Robot System for Forming a Structural Component of a Preimpregnated Fiber Reinforced Tape

The invention relates to a robot system for dispensing preimpregnated fiber reinforced tape or the like for use in a molding and bonding apparatus, for example, for producing large structural components such as aircraft bodies or aircraft wings or the like by using so-called prepregs in the form of tapes.

U.S. Pat. No. 4,512,837 (Sarh et al.) and U.S. Pat. No. 4,524,556 (Sarh et al.) corresponding to German Patent (DE-PS) 3,003,552, describe a system including a method and an apparatus for manufacturing large surface structural components, especially for aircraft, by using preimpregnated fiber reinforced tapes which are laminated to a frame structure and bonded, by curing, to each other and to the frame structure. Such a system operates to a large extent automatically with the aid of industrial robots as shown, for example, in FIG. 13 of these U.S. patents. The grid or frame structure is made of ribs having an I-cross-section and extending lengthwise and crosswise and the formation of these frame structures is largely automated. However, the application of the preimpregnated fiber reinforced tapes to the frame or grid structure requires a manual operation. Such manual application is limited in its speed and hence consumes a substantial number of man-hours, thereby driving up the manufacturing costs. Additionally, the manual application of the tapes is frequently not precise enough.

The automatic application of the prepreg tapes to the frame structure requires a tool that can be carried at the end of an arm of an industrial robot. Such tool must be able to cut prepreg tapes of different width and cut edges must run at different angles relative to the length of the tapes.

U.S. Pat. No. 3,859,879 (Spengler) discloses a sheet material cutting apparatus with a strip steel knife attached to a cutting roller along a portion of a helical curve. The cutting roller is mounted in a floor supported frame in such a way that the roller axis slants relative to a feed advance direction of material to be cut, whereby the helically curved knife and the slanting angle are so arranged relative to each other that the resulting scissor cut will extend perpendicularly to the feed advance direction and straight across the material being cut. Such a cutting apparatus is not suitable for the present purposes because the prepregs must be cut so that the cut edge has a predetermined slant relative to the length of the prepreg. The slants permit a lateral overlap of one prepreg tape end with the beginning of the next prepreg tape portion having the same slant. Such overlap is not possible with square cut tape ends.

In view of the foregoing it is the aim of the invention to achieve the following objects singly or in combination:

to provide a dispenser for preimpregnated, fiber reinforced tapes, so-called prepregs, which is capable of cutting and supplying these tapes substantially automatically to a molding apparatus, for example, for an automatic application of the tapes to a grid or frame structure to laminate these tapes onto the grid or frame structure;

to construct the dispenser in such a way that it can be attached to an arm of an industrial robot which uses the dispenser as a tool;

to construct the drive means of the tape dispenser in such a way that the drive means may be controlled in response to a program stored in a computer which may also control the industrial robot;

to include a cutting mechanism and cutter drives in the tape dispenser tool capable of handling tapes of different width and to cut these tapes at a slant relative to the tape length; and

to cut different tapes at different slants relative to the tape length.

The prepreg tape dispenser according to the invention is characterized in that a carrier frame supporting a supply reel for the tape is equipped with an adapter for attaching the dispenser to a robot such as the arm of an industrial robot. A tool support carries at least one feed roller for the tape and at least one cutting unit for severing portions from the continuous tape as it is dispensed by the supply reel. The support is mounted to the carrier frame or to an intermediate member by vertical guide elements and biasing spring members are inserted between the carrier frame or intermediate member and the tool support for biasing the tool support in such a way that the springs oppose a reduction in the distance between the carrier frame or intermediate member and the support. Further, all drive members, for example, for the feed rollers, for the cutting means, and so forth, are controllable in response to control signals, for example, provided by a control computer which in turn operates in accordance with a stored program and which may also control the robot.

The tool unit according to the invention is equipped with a cutting mechanism having at least one knife support cylinder with a first rotational axis carrying at least one helically curved knife secured to the surface of the knife support cylinder. An endless conveyor belt carried by conveyor rollers transports the tape to be cut to and past the helical knife for cutting. Counter pressure rollers support the tape carrying run of the endless conveyor belt for pressing the belt and thus the tape against the helically curved knife. The conveyor rollers have second axes extending in parallel to said first axis of said knife support cylinder so that the tape is cut at a slant relative to the tape length or longitudinal edge of the tape by the helically curved knife. This arrangement of the rollers and knife cylinder results in cut tape ends that have a slant for a lateral overlap of tape end in the mold or on a supporting grid or frame structure.

