Fiber application machines, commonly known as fiber placement machines, are known, for the application to a male or female mold of a wide strip formed of a number of flat fibers, of the ribbon type, impregnated with resin, particularly carbon fibers impregnated with a thermosetting or thermoplastic resin. These machines include a system for the displacement of a fiber application head, fiber storage means, and means for conveying fibers from said storage means to the application head.
Fiber placement heads traditionally include, as described in particular in international application WO2006092514, an application roller intended to come into contact against the mold in order to apply the strip, means for guiding the fibers on said application roller, cutting means in order to cut each fiber individually upstream of the roller, and rerouting means upstream of the cutting means so as to reroute each fiber that has just been cut in order to be able at any time to stop and resume the application of a strip, and to choose the width of the strip. The guide means include two systems of ducts or pulleys arranged in staggered rows along two guide planes that grow closer to each other from downstream to upstream so as to guide two layers or bundles of fibers separately towards the roller. For each fiber, the cutting means include a plane blade activated by a pneumatic jack and placed facing a fixed counter tool, and the rerouting means include kicking rollers activated by jacks and placed facing drive rollers. The blades and the kicking rollers of a first layer, and their associated activation jacks, are placed on the roller side, in other words downstream from the fibers relative to the forward movement of the head in use, whereas the blades and the kicking rollers of the other layer, and their associated activation jacks, are placed upstream of the fibers.
The upstream activation jacks must be placed high enough up, relative to the application roller, for the head to be able to be used on different concave surfaces, and particularly with low angles of attack between the laying surface and the strip of fibers emerging from the guide means. The fibers are cut substantially at the same distance from the roller for the two layers so that the handling of all the activation jacks can be simplified, thereby optimising the accuracy and reliability of the head. The downstream jacks are therefore positioned as high as the upstream jacks. This arrangement of the activation jacks restricts the chances of optimising the compactness of the head, and also restricts the accuracy with which the head can be rerouted, so as to obtain, for example, a strip start with fiber cutting edges as aligned as possible.
To stop the fibers from moving, blocking means are provided to block individually each fiber that has just been cut. These blocking means are placed conventionally upstream of the rerouting means and include their own activation jacks. Apart from space requirement problems, these new activation jacks are tricky to control. They require a complex and accurate control system so as to guarantee the blocking of each fiber that has just been cut.