A valve device for use in a feeding apparatus releases raw material into raw material processing machinery for the manufacture of high-voltage cable. The valve device includes a valve body including a first valve member having a conical shape and including at least one opening extending between a tip of the first valve member and a corresponding base portion of the first valve member, and a second valve member including at least one cover element. One of the valve members is rotatable with respect to the other valve member between a first operating position in which the at least one cover element uncovers the at least one opening, thereby allowing the raw material to flow through the valve device, and a second operating position in which the at least one cover element covers the at least one opening, thereby preventing raw material from flowing through the valve device.