Frame

Abstract

The present invention relates to a frame (1) for tensioning a flexible, preferably textile painting medium (5), such as a canvas, to a kit for a frame, to a combination of a frame and a painting medium, and to a kit for a combination of a frame and a painting medium. The frame comprises at least two frame elements (2), a connecting means (6) for connecting the frame elements, and a tensioning means (3, 10) for adjusting the relative arrangement of the frame elements with respect to each other. At least one of the frame elements comprises a composite of at least two material components, the first material component (7) comprising a wood, paper or plastic-based material and the second material component (8) comprising a metal-based material.

Description

[0001] Aylin Bönneken

[0002] Our reference number: 253614EP

[0003] Frame

[0004] SUBJECT OF THE INVENTION

[0005] The present invention relates to a frame for stretching a flexible, preferably textile, painting medium, such as a canvas, a kit for a frame, a combination of a frame and a painting medium, and a kit for a combination of a frame and a painting medium.

[0006] BACKGROUND OF THE INVENTION

[0007] In the art and exhibition trade, stretcher frames are commonly used, typically consisting of four frame strips mitered at their ends and joined together to form a rectangular or square frame. The canvas is stretched over this frame and secured on the back. To allow for initial or subsequent tensioning of the canvas, small wooden wedges are driven into the inner corner joints of the frame. This process usually requires the use of a tool, such as a hammer. Driving in the wedges spreads the frame strips apart, slightly increasing the outer dimensions of the frame and thus tensioning the canvas.

[0008] A disadvantage of these stretcher bars, known from the prior art, is that the material used, usually wood, is a natural material and reacts to changes in environmental conditions such as humidity and temperature. Wood, in particular, tends to absorb or release moisture, which can lead to swelling or shrinkage and thus to warping or "curving" of the individual frame members. This warping results in the canvas losing its tension, wrinkling, or even the entire frame losing its flatness, so that it no longer lies flat against the wall. This poses a significant problem, especially in professional contexts, for example, at exhibitions or in the art market, where artworks are transported and presented under varying climatic conditions. Therefore, to adequately present artworks on stretcher bars, constant monitoring and manual re-tensioning of the canvas has been necessary until now.This process is not only time-consuming but also requires carrying tools to adjust the wedges. The latter is particularly inconvenient for artists who want to ensure their work is presented in the best possible light at an exhibition. Furthermore, retensioning also carries the risk of damaging the canvas—and thus the artwork—or the frame through uneven or excessive tensioning.

[0009] The problem of warping in stretched canvas frames has been known for a long time, yet there are few suitable solutions in the prior art. For example, German patent DE 336164 C discloses a method for stiffening a wooden picture frame by inserting a frame formed from an upright metal rail into a groove on the back of the frame to counteract warping of the wooden frame itself. However, such an approach is unsuitable for stretched canvas frames, as the rigid connection prevents the necessary movement of the frame members relative to each other for retensioning. The targeted expansion of the frame using wedges or similar means is therefore no longer possible, thus negating the central function of a stretched canvas frame. This known stiffening solution is therefore not suitable for satisfactorily solving the specific problems of a stretched canvas frame.

[0010] Consequently, there is a need for an improved stretcher frame that offers both high dimensional stability – no “throwing” – and retains the basic functionality of a stretcher frame, namely the tensioning of canvases.

[0011] TASK

[0012] The present invention is therefore based on the objective of providing a frame for clamping a painting medium which has high dimensional stability and / or enables simple, preferably tool-free clamping, so that the disadvantages of the prior art are overcome.

[0013] DESCRIPTION OF THE INVENTION

[0014] The problem is solved with a frame having the features of claim 1.

[0015] The frame according to the invention serves to stretch a flexible painting medium, in particular a textile painting medium such as a canvas, and thus fulfills the basic functionality of a stretcher frame known from the prior art. The frame has a modular construction and comprises at least two frame elements, e.g., in the form of frame strips, which together form the outer contour of the frame. This contour can follow conventional shapes such as square, rectangle, circle, or oval, but can also assume unusual shapes such as polygonal, asymmetrical, or free-form contours. Connecting means are provided for joining the frame elements. These connecting means can be an integral part of the frame elements (e.g., by appropriate shaping of the ends), be materially and form-fittingly connected to them, or be designed as a separate component.The connection between the frame elements is preferably detachable and / or movable to allow adjustment of the frame elements relative to each other. For targeted adjustment of the relative arrangement of the frame elements, thereby enabling tensioning or retensioning of the painting medium, the frame also includes tensioning devices.

[0016] Optionally, the frame according to the invention can additionally include stiffening elements. Such elements, for example in the form of cross braces, central struts, or crosses, serve to further stabilize the frame. Such stiffening elements can be used, particularly in large frame formats, to further increase the overall stiffness.

[0017] The core of the invention lies in the specific structure of at least one of the frame elements. This comprises a composite consisting of at least two components, which are preferably joined together at least partially over a surface and preferably by a material bond, in particular by gluing. A material bond, such as gluing, ensures a permanent and strong connection of the components to form a quasi-monolithic component.

[0018] Preferably, the connecting surface is > 10%, more preferably 20%, more preferably > 50%, and particularly preferably > 80% of the total surface area of ​​the smaller of the two connected components.

[0019] This composite material comprises at least a first material component and a second material component, wherein the first material component comprises a wood-, paper-, or plastic-based material, preferably a wood-based material such as solid wood, plywood, or a wood-based composite, while the second material component comprises a metal-based material, such as a metal or a metal alloy. Aluminum is particularly advantageous here due to its low weight combined with high stiffness and corrosion resistance. In the context of the invention, "based" of the first material component means that the material component comprises or consists of a wood-, paper-, or plastic-based material, or a combination thereof, wherein the sum of the weight fraction of the component(s) is at least 50%, preferably 70%, and most preferably 100%.

[0020] "Paper material" in this context refers to a material formed from fiber-based raw materials, produced by dewatering and solidifying a fibrous material. This includes all web, sheet, or board materials made from fibers, including thin paper webs, cardboard, corrugated board, and other fiber-based molded parts or composite materials.

[0021] In the context of the invention, "based" means that the second material component comprises a metal or a metal alloy or a combination of the aforementioned, or consists of this material or these materials, wherein the sum total weight fraction of the component(s) is at least 50%, preferably 70%, and most preferably 100%.

