US3449759A - Electron beam recorder having sealing means - Google Patents

Description

v3,449,759 ELECITRON BEAM RECORDER HAVING SEALING MEANS Filed Feb. 27, 1967 J. K. WARREN June 10, 1969' Sheef a N W r H W m m 0 6 4 WW 1 6 a M K A 2\ K. I F c I a a A M L Jw. .2 2. "ma

w Mm 0. 1 r .Illr-ll a, 1 3/ 6 7 7 f m 6 79, F n H n FL Y M E lnHL L11 June 10, 1969 J. K. WARREN ELECTRON BEAM RECORDER HAVING SEALING MEANS Sheet 2 of 2 Filed Feb. 27, 1967 SOURCE OF #IR P35250195 l NVENTOR. JacxKlVfikps/v 43w??? TOR/V5. 5

United States Patent 3,449,759 ELECTRON BEAM RECORDER HAVING SEALING MEANS Jack K. Warren, Marine on St. Croix, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware.

Filed Feb. 27, 1967, Ser. No. 618,656 Int. Cl. G01d 9/42 US. Cl. 346-110 15 Claims ABSTRACT OF THE DISCLOSURE Apparatus comprising in combination an evacuated chamber capable of being pumped to a partial vacuum and a sealing means, such as a valve, is disclosed. The chamber encloses means for generating and directing an energy or corpuscular beam, such as an electron beam, through an aperture in the chamber which under certain conditions is sealed by the sealing means. The sealing means is adapted for movment between an unsealing and sealing position to isolate and maintain the vacuum within the chamber.

.Movement of a web through a gas seal or vacuum seal into a high vacuum chamber for treatment or bombardment by an energy beam is shown by the prior art. Such apparatus is disclosed in Patent No. 3,222,678 to D. A. Jones, and Jones application Ser. No. 515,049, filed Dec. 20, 1965, now abandoned and replaced with pending application Ser. No. 667,016, filed June 3-0, 1967, and Jones application Ser. No. 613,215, filed Jan. 31, 1967.

The apparatuses referenced above are used as recording and/or reproducing systems which bombard one surface of a moving web with a corpuscular beam, such as an electron beam. A high vacuum in an electron gun chamber is maintained by the vacuum seal and the effectiveness of the vacuum seal.

In apparatus disclosed in Patent No. 3,222,678, the surface of the web being treated is in sliding engagement with an outer wall of the chamber. Further, the surface of the web forms part of the vacuum seal by physically engaging and sealing an aperture'in the chamber wall through which the electron beam passes to treat the web. Conversely, in apparatus disclosed in Jones application Ser. No, 515,049, and Jones application Ser. No. 613,215, filed Jan. 31, 1967, the surface of the web being treated by the electron beam through an opening in the chamber wall does not contact any part of the chamber wall and does not contact the aperture. or opening. Effectiveness of the vacuum seal in this apparatus is dependent on continuously pumping a small volume or space which exists between the surface of the web being treated and the chamber wall. I

In either of the above apparatuses, the surface of the web breakage thereby protecting the beam generating through. an aperture in the chamber wall is in operative relationship with that aperture. The transporting and gas restricting means restricts movement of gas molecules from an ambient higher pressure atmosphere to the aperture as the one surface of the web is transported past the aperture.

If the moving web breaks thereby rupturing the vacuum seal, the electron beam chamber and the beam generating means are engulfed in the higher pressure atmosphere which normally contains oxygen, nitrogen and other gases. Sudden exposure of an operating beam generating means to oxygen in particular causes some elements, such as the cathode, to be either immediately destroyed or poisoned. When this occurs and before the apparatus can be rendered operative, the affected ele- See ments need to be replaced and the electron beam chamber repumped back to the desired vacuum.

The vacuum chamber valve of the present invention overcomes the disadvantages of the prior art in that the valve is capable of immediately isolating and retaining a vacuum within an evacuatable chamber in the event of web breakage thereby protecting the beam generating means.

