US2459071A - Sliding vane air compressor and exhauster - Google Patents

Description

Jan. 11, 1949. H. A. GARRISON i 2,459,071

SLIDING VANE AIR COMPRESSOR AND EXHAUSTER Filed Sept. 8, 1945 I 2 Sheets-Sheet 1 IN VEN TOR. HARRY A. GARE'ISOH AHbmeu Jan. 11, 1949.

H. A. GARR! SON 2,459,071

SLIDING VANE AIR COMPRESSOR AND EXHAUSTER Filed $91511. 8, 1945 2 Sheets-Sheet 2 I INVENT OR. HAEEI A GAREISON Patented Jan. 11, 1949 SLIDING VANE AIR COMPRESSOR AND EXHAUSTER Harry A. Garrison, Minneapolis, Minn, assignor of one-half to Joe F. Schwan, St. Paul, Minn.

Application September 8, 1945, Serial No. 615,152

6 Claims. 1

My invention relates to a rotary air compressor and exhauster and has for its object to provide in combination a gas compressor which also may be used as an exhauster for producing vacuum wherein a cylindrical rotor carries radially movable piston members, said rotor and members being mounted within a chamber whose outer surface is not circular in cross-section but is made up of a composite curve embodying in parts circular arcs concentric with the center of the rotor and in other parts non-circular arcs which are not concentric and which follow substantially the lines of an Archimedian spiral.

In connection with rotary compressors also used to produce high degrees of vacuum, the principle in general is to have a radially movable piston member operated by a cylindrical rotor within a cylindrical casing which is of larger diameter than the diameter of the rotor and has its central axis eccentric to the axis of the rotor. This leaves an elongated crescent-shaped chamber surrounding the rotor, one side of which has admitted thereto gas or air (or for that matter liquid fluid) at normal or vacuum pressures, and the other side of which receives this volume of gas or other fluid, and which, in front of the piston, is compressed and discharged through an opening or openings against the pressure of the fluid into which it is dischargedeither that of the compressed gas or the normal pressure of air when the device is used for producing vacuum.

There is thus in this form of apparatus always a differential pressure between th pressure side and the intake side of the compressor which difference may be very high with either high compression of gas or very low vacuum.

Because of this fact, the compression or evacuation of gas there is, of course, a strong tendency toward back pressure leakage past the contacting part of the radially movin rotating pistons from the pressure side to the intake side of the device. The pistons may have quite extensive plane faces engageable with side Walls, which, with an appropriate oil film, will effectively resist this tendency and prevent cross leakage.

The problem has always been to prevent leakage where the ends of the pistons engage the circular wall of the pumping chamber. The reason for this is that it has been found to be impractical or impossible to have any considerable extent of surface engaging the curved surface of this back wall. I

Thisapplication is an improvement of and an 2 advance over my Patent No. 2,046,873, granted July 7, 1936.

In that patent I proposed to remedy the abovenoted difiiculty by forming the chamber within Which the pistons operate not as truly circular in cross-section, but as made up in a series of arcs of circles excentrically disposed in such manner as to cause a gradual merging between the several circular arcs. I also formed' her at its widest part to give long contact at that point.

This arrangement has proved very effective for pumping liquid such as water, for which it was primarily designed. But in pumping gas for high compression or a high degree of vacuum the face of the piston in each case is tipped so there is substantially little more than a line contact along the important compression are where leakage is most likely to take place.

Another serious difiiculty which has been encountered in connection with rotary compressors and evacuators for various gases, has been that where the rotor is rotated at high speed there has resulted a great deal of unpleasant noise, usually in the form of a throbbing or thumping eiiect and this noise has generally been accompanied and probably caused by leakage of gas from the pressure to the intake sides of the rotating pistons. 1 V

I have discovered a manner of curvingthe inside walls of the pumping chamber which is not in cross-section circular or made up entirely of circular arcs, but in which the essential curves at the inlet side and particularly at the compression side of the pumping chamber follow the lines of an Archimedian spiral, so, when pistons having a multiplicity of appropriate curves thereon are employed, a substantial area of contact between the piston ends and such curved walls may be efiected.

