US2898032A - Sealed motor-compressor unit - Google Patents

Description

g- 4, 1959 B. KATZENBERGER SEALED MOTOR-COMPRESSOR UNIT 6 Sheets-Sheet 1 Filed May 18, 1956 Ill/Ill!!!I!!!IIIllIIII!!!IllIll/IIIIIl/lIl/I/Il/l/l/ n I I I n I 4, 1959 B. KATZENBERGER SEALED mowomcommsssoa UNIT 6 Sheets-Sheet 2 Filed May 18, 1956 6 Sheets-Sheet 3 Filed May 18, 1956 Ill/Ill? 6 Sheets-Sheet 4 Filed May 18, 1956 ,1959 B. KATZENBERGER 2,898,032

SEALED MOTOR-COMPRESSOR UNIT Filed May 18, 1956 6 Sheets-Sheet 6 mmmu 2,898,032 SEALED MOTOR-COMPRESSOR UNIT Application May 18, 1956, Serial No. 585,697

Claims priority, application German September 29, 1955 4 Claims. c1. 230-4139 My invention relates generally to' hermetically sealed motor compressor units of the rotary type and, in one of its more specific aspects, to rotary-piston compressors in which a crescent-shaped working space between piston and cylinder is partitioned by one or more sliders into variable-volume chambers which periodically induct fluid and from which the fluid, upon volume reduction of the chamber, is periodically discharged in compressed condition.

In the electrically driven units of the rotary-piston type as heretofore known, the crescent-shaped working space is located between the stator and the rotor of the electric motor. Aside from the fact that the rotor is subjected to eccentric unbalance forces so that considerable wear is imposed upon the bearings, the operation of the compressor unit is noisy to an extent particularly troublesome when the units are used in domestic refrigerators. The known motor-compressor units of this type further require insertion into an oil-filled capsule for sealing and cooling.

A further disadvantage of the known motor-compressor units of the rotary piston type is the fact that their size cannot be reduced below a certain minimum. Particularly the crescent-shaped working space cannot be reduced below a certain size determined by the minimum size of the rotor. In consequence, particularly with United States Patent i small-size cooling plants, such compressors, as a rule,

are overdimensioned' in relation to the required power output.

It is an object of the invention to eliminate or minimize the abovementioned disadvantages.

To this end, and in accordance with a feature of th invention, the working space in a motor-compressor unit is formed by a bore traversing the rotor of theelectric motor or other prime mover; the rotor being rotatable about a stationary shaft. l

According to another feature, relating to rotary-piston compressors with a crescent-shaped working space, the bore in the rotor of the drive motor is eccentric and the stationary shaft forms the pistonof the compressor and is provided with the slider or sliders for partitioning the crescent space.

In accordance with another feature of the invention the eccentrically bored rotor is'formed essentially as a cylinder and is journaled on both axial ends in respective shoulder structures that are firmly joined with the stationary central shaft and also provide a seal for the crescent-shaped working space. In a preferred embodiment of the invention the central shaft forms an integral piece with one of the two shoulder structures, whereas the second shoulder structure, after placing the rotor over the shaft, is subsequently fixed to the shaft, for instance by means of a screw bolt.

According to another feature of the invention the two shoulder structures on opposite sides ofthe rotor are provided with concentric ring-shaped grooves or steps,

and respective spring-biased sealing rings are seated in the grooves or on the steps so as to press against the ad- Patented Aug. 4, 1959 jacent repective front faces of the'rotor. These front faces are designed as slide rings into which the ring portions of the, rotor, when designed as'a squirrel-cage rotor, are inserted. However, it is also possible to design the ring-shaped conductors of the rotor themselves as slide rings for cooperation with the spring-biased sealing rings.

Instead. of providing the above-mentioned springbiased sealing rings, the seal may also be effected by means of labyrinth seals located between the. shoulder structures and the adjacent respective front faces of the rotor. This is particularly suitable when the stator of the unit is inserted into a capsule sealed by means of the stationary shoulder structures. Then, any average pressure within the capsule due to leakage losses of the gases to be compressed has no detrimentalefiect upon the efficiency of. the compressor.

