TECHNICAL FIELD

[0001] The present invention relates to a hot runner injection molding apparatus, and in particular, to a valve-gating nozzle tip for a hot runner system.

BACKGROUND

[0002] Misalignment between a valve pin and a mold gate can lead to premature wear of the valve pin and/or the mold gate, which results in molded articles exhibiting poor gate quality or other surface defects. To assist in aligning a valve pin with a mold gate, hot runner nozzles will often include a valve pin aligner which is supposed to center the valve pin to the mold gate as the valve pin is moved between open and closed positions. Unless the valve pin aligner is concentric with the the mold gate, the problem of wear is exacerbated as each time the mold gate is closed, the valve pin deflects to accommodate any lateral offset between the mold gate and the valve pin aligner.

SUMMARY

[0003] Embodiments hereof are directed towards a valve gating nozzle tip connectable to a hot runner nozzle. The nozzle tip includes a valve pin guiding component having an attachment portion for connecting the nozzle tip to the hot runner nozzle, a skirt projecting downstream from the attachment portion, the skirt having an alignment ring sized to mate with an alignment bore in a mold cavity component, and a bore extending through the attachment portion. The bore defines an inner attachment portion of the valve pin guiding component and a melt passage portion of the valve pin guiding component. The melt passage portion has a valve pin aligner extending inward from the bore, the valve pin aligner includes a valve pin guiding surface concentric with the alignment ring.

[0004] Embodiments hereof are directed towards a valve gating nozzle tip connectable to a hot runner nozzle. The valve gating nozzle tip includes a valve pin guide component and a melt outlet component that received in and attached to the valve pin guiding component. BRIEF DESCRIPTION OF DRAWINGS

[0005] The drawings may not be to scale.

[0006] FIG. 1 is a sectional view of the downstream end of a hot runner nozzle having a valve gating nozzle tip in accordance with an embodiment of the present disclosure. A valve pin associated with the hot runner nozzle and valve gating nozzle tip is shown in a closed position.

[0007] FIG. 2 is a sectional view of the downstream end of the hot runner nozzle and valve gating nozzle tip of FIG. 1 . The valve pin associated with the hot runner nozzle and valve gating nozzle tip is shown in an open position.

[0008] FIG. 3 is a sectional view of the valve gating nozzle tip of FIG. 1 isolated from the nozzle.

[0009] FIG. 4 is a rear perspective view of a valve pin guide component of the valve gating nozzle tip of FIG. 1 .

[0010] FIG. 5 is a rear perspective view of a melt outlet component of the valve gating nozzle tip of FIG. 1 .

[0011] FIG. 6 is a sectional view of a valve gating nozzle tip in accordance with another embodiment of the present disclosure.

[0012] FIG. 7 is a sectional view of a valve gating nozzle tip in accordance with yet another embodiment of the present disclosure.

DETAILED DESCRIPTION

[0013] In the following description, “downstream” is used with reference to the general direction of molding material flow from an injection unit to a mold cavity of an injection molding system and to the order of components, or features thereof, through which the molding material flows from an inlet of the injection molding system to the mold cavity. “Upstream” is used with reference to the opposite direction. Further, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, summary or the following detailed description.

[0014] Referring to FIGS. 1 and 2 which are a sectional view of the downstream end of a hot runner nozzle 100 having a valve gating nozzle tip 102 or nozzle tip 102 in accordance with an embodiment of the present disclosure connected thereto. In FIG. 1 a valve pin 104 that is associated with hot runner nozzle 100 and nozzle tip 102 is shown in a closed position and in FIG. 2 valve pin 104 is shown in an open position.

[0015] Hot runner nozzle 100 includes a nozzle body 106 and a heater 108. A nozzle channel 110 extends through nozzle body 106 and is in fluid communication between a source of molding material, for example, a hot runner manifold (not shown) and nozzle tip 102 which is secured to the downstream end of nozzle body 106.

[0016] Hot runner nozzle 100, and nozzle tip 102 are received in a mold member 112, which can be, for example, a gate insert or a mold plate which defines a mold gate 114 through which molding material is injected into a mold cavity 116.