Another advantage of the present invention is that the vacuum chamber valve is capable of maintaining a vacuum within the evacuatable chamber during web unloading and loading.

Yet another advantage of the present invention is that the vacuum chamber valve can be located either within the evacuatable chamber or alternatively in the ambient atmosphere surrounding the aperture directly communicating with the evacuatable chamber.

These and other advantages of the present invention will become readily apparent when considered in light of the following description taken in connection with the following drawing wherein:

FIGURE 1 is a diagrammatic representation of a front elevation view of a recording and/or reproducing apparatus having a vacuum chamber valve wherein a vacuum seal is utilized to maintain a high vacuum in an evacuatable chamber and afford movement of a web therethrough for bombardment of the web by an energy beam;

FIGURE 2 is a diagrammatic representation of a fragmentary vertical sectional view of the vacuum seal of FIGURE 1 illustrating one embodiment wherein the vacuum chamber valve is located within the high vacuum chamber;

FIGURE 3 is a detailed plan view of the vacuum chamber valve of FIGURE 2;

FIGURE 4 is a diagrammatic fragmentary elevational view, with a front plate removed and partly in cross: section, of a recording and/or reproducing apparatus wherein the vacuum chamber valve is located in the evacuatable chamber and is operated by a pneumatic member;

FIGURE 5 is a fragmentary detailed sectional view of the automatic vacuum chamber valve taken along the line 5-5 of FIGURE 4;

FIGURE 6 is a fragmentary detailed sectional view of yet another embodiment of the vacuum chamber valve which is slideably moved in an arcuate path between its sealing and unsealing position; 1

FIGURE 7 is a pictorial representation of a valve similar to that of FIGURE 6 showing a differentarcuate movement for the valve; and Y I FIGURE 8 is a pictorial representation ofa valve similar to that of FIGURE 6 wherein the valve is slideably moved in a straight path between its sealing and unsealing position. v

Briefly, the present invention relates to apparatus comprising in combination means for defining a chamber capable of being evacuated wherein the chamber includes a terminal wall portion having an aperture therein. The chamber encloses means for generating and directing an energy beam, such as an electron beam, through the aperture. Means which are operatively connected to the chamber are used for producing at least a partial vacuum within the chamber. Sealing means, for example a flap valve, are disposed adjacent the aperture and are adapted for movement into sealing position with the aperture for isolating and maintaining vacuum in the evacuated chamber when a condition occurs wherein the vacuum within the chamber would be poisoned from a higher pressure ambient atmosphere. The sealing means is adapted for movement into an unsealing position away from the aper ture when the vacuum condition can be safely maintained within the chamber for permitting the energy beam to pass through the aperture.

FIGURE 1 illustrates one embodiment of an apparatus for bombarding one surface of a web 10. The apparatus is in the form of an information recording system which includes means for generating an energy beam or a corpuscular beam, such as the illustrated electron gun 12. The electron gun 12 is enclosed within an electron gun chamber 14, which is at least a portion of an evacuatable chamber. The electron gun chamber 14 is capable of being evacuated by means for producing at least a partial vacuum in the chamber, such as a vacuum pump (not shown) through a conduit 16. The electron gun 12 typically includes a cathode 24, a control grid 26 and an accelerating grid 28 which produces an electron beam 30 which is directed in an axial direction through the chamber 14. The electron beam 30 is focused and deflected by conventional focusing and deflecting means, such as for example electromagnetic focusing coil 32 and electromagnetic deflecting coil 34.

In this embodiment, the chamber 14 encloses the electron gun 12. The web to be bombarded by the resulting electron beam is located outside of the chamber. Alternatively, the chamber 14 could be of sufficient size to enclose both the generating means and web. In such apparatus, the generating means is located in at least a portion of the chamber, say for example at one end thereof, which communicates via an aperture with the web enclosing portion of the chamber located, for example, at the other end thereof. Thus, the generating means enclosing portion of the chamber is capable of being physically separated from the web enclosing portion of the chamber.

