Hermetically Sealed Force Sensor Operating Unit for Surgical Tools

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Solution Overview

Problem

Conventional mechanical operating units in surgical power tools are unsuitable for sterilization due to their complex mechanical components, leading to issues with ingress of sterilization media and reduced durability after repeated sterilization cycles.

Innovation Solution

A finger-force-controlled operating unit with a hermetically sealed metal capsule housing a force sensor, which is resistant to sterilization media and features a contact surface with a clearly defined three-dimensional boundary for easy haptic detection, along with a signal processing circuit for converting sensor signals into usable outputs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional mechanical operating units (tumbler switches, rotary knobs) are used in surgical power tools, then the tools can be operated with simple controls, but the operating units cannot withstand sterilization cycles due to mechanical components and sealing difficulties

Engineering Contradiction:

Improveoperability of control unitVSAvoidwithstand sterilization cycles

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent replaces mechanical operating units (tumbler switches, rotary knobs) with an electronic operating unit based on a force sensor. The force sensor detects finger pressure directly through a capsule structure, converting mechanical force into electrical signals without moving mechanical parts. This substitution eliminates the sealing problems and mechanical wear issues that prevented conventional units from withstanding sterilization cycles, while maintaining ease of operation through intuitive pressure-based control.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs a capsule structure with a flexible housing section that transmits finger pressure to the force sensor. The capsule acts as a flexible shell that can be hermetically sealed to protect the force sensor from sterilization media while allowing force transmission. This flexible shell approach enables the operating unit to withstand repeated sterilization cycles without compromising either the sealing integrity or the force sensing capability.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If force sensors are housed in plastic casings to protect against sterilization media, then the sensors are protected from direct exposure, but maintenance or exchange is necessary after only a few sterilization cycles

Engineering Contradiction:

Improveprotection against sterilization mediumVSAvoidservice life through sterilization cycles

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent uses a composite structure combining a metal capsule with a flexible housing section. The metal capsule provides superior resistance to sterilization media compared to plastic casings, while the flexible housing section allows for force transmission. This composite material approach enables the operating unit to withstand a significantly larger number of sterilization cycles without requiring maintenance or exchange, extending the service life of the force sensor while maintaining protection against sterilization media.

Inventive Principle:

Principle #40Composite materials

3Reliability

If the contact surface is made flat and flush with the housing, then the sealing is improved, but the surgeon cannot easily locate the operating unit without visual attention

Engineering Contradiction:

Improvesealing integrityVSAvoidhaptic detectability

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent creates an asymmetric contact surface design where the capsule protrudes slightly from the housing surface in the direction of force application. This asymmetric geometry provides a clearly defined three-dimensional boundary that is easily detectable by the surgeon's finger, allowing intuitive location and operation without visual attention. The asymmetric design maintains sealing integrity through proper integration with the housing while enhancing haptic detectability through the protruding capsule structure.

Inventive Principle:

Principle #4Asymmetry

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 enables surgical power tools to withstand numerous sterilization cycles while maintaining operability and ease of use, as the hermetically sealed components prevent media ingress and the force sensor ensures reliable operation without the need for frequent maintenance.

Implementation Method 1

a force sensor arranged inside the capsule, which force sensor is in force-transmitting connection to the contact surface

Methodology Applied

Scientific EffectForce sensing: Piezoelectric Effect

Data Source

PatentUS8866419B2Surgical electrical tool, activation unit and calibration method therefor

Publication Date: 2014.10.21 STRYKER EUROPEAN OPERATIONS HOLDINGS LLC

AI summary

A sterilizable surgical power tool and an operating unit for the surgical power tool are described. The operating unit includes a hermetically sealed metal capsule for arrangement in the region of a housing of the surgical power tool, the capsule having a contact surface for a finger on an outer face. A force sensor which is in force-transmitting connection to the contact surface is arranged inside the capsule. At least one electrical contact leads out of the capsule. The capsule may be a low-cost standard transistor housing.