AU672499B2 - A process for producing a casing providing a screen against electromagnetic radiation - Google Patents

Abstract

A method for manufacturing a housing having an electromagnetic screen (1, 4), especially for electronic functional elements (2), having a screening profile (8) which is arranged in a predetermined section (3a) of at least one housing part (1) and has elastic as well as conductive material, the elastic as well as conductive material being applied by means of pressure from a needle (6) or nozzle directly onto that section (3a) of the housing part (1) on which the screening profile (8) is intended to be arranged, and a housing manufactured in accordance with this method. <IMAGE>

Description

1 i A process for producing a casing providing a screen against electromagnetic radiation Background of the Invention Field of the Invention The invention relates to a process for producing a casing providing a screen against electromagnetic radiation according to the preamble of claim 1, and a casing according to the preamble of claim 8.

Description of the Prior Art similar devices sensitive to interference by electromagnetic radiation require a screen against the electromagnetic fields present at the operational site in order to ensure a problem free operation.

6 They are therefore accommodated in screening cases which comprise conductive material in the walls and act as a Faraday cage.

Such casings are also used for equipment or components which, themselves, emit electromagnetic rays that must be a o excluded from the environment, in order for example, to prevent the emission of secret information or the malfunction of external appliances.

Today such a screening against the emission or irradiation of EMI must be more effective the more electronic appara- /2 i- 2 tuses are operated and the greater the proximity at which these apparatuses must operate next to each other.

Finally, the continuous increase in performance and sensitivity of such equipment also necessitates an improve- i ment of the screening measures for which increasingly less space is available, since the relevant appliances must, moreover, be miniaturised. Thus, apart from the actual operational properties of electronic appliances, the i "electromagnetic compatibility" is today a significant factor determining quality.

If, as is mostly the case in practice, the casings are multi-part constructions which must be capable of being opened occasionally in order to renew the energy source or for maintenance purposes), it is necessary to provide the parts of the casing to be separated from each other during opening and to be re-connected again during closing, with elastic conductive seals in order to achieve 4. *4 an effective screening.

Whilst, on the one hand, spring-like metal seals are known for this purpose, they are, however, comparatively expensive to construct and their operability may be greatly *affected by oxidation and soiling.

Furthermore, resilient sealing profiles made of elastomer which is conductive or has been made conductive, which has been mixed with carbon or metal particles in order to alak) it conductive, are known from e.g. US 46 59 869 or DE-OS 30 28 27 676.

3 i I Such sealing profiles are normally manufactured as separate seals. They may be moulded or extruded as a continuous section and then placed into the casing to be screened. i This is a labour-intensive operation and especially in small casings it causes difficulties as seals with correspondingly small dimensions are difficult to handle. i The provision of suitable guides (grooves) which facilitate the mounting on the casing requires an unreasonable amount of space and is thus a hindrance to the further miniaturisation of the appliances.

Intricately moulded seals likely to be needed for special casings require specific positioning equipment which makes the manufacture of the casing altogether more expensive.

.0 The exact positioning is, moreover, time-consuming and necessitates additional inspection.

The hot-moulding, in moulds, of such screening profiles onto the relevant casing portions or parts and the setting at a relatively high temperature and/or high pressure is also known.

.0 0 This process cannot be used with parts sensitiva to pressure and/or temperature such as printed circuit boards or metallised plastics casings and, as a result of the low tear resistance of the related materials, problems arise during the removal from the mould resulting in a relatively high number of rejects and, more particularly in intricately shaped casings and seals, also frequently /4 -4necessitating time-consuming and labour-intensive machining on the pressed-out edges.

Object of the Invention The invention has the object of providing a process of the above kind for producing protective screens, more particularly within the region of casing joints, which may be adapted, in a simple manner, to the most varied requirements, even in a miniaturised construction. It must also be possible to use the process according to the invention for casings to be produced in larger quantities; in a simple manner and at low cost. The casing produced according to this process must be provided with a screening profile which meets the electromagnetic and mechanical requirements and remains in good conditicn even after a repeated opening of the casing.

Summary of the Invention According to a first aspect of the present invention there is provided a process for producing a casing providing a screen against electromagnetic radiation, particularly for receiving electronic operational elements, comprising a screening profile arranged in is a given portion of at least one casing part, said screening profile comprising elastic and conductive material, characterised in that the elastic, conductive material is applied in i an originally pasty or liquid state, by means of pressure from a needle or nozzle, directly onto the open edge region of one part of the casing closable by another part of the casing, and is elastically solidifying, adhering to the surface of said one part of the S 20 casing.

