Tap-Changer Ring-Nut Flat Surface Design
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Solution Overview
Problem
High voltage tap-changers for oil-filled transformers require excessive effort to rotate and are prone to stopping at intermediate positions, posing safety risks and increasing costs due to the design of star-shaped gears and springs.
Innovation Solution
A tap-changer design featuring a ring-nut with flat surfaces and a core moved by elastic means, allowing for discrete and stable rotation with reduced torque requirements, preventing intermediate positions and ensuring automatic positioning at contact points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a star-shaped gear with rounded convex fittings and a ball-spring mechanism is used to achieve discrete movement, then the slides are positioned discretely with reduced implementation costs, but the rotation of the knob requires considerable effort and torque
Solution Approach 1:
The patent replaces the rounded convex fittings with rounded concave fittings in the star-shaped gear, and corresponds them with rounded convex projections on the ball. This inversion of curvature shapes reduces the contact area and mechanical interference during rotation, thereby reducing the torque required to rotate the knob while maintaining discrete positioning capability
Solution Approach 2:
The patent modifies the geometric parameters of the star-shaped gear fittings and ball projection, specifically changing from convex-convex contact to concave-convex contact. This parameter change optimizes the mechanical interaction, reducing friction and resistance during rotation while preserving the discrete positioning function
2Ease of manufacture
If a star-shaped gear with rounded convex fittings is used, then implementation costs are reduced, but the mechanism may stop at intermediate positions between contact points
Solution Approach 1:
The patent incorporates a detent mechanism where the rounded convex projection on the ball fits into the rounded concave fittings of the star-shaped gear. This creates a mechanical feedback system that provides tactile and positional confirmation, ensuring the mechanism stops precisely at intended contact positions and preventing intermediate positioning through self-locking at each discrete position
Solution Approach 2:
The rounded concave-convex geometry creates a self-centering effect during rotation, where the curved surfaces guide the ball into proper alignment with each fitting. This geometric design ensures accurate positioning at discrete points while maintaining manufacturing simplicity
3Ease of manufacture
If rounded convex fittings are used in the star-shaped gear, then manufacturing is simplified, but friction and decompression force cause the mechanism to potentially stop at unstable intermediate positions
Solution Approach 1:
The patent inverts the curvature configuration from convex-convex to concave-convex contact. The rounded concave fittings in the star-shaped gear配合with rounded convex projections on the ball create a stable nesting relationship that eliminates intermediate stable positions, ensuring the mechanism only rests at intended discrete positions while maintaining geometric simplicity for manufacturing
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
The design reduces the effort needed for tap-changing, prevents unwanted intermediate positions, and ensures automatic alignment at contact points, while maintaining cost competitiveness with existing solutions.
Implementation Method 1
a ball pushed towards the ring-nut thereof by a spring
Data Source
Figure 1~2
Figure 3~4
AI summary
A tap-changer for oil-filled electric transformers comprising: a guide element (2) provided with a plurality of electric contacts (3) and a slide (4) slidable along the guide element (2) to change the electric connection between two or more of the electric contacts (3); moving means (5) of the slide (4) comprising a driving group (6) having at least one rotatable portion (8) and defining a plurality of discrete positions of the slide (4) with respect to the guide element (2), each one corresponding to a different electric connection between the electric contacts (3). The moving means (5) comprising: a ring-nut (20) susceptible to be put in rotation by the driving group (6) and whose side surface has two or more flat surfaces (21); a core (23) counter-moved with the side surface of the ring-nut (20), the portion (24) of the core (23) faced towards the ring-nut (20) having a flat surface (25) susceptible to be arranged one-to-one with the flat surfaces (21) of the side surface of the ring-nut (20) when the slide (4) and the guide element (2) are placed in correspondence of one of the discrete positions.