Multi-Position THz Measurement for Container Pinch Welds
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Solution Overview
Problem
Conventional methods struggle to reliably measure the quality of pinch welds in blow-molded plastic containers, particularly those with non-parallel interfaces, which are critical for safety-relevant components like LNG or hydrogen cylinder liners, as they are difficult to detect due to their inward shape and non-parallel design.
Innovation Solution
A THz measuring method and device that adjusts a THz sensor relative to the container area, using techniques like synthetic aperture radar (SAR) and artificial intelligence to evaluate the seam's properties, such as length, layer thickness, and seam angle, by emitting divergent or convergent THz radiation and capturing reflections from various angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional THz or radar radiation methods are used to determine wall thickness, then layer thickness at parallel interfaces can be detected, but the beam is reflected laterally at non-parallel interfaces and cannot be detected
Solution Approach 1:
The measurement process is segmented into multiple discrete measurement positions around the container. Instead of attempting a single measurement at the non-parallel seam interface, the system takes multiple measurements at different angular positions and combines them to reconstruct the wall thickness profile, enabling detection of the seam structure that would otherwise reflect the beam away.
Solution Approach 2:
The system transitions from a single-point measurement approach to a multi-dimensional measurement approach by positioning the sensor at multiple angular positions around the container. This adds the angular dimension to the measurement space, allowing the system to capture reflections from the non-parallel seam interface that would be invisible from a single viewpoint.
2Ease of operation
If visual inspection by camera is used to assess the pinch weld, then the outer surface can be examined, but the inward shape with waves and indentation cannot be detected
Solution Approach 1:
The patent replaces the optical/mechanical camera-based visual inspection system with a THz electromagnetic radiation-based measurement system. THz radiation can penetrate the plastic material and detect the internal seam structure, whereas optical cameras can only see the external surface and miss the critical inward-facing seam geometry.
3Device complexity
If a single measurement position is used for THz sensor, then the measurement process is simple, but reflections from non-parallel surfaces cannot be captured
Solution Approach 1:
The system performs preliminary positioning of the THz sensor at multiple predetermined angular positions around the container before actual measurement begins. This pre-planned multi-position setup ensures that the sensor will be at the correct locations to capture reflections from the non-parallel seam interface, eliminating the need for complex real-time adjustment during measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable and efficient measurement of pinch welds with minimal effort, detecting potential defects like thin layers or acute angles that could lead to cracking under pressure, ensuring the seam's integrity.
Implementation Method 1
measuring radiation reflected by the body is detected
Implementation Method 2
the measuring radiation penetrates at least partially into the body
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a THz measuring method and a THz device for measuring a container (1) with a seam (4), in particular a blow-molded container with a crimp seam, wherein a THz sensor (8) is adjusted relative to a container area (3) to several positions (Pi) with different orientations of the optical axis (B), THz radiation is emitted as a non-parallel beam (20) from the THz sensor onto the container area, and partially reflected THz radiation (R) is received at the inner surface (17) and the outer surface (16) of the container area (3), and one or more of the following properties of the seam (4) are determined: a length in its longitudinal direction, a width in a transverse direction, a layer thickness profile of the layer thickness in the longitudinal and transverse directions (Q), a wave wall thickness of one or two waves formed on an inner surface, a residual wall thickness in a recess (15) between two waves,a seam angle of the seam on the inner surface in a depression between two waves.