US 3073951 A
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Description (OCR text may contain errors)
Jan. 15, 1963 c. E. BURDG 3,073,951
VACUUM LOCK Filed July 28, 1960 F'IGJ Z0 2 Sheets-Sheet 1 M ad INVENTOR CHARLES E- BURDG VW M ATTORNEY Jan. 15, 1963 c. E. BURDG Y 3,073,951
VACUUM LOCK Filed July 28, 1960 2 Sheets-Sheet 2 F'IC3-6 FIG-7 INVENTOR CHARLES E- BURDG BYW g M ATTO R N EY 3,073,951 VACUUM LOQK Charles E. Burdg, Granby, Conn, assignor to Combustion Engineering, Inc, New York, NY, a corporation of Delaware Filed .luly 28, 1960, Ser. No. 45,891 13 Uaims. (Cl. 250--41.9)
This invention relates to vacuum lock mechanism and particularly to mechanism for pro-exhausting sample receiving cavities in progressive stages and then presenting the pre-exhausted cavity to a high vacuum chamber.
An object of this invention is mechanism for rapidly presenting a series of specimens to be examined to a high vacuum chamber without materially affecting the vacuum in the chamber.
Another object is mechanism which may be readily indexed to present sealed Work chambers successively to a series of pumping stations before aligning them with a high vacuum test chamber.
A still further object is a movable work carrying element having cavities which may be sealed from the surrounding atmospheric or ambient pressure into and from which the work may be readily inserted and removed and which has provision for exhausting the work receiving cavities in progressive stages before presenting the pre-exhausted cavity to a high vacuum test chamber, and having means for relieving the vacuum in the cavity to permit changing the work piece.
Other objects and advantages will be apparent from the following specification and the accompanying drawings in which:
FIG. 1 is a schematic layout showing the environment in which this invention is used.
FIG. 2 is a sectional view, partially schematic, of the stationary disc.
FIG. 3 is a plan view, partially schematic, of the stationary disc.
FIG. 4 is a sectional View, partially schematic, of the rotary disc.
FIG. 5 is a plan view, partially schematic, of the rotary work receiving disc.
FIGS. 6 and 7 are a plan view of the assembled discs showing the relation of the sample receiving cavities and the pumping, testing, and relief stations.
In certain classes of work, such as a mass spectrometer, it is desirable to maintain a test or work chamber at a high vacuum, say on the order of 5 x 10-6 mm. to 5 x 10-7 mm. of mercury. In a mass spectrometer, for example, utilizing an ion beam, it is desirable to maintain this high vacuum throughout the path of the ion beam in order to restrict interference with the ions in moving along that beam. In examining a series of work pieces or samples, each piece must be brought individually into communication with and then removed from this high vacuum chamber. Because of the difficulty in obtaining and retaining this high vacuum and because of the length of time required to restore the high vacuum once it has been disturbed, it is desirable to have the work pieces at a vacuum substantially as high as that obtaining in the test chamber when they are presented to the high vacuum test chamber.
The present invention solves that problem and permits rapid testing of samples by providing a plate exposed to ambient pressure and having an opening communicating with the high vacuum chamber and constituting a test station, and having a plurality of pump inlets arranged around the plate and forming pumping stations. A rotatable plate, also exposed to ambient pressure and having a plurality of work receiving cavities, is mounted on 'said stationary plate in sealing relation therewith. Work carrying elements are readily inserted into said cavities in sealing relation therewith with respect to the surrounding ambient pressure and upon relief of the vacuum in said cavities to equalize the pressure on opposite sides of said elements may be readily removed therefrom. Rotation of the rotatable plate with respect to the fixed or stationary plate presents the work carrying cavities successively to the several pumping stations and then to the high vacuum chamber. The work receiving cavities remaining sealed against ambient pressure during the entire cycle.