[0022] The components of the composite can have any geometric shape. For example, the components can be designed as planar layers that are assembled into a multi-layered structure (a "sandwich structure"). Alternatively, the second material component can be a profile, such as a square tube, which is inserted into a milled groove in the first material component. Another possibility is that one component is designed as the core and the other as the shell, such as a wooden core enclosed by a thin metal shell, or vice versa. It is also conceivable that a metal strip, as the second material component, is attached only to one side of a first material component, such as a wooden strip, without covering its entire surface.

[0023] For the purposes of this invention, a "composite" refers to a material system consisting of at least two different, macroscopically identifiable individual components—for example, wood and metal—which may preferably be materially, form-fitted, or force-fitted and together possess mechanical or functional properties that neither of the individual components could achieve on its own. For the purposes of this invention, a "painting medium" refers to a support material for artistic creation. In particular, the term refers to flexible, planar materials that can be stretched over a frame to create a smooth and stable surface for painting or other artistic techniques. Typical examples of such painting media are textile fabrics such as canvas, for example, made from linen, hemp, or jute fibers, cotton fabrics, muslin, or even modern synthetic fabrics.However, the term is not limited to these examples and can, in principle, encompass any flexible material that is stretched over a frame for artistic purposes.

[0024] For the purposes of this invention, "frame elements" refers to the individual, often elongated strips or legs from which the entire frame is modularly assembled. These frame elements are usually straight, but they can also be angled or curved to create, for example, oval or other shaped frames. Typically, four such frame elements are joined to form a rectangular, e.g., square, frame; however, the invention is not limited to this number or shape.

[0025] For the purposes of this invention, "connecting elements" refers to devices that enable the frame elements to be connected to one another at their ends. This can be achieved by form elements permanently integrated into the frame elements (e.g., mortise and tenon joints) or by detachable, separate components (e.g., external springs such as knurled flat dowels). It is essential that the connecting elements allow for a relative displacement of the frame elements relative to one another in order to accommodate the expansion of the frame.

[0026] For the purposes of this invention, "tensioning devices" refer to devices by which a force can be exerted on the frame elements to push them apart and thus expand the frame in a controlled manner. This serves to tension or retension the painting medium. A classic example of this is wedges that are driven into the corner joints of the frame elements.

[0027] In the context of the invention, "stiffening elements" refer to optional components that serve to provide additional stabilization of the frame and are not primarily required for the frame's functionality. These include, in particular, cross braces (trusses) or center crosses that are inserted between opposing frame elements to prevent deflection of the frame elements, especially in the case of large-format frames—typically starting at a size of 60 x 80 cm—and to increase the overall stiffness of the structure. The composite structure of the frame elements according to the invention achieves a number of significant technical advantages.

[0028] First, the composite structure gives the frame elements significantly higher dimensional stability and flexural rigidity compared to conventional wooden frame elements. The second material component acts as a stabilizer, effectively counteracting the tendency of the first material component to warp, twist, or buckle in response to fluctuations in ambient temperature and humidity. The planarity of the entire frame is thus maintained even over long periods and under changing climatic conditions. The solution according to the invention can therefore prevent or at least delay the wrinkling or loss of tension of a painting medium stretched across the frame. This significantly reduces the maintenance required for retensioning, making the frame according to the invention a more reliable solution, particularly for exhibitions, than the conventional stretcher frames used to date.

[0029] At the same time, the fundamental and essential functionality of a stretcher frame—namely, the ability to expand in order to tension the painting medium—is fully retained. Since the dimensional stability is achieved within the individual frame elements, but the frame as a whole still consists of at least two elements movable relative to each other, it can be expanded in a controlled manner using the tensioning devices. The invention thus combines a dimensionally stable structure with the adjustability and expandability of the frame necessary for tensioning the painting medium.

[0030] A further advantage is that the appearance and handling of the frame according to the invention hardly change compared to a classic stretcher frame. In particular, when using a wood-based first material component, the classic look and feel of a wooden frame is retained. Furthermore, the handling for the user, for example an artist, does not change significantly compared to traditional solutions. Therefore, no adjustment is required for the user.

[0031] An advantageous further development of the invention provides that the composite comprises a multi-layered structure with at least two layers, preferably at least partially planar and preferably materially bonded to one another, in particular glued, wherein the first material component is a first planar material component layer comprising or consisting of a wood-, paper-based or plastic-based material and wherein the second material component is a second planar material component layer comprising or consisting of a metal-based material, preferably aluminum.

[0032] A multi-layered structure is particularly advantageous from a manufacturing perspective, as it allows the use of standardized semi-finished products such as wood panels and metal sheets. These can be joined together using established processes such as gluing or pressing. This enables efficient and cost-effective production with high repeatability.

[0033] The at least partially planar and preferably material-bonded connection of the layers also offers advantages from a mechanical perspective: Optimal transmission of shear forces between the layers is achieved, resulting in a highly integrated composite component with excellent bending and torsional stiffness. For example, in a wood-based first planar material layer, any tendency to warp induced by fluctuations in humidity is immediately absorbed and compensated by the entire surface of the dimensionally stable second planar material layer made of metal or a metal alloy. This large-area force distribution is significantly more effective than a point or line connection.

[0034] A multi-layered structure thus combines maximum dimensional stability with efficient and cost-effective production.

[0035] An advantageous further development of the invention provides that the multilayer structure has a third planar material component layer comprising or consisting of a wood-, paper- or plastic-based material, wherein the second planar material component layer, i.e. the metal-based layer, is arranged between the first and the third planar material component layer.

[0036] This arrangement creates a classic sandwich structure (for example, wood-metal-wood), in which the metal-based layer acts as the core and is enclosed on both sides by wood-, paper-based, or plastic-based layers. This symmetrical construction is particularly effective in preventing warping of the frame element. Forces arising from the natural movement of the wood-, paper-based, or plastic-based layers, especially in the case of wood-based layers (swelling or shrinkage) due to changes in ambient humidity, act on both sides of the central metal-based layer. Their potentially deforming effect, such as bending or twisting, is thus largely compensated and neutralized, further maximizing the dimensional stability of the frame element.