.According to a second aspect of the invention there is provided a casing particularly for operational elements, which shields its interior from electromagnetic radiation, having a screening profile arranged in a predetermined portion of at least one part of the casing, said screening profile comprising elastic, conductive material, characterised in that the screening profile made of the elastic as well as conductive material is formed directly on the open edge region of one part of the casing closable by another part of the casing and is adheringly connected thereto, so as to solidify and adhere to the edge region of one part of the casing at room temperature, said elastic conductive material being applied in an originally pasty or liquid state by means of j 303 pressure from a needle or nozzle, The invention in a preferred form is based on the concept of not producing the I screening profile separately but directly and without using a mould on the casing in one step or preferably in several steps by means of a hardening pasty or liquid compound with the required properties which issues from one or more openings guided over the geometrical extent to be sealed. Thereby, the handling problems of premanufactured sealing profiles and, on the other hard, the process-related disadvantages of compression moulding are avoided, and the possibility is opened to build up profi- SRA4 Od ,1_z_ les having very different special cross-sectional shapes and/or consisting of portions of different material properties (degree of elasticity, conductivity, thixotropy etc.) according to demand. Here, the material consists of a plastics compound which at least in portions contains conductive inclusions, more particularly in the form of metal or carbon particles.

If, for forming the profile, the guidance of the needle or nozzle over the portion of the casing part, on which the screening profile is intended to be mounted, is done by machine, more particularly controlled by computer, a high precision and great flexibility is ensured in shaping the profile so that moreover intricately moulded casings or openings of casings in small series may easily be provided with the necessary screening seal in an economic manner.

4 Special profiles, for example comprising undercuts, recesses etc., on the casing, are advantageously produced by 20 guiding the needle or nozzle several times or several needles of nozzles at least over predetermined regions of the portion on which the screening profile is intended to 444 be mounted, in order to produce a multi-layer screening .o4. profile, thereby forming an exactly predetermined profile section. The profile cross-section as requested is formed herein in several operations in succession or nearly siooe multaneously. The shape of the profile above all is determined by a suitable choice of number, cross-sectional sha- *~pe and dimension and scanning speed of the needle(s) or nozzle(s) and the spatial relation thereof during the several coating steps, but furthermore by the choice of the ./6 material properties such as viscosity, thixotropy and curing speed.

A special design of the process consists in that the several strands of elastic as well as conductive material are applied in a spatial configuration and a time-distance each to the other such that a partial curing of an applied strand has happened before a next strand touching the former one will be applied.

In this way cross-sectional profiles may preferably be produced which have given elasticity properties and do not acquire said elasticity because of their compressibility but because of a bending deformation, as is the case in bent lip sections or hollow sections.

a It is, in particular, not necessary to provide each strand of the material with conductive inclusions since linear S..conductors already provide a great screening effect.due to 20 the laws of the electromagnetic field. Of course, it is advantageous to provide a strand of highly conductive material so that it will touch the casing parts over a distance as long as possible. The sealing effect of this conduc- 54.4 tive strand is less important since one or more strands of 5 less or non-conductive but highly elastic material which primarily will fulfil the sealing function of the profile can be assigned to it.

S. The inventive measures also make it possible to produce Ocomplicated seal constructions with dimensions which vary along their extent, without special difficulties. Here, /7 i. i '2 -y of the elastic as well as conductive material is formed dirprtiv nn th n.

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according to the relevant requirements, the cross-section may vary along the edge to be sealed, within wide limits.

It is also possible to produce such constructions of screening profiles which are interconnected in a way that an individual production and mounting thereof, separate from the casing, would not have been possible. Any joints j in the extent of the screening seal are thus obviated by the measures according to the invention so that the i sealing effect is not interrupted.

Smaller casing zones or additions which are not made of metal or metallised, which would produce a break in the closed screen, may, in an operation carried out at the same time as the other seal is produced, be coated gridlike with the profile strands according to the invention, I so that homogenous screening conditions also exist in such regions.

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In this way elements of a Faraday cage may even be formed 20 from tracks of conductive plastics material and thus of the sealing compound itself, if they are mounted in the shape of a grid in a plane and conductively connected at the intersections of the grid.

Due to the fact that different elastic materials are applied when guiding the needle or nozzle several times over the predetermined regions, at least one application comprising conductive material, it is possible to produce ;casings with seals whose conductive, corrosive and elastic 30 properties have been optimised to advantage /8 -8 Casings allowing easier handling may be produced especially in such a way that the elastic conductive material is applied, by computer control, directly onto the edge region of a closable aperture of the casing so that the screening seal assumes a configuration enabling an easy opening and closing of the aperture.

