Flexible couplings

Direct or rigid couplings Flexible couplings Delayed-action couplings Construction and principle of operation Belt drives Checking the suitability of bearings Suitability of rotors for pulley drives... 

An approach which couples flexibility to a fairly simple analytical formulation is that suggested by Murrell and coworkers decomposing the potential energy in two and three body terms. These terms are then represented using polynomial expansions in physical coordinates damped by exponential or hyperbolic tangent factors. We have suggested... 

In 1986 when the oil price crashed to 10 a barrel, operators began to look very hard at the requirements for offshore developments and novel slimline, reduced facilities platforms began to be considered. The reduced capital outlay and early production start up capability, coupled with the added flexibility, ensured that all companies now consider subsea systems as an important field development technique. Although the interest and investment in subsea systems increased dramatically, subsea systems still had to compete with the new generation of platforms, which were becoming lighter and cheaper. 

Forbes M D E 1993 The effect of localized unsaturation on the scalar exchange coupling in flexible biradicals J. Phys. Chem. 97 3390-5... 

Another type of polyol often used in the manufacture of flexible polyurethane foams contains a dispersed soHd phase of organic chemical particles (234—236). The continuous phase is one of the polyols described above for either slab or molded foam as required. The dispersed phase reacts in the polyol using an addition reaction with styrene and acrylonitrile monomers in one type or a coupling reaction with an amine such as hydrazine and isocyanate in another. The soHds content ranges from about 21% with either system to nearly 40% in the styrene—acrylonitrile system. The dispersed soHds confer increased load bearing and in the case of flexible molded foams also act as a ceU opener. 

Disk Coupling. Diaphragms are used to transmit torque between the iaside and outside diameters of the flexible element ia disk coupling (Fig. 14b). Up to 0.1-mm (0.004-ia.) parallel misalignment can usually be tolerated. Whereas no oil lubrication is required as compared to gear couplings, disks ate limited to moderate torques. 

Grid-Type Couplings. Another type of flexible couplings, similar to disk couplings, is the grid type (Fig. 14c). These are appHed for moderate loads and allow parallel misalignment up to 0.1 mm (0.005 ia.). Lubrication is also requited. 

Textile fibers must be flexible to be useful. The flexural rigidity or stiffness of a fiber is defined as the couple required to bend the fiber to unit curvature (3). The stiffness of an ideal cylindrical rod is proportional to the square of the linear density. Because the linear density is proportional to the square of the diameter, stiffness increases in proportion to the fourth power of the filament diameter. In addition, the shape of the filament cross-section must be considered also. For textile purposes and when flexibiUty is requisite, shear and torsional stresses are relatively minor factors compared to tensile stresses. Techniques for measuring flexural rigidity of fibers have been given in the Hterature (67—73). 

DlsaZO Pigments. The diaiylide yeUows and oranges also known as benzidines are derivatives of benzidine coupled to two moles of substituted acetoacetanilide. Benzidine Yellows AAMX, AAOT, AAOA, and HR (PY 13, 14, 17, and 83) ate examples (Fig. 1). Yellows AAMX and AAOT are used in flexible vinyls. AAOA also colors polyethylene and polypropylene. These three differ only slightly in shade. Benzidine YeUow HR is redder. 

The number of speed reduetions is another way to classify conveyor drives. Most common of the speed-reduction methods is the two-step system, in which the motor is coupled to a speed reducer and the slow-speed shaft of the reducer is connected to the conveyor-drive shaft by a V belt or a roller chain. The second reduction not only permits the use of a simpler speed reducer but also allows a more flexible layout of the motor and reducer mounting plate. On many installations this eliminates the need for a specially designed drive mount. 

For instance, power can be transmitted from one machine to the other through shafts, flexible couplings, and gear reducers (mechanical equipment). Power can be transmitted through a torque converter (hydraulic equipment) or by a combination of mechanical and hydraulic equipment. 

Whenever the process machine operates at the same speed as its driver, the two can be directly coupled. This direct couphng stiU allows for a variable speed, through acuustments of the speed or the driver. Steam turbine speed can be easily adjusted, and electric motor speed can also be varied by the use of special drives that vaiw the frequency of the power applied to the motor. Wdiether the speed is fixed or variable, direci coupling of two machine shafts presents the problem of accommodation of misalignment. To this purpose, machines are coupled through a.flexible coupling. 

The load is now transmitted through ordinary couplings, one half mounted on the motor shaft and the other half on the driven shaft. They are bolted together with a rubber pad between the two. The motor and the driven machine are mounted on a common bed (Figure 8.2). They are now able to provide margin for misalignment of the two shaft ends and thus extend more flexibility. 

Figure 8.2 Flexible coupling (Courtesy Crompton Greaves Ltd)...

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