Multi shot injection molding apparatus

A multi shot injection molding apparatus comprising: a stationary machine platen, a first mold plate, a first injection unit connected to a first mold plate for delivering a first molding material to a plurality of first molding cavities, a movable machine frame, a carrier coupled to a movable machine platen, a second mold plate, a second injection unit for delivering a second molding material to a plurality of second molding cavities, a rotary handling unit having a first plurality of rotary handling unit mold cavity portions n and a second plurality of rotary handling unit mold cavity portions, wherein the rotary handling unit is positionable in a first position and is configured to remove the first portions of the molded parts, a first locking mechanism, a second locking mechanism, a processing station and an ejection station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of German patent application 10 2013 006 713.8 filed Apr. 19, 2013, the contents of all of which are incorporated by reference as if fully set forth in detail herein.

FIELD OF THE INVENTION

This invention is related to an injection molding apparatus and a method of making molded parts in two or more injection steps and in two or more injection molding cavities and a handing system to transport molded parts from one injection station to a subsequent injection station.

BACKGROUND OF THE INVENTION

It is known to form plastic parts in two or more injection steps using the same material or two different materials.

There is a need to further improve the equipment to mold these parts and the methods to mold these parts by simplifying the equipment.

SUMMARY OF THE INVENTION

An injection molding machine has a first injection unit to deliver a first molding material into a first group of mold cavities. A second injection unit coupled to a movable carrier is used to inject a second material into a second group of mold cavities where the second group of mold cavities is formed in a mold attached to the movable carrier. The first and second injection units inject the first and the second materials at the same time.

DETAILED DESCRIPTION

FIGS. 1 to 10show an injection molding apparatus20in accordance with a first embodiment of the present invention, for producing molded parts shown at25inFIG. 8. The injection molding apparatus20includes a stationary machine platen3, a first mold plate5, a first injection unit1, a movable machine frame10, a carrier6, a second mold plate7, a second injection unit2, a rotary handling unit8, a processing station14and an ejection station15. A base12is shown supporting the stationary machine platen3.

The first mold plate5is secured to the stationary machine platen3. The first injection unit1is secured to the stationary machine platen3and is sealingly connected to the first mold plate5for delivering a first molding material51to a plurality of first molding cavities50(FIG. 2). The first molding cavities50are configured to form first portions16(FIG. 5) of the molded parts25(FIG. 8). A first portion50aof each of the first molding cavities50is located on the first mold plate5.

Referring toFIG. 2, the movable machine frame10is movable along a first linear direction line (shown at D) relative to the stationary machine platen3. The carrier6is coupled to the movable machine platen or frame10for movement along the first direction line D so as to open and close the first molding cavities50. The carrier6is movable between a closed position shown inFIGS. 1-3, and an open position shown inFIGS. 4-9.

The movement of the carrier6is carried out by a plurality of first mold plate rams52, each of which has a housing54connected to the stationary machine platen3, and a piston56is movable in the housing54by hydraulic pressure, and which connects to a tie bar13. The tie bars13connect to the movable machine frame10. In the embodiment shown, there are four rams52.

The second mold plate7is positioned in association with the movable machine frame10. The second injection unit2is sealingly connected to the second mold plate7for delivering a second molding material91to a plurality of second molding cavities90. A first portion90aof each of the second molding cavities90is located on the second mold plate7. The second molding cavities90are configured to form second portions17of the molded parts25, which are overmolded on the first portions16. The second injection unit2and the second mold plate7are moveable together relative to the carrier6during the opening and closing of the second mold cavities90.

The movement of the second mold plate7and the carrier6is carried out by a plurality of second mold plate rams57. The second mold plate rams57each include a housing57aand a piston57bthat connects to a tie bar57c. In the example shown inFIGS. 1-10, the housing57aconnects to the carrier6and the tie bar57cconnects to the second mold plate7.

