An injection mechanism of an injection molding machine

Abstract

The invention discloses an injection mechanism of an injection molding machine, comprising an injection seat (1), a barrel (2) arranged on the injection seat (1) and provided with a screw (23) inside, a cylinder body (31), a piston (32) arranged inside the cylinder body (31), a rotation drive mechanism (5) driving the screw (23) to rotate, a sealing sleeve (7) sealably inserted in a mounting hole (311) of the cylinder body (31), and a transmission shaft (6) passing through the piston (32) and the sealing sleeve (7), wherein the transmission shaft (6) is connected to the piston (32) and can rotate around its own axis relative to the piston (32), the front end of the transmission shaft (6) is connected to the screw (23) and can rotate synchronously with the screw (23), and the rear end of the transmission shaft (6) is transmission-connected to the power output end of the rotation drive mechanism (5) through a retractable transmission mechanism. Compared with the prior art, the injection mechanism of the invention is not prone to oil leakage and has a low inertia.

Description

Technical Field

[0001] The present invention relates to the technical field of injection molding machines, and specifically refers to an injection mechanism of an injection molding machine. Background Art

[0002] An injection molding machine is a type of plastic machinery. With the thrust of a screw (or plunger), the plastic in a molten state (i.e., viscous flow state) that has been plasticized is injected into a closed mold cavity, and after curing and shaping, it becomes a molded product. An injection molding machine generally includes a mold mechanism, a mold clamping mechanism, and an injection mechanism. Injection molding machines can be divided into hydraulic cylinder injection molding machines and electric injection molding machines according to the types of their injection mechanisms. Hydraulic cylinder injection molding machines are further divided into single-cylinder injection molding machines and multi-cylinder injection molding machines.

[0003] In existing injection molding machines, the preplasticizing base, the motor on the preplasticizing base, and the screw are all fixedly connected to the piston rod of the oil cylinder. Therefore, during the injection process, the preplasticizing base and the motor on the preplasticizing base move together with the screw. The load on the screw during its reciprocating motion back and forth is very large, and the inertia is large, resulting in slow screw speed increase and difficult braking of the screw after injection. Therefore, precise control cannot be achieved, the requirements for high-precision plastic products cannot be met, and the cost is high and the mold life is short.

[0004] The utility model patent "Injection Molding Machine Piston Rotary Injection Oil Cylinder" with the patent application number CN02292978.9 (publication number CN2585748Y) discloses a similar low-inertia single-cylinder injection molding machine, which attempts to solve the problem of large screw inertia during injection. It is an injection mechanism of a hydraulic-driven single-cylinder injection horizontal injection molding machine, including an injection base and a barrel. The barrel is supported on the injection base, a screw is arranged in the barrel, a motor is arranged at the rear side of the injection base, and an oil cylinder is arranged on the injection base. One end of the piston rod of the oil cylinder is connected to the power output end of the motor through a keyway structure by a transmission shaft, and the other end is connected to the screw for transmission. During preplasticizing, the motor drives the piston to rotate, and then drives the screw in the barrel to rotate. The rotating screw pushes the plasticized melt to the front end of the barrel. At the same time, the screw retreats under the reaction of the material, and then pushes the piston to retreat to complete metering. During injection, the oil cylinder is filled with oil to drive the piston rod to move forward, and then pushes the screw to move forward to complete the injection action.

[0005] In existing single-cylinder injection mechanisms, there are mainly two ways to arrange the transmission shaft: the first is that the transmission shaft drives the piston and the screw to rotate together, and the second is that the transmission shaft passes through the piston and directly drives the screw to rotate, while the piston does not rotate. In both of these mechanisms, there is a rotating mechanism rotating in the high-pressure chamber of the oil cylinder, so there must be a rotating seal. Affected by processing accuracy, transmission swing, and high-pressure liquid pollution, the service life of the rotating seal ring is very short, and in high-pressure hydraulic transmission, oil leakage is very likely to occur. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an injection mechanism of an injection molding machine which is not prone to oil leakage and has low inertia in view of the current status of the prior art.

