US2998826A

US2998826A - Rotary pump valve

Info

Publication number: US2998826A
Authority: US
Inventors: Sadler Peter
Original assignee: N G N ELECTRICAL Ltd
Current assignee: N G N ELECTRICAL Ltd
Priority date: 1956-03-02
Filing date: 1959-10-20
Publication date: 1961-09-05
Anticipated expiration: 1978-09-05

Description

Sept. 5, 1961 P. sADLER 2,998,826

ROTARY PUMP VALVE Original Filed March 2, 1956 I 2 Sheets-Sheet 2 IAIVEA ToC 0231. ,dAwZ/L ym @14 M KZ/m United States Patent 2,998,826 ROTARY PUMP VALVE Peter Sadler, Salford, England, assignor to N.G.N. Electrical Limited, Manchester, England, a British comr y Original application Mar. 2, 1956, Ser. No. 569,004. Divided and this application Oct. 20, 1959, Ser. No. 851,490 Claims priority, application Great Britain Mar. 4, 1955 1 Claim. (Cl. 137'512.'4)

This application is a division of my co-pending application Serial No. 569,004, filed March 2, 195 6, now Patent No. 2,929,550.

This invention relates to an outlet value for 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.

It is an object of the invention to provide an outlet value for 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 guage.

The invention includes for a vacuum pump of the type described having a vane inclined upwardly from the displacer, a non-return valve for closing the outlet port, which valve consists of a flat seating comprising an outlet port and, overlying the outlet port, a sheet of flexible material such as synthetic rubber which is formed with a closed slit above the outlet port and is clamped on the flat surface surrounding the port at a sufiicient distance therefrom to permit the material of the valve element to bend away from the port under the pressure of fluid 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 accompany drawings in which:

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

FIGURE 2 is a sectional view along the axis of the crank shaft with the latter in a different position to that shown in FIGURE 1;

FIGURE 3 is a plan of the parts shown in FIGURE 2, with the outlet valve partly removed; and

FIGURE 4 is a perspective view of a valve-member shown in FIGURE 1.

Referring to FIGURES 1 and 2, the construction comprises a stationary body or pump casing 11 having a cylindrical interior bore in which works a displacer 13 mounted on an eccentric shown at 16 and held on a shaft by a pair of screws 37. A vane 12 set at an angle of 45 degrees to the horizontal slides through the body 13 and has a head 17 which is cylindrical in the direction parallel to the crank-pin 16 and is journalled in one side of the displacer 13. The eliect is that the displacer 13, while being carried round by the eccentric 16, does not rotate but acts as though it were a connecting rod which causes the vane 12 to reciprocate to and fro in its slot in the body 11. The interior of the casing is closed by two end-plates and the dimensions are such that the dis placer 13 fits the interior of the casing. The shaft 36 extends through one of the end-plates. Suitable screws 19 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 pipe is 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 top part, which is closed with a cover 22.

The discharge valve on the outlet port 15 consists of a sheet of resilient synthetic rubber-like material 23 preferably made from the material sold under the trade name of Nygon. The Nygon valve member is held down on the horizontal seating 24 by means of a rectangular clamping plate 25 which has a central aperture 26. In FIGURE 3 of the drawing the clamping plate is shown in position but it is supposed that part of the Nygon valve member 23 has been removed and it will be seen that the discharge port 15 is not a single port but consists of a row of drilled holes running across the body 11 from side to side. The Nygon valve member is shown in detail in FIGURE 4 and it will be seen that it has a central slit 27 which extends above the row of drilled holes of the outlet port 15. The slit 27 is punched through the Nygon sheet by a thin sharp-edged blade and the port holes 15 are entirely covered by the slit 27. In order to reduce the depth of the knife cut, the Nygon may be grooved on the underside, in the portion which overlies the port 15, as indicated at 30, FIGURE 1. Owing to the flexibility of the Nygon if there is pressure in the outlet ports 15 the edges of the material on each side of the slit will lift, and in lifting, the slit will open and allow the fluid under pressure to escape.

The Nygon sheet 23 is not clamped tight on the face 24 by the plate 25. The screws 35 which hold it down are machined with shoulders which permit the plate to rise a littleabout 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 conditions the sheet 23 and plate 25 rise to the heads of the screws 35 and let the air out all round. In the later stages of evacuation the air discharge is so small that the fine slit 27 serves the purpose much better.

The slitted Nygon makes an extremely simple form of valve and one which operates practically noiselessly. The valve moreover has the advantage of being fluidtight 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.

I claim:

A valve unit comprising a valve seating having port means therein; valve means comprising a deformable sheet having a normally closed slit overlying the port means, and a rigid backing reinforcing the sheet and having an opening therein surrounding the slit to allow deformation of the sheet about the slit; and screws passing through the rigid backing and entering the valve seating to locate the valve means on the valve seating,

3 '4 said screws having elongated shanks to allow -the valve 2,247,520 Paxton July 1, 19 1 means to freely move bodily ofi the valve seating. 2,348,097 Smith May 2, 1944 2,378,384 Baker June 19, 1945 References Cited in the file of this patent 2,630,178 Brown Mar. 3, 1953 UN STATES PATENTS 5 2, 7 ,7 D y 2, 1954 157,791 Cameron Dec. 15, 1874 FOREIGN PATENTS 2,186,082 Tamminga I an. 9, 1940 2,201,837 Schanck et a1. May 21, 1940 147,855 Germany 1902