CN118663760B - High-efficient shaping apparatus for producing of radome fairing - Google Patents

Abstract

The invention relates to the field of stamping forming processing, in particular to a high-efficiency forming production device for a fairing, which comprises a base, wherein two upright posts are fixed on the base, and the high-efficiency forming production device further comprises: the stamping forming mechanism is arranged on the upright post; the stamping forming mechanism comprises an upper die holder and a lower die holder, a female die cavity is formed in the bottom surface of the upper die holder, a plurality of hammer rods arranged along the ridge line of the female die cavity are arranged on the upper die holder, and a male die body corresponding to the female die cavity is fixed on the upper surface of the lower die holder; the upper die holder is arranged at the lower side of the lifting table, the lifting table is fixed at the end part of a piston rod of the hydraulic cylinder, the hydraulic cylinder is fixed in the middle of the upper cross brace, the two ends of the upper cross brace are respectively and fixedly connected with the upper ends of the two upright posts, the two ends of the lower die holder are respectively and fixedly connected with the supporting tables, and the two supporting tables are respectively and fixedly connected with the two upright posts. The high-efficiency forming production device for the fairing comprises a punch forming mechanism, a striking and forming mechanism, a forming edge line of the fairing, a forming machine and a forming machine.

Description

High-efficient shaping apparatus for producing of radome fairing

Technical Field

The invention relates to the field of stamping forming processing, in particular to a high-efficiency forming production device for a fairing.

Background

The aircraft cabin body adopts the fairing structure, so that friction between the cabin body and air flow can be well reduced, and the pneumatic heating effect can be well inhibited. In the existing forming production and processing technology of the fairing, after the fairing is subjected to stamping forming, the fairing is easy to rebound to cause certain return after stamping of the edge line position, so that the quality of a finished product is reduced, and in view of the fact, the efficient forming production device of the fairing is provided.

Disclosure of Invention

The invention aims to provide a high-efficiency forming production device for a fairing, which aims to solve the problems in the background technology. In order to achieve the above purpose, the present invention provides the following technical solutions: the utility model provides a high-efficient shaping apparatus for producing of radome fairing, includes the base, be fixed with the stand of two vertical upwards settings on the base, still include:

the stamping forming mechanism is arranged on the upright post;

The stamping forming mechanism comprises an upper die holder and a lower die holder, a concave die cavity is formed in the bottom surface of the upper die holder, a plurality of hammer rods arranged along the edge line of the concave die cavity are arranged on the upper die holder, and a convex die body corresponding to the concave die cavity is fixed on the upper surface of the lower die holder;

the upper die holder is arranged on the lower side of the lifting table, the lifting table is fixed on the end part of a piston rod of the hydraulic cylinder, the hydraulic cylinder is fixed in the middle of the upper cross brace, two ends of the upper cross brace are fixedly connected to the upper ends of the two stand columns respectively, supporting tables are fixed at two ends of the lower die holder respectively, and the two supporting tables are fixedly connected to the two stand columns respectively.

Preferably, two ends of the lifting platform are respectively fixedly connected with sliding sleeves, and the two sliding sleeves are respectively sleeved and connected to the two upright posts in a sliding manner.

Preferably, the upper surface of the upper die holder is fixedly provided with vertical upward sliding rods, the number of the sliding rods is not less than two, the upper ends of the sliding rods penetrate through and are connected to the lifting table in a sliding mode, the upper ends of the sliding rods are fixedly provided with limiting blocks, and the limiting blocks are connected with the upper surface of the lifting table through first springs.

Preferably, the upper die holder is provided with a striking shaping mechanism, the striking shaping mechanism comprises a plurality of slide ways arranged on the upper die holder, the slide ways are arranged along the ridge line of the cavity of the female die, the slide ways are arranged in one-to-one correspondence with the hammer bars, and the slide ways are communicated with the cavity of the female die.

Preferably, the fixed shaft on the upper surface of the upper die holder is rotationally connected with a plurality of chain wheels, a plurality of chain wheels are connected through chain transmission, and a plurality of chain wheels and a plurality of hammer rods are arranged in one-to-one correspondence.

