GB2238010A

GB2238010A - Bicylinder actuator for a plastics injection molding machine

Info

Publication number: GB2238010A
Application number: GB8924042A
Authority: GB
Inventors: Jui-Hsiang Yang Wang
Original assignee: HWA Chin Machinery Factory Co Ltd
Current assignee: HWA Chin Machinery Factory Co Ltd
Priority date: 1989-10-25
Filing date: 1989-10-25
Publication date: 1991-05-22
Anticipated expiration: 2009-10-25
Also published as: GB8924042D0; GB2238010B

Abstract

In a bicylinder actuator of a plastics injection moulding machine, each cylinder comprises a primary cylinder 1 coaxially attached to an auxiliary cylinder 2. A rod 16 connects the auxiliary cylinder piston 22 with the primary cylinder piston 12, the two primary cylinder piston rods 11 at the rotary shaft 72 of the screw conveyor 7 being connected to a cross feed (not shown) of the moulding machine. For very high pressure injection moulding fluid is admitted simultaneously to each cylinder 1, 2 and for high speed injection fluid is admitted only to the cylinder 2. <IMAGE>

Description

BICYLINDER ACTUATOR FOR A PLASTICS INJECTION MOLDING MACHINE BACKGROUND OF THE INVENTION This invention relates to an injection actuator for a plastics injection molding machine, and more particularly to an injection actuator having an auxiliary actuator for optional operations.

It is known that, usually, two parallel injection actuators 1 of single cylinder, as shown in FIG. 1, are used in a plastics injection mrjlding machine?. A pair of hydraulic actuators 1 are correspondingly mounted on two side of a screw conveyer 7. Said screw conveyer 7 is a well-known device in the field of plastics injection moulding technique and has a frame 71 with a rotary shaft 72 extending. outwardly rearwardly and a barrel 73 extending outwardly frontward ly therefrom.

Each of the hydraulic actuator 1 includes a cylinder 10 which h is closed at t;wo end. 14, 15 thereof and in which is mounted linearly a movable piston rod 11 in a fluid tight relationship with the closed end 14. At an end inside the cylinder 10 of the piston rod 11 is situated a linear piston 12 which is associated with appropriate piston packing. 121. The piston rod 11 protrudes from the closed end 14 and extends parallel to tile rotary shaft 72 of the screw conveyer 7.The two piston rods 11 and the rotary shaft. 72 terminate at a bearinrg tAct..

4, r. shown in FIG. 2, and secured thereto.

Referring to FIG. 2, the two hydraulic actuators l as.t3ociated with the screw conveyer 7, the bearing set 4 and an electricity-powered hydraulic motor 3 are mounted on a slidable plateform 51. In operation, the hydraulic motor 3 is turned ON to drive the rotary shaft 72 together with a screw (not shown) of the screw conveyer 7 to rotate so as to feed material, then the plateform 51 is slided frontwardly into a preset position by means of a hydraulic actuator 5 so that all of the hydraulic actuators 1, screw conveyer 7, bearing set 4 and the hydraulic motor 3, etc. are shifted into their injection positions.The hydraulic fluid or oil is admitted into the cylinders 10 that forces the pistons 12 and the piston rods 11 of the two actuators 1 to move frontwardly.

Said frontward movement of the two synchronous hydraulie actuators will drive the screw conveyer 7 to inject through the bearing set 4 so that the injection activity of its plastics injection moulding machine is accomplisbed. The plateform 51 is then slided backward into its original position for a second working cycle.

In practice, different products made through a plastics injection molding process may need different injection pressures. As the hydraulic actuators of a conventional molding machine are fixed in their dimensions. Said various injection pressures cali be achi eved only by adjusting output power of the hydraulic pump.It means a hydraulic pump of wide range in output power rendering high cost in manufacture is necessary to a conventional moulding machine. To this end, the inventor has attempted to make an improved hydraulic actuator used in a plastics injection moulding machine to overcome the drawbacks of a known one.

OBJECTS OF THE INVENTION An object of this invention is to provide a pair of hydraulic actuators used in a plastics injection iriolding machine which can diminish the disadvantages of e known one.

It is another object of this invention to provide a hydraulic actuator preferably used in pair in a plastics injection moulding machine with a construction allowing for optional operations both in ranges of irjjection pressure and speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional view of a pair of known hydraulic actuators secured to a knowti screw conveyer; FIG. 2 is a front elevational view of a plastic injection molding machine having a hydraulic actuator according to the present invention; FIG. 3 is @ partial cross-sectional view of a pair of hydraulie actuators according to the present invention secured to a know sorew conveyer; Fig. 4 is a cross-sectional and diagramatic view of a hydraulic actuator of the present invention in super high pressure injection operation; FIG. 5 is a cross-sectional and diagramatic view of a hydraulic actuator of the present invention in high speed injection operation; and FIG. 6 is a cross-sectional and diagramatic view of a hydraulic actuator of the present invention in super low speed injection operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 3, a pair of parallel bicylinder injection actuators for a plastics injection mo ] ding machine are correspondingly and laterally secured to two side of a frame 71 of a conventional screw conveyer 7 which is all the same as the srew conveyer shown in FIG. 1. Each of the hydraulic actuator is a bicylinder hydraulic actuator combining a primary actuator 1 and an auxiliary actuator 2 axially attached to the primary actuator 1.

