Tennis racquet string attachments giving spin to ball - have grooves fitting strings and corrugated surfaces, friction material, or protuberances

摘要

The tennis racquet accessory consists of a set of plastics blocks designed to fit onto the intersection points of the horizontal and vertical strings, and to give a very high degree of spin to the ball when struck by their impact surfaces. Each block has a groove (3) across one face and another groove (4) at right angles to it on the opposite face. The racquet strings fit into these grooves and retain the block. The faces have protuberances (6) which cause the ball to spin when struck by them. The depth of the grooves is 0.2 to 1m greater than the diameter of the strings. The protuberances can be spherical, or the surfaces can alternatively by corrugated. The protuberances may be bristles or of hair etc.