Variable Wheelbase Hand Truck Subframe Pivot
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Solution Overview
Problem
Conventional hand trucks, whether 2-wheel or 4-wheel, face limitations in maneuverability and stability, especially when transitioning between flat surfaces and obstacles like stairs, and convertible models are often cumbersome due to fixed wheelbases and complex reconfiguration requirements.
Innovation Solution
A hand truck with a variable wheelbase that can be selectively altered between short and long configurations while loaded, allowing for optimized stability and maneuverability without the need for separate actuators or controls, by changing the tilted orientation and speed to pivot the subframe between positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a hand truck uses a fixed wheelbase design, then the frame structure is simpler, but the maneuverability and stability are reduced when transitioning between flat surfaces and obstacles
Solution Approach 1:
The patent applies the dynamics principle by making the wheelbase adjustable between short and long configurations. The subframe can be pivoted between a first position (short wheelbase) and a second position (long wheelbase), allowing the hand truck to adapt its geometry dynamically based on the operational requirements - whether navigating flat surfaces or obstacles like stairs.
2Ease of operation
If a hand truck uses a 2-wheel configuration, then the maneuverability is improved, but the operator must partially support the load causing strain and fatigue
Solution Approach 1:
The patent resolves this contradiction by enabling dynamic configuration switching. When the subframe is in the second position (long wheelbase), the hand truck operates in a 4-wheel configuration that supports the entire load, eliminating operator strain. When in the first position (short wheelbase), it provides 2-wheel maneuverability for tight spaces, giving the operator choice based on the task at hand.
3Ease of operation
If a hand truck uses a 4-wheel configuration, then the load support is improved, but the maneuverability and stability when traversing obstacles are reduced
Solution Approach 1:
The patent applies dynamics by allowing the wheelbase to be adjusted between long and short configurations. The long wheelbase (second position) provides superior load support and stability on flat surfaces, while the short wheelbase (first position) enhances maneuverability for traversing obstacles like stairs, allowing the operator to optimize for each specific task.
4Adaptability or versatility
If a hand truck requires reconfiguration between 2-wheel and 4-wheel operation, then the functionality is improved, but the reconfiguration process is cumbersome and requires load removal
Solution Approach 1:
The patent applies the self-service principle through gravity-assisted automatic positioning. The subframe automatically pivots to the appropriate position (first or second) based on the operator's tilting action and the load's center of gravity, eliminating the need for manual reconfiguration mechanisms, latches, or load removal. The system self-adjusts based on operational conditions.
5Stability of the object's composition
If a hand truck has a long wheelbase configuration, then the stability is improved, but the maneuverability for tight spaces and obstacles is reduced
Solution Approach 1:
The patent resolves this stability-manueverability contradiction by making the wheelbase dynamically adjustable. The long wheelbase (second position) provides enhanced stability for transporting loads on flat surfaces, while the short wheelbase (first position) improves maneuverability for navigating tight spaces and obstacles, allowing the operator to select the optimal configuration for each situation.
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
This solution reduces operator strain and allows for seamless transitions between configurations, providing enhanced stability and control during both flat surface and obstacle navigation without requiring load removal or complex reconfiguration.
Implementation Method 1
When in the loaded position, the load automatically positions the wheelbase varying assembly in the second wheelbase position in response to a center of gravity of the load
Data Source
AI summary
A kit for modifying a wheeled apparatus comprises a set of caster unit mounts, a set of caster units, a subframe mounting structure, and a subframe. Each caster unit mount has a caster unit mounting structure and a main frame engaging structure attached to the caster unit mounting structure. The main frame engaging structure is attachable to a main frame and/or a load support structure of the wheeled apparatus. Each caster unit has a mounting portion configured for being secured to the caster unit mounting structure of a respective caster unit mount such that a first-size wheel thereof can rotate about of a rotational axis thereof and pivot about a pivot axis thereof. The subframe mounting structure, which is attachable to the main frame, has a first end portion pivotably attached to the subframe mounting structure and a second end portion having a second size wheel mounting structure integral therewith.