[0001] The present disclosure is generally related to a hot runner system, and more particularly related to a mechanism for opening and closing of a nozzle tip in a hot runner system.
BACKGROUND
[0002] The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology.
[0003] A conventional hot runner 100 with a pneumatic actuator arrangement is illustrated in Figure 1. The hot runner 100 comprises a piston/valve stem structure 102 and an injection nozzle 104 gated by an actuator assembly 106. The actuator assembly 106 is housed within a top plate 108. Further, the actuator assembly 106 includes a valve stem 110 and a pneumatic actuator 112 for moving the valve stem 110 during molding. The pneumatic actuator 112 is controllably pressurized in order to cause the valve stem 110 to move between an open position and a closed position in order to control the flow of molten plastic (not shown) out of the injection nozzle 104. Further, the piston/valve stem structure 102 includes a piston 114 against which the pressurized fluid acts in causing the valve stem 110 to move. Further, the hot runner 100 includes a manifold housing 116 having at least one manifold 118 for distributing the molten plastic from an inlet or

another manifold to each nozzle. The manifold 118 comprises heaters 120 for continuously heating the moltent plastic, and not allowing the molten plastic to cool down.
[0004] The conventional hot runner 100 with the pneumatic actuator arrangement is very costly. Further, the piston/valve stem structure 102 comprises of rubber and fiberglass seals. The rubber and fiberglass seals are prone to damages by moisture present in air. Thus, air trapped from the atmosphere, to be used in the pneumatic actuator arrangement, is heated to remove any moisture present within. The heated air is then utilized in the pneumatic actuator arrangement. Thus, the pneumatic actuator arrangement utilizes vast amount of energy for pumping of air and drying the air. Further, replacement of damaged rubber and fiberglass seals add to operational cost of the conventional hot runner 100.
[0005] A conventional hot runner 200 with a spring based mechanism 202 is illustrated in Figure 2. The hot runner 200 comprises a top plate 204 and a manifold housing 206 that lies below the top plate 204. The manifold housing 206 comprises at least one manifold 208 for distributing molten plastic (not shown) from an inlet or another manifold to each nozzle. The manifold 208 comprises heaters 210 for continuously heating the moltent plastic, and not allowing the molten plastic to cool down. Further, the hot runner 200 used for injection blow molding uses the spring based mechanism 202 for controlling movement of a valve stem 212. Further, movement of a spring 214 is controlled by pressure of the molten plastic flowing in the hot runner 200. However, such hot runner 200 utilizing the spring based mechanism 202 is inefficient in operation for being controlled by the pressure of the molten plastic, as movement of the valve stem 212 could not be accurately controlled by the pressure of a single flow of the molten plastic.
[0006] Therefore, there remains a need for an improved hot runner system that has reduced operational cost and maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The accompanying drawings illustrate various embodiments of systems, methods, and embodiments of various other aspects of the disclosure. Any person with ordinary skills in the art will appreciate that the illustrated element boundaries (e.g. boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. It may be that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of one element may be implemented as an external component in another, and vice versa. Furthermore, elements may not be drawn to scale. Non-limiting and non-exhaustive descriptions are described with reference to the following drawings. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating principles.
[0008] Figure 1 illustrates a cross-sectional view of a conventional hot runner 100 with a pneumatic actuator arrangement, in accordance with prior art.
[0009] Figure 2 illustrates a cross-sectional view of a conventional hot runner 200 with a spring based mechanism 202, in accordance with prior art.
[0010] Figure 3A illustrates a cross-sectional view of a mechanism for opening and closing of a nozzle tip 312 in a hot runner 300, in an embodiment.
[0011] Figure 3B illustrates a cross-sectional view of a tip housing 306 of the hot runner 300, in an embodiment.
[0012] Figure 3C illustrates a structural view of the nozzle tip 312 of the hot runner 300, in an embodiment.

[0013] Figure 3D illustrates a structural view of a valve stem 314 of the hot runner 300, in an embodiment.
[0014] Figure 3E illustrates a cross-sectional view of a valve stem guide bush 318 of the hot runner 300, in an embodiment.
[0015] Figure 3F illustrates a cross-sectional view of a valve stem stopper 324 of the hot runner 300, in an embodiment.

