Drive Assembly with Dual Cranksets for Compact Elliptical Motion
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Solution Overview
Problem
Existing aerobic exercise devices, such as elliptical machines, often cause discomfort and injury due to sustained saddle pressure, knee stress, and non-natural posture, while lacking the fluid, weight-bearing aspects of running and the efficiency of cycling.
Innovation Solution
A drive assembly for human-powered machines that incorporates a front and rear crankset with mechanically coupled foot platforms, creating a teardrop-like motion, allowing for efficient energy transfer and reducing the size and weight of the device, with foot platforms that rotate and slide to mimic the natural running motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional elliptical mechanisms are used, then low-impact exercise is provided, but the device becomes large and heavy with long foot links and guides
Solution Approach 1:
The patent divides the traditional single crank-elliptical guide mechanism into two separate cranksets (first and second cranksets) with different crank arm lengths. This segmentation allows each crankset to have optimized, shorter crank arms while collectively producing the desired elliptical foot path, eliminating the need for long foot links and reducing overall device size and weight.
Solution Approach 2:
The patent nests the two cranksets within a compact arrangement where the first crankset and second crankset share common structural elements and are positioned close together. The foot platforms connect the two cranksets in a nested configuration, allowing the entire drive mechanism to occupy a smaller space while maintaining the elliptical motion path.
2Shape
If long foot links are used in elliptical systems, then the elliptical motion path is achieved, but the device size increases and becomes cumbersome
Solution Approach 1:
The patent segments the foot link function across two separate cranksets with shorter individual crank arms. The first crankset produces part of the elliptical motion while the second crankset produces the complementary part, eliminating the need for a single long foot link and achieving the same elliptical path with shorter components.
Solution Approach 2:
The patent introduces a second crankset operating in a different spatial dimension or plane relative to the first crankset. By coordinating the motion of both cranksets through the foot platforms, the system achieves the elliptical motion path through a combination of motions rather than requiring a single long linear foot link.
3Shape
If traditional elliptical guides are used, then the elliptical stepping motion is provided, but the guides protrude forward beyond the motion of the feet
Solution Approach 1:
The patent eliminates the traditional elliptical guide structure by segmenting the motion generation function into two cranksets. The foot platforms themselves define the motion path through their connection to both cranksets, removing the need for protruding guides and allowing the mechanism to be more compact.
4Weight of stationary object
If short crank arms are used, then device size is reduced, but the ability to provide natural running-like motion is compromised
Solution Approach 1:
The patent uses two different crank arm lengths (shorter first crank arms and longer second crank arms) to segment the motion generation. This allows the system to produce a teardrop-shaped foot path that mimics natural running motion while keeping individual crank arms shorter than a single long crank would require, optimizing both compactness and biomechanical efficiency.
Data Source
AI summary
A drive assembly for a human-powered machine may include a front crankset spaced from a rear crankset, each rotatably coupled to a frame. Crank arms of the rear crankset are longer than crank arms of the front crankset. A left foot platform and a right foot platform each have a rear portion rotatably coupled to a distal end portion of the corresponding rear crank arm, and a front portion in sliding and rotating engagement with a distal end portion of the corresponding front crank arm. The front crankset and the rear crankset may be mechanically coupled to each other, such that the two cranksets turn together at the same rotational speed in terms of RPM. The two cranksets may also be operatively connected to the hub of a wheel.