It will be noted that the carrier6itself does not rotate. Instead, the rotary handling unit8is rotatably coupled to the carrier6and is movable with the carrier6along the first direction line D. The rotary handling unit8has a first plurality of rotary handling unit mold cavity portions58athereon and a second plurality of rotary handling unit mold cavity portions58bthereon. In the embodiment shown, the rotary handling unit8also has third and fourth pluralities of rotary handling unit mold cavity portions shown at58cand58drespectively. In the embodiment shown, the rotary handling unit mold cavity portions58a,58b,58cand58dare positioned on rotary handling unit supports60a,60b,60cand60d. Each support60a-60dincludes at least one arm62that is movable between a retracted position shown inFIG. 2wherein the associated support60a-60dis positioned proximate the carrier6, and an extended position shown inFIG. 5, wherein the associated support60a-60dis positioned away from the carrier6. Each arm62may form part of a fluid powered ram that is operable to drive the associated support60aand60dbetween the retracted and extended positions.

The rotary handling unit8is positionable in a first position (FIG. 2) in which the first plurality of rotary handling unit mold cavity portions58aare on a first side (shown at64) of the carrier6and cooperate with the first mold plate5to at least partially define the first mold cavities50and the second plurality of rotary handling unit mold cavity portions58bare on a second side66of the carrier6and cooperate with the second mold plate7to at least partially define the second mold cavities90.

The rotary handling unit8is configured to remove the first portions16of the molded parts25from the first side64of the carrier6and is movable to a second position (shown inFIG. 10) in which the first plurality of rotary handling unit mold cavity portions58aare on the second side66of the carrier6and cooperate with the second mold plate7to at least partially define the second mold cavities90.

The processing station14is positioned at a third side68of the carrier6, and may carry out any suitable action on the molded parts25that come from the second molding cavities90. For example, the molded parts25may be cooled at the processing station14(i.e. the processing station14may be a cooling station) and may have cooling cores or other cooling devices thereon. The ejection station15is the station at which the molded parts25are ejected from the injection molding apparatus20. This may be accomplished by any suitable means, such as by an air blast from within the carrier6into the molded parts25. A suitable conveyor or the like may be positioned beneath the molding apparatus20to transport the ejected molded parts25from the apparatus20.

A first locking mechanism is provided for selectively locking the position of each tie bar13and is shown at70. The first locking mechanisms70are operable to apply a first clamping force between the movable machine frame10and the stationary machine platen3so as to inhibit leakage of the first molding material51from the first molding cavities50when the first molding cavities50are closed. The first locking mechanisms70may have any suitable structure. For example, as shown inFIGS. 11a-11c, the first locking mechanism70may include a locking member72that is positioned in the stationary machine platen3and has four toothed portions74aspaced apart circumferentially by non-toothed portions74b. The locking member72is rotatable between an unlocked position (FIG. 11c) in which the toothed portions74aalign with non-toothed portions76bon the tie rods13thereby permitting extension and retraction of the tie rods13, and a locked position (FIGS. 11aand 11b) in which the toothed portions74aare aligned with and engage toothed portions76a, thereby locking the position of the tie rods13relative to the stationary machine platen3. The toothed portions76aon the tie rods13are engageable with the toothed portions74aon the locking members72when the movable machine frame10is in the closed position whereby the rotary handling unit mold cavity portions58a,58b,58cor58dengage the first mold plate5, such that the first mold cavities50are closed.

A second locking mechanism is shown at76is provided for selectively locking the position of each tie bar57c. The locking mechanisms76may be similar to the locking mechanisms70.

In the example embodiment shown inFIGS. 1-10, the molded parts25are bottle preforms. The mold cavities50are formed by the first portions50awhich are cavity portions located in the first mold plate5, rotary handling unit mold cavity portions58a,58b58cor58d, which are pairs of neck ring mold portion halves, and cores which are shown at18aand are provided on the first side64of the carrier6. Similarly, the second mold cavities90are formed by the first portions90awhich are cavity portions located in the second mold plate7, rotary handling unit mold cavity portions58a,58b58cor58d, and cores18bwhich are provided on the second side66of the carrier6.

