Multi-Leaf Collimator Actuator With Non-Rotating Screw Drive
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Solution Overview
Problem
Existing leaf actuators in multi-leaf collimators face a trade-off between speed, accuracy, stability, and durability, with conventional designs limiting the maximum possible linear speed due to vibration and positioning issues.
Innovation Solution
A leaf actuator design where the leaf actuator screw is rigidly attached to the leaf, allowing linear motion without rotation, using a rotatable part to translate rotational motion into linear motion, enhancing stability and durability while enabling higher speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional leaf actuator designs are used, then positioning accuracy and stability are maintained, but leaf movement speed is limited due to vibration and positioning issues
Solution Approach 1:
The actuator system is segmented into distinct functional components: a rotatable part (motor assembly) and a non-rotatable part (screw assembly rigidly attached to the leaf). This segmentation allows the rotatable component to provide driving torque while the non-rotatable component ensures stable, vibration-free linear motion, thereby increasing leaf movement speed without compromising reliability.
Solution Approach 2:
The patent introduces a threaded engagement mechanism as an intermediary between the rotatable part and the non-rotatable part. The rotatable part contains a threaded bore that engages with a threaded portion on the non-rotatable part, converting rotational motion into precise linear motion. This intermediary mechanism enables high-speed movement while maintaining positioning accuracy and actuator stability.
2Speed
If leaf actuator screw is allowed to rotate with the motor, then rotational motion is converted to linear motion, but vibration and positioning accuracy deteriorate at high speeds
Solution Approach 1:
Instead of allowing the screw to rotate with the motor (conventional approach), the patent inverts the approach by rigidly attaching the screw to the leaf so it remains non-rotatable. The motor assembly rotates around the stationary screw, converting rotational motion into linear motion through threaded engagement. This inversion eliminates vibration and maintains positioning accuracy even at high speeds.
Solution Approach 2:
The patent extracts the rotational function from the screw component and concentrates it in the motor assembly. The screw's sole function becomes providing linear motion guidance and force transmission, while the motor assembly handles all rotational motion. This separation of functions eliminates the vibration caused by rotating screws and improves positioning accuracy.
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 new design achieves faster and more accurate leaf movement, ensuring precise aperture shaping and radiation delivery even with patient movement, minimizing healthy tissue exposure.
Implementation Method 1
a leaf actuator design where the leaf actuator screw is rigidly attached to the leaf, allowing linear motion without rotation, using a rotatable part to translate rotational motion into linear motion
Data Source
AI summary
A leaf unit for a multi-leaf collimator may comprise a leaf, a leaf actuator screw, a rotatable part threadably engaged with the leaf actuator screw, a leaf actuator motor, and a supporting bracket. The leaf actuator screw including a first end fixedly attached to the leaf and the leaf actuator motor being coupled to the rotatable part. The support bracket comprising a first portion with a first opening arranged to receive and support the leaf actuator motor and a second portion with a second opening including a bearing. The second opening being arranged to receive and support the rotatable part. A center of the first opening is aligned with that of the second opening so that an axis of the leaf actuator motor and an axis of the rotatable part of each leaf actuator are colinear.