US2212717A - Rotary compressor for refrigerating apparatus - Google Patents

Description

Aug. 27, 1940. M, P, PENN 2,212,717

ROTARY COMPRESSOR FOR REFRIGERATING APPARATUS Filed March 31, 1956 3 Sheets-Sheet 1 INVENTOR.

BY I

Aug. 27, 1940. p, PENN 2,212,717

ROTARY COMPRESSOR FOR REFRIGERATING APPARATUS Filed March 31, 1936 3 Sheets-Sheet 2 EMFW ATTORNEYS Aug. 27, 1940. p, E N 2,212,717

ROTARY COMERESSOR FOR REFRIGERATING' APPARATUS Filed March 51, 1936 5 Sheets-Sheet 3 i v 178 M90 INVENTOR.

. ATTORNEYS Patented Aug. 27

PATENT OFFICE ROTARY CODIPRESSOR FOR REFRIGERAT- ING APPARATUS Melvin P. Pennfl layton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application March 31, 1936, Serial No. 71,852

2 Claims.

This invention relates to refrigerating apparatus and more particularly to novel compressors and pumps.

Rotary pumps and compressors have been replacing reciprocating pumps and compressors to a great extent within recent years. However, this change has only taken place mainly in the small sizes. In the larger sizes of pumps andcompressors, the reciprocating compressor is 10 standard. Some attempts have been made to provide large rotary pumps and compressors, but such attempts have not been entirely successful for the reason that most rotary compressors and pumps have a rather great degree of unbalance.

both static and dynamic, and particularly, large unbalanced pressures on the moving parts which impose large forces upon the bearings necessitating excessively large bearings.

' It is an object of my invention to combine the 20 desirable characteristics of reciprocating pumps and rotary pumps.

It is another object of my invention to provide a rotary pump wherein the moving parts are well balanced and in which the bearing loads are 25 small.

It is a further object of my invention to provide a pump which can be readily made in different capacities by slight changes in manufacture of one or more of the parts.

It is another object of my invention to provide an improved lubricating means and system for rotary pumps.

It is a still further object to provide an improved rotary pump having relatively great capacity and displacement for its size and weight.

It is still another object of my invention to provide a pump in which the moving parts are statically and dynamically balanced and in which the fluid pressures upon the moving parts are balanced.

' Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of thepresent invention is clearly shown.

' In the drawings:

Fig. 1 is a vertical sectional view of a rotary compressor embodying my invention taken along the lines l-i of Fig. 2 together with a diagrammatic representation of the remainder of refrigerant air conditioning system;

Pig. 2 is a sectional view taken along the lines 2-2 of Fig. 1;

Pig. 3 is a view looking at the left side of the compressor shown inFig. 1 with the end casing member removed; and

Fig. 4 is a sectional view taken along the line 4 of Fig. .1.

Briefly, in this application, I have disclosed a 5 refrigerant air conditioning system including a rotary compressor having an elliptical rotor or impeller rotatively mounted within a cylindrical casing. This cylindrical casing is provided with slots at the top and bottom receiving divider blocks which are held in engagement with the impeller by springs. The lower divider block dips into an oil reservoir and has an oil pump connected thereto which pumps oil to the rotor bearings as well as to the bearing surfaces of the upper divider block from which excess oil is conducted to the sealing surfaces of the compressor. This construction provides a symmetrical rotor and pumping chambers providing balanced fluid pressure forces upon the rotor.

Referring now to the drawings and more particularly to Fig. 1, there is shown a refrigerating system including an air conditioning cabinet provided with a refrigerant evaporating means 22 and a motor driven fan 24 for drawing air from the room 26 through an inlet opening 28 in the cabinet and discharging the air through an outlet opening 30 back into the air of the room. Refrigerant within the evaporating means 22 evaporates under reduced pressure and absorbs heat from the air circulated by the motor driven fan 24. This evaporated refrigerant is withdrawn from the evaporating means 22 through a return conduit 32 which connects tothe inlet of a rotary compressor 34. The rotary compressor 34 coma presses the refrigerant and forwards the compressed refrigerant though a-supply conduit 36 to a condenser 38 which liquefies the compressed refrigerant. This liquefied refrigerant is collected in a receiver 40 which is connected to the evaporating means 22 by a liquid conduit 42 provided with an automatic thermostatic expansion valve 44 provided with a thermostat control bulb 4G in contact with the outlet of the evaporating means 22. a

The compressor is driven by an electric motor ill, either directly through a detachable coupling or as shown through pulley and belt means 52. The electric motor is connected in series with a thermostatic switch means 54 exposed to the air in the room 26. The switch 54. together with the motor 50, are located in parallel electric circuit relation with the fan motor 24 and all of the elements of the electric circuit are located in series with the manual control switch 56. In I.

her which. is pressed into place.

this way, the fan may be kept in operation for ventilation, regardless of the operation of the motor-compressor unit.

