|Title of Invention||
CONDUCTIVE SEAL AS WELL AS A METHOD AND APPARATUS FOR ITS PRODUCTION
|Abstract||A conductive seal that is formed on a first sealing surface by extruding an elastically curing material intermixed with conductive particles is in addition intermixed with magnetic. After applying the material to the first sealing surface, its cross section profile is expanded to an adjustable level towards a second sealing surface and/or sealing rims are molded to it by a magnetic force from an electromagnetic plate. The magnetic and conductive particles are preferably concentrated in the marginal sections, particularly due to magnetic forces that act on the sealing roving in the extrusion process.|
|Full Text||FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION (See Section 10, rule 13)
CONDUCTIVE SEAL AS WELL AS A METHOD AND APPARATUS FOR ITS PRODUCTION
NEUHAUS ELEKTRONIK GMBH of DRONTHEIMER STRASSE 21, 13359 BERLIN, GERMANY, GERMAN National Company
The following specification particularly describes the nature of the invention and the manner in which it is to be performed : -
Conductive seal as we]1 as a method .aid apparatus for its production
This invention relates to a method and apparatus for producing a conductive seal from an ""lastically curing material intermixed with conductive particles that is applied from an extruder to a first scaling surface when it is not yet cured, and to a seal produced according to this method.
It ie known that electronic components, cause electromagnetic noise signals that travel outside via signal conductors through gaps in the housing of these components where they can spread, again through gaps in a receiving housing, to other electronic components and cause damage and malfunctions of these other electronic components.
To prevent these electromagnetic waveS that act as a noise signal from escaping from one housing and entering another housing whore they can impai the functioning of electronic components, the surfaces that form a gap in the hovising (scaling surfaces) are scaled against each other by a conductive seal. The housing that is also Conductive acts in conjunction wi"th t the conductive seal as a Faraday cage to prevent the emission of electromagnetic waves or shield elect ronie components from harmful radiation.
In addition to shielding perturbing "Loctromagnetic radiation due to the conductivity ot the-material used, another major function of such seals is protection of the
electronic device against, the efiect :: of dust particles, moisture, and toxic gases. The elect ionic seal thus also has to meet the requirments of a blocking seal commonly used in building and mechanical engineering to prevent transfer of substances between two rooms.
A seal freshly extruded according to the method mentioned above has a generally circular cross section. This cross section is elightly flattened after application onto the scaling surface of a housing part 01 another base because of its weight and its initial plastic state while the seal iff curing. The electronic shielding characteristics of such a seal are sufficient but its elastic properties do not meet the highest sealing requi cements as it has a high degree of hardness due to the conductive particles that are distributed across the enti.entire cross section. As these conductive particles are made of silver or a silver-plated material, such seals aro also relatively expensive.
DE 197 33 627 proposes an electronic seal that contains less ol the expensive silver while roil aiming its good electronic shielding characteristics and having Considerably improved elastic properties/for substance blocking. This seal consists of an internal sealing roving of an elastically curing roateiiai that does not contain any conductive particles encompassed by a thin conductive coat of a curing material intermixed with conductive particles.
Making a seal from two different materials or mixtures by CO-extrusion means higher tool expenses and involves the risk of cracks in the seal due to the distinct separation of the highly elastic internal layer and the less elastic brittle outer layer and their different curing behaviors. Some flattening of the seal during the curing of the
internal roving cannot be avoided GO that elasticity is reduced and an elastic tight fit of the seal to the opposite sealing surfaces is no longer guaranteed. But to select a different cross section other than circular for this type of electronic shielding seal to produce highly elastic cross sections or portions of cross sections would mean that the effort to design appropriate extrusion tools; is either excessive of technologically unfeasible.
The known conductive seals in particular fail to compensate- differences in sealing gap height that occur because of manufacturing tolerances in large-scale production as the extruded sealing material is always dimensioned the same for each seal and as any change in diameter would result in higher tool and material costs. It also frequently happens that a greater quantity of sealing material is applied onto the sealing surface at the beginning and end of each extrusion process, i.e. where the. two sealing ends abut. The sealing effect of the conductive seal is impaired in both cases.
