Two-Motion Cable Engagement Mechanism for Lawn Mower Safety
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Solution Overview
Problem
Existing cable control systems for walk-behind lawn mowers, such as those used in U.S. Pat. No. 4,930,369, suffer from rapid automatic movement of the lever when the deadman bar is released, leading to potential safety hazards and increased construction and assembly costs, while also allowing debris intrusion and user fatigue due to the need for constant grip to prevent accidental mechanism activation.
Innovation Solution
A two-motion actuation system with a shiftable lever and socket assembly that confines movement within a control housing, featuring a pivotable spool with grooves, a latching dog, catch, and pawl mechanism, which provides a perceptible click upon engagement and disengagement, and a design that allows for internal operation, reducing the force required to maintain the deadman handle position and ensuring fail-safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an external latch is activated when the deadman bar is pulled downwardly, then the lever can be moved to operate mechanisms, but release of the deadman bar causes rapid automatic movement of the lever leading to safety hazards
Solution Approach 1:
The control system is divided into two independent motion stages: first the deadman bar moves to activate the external latch, then the lever moves separately to operate mechanisms. This segmentation prevents the lever from moving rapidly when the deadman is released, as the latch mechanism holds the lever in position until deliberately moved by the operator.
Solution Approach 2:
The external latch acts as an intermediary mechanism between the deadman bar and the lever. When the deadman bar is pulled, it activates the latch which then permits lever movement. This intermediary prevents direct coupling that would cause rapid lever movement upon deadman release, thereby improving safety while maintaining operational capability.
2Ease of operation
If the operator must grasp the deadman and hold it in a particular position, then mechanisms can be operated, but user fatigue increases due to constant grip requirement
Solution Approach 1:
The latch mechanism provides self-service by automatically maintaining the engaged state once activated by the deadman bar. The operator does not need to continuously grip the deadman to keep mechanisms engaged; the latch holds the lever in position automatically, reducing user fatigue while maintaining control.
3Object-affected harmful factors
If the control mechanisms are housed internally within the control housing, then debris intrusion is minimized, but the structure becomes more complex
Solution Approach 1:
The control mechanisms are nested within the control housing, with the latch, lever, and other components arranged in a compact internal configuration. This nesting protects mechanisms from debris while maintaining a manageable structural complexity through efficient spatial arrangement.
4Reliability
If a latching dog and pawl mechanism is used to prevent rapid lever movement, then safety is improved, but the device complexity increases
Solution Approach 1:
The latching function is extracted as a separate, dedicated mechanism (latching dog and pawl) independent of the main lever assembly. This modular approach improves reliability by providing positive position control while managing complexity through functional separation, allowing each component to be optimized for its specific role.
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 system minimizes debris intrusion, reduces user fatigue, provides a safe and audible feedback mechanism, and prevents accidental lever movement upon release, enhancing safety and reducing construction costs by internalizing interactions and allowing easy disengagement of the control cable without handle movement.
Implementation Method 1
each of which are provided with a small spring which provides a radially outward biasing force to respectively urge a respective first part of each the catch and pawl outwardly
Implementation Method 2
the socket is provided with a bail return spring to move the socket to a disengaging position when the deadman handle is released
Implementation Method 3
Both the pivotable hub member and the socket are biased in a circumferential direction by respective return springs, whereby the lever returns to its initial position when an advancing force is removed
Data Source
AI summary
A method and apparatus for two motion cable engagement includes a housing adapted for attachment to a tubular member such as a handlebar or the like of a walk-behind lawnmower, a lever assembly pivotably mounted to the housing, and a socket operatively connectable to the lever assembly and actuatable by a deadman handle. The lever assembly preferably includes a lever, a hub connected to the lever, and a pivotable member which is selectively pivotably driven by the hub. When the socket is pivoted by the deadman handle from a primary position to an engaged position, movement of the lever from an initial position to an advanced position produces pivoting of the pivotable member and a control cable attached thereto. With the socket remaining in the engaged position, the lever may be permitted to return to the initial position, and the pivotable member remains advanced and held by the socket, keeping the control cable in the actuated condition until the deadman handle is released, whereupon tension on the control cable causes the pivotal member returned to its initial position and permits the control cable to extend and deactivate a controllable mechanism to which it is attached.