As shown in FIG. 1, the vacuum lock constituting the present invention and indicated generally at 10 is applied to a mass spectrometer indicated generally at 12. In this structure a sample carried by the vacuum lock mechanism 10 is brought into alignment with a highly evacuated tube 14 through which ions expelled from the electrically heated sample are propelled. A magnet 16 diverts ions of different mass weights difierent amounts, and directs the selected ions along the tube 18, also highly evacuated, to the detector where each ion produces a voltage pulse which is counted in the counter 22. The tubes 14 and 18 and the detector 20 are maintained at a high vacuum by pump mechanism,'such as a diffusion pump, not shown.
The work carrier and vacuum lock are shown in more detail in FIGS. 2 to 5. In FIGURE 2 the stationary plate 24 exposed to ambient pressure is secured to the highly evacuated tube 14, in airtight relation therewith, by any suitable means, such as the flange 26 and the screws 28. An O-ring 30' may be used to assist in sealing. A passageway 32 extends axially through the plate 24, which may be in the form of a disc as seen in FIG. 3, and is surrounded by a vacuum channel 34 which cooperates with the mating face of the rotatable disc 38 when it is assembled on the stationary disc 24 to provide a guard around the passageway 32. The stationary plate 24 is provided with a plurality of pumping stations arranged circumferentially around the plate, and are shown as vacuum passageways 49, 4-2, and 46, terminating in the surface 48 which is a highly finished surface mating with a similar surface 50 on the rotatable plate 38 when the two plates are assembled in operative relation as shown in FIGURE 1. These mating surfaces, when coated with a light vacuum grease, form a substantially airtight seal or joint sealing out the surrounding ambient pressure. Passageway 40 is connected by a pipe 52 with a source of reduced pressure 54 which may be any suitable means, such as a mechanical pump. Passageway 42 is connected by a pipe or conduit 56 with a source of reduced pressure 58 which may be a diffusion or a mechanical vacuum pump. Passageway 46 is connected by means of a pipe 69 with a suitable vacuum source such as a diffusion pump 62. Passageway -46 terminates in the surface 4-8 of the disc 24 adjacent the passageway 32 and is connected by means of a slot 64 with the vacuum channel 34 surrounding the passageway 32. Thus the passageway 46 acts to draw off any air that may tend to leak from the surrounding ambient pressure into the passageway 32 from between the discs 24 and 38. A small port 66 in the surface 48 is connected by a pipe 68 with a pair of valves 70 and 72. Valve 70 controls the connection of port 66 with ambient or atmospheric pressure and valve 72 controls the connection of port 66 with a source of reduced pressure such as vacuum pump 74. Disc 24 is provided'with any suitable indexing mechanism such as a spring pressed pin '76 supported in any suitable manner from the disc 24 and received in an indexing slot 78 in the disc 24 and in any of the series of similar slots 80 in the disc 38. A centrally located hole 82 in disc 24 and a similar hole 84 in disc 38 receive a shaft or axle for guiding the plate 38 in its rotary movement on the plate 24.
Plate or disc 38 exposed to ambient pressure has a 3 plurality of circumferentially arranged passageways or cavities, 86, 88, and 90, adapted to receive work or sample carriers 92 which may be readily inserted into and removed from the passageways 86,. 88, and 90 from the outwardly facing side of the disc 38. The sample carriers 92 each carry an O-ring seal 94 and when inserted into the passageways 86, 88, or 90, serve to seal the outer end of the passageways. Disc 38 may be rotated from one index station to the next by any suitable means such as a bar 96 and cables 98 coac'ting with upstanding pins 14H) secured to the disc 38'. r
The operation of the mechanism can best be describe by reference to FIGS. 6 and 7. With the rotatable plate in the position shown in FIGURE 7, the sample carrier may be inserted in the cavity or passageway $3. The valve 70 may then be closed and the valve 72 opened to start evacuation of the cavity 88. Disc 38 is then moved clockwise to the next index station which will position the plate as shown in FIGURE 6. While in the embodiment illustrated this is an inactive station for the carrier in the cavity 88, it could be an active station and it is an active station for other carriers as will presently appear. Plate '38 may then be indexed to the next position which would be that shown in FIGURE 7 again. Following the carrier selected for the explanation of the operation of the mechanism in its movements with plate 33 as plate 38 moves always in one direction, that carrier will now appear in the position indicated by the reference numetal 90 in FIGURE 7, where it will be in communication with the vacuum passageway 40 connected with the "pump 54 and will be further evacuated. The next index with the'pump 58 and be still further evacuated. The
