US1610940A - Piston pump for rarefying air and other gases - Google Patents

Description

PISTON PUMP FOR RAREFYING AIR AND OTHER GASES Filed Jan. 17, 1925 2 Sheets-Sheet 1 Dec. 14 1926. I 1,610,940

H. FRIBERG PISTON PUMP FOR RAREFYING AIR AND OTHER GASES Filed Jan. 17, 1925 2' Sheets-Sheet 2 J 2 5g I? a 4? .j ygnfor" A 2 I W 1 Patented Dec. 14, 1926.

UNITED STATES HJALMAR F RIBERG, F STOCKHQLM, SWEDEN.

PISTON PUMP FOR RAREFYIN G AIR AND OTHER GASES.

Application filed. January difficulties, and to produce a piston pump 1 by means of which a very high vacuum may be obtained. For this purpose the inve ution consists principally in the combination of the feature that the spring-loaded suction and pressure valves of the pump are combined 2U with one or more actuating members-cams or the like-which is or are coupled to the pump piston, or to the driving means of said piston, and which member is arranged in such manner that at the beginning of the suction stroke of the piston it causes the spring load to act on the pressure valve and positively opens the suction valve, and at the beginning of the pressure stroke of the piston it causes the spring load to act on the suction valve, and finally vduring the pressure stroke it relieves the pressure valve from the spring pressure, and the feature that the pressure valve, is formed as a lid of the pump cylinder which lid is arranged entirely outside the cylinder and is movable in'a direction towards and away from the one open end of said cylinder, while the suction valve is located in the face of the lid directed towards the pump piston.

40 By this arrangement of the positively controlled and operated valves, which will thusbe sure to open and close at the right moments, it is possible to reduce the clearance space practically to nil, as the two faces of the pump piston and of the lid directed towards each other may be given suchshapes that.they=' fit tightly to each other, and no passages are required between the cylinder and the valves. With a piston pump of this type it is therefore possible, as practical tests havejdemonstrated, to producea very high and very nearly complete vacuum, so that the pump may advantageously replace 17, 1925, Serial No. 2,975, and in Sweden October 17, 1924.

the considerably more expensive and fragile mercury air pumps heretofore used for this purpose.

In the accompanying drawings a few different embodiments of the inventionare illustrated by way of example. Fig. 1 shows in longitudinal section a vacuum pump according to the invention with the piston occupying its highest position, and Fig. 2 shows the same pump with the piston in its lowest position. Fig. 1 also shows a constructional form of the means for providing perfect tightness between the piston and the cylinder, and Fig. 2 shows another constructional form of such means. -Fig. 3 shows a piston construction with a third embodiment of the Y packing means. Fig. 4 shows, also in lon- 7 gitudinal section, a second embodiment of the vacuum pump, and Fig.6 shows a detail of this embodiment. Finally, Figs. (Sand 7 show two further modified embodiments of the pump.

In the pump illustrated in Figs. 1 and 2, 1 denotes the cylinder, and 2 denotes the pump piston, which is provided in the usual manner with ,elastic packing or piston rings 3 placed in circumferentiallyextending grooves, and is driven by a driving shaft provided with a crank, an eccentric, or the like,'not shown in the drawing. On the upper open end of the cylinder which is formed as a plane rim, a hollow cylinder lid 4 is provided, which forms the pressure valve of the pump, and which for this purpose is provided on its upper side with a cylindrical projection 5 by means of which the lid is guided in a yoke 6 or the like, which is rigidly connected with the cylinder .1, or the pump frame, in such manner that the lid is slidable in vertical direction towards and away from the cylinder 1 and may tightly close said cylinder at its upper end, see Fig. 2. In the lower face of the lid 4 directed towards the piston 2, which face is plane, as is also. the upper face of the piston 2, a suction valve 7 is provided the stem 8 of which extends through the cavity 9 in the lid and, packed in suitable manner, through the projection 5, so that its upper end projects some distance beyond said projection. In the hollow projection 5 and surrounding the stem 8 there is provided a coil spring 10 which tends to close the suction valve 7.' Finally, the

