Abstract:
A composite automation method and apparatus for the generation of short path course application of a composite lamina is realized by reconfiguring the functional mechanisms of the fiber placement head. Separating the fiber advance and retract functions, nesting the activation cylinders, and making use of push only activation results in a simplified, compact AFP delivery head. Uniform cutting is provided by a circular configuration fiber cutting blade, were at activation the blade both provides a progressive cutting force and rotates to providing a new cutting edge, and requires limited cutting edge guidance as all orientations cut equally well. The mechanism nested in functions and placed in close proximity to the compaction roller reduces the overall fiber course to the application point.

Description:
BACKGROUND 
     This application generally relates to automated methods and equipment for laying up plies of composite material, and deals more particularly with a method and apparatus for placing short courses of composite tape on a substrate during the layup process. 
     Composite structures such as those used in the automotive, marine and aerospace industries may be fabricated using automated composite material application machines, commonly referred to as automated fiber placement (AFP) machines. AFP machines may be used in the aircraft industry, for example, to fabricate structural components and skins by placing relatively narrow strips of composite, slit fiber tape or “tows” on a manufacturing tool. The tape may be placed on the tool in parallel courses that may be in substantially edge-to-edge contact to form a ply. 
     Known AFP machines employ a tape placement head that dispenses, cuts and compacts courses of tape onto the tool surface as a tape placement head is moved by a robotic device over the tool surface. These tape placement heads typically include a supply spool of tape, and a dispensing mechanism that draws the tape from the spool and guides the tape into a nip between a compaction roller and the tool surface. A cutter blade within the dispensing mechanism located upstream from the compaction roller cuts the tape to a desired course length. The minimum length of a tape course that can be placed by the tape placement head may therefore be governed by the distance between the point where the tape is compacted onto the tool surface and the point where the tape is cut by the blade. 
     In some applications, relatively short courses may be required which have a length less than the minimum course length that can be cut by known tape heads. In other words, a desired course length may be less than the distance from the compaction point to the point where the cut is made. Under these circumstances, it may be necessary to place courses that are longer than optimum course lengths, thereby adding weight and/or cost to the part, or prompting the need to trim the plies of excess tape, or to manually lay the short courses by hand, thereby adding undesired labor and expense to the manufacturing process. 
     SUMMARY 
     Accordingly, there is a need for a tape placement head and method for cutting courses of tape which allow placement of courses of shorter length. 
     The present application discloses various systems and methods to address the aforementioned challenges with existing tape heads. 
     In one example, an automated fiber placement (AFP) machine is disclosed for placing composite material on a substrate. The AFP machine comprises a first low-profile tow control module comprising one or more circular cutter blades, and a second low-profile tow control module comprising one or more circular cutter blades. The AFP machine further comprises a vee block coupled to the first and second low-profile tow control modules and located between the first and second low-profile tow control modules, the vee block comprising a plurality of air passages located therein. The AFP machine further comprises a plurality of air cylinders coupled to the vee block and nested between the first low-profile tow control module and the second low-profile tow control module, the plurality of air cylinders being aligned with the air passages located within the vee block. 
     The first and second low-profile tow control modules may have a height no greater than about ¾ inch. The circular cutter blades may have a height no greater than about ¾ inch. The AFP machine may further comprise a compaction roller having a diameter no greater than about ¾ inch. The circular cutter blades may be removably coupled to a cutter rocker arm configured to be rotated about an axle by a first, cutter extend piston and second, cutter retract piston. The substrate may comprise a flat or nearly-flat charge. The AFP machine may further comprise a control unit configured to access a file that includes computer readable instructions for fabricating a composite item. The AFP machine may further comprise one or more positioning devices configured to maneuver the substrate relative to a delivery head while the composite material is placed on the substrate. The positioning device(s) may comprise one or more NC machines, robotic arms, or mandrels. 