[0007] The first technical solution adopted by the present invention to solve the above technical problems is: an injection mechanism of an injection molding machine, comprising

[0008] Ejection seat;

[0009] The oil cylinder is arranged on the ejection seat, and comprises a cylinder body and a piston with a piston rod arranged inside the cylinder body, wherein the piston rod is exposed at the front end surface of the cylinder body and can move back and forth and telescope;

[0010] A barrel, which is disposed on the ejection seat and located at the front side of the oil cylinder, and has a screw in its internal cavity; and

[0011] A rotary drive mechanism, installed at the rear side of the oil cylinder, for driving the screw to rotate;

[0012] It is characterized by: it also includes a transmission shaft and a sealing sleeve;

[0013] A mounting hole is axially provided on the rear end surface of the cylinder body, the front end of the sealing sleeve is mounted on the rear part of the piston, the rear end of the sealing sleeve is inserted into the mounting hole and can slide forward and backward in the mounting hole, and a seal is formed between the sealing sleeve and the mounting hole;

[0014] A through hole is axially opened on the piston, and the transmission shaft is inserted into the through hole of the piston and the inside of the sealing sleeve, connected to the piston and rotatable around its own axis relative to the piston, so that the piston can drive the transmission shaft to reciprocate forward and backward but does not rotate with the transmission shaft, the front end of the transmission shaft is connected to the screw and can rotate synchronously with the screw, and the rear end of the transmission shaft is connected to the power output end of the rotary drive mechanism through a retractable transmission mechanism, so that the rotary drive mechanism can drive the transmission shaft to rotate but does not reciprocate forward and backward with the transmission shaft.

[0015] The second technical solution adopted by the present invention to solve the above technical problem is: an injection mechanism of an injection molding machine, comprising

[0016] Ejection seat;

[0017] The oil cylinder is arranged on the ejection seat, and comprises a cylinder body and a piston with a piston rod arranged inside the cylinder body, wherein the piston rod is exposed at the front end surface of the cylinder body and can move back and forth and telescope;

[0018] A barrel, which is disposed on the ejection seat and located at the front side of the oil cylinder, and has a screw in its internal cavity; and

[0019] A rotary drive mechanism, mounted on the rear side of the oil cylinder, for driving the screw to rotate;

[0020] It is characterized by: it also includes a transmission shaft and a sealing sleeve;

[0021] A mounting hole is axially provided on the rear end surface of the cylinder body, a through hole is axially provided on the piston, the rear end of the sealing sleeve is installed in the mounting hole, the front end of the sealing sleeve is slidably inserted in the through hole, and the sealing sleeve forms a seal with the mounting hole and the through hole respectively;

[0022] The transmission shaft is inserted into the through hole of the piston and the inside of the sealing sleeve, is connected to the piston and can rotate around its own axis relative to the piston, so that the piston can drive the transmission shaft to reciprocate back and forth but does not rotate with the transmission shaft, the front end of the transmission shaft is connected to the screw and can rotate synchronously with the screw, and the rear end of the transmission shaft is connected to the power output end of the rotary drive mechanism through a retractable transmission mechanism, so that the rotary drive mechanism can drive the transmission shaft to rotate but does not reciprocate back and forth with the transmission shaft.

[0023] In order to ensure that the transmission shaft can rotate relative to the piston around its own axis, a mounting groove is provided at the front end of the piston, a bearing is provided in the mounting groove, and the transmission shaft is installed on the inner ring of the bearing.

[0024] In order to avoid friction between the transmission shaft and the sealing sleeve to prevent the movement of the transmission rod from being hindered, a gap is provided between the transmission shaft and the sealing sleeve.

[0025] In order to realize the driving of the transmission shaft by the rotary drive mechanism, the rotary drive mechanism includes a power output wheel for driving the transmission shaft to perform rotational motion.

[0026] In order to make way for the transmission shaft and avoid collision between the motor and the transmission shaft during operation, the rotary drive mechanism also includes a motor and a transmission assembly. The output shaft of the motor is connected to the power output wheel through the transmission assembly. The motor and the transmission shaft are not coaxially arranged. The motor is installed above the oil cylinder through a pre-plastic seat. The power output wheel is installed on the pre-plastic seat and is coaxially arranged with the transmission shaft. The rear end of the transmission shaft is passed through the power output wheel and is connected to the power output wheel.