Preferably, the upper end of the hammer rod is fixedly connected with one end of a connecting rod, the other end of the connecting rod is fixedly connected with a roller in a fixed shaft rotation manner, the connecting rod is connected with the upper surface of the upper die holder through a second spring, a bulge is fixed on the upper surface of the chain wheel at a position far away from the circle center, and the roller rolls on the edge of the upper surface of the corresponding chain wheel and the bulge under the action of the second spring.

Preferably, the fixed shaft on the upper surface of the upper die holder is rotationally connected with a ratchet wheel, the outer ring of the ratchet wheel is connected with a chain in a transmission way, a twist rod vertically arranged upwards is fixed in the center of the upper surface of the inner ring of the ratchet wheel, a through hole is formed in the lifting table, a disc is fixed in the through hole, and a straight hole matched with the cross section of the twist rod is formed in the center of the disc.

Preferably, the pump wheel three and the pump wheel four are respectively fixed at two ends of the upper cross brace, the lower cross brace is arranged below the lower die holder, two ends of the lower cross brace are respectively and fixedly connected to the two upright posts, the pump wheel one and the pump wheel two are respectively fixed at two ends of the lower cross brace, and air pipes are respectively fixed on and communicated with the peripheral walls of the pump wheel one, the pump wheel two, the pump wheel three and the pump wheel four.

Preferably, the upper surface of the upper die holder is provided with a plurality of air passages communicated with the cavity of the female die, the bottom surface of the lower die holder is also provided with air passages, the air passages penetrate up to the upper surface of the male die body, and the air pipes are connected with the air passages.

Preferably, impeller shafts of the first pump wheel, the second pump wheel, the third pump wheel and the fourth pump wheel are coaxially and fixedly connected with wire wheels, hanging lugs are respectively fixed on the upper side and the lower side of two ends of the lifting platform, one end of a first pull rope is fixed on the hanging lugs on the upper side of the right end of the lifting platform, the other end of the pull rope bypasses the wire wheels on the fourth pump wheel and the wire wheels on the first pump wheel and then is fixedly connected with the hanging lugs on the lower side of the left end of the lifting platform, one end of the second pull rope is fixed on the hanging lugs on the upper side of the left end of the lifting platform, and the other end of the pull rope bypasses the wire wheels on the third pump wheel and the wire wheels on the second pump wheel and then is fixedly connected with the hanging lugs on the lower side of the right end of the lifting platform.

Compared with the prior art, the invention has the beneficial effects that:

According to the invention, the lifting table and the upper die holder are driven by the hydraulic cylinder to move downwards to punch and shape the workpiece blank of the fairing, and the distance between the lifting table and the upper die holder is shortened in the punching and forming process, so that the twist rod is inserted into a straight hole on the disc, and the striking and shaping mechanism is driven to hammer the shaping edge line of the fairing, so that the workpiece blank removes rebound stress after punching and deformation, the stability of the workpiece blank after punching and forming is maintained, and the forming quality of the fairing is improved.

According to the invention, the stamping forming mechanism drives the pump impeller I, the pump impeller II, the pump impeller III and the pump impeller four-way air pipe and the air channel to suck air in the process of driving the upper die holder and the lower die holder to be matched, so that internal clearance air is pumped out when the upper die holder and the lower die holder are matched, a workpiece blank is better attached to the inner wall of a cavity of a female die and the surface of a male die, the production quality of a fairing is further improved, and the pump impeller I, the pump impeller II, the pump impeller III and the pump impeller four-way air pipe and the air channel are simultaneously driven to blow in the process of driving the upper die holder and the lower die holder to separate the die, so that the formed fairing is conveniently separated from the inner wall of the cavity of the female die or the male die body, and the fairing is conveniently demoulded.