By virtue of the fact that the crescent space is located inside the rotor, the working space of the compressor can be made as small as may be desired. For instance, this space may be given a volume of 5 cmfi, corresponding to an axial length of the working space of 5 cm., a shaft diameter of 2.5 cm., and aneccentricity of the cylinder bore of approximately 2.7 mm. In such an embodiment, the rotor may have an outer diameter of approximately 5 cm., so that the mass forces due to unbalance can readily be balanced by a counter weight and cannot result in damage to the bearings. Since further the stator fully surrounds the rotor and is enveloped .within the sealed capsule, any operating noises, if at all observable, are damped to such an extent that the compressor operation is virtually noiseless.

The inner wall of the eccentric bore in the rotor is polished; or, when providing a correspondingly larger bore, an interiorly polished sleeve is inserted. In either case the spring-biased slider, disposed. in a longitudinal groove of the stationary center shaft, rests against a polished surface. Such an inserted sleeve can readily be exchanged if in time an appreciable amount of wear has occurred.

According to a modification within the invention, the above-mentioned two shoulderstructures are given identical design, and both are firmly joined with the center shaft, for instance :by screw bolts. This is advantageous for the manufacture of the unit because, if needed, the shoulder structures can be exchanged and the machining of the center shaft, such as the milling of the grooves and the polishing of the shaft surface, is facilitated. In principle, it is also possible to mount the slider or sliders on the rotor and to let them slide about the stationary shaft.

In 'both cases, the supply and discharge of the gas to be compressed, particularly of the cooling agent, can beeifected by means of ducts or bores which extend through one or both of the shoulder structures in angularly spacedrelation to each other. At least the duct on the pressure side of the compressor is provided with a check valve.

The stationary shaft may be provided with more than one slider and, accordingly, more than one pair of supply ducts may be provided in the shoulder structures. Depending upon 'the interconnection of the bores or ducts, the partial working spaces partitioned-off by means of the sliders from the total crescent-shaped working space, may be connected in parallel or in series relation with each other.

In the latter case it is particularly favorableto provide the stationary center shaft with two sliders, both extending parallel to the axial direction but forming an angle with each other so that 'a larger chamber and a smaller chamber are partitioned off the crescent-shaped total space. This affords two-stage compression by connecting the pressure side of the larger chamber through an intermediate cooler with the suction side of the smaller chamber.

The above-mentioned and further objects, advantages and features of the invention will be apparent from the following description of the embodiments shown by way of example on the accompanying drawings in which:

Fig. 1 is an axial section through a motor compressor unit.

Fig. 2 is a cross section through the same unit, the section being taken along the line denoted by IIII in Fig. 1.

Fig. 3 shows a modified detail of the rotor in the unit of Fig. 1 on a larger scale.

Fig. 4 is a cross section through a motor-compressor unit with two working chambers operating in parallel, the unit being otherwise similar to that shown in Figs. 1 and 2.

Fig. 5 shows a cross section through a motor-compressor unit, otherwise similar to the one illustrated in Figs. 1 and 2, but modified for two-stage operation.

Fig. 6 shows an axial section through a further motor compressor unit.

Fig. 7 is a cross section through the same unit, the section being taken along the line VII-VII indicated in Fig. 6.

Fig. 8 is a partial sectional view of the unit shown in Fig. 6, the section being taken along the line indicated at VIII-VIII in Fig. 6.

Fig. 9 is an axial section through still another motorcompressor unit.

Fig. 10 is a cross section through the same unit taken along the line XX indicated in Fig. 9; and

Figs. 11 and 12 show two partly sectional views of two further compressors according to the invention.

The motor-compressor unit according to Figs. 1 and 2 comprises the stator 1 and the rotor 2 of an electric induction motor. The stator 1 is enclosed by a capsule sleeve 3. The rotor consists mainly of a stack of laminations and has an eccentric bore lined by a metal sleeve 8. The rotor carries a squirrel-cage conductor structure with ring-shaped end-pieces 9, and is rotatable about a stationary shaft 5 which is centrally located and forms a crescent-shaped working space 4 together with the rotor.

The rotor is journaled between angular shoulders formed by respective shield structures 6 and 7. The lower shield structure 6 forms a single integral piece with the stationary shaft 5. The upper shield structure 7 is a separate piece but is rigidly connected with shaft 5 by means of a fastening screw 14.

The inner surface of sleeve 8 and the surface of shaft 5 are polished. The end faces of rotor 2 form slide rings and serve as a support for the ring members 10 of the squirrel-cage structure, although these ring members may also be formed as an integral part with the ends or slide rings 9 of the rotor as is shown in Fig. 3. The rings 9 slide on shoulder steps of the shield structures 6 and 7 respectively. The shoulder on the upper shield structure 7 is provided with a ring-shaped groove for a sealing ring 11 which is forced against the slide ring 9 of the rotor by an annular spring 17 or the like elastic member (Figs. 1, 3).

