US852947A - Means for producing high vacuums. - Google Patents

Description

' WITNESSES No. 852,947. PATENTED MAY 7, 1907.

. W.-GAEDE. MEANS FOR PRODUCING HIGH VAGUUMS.

APPLICATION FILED AUG. 17, 1906.

INVENTUF\ srrns ATENT @FFICE.

WOLFGANG GAEDE, OF FREIBURG, GERMANY.

MEANS FOR PRODUCING HIGH VACUUIVIS.

Specification of Letters Patent.

Patented May '7, 1907.

To all whom it may concern:

Be it known that I, WOLFGANG GAEDE, a subject of the German Emperor, residing at Freiburg i/Br., Salzstrasse l3,v Germany, have invented certain new and useful Improved Means for Producing High vacua; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The invention refers to apparatusfor producing a vacuum and more especially to that class of vacuum pumps in which a'drum con sisting of a plurality of suitably shaped chambers is immersed in a liquid bath and by rotation withdraws gas or air from the vessel that is to be exhausted and discharges said air either into the atmosphere or into a casing surrounding the drum and being partially exhausted by means of an auxiiary pump or other exhausting means such as are generally known in the art.

The invention consists in the hereinafter described special arrangement of the chambers constituting the rotating drum in this class of airpumps by which the apparatus is enabled to produce a considerably higher vacuum than was hitherto possible with similar devices.

In the accompanying drawing Figure 1 is a vertical section through the pump forming the subject of my invention, Fig. 2 is a cross section on line 2-2 of Fig. 1, Figs. 3 and 4 are likewise cross sections showing modifications and Fig. 5 is a perspective view of the complete apparatus.

In the drawing 1 is a stationary casing made of any suitable strong and gastight material, such as for instance cast iron. The casing 1 is provided at the center of one of its flat sides with a stuliing box 2 through which is introduced a shaft 3 carrying a pulley 4 or any other suitable means for imparting rotation to the shaft. Fixed to the shaft 3 is a drum 5 consisting of inner chambers 6 and an outer chamber 7. The inner and outer chambers are in communication by means of holes or openings 8 and 8 The outer chamber is also in communication with the interior of the casing 1 by means of a central opening 9. Through this central opening 9 a pipe 10 is introduced the inner end of which is bent upward. Thepipe 10 passes through a her-- metically sealed joint 11 in the wall of the casing at a point just opposite the opening 9. At a point near the top of the casing a stud 12 is likewise hermetically fixed into the wall of the casing.

In the example shown in Fig. 2 there are provided two inner chambers 6, designated y'the reference letters 6 and 6". They are separated from each other by radial walls and communicate with the interior of the casing 1 by means of helical channels 13 and 13 respectively, and with the outer chamber 7 by means of the abovementioned openings 8" and 8". At the center of the drum the radial walls, separating the single chambers 6 from each other, are cut away so that a wide opening 14 is formed by means of which all the chambers 6 are in intercommunication with each other. v

For the purpose of operation the casing 1 is filled with liquid of any suitable kind, preferably with mercury, up to a point slightly above the middle, that is to say, to such a height that the stuffing box 2 and the central opening 9 of the drum 5 are well below the surface of the liquid. The stud 12 is connected to any ordinary airpump or ejector capable of producing a vacuum of about 20 millimeters of quicksilver and the pipe 10 is put into communication with the vessel that is to be exhausted.

By means of the auxiliary pump, not shown in the drawing, the air contained by the casing and the vessel to be exhausted is drawn oif until the maximum of the capability of the auxiliary pump, that is to say, for instance, 20 millimeters of quicksilver, is reached. Then the drum is rotated by means of the pulley 4 or by hand in the sense indicated by the arrows in Figs. 2 to 4. In the position shown in Fig. 2 1t will be seen that by means of the opening 8 the inner chamber 6 is in communication with the outer chamber 7 and by means of the pipe 10 with the vessel to be exhausted. Since the mercury in the drum tends to maintain its level as the drum rotates in the sense of the arrow, a part of it will flow out into the helical channel 13 but the greater part will pass through the opening 14 in the center of the drum into the chamber 6*. Thereby the free space within the chamber 6 will increase and consequently the air contained in the vessel to be exhausted will be drawn off and will fill the chamber 6*. At the same time the air contained in the chamber 6 will be forced out into the channel 13 and as soon as the opening at the outer end of this chan nel emerges above the surface of the liquid it will be in communication with the air 1n the interior of the casing 1 and will be sucked off by the auxiliary pump. This process continues until the opening 8 is submerged, when the vessel to be exhausted will be altogether sealed for a short time, that is during the period in which both openings 8 an 8 are submerged. Then opening 8* will emerge and now the same play will be repeated, with this exception that the two chambers 6 and 6 have changed parts. It will be seen that by this means air is continually drawn from the vessel that is to be exhausted and is discharged into the interior of the casing whence it is drawn off by means of the auxiliary pump.

In the modification shown in Fig. 3 the channels 13 are cut off immediately beyond their inner ends. Thereby the action of the apparatus as described above is not altered, the only difference being that the air contained in the chamber that is discharging, is immediately put into communication with the interior of thecasing, whereas in the construction shown in Fig. 2 communication between the discharging chamber and the interior of the casing is intercepted until the discharging chamber is filled with liquid.

