The present invention relates to a plastic injection device having at least one injection station for manufacturing plastic work pieces. The injection station may comprise a mold, a plurality of mold bars, which are moveable relative to the mold, and a transfer system for moving mold bars into and out of the mold. Further, the present invention relates to a method for manufacturing molded plastic parts.
Especially in the field of mass production of plastic parts the use of mold bars is known to manufacture a high number of component parts at the same time. The mold bars are typically part of the mold cavity and are further used for transferring the molded parts to additional working stations. For example, mold bars may be used to transfer molded plastic parts from a first injection station to a second injection station in which the molded parts can be further over-molded. Such multi-component plastic parts have application e.g. in tooth brushes and razor blade holders to achieve mechanical, visual and/or haptic advantages compared with single component plastic parts.
Transfer systems for mold bars or mold plates are known e.g. from DE 195 42 102 B4, DE 10 2004 022 821 A1 and WO 2011/061361 A2. These transfer systems have in common that each mold bar or mold plate is individually engaged by a transfer device for moving the mold bar or mold plate from one station to another. This results in relatively high complexity of the machinery and further effects the cycle time.
Further, DE 102 08 599 A1 proposes a multi-component plastic brush manufacturing machine which has a molding tool with a rotatable multi-arm index plate with molding cavities in each arm. This system reduces complexity of the machinery and reduces the cycle time; however the concept of the rotatable multi-arm index plate limits the application spectrum due to reduced variability.
Therefore it is an object to provide a plastic injection device and a method for manufacturing plastic parts requiring a reduced complexity of the machinery and a low cycle time.
In accordance with one aspect, a plastic injection device is provided that has at least one injection station with a mold, a plurality of mold bars, which are movable relative to the mold, and a transfer system for moving mold bars into and out of the mold, wherein the transfer system comprises a feeding bar extending partially within and partially outside the mold and arranged to receive and guide at least two mold bars such that movement of a first mold bar within the feeding bar may be caused by movement of a second mold bar within said feeding bar.
In accordance with one aspect, a method is provided for manufacturing plastic parts in an injection station with a mold and a feeding bar extending partially within and partially outside the mold, the method comprising the steps of:
a) introducing a first mold bar into the feeding bar,
b) moving the first mold bar, which is guided in the feeding bar, in a first axial direction into the mold,
c) injection molding at least one plastic part,
d) moving the first mold bar, which is guided in the feeding bar, together with the at least one plastic part out of the mold,
e) removing the at least one plastic part from the first mold bar and/or removing the first mold bar from the feeding bar, wherein movement of the first mold bar during step a) and/or step d) is caused by axial movement of a second mold bar, which is guided in the same feeding bar and acts directly or indirectly on the first mold bar.
Further details and features of the invention may be obtained from the following description of embodiments in conjunction with the figures, which show:
According to the present disclosure, transfer of a mold bar is not affected by individually engaging the mold bar by an actuating member but rather to provide several mold bars in a common feeding bar and to displace the mold bars by displacing one of the mold bars. In other words, a chain of several mold bars may be pushed forward within a feeding bar by pushing on only one of the mold bars. Thus, one single actuating or driving member is sufficient to displace several mold bars. Such an actuating or driving member may be relatively simple because it has to perform only a mere pushing movement.
A plastic injection device according to the present disclosure comprises at least one injection station with a mold, a plurality of mold bars, which are moveable relative to the mold, an a transfer system for moving mold bares into and out of the mold, with the transfer system comprising a feeding bar which extends partially within and partially outside the mold. The feeding bar is designed and arranged to receive and guide at least two mold bars such that movement of a first mold bar within the feeding bar may be caused by movement of a second mold bar within the same feeding bar. The mold bars may directly abut on each other. As an alternative, spacer elements may be provided interposed between mold bars such that the mold bars do not directly abut on each other.
A feeding bar according to the present disclosure is a guide rail, slide or track allowing insertion and removal of mold bars and guiding the mold bars in an axial direction of the feeding bar. A feeding bar may be a single, unitary component. However, it is sensible if the feeding bar comprises at least two sections, wherein a first section extends within the mold and the at least one further section extends outside the mold. For example, the feeding bar comprises a first section located within the mold and two further sections extending on either side of the mold. The first section may be moveable with respect to the two further sections in a direction perpendicular to the longitudinal axis of the feeding bar e.g. during opening and/or closing of the mold. However, it is important that the first section located within the mold may be aligned with the at least one further section of the mold to form a continuous feeding bar allowing displacement of the mold bars.
The feeding bar may be designed to allow friction sliding movement of the mold bars within the feeding bar. Thus, the feeding bar may for example be a sliding bushing and/or may be provided with lubricant and/or may have a surface treatment, e.g. a DLC coating, reducing friction and wear. As an alternative, the mold bars may have a roller bearing within the feeding bar. Preferably, the feeding bar is designed as a floating bearing.
