CN117601294A - A solar cell welding precision cutting device - Google Patents

Abstract

The invention relates to the technical field of solar cell processing, in particular to a solar cell welding precision cutting device, which comprises a workbench, wherein a mounting frame is fixedly arranged on the workbench, a motor I is arranged at the top of the mounting frame, a sector gear is fixedly connected to an output shaft of the motor I, the sector gear is respectively meshed with a slicing mechanism, a blanking mechanism and a pushing mechanism which are arranged on the workbench intermittently, and the slicing mechanism is arranged between the blanking mechanism and the pushing mechanism; according to the solar cell welding precision cutting device, the sector gear can realize the interval operation of three steps in one rotation cycle, the automation of silicon wafer cutting can be realized, a driving source is simplified, a controller is not required to be added, a program is not required to be written to control the independent operation of each part, wiring is simple, equipment cost is reduced, operation delay of each part is low, and therefore the cutting processing efficiency of the silicon wafer is improved, and silicon wafers with different thicknesses can be cut.

Description

A solar cell welding precision cutting device

Technical field

The invention relates to the technical field of solar cell processing, specifically a solar cell welding precision cutting device.

Background technique

A solar cell cutting device is a device used in the solar cell production process to cut silicon wafers into thin slices of appropriate sizes for use in manufacturing solar cell sheets. In solar cell production, silicon wafers are typically cut using cutting machines.

At present, the steps for cutting and processing silicon wafers are: 1. Loading, placing the silicon block on the processing table; 2. Pushing, pushing the silicon block to the cutting position, and the advancing distance is the cutting thickness; 3. Cutting, The front end of the silicon block is cut and formed into silicon wafers; 4. Unloading, remove the cut silicon wafers from the workbench; however, the existing cutting device requires a single driving source (i.e. motor, etc.) to control each step. Therefore, it is necessary to add a controller and write a program to control the individual operation of each part, and the wiring problem also needs to be considered, which will lead to an increase in equipment cost, and there is a delay in the individual control of each step, which will also lead to the cutting and processing of silicon wafers. Efficiency is reduced.

Contents of the invention

In view of the shortcomings of the existing technology, the present invention provides a solar cell welding precision cutting device, which can realize the automation of silicon wafer cutting, simplify the driving source, simple wiring, reduce equipment costs, improve the cutting and processing efficiency of silicon wafers, and can The advantage of cutting silicon wafers of different thicknesses solves the problems raised in the above background art.

In order to solve the above technical problems, the present invention provides the following technical solution: a solar cell welding precision cutting device, including a workbench, a mounting frame is fixed on the workbench, and a motor is installed on the top of the mounting frame. A sector gear is fixedly connected to the output shaft. The sector gear is intermittently engaged with the slicing mechanism, the unloading mechanism and the pushing mechanism installed on the workbench. The slicing mechanism is between the unloading mechanism and the pushing mechanism.

Preferably, the circumference of the outer edge of the toothed sector gear is between one-sixth and one-third of the entire circumference.

Preferably, the slicing mechanism includes a column gear that meshes with a sector gear. The column gear is fixed at one end of the connecting shaft. The other end of the connecting shaft is fixed with a pulley. The pulley is connected to the pulley through the belt. Two-phase meshing, pulley two is fixed at one end of connecting shaft two, bevel gear one is fixed at the other end of connecting shaft two, bevel gear one meshes with bevel gear two, bevel gear two is fixed on the reciprocating screw At the top, the reciprocating screw is rotatably connected in the guide rail. The guide rail is fixed on the top of the two installation rods. Both installation rods are fixed on the workbench. The screw transmission connection on the reciprocating screw is provided with an inner slide slidingly arranged in the guide rail. block, a cutting frame is fixed on the side wall of the inner slide block, the bottom of the cutting frame is rotatably connected with two cutting wheels, and a diamond wire is wound between the two cutting wheels. The bottom of the cutting frame is also equipped with a cutting The wheel is connected to the motor two.

Preferably, a notch is provided on the surface of the workbench directly below the second motor.

