PRESSES, FORGING. hydraulic Forging.—Mr. W. I). Allen, in a paper read before the Iron and Steel Institute in 1891, describes as follows a hydraulic forging press which has been in operation some time in England. and has proven to be a most efficient and useful tool. In this press the force pump and the large or main cylinder of the press are in direct and constant communication. There arc no intermediate valves of any kind, nor has the pump any clack valves, hut it simply forces its cylinder full of water direct into the cylinder of the press, and receives the same water, as it were, back again on the return stroke. Thus, when both cylinders and the pipe connecting them are full, the large rain of the press rises and falls simultaneously with each stroke of the pump, keeping up a continuous oscillating motion ; the ram, of course, traveling the shorter distance, owing to the larger capacity of the press cylinder.
The press and pumps are shown in Figs. 1 and 2. The top and bottom portions of the framing, A A, are alike. The main columns, B B, are hollow. The large press cylinder, D, is fitted and held in the top frame: the anvil block rests in the bottom frame. B is the main ram. F is a steam-cylinder with piston, the piston-rod of which is attached to the shank of the ram. C is a cross-head working in guides, thus preventing the ram from turning round.
The force pumps are "duplex," the ends or faces of the two plungers, II H, advancing and receding to and from each other simultaneously at each stroke. They work intoopposite ends of the pump, I. This cylinder is simply a strong tube. The two plungers are worked by a three-throw crank,
various requirements of work in hand, and to effect this a. source of supply of water under a pressure of about 250 lbs. has to be provided, which, when admitted into the press cylinder, has sufficient force to overcome the power of the steam in the steam-cylinder, sending the steam back into the boilers. By this means the rain is rapidly brought down any required distance: on the other hand, the power of the steam immediately raises the ram upon the water being allowed to escape.
The valve used for the rapid admission arid escape of water becomes, therefore, rather an important feature, and is shown in Fig. 2. It consists of a cylindrical facing, having a hollow cylindrical valve or plunger, working endwise through hydraulic leathers ; at each end of this valve or plunger very fine slits are sawn lengthwise through its sides or walls, for allowing of the admission and escape of water, by moving the valve endwise until the fine slits pass the hydraulic leather ; the set of slits at one end of the valve being for the admis sion of water, and those at the other for the escape. L is the easing bored through and fitted with hydraulic leather, shown in section. _V is the inlet, 1ST, the outlet, and 0, a passage into the pipe, K. The valve is capable of being easily moved endwise. It is hollow, with a solid division in the center, the hollow portion forming a sort of cup on each side of the solid part, and through the side walls of these cups the fine slits are cut. When it is desired to bring the press ram clown, the valve is moved endwise to the left until the fine slits pass the hydraulic leather, and a passage is thereby opened from the inlet, if, through the slits, and water is admitted into the passage, 0, and then on to the pipe, A7, and the ram at once descends. When it is desired to raise the ram the valve is raised to the right, and water passes out through the other set of slits, and away by the outlet, /V, and the ram at once ascends by the action of the steam. At the time the slits pass the leather the low pres sure only is in operation, and at the moment of impact of the ram upon the work the valve is always in its neutral position, the position shown in the diagram, the plain body of the central portion of the valve, with a cup leather on each side, being all that is exposed to the great pressure.