Machine head for double-wall corrugated pipe production

Abstract

The invention discloses a machine head for double-wall corrugated pipe production, and belongs to the technical field of corrugated pipe forming equipment, the machine head comprises an inner-layer core mold, an inner-layer mouth mold and an outer-layer mouth mold which are sequentially sleeved from inside to outside, the outer-layer mouth mold is connected with a mold body, and one side, far away from the mold body, of the inner-layer core mold is connected with a water jacket; a gap between the inner-layer core mold and the inner-layer mouth mold forms an inner-layer discharging channel, a gap between the outer-layer mouth mold and the inner-layer mouth mold forms an outer-layer discharging channel, and four corners, close to one side of the mold body, of the inner-layer core mold and the inner-layer mouth mold are respectively provided with a first tangent plane and a second tangent plane corresponding to the discharging port; the top and the bottom of the vertical section of the water jacket main body are arc-shaped, and two sides of the vertical section are straight walls to form a straight wall part; an annular guide face is arranged on the end face, close to the mouth mold, of the water jacket body. The forming materials at the four corners of the corrugated pipe are supplemented through the first tangent planes and the second tangent planes, and therefore the problem that the wall thickness of the positions is small is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of corrugated pipe production equipment, and specifically, to a head for producing double-wall corrugated pipes. Background Art

[0002] At present, the pipes in the fields of power cables, communication sheaths, etc. are generally polypropylene and HDPE double-wall corrugated pipes, and most of them are circular double-wall corrugated pipes. The pipes are new structural wall pipe materials manufactured by high-strength waveform design and processing technology, and have a series of advantages such as novel structure, high pressure resistance, fast and convenient construction, high temperature resistance, flame retardancy, earthquake resistance, and long service life. However, due to the circular structure of the circular double-wall corrugated pipe, its vertical bearing capacity is weak, so its compressive strength is poor.

[0003] In order to improve the compressive capacity of the double-wall corrugated pipe, a corrugated pipe structure scheme with an outer wall approximately square has emerged on the market. For example, in the German patent with the publication number DE19817109C2, the top and bottom of its inner wall and outer wall are both arc-shaped, while the two sides are straight walls. Although the ring stiffness of this structure has been improved, due to the arc shape at the bottom, when the pipe is buried during construction, there are easily voids under the pipe body, which cannot provide effective support, resulting in the pipe body being prone to tilt and deform under pressure during long-term use.

[0004] In view of this, the applicant of this case designed a special-shaped double-wall corrugated pipe with an inner wall cross-section that is arc-shaped at the top and bottom and straight at the two sides, while the outer wall cross-section is straight at the top and bottom and arc-shaped at the two sides, effectively solving the problem that the pipe body is prone to tilt and deform under pressure in the above-mentioned scheme. However, this design scheme of the applicant brings new technical problems in production, that is, the wall thickness at the intersection of the arc-shaped edges and straight edges at the four corners of the inner and outer walls of the corrugated pipe is uneven, resulting in the compressive strength not meeting the standard.

[0005] In the aforementioned German patent with the publication number DE19817109C2, it designed a relatively long outer nozzle 100, inner nozzle 200, and a conveying channel or flow channel 400 for extruding the compound, so that the molten raw material gradually adapts to the shapes of the outer nozzle 100 and inner nozzle 200 in the relatively long conveying channel, and extrudes the material evenly at the outlet. The Chinese patent with the publication number CN218876220U also adopted this relatively long die to adapt to the processing of special-shaped corrugated pipes, so as to make the wall thickness of the corrugated pipe processed evenly. However, this design scheme will result in a relatively high die cost due to the relatively long special-shaped die. Summary of the Invention

[0006] The purpose of the present invention is to provide a head for producing double-wall corrugated pipes, so as to solve the problems that during the processing of special-shaped corrugated pipes with a specific shape in this application, the wall thickness is prone to be uneven, and the overall structure of the traditional special-shaped die is relatively long, resulting in a high die cost.

