CA1244902A - Electrically conductive tennis ball and line calling system - Google Patents
Electrically conductive tennis ball and line calling systemInfo
- Publication number
- CA1244902A CA1244902A CA000535493A CA535493A CA1244902A CA 1244902 A CA1244902 A CA 1244902A CA 000535493 A CA000535493 A CA 000535493A CA 535493 A CA535493 A CA 535493A CA 1244902 A CA1244902 A CA 1244902A
- Authority
- CA
- Canada
- Prior art keywords
- electrically conductive
- fibers
- cover
- strands
- fabric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE
An electrically conductive tennis ball comprising a cover of woven fabric in which the yarn used for weaving the fabric in at least one direction is made by twisting together a blend of electrically conductive and electrically nonconductive filament fibers. The electrically nonconductive fibers may predominate, and the woof yarn may be thicker than the warp yarn which may be so woven with the woof yarn that the latter occupies the major part of the ball's surface. To promote continuity of the electrical paths in the ball's cover, an electrically conductive adhesive, or mat, or scrim or other base may be interposed between the woven cover, and an electrically conductive coating may be applied to the inner, or back, side of the cover. Needling may also be employed to reorient the fibers in the cover and thereby enhance the conductivity of the electrical paths along the inner side of the cover. Features of the invention such as those just des-cribed reduce the number of electrically conductive fibers needed to make the ball operate satisfactorily, eliminating object-ionable discoloration of the ball attributable to those fibers and also eliminating changes in the playing characteristics of the ball which a greater number of those fibers might create.
Tennis balls as just described may be made more conductive than water to keep water on the court from generating a false signal.
An electrically conductive tennis ball comprising a cover of woven fabric in which the yarn used for weaving the fabric in at least one direction is made by twisting together a blend of electrically conductive and electrically nonconductive filament fibers. The electrically nonconductive fibers may predominate, and the woof yarn may be thicker than the warp yarn which may be so woven with the woof yarn that the latter occupies the major part of the ball's surface. To promote continuity of the electrical paths in the ball's cover, an electrically conductive adhesive, or mat, or scrim or other base may be interposed between the woven cover, and an electrically conductive coating may be applied to the inner, or back, side of the cover. Needling may also be employed to reorient the fibers in the cover and thereby enhance the conductivity of the electrical paths along the inner side of the cover. Features of the invention such as those just des-cribed reduce the number of electrically conductive fibers needed to make the ball operate satisfactorily, eliminating object-ionable discoloration of the ball attributable to those fibers and also eliminating changes in the playing characteristics of the ball which a greater number of those fibers might create.
Tennis balls as just described may be made more conductive than water to keep water on the court from generating a false signal.
Description
ELECTRICALLY CONDUCTIVE TENNIS BALL
AND L IN E CAI:.LING SYSTEM
FIELD OF THE INVENTICN
This invention relates to improvements in electrically conductive tennis balls which are used with auto~atic tennis court line calling systems to detect whe~her the ball lands in or out of a tennis court 10 playing area or strikes the top of the net. Line calling systems of this type have one or more sets of exposed~ spaced apart conductors extending along selected areas of the tennis court and the top of the net to sense touchdown of the electrically conductive 15 ball.
When the ball lands across two or more of the sensing conductor~, an electrical current-conducting circuit is completed throu~h the ball to signal the player~ that the ball touched down in an area occupied 20 by the oonductors.
Electrical conductivity of the tenni~ ball may be established by incorporating electrically conductive fibers into the cover of the ball.
25 SUMMARY AND C!E3JECTS OF I~IE INVENTION
In accordance with this invention, a blend of electrically conductive and nonconductive fibers are spun together to form yarn which is used to weave the 30 fabric for the tennis ball cover. The conductive and nonconductive fibers are random lengths of filaments, as opposed to staple fibers.
. .
The electrically conductive fibers may be made from stainless steel. Alternatively, other types of electrically conductive fibers may be used such as those described in U.S.
Patent No. ~,299,38~ which issued November 10, 1981, to John 5 A. Van Auken for ELECTRICALLY CONDUCTIVE GAME BALL.
One embodiment of this invention provides an electrically conductive tennis ball for use with an electrical detection circuit in which touchdown of the ball in a selected area is detected by completion of a circuit between spaced apart electrical conductors extending along that area. The electrically conductive tennis ball comprises an elastically deformable sphere, a cover of woven fabric covering the sphere with the fabric being woven with a set of warp strands interlaced with a set of woof strands, and with the strands of one of the sets comprising a quantity of electrically conductive fibers and a quantity of electrically nonconductive fibers, and the strands of the other of the sets being composed entirely of electrically nonconductive fibers.
In some oE the illustrated embodiments the tennis ball advantageously includes an electrically conductive base which lies between the woven cover and the elastically deformable core of the ball to enhance electrical continuity amongst -the conductive fibers in the cover. The electrically conductive base preferably extends entirely around the core, thus bridging the seams between the cover's panels to establish electrical continuity between the panels.
The electrically conductive base may be an electrically conductive adhesive which performs the additional function of adhering the cover to the core of the ball. Other types of electrically conductive bases may be employed.
For example, the electrically conductive base may be an electrically conductive scrim of fibers of the type described in U.S. Patent No. 4,299,384. Alternatively, the electrically conductive base may be in the form of a thin, llexible, woven or unwoven cloth or mat which may be bonded to the back side of the cover. An electrically conductive adhesive may also be used with the conductive scrim or ma-t to adhere the cover in place on the core of the ball.
An electrically conductive coating may also be applied S to the fabric which is used for the tennis ball cover -to enhance continuity of the electrically concluctive paths in the fabric~ The coating is applied to just the fabric's back side, which becomes the cover's inner side in the final construction of the ball. The coating may be applied before or after the tennis ball cover panels are cut from the fabric.
The woven fabric for the tennis ball cover may advantageously be needled to reorient a multitude of the electrically conductive and nonconductive fibers in the woven yarn preferably without fracturing the fibers in such a manner that the reoriented fibers extend more transversely of the plane of the fabric~ Because of this needling operation, free ends of other portions of a multitude of the electrically conductive fibers will project beyond the plane of the fabric at least on the back side of the fabric and will be embedded or otherwise engaged in the previously described electrically conductive base (if usad) or the prevlously described electrically conductive coating (if used) to enhance the electrical continuity of the ball's electrically conductive paths along the back side of the cover.
The fill yarn and the weaving pattern of the fill with the warp, as well as the other features of this invention, serve to reduce the number of electrically conductive fibers which are required to make the ball sufficiently conductive to operate the ball-sensiny circuits on the tennis court. By reducing the required number of electrically conductive fibers, objectionable discoloration of the ball is a~oided where the color of the fabric's electrically conductive fibers is dis-sirnilar to the color of the ball's cover. Furthermore, the fill yarn, the weaving pattern of the cover, and the other features of this invention do not impair the desirable playing characteristics of the ball even where stainless steel fibers are used.
%
In a further embodiment, the invention contemplates an electrically conductive tennis ball for establishing a current-conducting path across spaced apart: electrical conductors extending along a selected area of a tennis court and/or the top surface of a net. That electrically conductive tennis ball comprises an elastically deforrnable sphere and a cover of woven fabric covering the sphere with the fabric being uniform over the entire surface of the ball. The fabric has a set of strands of warp yarn interlaced with and extending transversely of a set of strands of woof yarn with the yarn for the strands in at least one of the sets being formed of a plurality of electrically conductive fibers with metal surfaces and electrically nonconductive fibers which are twisted together and wherein the number of the electrically non-conductive fibers exceeds the number of the electrically conductive fibers in the yarn for the strands of the at least one of the sets to the extent that excessive discoloration of the cover by the electrically conductive fibers is avoided.
Al-ternatively, the fabric has a set of warp strands interlaced with a set of woof strands with the strands of one of the last-mentioned sets comprising a quantity of electrically conductive filament fibers with metal surfaces and of random lengths and a quantity of electrically nonconductive filament fibers mixed with the conductive fibers, and with the conductive and non-conductive filament fibers being twisted together to form the yarn for the one of the sets of strands.
With the foregoing in mind, a major object of this invention is to provide a novel electrically conductive tennis ball which has a high degree of electrical conductivity, which is economical to manufacture, and which does not degrade the playing characteristics of the ball or objec~ionably discolor the ball.
A more specific object of thi~; invention is to provi.de a novel electrically conductive tennis ball in which the fabric's electrically ~ondu~ive fibers are electrically interconnected by treating the back side of 5 the fabric or the tennis cover with an electrically conductive material such as a coating, an electrically conductive ~&esive" an electrically conductive scrim, or an electrically conductive cloth.
Another im~rtant object of this invention is 10 to provide a novel electrically conductive tennis ball in which the electrical conductivi~y of the ball is greater ~han the conductivity of water.
Yet another object of this invention is to provide a novel line callinq system which senses 15 touc~hdown of an electrically conductive tennis ball, but not the presence of water on the tenni~ court, to avoid false signals due to water on the court.