lid 4 is provided with a tubular inlet 11 intended to be put in communication with the- ,which is not illustrated in the drawing, said shaft extending at right angles to the stem 8 and being connected by means of'a suitable gearing, such as for instance gear wheels, a chain and sprocket wheels, or the like, with the driving shaft of the pump in such mannor that it rotates with the same number of revolutions as said latter shaft in the direction indicated by the arrow in Fig. 1. A cam 13 is secured to the shaft 12 right above the stem 8, said cam forming in the present instance the above-mentionedactuating member which cooperates with the suction and pressure valves. The cam 13 actua-tes the stem 8 so that the suction valve 7 is positively opened at the beginning of the suction stroke of the piston 2, and also one arm 14 of a two-armed fork 15 which is pivotally journalled on a knife edge 16 at the end of an arm 17 secured to the cylinder 1, and the other arm 18 of which is intended to actuate the projection 5 of the lid 4 forming the pressure valve. The arm 18 is provided with an aperture through which the stem 8 extends and in which it is freely movable. The fork 15 is actuated by a strong coil spring 19 which, according to the position of the cam 13, forces the arm 14 against the c am, or the arm 18 against the projection 5 and thus the lid '4 against the cylinder 1.

In the position of the various parts illustrated in Fig. lithe pump piston 2 is supposed to have reached its highest position in which the cylinder lid 4 forming the pressure valve is raised slightly from the cylinder and rests on the piston 2 tightly bearing againstthe upper plane face of the piston. The suction valve 7 is then closed. When the piston 2 begins its downward movement, that is to say, its suction stroke, the shaft 12 is rotated in the direction of the arrow, when the arm 14 loses the support of the cam 13. Owing hereto the pressure exerted by the spring 19 will instead be transmitted through the arm 18 to the cylinder lid 4, so that said lid will immediately move along with the piston in the downward direction and will be forced with a certain pressure against the upper end of the cylinder 1. 'The spring load is thus brought to, bear on the pressure valve immediately at the beginning of the suction stroke of the piston, so that the pressure valve will then immediately be securely closed. Immediately after the pressure valve has been closed in this manner, the cam 13 begins, upon further rotation of the shaft 12, to actuate the stem 8 and force said stein downwards while compressing the spring 10, so that thus the suction valve is positively opened without the piston having In the position ofthe various parts shown in Fig. 2, the piston 2 is assumed to have reached its lowermost position, in which the cylinder lid isstill depressed by the spring l9, and the suction valve is held open by the cam 13. When the piston 2 starts its upward movement (the pressure stroke) the shaft 12 continues its rotation in the counterclockwise direction. The cam 13 now releases the stem 8, after which the spring 10 immediately closes the suction valve 7. On the continued upward movement of the piston 2, that is, on the continued rotation of the shaft 12, the cam 13 begins again to actuate the arm 14 so that the fork 15 is turned upwards and the arm 18 is raised from the projection 5. Owing hereto the lid 4 is relieved of the pressure from the spring 19, so that the lid may easily be raised by the air meanwhile compressed in the cylinder, and the air may freely flow out between the lid 4 and the upper rim of the cylinder 1. Shortly before the piston 2 again reaches its highest position in which it projects slightly above the upper end of the cylinder 1, Fig. 1, its plane upper face will come to bear against the likewise plane lower face of the lid 4, owing to which all air is forced out. The pump has thus practically no clearance space.

It-is a well-known fact that the usual elastic packing rings. 3 do not completely prevent air from. being drawn in between the piston and the cylinder walls, particularly when a high vacuum is about; to be reached. As even the very smallest air quantities which may in this manner pass into the suction chamber of the pump, considerably reduce the degree of rarefactionwhich may be attained by means of the pump, means are provided for producing perfect tightness between the pump iston and the cylinder.