If desired, such a sealing ring may also be provided on the shoulder of the other shield structure 6. This is preferable especially in designs where both shield structures are of identical shape and are both manufactured as separate pieces to be subsequently joined with the stationary shaft 5.

The upper shield structure 7 is provided with a suction duct 12 and a pressure duct 13. The two ducts, at their respective points of communication with the working space, are spaced from each other a distance equal to the thickness of a slider 15 which extends longitudinally through a groove in shaft 5. The slider 15 is biased against the wall of sleeve 8 by means of a spring 16 preferably consisting of a wavy leaf spring. The pressure duct 13 may be equipped with a check valve (not illustrated) In principal, the compressing operation of the illustrated unit is the same as that of the known rotary-piston compressors with crescent-shaped working space, except that according to the invention the piston consists of the stationary center shaft and that the cylinder, ro- 'tating about the shaft, is formed by an eccentric bore in the rotor of the electric drive motor itself.

While in the embodiment according to Figs. 1 and 2 only one slider 15 is provided on the center shaft 5, there are cases where it is desirable to operate with two sliders such as those shown in Figs. 4 and 5 with reference to a motor-compressor unit otherwise similar to the one according to Figs. 1 and 2. The two sliders 15 and 15a are biased by respective springs 16 and 1611 located in respective grooves of the stationary shaft. The provision of two such sliders makes it necessary to also provide the pressure and suction ducts 12, 12a and 13, 13a in pairs.

The unit according to Fig. 4 is designed for connecting the two suction ducts 12 and 12a in parallel and also connecting the two pressure ducts 13 and 13a in parallel. For this purpose, the two sliders 15 and 15a are disposed opposite each other.

In contrast thereto, the corresponding sliders shown in Fig. 5 form a right angle between each other so that the compressor chambers partitioned off by the two sliders are unequal. This design is intended for connecting the pressure duct 13 of the larger working chamber 4a with the suction duct 12a of the smaller working chamber for two-stage compression. In this case it is necessary to connect an intermediate cooler (not shown) between the ducts 12a and 13. The intermediate cooler may be located Within or on one of the two shield structures of the unit.

A motor-compressor unit according to the invention is applicable for various purposes, such as for the compression of coolants or the compression of gas or air. The unit can be given very small size, such as desired for the aerating of home aquariums. Such compressors are further suitable as liquid pumps.

Although the invention is of particular advantage for units of small size, it is also favorably applicable for units of large size. The design of the rotor as a squirrel-cage rotor of an induction motor is particularly suitable and simple for the purposes of the invention. In principle, however, any other type of rotor may also be used. The provision of an electric drive, furthermore, is not an indispensible requirement for all embodiments according to the invention. The eccentric bore for the crescent-shaped working space may also be provided within the rotor of other prime movers, for instance in the rotor of a turbine or similar rotary drive.

While the above-described embodiments are equipped with ring-shaped bearings which, if desired, may be given a self-lubricating design, it is also possible to operate with an oil-sump in the conventional manner. As mentioned above, labyrinth seals or the like may be used. In that case the rotor may also be journaled by means of ball bearings disposed between the front faces of the rotor and the shoulders of the stationary or capsule structure.

In the embodiment shown in Figs. 6 to 8, the electric motor of the unit is accommodated within a sealed capsule composed of two portions 18 and 19 which are hermetically sealed by welding along the seam denoted by 20. The motor comprises a stator 21 and a rotor 22, each comprising a stack of laminations. The rotor has an eccentric bore lined by the cylinder sleeve 24 of the compressor cylinder. The sleeve has its annular ends provided with respective slide rings 25 and 26. The slide rings 25, 26 are rigidly joined with the rotor 22 and the cylinder sleeve 24 and have their respective slide faces smoothly finished or polished. Located within the cylinder sleeve 24 is a second sleeve 24a to operate as a tumbling ring in accordance with a principle known as such for capsule-type blowers. The tumbling sleeve 24a, during operation of the unit, assumes a revolving speed smaller than that of the rotor.

