Abstract: A method for controlling a vitrector of a vitrectomy system includes emitting an optical signal over an opening in a body of the vitrector, the opening providing access to a cutting member within the body, and using an optical sensor provided on the vitrector to capture optical feedback produced when the optical signal interacts with material proximate to the opening. The presence of the material in a vicinity of the cutting member of the vitrector is determined based on the optical feedback. A control signal to alter operation of the vitrector is issued responsive to determining the presence of the material in the vicinity of the cutting member of the vitrector.

Abstract: A plurality of unidirectional sheets (30a, 30b, 30c) are superposed in different directions and they are bonded together. At least one of the unidirectional sheets is made by spreading a tow so as to obtain uniform thickness, width not less than 5 cm, and a weight of no more than 300 g/m2, cohesion being imparted to the sheet so as to enable it to be handled prior to being superposed with other sheets. Advantageously, the unidirectional sheets are made of carbon fibers and are obtained by spreading out large tows.

Abstract: A plurality of unidirectional sheets (30a, 30b, 30c) are superposed in different directions and they are bonded together. At least one of the unidirectional sheets is made by spreading a tow so as to obtain uniform thickness, width not less than 5 cm, and a weight of no more than 300 g/m2, cohesion being imparted to the sheet so as to enable it to be handled prior to being superposed with other sheets. Advantageously, the unidirectional sheets are made of carbon fibers and are obtained by spreading out large tows.

Abstract: Free fibers (10) are deposited on a rotary support turntable (30) by means of a hollow deposition cone (40) having an outer wall surrounding a chamber and pierced by multiple perforations. The fibers are delivered to the outer surface of the perforated wall of the cone (40) in a cone feed zone that is remote from the zone for deposition on the turntable (30), and they are then held by suction being established inside the chamber, leading to suction through the perforations in the cone, so as to be transported by rotation of the cone from the cone feed zone to the zone for deposition on the turntable, and the fibers cease to be held on the cone in the deposition zone by localized interruption of the suction through the perforations in the wall of the cone, at least in said zone, such that the transported fibers are deposited on the turntable which is rotated about its own axis simultaneously with the cone being rotated. The fibers deposited on the rotary turntable (30) may be compacted and needled.

Abstract: The present invention provides a method of fabricating an annular fiber structure, the method comprising the steps consisting in: providing a first fiber sheet made up of substantially unidirectional elements; forming a transverse, first annular sheet by laying the first fiber sheet in alternation in one direction and in the opposite direction between coaxial outer and inner circular rings with the sheets being held at said rings; providing a second fiber sheet made up of substantially unidirectional elements; forming a circumferential, second annular sheet by depositing the second fiber sheet in a circumferential direction between said outer and inner rings; bonding the transverse and circumferential annular sheets to each other; and driving the transverse and circumferential annular sheets in rotation about the axis of the outer and inner rings so as to perform a plurality of complete revolutions in order to obtain a thick annular fiber structure having layers made up by the transverse sheet alternating wit

Abstract: The present invention provides a method of fabricating an annular fiber structure, the method comprising the steps consisting in: providing a first fiber sheet made up of substantially unidirectional elements; forming a transverse, first annular sheet by laying the first fiber sheet in alternation in one direction and in the opposite direction between coaxial outer and inner circular rings with the sheets being held at said rings; providing a second fiber sheet made up of substantially unidirectional elements; forming a circumferential, second annular sheet by depositing the second fiber sheet in a circumferential direction between said outer and inner rings; bonding the transverse and circumferential annular sheets to each other; and driving the transverse and circumferential annular sheets in rotation about the axis of the outer and inner rings so as to perform a plurality of complete revolutions in order to obtain a thick annular fiber structure having layers made up by the transverse sheet alternating wit

Abstract: A plurality of unidirectional sheets (30a, 30b, 30c) are superposed in different directions and they are bonded together. At least one of the unidirectional sheets is made by spreading a tow so as to obtain uniform thickness, width not less than 5 cm, and a weight of no more than 300 g/m2, cohesion being imparted to the sheet so as to enable it to be handled prior to being superposed with other sheets. Advantageously, the unidirectional sheets are made of carbon fibers and are obtained by spreading out large tows.

Abstract: Free fibers (10) are deposited on a rotary support turntable (30) by means of a hollow deposition cone (40) having an outer wall surrounding a chamber and pierced by multiple perforations. The fibers are delivered to the outer surface of the perforated wall of the cone (40) in a cone feed zone that is remote from the zone for deposition on the turntable (30), and they are then held by suction being established inside the chamber, leading to suction through the perforations in the cone, so as to be transported by rotation of the cone from the cone feed zone to the zone for deposition on the turntable, and the fibers cease to be held on the cone in the deposition zone by localized interruption of the suction through the perforations in the wall of the cone, at least in said zone, such that the transported fibers are deposited on the turntable which is rotated about its own axis simultaneously with the cone being rotated. The fibers deposited on the rotary turntable (30) may be compacted and needled.

Abstract: A plurality of unidirectional sheets (30a, 30b, 30c) are superposed in different directions and they are bonded together. At least one of the unidirectional sheets is made by spreading a tow so as to obtain uniform thickness, width not less than 5 cm, and a weight of no more than 300 g/m2, cohesion being imparted to the sheet so as to enable it to be handled prior to being superposed with other sheets. Advantageously, the unidirectional sheets are made of carbon fibers and are obtained by spreading out large tows.

