Production of a molded part from glued layers of wood

Abstract

Vacuum infusion process for producing a molded part from glued layers of wood, in which a base layer made of wood is detachably attached to a template shape, Several layers of veneer are stacked on top of each other on the base layer, forming free intermediate layers, and held immovably. the stack of veneer layers is tightly enclosed by a foil covering, An inlet and an outlet are provided in the space formed by the foil covering, the inlet being connected to a reservoir filled with flowable resin and the outlet to a vacuum pump, and In one infusion step, the flowable resin is pumped from the reservoir to the outlet via the vacuum pump, penetrating the intermediate layers.

Description

[0001] The invention relates to a vacuum infusion process for producing a molded part from glued wood layers. The invention also relates to a hull, deck, or superstructure wall of a sailboat or motorboat produced using the process.

[0002] The vacuum infusion process for producing fiber-reinforced plastics has long been known. Such fiber-reinforced plastics have at least two components: the fiber reinforcement, which imparts the desired properties to the workpiece, and the synthetic resin matrix, which surrounds and protects the fibers. In the vacuum infusion process, the fibers are introduced dry into a mold, and the resin is "sucked" into the mold by applying a vacuum. The vacuum draws air bubbles out of the laminate and cures the laminate under pressure.

[0003] A process that uses vacuum bonding is also known from wooden boat building. For example, DE 28 30 938 discloses a process for producing hulls, decks, and superstructures from wood for sailing, rowing, or motorboats. In this process, several thin wooden layers (veneers) are first coated with an adhesive on at least one surface and then laid on top of one another. These sandwiches are then formed into a boat-sized wall shape and then vacuum-bonded to retain their shape. Vacuum bonding works in such a way that the sandwich is surrounded by a film from which the air is then extracted. Due to the vacuum, the ambient pressure presses the layers of the sandwich evenly against one another, allowing the adhesive to harden under pressure.

[0004] However, this process could not prevail in wooden boat building due to the great effort involved.

[0005] The object of the present invention is to make the vacuum infusion process attractive for boat building.

[0006] This object is achieved by the method according to claim 1. Particular embodiments are mentioned in the subclaims.

[0007] The special feature of the method according to the invention is that a stable sandwich of several veneer layers is first built on a template mold, which corresponds to the final molded part. A veneer layer can be formed as a single layer of several adjacent thin sheets of wood, the joints of which are at least partially permeable to flowable resin from layer to layer. In a particularly simple embodiment, the individual veneer layers are held together by staples. Due to the rough structure of the wood surfaces, the superimposed veneer layers form very narrow intermediate layers that allow the resin to flow across the surface. This sandwich is then sealed by a film wrapping before the flowable resin is vacuum infused into the film wrapping and thus into the sandwich.Contrary to the predictions of many experts in this field, the resin, which cannot pass through the individual wood sheets, is distributed homogeneously across the intermediate layers and the joints on the entire sandwich.

[0008] The claimed procedure is such that first a base layer of wood, which later forms a surface, is detachably attached to a prefabricated template mold. Several veneer layers are then stacked on top of this base layer, forming the remaining intermediate layers, and fixed immovably against each other. The stack of veneer layers is then sealed by a film wrapping, although this wrapping does not necessarily have to include the base layer. The base layer can also serve as a wall of the film wrapping and form a certain mold projection. In the space formed by the film wrapping, one or more inlets, distributed as evenly as possible, and at least one outlet are provided. The inlets are each connected to a reservoir filled with flowable resin, and the outlet is connected to a vacuum pump.The inlets are advantageously located at the bottom of the mold and the outlet at the top to ensure the resin spreads from bottom to top. Depending on the size of the molded part, it may also be advantageous to provide multiple outlets, i.e., suction points.

[0009] In a final infusion step, the flowable resin is then pumped from the reservoir to the outlet via the vacuum pump, penetrating the interlayers. To ensure complete resin penetration, a sufficient amount of resin is pumped through the sandwich. Resins commonly used in plastic boat building can be used. After the resin has dried, the sandwich or molded part can be removed from the template mold.

[0010] To determine saturation, the incoming resin flow can be compared with the outgoing resin flow. Once both flows have permanently equalized, saturation can be assumed and the flow can be stopped. For boat building, it has been found that saturation is approximately reached when approximately 500g of resin has been consumed per square meter of laminate. After saturation, the vacuum can be maintained to maintain pressure until the resin cures; in this case, it may be sufficient to simply close the inlet and outlet and turn off the pump.

[0011] The particular advantage of the inventive method is that veneers, especially from domestic softwoods such as pine, can be used. This makes the process particularly sustainable. It also allows for the production of particularly lightweight molded parts, which is particularly advantageous in shipbuilding.

