Screw casting device and screw casting method

Abstract

A screw casting apparatus is characterized by comprising a base sand core, a screw sand core, a casting sand core, and a filter screen. The base sand core has a feed inlet and a first region for forming at least one side of the screw's rotating shaft. The screw sand core has an inner cavity including a second region for forming screw blades and a third region for forming the other side of the screw's rotating shaft. The second region has an internal thread adapted to the screw blades. The casting sand core is longitudinally disposed on the base sand core and directly opposite the feed inlet. This invention also discloses a screw casting method. Compared with the prior art, the advantages of this invention are: reduced flash, improved quality, and reduced cost.

Description

Technical Field

[0001] This invention relates to an apparatus suitable for screw sand casting. The invention also relates to a screw casting method utilizing the sand casting apparatus. Background Technology

[0002] A screw refrigeration compressor is a refrigeration compressor that uses one or two rotors (screws) with helical grooves to rotate inside a cylinder to compress gas. Screw refrigeration compressors belong to the positive displacement compressor type, with a rotating working volume. Depending on the number of screw rotors, screw compressors are classified into twin-screw and single-screw types. Figure 1 As shown, the rotor 10 is the main component of the screw refrigeration compressor, including the shaft 1a and the screw blades 2a. Currently, an integral structure is often adopted, which integrates the shaft and the screw blades into one piece.

[0003] Existing methods:

[0004] The first method involves integral casting using iron-based alloys such as ductile iron. Bearings and pulleys are installed at both ends of the shaft, resulting in concentrated stress. Due to insufficient strength, it is prone to fracture. Furthermore, the large shrinkage during casting easily creates voids, leading to porous material and easy deformation. Relevant literature can be found in Chinese invention patent ZL201110361969.8, entitled "Screw Alloy for Twin-Screw Air Compressors and its Preparation Method" (authorization announcement number CN103103454B).

[0005] The second method involves lathe machining, using cylindrical blanks made of high-tensile-strength 40# and 45# steel. The screw blades are machined using a precision milling machine, resulting in poor wear resistance, high labor costs, and significant material waste, leading to increased manufacturing costs. Relevant literature can be found in Chinese invention patent application publication CN102489792A, entitled "Lathe and Method for Machining External Threads on Screws".

[0006] The third method is sand casting. First, a sand core is formed, then molten iron is poured into the sand core. After cooling, the casting sand is removed to obtain the screw. Existing technology can be found in Chinese invention patent application publication CN105170915A, entitled "Method for Preparing an Air Compressor Screw" (application number 201510682802.X). Another method uses a smaller sand cylinder containing a sand core matched to the screw's specifications, with molten iron poured from top to bottom. Currently, sand casting has the following shortcomings:

[0007] First, the casting process can easily erode the sand mold, causing resin sand to fall off and resulting in pinholes in the product, especially when casting from the top down.

[0008] Secondly, it can easily force air into the mold, making it difficult for the air to escape and causing air holes to form in the product.

[0009] Furthermore, each product will form a pouring gate, which will generate a lot of flash, resulting in about 15-20% waste. In addition, a filter screen is required each time.

[0010] Secondly, since the filter screen is installed directly at the pouring port, when the molten iron is poured in, due to the very short filtration time, some fine slag will still enter the finished product, affecting the product quality.

[0011] Finally, only one screw can be formed in a single casting, resulting in low production efficiency. Summary of the Invention

[0012] The first technical problem to be solved by the present invention is to provide a screw casting device without sand holes, in view of the above-mentioned technical status.

[0013] The second technical problem to be solved by the present invention is to provide a screw casting device with less flash.

[0014] The third technical problem to be solved by the present invention is to provide a screw casting method without sand holes.

[0015] The fourth technical problem to be solved by the present invention is to provide a screw casting method with less flash.

[0016] The first technical solution adopted by the present invention to solve the first and second technical problems mentioned above is: a screw casting device, characterized in that it includes...

