WO1985005281A1

WO1985005281A1 - Racket head for a table tennis racket

Info

Publication number: WO1985005281A1
Application number: PCT/EP1985/000217
Authority: WO
Inventors: Adolf K. W. Stroh
Original assignee: Stroh Adolf K W
Priority date: 1984-05-12
Filing date: 1985-05-10
Publication date: 1985-12-05
Also published as: DE3417728A1; EP0179890A1

Abstract

Racket head for a table tennis racket with a plurality of wooden layers (20) between which there is provided a glue layer (26) containing a fibre material (24) for reinforcement purposes. According to the present invention, the fibre material (24) is comprised with multifilaments bundles based on aramide and carbon fibres, whereas the wooden plies (20) consist of balsa wood in order to obtain an extremely light racket head.

Description

Racket blade for a table tennis racket

The invention relates to a racket blade for a table tennis racket with at least two wood layers and an adhesive layer containing a fiber material for reinforcement between each two adjacent wood layers.

It is known to make the racket blade of table tennis bats from several layers of wood connected by adhesive layers, whereby it should be noted that according to the applicable table tennis rules, at least 85% of the racket blade, measured in terms of its thickness, must consist of natural wood and that no single adhesive layer is stronger than 7.5% of the total thickness or 0.35 mm, depending on which of these two specified values is the smaller.

From DE-GM 79 36 785 it is also known to manufacture the racket blade of a table tennis racket from a balsa wood base plate, to which carbon fiber reinforced plastic is applied on both sides, to which outer layers of triple-glued plywood panels are glued. This known racket is also too heavy due to the use of plywood for the outer layers of the racket. According to DE-GM 75 38 642, it is also known to manufacture the blade and handle of a table tennis racket, at least partially, from a plate reinforced with carbon fibers from a hardened synthetic resin. Such a racket is also relatively heavy in the end and also does not comply with the applicable regulations of the table tennis associations. In the case of racket blades for table tennis bats, it is also known that an adhesive layer for reinforcement can contain a fiber material, such as carbon fibers or glass fibers, in order in this way to achieve the flexibility of the racket blade required by the table tennis rules. Furthermore, for the racket blades of the known table tennis rackets, in view of the requirement that the blade must be inflexible, relatively solid woods, which seem to be most suitable, have been used so far for the racket blade with the tight tolerances given above for the adhesive layers, in particular for their total proportion the thickness of the club blade to achieve sufficient rigidity.

It has been shown that the racket blades known hitherto generally meet the requirements in practice with regard to the rigidity and the durability with which the individual wood layers are connected to one another by the adhesive layers. On the other hand, the currently available table tennis rackets with the above-mentioned structure of the racket blade are perceived by the top players as too difficult with regard to the increasingly high speed of the swing changes in table tennis, so that the desire for lighter rackets has arisen, which is in view of the fixed demands of the players on the surface of the racket could only be met by lighter Schlägerblatt would be developed, which has not yet been achieved despite considerable efforts in this direction. Rather, it has been shown that even the lightest types of wood, which have a corresponding strength, such as certain birch woods, allow only a slight weight reduction of the order of a few percent.

Proceeding from the prior art, the invention has for its object to improve a racket blade of the type specified in such a way that an inflexible racket blade is obtained which adheres to the Tichtennis rules, which is significantly lighter than the previously available racket blades. This object is achieved in a racket blade of the type specified according to the invention in that the wood layers consist of balsa wood and in that the fiber material consists of multifilament bundles of aramid and carbon fibers.

The basic idea of the present invention is to achieve the required stiffness or inflexibility of the racket blade despite the severe restrictions that result from the table tennis rules in this regard, essentially with the aid of the adhesive layers containing the fiber material and thus the possibility of using the extremely light To open balsa wood, the mechanical strength of which is extremely low by nature It has been shown that when using multifilament bundles made of aramid fibers and carbon fibers to reinforce the adhesive layers, the required mechanical strength of the bat blade can also be achieved with balsa wood and that there is also the advantage that the pads of the bat blade have the same damping effect for the striking table tennis balls, in particular with a suitable choice of the orientation of the multifilament bundle, can be made thinner, since in this case the outer layers of balsa wood, due to the properties of the balsa wood, contribute significantly more to damping than the wood layers of harder types of wood, in particular if the outer wood layers in an embodiment of the invention a little thicker than the inner wood layers of the club blade. (Depending on the position or the orientation of the fiber material inside the racket blade, however, "hard" racket blades can also be obtained according to the invention.)

