Yo-yo players, especially beginners, have been assisted by the development of yo-yos provided with a means to automatically return the yo-yo to the player's hand before the yo-yo spins out completely. Such an arrangement is described, for example, in U.S. Pat. No. 4,332,102 to Caffrey.
The Caffrey patent discloses a yo-yo having a rotatable bearing pulley mounted on the axle to which the yo-yo string is attached. Adjacent the pulley section of the bearing there is provided a cylindrical friction or braking means that interacts with two clutch mechanisms. The surface of the friction or braking means has a slip resistant characteristic and is in practice one or a series of O-rings, which are subject to wear. The clutch mechanism is provided with weighting means such that when the yo-yo is thrown the clutch is released by the development of centrifugal forces. The centrifugal forces are counterbalanced by a spring-loaded force such that the clutch is activated when the yo-yo slows down. The clutch engages the cylindrical friction surface of the pulley extension while the yo-yo still has sufficient momentum to enable the automatic return of the yo-yo to the player's hand. The successful development of an automatically returning yo-yo has proven to be especially valuable to beginners. It is also viewed as a valuable assistance to less gifted or handicapped players.
The nature of the arrangement shown in Caffrey, however, is such that it tends to critically weaken the structural integrity of the yo-yo. The pulley bearing to gain access to the clutch mechanism housed within a yo-yo half requires part of the boss enclosing the axle to be removed in the plastic mold. To enable sufficient braking capacity to be applied, up to 80% of the plastic boss must be removed where the pulley extension friction surface meets the clutch mechanisms.
Also, because the pulley is also the string bearing means, problems occur when bearing lubrication applied in excess finds its way with the aid of centrifugal forces to the nearby contact area between clutch and pulley such that the clutch slips and fails to return the yo-yo successfully.
The arrangement disclosed in Caffrey, by linking the centrifugally operated clutch to a coaxial extension of the string bearing means, has intrinsically restricted options on varying the quality of the string bearing means. The use of a dual purpose bearing that combines a string securing means as well as a clutch interfacing means where the clutch means is operatively enclosed in the yo-yo half must by nature expand laterally along the axial member to accommodate both functions. Caffrey achieves a superior spinning automatically returning yo-yo is achieved by narrowing the string bearing means thereby reducing the area frictionally contacting the axial member. Having the centrifugally activated clutch operatively engage an integral extension of the string bearing means also necessitates the use of double-loop string attachment to inhibit the string from slipping on the bearing means and thereby reducing the clutch effectiveness. The general public have difficulty in tying a double-loop attachment.
Also, the Caffrey arrangement, at least in its commercial embodiments in which the clutch mechanism occupies only one yo-yo half, exhibits a weight differential between the two yo-yo halves that is believed to shorten free spinning time.
Another problem experienced with a conventional automatically returning yo-yo which has a static spacing between yo-yo halves is that different yo-yo manoeuvres, to be performed efficiently, require different yo-yo response tolerances. Tom Kuhn in his publication "SB2Flight Manual" in "The Art of Yo-Yo Choreography", indicates a narrower string gap is better for loop-the-loops and a wider string gap is better for complex spin tricks.