Safety device for rotary earth drilling apparatus
AssigneeJoy Manufacturing Company
InventorWilliam J. Weber
Life of this patent
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Abstract
A safety device for a drilling rig of the type wherein a drill-carrying cradle is caused to move upwardly or downwardly on a tower by a chain which traverses sprockets at opposite ends of the tower. Shock loads and vibration cause premature failures in the chain when withdrawing a drill string as the cradle is pulled upwardly on the tower. The present invention minimizes shock loads on the chain to minimize the possibility of a chain failure and, at the same time, prevents a fall of the cradle and drill carried thereby if the chain above it should break, this latter function being accomplished with the use of spring-loaded toothed dogs on the cradle which engage the tower and prevent movement of the cradle in the event of a chain failure.
Claims8
In a rotary and/or percussion drilling rig of the type having a vertically-extending tower provided with a guideway for a drill-carrying cradle, sprocket means at opposite ends of said tower, and chain means movable around said sprocket means and connected to said cradle whereby movement of the chain means will cause vertical movement of the cradle and a drill carried thereby;
- the improvement in said drilling rig of means for preventing said cradle and a drill carried thereby from dropping in the event of breakage of said chain means, said improvement comprising:
- a connecting member secured to a shaft pivotally carried on said cradle and having leg means pivotally connected to an end of said chain means,
- torsion spring means urging said shaft and said connecting member to rotate from a position where the connecting member is aligned with the chain means while it is under tension, and
- at least one toothed dog secured to said shaft and rotatable with the shaft under the force of said torsion spring means to engage said tower and secure the cradle against movement until tension is again restored to the chain means.
Dependencies are inferred from the claim text.