Drawings

FIG. 1 is a schematic diagram of the sectional structure of the assembly of the present invention;

FIG. 2 is a schematic diagram of a cross-sectional structure of a final assembly of the present invention;

FIG. 3 is an enlarged schematic view of the structure of FIG. 1 at A;

FIG. 4 is an enlarged schematic view of the structure at B in FIG. 3;

FIG. 5 is a top view of the ratchet and various sprocket constructions of the present invention;

Fig. 6 is a top view of a disk structure in accordance with the present invention.

In the figure: 1. a base; 2. a lower cross brace; 3. a pump wheel I; 4. a column; 5. a first pull rope; 6. hanging lugs; 7. an upper die holder; 8. a female mold cavity; 9. a twist stem; 10. a slide bar; 11. a second rope; 12. a support table; 13. a lower die holder; 14. a convex mold body; 15. a pump wheel II; 16. a lifting table; 17. a first spring; 18. a limiting block; 19. a sliding sleeve; 20. a hydraulic cylinder; 21. an upper cross brace; 22. a pump wheel III; 23. a pump wheel IV; 24. a through hole; 25. a disc; 26. a straight hole; 27. an airway; 28. an air pipe; 29. a chain; 30. a ratchet wheel; 31. a slideway; 32. a hammer rod; 33. a connecting rod; 34. a roller; 35. a sprocket; 36. a protrusion; 37. and a second spring.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which are obtained by a worker of ordinary skill in the art without creative efforts, are within the protection scope of the present invention based on the embodiments of the present invention.

Referring to fig. 1 to 6, the present invention provides a technical solution: the utility model provides a high-efficient shaping apparatus for producing of radome fairing, includes base 1, is fixed with the stand 4 of two vertical upwards setting on the base 1, still includes:

A press forming mechanism provided on the column 4;

The stamping forming mechanism comprises an upper die holder 7 and a lower die holder 13, a die cavity 8 is formed in the bottom surface of the upper die holder 7, a plurality of hammer rods 32 are arranged on the upper die holder 7 along the edge line of the die cavity 8, and a convex die body 14 corresponding to the die cavity 8 is fixed on the upper surface of the lower die holder 13;

the upper die holder 7 is arranged at the lower side of the lifting table 16, the lifting table 16 is fixed at the end part of a piston rod of the hydraulic cylinder 20, the hydraulic cylinder 20 is fixed at the middle part of the upper cross brace 21, two ends of the lifting table 16 are respectively fixedly connected with sliding sleeves 19, the two sliding sleeves 19 are respectively sleeved and slidingly connected on the two upright posts 4, two ends of the upper cross brace 21 are respectively fixedly connected with the upper ends of the two upright posts 4, two ends of the lower die holder 13 are respectively fixed with supporting tables 12, and the two supporting tables 12 are respectively fixedly connected on the two upright posts 4.

In this embodiment, the upper surface of the upper die holder 7 is fixed with vertically upward sliding rods 10, the number of the sliding rods 10 is not less than two, the upper ends of the sliding rods 10 penetrate through and are slidably connected to the lifting platform 16, the upper ends of the sliding rods 10 are fixed with limiting blocks 18, and the limiting blocks 18 are connected with the upper surface of the lifting platform 16 through springs one 17.

In this embodiment, be provided with on the upper die base 7 and hit the forming mechanism, and hit and form the mechanism including seting up a plurality of slides 31 on the upper die base 7, a plurality of slide 31 sets up along die cavity 8 crest line position, and a plurality of slide 31 and a plurality of hammer lever 32 one-to-one setting, slide 31 is linked together with die cavity 8, and upper surface dead axle of upper die base 7 rotates and is connected with a plurality of sprockets 35, and a plurality of between the sprocket 35 through chain 29 transmission connection, a plurality of sprocket 35 and a plurality of hammer lever 32 one-to-one setting, the upper end fixed connection connecting rod 33's of hammer lever 32 one end, the other end dead axle rotation of connecting rod 33 connects gyro wheel 34, and connecting rod 33 is connected with upper surface of upper die base 7 through spring two 37, and the upper surface of sprocket 35 is kept away from the centre of a circle position fixed with protruding 36, and makes gyro wheel 34 roll on corresponding sprocket 35 upper surface edge and protruding 36 under the effect of spring two 37, upper surface dead axle rotation connection ratchet 30, and the outer lane and 29 transmission connection of ratchet 30 are connected with, and the vertical upper surface of ratchet 30 is fixed with the one end of a round disc 25, and is provided with the round disc 25 of a round disc 25, and is equipped with the round through-hole 25 in the cross section is fixed with upwards, and is equipped with the round disc 25.

