US1890573A - Vacuum pump - Google Patents

Description

3 Sheetsheet 1 J. DUBRQVIN Dec. 13, 1932.

VACUUM PUMP Filed Dec. 5, 1929 J. DUBROVIN 'Dec- 13, 1932;

VACUUM PUMP Filed Dec. 5, 1929 3 Sheets-Sheet 2 `O/LL PMT'O 3 Sheqs--Shoot 3 J. DUBROVIN VACUUM UMP Filed Dec. 5. 192B Dec. '13, 1932.

Patented Dec. 13, 1932 UNITED STATES PATENT OFFICE `JOHN DUBBDVIN, OF- CHICAGO, ILLINOIS, ASSIGNOB T0 CENTRAL SCIENTIFICI COMPANY, L CORPORATION Ol' ILLINOIS vacuum ruin Application med December 5, 1829. Serial fo. 411,755.

y This invention relates to pumps, and particularly to those eccentric pumps commonly use d for producing high vacua. This application is a companion to my application Serial No. 411,754 filed December 5, 1929 for improvement in umps.

In my Patent o. 1,385,101 I disclosed a rotary pump which produced a lower vacuum in the same time than had hitherto been possible. I later discovered that the limit of vacuum which it would produce was not set by the vapor ressure of the oil (the theoretical limit of t e pump) but by the fact that gases dissolved and adsorbed in the oil were given up in the high vacuum chamber.

In my application Serial No. 411,754, I disclosed means to prevent gassy and polluted oils from reaching the high vacuum chamber and in the application described a pump which produces vacua at least six times lower than those produced by my prior des' gn.

For a long time it has been customary to o rate vacuum pumps immersed in a tank o oil which acts as the sealing liquid. yThe exhaust valve of the pumps are under the oil so that the discharge passes through it to reach the atmosphere. All parts of any sucli pump are reached, lubricated and sealed by the oil which is driven down the smallest mechanical clearances by the pressure diierential between the surface of the oil and the P inside of the pump. To immerse such a pum necessarily requires a large volume of oi nearly all of which ultimately is circulated through it, and all of which must be quite thoroughly outgassed before low pressures are attainable.

A further diiculty associated with immersed pumps is one of speed. The specific heat of oil is so low that a pump in a tank of oil must be rigidly limited in revolutions per minute to guard against liberating too mich mechanical energy and overheating the oi The primary object of my invention is to produce a pump having a better performance and producing lower pressures: and my incidental objects the"eto are to eliminate the oil tank; construct the pump casing to protect it against ingress of gases; reduce the volume of oil necessary for sealing and lubrication to the lowest possible limit; to expose the entire outer surface of the casing directly to the atmosphere to the end that the pump will run cooler at higher speeds; and to provide means for continuously outgassing the sealin medium.

urther objects and advanta s of the invention will be revealed as t e disclosure proceeds and the description is read in connection with the accompanying drawings, in which Fig. 1 is a longitudinal vertical section through a preferred embodiment of the invention in an eccentric vacuum pump;

Figs. 2 and 3 are sections taken on the line 2-2 of Fig. 1, Fig. 2 looking to the right and Fig'. 3 looking to the left;

Fig. 4 is a section taken on the line 4-4 of Fig. 1, looking to the right;

Fig. 5 is a transverse section taken on the line 5-5 of Fig. 4;

Fi 6 is a fragmentary sectional view taken 'on t e line 6-6 of Fig. 4;

Figs. 7 ,i 8 and 9 are reduced diagrammatic views similar to Fig. 2, andillustrating successive stages in the operation of the pump; and

Fig. 10 is a detail showing of the bushing 19 illustrating the sealing channels and gas assages therein: Fig. 11 is a detail perspective view of the blade showing the pistons.

Fig. 12 is a section similar to Fig. 1, illustrating an applicationof the invention to a two stage eccentric ump.

Fig. 13 is a. vertical partial section of the pump looking towards the right 1n Fig. 12 from behind the cover plate.

These specific illustrations and thecorrespondingly specific description are used for the purpose of disclosure only to illustrate the application of the invention, and in seeking the true scope thereof regard should be given to the substance of the improvements and not to vthe particular forms in which they are here embodied.

