Large cabin short rib welding production line

Abstract

The present invention relates to the technical field of welding production lines, and provides a large cabin short rib welding production line, including: an automatic feeding mechanism, an automatic assembly welding mechanism and an automatic unloading mechanism; the automatic feeding mechanism is configured at the input end of the large cabin short rib welding production line, and is used to sequentially input the panel and the web into the automatic assembly welding mechanism; the automatic assembly welding mechanism is configured between the automatic feeding mechanism and the automatic unloading mechanism, and is used to assemble and weld the panel and the web, including: two sets of ground rails arranged relatively parallel; two sets of ground rails are respectively slidably installed with relative automatic welding robots; an assembly unit is arranged at the position between the two sets of ground rails; the automatic unloading mechanism is configured at the output end of the large cabin short rib welding production line, and is used to output the assembled and welded panels and webs. The present invention can assemble and weld the panels and webs of irregularly shaped large cabin short ribs, and improve the working efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of welding production lines, and in particular to a large cabin short rib welding production line. Background Art

[0002] At present, most of the short rib welding operations in shipyards are manual operations. Short ribs are composed of panels and webs. Due to the irregular shapes and sizes of panels and webs, they are assembled by compacting with simple tooling before welding, and then welded manually.

[0003] Traditional manual operation is dangerous, difficult, and labor-intensive. Assembly and welding are carried out separately, resulting in low production efficiency and a low level of intelligence. Summary of the invention

[0004] The present invention mainly solves the technical problems that traditional manual operation is dangerous, difficult, labor-intensive, assembly and welding are carried out separately, production efficiency is low, and intelligence level is low. A large cabin short rib welding production line is proposed, which can assemble and weld the panels and webs of irregularly shaped large cabin short ribs, thereby improving the operation efficiency.

[0005] The present invention provides a large cabin short rib welding production line, comprising: an automatic feeding mechanism, an automatic assembly welding mechanism and an automatic unloading mechanism;

[0006] The automatic feeding mechanism is arranged at the input end of the large cabin short rib welding production line and is used to sequentially input the face plate and the web plate into the automatic assembly welding mechanism;

[0007] The automatic assembly and welding mechanism is arranged between the automatic feeding mechanism and the automatic unloading mechanism, and is used for assembling and welding the panel and the web, and comprises: two sets of ground rails arranged in parallel with each other; automatic welding robots are slidably mounted on the two sets of ground rails relative to each other; and an assembly unit is arranged between the two sets of ground rails;

[0008] The assembly unit comprises: an assembly base, a first panel clamping fixture and a web front side positioning mechanism; a follower workbench is installed on the assembly base via a rotating shaft; two sets of first panel clamping fixtures are slidably installed on the follower workbench along the length direction, and the first panel clamping fixtures are used to clamp the panel;

[0009] A web front side positioning mechanism is arranged at the front end of the follower workbench; the web front side positioning mechanism comprises: an arc-shaped rack, a motor driving gear and a pressing block;

[0010] Both sides of the follower workbench are provided with arc-shaped racks and motor drive gears; the motor drive gears are meshed with the arc-shaped racks; a pressing block is rotatably installed on the upper end of the arc-shaped racks; the two pressing blocks are arranged opposite to each other;

[0011] The two ends of the assembly base are swingably mounted with a web front side pressing arm and a web rear side pressing arm respectively; a web pressing module is rotatably mounted on the web front side pressing arm and the web rear side pressing arm;

[0012] The automatic unloading mechanism is arranged at the output end of the large cabin short rib welding production line, and is used for outputting the assembled and welded panels and webs.

[0013] Preferably, a contour scanner is installed between the automatic feeding mechanism and the automatic assembly welding mechanism.

[0014] Preferably, a plurality of panels bending correction mechanisms are installed on the follow-up workbench;

[0015] Multiple sets of panel bending correction mechanisms are distributed along the length direction of the follow-up workbench;

[0016] The panel bending correction mechanism comprises: a first oil cylinder and a correction mechanism pressing plate;

[0017] The first oil cylinder is rotatably mounted on the sliding block, and a correction mechanism pressing plate is mounted on the plunger of the first oil cylinder. The correction mechanism pressing plate is used to support the bottom surface of the panel.

