US3868239A

US3868239A - Sorption pump

Info

Publication number: US3868239A
Application number: US352583A
Authority: US
Inventors: Jan Visser
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1973-01-29
Filing date: 1973-04-19
Publication date: 1975-02-25
Anticipated expiration: 1992-02-25
Also published as: JPS567065B2; DE2400792A1; GB1456402A; FR2215544B1; DE2400792B2; CH592816A5; IT1006168B; NL7301204A; JPS49105221A; CA1009997A; DE2400792C3; FR2215544A1

Abstract

A sorption pumping device characterized in that a space to be evacuated can be connected to the sorption material successively at at least two different levels of the device.

Description

United States Patent Visser Feb. 25, 1975 [5 1 SORPTION PUMP [56] References Cited [75] Inventor: Jan Visser, Emmasingel, Eindhoven, UNITED STATES PATENTS Netherlands 2,413,771 l/l947 Luaces 55/179 1 3122222,: 2/22: 12:52: 2:151 1. 5 571%? York, 3,264,803 8/1966 Read 55/389 p 19, 3,283,479 Batzer et a1 1] PP 352,583 Primary Examiner-Bernard Nozick Attorney, Agent, or FirmFrank R. Trifari; J. David [30] Foreign Application Priority Data Damow Jan. 29, 1973 Nether1ands 7301204 [57] ABSTRACT 52 us. Cl 55/389, 55/419, 62/55.5 A Pumping device characterized in that a 51 Int. Cl B01d 53/04 SPace evacuate? can be cmmwed P the [58] new of Search u 62/555; 55/389 387, 269 non material successively at at least two different levels of the device.

4 Claims, 10 Drawing Figures PATENIED FEB 2 51975

sum

1 or 5 15 "mm Fig/ lb Fig. 1a

PATENTEB FEB 2 5 I975 SHED 2. [If 5 P(Torr) t(min) PATENTED FEB2 5 19. 5

saw u 0F 5 SORPTION PUMP BACKGROUND OF THE INVENTION The invention relates to a sorption pumping device, provided with a reservoir for sorption material which can be made to communicate, via an inlet duct, with a space to be evacuated. Sorption pumping devices of the subject kind are known as appears from British Pat. Nos. 921,666 and 939,395.

Known sorption pumping devices have a single, fixed inlet duct. A drawback of this construction is that, particularly at lower starting pressures in the space to be evacuated, effective use is only made of the layers of sorption material which are situated in the immediate vicinity of the opening of the inlet duct in the reservoir. These layers are most favourably situated with respect to the gases to be pumped from the space to be evacuated. Consequently, these layers obtain a comparatively dense population of gas molecules during pumping, while the population of the remaining layers, situated further from the inlet opening, remains comparatively small. The latter is also due to the fact that the gas diffusion from layers with dense population to layers of sparse population is low at the low operating temperature of the sorption material (usually liquid nitrogen temperature).

Because only a part of the sorption material is effec-- tively utilized, the pump as such is comparatively quickly saturated so that a frequent reactivation of the sorption material is required. Moreover, comparatively long pumping times are required in order to achieve a given minimum pressure. for example, the starting pressure for getter-ion pumps. Furthermore, it is difficult to realize low final pressures in the space to be evacuated.

So as to achieve a more effective use of the sorption material which is situated further from the inlet opening, it has been proposed (Review of Scientific Instruments 34, May 1963, pages 587-588) to sub-divide the sorption material into separate layers distributed over a large number of trays which are arranged in the reservoir. The gas which is sucked in is then more uniformly distributed between the sorption material surfaces on the various trays.

A pumping device of this kind, however, not only has a complex and expensive construction, but its action is not optimum either. The latter is mainly due to the fact that during one and the same pumping cycle from high to low pressure, the gas flow is always applied to the surface of the sorption material along the same course.

SUMMARY OF THE NEW INVENTION The invention has for its object to provide a sorption pumping device which has a simple construction, a high effective sorption capacity and a high pumping speed, and which produces a low residual pressure. A high effective sorption capacity implies that a large number of pumping cycles can be performed without intermediate reactivation of the sorption material.

