Pumping device and injection molding apparatus

Abstract

The application discloses a pumping device and an injection molding equipment. The pumping device comprises a support, a pumping mechanism, a piston shaft, a driving mechanism and a feeding mechanism. The pumping mechanism comprises a first cylinder vertically arranged on the support. A first piston is arranged in the first cylinder to divide the first cylinder into a first upper chamber and a first lower chamber. An upper part of the first cylinder is provided with a first discharge port communicated with the first upper chamber. A lower part of the first cylinder is provided with a second discharge port communicated with the first lower chamber. A first one-way valve is arranged at the first discharge port. A second one-way valve is arranged at the second discharge port. The piston shaft is vertically arranged in the first cylinder. The first piston is fixedly arranged on the piston shaft. The driving mechanism is arranged on the support and is used for driving the piston shaft to move up and down. The feeding mechanism is used for feeding liquid material with positive pressure to the first upper chamber when the piston shaft moves downward and is used for feeding liquid material with positive pressure to the first lower chamber when the piston shaft moves upward. The pumping device can realize continuous output of the liquid material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of injection molding, and in particular to a pumping device and an injection molding equipment. BACKGROUND

[0002] When processing products by using an injection molding equipment, liquid material contained in a material bucket is usually delivered to an injection device, and then the liquid material is injected into a mold by the injection device to form a target product.

[0003] However, the efficiency of delivering the liquid material to the injection device in the prior art is low, which cannot well meet the processing requirements. Therefore, the related art proposes a pumping device including a cylinder and a split piston movably arranged in the cylinder, the piston divides the internal space of the cylinder into an upper chamber and a lower chamber, the upper chamber is communicated with a material feeding pipeline for outputting the liquid material, and the lower chamber has a material inlet provided with a one-way valve. When the piston is driven to move upward, the piston seals and extrudes the liquid material in the upper chamber, so as to pump the liquid material in the upper chamber into the material feeding pipeline, and at the same time, a negative pressure is formed in the lower chamber to suck the liquid material in the material bucket into the lower chamber through the material inlet; when the piston is driven to move downward, the piston opens and extrudes the liquid material in the lower chamber, so that the liquid material in the lower chamber enters the upper chamber, and the piston is continuously driven to move downward, so as to pump part of the liquid material in the upper chamber into the material feeding pipeline.

[0004] However, in the working process of the above-mentioned pumping device, when the piston is driven to move downward, the piston needs to move downward by a distance to change the negative pressure in the lower chamber to positive pressure, and then the piston is continuously driven to move downward to normally pump the liquid material into the material feeding pipeline, so that the output of the liquid material is interrupted every time the working condition of the piston moving downward is switched during the continuous working process of the pumping device, and thus the continuous output of the liquid material cannot be realized. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a pumping device capable of realizing the continuous output of the liquid material.

[0006] The present application also proposes an injection molding equipment having the above-mentioned pumping device.

[0007] The pump device according to the first aspect of the present application comprises a support, a pumping mechanism, a piston shaft, a driving mechanism and a feeding mechanism. The pumping mechanism comprises a first cylinder vertically arranged on the support, a first piston arranged in the first cylinder, a first upper chamber and a first lower chamber separated by the first piston, a first discharge port arranged in an upper portion of the first cylinder and communicated with the first upper chamber, a second discharge port arranged in a lower portion of the first cylinder and communicated with the first lower chamber, a first one-way valve arranged at the first discharge port, and a second one-way valve arranged at the second discharge port. The piston shaft is vertically arranged in the first cylinder, and the first piston is fixedly arranged on the piston shaft. The driving mechanism is arranged on the support and configured to drive the piston shaft to move up and down. The feeding mechanism is configured to feed the liquid material with positive pressure to the first upper chamber when the piston shaft moves downward, and to feed the liquid material with positive pressure to the first lower chamber when the piston shaft moves upward.

