A heating device for plastic pipe hot-melt welding machine

Abstract

The present invention belongs to the field of pipe hot-melt connection equipment, and its purpose is to improve the heating efficiency and uniformity of pipes. The present invention relates to a heating device for a plastic pipe hot-melt welding machine, comprising an insulation box, a fluid heating unit, a pumping unit, a reversing conveying unit, and a heating unit. The insulation box is arranged on one side of the heating unit and is provided with a partition therein, dividing it into a fluid heating zone and a fluid conveying control zone. When the pipe is heated, the hot fluid medium in the fluid heating zone is selectively conveyed to the inner annular area or the outer annular area of ​​the heating unit via the front infusion line, the reversing conveying unit, the pumping unit, the middle infusion line, and the rear infusion line. When the pipe is heated, the fluid medium in the inner annular area or the outer annular area flows back to the heating zone of the insulation box. The present invention shortens the pipe welding time and provides more uniform heat within the heated pipe area.

Description

Technical Field

[0001] The invention relates to the field of pipeline hot-melt connection equipment, and in particular to a heating device for a plastic pipe hot-melt welding machine. Background Art

[0002] With the widespread use of PE (polyethylene) piping systems in water, gas, oil, coastal aquaculture, and other fields, the workload of laying pipes is increasing. Hot-melt welding machines can effectively weld pipes, reducing the workload. Existing hot-melt welding machines require the pipe to be heated using a heating plate within the machine. However, the entire heating process takes a long time, and some areas of the pipe may be heated unevenly, resulting in unnecessary energy loss in the heating plate across the pipe's inner diameter.

[0003] Utility model patent publication number CN203236711U addresses the uneven temperature distribution of various heating components. This invention addresses the issue of a heat-seal welding device. This device achieves uniform heating by placing different resistor wire spacings in different areas of the circular heating plate. However, this device still heats the entire circular heating plate, failing to reduce unnecessary energy waste. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a heating device for a plastic pipe hot melt welding machine which improves heating efficiency and heating uniformity and avoids unnecessary energy loss.

[0005] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0006] A heating device for a plastic pipe hot-melt welding machine comprises a heat preservation box, a fluid heating unit, a pumping unit, a reversing conveying unit, and a heating unit;

[0007] The thermal insulation box is arranged on one side of the heating unit; a partition is provided in the thermal insulation box to divide the interior of the thermal insulation box into a fluid heating area and a fluid delivery control area; the fluid heating unit is installed in the fluid heating area, and the main parts of the pumping unit and the reversing delivery unit are both installed in the fluid delivery control area; the heating unit is provided with an inner annular area and an outer annular area; the reversing delivery unit is connected to the heating area of ​​the thermal insulation box through the front infusion pipeline, the reversing delivery unit is connected to the pumping unit through the middle infusion pipeline, and the reversing delivery unit is connected to the inner annular area and the outer annular area of ​​the heating unit through the rear infusion pipeline;

[0008] When the pipeline is in the heating state, the hot fluid medium in the fluid heating zone is selectively transported to the inner annular area or the outer annular area of ​​the heating unit through the front infusion pipeline, the reversing conveying unit, the pumping unit, the middle infusion pipeline and the rear infusion pipeline;

[0009] When the pipeline heating is completed, the fluid medium in the inner annular area or the outer annular area of ​​the heating unit flows back to the heating area of ​​the insulation box through the rear infusion pipeline, the middle infusion pipeline, the pumping unit, the reversing conveying unit and the front infusion pipeline.

[0010] Furthermore, the fluid heating unit adopts a heating coil.

[0011] Moreover, the pumping unit includes a pumping motor, a crank-connecting rod structure, a pumping cylinder, a first mounting seat, and a second mounting seat; the first mounting seat and the second mounting seat are both fixedly mounted on the inner side wall of the insulation box; the pumping motor and the pumping cylinder are respectively fixedly mounted on the first mounting seat and the second mounting seat; the crank-connecting rod structure includes a crank disk, a connecting rod, and a piston push rod; the crank disk is coaxially fixedly mounted on the output shaft of the pumping motor, one end of the connecting rod is eccentrically connected to the crank disk, and the other end of the connecting rod is relatively rotatably connected to the outer end of the piston push rod; a piston head is provided at the inner end of the piston push rod; the pumping cylinder is a cylinder barrel provided with a liquid inlet and a liquid outlet, the piston head extends into the pumping cylinder, and forms a sealed sliding fit with the inner wall of the pumping cylinder; a suction control valve and a suction control valve are hinged at the inner ends of the liquid inlet and the liquid outlet, respectively.

