US3351272A

US3351272A - Vacuum pump

Info

Publication number: US3351272A
Application number: US518178A
Authority: US
Inventors: Irving C Jennings
Original assignee: Nash Engineering Co
Current assignee: Nash Engineering Co
Priority date: 1966-01-03
Filing date: 1966-01-03
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

Nov. 7, 1967 I. c. JENNINGS VACUUM PUMP 6 Sheets-Sheet 1 Filed Jan. 5, 1966 Nov. 7 1967 c. JENNINGS VACUUM PUMP 6 Sheets-Sheet 2 Filed Jan. 5, 1966 1N VENTOR. f? w/vg' a. Jaw/N45 Nov. 7, 1967 c. JENNINGS VACUUM PUMP 6 Sheets-Sheet 3 Filed Jan. 5, 1966 I. C JENNINGS VACUUM PUMP 6 Sheets-Sheet 4.

IN VENTOR. f? V/A/Q (f w/w/vg s Nov. 7, 1967 Filed Jan. 5, 1966 Nov. 7, 1967 c. JENNINGS 3,351,272

VACUUM PUMP Filed Jan. 5, 1966 6 Sheets-Sheet 5 Nov. 7, 1967 I. C.JENN|NGS VACUUM PUMP 6 Sheets-Sheet 6 Filed Jan. 5, 1966 INVENTOR. [kw/v4; 6'. JzvvA/m/gs I4770ENE YS United States Patent Oflice 3,351,272 Patented Nov. 7, 1967 3,351,272 VACUUM PUMP Irving C. Jennings, The Nash Engineering (10., South Norwalk, (form. 06856 Filed Jan. 3, 1966, Ser. No. 518,178 8 Claims. (Cl. 230-79) The present invention relates to multistage rotary pumps, and more particularly to a novel rotary pump of the Water ring having a multistage rotor of unitary construction and a stationary internal coaxial port member cooperating with the rotor to provide ,a multistage fluid pump.

Staging in known multistage rotary pumps involves a compartment having a rotary pump member for each stage, the stages being separated by pressure confining walls. Because of these complications a large high cost pump structure for a given capacity is required. Also, the distance between bearings for the shaft carrying the spaced rotary pump members is relatively large thereby a greater deflection of the shaft takes place leading to decreased efliciency and aifecting pump durability.

In accordance with the present invention a novel multistage pump is provided having a rotor comprising a' plurality of impellers and means for connection to a power input shaft combined in a unitary structure. The rotor has a central recess to receive a member having ports and passages which cooperate with the impellers for multistage operation. Passages in communication with appropriate ports in the port member conduct the pumped fluid from a suction line to a discharge line. As will appear more fully from the later detailed description, one of the passages has check valve means for starting the pump with combined outputs from both stages followed by operation as a multistage pump with the output of one stage passing through a successive stage. In .a preferred embodiment the rotor parts are integral. The invention, as embodied in a multistage vacuum pump, will be described in detail hereinafter to illustrate features and details of a fluid pump constructed in accordance with the invention, but the invention is equally applicable to a multistage compressor.

The projecting lobes of successive chamber cavities are preferably displaced successively in opposite directions with respect to the rotor axis to partially balance side thrust and to bring the discharge sector of one stage closer to the suction sector of the successive stage.

An object of the present invention is to provide a novel multistage fluid pump having a single unitary rotary member comprising a plurality of stage impellers.

Another object of the invention is to provide a novel multistage fluid pump having a member presenting fluid ports and passages nested in ,and cooperating with a single rotary pump member.

A further object of the invention is to provide a novel multistage fluid pump having a rotary pump member supported by a drive shaft and projecting into operative pumping position with respect to other pump parts.

Still another object of the invention is to provide a multistage fluid pump having novel means to facilitate starting.

A still further object is to provide a novel multistage pump comprising a single rotary pump member cooperat ing with an internal port member and a pump casing having lobes disposed to contribute to side thrust balance.

Illustrative embodiments of the invention are shown in structural detail in the accompanying drawing in which:

FIG. 1 is a transverse vertical section of a multistage liquid ring fluid pump embodying the invention;

FIG. 2 is a section taken along line 22 of FIG.

