US1374650A - Vacuum-pump - Google Patents

Description

l S. H. HALL.'A VACUUM PUMP. APPLICATION FILED FEB. 3. |920;v

Patented Apr. 12, 1921.

'arrancan S. H. HALL; VACUUM PUMP.

APPLICATION FILED'FEB. 3, 1920.

Patented Apr. 12, 1921.

`'Z SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

sELDEN H. HALL, or POUGHKEEPSIE, NEWv YORK, AssIGNoR rro THE DE LAVAL sEPAaA'rOR COMPANY, or NEW YORK, N. Y.,'A CORPORATION OF NEW JERSEY,

VACUUM-PUMP.

Specification of Letters Patent. Patented Apr. 12, 1921.

Application iiled February 3, 1920. Serial No. 355,999.

To all whom t may concern Be it -known that I, SELDEN H. HALL, a citizen of the United States,-residing at Poughkeepsie, county of Dutchess, and State of New York, have invented a new and useful Improvement in Vacuum-Pumps, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, which form a part of this specification.

My invention relates to pumps of the known type having an approximately cylindrical body in which there is eocentrically mounted a rotor carryingvanes adapted to slide outward and press against the inside of the body. The body, in well designed pumps of this type, varies from the cylindrical form enough to cause all chords drawn through the center of rotation of the rotor to be equal.

In order that this type of pump may run easily, appreciablel clearances must be left between the rotor and the body, between the ends of the vanes and the heads, and in the rotor at the sides of the vanes. Frequently a considerable quantity of oil is used to seal these clearances.

Many of these pumps are used in the operation of cow milking machines. In such cases the inlet to the pump is always at about half of atmospheric pressure (about 15-16 inches of vacuum) and the discharge is at atmospheric pressure.

Pumps of the general construction above specified exhibit three notable faults. First,l the discharge is very noisy; second, the discharged air carries with it a large quantity of oil in such a finely divided state that it is impossible to catch it in an oil separator;v

and third, the efficiency is low.

I have found that all three faults inoperation are due to one error in construction, namely: that the ports between the com- I pressing chamber and the discharge passage are allowed to open before the pressure 1n the compressing chamber is equal to that in the discharge passage. The result is that at every opening of the port there is a rush of air from the discharge passage into the compressing chamber and then, as the vane moves forward, this air, in addition to that drawn in at the suction inlet, has to be forced out through the discharge ports. With a four vane pump running ve hundred revolutions per minute there are two -thousand of these inward and outward rushes of air per minute, causing a very disagreeable pulsatmg noise. When the pump is oil-sealed, as it` must be to prevent exces-v sive leakage and insure suflicient lubrication, there is always some oil being carried out with the discharged air. The above mentioned pulsations tear this oil up and atomize it so thoroughly that it passes through any oil separator that may be provided and escapes in the form of a fog in the discharge,v

not waste oil'and will have la maximuml capacity and maximum eiiiciency.

I obtain maximum capacity by making the inlet ports of ample size and of such length that each vane crosses the port ends at the insta-nt that the volume between it and the vane ahead is at a maximum. I obtain quiet operatlon, conservation of oil and high etliciency by making the discharge ports of ample size and of such length that each vane crosses the port ends at the instant that the pressure in the space behind it is about equal to the pressure in the discharge passage.

, In the accompanying drawings, which show a pump embodying this invention in a preferred form:

Figure l is a section through the pump parallel to the shaft.

Fig. 2 is a section on line 2-2 of Fig. 1 at right angles to the shaft.

Fig..3 is a section on line 3 3 of Fig. 1, showing the Shape of the oil reservoir at the pulley end. l

The rotor a is mounted on a shaft b carried by bearings in the heads c and d. The rotor has four slots in which vanes or wings e slide toward and fromthe shaft. Spacers f maintain a uniform distance between opposite vanes. In the outer edges of the vanes e are'grooves in which semi-circular rods g Oscillate.

Between the having a bore of such shape that all diameters (or chords) measured through the cenheads Gand d is a housing bter of the shaft b are equal. At one Aside of the housing is an inlet chamber z' connected with the bore by the ports j' and at the other side is an outlet chamber k connected with the bore by the port Z.

The bottom end of the lower port j is so located that at the instant the tip g on the end of a vane e passes over and closes it, the space between that lvane and the vane ahead of it isat a maximum.

The lower end of port Z is so located that i the tip g of a vane e will pass over it and open the port at theftime thatthe'pressures on the two sides of such vane are equahand at the time that the volume betweenthat same ratio to the maximum volume that the inlet pressure dlvided by `its absolute temperature bears to the discharge pressure divided by the discharge temperature.

From-the outlet chamber c a passage m leads to the central chamber of the oil separator,ithe upper half of which-is separated /from the side chambers by the half partitions n and o. From the side chambers,

passages p lead to the exhaust pipe. Acrossv the bottom of the centraLcharnber is a dividing fence g. From the side chamber of the oil separator there lead to the shaft oil holes 1' and s having branches t and u communicating with the inside of the rotor a.

