Quick-Releasing Linear Actuator for Hospital Beds
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Solution Overview
Problem
Conventional linear actuators for electric hospital beds are bulky due to the internal worm gear mechanism, and require excessive force to operate, which is impractical during emergency situations like CPR, and can become non-functional if the motor fails.
Innovation Solution
A quick-releasing linear actuator design featuring a clutch mechanism that allows the screw to rotate freely from the worm gear, enabling rapid retraction of the telescopic rod without needing motor power, with a pulling arm mechanism that disengages the clutch and reduces the overall size and operational force required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the worm gear is positioned within the base and axially movable with respect to the screw, then the transmission function is achieved, but the space necessary for the base is larger and the overall size of the linear actuator is greatly increased
Solution Approach 1:
The worm gear is nested within the base structure, with the clutch mechanism integrated inside the base. The clutch base is fixedly connected to the screw, and the clutch is connected to the fixing sleeve, creating a compact nested arrangement that reduces the overall volume while maintaining functionality.
Solution Approach 2:
The transmission system is segmented into distinct functional components: the worm gear for transmission, the clutch mechanism for engagement/disengagement, and the fixing sleeve for positioning. This segmentation allows each component to be optimized independently and reduces the overall base space required.
2Speed
If the pulling arm directly pulls the engaging worm and worm gear, then the quick release function is achieved, but a lager pulling force is needed which easily causes a large movement or a large force incompatible with the emergency case like the CPR
Solution Approach 1:
The clutch mechanism acts as an intermediary between the pulling arm and the worm gear. When the pulling arm pulls the clutch, the clutch base rotates relative to the clutch, which in turn disengages the worm gear from the screw. This indirect mechanism reduces the pulling force required while maintaining quick release functionality.
Solution Approach 2:
The clutch mechanism introduces dynamic engagement and disengagement. The clutch can rotate relative to the clutch base, allowing the system to transition smoothly between engaged and disengaged states. This dynamic behavior reduces the impulse force during release while maintaining speed.
3Reliability
If the motor is out of order, then the worm becomes immobile and locked, but the pulling arm cannot pull out the worm gear along the screw, disenabling to function normally
Solution Approach 1:
The clutch mechanism is designed to be manually operable without requiring motor power. When the pulling arm pulls the clutch, the clutch base rotates relative to the clutch, automatically disengaging the worm gear from the screw. This self-service mechanism allows the system to function normally even when the motor is out of order.
Solution Approach 2:
The clutch mechanism introduces dynamic engagement and disengagement. The clutch can rotate relative to the clutch base, allowing the system to transition smoothly between engaged and disengaged states. This dynamic behavior reduces the impulse force during release while maintaining speed.
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 rapid position adjustment of hospital beds during emergencies, reduces the actuator's size and operational force, and maintains functionality even if the motor fails, meeting the demands of emergency medical situations.
Implementation Method 1
a worm gear connected to one end of the screw and engaged with the worm inside the base
Implementation Method 2
a telescopic tube threadedly connected to the other end of the screw
Implementation Method 3
By An external damper or braking system or by the internal friction of the actuator, the speed or the time to release the actuator can be adjusted depending the demand of the application
Implementation Method 4
a pulling arm means comprising a pulling arm pivotably connected to the outside of the base of the motor means, wherein the pulling arm is provided with poking portions corresponding to the clutch for controlling the clutching action between the clutch and the clutch base
Implementation Method 5
a telescopic tube threadedly connected to the other end of the screw
Data Source
AI summary
A quick-releasing linear actuator suitable for electric hospital beds includes a motor, a transmission device, a clutch device and a pulling arm device. With the pulling of the pulling arm of the pulling arm device, a clutch and a clutch base of the clutch device can be disengaged, such that the screw of the transmission device will not be impeded by the worm gear. When a force is exerted to the telescopic rod of the transmission device, the screw can rotate by itself to rapidly lower the telescopic rod, thereby to achieve the rapid releasing of the hospital beds.