next index step will bring the carrier to the position indicated by the reference numeral 86 in FIGURE 7 and place it in communication with the vacuum passageway 46 where it will be still further evacuated to a value equal to, or closely approximating, the vacuum being maintained in the tube 14. The next index step will bring the passageway or cavity containing the selected carrier to the position indicated by the reference numeral 86 in FIG. 6 and will align the carrier with its sample with the highly evacuated tube 14 in'position for testing the sample. When the passageway or cavity carrying the sample carrier arrives in this last mentioned position, it has already been so highly evacuatedthat little or 'no'air'is added to the highly evacuated system including the tube 14 so that the sample maybe tested without waiting for the chamber 14 to again be evacuated to the required or desired amount. While the sample is being tested, the next sample to be tested will be positioned over the passageway 42 and will be in the process of being evacuated during the entire time that the previous sa-mpleis being tested. After the sample has been tested, it is moved to the next index point indicated in FIGURE 7 and will be located at the position indicated by the reference numeral '88,
'where'it will'be'in communication with'the port 66 which isn-ow connected with ambient pressure by closing the valve 72 and opening the valve 70 so as to increase the .pressurein the cavity under the sample carrier to ambient pressure to equalize the pressure on opposite sides of the carrier and thus permit ready removal of the carrier.
Another sample carrier may now be placed in the cavity of being evacuated or tested during the entire cycle. In
the event that it is desired to test only one or two samples,
4 it is, of course, necessary to seal the unused cavities by any suitable means such as an empty carrier.
If desired, while the sample is in the position indicated by cavity 86 in FIG. 7, the sample may be heated to drive oif any moisture or other undesirable material associated with the sample and this moisture and undesirable material can thus be eliminated and discharged by the pump 62 before the sample reaches the testing chamber. It is thus possible to keep the testing chamber clean and substantially free from the undesirable material thrown off by the sample.
The above described mechanism permits vacuum pumping of a sample prior to introduction to the main system and thus prevents the main system from becoming unduly perturbed by large charges of gas carried in by or with a sample. The pre-pumping maybe performed on succeeding samples simultaneously with analysis of a sample aligned with the main system, and thus reduce the time between analyses to the time required to index the disc. In practise it has been found that a sample may be in position and condition fortest within ten minutes of the time it is inserted in the machine. Fabrication of the parts of the mechanism requires a minimum of high precision work, as only the two fiat mating surfaces are precise, and the rotary motion permits ready indexing by automatic means, if desired. 1
A significant advantage of this invention is that the wor is carried in simple cavities 86, 88, 90. This permits a high flexibility of configuration of the Work carrier 92. Vastly diiferent kinds of work can be run in rapid succession, with no change of the vacuum look. For example, a lens system which maybe installed in 32 may be examined by using a cup 92 that has a sealed glassor Plexiglas back and indexing the rotary disc 38 so as to align the glass with the aperture 32. The lens system may then be examined without breaking vacuum.
Similarly, different ion source designs may be experimented with by having a variety of cups avail-able, and one cup may be adapted to carry a vacuum gage so as to compare calibrations of other gages.
Although I have described one specific structure to illustrate my invention, it is obvious that various changes can "be made which would come'within the scope of the invenalignment, one at a time with said aperture, a series of vacuum apertures in said first plate arranged in the path of movement of said cavities.
2. A vacuum lock comprising a pair of relativelymovable plates having mating surfaces forming an air tight oint, a series of apertures in the-mating surface of one plate, one aperture of the series connected to a vacuum test chamber and'the others connected to pumping means, a sealed cavity in the mating surface of said other'plate,
and means for moving said other plate across said apertures in series in a direction to first present said sealed cavity to said apertures connected with said pumping means in succession and then to said vacuum test chamber.