In Fig. 4 another modification is shown which difiers from the construction according to Fig. 2 only in this, that the drum is divided into three chambers instead of two. The action is not altered thereby and it will be understood that any desired number of chambers might be employed. Two chambers however are sufficient and more than three would unnecessarily complicate the construc tion of the drum.

I am aware that several vacuum pumps are known the action of which resembles that of the pump according to my present invention. But in all known pumps of this kind there is set up a complete circulation of the mercury between the vacuum to be produced and the auxiliary vacuum established at the outlet of the casing. That is to say the mercury either continually enters the drum at a central opening and is dischargedtherefrom at the outer ends of helical channels or vice versa. Thus in these known devices the whole quantity of mercury contained in the drum is continually brought into contact with the auxiliary vacuum and the final vacuum in turns. Now I have found by experiment that if the mercury is exposed for some little time to a less high vacuum such as the auxiliary vacuum, it will absorb a certain quantity of gas and when reintroduced thereupon into the final vacuum which is a higher vacuum, it will under the influence of the lower pressure again set free this absorbed gas. Thus, though with pumps of this kind gas is continually being transportedfrom the final vacuum to the auxiliary vacuum by the normal action of the pump, at the same time 7 ported to the auxiliary vacuum, evidently the rotation of the pump may be continued any length of time without further reducing the pressure in the final vacuum.

The main novel feature by which'my invention differs from these known devices is the central intercommunication 14 between the inner chambers 6 of the drum. This opening 14 has the effect of considerably increasing the capacity of the pump and this effect is produced by the fact that in my pump only that part of the mercury filling the drum which enters the helical channels 13 is discharged into the casing. The rest passes continually from one of the inner chambers 6 to the other and vice versa. Therefore only a part of the total quantity of mercury being equal the interior volume of the helical channels is at all brought into contact With the auxiliary vacuum and thence returns by the central opening 9 and the immersed opening 8. It is true that the gas contained in the discharging chamber 6 IOC is forced into the narrow channel 13 and is 1 thus to a certain extent compressed and during the beginning of the operation it may happen that during this compression the pressure in the discharging chamber may rise as high as the pressure in the auxiliary vacuum established in the interior of the I casing surrounding the drum, or even higher.

But this can only take place at the beginning of the operation.

As the exhaustion proceeds the pressure in the final vacuum is late between the auxiliary and the final vacuums and the rest will continually remain under a pressure only slightly surpassing that of the final vacuum. Thus only one tenth or less of the liquid will have an opportunity to absorb gas and to reintroduce it into the final vacuum and consequently the pressure in the final vacuum can with my apparatus'be considerably reduced as compared tothe minimum pressures obtainable by the known apparatus of this class.

In the modification shown in Fig. 3, it is true, the mercury contained by the discharging chamber is immediately exposed to the pressure of the auxiliary vacuum, but nevertheless also the effect of this drum is considerably better than that of any of the known constructions. The reason is that the fiow of the mercury Within the drum is always away from the exhausting chamber 6 and toward the discharging chamber 6 and therefore what gas may be absorbed by "the contact of the mercury in the discharging chamber with gas of a higher pressure, is continually prevented from traversing the volume of mercury separatmg the two chambers and thus penetrating into the final vacuum.

Having now particularly described and ascertained the nature of my said invention, and in what manner the same is to be performed, I declare that what I claim is:

1. Means for producing high vacua, comprising a substantially cylindrical closed casing partly filled with liquid, a drum rotatably mounted in said casing and divided by radial walls into chambers which communicate with each other at the center of said drum by means of an opening between said walls, said chambers also communicating with the inte- 'rior of the casing at the periphery of the drum,

means whereby said drum may be rotated, and means for connecting the interior of the drum with the vessel to be exhausted.

2. Means for producing high vacua which means consistin the combination of a substantially cylindrical casing more than half filled with liquid of a drum rotatably mounted therein which drum is divided into inner chambers communicating with each other at the center of the drum and with the interior of the casing at the periphery, and an outer chamber having a central opening communicating with the interior of the casing and other openings placed near the periphery and communicating with the inner chambers, and of means for rotating the drum.

3. Means for producing high vacua'which means consist in the combination of a substantially cylindrical casing connected to an ordinary air pump and more than half filled with liquid, of a drum rotatably mounted therein, said drum being divided into inner chambers communicating with each other at the center of the drum and with the interior of the casing at the periphery of the drum and an outer chamber having a central opening below the surface of the liquid and peripheral openings communicating with the inner chambers, of helical channels interposed between the inner chambers of the drum and the interior of the casing and of a pipe connected to the vessel to be exhausted and passing through the central opening into the outer chamber, its end being bent upward therein to a level above the surface of the liquid.

4. Means for producing high vacua which means consist in the combination with a substantially cylindrical casing more than half filled with liquid, means for partially exhausting said casing, of a drum rotatably mounted Within said casing and being more than half immersed in said liquid, said drum being divided by substantially radial partitions into inner chambers communicating with. each other at a point continually immersed in the liquid and communicating with the interior of the casing by means of helical channels at the periphery of the drum and an outer chamber hermetically connected to the vessel to be exhausted and being in communication with the inner chambers by means of holes placed near the periphery of the drum and of means for rotating the drum.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing witnesses.

WOLFGANG GAEDE.

Witnesses:

WILH ENGLER, ROBERT BENDER.

Images