JPH0377766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for applying polymeric material to a workpiece.

In many technological endeavors, it is necessary to provide a relatively thin, uniform layer of polymeric material on the surface of a metal sheet. For example, such a need arises when an energy beam, such as an electron beam or a laser beam, is used to perforate a metal sheet. In such applications, the layer of polymeric material is called a backer, and the polymeric material is applied as a layer of uniform thickness and in close contact with the exit side of the workpiece in which the hole is to be drilled. It must be installed in such a condition. During the drilling process, the workpiece is mounted on a holder and the backer is clamped between the workpiece and the holder. U.S. Patent No. 4,239,954 with the same inventor and assigned to the same assignee as the applicant.
Several backers are disclosed in the issue.

Common titanium and iron based alloy sheets are generally very uniform in thickness. However, these sheets generally have some amount of bow. That is, the sheet does not lie in a flat plane, so if the backer is an independently extruded layer of material, the backer and metal sheet are mounted on the working surface of the drilling holder. In this case, the tight contact between the backer and the metal sheet is lost due to warping of the metal sheet. As a result, the back car will not be able to fully demonstrate its functions.

On the other hand, if the backer is applied directly to the surface of the metal sheet before it is attached to the workpiece holder, various problems arise in achieving the desired results. Although intimate contact between the workpiece and the backer is easily achieved, the warp cannot be corrected by applying a uniform layer over the warped workpiece. If a warp is present on the surface of the workpiece, the focus of the energy beam will change, making it impossible to drill a given hole. Furthermore, in the case of large and low polymeric materials, it is difficult to provide a uniform layer on the workpiece even if the workpiece is completely flat. These difficulties arise due to the flow and curing characteristics of the rubbers and waxes commonly used in backers.

One object of the present invention is to provide a method for uniformly applying a backer to a metal sheet. Another object of the present invention is to compensate for irregularities such as warping present in the metal sheet so that the sheet resting on the smooth surface of the workpiece holder is accurately positioned for electron beam drilling. and also to compensate for irregularities in the flow and curing properties of the polymer backer.

According to the invention, a metal sheet workpiece is placed on a smooth surface of a fixing device and is tightened to the smooth surface, such as by a vacuum generated in a narrow groove provided in said smooth surface. Gravitate. A flowable bucker material is then introduced onto the metal sheet, the material is leveled relative to the smooth surface, and then allowed to solidify. Some backer materials, such as RTV rubber, tend to solidify with a thickness near the center of the sheet that is less than the average thickness. For such materials, the leveling board is configured to slide across the fixture parallel to the smooth surface of the fixture. and in this case a leveling board with a concave lower edge is used so that the amount of backer material in the center of the sheet is increased compared to the case with a leveling board with a curved lower edge. be done. Thus, when the bucker material solidifies, the bucker has a uniform thickness.

Although a vacuum is preferred as a means of suctioning the sheet to the flat surface of the fixation device, other means of generating a uniform force may be used. If a vacuum is used, the surface of the fixation device is provided with a seal fitted into a recess, such as an O-ring. If the sheet is curled, the sheet is placed on the fixing device so that the ridged portion of the sheet is raised above the surface of the fixing device in a positive direction. Thus, by applying the backer material to the convex side of the sheet, the sheet will better conform to the surface of the workpiece holder when a subsequent drilling step is performed.

Preferably, a rail surrounds the locking device and is adapted to assist in clamping the metal sheet against the peripheral seal. After a vacuum is applied in the groove to draw the metal sheet flat against the surface of the fixture, liquid polymer is directed between the rails into the cavity above the sheet and hardens. If a leveling board with a curved lower edge is used, the backer will have a substantially uniform thickness after the sheet is removed from the securing device. However, depending on the backer material, capillary action occurs in the rail region, forming a meniscus in that region, thereby locally thickening the backer. This makes it impossible to accurately position the sheet during drilling. In order to eliminate the effects of such capillary action, a relief is provided around the periphery of the backer. That is, the backer is undercut at the edges where it rises. Preferably, the side edges of the rails are sloped outwardly so that a suitable undercut is formed when the bucker is molded within the fixture. When a sheet fitted with a backer is thus clamped onto a workpiece holder prior to drilling, the raised portions of the backer captured between the sheet and holder are easily compressed and compressed depending on the average thickness of the backer. This ensures that the sheet is positioned evenly. In general terms, according to the invention, by providing a relief in the backer when forming the backer or by providing a relief in the workpiece holder, the workpiece for electron beam drilling is formed around the periphery of the backer. A relief is provided between the holder and the sheet. Accurate backers are readily obtained in accordance with the present invention; for example, an RTV silicone rubber backer formed in accordance with the present invention and having a thickness of approximately 2.54 mm can secure workpieces with an accuracy of approximately ±0.1 mm or better. Space them evenly from the holder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