Fur~her objects of this invention will appear as the descripkion proceeds in connection ~ith the 20 below-described drawings and annexed claims.
BRIE~ DESCRIPTION ~F T~ D~AWINÇS
FIG. 1 is an elev~tion of an electrically 25 conductive tennis ball incorporating the principles of this invention, and showing the ball touching down against a tenni s court surf ace containing the ball-sensing conductors of an electrical line calling ~y~tem.
FIG. ~ is a simplified schematic circuit diagram of an electrical sensing circuit which is used to ~ense or de~ect ~ouchdown of ~he ball in a line calling ~yst~m;
~2~
FIG. 3 i6 a bott~ plan view of the ball as viewed from lines 3-3 of FIG. l;
FIG. 4 is an enlarged fragmenltary plan view showing the front face of the woven fabric from which 5 the balli6 cover is cut;
FIGo 5 is a section taken along lines 5~5 oiE
FIG. 4;
FIG. 6 is a view of a wocf strand used to we~ve the fabric shown in FIGo 4;
FIG. 7 is an er;l~ged section similar t:o FIG~, 5 and showing the reorientation of fiber~ after the fabric is needled;
FIG. 8 is an enlarged f ragmentary section taken alon~3 lines ~-8 of FIBJ l;
FIG. 9 is an enlarged section ~imi~ar to FIG. 8 but shawing a modification of the ball;
FIG. 10 is an enlarged section similar to FIG. 8 and shc~wing another modification of the ball;
~ IG. 11 is an enlarged section similar to 20 FIG. 8 and showing yet another modification of the ball;
FIS~ 12 is an enlarged section similar to FIG. 8 and showing yet another modificatior~ in whi~h s~me of the electrically conductive fibers have dangling ends lying in the seam between the panels of the cover 25 to establish electrical continuity be~een the cover's panels;
FIG,. 13 is a fragmentary plan view similar to FIGo 4, but showing ano~her embodiment o~ this invention; and FI~. 14 is a section similar to FIG. 3 but sho~7ing a tennis ball having a cover made fr~n the fabric of FIG. 13.
DETAILED DEscRIpTIc~a OF ~HE INVENTI~N
~ eferring to FIG. 1, the elect:rically conductive 'cennis ball incorporating the principles of 5 thi~ inventisn i~ îndicated at 20 and ccmprises an innerV hollow, elastic~ly deformable sphere or core 22 and a ~w~piece cover 2D.. ~re 22 is ~ any sui}able con~entional oonstrucgion and may be formed frcrQ rubber or other sui~able elastically defo~mable material. ~he io interior o~ core 22 may be filled with air or other gas under pressure.
Cover 24 is a>nvenltionally divided into two figure-eight- or dumbbell panels 26 and 28 which are s~ie cut frcm a bolt or sheet o~ woven fabric or cloth 30 15 (see FIG. 4) and which are glued, adhered or otherwise affixed to the outer suriEace of core ~;!2.
Ar~r suitable electrical sensing circuit may be used with ball 20 for sensin9 touc:hdown of the ball in selected areas on a tennis court. In FIG. 2, a 20 simplified foL~n of the electrical fien6ing circuit is - inaicated at 32 and is shadn to cc~nprise a plurality of expoæd, preferably parallel, spaced apart conductors 34. me conductors of the sensing circuit are preferably embedded in the tennis court to lie flu~h 25 or nearly ~lush witb ~urface 38~ In the illustrated example, alternate conductors of sen~ing circuit 32 are electrically connected to one tenminal of a suitable d.c. voltage ~ource 3~, and the remaining conductors in circuit 32 are electrically connected to the other 30 terminal of the vol~age source.
When ball 20 touches down on surface 38, it defonms to onn a generally flat, circular touchdown area or rebounding area 40 ~see FIG. 3) which i8 large ~2~ 2 enough to ~ridge at least two adjacent conductors in sensing circuit 32. The conductors in sensing circuit 32 are spaced apart by a ncminal distance which is determined by the ball's flattened touchdown area 40.
5 For example, the spacing between adjacent conductors in circuit 32 may be 3/16 inch fcr a touchdown area of as little as 1 inch in dicameter. Being electrically conductive, ball 20 will, upon touchdown in the area occupied by circuit 3~ bridge two or more adjacent 10 conductors in circuit 32 to thus ccmplete a current-conducting circuit between at least two adjacent conductors in the sensing circuit.
me completion of the circuit across adjacent conductors of circuit 32 results in the conduction of 15 current through ball 20 from source 37. This current is - utilized to operate an indicating device 41 to signal the players that the hall landed in the selected area occupied by the conductors of circuit 32.
A ~uitable sensing circuit of the type 20 described above is disclosed in U.S. Patent No. 4,109,911 which issued August 29, 1978.
Referring to FIGS. 4 and 5, the woven fabric 30 is a unique satin weave having a multiplicity of warp yarns 44 (or threads as they are sometimes called~, or strands as they may also be called, interlaced with and extending at right angles to, a multiplicity of rows or parallel lengths of woof or filling 46. It will be appreciated that multiple rows of the woof or filling 46 customarily form a part of a single yarn tor thread) by shuttling the filling yarn back and forth in the loom. These rows of parallel lengths of illing are therefore originally inter~onnected through the fabric's selvedges, but are separaked fran one another in the cover's panel~ 26 and 28 upon cutting the panels from fabric 30.
In this BpeCificatiOn~ the tenm "strandsn i~
8 u&ed to refer to the rows or parallel lengths of woof 46 i~ fabric 30 and in p~nels 26 and 28, which are cut frcm ~abric 30. q~he separate parallel lengths of warp yarn are also referred to a~ ~;trands. In FIG. 1, lines representing some of ~he paralleLlen~th~ or ~trand~ of 10 warp and woo~ are shawn to be spaced apart for purposes of illu~tration. m e actual spacing of the parallel lengths of woo~ 46 are more accurately represen~ed in FIG. 4.
Referring ~o FIG. 6, ~he woof yarn 46 is 15 canposed of a large n~nber of electrically nonconductive filament fibers 48 of random lengths and a sm~ller number of electrically conductive filament fibers 50 of randcm lengths, such as single untwisted synthetic filament~ or monofilament type fibers~ m e electrically 20 conductive fibers 50 are blended with the nonconductive fibers 48 so that the conductive fibers are distributed throughout the gro~p of nonconductive fiber~;. After the fibers are blended, they are twisted together as shown in FIG. 6 to form the filling 46.
me nonconductive fibers 48 may be fonmed from any suitable material used in manufacturing tennis ba:Ll covers such as ~rlon~ cotton, and/or wc~ol.. ffle electrically conductive fibers 50 are preferably thin, finely drawn sta nless steel fibers. Alternatively~ the 30 electrically conductive fibera 50 may be Nylon fibers coated with silver or other electrically conductive material such as the plated or coated fibers disclo~ed in U.S. Patent No. 4,299,384, which issued on November --1~
10, 1981.
Preferablyf the number of nonconductive fibers 48 is much greater than the number of electrically conductive fibers 50 especially where the electrically conductive fibers are stainless steel or other material having a color dissimilar to the nonconductive fibers 48. m e electrically conductive fibers may be in sufficient number to represent 10 to 30 percent of ~he total number of conductive and nonconducLive fibers in the yarn. In the illustrated embodiment, the nonconductive fibers 48 make up as much as 70 percent of the total number of fibers in the woof or filli~g, and the electrically conductive fibers 50 make up the remaining 30 percent. After being wvven, Pabric 30 may be dyed to provide the cover with a suitable color such as yellow. The Lectra-ConK 3-7093 yarn, manufactured by the Schlegel Corporation of Rochester, ~ew York, is made in accordance with the foregoing teachings for the fill yarn and may be used for the fill in weaving fabric 30; alternatively, Lectra-Con~ 060-150 co~ductive material can be used in manufacturing fill yarn such as the yarn typically used for manufacturing tennis ball covers.
The parallel lengths or strands of warp 44 are fonmed entirely of elec~rically nonconductive fibers such as Nylon~ cotton and/or wool. The warp fibers may also be filament fibers of randcm lengths~ such as single untwisted synthetic filaments or monofilament type fibers, and they are twisted together to fonm the warp strands used in weaving fabric 30. Thus, only the woof 46 of fabric 30 contains the electrically conductive fibers ~or making the ball's cover 24 electrically conductive.
Preferably, the warp strands 44 are very thin, and the yarn used for the woof ~6 is abou~ ten ~ne~ as 5 thick or coarse as ~he warp yarns or thread. ~he woof 45 therefore has about ten time~ as many ibers as the ~arp 44. Yarn having ~ Dtex o~ about 4400 to 5000 m~y be used for the woof.
me weave o~ fabric 30 i~ a co3lYentional type 10 used or tennis ball covers and is advantageollsly of the type in which each len~th or r~ of the woof or filling 46 passes or skips over more warp strands 4d~
than it passes under as view~d from the fabricls fro~t face. The fron~c face of fabric 30 is shawn in FIG. 4 15 and is used as the ou~er side of the termis ball co~rer 24 in the finished product.
