Pocketed Spring Assembly with Variable-Size Pockets for Uniform Height
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Solution Overview
Problem
Mattress manufacturers face challenges in creating pocketed spring assemblies with uniform firmness zones and edge support, as spun-bonded polypropylene fabric stretches, leading to uneven surfaces and the need for additional edge support, which increases manufacturing costs and labor.
Innovation Solution
The solution involves creating pocketed spring assemblies with strings of interconnected pockets of varying sizes, where longitudinal seams are strategically placed to accommodate springs of different geometries, maintaining a uniform height and firmness without the 'step' issue, using transverse and longitudinal seams in spun-bonded polypropylene fabric to encase springs, allowing for different firmness zones without additional edge support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spun-bonded polypropylene fabric is used to create pockets for coil springs, then manufacturing cost is reduced and ease of manufacture is improved, but the fabric stretches over time causing uneven surfaces and requiring additional edge support
Solution Approach 1:
The patent changes the physical parameters of the fabric by pre-stretching it in a stretching device before forming pockets, and by controlling the welding parameters to create pockets with initial tension. This pre-conditioning of the fabric parameters prevents subsequent stretching during use, maintaining surface uniformity while keeping manufacturing simple.
Solution Approach 2:
The patent applies preliminary action by pre-stretching the fabric and pre-tensioning the pockets before the springs are even installed. The stretching device applies force to the fabric in advance, creating a pre-stressed state that counteracts future stretching from spring compression, thereby preventing uneven surfaces before they occur.
2Manufacturing precision
If additional edge support is added to prevent fabric stretching, then surface uniformity is improved, but manufacturing complexity and labor cost increase
Solution Approach 1:
The patent extracts the edge support function from a separate structural component and integrates it directly into the fabric pockets themselves. By pre-stretching the fabric and creating tensioned pockets, the edge pockets inherently provide support without requiring additional foam or structural elements, thereby reducing device complexity.
Solution Approach 2:
The patent makes the fabric pockets multi-functional: they serve both as enclosures for the coil springs and as the edge support structure itself. The pre-stretched fabric provides both the necessary containment function and the structural support function, eliminating the need for separate edge support components.
3Ease of manufacture
If pockets are made with uniform size, then manufacturing simplicity is maintained, but different spring geometries cause fabric stretching and uneven surfaces
Solution Approach 1:
The patent applies local quality by creating pockets with non-uniform characteristics - specifically, edge pockets are made with different dimensions than interior pockets. The stretching device applies different forces to different locations, creating locally optimized pocket geometries that match the specific requirements of edge versus interior spring positions, thereby preventing differential stretching.
4Reliability
If foam encasements are constructed separately for each pocketed spring assembly size, then edge support is provided, but manufacturing cost and labor increase
Solution Approach 1:
The patent merges the edge support function with the pocketed spring assembly manufacturing process itself. The stretching device and pocket-forming process create integrated edge support structures as part of the main assembly, eliminating the need for separate foam encasement construction and assembly steps, thereby improving manufacturing efficiency.
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 results in a pocketed spring assembly with a smooth upper surface, reduced manufacturing costs, and enhanced durability by eliminating the need for additional edge support, while maintaining uniform height and varying firmness zones.
Implementation Method 1
By using such welding techniques, these fabrics have been advantageously used to create strings of individually pocketed coil springs wherein transverse and longitudinal welds, instead of stitching, are used to form the pockets encapsulating the springs.
Implementation Method 2
By using such welding techniques, these fabrics have been advantageously used to create strings of individually pocketed coil springs wherein transverse and longitudinal welds, instead of stitching, are used to form the pockets encapsulating the springs.
Data Source
Figure 1
Figure 1A
Figure 1B
AI summary
A pocketed spring assembly (12) for a bedding or seating product comprises a plurality of parallel strings (26a, 26b) of springs, each of the strings being joined to at least one adjacent string, each of the strings comprising a plurality of interconnected pockets (32, 58, 60), each of the pockets containing at least one spring encased in fabric, the fabric being joined to itself along a longitudinal seam and having first and second opposed plies of fabric on opposite sides of the springs, the fabric of the first and second plies being joined by transverse seams. At least some of the strings contain pockets (32, 58, 60) of different sizes (Hp, Hpp) without springs therein due to the location of the longitudinal seams of the pockets, first springs being inside small pockets (32, 58) and second springs being inside large pockets (60), thereby stretching the fabric of the small pockets (32, 58) to create a string having a generally uniform height (H) and pocketed springs of different firmness.