Absorbent Pad Channel Formation with Ultrasonic Welding
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Solution Overview
Problem
Existing methods for forming absorbent pads with channels in sanitary articles face issues such as adhesive spreading on channel zones, potential damage from pressure application, and precise calibration requirements, leading to unreliable and defective products.
Innovation Solution
An apparatus with a forming drum and suction system to prevent absorbent material retention in channels, combined with ultrasonic welding for secure joins and a removal system using negative pressure and centrifugal impellers to ensure clean welding zones, allowing for reliable and precise formation of absorbent pads with channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is spread on the sheets at the channels to join the layers, then the adhesion at the channels is improved, but the absorbent material sticks to the sheets in the channel zones causing potential damage or perforation
Solution Approach 1:
The adhesive application is segmented into two distinct zones: a first adhesive applicator applies adhesive upstream of the channel formation zone, and a second adhesive applicator applies adhesive downstream of the channel formation zone. This segmentation ensures that adhesive is applied to the sheets at the channels without absorbent material being present in the channel zones, thereby maintaining strong adhesion while preventing material sticking and potential damage.
Solution Approach 2:
The first adhesive applicator applies adhesive to the sheets in advance, upstream of where the channels will be formed. This preliminary adhesive application ensures that when the sheets are pressed together to form channels, the adhesive is already in place to bond the layers, preventing absorbent material from interfering with the bonding process at the channels.
2Strength
If pressure device is used to optimize adhesion at the channels, then the joining of sheets is improved, but the pressure can damage or perforate the pad if absorbent material is deposited between the pressure device and mating part
Solution Approach 1:
The pressure application process is segmented into two stages: first, a preliminary pressure is applied upstream of the channel formation zone to bond the adhesive applied by the first adhesive applicator; second, a final pressure is applied downstream of the channel formation zone to bond the adhesive applied by the second adhesive applicator. This segmentation ensures that pressure is applied to optimize adhesion without absorbent material being present in the channel zones, thereby preventing damage or perforation.
Solution Approach 2:
The preliminary pressure application occurs upstream of the channel formation zone, before the channels are formed. This preliminary pressure ensures that the adhesive applied by the first adhesive applicator is properly bonded to the sheets, creating a stable structure that can withstand subsequent channel formation and final pressure application without damage.
3Strength
If pressure device applies very precise and painstakingly calibrated pressure to obtain satisfactory join at channels, then the adhesion is improved, but the device complexity and calibration requirements increase
Solution Approach 1:
The pressure application is segmented into two distinct pressure devices: a first pressure device upstream of the channel formation zone and a second pressure device downstream of the channel formation zone. Each pressure device operates independently with simplified calibration requirements, applying pressure to bond adhesive in their respective zones. This segmentation eliminates the need for a single complex pressure device requiring painstaking calibration, while still achieving satisfactory adhesion at the channels.
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
The solution enables the production of absorbent pads with secure, reliable channels and edges, reducing defects and the need for precise pressure calibration, resulting in improved absorption and distribution performance.
Implementation Method 1
the forming drum comprises a suction system to create, for example on the first web advancing on the forming drum, a spread of absorbent material according to the absorbent material spreading pattern
Implementation Method 2
a welding system for welding the first web to the second web to join the first web to the second web at least at the channel without absorbent material
Implementation Method 3
The impellers generate a vortex at the inserts which forces any absorbent material that may be present there towards negative pressure zones of the forming drum
Data Source
Figure 1~2
Figure 3
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AI summary
A method for forming an absorbent pad comprising a first layer, a second layer and an absorbent material interposed between the first and the second layer and arranged according to a spreading pattern M1 having at least one channel which is free of absorbent material, comprises a step of feeding a first web (NW1), intended to form the first layer of the pad; a step of feeding a second web (NW2), intended to form the second layer of the pad; a step of spreading the absorbent material on the first web (NW1) according to the spreading pattern M1; a step of joining the first and second webs (NW1, NW2), a step of removing any absorbent material that may be present in the channel.