US3195470A

US3195470A - Rotary pump

Info

Publication number: US3195470A
Application number: US168407A
Authority: US
Inventors: Edwin E Smith
Original assignee: Fluid Dynamics Corp
Current assignee: Fluid Dynamics Corp
Priority date: 1962-01-24
Filing date: 1962-01-24
Publication date: 1965-07-20
Anticipated expiration: 1982-07-20

Description

2 Sheets-Sheet l I I l INVENTOR. Edwin E. Smith BXL/'ZM 69%.@

E. E. SMITH ROTARY PUMP Attorneys E. E. SMITH July20, 1965 ROTARY PUMP 2 Sheets-Sheet 2 mn .om

mw mv uw Nw uvm-.l `w NW mwN mv\\ vw mw v mm mm l l All lll lnlwml. HllVllvnl .l 91m Il... UVM) B\ mv @n mv mw mm om Attorneys United States Patent vO 3,195,470 ROTARY PUMP i Edwin E. Smith, Santa Clara, Calif., assignor tn Fhud Dynamics Corp., Santa Clara, Calif., a corporation of California Filed lan. 24, 1962, Ser. No. 168,407 14 Claims. (Cl. 103-131) rprovide a rotary pump which particularly lends itself to pumping liquid and semi-liquid food products.

Another object of the invention is to provide a rotary pump of the above character which particularly lends itself to the pumping of heavy or thick liquids such as molasses or chocolate.

Another object of the invention is to provide a rotary pump of the above character in which the pumping chambers and the piston are cantilevered on one end of the pump to facilitate disassembly and assembly of thepump.

Another object of the invention is to provide a rotary pump of the above character which can be readily disassembled for cleaning.

Another object of the invention is to provide a rotary pump of the above character in which there is substantially less wear than in conventional pumps.

Another object of the invention is to provide a rotary pump of the above character which creates an unusually high vacuum.

Another object of the invention is to provide a rotary pump of the above character in which the action of the piston is such that it minimizes viscous shearing and has a lesser tendency to homogenize materials.

Another object of the invention is to provide a rotary pump of the above character in which the pumping chambers are sealed from any lubrication provided for the pump as, for example, in the bearings.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawings.

Referring to the drawings:

FIGURE 1 is a front elevational View of a pump incorporating my invention.

FIGURE 2 is a cross-sectional View taken along the line 2-2 of FIGURE 1.

In general, my rotary pump consists of a housing in which a shaft is rotatably mounted in the housing. A flanged shaft is eccentrically journalled in the first named shaft and has its longitudinal axis parallel to the longitudinal axis of the first named shaft but spaced from the longitudinal axis of the first named shaft. A timing plate is affixed to the housing and means is provided forming a connection between the flanged shaft and the timing plate so that circular gyrating movement of the flanged shaft occurs without axial rotation as the first named shaft is rotated. A casing is mounted on the housing and is provided With inlet and outlet openings. The casing is also provided with concentric cylinder walls which define a working space. Partition means is provided in the work- 'ing space and serves to separate the inlet opening from the outlet opening in the casing. A piston is affixed to the flanged shaft and moves therewith. The piston is `provided with a cylinder which operates in the working space. The cylinder is formed with a slot to permit cirice cular gyratory movement of the piston about the partition means.

As shown in the drawings, my rotary pump consists of a shaft housing 11 which has mounted thereon two

feet

12 and 13 which serve as a base for the pump. The shaft housing 11 is substantially bell-shaped as shown in FIG- URE 2. A bell-shaped shaft 14 is rotatably mounted within the housing 11 by a pair of roller bearings 16 and 17. The bearing 16 is located at the input end of the housing 11, whereas the bearing 17 is located in the output end of the housing. The bearing 16 is mounted in an adjusting nut 18 which is threaded into the power input end of the housing. This adjusting nut is provided with tool receiving recesses 19 so that the nut canl be adjusted longitudinally of the housing 11 to obtain the proper clearance between the piston and the pump casing as hereinafter described. It is then locked in position by a bolt 25 extending through ears 20 provided on the shaft housing 11. The ball bearing 16 is held in place on the bellshaped shaft 14 by a lock nut 21 which is threaded onto the bell-shaped shaft as shown and a lock washer 22 disposed between the lock nut and the bearing 16. The bearing 17 is mounted in the housing 11 in a suitable manner such as by a press lit. An O-ring 23 is disposed between the adjusting nut 1S and the housing 11 to form an oil-tight seal between the adjusting nut and the housing. A seal 15 is provided in the adjusting nut 18 to prevent oil leakage from around the shaft 14.