[0007] To achieve the above object, the present invention provides a die head for producing double-wall corrugated pipes, which includes an inner layer core mold, an inner layer die orifice, and an outer layer die orifice that are sleeved in sequence from the inside out. The outer layer die orifice is connected to the die body. One side of the inner layer core mold away from the die body is connected to the water jacket main body. The gap between the inner layer core mold and the inner layer die orifice forms an inner layer discharge channel, and the shape of the discharge port of the inner layer discharge channel is an upper and lower arc-shaped edge, and the left and right sides are straight edges. The gap between the outer layer die orifice and the inner layer die orifice forms an outer layer discharge channel, and the shape of the discharge port of the outer layer discharge channel is also an upper and lower arc-shaped edge, and the left and right sides are straight edges. The contour of the inner layer core mold and the inner layer die orifice close to the die body gradually inclines and transitions from the four peripheral edges to the central axis of the die body and is connected to the die body. At the four corners of the inner layer core mold and the inner layer die orifice close to the die body, a first cut surface and a second cut surface corresponding to the discharge port are respectively provided. For a special-shaped double-wall corrugated pipe with an inner wall cross-section that is arc-shaped at the top and bottom and straight walls on both sides, while the outer wall cross-section is straight at the top and bottom and arc-shaped on both sides, in the production process, the position where the arc-shaped wall and the straight wall intersect at the four corners is prone to a thinner wall thickness. By providing the first cut surface and the second cut surface on the inner layer core mold and the inner layer die orifice, the molten polymer material can be drained, that is, the formed material at this place can be supplemented, so as to achieve the effect of uniform overall wall thickness of the inner and outer walls of the corrugated pipe.

[0008] Further, a ring-shaped guiding surface is provided on the end face of the water jacket main body close to the die orifice. The top and bottom of the vertical cross-section of the water jacket main body are arc-shaped, and both sides are straight walls, forming a straight wall part. The outer dimension of the water jacket main body is 1.02 to 1.15 times the size of the discharge port of the inner layer discharge channel in equal proportion.

[0009] Further, the opening sizes of the discharge ports of the inner layer discharge channel and the outer layer discharge channel are uniformly set. When the pressures at the discharge ports are the same, a corrugated pipe inner wall and an outer wall with a uniform wall thickness can be extruded. A first feeding channel and a second feeding channel respectively communicating with the inner layer discharge channel and the outer layer discharge channel are provided in the die body, which is convenient for separately controlling the feeding of the inner and outer walls of the corrugated pipe. The vertical cross-sections of the first feeding channel and the second feeding channel are both circular rings, which can be applied to the production of circular double-wall corrugated pipes.

[0010] Further, both the first cut surface and the second cut surface are elliptical cut surfaces. The extension lines of the long axes of the first cut surface and the second cut surface respectively correspond to the intersection points of the arc-shaped edge and the straight edge of the discharge port of the inner layer discharge channel and the outer layer discharge channel, and are used to supplement the thinner wall thickness at the intersection of the arc-shaped edge and the straight edge on the inner and outer walls of the corrugated pipe.

[0011] Furthermore, both the minor-axis radius and the major-axis radius of the first cross-section are smaller than the minor-axis radius a and the major-axis radius b of the second cross-section, where a ≤ 1 / 2b, guiding the molten material to flow from the center to the intersection of the arc edge and the straight edge of the discharge port.

[0012] Furthermore, a ≥ 5 mm, and the larger the specification of the special-shaped corrugated pipe, the larger the value of a.

[0013] Furthermore, the inner edge of the inner core mold is circular, and one side of the major axis of the first cross-section is in contact with the circular inner edge of the inner core mold. The circular inner edge of the inner core mold is used to correspond to the first feeding channel of the circular mold body.

[0014] Furthermore, a flow-dividing end face is arranged on one side of the inner die orifice close to the mold body. The inner edge of the flow-dividing end face is circular, and its outer edge protrudes from the mold body mounting surface and has the same shape as the discharge port of the outer discharge channel, that is, the outer edge of the flow-dividing end face protrudes from the bottom surface of the second feeding channel, and further mixing can be carried out before the material is extruded.

[0015] Furthermore, one side of the major axis of the second cross-section is in contact with the outer edge of the flow-dividing end face, and the distance c from the contact point to the center of the second cross-section satisfies 1 / 2b ≤ c < b. Since the outer edge of the flow-dividing end face protrudes from the bottom surface of the second feeding channel, more material tends to flow through the second cross-section to the discharge port at this time, which is beneficial to the realization of uniform wall thickness. The inner edge of the flow-dividing end face is used to connect with the mold body.

