Patent GB-189716643-A (GB)
Title: Improvements in Hydraulic Presses.
Inventor: LEAVITT FRANK MCDOWELL
Filed: 1897-07-13
Granted: 1898-05-14
Abstract: 16,643. Leavitt, F. McD. July 13. Drawing.-In hydraulic presses used for metal drawing, e.g. in making sheet-metal kettles or half barrels, two double-acting rams D and F are used as shown diagrammatically in Fig. 17. One ram D carries the punch or presser head a, and the other ram F actuates the movable die d through a system of toggle-levers g, h, i, i, in which the pivots H are held by the framing, so that, when the die d is lowered on the blank c on the fixed die e and the toggles g, h are straightened, the pressure on the punch a, as it draws the metal through the dies, is transmitted directly to the press framing and not to the ram F. In this way backing-ofr of the die d due to leakage, and the consequent puckering of the metal blank, are prevented. The dies d and e are preferably arranged above the frame C' to economize space. The die d is then carried on a block supported by screwed rods with adjusting-nuts from the frame C<1>. The liquid, preferably oil, for operating the press is supplied directly from a continuously-working high-speed pump, Fig. 5, enclosed in a tank L to which the oil is returned after use in the press. A balanced piston valve J directs the oil either to the press or back to the tank, and is operated by a cam 26 on an intermittently-actuated shaft M. The piston 28 of this valve is made slightly narrower than its port, in order that the oil may be partly directed to the press and partly back to the tank. and a reduced pressure obtained for working the press slowly during the adjustment of the dies. The valve is held in position for this purpose by a lever 104 and hand-wheel and screw 106. When the cam 26 depresses the valve against the action of the spring 30, the oil is cut off entirely from the press, and returned directly to the tank. A second balanced piston valve K regulates the operation of the press. Its casing has four ports communicating with the ends of the ram cylinders, and one of these ports 43 is in permanent connection with the port 29 leading from the valve J. The valve K is operated by a crank on the shaft M. This shaft is intermittently connected to a continuously-driven wheel M' by means of a clutch or catch 35 which is disengaged at each quarter revolution of the shaft M by cams or fingers k, k<2>, and two others not shown, and only permitted to re-engage when the press has completed the movement corresponding to the particular position of the valve K. The clutch 35 consists of a half-roun.1 spindle turning in a boss on the shaft M and having an arm 36 which is normally forced outwards by a spring 37 making the half-round spindle engage with one of the recesses 38 in the boss of the driving-wheel M' till the arm 36 is forced back by one of the cams k, k<2>, &c. When the press has performed one complete operation, it is brought to rest by the action of the cam M on the valve J giving time for the removal of the finished article and the introduction of another blank. The press is re-started by engaging the clutch 35 by hand, whereupon another complete operation is performed automatically.