Suction device for applying suction to an endless belt with a self-adjusting suction length

摘要

The invention relates to a suction device for applying suction to an endless belt, especially to a felt of a paper machine, having the following features: 1.1 A suction space extending over the entire machine width is provided; 1.2 A connection is provided between the suction space and a vacuum source; 1.3 A suction slot directed towards the belt and extending over the machine width is provided in this suction space; 1.4 An aperture device is provided for adjusting the effective suction length. The aperture device is characterised by the following features: 1.4.1 Provision is made of a first low-pressure space which can be varied in terms of its length extension, and whose one displaceable boundary is connected in a fixed manner to the boundary of the suction slot, decreasing pressure in the first low-pressure space effecting an increasing slot length; 1.4.2 Provision is made of at least one connecting line between the variable low-pressure space and the suction space, so that the same air pressure prevails in both spaces; 1.4.3 Pressure means are provided on the aperture device which effect a reduction of the slot length in the case of increasing pressure of the pressure means.