A snake bone structure and its parts preparation method

Abstract

The present invention discloses a snake bone structure and a method for preparing its parts. The snake bone structure has two pairs of double grooves and hinged ears for positioning and rotation, as well as an operating line insertion part, and the snake bone parts are prepared by metal injection molding. The preparation process is as follows: the metal powder raw material is dispersed, weighed with a binder according to a designed ratio, and then mixed evenly to obtain a feed material, and then injection molding, powder embedding, degreasing and sintering are performed in sequence, and components are obtained after heat treatment. The snake bone has a positioning structure that is easy to assemble, effectively improving assembly accuracy and efficiency, and its preparation method is simple, with high production efficiency and low cost, which is conducive to mass production.

Description

Technical Field

[0001] The invention relates to the field of medical equipment, and in particular to a snake bone structure and a method for preparing parts thereof. Background Art

[0002] Medical endoscopes bend inside the human body to obtain images at different locations and reach the surgical area. Most endoscopes on the market achieve this function through a snake bone connected by several snake bone parts.

[0003] The existing technology mostly uses mechanical processing to prepare snake bones, and uses riveting structures for connection. For example, in the patent "201510207482.2, Preparation method of snake bone device for endoscope", the stainless steel pipe is cut, leveled, stamped, polished and other processes to make the snake bone, which has low production efficiency and high cost. It is known that the injection molding method is used to prepare snake bones to improve production efficiency and reduce production costs. For example, the patent "201710985068.3 A metal powder injection molding method for processing endoscope snake bones" provides a method for metal injection molding preparation, but its snake bone connection is still in the form of riveting, and the riveting process has high requirements, which is prone to quality problems and low production efficiency. The existing technology "201780086240.X, bending part for endoscope" provides a snake bone without riveting structure, but there is no positioning device, and the assembly accuracy is difficult to guarantee.

[0004] In addition, in order to reduce the patient's pain during the use of the endoscope, it is hoped that the inner diameter and wall thickness of the snake bone are thinner. However, thin walls and microstructures are prone to defects such as under-injection, breakage and holes during injection, and are prone to deformation after degreasing and sintering, which puts higher requirements on the preparation process.

[0005] In view of the above problems, the present invention provides a snake-bone structure without rivets and easy to assemble, as well as a low-cost and high-efficiency snake-bone preparation method. Summary of the invention

[0006] In order to solve the existing snake bone preparation problems, a snake bone structure and a preparation method are provided. The snake bone structure has a positioning structure for easy assembly; a metal injection molding preparation method is provided to solve the problems of complex snake bone preparation process, high production cost, low efficiency, etc.

[0007] To achieve the above object, the present invention adopts the following scheme:

[0008] A preferred solution is a snake-bone structure and a method for preparing its parts, characterized in that the snake-bone structure has two pairs of double grooves and hinge ears for positioning and rotation, and an operation wire insertion portion, and the snake-bone parts are prepared by metal injection molding;

[0009] In the snake-bone structure, the snake-bone part is divided into an upper part and a lower part, and the upper part is provided with radially opposite special-shaped grooves, and the part close to the inner wall of the snake-bone part is an axial plane, and an axially open groove is opened on the plane, and the opening shape of the groove can be a rectangle, a trapezoid or a semicircle with an arc tangent to it at the end, and the size of the open groove does not exceed the special-shaped groove; the lower part is provided with a pair of hinge ears passing through the central axis plane and forming an angle of 90° with the upper special-shaped groove, and the inner surface of the hinge ear is an axial plane, and a positioning part is provided on the axis, and the positioning part can be a rectangle, a trapezoid, a semicircle or a circle with a tangent arc at the end, and the diameter of the arc or circle is less than or equal to the tangent arc at the end of the upper opening groove of the snake-bone; the operation line insertion part is located on the inner wall of the snake-bone part, parallel to the central axis of the part, and the axis of the insertion part is located in the same plane as the central axis of the part, the center line of the double groove or the hinge ear.

