Patent ID: 12257744

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of a tool apparatus, shown schematically inFIG.1and designated therein by10, comprises a forming tool12. The forming tool12has a contact region14for a workpiece16. The workpiece16is fabricated into a composite material component part, for example a fibrous composite material component part.

The contact region14is adapted in its shape to conform to a component part that is to be fabricated. The contact region14is shown as having a curved shape inFIG.1.

In an embodiment, the forming tool12is made of an electrically conductive material, such as a metallic material, and is in particular made entirely of a metallic material. It is also possible for the material to be for example non-metallic and to comprise electrically conductive fibres, such as carbon fibres, for providing an electrical conductivity of in particular at least 104S/m and preferably at least 0.5·106S/m.

An induction heating apparatus18is provided. This comprises an inductive heating mat20and a high frequency source device22.

Examples of embodiments of an induction heating apparatus18and, in particular, of an inductive heating mat20are described in more detail below.

The workpiece16is placed against the contact region14of the forming tool12. Here, the workpiece16is positioned between the inductive heating mat20and the forming tool12; the inductive heating mat20is positioned in spaced relation to the forming tool12and is thereby also in spaced relation to the contact region14of the forming tool12.

To fabricate a component part from a composite material, a structure of prepreg layers is used as the workpiece16, for example. These are layers of woven fabric which are impregnated with a resin. The resin can be cured by heating the workpiece16.

In accordance with the invention, provision is made for the forming tool12to be non-contact heated via the inductive heating mat20. The inductive heating mat20, when it has a corresponding alternating current applied thereto, causes a heating region24of the forming tool12to heat up. Said heating region24is located in the contact region14in particular. The inductive heating mat20, when it has a corresponding alternating current flowing therethrough, creates an alternating magnetic field which induces eddy currents in the forming tool12and, in particular, in the heating region24of the forming tool12. The eddy current losses lead to heating at the heating region24and therefore at the contact region14. This in turn allows the workpiece16, placed in contact against the contact region14, to be heated up.

The inductive heating mat20, positioned in spaced relation to the tool12, heats up the tool12at the heating region24thereof.

In addition, provision may be made that, in response to the current flow occurring in the inductive heating mat20, the inductive heating mat20itself is heated due to ohmic losses. When the heating mat20is placed to rest on the workpiece16or when it is placed to communicate with the workpiece16through a heat-conductive layer, then the workpiece16can also be heated directly via the heating mat20. In such an embodiment, the workpiece16receives heat from two sides, namely from the heating region24(with the eddy currents occurring there being caused by the inductive heating mat20), and from ohmic heating of the inductive heating mat20at an opposite side thereof.

An exemplary embodiment of an induction heating apparatus, shown in a top view inFIG.2and designated therein by110, comprises a carrier112. Said carrier112is configured in the form of a mesh network.

The corresponding induction heating apparatus is described in DE 20 2015 100 080 U1. This document is incorporated herein and made a part hereof by reference in its entirety and for all purposes.

The mesh network112is, for example, a textile structure, such as a woven fabric or a knitted fabric.

The mesh network112comprises meshes of strands that are, in particular, of a rectangular or square shape. The strands are made from a thread material for example.

The carrier112having the mesh network is capable of being flexed as a whole.

Arranged on the carrier112is a coil apparatus114. The coil apparatus is formed by a current-carrying high-frequency Litz wire116. An inductive heating mat115corresponding to the heating mat20is thereby formed.

The high-frequency Litz wire116serves to carry a high-frequency alternating current. The high-frequency Litz wire116is a wire bundle of individual wires, each wire being electrically insulated from another wire by an insulating material. It is thereby possible to effectively increase the cross-sectional area over which electrical current flows when compared to a solid wire, reducing the influence of the skin effect. Furthermore, the crowding of charge carriers towards one side of the corresponding conductor caused by the magnetic field of a coil produced therefrom (proximity effect) is also reduced.

The bundle of wires in an embodiment is arranged in a sheath118which is of multi-layer configuration in particular.

