Apparatus for inductively monitoring the movement of a piston within a cylinder of an injection molding machine

Claim 1

A measuring arrangement for use in an injection molding machine having a piston means, operatively mounted in hollow cylinder means, said arrangement measuring the extent of axial movement of one of said means relative to the other in response to introduction of fluid under pressure into said cylinder means, said arrangement comprising: inductive measurement transducer means for converting the movement of said one of said means with respect to the other of said means into an electrical magnitude, said transducer means including a piston inductive component forming part of said piston means and forming a bore in said piston means, said piston inductive component being at least partially formed of ferromagnetic material, and a cylinder component having a fixed position relative to said cylinder means, said cylinder component including a coil axially secured to said cylinder means and a ferromagnetic core surrounded by said coil, so as to be coaxially aligned therewith, said coil and core extending into said bore formed by said piston inductive component, said piston and cylinder components having an inductive operational relationship with each other, said cylinder means having in its interior a partition fluidtightly surrounding said piston means and separating in said cylinder means on one side of said partition a pressure chamber, and, in said cylinder means, on the other side of said partition, a chamber which is at atmospheric pressure, said piston means having a piston portion situated in said pressure chamber and an extension extending fluid-tightly through, said partition iNto said chamber which is at atmospheric pressure, the latter extension being formed with said bore and receiving said said cylinder component of said transducer means.