Stack molds have long been used for injection molding of plastic articles. For example, stack molds can include a moving mold plate, a mold center plate, and a fixed mold plate. The opposed faces of adjacent mold plates define one or more cavities which conform to a desired product. During operation, when the opposed faces of adjacent mold plates are brought together into abutting contact with each other, molten plastic is injected into the cavities through a conduit in one of the mold plates. The mold plates are then cooled which causes the molten plastic within the cavities to solidify to the desired shape. The mold plates are then separated and the finished plastic article is ejected from the stack mold.
To produce the finished plastic articles, conventional stack molds close and open the mold plates on a substantially continuous reciprocating basis. For example, to help separate the moving mold plates, conventional stack molds include a rack and pinion mechanism interconnected between adjacent mold plates. During operation, as the stack mold is opened and closed in the normal molding operation, the rack and pinion mechanism functions to separate, and maintain proper spacing between, the mold plates.
Conventional stack molds suffer from a variety of deficiencies. For example, standard clearances and manufacturing tolerances permit small variations in gear tooth size and pitch in the rack and pinion mechanisms in conventional stack molds. However, such variations cause the interacting surfaces of the meshing mechanisms to exhibit small gaps or spaces between their respective meshing teeth. The spaces can allow a limited amount of slack or backlash to enter into the system during operation of the rack and pinion mechanisms. With the presence of the backlash, the gears of the rack and pinion mechanisms are prone to wear and can require constant lubrication. Accordingly, conventional stack molds can be expensive to maintain. Additionally, the rack and pinion mechanisms limit the speed at which the mold plates can open and close relative to each other and to the mass that the centering device tries to move. For example, rack and pinion systems on conventional stack molds typically can open and close once every five seconds. This limits quantity of molded items that a stack mold system can produce.
By contrast to conventional stack molds, embodiments of the present innovation relate to a stack mold system having a hydraulic assembly configured to separate a set of mold plates and maintain substantially equidistant spacing between the parting lines of the mold plates in the system during operation. In one arrangement, the hydraulic system includes two opposed hydraulic elements that are disposed in fluid communication with each other via fluid conduits, such as fluid connectors or an internal manifold, to create a closed hydraulic system. During operation, as a moving mold section of the stack mold system translates away from a central mold section along a first direction, it pulls a first piston of the first hydraulic element and opens the first parting line. The movement of the piston forces fluid, such as oil, contained in the first hydraulic element into the second hydraulic element via a first fluid conduit. Flow of the fluid into the second hydraulic element causes the central mold section or sections to translate, relative to a second piston carried by the second hydraulic element, in the first direction away from a fixed mold section. This movement opens the second parting line and forces fluid contained by the second hydraulic element to flow into the first hydraulic element via a second conduit. The fluid flow within the stack mold system, as well as the translation of the moving mold section and the central mold section or sections, is reversed as the moving mold section of the stack mold system moves toward central mold section or sections.
Use of the hydraulic system maintains the substantially central positioning of the central mold section or sections within the stack mold system during operation. The hydraulic assembly also allows for relatively fast opening and closing of the stack mold system during operation increases the rate of opening and closing of the stack mold system to more than once every five seconds. This provides an increase in the production capability of the stack mold system.
In one arrangement, embodiments of the innovation relate to a stack mold system, comprising a stack mold assembly having a first mold section, a second mold section, and a central mold section disposed between the first and second mold sections and at least one hydraulic assembly connected to the first mold section, the second mold section, and the central mold section. The at least one hydraulic assembly comprises a first hydraulic element connected to the second mold section and to the central mold section and a second hydraulic element connected to the first mold section and to the central mold section, the second hydraulic element disposed in fluid communication with the first hydraulic element. The at least one hydraulic assembly is configured to translate the first mold section and the central mold section along a longitudinal axis relative to the second mold section
The foregoing and other objects, features and advantages will be apparent from the following description of particular embodiments of the innovation, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the innovation.
Embodiments of the present innovation relate to a stack mold system having a hydraulic assembly configured to separate a set of mold plates and maintain substantially equidistant spacing between the parting lines of the mold plates in the system during operation. In one arrangement, the hydraulic system includes two opposed hydraulic elements that are disposed in fluid communication with each other via fluid conduits, such as fluid connectors or an internal manifold, to create a closed hydraulic system. During operation, as a moving mold section of the stack mold system translates away from a central mold section along a first direction, it pulls a first piston of the first hydraulic element and opens the first parting line. The movement of the piston forces fluid, such as oil, contained in the first hydraulic element into the second hydraulic element via a first fluid conduit. Flow of the fluid into the second hydraulic element causes the central mold section to translate, relative to a second piston carried by the second hydraulic element, in the first direction away from a fixed mold section. This movement opens the second parting line and forces fluid contained by the second hydraulic element to flow into the first hydraulic element via a second fluid conduit. The fluid flow within the stack mold system, as well as the translation of the moving mold section and the central mold section, is reversed as the moving mold section of the stack mold system moves toward the central mold section.