For further details regarding the configuration of the high-frequency Litz wire116, reference is made to DE 10 2013 111 266 A1. This document is incorporated herein and made a part hereof by reference in their entirety and for all purposes.

The coil apparatus114has a high-frequency source device120associated therewith (cf.FIG.3). In use of the induction heating apparatus110, the individual wires in the bundle of wires of the high-frequency Litz wire116are operatively and electrically connected to corresponding terminals122a,122bof the high-frequency source device120.

To this end, the high-frequency Litz wire116has a terminal124at a first end thereof and has a terminal126at a second end thereof.

The high-frequency source device120serves to generate a high-frequency electromagnetic alternating field which is applied to the high-frequency Litz wire116. The frequency is at least 20 KHz and is typically approximately 150 kHz.

The high-frequency source device120comprises an electronic switching device for creating the corresponding alternating field when the primary electrical source is a direct current source.

The high-frequency Litz wire116is a linearly and flexurally flexible cable.

The coil apparatus114comprises a plurality of spiral-shaped windings128. These spiral-shaped windings128are arranged on the carrier112in rows130and columns132. For forming an area-type induction heating apparatus110, the spiral-shaped windings128are arranged on the carrier112in a uniformly distributed manner. The spiral-shaped windings128are formed on the high-frequency Litz wire116.

In particular, by virtue of the rows130and columns132, the spiral-shaped windings128are arranged on the carrier112in a two-dimensional grid. This two-dimensional grid is in particular a rectangular grid and is preferably a square grid.

A respective spiral-shaped winding128comprises a plurality of turns134which are related to a starting point136. A starting point136lies on a winding axis of the turns134of the spiral-shaped winding128. The winding axis is oriented perpendicularly to the carrier112. The spiral of a spiral-shaped winding128is defined as a curve receding from or approaching the starting point136, or winding axis. Here the recession can be increasing monotonically or the approach can be decreasing monotonically, or the recession and the approach can be increasing and decreasing in sections, respectively.

The arrangement of the spiral-shaped windings128on the carrier112determines the temperature distribution that will occur at an object that is to be heated.

The coil apparatus114is configured such that a homogeneous field distribution is achieved across the area of the coil apparatus114and such that, in the region between adjacent spiral-shaped windings128in particular, a “field cancellation” of the generated magnetic fields is prevented.

When a current is passed through a spiral-shaped winding128, the sense of rotation of the current flowing therethrough is in the same sense within a spiral-shaped winding128. In accordance with the invention, it is provided that in both rows130and columns132, the sense of rotation for the current flow through adjacent spiral-shaped windings138a,138band140a,140brespectively is in opposite senses. The described cancellation of the electromagnetic field can thereby be prevented.

The spiral-shaped windings128of the coil apparatus114are electrically connected in series. In the illustrated exemplary embodiment (FIGS.2,3), the spiral-shaped windings128are serially connected, one after another, in a row130. The corresponding rows130are themselves serially connected.

The coil apparatus114comprises two types of spiral-shaped windings128, namely a first type in which corresponding turns134run from the respective starting point136outwards at an increasing distance (at least in sections thereof) from the starting point136. InFIG.3, the spiral-shaped windings138aand140aare of the first type.

In the spiral-shaped windings128of a second type, the corresponding turns134run towards the starting point136, going from the outside to the inside, at a decreasing distance (at least in sections thereof) to the starting point136. In the exemplary embodiment in accordance withFIG.3, the spiral-shaped windings138band140bare of the second type.

Here the corresponding winding direction of the first type and of the second type is related to the corresponding flow of current.

In a row132, the spiral-shaped windings128of the first type and of the second type are arranged in an alternating manner.

Likewise, the spiral-shaped windings128of the first type and of the second type are arranged in an alternating manner within a column132.

This results in that both within a row130and within a column132, with respect to adjacent spiral-shaped windings128, when current flow occurs, the sense of rotation for the current is in opposite senses, in an alternating manner.

