METHOD OF FORMING A DEVICE OF COMPOSITE MATERIAL, A PATTERN, A DEVICE

Abstract

A method of forming a device of composite material includes providing a mold having an internal space forming a cavity with an inner surface, the cavity having a shape corresponding to an inner shape of the device to be formed, placing inserts at one or more pre-defined positions along the inner surface, holding the inserts at the one or more positions, introducing removable material into the cavity of the mold to form a pattern having the inserts fixed therein when the removable material is in solid form, and removing the pattern having the inserts fixed therein from the mold.

Claims

1. A method of forming a device of composite material, the method comprising: providing a mold having an internal space forming a cavity with an inner surface, the cavity having a shape corresponding to an inner shape of the device to be formed; placing inserts at one or more pre-defined positions along the inner surface; holding the inserts at the one or more positions; introducing removable material into the cavity of the mold to form a pattern having the inserts fixed therein when the removable material is in solid form; and removing the pattern having the inserts fixed therein from the mold.

2. The method according to claim 1, wherein the holding the inserts comprises holding the inserts through the application of a vacuum, using sliders, functional elements, or using magnets.

3. The method according to claim 1, wherein the inserts comprise at least one of magnetic material and metal.

1. The method according to claim 1, wherein at least one of the inserts is shaped to form a functional component or is a functional component of the device.

5. The method according to claim 1, wherein the pattern of removable material is formed in an injection molding process or a wax casting process.

6. The method according to claim 1, wherein the removable material is introduced into the cavity in liquid form.

7. The method according to claim 1, wherein the introducing the removable material into the mold comprises filling between 40 and 99% of the cavity with liquid removable material.

8. The method according to claim 7, further comprising: introducing gas into the removable material present in the mold and pressurizing the removable material present in the mold with a pressure difference between an outside of the pattern that is formed and a hollow space within the pattern selected in the range of 0.02 to 20 bar; or further comprising applying a pressure selected in a range of 0.02 to 0.95 bar in the cavity prior to the introduction of the removable material into the cavity; or further comprising moving the mold to completely coat the inner surface of the mold with the removable material in liquid form; and solidifying the removable material in the mold.

9-10. (canceled)

11. The method according to claim 1, further comprising: covering the pattern having the inserts with one or more layers of one or more types of fiber material.

12. The method according to claim 11, further comprising: placing the pattern having inserts and covered with the one or more layers of fiber material into a further mold.

13. The method according to claim 12, further comprising: heating the further mold to first, second or third temperatures in first, second or third temperature ranges.

14. The method according to claim 13, further comprising: introducing a resin into the further mold prior to or during the heating of the further mold to the first temperature.

15. The method according to claim 14, further comprising: curing the resin in the further mold to form the device, wherein the curing comprises at least one of application of heat and UV light.

16-17. (canceled)

18. The method according to claim 13, wherein the resin is one of a one-component resin, a two-component resin comprising a hardener, and a multi-component resin comprising one or several hardeners.

19. The method according to claim 13, wherein the resin comprises a resin on an epoxy basis, a resin on a polyurethane basis, a resin on a cyanate ester or another basis suitable for injection or infusion.

20. The method according to claim 11, wherein the one or more layers of one or types of fiber material comprise carbon fibers, glass fibers, basalt fibers, natural fibers, aramid fibers, polyester fibers in dry condition or as prepreg.

21. The method according to claim 15, further comprising: removing the removable material from the device.

22. The method according to claim 21 wherein the heating the further mold to the first, second or third temperatures in the first, second or third temperature ranges includes heating the further mold to the third temperature.

23. A pattern of removable material, the pattern comprising: one or more inserts placed at one or more predefined positions along an outer surface of the pattern.

24. The pattern according to claim 23, wherein the pattern of removable material has a melting point selected in a temperature range of 80 to 140° C.

25. The pattern according to claim 23, wherein the pattern of removable material remains stable in shape to temperatures selected in the range of 60 to 100° C.