[0027] In order to realize the transmission connection between the output shaft of the motor and the power output wheel, the transmission assembly includes

[0028] a driving pulley mounted on the output shaft of the motor; and

[0029] The transmission belt is sleeved on the driving pulley and the power output wheel to connect the driving pulley and the power output wheel.

[0030] Alternatively, the transmission assembly includes

[0031] a driving sprocket mounted on the output shaft of the motor; and

[0032] A chain is sleeved on the driving sprocket and the power output wheel to drive-connect the driving sprocket and the power output wheel.

[0033] Alternatively, the transmission assembly includes

[0034] a driving gear mounted on the output shaft of the motor, and the driving gear meshes with the power output wheel.

[0035] In order to realize the telescopic transmission between the transmission shaft and the power output wheel of the rotary drive mechanism, one of the outer peripheral wall of the transmission shaft and the inner peripheral wall of the power output wheel is provided with a convex key along the axial direction. Correspondingly, the other of the outer peripheral wall of the transmission shaft and the inner peripheral wall of the power output wheel is provided with a groove along the axial direction. The convex key is slidably inserted into the groove, and the convex key and the groove form the telescopic transmission mechanism.

[0036] Alternatively, the cross-section of the transmission shaft is triangular or polygonal, and the power output wheel has a groove that slidably fits with the sides or corners of the transmission shaft. The outer peripheral wall of the transmission shaft and the inner peripheral wall of the power output wheel form the telescopic transmission mechanism.

[0037] Alternatively, the transmission shaft is composed of multiple inserted rods, and the power output wheel is correspondingly provided with multiple insertion holes. Each inserted rod is inserted into each insertion hole and can slide back and forth in the insertion hole. The inserted rod and the insertion hole form the telescopic transmission mechanism.

[0038] Compared with the prior art, the advantages of the present invention are as follows:

[0039] (1) By sleeving the sealing sleeve on the outer periphery of the transmission shaft, in the first solution, the sealing sleeve is fixed on the piston and slides back and forth with the cylinder body. In the second solution, the sealing sleeve is fixed on the cylinder body and slides back and forth with the piston. In both solutions, due to the isolation of the sealing sleeve, the transmission shaft only passes through the piston and the isolation sleeve and has no direct contact with the high-pressure pressure. Moreover, both the sealing sleeve and the piston are linear sliding seals without rotational friction, so the sealing parts are not easily worn and the oil cylinder is not easily leaked. Therefore, the service life of the sealing parts at these two places is relatively long.

[0040] (2) By drivingly connecting the transmission shaft and the power output end of the rotary drive mechanism through a telescopic structure such as a keyway, during the injection process, the oil cylinder piston can drive the screw to reciprocate back and forth synchronously, but will not drive the pre-plasticizing seat and the rotary drive mechanism to reciprocate back and forth with the screw. This structure enables the injection mechanism to work, and the screw no longer bears the weight of the pre-plasticizing seat and the rotary drive mechanism during the reciprocating motion back and forth. Therefore, the load and inertia of the screw during the reciprocating motion back and forth are greatly reduced, the inertia of the injection mechanism is low, and thus precise control of injection molding can be truly realized, solving the problems of slow injection speed and difficult control due to large inertia after injection. Description of the Drawings

[0041] Figure 1 Schematic perspective view of Embodiment 1 of the injection mechanism of the injection molding machine of the present invention;

[0042] Figure 2 is Figure 1 Cross-sectional view of the injection mechanism in

[0043] Figure 3 is Figure 1 Cross-sectional view of the injection mechanism after the pre-plasticizing is completed in

[0044] Figure 4 Schematic perspective view of Embodiment 2 of the injection mechanism of the injection molding machine of the present invention;

[0045] Figure 5 is Figure 4 Cross-sectional view of the injection mechanism in

[0046] Figure 6 is Figure 4 Cross-sectional view of the injection mechanism after the pre-plasticizing is completed in Detailed implementation manners

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0048] Embodiment 1:

[0049] As Figures 1 to 3 shown, it is the first preferred embodiment of the injection mechanism of the injection molding machine of the present invention. The injection mechanism includes an injection seat 1, a barrel 2, an oil cylinder 3, a pre-plasticizing seat 4, a rotary drive mechanism 5, a transmission shaft 6, and a sealing sleeve 7.

