EP2297464A1

EP2297464A1 - Rotor assembly for rotary compressor

Info

Publication number: EP2297464A1
Application number: EP08783246A
Authority: EP
Inventors: Darryl Fleger; David Robert Gibbs
Original assignee: Randell Technologies Inc
Current assignee: Randell Technologies Inc
Priority date: 2008-04-28
Filing date: 2008-07-23
Publication date: 2011-03-23
Also published as: CA2636006A1; CA2636006C; US20110262291A1; WO2009132412A1; CN102076972A; US20180291898A1; US20150152867A1

Abstract

A traditional compressor unit of the sealed type suffers in that a failure of either the motor or the compressor require both to be discarded Provided is a compressor (1) having a rotor assembly (3) withm which a rotor (24) is rotated on an eccentric shaft (28) in a sealed chamber (23) Two or more intake ports (32, 33) are provided that open into the sealed chamber (23) and two or more exhaust ports (34, 35) are provided with one way valves (38), to permit compressed gas to exit the sealed chamber (23) The geometry of the rotor (24) and sealed chamber (23) and eccentric drive (28) are such that apices of the rotor (24) remain in contact with a peripheral wall (22) of the sealed chamber (23) as the rotor (24) rotates and apex seals (36) are provided on the apices of the rotor (24) to prevent leakage of the gas around the apices of the rotor (24) Pn a preferred embodiment the rotor (24) is a multi-lobed rotor orbiting withm a trochoidal chamber (23).

Description

ROTOR ASSEMBLY FOR ROTARY COMPRESSOR

FIELD OF THE INVENTION

This invention relates to rotor assemblies for rotary compressor units especially but not exclusively units for small refrigeration units such are suitable for use in small refrigerators and automotive air conditioners. Such units must be compact, quiet, reliable and economical to manufacture and operate.

BACKGROUND OF THE INVENTION Compressor units for domestic refrigerators are commonly of the sealed unit type in which both the compressor and a motor permanently coupled to the compressor is located within an enclosure that is completely and permanently sealed except for refrigerant connections to the remainder of the refrigeration unit. Such a unit has the disadvantages that failure of either the motor or the compressor requires both to be discarded, different sealed units are required for electrical supplies requiring different motors, even though the compressor is identical, and two devices, both of which generate unwanted heat, are thermally coupled within the same enclosure.

It is known in compressor units for automotive air conditioning systems, which are engine driven, and thus require a clutch mechanism, to utilize an electromagnetic clutch between a belt driven pulley and the compressor.

In the interests of smoother and more silent compressors, there has been some adoption of scroll type compressors in compression type refrigeration units, available for example from Lennox, Copeland and EDPAC International.

An alternative form of piston compressor which has been proposed, is the rotary piston compressor using a lobed rotor in a trochoidal chamber and having some resemblance to rotary piston engines such as the Wankel engine although the operating cycle is substantially different and the shaft is driven by an external power source rather than being driven by the rotary piston. Such compressors are exemplified in U.S. Patents Nos. 3,656,875 (Luck); 4,018,548 (Berkowitz); and 4,487,561 (Eiermann).

U.S. Patent 5,310,325 (Gulyash) discloses a rotary engine using a symmetrical lobed piston moving in a trochoidal chamber on an eccentric mounted on a rotary shaft and driven through a ring gear by a similarly eccentric planet gear rotated at the same rate as the eccentric, the gear ratio of the ring gear to the planet gear being equal to the number of lobes on the rotor, typically three. The apices of the lobes trace trochoidal paths tangent to the trochoidal chamber wall thus simplifying sealing.

U.S. Patent 6,520,754 (Randolphi) discloses a compressor for a refrigeration unit having a three lobed rotor orbiting in a chamber defined within a sealed casing and using a magnetic coupling outside of the casing to rotate the rotor.

SUMMARY OF THE INVENTION

The present invention relates to a compressor having a rotor assembly within which a rotor is rotated on an eccentric shaft in a sealed chamber. Two or more intake ports are provided that open into the sealed chamber and two or more exhaust ports are provided with one way valves, to permit compressed gas to exit the sealed chamber. The geometry of the rotor and sealed chamber and eccentric drive are such that apices of the rotor remain in contact with a peripheral wall of the sealed chamber as the rotor rotates and apex seals are provided on the apices of the rotor to prevent leakage of the gas around the apices of the rotor. In a preferred embodiment the rotor is a multi-lobed rotor orbiting within a trochoidal chamber.

