Linear Actuator Quick Release With Centrifugal Brake Control
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Solution Overview
Problem
Existing linear actuators used in hospital beds for adjusting back and leg rest sections lack controlled speed regulation during quick release, leading to unsafe and uncontrolled movements, potentially causing injury to patients and mechanical overload.
Innovation Solution
Incorporation of a centrifugal brake mechanism connected to the spindle or tube-shaped positioning element, which is activated during quick release, allowing for self-controlled speed regulation and optional automatic re-engagement for safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a quick release mechanism is used to enable rapid lowering of the back rest section, then the responsiveness and speed of operation are improved, but the control over lowering speed deteriorates leading to uncontrolled acceleration and collision
Solution Approach 1:
The centrifugal brake automatically activates based on the rotational speed of the spindle itself, without requiring external control input. As the spindle rotates faster during quick release, the centrifugal force automatically engages the brake pads against the brake drum, creating a self-regulating system that controls its own speed without operator intervention
Solution Approach 2:
The centrifugal brake mechanism provides automatic feedback control where the rotational speed of the spindle directly influences the braking force. The centrifugal force generated by rotating masses increases with speed, automatically applying greater brake pressure as the spindle accelerates, thereby regulating the lowering speed in real-time
2Ease of operation
If the spindle is non self-locking to allow free rotation during quick release, then the ease of operation is improved, but the safety deteriorates due to uncontrolled acceleration and potential injury
Solution Approach 1:
The centrifugal brake acts as an intermediary safety device between the non self-locking spindle and the patient. It mediates the uncontrolled rotational energy by converting kinetic energy into friction heat through the brake pads contacting the brake drum, thereby preventing the harmful uncontrolled acceleration while maintaining the ease of quick release operation
Solution Approach 2:
The centrifugal brake converts the harmful uncontrolled rotational kinetic energy of the accelerating spindle into beneficial controlled deceleration through friction. The very rotation that causes danger is transformed into the mechanism for control, as the centrifugal force generated by the rotation automatically activates the braking action
3Reliability
If conventional brake mechanisms are used with quick release, then the device complexity increases, but the manufacturing precision and reliability of speed control improve
Solution Approach 1:
The centrifugal brake is a self-activating mechanism that requires no external control system, actuators, or complex control circuitry. It automatically engages and disengages based solely on the rotational speed of the spindle, eliminating the need for additional control components and reducing overall device complexity while maintaining reliable speed control
Solution Approach 2:
The centrifugal brake mechanism extracts and utilizes the rotational kinetic energy already present in the spindle system rather than requiring an separate power source for brake actuation. By using the spindle's own rotation to activate the brake through centrifugal force, the design eliminates complex control systems while achieving reliable speed regulation
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
Ensures controlled and safe lowering of the back rest section, reducing the risk of injury and mechanical overload by regulating the speed of the spindle or positioning element, allowing operators to focus on patient care during critical situations.
Implementation Method 1
the braking means are constituted by a centrifugal brake connected to the spindle when the quick release is activated, alternatively that the braking means are constituted by a centrifugal brake connected to the tube-shaped positioning element
Data Source
Figure 1~13
Figure 3~4
Figure 5
AI summary
A linear actuator with a reversible electric motor (3,11,26,27,34), which over a transmission (4,12,24,25,35) drives a non-self locking spindle (5,14,22,23,36), by which a tube-shaped positioning element can be moved axially, in that it with one end is connected to a spindle nut (6,15) on a spindle (5,14,22,23,36). The actuator comprises a quick release (9,13) for releasing the tube- shaped positioning element (7,16,28,29,37) from the electric motor (3,11,26,27,34) and the part of the transmission (4,12,24,25,35) that lies from the motor (3,11,26,27,34) to the quick release (9,13) such that the spindle (5,14,22,23,36) is set to rotate by the load on the tube-shaped positioning element (7,16,28,29,37). The actuator further comprises braking means for controlling the speed of the tube- shaped positioning element (7,16,28,29,37) during the outer load, when the quick release (9,13) is activated. The braking means consists of a centrifugal brake (38,60), by which it is possible to provide a construction where the lowering speed is self-controlled when the quick release (9,13) is activated.