[0008] The pump device according to the present application has at least the following beneficial effects. When the piston shaft is driven by the driving mechanism to move upward, the first piston is driven to move upward, so that the volume of the first upper chamber is reduced, thereby extruding the liquid material in the first upper chamber to be discharged from the first discharge port to the injection device, and at the same time, the feeding mechanism feeds the liquid material with positive pressure to the first lower chamber. When the piston shaft is driven by the driving mechanism to move downward, the first piston is driven to move downward, so that the volume of the first lower chamber is reduced, thereby extruding the liquid material in the first lower chamber to be discharged from the second discharge port to the injection device, and at the same time, the feeding mechanism feeds the liquid material with positive pressure to the first upper chamber. Compared with the prior art, the pump device according to the present application can continuously output the liquid material when pumping, because the feeding mechanism can provide the liquid material with positive pressure, so that the first piston will not be interrupted in outputting the liquid material due to the need to eliminate negative pressure, whether in the upward moving condition or in the downward moving condition.

[0009] According to some embodiments of the present application, the feeding mechanism comprises a second cylinder vertically arranged on the support and below the first cylinder, a second piston arranged in the second cylinder to divide the interior space of the second cylinder into a second upper chamber and a second lower chamber, a first feeding port arranged on the lower end of the second cylinder and communicated with the second lower chamber, a third one-way valve arranged at the first feeding port, the lower part of the piston shaft penetrating through the first cylinder and extending into the second cylinder, an avoiding through hole arranged on the second piston, the lower part of the piston shaft penetrating through the avoiding through hole, the diameter of the lower part of the piston shaft being smaller than the diameter of the avoiding through hole, the lower part of the piston shaft being provided with a pushing part above the second piston and a first sealing part below the second piston, the distance between the pushing part and the first sealing part being greater than the dimension of the second piston along the axial direction of the piston shaft, the upper part of the first cylinder being provided with a second feeding port communicated with the first upper chamber, the lower part of the first cylinder being provided with a third feeding port communicated with the first lower chamber, the upper part of the second cylinder being provided with a third discharging port communicated with the second upper chamber, the third discharging port being communicated with the second feeding port and the third feeding port, a fourth one-way valve arranged at the second feeding port, and a fifth one-way valve arranged at the third feeding port.

[0010] According to some embodiments of the present application, the pump device further comprises a feeding pipeline arranged on the support or the first cylinder, the feeding pipeline extending from the upper part of the second cylinder to the upper part of the first cylinder, the second feeding port, the third feeding port and the third discharging port being all communicated with the feeding pipeline.

[0011] According to some embodiments of the present application, the pump device further comprises a return pipeline arranged on the support or the second cylinder, one end of the return pipeline being connected with the feeding pipeline, the other end of the return pipeline extending to the lower part of the second cylinder and being used to be communicated with a liquid material containing barrel, and an overflow valve arranged on the end of the return pipeline close to the feeding pipeline.

[0012] According to some embodiments of the present application, the pump device further comprises a discharging pipeline arranged on the support or the first cylinder, the first discharging port and the second discharging port being both communicated with the discharging pipeline, and one end of the discharging pipeline having a fourth discharging port.

[0013] According to some embodiments of the present application, the third one-way valve comprises a valve body and a valve core, the valve body is arranged at the first feeding port, a material passage is arranged on the valve body, and the valve core is movably arranged in the material passage, the diameter of the valve core is smaller than the diameter of the material passage, and a second sealing portion is arranged on the upper portion of the valve core and located above the valve body.

[0014] According to some embodiments of the present application, the lower end of the second cylinder is provided with a pressing disc, the pressing disc is used to block the barrel opening of the barrel containing the liquid material and adhere to the liquid surface of the liquid material.

[0015] According to some embodiments of the present application, the pressing disc is provided with an openable and closable exhaust port.

[0016] According to some embodiments of the present application, the driving mechanism is one of a linear motor, an electric push rod, a pneumatic cylinder and a hydraulic cylinder.

