KR20010106496A - Hybrid injection molding machine - Google Patents

Abstract

An electro-mechanical drive apparatus uses a single variable speed motor (20 ), two one-way clutches (42, 66), and a hydraulic accumulator (48) to provide both hydraulic power for the linear motion axes and rotation of the plasticizing screw (14) in an injection molding machine. When engaged, the first one-way clutch (42) couples the dri ve motor (20) to the pump stack (26), while the second one-way clutch (66) couples the motor (20) to the feed screw (14). During rotation of the drive motor (20) in a forward direction, (a) the first one-way clutch (42) engages, rotating the shaft of the hydraulic pump stack (26) to power the machines hydraulic systems and charge the accumulator (48); and (b) the second one-way clutch slips. When the driv e motor (20) is rotated in a reverse direction, (a) the second one-way clutch (66) engages, rotating the feed screw (14), and (b) the first one-way clutch (42) slips. Preferably, the drive apparatus is associated with a double shaft motor (20) mounted adjacent separate drive couplings for the feed screw (14) and hydraulic pump stack (26).

Description

Hybrid injection molding machine {HYBRID INJECTION MOLDING MACHINE}

The injection unit of a typical injection molding machine essentially provides two functions during its normal operation; It is an injection and an extruder. The injection function occurs when the feed screw moves straight forward (no rotation) to press the plastic melt into the mold. The extrusion function occurs when the feed screw is rotated to plasticize additional materials for the next shot. When the feed screw is rotated during the extrusion function, the plastic melt is pushed past the end of the screw and creates a pressure or action force which causes the screw to move backwards to its previous injection position when the melt accumulates. .

Both injection and extrusion functions require an associated drive within the injection unit. In the hydraulics of the prior art, the operation for the injection function is typically done by a hydraulic cylinder, but the rotation of the feed screw for the extrusion drive is usually done by a hydraulic motor. More recently, electric motors combined with mechanical systems have been used as direct power sources in injection units. Some prior art has used electrical systems to use separate motors for each function; For example, one motor for rotating the feed screw and a combination of mechanisms such as a ball screw were used to use the second motors to convert the rotational motion into linear motion required for injection. Another prior art, " hybrid " device was to rotate the feed screw as the remaining function of the device being hydraulically driven using one electric motor, and one or more of the power provided by the electric motor. It was to drive the hydraulic pump.

The "hybrid" device has some of the advantages of both electric (better control of screw rotation) and hydraulic (reduce overall cost) devices, but there is room for improvement. In particular, the excessive capacity of the electric motor to rotate the screw is a potential improvement for the implementation of a more economical system. Such a motor is only used in that part of the cycle where the thermoplastic material is extruded (plasticized) to form a shot. Since the motor and its associated variable speed drives have a relatively high cost, it is desired to maximize the utilization of such a motor. Moreover, for injection molding apparatuses with variable speed motors currently in use, the motors are specified for axes (when used with an electro-mechanical system) or are excessively applied to standard hydraulic circuits to allow for variable speed motors and drive systems. No economic control is achieved.

The present invention relates to an injection molding apparatus, and more particularly, to an injection molding apparatus configured to rotate a feed screw using a single electric motor and to drive a hydraulic pump stack.

It is therefore an object of the present invention to provide a drive which is simple to manufacture and which allows a variable speed motor to be used to effectively power a combination of mechanical and hydraulic components.

In brief, the present invention comprises a variable speed motor, preferably a brushless DC and general power transmission components, comprising (a) rotation of the feed screw in the injection unit of the injection molding apparatus, or (b) the apparatus. The invention relates to a drive for providing operation of a hydraulic pump stack to provide power for a hydraulic system. The drive device includes a first one-way clutch between the motor and the supply screw and a second one-way clutch between the motor and the hydraulic pump stack.

During most of the operation of the device, the drive motor is rotated in all directions (clockwise) to rotate the input shaft of the pump stack and provide hydraulic forces for the various operating axes, for example actuation elements such as clamps and injections. . And, the hydraulic force from the pump stack is operated to accumulate a hydraulic accumulator to store the hydraulic force for the section when the motor fails to drive the pump. In particular, during the forward rotation of the drive motor, (a) the first one-way clutch is engaged to rotate the shaft of the pump stack; And (b) the second one-way clutch slips.

The motor is rotated in the reverse direction (counterclockwise) to achieve the extrusion function, ie, to rotate the feed screw through an appropriate power transmission mechanism. In particular, during reverse rotation, (a) the second one-way clutch is engaged to rotate the feed screw at a predetermined speed through the pulley and drive belt and to plasticize the materials; And (b) the first one-way clutch slides.

A preferred embodiment of the drive device comprises a double-axis motor, which is mounted to engage the appropriate drive coupling to the supply screw and the hydraulic pump stack. Overall, the present invention provides a compact drive system for a single motor and operates all axes of the device; This improves the operation reliability and can obtain a faster response than conventional systems that require a shift mechanism to transfer power to different axes.

