GB1580434A

GB1580434A - Manufacture of balls

Info

Publication number: GB1580434A
Application number: GB22188/76A
Authority: GB
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1976-05-28
Filing date: 1976-05-28
Publication date: 1980-12-03
Also published as: AU508616B2; FR2352560B2; SE7706082L; DE2724127A1; ZA772978B; JPS5319227A; IT1115483B; AU2533577A; FR2352560A2

Description

(54) IMPROVEMENTS IN OR RELATING TO THE MANUFACTURE OF BALLS (71) We, DUNLOP LIMITED, an English Company, of Dunlop House, Ryder Street, St. James's London S.W.1, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to improvements in or relating to the manufacture of balls of the kind which comprise a core with discrete cover pieces wrapped around and adhesively secured to the core in edge-to-edge relation.

More particularly the invention relates to the manufacture of tennis balls wherein two felt Cassiniarl-shaped cover pieces are wrapped in mutually perpendicular relation around a resilient core and adhesively secured to the core in edge-to-edge relation.

The elimination of manual operations in the mass production of tennis balls presents great problems if the necessary high quality standards are to be attained. Previous proposals either require manual operations or produce a high proportion of defective balls and none is adapted to mass produce balls of high quality in a cost-effective manner.

One of the principal problems in the manufacture of tennis balls is to ensure that the felt cover pieces are accurately shaped when laid on the core since an enlargement of either of the two cover pieces will lead to the serious defect of overlapping whereas if either cover piece is too small the required edge-to-edge abutment of the two cover pieces will not be achieved. In view of the loose texture or composition of the felt cover pieces accurate shaping is difficult to ensure especially if they are stamped out in stacks of 5 or more, although it is economically more viable to cut the cover pieces in stacks rather than individually.If a number of cover pieces are cut in a single stamping operation compression of the felt layers will detract from the desired perpendicular edge of each cover piece and under the compressing and deforming force of the stamp the cover piece will tend to become processively smaller the lower they are in the stack.

On the other hand cutting the cover pieces in stacks facilitates the application of adhesive to the peripheral edge of each cut cover piece since the adhesive is applied to the sides of the stack before the cover pieces are individually peeled off.

An object of the present invention is to subject a cut cover piece to a shaping operation immediately before its application to the core. In this way variation of the cover from its cut shape, e.g. through stretching when it is peeled off the stack, is compensated.

According to the present invention there is provided a method of making a ball comprising a core with discrete cover pieces of a stretchable material wrapped around and adhesively secured to the core in edgeto-edge relation, the method comprising initially cutting the cover pieces approximately to a predetermined shape but undersize, stretching the cover pieces within a template so that each is given said predetermined shape by the template and adhesively securing the cover pieces to the core.

The method preferably comprises stretching felt cover pieces and adhesively securing them to a resilient core, and preferably two cover pieces are cut generally to a Cassinianshape and after stretching are wrapped around the core so as to be perpendicularly related.

Each cover piece is preferably subjected to opposite stretching forces acting longitudinally of the end portions thereof, the central or waist portion of each cover piece not being subjected to transverse stretching forces. The central or waist portion of each cover piece may be restrained while its end portions are subjected to opposite longitudinal stretching forces whereby said central or waist portion is not subjected to longitudinal stretching forces.

After cutting to shape but undersize the cover pieces required to cover a core are preferably placed flat in respective slots of a loading plate, each said slot constituting a said template, the cover pieces are stretched then while flat and in the respective slots to conform to the shape of the slots and the core is subsequently passed through the loading plate to carry the stretched cover pieces in sequence therewith into an enclosure whereby the cover pieces are wrapped around and adhered to the core.

This is preferably achieved using apparatus generally as described in the Complete Specification of Patent No. 1,517,502.

While in the flat state the generally Cassinian cover pieces are preferably stretched so as to have end edges with a smaller radius of curvature than the remainder of each end portion.