For each warp strand that passes under, filling 46 may pass over five to seven warp strands 44 (i.e. p under one and over five to seven~ O For each 20 group of eight sus::cessive warp strands 44 in the embodiment sh~wn in FIG. 4, each r~w of ~he wovf 46 passes under one warp strand and over the other seven.
Because of this type of weave and because of the mu~h grea'cer thickness of the woof 46, more fillings than 25 warp show on ~he ~ron~ ~ace of fabric 30 so that the fillings 46 daninate the ~Eront face of the fabric and occup~ most of the surf ace area on the f ront f ace of fabric 30. Because of thi~ fabric construction, the woof 46 will occuE~y a ~;ubstantially greater area of the 30 outer pe~iphery of the termis ball cover a~ canpared with the aeea occupied by the warp 44.
Because of the large n~nber of electrically nonconductive fibers and the relatively small number of electrically conduc~ive fiber~ in each of the woof strand~ 46, ~tainless s~eel fiber~ or ~he like may ke ~ed in the woof without causing any unacceptable di~coloration of the tennis ball coverO
After the weaving operation, fabric 30 may be felted by s~bjecting it in a conventional manner to pre~sure and heat ~o as to pres~ ~he woven fabricO
After the felting operation, fabric 30 may advantageously be ~ edled to reorient a substantial 10 majority o~ the electri~ally conductive fibers in the filling 56 without fracturing ~he conductive or nonconductive fiber~. The electrically nonconductive fibers in the warp 44 and woof 46 will al~o b~
reoriented by the needling operation, but only the 15 reorientation o~ the elec~rically conductive fibers is of significance.
Before needling, the fibers in warp 44 and woof 46 lie generally in the plane of fabric 30 as ~hown in FIG. 5. A~ter needling, a large n~mber of the 20 electrically conductive fibers 50 in the filling 46 will have portions 51 (FIG. 7) reorien~ed to extend generally transversely of the plane of fabric 30 as shown in ~IG. 7 so that the needled portion (which includes some free ends) of the electrically conductive fibers 50 25 extends beyond the plane of fabric 30 on the fabric's inner or reverse side, which will be used as the inner or ba~k side of cover 24. me needling operation may be such that portions of a multitude of the electrically conductive fibers 50 extend beyond the plane of the 30 fabric on both sides or faces of the fabric.
Any suitable needling machine having fine or t~in needles (not sh~wn) may be used to needle fabric 30 in the manner described above. ~ne suitable type of ~13--needle i8 described and shown in Patent No, 4,299,3~40 ~1 ~ernatively, needl es hav ing axi al ly opposi tely facing notches may be utili2:ed to catch ~he fibers during both the advancing and retracting strokes af the needles, 5 thu~ reorienting the caught fibers in ~3uch a way that E~ortions of the caught fibers project transver~ely frarn both sides or faces of fabric 30.
After fabric 30 is needled in 'che manner de~cribed abovef it then is advantageously napped orl the 10 front face. and sheered so ~hat cover 24 will h~ve the usual fuæziness on i~s outer periphery. ~ter these operations, panels 26 and 28 are die cut fram fabric 30.
It will be appreciated that the process steps of felting, needling and napping may be perf3rmed after 15 ~nels 26 and 28 are cut fr~m fabric 30, bu'c it obviously i~ more con~enient and econanical to perform these operation~ before the panels are cut fran the fabric.
Upon being cut fr~n the fabric, panels 26 20 and 28 are cemented or adhered to ~e ball's COrQ 22.
~n electrically nonconductive adhesive or cement may be used for this purpo6e, but an electrically conductive adhesive is preferred~ ~rhe electrically conductive adhesive fo~ns a thin layer 54 ~see FIG. 8~ perip~erally 25 around the entire outer surface of core 22 between core 22 and panels 26 and 28. An example of a ~uitable electrically conductive adhesive is the Vulcan Corporation partic:ula~e carbon a~c-72 uniformly mixed ~?ith any ~uitable rubber cement for manufacturing tenni~
30 balls in an amount suf:Eicient to achieve the ~lred conductivity of the ball. me conduc~ive and nonconductive fiber portions 51 whicb are reoriented by the previously described needling operation will be enbedded in adhesive layers 54 and will be securely fixed or held in place by the adhesiYe.
Because ibers 4B and 50 are relatively long and are twisted together to form the yarn iEor wea~ring 5 fabric 30, ~ey will be retained in place and therefore will no~ come loose and fall onlto the cour~ when subjected to impact forces during play~,, FurthenDoret retention of the fi~er~ which have been reoriented by the previously described needling operation is enhanc:ed 10 by embedding the reoriented portions 51 in adhesive layer 54. This construction 'chere~ore avoids the objectionable condition where conducltive fibers come loose and fall onto the sensing circuit 32 to produce a false signal.
Frosn the foregoing description, it will be appreciated that the electrically conductive fibers 50 create a maze of elect ically conductive networks 60 (FIG. 1) which are distributed throughout the entire periphery of the ball. Networ1cs 60 deine a 20 multiplici~r of current-conducting paths passing through cover 24 and extending along the outer si~le of cover 24 for completing a circuit between adjacent conductors in sensing circuit 32 upon touchdown of the tennis ball on circuit 32. Tlle portion~ of ne~orks 60 lying on the 25 outer periphery of cover 24 are distributed throughout the entire outer surface of the cover so that a signal is produced regardless of the orientation of the ball up~n touchdown on the conduc~oræ of sensing circuit 32.
In addition to being in contact with ~he 30 needled portio~s of fibers 50, the electrically cond~ctive adhesive layer 54 will also be in contact with some of the unneedled electrically condllctive fibers in the portions of fill 46 which loop under the warp 44 to appear on the back side of c:over 24. Most of the networks 60 are therefore interconnected through the electrically conductive adhesive layer 54 which fonms an electrically conductive base lying entirely along the 5 inner side of cover 24.
m e electrical conductivity of the tennis ball for si~naling touchdown of the ball on sensing circuit 32 i5 significantly enhanced because of the large exterior surface area occupied by the woof in 10 cover 24, the presence of the electrically conductive adhesive base 54 on the inner side of cover 24, and the reorientation of a multitude of the electrically sonductive fibers 50 by the previously described needling operation.
In a modified embodiment of the ball illustrated in FIG. 8, adhesive la~er 54 can be made of a nonconductive material; and an electrically conductive coating can be applied to the back of the cloth fonmed by warp 44 and fill 46. This elec~rically conductive 20 coa~in~ would substantially fill the spaces between the fibers of warp 44 and thus serve the same function as the electrically conductive adhesive layer 54.
~ eferring to FIG. 9, a seam 56 is conventionally formed between Fanels 26 and 28. m e 25 electrically conductive adhesive layer 54 bridges seam 56 to ensure electrical continuity between panels 26 and 28. Seam 56 is preferably filled with any suitable, conventional nonconductive cement.
Alternatively, a conductive seam cement may be used, but 30 the conductive carbon particles in the cement produce an undesirable discoloration of the ball. If panels 26 and 28 are closely matched, they will butt against each other at the apex of seam 56 to enhance electrical continuity be~ween panel~ 26 and 28.
In the embodiment shown in FIG. 9, an electrically conductive scrim 58 is ~an~wiched between 5 cover 24 and core 22 to establi~h the electrically conductive ba~e on ~he back ~ide of cover 24. Scrim 58 is made up of an unwoven oFen mesh of fibers ~trung together in an irregular array in a unitary unwo~en body. Preferably~ all o~ the ~ibers in ~crim 58 are 10 electri~ally conducti.ve. Scrim 58 extends around and cover~ ~he entire periphery of core 22. Scrim 58 therefore bridges seam 56 and lies entirely between core 22 and cover 24.
Like the previously described electrically 15 conductive adhesive layer 54~ ~crim 58 also lies in contact with needled portions of fibers 50 and alfio in contact with same of the ~nneedled elec~rically condu~tive fibers in the portions of fill 46 which loop under the warp 44, thus enhancing the conductivity of 20 the ball and establishing electrical continuity betwee3n panels 26 and 28. Scrim 58 may be adhered to core 22 and cover 24 with either an electrically nonconductive ~dhesive or an electrically ~onductive adhesive. It will be appreciated that scrim 58 is tightly pressed 25 between coYer 24 and core 22.
Scrim 58 may be arranged in a stretched-out ~heet on the back or reverse sides of panels 26 and 28, and the composite of each panel and the scrim may then be adhered or cemented to core 22 with an electrically 30 conductive or nonconductive adhesive. The usual nonconductive cement used for adhering 'che tennis ball cover to the core of the ball i8 considered to be one a~ailable type of adhesive. Scrim 58 may also be placed on the back or reverse sides of fabric 30 before the fabric is needled.
In the ~mbodiment shc;wn in FI~. 10~ scrim 5B
is replaced with a thin~ woven or urlwovlen doth or S mat 62 which is sandwiched between and adhered to cover 24 and core 22 with an electric~lly conductive or norlconductive adhe~;ive, Mat 62 may be Eoraned fr~n ar~, ~uitable materia3 and m~y be adhered to core 22 before application of cover 24. In the finished construction of b~l 2a, mat S2 contac~:s the needled portions of the electrically conduc~ive ~iber~ 50 and scme of ~he unneedled electrically conductive fihers in the portions of fill 46 which loop under 'che warp 44 to establish electrical continuity be~een panel~ 26 and 28.
