Zero-Turn Parking Brake Linkage for Tilted Lever Actuation
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Solution Overview
Problem
Existing zero-turn ride-on mowers lack an efficient and reliable mechanism for engaging and disengaging parking brakes, particularly in response to the outward lateral tilting of drive control levers, which can compromise safety and operational convenience.
Innovation Solution
A novel mechanical linkage-based parking brake control system is introduced, featuring a bell crank, lever connection link, and brake connection link, which allows the parking brake to be engaged or disengaged solely through the lateral tilting of the drive control levers in their neutral position, without interfering with the longitudinal pivoting for speed and direction control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a mechanical linkage system is used to connect drive control levers to parking brakes, then the parking brake can be engaged through lateral tilting of the levers, but the device complexity increases due to additional components like bell cranks and connection links
Solution Approach 1:
The drive control lever is designed to perform multiple functions: longitudinal pivoting for speed control and lateral tilting for parking brake engagement. This multi-functionality eliminates the need for separate brake control mechanisms, resolving the contradiction by making the existing control lever universal rather than adding separate components.
Solution Approach 2:
The patent combines the parking brake control function with the existing drive control lever system. By merging the brake engagement function into the lever's lateral tilting motion, the design avoids adding independent brake control components, thus reducing overall device complexity while maintaining ease of operation.
2Reliability
If the control lever is made laterally tiltable to engage parking brake, then the brake control becomes more intuitive and safe, but the control precision for speed and direction may be affected due to additional movement degrees of freedom
Solution Approach 1:
The control lever's movement is segmented into two independent degrees of freedom: longitudinal pivoting for speed control and lateral tilting for brake engagement. This segmentation allows each motion to be independently controlled and measured, maintaining positioning precision while enabling reliable brake control through distinct movement patterns.
Solution Approach 2:
The bell crank acts as an intermediary mechanism that converts the lateral tilting motion of the control lever into the appropriate motion for engaging the parking brake. This intermediary component isolates the brake control function from the speed control function, ensuring that lateral tilting reliably engages the brake without interfering with longitudinal pivoting precision.
3Reliability
If rigid mechanical links are used for brake control, then the brake engagement is reliable and direct, but the system becomes less adaptable to different operating conditions compared to flexible cables or electronic controls
Solution Approach 1:
The brake control linkage incorporates dynamic elements including the bell crank's rotational movement and the control lever's lateral tilting capability. These dynamic components allow the system to adapt to different operating conditions while maintaining reliable brake engagement, combining the reliability of mechanical links with the adaptability of movable joints.
Data Source
AI summary
A ride-on zero-turn work machine has two drive control levers longitudinally pivotable for locomotive and steering control, and laterally tiltable inboard and outboard for parking brake control. Two brake control linkages are each connected between one of the levers and one of the parking brakes. Each linkage features a rotatable bell crank, a brake connection link running from the bell crank to the parking brake, and a lever connection link having one end coupled to the bell crank, and another coupled to drive control lever through a ball joint that, in an inboard position of the lever, and throughout a full longitudinal pivot range thereof, lies on the lever's pivot axis, with no motive effect on the bell crank or parking brake. Laterally outward tilting of the lever moves the ball joint off axis, in a manner driving rotation of the bell crank, and thereby actuating the parking brake.