DE2038696C3 - Injection molding unit for processing thermoplastics - Google Patents

Description

The precisely adjustable pressure medium limiting valve 9 enables the plasticizing pressure to be precisely adhered to.

The sealing of the pneumatic pressure medium does not cause any difficulties, since the pressure vessel 8 does not require any moving seals and the pneumatic one present within the cylinder 5 Pressure medium delimited to the outside by the pressure chamber 6 filled with hydraulic pressure medium is. This is compared to purely pneumatic Injection units of the costly Verd.chter saved.

1 sheet of drawings

Claims (1)

Hand of the schematic drawings explain in more detail Claim: tert. . . The injection molding unit shown in FIG Spritznieüeinheit for processing thermoplastic conventional way a plasticizing screw 1. which circulates in permanent "plastics by means of a plasticizing 5 a screw cylinder 2, driven by a screw with a screw drive 3 axially in a cylinder and arranged with a sieve bar, with one in one beitskolben 4 is connected, the injection cylinder axially displaceable in the pressure chamber 6 injection cylinder of a cylinder 5 connected by a hydraulic pressure element working piston which is acted upon by medium, the pressure chamber (> a hydraulic pressure medium, which with an io via a Druckmiltelbegrenzungsventil 9 mn a hydraulic pump is in communication via a pressure medium valve hydraulic pump 11. Line is not connected to the tongue valve, and a closable nozzle (shown in more detail) forms the pressure medium which is connected to the front closure of the screw cylinder 2 via a shut-off valve.
is connected to a pressure vessel, the pressure chamber 6 is on which the Plasufizierschlag is, the pressure medium is separated by a 15 screw 1 on its rear facing away side in the cylinder axially movable partition ee of the working piston 4 from a separating piston 7 cind. characterized, whose side facing away from the hydraulic pressure of the pressure chamber 6 filled with the plasticizing screw (1) is adjoined by a working piston (4) on its side facing away from the plasticizing limit of a second pressure chamber in the cylindrical screw (1) Pressure 20 of 5 forms, which is acted upon by a pneumatic pressure medium and that the partition wall is medium filled and is connected to a pressure vessel 8 as an axially displaceable separating piston (7) via a shut-off valve 10,
forms is. The operation of the injection molding unit is as follows In the position shown in c '; r drawing is the 35 Injection process ended, and the plasticizing screw 1 is in its foremost position, with its tip on the closable nozzle on The invention relates to an injection molding unit against the front end of the screw cylinder 2.
Processing of thermoplastics by means of the hydraulic pump 11 is the pressure of a plasticizing screw with a hydraulic pressure medium in a cylinder 6 under pressure to the axially displaceable anec dneten, with an in and displaced the separating piston 7, an injection cylinder axially displaceable injection through the open shut-off valve 10 pneumaticiL-mcni vciimiuicucfi Arbcitskolucn, which is returned by a cal Diuckmittcl in the pressure vessel 8-hydraulic pressure medium which is conveyed with a hydraulic. After a required pump has been reached via a pressure medium limiting valve, the final compression pressure in the pressure vessel 8 is bound, and the liquid supply is switched off by a pneumatic pressure device and the blocking medium, which is closed via a blocking valve with a pressure valve 10. container is connected, is acted upon, after which the filling of the space in front of the pressure medium is separated by a plasticizing screw 1 which can be moved axially in the cylinder and has a plasticizable plastic partition. 40 substance introduced. An injection molding unit of this type is known from the USA.- a screw drive 3, the plasticizing screw 1, patent specification 2,380,882. set in rotation, with the plasticizing-Here is both the injection and the screw 1 and the working piston 4 under the backward thrust of the working piston, a control of the hydraulic pressure of the plastic melt and shift from the hydraulic and pneumatic systems. 45 the pressure chamber 6 hydraulic pressure medium ver-The invention is based on the object is when urges. The regulation of the pressure in the injection molding unit the plasticizing pressure takes place by keeping constant constant and, on the other hand, the injection flow rate in the pressure chamber 6 by means of high, this with the pressure medium limiting valve 9 if possible.
should be achieved with little effort. 50 After the space in front of the plasti-solver has been filled, this task is solved in the case of an injection molding screw 1 with plastic, the screw machine of the type mentioned at the beginning of the invention is switched off and the pressure chamber 6 is accordingly closed by closing the one with the plasticising screw. connected working piston on its plasticizing For the injection process is opened by opening the Helical side facing away from the pressure means 55 check valve 10 of the separating piston 7 on the one hand is acted upon and that the partition wall as an axial side with the pneumatic pressure medium under the displaceable separating piston is formed. Pressure of the pressure vessel 8 applied from where Due to the injection molding unit according to the invention, the force on the working piston 4 and the plasticizer the plasticizing pressure is transmitted through the hydraulic screw 1 and after opening the see pressure medium applied while pneumatically 60 nozzle at the front end of the screw cylinder 2 of the the high injection speed is achieved. The injection process takes place. Trennkolbcn creates the possibility because the pneumatic pressure medium in the connection pressure medium to separate, with this partition line between the pressure vessel 8 and cylinder not only one widening bubble (USA.Pad 5 does not find any resistance worth mentioning and tentschrift 2 380 882) with regard to the service life 65, the fluid friction in the pressure chamber 6 is only slight is superior, but also a minimum of additional, a very short-term injection process is more possible Friction work occurs. borrowed and connecting lines of large cross-section An embodiment of the invention is not required.