[0018] Preferably, an alignment positioning plate is provided at the rear end of the follower workbench.

[0019] Preferably, a web rear side positioning mechanism is installed on the alignment positioning plate;

[0020] The web rear side positioning mechanism comprises: second oil cylinders arranged oppositely on both sides of the web rear side positioning mechanism;

[0021] A positioning mechanism pressing plate is provided at the top end of the plunger of the second oil cylinder;

[0022] Two positioning mechanism clamping plates are used to press against both sides of the rear end of the web.

[0023] Preferably, the automatic loading mechanism comprises: a panel transfer tray, a web transfer tray and a loading truss robot;

[0024] The panel transfer tray and the web transfer tray are slidably arranged on the ground at the input end of the large cabin short rib welding production line;

[0025] The loading truss robot is slidingly arranged above the input end of the large cabin short rib welding production line; a first flipping mechanism is arranged at the terminal of the loading truss robot; a panel electromagnet and a second flipping mechanism are respectively installed on the first flipping mechanism, and a web electromagnet is installed on the second flipping mechanism.

[0026] Preferably, the loading truss robot is slidably arranged on a truss robot walking track, and the truss robot walking track is supported by a truss robot bracket.

[0027] Preferably, the automatic unloading mechanism comprises: an unloading transfer tray and an unloading truss robot;

[0028] The unloading transfer tray is slidably arranged on the ground at the output end of the large cabin short rib welding production line;

[0029] The unloading truss robot is slidably arranged above the output end of the large cabin short rib welding production line; and a unloading adsorption electromagnet is installed at the terminal of the unloading truss robot.

[0030] Preferably, it also includes: a manual grinding workbench;

[0031] The manual grinding workbench comprises: a manual grinding station slide seat slidably mounted on the ground;

[0032] Two groups of second panel clamping fixtures are slidably mounted on the manual grinding station slide.

[0033] The present invention provides a large cabin short rib welding production line with an ingenious structure and reasonable layout. When welding large cabin short ribs, the panel and the web can be automatically fed to the assembly welding mechanism for automatic assembly and automatic welding. After welding, they can be transferred to the manual repair workbench, and automatically unloaded after the repair is completed. The working speed is fast and the degree of automation is high, which can basically meet the needs of automatic assembly and welding of large cabin short ribs. The present invention can realize automatic loading and unloading, automatically assemble and weld the panel and the web, and automatically weld both sides of the web at the same time, which liberates a large amount of labor while improving work efficiency and saving costs. The above effects have greatly improved the existing situation and greatly met customer needs. It effectively solves the shortcomings of traditional manual operation such as danger, difficulty, and low intelligence level, thereby liberating labor and ultimately realizing intelligent automated production and processing management. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a three-dimensional structural schematic diagram of a large cabin short rib welding production line provided by the present invention;

[0035] Figure 2 It is a front structural schematic diagram of a large cabin short rib welding production line provided by the present invention;

[0036] Figure 3 It is a schematic diagram of the top view of the structure of the large cabin short rib welding production line provided by the present invention;

[0037] Figure 4 It is a side structural schematic diagram of a large cabin short rib welding production line provided by the present invention;

[0038] Figure 5 It is a structural schematic diagram of the ground rail and the automatic welding robot provided by the present invention;

[0039] Figure 6 It is a three-dimensional structural schematic diagram of the assembly mechanism provided by the present invention;

[0040] Figure 7 It is a schematic diagram (front view) of the assembly mechanism provided by the present invention when clamping the panel and the web;

[0041] Figure 8 It is a schematic diagram (stereoscopic) of the state of the assembly mechanism provided by the present invention when clamping the panel and the web.

