Rotatable Shaft Locking Plates for Breakaway Torque Control
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Solution Overview
Problem
Existing robotic grappling systems lack effective locking features that can prevent rotational movement of a second robotic part relative to a first robotic part, especially in dynamic environments, and conventional solutions have limited lifespan.
Innovation Solution
A device with a rotatable shaft featuring a stationary and rotary locking plate, a plunger, biasing element, and cross-pin slot, which selectively restricts or permits rotation based on applied force and torque, using radially disposed locking teeth and a biasing element to maintain engagement or disengagement, allowing for long-life operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional locking features (split beam clamping fingers or polymeric inserts) are used, then rotational movement can be prevented, but the lifespan of the locking feature is limited
Solution Approach 1:
The locking feature is divided into two separate locking plates (stationary and rotary) with distinct functions. The stationary locking plate provides structural support while the rotary locking plate rotates with the shaft. This segmentation allows each component to be optimized for its specific role, reducing wear on critical surfaces and extending overall system lifespan.
Solution Approach 2:
The locking mechanism transitions from a single-plane engagement to a multi-dimensional system. The locking teeth engage in both radial and axial directions, with the cross-pin slot providing axial movement capability. This dimensional approach distributes wear across multiple surfaces and movement planes, significantly extending the operational life of the locking feature.
2Reliability
If locking teeth are engaged to prevent rotation, then rotational restriction is achieved, but the device complexity increases
Solution Approach 1:
The locking and rotation control functions are merged into a single engagement mechanism. The locking teeth on both plates serve dual purposes: they prevent rotation when engaged and provide the rotational path when disengaged. The cross-pin slot integrates the plunger movement with the rotary locking plate displacement, eliminating the need for separate actuation mechanisms.
Solution Approach 2:
The locking mechanism is designed to be dynamically controllable. The cross-pin slot allows the rotary locking plate to move axially along the shaft, transitioning between locked and unlocked states. This dynamic capability is achieved through the biasing element and plunger system, which provide controlled movement without requiring complex actuators.
3Reliability
If a biasing element with pre-load is used to maintain engagement, then locking reliability is improved, but the force required to disengage increases
Solution Approach 1:
The disengagement force is distributed across multiple elements rather than concentrated on a single point. The cross-pin transfers the plunger force to the rotary locking plate, which then disengages the locking teeth progressively. This segmentation of the disengagement process reduces the peak force required while maintaining reliable locking engagement.
Solution Approach 2:
The cross-pin acts as an intermediary element between the plunger and the rotary locking plate. It translates the linear motion of the plunger into axial displacement of the rotary locking plate, providing mechanical advantage and reducing the force required to overcome the biasing element pre-load and disengage the locking teeth.
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 device provides reliable, long-life secondary or primary locking for robotic grapple applications, preventing rotation below a breakaway torque and allowing selective rotation when needed, reducing wear and increasing cycle durability.
Implementation Method 1
a biasing element disposed within and along the axis of rotation, abutting the second end of the plunger, the biasing element having an uncompressed state and a compressed state, the biasing element subjected to a pre-load
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A device and method for selectively restricting and for preventing rotation of a shaft are provided. The device includes a plunger disposed along an axis of rotation having first and second ends, a biasing element disposed along the axis abutting the second end, subjected to a pre-load, and a cross-pin slot, a stationary locking plate including first radially disposed locking teeth disposed at a first draft angle, a rotary locking plate including second radially disposed locking teeth disposed at a second draft angle, the radially disposed locking teeth configured to prevent rotation of the rotary locking plate when mutually engaged, a cross-pin disposed in the cross-pin slot and through the plunger perpendicular to the axis and received in the cross-pin hole. When sufficient force is applied to the first end, the second end compresses the biasing element, thereby permitting rotation. When torque applied is below breakaway torque, rotation is prevented.