[0012] To achieve better flow between the layers, or to be able to adjust this flow in a controlled manner, it is advantageous if veneer layers comprise several veneer sheets, adjoined by narrow joints, with parallel longitudinal edges and, in particular, grain running in the longitudinal direction. These joints enable controlled transfer of the resin between adjacent interlayers during the infusion step. It is advantageous if the veneer sheets have a thickness between 1 mm and 3 mm, in particular 2 mm, and a width between 10 cm and 20 cm, in particular 15 cm.

[0013] To improve and homogenize the flow properties in the planes of the interlayers, it is advantageous to provide the surfaces of veneer layers with grooves that accelerate the flow of the resin during the infusion step and promote its distribution across the surface. It is also advantageous if the grooves in a surface are aligned essentially in the direction of the veneer grain and, in particular, equidistant.

[0014] With regard to a homogeneous distribution of the resin, it has proven particularly advantageous to provide the grooves with a width of between 2 mm and 6 mm, in particular between 3 mm and 4 mm, and a depth of up to 1 mm, in particular 0.5 mm. Advantageously, the grooves have a spacing of between 10 mm and 40 mm, in particular 25 mm.

[0015] It is also advantageous if the veneer layers are stacked in a cross-grain direction. The immovable retention of the stacked layers can be ensured by connecting elements such as nails or staples, or by connecting adhesive points. To homogenize and improve resin flow, a flow aid, particularly in the form of a fabric, can be provided between the film wrapping and the outermost veneer layer.

[0016] Particularly in boatbuilding, it is advantageous to construct the template form from mall frames. When building sailboats, rowing boats, or motorboats, this process can be used to produce entire hulls, decks, or individual outer walls. To ensure sufficient stability of the molded parts, it has proven advantageous to apply a stack of approximately ten veneer layers to the base layer. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 28 30 938

[0003]

Claims

[1] Vacuum infusion process for producing a molded part from glued wood layers, characterized by , that a base layer of wood is detachably attached to a template form, that several veneer layers are placed on top of each other on the base layer, forming free intermediate layers, and are held immovably, that the stack of veneer layers is sealed by a foil wrapping, that an inlet and an outlet are provided in the space formed by the film envelope, the inlet being connected to a reservoir filled with flowable resin and the outlet being connected to a vacuum pump, and that the flowable resin is pumped from the reservoir to the outlet via the vacuum pump in an infusion step, penetrating the intermediate layers. [2] Method according to claim 1, characterized bythat a veneer layer comprises a plurality of veneer sheets with parallel longitudinal edges and, in particular, longitudinally extending fibers, which are adjacent to one another by means of narrow joints, wherein the joints allow the transfer of the resin between adjacent intermediate layers during the infusion step. [3] Method according to claim 2, characterized by that the veneer sheets have a thickness of between 1 mm and 3 mm, in particular 2 mm, and a width of between 10 cm and 20 cm, in particular 15 cm. [4] Method according to one of claims 1 to 3, characterized by that surfaces of veneer layers are provided with grooves that accelerate the flow of the resin during the infusion step and promote its distribution over the surface. [5] Method according to claim 4, characterized by that the grooves in a surface are aligned substantially in the direction of the grain of the veneer and, in particular, equidistant. [6] Method according to claim 4 or 5, characterized by that the grooves a width between 2 mm and 6 mm, in particular between 3 mm and 4 mm, a depth of up to 1 mm, in particular 0.5 mm, and a distance between 10 mm and 40 mm, in particular 25 mm. [7] Method according to one of the preceding claims, characterized by that the veneer layers are placed on top of each other in intersecting grain directions to form the stack. [8] Method according to one of the preceding claims, characterized by that the veneer layers are held immovably by connecting elements such as nails or staples, or by connecting adhesive points. [9] Method according to one of the preceding claims, characterized by that the film wrapping covers the stack of veneer layers and is sealed to the resin-impermeable base layer. [10] Method according to one of the preceding claims, characterized by that a flow aid, in particular in the form of a fabric, is provided between the film wrapping and the outermost veneer layer. [11] Method according to one of the preceding claims, characterized by that the inlet is located below and the outlet above the stack in the film wrapping. [12] Method according to one of the preceding claims, characterized by that several inlets and correspondingly connected reservoirs are introduced into the film casing, in particular evenly distributed. [13] Method according to one of the preceding claims, characterized by that the resin is dried while maintaining the vacuum and the molded part consisting of base layer and veneer layers is removed from the template mold. [14] Method according to one of the preceding claims, characterized by that the template form is constructed from mold frames. [15] Hull, deck or superstructure wall of a sailing or motor boat produced by the method according to one of the preceding claims. [16] Wall according to claim 15, characterized by that a stack of 10 veneer layers is applied to the base layer.