JPS5841954B2 - Sealing device for the movable vacuum chamber of charged particle beam machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to machining a workpiece with a beam of charged particles.

In particular, the present invention describes the use of charged particles, such as an electron beam, generated by a machine having a vacuum chamber (also referred to as a "beam column") that is emptied and moved against the material or workpiece being processed during operation. relating to performing operations on beams such as welding, cutting, melting, vaporizing, heating, machining or other processing steps.

The present invention relates to the problem of sealing a movable vacuum chamber relative to a workpiece.

Sealing the beam exit opening of the vacuum chamber of an electron beam welding machine to the workpiece by a compressible rubber sealing ring that is pressed against and slides over the workpiece is disclosed in U.S. Pat. No. 3,136,882. It is known by the number.

The gap between the two workpiece parts to be joined by welding and the weld seam produced by the machine are covered with an adhesive tape.

A groove-shaped metal member is attached to the back side of the workpiece with adhesive tape to seal the gap on the beam exit side of the workpiece.

Another known means of sealing a movable vacuum chamber to a workpiece is to use a pressure graduated seal.

That is, the vacuum relative to the atmosphere gradually increases (with several concentric zones up to the inner vacuum chamber where the beam gun is located).

The formation of a flexible seal for the vacuum chamber of an electron beam (E, B,) welder by means of a suspension of magnetizable particles in a carrier fluid, such as silicone oil, was also disclosed in British Patent No.
No. 292,338, German Patent No. 1,805,719 and French Patent No. 6,936,856.

The suspension is made quasi-elastic by a periodically varied unidirectional magnetic field.

A common problem with all known sealing devices of this type is the seal in which the area of the workpiece to be processed by the beam enters the vacuum chamber and/or the seal in which the area of the workpiece processed by the beam exits the vacuum chamber. It is important to ensure proper sealing within this range.

Below, ゛°Processing zone
)” is used both for the area of the workpiece to be machined by the beam and for the area of the workpiece that has been machined by the beam.

This is because sealing problems can arise both in the area to be processed and in the area that has already been processed.

The area to be machined often includes gaps or other structural features that allow air to enter the vacuum chamber, and the machined area, such as a weld bead, is typically rough, hot and over adjacent portions of the workpiece surface. protrudes to.

It is an object of the present invention to create a vacuum chamber capable of sealing rough, hot, uneven surfaces or other surfaces that are difficult to seal with known sealing devices without the use of adhesive tapes, sealants or other pretreatment means. The objective is to provide a suitable sealing device for this purpose.

To achieve this objective, the sealing area of the outlet section has a large radial width disposed radially across the circumferential sealing area of each stage to achieve sealing of the bead reinforcement. a housing comprising a sealed area having a large radial width, in which a backing of a highly heat resistant wire-like element having a free end is provided, and the free end of the wire-like element is connected to a workpiece; spring means for urging against the bead reinforcement of the wire-like element, said housing further having pads therein of a high temperature resistant deformable material extending parallel to and adjacent to each side of the wire-like element. and spring means for pressing the pad against the workpiece surface near the bead reinforcement.

Another approach is to provide one or several successive rollers rotatably attached to the casing.

The axial end of each roller rests tightly against the side wall of the casing, and its lower part rests in a sealed manner on the surface of the workpiece, e.g. Slide tightly and tightly over the

Instead of the rollers described above, chain or track devices (ie tracks used on large tractors) may be used.

Another approach is to use a bead of special or fine-grained or powdered material instead of the brass wire packing, filling the bead at the inner end and removing it at the outer end if desired, and refilling it if desired. circulate.

The beads consist of steel granules or sand. Thermoplastic materials may be used to smooth the surface and facilitate sealing.

Another approach is by applying a material that forms a continuous, elastic or flexible body or that can be shaped into such a body when applied to the processing area before passing through the confinement area. , the material conforms to the rough surface or surface topography to form an intermediate layer having a relatively smooth surface that is easily sealed by conventional sealing devices such as lip seals.

This material actually also forms an enlarged sealing area.

This material is pressed firmly onto the rough or uneven surface to be sealed and conforms to the topography of the surface due to its flexibility, flexibility or elasticity.

This material fits snugly and tightly into the sliding or rolling seal of the movable vacuum chamber.

The intermediate material can be removed from the workpiece surface in the extent that the workpiece has been released by the sealing device, ie the sealing area has slid or rolled over the material.

In certain embodiments, the material is then collected and recirculated through a vacuum lock to the side of the moving seal where the material is used.

