EP2002759A1

EP2002759A1 - Energy storing spring from wood

Info

Publication number: EP2002759A1
Application number: EP07011755A
Authority: EP
Inventors: Imre Dr. Szabó; László Eckhart; György Dr. Czél
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-06-15
Filing date: 2007-06-15
Publication date: 2008-12-17
Anticipated expiration: 2027-06-15
Also published as: EP2002759B1; ATE531298T1

Abstract

The invention relates to energy storing wood springs having the shape of a cylindrical compression spiral spring, a conical compression spiral spring, a double-cone compression spiral spring, a square-section compression or tension spring, a spiral flat spring, a coil-spring of cylindrical outer shape, a wave spring, or a layered flat spring, or possibly a tension, compression or torsion spring characterized by an arbitrary space curve. The essence of the invention is that, with spring geometries similar to those of metal springs, wood is also capable of performing energy storing and energy-releasing operations, especially when the material of the wood spring is compressed wood.

Description

The object of the invention is energy storing compressed wood springs, which can be used as energy storing elements installed primarily in mechanical or medical, or possibly toy structures. The use of compressed wood springs allows the performance of controlled movement or flexible load bearing, or possibly vibration damping. The field of application of the invention includes all places of use where springs of various geometries made of metal can be installed.
In Hungary the geometries of springs made of metal are specified in standard MSZ EN ISO 2161-1. The standard "Simplified representation of springs" originates from European standard EN ISO 2161-1, prepared in July 1996. The standard specifies in detail cylindrical compression coil-springs, conical compression coil-springs, and also double-cone coil-springs, but the standard also deals in detail with cylindrical compression coil-springs, conical compression coil-springs made of square cross-section material, and also covers the shapes and geometries of various torsion and Belleville springs. Spiral springs, as special springs, where the task of energy storing and displacement is performed by an Archimedean spiral, also form the subject of the standard specification. Furthermore, the well known plate springs and their shapes are also covered by the standard. Such springs can be seen generally in the vehicle industry, primarily in the underframes of railway cars. Standard EN ISO 2162-2 specifies in detail the technical parameters of the springs, such as the modulus of flexibility, the frequency of load changes, etc.
The object of this patent is not the expansion of the materials and geometries of customary and standardized metal springs, but their replacement by using an entirely new compressed wood material. The field of use of wood springs is in part related to the bending of wood, as a more or less rigid structural element.
The bending of wood is a very important method of wood processing. The main advantage of the bending of wood is that its application results in material saving. In the production of curved wood parts a higher strength can be achieved with smaller cross-sectional sizes, as in bending the fibres of the wood are not cut. The development of the best known and oldest bending technique is associated with the name of Michael Thonet, who in 1830 developed the so called Thonet chairs, well known both in the furniture industry and in interior decoration. They are made of bent wood structural elements, and the curved wood structural elements provide proper strength even at a load of 150 kg, while being graceful. Such curved wood elements, which are usually the products of the furniture industry, are made by sawing, the Thonet bending technique, or bending by high-frequency heating, or possibly by the bending and simultaneous gluing of thin wood plates, veneers. Thus the technique of steam bending of wood, as a heat bending technique, is well known in the furniture industry, and widely used for making springy surfaces as well. In the furniture industry usually layered, laminated structural elements are used for making wood springs, but then bending has its limits with respect to especially small radius bending. At a small bending radius the wood structure (due to its structure) cannot withstand the tensile stress arising in the outer fibres, and fibre breaking occurs. In the inner compressed fibres, on the other hand, the compressive stress can be so high that they collapse. This entails that such, usually bent flat springs can be bent at a much smaller bending radius at the ends, away from the centre of bending, that is the characteristics of the spring are different in the centre and at the ends, the structure of the spring is inhomogeneous from the point of view of springing.
Japanese patent No. JP2002191475 discloses the use of springy curved wood surfaces, implemented usually as bed bases, describing a complete bed base consisting of composite wood flat springs. Here the springing elements consist of laminated, that is layered wood plates, bound together with synthetic resin. To increase the rigidity of the springs, such laminated structures are often supplemented by inserting a fibre glass fabric, where that layer, as a matrix material, is bound to the laminated wood structure with synthetic resin. For such bed types proper springing at the ends of the curved wood structure is solved with various special spring cushions, as disclosed in patent description No. JP2004215717 entitled "Bed with wood springs". Special springs laminated from fibre-reinforced wood plates are protected by patent No. DE3703910 , in which ceramic fibres or carbon fibres are also used to increase rigidity. The uniform bending strength of springy curved flat springs, as generally used spring shapes, is protected by Hungarian patent No. 217506 , EU priority number DE19638582.2 , filed in September 1996, in which the ends of the laminated wood spring structure, where the bending radius fails to reach that of the central curved spring portion, gluing is omitted between the laminated plates, thus increasing the flexibility of the spring ends.
