This application is a U.S. National Stage Entry of International Patent Application Serial Number PCT/EP2014/068330, filed Aug. 29, 2014, which claims priority to German Patent Application No. DE102013109686.7 filed Sep. 5, 2013, the entire contents of both of which are incorporated herein by reference.
The present disclosure relates to apparatuses and methods for producing joining regions of a sandwich sheet having metal cover layers disposed about a plastic core layer.
Sandwich sheets, which usually have two outer metal cover sheets and at least one nonmetallic core layer arranged between the metal cover layers, said nonmetallic core layer preferably consisting of thermoplastic material, are used in order to provide composite sheet parts which have properties that are at least mutually exclusive in a sheet made of solid material. A sandwich sheet, in spite of its low weight, for example, allows locally very good stiffness and can simultaneously provide very good sound insulation properties. High tensile strengths with a simultaneously reduced weight can also be realized via sandwich sheets. Many applications require these sandwich sheets to be joined to other sheet parts or components. The joining methods that are frequently employed for sheets, for example fusion welding or soldering, cause problems, however, on account of their high heat input into the sandwich sheets. The thermoplastic layer usually used melts at least partially even in surrounding regions of the fastening or is damaged in some other way by the high heat input. In order to join a sandwich sheet to a further component, it is also possible to use a force-fitting and/or form-fitting joint, however, by using a fastening means, for example a screw or a rivet. However, it has been found that in the case of screwed joints or riveted joints, long-lasting firmness of these joints cannot be ensured on account of the creep behavior of the nonmetallic core layer, which generally consists of plastics material. The retaining force which the sandwich sheet has to provide with respect to the rivet or screw decreases on account of the creep behavior of the plastics material. As a result, or on account of the loss of the preloading force, the joint between the sandwich sheet and sheet or component loosens.
Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.
The present disclosure concerns apparatuses and methods for producing at least one joining region of a sandwich sheet that has at least two metal cover layers disposed about at least one core layer that comprises a plastics material. In some examples, the joining region is suitable for joining the sandwich sheet to a further component or sheet by using fastening mechanisms or a welded joint, for instance. The present disclosure also concerns receptacles for the sandwich sheet and mechanisms for displacing the plastics material out of the joining region.
Proceeding from the problem identified above, the present disclosure is based at least in part on the object of proposing a method and an apparatus for producing at least one joining region of a sandwich sheet, with which method or apparatus it is possible to create a joining region in a sandwich sheet which is suitable for joining the sandwich sheet to a further component or sheet via a welded joint or via fastening means, i.e. durably allows a form-fitting and/or force-fitting joint between the sandwich sheet and sheet (solid sheet or sandwich sheet) or component via fastening means. Furthermore, the joining region is intended to be produced as cost-effectively and reliably as possible.
According to a first teaching of the present invention, the object presented above is achieved for a method in that means for displacing the plastics material of the core layer out of the joining region are arranged in at least one joining region, the means for displacing the plastics material are preloaded such that a predetermined force is exerted perpendicularly to the surface of the at least one joining region of the sandwich sheet, the core layer of the sandwich sheet is heated such that, when the plastics material of the core layer of the sandwich sheet softens, the metal cover layers of the sandwich sheet are brought into contact by the force of the means for displacing the plastics material in at least one joining region by the plastics material being at least partially displaced.
As a result of the use of means for displacing the plastics material of the core layer that are able to be preloaded, the production of joining regions in sandwich sheets can take place independently of the provision of costly forming tools. As a result, costs for providing the joining regions can be reduced considerably and the flexibility in the arrangement of the joining regions can be increased. The joining regions can be used for welded joints but also for other durable joints between the sandwich sheet and further components by using fastening means, for example screws or rivets.
According to a first configuration of the method, the joining region therefore comprises an opening in the sandwich sheet, wherein the metal cover layers are brought at least partially into contact in the peripheral region of the opening by the plastics material being displaced. As a result, openings that are suitable for example for screwed joints can be provided in a sandwich sheet in that the substantially metal peripheral region of the opening can be used to build up the retaining forces of the screwed joint.
If, according to a further configuration of the method, a plurality of means for displacing the plastics material are arranged in a plurality of joining regions and at the same time the metal cover layers are brought at least partially into contact in a plurality of joining regions of the sandwich sheet, the method can be further improved in terms of its cost-effectiveness. This is allowed in particular by the use of the preloaded means for displacing the plastics material. These means can specifically be positioned and preloaded before the plastics material of the core layer is heated.
According to a further configuration, one metal cover layer or both metal cover layers are deformed in at least one joining region. If, for example, only one metal cover layer is deformed, the other metal cover layer can remain with its outer face in the plane of the sandwich sheet, and so the joining region results in a local depression in the sandwich sheet only on one side of the sandwich sheet. On the other hand, it is also possible for both metal cover layers to be deformed, such that the metal region which is used for example for a screwed joint can be arranged both in the plane between the two metal cover layers and outside the planes of the two metal cover layers.