A flanged shaft 26 is eccentrically mounted or mounted off center in the bell shaft 14 so that when the bell shaft 14 is rotated, an ececntric gyrating motion is suppliedto the shaft 26. To accommodate the flanged shaft 26, `the bell shaft 14 is provided with a cylindrical reces-s 27 which has a diameter which is substantially greater than the diameter of the flanged shaft. The inner end of the ilanged shaft is carried by a ball bearing 28 mounted within the bell shaft 14. The ball bearing 28 is held in position relative to the bell shaft 14 by a set screw 29 threaded into the bell `shaft 14. The shaft 26 is held in the ball bearing 28 by a snap ring 30 seated in a groove 31 in the shaft 26. Access to lthe set screw 29 is`provided by a plug 35 threaded into the housing 11. An intermediate portion of the flanged shaft 26 is carried by a roller bearing 32. The roller bearing 32 is held in place by a snap ring 33 seated in a groove 34 provided in the flanged shaft 26.

It will be noted that the bell shaft 14 is formed in such a manner that it is balanced with the flanged shaft 26 mounted therein which, as hereinafter described, includes the piston 54. It is for this reason that the upper portion of the bell shaft, as viewed in FIGURE 2, is of substantially greater thickness than the lower portion. The lower portion is also provided with an opening 36 to further decrease the weight of the lower portion to thereby provide a counterweight in the shaft 14 for the shaft 26 which is eccentrically mounted within the shaft 14.

Means is provided for preventing axial rotation of the flanged shaft 26 during the gyrating motion of Athe shaft 26 and consists of a timing plate 38 which is affixed to the housing 11 by suitable means such as cap screws 39. The timing plate 33, as shown in FIGURE 2, lies immediately behind the flanged portion 26a of the flanged shaft 26 and lies in a plane parallel thereto. The plate 38 is coupled to the flanged portion of the flanged shaft 26 by suitable means such as by pins 41 which are mounted in the flanged portion 26a of the flanged shaft 26 and which have rollers 42 rotatably mounted thereon and held in position by snap rings 43 seated in grooves 44 provided in the pins 41. The rollers 43 are disposed in circular openings 46 provided in the .timing plate and travel in the circular openings in a man-ner disclosed in my copending application Serial No. 53,970, filed Sept. 6, 1960, issued -as a-tent No. 3,125,027tofthereby permit Veccentric or gy- Y rating motion of the flanged shaft, while at the same time v preventing axial rotation of the flanged shaft.

Although the hanged shaft 26 isv shown as a unitary structure,"it is readily aparent that, if desired, the'ilanged portion could be a separate member which could be se'- cured toa separate shaft. 'y

A easing 45 is mounted on the housing l1 in a suitable manner such as by the use of studs 5t) which are threaded into the housing and hex nuts S5 which are threaded onto the studs. The casing is provided with inlet and

outlet openings

46 and 47 and concentric outer and innerl walls `4S and 49 vwhich define an'annularrworking vspace 51 L therebetween. Partition lmeans inthefform of Vva removupon the direction of rotation of arpiston 54 mounted.Y

in the casing of the pump.

