SLIP RING TECNOLOGY

BASICS

• The transmission of power across a large free inner bore is one of the key factors in a rotating system.

• Slip rings are electromechanical devices consisting of circular electrical conductive rings and brushes that transmit electrical energy across a moving interface.

• This technology is also called "rotary electrical joint" and "electric swivel" technology.

• A slip ring can be used in any electromechanical system that requires unrestrained, intermittent or continuous rotation while transmitting power and / or data.

ORIGINAL REQUIREMENT

• Slip rings were originally designed to carry AC and DC power from a rotating platform to a stationary structure, or vice versa.

• Many applications also required, and still require, the transmission of relatively low bandwidth analog and digital control signals. In this environment, the traditional slip ring performs extremely well.

• Modern control systems now also require the transmission of high bandwidth analog and digital signals through the slip rings.

BASIC DESIGN

• This transmission of power/data is made possible through electrical connections made by stationary brushes pressing against rotating circular conductors.

• The slip-ring design consists of sets of parallel conductive rings concentric to the gantry axis that connects to the tube, detectors, and control circuits by sliding contractors.

• These “sliding contractors” allow the scan frame to rotate continuously with no need to stop between rotations to rewind system cables.

ARRANGEMENT

• A ring assembly that provides one or more circuit paths. Each ring is electrically conductive and provides a circuit path over a full 360° of rotation of the ring assembly.

• Brushes provide electrical contact between the rotating (usually the ring) and the stationary parts of the assembly. The brushes ride on the ring, and are mounted in a brush block assembly, usually on the stationary structure.

• Input and output leads that connect the ring and brushes to the outside world.

• Connectors that connect to the slip ring assembly wiring. Connectors are optional, and are often specified by the customer.

• The shiny metal strips carry electric signals that are swept off by special brushes. The brushes are not in the form of bristles but rather of metal blocks (in this case a silver alloy).

• The five pairs of larger brushes provide the voltage required by the x-ray tube, and the three pairs of smaller ones transfer signals from the gantry controller.

• A slip ring passes electrical power to the rotating components (e.g., x-ray tube and detectors) without fixed connections.

• The idea is similar to that used by bumper cars; power is passed to the cars through a metal brush that slides along a conductive ceiling.

• Similarly, a slip ring is a drum or annulus with grooves along which electrical contactor brushes slide.

• Fiber brush is the term for a particular design of sliding electrical contacts. Fiber brushes are simply a group of individual metal fibers (wires) that are collimated by and terminated into a metal tube.

• In this cantilevered design, the free, unterminated end of the fiber brush bundle rides in a groove on the ring surface.

• Brushes are used to transmit electrical power to the CT scanner components. These brushes glide in contact grooves along the slip-ring. There are two types of brushes that can be used; wire and composite.

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