The vacuum lock can be a simple hole in the wall of the vacuum chamber, which is sealed by a material that is pressed.

The material may be, for example, a very soft rubber band, strip or cord with a textile band in the center or inside for reinforcement.

Alternatively, the material can be applied to the surface to be sealed in a powder, liquid or soft puddle state, and then changed to a continuous, solid-elastic state by a change in temperature to facilitate removal of the material from the workpiece after the sealing area. )be able to.

The material may include a high proportion of high atomic number materials such as lead to provide the necessary X-ray sealing.

This is a desirable but not necessary feature, and other means can be used if the X-ray sealing is provided by other means, such as for example asbestos, fiber strips or cords.

The problem of preventing x-rays from escaping from the interior of the vacuum chamber to the outside through the enclosed area must be taken care of in any enclosure used in charged particle beam machines.

Another important embodiment of the invention is a combination of a pressure stepped seal and a lip seal, such as a flexible lip seal at the edge of one or each pressure step of the pressure stepped seal. This device is designed to improve sealing and reduce leakage.

Further objects, features and advantages of the invention will become apparent from the following description of specific embodiments.

FIG. 1 schematically shows an electron beam (E, B,) welding machine 10 having a vacuum chamber 12 movable relative to a workpiece 14.

Vacuum chamber 12 has a beam exit aperture 16 (FIG. 2) that is sealed to a surface 18 of the workpiece for relative movement between the electron beam welders on the workpiece.

The illustrated workpieces form a gap 24 ("work area") 2
It consists of two plates 20, 22, and the plates 20, 22 are joined in the gap 24 by an electron beam 25 generated by a beam gun (not shown) disposed in a column section 26 of a vacuum chamber.

A beam that can be oscillated transversely with respect to the gap 24 melts the workpiece material to form a weld seam 28, which generally has an upper weld bead 30 and a lower weld bead 32. The weld bead is on plates 20 and 22.
0 has a rough and irregular surface that protrudes somewhat from the approximately flat surface.

In addition to the molten material formed at the welding location by the beam 25 (
Pool ) can be supplied with filler material or additives in the form of wires or rods 32 .

It is well known that a fairly high vacuum must be maintained in the interior 34 of the vacuum chamber in which the electron beam gun is housed during the propagation of the beam 25.

As is clear from Figure 2, 1. The interior 34 of the vacuum chamber, including the beam exit aperture 16, is surrounded by multiple circumferentially sealed areas in order to maintain such a vacuum;
These circumferentially sealed areas are made of flexible vacuum sealing elements well known in the art, such as rubber.

A sealing device having such a sealing area can be further divided into several sections.

These divisions are indicated by Roman numerals in Figures 1 and 2.

Namely, (i) the lateral section of the sealing device which seals the beam exit aperture 16 against the face of the opposing workpiece; (o) the section through which the workpiece area to be processed by the beam enters the vacuum chamber ( (2) A section through which the area machined by the beam passes when exiting the vacuum chamber (2) A sealing device that seals the beam exit side of the workpiece and (2) a lock section provided as needed to supply a roll-shaped or wire-shaped additive material 32 to the welding location.

□ Although the problem underlying the invention has been described with respect to electron beam welding, it may also be useful when attempting to form other processing operations with an electron beam or ion beam machine having a movable vacuum chamber that moves relative to the workpiece. A similar problem exists.

Such operations are, for example, cutting, melting, vaporizing, heating, machining, engraving (eg printing cylinders).

Although the invention is equally applicable to such other tasks,
The present invention will be described in the context of electron beam welding since electron beam welding is one of the most common electron beam processing operations.

Lateral sealing categories ■ and ■ are the least problematic.

This is because the surface of the workpiece is approximately smooth in this range.

Resilient sealing elements or pressure graduated seals as shown in US Pat. No. 3,136,882 generally provide sealing, but improved sealing arrangements for this section are described below.

Proper sealing in category ■ is generally more difficult to achieve.

This is because the processing area entering the vacuum chamber through this section is located in the gap 2 formed by the opposing leading edges of plates 20 and 22.
4, which makes sealing even more difficult.

In category ■, it is even more difficult to achieve a proper seal due to the irregular surface topography of the weld bead.

Since the essential part of the beam 250 emerges from the beam exit side of the workpiece, the rear sealing section 1 must be made so that it is not damaged by the beam.

The lock for the additive 32 of the sealing section (1) can be provided by an elastic sealing element or a pressure stepped seal, but
A combination of both is desirable.