Sometimes the sealing gap height is so immense that two seals have to be extruded on top of the each other onto the sealing surface in two subsequent operating cycles to achieve the required height of the seal. Overlaying two or multiple sealing ravings takes time and increases material costs.
It is therefore the problem of this invention to provide conductive seals of the type mention at the outset designed in such a way that high elasticity of the seal is ensured, that tolerance-related vai nations in the sealing gap height and/or the height of the extruded material"at the joint of the two roving ends are
compensated, and that safe sealing against substances and electronic shielding are ensured.
This problem is solved according to the invention by a method comprising the characteristic:" described in claim 1. The design of the /apparatus for carrying out the method and the characteristics of the seal produced according to the invention are described in claims 17 or 22, respectively.
Advantageous improvements and useful embodiments of the invention are described in the sub claims.
The inventive idea of a method for p? rousing a conductive seal consisting o£ an plastically cutting material intermixed with conductive particles that is applied after extrusion, while Still in a elastic state, in a generally circular shape onto « sealing surface of a housing is that the elastically curing material is further intermixed With magnetic partially prior to extrusion and that the extruded magnetic sealing roving that, adheres to a first sealing surface is attracted by the magnetic forces of an electromagnetic plate located on or above the sealing roving already cured on its outer surface, and thereby deformed. By placing the electromagnetic plate at a specific height above the sealing roving or by lifting the electromagnetic plate that is in contact with the seal and/or by using an electromagnetic plate with a profile that follows the flow of the sealing roving and has the shape of at least one groove, the sealing roving that adheres to the first sealing surface but is still plastic, inside is expanded towards the electromagnetic plate arid/or an opposite second sealing surface. The elasticity of a seal produced in this way is considerably improved by stretching the
longitudinal direction ol the sealing roving, and especially by forming a sealing rim in correspondence with the profile of the electromagnet is plate, the electromagnetic plate can be adjusted in height or set to a specific level above the first sealing surface, the height (expansion) of the seal can be adjusted to manufacturing conditions. The method cannot, only be used to compensate tolerances in the sealing gap height but also height variation in the sealing toving, Another important, advantage is that there is no more need to apply a particularly thick roving foil filling a very great sealing gap and achieving the required seal, height, when extruding or to stack multiple tovinys; all there is to do is to stretch a single layer to the required height. This reduces the manufacturing effort and material consumption.
To goes without, saying that the term extrusion refers to any kind of dispensing the sealing material in a plastic state onto a sealing surface using pleasure. This means that the sealing material can be fed to a nozzle or an extruder head vising a worm extruder, a reciprocating pump, a gear pump, just compressed air and the like.
T.n an advantageous improvement of the invention, the magnetic and the conductive particle:; are rolled into one-piece particles, i.e. the magnetic iron or nickel particles (or particles made of another magnetic material) are coated with a conductive layer. In the extrusion process, these particles can be drawn to the rim area of the extruded sealing roving by applying magnetic forces to increase conductivity in the rim of the seal and create a homogeneous transition between the highly elastic inner portion and the conductive outer portion of the seal. As the portion of elastically curing material is low in the perimeter rim area of the extruded
sealing roving, the outer surface hardens fast so that it can easily be removed from the electromagnetic plate after the sealing roving way atretched or a sealing rim was molded onto it. The single-piece conductive and magnetic particles can also be made i-nt.i rely of nickel, which is both conductive and magnetic. In addition to the separate or single-piece magnetic ami conductive particles, the sealing material may also contain single-piece conductive and magnetic particles plus conductive non-magnetic particles. The conductive magnetic particles may be fibers or laminae.
It is also conceivable that an internal roving made of elastically curing material free from magnetic and conductive particles" and coated with a thin coar. of elasstically curing materiel intermixed with conductive and magnetic particles is applied to the first sealing surface by co-extrusion. Using magnet ic particles encompassed by a conductive layer in co-extruded outer conductive coat ic advantageous in this case, too. A very low portion of magnetic particles can be mixed into the inner roving.
