CN113750483A

CN113750483A - Sports racket and manufacturing process

Info

Publication number: CN113750483A
Application number: CN202110600499.XA
Authority: CN
Inventors: 让-菲利普·理查德
Original assignee: Decathlon SE
Current assignee: Decathlon SE
Priority date: 2020-05-29
Filing date: 2021-05-31
Publication date: 2021-12-07
Also published as: FR3110858A1

Abstract

The invention relates to a sports racquet (1), particularly for ball or badminton games, having a shaft and a head, comprising: frame (2) with a rod having one or more receptacles (16), for example longitudinal grooves, in particular one or more adjusting devices (18) in terms of mass and/or balance, for example in the form of counterweights or weights, arranged in said receptacles of the frame rod, and means for retaining the adjusting devices (18) in said receptacles (16), which, with the adjusting devices arranged in said receptacles, cover the rod of the frame, wherein the retaining means comprise a heat shrink tube, for example formed by a heat shrink tube. The invention also relates to a process for manufacturing such a sports racquet.

Description

Sports racket and manufacturing process

Technical Field

The present invention relates to the field of sport accessories, and in particular to the field of sports racquets, in particular tennis racquets.

Background

It is known to manufacture racquets (particularly tennis racquets) from composite materials. These materials have the advantage of having a high mechanical resistance while maintaining a relatively low weight compared to other materials such as wood or aluminium.

In particular, the frame of a racquet, made of a composite material (such as an impregnated carbon or fiberglass matrix), is designed to surround an inflated bladder that allows appropriate pressure to be applied to the composite material as the matrix cures. The composite material is generally applied manually in the form of prepreg strips arranged in staggered rows around the bladder.

However, such a process for manufacturing composite parts results in frames with significant differences in quality and/or balance. More precisely, the frames thus obtained, from one racket to another, may have significant variations in mass and/or balance.

In order to reduce the difference in mechanical properties between the racquets, it is also known to provide one or more weights at the level of the stem portion of the frame, which weights are intended to compensate for variations in the mass and/or balance of the frame. These counterweights are in particular provided in receptacles provided in the rod portion of the frame for the following purposes: the weight may balance the frame of the racquet depending on the position of the weight in the pocket. Once the weight is placed in the frame bar, a sleeve made of a thermoset plastic (e.g., foamed polyurethane) is placed around the bar portion of the frame to hold the weight in place, and then the grip of the racquet is mounted on the sleeve.

However, such a process is not entirely satisfactory. In fact, despite the weight being placed on the shaft, there are still differences in mass and/or balance between the finished racquets, particularly due to the burrs that are created when the thermoset sleeve is formed.

Disclosure of Invention

The present invention is intended to solve the various technical problems set forth above. In particular, the present invention aims to propose a racket, in particular a sports racket, which is easier to manufacture than existing ones. More precisely, the present invention aims to propose a process for manufacturing a racket with low differences in mass and/or balance.

Thus, according to one aspect, there is provided a sports racquet, particularly for ball or badminton games, having a shaft and a head, the racquet comprising:

a frame having a bar with one or more receptacles, for example longitudinal grooves,

one or more adjusting devices, in particular in terms of mass and/or balance, for example in the form of counterweights or weights, are arranged in the receptacle(s) of the frame bar, and

-means for retaining the adjustment means in said housing(s), the retaining means covering the bars of the frame with said adjustment means arranged in said housing(s).

In particular, the holding means comprise a heat shrink tube, for example formed by a heat shrink tube.

The applicant has therefore realised that sleeves made of thermosetting plastic (in particular made of foamed polyurethane) also have differences in mass and/or balance between them, so that it is possible to reproduce the differences in mass between the racquets by installing a thermosetting plastic sleeve even if the differences between the frames have been corrected before. Due to the heat shrink tube, it is possible to keep the weight provided at the rod of the frame in place while ensuring that the difference between the rackets is not re-caused.

