Thin-wall extracorporeal circulation intubation molding process, and core rod assembly and equipment for coating machine head die adopted by thin-wall extracorporeal circulation intubation molding process

Abstract

The invention belongs to the technical field of plastic processing, and particularly relates to a thin-wall extracorporeal circulation intubation molding process and an adopted wrapping machine head die core rod assembly and equipment, the wall thickness of a pipe body can range from 0.5 mm to 1.0 mm, secondary wrapping molding is conducted according to the gravity negative pressure post-wrapping principle, and stable and continuous production can be achieved. Densely-wound reinforcing steel wires are embedded in the inner wall of the pipe body. The method is suitable for forming thin-walled pipes made of polyurethane, nylon, Pebax, PP and the like, and the pipe body wall of a product is thin, good in supporting degree, not prone to deformation, better in flexibility, larger in flow and good in wrapping integrity on the premise that the outer diameter is the same.

Description

Technical Field

[0001] The invention belongs to the technical field of plastic processing, and in particular relates to a thin-wall extracorporeal circulation cannula molding process and a coated die core rod assembly and equipment used therein. Background Art

[0002] Thin-walled reinforced tubing is in widespread demand in the medical device and aerospace sectors. During extracorporeal circulation surgery, blood pumps must deliver high blood flow rates with minimal priming. Traditional tubing, due to its thick walls (typically ≥1.2mm), limits the inner diameter to the same outer diameter, leading to insufficient flow or the need to increase the outer diameter, increasing the risk of surgical trauma. Vacuum suction during surgery can easily cause tubing collapse, and existing thin-walled tubing (wall thickness <0.8mm) cannot meet these negative pressure requirements.

[0003] Currently, there are two molding processes for thin-walled extracorporeal circulation cannulas: dip molding and conventional overmolding. The dip molding process is inefficient and has poor consistency. The steel wire skeleton is impregnated with polymer slurry and then cured. The single production cycle is >30 minutes, and the hourly production capacity is less than 150 pieces, making it difficult to scale up. Furthermore, the thickness fluctuates by ±0.3mm, and the wall thickness fluctuates greatly and is uneven. Furthermore, the dip molding layer has weak bonding with the steel wire and is prone to delamination under high pressure. The tube wall also has a high microporous defect rate, which can easily lead to blood residue and infection risks.

[0004] Due to melt strength limitations during conventional overmolding, the extrusion process requires a wall thickness of 1.0mm or greater to coat the steel wire, otherwise it is prone to rupture. Thicker walls increase the outer diameter, increasing surgical trauma and directly reducing flow efficiency. Furthermore, the steel wire's positioning can shift, causing it to float in the melt during extrusion. Eccentricity exceeding 10% can cause lumen deformation and uneven flow.

[0005] like Figure 1 、 2 As shown, the conventional coating extruder head is equipped with a die 5 and a core rod 6. A certain gap 7 is formed between the die 5 and the core rod 6, which serves as a flow channel for the molten material. A through hole is provided in the center of the core rod, through which the processed inner blank is passed from top to bottom into the extruder head for secondary coating.

[0006] The secondary overmolding of the existing technology adopts overmolding from top to bottom. During the overmolding process, the molten material flows downward under the action of gravity, and the molten material is coated on the outer surface of the tube by vacuuming and filling the spring gap. However, the wall thickness of the product processed by this process is relatively thick, generally around 1 mm, which cannot meet the thin-wall requirements in specific circumstances. Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides a thin-wall extracorporeal circulation cannula forming process with simple manufacturing process and precise dimensional control, as well as the coated die core rod assembly and equipment used therein.

[0008] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a covering machine head die core rod assembly, including a die and a core rod, a gap for feeding molten material is formed between the die and the core rod, a core rod center hole is provided in the center of the core rod, a straight groove is provided at the top outlet end of the die, and a funnel-shaped inclined groove is provided below the straight groove. The highest point of the straight section of the core rod is flush with the bottom surface of the inclined groove of the die, and a heat-insulating cover with a top opening is provided along the inner wall of the straight groove.

[0009] Furthermore, the slope of the inclined groove is 5°-45°, and the straight section size of the gap between the inclined groove and the core rod is 5-20 mm.

[0010] Furthermore, the heat-insulating cover extends out of the top surface of the die and is made of high-temperature resistant glass; the heat-insulating cover and the die are connected and fixed by screws.

[0011] Furthermore, the inner diameter of the upper part of the core rod hole is small, and the inner diameter of the lower part is large, and the intersection of the diameter changes is a smooth transition section.