In one arrangement, the first mold section 12 is configured as a linearly translatable element and the second mold section 16 is configured as a fixed element. For example, the first mold section 12 can be supported by a set of wheels 13 which are configured to roll on a base 19 to translate the first mold section 12 along axis 18 while the second mold section 16 can be secured or connected to the base 19. In one arrangement, the central mold section 16 is also configured as a linearly translatable mold section configured to translate along axis 24 relative to the second mold section 16 and in response to linear translation of the first mold section 12. For example, the third mold section 16 can be supported by a set of wheels 21 which are configured to roll on the base 19 to translate the third mold section 16 along axis 24.
A variety of devices or mechanisms can be utilized to translate the first and third mold sections 12, 16 relative to the second mold section 14. For example, a driver element 20, such as a hydraulic actuator, can be disposed in operative communication with the first mold section 12. In use, as the driver element 20 applies a hydraulic load 22 to the first mold section 12, the first mold section 12 linearly translates along axis 18 and the third mold section 14 translates along axis 24 relative to the second mold section 14.
As indicated above, the stack mold system 10 includes a hydraulic assembly 15 which is connected to the first, second, and central mold sections 12, 14, 16. In the arrangement illustrated, the central mold section 16 is disposed in operative communication with the first mold section 12 via a first hydraulic element 34 of the hydraulic assembly 15 and is disposed in operative communication with the second mold section 14 via a second hydraulic element 36 of the hydraulic assembly 15. In use, and as will be described in detail below, as the driver element 20 applies the hydraulic load 22 to the first mold section 12, with translation of the first mold section 12 along axis 18, the hydraulic assembly 15 causes the central mold section 16 to translate along the axis 24 relative to the second mold section 14.
The hydraulic assembly 15 is configured to maintain substantial co-linear alignment of the sections 12, 14, 16 during operation, relative to a longitudinal axis 17. For example, as indicated above, the first hydraulic element 34 connects the first and third mold sections 14, 16 and the second hydraulic element 36 connects the second and third mold sections 14, 16. During operation, this minimizes rotation or misalignment of the mold sections 12, 14, 16 relative to each other and relative to longitudinal axis 17 which, in turn, minimizes binding of the mold sections 12, 14, 16.
The hydraulic assembly 15 is also configured to maintain the central mold section 16 at a substantially central location relative to the first mold section 12 and the second mold section 14 when the first mold section 12 translates along axis 18. For example, the hydraulic assembly 15 maintains substantially equal distances 26, 28 between opposed faces 62, 64 and 66, 68 of the adjacent mold sections 12, 14, 16, regardless of whether the mold sections 12, 14, 16 are closed, open, or in transition between the closed and open states. The substantially equal distances 26, 28 between opposed faces of adjacent mold sections allows the mold sections 12, 14, 16 to create seals at the corresponding parting lines 30, 32 between the first and third mold sections 12, 16 and between the third and second mold sections 16, 14 when the stack mold system 10 is disposed in a closed state.
Each of the first and second hydraulic elements 34, 36 can be configured in a variety of ways. In one arrangement, the first hydraulic element 34 is configured as a double ended cylinder. For example, the first hydraulic element 34 includes a substantially hollow housing 39 connected to the central mold section 16 and which at least partially contains a first piston 41 and an associated first ram 70 connected to the first piston 41. The piston 41 includes a first end 84 which extends from a first end of the housing 39 and a second end 86 which extends from a second end of the housing 39. As indicated in
In one arrangement, the second hydraulic element 36 can also be configured as a double ended cylinder. For example, the second hydraulic element 36 includes a substantially hollow housing 35 coupled to the central mold section 16 and which at least partially contains a second piston 37 and an associated second ram 76 connected to the second piston 37. The piston 37 includes a first end 80 which extends from a first end of the housing 35 and a second end 82 which extends from a second end of the housing 35. As indicated in
As will be described in detail below, each piston 37, 41 includes a corresponding ram 70, 76 configured to assist in cycling a hydraulic fluid between the first and second hydraulic elements 34, 36 to drive the position of the first and central mold sections 12, 16. While the hydraulic fluid can be configured in a variety of ways, in one arrangement, the hydraulic fluid is oil or other substantially incompressible fluid held at a fluid pressure of about 3000 psi.
