Rotary Force Transfer Mechanism for Human-Powered Machines
Solution Overview
Problem
Conventional human-powered machines, such as bicycles, inefficiently convert reciprocating motion into rotary motion due to limited muscle engagement during pedaling, as only a quarter of the pedaling cycle utilizes strong leg muscles, and are hindered by physical limitations in joint range of motion.
Innovation Solution
A rotary force transfer mechanism that includes a guide and a drive element, such as a rack gear, which moves along a defined path to alternately engage and disengage with a gear, allowing for tangential force transmission and optimizing the downstroke and upstroke motions to engage stronger muscle groups and accommodate varying user capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional crank mechanism is used to convert reciprocating motion to rotary motion, then the structure is simple, but only about 1/4 of the pedaling cycle utilizes strong leg muscles effectively
Solution Approach 1:
The pedaling cycle is segmented into distinct phases (downstroke, upstroke, transition periods) with selective engagement. The drive element engages with the rotary structure only during specific portions of the cycle when strong muscle engagement is possible, rather than requiring continuous engagement throughout the entire rotation.
Solution Approach 2:
The mechanism transitions from a static continuous engagement to a dynamic selective engagement system. The drive element can alternately engage and disengage from the rotary structure based on the phase of the pedaling cycle, allowing the system to adapt to the varying strength characteristics of leg muscles during different portions of the motion.
2Adaptability or versatility
If continuous engagement of the drive element with the rotary structure is maintained, then power transmission is continuous, but users with limited joint range of motion cannot operate the machine
Solution Approach 1:
The drive element engages and disengages periodically throughout the pedaling cycle rather than maintaining continuous engagement. This periodic action allows users with limited joint range of motion to operate the machine by engaging the drive only during portions of the cycle that are within their capability, while the rotary structure maintains momentum during disengagement periods.
3Power
If the drive element transmits force radially to the rotary structure, then the transmission is straightforward, but the force is not applied tangentially to maximize rotational efficiency
Solution Approach 1:
The engagement interface between the drive element and rotary structure is designed with specific local geometries (such as cam surfaces or inclined contact points) that convert the primarily vertical input force into a tangential force component at the point of contact with the rotary structure, maximizing rotational efficiency at the critical engagement locations.
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 mechanism enhances the efficiency of human-powered machines by increasing the proportion of the pedaling cycle that utilizes strong muscle engagement, improving ergonomics, and allowing operation by individuals with limited joint mobility.
Implementation Method 1
the rotary structure comprises a gear with a plurality of gear teeth formed about the outer circumferential surface of the gear; the drive element comprises a rack gear with a plurality of rack gear teeth formed along a length thereof, the plurality of rack gear teeth of the drive element being configured to engage with the plurality of gear teeth of the gear for transmitting the input force to the gear
Data Source
AI summary
A rotary force transfer mechanism includes an input (e.g., a pedal or handle) that receives a substantially linear input force (e.g., from a human operator), a rotary structure (e.g., a gear), and a drive element for selective coupling with the rotary structure to transmit the input force to the rotary structure to cause a corresponding rotary motion of the rotary structure. When transmitting the input force to the rotary structure, the drive element engages with an outer circumferential surface of the rotary structure such that the input force is transmitted to the rotary structure in a direction tangential to a position where the drive element is coupled to the rotary structure.