As a further improvement, of the invention, the electromagnetic plate may be divided into individual magnetic segments that can be activat ed separately to apply different deforming forces and variably stretch the cross section. It. is finally conceivable that, the sealing roving can be deformed sideways using an electromagnetic plate that is located laterally to the housing/sealing roving. The sealing roving can also he extruded as a hollow body whose shape is either retained oz modified after extrusion by the magnetic foro-g.
The invention is not only applicable Ln the sector of shielding seals but can also be used to deform other seals"curing on a sealing surface.
Embodiments o£ the invention will be explained in more detail with reference to this attached figure, wherein it is assumed that the treatment according to the invention, for improving elasticity and for compensating tolerances refers to a aeal with accumulated conductive particles in its peripheral area; Wherein:
Fig. 1 is a schematic view of the seal production process according to the invention using an electromagnetic plate that has an approximately semicircular profile on its bottom side that follows the Clow of the sealing material and along which electromagnets are located;
Fig. 2 shows the method according to Fig. 1, here however the electromagnetic plate hao two profile grooves to mold a scaling roving with
two adjacent sealing rims;
Pig. 3 shows another design of the profile groove in
the electromagnetic plate t"> produce seals with differently shaped sealing rims;
Fig. 4 shows yet. another variant of the method in which the sealing roving is expanded by an approximately circular seal part and the cross section to deformed sideways using a laterally placed magnetic plate,- and
Fig. 5 shows still another variant of the method in
which an approximately squate sealing roving is
deformed by the pressure from a profiled electromagnetic plate.
Each of the sealo J or each of the sealing rovings 1 shown in Figs. 1 to 5 consists of a material that cures ela3tically 6t room temperature or at a higher temperature or when exposed to ultraviolet radiation (here, a silicone) and that is intermixed with conductive magnetic particles 2. The conductive magnetic particles 2 in this embodiment arc made of nickel or iron and coated with a silver layer so that, they bave both magnetic properties and high conductivity. The conductive magnetic particles 2 are concentrated in the 1m section of the seal 1/the sealing roving 1 thus forming an excellently, conductive and magnetic outer ring 3 and an inner roving 4 that is mainly free front conductive magnetic particles 2., This distribution o£ the conductive magnetic particles is achieved according to the invention by running the sealing material intermixed with the conductive magnetic particles 2 and still in its plastic state prior to or after extrusion through an annular magnetic group located at or around the extrusion head of an extruder (not shown), in this way, most of the conductive magnetic particles are drawn into the rim section of the seal 1 to form t..he narrow outer ring 3 enriched with conductive magnetic particles 2 while the inner roving 4 becomes either totally free from conductive magnetic particles 2 or contains only a small portion thereof.
Deviating from the embodiment described above, it is also conceivable that the enriched rim an-a is produced in a known way by co-extrusion of a mate* i a 1 intermixed with conductive and magnetic particles and a material free from conductive and magnetic particles wherein the material intermixed with, conductive particles forms a
magnetic roving than coats the inner" roving which is free £rbin conducti ve par t i c 1 e s.
In particular, it is possible that the sealing roving is homogeneously intermixed with conduct 1 v.e and magnetic particles across its entire cross section, or that the inner roving contains a smaller portion of the.required total quantity of conductive and magnetic particles that are drawn towards the outer rim section by the magnetic forces that act during extrusion.
The freshly extruded sealing roving 1 " for" the seal 1 is applied while still in a plastic .state onto"a first sealing surface 5 of the lower housing part 6 that, together with an upper housing part with a second scaling
surface of a ahown, forms a housing with a sealing gap
of a specific height between the two housing halves. According to Figs. "J to 4, the freshly extruded sealing roving 1" for the seal 1 initially has a circular and,
"0 after being applied onto the first scaling surface 5, a somewhat flattened cross section. The outer surface of " the sealing roving 1" that hardens first bonds in its still plastic state.at.e after extrusion with the sealing surface 5 of the housing part 6, but cures fact ac the curing parameters such as room temperatury and humidity, UV radiation or raised temperature are effective here first and the portion of material to be cured is relatively low due to the particles" incorporated in it. The sealing roving 1" can be exposed to short-term heat
or UV radiation to cause the outer surface of the seal to harden as fast as possible when curing takes place at increased temperature or under UV radiation.