[0017] The base sand core has a feed port and a first region for forming a screw shaft on one side, wherein a flow channel is provided between the feed port and the bottom of the first region, and the port of the first region faces upward.

[0018] The screw core is longitudinally disposed on the port of the aforementioned first region and has an inner cavity on its inner side. The inner cavity includes a second region for forming screw blades and a third region for forming the shaft on the other side of the screw. The aforementioned second region has an internal thread that is adapted to the screw blades.

[0019] A sand core is cast longitudinally onto the aforementioned base sand core and directly opposite the aforementioned feed inlet; and

[0020] The filter screen is located inside the aforementioned cast sand core.

[0021] The second technical solution adopted by the present invention to solve the first and second technical problems mentioned above is: a screw casting device, characterized in that it includes...

[0022] The base sand core has a feed port and a first region for forming a screw shaft on one side, wherein a flow channel is provided between the feed port and the bottom of the first region, and the port of the first region faces upward.

[0023] A screw core assembly includes a first screw core, a shaft core, and a second screw core connected sequentially from bottom to top. The first screw core is longitudinally disposed on the port of the first region and has an inner cavity. The inner cavity includes a second region for forming screw blades and a third region for forming the other side of the screw shaft. The second region has an internal thread adapted to the screw blades. The shaft core is hollow and has a fourth region for forming the screw shaft. The second screw core is longitudinally disposed on the port of the shaft core and has an inner cavity. The inner cavity includes a fifth region for forming screw blades and a sixth region for forming the other side of the screw shaft. The fifth region has an internal thread adapted to the screw blades.

[0024] A sand core is cast longitudinally onto the aforementioned base sand core and directly opposite the aforementioned feed inlet; and

[0025] The filter screen is located inside the aforementioned cast sand core.

[0026] Furthermore, the base sand core is mounted on the bracket; the screw sand core is mounted inside the sleeve; and the casting sand core is located inside the sleeve.

[0027] The sleeve includes a body portion for accommodating the second region of the screw sand core and an extension portion for accommodating the third region of the screw sand core. The extension portion protrudes from one end of the body portion. The inner wall of the body portion has an internal thread adapted to the screw, and the outer wall of the screw sand core has an external thread adapted to the inner wall of the body portion. The thickness of the inner and outer walls of the second region of the screw sand core is basically the same. This reduces the wall thickness, significantly decreasing the amount of casting sand used in the screw sand core, shortening the heating time of the screw sand core, and improving production efficiency. Simultaneously, previously, areas with thicker sand molds contained air, which could easily enter the product during pouring, causing porosity. Now, with a uniform thickness, the amount of air is reduced, making porosity less likely.

[0028] The third region of the screw core is provided with a riser core, which has an vent hole at its top. The riser core is also provided with an end cap on its outer periphery. Since the molten iron flows from bottom to top, the air inside the screw core is discharged through the vent hole as much as possible, thus ensuring that the product is free of porosity and providing casting quality.

[0029] The inlet and outlet ends of the cast sand core are respectively equipped with a first filter screen and a second filter screen, and the mesh size of the first filter screen is larger than that of the second filter screen. The axial length of the cast sand core can be appropriately extended to allow sufficient filtration time. Fine slag, being lighter than molten iron, will eventually float between the two filter screens and will not enter the product. In contrast, in existing technologies, the pouring port is relatively short, generally with only one filter screen. When molten iron is poured, due to the very short filtration time, some fine slag will still enter the finished product, affecting product quality.

[0030] Furthermore, the first area is arranged around the feed inlet, and each first area is connected to the feed inlet by a flow channel. The multiple flow channels are arranged radially around the feed inlet.

[0031] The first region consists of five areas, evenly distributed around the feed inlet, roughly in a plum blossom shape, capable of forming five screws at a time.

