A device to assist in demolding injection molded products.

Abstract

This invention relates to an injection molding machine device, and more particularly to a device for assisting in the demolding of injection-molded products. During the unloading process of the molded plastic stool, the moving mold body separates from the fixed mold body, exposing the plastic stool. To prevent adhesion during removal, it is first allowed to cool naturally. Then, the demolding gripping assembly is connected to the demolding ejector pin. When the demolding gripping assembly grips the product material, a demolding support assembly located at the bottom of the movable insert supports the bottom of the product material. This allows the support hydraulic cylinder to drive the product to demold during upward demolding. The four sets of demolding support assemblies simultaneously support the four feet of the plastic stool, ensuring even force distribution on the product during upward demolding. This effectively prevents product deformation caused by localized stress, thus improving processing efficiency and quality.

Description

Technical Field

[0001] This invention relates to an injection molding machine device, and more particularly to a device for assisting in the demolding of injection-molded products. Background Technology

[0002] Injection molding is a process in which molten material is fed into a steel ingot mold to form a part of a certain shape. Demolding refers to a series of operations that remove the molded object from the steel ingot mold after injection molding, and it is an important step in the injection molding process.

[0003] A Chinese patent document with authorization announcement number CN218948378U discloses a device for assisting in the demolding of injection-molded products in an injection molding machine. The device includes a drive motor, a ball screw mounted at the output end of the drive motor, a screw nut seat fitted on the outer side of the ball screw, a movable plate on one side of the screw nut seat, a cooling plate mounted on one side of the screw nut seat, a lower mold mounted on one side of the cooling plate, a cooling pipe installed inside the cooling plate, a connecting pipe on one side of the cooling pipe, and a water pump connected to the other end of the connecting pipe. The device works by starting the water pump to deliver coolant through the connecting pipe into the cooling pipe of the cooling plate. The coolant carries away heat from the lower mold, helping to quickly dissipate heat from the material in the lower mold, thereby improving demolding efficiency. Afterwards, the coolant enters the heat dissipation pipe, where a cooling fan dissipates its internal heat, thus forming a cooling cycle. In injection molding, after the moving mold and the fixed mold separate, some products are molded inside the mold cavity. In this case, the product inside the mold cavity needs to be cooled accordingly, usually by setting up a water-cooling or air-cooling structure in the fixed mold. Then, some products are molded and attached to the mold core, such as the processing and manufacturing of plastic stools, where the finished product is attached to the mold core on the fixed mold. For product removal, the moving mold is usually separated directly, and the product is exposed to the outside world for natural cooling. After a certain period of time, the worker removes the product by hand. This process lacks a suitable product demolding mechanism to assist in the demolding work, and needs to be improved and optimized.

[0004] Therefore, the present invention proposes a device to assist in demolding injection molded products to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a device for assisting in the demolding of injection-molded products from an injection molding machine, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a device for assisting in the demolding of injection-molded products of an injection molding machine, comprising a moving mold body and a fixed mold body, wherein the top of the moving mold body is provided with an injection port, the side wall of the moving mold body is provided with a lifting ring, and the bottom of the moving mold body is provided with a mold cavity and symmetrically arranged guide grooves; the top of the fixed mold body is provided with a mold core support and symmetrically fixed guide shafts; and a forming mold core is provided on the mold core support.

[0007] The bottom end of the fixed mold body is provided with a receiving cavity, and a support frame is fixedly provided at the opening of the receiving cavity. A loading groove is provided at the center of the support frame, and a mounting slot is provided at the opening of the loading groove. A demolding mechanism is provided in the receiving cavity.

[0008] Preferably, the demolding mechanism includes a supporting hydraulic cylinder, a mounting bracket, a demolding ejector pin, a connecting plate, a docking slot, a positioning slot, a demolding auxiliary component, and a demolding gripping component; the bottom end of the supporting hydraulic cylinder is fixedly provided with a mounting bracket, which is adapted to and engaged with the mounting slot, and the mounting bracket is fixed by bolts; the bottom end of the demolding ejector pin is fixedly provided with a connecting plate, which is fixedly provided on the top of the supporting hydraulic cylinder by screws; and the demolding ejector pin is connected to the demolding auxiliary component.

[0009] Preferably, the top of the demolding ejector pin is provided with a docking slot, the slot opening is square, and the four side walls of the docking slot are provided with positioning slots. The docking slot is connected to the demolding gripping component.

[0010] Preferably, the demolding auxiliary component includes a hollow cavity, an air outlet body, a connector, and a cooling air delivery pipe; the hollow cavity is disposed in the demolding top post, and the side wall of the hollow cavity is uniformly provided with air outlet bodies; the connector is fixedly disposed on the side wall of the demolding top post and is connected to the hollow cavity; the connector is connected to the cooling air delivery pipe.

[0011] Preferably, the demolding gripping assembly includes a carrier, a docking insert, a threaded groove, a drive screw, an auxiliary handle, a positioning chuck, a connecting spring, a movable pin, a support rod, an adjustment assembly, and a demolding support assembly. The bottom end of the carrier is fixedly provided with the docking insert, and the carrier is provided with a threaded groove extending into the docking insert. The threaded groove is threadedly connected to the drive screw. One end of the drive screw is fixedly provided with an auxiliary handle. Support rods are fixedly provided at equal intervals on the sidewalls of the carrier. The support rods are connected to the adjustment assembly, and the adjustment assembly is connected to the demolding support assembly.

[0012] Preferably, the mating insert is adapted to be inserted into the mating slot at the top of the demolding ejector pin, and a positioning clip is symmetrically and movably arranged in the demolding ejector pin. A movable pin is fixedly arranged at one end of the positioning clip, and the movable pin is movably inserted into the mating insert. One end of the movable pin extends into the threaded groove and has a spherical surface at its end. A connecting spring is fixedly arranged at the end of the positioning clip that is connected to the movable pin, and one end of the connecting spring is fixedly arranged in the mating insert.

[0013] Preferably, the control component includes an L-shaped rod, a movable slot, a first positioning screw, a first knob, a movable insert rod, a second positioning screw, and a second knob; the L-shaped rod has movable slots symmetrically arranged at both ends, the movable slot at one end of the L-shaped rod is movably connected to the support rod, and the movable slot at the other end of the L-shaped rod is movably connected to a movable insert rod.

[0014] Preferably, the L-shaped rod is provided in four sets. A first positioning screw is threadedly connected to one side of one end of the L-shaped rod. The first positioning screw presses and positions the support rod body. A first knob is fixedly provided at one end of the first positioning screw. A second positioning screw is threadedly connected to the other side of the L-shaped rod. The second positioning screw presses and positions the movable insert rod. A second knob is fixedly provided at one end of the second positioning screw.

[0015] Preferably, the bottom end of the movable insert is connected to a demolding support assembly, which includes a bearing plate, a movable pin, a connecting handle, an auxiliary spring, and a support hook. The bearing plate is fixedly disposed at the bottom end of the movable insert, and the movable pin is movably inserted into the bearing plate at equal intervals. One end of the movable pin is fixedly disposed with a connecting handle, and the other end of the movable pin is fixedly disposed with a support hook.

[0016] Preferably, the connecting handle is a circular plate shape, and an auxiliary spring is fixedly provided at the end of the connecting handle connected to the auxiliary spring. The other end of the auxiliary spring is fixedly provided on the bearing plate. The support hook is a semi-circular hook bar, and the number of sets of the support hook and the movable pin is the same.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] This invention relates to a demolding device for injection molded products. A receiving cavity is located at the bottom of the fixed mold body. A support frame is fixedly installed at the opening of the receiving cavity, and a loading groove is located at the center of the support frame. A mounting slot is located at the opening of the loading groove, and a demolding mechanism is installed within the receiving cavity. During the unloading process of the molded plastic stool, the moving mold body separates from the fixed mold body, exposing the plastic stool. To prevent adhesion during removal, it is first allowed to cool naturally. Then, the demolding gripping assembly is connected to the demolding ejector pin. When the demolding gripping assembly grips the product material, the bottom of the product material is supported by a demolding support assembly located at the bottom of the movable insert rod. This allows the support hydraulic cylinder to drive the product to demold during upward demolding. The four sets of demolding support assemblies simultaneously support the four feet of the plastic stool, ensuring even force distribution during upward demolding. This effectively prevents product deformation caused by localized stress, thus improving processing efficiency and quality. Attached Figure Description

[0019] Figure 1 This is a top view of the demolding structure connection of the injection mold of the present invention;

[0020] Figure 2 This is a bottom view of the demolding structure connection of the injection mold of the present invention;

[0021] Figure 3 This is a schematic diagram of the bottom connection of the fixed mold structure of the present invention;

[0022] Figure 4 for Figure 3 Enlarged schematic diagram of the structural connection at point A;

[0023] Figure 5 This is a schematic diagram of the demolding auxiliary component structure of the present invention;

[0024] Figure 6 This is a schematic diagram of the connection structure of the demolding gripping component of the present invention;

[0025] Figure 7 for Figure 6 Enlarged schematic diagram of the structural connection at point B;

[0026] Figure 8 for Figure 6 Enlarged schematic diagram of the structural connection at point C;

[0027] Figure 9 This is a schematic diagram of a partial structural connection between the carrier and the docking insert of the present invention;

[0028] Figure 10 This is an exploded view of the connection structure of the control component of the present invention;

[0029] Figure 11 for Figure 10 Enlarged schematic diagram of the structural connection at point D;

[0030] Figure 12 for Figure 10 Enlarged schematic diagram of the structural connection at point E in the middle.

[0031] In the diagram: 1. Moving mold body; 11. Injection port; 12. Lifting ring; 13. Mold cavity; 14. Guide groove; 2. Fixed mold body; 21. Guide shaft; 22. Mold core support; 23. Molding mold core; 3. Receiving cavity; 4. Support frame; 5. Loading groove; 6. Mounting slot; 701. Support hydraulic cylinder; 702. Mounting bracket; 703. Ejector pin; 704. Connecting plate; 705. Docking slot; 706. Positioning slot; 801. Hollow cavity; 802. Air outlet; 803. Connector; 804. Cooling air delivery pipe; 901. Bearing body; Docking. Insert body 902, threaded groove body 903, drive screw 904, auxiliary handle 905, positioning chuck 906, connecting spring 907, movable pin 908, support rod body 909, L-shaped rod 1001, movable slot 1002, first positioning screw 1003, first knob 1004, movable insert rod 1005, second positioning screw 1006, second knob 1007, bearing plate 1101, movable pin 1102, connecting handle 1103, auxiliary spring 1104, support hook body 1105. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0033] Example 1: Please refer to Figures 1-12 A device for assisting in demolding injection-molded products in an injection molding machine includes a moving mold body 1 and a fixed mold body 2. The moving mold body 1 has an injection port 11 at its top, a lifting ring 12 on its side wall, a mold cavity 13 at its bottom, and guide grooves 14 symmetrically arranged. The fixed mold body 2 has a mold core support 22 at its top and guide shafts 21 symmetrically fixed. A forming mold core 23 is provided on the mold core support 22. A receiving cavity 3 is provided at the bottom of the fixed mold body 2. A support frame 4 is fixedly arranged at the opening of the receiving cavity 3. A loading groove 5 is provided at the center of the support frame 4. A mounting slot 6 is provided at the opening of the loading groove 5. A demolding mechanism is provided in the receiving cavity 3.

[0034] When removing the molded plastic stool, the moving mold body 1 separates from the fixed mold body 2, exposing the plastic stool. To prevent sticking during removal, it is first allowed to cool naturally. Then, the demolding gripping assembly is connected to the demolding ejector pin 703. Holding the support body 901, the mating insert 902 at the bottom of the support body 901 is inserted into the mating slot 705 at the top of the demolding ejector pin 703. Simultaneously, the drive screw 904 is rotated via the auxiliary handle 905, causing one end of the drive screw 904 to press against the movable pin 908 extending into the threaded groove 903. This causes the movable pin 908 to push the positioning clip 906, engaging it with the positioning slot 706 on the side wall of the mating slot 705. The connection between the demolding gripping assembly and the demolding ejector pin 703 is thus quickly and easily completed. The bottom of the support hydraulic cylinder 701 in the demolding mechanism is fixedly equipped with a mounting bracket 702. The mounting bracket 702 is compatible with the mounting slot 6 and is fixed by bolts. A connecting plate 704 is fixedly installed at the bottom of the demolding top column 703. The connecting plate 704 is fixedly installed at the top of the supporting hydraulic cylinder 701 by screws. The demolding top column 703 is connected to the demolding auxiliary component. A docking slot 705 is provided at the top of the demolding top column 703. The slot of the docking slot 705 is square, and the four side walls of the docking slot 705 are provided with positioning slots 706. The docking slot 705 is connected to the demolding gripping component. The hollow cavity 801 in the demolding auxiliary component is set in the demolding top column 703. The side walls of the hollow cavity 801 are evenly provided with air outlets 802. The connector 803 is fixedly installed on the side wall of the demolding top column 703 and is connected to the hollow cavity 801. The connector 803 is connected to the cooling air delivery pipe 804.

[0035] When using the demolding gripping assembly to grip product materials, the bottom of the product material is supported by a demolding support assembly located at the bottom of the movable insert rod 1005. This allows the support hydraulic cylinder 701 to drive the product to demold when it pushes upwards for demolding. Specifically, the bottom of the carrier body 901 in the demolding gripping assembly is fixedly provided with a mating insert 902, and the carrier body 901 is provided with a threaded groove 903 extending into the mating insert 902. The threaded groove 903 is threadedly connected to the drive screw 904. One end of the drive screw 904 is fixedly provided with an auxiliary handle 905, and support rods 909 are fixedly provided at equal intervals on the side wall of the carrier body 901. The support rod 909 is connected to the control component, which is in turn connected to the demolding support component. The mating insert 902 is fitted into the mating slot 705 at the top of the demolding top post 703. A positioning clip 906 is symmetrically and movably arranged in the demolding top post 703. A movable pin 908 is fixedly arranged at one end of the positioning clip 906. The movable pin 908 is movably inserted into the mating insert 902, and one end of the movable pin 908 extends into the threaded groove 903. The end of the movable pin 908 has a spherical surface. A connecting spring 907 is fixedly arranged at the end of the positioning clip 906 that is connected to the movable pin 908. One end of the connecting spring 907 is fixedly arranged in the mating insert 902.

[0036] The bottom end of the movable insert rod 1005 is connected to a demolding support assembly, which includes a support plate 1101, a movable pin 1102, a connecting handle 1103, an auxiliary spring 1104, and a support hook 1105. The support plate 1101 is fixedly installed at the bottom end of the movable insert rod 1005, and the movable pin 1102 is movably inserted into the support plate 1101 at equal intervals. One end of the movable pin 1102 is fixedly installed with the connecting handle 1103, and the other end of the movable pin 1102 is fixedly installed with the support hook 1105. The connecting handle 1103 is circular, and the end of the connecting handle 1103 connected to the auxiliary spring 1104 is fixedly installed with the auxiliary spring 1104. The other end of the auxiliary spring 1104 is fixedly installed on the support plate 1101. The support hook 1105 is a semi-circular hook bar, and the number of sets of support hooks 1105 and movable pins 1102 are the same.

[0037] The support hook 1105 supports the bottom of the plastic stool. The support hook 1105 is used in conjunction with the movable pin 1102, the connecting handle 110, and the auxiliary spring 1104. The support hook 1105 has a flexible function in the horizontal direction. When the support hook 1105 moves down along the bottom of the plastic stool, the bottom of the stool squeezes the support hook 1105. When the support hook 1105 reaches the bottom of the bottom of the stool, the support hook 1105 rebounds under the rebound action of the auxiliary spring 1104, so that the support hook 1105 supports the bottom of the bottom of the stool.

[0038] To further improve the flexibility of the demolding support assembly, an adjustment component is incorporated. This component includes an L-shaped rod 1001, a movable slot 1002, a first positioning screw 1003, a first knob 1004, a movable insert rod 1005, a second positioning screw 1006, and a second knob 1007. The L-shaped rod 1001 has symmetrically arranged movable slots 1002 at both ends. One end of the L-shaped rod 1001 has a movable slot 1002 that is movably inserted into the support rod 909, while the other end has a movable slot 1002 that is movably inserted into the movable insert rod 1005. Four sets of L-shaped rods 1001 are provided. A first positioning screw 1003 is threadedly connected to one side of each L-shaped rod 1001. The first positioning screw 1003 presses and positions the support rod 909, and a first knob 1007 is fixedly attached to one end of the first positioning screw 1006. 4. A second positioning screw 1006 is threadedly connected to the other end of the L-shaped rod 1001. The second positioning screw 1006 presses and positions the movable insert rod 1005. A second knob 1007 is fixedly installed at one end of the second positioning screw 1006. The L-shaped rod 1001 and the support rod 909 are movably connected, allowing for flexible adjustment. After adjustment, the first positioning screw 1003 is used for positioning. That is, the first positioning screw 1003 is tightened by the first knob 1004, so that one end of the first positioning screw 1003 presses against the support rod 909 to achieve positioning. The L-shaped rod 1001 and the movable insert rod 1005 are movably connected, and the second positioning screw 1006 is tightened by the second knob 1007, so that one end of the second positioning screw 1006 presses against the movable insert rod 1005 to achieve positioning, which has good working flexibility.

[0039] After supporting the base of the plastic stool, the supporting hydraulic cylinder 701 pushes it upwards. In this invention, four sets of L-shaped rods 1001 act as a gripping claw. Simultaneously, four sets of demolding support components support the four bases of the plastic stool. During the upward demolding process, the product experiences even stress, effectively preventing deformation due to localized stress. The supporting hydraulic cylinder 701 pushes the product upwards, and simultaneously, the demolding auxiliary components connected to the demolding ejector pin 703 further assist in the upward movement. During the upward movement of the ejector pin 703, the air outlet 802 on the ejector pin 703 will be exposed. Cooling gas is transported through the cooling air delivery pipe 804. The cooling gas gathers in the hollow cavity 801 and is then sprayed out from the air outlet 802. The sprayed cooling air passes between the molding core 23 and the product, which can provide cooling assistance for both the molding core 23 and the product. On the one hand, it facilitates the rapid cooling of the product and the demolding process. On the other hand, it increases the cooling speed of the product and the molding core 23, which helps the next injection molding process and avoids the product from getting too hot to handle.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A device for assisting in demolding injection molded products of an injection molding machine, comprising a moving mold body (1) and a fixed mold body (2), wherein the moving mold body (1) is provided with an injection port (11) at the top, a lifting ring (12) is provided on the side wall of the moving mold body (1), and a mold cavity (13) and guide grooves (14) are symmetrically arranged at the bottom of the moving mold body (1), a mold core support (22) and guide shafts (21) are symmetrically fixed at the top of the fixed mold body (2), and a forming mold core (23) is provided on the mold core support (22); Its features are: The bottom end of the fixed mold body (2) is provided with a receiving cavity (3), a support frame (4) is fixedly provided at the cavity opening of the receiving cavity (3), a loading groove (5) is provided at the center of the support frame (4), an installation slot (6) is provided at the opening of the loading groove (5), and a demolding mechanism is provided in the receiving cavity (3). The demolding mechanism includes a supporting hydraulic cylinder (701), a mounting bracket (702), a demolding top column (703), a connecting plate (704), a docking slot (705), a positioning slot (706), a demolding auxiliary component, and a demolding gripping component; the supporting hydraulic cylinder (701) is fixedly provided with a mounting bracket (702) at its bottom end, the mounting bracket (702) is adapted to and engaged with the mounting slot (6), and the mounting bracket (702) is fixed by bolts; the demolding top column (703) is fixedly provided with a connecting plate (704) at its bottom end, the connecting plate (704) is fixedly provided with screws on the top of the supporting hydraulic cylinder (701); the demolding top column (703) is connected to the demolding auxiliary component. The demolding gripping assembly includes a carrier (901), a docking insert (902), a threaded groove (903), a drive screw (904), an auxiliary handle (905), a positioning chuck (906), a connecting spring (907), a movable pin (908), a support rod (909), an adjustment assembly, and a demolding support assembly. The bottom end of the carrier (901) is fixedly provided with a docking insert (902), and a threaded groove (903) is provided in the carrier (901). The threaded groove (903) extends into the docking insert (902). The threaded groove (903) is threadedly connected to the drive screw (904). One end of the drive screw (904) is fixedly provided with an auxiliary handle (905). Support rods (909) are fixedly provided at equal intervals on the side wall of the carrier (901). The support rods (909) are connected to the adjustment assembly, and the adjustment assembly is connected to the demolding support assembly.

2. The device for assisting in demolding injection-molded products in an injection molding machine according to claim 1, characterized in that: The top of the demolding top column (703) is provided with a docking slot (705), the slot of the docking slot (705) is square, and the four side walls of the docking slot (705) are provided with positioning slots (706). The docking slot (705) is connected to the demolding gripping component.

3. The device for assisting in demolding injection-molded products in an injection molding machine according to claim 1, characterized in that: The demolding auxiliary component includes a hollow cavity (801), an air outlet body (802), a connector (803), and a cooling air conveying pipe (804). The hollow cavity (801) is disposed in the demolding top post (703), and the side wall of the hollow cavity (801) is uniformly provided with air outlet bodies (802). The connector (803) is fixedly disposed on the side wall of the demolding top post (703), and the connector (803) is connected to the hollow cavity (801). The connector (803) is connected to the cooling air conveying pipe (804).

4. The device for assisting in demolding injection-molded products in an injection molding machine according to claim 2, characterized in that: The docking insert (902) is adapted to be inserted into the docking slot (705) at the top of the demolding top post (703), and a positioning clip (906) is symmetrically and movably arranged in the demolding top post (703). A movable pin (908) is fixedly arranged at one end of the positioning clip (906). The movable pin (908) is movably inserted into the docking insert (902), and one end of the movable pin (908) extends into the threaded groove (903). A spherical surface is provided at the end of the positioning clip (906) connected to the movable pin (908). A connecting spring (907) is fixedly arranged at one end of the connecting spring (907) in the docking insert (902).

5. The device for assisting in demolding injection-molded products in an injection molding machine according to claim 1, characterized in that: The control assembly includes an L-shaped rod (1001), a movable slot (1002), a first positioning screw (1003), a first knob (1004), a movable insert rod (1005), a second positioning screw (1006), and a second knob (1007). The L-shaped rod (1001) has movable slots (1002) symmetrically arranged at both ends. The movable slot (1002) at one end of the L-shaped rod (1001) is movably inserted into the support rod (909), and the movable slot (1002) at the other end of the L-shaped rod (1001) is movably inserted into the movable insert rod (1005).

6. The device for assisting in demolding injection-molded products in an injection molding machine according to claim 5, characterized in that: The L-shaped rod (1001) is provided in four sets. One end of the L-shaped rod (1001) is threaded with a first positioning screw (1003). The first positioning screw (1003) presses and positions the support rod (909). A first knob (1004) is fixedly provided at one end of the first positioning screw (1003). The other end of the L-shaped rod (1001) is threaded with a second positioning screw (1006). The second positioning screw (1006) presses and positions the movable insert rod (1005). A second knob (1007) is fixedly provided at one end of the second positioning screw (1006).

7. The device for assisting in demolding injection-molded products in an injection molding machine according to claim 5, characterized in that: The bottom end of the movable insert (1005) is connected to a demolding support assembly, which includes a bearing plate (1101), a movable pin (1102), a connecting handle (1103), an auxiliary spring (1104), and a support hook (1105). The bearing plate (1101) is fixedly installed at the bottom end of the movable insert (1005), and the movable pin (1102) is movably inserted into the bearing plate (1101) at equal intervals. One end of the movable pin (1102) is fixedly provided with a connecting handle (1103), and the other end of the movable pin (1102) is fixedly provided with a support hook (1105).

8. The device for assisting in demolding injection-molded products in an injection molding machine according to claim 7, characterized in that: The connecting handle (1103) is set in the shape of a circular plate, and the connecting handle (1103) is fixedly provided with an auxiliary spring (1104) at the end connected to the auxiliary spring (1104). The other end of the auxiliary spring (1104) is fixedly provided on the bearing plate (1101). The support hook (1105) is set as a semi-circular hook bar, and the support hook (1105) and the movable pin (1102) are set in the same number of sets.

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