Referring now more particularly to the compressor, there is shown a central casting 60 having a central cylindrical wall 62 enclosing a cylindrical chamber 64. This cylindrical chamber 64 is closed at its ends by inner end plates 66 and 68 which are fastened by bolts, studs or cap screws to the faces of the central casting 60. Outer end plates I and I2 are likewise fastened to the central casting by bolts, studs .or cap screws.

The end plates 66 and 68 are each provided with inserted bosses I4 and 16 provided with bearing bushings I8 and 80. The inserted boss I6 is closed at the end by a dished sheet metal mem- The bearing bushings I8 and 80 support the bearings 84 and 86 of a drive shaft 88 which extends from the bearing portion 84 through a boss and a sealing plate 90 formed in the end plate I0. A shaft seal is provided within this boss between the plate 90 and the bearing portion 84 of the shaft. This seal includes a rotatable seal ring' 94 provided with a wedge shaped gasket 96 of a compound containing chloro-Z-butadiene, 1,3. This wedge shaped gasket 96 is held in place by a washer 98 and a compression spring I02 which tends to hold the wedge shaped gasket in relatively tight engagement with the drive shaft 88 and the seal ring 94. The rotatable seal ring 94 has a sealing surface which is held in engagement with a stationary seal ring I04 supported within a recess in the plate 90 by a resilient gasket I06 of substantially the same material as the gasket 96...

Between the bearing portions 84 and 86 of the drive shaft 88 is an enlarged portion which is provided with a rotor or impeller I08 which may have its periphery elliptical in shape. However, other forms of surfaces may be adopted, such as a constant acceleration surface which will be later explained. This rotor or impeller is placed onto the enlarged portion of the shaft and locked from rotation thereon by a pair of half round keys IIO. Opposite the half round keys H0 is a key way I I2 in the rotor or impeller which serves another purpose. The drive shaft 88 is held in place by sets of thrust members and washers I and H6 which are mounted upon the bearing portions 84 and 86 of the drive shaft and set in between the enlarged portion of the shaft and the inner faces of the inner end plates 66 and 68. The rotor I08 also has its end portions fitting against the inner :faces of the end plates 66 and 68.

The housing 60 is provided with slots at the bottom and top designated by the reference characters II 8 and I20. These slots receive reciprocable divider blocks I 22 and I24 which are held in engagement with the peripheral surfaces of the rotor by pairs of compression type coil springs I26-and I28.- These compression type coil springs. extend from an inner face of the wall,

of the central casting'60 into drilled apertures in the divider blocks. Beneath the lower divider block there is provided a passage I30 which conand which connect to the passage I30 through nects with oil reservoir chambers" I32 and I34, which are located on either side of the lower half of the cylinder.62 and the lower divider block its end portion. Both of these oil reservoirs I32 and I34, as 'well as the passage I30, open into the .space between the inner end plate and the outer end plate I0 which also contains the shaft 7 the capacity of the compressor.

seal and serves as a discharge chamber I38 for the compressor. A passage I36 is provided in the central casting 60 directly above the upper divider block I24 which also communicates with the discharge chamber I38 located between the inner and outer end plates 66 and I0.

On the opposite side of the compressor between the inner and outer end plates 68 and 12, there is provided a suction or inlet chamber I40 for the compressor. For this purpose the outer end plate 12 is provided with an inlet opening I42 which connects to the return conduit 32 of the refrigerating system. The inner end wall or plate 68 is provided with upper and lower inlet openings I44 and I46, which extend from the chamber I40 into the cylindrical chamber 64 adjacent one side of the upper and lower divider blocks I24 and I22 respectively. These holes or inlet openings serve to supply the two compression chambers I48 and I50 which are formed between the small diameter portions of the elliptical surface and the inner face of the cylindrical wall 62. These compression chambers of course are not fixed as is usually the case, nor in one sense are they permanent.

In the other end plate- 66 there is provided a plurality of discharge openings I52 and I54 which are located upon the opposite side of the divider blocks from the inlet ports, in addition to being located upon the other wall. These outlets are each provided with spring flapper valves. I56 and I58 which control the discharge of compressed gas or fluid from the compression or pumping chambers to prevent compressed fluid from returning from the discharge chamber into the compression chamber. The outlet from the discharge chamber I38 is provided by a threaded ope ng I60 which connects with the supply conduit 36 connected to the condenser 38.

