US1890614A

US1890614A - klopsteg

Info

Publication number: US1890614A
Authority: US
Publication date: 1932-12-13
Anticipated expiration: 1949-12-13

Description

Dec. 13, 1932. p, KLQPSTEG 1,890,614

ECCENTRIC PUMP Filed Feb. 21. 1928 p 2 Sheets-Sheet 1 Dec. 13, p .KLOPSTEG ECCENTRIC PUMP Filed Feb. 21, 192s 2 Sheets-Sheet 2 I/I III/II I Patented Dec. 13, 1932 UNITED STATES PA ENT; OFFICE PAUL E. KLOPSTEG, OF CHICAGO, ILLINOIS, ASSIGNOR TO CENTRAL SCIENTIFIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS ECCENTRIC PUMP Application filed February 21, 1928. Serial No. 255,947.

This invention relates to pumps and particularly to those eccentric pumps commonly used for producing high vacua and'has for its principal objects to increase the efficiency of those pumps and thereby reduce the time necessary to effect the exhaustion of a given container.

Those pumps generally include a cylinder closed, except for intake and exhaust ports, an eccentric rotor having a relatively long zone of contact with the cylindrical wall and a yieldingly mounted blade bearing on the periphery of the rotor and dividing the intake from the exhaust side of the pump.

The rotors being eccentric they are inherently out of balance, and high speed rotation, necessary to rapid exhaustion, results in excessive vibration. According to this invention the thick or eccentric side of the rotors is cored out, or otherwise made hollow, so as to accurately balance the rotor with respect to the axis of rotation.

The final balancing must, of course, be effected by the cut and try method and this is most economically done when the hollow is open to permit convenient application of files or other tools. The periphery of the rotor is preferably solid and continuous and, hence, the opening is most conveniently made at one or both sides; and it might be expected that the opening or openings would be effectively closed and sealed by the contact of the rotor with the end walls of the cylinder, but that is not true in practice.

The air in the hollow of the rotor at the beginning of any given operation is at or near atmospheric pressure and the vacuum to be produced is frequently as low as .0003 mm. of mercury. Hence, the pressure differential between the hollow of the rotor and the pump chamber, or the vessel to be exhausted, is relatively very great as the exhaustion approaches the desired degree.

The amount of leakage from the hollow of the rotor into the system is comparatively small during that period of operation in which the pressure in the vessel to be exhausted, and hence in the system, is not very low. Perhaps this is true until the vacuum is a few millimeters. But as the pressure differential increases the leakage from the hollow of the rotor to the system increases and the speed of evacuation to the pumps limiting pressure is proportionately reduced.

lVith a standard pump of familiar structure heretofore in use, it requires forty-eight minutes to reduce the pressure to one thousandth of a millimeter, or a micron; and the additional time necessary to reduce the pressure to .0003 mm. is a matter of hours, and somewhat indefinite.

According to this invention this detrimental effect of leakage from the hollow rotor into the system is eliminated by aifording rapid communication between the hollow of the rotor and the low pressure system whereby the air in the rotor and the vessel to be exhausted is removed substantially simultaneously, and hence, there is no appreciable pressure differential and consequently no leakage.

In the drawings there are illustrated preferred forms of the invention.

Fig. 1 is a vertical section through a twostage eccentric pump mounted in an oil bath, the section through the second stage, and the intermediate plate 19, being on line 11, and that through the first stage being on the line 8-8 of Fig. 2;

Figs. 2 and 3 are sectional views taken on the lines 22 and 3-3 respectively, of Fig. 1, and lookingin the direction of the arrows;

Fig. 4 is a sectional View taken on the line 4-4 of Fig. 5;

Fig. 5 is a view similar to Fig. 1, illustrating a one-stage pump;

F igs. 6 and 7 are views similar to Figs. 4 and 5, illustrating a modification of the form .shown in Figs. 4 and 5, and

Fig. 8 is a view similar to Fig. 4, illustrating a rotor which is only approximately balanced.