The present invention is therefore directed to a silicone rubber backer that is attached to a titanium sheet metal panel when the sheet metal panel is electron beam perforated by wrapping the titanium sheet metal panel around a drum-shaped workpiece holder. Although described herein, the invention is also useful with other workpieces and workpiece holders. The present invention is also suitable for applications other than electron beam drilling where a thin polymer layer must be uniformly applied to an uneven sheet. The present invention may be used to install backers of various compositions, such as the backer described in U.S. Pat. No. 4,239,954.

FIG. 1 shows how a backer is used when drilling with an electron beam. The drum-shaped workpiece holder 20 is essentially a hollow cylinder with a precise outer circumferential surface 22 against which a metal sheet 24 as a workpiece draws its ends together. It is then clamped. A bucker 26 is disposed between the metal sheet 24 and the workpiece holder 20. The drilling of the hole 27 is carried out by a flow of electrons in the form of a beam 28 emitted by an electron gun 30 and directed into the workpiece, ie the metal sheet 24, through the hole 31 between the protective shields 32. Outer peripheral surface 2 of work piece holder 20
2 is precisely positioned at a distance D from the electron gun 30 (typically, the plane of the lower surface of the protective shield 32 is used as a preparation surface for such positioning). In order to accurately position the metal sheet 24 with respect to the electron gun 30, the metal sheet 24 must be spaced a certain distance E from the outer peripheral surface 22 of the workpiece holder 20. If the metal sheet is tightly clamped around the workpiece holder, the distance E will depend on the flexibility of the metal sheet and the backer 2.
6. The present invention relates to the manufacture of such a bucker and a method for clamping a metal sheet to a workpiece holder.

Figure 2 shows a sheet 34 having a length of approximately 145 cm, a width of approximately 46 cm, and a thickness of approximately 0.6 mm, and an apparatus of the present invention for receiving the sheet 34 to be fitted with a backer. The device of the invention has a base (anchoring device) with rails 38 and 40 on its periphery.
Contains 36. Seat 34 fits within a cavity defined by rails 38 and 40 and rests on a smooth upper surface 42 of base 36. The top surface 42 of the base 36 has a pattern of interconnected grooves 44 that are relatively narrow. FIG. 3 is a partial cross-sectional view of the apparatus of the invention showing details of how the seat engages the rail and base. The seat extends over the top surface 42 of the base and is spanned by a narrow groove 44. The rail 38 captures the edge of the sheet and moves the edge into a peripheral O
It is pressed against the ring seal 46. The seat and base thus define a sealed cavity that is accessible via groove 44 and, in one or more locations, via port 48. Therefore, a vacuum pump, not shown, is connected to port 48.
When connected to the base, the sheet is pulled tightly against the base. Of course, the width of the groove is kept to a minimum to resist curving the sheet too much downwardly into the groove.

To attach the backer to the seat, the backer material 4 is inserted into the cavity above the seat defined by the rails 38, 40 and the top surface 51 of the seat.
9 is poured, a vacuum is maintained within the groove 44.
One preferred backer material is the
RTV sold by General Electric Co.
-630 is a silicone rubber that hardens at room temperature. The semi-liquid RTV rubber is leveled by moving a leveling board 50 across the top surface of the rail 38. The leveling board 50 shown in FIG.
The tabs engage the outer edges of the rails 38 to provide lateral positioning of the leveling board. Further, the leveling board 50 is provided with a protrusion 54 that extends along the moving direction of the leveling board, so that when the leveling board moves along the longitudinal direction of the base 36, the rubber is attached to the leveling board. It moves in a direction perpendicular to the direction of movement of the device and acts to prevent leakage from the sides of the device of the present invention.

