4. Top Chains
4.1 What Is Top Chain? Top Chain has a plate to hold conveyed objects on its upper side. These chains were originally used for bottling and canning in the food industries. Today you will find them in a variety of applications, because they are conve- nient and economical (Figure 4.1). Top Chains are divided into two categories based on the type of movement: linear or curved. The chain may be constructed of engineered plastic, carbon steel, or stainless steel. Usually steel chains have stainless steel top plates; however, engineered plastic snap-on tops are sometimes used. There are several forms of Top Chains. Figure 4.2 shows the correlation between these chains. There are additional types of chains that are not illus- trated in Figure 4.2. These include the following: • TO type: Steel chains for horizontal circular conveyance. • TU type: Steel for universal movement. • TN type (linear conveyance) and TNU type (curved conveyance): Steel chains with snap-on top plates made of engineered plastic. • RS40P type, RS60P type: Small pitch chains made of engineered plastic. • RS60P-2 type, RS60PU-2 type: Double strand plastic chains. • Bel-Top Chain type: Small pitch, wide chain, which is closer in form to a belt than to standard-type chain. In the following section, we will look at the features and characteristics of Top Chains.
Engineered Plastic
Carbon Steel, Stainless Steel
TT, TS
TTP, TP
Straight Conveyor
Curved Conveyor
TTUP, TPU
TTU
Figure 4.2 Relationship Between Different Types of Top Chains
4.1.1 Plastic Materials for Top Chains Most Engineered Plastic Top Chains have molded parts; the pins are made of 304 stainless steel. They offer quiet operation, do not require additional lubri- cation, and do not scratch conveyed objects. Engineered Plastic Top Chains are divided into several types as follows: (1) Standard series. (2) Low-friction, wear-resistant series. In the low-friction series, the coefficient of friction (against guide rails or conveyed objects) is 15 to 45 percent lower, and wear life is 1.2 to 2 times longer than standard series.
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