[0017] The injection molding equipment according to the second aspect of the embodiments of the present application comprises the material pumping device according to the first aspect of the embodiments of the present application.

[0018] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0019] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0020] Figure 1 is a structural schematic view of the material pumping device of an embodiment of the present application when cooperating with the barrel;

[0021] Figure 2 is a sectional view of the material pumping device of an embodiment of the present application;

[0022] Figure 3 is Figure 2 is a partial schematic view of the first cylinder portion in FIG. 1;

[0023] Figure 4 is Figure 2 is a partial schematic view of the second cylinder portion in FIG. 1;

[0024] Figure 5 is a schematic view of the pushing portion of an embodiment of the present application when separated from the second piston and the first sealing portion abutting against the second piston;

[0025] Figure 6 is a schematic view of the first sealing portion of an embodiment of the present application when separated from the second piston and the pushing portion abutting against the second piston;

[0026] Figure 7 is a schematic view of a state when the second sealing part of an embodiment of the present application is separated from the valve body;

[0027] Figure 8 is a schematic view of a state when the second sealing part of an embodiment of the present application is in contact with the valve body.

[0028] Reference signs:

[0029] Bucket a, support 100, first cylinder 210, first piston 220, first one-way valve 230, second one-way valve 240, fourth one-way valve 250, fifth one-way valve 260, piston shaft 300, pushing part 310, first sealing part 320, driving mechanism 400, second cylinder 510, second piston 520, avoiding through hole 521, third one-way valve 530, valve body 531, material passage 5311, valve core 532, second sealing part 533, sixth one-way valve 540, feeding pipe 600, return pipe 700, overflow valve 710, discharge pipe 800, fourth discharge port 810, pressure plate 900. DETAILED DESCRIPTION

[0030] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only, and are used only for the purpose of explaining the present application, and cannot be understood as a limitation of the present application.

[0031] In the description of the present application, it should be understood that, if the orientation description is involved, for example, the orientation or position relationship indicated by the up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the purpose of describing the present application and simplifying the description, and therefore cannot be understood as a limitation of the present application, which indicates or implies that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation.

[0032] In the description of the present application, if the words such as several, more than, less than, exceed, above, below, within, etc. appear, wherein the meaning of several is one or more, the meaning of more than is two or more, more than, less than, exceed, etc. are understood as not including the number, above, below, within, etc. are understood as including the number.

[0033] In the description of the present application, if the words such as first, second, etc. appear, they are only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the sequence of indicated technical features.

[0034] In the description of the present application, the words such as arrangement, installation, connection and the like should be understood in a broad sense unless otherwise explicitly limited, and the specific meanings of the above words in the present application can be reasonably determined by those skilled in the art in combination with the specific content of the technical solutions.

[0035] With reference to Figures 1 to 8 The pumping device according to the embodiments of the present application comprises a bracket 100, a pumping mechanism, a piston shaft 300, a driving mechanism 400 and a feeding mechanism.

[0036] Specifically, the pumping mechanism comprises a first cylinder 210 vertically arranged on the bracket 100, a first piston 220 arranged in the first cylinder 210 to divide the internal space of the first cylinder 210 into a first upper chamber and a first lower chamber, a first discharge port communicated with the first upper chamber arranged at the upper part of the first cylinder 210, a second discharge port communicated with the first lower chamber arranged at the lower part of the first cylinder 210, a first one-way valve 230 arranged at the first discharge port, a second one-way valve 240 arranged at the second discharge port, the piston shaft 300 vertically penetrating the first cylinder 210, the first piston 220 fixedly arranged on the piston shaft 300, the driving mechanism 400 arranged on the bracket 100 and used to drive the piston shaft 300 to move up and down, and the feeding mechanism used to feed the liquid material with positive pressure to the first upper chamber when the piston shaft 300 moves downward and used to feed the liquid material with positive pressure to the first lower chamber when the piston shaft 300 moves upward.