The sorption pumping device according to the invention is characterized in that the device is constructed such that the space to be evacuated can be connected to the sorption material successively, at at least two different levels of the reservoir.

Within the scope of the present invention, different reservoir levels are not to be understood to mean exclu' sively different levels in the axial direction of the reservoir, but also mutually different locations, viewed in the transversal direction of the reservoir.

By admitting the gas of high pressure from the space to be evacuated to the sorption material which is situated at a given level during the beginning of the pumping cycle, this material sorbs gas molecules, but the sorption material which is situated at a different level remains substantially clean. By subsequently admitting, during the final period of the pumping cycle, the gas of low pressure to this substantially pure sorption material (and if desired, at the same time to the material already contacted by the gas of high pressure), effective and quick sorption also takes place at low pressure. The sorption material is thus very effectively utilized, whilst short pumping times and low residual pressures in the vacuum space are achieved.

In a preferred embodiment of the sorption pumping device according to the invention, the inlet duct is provided with a hollow tube which is arranged to be axially slidable and/or rotatable about its longitudinal axis in the reservoir and which is provided with at least two openings which are situated at a distance from each other in the axial direction of the tube, the said openings being successively released by axial displacement or rotation about the longitudinal axis of the tube.

The hollow tube can form an integral part of the inlet duct or be provided as a separate tube. The construction of this sorption pumping device is compact and simple.

A further preferred embodiment of the sorption pumping device according to the invention is characterized in that a hollow tube which is open on both ends is rigidly arranged inside the reservoir, one tube end being arranged, coaxial with the inlet duct, inside the opening of this duct into the reservoir and at a distance from the opening, so that an annular channel is formed, the inlet duct incorporating a closing member which is capable of successively releasing the opening in the said tube end and the annular channel.

A pumping device of this kind is also compact and can be readily manufactured by addition of the tube and the closing member to known pumping devices.

Another preferred embodiment of the sorption pumping device according to the invention is characterized in that the device is provided with at least a second inlet duct which can be closed and which is connected parallel to the inlet duct, all inlet ducts opening into the reservoir at mutually different levels.

According to the invention of at least one inlet duct, the level at which the said inlet duct opens into the reservoir is adjustable. This enables optimum local use of the sorption material.

The invention will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT The reference numeral 1 in FIG. 1 denotes a reservoir in which a sorption material 2, for example, a natural or synthetic zeolite, is present. The reservoir has an inlet duct 3 which can be connected to a space to be evacuated at the area of the flange 4. A hollow tube 5, arranged inside the reservoir and open on both ends, is arranged such that its upper end is situated inside and coaxial with inlet duct 3. The lower end of the tube is provided with side openings 6. A closing member 7, shown in two positions, comprises a valve body 8 which can cooperate with a valve seat 8a in a sealing manner. Valve body 8 is connected, via a valve rod 9, to a control member 10. The lower side of valve body 8 carries a flexible, annular diaphragm 11 which carries a cylindrical sleeve. This sleeve fits exactly about the end of tube 5 and can be slid thereon in a reciprocating manner. Radial openings 13 are provided above diaphragm 11. The diaphragm is capable of closing annular space The sorption pumping device furthermore comprises ducts (not shown) for cooling liquid (liquid nitrogen) for cooling the absorbent material, and an outlet (not shown) for the gases released during the reactivation of the adsorption material. The sorption pumping device is operated as follows. During the first period of the pumping cycle, when a higher pressure prevails in the space to be evacuated, the closing member 7 is in the position which is shown at the left in the drawing. Gas then flows via openings 13, tube 5 and openings 6 to the lower layers of the adsorption material 2 where it is adsorbed, while the annular space 14 is closed by diaphragm 11 so that the upper layers of adsorption material remain pure. During the second period of the pumping cycle, at a lower pressure in the space to be evacuated, closing member 7 is set to and held in the position which is shown at the right in the drawing. Annular space I4 is then released by diaphragm I1. Gas of lower pressure now flows to the upper pure layers of adsorption material via annular space 14 as well as to the lower layers via tube 5. After termination of the pumping cycle, closing member 7 is closed. Valve body 8 then bears on valve seat 8a, so that both tube 5 and annular space 14 are closed.