The piston 54 is aliixed to flanged shaft 267m a suitable manner .such as by means of a hex nut 56 which isthreaded y onto a threaded' extension 265 provided on the flanged Yshaft 26 and engaging a collar 58 which, engages the pisy ton. The piston 54 is provided with aV cylindrical pornular face yieldably urged vInorder to minimize theV wear into `engagement with the end plate portionV 5412 of the' piston by a pai-r of O-rings 67 mounted behindrthe annular sealing member 66. I have found it desirable to utilize two O-rings rather than one ora double O-ring for this purpose'because the two Of ringsor the double'O-ring urge substantially all portions of the Vannular member v66 intoengagement with the plate-like. portion vof the piston. If only a single O-ring were utilized,1the flat annular member 66 would Yhave a Vtendency to lbecome convex and, therefore, would not form as good a seal. I yhave found it `desirable to utilize plasticfor the sealing member 66 because if a small impurityshouldby chance scratch the surface of the sealingV member 66, the plastic would have a tendency to flow backto its original condition to provide a planar surface to again establish an excellent seal between the sealing Vmember andthe piston 54. n v Y ,between the outer extremity ofthe plate-like portion 54h of the pistn and the casing 41, -I have found it desirable to provide. an annular thrust washer or wear ring 68 whichis loosely mounted .in an annular recess 69 in casing 41 sothat its outer planar surface is engagedby the plate-likeportion 54h ofthe iston." This wear ring 68 clan'be formed of any suitable material suchfas bronze or brass. If the pump is utilized for pumping materials which'have ,acid in them which tion 54a which operates in Vthe working space 51 Vas shown K particularly in FIGURE 2 of the drawings. lthough not vshown in the drawings, additional means can be provided for allixing the piston 54 to the flanged shaft so that the piston will not rotatel with respect to thellanged shaft i under load, Forrexamplmone of the vpins 41 could be formed so that it extendsV through theiianged, portionlerz`v of the flangedshaft and so that it extends into a recess in the piston. Y l Y -K kThe piston`r54 is provided withv an end plate portion 541) whichV has a diameter which is substantially greater than the outer diameter of 4the cylindrical portion 54a of the piston and the inner diameter of the cylindrical wall 48 of the casing 41 so that the working space or Vpurnpbe sealed "olf from the remainder of able resilient material such as rubber. e The bonnet v61 l is secured to the metal cylindrical portion 54a in a suit able manner such as by molding or bonding. Y

I have found the use of the rubber bonnet 61 to be particularly advantageous when the pump is utilized for pumping food products because the rubber Vbonnet presents'a smooth surface to which the food product doesnot cling. In addition, the rubber bonnet makes it possible to eliminate the use of any seals vbetween the piston and the casing and still achieve excellent pumping` action in which there is little hydraulic slippage anda high vacuum .y

is maintained.4 `However, itlhas Vbeen found that the pump will still operate satisfactorily'without the useof such Ya `resilient bonnet provided on the k,cylindrical'por- Ytion 54a. However, if the bonnet is not used, the external diameter of the'cylindricalportion 54a must be increased to'take up'theV space which is taken up bythe' bonnet 61.

Y Sealing means'V is., provided for sealing the pumping chamber or working space 51 from the shaft and bearing chamber 62'in the housing 11, The sealing means yconsists of a compression seal 63 which is mounted inrecessesrin the outer end of theouter 'concentricv cylinder wall 48 of the casing-41 and a compression seal'64'which is mounted in the outer end of the cylindrical wall 49 of 4the casing 41." These compression seals 6?: vand 64 can Ytakeany suitable form. l'rlowever, I have found it desirable to utilize an annular member 66 of a suitablelma- 'terial such as -ametal lled plasticl having a planar anis mounted Yon the housing 11 as shownand which applies 'a suitable oil such as White mineral oil through a passage 71 into Contact with'the wear ring63. It is desirable td utilizemineral oil in certain Vapplications of the pump because if a small portion of the mineral oil should pass through thefsealV 63, the mineral ;oil will vnot spoil the product which is being pumped by the pump. However,

v any other lubricant compatible with the'pro'duct being pumped, such as water, may be used. s

It should be pointed out that the wear ring can be eliminated in many instances and Vthat it is only'v desirable toV provide such'a wear ring when the pump is manufactured vofmaterials whichr are particularly subjectto galling or f fretting, as', for example,when the ypumpisV manufactured from stainless steel. VIf 'thepunip is manufactured from cast iron, bronzes and the like, a wear ring should be unnecessary.

Sealing means is provided in the housing 11 tov prevent Aoil inthe chamber 62 inthe housingY 11 from coming in 'contact with the food being pumped in the pumping chamber.V Itconsist's of an annular seal'ring 74 mounted in an annular recess76 provided in the rear portion of the flanged portion 26a of theanged shaft 26. This seal can ,be of, any suitable typeV suchas a rubber Quad-ring manufactured by fthe Minnesota Rubber Co. y of Minneapolis, Minnesota., As can be seen from FIGURE 2 of the drawings', this Quad-ring engages the smooth faceof the timing'plate'SS to vprovide a seal betweenfthe timing nplate 38 and the flanged portion 26h to thereby isolate the pumping `,chamber 51 4from the oil-filled chamber 62 in the housing 11 in which the bearings and shafts 14 and26 aremounted. Y' V f As will Ybe noted from'FIGURE 2, thehousing 11 can Abe Vfilledthrough the plug 35 and can be-:lrained through Ythe drain plug 78. The bearingswithin the yhousing are ylubricated bythe splash of 'oil created as-the enlarged Vportion of the bell shaft 14 moves into and out ofthe oil ,witlnn thehousing. i