In the pump 'il ustrated in Fig. 1 there is for this purpose provided in the upper portion of the piston 2 a cavity 20 which communicates through fine passages 21 with tho grooves in the circun'iference of the piston, in which the tightening rings 3 are placed. The cavity 20 is filled with oil. which during the operation of the pump when vacuum is produced in the grooves, flows out into said grooves and fills the existing small. leaks. In the bottom of the cavity 20 an oil tube 22 Eli you

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is inserted, the length of said tube being so which opens when the piston 2 and the tube 1 move downwards, and thus allows oil to flow into the tube 22, but which closes when the tube again moves upward so that the oil is prevented from flowing back. The device th-us acts as an oil pum which pumps oil into the cavity 20, which is thus always filled. Such oil as will possibly flow out between the upper rim of the cylinder land the lid 4, is collected in a groove 25 extending around the cylinder, from which groove the oil may be returned through the tube 26 to the receptacle 23.

In Fig. 2 a second construction of the packing means for preventing air from passing into the suction chamber of the cylinder 1, is shown. An annular'receptacle 27 isprovided on the outside of the cylinder, said receptacle being filled with oil. The position of the receptacle on the cylinder is so chosen that the oil chamber surrounds the uppermost packing rings 3 in the piston 2 when said piston occupies its lowermost position. The oil space of the receptacle communicates through fine passages 28 with the interior of i the cylinder, so that also in this case oil will be drawn into the existing small leaks between the rings and the cylinder walls, and a good tightness will be obtained. Such oil as will possibly flow out between the upper rim of the cylinder 1 and the lid 4, is also in this case collected in a groove 29 from which it is returned through a tube 30 to the receptacle 27.

Finally, Fig. 3 shows a third constructional form of the packing means. The piston 2 is provided in its upper portion with a circumferential groove 31 of V-shaped cross section, the sides of said groove suitably forming approximately an angle of to each other, and its bottom being slightly rounded. A piece of tubing 32 of rubber or other elastic material is placed in said groove. The other portion of the groove is filled by two solid elastic rings 33 having approximately triangular cross section. Finally, over said rings and the tubing 32 a likewise elastic ring 34 of rubber, leather, or the like, having a trapezium-shaped cross section is ilaced. Then the piston 2 has been inserted in the cylinder 1, compressed air is pressed into the tubing 32 through the tube 35. The tubing 32 is thus expanded and presses directly and through the intermediary of the rings 33 which act as wedges, the ring 34 against the cylinder walls, owing to which the desired perfect tightness is attained.

The constructional form of the pump illustrated in Figs. 4 and 5 differs from the embodiment above described and illustrated in Figs. 1 and 2 principally in that the cylinder lid 4 forming the pressure valve has its projection 5 pivotally suspended in the free end, which is formed as a ring, of the long arm 36 of a bell crank lever which is pivoted at 37 to an arm 17 secured to the cylinder 1,

and the other short arm 38 of which is actuated by the spring 19'which tends to close the pressure valve. 'Further, the cam shaft 12 which is coupled to the driving shaft of the pump, is located further down at the side of the pump cylinder 1, and carries three camsthe middle one 39 of which actuates, throughthe intermediary of a push rod 40 and a lever 41 pivotally supported on the arm 36, the stem 8 of the suction valve 7 while the two cams 42 which are of equal shape and secured one on either side of the cam 39 actuate, through the intermediary of a hollow push rod 43 which surrounds the rod 40 and is slidable in the arm 17', the forked-shaped end of the arm 38 for relieving the cylinder lid 4 of the pressure of the spring 19. When the shaft 12' rotates in the direction of the arrow with the same speed as the driving shaft of the pump, the function above described is attained also in this instance, namely that at the beginning of the suction stroke of the piston 2 the rod .43,

on the one hand, loses the support of the cams 42 owing to which the pressure of the spring 19 is caused to act, through the intermediary of the bell crank lever 38, 36, on the lid 4 forming the pressure valve so that said lid is rapidly forced against the upper end of the cylinder 1, and on the other hand, the cam 39 will positively open the suction valve 7 through the intermediary of the rod 40, the lever 41, and the stem 8, and that at the be ginning of the pressure stroke the rod 40 loses the support of the cam 39, so that the suction valve 7 is closed by the spring 10, and finally, during the pressure stroke. the cams 42 slide the rod 43 upwards, so that the cylinder lid 4 is relieved of the pressure of the spring 19.