One importance lies in the design of the rails 38 and leveling board 50. FIG. 4 shows a backer 5 obtained when a leveling board with a straight lower edge and a rail 58 with a rectangular cross section are used.
6 is shown. A dashed line 60 indicates the cross-sectional shape of the rubber immediately after it is leveled in a semi-liquid state. This is because RTV-630 rubber does not shrink substantially. On the other hand, a solid line 62 shows a somewhat exaggerated actual cross-sectional shape of the rubber after it has hardened. As shown in FIG. 4, the rubber becomes thinner at a central portion 64 near the center of the sheet 34, and has a raised portion 66 at the periphery near the rail.
The reason why the rubber becomes thinner in the center is not fully understood, but although RTV-630 rubber has self-levelling properties, some kind of flow phenomenon is involved. considered to be a thing. The increased thickness at the periphery is believed to be due to the capillary action of the rubber against the rail 58. The backers thus formed are not useful with respect to drilling precise holes in the sheet 34. If such a sheet is mounted under tight tension around a workpiece holder, the thinner thickness of the backer at the center portion 64 will result in uneven thickness of the backer along the length of the holder. , the thickness of the backer is raised at the thicker peripheral edge 66.

In FIG. 2, when practicing the method of the present invention, the lower edge 68 of the leveling board 50 has a curvature R.
, and is raised at a distance S at its center. The inventors have found that for the 2.5 mm thick backer made of RTV rubber described above, the distance S should be approximately 0.46 mm. The shape and distance S of the leveling board may be varied depending on the thickness and type of material of the backer. FIG. 3 shows the upper surface 60a of partially cured rubber and the upper surface 62a after the rubber is cured when a leveling board with a curved lower edge is used. In this case as well, capillary action occurs at the outer peripheral edge 68 of the backer. However, the rail 38 is shaped to eliminate the adverse effects of such capillary action. That is, as shown in FIGS. 3 and 5,
The rail 38 is provided with an inner edge 70 that forms an angle B with respect to an imaginary plane perpendicular to the top surface 42 of the base 36 . An angle B of approximately 45° has been found to be sufficient, and angles between 30 and 60° are at least equally effective. As shown in FIG.
The sloped inner edge 70 of the rail need only extend over a portion of the vertical edge of the rail;
2 may remain.

FIG. 6 is an enlarged partial view showing the main part of FIG. 1, in which the inclined inner edge 70 of the rail evenly extends the sheet 24 from the upper surface 22 of the workpiece holder 20 at a distance E, that is, the nominal thickness of the backer. This shows how useful it is for spacing. Back car 2
The backer 26 in the state before the sheet 24 of No. 6 is pulled tightly against the workpiece holder 20
The shape is indicated by a dashed line 74. solid line 7
6 shows the backer flexed against the top surface 22 of the holder 20 when the sheet is wrapped tightly around the holder. The relief provided by the sloped inner edge of the rail between the backer and the seat prevents the raised edge 68 of the backer from deforming the outer edge of the seat 24 radially outward.

FIG. 7 shows another embodiment of the invention. The backer 26a is undercut, that is, the escape 7
8, the relief being provided by a rail with a stepped edge as opposed to a sloped inner edge. Although a sloped inner edge is preferred, the invention may be practiced with the embodiments described above and with other embodiments. The general form of this aspect of the invention is that the average thickness of the backer is such that it is flexible at its edges when the backer is compressed between the sheet and the workpiece holder. The goal is to reduce the thickness of the backer edge.

Of course, it is also possible to first form the backer using a rectangular cross-section rail and then trim the edges of the backer at an angle or remove excess material. However, due to the slight overlap of the rails on the seat, the effective width of the backer is reduced in such an approach due to the need to create a sufficient vacuum seal on the fasteners. Therefore, the method described above is less efficient than the previous embodiments in that the area of the sheet that can be perforated is reduced.