[0012] Moreover, the reversing conveying unit includes a first reversing sleeve, a second reversing sleeve, a first reversing column, a second reversing column, a first infusion line, a second infusion line, a third infusion line, a fourth infusion line, a fifth infusion line, a sixth infusion line, and an elastic limiting structure for stabilizing the first reversing column in two upper and lower working positions; the bottoms of the first reversing sleeve and the second reversing sleeve are fixedly mounted on the side wall of the incubator;

[0013] Four flow holes are evenly distributed along the circumferential direction on the side wall of the first reversing sleeve, namely flow hole A, flow hole B, flow hole C and flow hole D; flow hole A is arranged 180 degrees relative to flow hole B, and flow hole C is arranged 180 degrees relative to flow hole D; three flow holes are arranged on the upper edge of the side wall of the second reversing sleeve, namely flow hole E, flow hole F and flow hole G, flow hole E is arranged at a 90 degree angle to flow hole F, and flow hole F is arranged at a 90 degree angle to flow hole G. The flow hole G is arranged at a 90° angle; the flow hole A is connected to the heating area in the insulated box through the first infusion pipeline, the flow hole B is connected to the liquid inlet of the pumping cylinder through the second infusion pipeline, the flow hole C is connected to the liquid outlet of the pumping cylinder through the third infusion pipeline, the flow hole D is connected to the flow hole E through the fourth infusion pipeline, and the flow hole F and the flow hole G are connected to the outer annular area and the inner annular area of ​​the heating unit through the fifth infusion pipeline and the sixth infusion pipeline, respectively;

[0014] The outer diameter of the first reversing column is equal to the inner diameter of the first reversing sleeve. The first reversing column is inserted into the first reversing sleeve. The first reversing column is provided with upper and lower layers of holes, wherein the lower layer has four holes, and two holes in the lower layer that are 180 degrees opposite to each other are connected; the upper layer has four holes, of which two holes are connected at 90 degrees, and the other two holes are connected at 90 degrees; during the heating operation of the pipeline, the four holes in the lower layer of the first reversing column are aligned and connected with the four flow holes on the first reversing sleeve, respectively, so that the fluid flows into the heating unit; when the heating operation is completed, the four holes in the upper layer of the first reversing column are respectively connected with the four flow holes on the first reversing sleeve, so that the fluid flows back from the heating unit to the heating area of ​​the insulation box;

[0015] The outer diameter of the second reversing column is consistent with the inner diameter of the second reversing sleeve, and the second reversing column is inserted into the second reversing sleeve; two holes with a 90° angle are provided on the second reversing column, and the two holes are connected internally; one hole on the second reversing column is aligned and connected with the flow hole E on the second reversing sleeve; the other hole on the second reversing column is selectively aligned and connected with the flow hole F and the flow hole G on the second reversing sleeve.

[0016] Moreover, the elastic limiting structure includes a limiting baffle and two limiting springs; two spring mounting cavities are provided at the inner bottom of the first reversing sleeve, and the lower ends of the two limiting springs are respectively inserted and positioned in the two spring mounting cavities; a positioning shoulder is provided near the inner bottom of the first reversing sleeve; the limiting baffle is fixed to the upper end of the positioning shoulder; a clearance through-hole is provided on the limiting baffle corresponding to the position of the two limiting springs; a compression spring plate is provided at the lower end of the first reversing column, and the compression spring plate is in tight contact with the upper end of the limiting spring; when the two limiting springs are in a naturally extended state, the lower layer hole on the first reversing column is aligned with the flow hole on the first reversing sleeve; the first reversing column is pressed down so that the compression spring plate passes through the clearance through-hole on the limiting baffle, and after rotating 90°, the compression spring plate is limited to the lower end of the limiting baffle, so that the upper layer hole on the first reversing column is aligned with the flow hole on the first reversing sleeve.

[0017] Moreover, the heating unit as a whole is a disc-shaped shell structure, and an annular clamping pipe area is arranged on the periphery of the outer annular area; between the inner annular area and the outer annular area, the outer ring of the outer annular area is respectively provided with annular clamping grooves, and the inner ring of the inner annular area and the two annular clamping grooves are both installed with thermal insulation rings.