[0037] When using wood-based layers, a further advantage of this embodiment is that the frame element has the look, feel, and workability of wood or a wood-based material on both main surfaces. This not only preserves the traditional appearance of a stretcher frame but also facilitates handling of the frame according to the invention, for example, when attaching fasteners for the canvas.

[0038] An advantageous embodiment of the invention provides that the front and back sides are at least partially different from each other, with the front side preferably having a raised and rounded, in particular bead-shaped, outer edge.

[0039] This different design of the front and back of the frame according to the invention primarily serves to meet different functional requirements. For example, the front, which faces the painting medium, can have a design optimized for contact with the painting medium, such as a smooth surface or a specific shape. The back, on the other hand, can be simpler and, for example, provide grooves or recesses for attaching fasteners for wall mounting or for accommodating stiffening elements.

[0040] In an advantageous embodiment, the front side has a special shape or profile, namely a raised and rounded, in particular bead-like, outer edge.

[0041] This design fulfills an important technical function: the raised outer edge ensures that the stretched painting medium rests exclusively on this edge and maintains a defined distance from the rest of the frame's surface. This effectively prevents the inner edge or the flat structure of the frame from showing through on the front of the painting medium, especially when paint is applied or the medium ages. The rounded, beaded shape of the edge also ensures gentle contact with the painting medium. This minimizes the risk of damaging the medium during stretching—where the medium inevitably rubs against the outer edge—and prevents creases in the medium. In the case of a painting medium that has already been worked on—that is, one that bears an artwork—this special design of the outer edge on the front also prevents damage to the artwork, such as chipping.

[0042] Furthermore, this profiling improves air circulation behind the painting medium. The gap created by the profiling between the painting medium and the flat front surface of the frame element allows for air exchange. This can help prevent the formation of moisture pockets and thus enables even drying of the paint on the stretched painting medium.

[0043] An advantageous further development of the invention provides that the at least two frame elements are straight, angled or curved and preferably each have a miter cut at their ends.

[0044] Straight frame elements represent the simplest manufacturing method. By connecting four frame elements, they can be used to produce classic square or rectangular frames, or even polygonal frames such as hexagonal or octagonal shapes. Their simple geometry allows not only for easy and cost-effective production, but also for uncomplicated and space-saving packaging, for example, for shipping as a kit.

[0045] Angled or curved frame elements, while potentially more complex to produce and ship, can simplify frame assembly. For example, a complete rectangular or round frame can be assembled from just two L-shaped or semicircular frame elements. This can significantly simplify assembly for the end user and increase the overall stability of the frame, as there are fewer potentially moving joints.

[0046] Regardless of whether the frame elements are straight, angled, or curved, they preferably each have a miter cut at their ends to be joined, for example, a cut at a 45° angle to the longitudinal axis in the case of a right-angled frame, so that two frame elements can be joined to form a clean and interlocking corner. This creates an aesthetically pleasing, seamless appearance at the corner joint.

[0047] Furthermore, the miter cut creates a large and precisely fitting contact surface between the two frame elements. This surface acts as a precise guide during the frame's expansion by the clamping devices, ensuring that the frame elements remain perfectly aligned and do not tilt or twist during clamping. This guarantees stable and controlled frame expansion and contributes to the overall stability of the corner joint.

[0048] An advantageous further development of the invention provides that the wood-based material comprises wood, a wood-based material such as MDF or HDF; a wood-plastic composite material or combinations of the aforementioned.

[0049] The use of solid wood offers the classic look and feel associated with traditional stretcher frames. Preferably, lightweight and relatively dimensionally stable woods such as pine, spruce, or fir are used, which have a good strength-to-weight ratio. For particularly high-quality frames, woods such as linden or abachi can also be used, which are known for their low tendency to warp, but are comparatively expensive.

[0050] Engineered wood products, such as medium-density fiberboard (MDF) or high-density fiberboard (HDF), offer the technical advantage of high homogeneity and dimensional stability. Because these materials are industrially manufactured, they exhibit less tendency to react to fluctuations in humidity with swelling or shrinkage compared to solid wood. These materials can therefore further increase the dimensional stability of the frame element. Moreover, they represent a cost-effective alternative to solid wood.

[0051] MDF is a wood-based material made from very fine wood fibers bonded with resin, which are pressed into a board under pressure and heat. HDF, on the other hand, is manufactured using a similar process but under higher pressure, resulting in even greater density, hardness, and strength.

[0052] Wood-plastic composites (WPCs) combine wood fibers with a plastic component. This results in a material with extremely high resistance to moisture and therefore excellent dimensional stability. Frame elements containing WPCs are particularly durable and insensitive to environmental influences, as well as resistant to pests and fungal attack. However, they are more complex to manufacture and therefore usually more expensive than pure wood-based materials.

[0053] The preferably used wood-based material has a density in the range of 0.5 g / cm³. 3 up to 1.5 g / cm³ 3 preferred. A particularly advantageous range lies between 0.8 g / cm³. 3 and 1.0 g / cm² 3. This density range, typical of high-quality wood-based materials such as MDF or HDF, represents an optimal compromise: The material is dense enough to ensure high strength and stability, but not so dense that the overall weight of the frame becomes impractically high.

[0054] An advantageous further development of the invention provides that the composite comprises one or more planar material component layers comprising or consisting of a wood-, paper- or plastic-based material, which together have a thickness Sw, and one or more planar material component layers comprising or consisting of a metal-based material, which together have a thickness SM, wherein the following applies to the ratio of SM TO SW:

[0055] 0.01 < < 0.3.

[0056]

[0057] This ratio is a critical parameter for the design of the frame element, as it quantifies the balance between the stabilizing effect of the metal-based layer(s) and the properties of the wood-, paper-based or plastic-based layer(s), such as weight, machinability and appearance.

[0058] The lower limit of the ratio of 0.01 ensures that the metal-based layer(s) have a sufficient minimum thickness relative to the wood-, paper-, or plastic-based layer(s) to guarantee effective stabilization. If the ratio is below this value, the metal-based layer(s) would be so thin compared to the wood-, paper-, or plastic-based layer(s) that they would not be able to offer any significant resistance to any warping forces in the wood-, paper-, or metal-based material, for example, those induced by fluctuations in humidity. The technical benefit of increased dimensional stability would therefore not be achieved.

