Patent Description:
Injection molding machines are used to produce plastic molded parts such as, for example, preforms of the type that are blow moldable into beverage containers. A hot runner system may be provided in injection molding machines to inject molten plastic into a mold. The hot runner system is an assembly of heated components and the heat serves to maintain the molten plastic at a desired consistency. The hot runner system may be controlled by a controller which controls a heater based on a temperature measured at a temperature sensor.

A hot runner system may include a nozzle having a nozzle housing and a nozzle tip. The nozzle tip may be detachable from the nozzle housing to allow for replacement of the nozzle tip. Nozzles typically include torque features, such as wrench flats or hex or <NUM>-point sockets) to facilitate assembly and removal of the nozzle tip. However, these torque features often prevent efficient heat transfer from the nozzle heater to the nozzle tip and often cause the nozzle heater to be positioned away from a mold gate, causing poor control of the gate area and a poor thermal profile at the nozzle tip.

The present application describes injection molding machines and, more particularly, a removable nozzle tip and nozzle assembly for use with an injection molding machine and an engagement tool and methods for replacing a nozzle tip. Some embodiments of the present application may provide improved heating near a mold gate associated with a nozzle.

In a first aspect, the present application describes an injection molding machine according to claim <NUM>. The injection molding machine includes a nozzle for transferring melt to a mold cavity. The nozzle includes a nozzle housing and a nozzle tip threadably attached to the nozzle housing. At least a portion of an exterior wall of the nozzle housing and at least a portion of an exterior wall of the nozzle tip align to provide a concentric cylindrical surface. The nozzle tip does not include a torque feature.

Although not claimed, the present application also describes nozzle assembly. The nozzle assembly may include a nozzle for transferring melt to a mold cavity. The nozzle may include a nozzle housing and a nozzle tip threadably attached to the nozzle housing. At least a portion of an exterior wall of the nozzle housing and at least a portion of an exterior wall of the nozzle tip may align to provide a concentric cylindrical surface. The nozzle assembly may further include a tubular heater enclosing at least a portion of the concentric cylindrical surface. The nozzle tip does not include a torque feature in any location that is downstream of the tubular heater and upstream of a mold gate of the nozzle.

In another aspect, the present application describes an engagement tool according to claim <NUM>, for attaching or detaching a nozzle tip to a nozzle housing. The engagement tool includes a clutch for engaging a cylindrical surface of the nozzle tip and a torque feature attached to the clutch.

In yet another aspect, the present application describes a method of replacing a nozzle tip in an injection molding machine, according to claim <NUM>. The method includes: placing an engagement tool on the nozzle tip at a cylindrical surface of the nozzle tip, the engagement tool having a clutch for engaging the cylindrical surface and a torque feature attached to the clutch; and applying a torque to the torque feature using a tool.

Referring first to <FIG> and <FIG>, a conventional nozzle <NUM> for an injection molding machine is illustrated. <FIG> illustrates a perspective view and <FIG> illustrates a cross sectional view. The conventional nozzle <NUM> includes a nozzle housing <NUM> and a nozzle tip <NUM>. The nozzle housing <NUM> is located upstream while the nozzle tip <NUM> is located downstream. That is, the nozzle housing receives molten plastic and feeds it to the nozzle tip <NUM> which expels the molten plastic at a mold gate <NUM>.

The nozzle tip <NUM> is removably coupled to the nozzle housing <NUM>. The nozzle tip <NUM> may connect to the nozzle housing <NUM> by threaded engagement. To facilitate removal of the nozzle tip <NUM> from the nozzle housing <NUM>, the nozzle tip <NUM> may include one or more torque feature <NUM>. The torque features may be, for example, a wrench-engaging feature, such as a wrench flat, which allows a tool, such as a wrench, to be used to directly grip the nozzle tip <NUM>. A heater <NUM> encloses a portion of the nozzle <NUM>. Since the heater <NUM> is a tubular heater (i.e., is generally tube-shaped) positioned over the nozzle <NUM> and since the torque feature <NUM> removes material from the outside diameter of the nozzle, the heater <NUM> is positioned behind the torque feature <NUM>. That is, the heater <NUM> is positioned upstream with respect to the nozzle tip such that the distance between the torque feature <NUM> and the mold gate <NUM> is less than the distance between the heater <NUM> and the mold gate <NUM>. The built-in torque feature <NUM> provided on the nozzle tip <NUM> causes the heater to be positioned away from the mold gate since the heater <NUM> must be placed behind the torque feature <NUM>. Such positioning may yield poor thermal performance at the mold gate since the molten plastic may cool as it passes through the unheated portion of the nozzle tip <NUM>.