DETAILED DESCRIPTION
[0016] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising," "having," "containing," and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items.
[0017] It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any systems and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the preferred, systems and methods are now described.
[0018] Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings in which like numerals represent like elements throughout the several figures, and in which example embodiments are shown. Embodiments of the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The examples set forth herein are non-limiting examples and are merely examples among other possible examples.
[0019] A hot runner 300 is henceforth explained with reference to Figure 3A. The hot runner 300 may include a top plate 302 and a manifold housing 304 that may be disposed below the top plate 302. The manifold housing 304 may include a tip housing 306, as illustrated in Figure 3B, and at least one manifold 308. The at least one manifold 308 may be used for distributing fluid (not shown) from an inlet or another manifold to each nozzle. In an example, the fluid may be molten plastic. Further, the hot runner 300 may include a nozzle 310 that may be disposed within the tip

housing 306. The nozzle 310 may be used for injecting the fluid into a mold (not shown). Further, the nozzle 310 may be provided with a nozzle tip 312, as illustrated in Figure 3C. It should be noted that the hot runner 300 may include more than one nozzle, without departing from the scope of the disclosure.
[0020] Further, the hot runner 300 may include a valve stem 314, as illustrated in Figure 3D, that may be disposed within the nozzle 310. The valve stem 314 may be adapted to control flow of the fluid introduced into the nozzle 310. Further, the hot runner 300 may include one or more heaters 316 that may be disposed within the at least one manifold 308 surrounding the valve stem 314. The one or more heaters 316 may be configured to heat the fluid i.e., to prevent the fluid from cooling. In one case, the one or more heaters 316 may have a circular cross-section. It should be noted that the at least one manifold 308 may include a valve stem guide bush 318, as illustrated in Figure 3E. The valve stem guide bush 318 may be used for allowing the fluid to flow along a passage 320 formed between the valve stem 314 and the valve stem guide bush 318.
[0021] Further, the hot runner 300 may include a spring assembly 322 that may be coupled to the valve stem 314. The spring assembly 322 may be configured to operate the valve stem 314 based on flow of the fluid. The fluid may be supplied at a predetermined pressure. It should be noted that the spring assembly 322 may include one or more springs for operating the valve stem 314 based on flow of the fluid. In one case, when the predetermined pressure of the fluid reaches a threshold level, the valve stem 314 may move in an upward direction. Based at least on the movement of the valve stem 314, the spring assembly 322 may get compressed, and thereby the fluid may get allowed to flow through the nozzle tip 312. It should be noted that the nozzle tip 312 may remain open as long as the predetermined pressure remains above the threshold level. Further, the movement of the valve stem 314 in the upward direction may be restricted by a valve stem stopper 324, as illustrated in Figure 3F.

[0022] In another case, when the pressure of the fluid drops below the threshold level, the spring assembly 322 may move the valve stem 314 in a downward direction and thus closing the nozzle tip 312 i.e., automatically shutting off the flow of the fluid. It should be noted that the hot runner 300 may be operated within a temperature range of 150-300 degree Celsius. It will be apparent to one skilled in the art that the above mentioned spring assembly 322 may utilize coil spring(s) or leaf spring(s). In an embodiment, some other spring assembly may also be used, without departing from the scope of the disclosure.
[0023] It is evident from the above description that the hot runner 300 avoids usage of a pneumatic actuator arrangement that comprises rubber and fiberglass seals. The costs associated with pumping and heating of air utilized in the pneumatic actuator arrangement is thus avoided. Further, costs associated with maintenance and replacement of the rubber and fiberglass seals are also avoided. Thus, such arrangement and operation of the hot runner 300 results in efficient and cost effective.
[0024] It has thus been seen that the mechanism for opening and closing of the nozzle tip 312 in the hot runner 300 with the spring assembly 322 according to the present invention achieves the purposes highlighted earlier.
[0025] The hot runner 300 can in any case undergo numerous modifications and variations, all of which are covered by the same innovative concept; moreover, all of the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the shapes and sizes, can be whatever according to the technical requirements. The scope of protection of the invention is therefore defined by the attached claims.

CLAIMS

A mechanism for opening and closing of a nozzle tip (312) in a hot runner (300), the mechanism comprising:
a nozzle (310) disposed within a tip housing (306), the nozzle (310) comprising the nozzle tip (312);
a valve stem (314) disposed within the nozzle (310), wherein the valve stem (314) is adapted to control flow of a fluid introduced into the nozzle (310);
one or more heaters (316) disposed within at least one manifold (308) surrounding the valve stem (314), wherein the one or more heaters (316) are configured to heat the fluid; and
a spring assembly (322) coupled to the valve stem (314), wherein the spring assembly (322) is configured to operate the valve stem (314) based on flow of the fluid, thereby opening and closing of the nozzle tip (312) in the hot runner (300).
The mechanism as claimed in claim 1, wherein the fluid is molten plastic.
The mechanism as claimed in claim 1, wherein the fluid is supplied at a predetermined pressure.
The mechanism as claimed in claim 1, wherein the spring assembly (322) comprises at least one of a coil spring and a leaf spring.
The mechanism as claimed in claim 1, wherein the hot runner (300) is operated at a temperature ranging from 150-300 degree Celsius.

The mechanism as claimed in claim 1, wherein the one or more heaters (316) have a circular cross-section.
The mechanism as claimed in claim 1, wherein the at least one manifold (308) is disposed within a manifold housing (304).
The mechanism as claimed in claim 1, wherein the at least one manifold (308) comprises a valve stem guide bush (318) for allowing the fluid to flow along a passage (320) formed between the valve stem (314) and the valve stem guide bush (318).