Coil Formers

Although the nylons are not generally considered as outstanding electrical insulators, their toughness and, to some extent, their temperature resistance, have led to applications in coil formers and terminal blocks. Indeed, the new nylon 46 materials would appear to be of particular interest here. Acetal resins, polysulphones, modified PPO and polycarbonates, however, present a challenge to applications in this sphere. 

Radio and television uses largely arise from the ability to produce components with a high level of dimensional accuracy coupled with good dielectric properties, high heat distortion temperatures and the availability of selfextinguishing grades. Specific uses include coil formers, picture tube deflection yokes and insert card mountings. 

The heat and flame resistance coupled with good electrical insulation characteristics, which includes in some grades good arcing and arc tracking resistance, has led to PPS replacing some of the older thermosets in electrical parts. These include connectors, coil formers, bobbins, terminal blocks, relay components, moulded bulb sockets for electric power station control panels, brush holders, motor housings, thermostat parts and switch components. 

Amongst the diverse uses in the electrical/electronics field are coil formers, miniature circuit breakers, picture-tube mountings, edge connectors and telephone distribution boxes. 

As for /(-helical models in the context of prion variants, we note that /(-helices encompass quite a wide variety of cross-sectional shapes, each reflecting a different configuration of strands and turns in the coil (Hennetin et al., 2006 Kajava and Steven, 2006) thus it seems possible that different parts of the same prion domain could be assigned the role of coil-former and they would have different coil geometries whose distinctions could give rise to variant prions. However, we expect that variability of the /(-helices with more than one coil per subunit—already unlikely on other grounds, except for HET-s (Section VLB)—will be quite limited. 

Relay sockets, cable connectors, bulb sockets, coil formers. .. 

Most steatite ceramics are either dry mixed and pressed, or wet-mixed, spray-dried and pressed, but they can also be wet-mixed and extruded. Typical firing temperatures lie close to 1300 °C. Many small parts are made for the electronics components industry where low dielectric losses are required, for example for tie-bars and other parts for ganged capacitors, small trimmer capacitors, high-power capacitors (see Section 5.6.3), coil formers, lead-throughs and substrates for... 

Nylons reinforced with glass fibers are thus widely used in domestic appliances, in housings and casing, in car components, including radiator parts, and in the telecommunication field for relay coil formers and tag blocks. Glass-bad-filled nylons have found use in bobbins. Carbon-fiber reinforcement has been used with nylon-6 and nylon-6-nylon-12 mixtures. These materials have found use in the aerospace field and in tennis rackets. 

In some applications in the electrical and electronics industries PES is being used because its properties are necessary in the manufacture of the component rather than its in-service requirement. For example, in one established application PES is used for the coil formers of a line output transformer that is used in a oolour TV set to produce the 2 Kv for operation of the electron beam During normal use, temperatures above 173 F are rarely reaohed and therefore on tMs ba s alone several materials were contenders, with PES an expensive option PES was selected eventually because the former must withstand the 340-360°F baking temperature required to shrink the stretched polycarbonate interleaving film on the windings, and because if offered satisfactory electrical performance during use. The non-biu ning characteristics of PES are an added bonus for this type of application ... 

Other coil formers are made from PES because the mouldings do not deform when tags are dip soldered, and this ability to withstand solder temperature is leading to some very interesting applications. 

Fig. 5-19. In-line coil former, which can produce telephone cords, springs, and so on, using extruded round, square, hexagonal, and other shapes.

The company BASF (Germany) has launched the production of poly-ethersulfone labeled Ultrason E [169] representing amorphous thermoplastic product of polycondensation it can be characterized by improved chemical stability and fire-resistance. The pressed articles made of it differ in solidity and rigidity at temperature 200 °C. It is assumed to be expedient to use this material when producing articles intended for exposure to increased loadings when the sizes of the article must not alter at temperatures from -100 °C till 150 °C. These items are, for instance in electrotechnique, coils formers, printing and integrated circuits, midspan joints and films for condensers. 

Geometry. Dimensional constraints, coupled with the use of a flat-wound, porous conductor of somewhat low current density, necessitated a four-layer coil design to obtain the desired coil inductance. Each layer of the conductor is supported by a separate coil former shell, though the conductor itself is continuous from one coil terminal to the other. Together these formers provide the main... 

The coil formers had average diameters of 0.46, 0.49, 0.52, and 0.55 m. As shown in Fig. 2, the formers had a circumferential, helical, machined groove of 1.9 cm width to accept the superconductor and axial slots of approximately 0.6 cm width for liquid helium flow. After machining, the second, third, and fourth formers were axially slit so that they could be slipped onto the next smaller former after completion of its superconductor layer. Transition slots were provided, as seen in Fig. 2, for the continuous winding of the conductor from one layer to the next. 

Fig. 2. End portion of the outermost coil former, showing toothed machined surface and conductor transition slot.

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