A thermocouple <NUM> is also provided on or near the nozzle <NUM>. As illustrated in <FIG>, the thermocouple <NUM> is located behind the torque feature <NUM>. That is, the thermocouple <NUM> is upstream from the torque feature <NUM>. The thermocouple <NUM> generates a signal which indicates a temperature level. The signal is provided as an input to a hot runner controller (not shown) which controls the heater <NUM> to maintain a desired temperature. Notably, since the placement of the thermocouple <NUM> is restricted due to the presence of the torque feature <NUM>, the temperature level reflected by the thermocouple may not be reflective of the temperature at or near the mold gate <NUM>. That is, the torque feature <NUM> increases a gap between the thermocouple and the mold gate <NUM>, causing the temperature level measured at the thermocouple to not be reflective of the temperature at or near the mold gate <NUM>.

The gap that exists between the heater <NUM> (and/or the thermocouple) and the mold gate <NUM> can cause the molten plastic to assume a consistency that is not desired or optimal prior to expulsion through the mold gate <NUM>. For example, in order to achieve the desired consistency at the mold gate <NUM>, the hot runner controller may need to heat the molten plastic to a level that accounts for any cooling effects caused when the molten plastic passes through the non-heated portions of the nozzle <NUM>. Such a technique can, however, cause problems. For example, the cooling profile may vary depending on environmental effects, such as the ambient temperature and the hot runner controller may not be suitably configured for all operating environments.

Referring now to <FIG> and <FIG>, an example nozzle <NUM> and engagement tool <NUM> which may address one or more deficiencies of convention nozzles is illustrated. <FIG> illustrates an exploded perspective view of the nozzle <NUM>, together with the engagement tool <NUM>. <FIG> illustrates a perspective view of an assembled nozzle <NUM> with the engagement tool <NUM> applied thereon. <FIG> illustrates the assembled nozzle <NUM>. <FIG> illustrates a cross sectional view of the nozzle <NUM> and a tubular heater <NUM> provided thereon.

The nozzle <NUM> may be provided in an injection molding machine and may be for transferring melt (i.e., molten plastic) to a mold cavity. The nozzle <NUM> includes a nozzle housing <NUM> and a nozzle tip <NUM>. As illustrated, for example, in <FIG>, the nozzle tip <NUM> may be threadably attached to the nozzle housing <NUM>. More specifically, the nozzle tip <NUM> may include threading at an interior surface <NUM> and the nozzle housing <NUM> may include threading <NUM> at an exterior surface <NUM>. The threading provided on the nozzle tip <NUM> is configured to matingly engage the threading <NUM> on the nozzle housing <NUM>. For example, the nozzle tip <NUM> may have female threading whereas the nozzle housing <NUM> may have male threading.

As illustrated in <FIG>, when the nozzle tip <NUM> is attached to the nozzle housing <NUM>, a cylinder is formed. The cylinder is continuous and concentric. That is, at least a portion of an exterior wall <NUM> of the nozzle housing <NUM> and at least a portion of an exterior wall <NUM> of the nozzle tip <NUM> may align to provide a concentric cylindrical surface, which is a continuous cylindrical surface.

As illustrated in <FIG>, the cylindrical surface provided by the nozzle tip <NUM> and the nozzle housing <NUM> allows a tubular heater <NUM> to be placed atop the nozzle <NUM>. That is, the tubular heater <NUM> encloses at least a portion of the cylindrical surface provided by the nozzle tip <NUM> and the nozzle housing <NUM>. For example, the tubular heater encloses at least a portion of the exterior wall <NUM> of the nozzle tip <NUM> and at least a portion of the exterior wall <NUM> of the nozzle housing <NUM>.