I have discovered also that, by forming the piston members with ends, considerably wider than heretofore has been deemed desirable, and forming on the ends of said piston membersthree sets of curves corresponding to the sets of curvatures of the inner walls of the pumping chamber, I am able to maintain an extensive area of contact between the piston ends and the walls of the pumping chamber throughout the entire rotation of the pumping pistons.

I have also discovered that, if the pistons extend in opposite directions so as to have their ends engage the walls of the pumping chamber in opposite directions, by making said pistons sectional and providing spring means forcing them in opposite directions, a very firm and certain contact between the appropriate curved portions of the piston ends and of the inner walls of the pumping chamber may be maintained at all times, even when the rotor carrying the pistons is being rotated at very high speed, and the unpleasant throbbing and thumping will be almost entirely eliminated.

It is a principal object of my invention, therefore, to provide a cylindrical rotor having guideways extending radially through the same, in which operate radially movable piston members carried about the axis of the rotor with the rotor, inside of a pumping chamber of substantially larger cross-sectional area than the crosssectional area of the rotor, and wherein the inner walls of the pumping chamber and the outer ends of the pistons are severally provided with cooperating and differently curved surfaces such that there will at all times be an extended area of contact transversely between the ends of the pistons and the inner surface of the pumping chamber.

It is a' further object of my invention to provide a cylindrical rotor eccentrically mounted within a pumping chamber, so as to form a crescent-shaped pumping chamber proper, whose inner wallscomprise circular concentric arcs contactedonone side by the rotor and most widely spaced on the other side from the rotor and whose inner walls extend between the above-noted arcs substantially along the lines of an Archimedean spiral.

It is afurther object of my invention to provide radial slots extending through the body of the rotor and-to:mount in said slots radially movable piston members ,of considerable width and to form on the ends of said piston members sets of three curves each, the inner of which will be in the circular arc of the rotor and of the outer wall of the pumpingchamber where the two contact, andwill be concentric with the circular arc of the outer wall of the pumping chamber diametricallyopposed thereto, the other two curves of the ends of the pistons at each side of the circular'curves being that of the respective Archimedean spiral curves extending between the above-named circular arcs, which will thus effect extended transverse area of contact between the ends of the pistons and all parts of the inner walls of the pumping chamber.

It is a further object of my invention to provide the pumping chamber proper with a series of inlet openings leading through the walls thereof and-connected with any suitable source of gas either for compressing the same or for evacuating a chamber, andto provide one or more openings from the .compression side of the pumping chamher through which the compressed gas will be driven either to a receiver thereof where compression'is then sought, or to atmosphere where evacuation is being efi'ected.

It isafurther object of my invention to provide radialchannels within the body of the rotor which extend diametrically'across the same, and to mount in saidchannels pistons movable radially within the rotor, which occupy and substantially fill both ends of said channels but which are separated into two sets, slidable relatively to g the sets as such and to-each piston part of each of the pumping chamber throughout the movements of said pistons as the rotor is rotated.

The full objects and advantages of my invention will be apparent in connection with the description of its structure and mode of operation given in the appended specification, and the novel features of my invention as combined to produce the aforesaid advantageous results will be particularly pointed out in the claims.

In the drawings illustrating an application of my invention in one of its forms:

Fig. 1 is a plan view of the invention with the cover member removed and showing some parts broken away and in section.

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a sectional View taken on line 3-3 of Fi 1.

Fig. 4 is a sectional view taken on line 4 of Fig. 1.

Fig. 5 is a sectional view taken on line 5-5 of Fig. 1.

Fig. 6 is a sectional view taken on line 6-45 of Fig. l with some parts broken away and omitted.

Fig. 7' is a similar sectional view taken on line l'! of Fig. 1.

