| 摘要 |
PURPOSE:To attain the external control of the negative buoyancy by adding a negative buoyance control means to a negative buoyancy reduction means set at a floating surface part where the negative buoyance is produced. CONSTITUTION:A venthole 6 serving as a negative buoyancy reduction means is drilled at a negative pressure pocket part enclosed by a flat slider part 2 and a cross rail part 4. An electrostrictive element 8, for instance, is provided on the upper surface part of the venthole 6 as a negative buoyancy control means. A power supply 9 is connected to the element 8 via a switch 10. The negative buoyance is minimized in a start and stop modes and at a low speed mode to float a head quickly. Therefore the switch 10 is turned on to deform the element 8 and to open the venthole 6. The switch 10 is turned off at a steady operation speed to reset the element 8 to its original form. Then the venthole 6 is closed to produce the negative buoyancy. Thus the variance of the floating degree is minimized for the head. |