Returning to
The second hydraulic element 36 and the first hydraulic element 34 are disposed in fluid communication with each other. In one arrangement, the hydraulic assembly 15 includes a first and second fluid conduit 38, 40, each disposed in fluid communication with the first and second hydraulic elements 34, 36. For example, the first fluid conduit 38 is disposed in fluid communication with the first volume 103 of the first housing 39 and with the third volume 106 of the second housing 35. Further, the second fluid conduit 40 is disposed in fluid communication with the second volume 105 of the first housing 39 and the fourth volume 108 of the second housing. With such a configuration, the fluid conduits 38, 40 allow the fluid to cycle between the corresponding first and third volumes 103, 106 and between the second and fourth volumes 105, 108 to drive the first and second hydraulic elements 34, 36.
In one arrangement, the fluid conduits 38, 40 are configured as fluid connectors 90, 92 disposed substantially external to the hydraulic elements 34, 36 and to the stack mold system 10. During operation, as the first and third mold sections 14, 16 translate relative to the second mold section, the first and second connectors 90, 92 are configured to rotate relative to the first and second hydraulic elements 34, 36. For example, with reference to
Each of the first rotatable joints 44, 48 and the second rotatable joints 42, 49 are configured to allow rotation of the first and second connectors 90, 92 from a first position to a second position when the first mold section 12 translates between a first position and a second position along the longitudinal axis 17. For example, when the first mold section 12 translates along a first direction 120, the first and second connectors 90, 92 rotate in a counterclockwise direction about rotatable joints 42, 44, 48, 49. Further, when the first mold section 12 translates along a second direction 122, the first and second connectors 90, 92 rotate in a clockwise direction about rotatable joints 42, 44, 48, 49.
In order to minimize the presence of air or other compressible fluids within the hydraulic assembly, in one arrangement, and with continued reference to
In use, the hydraulic assembly 15 is configured to 15 maintain substantially equal distances 26, 28 between opposed faces 62, 64 and 66, 68 of the adjacent mold sections 12, 14, 16, regardless of whether the mold sections 12, 14, 16 are closed, open, or in transition between the closed and open states. For example, assume the case where, in a first or starting position as shown in
As the driver element 20 applies a load 22 to the first mold section 12 along direction 60, both the first mold section 12 and the central mold section 16 translate along direction 60. For example, with application of the load 22, the first mold section 12 begins to open the first parting line 30 and applies a load on the piston 41 of the first hydraulic element 34 along direction 60. This loading causes the piston 41 and corresponding ram 70 to translate within the housing 39 along direction 60 and drive the hydraulic fluid within the first volume 102 into the third volume 106 of the second hydraulic element 36 via the first fluid conduit 38.
With reference to
At the point where the stack mold system 10 is disposed in the second position, the driver element 20 can apply a load 23 to the first mold section 12 along a direction 61 as shown in
With continued reference to
With such a configuration, the hydraulic assembly 15 maintains the distance 28 between the opposed faces 62, 64 of the central mold section 16 and the second mold section 14 as substantially equal to the distance 26 between the opposed faces 66, 68 of the central mold section 16 and the first mold section 12. Accordingly, the use of the hydraulic assembly 15 maintains the substantially central positioning of the central mold section 16 during operation. The hydraulic assembly 15 also allows for relatively fast opening and closing of the stack mold system 10 during operation. For example, use of the hydraulic assembly 15 increases the rate of opening and closing of the stack mold system 10 to more than once every five seconds. This, in turn, provides an increase in the production capability (e.g., volume output) of the stack mold system 10. The use of the hydraulic assembly 15 also reduces costs associated with maintaining the stack mold system 10, as the hydraulic assembly 15 does not experience the wear or need for lubrication found with conventional rack and pinion assemblies.
While various embodiments of the innovation have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the innovation as defined by the appended claims.
As indicated above, the stack mold system 10 can include a single hydraulic assembly 15. Such indication is by way of example only. With reference to
As indicated above, the hydraulic elements 34, 36 are disposed in fluid communication with each other via fluid conduits 38, 40 to create a closed hydraulic system. With reference to
As indicated above, the stack mold system 10 includes a first mold section 12, a second, fixed mold section 14, and a central mold section 16 disposed between the first and second mold sections 12, 14. In one arrangement, the central mold section 16 is configured as a set of central mold section components. For example, the central mold section can be configured with two distinct mold sections. In another example, the central mold section can be configured with three mold sections. In such arrangements, the hydraulic assembly 15 can be connected between the multiple central mold sections. In use, the stack mold system 10 is configured to translate the first mold section 12 from the central mold section 16, translate the central mold section 16 from the fixed mold section 14, as described above, and is configured to open and close the individual mold sections of the central mold section 16 relative to each other.
This patent application claims the benefit of U.S. Provisional Application No. 61/904,230, filed on Nov. 14, 2013, entitled, “Stack Mold System,” the contents and teachings of which are hereby incorporated by reference in their entirety.
Number | Date | Country | |
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61904230 | Nov 2013 | US |