[0018] Moreover, the rear pipeline sections of the fifth and sixth infusion pipelines are placed in the annular clamping area. Both pipeline sections are semi-annular pipeline sections, and output elbows are provided at the ends of the pipeline sections. The elbow seal at the end of the fifth infusion pipeline passes through the inner wall of the annular clamping area, the annular clamping groove of the outer ring, and the thermal insulation ring in the groove, and then extends into the outer annular area. The elbow seal at the end of the sixth infusion pipeline passes through the inner wall of the annular clamping area, the annular clamping groove of the outer ring, the thermal insulation ring in the groove, and the annular clamping groove of the inner ring, and then extends into the inner annular area.

[0019] The present invention has the following advantages and positive effects:

[0020] 1. The present invention adopts the hierarchical heating principle and sets heating zones of different diameters on the heating unit. When heating the pipeline, only the area of ​​the pipeline diameter needs to be heated. Therefore, only the annular area suitable for the pipeline diameter needs to be heated on the heating plate. Therefore, the entire heating plate is divided into annular layers, and insulation rings are used between the layers for heat insulation treatment. The heating device keeps the temperature of the oil in the insulation box unchanged. When heating the pipeline, the pumping unit continuously passes high-temperature fluid into the heating area, and the reversing conveying unit controls the direction of the oil to switch different heating areas. After the heating is completed, the reversing conveying unit controls the direction of the fluid to recover the fluid in the heating area.

[0021] 2. This invention utilizes a hierarchical heating principle to heat pipes of different diameters at different levels, avoiding the need to heat the entire heating plate when heating pipes, thus preventing energy loss. Furthermore, this invention heats a specific annular area within the heating plate, significantly reducing the time required to heat the heating plate before heating the pipes, shortening pipe welding time, and providing more uniform heat distribution within the heated pipe area, compared to conventional methods that heat the entire heating plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the internal structure of the device of the present invention with one side of the outer shell removed;

[0023] Figure 2 It is a schematic diagram of the overall appearance of the present invention;

[0024] Figure 3 It is a three-dimensional exploded schematic diagram of the pumping state of the present invention;

[0025] Figure 4 It is a cross-sectional view of the pumping cylinder and related structural parts of the present invention;

[0026] Figure 5 This is an exploded view of the overall structure of the reversing conveying unit of the present invention;

[0027] Figure 6 It is an exploded schematic diagram of two reversing sleeves and two reversing posts of the present invention;

[0028] Figure 7 is a cross-sectional view of the first reversing column of the present invention;

[0029] Figure 8 It is a cross-sectional view of the first reversing column of the present invention in the upper working position;

[0030] Figure 9 It is a schematic diagram of the layout of the fifth infusion pipeline, the sixth infusion pipeline and the three insulation rings of the present invention.

[0031] Specific implementation methods

[0032] The structure of the present invention will be further described below with reference to the accompanying drawings and through examples. It should be noted that the present examples are descriptive rather than restrictive.

[0033] A heating device for a plastic pipe hot melt welding machine, see Figures 1-9 The invention point is: it mainly includes an insulation box 2, a fluid heating unit 3, a pumping unit 5, a reversing conveying unit 4, and a heating unit 6.

[0034] The heat preservation box is used to store high-temperature fluid, a fluid heating unit, a pumping unit, a reversing conveying unit and a part of the pipeline.

[0035] The heat preservation box is connected to one side of the heating unit. A partition is arranged inside the heat preservation box to separate the interior of the heat preservation box into a fluid heating area and a fluid delivery control area.

[0036] The fluid heating unit is arranged in the heating area of ​​the insulation box and adopts a heating coil. The heating coil is used to heat the fluid. The fluid can be silicone oil, which is an environmentally friendly fluid that can be heated to 250°C. The high-temperature silicone oil can heat the plastic pipe to the required 220-230°C through the heating unit. The temperature of the heating fluid can be monitored by the PT100 temperature sensor. PT100 is a high-temperature and corrosion-resistant sensor. When the temperature sensor detects that the temperature of the heating fluid reaches the required temperature, the heating fluid will maintain a certain temperature. A pipe hole is provided on the partition, and the first infusion pipeline is installed through the seal.

