Patent Application
20190076932
Sandwich panels with perforated skins are typically incorporated into aircraft engine nacelles to reduce the amount of engine noise reaching the ground during flight. The perforated skins include numerous holes, typically about 1 mm in diameter, which cover between 5% and 10% of a nacelle panel's surface area. This equates to roughly 1,000,000 holes in a single panel, and each nacelle may contain multiple panels.
The holes may be molded into composite skins using pinmats, but this process is labor and flow-time intensive, requires pre-curing of the skin prior to assembly of the sandwich panel, and necessitates tooling that would not otherwise be required. The holes may also be formed by an abrasive erosion process, but this too has drawbacks. Maskant must be applied to the skin manually, and as with the pinmat process, the skin must be pre-cured prior to assembly of the sandwich panel.
Mechanical drilling using a conventional drill bit overcomes some of these limitations, as mechanically drilled holes may be formed in a finished sandwich panel, thus eliminating separate curing operations for individual skins. However, prior art drilling equipment is too slow and expensive to cost-effectively drill the large number of holes required. To meet desired production rates, many expensive machines would be required, operating in parallel. In addition to the expense, these machines would consume a large amount of factory floor space and would increase the inventory that must be maintained in-process at any given time.
Some perforating robots are much less expensive than conventional drilling machines, and are also much more compact. Unfortunately, these robots lack the precision and stability to successfully serve as platforms for conventional drilling equipment operated in conventional means.
Thus, there is a need for an improved apparatus and method for perforating skins for nacelle sandwich panels.
Embodiments of the present invention solve the above-mentioned problems and provide a distinct advance in the art of nacelle sandwich panel fabrication. One embodiment of the invention is a drilling apparatus having an end effector, a drill bit attached to the end effector, and a control system. The drill bit may include a forward end, an aftward end opposite the forward end, a tip formed at the forward end, a widest portion aftward of the tip, and a narrow flute portion aftward of the widest portion. The flute portion may extend between the widest portion and the end effector. The flute portion may also have a smaller diameter than the widest portion. The control system may send control signals to actuators of the end effector commanding rotation of the drill bit and commanding the end effector to move the drill bit laterally outward and inward.
In another embodiment of the invention, the end effector may include an end effector housing, a drill bit attachment extending outward from the end effector housing, a rotation actuator, and a linear motion actuator. The rotation actuator may be coupled with the drill bit attachment for actuating rotation of the drill bit attachment. The linear motion actuator may actuate linear motion of the drill bit attachment toward and away from the workpiece. The drill bit may be attached to the drill bit attachment and may have a forward end, an aftward end opposite the forward end, a tip formed at the forward end, a widest portion aftward of the tip, and a narrow flute portion aftward of the widest portion. The flute portion may extend between the widest portion and the end effector, and may have a smaller diameter than the widest portion. Furthermore, the widest portion may have a smaller length than the narrow flute portion. The control system may send control signals to the end effector commanding the end effector to rotate the drill bit and commanding the end effector to move laterally outward and inward. In addition, the control system may command the end effector to move laterally outward toward the workpiece at a first speed and command the end effector to move laterally back inward away from the workpiece at a second speed. The second speed may be faster than the first speed.
In yet another embodiment of the invention, a drilling apparatus described above may be implemented in a method of drilling holes into a composite workpiece. The method may include the steps of actuating rotation of a drill bit attachment and a drill bit attached therein, then actuating the drill bit attachment linearly toward the composite workpiece at a first speed, thus forming a hole therethrough. The method may also include a step of actuating the drill bit attachment linearly away from the composite workpiece at a second speed that is greater than the first speed, thus limiting the amount of time the widest portion of the drill bit contacts workpiece while being withdrawn through the hole.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Other aspects and advantages of the current invention will be apparent from the following detailed description of the embodiments and the accompanying drawing figures.
Embodiments of the current invention are described in detail below with reference to the attached drawing figures, wherein:
The drawing figures do not limit the current invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.
The following detailed description of the invention references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the current invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the current invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.
In this description, references to “one embodiment”, “an embodiment”, or “embodiments” mean that the feature or features being referred to are included in at least one embodiment of the technology. Separate references to “one embodiment”, “an embodiment”, or “embodiments” in this description do not necessarily refer to the same embodiment and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, the current technology can include a variety of combinations and/or integrations of the embodiments described herein.
A drilling apparatus 10 constructed in accordance with embodiments of the present invention is illustrated in
As illustrated in
The drill bit attachment 24 may include a quill, drill chuck, drill bit spindle, and/or any type of clamp rotatably attached to the end effector housing 22 and suitable to hold the drill bit 18 in radial symmetry therein. At least a portion of the drill bit attachment 24 may extend outward from the end effector housing 22 and may be supported thereby. At least a portion of the drill bit attachment 24 may be actuatable at any desired drilling speed via the rotation actuator 26, thereby rotating the drill bit 18. For example, the drill bit attachment 24 may spin the drill bit 18 at a rate of 50,000 to 100,000 rotations per minute, or approximately 80,000 rotations per minute. However, other rotational speeds may be used without departing from the scope of the invention.
