Transfer seal for a removable nozzle tip of an injection molding apparatus

A two-piece transfer seal for coupling a nozzle tip to a nozzle of an injection molding apparatus includes a retaining member removably connected to a downstream end of the nozzle and a removably connected nozzle sealing member. The retaining member is comprised of a first material and at least the sealing face of the sealing member is comprised of a second material. In certain applications, the nozzle sealing member is a mold gate insert. In certain applications, the two-piece transfer seal does not retain the nozzle tip, which is metallurgically bonded to the nozzle.

FIELD OF THE INVENTION

The present invention relates generally to an injection molding apparatus and, in particular to a removable nozzle tip that is coupled to a nozzle by a transfer seal.

BACKGROUND OF THE INVENTION

Injection molding nozzle assemblies having a nozzle body and a separate nozzle tip are well known in the art. The nozzle tip may include a threaded portion to allow for direct coupling to threads on the nozzle body or, alternatively, a removable transfer seal may be provided to secure the tip to the nozzle body. The transfer seal typically includes a threaded portion for mating with threads on the nozzle body.

In addition to securing the nozzle tip to the nozzle body, the transfer seal functions to insulate the hot nozzle tip from the cold mold cavity plate. The nozzle tip is typically comprised of a highly thermally conductive material to facilitate heat transfer from heaters coupled to the nozzle to the melt flowing through the nozzle tip. The transfer seal is typically comprised of a low thermally conductive material, such as titanium, to insulate the nozzle tip from the cold mold cavity plate. The transfer seal further forms a seal with the cavity plate to prevent pressurized melt from escaping into the insulative air space that surrounds the nozzle.

A transfer seal is disclosed in U.S. Pat. No. 5,299,928 to Gellert. The one-piece transfer seal is comprised of a thermally insulative material and includes a portion that is located between the nozzle and the nozzle tip. This one-piece nozzle seal further includes a threaded portion to connect the seal to the nozzle.

As such, a need exists for a transfer seal that provides a good performance over a broader range of applications and that can be replaced in case of partial damage in a more efficient manner.

SUMMARY OF THE INVENTION

This invention teaches a novel injection nozzle in which a transfer seal that surrounds a nozzle tip is made of two members that are removably attached to the nozzle and to one another. Each member has a unique function such that each may be formed to accommodate different manufacturing tolerances and methods. For example, one member has a threaded portion to engage the nozzle and the other member acts as a seal, as an alignment surface and an insulator. The two members may be made of two different materials. Further, if the transfer seal is damaged during manufacturing or use, only the damaged member needs to be repaired or replaced. In one embodiment of the invention, one member of the transfer seal retains a nozzle tip. In another embodiment, the nozzle tip is metallurgically bonded to a nozzle body, and thus it is not retained by the transfer seal. Still, this second type of a tip can be removed by local heating.

According to an embodiment of the present invention there is provided a transfer seal for coupling a nozzle tip to a nozzle of an injection molding apparatus, the transfer seal including:a retaining member removably connected to a downstream end of the nozzle, the retaining member having an inwardly directed retaining flange provided at a downstream end of the retaining member;a sealing member having a mating flange sandwiched between the inwardly directed retaining flange and a step provided in the nozzle tip, the sealing member having a sealing face for abutting a surrounding wall of a mold cavity plate opening; and wherein the retaining member is comprised of a first material and at least the sealing face of the sealing member is comprised of a second material.

According to another embodiment of the present invention there is provided a transfer seal for coupling a nozzle tip to a nozzle of an injection molding apparatus, the transfer seal comprising:a retaining member removably connected to a downstream end of the nozzle, the retaining member having a shoulder for abutting a first step provided in the nozzle tip and an inwardly directed retaining flange provided at a downstream end of the retaining member;a sealing member having a mating flange sandwiched between the inwardly directed retaining flange and a second step provided in the nozzle tip, the sealing member having a sealing face for abutting a surrounding wall of a mold cavity plate opening; andwherein the retaining member is comprised of a first material and at least the sealing face of the sealing member is comprised of a second material.

According to an embodiment of the present invention there is provided a transfer seal for coupling a nozzle tip to a nozzle of an injection molding apparatus, the transfer seal including:a retaining member removably connected to a downstream end of the nozzle, the retaining member having a shoulder for abutting a first step provided in the nozzle tip and an inwardly directed retaining flange provided at a downstream end of the retaining member;a sealing member having a mating flange sandwiched between the inwardly directed retaining flange and a second step provided in the nozzle tip, the sealing member having a sealing face for abutting a surrounding wall of a mold cavity plate opening; andwherein the retaining member is comprised of a first material and at least the sealing face of the sealing member is comprised of a second material.