The respective spiral-shaped windings128comprise peripheral winding sections that face towards adjacent spiral-shaped windings. As an example, the spiral-shaped winding138ahas a peripheral winding section142awhich is adjacent to a corresponding peripheral winding section142bof the spiral-shaped winding138b.

Here the peripheral winding sections142aand142bare arranged such that, when current flow occurs in the coil apparatus114, they will carry the current in at least approximately the same direction.

A “cancellation” of the generated electromagnetic fields is thereby prevented in the corresponding region.

Correspondingly, peripheral winding sections144a,144bof spiral-shaped windings140a,140badjacent in a row are arranged such that they will carry the current in at least approximately the same direction.

The arrangement of the peripheral winding sections142a,142b,144a,144bis achieved by corresponding arrangement of spiral-shaped windings128of the first type and of the second type, which arrangement is an alternating arrangement in both the rows130and the columns132.

For establishing the series connection of the spiral-shaped winding128, adjacent spiral-shaped windings128within a row130are electrically interconnected to each other. Within a row130, a first type of connection146is provided in which starting points136of adjacent spiral-shaped windings128are connected together (by a corresponding section148of the high-frequency Litz wire116).

In a second type of connection150, the connection between adjacent spiral-shaped windings128is realized via a peripheral winding section152.

The first connection type146and the second connection type150succeed each other in an alternating manner between adjacent spiral-shaped windings128within a row130.

A third electrical connection type154is provided for effecting electrical connection between adjacent rows130. Here electrical connection is made between a starting point136and a peripheral winding section156.

The spiral-shaped windings128are arranged in the form of flat coils on the carrier112by a corresponding “laying” of the high-frequency Litz wire116.

In an exemplary embodiment, the spiral-shaped windings128(FIGS.2,3) have straight sections158. The spiral-shaped winding128is thereby not one that recedes from the corresponding starting point136in a monotonically increasing manner or that approaches same in a monotonically decreasing manner. But instead, with respect to these sections, the recession or approach from or to the corresponding starting point136increases or decreases in sections, respectively.

In the exemplary embodiment of spiral-shaped windings128having straight sections158, it is preferred for adjacent peripheral winding sections142a,142band144a,144b, respectively, to be oriented parallel to each other. This results in parallel current directions there.

It is, in principle, possible for adjacent spiral-shaped windings to be spaced apart from one another and for their corresponding adjacent peripheral winding sections to be spaced apart from one another.

This is how the spiral-shaped windings128in accordance with the exemplary embodiment ofFIGS.2,3are arranged.

It is also possible for adjacent spiral-shaped windings to overlap each other, thereby placing turns in overlying relationship. (The high-frequency Litz wire116is insulated towards the outside.)

It is thereby possible for peripheral winding sections that are adjacent to each other to cross each other (in the projection onto the carrier112).

Each spiral-shaped winding128of the coil apparatus114comprises a plurality of turns134. Preferably, each spiral-shaped winding128has at least two and preferably at least three turns134. It is further advantageous for each spiral-shaped winding128to comprise no more than eight and preferably no more than seven turns134.

It is, in principle, advantageous for the spiral-shaped windings128of at least the same type to be of identical configuration with respect to their number of turns and outer envelope area.

The mesh network has a first side168and a second side opposing the first side. It is preferred for the high-frequency Litz wire116to be arranged exclusively or for the most part on the first side168.

The corresponding winding axes of the spiral-shaped windings128are transverse and in particular perpendicular to the carrier112.

The high-frequency Litz wire116is held to the carrier112, and is in particular sewn in place together therewith, by way of one or more holding threads170. Such fixation via holding threads also provides the winding structure of the coil device114on the carrier112.

With respect to the fixation of the coil device114to the mesh network of the carrier112via holding threads, reference is made to DE 10 2013 111 266 A1. This document is incorporated herein and made a part hereof by reference in its entirety and for all purposes.