Abstract: A fiber preform for manufacturing a brake disk out of composite material is itself manufactured by superposing and bonding together fiber layers. Structural fiber layers (10) are used to form at least a first preform portion that is to constitute the fiber reinforcement of the brake disk core, while the or each preform portion that is to constitute the fiber reinforcement of a friction portion of the brake disk is constituted by a felt (16, 18), at least in its portion adjacent to the friction face.

Abstract: Method and machine for producing multiaxial fibrous webs. A plurality of unidirectional sheets (30a, 30b, 30c) are superposed in different directions and they are bonded together. At least one of the unidirectional sheets is made by spreading a tow so as to obtain uniform thickness, width not less than 5 cm, and a weight of no more than 300 g/m2, cohesion being imparted to the sheet so as to enable it to be handled prior to being superposed with other sheets. Advantageously, the unidirectional sheets are made of carbon fibers and are obtained by spreading out large tows.

Abstract: A plurality of unidirectional sheets (30a, 30b, 30c) are superposed in different directions and they are bonded together. At least one of the unidirectional sheets is made by spreading a tow so as to obtain uniform thickness, width not less than 5 cm, and a weight of no more than 300 g/m2, cohesion being imparted to the sheet so as to enable it to be handled prior to being superposed with other sheets. Advantageously, the unidirectional sheets are made of carbon fibers and are obtained by spreading out large tows.

Abstract: A fiber structure for needling is driven so as to impart a speed of advance thereto past a needling head carrying a plurality of needles that are driven with reciprocating motion during which they penetrate into the fiber structure and are extracted therefrom. The instantaneous speed of advance of the fiber structure decreases in response to the resistance to advance caused by the needles penetrating and subsequently increases on the needles being withdrawn. The force exerted on the needles by the advance of the structure is thus limited, without completely interrupting advance throughout the time that needles are present within the structure. The fiber structure can be caused to advance by means of a transmission presenting mechanical slack suitable for absorbing the decrease in the speed of advance caused directly by the resistance to advance that is exerted by the needles.

Abstract: A fiber structure for needling is driven so as to impart a speed of advance thereto past a needling head carrying a plurality of needles that are driven with reciprocating motion during which they penetrate into the fiber structure and are extracted therefrom. The instantaneous speed of advance of the fiber structure decreases in response to the resistance to advance caused by the needles penetrating and subsequently increases on the needles being withdrawn. The force exerted on the needles by the advance of the structure is thus limited, without completely interrupting advance throughout the time that needles are present within the structure. The fiber structure can be caused to advance by means of a transmission presenting mechanical slack suitable for absorbing the decrease in the speed of advance caused directly by the resistance to advance that is exerted by the needles.

Abstract: In a circular needling machine for needling an annular preform and comprising both a vertically movable needling table serving as a horizontal support for said annular preform, and a needling head having a determined number of barbed needles disposed over the needling table in a needling zone and driven with vertical reciprocating motion, provision is made for the annular preform to be placed directly on the needling table and for it to be driven in rotation on the needling table by drive means while the needling table remains rotationally stationary during said rotation. The drive means comprise a set of conical friction rollers kept continuously in contact with the annular preform.

Abstract: A machine for needling a textile structure built up from a wound strip of material to be needled that is delivered by strip supply means comprising a storage drum containing said wound strip of textile material, an unwinding assembly for continuously extracting said strip from said storage drum, and a helical chute or “twist” for taking up said extracted strip unwound from said drum and for bringing it up to a needling table where there are friction drive means. The storage drum and the helical chute have the same axis C as the needling table.

Abstract: A needled fiber structure is made by stacking fiber plies on a platen, by needling the plies as the stack of plies is built up by means of needles driven with reciprocating motion in a direction that extends transversely relative to the plies, and by varying the distance between the platen and an end-of-stroke position of the needles while building up the stack so as to obtain a desired distribution of needling characteristics through the thickness of the fiber structure. The instantaneous force exerted during needle penetration is measured (sensors) and a magnitude representative of needling force or penetration energy is evaluated on the basis of the instantaneous force, and the evaluated magnitude is verified for compliance with at least one predetermined condition to monitor proper operation of the process or to act on the way the distance between the platen and the end-of-stroke position of the needles is varied.

Abstract: A machine for needling a textile structure built up from a helical strip delivered by strip supply means, said machine comprising a needling table, a needling head, cutting means for cutting the helical strip, and conical roller drive means for rotating said strip on the needling table, at least a fraction of said conical roller drive means being retractable so as to release an empty space on said needling table enabling ejector means to remove the textile structure from the needling table.

Abstract: A yarn is formed from discontinuous parallel fibers which are not twisted and which are held together by a covering yarn of sacrificial material wound around the fibers. The fibers comprise an intimate mixture of fibers of at least two different natures selected from carbon fibers or pre-oxidized polyacrylonitrile based carbon precursor fibers, or anisotropic or isotropic pitch based carbon precursor fibers, or phenolic or cellulosic based carbon precursor fibers, and ceramic fibers or ceramic precursor fibers. The mixture of fibers comprises, in its carbon state, at least 15% by weight of high strength fibers, having a tensile strength of at least 1500 MPa and a modulus of at least 150 MPa, and at least 15% by weight of fibers with a low Young's modulus of at most 100 GPa.

Abstract: A three-dimensional fiber structure is formed by superposing layers of felt and by bonding them together by needling, then the structure is compressed to obtain a preform having a fiber volume fraction of not less than 20%. The preform is held in its compressed state by being impregnated with a liquid composition containing a bonding agent capable of bonding the fibers of the preform together. Thereafter, the preform consolidated in this way is densified, e.g. by chemical vapor infiltration.