According to another embodiment of the present invention there is provided an injection molding apparatus including:a manifold having a manifold channel for delivering a melt stream of moldable material to a nozzle channel of a nozzle, the nozzle being received in a mold cavity plate opening;a nozzle tip nested in a downstream end of the nozzle, the nozzle tip having a melt channel in communication with the nozzle channel for receiving the melt stream from the nozzle channel;a mold cavity for receiving the melt stream from the melt channel of the nozzle tip through a mold gate;a transfer seal having a retaining member and a sealing member for coupling the nozzle tip to the nozzle, the retaining member being removably connected to the downstream end of the nozzle and having an inwardly directed retaining flange, the sealing member having an outwardly directed mating flange that is sandwiched between the inwardly directed retaining flange and a step provided in the nozzle tip, a sealing surface of the sealing member abutting a surrounding wall of the mold cavity plate opening; andwherein the retaining member is comprised of a first material and at least the sealing face of the sealing member is comprised of a second material.

According to yet another embodiment of the present invention there is provided an injection molding apparatus including:a manifold having a manifold channel for delivering a melt stream of moldable material to a nozzle channel of a nozzle, the nozzle having a threaded downstream end;a nozzle tip located adjacent the threaded downstream end of the nozzle, the nozzle tip having a melt channel in communication with the nozzle channel for receiving the melt stream from the nozzle channel;a mold cavity for receiving the melt stream from the melt channel of the nozzle tip through a mold gate;a transfer seal for securing the nozzle tip to the nozzle, the transfer seal having a retaining member for mating with the threaded downstream end of the nozzle, a shoulder for abutting at least a portion of an outer wall of the nozzle tip and a sealing member having a sealing face for abutting a cavity plate surrounding the mold gate;wherein an outwardly directed flange of the sealing member is sandwiched between an inwardly directed flange of the retaining member and a step provided in an outer wall of the nozzle tip.

DETAILED DESCRIPTION OF THE INVENTION

Referring now toFIG. 1, an injection molding apparatus is generally shown at10. The injection molding apparatus10comprises a manifold12having a manifold melt channel14for receiving a melt stream of moldable material under pressure from a manifold bushing16. The manifold bushing16is in communication with a machine nozzle (not shown).

Nozzles18are coupled to respective outlets20of the manifold12. A nozzle channel22, which is generally aligned with axis23, extends through each nozzle18to receive the melt stream of moldable material from the manifold12. A nozzle tip24is coupled to a downstream end of each nozzle18. Each nozzle tip24includes a melt channel26that is aligned with a respective nozzle channel22for receiving the melt stream therefrom. The nozzle tip24is comprised of a highly thermally conductive material such as Beryllium-Copper, for example. The nozzle tip24may alternatively be made of other materials including, Copper Alloy, Beryllium-free Copper, TZM, Tungsten Carbide, Tool Steel, Hardened Steel, H13, AerMet™ 100 or 310 Alloys (e.g., an iron-cobalt-nickel alloy that has been strengthened by carbon, chrome, and molybdenum, Ampco™ (e.g., alloys based on copper, bronze, aluminum, tin, brass, and also containing beryllium) and Stainless Steel.

Mold gates30are provided in a mold cavity plate32. The mold gates30are openable to allow delivery of melt to respective mold cavities34in the injection molding apparatus10. The mold gates30are thermal gated, however, may alternatively be valve gated. Both thermal gated and valve gated nozzles are well known in the art and therefore will not be described herein.

Manifold heaters (not shown) and nozzle heaters42heat the manifold12and nozzles18respectively in order to maintain the melt stream at a desired temperature. Cooling channels44are provided adjacent the mold gates30and the mold cavities34in order to facilitate cooling of the melt in the mold cavities34.

As shown inFIG. 2, a transfer seal46is comprised of a retaining member48and a separate sealing member70. The retaining member48includes an inner surface80for abutting an outer wall66of a nozzle tip24and an outer surface60having threads50formed therein. The threads50mesh with threads54that are formed on an inner surface78of the nozzle18.