However, these specific illustrations and the correspondingly specific description are intended for the purpose of disclosure only and are not to indicate the scope of the invention or to impose limitations on the claims.

The pump casing, illustrated in Figs. 1,

2 and 3, includes two cylindrical rings 10 and 11 split at 12 to receive the blades 13, which are constantly urged in'contact with the periphery of-the rotors 14 and 15 by levers 16 and springs 17. The cylindrical rings are closed at their ends by

plates

18, 19 and 20. The rotors are fixed to a shaft 21, which passes through the

plates

18, 19 and 20. For convenience the pump casing is carried by the removable wall 23 of the oil bath 24.

The intake port 25 of the first stage of the pump is enlarged at 26 within the removable wall 23, to form an oil trap to prevent oil from passing to the vessel to be exhausted which is suitably connected with the tube 27. The entrance to the pump chamber 28 is conveniently made by drilling through the plate 20 in appropriate relation to the blade 13 of the first stage. I

Exhaust port 29 of the first stage, which is also the intake port of the second stage, is made by drilling through the intermediate plate 19. The exhaust port 30 of the second stage is made through the ring 10 and isprovided with a ball check valve 31, the blade 13 of this stage being appropriately .located between the intake 29 and the exhaust 30.

The eccentric rotors 14 and 15 are cored out, or otherwise formed hollow and worked until they are accurately balanced with respect to the axis of the shaft 21. The general form of opening indicated at 32 in Fig. 2 is very satisfactory, and by providing the flanges 33 the removal of the small amounts of metal necessary to the final balancing operations is facilitated. In addition, these flanges provide a wide contact with the end walls of the pump.

The communications between the hollow of the rotor 15 of the first stage and the system is made by milling a groove 34 in the inner face of the plate 20, extending from the intake port 25, inwardly a suflicient distance to register with the opening 32, during a considerable portion of a revolution, as will be apparent from Fig. 2. This groove actually makes a passage leading from the hollow of the rotor to the intake side of the pump and, in effect, addsthe volume of the hollow in the rotor to the volume of the system to be exhausted, and it affords such rapid communication that no appreciable pressure differential occurs during the exhaustion.

In the second stage of the pump the communication is effected by a groove 36 in the left face of the intermediate plate 19 extending inwardly from the port 29 beyond the flange 33.

Referring now to Figs. 4 and 5, which illustrate a one-stage pump, the removable wall of the bath is 38, the cylindrical wall of the pump 39, the end closures 40 and 41, and the rotor 42. The communication in this instance is made by a circular groove 43, connecting with a groove 44, extending inwardly from the intake port 45. It will be understood, however, that the circular groove is not indispensable to a one-stage pump, and it maybe used in multi-stage pumps.

The circular groove 43 being always in register with the hollow of the rotor, the communication is continuous, instead of intermittent, as in the form shown in Figs; 1, 2 and 3.

This form of communication is also particularly well adapted for pumps where the rotor is only approximately balanced by drilling, as indicated at 46, Fig. 8, though, of course, even in such a structure, the circular groove is not indispensable.

In Figs. 6 and 7 the communication is made between the hollow of the rotor and the exhaust side of the pump by a groove 47 in the right face of the plate 48 and a slot 49 in the flange 50 on the rotor, these being so placed that the communication takes place only at the beginning of the exhaust stroke when the pressure in that part of the system is approximately the same as in the vessel to be exhausted.

These illustrations will be sufiicient to show that by the simple expedient of affording rapid communication between the hollow of the rotor and the system, the pressure differential and consequent leakage heretofore obtaining in these pumps is eliminated.

