US2445243A - Assembly for electron microscopes - Google Patents

Description

July 13, 1948. F, RUNG 2,445,243

ASSEMBLY FOR ELECTRON MICROSCOPES Filed April 12, 1944 3 Sheets-Sheet 1 14 TTOE/VEY July 13, 1948. RUNGE 2,445,243

ASSEMBLY FOR ELECTRON MICROSCOPES Filed April 12, 1944 ESheets-Sheet 2 4? 5 s) fir j z A I j y 7/ 6.11M if nrmnvff INVENTO Patented July 1 3, 1948 V'UNITED STATES PATENT OFFICE Frank E.'Runge, HaddonHeights, N. -J., assignor to Radio Corporation of America, a corporation of Delaware Application April 12, 1944,

6 Claims. (01. 25049.5)

1 The'present invention relates to electron microfscopes and more particularly to the assembly of thecolumn of which the channel for the electron stream'is apart.

-- 1 In columns of electron microscopes heretofore in use,-certain units have been soldered or other- ''-wise permanently secured together and thus internal parts, such as pole pieces, focusing apertures,'- and other parts requiring repair, replacementor cleaning are accessible only after hours of'labor by highly skilled engineers, the latter beingnecessary by reason of the knowledge required to dismantle the column and reassemble the'delicate' and intricate parts. Furthermore, difllculty was experienced in maintaining vacuum tightjoints because split clamping rings used to secure the gaskets were not entirely reliable. Also, certain joints in the column requiring lateral flexibility for alinement adjustment purposes were equipped with metallic bellows fixedly soldered in place. Such construction was very objectionable because replacement of bellows by even competent service engineers was extremely difficult. I

"some ofthe objects of the present invention are: to provide an improved column assembly of "an-electronmicroscope; to provide improved easily removable flexible units as apart ofthe evacuated-channel of an electron microscope; to provide effective sealing of the evacuated channel of an-electron microscope, while maintaining the =required articulation necessary for proper adjustment; to provide a novel collapsible, self-sealing unit asa portion of the evacuated channel of an electron microscope; to provide means for readily gaining access to the interior of the column of I an electron microscope in order to remove, clean and replace polepieces, apertures, etc.; to provide means for maintaining vacuumtight joints without the use of mechanical fastening means but using'instead either weight of the parts, spring pressure or atmospheric pressure, or combinations' thereof; and to provide other improvements as will hereinafter appear. In the accompanying drawings, Figure 1 represents a fragmentary elevation of the column of an electronic microscope embodying the pres- "ent invention; Figure 2 represents a sectional elevation of the same; Figure 3 represents an ele- 'vation of one side of a bellows unit embodying one form of the present invention; Figure 4 represents an elevation ofthe opposite side of the --bellows unit; Figure 5 represents a plan of the unit; Figure 6 represents a section on line6-6 ot Figure 3; Figure '7 represents an enlarged sec-- Serial No. 530,584

tional'elevation of the specimen chamber. and contained parts; Figure 8 represents a plan of another form of bellows unit; Figure 9 represents a side elevation of one form of gripping tool for use in removing the bellows unit of Figure-3; and Figure 10 represents a plan of the tool.

Referring to the drawings, the present invention is shownas assembled in association with those parts of an electronic microscopeto which the invention relates. The parts thus illustrated are a portion of the column or envelope 9 having an evacuated channel Ill by way of which the cathode ray stream successively traverses the centering apertured member II, the electronic condensing lens l2, the specimen holder I3, the objective lens M, the image focusing apertured intermediate viewing screen I5, the projecting lens 16, and finally impinges on the image screen (not shown). The channel I0 leads linearlyfrom the discharge end of the electronic gun 8 to the image screen or photographic area. Since the microscope embodying the present invention differs from the conventional type in thatthe separate parts are easily disconnectable and include accessible features, instead of parts soldered oriotherwise united together and generally inaccessible, without the .use of experts and .hours of labor, the present description will take, these features up in order and thereafter summarize the general assembly.

Inorder to properly space the objective lens 14 from, the projecting lens l6, and also to provide'fiexibility for axial alinement between them, afi'anged tubular section I! forms a chamber 18,

through which'a portion of the channel [0 passes.

As shown, this portion is formed by a removable flanged housing 20, which includes a window, and

a bellows unit 2|, the former being seated on the next adjacent lower section 22 of the column 9 throughv anintermediate gasket 23 to seal hermetically the .interior of the sleeve from the exterior, whilerthe' latter seats on the housingZil through a-gask'et 24 and bears against the next adjacent upper section 25 of the column through a gasket 26 and to be thereby hermetically sealed at. both ends.

Inorder toprovide for the-quick removalyof the bellows unit 2|, so that ready accessto the pole pieces [9 and [90 may be had for cleaning or otherpurposes, the unit 2i is of a novel structure comprising two annular heads .33and34, spaced apart by a, tubular flexible bellows 35, the

ends of? which seatin and are soldered into the respective heads 33 and 34 as shown in Figs. 3, 4,

..5.and 6: I he head33cooperates with twosockets 36 free to slide laterally in any direction and two centering pins 31, fixed in head 34 and extending parallel to the axis of the head, while the head 34 cooperates with two like sockets 38 and two centering pins 49, also parallel to the axis of the head. Entering the sockets and encircling the respective pins are coil springs 4| under compression to exert a relatively heavy repelling pressure of one head with respect to the other. This pressure serves to compress the gaskets 2d and 23 and eifect a complete sealing action.