Advantages of the preferred embodiment include the use of improved motor performance, improved energy efficiency, reduced overall equipment cost and more accurate feed screw rotation control.

Brief description of the drawing.

1 is a side view of an injection molding apparatus having a drive device according to the present invention.

2 is a right side view of the injection molding apparatus shown in FIG. 1;

3 is a plan view of the upper side of the injection molding apparatus shown in FIG.

4 is a partially enlarged enlarged cross-sectional side view taken along line 4-4 of FIG.

FIG. 5 is a partial cutaway enlarged side cross-sectional view of the drive device shown in FIG. 4, to more clearly show any portion.

Hereinafter, the present invention will be described in more detail with reference to the drawings. A typical injection molding apparatus 1 includes a clamping system 2 and an injection unit 10. As shown in Figs. 1 and 4, the injection unit 10 is moved by a horizontal support rod 4 fixed to the base 8 of the injection molding apparatus 1. The injection unit 10 is to move along the support rods 4 so as to be coupled to a mold (not shown) attached to a position adjustment, that is, stationary platen 6.

The critical part of the injection unit 10 is equipped with barrel 12, including feed screw 14 (FIG. 4), which plasticizes the thermoplastic material so that it enters barrel 12 through the housing 15 from the hopper 16. The operating function of the injection molding apparatus 1 including the injection unit 10 is to be initiated by the drive assembly 18. The drive assembly 18 of the injection unit 10 includes an electric drive motor 20, a pump drive coupling 22, an extruder drive coupling 24, a hydraulic pump stack 26, a support housing 28, and the like (see FIGS. 2 and 4).

As detailed below, the drive assembly 18 rotates the feed screw 14 to plasticize the material during the extrusion function and generate the hydraulic force necessary for other mechanical functions.

5, the drive assembly 18 includes a pump drive coupling 22 that connects the motor 20 to the hydraulic pump stack 26. Mounted on the shaft 38 of the motor 20 are the one-way clutch 42 and the two ball bearing assembly 44, which collectively serve to support and engage the connector sleeve 40 directly attaching to the shaft 34 of the pump stack 26. As will be explained in more detail below, the motor 20 can be rotated in each direction, but the one-way clutch 42 allows the pulley 40 to rotate in only one direction. In the present disclosure, each element described as "one-way clutch" is preferably a mechanical cam type clutch adapted to couple a rotating cylindrical element to its enclosure member for rotation in one direction; If the element is rotated in the opposite direction there is essentially no resistance from the clutch. Morse Industrial, Emerson Power Transmission Corp., is a well-known supplier of clutches of this type.

The motor mounting plate 51 is connected directly to the support housing 36 and is configured to move with the support housing 28 along the guide rod 30. As shown, the motor 20 rests directly on top of the mounting plate 51.

The drive assembly 18 also includes an extruder drive coupling 24 to connect the motor 20 to the feed screw 14. In a manner similar to that described above, for the pump drive coupling 22, the extruder drive coupling 24 comprises a pulley 64 mounted via a one-way clutch 66 and a bearing 68 on the motor shaft 38. The second pulley 72 of the extruder drive coupling 24 is connected to the feed screw 14 and driven by the pulley 64 via the drive belt 70.

The operation of the drive assembly 18 will now be described. To start the extrusion function, motor 20 is operated and rotated counterclockwise. This rotation of the motor shaft 38 causes the one-way clutch 66 to engage the pulley 72 by means of the drive belt 70 and consequently by the drive belt 70. Rotation of the pulley 72 imposes rotation on the feed screw 14. When the feed screw 14 is rotated, the material supplied from the hopper 16 is fed through the housing 15 and plasticized in the barrel 12. The rotation of the feed screw 14 directs the material to the nozzle (discharge) end of barrel 12, so that as the materials begin to accumulate, the pressure of the melt increases at the end of screw 14. When the pressure of the plastic melt reaches a certain level, it will push the feed screw 14 to the rear side, and thus the whole drive assembly 18 will try to move to the rear side of the injection unit 10. In particular, the rearward movement of the feed screw 14 forces the housing 36 to cause the housing 36 to be moved to the rear side, which entails movement of the motor 20, the pump stack 26 and the associated drive components.

The reverse speed of the feed screw 14 can be controlled by a hydraulic cylinder 46 connected to both sides of the housing 36 (see FIG. 1). Proper valve actuation of the fluid in the cylinder 46 is reversed (not rotated) of the feed screw 14. This can slow down and thus increase the back pressure of the plastic melt. Alternatively, the inlet cylinder 46 can be used to apply a force to the housing 36 to increase the speed at which the feed screw moves to the back side and to reduce the back pressure of the melt.

By rotating the motor 20 counterclockwise during extruder operation, the one-way clutch 42 causes the shaft 38 to slide so that no rotational force is transmitted to the pump shaft 34. The extrusion operation is completed when sufficient charge of the plastic melt is made in front of the feed screw 14, ie, when the cavity of the mold mounted on the stationary platen 6 is sufficiently filled.