[0016] Furthermore, the distance from the first cross-section to the discharge port of the inner discharge channel and the distance from the second cross-section to the discharge port of the outer discharge channel are both greater than or equal to 30 mm. At the discharge ports of the inner discharge channel and the outer discharge channel, the inner core mold, the inner die orifice, and the outer die orifice are used to enclose a discharge channel with a length of at least 30 mm, so that the pressure at the discharge port is balanced, which is beneficial to the realization of uniform wall thickness of the overall corrugated pipe.

[0017] Obviously, the elements or features described in the above individual embodiments can be used alone or in combination in other embodiments.

[0018] The present invention provides the first and second cut surfaces corresponding to the intersection of the arc edge and the straight edge on the inner wall and the outer wall of the special-shaped corrugated tube at the four corners of the inner core mold and the inner mouth mold, so as to drain the molten polymer material in a targeted manner, that is, to supplement the molding material at the intersection of the arc edge and the straight edge, thereby solving the problem of thin wall thickness at this location; and the solution to this problem is achieved by utilizing the mutual cooperation between the inner core mold, the inner mouth mold and the outer mouth mold. The mold body part still uses the circular mold body on the existing circular double-wall corrugated tube production equipment, and does not need to be replaced with a special-shaped mold body, which can greatly reduce the mold processing cost, and the inner core mold, the inner mouth mold and the outer mouth mold can be quickly replaced when necessary, which can be suitable for the rapid switching of different production requirements of special-shaped corrugated tubes and traditional circular corrugated tubes in the background technology.

[0019] In addition, since the water jacket body is mainly used to cool, form and move the inner wall of the special-shaped corrugated pipe, the outer shape of the water jacket body matches the shape of the discharge port of the inner layer discharge channel, both of which are to adapt to the shape of the inner wall of the special-shaped corrugated pipe; at the same time, the outer size of the water jacket body is set to be slightly larger than the shape of the discharge port of the inner layer discharge channel in proportion, which is beneficial to the molten material being proportionally expanded after coming out of the discharge port of the inner layer discharge channel, which is beneficial to improving the uniformity of the wall thickness of the inner wall of the corrugated pipe. If the outer size of the water jacket body is smaller than the discharge port of the inner layer discharge channel, excess material will be squeezed out, and this part of the material will be difficult to be evenly squeezed on the water jacket body to various places on the inner wall of the corrugated pipe, which will cause uneven wall thickness of the inner wall of the corrugated pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the drawings, the sizes and proportions do not represent the sizes and proportions of actual products. The drawings are merely illustrative, and some non-essential elements or features are omitted for clarity.

[0021] Figure 1 It is a cross-sectional schematic diagram of the mouth die and the die body of the present invention;

[0022] Figure 2 yes Figure 1 The enlarged view of point A in the middle;

[0023] Figure 3 It is a schematic diagram of the structure of the inner core mold and the inner die;

[0024] Figure 4 It is a cross-sectional schematic diagram of a special-shaped double-wall corrugated pipe;

[0025] Figure 5 It is a structural schematic diagram of a machine head for producing double-wall corrugated pipes according to the present invention;

[0026] Figure 6 The present invention is a schematic diagram of the water jacket structure of a machine head for producing double-wall corrugated pipes.

[0027] Description of Reference Numerals

[0028] 1. Inner core mold; 2. Inner mouth mold; 3. Outer mouth mold; 4. Mold body; 5. Inner discharge channel; 6. Outer discharge channel; 7. First section; 8. Second section; 9. First feed channel; 10. Second feed channel; 11. Diversion end face; 100. Water jacket body; 101. Straight wall; 102. Vacuum groove; 103. Negative pressure suction hole; 104. Guide surface. DETAILED DESCRIPTION

[0029] The present invention will be described in detail below with reference to the accompanying drawings. What is described here is only a preferred embodiment of the present invention, and those skilled in the art can think of other ways to implement the present invention based on the preferred embodiment, and other ways also fall within the scope of the present invention.