Preferably, the unloading mechanism includes a second column gear meshed with a sector gear. The second column gear is rotatably connected to the side wall of the mounting frame. An eccentric wheel is fixed on the side wall of the second column gear, and the eccentric wheel is connected to the upper side. One end of the rod is hinged, and the other end of the upper connecting rod is hinged with the hinge block. The hinge block is fixed on the side wall of the adsorption rack. Two vacuum suction cups are installed at both ends of the adsorption rack. The limit rod is also fixedly connected. The limit rod is set in the sliding sleeve. A rotating pin is fixed on the side wall of the sliding sleeve. The rotating pin is rotationally connected to one end of the fixed frame. The fixed frame is fixed to the side wall of the workbench. , a lower link is rotatably connected between the upper link and the hinge block, the bottom of the lower link is rotatably connected to one end of the hinge plate, and the hinge plate is installed on the side wall of the workbench.

Preferably, the pushing mechanism includes a column gear three that meshes with a sector gear. The column gear three is fixed at one end of the connecting shaft three. The other end of the connecting shaft three is fixed with a pulley three. The pulley three is connected to the pulley three through the belt two. The four pulleys are connected in transmission. The four pulleys are fixedly connected to one end of the connecting shaft four. The other end of the connecting shaft four is fixedly connected with a gear change piece. The gear change piece is intermittently meshed with the tooth plate. One end of the bottom of the tooth plate is fixedly connected with a push plate. The bottom of the tooth plate is set on the guide seat, and the guide seat is fixed on the workbench.

Preferably, the tooth changing component includes a rotating drum fixed at four ends of the connecting shaft. A plurality of tooth slots are provided on the outer wall of the rotating drum, and tooth blocks are detachably installed in the tooth slots through bolts.

Preferably, a conveyor belt is provided on one side of the workbench directly below the unloading mechanism.

Through the above technical solutions, the present invention provides a solar cell welding precision cutting device, which at least has the following beneficial effects:

1. This solar cell welding precision cutting device is equipped with a sector gear, a slicing mechanism, a blanking mechanism and a pushing mechanism. When the sector gear meshes with the pushing mechanism, the silicon block can be pushed a certain distance, and the advancing distance is the cutting distance. Thickness, when the sector gear meshes with the slicing mechanism, the front end of the silicon block can be cut. When the sector gear meshes with the unloading mechanism, the cut silicon wafers can be placed on the conveyor belt. One rotation cycle of the sector gear can achieve The three-step interval operation can realize the automation of silicon wafer cutting, simplifying the driving source. There is no need to add a controller and write a program to control the separate operation of each part. The wiring is simple, the equipment cost is reduced, and the operation delay of each part is relatively short. Low, thus improving the cutting and processing efficiency of silicon wafers.

2. This solar cell welding precision cutting device can control the moving distance of the silicon block by setting the tooth changing part and changing the number of tooth blocks on the changing tooth part, so that the thickness of each cutting can be constantly adjusted, and different shapes can be cut. thickness of the silicon wafer.

Description of drawings

The accompanying drawings described herein are included to provide a further understanding of the invention, and constitute a part of this application:

Figure 1 is a schematic diagram of the overall three-dimensional structure of the present invention;

Figure 2 is a schematic structural diagram of the rear side of the present invention;

Figure 3 is a schematic structural diagram of the slicing mechanism of the present invention;

Figure 4 is a schematic structural diagram of the unloading mechanism of the present invention;

Figure 5 is a schematic structural diagram of the pushing mechanism of the present invention;

Figure 6 is a schematic structural diagram of the gear changing component of the present invention;

Figure 7 is a schematic structural diagram of the workbench of the present invention;

Figure 8 is a schematic structural diagram of the sector gear of the present invention rotating to three positions to form three working states.