[0050] Among them, the barrel 2 is arranged on the front side of the injection seat 1. The barrel 2 has a receiving cavity 21 and a feed port 22 communicating with the receiving cavity 21. A screw 23 is arranged inside the receiving cavity 21.

[0051] The oil cylinder 3 is arranged on the rear side of the injection seat 1. The oil cylinder 3 includes a cylinder body 31 and a piston 32 with a piston rod arranged inside the cylinder body 31. The piston rod of the piston 32 exposes from the front end face of the cylinder body 31 and can perform reciprocating back-and-forth movement inside the cylinder body 31. In addition, an installation hole 311 is axially opened on the rear end face of the cylinder body 31, and a through hole 321 is axially opened on the piston 32.

[0052] The pre-plasticizing seat 4 is installed behind the oil cylinder 3 and is spaced apart from the rear end face of the cylinder body 31 by a certain distance.

[0053] The rotary drive mechanism 5 is mounted on the plasticizing base 4. In this embodiment, the rotary drive mechanism 5 includes a motor 51, a transmission assembly 52, and a power output wheel 53. Specifically, the motor 51 is arranged non-coaxially with the screw 23, and is mounted on the front side of the plasticizing base 4 and above the oil cylinder 3. The power output wheel 53 is mounted on the plasticizing base 4 and is arranged coaxially with the screw 23. The transmission assembly 52 includes a driving pulley 521 and a transmission belt 522. The output shaft of the motor 51 passes backward through the plasticizing base 4 and is connected to the driving pulley 521. The transmission belt 522 is sleeved on the driving pulley 521 and the power output wheel 53 so that the driving pulley 521 and the power output wheel 53 are drivingly connected.

[0054] The front end of the sealing sleeve 7 is mounted on the rear part of the piston 32. The rear end of the sealing sleeve 7 is sealingly inserted into the mounting hole 311 of the cylinder body 31 and can slide back and forth in the mounting hole 311. During the entire working process, when the piston 32 moves back and forth, the sealing sleeve 7 moves back and forth synchronously with it. In this embodiment, the sealing sleeve 7 and the piston 32 are provided as an integral part.

[0055] The transmission shaft 6 passes through the through hole 321 of the piston 32 and the inside of the sealing sleeve 7. The transmission shaft 6 is connected to the piston 32 and can rotate relative to the piston 32 about its own axis, so that the piston 32 can drive the transmission shaft 6 to move back and forth but does not rotate with the transmission shaft 6. There is a gap between the transmission shaft 6 and the sealing sleeve 7 to avoid the frictional force between the two from hindering the movement of the transmission shaft 6. In this embodiment, an installation groove 322 is provided at the front end of the piston 32, and a bearing 323 is provided in the installation groove 322. The transmission shaft 6 is installed on the inner ring of the bearing 323. In this embodiment, the rear ends of the transmission shaft 6 and the sealing sleeve 7 are also connected by a similar structure so that the transmission shaft 6 can rotate relative to the sealing sleeve 7 about its own axis.

[0056] The front end of the transmission shaft 6 is connected to the screw 23 and can rotate synchronously with the screw 23. The rear end of the transmission shaft 6 passes through the central hole of the power output wheel 53 and is drivingly connected to the power output wheel 53 through a telescopic transmission mechanism, so that the rotary drive mechanism 5 can drive the transmission shaft 6 to rotate but does not move back and forth with the transmission shaft 6. In this embodiment, a convex key 61 is provided on the outer peripheral wall of the transmission shaft 6 along the axial direction. Correspondingly, a groove 531 is provided on the inner peripheral wall of the power output wheel 53 along the axial direction. The convex key 61 is slidably inserted into the groove 531, and the convex key 61 and the groove 531 form the above-mentioned telescopic transmission mechanism.

[0057] In this embodiment, a seal is formed between the sealing sleeve 7 and the mounting hole 311 to prevent oil leakage caused by the rotation and forward and backward movement of the transmission shaft 6.

