Abstract: Device for measuring the two-dimensional velocity of a moving paper web having opposed first and second surfaces, wherein comprising: at least one light source directed at said first surface and arranged to transmit light through said paper web; at least one image capturing device directed at said second surface, and arranged to receive said transmitted light and produce a two-dimensional image of a section of said paper web; a control unit, arranged to control said at least one light source and at least one image capturing device, and to receive two-dimensional images from said at least one image capturing device, and comprising computation means arranged to compute the velocity component of said paper web in the machine direction and/or the cross direction by calculating the cross correlation of two two-dimensional images.

Abstract: Device for measuring the two-dimensional velocity of a moving paper web having opposed first and second surfaces, wherein comprising: at least one light source directed at said first surface and arranged to transmit light through said paper web; at least one image capturing device directed at said second surface, and arranged to receive said transmitted light and produce a two-dimensional image of a section of said paper web; a control unit, arranged to control said at least one light source and at least one image capturing device, and to receive two-dimensional images from said at least one image capturing device, and comprising computation means arranged to compute the velocity component of said paper web in the machine direction and/or the cross direction by calculating the cross correlation of two two-dimensional images.

Abstract: In a machine for forming a layered fibrous web, at least two different fiber suspensions are led through a head box (10), the fiber suspensions are separated from each other by a blade device (18, 180), the fiber suspensions are supplied to a web forming device (24) and a water layer is formed having a transversely uniform flow at an outlet at the end of the blade device (18, 180), such that the water layer constitutes an extension of the blade device and thereby prevents mixing of the fiber suspensions. The blade device (18, 180) can be freely movable in a substantially vertical direction in order to permit an equalization of pressure between the fiber suspension layers separated by the blade device and thereby reducing wake effects downstream the edge of the blade device.

Abstract: In a method of forming a layered fibrous web, the method includes the steps of leading at least two different fiber suspensions through a head box (10), separating the fiber suspensions from each other by a blade device (18, 180), supplying the fiber suspensions to a web forming device (24) and forming a water layer having a transversely uniform flow at an outlet at the end of the blade device (18, 180), such that the water layer constitutes an extension of the blade device and thereby prevents mixing of the fiber suspensions. The blade device (18, 180) can be freely movable in a substantially vertical direction in order to permit an equalization of pressure between the fiber suspension layers separated by the blade device and thereby reducing wake effects downstream the edge of the blade device. A paper machine for carrying out the method is also disclosed.