MXPA06003290A - Hot edge diaphragm gate for injection mold - Google Patents

Abstract

An injection molding machine having a first mold portion and a second mold portion. The second mold portion being movable relative to the first mold portion and together defining a mold cavity. The injection molding machine includes a fluid path extending through the first mold portion. The fluid path has an inlet and a radially continuous circumferential outlet in fluid communication with the mold cavity. The injection molding machine further having a gating device operably coupled to the first mold portion generally adjacent the circumferential outlet. The gating device is positionable in an opened position to permit flow of the molding material from the fluid path to the mold cavity and a closed position to obstruct flow of the molding material from the fluid path to the mold cavity. The injection molding machine further includes a heating assembly in thermal communication with at least a portion of the fluid path to maintain the molding material in an uncured state for thermoset rubbers and plastics, and in a molten state for thermoplastics.

Description

HOT EDGE DIAPHRAGM GATE FOR INJECTION MOLD FIELD OF THE INVENTION The present invention relates to injection molding and more particularly refers to injection molding, which uses a hot edge diaphragm gate. BACKGROUND OF THE INVENTION As is widely known, injection molding of plastic materials is often used to form a variety of parts that have intricate shapes and require tight dimensional tolerances. This injection molding can be achieved using a wide variety of materials, such as thermoset plastics, rubber or similar materials. Many conventional injection molding machines employ a stationary plastic extruder operable to pass a material through a series of channels to one or a plurality of mold cavities. These mold cavities are formed between a pair of separable mold dies and are configured to closely conform to a predetermined shape. A riser and a plurality of channels or sprues are used to direct material to each mold cavity. That is, once the die molds are closed, the extruder is driven to inject a "load" of material (i.e., plastic or rubber) into the die, channels and mold cavities. After the material has had enough time to solidify, the mold dies are separated and the parts are ejected therefrom. Generally, when the parts are ejected from the mold dies, the associated channels and riser also eject coupled with the molded parts. The solidified lining and channel material must be separated from the molded parts and finally discarded. In some cases, this discarded material can be recycled back into the manufacturing process. However, often, customer requirements limit the amount of recycled material that can be used. As will be appreciated, when molding small parts with relatively large channels and feeders, the quantities of material discarded can often exceed the material amount that is allowed to be recycled. Therefore, this excess material can not be used. This leads to increased costs associated with the discarded material and the disposal of the discarded material. Similarly, it is often necessary to perform additional machining of the formed parts, to achieve the desired surface treatments at these gate locations. The removal of the material of lingo and channels and the machining, typically necessary to achieve the desired final quality. In this way, it is convenient to choose a location so that driving by gate minimizes the need for post-molded machining, however maintain an adequate flow of material. This is particularly necessary in the formation of cylindrical seals and sleeves. One attempt to simplify the injection molding of thermoplastic parts or parts has been the use of "hot runner" systems, wherein the channels of the plastic extruder to the mold cavity are maintained at an elevated temperature. With this system, the plastic in the channels is maintained above the melting temperature with only the plastic in the mold cavity that is solidified. In this way, only the parts of the mold cavity are expelled substantially without channels to be removed therefrom. The step of removing the lugs and channels from the finished parts or parts, is substantially eliminated with this system. Accordingly, there is a need in the relevant art to provide an injection molding machine that is capable of minimizing or reducing the amount of waste material produced during manufacturing.