[0042] Figure numerals: 1, ground rail; 2, automatic welding robot; 3, assembly mechanism; 4, assembly base; 5, follow-up workbench; 6, first panel clamping fixture; 7, motor drive gear; 8, alignment positioning plate; 9, truss robot bracket; 10, truss robot walking track; 11, first oil cylinder; 12, correction mechanism clamping plate; 13, second oil cylinder; 14, positioning mechanism clamping plate; 15, arc rack; 16, clamping block; 17, lower rear side of web Pressing arm; 18. Web pressing module; 19. Panel transfer tray; 20. Web transfer tray; 21. Loading truss robot; 22. Contour scanner; 23. Unloading transfer tray; 24. Unloading truss robot; 25. Panel electromagnet; 26. Web electromagnet; 27. Web front pressing arm; 28. Unloading adsorption electromagnet; 29. ​​Manual grinding station slide; 30. Second panel clamping fixture; 31. First flipping mechanism; Second flipping mechanism. DETAILED DESCRIPTION

[0043] In order to make the technical problems solved by the present invention, the technical solutions adopted and the technical effects achieved clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for the convenience of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all the contents.

[0044] like Figure 1-4 As shown, the large cabin short rib welding production line provided by the embodiment of the present invention includes: an automatic loading mechanism, an automatic assembly welding mechanism and an automatic unloading mechanism.

[0045] The automatic feeding mechanism is arranged at the input end of the large cabin short rib welding production line, and is used to sequentially input the face plate and the web into the automatic assembly welding mechanism.

[0046] The automatic loading mechanism includes: a panel transfer tray 19, a web transfer tray 20 and a loading truss robot 21. The panel transfer tray 19 and the web transfer tray 20 are slidably arranged on the ground at the input end of the large cabin short rib welding production line. The panel transfer tray 19 and the web transfer tray 20 are placed side by side, and the panel transfer tray 19 and the web transfer tray 20 are slidable by rails, the panel is placed on the panel transfer tray 19, and the web is placed on the web transfer tray 20.

[0047] The loading truss robot 21 is slidably arranged above the input end of the large cabin short rib welding production line; the first flip mechanism 31 is arranged at the terminal of the loading truss robot 21; the panel electromagnet 25 and the second flip mechanism 32 are respectively installed on the first flip mechanism 31, and the web electromagnet 26 is installed on the second flip mechanism 32. The first flip mechanism 31 and the second flip mechanism 32 can both flip 90 degrees. When the panel is adsorbed, the panel electromagnet 25 faces downward and the web electromagnet 26 faces outward. The panel electromagnet 25 adsorbs the panel and then transports it to the automatic assembly welding mechanism; when the web is adsorbed, the first flip mechanism 31 rotates so that the panel electromagnet 25 faces outward and the web electromagnet 26 faces downward. After the web is adsorbed, the loading truss robot 21 rises to the flip safety distance. The second flip mechanism 32 flips and then transfers it to the automatic assembly welding mechanism.

[0048] Specifically, the loading truss robot 21 is slidably arranged on the truss robot walking track 10 , and the loading truss robot 21 can realize movement in the directions of X-axis, Y-axis, and Z-axis; the truss robot walking track 10 is supported by the truss robot bracket 9 .

[0049] Furthermore, a contour scanner 22 is installed between the automatic feeding mechanism and the automatic assembly welding mechanism.

[0050] The automatic assembly and welding mechanism is arranged between the automatic loading mechanism and the automatic unloading mechanism, and is used to assemble and weld the face plate and the web. Figure 5 As shown, it comprises: two sets of ground rails 1 arranged in parallel with each other; automatic welding robots 2 are slidably mounted on the two sets of ground rails 1, and the automatic welding robots 2 are used to automatically weld the panel and the web. An assembly unit 3 is arranged between the two sets of ground rails 1, and is used to automatically assemble the panel and the web.

[0051] like Figure 6-8As shown, the assembly unit 3 includes: an assembly base 4, a first panel clamping fixture 6 and a web front positioning mechanism; a follower workbench 5 is installed on the assembly base 4 through a rotating shaft, and the follower workbench 5 can be driven to rotate by the rotating shaft, and the rotating shaft is driven by a motor. Two groups of first panel clamping fixtures 6 are slidably installed on the follower workbench 5 along the length direction, and the first panel clamping fixtures 6 are used to clamp the panel. Claws are set on both sides of the first panel clamping fixture 6 to clamp both sides of the panel. Specifically, the sliding action of the first panel clamping fixture 6 is realized by gear rack and motor drive, and the first panel clamping fixture 6 drives the claws on both sides to move inward and clamp by the lead screw (using the same trapezoidal lead screw, and realizing synchronous movement through two positive and negative lead screw nuts to achieve the purpose of centering clamping, and the drive can be a stepper motor acceleration and reduction gear).