According to a further configuration of the method, the sandwich sheet is first of all introduced into a receptacle, at least one means for displacing the plastics material is positioned on that side of the sandwich sheet that is the far side from the receptacle in the region of the joining region to be produced, via form-fitting and/or force-fitting means, a joint that is suitable for force transmission is produced between the means for displacing the plastics material and the sandwich sheet via the receptacle, the means for displacing the plastics material are preloaded, and the core layer of the sandwich sheet is heated at least in the region of the joining region until it softens. As a result of the use of a receptacle for the sandwich sheets, the means for displacing the plastics material can be positioned much more precisely on that side of the sandwich sheet that is remote from the receptacle. The form-fitting and/or force-fitting means, which ensure force transmission from the means for displacing the plastics material to the sandwich sheet via the receptacle, can also be used to position the means for displacing the plastics material or the sandwich sheet. The heating of the sandwich sheet can take place easily in the receptacle. Furthermore, the joining regions can be formed differently by an appropriate design of the receptacle in the joining regions, such that, for example in different joining regions, both metal cover layers or only one of the metal cover layers are/is deformed when the plastics material is displaced.
According to a further configuration of the method, the core layer of the sandwich sheet is heated by using means for convective, conductive or radiative heat transfer. Means for convective heat transfer, for example hot air fans, can transfer the heat to the metal cover layers of the sandwich sheet very quickly and efficiently. On account of the good heat conduction, the heat in the metal cover layers is passed on quickly to the core layer, consisting of plastics material, of the sandwich sheet. Conductive heat transfer can take place for example via heating elements provided in the receptacle, these having very precise temperature control. Radiative heat transfer is contactless and can be provided for example via infrared radiators, LEDs or other electromagnetic radiation sources.
According to a preferred embodiment of the method, the core layer of the sandwich sheet is heated by using ultrasonic vibrations. The use of ultrasonic vibrations can result in very precise heating of the core layer of the sandwich sheet, in particular on account of the different sound-conducting capabilities of the materials metal and plastics material.
Preferably, the means for displacing the plastics material displace the plastics material out of the joining region by using a punch guided perpendicularly to the sandwich sheet surface, wherein optionally the punch has a recess for receiving the displaced plastics material. The guidance of the punch makes it possible to introduce the force uniformly and precisely into the sandwich sheet in order to displace the plastics material. As a result, the entire region which is engaged by the punch is subjected to a predefined force such that the plastics material is pressed very precisely out of the entire region covered by the punch.
According to a further configuration of the method, the force of the means for displacing the plastics material is generated at least in part pneumatically, hydraulically and/or via a mechanical spring. Pneumatic and hydraulic generation of the force of the means for displacing the plastics material can be controlled easily, such that for example when a plurality of means for displacing the plastics material are used in a plurality of joining regions, an identical force can be applied to the sandwich sheet easily in every joining region. The use of a mechanical spring represents a particularly simple and cost-effective provision of the force for displacing the plastics material out of the joining region.
If the means for displacing the plastics material are positioned in a manner guided via guide means of the receptacle for the sandwich sheet, the positioning accuracy of the means for displacing the plastics material can be increased further. Suitable guide means may be for example pins which are arranged in the receptacle.
According to a further configuration of the method, a plurality of means for displacing the plastics material are positioned simultaneously via positioning means, wherein the positioning means predetermine the position of the individual means for displacing the plastics material and, as form-fitting and/or force-fitting means, produce a joint, suitable for force transmission, between the means for displacing the plastics material and the sandwich sheet via the receptacle for the sandwich sheet.
Appropriate positioning means can be for example a simple profile in which a plurality of means for displacing the plastics material are arranged and the profile is positioned in engagement with form-fitting or force-fitting means, provided therefor, of the receptacle. As a result, it is possible to simultaneously position a multiplicity of means for displacing the plastics material. The effort required for providing the sandwich sheet for the introduction of the joining regions can thereby be reduced.
According to a further teaching of the present invention, the object presented is achieved by an apparatus of the generic type in that the means for displacing the plastics material are preloadable with a predetermined force and the predetermined force can be exerted on the sandwich sheet such that when the plastics material of the core layer of the sandwich sheet softens, the plastics material can be displaced out of the joining region via the preloaded means for displacing the plastics material.
By way of the means for displacing the plastics material that are preloaded by a predetermined force, it is possible to create one or more joining regions in the sandwich sheet, these allowing a welded joint, for example a spot weld, or to provide openings with a metal periphery for the use of fastening means by way of a simple process for heating the core layer. Preloadable within the meaning of the present invention means that the means for displacing the plastics material are able to be activated, after being positioned in the joining region of the sandwich sheet, such that they exert a force on the sandwich sheet, said force sufficing to displace the plastics material out of the core layer of the sandwich sheet when the plastics material is heated. As a result, it is possible to initially position the means for displacing the plastics material easily and precisely in a non-preloaded state. After positioning, the force can be exerted on the joining region of the not yet heated sandwich sheet by preloading the means for displacing the plastics material. The displacement process can thus be extended simultaneously to a plurality of heated joining regions of the sandwich sheet.