The retaining member48is comprised of a thermally conductive material in order to facilitate heat flow from the nozzle18to the nozzle tip24. This allows heat provided by the nozzle heater42to be transferred efficiently to the nozzle tip24. The retaining member48does not directly contact the cold mold plate32, therefore, it is not necessary for the retaining member48to be an insulator. The retaining member48may be comprised of a conductive material such as Beryllium-Copper, Copper Alloy, Beryllium-free Copper, TZM, Tungsten Carbide, Tool Steel, Hardened Steel, H13, AerMet™ 100 or 310 Alloys, Ampco™, Stainless Steel or any other suitable thermally conductive material.

In applications having processing conditions in which thread galling is likely to occur, a lubricant is applied to the threads to reduce the amount of friction therebetween. A lubricant such as any Loctite® anti-seize compound manufactured by Loctite America or any other suitable lubricant may be used. Another method for reducing the occurrence of thread galling is to adjust the thread geometry of the nozzle18and transfer seal46.

The retaining member48of transfer seal46may alternatively be coupled to the nozzle18by one of brazing, welding, fusion or any other bonding process that may or may not require the use of a bonding material between retaining member48and the nozzle18. There are no threads therefore thread galling cannot occur. In this arrangement, the retaining member48is removable from the nozzle18by raising the temperature at the brazed joint to a de-coupling temperature, which is above the operating temperature of the injection molding apparatus10. In another embodiment of the present invention, not shown in the figures, nozzle tip24,24band24cdepicted inFIG. 2,FIG. 3,FIG. 4andFIG. 5is attached to the nozzle by one of brazing, welding, fusion or any other bonding process that may or may not require the use of a bonding material between the nozzle tip and the nozzle18. Reference is made in this regard to U.S. Pat. No. 6,009,616, U.S. Pat. No. 6,302,680, and U.S. Pat. No. 6,318,990 each of which is incorporated by reference in its entirety herein.

A shoulder62is provided on the end of the transfer seal46upstream of the threads50. The shoulder62abuts a step86that is provided in the outer wall66of the nozzle tip24to secure the nozzle tip24to the nozzle18. A retaining flange82extends inwardly from a downstream end of the retaining member48.

The sealing member70, which is located downstream of the retaining member48, includes a mating flange84for interlocking with the retaining flange82of the retaining member48. The mating flange84is sandwiched between the retaining flange82of the retaining member48and the outer wall66of the nozzle tip24to hold the sealing member70in position. A second shoulder62′, which is provided on an upstream end of the mating flange84, abuts a second step86′ of the nozzle tip24. The second shoulder62′ is held in abutment with the nozzle tip24by the retaining flange82of the retaining member48. The transfer seal46is sized so that both shoulders62and62′ are in abutment with the nozzle tip24, however, it will be appreciated that only one shoulder is necessary to hold the nozzle tip24in position, as is shown in the embodiment ofFIG. 3. Further, it will be appreciated by a person skilled in the art that the shoulders62,62′ may be horizontal or alternatively may be sloped at any angle to accommodate various nozzle tip designs.

The sealing member70includes a sealing face72that abuts a surrounding wall76of an opening74in the mold cavity plate32. At least the sealing face72of the sealing member70is comprised of a material having good thermal insulating properties, such as titanium, ceramic, thermally coated steel or a polyimide material, such as Vespel®, which is manufactured by Dupont, for example. The sealing face72insulates the nozzle tip24so that heat transfer from the cold mold plate32is reduced.

The outer wall60of the retaining member48of the transfer seal46includes a hexagonal nut-shaped portion61for mating with a tool to allow for tightening or loosening of the transfer seal46.

In operation, the melt stream flows under pressure though the manifold channel14of the manifold12and into the nozzle channels22of a plurality of nozzles18of the injection molding apparatus10. The melt flows from the nozzle channels22into the melt channels26of the respective nozzle tips24, past the mold gates30and into the mold cavities34. The mold cavities34are then cooled by the coolant flowing through the cooling ducts44. Once a predetermined amount of time has elapsed, the molded parts are ejected from the mold cavities34.

The retaining member48of the transfer seal46maintains the nozzle tip24in abutment with the nozzle18and the sealing member70provides a seal between the surrounding wall76of the mold cavity plate opening74and a sealing face72thereof to prevent melt from escaping into the insulative air space that surrounds the nozzle18. Further, the sealing member70insulates the hot nozzle tip24from the cold mold cavity plate32.

The two-piece transfer seal46provides an advantage in that the retaining member and sealing member may be made from different materials. Further, if one of the parts is damaged it is not necessary to replace the entire transfer seal46, only the damaged portion.

