Technical Field
The utility model relates to a constant vacuum frequency controlled shaping device for corrugated plastic sheets, belonging to the field of plastic machinery. It is mainly used for vacuum extraction during sheet shaping after extrusion in the production of corrugated plastic boards from powdery raw materials. The vacuum adsorption fixes sheets onto shaping moulds to guarantee precise sheet thickness and geometry.
Background Art
At present, during the shaping process of corrugated plastic sheets between shaping moulds, vacuum degree is controlled in an intermittent and jump mode. This leads to low control precision and severe vacuum fluctuation, which greatly impairs the quality of corrugated plastic sheets.In view of the current situation of corrugated plastic sheet manufacturing machinery, there is an urgent demand for a shaping device with stable shaping vacuum, small fluctuation range and improved sheet quality.
Contents of the Utility Model
The purpose of the utility model is to provide a constant vacuum frequency controlled shaping device for corrugated plastic sheets, which overcomes the drawbacks of existing corrugated plastic sheet manufacturing equipment. The device realizes stable shaping vacuum, small fluctuation range and superior finished sheet quality.
The technical solution is as follows: the device comprises a shaping frame, lifting assemblies, shaping moulds and a vacuum control unit.The shaping frame includes a base frame, vertical plates, platform plates, cross frames, adjusting seats, lower mould screws and lower mould cushion blocks. The planar rectangular base frame is placed on the ground. A vertical plate is fixed on the outer side of each lengthwise end of the upward frame plane, with the plate surface perpendicular to the base frame plane. One platform plate is fixed to the upper edge of each vertical plate, and each platform plate is parallel to the base frame plane.The cross frame assembled by mutually perpendicular long flat plates and short flat plates is fixed between edges of the two vertical plates away from the base frame. The upper surface of the cross frame is parallel to the base frame plane. Multiple adjusting seats are mounted above each intersection of the crossed flat plates. One end of each lower mould screw is screwed into the threaded hole of an adjusting seat, and the upward end is fitted with one lower mould cushion block.
The lifting assembly includes lifting frames, lifting cylinders, guiding assemblies, upper mould cushion blocks, upper mould screws and connecting blocks. Two planar rectangular lifting frames are supported on the two platform plates of the shaping frame via lifting cylinders at both ends. The plane of each lifting frame is parallel to the upper surface of the cross frame. Round holes are arranged inside the lifting cylinders at both ends of the two long borders of each lifting frame, and the axes of the four round holes are perpendicular to the lifting frame plane.Each guiding assembly consists of a guiding cylinder, a guiding toothed column, a connecting plate, transmission shafts, bearing seats and gears. One end of one guiding cylinder and one guiding toothed column are connected by a connecting plate. The guiding cylinder and guiding toothed column are parallel, and the teeth of the guiding toothed column face toward the guiding cylinder. Four sets of guiding cylinder-toothed column assemblies are installed in the round holes at both ends of the two lifting frames. All connecting plates are positioned above the lifting frames, and the tail ends of the guiding cylinders and guiding toothed columns away from the connecting plates are mounted on the two platform plates of the shaping frame.Two transmission shafts are mounted on the upper plane of the two lifting frames via bearing seats at both ends. The axis of each transmission shaft is parallel to the long border of the lifting frame and located between the guiding cylinder and guiding toothed column at corresponding ends. One gear is installed on each outward extending end of the transmission shafts passing through the bearing seats, and each gear meshes with the teeth of the corresponding guiding toothed column.A plurality of upper mould cushion blocks are divided into four rows, with two rows evenly arranged along the long border on the upper plane of each lifting frame. One end of each upper mould screw is mounted on an upper mould cushion block, and the downward end penetrating the long border of the lifting frame is equipped with a connecting block.
