Centrifugal Coil Spring Brake for Lawnmower Shaft
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing braking mechanisms for larger lawnmowers are overly complex and expensive due to the need for separate braking elements and retraction springs, which are not efficiently addressed by existing technologies.
Innovation Solution
A brake mechanism utilizing coil springs mounted in a carrier that moves away from and towards a braking surface as rotational speed increases and decreases, respectively, providing a frictional braking force without the need for separate components, leveraging centrifugal force and torsional spring action to slow the shaft effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate braking elements and retraction springs are used in existing braking mechanisms, then the braking function can be achieved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the braking element and retraction spring functions into a single coil spring component. The coil spring serves dual purposes: it provides the braking force through friction when engaged with the braking surface, and it automatically retracts by unwinding from the shaft. This merging of functions eliminates the need for separate braking elements and retraction springs, directly resolving the technical contradiction between achieving reliable braking and reducing device complexity
Solution Approach 2:
The coil spring is designed as a multi-functional component that simultaneously performs braking, retraction, and energy storage functions. When the shaft rotates, the coil spring winds around it, storing elastic potential energy while maintaining frictional contact for braking. When engagement is released, the stored energy automatically propels the spring outward to disengage from the braking surface. This universal design allows a single component to replace multiple specialized parts, reducing overall system complexity while maintaining braking reliability
2Reliability
If multiple separate components are used for braking, then the braking mechanism can be designed, but the manufacturing cost increases
Solution Approach 1:
The patent merges multiple discrete components (braking elements, retraction springs, mounting hardware) into a single integrated coil spring assembly. This reduction in component count directly lowers manufacturing costs by eliminating multiple fabrication processes, material purchases, and assembly operations. The single coil spring can be manufactured as one piece through standard spring-making processes, then installed as a single unit, significantly simplifying production compared to assembling multiple separate braking components
Solution Approach 2:
The coil spring is designed to be self-contained and self-actuating, requiring no external actuators, control systems, or additional mechanical linkages. The spring's own elastic properties provide both the braking force and the retraction mechanism. This self-service design eliminates the need for complex control systems and additional actuating components, reducing both manufacturing cost and system complexity while maintaining reliable braking performance
3Ease of manufacture
If the coils of the spring are oriented perpendicular to the direction of motion, then the spring can be mounted, but abrasion of the braking surface increases
Solution Approach 1:
The patent employs an asymmetric coil orientation where the coils are deliberately positioned at an angle that is neither perfectly parallel nor perpendicular to the direction of motion, but optimized to minimize abrasive contact. This asymmetric arrangement allows the spring to engage the braking surface effectively for braking while reducing the sliding friction and abrasion compared to a perpendicular orientation. The asymmetric design balances manufacturing ease with reduced wear on the braking surface
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 enables quick stopping of the shaft within the required three seconds, meeting European standards with fewer components, reducing manufacturing costs and maintaining efficiency across multiple braking cycles.
Implementation Method 1
as the rotational speed at which the carrier is rotated by the shaft increases, the coils of the spring move away from the shaft and the braking surface
Implementation Method 2
each, spring will comprise a torsion spring, with the coils having two ends, the spring being arranged to exert a torque that resists relative rotational movement of the two ends
Implementation Method 3
the coils of the spring move towards the shaft and the braking surface and come into contact with the braking surface so as to exert a braking force on the shaft
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A brake (3) for a shaft (2), such as the output shaft of the motor (41) of a lawnmower(40), comprising a carrier (4) arranged to be fixed to the shaft (2) for rotation therewith; at least one coil spring (7) having coils (8); and a braking surface (5) arranged to be fixed so that theshaft (2) rotates relative to the braking surface (5), each coil spring (7) being mounted in the carrier (4) such that, as a rotational speed at which the carrier (4) is rotated by the shaft (2) increases, the coils (8) of the spring (7) move away from the shaft (2) and the braking surface (5) and, as the rotational speed at which the carrier (4) is rotated by the shaft (2) decreases, the coils (8) of the spring (7) move towards the shaft (2) and the braking surface (5) and come into contact with the braking surface (5) so as to exert a braking force on the shaft (2).