In accordance with another aspect of the invention there is provided apparatus suitable for use in carrying out the method described in the six preceding paragraphs, the apparatus comprising a loading plate having a slot generally of Cassinian shape to receive an undersized cover piece in the flat state and means relatively movable toward and away from a central area of the slot to engage or release a cover piece in the slot, the stretching means comprising at least two members which are mutually separable in a direction parallel with the axis of the slot while in engagement with a cover piece therein longitudinally to stretch the cover piece to the shape of the slot.

The slot is preferably profiled so that when stretched to conform thereto the cover piece has end edges of smaller radius of curvature than the remainder of each end portion thereof.

Each of said members preferably has on its face presented to the slot an array of pointed projections to bite into a cover piece in the slot.

The stretching means preferably additionally comprises a stationary member interposed between said mutually separable members and arranged to clamp the central or waist portion of a cover piece in the slot while the end portions thereof are stretched by the separable members, and this has on its face presented toward the slot pointed projections to bite into a cover piece in the slot.

The stretching means preferably additionally comprises a perforated stripper plate arranged to overlie a cover piece in the slot and movable relative to said separable or said separable and stationary members whereby said pointed projections are movable through respective perforations of the stripper plate into and out of engagement with a cover piece in the slot.

Means is preferably provided biassing the stripper plate away from said members and for arresting it at a position spaced from and parallel therewith such that the pointed projections are retracted into the perforations, the arrangement being such that as the stretching means is advanced to the loading plate the stripper plate contacts the loading plate and continued movement of the stretching means toward the loading plate causes the pointed projections to project through the perforations as the biassing means is overcome. The perforations of the stripper plate through which the pointed projections of said separable members are movable are preferably elongated in the direction of separating movement of said members.

Means is preferably provided for moving the loading plate so that two similar slots therein are advanced successively to a station where the stretching means is applied to a cover piece in the slot and to a station where a core is passed through the loading plate so as to carry the stretched cover piece in the slot with the core into an enclosure adjacent the loading plate, thereby wrapping the cover piece around and adhesively securing it to the core and the arrangement of said two slots in the loading plate is preferably such that their axes are mutually perpendicular in the positions they occupy at both said stations and the stretching means may comprise four members which are mutually separable in perpendicularly related directions corresponding to said perpendicular axes.

A single stripper plate may be associated with all four said separable members.

Each said separable member is preferably guided for longitudinal movement in a respective channel and all of the separable members are preferably articulated to a common rotary member, the arrangement being such that angular movement of the rotary member imparts a similar reciprocating movement to the separable members in their respective channels.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a sectional elevation of stretching means in accordance with the present invention taken on the line I-I of Figure 2; Figure 2 is a sectional plan view taken on the lines Il-Il of Figure 1; Figure 3 is a sectional elevation with parts removed taken on the line Ill-Ill of Figure 2; Figure 4 is a view from below of the stretching means; Figure 5 is a view from below of the stretching means with the stripper plate removed taken on the line V-V of Figure 3, and Figure 6 is a plan view of a loading plate template in which a felt cover piece is to be located to be stretched by the apparatus of Figures 1 to 5.

As shown in Figures 1 to 5 the stretching means comprises a plate 15 formed with four rectangular recesses 11 in which mem- bers 12 are respectively movable. A plate 13 is bolted on top of the plate 15 and has flanges 14 which overlie the members 12 and define with the plate 15 cruciform guidance channels in which the members 12 are guided for movement in perpendicularly related directions. The apparatus can be mounted on means (not shown) whereby it is bodily movable up and down to advance it toward or retract it away from a template 16 (Figure 6).

Bolted on top of the plate 15 is an annular housing 16 having spaced-apart bearings 17 for a sleeve 18 which is integral at its upper end with a lever 19 and at its lower end with a flanged bush 20 so that by moving the lever 19 the sleeve 18 and bush 20 are rotatable relative to the housing 16 and the plates 15 and 13. The bush 20 has a flange 21 to which four links 22 are pivotally connected at equally angularly spaced positions while the other end of each link 22 is pivotally connected to a respective one of the members 12. It will be apparent that by rotation of the lever 19 the members 12 are jointly extended or retracted relative to the plate 15.

