Multifunctional clamp

Abstract

A multifunctional clamp relates to a clamp, including a mounting seat, a clamping block, a screw rod, a screw rod nut, a push rod, and a guide rod. The mounting seat is provided with a center block at the inner center, and the mounting seat is provided with a guide groove for the rod at both ends, and the guide groove for the rod is slidably matched with the two ends of the push rod. The mounting seat is also connected to the two ends of the screw rod, and the two ends of the screw rod have different screw directions; the mounting seat is provided with a centrally symmetrical clamping block guide groove; the middle part of the push rod is fixedly connected with the screw nut; the push rod is respectively sleeved with a clamping block support on both sides of the screw nut, the middle part of the clamping block support is slidably matched with the clamping block guide groove, the upper part of the clamping block support is fixedly connected with the clamping block, and the clamping block support is also sleeved on the guide rod, one end of the guide rod is connected to the four corners of the mounting seat, and the other end is connected to the center block. The invention has the characteristics of reliable and reasonable structure, diversification of functions, high positioning and clamping precision, and high clamping efficiency, and is easy to promote and use.

Description

Technical Field

[0001] The invention relates to a clamp, in particular to a multifunctional clamp. Background Art

[0002] In the field of mechanical processing, a clamp is usually required to position and clamp the workpiece. The utility model patent with the authorization announcement number CN207223853U discloses a self-centering clamp for square specimens. The clamp can realize the self-centering clamp for square specimen workpieces, but has the following disadvantages: 1. It can only center square-shaped workpieces, and the function is single; 2. The structure is not reasonable enough. During the movement, when the connecting rod is parallel to the threaded rod, this position is the "dead point position". At this dead point position, the opening of the clamp cannot be controlled by the handle. The clamp must be removed and moved out of the dead point position before it can work again. 3. The positioning and clamping is achieved by rotating the hinge mechanism of the connecting mechanism, and then converted into the sliding of the adjusting block. In the process of converting the rotation into the sliding, its accuracy will become lower, and it is difficult to ensure the centering after a long working time. 3. Only single-axis centering can be achieved, and the centering accuracy is not high. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a multifunctional clamp to solve the shortcomings of the prior art, such as single function, unreasonable structure and low positioning and clamping accuracy.

[0004] The technical solution to solve the above technical problems is: a multifunctional clamp, including a mounting seat, a clamping block located on the upper surface of the mounting seat for clamping a workpiece, a screw and a screw nut located in the mounting seat, and also including two pushing light rods and four guide rods located in the mounting seat. The mounting seat is a square split structure with a cavity inside, and a center block is installed at the center of the interior of the mounting seat. The mounting seat is provided with light rod guide grooves on the front and rear end surfaces respectively, and the light rod guide grooves are slidably matched with the two ends of the two pushing light rods, and the two pushing light rods are respectively located on both sides of the center block; the left and right end surfaces of the mounting seat are respectively connected to the two ends of the screw, and the two ends of the screw have different thread rotation directions; the upper surface of the mounting seat is between its four corners and the center The connecting line positions are respectively provided with centrally symmetrical clamping block guide grooves; the middle part of the pushing light rod is fixedly connected to the screw nut, the screw nut is connected to the screw, and the screw is also connected to the power device; each pushing light rod is respectively sleeved with clamping block support members on both sides of the screw nut, the middle part of the clamping block support member is slidably matched with the clamping block guide groove on the mounting seat, the upper part of the clamping block support member passes through the upper surface of the mounting seat and is fixedly connected to the clamping block, and the clamping block support member is also sleeved on the guide rod, which is arranged along the bottom of the clamping block guide groove, and one end of the guide rod is connected to the four corners of the mounting seat, and the other end of the guide rod is connected to the center block; positioning plates of different shapes are respectively fixed to the surrounding surfaces of the clamping block.

[0005] A further technical solution of the present invention is: the mounting seat includes an upper end cover and a base; the upper end cover is a cover body with a square cross-section and a closed top surface, the center block is fixed at the center position of the bottom surface of the upper end cover by fasteners, and the center block coincides with the center position of the upper end cover; the upper surface of the upper end cover is respectively provided with the centrally symmetrical clamping block guide grooves at the connecting line positions between the four corners of the upper end cover and the center block; the front and rear end surfaces of the upper end cover are respectively provided with the light rod guide grooves; the base is a frame body with a square cross-section, and is connected to the upper end cover by fasteners to form a cubic shell; the four corners of the base are respectively movably connected to the guide rod by fixing pins and nuts.