[0030] Example 1

[0031] Reference Figures 1 - 6 A die for producing a double-wall corrugated pipe comprises an inner core die 1, an inner die 2 and an outer die 3 which are sequentially sleeved from the inside to the outside, the outer die 3 is connected to a die body 4, a water jacket body 100 is connected to the inner core die 1 on a side away from the die body 4, an inner discharge channel 5 is formed by a gap between the inner core die 1 and the inner die 2, and the discharge port of the inner discharge channel 5 is in the shape of upper and lower arc-shaped edges, and the left and right sides are straight edges; the outer die 3 and the inner die 2 are connected to a water jacket body 100, and the inner core die 1 ... The gap between the inner and outer layers forms an outer layer discharge channel 6, and the discharge port of the outer layer discharge channel 6 is also in the shape of upper and lower arc-shaped edges, and the left and right sides are straight edges, and the outer wall of the corrugated tube with upper and lower straight edges and left and right sides as arc-shaped edges is mainly realized by the corrugated tube outer wall forming device (not shown) arranged on the machine head, which is a prior art and will not be described in detail in this embodiment; this embodiment mainly provides a die that can uniformly extrude the materials required for the inner and outer walls of the corrugated tube. Through the above arrangement, the inner layer discharge channel 5 is used to extrude the inner wall of the special-shaped double-wall corrugated tube, and the outer layer discharge channel 6 is used to extrude the outer wall of the special-shaped double-wall corrugated tube. The contour of one side of the inner core mold 1 and the inner mouth mold 2 close to the mold body 4 gradually tilts from the edges around to the central axis of the mold body 4 and transitions to a circle, and is connected to the mold body 4. The four corners of the inner core mold 1 and the inner mouth mold 2 close to the mold body 4 are respectively provided with a first section 7 and a second section 8 corresponding to the discharge port, wherein the first section 7 and the second section 8 are used to guide the molten material to improve the uniformity of the wall thickness of the inner and outer walls of the corrugated tube.

[0032] The end face of the water jacket body 100 close to the die is provided with an annular guide surface 104 , which is an inclined surface inclined from the die body 4 toward the water jacket body 100 , and has a height of 25 mm and a width of 10 mm, and is used to guide the molten material to the water jacket body 100 . The top and bottom of the vertical cross-section of the water jacket body 100 are arc-shaped, and the two sides are straight walls to form a straight wall portion. The outer dimensions of the water jacket body 100 are 1.02 to 1.15 times the size of the outlet port of the inner layer outlet channel 5 in proportion. The value in this embodiment is 1.06 times, which is used to evenly expand and support the molten material coming out of the outlet port of the inner layer outlet channel 5, which is beneficial to improve the uniformity of the thickness of the inner wall of the bellows. If the outer dimensions of the water jacket body 100 are smaller than the outlet port of the inner layer outlet channel 5, excess material will be squeezed out, and this part of the material will be difficult to be evenly squeezed to various places on the inner wall of the bellows on the water jacket body 100, which will cause uneven wall thickness of the inner wall of the bellows.

[0033] The mold body 4 is provided with a first feed channel 9 and a second feed channel 10 which are respectively connected to the inner layer discharge channel 5 and the outer layer discharge channel 6. In this embodiment, the vertical cross-sections of the first feed channel 9 and the second feed channel 10 are both circular, so they can be adapted to the production and processing of circular double-wall corrugated pipes.

[0034] In the prior art, in the production equipment of circular double-wall corrugated pipes, the shape of the discharge port surrounded by the inner core mold, the inner mouth mold and the outer mouth mold is circular, and the vertical sections of the first feed channel and the second feed channel in the mold body are both circular rings. The structure of the mold body 4 in this embodiment is the same as the structure in the prior art, except that the first section 7 and the second section 8 are set on the inner core mold and the inner mouth mold in the mouth mold, and the shape of the discharge port matches the inner and outer wall shapes of the special-shaped double-wall corrugated pipe. Therefore, the mouth mold in this application is directly replaced with the mouth mold of the circular double-wall corrugated pipe in the prior art, so that the production of special-shaped double-wall corrugated pipes can be realized. There is no need to prepare a longer special-shaped mold body, thereby saving mold costs. It can also be suitable for the rapid switching of the production needs of circular double-wall corrugated pipes and special-shaped double-wall corrugated pipes in actual production, thereby improving the line change efficiency of the production line.

