Bistable attaching foot with mechanical lock

Abstract

The invention relates to a bistable attachment foot with a mechanical lock, which belongs to the technical field of robot actuating mechanisms, and comprises a shell and a connecting cover capable of covering the end part of the shell and forming a cavity with the shell, the central sliding block and a tubular column formed on the target surface side of the shell slide in a reciprocating mode, a plurality of cranks which penetrate through the sleeve and can swing in the sliding direction of the central sliding block relative to the sleeve are hinged to the central sliding block in the circumferential direction in an array mode, and the tail ends of the cranks are fixedly connected with adhesive materials. The locking mechanism is fixedly connected in a cavity at the top end of the shell; the center sliding block is provided with a locking groove. In the locking state, the center sliding block moves in the direction of the connecting cover and synchronously drives the crank to swing in the direction away from the connecting cover, and therefore the adhesive material is attached to a target object, and the locking mechanism can be locked with the locking groove. The stability and strength of the attachment action of the attachment foot are effectively improved, and the attachment firmness and reliability of the attachment foot are improved.

Description

Technical Field

[0001] The invention relates to the technical field of robot actuators, and in particular to a bistable adhesion foot with a mechanical lock for realizing adhesion and grasping actions of a robot end actuator. Background Art

[0002] The rapid development of robotics technology has put forward more requirements for the design of the end-effector of the manipulator. The traditional bistable attachment foot can help the manipulator to attach and automatically detach. With the help of the adhesion of the adhesion material at the end of the attachment foot, a more solid attachment action can be achieved. In order to further improve the adhesion stability of the attachment foot and enhance the firmness of the attachment action, the adhesion action of the attachment foot is fixed by adding a limit lock to the attachment foot mechanism. Based on the study of the mechanical properties of the adhesion material, it is found that for sticky materials, the normal adhesion ability is usually much greater than the tangential adhesion ability. Therefore, by integrating the tangential motion into the detachment action and changing the way the end of the attachment foot is lifted, the detachment process of the adhesion material of the attachment foot can be achieved with less effort. Summary of the invention

[0003] In order to solve the technical problems existing in the above-mentioned prior art, the object of the present invention is to provide a bistable attachment foot with a mechanical lock which can improve the attachment firmness and reliability of the attachment foot.

[0004] To achieve the above-mentioned purpose, the present invention provides a bistable attachment foot with a mechanical lock, comprising: a housing;

[0005] A connecting cover capable of covering the end of the housing and forming a chamber with the housing; and

[0006] A central slider that performs reciprocating sliding motion with the shell forming a pipe column on the target surface side, wherein the central slider is hingedly connected in a circumferential array with a plurality of cranks that penetrate the casing and can swing relative to the casing along the sliding direction of the central slider, and the ends of the cranks are fixedly connected with adhesive material; and further comprising:

[0007] A locking mechanism fixedly connected to the chamber at the top end of the housing;

[0008] Wherein, the central slider is provided with a locking groove;

[0009] In the locked state, the central slider moves toward the connection cover and simultaneously drives the crank to swing away from the connection cover, so that the adhesive material adheres to the target object so that the locking mechanism can be locked with the locking groove.

[0010] Further, the locking mechanism includes a locking motor and a locking tongue;

[0011] The motor shaft of the locking motor is inserted with the locking tongue with an L-shaped structure. The motor shaft of the locking motor can drive the locking tongue to make a reciprocating rotation from -90° to 90°, so as to achieve the purpose of locking or disengaging the locking tongue from the lock slot.

[0012] Furthermore, the center slider makes a linear sliding motion along the sleeve to drive the crank to swing. When the center slider moves to the top of the sleeve, the locking groove of the center slider is placed inside the chamber to receive the locking tongue. When the attachment foot is attached to the target surface, the locking tongue is driven by the locking motor to lock with the locking groove, thereby locking the crank of the attachment foot, thereby increasing the stability and strength of the attachment action of the attachment foot.

[0013] Furthermore, a platform is formed at the top of the sleeve of the outer shell, a main shaft is threadedly connected to the central mounting hole in the middle of the platform, a central slider in a circular tube structure is mounted on the outside of the main shaft, a connecting piece is fixedly connected to the lower part of the locking motor, and the connecting piece is connected to the platform by bolts.

