Patient Support Load Cell Assembly for Self-Aligning Weight Measurement

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Solution Overview

Problem

Conventional patient support apparatuses face challenges in achieving repeatable and high-accuracy weight and movement detection due to manufacturing inconsistencies, tolerance stack-up, wear, and patient weight shifting, leading to inaccurate load cell readings.

Innovation Solution

A patient support apparatus with load cell assemblies featuring a bushing and shaft configuration that allows for limited pivoting and translational movement, utilizing a bushing with tapered regions and a central region to maintain alignment and minimize mechanical binding, ensuring accurate load measurements despite shifting loads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional rigid load cell assemblies are used, then structural stability is maintained, but measurement precision deteriorates due to mechanical binding and alignment issues from manufacturing inconsistencies and wear

Engineering Contradiction:

Improveload measurement accuracyVSAvoidreading consistency

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The load cell assembly incorporates a shaft that can pivot and translate within the bushing, transforming the rigid structure into a dynamic system. This allows the shaft to self-align with the central region of the bushing in response to varying load positions, preventing mechanical binding and maintaining measurement accuracy despite manufacturing tolerances and wear

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The design changes the operational parameters of the load cell by allowing limited pivoting and translational movement of the shaft. This parameter change enables the system to adapt to load shifting and maintain alignment between the shaft and bushing central region, thereby preserving measurement precision under varying conditions

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If rigid mounting is used to ensure structural stability, then ease of manufacture is improved, but adaptability deteriorates due to inability to accommodate load shifting and manufacturing variations

Engineering Contradiction:

Improveaccommodation of load shiftingVSAvoidbushing and shaft configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The bushing acts as an intermediary element between the fixed body and the movable shaft. It provides a controlled environment for the shaft to pivot and translate while maintaining alignment through its central region geometry, mediating between the rigid mounting structure and the dynamic load-bearing shaft

Inventive Principle:

Principle #24Intermediary (Mediator)

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 ensures precise and repeatable load measurements by allowing limited movement of the shaft within the bushing, preventing mechanical binding and maintaining accurate readings even with shifting loads, thereby improving the reliability of weight and movement detection.

Implementation Method 1

permit limited pivoting and translational movement between the shaft and the bushing in response to load shifting between the plurality of load cell assemblies

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

urge the reduced diameter region of the shaft into alignment with the central region of the bushing

Methodology Applied

Scientific EffectNormal force: Mechanical Force

Data Source

PatentUS20260041593A1Load Cell Assembly For A Patient Support Apparatus

Publication Date: 2026.02.12 STRYKER CORP

AI summary

A patient support apparatus includes a support structure including a base, an intermediate frame, and a patient support deck and a lift mechanism for moving the patient support deck relative to the base. A plurality of load cells are interposed between the lift mechanism and the support structure to measure load about the patient support surface. Each of the plurality of load cell assemblies includes a body, a bushing, and a shaft. The bushing is configured to be received by the body and defines opposing tapered regions and a central region. The shaft is configured to be received by the bushing and defines a reduced diameter region arranged to engage the central region of the bushing to urge the shaft into alignment with bushing and to permit limited pivoting and translational movement between the shaft and the bushing in response to load shifting between the plurality of load cell assemblies.