As illustrated schematically in
The linear motion actuator 28 may be configured for converting rotary motion into linear motion, thus driving the drill bit 18 into the workpiece 14. Specifically, as illustrated in
In some embodiments of the invention, the secondary rotary motor 32 is a continuously-variable motor or servo motor which may be controlled by the control system 20 to have a first speed of linear insertion into the workpiece 14 and a second speed of linear withdrawal when the drill bit 18 is pulled out, away from the workpiece 14. The second speed may be faster than the first speed. For example, servo feedback from the servo motor may be used by the control system 20 or other circuitry to govern speed thereof depending on angle readings or other position information obtained via the servo feedback. Alternatively, a stepper motor may be used to selectively switch the speed of the rotary-to-linear motion converter 34 between two or more speeds. In yet another embodiment of the invention, a cam with a predefined mechanical profile may be used to switch the speed of the rotary-to-linear motion converter 34 and thus withdrawal the drill bit 18 at a faster speed than the drill bit's insertion. In yet another embodiment of the invention, as illustrated in
In some embodiments of the invention, the rotary-to-linear motion converter 34 may allow the secondary rotary motor 32 to continuously run in a single direction for both forward and backward motion of the drill bit attachment 24 and/or the drill bit 18 toward and away from the workpiece 14. Because the secondary rotary motor 32 does not need to reverse directions to retract the drill bit 18 from the workpiece 14, this results in quicker acceleration and eliminates any lag time present in prior art systems during withdrawal of the drill bit 18 from the hole 12 created. However, other embodiments of the invention may include a linear motion actuator 28 configured such that the secondary rotary motor 32 does reverse directions to retract the drill bit 18 from the workpiece 14. For example, as illustrated in
Alternatively, the secondary rotary motor 32 may be omitted and the primary rotary motor of the rotation actuator 26 may be used to both rotate the drill bit attachment 24 and/or drill bit 18 and to actuate the linear motion thereof via attachment with the rotary-to-linear motion converter 34. In particular, a speed reducing gear train or the like may be utilized between the rotation actuator 26 and the rotary-to-linear motion converter 34. Alternatively, the primary motor of the rotation actuator 26 could be omitted and the secondary rotary motor 32 may be used to rotate both the drill bit attachment 24 and/or the drill bit 18 and to actuate the linear motion thereof via attachment with the rotary-to-linear motion converter 34. Specifically, a speed-increasing gear train or the like may be utilized between the secondary rotary motor 32 and the drill bit attachment 24.
The drill bit 18, as illustrated in
The widest portion 44 may have a length smaller than the flute portion 46 or may even merely be an edge at which the flute portion 46 and the included angle 50 meet. The flute portion 46 of the drill bit 18, between the shank 48 and the widest portion 44 of the drill bit 18, may have a reduced diameter as compared to a diameter of widest portion 44. For example, the flute portion 46 may taper from the widest portion 44 down to a narrower point closer to or at the shank 48 positioned in the drill bit attachment 24. However, other shapes, profiles, or configurations of the flue portion 46 having a smaller diameter than the widest portion 44 may be used without departing from the scope of the invention.
The shank 48 as illustrated in
In one alternative embodiment of the drill bit 18, the flute portion 46 may have a substantially uniform diameter from the widest portion 44 to the shank 48, so long as the flute portion's diameter is less than the diameter of the widest portion 44. For example, as illustrated in
The control system 20, as illustrated in
The control system 20 may implement a computer program and/or code segments to perform some of the functions and method described herein. The computer program may comprise an ordered listing of executable instructions for implementing logical functions in the control system. The computer program can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, and execute the instructions. In the context of this application, a “computer-readable medium” can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-readable medium can be, for example, but not limited to, an electronic, magnetic, optical, electro-magnetic, infrared, or semi-conductor system, apparatus, or device. More specific, although not inclusive, examples of the computer-readable medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable, programmable, read-only memory (EPROM or Flash memory), an optical fiber, and a portable compact disk read-only memory (CDROM).
The features of the control system 20 may be implemented in a stand-alone device, which is then interfaced to other components of the drilling apparatus 10. The control features of the present invention may also be distributed among the components of the drilling apparatus 10. Thus, while certain features are described as residing in the control system 20, the invention is not so limited, and those features may be implemented elsewhere. The control system 20 and computer programs described herein are merely examples of computer equipment and programs that may be used to implement the present invention and may be replaced with or supplemented with other controllers and computer programs without departing from the scope of the present invention.
In some embodiments of the invention, the control system 20 may include or may be communicably coupled with a position sensor 52 attached to the end effector housing 22 and configured to provide the control system 20 with data regarding the end effector's distance from the workpiece 14 along a z-axis and/or its relevant position along a surface of the workpiece 14 along an x-axis and/or a y-axis. For example, the position sensor 52 may be a laser distance sensor configured to transmit information corresponding to the end effector's distance from the workpiece 14 along a z-axis.