In~tead of a~plying mat 62 to core 22 before placing cover 24 on the core, mat 62 may be adhered to the back or reverse side of fabric 30 with an electrically conductive or nonconductive adhesive before the fabric is needled and before panels 26 and 28 are 20 cut frcm the fabric. After the panels are cut fr~m fabric 30, the panel and ma~ composite may then be adhered to core 22 wi~h an electrically conductive or nonconductive adhesive.
Instead of e~ploying scrim 58 or mat 62, the 25 reverse or back side of fabric 30 (i.e., the side which becomes the inner side of cover 24) may ~e coated throughout with an electrically conductive coating 64 (~ee FIG. 111 after f~bric 30 is needled in the manner de~cribed above and preferably after fabric 30 is n~pped 30 and before panels 26 and 28 are cut from the fabric.
Coating 64 is applied with sufficient thickness and in su~h a manner that the reoriented portions of the needled ibers, including fibers 50, become embeddecl and ~2~
-lB-fixed in coating 64 to enhance the electrical conduc~tivi~y o~ the ball. Pdditionally, coating 64 will partially ~pregnate fabric 30 :Er~n the re~er~e side thereof to electrically interconnect a large nunber of S the unneedled electrically conductive woof fiber~ 50 still lying in the plane of fabric 3û.
Coating 64 may be co~ventional and ma~ be of any ~ui~able type. For example, coating S4 m~y be Schlegel Corporation's 12ltex base coating R3115-00-2.
After coati~g 64 is applied, panel~ 2b and 28 are die cut fram fabric: 3û. mus, coating 64 will fonn a continuous unin~errupted electrically condactive ba~ie along the entire inner surface area of each of the panels 26 and 28 after the panels are cut frclm 15 ~abric 30,, It will l~e appreciated that oating 64 m~y alternatively be applied to panels 26 and 28 after they are cut from ~abric 30.
~ pon being s::ut fr~n ~he c:oated fabric, 20 panels 26 and 28 are adhered to the ball's core 22 by an electris::ally conductive or. nonconductive adhe~ive.
Flectrical continui~ bet~een panel~ 26 and 28 may be established bs~ separating the panels fran fabric 30 in such a wa~ that a ~;ubstantial n~er of the 25 conductive fibers 50 are left with ends 66 (FIG. 12) that dangle fr~xn the ed~e of each panel. This ma~ be accomplished by only partially die cutting panels 26 and 28 from fabric 30 (that is cutting the fabric only p~rtially around the periphery of each of lthe panels or 30 cutting only partially through the ~abric on spaced apart regions) and by pulling the partially cut panels loose frcsn Jche remainder o 'che fabric in ~uch a manner that ends 66 dangle fram the edge oiE eacb of the p~nels at the regions where the panels were not fully cut from the fabric, Upon adhering panels 26 and 23 in place on the core of the ball, the dangling ends 6b frc~m the ~dO
S panel~ will in~erengage or bec~ne entanlgled to e tablish electrically conductive E~ath8 ~his::h bridge the ~eaan between the ~s: panel~;. EndE; 66 ~7ill be enbedded in the ~eam cement 67 ~FIG. 123 or o~her material used to fill ~eam 56 ~d ~chu~ will be fixed in place b~ the ~eam 10 cementr If desired, the seam material mz~ be electric~lly conductive.
By utilizing.the fiber ends 66 to establish electrical continuit~r be~een panels 2~ and 28 ~nd b~
usin~ electri~lly conductive warp strands, the 15 e:lectrically conductive base (namely, ~dhe~ive layer 54 scrim 58 or mat 62) ma~ be crnitted :fr~sn the ball, and cover 24 may be adhered to core 22 with an electrically nonconductive adhesive. Close matching of panels 26 and 28 which butt together at the apex of seam 56 may 20 even e~;tablish sufficient electrical continuity bebween panels 26 and 28 to vbviate the need for panels with the dangling ends 66 or an electrically conductive seamrbridging baseO
In accordance with a further feature of this 25 invention, the electrically conductive networks 60 are made significantly more conductive than water, and the ball-sensing circuit 32 is designed so that it is insensitiqe to wat r on the tennis court surface. This may be accomplished by providing an adju6table 30 resistance 76 (see ~IG. 2~ in serie~ with the voltage power source 37. Alternativelyt a comparator (not shown) may be used to compare the ball-produced electrical signal with a fixed reference signal in ~uch a way that a false signal produced by water bet:w~en adjacent conductors in circuit 32 is insufficient to ~;witch the output of the comparator. Hc~7ever, the ~tronger signal produced by the more conductive tenni~
5 ball will swi~ch the c:ompara or's ou~put, thus ~ignalling touchdown o~ the ball in the area occu~ied by ~e ~ensin~ circuit.
Preferably, the resitivity (which is the reciprocal of c:onductivity~ of the electri¢ally 10 conductive l:ennis ball of this invention is equal to between 10 and 500 ohns per square.
Referring to FIGS,, 13 and 14, an al'cerna~e woven fabric 30a may be used for cover 24. It is the same as fabric 30 except that the warp yarn or 15 strands 44a in fabric 30a also contain electrically conductive fibers to further enhance the electrical conductivity of the ball and to negate the need for scri~s, conductive coatings or conductiYe adhesives.
The fill in fabric 30a is the s~me as the fill in 20 fabric 3n. Like reference n~merals have been therefore applied to de~ignate like elements of the fill yarns for ~he two fabrics.
In the embodiment of FI~S. 13 and 14, a quantity of electrically conductive fibers 50a are 25 blended with a much larger number of electrically nonconductive fibers 48a, and the blended fibers are twisted or spun together to form the yarn for the warp 44a. ffl e ratio of conductive fibers to nonconductive fibers in warp 44a preferably is less tban 30 but may be the same a6 or greater than ~he ratio of conductive fibers to nonconductive fibers in the fill 46. Fibers 50a are preferably the same as fibers 50, ~nd fibers 48a may be the same as fibers 48.
l~e woven Fattern of fabric 30a is the ~ame as that of f~bric 30.
In this specification (including the claim~
herein) the term ~yarn" is considered to include a 5 thread and any other type of yarn~ A thread is considered to be a yarn having a noticeable ~wist~
The invention may ~e embodi~d,in other specific fonms withou~ departing ~rom the spirit or es~ential characteristics thereof. m e present 10 embodLments are therefore to be oonsidered in all respect~ as illustrative and not restrictive, the ~cope of the invention being indicated by the appended claims rather than by the foregoiny description; and all changes which came within the meaning and range of 15 ~quivalency are therefore intended to be ~mbraced therein O
AND L IN E CAI:.LING SYSTEM
FIELD OF THE INVENTICN
This invention relates to improvements in electrically conductive tennis balls which are used with auto~atic tennis court line calling systems to detect whe~her the ball lands in or out of a tennis court 10 playing area or strikes the top of the net. Line calling systems of this type have one or more sets of exposed~ spaced apart conductors extending along selected areas of the tennis court and the top of the net to sense touchdown of the electrically conductive 15 ball.
When the ball lands across two or more of the sensing conductor~, an electrical current-conducting circuit is completed throu~h the ball to signal the player~ that the ball touched down in an area occupied 20 by the oonductors.
Electrical conductivity of the tenni~ ball may be established by incorporating electrically conductive fibers into the cover of the ball.
25 SUMMARY AND C!E3JECTS OF I~IE INVENTION
In accordance with this invention, a blend of electrically conductive and nonconductive fibers are spun together to form yarn which is used to weave the 30 fabric for the tennis ball cover. The conductive and nonconductive fibers are random lengths of filaments, as opposed to staple fibers.
. .
The electrically conductive fibers may be made from stainless steel. Alternatively, other types of electrically conductive fibers may be used such as those described in U.S.
Patent No. ~,299,38~ which issued November 10, 1981, to John 5 A. Van Auken for ELECTRICALLY CONDUCTIVE GAME BALL.
One embodiment of this invention provides an electrically conductive tennis ball for use with an electrical detection circuit in which touchdown of the ball in a selected area is detected by completion of a circuit between spaced apart electrical conductors extending along that area. The electrically conductive tennis ball comprises an elastically deformable sphere, a cover of woven fabric covering the sphere with the fabric being woven with a set of warp strands interlaced with a set of woof strands, and with the strands of one of the sets comprising a quantity of electrically conductive fibers and a quantity of electrically nonconductive fibers, and the strands of the other of the sets being composed entirely of electrically nonconductive fibers.
In some oE the illustrated embodiments the tennis ball advantageously includes an electrically conductive base which lies between the woven cover and the elastically deformable core of the ball to enhance electrical continuity amongst -the conductive fibers in the cover. The electrically conductive base preferably extends entirely around the core, thus bridging the seams between the cover's panels to establish electrical continuity between the panels.