The effectiveness of this improvement is well illustrated in the following table:

First stage of a two-stage pump improved according to this invention Time in minutes 2 3 4 5 Microns 700 29 3.5

Both stages improved in accordance with this invention Time in minutes 2 3 4 5 6 8 Microns 490 19 1.9 .5 .4

When the pump is idle there is a tendency for oil to leak from the bath into the space between the rotor and the cylindrical wall. The passages provided for gases are not sufficiently large to permit the escape of this oil with the rapidity necessary to prevent the development of undesirable stresses in the pump. To take care of this condition special relief ports are provided by drilling through the outside plate of the last stage, or the corresponding plate of the single stage pump, as indicated at 60 in Fig. 1 and 61 in Fig. 5, in line with the vane. After this provision is made the pressure on the oil will lift the vane a shoft distance beyond its normal outward position and establish communication from the pump chamber through the drilled hole to the bath, and thus quickly correct the condition.

I claim as my invention:

1. In a device of the class described, a pump casing comprising a cylindrical wall with end closures and having inlet and exhaust ports, a hollow rotor eccentrically mounted in the casing with end surfaces in contact with the end closures and a peripheral surface having a zone of contact with the lnner periphery of the cylindrical wall whereby the space betweenthe cylindrical wall and the rotor forms a pump chamber, a blade projecting through the cylindrical wall into contact, with the periphery of the rotor and di viding the .intake from the exhaust, a long groove in the innerface of one'end closure in register with the hollow of the rotor and a passage connecting said groove with the pump chamber.

2 In a device of the class described, a pump casing comprising a cylindrical wall with end closures and having inlet and exhaust ports, a hollow rotor eccentrically mounted in the casing with end surfaces in contact with the end closures and a peripheral surface having a zone of contact with the inner periphery of the cylindrical wall whereby the space between the cylindrical wall and the rotor forms a pump chamber, a blade projecting through the cylindrical wall into contact with the periphery of the rotor and dividing the intake from the exhaust, a circular groove in the inner face of one end closure in register with the hollow of the rotor and a passage connecting said groove with one of said ports.

3. In a plural stage pump, a casing comprising a plurality of cylindrical walls with end closures, a hollow rotor eccentrically mounted Within each cylindrical wall with end surfaces contacting with the end closures and a peripheral surface having azone of contact with the inner periphery of the cylindrical wall whereby the space between each cylindrical wall and its rotor forms a pump chamber, each said pump chamber having inlet and exhaust ports, a blade projecting through each cylindrical wall into contact with the periphery of the corresponding rotor and dividing the intake from the exhaust, a passage connecting the hollow of the rotor in the first stage with the pump chamber of that stage and a passage connecting the hollow of the rotor in the last stage with the intake of that stage.

4. .In a pump, a casing including a cylindrical wall and end closures, a hollow rotor eccentrically mounted in the'casing in contact with the end closures and having a .zone of contact with the inner periphery of the cylindrical wall whereby there is formed a pump chamber between therotor and the cyllndrical wall, a blade mounted in the cylindrical wall and bearing on the rotor to divide the intake from the exhaust, intake and exhaust ports for the casing, and means for .efiecting a communication between the hollow of the rotor and the pump chamber.

5. In a pump, a casing including a cylindrical Wall and end closures and having intake and exhaust'ports, a hollow rotor eccentrically mounted in the casing in contact with the end closures and having azone of contact With the inner-periphery of the cylindrical Wall whereby there is formed a pump chamber between the rotor and the cylindrical wall, a blade mounted in the cylindrical wall and bearing on the rotor to divide the intake from the exhaust, there being a passage connecting the hollow of the rotor with one of said ports.

6. A pump comprising a hollow cylinder closed at its ends and having a peripheral slot and also intake and exhaust ports, a hollow eccentric rotor having a zone of contact with the inner periphery of the cylinder and bearing at its ends on the ends of the cylinder, a blade movable in the slot and bearing on the periphery of the rotor, there being a passage connecting the hollow of the eccentric rotor with the system to be exhausted.