The features of the present invention will be apparent from the following description of a presently preferred embodiment thereof. SHORT DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front schematic perspective view of a compressor having a rotor assembly in accordance with the present invention and magnetic drive assembly within a sealed outer casing; Fig. 2 is a cross sectional schematic view of the compressor of Fig. 1 through line

2-2 with an outer magnetic drive;

Fig. 3 is a perspective view of the rotor assembly for the compressor of Fig. 1 ;

Figs. 4 and 5 are cross-sections of the rotor assembly of Fig. 3 on the line 4-4 showing different phases of its operation; Fig.6. is a cross sectional schematic view of the rotor assembly of Fig. 4 on the line 6-6;

Fig.7. is a cross sectional schematic view of the rotor assembly of Fig. 4 on the line 7-7;

Fig.8. is a cross sectional schematic view of the rotor assembly of Fig. 4 on the line 8-8;

Fig. 9 is a schematic view of a flapper valve assembly contained within the rotor housing of Fig. 3;

Fig. 10 is a cross section of the flapper valve assembly on the line 9-9 in Fig. 9.

Fig. 11 is a top plan view of another embodiment of a compressor having a rotor assembly in accordance with the present invention without the magnetic drive assembly and sealed outer casing as shown in Fig. 1 and showing major internal components in dotted lines;

Fig. 12 is a cross sectional schematic view of the compressor of Fig. 9 through the line 12-12; Fig 13 is a cross sectional schematic view of the compressor of Fig. 9 through the line 13-13.

Fig. 14 is a perspective view of another embodiment of a compressor having a rotor assembly in accordance with the present invention;

Fig. 15 is a top schematic view of the compressor of Fig. 14 showing the assembly transparently; Fig. 16 is a rear perspective view of the compressor of Fig. 14 showing the assembly transparently.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures 1-8, a compressor, generally indicated at 1 in Figs. 1 & 2, comprises a sealed outer casing generally indicated at 2 retains a rotor assembly in accordance with one embodiment of the present invention, generally indicated at 3 and an inner magnetic drive assembly generally indicated at 5. The compressor 1 in one application may be connected (as shown in Fig 2) by an intake 90 and outlet 91 such as to an evaporator and a condenser of a refrigeration unit. In the embodiment illustrated the sealed outer casing 2 has a canister section 6 which holds the rotor assembly 3 and inner magnetic drive assembly 5 and a lid section 7 which fits over the inner magnetic drive assembly 5 and onto the canister section 6 with a pair of O-rings 8,9 to seal the outer casing. In the embodiment illustrated the canister section 6 has a cylindrical outer wall 10 closed at one end by plate section 11. A peripheral flange 12 extends outwardly from the top 13 of the cylindrical outer wall 10. The thickness of cylindrical outer wall 10 in a first section 14 adjacent the plate section 11 is greater than the thickness of a second section 15 which in turn is thicker than a third section extending 16 from the top 13 of the cylindrical outer wall 10. The reduction in thickness in the outer cylindrical wall 10 forms a pair of lips 17, 18 on its inner surface 4.

The rotor assembly 3, in the embodiment illustrated in Figs. 2-8, is comprised of a back plate 19, rotor housing 20 and front plate 21. The inner peripheral wall 22 of the rotor housing 20 together with the inner surfaces 25, 26 of back plate 19 and front plate 21 define a sealed chamber 23 within which a rotor 24 is rotated. One end 27 of an eccentric shaft 28 on which the rotor 24 is mounted, is journal led in bearings 29 housed within the back plate 19. A timing pinion 30 is attached to the inner surface 25 of back disk 19 and mates with a ring gear 31 attached to rotor 24. In the embodiment illustrated the timing pinion 30 is ²A the diameter of the ring gear 31. A pair of intake ports 32, 33 (see Figs 4, 5 & 7) are provided in back plate 19 that open into the sealed chamber 23. A pair of exhaust ports 34, 35 are provided in the rotor housing 20 (see Fig. 6). One way valves generally indicated at 38 (see Fig.9), shown as flapper valves in the drawings, permit compressed gas to exit the sealed chamber 23 but do not allow any return flow back through the exhaust ports 34,35 into the chamber 23.