The chamber 14 terminates in a terminal member 38 having an aperture 40 formed therein through which the electron beam 30 is directed. An outer surface 42 of terminal member 38 forms an outer terminal wall portion. The outer surface 42 defines a surface around which the web travels as it is passed to and through an area exposed to the chamber 14 for bombardment of one surface thereof by the electron beam 30. It is contemplated that terminal member 38 and aperture 40 could be located in other than axial alignment with the electron gun 12, such as for example at a 90 angle. In such an apparatus, the electron beam 30 is deflected through a 90 angle by conventional beam deflection means.

A conduit 44 is connected between the cylindrical chamber 14 including terminal member 38 and a source of reduced pressure or means for producing at least a partial vacuum, such as a vacuum pump (not shown). The conduit 44 serves to supply subatmospheric pressure to the terminal member 38.

"A complementary shaped guide member 46 is positioned below the terminal member 38 and is mounted to be readily removed and replaced to facilitate threading the web 10 in the apparatus. The guide member 46 also coacts with the terminal member 38 to maintain the web 10 in its path and under desired pressure conditions. The web 10 in the illustrated embodiments is a medium sensitive to an electron beam, for example a film or treated paper. The web 10 is progressively unwound from a supply roll (not shown) over a roller 48 and between the terminal member 38 and guide member 46. The web 10 is threaded between a driven capstan 50 and a resilient pressure roller 52 which coacts with the capstan 50 to maintain web 10 in frictional contacting driving engagement therebetween. During a recording operation, the capstan 50 is adapted to drive the web 10 at a constant speed and the web 10 is rewound upon a take-up spool (not shown). A vacuum'chamber valve, generally designated as 56, is located in the terminal member 38.

- FIGURE 2 illustrates a preferred embodiment of the vacuum chamber valve of the present invention. In this embodiment, the terminal member 38 is joined with the cylindrical chamber 14 to form a lower terminal chamber, generally designated as 58, of the electron gun chamber.

The chamber 58 within the terminal member 38 has the opening or aperture 40 formed therein. In this embodiment, the aperture 40 contains a relatively smooth planar surface which is in the form of a raised protruding lip or border 62 on the inner surface of terminal member 38 within chamber 58. In other applications, it may be desirable to have the smooth planar surface recessed. In either application it is desirable to have the surface relatively well-machined.

A sealing means, such as flap valve 56, is disposed adjacent the aperture 40 and is adapted for movement into sealing engagement across the aperture 40 as illustrated in FIGURE 2. Alternatively, the flap valve 56 is adapted for movement into an unsealing position away from the opening in the position illustrated by the dotted lines.

The outer surface 42 of terminal member 38 is smooth to provide a low friction surface over which the web 10 may be passed as indicated by the arrow in FIGURE 2 without wrinkling. The outer surface 42 is arcuate in the lengthwise direction of the web and has a straight dimension in the transverse or widthwise direction of the web. The aperture 40 is positioned intermediate the ends of this surface 42 and communicates directly with the chamber 58. The arcuate surface 42 of terminal member 38 has a groove 68 disposed therein which surrounds the aperture 40. A surface portion or land 70 remaining between the groove 68 and the aperture 40 forms a sealing lip around the aperture 40. A suitable passage 72 is formed in the terminal member 38 and is connected to the conduit 44 such that the groove 68 is connected to a source of subatmospheric pressure to draw at least a partial vacuum in the groove 68.

The guide member 46 is formed with a generally rectangular dished-out cavity or recess 74 generally centrally thereof. The recess 74 has a transverse dimension equal to the transverse length of the groove 68. The recess 74 communicates through the end portions of the groove 68 with the source of subatmospheric pressure to which the passage 72 is connected such that the pressure in the recess 74 is substantially identical to the pressure in the groove 68 during operation of the apparatus.