The shaping moulds include lower shaping moulds, upper shaping moulds and No. 1 pipe connectors. Each lower shaping mould and upper shaping mould is a rectangular flat plate. Three rows of multiple threaded holes are arranged on one plate surface along the length direction. Multiple round holes equal in quantity to each row of threaded holes are arranged inside the mould near the plate surface without threaded holes. The axes of all round holes are parallel to the plate length direction and evenly distributed along the width direction. The three rows of threaded holes are in spaced communication with the round holes respectively.A number of tiny holes communicating with the round holes are arranged on the plate surface without threaded holes. The density of tiny holes gradually decreases from one widthwise side to the other side of the rectangular plate.Two lower shaping moulds are mounted on the lower mould cushion blocks with the threaded-hole surface facing downward. Their plate surfaces are parallel to the upper surface of the cross frame, and the length direction of each rectangular mould is parallel to the long border of the base frame.On the upward surface of one lower shaping mould, tiny hole density decreases gradually from the outboard side close to the cross frame toward the middle of the cross frame. On the upward surface of the other lower shaping mould, tiny hole density decreases gradually from the cross frame middle toward the outboard side. The maximum hole density at the cross frame middle matches the minimum density at the adjacent edge of the paired lower shaping mould.Two upper shaping moulds are mounted on the connecting blocks of the lifting assemblies with the threaded-hole surface facing upward. Their plate surfaces are parallel to the rectangular plane of the lifting frames, and the length direction of each rectangular mould is parallel to the long border of the lifting frame.On the downward surface of one upper shaping mould, tiny hole density gradually decreases from one long border (corresponding to the densest tiny hole side of the matched lower shaping mould) to the opposite long border, and the hole density at each position matches that of the matched lower shaping mould.On the downward surface of the other upper shaping mould, tiny hole density gradually decreases from one long border close to the cross frame middle (the densest tiny hole zone) to the opposite long border, and the hole density at each position matches that of the matched lower shaping mould. Tiny hole density is equal at the adjacent edges of the two upper shaping moulds.No. 1 pipe connectors equal in number to the three rows of threaded holes of the shaping moulds are installed on the threaded holes of the lower shaping moulds and upper shaping moulds.
The vacuum control unit includes a vacuum pump, pressure stabilizing tank, frequency converter and No. 2 pipe connectors. The vacuum pump, pressure stabilizing tank and frequency converter are all mounted on the base frame of the shaping frame. One No. 2 pipe connector is fitted at the air inlet and air outlet of the pressure stabilizing tank. The No. 2 pipe connector at the air outlet is connected to the inlet of the vacuum pump. The No. 2 pipe connector at the air inlet is connected to all No. 1 pipe connectors of the lower shaping moulds and upper shaping moulds of the shaping mould assembly.
Working principle: During equipment commissioning or product changeover for corrugated sheets of different thicknesses, the telescopic rods of lifting cylinders extend or retract to lift or lower the lifting frames. However, it is difficult for the lifting cylinders at both ends of one lifting frame to extend and retract completely synchronously. The inclined lifting frame may cause jamming between the lifting frame and guiding cylinders and guiding toothed columns.Transmission shafts are installed on the two lifting frames via bearing seats, and gears at both ends of each transmission shaft mesh with guiding toothed columns mounted on the two platform plates of the shaping frame. Namely, gears at both ends of a single transmission shaft engage with two guiding toothed columns at both ends simultaneously.If one lifting cylinder at one end of the lifting frame operates faster than the cylinder at the other end, the gear meshed with the local guiding toothed column drives the gear at the opposite end to rotate faster through the transmission shaft, and vice versa.
After the lifting frame lifts the upper shaping mould, the freshly extruded soft corrugated plastic sheet is fed into the gap between upper and lower shaping moulds from the side with the densest tiny holes communicating with round holes. Afterwards, the lifting frame drives the upper shaping mould to descend and stop when the clearance between upper and lower moulds reaches the preset value.The vacuum control unit is activated. The vacuum pump extracts air from lower and upper shaping moulds through the pressure stabilizing tank, continuously raising the vacuum level inside mould cavities and the mould gap. The soft incoming corrugated sheet is rapidly adsorbed onto upper and lower shaping moulds, ensuring that the thickness of shaped sheets is consistent with the preset mould clearance.The adsorbed sheet moves forward continuously and is gradually shaped. The tiny holes on upper and lower shaping moulds become sparser gradually, and the vacuum weakens accordingly, effectively reducing friction between the corrugated sheet and the shaping moulds.During continuous production, once vacuum degree varies in different zones of the shaping device, the frequency converter of the vacuum control unit adjusts frequency in real time to change the rotating speed of the vacuum pump. It maintains constant vacuum in all zones and ensures the corrugated sheet thickness meets design requirements.
Compared with existing technology, the utility model delivers the following advantages:With the guiding assembly adopted, gears at both ends of each transmission shaft engage with two guiding toothed columns simultaneously. If one lifting cylinder operates faster than the cylinder at the opposite end, the local gear drives the gear on the other end via the transmission shaft. This ensures synchronous lifting at both ends of the lifting frame and completely eliminates jamming risks caused by inclined lifting frames.When soft extruded corrugated plastic sheets enter the gap between upper and lower shaping moulds from the side with densest tiny holes, sheets are rapidly adsorbed onto mould surfaces, so the finished sheet thickness matches the preset mould clearance.The tiny holes on shaping mould surfaces gradually decrease in density from one widthwise side to the other, leading to gradual vacuum attenuation. This reduces friction between gradually shaped sheets and mould surfaces.Vacuum pumping is controlled via frequency conversion. The frequency converter adjusts pump speed dynamically when vacuum fluctuates in different mould zones to stabilize regional vacuum, further improving the quality of finished corrugated plastic sheets.