In order to apply the screening profiles according to the invention, computer-controlled handling appliances may be used which allow a three-dimensional guidance of the needle or nozzle, a fourth variable relating to the metering of the still liquid or pasty material, as a function of the forward movement. By means of a fifth control variable it is additionally possible to select a material, i.e. various strands of material which may also be of a different composition and may be applied alternatingly, or simultaneously in "one single operation", so that the material characteristics of the entire section, with .regard to its cross-section or its extent, may be varied 20 locally. These varying characteristics include the conductivity, elasticity (bendability or compressibility) and/or hardening or adhesive properties of the material.

A firm closure through adhesion can als) be achieved by means of the screening sealing elements, if adjacent 25 material strands have corresponding characteristics, e.g.

if they are the two components of a two-component adhei "sive. i In other advantageous embodiments of the invention, instead of parts of the casing, parts of printed circuit boards projecting beyond the outer surface of the /9 3.

L y p i: appliance may also take over screening functions, 6nd for adaption to adjacent screening members may be provided with the features according to the invention.

Other advantageous further developments of the invention are characterised in the sub claims and are hereinafter more fully explained in the description of preferred embodiments of the invention, with reference to the Figures.

Brief Description of the Drawings Figure la and lb basic diagrams of two embodiments of the process according to the invention; Figure ic a detail of Figure la; Figures 2a to 2k schematic, partial cross-sectional diagrams of screening profiles which are part of embodiments of the casing according to the invention and may be 20 produced using embodiments of the process according to the invention, as well as Figure 3 a schematic drawing of the length of an edge with screening profile of a casing according to the invention, S 25 in one embodiment.

Description of the Preferred Embodiments S. Figure la shows an aluminium screening casing 1 for an 30 electronic circuit component 2, which has a cavity 3 for inserting the circuit component, said cavity being closed with a lid 4 after the insertion of the component.

.o .1 C. Figure la also shows how a screening profile 8 is applied to the edges of the cavity 3 by an application needle 6 airtightly connected to a piston-cylinder device 5, said application njedle being guided, together with the pistoncylinder device 5, by a computer-controlled robot arm 7 which exerts a pressure p onto the piston 5a of the device at a small and precisely maintained spacing from the casing 1, and at the speed v, along the surrounding edge 3a. The automatic arm may be guided in the thzee spatial directions x, y and z.

Cylinder 5b of device 5 is filled with a quickly air- and room-temperature-drying silicone mixture 8a at ambient temperature with included metal particles, which, as a result of the pressure exerted onto the piston 5a, is pressed ("dispensed") through the channel fa of the needle 0 0 6 onto the surface of the casing, to which it adheres and Where it hardens under the influence of air., to form the elastic screening profile 8.

The cross-sectional dimensions and shape of the screening profile 8 are primarily determined by the physicochemical-properties of the conductive plastics material used, more particularly the hardening speed, viscosity, S.A 25 surface tension with regard to the casing material, and the thixotropy thereof, as well as by the cross section of the channels, the pressure exerted onto the piston, the sspeed of the needle movement and by the environmintal influences such as temperature or air humidity at the manufacturing site and may be predetermined by a suitable selection of said parameters.

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CA0 i: C 11 0 4 *40 0 *r 4 4i 44 4 4 44 44 4 4: 4 04 In the casing 1, shown in Figure 1, 'c.mprising a flap cover 4 mounted on one side to a hLnge, it may be of advantage if the application needle 6 is guided along one edge portion of the opening 3 at a higher speed than in the other portions. A profile with a smaller cross section than that in the other edge portions would be formed here and the lid could be closed more easily. It is possible to adjust the characteristics of the plastics material, particularly by adding fillers (carbon or the like), metal binders, surfactants and hardening catalysts or cross-linking agents. The kind and grain aize of the admixture ensuring conductivity, such as carbon, silver, silver- or gold-coated copper particles or the like, not only influence the electrical but also the mechanical and processing properties of the conductive elastic material.

Fig. Ic shows an enlarged representation of the unit 5 as a detail of Fig. la. In addition to the elements referenced by identical numbers there are shown a plunger in a cylinder 5b containing a supply of the elastic and conductive material 8a later forming the screening profile 8 in a still pasty and unsolidified state.