For example, each mold bar may comprise at least one T-shaped or dove tail sliding block and the feeding bar may comprise a guide slot extending in a guiding direction and shaped to receive the at least one T-shaped or dove tail sliding block. In a sectional view perpendicular to the guiding direction the feeding bar may have a C-shape configuration.
In some embodiments, the feeding bar and the mold bars are adapted to each other to guide the mold bars with play in at least one direction perpendicular to the guiding direction within the feeding bar. In other words, there may be a small air gap allowing displacement of the mold bars within the feeding bar without disengagement of the mold bars from the feeding bar.
There are several ways to allow insertion of mold bars into the feeding bar and to allow removal of mold bars from the feeding bar. For example, the feeding bar may be open ended to allow insertion and removal of mold bars in the guiding direction. As an alternative, the guide slot of the feeding bar may comprise at least one clearance shaped for insertion and/or removal of the at least T-shaped or dove tail sliding block in a direction inclined to the guiding direction, optionally perpendicular to the guiding direction. This embodiment has the advantage that insertion and removal of the mold bars does not interfere with an actuating or driving member for axially transferring the mold bars within the feeding bar.
The axial position of the mold bars within the feeding bar may be determined with high precision by defined displacement via the actuating or driving member. However, for precision injection molding it is also sensible if the mold bar is located in a well-defined position in the directions perpendicular to the axial guiding direction. In this respect, it is sensible if the mold bar is fixed within the mold during injection molding. According to an aspect of the present disclosure, the forces exerted to the mold bar during injection molding are not or not only reacted by the feeding bar, but also, optionally fully, by the mold and/or the injection station. In other words, although the mold bar is guided by the feeding bar during transfer, the mold bar may be fixed during injection molding irrespective of the feeding bar. This may be achieved by guiding the mold bar within the feeding bar in a floating manner, e.g. with an air gap allowing small displacement of the mold bar relative to the feeding bar to constrain the mold bar to the mold or the like during injection molding.
According to some embodiments of the present disclosure, the mold comprises two inclined support surfaces forming a tapered holder for a mold bar and the mold comprises a corresponding taped support. The corresponding tapered holder and tapered support are suitable for aligning a mold bar within the mold. The transfer system may further comprise a plunger or the like for lifting a mold bar relative to the tapered holder and the feeding bar. In other words, a plunger may be used for either pressing the tapered support of the mold bar in the tapered holder of the mold and/or to disengage the tapered support from the tapered holder for transfer movement.
Axial movement of the mold bars in the guiding direction within the feeding bar may be effected by a drive member dedicated to the feeding bar. The drive member may e.g. be designed as a plunger, as a cylinder or as a drive spindle. If more than one feeding bar is provided, the drive member may act on several mold bars provided in different feeding bars.
Further, the transfer system may comprise an actuation member dedicated to the feeding bar for displacement of a mold bar perpendicular to said feeding bar. This actuation member may be used for insertion and/or removal of a mold bar. Again, the actuation member may be kept quite simple to perform mainly an axial movement. However, more complex actuation members may be provided if required.
In some embodiments of the plastic injection device, the feeding bar extends from the mold to at least one further mold, a mold bar insertion station, a mold bar removal station, a cooling station, a heating station, a printing station and/or a machining station. In other words, the concept of the feeding bar guiding several mold bars is not limited to insertion of a single mold bar into a mold and removal of this mold bar from the mold. Rather, a single feeding bar may extend to several stations of the plastic injection device with the transfer system providing synchronized and intermitted displacement of the mold bars from one station to another. For example, the space between two stations may be designed longer to allow cooling and/or heating of the molded plastic parts, if required. As an alternative, two stations of the plastic injection device may be arranged directly next to each other such that a mold bar is transferred from one station directly into the next station, if desired.
The movement of the mold bars within the feeding bar is not limited to an axial movement in a single guiding direction. Rather, a reciprocal movement of a mold bar may occur, if desired. In addition, it is possible to arrange several feeding bars and to provide a transfer system allowing removing a mold bar from one feeding bar and inserting into another feeding bar. This may be advantageous if two injection molding stations are provided above each other rather than next to each other. In other words, the path of a mold bar through the plastic injection device may be linear or may be meandering with several feeding bars.
A method for a manufacturing plastic parts according to the disclosure comprises the steps of introducing a fist mold bar into the feeding bar, moving the first mold bar which is guided in the feeding bar in a first axial direction into the mold, injection molding at least one plastic part within the mold, moving the first mold, which is guided in the feeding bar, together with the at least one plastic part out of the mold and removing the at least one plastic part from the first mold bar and/or removing the first mold bar from the feeding bar, wherein movement of the first mold bar during the steps of introducing the mold bar into the mold and/or removing the mold bar from the mold is caused or effected by axial movement of a second mold bar which is guided in the same feeding bar and acts directly or indirectly on the first mold bar.