Reference signs:

1. Workbench; 2. Mounting frame; 3. Motor one; 4. Sector gear; 5. Slicing mechanism; 51. Column gear one; 52. Connecting shaft one; 53. Pulley one; 54. Pulley two; 55. Connection Shaft two; 56, bevel gear one; 57, bevel gear two; 58, reciprocating screw; 59, guide rail; 510, mounting rod; 511, inner slider; 512, cutting frame; 513, cutting wheel; 514, diamond wire ; 515. Motor two; 6. Unloading mechanism; 61. Column gear two; 62. Eccentric wheel; 63. Upper connecting rod; 64. Hinge block; 65. Lower link; 66. Hinge plate; 67. Adsorption rack; 68. Vacuum suction cup; 69. Limiting rod; 610. Sliding sleeve; 611. Rotating pin; 612. Fixed frame; 7. Pushing mechanism; 71. Column gear three; 72. Connecting shaft three; 73. Pulley three; 74 , Four pulleys; 75, Four connecting shafts; 76, Gear changing parts; 761, Rotary drum; 762, Teeth block; 763, Bolts; 77, Tooth plate; 78, Push plate; 79, Guide seat; 8, Bearing frame ; 9. Conveyor belt.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

A solar cell welding precision cutting device provided by some embodiments of the present invention will be described below with reference to the accompanying drawings.

Example 1:

As shown in Figures 1-8, the invention provides a solar cell welding precision cutting device, which includes a workbench 1. A mounting frame 2 is fixed on the workbench 1, and a motor 3 is mounted on the top of the mounting frame 2. The setting of the motor 13 provides power for the operation of the overall structure. The output shaft of the motor 3 is fixed with a sector gear 4. One rotation cycle of the sector gear 4 can realize the interval operation of three steps, which can realize the automation and simplicity of silicon wafer cutting. Without the driving source, there is no need to add a controller or write a program to control the separate operation of each part, and the wiring is simple, reducing equipment costs. The sector gear 4 is respectively connected with the slicing mechanism 5, the unloading mechanism 6 and the slicing mechanism 5 installed on the workbench 1. The pushing mechanism 7 is intermittently meshed, and the slicing mechanism 5 is between the unloading mechanism 6 and the pushing mechanism 7. When the sector gear 4 meshes with the pushing mechanism 7, the silicon block can be pushed a certain distance, and the distance pushed is the cutting thickness. , when the sector gear 4 meshes with the slicing mechanism 5, the front end of the silicon block can be cut. When the sector gear 4 meshes with the unloading mechanism 6, the cut silicon wafer can be placed on the conveyor belt 9.

Specifically, the circumference of the toothed outer edge of the sector gear 4 is between one-sixth and one-third of the circumference of the entire circle; ensure that the sector gear 4 is only connected with the slicing mechanism 5, the unloading mechanism 6 and the pushing mechanism One of the mechanisms in 7 is meshed to avoid serial movement between the two mechanisms.

Furthermore, a conveyor belt 9 is provided on one side of the workbench 1 directly below the unloading mechanism 6 for receiving the removed silicon wafers.

According to the embodiment, after placing the silicon block on the workbench 1, start the motor 3 and drive the sector gear 4 to rotate. When the sector gear 4 meshes with the pushing mechanism 7, the silicon block can be pushed for a certain distance. The distance is the cutting thickness. When the sector gear 4 meshes with the slicing mechanism 5, the front end of the silicon block can be cut. When the sector gear 4 meshes with the unloading mechanism 6, the cut silicon wafer can be put into the conveyor belt 9 superior.

Example 2:

As shown in Figure 1, Figure 2, Figure 3 and Figure 7, based on the first embodiment, the slicing mechanism 5 includes a column gear 51 meshed with the sector gear 4, and the column gear 51 is fixedly connected to the connecting shaft. At one end of the connecting shaft 52, a pulley 53 is fixedly connected to the other end of the connecting shaft 52. The pulley 53 meshes with the pulley 2 54 through the belt 1. The pulley 54 is fixed at one end of the connecting shaft 55. The connecting shaft 2 The other end of 55 is fixed with a bevel gear 56. The bevel gear 56 is meshed with the bevel gear 2 57. The bevel gear 57 is fixed on the top of the reciprocating screw 58. The reciprocating screw 58 is rotatably connected in the guide rail 59. The guide rail 59 is fixed on the top of the two installation rods 510, and the two installation rods 510 are both fixed on the workbench 1. The reciprocating screw 58 is spirally connected with an inner slider 511 that is slidably arranged in the guide rail 59. A cutting frame 512 is fixed on the side wall of the block 511. Two cutting wheels 513 are rotatably connected to the bottom of the cutting frame 512. A diamond wire 514 is wound between the two cutting wheels 513. The bottom of the cutting frame 512 is also equipped with a One of the cutting wheels 513 is connected to the second motor 515 .