Additionally, there is a need in the relevant art for providing an injection molding machine that is capable of reducing the need for post-molding machining. In particular, there is a need in the relevant art for providing an injection molding capable of driving a cylindrical piece by gate to reduce the need for post-molding machining. Finally, there is a need in the relevant art for overcoming the disadvantages of the prior art. COMPENDIUM OF THE INVENTION In accordance with the principles of the present invention, an injection molding machine is provided having an advantageous construction. The injection molding machine includes a first mold portion and a second mold portion. The second mold portion is movable relative to the first mold portion and joints define a mold cavity. The injection molding machine includes a fluid path that extends through the first mold portion. The fluid path has a radially continuous circumferential inlet and outlet in fluid communication with the mold cavity. The injection molding machine further has a gate device operatively coupled with the first mold portion generally adjacent the circumferential outlet. The gate type device is located in an open position to allow flow of the molding material from the fluid path to the mold cavity and a closed position to obstruct the flow of the molding material from the fluid path to the mold cavity. The injection molding machine further includes a heating assembly in thermal communication with at least a portion of the fluid path to keep the molding machine in an uncured state. Additional areas of applicability of the present invention will be apparent from the detailed description that is provided below. It will be understood that the detailed description and specific times, while indicating the preferred embodiment of the invention, are intended for the purposes of the partner only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood from the detailed description and the accompanying drawings, wherein: Figure 1 is a cross-sectional view illustrating an injection molding machine according to a first embodiment of the present invention; Figure 2 is a side cross-sectional view illustrating the injection molding machine according to the first embodiment of the present invention; Figure 3 is a perspective view of a molded member formed in accordance with the first embodiment of the present invention; Figure 4 is a schematic cross-sectional view illustrating a choir injection molding machine according to a second embodiment of the present invention; and Figure 5 is a perspective view of a molded member formed in accordance with the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. Now with reference to Figures 1 and 2, an injection molding machine 10 for forming a molded member 1000. With reference to Figures 1-3, the molded member 1000 is an O-ring. However, it will be understood that the principles of the present invention are equally applicable to a wide variety of parts, and thus, the present disclosure should not be construed to limit the scope of the present invention to any particular product or part. Briefly, as seen in Figure 3, the molded member 1000 is generally circular with an outer diameter portion 1002, an inner diameter portion 1004, an upper portion 1006, and a bottom portion 1008. Each of these portions may intersect in a corner (as illustrated) or can be mixed together in such a way that no discernible edge is present. In the present embodiment, it is considered that the molded member 1000 is to be used in such a manner that the upper portion 1006 and the bottom portion 1008 each engage a surface to define a seal coupling. Therefore, it is desirable that the upper portion 1006 and the bottom portion 1008 be free of defects including gate, flow boundaries and the like. The injection molding machine 10 generally includes a first mold section 12 and a second mold section 14. The first mold section 12 is movable relative to the second mold section 14 on a straight path (generally vertical in Figures 1) and 2) and between an operative or closed position (see Figures 1 and 2), wherein the surface 16 of the first mold section 12 buttresses a surface 18 of the second mold section 14 on a plane A, and a inoperative or open position, wherein the surface 16 of the first mold section 12 is separated from the surface 18 of the second mold section 14 to reveal mold material 20. It will be understood that it is generally inconsequential that the first section of mold 12 or the second mold section 14 is mobile, as long as they are mobile to each other. The mold cavity 20 is formed to be adopted closely to the desired shape of the molded member 1000. The mold cavity 20 can be increased in size to take into account the shrinkage of material during molding. Still referring to Figures 1 and 2, the injection molding machine 10 further includes a nozzle member 22 and a diaphragm member 24, fixed couplers within the first molding section 12. The diaphragm member 24 is generally a an inverted T-shaped member, threadedly coupled to the nozzle member 22, at 23. The nozzle member 22 is generally cylindrical, with a flanged top portion and is oriented normal to the A plane and parallel to the mobile the first section 12. The nozzle member 22 and the diaphragm member 24 together include a central bore 26 adapted to receive the molding material at an inlet 28. The central bore 26 has a first portion 30 aligned coaxially with the second portion 32. on a B axis and a neck portion 34 extending between them.

A diameter of the second portion 32 is smaller than a diameter of the first portion 30, to increase the speed of the through molding material.

