GOLF BALLS HAVING ELECTRONICALLY - DETECTABLE INSERTS

Abstract

Golf ball with a central cavity (6, 23) having an RFID/electronic tag (4, 24) located therein. The tag is immersed in a medium (5) which, in response to striking of the ball, flows around the tag to damp transitional movement and vibration. For retro-fit of an already-manufactured standard ball, entry of aqueous liquid into the cavity (6) is from a borehole-opening (3) which is centered within a dimple of the outer cover (1) of the ball and sealed (8), following introduction of a gelling agent (9). After the central cavity (22) is filled with a liquid medium (23), it is closed by a plastics plug (25). The tag (42) of a used/damaged ball (39) can be retrieved and recycled by an automated machine (30) that cuts a circumferential slit (40) through the cover and then impacts blades of a chisel (38) split the ball in two to reveal the tag.

Description

This application claims priority from United Kingdom application no. 1319959.1 filed Nov. 12, 2013 which claims priority from United Kingdom application no. 1308041.1 filed May 3, 2013.

FIELD OF THE INVENTION

This invention relates to golf balls of the kind having an electronically-detectable insert, and to their manufacture.

BACKGROUND OF THE INVENTION

Golf balls of the above kind are used, for example, in conjunction with detectors/readers at target-locations of golf-driving ranges to identify players who land their golf balls successfully at those locations. The inserts used are typically radio-frequency identification (‘RFID’) tags, and RFID readers are installed in instrumented targets that have associated data links, computer systems and user-interface displays. Alternative forms of insert may be used, such as magnets, ferrite rods and devices involving one or more resonant circuits.

Golf balls are subjected to exceptionally high shock, with peak accelerations when struck frequently exceeding 40,000 g. This potentially reduces the useful service life of most golf balls of the kind having an electronically-detectable insert, and objects of the present invention are to provide a form of golf ball of this kind, and a method of its manufacture in which the effect of shock is to a large extent minimized.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided a golf ball of the kind having an electronically-detectable insert, wherein the insert is located in a cavity within the body of the ball immersed in a medium which in response to striking of the ball flows as a liquid round the insert within the cavity.

According to another aspect of the invention a method of manufacturing a golf ball of the kind having an electronically-detectable insert, includes the steps of forming a cavity within a core of the golf ball, entering the insert in the cavity immersed in a medium which in response to striking of the ball flows as a liquid round the insert within the cavity.

In both aspects of the invention, the medium in which the insert is immersed may be an aqueous liquid or a thixotropic gel or a medium that is part liquid and part thixotropic gel. The liquid flow round the insert in response to the ball being struck tends by virtue of hydrodynamic drag to damp translational movement and vibration of the insert to an enhanced degree compared with that obtained with a resilient or cushioning medium in the cavity.

The cavity in which the insert is located may be centrally of the ball, and in all its dimensions may be at least twenty per cent, or preferably, thirty-three per cent, larger than the corresponding dimensions of the insert. Also, entry into the cavity may extend radially into the ball from a sealed opening through the outer surface of the ball, and where the outer surface of the ball is dimpled, the sealed opening may be centred on a dimple of the outer surface. Furthermore, the cavity may be located in the blind bottom of a radial borehole that is bored through the centre of the golf ball and is sealed closed with the insert located centrally of the ball.

The immersed insert may be a magnet, a ferrite rod, a device that involves one or more resonant circuits, or an RFID tag.

A further object of the present invention is to facilitate recycling of golf balls of the kind having an electronically-detectable insert, or at least of the insert. It is often the case with golf balls of the present invention that the ball itself or its outer cover needs to be replaced before the insert has reached the end of its useful life. More particularly, where a ball with a damaged cover is involved it can be cost-effective and environmentally desirable to remove the cover, and after retaining the one-piece or multi-piece core with the insert within it, fit a new cover over the retained core. Methods of removing covers from golf balls are well known and typically involve applying heat to soften the cover (which is usually of thermoplastic that has a much lower melting point than the rubber-compound of the core), and then using sharp edges to bite into the cover and scrape or pull it away from the core. These methods may abrade or cut the surface of the core or break off strongly adhering parts of it so that it is unsuitable for re-use. In these circumstances recovery and separation of the RFID tag or other insert from the core for re-use, becomes desirable for recycling and/or economic purposes, and according to a further aspect of the invention, the recovery of the insert from a golf ball of the kind having an outer cover and an electronically-detectable insert within a core of the ball, comprises the steps of cutting a circumferential slit in the ball, the slit having a depth that extends through the outer cover and partly into the surface of the core, locating chisel blades in the slit parallel to one another on opposites sides of the centre of the ball, impacting the chisel blades to split the core in half, and removing the insert from the split core for re-use.