The primal actuator 1 has a primary cylinder 10 which is closed at two ends thereof by means of a leading end packing gland 15 and a lagging end packing gland 14. -A movable piston rod 11 is linearly mounted in fluid-tight relationship with the lagging end packing gland 14 in the primary cylinder 10.At an end inside the primary cylinder 10 of the piston rod 11 is situated a linear piston 12 which is associated with appropriate piston packing 121. The piston rod 11 protrudes from the closed end 14 and extends parallel to the rotary shaft 72 of the screw conveyer 7. The two piston rods 11 and rotary shaft 72 terminate at a bearing set 4, as shown in FIG. 2, and secured thereto.

At the closed ends, the leading end packing gland 15 and the lagging end packing gland 14, of the primary cylinder 10 are respectively provided with two ports 141, 152 leading to a lagging end chamber 101 and a leading end chamber102 divided by the piston 12 in the inner chamber thereof.

The auxiliary actuator 2 also has an auxiliary cylinder 20 which is axially attached to the primary cylinder 10 by means of the leading end packing gland 15. The auxiliary cylinder 20 is preferably smaller in dirlensiorl than the primary cylinder 10, and preferably the auxiliary cylinder 21 is smaller in cross-sectional dimentsion yet the same or even longer in length in comparison with the primary cylinder 10. The auxiliary cylinder 21 has an auxiliary piston 22 therein which is associated with an appropriate piston packing 221.

The auxiliary piston 22 and the primary piston 12 are interconnected by an axial connecting rod 16 which passes slideably through and is kept in a fluid-tight relationship with the leading end packing gland 15 and terminated with nuts 251 to secure the auxiliary piston 22 thereto.The leading end packing gland 15 is further proid ed with a port 151 leading to the inner chamber of of the auxiliary cylinder 20 of which the leading end is fitted with a circular cap 25 having an axial hole 250 therein which allows the nuts 251 to pass in reciprocation therethrough.

The provision of the auxiliary hydraulic actuator 2 allows optional operations both in the ranges of injection pressure and injection speed of a plastics ejection moulding machine hereof. In super high pressure ejection operation, as shown in FIG. 4, the hydraulic fluid or oil is pumped by the hydraulic pump and is admitted into the chambers 101, 201 through the ports 141, 152, and the hydraulic fluid or oil in the leading chamber 102 is returned through the port 152.Due to the entering hydraulic fluid or oil in the chambers 101, 201, the two pistons 12, 22 are synchronously moved frontward ly to inject molten plastic material into a mould therewith. Viceversa, the hydraulic fluid or oil is admitted into the leading chamljer 102 of the primary cylinder 10 through the port 152 to return the two pistons 12, 22 and the hydraulic fluid or oil in the chambers 101, 201 are returned through the ports 141, 152.A super high pressure injection is rendered by the movements of the auxiliary piston 22 as well as the primary piston 12.

In high speed injection operation, as shown in FIG.

5, the primary actuator 1 is idle and the hydraulic fluid or oil l is admitted only into the chamber 201 !If the auxiliary cylinder 20. Due to the all size of the auxiliary cylinder 20, the injection speed actuated by the piston 22 is fast. The pistons 12, 22 can be returned by admitting the hydraulic fluid or oil into the leading end chamber 102 of the primary cylinder 10.

Similarly, a low speed ejection can be performed by admitting the hydraulic fluid or oil only into the lagging end chamber 101 of the primary cylinder 10 through the port 141.

In super low speed injection operation, as shown in FIG. 6, the hydraulic fluid or oil is admitted simultaneously into the chambers 101, 201. Due to an enlarged capacity of the bicylinder aftuator hereof to the hydraulic fluid or oil, a super low speed injection is performed.

Wil the invention has been described with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent, structure.

Claims

WHAT IS CLAIMED IS:

1. A bicylinder actuator for a plastics injection molding machine comprising: a first cylinder having two closed ends including a leading closed end and a lagging closed end for receiving a hydraulic fluid, a first piston slidably mounted within the first cylinder and bounding a leading chamber and a lagging chamber in the first cylinder, first port means for admitting and returning the hydraulic fluid respectively communicated with the leading chamber and the lagging chamber and an axial piston rod slid ably mounted through the lagging closed end in a fluid-tight relationship with an end outside the first cylinder thereof connected to a bearing set of a plastics injection molding machine and its other end inside the first cylinder attached to the first piston; and a second cylinder coaxially attached to the leading closed end of the first cylinder, a second piston slidably mounted within the second cylinder and having its peripery sealingly engaged with an inner surface of the second cylinder to form a variable chamber in the second cylinder for receiving a hydraulic fluid, a second port means for admitting or returning the hydraulic fluid communicated with the chamber in the second cylinder and an axial connecting rod slidahly mounted through the leading closed end in a fluid-tight relationship and interconnecting the first piston of the first cylinder and the second piston of the second cylinder.

2. A bicylinder actuator for a plastics injection moulding machine as claimed in Claim l, wherein one end opposed to the end attached to the first cylinder of the second cylinder is fitted with a circular cap member having an axial hole.