`,extremityofthe vflanged portion Z641v of the shaft 26 to Anr annular chamber 81 is. provided beyond the outer collectrmaterialin the eventfthere is some flow of material tllroughtthe-.seals l74 and the seals 63 and 64. A

fdrain (not-shown) is provided for draining this chamber. 4ThusLlzvy `r chancev if some oil fromlthehousing 11 should flow past the seal 74, the oil can be drained from the chamber before it builds up sufficient pressure so that it can pass into the pumping chamber 51. Also, if some of the product being pumped should pass the seal 63, it also can be `drained from the chamber before it passes into the housing 11.

To provide additional assurance that there will be no cross-flow of material from the chamber `62 in the housing 1K1 to the pumping chamber 51 or vice versa, I have provided an annular diaphragm 82 which is formed of a suitable material such as rubber. The outer margin of the diaphragm is secured to thehousing 11 in a suitable manner such as by a snap ring 83. The inner margin of the diaphragm 82 is beaded as shown `and is seated in .a recess 86 in the flanged portion 26a of the shaft 26. From this construction, it can be seen that the diaphragm 82 provides an additional seal between the pumping chamber 51 and the chamber 62 within the housing 11.

Operation of my rotary pump may now be brieily described as follows. Let it be assumed that the pump is in the position shown in dotted lines in FIGURE 1. As is shown therein, the working space 51 is divided into an outer pumping chamber A which is formed between the piston and the outer cylindrical wall 48 and an inner pumping chamber B which is formed between the piston and the inner wall 49. Also, let it be assumed that the shaft 14 is being rotated in a counterclockwise direction as viewed in FIGURE l. In the position shown, the outer chamber A is discharging out the outlet opening 47. At the same time, the inner chamber B is completing its intake. Continued oscillation or gyratory movement of the piston 54 causes the outer chamber to continue its discharge, the intake end of the inner chamber to be sealed andthe outer ch-amber to begin its intake. Continued -oscillation causes the outer chamber to complete f its intake and the inner chamber to begin discharging. Further oscillatory or gyratory movement of the piston 54 causes `the outer chamber to be sealed, the inner chamber to continue its discharge and also to commence its next intake. Thereafter, the outer chamber begins its discharge and the inner chamber continues its intake to return to the positions shownin FIGURE 1 after which the ysame sequence of operations take place. This operation is described in detail in my copending application Serial No. 53,970, filed September 6, 1960, issued as Patent No. 3,125,032.

Although the basic mode of operation of my pump is substantially conventional, my pump has many advantages. For example, it should be noted that the casing 41 and the piston 54 are cantilevered on one end of the shaft and bearing housing 11. This facilitates easy removal of the casing and piston. For example, the casing can be removed merely by removing the nuts 43. This exposes the working space 51 provided between the

concentric cylinder walls

48 and 49 and also exposes the piston 54 so that all the surfaces which come in contact with the product being pumped can be readily cleaned without difficulty.

From this construction, it can be seen that the pump particularly lends itself to food processing applications in which frequent cleaning and repair are required.

The pump also lends itself to food processing applications and other applications in which the product being pumped must be completely isolated from the remainder of the pump. As can be seen, a multiplicity of seals have been provided to ensure that there will be no intermixing of the product from the pumping chamber 51 and the oil in the oil chamber 62 provided within the housing 111, This has a distinct advantage in that the oil in the oil chamber will not become contaminated and also that the product being pumped will not be contaminated with oil. The construction is such that even if there should be a small quantity of material pass through the seals, it is collected on the outside of the chamber 81 by the diaphragm 82 and can be readily drained off and washed out by removal of the casing 41 and the piston 54.