In this embodiment, the pump wheel three 22 and the pump wheel four 23 are fixed at two ends of the upper cross brace 21 respectively, the lower cross brace 2 is arranged below the lower die holder 13, two ends of the lower cross brace 2 are fixedly connected to the two upright posts 4 respectively, the pump wheel one 3 and the pump wheel two 15 are fixed at two ends of the lower cross brace 2 respectively, the pump wheel one 3, the pump wheel two 15, the pump wheel three 22 and the pump wheel four 23 are fixed on the peripheral walls and communicated with an air pipe 28, a plurality of air passages 27 communicated with the die cavity 8 are formed in the upper surface of the upper die holder 7, the air passages 27 are also formed in the bottom surface of the lower die holder 13, the air passages 27 are upwards penetrated to the upper surface of the convex die body 14, the air pipes 28 are connected with the air passages 27 respectively, the impeller shafts of the pump wheel one 3, the pump wheel two 15, the pump wheel three 22 and the pump wheel four 23 are coaxially and fixedly connected with wire wheels, the two upper and lower sides of the two ends of the lifting platform 16 are fixedly connected with the hanging lugs 6, one end of the pull rope one 5 is fixed on the hanging lugs 6 on the right side of the lifting platform 16, the other end of the lifting platform is wound around the wire one end of the pump wheel four wheels 23, the upper hanging lugs 16 and the two ends of the two hanging lugs 16 are connected with the left end of the hanging lugs 16 and the wire two hanging lugs 16 are fixedly connected with the hanging lugs 6.

The invention has the working principle and advantages that: when the high-efficiency forming production device for the fairing is used, the working process is as follows:

In the initial state, as shown in fig. 1, at this time, the fried dough twist rod 9 is not contacted with the straight hole 26, the lower end surface of the hammer rod 32 is in level transition with the inner wall of the die cavity 8, a workpiece blank body of the fairing is placed between the upper die holder 7 and the lower die holder 13, then the hydraulic cylinder 20 is started to work, the hydraulic cylinder 20 drives the lifting table 16 to move downwards, the sliding sleeves 19 at two ends of the lifting table 16 start the positioning guiding function, the descending state of the lifting table 16 is kept stable, the lifting table 16 descends and simultaneously drives the upper die holder 7 to move downwards through the first spring 17 and each sliding rod 10, so that the upper die holder 7 punches the workpiece blank body, when the upward reaction force of the lower die holder 13 and the workpiece blank body is kept in level with the upper die holder 7, the lifting table 16 continues to move downwards and continuously applies punching force to the workpiece blank body through the first spring 17 and each sliding rod 10, and the first spring 17 continues to stretch, when the twist rod 9 starts to be inserted into the straight hole 26 on the disc 25, the gap between the lifting table 16 and the upper die seat 7 is gradually reduced, the side wall of the straight hole 26 applies torque to the twist rod 9 so that the twist rod 9 drives the inner ring of the ratchet wheel 30 to rotate, as shown in fig. 2, 3, 5 and 6, the inner ring of the ratchet wheel 30 drives the outer ring to synchronously rotate, the outer ring of the ratchet wheel 30 drives each chain wheel 35 to rotate through the chain 29, the chain wheels 35 drive the protrusions 36 on the chain wheels to synchronously rotate, the protrusions 36 are in intermittent contact with the corresponding rollers 34, the rollers 34 are lifted up and lifted up, the connecting rod 33 stretches the spring II 37 and simultaneously drives the hammer rod 32 to be lifted, when the protrusions 36 are separated from the rollers 34, the connecting rod 33 and the hammer rod 32 are driven to move downwards under the action of the spring II 37 and hammer the edge line position of the inner wall of the concave die cavity 8, so that rebound stress is removed after the workpiece blank is deformed, thereby maintaining the stability of the workpiece blank after stamping forming and further improving the forming quality of the fairing.