A plurality of knife carrying cylinders having increasing axial lengths may be arranged in a row with the cylinder axes extending in parallel, whereby tapes of different widths may be cut. These cylinders may carry knives all of which have the same pitch in their helical curvature or they may have different pitches from knife to knife. Knives with the same pitch cut tape ends with the same slant. Knives with different pitches cut tape ends with different slants. Both features are desirable depending on the type of tape used and on the purpose for which the tapes are used. The slant at the tape end is flat or steep, depending on pitch angle of the helical knife on the speed of the conveyor belt, and on the speed of the knife carrying cylinders.

The combination of these features according to the invention makes the tape supply substantially automatic, whereby the manufacturing costs, especially the man-hour costs, are substantially reduced. Simultaneously, the manufacturing precision is increased because the robot arm can locate the dispenser in a very precise manner for a stepwise or continuous tape dispensing and cutting.

In order that the invention may be clearly understood, it will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a side view of the dispenser according to the invention in which the tape is cut by a rotatable disk knife;

FIG. 2 is a view in the direction of the arrow II in FIG. 1, and partially in section;

FIG. 3 is a side view similar to that of FIG. 1, but showing the dispenser as it dispenses a length of tape;

FIG. 4 shows the severing of a length of tape when the application of that length or portion is completed;

FIG. 5 illustrates a side view of another embodiment of a dispenser according to the invention in which the tape is cut by a knife carried on a knife bar which is rotatable about its longitudinal axis;

FIG. 6 is a view of the embodiment of FIG. 5, taken in the direction of the arrow VI in FIG. 5;

FIG. 7 is a view in the direction of the arrow VII in FIG. 5;

FIG. 8 is a view in the direction of the arrow VIII in FIG. 5

FIG. 9 illustrates a partial view of a modified cutting mechanism in which knife cylinders carry helically curved knives for cutting a moving tape at a slant;

FIG. 10 is a view in the direction of the arrow X in FIG. 9; and

FIG. 11 shows a length of tape cut by a knife carried by one of the cylinders shown in FIGS. 9 and 10.

FIGS. 1 and 2 illustrate an embodiment of the present dispenser in which the prepreg tape 15 is pulled off a supply reel 3 rotatably mounted on a carrier frame 1. An adapter 2 secured at one end thereof to the carrier frame 1 permits attaching the dispenser to the arm of an industrial robot such as shown in the above two U.S. patents to Sarh et al. A drive member such as a compressed air motor 4 mounted to the frame 1 drives the supply reel 3 for dispensing tape 15.

A tool support member 5 is operatively secured to the lower end of the frame 1 by means of mounting guide rods 16. The lower end of each mounting guide rod 16 is rigidly secured to the tool support 5. The upper end of each rod is movably held, for example by a ball box, in the frame structure 1. A spring 6 is mounted so that it is effective between the frame 1 and the tool support 5. As shown, the spring 6 surrounds a portion of the guide rod 16 and bears with one end against the support 5 and with its other end against the frame 1 thereby tending to push the support 5 away from the frame 1 and to oppose a movement of the support 5 toward the frame 1. A flange at the upper end of each guide rod 16 limits the spacing between the support 5 and the frame 1.

The tool support 5 carries two rollers 7 and 8 for feeding, guiding, and pressing the tape 15 against a structural component being manufactured and shown at 21 in FIG. 3. If the prepreg tape is provided with a backing strip 20, a take-up roller 9 driven by a drive member 10, such as a compressed air motor, is provided for rolling-up the backing strip 20 as it is being separated from the tape 15. A cutting unit 11 is also attached for a tilting movement to the tool carrier 5. The cutting unit 11 comprises substantially a knife carrier 12 and a rotatable cutting disk 13 secured to the knife carrier 12, as well as a stripping and guide blade 14 for the tape 15. A piston cylinder device 17 mounted to the tool support 5, drives the cutting unit and thus the disk knife 13 across the tape 15 into the dash-dotted knife end position 13a shown in FIG. 2. The cutting unit 11 with its knife carrier 12 is also tiltable from the dashed line position shown in FIG. 3 into the cutting position shown in FIG. 4. This movement can also be derived from the compressed air piston cylinder device 17. As shown in FIG. 4, in the cutting position the knife disk 13 cooperates with a counter cutting edge 18 held in a stationary position by the tool carrier 5. Thus, the knife disk 13 and the counter edge 18 cooperate in severing a portion of the tape 15. Once a portion is severed the robot arm moves the dispenser back into a starting position for a repeated dispensing. As the cutting unit 11 is being tilted, a lever 19 carrying a pin 19a is tilted simultaneously for properly guiding the tape 15.

