Plastic pipe blow molding locking and sealing device

Abstract

The present invention discloses a locking and sealing device for blow molding of plastic pipes, which includes a molding die barrel and an inflation mandrel passing through the molding die barrel; a convex ring is fixedly arranged on the inner circumference of the molding die barrel, and several radial stepped holes are arranged in the molding die barrel on the inner side of the convex ring in the axial direction. A stepped special-shaped steel ball is slidably arranged in each step, and a return spring is arranged outside the special-shaped steel ball; a sealing nested sleeve is slidably arranged on the inflation mandrel, and an annular knife is fixedly arranged on the inner side in the axial direction of the sealing nested sleeve; a clamping push barrel is sleeved outside the special-shaped steel ball, outside the outer end of the molding die barrel and outside the sealing nested sleeve. The clamping push barrel is fixedly connected with a radial push plate, and the inner circumference of the clamping push barrel is provided with a sequentially connected initial cylindrical surface, a shrinking conical surface, and a locking cylindrical surface; the present invention not only has a good locking effect and is easy to demold, but also ensures the sealing effect of thermoplastic plastics in a viscous flow state under a relatively high pressure, and can improve the molding quality and efficiency.

Description

Technical Field

[0001] The present invention relates to a locking and sealing device for blow molding of plastic pipes, in particular to a locking and sealing device for blow molding of PVC-O pipes. Background Art

[0002] PVC-O (biaxially oriented polyvinyl chloride) is the latest evolution form of current PVC pipes. It axially stretches and radially stretches the PVC-U pipes produced by the extrusion method, enabling the long-chain molecules of PVC in the pipes to be regularly arranged in a biaxial direction. Through this special orientation processing technology, new PVC pipes with high strength, high toughness, high impact resistance, and fatigue resistance can be obtained.

[0003] Currently, there is a two-step processing method for the new production of PVC-O pipes. The two-step processing method is to heat and blow-expand the extruded and already cooled PVC-U pipe segments (thick blanks) in a mold to the required size to achieve orientation. The two-step pipe production has its unique pressure-forming method, which requires a locking and sealing operation on the hot blank pipe in the mold. Since the blank pipe is in a thermoplastic state at this time, it is easy to lock the blank pipe, but it is very difficult to seal the viscous-flowing hot plastic. For example, the US patent with the publication number US2011163489A1 discloses a locking device for the two-step production of PVC-O pipes by Molecor Company in Spain. This device includes the operation of locking the hot blank pipe mentioned above. Its main composition is to lock both ends of the hot plastic blank pipe. The fixed end uses an external locking method, and the moving end uses an internal locking method; both locking methods use a specific track to cooperate with steel balls, and the steel balls move radially through axial movement to achieve locking; this patent can effectively solve the problem of locking the thermoplastic blank pipe, but does not mention the sealing of the blank pipe; in addition, the steel ball locking method adopted in this patent does not consider the problem that the steel balls are not reset after being embedded in the blank pipe, resulting in the blank pipe being unable to be smoothly demolded; the domestic patent with the publication number CN208565938U discloses a device for locking and sealing pipes. This patent relates to the field of pipe locking and sealing. Its specific implementation method is to force the radial deformation of the rubber sealing sleeve by the axial movement of the inner cone nesting to form an interference and clearance fit with the pipe to achieve the effects of locking and sealing and loosening. This patent provides a locking and sealing method for hard pipes, which can work when the pressure inside the pipe is low and solve the problem of locking and sealing hard pipes, but it is essentially different from the locking and sealing of plasticized plastic pipes and cannot be applied to high-pressure working conditions. Summary of the Invention

[0004] The purpose of the present invention is to provide a locking and sealing device for blow molding of plastic pipes in view of the deficiencies of the prior art. It not only has good locking effect, is easy to demold, but also ensures the sealing effect of thermoplastic plastics in a viscous-flow state under high pressure, and can improve the molding quality and efficiency.

