Abstract: Improved mud pump comprised of plural cylinder pumping units, each cylinder unit consisting of a pumping compression chamber and two or more hydraulic driven expansion chambers, with one or more expansion chambers being employed to drive a pumping plunger to cause fluid to be pumped through the compression chamber, also one or more of said expansion chambers being employed to return the plunger; the plunger further being employed as the housing for one or more of the said expansion chambers. The invention includes novel hydraulic drive circuitry and novel hydraulic distribution valving means for control of the hydraulic drive fluid that is utilized to drive the expansion chamber of each cylinder pumping unit. The invention also includes novel positioning means for the unidirectional inlet and outlet mud pumping valves.

Abstract: A leak-proof filling valve for a paper sack is formed by folding a composite sheet formed from Kraft paper 1 on top of which is laid relatively flexible polythene 2. The folded sheet is secured between end flaps 10A, 12 of a paper sack. The sack is charged with material 16 through a mouth 15 and passes through a short inner channel between parts 1C, 1D, and a longer outer channel between parts 2A, 2B. Reverse flow between parts 2A, 2B is prevented by material which percolates into pocket 17, assisted by the different flexibilities of the parts 1A, 2A. Any material which nevertheless does pass into space 18 is prevented from escaping between parts 1C, 1D by accumulation of material in pocket 19 this being assisted by the different flexibilities of parts 1C, 2C.