The electrically conductive base may be an electrically conductive adhesive which performs the additional function of adhering the cover to the core of the ball. Other types of electrically conductive bases may be employed.
For example, the electrically conductive base may be an electrically conductive scrim of fibers of the type described in U.S. Patent No. 4,299,384. Alternatively, the electrically conductive base may be in the form of a thin, llexible, woven or unwoven cloth or mat which may be bonded to the back side of the cover. An electrically conductive adhesive may also be used with the conductive scrim or ma-t to adhere the cover in place on the core of the ball.
An electrically conductive coating may also be applied S to the fabric which is used for the tennis ball cover -to enhance continuity of the electrically concluctive paths in the fabric~ The coating is applied to just the fabric's back side, which becomes the cover's inner side in the final construction of the ball. The coating may be applied before or after the tennis ball cover panels are cut from the fabric.
The woven fabric for the tennis ball cover may advantageously be needled to reorient a multitude of the electrically conductive and nonconductive fibers in the woven yarn preferably without fracturing the fibers in such a manner that the reoriented fibers extend more transversely of the plane of the fabric~ Because of this needling operation, free ends of other portions of a multitude of the electrically conductive fibers will project beyond the plane of the fabric at least on the back side of the fabric and will be embedded or otherwise engaged in the previously described electrically conductive base (if usad) or the prevlously described electrically conductive coating (if used) to enhance the electrical continuity of the ball's electrically conductive paths along the back side of the cover.
The fill yarn and the weaving pattern of the fill with the warp, as well as the other features of this invention, serve to reduce the number of electrically conductive fibers which are required to make the ball sufficiently conductive to operate the ball-sensiny circuits on the tennis court. By reducing the required number of electrically conductive fibers, objectionable discoloration of the ball is a~oided where the color of the fabric's electrically conductive fibers is dis-sirnilar to the color of the ball's cover. Furthermore, the fill yarn, the weaving pattern of the cover, and the other features of this invention do not impair the desirable playing characteristics of the ball even where stainless steel fibers are used.
%
In a further embodiment, the invention contemplates an electrically conductive tennis ball for establishing a current-conducting path across spaced apart: electrical conductors extending along a selected area of a tennis court and/or the top surface of a net. That electrically conductive tennis ball comprises an elastically deforrnable sphere and a cover of woven fabric covering the sphere with the fabric being uniform over the entire surface of the ball. The fabric has a set of strands of warp yarn interlaced with and extending transversely of a set of strands of woof yarn with the yarn for the strands in at least one of the sets being formed of a plurality of electrically conductive fibers with metal surfaces and electrically nonconductive fibers which are twisted together and wherein the number of the electrically non-conductive fibers exceeds the number of the electrically conductive fibers in the yarn for the strands of the at least one of the sets to the extent that excessive discoloration of the cover by the electrically conductive fibers is avoided.
Al-ternatively, the fabric has a set of warp strands interlaced with a set of woof strands with the strands of one of the last-mentioned sets comprising a quantity of electrically conductive filament fibers with metal surfaces and of random lengths and a quantity of electrically nonconductive filament fibers mixed with the conductive fibers, and with the conductive and non-conductive filament fibers being twisted together to form the yarn for the one of the sets of strands.
With the foregoing in mind, a major object of this invention is to provide a novel electrically conductive tennis ball which has a high degree of electrical conductivity, which is economical to manufacture, and which does not degrade the playing characteristics of the ball or objec~ionably discolor the ball.
A more specific object of thi~; invention is to provi.de a novel electrically conductive tennis ball in which the fabric's electrically ~ondu~ive fibers are electrically interconnected by treating the back side of 5 the fabric or the tennis cover with an electrically conductive material such as a coating, an electrically conductive ~&esive" an electrically conductive scrim, or an electrically conductive cloth.
Another im~rtant object of this invention is 10 to provide a novel electrically conductive tennis ball in which the electrical conductivi~y of the ball is greater ~han the conductivity of water.
Yet another object of this invention is to provide a novel line callinq system which senses 15 touc~hdown of an electrically conductive tennis ball, but not the presence of water on the tenni~ court, to avoid false signals due to water on the court.
Fur~her objects of this invention will appear as the descripkion proceeds in connection ~ith the 20 below-described drawings and annexed claims.
BRIE~ DESCRIPTION ~F T~ D~AWINÇS
FIG. 1 is an elev~tion of an electrically 25 conductive tennis ball incorporating the principles of this invention, and showing the ball touching down against a tenni s court surf ace containing the ball-sensing conductors of an electrical line calling ~y~tem.
FIG. ~ is a simplified schematic circuit diagram of an electrical sensing circuit which is used to ~ense or de~ect ~ouchdown of ~he ball in a line calling ~yst~m;
~2~
FIG. 3 i6 a bott~ plan view of the ball as viewed from lines 3-3 of FIG. l;
FIG. 4 is an enlarged fragmenltary plan view showing the front face of the woven fabric from which 5 the balli6 cover is cut;
FIGo 5 is a section taken along lines 5~5 oiE
FIG. 4;
FIG. 6 is a view of a wocf strand used to we~ve the fabric shown in FIGo 4;
FIG. 7 is an er;l~ged section similar t:o FIG~, 5 and showing the reorientation of fiber~ after the fabric is needled;
FIG. 8 is an enlarged f ragmentary section taken alon~3 lines ~-8 of FIBJ l;
FIG. 9 is an enlarged section ~imi~ar to FIG. 8 but shawing a modification of the ball;
FIG. 10 is an enlarged section similar to FIG. 8 and shc~wing another modification of the ball;
~ IG. 11 is an enlarged section similar to 20 FIG. 8 and showing yet another modification of the ball;
FIS~ 12 is an enlarged section similar to FIG. 8 and showing yet another modificatior~ in whi~h s~me of the electrically conductive fibers have dangling ends lying in the seam between the panels of the cover 25 to establish electrical continuity be~een the cover's panels;
FIG,. 13 is a fragmentary plan view similar to FIGo 4, but showing ano~her embodiment o~ this invention; and FI~. 14 is a section similar to FIG. 3 but sho~7ing a tennis ball having a cover made fr~n the fabric of FIG. 13.
DETAILED DEscRIpTIc~a OF ~HE INVENTI~N
~ eferring to FIG. 1, the elect:rically conductive 'cennis ball incorporating the principles of 5 thi~ inventisn i~ îndicated at 20 and ccmprises an innerV hollow, elastic~ly deformable sphere or core 22 and a ~w~piece cover 2D.. ~re 22 is ~ any sui}able con~entional oonstrucgion and may be formed frcrQ rubber or other sui~able elastically defo~mable material. ~he io interior o~ core 22 may be filled with air or other gas under pressure.
Cover 24 is a>nvenltionally divided into two figure-eight- or dumbbell panels 26 and 28 which are s~ie cut frcm a bolt or sheet o~ woven fabric or cloth 30 15 (see FIG. 4) and which are glued, adhered or otherwise affixed to the outer suriEace of core ~;!2.
Ar~r suitable electrical sensing circuit may be used with ball 20 for sensin9 touc:hdown of the ball in selected areas on a tennis court. In FIG. 2, a 20 simplified foL~n of the electrical fien6ing circuit is - inaicated at 32 and is shadn to cc~nprise a plurality of expoæd, preferably parallel, spaced apart conductors 34. me conductors of the sensing circuit are preferably embedded in the tennis court to lie flu~h 25 or nearly ~lush witb ~urface 38~ In the illustrated example, alternate conductors of sen~ing circuit 32 are electrically connected to one tenminal of a suitable d.c. voltage ~ource 3~, and the remaining conductors in circuit 32 are electrically connected to the other 30 terminal of the vol~age source.
When ball 20 touches down on surface 38, it defonms to onn a generally flat, circular touchdown area or rebounding area 40 ~see FIG. 3) which i8 large ~2~ 2 enough to ~ridge at least two adjacent conductors in sensing circuit 32. The conductors in sensing circuit 32 are spaced apart by a ncminal distance which is determined by the ball's flattened touchdown area 40.
5 For example, the spacing between adjacent conductors in circuit 32 may be 3/16 inch fcr a touchdown area of as little as 1 inch in dicameter. Being electrically conductive, ball 20 will, upon touchdown in the area occupied by circuit 3~ bridge two or more adjacent 10 conductors in circuit 32 to thus ccmplete a current-conducting circuit between at least two adjacent conductors in the sensing circuit.
me completion of the circuit across adjacent conductors of circuit 32 results in the conduction of 15 current through ball 20 from source 37. This current is - utilized to operate an indicating device 41 to signal the players that the hall landed in the selected area occupied by the conductors of circuit 32.
A ~uitable sensing circuit of the type 20 described above is disclosed in U.S. Patent No. 4,109,911 which issued August 29, 1978.
