Nested Piston Hydraulic Cylinder for MRI Bed Height Adjustment
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Solution Overview
Problem
Existing hydraulic cylinders used in beds, such as MRI beds, face size constraints and structural weaknesses due to side loads, limiting their ability to efficiently raise and lower beds across a range of patient heights.
Innovation Solution
A two-piston hydraulic cylinder design with nesting pistons, where one piston rod has a cavity and the other has a smaller outer diameter, allowing for a shorter closed configuration while maintaining the same extended length, and featuring adjustable heads and stop members for fluid injection and prevention of piston extension beyond the cylinder ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a traditional single-piston hydraulic cylinder is used, then the structure is simple, but the closed configuration length is excessive and limits bed height adjustment range
Solution Approach 1:
The patent implements a nested piston configuration where a first piston rod with a cavity contains a second piston rod with a smaller outer diameter. When retracted, the second piston rod nests within the cavity of the first piston rod, both housed inside the cylinder body. This nesting arrangement significantly reduces the closed configuration length compared to traditional single-piston cylinders, enabling compact storage while maintaining full extension capability for bed height adjustment.
2Strength
If the cylinder diameter is increased to accommodate larger piston rods, then the structural strength improves, but the size constraints are violated
Solution Approach 1:
By nesting the second piston rod within the cavity of the first piston rod, the design achieves adequate structural strength for both piston rods without requiring an increase in overall cylinder diameter. The nested arrangement allows each piston rod to maintain its required strength characteristics while occupying the same radial space, thus satisfying size constraints for MRI bed applications.
Solution Approach 2:
The invention transitions from a single-dimensional piston arrangement to a multi-dimensional nested configuration. The first piston rod provides structural strength in one dimension while the second piston rod utilizes the internal cavity space, effectively distributing structural requirements across different spatial dimensions without increasing the external cylinder diameter.
3Adaptability or versatility
If side loads are applied to the cylinder, then the cylinder can accommodate lateral forces, but structural weak points develop
Solution Approach 1:
The dual-piston design segments the load-bearing function into two separate piston rods, each capable of independently handling side loads. This segmentation distributes the mechanical stress that would otherwise concentrate at single weak points in a traditional cylinder, enhancing reliability while maintaining the ability to accommodate lateral forces during bed operation.
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 design enables a larger range of bed height adjustments, accommodating patients of varying sizes without increasing cylinder diameter or adding complexity, thus enhancing reliability and reducing manufacturing costs.
Implementation Method 1
a first injection port on the first head, for injecting hydraulic fluid into the hydraulic cylinder, and a second injection port on the second head, for injecting hydraulic fluid into the hydraulic cylinder
Data Source
AI summary
A hydraulic cylinder may include a cylindrical body, a first piston rod coupled with a first end of the body, and a second piston rod coupled with a second end of the body. The first piston rod may include a cavity with an inner diameter, and the second piston rod may have an outer diameter that is smaller than the inner diameter of the cavity. The hydraulic cylinder is adjustable from a closed position, in which a length of the first piston rod is housed inside the body and a length of the second piston rod is housed inside the cavity of the first piston rod, to an extended position, in which the first piston rod extends through the first end of the body and the second piston rod extends through the second end of the body.