In the embodiment illustrated, the rotor 24 is mounted on an eccentric shaft 28 for orbital movement along a path within chamber 23. The profile of chamber 23 is an outline of the path that the tips of the lobes A, B, C of the rotor 24 follows. The ratio of the ring gear 31 to the eccentric gear 30 (or timing pinion) is equal to the number of lobes, in this case three, of the rotor 24. In the embodiment illustrated in Figs. 1 to 8, the end 32 of the eccentric shaft 28 remote from the rotor 24 is attached to an inner magnetic drive assembly generally indicated at 5. The inner magnetic drive assembly 5 has an inner magnetic drive element 33 attached to the eccentric shaft 28 where the shaft 28 extends from the front plate 21 of the rotor assembly 3. A cap portion 37 of lid section 7 of the sealed outer casing 2 encloses the inner magnetic drive assembly 5. An outer magnetic drive 38 is attached to a source of rotation (not shown) and rotates about the cap portion 37 of lid section 7 providing a mating magnetic force to turn the inner magnetic drive element 33.

Fig. 4 shows the position of the rotor 24 when the eccentric shaft 28, timing pinion 30 and ring gear 31 are as seen in the drawing. The direction of rotation in this example is clockwise, and the apices of the lobes of the rotor are labeled A, B and C for convenient reference. The geometry of the rotor 24 and chamber 23 and of the drive are such that the apices remain in contact with the inner wall 25 of the sealed chamber 23. Apices A, B and C of rotor 24 divide the sealed chamber 23 into three parts labeled D, E and F. Gas is introduced into the sealed chamber 23 through intake ports 32.32A. As the rotor 24 rotates the gas in the parts D, E and F of the chamber 23 is compressed as the rotation of the rotor 24 reduces the size of part D, E and F of the chamber. Fig. 5 shows the position of the rotor 24 rotated from the position in Fig. 4 with the eccentric shaft 28, timing pinion 30 and ring gear 31 positioned as seen in the drawing. The part F of the sealed chamber 23 has been reduced, compressing the gas in that section. The compressed gas is exhausted through exhaust port 34. As the rotor moves clockwise, gas is drawn through the intake port 32.32A into the parts D, E and F of chamber 23, the gas is compressed and forced out of the chamber 23 through exhaust ports 34, 35 past flapper valves 38.

In order to prevent compressed gas leaking from part D, E or F of chamber 23 into one of the other parts D, E or F of chamber 23 as the rotor 24 is rotated, apex seals 36 are provided in a slot 36A in the apex A, B and C of rotor 24. In the embodiment illustrated in figs. 1-8, the back side of the rotor 24 fits tight against the inner surface 25 of back plate 19 and together with a lubricant provides a seal. Similarly the front side of the rotor 24 fits tight against the inner surface 26 of front plate 21 and together with a lubricant provides a seal. As an alternative to relying on the tight fit and lubricant to form a seal, side seals may be inserted to prevent gas from leaking around the front and back sides of the rotor.

Fig. 6 illustrates a cross section of the rotor assembly 3 of Fig. 4 on line 6-6. The exhaust ports 34, 35 are shown in the rotor housing 20. Fig. 7 illustrates a cross section of the rotor assembly 3 of Fig. 4 on line 7-7. In this view the intake ports 32, 32A are shown in the back plate 19 although they could be located in the front plate 21 if desired. Fig. 8 illustrates a cross section of the rotor assembly 3 of Fig. 4 on line 8-8. In this view the apex seals 36 on apex B of rotor 24 are shown. The apex seals 36 are preferably compression seals retained within slots 37 on rotor 24. The apex seals 36 run on the peripheral wall 22 of the chamber 23 defined by rotor housing 20 and as noted previously prevent leakage across the tips of the rotor 24. An apex seal spring (not shown) provides the force to keep the apex seals 36 in contact with the profile of the chamber 23. In the embodiment illustrated the apex seal springs are coil springs but a leaf spring or other suitable design can be used.