The heat shrinkable tube is in the form of a sleeve having an inner diameter larger than that of the frame bar. Before being heated, a heat shrink tube is disposed around the frame bar with the weight to shrink over the frame bar and the weight to conform to the contour. Thus, the heat shrink tubing can accommodate any kind of frame bar, and since the heat shrink tubing has a much larger inner diameter than the frame, its mounting on the frame will not be hindered or affected by the surface condition of the frame bar. Once heat shrunk, the tube conforms and adjusts to the dimensions of the frame bar and allows the previously placed weights to remain in place.

In addition, heat shrinkable tubes have very low mass dispersion and are easier to repeat and produce similarly than thermoset plastic sleeves.

Heat shrinkable tubing also has the advantage of having a surface condition suitable for mounting a grip thereon, whereas some thermoset plastic sleeves (particularly molded sleeves) may have an overly slippery surface condition due to the residue of mold release agent added during demolding. In this case, if it is desired to avoid the grip portion falling off the thermosetting plastic sleeve in use, it is necessary to provide a step of cleaning the surface of the thermosetting plastic sleeve before the grip portion is applied.

Finally, by removing the thermoset plastic sleeve, the present invention also avoids the risk of cracks or the occurrence of plastic chips that may move within the racquet (particularly in the frame), thereby creating a noise hazard with each movement of the racquet and/or each impact of the ball. In particular, these cracks in the thermosetting plastic can occur when the cap is nailed on the end of the stem and also create a noise hazard during use.

Preferably, the heat shrinkable tube is made of a thermoplastic material. Unlike thermoset plastic sleeves, heat shrink tubing made of thermoplastic material can be recycled and is less polluting.

Preferably, the heat shrinkable tube includes or is made of an oriented polyolefin (e.g., oriented polyethylene and/or oriented polystyrene).

Preferably, the receptacle comprises two longitudinal grooves arranged on each side of the frame.

The longitudinal grooves are thus arranged along the frame bars and make it possible to arrange one or more counterweights needed for balancing the frame at desired positions. In particular, the grooves allow for more precise adjustment of the position of the counterweight, and also allow for multiple counterweights to be positioned along a single groove.

Preferably, the heat shrinkable tube is provided on the frame bar.

Therefore, it is not necessary to provide a layer or a spacer between the frame bar and the heat shrinkable tube. Instead, by placing the heat shrink tubing in direct contact with the frame bar, the weight is better held in place in the groove and a much better grip support surface is created, replacing the imperfect surface of the frame bar. In another aspect, the heat shrinkable tube may include an adhesive layer on an inner surface, and/or the surface of the frame bar may include an adhesive layer on an outer surface to improve mechanical strength of the heat shrinkable tube on the frame.

Preferably, the heat shrink tubing conforms to the outer surface of the frame bar except for the receptacle(s).

The heat shrink tubing and/or the receptacles in the frame bars may be designed to limit insertion of the tubing into the receptacles when shrunk. This restricts the surface relief of the heat shrinkable tube, which can be felt by the user through the grip portion.

Preferably, the frame bar having the one or more receiving portions has a cylindrical shape having an octagonal cross section, and the heat shrinkable tube has a cylindrical shape having an octagonal cross section.

Thus, the heat shrink tubing has substantially the same geometry as the frame bar.

Preferably, the frame is made of a composite material, for example glass fibres pre-impregnated with a thermosetting resin or carbon fibres pre-impregnated with a thermosetting resin.

Preferably, the thermosetting resin is an epoxy resin.

Preferably, the racket further comprises a grip portion disposed over, preferably on, the heat shrink tubing.

Preferably, the shaft of the racquet has no longitudinal portion made of molded or injection molded plastic, e.g., has no overmolded longitudinal sleeve made of a thermoset plastic such as foamed polyurethane.