The plate 10 has four straight rows of pointed projections 23 each spaced inwardly from and parallel with the rear end of one of the recesses 11, while each member 12 has an arcuate array of similar pointed projections 24.

Beneath the plate 10 is a stripper plate 25.

This is maintained parallel with the plate 10 by enlarged portions 26 of four bolts 27 integral with the stripper plate 25 and upstanding therefrom and each extendingthrough a relatively large bore 28 in the plate 13 and a relatively smaller bore 29 in the housing 16. Nuts 30 threaded onto the bolts 27 limit the displacement of the stripper plate 25 away from the plate 10 by compression springs 31 trapped in the bores 28 between the enlarged portion 26 of the bolts and the housing 16.The nuts 30 are positioned so that in the normal position of the stripper plate 25 spaced from the plate 10 all of the pointed projections 23 and 24 are retracted, the projections 23 of plate 10 within an elongate slot 32 for each row and each projection 24 within a respective slot 33 in the stripper plate, the length of each slot 33 in the direction of permitted movement of the associated member 12 being equal to the possible displacement of said member 12 in the channel 11 thereof when the lever 19 is rotated.

The apparatus of Figures 1 to 5 is intended for use in association with apparatus generally as described in the Complete Specification of Patent No. 1,517,502, i.e.

apparatus in which felt cover pieces cut generally to Cassinian shape are placed flat in respective slots therefor in a loading plate and are transported by the loading plate to stations where a ball core is passed through the loading plate perpendicularly to the plate of the slots to carry the cover pieces with it into generally spherical enclosures whereby the cover pieces are wrapped around and adhesively secured to the core. In Figure 6 there is shown one slot 34 in a loading plate 16 but it will be appreciated that to wrap two Cassinian cover pieces around the same core it is necessary to present them to the core in perpendicular relation. For this purpose two slots are provided in the same loading plate in relative positions such that the axes of the slots are perpendicularly related when the slots are positioned for movement therethrough of the same core.It is therefore convenient that the same stretching means should be capable of engaging and stretching cover pieces presented to it in perpendicularly related positions and it is for this purpose that the apparatus illustrated has four separable members 12 instead of only two although it is to be appreciated that only two of the members 12 moving on the same axis engage a cover piece in a given stretching operation.

It will also be apparent that the stretching means of Figures 1 to 5 does not lend itself to incorporation in the apparatus illustrated in the drawings of our said co-pending Application without modification. The loading plate 16 of Figure 6 of the present Application can be a template separate from the slots of the loading plates of the apparatus of our said co-pending Application but this is not the optimum arrangement since each felt after stretching would have to be transferred from the slot of the template of Figure 6 to one of the slots of the loading plate of the apparatus of our said co-pending Application e.g. by hand.Any such transfer stage is undesirable not only for economic reasons but because the time elapsing between stretching the felt in the slot 34 and its application to the ball core should be kept to a minimum to avoid any tendency of the stretched felt to resume its pre-stretched shape.

It is therefore preferred that the template 16 of Figure 6 is the loading plate used in apparatus resembling that of our said Co- pending Application so that the slot 34 is a slot through which the ball core is subsequently passed into a part-spherical enclosure to wrap the stretched felt around and adhere it to the ball core. After peeling it off the stack of cut cover pieces an individual cover piece is placed in the slot 34 of Figure 6 and is passed on the loading plate below the stretching means of Figures 1 to 5 and thence directly and without removal from the slot 34 to the station between the two enclosures illustrated in our said co-pending Application.This can be achieved by enlargement of the rotary loading plate of our said co-pending Application or the rotary loading plate can be replaced by a linear arrangement on which individual loading plates each formed with two perpendicularly related slots 34 are transported on a conveyor in sequence to the stretching means of Figures 1 to 5 and thence to apparatus similar to that illustrated in our said co-pending Application.