Figs. 9 and 10 illustrate schematically the one way flapper valves 38 in the exhaust ports 34,35 which allow the compressed gas to exit the compressor yet allow no return flow back. The flapper valves 38 have a disk 39 connected to one end of a spring 40 attached to a plug 42. The spring 40 keeps disk 39 in sealing engagement with the inlet 43 of exhaust port 34 or 35 until the pressure of the compressed gas is sufficient to push the disk 39 to open the inlet 43 and permit the compressed gas to exit through outlet 44. Alternatively the flapper valve design can be different. For example the valve may be secured on one end and flexes to allow gas to exit the compressor.

Figs. 11 -13 illustrate another embodiment of a compressor (suitable for use as in refrigerators although many other applications are possible) having a rotor assembly in accordance with the present invention with a direct shaft drive. The compressor, generally indicated at 51 in Figs. 11-13, comprises a rotor assembly, generally indicated at 53 and a vector plate assembly generally indicated at 55. In the embodiment illustrated the vector plate assembly 55 comprises a rear vector plate 56 and a seal retention plate 57 which are attached to the rotor assembly 53. Pressure and suction lines are attached to the rear vector plate 56 which is in turned bolted to the back plate 59 of the rotor assembly 53. A refrigerant gas coming into the compressor by the suction line is collected in the internal cavity 58 formed by the mating of the rear vector plate 56 and back plate 59 of the rotor assembly 53.

The rotor assembly 53 is similar to the rotor assembly 3 shown in Figs, 3, 4 and 5. It comprises a back plate 59, rotor housing 60 and front plate 61. The inner peripheral wall 62 of the rotor housing 60 together with the inner surfaces 65, 66 of back plate 59 and front plate 61 define a sealed chamber 63 within which a rotor 64 is rotated. One end 67 of an eccentric shaft 68 on which the rotor 64 is mounted, is journalled in bearings 69 housed within the back plate 59. A tinning pinion is attached to the inner surface 65 of back plate 59 and mates with a ring gear 71 attached to rotor 64. In the embodiment illustrated the timing pinion is ²A the diameter of the ring gear 71. Intake ports are provided in back plate 59 from cavity 58 and open into the sealed chamber 63. In large models the refrigerant may also pass from cavity 58 through internal passages to the front of the compressor and then through intake ports in the front plate 61 into chamber 63. In situations where intake ports are provided in the front plate 61 the seal retention plate 57 is replaced with a front vector plate. A pair of exhaust ports 74,75 are provided in the rotor housing 60 (see Fig. 13). One way valves generally indicated at 78 (see Fig.13), shown as flapper valves in the drawings, permit compressed gas to exit the sealed chamber 63 but do not allow any return flow back through the exhaust ports 74,75 into the chamber 63.

In the embodiment illustrated, the rotor 64 is mounted on an eccentric shaft 68 for orbital movement along a path within chamber 63. The profile of chamber 63 is an outline of the path that the tips of the lobes of the rotor 64 follows. The ratio of the ring gear 71 to the eccentric gear or timing pinion is equal to the number of lobes, in this case three, of the rotor 64. In the embodiment illustrated in Figs. 11 to 13; the end 82 of the eccentric shaft 68 remote from the rotor 64 may be attached to direct drive assembly (not shown). The seal retention plate 57 retains a shaft seal 81 around the shaft 68 as it passes through the seal retention plate 57.

The operation of the rotor 64 in Figs 11 -13 is the same as in Figs 3-5. With the eccentric shaft 68, timing pinion and ring gear 71 as described, rotation of the rotor 64 is such that the apices of the rotor 64 remain in contact with the inner wall 62 of the sealed chamber 63. The apices of rotor 64 divide the sealed chamber 63 into three parts. Gas is introduced into the sealed chamber 63 through the intake ports. As the rotor 64 rotates the volume of each part of chamber 63 between the lobes of the rotor is continuously varied. As the volume of the chambers increases refrigerant is drawn into the compressor, inversely as the volume decreases the now compressed gas is exhausted out of the compressor. The three parts of chamber 63 are never compressing at once, each is in a different phase of what could be considered a 2 phase cycle - intake and exhaust. As the size of a part of the sealed chamber 63 is reduced, the gas in that section is compressed. The compressed gas is exhausted through exhaust port 74. As the rotor moves clockwise, the part of the chamber from which the compressed gas has been exhausted, increases in size and gas is drawn through the intake port into that part of chamber 63. As the rotor 64 continues to rotate, the gas is again compressed and forced out of the chamber 63 through the other exhaust port 75 past flapper valves.

