Sliding Pin-Yoke Bushing Mechanism for Lower-Force Shaft Rotation
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Solution Overview
Problem
Traditional scotch yoke mechanisms require tight machine tolerances and are prone to deformation due to high contact forces, making them difficult to assemble and maintain, especially in dual slot configurations where pins need to be aligned with tightly machined slots.
Innovation Solution
A linear actuation system where a pin pivotably connected to an output rod of a linear actuator slides into and out of a bushing in a rotatable output shaft, allowing for rotation while the bushing serves as both a pivot point and a structure for the pin, reducing contact forces and improving assembly by using a ball nut and screw thread configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional scotch yoke mechanism is used with a pin sliding along a tightly machined slot, then rotational motion can be achieved, but tight machine tolerances are required and high contact forces cause deformation of the pin or slot
Solution Approach 1:
The patent introduces a bushing as an intermediary component between the pin and the output shaft. The pin slides within the bushing rather than directly against the output shaft slot, distributing contact forces across a larger area and reducing deformation. The bushing absorbs wear and deformation, protecting the precision-machined output shaft from direct contact stresses.
Solution Approach 2:
The patent changes the geometric parameters of the contact interface by transitioning from a pin sliding along a slot to a pin sliding within a bushing. This modifies the contact area and force distribution, allowing for larger tolerances while maintaining reliability. The bushing's internal geometry is designed to accommodate variations in pin position and reduce stress concentrations.
2Reliability
If a traditional scotch yoke mechanism is used with pins aligned in tightly machined slots, then rotational motion is achieved, but assembly becomes difficult
Solution Approach 1:
The bushing serves as a mediator that simplifies assembly by providing a forgiving interface. The pin can be inserted into the bushing with greater tolerance than required for direct insertion into the output shaft slot. The bushing's larger internal dimensions and flexible material properties allow for easier alignment and insertion during assembly, while still maintaining the required rotational functionality.
Solution Approach 2:
The patent segments the contact interface into two separate components: the bushing and the output shaft. This segmentation allows the bushing to be pre-assembled with the pin, creating a sub-assembly that can then be easily installed into the output shaft. The bushing acts as an intermediate layer that decouples the assembly requirements of the pin from the precision requirements of the output shaft.
3Force
If high contact forces are applied in a traditional scotch yoke, then rotational motion is driven effectively, but deformation of the pin or slot occurs
Solution Approach 1:
The bushing acts as a force-distributing intermediary between the pin and the output shaft. It receives the high contact forces from the pin and distributes them across a larger area of the output shaft, preventing stress concentrations that would cause deformation. The bushing material is selected to withstand these forces while protecting the more brittle or precisely machined output shaft from direct high-stress contact.
Solution Approach 2:
The patent employs composite material construction where the bushing is made from materials with high compressive strength and wear resistance, such as bronze or polymer composites. These materials are specifically chosen to withstand high contact forces without deforming, while the output shaft can be made from different materials optimized for rotational strength. The composite structure of pin-bushing-output shaft creates a system where each component is optimized for its specific stress conditions.
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 solution reduces the risk of deformation, simplifies assembly, and allows for higher stress load absorption, such as up to 20,000 g-force, while providing a more compact design with increased torque output as the output shaft rotates.
Implementation Method 1
a pin pivotably connected to an output rod of a linear actuator to pivot about the output rod as the linear actuator moves the output rod. The pin is further configured to slide into and out of a bushing in an output shaft as the pin pivots to rotate the output shaft.
Data Source
AI summary
A linear actuation system includes a pin pivotably coupled to an output rod of a linear motion actuator and a rotatable output shaft that includes a bushing therein. The pin can be configured to slide in and out of the bushing in response to movement of the linear motion actuator. The linear motion actuator and the output shaft can be arranged such that travel of the pin in the bushing causes rotation of the output shaft.