Rotary Joint Inductive Power Transfer Without Slip Ring Wear
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Solution Overview
Problem
Traditional rotary joints used in motor-driven systems for transferring electrical power across rotational joints face issues such as electrical arcing, noise, wear, and limited rotational freedom due to the use of conductive wires.
Innovation Solution
A wireless power transfer system integrated with a motor, utilizing concentric power transmit and receive magnetic cores with coils wound around them, allowing for inductive power transfer without mechanical interference, enabling continuous rotation and high power transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional rotary contacts (slip rings or wiring harness) are used to transfer electrical power across rotary joints, then electrical power can be delivered to distal portions, but electrical arcing, noise, wear, and limited rotational freedom occur
Solution Approach 1:
The patent replaces the mechanical contact-based power transfer system (slip rings or wiring harness) with an inductive wireless power transfer system using magnetic cores and coils. The transmit coil and receive coil are positioned on opposite sides of the rotary joint, with magnetic cores concentrating the magnetic field. This allows electrical power to be transferred through electromagnetic induction without physical contact, eliminating electrical arcing, noise, and wear while enabling continuous rotation beyond the limitations of wire length.
2Power
If wiring harness is used to deliver power, then electrical power can be transferred, but rotational freedom is limited by wire length
Solution Approach 1:
The patent eliminates the mechanical constraint of wire length by replacing the wiring harness with an inductive power transfer system. The transmit coil is positioned on the stationary side of the rotary joint, and the receive coil is positioned on the rotating side. Power is transferred wirelessly through the magnetic field generated by the transmit coil, which couples with the receive coil. This allows the distal portion to rotate freely without restriction from wire length, while still receiving substantial electrical power.
3Power
If rotary contacts are used, then power transfer is possible, but maintenance is required due to wear and contaminants
Solution Approach 1:
The patent replaces the consumable rotary contacts that require maintenance with a non-contact inductive power transfer system. The magnetic cores are positioned with their flat faces parallel to each other, creating a concentrated magnetic field path through the rotary joint. The coils are wound around these cores, and power is transferred through electromagnetic coupling without any physical contact. This eliminates wear, prevents contaminant release, and removes the need for ongoing maintenance while maintaining substantial power transfer capability.
4Reliability
If inductive power transfer with magnetic cores is used, then rotational freedom and reliability are improved, but device complexity increases
Solution Approach 1:
The patent divides the power transfer system into two separate segments positioned on opposite sides of the rotary joint: a transmit side with a magnetic core and coil, and a receive side with a magnetic core and coil. This segmentation allows each component to be optimized independently and simplifies the overall structure by eliminating the need for complex rotating contacts. The magnetic cores are positioned with their flat faces parallel to each other, creating a direct magnetic coupling path that enhances efficiency while maintaining simplicity.
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 system effectively transfers substantial quantities of electrical power across rotary joints without limiting rotation, reducing maintenance needs, and minimizing electrical interference, supporting power transfers exceeding 40 watts and potentially hundreds of watts.
Implementation Method 1
A power transmit coil may be linearly wound around this core. A second portion of the apparatus includes a second portion of the motor, such as a stator. Arranged concentrically around the axis is a power receive magnetic core. A power receive coil is linearly wound around this core. When assembled, the power transmit coil is proximate to the power receive coil... an alternating current signal is provided to the power transmit coil, and energy from the resulting electromagnetic field is inductively coupled to the power receive coil
Data Source
AI summary
Inductive power transfer across a rotary joint including a motor comprises a first portion with a magnetically permeable power transmit core with a power transmit coil and a second portion comprising a magnetically permeable power receive core with a power receive coil. The core material in the respective cores directs a time-varying electromagnetic field emitted by the power transmit coil toward the power receive coil where the field is contained. As a result, adjacent devices on a side opposite the coil that utilize magnetic fields, such as motor coils, may operate without interference. For example, a brushless direct current motor comprising a stator in the first portion and a rotor in the second portion may operate while power is transferred. Data may be wirelessly transmitted between the first portion and the second portion.