US2073188A - Rotary pump - Google Patents

Description

March 9, 1937. c. J. WESTIN 2,073,188

ROTARY PUMP Filed May 28, 1934 2 Sheets-Sheet l March 9, 1937. c, wEs 2,073,188

ROTARY PUMP Filed May 28, 1934 2 Sheets-Sheet 2 Illllllll i L wuum r\ 66 3 F WI Charlasdhs fipm,

Patented 9, 1937 PATENT OFFICE ROTARY PUMP Charles J. Westin, Philadelphia, Pa., assignor to F. J. Stokes Machine Company, a corporation of Pennsylvania Application May 2a, 1934, Serial No. 728,006

2 Claims.

This invention relates to improvements in mechanical gas pumps and particularly to the type of pump used either as compressors or as vacuum pumps. One form of this type of pump 5 is shown and disclosed in U. S. Letters Patent No. 1,899,904, granted to O. S. Sleeper and C. J. Westin on February 28, 1933. Another form is disclosed in my co-pending application Serial No. 724,974, filed May 10, 1934, now Patent No.

One object of my invention is to provide new and improved means for automatically separating the air and gas from the sealing medium..

Another object is to provide improved means for condensing the vapors coming through the pump or the vapors created by the rapid flow and the pressure in the pump.

It is also an object of my invention to arrange the de-gasing and de-vaporizing means so that the sealing medium is automatically returned to the reservoir for recirculation.

A further object of my invention is to provide a novel separator structure for separating vaporized oil or liquids from the exhaust gases, the

separator being formed as an independent unit mounted upon the base of the pump andhaving a duct for returning the condensed or separated oil to the ofl reservoir within the base of the pump.

By means of these and other improvements which will be understood from the specification, I obtain several advantages: such as, increased capacity to handle larger volumes of gas in the same space of time; a lower operating temperature; a higher vacuum for the same operating speed; a saving in the amount of lubricating and sealing oil used; and in general a cleaner operating machine.

In order to operate at practical efficiency, all

moving parts must be machined to close fits or small clearances so that they will cooperate throughout the cycle 'with'the lubricating and sealing medium in forming a perfect or nearly perfect seal between the high and low pressure sides of the pump. It is of utmost importance that the sealing medium entering the pump system should be demulsified or freed of all air, gases or water. Thesealing medium, of course, is brought in close contact with all the moving parts of the pump and should therefore embody such properties as make it suitable as a lubricating medium. The sealing-lubricating medium, which hereafter will be referred to merely as oil will therefore serve a dual purpose and should have certain desirable properties, such as low percent- (Cl. 23(l207) "ly circulating from atmospheric pressure, through age of volatile constituent and a low demulsibil ity. Oil will, however, absorb gas in considerable quantities, particularly when churned around with gas under pressure as is the casein machines of the type here described. As the oil is continualthe low pressure stage approaching the high pressure, and being expelled at high pressure into atmospheric pressure again, it is bound to become more and more polluted, thereby gradually dem creasing the efliciency of the pump. Furthermore, the oil and gas are discharged at considerable speed and pressure through comparatively small discharge ports, and this has a tendency to vaporize or atomize some of the oil, which vapors 15 or atomized oil would pass 01! with the gas and be lost unless properly trapped and separated from the free gases before these reach the outside space.

In medium sized and larger pumps of for example 50 cubic feet capacity and over, I find that, on account of the large volume of gases handled, the separator should be of considerable size to effectively devaporize the gases. For this reason it is preferable to place the separator outside the housing or oil reservoir. It is also a convenience in manufacture.

I have also found it very helpful to chill the gases as they enter the separator so as to cool and condense out the vapors entrained in the 30 hot gases.

The principles of construction and novel arrangement of parts will be readily understood by reference to the annexed specification and draw- IDES. 35

In the drawings, Figure 1 is a vertical view of my invention showing the pump with the exhaust separator, the pump being shown in full section and the separator in part section;

Figure 2 is a vertical section showing the de- 40 tails of construction of the separator unit;