For manually compressing-'the'heads- 33and 3t against the action of the springs 44, to shorten the unit for convenient removal; the'head 33 is provided with four bearing pins-42'; 43; 44- and 45, projecting in pairs from opposite sides of the head and transversely alined. The pin 42 rides irr a slot 46 of a lever 47; the pin 43 rides ina slot 48 of a lever 50; the pin 44 rides in a slotl of-a legwer 52; and the pin 45 rides in a slot 53 of a lever54; Likewise, the head 34- is providedwith four bearing pins 55; 56, 51 and 53,. projecting pairs from opposite sides of the-head and transversely'alined witheach other and with the pins of the'head 33. The'pin 55 rides in. a slot 60 of the lever '50; the pin 56 rides in a slot 6| of the lever 41; theipin 51 ridesin a slot 62 of the lever '52; and the pin 58 rides in a slot 63of the lever 54. The two levers 47 and 50 are relatively movable about a common pivot-64, and thetwo levers 52 and54 are relatively movable about a common pivot 65, so that the two pairs of levers form a balanced lazy-tongs structure arranged to be operated by pinching two rods 66- and 61 towards each other. The rod 66 has its ends respectively pivotally connected to the projecting short arms 68l and 69 of the respective levers 50 and 52, while therodli'! has its ends respectively pivotally connected to the projecting short arms and 10' of the respective levers 41 and 54. It should be noted moving. the unit 2 i from the chamber [8, a novel tool has been devised comprising, in the present instance, a U-shaped member forming a handle 12 at one end and two spacedjaws l3 at'the other end. The associated member of the tool comprises a strip having a handle 14 atone end and ajaw 75 at theother end, this strip being pivoted at16- to the other member of the tool. In closed position, one part of the tool lies within, or in the plane of, the other to form a compact unit. The jaws 13 are respectively provided with curved seats Tl, laterally in register and positioned to function in the opposite direction to a like seat -18 on the jaw 15. As shown, the curvature of the three seats is complemental to the contour of'the rods 66' and 61. The length of the jaws and the radius of swing is such that the seats of the bifurcated member can :engage'one' side of one of the rods 66 or 61 while the seat of the other member can engage the opposite side of the other rod.

"When so positioned, squeezing together of the handles causes the jaws to draw the rods 68 and 61 towards each other and to thereby retract the heads 33 and 34, sufliciently to permit the bellows unit to be removed through alined doorways formed respectively in the innerelectro-static shield 89 and the outerelectro static shield 80a 'forthe wall of the section l1. 'rnounted to slide ci-rcumferentially about the A door-19 is noted that a plurality of equally spaced thumbscrews I98 (here shown as four), are adjustably mounted to cooperate respectively with fiat surfaces on the periphery of the adjacent section 25,

and'hencemanipulation of these screws serves as a means toaline the pole pieces in the objective and projecting coils.

In order to provide for the desired lateral flexibility of the column between the condenser and objective coils, the chamber 82, in which the specimen holder I3 is located, is formed by a tubular flanged coupling 83 which seats. upon, the upper end of the frame 25in which the coilsare located as a part of the objective lens; l4.- A gasket 85 is interposed between the coupling 83 and the frame 25 and serves as a seal under the weight of the coupling and atmospheric pressure. The upper end of the coupling member 83 is of larger internal diameter to receive an annular sealing unit, which forms a part of the channel It} and, in the present instance, comprises atubular bellows 86 mounted between two heads Blend 88. A coiled spring 89encircles the bellows 86 and seats at opposite ends respectively-against the heads 87 and 88. The head 81 seats on member 83 through a sealing gasket 99, the assembling being such that the bellows 86 is alinedwith and forms a part of the column channel [0. The-head 88 seats against the next adj acent-annular frame 9!, in which the coils 92 of the condensinglens I2 are located. A gasket 93 is interposed between the head'88 and the frame 9 l for sealing purposes. A ring 94 encircles the head 88- as analinement guide and is removably fastened to the frame'9l.

Thus it will be seen that the sealing unit is freely mounted between the member 83 and the frame 9|, being held by the weightof the'frame 9I,- and hermetically sealed by-the compressed bellows 86 and spring 89, and the exterior atmospheric pressure. The removal of the sealing unit is easily made because it is not solderedv or otherwise fixed in place, and consequently when the vacuum is broken, the condenser coil and parts above may be lifted on and the unit removed without tools. One side wall of the member 83 is provided with an access hole arranged to be closed by a plug type closure 95 having a flange 96 to seat against a gasket 97 and be held sealed, by atmospheric pressure when the column is evacuated.

