| 摘要 |
The present invention relates to a device in connection with a filter, especially an active electret filter for air cleaning, said filter comprising an ionisation portion (10; 10'), said portion (10; 10') having a high voltage source at a certain potential, and a precipitator portion (18; 18'), said portion (18; 18') having a downstream side facing away from the ionisation portion (10; 10'). In known electret filters the fibre material eventually loses its charge, alternatively is it necessary to use a fibre material that is easily polarised when an electrical field is applied. The aim of the present invention is to define a filter of the previously mentioned type that is characterised in that as filter material a number of different pre-filter media are useful and that at the downstream side of the filter a layer (22; 22') of electrically conductive material is applied, said material having an absolute potential that is lower than the potential of the high voltage source (12). |