FIG. 3 is a section taken along line 3-3 of FIG. ,5 with a partial section at the drive shaft axis;

FIG. 4 is a fragmentary sectional View taken along line 44 of FIG. 5;

FIG. 5 is a sectional View in plan taken along the line 55 of FIG. 1;

FIG. 6 is a transverse horizontal section of a modification of the invention employing two port members;

FIG. 7 is a View in side elevation of the modification of FIG. 6 showing external manifolding;

FIG. 8 is a fragmentary section of the modification of FIG. 6 showing sealing details;

FIG. 9 is a partial section of a further modification, symmetrical about the line to the left of the figure, having three stages;

FIG. 10 is a partial section of the modification of FIG. 9 showing sealing details; and

FIG. 11 is a view in plan of a two stage pump illustrating the principle of operation of the liquid ring pump.

Referring to the drawing, FIGS. 1 to 5 show a two stage liquid ring vacuum pump embodying the invention. The theory of liquid ring pumps is described, by way of example, in United States Patent Nos. 1,797,980 and 1,718, 294, dated Mar. 24, 1931 and June 25, 1929, respectively.

A casing 10 rests on and is secured by suitable means (not shown) to a base 12. The casing supports a drive motor 15 having a shaft 16 projecting into the housing through a packing gland 18. The rotor 21 includes a radial top saver or shroud 23, a partition wall or second radial shroud 24 and a bottom cover or shroud 26. The first pumping stage impeller 28 comprises the top shroud 23 and the second shroud 24, joined by blades or vanes 29. Radially extending pumping chambers 31 (FIG. 5) are defined by the shrouds 23 and 24 and the vanes 29. The second pumping stage impeller 33 comprises the shrouds 24 and 26 and vanes 34. Pumping chambers 36 are defined in the manner mentioned above. A hub 37 located centrally of the shroud 23 is secured to the motor shaft 15 by a shaft shoulder and nut combination, as shown, or by other suitable means. In a preferred form of the invention, the rotor is an integral structure. However, the rotor parts may be secured together in any known and suitable manner to form a unitary structure.

The casing 10 has crescent-shaped lobes 39 and 40 (FIG. 5) to cooperate with the impeller chambers 31 and 36, respectively, to provide a pumping action as the rotor 21 turns in the direction of the arrow. This pumping action (FIG. 11) is secured by a Water or liquid seal 42 revolving in a circular or elliptical path within the lobe 39 by the action of vanes 29 of the first stage impeller 23, and a similar pumping action is secured by a Water ring seal 42' revolving in a circular or elliptical path Within the lobe 40 by the action of vanes 33 and second stage impeller chambers 36.

The liquid 42, conforming to the lobe due to centrifugal force, alternately recedes from and is forced back into the displacement chambers 31 within the impeller during rotation thereof. Stationary inlet ports 43 and 44 and outlet ports 46 and 48, later described, cooperate with the rotor pumping chambers to permit air or gas to be drawn into and discharged from the chambers after compression.

The

lobes

39 and 40, as they project eccentrically with respect to the rotor 21, are diametrically opposed with respect to the axis of the rotor so that the side thrust in one impeller caused by fluid compression in progressively presented chambers is balanced by side thrust in the next adjacent chamber. Also, as will appear, the discharge port of one stage is adjacent the intake port of the successive stage.

The hub 37 and shrouds 24 and 26 have openings machined to receive a tapered central member 51 having an inlet passage 52 and an outlet passage 53. The central member 51 is secured to the base 12 as indicated at 54. The member 51, described as being tapered, may be cylindrical within the scope of the invention. The arcuate length of the port 43 serves to place those chambers 31 of the impeller 28, that are increasing in volume as the seal liquid recedes in communication with the passage 52 in the central member 51. The inlet passage 52 communicates with a continuation passage 52a in the base 12. A pipe coupling at the end of the passage 52a receives any desired input conduit or pipe 56. The latter serves as a suction or vacuum line to a vacuum process chamber or other vacuum apparatus.

The outlet passage 53 communicates with the chambers 31 in which compression is occurring through the port 46. This passage is continued by a cavity 53a in the base 12. The valve seat 58 of a check valve 59 is mounted on the base 12 over the cavity 53a. A cap member 61 in fluid tight relationship to the base 12 connects the check valve outlet to a second cavity 63 in the base by way of a port 64. The cavity 63 connects directly with the output port 48 of the second stage by way of a passage 66. Coupling means 68 is secured to the base 12 to receive an outlet or discharge pipe 71. The latter may and usually does discharge fluid to the atmosphere but it may discharge against a higher pressure to any following apparatus.