To provide for lateral flexibility ofthe column includin the electron gun 8, an annular member 98 is seated upon condenser lens I 2. A frame l.06,'

which supports the gun section Hill. is mounted for lateral movement on the annular member 98. A gasket ifll hermetically seals the joint between thernember-Elfi and the lens I2; by reason of, the weight of the member 8 and associated members plus atmospheric pressure. A like: gasket N32, is disposed between the member 98 and the gun section Hi9, and seals the joint therebetween in'the-same manner. The lower'end portion of the. member'98 encircles the centering-aperture tnember H34, and includes a Window/ 103 for viewing the inclined'face' of the memberl04, said face being coated with'afiuorescent material.

against end sealing gaskets.

A sight opening IE5 is registered with the window Hi3, and is formed in an outer surrounding fram iiifi, which is a part of an adjustment structure not here necessary to be described, as it is fully disclosed and claimed in my earlier Patent No. 2,418,317, granted April 1, 1947. A sealing unit it! is interposed between the gun section Hill and the annular member Q8, and is similar to the sealing unit heretofore described in that it is formed of annular heads spaced apart by a bellows iill and hermetically sealing the column by atmospheric pressure and the pressure of the compressed bellows and spring actin This unit is like wise freely mounted in the column so that not only is flexible lateral adjustment possible but also ready removal of the unit when the column is to be taken apart.

From the foregoing it will be apparent that the column forming the channel to be evacuated consists of a plurality of disconnectable sections arranged in superposed relation and hermetically sealed with respect to each other. Certain of the sections serve as frames for the coils of the electronic lenses, while others respectively provide chambers in which parts of the column are formed by bellows units which contribute to easy adjustment, since each bellows unit is capable of lateral deflection as well as axial or endwise movement. One of the chambers serves to receive the specimen and its holder, while others contain respectively the adjustable apertures for focusing the stream of electrons.

In connection with the chamber between the objective lens and the projection lens, it should be noted that by breaking the vacuum in the channel I I], the door 19 and the outer member including the aperture 8| can be opened, allowing access to the bellows unit 2|. The tool can now be inserted to bring the jaws 13 and 15 respectively into gripping relation with the rods 66 and 61, whereupon the unit 2| can be squeezed together and removed. With this unit out of the way, flanged housing 20, the aperture member l5 and pole pieces [9 and 19a can be removed for cleaning or other purposes.

It will now be apparent that a complete unitary column assembly has been devised wherein collapsible, self-sealing units fonm parts of the evacuated channel and which are so arranged and assembled as to be held in leak-proof 'relation under all operating conditions. These units are not attached to adjacent parts by soldering or other fastening means, but are maintained solely by weight of adjacent parts plus atmospheric pressure. With the present novel construction the column becomes a single, elongated, articulated chamber, certain essential portions thereof adjacent the pole pieces being readily accessible in a minimum of time and by unskilled workmen. Furthermore, by taking advantage of atmospheric pressure all joints are automatically held tight and leak-proof. Also, by providing a special tongs the collapsible units can be reached and quickly removed in order to expose the pole pieces, and focusing apertures for removal.

I claim as my invention:

1. In an electron microscope, a column portion formed by electron lens sections and an intermediate section forming a chamber, said intermediate section having an access opening and a door for said opening, a bellows unit in said intermediate chamber and forming a portion of the electron channel of said column, and means accessible through opening for collapsing said unit for removal. I

2. In an electron microscope, a column portion formed by electron lens sections and an intermediate section forming a chamber, said intermediate section having an access opening and door for said opening, a bellows unit in said in termediate chamber and forming a portion of the electron channel of said column, means accessible through said opening for collapsing said unit for removal, and means for hermetically sealing the joints between the respective ends of unit and adjacent parts.

3. A bellows unit for the column of an electron microscope comprising a pair of annular heads, a tubular flexible bellows between said heads, spring means normally repelling one head with respect to the other, and manually operable means for squeezing said heads toward each other to reduce the length of the unit for removal and replacement from the column.

4. A bellows unit for the column of an electron microscope comprising a pair of annular heads, a. tubular flexible bellows between said heads, and levers forming a pair of lazy tongs for manually squeezing said heads towards each other to reduce the length of the unit for removal and replacement from the column.

5. In an electron microscope, the combination of a tubular column formed by a plurality of alined sections, at least one of which is a bellows unit comprising two annular heads, a tubular bellows between said heads, coil springs normally repelling one head with respect to the other, and accessible manually operable means in said columns for squeezing said heads towards each other to reduce the length of the unit for removal from said column.

6. In an electron microscope, the combination of a tubular column formed by a plurality of alined sections, at least one of which is a bellows unit comprising two annular heads, a tubular bellows between said heads, coil springs normally repelling one head with respect to the other, manually operable means in said column for squeezing said heads towards each other for removal from said column, and a casing about said column having a door controlled opening registered with said bellows unit for access to said squeezing means.

FRANK E. RUNGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 736,671 Aksila Aug. 18, 1903 1,475,289 Diescher Nov. 27, 1923 1,923,124 Stanley Aug. 22, 1933 2,347,348 Young Apr. 25, 1944 2,356,963 Young Aug. 29, 1944 2,360,677 Hillier Oct. 17, 1944

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