[0035] The opening sizes of the discharge port of the inner layer discharge channel 5 and the discharge port of the outer layer discharge channel 6 are evenly set, respectively consistent with the inner wall and outer wall thickness of the double-wall corrugated pipe to be processed. This is the basic condition for the uniform wall thickness of the inner and outer walls of the corrugated pipe. When the pressure at the discharge port is consistent, the inner and outer walls of the corrugated pipe with uniform wall thickness can be extruded.

[0036] Both the first cutting plane 7 and the second cutting plane 8 are elliptical cutting planes; the extension lines of the major axes of the first cutting plane 7 and the second cutting plane 8 respectively correspond to the intersections of the arc-shaped edges and straight edges of the discharge ports of the inner discharge channel 5 and the outer discharge channel 6, and are used for feeding the thinner wall thickness parts at the intersections of the arc-shaped edges and straight edges on the inner and outer walls of the corrugated pipe. This setting can, on the one hand, better guide the molten material and improve the material replenishment effect. On the other hand, compared with the die without processing the first cutting plane 7 and the second cutting plane 8, after processing the first cutting plane 7 and the second cutting plane 8 on the inner core mold 1 and the inner die 2 in this embodiment, the chamber volumes at the corresponding four corners of the inner discharge channel 5 and the outer discharge channel 6 also become larger, which is equivalent to being able to store a part of the material more. During the extrusion molding, it can realize the replenishment of the material at the four corners, which is further beneficial to solving the problem of uneven wall thickness at the four corners.

[0037] Both the minor axis radius and the major axis radius of the first cutting plane 7 are smaller than the minor axis radius a and the major axis radius b of the second cutting plane 8, where a ≤ 1 / 2b and a ≥ 5 mm. The larger the specification of the special-shaped corrugated pipe, the larger the value of a. In the production of double-wall corrugated pipes, the outer wall needs to be prepared with corrugations through compressed air and a corrugation forming module, and consumes more molten material per unit time than the inner wall. Therefore, it is more likely to have the problem of wall thickness thinning caused by material shortage. Therefore, the specification of the first cutting plane 7 is smaller than that of the second cutting plane 8.

[0038] The inner edge of the inner core mold 1 is circular, and one side of the major axis of the first cutting plane 7 is connected to the circular inner edge of the inner core mold 1. The circular inner edge of the inner core mold 1 is used to correspond to the first feeding channel 9 of the circular mold body 4.

[0039] A flow splitting end face 11 is provided on one side of the inner die 2 close to the mold body 4. The inner edge of the flow splitting end face 11 is circular, and its outer edge protrudes from the mold body mounting surface and has the same shape as the shape of the discharge port of the outer discharge channel 6, that is, the outer edge of the flow splitting end face 11 protrudes from the bottom surface of the second feeding channel 6, which can assist in further mixing before the material is extruded.

[0040] One side of the major axis of the second cutting plane 8 is connected to the outer edge of the flow splitting end face 11, and the distance from the connection point to the center of the second cutting plane 8 is c, satisfying 1 / 2b ≤ c < b. Its value is mainly determined by the wall thickness of the outer wall of the corrugated pipe and the overall specification size of the corrugated pipe. The thicker the wall thickness of the outer wall or the larger the overall specification of the corrugated pipe, the larger the value of c. The setting that one side of the major axis of the second cutting plane 8 is connected to the outer edge of the flow splitting end face 11 is equivalent to setting a notch on the outer edge of the flow splitting end face for the second cutting plane 8. Since the outer edge of the flow splitting end face 11 protrudes from the bottom surface of the second feeding channel 10, more material tends to flow through the second cutting plane 8 to the discharge port when extruding the material, which is beneficial to replenishing the material at the four corners of the corrugated pipe and promoting the realization of uniform wall thickness of the outer wall. The inner edge of the flow splitting end face 11 is used to connect to the mold body 4.

