Multiple Hirth Joint for Adjustable Lawn Mower Control Arms
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Solution Overview
Problem
Existing lawn mower control systems lack the ability to be easily adjusted for operators of varying sizes, limiting comfort and efficiency due to rigid joint configurations that do not allow for simultaneous linear and angular adjustments.
Innovation Solution
A multiple Hirth joint system with a slot and actuator that allows for simultaneous loosening and tightening of the joint, enabling relative linear and angular movement between components, accommodating operator size through a combination of face teeth interfaces and a movable fastener, thereby adjusting the control handle's position and attitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a rigid joint configuration is used, then structural stability is maintained, but adaptability to different operator sizes is lost
Solution Approach 1:
The joint configuration transitions from a static rigid structure to a dynamic adjustable structure. The control arm assembly allows the upper arm to be repositioned relative to the lower arm through the Hirth joint mechanism, enabling the joint to adapt its configuration based on operator size requirements while maintaining structural integrity during operation.
Solution Approach 2:
The control arm is divided into separate segments (lower arm and upper arm) connected by the adjustable joint. This segmentation allows independent positioning of each arm segment, with the upper arm being adjustable along the slot and angularly positioned via Hirth joint teeth engagement, providing adaptability while maintaining overall structural stability.
2Ease of operation
If a single joint allows simultaneous linear and angular adjustment, then ease of operation is improved, but device complexity increases
Solution Approach 1:
The mechanism merges linear adjustment (via slot movement) and angular adjustment (via Hirth joint teeth engagement) into a single integrated joint structure. The actuator simultaneously controls both degrees of freedom, allowing the upper arm to be positioned in both linear and angular dimensions through one adjustment mechanism rather than separate mechanisms.
Solution Approach 2:
The adjustable joint serves multiple functions within a single mechanism: it provides linear positioning along the slot, angular positioning through tooth engagement, and structural support. The Hirth joint interface universally handles both translational and rotational adjustments, reducing the need for multiple separate adjustment mechanisms.
3Adaptability or versatility
If the control handle is made adjustable for different operators, then adaptability is improved, but manufacturing complexity increases
Solution Approach 1:
The joint incorporates dynamic adjustment capabilities through the slot and Hirth tooth mechanism, allowing the upper arm to be repositioned to multiple discrete positions. The slot provides linear adjustment range while the circumferential teeth provide angular positioning, creating a multi-position adjustable system that accommodates different operator sizes.
Solution Approach 2:
The control arm assembly is segmented into the lower arm, upper arm, and adjustable joint components. This segmentation allows the joint to be manufactured as a separate module with pre-formed slot and Hirth tooth interfaces, facilitating assembly and adjustment while maintaining manufacturing feasibility through modular construction.
Data Source
AI summary
A multiple Hirth joint for permitting linear and angular adjustment of an upper control arm with respect to a lower control arm. The joint includes a multiple Hirth interface having a slot through it, a confronting single Hirth interface, and an actuator. The actuator permits manual loosening and tightening of the multiple Hirth interface and single Hirth interface to permit linear and angular adjustment. Loosening of the actuator simultaneously permits linear and angular adjustment and tightening of the actuator simultaneously lock the joint into the selected linear and angular position.