[0012] A cladding machine for secondary molding of thin-walled reinforced tubes adopts the above-mentioned cladding machine head die core rod assembly, the center hole of the core rod is connected to the center hole of the machine head, and the center lines are on the same straight line. A vacuum chamber is connected below the machine head, and the center hole of the vacuum chamber is connected to the center hole of the machine head and the center hole of the core rod; the lower end of the vacuum chamber is connected to a sealing gasket, and the sealing gasket is provided with a through hole allowing the tube blank to pass through, and the vacuum chamber is externally connected to an adjustable pressure vacuum air source.

[0013] A thin-wall extracorporeal circulation cannula forming process comprises the following steps: S1. Make a soft mandrel by extruder; S2. Coaxially wrapping a layer of inner blank on the outside of the soft mandrel; S3 inner blank sleeve reinforcement lining, the reinforcement lining is stainless steel wire; S4. The tube with the flexible mandrel, inner blank, and reinforced liner is fed into the aforementioned cladding machine for secondary molding of thin-walled reinforced tubes. The tube moves upward, and the molten material enters the die mandrel assembly of the cladding machine head, forming a molten material pool between the inclined groove and the straight groove of the die. As the tube passes through the molten material pool, the vacuum chamber is evacuated, causing the molten material to adhere to the outer surface of the tube under the action of gravity and negative pressure, filling the gaps between the stainless steel wires. S5. The tube blank after overmolding is cooled and then withdrawn from the soft mandrel.

[0014] Furthermore, the soft core shaft has an internal hollow structure or a solid structure, and the material of the soft core shaft is PTFE, POM, PP or HDPE; the wall thickness of the inner blank is 0.2-0.5 mm, and the material of the inner blank is polyurethane, nylon, Pebax or PP.

[0015] Furthermore, the stainless steel wire is tightly wound around the outer side of the inner blank by a spring winding machine, or a preformed stainless steel wire spring is rewound around the outer side of the inner blank by a rewinding machine.

[0016] Furthermore, in S4, a thin-walled reinforced tube of corresponding size is obtained by adjusting the extruder speed and the stretching rate, and the vacuum degree of the vacuum pump during the coating process is 10-20 kPa.

[0017] Furthermore, the steel wire is a round wire or a flat wire, the diameter of the round wire is 0.1-0.3mm, and the pitch is 0.3-0.5mm; the thickness of the flat wire is 0.1-0.3mm, the width is 0.5-0.7mm, and the pitch is 0.6-0.8mm, and the thin wall of the obtained thin-walled reinforced tube is less than 1.0mm.

[0018] The advantages and positive effects of this invention include simple operation steps, precise control of wall thickness, and the ability to process thin-walled reinforced tubes with a wall thickness of less than 1.0 mm and internally embedded steel wire, thereby increasing liquid flow while maintaining the product's outer diameter. The resulting thin-walled reinforced tubes have stable dimensions, thin walls, and excellent negative pressure resistance, enabling continuous production and high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural diagram of the die core rod assembly of the existing covering die head.

[0020] Figure 2 It is a structural schematic diagram of the inner blank entering the coating machine head after coating in the prior art.

[0021] Figure 3 It is a structural schematic diagram of the cladding die head core rod assembly of the present invention.

[0022] Figure 4 It is an enlarged schematic diagram of the principle of the gravity negative pressure coating process of the present invention.

[0023] Figure 5 It is a schematic diagram of the principle of the gravity negative pressure coating process of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] In the description of the present invention, it should be noted that the terms "upper", "middle", "lower", "inner", "outer", "both sides", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only simplified descriptions for the convenience of describing the present invention, 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 on the present invention.

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "provided with," "connected," etc., should be understood in a broad sense. For example, "connected" may refer to a fixed connection, a detachable connection, or an integral connection; it may refer to a mechanical connection or an electrical connection; it may refer to a direct connection or an indirect connection through an intermediate medium; it may refer to internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0027] like Figure 3 、 4 As shown, the coating machine head die core rod assembly of the present invention includes a die 13 and a core rod 11. A gap 16 for feeding the molten material 25 is formed between the die 13 and the core rod 11. A core rod center hole 12 is provided at the center of the core rod. A straight groove 15 is provided at the top outlet end of the die 13. A funnel-shaped inclined groove 14 is provided below the straight groove 15. The highest point of the straight section of the core rod 11 is flush with the bottom surface of the inclined groove 14 of the die. A heat-insulating cover 29 with a top opening is provided along the inner wall of the straight groove 15.

[0028] Furthermore, the slope of the inclined groove 14 is 5°-45°, and the straight section size of the gap 16 between the inclined groove 14 and the core rod is 5-20 mm.

[0029] Furthermore, the heat-insulating cover 29 extends out of the top surface of the die 13 and is made of high-temperature resistant glass; the heat-insulating cover 29 and the die 13 are connected and fixed by a screw member 31 .

