Expansion Bolt Joint for Rotatable Cutting Tool Tension Locking

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Solution Overview

Problem

Existing joint mechanisms for rotatable cutting tools, such as those using a bolt and nut, face issues with accidental rotation leading to inconsistent tension, affecting the cutting accuracy of blades.

Innovation Solution

Incorporating an expansion bolt within a cavity at the end of the bolt, which expands to lock the nut in place, preventing accidental rotation and allowing for easy adjustment of tension by moving the expansion bolt into or out of the cavity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a bolt and nut are used to attach cutting blades rotatably, then the joint can be assembled and tension adjusted, but the bolt and nut may accidentally rotate leading to inconsistent tension

Engineering Contradiction:
Improvetension adjustmentVSAvoidjoint stability
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The expansion bolt is nested within a cavity in the bolt, allowing the bolt to expand radially when the expansion bolt is rotated. This nested structure enables the locking function while maintaining a compact design, preventing accidental rotation of the nut relative to the bolt.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The bolt transitions from a static state to a dynamic expanded state when the expansion bolt is rotated. This dynamic expansion creates friction or mechanical interference that locks the nut in place, preventing accidental rotation while allowing intentional adjustment when needed.

Inventive Principle:
Principle #15Dynamics

2Manufacturing precision

If the joint tension is adjusted by rotating the bolt and nut, then the cutting accuracy can be optimized, but the adjustment mechanism is complex and time-consuming

Engineering Contradiction:
Improvecutting accuracyVSAvoidadjustment time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The adjustment mechanism is segmented into two independent functions: tension adjustment (via nut rotation) and locking (via expansion bolt rotation). This segmentation allows for quick locking without requiring complex adjustment mechanisms, reducing adjustment time while maintaining cutting accuracy.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The expansion bolt acts as an intermediary locking mechanism that secures the nut in place after tension adjustment. This intermediary element prevents the need for complex anti-loosening mechanisms during adjustment, simplifying the overall process and reducing time loss.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If an expansion bolt is used to prevent accidental rotation, then the joint stability is improved, but the device complexity increases

Engineering Contradiction:
Improvejoint stabilityVSAvoidjoint structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The expansion bolt is merged with the existing bolt structure, utilizing the same axial space and integration points. This merging approach adds the locking function without requiring separate components or complex assembly procedures, minimizing the increase in device complexity.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The bolt serves multiple functions: it provides the primary mechanical connection, allows for tension adjustment through nut rotation, and prevents accidental rotation through expansion. This multi-functionality reduces the need for additional components, keeping the device complexity low while improving reliability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 solution ensures consistent tension in the joint, preventing accidental loosening and allowing for repeated, user-friendly adjustments without compromising functionality.

Implementation Method 1

an expansion bolt (12) arranged within a cavity (14) in the second end (9) of the bolt (5), which when rotated in relation to the bolt (5) expands the second end (9) of the bolt (5)

Methodology Applied
Scientific EffectMechanical expansion: Elasticity

Data Source

PatentEP3070346B1joint
Publication Date: 2019.10.16 FISKARS FINLAND OY AB
  • EP3070346B1 patent drawingFigure 1~4

AI summary

The invention relates to a joint (2) comprising a bolt (5) with a head (6) in a first end (7), with a thread (8) in a second end (9), and with an intermediate section (10) between the first end (7) and the second end (9) which during attachment of two objects rotatably to each other protrudes trough openings in said objects. A nut (11) is received on said thread (8). In order to provide an easy solution for adjusting the tension of the joint at the same time as accidental loosening of the joint may be efficiently prevented the bolt (5) is provided with a cavity (14). An expansion bolt (12) with a threaded end (13) protrudes into said cavity (14) and expands the second end (9) of the bolt.