Positioning Arm With Cam-Actuated Joint Locking
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Solution Overview
Problem
Existing positioning arms for medical instruments face challenges in ergonomics, usability, and reliability, requiring high forces for operation and being prone to misalignment, especially in sterile environments, with complex and costly designs that compromise sterility and durability.
Innovation Solution
A positioning arm with a central joint and additional joints, featuring a blocking device operated via a transmission device formed by pincer arms, allowing for low actuation forces and easy operation, independent of user strength, with a compact and easily sterilizable design suitable for MRI environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a ratchet is used to lock the rotary joint, then the locking force required is reduced and operation in sterile environment is enabled, but the operation remains dependent on user skill and residual misalignment risk persists
Solution Approach 1:
The positioning arm enables self-positioning through the interaction of spring elements and cam surfaces. The spring elements automatically engage with the cam surfaces at predetermined angles, causing the arm to self-lock at specific positions without requiring user skill or intervention. This eliminates the dependency on user expertise while maintaining reliability in sterile environments.
2Stability of the object's composition
If high closing forces are applied to lock joints securely, then positioning stability is improved, but the actuation force required increases and operation becomes difficult
Solution Approach 1:
The cam surfaces are designed with specific curved geometries that convert a small actuating force into a large locking force. As the positioning arm moves along the curved cam surface, the normal force increases progressively, generating high closing forces for secure locking while requiring minimal actuation force from the user.
Solution Approach 2:
The spring elements provide dynamic force multiplication. When the positioning arm is actuated, the spring elements are compressed and store energy, then release this energy to generate high closing forces during the locking process. This dynamic mechanism allows secure locking with minimal actuation force.
3Strength
If traditional three-joint support arms are designed with high strength materials, then durability and load bearing capacity are improved, but the design complexity increases and sterility becomes difficult to maintain
Solution Approach 1:
The positioning arm is divided into modular components including arm elements, spring elements, and locking elements that can be independently manufactured and assembled. This segmentation allows each component to be optimized for its specific function while simplifying the overall design and enabling easy sterilization of individual parts without affecting the entire system.
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 provides a robust, ergonomic, and rapid operation of positioning arms, ensuring secure and precise positioning of medical instruments with minimal force requirement, enhanced sterility, and reduced complexity, while maintaining stability and durability.
Implementation Method 1
a spring element (135) is provided by means of which the first arm element (110) and the second arm element (120) are resiliently preloaded in a defined position relative to one another
Implementation Method 2
the transmission device is formed by at least one pair of pincer arms... the pincer arms each comprise a longer lever arm and a shorter gripping arm
Data Source
AI summary
A positioning arm for positioning instruments, devices or tools, is disclosed. The positioning arm includes at least two arm elements pivotably connected to one another about a pivot axis via a central joint. At least one of the arm elements includes a further joint at an end opposite the central joint. The positioning arm includes a blocking device for blocking and releasing the central joint and the at least one further joint. The blocking device is arranged on the central joint and effects the blocking and release of the further joints via at least one transmission device formed on the arm elements. The transmission device is formed by a pair of gripper arms which also form the arm elements.