[0010] Preferably, the preparation method comprises the following preparation steps:

[0011] S1. Dispersion treatment: 17-4ph stainless steel pre-alloyed powder with spherical or nearly spherical shape and average particle size of 1 to 10 μm is added with 2 to 5% oleic acid for ball milling, with a ball-to-material ratio of (0.5 to 1): 1;

[0012] S2, mixing, mixing the metal powder raw material and the binder evenly;

[0013] S3, injection, injection molding the feed material with an injection molding machine, the injection temperature is 170-180°C, and the mold temperature is 100-120°C;

[0014] S4, burying powder, burying the injection blank in alumina powder, and vibrating it to make the alumina powder fill the gap;

[0015] S5, debinding, the debinding process includes solvent debinding and thermal debinding, and thermal debinding and sintering are integrated processes;

[0016] S6, thermal debinding and sintering, placing the solvent debinded blank in a sintering furnace for debinding and sintering;

[0017] S7, heat treatment, placing the snake bone in a heat treatment furnace for solution treatment and aging treatment.

[0018] In a preferred embodiment, the chemical mass ratio of the binder is:

[0019] Paraffin (POM) 30-50%;

[0020] High-density polyethylene (HDPE) 30-40%;

[0021] Ethylene-vinyl acetate copolymer (EVA) 10-20%;

[0022] Polypropylene (PP) 10-20%.

[0023] In a preferred embodiment, the powder loading amount in the mixing process is 50-55%, that is, the metal powder accounts for 50-55% of the total volume, the mixing temperature is 190-200° C., and the mixing time is 0.5-1 h.

[0024] In a preferred embodiment, the solvent in the solvent degreasing is n-heptane, the temperature is 30-40° C., and the time is 5-7 hours.

[0025] The preferred scheme is the integrated process of thermal debinding and sintering, which is as follows: vacuumizing, heating to 230-250°C at 1.5-3°C / min, keeping warm for 30-60min, heating to 300-350°C at 1.5-3°C / min, keeping warm for 60-90min, heating to 400-450°C at 1.5-3°C / min, keeping warm for 60-90min, heating to 800-900°C at 3-10°C / min, keeping warm for 20-30min, heating to 1300-1380°C at 3-10°C / min, keeping warm for 2-3h, and cooling with the furnace.

[0026] In a preferred embodiment, the heat treatment process is salt bath heating to 1030-1080°C for solution treatment for 2-3 hours and aging at 450-500°C for 4-6 hours.

[0027] In a preferred embodiment, the snake bone density is 7.5 to 7.8 g / cm 3 .

[0028] Principles and advantages:

[0029] The present invention uses metal injection molding technology to prepare snake bones. The advantages of metal injection molding that complex structural parts can be molded at one time and the characteristics of low mass production cost and high material utilization rate are used to design a snake bone structure with high dimensional accuracy and easy assembly. In the snake bone structure, hinged ears and double groove structures are used to connect in a hinged manner instead of a riveted manner. On the one hand, the production efficiency and yield rate are improved; on the other hand, the double groove structure is connected with the hinged ears with positioning parts for assembly, which can realize the positioning between the front and rear snake bone parts, greatly reducing the assembly requirements. The connection between the snake bone parts can be completed without high proficiency, and the assembly accuracy is effectively guaranteed.

[0030] The snake bone parts are prepared by metal injection molding to achieve one-step molding of complex shapes. For example, the hinged ear and double groove structure that realize the rotation and positioning functions in the present invention require multiple processes and are difficult to process by mechanical processing. However, metal injection molding has great freedom in the design of complex small parts and can realize structures that are difficult to achieve by conventional preparation methods. The hinged ear and double groove structure that realize the rotation and positioning functions in the present invention can be molded in one step without subsequent processing.

[0031] Powder dispersion treatment is introduced, and 2-5% oleic acid is added for ball milling. The purpose is to disperse the agglomerated powder through ball milling to prevent the agglomeration of raw material powders, which causes uneven feed composition, reduces feed fluidity, and cannot effectively fill the mold, causing injection defects. Oleic acid adheres to the surface of the powder to prevent subsequent agglomeration; in addition, adsorption of oleic acid on the surface of the powder helps to combine with other organic binders in the subsequent mixing process. Among the binder components, the paraffin content is low, and the content of other components HDPE, EVA and PP is relatively high, which is conducive to improving the strength and shape retention of the green body, avoiding dissolution deformation, and preventing microstructure fracture during injection demolding. The purpose of using higher injection temperature and mold temperature is to improve the fluidity of the feed, so as to avoid defects such as under-injection and holes caused by premature solidification due to rapid heat loss during injection. The injection blank is buried with powder before dissolution, and the support effect of alumina powder is used to prevent deformation during degreasing and sintering. The heating rate of the hot degreasing process is low, and the heat is kept in sections, so that HDPE, EVA and PP are removed in stages to prevent thermal deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Illustration of snake bone parts

