with reference to the drawings , wherein like numerals represent like parts , fig1 shows an isometric view of a bearing sleeve 10 or ball - bearing outer race of an embodiment of the present invention wherein the outer quasi - cylindrical face 20 is provided with a broad concave shaped outer surface 30 able to accept more than one lay of string . the distance c is the axial width of a contained bearing 40 in the case of a bearing sleeve , or of the inner race and the ball - race with dust - covers in the case of being a ball - bearing outer race . fig2 shows another view of the same embodiment , rotated horizontally through some 45 or so degrees from the previous figure , which shows the extension 50 of the outer surface 20 to accommodate a friction braking member ( not shown ) to be seated in groove 52 . another embodiment of a bearing sleeve 10 is illustrated in fig3 and 4 . with reference to fig5 and 6 , a yo - yo 100 which employs the bearing sleeve 10 includes yo - yo halves 102 and 104 connected by a threaded axle 110 which mounts a bearing 40 disposed between the halves . the bearing sleeve 10 is preferably in the form of a spool . outer surface 30 is generally symmetric about an axial midpoint m . the spool is symmetric about an axis of rotation a which is the central axis of the yo - yo . the axial distance of the concave surface d is defined between axially extreme circular edges 32 and 34 which have a radius greater than the distance from the axis to the string bearing surface . the inner cylindrical surface of the spool has an axial length c . the axial distance d is preferably greater than the length c . the distance d is also greater than the radial spacing or thickness t between the outer concave string bearing surface and the inner surface . the yo - yo halves further respectively include recesses 106 and 108 adjacent their inner central portions for receiving the axially extreme portions of the spool . the axial distance d preferably exceeds the axial width c by at least 10 % of the roller bearing width c . one embodiment of the present invention is a bearing sleeve 10 or bearing outer race that facilitates an effective string gap ( greater than that previously provided ) of around 0 . 18 ″ or 4 . 5 mm to achieve complicated binds and double binds wherein the wider effective string gap must be wide enough to fit multiple lays of string : in the case of a double bind manoeuvre , of a double string lay crossed twice by a single string . the axial width c of the inner race of the bearing 40 or the contained bearing in the case of a bearing sleeve is maintained at a minimum width . in another embodiment of the present invention , where considerations of stability demand it , more than one ball - bearing may be used in a bearing sleeve . in an embodiment of the present invention where the primary string attachment to the yo - yo is restrained at the midpoint of the bearing sleeve 10 it is believed that it is possible to create yo - yo play possibilities for a more orderly and effective lay of strings by profiling the cylindrical outer face of the bearing or bearing sleeve . further effectiveness is achieved by shaping the bearing sleeve 10 or outer race in a manner that encourages the most efficient lay of string in the confines of a space created by an effective string gap of 4 . 0 to 4 . 5 mm ( 0 . 16 ″ to 0 . 18 ″) optionally in conjunction with or by means of a bearing surface that encourages the lay of strings away from the string snagging means 120 . this is achieved by the concave surface 30 having the gradual slope or gradient m which urges the string toward the midpoint m . the preferred gradient m is approximately 13 °. the yo - yo can still be recalled by a flick of the player &# 39 ; s wrist at this expanded effective string gap and effective greater string lay space created by the present invention . it is foreseeable that the effective string gap width of the present invention can be further extended by improved yo - yo string snagging means 120 . it is also possible to increase the effective string gap by reducing the caliper of the yo - yo string ( not illustrated ). many factors combine to set a range of minimum and maximum effective bearing and bearing sleeve inside and outside diameters . the size of the player &# 39 ; s hand determining the overall yo - yo diameter y and the yo - yo axle determining the diameter of the ball bearing inner race inside diameter b are two primary design limitations for high performance spinning yo - yos . the size of players &# 39 ; hands in the united states where modern yo - yo design evolved has dictated the external diameter y of the yo - yo to between 54 mm and 62 mm . string rewind inefficiencies start to progressively become evident above the typical united states ½ ″ bearing external diameter ( o . d .) or 12 . 7 mm . by using a bearing sleeve or by thickening the outer race of the ball - bearing of the present invention , the external diameter of the effective bearing surface may be extended to this approximate diameter yet utilize a small enclosed ball bearing , or ball race with a small diameter inner race , to promote a high speed long spinning yo - yo . typically , in ball - bearings of this scale , the radial thickness of the inner race is 25 - 33 % of the radial thickness of the annulus of the ball - bearing assembly , the outer race the same , and the ball race itself between 33 % and 50 %. the present invention envisages increasing the thickness of the effective outer race beyond 33 % to up to 60 - 70 % of the annular thickness of the bearing assembly . this enables various string - restraining modalities of shape such as the outer surface described above to be incorporated within the thickness of the outer race . the effective outer race of the bearing comprises the major radial