     In another example, a delivery head of an automated fiber placement (AFP) machine comprises a vee block having a plurality of air passages located therein, and a first tow control module coupled to the vee block. The first tow control module comprises a tow guide tray, a support frame, a cutter rocker arm with an attached cutter blade, and a pinch/feed rocker with an attached pinch roller. The cutter rocker arm is coupled to the support frame by a cutter rocker axle. The pinch/feed rocker is nested within the cutter rocker arm and is coupled to the support frame by a pinch/feed rocker axle. A plurality of pistons are positioned in cavities located within the vee block and coupled to the air passages, the pistons being aligned with the cutter rocker arm and the pinch/feed rocker. 
     The attached cutter blade may comprise a circular cutter blade. The pistons may comprise a first, cutter extend piston and second, cutter retract piston, which are configured to rotate the cutter rocker arm about the cutter rocker axle. The tow guide tray may define a plurality of tow guide paths, and the first tow control module may comprise a corresponding plurality of cutter rocker arms and pinch/feed rockers. The delivery head may be configured to place composite material on a flat or nearly-flat charge. The delivery head may further comprise a second tow control module coupled to the vee block, the second tow control module comprising substantially identical components as the first tow control module, located in complementary positions. 
     In another example, a method of placing a course of composite material on a substrate is disclosed using an AFP machine with a low-profile delivery head and a circular cutter blade. The method comprises feeding one or more tows of composite material through the delivery head by extending a feed piston to bring a pinch roller into contact with a feed roller, thereby causing the tow(s) of composite material to be pulled between the pinch roller and the feed roller along a tow guide channel. The method further comprises cutting the tow(s) of composite material to a desired length by extending a cutter extend piston and retracting a cutter retract piston, thereby causing a cutter rocker arm to rotate about an axis and lower the circular cutter blade through the tow guide channel. The method further comprises retracting the circular cutter blade by extending a cutter retract piston and retracting a cutter extend piston, thereby causing a cutter rocker arm to rotate about an axis and raise the circular cutter blade out of the tow guide channel. 
     The method may further comprise rotating the circular cutter blade to provide a new cutting edge. The method may further comprise clamping the tow(s) of composite material in place in the tow guide channel by extending a clamp piston at substantially the same time as the circular cutting blade is lowered. Extending the pistons may comprise supplying air pressure to the pistons through passages formed within a vee block. The substrate may comprise a flat or nearly-flat charge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of one example of an automated fiber placement (AFP) machine in accordance with the present application. 
         FIGS. 2A and 2B  are schematic diagrams illustrating one example of an AFP machine in accordance with the present application. 
         FIG. 3  illustrates a partial cross-sectional view of one example of a delivery head for an AFP machine. 
         FIG. 4  illustrates an exploded view of one example of a delivery head for an AFP machine. 
         FIGS. 5A through 5D  illustrate the positions of a pushrod/piston subassembly during various stages of the AFP process. 
         FIG. 6  is an illustration of a flow diagram of aircraft production and service methodology. 
         FIG. 7  is an illustration of a block diagram of an aircraft. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that various changes may be made without departing from the spirit and scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense. 
     The present application discloses a system for placing composite lamina plies to fabricate a composite item and a method of using this system. Specifically, the system provides for the short path course application of a composite lamina by reconfiguring the functional mechanisms of a fiber placement head. In some examples, the system includes an automated lamination device such as, for example, an automated fiber placement (AFP) machine. This lamination device includes one or more dispensing heads to place plies of composite material upon a mandrel, layup mold or tool. In addition, the lamination device includes a cutting device to cut the composite material. Additional details and variations regarding the configuration and operation of the system will be apparent to those of ordinary skill in the art, having the benefit of this disclosure. 
       FIG. 1  is a block diagram of one example of an automated fiber placement (AFP) machine  100  in accordance with the present application. In the example shown in  FIG. 1 , the AFP machine  100  includes a placement head  105  that is positioned by a corresponding positioning device  110 . The placement head  105  is configured to place  115  composite material upon a substrate  120 . The substrate  120  includes the surface of a workpiece  125 , such as, for example, a mandrel, tool, layup model, or any other suitable surface on which composite material is placed. In addition, the substrate  120  may include any previously applied composite material, tackifier, and the like that is previously laid down on the workpiece  125 . The workpiece  125  is rotated or otherwise positioned by a drive apparatus  130 . The drive apparatus  130  and/or the positioning device  110  are controlled by a control unit  135 . The control unit  135  accesses a file  140  that includes computer readable instructions for fabricating a composite item. 