When the sealing roving 1" has been .spplied onto the sealing surface ":>, an electromagnetic plate 7 is moved over the lower housing part 5 and positioned directly on
or at a specific distance above the sealing roving 1". A profile 8 that has the shape of one or more grooves is recessed into the bottom side of the electromagnetic plate that faces the seal 1, and a multitude of solenoids 10 is arranged one after the other in that profile 8 that can be activated individually or in groupa. The orientation of the profi1e B in the electromagnetic plate 7 matches that of the seal 1 or the sealing roving 1" on the revolving sealing surface 5. The set height level of the electromagnet ic plate ? plus the depth of the profile 8 match the height of the finished expanded and/or profiled seal 1 which is based on the respective height of t-he sealing gap.
The profile 8 of the electromagnetic plate 7 shown in Pigs. 1 to 4 is optional, which mean that"the electromagnetic plate 7 may be eompletly even on its bottom aide. In this case, however, the electromagnetic "plate 7,has to be positioned at a specific distance above the sealing roving 1" to stretch the sealing roving 1" and change ita profile in doing so.
The electromagnetic plate 7 is now connected to a power source (not shown) for a short time. The magnetic sealing material is drawn onto the electromagnetic plate 7 or onto/into the profile 3 on its bottom side because of the magnetic particles. 2 that are contained in the still plastic and deformable sealing roving 1", i.e. the silver-coated magnetic particles embedded in the curing mold, and because of the magnetic forces of attraction, the solenoids 10 of the electromagnetic plate 7 apply to these particles. As Figs. 1 to 4 show, a specific height of the seal 1 can be set, meaning that the sealing roving 1" for the seal 3 can be stretched wards and thus made more elastic, and a specific higher elastic profile can be molded in the section of the seal 1 that faces the
scaling surface on the opposing housing part. This molding is possible because at that me only the surface area of the sealing roving 1" has haideried but. is still Butficiently flexible to give way to !:he molding forces while the major portion of the elastically curing sealing material is still plastically formable and the magnetic particles 2 are bound in the rim arot (outer ring 3).
After setting the height and uhaping (stretching and profiling) of the sealing roving 1", the electromagnetic plate 7 is detached from the finished seal 1. The , electromagnetic plate 7 can be easily detached from the finished seal 1 as at least the surf-ice of the seal was hardened during shaping and was only kept on the electromagnetic plate 7 by the magnetic forces. The seal 1 is sufficiently hardened at the time when the electromagnetic plate 7 is detached that it keeps the shape it has been molded into by the magnetic forces. If the material cures under the influnces. of heat, the electromagnetic plate 7 may supply heart. to accelerate the curing of the sealing material and i."> stabilize the shaping by the magnetic forces.
The left half of Fig. 1 shows a freshly extruded sealing roving 1" and an electromagnetic plate 7 positioned very Closely above it. The profile 8 on tins bottom side of the electromagnetic plate 7 is an approximately semicircular groove. The central part of Fig. 1 sliows the seal 1 while it is drawn onto the electromagnetic plate 7 or into the profile 8. The right-hand part, of the figure shows the finished seal 1 that has the predefined (expanded) height and the narrower and therefore higher elastic upper portion (sealing rim 9). A comparable embodiment with two adjacent and mainly tapered sealing ims 9 is shown in Fig. 2. Here the profile R in the el"cr.romagnetic plate 7 (or the solenoid 10) consists of two triangular notches.