26. The pattern according to claim 23, wherein the pattern of removable material remains stable in shape at temperatures below a melting point of the removable material.

27. The pattern according to claim 23, wherein the inserts comprise at least one of magnetic material and metal.

28. The pattern according to claim 23, wherein the one or more inserts have a shape corresponding to a shape of one or more functional components or are functional components of a device.

29. A device of composite material, comprising: one or more functional components placed at one or more predefined positions along an inner surface of the device, the functional components being integrally formed in one piece with the device, or embedded within a structure integrally formed in one piece with the device.

30. The device according to claim 29, wherein at least one of the functional components is selected from a group of members consisting of a tappet with an undercut, a pocket with an under-cut, an internal seat, a bearing seat, a t-shaped groove, outer threads, inner threads, bayonet connections, open wedge sockets, eyelets, ball studs, dowels and dowel pins, hooks, spring elements, bearing blocks, bearing blocks with clamping, saw tooth pins, sleeves, apertures, supports for one or more of the foregoing and combinations of the foregoing.

31. A The device according to claim 29, wherein the device has a pre-definable wall thickness with a tolerance of the wall thickness lying in a range of ±0.5 mm for a wall thickness selected in a range of 1 to 4 mm.

32. The device according to claim 29, wherein the device has a tolerance of a wall thickness lying in a range of ±0.3 mm for a wall thickness selected in a range of 1 to 4 mm.

33. The device according to claim 29, wherein the device has a tolerance of a surface profile of ±0.1 mm.

34. The device according to claim 28, wherein the device has a tolerance of a surface profile of ±0.05 mm a position of at least one of the functional components forming a second insert.

35. The device according to claim 28, wherein the one or more inserts includes two or more inserts and an angular tolerance of positioning between two of the two or more inserts in the device is less than 0.3° and when the two inserts are fixed relative to one another in the pattern then the angular tolerance between the two inserts is less than 0.1°; or an axial tolerance of positioning between the two inserts in the device is less than 0.2 mm, and when the two inserts are fixed relative to one another in the pattern then the axial tolerance between the two inserts is less than 0.1 mm; or a tolerance of positioning between the two inserts at a spacing between the two inserts in the device is less than 0.1 mm+1 mm/m, and when the two inserts are fixed relative to one another in the pattern then the positioning tolerance between the two inserts is less than 0.05 mm+0.5 mm/m.

36. The device according to claim 29, wherein the device is a head of a golf club and the one or more functional components is at least one of a weight integrated into the golf club, a shaft connector insert forming a connector to a shaft of the golf club, and a surface acting as a face of the golf club.

3. The device according to claim 36, wherein the one or more functional components act as one or more weights of the head, a first functional component of the one or more functional components acts as the shaft connector insert and a second functional component of the one or more functional components acts as a face of the head of the golf club.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0056] The invention will be explained in more detail hereinafter with reference to the drawings.

[0057] FIG. 1 is a perspective view of functional components placed at one or more predefined positions along an inner surface of a device;

[0058] FIG. 2 is a part schematic sectional side view of a mold for forming a pattern for a device showing various inserts;

[0059] FIG. 3 is a part schematic sectional side view of a mold for forming a pattern for a device showing inserts present in the mold;

[0060] FIG. 4 is a part schematic sectional side view of a mold for forming a pattern for a device with removable material filed in the device around the inserts;

[0061] FIG. 5 is a sectional view similar to that of FIG. 4, with the pattern having the inserts embedded therein removed from the mold;

[0062] FIG. 6 is a sectional view similar to that of FIG. 5, with the pattern having been covered with layers of fiber material;

[0063] FIG. 7 is a sectional view similar to that of FIG. 6, with the covered pattern having been placed into a further mold;

[0064] FIG. 8 is a sectional view similar to that of FIG. 7, with the space around the layers of fibers between the pattern and an internal surface of the further mold filled with a resin;

[0065] FIG. 9 is a sectional view similar to that of FIG. 8, with the device having been removed from the further mold;