Referring to FIGS. 4 and 5, the woven fabric 30 is a unique satin weave having a multiplicity of warp yarns 44 (or threads as they are sometimes called~, or strands as they may also be called, interlaced with and extending at right angles to, a multiplicity of rows or parallel lengths of woof or filling 46. It will be appreciated that multiple rows of the woof or filling 46 customarily form a part of a single yarn tor thread) by shuttling the filling yarn back and forth in the loom. These rows of parallel lengths of illing are therefore originally inter~onnected through the fabric's selvedges, but are separaked fran one another in the cover's panel~ 26 and 28 upon cutting the panels from fabric 30.
In this BpeCificatiOn~ the tenm "strandsn i~
8 u&ed to refer to the rows or parallel lengths of woof 46 i~ fabric 30 and in p~nels 26 and 28, which are cut frcm ~abric 30. q~he separate parallel lengths of warp yarn are also referred to a~ ~;trands. In FIG. 1, lines representing some of ~he paralleLlen~th~ or ~trand~ of 10 warp and woo~ are shawn to be spaced apart for purposes of illu~tration. m e actual spacing of the parallel lengths of woo~ 46 are more accurately represen~ed in FIG. 4.
Referring ~o FIG. 6, ~he woof yarn 46 is 15 canposed of a large n~nber of electrically nonconductive filament fibers 48 of random lengths and a sm~ller number of electrically conductive filament fibers 50 of randcm lengths, such as single untwisted synthetic filament~ or monofilament type fibers~ m e electrically 20 conductive fibers 50 are blended with the nonconductive fibers 48 so that the conductive fibers are distributed throughout the gro~p of nonconductive fiber~;. After the fibers are blended, they are twisted together as shown in FIG. 6 to form the filling 46.
me nonconductive fibers 48 may be fonmed from any suitable material used in manufacturing tennis ba:Ll covers such as ~rlon~ cotton, and/or wc~ol.. ffle electrically conductive fibers 50 are preferably thin, finely drawn sta nless steel fibers. Alternatively~ the 30 electrically conductive fibera 50 may be Nylon fibers coated with silver or other electrically conductive material such as the plated or coated fibers disclo~ed in U.S. Patent No. 4,299,384, which issued on November --1~
10, 1981.
Preferablyf the number of nonconductive fibers 48 is much greater than the number of electrically conductive fibers 50 especially where the electrically conductive fibers are stainless steel or other material having a color dissimilar to the nonconductive fibers 48. m e electrically conductive fibers may be in sufficient number to represent 10 to 30 percent of ~he total number of conductive and nonconducLive fibers in the yarn. In the illustrated embodiment, the nonconductive fibers 48 make up as much as 70 percent of the total number of fibers in the woof or filli~g, and the electrically conductive fibers 50 make up the remaining 30 percent. After being wvven, Pabric 30 may be dyed to provide the cover with a suitable color such as yellow. The Lectra-ConK 3-7093 yarn, manufactured by the Schlegel Corporation of Rochester, ~ew York, is made in accordance with the foregoing teachings for the fill yarn and may be used for the fill in weaving fabric 30; alternatively, Lectra-Con~ 060-150 co~ductive material can be used in manufacturing fill yarn such as the yarn typically used for manufacturing tennis ball covers.
The parallel lengths or strands of warp 44 are fonmed entirely of elec~rically nonconductive fibers such as Nylon~ cotton and/or wool. The warp fibers may also be filament fibers of randcm lengths~ such as single untwisted synthetic filaments or monofilament type fibers, and they are twisted together to fonm the warp strands used in weaving fabric 30. Thus, only the woof 46 of fabric 30 contains the electrically conductive fibers ~or making the ball's cover 24 electrically conductive.
Preferably, the warp strands 44 are very thin, and the yarn used for the woof ~6 is abou~ ten ~ne~ as 5 thick or coarse as ~he warp yarns or thread. ~he woof 45 therefore has about ten time~ as many ibers as the ~arp 44. Yarn having ~ Dtex o~ about 4400 to 5000 m~y be used for the woof.
me weave o~ fabric 30 i~ a co3lYentional type 10 used or tennis ball covers and is advantageollsly of the type in which each len~th or r~ of the woof or filling 46 passes or skips over more warp strands 4d~
than it passes under as view~d from the fabricls fro~t face. The fron~c face of fabric 30 is shawn in FIG. 4 15 and is used as the ou~er side of the termis ball co~rer 24 in the finished product.
For each warp strand that passes under, filling 46 may pass over five to seven warp strands 44 (i.e. p under one and over five to seven~ O For each 20 group of eight sus::cessive warp strands 44 in the embodiment sh~wn in FIG. 4, each r~w of ~he wovf 46 passes under one warp strand and over the other seven.
Because of this type of weave and because of the mu~h grea'cer thickness of the woof 46, more fillings than 25 warp show on ~he ~ron~ ~ace of fabric 30 so that the fillings 46 daninate the ~Eront face of the fabric and occup~ most of the surf ace area on the f ront f ace of fabric 30. Because of thi~ fabric construction, the woof 46 will occuE~y a ~;ubstantially greater area of the 30 outer pe~iphery of the termis ball cover a~ canpared with the aeea occupied by the warp 44.
Because of the large n~nber of electrically nonconductive fibers and the relatively small number of electrically conduc~ive fiber~ in each of the woof strand~ 46, ~tainless s~eel fiber~ or ~he like may ke ~ed in the woof without causing any unacceptable di~coloration of the tennis ball coverO
After the weaving operation, fabric 30 may be felted by s~bjecting it in a conventional manner to pre~sure and heat ~o as to pres~ ~he woven fabricO
After the felting operation, fabric 30 may advantageously be ~ edled to reorient a substantial 10 majority o~ the electri~ally conductive fibers in the filling 56 without fracturing ~he conductive or nonconductive fiber~. The electrically nonconductive fibers in the warp 44 and woof 46 will al~o b~
reoriented by the needling operation, but only the 15 reorientation o~ the elec~rically conductive fibers is of significance.
Before needling, the fibers in warp 44 and woof 46 lie generally in the plane of fabric 30 as ~hown in FIG. 5. A~ter needling, a large n~mber of the 20 electrically conductive fibers 50 in the filling 46 will have portions 51 (FIG. 7) reorien~ed to extend generally transversely of the plane of fabric 30 as shown in ~IG. 7 so that the needled portion (which includes some free ends) of the electrically conductive fibers 50 25 extends beyond the plane of fabric 30 on the fabric's inner or reverse side, which will be used as the inner or ba~k side of cover 24. me needling operation may be such that portions of a multitude of the electrically conductive fibers 50 extend beyond the plane of the 30 fabric on both sides or faces of the fabric.
Any suitable needling machine having fine or t~in needles (not sh~wn) may be used to needle fabric 30 in the manner described above. ~ne suitable type of ~13--needle i8 described and shown in Patent No, 4,299,3~40 ~1 ~ernatively, needl es hav ing axi al ly opposi tely facing notches may be utili2:ed to catch ~he fibers during both the advancing and retracting strokes af the needles, 5 thu~ reorienting the caught fibers in ~3uch a way that E~ortions of the caught fibers project transver~ely frarn both sides or faces of fabric 30.
After fabric 30 is needled in 'che manner de~cribed abovef it then is advantageously napped orl the 10 front face. and sheered so ~hat cover 24 will h~ve the usual fuæziness on i~s outer periphery. ~ter these operations, panels 26 and 28 are die cut fram fabric 30.
It will be appreciated that the process steps of felting, needling and napping may be perf3rmed after 15 ~nels 26 and 28 are cut fr~m fabric 30, bu'c it obviously i~ more con~enient and econanical to perform these operation~ before the panels are cut fran the fabric.
Upon being cut fr~n the fabric, panels 26 20 and 28 are cemented or adhered to ~e ball's COrQ 22.
~n electrically nonconductive adhesive or cement may be used for this purpo6e, but an electrically conductive adhesive is preferred~ ~rhe electrically conductive adhesive fo~ns a thin layer 54 ~see FIG. 8~ perip~erally 25 around the entire outer surface of core 22 between core 22 and panels 26 and 28. An example of a ~uitable electrically conductive adhesive is the Vulcan Corporation partic:ula~e carbon a~c-72 uniformly mixed ~?ith any ~uitable rubber cement for manufacturing tenni~
30 balls in an amount suf:Eicient to achieve the ~lred conductivity of the ball. me conduc~ive and nonconductive fiber portions 51 whicb are reoriented by the previously described needling operation will be enbedded in adhesive layers 54 and will be securely fixed or held in place by the adhesiYe.
Because ibers 4B and 50 are relatively long and are twisted together to form the yarn iEor wea~ring 5 fabric 30, ~ey will be retained in place and therefore will no~ come loose and fall onlto the cour~ when subjected to impact forces during play~,, FurthenDoret retention of the fi~er~ which have been reoriented by the previously described needling operation is enhanc:ed 10 by embedding the reoriented portions 51 in adhesive layer 54. This construction 'chere~ore avoids the objectionable condition where conducltive fibers come loose and fall onto the sensing circuit 32 to produce a false signal.