According to another aspect, it is also proposed a process for manufacturing a sports racquet (in particular for ball or badminton games), comprising the following steps:

a step of manufacturing a frame having a bar with one or more housing portions, for example longitudinal grooves,

-a step of providing one or more adjustment means, for example in the form of counterweights or weights, in said housing(s) of the frame bar(s) to adjust the weight and/or balance of the frame, and

-a step of covering the frame bar and the adjusting means with a holding means.

In particular, the step of covering the frame bar comprises:

-providing a heat shrink tube, preferably cylindrical, around the frame bar and the adjustment means, and-shrinking the heat shrink tube around the frame bar and the adjustment means by applying heat to the heat shrink tube.

This process makes it easier and cheaper to manufacture a balanced racquet with a composite frame. In particular, the manufacture of the shaft of the racket is simpler, while ensuring low differences in quality and balance between rackets produced in the same way.

By facilitating the manufacturing process, the process time is reduced, thereby reducing costs while providing a more uniform characteristic to the racquet.

Drawings

Fig. 1 shows a tennis racket according to the present invention;

FIG. 2 illustrates the composite frame of the racquet shown in FIG. 1 during the manufacturing process, after balancing;

FIG. 3 shows the frame of FIG. 2 with a heat shrink tube disposed around the frame; and

FIG. 4 shows the frame of FIG. 2 with heat shrink tubing at the rods.

Detailed Description

Fig. 1 schematically shows a racket 1 according to the present invention. The racket 1 may be a tennis racket, a cricket racket, a badminton racket, or the like.

Conventionally, a racquet 1 includes a frame 2 having a head 3 and a shaft 5, the head 3 defining a stringing surface forming a mesh 4. The stem 5 comprises a handle 6 and two connecting

branches

8 and 10, the grip 7 being arranged at the level of the handle 6, the two connecting

branches

8 and 10 being mounted in the extension of the head 3 and delimiting a hollow space 12 allowing the passage of air.

According to a variant not shown, the handle 6 can be connected to the head of the frame 2 by a single central branch.

According to the invention, the frame 2 of the racket comprises at least one layer of composite material. Preferably, the frame 2 is made of a composite material arranged around the bladder, which is used during the manufacturing process.

Thus, the frame 2 of the racket 1 may be made of a composite material, for example of glass and/or carbon fibre pre-impregnated with a thermosetting resin, such as epoxy resin.

The frame 2 of the racket 1 is formed by applying a strip of composite material arranged on the exposed surface of an internal bladder, the ends 14 of which remain inflatable. The assembly is then placed in a mould and the bladder is inflated to effect curing of the composite strip under heat and pressure to obtain the final frame.

Fig. 2 shows a composite frame 2 obtained after curing the composite material. Thus, the frame 2 has a general shape similar to the racket 1. Fig. 2 to 4 show various subsequent steps of manufacturing the shaft 5 (and in particular the handle 6) of the racket 1.

Since the arrangement of the prepreg strips is usually done manually, it is common for the resulting frame 2 to have properties that vary between them, in particular in terms of mass and balance. To even out these characteristics between the racquets, receptacles (such as longitudinal grooves) are provided in the frame 2 at the level of the handle 6 to place one or more rebalancing weights 18. In the case shown in fig. 2 to 4, 3 weights are placed in the recess 16 such that a frame 2 with the desired mass and balance is obtained.

Due to the weight 18, differences in the mass and/or balance of the racket 1 may be reduced.

However, in order to hold the weight 18 in place and complete the handle 6, it is known to surround the frame bar 2 with plastic (typically thermosetting). However, the addition of such plastic elements may recreate the difference in mass and/or balance. Moreover, the plastic element may also break and create small pieces that can move around in the racquet, causing harm (particularly sound) to the user. Finally, depending on the manufacturing process of the plastic element, it may have surface conditions incompatible with holding it easily and effectively.

