Diaper Sheet Fixing Device Inversion for Welding Strength
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Solution Overview
Problem
The existing ultrasonic welding devices for disposable diapers face strength reduction issues when fixing elastic and low-stretchable sheets due to the larger protrusions and surface portions sandwiching the sheets, leading to inadequate bonding strength.
Innovation Solution
A fixing device and method where the low-stretchable sheet is wrapped around the rotating member and positioned between the elastic sheet and protrusions, with a larger surface portion than the protrusions, to prevent excessive stretching and ensure sufficient sheet material for strong bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the elastic sheet is positioned on the anvil roller side including protrusions, then the sheets can be sandwiched and fixed, but the elastic sheet is thinly stretched due to high stretchability, reducing the amount of sheet material and welding strength
Solution Approach 1:
The patent inverts the conventional arrangement by positioning the low-stretchable sheet on the anvil roller side with protrusions instead of the elastic sheet. This inversion prevents the elastic sheet from being thinly stretched during fixation, maintaining sufficient sheet material and welding strength while still achieving proper sheet bonding.
2Productivity
If the area of the vibrating surface is larger than the top surface of each protrusion, then the sheets can be effectively sandwiched, but the elastic sheet is overly stretched, reducing welding part strength
Solution Approach 1:
The patent applies local quality by having the low-stretchable sheet contact the protrusions at specific locations where controlled stretching is needed for fixation, while the elastic sheet contacts the larger vibrating surface area where excessive stretching should be avoided. This spatial differentiation of material functions maintains both fixation efficiency and welding strength.
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
This approach effectively suppresses strength reduction of the fixing parts by maintaining sufficient elastic and low-stretchable sheet material on the protrusions, resulting in stable and strong bonding between the sheets.
Implementation Method 1
the surface 15hs vibrates in a direction in which the space between the outer peripheral surface 15as and the surface 15hs is expanded or contracted... ultrasonic vibration energy is selectively charged into respective sandwiched portions of both the sheets 8a and 9a to melt them
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
A fixing device that fixes an elastic sheet (8a) that is transported along a transport direction and a low-stretchable sheet (9a) that has lower stretchability than that of the elastic sheet via a plurality of fixing parts (j) while superposing the elastic sheet and the low-stretchable sheet in a thickness direction. The fixing device includes: a rotating member (15a) that includes a plurality of protrusions (15at) on an outer peripheral surface to form the plurality of fixing parts and rotates along the transport direction; and a sandwiching member (15h) that is arranged at a predetermined position of the rotating member in a rotational direction, and sandwiches the elastic sheet and the low-stretchable sheet by a surface portion (15hs) in cooperation with each of the protrusions to form the fixing parts when each of the protrusions passes through the predetermined position, the surface portion being larger than a top surface of each of the protrusions. At a sandwiching position in which the elastic sheet and the low-stretchable sheet are sandwiched cooperatively by the sandwiching member and the rotating member, the low-stretchable sheet is located between the elastic sheet and the top surface of each of the protrusions of the rotating member.