One of several measures that can be taken individually or in combination according to the invention is to increase the width of the closure device in the processing area exit area and/or in the processing area entry area.

Thus, for example, by widening the edges of a vacuum chamber with a wall separating two pressure stages in the direction of movement relative to the processing area of the workpiece, a restricted flow path length for the air is created.

FIGS. 3A and 3B show a vacuum chamber with two pressure stages and a processing zone exit range 1 considered according to the concepts described above.

The pressure graduated sealing device includes an inner wall 40 separating an inner vacuum chamber 34 from an angular intermediate vacuum chamber 42, which has an outer wall 4 separating the intermediate vacuum chamber from the surrounding atmosphere.
It has 4.

On the processing area exit side, where the upper weld bead 30 leaves the vacuum chamber, the wall 40 is enlarged and has a □ wide section 40a.

The wall 44 has a similar section 44a, the width of which is increased in the direction of movement relative to the weld bead 30.

The forward ends of the enlarged wall portions 40a, 44a shown in FIG. 3A can form channel-shaped slots 40b, 44b (FIG. 30) to accommodate the forward end of the projecting upper weld bead 30.

The inner chamber 34 and intermediate chamber 42 are each connected to a suitable vacuum pumping system 46, 48, as is known in the art.

In order to provide a suitable seal at the processing area entrance section, the gap 24 can be sealed by two tapes 50 made of metal foil and adhesively adhered to the workpiece.

A closure device 52 similar to the closure device described above may be provided on the beam exit side of the workpiece.

A preferred variant of the closure device for the rear part of the processing area that is welded by the beam will be described below with reference to FIG.

4 and 5 show a preferred embodiment of the processing zone exit section of the closure device according to the invention.

As shown, the wall 60 of the vacuum chamber is provided with a box-shaped extension 62 that forms an exit section for the weld bead 30.

Wall 60 with box-shaped extension 62 may replace flared walls 40a and/or 44a of the embodiment of FIG. 3, or may be a separate wall separating vacuum chamber 34 from the surrounding atmosphere. .

The box-shaped extension 62 divides the space inside the box 62 into a central compartment.
It is provided with two intermediate walls 64, 66 which divide it into two lateral compartments.

A central compartment contains a brush-like bundle of metal wires 68 which are urged at one end by a spring 70 against the weld bead.

The side compartments are each padded with a deformable or flexible material, for example mineral fibers such as asbestos or glass fiber fabric or felt or fleece padding 7
Contains 2.

Side wall 62A and intermediate wall 64,66 of box-shaped extension 62
0, the lower end is tapered in the direction away from the pad 72 as shown in FIG.
may be expanded somewhat.

A lip sealing device 7 is attached to the wall 60 on both sides of the box-shaped extension 620.
It is desirable to provide 4.

This lip seal significantly reduces leakage through the narrow gap 76 present in all conventional pressure stepped seals.

Lip sealing device 74 includes an elongated strip-like sheet member 76 of resilient material, preferably synthetic rubber, and a film 78 of low friction material, such as polytetrafluoroethylene or similar polymeric material.

Lip seals 76-78 or spring loaded metal backing plates 80
is pressed against the surface of the work piece.

Rubber (-/-) 76 has an increased wall thickness adjacent extension 62, which is box-shaped as shown.

FIG. 6 shows a preferred embodiment of the sealing device which is a combination of a pressure stepped sealing device and a lip sealing device.

This sealing device is preferably used to seal the vacuum chamber of side section (2) (FIG. 2) and the parts of sealing sections (1) and (2) adjacent to the processing area sealing section.

The pressure stepped sealing device shown in FIG.
and three walls 82, 84, 86 (similar to the closure shown in FIG. 2) forming two intermediate vacuum chambers 42a and 42b.

The lower edges of the walls 82, 84, 860 form small gaps 76a, 76b, 76c, respectively, just in front of the surface of the workpiece.

To reduce leakage through each of these gaps, an additional lip seal is provided to seal each of these gaps, the lip seal being similar to seal 74 described above.

Thus, each lip seal comprises a flexible sheet 76, preferably made of synthetic soft rubber, approximately 5 mm thick, and a film 7 of a low friction material, such as polytetrafluoroethylene.
8.

A strip-like structure formed by sheet 76 and film 78 is attached to each wall in a gas-tight manner, such as by clamping, and the other end is pressed against the workpiece by a series of springs 88.

The spring 88 is attached between the other leg of an L-shaped backing plate 90, one leg of which is attached to each wall, and the backing plate 80 resting on a rubber sheet.