       FIG. 2A  is a schematic diagram illustrating one example of an automated fiber placement (AFP) machine  200  in accordance with the present application. In general, the AFP machine  200  is configured to maneuver a substrate  210 , such as a tool or a flat charge layup mold, relative to a fiber placement head assembly, or delivery head  215 , while tows of composite material are placed on the substrate  210 . For instance, in the specific example illustrated in  FIG. 2A , the AFP machine  200  comprises a numerical control (NC) machine  205 , such as a robotic arm, which is configured to manipulate the substrate  210  while the delivery head  215  remains stationary. In other cases, the AFP machine  200  may comprise an NC machine  205  that is configured to move the delivery head  215  while the substrate  210  either remains fixed or moves in one or more additional axes of motion. Beyond these examples, other alternative mechanisms may be utilized for moving the substrate  210  relative to the delivery head  215 , as will be appreciated by those of ordinary skill in the art. 
     The delivery head  215  is shown in greater detail in  FIG. 2B . The AFP machine  200  further comprises a tow supply system  220  including a set of storage spools  225 , or creels, as well as a series of tow guides, e.g., redirect rollers  230  and redirect pulleys  235 , as well as a tension brake system  250 . For simplicity, the complete roller support framework for the AFP machine  200  is not shown in its entirety in  FIGS. 2A and 2B . The AFP machine  200  may also comprise various standard control components, such as pneumatic cylinders, electro-servo actuators, control wires, hoses, etc. (not shown) that control the operation of the AFP machine  200  under the direction of a suitable control module, such as the control unit  135  shown in  FIG. 1 . 
     In operation, the AFP machine  200  pulls tows  240  of a composite material, such as carbon fiber-epoxy, from the storage spools  225  around redirect rollers  230 , which function to maintain a predetermined tension onto the each fiber or tow  240 , and through redirect pulleys  235  to the delivery head  215 . Each tow  240 , in turn, is cut to the correct length by a cutting blade in response to a command from a control unit  135 , as the material course, also called a tow band, is laid over the substrate  210 . Each tow  240  has a corresponding cutting blade, however the number of blades may vary depending upon the number of tows  240  and the width of each tow  240 . As the tows  240  emerge from the delivery head  215 , they pass over a compaction roller  245  which applies and compresses the tows  240  onto the surface of the substrate  210  as it moves relative to the delivery head  215 . Heat may be applied to the tows  240  immediately before they are placed on the substrate  210  in order to increase the surface tackiness of the resin impregnated tow. Tension can be maintained on the tows  210  to assist in pulling them through the AFP machine  200  as sensed by redirect rollers  230  controlling the tension brake system  250 . 
       FIGS. 3 and 4  illustrate a partial cross-sectional view and an exploded view, respectively, of one example of a delivery head  215 . In the example shown in  FIGS. 3 and 4 , the delivery head  215  comprises a “vee block”  350  having a plurality of air fittings  384  coupled to passages  352  located within the vee block  350 , through which air pressure can be ducted during operation. The air fittings  384  are compatible with conventional pneumatic valves configured to control the operation of the delivery head  215  per predetermined instructions from the control unit  135 . The delivery head  215  is comprised of a first, upper tow control module  354 A and a second, lower tow control module  354 B, which contain substantially identical components located in complementary positions. The tow control modules  354 A,  354 B guide the tows  240  through the delivery head  215  during operation, as described above. For simplicity, only the components of the upper tow control module  354 A are separated in the exploded view of  FIG. 4 . 