[0066] FIG. 10 is a sectional view similar to that of FIG. 9, with the pattern having been removed from the device;

[0067] FIG. 11 is a sectional view similar to that of FIG. 10, with the inserts having been removed from the device;

[0068] FIG. 12 is a sectional view similar to that of FIG. 10, with a further type of functional component inherently present at the inner surface of the device;

[0069] FIG. 13 is a sectional view similar to that of FIG. 10, with a further type of functional component inherently present at the inner surface of the device;

[0070] FIG. 14 is a sectional view similar to that of FIG. 10, with a further type of functional component inherently present at the inner surface of the device, with the further type of functional component being the insert which was previously embedded within the pattern;

[0071] FIG. 15 is a sectional view similar to that of FIG. 14, with a further type of functional component inherently present at the inner surface of the device, with the further type of functional component being the insert which was previously embedded within the pattern;

[0072] FIG. 16 is a schematic view of internal components of a device in which bearing supports are integrally formed in one piece with the device;

[0073] FIG. 17 is a view of a head of a golf club; and

[0074] FIG. 18 is a view of a pattern fora head of a golf club.

DETAILED DESCRIPTION

[0075] In the following the same reference numerals will be used for parts having the same or equivalent function. Any statements made having regard to the direction of a component are made relative to the position shown in the drawing and can naturally vary in the actual position of application.

[0076] FIG. 1 shows a perspective view of functional components 12, 12′ placed at one or more predefined positions along an inner surface 14 of a housing 16 of a device 10. The functional components 12 can either be formed by and in the housing 16 of the device 10 itself. Alternatively the functional components 12′ can be supported directly within the housing 16 of the device 10 by supports formed within the housing 16.

[0077] The functional components 12′ shown in FIG. 1 are a hook 12′ and bolt 12′ which are formed by inserts which were present in a pattern 54 for the device and have been embedded within the device 10 during the manufacture of the device 10. The supports for functional components 12 shown in FIG. 1 are a pocket 12 with an undercut, an internal seat 12 (cylindrical), a support 12 for a nut, a bearing seat 12, an inwardly t-shaped groove 12 and a sleeve 12.

[0078] The functional component or support for a functional component can be one of the following types of functional components 12, 12′ which are selected from the group of members consisting of a tappet with an undercut, a bearing seat with points of insertion for a circlip, an outwardly t-shaped groove, outer threads, such as bolts or studs with outer threads, inner threads such as sleeves with an inner thread or a nut, bayonet connections, open wedge sockets, eyelets, ball studs, dowels and dowel pins both optionally with points of insertion for a circlip, spring elements, bearing blocks, bearing blocks with clamping, saw tooth pins/couplings with or without bores, apertures, supports for one or more of the foregoing and combinations of the foregoing.

[0079] In order to form the device 10, a pattern 54 of removable material M (see FIG. 4) is initially formed in a mold 18. FIG. 2 shows a part schematic sectional side view of the mold 18 for forming the pattern 54 of the device 10. The mold comprises top and bottom halves 18′, 18″, which together define a cavity 20 having an inner surface 22

[0080] A seal 19 is present between the top and bottom halves 18′, 18″ in order to seal off the cavity from the outside. Such seals 19 can for example be formed by an O-ring.

[0081] First and second kinds of inserts 24, 24′ are arranged and held at the inner surface 22. The first kind of insert 24 is formed by structures that can be inserted into the cavity 20 via e.g. a slider 26, and thus project into the cavity prior to and during the manufacture of the pattern 54 for the device 10 to form a structure at an outer surface 56 (see FIG. 4) of the pattern 54. The structure can thereby form a recess in the pattern 54 which can be filed with a material forming the device 10.

[0082] The second kind of insert 24′ is an insert that is intended to remain within the pattern 54 after this has been formed. This second kind of insert 24′ can likewise form structures at the outer surface 56 of the pattern 54. These structures can either form supports for the functional components 12, i.e. have a shape complementary to the functional component 12′. Alternatively the second kind of insert 24′ is the functional component 12 (see FIGS. 14 and 15). The functional component 12′ is then bonded to the device 10 via, the structures present at the outer surface 56 of the pattern 54.