[0058] The working principle of Embodiment 1 of the present invention is as follows:

[0059] (1) During plasticizing, the output shaft of the motor 51 drives the driving pulley 521 to rotate. The driving pulley 521 drives the power output wheel 53 to rotate through the transmission belt 522. The power output wheel 53 then drives the screw 23 in the barrel 2 to rotate through the transmission shaft 6. The rotating screw 23 pushes the plasticized melt to the front end of the barrel 2. During this process, since the transmission shaft 6 is rotatably connected to the piston 31, the piston 31 will not rotate with the screw 23 and the transmission shaft 6;

[0060] At the same time, the screw 23 and the transmission shaft 6 retreat under the reaction of the material, and then push the piston 32 and the sealing sleeve 7 to move backward to complete metering. During this process, since the central holes of the screw 23 and the power output wheel 53 are telescopically connected through the transmission shaft 6, the preplasticizing seat 4 and the rotary drive mechanism 5 will not move back and forth with the screw 23;

[0061] (2) During injection, the oil cylinder 3 is filled with oil to drive the piston 32 and the sealing sleeve 7 to move forward, and then drive the transmission shaft 6 to move forward, and finally drive the screw 23 to move forward to complete the injection action. Similarly, during this process, since the central holes of the screw 23 and the power output wheel 53 are telescopically connected through the transmission shaft 6, the preplasticizing seat 4 and the rotary drive mechanism 5 will not move back and forth with the screw 23.

[0062] Embodiment 2:

[0063] As Figures 4 to 6 shown, it is the second preferred embodiment of the injection mechanism of the injection molding machine of the present invention. The difference between this embodiment and Embodiment 1 is that:

[0064] The rear end of the sealing sleeve 7 is hermetically installed in the mounting hole 311, and the front end of the sealing sleeve 7 is slidably inserted into the through hole 321, that is, the piston 32 is sleeved on the outer periphery of the sealing sleeve 7 so as to be able to slide back and forth. During the whole working process, the sealing sleeve 7 will not move back and forth with the piston 32 and the sealing sleeve 7 is always in a static state. Therefore, in this embodiment, the preplasticizing seat 4 is arranged close to the rear end face of the cylinder body 31, and there is no need to space them apart, thereby reducing the overall occupied space of the injection mechanism.

[0065] In this embodiment, seals are respectively formed between the sealing sleeve 7 and the mounting hole 311 and the through hole 321 to prevent oil leakage caused by the rotation and forward and backward movement of the transmission shaft 6.

[0066] The working principle of Embodiment 2 of the present invention is as follows:

[0067] (1) During plasticizing, the output shaft of the motor 51 drives the driving pulley 521 to rotate. The driving pulley 521 drives the power output wheel 53 to rotate through the transmission belt 522. The power output wheel 53 then drives the screw 23 in the barrel 2 to rotate through the transmission shaft 6. The rotating screw 23 pushes the plasticized melt to the front end of the barrel 2. During this process, since the transmission shaft 6 is rotatably connected to the piston 31, the piston 31 will not rotate with the screw 23 and the transmission shaft 6;

[0068] Meanwhile, the screw 23 and the transmission shaft 6 retreat under the reaction of the material, thereby pushing the piston 32 to move backward to complete metering. During this process, since the central hole of the screw 23 and the power output wheel 53 is telescopically connected through the transmission shaft 6, the preplasticizing seat 4 and the rotary drive mechanism 5 will not move back and forth with the screw 23;

[0069] (2) During injection, the oil cylinder 3 is filled with oil to drive the piston 32 to move forward, thereby pushing the transmission shaft 6 to move forward, and finally driving the screw 23 to move forward to complete the injection action. Similarly, during this process, since the central hole of the screw 23 and the power output wheel 53 is telescopically connected through the transmission shaft 6, the preplasticizing seat 4 and the rotary drive mechanism 5 will not move back and forth with the screw 23.