3. A vacuum lock as claimed inclaim 2 in which said sealed cavity comprises a passageway through said other 'plate having an end exposed in the plate surface opposite said mating surface and a removable ion source carrier in said passageway having means sealing the exposed end of said'passageway.
4. Means for presenting a series of samples to a vacuum chamber without seriously afiecting the vacuum in said chamber comprising a sample carrier adapted to simultaneously support a series of spaced samples in separate openings in said carrier exposed to one face of said carrier, means sealing said face around said openings, a series of pumping stations including cavities in said sealing means, means for moving said carrier to progressively present each sample and opening to said pumping stations and cavities clear of said sealing means and then to said chamber to progressively reduce the pressure around each said sample before presenting the sample to said chamber.
5. Means for presenting a work piece to a vacuum chamber comprising a work piece carrier adapted to support a work piece in an opening in said carrier exposed to one face of said carrier, means sealing said face from the surrounding atmosphere, a series of pumping stations, and a vacuum chamber arranged along a selected path and com prising apertures in said sealing means, means moving said carrier relative to said sealing means to move said work piece and opening along said path to present said work piece and opening clear of said sealing means successively to said series of pumping stations and then to said chamber to progressively reduce the pressure insaid opening and around said work piece before presenting said work piece to said vacuum chamber.
6. In combination a pair of discs stacked in aligned relation with their mating surfaces forming a substantially air tight joint, means fixing one disc against rotation and means for rotating the other disc on the common axis of said discs, a passageway extending axially through the fixed disc to a vacuum chamber, a vacuum channel in the mat"- ing surface of said fixed disc around said passageway,'
additional vacuum passageways in said fixed disc terminating at spaced points around said fixed disc mating surface, a relief passageway in said fixed disc, a plurality of spaced passageways in said movable disc positioned to be brought, one at a time, into communication successively with each of said additional vacuum passageways, said channel, said through passageway and said relief passageway by rotation of said rotatable disc, each of said passageways in said rotatable disc adapted to receive a sample carrier sealing the outer terminus of the respective rotatable disc passageway.
7. A combination as claimed in claim 6 including means for indexing said rotatable disc to position one of the passageways in said rotatable disc in communication with one of said additional vacuum passageways and simultaneously align another one of said rotatable disc passageways with said axially extending passageway in said fixed disc.
8. A combination as claimed in claim 6 including means for indexing said rotatable disc to position one of said passageways in said rotatable disc in communication with one of said additional vacuum passageways, and simuling a through passageway aligned with said elongated chamber, a movable disc axially aligned with and mating with said stationary disc, means for rotating said movable disc on the common axis of said discs, the mating surfaces of saiddiscs forming a substantially air tight joint, a 7
channel in the mating face of said stationary disc around said passageway connected with pumping means, additional passageways in said stationary disc terminating in spaced relation around the mating face of said stationary disc connected with additional pumping means, a relief passageway terminating in the mating face of said stationary disc connected to ambient pressure, a plurality of spaced passageways in said movable disc positioned to be brought one at a time into communication successively with each of said additional passageways, said channel, said through passageway and said relief passageway by rotation of said movable disc, each of said passageways in said movable I disc adapted to receive a sample carrier sealing the outer' terminus of the respective movable disc passageway.
11. A vacuum lock as claimed in claim 1 in which the plate members are exposed to ambient pressure.
12. A combination as claimed in claim 6 in which the vacuum channel is connected with pumping means, the vacuum passageways are connected with additional pumping means, and the relief passageway is connected with ambient pressure. 1
"13. A combination as claimed in claim 6 in which the pair of discs are exposed to ambient pressure.
References Qited in the file of this patent UNITED STATES PATENTS 7 2,284,710 Zworykin et al. June 2, 1942 2,618,750 Parsegian et al Nov. 18, 1952 2,849,619 Eisfeldt Aug. 26, 1958 I v FOREIGN PATENTS V 955,197 France June 27, 1949 895,636 Germany Nov. 5, 1953 972,421
Germany July 16, 1959