The piston 27 of the compressor is stationary and is rigidly connected or integral with a shaft 28. The piston 27 is further rigidly connected with a valve plate 29 and with a sealing ring 30. The valve plate 29 accommodates a pressure valve 31 and the bore for the suction duct 32. Guided in a longitudinal groove of the piston 27 is a slider 35 biased by a spring 36 to divide the suction chamber from the pressure chamber of the cylinder space.

The shaft 28 is journaled in a bearing 33 which is rigidly connected with the rotor 22 by means of webs 34. Schematically indicated at 34 are balance weights which are mounted on the web 34 for compensating the mass forces resulting from the unbalance of the rotor 22. The piston 27, the shaft 28' and the valve plate 29 may be formed of a single piece. v

Due to the careful machining or polishing of the surfaces between the sealing ring 30, the valve plate 29 and the slide rings 25, 26, a sufiicient seal between the pressure side and suction side is as a rule secured. However, if in any particular case this type of seal is not sufficient and a spring-biased design of the sealing part is desired, then a modified construction as represented, in Figs.-9 and may be given preference.

.According to Figs. .9 and 10 the capsule of the unit is composed of three parts 37, 38, 39, hermetically joined with each other by welding seams 40. The cylindrical middle portion 37 of the capsule carries the stator 41 of the electric motor. The bottom portion 38 of the capsule is provided with openings for the suction duct 52 and the pressure duct 51. The cover portion 39 may receive a bore for a second suction duct 52a, aside from carrying the electric connection components 62 and 63.

The rotor 42 has an eccentric bore lined by a cylinder sleeve 44 within which the crescent-shaped working space 43 of the compressor is formed. As in the embodiment of Figs. 6 to 8, the cylinder sleeve 44 has its front faces provided with slide rings 45, 46 which cooperate with sealing rings 49, 50 biased by springs 56, 58. The springs 56, 58 bear against shoulder plates 55, 57 on the stationary center shaft 48. Shaft 48 also carries the piston 47 which may be formed of a single piece together with the shaft 48 and together with at least one of the shoulder plates 55 or 57. The piston 47 has a longitudinal groove for the slider 59 which, biased by a spring'60, separates the pressure and suction chambers of the working space 43 from each other.

The rotor 42 has projections 64 and 64a which, together with bridge pieces 53 and 53a, enclose the springy sealing parts 49, 55, 56 and 50, 57, 58, and are guided on rings 54, 54a mounted on the shaft 48. The rings 54 and 54a serve to journal the rotor on shaft 48.

The arrangement of the compressor within the rotor of a drive motor can also be realized if the rotor is bored centrically and possesses on its inner side vanes or similar parts that act upon the flow of fluid by axial-compressing operation or the like, or if the inner side of the rotor possesses a slide way for a reciprocating piston.

Embodiments of this kind are illustrated in Figs. 11 and 12. Fig. 11 exemplifies the application of the invention to a coolant compressor for operation in a closed circulating system. Fig. 12 shows an air compressor of a similar design. Corresponding parts in these two embodiments are denoted by the same respective reference numerals. According to each of Figs. 11 and 12, the stator housing of the electric motor driving the com pressor is composed of a cylindrical portion closed at both ends by shields 68 and 69 which are mounted on respective flanges 17 of the cylindrical portion. The stator package of larninations 71 and the appertaining stator windings are mounted on the cylindrical member 67.

The shields 68 and 69 of the stator housing are rigidly connected with the stationary shaft of the electric motor by means of fastening screws. In the embodiment of Fig. 11 the shaft 80 has central bores in both ends 79 and 89 respectively. These bores form part of the pressure conduit 81 and suction conduit 91 respectively. Both conduits branch at their respective inner ends into several passages which open into the working space 73 of the rotor. This working space is formed between a sleeve 74 which carries the lamination stack 72 and windings of the motor armature, and is limited by front members 82 and 83 which are sealed against the stack 72. The inside of sleeve 74 is provided with impellor vanes that project radially inward and are fastened to the sleeve by means of part 75. The stationary shaft 80 carries several rows of guiding vanes 77 fastened by means of members 78. The front members 82 and 83 of the rotor structure form also the bearings and guides for the rotor. For this purpose the members 82 and 83 have guiding faces cooperating with slide rings 84 which are pressed against the rotor structure by means of springs 85' bearing against the respective shields 68 and 69 of the stator housing. In addition a spring bellows 86 is provided on each axial side of the rotor for additional sealing, particularly of the annular gap between the slide rings 84 and the stationary shaft 80.