[0059] The upper limit of 0.3 ensures that the frame element retains its character as a wood-, paper-, or plastic-based composite component. A ratio above this value would result in a disproportionately high metal content. This would lead to an undesirably high overall frame weight, significantly higher material, processing, and transport costs, as well as more difficult machining, since the metal's properties would dominate. The frame would lose its lightweight, wood-like character. The specified range of 0.01 to 0.3 thus defines an optimal technical and economic compromise.Within this area, the metal-based layer(s) are strong enough to significantly improve the dimensional stability of the frame element, while the proportion of wood-, paper- or plastic-based material remains large enough to ensure a moderate overall weight, good machinability and the desired feel and appearance.

[0060] In a further advantageous embodiment, the frame element has a total frame thickness, measured at its inner edge, ranging from 5 mm to 60 mm. A thickness of less than 5 mm would offer insufficient stability, while a thickness greater than 60 mm would result in an unwieldy and heavy frame for most applications. Standard thicknesses of 19 ± 2 mm and 44 ± 2 mm have proven particularly advantageous, as they offer an excellent balance of stability and manageability for a wide range of frame sizes; preferably, the total frame thickness is between 17 and 46 mm. To this basic thickness, the height of the bead-like profile is added at the outer edge, which can be up to 15 mm, preferably about 5 mm, to ensure the distance between the painting medium and the frame surface.

[0061] The thickness of a single wood-, paper-, or plastic-based layer within the multilayer structure is preferably in the range of 2 to 30 mm, and particularly preferably from 10 to 25 mm. This range ensures that the wood-, paper-, or plastic-based layer is thick enough to guarantee the desired appearance and machinability, while also being in a reasonable proportion to the stabilizing metal-based layer and the overall frame thickness.

[0062] The width of the frame elements, i.e., the measurement from the inner to the outer edge, is preferably 1 to 10 cm, particularly preferably 4 to 8 cm. These widths ensure a sufficient support surface for the painting medium and high inherent stability of the frame element against bending, especially in larger formats.

[0063] An advantageous further development of the invention provides that the thickness SM of one or more planar material component layers comprising or consisting of a metal-based material is 0.5 to 10 mm, preferably 1 to 5 mm, particularly preferably 1.5 to 3 mm.

[0064] An insufficient thickness of the metal-based layer(s) (below 0.5 mm) might not provide sufficient stiffness to effectively counteract the warping forces of the wood-, paper-, or plastic-based layer(s), thus preventing frame warping. Therefore, the minimum thickness of the metal-based layer(s) is preferably 0.5 mm, more preferably 1 mm, and most preferably 1.5 mm.

[0065] At the same time, an excessive thickness of the metal-based layer(s) (over 10 mm) would be disadvantageous, as this would lead to a disproportionately high frame weight and significant material and processing costs. Therefore, the maximum thickness of the metal-based layer(s) is preferably 10 mm, more preferably 5 mm, and most preferably 3 mm.

[0066] For a wide range of common frame sizes, a thickness of 1 to 5 mm for the metal-based layer(s) has proven particularly advantageous. This range achieves an optimal compromise: the stabilizing effect is already excellent, while the additional weight and costs remain within an economically and practically reasonable range. A thickness of 1.5 to 3 mm is considered especially preferred, as it represents an ideal balance between outstanding dimensional stability and moderate weight. However, in the case of very large frames subject to particularly high static requirements, thicker layers may be necessary to ensure the required stability.

[0067] An advantageous further development of the invention provides that the at least two frame elements are connected to each other by means of the connecting means via a plug connection, such as a slotted and tenon connection, external spring connection, lap joint or galvanizing.

[0068] A plug-in connection is purely mechanical in nature; that is, the components interlock due to their geometric shape and are held together without the need for a material bond such as adhesive at the connection point. This is crucial to ensure the relative sliding motion of the frame elements relative to each other, which is necessary for tensioning the frame.

[0069] For example, the joint can be a mortise and tenon joint, where a mortise is cut into one frame member and a corresponding tenon is cut into the frame member to be joined. This classic joinery technique is very strong, ensures precise alignment of the elements, and prevents the corner from twisting. Another option is the spline joint, where a groove is milled into the ends of both frame members, and a separate component, the spline, is inserted into both grooves to create the connection. This technique allows for a precise and stable joint that is easy to implement in manufacturing.

[0070] The use of special end-grain connectors is also conceivable. These are mechanical fittings or connectors specifically designed for the stable connection of end-grain surfaces and often allow for easy assembly. "End-grain surfaces" in this context refers to the cut surfaces at the end of a piece of wood that run perpendicular to the longitudinal axis or grain direction of the wood.

[0071] Furthermore, the joint can be executed as a lap joint. In this case, the ends of the frame elements to be joined are each trimmed by half their material thickness, so that they form a flush, flat connection when joined. This type of joint is very easy to manufacture and offers a large contact area, which contributes to good stability of the corner joint.

[0072] Furthermore, the connection can be achieved through galvanizing, where the ends of the frame elements are fitted with interlocking, wedge-shaped prongs (dovetail jointing) or straight fingers (finger jointing). This type of connection offers very high mechanical strength, while, with appropriate design, still allowing the necessary movement in the expansion direction for clamping.

[0073] The common technical advantage of these plug connections is that they create a stable and angularly accurate corner connection, which at the same time enables the controlled expansion of the frame elements by the clamping means, which is essential for the function of a stretcher frame.

[0074] An advantageous embodiment of the invention provides that the at least two frame elements are connected to each other by means of the connecting means via a spring connection, wherein the connecting means are springs, in particular flat or round dowels, preferably made of wood or aluminum.

[0075] A splined connection is an optimal solution for ensuring the precise and smooth movement of the frame elements required for tensioning the frame. Compared to other plug-in connections, such as integral mortise and tenon joints or galvanizing, this type of connection also offers significant advantages in manufacturing and handling. Instead of laboriously forming the ends of the frame elements into tenons or pins, only simple, identical grooves need to be milled. This significantly simplifies and reduces the cost of the manufacturing process. Separate splined connectors, such as knurled flat dowels or round dowels, are then inserted into the corresponding grooves to create the connection between the frame elements. This makes assembly particularly easy for the end user.

[0076] Another advantage of the external spring connection is that the external springs can be easily replaced in case of wear or damage without having to replace the entire frame element. This means the frame can, in principle, be disassembled and reassembled as often as needed, for example, during repairs or transport. Overall, this significantly increases the frame's service life, making the frame according to the invention a sustainable solution.