`As explained, the rubber-covered piston disclosed in the pump also provides numerous advantages. In addition to being particularly adapted for many food processing applications because of the fact that it presents a smooth surface to which food does not cling, it also maintains a high vacuum without the use of complicated seals. Also, the rubber facing or bonnet provided on the piston permits greater latitude in manufacturing tolerances. Also, it has been found to give lesser pulsations in the fluid being pumped because of the compressibility of the rubber bonnet. The rubber-covered piston also decreases hydraulic slip or, in other words, my pump has less hydraulic slip at =a given pressure and given capacity than conventional pumps. For example, in one embodiment of my pump, I found that the pump could pump 48 gallons at no pressure and could still pump 44 gallons per minute at pounds pressure. This indicated that the hydraulic slip was only 4 gallons per minute aft 100 pounds pressure.

As .also described previously, although my pump has been disclosed as being provided with a rubber bonnet, other types of materials can be utilized for the cylindrical piston. For example, the piston could be faced with a plastic material such as nylon or Teilen, or it could be coated with a ceramic or faced with `a very hard facing material and still operate satisfactorily. With such hard surfaces, it is possible to pump liquids containing materials which .are very hard.

My rotary pump also has other advantages. For example, lthe gentle rolling action of the piston within the smooth bore of the pumping chamber minimizes viscous shearing and exhibits far less tendency to homogenize materials than conventional pumps. It is for this reason that my rotary pump can handle materials having a relatively low viscosity up to viscosities of oneI million SSU without changing internal clearances in the pump. Also, due to the gyratory or rocking motion of the piston, nails and other foreign matter can usually pass through the pump without damaging the pump.

From the foregoing description, it can be seen that my rotary pump is a piston type rotary displacement pump in which the piston gyrates instead of rotating. The pumping chamber is completely isolated from all the parts of the pump. As explained above, two separate pumping chambers A and B are formed by the oscillating piston.

In operation, the rotating point of contact between the piston and the concentric cylinder walls of the casing serves both to push fluid out (discharge pressure) and to pull Huid in (intake vacuum). The two pumping chambers are phased apart to provide continuous positive displacement.

It is apparent from the fore-going that I have provided a new and improved rotary pump which has a particularly unique construction which |lends itself to simple disassembly for cleaning and maintenance. Also, the construction of my pump is such that it lends itself to applications in which the pumping chamber must be completely isolated from the remainder of the pump.

I claim:

l. In a rotary pump, a housing, a rst shaft rotatably mounted in said housing, a second shaft eccentrically journalled in said rst shaft, a timing plate aflixed to the housing, means forming a connection between the second shaft and the timing plate to prevent rotation of the seeond shaft but permitting circular gyratory movement of the second shaft as the first shaft is rotated, a separate `casing removably mounted on said housing and having inlet and outlet openings, said casing also having inner and outer concentric cylinder walls deiining a working space, partition means carried by the casing in the Workrng space separating the inlet opening from the outlet opening, and a pi-ston aiixed to said second shaft and movable therewith, said piston having a radially extending Y tend outwardly and away from said housing.v 'l

3. A rotary pump as in claim lll wherein-said cylinderV rtintas/,47o

the piston having a cylinder operating in said working space to provide two pumping chambers in the working space, said piston having a Vslotstraddling said partition meansl forpermitting circular gyratory movement of the piston about the partition` means.

2. A rotary pump asin claim 1 wherein said housing Vis formed with a base and wherein said casing and said piston are cantilevered on said 'housing Aso that-they exhas inner and outer concentric walls together-'With a covering of resilient material bondedto said inner and outer walls of the cylinder for movement therewith, said resilient covering engaging the concentric innerV and outer cylinder walls of the casing and being-free of. engagement with said partition means. i

4. A rotary pump as in claim 1 together' with an intef gral bonnet .of resilient material bonded toA said cylinder for movement therewith and engaging the inner and outer concentric wallsrof the casing, 4said bonnet being free of engagement with said partition means. 7

5. A rotary pump as in claiml'together with a piston continuously engages the wear ringdurlng its gyratory motion. 6. A rotary pump as in olaim applying a lubricant to the wear ring.`

7. A rotary pump as in claim v1 togetherv fwith Vsealing .means mounted between the casing and the piston,y said sealing means including an annular member" having a planar surface engaging the piston, and means comprising Y a pair of O-rings disposed on the other side of theannular member and yieldably urging they annularl member into engagement with the piston.