[0083] The second kind of insert 24′ can be held within the cavity 20 of the mold via one or more magnets 28 or through the application of a vacuum V. For this purpose, the second kind of insert 24′ is connected via a vacuum passage 30 to a vacuum pump 32 that is connected to the mold 18 via a vacuum port 36.

[0084] In order to form the pattern removable material M (see e.g. FIG. 4) is introduced into the cavity 20 from a reservoir 38 of removable material which can be a wax W. The removable material M is introduced via a port 40 and a line 42 into the cavity 20 in liquid form. In fact a volume of the cavity 20 of the mold 18 is only filled to 40 to 98% with liquid removable material M.

[0085] In order to pressurize the pattern 54 a gas G can be introduced into the removable material M via a gas supply 44 which is connected to the mold 18 via a gas port 46 and a gas line 48. Additionally or alternatively, the cavity 20 is sealed off in such a way or can be sealed off, such that gas present in the cavity is compressed on the introduction of the removable material M to form pressurized gas G within the cavity.

[0086] As indicated in FIG. 4 in each case the gas G produces a hollow space 54′ within the pattern 54. The gas can fill this cavity 54′ and pressurize the removable material M present in the mold 18 such that the wax 20 covers the complete surface of the cavity 20. A pressure difference between an outside of the formed pattern 54 and the hollow space 54′ within the pattern 54 is selected in the range of 0.02 to 19 bar, i.e. the pressure in the hollow interior of the wax pattern can be selected to lie in the range from 1.02 to 20 bar prior to the solidification of the wax, i.e. when the wax is in the molten state. In this connection it should be noted that the pressure in the hollow interior of the wax pattern can be less after the wax has solidified than before the wax has solidified, this is due to the shrinkage of the wax when this solidifies.

[0087] Typically the wax can be selected to be a wax molten at a higher temperature in range from 60 to 140° C., in particular 70 to 120° C. and to be solid at a lower temperature in a range from 30 to 100° C., in particular 60 to 90° C. The temperature difference between the higher temperature and the lower temperature is preferably selected to be less than 40° C., preferably less than 30° C., in particular less than 20° C. and especially less than 10° C.

[0088] The wax can have a viscosity of greater than 2000 mPas for a temperature of less than 85° C. and a viscosity of less than 800 mPas for a temperature greater than 105° C. Such waxes have found to be particularly stable in shape up to their melting point and the transition between the liquid state and the solid state takes place over comparatively small temperature ranges making the waxes more cost effective in their use.

[0089] On forming the wax pattern 54 the mold 18 can be heated to a temperature below a solidification temperature of the wax, in particular to a temperature selected in the range of 1 to 40° C., in particular 5 to 25° C., below the solidification temperature of the wax. In this way the wax can be solidified in a more controlled manner and the shrinkage effects at the surface of the wax pattern can be reduced as the wax does not automatically solidify on contact with the surface of the mold cavity.

[0090] The mold cavity can be evacuated to a pressure selected in the range of 0.02 to 0.95 bar, in particular to a pressure selected in the range of 0.05 to 0.5 bar.

[0091] Following this the mold can be rotated about one or more axes of rotation. The first possible axis is indicated about the vertical axis 36 in which case the mold 18 can be rotated in or against the direction of the arrow indicated about the vertical axis 36. The second possible axis of rotation is about a horizontal axis H, in which case the mold 18 can be rotated in or against the direction of the arrow indicated about the horizontal axis H. By moving the mold 18 in this way the centrifugal force or gravity urges the pressurized removable material towards the inner surface 22 of the mold 18, so that this is completely coated with the removable material and the resultant pattern has an outer surface 56 (see FIG. 4) which is essentially free of shrinkage and other forms of defects. During the rotation of the mold 18 this can be cooled e.g. using water cooling bringing about a solidification of the removable materials M in the mold 18.