The operation of the apparatus illustrated in Figures 1 to 5 is as follows: A number of cover pieces are cut from superimposed layers of felt, each having adhesive on one side, in a single stamping operation. The cut cover pieces are stacked and adhesive is applied to the sides of the stack so that the peripheral edge of each cover piece is coated with adhesive. The cover pieces are then peeled off individually and each is placed in a respective slot 34 in a loading plate 16. The two cover pieces which are to be applied to the same ball core are located in similar slots 34 with their adhesive covered sides oppositely presented and the two slots are arranged in the same loading plate 16 so that when presented in sequence to apparatus similar to that illustrated in our said co-pending Application the axes of the slots are perpendicularly related.It will normally be convenient for the slots to be perpendicularly related when presented to the stretching means of Figures 1 to 5. On this assumption a first slot 34 arrives beneath the stretching means of Figures 1 to 5 with its axis parallel with the common direction of movement of two of the members 12. The stretching means of Figures 1 to 5 is then lowered until the stripper plate 25 rests on the loading plate 16. Continued downward movement of the stretching means will cause compression of the springs 31 so that the pointed projections 23 and 24 extend through the slots 32 and 33 of the stripper plate. Two of the parallel rows of stationary projections 23 will engage the felt cover piece 50 in the slot 34 at opposite ends of its central or waist portion 51 while the movable projections 24 engage the end portions of the cover piece.At this time it is assumed that the two members 12 are in the inwardly retracted position relative to the plate 15. The lever 19 is now turned causing all of the members 12 to be extended relative to the plate 15 so that the projections 24 engaging the end portions of the felt move to the outermost position in which they are illustrated in Figures 1, 4 and 5. In so doing the movable projections 24 stretch the felt 50 in the slot 34 and it will be appreciated that the felt is subjected substantially wholly to longitudinal forces.

Furthermore the stationary projections 23 substantially prevent the application of any stretching forces to the central or waist portion 51 of the cover piece.

Each cover piece is cut slightly undersize relative to the slot 34 into which it is placed but the central or waist portion of the cover piece is cut generally to the final shape, the reduction in size of the cover piece being primarily in the longitudinal direction.

Because of the tendency of each cover piece when wrapped around the spherical core to become squared off at its extreme ends the slot 34 is, as shown, provided with end recesses 35 of a smaller radius of curvature than the remainder of the slot. Squaring off of the ends of the cover piece when wrapped around the ball core will result in the cover piece regaining a true Cassinian shape so as to make proper fitting contact with the other cover piece wrapped on the same core.

The result of the stretching operation is that each cover piece has a precisely predetermined shape imparted to it by the shape of the slot 34 immediately prior to application to the ball core.

WHAT WE CLAIM IS:- 1. A method of making a ball comprising a core with discrete cover pieces of a stretchable material wrapped around and adhesively secured to the core in edge-toedge relation, the method comprising initially cutting the cover pieces approximately to a predetermined shape but undersize, stretching the cover pieces within a template so that each is given said predetermined shape by the template and adhesively securing the cover pieces to the core.

2. A method as claimed in claim 1, comprising stretching felt cover pieces and adhesively securing them to a resilient core.

3. A method as claimed in either preceding claim wherein two cover pieces are cut generally to a Cassinian shape and after stretching are wrapped around the core so as to be perpendicularly related.

4. A method as claimed in claim 3, wherein each cover piece is subjected to opposite stretching forces acting longitudinally of the end portions thereof, the central or waist portion of each cover piece not being subjected to transverse stretching forces.