According to Fig. 6 the cam shaft 12 is divided into two cam shafts 12 and 12 which are journalled one on either side of the pump piston 1, and both of which are coupled to the driving shaft of the pump so that. said shafts rotate with the same'speed as said driving shaft. The shaft 12 supports the cam 39'which, as in Fig. 4, through the intermediary of the push rod 40 and the lever 41 actuates the stem 8 of the valve 7 and the shaft 12 supports a cam 42 which through the intermediary of the push rod 43 actuates the bell crank lever 33, 36 and thus causes the pressure of the spring 19 to act on the lid 4, or relieves said lid of the pressure of said spring. The operation of the device will thus also in this case be the same as that above described with reference to Fig. 4. M

The embodiment illustrated in Fig. 7 cor responds substantially to that shown in Fig. 4, but differs from the samein that in this instance the projection 5 on the lid 4 is slidable. in a stationary yoke 6, as in Fig. 1. In accordance herewith the bell crank lever 38,

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36 in Fig. 4 is replaced by a singlearmed lever 44 which is actuated by the spring 19 anid transmits its pressure to the cylinder li The constructional forms above described and illustrated in the drawings are only to be regarded as examples, and their details mayobviously be further modified in several various ways without departing from the principle of the invention.

I claim:

1. In a piston pump for rarefying air and other gases the combination of a pump cylinder, a piston in said cylinder, springloaded suction and pressure valves, said pressurevalve consisting of a lid of said cylinder located outside the same and movable in directions towards and away from one open end of said cylinder, said suction valve being located in the face of said lid directed towards said piston, and an actuating member coupled to said piston and combined with said suction and pressure. valves in such manner that at the beginning of the suction stroke of said piston said member causes the spring load to act on said pressure valve and positively opens the suction valve and at the beginning of the pressure stroke of said piston causes the spring load to act on said suction valve and during the pressure stroke. relieves said pressure valve from the spring pressure.

2. In a piston pump for rarefying air and other gases the combination of a pump cylinder, a piston in said cylinder, springloaded suction and pressure valves, said pressure valve consisting of a hollow lid of said cylinder located outside the same and movable in directions towards and away from one open end of said cylinder, said lid having a tubular inlet intended to be put in communication with the vessel in which the gas is to be rarefied, said suction valve of the suction stroke of said piston said member causes the spring load to act 011 said pressure valve and positively opens the suction valve and at the beginning of the pressure stroke of said piston causes the spring load to act on said suction valve and during the pressure stroke relieves said pressure valve from the spring pressure.

3. In a piston pump for rarefying air and other gases the combination of a, pump cylinder, a piston in saidcylinder, springloaded suction and pressure valves, said pressure valve consisting of a lid of said cylinder located outside the same and movable in directions towards and away from one open end of said cylinder, said suction valve being located in the face of said lid directed towards said piston, an actuating member coupled to said piston and combined with said suction and pressure valves in such manner that at the beginning of the suction stroke of said piston said member causes the spring load to act on said pressure valve and positively opens the suction valve and at the beginning of the pressure stroke of said piston causes the spring load to act on said suction valve and during the pressure stroke relieves said pressure valve from the spring pressure, an arm combined with said movable cylinder lid, and a spring actuating said arm so as to move said lid against the end of said cylinder, said arm being adapted to be actuated by said regu lating member in such manner as to relieve said lid of the pressure of said spring.

HJALMAR FRIBERG.

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