A dynamic pressure maintaining device for use in a screw barrel

Abstract

A dynamic pressure maintaining device for screw machine cylinder, comprising a pressure maintaining part connectable to the material pipe group of an injection molding machine, a material outlet channel is arranged in the pressure maintaining part, the inlet of the material outlet channel is arranged on the material pipe group connecting surface of the pressure maintaining part, the material pipe group connecting surface is sealably attached to the end surface of the material pipe group, the inlet is in communication with the material outlet of the material pipe group, the outlet of the material outlet channel is arranged on the other end of the pressure maintaining part, a valve structure capable of opening and closing the material outlet channel is arranged in the material outlet channel close to the inlet, one end of the valve structure extends out of the pressure maintaining part and is connected to the valve driving structure, a pressure maintaining structure capable of compressing the material in the material outlet channel is arranged in the material outlet channel close to the outlet, one end of the pressure maintaining structure extends out of the pressure maintaining part and is connected to the pressure maintaining driving structure. The advantage of the present application is that the material pressure maintaining is realized independently by the pressure maintaining part, the pressure maintaining and the injection operation of the injection molding machine are independent of each other, and the operation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of injection molding machine technology, and more particularly to a dynamic pressure holding device for use in screw barrels. Background Technology

[0002] In the field of plastic injection molding, the core working components of an injection molding machine are the barrel assembly, namely the barrel and the screw. In traditional injection molding processes, the two key actions of injection and holding pressure are both completed by the screw. The workflow is as follows: the screw moves forward like a plunger, injecting the molten plastic stored at the front end of the barrel into the mold cavity—this is the injection operation; after the injection is completed, the screw head must maintain forward pressure, acting on the plastic inside the mold to compensate for the plastic's cooling and shrinkage, preventing defects such as shrinkage cavities and depressions in the product—this is the holding pressure operation.

[0003] The screw must remain in the forward position throughout the injection and holding pressure processes and cannot immediately retract to prepare for the next mold. This means that the plasticizing process of the next mold must wait until the holding pressure stage ends and the screw retracts before it can begin, creating a sequential action that prolongs the overall molding cycle and reduces production efficiency. Furthermore, during the holding pressure process, the screw's sealing relies primarily on the fit between the screw head and the inner wall of the barrel. Since the screw itself needs to rotate for plasticizing, a gap inevitably exists between them, making it prone to molten material flowing back from the screw grooves to the rear end during holding pressure—a phenomenon known as "backflow." This pressure leakage leads to unstable holding pressure, reduced shrinkage compensation, and difficulty in accurately controlling product dimensions and internal quality. Moreover, the screw needs to simultaneously perform multiple functions such as conveying, melting, mixing, injection, and holding pressure, placing extremely high demands on its design and materials. During the holding pressure stage, the screw endures high pressure, which can exacerbate wear between it and the barrel, affecting its lifespan and consequently increasing the overall cost of injection molding, hindering large-scale production. Therefore, the injection structure of existing injection molding machines requires further improvement. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dynamic pressure holding device for screw barrels that can extend the service life of injection molding machine barrel assembly and improve injection efficiency, in view of the above-mentioned existing technology.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: This dynamic pressure holding device for screw barrels is characterized in that it includes a pressure holding part that can be connected to the material tube assembly of an injection molding machine, the pressure holding part is provided with a discharge channel, the inlet of the discharge channel is provided on the material tube assembly connecting surface of the pressure holding part, the material tube assembly connecting surface can be sealed against the end face of the material tube assembly, the inlet can be connected to the discharge port of the material tube assembly, the outlet of the discharge channel is provided at the other end of the pressure holding part, a valve structure that can open and close the discharge channel is provided in the discharge channel near the inlet, one end of the valve structure extends out of the pressure holding part and is connected to the valve driving structure, and a pressure holding structure that can compress the material in the discharge channel is provided in the discharge channel near the outlet, one end of the pressure holding structure extends out of the pressure holding part and is connected to the pressure holding driving structure.

[0006] As an improvement, the discharge channel can preferably be divided into a pressure-holding chamber and a storage chamber. The radial width of the pressure-holding chamber is greater than the radial width of the storage chamber. The storage chamber is located near the inlet, the valve structure is disposed in the storage chamber, and the pressure-holding structure is disposed in the pressure-holding chamber. This facilitates pressure holding and discharge, resulting in better performance.