During operation, the apparatus closes as inFIGS. 1-3, opens as inFIGS. 4-6. InFIGS. 7-9the rotary handling unit8rotates to remove the first portions16from the first side64of the carrier6and move them to the second side66as shown inFIG. 10. At this point the apparatus closes again so that the second material can be injected into the second mold cavities. The apparatus20then opens again and the rotary handling unit8rotates the molded parts25to the processing station14where they may be processed (e.g. cooled). The apparatus then opens again and the rotary handling unit then rotates the parts25to the ejection station15where they are ejected. Each time the rotary handling unit8rotates and the apparatus closes again, new first material51is injected into the first cavities50, new second material91is injected into the second cavities90a the same time, parts25are cooled in the processing station14, and cooled parts25are ejected from the apparatus20.

It will be understood, however, that, in some embodiments, the first and second mold cavities may be defined solely by cooperation between rotary handling unit mold cavity portions with first portions in the first mold plate or in the second mold plate, as the case may be. For example, as shown inFIGS. 12a-13d, an injection molding apparatus120is provided and which has first mold cavities shown at150which are defined by first portions150ain the first mold plate5, and rotary handling unit mold cavity portions158a,158b,158cor158don the rotary handling unit8. The second mold cavities are shown at190and are defined by first portions190ain the second mold plate7and the rotary handling unit mold cavity portions158a,158b,158cor158d.

In the apparatuses20and120the second mold plate7and the second injection unit2are mounted directly to the carrier6via the rams57. In an alternative embodiment of an injection molding apparatus220shown inFIGS. 14a-15c, the second mold plate7and the second injection unit2are mounted via rams257to the movable machine frame10via a support bracket9.

In the apparatuses20,120and220, the second side66of the carrier6(i.e. the side on which the second injection unit2is positioned) is positioned at 90 degrees from the first side64of the carrier6. This permits an advantageous construction for the apparatuses20,120and220in that it permits easy removal of the carrier6and its attendant components such as the rotary handling unit8for replacement for example with a different one. This is achieved by providing a withdrawal space99that is on the third side68of the carrier6and by providing an open side on the movable machine frame10. In this way, the carrier6can be disconnected from the movable frame10and withdrawn therefrom into the withdrawal space99.

However, in an alternative embodiment, the carrier6may have the second side66be positioned at 180 degrees from the first side64of the carrier6, as shown inFIGS. 17a-18c. In the embodiment shown inFIGS. 17a-18c, a processing station (e.g. a cooling station) is provided on the third side68of the carrier6which is between the first and second side64and66.

Other stations can be added such a in-mold label station between these stations. Because carrier6is attached to machine frame10and because the clamping unit of apparatus20is located along the first injection unit1, there is ample space behind carrier6to do additional molding or post molding operations. Because the 2ndinjection unit is movable and coupled to the carrier6many molded parts can be manufactured using different materials in injection units1and2or the same material (for example to reduce the cooling time and the cycle time when thick parts need to be molded of a single material. Because carrier6is not rotatable the transfer of molded parts between the stations is done by the rotary handling unit8.

FIGS. 16a-16cshow a fourth embodiment in which preforms are made on a unit where the second injection unit is supported on a support bracket9on the movable machine frame10.

REFERENCE NUMBERS OF SOME ELEMENTS

1first injection unit2second injection unit3stationary platen4clamping cylinder5mold cavity plate of the first mold cavity6carrier7mold cavity plate of the second mold cavity8rotary handling unit10frame12base13tie bar14cooling station15ejection station16first portion of molded parts17second portion of molded parts18first injection core19cooling core20multi-shot injection molding apparatus23cooling cavity25molded part