The second portion 32 of the central bore 26 terminates in and is in fluid communication with the diaphragm member 24. The diaphragm member 24 defines a volume of diaphragm 38 for receiving molded material there. The diaphragm member 24 further defines a circumferential outlet 40 radiating from a central axis B. That is, the diaphragm member 24 receives the molding material from the central bore 26 and outputs the through molding material to a circumferential outlet. continues and not obstructed 40. The circumferential outlet 40 is in fluid communication with the mold cavity 20. The central bore 26, the diaphragm volume 38 and the circumferential outlet together define a fluid path of molding material. From a molding point of view, the circumferential outlet 40 provides a number of advantages over conventional injection nozzle methods. Specifically, by having a simple, continuous injection outlet 40, radiating from a central location, the molding material can be evenly distributed through the cavity of the mold 20, quickly and consistently, without resulting in molding seams or Undesirable bond lines Injection molding of hollow members using conventional gate-type assemblies often leads to seams, tie lines or other molding irregularities in the final part. These molding irregularities occur when molded material is injected into the mold cavity, only at separate sites. The molding material must run around the mold cavity and meet on a back side interface. Often, the molding material is no longer at a suitable temperature or workability and thus the seam or joint line where the flows of these two materials meet, is formed poorly. This seam or joint line can lead to seal failures, when these molded o-rings are used or to undesirable surface qualities when other parts are molded. When using the non-obstructed and continuous circumferential outlet of the present invention, these seams or joining lines are avoided, since the flow of molding material does not gather at one interface nor must it travel more than the thickness of the piece being formed. mold As can be seen in Figures 1 and 2, by virtue of the diaphragm volume 38 and the circumferential outlet 40, the diaphragm member 24 is divided into an upper half 42 and a lower half 44. The upper half 42 of the diaphragm member 24 engages with the lower half 44 by a plurality of clamping mounts 46 spaced radially about an axis B such that both the upper half 42 and the lower half 44 are transported by the first mold section 12. As best see in Figure 1, each fastening assembly 46 may include a through member 48 such as a threaded fastener, extending from the upper half 42 to the lower half 44 to engage the upper half 42 and the lower half 44, together. It should be appreciated that each fastening assembly 46 is located sufficiently inwardly relative to the circumferential outlet 40, to minimize any flow disturbances to the molding material. In other words, as illustrated in Figure 1, the clamping mounts 46 interrupt the volume of diaphragm 38 and thus interrupt the flow of the molding material passing through the volume of diaphragm 38 to the circumferential outlet. 40. Fastening mounts 46 are located sufficiently inside, so that the molding material flows around each clamping assembly 46 and they meet and again mix downstream, before entering the mold cavity 20. Remain sufficient distance downstream of the clamping assembly 46 to ensure that the molding material does not degrade to a level that may affect the quality ends! of the molding member 1000. This arrangement or arrangement reduces the occurrence of flow problems that can lead to faults or binding boundaries. The injection molding machine 10 further includes a gate device 49 having a first gate ring 50 and a second gate ring 52 located above and below the circumferential outlet 40., respectively. The first gate ring 50 and the second gate ring 52 are generally circular and continuous. The first gate ring 50 and the second gate ring 52 are movable with each other, to control the flow of molding material from the circumferential outlet 40. The first gate ring 50 and the second gate ring 52 are located in a position open to allow the flow of molding material from the diaphragm volume 38 to the mold cavity 20 and a closed position to obstruct the flow of molding material from the diaphragm volume 38 to the molding cavity 20 by a control system 55. Therefore, the first gate ring 50 and the second gate ring 52 serve to control the flow of molding material that is introduced into the mold cavity 20. As will be appreciated, the gate device 49 is located close to a border of the mold cavity 20, to reduce any excess material that may require removal in post-bonded processing. Additionally, by locating the gate device 49 adjacent the boundary of the mold cavity 20, the waste of molding material can be reduced and / or eliminated. To keep the molding material in an uncured state, the injection molding machine 10 