Referring to FIG. 3, the robot arm moves the dispenser from right to left as indicated by the arrow 22 for dispensing a length of tape 15, whereby one or several tape layers may be applied to a structural component 21 located in a molding apparatus as described in the above mentioned two U.S. patents to Sarh et al. The robot arm brings the dispenser into a starting position determined by a program in a control computer and presses the rollers 7 and 8 against the molding apparatus to thereby firmly press the tape 15 against a grid structure 21. Thus, the tape which at this point is still rather sticky since it has not been cured, adheres to the frame structure or to a previously laid down layer of tape 15. As the robot arm moves the dispenser in the direction of the arrow 22, tape is unreeled from the supply roller 3 and deposited as described in accordance with program steps. During this dispensing and depositing of tape the motor 4 applies a torque moment to the supply reel 3 as indicated by the arrow 23 to make sure that the tape that is being dispensed is sufficiently taut to avoid wrinkling. A motor 10 drives the take-up roller 9 for winding up the backing strip 20. When the end of a layer is reached, as shown in FIG. 4, the movement in the direction of the arrow 22 is stopped and the cutting is performed at the end of a layered section on a structural component 21. At this point the knife carrier 12 and its disk knife 13 are moved into the position shown in FIG. 4 by the piston cylinder device 17 which is operated, for example, by a magnetic valve not shown, whereby the pin 19a of the arm 19 properly presents the tape to the knife 13 and edge 18. Thereafter, the piston cylinder device 17 moves the cutting mechanism crosswise relative to the length of the tape for the severing by rolling the knife 13 along the edge 18 for a clean cut of the tape 15. The guide blade 14 makes sure that even after the severing the remaining or free end of the tape 15 remains attached to the end of the pressed down roller 7. The just described operation is repeated as often as is required for laying the prescribed number of tape layers onto the structural component until the intended thickness of the laminate structure is achieved.

Incidentally, the supply reel 3 and the take-up roller 9 may be constructed as a cassette type unit which is easily exchanged when the supply of tape is exhausted. Additionally, the used up backing strip present on the take-up roller 9 when the supply of tape on the reel 3 has been exhausted, may be removed and the cassette may be replenished with a fresh tape supply. In any event, the replacing of an empty cassette by a full cassette may be quickly done either by an operator or even by the robot.

FIGS. 5 and 6 show another embodiment of a preimpregnated tape dispenser, wherein the cutting operation may be performed by any one of a number of selectable knives supported on a rotatable knife bar 46. In this embodiment a tool support 51 and a carrier frame 25 form a unit constructed for attachment to a robot arm, not shown, through an intermediate member and an adapter 54. The tool support 51 is connected to the intermediate member 53 in the same manner as the tool support 5 in FIG. 1 is connected to the frame 1, as will be described in more detail below. A tape supply reel 26 is rotatably mounted on an arm 25' of the frame 25. Press down rollers 27 and 28 function in the same manner as the rollers 7 and 8 in the above described first embodiment. Guide rollers 29, 30, 31, and 32 guide the tape on its way from the reel 26 to the press down rollers 27, 28. A conveyor comprising an endless conveyor belt 33 is arranged on rollers 34 and 35, the axes of which extend in parallel to each other and perpendicularly to the plane of the frame 25 for guiding the tape 15 past a cutting station to be described below. The right-hand run of the belt 33 moves upwardly while the left-hand run of the belt 33 moves downwardly. The rollers 34 and 35 have the same diameter and are arranged vertically one above the other. The arrangement is such that the press down roller 27 drives the conveyor belt roller 35 and thus the belt 33 through a magnetic clutch 36 and through a gear belt 36a. The rotational speed of the rollers 34 and 35 is so selected that the speed of the tape 15 and the speed of the conveyor belt 33 is the same during the dispensing and applying, especially along the downward run of the conveyor belt 33 between the roller pair 30 and 34 on the one hand, and the roller pair 31 and 32 on the other hand.