In that form shown in Figs. 1 to 11, the pump casing includes a ring or cylinder block 10, and two plates or heads 11 and 12 clamped to the opposite sides thereof by bolts 13 passeab ders, and the blade ing through suitable perforations in the lates and in thickened portions on the ring.

he inner surface 14 of the ring 10 is cylindrical for cooperation with a zone or area 15 on an eccentrlc rotor 16, mounted on a shaft 17 passing through the plates or heads 11 and 12, and journaled in bushings 18 and 19 mounted therein. The intake port is provided by a pipe 2O (Fig. 2), threaded into the ring 10 and communicating with a groove 21 in its inner periphery; and the exhaust port is made at `22 through the periphery of the ring 10 at alittle distance from the groove 21.

The ring 10 is provided with a lateral extension 23, which is slotted at 24 (Fig. 2) to receive a valve or blade 25, the inner end of which constantly engages the eriphery of the rotor 16 and divides the inta e from the exhaust. The plates 11 and 12 have similar extensions 26 which cooperate with the edges of the valve.

The extensions 26 are provided with spring bores 27, equipped with pins 28 near the bottom between which and a yoke 29 on top of the blade or valve 25 are stretched helical tension springs 30, which serve to urge the valve or blade into contact with the periphery of the rotor. As shown, the springs are arranged to act substantially parallel to the direction of movement of the blade, whereby friction and binding is reduced to a minimum.

Many pumps of this general type in common use include two eccentric units, but in the form illustrated in Figs. 1 to 9 of this application one of the eccentric units is replaced by a much cheaper pumping unit operated by the valve or blade, or whatever mechanical movement is used to separate the intake and exhaust of the eccentric unit, somewhat after the manner illustrated in my ap-v pigcsation Serial No. 311,733, filed October 11, 1

The eccentric unit, in this instance, will for convenience be referred to as the finishing stage, and the other unit will be referred to as the roughing stage.

As shown in Fig. 2, the slot 24 for the blade 25 is enlarged laterally in its intermediate portion to form, with the companion walls of the plates 11 and 12, chambers 31 and 35 which, for convenience, may be called cylin- 25 is equipped with intermediately located projections 32, 33, which for the same reason may be called pistons, and which, of course, are fitted to the walls of the corresponding cylinders.

The bottom wall 34 of the cylinder 31 is inclined at 36, where it approaches the exhaust port 22, and communication through this port is controlled by a check-valve consisting of 'a cylinder 37, having its periphery cooperating with the adjacent surfaces of the blade or valve 25, and the inclined portion 36 of the bottom 34, and also having its ends caring against the inner surfaces of the LeadersA plates 11 and 12. The cylinder 37 is confined within suitable limits by L-shaped blocks 38, secured to the bottom 34, and the left edges 39 of these blocks serve as auxiliary supports for the lower end of the blade 25.

The pistons 32 and 33 are equipped with a plurality of ball chack-valves 42 of familiar construction.

No inlet passage for the oil is shown. It exists in fact, however, in the mechanical clearance between the'piston and the cylinder wall and between the blade and the casing. The pressure differential (almost the total atmospheric pressure) between the exhausted space and the exposed surface of the oil is sufficient to drive the oil through the most minute clearances with the single exception, however, that no pressure differential exists between the atmosphere at the top of the pistons 32 and 33, and the atmosphere above the oil. With no differential the valves 43` 43 are effective oil seals, and the oil must be admitted below the valve by the following expedient. The upper portion of the valve 25 is provided with slots 40, which on the down-stroke are exposed about oneeighth of an inch below the top wall 41 of the cylinders 31 and 35, whereby a small amount of oil is supplied to the cylinders at each stroke.

The operation of the eccentric or finishing stage is familiar, and is illustrated in Figs. 2, 7, 8 and 9, which show the parts in four successive positions in the cycle of operations. As the rotor turns counter-clockwise from the position shown in Fig. 2, air or other material in the pump chamber is forced through the exhaust port 22. At the same time suction through the intake port 20 is created and constantly increased on the opposite side of the blade 25. As the parts pass through the successive positions shown in these figures. the contents of the pump chamber of the finishing stage are delivered through the exhaust port 22 into the cvlinder 31, and a new charge is drawn into the the intake port 20.

As the rotor moves successively from the position shown in Fig. 2 through that shown in Fig. 7, to that shown in Fig. 8, the blade 25, with its piston 32, descends and the air forced from the finishing stage through the exhaust 22 passes the check-valves 42, except a small portion remaining above the blocks 38 in the position shown in Fig. 8.