FIG. lb shows a variant of the inner part of the pumpi ing device of FIG. la. The same reference numerals but with a suffix a are used for corresponding parts. In the present case sleeve 12a slides inside tube 5a, the lower side of which is provided with a number of slots 150 which are distributed over the circumference and through which gas can flow the adsorption material. Valve body 8a now also carries a further valve body 16a. In the position shown, annular space 14a is closed by diaphragm Ila and tube 5a is accessible via openings 13a. When valve body 8a is moved upwards, diaphragm Ila releases annular space 14a, while the upper side of the further valve body 16a also moving upwards closes tube 5a.

Using the sorption pumping device shown in FIG. la, a space in which air was present at a pressure of 0.55 torr (l torr l mercury presure) was evacuated. The pressure P as a function of the time I for the first pumping cycle is denoted in FIG. 2 by curve I. Point A denotes the switching point at which a change-over was made from pumping exclusively through the lower layers of adsorption material via tube 5 to pumping through both the upper clean layers via annular space 14 and the said lower layers.

Curve II shows the result for the first pumping of the same space, in which air under a pressure of 0.55 torr was again present, through the same quantity of the same clean adsorption material as in the first case. This material was situated in a pump as shown in FIG. 1a in which now, however, tube 5, sleeve 12 and diaphragm 13 were lacking, so that via inlet duct 3 pumping was effected in known manner exclusively from the upper layers of adsorption material.

The graph clearly shows that shorter pumping times and lower final pressures are achieved by means of the pumping device according to FIG. 1a than by means of the known pumping device.

FIG. 3 shows the pumping curves for air for the above sorption pumping devices, the space to be evacuated being pumped down from torr, after seven pumping cycles from 80 Torr had already been performed in both cases and the adsorption material thus already having been saturated to a given extent.

A comparison of the two curves shows that the sorption pumping device according to FIG. 1a also has a higher effective sorption capacity than the sorption pumping device of known construction.

Parts of the sorption pumping devices accordingg to the FIGS. 4 to 8 which correspond to the device according to FIG. 1a are denoted by the same reference numerals but with a suffix b for FIGS. 4a and 4b, c for FIG. 5, d for FIG. 6, e for FIG. 7, and ffor FIG. 8.

In the sorption pumping device according to FIG. 4, the inlet duct 3b comprises a flexible portion 3a which is constructed as a bellows, and an end portion 3b in the form of a hollow tube which is axially slidable with respect to the reservoir inside duct 20b, the said duct being separated from the adsorption material by a gauze layer 21b. The end portion comprises openings, 22b and 23b, at two different levels. When end portion 3b is moved up and down, openings 22b can be alternately closed and released by cylindrical sleeve 24b, and openings 23b by cylindrical sleeve 25b, however, such that while openings 22b are closed openings 23b are released and vice versa. FIG. 4a shows the position in which openings 22 are released and openings 23b are closed, while the reversed situation is shown in FIG. 4b. A space to be evacuated can thus be successively connected at different levels to the adsorption material, first via openings 23b and subsequently via openings 22b. End portion 3b can also be constructed as a separate sleeve, the upper end of which slides through inlet duct 3b.

In the sorption pumping device shown in FIG. 5, tube 300 is arranged to be rotatable about its longitudinal axis inside reservoir ic. Due to the rotation, the openings 22c are alternately closed and released. The gas which is drawn from the space to be evacuated can first be exclusively applied to the lower layers of sorption material via openings 31c, tube 30c and openings 23c, and subsequently, as a result of the release of openings 220, it can be applied mainly to the upper layers and to a lesser extent to the lower layers.

It is obvious that constructions are alternatively feasible in which the passage openings for drawn-in gas can be released and closed by combined sliding and rotation of the tube.

