Gas Valve Stem Bushing for Stable Control Knob Positioning

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Solution Overview

Problem

Gas appliance control knobs experience undesirable wobble due to the length of the stem and angular play in the gas valve and stem assembly, leading to a loose and imprecise operation compared to other types of control knobs.

Innovation Solution

A control knob assembly that includes a valve restraint, such as a bushing, fixed relative to the frame, which limits lateral movement of the valve stem and control knob, reducing wobble by minimizing clearance between the valve restraint and the valve stem.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a long stem is used to connect the control knob to the valve body, then the control knob can be positioned at a convenient distance from the valve body, but lateral wobble and play in the control knob increases

Engineering Contradiction:

Improvecontrol knob positioningVSAvoidcontrol knob stability

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

A bushing is introduced as an intermediary component between the control knob and valve stem. The bushing has a inner diameter that receives the valve stem and an outer diameter that fits within the control knob, creating a mediator structure that reduces lateral play while maintaining the operational distance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution addresses the lateral wobble problem by adding structural support in the radial dimension through the bushing, while maintaining the axial dimension (length) of the stem for proper positioning. This dimensional approach allows the long stem to be retained for operational convenience while the bushing provides lateral stability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Stability of the object's composition

If clearance between the valve restraint and valve stem is reduced to minimize wobble, then lateral movement is limited, but axial travel and rotation may be restrained

Engineering Contradiction:

Improvelateral movement controlVSAvoidaxial travel and rotation freedom

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The bushing is designed with different dimensional clearances for different directions of movement. The radial clearance between the bushing's inner diameter and the valve stem is minimized to reduce lateral wobble, while the axial clearance and rotational clearance are maintained to allow free axial travel and rotation of the valve stem.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of trying to make the valve stem itself more rigid or shorter, the invention inverts the approach by adding a separate bushing structure that selectively constrains lateral movement while leaving axial and rotational movements unrestricted. This inverted thinking solves the problem by addressing lateral play independently from the stem design.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS8662102B2Apparatus for reducing knob wobble

Publication Date: 2014.03.04 HAIER US APPLIANCE SOLUTIONS INC

AI summary

A gas appliance including a frame and a control knob assembly connected to the frame, the control knob assembly including a gas valve with a valve stem, a control knob attached to the valve stem, and a valve restraint. The valve restraint is substantially fixed relative to the frame and longitudinally disposed substantially between the gas valve and control knob, and is configured to limit lateral movement of the valve stem.