Patent No. EP0694272 entitled "Spring mattress", in which springs made of rattan reed are used as mattress springs, is close to the object of this description. Such mattress springs replace the customary steel spiral springs, by making use of the property of reed that it is easily and well bendable, thus it can be coiled even on a core rod of a small core diameter. This patent proposes the construction of generally mattress springs, thus it is intended for use in the furniture industry.
The compression wood bending technology was discovered in the 1990s in Finland. This compression technique in the wood industry allowed the production of so called compressed wood. The essence of the compression technique is that sawn wood is cut to the required size, softened by heating (without chemicals), then placed into compressing equipment. In the compressing machine, through shrinking in the direction of the fibres, the fibre walls fold like the bellows of an accordion, the wood is compressed, and thereby becomes bendable. After drying the compressed wood retains the required shape. However, not all wood species are suitable for this bending method. Ash, beech, elm, maple, oak and black nut proved to be well compressible wood species. During compression the moisture content of the wood is about 20-25%. Before placing into the compressing machine, then after softening by steaming, the longitudinal strain, that is the decrease in length is about 10-30%, and the permanent set after drying is 3-10%. This technique was developed primarily for the furniture industry in order to make curved furniture parts without cutting, thus eliminating waste. This technical solution, however, has another especially important result, namely that by applying this bending method wood can be bent to a much smaller radius.
The primary task of springs made of metal is to store energy, and to release energy in various, generally technical equipment. The spring shapes support this application. Knowing that the different spring geometries produce different spring characteristics, the exerted spring force can be varied, as a function of compression.
The novelty of this invention is that, with a suitable spring geometry, wood is also capable of performing such energy storing and releasing operations, especially when the wood spring is made of compressed wood.
Wood springs can be suitable for the industry in numerous places. The fields of use of compressed wood springs of various geometries include all technical constructions where a springing element, that is mechanical energy storage, or a damping element providing springy support is required.
In the vehicle industry, for example, in the development of vehicle seats, it is conceivable that a wood motor-vehicle seat can be constructed of natural materials made of renewable energy sources, comprising fully recyclable materials. Furthermore, compressed wood springs can be dimensioned to break upon excitation at own frequency under specific stress conditions, and as they are made of renewable energy sources, they can be reconstructed. Thus, for example, a field of use can be the construction of safety seats for various machines generating vibration. When the harmful vibration frequency reaches the range and energy density harmful to humans, the wood springs break and thus damp the mechanical effects affecting the human organism.
Toy manufacturing and the toy industry is also a field of use of energy storing compressed wood springs, where a special generation of wood toys, primarily wood cars can be implemented by using energy storing wood spiral springs made of compressed wood. The electric industry uses a large amount of metal springs, which usually operate connecting elements, switching equipment. They are activated (wound up) before operation, then release the stored energy, thereby performing the switching. The springs used in the electric industry are usually made of metals conducting electricity, which under certain circumstances can cause a short-circuit due to their conductivity. This can be avoided with wood springs made of compressed wood, which do not conduct electricity. The furniture industry is also a field of use of springs made of compressed wood, where compressed wood springs can replace, for example, the rattan reed furniture elements having poor fatigue properties. Energy storing compressed wood springs can also be applied in the field of medicine, where wood springs of special geometries made of compressed wood can be used as medical aids. In medicine wood springs can be adjusted to injured limbs, that is they can be customized, and thus springy parts can be made with them. Physical therapists can successfully apply compressed wood springs. In this field, for example, they can be used for moving, exercising broken limbs in such a manner that the wood spring, as a soft spring, fastened to the broken limb, bent by muscle force, controls the movement thereof, and returns the limb to its original position.
Such an application can be a wood spring for developing manual force, muscle force, to support the regeneration, strengthening of hand muscles.
The solution according to the invention presents several springs made of compressed wood, having different characteristics. These special springs have the spring shapes already customary in mechanical engineering, the operation of the springs is also the same as customary in mechanical engineering, only they are made of wood. That is, the springs can be wound up by turning, pressing or pulling, namely they play an energy-absorbing role with external work, then most of this energy can be released and transferred to the environment.
The energy storing compressed wood springs according to the invention are shown in detail in the following figures, where