[0030] Furthermore, the inner diameter of the upper portion of the core rod hole 12 is smaller than that of the lower portion, and the junction of the diameter changes is a smooth transition section.

[0031] like Figure 5 As shown, the cladding machine for secondary molding of thin-walled reinforced tubes of the present invention adopts the above-mentioned cladding machine head die core rod assembly, the core rod center hole 12 is connected to the machine head center hole 17, and the center lines are on the same straight line, and a vacuum chamber 20 is connected below the machine head 24, and the vacuum chamber center hole 18 is connected to the machine head center hole 17 and the core rod center hole 12; the lower end of the vacuum chamber is connected to a sealing gasket 19, and the sealing gasket 19 is provided with a through hole allowing the tube blank to pass through, and the vacuum chamber 20 is externally connected to an adjustable pressure vacuum air source.

[0032] The thin-wall extracorporeal circulation cannula forming process of the present invention comprises the following steps: S1. Make a soft mandrel by extruder; S2. Coaxially wrapping a layer of inner blank on the outside of the soft mandrel; S3 inner blank sleeve reinforcement lining, the reinforcement lining is stainless steel wire; S4. The tube with the flexible mandrel, inner blank, and reinforced liner is placed in the cladding machine described above for secondary molding of thin-walled reinforced tubes. The tube moves upward, and the molten material enters the die mandrel assembly of the cladding machine head, forming a molten material pool between the inclined groove and the straight groove of the die. As the tube passes through the molten material pool, the vacuum chamber is evacuated, causing the molten material to adhere to the outer surface of the tube under the action of gravity and negative pressure, filling the gaps between the stainless steel wires. S5. The tube blank after overmolding is cooled and then withdrawn from the soft mandrel.

[0033] Furthermore, the soft core shaft has an internal hollow structure or a solid structure, and the material of the soft core shaft is PTFE, POM, PP or HDPE; the wall thickness of the inner blank is 0.2-0.5 mm, and the material of the inner blank is polyurethane, nylon, Pebax or PP.

[0034] Furthermore, the stainless steel wire is tightly wound around the outer side of the inner blank by a spring winding machine, or a preformed stainless steel wire spring is rewound around the outer side of the inner blank by a rewinding machine.

[0035] Furthermore, in S4, a thin-walled reinforced tube of corresponding size is obtained by adjusting the extruder speed and the stretching rate, and the vacuum degree of the vacuum pump during the coating process is 10-20 kPa.

[0036] Preferably, the steel wire is a round wire or a flat wire, the round wire diameter is 0.1-0.3mm, the pitch is 0.3-0.5mm; the flat wire thickness is 0.1-0.3mm, the width is 0.5-0.7mm, the pitch is 0.6-0.8mm, and the thin wall of the obtained thin-walled reinforced tube is less than 1.0mm.

[0037] Specifically, the mandrel's central hole 12 communicates with the die's central hole 17, with their centerlines aligned. The lower portion of the die 24 is threadedly connected to a vacuum chamber 20, and the central hole 18 of the vacuum chamber communicates with both the die's central hole 17 and the mandrel's central hole 12. One end of the vacuum chamber is connected to a sealing gasket 19, which has a through-hole to allow the tube to pass through, thus providing a seal. The vacuum chamber 20 is connected to an external, adjustable-pressure vacuum source.

[0038] During secondary molding, the tube with a steel wire reinforcement liner is first passed from bottom to top, sequentially through the sealing gasket 19, the hole 18 in the vacuum chamber, the hole 17 in the die head, and the hole 12 in the mandrel, and then through the traction guide roller 27 and the pulling roller 28. The tube moves upward under the traction of the traction machine. The raw material enters the extruder 23 from the barrel 22. The molten material 25 passes through the extruder head and enters the gap 26 between the die head and the mandrel, and the gap 16 between the die 13 and the mandrel 11, forming a molten material pool 21 between the inclined groove 14 and the straight groove 15 of the die. As the tube passes through the molten material pool 21, the vacuum chamber is evacuated, causing the molten material to adhere to the outer surface of the tube under the action of gravity and negative pressure, filling the gaps between the steel wires. 23 is the extruder.

[0039] The main parameters of secondary coating extrusion include: a. Extruder: screw diameter: 25-30mm, screw speed: 0-100rpm; b. Extruder head: by replacing the die and mandrel, the coating diameter is 3-18mm; c. Air pressure control system adjustment: Air pressure adjustment range is -20-20kPa. Time: 0-10s, adjustable; d. Traction machine: traction speed 0-10m / s.