further includes a heating or cooling device for controlling the heat within the central bore 26 and the diaphragm member 38. In this respect, the machine Injection molding 10 is adapted for use with any material cured through cooling (ie, thermofixed plastic) or cured material - through heating (ie rubber). As seen in Figures 1 and 2, the injection molding machine 10 includes a first heating assembly 60 and a second heating assembly 61. The first heating assembly 60 is preferably a square coil heater 62, however other heating or cooling devices can be used. The first heating assembly 60 generally encloses an elongated section 64 of the nozzle member 22 and is in thermal contact with it, to provide sufficient heat to the central bore. 26. When thermoset plastics are used, this heat keeps the thermofixed plastic within the central perforation 26 in a molten and fluid state. The first heating assembly 60 is controllable to maintain a desired temperature within the central bore 26 by a control system 57. It should be understood that the first heating assembly 60 may be a cooling element that is capable of cooling the central bore 26 to maintain a thermosetting material in a fluid state. The second heating assembly 61, preferably, is a plurality of plate heaters 66 located generally adjacent to and on the upper half 42 and the lower half 44 of the diaphragm member 24. The plurality of plate heaters 66 are generally mounted on a portion of the back side 68 of the upper half 42 and a portion of the back side 70 of the lower half 44 and is in thermal contact with it, to provide sufficient heat to the volume of the diaphragm 38. It should be considered that other element devices may be used. of heating. When thermoset plastics are used, this heat keeps the thermoset plastic within diaphragm volume 38 in a molten and fluid state. The second heating assembly 61 is controlled to maintain a desired temperature within the diaphragm volume 38 by the control system 57. Again it should be understood that the second heating assembly 61 may be a cooling element that is capable of cooling the diaphragm volume 38 to maintain a thermosetting material in a fluid state. As will be appreciated by a person skilled in the art, the first heating assembly 60 and the second heating assembly 61 provide a number of advantages when combined with the circumferential outlet 40 and the gate type device 49. Specifically, the device type gate 49 and heating assemblies 60, 61 together serve to provide a means for adequately maintaining the molding material in an uncured state and eliminating waste material, while the circumferential outlet 40 reduces and / or eliminates seams, lines of union, and irregularities of molding. Turning now to Figures 4 and 5, an injection molding machine 100 is provided to form a molded member 2000. Referring to Figures 4 and 5, the molded member 2000 is a cylindrical wear ring. Briefly, the molding member 2000 is generally circular having an outer diameter portion 2002, an inner diameter portion 2004, a top portion 2006 and a bottom portion 2008. Each of these portions may intersect at a corner (as shown in FIG. illustrate) or may be mixed together such that no discernible edge is present. In the present embodiment, it is considered that the molded member 2000 is to be used in such a way that the outer diameter portion 2004 couples a moving member to define a seal. Therefore, it is desirable that the inner diameter portion 2004 be free of defects, including gates, flow boundaries and the like. The injection molding machine 100 generally includes a first mold section 112 and a second mold section 114, each illustrated schematically. The first mold section 112 is movable relative to the second mold section 114 on a straight route (generally vertical in Figure 4) and between an operative or open position (see Figure 4), wherein a surface 116 of the first section of mold 112, abuts a surface 118 of the second mold section 114 on a plane A, and an inoperative or open position, wherein the surface 116 of the first mold section 112 is spaced apart from the surface 118 of the second mold section 114, to reveal a mold cavity 120. The mold cavity 120 is formed to closely match the desired shape of the molded member 2000. Still with reference to Figure 4, an injection molding machine 100 further includes a central bore 116 adapted to receive the molding material at an inlet 128. The central bore 126 terminates at and is in fluid communication with a diaphragm 136. The diaphragm 136 defines a volume of diaphragm 138 to receive the molding material there. The diaphragm 136 further defines a circumferential outlet 140. That is, the diaphragm 136 receives the molding material from the central bore 116 and outputs the molding material through an uninterrupted and continuous circumferential outlet 140. The circumferential outlet 140 is in fluid communication with the mold cavity 120 on the upper portion and the molded member 2000.