[0017] Valve pin 104 extends through hot runner nozzle 100 and nozzle tip 102 to mold gate 114.Valve pin 104 is coupled to an actuator (not shown) which translates valve pin 104 between the closed position (see FIG. 1 ) and the open position (see FIG. 2). In the closed position, valve pin 104 is positioned to block mold gate 114 to prevent moldable material from entering mold cavity 116; in the open position, valve pin 104 is separated from mold gate 114 to allow molding material to be injected into mold cavity 116.

[0018] In accordance with an embodiment of the present disclosure nozzle tip 102 includes a valve pin guiding component 118 or guiding component 118 and a melt outlet component 120 or outlet component 120 that is received in guiding component 118 and fixed thereto.

[0019] Referring now to FIG. 3, which is a sectional view of nozzle tip 102 of FIG. 1 isolated from nozzle 100. Guiding component 118 includes a cylindrical attachment portion 122 through which nozzle tip 102 is connected to hot runner nozzle 100, and a skirt 124 that projects downstream from attachment portion 122. Skirt 124 has an external alignment ring 126 which locates nozzle tip 102 relative to mold gate 114. Alignment ring 126 is concentric with a central axis Ac of nozzle tip 102 and is sized to mate with an alignment bore 128 in mold member 112 (see FIG. 2) that is concentric with mold gate 114. An axial bore 130 extends through attachment portion 122. Bore 130 defines an inner attachment portion 132 of valve pin guide component 118 and a melt passage portion 134 of guiding component 118. Melt passage portion 134 includes a valve pin aligner 136 that extends inward from bore 130. Valve pin aligner 136 has a valve pin guiding surface 138 that slidably engages valve pin 104 as valve pin 104 is moved between the closed and open positions. Valve pin guiding surface 138 is concentric with central axis Ac and external alignment ring 126. Valve pin aligner 136 and alignment ring 126 being portions of a unitary component, i.e. guiding component 118, promotes axial alignment between valve pin 104 and mold gate 114 by reducing or eliminating misalignment caused by tolerance stack-up of assembled separate components.

[0020] Molding material flows through outlet component 120 towards mold gate 114. Outlet component 120 is received in guiding component 118. Outlet component 120 includes an outer attachment portion 140, an extension portion 142, and a melt passageway 144 in fluid communication with melt passage portion 134 of guiding component 118. which extends through outer attachment portion 140 and extension portion 142. Outer attachment portion 140 engages with inner attachment portion 132 of guiding component 118 to attach outlet component 120 to guiding component 118. Extension portion 142 projects downstream from outer attachment portion 140 and is surrounded by skirt 124.

[0021] Continuing with FIG. 3 and referring to FIG. 4 which is a rear perspective view of guiding component 118. Valve pin aligner 136 maintains axial alignment between valve pin 104 and mold gate 114 as valve pin 104 is translated between the closed and open positions. As shown, valve pin aligner 136 includes a guide sleeve 146 that is suspended within melt passage portion 134 of guiding component 118 by a support member 148 that extends inward from bore 130. Although support member 148 is shown as an elongate fin shaped structure, other configurations of support member 148 are contemplated such as a cylindrical shaped support member or a helical shaped support member. An inner surface of guide sleeve 146 defines valve pin guiding surface 138. As shown by way of example, guide sleeve 146 is suspended within melt passage portion 134 by a plurality of support members 148 that are equally spaced around a central axis Ac (see FIGS. 3 and 4) of nozzle tip 102.

[0022] In an alternative embodiment (not shown) guide sleeve 146 is omitted and the valve pin aligner is formed by at least three support members (fin shaped or otherwise shaped) that extend inward from bore 130 and are equally spaced around central axis Ac. In such a configuration, each of the support members has a respective valve pin guiding surface portion that is concentric with alignment ring 126. [0023] Continuing with FIG. 3 and referring to FIG. 2, In the illustrated embodiment of FIGS. 1-3, a downstream end of melt passageway 144 tapers toward central axis Ac to define a melt outlet 150 through which molding material exits nozzle tip 102. When valve pin 104 in the open position, valve pin 104 is withdrawn from melt outlet 150, and when valve pin is in the closed position, valve pin 104 extends through melt outlet 150 to block mold gate 114. Ideally, melt outlet 150 and valve pin guiding surface 138 are axially aligned. In this configuration melt outlet 150 can be considered a valve pin aligner which helps to center valve pin 104 as it moves towards the closed position. Relative to the diameter of valve pin guiding surface 138 and/or the diameter of valve pin 104 where it extends through melt outlet 150, melt outlet 150 can be sized in a variety of configurations. In one configuration, a diameter of melt outlet 150 is greater than diameter of a valve pin 104 where it extends through melt outlet 150. This configuration may be beneficial if the diameter of melt outlet 150 is finished prior to attaching outlet component 120 to guiding component 118. In another configuration, a diameter of melt outlet 150 is equal to a diameter of valve pin guiding surface 138 of valve pin aligner 136. This configuration may be beneficial if melt outlet 150 and valve pin guiding surface 138 are formed in the same manufacturing operation or set-up, which may also promote axial alignment of melt outlet 150 and valve pin guiding surface 138.