[0037] When the piston shaft 300 is driven by the driving mechanism 400 to move upward, the first piston 220 is driven to move upward, so that the volume of the first upper chamber is reduced, thereby extruding the liquid material in the first upper chamber to make the liquid material in the first upper chamber extruded from the first discharge port to the injection device, and at the same time, the feeding mechanism feeds the liquid material with positive pressure to the first lower chamber. When the piston shaft 300 is driven by the driving mechanism 400 to move downward, the first piston 220 is driven to move downward, so that the volume of the first lower chamber is reduced, thereby extruding the liquid material in the first lower chamber to make the liquid material in the first lower chamber extruded from the second discharge port to the injection device, and at the same time, the feeding mechanism feeds the liquid material with positive pressure to the first upper chamber. Compared with the prior art, the pumping device according to the embodiments of the present application can provide the liquid material with positive pressure when pumping, so that the first piston 220 will not appear the output interruption of the liquid material due to the need to eliminate negative pressure regardless of the working condition of upward movement or downward movement, thereby realizing the continuous output of the liquid material.

[0038] The first one-way valve 230 is used to prevent the pumped liquid material from flowing back to the first upper chamber through the first discharge port, and the second one-way valve 240 is used to prevent the pumped liquid material from flowing back to the first lower chamber through the second discharge port.

[0039] Referring to Figures 3 to 6 In some embodiments, the feeding mechanism comprises a second cylinder 510 vertically arranged on the support 100 below the first cylinder 210, a second piston 520 arranged in the second cylinder 510 to divide the interior space of the second cylinder 510 into a second upper chamber and a second lower chamber, a first feeding port communicated with the second lower chamber arranged at the lower end of the second cylinder 510 (i.e. the end of the second cylinder 510 away from the first cylinder 210), a third one-way valve 530 arranged at the first feeding port, the lower part of the piston shaft 300 penetrating the first cylinder 210 and extending into the second cylinder 510, an avoiding through hole 521 vertically penetrating the second piston 520 arranged on the second piston 520, the lower part of the piston shaft 300 penetrating the avoiding through hole 521, the diameter of the lower part of the piston shaft 300 being smaller than the diameter of the avoiding through hole 521, so that there is a gap between the part of the piston shaft 300 located in the avoiding through hole 521 and the hole wall of the avoiding through hole 521, the lower part of the piston shaft 300 corresponding to the second piston 520 being provided with a pushing part 310 and a first sealing part 320, the pushing part 310 being located above the second piston 520 and used to push the second piston 520 to move downward, the first sealing part 320 being located below the second piston 520 and used to block the avoiding through hole 521 and push the second piston 520 to move upward, the distance between the pushing part 310 and the first sealing part 320 being greater than the dimension of the second piston 520 along the axial direction of the piston shaft 300, the upper part of the first cylinder 210 being provided with a second feeding port communicated with the first upper chamber, the lower part of the first cylinder 210 being provided with a third feeding port communicated with the first lower chamber, the upper part of the second cylinder 510 being provided with a third discharging port communicated with the second upper chamber, the third discharging port being communicated with the second feeding port and the third feeding port, a fourth one-way valve 250 arranged at the second feeding port, and a fifth one-way valve 260 arranged at the third feeding port.

