GB551301A - Improvements in or relating to power stamps, hammers, and like machines - Google Patents

Abstract

551,301. Power hammer. MASSBY, Ltd., B. & S., and MASSEY, H. F. July 12, 1941, No. 8843. [Class 83 (iv)] Double drive hammers having a combined anvil block and tup assembly suspended or balanced by a pneumatic spring as described in Specification 497,826, have the air spring acting through an oil seal to prevent leakage, and means for varying the pressure of the air spring. The anvil block 11, Fig. 1, and the guides for the tups 12 are suspended from the fixed frame by pistons 13 in oil cylinders 14 connected to the bottom of the top compartment 18 of three compartments in a tubular column 15 connected at 17 to a second column 16 both columns being closed at the bottom. The column 16 contains the airspring that presses on the oil in the compartment 18. The spring is loaded to the requisite pressure by a pump 21 that draws oil from the bottom compartment 20 and delivers it to the compartment 19 forcing air through a valve 23, pipe 24 and non-return valve 25. When the compartment 19 is full of oil the valve 23 is closed, the compartment is connected to atmosphere and the oil returns to 20 through a transfer valve 26. This cycle is repeated until the air spring has the required pressure. In operation, a motor driven pump 27 delivers oil past a valve 30 to a cylinder 29 thus separating the tup and anvil, till a trip mechanism shifts the valve allowing the oil to return and the tup to fall. The pistons 13 being thus temporarily relieved of the weight of the tup raise the anvil to meet the falling tup and on impact the momentum approximately cancels out. The valve 30 may be such as to cause a succession of blows until the valve is locked in a neutral position. In a modification adapted for the automatic charging of the air spring a pump 21a, Fig. 6, delivers oil from the sump 36 at 3211 below a piston 31 working in the part of the column 15a occupied by the middle and lower compartments in the above form. Oil pressure at 321 raises the valve 33 closing passages 34, 35. The oil is delivered below the piston causing it to rise and free air from above it through valves 23a ... 25a as before. At the top of its stroke the piston uncovers a passage 38 admitting oil above the valve 33 and forcing the latter to its lower position in which oil returns from below the piston via passages 34 and 35 to the sump. At the end of the down stroke of the piston the passages 34, 38 are closed and the valve 33 is raised the cycle repeating till the air spring is charged. In a further modification a second piston is employed in an auxiliary column one piston comprising air whilst the other returns the valve 33 being made double acting. Further to increase the rapidity of action the pistons may be supplied with compressed air instead of with air at atmospheric pressure. Instead of the columns horizontal or other air vessels may be employed.