[0014] Furthermore, the sleeve of the housing and the cylindrical surface of the central slider are provided with rectangular mounting holes for the crank to pass through;

[0015] A first mounting hole is provided at the root of the crank, and a sliding groove is provided near the root end of the crank;

[0016] The first mounting hole is coaxial with the second through hole opened on the side wall of the rectangular mounting hole of the central slider and is provided with a first bolt, and the first bolt is rotatably connected to the crank;

[0017] A first through hole is formed on a side wall of the rectangular mounting hole of the housing, a second bolt is mounted on the first through hole, and the second bolt passes through the slide groove of the crank.

[0018] Furthermore, it also includes a return spring, one end of which is connected to the central slider and the other end is connected to the sleeve, and provides a pulling force to drive the central slider to return to its original position and drive the crank away from the target surface.

[0019] Furthermore, a spring screw is threadedly connected to the bottom of the sleeve of the shell through a threaded hole, a boss is formed in the middle of the central slider, the boss is provided with a spring mounting hole, one end of the return spring is connected to the spring screw, and the other end is connected to the spring mounting hole.

[0020] Furthermore, a second mounting hole is formed at the end of the crank, and a sloped mounting surface is formed on the cross section of the end of the crank;

[0021] A truncated cone-shaped mounting column is formed on the upper part of the adhesive material body, the truncated cone-shaped mounting column is connected to the second mounting hole, and a flange with a diameter larger than the diameter of the second mounting hole is formed at the end of the truncated cone-shaped mounting column, the flange is used to limit the axial movement of the adhesive material along the second mounting hole to prevent the adhesive material from falling off, and a wedge is formed on one side of the adhesive material body located on the truncated cone-shaped mounting column, and the wedge is fitted with the sloped mounting surface through an inclined surface.

[0022] Furthermore, the crank is constructed as a rod-shaped structure, comprising a straight rod formed at the head end of the crank and a curved rod connected to the straight rod, wherein the curved rod is an arc, a B-spline curve or a parabola, wherein, in a working state, the curved outer side surface of the curved rod faces the target attachment surface, for simulating the upwardly curled toes of the gecko's foot, thereby providing sufficient adhesion while ensuring efficient desorption capability.

[0023] Furthermore, a cylindrical tube extending downward is formed at the edge of the connection cover, and a third through hole is opened on the connection cover;

[0024] A step groove is formed at the edge of the platform at the top of the shell, the lower end surface of the cylindrical tube is fitted with the shoulder surface of the step groove, and the inner wall of the cylindrical tube is fitted with the side wall of the step groove, wherein the platform is provided with a mounting hole coaxial with the third through hole, and is connected to the robotic arm by bolts penetrating the mounting hole and the third through hole.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The bistable attachment foot with a mechanical lock designed in the present invention has a connecting cover that covers the end of the outer shell and forms a chamber with the outer shell, and the central slider performs reciprocating sliding motion in the outer shell column. The central slider is circumferentially hinged with multiple cranks, which penetrate the sleeve and can swing relative to the sleeve along the sliding direction of the central slider. The locking mechanism is fixedly connected to the top chamber of the outer shell. In the locked state, the central slider is displaced toward the connecting cover and synchronously drives the crank to swing away from the connecting cover, so that the adhesive material is attached to the target object. At this time, the locking mechanism can be locked with the locking groove. After the attachment foot crank is attached to the target object, it is locked with the locking groove through the locking mechanism, which effectively increases the stability and strength of the attachment action of the attachment foot, thereby improving the attachment firmness and reliability of the attachment foot. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 It is a schematic diagram of the unfolded state of the bistable attachment foot with a mechanical lock disclosed in the present invention before attachment;

[0029] Figure 2 It is a schematic diagram of the state of the front lock tongue attached to the bistable attachment foot with a mechanical lock disclosed in the present invention;

[0030] Figure 3 It is a schematic diagram of the internal cross-section of the bistable attachment foot with a mechanical lock disclosed in the present invention;

[0031] Figure 4 It is a bottom view of the bistable attachment foot with a mechanical lock disclosed in the present invention;