A drop shape with a tapering on top (not shown) can also be produced using an electromagnetic plate 7 with an even bottom side (without a profile groove) that io positioned at a" certain distance above the extruded and still round sealing roving 1. Unlike these embodiments, the electromagnetic plate 7 with a profile 8 may also be placed directly onto the seal to just cause stretching of the molded-on sealing rim 9. It is a I .so conceivable to lower the electromagnetic plate to piodueo a flattened form of tho seal 1, with or without sealing rim, or to stretch the cross section in its height by lifting the electromagnetic plate that is placed directly on the sealing roving 1.
Figs. 3, 4 and 5 show other embodiments of producing a seal 1 with one or two sealing rims having varying profiles, wherein the seal is stretched upwards to the height of. the sealing rim(s) 9, not only to increase the elasticity of the seal in this section by stretching and profiling tho sealing roving 1" but also to compensate differences in height resulting from applying tho sealing material and from the housing to be sealed, to be able to define a uniform height of the seal 1 and to achieve this predefined great height without stacking two or more extruded sealing rovings on top o£ each other and thus reduce material consumption.
Fig. d shows another embodiment of the invention wherein not only the height of the cross soft ion is increased and a sealing rim molded to the peal but the cross section of the sealing roving 1" is influenced in lateral direction by a movable electromagnetic plate 1" with solenoids 10" that is placed sideways from the roving.
1. A method for producing a conductive seal made of an elastically curing
material intermixed with conductive particles that is directly applied from an
extruder onto a first sealing surface while still in its plastic state, characterized in
that magnetic particles are intermixed with the sealing material prior to or after
extrusion and that, after the sealing material has been applied onto a first sealing
surface (5) and subsequent curing of just a surface layer, a magnetic field is
generated over a specific period of time using an electromagnetic plate (7) placed
above the extruded sealing roving (l1) and the sealing roving (l1) that adheres to
the sealing surface (5) is stretched towards the electromagnetic plate (7) and
molded into the finished seal (1) due to the action of the magnetic forces on the
2. The method as claimed claim 1, wherein the electromagnetic plate (7) is set to a level above the sealing roving (1") extruded onto the sealing surface (5) that corresponds to the height of the sealing gap, and that the cross section of the sealing roving (l1) is stretched to this height to form the finished seal (1).
3. The method as claimed in claim 1, wherein the electromagnetic plate (7) is placed upon the extruded sealing roving (l1) and that its cross section is set to a specific uniform height of the finished seal (1) by a limited upward motion of the electromagnetic plate (7).
4. The method as claimed in any one of claims 1 through 3, wherein the sealing roving (l1) is applied as a one-layer coat onto the sealing surface (5) and stretched to the height required to fill the sealing gap.
5. The method as claimed in any one of claims 1 through 3, wherein a groove-like profile (8) that correspond to the orientation of the seal (1) and is cut into the electromagnetic plate (7) magnetically molds elastic sealing rims (9) in the free sealing section of the seal (1) that faces an opposite second sealing surface.
6. The method as claimed in any one of claims 1 through 3, wherein the sealing material cures elastically at room temperature or at increased temperature or when exposed to UV radiation.
7. The method as claimed in claim 6, wherein the heat for a material curing at increased temperature is supplied by the electromagnetic plate (7).
8. The method as claimed in any one of claims 1 through 3, wherein the magnetic forces or a vacuum hold the seal (1) that is magnetically stretched and deformed on the electromagnetic plate (7) until it reaches dimensional stability.
9. The method as claimed in any one of claims 1 through 3, wherein single-piece particles coated with a conductive layer, or nickel particles that are both conductive and magnetic, or conductive magnetic and conductive non-magnetic particles are intermixed with the sealing material prior to extrusion.
10. The method as claimed in claim 9, wherein the conductive layer is made of silver and the magnetic particles are made of iron, nickel, or another magnetic material.
11. The method as claimed in any one of claims 1 through 3, wherein, to achieve excellent conductivity and magnetic effect and to reduce material consumption, the single-piece conductive and magnetic particles are concentrated along the perimeter of the seal (1) extruded onto the sealing surface (5) by generating magnetic forces section by section and at independent times that draw the conductive and magnetic particles towards the outer rim of the seal to create a conductive and magnetic rim section and a highly elastic inner roving.