Formed within the heads c and d are oil reservoirs /v and 'w communicating with the inside of the rotor a by holes w and y having their lower edges above the bottom of the inside of the rotor. One head d carries a hollow axle 10 around which the pulley 11 revolves on bearing rollers 12 and drives the shaft b through the liexible coupling 13.

In order to have an easy running pump the rotor a is made slightly shorter than the housing k, giving clearance between `it and the heads, and it is so located that there is an appreciable clearance between the top of the rotorrand the top of the housing. The vanes e are made easy fits in their slots and the separators f are made so short that the vanes turn freely in the housing.V These clearances, while, desirable for easy running, all tend to cause leakage.

When in operation, the pump should contain suiiicient oil to cause the level in the reservoirs 'v and w to reach about one-quarto the' shell of the rotor. Centrifugal force,

due to the rapid rotation of this oil, will prevent the entrance of excess oil. Cen-r trifugal force will alsokforce the oil into all the clearance spaces and so seal them. Oil

that passes outward between the rotor andv the heads and through the clearances at the Sides of the vanes will seal the ends 'and outer edges of the wings. Any excess oil 1 reaching the spaces between the rotor and the housing will be thrown, with the discharging air, outward throughv the port Z into the lchamber 7c and then upward at high velocity through the passage m. Because of the circular path that the air is compelled to take in the `oilI separator, all

oil in appreciable sized, drops will be thrown against thewall andwill collect in the bottom, while the air will pass under .the partitions 'n`- and o, upward through the passages p and out `through the exhaust pipe. If the oilwere so finely divided yas to form a fog, some of it would be carried around and out with the air; but by arrangf ing the discharge port as hereinbefore dej scribed, with consequent avoidanceofpuly sations at the discharge, the atomization of l p `vre5 wall of'v n oil is prevented and its waste avoided.

As the oil flows down .the back the separator, it will bey divided, by the fence g, into two streams, one lflowing to each end of the separator and thence downward through the holes 1' and s to lubricate the bearings. All oill in excess of thatv re- -quired for the bearings will flow through the holes t and u to the-interior of the rotor, l

"supply forces some out through thel hole 22 in the inner ange of the hub and it escapes into the reservoir fw.

When the pump stops, all the oil from the annulus inside the rotor, with all oil from the separator, falls to the bottom of the rotor and a large part of it flows outward through the holes and y, to be stored in the reservoirs fu and lw untilneeded again.

If the pump stands idle for a long time,

much of the oil from the reservoirs lv and lw may leak past the rotor into the bottom of the housing. yWhen the pump .is started, the first turn will throw this oil up into the separator, whence it will flow, partly by the holes 7' and t and partly by the holes s and u', to the .insideof the rotor, ready to perform its sealing and lubricating function.

With the described porting, the pump has a maximum capacity for its size, the discharge isrelatively quietLand the oil sent out of the pump with the discharge will be insuch large drops that practically all of it will be caught in the oil separator and re-v turned to the pump.

Certain novel features of the construction herein shown, particularly the arrangement of oil reservoirs below the bearing and open to the atmosphere and adapted to\ catchv drips from the bearings and thepulley hub,

to supply oil to form a sealingannulus within the rotor and to receive' 011 without overi type designed for producin n gree of'exhaustion, the com inatlon with a.

ters Patent is;`

flow when thepump stops, are not herein claimed, asthey are not my invention, but form the sub'ect-matter of another application filed by eredith Leitch filed February 3, 1920, Serial No. l56014.

AHaving now fully described my invention, what I claim and desire to protect by Let- 1. In a vacuum pump rotor and sliding vanes, of a body having'a discharge port extending through such arc of the body as to be opened by a vane passing over it at substantially the time that the pressures on the two `sides, of the vane are equal.

2. In a vacuum pump of the sliding vane type, `the combination with a body having an inlet and a discharge, a contained rotor and sliding vanes on the rotor, said rotor and vanes having appreciable clearances, of means to seal said clearances Wlth a body of oil, and means to minimize atomization of oil in the discharge, said means comprising vthe positioning of the port communlcating with the discharge so thatit Will be uncovered by a-vane at the time that the pres- Qf the sliding van@ a specific de- `sules on the two sides' ofthe vaneare substantially equal.

3'. In a' vacuum pump ofthesliding vane I type, the combination with a body having,

Y an inlet and a discharge, a contained rotor and sliding'vaneson the rotor,`said.r0tor and Avanes having appreciable clearances, of .means to seal said clearances with a body of preventpulsationvof air vfsubst'antiall the same time that the volume between suc vane and `the vane in advance -thereof is at a maximum, said body having an outlet port'so positioned as to 4be opened by a. vane passing over it at the ltime that the pressures'on the two sides of the vane are .substantially equal.

In testimony of which invention, I have hereunto set my hand, at Poughkeepsie,

of Januar 1920.

N. Y., on this 29 da Y, ELDENv HALL;

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