[0032] Figure 5 It is a schematic diagram of the structure of the bistable attachment foot housing with a mechanical lock disclosed in the present invention;

[0033] Figure 6 It is a schematic diagram of the structure of the bistable attachment foot crank with mechanical lock disclosed in the present invention;

[0034] Figure 7 It is a schematic diagram of the structure of the bistable attachment foot center slider with a mechanical lock disclosed in the present invention;

[0035] Figure 8 It is a schematic diagram of the structure of the bistable adhesion foot adhesion material with mechanical lock disclosed in the present invention;

[0036] Fig. 9 It is a schematic diagram of the state of the lock tongue in the adhesion state of the bistable attachment foot with a mechanical lock disclosed by the present invention.

[0037] Description of reference numerals:

[0038] 1. Shell; 2. Connecting cover; 3. Locking motor; 4. Lock tongue; 5. Center slider; 6. Spindle; 7. Crank; 8. Adhesive material; 9. Reset spring; 10. Spring screw; 12. Connector;

[0039] 101, center mounting hole; 102, mounting hole; 103, motor mounting hole; 104, first through hole; 105, threaded hole; 106, first rectangular mounting hole;

[0040] 201, lower end surface of cylindrical tube; 202, third through hole;

[0041] 501, second through hole; 502, lock slot; 503, spring mounting hole; 504, second rectangular mounting hole;

[0042] 701, first mounting hole; 702, slide groove; 703, second mounting hole; 704, slope mounting surface; 705, curved outer side surface;

[0043] 801. Truncated cone-shaped mounting column. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the implementation of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention.

[0045] Figure 1 It is a schematic diagram of the unfolded state of the bistable attachment foot with mechanical lock before attachment;

[0046] The present invention discloses a bistable attachment foot with a mechanical lock, comprising:

[0047] A shell 1, a connecting cover 2, the connecting cover 2 can cover the end of the shell 1 and form a chamber with the shell 1, a central slider 5 is installed inside the shell 1, and can make reciprocating sliding motion with the shell 1 to form a pipe column on the target surface side, the central slider 5 is hinged with a plurality of cranks 7 in a circumferential array, the crank 7 can penetrate the casing and can swing relative to the casing along the sliding direction of the central slider 5, and an adhesive material 8 is fixed to the end of the crank 7;

[0048] The attachment foot also includes a locking mechanism, which is fixedly connected to the top chamber of the shell 1. The central slider 5 is provided with a locking groove 502. In the locked state, the central slider 5 moves toward the connecting cover 2 and synchronously drives the crank 7 to swing away from the connecting cover 2, so that the adhesive material 8 is attached to the target object. At this time, the locking mechanism can be locked with the locking groove 502.

[0049] Figure 2 Schematic diagram of the state of the lock tongue before the bistable attachment foot with mechanical lock is attached;

[0050] The locking mechanism includes a locking motor 3 and a locking tongue 4. The motor shaft of the locking motor 3 is inserted with the locking tongue 4 having an L-shaped structure. The motor shaft of the locking motor 3 can drive the locking tongue 4 to make a reciprocating rotation from -90° to 90°, thereby achieving the purpose of locking or disengaging the locking tongue and the lock groove. The center slider 5 drives the crank 7 to swing by making a linear sliding motion along the sleeve. When the center slider 5 moves to the top of the sleeve, the lock groove 502 of the center slider 5 is placed inside the chamber to receive the locking tongue 4.

[0051] When the central slider 5 of the bistable adhesion foot with a mechanical lock reciprocates along the main shaft 6 in the casing of the housing 1, the crank 7 is driven to rotate, and the crank 7 is used to press and assist the adhesion material 8. When the adhesion foot is attached to the target surface, the adhesion foot controls the action of the locking motor 3 of the locking mechanism to lock and unlock the adhesion foot crank 7, thereby increasing the stability and strength of the adhesion action of the adhesion foot.