[0037] The pumping unit and the reversing delivery unit are arranged in the fluid delivery control area.

[0038] The pumping unit mainly includes a pumping motor 5.3, a crank-connecting rod structure, a pumping cylinder 5.9, a first mounting seat 5.6, a second mounting seat 5.10, etc. The first mounting seat and the second mounting seat are both fixedly mounted on the side wall of the thermal insulation box. A semicircular mounting groove matching the shape of the motor is provided on the first mounting seat for the pumping motor to be embedded and positioned, and T-shaped mounting grooves are provided on both sides of the semicircular groove on the first mounting seat. The pumping motor is fixed on a motor seat 5.2, and two T-shaped mounting strips are provided at the lower end of the motor seat. The two T-shaped mounting strips are respectively inserted into the two T-shaped mounting slots to fix the pumping motor on the first mounting seat. The pumping cylinder is fixed to the second mounting seat through the cylinder seat in the same manner as the pumping motor.

[0039] The crank-connecting rod structure includes a crank disk 5.4, a connecting rod 5.5, and a piston push rod 5.7. The crank disk is coaxially fixedly mounted on the output shaft of the pumping motor. One end of the connecting rod is connected to an eccentric portion on the crank disk for relative rotation, and the other end of the connecting rod is connected to the outer end of the piston push rod for relative rotation. A piston head 5.8 is provided at the inner end of the piston push rod. The pumping cylinder is a cylinder provided with a liquid inlet 5.9.1 and a liquid outlet 5.9.2. The piston head extends into the pumping cylinder and forms a sealed sliding fit with the inner wall of the pumping cylinder. The rotation of the crank disk drives the piston push rod to perform reciprocating linear motion through the connecting rod, so that the fluid is sucked in through the liquid inlet and then discharged through the liquid outlet. The suction control valve 5.11 and the suction control valve 5.12 are hinged at the inner ends of the liquid inlet and the liquid outlet, respectively. Specifically:

[0040] When the piston push rod moves out of the pumping cylinder, negative pressure is formed in the cylinder, the suction control valve is pushed up, and at this position it is connected to the external pipeline, allowing external fluid to enter the cylinder. When the piston push rod moves inward, positive pressure is formed in the cylinder, the suction control valve returns to its original position, and the suction control valve at the outlet is pushed up, allowing the fluid in the cylinder to flow out of the outlet. In this way, the reciprocating motion of the piston push rod drives the fluid in the pipeline.

[0041] The reversing conveying unit includes a first reversing sleeve 4.1, a second reversing sleeve 4.3, a first reversing post 4.2, a second reversing post 4.4, a first infusion line 4.9, a second infusion line 4.5, a third infusion line 4.10, a fourth infusion line 4.6, a fifth infusion line 4.7, a sixth infusion line 4.8, a stopper 4.12, and a spring 4.11. The bottoms of the first and second reversing sleeves are fixedly mounted on the side walls of the incubator.

[0042] Four flow holes 4.1.1 are evenly distributed along the circumference of the sidewall of the first reversing sleeve: flow hole A, flow hole B, flow hole C, and flow hole D. Flow hole A and flow hole B are arranged at a 180° angle to each other, while flow hole C and flow hole D are arranged at a 180° angle to each other. Three flow holes are also provided along the upper edge of the sidewall of the second reversing sleeve: flow hole E, flow hole F, and flow hole G. Flow hole E is arranged at a 90° angle to flow hole F, and flow hole F is arranged at a 90° angle to flow hole G. The flow hole A is connected to the heating area in the insulation box through the first infusion pipeline (the front infusion pipeline), the flow hole B is connected to the liquid inlet of the pumping cylinder through the second infusion pipeline (the middle infusion pipeline), the flow hole C is connected to the liquid outlet of the pumping cylinder through the third infusion pipeline (the middle infusion pipeline), the flow hole D is connected to the flow hole E through the fourth infusion pipeline (the middle infusion pipeline), and the flow hole F and the flow hole G are respectively connected to one end of the fifth infusion pipeline (the rear infusion pipeline) and the sixth infusion pipeline (the rear infusion pipeline).

