Pawl Carrier Stop Module Eliminates Frictional Drag
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Solution Overview
Problem
Rotary drive systems face inefficiencies due to viscous drag and accuracy loss in travel limits caused by brake plates, particularly at low temperatures and over time, leading to unwanted power losses and over-travel.
Innovation Solution
A stop module with a pawl carrier and pawl members that axially travel and pivot to engage stop elements, replacing brake plates and providing a mechanical stop without frictional losses, allowing for precise control of rotational limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brake plates are used to limit rotation, then the stop module can arrest rotational motion, but viscous drag and power losses increase, particularly at low temperatures
Solution Approach 1:
The patent removes the brake plates entirely from the stop module, replacing the friction-based braking mechanism with a pawl-and-stop element mechanical locking mechanism. This extraction of the harmful brake plate component eliminates the source of viscous drag and energy loss while maintaining the ability to arrest rotational motion through the pawl carrier engaging with stop elements.
Solution Approach 2:
The patent replaces the friction-based mechanical braking system (brake plates) with a positive mechanical locking system (pawl members engaging stop elements). This substitution transitions from a friction-dependent mechanism that suffers from viscous drag to a geometric interlocking mechanism that provides reliable motion arrest without continuous energy dissipation.
2Reliability
If brake plates are used to limit rotation, then the stop module can control travel limits, but wear over time alters stroke length and causes over-travel
Solution Approach 1:
The patent extracts the wear-prone brake plate components from the system and replaces them with a wear-resistant pawl-and-stop element mechanism. The pawl members pivot on pins and engage with fixed stop elements through geometric interlocking, eliminating the sliding friction and wear that occurred with brake plates, thereby maintaining precise travel limits over extended operational periods.
Solution Approach 2:
Instead of using friction to create a stopping force that degrades over time, the patent inverts the approach by using geometric interlocking where the pawl member's physical shape and the stop element's configuration create a deterministic mechanical stop. This inversion from friction-based to geometry-based stopping eliminates wear-induced dimensional changes.
3Power
If brake plates are used, then rotational motion can be arrested, but the system efficiency decreases due to frictional losses
Solution Approach 1:
The patent substitutes the friction-based brake plate system with a positive mechanical locking system using pawl members that engage stop elements. This replacement eliminates continuous frictional losses during operation while maintaining the ability to arrest rotation when needed, thereby preserving overall system efficiency and productivity.
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 solution significantly reduces viscous drag, maintains accuracy by eliminating wear-induced inaccuracies, and enhances overall efficiency by using a pawl lockout mechanism instead of brake plates, ensuring precise rotational control.
Implementation Method 1
the pawl carrier includes a screw portion mated with the nut such that rotation of the pawl carrier with the shaft causes the pawl carrier to travel axially along the shaft
Implementation Method 2
the pawl member is interfered with by the stop element as the pawl carrier rotates about the rotational axis of the shaft so as to stop rotation of the input shaft and pawl carrier
Data Source
AI summary
A stop module halts rotation of a shaft of a rotational drive system when an axial stroke limit is reached without the use of frictional brake plates. The module has a fixed nut and a pawl carrier coaxially mounted on the shaft for axial travel along the shaft and rotation with the shaft. The pawl carrier includes a screw portion mated with the nut such that rotation of the pawl carrier with the shaft causes the pawl carrier to travel axially along the shaft. A pawl member is pivotally coupled to the pawl carrier, and a stop element is fixed at an axial limit location. The pawl carrier is axially displaceable from a non-limit position wherein the pawl member is clear of the stop element during rotation to a limit position wherein the pawl member is interfered with by the stop element during rotation to stop rotation of the shaft.