8. A rotary pump as-in'claim'7 together sealing meansdisposed between the ange and the timing plate.

9. A rotary'pump as in claim 1 together with an annular diaphragm of pliable material and means for axing the outer margin of the annular diaphragm tothe housing and the inner margin ofthe diaphragm. to the.

withadditionar a' bell-shaped housinga, bell-` .Y

wear ring mountedin said casing and wherein the iiange of theV 5V together Ywith'mearns for tion of the piston said bonnet' being 5 1 having inlet and outlet openings, said casing Yextending outwardly of the housing and having concentric inner and vouter cylinder walls defining a working space, partition ing a cylindrical portionwithinu'er and outer concentric Walls operating'in said Working space and dividing said working space intoz-outer andY inner pumping chambers, said eylindrical'portion having a slot straddling said `partition means to permit'circular gyratory movement of the piston about the partition'means. Y, `f

, Y11. A rotary pump as 'in-claim 10 wherein'said bellshaped shaft is counter-balanced tocompensa 1teV for the oit-center mounting of the secondnamed shaft.

v12. yA rotary pump as in claim 10,4 together with sealing means'Y for isolating the pumping chambers from the housmg. Y V13. A rotary pumpv as in claimA ltltogether with abonnet of resilient material eov'eringand being bonded to the inner, and `outer concentric walls of the cylindrical porfree of engagement with the partition means. n y,

Vr1d; A rotary pump asin claim 10v wherein the piston is formed with aradially extending end plate having a diameter substantially greater than" the'diameter of the outer cylindrical wall portion lof the casing together with a wear plate mounted in said casing and vengaged by said end plate as the piston opera-tes. f

References.Citedl by theiExamner UNrrED sTMri-:sY PATENTS o Planche 103-130 1,685,397 9/28 Carrey 1 f 230-145 2,073,101 3/37 Fox 103-13'1 2,091,485 v 8/37 'Panzegrau1 27,7-83 2,133,358 10/,38- McCormack 230-147 2,423,507 7(47 Lawton 103j-132V 2,460,617 l2/749 Balogh 103,-132

Y V,2,538,598 1/51 Stratveit 103-13] 2,713,828 7/55 ,-Huber 103--130 2,759,427 f8/56 .Holstein 103-133 2,841,089 V7/58 VJones 103.--131 2,849,962V 79/58. Musser 103-131 2,884,268 4/59 Amirault `etal.- 277--83 FOREIGN PATENTS` 55,178 `10751 France. I. 636,071n Y3/28 France. Y

647,172v 71/36 Germany. I

BRANSON, IR., Prl-`miary Examiner. .y

Claims

1. IN A ROTARY PUMP, A HOUSING, A FIRST SHAFT ROTATABLY MOUNTED IN SAID HOUSING, A SECOND SHAFT ECCENTRICALLY JOURNALLED IN SAID FIRST SHAFT, A TIMING PLATE AFFIXED TO THE HOUSING, MEANS FORMING A CONNECTION BETWEEN THE SECOND SHAFT AND THE TIMING PLATE TO PREVENT ROTATION OF THE SECOND SHAFT BUT PERMITTING CIRCULAR GYRATORY MOVEMENT OF THE SECOND SHAFT AS THE FIRST SHAFT IS ROTATED, A SEPARATE CASING REMOVABLY MOUNTED ON SAID HOUSING AND HAVING INLET AND OUTLET OPENINGS, SAID CASING ALSO HAVING INNER AND OUTER CONCENTRIC CYLINDER WALLS DEFINING A WORKING SPACE, PARTITION MEANS CARRIED BY THE CASING IN THE WORKING SPACE SEPARATING THE INLET OPENING FROM THE OUTLET OPENING, AND A PISTON AFFIXED TO SAID SECOND SHAFT AND MOVABLE THEREWITH, SAID PISTON HAVING A RADIALLY EXTENDING FLANGE ENGAGING THE OUTER CONCENTRIC WALL OF THE CASING, THE PISTON HAVING A CYLINDER OPERATING IN SAID WORKING SPACE TO PROVIDE TWO PUMPING CHAMBERS IN THE WORKING SPACE, SAID PISTON HAVING A SLOT STRADDLING SAID PARTITION MEANS FOR PERMITTING CIRCULAR GYRATORY MOVEMENT OF THE PISTON ABOUT THE PARTITION MEANS.