Linear Actuator Brake Coupling for Controlled Back-Rest Lowering
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Solution Overview
Problem
Current linear actuators in hospital beds with quick release mechanisms experience uncontrolled and abrupt movement when lowering the back-rest section, causing harm to patients and structural overload, and existing solutions like gas springs complicate the structure and increase costs.
Innovation Solution
A linear actuator design featuring a coupling between the brake means and spindle, allowing the brake to engage or disengage at a predetermined position, reducing the lowering time and maintaining a controlled speed through a rotational damper and gearing system, which is cost-effective and does not require additional structural components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a quick release mechanism is used to enable momentary lowering of the back-rest section, then the lowering speed is improved, but the movement becomes uncontrolled and abrupt causing harm to patients and structural overload
Solution Approach 1:
A brake means is introduced as an intermediary element between the quick release mechanism and the spindle. The brake means includes a brake shoe that can be pressed against a brake drum connected to the spindle, providing controlled resistance to the spindle's rotation during lowering, thereby preventing uncontrolled abrupt movement while maintaining improved lowering speed
Solution Approach 2:
A coupling mechanism with a contact element is implemented that detects the spindle's position and provides feedback control. When the contact element engages with the coupling, it activates the brake means to engage the brake shoe against the brake drum, creating a feedback loop that maintains controlled speed throughout the lowering process
2Object-affected harmful factors
If gas springs are added to dampen the movement during lowering, then the harmful effects are reduced, but the structure becomes more complicated and expensive
Solution Approach 1:
The brake means is merged with the existing quick release mechanism by integrating the brake shoe, brake drum, and coupling elements into the same housing structure. The brake drum is connected to the spindle within the existing actuator assembly, and the coupling mechanism utilizes the same contact element already present in the quick release mechanism, thereby dampening harmful effects without requiring separate gas spring components or additional structural brackets
Solution Approach 2:
The coupling mechanism serves multiple functions: it acts as both the activation mechanism for the quick release and the activation mechanism for the brake means. The contact element simultaneously controls both the disengagement of the drive connection and the engagement of the brake shoe, eliminating the need for separate control systems and reducing overall structural complexity
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 achieves a controlled and faster lowering of the back-rest section, reducing the risk of injury and structural overload while maintaining a cost-effective and simplified design.
Implementation Method 1
a rotational damper (51) of the fluid type... which generates a dampening effect, which dampens the speed of the spindle (22)
Implementation Method 2
brake means (52) for controlling the speed of the spindle (22)... where the brake means can be brought into direct or indirect engagement with the spindle (22)
Data Source
AI summary
Linear actuator comprising a reversible electric motor (20), a transmission (21), a non-self-locking spindle (22), where the reversible electric motor (20) through the transmission (21) drives the non-self-locking spindle (22) and a spindle nut (23) on the spindle (22). The actuator further comprises an adjustment element (24) secured against rotation and where the adjustment element (24) can be moved axially, as it is connected to or integrated with the spindle nut (23) on the spindle (22). Further, that actuator comprises position means for determining the position of the spindle nut (23), brake means for controlling the speed of the spindle nut (23) under the external load. Between the brake means and the spindle there is a coupling in connection with the position means for determining the position of the spindle nut (23). The coupling engages the brake means to the spindle or disengages the brake means from the spindle, when the spindle nut (23) is in a predetermined position on the spindle (22).