US2929550A - Rotary pumps and valves therefor - Google Patents

Description

March 22, 1960 P. sADLER 2,929,550

ROTARY PUMPS AND VALVES THEREFOR Filed March 2, 1956 4 Sheets-Sheet l INVENTOR PETER SADLER March 22, 1960 P. sADLER ROTARY PUMPS AND VALVES THEREFOR 4 Sheets-Sheet 2 Filed March 2, 1956 mvEm'oR PETER SADLER :J4/JM, 6042 Mu, www

ATTORNEYS March 22, 1960 P. sADLER ROTARY PUMPS AND VALVES THEREFOR 4 Sheets-Sheet 3 Filed March 2, 1956 INVENTORS PETER SAnLER March 22, 1960 P. sADLl-:R 2,929,550

ROTARY PUMPS AND VALVES THEREFOR Filed March 2, 1956 4 Sheets-Sheet 4 l l g I 1:11:55: 1111- l l l I I PS, .l

ATTORNEYS ROTARY PUMPS AND VALVES THEREFR Peter Sadler, Salford, England, assignor to N.G.N. Electn'cal. Limited, Manchester, England, a British company Application MarchZ', 1956, Serial No. 569,005

Claims priority, application Great Britain March 4, i355 4 Claims. (Cl. 23d-147) This invention relates to the type of pump which comprises a hollow casing, a crank rotatable therein, a displacer on the crank, of such size and shape that if carried round by the crank it will make contact or near-contact continuously with the interior of the casing walls, a vane slidable in a slot in the wall of the casing so as to engage the displacer and with it to divide the casing into two chambers of variable volume, an inlet to the casing at one side of said vane and a delivery port at the other side thereof. Under the term crank is included not only a crank properly so called but also an eccentric, which is its equivalent.

lt is an object of the invention to provide a pump suitable for use as a vacuum pump and capable of evacuating to high vacua, such as corresponds to an` absolute pressure of the order of a few microns on the mercury gauge.

lt is a feature of the invention that a pump of the type described is madewith a large inlet pipe and vacuumtight discharge valve so as to be suitable for use as a vacuum pump and with a casing the peripheral wall of which is slotted right through to allow the vane to pass to the exterior of the casing. In any such pump the sliding vane must be well lubricated and by the construction described the internal vacuum created when the pump is operating tends to draw oil into the interior of the pump along the faces of the vane. Such oil acts to reduce the clearance volume in the casing at discharge and so to increase the vacuum obtainable.

In the preferred construction the axis of the crank extends in a substantially horizontal direction and the vane in an inclined direction upwardly from the displacer, the inlet being below and delivery port above the vane. This disposition of the parts has the advantage that lubricant tends to collect in the pocket formed between the upper face of the vane and the displacer and at each rotation, when the displacer forces air before it into the delivery port, the lubricant reduces the clearance volume as well as acting as a seal. 'Ihe shaft need not be exactly horizontal but it must be preponderatingly so, to form said oil pocket.

Preferably the delivery port is located as closely as practicable to the vane and from it there extends a substantially vertical passage to the outlet valve. Such an arrangement makes it easy to avoid all such internal recesses as might trap air without allowing it to be discharged, aud leaves ample room for the delivery valve itself.

With a view to enabling the lowest pressure on the vacnum side to be reached, the pump according to this invention is preferably operated while totally enclosed in an oil bath, the delivery valve being below the normal oil level of the bath. further regulated quantity of oil beyond that admitted by the sliding vane, to the vacuum space in the interior of the pump. lt too little oil is admitted the pump will be inethcient; if too much it will knock. By regulating the admission, efficiency can` be reached and knocking Means may be provided to admit a 2,929,550 Fatented Mar. 22, 1360 avoided. The displacer, when the pump is adequately lubricated, need not actually touch the interior of the casing as the oil provides a seal; the clearance between displacer and' casing may be of the order of three thousandths of an inch approximately Without causing linkage and thus obviates Wear of the parts.

The invention includes a vacuum pump of the type described having a vane inclined upwardly from the displacer, wherein the outlet port is closed by a non-return valve which consists of a at seating comprising an outlet port and, overlying the outlet port, a sheet of flexible vmaterial such as synthetic rubber which is formed with a closed slit above the outlet port and is clamped on the dat surface surrounding the port at a sufficient distance therefrom to permit the material of the valve element to bend away from the port under the pressure of uid issuing from the port and so to open the slit.