Preferably, the means for displacing the plastics material have means for the pneumatic, hydraulic and/or spring-elastic generation of the predetermined force. Although pneumatic or hydraulic means for generating the predetermined force have a more complex structure than spring-elastic means, they can be preloaded in a particularly easy manner. Spring-elastic means for generating the predetermined force consist for example of a mechanical spring and therefore have a particularly simple structure. They are therefore particularly cost-effective.
According to a further configuration of the apparatus, the receptacle for the sandwich sheet is configured as a clamping apparatus, wherein the means for displacing the plastics material are integrated into the clamping apparatus. The receptacle configured as a clamping apparatus can have for example spring-elastic means which clamp the joining region to be produced in place between two receiving plates and subject it to a force such that when the core layer is heated, the latter is accordingly deformed. As a result, it is possible for example for peripheral regions of sandwich sheets to be equipped particularly easily with corresponding joining regions.
Preferably, according to a further configuration, the means for displacing the plastics material are positionable individually or in groups on the receptacle for the sandwich sheet and have a punch that is movable perpendicularly to the surface of the sandwich sheet, said punch being preloadable pneumatically, hydraulically or via a mechanical spring. By way of corresponding means for displacing the plastics material, joining regions can be produced at different positions on the sandwich sheet with little effort. The punch geometry can in this case be adapted to the joining regions to be produced, such that it is for example also possible to produce different geometrically distinctive joining regions by using individual means for displacing the plastics material or means for displacing the plastics material that are positionable in groups on the receptacle of the sandwich sheet.
According to a further configuration of the apparatus, the receptacle for the sandwich sheet has embossing regions in the region of joining regions of the sandwich sheet that are to be produced, such that for example when means for displacing the plastics material that are positionable on the receptacle of the sandwich sheet are used, the deformation of the metal cover layers of the sandwich sheet in the joining regions can be controlled via the embossing regions.
According to a further configuration of the apparatus, means for heating the core layer of the sandwich sheet can be provided, such that the apparatus as such is capable, even without additional further devices, of producing the joining regions after the means for displacing the plastics material have been preloaded.
Preferably, means for heating the core layer are provided, said means heating the core layer of the sandwich sheet by using ultrasonic vibrations. It has been found that the use of ultrasonic vibrations affords a particularly simple possibility of heating for example a sandwich sheet, which is positioned in a receptacle, over its entire surface by way of ultrasonic vibrations transmitted from the receptacle, such that uniform heating of the core layer of the sandwich sheet is achieved. In particular, it is possible as a result to prevent the entire apparatus from being heated fully.
Finally, according to a further variant, positioning means by way of which the means for displacing the plastics material can be positioned individually or in groups are provided. Via positioning means, for example simple profiles or templates, the positioning of the means for displacing the plastics material can be considerably simplified. In particular, the positioning means can also use form-fitting means of the receptacle in order to ensure the transmission of force to the sandwich sheet. Furthermore, guide means for positioning a plurality of means for displacing the plastics material can be used.
The apparatus 1 for producing at least one joining region comprises a receptacle 4 for the sandwich sheet 2, in which, in the present exemplary embodiment, a positioning aid 5 for positioning the sandwich sheet 2 is provided. Furthermore, the apparatus has means 6 for displacing the plastics material, said means being preloaded with a predetermined force. The means 6 for displacing the plastics material have a punch 8 that is mechanically preloaded via a spring 7, wherein the predetermined force which the punch 8 exerts on the sandwich sheet 2 is settable via a punch holder 9, the vertical position of which is variable. Furthermore, the predetermined force with which the punch 8 is intended to be pressed against the sandwich sheet can be additionally predetermined by the selection of a suitable spring 7. The means 6 for displacing the plastics material are arranged on the receptacle 4 of the sandwich sheet via guide pins 10. By screwing the means 6 for displacing the plastics material to the receptacle 4, for example via the guide pins 10, a suitable joint is produced, via a form-fit, between the means 6 for displacing the plastics material and the sandwich sheet 2 via the receptacle 4. In this position, the punch 8 presses against the joining region of the sandwich sheet 2 with a predetermined force perpendicularly to the surface of the sandwich sheet 2, said joining region corresponding in the present case to the peripheral region of the opening 3. If the core layer 2c of the sandwich sheet 2 is now heated sufficiently so that it softens, the plastics material is displaced out of the peripheral region of the opening 3 into the opening itself via the punch 8. In order to make this easier, the punch 8 additionally has an opening 8a through which the pressed-out plastics material can flow.
The exemplary embodiment of an apparatus schematically illustrated in
Finally,
An exemplary embodiment of the method according to the invention is illustrated in a schematic flow chart in
Method step 103 is schematically illustrated in
In a schematic sectional view in
In
Positioning means in which the means 6 for displacing the plastics material are arranged are illustrated in a perspective view in
Finally,
Number | Date | Country | Kind |
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10 2013 109 686 | Sep 2013 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/068330 | 8/29/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2015/032693 | 3/12/2015 | WO | A |
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Entry |
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Machine translation of EP1679147A2, Feller et al., pp. 1-25, translated on Feb. 28, 2017. |
Int'l Search Report for PCT/EP2014/068330 dated Nov. 26, 2014 (mailed Dec. 5, 2014). |
Number | Date | Country | |
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20160200041 A1 | Jul 2016 | US |