Coil-in-coil spring with variable loading response and mattresses including the same
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Solution Overview
Problem
Conventional coil springs exhibit a linear response to compression, which does not provide adequate support for varying body loads, while foam mattresses offer non-linear support but have mechanical property degradation and higher production costs.
Innovation Solution
A coil-in-coil spring design featuring a continuous wire with a conical inner coil and cylindrical outer coil, where the inner coil's diameter and pitch progressively decrease, providing a variable loading response by engaging both coils at different compression stages, mimicking the non-linear support of foam mattresses without material degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional wire coil springs are used, then the mattress is inexpensive to manufacture, but the spring provides a firm and rigid mattress surface with linear response that does not provide adequate support for varying body loads
Solution Approach 1:
The spring is segmented into two distinct coils: an outer coil and an inner coil. Each coil has different geometric properties (different wire diameters, coil diameters, and pitch) that allow them to engage at different compression stages. This segmentation enables the spring to provide different levels of support resistance depending on the applied load, resolving the contradiction between manufacturing simplicity and adaptive support response.
Solution Approach 2:
The inner coil is nested within the outer coil, creating a coil-in-coil structure. This nesting arrangement allows both coils to occupy the same spatial envelope while maintaining independent mechanical functions. The inner coil engages first during compression, providing initial support, while the outer coil engages subsequently, providing additional support for heavier loads. This nested configuration achieves non-linear response characteristics similar to foam mattresses while maintaining the cost-effectiveness of metal spring manufacturing.
2Adaptability or versatility
If foam mattresses are used, then the mattress provides non-linear response with improved sleep comfort, but the mechanical properties of certain foam may degrade over time and production costs are higher
Solution Approach 1:
The patent replaces the foam material's mechanical compression characteristics with a metal spring mechanical system. Instead of relying on foam cell collapse and material deformation, the coil-in-coil spring uses elastic deformation of metal coils to produce non-linear force-displacement behavior. This substitution eliminates the mechanical property degradation issues inherent in foam materials while maintaining the desired non-linear support response that adapts to varying body loads.
3Adaptability or versatility
If foam mattresses are used, then the mattress provides non-linear response with improved sleep comfort, but the production costs are often more costly than metal spring mattresses
Solution Approach 1:
The patent copies the non-linear support response characteristic of foam mattresses by designing the outer and inner coils with specific geometric progressions. The wire diameter, coil diameter, and pitch are varied along the length of each coil to replicate the progressive compression behavior of foam. This allows the metal spring system to mimic foam's adaptive support properties while benefiting from the lower manufacturing costs and durability of metal spring production processes.
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 coil-in-coil spring design offers enhanced support by initially using the outer coil and then engaging the inner coil as compression increases, providing a variable and non-linear response similar to foam mattresses while maintaining durability and cost-effectiveness.
Implementation Method 1
the spring exhibits a linear compression rate. That is to say, it takes twice as much force to compress a typical spring two inches as it does to compress the same spring one inch. The linear response of springs is expressed by Hooke's law which states that the force (F) needed to extend or compress a spring by some distance (D) is proportional to that distance.
Data Source
AI summary
A coil-in-coil spring is provided that exhibits a variable loading response as the spring is compressed. The coil-in-coil spring comprises a continuous wire forming’ an inner coil having a substantially conical shape and an outer coil extending around the inner coil and having a substantially cylindrical shape. The inner coil includes a plurality of helical convolutions with diameters that progressively decrease as the plurality of helical convolutions extend from a lower end of the coil-in-coil spring to an upper end convolution of the inner coil. The inner coil also has an uncompressed height that is about 75% of the uncompressed height of the outer coil, A mattress is further provided and includes the coil-in-coil springs arranged in a matrix.