Figure 3 is a sectional view of Fig. 2 taken along line 33; and

Figure 4 is a sectional view of Fig. 2 taken along line 1-4. 15

Referring to the drawings, there is shown a rotary pump having a housing l0 mounted on a hollow base i I. In the housing is formed a cylinder l2, closed at both ends by end-plates, and partially surrounded by a space l3 adapted to 50 receive water or other cooling medium, and having a passage l4 for conducting the discharge gases and oil from the discharge valve into hollow base II. The housing I0 is extended at the top to form aninlet compartment l5 of rectangular outline connected directly to and extending the full length of cylinder l2 and being closed at both ends by extensions on the cylinder endplates. The inlet compartment II has a lateral extension Ila to which an intake connection I. is secured. Alongside the intake compartment i5 in the extension of housing II is formed the outlet compartment with suitable accommodations for the outlet valve assembly I! arranged over a row of cylindrical discharge ports is connecting the outlet compartment I! with the cylinder I2. One wall of compartment I1 is formed as a cover-plate 2I which is made hollow so as to provide a free passage 2| for the discharged gases and sealing medium into the corresponding passage of the housing to which it is connected. The inside wall 22 of the passage 2| in coverplate 20 is made of such height that it will act as a dam to retain a sumcient amount of the sealing medium in the outlet compartment l'l to completely cover or submerge the outlet valve arranged over ports is, only the excess of sealing medium spilling over the dam 22 and escaping down into the base ll together with the free gases and vapors. The details of the outlet valve construction are fully described and claimed in my copendlng application Ser. No. 724,974, filed May 10, 1934, now Patent No. 2,070,151.

Through the center of cylinder I2 is mounted a shaft 23 with supporting bearings in the cylinder end-plates and driven from any suitable source of power. Keyed or otherwise fastened to shaft 23 is the rotary eccentric 24 which carries on the outer surface the tube-shaped oscillating piston 25. A slide valve 26 is fastened to the piston 25.

by means of a hinge 21 of such construction as to provide a gas-tight and flexible connection between piston 25 and valve 23. This construction is described in greater detail and is claimed in the Sleeper and Westin patent referred to above. Through this connection, valve 26 receives a reciprocating rectilineal motion in the rectangular inlet compartment l5, and as the valve 26 slides back and forth, the inlet ports 28 in the valve connect the inlet compartment l5 with the cylinder 12 at the proper time in the cycle.

All discharge gases, vapors and oil must pass over dam 22, through passages 2| and I4 down into the oil reservoir II in the base II. This reservoir is of such construction as to provide ample space for the storing of the sealing medium or oil and also provides head-room or air space above the oil level for the gases to pass on to the separator 53 mounted upon a lateral extension Ila of the base ll. Connections are made from an oil filter 30 in the reservoir 4!, through pipe line 3| to a valve 32, through which clean oil is drawn into the reciprocating valve chamber for lubricating and sealing purposes. A cooling coil 33 is usually provided in reservoir 4| and materially aids in keeping the operating temperature of the pump low by cooling the oil. Coil 33 is connected to the space I3 by pipe 3| for circulation of water through the coil.

A separator and other baiiie arrangement may be used in the base but to get satisfactory separation these parts would have to be so large as to make the size of the base out of proportion. I, therefore, prefer to placea separator 53 of suitable size outside of the housing or reservoir and lead the gases and vapors from the reservoir into the separator through the duct 52 formed by extension Ila on which the separator is supported.

It is desirable that only the gases are allowed to pass of! while the oil entrained in the gases or vaporized during the cycle of operation is separated out and returned to the reservoir for recirculation. Without proper means for perfect separation a considerable volume of vapors pass out into the surrounding room, particularly when starting the pump or when operating at low pressures, thus filling the room with disagreeable smoke. While, of course, it is possible to eliminate the smoke nuisance by connecting the discharge to the outside of the building, this does not prevent the resulting waste of good lubricating and sealing oil.

The above diillculties and losses have been eliminated through the use of separators constructed according to my invention. The separator construction is formed as a unitary structure bolted to a flange on base extension Ila. The separator consists of a casing 53, which may be of any outline, but for the sake of simsimplicity it is here shown as a cylinder. The bottom 54 has two openings communicating with the hollow base II. The large opening 56 provides free passage for gases and vapors from outlet duct 52 into the separator. It will be noticed that a rim 5! is provided around opening 56. This rim forms an annular reservoir surrounding the inlet opening 58 and serves the purpose of keeping the separated oil from' running back into the duct 52 where the current of gases may tend retard the flow back into the reservoir or might pick up some additional 011 particles. The oil flows back through the return passage or opening 55, which has a pipe 58 leading down into the reservoir 4| well below the oil level.

The top or head 53 of the separator has an exhaust connection 60 which may be a pipe line or duct through which the obnoxious gases may be discharged outside the building.

The separator casing may be of any suitable diameter and height to accommodate the proper size and number of shelves or baiiies necessary for proper separation. The spacing of the baiiies should be such that the current of gases will pass through at a comparatively rapid rate of flow without creating any noticeable back-pressure. At the same time it is desirable to arrange the baflles so that the current will strike against the baflie-surfaces, causing some of the entrained oil to adhere to these, as well as force the current to make short bends or turns where the heavier oil particles are thrown against each other and unite into drops which fall down onto the sloping bailie surfaces below.

The whole separator casing may be filled with cooled baflies of the hollow-shelf type or with a combination of plain and cooled type'as shown in Figures 2 to 4. A plain type of bailie is one of the simple plate construction as compared with the hollow box-like shelf or baille which will be referred to as cooling shelves or cooling baiiies.