[0092] To form the pattern 54 having functional components 12, 12′ placed at one or more predefined positions a vacuum can be applied at the mold 18 using a vacuum pump. Once the desired vacuum of e.g. 0.3 bar is achieved in the mold 18, a valve can be closed to maintain the pressure within the cavity. Thereafter a liquid form of the removable material M can be introduced into the mold 18. For example 80% of the volume of the mold 18 can be filled with liquid material M, e.g. wax W. Thereby the residual air in the mold is compressed through the addition of the wax W in such a way that the pressure in the mold can now be in the range of 1.02 to 4 bar depending on the initial vacuum pressure and the amount of wax added.

[0093] The mold 18 can then be rotated about an axis of rotation while the mold is cooled, due to the pressurized gas in the mold and the rotation of the mold, the initially liquid wax covers the complete surface of the mold such that a wax pattern can be formed having the outer shape resembling that of the inner shape of the mold, with the wax pattern having a hollow interior.

[0094] If a pattern having a particularly complex outer shape is to be formed, additional gas can be added to the mold prior to, during and/or after the addition of the liquid removable material M. Additionally or alternatively more than 80% of the volume of the cavity 20 can be filled with the removable material M. This additional pressure in the mold can guide the liquid removable material into the complex negative geometries of the mold to ensure that a pattern having an outer surface substantially free of defects can be formed.

[0095] FIG. 3 shows a part schematic sectional side view of the mold in which rather than using a moveable insert 12 that can be moved into the cavity 20, the inner surface 22 of the mold 18 comprises a projection 52 at the inner surface which takes on the function of an insert 12 to form a support structure for a functional component 12′. The second kinds of inserts 24′ are inserted into the mold 18. The left hand insert 24′ is held at the inner surface 22 via a magnet. The right-hand insert 24 is held in place via vacuum V, a seal 50 in the form of an O-ring seals between the mold 18 and the insert 24′.

[0096] FIG. 4 shows a part schematic sectional side view of the mold of FIG. 3 into the removable material M has been introduced. Also visible is the hollow space 54′.

[0097] FIG. 5 shows a sectional view similar to that of FIG. 4, in which the removable material has solidified and the pattern 54 is removed from the mold 18. The inserts 24′ are held at pre-defined positions within the pattern 54 at the outer surface 56. The pattern 54 further comprises recess 58 in the outer surface 56.

[0098] The pattern 54 comprises two inserts 24, 24′ placed at one or more predefined positions along the outer surface 56. The pattern 54 of removable material M can have a melting point selected in the temperature range of 80 to 130° C., preferably in the range of 95 to 120° C. The pattern 54 can remain stable in shape to temperatures selected in the range of 60 to 100° C., preferably in the range of 70 to 95° C. Generally speaking the pattern 54 of removable material M can remain stable in shape at temperatures below a melting point of the removable material M.

[0099] FIG. 6 shows a sectional view similar to that of FIG. 5, with the pattern 54 having been covered with layers of fiber material 60, 62. Woven layers of fiber material 60 are placed directly at the outer surface 56, whereas tows of fibers 62 have been inserted into the recess and the free spaces of the inserts accessible from the outer surface 56 of the pattern 54.

[0100] The one or more layers of fiber material 60, 62 can comprise carbon fibers, glass fibers, basalt fibers, wood fibers, hemp fibers, aramid fibers, polyester fibers, in dry condition or as prepreg.

[0101] Thus, the pattern 54 of removable material M can be used as a mold in resin transfer molding (RTM) processes to form composite devices in a manner known per se.

[0102] FIG. 7 shows a sectional view similar to that of FIG. 6, with the covered pattern 54 having been placed into a further mold 64. The further mold 64 has an internal surface 64′. The layers of fiber material 60, 62 are thus placed between the internal surface 64′ of the further mold 64 and the outer surface 56 of the pattern 54.

[0103] FIG. 8 shows a sectional view similar to that of FIG. 7, with the space around the layers of fibers 60, 62 between the pattern 54 and the internal surface 64′ of the further mold 64 filled with a resin R. The resin R is introduced from a reservoir 66 via a supply line 68.