[0040] In use, the first inlet is communicated with a tank a containing liquid material. When the piston shaft 300 is driven upward by the driving mechanism 400, the first sealing portion 320 is brought into abutment against the second piston 520 to block the bypass hole 521 and push the second piston 520 upward, so that the volume of the second upper chamber is reduced to press the liquid material in the second upper chamber, and the liquid material in the second upper chamber is extruded out of the third outlet, at this time, the first upper chamber is in a positive pressure state due to the upward movement of the first piston 220, so the liquid material extruded out of the third outlet is extruded into the first lower chamber through the third inlet to supply the liquid material with positive pressure into the first lower chamber, at the same time, the volume of the second lower chamber is increased to form a negative pressure, so that the liquid material in the tank a is sucked into the second lower chamber through the third one-way valve 530. When the piston shaft 300 is driven downward by the driving mechanism 400, the first sealing portion 320 is separated from the second piston 520 to unblock the bypass hole 521, at the same time, the pushing portion 310 is brought into abutment against the second piston 520 and pushes the second piston 520 downward, in this process, the height of the second upper chamber and the second lower chamber changes by the same amount, and the volume of the second upper chamber is increased and the volume of the second lower chamber is decreased due to the piston shaft 300 passing through the second upper chamber, so that the liquid material in the second lower chamber is extruded out of the bypass hole 521 into the second upper chamber, in addition, the effective volume of the second upper chamber is much smaller than that of the second lower chamber due to the internal space occupied by the piston shaft 300, when the second upper chamber is filled with liquid material, the liquid material in the second lower chamber extruded out of the bypass hole 521 into the second upper chamber is extruded out of the third outlet, at this time, the first lower chamber is in a positive pressure state due to the downward movement of the first piston 220, so the liquid material extruded out of the third outlet is extruded into the first upper chamber through the second inlet to supply the liquid material with positive pressure into the first upper chamber.

[0041] It can be understood that when the feeding mechanism adopts the above structure, the driving mechanism 400 only needs to provide a driving force to drive the piston shaft 300 to move upward and downward, at this time, the piston shaft 300 can not only drive the first piston 220 to move upward and downward to continuously output the liquid material to the injection device by the first cylinder 210, but also drive the second piston 520 to move upward and downward to continuously supply the liquid material with positive pressure to the first cylinder 210 by the second cylinder 510.

[0042] The third one-way valve 530 is used to prevent the liquid material in the second lower chamber from flowing back through the first feeding port when the second piston 520 moves downward, the fourth one-way valve 250 is used to prevent the liquid material in the first upper chamber from flowing back through the second feeding port when the first piston 220 moves upward, and the fifth one-way valve 260 is used to prevent the liquid material in the first lower chamber from flowing back through the third feeding port when the first piston 220 moves downward.

[0043] With reference to Figures 2 to 4 In some embodiments, a sixth one-way valve 540 is arranged at the third discharging port to prevent backflow.

[0044] With reference to Figures 1 to 4 In some embodiments, the pump device further comprises a feeding pipe 600 arranged on the bracket 100 or the first cylinder 210, the feeding pipe 600 extending from the upper portion of the second cylinder 510 to the upper portion of the first cylinder 210, and the second feeding port and the third feeding port are both communicated with the feeding pipe 600. The second feeding port and the third feeding port share one feeding pipe 600, which is conducive to simplifying the pipeline structure. Of course, the second feeding port and the third feeding port can also be respectively connected with one feeding pipe 600 communicated with the third discharging port, which is not limited herein.

[0045] With reference to Figures 1 to 4 In some embodiments, the pump device further comprises a return pipe 700 arranged on the bracket 100 or the second cylinder 510, one end of the return pipe 700 being connected with the feeding pipe 600, the other end of the return pipe 700 extending to the lower portion of the second cylinder 510 and being used to communicate with the liquid material container a, and the end of the return pipe 700 close to the feeding pipe 600 being provided with an overflow valve 710. In the process of the second cylinder 510 supplying the liquid material with positive pressure to the first cylinder 210, when the first cylinder 210 is filled with the liquid material, the liquid material continuously supplied by the second cylinder 510 will increase the pressure in the feeding pipe 600, and when the pressure in the feeding pipe 600 reaches a preset value, the overflow valve 710 can be opened to make the liquid material in the feeding pipe 600 flow back to the liquid material container a through the return pipe 700, thereby playing a role of pressure relief, and further being conducive to improving the stability and reliability of the pump device.

[0046] It should be noted that the overflow valve 710 is also called a safety valve, which is divided into two categories of spring type and rod type, and belongs to the prior art, and the specific structure and working principle thereof are not described herein.

