Helical Rotary Actuator Torque Density and Shaft Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Standard helical rotary actuators face limitations in torque output due to reduced working area caused by a stepped shaft diameter, and the splined output shafts are unstable and prone to wobble, leading to wear.
Innovation Solution
The design includes a housing with a shaft having the same diameter for both the piston sleeve and output portions, featuring a collar and support ring to create a larger working area and stabilize the output shaft, allowing for increased torque output without increasing the actuator size and providing enhanced stability through a secure connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the shaft diameter is stepped to create a shoulder for bearing support, then the bearing has a support surface, but the working area of the actuator is reduced
Solution Approach 1:
The shaft is divided into two distinct sections: a first section with a larger diameter that provides the bearing support surface, and a second section with a smaller diameter that serves as the output shaft. This segmentation allows each part to fulfill its specific function optimally without compromising the other.
Solution Approach 2:
The shaft exhibits different diameters at different locations to satisfy local functional requirements. The first section has a larger diameter specifically where bearing support is needed, while the second section has a smaller diameter for output purposes, creating local quality variations that resolve the contradiction between support stability and working area.
2Ease of manufacture
If the splines are cut with tool clearance, then the splining can be manufactured, but the hub is not fully supported causing wobble and wear
Solution Approach 1:
A collar is introduced as an intermediary component that fits over the first section of the shaft. This collar provides the necessary support surface for the hub while allowing the splines to be manufactured with appropriate clearance. The collar acts as a mediator between the manufacturing requirements and the stability requirements.
Solution Approach 2:
The support function is moved from the shaft surface to a separate collar component, adding a dimensional layer to the solution. This allows the splines to be cut with clearance on the shaft while the collar provides the full support surface needed for hub stability.
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 configuration enhances torque density and stability, enabling higher torque output from a compact actuator size and preventing wear by ensuring the output shaft is fully supported and secure.
Implementation Method 1
The helical-spline actuator has a long, slender configuration and uses a sliding helical splined gear operating concept to convert linear piston motion into shaft rotation.
Implementation Method 2
When hydraulic pressure is applied to the port to the left of the piston, three events occur simultaneously. The piston sleeve is displaced axially, moving to the right; it rotates clockwise (as viewed from the output shaft) as the gearing on its outside diameter and the housing's ring gear forces its rotation
Data Source
AI summary
A fluid-powered, helical rotary actuary is provided. The actuary includes a housing, a shaft with output ends positioned in the housing, and a piston sleeve surrounding the shaft and also positioned within the housing. The shaft includes a groove for receiving a collar. The collar creates a false shoulder such that the shaft is able to have the same diameter along the length of the shaft, thus allowing for a larger working area and more torque output density. The actuary also includes a support ring positioned on the shaft near the splined portion of the output end. The support ring is used to stabilize the attachment of an external member, and also to protect the shaft from damage caused by the splined receiving portion of the external member, or hub.