Provision may be made for the coil apparatus114to have associated therewith a magnetic flux concentrator layer which is in particular arranged on the side of the carrier112that faces away from the first side168. Such a magnetic flux concentrator layer which is made of a material of corresponding magnetic permeability serves to concentrate the magnetic flux generated during operation of the coil apparatus114into a field in front of the first side168.

Furthermore, outer electrical insulating layers can be provided between which the carrier112having the coil apparatus114fixed thereto and, optionally, the magnetic flux concentrator layer are then arranged. Such outer electrical insulating layers are, for example, made of a silicone material.

The outer electrical insulating layers and the magnetic flux concentrator layer are of flexible configuration.

The carrier112is capable of being flexed. The high-frequency Litz wire116can be flexed together with the carrier112. The connection of the high-frequency Litz wire116to the carrier112via the one or more holding threads provides the capability of flexing. The carrier112together with the coil apparatus114forms a flexible heating mat172.

The induction heating apparatus110can be formed into a variety of different geometric shapes. For example, single curvature shapes or multiple curvature shapes are possible.

The induction heating apparatus is configured as an area induction heating apparatus in which, by the arrangement of the spiral-shaped windings128, regions having electromagnetic fields that cancel each other out are avoided. It is thereby possible to achieve homogeneous heating with high flexibility.

The spiral-shaped windings128on the carrier112form field-generating islands. By a corresponding configuration of the islands, the “heating surface” can, in principle, be arbitrarily extended or its size can be adjusted. This is then achieved by a corresponding “laying” of the high-frequency Litz wire116on the carrier112.

It is also possible for the induction heating apparatus to comprise, as a heating mat, a coil apparatus having a plurality of spiral-shaped windings which are arranged in rows and/or columns, wherein the at least one coil apparatus is formed by a tube through which a heat transfer medium can be flowed.

The tube can be arranged on a carrier, or a carrier-free heating mat, and in particular, a flexible (and also shape-retaining, flexible) heating mat can be formed by the tube. In this context, reference is made to the German utility model application No. 20 2018 103 385.9 of Jun. 15, 2018 of the same applicant. This document is incorporated herein and made a part hereof by reference in its entirety and for all purposes.

It is, in principle, possible for the corresponding inductive heating mat20to be of a shape-retaining configuration. Here the shape retention can be permanent or it can be variable. For example, where the coil apparatus is formed by a tube, the corresponding heating mat can easily be formed to a shape-retaining configuration.

The heating mat can be of flexible configuration or configured with a capability of being flexed. Here it can be configured to be flexurally limp or it can be configured to be flexurally flexible in the manner of a plastic deformability. For example, if the carrier112is correspondingly configured, a flexurally flexible configuration can be achieved. Thus, the heating mat20can also be flexurally flexible and shape-retaining.

A further exemplary embodiment of a tool apparatus, shown schematically inFIG.4, is constructed in generally the same manner as the tool apparatus10having the forming tool12and the inductive heating mat20.

In this embodiment, at least one susceptor26is provided, said susceptor26being positioned between the inductive heating mat20and the forming tool12and hence the contact region14. The susceptor26forms a corresponding intermediate layer between the inductive heating mat20and the workpiece16.

The (at least one) susceptor26serves to assist the heating process.

By way of example, the susceptor26is formed as a metal sheet or metal foil. It is also adapted to the shape of the workpiece or the component part that is to be produced.

Here, the susceptor26is configured in such a manner that it is permeable to the electromagnetic fields of the inductive heating mat20such that the inductive heating mat20can inductively heat the corresponding heating region24at the forming tool12. Furthermore, the susceptor26is configured such that it can also have eddy currents induced therein so that eddy current losses occur, thereby enabling the workpiece16to also be inductively heated from the side of the inductive heating mat20via the susceptor26.

The inductive heating mat20thereby inductively heats the susceptor26and the forming tool12. In addition, by corresponding adjustment of an operating point, the susceptor26can further be heated by ohmic losses via the inductive heating mat20.

