Induction Heating Circuit for Medical Sharps Removal

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Solution Overview

Problem

Existing medical sharp removal devices leave a portion of the needle in the holder, posing a needle-stick injury risk and requiring disposal as medical waste, and induction heating methods struggle to efficiently concentrate RF energy on small metallic bodies like pen needle cannulas due to physical constraints and regulatory concerns.

Innovation Solution

A specially shaped induction coil with a stepped configuration and optimized frequency in the ISM bands is used to concentrate RF energy at the metal/plastic interface, leveraging the skin effect for efficient separation and sterilization of medical sharps from their holders without direct contact.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If mechanical engagement methods (sieves, screens, hoppers) are used for sharps removal, then device complexity is reduced, but reliability is insufficient due to inability to guarantee complete capture of all sharps

Engineering Contradiction:
Improvesharps capture reliabilityVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical engagement methods (sieves, screens, hoppers) with an induction heating system that uses electromagnetic fields to heat and melt sharps. This substitution eliminates the need for complex mechanical capture mechanisms while achieving complete sharps removal through thermal processing, thereby improving reliability without proportionally increasing device complexity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state of sharps from solid to liquid/melted state through induction heating. By controlling temperature parameters and heating cycles, the system ensures complete melting and capture of sharps in the melt well, achieving reliable capture that mechanical systems cannot guarantee.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If induction heating is used to melt and capture sharps, then reliability of sharps capture is improved, but energy consumption increases

Engineering Contradiction:
Improvesharps capture reliabilityVSAvoidenergy consumption
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent employs periodic heating cycles with distinct phases: an initial heating phase to melt sharps, followed by a cooling phase where the induction heater is deactivated. This periodic operation allows the system to achieve complete sharps melting during active heating while reducing energy consumption during cooling periods, balancing reliability with energy efficiency.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent maintains continuous operational readiness by keeping the induction heater in a controlled state that can quickly transition to heating when needed. The system continuously monitors and prepares for sharps melting operations, ensuring immediate response capability while minimizing idle energy consumption through intelligent power management.

Inventive Principle:
Principle #20Continuity of useful action

3Device complexity

If induction heating circuit is integrated into the plunger assembly, then device complexity is reduced by consolidating components, but manufacturing precision requirements increase

Engineering Contradiction:
Improvedevice complexityVSAvoidmanufacturing precision
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The patent integrates the induction heating circuit directly into the plunger assembly by incorporating the induction heater within the plunger body structure. This merging of components eliminates separate heating units and reduces overall device complexity, while the integrated design allows for standardized manufacturing processes that manage precision requirements.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The induction heater is designed to generate its own magnetic field and heat directly at the target location without requiring external heating mechanisms. This self-service capability eliminates the need for complex external heating systems and reduces manufacturing precision requirements for alignment and integration with other components.

Inventive Principle:
Principle #25Self-service

4Productivity

If higher power induction heating is used to reduce melting time, then productivity is improved, but energy consumption and heat loss increase

Engineering Contradiction:
Improvesharps processing speedVSAvoidenergy loss
Core Design Contradiction:
ProductivityVSLoss of energy

Solution Approach 1:

The patent uses periodic heating cycles that alternate between high-power heating phases and cooling phases. During high-power phases, productivity is maximized by rapidly melting sharps. During cooling phases, energy consumption is reduced and heat loss is minimized. This periodic approach balances productivity improvements with energy efficiency.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent recovers thermal energy by allowing the system to retain heat in the melt well during cooling phases rather than immediately dissipating it. The retained heat is reused in subsequent heating cycles, reducing overall energy consumption and minimizing energy loss while maintaining high productivity across multiple processing cycles.

Inventive Principle:
Principle #34Discarding and recovering

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 safe, efficient, and complete removal of medical sharps from their holders, reducing needle-stick risks and allowing recyclable disposal of non-sharp components, while minimizing RF emissions and regulatory compliance issues.

Implementation Method 1

the induction heater generates an oscillating magnetic field that induces eddy currents in the Sharps, heating and melting them

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

the induction heater generates an oscillating magnetic field that induces eddy currents in the Sharps, heating and melting them

Methodology Applied
Scientific EffectEddy currents: Eddy Currents

Implementation Method 3

the induction heater generates an oscillating magnetic field that induces eddy currents in the Sharps, heating and melting them

Methodology Applied
Scientific EffectInduction heating: Induction Heating

Data Source

PatentEP3648724B1Induction heating circuit for medical sharps removal device
Publication Date: 2026.04.08 BECTON DICKINSON & CO
  • EP3648724B1 patent drawingFigure 1
  • EP3648724B1 patent drawingFigure 2
  • EP3648724B1 patent drawingFigure 3

AI summary

Induction heating from an induction coil (108) is used to separate a metal medical sharp (144) from its holder (142) by applying a high-frequency oscillating magnetic field that excites eddy currents and resistance heating in the sharp. The heated metal sharp melts the adhesive or plastic securing the sharp to its holder. The use of induction heating is advantageous in that it does not require direct contact between the electrical circuit and the sharp or its holder. The heating can also act to sterilize the sharp and thereby render it less hazardous at the same time that it separates the sharp from its holder. The induction coil can have a stepped or conical shape to concentrate the RF energy at the interface between the metal sharp and its holder.