摘要 |
<p>The tank (10) has a rectangular opening at its upper end, and two edges (16) connected at small sides of the opening, where the tank is made of plastic material. A flap (18) partially closes the opening. The flap is extended in a plane of the opening from an edge of the opening in a direction of opposite edge. A pin maintains the flap in closing position. The flap interdicts the retraction of a ball contained in the tank. The ball is made of ferromagnetic material.</p> |