walls of the cylinders.

The connecting arms have been shown herein as being fixedly attached to the pistons, while the cylinders are pivotably coupled to a fixed structure. However, it is also within the scope of the present invention for the connecting arms to be fixedly attached to the cylinders, with the pistons being pivotably coupled to a fixed structure.

In the embodiments shown herein, the compressors include piston and cylinder mechanisms. However, it is to be understood that the present invention can also be used in conjunction with different types of compression mechanisms.

The linear motor embodiments shown herein also disclose the vapor compression apparatus reaching a bottom dead center position in the cycle whereat the pistons are inserted into the cylinders to a maximum degree. However, it is also within the scope of the present invention for the connecting arms to oscillate between two positions such that the pistons are never fully inserted into the cylinders. For example, the connecting arms may oscillate between a first position in which the connecting arms form a 30 degree angle with the rod and a second position in which the connecting arms form a 60 degree angle with the rod.

While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.