Frosn the foregoing description, it will be appreciated that the electrically conductive fibers 50 create a maze of elect ically conductive networks 60 (FIG. 1) which are distributed throughout the entire periphery of the ball. Networ1cs 60 deine a 20 multiplici~r of current-conducting paths passing through cover 24 and extending along the outer si~le of cover 24 for completing a circuit between adjacent conductors in sensing circuit 32 upon touchdown of the tennis ball on circuit 32. Tlle portion~ of ne~orks 60 lying on the 25 outer periphery of cover 24 are distributed throughout the entire outer surface of the cover so that a signal is produced regardless of the orientation of the ball up~n touchdown on the conduc~oræ of sensing circuit 32.
In addition to being in contact with ~he 30 needled portio~s of fibers 50, the electrically cond~ctive adhesive layer 54 will also be in contact with some of the unneedled electrically condllctive fibers in the portions of fill 46 which loop under the warp 44 to appear on the back side of c:over 24. Most of the networks 60 are therefore interconnected through the electrically conductive adhesive layer 54 which fonms an electrically conductive base lying entirely along the 5 inner side of cover 24.
m e electrical conductivity of the tennis ball for si~naling touchdown of the ball on sensing circuit 32 i5 significantly enhanced because of the large exterior surface area occupied by the woof in 10 cover 24, the presence of the electrically conductive adhesive base 54 on the inner side of cover 24, and the reorientation of a multitude of the electrically sonductive fibers 50 by the previously described needling operation.
In a modified embodiment of the ball illustrated in FIG. 8, adhesive la~er 54 can be made of a nonconductive material; and an electrically conductive coating can be applied to the back of the cloth fonmed by warp 44 and fill 46. This elec~rically conductive 20 coa~in~ would substantially fill the spaces between the fibers of warp 44 and thus serve the same function as the electrically conductive adhesive layer 54.
~ eferring to FIG. 9, a seam 56 is conventionally formed between Fanels 26 and 28. m e 25 electrically conductive adhesive layer 54 bridges seam 56 to ensure electrical continuity between panels 26 and 28. Seam 56 is preferably filled with any suitable, conventional nonconductive cement.
Alternatively, a conductive seam cement may be used, but 30 the conductive carbon particles in the cement produce an undesirable discoloration of the ball. If panels 26 and 28 are closely matched, they will butt against each other at the apex of seam 56 to enhance electrical continuity be~ween panel~ 26 and 28.
In the embodiment shown in FIG. 9, an electrically conductive scrim 58 is ~an~wiched between 5 cover 24 and core 22 to establi~h the electrically conductive ba~e on ~he back ~ide of cover 24. Scrim 58 is made up of an unwoven oFen mesh of fibers ~trung together in an irregular array in a unitary unwo~en body. Preferably~ all o~ the ~ibers in ~crim 58 are 10 electri~ally conducti.ve. Scrim 58 extends around and cover~ ~he entire periphery of core 22. Scrim 58 therefore bridges seam 56 and lies entirely between core 22 and cover 24.
Like the previously described electrically 15 conductive adhesive layer 54~ ~crim 58 also lies in contact with needled portions of fibers 50 and alfio in contact with same of the ~nneedled elec~rically condu~tive fibers in the portions of fill 46 which loop under the warp 44, thus enhancing the conductivity of 20 the ball and establishing electrical continuity betwee3n panels 26 and 28. Scrim 58 may be adhered to core 22 and cover 24 with either an electrically nonconductive ~dhesive or an electrically ~onductive adhesive. It will be appreciated that scrim 58 is tightly pressed 25 between coYer 24 and core 22.
Scrim 58 may be arranged in a stretched-out ~heet on the back or reverse sides of panels 26 and 28, and the composite of each panel and the scrim may then be adhered or cemented to core 22 with an electrically 30 conductive or nonconductive adhesive. The usual nonconductive cement used for adhering 'che tennis ball cover to the core of the ball i8 considered to be one a~ailable type of adhesive. Scrim 58 may also be placed on the back or reverse sides of fabric 30 before the fabric is needled.
In the ~mbodiment shc;wn in FI~. 10~ scrim 5B
is replaced with a thin~ woven or urlwovlen doth or S mat 62 which is sandwiched between and adhered to cover 24 and core 22 with an electric~lly conductive or norlconductive adhe~;ive, Mat 62 may be Eoraned fr~n ar~, ~uitable materia3 and m~y be adhered to core 22 before application of cover 24. In the finished construction of b~l 2a, mat S2 contac~:s the needled portions of the electrically conduc~ive ~iber~ 50 and scme of ~he unneedled electrically conductive fihers in the portions of fill 46 which loop under 'che warp 44 to establish electrical continuity be~een panel~ 26 and 28.
In~tead of a~plying mat 62 to core 22 before placing cover 24 on the core, mat 62 may be adhered to the back or reverse side of fabric 30 with an electrically conductive or nonconductive adhesive before the fabric is needled and before panels 26 and 28 are 20 cut frcm the fabric. After the panels are cut fr~m fabric 30, the panel and ma~ composite may then be adhered to core 22 wi~h an electrically conductive or nonconductive adhesive.
Instead of e~ploying scrim 58 or mat 62, the 25 reverse or back side of fabric 30 (i.e., the side which becomes the inner side of cover 24) may ~e coated throughout with an electrically conductive coating 64 (~ee FIG. 111 after f~bric 30 is needled in the manner de~cribed above and preferably after fabric 30 is n~pped 30 and before panels 26 and 28 are cut from the fabric.
Coating 64 is applied with sufficient thickness and in su~h a manner that the reoriented portions of the needled ibers, including fibers 50, become embeddecl and ~2~
-lB-fixed in coating 64 to enhance the electrical conduc~tivi~y o~ the ball. Pdditionally, coating 64 will partially ~pregnate fabric 30 :Er~n the re~er~e side thereof to electrically interconnect a large nunber of S the unneedled electrically conductive woof fiber~ 50 still lying in the plane of fabric 3û.
Coating 64 may be co~ventional and ma~ be of any ~ui~able type. For example, coating S4 m~y be Schlegel Corporation's 12ltex base coating R3115-00-2.
After coati~g 64 is applied, panel~ 2b and 28 are die cut fram fabric: 3û. mus, coating 64 will fonn a continuous unin~errupted electrically condactive ba~ie along the entire inner surface area of each of the panels 26 and 28 after the panels are cut frclm 15 ~abric 30,, It will l~e appreciated that oating 64 m~y alternatively be applied to panels 26 and 28 after they are cut from ~abric 30.
~ pon being s::ut fr~n ~he c:oated fabric, 20 panels 26 and 28 are adhered to the ball's core 22 by an electris::ally conductive or. nonconductive adhe~ive.
Flectrical continui~ bet~een panel~ 26 and 28 may be established bs~ separating the panels fran fabric 30 in such a wa~ that a ~;ubstantial n~er of the 25 conductive fibers 50 are left with ends 66 (FIG. 12) that dangle fr~xn the ed~e of each panel. This ma~ be accomplished by only partially die cutting panels 26 and 28 from fabric 30 (that is cutting the fabric only p~rtially around the periphery of each of lthe panels or 30 cutting only partially through the ~abric on spaced apart regions) and by pulling the partially cut panels loose frcsn Jche remainder o 'che fabric in ~uch a manner that ends 66 dangle fram the edge oiE eacb of the p~nels at the regions where the panels were not fully cut from the fabric, Upon adhering panels 26 and 23 in place on the core of the ball, the dangling ends 6b frc~m the ~dO
S panel~ will in~erengage or bec~ne entanlgled to e tablish electrically conductive E~ath8 ~his::h bridge the ~eaan between the ~s: panel~;. EndE; 66 ~7ill be enbedded in the ~eam cement 67 ~FIG. 123 or o~her material used to fill ~eam 56 ~d ~chu~ will be fixed in place b~ the ~eam 10 cementr If desired, the seam material mz~ be electric~lly conductive.
By utilizing.the fiber ends 66 to establish electrical continuit~r be~een panels 2~ and 28 ~nd b~
usin~ electri~lly conductive warp strands, the 15 e:lectrically conductive base (namely, ~dhe~ive layer 54 scrim 58 or mat 62) ma~ be crnitted :fr~sn the ball, and cover 24 may be adhered to core 22 with an electrically nonconductive adhesive. Close matching of panels 26 and 28 which butt together at the apex of seam 56 may 20 even e~;tablish sufficient electrical continuity bebween panels 26 and 28 to vbviate the need for panels with the dangling ends 66 or an electrically conductive seamrbridging baseO
In accordance with a further feature of this 25 invention, the electrically conductive networks 60 are made significantly more conductive than water, and the ball-sensing circuit 32 is designed so that it is insensitiqe to wat r on the tennis court surface. This may be accomplished by providing an adju6table 30 resistance 76 (see ~IG. 2~ in serie~ with the voltage power source 37. Alternativelyt a comparator (not shown) may be used to compare the ball-produced electrical signal with a fixed reference signal in ~uch a way that a false signal produced by water bet:w~en adjacent conductors in circuit 32 is insufficient to ~;witch the output of the comparator. Hc~7ever, the ~tronger signal produced by the more conductive tenni~
5 ball will swi~ch the c:ompara or's ou~put, thus ~ignalling touchdown o~ the ball in the area occu~ied by ~e ~ensin~ circuit.
