Pultrusion method and apparatus

Abstract

Provided is a method of manufacturing a pultruded strip for an elongate structure. The method includes the step of: providing a pultrusion apparatus including at least a pultrusion die through which a plurality of fibers are pulled to be soaked in a resin, and changing the conduction properties of selected points along the plurality of fibers upstream the pultrusion die.

Claims

1. A method of manufacturing a pultruded strip for an elongate structure, the method comprising: providing a pultrusion apparatus including at least a pultrusion die through which a plurality of fibers are pulled to be soaked in a resin; and changing conduction properties of selected points along the plurality of fibers upstream from the pultrusion die by injecting or depositing discrete drops of a conductive glue onto the plurality of fibers.

2. The method of manufacturing as claimed in claim 1, wherein the elongate structure is a portion of a wind turbine blade.

3. The method of manufacturing according to claim 1, wherein the plurality of fibers are spaced apart from each other during the changing of conduction properties.

4. The method of manufacturing according to claim 1, wherein a selected point along an individual fiber is a discrete location on the individual fiber, and areas of the individual fiber adjacent to the selected point remain unchanged.

5. The method of manufacturing according to claim 1, wherein a plurality of nozzles are used to inject or deposit the discrete drops of conductive glue.

6. A method of manufacturing a pultruded strip for an elongate structure, the method comprising: providing a pultrusion apparatus including at least a pultrusion die through which a plurality of fibers are pulled to be soaked in a resin; and changing conduction properties of selected points along individual fibers of the plurality of fibers upstream from the pultrusion die by: (i) mashing or squeezing the plurality of fibers to change a size of the plurality of fibers, or (ii) locally removing or breaking a covering surface of at least one of the plurality of fibers to change the size; wherein the mashing and squeezing the plurality of fibers, or the locally removing or breaking the covering surface, is a function of the individual fibers being physically pinched between two surfaces.

7. The method of manufacturing as claimed in claim 6, wherein the elongate structure is a portion of a wind turbine blade.

8. The method of manufacturing according to claim 6, wherein the plurality of fibers are spaced apart from each other during the changing of conduction properties.

9. The method of manufacturing according to claim 6, wherein the changing conduction properties of selected points along the plurality of fibers occurs when the covering surface of the plurality of fibers is broken.

10. The method of manufacturing according to claim 6, wherein a selected point along an individual fiber is a discrete location on the individual fiber, and areas of the individual fiber adjacent to the selected point remain unchanged.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

(2) FIG. 1 shows a schematic layout of a portion of a first embodiment of a pultrusion apparatus;

(3) FIG. 2 shows a schematic layout of a portion of a second embodiment of a pultrusion apparatus; and

(4) FIG. 3 shows a schematic section of a wind turbine including a component according to tan embodiment of the present invention.

DETAILED DESCRIPTION

(5) The illustrations in the drawings are schematic. It is noted that in different figures, similar or identical elements are provided with the same reference signs.

(6) FIG. 1 shows a first embodiment of a pultrusion apparatus 100 extending along a longitudinal pultrusion direction X. The pultrusion apparatus 100 comprises a pultrusion die 20 through which a plurality of fibers 110 are pulled to be soaked in a resin.

(7) The pultrusion die 20 has a rectangular cross-section.

(8) The pultrusion die 20 is conventional and already known in the pultrusion technical field and therefore not described in further detail.

(9) With reference to the pultrusion direction X, downstream the pultrusion die 20 at least a partially formed pultruded strip 50 is delivered.

(10) With reference to the pultrusion direction X, upstream the pultrusion die 20 a roving section 80 is provided. In the roving section 80 a plurality of fibers 110, for example coming from a plurality of fiber bobbins (not shown), are collected and led towards the pultrusion die 20.

(11) The roving section 80 may be used to change the conduction properties of selected points 200 along the plurality of fibers 110 upstream the pultrusion die 20, i.e. before they enter the pultrusion die 20.

(12) The points 200 can be selected according to a plurality of criteria, for example they be uniformly distributed along the plurality of fibers 110.

