Metal domes

Metcalf, G.S. and White, W.E. 2003. Method of constructing insulated metal dome structure for a rocket motor. U.S. Patent 6,544,936. 

DISPOSAL AND STORAGE METHODS may be subjected to ultimate disposal by controlled incineration may be stored in liquefied form under its vapor pressure at normal atmospheric temperatures both above and below ground refrigerated liquid storage at atmospheric pressure may be used systems are closed and insulated, and the liquid petroleum gas vapor serves as the refrigerant for the system as it is circulated through pumps and compressors may also be stored in pits in the earth capped by metal domes, and in underground chambers. 

The main vessel is closed above the free level of sodium and argon cover gas by the slab which contains in its central section two eccentric rotating plugs and the core cover plug which supports the control rod drive mechanisms and the core instrumentation. It is surrounded by the safety vessel, welded to the slab, which is itself topped by a metallic dome. This dome can resist a pressure of 3 bar at a temperature of 180 C. The safety vessel and the dome make up the primary boundary, and the reactor building in reinforced concrete constitutes the secondary boundary. 

Keypads that are ever-present in cell phones, pagers and automotive or consumer appliances generally feature a delicate but reliable switch behind the buttons, implemented with a metal dome placed on the PCB or flex-foil. The domes are secured mechanically to the PCB or flex-foil with a sticky foil, so they will not shift during use. Per module, all domes are placed on one sticky foil, then the backing paper is peeled away and the assembly is applied upside-down onto the device. 

The use of flex-foil instead of standard SMD substrates, such as PCBs, lends itself to automated production of metal-dome switch contacts. The process requires a solution for placing the domes, which can be less than 60-pm thick, onto the sticky foils. 

Leaders in the design and manufacture of metal-dome switch contacts and complementary equipment for membrane switches and related mechanical-switch industries are seeing higher demand. This, in turn, is increasing the need for fully automated high-speed production methods. 

This article describes the development of a reel-to-reel system that handles the first stage in the process —placing the metal domes onto a flex-foil substrate. 

A de-reeler feeds a continuous roll of paper into a punching unit, which punches out a hole for each dome. The paper then is laminated with a sticky plastic foil and this substrate is fed into the placement machine, t5q)ically carrpng multiple keypad foils across the width of the roll. A customized feeder, which was developed on an existing intelligent feeder platform, punches the metal domes out of a preformed metal tape. 

Designed in 1984, the Bath and Wessex prosthesis (Howmedica International) was a multi-axial, cemented two-part prosthesis [48, 49]. It had a metal dome for the... 

In America, the sulphur deposits (mostly in Louisiana and Texas) are dome-shaped layers about 30 cm thick, between limestone above and anhydrite below. From these, the sulphur is extracted by the Frasch process. A metal tube, about 15 cm diameter and containing two concentric inner tubes (Figure 10.1) is sunk into the top of the deposit. Water, superheated to 450 K, is forced... 

Jets for continuous filament textile yam are typically 1 cm diameter gold—platinum ahoy stmctures with 20—500 holes of 50—200 p.m diameter. Tire yam jets are also 1 cm in diameter but typicahy use 1000—2000 holes to give the required balance of filament and yam denier. Staple fiber jets can have as many as 70,000 holes and can be made from a single dome of ahoy or from clusters of the smaller textile or tire yam jets. The precious metal ahoy is one of the few materials that can resist the harsh chemical environment of a rayon machine and yet be ductile enough to be perforated with precision. Glass jets have been used for filament production, and tantalum metal is a low cost but less durable alternative to gold—platinum. 

Sulfur constitutes about 0.052 wt % of the earth s cmst. The forms in which it is ordinarily found include elemental or native sulfur in unconsohdated volcanic rocks, in anhydrite over salt-dome stmctures, and in bedded anhydrite or gypsum evaporate basin formations combined sulfur in metal sulfide ores and mineral sulfates hydrogen sulfide in natural gas organic sulfur compounds in petroleum and tar sands and a combination of both pyritic and organic sulfur compounds in coal (qv). 

Sodium metal is produced commercially on the kilotonne scale by the electrolysis of a fused eutectic mixture of 40% NaCl, 60% CaCh at 580°C in a Downs cell (introduced by du Pont, Niagara Falls, 1921). Metallic Na and Ca are liberated at the cylindrical steel cathode and rise through a cooled collecting pipe which allows the calcium to solidify and fall back into the melt. Chlorine liberated at the central graphite anode is collected in a nickel dome and subsequently purified. Potassium cannot be produced in this way because it is too soluble in the molten chloride to float on top of the cell for collection and because it vaporizes readily... 

The tank is typically about sixteen inches in diameter and about four to five feet tall. The top of the tank is domed upward and the bottom of the tank is also domed upward in a concave manner. The outside of the tank is insulated with a polyurethane foam insulation that is squirted into the gap between the tank and a thinner sheet metal jacket. The polyurethane is made of two different components that react and harden when mixed. Included in the mixture is a blowing agent that causes the polyurethane to expand in a foam-like manner. Prior to about 1980, water heaters were insulated with fiberglass insulation. The foam insulation process was developed to allow automation and increased manufacturing speed and reduced costs. A side benefit was improved insulating ability leading to a slight increase in efficiency. 

The reverse-buckling disk, without knives but wth a pre-scored disk surface, offers some features that do not depend on the knives being in place because the thickness of the metal disk dome along the score line determines the bursting pressure of the disk. 

The rigidity of the y axis prevents the development of spherical surfaces for all but very small displacements. Morton suggests that the limit is reached when the displacement is equal to the metal thickness. This condition was satisfied in the high-temperature studies of Appleby and Tylecote and spherical doming of the disc specimen occurred. When the oxide is not very thin compared with the metal both the moduli for oxide and metal must be considered. Stringer" , in his excellent review of stress generation and relief in oxide layers, quotes a corrected formula, originally due to Brenner and Senderoff ... 

Fig. 25. The effect of metal ion size on porphyrin ruffling. Very small metal ions [P(V) with an ideal P-N bond length of 1.84 A and low-spin Ni(II) with an ideal Ni-N length of 1.90 A in (a) and (b)) cause extensive S4 ruffling. Metal ions close to the right size (M-N = 2.035 A) give planar structures [Zn(II) in (c)]. Metal ions that are too large [Pb(II) at (d) with ideal Pb-N of 2.39 A] are extruded from the plane of the porphyrin and cause it to dome. For clarity, substituents on the porphyrins such as phenyl or ethyl groups have been omitted. Modified after Ref. (77).

The functionalization of zinc porphyrin complexes has been studied with respect to the variation in properties. The structure and photophysics of octafluorotetraphenylporphyrin zinc complexes were studied.762 Octabromoporphyrin zinc complexes have been synthesized and the effects on the 11 NMR and redox potential of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraarylporphyrin were observed.763 The chiral nonplanar porphyrin zinc 3,7,8,12,13,17,18-heptabromo-2-(2-methoxyphenyl)-5,10,15,20-tetraphenylporphyrin was synthesized and characterized.764 X-ray structures for cation radical zinc 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin and the iodinated product that results from reaction with iodine and silver(I) have been reported.765 Molecular mechanics calculations, X-ray structures, and resonance Raman spectroscopy compared the distortion due to zinc and other metal incorporation into meso dialkyl-substituted porphyrins. Zinc disfavors ruffling over doming with the total amount of nonplanar distortion reduced relative to smaller metals.766 Resonance Raman spectroscopy has also been used to study the lowest-energy triplet state of zinc tetraphenylporphyrin.767... 

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