US 2292087 A
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Description (OCR text may contain errors)
4, 1942. s. RAMO I EVACUATED ELECTRONIC APPARATUS Filed Sept 19, 1941 Pig I.
H To Foa: 6B
T0 HIGH VACUUM Inventor: Sim on Ram o,
by 7V is Attorney Patented Aug. 4, 1942 UNITED STATES PATENT OFFICE EVACUATED ELECTRONIC APPARATUS Simon Ramo, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application September 19, 1941, Serial No. 411,515
The present invention relates to an improved arrangement for facilitating the introduction of specimens or objects into a vacuum chamber, such as the enclosure of an electron microscope, without destroying the vacuum of the entire chamber.
It has previously been proposed in this connection to equip the vacuum apparatus in question with an auxiliary chamber which is capable of being temporarily cut oif from the main vacuum chamber and into which specimens may be introduced as a preliminary to their introduction into the main chamber. However, arrangements of this kind which have been heretofore provided are of complicated construction and are relatively expensive to produce. It is an object of the present invention to provide simplified means for isolating the object supported from the remainder of the apparatus enclosure during introduction of specimens.
The foregoing object is accomplished in accordance with one embodiment of the invention by providing the main wall of the apparatus enclosure with a deformable section having an operating connection with a pair of concurrently movable closure members which are within the enclosure and which are adapted to isolate the object support in the desired manner. In the preferred construction, the object support is itself r connected to the deformable wall part so that the Y motion of this part can additionally be employed to move the object support from an object-receiving position to an object-viewing position, and vice versa, or to adjust it for focusing purposes when it is in the object-viewing position.
The features which I desire to protect herein are pointed out with particularity in the appended claims. The invention itself, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the drawing in which Fig. 1 represents in partial section an electron microscope suitably embodying the invention, and Fig. 2 is an enlarged fragmentary sectional View showing in detail certain of the operative parts of the construction of Fig. l.
Referring particularly to Fig. 1, there is shown an elongated discharge enclosure of which the principal wall part comprises an elongated metal cylinder I Il. This connects at its upper extremity with a glass insulator I I which closes the end of the vacuum chamber and which further serves as a supporting means for a lamentary cathode I3. The cathode is supplied with heating current from an external source I4 and is associated with an apertured anode I6 which acts to focus electrons released from the cathode into a narrow beam and to project them axially of the microscope structure. To this end the anode I6 may be maintained at a positive potential with respect to the anode by connection to a unidirectional potential source IB. An apertured diaphragm 20 which is supported in direct contact with the wall of the enclosure I0 is connected through the enclosure and through ground to the positive terminal of the potential source I8 so that it has the effect of accelerating the electrons to a high velocity as they pass through the diaphragm. After traversing the diaphragm 20 the electron beam is caused to pass through an object support 2I (shown in dotted outline in Fig. l and in full in Fig. 2') which is adapted to mount an object or specimen desired to be examined electronoptically. For this purpose the specimen (not shown in the drawing) is supported in an aperture 23 formed in the extremity of the object support so that it is in the direct path of the electron beam. Under these circumstances, the section pattern of the electron beam is modied in accordance with the structural character of the object under investigation as the beam traverses the object.
In order that the beam, thus conditioned, may be caused to provide an enlarged visible image of the object in accordance with the intended method of use of the microscope, the beam, after passing through the object, is caused to traverse an electron lens system of known character. In the arrangement shown the lens system is in two parts and includes as a rst part a series of three diaphragms numbered 26 to 28 inclusive. The diaphragms 2'6 and 28 are maintained at the potential of the casing I0 (i. e., at ground potential) and the intermediate diaphragm 21 being insulatingly supported, is biased to cathode potential through a terminal connection 30 which is brought into the microscope enclosure through an insulating bushing 3|. Because of the resultant difference in potential between the diaphragm 2'I and diaphragms 26 and 28, lens elds are established between these diaphragms which have the effect of refracting the electron beam in a manner analogous to the refraction of a light beam by an optical lens. The second part of the lens system comprises another series of three diaphragms, 34, 35 and 35, of which the central diaphragm is biased to a potential considerably below that of the outer diaphragms by a terminal connection 38 sealed through an insulating bushing 39. Accordingly, additional lens elds are formed within the spaces which separate the various diaphragms last referred to.