[0052] Figure 3 It is a schematic diagram of the internal cross section of the bistable attachment foot with a mechanical lock;

[0053] Figure 4 It is a bottom view of the bistable attachment foot with a mechanical lock;

[0054] Figure 5 It is a schematic diagram of the structure of the bistable attachment foot housing with a mechanical lock;

[0055] The shell 1 is the main body of the attachment foot structure. A platform is formed at the top of the sleeve of the shell 1. A through hole is opened on the platform corresponding to the position of the lock slot 502. The protrusion of the center slider 5 with the lock slot 502 passes through the through hole. The center mounting hole 101 in the middle of the platform is threadedly connected to the main shaft 6. The center slider 5 with a circular tube structure is mounted on the outside of the main shaft 6. The center slider 5 can slide axially along the main shaft 6. A connecting part 12 is fixedly connected to the lower part of the locking motor 3. Both ends of the connecting part 12 are connected to the motor mounting holes 103 opened on the platform by bolts. A lock tongue 4 is coaxially inserted on the outside of the motor shaft of the locking motor 3. The connecting cover 2 is connected to the manipulator and the attachment foot shell 1 by bolts to provide an installation space for the locking motor 3.

[0056] Figure 7 It is a schematic diagram of the structure of a bistable attachment foot center slider with a mechanical lock;

[0057] See also Figure 5 , 7 As shown, the sleeve of the outer shell 1 is provided with a first rectangular mounting hole 106, and the cylindrical surface of the center slider 5 is provided with a second rectangular mounting hole 504 corresponding to the first rectangular mounting hole 106. The rectangular mounting holes are used for the crank 7 to pass through and install it on the attachment foot outer shell 1 and the center slider 5. Specifically, the crank 7 is distributed in an array along the circumference of the outer shell 1, and the number of arrays can be designed as needed, with a corresponding number of first rectangular mounting holes 106 and spring threaded holes 105 of the outer shell 1, and second rectangular mounting holes 504 and spring mounting holes 503 of the center slider 5.

[0058] The crank 7 has a first mounting hole 701 at its root, and a slide groove 702 is provided at a position 3.11 mm away from the first mounting hole near the root end of the crank 7. The first mounting hole 701 is coaxial with a second through hole 501 provided on the side wall of the rectangular mounting hole of the center slider 5 and is provided with a first bolt. After assembly, the first bolt is rotatably connected to the crank 7, so that the crank 7 can rotate around the second through hole 501 on the side wall of the second rectangular mounting hole of the center slider 5 while sliding along the main shaft 6 with the center slider 5.

[0059] A first through hole 104 is formed on the side wall of the first rectangular mounting hole on the housing 1 . A second bolt is installed in the first through hole 104 . The second bolt passes through the slide groove 702 of the crank 7 to form a slider mechanism for limiting the position of the crank 7 when it rotates with the central slider 5 .

[0060] See also Figure 4 , 7As shown, the attachment foot also includes a return spring 9, one end of which is connected to the central slider 5 and the other end is connected to the sleeve, and provides a pulling force to drive the central slider 5 to return and drive the crank 7 away from the target surface.

[0061] The bottom of the sleeve of the housing 1 is threadedly connected with a spring screw 10 through a threaded hole 105. A boss is formed in the middle of the center slider 5. The boss is provided with a spring mounting hole 503. One end of the return spring 9 is connected to the spring screw 10, and the other end is connected to the spring mounting hole 503. The return spring 9 contracts to provide a return force for the center slider 5.

[0062] Figure 6 It is a schematic diagram of the structure of a bistable attachment foot crank with a mechanical lock;

[0063] Figure 8 Schematic diagram of the structure of the bistable adhesion foot adhesion material with mechanical lock;

[0064] A second mounting hole 703 is provided at the end of the crank 7, and a sloped mounting surface 704 is formed on the cross section of the end of the crank 7. A truncated cone-shaped mounting column 801 is formed on the upper part of the adhesive material 8 body, and the truncated cone-shaped mounting column 801 is connected to the second mounting hole 703, and a flange with a diameter larger than the diameter of the second mounting hole 703 is formed at the end of the truncated cone-shaped mounting column 801. The flange limits the axial movement of the adhesive material along the second mounting hole 703 to prevent the adhesive material from falling off. A wedge is formed on the adhesive material 8 body on one side of the truncated cone-shaped mounting column 801, and the wedge is fitted with the sloped mounting surface 704 through an inclined surface.

