A method for the production of hyaluronic acid with a low molecular weight.

摘要

PURPOSE:To apply a double cylinder to a small and an intermediate molding machine, too, and to miniaturize an outer hydraulic device and to reduce its cost by reciprocating built-in oil between a built-in oil sump and a lower oil sump with the vertical movement of a ram. CONSTITUTION:When the ram 33 is at the falling end, a built-in oil sump 40 and a lower oil sump 37 are filled with oil. When hydraulic pressure is given to the oil sump 38 for elevating the ram under this state, the ram 33 is elevated by reaction because the lower end of a rod 35 is fixed to the bottom part 36 of a large cylinder 31. At this time, since a negative pressure acts on the lower oil sump 37, oil in the built-in oil sump is sucked into the lower oil sump through a pilot check valve 53. When hydraulic pressure is given to the oil sump 39 for lowering the ram at the rising position of the ram 33, force acts in the direction for lowering the ram 33 and the ram 33 is lowered. At this time, pressure in the oil sump for lowering the ram opens a pilot check valve 53 through a pilot pressure passage 54 and oil in the lower oil sump flows back into the built-in oil sump 40 through the pilot check valve 53.