The following is a description by way of example of certain constructions in accordance with the invention, reference being made to the accompanying drawings in which:

Figure 1 is a sectional view at right angles to the axis of the crank shaft;

Figure 2 is a section upon the line 2 2 of Figure l looking in the direction of the arrows;

Figure 3 is a view similar to Figure l but showing an oil bath and a somewhat different construction;

Figure 4 is a section -upon the line 4-4 of Figure 3 looking in the direction ofthe arrows;

Figure 5 is a plan of the parts shown in Figure 4, with the outlet valve partly removed;

Figure 6 is a perspective Y viewl of a valve-member shown in Figures 2 and 3; and

Figure 7 is a detail.

Referring to Figures l and 2, the construction comprises a stationary body B having a cylindrical interior bore B1 in which works a displacer R mounted on a crank-pin C. The crank-pin C is supported on a crankdisc D1 carried by a crank-shaft D. A vane A set at an angle of 45 degrees to the horizontal slides through the body B and has a head A1 which is'cylindrical in the direction parallel to the crank-pin C and is journalled in one side of the displacer R. The effect is that the displacer R, while being carried round by the crank-pin C, does not rotate but acts as though it were a connecting rod which causes the vane A to reciprocate to and fro in its slot in the body B. The interior B1 of the casing is closed by two end-plates E, E1 and the dimensions are such that the displacer R lits the interior of the casing. The shaft D extends through a boss E2 in the end-plate El and the crank-disc D1 is recessed into and lits in the plate E1. Suitable screws which Vare not shown hold the end-plates on to the body. The side edges of the vane A also tit against the end-plates.

The pump body has an. inlet port I connected to the vessel or apparatus to be evacuated and located just below the vanerA. lt has an outlet port O just above the vane A leading upwards to a horizontal annular seating S on which seats a plate-valve member P urged on to the seating by a spring Y. The lift of the plate-valve P is limited by means of an adjustable screwed stop X. The strength of the spring Y can be adjusted by means of a screw-threaded thrust-member T supported by a bridge Tl carried on pillars T2, T3 supported on the end-plates El, E2. The stop-member X has a stem X1 which extends through the thrust-member T so as to permit it to The vane A is'of the same width as the casing body I and projects clear through the casing into the space outside it. If the vane is oiled externally therefore, the vacuum inside the casing will drawin oil, keep the'vane surfaces fully lubricated and maintain a good oilV seal (which is most important) between the vane surfaces and the casing and end plates. lThe easiest way of ensur-ing this is to run the pump immersed in oil.

It will be noted that owing to the inclinedY disposition of the vane A, the lubricant which is necessary in a rotary pump tends to collect in the pocket formed between the base of the vane A, where it is pivoted in the displacer R and the upper surface of the displacer itself as indicated at L. Owing to the close proximity of the discharge port to the vane A, this pocket of oil iscarried upwards at each revolution and forced upwards through the port so as to'llthe volume of the port and reduce the elective clearance volume ofr theVA pump at discharge to zero, 'which' is an important point in eiciency when high vacuaV are` concerned. Moreover, the lubricant Vcarried at this point ensures that the walls of the upper part of the casing are well lubricated. An oil inlet is `indicated at M which is preferably located in the suction partof the casing and is preferably regulable. Any excess oil will escape through'the valve P-but`the oil'inlet is best regulated so as to minimise such escape practically to zero, because otherwise Vit may cause knocking.

Figures 3 to 7 show an alternative construction including the oil bath, although itV will be appreciated that the oil bath could rbe adoptedvif desired in connection with the construction shown in Figures l'and 2.

vIn Figure 3 there is a vpump casingY 11 Vcorresponding tothe casing B of Figures l and 2, havinga cylindrical interior, a vane 12 similar to the vane A, a displacer 13 'similar in function to the displacer R, aninlet. port 1li similar to the port I and an outlet port 15 similar to the port O. The displacer works as before butV is mounted on an eccentric shown at 16 and held on the shaft 36 by a pair of screws 37, 38. Thevane 12'has Va cylindrical head 17 journalled in the displacer 13. All these parts are shown as immersed in anoil bath19 contained in a hollow base 20 for the pump and the inlet port 14 is connected to a large suction pipe 21 coming in from outside the casing. The suction lpipe as inclined as shown to ensure that no oil can collect in it. The base 20 is provided with a large opening 21 above the oil bath in its toppart, which is closed with a cover 22.