Similar to the circumferential outlet 40, the circumferential outlet 140 provides a number of advantages over conventional fuel injection methods. Specifically, by having a simple, continuous injection outlet 140, the molding material can be evenly distributed through the mold cavity 120, rapidly and consistently, without resulting in undesirable stitching or molding bond lines. These seams or lines of union are avoided because the flow of molding material does not meet in an interface nor must go more than the thickness of the piece to be molded. The injection molding machine 100 further includes a gate device 149 having a valve ring 150 located on the circumferential outlet 140. The valve ring 150 is movable relative to the circumferential outlet 140, to control the flow of molding material through the circumferential outlet 140. The valve ring 150 is located in an open position to allow the flow of molding material from the diaphragm volume 138 to the mold cavity 120 through the circumferential outlet 140 and a closed position to obstruct the flow of molding material from the diaphragm volume 138 to the mold cavity 120. Therefore, the valve ring 150 serves to control the flow of molding material that is introduced into the mold cavity 120. movement of the valve ring 150 between the open position and the closed position is controlled by an actuation device 153. The action device Assembly 153 may include any drive device such as a pneumatic actuator, a hydraulic actuator, a solenoid and the like. As will be appreciated, an edge 152 of the gate device 149 is located near a border of the mold cavity 120 to reduce any excess material that may require removal in post-molding processing. Additionally, by locating the edge 152 of the gate device 149 adjacent the boundary of the mold cavity 120, the waste of molding material can be reduced and / or eliminated. To keep the molding material in an uncured state, the injection molding machine further includes a heating or cooling device for controlling heat within the central bore 126 and the volume of diaphragm 138. As seen in Figure 4 , the injection molding machine 100 includes a heating assembly 160. the heating assembly 160 can be a square coil heater, plate heater or any conventional heating device. As illustrated, the heating assembly 160 generally surrounds the central bore 126 and the diaphragm volume 38. When thermoset plastics are used, applying heat maintains thermoset plastic within the central bore 126 and the diaphragm volume 38 in a molten and fluid state. The heating assembly 160 is controlled to maintain a desired temperature within the central bore 126 and the diaphragm volume 38. It should be understood that the heating assembly 160 may be a cooling element that is capable of cooling the central bore 126 and the diaphragm volume 38 to maintain thermosetting material in a fluid-state. As will be appreciated by a person skilled in the art, the heating assembly 160 provides a number of advantages when combined with the circumferential outlet 140 and the gate device 149. Specifically, the gate device 149 and the heating assembly 160 , together serve to provide a means for adequately maintaining the molding material in an uncured state and eliminating material waste while the circumferential outlet 140 reduces and / or eliminates seams and bond lines. The description of the invention is simply exemplary in nature and in this manner, variations that do not deviate from the essence of the invention, are intended within the scope of the invention. These variations should not be considered as a separation of the spirit and scope of the invention.

Claims (19)

1. CLAIMS 1. An injection molding machine, characterized in that it comprises: a first mold portion; a second mold portion, movable relative to the first mold portion, the first mold portion and the second mold portion, together define a mold quality; a fluid path extending through the first mold portion, to receive molding material, the fluid path has a radially continuous circumferential inlet and outlet, the circumferential outlet is in fluid communication with the mold cavity; a gate device operatively coupled to the first mold portion, generally adjacent to the circumferential outlet, the gate device is located in an open position, to allow flow of molding material from the fluid path to the mold cavity and a closed position to obstruct fluid from the molding material from the fluid path to the mold cavity; and a heating assembly, in thermal communication with at least a portion of the fluid path, the heating assembly keeps the molding material in an uncured state for thermoset rubbers and plastics, and in a molten state for thermoplastics.
2. 2. The injection molding machine according to claim 1, characterized in that the fluid path comprises: a central perforation positioned in the first mold portion, the central perforation is operated to receive the molding material, and a member of diaphragm positioned in the first mold portion, the diaphragm member has a diaphragm volume in fluid communication with the central bore and has the circumferential outlet.
3. 3. The injection molding machine according to claim 2, characterized in that the heating assembly comprises: a first heating element in thermal communication with the central perforation; a second heating element in thermal communication with the diaphragm volume.
4. The injection molding machine according to claim 1, characterized in that the gate device comprises: a first gate ring that is substantially continuous, a second gate ring is spaced from the first gate ring, the first gate ring The gate and the second gate ring are movable between each other, between the open position and the closed position.
5. 5. The injection molding machine according to claim 1, characterized in that the gate device is placed immediately adjacent to the mold cavity.
6. The injection molding machine according to claim 1, characterized in that the fluid path comprises: a nozzle member positioned in the first mold position, the nozzle member has a central bore, the central bore is operable for receive the molding material; and a diaphragm member positioned in the first mold position, the diaphragm member has a diaphragm volume in fluid communication with the central bore and has the circumferential outlet.
7. The injection molding machine according to claim 6, characterized in that the diaphragm member comprises: an upper portion; a lower portion; and a plurality of fastening mounts, which couple the upper portion and the lower portion, the plurality of fastening mounts each extend through the diaphragm volume, the plurality of fastening mounts being spaced from the circumferential outlet so as not to obstruct substantially the flow of molding material leaving the circumferential outlet.
8. 8. The injection molding machine according to claim 7, characterized in that the heating assembly comprises: a first heating element that surrounds the nozzle member and that is in thermal communication with the central bore; and a second heating element in thermal communication with the diaphragm volume.