[0040] The present invention resolves the inherent contradictions between dipping and conventional coating extrusion processes in the coordinated control of thin walls (<1.0mm) and steel wire reinforcement. The present invention leverages the fluidity and viscoelasticity of the polymer melt to enable it to be embedded in the gaps of the steel wire reinforcement lining and adhere to the outer surface of the tube body under the action of gravity and negative pressure through the coordinated coordination of the extrusion rate and the pulling rate. Thus, through a new coating extrusion process, zero-eccentric embedding of the steel wire reinforcement structure is achieved, and the inner and outer layers achieve a high degree of fit, resulting in a thin-walled reinforced tube with excellent negative pressure resistance. This thin-walled reinforced tube can meet the triple requirements of extracorporeal circulation surgery for high flow, low trauma, and safety, while also meeting the aerospace requirements for low weight and high throughput.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A covering die core rod assembly, comprising a die (13) and a core rod (11), wherein a gap (16) is formed between the die (13) and the core rod (11) for feeding a molten material (25), and a core rod center hole (12) is provided at the center of the core rod, characterized in that: A straight groove (15) is provided at the top outlet end of the die (13), a funnel-shaped inclined groove (14) is provided below the straight groove (15), the highest point of the straight section of the core rod (11) is flush with the bottom surface of the inclined groove (14) of the die, and a heat-insulating cover (29) with a top opening is provided along the inner wall of the straight groove (15).

2. The covering die core rod assembly according to claim 1, characterized in that: The slope of the inclined groove (14) is 5°-45°, and the straight section size of the gap (16) between the inclined groove (14) and the core rod is 5-20 mm.

3. The covering die core rod assembly according to claim 1, characterized in that: The heat-insulating cover (29) extends out of the top surface of the die (13) and is made of high-temperature resistant glass; the heat-insulating cover (29) and the die (13) are connected and fixed via a screw member (31).

4. The covering die core rod assembly according to claim 1, characterized in that: The core rod central hole (12) has a small inner diameter at the upper portion and a large inner diameter at the lower portion, and the junction of the diameter changes is a gentle transition section.

5. A cladding machine for secondary molding of thin-walled reinforced tubes, characterized in that: The cladding die core rod assembly according to any one of claims 1 to 4 is adopted, the center hole (12) of the core rod is communicated with the center hole (17) of the die, and the center lines are on the same straight line, a vacuum chamber (20) is connected below the die (24), the center hole (18) of the vacuum chamber is communicated with the center hole (17) of the die and the center hole (12) of the core rod; the lower end of the vacuum chamber is connected to a sealing gasket (19), a through hole is opened on the sealing gasket (19) to allow the tube blank to pass through, and the vacuum chamber (20) is externally connected to an adjustable pressure vacuum air source.

6. A thin-wall extracorporeal circulation cannula forming process, characterized in that: The following steps are involved: S1. Make a soft mandrel by extruder; S2. Coaxially wrapping a layer of inner blank on the outside of the soft mandrel; S3 inner blank sleeve reinforcement lining, the reinforcement lining is stainless steel wire; S4. The tube with the flexible mandrel, inner blank, and reinforced liner is fed into the cladding machine for secondary molding of thin-walled reinforced tubes as described in claim 5. The tube moves upward, and the molten material enters the die and mandrel assembly of the cladding machine head, forming a molten material pool between the inclined groove and the straight groove of the die. As the tube passes through the molten material pool, the vacuum chamber is evacuated, causing the molten material to adhere to the outer surface of the tube under the action of gravity and negative pressure, filling the gaps between the stainless steel wires. S5. The tube blank after overmolding is cooled and then withdrawn from the soft mandrel.

7. The thin-wall extracorporeal circulation cannula forming process according to claim 6, characterized in that: The soft core shaft has an internal hollow structure or a solid structure, and the material of the soft core shaft is PTFE, POM, PP or HDPE; the wall thickness of the inner blank is 0.2-0.5 mm, and the material of the inner blank is polyurethane, nylon, Pebax or PP.

8. The thin-wall extracorporeal circulation cannula forming process according to claim 6, characterized in that: The stainless steel wire is tightly wound around the outside of the inner blank by a spring winding machine, or a preformed stainless steel wire spring is rewound around the outside of the inner blank by a rewinding machine.

9. The thin-wall extracorporeal circulation cannula forming process according to claim 6, characterized in that: In the above S4, a thin-walled reinforced tube of corresponding size is obtained by adjusting the extruder speed and the stretching rate. During the coating process, the vacuum degree of the vacuum pump is 10-20 kPa.

10. The thin-wall extracorporeal circulation cannula forming process according to claim 6, characterized in that: The steel wire is a round wire or a flat wire, the diameter of the round wire is 0.1-0.3mm, the pitch is 0.3-0.5mm; the thickness of the flat wire is 0.1-0.3mm, the width is 0.5-0.7mm, the pitch is 0.6-0.8mm, and the wall of the obtained thin-walled reinforced tube is less than 1.0mm.

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