[0065] The crank 7 is a rod-shaped structure, including a straight rod formed at the head end of the crank 7 and a curved rod connected to the straight rod, and the curved rod is a circular arc, a B-spline curve or a parabola, etc. When installed, the curved outer side 705 of the crank 7 faces the target attachment surface of the attachment foot, which is used to simulate the toes rolled up at the end of the gecko's foot, and ensures efficient desorption ability while providing sufficient adhesion.

[0066] See also Figure 2 As shown, the connecting cover 2 is in the shape of a sealing cylindrical tube, a cylindrical tube extending downward is formed at the edge of the connecting cover 2, a third through hole 202 is formed on the connecting cover 2, a step groove is formed at the edge of the platform at the top of the shell 1, the lower end face 201 of the cylindrical tube is fitted with the shoulder surface of the step groove, and the inner wall of the cylindrical tube is fitted with the side wall of the step groove, wherein the platform is provided with a mounting hole 102 coaxial with the third through hole 202, and is connected to the end of the robot arm by bolts penetrating the mounting hole 102 and the third through hole 202, while protecting the locking motor 3 and the lock tongue 4.

[0067] In the above technical solution, the present invention discloses a bistable attachment foot with a mechanical lock, the working principle of which is:

[0068] Fig. 9It is a schematic diagram of the state of the lock tongue in the adhesion state of the bistable attachment foot with a mechanical lock;

[0069] See also Fig. 9 As shown, when the attachment foot contacts the target surface, as the attachment foot moves downward, the lower end of the center slider 5 is pushed by the target surface to slide upward relative to the attachment foot housing 1, and overcomes the elastic force of the reset spring 9. Driven by the center slider 5, the attachment foot crank 7 rotates around the second through hole 501 on the side wall of the rectangular mounting hole of the center slider 5, and under the limitation of the first through hole 104 on the side wall of the rectangular mounting hole of the housing 1, one end of the crank 7 is close to the target surface, and the adhesive material 8 contacts the target surface, generating an adhesive force to prevent separation. After the crank 7 contacts the target surface, the locking motor 3 drives the lock tongue 4 to rotate to the lock groove 502 at the top of the center slider 5, completing the attachment state position locking;

[0070] See also Figure 1 As shown, when the desorption action is performed, the locking motor 3 first drives the lock tongue 4 to rotate out of the lock groove 502 at the top of the center slider 5, and under the elastic force of the reset spring 9, it moves in the direction away from the target surface in coordination with the movement of the adhesion foot lifting. The center slider 5 moves downward along the main axis 6, driving the crank 7 to rotate around the second through hole 501 on the side wall of the rectangular mounting hole of the center slider 5 and lift it upward, and the crank 7 drives the adhesive material 8 to debond, completing the desorption action.

[0071] The bistable attachment foot with a mechanical lock achieves locking and unlocking of the attachment foot crank 7 by controlling the action of the locking motor 3 of the locking mechanism, thereby increasing the stability and strength of the attachment action of the attachment foot, and improving the attachment firmness and reliability of the attachment foot.

[0072] The above description is only an illustrative embodiment of the present application and is not intended to limit the scope of the present application. Any equivalent changes, modifications and combinations made by any technician in the field without departing from the concept and principle of the present application shall fall within the scope of protection of the present application.

Claims

1. A bistable attachment foot with a mechanical lock, characterized in that: include: A housing (1), and a connecting cover (2) capable of covering an end of the housing (1) and forming a chamber with the housing (1); as well as A central slider (5) that performs reciprocating sliding motion with the casing (1) formed on the target surface side, the central slider (5) being hingedly connected in a circumferential array with a plurality of cranks (7) that penetrate the casing and can swing relative to the casing along the sliding direction of the central slider (5), and an adhesive material (8) is fixedly connected to the end of the crank (7); and further comprising: A locking mechanism fixedly connected to the chamber at the top end of the housing (1); Wherein, the central slider (5) is provided with a locking groove (502); In the locked state, the central slider (5) moves toward the connection cover (2) and simultaneously drives the crank (7) to swing away from the connection cover (2), so that the adhesive material (8) adheres to the target object so that the locking mechanism can lock with the locking groove (502).

