Take-up bearing. Take-up frame. Take-up assembly
Image Credit: ABT Bearing | Baldor Electric Company | SKF
Take-up bearings are a type of mounted bearing primarily used for adjusting and maintaining conveyor belt tension. Take-up is the process of adjusting the length of the belt and chain to compensate for stretch, shrinkage, or wear, and to maintain proper tension. This is done with the assembly of the necessary structural and mechanical parts, including take-up bearings. The take-up bearing assembly consists of a housed that is mounted to a frame. The bearing is guided along the frame by a slot int he bearing housing or other means. The take-up assembly contains a screw or other mechanism for adjusting its location along the frame. A shaft connects two take-up bearings, one mounted on each side of the assembly. When a conveyor belt or chain needs to be replaced or tightened, the take-up bearing is adjusted via the screw or other mechanism to provide the appropriate amount of tension on the system.
Image Credit: Control Engineering Europe
Take-up Bearing Component
Take-up bearings are used in conjunction with take-up frames. Take-up bearings and take-up frames can be sold as a unit (assembly) or as individual components.
Take-up assembly (frame with bearings) - They often include a take-up assembly that consists of a guide frame, positioning screw, and hardware for position adjustment.
Take-up bearing- Take-up bearings may be plain bearings, roller bearings, or ball bearings.
Take-up frame- The frame is available in various sizes and housing styles.
Image Credit: Twentebelt
There are many specifications to consider when selecting a bearing for an application. Below is a condensed list of bearing specifications as they relate to take-up bearings.
Types of Bearings
There are three basic types of bearings used in take-up bearings: plain bearings, ball bearings, and roller bearings.
- Plain bearings provide continuous surface contact between inner and outer races, but do not include rolling elements. They are used to constrain, guide, or reduce friction in rotary or linear applications.
Ball bearings use balls between the inner and outer races to reduce friction.
Roller bearings use rollers between the inner and outer races to reduce friction. They provide smooth, low friction motion in rotary applications.
Take-up bearings vary in terms of physical dimensions and operating specifications. Suppliers that use English design units measure bearings in inches (in) or fractions of an inch. Suppliers that use metric design units measure bearings in millimeters (mm) or centimeters (cm).
- Bore diameter is the most important physical dimension to consider. It is defined as the inner diameter of the bearing and fits the shaft of axle.
Bearing width is proportional to the maximum load the bearing can support. When specifying a replacement bearing, it is important to select the appropriate width to ensure the bearing is compatible with the take-up frame.
In terms of operating specifications, the most important factors to consider are:
- Maximum speed- Maximum speed is the top rotational speed of the take-up bearing in revolutions per minute (rpm). Maximum speed is determined by the size of the bearing, lubrication, bearing material, cage material, and the desired lifespan of the bearing. In general, smaller bearings accelerate faster, but larger bearings hold speed better.
Selection Tip: Use a larger bearing for applications where continuous operation is necessary. Use a smaller bearing when the application requires direction changes or quick accelerations.
- Dynamic load- Dynamic load is measured in pounds (lbs) or Newtons (N) and represents the maximum rated radial load for a defined bearing life at the rated speed.
Ball and roller take-up bearings are usually made from a carbon or stainless steel. Plain bearing take-ups are made from bronze or plastics such as polytetrafluoroethylene (PTFE), nylon, and Acetal polymers. Polytetrafluoroethylene (PTFE), a heat-tolerant polymer, is a fluorinated thermoplastic with outstanding chemical resistance, low leachability, and excellent lubricity. Teflon®, a registered trademark of DuPont Dow Elastomers, is a proprietary form of PTFE used with many take-up bearings. Nylon, a category that comprises several grades of polyamides, is commonly used as a bearing surface material because of its toughness, resistance, and pressure ratings. Semi-crystalline Acetal polymers offer excellent lubricity, fatigue resistance, and chemical resistance; however, they suffer from outgassing problems at elevated temperatures and become brittle at low temperatures.
Bearing housings are usually manufactured from cast iron or steel, while take-up frames are typically made of steel or cast iron.
Bearings can be designed with features that help improve their performance in an application. These features include:
Self-lubricating- Ball and liner materials self-lubricate or do not require lubrication.
Lubrication port- Bearing has an opening (port) for providing grease or oil relubrication.
Corrosion resistant- Bearings are resistant to corrosion, rust, pitting, and discoloration.
Self-aligning- Bearings can correct for a small amount of angular misalignment.
Split bearing- The housing and/or bearing is split into two pieces and bolted together.
- Slot width- The slot that the take-up bearing rides on (if present), can either be narrow or wide. The take-up bearing slides along this slot in the frame to adjust the tension on the conveyor. It is important to ensure the take-up bearing fits and runs smoothly on the width of the slot in the frame.
Narrow Slot | Wide Slot
Image Credit: APEX | Fastenal
Take-up Frame Specifications
The frame is what holds the bearing and it comes with its own set of specifications to consider when selecting a take-up bearing.
Take-up Pull Configuration
Center-pull products locate the adjustment pull axis through the center of the bearing.
Image Credit: CCIPulley
Top-pull devices have the pull screw drive on the topside of the bearing.
Image Credit: Martin Sprocket
Bottom-pull take-up bearings have the pull screw drives on the bottom of the bearing.
Image Credit: Take-up Frames Unlimited
Tube take-up bearings have a screw encapsulated in a tube, with the bearing mounted to the end of the tube.
Image Credit: CCI
Take-up Frame Specifications
- Frame length- Frame length is determined by the length of the drum, or system which the frame will be attached to. The length must be long enough to ensure enough tension can be placed on the conveyor when tightened.
- Frame width- The width of the frame.
- Top angle- Top of the frame is shaped triangularly as shown in the picture below.
Protected screw- Screw has a shield or cover for protection against debris, liquids, etc.
Image Credit: CCIPulley
Take-up travel- The total adjustment range of bearing in frame.
Take-up Bearings Applications
Take-up bearings are used in applications with conveyor belts such as, fans and blowers, food processing equipment, and agriculture equipment.
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Hanger bearings are used as rotational bearings for drive and screw conveyor shafts that are enclosed with a housing or trough.
Linear bearings are used in applications where a component needs to be moved along a straight line with high accuracy.
Pillow Block Bearings
Pillow block bearings are mounted bearings that are used to provide load support for a rotating shaft’s axis.
Plain Bearings and Sleeve Bearings
Plain bearings and sleeve bearings (also referred to as bushings or journal bearings) are used to constrain, guide or reduce friction in rotary or linear applications. They function via a sliding action.