[0006] A further technical solution of the present invention is that: the upper end cover is also equipped with a scale above the polished rod guide groove, which can read the size of the clamped workpiece from the position where the polished rod is pushed; and the base is also provided with a fixing groove for fixed connection with the processing workbench through a fastener.

[0007] A further technical solution of the present invention is: one end of the screw rod is a triangular left thread, and the other end is a triangular right thread, and the screw rod nut includes a screw rod left nut and a screw rod right nut, and the screw rod left nut and the screw rod right nut respectively cooperate with the left thread and the right thread of the screw rod.

[0008] A further technical solution of the present invention is: the guide rod is a long rectangular structure; the upper part of the clamping block support is a threaded column, the threaded column passes through the clamping block and is fastened to the clamping block nut above the clamping block; the middle part of the clamping block support is a guide body, which slides with the clamping block guide groove; the bottom of the clamping block support is respectively provided with a round hole and a square hole, the round hole is clearance-matched with the pushing rod, and the square hole is clearance-matched with the guide rod.

[0009] A further technical solution of the present invention is: a guide keyway is opened in the middle of the clamp block, and a guide key is installed between the threaded column and the guide body of the clamp block support, and the guide keyway of the clamp block is matched and connected with the guide key on the clamp block support.

[0010] A further technical solution of the present invention is: the positioning plate includes a curved positioning plate, a flat positioning plate, and an inclined positioning plate.

[0011] A further technical solution of the present invention is: the power device includes a screw transmission gear, a motor transmission gear, and a motor, the motor is fixed in the mounting seat through a motor fixing seat, the output shaft of the motor is connected to the motor transmission gear, the motor transmission gear and the screw transmission gear are meshed with each other, and the screw transmission gear is installed on the screw.

[0012] A further technical solution of the present invention is that a load regulator for adjusting the clamping force of the clamp and overload protection is also installed at the input end of the motor.

[0013] A further technical solution of the present invention is: the power device also includes a manual adjustment handle, and the manual adjustment handle is installed on one end of the screw rod.

[0014] Due to the above structure, the multifunctional clamp of the present invention has the following beneficial effects compared with the prior art:

[0015] 1. Can realize a variety of positioning and clamping functions

[0016] (1) Realize self-centering positioning function: When the workpiece is a symmetrical part, the fixture can realize unilateral symmetrical positioning, bilateral symmetrical positioning or central symmetrical positioning according to the shape of the workpiece. It can also realize surface contact positioning, line contact positioning and point contact positioning.

[0017] (2) Realize arbitrary positioning function: When the workpiece is asymmetrical, the fixture can automatically position and clamp the workpiece at a certain point (self-centering principle), or use different positioning surfaces of the clamp block, or remove the clamp block support parts that are not used for positioning.

[0018] (3) Realize clamping functions in multiple directions: By using different working surfaces of the clamp block, it is possible to apply a clamping force perpendicular to the horizontal plate (using the inclined surface of the clamp block) or a clamping force parallel to the horizontal plane (using the curved surface or flat surface of the clamp block).

[0019] 2. Reliable and reasonable structure

[0020] The present invention comprises a mounting seat, a clamping block, a lead screw located in the mounting seat, a lead screw nut, two push polished rods, and four guide rods. A center block is installed at the inner center of the mounting seat. The mounting seat is provided with polished rod guide grooves at the front and rear end surfaces, respectively. The polished rod guide grooves are slidably matched with the two ends of the two push polished rods. The left and right end surfaces of the mounting seat are respectively connected to the two ends of the lead screw, and the two ends of the lead screw have different screw directions. The upper surface of the mounting seat is provided with centrally symmetrical clamping block guide grooves at the connection positions between the four corners and the center. The middle part of the push rod is fixedly connected with the screw nut, and the screw nut is connected to the screw; each push rod is respectively sleeved with a clamping block support on both sides of the screw nut, the middle part of the clamping block support is slidably matched with the clamping block guide groove on the mounting seat, the upper part of the clamping block support passes through the upper surface of the mounting seat and is fixedly connected with the clamping block, and the clamping block support is also sleeved on the guide rod, which is arranged along the bottom of the clamping block guide groove, and one end of the guide rod is connected to the four corners of the mounting seat, and the other end of the guide rod is connected to the center block. Therefore, the present invention adopts diagonal centering clamping, and the push rod will not have a "dead point position" at any position in the process of pushing the clamping block support to move along the guide rod, and its structure is reliable and reasonable.