The lip seal includes two spaced apart springs 88a, 88b as shown in combination with a wall 86 in contact with the outside air.
Further enlargement can be achieved by providing rows of , but other walls may also be provided with such enlarged lip seals.

The lip seal device described with reference to FIG. 6 can also be used in a seal device having only a single wall separating the high vacuum chamber from outside air.

FIG. 7 shows a simpler combination of a pressure stepped seal and a lip seal.

The sealing device shown in FIG. 7 consists of a rubber sheet 76 and an anti-friction film 7.
The sealing device is substantially identical to the sealing device described with reference to FIG. 6, except that the spring member pressing the sealing lip of 8 against the workpiece surface is omitted.

In this case, the film 78 ends at some distance in front of the free end of the rubber sheet or the film 78 is
It is desirable to attach it firmly to 6.

FIG. 8 shows a preferred embodiment of the sealing section (2) which seals off the rear or beam exit side of the workpiece.

The sealing section shown in FIG. 8 has a channel 92 forming a chamber 94 behind the working area of the workpiece.

A resilient seal 93 seals the chamber 94 against outside air.

Chamber 94 includes two side portions 96 communicating with exhaust pipe 98 and an increased depth central portion 100 containing particulate material 102 such as metal powder or granules; The purpose is to disperse the emerging portion of the electron beam 25 and/or to prevent molten material from flowing out from the welding side.

Material 102 may be, for example, relatively coarse metal powder or granules, or sand.

The body 92 is pressed against the rear side of the workpiece by a plunger 106, and spacing pieces 104 are provided along the length of the body 92 at spaced locations to prevent the body from bending.

The sealing device shown in FIGS. 9-11 is used to seal a material that forms a continuous, elastic or flexible body or that can be formed into the shape of such a body when applied to the workpiece onto the surface of the workpiece. A seal can be adapted to the topography to form a relatively smooth surface that can be easily sealed by pressure graduated seals and/or tongue seals.

9 and 10 illustrate one embodiment of a sealing device useful on the processing area entrance side of the sealing device of an electron beam welding machine.

This sealing device is suitable for sealing relatively wide and irregular gaps 24 between opposite front surfaces of two workpiece parts to be joined by electron beam welding.

Sealing devices 134 in FIG. 9 are on both sides of the workpiece.

It includes a two-stage closure device of the type described with reference to FIGS. 6 or 7.

To seal the gap 24, a sealing material such as a preheated thermoplastic polymer material is applied to the gap 24 in a liquid or plastic state.
(injected or jetted) and its upper and lower sides are smoothed by smooth plates or shoes 138 (or rollers).

The material is selected such that upon cooling and/or polymerization, it achieves a highly viscoelastic or solid-elastic state within the gap, and that state forms a continuous body or band after the material passes through the sealed region 134. It is in a state where it can be taken out from the gap in the form of 140.

The material may be removed from the gap by a suitably driven take-up reel as described below with reference to FIG.
Alternatively, it may be taken out by a pair of rollers 139.

In the latter case, the material can be recirculated to the atmosphere through the locking device 142 where it can be used again by the nozzle 136 by applying heat in the supply vessel 144 to liquefy it again.

To increase the tear strength and continuity of the material used so that the strip 140 does not tear while moving through the gap 24, the material may include elongated flexible fibers, such as polyester or glass fibers, or similar reinforcing materials.

Preferably, the workpiece defines a wedge-shaped gap 24 as shown in FIG.

FIG. 11 shows an embodiment of a processing area exit section of a closure device of an electron beam welding machine with a vacuum chamber having walls 114.

Cords or strips 112 of mineral or glass fibers, such as asbestos, are used to smooth the rough surfaces, including the weld bead 30 of the weld seam.

The workpiece with weld bead 30 moves relative to wall 114 in the direction of arrow 120.

The strip 112 is fed from a supply reel 122 rotatably supported by means not shown and is attached to the wall 114.
It passes under a closure device 110 that includes a box-shaped extension 115 of.

The bottom side of the box-shaped extension 115 is formed by a flexible sheet 128 of a low-friction material such as polytetrafluoroethylene, and the flexible sheet or spring 13'0 holds the strip 1
12 and pressed against the workpiece surface.

The flexible film or sheet 128 provides a low leak rate seal as the strips 112 smooth out rough surface topography.

After the strip 112 passes through the sealing device, the take-up reel 12
4.

Alternatively, the strip 112 may be impregnated with a low vapor pressure liquid such as a heat-resistant silicone compound or a substance containing fat to improve sealing performance.