2. A bistable attachment foot with a mechanical lock according to claim 1, It is characterized by: The locking mechanism comprises a locking motor (3) and a locking tongue (4); The motor shaft of the locking motor (3) is inserted with the locking tongue (4) having an L-shaped structure, and the motor shaft of the locking motor (3) can drive the locking tongue (4) to perform reciprocating rotation within a range of -90° to 90°.

3. A bistable attachment foot with a mechanical lock according to claim 2, characterized in that ； The central slider (5) moves linearly along the sleeve to drive the crank (7) to swing. When the central slider (5) moves to the top of the sleeve, the locking groove (502) of the central slider (5) is placed inside the chamber to receive the locking tongue (4).

4. A bistable attachment foot with a mechanical lock according to claim 1, characterized in that ； A platform is formed at the top end of the sleeve of the housing (1); a main shaft (6) is threadedly connected to a central mounting hole (101) in the middle of the platform; a central slider (5) in a round tube structure is sleeved on the outside of the main shaft (6); a connecting piece (12) is fixedly connected to the lower part of the locking motor (3); and the connecting piece (12) is connected to the platform by bolts.

5. A bistable attachment foot with a mechanical lock according to claim 1 or 4, characterized in that ； The sleeve of the housing (1) and the cylindrical surface of the central slider (5) are provided with rectangular mounting holes for the crank (7) to pass through; The crank (7) is provided with a first mounting hole (701) at the root thereof, and a sliding groove (702) is provided near the root end thereof; The first mounting hole (701) is coaxial with a second through hole (501) opened on the side wall of the rectangular mounting hole of the central slider (5) and is provided with a first bolt, wherein the first bolt is rotatably connected to the crank (7); A first through hole (104) is provided on the side wall of the rectangular mounting hole of the housing (1), a second bolt is installed in the first through hole (104), and the second bolt passes through the slide groove (702) of the crank (7).

6. A bistable attachment foot with a mechanical lock according to claim 1, characterized in that ； It also includes a return spring (9), one end of which is connected to the central slider (5) and the other end of which is connected to the sleeve, and provides a pulling force to drive the central slider (5) to return to its original position and drive the crank (7) away from the target surface.

7. A bistable attachment foot with a mechanical lock according to claim 6, characterized in that ； A spring screw (10) is threadedly connected to the bottom of the sleeve of the housing (1) through a threaded hole (105); a boss is formed in the middle of the central slider (5); a spring mounting hole (503) is formed on the boss; one end of the return spring (9) is connected to the spring screw (10) and the other end is connected to the spring mounting hole (503).

8. A bistable attachment foot with a mechanical lock according to claim 1, It is characterized by: A second mounting hole (703) is formed at the end of the crank (7), and a sloped mounting surface (704) is formed on the cross section of the end of the crank (7); A truncated cone-shaped mounting column (801) is formed on the upper part of the adhesive material (8) body, the truncated cone-shaped mounting column (801) is connected to the second mounting hole (703), and a flange having a diameter greater than the diameter of the second mounting hole (703) is formed at the end of the truncated cone-shaped mounting column (801), and a wedge is formed on one side of the adhesive material 8 body located on the truncated cone-shaped mounting column (801), and the wedge is fitted with the slope mounting surface (704) via an inclined surface.

9. A bistable attachment foot with a mechanical lock according to claim 1 or 8, characterized in that; The crank (7) is constructed as a rod-shaped structure, comprising a straight rod formed at the head end of the crank (7) and a curved rod connected to the straight rod, wherein the curved rod is a circular arc, a B-spline curve or a parabola; Wherein, in the working state, the curved outer side surface (705) of the crank (7) faces the target attachment surface.

10. A bistable attachment foot with a mechanical lock according to claim 1, characterized in that; A cylindrical tube extending downward is formed at the edge of the connection cover (2), and a third through hole (202) is formed on the connection cover (2); A step groove is formed at the edge of the platform at the top of the shell (1), the lower end surface (201) of the cylindrical tube is in contact with the shoulder surface of the step groove, and the inner wall of the cylindrical tube is in contact with the side wall of the step groove, wherein the platform is provided with a mounting hole coaxial with the third through hole (202), and is connected to the robot arm by means of bolts penetrating the mounting hole and the third through hole (202).

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