[0052] The front end of the follower workbench 5 is provided with a web front side positioning mechanism; the web front side positioning mechanism includes: an arc-shaped rack 15, a motor-driven gear 7 and a clamping block 16. The two sides of the follower workbench 5 are provided with an arc-shaped rack 15 and a motor-driven gear 7; the motor-driven gear 7 is meshed with the arc-shaped rack 15; the clamping block 16 is rotatably installed on the upper end of the arc-shaped rack 15, and the clamping block 16 can follow the movement to increase the positioning effect; the two clamping blocks 16 are arranged opposite to each other. The motor-driven gear 7 rotates under the drive of the motor, and the rotation of the motor-driven gear 7 can drive the arc-shaped rack 15 to close and open. The arc-shaped racks 15 on both sides are closed, which can make the clamping blocks 16 press on the two sides of the front side of the web to position the front side of the web.

[0053] Multiple groups of panel bending correction mechanisms are installed on the follow-up workbench 5; the multiple groups of panel bending correction mechanisms are distributed along the length direction of the follow-up workbench 5. The panel bending correction mechanism includes: a first oil cylinder 11 and a correction mechanism clamping plate 12; the first oil cylinder 11 is rotatably installed on a slider, and the correction mechanism clamping plate 12 is installed on the plunger of the first oil cylinder 11, and the correction mechanism clamping plate 12 is used to support the bottom surface of the panel. The slider rotatably installed on the first oil cylinder 11 shares a sliding track with the first panel clamping fixture 6. The sliding setting of the first oil cylinder 11 can adjust the position of the top pressure panel, and can support the position of the panel plane or the place where the deformation of the top panel is large, so that the panel is close to the edge of the web to eliminate the gap.

[0054] The rear end of the follower workbench 5 is provided with an alignment positioning plate 8. The web rear side positioning mechanism is installed on the alignment positioning plate 8. The web rear side positioning mechanism comprises: a second oil cylinder 13 arranged oppositely on both sides of the web rear side positioning mechanism, and a positioning mechanism pressing plate 14 is arranged at the top of the plunger of the second oil cylinder 13; the two positioning mechanism pressing plates 14 are used to press against both sides of the rear end of the web.

[0055] The two ends of the assembly base 4 are respectively swingably mounted with a web front side pressing arm 27 and a web rear side pressing arm 17, and the swinging action is realized by connecting with an oil cylinder; a web pressing module 18 is rotatably mounted on the web front side pressing arm 27 and the web rear side pressing arm 17. The swinging of the web front side pressing arm 27 and the web rear side pressing arm 17 can make the web pressing module 18 press on the upper edges of the two ends of the web, so as to stabilize the web.

[0056] The automatic unloading mechanism is arranged at the output end of the large cabin short rib welding production line, and is used to output the assembled and welded panels and webs. The automatic unloading mechanism includes: an unloading transfer tray 23 and an unloading truss robot 24; the unloading transfer tray 23 is slidably arranged on the ground at the output end of the large cabin short rib welding production line; the sliding is achieved through a track, and the track is arranged from the bottom of the truss robot walking track 10 to the outside of the truss robot walking track 10, which is convenient for product output.

[0057] The unloading truss robot 24 is slidably arranged above the output end of the large cabin short rib welding production line, specifically, it is slidably installed on the truss robot walking track 10, and the unloading truss robot 24 moves back and forth on one side of the output direction, and can realize movement in the X-axis, Y-axis, and Z-axis directions; the unloading truss robot 24 terminal is installed with an unloading adsorption electromagnet 28, and the direction of the unloading adsorption electromagnet 28 is facing the side, which can adsorb the welded web to realize product handling.

[0058] On the basis of the above scheme, the large cabin short rib welding production line of this embodiment further includes: a manual grinding workbench; the manual grinding workbench includes: a manual grinding station slide 29 slidably mounted on the ground; two sets of second panel clamping fixtures 30 are slidably mounted on the manual grinding station slide 29. The second panel clamping fixture 30 can clamp the welded panel, and the operator performs manual grinding on the manual grinding workbench.