After the upper die holder 7 and the lower die holder 13 punch-form the workpiece blank body stably, the hydraulic cylinder 20 is started to move upwards, so that the hydraulic cylinder 20 drives the lifting table 16 to move upwards, the upper die holder 7 moves downwards relative to the lifting table 16 under the action force of the first spring 17, the disc 25 drives the twist rod 9 to rotate reversely, the twist rod 9 drives the inner ring of the ratchet wheel 30 to rotate reversely, the outer ring of the ratchet wheel 30 cannot drive the chain wheels 35 to rotate through the chain 29, and after the twist rod 9 is separated from the straight hole 26, the hydraulic cylinder moves upwards and resets along with the lifting table 16 under the action force of the first spring 17, so that the punch-forming processing of the fairing is completed.

As described above, the lifting platform 16 moves downwards and drives the lead wheels on the first pump wheel 3, the second pump wheel 15, the third pump wheel 22 and the fourth pump wheel 23 through the first pull rope 5 and the second pull rope 11, so that the lead wheels drive the impeller shafts on the corresponding pump wheels to rotate, the first pump wheel 3, the second pump wheel 15, the third pump wheel 22 and the fourth pump wheel 23 suck air through the air pipe 28 and the air channel 27, and then the clearance air inside the upper die holder 7 and the lower die holder 13 are pulled out when the upper die holder 7 and the lower die holder 13 are combined, so that a workpiece blank is better attached to the inner wall of the die cavity 8 and the surface of the male die body 14, the production quality of the fairing is further improved, and when the lifting platform 16 moves upwards, the lead wheels on the first pump wheel 3, the second pump wheel 15, the third pump wheel 22 and the fourth pump wheel 23 are driven by the first pull rope 5 and the second pull rope 11 to rotate reversely, so that the lead wheels drive the impeller shafts on the corresponding pump wheels to rotate reversely, and the first pump wheel 3, the second pump wheel 15, the third pump wheel 22 and the fourth pump wheel 23 are convenient to detach from the die cavity 8 through the air pipe 28 and the air channel 27, so that the die body 8 and the die body is convenient to detach from the die cavity 8 after the die cavity 14 is formed or the die body is convenient to blow.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," "tail," and the like are used as an orientation or positional relationship based on that shown in the drawings, merely to facilitate description of the invention and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "connected," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

Claims (5)

1. The utility model provides a high-efficient shaping apparatus for producing of radome fairing, includes base (1), be fixed with stand (4) that two are vertical upwards to set up on base (1), its characterized in that: further comprises:

a stamping forming mechanism arranged on the upright post (4);

the stamping forming mechanism comprises an upper die holder (7) and a lower die holder (13), a female die cavity (8) is formed in the bottom surface of the upper die holder (7), a plurality of hammer rods (32) are arranged on the upper die holder (7) along the edge line position of the female die cavity (8), and a male die body (14) corresponding to the female die cavity (8) is fixed on the upper surface of the lower die holder (13);

The upper die holder (7) is arranged at the lower side of the lifting table (16), the lifting table (16) is fixed at the end part of a piston rod of the hydraulic cylinder (20), the hydraulic cylinder (20) is fixed at the middle part of the upper cross brace (21), two ends of the upper cross brace (21) are respectively and fixedly connected to the upper ends of the two upright posts (4), two ends of the lower die holder (13) are respectively and fixedly connected to the supporting tables (12), and the two supporting tables (12) are respectively and fixedly connected to the two upright posts (4);

The upper surface of the upper die holder (7) is fixedly connected with a plurality of chain wheels (35) in a rotating manner, the plurality of chain wheels (35) are in transmission connection through chains (29), and the plurality of chain wheels (35) and the plurality of hammer rods (32) are arranged in one-to-one correspondence;