BRIEF DESCRIPTION OF THE DRAWINGS

Golf balls of a kind having an electronically-detectable insert, and methods of their manufacture and recovery of their electronically-detectable inserts for recycling, all according to the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic sectional view of a first form of golf ball having an RFID-tag insert, according to the invention;

FIG. 2 is a schematic sectional view of the golf ball of FIG. 1 during an intermediate stage in its manufacture;

FIG. 3 is a schematic sectional view of a second form of golf ball having an RFID-tag insert, according to the invention;

FIG. 4 is a schematic sectional view of the core of the second form of golf ball during an intermediate stage in the golf-ball manufacture, the section in this case being taken in a plane at right angles to the section of FIG. 3;

FIG. 5 is a schematic part-sectional side-view of a machine for automated slitting and splitting according to the invention of golf balls of the kind having an electronically-detectable insert;

FIG. 6 is a sectional view taken on the line A-A of the ball-slitting machine of FIG. 5 at a stage prior to splitting of a circumferentially-slit golf-ball in the recovery for recycling of its electronically-detectable insert; and

FIG. 7 is an end view of the ball-slitting machine of FIG. 5 during a stage in the recovery of the electronically-detectable insert of a circumferentially-slit golf-ball.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, the golf ball in this example is a two-piece golf ball conforming to standard diameter and weight, with an outer dimpled-cover 1 and a solid core 2 (which may be single- or multi-layered). It includes within a radial borehole 3, an RFID-tag insert 4 located centrally of the ball. The borehole 3 extends through the cover 1 preferably centred on a surface dimple of the cover 1, and passes through the centre of the core 2 with its depth limited to leave a clearance dimension CD of not less than 10-13 millimetres between the blind end of the borehole 3 and the outer cover 1. The RFID-tag 4 is immersed in a liquid 5 that fills a cavity 6 defined at the bottom of the borehole 3 beneath a solid gel surface-layer 7 of the liquid 5 in the cavity 6. The borehole 3 above the layer 7 is plugged by a sealant 8; as described below, the layer 7 acts as a barrier while the sealant 8 is setting during manufacture of the ball.

The liquid 5 filling the cavity 6 is, for example, a mixture of fifty per cent de-ionized water and fifty per cent ethylene glycol. This mixture ensures that the freezing point of the liquid 5 is below −25 degrees Celsius, and thereby ensures that when the ball is struck during normal use, there is liquid-flow round the insert 4 within the cavity 6. The hydrodynamic drag on the insert 4 created by this flow damps translational movement and vibration of the insert 4.

While the ball is being struck, there is a possibility of the cavity 6 being deformed into a shape that might result in damage to the insert 4. As a precaution against damaged of this nature, the configuration of the cavity 6 is chosen to be in all its dimensions at least twenty to thirty-three per cent larger than the corresponding dimensions of the insert 4. In one implementation of the ball of FIG. 1, the borehole 3 has a diameter of 3.6 millimetres and the length of the cavity 6 is 16 millimetres, whereas the insert 4 as enclosed within its cylindrical glass-envelope and weighing 100 milligrams, has a diameter of 2.12 millimetres and a length of 12 millimetres.

Manufacture of the ball involves boring the radial borehole 3 centred on a suitable dimple of the outer cover 1, and then partially filling the borehole 3 with the aqueous solution of ethylene glycol. The insert 4 is then entered in the borehole 3 to be fully immersed in the liquid 5 throughout a depth appropriate to definition of the cavity 6 at the blind end of the borehole 3. This is followed, as illustrated in FIG. 2, by a step in which a small quantity of gelling agent 9, which may be in a powder (as illustrated) or liquid form, is poured onto the surface of the liquid 5 via a small funnel 10 entered in the borehole 3. Where a powder is used it may be an animal-gelatine with powder-grain between 0.5 to 1.0 millimetres so that it falls cleanly through the funnel 10.

