BACKGROUND OF THE INVENTION

Field of the Invention

The present invention lies in the field of devices and methods for injection molding, namely of plastic products.

Discussion of Related Art

From the prior art devices for injection molding of plastic products are known which comprise a first outer mold half and a thereto along tie bars of an injection molding machine in a first direction relative to the first outer mold half displaceable second outer mold half. Between the first and the second outer mold half a center part is arranged rotatable around a center axis extending in vertical direction. The center part comprises at least two but more often four side faces which are arranged in pairs parallel to each other and which each carry an inner mold half. The inner mold halves in a closed position of the injection molding device interact with the first and the second outer mold halves in a first and in a second separation plane forming cavities suitable to receive melted plastic material injected through a sprue channel into the cavities to form objects consisting at least partially from the melted plastic material. After the melted plastic material has sufficiently cured, the injection molding device is opened in the area of the first and second separation planes and the center part is rotated by an appropriate angle, normally at least 90°, around the center axis such that another two inner mold halves can be interconnected to the first and the second outer mold half forming cavities there between as described above.

The center part and the thereto attached inner mold halves must be supplied with various process media such as cooling water, hydraulic oil, pneumatic air or a selection thereof. The transfer of said process media requires special devices which are nowadays normally arranged outside of the center part. In addition, such devices need frequent maintenance during operation. This can only be achieved by time consuming disassembly of the devices which is a drawback as down time has a negative impact on the operation cost of the device.

On behalf of the same applicant WO2013001022 was published in January 2013. It describes a rotation device for an injection molding device and an injection molding device comprising such a rotation device. The rotation device is for rotating a center part in an injection molding device. The rotation device comprises a column around which a sleeve is arranged rotating with the center part. Process media is transferred between the column and the sleeve.

SUMMARY OF THE INVENTION

An injection molding device according to the invention normally comprises a rotating device, an injection mold and an injection molding machine. The injection mold comprises a first outer mold half and a thereto along tie bars of the injection molding machine in a first direction relative to the first outer mold half displaceable second outer mold half. Between the first and the second outer mold half a center part is arranged rotatable around a center axis extending in vertical direction. The center part can comprise at least two, but more often four or even six side faces, etc., which are arranged in pairs parallel to each other and which carry inner mold halves of the injection mold. The rotating device is for holding and rotating the center part of the injection mold in the injection molding device. The inner mold halves in a closed position of the injection molding device interact with the first and the second outer mold halves in a first and in a second separation plane forming cavities there between suitable to receive melted plastic material injected through a sprue channel into the cavities to form objects consisting at least partially from the melted plastic material. After the melted plastic material has sufficiently cured, the injection molding device is opened in the area of the first and second separation planes and the center part is rotated by the rotating device by an appropriate angle which depends on the number of side faces of the center part around the center axis such that another two inner mold halves can be interconnected to the first and the second outer mold half forming cavities there between as described above.

In difference to the prior art, the rotating device according to the invention offers the advantage that it can be very easily and efficiently assembled and disassembled, e.g. for maintenance reasons. The maintenance time can thereby be significantly reduced, up to 60% and more, compared to the prior art. The invention offers the advantage that, depending on the field of application, the heavy and bulky injection molds do not need to be removed from the injection molding machine to which it is installed.

In the devices known from the prior art the maintenance time is a critical aspect as they require a complete disassembly which usually is very time consuming. Especially the transfer areas for the process media in the rotating device are critical, as the required seals must frequently be checked and if necessary replaced. For obtaining access to the critical areas the injection molding device must be stopped, cooled down and then dismantled to gain access to the critical areas. One significant disadvantage is that the heavy and bulky injection molds consisting of the first and second outer mold halves, as well as the center mold part must be at least partially removed from the injection molding machine in which they are installed.

An injection molding device according to the invention comprises a center part and a rotating device for holding and rotating the center part in the injection molding device. The rotating device comprises a base supported with respect to an injection molding machine, e.g. a machine bed and/or lower tie bars of the injection molding machine. Furthermore, the injection molding device comprises a column attached to the base and extending in an axial direction above the base. A sleeve is arranged on and coaxially surrounds the column. For performance reason and easier handling, the sleeve is at least partially arranged in the center part which is preferably made from a material which has a lower density then the material of the sleeve. Good results can be achieved when the sleeve is made from steel or the like and the center part is made from aluminum or the like. The sleeve rotates with the center part around the column. Grooves arranged between the sleeve and the column are used to exchange liquid and/or gaseous media between the column and the sleeve, respectively the center part.

