Two-Speed Trailer Jack Dog Clutch for Faster Extension
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Solution Overview
Problem
Conventional linear trailer jacks require numerous rotations to extend or retract due to a constant small thread pitch, balancing mechanical advantage with time efficiency, leading to cumbersome operation.
Innovation Solution
A two-speed lifting device with a high-speed assembly and a low-speed assembly, automatically switching modes based on ground contact, utilizing different thread pitches to reduce rotations and enhance mechanical advantage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a constant small thread pitch is used in conventional linear trailer jacks, then mechanical advantage is improved for lifting heavy loads, but the number of rotations required to extend or retract the jack increases, worsening operation time and ease of use
Solution Approach 1:
The patent applies dynamics by making the thread pitch variable rather than constant. The jack transitions between a first thread pitch for high-speed extension and a second thread pitch for low-speed retraction, allowing the system to optimize between speed and mechanical advantage dynamically during operation
Solution Approach 2:
The patent segments the operation into two distinct phases with different thread pitches. The first thread pitch is used for rapid extension when the jack needs to reach ground level quickly, while the second thread pitch is used for controlled retraction when lifting the trailer, dividing the operational requirements into separate functional segments
2Strength
If a constant small thread pitch is used in conventional linear trailer jacks, then mechanical advantage is improved for lifting heavy loads, but the number of hand crank rotations required increases, worsening ease of operation
Solution Approach 1:
The patent makes the thread pitch dynamic, switching between a coarser first thread pitch for rapid extension and a finer second thread pitch for controlled retraction. This dynamic adjustment allows operators to benefit from faster operation during extension while maintaining mechanical advantage during retraction, significantly improving overall ease of operation
Solution Approach 2:
The patent changes the thread pitch parameter based on operational phase. By using a first thread pitch with fewer threads per inch for extension and a second thread pitch with more threads per inch for retraction, the system optimizes both speed and control, making the jack easier to operate while maintaining lifting capability
3Loss of time
If a two-speed assembly with different thread pitches is used, then operation time is reduced and ease of use is improved, but device complexity increases due to multiple thread pitches and switching mechanisms
Solution Approach 1:
The patent uses nesting by placing the second sleeve inside the first sleeve, with the second rotating screw inside the first rotating screw assembly. This nested configuration allows two different thread pitch systems to coexist in a compact arrangement, reducing the space required and simplifying the overall structure despite the increased functional complexity
Solution Approach 2:
The patent merges two screw mechanisms with different thread pitches into a single integrated assembly. Both rotating screws share a common axis and are driven by the same hand crank, combining two functions into one unified structure that reduces complexity compared to having separate mechanisms
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 quickly extends to ground level with fewer rotations, improving ease of use and reducing operation time while maintaining the ability to lift heavy loads.
Implementation Method 1
a first rotating screw, a coarse nut, a first sleeve... The first rotating screw is configured to rotate relative to the outer tube. The coarse nut is threadedly coupled to the first rotating screw. The first sleeve is configured to translate with respect to the outer tube
Implementation Method 2
a dog clutch disposed between the first sleeve and the coarse nut, and with the first sleeve in the first position the dog clutch secures the coarse nut from rotating together with the first rotating screw
Data Source
AI summary
A linear jack includes an outer tube, a first rotating screw configured to rotate relative to the outer tube, a coarse nut threadedly coupled to the first rotating screw, and a first sleeve configured to translate with respect to the coarse nut between a first position, wherein the first sleeve is meshingly engaged with the coarse nut, and a second position, wherein the first sleeve is meshingly disengaged from the coarse nut.