Railway Switch Locking Device Hollow Screw Stress Distribution

Solution Overview

Problem

Hollow bolts in railroad switch locking devices are prone to breaking due to concentrated mechanical stresses and vibrations, particularly at the connection between the screw body and hammer head, leading to reduced reliability and increased maintenance needs.

Innovation Solution

The hollow screw is designed as a separate screw body and hammer head, mechanically linked by conical fitting, distributing stresses along the entire length of the interface and reducing concentration at the base of the hammer head, with optional anti-rotation and centering features for improved assembly and operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the hollow screw is designed as a single integral piece with hammer head, then the manufacturing is simpler, but the mechanical stress concentrates at the base of the hammer head causing breakage

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidresistance to breakage

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The hollow screw is divided into two separate components: a screw body and a hammer head. These components are assembled together rather than being manufactured as a single integral piece. This segmentation allows the mechanical stresses to be distributed along the entire length of the interface between the screw body and hammer head, rather than concentrating at the base of the hammer head, thereby significantly increasing force resistance and reducing breakage by at least 50%.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If the hollow screw is designed as a single integral piece, then there are fewer parts to assemble, but the stress concentration leads to frequent breakages and maintenance

Engineering Contradiction:

Improvenumber of componentsVSAvoiddurability under vibration and stress

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The hollow screw is divided into two separate components: a screw body and a hammer head. These components are assembled together rather than being manufactured as a single integral piece. This segmentation allows the mechanical stresses to be distributed along the entire length of the interface between the screw body and hammer head, rather than concentrating at the base of the hammer head, thereby significantly increasing force resistance and reducing breakage by at least 50%.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the screw body and hammer head are separately assembled, then stress distribution improves, but the assembly process becomes more complex

Engineering Contradiction:

Improveforce resistanceVSAvoidassembly complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The hollow screw is divided into two separate components: a screw body and a hammer head. These components are assembled together rather than being manufactured as a single integral piece. This segmentation allows the mechanical stresses to be distributed along the entire length of the interface between the screw body and hammer head, rather than concentrating at the base of the hammer head, thereby significantly increasing force resistance and reducing breakage by at least 50%.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of creating a complex integral structure that requires sophisticated manufacturing processes to avoid stress concentrations, the invention inverts the approach by using separate simple components assembled together. The complexity is shifted from manufacturing to assembly, where standard fastening procedures can be used, and the stress distribution problem is solved through the design of the interface between components rather than through complex monolithic geometry.

Inventive Principle:

Principle #13The other way round (Inversion)

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 significantly increases the force resistance of the screw and bolt, reducing breakage by at least 50% and minimizing operator interventions, thereby enhancing the durability and reliability of the locking device.

Implementation Method 1

conical fitting of the screw body into the orifice made in the hammer head... the mechanical stresses are distributed over the entire length of the interface, for example conical in the case of a conical fitting, between the two parts

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentEP2412602B1Railway switch locking device

Publication Date: 2013.04.10 ALSTOM TRANSPORT SA

Figure 1~2
Figure 3~6

AI summary

The device has a fixed part (PF) secured to a stock rail, and a movable part movable with respect to the fixed part. The movable part is fixed on a switch point rail. The movable part allows application and locking of the switch point rail on the stock rail by using a metal locking arm. The fixed part includes a bolt (7) with a socketed screw in which a bronze piston slides. The piston is actuated by the switch point rail to control a controller of the device. The screw comprises a threaded rod (71) and a hammer head (72) that is distinct from the threaded rod and secured to the threaded rod.