[0041] The distances from the first cutting plane 7 to the discharge opening of the inner discharge channel 5 and from the second cutting plane 8 to the discharge opening of the outer discharge channel 6 are both greater than or equal to 30 mm. At the discharge openings of the inner and outer discharge channels, an inner core mold, an inner die, and an outer die are used to enclose a discharge channel with a length of at least 30 mm, which is beneficial to the pressure balance at the discharge opening and thus conducive to the realization of a uniform wall thickness of the overall corrugated pipe.

[0042] This embodiment provides a comparative example and an improved embodiment for comparison. The melt index of the molten material in both the comparative example and the embodiment is 1.2 g / 10 min, the heating temperature of the molten material in the mold body 4 is 200 °C, the radius of the upper and lower arc edges of the inner wall of the corrugated pipe is 147 mm, the left and right straight wall dimensions are 170 mm, the radius of the left and right arc edges of the outer wall is 220 mm, the dimensions of the upper and lower straight edges are 110 mm. After improvement, the minor axis radius of the first cutting plane 7 is 10 mm, the major axis radius is 15 mm, the minor axis radius of the second cutting plane 8 is 15 mm, the major axis radius is 20 mm, the distance c from the connection of the second cutting plane 8 and the flow splitting end face 11 to the center of the second cutting plane 8 is 10 mm, the designed wall thickness of the inner wall of the special-shaped corrugated pipe is 2 mm, and the designed wall thickness of the outer wall is 2.5 mm. Three points are selected for detection at the four corners where the straight edges and arc edges of the inner and outer walls of the corrugated pipe intersect. The comparison data of the wall thickness before and after improvement are shown in the following table:

[0043]

[0044]

[0045] Refer to Figure 2, the water jacket body 100 in the present invention extends axially and is hollow inside, and is provided with cooling water pipes for cooling and forming the corrugated pipe. In this application, it is also used to arrange air pipes to form a negative pressure air passage (not shown in the figure). The double-wall corrugated pipe forming equipment in the prior art also includes a mold for forming the wave crest and wave trough structure of the outer wall of the corrugated pipe, and generally adsorbs the outer wall to the groove of the mold through negative pressure to form the wave crest. Therefore, the negative pressure equipment is one of the auxiliary facilities of the double-wall corrugated pipe forming equipment. The negative pressure air passage in this application is connected to this negative pressure equipment. The vertical cross-section of the inner wall of the common double-wall corrugated pipe is circular. In this application, in order to cooperate with the special-shaped corrugated pipe with a circular arc at the top and bottom and straight walls on both sides of the vertical cross-section, the top and bottom of the vertical cross-section of the water jacket body 100 are circular arcs, and both sides are straight walls, forming a straight wall portion 101; a vacuum groove 102 spirally surrounding its outer wall is provided on the outer surface of the water jacket body 100, and at least one negative pressure suction hole 103 is provided at the bottom of the vacuum groove 102. The negative pressure suction hole 103 is connected to an external negative pressure equipment (not shown in the figure) through the negative pressure air passage inside the water jacket body 100. By using the external negative pressure equipment, the negative pressure air passage, the negative pressure suction hole and the vacuum groove, when the water jacket is working, the inner wall of the corrugated pipe wrapped on the outer surface of the water jacket body 100 is adsorbed, so that the inner wall of the formed and extruded corrugated pipe can adhere to the surface of the water jacket and move. Moreover, since the negative pressure area is formed on the outer wall of the water jacket body 100 through the spirally arranged vacuum groove 102, the adsorption effect is better than that in the background technology.

[0046] For the special-shaped double-wall corrugated pipe with a circular arc at the top and bottom and straight walls on both sides of the vertical cross-section of the inner wall, due to its own structural characteristics, it is difficult for the straight wall parts on both sides of the inner wall of the just-formed and extruded corrugated pipe to adhere to the side wall surface of the water jacket body 100. Therefore, the negative pressure suction holes 103 are located in the straight wall portion 101 of the water jacket body 100.

[0047] The distances from both ends of the vacuum groove 102 to both ends of the water jacket body 100 are greater than 0. That is, both ends of the vacuum groove 102 do not extend to the end faces of the water jacket body 100, so as to prevent the opening of the vacuum groove 102 from connecting to the end face of the water jacket body 100. An air inlet passage will be formed here during operation, and external gas will enter the vacuum groove 102, thereby affecting the negative pressure adsorption effect.

