Digital Micrometer Rotor Bushing Alignment Mechanism
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Solution Overview
Problem
Digital displacement measuring instruments face rotation transfer errors due to changes in the depth position of the engaging key relative to the key groove, which complicates assembly and can prevent smooth spindle movement.
Innovation Solution
A digital displacement measuring instrument with a rotor bushing restrictor and attitude retainer that keeps the rotor bushing orthogonal to the spindle axis, preventing inclination and maintaining a constant gap between the rotor and stator, thereby reducing rotation transfer errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a plate spring is used to press the engaging key into the key groove to prevent rotation transfer errors, then the rotation transfer precision is improved, but the device complexity increases and assembly becomes complicated
Solution Approach 1:
The patent removes the plate spring pressurization mechanism from the system. Instead of using a spring to continuously press the engaging key into the key groove, the design relies on the inherent fit between the key and groove without additional pressurization components, thereby reducing device complexity while maintaining rotation transfer precision.
Solution Approach 2:
The engaging key and key groove are designed to self-align and maintain proper engagement through their geometric configuration alone. The key groove width is controlled to be within a specific range that allows the key to fit tightly without requiring external pressurization, enabling the system to maintain precision through its own structural design rather than additional active components.
2Manufacturing precision
If a plate spring is used to press the engaging key into the key groove, then the rotation transfer precision is improved, but the number of parts increases
Solution Approach 1:
The patent eliminates the plate spring component entirely from the assembly. By controlling the key groove width to be within a specific range (0.95-1.05 times the key width), the design achieves proper engagement without requiring the additional pressurization part, thereby reducing the total number of components.
3Manufacturing precision
If too much biasing force is applied by the plate spring, then the engaging key is tightly fitted with the key groove, but the spindle is prevented from smooth advancement and retraction
Solution Approach 1:
The patent changes the critical parameter from biasing force to groove width. By controlling the key groove width to be within a specific range (0.95-1.05 times the key width), the design achieves tight engagement without requiring excessive force, thereby allowing smooth spindle movement while maintaining engagement precision.
4Manufacturing precision
If the depth position of the engaging key is precisely adjusted to contact the key groove, then rotation transfer errors are reduced, but the assembly difficulty increases
Solution Approach 1:
The patent shifts the precision requirement from depth position adjustment to groove width control. By specifying the groove width within a tight range (0.95-1.05 times the key width), the design achieves proper engagement through a parameter that is easier to control during manufacturing, reducing assembly difficulty while maintaining rotation transfer precision.
Data Source
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AI summary
A digital micrometer (100) comprising a body (10), a spindle (2) slidably provided on the body and an encoder (40) that detects the displacement of the spindle. The encoder comprises a rotor (41) that rotates with the spindle and a stator (42) that is fixed on the body and spaced apart from the rotor by a predetermined gap. The rotor is supported by a rotor bushing (44) comprising an engaging key (43) cooperating with a groove (23) axially provided on the spindle. A rotor bushing restrictor (50) with a fixing member (51) connected to the body prevents the rotor bushing from moving away from the stator along the axial direction of the spindle. A rotor bushing attitude retainer (52) is placed between the rotor bushing and the fixing member. Two first abutment portions (522) of the rotor bushing attitude retainer contact the rotor bushing and two second abutment portions (523) of the rotor bushing attitude retainer contact the fixing element in order to keep the rotor bushing in a proper position without being inclined against the spindle. The two abutment portions of each pair are symmetrically placed to each other with respect to the axis of the spindle and the lines connecting the two abutment portions of each pair are orthogonal to each other.