[0021] 3. The clamping block is easy to disassemble and assemble, and has a variety of positioning surfaces.

[0022] The clamping block of the present invention adopts a spline installation, so it is easy to disassemble and assemble, and can be installed by 360-degree multi-directional rotation; the positioning surface is diversified, and positioning clamping in various shapes and directions can be achieved. When the workpiece to be positioned is a special-shaped part, the positioning plate that matches the shape of the corresponding special-shaped part can also be replaced, and it only needs to be fixed on the clamping block.

[0023] 4. High positioning accuracy

[0024] Since the transmission mechanism of the clamp adopts screw drive and sliding guide rail drive, its transmission positioning accuracy is high. In addition, the clamp adopts diagonal centering clamping, which can limit multiple degrees of freedom at the same time to ensure the processing accuracy during milling.

[0025] 5. Manual / automatic clamping can be realized at the same time, with reliable clamping and high efficiency.

[0026] When the present invention performs batch workpiece clamping processing, a motor can be used to realize the automatic clamping release function, which can greatly improve the processing efficiency; when the clamped workpiece is easy to deform, the manual clamping release function can also be used to ensure reliable processing of the workpiece.

[0027] 6. The clamping force is adjustable and has overload protection function.

[0028] The clamping force of the clamp can be set manually according to the material of the workpiece, and it has an overload protection function. When the clamping force reaches the set clamping force, the clamp will automatically stop clamping.

[0029] 7. Long service life and low maintenance cost.

[0030] The upper end cover of the present invention adopts a closed structure, which can prevent cutting chips or coolant from entering the transmission system, greatly reduce the failure rate and maintenance cost, and increase the service life of the clamp.

[0031] The technical features of the multifunctional clamp of the present invention are further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 : A schematic diagram of the structure of the multifunctional clamp of the present invention,

[0033] Figure 2 : A top view after removing the upper end cover in Example 1,

[0034] Figure 3 : A schematic diagram of the three-dimensional structure after removing the upper end cover in the first embodiment,

[0035] Figure 4 : Schematic diagram of the three-dimensional structure of the clamping block in Example 1 Figure 1,

[0036] Figure 5 : Schematic diagram of the three-dimensional structure of the clamping block in Example 1 Figure 2 (Looking from the other direction),

[0037] Figure 6 : Schematic diagram of the three-dimensional structure of the clamping block support member in Example 1.

[0038] In the above drawings, the descriptions of the reference numerals are as follows:

[0039] 1-mounting seat, 101-upper end cover, 102-base, 1021-fixing groove, 103-center block, 104-light rod guide groove,

[0040] 105-clamp guide groove, 106-scale,

[0041] 2-Clamp block,

[0042] 201-guide keyway, 202-positioning plate, 2021-arc surface positioning plate, 2022-flat surface positioning plate, 2023-inclined surface positioning plate,

[0043] 3-screw, 301-left thread, 302-right thread,

[0044] 4-screw nut, 401-screw left nut, 402-screw right nut,

[0045] 5- push rod, 6- guide rod,

[0046] 7-clamp support, 701-threaded column, 702-guide body, 703-round hole, 704-square hole, 705-guide key,

[0047] 8- Power unit,

[0048] 801-screw transmission gear, 802-motor transmission gear, 803-motor, 804-motor fixing seat, 805-coupling,

[0049] 806-load adjustment nut, 807-load adjuster, 808-manual adjustment handle,

[0050] 9-clamp nut, 10-bearing end cover. DETAILED DESCRIPTION

[0051] Embodiment 1:

[0052] A multifunctional clamp comprises a mounting seat 1, a clamping block 2 for clamping a workpiece located on the upper surface of the mounting seat 1, a screw rod 3 located in the mounting seat 1, a screw rod nut 4, two push rods 5, and four guide rods 6, wherein:

[0053] The mounting base 1 is a square split structure with a cavity inside, and the mounting base 1 includes an upper end cover 101 and a base 102; the upper end cover 101 is a cover body with a square cross-section and a closed top surface, and the upper end cover 101 is made into a closed type to prevent cutting fluid and cutting chips from falling into the base 102 and damaging the transmission parts; a center block 103 is installed at the center position of the bottom surface of the upper end cover 101 through fasteners, and the center block 103 coincides with the center position of the upper end cover 101; the front and rear end surfaces of the upper end cover 101 are respectively provided with light rod guide grooves 104; the upper surface of the upper end cover 101 is respectively provided with center-symmetrical clamping block guide grooves 105 at the connecting line positions between the four corners of the upper end cover and the center block, and the upper end cover 101 is also installed with a scale 106 above the light rod guide groove 104, which can read the size of the clamped workpiece from the position where the light rod is pushed. The base 102 is a frame with a square cross section, and is connected to the upper end cover 101 through fasteners to form a cubic shell. The front and rear ends of the base 102 are also provided with fixing grooves 1021 for fixing to the processing workbench through fasteners.

[0054] The clamping block 2 is mainly used for clamping the workpiece for processing, and a guide keyway 201 is opened in the middle thereof. Positioning plates 202 of different shapes are fixed on the four sides of the clamping block 2, respectively. The positioning plates 202 include an arc positioning plate 2021, a plane positioning plate 2022, an inclined positioning plate 2023, etc. When the arc workpiece needs to be clamped, the clamping block 2 only needs to be rotated 90 degrees so that the arc positioning plate 2021 faces the arc workpiece; similarly, the same is true for the plane positioning plate 2022 and the inclined positioning plate 2023.

[0055] The two ends of the screw rod 3 are fixed to the left and right ends of the base 102 through bearings. The left end of the screw rod 3 is a left thread 301, and the right end is a right thread 302. Both the left and right threads are triangular threads with self-locking function, and the left thread 301 is matched with a screw rod left nut 401, and the right thread is matched with a screw rod right nut 402. When the screw rod 3 rotates, the screw rod left nut 401 and the screw rod right nut 402 will move outward or inward at the same time.

[0056] The pushing light rod 5 is provided on the left and the right, respectively, and is located on both sides of the center block 103. The two ends of the two pushing light rods 5 are respectively slidably matched with the light rod guide groove 104 of the upper end cover 101. The middle parts of the two pushing light rods 5 are respectively fixed on the left screw nut 401 and the right screw nut 402. Each pushing light rod 5 is respectively sleeved with a clamping block support 7 on both sides of the left screw nut 401 or the right screw nut 402. When the left screw nut 401 and the right screw nut 402 move inward or outward at the same time, the pushing light rod 5 will drive the four clamping block support 7 to move toward the four corners or the center point of the base 102 at the same time.

[0057] The guide rods 6 are long rectangular structures, with four in total. Each guide rod 6 is arranged along the bottom of the clamping block guide groove 105, and one end of the four guide rods 6 is movably connected to the four corners of the base 102 through fixing pins and nuts, and the other ends of the four guide rods 6 are respectively connected to the center block 103.

[0058] The clamping block support 7 has a threaded column 701 on the upper part, a guide body 702 in the middle part, and a round hole 703 and a square hole 704 on the bottom, and a guide key 705 is installed between the threaded column 701 and the guide body 702; the threaded column 701 passes through the guide key slot 201 of the clamping block 2 and is fastened to the clamping block nut 9 above the clamping block 2, so as to fix and tighten the clamping block 2 and prevent the clamping block 2 from moving up and down; the guide key 705 is connected with the guide key slot 201 of the clamping block 2; the guide body 702 is slidably matched with the clamping block guide slot 105 of the upper end cover 101; the round hole 703 at the bottom of the clamping block support 7 is clearance matched with the pushing light rod 5; the square hole 704 at the bottom of the clamping block support 7 is clearance matched with the guide rod 6, which is used to limit the five degrees of freedom of the clamping block support 7, so that the clamping block support 7 can be reliably moved and positioned.