Following starting of the pump of FIGS. 1 to 5, the pumped fluid, usually air, is drawn through the inlet passage 56 and port 43 by the first stage and is compressed. The air after compression, but not usually at a high absolute pressure, flows through the port 46, the check valve 59, the port 64 into the cavity 63 and outlet pipe 71. A portion of this air fro-m the port 46 is pumped by the second impeller stage through the port 44 and from the port 48 directly to the cavity 63 then to pipe 71. There are at this time two parallel discharge paths from the first and second stage pumps to the pipe 71. When the vacuum in the first stage impeller 28 reaches a point where it is becoming reduced due to its high compression ratio, the check valve closes and the impeller 33 draws air discharged by the first stage pump through port 46 in through the port 44 and discharges it into the passage 66 and cavity 63. The impeller 33 is now in full operation as the second stage of a two stage pump.

To seal the first stage from the second stage the recess 74 (FIG. 4) is connected through passages 76, 77 and 78 to the lobe of the second stage. The pressure of the water ring in the second stage is applied to the recess 74 to seal the impellers of both stages.

The pipe 81 and passage 83 supplies normal sealing water to the first stage. This water enters through the slight clearance between the port member and the rotor and an orifice (not shown) connected to the inlet passage 52 and supplies the necessary cooling water, The excess water is discharged through the passage 53 to the passage 53a until a high vacuum is reached, when this water is handled by the second stage impeller through the port 44, then discharged into the cavity 63.

At low vacuum, seal water is forced into the chambers and into spaces between the end shrouds and the pump casing to cause surging. This is relieved by venting the water from the shroud spaces through an orifice 17, and water is returned to the shroud when the vacuum is high, from a water pool formed in the space 82 through conduit 85. A surge relief system is fully described, by way of example, in United States Patent No. 3,217,975, granted Nov. 16, 1965. Cooling Water for the gland 18 flows from the lobe 39 through the passages 83 and 84.

FIG. 6 shows a modification of the invention as embodied in a duplex pump having two pump sections 86 and 88 employing two central ported members 510 and 51d. Ports and passages in the pump sections serving the same purpose as in FIGS. 1 to 5 are designated by the same reference characters with the sufiixes c and d added.

The piping and manifolding of FIG. 7 serves the same purpose for the combined output of the pump sections as the passages and cavities of FIGS. 1 to 5.

FIG. 8 is analogous in its manner of presentation to FIG. 4 and shows the sealing means employed in the embodiment of FIG. 6.

FIG. 9 shows a modification with three stages per pump section. Only one-half of the pump is shown since it is symmetrical about the line 91. It is noted that the lobe of the third stage 90 is in phase or line with that of the first stage and diametrically opposed to the one of the second stage. Reference characters are designated by suffixes e and f and g. In this pump the air is drawn in through the passage S2e and discharged into the passage 53c through a check valve 592'. When the vacuum reaches a point where second stage operation occurs, air is discharged through 63s. When the third stage is required, a check valve closes and all the air and water are discharged through a pipe 97.

FIG. 10 illustrates the method of sealing the three stages from each other as used for the two stage pump of this invention, wherein somewhat similarly to the prior embodiments, the pressure of the water ring in the third stage is applied to recesses 74g and 7411 through passages 76g, 77g and 78g.

It is seen that the invention provides an integrally formed multistage fluid pump of the liquid ring type, in which the rotors of the successive stages are integral and cooperate through a central port member thereby eliminating the need for separate compartments for the hitherto individually arranged rotors which in turn required large spacing between the supporting structures causing pronounced structural disadvantages leading to shortened and decreased durability of the apparatus.

lthough the invention has been described with reference to specific embodiments thereof, it is not intended that the invention should be limited to such specific embodiments only, but rather defined in the light and scope of the appended claims.

What I claim is:

1. A multistage pump comprising a casing, a rotatable drive shaft projecting into said casing, said casing surrounding a plurality of stage lobes disposed progressively in the direction of the axis of said drive shaft, a centrally recessed rotor comprising a plurality of successive stage impeller means in communication with said recess, and a stationary member having an inlet and an outlet port for each stage, said member having internal inlet and outlet passages in communication with said ports, said member nested in and coaxial with said central recess in said rotor, said ports and passages placing each outlet passage in communication with an inlet passage of an axially successive stage.

2. A multistage fluid pump comprising a plurality of pumping stages, each stage having fluid inlet and outlet means, total outlet means for said stages, a connection having a check valve from an early stage of said pump to said total outlet means, connection means from said early stage to a later stage, direct connection means from a later stage to said total output means, said check valve means being operative to close when the fluid pressure in said first stage is reduced thereby to cause said pump stages to operate as a multistage pump.