5. A method as claimed in claim 4, wherein the central or waist portion of each cover piece is restrained while its end portions are subjected to opposite longitudinal stretching forces whereby said central or

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. it off the stack of cut cover pieces an individual cover piece is placed in the slot 34 of Figure 6 and is passed on the loading plate below the stretching means of Figures 1 to 5 and thence directly and without removal from the slot 34 to the station between the two enclosures illustrated in our said co-pending Application. This can be achieved by enlargement of the rotary loading plate of our said co-pending Application or the rotary loading plate can be replaced by a linear arrangement on which individual loading plates each formed with two perpendicularly related slots 34 are transported on a conveyor in sequence to the stretching means of Figures 1 to 5 and thence to apparatus similar to that illustrated in our said co-pending Application. The operation of the apparatus illustrated in Figures 1 to 5 is as follows: A number of cover pieces are cut from superimposed layers of felt, each having adhesive on one side, in a single stamping operation. The cut cover pieces are stacked and adhesive is applied to the sides of the stack so that the peripheral edge of each cover piece is coated with adhesive. The cover pieces are then peeled off individually and each is placed in a respective slot 34 in a loading plate 16. The two cover pieces which are to be applied to the same ball core are located in similar slots 34 with their adhesive covered sides oppositely presented and the two slots are arranged in the same loading plate 16 so that when presented in sequence to apparatus similar to that illustrated in our said co-pending Application the axes of the slots are perpendicularly related.It will normally be convenient for the slots to be perpendicularly related when presented to the stretching means of Figures 1 to 5. On this assumption a first slot 34 arrives beneath the stretching means of Figures 1 to 5 with its axis parallel with the common direction of movement of two of the members 12. The stretching means of Figures 1 to 5 is then lowered until the stripper plate 25 rests on the loading plate 16. Continued downward movement of the stretching means will cause compression of the springs 31 so that the pointed projections 23 and 24 extend through the slots 32 and 33 of the stripper plate. Two of the parallel rows of stationary projections 23 will engage the felt cover piece 50 in the slot 34 at opposite ends of its central or waist portion 51 while the movable projections 24 engage the end portions of the cover piece.At this time it is assumed that the two members 12 are in the inwardly retracted position relative to the plate 15. The lever 19 is now turned causing all of the members 12 to be extended relative to the plate 15 so that the projections 24 engaging the end portions of the felt move to the outermost position in which they are illustrated in Figures 1, 4 and 5. In so doing the movable projections 24 stretch the felt 50 in the slot 34 and it will be appreciated that the felt is subjected substantially wholly to longitudinal forces. Furthermore the stationary projections 23 substantially prevent the application of any stretching forces to the central or waist portion 51 of the cover piece. Each cover piece is cut slightly undersize relative to the slot 34 into which it is placed but the central or waist portion of the cover piece is cut generally to the final shape, the reduction in size of the cover piece being primarily in the longitudinal direction. Because of the tendency of each cover piece when wrapped around the spherical core to become squared off at its extreme ends the slot 34 is, as shown, provided with end recesses 35 of a smaller radius of curvature than the remainder of the slot. Squaring off of the ends of the cover piece when wrapped around the ball core will result in the cover piece regaining a true Cassinian shape so as to make proper fitting contact with the other cover piece wrapped on the same core. The result of the stretching operation is that each cover piece has a precisely predetermined shape imparted to it by the shape of the slot 34 immediately prior to application to the ball core. WHAT WE CLAIM IS:-

1. A method of making a ball comprising a core with discrete cover pieces of a stretchable material wrapped around and adhesively secured to the core in edge-toedge relation, the method comprising initially cutting the cover pieces approximately to a predetermined shape but undersize, stretching the cover pieces within a template so that each is given said predetermined shape by the template and adhesively securing the cover pieces to the core.

waist portion is not subjected to longitudinal stretching forces.