7. In a pump, a casing including a cylindrical wall provided with a peripheral slot and plates closing the ends of the cylindrical wall and having inlet and exhaust ports, a rotor eccentrically mounted in the casing in contact with the plates and having a zone of contact with the inner periphery of the cylindrical wall, a blade mounted in the slot and bearing on the rotor, one of said end plates having a port located above the normal position of the blade connecting the slot with the exterior of the casing, and means allowing the blade to rise and uncover the port under influence of excess pressure. V

8. A vacuum pump comprising a hollow cylinder closed at its ends, an eccentric rotor provided with a balancing cavity therein and having a zone of contact with the inner periphery of said cylinder, said pump being provided with intake and discharge passages, and means separating said passages for preventin g air from passing from said discharge to said intake passage, said pump belng provided with means to cause the gas within the balancing cavity to be maintained at a pressure substantially equal to the pressure in the inlet of said pump.

9. A pump comprising a hollow cylinder closedat its ends and having a peripheral slot and also intake and exhaust ports, an eccentric rotor having a zone of contact with theinner periphery of the cylinder and hearing at its ends on the ends of the cylinder, a blade movable in the slot and bearing on the periphery ofthe rotor, an emergency port connecting the slot with the'exterior of the pump located above the normal position of the blade, and means allowing the blade to rise and uncover the port under influence of,

excess pressure.

10. In a device of the class described, an oil bath, a pump immersed in the oil bath comprising a hollow cylinder closed at its ends and having a peripheral slot and also intake and exhaust ports, an eccentric rotor having a zone of contact with the inner periphery of the cylinder and bearing at its ends on the ends of the cylinders, a blade movable'in the slot bearing on the periphery of the eccentric rotor, means to discharge excess oil which seeps into the pump on standing including an emergency port connecting the slot with the oil bath located above the normal position of the blade and below the oil level in the bath, and means allowing the blade to rise and uncover the port under infiuence of excess pressure.

11. In a pump designed to handle compressible fluids, but sealed with an incompressible fluid, a casing, a pump chamber within the casing provided with intake and exhaust ports, a rotatable eccentric contacting with the wall of the pump chamber at a point on its periphery, a freely movable blade cooperating with the eccentric and slidable in a slot within the casing, and means to prevent an excess of incompressible fluid within the pump from exerting excessive strains upon the pump which comprises a relief port communicating with the slot which port is uncovered by the blade Whenever excessive pressure is applied to the inner working end thereof.

12. In a device of theclass described, an oil bath, a pump within said bath, said pump comprising a casing having a chamber with a high and a low pressure portion therein, an eccentric rotor provided with a balancing cavity therein and having a zone of contact with the inner periphery of said chamber, said pump having intake and discharge passages, means separating said passages for preventing gas from passing from one passage to the other, and means for maintaining communication between said cavity and the lowpressure portion of said chamber only whereby the pressure in said cavity will be maintained substantially the same as that in said low pressure chamber portion during the operation of said pump.

13. A high vacuum pump having a capacity for reducing the pressure of a gas in a container below one micron, comprising a casing havinga chamber with a high and a low pressure portion therein, intake and discharge passages for said chamber, movable means including a rotary pist on for causing a gas to enter said chamber through said inta e passage and be discharged therefrom through sald discharge passage, said piston having a balancing cavity therein, means for liquid-sealing r the movable parts of said pump, and means for maintaining communication between said cavity and the low pressureportion of said chamber only whereby the pressure in said cavity will be maintained substantially the same as that in said low pressure chamber portion during the operation of said pump.

14. A plural stage eccentric vacuum pump comprising, in combination, a casing provided with a first pump chamber and a second pump chamber and an intake and exhaust port for each chamber, a hollow eccentric rotor in each pump chamber, and a blade projecting into each chamber and cooperating with the periphery of the corresponding rotor, said casing having a passage connecting the hollows of the rotors with the intake port of the second chamber.

15. A plural stage vacuum pump comprising, in combination, a casing provided with a pump chamber having intake and exhaust ports, a hollow eccentric rotor in the pump chamber, a blade projecting into the chamber and cooperating with the periphery of the rotor, a second pump chamber having intake and exhaust ports, and means for connecting the hollow of the rotor to the intake port of the second pump chamber.

In testimony whereof I affix my signature.

PAUL E. KLOPSTEG.