Fig. 8 is a front elevation View of the rotor showing the guide channels of the radially movable piston.

Fig. 9 is an enlarged view of one of the piston ends showing the character of curve at such ends.

As shown, my device embodies a main frame casting it! which includes an annular flange member H. This flange, with a cover plate later described, encloses a cup-shaped chamber portion I 2.

From the chamber 52 extends a depressed part I3 circular in cross-section, said depressed part, shown in Fig. 5 and in dotted lines in Fig. 3, having its center eccentric in a diametric line with respect to the inner walls 14- of the chamber I2.

The casting leis provided with a boss i5, Fig. 5, which has through it a circular opening 16 concentric with the axis of the depressed portion l3. In the opening 15 is a shaft ll adapted to be connected at IS, in any well-known way, with means for rotating the shaft. The other end of shaft H has integrally connected therewith a rotor 19 which is shown in both Figs. 1 and 5.

The rotor comprises a supporting member 29 fitted and operative within the depressed portion l3. This member 29 is integral with shaft l1. Within the chamber !2 and formed integral withmember 28 are sections 2!, 22, 2.1 and 2d of the rotor proper, as shown clearly in Figs. 1 and 8.

The face of the rotor is provided with two transverse channels 25 and 26, these channels being rectangular in cross-section as shown and being closed by a face plate 21. This plate has its inner surface milled and ground and smoothed to. a true plane, and the outer edges 28 of the flange member I i also are ground in a true plane.

A series of bosses 29 are cast on the outside of the flange member I l and are provided with bolt holes. Set bolts 30 are screwed into these holes, thus holding the plate 21 in firm metal to metal sealing contact with the edges of the flange member H, and completely enclosing the chamber 52. The rotor thus operates within that chamber be tween the opposed faces of the casting ii! and the plate 21.

All of the foregoing faces are finished with plane surfaces so a close contact is secured. Actually there will be some slight tolerance, as, for

example, one one-thousandth to two one-thousandths of one inch. By any known and suitable oiling method, not shown, a film of oil-will be established between all of these edge surfaces of the pistons, effecting a complete seal against the possibility of air leakage between such surfaces.

' This is made possible and certain because such' large areas of surface are together, and the oil film extending over such large areas will be able to wholly prevent leakage regardless ofthe pressures built up at any point. Some little tolerance is necessary, of course, to prevent striking of the pistons, hereinafter described, operative in the channels 25 and 26, particularly whenslight expansion occurs from heating. Tests have shown that the rotor operates fully and with relative small consumption of power, in the arrangement above outlined, with very small consumption of oil. I

As clearly shown in Fig. 1, there is a, space,

crescent-shaped in cross-section, which is be-' tween the outer surface 3| of the rotor l9 and the inner face [4 of flange H, with the rotor rotating in the direction of the arrows. crescent-shaped space may be'divided into four parts: an intake part 32 extending substantially from its beginning at about 33 to its termination at about 34, a compression part extending from about 35 to its ending about the point 36, a sealing part between 33 and 36 where the outer rotor wall 3| substantially contacts the inner flange Wall M at 33 and a neutral part between 34 and 35 which affects neither inlet nor compression.

The inlet gas will enter the inlet part 32 through 1 'go to atmosphere as may be desired. Another and smaller opening 43 may connect by pipe 44 with the boss 4! to prevent any tendency toward thumping, resulting from forcing the compressed gas through a single opening.

The formation of the curve of the inner surface of the flange II is a highly important feature of my invention. This curve between the points 33 and 35 will be the arc of a circle having'its center at 45 which is the axis of the rotor I9. This curve of the inner surface of flange II will be, therefore, that or substantially that, of the outer surface of rotor I9.

The curve between points 34 and 35 is likewise the arc of a circle struck from the center 45 at the axis of the rotor, and hence is not only spaced from but is concentric with the outer surface of the rotor. This curve 34-35 has greater radial angularity at its ends than is true of the curve 3336 to give an addition in length equal to twice the width of the center curve at the end of the piston.