The groove 68 forms areas of reduced pressure at the surface of the terminal member 38 forwardly and rearwardly of the aperture 40, in the direction of movement of the web 10, such that any gas molecules trapped between the web 10 and the outer surface 42 of the terminal member 38 are drawn away before the web crosses the land 70 and aperture 40. These areas of at least a partial vacuum serve to prevent any gas from being carried into the chamber 58 and thus form at least a partial seal between the treatment chamber and the atmosphere. In this embodiment, the surface of web 10 is in operative engagement with the aperture 40 by physically contacting land 70 which forms a border around aperture 40. The partially evacuated recess 74 in the guide member 46 serves to withdraw any gas which otherwise might reach the aperture 40 and provides an equilibrium condition on the web 10 tending to negate the force on said web and to reduce the frictional force present between the web 10 and the surface of the terminal member 38.

In operation, the curved surface 42 of the terminal member 38 around which the web 10 is drawn permits said web to be brought into operative engagement with aperture 40. The web intimately contacts the land 70 around the aperture 40 and the force placing the web in contact with terminal member 38 may be increased by applying a controlled braking forcesuch that a tension is placed in the web between the nip area of the driven capstan 50 and the pressure roller 52 and the supply roll (not shown). In this embodiment, as the web 10 is drawn across the aperture 40 the electron beam 30 (see FIGURE 1) scans the exposed surface portion of the web and as the electrons strike the web,

they treat the surface thereof to produce a latent or a visible image on the surface of said web as defined by the information-input to the electron gun 12 and type of web material.

In the event the Web becomes broken, the surface of the web 10 no longer engages land 70 of aperture 40. When the surface of the web 10 ceases to contact land 70, the effective seal between the chamber 58 and the-ambinet hgher pressure atmosphere surrounding the terminal member 38 and guide member 46 is either reduced or terminated. When this occurs, the higher pressure atmosphere enters the aperture 40 and chamber 58 thereby decreasing the vacuum and eventually engulfing the electron gun 12 in a poison atmosphere. Certain of the electron gun elements, such as the cathode 24, may need replacement because of exposure to the higher pressure atmosphere as discussed hereinbefore.

The flap valve 56 can be operatively connected to an acuating means which is responsive to an abrupt change in vacuum in the proximity of the aperture 40. A vacuum sensing transducer may be positioned within the aperture 40, the chamber 58 or groove 68. The vacuum sensing transducer may comprise, for example, a known vacuum gauge which employs a thermocouple Whose voltage varies in proportion to the number of air molecules in the vacuum. In the event the vacuum pressure within the aperture 40, chamber 58 or groove 68 reaches a predetermined low level, the vacuum sensing transducer activates an actuating means which rapidly closes the flap valve 56 into sealing engagement with lips 62. A loss of vacuum in chamber 58 is almost immedately followed by a reduced vacuum or vacuum loss in both the chambers 14 and 58 and within groove 68. Thus, detection of vacuum loss in any of the above areas provides sufficient reliability for purposes of actuating an actuating means to move the flap valve 56 into sealing engagement across aperture 40.

In this manner, the vacuum in the chamber 58 is isolated and maintained while only the vacuum in the aperture 40 is destroyed by the higher pressure atmosphere. When the web 10 is rethreaded into the apparatus and into sealing engagement with land 70 around aperture 40, the flap valve 56 is moved into its open or unsealing position. The small volume of gas molecules contained within the aperture 40 is easily removed by the vacuum pump pumping the chambers 14 and 58.

Alternatively, the flap valve 56 can be used during unloading and loading of the Web 10. Closure of the flap valve 56 during reloading isolates the Partial vacuum in the chamber as described. The cycle time of unloading and reloading of web 10 and pumping the chamber 58 is a function of pump down time required for obtainng the necessary vacuum in chambers 14 and 58 and aperture 40. The reloading cycle is substantially reduced by the teachings of the present invention since only a small volume of atmosphere need be removed after the reloading operation.