According to the invention, a heat shrink tube 20 is used to hold the weight 18 in place and to form a support surface for mounting the grip portion 7. More specifically, the heat shrinkable tube 20 is disposed around the frame bar 2 so that it can cover the longitudinal groove(s) 16 and the weight(s) 18 (see fig. 3).

The heat shrinkable tube 20 may be made of a thermoplastic material. For example, the heat shrink tubing may comprise an oriented polyolefin (such as oriented polyethylene and/or oriented polystyrene).

The heat shrink tubing 20, on the inner surface intended to come into contact with the frame 2, may comprise an adhesive layer (not shown) intended to improve the mechanical strength of the tubing on the frame 2.

Once set, the heat shrink tubing 20 is heated causing it to shrink to enclose the rod portion of the frame 2 along with the weight 18. Thereby obtaining a frame 2 having a heat shrinkable tube 22 surrounding the rod portion (see fig. 4).

Advantageously, the heat shrink tubing 22 does not conform to the shape of the receiving portion (i.e., the shape of the longitudinal groove 16 in the current embodiment), which prevents the user from being able to feel them through the grip portion 7.

Once the heat shrink tube 22 is in place, all that is needed is to attach an end cap covering the distal end of the rod 5 and to place the grip portion 7 on the heat shrink tube 22 to obtain a racket 1 with similar features as other rackets manufactured according to the same process.

Thus, thanks to the heat shrinkable tube according to the present invention, it is possible to simply and reliably manufacture (particularly in terms of mass and balance) a racket having these characteristics, which are more uniform among them, while also improving the reliability of the racket for a long time.

Claims

1. A sports racquet (1), in particular for the playing of balls or shuttlecocks, having a shaft (5) and a head (3), said racquet (1) comprising:

-a frame (2) having a rod with one or more receptacles (16),

-one or more adjustment devices (18) arranged in said housing (16) of the rods of the frame, and

-a holding device (22) for holding the adjusting device (18) in the housing (16), which, with the adjusting device arranged in the housing, covers the rods of the frame,

characterized in that the holding means (22) comprises a heat shrink tube.

2. A sports racquet (1) according to claim 1, wherein said housing (16) comprises two longitudinal grooves arranged on each side of said frame (2).

3. A sports racquet (1) according to claim 1, wherein said heat shrink tubing (22) is provided on the stem of said frame (2).

4. A sports racquet (1) according to claim 1, wherein said heat shrink tubing (22) conforms to the outer surface of the stem of the frame, except for the housing (16).

5. A sports racquet (1) according to claim 1, wherein the stem of the frame with one or more housing portions has a cylindrical shape with an octagonal cross-section, and wherein the heat shrink tubing (22) has a cylindrical shape with an octagonal cross-section.

6. A sports racquet (1) according to claim 1, wherein said frame (2) is made of composite material.

7. A sports racquet (1) according to claim 6, wherein said frame is made of glass fibers pre-impregnated with thermosetting resin or of carbon fibers pre-impregnated with thermosetting resin, and wherein the thermosetting resin is an epoxy resin.

8. A sports racquet (1) according to claim 1, further comprising a grip (7) provided on said heat shrink tubing (22).

9. A sports racquet (1) according to claim 1, wherein the shaft of the racquet has no longitudinal portion made of molded or injection-molded plastic.

10. A process for manufacturing a sports racquet, in particular for the playing of balls or shuttlecocks, comprising the following steps:

-a step of manufacturing a frame (1), the frame (1) having a rod with one or more receptacles (16),

-a step of arranging one or more adjustment devices (18) in the housing (16) of the bars of the frame, to adjust the weight and/or balance of the frame, and

-a step of covering the rods of the frame and the adjusting means (18) with retaining means,

characterized in that the step of covering the rods of the frame comprises:

-providing a heat shrink tube (20) around the rods of the frame and the adjustment means, and

-shrinking the heat shrink tubing around the rods of the frame and the adjustment means by applying heat to the heat shrink tubing (20).