CLOSING UNIT FOR AN INJECTION MOULDING MACHINE

Abstract

A closing unit of an injection molding machine includes a moveable mold mounting plate and a fixed mold mounting plate, a hydraulic pressure mechanism for building up a closing pressure, at least one column provided with an external profile, and at least one two-part nut which is provided with an internal profile and the halves of which are coupled in motionally opposite relationship. The at least one column in the closed condition of the two-part nut is lockable by a positively locking relationship between the internal profile and the external profile relative to the moveable mold mounting plate or relative to the pressure mechanism. There is also provided an electric drive for opening and closing the two-part nut.

Description

The invention concerns a closing unit of an injection molding machine having the features of the classifying portion of claim 1.

An injection molding process generally begins with closure of the closing unit, by the moveable mold mounting plate being moved towards the fixed mold mounting plate by a fast-action stroke device. The moveable mold mounting plate is then locked with the pressure-applying piston member of a pressure mechanism and the pressure mechanism builds up the closing pressure necessary for the injection process.

Frequently one or more columns are used for guiding the moveable mold mounting plate. In the case of an injection molding machine having one column the pressure mechanism is often a hydraulic cylinder whose piston exerts a pressure on the moveable mold mounting plate by way of the column. The case of an injection molding machine having four columns, then also referred as bars, is also a familiar structure. Here the pressure mechanism is often in the form of a pressure cushion between the mold mounting plates or at the ends of the bars. Those pressure cushions are also often hydraulic as high pressures have to be built up in a relatively short time.

The subject-matter of the invention is closing units of injection molding machines, in which after the working operation of the fast-action stroke, the columns are locked and the pressure mechanism is supported by way of the columns. In the foregoing examples on the one hand the columns are locked to the piston member of the pressure mechanism and on the other hand the bars are locked to the moveable mold mounting plate.

Locking actions of that kind are often implemented by two-part nuts which embrace the columns of the closing unit. That applies both in regard to closing units having one column and also closing units having four columns. To be able to easily open and close the two-part nut it is advantageous for the halves of the nuts to be mechanically coupled in motionally opposite relationship to each other. Since, as in the above-described examples, the devices necessary for the hydraulic arrangement are often already present there, it is standard procedure in the state of the art to actuate both the fast-action stroke and also the two-part nuts hydraulically.

A disadvantage with hydraulic opening and closing of the nuts are a relatively long reaction time on the part of the hydraulic system and a lack of precise positional detection of the two-part nuts. On the one hand, that means that time is lost in each injection molding process. On the other hand, that can lead to disturbances in operation or even to damage to the closing unit if the nut is not properly closed and consequently locking of the column is incomplete.

The aim of the invention is to provide a closing unit having a locking mechanism which does not suffer from the above-described disadvantages.

That object is attained by a closing unit having the features of claim 1, that is to say in that there is provided an electric drive for opening and closing the halves of the nut.

Actuation and at the same time the above-mentioned coupling of the halves of the nut, which occurs in motionally opposite relationship, can be achieved in a mechanically particularly simple fashion by two eccentrics which are connected to the electric drive and to a respective half of the two-part nut.

In a further example there can be provided only one eccentric connected to the electric drive and a half of the two-part nut. In that case the coupling of the halves of the nut, which is in motionally opposite relationship, can be implemented by a rotatably mounted rocker connected at its ends to a respective half of the two-part nut. To avoid tilting of that rocker mechanism there can particularly preferably also be provided two such rockers.

To provide a compact structure, in a further embodiment of such a closing unit having a plurality of bars it can be provided that two two-part nuts are opened and closed by an electric drive. In that respect it can be provided that a linkage couples the opening and closing movements of the nuts.

Further advantages and details of the invention will be apparent from the Figures and the accompanying specific description. In the drawing:

FIG. 1 shows a cross-sectional view of a part of a closing unit according to the invention with one column,

FIG. 2 shows a diagrammatic side view of closing unit according to the invention with four columns,

FIG. 3 a shows an opened two-part nut with electric drive, the halves of the nut being connected to the drive by way of two eccentrics,

FIG. 3 b shows the two-part nut from FIG. 3a in the closed condition,

FIG. 4 a shows an open two-part nut with electric drive, wherein only one half is connected to the drive by way of an eccentric and coupling of the halves in motionally opposite relationship is achieved by two rocker mechanisms, and

FIG. 4 b shows the two-part nut of FIG. 4a in the closed condition.

