Rotary Valve Stem Locking Structure for Pullout Prevention

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Solution Overview

Problem

Conventional rotary valves require special processing and additional components to prevent stem pullout, leading to increased size, complexity in assembly, and potential sealability issues due to gland tilting and insufficient seal surface pressure.

Innovation Solution

A rotary valve design featuring a diameter-reduced step surface on the stem, which locks with a packing retaining member to prevent pullout, ensuring compact size and easy assembly without additional components, while maintaining excellent sealability by uniformly pressing the packing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a stem hole is formed in the gland to allow the locking portion to rise, then stem pullout prevention is achieved, but the gland becomes long and the valve size increases

Engineering Contradiction:

Improvestem pullout preventionVSAvoidgland length and valve size

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The invention changes the pullout prevention mechanism from axial movement (stem rising through a long stem hole) to radial interference (locking portion with larger outer diameter than packing retaining member inner diameter). The locking portion engages the packing retaining member radially, eliminating the need for a long axial stem hole and reducing gland length.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Instead of allowing the locking portion to rise axially through a stem hole, the invention inverts the approach by having the locking portion engage radially with the packing retaining member. The locking portion's outer diameter is made larger than the packing retaining member's inner diameter, creating an interference fit that prevents pullout without requiring axial movement space.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If special processing is performed on the stem and gland to provide locking portions and stem holes, then stem pullout prevention is achieved, but manufacturing complexity increases

Engineering Contradiction:

Improvestem pullout preventionVSAvoidprocessing requirements

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention merges the locking portion with the stem and the packing retaining member with the gland as integral components. The locking portion is formed directly on the stem, and the packing retaining member is formed directly on the gland, eliminating the need for separate retaining rings and reducing the number of parts and assembly steps.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The packing retaining member serves multiple functions: it retains the packing, provides a locking interface for the locking portion, and integrates with the gland structure. This multi-functionality reduces the need for separate components and simplifies manufacturing.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of operation

If a large space is provided between the stem hole inner circumference and stem outer circumference, then the locking portion can move freely, but the gland diameter must be enlarged to ensure strength

Engineering Contradiction:

Improvelocking portion movementVSAvoidgland diameter

Core Design Contradiction:

Ease of operationVSArea of stationary object

Solution Approach 1:

The invention eliminates the need for radial clearance space by changing from axial movement to radial interference engagement. The locking portion's outer diameter is made larger than the packing retaining member's inner diameter, creating an interference fit that provides both strength and locking functionality without requiring additional radial space.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Strength

If the gland diameter is enlarged to ensure strength, then the gland can accommodate the stem hole and locking portion, but the valve size around the rotation axis increases

Engineering Contradiction:

Improvegland strengthVSAvoidvalve size around rotation axis

Core Design Contradiction:

StrengthVSArea of stationary object

Solution Approach 1:

The invention achieves gland strength through radial interference engagement between the locking portion and packing retaining member, eliminating the need for a large stem hole. This allows the gland to maintain its original diameter without enlargement, keeping the valve compact around the rotation axis.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS20260071683A1Rotary valve

Publication Date: 2026.03.12 KITZ CORP

AI summary

A packing accommodation chamber is provided inside a stem shaft insertion portion on an operating portion side, a diameter-reduced portion is provided on the operating portion side, a diameter-enlarged portion is provided on a valve disk side of the stem, a diameter-reduced step surface is formed at a boundary portion therebetween, a gland having a packing pressing portion is provided on the operating portion side, a packing retaining member is interposed between a lower end face of the packing pressing portion and a packing. The diameter-reduced step surface is arranged at least lower than the packing retaining member, the diameter-enlarged portion has an outer diameter S2 larger than an inner diameter S7 of the packing retaining member and, when the stem rises to the operating portion side, the diameter-reduced step surface is locked to the packing retaining member to prevent pullout of the stem to the operating portion side.