[0043] The outer diameter of the first reversing column is equal to the inner diameter of the first reversing sleeve. The first reversing column is inserted into the first reversing sleeve. The first reversing column is provided with upper and lower layers of holes 4.2.1, of which there are four holes 4.2.1B in the lower layer, and two holes in the lower layer that are 180 degrees opposite to each other are connected. There are four holes 4.2.1A in the upper layer, of which two holes at 90 degrees are connected, and the other two holes at 90 degrees are also connected. During the heating operation of the pipeline, the four holes in the lower layer of the first reversing column are aligned and connected with the four flow holes on the first reversing sleeve, allowing the fluid to flow into the heating unit. When the heating operation is completed, the first reversing column is pressed down, so that the four holes in the upper layer of the first reversing column are connected with the four flow holes on the first reversing sleeve. At this time, the fluid in the heating unit flows back to the heating area of ​​the insulation box, realizing fluid recovery.

[0044] The first reversing column has two working positions within the first reversing sleeve: a lower working position and an upper working position. In the upper working position, the lower hole aligns with the hole on the first reversing sleeve, while in the lower working position, the upper hole aligns with the hole on the first reversing sleeve. To ensure the positional accuracy of the two working positions, the position is limited by a limit structure composed of the limit block and limit spring. Specifically:

[0045] Two spring mounting cavities are provided at the inner bottom of the first reversing sleeve, and the lower ends of the two limit springs are respectively inserted and positioned in the two spring mounting cavities; a positioning shoulder is provided near the inner bottom of the first reversing sleeve, and the positioning shoulder is at a certain height from the inner bottom surface. The limit baffle is fixed to the upper end of the positioning shoulder. A clearance through hole is provided on the limit baffle corresponding to the position of the two limit springs, and the clearance through hole is a long slot hole. A compression spring plate 4.2.2 is provided at the lower end of the first reversing column, and the compression spring plate is in tight contact with the upper end of the limit spring. When the two limit springs are in a naturally extended state, the lower hole on the first reversing column is aligned with the flow hole on the first reversing sleeve. When the first reversing column is pressed down, the compression spring plate passes through the clearance hole on the limit baffle, and after rotating 90°, the compression spring plate is limited by the lower end of the limit baffle. At this time, the upper hole on the first reversing column is aligned with the flow hole on the first reversing sleeve, thereby achieving position guarantee of the two working positions through the limit structure.

[0046] The outer diameter of the second reversing column is consistent with the inner diameter of the second reversing sleeve, and the second reversing column is inserted into the second reversing sleeve. Two holes 4.4.1 are provided on the second reversing column at an angle of 90 degrees, and the two holes are connected internally. One hole on the second reversing column is aligned and connected with the flow hole E on the second reversing sleeve. Another hole on the second reversing column is selectively aligned and connected with the flow hole F and the flow hole G on the second reversing sleeve. When connected with the flow hole F, the fluid is transported to the heating unit through the fifth infusion line, and when connected with the flow hole G, the fluid is transported to the heating unit through the sixth infusion line.

[0047] The heating unit comprises a disc-shaped shell structure, internally arranged from inside to outside: an inner annular area 6.1, an outer annular area 6.2, and an annular clamping area 6.3. Between the inner and outer annular areas, an annular clamping groove is provided on the outer ring of the outer annular area. Thermal insulation rings 6.4 are installed within the inner ring of the inner annular area and both annular clamping grooves. These insulation rings are made of polystyrene board, a material with excellent thermal insulation and high temperature resistance, thus insulating the two annular areas. The inner and outer annular areas heat pipes of different diameters, respectively. The annular clamping area houses the rear sections of the fifth and sixth infusion lines. Both sections are semi-annular, with output elbows at their ends. The elbow at the end of the fifth infusion line seals through the inner wall of the annular clamping area, the annular clamping groove on the outer ring, and the thermal insulation ring within the groove, then extends into the outer annular area, heating the large-diameter pipes. The elbow seal at the end of the sixth infusion pipeline passes through the inner wall of the annular clamping area, the annular clamping groove of the outer ring and the thermal insulation ring in the groove, and the annular clamping groove of the inner ring and the thermal insulation ring in the groove, and then extends into the inner annular area to achieve heating of the small diameter pipeline.

[0048] In the above technical solution, a switch button 5.1 is provided on the outside of the insulated box at a position corresponding to the pumping motor, which is used to connect the pumping motor and start the pumping. In addition, the upper ends of the first and second reversing posts extend outside the insulated box to facilitate reversing operation.