[0077] In a particularly advantageous embodiment, the external springs are flat dowels, especially knurled flat dowels. "Knurled" here means that the surface of the flat dowels is provided with a fine texture, such as longitudinal grooves. This knurling ensures a precise, play-free fit of the flat dowel in the groove. It thus prevents tilting or wobbling of the connection perpendicular to the expansion direction, while the longitudinal displacement required for clamping remains easily possible.

[0078] The flat dowels are preferably made of wood or aluminum. A wooden flat dowel is a cost-effective and proven solution that offers good dimensional accuracy. Using an aluminum flat dowel, on the other hand, offers additional advantages. First, aluminum is extremely dimensionally stable and does not react to fluctuations in humidity, ensuring that the connection remains smooth even after extended periods and does not seize due to swelling wood. Furthermore, an aluminum dowel can be manufactured with very tight tolerances, guaranteeing play-free yet easily sliding guidance of the frame elements during clamping. The high strength and wear resistance of aluminum also ensure the durability and lasting precision of the corner joint.An advantageous embodiment of the invention provides that the clamping means comprise wedges which engage in complementary recesses in the inner connection areas of two adjacent frame elements. The frame is then a so-called wedge frame.

[0079] When the wedges are driven into the recesses in the corners of the frame according to the invention by external force – usually by striking them with a hammer – they exert a spreading force on the two adjacent frame elements. This force pushes the frame elements apart. If this is carried out uniformly in all corners of the frame, it leads – with moderate force applied – to a slight but effective expansion of the entire frame, whereby the composite structure of the frame elements according to the invention effectively prevents twisting. This expansion tightens or retensions the painting medium stretched on the frame.

[0080] The advantage of this solution lies in its simplicity, robustness, and cost-effectiveness. It is a purely mechanical, proven mechanism that allows for controlled, incremental adjustment of the painting medium tension and is intuitive and familiar to users, such as artists.

[0081] An advantageous embodiment of the invention provides that the clamping means comprise a clamping device with two mounting elements, such as mounting plates, each designed for attachment to one of two adjacent frame elements, and a length-adjustable clamping element, such as a turnbuckle, which connects the two mounting elements to each other, preferably via hinges, wherein the clamping device is set up and designed in such a way that the distance between the mounting elements can be changed.

[0082] The two mounting elements of the clamping device are attached at an angle to two adjacent frame elements, for example, by screws. The two mounting elements are connected by a length-adjustable clamping element, such as a turnbuckle. Extending the clamping element increases the distance between the mounting elements, creating a spreading force that forces the two frame elements apart, thus expanding the frame to tension the painting medium.

[0083] The angle between the mounting elements and the clamping element is determined by the frame geometry. To adapt the clamping device to specific frame shapes, the connection between the clamping element and the mounting elements is preferably achieved via hinges or joints. This allows for a high degree of adaptability to frames with varying corner angles. The hinges also enable a stress-free connection between the straight clamping element and the angled mounting elements, ensuring that the applied force acts purely as a tensile or compressive force to expand the frame, without introducing unwanted bending moments into the device that could lead to jamming or damage.

[0084] The key advantage of the tensioning device lies in the fact that the frame expansion, and thus the tensioning and retensioning of the painting medium, can be done easily and preferably without tools by hand. A turnbuckle can, for example, be equipped with a knurled nut or an integrated lever that allows for manual operation. Alternatively, tensioning can be accomplished using a handy tool such as a pen or wrench. This completely eliminates the need to carry bulky tools like a hammer, which significantly simplifies handling, especially at exhibitions, and greatly increases user convenience.

[0085] Furthermore, the clamping device allows for a very precise and finely adjustable tension of the painting medium. Unlike the jerky and difficult-to-control driving of wedges, the tension can be increased or decreased continuously and in a controlled manner using the clamping device. This minimizes the risk of uneven tension or damage to the painting medium due to excessive force.

[0086] In an advantageous embodiment, the clamping device is made of a metallic material, preferably aluminium.

[0087] An advantageous further development of the invention provides that the frame is equipped with a flame retardant coating.

[0088] The flame-retardant finish of the components of the frame according to the invention—frame elements, tensioning devices, connecting elements, and / or stiffening elements—reduces its flammability and slows the spread of fire in the event of a blaze, thus meeting a higher safety standard. This is particularly important for use in public or commercial spaces, such as hospitals, hotels, government offices, or office buildings, where strict fire protection regulations (e.g., fire protection class B1 according to DIN 4102-1 or Euroclass B / C) often apply, making conventional wooden stretcher frames unsuitable. The flame-retardant finish of the frame according to the invention can be implemented in various ways. Generally, substances are used that either make it more difficult for the material to ignite, slow the spread of flames, or form a protective barrier.This includes, in particular, mineral flame retardants such as boron compounds (e.g., borax), phosphorus compounds (e.g., sodium or calcium phosphate or ammonium polyphosphate), metal hydroxides (e.g., aluminum or magnesium hydroxide), and carbonates. Furthermore, intumescent systems that foam up when heated and form an insulating carbon layer, or special fire-retardant paints and impregnations can be used.

[0089] The application of these substances depends on the material used. For wood or paper-based materials such as MDF or HDF, the flame retardants, typically in finely ground form, are incorporated directly into the mixture of wood or paper fibers and binder and pressed together to create a fully protected material. For solid wood, treatment is preferably achieved through impregnation, in which flame-retardant salts are forced deep into the wood structure under pressure (pressure impregnation), or through the surface application of fire-retardant coatings. For plastics or wood-plastic composites (WPC), the flame retardant additives are mixed into the plastic or the plastic-wood fiber mixture before the forming process, such as extrusion.

[0090] Metallic components, such as the metal frame elements or aluminum fasteners, are inherently non-combustible and do not require any additional flame-retardant treatment. Their material properties inherently contribute to increasing the fire safety of the overall system.

[0091] Any substances used to manufacture the composite of wood and metal components, such as adhesives, are preferably also flame-retardant.

[0092] An advantageous further development involves coating and / or painting at least sections of the frame elements. Such surface treatment of the frame elements can serve both functional and aesthetic purposes, and can be implemented individually or in combination.