From 35 to 36, on the compression side, and from 34 to 33, on the inlet side, the curve of the inner wall of the pumping chamber is not in the are of a circle but is a curve with a constantly varying radius vector, which, in each instance, connects the ends of the arc curve at 35 and 34 respectively with the ends of the arc curve at 36 and 33 respectively along substantially the line of an Archimedean spiral.

This

While the "actual dimensions of the chamber formed inside of the flange portion II, on lines taken through the'substantial center of that chamber are such that the chamber as a whole will be wider transverselyof its position in Fig. 1,

than it is perpendicularly in reference to that figure, the contact distances between the portions of the heads in actual engagement with the outer walls of this chamber are the same throughout the entire circumferential extent of those outer walls. These distances do not go-through'the center of the rotor 22 but in each instance are chords offset from said center so as to pass substantially through the centers of the opposed contact surfaces at'the end of the pistons.

However, since there may be some expansion of the piston members'from heat and for other reasons, I have found that better results are obtained by making the piston members in each instance separate members thrust outwardly by springs, rather than each a single piston member,

as in my former patent.

This has two important eifects. First, it increases the aggregate cross-sectional area and cubical contents of the compression chamber, and

the inlet chamber, thus giving greater volume for a given size rotor, and'it produces the form of curve heretofore defined, which in conjunction with the three types of curves at the ends of the pistons enables an extensive area of actual contact between the ends of the pistons and the inner walls of these chambers to be established I at all times.

Although the channels 25 and 26 in which the pistons operate extend across each other at right angles radially through. the center of the rotor, and are the same length, even though the operativee'xtent of piston lengths in these channels are the same, I do not make the piston member as a unit extending'through each channel but form each piston" member in two parts adapted to move longitudinally relatively the one to the other, but operating in the same identical channels, and having the same identical cross-sectional areas at their operative ends.

In addition to the action of centrifugal force, which tends to'maintain the piston endsin contact with the inner walls of the pumping chamber, spring means are also provided to make certain that there is constant contact between the respective piston ends and said outer wall, to

control relative longitudinal movements thereof,

to compensate for expansion from heat, and also tocompnsate for any wear of the piston contact surfaces.

As clearly shown in Fig. 4, the main body of eachof the pistons comprises a, head designated by the numeral 46; which, as clearly shown in Fig. 4, is rectangular incross-section. In Fig. 4 this is shown as square in cross-section,.but obviously it may bean elongated rectangle if it is desired 'in' two crossing layers, the' bottom layer 41, 48

and the top layer 49, 50, as shown in their diagonal extent in Fig. 5. The bottom layer 47, 4 8 lies'underneath' the top layer 49, 50, Fig.6, and

the top layeii 49; 50- overliesthebottom:layerjfl, 48; Fig.7. They;cross at thecenter, ,as shown in Fig;l5, directly at right angles, and are=relatively movable with respect to the members of each pair and'with respect to each pair of members to ,thefiother pair. r v

Each 'oithe fingers is provided with a socket i inits end, as clearly shown in. Figs. 1, 2 and 3. Within each of the sockets isQa coiled compression spring 52, as clearly shown. It will'be p-v parent, therefore, that each pair of piston members 41, 28 and 49, 50,respectively hasa pair oi springs operative to mutually force the piston heads-d8 against the inner wall M of the pumping. chamber iii." These partslare thus held in the guide slots for longitudinal movement. Continually therais added to the action of centriiugal force the constant pressure of two springs 52,.urging'the faces of the body of the. pistons diiagainst the inner wall Id of the pumping: chamber.