[0049] In the above technical solution, handles 1 are installed on both sides of the outside of the heat preservation box, and the staff can hold the handles tightly to move and place the heating device, which facilitates operation.

[0050] The working principle of the heating device of this plastic pipe hot melt welding machine:

[0051] According to the diameter of the pipe to be welded, the second reversing column is rotated to select different annular areas in the heating unit. The heating coil is then energized. When the fluid in the heating area reaches a stable heating temperature, the pumping motor is started, causing the hot liquid in the heating area to pass through one of the first, second, third, fourth, fifth, or sixth infusion lines and enter the corresponding annular area. This area is then brought into contact with the end face of the pipe to achieve heating of the pipe end face. After the pipe welding is completed, the first reversing column is pressed downward and rotated 90 degrees. At this time, the direct connection between the first and second infusion lines is severed, and the second and fourth infusion lines are directly connected, while the first and third infusion lines are directly connected. In this connected state, the hot fluid in the heating unit flows back through the fifth or sixth infusion line, and then through the fourth, second, third, and first infusion lines, and finally back to the heating area, achieving fluid recovery.

[0052] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various replacements, changes and modifications are possible without departing from the spirit of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A heating device for a plastic pipe hot melt welding machine, characterized in that: It includes an insulation box, a fluid heating unit, a pumping unit, a reversing conveying unit, and a heating unit; The thermal insulation box is arranged on one side of the heating unit; a partition is provided in the thermal insulation box to divide the interior of the thermal insulation box into a fluid heating area and a fluid delivery control area; the fluid heating unit is installed in the fluid heating area, and the main parts of the pumping unit and the reversing delivery unit are both installed in the fluid delivery control area; the heating unit is provided with an inner annular area and an outer annular area; the reversing delivery unit is connected to the heating area of ​​the thermal insulation box through the front infusion pipeline, the reversing delivery unit is connected to the pumping unit through the middle infusion pipeline, and the reversing delivery unit is connected to the inner annular area and the outer annular area of ​​the heating unit through the rear infusion pipeline; The reversing conveying unit includes a first reversing sleeve, a second reversing sleeve, a first reversing post, a second reversing post, a first infusion line, a second infusion line, a third infusion line, a fourth infusion line, a fifth infusion line, a sixth infusion line, and an elastic limiting structure for stabilizing the first reversing post in two upper and lower working positions; the bottoms of the first reversing sleeve and the second reversing sleeve are fixedly mounted on the side wall of the incubator; Four flow holes are evenly distributed along the circumferential direction on the side wall of the first reversing sleeve, namely flow hole A, flow hole B, flow hole C and flow hole D; flow hole A is arranged 180 degrees relative to flow hole B, and flow hole C is arranged 180 degrees relative to flow hole D; three flow holes are arranged on the side wall of the second reversing sleeve, namely flow hole E, flow hole F and flow hole G, flow hole E is arranged at a 90 degree angle to flow hole F, and flow hole F is arranged at a 90 degree angle to flow hole G. The flow holes G are arranged at a 90° angle; the flow hole A is connected to the heating zone in the insulated box through the first infusion pipeline, the flow hole B is connected to the liquid inlet of the pumping cylinder through the second infusion pipeline, the flow hole C is connected to the liquid outlet of the pumping cylinder through the third infusion pipeline, the flow hole D is connected to the flow hole E through the fourth infusion pipeline, and the flow hole F and the flow hole G are connected to the outer annular area and the inner annular area of ​​the heating unit through the fifth infusion pipeline and the sixth infusion pipeline, respectively; The outer diameter of the first reversing column is equal to the inner diameter of the first reversing sleeve. The first reversing column is inserted into the first reversing sleeve. The first reversing column is provided with upper and lower layers of holes, wherein the lower layer has four holes, and two holes in the lower layer that are 180 degrees opposite to each other are connected; the upper layer has four holes, of which two holes are connected at 90 degrees, and the other two holes are connected at 90 degrees; during the heating operation of the pipeline, the four holes in the lower layer of the first reversing column are aligned and connected with the four flow holes on the first reversing sleeve, respectively, so that the fluid flows into the heating unit; when the heating operation is completed, the four holes in the upper layer of the first reversing column are respectively connected with the four flow holes on the first reversing sleeve, so that the fluid flows back from the heating unit to the heating area of ​​the insulation box; The outer diameter of the second reversing post is consistent with the inner diameter of the second reversing sleeve, and the second reversing post is inserted into the second reversing sleeve; two holes are provided on the second reversing post at a 90° angle, and the two holes are internally connected; one hole on the second reversing post is aligned and connected to the flow hole E on the second reversing sleeve; the other hole on the second reversing post is selectively aligned and connected to the flow hole F and the flow hole G on the second reversing sleeve; When the pipeline is in the heating state, the hot fluid medium in the fluid heating zone is selectively transported to the inner annular area or the outer annular area of ​​the heating unit through the front infusion pipeline, the reversing conveying unit, the pumping unit, the middle infusion pipeline and the rear infusion pipeline; When the pipeline heating is completed, the fluid medium in the inner annular area or the outer annular area of ​​the heating unit flows back to the heating area of ​​the insulation box through the rear infusion pipeline, the middle infusion pipeline, the pumping unit, the reversing conveying unit and the front infusion pipeline.

