| 摘要 |
<p>A control is disclosed for inhibiting the tilting of an earth drilling machine that is supported on hydraulic jacks. A hydraulic downfeed motor for the drill string is operated by a control that has pressure responsive switches connected to the hydraulic jacks, and in the event the drilling machine starts to rise upwardly during drilling one of the pressure responsive switches will operate to shut off fluid pressure to the downfeed motor and to entrap fluid within the motor. The entrapment of fluid in the motor maintains a drilling pressure that permits drilling to continue with a drilling force that will not allow the machine to rise upwardly on the supporting jacks.</p> |