The rotor or impeller I08 is shown as having its major axis substantially equal to the diameter of the inner cylindrical face of the wall 62. The amount of clearance provided between the major diameter of the rotor and the inner cylindrical surface is preferably between 0.0005 and 0.001 of an inch. However, a slightly greater amount of clearance may be used in many cases depending upon the fluid pumped and the lubricant used. The minor axis may be reduced or enlarged as desired to increase or decrease Incidentally, this forms a very convenient means for providing compressors of different capacities without changing their external dimensions or any of the parts excepting the rotor or impeller. is an extremely important advantage in the larger sizes of compressors since theproduction upon these sizes is relatively low and the cost of providing tools is relatively great. Therefore, by making it possible to use the same parts for a number of different sizes of compressors, a considerable saving in manufacturhig costs Is thus made possible. Of course, it is also possible to change the capacity by varying the speed of the compressor or. the length or diameter of the cylinder.

The rotor or impeller is preferably made of some form, of alloy steel such as nitralloy or mianite and has its outer surfaces case hardened and ground. In addition, the outer surfaces may, if desired, be plated with chromium or other plating capable of forming an excellent wearing surface. j

The inner side plates, as well as the divider blocks, may also be made of a similar material or a material capable of providing a good wearing surface together with such a material. Preferably, the divider blocks are made of a slightly softer material than the rotor or impeller so that the rotor or impeller will have as little wear as possible due to the sliding contacts of the divider block with its surface. However, since the pressure of the divider blocks upon the rotor is small, the wear will naturally be very small.

Instead of an elliptical periphery, the rotor may have a surface which provides constant acceleration and deceleration to the divider blocks so that the force that it is necessary to employ to hold the divider blocks in contact with the periphery of the rotor may be made as small as possible. Such a constant acceleration periphery may have its minor axes varied in a similar manher to the elliptic contour in order to provide diflerent capacities.

The lower divider block I22 operates in a bath of lubricant designated by the reference character I62 which fills the lower portions of the oil reservoirs I32 and I34, as well as the lower portion of the discharge chamber I38 and the passage I 38 beneath the divider block. This lower divider block I22 is therefore provided with an ample supply of lubricant. The movement of this divider block, however, also serves to actuate an oil pump which supplies oil under pressure to the bearings of the drive shaft 88 as well as to the passage I36 provided directly above the upper divider block I24 for providing direct lubrication to this upper divider block.

The piston I64 of this oil pump is provided with a flange at one end which is clamped to the outer end of the divider block by a plate I66 provided with a recessed portion containing an opening which receives the flanged end of the piston I64. This plate is fastened to the outer surface of the lower divider block by a plurality of screws located upon opposite sides of the piston I64. The piston is received within a cylinder formed in the upper end of the threaded plug I68 provided with a hex head. This threaded plug is threaded into the bottom of the central casting from beneath and has an inlet part III] in one wall which opens into a cut away portion I12 for feeding the oil from the passage I into the cylinder. This inlet opening is of the port type and permits oil to flow into the cylinder when the lower divider block and the piston moves upwardly to their uppermost positions.

At the bottom of the cylinder outlets on both sides are provided which are connected by a pair of passages I" to a pair of inserts I18 and I36, each provided with ball type check valves which act as discharge valves for the oil pump. One of these check valves is connected by a passage and a tubular connection I82 with the bearing bushing 88 and the bearing 86. The oil supplied through this tubular connection I82 spreads itself around the bearing in both directions and the portion leaking from the end of the bearing is conducted through a. passage I85 to a chamber formed in the side thrust washer or member I I6, which washer is provided with an aperture leading to the passage H2. The above mentioned chamber also receives excess lubricant from the other end of the bearing 86. The lubricant passes through this passage 2 to the chamber surrounding the thrust washer or member "'4 which is also provided with an aperture leading to a chamber formed in the thrust member directly at the face of the bearing bushing so that lubriquate supply of lubricant for the upper divider block. From this chamber I36 the lubricant flows through a cut I 98 made in the side plate 66 into a trough I92 which conducts this lubricant to a collecting basin I94 from which the lubricant by gravity passes through an oil passage I96 to a point over the shaft sealing ring 84 so that the shaft seal will be provided with an adequate supply of lubricant. The side portions of the rotor will be lubricated by, lubricant which is thrown out by centrifugal force from the chambers formed in the rotor to receive the thrust members. The periphery of the rotor may receive lubricant from that which lubricates its side faces and from the lubricant whichlubricates the divider blocks. The oil or lubricant reservoir is located upon the discharge side of the compressor so that only several pounds more than discharge pressure is required to circulate the lubricant to all parts of the compressor. By providing a lubricant reservoir upon the discharge side of the compressor, lubricating difflculties peculiar to refrigerating systems are avoided to a great extent.