[0047] With reference to Figures 1 to 4In some embodiments, the pump device further comprises a discharge pipe 800 arranged on the support 100 or the first cylinder 210, the first discharge port and the second discharge port are both communicated with the discharge pipe 800, one end of the discharge pipe 800 is provided with a fourth discharge port 810 for being communicated with the injection device. The first discharge port and the second discharge port share one discharge pipe 800, which is beneficial to simplify the pipeline structure. Of course, the first discharge port and the second discharge port can also be respectively connected with one discharge pipe 800 communicated with the injection device, which is not limited herein.

[0048] With reference to Figure 4 、 Figure 7 and Figure 8 In some embodiments, the third one-way valve 530 comprises a valve body 531 and a valve core 532, the valve body 531 is arranged at the first feeding port, the valve body 531 is provided with a material passage 5311 penetrating the valve body 531 in the vertical direction, the valve core 532 is movably arranged in the material passage 5311, the diameter of the valve core 532 is smaller than the diameter of the material passage 5311, so that there is a gap between the part of the valve core 532 located in the material passage 5311 and the inner wall of the material passage 5311, the upper part of the valve core 532 is provided with a second sealing part 533 located above the valve body 531, the second sealing part 533 is used for blocking the material passage 5311. When the piston shaft 300 is driven to move upward by the driving mechanism 400, the second piston 520 is driven to move upward, so that the volume of the second lower chamber is increased to form a negative pressure, so that the second sealing part 533 is separated from the valve body 531 to unblock the material passage 5311, and then the liquid material in the material bucket a can be sucked into the second lower chamber through the material passage 5311. When the piston shaft 300 is driven to move downward by the driving mechanism 400, the second piston 520 is driven to move downward, so that the volume of the second lower chamber is reduced to form a positive pressure, so that the second sealing part 533 abuts against the valve body 531 to block the material passage 5311, and then the liquid material in the second lower chamber can be prevented from flowing back through the material passage 5311 when the second piston 520 moves downward.

[0049] With reference to Figure 1 、 Figure 2 and Figure 4 In some embodiments, the lower end of the second cylinder 510 is provided with a pressure plate 900 for blocking the bucket opening of the material bucket a containing the liquid material and abutting against the liquid surface of the liquid material, when the second piston 520 moves upward, the pressure plate 900 can prevent gas from entering the material bucket a containing the liquid material, so that the negative pressure in the second lower chamber can be better formed to suck the liquid material in the material bucket a.

[0050] It should be noted that in some embodiments, the pressure plate 900 is provided with an openable and closable exhaust port (not shown in the figure), and during the process of loading the pressure plate 900 into the material barrel a containing the liquid material, the exhaust port is opened to exhaust air between the pressure plate 900 and the liquid surface of the liquid material, so that the pressure plate 900 can be attached to the liquid surface of the liquid material, and after the pressure plate 900 is attached to the liquid surface of the liquid material, the exhaust port is closed to prevent the liquid material from overflowing through the exhaust port. Specifically, a manual switch valve or an electromagnetic valve can be provided at the exhaust port to control the opening and closing of the exhaust port, or a detachable sealing plug can be provided at the exhaust port to achieve the opening and closing of the exhaust port, which is not limited herein.

[0051] It should be noted that in some embodiments, the driving mechanism 400 is one of a linear motor, an electric push rod, an air cylinder, and a hydraulic cylinder.

[0052] The injection molding equipment according to the embodiments of the present application comprises the above-described material pumping device.

[0053] It can be understood that, since the injection molding equipment according to the embodiments of the present application comprises the above-described material pumping device, the injection molding equipment according to the embodiments of the present application has all the technical effects of the above-described material pumping device.

