Traditional Belt Conveyors (ie. Friction/Negative Drive)
When most people think of belt conveyors they think of belt tensioned around drives and being moved by the friction between the belt and drive. This is the most common method but requires more maintenance and drive adjustment in heavy applications. This is because more weight means not only more strain on the belt, but more slippage and wear. Additionally, they take more work to clean in sanitary applications because tension has to be removed in order to clean under the belt. But for most applications the negative drive belt remains the most practical and cost-effective option.
Positive Drive Conveyors
Positive drive conveyors use direct force instead of friction to move belt; this is achieved with recessed notches in the belt and geared drives with cogs (or visa-versa). These cogs fit into the notched belt (or visa-versa) which is moved directly, without any slippage. Because this method does not require tension to operate, it doesn’t need to be adjusted as much and is easier to clean. An example from Intralox is shown here.
Drives are placed at the head (discharge) whenever possible because that’s where they perform best. When driven at the tail, there is no direct force on the load-bearing side of the belt (you can’t convey boxes by pushing a rope they’re sitting on). The belt must be pulled, which means pulling the belt around the opposite side, inflicting double the wear because it’s being tensioned around two points.
There are, however, special applications where placing the drive at the tail will provide more value than it consumes. For example, if the belt is discharging into a sanitary environment, close proximity of gearboxes and non-sanitary components is not acceptable. It could also simply make more sense service-wise if the drive is inaccessible at the head.
Drives can also be placed in the middle of the belt in special circumstances, such as when you’re loading the belt in the center and swapping the conveyance direction to discharge at alternating sides.
Conveyor belts can be made of various materials depending on the product, including inter-linked plastic which can shift and convey about corners. Material type largely depends on product temperature, mass, abrasiveness, and sanitation requirements.
Most Common Material and Application Pairings
Metal – Filter, heat, bakery, de-oiling, de-watering
Rubber – (Most common type of belt), aggregate, packaging, most non-food applications
Plastic – Food
Fabric – Specialty applications (mostly obsolete)
Neoprene – Packaging (because of its oil-resistant nature)
Poly Belt – Packaging (because of its oil-resistant nature)
Linked plastic (modular) – When practical because of its affordability, (does not bode well in high-impact applications
Drive pulleys can be crowned (wider in the center) to help keep the belt from walking, and standard pulleys can be placed in a number of configurations to handle slack. Crowned pulleys are most common for receiving raw product like beets & potatoes and are not necessary in positive drive applications.
Conveyor belts may have a number of different frame configurations depending on what the application yields itself to. But whether you can use hollow support points depends on regulations. (FDA allows hollow support points, USDA does not.)
The beds for conveyors are usually flat and only meant to support the belt, but they can also be fitted with sidewalls to help contain and protect product. But because of the contact between side-walls and product, trough belt conveyors are used for particularly abraisive or delicate materials and foods. Trough belt conveyors are also preferred over walled flat conveyors in sanitary applications because they’re much easier to clean.
Flat-belts can be fitted with a huge variety of rejects, all of which we build for the application. The techniques used could include diverters, push-arms (pneumatic or electric), drop-panels, air blast, magnets, and others. In bulk applications where rejection of good product with the bad cannot be avoided, accuracy must be maximized to reduce the effect.
From simple installations to complete system design and integration, we help move bulk dry goods efficiently. Whether it’s food, pharma, or industrial, there is a best method for moving every product and we deliver the appropriate level of speed and gentleness, all backed by 24/7 service.
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