The tubular heater <NUM> is electrically connected to a hot runner controller (not shown) which controls the tubular heater <NUM> to maintain a predetermined temperature condition. The hot runner controller is also electrically connected to a temperature sensor, such as a thermocouple <NUM> which generates an electrical signal based on a sensed temperature. As illustrated, the thermocouple <NUM> is located near a mold gate <NUM> associated with the nozzle <NUM>. For example, the thermocouple <NUM> may be located within <NUM> millimeters of the mold gate <NUM>. The thermocouple <NUM> may be positioned proximate to the mold gate <NUM> since the nozzle tip <NUM> does not include a torque feature in any location that is downstream of the tubular heater and upstream of the mold gate <NUM> of the nozzle <NUM>. The thermocouple <NUM> may be positioned, for example, such that at least a portion of the thermocouple <NUM> is located between the mold gate <NUM> and threading provided internally on the nozzle tip <NUM>. That is, at least a portion of the thermocouple <NUM> may be located downstream of the threading but upstream of the mold gate <NUM>. As noted previously, the threading allows for attachment of the nozzle tip <NUM> to the nozzle housing <NUM>.

The close proximity between the thermocouple <NUM> and the mold gate <NUM> allows the thermocouple to sense a temperature that is reflective of the temperature at the mold gate <NUM>. Since this temperature may be used by the hot runner controller to control the tubular heater <NUM>, the tubular heater may be controlled to produce a desired melt consistency at the mold gate <NUM>.

Since the nozzle tip <NUM> does not include a torque feature (such as wrench flats or hex or <NUM>-point sockets or another wrench-engaging feature), the tubular heater <NUM> may be placed in close proximity to the mold gate <NUM>. For example, the tubular heater <NUM> may be located within <NUM> millimeters of the mold gate <NUM>. It may be noted that, in the example illustrated, the nozzle tip <NUM> does not include any torque feature in any location that is downstream of the tubular heater <NUM> and upstream of the mold gate <NUM> of the nozzle <NUM>.

Since the nozzle tip <NUM> does not include a torque feature, a wrench cannot directly engage the nozzle tip <NUM> to remove or attach the nozzle tip <NUM> to the nozzle housing <NUM>. Instead, an engagement tool <NUM> may be used to facilitate attachment or detachment of the nozzle tip <NUM>. The engagement tool <NUM>, which is illustrated in <FIG>, includes a clutch <NUM> for engaging a cylindrical surface and a torque feature <NUM> attached to the clutch <NUM>. The clutch <NUM> may be a one way rotation coupling that transmits torque in one direction and allows idling in the opposite direction and may, therefore, be referred to as a one-way clutch.

The clutch <NUM> may take various forms and may, for example, be a roller ramp clutch or a sprag clutch. The torque feature <NUM> may be a wrench-engaging feature such as wrench flats or a hex or <NUM>-point socket.

The engagement tool <NUM> of <FIG> includes a torque feature <NUM> that encloses the clutch <NUM>. That is, the torque feature <NUM> houses the clutch such that the clutch <NUM> is provided internally within the torque feature <NUM>. The engagement tool <NUM> of <FIG> may have two open ends. For example, the engagement tool <NUM> may be placed on the nozzle tip <NUM> such that the nozzle tip <NUM> extends through the engagement tool <NUM>. Then, an operator may apply a torque to the torque feature <NUM> using a tool such as a wrench in order to attach or detach the nozzle tip <NUM> while replacing a nozzle tip <NUM>. Torque may be applied in one direction to remove the nozzle tip <NUM> from the nozzle housing <NUM> to which it is attached or torque may be applied in another direction to attach the nozzle tip <NUM> to the nozzle housing <NUM>. Due to the one-way nature of the clutch, the engagement tool <NUM> may be placed on the nozzle tip in a different orientation for attachment than for detachment. It may be noted, however, that the two open ends of the engagement tool <NUM> of <FIG> may allow the same engagement tool <NUM> to be used for both attachment and removal. The engagement tool <NUM> may receive the nozzle tip <NUM> through a different one of the openings during attachment than detachment.

