Elastic Carburetor Coupling for Tolerance Compensation

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Solution Overview

Problem

Existing carburetors require additional space and complexity for axial displacement or tilting of coupling elements to release locking, which complicates the operating sequence and secure locking of throttle and choke elements, especially under manufacturing tolerances.

Innovation Solution

A carburetor design featuring elastic and dimensionally stable coupling elements, where the elastic coupling element is hook-shaped and made of plastic (POM), and the dimensionally stable element is connected to the throttle shaft, ensuring precise locking positions without additional components. The coupling device allows limited mobility to compensate for manufacturing tolerances, ensuring secure closure and easy release of the choke element.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If additional components are added to ensure secure locking and compensate for manufacturing tolerances, then locking reliability is improved, but device complexity increases

Engineering Contradiction:
Improvelocking reliabilityVSAvoidstructure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the material parameter of the coupling element from rigid to elastic, allowing it to deform under manufacturing tolerances while maintaining secure locking. The elastic deformation capability compensates for tolerance variations without requiring additional adjusting components, thus improving reliability while keeping the structure simple.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The coupling element is segmented into a hook-shaped section with specific elastic properties and a blocking contour section. This segmentation allows different parts of the same component to fulfill different functions: the hook-shaped section provides elastic deformation for tolerance compensation, while the blocking contour ensures secure locking, eliminating the need for separate components.

Inventive Principle:
Principle #1Segmentation

2Ease of operation

If axial displacement or tilting movement of coupling elements is allowed to release locking, then ease of operation is improved, but installation space requirement increases

Engineering Contradiction:
Improvelocking release easeVSAvoidinstallation space
Core Design Contradiction:
Ease of operationVSArea of stationary object

Solution Approach 1:

Instead of allowing axial displacement or tilting movement to release locking as in conventional designs, this patent inverts the approach by using elastic deformation in the planar direction. The coupling element deforms elastically when the choke shaft is rotated, allowing locking release without requiring additional spatial movement, thus maintaining ease of operation while reducing installation space.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the deformation mode from axial displacement/tilting to elastic deformation in the planar direction. This parameter change allows the coupling element to accommodate rotational movement through elastic deformation rather than requiring additional space for axial or angular displacement, resolving the contradiction between ease of operation and space requirement.

Inventive Principle:
Principle #35Parameter changes

3Ease of operation

If the choke element can be easily released without acceleration, then ease of operation is improved, but unintended setting by operator becomes more likely

Engineering Contradiction:
Improvechoke release easeVSAvoidoperating sequence control
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The blocking contour is designed to preemptively prevent unintended choke engagement by requiring a specific sequence: the throttle element must be opened first to create sufficient clearance. This preliminary anti-action ensures that the choke can only be engaged after the throttle is opened, preventing accidental locking while maintaining easy release capability through elastic deformation.

Inventive Principle:
Principle #9Preliminary anti-action

Solution Approach 2:

The design requires the preliminary action of opening the throttle element before the choke element can be engaged. This preliminary action creates the necessary spatial clearance for the coupling elements to interact properly, ensuring that choke engagement cannot occur accidentally and must follow the correct operating sequence, while still allowing easy release through elastic deformation.

Inventive Principle:
Principle #10Preliminary action

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 simplifies the structure, reduces space requirements, and ensures a secure and precise operating sequence by allowing the choke element to be securely closed and easily released, even with manufacturing tolerances, without additional securing elements.

Implementation Method 1

at least one of the two coupling elements is at least partially elastic and deforms elastically when the choke shaft is rotated in the opening direction

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

The coupling element advantageously has a hook-shaped section which is elastic. Due to the hook-shaped design, a high level of elasticity is achieved. The hook-shaped section also forms a favorable contour for latching the two coupling elements.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP2441945B1Carburettor
Publication Date: 2014.08.27 ANDREAS STIHL AG & CO KG
  • EP2441945B1 patent drawingFigure 1~4
  • EP2441945B1 patent drawingFigure 5~9
  • EP2441945B1 patent drawingFigure 10~14

AI summary

The carburetor has a rotary mounted throttle element with a throttle shaft (20) and a rotary mounted choke element with a choke shaft (18), where coupling elements define a start position of throttle element and choke element in a latching position. One of the two coupling elements is formed in partially elastic manner, and the elastic coupling element is elastically deformed during rotation of the choke shaft from the latching position in an opening direction.