[0033] Figure 2 Front view of the snake bone part

[0034] Figure 3 Top view of the snake bone part

[0035] Figure 4 Schematic diagram for snake bone assembly

[0036] Figure 5 Schematic diagram of snake bone connection bending

[0037] Figure 6 Schematic diagram of snake bone part deformation 1

[0038] Figure 7 Schematic diagram of snake bone part deformation 2 DETAILED DESCRIPTION

[0039] The embodiments of the present invention are described below with reference to the accompanying drawings. The accompanying drawings are schematic pictures, and the thickness and proportions are different from the actual ones, which are only used to explain the product features, and there are parts with different size relationships and proportions between the drawings.

[0040] Example 1

[0041] A snake bone structure and a method for preparing parts thereof, such as Figure 1The snake-bone structure shown has two pairs of double grooves 1a and hinge ears 1b for positioning and rotation, and an operation wire insertion portion 1c. In the snake-bone structure, the snake-bone part is divided into an upper part and a lower part, the upper part is provided with radially opposite special-shaped grooves 1a1, the part close to the inner wall of the snake-bone part is an axial plane, and an axially open groove 1a2 is opened on the plane, the opening shape of the groove can be rectangular, and the end is a circular arc tangent thereto, the size of the open groove does not exceed the special-shaped groove, and the radius of the arc 1a2 is smaller than the arc in the special-shaped groove 1a1; the lower part is provided with a pair of hinge ears 1b passing through the central axis plane and forming an angle of 90° with the upper special-shaped groove, the inner surface 1b1 of the hinge ear is an axial plane, and a positioning part 1b2 is provided on the axis, the positioning part 1b2 can be circular, and the diameter of the circle is less than or equal to the tangent arc at the end of the upper opening groove 1a2 of the snake-bone; the operation wire insertion part 1c is located on the inner wall of the snake-bone part, parallel to the central axis of the part, and the axis of the insertion part is located in the same plane as the central axis of the part, the double groove or the center line of the hinge ear.

[0042] The preparation process is as follows:

[0043] A. Raw material dispersion treatment: 3% oleic acid is added to spherical or nearly spherical 17-4ph stainless steel pre-alloyed powder with an average particle size of 4 μm and ball-milled, with a ball-to-material ratio of 0.5:1.

[0044] B mixture: the binder is mixed at a loading rate of 50%, the temperature is 190°C, and the time is 1 hour, wherein the binder components are paraffin (POM) 40%, high-density polyethylene (HDPE) 30%, ethylene-vinyl acetate copolymer (EVA) 20%, and polypropylene (PP) 20%.

[0045] C Injection: The obtained feed material is injected by a molding machine with an injection temperature of 170°C and a mold temperature of 110°C.

[0046] D. Burying powder: bury the injection blank in alumina powder and vibrate it to make the alumina powder fill the gap.

[0047] E solvent degreasing: 40℃ n-heptane solution, degreasing time 6h.

[0048] F Thermal debinding and sintering: Thermal debinding and sintering are carried out simultaneously, and the process is: vacuumize, heat up to 250℃ at 1.5℃ / min, keep warm for 60min, heat up to 320℃ at 1.5℃ / min, keep warm for 60min, heat up to 450℃ at 1.5℃ / min, keep warm for 90min, heat up to 900℃ at 8℃ / min, keep warm for 20min, heat up to 1380℃ at 8℃ / min, keep warm for 2h, and cool with the furnace.

[0049] G Heat treatment: The sintered parts are subjected to solution treatment + aging treatment, specifically, salt bath heating to 1050℃ for solution treatment for 2h, aging at 480℃ for 4h, and the density of the parts obtained after cooling is 7.8g / cm3 .

