Closure device for an injection molding machine or injection press

Claim 1

In a closing unit for an injection moulding machine or transfer moulding press with a frame (1), a first tool carrier (4) fixedly connected therewith, a second displaceable tool carrier (5) and hydraulic displacing devices (10, 11), which are eccentrically arranged with respect to the tool carriers (4, 5) and of which each displacing device (10, 11) possesses a hollow cylinder (17, 18) fastened to the frame (1) and a piston (19, 20), which is displaceably guided in the hollow cylinder (17, 18), each piston (19, 20) being provided on one side with a first shaft (21, 22) and on the other side with a second shaft (25, 26), wherein the first shafts (21, 22) are arranged in such a manner that they are drawn into the hollow cylinders (17, 18) when the tool carriers (4, 5) are brought nearer to each other, and wherein one each of the two shafts (21, 22, 25, 26) of the pistons (19, 20) is fixedly connected with the second tool carrier (5), the improvement which comprises: that at least two first pistons (19) are provided in respective hollow cylinders (17), the first shaft (21) of each first piston (19) having a smaller diameter than its associated second shaft (25), that at least two second pistons (20) are, provided in respective hollow cylinders (18), the first shaft (22) of each second piston (20) having a greater diameter than its associated second shaft (26), all said first shafts (21, 22) being connected with the second tool carrier (5), each hollow cylinder (17, 18) having an inside diameter (17a, 18a) greater than the outside diameter of the respective first and second piston (19, 20) associated therewith, the difference between each cylinder diameter and its associated piston diameter defining an annular gap therebetween and a valve closing ring (27, 28) arranged in each hollow cylinder (17, 18) between the inside diameter (17a, 18a) of such cylinder and the outside diameter of the second shaft (25, 26) of the piston associated with such cylinder, means forming a seal between each valve closing ring (27, 28) and the inside diameter (17a, 18a) of the cylinder (17, 18) associated therewith and between each valve closing ring (27, 28) and the second shaft (25, 26) of the piston associated with such cylinder, each valve closing ring (27, 28) having valve seat means (27d, 28d) for sealingly engaging the piston (19, 20) associated therewith.