Specifically, a gap is provided on the surface of the workbench 1 directly below the second motor 515 to avoid collision between the second motor 515 and the workbench 1 when the slicing mechanism 5 moves up and down.

According to the embodiment, when the sector gear 4 meshes with the slicing mechanism 5, the sector gear 4 drives the connecting shaft 52 to rotate through the meshing effect of the column gear 51, and the connecting shaft 52 drives the connecting shaft 52 through the transmission effect of the pulley 53 and the pulley 2 54. The second connecting shaft 55 rotates. The second connecting shaft 55 drives the reciprocating screw 58 to rotate through the meshing effect of the column gear 1 51 and the column gear 2 61. The reciprocating screw 58 drives the cutting frame 512 to move through the spiral transmission with the inner slide block 511. Then the second motor 515 can drive the cutting wheel 513 to rotate. The cutting wheel 513 drives the diamond wire 514 to move. The diamond wire 514 is used to cut the front end of the silicon block. As the cutting frame 512 moves up and down, the cutting operation can be repeated.

Embodiment three:

As shown in FIG. 1 , FIG. 2 and FIG. 4 , based on the first embodiment, the unloading mechanism 6 includes a second column gear 61 meshed with the sector gear 4 . The second column gear 61 is rotatably connected to the mounting frame 2 . On the side wall, an eccentric wheel 62 is fixed on the side wall of the second column gear 61. The eccentric wheel 62 is hinged with one end of the upper connecting rod 63, and the other end of the upper connecting rod 63 is hinged with the hinge block 64. The hinge block 64 is fixed. It is connected to the side wall of the adsorption frame 67. Two vacuum suction cups 68 are installed at both ends of the adsorption frame 67. The limit rod 69 is also fixed on the side wall of the adsorption frame 67. The limit rod 69 is set in the sliding sleeve. In 610, a rotating pin 611 is fixed on the side wall of the sliding sleeve 610. The rotating pin 611 is rotationally connected to one end of the fixed frame 612. The fixed frame 612 is fixed on the side wall of the workbench 1. The upper connecting rod 63 and the hinge block A lower link 65 is rotatably connected between 64, and the bottom of the lower link 65 is rotatably connected to one end of the hinge plate 66. The hinge plate 66 is installed on the side wall of the workbench 1.

According to the embodiment, when the sector gear 4 meshes with the unloading mechanism 6, the sector gear 4 drives the eccentric 62 to rotate through the meshing effect with the column gear 2 61. The eccentric 62 passes through the upper connecting rod 63, the lower connecting rod 65 and the limiter. The action of the position rod 69 drives the adsorption frame 67 to rotate 90°. At this time, the vacuum suction cup 68 sucks the cut silicon wafer and places it on the conveyor belt 9. Then, after the eccentric wheel 62 rotates exactly one circle, the adsorption frame 67 Drive the vacuum suction cup 68 to reset, and then repeat the work.

Embodiment 4:

As shown in Figure 1, Figure 2, Figure 5 and Figure 6, on the basis of the first embodiment, the pushing mechanism 7 includes a column gear 71 meshing with the sector gear 4, and the column gear 71 is fixedly connected to the connecting rod. At one end of shaft three 72, the other end of connecting shaft three 72 is fixedly connected with pulley three 73. Pulley three 73 is drivingly connected to pulley four 74 through belt two. Pulley four 74 is fixed at one end of connecting shaft four 75, and the connecting shaft The other end of the tooth plate 75 is fixedly connected with a tooth change member 76, which is intermittently meshed with the tooth plate 77. One end of the bottom of the tooth plate 77 is fixedly connected with a push plate 78, and the bottom of the tooth plate 77 is sleeved on the guide seat 79. The guide seat 79 is fixed on the workbench 1 .

Specifically, the tooth changing member 76 includes a rotating drum 761 fixed at one end of the connecting shaft 475. A plurality of tooth slots are provided on the outer wall of the rotating drum 761, and the tooth slots are detachably installed with bolts 763. Teeth blocks 762; changing the number of tooth blocks 762 on the tooth change member 76 can control the moving distance of the silicon block, so that the thickness of each cutting can be constantly adjusted, and silicon wafers of different thicknesses can be cut.