In the arrangement of Fig. la the robot arm 7 bearing the device 5 can be guided along the edge portion of the opening 3 several times to apply several strands of the silicon gum side by side and/or one on top of the other or in other spatial relation (as exemplified below). In this way profile cross-sections having especially advantageous sealing and.for screening properties can be formed.

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12- Alternatively hereto as shown in Fig. lb the use of a multi-nozzle coating device is possible which can be used to apply several material strands approximately at the same time, The casing parts shown in Fig. lb correspond to those of Fig. la and will, therefore, not be described once again.

The coating device 150 comprises four coating modules 151 to 154 each comprising a nozzle 161 to 164 for ejecting a material strand and, furthermore, a (not specially designated) piston-cylinder device similar to the coating device 5 of Fig. la. The modular structure of the device enables the combination of any number of modules, on demand even staggered such that the application moments of 15 the different strands can ba shifted relative to each other. Since, furthermore, the device 150 is borne in a rotating plate 171 in the robot arm 170 the position of material strands 181 to 184 applied therewith relative to each other and to the surface of the casing can be varied by predetermining the angular position of the rotating plate 171.

r** The modules have separate material containers and can com- ,9 prise different nozzle dimensions such that strands of 25 different material as well as of different shape can be combined with each other.

Figures 2a to k show examples of different profile cross sections for casings -which may be manufactured in several applicational steps using the process according to the invention. It is, however, apparent when using the /13

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'i -13 measures according to invention, that the cross sections may also vary in the longitudinal direction of the profile, in the geometrical dimensions and material characteristics thereof.

Figures 2a to 2d show a combination of conductive, less elastic sealing parts (hatched) and non-conductive sealing parts which are more elastic because of the missing metal admixture, thereby achieving a combined optimal effect of sealing and screening.

Figure 2a shows a screening and sealing construction formed by profiles 81a and 81b with a substantially circ. cular cross section, arranged side by side in two applica- 15 tional steps on the surface of a casing part Ii. Such a 1 structure is produced, when the elastic material slightly wets the surface of the casing.

Figure 2b shows a profile structure produced in three steps, consisting of a flat-domed, broad conductive profile part 82a and a conductive part 82c "dispensed" thereon and a non-conductive part 82b on a casing portion 12, the parts 82b and 82c having a substantially circular cross section.

Suh a structure is obtained if a material of the first "profile part 82a wets the surface of the casing to a great Sextent and/or was applied with a relatively broad nozzle instead of the needle 6 shown in Figure 1, whereas the material of parts 82b and 82c have a mild wetting tendency with respect to the surface of part 82a.

/14 12 h at 2 n 2 aigasbtnilycrua crs seton 14 Figure 2c shows a structure which is similar to that of Figure 2b. Here, two approximately semi-circular, conductive screening profile parts 83b and 83c are arranged on either side of a nearly semi-circular, non-conductive, highly elastic sealing profile 83d centrally arranged on a lower, broad profile part 83a positioned on a casing surface 13.

This last profile shows great stability with respect to I forces acting parallel to the casing surface, but it has a comparatively lower elasticity. It may, therefore, be particularly suitable for sliding closures.

By contrast, the profile shown in Figure 2d, which con- 15 sists of a semi-circular elastic, non-conductive profile part 84a pressed onto a casing surface 14, and a conductive coating 84b covering the surface o: said profile part 84a, has extremely satisfactory elasticity properties.

A high wetting ability and satisfactory adhesion between *the surfaces of the two materials are necessary for the •manufacture of the profile which is very suitable for hinged covers, especially if there is a relatively great play between the closure and casing part, or if they, 25 themselves, have a certain elasticity.

I '41e Figures 2e to 2i show screening profiles which consist exclusively of conductive material.

Figure 2e shows a specially formed, single-part profile positioned on a casing surface 15 which has two beads I *ii L niT4---g- and 85b connected by a flat path. In the shape as shown or a similar one, it can especially be built up from two or three single strands; in the latter case, the central strand can especially be formed from a material of low viscosity and/or good wetting properties which will run relatively flat between the outer, previously initially i cured strands. Such a profile may be suitable for casings with hinged covers which have shaped edges. 'i i Figure 2f shows a semi-circular screening profile 86 on a casing surface 16 which consists of a plurality of circular profile strands of the same, highly conductive material, said screening profile, together with said casing surface, enclosing an air space 86a.