The column is arranged removable with respect to the center part. In a preferred variation the column is interconnected detachable to the base as will be described in more detail hereinafter. Good results can be achieved when the column along its axial direction has a variable diameter. Depending on the design the variable diameter can be e.g. linearly varying. Alternatively, or in addition the column can have a staggered design, with at least two sections arranged coaxially and adjacent to each other with respect to the axial direction of the column. In a preferred variation the sections are having decreasing diameters in the direction of the base of the rotation device such that the column can be removed from the center part, respectively the sleeve in an upward direction away from the base. The column is therefore interconnected detachably to the base as will be described in more details hereinafter. In principle it would also be possible to arrange the decreasing diameter in the opposite direction, i.e. reduction of diameters away from the base. Thereby it would be possible to leave the column attached to the base and remove the center part in an upward direction away from the base. Alternatively, or in addition a separation of the center part with respect to the rotating device can be achieved by designing the sleeve removable from the center part as such. E.g. the column and the sleeve can be removed from the center part in an upward direction which remains in the injection molding machine resting on the base.

The sleeve and the column may form a transfer unit which can be assembled and disassembled independent of the center part. The transfer unit preferably comprises a first and a second media interface through which liquid and/or gaseous media can be exchanged with the inner mold halves attached to the center part. Therefore, the center part may comprise a third and the base a fourth media interface which are compatible to the first and the second media interface. Alternatively, or in addition pipes for media may be interconnected directly to the lower end of the column, respectively the first media interface. Good results can be achieved when the second media interface is arranged at the upper end of the sleeve, while the first media interface is arranged at the lower end of the column. At least the second and the third media interface may be interconnected indirectly to each other via a link element, e.g. in the form of a ring in a mounted position interconnecting to the upper end of the sleeve with the center part.

In a variation at least one section comprises at least one groove used to exchange liquid and/or gaseous media between the column and the sleeve. The at least one groove can be arranged along on outer surface of the column and or a thereto corresponding inner surface of the sleeve. Normally on both sides adjacent to the at least one groove for the liquid and/or gaseous media a groove is arranged to receive a sealing means. Good results can be achieved when between two adjacent sections a smooth transition surface is arranged which supports assembly and disassembly of the sleeve with respect to the column. If appropriate the sleeve can be integrated in the center part.

In a preferred variation the base comprises a detachable fixture for the column which allows to detach the column from the base even when the center part is arranged on the base. This offers the advantage that the maintenance becomes possible without removing the center part from the holding device. If appropriate the fixture may comprise at least one radial and/or axial supporting surface to support the center part in radial and/or axial direction with respect to the base. The radial and/or axial supporting surface can be foreseen to receive at least one bearing, e.g. in the form of a ball or a needle bearing. Alternatively, or in addition other fixation means can be foreseen by which the center part can be temporarily fixed to the base to provide a stable support while the column is removed from the center part. The center part as well as the base comprise thereto compatible abutments. The fixation means can e.g. be in the form of a threaded support preferably arranged between the center part and the base. The fixation means must be able to securely hold and position the weight of the center part and the thereto attached elements with respect to the base in a manner, such that the column can be removed from the sleeve, respectively the center part and vice-versa.

In a variation the rotating device comprises a drive with a stationary part and a rotary part which is interconnected to the rotating center part by a quick release coupling such that the drive is easily detachable from the center part. Good results can be achieved when the drive sits above the center part, respectively the column, e.g. the stationary part of the drive is interconnected via a yoke to the injection molding machine by at least one upper tie bar. Preferably, the stationary part of the drive is detachably interconnected to the column, e.g. by a quick release coupling a first and a thereto interconnectable second part which transfer torque between the drive and the center part. For additional centering the first and the second part of the quick release coupling can be self-centering with respect to each other. The drive may comprise a gear box which is preferably arranged on the stationary side.

Disassembling of the rotating device, e.g. for maintenance, can be executed as described hereinafter:

(a) Providing injection molding device comprising a center part and a rotating device for holding and rotating the center part in the injection molding device, the rotating device comprising a base supported with respect to an injection molding machine, a column attached to the base extending in an axial direction above the base and a sleeve coaxially surrounding the column and being at least partially arranged in the center part, wherein the sleeve rotates with the center part around the column.

(b) Separating the column from the center part alone or in combination with the sleeve. If appropriate the separation takes place outside of the injection molding machine or inside the injection molding machine, i.e. while the column or the center part remain in the injection molding device.

(c) If appropriate, the center part is temporarily fixed with respect to the base before releasing a fixture holding the column with respect to the base.

(d) Either: removing the column from the center part in an upward direction away from the base.

(e) Or: Removing the column from the center part in a downward direction in that the center part is lifted away from the base in an upward direction.

It is to be understood that both the foregoing general description and the following detailed description present embodiments, and are intended to provide an overview or framework for understanding the nature and character of the disclosure. The accompanying drawings are included to provide a further understanding, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments, and together with the description serve to explain the principles and operation of the concepts disclosed.