     Each tow control module  354  comprises a tow guide tray  356  coupled to the vee block  350 , which establishes the configuration of the tow feed path as set by the tow channel dimensions  358  within the tow guide tray  356 . The total bandwidth output is defined by a plurality of tow guide channels  358  corresponding to the number of tows  240  for which the delivery head  215  is designed. For example, in the specific case illustrated in  FIGS. 3 and 4 , both the upper tow control module  354 A and the lower tow control module  354 B include a tow guide tray  356  having three tow guide channels  358  each, meaning that the delivery head  215  is configured to place up to six tows  240  of composite material (three tows  240  from the upper tow control module  354 A and three tows  240  from the lower tow control module  354 B) simultaneously on the substrate  210  during each course in an aligned edge on edge pattern. 
     The delivery head  215  further comprises a plurality of pushrod/piston subassemblies  360 , corresponding to the selected number of tow guide channels  358 . Each pushrod/piston subassembly  360  comprises a first, cutter retract piston  360 A, a second, clamp piston  360 B, a third, feed piston  360 C, and a fourth, cutter extend piston  360 D. In the illustrated example, the cutter retract piston  360 A, clamp piston  360 B, feed piston  360 C, and cutter extend piston  360 D all include bias springs  362 . Each pushrod/piston subassembly  360  is located in a series of cavities  364  in the vee block  350 , which are aligned with a corresponding tow guide channel  358 . 
     Each tow control module  354  also comprises a support frame  366  coupled to the tow guide tray  356 , as well as a cutter rocker arm  368  with an attached cutter blade  370  and a pinch/feed rocker  372  with an attached pinch roller  374  for each tow guide channel  358 . Each cutter rocker arm  368  is coupled to the support frame  366  by a first, cutter rocker axle  376 A, on which the cutter rocker arm  368  pivots during operation. Similarly, each pinch/feed rocker  372  is coupled to the support frame  366  by a second, pinch/feed rocker axle  376 B, on which the pinch/feed rocker  372  pivots during operation. Although the first, cutter rocker axle  376 A is illustrated as a single, unitary member for all three cutter rocker arms  368  shown in  FIG. 4 , in some cases, the first, cutter rocker axle  376 A may be subdivided into multiple members, each one corresponding to an individual cutter rocker arm  368 . Each tow control module  354  also comprises one or more blade covers  378  coupled to the support frame  366 , which are configured to cover the cutter blades  370  during operation. 
     The cutter rocker arms  368  and pinch/feed rockers  372  of the delivery head  215  are substantially symmetric, which may advantageously reduce twist and binding distortions in some instances. Each pinch/feed rocker  372  nests in a pocket of a corresponding cutter rocker arm  368 , except near the back end, where tabs extend for engagement by a feed piston  360 C. At the locations of the tabs in each pinch/feed rocker  372 , the corresponding cutter rocker arm  368  steps up to allow adequate rotation of the pinch/feed rocker  372 . Each cutter rocker axle  376 A is located high enough to allow the corresponding pinch/feed rocker  372  to rotate, and the tow control module  354  is preferably designed to substantially minimize the amount of overall rotation required. 
     The delivery head  215  further comprises a compaction roller  245  coupled to the vee block  350  configured to contact the substrate  210  where the vee block  350  forms a nip point at the intersection of the vee pattern fiber feed to a contact intersection point under the compaction roller  245 . In addition, the delivery head  215  comprises a first, upper feed roller  382 A and a second, lower feed roller  382 B coupled to one or more suitable drive mechanisms, such as a servo actuator. The feed rollers  382 A,  382 B form a nip compaction pull force when pinch roller  374  is activated by pistion  360 C acting on pinch/feed rocker  372  to contact feed roller  382 . The force acts to pull the tows  240  of composite material through the upper and lower tow control modules  354 A,  354 B, respectively, at a desired speed and for a desired time duration, under the direction of a suitable control module, such as the control unit  135  shown in  FIG. 1 . 
     Unlike conventional AFP delivery heads, the delivery head  215  of the present application includes various distinctive features that optimize the delivery head  215  for short courses and flat or nearly-flat charges. For example, the total distance from the tow drop off or cutting point to the roller nip area is reduced by compaction roller  245 , which is substantially smaller in diameter than a conventional compaction roller, and additionally by the compact design of the tow cut add mechanism which places the cut off point to the nip point closer. Specifically, in some cases, the compaction roller  245  has a diameter of no more than about ¾ inch. 