The cutting mechanism comprises a cutting counter rail 41 rigidly secured to the frame 25 and a cutting bar 46 also secured to the carrier frame 25 by mounting brackets 37 and 38 equipped with drive means such as pneumatic piston cylinder devices 39 and 40 for pressing the cutting bar 46 against the tape to be severed. The journal ends of the cutting bar 46 are rotatably supported in slide bearings 43, 44 carried by the brackets 37 and 38. The piston cylinder devices 39 and 40 are effective on the slide bearings 43, 44 for moving the knife bar 46 into the cutting position. The knife bar 46 is rotatably mounted in the slide bearings 43 and 44. A drive member 50 operatively connected to the knife bar 46 can rotate the knife bar 46 in 90.degree. steps for the selection of any one of different knives 47, 48, and 49. These knives are secured to sides of the knife bar 46 which has an approximately square cross-section.

The tool support 51 is rigidly secured to the frame 25, whereby the support 51 and the frame 25 form a unit carrying the tools and the supply reel 26, as well as take-up reels 56 and 57 to be described below. The entire unit is movably secured to the adapter 54 for connection to a robot arm not shown. The intermediate member 53 is arranged between the adapter 54 and the tool support 51, whereby guide bars. 52 and springs 55 function in the same way as has been described above for compensating for an uneven surface on a structural component 21. The entire unit 25, 51 is movable against the force of the spring toward the intermediate carrier 53.

The sequence of work steps performed by the apparatus of FIGS. 5 and 6 is substantially the same as that described above with reference to FIGS. 1 to 4. The robot arm will move the dispenser of FIGS. 5 and 6 in a dispensing direction from right to left, whereby impregnated tape will be withdrawn from the supply reel 26. Certain deviations of the surface of the work piece to which the tapes are to be applied, from a level plane, will b accommodated by the springs 55. Two take-up rollers 56 and 57 are provided for handling tapes 15 having a backing strip as well as a protective film. The take-up rollers 56 and 57 are located as shown. The protective film will be separated from tape 15 prior to reaching roller 29 and will be led by roller 57' to roller 57.

When it becomes necessary to sever the tape at a location determined by a control program, the dispensing operation is automatically stopped when the predetermined cutting location has reached the respective knife 49. Then, the pneumatic cylinders 39 and 40 are operated to firmly press the knife 49 against the tape 15, whereby the endless belt 33 which is made of a suitable elastic material, provides a required backing for the cutting operation because the belt 33 can bear against the counter cutting rail 41. Since the selectable knives 47, 48, 49 have different angular slants relative to the travel direction of the tape 15, it is possible to make angular cuts with respective slants.

In those instances where the tape 15 does not have any backing strip nor any protective film, the tape 15 will adhere to the conveyor belt 33 because the resin in the tape 15 has not yet been cured. However, this adhesion between the tape 15 and the belt 33 is easily removed again when the tape 15 and the belt 33 come into the zone of the two rollers 32 and 35 which apply a peeling action. This peeling action is sufficient for again separating the tape 15 from the endless belt 33 without the need for any shearing forces.

FIG. 7 shows the mounting bracket 38 with the piston cylinder device 40 for moving the slide bearing 44 shown in FIG. 5 horizontally back and forth, whereby the slide bearing 44 is guided in the guide slot 38a in the bracket 38. A journal end 45 of the knife bar 46 is rotatably received in the slide bearing 44 for rotating the knife bar 46 with the aid of a drive member such as a pneumatic piston cylinder device 50a, the piston rod of which is connected to a toothed rack 50b cooperating with a gear wheel or pinion 50c connected to the lower end of the knife bar 46. Thus, operation of the piston cylinder device 50a in accordance with a manual or program selection, will rotate the knife bar 46 in 90.degree. steps.

FIG. 8 shows the upper mounting bracket 37 with the cylinder 39 which operates the slide bearings 43 through its piston rod 42. The upper journal end or stud 47 of the knife bar 46 is rotatably mounted in the slide bearing 43.

FIGS. 9 and 10 illustrate a dispenser similar to that described above with reference to FIGS. 5 and 6, however, with a modified cutting mechanism which permits continuing the tape motion during the cutting operation. The carrier frame 25 supports the conveyor endless belt 33 on rollers 34 and 35 and guide rollers 29 and 30 hold the belt 33 on track. A plurality of knife rollers 58, 59, 60 and 61 are rotatably mounted to a bracket extension of the carrier frame 25. Each cylindrical jacket surface of these knife rollers carries a respective helically curved knife 62, 63, 64, and 65. Counterholding or support rollers 66, 67, 68, and 69 are also rotatably mounted to the frame 25 in positions for cooperation with the respective knife roller or cylinder and for cooperation with the endless belt 33. The spacing between the edges of the knives 62, 63, 64, 65 and the belt 33 is such that the tape T shown in FIG. 11 will be severed but the belt 33 will not be cut.