[0054] In the description of the present specification, if the description involves the description of the terms such as “one embodiment”, “some embodiments”, “exemplary embodiment”, “example”, “specific example”, and “some examples”, it means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0055] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A pumping device, characterized in that, The pump device comprises: a support; a pumping mechanism, which comprises a first cylinder vertically arranged on the support, a first piston arranged in the first cylinder to divide the interior space of the first cylinder into a first upper chamber and a first lower chamber, a first discharge port arranged on the upper part of the first cylinder and communicated with the first upper chamber, a second discharge port arranged on the lower part of the first cylinder and communicated with the first lower chamber, a first one-way valve arranged at the first discharge port, and a second one-way valve arranged at the second discharge port; a piston shaft vertically arranged in the first cylinder, and the first piston is fixedly arranged on the piston shaft; a driving mechanism arranged on the support and used for driving the piston shaft to move up and down; a feeding mechanism used for feeding liquid material with positive pressure to the first upper chamber when the piston shaft moves downward, and used for feeding liquid material with positive pressure to the first lower chamber when the piston shaft moves upward; the feeding mechanism comprises a second cylinder vertically arranged on the support and below the first cylinder, a second piston arranged in the second cylinder to divide the interior space of the second cylinder into a second upper chamber and a second lower chamber, a first feeding port arranged on the lower end of the second cylinder and communicated with the second lower chamber, a third one-way valve arranged at the first feeding port, the lower part of the piston shaft penetrating through the first cylinder and extending into the second cylinder, an avoiding through hole arranged on the second piston, the lower part of the piston shaft penetrating through the avoiding through hole, the diameter of the lower part of the piston shaft being smaller than the diameter of the avoiding through hole, the lower part of the piston shaft being provided with a pushing part above the second piston and a first sealing part below the second piston, the distance between the pushing part and the first sealing part being greater than the dimension of the second piston along the axial direction of the piston shaft, a second feeding port arranged on the upper part of the first cylinder and communicated with the first upper chamber, a third feeding port arranged on the lower part of the first cylinder and communicated with the first lower chamber, a third discharge port arranged on the upper part of the second cylinder and communicated with the second upper chamber, the third discharge port being communicated with the second feeding port and the third feeding port, a fourth one-way valve arranged at the second feeding port, and a fifth one-way valve arranged at the third feeding port.

2. The apparatus of claim 1, wherein The pump device further comprises a feeding pipeline arranged on the support or the first cylinder, the feeding pipeline extending from the upper part of the second cylinder to the upper part of the first cylinder, and the second feeding port, the third feeding port and the third discharge port are all communicated with the feeding pipeline.

3. The pump apparatus of claim 2, wherein The pump device further comprises a return pipeline arranged on the support or the second cylinder, one end of the return pipeline being connected with the feeding pipeline, the other end of the return pipeline extending to the lower part of the second cylinder and being used for being communicated with a liquid material barrel, and an overflow valve being arranged at the end of the return pipeline close to the feeding pipeline.

4. The apparatus of claim 1 wherein, The pump device further comprises a discharge pipeline arranged on the support or the first cylinder, the first discharge port and the second discharge port are both communicated with the discharge pipeline, and one end of the discharge pipeline is provided with a fourth discharge port.

5. The apparatus of claim 1 wherein, The third one-way valve comprises a valve body and a valve core, the valve body is arranged at the first feeding port, a material passage is arranged on the valve body, the valve core is movably arranged in the material passage, the diameter of the valve core is smaller than the diameter of the material passage, and a second sealing portion located above the valve body is arranged on the upper portion of the valve core.

6. The apparatus of claim 1, wherein A pressing disc is arranged at the lower end of the second cylinder, the pressing disc is used for sealing the barrel opening of the barrel containing the liquid material and adhering to the liquid surface of the liquid material.

7. A pump apparatus as claimed in claim 6, wherein An openable and closable exhaust port is arranged on the pressing disc.

8. The apparatus of claim 1 wherein, The driving mechanism is one of a linear motor, an electric push rod, an air cylinder and a hydraulic cylinder.

9. An injection molding apparatus characterized by, The pump device comprises the pump device according to any one of claims 1 to 8.

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