     In addition, the delivery head  215  includes cutter blades  370  with a unique circular cutter geometry, rather than the traditional rectangular shape utilized in conventional cutter blades. The circular cutter blade design advantageously allows the delivery head  215  to utilize cutter blades  370  that are substantially shorter than conventional AFP cutters. Specifically, in some cases, the cutter blades  370  have a maximum length of no more than about ¾ inch. The circular cutter blade design also advantageously eliminates the need for blade guides, because the cutter blades  370  can cut equally well in every orientation. Additionally cutter life is extended by cutter rotation during use about the center cutter mounting point. The circular cutter blades  370  are also easily accessible, removable, and replaceable. 
     In conventional AFP machines, the pneumatic conduits and other equipment used to actuate the pushrods and pistons are typically coupled to the exterior of the tow control modules and the vee block. As a result, conventional AFP delivery heads can be bulky and cumbersome, making it difficult fabricate small composite parts with short course lengths. The delivery head  215  of the present application, by contrast, employs a unique design in which the air fittings  384  are nested between the upper and lower tow control modules  354 A,  354 B, and air pressure is ducted through passages  352  located within the vee block  350  to control the operation of the pushrod/piston subassemblies  360 . This compact configuration advantageously enables the delivery head  215  to utilize a low-profile design for the tow control modules  354 . Specifically, in some cases, the tow control modules  354  have a maximum height of no more than about ¾ inch. 
       FIGS. 5A through 5D  illustrate the positions of a pushrod/piston subassembly  360 A- 360 D during various operational stages of the AFP process. In general, the pistons  360 A- 360 D are spring biased in a retracted position, and can be extended by supplying air pressure to the desired cylinder bore cavities  364  of the associated activation pistons  360 A- 360 D through the corresponding air fittings  384  and passages  352 . This can be accomplished with various control valves and other control equipment (not shown) using conventional techniques and control methods processed within control unit  135  that are well-known to those of ordinary skill in the art. 
       FIG. 5A  illustrates the “tow feed” stage of the AFP process, during which a tow  240  of composite material is pulled through the delivery head  215  by the feed roller  382 . During this tow feed stage, as shown in  FIG. 5A , the cutter retract piston  360 A is extended and the cutter extend piston  360 D is retracted, to prevent the front end of the cutter rocker arm  368  from lowering to engage the cutter blade  370 . In addition, the feed piston  360 C is extended, which lowers the front end of the pinch/feed rocker  372  and brings the pinch roller  374  into contact with the feed roller  382  in contact with pinch roller  374  as activated by feed piston  360 C. The clamp piston  360 B is retracted to ensure that the tow  240  of composite material can be pulled through the corresponding tow guide channel  358  under the control of the feed roller  382 , at the desired speed and for the desired duration. 
       FIG. 5B  illustrates the “free run” stage of the AFP process, during which a tow  240  of composite material passes through the delivery head  215  as the desired material course is placed on the substrate  210 . During this free run stage, as shown in  FIG. 5B , the feed piston  360 C is retracted, while all the other pistons remain in the same position as during the tow feed stage shown in  FIG. 5A . The retraction of the feed piston  360  causes the pinch/feed rocker  372  to pivot around the pinch/feed rocker axle  376 B, lowering the back end and raising the front end of the pinch/feed rocker  372 . This rotation, in turn, causes the pinch roller  374  to disengage from the feed roller  382 , thereby allowing the tow  240  of composite material to pass freely through the tow guide channel  358  due to the movement of the substrate  210  and/or the delivery head  215  during the placement of the material course on the substrate  210 . 
       FIG. 5C  illustrates the “tow cut” stage of the AFP process, during which a tow  240  of composite material is cut to a desired length by the cutter blade  370 . During this tow cut stage, as shown in  FIG. 5C , the cutter retract piston  360 A is retracted and the cutter extend piston  360 D is extended, while all the other pistons remain in the same position as during the free run stage shown in  FIG. 5B . The retraction of the cutter retract piston  360 A and extension of the cutter extend piston  360 D cause the cutter rocker arm  368  to pivot around the cutter rocker axle  376 A, thereby lowering the front end of the cutter rocker arm  368  and causing the cutter blade  370  to pass through the tow guide channel  358  and cut the tow  240  of composite material to the desired length. 