As the rotor moves from the position shown in that figure'through that shown in Fig. 9 to that shown in Fig. 2, the charge in the cylinder 31 is discharged, through checkvalves 43 in the head 41, into a chamber 44 formed by securing the oil cap 45 to the top of the pump casing.

With theproportions of the parts shown the volume delivered by the eccentric or finishing stage, when the vessel to be exhausted pump through the previous charge.

43 throughout t e greater .part of the rotors revolution; but as the pressure in the vessel to be exhausted is decreased the condition changes, and at len h the c linder'31 will be able to take the ex aust o the eccentric or finishing stage between the positions shown in Figs. 2, 7 and 8, during which time the pistonl 32 will exhaust from the cylinder 31 moves between the positions shownin Fig. 8 to Fig. 2, the exhaust from the finishing stage will pass the valves 37 and 42 in almost equal amounts.

The oilbath illustrated in my prior'application No. 311,733 is eliminated inthe embodinient shown in this a plication. The innerfaces of the plates orllieads 11A and 1 2 are provided with grooves 46 (Fig. 2), which almost entirely surround the several pump chambers, and are provided with lateral extensions 47 which communicate with the cyhnder 35. The area outside of the roove 46, and generally indicated in Fig. 2 gy the reference numeral 48, is treated with shellac or other gasket cement, but thearea on the opposite side ofthe groove 46, and generally indicated by 49, is not so treated.

The grooves 46 are filled with oil, and this may be easily accomplished by supplying a suitable amount of oil to the chamber 44 through the opening 50 in the cap 45, whence it will descend through the check valves and enter the grooves 46, after which the oil should be at about the level indicated in Filg). 2.

uring the operation of the pump de-V scribed above the piston 33 will reciprocate in the cylinder35 and pump air or other volatiles out through the head 41 into the oil chamber 44.. This will have the effect of applying a partial vacuum 'to the area. repre'-` sented by t l 4 the extraction from the oil of all absorbed air and volatiles. It also results in reducing the pressure dill'erential between the area represented by the grooves 46 and' the'interior ofthe ump chambers. Anyrlluids passing throng the area 48 along the joints tov the oil grooves are thus removed and there is but slight tendency for the oil in the grooves 46 `to seep into the pump chambers; and su'ch oil as does so seep has already been relieved vof any volatiles that would seriously interfere with the. speed Vor eiliciency of the finishing and roughing stages of the pump.

The rotor 16 is hollowed 'out at 51-to pro duce balance and' prevent vibration,l and the inner faces .ofthe plates 11 and 12 are provided withgrooves 52 to connect the' hollow of the rotor with the chamber of the iinishing stage, thereby adding the volume of theV Later as the rotor v69 inclinin e groove 46, and will result inA hollow to the system to be exhausted and perl mittin the pump to reduce the pressure in tfhe w ole system with substantial yuni-l ormit Incidentally the walls of the grooves 52- also serve to scra lubricant from thel sides of the rotor and eliver it, v throu h the openings 53 in the bushin s 18 an 19, to the shaft 17 along which it is fed through the grooves 54.

The bushing 19 (Fig. 1) terminates at the left in a narrow annular ring 55. The plate 12 is equipped with a ring 56 and a soft metal' disc 57 secured in place by bolts 58. The disc 57 has a narrow annular flange 59, similar to and facing the tlan el 55. Between these flanges are two cuppe rin 66, urged apart by springs 61=an`d containing yielding 'A Vwashers 62. The left cup, 60,' is also equipped with a hardened steel ring 63, yieldingly supported on the shaft by the rubber washers 62 and urged againstV the annular flange 59. The cu p'ed ring on the rght has a similar hardened) steel ring 64, also yieldingly held to the shaft and urged `against the flan e 55. v p

e net effect of this structure is to provide a sealing contact or stung box atV 65, between the shaft and the disc 57, and therefore the casing, and another sealing contact at 66 between the shaft and the llange 55.

Between these two sealing contacts is an air space or chamber 67 surrounding the shaft.

By providing a. passage between this chamber and the cylinder 35, a partial vacuumi is ino maintained therein, and hence the pressure y providing the bushingi19 with a longitudinal slot 68, which communicates with a bore upward and outward in the plate 12, an in turn communicating with an inwardly directed bore 70 which communicates with the groove 46, and therefore with the chamber 3 Figs. 12 and 13 illustrate a two stage ecn centric pump, in somev respects like the pump illustrated in Figs. 1 to 9 and in other respects like the pump illustrated in my companion application above referred to. As far as possible the corresponding parts are marked with the same numerals as used `in,

Figs. 1 to 9. l y p There are two cylinder rings 10,-and two eccentric rotors 16 separated byan .intermediate plate 71.