It is contemplated that the sealing means of the present invention could beused equally well in the apparatus described hereinbefore wherein the evacuatable chamber encloses both the generating means and the web. During operation, the entire chamber is pumped to approximately the same vacuum level. In this type of apparatus, the vacuum sealing means, such as a flap valve, is moved into a sealing position relative to the aperture between portions of the chamber. In this manner, the vacuum level in at least the generating means enclosing portion of the evacuatable chamber can be isolated and -maintained independent of the vacuum level in the web enclosing portion of the chamber. With the flap valve in sealing position, the vacuum in the web enclosing portion of the vacuum chamber can be safely reduced and the web reloaded. After reloading, the web and the web enclosing portion of the chamber are repumped back to the desired vacuum level and the flap valve is moved to its unsealing position whereby the electron beam can bombard the web through the unsealed aperture.

FIGURE 3 is a diagrammatic represenation of an elevated view of the flap valve 56. The flap valve 56 comprises a planar valve member 78 which has a resilient sealing insert 80 attached thereto. The resilient sealing insert 80 is formed in the shape of the lip 62 to be covered thereby. The valve member 78 has a hollowed-out edge wall 82 through which a pin member 84 projects and about which the valve member 78 of flap valve 56 pivots. The edge wall 82 extends to the outside surface of the terminal member 38 and has a lever arm 86 keyed thereto. The lever arm 86 can either be flipped manually and held in place by a spring means (not shown) or alternatively operatively connected to an actuating means such as an electric solenoid (not shown). When the flap valve 56 is in sealing position, the resilient sealing insert 80 (as illustrated in FIGURE 2) is in sealing engagement with the lip 62. i

In one application, a rotary valve was used in place of the flap valve 56 in FIGURE 2. Due to space requirements and other operating problems, the rotary valve, although operative, did not provide the flexibility and operating characteristics as desired, and the flap valve 56 is preferred for these reasons. One such disadvantage is the increased spacing between the outer surface of the terminal member and the chamber 58.

In the embodiment of FIGURE 2, a holding pressure is necessary to hold the flap valve 56 in a closed position. By experimentation, it appears that a holding force in the order of 1% times that of the ambient atmosphere assures a good seal between the flap valve 56 and the lips 62.

FIGURE 4 illustrates another embodiment of the vacuum chamber valve in its sealing position adapted for use in a 35 mm. electron beam recording and/or reproducing system. FIIURE 4 is a fragmentary elevational view, having a front plate removed and partly in crosssection to illustrate the interior members, and discloses the relationship between the vacuum seal, designated generally as 88, and a flap valve, designated generally as 90, disposed in the end of a chamber 122 housing generating means for a corpuscular beam. In this embodiment, a continually moving band 92 moves a media 94, which is in intimate removable contact therewith, such as a 35 mm. film, through an arcuate high impedance path forming the vacuum seal 88 between a higher atmospheric pressure to an inner chamber or evacuated area and a treatment aperture or opening 96. When the media 94 is disposed in register with the aperture 96, the flap valve 90 is normally in the open position. When the flap valve 90 is in the open position, an electron beam is used to bombard the meilia 94 which is disposed in a planar position across the aperture 96 and at this time has been lifted from the transport band 92. In this apparatus, the width of spacing between the media 94 and a chamber wall 98 is in the order of A. the media thickness. Thus, when the media is within the vacuum seal, only .a small space in the order of /2 the width of the media need be continuously pumped to maintain the vacuum. In this vacuum seal, the surface of themedia to be treated or bombarded does not engage or touch any surface of the chamber wall 98 but is maintained in operative relationship with opening 96.

The remaining portion of a transport means, generally designated as 100, illustrates associated elements of a recording and/or reproducing apparatus.

The flap valve 90 in FIGURES 4 and 5 comprises an impervious rigid support member 102, such as steel, having an external dimension and cross-section which adequately covers aperture 96. The member 102 has a resilient sealing insert 104 capable of providing a good seal between the member 102 .and the chamber wall 98. A connecting link 108 is operatively connected to a fastener 110, which fastener 110 has an enlarged end 112 which is movably secured by means of plate 116 in a centrally recessed or hollowed-out area 114 in member 102. The end 112 and hollowed-out area 114 provide a ball and socket therebetween. The use of a ball and socket or universal connection is preferred but it is contemplated that a rigid connection could be employed as in FIGURE 2. This connection permits flap valve 90 to be self-aligning such that when member 102 covers aperture 96, sealing insert 104 comes into positive engagement with chamber wall 98 around the periphery of aperture 96. Fastening means, in the form of a nut 118, secures the fastener 110 to link 108.