The engagement tool may take other forms. For example, as illustrated at <FIG>, a torque feature <NUM> may be located at an end of the engagement tool <NUM>. In this configuration, the torque feature <NUM> acts as a cap for an interior space provided by the clutch <NUM>. That is, the engagement tool <NUM> of <FIG> allows for single directional insertion since it only has one opening for receiving the nozzle tip. An open end <NUM> of the engagement tool <NUM> receives the nozzle tip <NUM> and a closed end <NUM>, which may be closed in whole or in part by the torque feature <NUM> or by another feature, cannot receive the nozzle tip <NUM>.

Due to the one-way nature of the clutch and since the engagement tool <NUM> of <FIG> only allows for one-way insertion within the clutch, a different engagement tool <NUM> may be used for attaching the nozzle tip <NUM> than is used for detaching the nozzle tip <NUM>. The engagement tool <NUM> may have indicia printed thereon indicating whether the engagement tool <NUM> is one that may be used for attachment or whether it is one that may be used for removal.

The nozzle tip <NUM> described above may be configured for engagement by the engagement tool <NUM>, <NUM> and may, for example, include one or more feature to facilitate engagement by the engagement tool. Such features may include lead-in chamfers, blended radii, etc..

The nozzle assembly described herein, including the nozzle <NUM>, the tubular heater <NUM> and the thermocouple <NUM>, may be provided in an injection molding machine.

The present disclosure also contemplates methods of replacing, removing, and attaching a nozzle tip <NUM> of the type described herein on an injection molding machine.

For example, a method of replacing a nozzle tip <NUM> of a type described above with reference to <FIG> in an injection molding machine may include placing an engagement tool <NUM>, <NUM> on the nozzle tip <NUM> at a cylindrical surface of the nozzle tip <NUM>. The engagement tool <NUM>, <NUM> may be of the type described above with reference to <FIG> or may be of the type described above with reference to <FIG>. Where the engagement tool is one that allows for both removal and attachment, the engagement tool <NUM> is placed on the nozzle tip <NUM> in a first orientation if attachment is desired and is placed in a second orientation if detachment is desired. Where the engagement tool is one that allows for only one of removal and attachment, an appropriate engagement tool may first be selected depending on whether attachment or detachment is to be performed.

After the engagement tool is placed to engage the nozzle tip, an operator may apply a torque to the torque feature <NUM> using a tool such as a wrench in order to attach or detach the nozzle tip <NUM> while replacing the nozzle tip <NUM> with another nozzle tip. Torque may be applied in one direction to remove the nozzle tip <NUM> from the nozzle housing <NUM> to which it is attached or torque may be applied in another direction to attach the nozzle tip <NUM> to the nozzle housing <NUM>.

The engagement tool may take other forms. For example, in another embodiment, a collet-type device or chuck-type device could be used to grip the nozzle tip and then torque could be applied to the collet-type device or chuck-type device using a torque feature provided on or with the collet-type device or the chuck type device.

The terms upstream and downstream, as used herein convey locations associated with a nozzle assembly based on the direction of melt flow. It will be appreciated that melt flows through the nozzle so as to be expelled from the mold gate and so a location that is upstream from another location is one that is further from the mold gate than the other location whereas a location that is downstream from another location is one that is closer to the mold gate than the other location.

Claim 1:
An injection molding machine comprising:
a nozzle (<NUM>) for transferring melt to a mold cavity, the nozzle comprising:
a nozzle housing (<NUM>) defining an exterior surface, the nozzle housing including threading along the exterior surface; and
a nozzle tip (<NUM>) defining an interior surface, the nozzle tip including threading along the interior surface that matingly engages the threading on the nozzle housing such that at least a portion of an exterior wall of the nozzle housing and at least a portion of an exterior wall (<NUM>) of the nozzle tip aligns to form a single cylinder comprising a continuous cylindrical surface (<NUM>, <NUM>) when the nozzle tip is threadably attached to the nozzle housing;
wherein the nozzle tip does not include a torque means to facilitate assembly and
removal of the nozzle tip; characterised by a tubular heater enclosing an exterior wall of the cylinder, wherein the nozzle tip does not include a torque means in any location that is downstream of the tubular heater and upstream of a mold gate of the nozzle; and
an engagement tool for attaching or detaching the nozzle tip to the nozzle housing, the engagement tool comprising:
a clutch for engaging the cylindrical surface; and
a torque feature attached to the clutch.