The Complete Guide to Chain

3.1 Bearing Bush Chain

Light to heavy conveyance: No elongation, electric, electronic, precision machinery industries

Application Examples

Bearing Bush Chain (Figure 3.3) is used in automatic assembling, packaging, filling, and parts installation for a variety of industries, including electric, electronic, semiconductor, automobile, and food as well as in other precision machinery. It includes the following features:

  1. High accuracy and no elongation.
  2. Interchangeability with other double pitch roller chains and large pitch conveyor chains.
  3. Low cost.

Figure 3.3 Bearing Bush Chain
Figure 3.3 Bearing Bush Chain

Constructions and Features

Usually chains are designed with gaps between the pins and bushings for proper operation. With Bearing Bush Chain, needle bearings are installed between the pins and bushings. These add rolling elements between these components and eliminate the sliding friction (Figure 3.4).

Figure 3.4 Needle Bearings in Precision Chain
Figure 3.4 Needle Bearings in Precision Chain

The advantages of this design include:

  1. Immediately after installation, the chain stretches a little (less than 0.03 percent) to fit the contacting surface of chain parts. After that, it doesn't stretch (Figure 3.5). The results include the following points:
    1. Accurate positioning in a high-speed or indexing drive. For example, in an application of automatic installation of electronic parts with 30 stations, a conveying speed of 10 m/min., and an index of 0.6 seconds, the positioning accuracy is ± 0.2 mm (using a positioning pin).

      Figure 3.5 After Installation, Precision Chain Has No Elongation
      Figure 3.5 After Installation, Precision Chain Has No Elongation

    2. No annoying position-adjustment maintenance.
    3. No take-up adjustment or lubrication.
  2. The main dimensions are the same as double pitch roller chain and large pitch conveyor chain (R-rollers). That gives you the following benefits:
    1. Change from standard chains to Bearing Bush Chains with minimal redesign of the equipment.
    2. Low-cost standard sprockets can be used (special made-to-order sprockets are required for high accuracy).
    3. Available with a variety of attachments.
  3. Relatively low cost.

Bearing Bush Chain has many sizes from small to large (Table 3.1).

Sprockets

For double pitch roller chain type, standard sprockets are used for general applications. When the application requires high accuracy, special-order sprockets are needed.

For Engineering Class conveyor chains, machined-tooth sprockets (made to order) are used instead of standard flame-cut sprockets.

Table 3.1 Precision Conveyor Chain
Double Pitch Chain
Chain No.		 Maximum Allowable
Load (kN)		 Engineering Class Chain
Chain No.		 Maximum Allowable
Load (kN)
RFN2040R 0.78 RFN03075R 2.45
RFN2050R 1.27 RFN05100R 4.90
RFN2060R 1.76 RFN10150R 7.85
RFN2080R 2.94 RFN12200R 9.81
RFN17200R 12.70
RFN26250R 19.60
RFN36300R 24.50

Points of Selection and Handling

  1. In Bearing Bush Chain, the contacting surfaces between pins and needles or needles and bushings are small. If these parts are subjected to a load larger than the allowable static load of the needle bearing, permanent deformation will occur, and the chain will not operate correctly. The chain tension, including inertia, should be lower than the rated allowable load.
  2. Due to the low bending resistance, the chains will vibrate at the low-tension return side. Guide rails or guide rollers help to prevent vibration.
  3. A "high-precision type," which is more accurate in the overall chain length and the dimension of attachments, is available.
  4. The double pitch chain type is basically an inch-pitch series, but there are some metric pitches available.

Application Series

Link plates of Bearing Bush Chain are nickel-plated to avoid rusting in indoor use.

Stainless steel Bearing Bush Chain is available for corrosive conditions. However, the allowable load is limited because of the low hardness of the contacting parts. In addition, the chain will elongate gradually (Figure 3.6).

Heat-resistant Bearing Bush Chain is available for temperatures up to 150°C.

Figure 3.6 Elongation of Stainless Steel Precision Chain
Figure 3.6 Elongation of Stainless Steel Precision Chain

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