[0032] To facilitate the fabrication of the base sand core, the base sand core includes a main body and a bottom cover located at the bottom of the main body. The main body of the first region and the flow channel is located on the main body, and the bottom plate of the flow channel is located on the bottom cover.

[0033] The technical solution adopted by the present invention to solve the third and fourth technical problems mentioned above is: a screw casting method, comprising the following steps:

[0034] Multiple screw cores or screw core assembly cores are placed on the port of the first area of ​​the base core. The casting core is placed on the feed port of the base core. Molten metal is poured in from the top port of the casting core. The molten metal enters the base core from the feed port, and then flows from bottom to top into the screw core or screw core assembly after passing through the guide channel and the first area. After cooling, it is taken out and the flash waste is removed to obtain multiple screws at one time.

[0035] Compared with existing technologies, the advantages of this invention are as follows: Firstly, during casting, molten iron enters the screw core from bottom to top, resulting in less impact on the core and maintaining the integrity of the mold, thus preventing sand holes. Secondly, there is only one pouring port corresponding to the casting core. Therefore, the flash after cooling consists of only one pouring port and multiple flow channels, whereas existing technologies require one pouring port for each screw, leaving a large amount of flash at each port. This flash needs to be remelted before use. Therefore, the flash material usage is significantly reduced, saving processing costs. Furthermore, multiple screws can be formed in a single casting, greatly improving overall production efficiency. Existing technologies require at least one filter screen at each pouring port to filter the molten iron; this invention only requires installing a filter screen on the casting core, thus greatly reducing the amount of filter screens used and lowering production costs. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the screw structure in the prior art.

[0037] Figure 2 This is a schematic diagram of the structure of Example 1.

[0038] Figure 3 for Figure 2 The exploded diagram.

[0039] Figure 4 This is an exploded view from another perspective of Example 1.

[0040] Figure 5 for Figure 3 Exploded view of the inner sleeve and the cast sand core.

[0041] Figure 6 for Figure 3 Exploded view of the screw core, sleeve, riser core and end cap.

[0042] Figure 7 for Figure 6 A breakdown diagram from another perspective.

[0043] Figure 8 This is a schematic diagram of the structure of Example 2.

[0044] Figure 9 for Figure 8 Exploded view of the middle screw core assembly. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0046] Example 1, as Figure 2 , Figure 3 and Figure 4 As shown, the screw casting device in this embodiment includes a bracket 4, a sleeve 6, a tube 5, a base sand core 1, a screw sand core 3, a casting sand core 2, and a filter screen. The base sand core 1 is mounted on the bracket 4; the screw sand core 3 is located inside the sleeve 6; and the casting sand core 2 is located inside the tube 5.

[0047] The base sand core 1 has a feed inlet 13 and five first regions 14 for forming one side of the screw shaft. A guide channel 15 is provided between the feed inlet 13 and the bottom of each first region 14. The five guide channels 15 are arranged radially around the feed inlet 13, with the ports of the first regions 14 facing upwards. Specifically, in this embodiment, the base sand core 1 includes a main body 11 and a bottom cover 12 located at the bottom of the main body 11. The main bodies of the first regions 14 and the guide channels 15 are located on the main body 11, and the bottom plate of the guide channels 15 is located on the bottom cover 12.

[0048] Each first region 14 is equipped with a screw core 3, which is longitudinally disposed at the port of the first region 14 and has an inner cavity. This inner cavity includes a second region 31 for forming screw blades and a third region 32 for forming the shaft on the other side of the screw. The second region 31 has an internal thread formed inside to fit the screw blades. Figure 6 and Figure 7 As shown, a riser sand core 7 is provided at the upper end of the third region of the screw sand core 3. An air outlet 71 is formed at the top of the riser sand core 7, and an end cap 8 is provided on the outer periphery of the riser sand core 7.