[0007] In a further improvement, the pressure-holding structure can preferably be a pressure-holding plunger. A through-hole is provided on the pressure-holding part, allowing the plunger to extend into it. One end of the through-hole communicates with the pressure-holding chamber. The pressure-holding plunger can be inserted into the through-hole in a forward and backward manner. One end of the plunger extends out of the pressure-holding part, and the other end extends into the pressure-holding chamber. Linear control of the material pressure in the pressure-holding chamber allows for better pressurization of the material and higher pressurization accuracy.

[0008] In a further improvement, the through-hole can preferably be positioned obliquely downwards at the upper part of the pressure-holding section, with the bottom opening of the through-hole close to the outlet of the pressure-holding chamber. This results in higher structural stability.

[0009] In a further improvement, the radial cross-section of the pressure-holding plunger is preferably circular, and an end protrusion with a diameter larger than that of the pressure-holding plunger is provided at the top of the pressure-holding plunger. The end protrusion can abut against the outer wall of the pressure-holding part and prevent the pressure-holding plunger from advancing further. This makes it safer to use.

[0010] As a further improvement, an annular groove can preferably be provided on the inner wall of the through-hole near the end protrusion, and a sealing ring is filled in the annular groove. This further improves the structural sealing performance.

[0011] As an improvement, the valve structure can preferably be a valve core column. A through-hole is provided on the side of the pressure-holding part, allowing the valve core column to extend into it. The middle of the through-hole communicates with the storage chamber. The valve core column is rotatably connected to the through-hole, with one end extending out of the pressure-holding part and the other end extending into it. A through-hole is provided in the middle of the valve core column, connecting to the storage chamber and isolating it after rotation. The structure is simple, the opening and closing of the discharge channel is easy, and the sealing effect is good when the discharge channel is sealed.

[0012] A further improvement is made by preferably providing annular sealing grooves on the valve core on both sides of the valve core through hole, with sealing gaskets embedded in the sealing grooves. This further enhances the sealing effect of the valve core.

[0013] As an improvement, the pressure-holding section may preferably include a storage body and a connecting body, which are detachably connected together, and the pressure-holding structure and valve structure are connected to the storage body. This results in higher connection stability.

[0014] In a further improvement, the storage body may preferably include a storage seat and a discharge nozzle, the storage seat and the discharge nozzle being detachably connected together, and the pressure-holding structure and valve structure being connected to the storage seat. This results in better material injection performance.

[0015] Compared with existing technologies, the advantages of this invention are as follows: By adding a pressure-holding section to the injection molding machine's feed tube assembly, the "injection" and "pressure-holding" actions of the injection molding machine are separated. The screw is responsible for high-speed, high-efficiency injection, while the newly added independent pressure-holding section is responsible for pressure holding. This division of labor and cooperation shortens the molding cycle, improves pressure-holding accuracy, prevents molten material backflow, and reduces the combined load on the screw. Since pressure holding and material storage can be carried out simultaneously, the serial steps in the traditional process are transformed into parallel steps, effectively shortening the cycle time of a single molding cycle. Calculations show that this can increase production efficiency by 10-20%. The valve mechanism can tightly seal the discharge channel, thereby preventing material backflow to the rear section of the barrel, reducing pressure loss, and making the pressure holding pressure more stable. This effectively improves the dimensional accuracy of the product and reduces defects such as shrinkage cavities and flash. The screw no longer bears the pressure-holding function, reducing its residence and wear under high pressure, improving the working environment, and helping to extend the service life of the screw and barrel. The independent pressure-holding section can better control the pressure holding and holding time, which is beneficial for the processing and manufacturing of precision products. Attached Figure Description

[0016] Figure 1 This is a perspective view of an embodiment of the present invention; Figure 2 for Figure 1 A three-dimensional image from another angle; Figure 3 yes Figure 1 Side projection view; Figure 4 yes Figure 3 Cross-sectional view along line AA; Figure 5 yes Figure 2 Exploded structural diagram; Figure 6 yes Figure 5 A structural breakdown diagram from another perspective; Figure 7 yes Figure 6 Further structural decomposition diagram; Figure 8 yes Figure 4 Enlarged view of section I; Figure 9 yes Figure 7 Enlarged view of Part II. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] like Figures 1 to 9 As shown, the dynamic pressure holding device for a screw press barrel in this embodiment includes a pressure holding section that can be connected to the material tube assembly of an injection molding machine. The pressure holding section is provided with a discharge channel. The inlet of the discharge channel is located on the material tube assembly connecting surface of the pressure holding section. The material tube assembly connecting surface can be sealed against the end face of the material tube assembly. The inlet can be connected to the discharge port of the material tube assembly. The outlet of the discharge channel is located at the other end of the pressure holding section. A valve structure that can open and close the discharge channel is provided in the discharge channel near the inlet. One end of the valve structure extends out of the pressure holding section and is connected to the valve drive structure. A pressure holding structure that can compress the material in the discharge channel is provided in the discharge channel near the outlet. One end of the pressure holding structure extends out of the pressure holding section and is connected to the pressure holding drive structure.

