Linear Motor Contour Collimator Eliminates Backlash
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Solution Overview
Problem
Existing multi-leaf collimators for radiotherapy face challenges in achieving high precision and compactness due to mechanical backlash and the need for numerous drive transmission parts, which affect the accuracy and dynamic behavior of diaphragm element movement.
Innovation Solution
A contour collimator design utilizing linear motors with directly fixed rods to diaphragm elements, eliminating mechanical backlash and reducing the number of transmission parts, allowing for precise and dynamic movement without additional position sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electric motors with mechanical transmission are used to drive each diaphragm element, then the diaphragm elements can be positioned with acceptable accuracy, but mechanical backlash and numerous transmission parts reduce positioning precision and increase device complexity
Solution Approach 1:
The patent extracts and eliminates the mechanical transmission components (gears, belts, linkages) from the drive system. By using linear motors that directly drive the diaphragm elements without intermediate transmission mechanisms, the design removes the source of mechanical backlash while reducing the number of parts, thereby improving positioning accuracy and simplifying the overall device structure
Solution Approach 2:
The patent replaces the conventional mechanical motor-transmission system with a direct-drive linear motor system. This substitution eliminates mechanical backlash by removing the mechanical transmission chain entirely, using electromagnetic force directly to position the diaphragm elements with high precision, thus resolving the contradiction between positioning accuracy and device complexity
2Manufacturing precision
If more and thinner leaves are used to precisely recreate the shape of the treatment object, then the contour accuracy is improved, but the number of motors and drive transmissions increases, requiring more space and increasing weight
Solution Approach 1:
The patent extracts and removes the heavy mechanical transmission components from each leaf module. By eliminating gears, belts, and linkages that would be required to drive each thin leaf individually, the design significantly reduces the weight of the moving collimator assembly while maintaining the capability to precisely position numerous thin leaves for accurate contour recreation
Solution Approach 2:
The patent replaces the mechanical motor-transmission system with direct-drive linear motors. This substitution eliminates the need for heavy transmission parts while enabling precise control of multiple thin leaves, thus achieving high contour accuracy without proportionally increasing the weight of the collimator assembly
3Length of moving object
If a compact and lightweight collimator design is implemented, then the irradiation head can be moved more easily to various angles, but reducing the number of drive transmission parts may compromise positioning accuracy
Solution Approach 1:
The patent replaces mechanical transmission systems with direct-drive linear motors, eliminating the need for complex gear trains and linkages that would occupy significant space. This substitution enables a compact collimator design that can be easily moved to various irradiation angles while maintaining high positioning accuracy through the precise control capabilities of linear motors
Solution Approach 2:
The patent changes the fundamental operating parameters of the drive system by transitioning from rotary motors with mechanical transmission to linear motors with direct electromagnetic drive. This parameter change enables compact positioning of diaphragm elements without compromising accuracy, as linear motors provide high precision control in a space-efficient configuration
4Measurement precision
If linear motors with direct rod fixation are used, then mechanical backlash is eliminated and positioning accuracy is improved, but the direct connection requires precise manufacturing of the rod-diaphragm interface
Solution Approach 1:
The patent merges the drive rod and diaphragm element into a single integrated component or precisely coupled assembly. By combining these elements, the design eliminates the need for separate mating interfaces that could introduce backlash, while the manufacturing precision requirements are concentrated into a single integrated structure rather than multiple separate parts
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 design achieves high position accuracy, reduced assembly size and weight, and enhanced dynamic movement capabilities, simplifying control and serviceability while maintaining precision and stability.
Implementation Method 1
The drive is a linear motor, wherein each linear motor comprises a linearly movable rod directly fixed to each diaphragm element
Data Source
AI summary
The invention relates to a contour collimator for radiotherapy, comprising a plurality of plate-shaped diaphragm elements provided in a guiding block and movably arranged with respect to one another to form a contour diaphragm for a radiation beam emitted by a radiation source towards the collimator, and at least one drive for moving the diaphragm elements, wherein a drive of its own is associated with each diaphragm element, the drives of a group of diaphragm elements are arranged substantially adjacent to one another, and the drive is a linear motor, wherein each linear motor comprises a linearly movable rod directly fixed to the associated diaphragm element. The invention facilitates a design of a contour collimator with a shape being as compact as possible, and wherein both precise and stable adjustability of the diaphragm elements is achieved without a backlash. In this way improvements to contour collimators are provided.