9. The injection molding machine according to claim 8, characterized in that the second heating element comprises: a first heating plate placed in the upper portion of the diaphragm member; and a second heating plate placed in the lower portion of the diaphragm member.
10. 10. An injection molding machine characterized in that it comprises: a first mold portion; a second mold portion movable relative to the first mold portion, the first mold portion and the second mold portion, together define a mold cavity; a nozzle member positioned in the first mold portion, the nozzle member has an inlet in fluid communication with a central bore, the central bore is operable to receive the molding material; a diaphragm member positioned in the first mold portion, the diaphragm member has a diaphragm volume in fluid communication with the central bore and has a radially continuous circumferential outlet, the circumferential outlet is in fluid communication with the mold cavity; A gate device is operatively coupled with the first mold portion generally adjacent the circumferential outlet, the gate device is located in an open position, to allow flow of molding material from the circumferential outlet to the mold cavity and a position closed to obstruct the flow of molding material from the circumferential outlet to the mold cavity; and a heating assembly in thermal communication with at least one of the central perforation and the circumferential outlet, the heating assembly keeps the molding material in an uncured state for thermosetting rubbers and plastics and in a molten state for thermoplastics.
11. The injection molding machine according to claim 10, characterized in that the heating assembly comprises: a first heating element in thermal communication with the central bore; and a second heating element in thermal communication with the diaphragm volume.
12. 12. The injection molding machine according to claim 10, characterized in that the gate device comprises: a first gate ring that is substantially continuous; a second gate ring that is substantially continuous, the second gate ring is spaced from the first gate ring, the first gate ring and the second gate ring are movable with each other between the open position and the closed position.
13. The injection molding machine according to claim 10, characterized in that the gate device is located immediately adjacent to the mold cavity.
14. The injection molding machine according to claim 10, characterized in that the diaphragm member comprises: an upper portion; a lower portion and a plurality of fastening assemblies coupling the upper portion and the lower portion, the plurality of fastening assembly each extend through the diaphragm volume, the plurality of fastening mounts being spaced from the circumferential outlet for not substantially obstructing the flow of molding material leaving the circumferential outlet.
15. 15. The injection molding machine according to claim 14, characterized in that the heating assembly comprises: a first heating element that surrounds the nozzle member and that is in thermal communication with the central bore; and a second heating element in thermal communication with the diaphragm volume.
16. The injection molding machine according to claim 15, characterized in that the second heating element comprises: a first heating plate placed in the upper portion of the diaphragm member; and a second heating plate placed in the lower portion of the diaphragm member.
17. 17. An injection molding machine, characterized in that it comprises: a first mold portion; a second mold portion movable relative to the first mold position, the first mold portion and the second mold portion together define a mold cavity; a nozzle member positioned in the first mold portion, the nozzle member has an inlet in fluid communication with a central bore, the central bore is operable to receive molding material; a diaphragm member positioned in the first mold portion having an upper portion and a lower portion, the diaphragm member has a diaphragm volume in fluid communication with the central perforation and has a radially continuous circumferential outlet, the circumferential outlet is in fluid communication with the mold cavity; a gate device operatively coupled with the first mold portion generally adjacent the circumferential outlet, the gate device is located in an open portion, to allow flow of molding material from the circumferential outlet to the mold outlet and a closed position for obstructing flow of molding material from the circumferential outlet to the mold cavity; and a heating assembly in thermal communication with at least one of the central perforation and the circumferential outlet, the heating assembly keeps the molding material in an uncured state.
18. 18. The injection molding machine according to claim 17, characterized in that the gate device comprises: a first gate ring that is substantially continuous; a second gate ring that is substantially continuous, the second gate ring is spaced from the first gate ring, the first gate ring and the second gate ring are movable with each other, between the open position and the closed position.
19. 19. The injection molding machine according to claim 17, characterized in that the heating assembly comprises: a first heating element that surrounds the nozzle member and that is in thermal communication with the central bore; and a first heating plate placed in the upper portion of the diaphragm member and in thermal communication with the diaphragm volume; and a second heating plate placed in the lower portion of the diaphragm member and in thermal communication with the diaphragm volume.