Walk Power Mower Dual Transmission Reverse Drive
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Solution Overview
Problem
Self-propelled walk power mowers often require manual effort to maneuver in reverse, especially on hills or in tight spaces, as their traction drive systems are typically unpowered during reverse motion, making it difficult for users to operate effectively.
Innovation Solution
A variable speed traction drive system with dual transmissions for both front and rear wheels, controlled by a slidable handle grip that activates one transmission for forward motion and another for reverse motion, allowing powered operation in both directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a one-way clutch is used to allow free-wheeling during reverse motion, then the user is not pulled back against resistance, but the drive wheels become unpowered during reverse motion requiring manual effort
Solution Approach 1:
The traction drive system is divided into two independent transmissions: a rear transmission for forward motion and a front transmission for reverse motion. Each transmission can be independently engaged or disengaged, allowing powered reverse motion without requiring the drive wheels to free-wheel. This segmentation resolves the contradiction by providing powered capability in reverse while maintaining ease of operation.
Solution Approach 2:
The system dynamically selects which transmission to engage based on the desired direction of motion. The control system activates the front transmission when reverse motion is needed and the rear transmission for forward motion, allowing the mower to be powered in both directions. This dynamic switching resolves the contradiction between ease of reverse operation and powered motion capability.
2Device complexity
If only one transmission is used for forward motion, then the system is simpler, but reverse motion cannot be powered requiring manual manhandling
Solution Approach 1:
The transmission system is segmented into two separate transmissions: a rear transmission for forward motion and a front transmission for reverse motion. This segmentation allows each transmission to be optimized for its specific function while keeping the overall system manageable. The rear transmission handles forward propulsion while the front transmission provides powered reverse motion, resolving the contradiction between simplicity and ease of reverse operation.
Solution Approach 2:
The control system provides universal control over both transmissions through a single interface on the handle. The user can select either the rear transmission for forward motion or the front transmission for reverse motion through the same control mechanism. This multi-functionality resolves the contradiction by providing reverse powered capability without proportionally increasing system complexity.
3Device complexity
If the mower is designed for forward self-propelled motion only, then the traction drive system is simpler, but manual effort is required for reverse motion especially on hills
Solution Approach 1:
The traction drive system is segmented into two independent transmission paths: rear transmission for forward motion and front transmission for reverse motion. This segmentation allows the system to provide powered capability in both directions while keeping each individual transmission relatively simple. The rear transmission handles forward propulsion and the front transmission provides reverse propulsion, reducing the overall physical effort required from the user on hills or difficult terrain.
Solution Approach 2:
The mower's prime mover automatically provides power for reverse motion through the front transmission when the user needs to maneuver backward, eliminating the need for manual pushing or manhandling. The system serves itself by automatically engaging the appropriate transmission based on the desired direction of motion, thereby reducing the physical effort the user must expend, especially on hills.
Data Source
AI summary
A walk power mower has a traction drive system that includes a front transmission powering a pair of front wheels and a rear transmission powering a pair of rear wheels. A first one of the transmissions provides forward motion of the mower when it is active and a second one of the transmissions provides rearward motion of the mower when it is active. A slidable handle grip on the handle having a cross bar long enough to be gripped by both hands of the user activates the first one of the transmission when it is slid downwardly on a handle out of a neutral position thereof. The slidable handle grip activates the second one of the transmissions when it is slid upwardly on the handle out of the neutral position.