As soon as the extrusion operation is completed, the motor 20 rotates counterclockwise and rotates clockwise, with the result that the one-way clutch 42 engages the shaft 38, the rotating connecting sleeve 40 and the axis 34 of the hydraulic pump stack 26. The hydraulic energy generated by the pump stack 26 is used to operate the machine and / or to charge the hydraulic accumulator 48 as determined by the sequence of the injection molding apparatus 1. For example, to carry out the injection operation, the hydraulic energy is directed to the hydraulic cylinder 46 through a suitable valve operation (not shown); The cylinder operates to provide parallel (linear) movement to the feed screw 14 by exerting a force on the housing 36.

The forward movement of the feed screw 14 causes the plastic melt to accumulate at the end of the barrel to flow out of the barrel and into the mold space. Upon injection, the brake actuating motor 50 is operated to transmit sufficient force to the drive belt 70 so that the feed screw 14 does not rotate clockwise as it moves forward in the direction of ejecting the plastic melt. The action of the plastic melt on the flight of s generates a torque to rotate the feed screw 14). Upon completion of the injection operation, the cylinders 46 maintain (press and hold) the pressure applied to the plastic melt to ensure that the injection part is molded.

At the start of the pressing and holding period, the motor 20 switches rotation to start another extrusion operation as described above. The accumulator 48 provides the hydraulic energy necessary to maintain the operation of the cylinders 46 while the motor 20 rotates the feed stream. Likewise, the accumulator 48 will provide hydraulic energy for opening the mold after pressing and holding is complete. As the extrusion operation continues, as the hydraulic energy required to operate the eject system and / or to close the clamp system in preparation for the injection operation is required by the components of the injection molding apparatus 1, Provided by the accumulator 48 and / or pump stack 26.

Overall, the present invention provides a simplified drive system that runs the axes of all machines as one motor; This improves reliability and allows for a faster response than conventional systems that require a separate mover to transfer power to the various axes. The preferred embodiment has the advantage of including improved motor capacity, improved energy efficiency, reduced cost for all machines, and more precise rotational control of the feed screw.

Although the present invention has been shown in some detail with respect to the preferred embodiments in the accompanying drawings, while such a preferred embodiment has been described in detail, it is by no means limited to the invention only. On the contrary, all modifications, improvements and equivalents are included within the scope of the appended claims. For example, although the drive coupling is conventionally described as a belt and a pulley, other mechanical couplings, ie suitable gear actuators, can be used to perform the same function.

Claims (3)

Hydraulically actuated clamping system (2), injection unit (10) with feed screw (14) capable of rotation and parallel movement in barrel (12), hydraulic pump (26), variable speed electric drive motor (20), etc. In the injection molding apparatus comprising a, It further includes power transmission means (42, 66) for selectively transmitting power from the drive motor (20) (a) to rotate the supply screw (14), (b) to operate the hydraulic pump (26). Operation of the drive motor 20 in one direction rotates the supply screw to plasticize the material in the barrel of the injection unit, and operation of the drive motor 20 in the opposite direction operates the hydraulic pump 26. Injection molding device, characterized in that the operation of the clamping system and the parallel movement of the feed screw in the barrel of the injection unit. The method of claim 1, wherein the power transmission means, (a) a first one-way clutch 42 disposed between the drive motor 20 and the hydraulic pump 26, and (b) including a second one-way clutch 66 disposed between the drive motor 20 and the supply screw 14, when the drive motor 20 is operated in the forward direction, (i) the first one-way clutch 42 is coupled to actuate the hydraulic pump 26 to generate hydraulic pressure to operate the clamping system 2, initiate the translation of the feed screw 14, and (ii) the second one-way clutch 66 slides; When the drive motor 20 is operated in the reverse direction, (iii) the second one-way clutch 66 is coupled to rotate the feed screw 14, (iv) an injection molding apparatus, characterized in that the first one-way clutch (42) slips. Hydraulically actuated clamping system (2), injection unit (10) with feed screw (14) rotated and translated in barrel (12), hydraulic pump (26), variable speed electric drive motor (20), etc. In the molding apparatus comprising a, It further comprises a power transmission means (42,66) for selectively transmitting power from the drive motor 20 to the supply screw 14 and the hydraulic pump 26, The power transmission means, (a) a first one-way clutch 42 disposed between the drive motor 20 and the hydraulic pump 26, (b) including a second one-way clutch 66 disposed between the drive motor 20 and the supply screw 14, when the drive motor 20 is operated in a forward (pump) direction, (i) the first one-way clutch is coupled to operate the hydraulic pump 26 to generate power to operate the clamping system 2, initiate the translation of the feed screw 14, and (ii) the second one-way clutch 66 slides; When the drive motor 20 is operated in the reverse direction (extrusion), (iii) the second one-way clutch 66 is coupled to rotate the feed screw 14, (iv) The molding apparatus, characterized in that the first one-way clutch 42 slips.