[0093] From a functional perspective, a coating and / or paint finish primarily serves to protect the frame element from environmental influences. For example, a protective coating can seal its surface, further reducing the absorption or release of moisture. This also increases the frame's dimensional stability. Furthermore, paints can be formulated with UV protection additives to prevent yellowing or fading of the frame elements due to sunlight. For use in humid environments or for long-term archiving, coatings with fungicidal or insecticidal properties can also be applied to protect the material from mold, fungal growth, or pest infestation.

[0094] From an aesthetic point of view, coating and / or varnishing allows for a wide variety of frame designs. By using colored varnishes or stains, the frame can be customized to match the artwork, the interior design, or specific exhibition requirements. Alternatively, a transparent clear varnish can be used on wood-based materials to emphasize and highlight the natural grain and color of the wood. Furthermore, traditional finishing techniques such as applying metal leaf, for example, gold or silver leaf, can be used as a coating to achieve a particularly high-quality appearance. Powder coating or foil application are also possible options.

[0095] Furthermore, an opaque coating or paint can serve to visually conceal and seal the joints between the different material layers. This creates a frame element with a completely homogeneous and monolithic appearance, while simultaneously protecting the joints from moisture penetration.

[0096] Coatings and / or paints often combine functional and aesthetic properties, for example, by serving as colored protective coatings that both enhance the appearance and provide lasting protection. The coating and / or paint can be applied to the entire frame element or only to selected areas, such as the visible exterior surfaces.

[0097] The invention further relates to a kit for a frame according to the invention comprising at least the following components: frame elements, clamping devices and connecting devices, in particular flat dowels, preferably made of wood or aluminium.

[0098] Such a kit enables an end user, such as an artist or gallery, to assemble the frame according to the invention themselves, as all the core components required for assembly are provided in a disassembled state. These include the frame elements according to the invention with their composite structure, the clamping devices (for example, in the form of wedges or the mechanical clamping device), and the connecting elements, in particular the separate external springs such as flat dowels made of wood or aluminum. Optionally, the kit can also include stiffening elements, such as cross braces or crosses, for the assembly of large-format frames.

[0099] Providing the frame according to the invention as a kit offers significant logistical and practical advantages, particularly in the case of large-format frames. Since the individual components are supplied unassembled, the packaging volume is drastically reduced compared to a fully assembled frame. This allows for significantly more space-saving and cost-effective transport, as well as simpler storage. The user can assemble the frame as needed, immediately before stretching the canvas, which simplifies handling and eliminates the risk of transport damage to the assembled frame.

[0100] The invention further relates to a combination of a frame and a painting medium comprising a frame according to the invention and a flexible, preferably textile, painting medium, such as a canvas, wherein the painting medium is stretched over the frame and attached to its back, preferably with staples or nails, and wherein the painting medium is in particular flame-retardant.

[0101] This combination represents the finished, ready-to-use product, as it can be used, for example, by an artist. Due to the composite structure of the frame elements according to the invention and the resulting dimensional stability of the frame, re-tensioning of the painting medium is only necessary in exceptional cases or after a longer period of time – should the painting medium itself yield. Furthermore, tensioning / re-tensioning using the tensioning device according to the invention as a clamping element is possible at any time, preferably without tools or with a handy tool such as a wrench or a pin.

[0102] In a particularly advantageous embodiment of the invention, in addition to the frame according to the invention, the painting medium itself is equipped with a flame-retardant coating in order to provide an overall system that fully complies with strict fire protection regulations, such as those that apply in public buildings such as hospitals.

[0103] The painting medium, preferably textile, can consist of materials such as linen, cotton, or, most preferably, polyester. Flame retardancy is typically achieved by impregnating the fabric. Phosphorus salts or organophosphorus compounds are preferably used for this purpose. Since a painting medium for artistic purposes is generally not washed, such impregnation is a sufficiently durable and effective solution to ensure fire protection properties throughout the artwork's entire lifespan.

[0104] Another significant technical advantage of the combination of the dimensionally stable frame according to the invention and the stretched painting medium lies in its acoustic effect. The combination can act as an effective sound absorber, with the painting medium functioning as a vibrating membrane and the air space behind it as a spring. The dimensional stability of the frame according to the invention supports this effect. A conventional, lightweight wooden frame would vibrate along with the frame and thus reduce the sound-absorbing effect. Additionally, the cavity defined on the back of the frame by the frame elements can be filled with a porous, sound-absorbing material, such as acoustic foam, mineral or rock wool, polyester fleece, or other sound-permeable fiber materials, to further enhance the sound-absorbing effect. Preferably, this sound-absorbing material is also flame-retardant.The combination according to the invention can thus contribute to improving room acoustics, for example in offices, living spaces or public buildings.

[0105] Alternatively or additionally, the cavity defined on the back of the frame by the frame elements can also be filled with a thermally insulating, preferably flame-retardant material to protect the artwork on the painting medium from any temperature fluctuations.

[0106] In an advantageous embodiment of the invention, the combination of the frame and the painting medium is placed in an outer decorative frame for further aesthetic refinement.

[0107] Such a decorative frame could, for example, be a so-called shadow gap frame. In this technique, widely used in galleries and exhibitions, the stretched canvas is inserted into an outer decorative frame in such a way that a gap, the eponymous shadow gap, is created between the edge of the artwork and the inner edge of the frame. This creates the optical illusion that the artwork is floating within the frame.

[0108] The high dimensional stability of the frame according to the invention is also a considerable advantage here, as it ensures a permanently precise and centered alignment of the artwork within the outer decorative frame and prevents warping of the overall system. The design of the decorative frame, for example, its color, shape, or pattern, can be adapted to the artwork, the exhibition conditions, or simply to personal preferences. For example, the combination of frame and painting medium according to the invention can be inserted into a traditional, ornamental decorative frame, such as a baroque-style plaster or wooden frame, which classically frames the artwork.

[0109] Furthermore, to maintain or even improve the stability and safety of the overall system, the decorative frame itself can also include a metal component to increase its dimensional stability. Preferably, this outer decorative frame is also flame-retardant to meet the highest safety requirements in combination with the frame according to the invention and a flame-retardant painting medium.

[0110] The invention further relates to a kit for a combination of a frame and a painting medium comprising at least the following components: frame elements, tensioning means, connecting means, in particular flat dowels preferably made of wood or aluminium, and a flexible, preferably textile, painting medium, such as a canvas, wherein the painting medium is preferably flame-retardant.