[0059] The power device 8 includes a screw transmission gear 801, a motor transmission gear 802, a motor 803 and a manual adjustment handle 808; the motor 803 is fixed in the mounting seat 1 through a motor fixing seat 804, the output shaft of the motor 803 is connected to the motor transmission gear 802 through a coupling 805, the motor transmission gear 802 and the screw transmission gear 801 are meshed with each other, and the screw transmission gear 801 is installed on the screw 3. A load regulator 807 is also installed at the input end of the motor 803, and the load regulator 807 is mainly used to adjust the clamping force of the fixture and the overload protection function. Before clamping a workpiece, the clamping force is set according to the material of the workpiece and the required clamping force, and then through the load adjustment nut 806. When the output load of the motor 803 reaches the value set by the load regulator 807, the load regulator 807 automatically disconnects the power supply of the motor 803 to achieve the function of adjustment and overload protection. The manual adjustment handle 808 is installed on one end of the screw rod 3, and can be manually clamped through the manual adjustment handle 808 when the motor 803 is not working.

[0060] As a variation of the first embodiment, the positioning plates 202 on the four sides of the clamping block 2 may also be in other shapes that match the shape of the workpiece.

[0061] As a variation of the first embodiment, the manual adjustment handle 808 may not be installed.

[0062] As another variation of the first embodiment, when the centering function is not needed in a certain direction, the push polished rod in that direction can be removed.

[0063] The working process of the present invention is as follows:

[0064] 1) Automatic clamping process: predict the required clamping force, adjust the load adjustment nut 806 on the load regulator 807, and set the clamping force value. Then, according to the size of the clamped workpiece, energize the motor 803 to reverse, push the light rod 5 to move to the size indicated by the scale 106, and when it is larger than the size of the workpiece, stop the motor 803, put the workpiece in the middle of the upper end cover 101, and then energize the motor 803 to rotate forward. The motor 803 drives the motor transmission gear 802 through the coupling 805 on the rotating shaft. The motor transmission gear 802 and the screw transmission gear 801 on the screw 3 are meshed, driving the screw 3 to rotate. Since the left and right sides of the screw 3 are the left thread 301 and the right thread 302, respectively, the screw left nut 401 and the screw right nut 402 on the screw 3 move to the center position under the drive of the screw 3. At the same time, the push rod 5 is fixed on the left screw nut 401 and the right screw nut 402, respectively, and the clamping block support 7 sleeved on the push rod 5 moves in the clamping direction while pushing the rod 5. Since the base 102 is a square, the four guide rods 6 are all centered on the center of the base 102, and the length of the guide rod 6 is the radius, so the four clamping blocks 2 achieve the function of centering and clamping during the movement of the four clamping block support 7. In the process of clamping the workpiece, as the clamping force of the clamping block 2 continues to increase, the load output by the motor 803 also continues to increase. When the output load of the motor 803 reaches the set value of the load regulator 807, the load regulator 807 will automatically disconnect the power supply of the motor 803. Since the screw rod 3 is a triangular thread, it has a self-locking function when clamping.

[0065] 2) Automatic loosening process: The automatic loosening process is opposite to the automatic clamping process. When the workpiece needs to be loosened, the motor is powered on to reverse the rotation, and the clamp 2 moves in the opposite direction to loosen the workpiece.

[0066] 3) Manual clamping and loosening process: When the material of the clamped workpiece is easily deformed, the required clamping force cannot be determined, or the automatic function is damaged, the screw rod 3 can be twisted by manually adjusting the handle 808 to achieve clamping or loosening.

