Rotary Mower Blade Bolt Shank Design for Stress Distribution
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Solution Overview
Problem
Existing rotary mower blade bolts with sharp corners cause stress concentrations that can lead to cracking or stripping, making them prone to failure when attaching blades to a rotating mower pan.
Innovation Solution
A blade bolt design featuring a rounded, non-cylindrical shank cross-section that prevents rotation within correspondingly shaped pan apertures, distributing stress over a wider surface area and eliminating sharp corners, combined with a cylindrical shoulder for free blade pivoting and a threaded portion for secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a square or hexagonal shank is used to prevent bolt rotation, then the bolt is prevented from rotating in the pan aperture, but stress concentrations at the corners cause the pan to crack and break or the corners to strip
Solution Approach 1:
The patent applies the spheroidality principle by replacing the angular square or hexagonal shank cross-section with a rounded non-cylindrical cross-section (such as oval, elliptical, or circular with flattened portions). This curvature eliminates the sharp corners that cause stress concentrations, while the non-cylindrical shape (non-circle) maintains the ability to prevent rotation in a correspondingly shaped pan aperture. The rounded corners distribute stress evenly across the pan surface, preventing cracking and stripping while still providing reliable rotation prevention.
2Object-generated harmful factors
If a circular head is used to reduce vegetation catching, then vegetation catching is reduced, but the bolt becomes difficult to grasp with a wrench for tightening
Solution Approach 1:
The patent applies segmentation by dividing the bolt into distinct functional zones: the head remains circular to minimize vegetation catching, while the shank is given a rounded non-cylindrical cross-section to prevent rotation. This segmentation allows each part of the bolt to optimize its shape for its specific function - the circular head for reducing vegetation interference and the non-cylindrical shank for rotation prevention - without compromising either function.
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
The solution effectively prevents bolt rotation and distributes stress evenly, reducing the risk of cracking and stripping, ensuring secure blade attachment and prolonged mower component durability.
Implementation Method 1
distributes stress forces from the bolt to the pan through a wider surface area
Implementation Method 2
The pan rotates at high speed, and centrifugal force causes the blades to extend radially from the rotational axis of the pan
Data Source
AI summary
A blade bolt for attaching a blade to a rotating member of a rotary mower has a head at a lower end, a cylindrical shoulder portion extending from the head, a shank extending from the shoulder portion, the shank having a cross-section that is rounded and non-cylindrical, and a threaded portion extending from the shank. The shoulder portion extends laterally beyond at least a portion of the shank such that the shoulder portion bears against the rotating member when the shank is inserted into a mounting aperture defined by the mounting member that has a shape corresponding to the cross-section of the shank. The rounded and non-cylindrical shank prevents rotation of the bolt, and distributes stress forces across a wider area compared to the prior art.