In operation, evaporated refrigerant passes into the chamber I40 between the inner and outer end plates 68 and 12 through the inlet opening I42 and thence passes into the cylinder through the inlet openings I44 and I46, during the suction strokes of the compressor. The suction strokes begin whenever the major axis of the rotor passes each of these inlet parts I 44 and I46 and each suction stroke continues untilthe rotor has turned exactly 180". At the same time the gas already drawn into the cylinder in the two spaces between the inner wall of the cylinder and the flattened portions of the rotor is trapped between noses or lobes of the rotor and the divider blocks. Further movement of the rotor raises the pressure of this trapped gas or liquid and forces this trapped.- gas or liquid out through the discharge openings I52 and I54 which are controlled by the flapper valve I56 and I58. This places the compressed liquid or gas in the chamber I38 from which it escapes through the threaded outlet opening I 68 which connects to the supply conduit 36. This threaded outlet opening is located in the upper portion of the discharge chamber I38 and is protected by the trough I92 so that any lubricant carried from the compressor or pumping chamber may fall by gravity to the oil level I62 while the gas freed from lubricant is discharged through the opening I68.

As mentioned before the reciprocation of the lower divider. block operates the piston I64 in the cylinder formed as a part of plug I68. This plug is provided with discharge openings connected by passages I" to a plurality of check valves which in turn are connected by tubular connections and passages with the bearings of the drive shaft and the upper divider block.

It should be noted that the rotating parts are entirely symmetrical excepting for the two half round keys III) which might also be placed on the opposite side if desired. However, the weight of these keys is rather insignificant as compared to the weight of the rotor. All the rotating parts may be said to be statical and dynamically balanced, thus providing a unit which may operate at rather high speed without appreciable vibration. The divider blocks operate in exactly the opposite directions at exactly the same speed so that these plugs which are substantially the same in weight are substantially dynamically balanced. The piston of the oil pump and its connecting plate and screws are insignificant in weight as compared to the weight of the divider blocks and the mass of the compressor. However, if it is desired to correct for this additional weight the lower divider block may be drilled in order to reduce its weight a corresponding amount. Likewise, the rotor may be drilled on the side adjacent the half round keys an amount equal to the weight of keys, or similar keys may be placed in the passage H2 and another passage provided for lubricant. Thus, unbalance tending to promote vibration is almost entirely eliminated.

A more important feature of this pump, however, is the fact that the forces upon the rotor are balanced. The rotor I08 is perfectly symmetrical and has opposite fluid forces upon opposite sides of all planes passing through its axis. Likewise, the force of the divider blocks upon the rotor balance against each other. This makes it possible to make the bearings of the drive shaft comparatively small. This is of a great advantage in large rotary compressors and has solved one of the most perplexing problems in this type and size of compressor. This compressor is intended to operate at a motor speed of 1750 to 1800 R. P. M. However, it may also be operated at other speeds.

While this pump is particularly intended to be used for pumping gases in a refrigerating system, it may also be used for pumping either gases or liquids in other forms of apparatus with little or no modification except whatever is necessary to avoid contamination of the lubricant. This type of pump is much smaller and simpler than the conventional large size reciprocating pump and is readily applicable to all sizes, particularly to sizes of compressors of V. ton up to ten tons and more refrigeration capacity.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A rotary compressor having a casing .provided with a rotor and a plurality of divider blocks extending into contact with the rotor positioned in slots in the wall of the casing, said slots being located in the top and bottom of the casing, a drive shaft for said rotor extending outside the said casing through an aperture in the casing, a shaft seal for said drive shaft to prevent the escape of fluid from the casing, said casing being provided with lubricant confining walls above the upper divider block and below the lower divider block, and means for taking lubricant from the slot beneath the lower divider block and discharging the lubricant upon the upper divider block, and means for discharging .the surplus lubricant from the upper divider block upon the shaft seal for lubricating the shaft seal.

2. A rotary compressor having a casing pro-w vided with a rotor and a plurality of divider blocks extending into contact with the rotor positioned in slots in the wall of the casing, said slots being located in the top and bottom of the casing, said casing being provided with lubricant com fining walls above the upper divider block and below the lower divider block, means for taking lubricant from beneath the lower divider block and discharging the lubricant upon the upper divider block, said compressor being provided with an rotor shaft and a bearing surface outside the rotor chamber surrounding the rotor shaft, and means for conducting lubricant from said upper divider block to said bearing surface.

MELVIN P. PENN.

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