The strip 112 can also be recycled as shown in FIG.

FIG. 12 shows another variation of a closure device suitable for use in the processing zone exit section.

The overall device is similar to that shown in FIGS. 4 and 5, except that the wire bundle 68 in the central compartment of the box-shaped extension is provided with a surface layer 152 of a flexible or elastic material such as metal felt.
The difference is that it is replaced by one or several rollers 150 having .

The roller rests in a sealed manner on the surface of a workpiece 154 containing a weld bead 30, which is contained by an elastic layer 152.

The axial end of each roller tightly abuts the side wall of the box 62', and the periphery of the roller opposite the workpiece tightly abuts the inside surface of the earthen wall of the box or other sealing element, such as the tongue seal 156. Sliding in a sealed state.

If several successive rollers 150, 150', 150 drops are used, an exhaust tube, indicated schematically by arrow 158, can be connected to the space between two successive rollers to create a certain pressure stage. A formula seal can be provided.

The embodiment of FIG. 13 differs from the embodiment shown in FIG. 12 primarily in that rollers 150 are replaced by meeting rollers 150a, 150b supporting an endless loop 152' of resilient material. .

Loop 152' may be constructed of metal fiber felt or asbestos or mineral fiber fabric, preferably impregnated with a low vapor pressure liquid or grease, such as a silicone compound.

A pair of rollers 150a, 150b having an orbital endless loop or band 152' is similar to roller 150. of FIG.
162.

However, the device of FIG. 13 provides a leakage path of increased length compared to roller 150.

Of course, several pairs of rollers may be used in succession.

Although a preferred embodiment of the invention has been shown, it is to be understood that the invention has been described by way of illustration rather than limitation.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a part of an electron beam welding machine and a welded workpiece, FIG. 2 is a schematic plan view of a sealing device 6 of the machine of FIG. 1, and FIG. 3A is an embodiment of the present invention. Bottom view of the pressure-graded sealing device according to the example, FIG. 3B is line 1r-H in FIG. 3A.
Figure 3C is a field analysis plan cut along line C- in Figure 3A.
4 is a partial perspective view of a part of a sealing device according to an embodiment of the present invention, and the 1st figure is a cross-sectional view taken along the plane ■-■ of FIG. 4. , FIG. 6 is a cross-sectional view of a portion of a preferred embodiment of a pressure graduated sealing device, FIG. 7 is a cross-sectional view of another embodiment of a pressure graduated sealing device having an additional resilient lip sealing element, and FIG. FIG. 9 is a sectional view of a sealing device for the beam exit side of workpieces welded by an electron beam; FIG. , FIG. 10 is a sectional view taken along plane XX in FIG. 9, and FIG. 11 is a simplified sectional view of the machining side exit section of a sealing device of the type shown in FIGS. 9 and 10. , FIG. 12 is a sectional view of a modification of the sealing device shown in FIGS. 4 and 5, and FIG. 13 is a partial view of another modification of the sealing device shown in FIGS. 4 and 5. 1
FIG. 4 is a front end view of the closure device of FIGS. 12 and 13. 12.34.42...Vacuum chamber, 16...
・Beam exit aperture, 20, 22... Processed piece, ■
... Entrance section of sealed area, ■... Exit section of sealed area, 25... - Electron beam, 40a
, 44a... Expanded width.

Claims (1)

[Claims] 1 A sealing device for a vacuum chamber of a machine arranged to be attached to a workpiece for processing the workpiece with a beam of charged particles generated by a beam gun mounted in the vacuum chamber, the vacuum chamber being a beam exit aperture formed by the annular end of the vacuum chamber, the beam exit aperture being arranged to mount to the workpiece in such a manner as to allow relative movement thereto; The multi-stage circumferentially sealed area is surrounded by a surface area through which the machined workpiece portion having a hot and relatively rough surface passes as it exits the vacuum chamber in a radial direction relative to the circumferentially sealed area. In a sealing device with an outlet section, at least the sealing area of the outlet section has a large radial width disposed radially across the circumferential sealing area of each stage to achieve sealing of the bead extension. A housing comprising a region and provided in said closed region of large radial width has a backing therein of a wire-like element of high temperature resistance having a free end, and a backing of a wire-like element having a free end and a bead of the workpiece. spring means for urging against the backing, said housing further having pads therein of a highly heat resistant deformable material extending parallel to and adjacent to each side of the wire-like element; and spring means for pressing against the workpiece surface near the padded bead reinforcement.