[0048] The negative pressure suction holes 103 are located in the middle and lower part of the straight wall portion 101. For the above-mentioned special-shaped double-wall corrugated pipe, the middle and lower parts of the straight walls on both sides of its inner wall are farther away from the side wall of the water jacket body 100 than the upper part during the forming and extrusion process. The negative pressure suction holes 103 are arranged at this position, which can better adsorb the inner wall of the corrugated pipe on the water jacket body 100.

[0049] The number of the negative pressure suction holes 103 is greater than or equal to 2, and at least two negative pressure suction holes 103 are respectively located on the straight wall parts 101 on both sides of the water jacket body 100. For bellows with a larger thickness or inner diameter, the water jacket body 100 will be made larger. To ensure the negative pressure adsorption effect, a larger number of negative pressure suction holes 103 are required, and the adsorption effect of the negative pressure suction holes 103 located on both sides is better.

[0050] The groove width of the vacuum groove 102 is 2 - 8 mm, and the groove depth is 2 - 6 mm. Since the inner wall of the bellows formed by extrusion is relatively soft, has strong plasticity, and even still has a certain fluidity before cooling to a certain temperature, a wider vacuum groove 102 will bring greater resistance to the movement of the inner wall of the bellows along the surface of the water jacket body 100, and will also affect the surface forming effect of the inner wall of the bellows. However, for the inner wall of a bellows with a larger diameter, if the width of the vacuum groove is small, the negative pressure suction force is insufficient, which will also cause the inner wall of the bellows to not be able to adhere to the outer wall of the water jacket body 100 as a whole. Therefore, the settings of the groove width and groove depth need to be jointly determined according to factors such as the material and specifications of the bellows.

[0051] The diameter of the negative pressure suction hole 103 is 2 - 4 mm. The diameter of the negative pressure suction hole 103 should not be set too large to avoid sucking the soft inner wall material with a certain fluidity that has just been extruded and not yet cooled in place into the negative pressure suction hole 103.

[0052] The water jacket body 100 is arranged at the discharge end of the die and is connected to the inner layer core mold 1. This die is applicable to the special-shaped double-wall bellows with a vertical cross-section of the inner wall having a circular arc at the top and bottom and straight walls on both sides.

[0053] The vacuum groove 102 is spirally wound with multiple turns, and the distance between adjacent two turns of the vacuum groove 102 gradually becomes narrower in the direction away from the die body 4. For the bellows just formed and extruded through the die, the closer it is to the die part, the softer it is, and even still has a certain fluidity. When it moves while adhering to the outer wall of the water jacket body 100, the frictional force is large. If the number of turns of the vacuum groove 102 is set denser near the die, it will increase the frictional force of the bellows and affect the movement and normal cooling and forming of the bellows. And the groove depth of the vacuum groove 102 can gradually become shallower in the direction away from the die body 4. Since the bellows on the side away from the die body 4 has gradually cooled and solidified, the suction force of the vacuum groove 102 can be appropriately weakened. Considering energy conservation, the depth of the vacuum groove 102 can be adjusted to become shallower.

[0054] There are multiple vacuum grooves 102, and each vacuum groove 102 is at least spirally wound for 3 turns. The distance between adjacent two vacuum grooves 102 can be adjusted according to factors such as the material and specification of the bellows, the moving speed on the water jacket body 100, and the requirement for the smooth effect of the inner wall surface of the bellows. The negative pressure air channels corresponding to the negative pressure suction holes 103 in different vacuum grooves 102 can be communicated with each other, so that the negative pressure air channel structure inside the water jacket body 100 is simple and the processing cost is low; they can also not be communicated. For the solution where the negative pressure suction holes 103 are not communicated with each other, it is convenient to independently control the negative pressure adsorption force of each vacuum groove 102, so as to adapt to different cooling stages in the bellows forming process. Specifically, how to independently control the adsorption force of each negative pressure suction hole 103 through a controller and an air valve is the prior art and will not be elaborated in this application.