[0050] H Assembly: Assembly method as Figure 4 As shown, since the hinge ears and double grooves of the two parts are mutually matched structures, the hinge ear 2b of the No. 2 snake bone part can be directly inserted into the No. 1 double groove 1a along the axial direction during assembly. The inner groove surface of the double groove determines the radial position of the front and rear connected snake bone parts to prevent axial rotation or misalignment during assembly. The inner groove 1a2 of the No. 1 double groove and the positioning device 2b2 on the hinge ear ensure that the snake bone can be rotated at a certain angle. During operation, the operation line is controlled to rotate, such as assembly. Figure 5 As shown in , the operating line is not shown in the figure.

[0051] Example 2

[0052] A snake bone structure and a method for preparing parts thereof, such as Figure 6 The snake-bone structure shown has two pairs of double grooves and hinge ears for positioning and rotation, and an operation line insertion part. In the snake-bone structure, the snake-bone part is divided into an upper part and a lower part. The upper part is provided with radially opposite special-shaped grooves. The part close to the inner wall of the snake-bone part is an axial plane. An axially open groove is opened on the plane. The opening shape of the groove can be a trapezoid, and the end is a circular arc tangent thereto. The size of the open groove does not exceed the special-shaped groove, and the radius of the circular arc is smaller than the circular arc in the special-shaped groove; the lower part is provided with a pair of hinge ears passing through the central axis plane and forming an angle of 90° with the upper special-shaped groove. The inner surface of the hinge ears is an axial plane, and a positioning part is provided on the axis. The positioning part is in the shape of a trapezoid with a tangent circular arc at the end, and the diameter of the circular arc is less than or equal to the tangent circular arc at the end of the upper opening groove of the snake-bone; the operation line insertion part is located on the inner wall of the snake-bone part, parallel to the central axis of the part, and the axis of the insertion part is located in the same plane as the central axis of the part, the center line of the double groove or the hinge ear.

[0053] The preparation process is as follows:

[0054] A. Raw material dispersion treatment: 4% oleic acid is added to spherical or nearly spherical 17-4ph stainless steel pre-alloyed powder with an average particle size of 4 μm and subjected to ball milling treatment, with a ball-to-material ratio of 0.7:1.

[0055] B mixture: the binder is mixed at a loading rate of 55%, the temperature is 190°C, and the time is 1 hour, wherein the binder components are paraffin (POM) 40%, high-density polyethylene (HDPE) 30%, ethylene-vinyl acetate copolymer (EVA) 20%, and polypropylene (PP) 20%.

[0056] C Injection: The obtained feed material is injected by a molding machine with an injection temperature of 175°C and a mold temperature of 100°C.

[0057] D. Burying powder: bury the injection blank in alumina powder and vibrate it to make the alumina powder fill the gap.

[0058] E solvent degreasing: 40℃ n-heptane solution, degreasing time 6h.

[0059] F Thermal debinding and sintering: Thermal debinding and sintering are carried out simultaneously, and the process is: vacuumize, heat up to 250℃ at 1.5℃ / min, keep warm for 60min, heat up to 320℃ at 1.5℃ / min, keep warm for 60min, heat up to 450℃ at 1.5℃ / min, keep warm for 90min, heat up to 900℃ at 8℃ / min, keep warm for 20min, heat up to 1350℃ at 8℃ / min, keep warm for 2h, and cool with the furnace.

[0060] G Heat treatment: After sintering, the parts are subjected to solution treatment + aging treatment, specifically, salt bath heating to 1080℃ for solution treatment for 2h, aging at 500℃ for 4h, and the density of the parts obtained after cooling is 7.6g / cm 3 .

[0061] H Assembly: Assembly method as Figure 4 As shown, during assembly, the hinge ear 2b of the No. 2 snake bone part can be directly inserted into the No. 1 double groove 1a along the axial direction. The inner groove surface of the double groove determines the radial position of the front and rear connected snake bone parts to prevent rotation or dislocation along the axis during assembly. The inner groove 1a2 of the No. 1 double groove and the positioning device 2b2 on the hinge ear ensure that the snake bone can be rotated at a certain angle. During operation, the operation line is controlled to rotate, such as assembly. Figure 5 As shown in , the operating line is not shown in the figure.