(13) To such purpose, the roving section 80 comprises one or more nozzles 82 (two nozzles 82 in the embodiment of FIG. 1) for injecting or depositing drops 60 of a conductive glue selected points 200 along the plurality of fibers 110. The nozzles are mounted on a plurality of respective arms 83, which are movable according to a direction Z, transversal to the pultrusion direction X, to reach the selected points 200 the plurality of fibers 110.

(14) According to other embodiments of the present invention, the arms 83 may be movable on a plane or on a three-dimensional space.

(15) The arms 83 may be movable above or below the plurality of fibers 110.

(16) By injecting or depositing drops 60 of a conductive glue at the selected points 200 along the plurality of fibers 110,

(17) the conduction properties at the pultruded strip 50 are changed locally. The drops 50 of conductive glue provide a local connection between adjacent fibers 110 which improve the overall conductivity of the pultruded strip 50.

(18) FIG. 2 shows a second embodiment of a pultrusion apparatus 100 extending along a longitudinal pultrusion direction X. According to the second embodiment, changing the conduction properties of selected points 200 along said plurality of fibers 110 is performed by changing the size or the surface of the fibers 110 in the selected points 200. In particular, changing the size or the surface of the fibers may be performed by mashing or squeezing. The smashing or squeezing of the fibers interrupts the covering surface of the fibers 110, which has poor conductive properties. Removing or breaking the covering surface of the fibers 110 exposes the carbon core to the exterior and thus locally improves the conductivity of the pultruded strip 50.

(19) To such purpose, in such embodiment the roving section 80 comprises a wheel 85 rotating around a rotating axis Z, transversal to the pultrusion direction X, and a stationary plate 86. The wheel 85 comprises a plurality of radial protrusions 87, regularly distributed about the rotating axis Z (four radial protrusions 87 in a cross configuration, at regular angular distances of 90 deg from each other). The radial protrusions 87 are made of soft material, for example a soft plastic material. The stationary plate 86 is provided with an uneven rigid surface 88 having a plurality of discontinuities. For example, the surface 88 may be made of sand surface. In the roving section 80 the fibers 110 passes between the wheel 85 and the stationary plate 86. The mutual distance between the wheel 85 and the stationary plate 86 is chosen in such a way that, during the rotation of the wheel 85 around the rotational axis Z, the fibers 110 are periodically pinched between each of the radial protrusions 87 and the uneven rigid surface 88 at the selected points 200. The irregularities of the rigid surface 88 causes the covers of the fibers 110 to crack, thus exposing the carbon core to the exterior. The soft material of the radial protrusions 87 prevents the fibers 110 from completely breaking. Alternatively the radial protrusions 87 may be made of an hard material and the wheel 85 provided with an elastic support, which is able to limit pressure and friction between the arms and the stationary plate 86, with the same purpose of preventing the fibers 110 from breaking.

(20) FIG. 3 shows a wind turbine 1 including components according to the embodiments of the invention. The wind turbine 1 comprises a tower 2, which is mounted on a non-depicted fundament. A nacelle 3 is arranged on top of the tower 2.

(21) The wind turbine 1 further comprises a wind rotor 5 having two, three or more blades 4 (in the perspective of FIG. 1 only two blades 4 are visible). The wind rotor 5 is rotatable around a rotational axis Y. The blades 4 extend radially with respect to the rotational axis Y.

(22) The wind rotor 5 is rotationally coupled with an electric generator 30 by means of a rotatable main shaft 9.

(23) According to other possible embodiments of the present invention (not represented in the attached figures), the wind rotor 5 is rotationally coupled directly with the electric generator 30 (direct-drive generator configuration).

(24) A schematically depicted bearing assembly 8 is provided in order to hold in place the rotor 5. The rotatable main shaft 9 extends along the rotational axis Y.

(25) The blades 4 comprise one or more elongated structure 50 obtained through the present embodiments of the invention.

(26) Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

(27) For the sake of clarity, it is to be understood that the use of ‘a’ or ‘an’ throughout this application does not exclude a plurality, and ‘comprising’ does not exclude other steps or elements.