Lever-Based Post Removal Device with Curved Grippers
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Solution Overview
Problem
Existing devices for removing star pickets, which are firmly embedded in the ground, are not commercially successful due to their complexity and inefficiency in gripping and lifting the posts.
Innovation Solution
A post removal device featuring a rotatable lever with a gripping arrangement that includes curved, serrated grippers, allowing for effective gripping and lifting of star pickets by rotating the lever to move the grippers from an open to a gripping condition, enabling the posts to be lifted and removed from the ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If existing post removal devices are used, then posts can be removed, but the devices are complex and not commercially successful
Solution Approach 1:
The device is divided into distinct functional segments: a lever arm for mechanical advantage, a fulcrum for pivot rotation, and separate gripping elements that can independently engage the post. This segmentation allows each component to be simple in design while collectively achieving reliable post removal.
Solution Approach 2:
Instead of trying to pull the post directly upward, the device uses the fulcrum to invert the force application - pushing down on one end of the lever causes the gripping end to lift upward, extracting the post from the ground through mechanical inversion of the applied force.
2Force
If posts are firmly embedded in the ground, then they are securely installed, but they become difficult to remove
Solution Approach 1:
The fulcrum acts as a counterbalance point that allows a relatively small downward force on the lever to generate a much larger upward lifting force on the post. The mechanical advantage created by the lever arm ratios enables the operator to overcome the firmly embedded post with minimal effort.
Solution Approach 2:
The gripping elements feature curved or serrated surfaces that conform to the cylindrical shape of the post, maximizing contact area and friction. This curvature allows the grippers to securely engage the round post surface, preventing slippage during the lifting operation.
3Strength
If the grippers need to grip firmly, then the post can be lifted, but the gripping mechanism becomes complex
Solution Approach 1:
The gripping elements are designed to dynamically adapt to the post during the lifting process. As the lever rotates and applies force, the grippers naturally conform to the post's position and orientation, maintaining optimal grip strength without requiring complex adjustment mechanisms.
Solution Approach 2:
The arms serve as intermediary elements that transmit the lifting force from the lever to the grippers while allowing relative movement and adjustment. This intermediary mechanism enables the grippers to maintain firm contact with the post without requiring direct rigid connection, simplifying the overall gripping mechanism.
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 device provides a simple and effective method for removing star pickets, allowing for easy operation by one laborer to lift the post, with the ability to grip and lift firmly embedded posts using minimal lifting movements, making the process straightforward and efficient.
Implementation Method 1
a lever which is rotatable about the fulcrum through a substantially vertical plane; the lever extending on either side of the fulcrum to define a first portion on one side and a second portion on the other side, whereby downward movement of the first portion results in upward movement of the second portion
Implementation Method 2
each of the post grippers include a gripping surface for gripping a post and that surface be a curved, serrated surface. Such a surface can provide extremely good gripping characteristics against opposite sides of a post
Data Source
AI summary
A post removal device (10), including a support (11), and a lever (12) which is rotatable about a fulcrum (13). The lever (12) extends on either side of the fulcrum (13) to define a first portion (14) and a second portion (15), whereby downward movement of the first portion (14) results in upward movement of the second portion (15). The second portion (15) is connected to a gripping arrangement (19) which includes a pair of post grippers (23), which are movable during rotation of the lever (12), from an open condition to a gripping condition. The extent of rotational movement of the lever (12) is sufficient for the grippers (23) to move from the open condition to the gripping condition and for the gripping arrangement (19) to be lifted with the grippers (23) in the gripping condition for lifting a post.