Bed Exit Detection Using Tactile Switches in Mattress Gap
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Solution Overview
Problem
Existing devices for detecting a person's presence or change in body position on a bed face issues with sensitivity control, high manufacturing and maintenance costs, and difficulty in attachment and detachment, particularly when using piezoelectric elements or pressure-sensitive sensors.
Innovation Solution
The use of tactile switches, commonly found in computer keyboards, arranged in a specific gap beneath a mattress biased by elastic members to detect the presence or absence of a person and changes in body position, allowing for easy attachment and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoelectric element is used as a sensor, then detection sensitivity is improved, but manufacturing cost and maintenance cost increase
Solution Approach 1:
The patent replaces expensive piezoelectric elements with inexpensive pressure-sensitive sheets that can be easily replaced. The pressure-sensitive sheet is a low-cost consumable item that maintains adequate detection sensitivity while significantly reducing both manufacturing and maintenance costs compared to piezoelectric sensors.
Solution Approach 2:
The patent substitutes the mechanical piezoelectric sensing mechanism with a simpler pressure-sensitive sheet mechanism. This replacement uses basic pressure sensitivity rather than piezoelectric crystal effects, simplifying the system while maintaining functional adequacy for bed exit detection.
2Ease of manufacture
If a pressure-sensitive sensor sheet is used, then manufacturing cost is reduced, but attachment to mattress becomes difficult
Solution Approach 1:
The patent divides the sensing system into separate functional components: the pressure-sensitive sheet and the mattress. The sheet is positioned in the gap between the mattress and bed frame, eliminating the need to attach sensors directly to the mattress while maintaining sensing functionality.
Solution Approach 2:
The patent introduces the gap space between the mattress and bed frame as an intermediary location for placing the pressure-sensitive sheet. This intermediary position allows the sheet to function without direct attachment to the mattress, solving the attachment difficulty while maintaining cost advantages.
3Device complexity
If a sensor is placed on the floor beside the bed, then device complexity is reduced, but detection reliability deteriorates
Solution Approach 1:
The patent moves the sensor placement from the horizontal plane (floor beside bed) to the vertical dimension (gap between mattress and bed frame). This dimensional change allows direct detection of mattress pressure changes while maintaining simple device structure.
4Reliability
If a sensor is placed on the bed mat, then detection reliability is improved, but patient comfort deteriorates
Solution Approach 1:
The patent extracts the sensor from the mattress surface itself and places it in the gap below the mattress. This extraction removes the harmful factor of sensor presence affecting patient comfort while preserving the detection function through indirect pressure sensing.
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 solution provides reliable detection of getting out of bed, prevents bedsores, and is cost-effective, with easy installation and maintenance, as tactile switches are inexpensive and can be easily replaced.
Implementation Method 1
an elastic member that biases the lower surface of a mattress upward
Implementation Method 2
a tactile switch, which is applied to a keyboard of a personal computer and the like, as a sensor part
Data Source
Figure 1
Figure 2A~3A
Figure 3B~4
AI summary
A device 1 for checking getting out of bed for use in a bed includes a plurality of tactile switches 6, and a controller 3 that detects the presence or absence of a person and/or change of the body position of the person on a mattress 21 on the basis of ON or OFF of the tactile switches 6. The tactile switches 6 are arranged in a gap 25 formed while a person is not present on the mattress 21 between a lower surface 21a of the mattress 21 and a floor material 26 of a bed 20 to hold the mattress 21 thereover by an elastic member (butterfly spring 23 or resin elastic member 10) that biases the lower surface 21a of the mattress 21 upward. The device 1 for checking getting out of bed can be provided at low cost, easy to attach to and detach from a bed, and easy to maintain.