Apparatus for forming a web

Plastic composites reinforced with fibers are known and used in a wide variety of aerospace, industrial, .and sporting applications,. Initially, the reinforcing structures were woven fabrics which provided uniformity throughout the composite. However, nonwoven webs are now being used because they are less expensive than woven fabrics. Normally, such webs have been laid down randomly or in a semi-ordered fashion. It is now recognized that improved composites can be produced if the nonwoven web is laid down in a. precisely ordered fashion. ’ In some composites, complete uniformity is required, whereas, in other composites, the fiber density should be greater at the locations where the stresses are greater. .

SUMMARY

With the apparatus of the present invention reinforcing webs are׳ formed by depositing a continuous, filamentary strand in a bed of deflectible pins according to a desired pattern. The apparatus has a robotized head which includes a freely rotatable, strand-guiding tube which projects into the bed and terminates a in a .:curved length adapted to deflect the pins it engages as a strand is deposited beneath the tops of the pins.

This apparatus .can therefore .lay down the strands in a.very precise pattern, repetitively with more uniformity than what has previously been attainable with prior art filament depositing apparatuses, such as those disclosed in U.S. 3,902,644 or de 2,452,310, which deposit the strands above the pins or laydown surface.

DRAWINGS

Figure 1 is a schematic illustration of the manner in which the apparatus of the invention , is used to form a web.

Fig. 2 is a fragmentary, perspective enlargement of the apparatus.

Figs. •3-5 are. front, top and side views of ,the winding head shown in Figs. 1. and 2, Fig. 5 having

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' 2 י been taken on line 5-5 in Fig. 4.

Fig. 6 shows fragments of a web formed with precise uniformity on the apparatus of the present invention.

Figs. 7 and 8 are side and top views of a device for transferring a web from the bed of pins shown in Figs. 1 and 2.

Fig. 9.illustrates transfer of a web from the bed on which it was formed.

Fig. 10 is a fragmentary, enlarged view of the bed shown in Figs. 1, 2 and 7-9.

Fig. 11 is a perspective view of a modification of the apparatus.

DESCRIPTION

In Fig. 1, the apparatus of the present invention is shown in association with other elements of a web-forming installation. On the arm of a robot 10, there is a dispensing head 12 through which a filamentary yarn 14 is pulled from a package 16 on,a creel 18. Robot 10 functions as an automatic manipulator for moving head 12 relative to a bed 20 of deflectible pins according to a program set in a microprocessor within a controller 22. Other elements coupled to the contrailer are a CRT terminal 24, a direct current (de) power supply 26 and a teach pendant or manual controller 28. As will be explained more fully hereinafter, yarn 14 is held by its engagement with pins in bed 20 and pulled from package 16 by the movement of head 12 in response to instructions from the programmed controller 22, i.e., according to the pattern desired for a given web.

Referring to Figs. 2-5, the robotized winding head 12 includes a block 30 having a step 32 provided with threaded passages 34 for one or more strand-guidED-0331 ing tubes 35. Block 30 is fastened to a bracket 36

ED-0331 which, in turn, is fastened to a mounting disc at the end of the arm on robot 10.

Each tube 35 has a straight length that extends through a threaded housing 38 and terminates in a curved length or horn 40. The straight length is freely rotatable in spaced sleeve bearings, 42 in housing 38 and is retained by collars 44, 45. Housing 38 is mounted in one of the threaded passages 34.

Referring now to Figs. 2, 5 and 10, horn 40 on tube 35 projects into the bed 20 of pins 50 and trails the straight length.as head 12 is moved by robot 10. Pins 50 are deflected as horn 40 moves through the bed. Due to the resilience of their mounting, the pins spring back toward a normally upright position and hold yarn 14 in the desired pattern. As noted above, yarn 14 is anchored in the bed by frictional engagement with the pins, and is pulled from package 16 by the.programmed movement of dispensing head 12. Horn 40 dispenses yarn 14 beneath the tops of the pins 50 and also engages preceding loops to insure their placement at the desired depth in the bed 20.

With the winding head 12 fixed to the robot, as shown in Fig. 2, a web of the type shown in Fig. 6 is formed by programming the robot to move the head in a circular motion as it is advanced longitudinally through the length of the pattern. At the end of each row, the head is traversed laterally and advanced longitudinally in the reverse direction. In actuality, the circular motion is a succession of orthogonal, linear steps but the yarn is deposited in a shingled series of in-line loops due to the manner in which pins 50 spring back toward their normal, upright position. .,

A transfer device 60 for removing a web from the bed of pins 50is shown in Figs. 7 and 8. Device 60 ⁴includes a plurality of spaced blades 62 attached at one end to a bar 64. The free ends of the blades 62 are held in alignment by a sliding bar 66 as. they are inserted into the bed of pins beneath a formed web. Once passed beneath the web, the ends of blades 62 are retained in another bar 68.' A second device 60 is located as shown in Fig. 9 and the assembly is then used to remove the web from the bed of pins. A binder resin is.applied to insure the integrity of the web which can then be transferred to a suitable mold for fabrication of a composite structure.

Details of a base and retainer for the bed of pins 50 appear in Fig. 10 where it will be seen that the shanks of the pins project through holes 70 in an elastomeric sheet 72. The heads of the pins are embedded in a layer 74 of elastomeric adhesive which also serves to adhere sheet 72 to a retainer plate 76. A selected number of retainers is assembled and each is fastened to a base plate 78 by screws 80.

The modification shown in Fig. 11 has a head 12’ adapted for attachment to the arm of a robot. Head 12' includes a block 30’ provided with an aperture 90 which receives a rotor 92, a belt 93 and a pulley 94. A motor 96 is coupled to the pulley 94 for driving rotor 92. A strand-guiding tube 35' is mounted eccentrically in rotor 92. With this embodiment, the robot can be programmed to move head 12' linearly and the rotary movement of rotor 92 causes a shingled series of in-line loops to be deposited in the bed of pins. The curved horn oh strand-guiding tube 35' pushes successive loops to the same level in each row, thus forming an ordered array of the type shown in Fig. 6.

The nonwoven webs produced by the apparatus of this invention can be used for many purposes. For ED-0331 example, webs with a uniform, precisely ordered laydown of the type shown in Fig. 6 have been formed and used as reinforcements in composite panels. In addition to their use as reinforcing fabrics, the precisely ordered webs could be used as base material for coating or tufting and for making rieedled nonwovens.

In the end uses where composites are rein־^ forced with a nonwoven web and subjected to localized stresses, the apparatus of this invention is capable of precisely locating extra fibers at the needed locations to handle these localized stresses.

Further, many composites in their final form have openings in them. In the past, the fabric would be cut and removed to accommodate the openings. This . causes fabric waste and fiber discontinuities. The apparatus disclosed herein can precisely lay down fibers around such openings, providing improved reinforcement and reduced fiber waste.

Where used herein, the term strand is meant to denote a yarn of continuous filaments or a yarn spun from staple fibers. It also denotes such a yarn joined with another of the same or a different composition. In the latter respect, yarns of graphite, polyamide and polyester have been used in webs formed on the apparatus of the present invention.