[0049] The casting sand core 2 is longitudinally positioned on the base sand core 1 and directly opposite the feed inlet 13; the filter screen is located inside the casting sand core 2. Figure 5 As shown, the sleeve 5 in this embodiment includes an upper tube 51, a lower tube, an upper iron clamp 52, and a lower iron clamp 53, wherein the lower tube is composed of half 53 and half 54 joined together. The filter screen includes a first filter screen 21 and a second filter screen 22. Specifically, the inlet end and outlet end of the casting sand core 2 are respectively provided with the first filter screen 21 and the second filter screen 22, and the mesh size of the first filter screen 21 is larger than that of the second filter screen 22.

[0050] Combination Figure 6 and Figure 7 As shown, the sleeve 6 includes a body portion 61 for accommodating the second region of the screw core and an extension portion 62 for accommodating the third region of the screw core. The extension portion 62 protrudes from one end of the body portion 61. The inner wall of the body portion 61 has an internal thread adapted to the screw, and the outer wall of the screw core 3 has an external thread adapted to the inner wall of the body portion 61. The thickness of the inner and outer walls of the second region of the screw core 3 is substantially the same.

[0051] The screw casting method includes the following steps: five screw sand cores 3 are placed on the port of the first area 14 of the base sand core 1, the casting sand core 2 is placed on the feed port 13 of the base sand core 1, the molten metal is poured in from the top port of the casting sand core 2, the molten metal enters the base sand core 1 from the feed port 13, and then flows from bottom to top into the screw sand core 3 after passing through the guide channel 15 and the first area 14. After cooling, it is taken out, the riser and flash waste are removed, and five screws are obtained at one time.

[0052] The riser sand core has vent holes at the top to completely release air from the mold cavity. After casting, approximately 5% flash remains inside the sleeve and guide channel, compared to approximately 15-20% in existing technologies. This significant reduction in flash facilitates its removal, and the flash can be remelted for reuse, thus lowering processing costs. Molten iron flows from bottom to top within the screw sand core, maintaining the integrity of the mold. The overall thickness of the screw sand core is more uniform. Compared to existing screw sand cores, some sections have thinner walls, significantly reducing the amount of casting sand required. This shortens heating time and allows for faster product cooling, minimizing quality defects caused by shrinkage. Previously, thicker areas of the screw sand mold contained air, which could easily enter the product during casting, causing porosity. Now, with a uniform thickness, air is reduced, making porosity less likely. The ability to mold five screws at once greatly improves efficiency. In existing technologies, the pouring gate is relatively short, typically with only one filter screen. When molten iron is poured, due to the very short filtration time, some fine slag particles still enter the finished product, affecting product quality. In this embodiment, the axial length of the pouring sand core can be appropriately extended, allowing sufficient filtration time. Because fine slag particles are lighter than molten iron, they will ultimately float between the two filter screens, resulting in more thorough filtration and preventing them from entering the product.

[0053] Example 2, as Figure 8 and Figure 9 As shown, the screw core assembly in this embodiment includes a first screw core 3a, a shaft core 3b, and a second screw core 3c connected sequentially from bottom to top. The first screw core 3a is longitudinally disposed on the port of the first region 14 and has an inner cavity. The inner cavity includes a second region 31a for forming screw blades and a third region 32a for forming the other side of the screw shaft. The second region 31a has an internal thread adapted to the screw blades. The shaft core 3b is hollow and has a fourth region 31b for forming the screw shaft on one side. The second screw core 3c is disposed on the port of the shaft core 3b and has an inner cavity. The inner cavity includes a fifth region 31c for forming screw blades and a sixth region 32c for forming the other side of the screw shaft. The fifth region 31c has an internal thread adapted to the screw blades. A riser core 7 is located at the upper end of the sixth region 32c. An vent hole 71 is formed at the top of the riser core 7, and an end cap 8 is provided on the outer periphery of the riser core 7. In this embodiment, a first sleeve 6a is provided on the outer periphery of the first screw core 3a, a second sleeve 6b is provided on the outer periphery of the second screw core 3c, and a shaft sleeve 9 is provided on the outer periphery of the shaft core 3b. The shaft sleeve 9 is composed of two symmetrical halves 91 and 92 joined together. Other structures are described in Embodiment 1.