[0055] The number of the negative pressure suction holes 103 is greater than or equal to 2, and the aperture of the negative pressure suction hole 103 close to the die body 4 is smaller than that of the negative pressure suction hole 103 far from the die body 4. Since the inner wall material of the bellows in the part close to the die body 4 may still have a certain fluidity, the negative pressure suction hole 103 should not be too large.

[0056] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "front", "rear", "left", "right", "upper", "lower", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0057] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0058] The protection scope of the present invention is only defined by the claims. Benefiting from the teachings of the present invention, those skilled in the art can easily recognize that the alternative structures of the structures disclosed in the present invention can be used as feasible alternative embodiments, and the embodiments disclosed in the present invention can be combined to generate new embodiments, which also fall within the scope of the appended claims.

Claims

1. A head for producing double-wall corrugated pipes, comprising an inner core die, an inner die head and an outer die head which are sleeved in sequence from the inside outwards. The outer die head is connected to a die body, and one side of the inner core die away from the die body is connected to a water jacket body. It is characterized in that, The gap between the inner core die and the inner die orifice forms an inner discharge channel, and the gap between the outer die orifice and the inner die orifice forms an outer discharge channel. The discharge orifices of the inner discharge channel and the outer discharge channel are both in the shape of upper and lower arc-shaped edges, and the left and right sides are straight edges. The contour of the inner core die and the inner die orifice on the side close to the die body gradually slopes towards the central axis of the die body from the four peripheral edges and is connected to the die body. At the four corners of the inner core die and the inner die orifice on the side close to the die body, a first cutting surface and a second cutting surface corresponding to the discharge orifice are respectively provided.

2. The nose for producing double-wall corrugated pipes according to claim 1, characterized in that, The end face of the water jacket body close to the die orifice is provided with an annular guiding surface. The top and bottom of the vertical section of the water jacket body are arc-shaped, and both sides are straight walls, forming straight wall parts. The outer dimension of the water jacket body is 1.02 - 1.15 times the size of the discharge orifice of the inner discharge channel in equal proportion.

3. The nose for producing a double-wall corrugated pipe according to claim 1, characterized in that, The opening sizes of the discharge orifices of the inner discharge channel and the outer discharge channel are evenly set. In the die body, a first feeding channel and a second feeding channel respectively communicating with the inner discharge channel and the outer discharge channel are provided, and the vertical sections of the first feeding channel and the second feeding channel are both circular rings.

4. The head for producing a double-wall corrugated pipe according to claim 3, characterized in that, Both the first cutting surface and the second cutting surface are elliptical cutting surfaces. The extension lines of the long axes of the first cutting surface and the second cutting surface respectively correspond to the intersections of the arc-shaped edges and the straight edges of the discharge orifice of the inner discharge channel and the discharge orifice of the outer discharge channel.

5. The head for producing a double-wall corrugated pipe according to claim 4, characterized in that, The minor axis radius and the major axis radius of the first cutting surface are both smaller than the minor axis radius a and the major axis radius b of the second cutting surface, and a ≤ 1 / 2b.

6. The head for producing a double-wall corrugated pipe according to claim 5, characterized in that, a ≥ 5mm.

7. The head for producing double-wall corrugated pipes according to claim 5, characterized in that, The inner edge of the inner core die is circular, and one side of the long axis of the first cutting surface is connected to the circular inner edge of the inner core die.

8. The head for producing double-wall corrugated pipes according to claim 7, characterized in that, On the side of the inner die orifice close to the die body, a flow splitting end face is provided. The inner edge of the flow splitting end face is circular. The outer edge of the flow splitting end face protrudes from the die body mounting surface, and its shape is the same as the shape of the discharge orifice of the outer discharge channel.

9. The head for producing double-wall corrugated pipes according to claim 8, characterized in that, One side of the long axis of the second cutting surface is connected to the outer edge of the flow splitting end face, and the distance c from the connection point to the center of the second cutting surface satisfies 1 / 2b ≤ c < b.

10. The nose for producing double-wall corrugated pipes according to claim 8, characterized in that, The distances from the first cutting surface to the discharge orifice of the inner discharge channel and from the second cutting surface to the discharge orifice of the outer discharge channel are both greater than or equal to 30mm.

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