Viewing the lens system as a Whole, it may be said that the diaphragms 26, 21 and 28 form an objective lens, whereas the diaphragms 34, 35 and 36 form a projecting lens. In order that the image produced by the latter may be made visible there is provided at the image plane of the lens an image-reproducing surface (indicated in dotted outline at 4|) which may comprise an electron-sensitive fluorescent screen. This screen may be viewed from outside the microscope through an appropriately positioned transparent eye-piece 42.
In the use of the apparatus, it is a prerequisite that the microscope enclosure shall be highly evacuated and to this end there is provided in connection with the enclosure an evacuating system including pipes 44, 45 and 46, all of which may be connected to vacuum pumping apparatus (not shown).
In order to facilitate the removal of examined objects from the object support 2| and to facilitate the introduction of new objects, the wall of the microscope enclosure in proximity to the object support is provided with an opening 41 having an externally operable closure member 48. This includes a rubber gasket part 49 which is adapted to seal tightly against an upset embossment 50 provided around the circumference of the opening 41. If desired, the closure member 48 may be provided with locking means as indicated at 53, but under operating conditions it will, if appropriately constructed, be held tightly closed merely by the action of the differential pressures existing outside and inside the microscope enclosure.
In introducing new specimens into the microscope enclosure, it is desirable insofar as possible to avoid destroying the vacuum within the entire enclosed space, the most important consideration in this connection being the relatively long time required fully to re-exhaust the space, once air has been admitted. It is a principal concern of the present invention to provide a simple and reliable means by which the principal Vacuum may be protected during the object-introducing operation.
The means provided in this connection include in the first instance a pair of movable closure members 56 and 51, the rst of these being :associated with the accelerating electrode and the second with the lens diaphragm 26. As clearly appears in Fig. 2, these closure members are on opposite sides of the object support 2| and when closed have the effect of isolating the object support from the remainder of the vacuum enclosure. Each closure member is provided with a rubber gasket (56, 51) which permits it to seal tightly against an appropriately formed embossment on the cooperating diaphragm part.
In order that the motion of `the closure members 56 and 51 may be controlled externally of the microscope enclosure, the enclosure wall is provided with an integrally formed deformable section comprising a collapsible, corrugated ring having two annular parts 60 and 6|. This ring is deformable in the longitudinal direction and to a smaller degree in the transverse direction. Extending inwardly from the inner surface of the ring there is provided an annular diaphragm or frame 63 on the central portion of which the object support 2| is mounted. Linkage members 65 and 66 serve to connect the opposite surfaces of this frame with the closure members 56 and 51 in such a way that displacement of the frame serves to produce concurrent and oppositely directed motions of the members.
Accurately controlled motion of the deformable ring system 68, 6| is accomplished through the use of a threaded collar 61 which rides on a correspondingly threaded surface 61 provided in connection with the enclosure cylinder I8. This collar loosely engages a pair of annular members 68 and 69 which slide in grooves provided in the outer surface of the collar and which connect with an externally projecting portion of the frame 63 through an axially extending cylinder 1|. Accordingly, if the collar 61 is rotated, for example, by means of handles 12, the the frame 63 is driven either up or down in accordance with the deformation of the parts 60 and 6| as determined by the direction of rotation of the collar. No twisting of the parts is permitted, because of the circumferential rigidity of the ring structure. The range of movement obtainable in this manner is suiliciently great to enable the object support 2| to be moved from the object-receiving position which it occupies in the full line representation of Fig. 2 to the object-viewing position which is indicated by the dotted outline 2 I in the same figure.