Claims

1. A multifunctional clamp, comprising a mounting seat (1), a clamping block (2) located on the upper surface of the mounting seat (1) for clamping a workpiece, a screw (3) located in the mounting seat (1), and a screw nut (4), characterized in that: The mounting seat (1) is a square split structure with a cavity inside, and a center block (103) is installed at the center of the mounting seat (1). The mounting seat (1) is provided with a light rod guide groove (104) on the front and rear end surfaces, respectively. The light rod guide groove (104) is slidably matched with the two ends of the two driving light rods (5). The two driving light rods (5) are respectively located on both sides of the center block (103); the left and right end surfaces of the mounting seat (1) are respectively connected to the two ends of the screw rod (3), and the two ends of the screw rod (3) are threaded. The rotation direction is different; the upper surface of the mounting seat (1) is provided with a centrally symmetrical clamping block guide groove (105) at the position of the connection line between its four corners and the center; the middle part of the pushing light rod (5) is fixedly connected to the screw nut (4), the screw nut (4) is connected to the screw (3), and the screw (3) is also connected to the power device (8); each pushing light rod (5) is respectively sleeved with a clamping block support member (7) on both sides of the screw nut (4), the middle part of the clamping block support member (7) is slidably matched with the clamping block guide groove (105) on the mounting seat (1), and the upper part of the clamping block support member (7) passes through the mounting seat The upper surface of the seat (1) is fixedly connected to the clamping block (2), and the clamping block support member (7) is also sleeved on the guide rod (6). The guide rod (6) is arranged along the bottom of the clamping block guide groove (105), and one end of the guide rod (6) is connected to the four corners of the mounting seat (1), and the other end of the guide rod (6) is connected to the center block (103); positioning plates (202) of different shapes are fixed to the four sides of the clamping block (2); the guide rod (6) is a long rectangular parallelepiped structure; the upper part of the clamping block support member (7) is a threaded column (701), and the threaded column (7 01) passes through the clamping block (2) and is fastened to the clamping block nut (9) above the clamping block (2); the middle part of the clamping block support (7) is a guide body (702), and the guide body (702) is slidably matched with the clamping block guide groove (105); the bottom of the clamping block support (7) is respectively provided with a round hole (703) and a square hole (704), the round hole (703) and the push rod (5) are clearance matched, and the square hole (704) and the guide rod (6) are clearance matched; the positioning plate (202) includes a curved positioning plate (2021), a flat positioning plate (2022), and an inclined positioning plate (2023).

2. The multifunctional clamp according to claim 1, characterized in that: The mounting seat (1) comprises an upper end cover (101) and a base (102); the upper end cover (101) is a cover body with a square cross section and a closed top surface; the center block (103) is fixed to the center position of the bottom surface of the upper end cover (101) by fasteners, and the center block (103) coincides with the center position of the upper end cover (101); the upper surface of the upper end cover (101) is provided with the clamping block guide grooves (105) which are symmetrical at the connection positions between the four corners of the upper end cover and the center block; the front and rear end surfaces of the upper end cover (101) are provided with the light rod guide grooves (104) respectively; the base (102) is a frame body with a square cross section, and is connected to the upper end cover (101) by fasteners to form a cubic shell; the four corners of the base (102) are movably connected to the guide rod (6) by fixing pins and nuts.

3. The multifunctional clamp according to claim 2, characterized in that: The upper end cover (101) is also provided with a scale (106) above the polished rod guide groove (104) for reading the size of the clamped workpiece from the position where the polished rod is pushed; and the base (102) is also provided with a fixing groove (1021) for fixing to the processing workbench via a fastener.

4. The multifunctional clamp according to claim 1, characterized in that: The screw rod (3) has a triangular left thread (301) at one end and a triangular right thread (302) at the other end. The screw rod nut (4) comprises a left screw rod nut (401) and a right screw rod nut (402). The left screw rod nut (401) and the right screw rod nut (402) respectively cooperate with the left thread (301) and the right thread (302) of the screw rod (3).

5. The multifunctional clamp according to claim 1, characterized in that: A guide keyway (201) is provided in the middle of the clamp block (2), and a guide key (705) is installed between the threaded column (701) and the guide body (702) of the clamp block support (7), and the guide keyway (201) of the clamp block (2) is connected in a cooperative manner with the guide key (705) on the clamp block support (7).

6. The multifunctional clamp according to claim 1, characterized in that: The power device (8) comprises a screw transmission gear (801), a motor transmission gear (802), and a motor (803); the motor (803) is fixed in the mounting seat (1) via a motor fixing seat (804); the output shaft of the motor (803) is connected to the motor transmission gear (802); the motor transmission gear (802) and the screw transmission gear (801) are meshed with each other; and the screw transmission gear (801) is mounted on the screw (3).

7. The multifunctional clamp according to claim 6, characterized in that: The input end of the motor (803) is also equipped with a load regulator (807) for adjusting the clamping force of the clamp and for overload protection.

8. The multifunctional clamp according to claim 6, characterized in that: The power device (8) further comprises a manual adjustment handle (808), wherein the manual adjustment handle (808) is mounted on one end of the screw rod (3).

Images