Rotary Coupling Teeth Structure for Thermal Expansion Mismatch
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Solution Overview
Problem
Couplings with different material expansion coefficients face issues with reliable torque transmission due to uneven expansion, leading to material damage or excessive play at varying temperatures, which compromises the rotational connection.
Innovation Solution
The coupling features retaining teeth on one component and longitudinal or transverse projections on the other, with the projections being harder than the teeth, allowing for deformation and preventing relative movement, especially when made of plastics like polyoxymethylene, which can expand radially without damaging the connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If connection partners with different expansion coefficients are used, then the coupling can accommodate thermal expansion differences, but the outside diameter of the pin expands excessively at unfavorable temperature ratios, destroying the part with the recess or creating excessive play
Solution Approach 1:
The patent changes the physical state and mechanical properties of the connection elements by using a plastics material for the retaining teeth that can undergo controlled deformation. The plastics material's ability to change shape under thermal stress allows the coupling to accommodate expansion differences while maintaining connection integrity, resolving the contradiction between adaptability and reliability.
Solution Approach 2:
The design incorporates a press-fit connection where the retaining teeth are inserted into recesses with intentional interference fit. This pre-compression creates a cushioning effect that absorbs thermal expansion forces before they can cause damage or excessive play, maintaining reliable connection despite temperature variations.
2Strength
If the pin material is harder than the recess material, then the pin resists wear and deformation, but the recess material is destroyed under unfavorable temperature ratios
Solution Approach 1:
The patent uses a plastics material for the retaining teeth that changes its mechanical properties with temperature. The plastics can deform elastically and plastically under thermal stress, preventing the hard pin material from causing damage to softer components while maintaining adequate wear resistance through the interference fit design.
Solution Approach 2:
The patent converts the potentially harmful effect of hard pin material against soft recess material into a beneficial press-fit connection. The intentional interference fit creates pre-compression that improves torque transmission and prevents relative movement, while the plastics material's deformation capability prevents damage under thermal expansion.
3Temperature
If the recess diameter expands significantly with heating, then the coupling accommodates thermal expansion, but the play between parts becomes so great that reliable movement transmission is not ensured
Solution Approach 1:
The press-fit connection with interfering dimensions creates pre-compression between the retaining teeth and recesses. This pre-compression acts as a cushioning mechanism that maintains contact pressure and prevents excessive play even when thermal expansion occurs, ensuring reliable movement transmission across temperature ranges.
Solution Approach 2:
The plastics material's ability to undergo elastic and plastic deformation allows the connection to accommodate thermal expansion dynamically. As temperature changes, the plastics teeth can deform to maintain optimal contact with the pin, preventing both excessive play and material damage.
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 ensures a stable, rotationally fixed connection by allowing for material deformation that prevents damage and maintains secure force transmission across temperature changes, ensuring reliable operation from -40° to 80° Celsius.
Implementation Method 1
the longitudinal projections and/or the transverse projections have a greater hardness than the retaining teeth. In accordance with the radial dimensional overlap with respect to the longitudinal central axis, upon mounting the softer material of the retaining teeth is deformed by the harder material
Implementation Method 2
a root diameter of the retaining teeth is smaller than a tip diameter of the longitudinal projections and/or of the transverse projections. In the event of the material being expanded significantly, by heating, the material then still has sufficient free space in order to deform radially, in particular expand
Data Source
AI summary
The invention relates to a device comprising a first component (11) and a second component (12). The first component (11) comprises a cylindrical outer surface (13), and the second component (12) comprises a cylindrical inner surface (17) which is arranged on the outer surface (13) coaxially with a longitudinal central axis (m). First connection surfaces of the first component interact with second connection surfaces of the second component in order to prevent a relative rotational movement of the components (11, 12). The invention is characterized in that one of the connection surfaces forms a remaining toothing (22), and the other connection surface forms mutually spaced longitudinal protrusions (18) which are distributed over the circumference and the tooth flanks of which extend parallel to the longitudinal central axis (m).