Adjusting Element Threaded Section for High Clamping Force

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Solution Overview

Problem

Existing motor saws with saw chains face limitations in transmitting high clamping forces due to the small diameter of the screw shank, requiring significant torque for tensioning and resulting in limited clamping forces.

Innovation Solution

The design features a large outer circumference for the threaded section of the adjusting member, with an actuating contour that overlaps the thread, allowing for the transmission of high forces without additional components, and includes a compact, lightweight structure with a sprocket cover for easy access and dirt removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a small diameter screw shank is used for the adjusting element, then the device complexity is reduced and the design is simplified, but the transmissible tensioning forces are limited and high torque is required for operation

Engineering Contradiction:
Improvedesign simplicityVSAvoidtransmissible tensioning force
Core Design Contradiction:
Device complexityVSForce

Solution Approach 1:

The invention transitions from a conventional small-diameter screw shank to a large outer circumference threaded section, effectively changing the dimensional scale of the force transmission interface. This dimensional change allows significantly larger forces to be transmitted through the threaded connection between the adjusting element and clamping element, resolving the limitation of small screw shanks while maintaining design simplicity.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Force

If a large outer circumference threaded section is used for the adjusting element, then high clamping forces can be transmitted, but the overall length of the adjusting element increases

Engineering Contradiction:
Improveclamping force transmissionVSAvoidadjusting element length
Core Design Contradiction:
ForceVSLength of moving object

Solution Approach 1:

The invention nests the actuating contour within the threaded section by making them overlap along the axial direction. The actuating contour is positioned such that it occupies the same radial space as the threaded section, allowing the adjusting element to maintain a compact axial length while providing both the large outer circumference needed for force transmission and the actuating interface for operation.

Inventive Principle:
Principle #7Nested doll (Nesting)

3Ease of operation

If the actuating contour and threaded section are separated into distinct sections, then the adjusting element can be made longer for better operation, but the overall length and weight of the tool increase

Engineering Contradiction:
Improveactuating contour accessibilityVSAvoidtool weight
Core Design Contradiction:
Ease of operationVSWeight of moving object

Solution Approach 1:

The invention merges the actuating contour and threaded section into a single integrated structure that overlaps axially. This combination allows the adjusting element to serve both functions (actuation and force transmission) simultaneously within a compact form, eliminating the need for separate sections and thereby reducing the overall length and weight of the tool while maintaining ease of operation.

Inventive Principle:
Principle #5Merging (Combining)

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 enables the transmission of high clamping forces with reduced operator effort, achieving a compact and lightweight design that effectively tensions the saw chain while maintaining ease of use and accessibility.

Implementation Method 1

The adjusting element (17) is connected to the clamping element (16) via a threaded connection (20). Turning the adjusting screw causes a longitudinal displacement of the guide bar via the threaded connection, thus tensioning the saw chain.

Methodology Applied
Scientific EffectScrew mechanism: Screw

Implementation Method 2

Due to the comparatively large outer circumference of the threaded section compared to the outer circumference of the actuating contour, large forces can be transmitted from the adjusting element to the clamping element.

Methodology Applied
Scientific EffectMechanical advantage through increased radius: Mechanical Advantage

Data Source

PatentEP3197651B1Work device
Publication Date: 2021.11.03 ANDREAS STIHL AG & CO KG
  • EP3197651B1 patent drawingFigure 1~3
  • EP3197651B1 patent drawingFigure 4~6
  • EP3197651B1 patent drawingFigure 7~9

AI summary

The invention relates to a work device with a guide rail (4) on which a chain (5) is driven in a circulating manner. The work device has a clamping device (15) for the chain (5). The clamping device (15) has a clamping element (16) which acts on the guide rail (4) in the direction (19) of the longitudinal central axis (18) of the guide rail (4). The clamping device (15) has a rotatably mounted adjusting element (17) which is connected to the clamping element (16) via a threaded connection (20). A rotation of the adjusting element (17) about its rotational axis (21) causes a movement of the clamping element (16) in the direction (19) of the longitudinal central axis (18) of the guide rail (4). The outer circumference of the adjusting element (17) has a threaded portion (22) with at least one turn (23), said threaded portion being provided for engaging with at least one threaded portion (24) of the clamping element (16). The adjusting element (17) has an actuating contour (39) so that a user can rotate the adjusting element (17), said actuating contour comprising at least one depression. The largest spacing (b) between the threaded portion (22) of the adjusting element (17) and the rotational axis (21) is at least as large as the largest spacing (a) between the actuating contour (39) and the rotational axis (21).