According to the embodiment, when the sector gear 4 meshes with the pushing mechanism 7, the sector gear 4 drives the connecting shaft three 72 to rotate through the meshing effect with the column gear three 71, and the connecting shaft three 72 is driven by the pulley three 73 and the pulley four 74. The connecting shaft 75 drives the connecting shaft 475 to rotate, and the connecting shaft 75 drives the tooth plate 77 to move through the gear change member 76. The bottom of the tooth plate 77 pushes the silicon block to move, which can push the silicon block a certain distance, and the advancing distance is the cutting thickness, and By changing the number of tooth blocks 762 on the tooth changing member 76, the moving distance of the silicon block can be controlled, so that the thickness of each cutting can be constantly adjusted, and silicon wafers of different thicknesses can be cut.

It can be seen from the above embodiments that the use process of this device is as follows: after placing the silicon block on the workbench 1, start the motor 3 to work and drive the sector gear 4 to rotate. When the sector gear 4 meshes with the pushing mechanism 7, the sector gear 4. The connecting shaft three 72 is driven to rotate by meshing with the column gear three 71. The connecting shaft three 72 drives the connecting shaft four 75 to rotate through the transmission of the pulley three 73 and the pulley four 74. The connecting shaft four 75 drives the gears through the gear changing member 76. The plate 77 moves, and the bottom of the tooth plate 77 pushes the silicon block to move, which can push the silicon block a certain distance. The distance pushed is the cutting thickness, and the movement of the silicon block can be controlled by changing the number of tooth blocks 762 on the tooth changing member 76 distance, so that the thickness of each cutting can be constantly adjusted, and silicon wafers of different thicknesses can be cut. After a single push is completed, the sector gear 4 continues to rotate. When the sector gear 4 meshes with the slicing mechanism 5, the sector gear 4 The connecting shaft one 52 is driven to rotate by the meshing effect of the column gear one 51. The connecting shaft one 52 drives the connecting shaft two 55 to rotate through the transmission of the pulley one 53 and the pulley two 54. The connecting shaft two 55 is driven by the column gear one 51 and the column gear two. The meshing effect of 61 drives the reciprocating screw 58 to rotate. The reciprocating screw 58 drives the cutting frame 512 to move through the spiral transmission with the inner slider 511. Then the second motor 515 works to drive the cutting wheel 513 to rotate, and the cutting wheel 513 drives the diamond wire 514. movement, using the diamond wire 514 to cut the front end of the silicon block. After the single cutting is completed, the sector gear 4 continues to rotate. When the sector gear 4 meshes with the unloading mechanism 6, the sector gear 4 meshes with the column gear 2 61 The eccentric wheel 62 is driven to rotate, and the eccentric wheel 62 drives the adsorption frame 67 to rotate 90° through the action of the upper link 63, the lower link 65 and the limit rod 69. At this time, the vacuum suction cup 68 will suck the cut silicon wafer and Just place it on the conveyor belt 9. Then, after the eccentric wheel 62 rotates exactly once, the adsorption frame 67 drives the vacuum suction cup 68 to reset. At this time, the sector gear 4 rotates exactly once, and then the sector gear 4 continues to repeat the above steps to carry out the silicon block. Just keep cutting.

It should be noted that the terms "comprises," "comprises" or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements not only includes those elements, but also includes none. Other elements expressly listed, or elements inherent to such process, method, article or equipment.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will understand that various changes, modifications, and substitutions can be made to these embodiments without departing from the principles and spirit of the invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (8)

1. The utility model provides a solar cell welding precision cutting device, includes workstation (1), its characterized in that: the device is characterized in that the workbench (1) is fixedly provided with the mounting frame (2), the top of the mounting frame (2) is provided with the motor I (3), the output shaft of the motor I (3) is fixedly connected with the sector gear (4), the sector gear (4) is respectively meshed with the slicing mechanism (5), the blanking mechanism (6) and the pushing mechanism (7) which are arranged on the workbench (1), and the slicing mechanism (5) is positioned between the blanking mechanism (6) and the pushing mechanism (7).

