Unilateral dual display device for use in tennis racket, has two tanks filled with fluid material, where each tank has display window communicating with other tank by opening that delays flow of material from one tank to other

摘要

The device (5) has two tanks (33, 43) having equal volume and filled with a fluid material (50). Each tank has a display window communicating with the other tank by a communication opening (41, 44). The openings delay the flow of material from one tank to the other. The device is reverted by a handle axis and a center of a racket to provoke a display of an inscription by action of gravity on the material.