Segmented Pulley Assembly With Transition Segments for Load Shifting
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Solution Overview
Problem
Clutchless multi-ratio transmissions face challenges in functioning effectively at high speeds or under significant loads due to issues like ratcheting, slippage, and tensioning, which limit their commercial viability and reliability.
Innovation Solution
A segmented pulley transmission system with transition segments and an actuator system that allows for smooth shifting between pulleys using electromotive force, enabling independent movement of pulley segments and transition segments between engaged and disengaged regions, thereby reducing intermittent forces and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If clutchless multi-ratio transmission is used to change ratio under load, then transmission can operate without clutch, but mechanical problems such as ratcheting, slippage, and tensioning occur that limit reliability and efficiency
Solution Approach 1:
The pulley system is divided into multiple independently controllable pulley segments that can be selectively engaged or disengaged from the endless member. Each segment can be independently positioned to engage or disengage from the endless member, allowing smooth ratio changes without clutching mechanisms, thereby maintaining reliability while enabling clutchless operation.
2Productivity
If pulley segments are engaged under load, then transmission can change ratio under load, but ratcheting and slippage occur that decrease efficiency
Solution Approach 1:
Pulley segments are moved into or out of engagement with the endless member in advance, during the non-contact zone, before the engaged zone is reached. This preliminary positioning ensures that segments are already in place when load is applied, preventing ratcheting and slippage by eliminating the delay between engagement command and actual engagement, thus maintaining continuous operation without energy loss.
3Adaptability or versatility
If multiple pulley segments are used for ratio changes, then multi-ratio transmission is achieved, but device complexity increases
Solution Approach 1:
Multiple pulley segments are combined into a unified stack that moves together as a single assembly. The segments share common support structures, actuation mechanisms, and mounting features, allowing multi-ratio capability to be achieved while reducing overall system complexity through integration and standardization of components.
4Adaptability or versatility
If key pulley segment teeth are trimmed or elongated to enable engagement, then segment interchangeability is improved, but manufacturing precision requirements increase
Solution Approach 1:
Different tooth profile characteristics are applied to different segments within the pulley assembly. Key segments have modified tooth profiles (trimmed or elongated) while other segments have standard profiles. This local differentiation enables segment interchangeability and smooth engagement while maintaining manufacturing precision by only modifying specific segments rather than requiring all segments to meet stringent precision requirements.
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 system enhances the reliability and efficiency of the transmission by allowing smooth transitions and reducing wear, enabling effective operation under load conditions.
Implementation Method 1
A segmented pulley transmission system with transition segments and an actuator system that allows for smooth shifting between pulleys using electromotive force
Data Source
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AI summary
A pulley assembly (120) for engaging an endless member (118) includes a first pulley (124), a second pulley (126) and at least one transition segment set (128, 130) comprising one or more transition segments (152, 162a, 162b) that are independently movable between an engaged region and a disengaged region to transition the endless member (118) between the first pulley (124) and the second pulley (126). An actuator system (122) includes a support structure (220), an actuator subassembly (222, 226) secured to the support structure (220) and a stator (224, 228). The actuator subassembly (222, 226) includes a follower (250) and a sled (248), which is movable in a circumferential direction between an advanced position and a retreated position, in response to an electromotive force generated on the sled (248) by the stator (224, 228). The follower engages the cam surface (262) of the sled (248) to move in an axial direction between an extended position and a retracted position as the sled (248) moves between the advanced and retreated positions.