Introduction of the gelling agent into the cavity 6 causes the surface of the liquid 5, and possibly the liquid medium deeper, to solidify into a thixotropic gel. When powder is used, the grains of gelatine are held by surface tension at the surface-level of the liquid and quickly swell and congeal. There is a corresponding outcome when a liquid gelling agent is used, the result in both cases being the formation at least at the surface of the liquid 5 in the cavity 6 of the layer 7 of solid thixotropic gel. This layer is maintained during the filling of the remainder of the borehole 3 with the sealant 8 and until the sealant has set, so as to establish a barrier to sealant entering the liquid 5.

Once the sealant 8 has set, the ball can be taken into use and in this a drive shot played by a typical male golfer will accelerate the ball during impact to speeds of around 60 metres per second. The contact duration during this impact is of the order of 0.4 milliseconds so the glass-encased tag 4 of the ball experiences an average force of about 15 Newtons during impact. This force propels the tag 4 through the liquid/gel content of the cavity 6, and the combination of rapid movement of the tag 5 and the walls of the cavity 6 provides intense mechanical agitation that liquefies the thixotropic gel. The consequent liquid-flow within the cavity 6 and round the tag 4 is dissipative and provides high viscous-damping. Internal components (such as the ferrite rod aerial and its resilient encapsulant) of the tag 4 are also damped by coupling through its glass envelope. By comparison with this situation, an RFID tag of finite mass embedded in a resilient compound will oscillate at near the resonant frequency of the mass-spring system formed by the tag and the elastic coupling to the core, and this oscillation will contribute significantly to stress levels within the tag and reduce its service life. The present invention enables significant improvement over this.

Small air bubbles may get trapped inside the cavity 6, and will increase the initial compressibility of the medium within the cavity 6. This is not a disadvantage provided that there is ample clearance between the walls of the cavity 6 and the insert 4. The entrained air will rapidly compress under impact and the effective compressibility will then revert to the intrinsic value of the air-free cavity 6. Slight compressibility allows for differential thermal expansion between the material of the core 2 and the liquid medium within the cavity 6.

The method of manufacture of the ball of FIG. 1 described above is applicable to the retro-fitting of an already-manufactured golf ball with an electronically-detectable insert. FIGS. 3 and 4 on the other hand illustrate an implementation of the invention where an RFID tag is inserted during manufacture of a golf ball.

Referring to FIGS. 3 and 4, the golf ball in this case has a core 20 within an overall outer cover 21 where a cavity 22 is formed in the core 20 during manufacture of the core 20 itself. The cavity 22 is filled initially with a liquid 23 and an RFID tag 24 is fully immersed in it at the centre of the core 20.

In this version of ball, the RFID tag 24 used is an ultra high frequency (UHF) 6 mm square EMBItag type 130006006 available from Wurth Elektronic GmbH. This form of tag is very robust as it is manufactured from fibreglass printed-circuit layers with a silicon chip embedded within the layers. It is thus monolithic and effectively one solid piece, 0.7 millimetres thick and weighs only 50 milligrams, In order to accommodate the larger shape of tag without removing more material of the core 20 than is necessary, the opening to the cavity 22 in the core 20 is preferably of rectangular or elongate cross-section and tapered to be compatible with a moulding process.

As shown in FIG. 4, a moulded elastomer-plug 25 is inserted into the cavity 22 and displaces the liquid 23, which spills out as shown at 26 in FIG. 4. The outer portion of the plug 25 is a tight fit into the mouth of the cavity 22 and may be provided with surface serrations to ensure that it locks in place but also allows excess liquid to flow out. If preferred, the upper portion of the plug 25 can have a circular rather than a rectangular cross-section to aid the sealing and locking action.

FIG. 3 shows the plug 25 fully inserted into the core 20 leaving the bottom part of the cavity 22 housing the RFID tag 24 immersed in the liquid 23.