In order to prevent compressed gas leaking from one part of chamber 63 into another one of the other parts of chamber 63 as the rotor 24 is rotated, apex seals 76 are provided on the apices of rotor 64 as shown in Fig 12.

Fig. 12 illustrates a cross section of the compressor 51 of Fig. 11 on line 12-12. Fig. 13 illustrates a cross section of the compressor 51 of Fig. 11 on line 13-13. In this view the exhaust ports 74, 75 are shown in the rotor housing 60.

Figs. 14 -16 illustrate another embodiment of a compressor (suitable for use as in automotive air conditioners although many other applications are possible) having a rotor assembly in accordance with the present invention with a direct shaft drive. The compressor, generally indicated at 101 in Figs. 14-16, comprises a rotor assembly and a vector plate assembly. In the embodiment illustrated the vector plate assembly comprises a rear vector plate 106 and a front vector plate 107 which are attached to the rotor assembly 103. Pressure and suction lines are attached to the rear vector plate 106 at suction inlet 104A and pressure outlet 104B respectively which is in turned bolted to the back plate 109 of the rotor assembly 103. A refrigerant gas coming into the compressor by the suction line is collected in the internal cavity 108 formed by the mating of the rear vector plate 106 and back plate 109 of the rotor assembly 103. In this embodiment one or more internal passages 108A connects the internal cavity 108 formed by the mating of the rear vector plate 106 and back plate 109, with a similar internal cavity 108B formed by the mating of the front vector plate 107 and front plate 111 of the rotor assembly 103.

The rotor assembly 103 is similar to the rotor assembly 3 shown in Figs, 3, 4 and 5. It comprises a back plate, rotor housing and front plate similar to the embodiments shown in the other figures although relative dimensions are different. The inner peripheral wall of the rotor housing together with the inner surfaces of back plate 109 and front plate 111 define a sealed chamber within which a rotor is rotated. One end of an eccentric shaft 118 on which the rotor is mounted, is joumalled in bearings housed within the back plate 109. A timing pinion is attached to the inner surface of back plate 109 and mates with a ring gear attached to rotor. In the embodiment illustrated the timing pinion is % the diameter of the ring gear. Intake ports are provided in back plate 109 from cavity 108 and front plate 111 from cavity 108B and open into the sealed chamber. A pair of exhaust ports are provided in the rotor housing. One way valves preferably flapper valves, permit compressed gas to exit the sealed chamber at pressure outlets 104B but do not allow any return flow back through the exhaust ports into the chamber.

In the embodiment illustrated, the rotor is mounted on an eccentric shaft 118 for orbital movement along a path within chamber. The profile of the chamber is an outline of the path that the tips of the lobes of the rotor follow. The ratio of the ring gear to the eccentric gear or timing pinion is equal to the number of lobes, in this case three, of the rotor. In the embodiment illustrated in Figs. 14 to 16; the end 132 of the eccentric shaft 118 remote from the rotor may be attached to direct drive assembly (not shown). The front vector plate 107 retains a shaft seal around the shaft 118 as it passes through the front vector plate 107. The operation of the rotor in Figs 14-16 is the same as in Figs 3-5. Rotation of the rotor is such that the apices of the rotor remain in contact with the inner wall of the sealed chamber. The apices of rotor divide the sealed chamber into three parts. Gas is introduced into the sealed chamber through the intake ports. In the embodiment illustrated there are intake ports provided in the back plate 109 and additional intake ports in the front plate 111. As the rotor rotates the volume of each part of the chamber between the lobes of the rotor is continuously varied. As the volume of a part of the chamber increases refrigerant is drawn into the compressor, inversely as the volume decreases the now compressed gas is exhausted out of the compressor. The three parts of chamber are never all compressing at the same time, each is in a different phase of what could be considered a 2 phase cycle - intake and exhaust. As the size of a part of the sealed chamber is reduced, the gas in that section is compressed. The compressed gas is exhausted through exhaust port which is connected to pressure outlet 104B. As the rotor moves clockwise, the part of the chamber from which the compressed gas has been exhausted, increases in size and gas is drawn through the intake port into that part of chamber. As the rotor continues to rotate, the gas is again compressed and forced out of the chamber through the other exhaust port past flapper valves to pressure outlet 104B.