In the construction shown, the casing 53 is provided with a number of baflies arranged across the casing, extending alternately from opposite sides of the casing past the middle thereof, thereby forming a zigzag path for the gases passing through the separator.

The first few shelves or baiiies 5|, 52 and 63 adjacent the inlet opening 55 are made hollow, and have connections so that a cooling medium, such as water, may be circulated through them to chill the gases and vapors as they enter the separator. The various shelves Si, 62 and 63 are connected by communicating passages such as the hollow partitions or ducts 54 and a to Ben mit the cooling fluid to be passed from one baille to another. The water enters at 65, circulates through the hollow battles and is discharged at 66. The edge 12 of the baille which comes nearest the open passage will be referred to here as the front of the battle or shelf.

It will be noticed that the baflles are mounted at an angle with the horizontal, sloping down diagonally towards the front as well as towards one side of the front edge. The reason for this slope or incline is to guide the oil collecting on top of the shelf towards one side where it will run down along the wall of the separator casing instead of, as otherwise might happen, anywhere and everywhere along the front edge in the path of the current. The angle of slope may be any. suitable angle as long as the slope is suflicient to make the oil run oif fast enough to prevent the forming of a drop. It will be noticed from the drawings that the first shelf BI is supported in the separator so that it has an incline slope from right to left or from the casing to the right sloping down past the center to the front. At the same time it should also be noted that the far side of the shelf is higher than the near side, that is, the shelf is sloping from the far side wall to the near side wall and thus has a slope in two directions. The other shelves and battles are arranged in a similar manner.

Another novel feature is the provision of a gutter 81 under the front edge of each baiile. The current of gases and vapors will strike against the bottom of the battle and a portion of the;

entrained oil will adhere to this surface. When a-suilicient quantity of oil has accumulated on the surface, this will flow towards the front and, instead of dropping off in the path of the current, will be collected in the gutter and run to the side and then down the wall of the casing. Thus, means are provided to prevent reabsorption of any oil which has been removed from the gases. It will be understood that the gutters 61 are not essential but will improve the efliciency of the separator.

The plain baiiles consist of flat plates 68 which may or may not have gutters 69 of similar construction to 61 and serve the same purpose as described for the gutters on the cooling baflies. I prefer to arrange the plain bailles 68 according to the same principles described for the cooling bailles, that is, with the surfaces suitably sloping towards the front and one side in order to provide for the proper draining of the oil. l gr certain vacuum work I have found that theplain bailes 68 are quite satisfactory, and, of course, considerably cheaper to manufacture, and therefore a separator having only plain baflles would mean a considerable economy.

It will be observed that in the construction shown, the exhaust gases from the pump first pass from the outlet valve chamber l'l down through the passage ll into the air space above the oil reservoir 4| in the base of the pump, and then out through the separator 53. BY this arrangement, the gases are first freed of all oil which may be separated by gravity, and are par-. tially cooled by passing over the oil reservoir before they reach the separator. In this way, a partial separation takes place as the gases flow through the air space above the reservoir, and I the separator acts with greater emciency in completing the separation process.

I have herein described the principle of my invention and illustrated a preferred embodiment thereof. Various modifications will occur to those skilled in the art, and I desire it to be understood that all modifications which fall within the terms of the appended claims are to be considered as falling within the scope of my invention.

What I claim is:

1. In combination, a hollow base provided with an oil reservoir therein, a vacuum pump mounted on the top of said base, a gas inlet in said base on one side of said pump, a gas outlet in said base on the other side of said pump, a conduit connecting the pump outlet with the gas inlet in said base, a unitary separator detachably mounted on said base having an inlet arranged over the gas outlet on said base and having an outlet communicating with the atmosphere, said separator being so constructed that the separated oil is maintained substantially out of the path of the discharge gases and embodying a reservoir for collecting all of the separated oil, and a conduit carried by said separator and extending from said separator reservoir to a point below the surface of the oil in said base reservoir for returning separated oil to said base reservoir out of the path of said gases, whereby the exhaust gas discharged into the atmosphere is substantially free from entrained oil and the oil supply is thereby conserved.

2. In combination, a hollow base provided with an oil reservoir therein, a vacuum pump mounted on the top of said reservoir, a gas inlet and a gas outlet formed in said base and communicating with the air space above said oil reservoir, means for passing exhaust gases from said pump into said gas inlet, a unitary separator detachably mounted on said base having an inlet arranged .over the gas outlet in said base and having an outlet communicating with the atmosphere, said separator being so constructed that the separated oil is maintained substantially out of the path of the discharge gases and having an annular reservoir surrounding its inlet opening for collecting all of the separated oil, and a pipe secured to and carried by said separator for returning oil from said annular reservoir to a point below the surface of the oil in said base reservoir out of the path of said gases, whereby the exhaust gas discharged into the atmosphere is substantially free from entrained oil and the oil supply is thereby conserved.

CHARLES J. WEBTIN.

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