[0062] Example 3

[0063] A snake bone structure and a method for preparing parts thereof, such as Figure 7 The snake-bone structure shown has two pairs of double grooves and hinge ears for positioning and rotation, and an operation line insertion part. In the snake-bone structure, the snake-bone part is divided into an upper part and a lower part. The upper part is provided with radially opposite special-shaped grooves, and the part close to the inner wall of the snake-bone part is an axial plane, and an axially open groove is opened on the plane. The opening shape of the groove can be semicircular, and the size of the open groove does not exceed the special-shaped groove, and the arc radius is smaller than the arc in the special-shaped groove; the lower part is provided with a pair of hinge ears passing through the central axis plane and forming an angle of 90° with the upper special-shaped groove. The inner surface of the hinge ears is an axial plane, and a positioning part is provided on the axis. The positioning part is in the shape of a semicircle, and the diameter of the arc is less than or equal to the tangent arc of the end of the upper opening groove of the snake-bone; the operation line insertion part is located on the inner wall of the snake-bone part, parallel to the central axis of the part, and the axis of the insertion part is located in the same plane as the central axis of the part, the center line of the double groove or the hinge ear.

[0064] The preparation process is as follows:

[0065] A. Raw material dispersion treatment: 17-4ph stainless steel pre-alloyed powder with an average particle size of 8.3 μm and spherical or nearly spherical shape is added with 4% oleic acid for ball milling, with a ball-to-material ratio of 1:1.

[0066] B Feed preparation: Mix the binder at 50% loading, temperature 190°C, time 1h, wherein the binder components are paraffin (POM) 30%, high-density polyethylene (HDPE) 40%, ethylene-vinyl acetate copolymer (EVA) 20%, and polypropylene (PP) 20%.

[0067] C Injection: The obtained feed material is injected by a molding machine with an injection temperature of 170°C and a mold temperature of 120°C.

[0068] D. Burying powder: bury the injection blank in alumina powder and vibrate it to make the alumina powder fill the gap.

[0069] E solvent degreasing: 40℃ n-heptane solution, degreasing time 5h.

[0070] F Thermal debinding and sintering: Thermal debinding and sintering are carried out simultaneously, and the process is: vacuumize, heat up to 250℃ at 1.5℃ / min, keep warm for 60min, heat up to 320℃ at 1.5℃ / min, keep warm for 60min, heat up to 450℃ at 1.5℃ / min, keep warm for 90min, heat up to 900℃ at 8℃ / min, keep warm for 20min, heat up to 1300℃ at 8℃ / min, keep warm for 2h, and cool with the furnace.

[0071] G Heat treatment: After sintering, the parts are subjected to solution treatment + aging treatment, specifically, salt bath heating to 1030℃ for solution treatment for 2h, aging at 450℃ for 5h, and the density of the parts obtained after cooling is 7.5g / cm 3 .

[0072] H Assembly: Assembly method as Figure 4 As shown, during assembly, the hinge ear 2b of the No. 2 snake bone part can be directly inserted into the No. 1 double groove 1a along the axial direction. The inner groove surface of the double groove determines the radial position of the front and rear connected snake bone parts to prevent rotation or dislocation along the axis during assembly. The inner groove 1a2 of the No. 1 double groove and the positioning device 2b2 on the hinge ear ensure that the snake bone can be rotated at a certain angle. During operation, the operation line is controlled to rotate, such as assembly. Figure 5 As shown in , the operating line is not shown in the figure.

[0073] Comparative Example 1

[0074] This comparative example adopts the same method as Example 1, except that the raw material powder is not dispersed, and micropores appear on the surface of the final product with a density of 7.3 g / cm 3 .

[0075] Comparative Example 2

[0076] This comparative example adopts the same method as Example 1, except for the injection temperature and the mold temperature. The results are as follows:

[0077] Serial number Injection temperature / ℃ Mold temperature / ℃ result 1 170 60 Underpayment 2 170 130 Internal pores 3 150 100 Underpayment 4 190 100 Produce flash and internal pores

[0078] Comparative Example 3

[0079] This comparative example adopts a method substantially the same as that of Example 1, except that no powder embedding treatment is performed. As a result, the thin wall is deformed after dissolution and sintering.