The knife cylinders 58 59, 60, and 61 are driven in unison by a pulley 70 through a drive belt 71 driving the driven shaft 72 carrying a gear wheel 73. The pulley 70 is mounted on a shaft 70a driven by a motor 70'. The drive of the shaft 72 is transmitted to the roller 58 through a magnetic clutch 74. A pinion 75 transmits the rotation of the gear wheel 73 to a further gear wheel 76 driving the knife cylinder 59 through a further magnetic clutch 77. Similarly, the rotation of the gear wheel 76 is transmitted to the gear wheel 78 for driving the knife roller or cylinder 60 through a magnetic clutch 80. The rotation of the gear wheel 78 is transmitted to the gear wheel 79 for rotating the knife roller or cylinder 61 through the magnetic clutch 81. The gear wheels 73, 76, 78, and 79 are dimensioned for driving the respective knife roller 58, 59, 60, 61 with the speed required for the respective cut.

The drive train 70 to 79 may be continuously driven, for example, by the above mentioned motor 70' mounted to the frame 25. However, the individual knife cylinders 58, 59, 60, and 61 are selectively driven, for example, in response to a program taking the tape width and the slanting of the cut to be made into account. For this purpose each magnetic clutch 74, 77, 80, and 81 has its own individual energizing circuit 74', 77', 80', and 81' operatively connected to the control computer. As best seen in FIG. 10, tapes of four different widths and four different angular slants of the cut may be handled by the present cutting mechanism.

The knives 62, 63, 64 and 65 cover a sufficient circumferential, helical length around the surface of the respective knife cylinder 58, 59, 60, and 61 so that one revolution of the respective knife cylinder is sufficient to sever the tape. Although the knives are shown to cover at least 180.degree. on the respective circumferential roller surface, a lesser coverage may be suitable, e.g., for narrow tapes. In operation, each magnetic clutch 74, 77,80, 81 is stopped when the respective knife cylinder has made one revolution. For this purpose, knife cylinder operated switches 82, 83, 84, and 85 are arranged for interrupting the energization of the respective magnetic clutch in response to the rotation of the respective knife cylinder. For this purpose, each switch is equipped with a sensor 86. Only one sensor is shown for the switch 85. The sensor 86 reaches into a recess 87 on the circumference of the respective knife cylinder. The contacts of the switches 82, 83, 84, and 85 are brake-before-make contacts so that the energizing circuit for the respective magnetic clutch is each time prepared to be energized by an energizing signal from the control program and so that the energization may be interrupted when the respective knife cylinder has made its cutting revolution. The operation of the energizing circuits 74', 77', 80', and 81 is synchronized with the switch actuation by the knife cylinders.

FIG. 10 shows a construction in which the frame member 25 carries components on both sides, namely the knife rollers 58, 59, 60, and 61, the support rollers 66, 67, 68, and 69, and the conveyor means 33, 34, 35 on one side, and the drive means 70, 70' to 81' for the knife rollers on the opposite side. Such a structure facilitates the maintenance because it provides easy access to all components.

FIG. 10 further shows that each of the four knives 62, 63, 64, 65 has a different slant relative to the rotational axis of the respective roller 58, 59, 60, and 61 for achieving respective different slants .alpha.1, .alpha.2 as shown in FIG. 11 of the cut edges of the tape T relative to the longitudinal tape edge. Cutting the tapes for the present purposes, e.g. forming an aircraft wing, with a slant at the tape ends is desirable because it permits forming a lateral overlap LO as shown in FIG. 11 between two tape sections T1 and T2 following each other, for example when these tapes are laminated to a frame structure to form an aircraft component. The different knife slants shown in FIG. 10 also provide a capability for cutting tapes of different widths. Knife 62 cuts the narrowest tapes with a substantial slant. Knives 63, 64, 65 cut progressively wider tapes with slants that get smaller for wider tapes. However, the axial length of all knife carrying rollers is the same and extends perpendicularly to the tape advance direction.

It will be appreciated that even wider tapes can be cut with a substantial slant depending on the dimensions of the respective roller and the slanting of the knife on the roller surface, which determines the slant of the cutting angle.

The program in the control computer for operating the clutches 74, 77, 80, 81 will determine which knife is selected for cutting a particular tape.

Although the invention has been described with reference to specific example embodiments, it will be appreciated, that it is intended to cover all modifications and equivalents within the scope of the appended claims.