In order to prevent compressed gas leaking from one part of chamber into another one of the other parts of chamber as the rotor is rotated, apex seals are provided on the apices of rotor.

The rotor assembly of the present invention is particularly useful in compressors in various applications including (but not limited to) consumer household, automotive air conditioners, industrial, portable, transportable, commercial, scientific, medical, environmental and military disciplines. If required, multiple rotors or multiple rotor assemblies can be provided in a compressor in accordance with present invention. A number of the advantages of the present invention over conventional compressor designs are as follows: (a) only two major moving parts in the compressor

(b) light weight

(c) shaft driven rotor in combination with a simplified gear reduction drive

(d) apex seals on the rotor prevent loss of compression (e) can utilize a variable speed drive

(f) can obtain variable output

It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended to limit the broader aspects of the present invention.

Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, which variations may be made thereto without departing from the spirit of the invention or the scope of the appended claims.

Claims

CLAIMS:

1. A compressor having a rotor assembly within which a rotor is rotated on an eccentric shaft in a sealed chamber, two or more intake ports are provided that open into the sealed chamber, two or more exhaust ports are provided with one way valves, to permit compressed gas to exit the sealed chamber, the geometry of the rotor and sealed chamber and eccentric drive are such that apices of the rotor remain in contact with a peripheral wall of the sealed chamber as the rotor rotates and apex seals are provided on the apices of the rotor to prevent leakage of the gas around the apices of the rotor.

2. A compressor according to claim 1 , wherein the rotor is a multi-lobed rotor orbiting within a trochoidal chamber.

3. A compressor according to claim 2, wherein the rotor is a three lobed rotor journalled on a shaft and having a ring gear driven by timing pinion, the gear ratio of the ring gear to the timing pinion being three to one.

4. A compressor according to any one of claims 1 , 2 or 3 wherein the apex seals are compression seals that remain in contact with the peripheral wall of the sealed chamber as the rotor rotates.

5. A compressor according to claim 4 wherein the apex seals have an apex seal spring to maintain the apex seal in contact with the peripheral wall of the sealed chamber as the rotor rotates.

6. A compressor according to any one of claims 1 to 5 wherein the rotor assembly comprises a back plate, rotor housing and front plate wherein an inner peripheral wall of the rotor housing together with inner surfaces of the back plate and front plate define the sealed chamber within which the rotor is rotated on an eccentric shaft.

7. A compressor according to claim 6 having a pair of intake ports provided that open into the sealed chamber and a pair of exhaust ports provided in the rotor housing with one way valves, to permit compressed gas to exit the sealed chamber as the rotor rotates.

8. A compressor according to claim 7 wherein the pair of intake ports are provided in the back plate.

9. A compressor according to claim 7 wherein the pair of intake ports are provide PHd i inn t thhιe=> f frroonntt n pllaattpe.

10. A compressor according to claim 6 having a one or more intake ports provided in the back plate and one or more intake ports in the front plate, all of said intake ports opening into the sealed chamber and a pair of exhaust ports provided in the rotor housing with one way valves, to permit compressed gas to exit the sealed chamber as the rotor rotates.

11. A compressor according to any one of claims 1 to 10 having a rotary drive enclosed by a sealed casing and orbiting the rotor, a driven element of a magnetic coupling in driving connection with the rotary drive and orbiting the rotor, the driven element enclosed by the sealed casing and including at least one magnet, a driving element of the magnetic coupling outside of the casing in close proximity to the driven element, and an arrangement for rotating the driving element.

12. A compressor according to claim 11 , wherein the arrangement for rotating the driving element includes an electric motor.

13. A compressor according to claim 12, wherein the magnet includes a plurality of electromagnets.

14. A compressor according to claim 13, wherein the driving element includes a plurality of electromagnets.

15. A compressor according to any one of claims 1 to 10 having a rear vector plate to cap the back of the rotor assembly.

16. A compressor according to claim 16 having a seal retention plate to cap the front of the rotor assembly and having an opening through which the shaft extends to permit an end of the shaft to be connected to a direct drive.

17. A compressor according to claim 16 having a seal around that portion of the shaft passing through the opening in the seal retention plate.