It is generally desirable that the rails 40, which receive the longitudinal ends of the sheets, be sloped as well. However, since there is actually a somewhat greater degree of freedom at the longitudinal ends of the sheet, trimming may be employed.
Typically, the ends of the sheet are drilled with holes for engaging clamps that pull the ends of the sheet together and tension the sheet around the workpiece holder.

In use of the apparatus of the present invention, the rail is clamped onto the sheet and the interior of the groove is then evacuated to approximately 7 kPa to create a pressure differential sufficient to pull the sheet flat. The silicone rubber is mixed with the catalyst by mechanical stirring and then vacuum degassed for about 15 minutes to remove any air trapped inside the rubber. After the rubber is poured between the rails and leveled, the gum is cured at room temperature for approximately 16 hours. The sheet, together with the partially cured backer, is removed from the fixing device and cured in an oven at about 100 DEG C. for one hour, thereby making it ready for use.
Applying a mold release agent on the rail is not necessary, but may be used if desired. Of course, the sheet is carefully sanded and cleaned prior to applying the backer to the sheet to facilitate adhesion of the backer to it.

The manner in which the sheet is placed on top of the base is important. In general, sheets tend to be biased into a curled condition. That is, the sheet is raised more relative to its general plane in one direction than in the other direction. The sheet must be secured to the top surface so that its bow is in a positive direction relative to the top surface of the base. This is shown in FIG. 8, where a cavity 82 is formed between the sheet 84 and the upper surface 42 of the base 36 by the forward displacement of the ridge 80. By attaching the sheet in this manner, the sheet is more easily pulled flat. However, when the sheet is installed in the workpiece holder, the ridges are displaced in the negative direction relative to the holder, and the resistance force of the bucker returns the sheet in the positive direction to a position a desired distance E from the holder. It is even more important that

We used a differential pressure generated by atmospheric pressure in combination with a vacuum. Other differential pressures may be used. Also, if the sheet is magnetic, magnetic attraction may be used instead of differential pressure. In that case, there is no need for the upper surface of the fixing device to be provided with a groove. Other mechanical or electrical means compatible with the requirements of the invention may be used so that a uniform force is applied to the sheet to press it against the fixing device.

Although the polymer herein is RTV silicone rubber, other polymers such as waxes and various other materials may be used in the practice of the present invention. These materials must be flowable in the sense that they have a sufficiently low viscosity that they form a uniform layer parallel to the surface of the fixation device. The materials also solidify by cross-bonding (curing) or other mechanisms so that the sheet can be removed from the fixture with a layer of sufficient viscosity to retain its shape during handling and electron beam drilling. It must be possible. Thus, if the nature of the backer is such that it forms a layer of uniform thickness on the surface of the sheet in its flowable state, a leveling board with a curved lower edge may not be used. The method of the invention may be carried out in the following manner.

If a backer that cures more quickly than RTV rubber is used, and if due control is required for manufacturing, the backer should be It may be worn continuously as a long sheet. If such continuous application occurs, the bucker will solidify rapidly and the sheet will be drawn onto a flat surface or onto the outer circumference of a smooth cylindrical drum. A backer is formed by appropriately positioned leveling boards and edge moldings. Thus, although the preferred embodiment of the invention has been described in the context of a fixation device having a smooth, planar surface, the surface of the fixation device need not be planar in practicing the method of the invention. The surface of the fixing device need only be smooth so that warping of the sheet is eliminated by applying pressure to the sheet and the leveling board is spaced at a certain distance from the surface of the sheet. . Another somewhat different embodiment of the invention useful is shown in FIG. A rail with straight sides is used to form the periphery of the backer 26b, thus forming a raised portion 86 at the periphery of the backer. The smooth outer surface 90 of holder 20b has a circumferentially extending groove 88. Sheet 24b to which backer 26b is attached
is positioned such that the raised edge 86 is located within the groove 88. Thus, the relief at the periphery of the sheet in this embodiment of the invention is provided in the holder rather than in the backer itself. However, this embodiment requires that the sheet be accurately positioned on the workpiece holder;
A disadvantage is that different workpiece holders must be used for sheets of different widths.

Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to such embodiments, and various embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a side view of the main parts of an electron beam apparatus showing how a workpiece clamped around a drum-shaped workpiece holder is perforated by an electron beam. FIG. 2 is an illustrative perspective view of the apparatus of the invention showing how the sheet is received and how the leveling board is moved along the length of the fixation device. FIG. 3 is an enlarged partial cross-sectional view of a portion of the fixation device shown in FIG. Materials shown. FIG. 4 is an enlarged partial cross-sectional view similar to FIG. 3, illustrating the problem solved by the curved lower edge leveling board and angled rail of the present invention. FIG. 5 is an enlarged partial cross-sectional view of one embodiment of a sloped siderail. FIG. 6 is an enlarged partial cross-sectional view of the bucker captured between the workpiece holder and workpiece shown in FIG. 1, illustrating the advantage of having sloped edges of the bucker; . FIG. 7 is an enlarged partial sectional view similar to FIG. 6, showing another embodiment of the relief provided at the edge of the backer. 8th
The figure is an enlarged partial cross-sectional view similar to FIGS. 3 and 4 showing how the metal sheet is positioned in the fixation device with respect to bowing of the metal sheet. FIG. 9 shows another embodiment of the present invention in which the workpiece holder is constructed to have a recess at its periphery for receiving a backer formed by a fixing device having a rail with a rectangular cross section. FIG. 8 is an enlarged partial cross-sectional view similar to FIGS. 20...Work piece holder, 22...Outer peripheral surface, 2
4...metal sheet, 26...backer, 27...
Hole, 28...beam, 30...electron gun, 31...
Hole, 32... Protective shield, 34... Sheet, 3
6... Base (fixing device), 38, 40... Rail, 42... Top surface, 44... Groove, 46... O-ring seal, 48... Port, 49... Backer material, 50... Leveling board, 52... Guide tab, 54... Protrusion, 56... Backer, 58...
...Rail, 64... Central portion, 66... Raised portion (periphery), 68... Lower edge, 70... Inner edge,
72... Vertical portion, 78... Relief, 80... Ridge, 82... Cavity, 84... Sheet, 86
...Raised portion, 88...Groove, 90...Outer peripheral surface.

Claims (1)

[Scope of Claims] 1. A method of attaching a backer material to the surface of a metal sheet workpiece having a ridged surface, wherein the warped region is displaced from the smooth surface of a fixing device, whereby the warped region of the sheet is displaced from the smooth surface of a fixing device. positioning the first side of the sheet on the smooth surface of the fixation device such that the first side of the sheet cooperates with the surface to define a cavity in a region; the first side of the sheet by creating a vacuum between the first side of the sheet and the surface of the fixing device and allowing atmospheric pressure to act on a second side of the sheet. applying pressure against the surface of the fixation device; and directing a liquid polymer to the second side of the sheet to at least partially cure the polymer, causing the polymer to adhere to the sheet. and the shape of the portion of the fixing device that abuts the outer periphery of the polymer forms an escape space around the outer periphery of the cured polymer where the polymer adheres to the sheet, thereby making the thickness of the cured polymer uniform. directing a greater amount of uncured polymer to the center of the sheet than to the periphery of the sheet to increase the temperature of the sheet; and releasing the vacuum and removing the sheet from the fixing device. 2. A fixing device for adhering a uniform layer of solidified material, such as a backer for electron beam perforation, to the surface of a warped sheet, having a smooth surface provided with grooves and configured to receive the sheet. and means for connecting the groove to a vacuum source; and applying a peripheral edge of the sheet against the surface such that a vacuum is created between the sheet and the surface and the vacuum presses the sheet against the surface. means for sealing, and forming a cavity above the surface of the sheet mounted on the fixation device into which a flowable material is introduced which is solidified and adhered to the sheet in a layer. rails removably attached to the surface and surrounding the periphery of the fastening device in which the sheet is received, at least one rail surrounding the periphery of the material at the periphery of the layer in a direction transverse to the layer; a flowable rail disposed between the rails having an edge forming a relief in the layer such that the overall amount is less than the average amount of the material in the remainder of the layer; a leveling board guided by said rail for leveling of polymer, said leveling board having a concavely curved leveling surface facing said surface of said fixation device.