Actuator-Integrated Strain Gauges for Bed Egress Detection
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Solution Overview
Problem
Current hospital and care beds with weighing systems for monitoring patient position are expensive due to the use of high-resolution load cells, limiting their widespread use in hospitals and nursing homes, where an egress function to detect patients leaving or attempting to leave the bed is necessary but not economically feasible for all beds.
Innovation Solution
Incorporating a simple, low-resolution strain gauge or piezoelement into the actuator system to detect relative changes in load, allowing for an egress function that triggers alarms when predefined thresholds are exceeded, and integrating this system into existing actuators to provide a cost-effective solution for implementing egress functionality in hospital and care beds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution load cells are used for weighing and monitoring patient position, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the egress detection function from the comprehensive weighing and monitoring system. By using simple strain gauges on actuators to detect only load changes indicating patient egress, rather than full weighing capabilities, the system achieves the necessary safety function with much simpler and less expensive components.
Solution Approach 2:
The patent employs inexpensive strain gauges mounted on existing actuator components rather than expensive, high-precision load cells. These simple strain gauges provide sufficient information for egress detection without the need for high-resolution weighing capabilities, significantly reducing system cost and complexity.
2Measurement precision
If high-resolution load cells are used for weighing systems, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent replaces expensive high-resolution load cells with inexpensive strain gauges that are already present in the actuator components. This substitution maintains sufficient measurement capability for egress detection while dramatically reducing manufacturing costs, enabling widespread deployment in hospitals and nursing homes.
Solution Approach 2:
The patent makes the existing actuator components serve dual functions: both actuation and egress detection. By mounting strain gauges on the actuator thrust rods or mounting brackets, the same mechanical components perform both their primary actuation function and the secondary function of detecting patient egress through load changes.
3Measurement precision
If strain gauge is mounted separately on actuator, then measurement capability is achieved, but device complexity increases
Solution Approach 1:
The patent merges the sensing function with the actuator structure by mounting strain gauges directly on the actuator thrust rods or mounting brackets. This integration combines the actuation mechanism and the sensing element into a single unified component, eliminating separate sensing assemblies and reducing overall system complexity.
Solution Approach 2:
The actuator components are designed to serve multiple functions: the thrust rod provides both actuation force and serves as the mounting substrate for the strain gauge. This multi-functionality eliminates the need for separate sensing components and their associated mounting hardware, simplifying the overall system.
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
Enables the widespread implementation of egress functions in ordinary hospital beds, care beds, and leisure chairs, improving patient care and staff working conditions by providing an economical solution for detecting patient movement and preventing accidents, while also allowing for easy upgrading of existing beds.
Implementation Method 1
the at least one strain gauge is integrated in the actuator... the egress function is based on relative changes in the load on the strain gauge from a preset reference
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A piece of resting furniture such as a bed or chair comprising a least one actuator (4,5) and a control unit (11) and at least one control panel (9,10) to bring about an adjustment of the piece of furniture, and further comprising at least one strain gauge (18,19) connected to an alarm to detect whether a person is occupying the piece of furniture or not wherein the strain gauge (18,19) is located in connection with the actuator (4,5). The function is based on relative changes in the load on the strain gauge (18, 19) from a preset reference thereby allowing use of sensors with low resolution, which thereby are comparatively cheap. Moreover, when placing the strain gauge (18,19) in connection with the actuator (4,5) this simplifies the incorporation thereof in the piece of furniture. Not least the construction also renders it possible in an easy manner to upgrade existing hospital and care beds with an egress function.