Controlling palletised loads moving in automated processes

Jon Lawson

Automated materials handling is a vital part of modern manufacturing, production, warehousing and distribution operations. Most loads need gentle handling and stopping, so here Ian Carr explains the vital role played by stops and dampers

Falling off a 10 storey building won’t harm you – it’s the sudden stop at the end that does the damage! This interpretation of Newtonian mechanics is perfectly applicable to palletised loads moving along conveyor belts, and similar movements in automated industrial environments. Generally, the travel is harmless, but care needs to be taken to achieve a gentle stop.

This can be accomplished by using dampers such as WörneR Stops, which are modular, compact, adaptable stopping and separating devices for automated material handling. These are available in damped and undamped versions; are easy to fit to most belt and roller conveyors; are adjustable to suit load and speed requirements; and can be set up for either local or central control.

In addition, they reduce noise emissions, protect the plant from shock and vibrations, can provide anti-bounce and indexing capabilities and can be integrated with sensors and other automation equipment. Stops are available with manual operation or with pneumatic and electromechanical drives. In addition, customised and bespoke units can be made if required.

In order to understand the capabilities of stops and dampers, it is best to identify the main types of unit that are available as standard products. These will meet the vast majority of requirements, keeping the need for bespoke items to a minimum.

* The first type to recognise is the ‘damped separating stop’. These gently decelerate and stop pallets as they arrive at a desired location, protecting the load from damage, preventing rebound and reducing shock loads into the plant.

* Related to these are ‘undamped stops’, an economical basic design of stop. Because they are undamped they need to be of robust construction and are usable where the pallet, load and plant are equally tough. Their main purpose is to stop one or more pallets in a desired location with very short cycle times, possibly a staging post where pallets collect prior to the next step of the processing operation.

* Anti-bounce stops are normally spring loaded stops used in systems with little fiction between the means of conveyance and the pallet, where the risk of a rebound is especially high.

* Lifting stops, or indexing cylinders, are used to lift the pallet a set distance off the conveyor and hold it in position. The conveyor continues to run, but does not impart vibration to the pallet because there is no physical contact. This arrangement has three advantages: it can protect delicate loads, it is good in high speed applications where vibration levels would be high, and it provides precise positioning of the pallet. Often, lifting stops are used in association with damped stops which halt the pallet before it is raised up.

* Angle dampers are used not for stopping, but rather for assisting. When a pallet is required to change its direction of travel and its load is fragile, shock sensitive or liable to topple over.

* Bespoke and customised dampers can be designed for specific application needs. These may be to accommodate high speeds or extra loads, to provide alternating stopping positions or other requirements.

Each installation of a damper or stop needs to be considered individually, with speed and load being the first considerations. There is then the need to consider the best type of damper for the situation and the stopping performance required of it. Space constraints can be consideration along with access for cleaning and maintenance.

If the stop is to be used in an automated system, there is probably going to be a need for some nearby sensors to detect pallet presence/absence, count their throughput etc. This information will be send back to the central computer that controls operations. Theoretically at least, the computer could also be sending signals to electromechancial and pneumatic stops to control their functioning in real time.

In conclusion we can say while stops and dampers may not be the most glamorous elements in automated production plants and warehouses, they are hugely important. They allow operations to proceed at a relatively high speed by controlling and positioning products while also protecting products and plant from shocks loads and vibrations. In fact it would be fair to say that without stops and dampers, automation would probably be a non-starter.

Ian Carr is with Drive Lines Ltd