Height-Adjustable Table with Block-and-Tackle Spring Counterbalance
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Solution Overview
Problem
Existing height-adjustable tables with counter-balance mechanisms often require significant user effort to adjust the work surface height due to fixed cross-beams and limited mechanical advantage, leading to inefficient load distribution and aesthetic constraints.
Innovation Solution
A height-adjustable table design featuring a pulley mechanism, a spring with a load adjustment mechanism, and a block-and-tackle assembly that transfers the upward force exerted by the spring over a greater distance, allowing for smoother and easier vertical movement of the work surface, with a mechanical advantage of at least 10:1, and housing components within a vertically movable frame for aesthetic and space benefits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixed cross-beam is used to house counter-balance mechanism components, then the structural stability is improved, but the aesthetic appeal and space utilization deteriorate
Solution Approach 1:
The counter-balance mechanism components (spring, pulleys, tension lines) are extracted from the traditional fixed cross-beam location and relocated to the hollow interior space of the vertically movable frame. This extraction allows the mechanism to be hidden within the frame structure, improving aesthetic appeal while maintaining structural stability through the frame's telescoping leg design.
Solution Approach 2:
The counter-balance mechanism components are nested within the hollow frame structure. The spring, pulley mechanism, and tension lines are contained inside the frame's interior space, allowing the mechanism to be integrated into the frame's vertical movement capability. This nesting eliminates the need for external cross-beams while maintaining structural integrity.
2Device complexity
If a simple spring mechanism is used for height adjustment, then the device complexity is reduced, but the user effort and mechanical advantage deteriorate
Solution Approach 1:
A pulley mechanism acts as an intermediary between the spring and the frame. The pulleys redirect and multiply the force generated by the spring, providing mechanical advantage to the user. This intermediary system allows a relatively simple spring to generate sufficient lifting force while reducing the effort required by the user to adjust the table height.
Solution Approach 2:
The block-and-tackle assembly with multiple pulleys creates a mechanical advantage system where the tension line moves through a series of pulleys in a periodic fashion. This multi-stage force transmission allows the spring's force to be amplified and distributed efficiently, reducing user effort while maintaining operational simplicity.
3Force
If the spring force is applied directly to the frame, then the mechanical advantage is improved, but the range of movement and smoothness of adjustment deteriorate
Solution Approach 1:
The pulley mechanism and block-and-tackle assembly serve as intermediaries that extend the distance over which the spring force is applied. By routing the tension line through multiple pulleys, the system converts the spring's limited displacement into a greater vertical movement range for the frame, while maintaining smooth force application throughout the adjustment range.
Solution Approach 2:
The pulley system transforms the one-dimensional linear motion of the spring into a multi-dimensional force application path. The tension line travels through multiple pulleys in different spatial orientations, effectively extending the range of movement and smoothing the load curve across the entire adjustment range while preserving mechanical advantage.
4Force
If variable radius force-exchange wheels are used to adjust load curve, then the load distribution is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of using variable radius wheels with complex geometries, the patent achieves load curve adjustment by changing the configuration and arrangement of fixed pulleys in the block-and-tackle assembly. The mechanical advantage and load distribution are controlled by the number and arrangement of pulleys, which can be manufactured with standard dimensions and assembled in different configurations to achieve desired load characteristics.
Solution Approach 2:
The force-exchange function is segmented into multiple discrete pulley stages rather than requiring a single complex variable radius wheel. Each pulley in the block-and-tackle assembly provides a fixed mechanical advantage, and the cumulative effect of multiple pulleys achieves the desired variable load curve. This segmentation allows each component to be manufactured independently with standard tolerances.
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 solution provides a more efficient and user-friendly height adjustment mechanism with a smoother load curve over a greater range of movement, reducing user effort and enhancing the aesthetic appeal by concealing the counter-balance components within a hollow frame.
Implementation Method 1
The spring can have a fixed end connected to the frame and a movable end adapted to move a first distance relative to the fixed end. The spring can be adapted to exert an upward force on the frame over the first distance.
Implementation Method 2
The pulley mechanism can include a first plurality of pulleys located in the passage, a first tension line, and a second tension line. The block-and-tackle assembly can include a fixed block having a second plurality of pulleys and being connected to the frame; a movable block having a third plurality of pulleys
Implementation Method 3
The block-and-tackle assembly can be adapted to cooperate with the pulley mechanism to transfer the upward force exerted by the spring over the first distance to the frame, wherein the force exerted by the spring over the first distance contributes to upward vertical movement of the frame over a second distance. The second distance can be greater than the first distance.
Implementation Method 4
The first and second tension lines can pass through the first plurality of pulleys. The first line can be adapted for vertically moving the first upper leg within the first lower leg and the second line can be adapted for vertically moving the second upper leg within the second lower leg.
Data Source
AI summary
A height-adjustable table includes a frame supporting a work surface; a pair of lower legs supporting the frame; a pulley mechanism coupling the frame and the lower legs for vertically moving the frame relative to the lower legs; and a spring located within a passage extending through the frame. The spring has a fixed end secured to the frame and a movable end movable relative to the frame over a first distance for exerting a force over the first distance. The table further includes a block-and-tackle assembly located within the passage. The block-and-tackle assembly couples the movable end of the spring to the pulley mechanism for transferring the force exerted by the spring over the first distance to vertical movement of the frame relative to the lower legs over a second distance greater than the first distance.