[0059] In addition, the large cabin short rib welding production line of this embodiment is also provided with a numerical control operation box and a hydraulic pump. The driving motor, mechanical arm, welding assembly, contour scanner, etc. are all controlled by a control system provided in the numerical control operation box.

[0060] The working process of the large cabin short rib welding production line of the present invention is as follows:

[0061] Automatic panel loading: The upper panel electromagnet 25 of the loading truss robot 21 absorbs the panel from the panel transfer tray 19 and transfers it to the follower workbench 5 of the assembly unit 3. The follower workbench 5 swings a certain angle on the assembly base 4, and the panel slides to the alignment positioning plate 8 by its own gravity. After the first panel clamping fixture 6 clamps the panel, the follower workbench 5 swings back to the horizontal position. In the process of panel transfer, the contour scanner 22 scans the panel contour to obtain the welding path.

[0062] Automatic loading of the web: the first flipping mechanism 31 on the loading truss robot 21 flips 90°, and the web electromagnet 26 absorbs the web from the web transfer pallet 20; the loading truss robot 21 rises to the flipping safety distance, and the second flipping mechanism 32 flips 90°, and then transfers the web to the web assembly line on the clamped panel; the second cylinder 13 of the positioning mechanism on the rear side of the web extends out, the positioning mechanism clamping plate 14 clamps the web, and the arc-shaped rack 15 of the positioning mechanism on the front side of the web closes and clamps the web.

[0063] The follower workbench 5 swings a certain angle on the assembly base 4, and the web front side pressing arm 27 and the web rear side pressing arm 17 swing at the same time, so that the web pressing module 18 presses on the upper edges of both ends of the web to stabilize the web. After the multiple sets of panel bending correction mechanisms slide and adjust to the appropriate position, the first oil cylinder 11 extends, and the correction mechanism pressing plate 12 presses against the bottom surface of the panel, so that the panel is close to the edge of the web, and the assembly gap between the panel and the web is eliminated.

[0064] Automatic welding by automatic welding robot 2: Automatic welding robot 2 is installed by sliding, and spot welding is performed according to the welding path. After the rib is assembled by spot welding, the loading truss robot 21 withdraws, the web front positioning mechanism and the web rear positioning mechanism on the assembly unit are released, the web front lower pressure arm 27 and the web rear lower pressure arm 17 are reset, the follow-up workbench 5 automatically adjusts the follow-up angle, and cooperates with the automatic welding machine 2 to perform forming welding, and a short rib is formed after welding.

[0065] Manual grinding and automatic unloading: After the short rib welding is completed, the follower workbench 5 returns to the horizontal position, and the short rib is transferred to the manual grinding workbench by the unloading truss robot 24. The manual grinding workbench moves to the outside of the activity range of the unloading truss robot 24, and the welding quality and repair work are manually checked. Finally, the unloading truss robot 24 transfers it to the unloading transfer pallet 23, and the unloading transfer pallet 23 flows out from the side ground rail of the assembly line and is then transported by a forklift.