[0024] Continuing with FIG. 3, in the illustrated embodiment of FIGS 1-3, outlet component 120 is releasably attached, i.e., is separably attached, to guiding component 118. An example of releasably attached includes outer attachment portion 140 of outlet component 120 engaging with inner attachment portion 132 of guiding component 118 by way of complementary inner and outer threads respectively formed on inner attachment portion 132 of guiding component 118 and outer attachment portion 140 of outlet component 120. To facilitate coupling and decoupling of outlet component 120 and guiding component 112, such as wrench flats, or a hex formed on extension portion 142.

[0025] Referring to FIG. 3, guiding component 118 includes a first downstream facing surface 154 that is between melt passage portion 134 and inner attachment portion 132, and against which an upstream facing end 164 of outlet component 120 is seated. In the illustrated embodiment of FIGS. 1-3, first downstream facing surface 154 and upstream facing end 164 are perpendicular to central axis Ac of nozzle tip 102, however, other configurations are contemplated. For example, downstream facing surface 154 and upstream facing end 164 taper outward in the downstream direction.

[0026] Guiding component 118 further includes a second downstream facing surface 156 that extends between an inner surface 158 of skirt 124 and inner attachment portion 132 of bore 130. In the illustrated embodiment of FIG. 1-3, second downstream facing surface 156 is perpendicular to central axis Ac of nozzle tip 102, however, other configurations are contemplated, for example, second downstream facing surface 156 can taper outward in the downstream direction.

[0027] In the illustrated embodiment of FIGS. 1-3, outlet component 120 includes a flange 160 which extends around outlet component 120, between outer attachment portion 140 and extension portion 142. Flange 160 includes an upstream side 162 that opposes second downstream facing surface 156 of guiding component 118. Outlet component 120 is sized such that an axial distance D1 between upstream side 162 of flange 160 and upstream facing end 164 of outlet component 120 is greater than an axial distance D2 between first and second downstream facing surfaces 154, 156 of guiding component 118. In one configuration, distances D1 and D2 are sized such that when outlet component 120 is threadably engaged with guiding component 118 and is tightened to a first torque value, upstream end 164 of outlet component 120 is seated against first downstream facing surface 154 and upstream facing surface 162 of flange 160 is separated from second downstream facing surface 156 by a gap.

[0028] In another configuration, distances D1 and D2 are sized such that when outlet component 120 is threadably attached to guiding component 118 and is tightened to a first torque value, upstream end 164 of outlet component 120 is seated against first downstream facing surface 154 and upstream facing surface 162 of flange 160 is separated from second downstream facing surface 156 of guiding component 118 by a gap, and when outlet component 120 is tightened to a second torque value greater than the first torque value, the gap is eliminated such that upstream facing surface 162 of flange 160 is seated against second downstream facing surface 156 of guiding component 118. In FIG. 3, nozzle tip 102 is shown having upstream facing surface 162 seated against second downstream facing surface 156. [0029] To help axially align outlet component 120 and guiding component 118, bore 130, which extends through attachment portion 122, includes an internal circumferential locating surface 166 between melt passage portion 134 and inner attachment portion 132 that is sized to mate with an external circumferential locating surface 168 adjacent to the upstream facing end 164 of outlet component 120. Internal locating surface 166 and external locating surface 166 are optional and may be omitted if not required.