According to some embodiments of the present disclosure, the first mold bar may be in a transport position lifted relative to the feeding bar at least during insertion of the mold bar into the mold and/or removal of the first mold bar from the mold. Further, during injection molding the first mold bar is usually in a centered position engaging a holder of the mold.
The method of the present disclosure may comprise the additional step of feeding back the first mold bar into a position allowing re-introducing the first mold bar into the feeding bar after removal of the at least one plastic part from the mold bar and/or after removal of the first mold bar from the feeding bar. In other words, a mold bar may be transferred in a closed cycle which may also include a cleaning station for the mold bar.
After the step of injection molding at least one plastic part the first mold bar may be introduced to at least one further mold, a cooling station, a heating station, a printing station and/or machining station wherein said movement of the mold is effected or caused by axial movement of the second mold bar and/or a further mold bar which is guided in the same feeding bar and acts directly or indirectly on the first mold bar. As an alternative, after removal of the first mold bar from the feeding bar, the first mold bar may thereafter be removed to and introduced into a further feeding bar and moved while being guided in the further feeding bar to at least one further mold, a cooling station, a heating station, a printing station and/or a machining station wherein said axial movement of the first mold bar within the further feeding bar is effected or caused by axial movement of a second and/or a further mold bar which is also guided in said further feeding bar and acts directly and indirectly on the first mold bar.
According to some embodiments of the present disclosure, the feeding bar comprises at least two sections wherein a first section extends within the mold and the at least one further section extends outside the mold with the first section being moved relative to the mold prior to and/or after the step of injection molding at least one plastic part. Preferably, the first section is aligned with the at least one further section after the step of injection molding at least one plastic part.
Feeding bars 4 are provided on either side of the middle block 1. Each feeding bar 4 is a longitudinal track extending perpendicular to the plane of the drawing. In the example embodiment of
The separation of a feeding bar 4 into sections 4a, 4b is shown in the figures as an optional feature. It is not required to separate a feeding bar 4. Rather, the feeding bar 4 could be a single continuous bar which is either fixed or movable. If the feeding bar 4 is a single continuous bar which is permanently fixed it may be sensible to provide the middle block 1 and the injection station(s) 2a, 2b movable relative to the feeding bar 4 to allow opening and closing of the mold cavities.
The design and function of the feeding bars is further shown in
The length of the section 4a extending within the mold may be identical to the length of a mold bar 5. Thus, the mold bar 5 is then movable together with the feeding bar section 4a. To allow opening and closing of the mold cavities without interfering with other mold bars 5, the feeding bar section 4a extending within the mold may protrude laterally from the mold or may correspond to the width of the mold.
In the embodiment of
If the sections 4a, 4b of the feeding bars 4 are aligned with each other as shown in
In the following, the path of a mold bar 5 and the production of a finished plastic part 6″ are described in more detail with reference to
In the state of
The next step (not depicted) is a retraction of the drive member 7 to allow insertion of a new mold bar 5 into the left hand side of lower level feeding bar 4 and removal of mold bar 5 with the two base bodies 6 to the right hand side of the middle level. The result of this transfer step is shown in the middle level of
As can be seen from
The process of manufacturing the finished parts 6″ may comprise one or more additional steps. For example, the mold cavities have to be opened and closed which may include movement of the feeding bar section(s) 4a as mentioned above. Further, instead of directly transferring a mold bar from one level to another level as described above and/or after removal of a mold bar from the upper level, a mold bar could be transferred to a cooling station, a heating station, a printing station and/or any other suitable machining station. Such additional stations may be disposed in one of the depicted levels, e.g. by extending one or more feeding bars in the guiding direction, or may be located separate from the injection station. Further, mold bars with base bodies 6 or semi-finished parts 6′ may be transferred to a storage reservoir prior to further processing and/or molding.
In
Mold bar Sc in turn abuts a fourth mold bar 5d which is located within the second injection station 2b to produce finished parts 6. Further, an additional mold bar 5e with two finished parts 6″ is shown on the right hand side of injection station 2b as being removed from the feeding bar 4.
It will be understood from the above embodiments, that variations of the process of manufacturing molded plastic parts are possible without departing from the scope of the present disclosure to displace a mold bar within a feeding bar by displacement of another mold bar which contacts (directly or indirectly) the mold bar.
The design of the feeding bars 4 and the mold bars 5 is shown in
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm”
Number | Date | Country | Kind |
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15180583.5 | Aug 2015 | EP | regional |
2016/044970 | Aug 2016 | WO | international |