[0104] The further mold 64 can be heated to first, second and/or third temperatures in first, second and/or third temperature ranges via a heating and/or cooling device 96.

[0105] In this connection it should be noted that when the further mold 64 is heated to one of the first, second and third temperatures, the heating steps can be carried out gradually in a stepwise manner or continuously.

[0106] Particularly during RTM processes, it should be noted that the composite of fiber and resin is typically heated in steps to below the glass transition temperature of the resin in order to prevent the device to be formed from becoming soft and thereby obtaining a device with a deformed outer and/or inner surface.

[0107] In this connection it should be noted that the top half 18′ of the mold 18, the bottom half 18″ of the mold 18 and the further mold 64 are each preferably formed from a thermally conductive and non-magnetic material, such as aluminum or an aluminum alloy.

[0108] The resin R is introduced into the further mold 64 during the step of heating of the further mold 64 to the first temperature. The resin R is heated to below a curing temperature of the resin R on the introduction of the resin R into the further mold 64. In order to enhance a flow of the resin R of runny consistency a vacuum V can be applied simultaneously via a vacuum pump 74 connected to a vacuum line 78 via a port 76.

[0109] The resin R is cured in the further mold 64 to form the device 10. The step of curing comprises heating the further mold 64 to the second temperature. The second temperature is higher than the first temperature.

[0110] The resin R can be one of a one-component resin R, a two-component resin R comprising a hardener, and a multi-component resin R comprising one or several hardeners. The resin R comprises a resin on an epoxy basis, a resin on a polyurethane basis, a resin on a cyanate ester or another basis suitable for injection or infusion.

[0111] Thus in the RTM process described in the foregoing at least one layer of roving is provided as a first layer of fiber material 60 optionally also a second layer or several layers of fiber material 62 is provided. The pattern 54 covered with the first layer of fiber material 60 and optionally also the second layer of fiber material 62 is then placed into the further mold 64. The further mold 64 is then evacuated to create a vacuum in the further mold 64. The resin R is then injected into the further mold 64 at a temperature above room temperature but below the ideal hardening temperature of the resin R possibly under pressure. The resin R at elevated temperature and which is possible pressurized is more flowable than unpressurized resin R at room temperature and hence can flow more easily through the roving and the further mold 64 in order to ensure, if possible, that no air pockets are formed in the composite material of the final device.

[0112] The resin R is then permitted to solidify, i.e. harden, at a temperature selected below the melting temperature of the wax pattern 54, preferably while gradually increasing the temperature of the mold between the boundaries of the second temperature range from the lower temperature to the higher temperature, e.g. from 90° C. to 100° C. If required, openings and/or apertures can be applied at the hardened composite device. Following which the temperature of the further mold 64 is gradually increased from e.g. 100° C. to 120° C. in order to melt out the wax pattern 54. The melting out of the wax pattern 54 can optionally also be carried out outside the mold 64, for example in an oven.

[0113] As is known to the person skilled in the art of RTM processes, the glass transition temperature of the resin can be increased temporarily in the mold during the stepwise gradual increase in temperature to above the melting point of the wax to form the device. The liquid wax can then be removed via the openings and/or apertures applied at the device 10.

[0114] Also the inserts 24′ can be removed following the removal of the liquid wax in order to enable the placement of functional components at the position where a support therefore has been formed. For example, in FIG. 16 an insert 24′ forms a support for a bearing and the bearing 84 is then placed at the bearing support 12 inherently formed in the device 10.

[0115] FIG. 9 shows a sectional view similar to that of FIG. 8, with the device 10 having been removed from the further mold 64. The removable material M of the pattern 54 is still present within the device 10.

[0116] FIG. 10 shows a sectional view similar to that of FIG. 9, with the pattern 54 having been removed from the device 10 due to the application of a heating step which heated the removable material M to above its melting point by heating the further mold 64 to the third temperature.