The discharge valve on the outlet port 15 in this case consists of a sheet of resilient synthetic rubber-like material 23 preferablymade from` the material sold under the trade name of Nygonf The Nygon valve member is held down on a horizontal face V24 formed on the top of the body of the casing 11 by means of a rectangular clamping plate 25 which has a central aperture`26. In Figure of the drawing the clamping plate is shown in position but it is supposed that part of the Nygon valve member 23 hasA been removed and it will be seen that the .discharge port l5 is nota single port but'consists of a row of drilled holes running across the body 11 from sidel to side. shown in detail in Figure 6 and it will'be seen that it has a central slit 27 which extends above Ythe row of drilled holes of the outlet port 15.V The slit V27 is punched through the Nygon sheet by a thin sharp-edged blade and the port holes 15 are entirely covered by the slit 27. 1n order to reduce the depth of the knife cut, the

Nygon may be grooved on the'underside, in the por' slit will `open and allow the lluid under pressure toY escape. Y

The Nygon sheet 23 is not clamped tight on the face 24 by the plate 25. The.,screws 35 which hold it down The Nygon valvemember is.

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are machined with shoulders which permit the plate to rise a little-about one thirty-'second of an inch-but when the pump -is working under a substantial vacuum the sheet 23 is held down by the vacuum and does not rise. In the initial stages of evacuation however the discharge of air is very heavy and under these condtiions of valve and one which operatesV practically noiselessly.

Thervalve moreover has the advantage of being uidtight without depending upon making a close seating on the metal below; it closes'` the two sides of the slit against themselves. Furthermore, there is a minimum of vacant space beneath the valve when lifted. All these features make the valve particularly suitable for use in a vacuum Pump lnrthe case of the pump shown'in Figures 3 to 7, there is an oil inlet 31 locatedon the part ofthe casing furthest from the air inlet 14 and thisoil inlet is controlled by a regulating valve 32screwed into one of the end discs 42 of the casing. The valve 32 has an axial needle valve inside it and a lateralrinlet so that oil can flow in from the oil-bath 19, and this orifice can be regulated by rotating the needle valve. Oil also enters on the surfaces of the vane 12. As before, the oil which is allowed into the interior of the casing is carried upwardly by the displacer 13 and tends to collect in the pocket formed between the vane 12 and the top ofthe displacer and to be forced up the outlet ports 15 when the displacer, in the course of the revolution'ofthe eccentric 16 rises tothe upper part of the casing. Y 'A There is, moreover an air-inlet`40 on the edge of flange 41 which forms part of the side of the oil ybath 19 and supports the pump, as shown in Figures 4 and 5. The air inlet is controlled by a needle Vvalve 42 and leads to passage 43, which opens into thecasing 11 of the pump close` to the discharge port 15. The purpose of this is to admit a regulated amount V(very small) of air to the discharge side of the pump, atY a place where itY will never be effectively open Vto the inlet port 14. This prevents condensation of water vapour in the discharge. It will be appreciated that there is usually water vapour as well as air to be drawn in through 14. At high vacua,

the ratio of compression is very high and the'vapour is inclined slot in its peripheral wall, the slot beingup-Y wardly inclined to the vertical and horizontal planes; aV

drive shaft the axisof which passes through the casing; a driving element, eccentrically disposed on saidshaft within said casing; a displacer in the Vcasing mounted on said driving element and dimensioned to make a sliding fit with the casing asrit is carried roundby the driving element; a vane pivoted to the displacer and extending therefrom through said upwardly inclined slot to the exterior thereof; an'inlet port tothe casing located below the vane; an outletY port leading vertically directly upward through thecasing wall immediately above the vane; a deliveryliftvalve above said outlet port and kan oil inlet in .thecasingin such fa positionas to direct oil into the casingrabove the displacer on the compression side thereof during a part of the compression partir/JnI of the cycle but to be obturated by the displacer before delivery occurs through the valve.

2. A vacuum pump as claimed in claim 1 wherein an inlet port for ballast air is located on the casing at such a point as to be obturated by the displacer during part of the compression portion of the cycle after the oil inlet has been obturated.

3. A vacuum pump as claimed in claim 1 further-comprising a regulating valve in communication with the oil inlet to control said oil inlet.

4. A vacuum pump as claimed in claim 3 in which the pump is enclosed in an oil bath, and the regulating valve is below the normal oil level of the bath wherein the regulating valve comprises a needle valve, having a lateral inlet from cil from the oil bath.

References Cited in the le of this patent UNITED STATES PATENTS 6 Keenan July 5, 1932 Cuthbert Aug. 14, 1934 Hull et al. Nov. 8, 1938 Docg Iuly ll, 1939 Schanck July 18, 1939 Albertson Aug. 8, 1939 Gaede Feb. 20, 1940 Schanck et al. May 21, 19'40 Rhodes Nov. 9, 1943 Knowles June 24, 1947 Langdon Feb. 24, 1953 Makaro et al June 30, 1953 Klingler July 7, 1953 Bram July 21, 1953 FOREIGN PATENTS Australia Oct. 19, 1950 Sweden Mar. 30, 1954 Great Britain May 26, 1921 France June 15, 1953

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