Oversized Threaded Rod Locking for Tight Oblong-Hole Fixation

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Solution Overview

Problem

Existing methods for securing a first part with a locking oblong hole to a second part are inefficient in providing a height-adjustable and tight fixation.

Innovation Solution

A method involving an oversized locking threaded rod that widens the locking oblong hole during insertion, creating an undercut for secure engagement, optionally combined with a pre-fixing threaded rod to prevent material accumulation and enhance stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If an oversized locking threaded rod is used to widen the locking oblong hole for tight fixation, then the connection strength and fixation tightness are improved, but the manufacturing precision of the hole is compromised due to material displacement

Engineering Contradiction:
Improveconnection strengthVSAvoidhole geometry precision
Core Design Contradiction:
StrengthVSManufacturing precision

Solution Approach 1:

A pre-fixing threaded rod is inserted through the locking oblong hole before the locking threaded rod to perform preliminary fixation. This pre-fixing action stabilizes the workpiece and prevents unwanted displacement during the subsequent hole-widening operation, allowing the locking threaded rod to create the undercut without compromising overall positioning accuracy

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The material displacement caused by the oversized locking threaded rod is converted from a harmful effect into a beneficial feature. By intentionally designing the rod to be oversized, the patent creates an undercut geometry within the hole that provides mechanical interlocking and enhanced fixation, transforming the precision loss into a strength gain

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If the locking threaded rod is oversized to create an undercut for geometric interlock, then the fixation reliability is improved, but the ease of operation deteriorates due to difficulty in insertion

Engineering Contradiction:
Improvefixation reliabilityVSAvoidinsertion ease
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The pre-fixing threaded rod is inserted first to establish initial contact and stability between components. This preliminary action creates a controlled state that facilitates the subsequent insertion of the larger locking threaded rod, reducing resistance and making the operation easier while maintaining reliability

Inventive Principle:
Principle #10Preliminary action

3Reliability

If material displacement occurs during the widening process, then the interlock engagement is improved, but the load transfer capability may be compromised due to potential gaps

Engineering Contradiction:
Improveinterlock engagementVSAvoidload transfer capability
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The pre-fixing threaded rod performs preliminary fixation before the locking threaded rod creates the undercut. This sequence ensures that components are properly positioned and any potential gaps are minimized before the final interlock is created, maintaining both interlock engagement and load transfer capability

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent changes the dimensional parameters of the locking threaded rod relative to the hole, using an oversized rod that creates controlled material displacement. This parameter change transforms the geometry to create an undercut that enhances both interlock engagement and load distribution, improving load transfer capability while maintaining reliable engagement

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP4189255B1Use of an oversized threaded rod in a locking oblong hole
Publication Date: 2025.06.25 HILTI AG
  • EP4189255B1 patent drawingFigure 1
  • EP4189255B1 patent drawingFigure 2
  • EP4189255B1 patent drawingFigure 3

AI summary

The invention relates to a method for securing a first part, which is provided with a locking oblong hole, to a second part, comprising passing a locking threaded rod through the locking oblong hole into the second part, wherein the locking threaded rod is oversized with respect to the width of the locking oblong hole, so that the locking threaded rod widens the locking oblong hole as it is passed through the locking oblong hole. The invention also relates to an arrangement which can be obtained using the method, and an installation set that can be used for performing the method.