US1665598A - Restretchabije tennis racket - Google Patents

Description

April 10, 1928.

H. MAY

RESTRETGHABLE TENNIS RACKET 2 Sheets-Sheet l Filed April 26. 15526 April 10, 1928.

H. MAY

RESTRETCHABLE TENNIS RACKET Filed April 26, 192 2 Sheets-Sheet 2 Patented Apr. 10, 1928.

UNITED STATES v 1,665,598 PATENT. oFF lCE.

HEINZ MAY, orHANovnn, GERMANY.

RESTRETCHAIBLE. TENNIS RACKET.

vApplication filed April 26. 1926, serial No.

This invention relates to a re-stretchable.

the tensile stress and the distribution of the same over .the Whole net has theefiiect that the strings inthe eentralportion of the net, i

which are .ll'iOSl). struck are spared andthat breaking of the strings or slackening ofv the tension "of the ,net are prevented. The

means used, .for the purpose aimed at, prevent further rupture of the strings at the edges of the l oles'through which the strings are passed through the frame. and these means make it possible to re-stretch the strings if theyget slack.

Several embodiments of the invention are shown, byway of example, in the accompanying drawings, in which;

Figs. 1, E2, 3 and 4- show each in front elevation atennis racket stringed in a difierent manner. A y f Fig. 5 is a diagram illustrating the main nor in which the stringing of the racket 2 the woodentrame.

' shown in Fig. 4 is carried out.

Fig. (5 is a part-section through the plane of the racket frame on, line VI-VI of Fig. 9.

Fig.7 is a cross section of Fig. 6.

Fig. 8 is a part section through, the plane of the frame showing how'the ends of the strings are fixed.

Fig. 9. shows in plan View the outer-side" oi" the racketfranie.

Fig.10 is a part section through the plane oi. the net similar to Fig. 6 but showing another form of stringing.

. Fig. 11 is a ross section of Fig. 10.-

Fur. 12 is a SGCtIOH OIl line XIL-XI'I of Fig. 1.3 shows in plan View a portion of the racket frame and illustrates the method and means 'l'iorre-strctching the strings. Fig. 14 is a cross sectionof Fig. 13.

Fig. 1.5 shows in plan View a portion of the racket ti'a.nie and. illustrates another method and means for re-stretching two, dilierent positions. p

Fig. 16 shows in plan view a' portion of the racketjt'rame. and illustrates in, the left of the ratchet frame, around the net.

104,701, and.in Qermany August n, 1825.:

half a third and in the right half, a fourth method and means for re stretching the strings. l 'The fundamental idea of the invention inner surface of the frame, movablebearings which, byv sliding to and fro on the 160 consists in providing for the strings, at, the points wliere they enter into the holes in; theframe or at a slight distance from the i inner surface of the frame, efiectanequalfi zation of tension. between the two strings";

held by one bearing, said bearings leading the strings in such a. manner into the iram'ie-i; holes that friction of the strings on the edges of the frame holes is avoided; As

bearings serve rings (Z, d situated front of the frame holes and designed to receive each one pair of strings or the loops f of a cord e extending, closetotheinner surface these ineansinay 'be used together. c

Figs. 1 and 2 show in which manner the frame of a tennis racket can be stringed."

The stringing shown in Fig. 2 willbe pref-' erably used, as at the playing the ball strikes, in most cases, not at rightangles to the net whereby the stress upon the s'trings ,'i it diagonal stringing is used, is morefavo'ray able and consequently less strain is caused than if the'bearings for the strings are in d, the tension of the strings is transmitted Owing to the continuous cord 0, which in tightly tied loops f is. tied around the strings I), and bytherings:

upon other strings not directly str uok by the ball.

The arrangement of the rings is shown on larger scale in Figs/6 and 7. By one ring two adjacent strings 'bareheld together, so

' that the directionof the pull of a string put under stress, owing to the pushing of the ring in lateral directioncaused herebyyistranss mitted also upon the adjacent string which is pulled bythe ring. The rings formthere fore slidab'le bearings for thefistrin'gs and they rest upon the inner surface of the r racket frame (i in front of the holese or l Thestrings pass through the hole'sl i iii-the wooden frame a. The holes are enlargedin the plane of the net towards both sides so that. the'strings b are free to movein 'the holes at 6 towards both sides without'rubq hing on the edges of the holes. The. holesj i are displaced and arrangedlin a zigzag shaped groove 9 in the outer surfaceof the frame, as shown in Fig. {hand they merge,

ill

ball, the pulling effect is not only transmitted upon the adjacent strings but in a lesser measure also upon all other strings.