The upper end of the hammer rod (32) is fixedly connected with one end of a connecting rod (33), the other end of the connecting rod (33) is fixedly connected with a roller (34) in a rotating way, the connecting rod (33) is connected with the upper surface of the upper die holder (7) through a second spring (37), a boss (36) is fixed on the upper surface of the chain wheel (35) at a position far away from the circle center, and the roller (34) rolls on the edge of the upper surface of the corresponding chain wheel (35) and the boss (36) under the action of the second spring (37);

the upper surface of the upper die holder (7) is fixedly connected with a ratchet wheel (30) in a rotating way, the outer ring of the ratchet wheel (30) is in transmission connection with a chain (29), a twist rod (9) which is vertically and upwards arranged is fixed in the center of the upper surface of the inner ring of the ratchet wheel (30), a through hole (24) is formed in the lifting table (16), a disc (25) is fixed in the through hole (24), and a straight hole (26) which is matched with the cross section of the twist rod (9) is formed in the center of the disc (25);

The two ends of the upper cross brace (21) are respectively fixed with a pump wheel III (22) and a pump wheel IV (23), the lower cross brace (2) is arranged below the lower die holder (13), the two ends of the lower cross brace (2) are respectively fixedly connected to the two upright posts (4), the two ends of the lower cross brace (2) are respectively fixed with a pump wheel I (3) and a pump wheel II (15), and the peripheral walls of the pump wheel I (3), the pump wheel II (15), the pump wheel III (22) and the pump wheel IV (23) are respectively fixed with an air pipe (28) in a communicating manner;

The upper surface of the upper die holder (7) is provided with a plurality of air passages (27) communicated with the female die cavity (8), the bottom surface of the lower die holder (13) is also provided with the air passages (27), the air passages (27) penetrate up to the upper surface of the male die body (14), and the air pipes (28) are connected with the air passages (27).

2. The efficient fairing forming and producing device as recited in claim 1, wherein: two ends of the lifting table (16) are respectively fixedly connected with sliding sleeves (19), and the two sliding sleeves (19) are respectively sleeved and connected onto the two upright posts (4) in a sliding manner.

3. The efficient fairing forming and producing device as recited in claim 1, wherein: the upper surface of the upper die holder (7) is fixedly provided with vertical upward sliding rods (10), the number of the sliding rods (10) is not lower than two, the upper ends of the sliding rods (10) penetrate through and are connected to the lifting table (16) in a sliding mode, the upper ends of the sliding rods (10) are fixedly provided with limiting blocks (18), and the limiting blocks (18) are connected with the upper surface of the lifting table (16) through springs I (17).

4. A fairing high efficiency molding production apparatus as set forth in claim 3, wherein: the upper die holder (7) is provided with a striking shaping mechanism, the striking shaping mechanism comprises a plurality of slide ways (31) arranged on the upper die holder (7), the slide ways (31) are arranged along the ridge line position of the female die cavity (8), the slide ways (31) and the hammer rods (32) are arranged in one-to-one correspondence, and the slide ways (31) are communicated with the female die cavity (8).

5. The efficient fairing forming and producing device as defined in claim 4, wherein: impeller shafts of the first pump impeller (3), the second pump impeller (15), the third pump impeller (22) and the fourth pump impeller (23) are all coaxially and fixedly connected with wire guide wheels, hanging lugs (6) are respectively fixed on the upper side and the lower side of two ends of the lifting platform (16), one end of a first pull rope (5) is fixed on the hanging lugs (6) on the upper side of the right end of the lifting platform (16), the other end of the pull rope bypasses the wire guide wheels on the fourth pump impeller (23) and the wire guide wheels on the first pump impeller (3) and then is fixedly connected with the hanging lugs (6) on the lower side of the left end of the lifting platform (16), one end of the second pull rope (11) is fixed on the hanging lugs (6) on the upper side of the left end of the lifting platform (16), and the other end of the pull rope bypasses the wire guide wheels on the third pump impeller (22) and the wire guide wheels on the second pump impeller (15) and then is fixedly connected with the hanging lugs (6) on the lower side of the right end of the lifting platform (16).