Flat-Top Chain

Straight-running flat-top chains are standardized in ASME B29.17M, Hinge Type Flat Top Conveyor Chains and Sprocket Teeth. 

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There are basically two types of conveyors available belt and flat-top chain. Both do the same job, but a belt conveyor is quieter and can offer more conveying surface. Also, from a maintenance standpoint, a belt conveyor is easier to use. 

Continuing developments in the food and beverage industries produced the need for flat-top chains made from materials other than steel. By the 1960s, flat-top chains made from plastic were widely available (Figure 1-29). 

A straight conveyor is not always possible, due to flow processes, obstructions in the plant, etc., so side-flexing flat-top conveyor chains were developed. These chains are based on straightrunning designs, but have additional clearance in the joint that permits the chain to traverse curves in one or two directions (Figure 1-30). Side-flexing flat-top chains are not covered by any ANSI standard, but they are an important item in the flat-top product line and will be covered further in this book. 

In ehapter 1, the evolution of the chain industry was ouflined from the first cast chains to flat-top chains. This book outlines four major kinds of chain from an industry standpoint roller chains, silent chains, engineering steel chains, and flat-top chains. 

Rollerless chain is similar in appearance to chain with rollers, and is used for applications where rollers are not required. Most rolleriess chains are engineering steel chains. There are other types of chain that do not have rollers, because rollers would obviously not be appropriate. Examples are bar-link, silent, and flat-top chains, which were shown in Figures 1-22, 1-25, and 1-28. 

Many other types of engineering steel chains exist, although most of them are not the subjects of published standards. Special-purpose chains for handling materials, such as double-flex conveyor chains, welded rooftop and flat-top chains, steel detachable chains, and steel fabricated chains with plastic bushed rollers for use where lubrication is unacceptable, are only a few of the products available. All of these may be found in manufacturers catalogs. 

The flat-top chains covered in this handbook are made of simple, two-piece ass bled links with... 

ASME standard B29.17 covers only three basic models of straight-running flat-top chain. A basic steel chain, a normal-duty plastic chain, and a heavy-dnty plastic chain. The standard fists limiting dimensions that ensure the chains are interchangeable. The standard requires that the standard chain from one manufacturer will run on the standard sprockets from another manufacturer, and that a standard chain from one manufacturer will interconnect with the standard chain from another manufacturer. The pitch of all the standard chains is IV2 inches. The standard steel chains may be made of either corrosion-resistant or carbon steel. Top-plate width is not covered by the standard. The designer must consult manufacturers catalogs for such information. 

Standard flat-top chains are exclusively intended for use on conveyors. They are widely used in straight-running flat-top conveyors in the beverage bottling and canning, food processing, and product packaging industries. 

There are a great many nonstandard flat-top chains available for just about any special conveying need one can imagine. There are heavy-duty steel flat-top chains to carry larger loads than... 

The best known, and possibly the most commonly used, of the nonstandard flat-top chains are the side-flexing flat-top chains. Obstructions and nonlinear process flows do not always allow the use of straight-running conveyors. So side-flexing flat-top ehains were developed. 

The number 881 is often used to identify steel side-flexing flat-top ehain. The number 880 is often used to identify plastic, normal-duty, side-flexing flat-top chain. And the number 882 is often used for plastic, heavy-duty, side-flexing flat-top chain. 

This section reviews the general considerations for the design of roller, silent, engineering steel, and flat-top chains. The considerations differ as the functions of each type of chain differ. The specific design considerations for each class of chain will be covaed later. 

Joint wear is wear between a pin and its mating surface that causes the chain to get longer. The mating surface may be a bushing, a link plate, or an integral link of the chain (as in block and bar or flat-top chains). It could even be another pin in silent chain. Joint wear probably is the main concern in almost all chain design. That is because chain wear elongation is often the reason a chain has to be replaced. 

Hat-top chains are used almost exclusively on eonveyors. In praetiee, the flat-top chains covered here are basically special types of slat conveyors. Hat-top ehain eonveyor speeds are generally less than 300 ft./min and the maximum chain pull is usually much less than 1000 lb. The major design considerations for flat-top chains to be used in conveyors are several of the tensile loads, several types of wear, lubiieation, and environment. 

The tensile loads of greatest coneem are the nominal traisile loads, shock loads, and inertia loads. The main strength properties that a flat-top chain must have are discussed below. 

Ultimate tensile strength is not a major considCTation in the design of flat-top chains. 

For the reasons stated earlier, yield strength is an important consideration in designing flat-top chains. 

Wear may be the most important consideration in designing flat-top chains. Joint wear and top plate and track wear are certainly the greatest concerns. Top plate and sprocket wear are also of some concern. 

Joint wear is a very important consideration in designing flat-top chains. As the chain runs over sprockets, the joints articulate and material is worn off the outside diameter of the pins and the inside diameter of the top plates, and as this material is worn away the chain gets longer. 

The sprockets for flat-top chains are not designed to accept much wear elongation. Thus, when the chain elongates even a moderate amount, it will no longer fit the sprocket and the conveyor will not function properly. 

Top plate and sprocket wear is not a major concern in designing flat-top chains because the chain spends only a small part of the cycle articulating on the sprocket teeth. 

Lubrication, or lack of it, is a major concern in designing flat-top conveyor chains. Many flat-top chains must work with httle or no lubrication. When the chain must opaate with no lubrication, selecting materials for the top plates and tracks is extremely important. 

Environment is a major consideration in designing flat-top chains. Many flat-top chains must operate in very abrasive or corrosive conditions and some flat-top chains must operate in very low or very high temperatures. Material selection is critical in designing a chain that will woik well in these conditions. 

Flat-Top Chain Construction and Components Straight-Running Steel Flat-Top Chain... 

Side-flexing steel flat-top chain is similar to the straight-rumung type with one major difference. The barrels in which the pins are free to turn are specially formed to permit the joint to flex sideways. Thus, the chain can flex in two planes. The amount of side flexing is limited so that the chain retains enough strength and bearing area to work well as a conveyor. 

As a side-flexing chain is pulled aroimd a curve, it is often pulled up and out of the track. Thus, side-flexing flat-top chains have bevels or tabs to hold them down in the tracks as they round a curve. Figure 3-44 shows a side-flexing steel flat-top chain with tabs. 

FIGURE 3-43 Typical straight-running steel flat-top chain construction. 

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