Concurrently with motion of the object support from its object-receiving position to its object-viewing position, the closure members 56 and 51 are moved to the open positions 56 and 51 in which they appear in dotted outline in Fig. 2. The converse motion of the closure members obviously occurs when the object support is returned to its object-receiving position. In the use of the apparatus, after a given object has been investigated to the desired extent (i. e., with the object support in the position 2|) the collar 61 is turned in the proper direction to bring the object support into its object-receiving position. Under these circumstances the closure members 56 and 51 are closed so that the object support is segregated from the remainder of the microscope enclosure as previously speciiied. Accordingly, the closure 48 may now be opened with the assurance that only the vacuum in the relatively small compartment between the diaphragms 20 and 26 will be lost. With this compartment open to the air, the examined object may be removed and a new object put in place in the object support, being introduced through an opening 13 formed in the side of the supporting structure. (If desired, auxiliary mechanisms, not shown in the drawing, may be employed to assist in manipulating the object into the proper position in the object holder.) With the new object in place, the closure member 48 is again closed and with the closure members 56 and 51 also retained in closed position, the air-lled compartment is connected to the fore-vacuum pump (not shown). This connection may be made, for example, through the agency of a three-way valve 15 located in the pipe 45. (This valve may also be used to cut the object compartment off from the pumping system and thereafter to break the vacuum in the compartment during object-changing periods.) After the fore-vacuum pump has reduced the pressure suiciently, the valve 15 may be turned to a second position to reconnect the compartment with the high vacuum pump. Finally, when high vacuum conditions are achieved, the collar 61 may be again rotated to lower the .object support 2| to the object-viewing position and concurrently, to open the closure members 56 and51. The last few turns of the collar 61 may be used for the purpose of focusing the system, that is to say, for manipulating the object into proper relation with respect to the lens system of the microscope.
In connection with the last-named operation (i. e., the focusing of the microscope) it is frequently necessary to provide for transverse adjustment of the object support in order to permit the object to be brought into a perfectly centered position. This is accomplished in accordance with a further feature of the present invention by providing means for exerting lateral force on the externally projecting part of the frame 63. An arrangement which may be employed in this connection is shown as comprising a micrometer screw 18 which is set into the laterally immovable cylinder 1| and which acts against the edge of the frame 63. The frame is slidably supported by annular plates 80 and 8| which are placed above and below it and moves against a compression spring 82. In view of the inherent flexibility of the deformable parts 60 and 6l, the region at which they are secured to the frame 63 is capable of appreciable transverse displacement. Accordingly, by proper adjustment of the micrometer screw 18 and by the use cf a second screw (not shown) acting at right angles to the screw 18 the position of the object support with respect to the axis of the electron microscope may be very accurately controlled.
It will be seen that the construction provided is of an extremely simple and compact character and that it adds very little to either the bulk or the cost of the microscope apparatus as a whole. Moreover, its ease and certainty of operation is such as to recommend it for use in microscopic apparatus for general application.
It is apparent, further, that the structure which has been described may be used in other ways than for the introduction of specimens into the specimen chamber of an electron microscope. For example, a generally similar arrangement could obviously be used to facilitate the introduction of photographic lms into the viewing chamber of such a microscope in order to obtain a photographic record of the specimen under investigation. Accordingly, Where the term object is used in the appended claims I intend to designate not only specimens desired to be investigated microscopically but also other articles which may require from time to time to be introduced into or removed from a vacuum chamber.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. An electronic apparatus comprising a vacuum enclosure in the form of an elongated container which is of cylindrical coniiguration over at least a portion of its length, an object support positioned within the enclosure, means for permitting the introduction of objects into the enclosure in proximity to the object support, and an arrangement for making possible the introduction of such objects without destroying the vacuum in the entire enclosure, said arrangement comprising movable closure means positioned within the enclosure and adapted when in closed position to isolate the object support from the remainder of the enclosure, a deformable metal ring forming an integral part of the wall structure of that portion of said container which is of cylindrical configuration, and means operatively connecting the said ring to the said closure means, whereby upon appropriate deformation of the ring, the said closure means may be moved from open to closed position and vice versa.