In the stringmg shown in Fig. 2 two separate cordsc are used at the transverse sides of the frame in order to equalize the tension especially in the longitudinal direction of the-frame. A string could not be used in stead of this cord, as a string, owing to its hardness would embrace the strings bin one line and cut at first, owing to tension which occurs, into the strings and damage them. An ordinary cord of the same thickness as the stringsis best suited, the cord being tied and knittedaround the strings, and, if the net is finished, impregnated with oil and varnish. The bearings for the strings formed by the knots f of the cord 0 embrace the strings band-like'and the desired resistance and solidity is given to the same by the subsequent treatment with oil and varnish. The effect is obtained that the connecting cord in consideration of its function, e. g. the interception of slighter tensions, is of the same durability as the strings.

In the form of stringing shown in Fig. 3 the rings a? are suppressed and a cord 0 is substituted for the same, the'tightly tied loops fv of which are not tied around the points of intersection of the strings but enclose the strings at the points where, they come out of the holes 6 of the frame. The loops f therefore take over the function of the rings 03 and the cord 0' fulfills at the same time the functionv of the cord. 0 usedfin theforms of construction shown in Figs. 1, 2 and 6.

In the form of construction, as shown in Fig. 4, no connecting cord is used and the .efi'ects of the pull are distributed with the "aid of a certain scheme for inserting the strings, by which the frame itself is rendered elastic ininward direction and the tensile stresses are distributed so that the elasticity of the frame is thereby produced. In this stringing the rings a? are arrangedin four.

groups, one larger group, of for instance 15 rings at each long side m, m of the racketframe, and one smaller group, of for instance 10 rings, at each short side-n, a of the racket-frame 0;. To a selected number of rings on the short sidescorrespond a de-' termined number of rings on the long sides,

Lemmas so that therelation of the longitudinal axis of the frame to the transverse axis of the same and the plane-shape of the frame are determined or influenced by the number of rings. Between the long sides m, m and the short sides a, n of the frame are the portions 9, g and 0, 0" into each of which 5' strings are strung without rings, so that these strings are stationary. The net of the racket consists essentially of two string lengths pand 9 extending through the entire net and being clamped alternately so that they intersect one another, in order to obtain a symmetrical figure with regard to the main axis of the racket. The two long strings p and q begin at the points r and they end, after the net has been finished, at r and s. The rings 0? are strung in together with the insertion of the strings.

If one string-portion of the net, between every two holes of the frame, is called a stretch, each of the two long strings form 30 stretches if the net is finished, or together 60 stretches. If one follows the stringstretches coming out of the holes, 1, 2, 3, 4, 5 or 6, 7, 8, 9, 10 of the frame-portions g and 0, one will see from the diagram of plaiting shown in Fig. 5, that each string 12 and 9 forms from the frame-portion g to g or 0 to 0" each 5 by 6 stretches, of which always the first stretch begins at one of the fixed hearing points 1 10, and ends in one of the fixed bearing points 1, 2 10', so that by these 60 stretches the entire net is formed. The net can be imagined as formed of portions of strings beginning at the points 1 to 10 and ending at the points 1 to 10, each string-portion between the startingand end-pointforming six stretches of the net. Only the startingand end-points represent stationary bearings, as at-these points no rings are used and'the strings are not yieldably mounted in these frame holes which form the starting and end-points. Through all the other frame holes the strings are passed through the intermediary of bearingrings (Z or d (Fig. 10) so that said strings are yieldable. At the points 1 to 10 and 1 to 10, or inthe frame-portions g, 0 and r, 0' no transmission of the pulling effect from one upon the other stretch of strings takes place, whilst at all other passage-holes of the portions m, m and n, n of the frame rings (l or cl are arranged, according to Figs. 6 or 10, and a transmission of the pulling-effect from one upon all other points (movable bearings) takes place. At the frame-portions m, m and 12., n act consequently 30 or 20 stringstretches together at the same time, and these pulling-effects are supported towards the frame-portions g, 0 and g, 0" which form the counter-bearings. At the points g, g, 0. 0 the tensile force acts in the direction of the string stretches and on the portions m, m or n, n of the frame acts, in consequence of nae-mas the equalization bythe rings, one results. ing force for each portion at right anglesv to" the frame-towardsthe centre of the net-.J

The latter forces eifecta vibration ofthe fltLIIlBzPOLtlODS m, m or n, a withregardjto.

one another-a By this stringing the rigid. wooden frame is made elastic-in such a mannner thatythe principal vibrations'in the centralportion of the net are damped in first instance by the stringing :which gets ,denser towards the. frame. By the fact that the long sides of H the frame vibrate with the. strings the vibrations are propagated'until they. arriveat the four rigid portions 9,9, 0, 0' ofthe frame; The long sides of the frame yield under the vibrations which occur in theplane of the net, so that the net plane is elastic in'the longitudinal direction, being. in this direction elasticallylield by. the short sides of the frame. An equalization of the tension takes place directly after the strings have been put under stress.

