Sheet Brake Vacuum Control
wicket oven
When coating line speeds are increased, sheets may crash at the entrance to the wicket oven. Installing a vacuum box under the end of the belt helps to prevent this, but precise control over the switch timing of the vacuum is required. Sencon's LST22 high speed solenoid drive system is ideal for this application due to its specially tailored power profile to give fast solenoid response times.
- benefits
- Bring moving sheets under control at the entrance to the wicket oven
- Stop edge damage to sheets on fast moving coating lines
- Ultra fast switching of a vacuum generator for precise timing of the sheet brake
- Simple digital adjustment for accurate sheet positioning as they are picked up by the wickets.
- Promote better operator training
- Increase plant efficiency
Vacuum brakes for sheet control
When conveyor speeds on coating lines are increased, sheets may start to crash into the wicket end stops at the entrance to the wicket oven, damaging the edges of the newly coated sheets. A number of dedicated braking solutions are available to overcome this problem. One very efficient method involves installing a vacuum box under the end of the belt. This simply sucks the sheets to a stop, thus allowing the wickets to lift the sheets smoothly without them banging into the wicket end stops.
precise timing required
However, this technique still requires precise control over the switch timing of the vacuum. Incoming sheets need to be brought to a halt exactly when the moving wicket becomes parallel to the conveyor. The vacuum must also be released immediately so that the sheet can be lifted by the wicket. The preferred method for quickly creating a vacuum is to switch positive pressure using a high-speed solenoid valve that is connected to a vacuum generator. This setup allows close mounting of the vacuum source to the opening in the brake shoe, which leaves minimal volume to evacuate before a reasonable level of vacuum is achieved. Maximum achievable vacuum is adjustable by regulating incoming pressure to the system.
sencon’s ultra fast solenoid triggering
Sencon's LST22 high speed solenoid drive system is ideal for this application. Originally developed for inside spray systems on beverage can lines, it has a specially tailored power profile to give fast solenoid response times, which in this instance is used to control the timing of the vacuum generator. Main braking adjustment is achieved via the “On Time” setting on the LST.
positional accuracy
This means that the sheet brake can be turned on and off again quickly and precisely to decelerate incoming sheets at the desired location. In addition, the whole system can be rapidly adjusted using the LST22’s digital control box, so that after just a few trial sheets they are brought to a halt at the exact point required.