Preferably, the resitivity (which is the reciprocal of c:onductivity~ of the electri¢ally 10 conductive l:ennis ball of this invention is equal to between 10 and 500 ohns per square.
Referring to FIGS,, 13 and 14, an al'cerna~e woven fabric 30a may be used for cover 24. It is the same as fabric 30 except that the warp yarn or 15 strands 44a in fabric 30a also contain electrically conductive fibers to further enhance the electrical conductivity of the ball and to negate the need for scri~s, conductive coatings or conductiYe adhesives.
The fill in fabric 30a is the s~me as the fill in 20 fabric 3n. Like reference n~merals have been therefore applied to de~ignate like elements of the fill yarns for ~he two fabrics.
In the embodiment of FI~S. 13 and 14, a quantity of electrically conductive fibers 50a are 25 blended with a much larger number of electrically nonconductive fibers 48a, and the blended fibers are twisted or spun together to form the yarn for the warp 44a. ffl e ratio of conductive fibers to nonconductive fibers in warp 44a preferably is less tban 30 but may be the same a6 or greater than ~he ratio of conductive fibers to nonconductive fibers in the fill 46. Fibers 50a are preferably the same as fibers 50, ~nd fibers 48a may be the same as fibers 48.
l~e woven Fattern of fabric 30a is the ~ame as that of f~bric 30.
In this specification (including the claim~
herein) the term ~yarn" is considered to include a 5 thread and any other type of yarn~ A thread is considered to be a yarn having a noticeable ~wist~
The invention may ~e embodi~d,in other specific fonms withou~ departing ~rom the spirit or es~ential characteristics thereof. m e present 10 embodLments are therefore to be oonsidered in all respect~ as illustrative and not restrictive, the ~cope of the invention being indicated by the appended claims rather than by the foregoiny description; and all changes which came within the meaning and range of 15 ~quivalency are therefore intended to be ~mbraced therein O
Claims (15)
1. An electrically conductive tennis ball for use with an electrical detection circuit in which touchdown of the ball in a selected area is detected by completion of a circuit between spaced apart electrical conductors extending along said area, said electrically conductive tennis ball comprising an elastically deformable sphere, a cover of woven fabric covering said sphere, said fabric being woven with a set of warp strands interlaced with a set of woof strands, the strands of one of said sets comprising a quantity of electrically conductive fibers and a quantity of electrically nonconductive fibers, and the strands of the other of said sets being composed entirely of electrically nonconductive fibers.
2. The electrically conductive tennis ball defined in Claim 1 wherein said fabric has a weave in which the area occupied by the strands of said one of said sets on the outer surface of said cover is greater than the area occupied by the strands of said other of said sets.
3. The electrically conductive tennis ball defined in Claim 2 wherein the strands of said one of said sets are thicker than the strands of the other of said sets.
4. An electrically conductive tennis ball for establish-ing a current-conducting path across spaced apart electrical conductors extending along a selected area of a tennis court and/or the top surface of a net, said electrically conductive tennis ball comprising an elastically deformable sphere and a cover of woven fabric covering said sphere, said fabric being uniform over the entire surface of the ball and: (a) having a set of strands of warp yarn interlaced with and extending transversely of a set of strands of woof yarn with the yarn for the strands in at least one of said sets being formed of a plurality of electrically conductive fibers with metal surfaces and electrically nonconductive fibers which are twisted together and the number of said electrically nonconductive fibers exceeding the number of said electrically conductive fibers in the yarn for the strands of said at least one of said sets to the extent that excessive discoloration of said cover by said electrically conductive fibers is avoided, or (b) having a set of warp strands interlaced with a set of woof strands with the strands of one of said last-mentioned sets comprising a quantity of electrically conductive filament fibers with metal surfaces and of random lengths and a quantity of electrically nonconductive filament fibers mixed with said conductive fibers, said conductive and nonconductive filament fibers being twisted together to form the yarn for said one of said sets of strands.
5. The electrically conductive tennis ball defined in Claim 4 comprising a base of electrically conductive material formed separately of said cover and lying between said cover and said sphere without passing through said cover, said base being in contact with and electrically interconnecting at least some of said electrically conductive fibers to provide at least one electrically conductive network for conducting electrical current through one or more of the electrically interconnected, electrically conductive fibers from the outer side of the cover to said base, through said base along the inner side of the cover, and through one or more additional ones of the electrically interconnected, electrically conductive fibers from said base to the outer side of said cover.
6. The electrically conductive tennis ball defined in Claim 5 wherein said cover comprises a pair of panels which are divided by a seam and wherein said base bridges said seam to establish electrical continuity between said panels.
7. The electrically conductive tennis ball defined in Claim 6 wherein said base is an electrically conductive adhesive which adheres said panels to said sphere.
8. The electrically conductive tennis ball defined in Claim 6 wherein said base is a scrim comprising unwoven electrically conductive fibers, there being an adhesive for adhering the composite of said cover and scrim to said sphere.
9. The electrically conductive tennis ball defined in Claim 6 wherein said base is an electrically conductive mat.
10. The electrically conductive tennis ball defined in Claim 4 wherein said electrically conductive fibers form a part of the woof of said fabric, wherein the warp strands of said fabric are composed entirely of electrically non-conductive fibers, and wherein said fabric has a weave in which the area occupied by the woof of said fabric on the outer surface of said cover is greater than the area occupied by the warp of said fabric.
11. The electrically conductive tennis ball defined in Claim 4 wherein the yarn defining the strands in the other of said sets is formed by electrically conductive and electrically nonconductive fibers which are intermixed and twisted together.
12. The electrically conductive tennis ball defined in Claim 4 wherein at least some of said electrically conductive fibers each have at least one portion which is reoriented after said fabric is woven to extend transversely of the plane of the fabric.
13. The electrically conductive tennis ball defined in Claim 4 wherein said fabric has a weave in which the area occupied by the strands of said one of said sets on the outer surface of said cover is greater than the area occupied by the strands of the other of said sets.
14. The electrically conductive tennis ball defined in Claim 4 wherein only the yarn in said woof contains electrically conductive fibers and wherein each of said woof strands is passed over a larger number of warp strands than it is passed under to increase that portion of the exposed surface of the covering that is covered by the woof.
15. An electrically conductive tennis ball as defined in Claim 1 or in Claim 4 in which the conductivity of the conductive fibers is greater than the conductivity of water found on the surface of the court on which the ball is played.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000535493A CA1244902A (en) | 1987-04-24 | 1987-04-24 | Electrically conductive tennis ball and line calling system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000535493A CA1244902A (en) | 1987-04-24 | 1987-04-24 | Electrically conductive tennis ball and line calling system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1244902A true CA1244902A (en) | 1988-11-15 |
Family
ID=4135491
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000535493A Expired CA1244902A (en) | 1987-04-24 | 1987-04-24 | Electrically conductive tennis ball and line calling system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1244902A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6816185B2 (en) | 2000-12-29 | 2004-11-09 | Miki Harmath | System and method for judging boundary lines |
-
1987
- 1987-04-24 CA CA000535493A patent/CA1244902A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6816185B2 (en) | 2000-12-29 | 2004-11-09 | Miki Harmath | System and method for judging boundary lines |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| AU619446B2 (en) | Conductive tennis ball | |
| US4664378A (en) | Electrically conductive tennis ball | |
| CA1235628A (en) | Woven fabric for belt | |
| CA1281767C (en) | Conductive wrist band | |
| KR920004512Y1 (en) | Panel heater | |
| US4259394A (en) | Papermaking fabrics with enhanced dimensional stability | |
| EP1609899B1 (en) | Conveyor belt with high tear interwoven fabric | |
| US8393282B2 (en) | Sewn product and clothes | |
| KR101682429B1 (en) | Work glove | |
| US4861645A (en) | Fencing tape with electrically conducting wires | |
| WO2009107905A1 (en) | Textile digital band and fabriticating method thereof | |
| US4328840A (en) | Double side fabric | |
| FI944772A (en) | Heat-sealable interlining comprising a layer of fibers intertwined with woven weft yarns and a method of making the same | |
| JP3880743B2 (en) | Woven fabric and dust-proof garment with excellent conductivity and antistatic properties | |
| CZ295604B6 (en) | Pressing cushion | |
| CA1244902A (en) | Electrically conductive tennis ball and line calling system | |
| KR20030081432A (en) | Fiber complex and its use | |
| US4299384A (en) | Electrically conductive game ball | |
| US20040214494A1 (en) | Stretch fabric | |
| US4433840A (en) | Electrically conductive game ball | |
| CN216579600U (en) | Wear-resistant anti-wrinkle knitted fabric | |
| JPH02501043A (en) | Conductive tennis ball and line determination device | |
| CN211947456U (en) | Elastic conductive wire | |
| CN215203770U (en) | Oxter sweat-absorbing garment fabric | |
| CN219789520U (en) | Tear-resistant leather base cloth |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |