Three-stage center-to-center pre-press forming machine and its usage method

Abstract

The present invention discloses a three-stage center-to-center pressing preforming machine and its usage method, including: a frame, on which a top plate is provided, on the top plate there is a discharge hopper and a lower pushing oil cylinder with an upper pressing head, on the frame there is an orifice plate, on the orifice plate there is an upper sliding plate that can slide left and right, on the upper sliding plate there is a feeding cylinder, on the frame there is a bottom plate, on the bottom plate there is an upper jacking oil cylinder, a blanking cylinder and a lower sliding plate that can slide left and right, on the lower sliding plate there is a fixed blanking cylinder and a supporting frame, in the blanking cylinder there is a lower pressing head that is movably sealed, on the supporting frame there is a hinged seat, on the hinged seat there is a liftable support plate, on the support plate there is a detachable middle material cylinder, on the side walls of the feeding cylinder, the middle material cylinder and the blanking cylinder there are all pinholes, and on the frame there is a feeding mechanism. The present invention can improve the density of plastics and the working efficiency.

Description

Technical Field

[0001] The present invention relates to the field of plastic molding equipment, and particularly to a three-stage center-to-center pre-pressing molding machine and its usage method. Background Art

[0002] When extruding using a plunger extruder, it is necessary to push the plastic forward through the reciprocating motion of the plunger. Since the plunger works intermittently and advances a certain amount of plastic each time it moves, if the plastic itself has insufficient density or contains air, it may cause unstable pressure during the extrusion process, resulting in product defects such as pores or uneven surfaces. This requires pre-pressing the loose plastic to expel the air in the plastic and increase its density. Currently, traditional pre-pressing equipment generally uses a single oil cylinder to squeeze the loose plastic downward. When squeezing unidirectionally, the plastic is only pressed from one direction, and affected by the frictional force of the barrel wall, the pressure gradually attenuates along the transmission direction. The area far from the pressure source may have reduced density due to insufficient pressure, forming a density gradient. At the same time, the bubbles or voids in the plastic may be pushed to the end during unidirectional extrusion and are difficult to completely expel, forming defects. Moreover, when loading and unloading materials, it is necessary to take out the compacted plastic before putting in the loose plastic for pre-pressing, which reduces the working efficiency. Summary of the Invention

[0003] The object of the present invention is to provide a three-stage center-to-center pre-pressing molding machine and its usage method that can improve the pre-pressing effect and facilitate loading and unloading of materials.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a three-stage center-to-center pressing pre-pressing forming machine, including: a frame, a top plate is provided on the top of the frame, a liftable discharge hopper and a lower pushing oil cylinder are provided on the top plate, an upper pressing head is provided on the lower pushing oil cylinder, a liftable orifice plate is provided on the frame below the top plate, an upper slide plate is slidably arranged left and right on the orifice plate, a feeding cylinder passing through the orifice plate is fixedly arranged on the upper slide plate, a left upper limit seat is provided on the left side of the orifice plate, when the upper slide plate abuts against the left upper limit seat, the feeding cylinder is coaxially aligned with the upper pressing head, two counterweights are symmetrically arranged front and back on the left side wall of the upper slide plate, a bottom plate is provided at the bottom of the frame, an upper lifting oil cylinder and a lower slide plate that can slide left and right are provided on the bottom plate, a through hole is provided on the lower slide plate, a blanking cylinder and a lifting frame are fixedly arranged on the lower slide plate, a left lower limit seat and a right lower limit seat are respectively provided on the left and right sides of the bottom plate, the left lower limit seat is vertically aligned with the left upper limit seat, when the lower slide plate abuts against the right lower limit seat, the blanking cylinder is coaxially aligned with the discharge hopper, a lower pressing head is movably and sealingly arranged in the blanking cylinder, a material pushing cylinder is provided on the bottom plate, a strong magnetic block is provided on the piston rod of the material pushing cylinder, a hinge seat is hinged on the lifting frame, a lifting cylinder is provided on the hinge seat, the piston rod of the lifting cylinder is connected to a support plate, two rows of linear bearings are provided on the support plate, guide rods are slidably arranged in the linear bearings on the same side, the guide rods are fixed in the hinge seat, a removable middle material cylinder is provided on the support plate, a turning cylinder is hinged on the lifting frame, a connecting shaft plate is arranged between the two guide rods, the piston rod of the turning cylinder is hinged to the connecting shaft plate, vertical limit seats are provided at both the front and rear ends of the lifting frame, pin holes are provided on the side walls of the feeding cylinder, the middle material cylinder and the blanking cylinder, the bottom end of the feeding cylinder can be docked with the top end of the middle material cylinder, the bottom end of the middle material cylinder can be docked with the top end of the blanking cylinder, and a feeding mechanism capable of feeding materials into the discharge hopper is provided on the frame.

[0005] Further, in the above-mentioned three-stage center-to-center pressing pre-pressing forming machine, the feeding mechanism includes: the connection structure between the feeding hopper and the frame is: a fixing plate provided at the rear side of the frame, two guide rail seats and a double-shaft reduction motor are vertically arranged on the fixing plate, driving gears are connected to the two output shafts of the double-shaft reduction motor, a rotating shaft is rotatably arranged between the tops of the two guide rail seats, driven gears are arranged at both ends of the rotating shaft, transmission chains are connected between the driving gears and the driven gears on the same side, chain connection pins are arranged on both sides of the transmission chains, a connecting shaft is rotatably arranged between the two chain connection pins, straight guide rails are arranged on the guide rail seats, arc-shaped guide rails are extended at the tops of the straight guide rails, the arc-shaped guide rails are connected to the top plate, guide wheels are rollably arranged in the two straight guide rails, a moving shaft is rotatably arranged between the two guide wheels, a feeding hopper is arranged between the connecting shaft and the moving shaft, and the moving shaft is located at the discharging end of the feeding hopper.

[0006] Further, for the aforementioned three-stage center-to-center pressing preforming machine, a chute is provided at the top of the guide rail base, a sprocket slider is slidably clamped in the chute, the rotating shaft is rotatably arranged in the sprocket slider, an adjusting block is arranged on the chute, an adjusting bolt is threadedly connected in the adjusting block, and the adjusting bolt is rotatably clamped in the sprocket slider.

[0007] Further, for the aforementioned three-stage center-to-center pressing preforming machine, the connection structure between the discharge hopper and the top plate is as follows: a fixed frame is surrounded on the outer side wall of the discharge hopper, four upper spring seats are arranged around the fixed frame, a buffer frame is arranged below the fixed frame, four lower spring seats are arranged around the buffer frame, buffer springs are arranged between the upper spring seats and the lower spring seats that are aligned vertically, four sliding sleeves are arranged on the buffer frame, the four sliding sleeves are symmetric in pairs, four guide posts are arranged on the top plate, the four sliding sleeves are slidably arranged on the four guide posts, two mounting blocks are symmetrically arranged on the buffer frame, two pulling air cylinders are arranged on the top plate, and the piston rods on the two pulling air cylinders are respectively connected to the two mounting blocks.

[0008] Further, for the aforementioned three-stage center-to-center pressing preforming machine, a material shielding plate is sleeved on the discharge end of the discharge hopper, and a vibration motor is arranged on the fixed frame.

[0009] Further, for the aforementioned three-stage center-to-center pressing preforming machine, the connection structure between the orifice plate and the machine frame is as follows: an intermediate plate is arranged on the machine frame, an avoidance hole is opened on the intermediate plate, four columns are arranged between the intermediate plate and the top plate, the four columns are symmetric in pairs, two lifting air cylinders are symmetrically arranged on the intermediate plate, the piston rod of the lifting air cylinder is connected to the orifice plate, a reinforcing plate is slidably arranged between the two columns on the same side, two reinforcing rods are arranged between the reinforcing plate and the orifice plate, two chain screws are symmetrically arranged on the front and rear sides of the left side wall of the upper slide plate, a counterweight chain is connected to the chain screw, a counterweight block is connected to the counterweight chain, two gear seats are symmetrically arranged on the front and rear sides of the left side wall of the orifice plate, a counterweight sprocket is rotatably arranged on the gear seat, the counterweight chain is connected to the counterweight sprocket on the same side, two upper guide rails are symmetrically arranged on the front and rear sides of the orifice plate, a plurality of upper sliders are symmetrically arranged on the front and rear sides of the upper slide plate, the upper sliders are slidably clamped on the corresponding side of the upper guide rail, a mounting hole is arranged on the upper slide plate, and an upper hoop coaxial with the mounting hole is arranged on the upper slide plate, and the upper hoop clamps the feeding cylinder.

[0010] Further, for the aforementioned three-stage center-to-center pressing preforming machine, a first positioning ring is sleeved at the bottom end of the feeding cylinder. The first positioning ring extends downward beyond the feeding cylinder. The distance between the bottom wall of the first positioning ring and the bottom wall of the feeding cylinder is H. A first limiting ring is sleeved at the top end of the middle feeding cylinder. The distance between the top wall of the first limiting ring and the top wall of the middle feeding cylinder is also H. A second positioning ring is sleeved at the bottom end of the middle feeding cylinder. The second positioning ring extends downward beyond the middle feeding cylinder. The distance between the bottom wall of the second positioning ring and the bottom wall of the middle feeding cylinder is h. A second limiting ring is sleeved at the top end of the discharging cylinder. The distance between the top wall of the second limiting ring and the top wall of the discharging cylinder is also h.

[0011] Further, for the aforementioned three-stage center-to-center pressing preforming machine, the connection structure between the support plate and the middle feeding cylinder is as follows: positioning plates are provided at both the upper and lower ends of the support plate. Arc-shaped holes are provided on the positioning plates. Clamping plates are rotatably arranged on the positioning plates. Arc-shaped holes are also provided on the clamping plates. After the clamping plates and the positioning plates are rotationally aligned, the middle feeding cylinder is clamped through the two arc-shaped holes. A lower hoop is arranged surrounding the outer side wall of the middle feeding cylinder. The lower hoop abuts against the positioning plate and the clamping plate located at the upper end of the support plate. A locking member capable of locking the positioning plate and the clamping plate is provided between the positioning plate and the clamping plate. The locking member includes: a sliding sleeve seat fixed on the side wall of the positioning plate and a top block fixed on the side wall of the clamping plate. A top rod is slidably arranged at one end of the sliding sleeve seat close to the top block. A grip is hinged at one end of the sliding sleeve seat far from the top block. A connecting rod is hinged between the grip and the top rod. An adjusting screw is threadedly connected to one end of the top rod close to the top block. A locking nut is threadedly connected to the adjusting screw. The locking nut is screwed and abuts against the top rod.

[0012] Further, for the aforementioned three-stage center-to-center pressing preforming machine, two lower guide rails are provided on the bottom plate. A push-pull cylinder is horizontally arranged on the bottom plate between the two lower guide rails. The piston rod of the push-pull cylinder is connected to the lower sliding plate. A plurality of lower sliding blocks are provided on the front and rear sides of the lower sliding plate. The lower sliding blocks are slidably clamped on the corresponding lower guide rails.

[0013] The method for using the three-stage center-to-center pre-pressing forming machine is as follows: the middle barrel is mounted on the support plate, the flip cylinder pushes the support plate to a vertical state, the middle barrel and the lower barrel are coaxially aligned, the lifting cylinder drives the support plate to descend, the middle barrel and the lower barrel are docked, the lower slide plate moves to the left and rests on the lower left limit seat, the middle barrel and the upper barrel are coaxially aligned, the orifice plate drives the upper barrel to descend, the upper barrel and the middle barrel are docked, and the lower slide plate carries the docked lower barrel, middle barrel and The upper barrel moves to the right and abuts against the lower right limit seat, the discharge hopper presses downward against the upper barrel, the feeding mechanism feeds the plastic into the discharge hopper and flows from the discharge hopper into the docked lower barrel, middle barrel and upper barrel. After the discharge is completed, the discharge hopper rises and leaves the upper barrel, and the lower slide drives the docked lower barrel, middle barrel and upper barrel to move to the left and abut against the lower left limit seat, the lower push cylinder drives the upper pressure head to extend into the upper barrel, and the upper push cylinder passes through the lower The slide plate extends into the lower barrel and pushes the lower pressure head. The upper and lower pressure heads squeeze the plastic at the same time, so that the plastic is compacted in the middle barrel. The lower push cylinder drives the upper pressure head to reset upward and disengage from the upper barrel, and the upper lifting cylinder resets downward and disengages from the lower slide plate. The orifice plate drives the upper barrel to rise and disengage from the middle barrel. The lower slide drives the middle barrel and the lower barrel to move right and rest against the right lower limit seat. The lifting cylinder drives the strong magnetic block to pass through the lower slide and adsorb on the lower pressure head and push the lower pressure head to the top of the lower barrel. The lifting cylinder drives the pallet to rise, and the middle barrel is separated from the lower barrel. The flip cylinder pushes the pallet and the middle barrel on the pallet to rotate to a horizontal state. The upper pressure head blocks the dense plastic from falling out of the middle barrel, and the lifting cylinder drives the strong magnetic block to reset downward with the lower pressure head. The lower pressure head returns to the lower barrel, and the staff removes the middle barrel filled with dense plastic from the pallet, and then installs the new middle barrel on the pallet.

[0014] The advantages of the present invention are: the upper pressure head and the lower pressure head extrude the plastic at the same time, and the bidirectional extrusion applies pressure on both sides at the same time, which effectively offsets the attenuation effect of friction, makes the overall force of the material more uniform, the density distribution more consistent, and reduces the internal loose area, and the bidirectional extrusion compresses the plastic from two directions, forcing the bubbles to be discharged outward through the pinholes, thereby reducing internal defects and improving the compactness of the plastic. The upper pressure head and the lower pressure head apply force at the same time to perform bidirectional extrusion, which can compact the plastic and accumulate it in the middle barrel, and then rotate the middle barrel to a horizontal state and remove it from the pallet, transport the middle barrel filled with dense plastic to the next station for material collection, and install the new middle barrel on the pallet to re-perform pre-compression work, so that the staff can continue to perform pre-compression work while the equipment is taking the material, thereby improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the three-stage center-pressure pre-pressing molding machine described in the present invention.

[0016] Figure 2 yes Figure 1Schematic diagram of the connection structure between the middle discharge hopper and the top plate.

[0017] Figure 3 is Figure 1 Schematic diagram of the connection structure between the upper feeding cylinder and the frame in the above.

[0018] Figure 4 is Figure 3 The sectional structure schematic diagram in the above.

[0019] Figure 5 is Figure 1 Schematic diagram of the connection structure between the lower feeding cylinder and the middle feeding cylinder and the bottom plate in the above.

[0020] Figure 6 is Figure 5 The sectional structure schematic diagram in the above.

[0021] Figure 7 is Figure 5 Schematic diagram of the connection structure between the middle support plate and the middle feeding cylinder in the above.

[0022] Figure 8 Schematic diagram of the structures of the upper feeding cylinder, the middle feeding cylinder and the lower feeding cylinder.

[0023] Figure 9 is Figure 1 Schematic diagram of the structure of the middle feeding mechanism in the above.

[0024] Figure 10 Schematic diagram of the structure of the three-stage center-to-center pressing preforming machine according to the present invention when disassembling and assembling the middle feeding cylinder. Detailed implementation manners

[0025] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0026] As Figures 1 to 10As shown in the figure, the three-stage center-to-center pressing pre-forming machine of the present invention includes: a frame 1, a top plate 11 is provided at the top of the frame 1, a liftable discharge hopper 2 and a lower push oil cylinder 12 are provided on the top plate 11, an upper pressing head 121 is provided on the lower push oil cylinder 12, and a liftable hole plate 13 is provided on the frame 1 below the top plate 11. The connection structure between the hole plate 13 and the frame 1 is as follows: an intermediate plate 15 is provided on the frame 1, an avoidance hole is opened on the intermediate plate 15, four upright columns 151 are provided between the intermediate plate 15 and the top plate 11, the four upright columns 151 are symmetric in pairs, two lifting cylinders 152 are symmetrically provided on the intermediate plate 15, and the piston rod of the lifting cylinder 152 is connected to the hole plate 13. A reinforcing plate 153 is slidably provided between two upright columns 151 on the same side, and two reinforcing rods 154 are provided between the reinforcing plate 153 and the hole plate 13. The lifting cylinder 152 can drive the hole plate 13 to lift and lower. By adding the reinforcing rods 154 and the reinforcing plate 153, the lifting stability of the hole plate 13 can be improved. Two upper guide rails 131 are symmetrically provided on the front and rear of the hole plate 13, upper sliders 132 are slidably clamped on the upper guide rails 131 left and right, an upper slide plate 133 is provided between the upper sliders 132, an installation hole is provided on the upper slide plate 133, and an upper hoop 1331 coaxial with the installation hole is provided on the upper slide plate 133. A feeding cylinder 3 is provided in the installation hole. The feeding cylinder 3 extends downward beyond the intermediate plate 15 after passing through the hole plate 13 and the avoidance hole of the intermediate plate 15. The upper hoop 1331 clamps on the feeding cylinder 3 to fix the feeding cylinder 3 on the upper slide plate 133. A left upper limit seat 134 is provided on the left side of the hole plate 13. When the upper slide plate 133 abuts against the left upper limit seat 134, the feeding cylinder 3 is coaxially aligned with the upper pressing head 121. Two chain screws are symmetrically provided on the front and rear of the left side wall of the upper slide plate 133. A counterweight chain 1332 is connected to the chain screws, and a counterweight block 1333 is connected to the counterweight chain 1332. Two gear seats are symmetrically provided on the front and rear of the left side wall of the hole plate 13. A counterweight sprocket 135 is rotatably provided on the gear seat. The counterweight chain 1332 is connected to the counterweight sprocket 135 on the same side. The upper slide plate 133 will automatically abut against the left upper limit seat 134 under the gravity pull of the counterweight block 1333 and be coaxially aligned with the upper pressing head 121 on the lower push oil cylinder 12.

[0027] A bottom plate 14 is provided at the bottom of the frame 1. An upper jacking oil cylinder 141 and a lower sliding plate 142 that can slide left and right are provided on the bottom plate 14. Two lower guide rails 143 are provided on the bottom plate 14. A push-pull air cylinder 144 is horizontally provided on the bottom plate 14 between the two lower guide rails 143. The piston rod of the push-pull air cylinder 144 is connected to the lower sliding plate 142. A number of lower sliding blocks 1421 are provided on the front and rear sides of the lower sliding plate 142. The lower sliding blocks 1421 are slidably clamped on the corresponding side of the lower guide rail 143. A lower left limit seat 145 and a lower right limit seat 146 are respectively provided on the left and right sides of the bottom plate 14. The lower left limit seat 145 is vertically aligned with the upper left limit seat 134. A through hole 1422 is provided on the lower sliding plate 142. A blanking cylinder 4 is connected to the lower sliding plate 142 by bolts. The blanking cylinder 4 is coaxially aligned with the through hole 1422. An elevated frame 5 is fixedly provided on the lower sliding plate 142. When the push-pull air cylinder 144 drives the lower sliding plate 142 to abut against the lower left limit seat 145, the blanking cylinder 4 is coaxially aligned with the feeding cylinder 3 on the upper sliding plate 133 that abuts against the upper left limit seat 134 and the upper jacking oil cylinder 141. When the push-pull air cylinder 144 drives the lower sliding plate 142 to abut against the lower right limit seat 146, the blanking cylinder 4 is coaxially aligned with the discharge hopper 2. A lower pressing head 41 is movably and sealingly provided in the blanking cylinder 4. The lower pressing head 41 abuts against the lower sliding plate 142 under its own weight. A material pushing air cylinder 147 is provided on the bottom plate 14. A strong magnetic block 1471 is provided on the piston rod of the material pushing air cylinder 147. When the material pushing air cylinder 147 is in a contracted state, the strong magnetic block 1471 does not interfere with the movement of the lower sliding plate 142. When the lower sliding plate 142 abuts against the lower right limit seat 146, the through hole 1422 on the lower sliding plate 142 is vertically aligned with the material pushing air cylinder 147. The piston rod in the material pushing air cylinder 147 passes upward through the through hole 1422 on the lower sliding plate 142 and contacts the lower pressing head 41 in the blanking cylinder 4, so as to be able to push the lower pressing head 41 upward.

[0028] A hinge seat 51 is hinged on the elevated frame 5. A lifting cylinder 52 is arranged on the hinge seat 51. The piston rod of the lifting cylinder 52 is connected to the support plate 6. Two rows of linear bearings 61 are arranged on the support plate 6. Guide rods 62 are slidably arranged in the linear bearings 61 on the same side. The guide rods 62 are fixed in the hinge seat 51. A detachable middle material cylinder 7 is arranged on the support plate 6. A turning cylinder 53 is hinged on the elevated frame 5. A coupling plate 63 is arranged between the two guide rods 62. The piston rod of the turning cylinder 53 is hinged to the coupling plate 63. Vertical limit seats 54 are arranged at both the front and rear ends of the elevated frame 5. When the piston rod in the turning cylinder 53 extends, it can push the support plate 6 and the hinge seat 51 connected to the support plate 6 to rotate counterclockwise through the coupling plate 63. When the support plate 6 rotates and abuts against the vertical limit seat 54, the support plate 6 and the middle material cylinder 7 on the support plate 6 are in a vertical state, and the lifting cylinder 52 can drive the support plate 6 to lift and lower. When the piston rod in the turning cylinder 53 contracts, it can pull the support plate 6 to rotate clockwise. When the piston rod in the turning cylinder 53 contracts in place, the support plate 6 rotates to a horizontal state.

[0029] Pin holes are arranged on the side walls of the feeding cylinder 3, the middle material cylinder 7 and the discharging cylinder 4. A first positioning ring 31 is sleeved at the bottom end of the feeding cylinder 3. The first positioning ring 31 extends downward from the feeding cylinder 3. The distance between the bottom wall of the first positioning ring 31 and the bottom wall of the feeding cylinder 3 is H. A first limiting ring 71 is sleeved at the top end of the middle material cylinder 7. The distance between the top wall of the first limiting ring 71 and the top wall of the middle material cylinder 7 is also H. When the feeding cylinder 3 is docked with the middle material cylinder 7, the bottom wall of the feeding cylinder 3 abuts against the top wall of the middle material cylinder 7. The first positioning ring 31 on the feeding cylinder 3 is sleeved on the outer side wall of the middle material cylinder 7 and abuts against the first limiting ring 71 of the middle material cylinder 7. A second positioning ring 72 is sleeved at the bottom end of the middle material cylinder 7. The second positioning ring 72 extends downward from the middle material cylinder 7. The distance between the bottom wall of the second positioning ring 72 and the bottom wall of the middle material cylinder 7 is h. A second limiting ring 42 is sleeved at the top end of the discharging cylinder 4. The distance between the top wall of the second limiting ring 42 and the top wall of the discharging cylinder 4 is also h. When the middle material cylinder 7 is docked with the discharging cylinder 4, the bottom wall of the middle material cylinder 7 abuts against the top wall of the discharging cylinder 4. The second positioning ring 7 on the middle material cylinder 7 is sleeved on the outer side wall of the discharging cylinder 4 and abuts against the second limiting ring 42 of the discharging cylinder 4.

[0030] A feeding mechanism 8 capable of feeding materials into the discharge hopper 2 is arranged on the frame 1. The feeding mechanism 8 includes: a fixing plate 81 arranged at the rear side of the frame 1. In this embodiment, the load of the frame 1 is relatively heavy. In order to improve the installation strength of the frame 1, the support feet are generally embedded underground, and then the bottom plate 14 is fixed on the support feet and abuts against the ground. However, the load of the feeding mechanism 8 is relatively light, so the fixing plate 81 is directly connected to the ground. Figure 1 and Figure 10As can be seen, the fixed plate 81 is flush with the bottom plate 14. Two guide rail seats 811 and a double-shaft reduction motor 812 are vertically arranged on the fixed plate 81. Driving gears 82 are connected to the two output shafts of the double-shaft reduction motor 812. A chute is formed at the top of the guide rail seat 811. A sprocket slider 83 is slidably clamped in the chute. An adjusting block 831 is arranged on the chute. An adjusting bolt 832 is threadedly connected to the adjusting block 831. The adjusting bolt 832 is rotatably clamped in the sprocket slider 83. A rotating shaft 813 is rotatably arranged between the sprocket sliders 83 of the two guide rail seats 811. Driven gears 814 are arranged at both ends of the rotating shaft 813. A transmission chain is connected between the driving gear 82 and the driven gear 814 on the same side. The transmission chain is not shown in the figure. By rotating the adjusting bolt 832, the vertical position of the sprocket slider 83 can be adjusted through the threaded transmission between the adjusting bolt 832 and the adjusting block 831, so as to adjust the tension of the transmission chain. Chain connection pins 84 are arranged on both sides of the transmission chain. The connection structure between the chain connection pin 84 and the transmission chain is the prior art. In the case where the transmission chain is not shown, those skilled in the art know the connection structure between the chain connection pin 84 and the transmission chain. A connecting shaft 841 is rotatably arranged between the two chain connection pins 84. A straight guide rail 85 is arranged on the guide rail seat 811. An arc guide rail 851 extends at the top of the straight guide rail 85. The arc guide rail 851 is connected to the top plate 11. Guide wheels 86 are rotatably arranged in the two straight guide rails 85. A moving shaft 861 is rotatably arranged between the two guide wheels 86. A feeding hopper 87 is arranged between the connecting shaft 841 and the moving shaft 861. The moving shaft 861 is located at the discharging end of the feeding hopper 87. Starting the double-shaft reduction motor 812 can drive the transmission chain to move clockwise or counterclockwise between the driving gear 82 and the driven gear 814, thereby driving the chain connection pin 84 to move up and down. During the up and down movement of the two chain connection pins 84, the feeding hopper 87 will be driven to move up and down through the connecting shaft 841. During the up and down movement of the feeding hopper 87, the two guide wheels 86 will be driven to move along the straight guide rail 85 and the arc guide rail 851 through the moving shaft 861. When the guide wheel 86 enters the arc guide rail 851, the feeding hopper 8 will rotate, and the discharging end of the feeding hopper 8 will be tilted onto the discharging hopper 2 on the top plate 11, so as to pour the materials in the feeding hopper 8 into the discharging hopper 2.

[0031] In use, the middle cartridge 7 is installed on the pallet 6 in a horizontal state, and then the pallet 6 is rotated to a vertical state by the flipping cylinder 53. At this time, the middle cartridge 7 is coaxially aligned with the lower cartridge 4. Then, the pallet 6 and the middle cartridge 7 on the pallet 6 are driven to descend by the lifting cylinder 52 until the lower end of the middle cartridge 7 is engaged with the upper end of the lower cartridge 4. Then, the sliding plate 142 is driven to move leftward by the push-pull cylinder 144 until the sliding plate 142 abuts against the lower left limit seat 145. At this time, the butted lower cartridge 4 and middle cartridge 7 are both coaxially aligned with the upper cartridge 3 on the upper sliding plate 133 that abuts against the upper left limit seat 134. The orifice plate 13 descends to dock the upper cartridge 3 and the middle cartridge 7. The push-pull cylinder 144 drives the sliding plate 142 to move rightward until the sliding plate 142 abuts against the lower right limit seat 146. Since the upper cartridge 3 and the middle cartridge 7 are docked, the sliding plate 142 will drive the upper sliding plate 133 and the upper cartridge 3 to move rightward together during the rightward movement. In order to prevent the discharge hopper 2 from interfering with the movement of the upper cartridge 3, the discharge hopper 2 needs to be lifted upward. When the sliding plate 142 abuts against the lower right limit seat 146, the butted upper cartridge 3, middle cartridge 7 and lower cartridge 4 are coaxially aligned with the discharge hopper 2. Then, the discharge hopper 2 descends and extends into the upper cartridge 3, and the plastic is poured into the feed hopper 87 in the feeding mechanism 8. The feed hopper 87 moves along the straight guide rail 85 and the arc guide rail 851 driven by the transmission chain. When the feed hopper 87 flips, the plastic is poured into the discharge hopper 2, and then flows into the lower cartridge 4, middle cartridge 7 and upper cartridge 3 from the discharge hopper 2. Since the lower cartridge 4 is blocked by the lower pressing head 41, the plastic will not overflow. At the same time, the pinhole apertures on the side walls of the upper cartridge 3, middle cartridge 7 and lower cartridge 4 are relatively small, and the plastic has a high viscosity and a large surface tension, so the plastic cannot overflow from the pinholes. After the feeding work is completed, the discharge hopper 2 is lifted upward, and the push-pull cylinder 144 drives the sliding plate 142 to move leftward again until the sliding plate 142 abuts against the lower left limit seat 145. The lower push cylinder 12 drives the upper pressing head 121 to extend into the upper cartridge 3, and the upper pressing head 121 is movably sealed with the upper cartridge 3. The piston rod of the upper lifting cylinder 141 passes through the through hole 1422 on the sliding plate 142 and extends into the lower cartridge 4 to abut against the lower pressing head 41. Then, the lower push cylinder 12 and the upper lifting cylinder 141 are started simultaneously. The lower push cylinder 12 drives the upper pressing head 121 to squeeze the plastic downward, and the upper lifting cylinder 141 drives the lower pressing head 41 to squeeze the plastic upward. The plastic will be compacted in the middle cartridge 7 under the double-sided extrusion of the upper pressing head 121 and the lower pressing head 41. During the extrusion process, the air in the plastic is discharged outward through the pinholes. After the extrusion is completed, the lower push cylinder 12 drives the upper pressing head 121 to move upward away from the upper cartridge 3, and the upper lifting cylinder 141 drives the piston rod to move downward away from the lower cartridge 4 and the sliding plate 142. When the lower pressing head 41 loses the support of the upper lifting cylinder 141, the compacted plastic and the lower pressing head 41 are likely to fall into the lower cartridge 4 under their own weight. The orifice plate 13 rises to separate the upper cartridge 3 from the middle cartridge 7.Under the pulling force of the counterweight 1333, the upper slide plate 133 abuts against the upper left limit seat 134. The push-pull cylinder 144 drives the lower slide plate 142 to move rightward again until the lower slide plate 142 abuts against the lower right limit seat 146. At this time, the through hole 1422 on the lower slide plate 142 is vertically aligned with the ejector cylinder 147. The ejector cylinder 147 drives the strong magnetic block 1471 to pass upward through the through hole 1422 and then magnetically attracts the lower pressing head 41, and then pushes the lower pressing head 41 upward to push the lower pressing head 41 to the top of the blanking cylinder 4. At this time, the dense plastic stacked on the lower pressing head 41 is in the middle material cylinder 7. Then the lifting cylinder 52 drives the support plate 6 to rise, and the middle material cylinder 7 on the support plate 6 is separated from the blanking cylinder 4. Then the flipping cylinder 53 is used to push the support plate 6 and the middle material cylinder 7 to rotate to the horizontal state. During the flipping process, the dense plastic will flip together with the middle material cylinder 7. The lower pressing head 41 blocks the dense plastic to prevent the dense plastic from falling out of the middle material cylinder 7. When the dense plastic flips together with the middle material cylinder 7, the contact surface with the lower pressing head 41 will be reduced. During the tilting process of the middle material cylinder 7, the adhesion strength between the dense plastic and the side wall of the middle material cylinder 7 will increase under the action of gravity. Therefore, the closer the middle material cylinder 7 is to the horizontal state, the greater the adhesion strength between the dense plastic and the middle material cylinder 7. So the lower pressing head 41 only needs to block the dense plastic when the middle material cylinder 7 is in the vertical state. After the middle material cylinder 7 starts to tilt, the dense plastic is not easy to fall out of the middle material cylinder 7. After the middle material cylinder 7 rotates to the horizontal state, the ejector cylinder 147 drives the strong magnetic block 1471 to retract with the lower pressing head 41 in place. The lower pressing head 41 returns to the blanking cylinder 4, and the strong magnetic block 1471 retracts to a position where it does not interfere with the movement of the lower slide plate 142. The staff removes the middle material cylinder 7 filled with dense plastic from the support plate 6 and sends it to the next station for processing, and then installs the empty middle material cylinder 7 on the support plate 6 for subsequent work.,

[0032] In order to improve the connection strength and disassembly and assembly efficiency between the middle barrel 7 and the pallet 6, in this embodiment, the connection structure between the pallet 6 and the middle barrel 7 is as follows: positioning plates 64 are provided at both the upper and lower ends of the pallet 6. Arc-shaped holes are provided on the positioning plates 64. A transfer plate 641 is rotatably provided on the positioning plates 64. A clamping plate 65 is provided on the transfer plate 641. Arc-shaped holes are also provided on the clamping plate 65. After the clamping plate 65 and the positioning plate 64 are rotationally aligned, the middle barrel 7 is clamped through the two arc-shaped holes. A lower retaining hoop 73 is provided around the outer side wall of the middle barrel 7. The lower retaining hoop 73 abuts against the positioning plate 64 and the clamping plate 65 located at the upper end of the pallet 6. The positioning plate 64 and the clamping plate 65 located at the lower end of the pallet 6 abut against the second positioning ring 72 of the middle barrel 7. A locking member capable of locking the positioning plate 64 and the clamping plate 65 is provided between the positioning plate 64 and the clamping plate 65. The locking member includes: a sliding sleeve seat 66 fixed on the side wall of the positioning plate 64 and a top block 67 fixed on the side wall of the clamping plate 65. A top rod 661 is slidably provided at one end of the sliding sleeve seat 66 close to the top block 67. A grip 662 is hinged at the end of the sliding sleeve seat 66 away from the top block 67. A connecting rod 663 is hinged between the grip 662 and the top rod 661. An adjusting screw 664 is threadedly connected to one end of the top rod 661 close to the top block 67. A locking nut 665 is threadedly connected to the adjusting screw 664. The locking nut 665 is screwed and abuts against the top rod 661 to lock the adjusting screw 664. When disassembling and assembling the middle barrel 7, the pallet 6 is rotated to a horizontal state, the lower retaining hoop 73 is removed, and then the grip 662 is pulled in a direction away from the top block 67. The grip 662 pulls the top rod 661 away from the top block 67 through the connecting rod 663. The clamping plate 65 is opened, and the middle barrel 7 filled with dense plastic can be taken out from the positioning plate 64. Then, the new middle barrel 7 is placed in the arc-shaped holes of the two positioning plates 64. The second positioning ring 72 of the new middle barrel 7 abuts against the positioning plate 64 and the clamping plate 65 located at the lower end of the pallet 6. In this way, the new middle barrel 7 can be quickly positioned. When the pallet 6 is in a horizontal state, the positioning plate 64 and the clamping plate 65 located at the lower end of the pallet 6 are on the left side. Then, the clamping plate 65 is rotated and aligned. Then, the grip 66 is pulled in the direction of the top block 67, driving the top rod 661 to abut against the top block 67, so that the positioning plate 64 corresponding to the clamping plate 65 clamps the middle barrel 7. Then, the lower retaining hoop 73 is put on the middle barrel 7 and abuts against the positioning plate 64 and the clamping plate 65 located at the upper end of the pallet 6.

[0033] When compressing different types of plastics, since the compression ratios of different types of plastics are different, it is necessary to replace the feeding cylinder 3, the middle cylinder 7 and the discharging cylinder 4 with different diameters according to different types of plastics. When replacing the feeding cylinder 3, only by replacing the matching upper hoop 1331 can the feeding cylinder 3 with different diameters be fixed on the upper slide plate 133. When replacing the discharging cylinder 4, it can be directly fixed on the lower slide plate 142 through bolts. When replacing the middle cylinder 7, not only the matching lower hoop 73 needs to be replaced, but also the adjusting screw 664 needs to be screwed to extend or shorten the length of the ejector rod 661. After the length of the ejector rod 661 is extended, when the ejector rod 661 pushes against the top block 67, the rotation angle of the clamping plate 65 will increase, thereby reducing the clamping aperture between the clamping plate 65 and the positioning plate 64, and the clamping plate 65 and the positioning plate 64 can clamp the middle cylinder 7 with a smaller diameter. When the length of the ejector rod 661 is shortened, when the ejector rod 661 pushes against the top block 67, the rotation angle of the clamping plate 65 will decrease, thereby increasing the clamping aperture between the clamping plate 65 and the positioning plate 64, and the clamping plate 65 and the positioning plate 64 can clamp the middle cylinder 7 with a larger diameter, improving the scope of application.

[0034] In this embodiment, the connection structure between the discharge hopper 2 and the top plate 11 is as follows: a fixed frame 21 is provided around the outer side wall of the discharge hopper 2. Four upper spring seats 211 are provided around the fixed frame 21. A buffer frame 22 is provided below the fixed frame 21. Four lower spring seats 221 are provided around the buffer frame 22. A buffer spring 23 is provided between the upper spring seat 211 and the lower spring seat 221 that are aligned vertically. Four sliding sleeves 222 are provided on the buffer frame 22, and the four sliding sleeves 222 are symmetrically arranged in pairs. Four guide posts 111 are provided on the top plate 11, and the four sliding sleeves 222 are slidably arranged on the four guide posts 111. Two mounting blocks 223 are symmetrically provided on the buffer frame 22. Two pulling cylinders 112 are provided on the top plate 11, and the piston rods on the two pulling cylinders 112 are respectively connected to the two mounting blocks 223. A shielding plate 24 is sleeved on the discharge end of the discharge hopper 2, and a vibration motor 212 is provided on the fixed frame 21. The pulling cylinder 112 can drive the discharge hopper 2 to lift and lower. When the feeding cylinder 3 and the discharge hopper 2 are coaxially aligned, the pulling cylinder 112 drives the discharge hopper 2 to descend, and the discharge hopper 2 extends into the feeding cylinder 3. The shielding plate 24 on the discharge hopper 2 abuts against the feeding cylinder 3 to play a limiting role. When the discharge hopper 2 discharges materials, the vibration of the vibration motor 212 can improve the discharging effect and efficiency of the plastic. Due to the buffering effect of the buffer spring 23 when the vibration motor 212 vibrates the discharge hopper 2, the vibration effect will not be transmitted to the top plate 11 to cause resonance.

[0035] In this embodiment, the automation degree and operation precision are improved by adding some inductive switches electrically connected to the PLC device. The pulling cylinder 112 is a through-type cylinder, that is, the piston rod of the pulling cylinder 112 penetrates the whole cylinder and extends out from both ends. The upper end of the piston rod of the pulling cylinder 112 is connected to the mounting block 223. A first induction block 1121 is arranged at the lower end of the piston rod of the pulling cylinder 112. A first switch support rod 1122 is vertically arranged on the pulling cylinder 112. A first upper limit induction switch 1123 and a first lower limit induction switch 1124 are respectively arranged at the upper and lower ends of the first switch support rod 1122. When the pulling cylinder 112 drives the discharge hopper 2 to lift or lower, the first induction block 1121 on the pulling cylinder 112 can be sensed by the first upper limit induction switch 1123 or the first lower limit induction switch 1124. When the first induction block 1121 on the pulling cylinder 112 is sensed by the first upper limit induction switch 1123, it indicates that the discharge hopper 2 has risen to the position where it will not interfere with the movement of the feeding cylinder 3. When the first induction block 1121 on the pulling cylinder 112 is sensed by the first lower limit induction switch 1124, it indicates that the discharge hopper 2 has descended to extend into the feeding cylinder 3 and the material shielding plate 24 on the discharge hopper 2 abuts against the feeding cylinder 3.

[0036] The lifting cylinder 152 is also a through-type cylinder. A second induction block 1521 is arranged at the lower end of the piston rod of the lifting cylinder 152. A second switch support rod 155 is arranged on the middle plate 15. A second upper limit induction switch 1551 and a second lower limit induction switch 1552 are respectively arranged at the upper and lower ends of the second switch support rod 155. When the lifting cylinder 152 drives the orifice plate 13 to lift or lower, the second induction block 1521 on the lifting cylinder 152 can be sensed by the second upper limit induction switch 1551 or the second lower limit induction switch 1552. When the second induction block 1521 is sensed by the second upper limit induction switch 1551, it indicates that the feeding cylinder 3 on the orifice plate 13 has moved upward to a height position where it is separated from the middle material cylinder 7. When the second induction block 1521 is sensed by the second lower limit induction switch 1552, it indicates that the feeding cylinder 3 on the orifice plate 13 has moved downward and is clamped in place with the middle material cylinder 7.

[0037] On the left and right sides of the orifice plate 13, a left induction switch 136 and a right induction switch 137 are respectively arranged. The distance between the left induction switch 136 and the right induction switch 137 is greater than the left and right width of the upper slide plate 133. When the upper slide plate 133 abuts against the upper left limit seat 134, the left induction switch 136 senses the upper slide plate 133, and the right induction switch 137 does not sense the upper slide plate 133. If at this time the second upper limit induction switch 1551 senses the second induction block 1521, it indicates that the orifice plate 13 and the feeding cylinder 3 are in a lifting state, that is, the feeding cylinder 3 and the middle material cylinder 7 are in a separated state and the feeding has not been completed. The lower push oil cylinder 12 and the upper top oil cylinder 141 will not act. If at this time the second lower limit induction switch 1552 senses the second induction block 1521, it indicates that the orifice plate 13 and the feeding cylinder 3 are in a descending state, that is, the feeding cylinder 3 and the middle material cylinder 7 are in a butting state and the feeding has been completed. The lower push oil cylinder 12 and the upper top oil cylinder 141 will start to act. When the upper slide plate 133 moves to the right and is sensed by the right induction switch 137 and the left induction switch 136 does not sense the upper slide plate 133, the lower slide plate 142 abuts against the lower right limit seat 146. Since the upper slide plate 133 must rely on the push-pull cylinder 144 to drive the lower slide plate 142 to move to the right, when the upper slide plate 133 is sensed by the right induction switch 137, it indicates that the feeding cylinder 3, the middle material cylinder 7 and the discharging cylinder 4 are butted together in sequence and are coaxially aligned with the discharging hopper 2. The feeding mechanism 8 can send the plastic into the discharging hopper 2 and then flow into the butted feeding cylinder 3, middle material cylinder 7 and discharging cylinder 4.

[0038] A tension sensor 113 and a transition roller 114 are arranged on the top plate 11. The pull rope in the tension sensor 113 bypasses the transition roller 114 and is connected to the upper pressing head 121. When the lower push oil cylinder 12 drives the upper pressing head 121 to move downward, it will pull the pull rope in the tension sensor 113. The tension sensor 113 can record the running speed and distance of the upper pressing head 121, which is convenient for PLC control. A third upper limit induction switch 115 is arranged on the top plate 11. The third upper limit induction switch 115 cooperates with the upper pressing head 121. When the upper pressing head 121 is reset upward to the position where it is sensed by the third upper limit induction switch 115, it indicates that the upper pressing head 121 has risen to a position where it will not interfere with the movement of the feeding cylinder 3. A third lower limit induction switch 148 is arranged on the bottom plate 14. The third lower limit induction switch 148 cooperates with the piston rod in the upper top oil cylinder 141. When the piston rod in the upper top oil cylinder 141 is reset downward to the position where it is sensed by the third lower limit induction switch 148, it indicates that the piston rod in the upper top oil cylinder 141 has descended to a position where it will not interfere with the movement of the lower slide plate 142.

[0039] Fourth upper limit induction switches 8111 and fourth lower limit induction switches 8112 are respectively arranged at the upper and lower ends of two guide rail seats 811. When the feeding hopper 87 is at the lowest position, the connecting shaft 841 on the feeding hopper 87 can be sensed by the two fourth lower limit induction switches 8112. When the feeding hopper 87 is flipped for discharging under the guiding action of the arc guide rail 851, the connecting shaft 841 on the feeding hopper 87 can be sensed by the two fourth upper limit induction switches 8111. A speed limit induction switch 8113 is arranged on any one of the guide rail seats 811. The position of the speed limit induction switch 8113 is lower than the transition between the straight guide rail 85 and the arc guide rail 851. The feeding hopper 87 can move up and down at a relatively fast speed in the straight guide rail 85. When the moving shaft 861 on the feeding hopper 87 is sensed by the speed limit induction switch 8113, it indicates that the feeding hopper 87 is about to enter the arc guide rail 851 for flipping and discharging. At this time, the PLC can control the two-axis reduction motor 812 to reduce the speed so as to reduce the running speed of the feeding hopper 87, preventing the situation that the flipping speed is too large due to too fast running speed and causing material scattering. When flipping and discharging, the connecting shaft 841 on the feeding hopper 87 will continue to move upward and be sensed by the speed limit induction switch 8113. After the speed limit induction switch 8113 continuously senses the moving shaft 861 and the connecting shaft 841, a control node will be formed in the PLC. When the feeding hopper 87 finishes discharging and is reset, the connecting shaft 841 and the moving shaft 861 on the feeding hopper 87 are continuously sensed by the speed limit induction switch 8113, and the PLC can control the two-axis reduction motor 812 to increase the speed so as to increase the running speed of the feeding hopper 87, achieving the effect of rapid reset.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present invention can still be modified or equivalently replaced. Any modification or equivalent replacement without departing from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. Three-stage center-pressure pre-pressing forming machine, including: The frame is characterized in that: a top plate is arranged on the top of the frame, a liftable discharge hopper and a push-down cylinder are arranged on the top plate, an upper pressure head is arranged on the push-down cylinder, a liftable orifice plate is arranged on the frame below the top plate, an upper slide plate is arranged on the orifice plate for sliding left and right, a loading barrel passing through the orifice plate is fixedly arranged on the upper slide plate, a first positioning ring is sleeved on the bottom end of the loading barrel, the first positioning ring extends downward from the loading barrel, the distance between the bottom wall of the first positioning ring and the bottom wall of the loading barrel is H, a left upper limit seat is arranged on the left side of the orifice plate, and when the upper slide plate abuts against the left upper limit seat, the upper The barrel is coaxially aligned with the upper pressure head, two counterweights are symmetrically arranged on the left side wall of the upper slide, a bottom plate is arranged at the bottom of the frame, an upper cylinder and a lower slide that can slide left and right are arranged on the bottom plate, a through hole is arranged on the lower slide plate, a lower barrel and a heightening frame are fixedly arranged on the lower slide plate, a second limit ring is mounted on the top of the lower barrel, the distance between the top wall of the second limit ring and the top wall of the lower barrel is h, a left lower limit seat and a right lower limit seat are respectively arranged on the left and right sides of the bottom plate, the left lower limit seat is aligned with the left upper limit seat up and down, and when the lower slide plate abuts against the right lower limit seat, the material is unloaded. The cylinder is coaxially aligned with the discharge hopper, a lower pressure head is provided in a movable seal in the lower material cylinder, a material ejecting cylinder is provided on the bottom plate, a strong magnetic block is provided on the piston rod of the material ejecting cylinder, an articulated seat is hinged on the elevated frame, a lifting cylinder is provided on the articulated seat, the piston rod of the lifting cylinder is connected to the support plate, two rows of linear bearings are provided on the support plate, a guide rod is slidably provided in the linear bearing on the same side, the guide rod is fixed in the articulated seat, a detachable middle material cylinder is provided on the support plate, a first limiting ring is provided on the top end of the middle material cylinder, the distance between the top wall of the first limiting ring and the top wall of the middle material cylinder is H, and the middle material cylinder is provided with a plurality of intermediate material cylinders. A second positioning ring is mounted on the bottom end of the barrel, and the second positioning ring extends downward from the middle barrel. The distance between the bottom wall of the second positioning ring and the bottom wall of the middle barrel is h. A turning cylinder is hinged on the elevated frame, and a coupling plate is arranged between the two guide rods. The piston rod of the turning cylinder is hinged to the coupling plate. Vertical limit seats are arranged at the front and rear ends of the elevated frame, and pinholes are arranged on the side walls of the upper barrel, the middle barrel and the lower barrel. The bottom end of the upper barrel can be connected with the top end of the middle barrel, and the bottom end of the middle barrel can be connected with the top end of the lower barrel. A feeding mechanism capable of feeding materials into the discharge hopper is arranged on the frame.

2. The three-stage center-pressure pre-pressing forming machine according to claim 1 is characterized in that: The feeding mechanism includes: a connection structure between the feeding hopper and the frame: a fixed plate arranged at the rear side of the frame, two guide rail seats and a double-axis reduction motor are vertically arranged on the fixed plate, a driving gear is connected to the two output shafts of the double-axis reduction motor, a rotating shaft is rotatably arranged between the tops of the two guide rail seats, a driven gear is arranged at both ends of the rotating shaft, a transmission chain is connected between the driving gear and the driven gear on the same side, a chain connecting pin is arranged on the transmission chains on both sides, a connecting shaft is rotatably arranged between the two chain connecting pins, a straight guide rail is arranged on the guide rail seat, an arc guide rail is extended from the top of the straight guide rail, the arc guide rail is connected to the top plate, a guide wheel is rotatably arranged in the two straight guide rails, a moving shaft is rotatably arranged between the two guide wheels, a feeding hopper is arranged between the connecting shaft and the moving shaft, and the moving shaft is located on the discharge end of the feeding hopper.

3. The three-stage center-pressure pre-pressing forming machine according to claim 2 is characterized in that: A slide groove is provided on the top of the guide rail seat, a sprocket slider is slidably clamped in the slide groove, a rotating shaft is rotatably arranged in the sprocket slider, an adjusting block is arranged on the slide groove, an adjusting bolt is threadedly connected in the adjusting block, and the adjusting bolt is rotatably clamped in the sprocket slider.

4. The three-stage center-pressure pre-pressing forming machine according to claim 1 is characterized in that: The connection structure between the discharge hopper and the top plate is as follows: a fixed frame is provided on the outer side wall of the discharge hopper, four upper spring seats are provided around the fixed frame, a buffer frame is provided below the fixed frame, four lower spring seats are provided around the buffer frame, a buffer spring is provided between the upper and lower spring seats aligned up and down, four sliding sleeves are provided on the buffer frame, the four sliding sleeves are symmetrical in pairs, four guide pillars are provided on the top plate, the four sliding sleeves are slidably provided on the four guide pillars, two mounting blocks are symmetrically provided on the buffer frame, two tension cylinders are provided on the top plate, and the piston rods on the two tension cylinders are respectively connected to the two mounting blocks.

5. The three-stage center-pressure pre-pressing forming machine according to claim 4 is characterized in that: A material shielding plate is mounted on the discharging end of the discharging hopper, and a vibration motor is arranged on the fixing frame.

6. The three-stage center-pressure pre-pressing forming machine according to claim 1 is characterized in that: The connection structure between the orifice plate and the frame is as follows: an intermediate plate is arranged on the frame, an avoidance hole is opened on the intermediate plate, four columns are arranged between the intermediate plate and the top plate, the four columns are symmetrical in pairs, two lifting cylinders are symmetrically arranged on the intermediate plate, the piston rods of the lifting cylinders are connected to the orifice plate, a reinforcing plate is slidably arranged between the two columns on the same side, two reinforcing rods are arranged between the reinforcing plate and the orifice plate, two chain screws are symmetrically arranged on the left side wall of the upper slide plate, and the chain screws are connected to the chain screws. A counterweight chain is connected, and the counterweight block is connected to the counterweight chain. Two gear seats are symmetrically arranged on the left side wall of the orifice plate. A counterweight sprocket is rotatably arranged on the gear seat. The counterweight chain is connected to the counterweight sprocket on the same side. Two upper guide rails are symmetrically arranged on the orifice plate. Several upper sliders are symmetrically arranged on the upper slide. The upper sliders are slidably clamped on the upper guide rails on the corresponding side. A mounting hole is arranged on the upper slide. An upper clamp coaxial with the mounting hole is arranged on the upper slide, and the upper clamp is clamped on the upper barrel.

7. The three-stage center-pressure pre-pressing forming machine according to claim 1 is characterized in that: The connecting structure between the support plate and the middle barrel is as follows: a positioning plate is provided at the upper and lower ends of the support plate, an arc hole is provided on the positioning plate, a clamping plate is rotatably provided on the positioning plate, and an arc hole is also provided on the clamping plate. After the clamping plate and the positioning plate are rotated and matched, the middle barrel is clamped through the two arc holes. A lower clamping hoop is surrounded and provided on the outer wall of the middle barrel, and the lower clamping hoop abuts against the positioning plate and the clamping plate at the upper end of the support plate. A locking member capable of locking the positioning plate and the clamping plate is provided between the positioning plate and the clamping plate. The locking member comprises: a sliding sleeve seat fixed on the side wall of the positioning plate and a top block fixed on the side wall of the clamping plate, a push rod is slidably provided at one end of the sliding sleeve seat close to the top block, a grip is hinged at one end of the sliding sleeve seat away from the top block, a connecting rod is hinged between the grip and the push rod, an adjusting screw is threadedly connected at one end of the push rod close to the top block, a locking nut is threadedly connected on the adjusting screw, and the locking nut is screwed and abutted against the push rod.

8. The three-stage center-pressure pre-pressing forming machine according to claim 1 is characterized in that: Two lower guide rails are arranged on the bottom plate, a push-pull cylinder is arranged horizontally on the bottom plate between the two lower guide rails, the piston rod of the push-pull cylinder is connected with the lower slide plate, a plurality of lower slide blocks are arranged on the front and rear sides of the lower slide plate, and the lower slide blocks are slidably clamped on the lower guide rails on the corresponding sides.

9. A method for using the three-stage center-pressure pre-pressing molding machine according to any one of claims 1 to 8, characterized in that: The upper and lower limit seats are aligned coaxially, and the lower push cylinder drives the upper pressure head to extend into the upper barrel, and the upper top cylinder passes through the lower slide and extends into the middle barrel to push the upper barrel in the middle position. The upper and lower pressure heads are pushed down, and the upper and lower pressure heads squeeze the plastic at the same time, so that the plastic is compacted in the middle barrel. The lower push cylinder drives the upper pressure head to reset upward and disengage from the upper barrel, and the upper lifting cylinder resets downward and disengages from the lower slide. The orifice plate drives the upper barrel to rise and disengage from the middle barrel, and the lower slide drives the middle barrel and the lower barrel to move to the right and rest against the lower right limit seat. The lifting cylinder drives the strong magnetic block to pass through the lower slide and adsorb on the lower pressure head and push the lower pressure head to the top of the lower barrel. The lifting cylinder drives the pallet to rise, and the middle barrel is separated from the lower barrel. The flip cylinder pushes the pallet and the middle barrel on the pallet to rotate to a horizontal state. The upper pressure head blocks the compacted plastic from falling out of the middle barrel, and the lifting cylinder drives the strong magnetic block to reset downward with the lower pressure head, and the lower pressure head returns to the lower barrel. The staff removes the middle barrel filled with compacted plastic from the pallet, and then installs the new middle barrel on the pallet.

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