In use, the drilling apparatus 10 may be utilized for performing a method for perforating or drilling holes into the workpiece 14. The method may include clamping the drill bit 18, having the narrow flute portion 46, as described above, into the drill bit attachment 24. Next, the method may include the steps of positioning the drilling apparatus 10 at a desired location relative to the workpiece 14 and actuating the rotation actuator 26, thereby rotating the drill bit 18 about its axis. Then, the method may include a step of actuating the drill bit 18 toward and into the workpiece 14 at the first speed until the widest portion has cleared the workpiece 14, such that space exists between boundaries of the hole 12 formed thereby and the flute portion 46 of the drill bit 18. The method may further include a step of actuating the drill bit 18 in a direction back through the hole 12 and away from the workpiece 14 at the second speed. The second speed may be greater than the first speed.
Method steps for perforating or drilling holes into the workpiece will now be described in more detail, in accordance with various embodiments of the present invention. The steps of the method 1000 may be performed in the order as shown in
As illustrated in
The method 1000 may then include a step of actuating the rotation actuator 26, as depicted in block 1006, thereby rotating the drill bit 18 about its axis. Actuation of the rotation actuator 26 may be triggered by merely turning on or connecting electrical power to the drilling apparatus 10 via an electrical plug, a battery, and/or a switch, button, or the like. Additionally or alternatively, actuation of the rotation actuator 26 may be accomplished via instructions from the control system 20 communicated via wired or wireless communication channels to the rotation actuator 26.
In addition, the method 1000 may include a step of actuating the drill bit 18 toward and into the workpiece 14 at the first speed, as depicted in block 1008, thereby plunging the drill bit 18 into the workpiece 14 until the widest portion 44 of the drill bit 18 has cleared the workpiece 14. Due to the design of the narrow flute portion 46 described above, when the widest portion 44 clears the workpiece 14, forming the hole 12 therethrough, space should exist between boundaries of the hole 12 and the flute portion 46 of the drill bit 18. Actuation of the drill bit 18 toward the workpiece 14 may be performed by instructions provided from the control system 20 to the linear motion actuator 28.
Finally, the method 1000 may include a step of actuating the drill bit 18 in a direction back through the hole 12 and away from the workpiece 14 at the second speed, as depicted in block 1010. The second speed may be greater than the first speed. Specifically, the control system 20 may send a control signal to the linear motion actuator 28, commanding the linear motion actuator 28 to increase the speed of the secondary rotary motor 32 to the second speed. For example, this method step may include receiving a sensor signal indicating a rotational location of the secondary rotary motor 32, such that the sensor signal indicates a position at which the drill bit 18 begins to retract in a direction away from the workpiece 14. Alternatively, this method step may include the control system 20 accessing rotational speed data stored therein or sensed thereby, or any other data sufficient to calculate when the secondary rotary motor 32 should increase to the second speed. In some embodiments of the invention, as described above, step 810 may be performed substantially automatically via cams or oblong-shaped gears driven by the secondary rotary motor 32.
The drilling apparatus 10 and methods described herein advantageously provide the benefits and conveniences of robotic drilling while producing hole quality typical of slow and expensive machine tools. Prior art drilling equipment tends to operate at either a constant force or a constant feed rate. By allowing a continuously variable feed rate profile, the drilling apparatus 10 enables a process that requires different rates at different parts of the drilling cycle. By utilizing the rotary-to-linear motion converter 34, the secondary rotary motor 32 actuating linear motion of the end effector 16 and/or drill bit 18 is kept running in a single direction, resulting in quicker acceleration and eliminating any lag time present when reversing motor directions in prior art systems during withdrawal of the drill bit from the hole 12 created.
Furthermore, the drilling apparatus 10 and methods described herein are designed to minimize the time during which exterior sides of the drill bit 18 are in contact with interior sides of the holes created thereby. Specifically, applicants have discovered that anytime there is contact between the sides of the holes and the sides of the drill bit 18, relative motion between the drill and the workpiece 14 may cause elongation of the hole 12. Applicants have further discovered that this elongation requires not only contact, but some amount of residence time. If side-to-side contact between the drill bit 18 and hole 12 takes place, a hole without significant elongation may still be produced, provided that the duration of the contact is minimized. Due to variations in the workpiece's thickness, positioning accuracy of the workpiece 14, drill bit installation depth, robot accuracy, and other factors, the drill bit 18 must be inserted into the workpiece 14 well beyond a point at which the hole 12 is fully formed. It is during this extra insertion that the reduced diameter of the drill bit 18 along the flute portion 46 provides clearance and prevents side-to-side contact. When the drill bit 18 is withdrawn from the hole 12, it will necessarily return the widest portion 44 of the drill bit 18 to the hole 12, and for a time, no clearance will exist during the withdrawal. However, the continuously variable linear motion or feed capabilities of the end effector 16 permit the extraction rate to be increased well beyond the rate used during insertion of the drill bit 18 and hole formation. This advantageously minimizes elongation during withdrawal.
Although the invention has been described with reference to the embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.