[0005] To achieve the above object, the plastic pipe blow molding locking and sealing device of the present invention includes a molding die cylinder and an inflation mandrel passing through the molding die cylinder; it is characterized in that: a convex ring is fixedly provided on the inner circumference of the molding die cylinder, and several radial stepped holes are provided in the molding die cylinder on the axial inner side of the convex ring. An abnormally shaped steel ball is slidably provided in each step. The radially outer end of the abnormally shaped steel ball is arc-shaped and located on the radially outer side of the stepped hole. A step is provided in the middle of the abnormally shaped steel ball. A return spring is provided in the large-diameter hole of the stepped hole, and the return spring is sleeved on the abnormally shaped steel ball on the inner side of the step; a sealing sleeve is slidably provided on the inflation mandrel on the axial outer side of the convex ring. The sealing sleeve is provided with a limit step that cooperates with the convex ring. The axial inner end of the limit step is located in the molding die cylinder on the axial outer side of the convex ring. More than one sealing ring is provided on the inner circumference of the sealing sleeve; an annular knife is fixedly provided on the axial inner side of the sealing sleeve, and the outer diameter of the annular knife is smaller than the inner diameter of the convex ring; a clamping push cylinder is sleeved outside the abnormally shaped steel ball, outside the outer end of the molding die cylinder, and outside the sealing sleeve. A radial push plate located on the axial rear side of the sealing sleeve is fixedly connected to the axial outer end of the clamping push cylinder. The radial push plate pushes the sealing sleeve, and its annular knife inserts into the end of the blank tube to seal the end; the inner circumference of the axial inner end of the clamping push cylinder is provided with an initial cylindrical surface, a shrinking conical surface, and a locking cylindrical surface that are connected in sequence from the inside to the outside. The diameter of the initial cylindrical surface is larger than the diameter of the locking cylindrical surface.

[0006] During use, connect the molding die cylinder to the mold, put the end of the blank tube on the inflation mandrel between the molding die cylinder and the convex ring, and its end face is in close contact with the convex ring. Push the clamping push cylinder axially inward, and radially push each abnormally shaped steel ball inward through the shrinking conical surface on its inner circumference until the radially inner ends of each abnormally shaped steel ball are squeezed into the blank tube and the radially outer ends enter the locking cylindrical surface to complete the locking and fixing of the blank tube. At the same time, the radial push plate pushes the sealing sleeve, and its annular knife inserts into the end of the blank tube to seal the end, realizing the sealing. Since the abnormally shaped steel balls will pass through three sections: the initial cylindrical surface, the shrinking conical surface, and the locking cylindrical surface, the entire mechanism can achieve the effect of locking first and then sealing; introduce hot high-pressure gas into the inflation mandrel to realize blow molding; after molding, pull the clamping push cylinder axially outward, and the return spring pushes each abnormally shaped steel ball to automatically reset radially and return to the initial cylindrical surface to unlock and demold; it can be seen that this device not only has a good locking effect and is easy to demold, but also ensures the sealing effect of thermoplastic plastics in a viscous flow state under high pressure, which can improve the molding quality and efficiency; the sealing effect can be further improved through the sealing ring to withstand high pressure; the limit step can radially pre-position the sealing sleeve, ensure smooth axial movement, and axially limit it during sealing

[0007] As a further improvement of the present invention, the radially inner end of the abnormally shaped steel ball is arc-shaped, and its radius is smaller than the radius of the radially outer end; this can increase the pressure during locking and facilitate automatic reset;

[0008] In summary, the present invention can maintain its shape after pretreatment, facilitate assembly with the mold, and is easy to demold and avoid damage after molding, improving the quality of the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is the front view of the embodiment of the present invention.

[0010] Figure 2 It is the front view of the working state of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0011] In order to more clearly understand the purpose, technical solution and beneficial effects of the present invention, the present invention will be further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following embodiments.

[0012] As Figure 1 shown, the blow molding locking and sealing device for plastic pipes of this embodiment includes a molding die barrel 1 and an inflation mandrel 2 passing through the molding die barrel 1; a convex ring 3 is fixedly arranged on the inner circumference of the molding die barrel 1, and several radial stepped holes are arranged in the molding die barrel 1 on the inner side of the convex ring in the axial direction. An irregular steel ball 4 is slidably arranged in each step. The radially outer end 5 of the irregular steel ball 4 is arc-shaped and located on the radially outer side of the stepped hole. A step is arranged in the middle of the irregular steel ball 4. A return spring 7 is arranged in the large-diameter hole of the stepped hole. The return spring 7 is sleeved on the irregular steel ball 4 on the inner side of the step. The radially inner end 6 of the irregular steel ball 4 is arc-shaped, and its radius is smaller than the radius of the radially outer end 5; a sealing sleeve 8 is slidably arranged on the inflation mandrel 2 on the outer side of the convex ring in the axial direction. An annular knife 9 is integrally fixed on the inner side of the sealing sleeve 8 in the axial direction. The outer diameter of the annular knife 9 is smaller than the inner diameter of the convex ring 3. The sealing sleeve 8 is provided with a limiting step 10 that cooperates with the convex ring 3. The axially inner end of the limiting step 10 is located in the molding die barrel 1 on the outer side of the convex ring in the axial direction. Two sealing rings 11 are arranged on the inner circumference of the sealing sleeve 8; an actuating cylinder 12 is sleeved outside the irregular steel ball 4, outside the outer end of the molding die barrel 1 and outside the sealing sleeve 8. A radial push plate 13 located on the rear side of the sealing sleeve 8 in the axial direction is integrally fixed to the axially outer end of the actuating cylinder 12. The sealing sleeve 8 and its annular knife 9 are pushed through the radial push plate 13 into the end of the blank tube to close the end; the inner circumference of the axially inner end of the actuating cylinder 12 is provided with an initial cylindrical surface 14, a shrinking conical surface 15, and a locking cylindrical surface 16 that are connected in sequence from the inside to the outside. The diameter of the initial cylindrical surface 14 is larger than the diameter of the locking cylindrical surface 16.