6. A method as claimed in any preceding claim, wherein after cutting to shape but undersize the cover pieces required to cover a core are placed flat in respective slots of a loading plate, each said slot constituting a said template, wherein the cover pieces are stretched while flat and in the respective slots to conform to the shape of the slots and wherein the core is subsequently passed through the loading plate to carry the stretched cover pieces in sequence therewith into an enclosure whereby the cover pieces are wrapped around and adhered to the core.

7. A method as claimed in claim 3, or any of claims 4--6 as appendent to claim 3, wherein while in the flat state the generally Cassinian cover pieces are stretched so as to have end edges with a smaller radius of curvature than the remainder of each end portion.

8. Apparatus suitable for use in carrying out the method claimed in any preceding claim, comprising a loading plate having a slot generally of Cassinian shape to receive an undersized cover piece in the flat state and stretching means relatively movable toward and away from a central area of the slot to engage or release a cover piece in the slot, the stretching means comprising at least two members which are mutually separable in a direction parallel with the axis of the slot while in engagement with a cover piece therein longitudinally to stretch the cover piece to the shape of the slot.

9. Apparatus as claimed in claim 8, wherein the slot is profiled so that when stretched to conform thereto the cover pieces has end edges of smaller radius of curvature than the remainder of each end portion thereof.

10. Apparatus as claimed in claim 8 or claim 9, wherein each of said members has on its face presented to the slot an array of pointed projections to bite into a cover piece in the slot.

11. Apparatus as claimed in any of claims 8-10 wherein the stretching means additionally comprises a stationary member interposed between said mutually separable members and arranged to clamp the central or waist portion of a cover piece in the slot while the end portions thereof are stretched by the separable members.

12. Apparatus as claimed in claim 11, wherein the stationary member has on its face presented toward the slot pointed projections to bite into a cover piece in the slot.

13. Apparatus as claimed in claim 10, or claim 11 or claim 12 as appendent to claim 10, wherein the stretching means additionally comprises a perforated stripper plate arranged to overlie a cover piece in the slot and movable relative to said separable or said separable and stationary members whereby said pointed projections are movable through respective perforations of the stripper plate into and out of engagement with a cover piece in the slot.

14. Apparatus as claimed in claim 13, wherein means is provided biassing the stripper plate away from said members and for arresting it at a position spaced from and parallel therewith such that the pointed projections are retracted into the perforations, the arrangement being such that as the stretching means is advanced to the loading plate the stripper plate contacts the loading plate and continued movement of the stretching means toward the loading plate causes the pointed projections to project through the perforations as the biassing means is overcome.

15. Apparatus as claimed in claim 13 or claim 14, wherein the perforations of the stripper plate through which the pointed projections of said separable members are movable are elongated in the direction of separating movement of said members.

16. Apparatus as claimed in any of claims 8-15 and comprising means for moving the loading plate so that two similar slots therein are advanced successively to a station where the stretching means is applied to a cover piece in the slot and to a station where a core is passed through the loading plate so as to carry the stretched cover piece in the slot with the core into an enclosure adjacent the loading plate, thereby wrapping the cover piece around and adhesively securing it to the core, wherein the arrangement of said two slots in the loading plate is such that their axes are mutually perpendicular in the position they occupy at both said stations and wherein the stretching means comprises four members which are mutually separable in perpendicularly related directions corresponding to said perpendicular axes.

17. Apparatus as claimed in claim 16 as appendent to any of claims 13-15, wherein a single stripper plate is associated with all four said separable members.

18. Apparatus as claimed in any of claims 8-17, wherein each said separable member is guided for longitudinal movement in a respective channel and all of the separable members are articulated to a common rotary member, the arrangement being such that angular all of the separable members are movement of the rotary member imparts a similar reciprocating movement to the separable members in their respective channels.

19. A method of making a ball com prising a core with discrete curved pieces of a stretchable material wrapped around and adhesively secured to the core in edge-toedge relation substantially as herein described.

20. Apparatus for carrying out the method claimed in any of claims 1-7 and 18 constructed and arranged substantially as herein described and as shown in the accompanying drawings.