[0019] The discharge channel is divided into a pressure holding chamber 11 and a storage chamber 12. The radial width of the pressure holding chamber 11 is greater than that of the storage chamber 12. The storage chamber 12 is close to the inlet. The valve structure is located in the storage chamber 12, and the pressure holding structure is located in the pressure holding chamber 11.

[0020] The pressure-holding structure is a pressure-holding plunger 4. A through-hole 13 is provided on the pressure-holding part, allowing the plunger 4 to extend into it. One end of the through-hole 13 communicates with the pressure-holding chamber 11. The pressure-holding plunger 4 can be inserted into the through-hole 13, moving forward and backward. One end of the plunger 4 extends out of the pressure-holding part, and the other end extends into the pressure-holding chamber 11. The pressure-holding drive structure is a hydraulic actuator or servo motor located outside the pressure-holding part. The specific structure of the pressure-holding drive structure and the connection structure for driving the pressure-holding plunger 4 forward and backward are existing technologies and will not be described further. The pressure-holding drive structure can precisely control the depth to which the pressure-holding plunger 4 extends into the pressure-holding chamber and maintain a stable depth, thereby better controlling the pressure applied to the material and maintaining the stability of the pressurization. This precise control of the pressure-holding plunger's movement distance and its ability to keep the plunger stationary after movement are existing functions in the prior art, and their working principle is also existing technology and will not be described further.

[0021] The through-hole 13 is obliquely downward disposed on the upper part of the pressure-holding section, and the bottom opening of the through-hole 13 is close to the discharge port of the pressure-holding chamber 11. The radial cross-section of the pressure-holding plunger 4 is circular, and an end protrusion 41 with a diameter larger than the diameter of the pressure-holding plunger is provided at the top of the pressure-holding plunger 4. The end protrusion 41 can abut against the outer wall of the pressure-holding section and prevent the pressure-holding plunger 4 from advancing further. An annular groove 131 is provided on the inner wall of the through-hole 13 near the end protrusion 41, and a sealing ring 132 is filled in the annular groove 131.

[0022] The valve structure consists of a valve core column 5. A through-hole 14, allowing the valve core column 5 to extend into the pressure-holding section, is provided on the side of the pressure-holding section. The middle of the through-hole 14 is connected to the storage chamber 12. The valve core column 5 is rotatably connected to the through-hole 14. One end of the valve core column 5 extends out of the pressure-holding section, and the other end extends into the pressure-holding section. A through-hole 51, connecting to the storage chamber 12 and isolating it after rotation, is provided in the middle of the valve core column 5. Annular sealing grooves 52 are provided on the valve core column 5 on both sides of the through-hole 51, and sealing gaskets are embedded in the sealing grooves 52. The valve drive structure and the connection structure between the valve drive structure and the valve core column 5 are known technologies and will not be described further.

[0023] The pressure-holding section includes a storage body and a connecting body 3, which are detachably connected together. The pressure-holding structure and the valve structure are connected to the storage body. The storage body includes a storage seat 1 and a discharge nozzle 2, which are detachably connected together. The pressure-holding structure and the valve structure are connected to the storage seat 1.

[0024] Working principle: In the feed tube assembly of the injection molding machine, that is, in the combination structure of the barrel and screw, the screw rotates and advances to transport and store the plasticized molten material in the storage chamber of the storage seat. At this time, the valve core is in the open state, and the valve core through hole is connected to the storage chamber; After the material storage is completed, the valve core rotates to separate the storage chamber, and the valve core through hole is no longer connected to the storage chamber. Thus, the storage chamber is disconnected from the inner cavity of the barrel. At this time, the screw rotates back. Since the storage chamber is disconnected from the inner cavity of the barrel, the screw will not affect the material in the storage chamber when it retracts. When the screw retracts, the pressure-holding plunger is activated, compressing the melt in the storage chamber forward, providing precise and continuous feeding and pressure holding for the material in the storage chamber. Since the storage chamber is isolated from the barrel, the screw can immediately begin to retract and rotate while the pressure-holding plunger is holding pressure, to plasticize and store material for the next mold. The storage action and the pressure holding action are performed in parallel. When the holding time ends and the screw has finished storing material for the next mold, the valve core reopens, and the storage chamber is connected to the barrel again. The newly plasticized molten material at the front end of the screw pushes the material that has completed the holding time in the storage chamber into the nozzle for injection. The newly pushed material remains in the holding chamber, and a new cycle begins.