[0066] The present invention can automatically identify and load the panels and webs of the rib's special-shaped ends, and can automatically assemble and weld the workpieces; the welding path is automatically tracked, and the ground rail welding equipment is automatically controlled to automatically assemble and weld the large cabin ribs; after welding, the automatic truss robot is used to transfer them to the unloading station. While freeing up a large amount of labor, it improves work efficiency and saves costs.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that modifying the technical solutions described in the aforementioned embodiments, or replacing some or all of the technical features therein by equivalents, does not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A large cabin short rib welding production line, characterized in that: include: Automatic feeding mechanism, automatic assembly welding mechanism and automatic unloading mechanism; The automatic feeding mechanism is arranged at the input end of the large cabin short rib welding production line and is used to sequentially input the face plate and the web plate into the automatic assembly welding mechanism; The automatic assembly and welding mechanism is arranged between the automatic loading mechanism and the automatic unloading mechanism and is used for assembling and welding the face plate and the web, comprising: two sets of ground rails (1) arranged relatively parallel to each other; automatic welding robots (2) respectively slidably mounted relatively to each other on the two sets of ground rails (1); and an assembly unit (3) is arranged at a position between the two sets of ground rails (1); The assembly unit (3) comprises: an assembly base (4), a first panel clamping fixture (6) and a web front positioning mechanism; a follower workbench (5) is mounted on the assembly base (4) via a rotating shaft; two sets of first panel clamping fixtures (6) are slidably mounted on the follower workbench (5) along the length direction, and the first panel clamping fixtures (6) are used to clamp the panel; A web front side positioning mechanism is provided at the front end of the follower workbench (5); the web front side positioning mechanism comprises: an arc-shaped rack (15), a motor drive gear (7) and a pressing block (16); Both sides of the follower workbench (5) are provided with arc-shaped racks (15) and motor drive gears (7); the motor drive gear (7) is meshed with the arc-shaped rack (15); a pressing block (16) is rotatably mounted on the upper end of the arc-shaped rack (15); the two pressing blocks (16) are arranged opposite to each other; The two ends of the assembly base (4) are respectively swingably mounted with a web front side pressing arm (27) and a web rear side pressing arm (17); a web pressing module (18) is rotatably mounted on the web front side pressing arm (27) and the web rear side pressing arm (17); The automatic unloading mechanism is arranged at the output end of the large cabin short rib welding production line, and is used to output the assembled and welded panels and webs; An alignment positioning plate (8) is provided at the rear end of the follower workbench (5); a web rear side positioning mechanism is installed on the alignment positioning plate (8); the web rear side positioning mechanism comprises: second oil cylinders (13) arranged oppositely on both sides of the web rear side positioning mechanism; a positioning mechanism clamping plate (14) is provided at the top end of the plunger of the second oil cylinder (13); the two positioning mechanism clamping plates (14) are used to press against both sides of the web rear end.

2. The large cabin short rib welding production line according to claim 1 is characterized in that: A contour scanner (22) is installed between the automatic feeding mechanism and the automatic assembly welding mechanism.

3. The large cabin short rib welding production line according to claim 1 is characterized in that: A plurality of panel bending correction mechanisms are installed on the follower workbench (5); A plurality of panel bending correction mechanisms are distributed along the length direction of the follower workbench (5); The panel bending correction mechanism comprises: a first oil cylinder (11) and a correction mechanism pressing plate (12); The first oil cylinder (11) is rotatably mounted on the slide block, and a correction mechanism clamping plate (12) is mounted on the plunger of the first oil cylinder (11), wherein the correction mechanism clamping plate (12) is used to support the bottom surface of the panel.

4. The large cabin short rib welding production line according to claim 1 is characterized in that: The automatic loading mechanism comprises: a panel transfer tray (19), a web transfer tray (20) and a loading truss robot (21); The panel transfer tray (19) and the web transfer tray (20) are slidably arranged on the ground at the input end of the large cabin short rib welding production line; The loading truss robot (21) is slidably arranged above the input end of the large cabin short rib welding production line; a first flipping mechanism (31) is arranged at the terminal of the loading truss robot (21); a panel electromagnet (25) and a second flipping mechanism (32) are respectively installed on the first flipping mechanism (31), and a web electromagnet (26) is installed on the second flipping mechanism (32).

5. The large cabin short rib welding production line according to claim 4 is characterized in that: The loading truss robot (21) is slidably arranged on a truss robot walking track (10), and the truss robot walking track (10) is supported by a truss robot bracket (9).

6. The large cabin short rib welding production line according to claim 5 is characterized in that: The automatic unloading mechanism comprises: an unloading transfer tray (23) and an unloading truss robot (24); The unloading transfer tray (23) is slidably arranged on the ground at the output end of the large cabin short rib welding production line; The material unloading truss robot (24) is slidably arranged above the output end of the large cabin short rib welding production line; and a material unloading adsorption electromagnet (28) is installed at the terminal of the material unloading truss robot (24).

7. The large cabin short rib welding production line according to claim 1 is characterized in that: Also includes: manual grinding workbench; The manual grinding workbench comprises: a manual grinding station slide seat (29) slidably mounted on the ground; Two sets of second panel clamping fixtures (30) are slidably mounted on the manual grinding station slide (29).

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