The nature of heads 43 isshow-n in Fig. 1 and inenlarged scale in Fig. 9. The end of each head is provided with a central curved portion 53 and other curved portions 54 and 55 on each side of the curved portion 53; The. curved portion 53 is the arc of a circle -struck from the center 45- of the rotor andhaving'thesame radius as the rotorand thus is adapted to engage with its whole surface-the are 33-35 at one part of itsv movement, and toengage the are 34-35" with a substantial part of its surface at the other part of its movement. Each of. these arcs 33-36; and 34-35 are con-- centric. contact of the curved portion 53 across the whole of arc 33-35, there will be something less than complete contact-of-these arcs-acrossthe are This is not important, however, since the crosssectional area of the pumping chamber between 34-35 does not change-substantially from end to end and consequently there is little or no dif-. ferential pressure on opposite sides of the piston. along this stretch of the pumping chamber, and leakage is easily prevented. I

0n the other hand, the pressure differential between the points 33-36 along the circle are there is at substantially the highest point and hence the complete contact of the portion of the curve 53 on the ends of piston members 46 effects complete sealing along this critical area.

, An important feature of the inventionis that while arc 3 5-35 and are 33-36 are made. on circles whose diameters differ; the angular length of the 3435 is greater than the angular lengthof the are 33-36 by a specific distance. previously explained, and as clearly shown in Fig. 1, the angular lengthof are 34-35, is equal to the angular length of are 36-33 plus twice the width of the central curve 53 on the end of each of the pistons 46. Thus a'first line A-B drawn from point 36 through the center- 350f rotor i9, and a second line C-D drawn from the point as through the center of rotor l9 will" each be separated from the points '34 and. 35by the distance designated at 53a which is equal to the width. of. the curve 53 on theend of each 'of pistons 46. In this manner, when the curve 53 on the end of one of the pistons has completely entered are 34-35, a similar curve on theend of a diametrically opposite piston will commence to enter arc 38-33 to thereby prevent leakage past the ends of these two oppositely disposed pistons when they arein. the critical position. of

It follows that while there is completesealing the low pressure side 32 from the-high- Since are 35-35 is longer than are 33-33 by twice'the width of curve 53-, the.

pressure side 40.

pistonstructure' has cleared point 33, curve 53' on the other end of the piston structure will be between the line C-D and point 35. Thereafter, as curve- 55 on the first end of the pistonstr-ucture begins to contact the non-circular curve 33-34, curve 5 on the other end of the piston structure makes full contact with the other noncircularcurve 35-36, until the point 36 is reached and passed, at which time the curved portion. 55; on the first end of the piston structure has initially reached point 34, thereby providing a continuous seal between opposite lateral sidesof each piston and continuous longitudinal control of the pistons during a complete revolution. oigthe-rotor; The curves at the ends of the pistons, designated as 54 and 55, respectively, as

clearly shown in Figs. 1 and 9, follow the same lines of the -Archimedian spiral as the curves of the inner. walls of the compression chamber M and the inlet chamber 32. When the piston end leaves the are 34 and 35 it will be tipped, as shown atSG in. Fig. l, bringing the are curve 53 out of contact with thewall of the compression chamber '43 and at the same time bringing the curve 54. into contact with the stretch of compression chamber wall 35-36.

Sincethe curve .54 corresponds to the curve of the stretch of compression chamber wall 35-35, as the piston. is carried forward in its slot, moving inwardly while the companion piston moves, outwardly, the curved portion 5 will, throughout its length, contact the inner wall 14 of compression chamber 43 and will continue to do so until the point 36 has been reached and passed when the piston head again will be rocked relatively to the arc section 33-36 and the centralarc curve 53 will there contact and seal that section.

, Following this, when the piston passes th point 33 it will still further rock relatively taking the curve 53 out of contact with the wall of inlet cylinder 32 and swinging the curve 55 on the opposite side of the piston into engagement with thecurve extending along the inner wall of inletchamber 32.

