Pre-loaded Piezoelectric Stack Actuator with Adjustable Spring Plates
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Solution Overview
Problem
Current pre-loaded piezoelectric stack actuators require custom manufacturing of parts, such as tubes and spring washers, and are not adaptable for smaller designs or easy disassembly, leading to high costs and variable performance.
Innovation Solution
A pre-loaded piezoelectric stack actuator design featuring elongate spring plates with alternating slots and fingers on end caps, allowing for adjustable pre-loading without custom manufacturing, enabling the use of off-the-shelf components and easy assembly/disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If custom parts (tubes and spring washers) are manufactured to match desired stack length, then the actuator can achieve precise pre-loading, but manufacturing cost and complexity increase
Solution Approach 1:
The spring plate is designed with multiple slots that can accommodate different stack lengths, making a single component design universal for multiple applications. The slots allow the spring plate to be configured for different pre-loading requirements without requiring custom manufacturing for each specific length.
Solution Approach 2:
The spring plate incorporates slots that allow dynamic adjustment of the pre-loading force. By positioning the attachment points at different locations along the slots, the effective length and pre-loading characteristics can be varied to match different stack configurations.
2Force
If elongated undulated or wave springs are used for pre-loading, then pre-load force can be generated, but the design cannot be easily disassembled and adapted for smaller piezoelectric designs
Solution Approach 1:
The spring plate is segmented with multiple slots that divide the continuous structure into adjustable sections. This segmentation allows the same spring plate design to be configured for different stack sizes by selecting appropriate slot positions, enabling adaptation to both larger and smaller piezoelectric designs.
Solution Approach 2:
The design allows changing the effective parameters (length, pre-load force) by selecting different slot configurations rather than manufacturing different components. This parameter adjustment capability enables the same spring plate to work with various piezoelectric stack sizes.
3Force
If laser welded rigid tubes are used to enclose the piezoelectric stack, then pre-loading can be achieved, but the design is not adapted for smaller designs and cannot easily be disassembled
Solution Approach 1:
The spring plate is pre-loaded through the slots during assembly, creating the necessary pre-load force before the actuator enters service. This preliminary action allows the rigid tube enclosure to be replaced with a more easily disassembled spring plate mechanism that achieves the same pre-loading function.
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 design reduces manufacturing costs, allows for flexibility in actuator size, and improves performance by providing a consistent pre-load mechanism, enhancing stiffness and displacement capabilities.
Implementation Method 1
a first elongate pre-loaded spring plate on a side of the piezoelectric stack... and a second elongate pre-loaded spring plate on an opposite side of the piezoelectric stack
Implementation Method 2
Piezoelectric stack actuators are well known in the art... comprising a piezoelectric stack, a first electrode on a first side of the piezoelectric stack
Data Source
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AI summary
A pre-loaded piezoelectric stack actuator (10) comprising a stack (12) of piezoelectric material. Caps (24, 26) are coupled at opposed ends of the stack. Each of the caps includes projecting fingers (25A, 25B). Insulating plates (20) are stacked between the ends of the stack and the caps. A pair of pre-loaded spring plates (30, 32) are coupled to the stack. The spring plates define slots (34, 46). The fingers (25a, 25b) on the caps extend through respective ones of the slots (34, 36) at respective ends of the spring plates for coupling the spring plates to the stack. A method of pre-loading the piezoelectric stack actuator includes the step of mounting the stack, the caps, the insulating plates, and the spring plates in a pre-load tool that applies a pre-load tensile stretching force to the spring plates. The pre-load tensile force is subsequently released and the actuator is removed from the tool.