Claims

1. A dynamic pressure holding device for use in a screw compressor barrel, characterized in that: The device includes a pressure-holding section that can be connected to the material tube assembly of an injection molding machine. The pressure-holding section has a discharge channel, the inlet of which is located on the material tube assembly connection surface of the pressure-holding section. The material tube assembly connection surface can be sealed against the end face of the material tube assembly. The inlet can communicate with the discharge port of the material tube assembly. The outlet of the discharge channel is located at the other end of the pressure-holding section. A valve structure that can open and close the discharge channel is provided in the discharge channel near the inlet. One end of the valve structure extends out of the pressure-holding section and is connected to a valve drive structure. A pressure-holding structure that can compress the material in the discharge channel is provided in the discharge channel near the outlet. One end of the pressure-holding structure extends out of the pressure-holding section and is connected to a pressure-holding drive structure.

2. The dynamic pressure holding device according to claim 1, characterized in that: The discharge channel is divided into a pressure holding chamber (11) and a storage chamber (12). The radial width of the pressure holding chamber (11) is greater than the radial width of the storage chamber (12). The storage chamber (12) is close to the inlet. The valve structure is located in the storage chamber (12). The pressure holding structure is located in the pressure holding chamber (11).

3. The dynamic pressure holding device according to claim 2, characterized in that: The pressure-holding structure is a pressure-holding plunger (4). A through hole (13) is provided on the pressure-holding part, which can extend into the pressure-holding plunger (4). One end of the through hole (13) is connected to the pressure-holding cavity (11). The pressure-holding plunger (4) can be inserted into the through hole (13) in a forward and backward manner. One end of the pressure-holding plunger (4) extends out of the pressure-holding part, and the other end of the pressure-holding plunger (4) extends into the pressure-holding cavity (11).

4. The dynamic pressure holding device according to claim 3, characterized in that: The through-hole (13) is obliquely downward disposed on the upper part of the pressure-holding part, and the bottom opening of the through-hole (13) is close to the discharge port of the pressure-holding chamber (11).

5. The dynamic pressure holding device according to claim 4, characterized in that: The radial cross section of the pressure-holding plunger (4) is circular. An end protrusion (41) with a diameter larger than that of the pressure-holding plunger is provided at the top of the pressure-holding plunger (4). The end protrusion (41) can abut against the outer wall of the pressure-holding part and prevent the pressure-holding plunger (4) from advancing further.

6. The dynamic pressure holding device according to claim 5, characterized in that: An annular groove (131) is provided on the inner wall of the through hole (13) near the end protrusion (41), and a sealing ring (132) is filled in the annular groove (131).

7. The dynamic pressure holding device according to any one of claims 2 to 6, characterized in that: The valve structure is a valve core column (5). A through hole (14) that can extend into the valve core column (5) is provided on the side of the pressure holding part. The middle part of the through hole (14) is connected to the storage chamber (12). The valve core column (5) is rotatably connected in the through hole (14). One end of the valve core column (5) extends out of the pressure holding part, and the other end of the valve core column (5) extends into the pressure holding part. A valve core column through hole (51) that can connect to the storage chamber (12) and isolate the storage chamber (12) after rotation is provided in the middle of the valve core column (5).

8. The dynamic pressure holding device according to claim 7, characterized in that: An annular sealing groove (52) is provided on the valve core column (5) on both sides of the valve core column through hole (51), and a sealing gasket is embedded in the sealing groove (52).

9. The dynamic pressure holding device according to any one of claims 1 to 6, characterized in that: The pressure-holding part includes a storage body and a connecting body (3), which are detachably connected together. The pressure-holding structure and the valve structure are connected to the storage body.

10. The dynamic pressure holding device according to claim 9, characterized in that: The storage body includes a storage seat (1) and a discharge nozzle (2), which are detachably connected together. The pressure holding structure and valve structure are connected to the storage seat (1).

Images