Ultrasonic method and device for indirectly measuring cavity pressure of injection molding machine

Patent metadata

Field	Value
Publication number	US-11573146-B2
Application number	US-201917256524-A
Country	US
Kind code	B2
Filing date	Sep 19, 2019
Priority date	Sep 21, 2018
Publication date	Feb 7, 2023
Grant date	Feb 7, 2023

Abstract

The present invention discloses a ultrasonic method for indirectly measuring a pressure of a cavity of an injection molding machine, comprising: emitting ultrasonic wave to each pull rod along an axial direction of the pull rod respectively at the same time, detecting an ultrasonic wave echo time difference of each pull rod, and obtaining an average pressure inside a cavity of the injection molding machine. By the detection method and detection device of the present invention, the pressure inside the cavity may be detected in a certain state, the pressure inside the cavity in the injection molding process may be detected in real time, and the detection process is simple and the accuracy is high.

First claim

The invention claimed is:

1. An ultrasonic method for indirectly measuring a pressure of a cavity of an injection molding machine, comprising:
emitting ultrasonic wave to each pull rod along an axial direction of the pull rod respectively at the same time, detecting a time difference between an ultrasonic wave echo on each pull rod in an injection molding process and an ultrasonic wave echo when the pull rod is under minimal strain, and obtaining an average pressure P inside the cavity of the injection molding machine according to the following formula:

P
⁢

=

π
⁢

R
2

·
W
·
Δ

⁢

t
total

/
A

wherein R is the section radius of the pull rod; Δt total is the sum of echo time differences of all the pull rods; W is a constant at least partially determined based on one or more Murnaghan constants and one or more Lamé constants of the material of the pull rod; and A is the projection area of the cavity on a plane perpendicular to the axial direction of the pull rod;
wherein there are four pull rods; wherein an ultrasonic probe is arranged at the tail end of each pull rod;
wherein the W is acquired by the following method: before detection, for the pull rod with the same material, conducting detection by a mold locking force sensor under different mold locking forces to acquire multiple groups of σ−Δt data, and fitting a straight line passing through the origin of σ−Δt data, and evaluating the slope of the straight line to acquire the W, where the σ is a stress on the pull rod as a y-coordinate and the Δt is a time difference of ultrasonic wave echoes, as an x-coordinate.

2. The ultrasonic method for indirectly measuring a pressure of a cavity of an injection molding machine according to claim 1 , wherein the ultrasonic wave is emitted to each pull rod continuously in the injection molding process, and the average pressure in the cavity of the injection molding machine in the injection molding process is displayed in real time.

3. The ultrasonic method for indirectly measuring a pressure of a cavity of an injection molding machine according to claim 1 , wherein a curve of time and average pressure inside the cavity of the injection molding machine is output in real time.

4. The ultrasonic method for indirectly measuring a pressure of a cavity of an injection molding machine according to claim 1 , wherein a recording frequency of an ultrasonic wave echo signal is higher than or equal to 20 Hz.

Assignees

• Univ Zhejiang

Inventors

• Zhao Peng
• Zhang Jianfeng
• Zhao Yao
• Gu Fu
• Huang Junye
• Xia Neng
• Fu Jianzhong

Classifications

• B29C2945/76076

  duration · CPC title

• B29C2945/76234

  tie-bars · CPC title

• B29C45/77

  of velocity or pressure of moulding material · CPC title

• B29C2945/76471

  Acoustic · CPC title

• B29C45/0082

  Reciprocating the moulding material inside the mould cavity, e.g. push-pull injection moulding · CPC title