'1 The effect of the profile, in co-operation with said "air chamber", ensures a high elasticity of the entire profile despite a comparatively unsatisfactory elasticity of its components. c :Figure 2g shows a lip-shaped screening profile 87 on a casing surface 17, which consists of a plurality of circular profile strands laid one on top of the other staggering the long axes to each other. It is suitable for hin- 25 ged covers as well.

Figure 2h shows a T-shaped profile 88, positioned on a casing surface 18 with a rectangular groove 18a, said profile engaging with a broad centre part 88a in the groove 18a and having a planar surface parallel to the casing surface 18 outside the groove 18a. It can be formed by S. /16 cain sufc 8wt etnua roe1a adpo 16 l i first filling the groove with a first, highly wetting material strand (which preferably has been given a corresponding cross-sectional shape by means of a nozzle shaped corresponding to the groove) and then prior to curing of the surface of the first strand dispensing a second strand on top of the first strand, the second strand being as well pre-formed in rectangular shape by an even broader nozzle opening.

This screening profile has not only a material connection but also a positive connection with the casing surface which further increases the stability.

Figure 2i shows a profile structure consisting of a block 15 89a with an approximately rectangular cross section and made of conductive, elastic material, and two flat-domed profile parts 89b and 89c arranged side by side on top of said block.

Because of its large cross section this profile structure is especially suitable as a screen with respect to strong fields, but because of the added-on sealing lips 89b and 89c it is also provided with sufficient elasticity.

25 It is obvious that other cross sections (almost of any kind) are possible depending on the requirements to be met.

For specific applications, a combination of prefabricated, inserted sealing profiles and of profiles produced according to the invention may also prove suitable.

/17 .w i 17 Figure 2k shows a further embodiment of a casing provided with a sealing according to the invention in the region of an abutting edge. The casing consists of an upper part 4' which is provided with a surrounding tongue which engages in a corresponding surrounding groove 3b of the bottom part of the casing. The groove and tongue 3b and 3c taper, thus ensuring a relatively tight closure of the casing, but the mutual distance of the casing parts may i j vary because of manufacturing tolerances. The profile part 8' according to the invention therefore provides an additional screen within the region of the edge which, irrespective of the relative position of the two casing parts, is highly effective because of its elasticity and the incorporated conductive materials. Because of the 15 inclination of its maximum cross sectional extent with Srespect to the direction in which the two casing parts 5 close together, the elasticity is enhanced both by the compressibility and the flexural deformability of the profile part. In this way, any existing slight inhomogenieties in the sealing of the screen are reliably overcome because of the fit of the casing, and an excellent electromagnetic compatibility may, on the whole, be achieved.

25 Fig. 3 shows, schematically, the length of a screening profile 108 along the edge of a casing 101, according to the invention, which has, by way of example, a rectangular S edge projection 101a and a semi-circular curvature 101b.

The process according to the invention enables the production of any sealing profile, as desired, so that screens of a high quality may be obtained.

/18 :Ma 18 i The above description of casings and parts thereof also relates to components which act both as electrical and mechanical carriers and casings, for example a printed circuit board which is simultaneously used as a casing part.

Thus, the proposed solution also applies to profiles of covers in the form of a grid or basket provided in screening devices or parts thereof.

In its construction, the invention is not restricted ;o the above preferred embodiment. On the contrary, many variants are feasible which make use of the above solution i even if they are basically of a different construction.

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Claims (13)

1. A process for producing a casing providing a screen against electromagnetic radiation, particularly for receiving electronic operational elements, comprising a screening profile arranged in a given portion of at least one casing part, said screening profile comprising elastic and conductive material, characterised in that the elastic, conductive material is applied in an originally pasty or liquid state, by means of pressure from a needle or nozzle, directly onto the open edge region of one part of the casing closable by another part of the casing, and is elastically solidifying, adhering to the surface of said one part of the casing.

2. A process according to claim 1, characterised in that the needle or nozzle is driven mechanically, more particularly by computer control, over the portion of the casing part on which the screening profile is to be arranged. i

3. A process according to claim 1, characterised in that, in order to produce a multi-layered screening profile, the needle or nozzle guided several times or several needles or nozzles are guided at least over predetermined regions of the portion on which the screening profile is to be arranged, so that a predetermined cross-section is built up from several strands of elastic as well as conductive material, which together form a sealing profile with a cross-sectional shape being predetermined essentially by the number, ejecting cross-section, scanning speed and spatial relation of the needle(s) S 20 or nozzle(s). 'I 4. A process according to claim 3, characterised in that different elastic materials are applied, when the needle or nozzle is guided several times over the predetermined regions, conductive material being applied in at least one application such that by mean. of this strand in the closed condition of the casing a continuous 25 conductive connection between the parts thereof is made. 5, A process according to claim 3 or 4, characterised in that the several e4 strands of elastic as well as conductive material are applied in a spatial configuration S. and a distance in time to each other such that a partial curing of an applied strand has happened before a next strand touching the former one will be applied. 30 6. A process according to claim 1, characterised in that the elastic, conductive material is applied by computer control directly onto the edge region of a closable opening of the casing so that the screening seal assumes a configuration which I enables an easy opening and closing of the opening.