Thisoperation will be continuously repeated byeach of the'four piston ends producing an important and heretofore unsecured result of a constant 'contact of a substantial area of the piston head with all parts of the curved walls of the pumping chamber.-'

I claim:

1. In arotary compressor, a cylindrical rotor. acasing surrounding the rotor of greater crosssectional area than that of the rotor, said rotor having a portion contacting the circumferential wa l of the'casing so as to leave a generally crescent-shaped pumping chamber between the outer wall of the rotor and the inner Wall of the'casing, said inner wall having its cross-sectional curvature partly. in arcs of a circle and partly in non-circular curves and pistons carried by the rotor and movable outwardly relative thereto to contact the inner-wall of the pumping chamber,

each of' said pistons having a multiplicity of curved contact faces at each end which respecof contact between the piston heads and the "chamber walls are secured throughout the movement of the piston heads about the full surrounding extent of said contacted Walls.

2. In a rotary compressor, a cylindrical rotor, a casing surrounding the rotor of greater crosssectional area than that of the rotor, said rotor having a portion contactin the inner circumferential wall of the casing so as to leave a generally crescent-shaped pumping chamber between the outer wall of the rotor and the inner wall of the casing, said inner wall having portions of its cross-sectional curvature in the region where the rotor makes contact and diametrically opposite to that region in arcs of a circle and having the intervening parts of its cross-sectional curvature in non-circular curves, and pistons carried by the rotor and movable outwardly relative thereto to contact the inner wall of the pumping chamber, each of said pistons having a multiplicity of curved contact faces at each end, one of said faces curved to contact the arc areas of the inner wall of the chamber and the others of said faces curved to match the non-circular curved faces of the inner wall thereof to secure large areas of contact between the end of the piston and the non-circular curved faces.

3. In a rotary compressor, a cylindrical rotor, a casing surrounding the rotor of greater cross sectional area than that of the rotor and contacting the rotor at one area, said casing having spaced parallel walls and a circumferential wall perpendicular thereto, the inside surface of said circumferential inner wall comprising a circular are curved portion at the area of contact and another arc portion of greater radius diametrically opposed thereto and having non-circular curved portions extending between the respective adjacent sets of ends of the curved arc portions, said non-circular portions being curved along the line of an Archimedian spiral, said rotor being provided with a radial slot, and a piston movable endwise in said slot and having a head with three curved contacting faces thereon to engage successively all the curves of said circumferential wall as the rotor is rotated.

4. In a rotary compressor, a cylindrical rotor, a casing surrounding the rotor of greater crosssectional area than that of the rotor and contacting the rotor at one area, said casing having spaced parallel walls and a circumferential wall perpendicular thereto, the inside surface of said circumferential inner wall comprising a circular are curved portion at the .area of contact and another are portion of greater radius diametrically opposed thereto and having non-circular curved portions extending between the respective adjacent sets of ends of the curved arc portions, said non-circular portions being curved along the line of an Archimedian spiral, said rotor being provided with a radial slot, a piston movable endwise in said slot and having a head, said head being formed with a central circular arc curve and other curves following the line of an Archimedian spiral at each side of the central curve to engage successively all of the curves of said circumferential wall as the rotor is rotated.

5. In a rotary compressor, a cylindrical rotor having a radial slot therein, and a piston member movable endwise in said slot, said piston having a head portion with three curved faces on the outer end thereof.

6. A rotary compressor, comprising a cylindrical rotor, a piston carried by said rotor and movable diametrically relative thereto, said piston on each of its opposite outer ends having a central curved portion and other curved portions on each side of the central curved portion, and a casing surrounding said rotor having'an inner wall with a first portion and a portion oppositely disposed therefrom being formed of non-circular curves and a second portion and a portion diametrically opposed thereto being formed as arcs of circles whose diameters differ, the angular length of one of said arcs being greater than the angular length of the other arc by substantially twice the length of the central curved portion on the ends of said piston to thereby provide both a continuous seal between the central curved portion of the piston and the arcuate portions of the casing and to assure continuous contact between one of the other curved portions at each end of the piston and the oppositely disposed non-circular portions of the casing.

HARRY A. GARRISON.

REFERENCES CITED The following references are of record in the file of this patent: 1

UNITED STATES PATENT

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