Method for manufacturing headrest, and headrest
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Solution Overview
Problem
Conventional headrest manufacturing methods face challenges in evenly foaming polyurethane foam when mechanisms with various functions are incorporated, leading to underfill and gas accumulation issues, which affect the thickness and weight of the pad layer.
Innovation Solution
A method involving an injection-passage-forming member with a foaming raw material injection passage along the vertical direction of the headrest, allowing the foam to spread and foam between the skin member and functional parts, including a head part supporting plate that swings due to flow pressure to facilitate even foaming and prevent underfill.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanisms for reducing pad layer thickness, adjusting headrest position, or providing sound are incorporated in the headrest, then weight reduction and functionality improvement are achieved, but foaming cannot be performed evenly and underfill is generated due to gas accumulation
Solution Approach 1:
The injection passage is divided into multiple sections: a first injection passage for injecting foaming raw material, and a second injection passage for injecting gas. This segmentation allows independent control of foam injection and gas injection processes, enabling even foaming despite the presence of functional mechanisms that would otherwise obstruct the foaming process.
Solution Approach 2:
Gas is introduced as an intermediary substance through the second injection passage to displace air trapped by functional mechanisms and promote uniform foam expansion. The gas acts as a mediator that facilitates even foaming by removing air pockets that would otherwise cause underfill and irregular foam distribution.
2Ease of manufacture
If the entire range in the skin member becomes a pad layer by foaming of polyurethane foam raw material, then simple manufacturing is achieved, but mechanisms for various functions cannot be incorporated without preventing foaming
Solution Approach 1:
The injection system is segmented into multiple passages with different functions. The first injection passage handles foaming raw material while the second injection passage handles gas injection. This segmentation enables the manufacturing process to accommodate functional mechanisms by providing separate pathways for foam and gas injection, maintaining manufacturing simplicity while enabling versatility.
Solution Approach 2:
The injection system is designed with multi-functionality to serve both simple foam injection and complex gas-assisted foaming operations. The presence of multiple injection passages allows the same manufacturing setup to handle both basic pad layer formation and advanced applications where functional mechanisms are incorporated, making the manufacturing process universally applicable.
3Strength
If a head part supporting plate is provided in the front surface of the functional part, then shock absorption performance is improved, but the gap between the plate and skin member creates difficulty for foaming raw material flow
Solution Approach 1:
Gas is introduced through the second injection passage as an intermediary to facilitate foam raw material flow into the narrow gap between the head part supporting plate and skin member. The gas bubbles through the gap, carrying the viscous foam material with it, thereby enabling complete filling of the gap region that would otherwise be difficult to reach.
Solution Approach 2:
The viscosity and flow characteristics of the foaming raw material are effectively changed by introducing gas through the second injection passage. The gas-foam mixture has different flow properties compared to pure foam, allowing it to penetrate the narrow gap more easily while still providing the required shock absorption performance when cured.
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 method ensures a thinner, lighter pad layer with improved shock absorption and acoustic performance while preventing gas accumulation and maintaining the original functions of the headrest.
Implementation Method 1
injecting the foaming raw material, spreading the foaming raw material to the outer side of the headrest that is closer to the skin member from a center of the headrest including a gap between the skin member and the injection-passage-forming member, via the foaming raw material injection passage, foaming the foaming raw material, and performing integral foam molding of the pad layer with the skin member
Implementation Method 2
when the foaming raw material spreads in a gap between the head part supporting plate and the skin member, the head part supporting plate swings due to a flow pressure of the foaming raw material, and flow of the foaming raw material in the gap is prompted
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(d)
Figure 3(a)~3(c)
AI summary
Provided is a headrest in which a pad layer is integrally formed, including a portion with a narrow gap, between a mechanism having various types of incorporated functions and a skin member. A shock absorbing member (30) that is an injection-passage-forming member having a foaming raw material injection passage (311) formed so as to run substantially along a direction that is the vertical direction of the headrest in orientation of when a seat is attached, is set in the inside of a skin member (50), and a foaming raw material for forming the pad layer is injected through the foaming raw material injection passage (311). The configuration preferably causes the foaming raw material to spread by the foaming start time, as the foaming raw material spreads to the outer side of the headrest (10), that is, to the inner surface of the skin member (50), where the pad layer is required to be formed. Therefore, the pad layer is reliably formed between the inner surface of the skin member (50) and the outer surface of the shock absorbing member (30) when foaming starts after the foaming raw material has spread.