Chains offset link

There are six types of chains used for power transmission. These are roller, silent (inverted tooth), offset link (Ewart with bushing), detachable (open Ewart), pintle (closed Ewart), and bead,... 

Some of these are shown in Figure 3-26. Because most modern power transmissions use roller chains, silent chains or the offset link (Ewart) chains, these will be the only chain types discussed since they are quite important in oil field applications. 

Offset Link (Ewart with Bushing), API Chain... 

The offset link type of chain can be further improved by the use of a bushing, as shown in Figure 3-38. The improved or modified offset link can be used for more severe service conditions, but its safe maximum speed should, however, not exceed 400 ft/min. The offset link chain with bushing is known as the API chain [16]. These... 

Equation 3-30 does not often result in an even number of pitches. Thus, the results must be rounded off to a whole number, preferably an even whole number to avoid the specification of an offset link chain. 

In what follows, the pertinent design data are given for the roller chain, silent chain, and the offset link chain (API chain). 

The length obtained by this formula should be rounded upward to the nearest whole number. For a roller chain, the resultant number must be raised to the nearest even whole number of pitches or an offset link must be used to obtain the proper installed length. The proper chain length in inches is found by multiplying L by the pitch for the ASA type from Table 58.7. 

Next to batch production, where exact quantities of a product have to be produced many times over, it is minimum lot sizes that deserve particular consideration. This is usually the case when products are manufactured in large campaigns. Here, products are usually manufactured in a continuous process, with different production processes being combined within the framework of the process chain. When linking the individual production stages to each other it is important to also consider offset times. These can for example include the transportation and analysis time between two production stages. 

The most common type of chain tightener is an idler sprocket mounted on an adjustable bracket, either manually adjusted or spring loaded. Rollers, shoes, and vibration dampeners are also used for regulating chain excess tension. The idler design and installation should be capable of providing enough adjustment to remove two full pitches of chain. This avoids the need for a less desirable offset link. 

Offset link chains, which have all links alike. These include integral link chains, such as bar-link, flat-top, and welded steel chains, where internal rollers cannot be installed. 

Figure 2-1 illustrates typical straight and offset link chains. The configuration of the tension members of these chains (in this case, sidebars, as these are engineering steel drive chains) may be the only difference in the construction of the two chains. If pitch and joint details are identical and the sidebar cross sections are identical, so that the only differraice is straight or offset link construction, the chains can be operated over the same sprockets and for the same purpose. But they should not be mixed by intercoupling Unks of one into the otha- unless the manufacturer specifies that this is permissible. 

The differences in use for a given application stran from the fact that straight link chains consist of inside and outside links and that offset links are all alike. For this reason, strands of straight link chains must be used with an even number of links unless one special offset link (Figure 2-2) is used. On the otha- hand, offset chain strands can be used with eitha- an odd or even number of links. Straight link chains operate equally well in dther direction of travel, but offset chains should opraate in a specific direction (referring to closed or open end forward) to obtain the best service. The recommended direction of travel for offset chain strands varies with the application, and manufacturers recommmdations should be followed. The details of travel direction are discussed in subsequent chapters. 

To a user, the presence or absence of rollers is probably of far greater interest than whether straight or offset links are present in a chain being considered for an application. The major piupose of rollers is to reduce friction, but the rollers in chains have two separate functions, the two fimctions usually being provided by the same roller. These functions are... 

The standards also specify connecting links, offset links, and offset sections that are used to connect the free ends of roller chain. 

Offset finks generally do not meet the ACA power ratings for standard roller chains. The offset bend, the slip fit pin, and the D-shaped hole in one offset hnk plate greatly reduce the capacity of an offset link. 

An offset section is an assembly of a standard roller link and an offset link that is connected by a riveted pin (Figure 3-19). The pin is press ht into the offset link plates. This provides much greater operating strength than a single-pitch offset hnk. Because the pin is press ht in the offset link plates, two standard connecting links mnst be nsed to coimect the offset sechon to the chain and make it endless. 

A discussion of other roller chain parts, such as offset link plates, cotters, and spring clips is beyond the scope of this book. 

An offset link for a silent chain is shown in Figure 3-31. It is a factory assembly of three or more pitches in length with the middle pitch (row) being offset by link plates. The offset link plates are half the thiekness of the normal driving link plates and have an offset bend that lets them connect to the ends of a chain with an odd number of pitches. 

Offset sidebar drive ehain is a series of identical offset links. The pins are free to articulate in the bushings and the rollers are free to turn on the bushings. The rollers are uniformly spaced so they can engage the teeth on a sprocket and transmit motion and force. The components of such a chain are shown in Figure 3-36. The diameter of the rollers in this type of chain is less than the sidebar height. 

Chain length mnst always be an integral nnmber of pitches. Design the drive to nse an even number of pitches whenever possible. An offset link is required in a chain with an odd nnmber of pitches. Avoid using offset links becanse they reduce chain capacity 30% or more and are expensive. 

Chain length must always be an integral number of pitches. If straight sidebar chain is used, the chain length should be an even number of pitches to avoid the use of one offset link in the chain. 

When the narrow end of the offset link faces the sprocket, sliding also takes place between the pin and bushing bore, but the load quickly decreases between these parts as articulation starts. The full load between the sprocket tooth and the tight-side strand is transferred from roller to bushing to sidebar. Wear between the pin and the bushing bore is at a minimum. Wear elongation is less rapid in this case and the chain will need to be replaced less often. 

Inspect roller chains for unusual wear on the inside of the roller hnk plates. Inspect engirreoing steel chains for unusual wear inside the narrow ends of the offset links. Irrspect silent chains for... 

Where accurate and higher-speed chain drives are required, roller chains are used. Roller chains are fundamentally a development of the block chain in which rollers have been inserted. The addition of the rollers increases the overall efficiency of the chain and permits it, in its ordinary form, to be operated at high speeds a rate of 600-800 ft/min is usually recommended. The links can be furnished in a multitude of shapes, one common form being the offset shown in Fig. 3-28. This type of chain is furnished in pitches, i.e., center distance between rollers, from up to 2 in. and in breaking strengths, dependent upon the materials and the construction used, from about 10,000 to 200,00 lb [8,11]. 

Coherent excitation of quantum systems by external fields is a versatile and powerful tool for application in quantum control. In particular, adiabatic evolution has been widely used to produce population transfer between discrete quantum states. Eor two states the control is by means of a varying detuning (a chirp), while for three states the change is induced, for example, by a pair of pulses, offset in time, that implement stimulated Raman adiabatic passage (STIRAP) [1-3]. STIRAP produces complete population transfer between the two end states 11) and 3) of a chain linked by two fields. In the adiabatic limit, the process places no temporary population in the middle state 2), even though the two driving fields - pump and Stokes-may be on exact resonance with their respective transitions, 1) 2)and... 

Figure 53. The crystal structures of gladiusite and lipscombite (a) gladiusite projected onto (010) (b) in gladiusite, the linking of adjacent pairs of chains to form a triplet of offset chains with Unking (PO4) tetrahedra (c) gladiusite projected onto (001) (d) lipscombite projected onto 100) (e) lipscombite projected onto (001). ( Fe, Fe c )6) octahedra are shadow-shaded.

By proper choice of either the isocyanate or the polyol, actual chemical cross-links can be introduced in either the hard or soft segments that may be beneficial to some properties. The effectiveness of these cross-links is offset by a disruption of the hydrogen bonding between polymer chains. Highly cross-linked polyurethanes are essentially amorphous in character exhibiting high modulus, hardness, and few elastomeric properties. Many adhesives fall into this category. 

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