Figure 1: Cylindrical compression spiral spring made of compressed wood
Figure 2: Conical compression spiral spring made of compressed wood
Figure 3: Double-cone compression spiral spring made of compressed wood
Figure 4: Square-section compression or tension spring made of compressed wood
Figure 5: Conical spiral flat spring made of compressed wood
Figure 6: Coil spring of cylidrical outer shape made of compressed wood
Figure 7: Wave spring made of compressed wood
Figure 8: Layered flat spring made of compressed wood
Figure 9: Wood spring with a unique space curve

The springs made of compressed wood according to the invention can be constructed as a cylindrical compression spiral spring (Figure 1), a conical compression spiral spring (Figure 2), a double-cone compression spiral spring (Figure 3), a square-section compression or tension spring (Figure 4), a spiral flat spring (Figure 5), a spiral spring (Figure 6), and according to special embodiments as a wave spring (Figure 7), a layered flat spring (Figure 8), or a spring with a unique space curve (Figure 9). The cross-section of the spring material of the cylindrical, conical and double-cone compression spiral springs is round or square-shaped. The direction of coiling is righthand or left-hand. The shape of the spring ends is planed. The cross-section of the conical spiral flat spring is an elongated rectangle. The shape of the spiral spring follows the shape of an Archimedean spiral. The shape of the wave spring can be characterized as a continuum of curved elements connected by straight sections. The layered flat spring comprises a plurality of plane compressed wood layers, held together by a screw 1 in the centre. The cross-section of the spring following an arbitrary space curve (Figure 9) is an arbitrary plane figure, which may change as a function of length.
The energy storing compressed wood springs have the spring shapes already customary in mechanical engineering, the operation of the springs is also the same as customary in mechanical engineering, only they are made of wood, preferably compressed wood. The stored mechanical energy can be released and transferred to the environment with the termination of the deformation.
All springs shown in Figures 1-9 are compressed wood springs capable of withstanding axial tensile-compressive or torsional stress. These springs undergo a one-, two- or three-dimensional deformation due to the loading force. The stored energy is given by the product of the deformation path and the force. After displacement (winding up) the compressed wood springs retain their shape only until the cessation of the winding-up force. (Then the wood structure regains its shape.) In the course of their movement compressed wood springs, in addition to energy storage, can be used for damping as well, as they absorb a part of the mechanical energy input during compression. The energy storing compressed wood spring can also be a spatial element having a unique shape (e.g. Figure 9), developed by the user, which is deformed in space, implementing a two- or three-dimensional springing movement. Any point of a spring made in this manner is springy even locally, and thus has an energy-absorbing or energy-releasing, or possibly energy-damping function.

Claims

Energy storing wood springs having the shape of a cylindrical compression spiral spring, a conical compression spiral spring, a double-cone compression spiral spring, a square-section compression or tension spring, a spiral flat spring, a coil spring of cylindrical outer shape, a wave spring, or a layered flat spring, wherein the material of the springs is compressed wood.
Energy storing wood springs according to claim 1, wherein the direction of coiling of the springs made of compressed wood can be either direction.
Energy storing wood springs according to claim 1, wherein the spring geometry can be an arbitrary spatial element and the material of the spatial element is compressed wood.
Energy storing wood springs according to claims 1-3, wherein the cross-section of the spring material or springy spatial element is round, square, rectangle, rhombus or an arbitrary plane figure.