Abstract: An automatic variable speed centrifugal clutch belt tightening assembly is characterized by even transmission of rotational drive to a pair of belts and includes a rotating spindle and clutch plate having an adjustable centrifugally operable belt tightening mechanism. The belt tightening mechanism includes a clutch drum and a spacer which define recesses for receiving the belts to be driven. The spacer is mounted on the spindle by a bearing assembly affording free rotational and limited longitudinal movement relative to the spindle. As the spindle rotates, the clutch drum presses the spacer against a flange of the spindle to evenly drive the belts while compensating for differences in belt size.

Abstract: A pump is provided for circulating drilling fluid and the like into a well during a well drilling process. The pump comprises a pair of double-ended piston assemblies hydraulically reciprocated in opposite directions by a common hydraulic drive arrangement, wherein each piston assembly has a relatively large piston at one end and a relatively small piston at an opposite end. The various pistons reciprocate within appropriately sized cylinders each having a working end with a one-way intake valve through which drilling fluid is drawn from a supply tank and a one-way discharge valve through which drilling fluid is discharged to the well.