[0111] This kit represents a comprehensive, all-in-one package for the end user, such as an artist, containing all the essential components for creating a fully stretched canvas frame. In addition to the disassembled frame elements, tensioning devices, and connectors, the kit also includes a suitable, flexible painting medium, such as a rolled or folded canvas. Optionally—especially in the case of large-format frames—the kit also includes stiffening elements, such as cross braces or crosses.

[0112] A key advantage of this kit lies in its user-friendliness and the guaranteed compatibility of its components. The user receives all necessary parts from a single source and does not need to procure and match frames and painting media separately. The dimensions of the included painting media are precisely matched to the size of the frame according to the invention, which avoids errors during cutting and stretching and simplifies the work process.

[0113] In addition, this kit, like the "frame kit," offers logistical advantages such as a small packaging volume and cost-efficient transport. If the frame components and the included painting medium are also flame-retardant, the kit provides a complete, coordinated, and safe solution that ensures compliance with strict fire protection requirements and thus enables use, for example, in public buildings without time-consuming individual component testing.

[0114] In an advantageous embodiment, the frame elements and / or the painting medium can also be equipped with a machine-readable data carrier to enable interaction between the viewer and digital content.

[0115] The machine-readable data carrier can preferably be read using standard mobile devices such as smartphones. Suitable data carriers include optically readable codes, such as QR codes or barcodes, as well as radio-based transponders, such as NFC or RFID chips. The data carrier can be attached in a variety of ways, for example, by printing, engraving, as a label, or by structural integration into the frame or painting medium. The data carrier can also be designed as a visible branding element.

[0116] The information accessible via the data carrier can include, for example, certificates of authenticity and provenance, artwork and artist information, or data for logistics and administration. Furthermore, interactive experiences, such as those offered in an interactive, hands-on exhibition, are also possible. This design thus combines high-quality, innovative picture frames with state-of-the-art technology and creates a direct connection to digital content and services, which can be provided, for example, via an AI-supported platform. This enables advanced functionalities such as intelligent matching of artworks.

[0117] The invention also relates to a stretcher frame that can be covered with a textile fabric as a canvas and consists of a plurality of stretcher bars connected to one another to form the stretcher frame, which are flame-retardant, characterized in that the stretcher bars are designed in such a multi-layered manner that two outer bars made of wood or wood fibers enclose and are connected to an inner bar made of metal. Such a stretcher frame can be combined with the features mentioned above and in the claims. REFERENCE MARK

[0118] 1 frame

[0119] 2 frame elements

[0120] 3 clamping devices

[0121] 4 stiffening element

[0122] 5 painting medium

[0123] 6 Fasteners

[0124] 7 layers of wood

[0125] 8 metal layer

[0126] 9 Nut

[0127] 10 Clamping device

[0128] 11 Mounting plate

[0129] 12 clamping elements

[0130] 13 hinge

[0131] BRIEF DESCRIPTION OF THE FIGURES

[0132] Fig. 1 : Schematic representation of the rear view of a frame 1 according to the invention covered with a painting medium 5, comprising frame elements 2, tensioning means 3 and stiffening means 4.

[0133] Fig. 2 : Partial exploded view of a corner joint of the frame 1 with two frame elements 2 which can be connected via connecting means 6.

[0134] Fig. 3 : Schematic representation of the front face of a frame element 2 according to the invention in cross-section with a multi-layered structure comprising two wood layers 7 and a central metal layer 8.

[0135] Fig. 4: Exemplary schematic representation of a clamping device 10 with mounting plates 11, which are connected to each other via a clamping element 12 and hinges 13.

[0136] Fig. 5 : Schematic, partial representation of the corner area of ​​the frame 1 according to the invention with clamping device 10 mounted.

[0137] DETAILED DESCRIPTION OF THE FIGURES

[0138] Figure 1 shows a schematic representation of the rear view of an embodiment of the frame 1 according to the invention. The rectangular frame 1 is composed of four straight frame elements 2 and covered with a painting medium 5. Three wedges are provided in the inner corner areas as tensioning devices. When driven into corresponding slots, these wedges spread the frame elements 2 apart, thus tensioning the painting medium 5. For additional stabilization, particularly in large formats, a centrally arranged stiffening element 4 in the form of a cross brace is inserted between the opposing frame elements 2. Other geometries, such as cross braces, can also be used.

[0139] Figure 2 shows a partial, schematic exploded view of a corner joint of frame 1. The ends of two frame elements 2, mitered to each other, are shown. A separate spline in the form of a flat dowel is provided as the connecting element 6. A corresponding groove 9 (see Fig. 3) is provided in the end face of each frame element 2 to receive the connecting element 6. The connection is made by inserting the connecting element 6 into the grooves 9 of both frame elements 2, creating a stable connection that is nevertheless movable for clamping.

[0140] Figure 3 shows a schematic cross-sectional view of the end face of a frame element 2 according to the invention. An embodiment with a multi-layered sandwich construction is shown. The frame element 2 comprises two outer wood layers 7 and a central metal layer 8 arranged between them. The three layers are bonded together, forming a stable composite. The groove 9 for receiving the connecting element 6 (see Fig. 3) is provided on the mitered surface of the frame element 2.

[0141] 2) to be recognized. The profile of the frame element 2 also has a raised, bead-like outer edge, which ensures that the stretched painting medium 5 does not rest on the flat front of the frame 1.

[0142] Figure 4 shows an exemplary, schematic representation of an alternative embodiment of a clamping device in the form of a mechanical clamping device 10. The clamping device 10 comprises two mounting plates 11, which are designed for attachment to two adjacent frame elements 2. The mounting plates 11 are connected to each other via a length-adjustable clamping element 12, which here is designed as a turnbuckle with a central knurled handle for tool-free operation. The connection between the clamping element 12 and the mounting plates 11 is realized by hinges 13, which enable a flexible and stress-free connection.

[0143] Figure 5 shows a schematic, partial view of the inner corner region of a frame 1 according to the invention, in which the clamping device 10 shown in Figure 4 is mounted as a clamping element. The clamping device 10 is attached at a corner to the two adjacent frame elements 2, for example, by screws. By changing the length of the clamping element 12 (see Figure 4), a spreading force is exerted on the frame elements 2, which drives them apart and thus expands the frame 1. The clamping device 10 therefore represents a tool-free and precisely adjustable alternative to conventional clamping wedges. EXAMPLE

[0144] A specific embodiment of the invention is described in detail below.