[0080] Comparative Example 4

[0081] This comparative example adopts a method basically the same as that of Example 1, except that the content of the binder paraffin is higher, specifically: paraffin (POM) 60%; high-density polyethylene (HDPE) 20%; ethylene-vinyl acetate copolymer (EVA) 10%; polypropylene (PP) 10%. The result is that deformation occurs at the thin wall after solvent degreasing.

[0082] The above-described examples are only preferred implementation methods of the present invention, and therefore cannot be used to limit the scope of implementation of the present invention. Other equivalent changes, modifications, substitutions and combinations made in accordance with the principles and contents of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for preparing snake bone parts, characterized in that: The snake-bone structure has two pairs of double grooves and hinged ears for positioning and rotation, as well as an operation line insertion part. The snake-bone structure parts are prepared by injection molding; In the snake-bone structure, the snake-bone part is divided into an upper part and a lower part. The upper part is provided with a plane passing through the central axis and a radially opposite special-shaped groove. The part close to the inner wall of the snake-bone part is a plane along the axial direction. An open groove along the axial direction is opened on the plane. The opening shape of the groove is a rectangle, a trapezoid or a semicircle with an arc tangent to it at the end. The size of the open groove does not exceed the special-shaped groove; the lower part is provided with a pair of hinge ears passing through the central axis plane and forming an angle of 90° with the upper special-shaped groove. The inner surface of the hinge ear is a plane along the axial direction. A positioning part is provided on the axis. The positioning part is in the shape of a rectangle, a trapezoid, a semicircle or a circle with a tangent arc at the end. The diameter of the arc or circle is less than or equal to the tangent arc at the end of the opening groove of the upper part of the snake-bone; the operation line insertion part is located on the inner wall of the snake-bone part, parallel to the central axis of the part, and the axis of the insertion part is located in the same plane as the central axis of the part, the center line of the double groove or the hinge ear; The preparation method comprises the following preparation steps: S1. Dispersion treatment: spherical 17-4ph stainless steel pre-alloyed powder with an average particle size of 1 to 10 μm is added with 2 to 5% oleic acid for ball milling, with a ball-to-material ratio of (0.5 to 1): 1; S2, mixing, mixing the metal powder raw material and the binder evenly, wherein the chemical mass ratio of the binder is: paraffin wax (POM) 30-50%, high-density polyethylene (HDPE) 30-40%, ethylene-vinyl acetate copolymer (EVA) 10-20%, polypropylene (PP) 10-20%; S3, injection, injection molding the feed material with an injection molding machine, the injection temperature is 170-180°C, and the mold temperature is 100-120°C; S4, burying powder, burying the injection blank in alumina powder, and vibrating it to make the alumina powder fill the gap; S5, debinding, the debinding process includes solvent debinding and thermal debinding, and thermal debinding and sintering are integrated processes; S6, thermal debinding and sintering, the solvent debinding blank is placed in a sintering furnace for thermal debinding and sintering, and the density is 7.5-7.8g / cm 3 ; S7, heat treatment, placing the snake bone in a heat treatment furnace for solution treatment and aging treatment.

2. The method for preparing a snake bone part according to claim 1, characterized in that: The powder loading amount during the mixing process is 50-55%, that is, the metal powder accounts for 50-55% of the total volume, the mixing temperature is 190-200° C., and the time is 0.5-1 hour.

3. The method for preparing a snake bone part according to claim 1, characterized in that: The solvent in solvent degreasing is n-heptane, the temperature is 30-40°C, and the time is 5-7h.

4. The method for preparing a snake bone part according to claim 1, characterized in that: The integrated process of thermal debinding and sintering is as follows: vacuumize, heat up to 230-250℃ at 1.5-3℃ / min, keep warm for 30-60min, heat up to 300-350℃ at 1.5-3℃ / min, keep warm for 60-90min, heat up to 400-450℃ at 1.5-3℃ / min, keep warm for 60-90min, heat up to 800-900℃ at 3-10℃ / min, keep warm for 20-30min, heat up to 1300-1380℃ at 3-10℃ / min, keep warm for 2-3h, and cool with the furnace.

5. The method for preparing a snake bone part according to claim 1, characterized in that: The heat treatment process is salt bath heating to 1030-1080℃ for solution treatment for 2-3h and aging at 450-500℃ for 4-6h.

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