It has also proven to be advantageous if the multifilament bundles are arranged, at least essentially parallel to one another, in particular in a flat position, in such a way that the thickness of the layer is equal to the diameter of the multifilament bundle, so that, for example, with a bundle diameter of 0, 13 mm adhesive layers with a total thickness of 0.15 mm can be realized, an epoxy resin preferably being used as the adhesive. In a racket blade according to the invention, multifilament bundles of monofilaments with a diameter of approximately 10 µm are preferably used for the reinforcement. It has also proven to be advantageous if each individual bundle contains only one type of fiber and if multifilament bundles made of aramid fibers and multifilament bundles made of carbon fibers follow one another in alternation. The multifilament bundles can optionally be arranged in a star shape, starting from the center of the racket blade. In an embodiment of the invention there is also the possibility of inserting fabrics made of multifilament bundles of aramid fibers and carbon fibers into the adhesive layers for reinforcement.

The invention is explained in more detail below with reference to a drawing. Show it:

Figure 1 is a plan view of a table tennis racket.

FIG. 2 shows a partial cross section through the table tennis racket according to FIG. 1 along the line 2-2 in this figure;

Fig. 3 shows a greatly enlarged section A of Fig. 2 and

Fig. 4 is an end view of the detail of FIG. 3, seen in the direction of arrow B in this figure. 1 shows a table tennis racket 10 which has a racket blade 12 according to the invention as the main element. As is clear from FIGS. 1 and 2, the club blade 12 is provided on its two main surfaces with a covering 14 which is glued to the club blade 12 via an adhesive layer 16. The coverings 14 in FIGS. 1 and 2 are set back somewhat inwards relative to the outer edge of the club blade 12 with the aim of a clearer drawing, although in practice they usually end flush with the outer edge or with the narrow side of the club blade, which is usually covered with a circumferential tape (not shown). The saw blade 14 of the racket blade 12 can consist of nub rubber or sandwich rubber in the usual way and are selected by the respective player in accordance with his playing technique, whereby different coverings are often chosen for the two sides of the table tennis bat. Furthermore, the club blade 12 is provided with glued-on grip parts 13 in the region of its grip extension 12a.

As is clear from FIG. 2, the club blade 12 itself consists of a plurality of wood layers 20 which are connected to one another via adhesive layers 22 located therebetween, a plurality of inner wood layers 20 generally being arranged between the outer wood layers 20 to which the coverings 14 are glued , as indicated in Fig. 2. The number of inner Layers of wood depend on the total thickness of the club blade 12 and can fluctuate between about two and sixteen at club blade thicknesses between approximately 2.5 and 8 mm.

According to the invention, the adhesive layers 22 contain multifilament bundles 24 for reinforcement, which, as is particularly clear from FIGS. 3 and 4, are embedded in an adhesive matrix 26, which preferably consists of an epoxy resin. The multifilament bundles 24 are preferably arranged parallel to one another in a single layer and have a diameter which is only insignificantly smaller than the total thickness of the adhesive layer 22, so that the multifilament bundles 24, which are preferably alternately composed of aramid and carbon monofilaments or fibers consist, develop an extraordinarily high reinforcing effect and thus result in a club blade 20 with sufficient rigidity even when using the light, mechanically less resistant balsa wood for the wood layers 20.

For example, the multifilament bundles 24 can have a diameter of 0.13 mm, while the total height of an adhesive layer 22 is only 0.15 mm, so that the thickness of the adhesive matrix between the individual multifilament bundles 24 and the adjacent wood layers 20 is only a maximum of 0.02 mm and can be on average 0.01 mm and thus is in the order of the diameter of a monofilament.

By using balsa wood for the wood layers and aramid / carbon multifilament bundles to reinforce the adhesive layers - the ratio of aramid fibers to carbon fibers is preferably about 1: 1 - according to the invention, the weight of the club blade compared to the lightest, previously available club blades same dimensions, for example with a club blade thickness of 4 mm, of about 80 g. reduce about 30 g.

In addition, because of the strong damping effect of balsa wood, the thickness of the coverings can also be reduced, in particular if the outer wood layers are made somewhat thicker, for example with a thickness of 0.8 mm, than the inner wood layers, which for example have a thickness of approximately 0 , 6 mm.

Claims

EXPECTATIONS

1. bat blade for a table tennis racket with at least two wood layers and an adhesive layer for reinforcement containing a fiber material between each two adjacent wood layers, characterized in that the wood layers (20) consist of balsa wood and that the fiber material consists of multifilament bundles (24) made of aramid and carbon fibers .

2. bat blade according to claim 1 with two outer and at least one inner wood layer, characterized in that each of the outer wood layers (20) is thicker than an inner wood layer.

3. bat blade according to claim 1 or 2, characterized in that the multifilament bundle (24) are arranged at least substantially parallel to each other.

4. bat blade according to claim 3, characterized in that the multifilament bundle (24) are arranged in a flat multifilament bundle layer such that the thickness of the layer is equal to the diameter of the multifilament bundle.

5. racket blade according to one of claims 1 to 4, characterized in that the multifilament bundle (24) are embedded in an Epαxidharzmatrix (26).

6. bat blade according to one of claims 1 to 5, characterized in that in a flat layer of multifilament bundles, a multifilament bundle made of aramid fibers and a multifilament bundle made of carbon fibers alternate in succession.