RFID tags are constantly being developed so new types of small RFID that can be read from the centre of a golf ball will become available. For example, a different shaped version of the EMBItag could be produced to allow a narrower cavity opening or insertion into a borehole of 4.0 millimetres diameter through the cover of a golf ball as a retro-fit. Preferably the borehole diameter is not more than 4.0 millimetres so as to be contained within the diameter of a large dimple on a typical standard golf ball. The EMBItag can be used in near-field mode without an external antenna but its sensitivity is dependent on the area of its inbuilt loop antenna, so very small area dimensions are not practical. However, in the instrumented golf target application, a short read range of 30 millimetres or so is acceptable. Currently, a high frequency ‘NeoTAG®’ device, type F262, is available from NEOSID Pemetzrieder GmbH. This device operates at 13.56 MHz with diameter and height dimensions of 2.6 millimetres maximum and is thus ideally suited to the present application.

In the illustrative examples of FIGS. 1 to 4 the RFID tags are immersed in a thermo-reversible gel which is solid at room temperature but has low melting point (for example about 30 degrees Celsius). Curing gels which are liquid when injected into the core-cavities and which solidify on curing, could be used, and liquids could be used in place of gels. In all cases the essential requirement is that the RFID tag is cocooned within a filled cavity where the filler-medium is a liquid or becomes liquid during high-shock impact of the golf ball. It is important that the cavity does not collapse during impact and in this respect the elastic bulk modulus of the liquid or gel should be comparable to that of the golf-ball core material and preferably not less than 1.0 gigapascal.

As indicated above, it may become desirable in certain circumstances for recycling and/or economic purposes, to recover the RFID tag or other insert from a damaged golf ball. Recovery of the insert is carried out according to the present invention by a method that involves cutting a circumferential slit in the ball to a depth that extends through the outer cover of the ball and partly into the surface of the core. Chisel blades are then located in the slit parallel to one another on opposites sides of the centre of the ball, and are impacted to split the core of the ball into two and allow the insert to be removed for re-use. A machine for automating the slitting and splitting steps of the method, is illustrated in FIGS. 5 to 7 and will now be described.

Referring to FIGS. 5 and 6, the main components of the ball slitting and splitting machine 30 comprise a feed hopper 31, a rotating ball escapement 32, downwardly-slanted rails 33, a rotating circular saw blade 34, a rotating belt 35, belt-loading rollers 36, guide fin 37 and an impact chisel 38. The blade of the chisel is divided into two by a central cut-away as shown.

FIG. 5 shows a small quantity of balls held in the feed hopper 31 but in practice the capacity of the hopper 31 could be greatly increased. Balls are distributed individually from the hopper 31 by the escapement 32 to drop onto the downwardly-slanted rails 33 and pass separately into the machine without collision or interrupting continuous operation of the machine.

A golf ball 39 with contained RFID tag 42 is shown in FIG. 5 in three successive positions 39(a), 39(b) and 39(c) as it passes through the machine. After dropping onto the downwardly-slanted rails 33, the ball rolls with represented clockwise rotation into the belt 35. The belt 35 rotates in the opposite, anti-clockwise sense to assist ball rotation along the rails 33 into position 39(a) and then into an upper portion of the saw blade 34. The blade 34 rotates in the represented anti-clockwise sense at high speed and cuts a circumferential slit through the cover of the ball and partly into its core. The belt-loading rollers 36 press the ball firmly onto the rails 33 as it passes through the saw blade 34 and prevents any tendency for self-feed or slipping. As the ball rolls through the blade 34, the depth of cut varies from a minimum at the beginning and end of the cut and a maximum at the middle. This results in a ‘tear shaped’ slit 40 as shown in 39(b).

Once the ball has rolled off the blade 34, its slit 40 (see FIG. 6) is engaged by the guide fin 37. The fin 37 keeps the ball correctly aligned as it rolls towards the end of the rails 33 where it then engages with stop pegs 41 under the impact chisel 38. The top part of the guide fin 37 is designed to fit freely inside the slit 40 as the ball rolls from position 39(b) to position 39(c) but increases in thickness to hold the ball steady once it reaches position 39(c).

It is important that the minimum depth of slit cut into the ball is sufficient to cut through the outer cover of the ball since the cover is generally very tough, malleable and difficult to break other than by cutting with the saw blade. However, the maximum slit depth should not exceed CD (FIG. 1) as this could damage the cocooned RFID tag 42. In order to minimize the variation in slit depth, the roll radius RR (FIG. 6) is chosen to be smaller than the ball diameter so that the ball rotates through a complete turn in a shorter distance compared with the circumference of the ball. This is achieved by arranging that the contact surfaces of the rails 33 are inclined downwardly so that the roll radius RR is then proportional to the sine of the tilt angle TA as shown in FIG. 6. In one example of the machine of FIG. 5, the saw blade 34 used is a thin kerf crosscut blade of 300 millimetres diameter, the tilt angle TA is 35 degrees, and the maximum depth of slit is set to 11 millimetres; this results in a minimum depth at the slit cusp of about 6 millimetres.