Connecting link 108 is rigidly connected to a rotatable shaft 120. Shaft 120 extends from within an electron beam chamber 122 through a hermetically sealed hearing 124 to a crank arm 126. Crank arm 126 is operatively connected to an actuation device such as a pneumatic cylinder 130. The cylinder 130 is operated by air pressure applied thereto through various air lines, generally represented by line 134. An electrically operated solenoid valve 136 is utilized to direct the air pressure from a source of air pressure 138 to cylinder 130 via the air lines 134 in response to a Signal from a sensing device, such as a pressure sensing transducer 140, located within the chamber 122, for example.

The transducer 140 is electrically connected to and is capable of actuating a control circuit 142 when a vacuum loss in chamber 122 exceeds a predetermined level. The reference to the type of and placement of the vacuum or pressure sensing transducer described relative to FIGURE 2 is equally applicable in this embodiment and therefore does not need to be repeated here.

Control circuit 142, when actuated by pressure sensing transducer 140, energizes the electrical solenoid valve 136 which applies an air pressure from air pressure source 138 via air lines 134 to actuate pneumatic cylinder 130 which abruptly moves the flap valve 90 from its open or unsealing position to its closed or sealing position. When closed, the flap valve 90 has a holding force of at least 1% times atmosphere applied thereto from the cylinder 130 via crank arm 126, shaft 120, connecting link 108 and fastener 110. The holding force exerted on valve 90 is suificient to urge the support member 102 and sealing edge against wall 98 to form an elfective hermetic seal between aperture 96 containing a higher pressure atmosphere and the evacuated electron beam chamber 122.

In the event of web breakage, immediate closure of flap valve 90 isolates the partial vacuum in electron beam chamber 122 from the higher external pressure in aperture 96. When the broken media is replaced and the vacuum seal 88 is rendered operative, flap valve 90 is moved back to its open or unsealing position.

The atmosphere within the aperture 96 immediately dissipates into the much larger electron beam chamber 122 and is removed by means of the vacuum pumps (not shown). In FIGURE 4, the volume of aperture 96 is generally substantially smaller than the total volume of the electron gun chamber 122 such that the air molecules from aperture 96 which immediately dissipate within the vacuum do not significantly change the vacuum level in the chamber 122.

It is envisioned that the vacuum chamber valve of the present invention could be utilized in other embodiments. For example, the vacuum chamber valve could be positioned adjacent the opening but external to the chamber. In FIGURE 5, this would be paramount to placing the flap valve 90 in aperture 96 as depicted by the dotted lines which illustrate a flap valve 90'. In such an embodiment, the higher pressure atmosphere exerts a holding force on the member 102 due to the pressure dilferential developed thereacross between aperture 96 and electron beam chamber 122. In such an arrangement, the aperture 96, of necessity, would be increased both in cross-sectional area and in axial length to provide clearance for movement of flap valve between its sealing position and unsealing position. Use of the vacuum chamber valve in such an apparatus requires increasing the volume of aperture 96 which may or may not be desirable depending on the application and apparatus.

FIGURE 6 is a fragmentary detailed sectional view of a slideably operating vacuum chamber valve 150. Valve includes a rigid member 152 which is secured to a ball and socket joint 154 by means of a fastener 156 in a manner similar to that in the valve of FIGURES 4 and 5. The rigid member 152 has a resilient sealing insert 158 operatively connected thereto. An aperture 160, which is to be sealed by the valve 150, has rounded edges 162 around the outer border thereof. The rounded edges 162 permit the resilient sealing insert 158 to yieldably slideably engage the rounded edges 162 without damage to the resilient sealing insert 158, as the valve 150 is slideably moved into sealing position. In the embodiment of FIG- URE 6, the valve 150 is slideably moved in an arcuate path between its unsealing and sealing positions by connecting link 164 being moved in an arcuate path due to angular rotation of shaft 166 by a selectively actuatable device, such as pneumatic cylinder 168.