7. A process according to claim 1, characterised in that the elastic as well as conductive material is applied at room temperature,

8. A casing particularly for operational elements, which shields its 'j~1 interior from electromagnetic radiation, having a screening profile arranged in a predetermined portion of at least one part of the casing, said screening profile SAQ comprising elastic, conductive material, characterised in that the screening profile made T 0 I4 of the elastic as well as conductive material is formed directly on the open edge region of one part of the casing closable by another part of the casing and is adheringly connected thereto, so as to solidify and adhere to the edge region of one part of the casing at room temperature, said elastic conductive material being applied in an originally pasty or liquid state by means of pressure from a needle or nozzle.

9. A casing according to claim 8, characterised in that the screening profile is made of a material which becomes cross-linked or hardens at room temperature. A casing according to claim 8, characterised in that the screening profile is composed of several material strands at least in certain regions, each strand being formed on top or side by side of another strand and being adheringly connected 4 thereto or to the casing part.

11. A casing according to claim 10, characterised in that the screening profile is composed of different elastic materials at least in certain regions, at least one i is strand being made of conductive material which forms a con-nection between the parts of the casing.

12. A casing according to claim 8, characterised in that the screening 1 profile is arranged in the edge region of a closable opening of the casing and, in adaptation to the shape of the opening and the kind of closure, its configuration is such 20 that the casing may easily be opened and closed. 4 4 13. A casing according to claim 11, characterised in that the screening profile consists of a layer of material which is highly elastic but not or little conductive, and a layer of material which is little elastic but highly conductive,

14. A casing according to claim 8, characterised in that the cross-section of the sealing produced by several strands of material is lip-shaped. f, 15. A casing according to claim 8, characterised in that the cross-section of the seal produced by several strands of material forms a hollow profile. 16, A casing according to claim 8, characterised in that, between adjacent material strands containing conductive inclusions, there is at least one material strand 3 which does not contain such inclusions. 7, y17, A casing according to claim 8, characterised in that the screening profile providing conductive members covers the remainder of the casing, which is substantially non-conductive, like a grid, 18, A casing according to claim 8, chracterised in that at least one printed circuit board is included in the screening outer shape. 19, A casing according to claim 8, characterised in that adjacent material strands and/or material strands adjoining one another in the longitudinal direction have different characteristics, more particularly with regard to compressibility, elasticity, I t Z. tendability, adhesiveness and/or hardness, .X0 II i- 1R i 1 I li -21- A casing according to claim 8, characterised in that the material strands coming into contact with each other for the first time deiing the closure of the casing provide the two components of a two-component adhesive.

21. A casing according to claim 8, characterised in that at least one material strand has thixotropic properties.

22. A casing according to claim 8, characterised in that the screening profile extends substantially parallel, and more particularly parallel inside, to casing regions which engage in a tongue-and-groove manner.

23. A casing substantially as hereinbefore described with reference to the accompanying drawings.

24. A process for producing a casing substantially as hereinbefore described with reference to the accompanying drawings. Dated 9 July, 1996 EMI-Tec Elektronische Materialien GmbH Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON 4 .4 4 4.4 4 4 .4* *i 4 4. 4 4 4 '.4 4' *r 4 4* 4 4.44 .444r 4 .4 4 I I £t 4 iii 'ii if L 9 I_ i i II p -yA ,i M *4 S 9 95a 9544; .495 44 4 499, 4 44 t lt A PROCESS FOR PRODUCING A CASING PROVDING A SCREEN AGAINST ELECTROMAGNETIC RADIATION Abstract A process for producing a casing acting as a screen against electromagnetic radiation, more particularly intended for electronic operational elements, comprising a screening profile arranged in a predetermined portion (3a) of at least one part of the casing said screening profile being made of elastic, conductive material, the elastic, conductive material being applied, by means of pressure from a needle or nozzle directly onto the portion (3a) of the casing part, on which the screening profile is to be arranged, arid a casing produced according to said process. Figure la KMH/3269W .i