Load-Activated Ratchet Block with Pivoting Sheave
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Solution Overview
Problem
Ratchet blocks used in sailing require frequent switching between active and inactive settings based on the direction of line operation, leading to inefficiencies when handling high loads, especially in racing conditions.
Innovation Solution
A load-activated ratchet block with a pivoting sheave assembly and an over-center mechanism that automatically engages or disengages the ratchet mechanism based on applied load, using a spring bias and actuator to move the pawl between engaged and free settings, allowing smooth operation without manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a manually-operable ratchet mechanism is used, then the ratchet can be switched between active and inactive settings, but frequent manual switching reduces efficiency and increases complexity of operation under high loads
Solution Approach 1:
The ratchet mechanism automatically switches between active and inactive states based on the direction of load applied to the sheave. When load is applied in the hauling direction, the pawl engages with ratchet teeth to prevent rotation. When load is applied in the paying-out direction, the sheave pivots on its mounting axis, causing the pawl to disengage and allowing free rotation. This self-activating mechanism eliminates the need for manual switching while maintaining operational control.
2Reliability
If the ratchet mechanism is set to active position to prevent rotation, then the line can be held under load, but the line cannot run smoothly through the block when paying out
Solution Approach 1:
The ratchet mechanism transitions from a static fixed-state design to a dynamic load-activated design. The sheave is mounted to pivot on a horizontal axis spaced from its rotational axis, allowing it to tilt in response to load direction. This dynamic positioning automatically engages or disengages the pawl from ratchet teeth based on whether the load is in the hauling or paying-out direction, enabling smooth operation in both modes without manual intervention.
3Productivity
If an automatically operating ratchet mechanism is provided, then manual switching is eliminated, but manufacturing complexity and reliability may increase
Solution Approach 1:
The block is divided into functionally independent segments: the sheave assembly that pivots on a horizontal axis, the ratchet teeth formed on the sheave periphery, the pawl mounted on the block body, and the spring mechanism. This segmentation allows each component to be manufactured separately using standard machining operations and then assembled, simplifying the manufacturing process while achieving automatic operation. The pawl is spring-loaded to maintain engagement pressure without requiring complex actuation mechanisms.
4Reliability
If the pawl is spring-loaded to engage ratchet teeth, then the ratchet remains active under load, but the spring force must be carefully controlled to ensure reliable engagement without excessive wear
Solution Approach 1:
The spring force parameter is optimized to provide sufficient engagement pressure for reliable ratchet activation under sailing loads while avoiding excessive force that would cause premature wear or binding. The spring is positioned to apply force at a specific angle and location on the pawl, creating a mechanical advantage that amplifies the spring's effect. This parameter optimization achieves reliable operation with a simple, easily manufactured spring mechanism rather than requiring complex force control systems.
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
Enables reliable and efficient operation by automatically adjusting the ratchet mechanism's state based on load direction, reducing the need for manual switching and ensuring smooth line operation regardless of load direction, while being easy to manufacture and user-adjustable.
Implementation Method 1
spring means biasing the hub to said unloaded limiting position
Implementation Method 2
a ratchet mechanism comprising ratchet teeth provided on the sheave, a pawl mounted on one of the hub and a side cheek for movement between an engaged setting where the ratchet mechanism is active and a free setting where the ratchet mechanism allows free rotation of the sheave
Data Source
AI summary
The present invention provides a ratchet block with a block body 10 having a pair of side cheeks 11,12 and a sheave assembly 15 therebetween, which comprises a hub 16 supporting an annular sheave 17 for rotation about a principal axis. The ratchet block also includes a ratchet mechanism comprising ratchet teeth 19 on the sheave and a pawl 20 mounted on the hub 16 or a side cheek 11,12 for movement between an engaged setting, where the ratchet mechanism is active, and a free setting where the ratchet mechanism allows free rotation of the sheave. An actuator 25 is also mounted on the hub 16 or said side cheek 11,12 and linked to the pawl 20 to effect movement thereof between its engaged and free settings. Means are provided for pivoting the hub between loaded and unloaded limiting positions about an axis parallel to but spaced from the hub's principal axis. Spring means 33 are provided for biasing the hub 16 to said unloaded limiting position. There are also included means 38 for interconnecting the actuator 25 and the other of the hub 16 and said side cheeks 11,12. Pivoting movement of the hub from its unloaded position against the action of the spring means 33 under an applied load on the sheave 17 causes the actuator to effect movement of the pawl 20 to its engaged setting.