The advantagesresulting from this stringc.

ing consist in that breaking oflthe strings or .warping'of the frame owingto the illfiuences of temperature and. moistness, I and excessiyenslackening-of the strings due to the playingor storingare-avo1ded. In the i 'stringings' of knownztype, which aremostly rectangular, the pointsxg and g" and 0 and 0 cause mainly warping of the frameastwo string stretches act with different force in might evenhave aiprejudiciah effect: on the stringing-as it prevents the equalization of the tensions in the frame and in the strings or temporarily brakesthe movement 1n the frame caused by influences of temperature so that, after the frame press. has been-res moved, breaking of the strings could be caused by a one-sided sudden Warping of the frame. i

In the form of stringing shown inFigset the bearing rings (Z are preferably ofa special shape as shown in Figs. 10 and lli;

Theyare enlarged atone end and have at the other endacircular flange, their. en-

larged front endholding two strings blend? 7) so that they lead the. tension of. the": strings gradually over to the reinforced foot and thence to the frame.

In Figs-8 and9 thefixation. of endsisillustrated- In thewstringings :of tennis rackets commonly v used*up to the present strings had tobe used which are as'lo'ng as possible as it was dnficultto fixz the ends of the strings Well. Two strings were used for the long and cross stringing. lfu-epziirs had to be done by replacing certain string-stretches a special diiiiculty.

the string arose, and besidesikbyf making knots in the strings .t-he ends of; the .same were held in the frame by means of wooden wedges; I

;In the stringing, according to the inven .tion, the fixation .of the ends is carried out. in the following manner. 'In the outersur- .face of the frame, between every twoholes i, if, 11? {an incision h intersecting the zig-zag groove 6 at right angles is arranged. 1

,The end of the string 6" (Fig. 8) is passed through the hole a in the direction .of-the. A arrow, then over the frame-bearing /a through tlie.second hole at and under the bearing It" inside the frame, through the.

hole Hi0. theouter. side. The, projecting end of the string is then passed through the incision It at the left of thezhole s ,and-

pulledfin upward and lateral direction. ,The.

string 6 gets at'this-occasion betweenthe stretched string 1)? and the bearing Zdand slips underneath the; rounded portion l of the bearing is. passed: through the incision hfatthe right The stringend I) istheny of hole. 6 and stretched. Bytheialternatey use of the incisionsh and h and by thepassmg of the string end b; cover therounded are,,;wound around in spiral-shape.

The right side of Figsa8 and 9-sliows the string .end 7), afterthe incision h has been used, and ShOWs further how the string end end, 6". On this string .end the tying. up

througlrthe two incisions at the left and right ofth'e hole i has. been causedalready and the endgbf is stringb and the bearing 4 Thetying can be further extended in a similar manner and theincision ,of bearing 7,: .can eventually/be utilizedalsoiforthe tying. It is however advisable tojleave the string end clamped finally between a bearing in 1 and the string'b,.as this is shown at b. .By

thismanner of fixationit ispossihley to fix alsoshort strings securely and inanot coni splcuous manner, as is necessaryfor repairs.

At the same time two strings (I) and if?!) are tightly tied aroundby the tying in one hole (6 a) sothat the string (5 'or b which is put under stress in the racket-net transmitsits tension upon two stiingsin the is pulled through the incision h. The left 1 side of .thesefigures shows another stringv clamped 1 between the stationary bearing 70. andathe 'dangerous.

cross section .of the string, which situated. where the, string rubs onv the wood, is as I f good a-ssuppressed; t i

.A further. inconvenience, .which.leyeryf:. racket-net possesses, s the slacken ngof the stretched Si311I1gS,,61the1' ow ng tothe use at,

pliltzying or to the influences of temperature. 7

igs 13, 114515 andltlsshow inetliodsand means for re-stretching the strings. [In the form. of construction shown in Figs. 1'3 and 14 thegl'ings 21 are pulled away froin the frame a, on the strings which they enclose,

by a cord t, whichis guided between the two strings coming from the hole 6 passes around the outer side of ring d, is pulled towards the next following intersection u of the strings and stretched. The rings (Z are thereby all pulled away more or less from the frame. By the shortening of the stringstrings is effected.