FIGURE 7 depicts an alternate arrangement wherein a bell crank 170 is rigidly connected to and moves a valve 172 between its sealing and unsealing positions. In FIG- URE 7 reciprocal motion is applied to bell crank 170 by means of an actuating device, such as a pneumatic cylinder 174.

FIGURE 8 is a pictorial representation of yet another valve which is similar to that of FIGURE 7. In FIGURE 8 a valve 178 is slideably moved in a straight path between its sealing and unsealing positions by means of a rigid support member 180 operatively connected to a pneumatic cylinder 182 which selectively supplies the reciprocal motion.

The apparatus of FIGURE 6 can be easily modified to provide the necessary volume and pivot points such that the various valves of FIGURES 6 through -8 can be slideably moved in a predetermined path between their sealing and unsealing positions.

The vacuum chamber valve described in FIGURES 6 through 8 are located external to the electron gun chamber. The presence of an external higher pressure atmos phere, after the valves are in sealing position, urges the valves into effective sealing engagement across the aperture being sealed by the valves due to the pressure differential thereacross.

It is contemplated that the valves could similarly be located within the electron gun chamber. For example, the valve 160 of FIGURE 6 could be located on the opposite side of aperture 160. In such an application, the resilient sealing insert 158 is selected to be a material which can withstand both the slideable contact with the rounded edges of the aperture 160 and application of a sealing pressure necessary to overcome the pressure differential from the higher pressure surrounding aperture 160 thereby providing an effective seal between aperture 160 and the external higher pressure.

What is claimed is:

1. Apparatus comprising in combination means defining a chamber capable of being evacuated, said chamber including a wall portion having an aperture therein;

means enclosed within said chamber for generating an energy beam adapted to be directed through said aperture;

means positioned relative to said generating means and said chamber for directing said energy beam through said aperture;

means operatively coupled to said chamber for producing at least a partial vacuum therein;

sealing means disposed adjacent said aperture and adapted for movement into sealing position with said aperture for selectively isolating and maintaining the vacuum in at least the portion of the evacuated chamber enclosing said generating means, said sealing means being adapted for movement into an unsealing position away from said aperture when said vacuum in at least said portion of the chamber enclosing said generating means can be retained while said energy beam is directed through said aperture;

actuating means operatively coupled to said sealing means for selectively moving said sealing means between said sealing position and unsealing position; and

pressure sensing means disposed in proximity of said aperture for detecting an abrupt loss in vacuum in the vicinity of said aperture and when said vacuum loss exceeds a predetermined level for energizing said actuating means to move said sealing means from an unsealing position into a sealing position.

2. The appartus of claim 1 wherein said generating means is located at one end of said chamber and said wall portion containing said aperture is located at an opposite end of said chamber and in a generally aligned relationship with said generating means and wherein said sealing means comprises a flap valve having a resilient sealing insert which hermetically seals about said aperture when said flap valve is in said sealing position.

3. The apparatus of claim 1 wherein said sealing means is located within said evacuated chamber and wherein said actuating means urges and holds said sealing means in sealing engagement across said aperture with suflicient force to overcome the pressure differential existing between said evacuated chamber and a higher pressure ambient atmosphere located in the vicinity of said aperture.

4. The apparatus of claim 1 wherein said sealing means is located in an external higher pressure atmosphere located in the vicinity of said aperture, said sealing means being urged into said sealing position by said actuating means and being held in sealing engagement across said aperture by said higher pressure atmosphere due to the pressure differential across said sealing means between said atmosphere and evacuated chamber.

5. The apparatus of claim 1 wherein said sealing means comprises an impervious rigid support member having a cross-see tional area which is slightly greater than the crosssectional area of said aperture; and

a resilient sealing insert connected to said support member, said sealing insert having a shape which conforms to the border of said aperture such that when said support member is in said sealing position said sealing insert is in sealing engagement with said aperture border forming a vacuum tight seal.

6. The apparatus of claim 5 wherein said chamber aperture has a rectangular border and wherein said support member is rectangular in cross-section having dimensions which are slightly greater than those of said aperture and said resilient sealing insert is rectangular in shape having dimensions which are substantially the same as said aperture border whereby when said support me her is in sealing position said resilient sealing insert is in sealing engagement with said aperture border forming a vacuum tight seal.

7. The apparatus of claim 5 wherein said support member is adapted to be self-aligning to urge said resilient sealing insert into positive sealing engagement across said aperture.

8. The apparatus of claim 5 further including actuating means operatively coupled to said support member adapted to be selectively energized to move said support member containing said resilient sealing insert between its sealing position and its unsealing position.

9. The apparatus of claim 8 further including a pressure sensing transducer for detecting vacuum loss in proximity of said aperture and for actuating said actuating means when said vacuum loss exceeds a predetermined level.

10. The apparatus of claim 9 wherein said pressure sensing transducer is positioned within said evacuated chamber adjacent said aperture.

.11. The apparatus of claim 9 wherein said pressure sensing transducer is positioned within said aperture.

12. The apparatus of claim 9 wherein said pressure sensing transducer is positioned Within said vacuum seal.

13. The apparatus of claim 5 further including a connecting member operatively coupled to said support memher, said connecting member being adapted to slideably move said support member and said sealing insert across said aperture when traversing said support member and said sealing insert between said sealing and unsealing positions.

14. Apparatus for bombarding one surface of a web with a beam of energy in the presence of at least a partial vacuum comprising means defining a chamber capable of being evacuated,

said chamber including a wall portion having an aperture therein extending into said chamber through which said energy beam is to be directed to bombard said one surface of a web;

means located within said chamber for generating an energy beam;

means positioned relative to the energy beam for directing said energy beam through said aperture to bombard said one surface of the web;

means for producing at least a partial vacuum in said chamber;

transporting and gas restricting means for restricting movement of gas molecules from an ambient higher pressure atmosphere to said aperture as said one surface of said web is transported past said aperture;

a vacuum chamber valve positioned adjacent said wall portion, said vacuum chamber valve being capable of movement into sealing engagement across said aperture when said partial vacuum producing means becomes incapable of forming a partial vacuum to prevent said vacuum in said chamber and said generating means from being poisoned by gas molecules from said ambient higher pressure atmosphere, said vacuum chamber valve being ,capable of movement to an unsealing position when said partial vacuum producing means is capable of forming a partial vacuum and said web is positioned relative to said aperture for bombardment by said energy beam;

actuating means operatively coupled to said sealing means for selectively moving said sealing means between said sealing position and said unsealing position; and

pressure sensing means disposed in proximity of said aperture for detecting an abrupt loss in vacuum in the vicinity of said aperture and when said vacuum loss exceeds a predetermined level for energizing-said actuating means to move said sealing means from an unsealing position into a sealing position.

15. The apparatus of claim 14 adapted for a recording/reproducing system wherein said web is a photographic film and said beam of energy is an electron beam and wherein said vacuum chamber valve comprises an impervious rigid support member having a crosssectional area which is slightly greater than the crosssectional area of said aperture; and

a resilient sealing insert connected to said support member, said sealing insert having a shape which conforms to the border of said aperture such that when said support member is in said sealing position said sealing insert is in sealing engagement with said aperture border forming a vacuum tight seal.

(References on following page) 1 1 References Cited UNITED STATES PATENTS 3 /1942 Ackermann 313-175 12/1965 Jones 346-1 10/1967 Dubbe 346-110 5/1940 Marton 346-107 12 2,292,087 8/1944 Rafno 250-495 RICHARD B. WILKINSON, Primary Examiner.'

JOSEPH W. HARTARY, Assistant Examiner.

US. Cl. X.R. 313-175

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