Drive systems for mining apparatus

摘要

A drive system, particularly for mining apparatus employing chains, which has a fluid control circuit coupled to a ring gear of planetary gearing transmitting drive from a motor. The control circuit has a pump drivably coupled to the ring gear and the fluid outlet from the pump can be blocked to lock the ring gear and permit transmission of force through the planetary gearing. In the event of abnormal loading the outlet from the pump is opened automatically to allow fluid to flow at a pre-determined flow rate. This in turn allows the ring gear to rotate to break the transmission and the system can be gently braked without danger.