Referring toFIG. 3, another embodiment of an injection molding apparatus10bis shown. Like reference numerals have been used to denote like parts and only differences relative to the injection molding apparatus ofFIGS. 1 and 2will be discussed in detail.

In this embodiment, step86in nozzle tip24bhas been eliminated. As such, nozzle tip24bis held in position by mating flange84bof sealing member70b. The shoulder62b′ of mating flange84bof sealing member70bis held in abutment with step86b′ of nozzle tip24bby retaining flange82bof the retaining member48b, which in turn is coupled to nozzle18bby threads50b. The retaining member48may be comprised of a material such as Beryllium-Copper, Copper Alloy, Beryllium-free Copper, TZM, Tungsten Carbide, Tool Steel, Hardened Steel, H13, AerMet™ 100 or 310 Alloys, Ampco™, Stainless Steel or any other suitable thermally conductive material.

Referring toFIG. 4, another embodiment of an injection molding apparatus10cis shown. Like reference numerals have been used to denote like parts and only differences relative to the injection molding apparatus ofFIGS. 1 and 2will be discussed in detail.

Similar to the transfer seal46and46bof the previous embodiments, transfer seal46cis comprised of a retaining member48cand a separate sealing member70c. The retaining member48cincludes an inner surface80chaving threads50cformed therein. The threads50cmesh with threads54cthat are formed on the outer surface19cof the nozzle18c. A retaining flange82cextends inwardly from a downstream end of the retaining member48c. The retaining member48cmay be comprised of any of the thermally conductive materials identified in relation to the retaining members of the previous embodiments. In this embodiment, the retaining member48cis not located between the heater and the nozzle tip and therefore can be made out of a wider variety of materials with a wider range of thermal conductivity. Thus, retaining member48ccan be made of Vespel®, Titanium, H13 or Tool Steel.

The sealing member70cthat is located downstream of the retaining member48c, includes a mating flange84c. A shoulder62cof the mating flange84c, which is provided at an upstream end of the sealing member70c, abuts a step86cthat is provided in an outer wall66cof the nozzle tip24c. The retaining flange82cof the retaining member48csecures the mating flange84cin abutment with the nozzle tip24cto couple the nozzle tip24cto the nozzle18cwhile holding the sealing member70cin position.

The sealing member70cfurther includes a sealing face72cthat abuts a surrounding wall76cof an opening74cin the mold cavity plate32c. At least the sealing face72cis comprised of a material having good thermal insulating properties, such as titanium, ceramic, thermally coated steels or a polyimide material, such as Vespel®, which is manufactured by Dupont, for example.

The transfer seal46cperforms similar securing, insulating and sealing functions as have been described with respect to the previous embodiments.

Referring toFIG. 5, another embodiment of an injection molding apparatus10dis shown. Like reference numerals have been used to denote like parts and only differences relative to the injection molding apparatus ofFIGS. 1 and 2will be discussed in detail.

In this embodiment, transfer seal46dis comprised of a retaining member48and a separate mold gate insert71. The retaining member48is identical to that shown inFIG. 2, but the retaining member configurations shown inFIGS. 3 and 4are equally applicable to this embodiment. The retaining member48may be comprised of any of the thermally conductive materials identified in relation to the retaining members of the previous embodiments.

The mold gate insert71, which is located downstream of the retaining member48, includes a mating flange84d. A shoulder62d′ of the mating flange84d, which is provided at an upstream end of the mold gate insert71, abuts a step86′ that is provided in an outer wall66of the nozzle tip24. The retaining flange82of the retaining member48secures the mating flange84din abutment with the nozzle tip24to couple the nozzle tip24to the nozzle18while holding the mold gate insert71in position.

The mold gate insert71includes a mold gate orifice30dand abuts a surrounding wall76of mold cavity plate32. In this embodiment, nozzle tip24is made from a highly thermally conductive material, such as, Beryllium-Copper, Beryllium-free Copper, TZM, or Ampco™. The mold gate insert71is comprised of a material having lower thermal conductivity and better wear resistance than the nozzle tip, such as, tool steel or hardened steel. The retaining member48is comprised of a material having good thermal conductivity from the same family of materials as the nozzle tip24so that this member does not retain any heat from heater42of the nozzle. If mold gate insert71is retained by a retaining member similar to48cfromFIG. 4, which is threaded onto the outer surface of the nozzle body18, then retaining member48ofFIG. 5can be made of a material with thermal insulating properties, such as, titanium, ceramic, thermally coated steels or a polyimide material, such as Vespel®.