3. A multistage rotary pump having a central drive shaft, a pair of spaced centrally recessed rotors secured to said shaft in spaced relationship, a casing surrounding a plurality of sets of stage lobes disposed progressively in the direction of the axis of said shaft, each rotor having a plurality of impeller means, one for each lobe of said sets of lobes, a plurality of stationary members, one for each set of stage lobes, said stationary members having an inlet and an outlet port for each stage and internal inlet and outlet passages in communication with said ports, each of said means nested in and coaxial with said central recess in its respective rotor, and said ports and passages placing each outlet passage in communication with an inlet passage of an axially successive stage.

4. A multistage pump as claimed in claim 1, operable with a liquid ring seal, further including means for sealing the respective stages of said pump from one another by diverting a portion of said sealing liquid into a recess formed between said stages.

5. A multistage pump as claimed in claim 1, wherein the lobes of adjacent stages are disposed in a diametrically opposing manner.

6. A multistage liquid ring pump comprising a casing member having a plurality of inside cylindrical portions, a base member having a plurality of fluid conducting passages, a shaft extending into said casing member, a recessed rotor having -a plurality of vaned pump stage impeller means, means adjacent one end of said rotor for securing said rotor to said shaft with the outer periphery of said impeller means in non-contacting eccentric relationship with said casing member cylindrical inside portions, a stationary port member circular in cross-section secured to said base and extending into said rotor recess in coaxial relationship therewith, a plurality of pairs of inlet and outlet passages in said port member with each pair in operative register with a corresponding impeller means connecting the outlet passage of one pair to the inlet passage of a succeeding pair operating at a higher absolute pressure, hydraulic surge preventing means for said pump operative during pump operation at low absolute pressures, and pump discharge means responsive to fluid pressure change in one of said impeller stages to cause at least two of said stages to pass fluid to the pump discharge means under one pressure condition and upon a pressure change to pass the total pumped fluid to said pump discharge means.

7. A multistage pump as claimed in claim 1, operable with a seal liquid, further comprising conduit means in communication with said stage lobes and means for removing seal liquid from said stage lobes through said conduit means to prevent surging when said pump is operated at low vacuum levels below the normal operational vacuum level thereof.

8. A multistage liquid ring pump comprising a casing member having a plurality of inside cylindrical portions, a base member having a plurality of fluid conducting passages, a shaft extending into said casing member, a recessed rotor having a plurality of vaned pump stage impeller means, means adjacent one end of said rotor for securing said rotor to said shaft with the outer periphery of said impeller means in non-contacting eccentric relationship with said casing member cylindrical inside portions, a stationary port member circular in cross-section secured to said base and extending into said rotor recess in coaxial relationship therewith, a plurality of pairs of inlet and outlet passages in said port member with each pair in operative register with a corresponding impeller means connecting the outlet passage of one pair tothe inlet passage of a succeeding pair operating at a higher absolute pressure, and pump discharge means responsive to fluid pressure change in one of said impeller stages to cause at least two of said stages to pass fluid to the pump discharge means under one pressure condition and upon a pressure change to pass the total pumped fluid to said pump discharge means.

References Cited UNITED STATES PATENTS 1,797,980 3/1931 Jennings 23079 2,195,174 3/1940 Jennings 23079 2,211,316 8/1940 Blom et al. 23079 3,154,240 10/1964 Jennings 23079 3,209,987 10/ 196-5 Jennings 23079 3,217,975 11/1965 Jennings 23079 DONLEY J. STOCKING, Primary Examiner. HENRY F. RADUAZO, Examiner.

Claims

1. A MULTISTAGE PUMP COMPRISING A CASING, A ROTATABLE DRIVE SHAFT PROJECTING INTO SAID CASING, SAID CASING SURROUNDING A PLURALITY OF STORAGE LOBES DISPOSED PROGRESSIVELY IN THE DIRECTION OF THE AXIS OF SAID DRIVE SHAFT, A CENTRALLY RECESSED ROTOR COMPRISING A PLURALITY OF SUCCESSIVE STAGE IMPELLER MEANS IN COMMUNICATING WITH SAID RECESS, AND A STATIONARY MEMBER HAVING AN INLET AND AN OUTLET PORT FOR EACH STAGE, SAID MEMBER HAVING INTERNAL INLET AND OUTLET PASSAGES IN COMMUNICATION WITH SAID PORTS, SAID MEMBER NESTED IN AND COXIAL WITH SAID CENTRAL RECESS IN SAID ROTOR, SAID PORTS AND PASSAGES PLACING EACH OUTLET PASSAGE IN COMMUNICATION WITH AN INLET PASSAGE OF AN AXIALLY SUCCESSIVE STAGE.