Rotary Encoder Flexure Mounting for Precise Radial Alignment
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Solution Overview
Problem
Existing methods for mounting rotary encoders, particularly for thin and compact designs, fail to achieve precise self-centering and radial alignment, leading to potential deformation and impaired metrological performance.
Innovation Solution
A method involving push/force fitting a rotary scale member with flexures that form a friction fit, followed by fine-tuning the radial location using a radial adjustment device to ensure precise alignment without significant deformation of the scale features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the rotary scale member is made thin and compact, then the encoder size is reduced, but the self-centering ability and alignment precision deteriorate
Solution Approach 1:
The mounting structure is divided into a rigid body portion and separate flexible mounting elements (flexures), allowing the thin scale body to be segmented from its mounting mechanism. This enables the scale member to maintain its compact size while the flexures provide the necessary compliance for self-centering.
Solution Approach 2:
The flexure elements change their mechanical parameters (flexibility, compliance) to enable self-centering. By designing flexures with specific geometric parameters and material properties, the system achieves automatic radial location and alignment without requiring the thin scale body itself to have self-centering capability.
2Manufacturing precision
If force fitting is used to mount the rotary scale member, then the initial alignment is improved, but deformation of the scale features occurs
Solution Approach 1:
The flexure elements act as flexible mounting structures that can elastically deform during assembly to accommodate force fitting, while the rigid scale body with its precision features remains protected from deformation. The flexures absorb the mechanical stress that would otherwise be transmitted to the thin scale features.
Solution Approach 2:
The flexure elements serve as intermediary components between the mounting structure and the rotary scale body. They mediate the force transmission during assembly, allowing force fitting to achieve good initial alignment while preventing excessive forces from deforming the delicate scale features on the thin body.
3Manufacturing precision
If the radial location is adjusted after assembly, then the alignment precision is improved, but the device complexity increases
Solution Approach 1:
The flexure elements provide self-service by automatically enabling radial adjustment through their inherent flexibility. When radial adjustment devices apply forces to the body, the flexures accommodate these adjustments without requiring complex disassembly or specialized tools, allowing precision alignment to be achieved and maintained.
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
Achieves consistent and reliable self-centering with minimal deformation, enhancing encoder performance by allowing precise radial adjustment of the rotary scale member.
Implementation Method 1
whereby the flexure is displaced by the cylindrical part and thereby urges the rotary scale member (via a radial reaction force) into engagement with the part so as to form a friction fit with the part
Data Source
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AI summary
A method of mounting a rotary scale member on a part (e.g. of an articulated joint), the rotary scale member comprising a body on which a series of position features defining a scale is provided, and at least one mounting flexure configured to engage the part, the method comprising: force-fitting the rotary scale member and the part together, whereby the at least one flexure is displaced by the part and thereby urged via a radial reaction force into engagement with the part so as to form a friction fit with the part such that the body of the rotary scale member self- locates at an initial default radial location with respect to the part; and tweaking the radial location of the body relative to the part away from its initial default radial location to a new radial location.