Quick-Release Linear Actuator With Centrifugal Brake Coupling
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Solution Overview
Problem
Existing linear actuators used in hospital and care beds are unable to rapidly lower the back-rest section from a raised position to a horizontal position without causing a collision-like braking, which can be injurious to patients and overloads the bed structure.
Innovation Solution
The linear actuator incorporates a centrifugal coupling connected to brake means, allowing the brake to be activated only when the centrifugal coupling is engaged, thereby controlling the spindle's rotational speed and preventing wear during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the spindle is disengaged from the motor and transmission to enable quick release, then the lowering speed is improved, but collision-like braking occurs causing patient injury and structural overload
Solution Approach 1:
A centrifugal coupling device is introduced as an intermediary between the spindle and brake means. This coupling engages the brake only when centrifugal force from rapid rotation activates it, thereby mediating between the quick release function and the need to prevent collision braking. The centrifugal coupling acts as a speed-sensitive switch that automatically activates braking only when necessary.
Solution Approach 2:
The centrifugal coupling provides automatic feedback control based on rotational speed. When the spindle rotates rapidly during quick release, the centrifugal force generated feeds back to engage the brake means, creating a closed-loop control system that automatically regulates speed without external intervention. This prevents collision braking while maintaining quick release capability.
2Object-affected harmful factors
If brake means are always engaged to prevent collision braking, then patient safety is improved, but wear occurs during normal operation reducing reliability
Solution Approach 1:
The brake engagement state is made dynamic rather than static. The centrifugal coupling causes the brake to be engaged only when the spindle rotates above a certain speed threshold, and disengaged during normal low-speed operation. This dynamic engagement pattern eliminates unnecessary wear during normal use while maintaining protection against collision braking when needed.
Solution Approach 2:
The brake means serves itself by being automatically engaged and disengaged through the centrifugal coupling mechanism. The system self-regulates brake engagement based on operational conditions without requiring external control, ensuring the brake is active only when necessary to prevent collision while remaining inactive during normal operation to avoid wear.
3Object-affected harmful factors
If gas springs are added to dampen the movement, then collision braking is prevented, but device complexity and manufacturing costs increase
Solution Approach 1:
The centrifugal coupling serves multiple functions: it acts as a speed-sensing device, a control switch, and an actuator for the brake means. By integrating these functions into a single component that leverages the existing spindle rotation, the solution prevents collision braking without adding separate damping mechanisms like gas springs, thereby avoiding increased structural complexity.
Solution Approach 2:
The passive mechanical damping system (gas springs) is replaced with an active mechanical control system (centrifugal coupling with brake means). Instead of relying on passive elastic elements to absorb energy, the invention uses centrifugal force to actively engage a brake, achieving collision prevention through a different mechanical principle that integrates with the existing drive mechanism.
4Reliability
If a centrifugal coupling is used to control brake activation, then brake wear is reduced, but the coupling mechanism adds device complexity
Solution Approach 1:
The centrifugal coupling is a self-actuating device that uses the kinetic energy of the rotating spindle itself to activate the brake. No external power source, control system, or additional actuation mechanism is required - the system uses its own operational parameters (rotation speed) to control the brake, minimizing added complexity while achieving reliable wear reduction.
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 enables controlled and rapid lowering of the back-rest section without the risk of collision-like braking, ensuring patient safety and reducing the risk of bed structural overload.
Implementation Method 1
a centrifugal coupling connected to the brake means, where the brake means is configured to be in either an active state, where the rotation of the spindle is braked, or an inactive state, where the rotation of the spindle is not braked
Data Source
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AI summary
Linear actuator (8) comprising a quick release (27) for disengagement of an adjustment element (23) from an electric motor (19) and the part of a transmission (20) extending from the electric motor (19) to the quick release (27), such that the spindle (21) of the linear actuator is rotated under the load on the adjustment element (23). Further, the linear actuator comprises brake means (28) connected to the spindle (21) for controlling the speed of the adjustment element (23), when the quick release (27) is activated. A coupling (34;52,53,54) connected the brake means (28) is configured to set the brake means (28) in an active state, when the coupling (34; 52,53,54) is engaged, or in an inactive state, when the coupling (34;52,53,54) is slipping or disengaged.