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Portec Knife-Edge® Technical Specifications

This is only a small example of the model sizes available from Portec. There are 3 standard family sizes of Portec Knife-Edge Curves based upon the outside conveying radius (C) and a range of belt widths (D). Any belt width within the available range and having one of the 3 standard outside conveying radii would be considered a standard model. While Portec frequently designs and builds special radius Knife-Edge curves, the standard models represent the best value and shortest production lead-time.

Frame Assembly:

The all-metal frame is fabricated using the following materials:

Welded 3/16” thick angle steel cross members provide a solid conveyor platform. The lower edge of the side frame has a 1-1/2” wide inward flange to attach floor supports. Bearings are mounted to bearing plates and attached to the frame.

Frame Height: Standard frame height is 14" / 356mm and 16" / 406mm.

Belt Drive system: Unlike friction drive straight conveyors, the Portec Knife-Edge conveyor does not use the end roll to drive its conveyor belt. The belt is driven by its outside edge by the belt drive chain. Special attachment links connect the belt drive chain to a series of grommetted holes along the outside edge of the belt. The drive chain is positively driven by a shaft-mounted sprocket. This positive drive arrangement is unaffected by changes in loading, tension, temperature, humidity and foreign material getting between the bottom of the belt and the end rolls. When conditions change, there is no requirement for immediate attention to maintain the functional operation of the conveyor. Because the belt is merely a carrying surface and high tension is not required for operation of a chain driven conveyor, belt life, as well as integrity of belt joints, is greatly enhanced. The positive drive design is also very conducive to using mechanical lacing because concerns of damage to the end roll lagging (no lagging is required) are non-existent. Even in difficult access areas of a conveyor system, mechanical lacing allows for fast and efficient belt changes because, unlike conveyors with vulcanized endless splice belts, extensive disassembly of the conveyor is not required.

In contrast, friction driven belt conveyors require exact tension control and adjustment to continue operation, and small changes in conditions can immediately affect functionality. On friction drive units, high belt tension to maintain driveability transmits high stress levels to the belt joints; decreasing belt life and increasing maintenance demands. Also on friction driven units, end roll components (shafts, bearings, pulleys) are subjected to much higher stress levels due to the required belt tension. Life expectancy of these components is necessarily shorter.

Belt Drive Chain: #50 sidebow steel chain with belt attachment links

Nickel-plated chain and attachment hardware is available as an option. The chain guide material can easily be replaced as slide-out/slide-in strips with a fastener on each end.

Positive Drive Belt System:   The conveyor belt is positively driven by a shaft mounted sprocket engaging a precision sidebow chain which is attached directly to the outside edge of the belt. This positive drive system is unaffected by changes in loading, tension, temperature, humidity, and foreign material on the belt . The Portec positive drive belt system ensures continuous, reliable operation even in harsh and difficult environments with minimal maintenance.

End Roll Bearings: All bearings are precision, sealed for life, and fitted in a cast iron housing. While additional lubrication is normally not required, a grease fitting can be installed for severe environments to lubricate the self-aligning feature of the bearing unit within the cast iron housing. Nickel-plated housings are available as an option.

End Roll Sprockets: Steel beveled tooth sprockets for #50 sidebow chain. Stainless steel or hardened tooth sprockets are available as options for special applications.

End Rolls and Shafts: The all-steel end rolls are formed using 12 gauge or 14 gauge steel. The hubs are machined from cold rolled steel and welded in each end. Stainless steel or solid plastic end rolls are available to meet sanitary requirements or for corrosive environments.

The end roll shaft is turned, ground and polished 1045 or 1144 stress-proof steel. Each shaft is keyed to fit the end roll. A drive shaft extension is provided on one corner as specified. Extra shaft extensions can be provided as required. Stainless steel or metric shafting is available as an option.

The end roll assemblies are easily replaced as drop-in assemblies. This is especially convenient in confined spaces.

Return Rolls: The returning belt is supported by several rubber covered, precision ball bearing wheels spaced across a 5/8” diameter steel shaft or on hanger brackets. This system is considerably quieter than hollow cylindrical steel rollers, which are often used on belt conveyors.

Stainless steel shafts are available as an option.