Planar Spiral Contact Spring for Cardiac Electrode Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing screw-in electrode probes face challenges in maintaining a reliable electrical connection between the metal housing and electrode shaft due to complex assembly requirements and limited space, with known contact spring solutions either being too large or providing insufficient contact stability.
Innovation Solution
A planar spiral spring is used, rotating around the shaft with sliding contact ends, providing a high spring length and flat spring characteristic to ensure reliable contact despite axial and rotational movements, without the need for welding or soldering, thus minimizing space requirements and maintaining contact stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clock spring is used for electrical connection between housing and shaft, then contact connection is achieved, but assembly becomes complex and sensitive with large installation space required
Solution Approach 1:
The patent transitions from a three-dimensional coiled compression spring to a two-dimensional planar spiral spring. This dimensional reduction allows the spring to achieve the required contact force and displacement compensation within the limited radial space of the electrode head, eliminating the need for large axial space while simplifying the assembly process by removing welding requirements.
Solution Approach 2:
The patent changes the geometric parameters of the spring from a coiled configuration with large axial displacement to a planar spiral configuration with controlled radial and axial movement. The planar spiral design provides sufficient spring force and displacement compensation (up to 2mm axial + rotational displacement) within a compact form factor, reducing both installation space and assembly complexity.
2Force
If a coiled compression spring is used between housing and shaft, then contact force is provided, but installation space in axial direction becomes large
Solution Approach 1:
The patent replaces the axial-oriented coiled compression spring with a radially-oriented planar spiral spring. This dimensional change allows the spring to generate contact force primarily in the radial direction while accommodating axial and rotational displacements through its spiral geometry, thereby reducing the axial installation space from several millimeters to a compact radial configuration.
3Length of stationary object
If a torsion spring is used between electrode shaft and housing, then contact connection is achieved, but contact force becomes insufficient due to small installation space
Solution Approach 1:
The patent optimizes the spring parameters by using a planar spiral configuration with carefully selected dimensions: outer diameter of 0.8-1.5mm, inner diameter of 0.4-0.8mm, and wire diameter of 0.05-0.1mm. These parameters enable the spring to generate sufficient contact force (0.1-1N) within the limited installation space by leveraging the spiral geometry's mechanical advantage and the material's elastic properties.
Solution Approach 2:
The patent specifies using spring steel or stainless steel for the planar spiral spring, utilizing the high elastic modulus and fatigue resistance of these materials to maximize contact force output within the constrained dimensions. The material selection compensates for the small size by providing superior mechanical properties that enable sufficient contact force generation.
4Reliability
If welding is used to fix clock spring ends to shaft and housing, then contact stability is improved, but assembly sensitivity and complexity increase
Solution Approach 1:
The patent incorporates the spring's attachment points directly into the molded housing and shaft structures during the injection molding process. The housing includes integrated attachment protrusions and the shaft includes corresponding recesses that receive the spring ends, eliminating the need for separate welding or soldering steps. This preliminary integration maintains contact stability while dramatically simplifying assembly to a single snap-fit operation.
Solution Approach 2:
The patent merges the spring attachment function with the housing and shaft structural elements. The attachment protrusions and recesses are formed as integral parts of the molded components, combining the mechanical support and electrical contact functions into unified structures. This integration eliminates separate assembly steps for fixing the spring while ensuring reliable electrical connection.
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 ensures a stable and uniform electrical connection with low inclination tendency, even with radial oscillations, and allows for effective axial and rotational displacement of the screw-in electrode while maintaining contact force, addressing the limitations of prior contact spring designs.
Implementation Method 1
configuring the contact spring as an essentially planar spiral spring rotating around the shaft under spring tension, whose leg ends are in sliding contact with the housing or the shaft while exerting a radially directed spring force
Implementation Method 2
providing a high spring length and flat spring characteristic to ensure reliable contact despite axial and rotational movements
Data Source
AI summary
A screw-in electrode probe for cardiological application comprises an oblong electrode body (1), a supply line (10) running therein, and an electrode head (3) on the distal end (2). The latter is provided with housing (5), a shaft (6) mounted therein so it is rotatable and axially displaceable, and a corkscrew-like screw-in electrode (4) on the shaft (6). A contact spring in the form of an essentially planar spiral spring (11) is situated between these components, whose leg ends (12, 13) are in sliding contact with the housing (5) or the shaft (6), respectively, while exerting a radially directed spring force (F).