2. The solar cell welding precision cutting device according to claim 1, wherein: the toothed outer edge circumference of the sector gear (4) is between one sixth and one third of the full circumference.

3. The solar cell welding precision cutting device according to claim 1, wherein: the slicing mechanism (5) comprises a first cylindrical gear (51) meshed with the sector gear (4), the first cylindrical gear (51) is fixedly connected at one end of a first connecting shaft (52), the other end of the first connecting shaft (52) is fixedly connected with a first belt pulley (53), the first belt pulley (53) is meshed with a second belt pulley (54) through the first belt pulley, the second belt pulley (54) is fixedly connected at one end of a second connecting shaft (55), a first bevel gear (56) is fixedly connected at the other end of the second connecting shaft (55), the first bevel gear (56) is meshed with a second bevel gear (57), the second bevel gear (57) is fixedly connected at the top of a reciprocating screw (58), the reciprocating screw (58) is rotationally connected in the guide rail (59), the guide rail (59) is fixedly connected at the top of two mounting rods (510), the two mounting rods (510) are fixedly connected on the workbench (1), a cutting frame (512) is fixedly connected on the side wall of the second inner sliding block (511) which is slidingly arranged in the guide rail (59), the bottom of the second bevel gear (512) is rotationally connected with a second bevel gear (513), two diamond wires (514) are arranged between the two diamond wires (513), the bottom of the cutting frame (512) is also provided with a motor II (515) connected with one of the cutting wheels (513).

4. The solar cell welding precision cutting device according to claim 3, wherein: a gap is formed in the position, right below the motor II (515), of the surface of the workbench (1).

5. The solar cell welding precision cutting device according to claim 1, wherein: the blanking mechanism (6) comprises a column gear II (61) meshed with the sector gear (4), the column gear II (61) is rotationally connected to the side wall of the mounting frame (2), an eccentric wheel (62) is fixedly connected to the side wall of the column gear II (61), the eccentric wheel (62) is hinged to one end of an upper connecting rod (63), the other end of the upper connecting rod (63) is hinged to a hinging block (64), the hinging block (64) is fixedly connected to the side wall of the adsorption frame (67), two vacuum suckers (68) are respectively installed at two ends of the adsorption frame (67), a limiting rod (69) is fixedly connected to the side wall of the adsorption frame (67), the limiting rod (69) is sleeved in the sliding sleeve (610), a rotating pin (611) is fixedly arranged on the side wall of the sliding sleeve (610), the rotating pin (611) is rotationally connected to one end of the fixing frame (612), the fixing frame (612) is fixedly connected to the side wall of the workbench (1), a lower connecting rod (65) is rotationally connected between the upper connecting rod (63) and the hinging block (64), one end of the lower connecting rod (65) is rotationally connected to the side wall of the adsorption frame (67), and the side wall of the hinge plate (66) is installed on the workbench (1).

6. The solar cell welding precision cutting device according to claim 1, wherein: the pushing mechanism (7) comprises a post gear III (71) meshed with the sector gear (4), the post gear III (71) is fixedly connected to one end of a connecting shaft III (72), the other end of the connecting shaft III (72) is fixedly connected with a belt pulley III (73), the belt pulley III (73) is in transmission connection with a belt pulley IV (74) through a belt II, the belt pulley IV (74) is fixedly connected to one end of the connecting shaft IV (75), the other end of the connecting shaft IV (75) is fixedly connected with a tooth changing piece (76), the tooth changing piece (76) is intermittently meshed with a toothed plate (77), one end of the bottom of the toothed plate (77) is fixedly connected with a push plate (78), the bottom of the toothed plate (77) is sleeved on a guide seat (79), and the guide seat (79) is fixedly connected to the workbench (1).

7. The solar cell welding precision cutting device according to claim 6, wherein: the tooth changing piece (76) comprises a rotary drum (761) fixedly connected to one end of a connecting shaft IV (75), a plurality of tooth grooves are formed in the outer wall of the rotary drum (761), and tooth blocks (762) are detachably arranged in the tooth grooves through bolts (763).

8. The solar cell welding precision cutting device according to claim 1, wherein: one side of the workbench (1) is provided with a conveyor belt (9) which is positioned under the blanking mechanism (6).