2. The heating device for plastic pipe hot melt welding machine according to claim 1, characterized in that: The fluid heating unit adopts a heating coil.

3. The heating device for plastic pipe hot melt welding machine according to claim 1, characterized in that: The pumping unit includes a pumping motor, a crank-connecting rod structure, a pumping cylinder, a first mounting seat, and a second mounting seat; the first mounting seat and the second mounting seat are both fixedly mounted on the inner side wall of the insulation box; the pumping motor and the pumping cylinder are respectively fixedly mounted on the first mounting seat and the second mounting seat; the crank-connecting rod structure includes a crank disk, a connecting rod, and a piston push rod; the crank disk is coaxially fixedly mounted on the output shaft of the pumping motor, one end of the connecting rod is eccentrically connected to the crank disk, and the other end of the connecting rod is relatively rotatably connected to the outer end of the piston push rod; a piston head is provided at the inner end of the piston push rod; the pumping cylinder is a cylinder barrel provided with a liquid inlet and a liquid outlet, the piston head extends into the pumping cylinder, and forms a sealed sliding fit with the inner wall of the pumping cylinder; a suction control valve and a suction control valve are hinged at the inner ends of the liquid inlet and the liquid outlet, respectively.

4. The heating device for a plastic pipe hot-melt welding machine according to claim 1, characterized in that: The elastic limiting structure includes a limiting baffle and two limiting springs; two spring mounting cavities are provided at the inner bottom of the first reversing sleeve, and the lower ends of the two limiting springs are respectively inserted and positioned in the two spring mounting cavities; a positioning shoulder is provided near the inner bottom of the first reversing sleeve; the limiting baffle is fixed to the upper end of the positioning shoulder; a clearance through-hole is provided on the limiting baffle corresponding to the position of the two limiting springs; a compression spring plate is provided at the lower end of the first reversing column, and the compression spring plate is in tight contact with the upper end of the limiting spring; when the two limiting springs are in a naturally extended state, the lower layer hole on the first reversing column is aligned with the flow hole on the first reversing sleeve; the first reversing column is pressed down so that the compression spring plate passes through the clearance through-hole on the limiting baffle, and after rotating 90°, the compression spring plate is limited to the lower end of the limiting baffle, so that the upper layer hole on the first reversing column is aligned with the flow hole on the first reversing sleeve.

5. The heating device for plastic pipe hot melt welding machine according to claim 1, characterized in that: The heating unit is a disc-shaped shell structure as a whole, and an annular clamping area is provided on the periphery of the outer annular area; between the inner annular area and the outer annular area, an annular clamping groove is provided on the outer ring of the outer annular area, and an insulation ring is installed in the inner ring of the inner annular area and the two annular clamping grooves.

6. The heating device for the plastic pipe hot-melt welding machine according to claim 5, characterized in that: The rear sections of the fifth and sixth infusion pipelines are placed in the annular clamping area. Both pipeline sections are semi-annular pipeline sections, and output elbows are provided at the ends of the pipeline sections. The elbow seal at the end of the fifth infusion pipeline passes through the inner wall of the annular clamping area, the annular clamping groove of the outer ring, and the thermal insulation ring in the groove, and then extends into the outer annular area. The elbow seal at the end of the sixth infusion pipeline passes through the inner wall of the annular clamping area, the annular clamping groove of the outer ring, the thermal insulation ring in the groove, and the annular clamping groove of the inner ring, and then extends into the inner annular area.

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