Light curtain redefines entry/exit control

Edited by the Engineeringtalk editorial team Jul 6, 2005

A new access-point light curtain system overcomes the performance limitations of muting light guards in pallet-based logistical environments.

By intelligently monitoring broken-beam patterns, Sick has developed an access-point light curtain system, designed specifically for pallet-based logistical environments, that overcomes the performance limitations of muting light guards.

Not only does the C4000 Palletizer offer enhanced safety features but also, by removing the complexities required by a muting approach, is both faster and simpler to install.

The concept of guarding an access point, where products or work can pass into and out of a hazardous area, but personnel cannot, is not new; but one area of guarding that is crying out for a fresh approach is entry/exit light guarding where traditionally a multibeam light curtain is muted by a pallet or skid carrying goods.

A typical solution to this application involves the use of muting sensors.

Today's entry/exit guarding solutions all work on this tried and tested principle but all of them suffer from the same operational problems: sensor failure and misalignment; incorrect and unsafe installation; muting lamp failure; and the possibility of external manipulation.

Due to the fragility of this approach and the number of individual components, the downtime or availability of the line can be adversely affected, losing production and profit - an automotive manufacturer can lose more than GBP 5000 a minute because of line stoppages.

Sick has taken a fresh look at the applications that are most common in the pallet handling sectors and redefined the entry/exit light curtain.

By asking the following questions: "why does the light curtain have to mute?" and "why not use sensor intelligence to distinguish between objects and people?" it continued on a train of thought that lead to the development of the C4000 Palletizer.

Mounted in the horizontal plane, the C4000 Palletizer allows entry or exit by dynamically monitoring the broken beam pattern in the light curtain field.

Certain objects are able to move through the light curtain field, provided that they do not exceed a certain size and that their relative proximity to each other, while in the field, remains constant.

This is quite unlike the beam pattern created by a person walking through the light curtain.

They are instantly detected, even if they are walking alongside a legitimate load.

The clear advantage of this technology is that the light curtain remains active for the detection of people during the process of entry or exit.

It is then possible to detect entry of people either side of the pallet or object, removing the need for silhouettes and other protective measures.

There are no muting lamps to maintain or replace because the system never mutes and there are no muting sensors to mount, align and maintain.

Removing all these elements can only lead to greater reliability, improved protection, reduced installation cost and reduced downtime.

The C4000 Palletizer is TUV certified to EN61294-1 and 2 Type 4 and IEC61508 SIL 3 making it suitable for applications that have requirements up to control Category 4 EN954-1.

Examples where this equipment would bring significant benefits include palletisers and depalletisers, strapping machines, stretch wrappers, robot cells and other automated handling machinery.