Once the ball is located at position 39(c), the impact chisel 38 is operated to split the ball in two as illustrated by FIG. 7. The embedded tag 42 is exposed by this and can be removed from the body of the ball by washing out with warm water.

During a recycling and salvaging process carried out on a ball as manufactured as described with reference to FIG. 1, the slit cut into the ball may have a depth of 12 millimetres in any orientation of the ball without cutting into the cavity 6. The thixotropic gel formed as described by way of example above, has a melting point below 30 degrees Celsius and an absolute viscosity below 100 centipoise when agitated. This allows the insert 4 to be easily extracted from the split golf ball by washing out with water as referred to above, or by applying heat or both. The use of a high viscosity medium for the filler of the cavity would be likely to be counter-productive as this would tend to retain the insert within the cavity. Without limitation, it is preferable for the medium filling the cavity 9 to have an absolute viscosity less than 1000 centipoise, at 20 degrees Celsius.

Claims

1. A golf ball of a kind having an electronically-detectable insert, wherein the insert is located in a cavity within the body of the ball immersed in a medium which in response to striking of the ball flows as a liquid round the insert within the cavity.

2. A golf ball according to claim 1, wherein the medium in which the insert is immersed is an aqueous liquid.

3. A golf ball according to claim 1, wherein the medium in which the insert is immersed comprises a thixotropic gel.

4. A golf ball according to claim 1, wherein the cavity is located centrally of the ball.

5. A golf ball according to claim 1, wherein the cavity in all its dimensions is at least twenty per cent larger than corresponding dimensions of the insert.

6. A golf ball according to claim 1, wherein the cavity in all its dimensions is at least thirty-three per cent larger than corresponding dimensions of the insert.

7. A golf ball according to claim 1, wherein entry into the cavity extends radially into the ball from a sealed opening through an outer surface of the ball.

8. A golf ball according to claim 7 wherein the outer surface of the ball is dimpled and the sealed opening is centred within a dimple of the outer surface.

9. A golf ball according to claim 1, wherein the electronically-detectable insert is one of a magnet, a ferrite rod and a device involving at least one resonant circuit.

10. A golf ball according to claim 1, wherein the electronically-detectable insert is an RFID tag.

11. A method of manufacturing a golf ball of a kind having an electronically-detectable insert, comprising the steps of forming a cavity within a core of the golf ball, and entering the insert in the cavity immersed in a medium which in response to striking of the ball flows as a liquid round the insert within the cavity.

12. A method according to claim 11, wherein the cavity is filled with a liquid medium via a feed passageway that opens into the cavity, the electronically-detectable insert is entered in the cavity through the feed passageway to be immersed in the liquid medium within the cavity, and plugging the feed passageway.

13. A method according to claim 12, wherein following entry of the electronically-detectable insert into the cavity, a gelling agent is added to the liquid medium within the cavity to create a gel within at least part of the cavity.

14. A method according to claim 11, wherein the medium in which the insert is immersed is an aqueous liquid.

15. A method according to claim 11, wherein the medium in which the insert is immersed comprises a thixotropic gel.

16. A method according to claim 11, wherein the cavity is located centrally of the ball.

17. A method according to claim 11, wherein the electronically-detectable insert is one of a magnet, a ferrite rod and a device that involves at least one resonant circuits.

18. A method according to claim 11, wherein the electronically-detectable insert is an RFID tag.

19. A method for the recovery of an insert from a golf ball of a kind having an outer cover and an electronically-detectable insert within a core of the ball, comprising the steps of cutting a circumferential slit in the ball, the slit having a depth that extends through the outer cover of the ball and partly into the core, locating chisel blades in the slit parallel to one another on opposites sides of a centre of the ball, impacting the chisel blades to split the core in two, and removing the insert from the split core for re-use.

20. A method according to claim 19, wherein the electronically-detectable insert is an RFD tag.