[0030] Continuing with FIG, 3, and referring also to FIG. 5 which is a rear perspective view of outlet component 120. Upstream side 162 of flange 160 includes a groove 170 formed therein. Groove 170 extends from a periphery 172 of flange 160 to outer attachment portion 140. More specifically, groove 170 extends from periphery 172 of flange 160 to an under cut or circumferential groove 174 (See FIGS. 3 and 5) at the downstream end of outer attachment portion 140. Although groove 170 is shown as spiral shaped, groove 170 can have other configurations, such as a plurality of grooves (not shown) that extend radially inward from periphery 172 of flange 160 to circumferential groove 174 in outer attachment portion 140.

[0031] When outlet component 120 is installed in guiding component 118 such that upstream side 162 of flange 160 is seated against second downstream facing surface 156, groove 170 and second downstream facing surface 156 form a channel 176 (see FIG. 3) in fluid communication between an annular gap 178 formed between extension portion 142 and skirt 124 and threaded engagement between inner attachment portion 132 and outer attachment portion 140. In operation, molding material migrates through channel 176 and into the threaded engagement of inner attachment portion 132 and outer attachment portion 140 to surround outlet component 120. In this configuration, during injection of molding material to fill mold cavity 116, melt pressure acts upon both the inside (via melt passageway 144) and outside of outer attachment portion 140 which may increase the injection pressure range that outlet component 120 can withstand. In an alternative configuration (not shown), channel 176 can be formed as a groove in second downstream facing surface 156 which is enclosed by upstream facing surface 162 of flange 160. Groove 170 and channel 176, formed in part by groove 170, are optional and may be omitted if not needed in a particular molding application. [0032] Referring now to FIG. 6 which is a sectional view of a nozzle tip 102a in accordance with another embodiment of the present disclosure in which outlet component 120a of nozzle tip 102a is non-releasably attached, i.e. is permanently attached, to guiding component 118a of nozzle tip 102a. An example of non-releasably attached includes outer attachment portion 140a of outlet component 120a attached to inner attachment portion 132a of guiding component 118a by way of a brazed connection therebetween which permanently connects outlet component 120a to guiding component 118a. In a brazed, non-releasably attached configuration, groove 170 and channel 176 (shown in FIGS. 3 and 5) are omitted.

[0033] Referring now to FIG. 7 which is a sectional view of a nozzle tip 102b in accordance with yet another embodiment of the present disclosure. Nozzle tip 102b includes guiding component 118b and outlet component 120b which is attached to guiding component 118b. Melt passageway 144b, which extends through outlet component 120b, includes a lateral bore 180b that extends to an outer circumferential surface 182b of extension portion 142b. Bore 180b can function as melt outlet, in addition to or instead of melt outlet 150b depending on whether valve pin 104 is retracted from melt outlet 150b when valve pin is moved to the open position . In the illustrated embodiment of FIG. 7, bore 180b extends at an acute angle a to central axis Ac of nozzle tip 102b. Alternatively (not shown) bore 180 is disposed at an angle which is perpendicular to central axis Ac. In the illustrated embodiment of FIG. 7 outlet component 120b is shown attached to guiding component 118b by a releasable connection, i.e. a threaded connection between outer attachment portion 140b and inner attachment portion 132b; however, outlet component 120b can also be attached to guiding component 118b by a non-releasable connection. Also, in the illustrated embodiment of FIG. 7, outlet component 120b does not include a flange such as flange 160 of outlet component 120 of the illustrated embodiment of FIGS. 1-3.

[0034] Nozzle tips 102 disclosed herein can be made from a variety of materials and/or combinations of materials which are used to form nozzle tips for hot runner nozzles. In some applications, it is desirable to form guiding component 118 from a material that is more wear resistant than the material from which outlet component 120 is made, and to form outlet component 120 from a material that is more thermally conductive than the material from which guiding component 118 is made. Such a combination may be helpful to promote the service life of guiding component 118, against which valve pin 104 slides, while also promoting heat transfer from nozzle 100 to outlet component 120. An example of a suitable material combination for guiding component 118 and outlet component 120 which are releasably connected together include M2 High Speed Steel for guiding component 118 and MOLDMAX HH for outlet component 120. An example of a suitable material combination for guiding component 118 and outlet component 120 which are non- releasably connected together include H13 for guiding component 118 and TZM for outlet component 120.

[0035] While various embodiments have been described above, they are presented only as illustrations and examples, and not by way of limitation. Thus, the present invention should not be limited by any of the above-described embodiments but should be defined only in accordance with the appended claims and their equivalents.