The intake to the iinishing 4 stage consists ofthe pipe 2() and the groove 21, as shown in Fig.'2, but the exhaust of the finishing stage and the intake of the roughing stage consist of apassage 72 drilled through the intermediate plate7 1. The exhaust of the roughiis ies

the le t rin in rin 10 at 73 v ves 4.

The hollows of the two eccentrics are connected by a bore 75 in the intermediate plate, which in turn is connected with the passage 72 by the passage 76.

The chamber 67 is connected with the bore 75, and therefore with the intake of the roughing stage, by a groove 77 in the lbushing 78, a passa e 79 in the plate 12, a passage 80 in 10, and passa 81 and 82 in the interme iate plate 71. he grooves 46 in the faces of the several plates are connected with the passage 82 by the passages 80 and 81.

The blade or valve 83 of the finishing stage is surrounded by a groove 84, as in the companion application referred to, and this groove is connected with the passage 72 by a ve 85 in the corresponding wall of the intermediate plate 71. The puin issealed by the cover plate 87 held to the ead 11 by cap screws, vas shown. A clean out lu is and Iitting it with suitable screwed into the tapped hole88 in t e ring 56. Both the plate 87 and the plug are forced home after being coated with a special cement.

From this description it will be obvious that the oil bath is omitted, and the var iouii-A sealing surfaces are connected with the intake of the rougliing stage whereby oil in them is subjected to a partial vacuum and any iiuid enterin them from the outside is intercepted fore it reaches the finishing stage, and therefore before it can interfere with the eiliciency of the pump. Although it is not shown in detail in Figs. 12 and 13, for lack of space, it will be obvious that the top of the pump is fitted with an oil cap 45, similar to that shown in Fig. 2.

In each of the several forms illustrated in this and the companion application, the joints along the intermediate area are subjected to a partial vacuum by means of which air seeping in or absorbed in the oil, and all fractions ofV the oil which are volatile at the temperature and pressure existing in the partial vacuum, are removed, together with any excess of oils. And the pressure differential between this partial vacuum and the pum chamber being relatively small, a sma amount of seepage through the remaining area of the joint into the pump chamber is insuiiicient to seriously interfere with the eili-l ciency of the pump.

I claim as my invention- 1. A vacuum pump comprising, in combi-l y nation, a casing provided with a pump chamber and including two structurally separate parts having contacting surfaces where they join, one of the contacting surfaces having a groove between the pump chamber and the exterior of the casing, a sealing liquid filling thegroove, an eccentric rotor in the puinp chamber, a reciprocating valve in the casing and cooperatingwith the rotor, and a second nected with the pump operated by said 'valve and connected with the groove to reduce the gaseous con tent of the sealing liquid.

2. A vacuum pump comprising, in combi;

nation, a casing providing a ump chamber with inlet and outlet ports andJ including two structurall separate parts having contacting surfaces w ere they join, one of the surfaces having a groove between the pump chamber and the exterior of the casing, a sealing liquid fillin the groove, an eccentric rotor in the cham er, a blade projecting into the chamber and cooperating with the rotor, and two additional pumps operated by the blade one connected with the exhaust port of the main pump and the other connected with the groove for outgassing said sealing fluid. p

3. In a vacuum pump comprising, in combination, a casing provided with al pump chamber and including two structurally separate parts having contacting surfaces where they join, one of the contacting surfaces having a groove between the pump chamber and the exterior of the casing, a sealing liquid filling the groove, and suction means conooveand removing air adsorbed by said liquid. p,

4. In a vacuum pump comprising, in combination, a casing providing a pump chamber with inlet and outlet ports and including two structurally separate parts having contacting surfaces where they join, one of the surfaces having a groove between the ump chamber and the exter or of the casing, a sealing liquid in said groove, piston means cooperating with the chamber, and a second pump having an inlet port connected with the groove whereby the lilid will be outgassed and fluid entering e joint between the se arate parts of the casing is intercepted 4andJ removed by the second puindp.