The sorption pumping device shown in FIG. 6 comprises a second inlet duct 40d which is connected parallel to inlet duct 3d and which opens into reservoir 1d at a different level. A closing member 41d, 42a is incorporated in each of the ducts 3d and 40d, respectively.

The sorption pumping device shown in FIG. 7 comprises a three-way valve 43c by means of which the inlet ducts 3e and 40e can be separately and simultaneously connected to the space to be evacuated.

The sorption pumping device shown in FIG. 8 also comprises a three-way valve 44f. Inlet duct 40f comprises a flexible intermediate portion 40f which is constructed as a bellows and which enables reciprocating movement of the lower portion 40f in duct45f inside reservoir If. A gauze layer 46fseparates the adsorption material, 2f from the duct 45f. A second bellows 47f, connected on the one side to the reservoir and on the other side to lower portion 4f, acts as a flexible sealing. This construction enables evacuation at more than two different levels of the reservoir, even though only two inlet ducts are present.

In addition to the embodiment shown, there are of course other feasible embodiments, for example, constructions in which the two inlet ducts are connected at (diametrically) opposed locations on the sidewalls of the reservoir, or constructions in which more than two inlet ducts are present.

What is claimed is:

1. In a sorption pumping device for connection to a space to be evacuated, including a housing defining therein a reservoir including an inlet passage connectible to said space, and a quantity of sorption material in said reservoir, the improvement in combination therewith wherein said material is situated at at least two relatively different levels, said device further comprising duct means extending through said reservoir and into the material and having spaced ports material for communication with said material at said different levels, and valve means in said inlet passage connected to said duct means for selectively interconnecting said space successively and directly with said different ports in said duct means and said material at said different levels.

2. Apparatus according to claim, 1 which (when oriented vertically) has an upper part of the reservoir ineluding said inlet duct and a lower part, and corresponding upper and lower levels of said material in the reservoir, said duct means being a tube having an upper part with a first of said ports therein for communicating with said inlet duct and a lower part with a second of said ports therein for communicating with said lower level material, whereby said valve means is operable successively to communicate the inlet duct with the lower level material through said tube bore via said'first and second openings thereof and to communicate said inlet duct directly with said upper level of said material.

3. Apparatus according to claim 2 wherein said inlet duct defines a passage of first diameter, and said upper part of the tube is situated in said passage and has a smaller diameter with an annular space defined therebetween, and said valve means further comprises a diaphragm for sealing said annular space, and means for moving said diaphragm selectively to seal said annular space and to expose same.

4. Apparatus according to claim 3 wherein said diaphragm is secured to said tube, and said valve further comprises means for moving said tube and diaphragm axially for selectively sealing and unsealing said annular UNITE STATES PATENT OFFIQE QEMMQATE 0F QGECTEN Patent N0, 3,868,239 Dated February 25, 1975 InventoflX) JAN VISSER It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

C01,, 1, line 65, "at at" should be at, at-- W Col, 3,, line 7, after "space" should be -4sline 25, "absorbent" should be adsorbent Col, 4, line 28, delete "accordingg" and insert -according Col. 5, line 14, "40f" should be -40f'- line 18, "4f" should be --40f Claim 1, line 9, cancel "material" (second occurrence) fifth "ii my 0? August 1975 {SEAL} Attesr:

RUTH C. MASON C. MARSHALL DANN R ff (mnmissimu'r nj'lan'ms and Trarlwnurks

Claims

2. Apparatus according to claim 1 which (when oriented vertically) has an upper part of the reservoir including said inlet duct and a lower part, and corresponding upper and lower levels of said material in the reservoir, said duct means being a tube having an upper part with a first of said ports therein for communicating with said inlet duct and a lower part with a second of said ports therein for communicating with said lower level material, whereby said valve means is operable successively to communicate the inlet duct with the lower level material through said tube bore via said first and second openings thereof and to communicate said inlet duct directly with said upper level of said material.

4. Apparatus according to claim 3 wherein said diaphragm is secured to said tube, and said valve further comprises means for moving said tube and diaphragm axially for selectively sealing and unsealing said annular space.