Another possibility of regulating the tension in the racket-net within certain limits is the arrangement of the incisions h as shown in Figs. 8 and 9. Pieces of thick cord are pulled through the incisionsand brought, at the right and'left of the incision, upon the bearing 71;: of the frame so that'the cords rest between the string and the bearing Zc Shortening of the string for up to double the depth of the incision can thus be'obtained.

Fig. 15 shows an automatic regulation of the tension of the racket net.

Instead of one, two rings d, (Z are stringedinto the net at every'hole in the frame, a

spiral spring 0 being inserted between said each other whereby these rings have reestablished the tension of the strings after the same principle asin Fig. 13.

By means of the rings cl which are of special shape the re -stretching can be effected by means of cords, as shown in Fig. 16. The cord w is strongly jammed, in the form of construction shown in the left'half of Fig. 16, between the inner side of the frame and the collar of the ring d which bears against the frame, and wound as often as possible around the strings I), b guided in the ring, the turns of the cord touching one another. The ring is thus pushed away from the frame, whereby the strings are restretched as in Fig. 18. The cord extends from one ring to the other.

In the form of re-stretching shown at the right half of Fig. 16 the cord w is wound only once around the strings b, b the rings being further pushed away from the frame by a second cord 00 which extends, between the attached portion of the cord w, from one ring to the other, and guided around the next following point of intersection of the strings at 1 and pulled tight. The action of this cord w is similar as that of the cord t in Fig. 13.

I claim z 1. A re-stretchable tennis racket-,comprlsing in combination with the frame and with rear end.

memes the net, movable hearings in the shape of. rings each ring enclosing one pair of strings at the points where the strings pass through the frame said strings serving to transmit the tension from one string to the adjacent string, to other strings of the racket-net and to certain portions of the frame. stretches caused hereby re-stretching of the I 2. A re-stretchable tennis-racket, comprising in combination with the frame and with the net, movable bearings in the shape of rings each ring enclosing one pair of strings at the points where the strings pass through the frame said strings serving to transmit the tension from one string to the adjacent string, to other strings of the racket-net and to certain portions of the frame, and a cord extending at a short distance from the inner side of the frame and from said rings around the not said cord embracing in loopor knot-shape the strings at the points of intersection in order to distribute the pulling action of the strings over the entire net.

3. A re-stretchable tennis racket, comprising in combination with the frame and with the net, movable bearings in the shape of rings each ring enclosing one pair of strings at the points where the strings pass through the frame said strings serving to transmit the tension from onestring to the adjacent string, to other strings of the racket-net and to certain portions of the frame, and pieces of acord extending at a short distance from the inner side of the frame and from said 1 rings around portions of the net said pieces so that the'tension of the net is transmitted upon the four main portions of the frame to which thus a certain elasticity is given.

5. In a re-stretchable tennis racket as claimed in claim 4: the rings having an enlarged front end and a collar at the rear end so that they take up the tension gradually and guide it over ontothe reinforced 6. In a re-stretchable tennis racket as claimed in claiml comprising in combination with the ring and the strings a cord wound in zig-zag shape around'the rings and the first points of intersection of the strin s in order to pull the rings away from the rame.

7. In a re-stretchable tennis racket as claimed in claim 1 comprising in combinalit tion with the frame, the strings and the rings, cords clamped between the inner side of said frame and said rings and wound around these portions of the said strings in order to pull the rings away from the frame for restretching the net.

8. In a restretchable tennis racket as claimed in claim 1 comprising in combination with the frame the strings and the rings, a stretching cord wound around each string between the inner side of the frame and the rings, a second cord stretched in zig-zag shape between the first point of intersection of two strings and the connecting portion of said stretching cord from one ring to the other ring in order to push said rings away from said frame and for restretehing the net.

9. A re-stretchab1e tennis racket, comprising in combination with the frame and with the net, two rings mounted on every two, strings at the point where said strings enter into said frame, and a spiral spring be tween said two rings which pushes the rings away the one from the other and effects thus 25 the re-stretching of the net.

In testimony whereof I aflix my signature.

HEINZ MAY.

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