5. 'In a vacuum pump exposed irectly to the atmosphere, having a casing made of joined arts, and a high vacuum cylinder within t e casing, that 'method of protecting the hi h vacuum cylinder from the ingress of gas w ich consists in forming channels in the contacting faces of the joined arts, continuously filling the channels wi a liquid having a vapor-pressure below that attain`- able with the um and continuously subljecting the li ui wit in the channels to a igh ration of the vacvacuum uring the o V'ultim pump for out assing said liquid.-

liquid seale vacuum ump comprising a casing made of joine parts having cllliannels in 1the olitacting surfaces where t e 'oin a i ui av a vapor ressure beldrw;I thepresgure whiclilgan be prodiicedby the pump lilling the channels and forming simultaneously the sealing and lubricating means, a high vacuum pum ing element and a second vacuum pumping e ement within the casing, the intake of the lsecond element being connected to the channelsfor outgassing iis the sealing liquid and for removing the entrained pollutmg substances therefrom durin the operation of the pump.

g. A liquid sealed vacuum pump having a casing directly exposed to the atmosphere,- means for sealing the casing comprising a low vapor-pressure liquid occupying channels formed in the casing, a vacuum cylinder within the casing having inlet and exhaust ports thereto, and a second vacuum pump acting upon the sealin liquid for removing adsorbed and dissolve gases therefrom.

8. A liquid sealed vacuum pump having a easing made of joined parts, and having channels in the mating surfaces where they join, an oil reservoir within said casing, a piston chamber within said casinv, a piston or said chamber, said chamber being supplied with oil from said reservoir, means for sealing the casing comprising a liquid in the channels and means to remove the adsorbed air and dissolved gases in the liquid supplied to said chamber and to said grooves.

9. A vacuum pump comprising, in combination, a casing havin a pump chamber therein, a rotary piston or said chamber, intake and exhaust ports for said casing, a shaft member for said piston, bearing members for said shaft members, certain of said members having grooves therein for containing a lu bricant, a reciprocating blade for engaging said rotary piston, a pump chamber at each side of said blade, a piston on said blade at each side thereof for said last named chambers, one of said chambers being in communication withsaid first named pump chamber for receiving gas discharged therefrom and discharging the same into the air, and the other in communication with said grooves for lowering the pressure therein and for outgassing the lubricant contained therein.

In testimony whereof I aliix m signature.

JOHN DU ROVIN.

CERTIFICATE or CORRECTION.

mem No. 1,890,573, i i' l Jona DURovm It is hereby certified that error appears in the printed specification of the above numbered patent requiring'correcton as follows: Page 4, lines 83 and 93, claims 3 and 4, respectively, for "ln a" read "A"; and that the said Letters Patent should be read with these corrections therein that the same may Conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of February, A. D. 1933.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

December lf),v 1932.

the sealing liquid and for removing the entrained pollutmg substances therefrom durin the operation of the pump.

g. A liquid sealed vacuum pump having a casing directly exposed to the atmosphere,- means for sealing the casing comprising a low vapor-pressure liquid occupying channels formed in the casing, a vacuum cylinder within the casing having inlet and exhaust ports thereto, and a second vacuum pump acting upon the sealin liquid for removing adsorbed and dissolve gases therefrom.

8. A liquid sealed vacuum pump having a easing made of joined parts, and having channels in the mating surfaces where they join, an oil reservoir within said casing, a piston chamber within said casinv, a piston or said chamber, said chamber being supplied with oil from said reservoir, means for sealing the casing comprising a liquid in the channels and means to remove the adsorbed air and dissolved gases in the liquid supplied to said chamber and to said grooves.

9. A vacuum pump comprising, in combination, a casing havin a pump chamber therein, a rotary piston or said chamber, intake and exhaust ports for said casing, a shaft member for said piston, bearing members for said shaft members, certain of said members having grooves therein for containing a lu bricant, a reciprocating blade for engaging said rotary piston, a pump chamber at each side of said blade, a piston on said blade at each side thereof for said last named chambers, one of said chambers being in communication withsaid first named pump chamber for receiving gas discharged therefrom and discharging the same into the air, and the other in communication with said grooves for lowering the pressure therein and for outgassing the lubricant contained therein.

In testimony whereof I aliix m signature.

JOHN DU ROVIN.

CERTIFICATE or CORRECTION.

mem No. 1,890,573, i i' l Jona DURovm It is hereby certified that error appears in the printed specification of the above numbered patent requiring'correcton as follows: Page 4, lines 83 and 93, claims 3 and 4, respectively, for "ln a" read "A"; and that the said Letters Patent should be read with these corrections therein that the same may Conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of February, A. D. 1933.

M. J. Moore,

(Seal) Acting Commissioner of Patents.

December lf),v 1932.

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