interval of the radius s of the bearing / bearing sleeve assembly and may comprise upwards of fifty per cent of the radial thickness s of the annular bearing assembly . the effective outer race r of the bearing in the present context is taken to mean either a unitary piece of suitable machined or moulded material , suitably dimensioned so as to constitute a functional ball - bearing assembly in combination with an inner race and a ball - race in accordance with the present invention , or a bearing sleeve , suitably shaped and dimensioned , mounted on a suitably dimensioned prior art ball - bearing . of course , a unitary bearing spool of suitable shape and dimensions , made of a suitable material such as acetyl , teflon ® or nylon materials and having the axial extension of its outer face greater than the axial extension of its inner face closest to the axle may be provided to achieve a similar thickening effect , also within the scope of the present invention . the above mentioned multi - lay string tricks require the wider string gap setting as well as high speed capacity to complete sequences of the above mentioned trick routines . the present invention may be shaped to allow these ideal settings of internal and external diameters of the effective bearing housing to optimize play performance and deliver comfort to the player . it is further understood that the efficient combination of the ratio of sizes of the fore - mentioned variables allows the design of a lighter yo - yo that further reduces the strain experienced by top performers who must play and perform for hours . the term string is used throughout this present patent specification to effectively include other cord like materials and other cord end shapes , knots , ties or attachments that facilitate attachment or other superior string performance functions . the yo - yo “ string ” may be an extruded or moulded material . the present invention , by incorporating a bearing sleeve 10 or 10 ′ of light - weight material , allows the economical construction of a wider setting yo - yo with small internal diameter ball - or roller - bearings and small internal diameter surface friction thereby maximizing spin time and at the same time allowing a larger external diameter string bearing surface to optimize yo - yo recall . the above - mentioned efficiency ratios then allow for the reduction of yo - yo weight near the axis of rotation while still achieving the required complex string trick routines . by contrast , prior art ( u . s . pat . no . 6 , 565 , 408 marcantonio ) has disclosed a bearing sleeve where the width is limited to the width of the enclosed bearing and has restraining flats . the corresponding width is further limited by the perceived need to utilize star burst configurations ( radial ribs ) on the yo - yo inner faces . prior art u . s . pat . no . 4 , 895 , 547 ( amaral ) has effectively shown that the ideal width between the two star burst patterns of the medial faces of the yo - yo halves to be about 0 . 073 ″ to 0 . 090 ″. in practical design the bearing width is therefore limited to the ⅛ ″ ( 0 . 125 ″), i . e . 3 . 15 mm , width range . using a bearing 3 . 15 mm ( ⅛ ″) wide , seated in a bearing pocket in each yo - yo half , with the medial faces of the yo - yo halves set at 2 . 8 mm and with the intrusion of a starburst pattern snaring means raised 0 . 3 mm from each medial face , the effective string gap of the amaral prior art is 2 . 2 mm . by contrast , in the present invention , an increase of 10 per cent in the axial width of the bearing sleeve 10 or outer race of the bearing to 3 . 465 mm , in conjunction with non - intrusive snaring means 120 , yields an increase in the effective string gap of 0 . 915 mm , or 42 %. at a 20 per cent increase to 3 . 78 mm , again with non - intrusive snaring means , the effective string gap is increased to 3 . 43 mm , an increase of 1 . 23 mm or 56 %. it can be extrapolated that considerable gains are also made at differentials below 10 per cent , also within the scope of the present invention . by holding the axial width of the inner race and the ball race constant , there is no increase in friction . the discussed range of settings was arrived at based on a standard eight ply 100 % cotton string . the caliper of this string can vary depending on many string manufacturing factors , such as adjusting the tension between the string plies . an eight ply white string not under tension is approximately 1 mm in caliper . it follows that discussed the prior art does not envisage more than the primary string and one extra lay from a trick mount , such as “ the elevator ” ( old school ! ), since at an effective string gap of 2 . 2 mm , a third thickness of string , making 3 . 0 mm of string thickness , would necessarily snag . it is understood that the above description is intended to be illustrative and that other embodiments may be apparent to those skilled in the art without departing from the spirit of the present invention .
the invention relates to yo - yos and in particular high - performance ball - or roller - bearing yo - yos capable of extremely wide string - gap settings suitable for “ new school ” yo - yo tricks . the present invention addresses the need to center the yo - yo string on the bearing or bearing sleeve along the axial extension of the outer surface of the yo - yo bearing or bearing sleeve or in relation to the effective “ string gap ” between the opposed inner faces of the two yo - yo halves . the present invention also provides an effective and economical string - bearing surface able to span the wider string gap required by “ new school ” styles and modes of play . the present invention enables the variable stacking of successive lays of string either side of the securing loop during complicated yo - yo string trick routines .