[0145] To produce a frame for use in an exhibition in a public building, such as a hospital, a frame element with a three-layer structure (sandwich construction) is manufactured. This frame element consists of two outer wood-based layers and a central metal-based layer.

[0146] The two wood-based layers consist of a 19 mm thick, flame-retardant medium-density fiberboard (MDF FR). These boards are primarily composed of wood fibers bonded with a binder, such as a synthetic resin. To achieve flame-retardant properties, a corresponding proportion of flame retardants is added to the mixture. Additional additives, such as water repellents to reduce water absorption or colorants, may also be present. The middle, metal-based layer consists of a 3 mm thick aluminum sheet. The three layers are bonded together under full pressure to create a highly stable composite component with a total thickness of 41 mm.On the front of the frame element, a bead-like profile with a height of 4.5 mm is formed by machining, so that the total thickness of the frame element at the inner edge is 36.5 mm.

[0147] Four of these frame elements are mitered at their ends and joined to form a rectangular frame using a splined connection with knurled aluminum flat dowels. A mechanical clamping device with a turnbuckle is also installed in each of the four inner corners to allow for precise, tool-free expansion of the frame.

[0148] A work of art, mounted on a flame-retardant polyester canvas, is stretched onto the fully assembled frame and secured on the back with staples. For the final presentation, this combination of frame and canvas is placed inside an outer shadow gap frame.

[0149] The resulting artwork meets high fire safety requirements thanks to the consistently flame-retardant finish of all components. At the same time, the dimensionally stable construction of the inner frame ensures a permanently flat and wrinkle-free presentation of the artwork, while the tensioning device allows for easy, tool-free readjustment directly at the exhibition venue.

Claims

Patent claims 1. A frame for covering with a flexible, preferably textile, painting medium, such as a canvas, at least comprehensively: ■ at least two frame elements from which the frame is modularly composed; ■ a connecting means for connecting the at least two frame elements; ■ a clamping device for adjusting the relative arrangement of at least two frame elements to each other, wherein the at least two frame elements are connected to each other by means of the connecting element, preferably detachably and / or slidably, and wherein the frame has a front side facing the painting medium when covered with the textile painting medium and a back side opposite this, wherein the connecting element is permanently or detachably connected to the at least two frame elements, characterized by the fact that at least one of the at least two frame elements comprises a composite of at least two components, preferably joined together in a planar and preferably material-bonded manner, in particular glued, the group includes at least the following components: a) a first material component comprising or consisting of a wood-, paper- or plastic-based material and b) a second material component comprising or consisting of a metal-based material, preferably aluminium.

2. Frame according to claim 1, wherein the composite comprises a multi-layered structure with at least two layers, preferably at least partially planar and preferably materially bonded to one another, in particular glued, wherein the first material component is a first planar material component layer comprising or consisting of a wood-, paper-based or plastic-based material, and wherein the second material component is a second planar material component layer comprising or consisting of a metal-based material, preferably aluminum.

3. Frame according to claim 2, wherein the multilayer structure comprises a third planar material component layer comprising or consisting of a wood-, paper- or plastic-based material, wherein the second planar material component layer is arranged between the first and the third planar material component layer.

4. Frame according to one of the preceding claims, wherein the front and back sides are at least partially different from each other, the front side preferably having a raised and rounded, in particular bead-shaped, outer edge.

5. Frame according to any of the preceding claims, wherein the wood-based material comprises wood, a wood-based material such as MDF or HDF; a wood-plastic composite material or combinations thereof.

6. Frame according to one of claims 2 to 5, wherein the composite comprises one or more planar material component layers comprising or consisting of a wood-, paper- or plastic-based material, which together have a thickness Sw, and one or more planar material component layers comprising or consisting of a metal-based material, which together have a thickness SM, wherein the ratio of SM TO SW is: 0.01 < < 0.

3.

7. Frame according to any one of claims 2 to 6, wherein the thickness SM of one or more planar material component layers comprises or consists of a metal-based material 0.5 to 10 mm, preferably 1 to 5 mm, particularly preferably 1.5 to 3 mm.

8. Frame according to one of the preceding claims, wherein the at least two frame elements are connected to each other by means of the connecting means via a plug connection, such as a slotted and tenon connection, external spring connection or galvanizing.

9. Frame according to claim 8, wherein the at least two frame elements are connected to each other by means of the connecting means via a spring connection, wherein the connecting means are springs, in particular flat dowels preferably made of wood or aluminium.

10. Frame according to one of the preceding claims, wherein the clamping means comprise wedges that engage in complementary slots in the inner connection areas of two adjacent frame elements.

11. Frame according to one of the preceding claims, wherein the clamping means is a clamping device comprising: ■ two mounting elements, such as mounting plates, each designed for attachment to one of two adjacent frame elements; and ■ a length-adjustable clamping element, such as a turnbuckle, which connects the two mounting plates, preferably via hinges, comprising, wherein the clamping device is set up and designed in such a way that the distance between the mounting elements can be changed.

12. Frame according to one of the preceding claims, wherein the frame is flame-retardant.

13. Kit for a frame according to any one of claims 1 to 12, comprising at least the following components: A) Frame elements according to any one of claims 1 to 12; B) Clamping device according to any one of claims 1 to 12; C) Fasteners according to any one of claims 1 to 12, in particular flat dowels, preferably made of wood or aluminium.

14. Combination of a frame and a painting medium, comprising: ■ a frame according to any one of claims 1 to 12; and ■ a flexible, preferably textile painting medium, such as a canvas, wherein the painting medium is stretched over the frame and attached to its back, preferably with clamps or nails and the painting medium is specifically flame-retardant.

15. Kit for a combination of a frame and a painting medium, comprising at least the following components: A) Frame elements according to any one of claims 1 to 12; B) Clamping device according to any one of claims 1 to 12; C) Fasteners according to any one of claims 1 to 12, in particular flat dowels, preferably made of wood or aluminium; and D) a flexible, preferably textile, painting medium, such as a canvas, wherein the painting medium is preferably flame-retardant.

Images