[0117] FIG. 11 shows a sectional view similar to that of FIG. 10, with the inserts 24′ having been removed from the device 10. The left hand-insert in FIG. 10 was used to form an aperture 80 in the housing 16 of the device 10. The right-hand insert was used to form a support for a bearing, i.e. the bearing race can be assembled at the functional component 12 shown on the right in FIG. 11. The left-hand functional component 12 is an internal seat for a component that can cooperate with the bearing seat.

[0118] The device 10 of composite material, thus comprises two functional components 12 placed at two predefined positions along the inner surface 14 of the device 10. The functional components 12 are integrally formed in one piece with the device 10.

[0119] The device 10 can have a pre-definable wail thickness with a tolerance of the wall thickness lying in the range of ±0.5 mm for a wall thickness selected in the range of 1 to 4 mm, in particular for a length of material of the device 10 cut from the device 10 in the range of 1 to 5 cm and at a width selected in the range of 0.5 to 2.5 cm.

[0120] FIG. 12 shows a sectional view similar to that of FIG. 10, with a seat 12 for a nut, i.e. a component having an internal thread inherently present at the inner surface 14 of the device 10.

[0121] FIG. 13 shows a sectional view similar to that of FIG. 10, with a T-shaped groove provided as the functional component 12 inherently present at the inner surface 14 of the device 10.

[0122] FIG. 14 shows a sectional view similar to that of FIG. 10, with the functional component 12′ in the form of a threaded bolt is embedded within material of the device 10 at the inner surface 14 of the device 10. The threaded bolt has been bonded into place by an insert surrounding the bolt 12′ which held the bolt 12′ in place within the pattern and which enabled a permanent bond to be formed between the bolt 12′ and the device 10 during the step of curing the resin R to form the device 10. The bolt 12′ is in this way integrally embedded in one piece with the device 10.

[0123] FIG. 15 shows a sectional view similar to that of FIG. 14, with a sleeve 12′ having an inner thread inherently present at the inner surface 14 of the device 10. Like with the bolt 12′ of FIG. 14, the sleeve 12′ has been bonded to the device during the step of curing the resin R used to form the housing 16 of the device 10

[0124] FIG. 16 shows a schematic view of internal components of the device 10. The device 10 comprises a shaft 82 extending along the horizontal axis of the device 10, in which a ball bearing 84 is affixed to the device at a bearing support 12′ which is integrally formed in one piece with the device 10. The shaft 82 is also journaled at the device 10 in a sleeve 86 and a sleeve 88. The shaft 82 is connected to an electric motor 94 via a transmission 92 and a drive shaft 90.

[0125] In FIG. 16 the angular tolerance between the sleeve 86 and the ball bearing 84 is less than 0.1°, since the inserts 12 used for the two components were fixed relative to one another on forming the wax pattern 45. Angular tolerances of less than 0.05° are achievable by the present teaching. Moreover, an axial tolerance of positioning between the inserts 12 of the sleeve 86 and of the ball bearing 84 is less than 0.1 mm, preferably less than 0.05 mm. Similarly a tolerance of positioning between the inserts 12 of the sleeve 86 and of the ball bearing 84 is less than 0.05 mm+0.5 mm/m, preferably less than 0.05 mm+0.2 mm/m.

[0126] FIG. 17 shows the device 10 to be a head of a golf club 96. The head 96 comprises a front face 98 and a body 100. The head can be connected to a shaft (not shown) via a shaft connector 102 in a manner known per se.

[0127] Not shown in FIG. 17, but indicated in FIG. 18, two weights 104, for example formed by tungsten inserts, can be provided as inserts 12′ at the wax pattern 54.

[0128] As also indicated in FIG. 18 a further insert 12′ is embedded within the wax pattern 54. This further insert 12′ is a shaft connector insert 106 which permits an accurate connection of the shaft at a pre-defined angle to the front face and a base 108 of the golf club 10′. In this way the angle between the shaft of the golf club and the front face can be reliably formed with an improved alignment quality in comparison to the prior art.