The compressor according to Fig. 11 is particularly suitable for compression of a coolant in a refrigerating circulation system. The embodiment of Fig. 12 is particularly designed as an air compressor.

In the compressor according to Fig. 12 the pressure side is designed in the same manner as described above with reference to the embodiment Fig. 11. However, on the suction side of the compressor the shield 68 of the stator housing and also the adjacent member 82 of the rotor are provided with openings 91 for the entrance of the air to be compressed. The bearing portion 90 of the rotor adjacent to shield 68 is not sealed against the ambient air but is simply journaled on the stationary shaft in a suitable manner.

According to all illustrated embodiments, the invention affords in rotary-piston motor-compressor units a considerable reduction in overall space requirements and also facilitates completely capsulating the unit.

It will be apparent to those skilled in the art, upon a study of this disclosure, that my invention permits of various modifications and may be embodied in structures other than those specifically illustrated and described, without departing from the essential features of the invention and within the scope of the claims annexed hereto.

I claim:

1. A sealed motor-compressor unit, comprising an electric motor having a totally enclosed stator structure and a rotor mounted Within and journaled on said structure in concentric relation thereto, said rotor having an annular stack of laminations, a cylinder sleeve extending through said stack parallel to the axis thereof and eccentrically positioned with respect to the said rotor, said cylinder sleeve being firmly seated within and joined with said stack along substantially the entire length and periphery of said cylinder sleeve so as to form a rigid unit with said stack, an inner sleeve loosely positioned within said cylinder sleeve and forming a tumbling ring slidingly engageable with said cylinder sleeve so as to rotate at a speed of rotation less than that of said rotor, a stationary shaft concentric with respect to the periphery of said rotor extending through said inner sleeve and forming with the inner surface of said inner sleeve a rotatable crescent-shaped compressor space around said shaft, said shaft being rigidly joined with said stator structure and having slot means formed radially therein, compressor blade means slideably positioned Within said slot means and extending radially from said shaft into said compressor space and against the inner surface of said inner sleeve to partition said compressor space, means fixedly attachedto said shaft for closing in the ends of said compressor space, inlet and outlet duct means extending through and. fixedly located within said stator structure and forming respective openings at stationary and angularly mutually spaced locations within said crescentshaped compressor space, said outlet duct means being provided with check valve means, whereby as said rotor rotates with respect to said shaft the volume of said crescent-shaped space changes to pass fluid through said compressor space and through said duct means.

2. A sealed motor-compressor unit according to claim 1, including resilient means within said slot means for urging said blade means radially outward from said shaft, and counterweights joined with said rotor for compensating the mass forces resulting from the unbalance due to the eccentric position of said cylinder sleeve with respect to the periphery of said rotor.

3. A sealed motor-compressor unit according to ciaim 1, said means for closing in the ends of said compressor space comprising annular shoulder members rigidly joined at each end of said shaft, the ends of said rotor forming journalling means with said shoulder members, sealing ring means between said annular shoulder members and the ends of said rotor, and biasing means positioned within said shoulder members and operative to urge said sealing ring means against the ends of said rotor.

4. A sealed motor-compressor unit according to claim 1, said compressor blade means comprising two sliders, both extending parallel to the axial direction of said shaft and forming an angle with each other to thereby partition off said compressor space into a larger chamber and a smaller chamber, said outlet duct means including means connecting the'pressure side of said larger chamber with the suction side of said smaller chamber to afi'ord'tWo-stage compression in said compressor space.

References Cited in the file of thispatent UNITED STATES PATENTS 425,106 Nichols Apr. 8, 1890 1,888,544 Simmen Nov. 22, 1932 1,929,996 Wilson Oct. 10, 1933 1,929,997 Wilson Oct. 10, 1933 1,929,998 Wilson Oct. 10, 1933 1,960,267 Kagi May 29, 1934 1,983,997 Rolaff Dec. 11, 1934 2,091,752 Davis Aug. 31, 1937 2,100,014 McCracken Nov. 23, 1937 2,194,561 Mason Mar. 26, 1940 2,249,059 Stenger 3 July 15, 1941 2,319,730 Garraway May 18, 1943 2,344,028 Curry Mar. 14, 1944 2,380,819 Allbaugh July 31, 1945 2,430,509 Hoover Nov. 11, 1947 2,670,895 Steensen Mar. 2, 1954 2,693,313 McAdam Nov. 2, 1954 2,711,286 McAdam June 21, 1955

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