초록 ▼

A plastic resin pelletizer system for controlling the position of the pellet cutting knife blades in relation to a die plate face includes vibration detection pick-up in the form of a piezoelectric accelerometer mounted to the pelletizer die plate. Characteristic frequencies or a signature output is

A plastic resin pelletizer system for controlling the position of the pellet cutting knife blades in relation to a die plate face includes vibration detection pick-up in the form of a piezoelectric accelerometer mounted to the pelletizer die plate. Characteristic frequencies or a signature output is identified as representing the condition of contact between the blades and the die face, and the amplitude of the characteristic signature is used to indicate the extent or degree of pressure of the contact, in controlling the position of the knives with respect to the die plate.

대표청구항 ▼

In a pelletizer having a die plate body in which plastic resin material at an elevated temperature is extruded through a plurality of orifices formed in the face of an annular die plate in said die plate body, a hub which has pellet cutting knife blades therein, said hub being mounted on a drive sha

In a pelletizer having a die plate body in which plastic resin material at an elevated temperature is extruded through a plurality of orifices formed in the face of an annular die plate in said die plate body, a hub which has pellet cutting knife blades therein, said hub being mounted on a drive shaft with said blades coacting with said die plate face for severing pellets of said resin material at said die plate face, and in which said drive shaft hub and blades are movable by shaft positioning means axially of the direction of shaft rotation toward and away from said die plate face to control the spacing between said blades and said face, the improvement in means for positioning said blades in relation to said die plate face, comprising: piezoelectric accelerometer means mounted on said die plate body and operable to provides an electric analog signal representative of the vibrational accelerations of said die plate, a computer, means in said computer receiving said analog signal and converting said signal to a digital signal, means in said computer receiving said digital signal effecting a Fast Fourier Transform thereon and providing a frequency domain output, signal processing means connected to receive said frequency domain output and responding to the occurrences of said accelerations at a discrete portion of said frequency domain output representing contact by said blades against said die plate face and providing a contact signal output, and means connected to receive said contact signal output for controlling said shaft positioning means.