[0013] When in use, as Figure 2As shown, connect the forming die barrel 1 with the die, put the end of the blank tube 17 between the inflation mandrel 2 and the forming die barrel 1, and make its end face closely contact with the convex ring 3. Push the clamping push barrel 12 axially inward. Through the shrinking conical surface 15 on its inner circumference, push various special-shaped steel balls 4 radially inward until the radially inner ends 6 of various special-shaped steel balls 4 are squeezed into the blank tube 17, and the radially outer ends 5 enter the locking cylindrical surface 16 to complete the locking and fixation of the blank tube 17. At the same time, the radial push plate 13 pushes the sealing sleeve 12, and its annular knife 9 inserts into the end of the blank tube 17 to seal the end. Adding two sealing rings 11 to seal the outer circumference of the inflation mandrel 2 realizes reliable overall sealing. Since the special-shaped steel balls 5 will pass through three sections: the initial cylindrical surface 14, the shrinking conical surface 15, and the locking cylindrical surface 16, the whole mechanism can achieve the effect of locking first and then sealing; Pass hot high-pressure gas into the inflation mandrel 2 to realize blow molding; After molding, pull the clamping push barrel 12 axially outward, and the return spring 7 pushes various special-shaped steel balls 4 to automatically reset radially and return to the initial cylindrical surface 14 to unlock and demold; The axial front end of the limit step 10 is located in the forming die barrel 1 on the axial outer side of the convex ring 3, which can pre-position the sealing sleeve 8 radially and ensure smooth movement in the axial direction. The limit step 10 axially limits the sealing sleeve 8 during sealing; The radially inner end 6 is an arc with a smaller area compared to the radially outer end 5, which can increase the pressure during locking and facilitate automatic reset; In summary, this device not only has a good locking effect and is easy to demold, but also ensures the sealing effect of thermoplastic plastics in the viscous flow state under high pressure, and can improve the molding quality and efficiency;

[0014] The present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A locking and sealing device for blow molding of plastic pipes, comprising a molding die barrel and an inflation mandrel passing through the molding die barrel; characterized in that: A convex ring is fixedly arranged on the inner circumference of the forming die barrel. A plurality of radial stepped holes are arranged in the forming die barrel on the inner side of the convex ring in the axial direction. A special-shaped steel ball is slidably arranged in each step. The outer end of the special-shaped steel ball in the radial direction is arc-shaped and is located on the outer side of the stepped hole in the radial direction. A step is arranged in the middle of the special-shaped steel ball. A return spring is arranged in the large-diameter hole of the stepped hole. The return spring is sleeved on the special-shaped steel ball on the inner side of the step; A sealing sleeve is slidably arranged on the inflation mandrel on the outer side of the convex ring in the axial direction. The sealing sleeve is provided with a limiting step matched with the convex ring. The inner end in the axial direction of the limiting step is located in the forming die barrel on the outer side of the convex ring in the axial direction. More than one sealing ring is arranged on the inner circumference of the sealing sleeve; An annular knife is fixedly arranged on the inner side in the axial direction of the sealing sleeve. The outer diameter of the annular knife is smaller than the inner diameter of the convex ring; A clamping push barrel is sleeved outside the special-shaped steel ball, outside the outer end of the forming die barrel and outside the sealing sleeve. A radial push plate located on the rear side of the sealing sleeve in the axial direction is fixedly connected to the outer end in the axial direction of the clamping push barrel. The radial push plate pushes the sealing sleeve, and its annular knife is inserted into the end of the blank tube to seal the end; The inner circumference of the inner end in the axial direction of the clamping push barrel is provided with a sequentially connected initial cylindrical surface, a shrinking conical surface and a locking cylindrical surface from the inside to the outside. The diameter of the initial cylindrical surface is larger than the diameter of the locking cylindrical surface.

2. The plastic pipe blow molding locking and sealing device according to claim 1, characterized in that: The inner end in the radial direction of the special-shaped steel ball is arc-shaped, and its radius is smaller than the radius of the outer end in the radial direction.

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