Shearless Bed Pivot Assembly for Patient Repositioning
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Solution Overview
Problem
Existing patient support systems, such as hospital beds, generate shear forces between the patient and the bed when the upper body section is pivoted, leading to discomfort and sliding motion due to misalignment of the patient's hip joint axis and the bed's pivot axis.
Innovation Solution
A shearless pivot assembly that maintains a stationary pivot axis during initial pivoting from a horizontal to an intermediate orientation, then moves vertically as the head section is raised further, utilizing a combination of actuator, low-friction members, and tracks to reduce shear forces by altering the pivot axis location and providing a stable, user-friendly pivoting mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the Fowler section is rotated upwardly from the horizontal orientation, then the patient's upper body is raised from the flat position, but shear forces are generated between the patient and the bed causing sliding motion
Solution Approach 1:
The pivot axis is made dynamic rather than fixed. During pivoting, the pivot axis moves vertically upward along with the head section, changing its position relative to the patient's body. This dynamic adjustment allows the pivot axis to remain aligned with the patient's hip joint throughout the motion, eliminating shear forces while maintaining ease of patient positioning.
2Device complexity
If a fixed pivot axis is used for the head section, then the structure is simple, but shear forces are generated due to misalignment with the patient's hip joint
Solution Approach 1:
The pivot axis transitions from a fixed position to a dynamic position that moves during operation. The head section's pivot axis is coupled to move vertically upward as the section pivots, maintaining alignment with the patient's hip joint. This dynamic mechanism eliminates shear forces while adding only minimal structural complexity through the coupling arrangement.
3Device complexity
If the pivot axis remains stationary during pivoting, then the mechanism is simple, but the patient's back and buttocks are forced to slide along the bed sections
Solution Approach 1:
The pivot axis is designed to move dynamically during the pivoting operation. As the head section rotates upward, the pivot axis moves vertically upward in coordination with the motion. This dynamic movement prevents the patient's back and buttocks from sliding along the bed sections, significantly improving patient comfort while maintaining a relatively simple pivoting mechanism through the coupling design.
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 significantly reduces shear forces between the patient and the bed, enhancing comfort and stability during pivoting, allowing for smooth transitions from a horizontal to a raised position without the need for patient re-adjustment.
Implementation Method 1
low-friction members coupled to the intermediate section that are adapted to translate horizontally in the tracks as the head section is pivoted
Data Source
AI summary
A patient support apparatus, such as a bed, stretcher, or the like, includes a support deck with a head section pivotable between a generally flat orientation and a raised orientation. As the head section pivots from the flat orientation to an intermediate orientation, the pivot axis of the head section remains generally stationary. As the head section pivots from the intermediate orientation to the raised orientation, the pivot axis of the head section moves. The support deck may include an intermediate section attached to the head section wherein a foot end of the intermediate section moves linearly in a horizontal plane as the head section pivots from the intermediate orientation toward the raised orientation.