In a further exemplary embodiment of a tool apparatus, shown schematically inFIG.5and designated therein by28, there is provided a forming tool30made of an electrically non-conductive material, such as a non-metallic material. A layer32of electrically conductive material, such as a metallic material, is arranged on the forming tool30. In an embodiment, this layer32is a coating of a metallic material that is applied to a support region34of the forming tool30. For example, a corresponding metallic layer is electrodeposited on the support region34.

In an alternative embodiment, the layer32of electrically conductive material is placed upon the forming tool30; by way of example, the layer32is placed thereon in the form of a metallic foil.

The workpiece16is positioned on the layer32. The layer32thereby forms the contact region14of the forming tool30.

As above, an inductive heating mat20is positioned in spaced relation to the forming tool30including the layer32, i.e. the inductive heating mat20is in spaced relation to the layer32. The workpiece16is positioned between the inductive heating mat20and the layer32.

The inductive heating mat20induces eddy currents in the layer32of electrically conductive material. No eddy currents are generated in the forming tool30outside the layer32.

The layer32thereby forms the heating region24.

Otherwise, the tool apparatus28works in the same manner as discussed for the tool apparatus10. In particular, one or more susceptor layers can be used with the tool apparatus28.

A further exemplary embodiment of a tool apparatus, shown inFIG.6, is constructed in generally the same manner as the tool apparatus10. Like reference numerals indicate like elements.

A punch36is provided as a counter-element to the corresponding forming tool12. The workpiece16can be formed on a first side38thereof via the forming tool12. It can be formed on a second, opposite side40thereof via the punch36.

Here, it is possible for the inductive heating mat20to be integrated into the punch36or to be part of the punch. Preferably, the punch36is then not made of a metallic material, or the punch36is made of metallic material in a region thereof that is separated by a sufficiently large distance from the inductive heating mat20.

In accordance with the invention, a tool apparatus is provided in which a heating region24is heated against which a workpiece16is in contact. The heating region24is heated by inductive heating via eddy current losses via an inductive heating mat20.

For example, this can also be utilized as a retrofit application for heating a pre-existing forming tool12without need for having heating cartridges, or the like, integrated thereinto.

Component parts formed of composite materials can be produced on a corresponding tool apparatus10without the need for employing an autoclave.

Sheet-like component parts in particular can be produced on a forming tool12.

The use of an inductive heating mat20provides great flexibility in shaping the component part. By the inductive heating of the heating region24, heat from the heat source reaches the component part to be heated not only by heat conduction.

The forming tool12can be configured independently of the heating because, via the spaced inductive heating mat20, the heating is contactless. Use of the induction heating technology as a retrofit to a forming tool12is possible.

Near-surface heating is possible.

Moving workpieces16, for example, can also be easily heated.

The inductive heating mat20, adapted to a size of a component part that is to be fabricated, allows localized and near-surface heating to be achieved on the forming tool12.

If the inductive heating mat20is operated at a corresponding operating point, an ohmic resistance at the inductive heating mat20and a corresponding ohmic heat can additionally be utilized to heat a workpiece16.

The component part to be produced can be a composite material component part formed entirely of composite, or it can be a component part comprising a composite material component. For example, a tool apparatus in accordance with the invention can also be employed for joining together a metal part and a composite material component part for example.

LIST OF REFERENCE CHARACTERS

10tool apparatus12forming tool14contact region16workpiece18induction heating apparatus20inductive heating mat22high frequency source device24heating region26susceptor28tool apparatus30forming tool32layer of electrically conductive material34support region36punch38first side40second side110induction heating apparatus112carrier114coil apparatus115inductive heating mat116high-frequency Litz wire118sheath120high-frequency source device122aterminal122bterminal124terminal126terminal128spiral-shaped winding130row132column134turn136starting point138aspiral-shaped winding138bspiral-shaped winding140aspiral-shaped winding140bspiral-shaped winding142aperipheral winding section142bperipheral winding section144aperipheral winding section144bperipheral winding section146first connection type148section150second connection type152peripheral winding section154third electrical connection type156peripheral winding section158straight section170holding thread172heating mat