12. The method as claimed in any one of claims 1 through 3, wherein a sealing material intermixed with single-piece conductive and magnetic particles and a sealing material that is free from conductive and magnetic particles are applied by co-extrusion as a sealing roving (l1), and in that the sealing material intermixed with conductive and magnetic particles encompasses the sealing material without additives like a coating.
13. The method as claimed in claim 12, wherein a reduced portion of conductive magnetic particles is added by mixing to the outer roving and the remaining conductive and magnetic particles that are magnetically drawn to the outer rim during extrusion are added by mixing to the inner roving to reduce extrusion pressures.
14. The method as claimed in any one of claims 1 through 3, wherein conductive and magnetic particles in the form of fibers or laminas are used.
15. The method as claimed in any one of claims 1 through 3, wherein the sealing roving (l1) is applied to the sealing surface as a hollow roving and that the cross sectional profile is held, expanded, and/or profiled further by the magnetic forces of the electromagnetic plate.
16. The method as claimed in any one of claims 1 through 3, wherein the cross sectional surface of the sealing roving (1") is deformed by the magnetic forces of a laterally positioned movable electromagnetic plate (71).
17. An apparatus for executing the method as claimed claim 1 with an extruder that can be moved in accordance with the curvature of a sealing surface above said sealing surface to dispense the sealing material onto a first sealing surface, characterized by an electromagnetic plate (7) that can be moved horizontally and vertically, that can for a limited time be connected to a power source to generate a magnetic field, and that can be positioned at a specific height on, or at a distance above the extruded sealing roving (1").
18. The apparatus as claimed in claim 17, wherein the electromagnetic plate (7) is either even on the side that faces the seal or comprises a profile (8) of at least one prominence/ indentation that matches the orientation of the seal.
19. The apparatus as claimed in claim 17, wherein the profile (8) is variably dimensioned to compensate graduations in the sealing surfaces of the housing.
20. The apparatus as claimed in claim 18 or 19, wherein subsequent solenoid segments (10) are provided along the profile (8) that can be activated at intervals using varying magnetic force.
21. The apparatus as claimed in claim 17, wherein the electromagnetic plate (7) is coated with a parting compound on the side that faces the sealing roving (1").
22. A seal for electromagnetic and material sealing between a first sealing surface and a second sealing surface consisting of an elastically curing material that is directly extruded onto the sealing surface and adheres to it, intermixed with conductive particles, produced in accordance with the method as claimed in claim 1, characterized in that the elastically curing material contains magnetic particles and in that the seal has a cross section that stretches towards the sealing surfaces to improve the sealing effectand to compensate height variation of the sealing gap and the freshly extruded (l1) sealing roving.
23. The seal as claimed in claim 22, wherein at least one protrusion/indentation is molded onto the side of the seal that faces the second sealing surface to form at least one highly elastic sealing rim (9).
24. The seal as claimed in claim 22 or 23, wherein the elastic material for the seal is rubber or foam elastic and cures at room temperature, increased temperature, or when exposed to UV radiation.
25. The seal as claimed in claim 22 or 23, wherein the conductive particles and the magnetic particles are single-piece particles made of a silver-coated core of iron or nickel or another magnetic material or just of nickel, or that they each include separate conductive and magnetic particles.
26. The seal as claimed in claim 22 or 23, wherein the separate or single-piece and magnetic particles are concentrated in the perimeter portion of the seal (1).
Dated this on 9th day of April 2003
HIRAL CHANDRAKANT JOSHI AGENT FOR
NEUHAUS ELEKTONIK BMBH, GERMANY
|Indian Patent Application Number||353/MUM/2003|
|PG Journal Number||13/2008|
|Date of Filing||09-Apr-2003|
|Name of Patentee||NEUHAUS ELEKTRONIK GMBH|
|Applicant Address||DRONTHEIMER STRASSE 21, 13359 BERLIN,|
|PCT International Classification Number||F16J 15/14|
|PCT International Application Number||N/A|
|PCT International Filing date|