Claims

1. An injection mechanism of an injection molding machine, comprising Ejector seat (1); The oil cylinder (3) is arranged on the ejection seat (1), and comprises a cylinder body (31) and a piston (32) with a piston rod arranged inside the cylinder body (31). The piston rod of the piston (32) is exposed at the front end surface of the cylinder body (31) and can move back and forth in a telescopic manner. The barrel (2) is arranged on the ejection seat (1) and located in front of the oil cylinder (3), and a screw (23) is arranged in the internal cavity; and A rotary drive mechanism (5) is installed at the rear side of the oil cylinder (3) and is used to drive the screw rod (23) to rotate; It is characterized in that: It also includes a transmission shaft (6) and a sealing sleeve (7); A mounting hole (311) is axially provided on the rear end surface of the cylinder body (31), the front end of the sealing sleeve (7) is mounted on the rear part of the piston (32), the rear end of the sealing sleeve (7) is inserted into the mounting hole (311) and can slide forward and backward in the mounting hole (311), and a seal is formed between the sealing sleeve (7) and the mounting hole (311); The piston (32) is provided with a through hole (321) in the axial direction. The transmission shaft (6) is passed through the through hole (321) of the piston (32) and the interior of the sealing sleeve (7), is connected to the piston (32) and can rotate relative to the piston (32) around its own axis, so that the piston (32) can drive the transmission shaft (6) to make a forward and backward reciprocating motion but does not rotate with the transmission shaft (6). The front end of the transmission shaft (6) is connected to the screw rod (23) and can rotate synchronously with the screw rod (23). The rear end of the transmission shaft (6) is connected to the power output end of the rotary drive mechanism (5) through a retractable transmission mechanism, so that the rotary drive mechanism (5) can drive the transmission shaft (6) to rotate but does not make a forward and backward reciprocating motion with the transmission shaft (6). The sealing sleeve (7) and the piston (32) are arranged as an integral part; The front end of the piston (32) is provided with a mounting groove (322), a bearing (323) is provided in the mounting groove (322), the transmission shaft (6) is mounted on the inner ring of the bearing (323), and the rear ends of the transmission shaft (6) and the sealing sleeve (7) are also connected via the bearing; There is a gap between the transmission shaft (6) and the sealing sleeve (7).

2. The injection mechanism according to claim 1, wherein: The rotary drive mechanism comprises a power output wheel (53) for driving the transmission shaft (6) to perform rotary motion.

3. The injection mechanism according to claim 2, characterized in that: The rotary drive mechanism (5) further comprises a motor (51) and a transmission assembly (52); the output shaft of the motor (51) is transmission-connected to a power output wheel (53) via the transmission assembly (52); the motor (51) and the transmission shaft (6) are not coaxially arranged; the motor (51) is mounted above the oil cylinder (3) via a pre-plasticizing seat (4); the power output wheel (53) is mounted on the pre-plasticizing seat (4) and is coaxially arranged with the transmission shaft (6); the rear end of the transmission shaft (6) is passed through the power output wheel (53) and is transmission-connected to the power output wheel (53).

4. The injection mechanism according to claim 3, characterized in that: The transmission assembly (52) comprises A driving pulley (521) mounted on the output shaft of the motor (51); and The transmission belt (522) is sleeved on the driving pulley (521) and the power output pulley (53) so that the driving pulley (521) and the power output pulley (53) are in transmission connection.

5. The injection mechanism according to claim 2, characterized in that: One of the outer peripheral wall of the transmission shaft (6) and the inner peripheral wall of the power output pulley (53) is axially provided with a convex key (61). Correspondingly, the other of the outer peripheral wall of the transmission shaft (6) and the inner peripheral wall of the power output pulley (53) is axially provided with a groove (531). The convex key (61) is slidably inserted into the groove (531), and the convex key (61) and the groove (531) form the telescopic transmission mechanism.

6. The injection mechanism according to claim 2, characterized in that: The cross section of the transmission shaft (6) is triangular or polygonal, and the power output pulley (53) has a groove that slidably mates with the sides or corners of the transmission shaft (6). The outer peripheral wall of the transmission shaft (6) and the inner peripheral wall of the power output pulley (53) form the telescopic transmission mechanism.

7. The injection mechanism according to claim 2, wherein: The transmission shaft (6) is composed of multiple inserted rods, and the power output pulley (53) is correspondingly provided with multiple insertion holes. Each of the inserted rods is inserted into each of the insertion holes and can slide back and forth in the insertion holes. The inserted rods and the insertion holes form the telescopic transmission mechanism.

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