FIG. 1 shows a sectional view through the part of a closing unit 1 with one column 4, which has the pressure mechanism 14 and the moveable mold mounting plate 2. The internal profile 7 of the halves 12 of the two-part nut 6 (see also FIGS. 3 and 4) engages into the external profile 5 on the column 4. In that way the piston member 15 of the hydraulic pressure mechanism 14 can apply pressure to the moveable mold mounting plate 2. It will further be seen that the electric drive 8 in this embodiment is fixed to the piston member 15 of the pressure mechanism 14 and actuates one half 12 of the divided nut 6 by way of an eccentric 9. In this embodiment the fast-action device 16 is in the form of a spindle mechanism in the interior of the column 4.

FIG. 2 shows an embodiment of a closing unit 1 having four columns, in which opening and closing of the halves 12 of two nuts 6 is effected by an electric drive 8 fixed to the moveable mold mounting plate 2. Here the linkage 13 couples the opening and closing movements of the two-part nuts 6. In addition it is possible to see here the bars 4 with external profile 5, which pass through the moveable mold mounting plate 2. The fast-action stroke device 16 as well as the pressure mechanism 15 with the piston member 14 are also diagrammatically indicated. The implementation of such a pressure cushion is known to the man skilled in the art.

FIGS. 1 and 2 respectively admittedly show horizontally closing closing units. The invention however can also be used in vertical machines.

The two-part nut 6 shown in FIG. 3a comprises two halves 12 which are each provided with an internal profile 7. It is also possible to see two eccentrics 9 by which the electric drive 8 actuates the two halves 12 of the two-part nut 6.

FIG. 3 b shows the same two-part nut 6 but in the closed condition.

FIG. 4 a shows a further embodiment with only one eccentric 9. Coupling of the two halves 12 of the two-part nut 6, which is in motionally opposite relationship, is effected here by way of the two rotatably mounted rockers 10, the ends 11 of which are fixed to a respective one of the halves 12 of the divided nut 6.

FIG. 4 b shows the divided nut from FIG. 4a in the closed condition.

Claims

1. A closing unit (1) of an injection molding machine comprising a. a moveable mold mounting plate (2) and a fixed mold mounting plate (3),b. a hydraulic pressure mechanism (14) for building up a closing pressure,c. at least one column (4) provided with an external profile (5), andd. at least one two-part nut (6) which is provided with an internal profile (7) and the halves (12) of which are coupled in motionally opposite relationship, wherein the at least one column (4) in the closed condition of the two-part nut (6) is lockable by positively locking relationship between the internal profile (7) and the external profile (5) relative to the moveable mold mounting plate (2) or relative to the pressure mechanism (14), and wherein there is provided an electric drive (8) for opening and closing the two-part nut (6).

2. A closing unit as set forth in claim 1, wherein there are provided two eccentrics (9) connected to the electric drive (8) and a respective half (12) of the two-part nut (6).

3. A closing unit as set forth in claim 1, wherein there is provided precisely one eccentric (9) connected to the electric drive (8) and a half (12) of the two-part nut (6).

4. A closing unit as set forth in claim 3, wherein there is provided at least one rotatably mounted rocker (10) having two ends (11), the ends (11) of which are connected to a respective half (12) of the two-part nut (6).

5. A closing unit as set forth in claim 4, wherein there are provided two rockers (10).

6. A closing unit as set forth in claim 1 comprising a further two-part nut (6) which is provided with an internal profile (7) and the halves (12) of which are coupled in motionally opposite relationship, wherein a further column (4) in the closed condition of the further two-part nut (6) is lockable by positively locking relationship between the internal profile (7) and the external profile (5), wherein there is provided a linkage (13) which couples opening and closing movements of the nuts (6).