       FIG. 5D  illustrates the “tow clamped” stage of the AFP process, during which a tow  240  of composite material is held in place in the delivery head  215  after being cut by the cutter blade  370 . During this tow clamped stage, as shown in  FIG. 5D , the cutter retract piston  360 A is extended and the cutter extend piston  360 D is retracted to disengage the cutter blade  370 . During this step, the circular cutter blade  370  may rotate due to vibrations or other forces, thus advantageously providing a new cutting edge on the same cutter blade  370  for the next tow cut. At substantially the same time, the clamp piston  360 B is extended to exert a force on the tow  240  and hold it stationary in the tow guide channel  358 . Without this clamping step, the tow  240  may have a tendency to recoil after being cut due to the tension caused by the remaining length of tow material stored on the corresponding storage spool  225 . By holding the tow  240  stationary, however, the AFP machine  200  can accurately determine the location of the end of the tow  240 , and can thus accurately position the delivery head  215  for placement of the subsequent course of composite material on the substrate  210 . 
     In conventional AFP machines, the cutter blade is normally actuated by a single, dual-acting air cylinder, i.e., a single air cylinder that “pushes” the cutter blade to engage the cutter and “pulls” the cutter blade to disengage the cutter. In the AFP machine  200  of the present application, by contrast, the advance and retract functions of the cutter blade  370  are separated into two pistons (e.g., the cutter retract piston  360 A and the cutter extend piston  360 D). This configuration advantageously eliminates the need for at least one rod seal and simplifies the mechanism by using only pushrods with no “pull” requirement. 
     As a result of the features described above, the AFP machine  200  of the present application advantageously has a minimum cut length that is substantially shorter than the minimum cut length of a conventional AFP machine. For example, in some cases, the AFP machine  200  of the present application can cut tows  240  of composite material to lengths as short as about 1½ inches. As a result, the AFP machine  200  of the present application advantageously allows economical application of the AFP process to small composite parts, especially flat or nearly-flat charges. This may include certain composite parts (e.g., spars, etc.) in which an area being compacted by the AFP machine  200  is flat or nearly-flat locally, while the composite part(s) may have curved portions, e.g., a tight convex curvature at a radius from a web to a flange. 
     Referring to  FIGS. 6-7 , the systems and methods of the present application may be implemented in the context of an aircraft manufacturing and service method  600  as shown in  FIG. 6  and an aircraft  700  as shown in  FIG. 7 . During pre-production, exemplary method  600  may include specification and design  602  of the aircraft  700  and material procurement  604 . During production, component and subassembly manufacturing  606  and system integration  608  of the aircraft  700  takes place. Thereafter, the aircraft  700  may go through certification and delivery  610  in order to be placed in service  612 . While in service  612  by a customer, the aircraft  700  is scheduled for routine maintenance and service  614  (which may also include modification, reconfiguration, refurbishment, and so on). 
     Each of the processes of method  600  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
     As shown in  FIG. 7 , the aircraft  700  produced by exemplary method  600  may include an airframe  720  with a plurality of systems  722  and an interior  724 . Examples of high-level systems  722  include one or more of a propulsion system  726 , an electrical system  728 , a hydraulic system  726 , and an environmental system  728 . Any number of other systems may be included. Although an aerospace example is shown, the principles of the disclosed embodiments may be applied to other industries, such as the automotive industry. 
     Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method  600 . For example, components or subassemblies corresponding to production process  606  may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft  700  is in service  612 . Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages  606  and  608 , for example, by substantially expediting assembly of or reducing the cost of an aircraft  700 . Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft  700  is in service  612 , for example and without limitation, to maintenance and service  614 . 
     Although this disclosure has been described in terms of certain preferred configurations, other configurations that are apparent to those of ordinary skill in the art, including configurations that do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of the present disclosure is defined only by reference to the appended claims and equivalents thereof.