[0054] The screw casting method includes the following steps: placing five screw sand core assemblies on the port of the first region 14 of the base sand core 1, placing the casting sand core 2 on the feed port 13 of the base sand core 1, pouring molten metal from the top port of the casting sand core 2, the molten metal entering the base sand core 1 from the feed port 13, and then flowing from bottom to top into the first screw sand core 3a, the shaft sand core 3b and the second screw sand core 3c after passing through the guide channel 15 and the first region 14. After cooling, the screws are removed, and the risers and flash are removed to obtain five screws at once.

[0055] This embodiment uses two stacked screw sand cores to achieve casting, which greatly improves work efficiency compared to embodiment 1, and can obtain ten screws at a time. In addition, two screw sand cores will only produce one riser, thus greatly reducing the material used for the riser and reducing processing costs.

Claims

1. A screw casting device, characterized in that... include The base sand core (1) has a feed port (13) and a first region (14) for forming a rotating shaft on one side of the screw, wherein a flow channel (15) is provided between the feed port (13) and the bottom of the first region (14), and the port of the first region (14) faces upward. The screw core (3) is longitudinally disposed on the port of the aforementioned first region (14) and has an inner cavity on the inside. The inner cavity includes a second region (31) for forming screw blades and a third region (32) for forming the shaft on the other side of the screw. The aforementioned second region (31) has an internal thread that is adapted to the screw blades. A casting sand core (2) is longitudinally positioned on the aforementioned base sand core (1) and directly opposite the aforementioned feed inlet (13); and A filter screen is installed inside the aforementioned cast sand core (2); The base sand core (1) is mounted on the bracket (4); the screw sand core (3) is mounted inside the sleeve (6); and the casting sand core (2) is located inside the sleeve (5). The sleeve (6) includes a body portion for accommodating the second region of the screw core and an extension portion for accommodating the third region of the screw core. The extension portion protrudes from one end of the body portion. The inner wall of the body portion has an internal thread adapted to the screw. The outer wall of the screw core (3) has an external thread adapted to the inner wall of the body portion. The thickness of the inner and outer walls of the second region of the screw core (3) is basically the same; The inlet and outlet ends of the cast sand core (2) are respectively provided with a first filter screen (21) and a second filter screen (22), and the mesh size of the first filter screen (21) is larger than that of the second filter screen (22). The base sand core (1) includes a main body (11) and a bottom cover (12) located at the bottom of the main body (11). The main body of the first region (14) and the main body of the flow channel (15) are located on the main body (11), and the bottom plate of the flow channel (15) is located on the bottom cover (12).

2. The screw casting device according to claim 1, characterized in that... The upper end of the third region of the screw core (3) is provided with a riser core, the top of which has an air vent, and the outer periphery of the riser core is provided with an end cap.

3. The screw casting device according to claim 1, characterized in that... The first region (14) is arranged around the feed inlet (13), and each first region (14) and the feed inlet (13) form a guide channel (15). The multiple guide channels (15) are arranged radially with the feed inlet (13) as the center.

4. A screw casting method using any one of the screw casting devices according to claims 1 to 3, comprising the following steps: Multiple screw cores (3) or screw core assemblies are placed on the port of the first region (14) of the base core (1). The casting core (2) is placed on the feed port (13) of the base core (1). Molten metal is poured in from the top port of the casting core (2). The molten metal enters the base core (1) from the feed port (13), and then flows from bottom to top into the screw core (3) or screw core assembly after passing through the guide channel (15) and the first region (14). After cooling, the screw cores are removed, and the flash waste is removed to obtain multiple screws at once.

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