2. An electron microscope having an object support positioned Within the microscope enclosure, a closable opening in the said enclosure for facilitating the introduction of objects into the enclosure in proximity to the said object support, movable closure means within the enclosure and adapted when in closed position to isolate the object support from the remainder of the enclosure, a deformable metal ring forming an integral part of the Wall of the said enclosure and having an intermediate portion thereof capable of displacement in the axial direction, and connections between said intermediate portion and said closure means, whereby upon appropriate axial displacement of said portion the closure means can be moved from open to closed position and vice versa so as to permit the introduction of objects through said closable opening without destroying the vacuum of the entire enclosure.
3. An electronic apparatus comprising a vacuum enclosure, an object support Within the enclosure, a closable opening in the enclosure for facilitating the introduction of objects into the enclosure in proximity to the said object support, movable closure means within the enclosure and adapted when in closed position to isolate the object support from the remainder of the enclosure, an axially deformable metal ring forming an integral part of the wall of the enclosure, a connection between said ring and said closure means whereby the motion of the latter may be controlled by deformation of the former, an internally threaded collar riding upon a cooperatively threaded external surface of the enclosure, and a connection between said collar and said ring, whereby rotation of the former produces controlled deformation of the latter.
4. An electron microscope including an object support positioned at an intermediate point along the axis of the microscope enclosure, a closable opening in the enclosure for facilitating the introduction of objects into the enclosure in proximity to the said object support, a pair of movable closure elements positioned within the microscope enclosure on opposite sides of the object support and adapted when in closed position to isolate the object support from the remainder of the enclosure, a collapsible metal ring forming an integral part of the wall of the enclosure and having an intermediate portion thereof capable of both axial and transverse displacement, connections between said intermediate portion of the ring and said closure members whereby upon appropriate axial displacement of said portion said closure members may be moved from open to closed position and vice versa, and a further connection between said intermediate portion and the object support whereby through transverse motion of said portion the object support may be manipulated into alignment with the axis of the enclosure.
5. An electron microscope including Within the microscope enclosure an object support having an object-receiving position and an object-viewing position, a closable opening in the wall of the microscope enclosure for facilitating the application of objects to the object support when the latter is in its object-receiving position, a pair of closure members respectively positioned on opposite sides of the object support and adapted when in closed position to isolate the object support from the remainder of the enclosure thereby to avoid destroying the vacuum of the entire closure while objects are being introduced through said closable opening, `a deformable structure forming a part of the Wall of the microscope enclosure While objects are being introduced support and the said structure for permitting the position of the object support to be controlled externally of the enclosure through deformation of the said structure, and further connections between the said structure and the said closure member by which said members are moved from an open to a closed position concurrently with the motion of the obj ect support from its objectviewing to its object-receiving position.
6. An electron microscope including an object support positioned Within the microscope enclosure, a closable opening in the enclosure for facilitating the introduction of objects into the enclosure in proximity to the said object support, a pair of movable closure members Within the enclosure on opposite sides of the object support and adapted when in closed position to isolate the object support from the remainder of the enclosure, a collapsible metal ring forming an integral part of the Wall of the enclosure, a frame extending inwardly from the said ring for securing the object support to the ring, linkages eX- tending from the frame to the said closure members for controlling the movement of the mem-- bers in accordance with the movement of the frame, and means accessible outside of the enclosure for controllably deforming the said ring, thereby to control through the resultant motion of the said frame both the said closure members and the said object support.
CERTIFICATE op CORRECTION. Patent No.' 2,292,087. Auggst LI, I9LI2.
It is hereby certified that error appears in theV printed specification of the above numbered patent requiring correction as follows: Page )4, first column, line 2, for the wordv "closure" read --encl'osure; 'line 5, for enclosure while objects are being introduced read "enclosure, a connection between the said obJect-; and that the said Letters Patent should be read with this correction 'therein that the same may oonfom to the record of the case in the Patent Office.
Signed and sealed this 8th day of September, A. D. 1914.2.
Henry Van Arsdale, (Seal) Acting Commissioner` of Patents.