Compact cartridge hot runner nozzle Number:7,438,551 from the United States Patent and Trademark Office (PTO) owispatent The present invention provides an electrically heated nozzle for injection molding which is insulated to prevent conduction of electricity and loss of thermal transmission to the casing, wherein at least a part of the electrical insulation comprises a layer of dielectric insulator material with an electrical resistance wire wound spirally thereabout and another dielectric insulator layer thereover. Also disclosed is a method for making such a nozzle which includes the steps of applying a first insulator layer, winding electrical resistance wire about the first insulator layer, applying a second insulator layer, and applying a casing layer thereover. The first and second insulating layers may be provided by spraying or through telescoping, self-supporting sleeves.<H cartridge, Compact, Compact, cartrid, 7438551.html, Patent, pto, 7438551

Title: Compact cartridge hot runner nozzle

Abstract: The present invention provides an electrically heated nozzle for injection molding which is insulated to prevent conduction of electricity and loss of thermal transmission to the casing, wherein at least a part of the electrical insulation comprises a layer of dielectric insulator material with an electrical resistance wire wound spirally thereabout and another dielectric insulator layer thereover. Also disclosed is a method for making such a nozzle which includes the steps of applying a first insulator layer, winding electrical resistance wire about the first insulator layer, applying a second insulator layer, and applying a casing layer thereover. The first and second insulating layers may be provided by spraying or through telescoping, self-supporting sleeves.

Patent Number: 7,438,551 Issued on 10/21/2008 to Gellert, et al.

Inventors: Gellert; Jobst U. (Oakville, CA), Babin; Denis (Georgetown, CA)
Assignee: Mold-Masters (2007) Limited (Georgetown, Ontario, CA)

Appl. No.: 11/685,266

Filed: March 13, 2007

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
11510994	Aug., 2006
10601190	Sep., 2006	7108502
10025767	Oct., 2003	6638053
09520843	May., 2002	6394784

Current U.S. Class: 425/549

Current International Class: B29C 45/20 (20060101)

Field of Search: 425/549 264/328.15

References Cited [Referenced By]

U.S. Patent Documents


2088586	August 1937	Cole et al.
2378530	June 1945	Bailie et al.
2522365	September 1950	Greene
2769201	November 1956	Lorenian
2794504	June 1957	Carpenter
2814070	November 1957	Bulkley et al.
2875312	February 1959	Norton
2987300	June 1961	Greene
2991423	July 1961	Vackar
3062940	November 1962	Bauer et al.
3550267	December 1970	Williams
3553788	January 1971	Putkowski
3677682	July 1972	Putkowski
3800027	March 1974	Tsutsumi
3812323	May 1974	Pink
3831004	August 1974	Wallstrom
3849630	November 1974	Halliday
3911251	October 1975	Day
3912907	October 1975	Lodi
3970821	July 1976	Crandell
4032046	June 1977	Elliot et al.
4120086	October 1978	Crandell
4238671	December 1980	Gellert
4268241	May 1981	Rees et al.
4304544	December 1981	Crandell
4373132	February 1983	Vartanian
4376244	March 1983	Gellert
4386262	May 1983	Gellert
4403405	September 1983	Gellert
4438064	March 1984	Tsutsumi
4438322	March 1984	Sylvia
4485387	November 1984	Drumheller
4492556	January 1985	Crandell
4501550	February 1985	Nikkuni
4516927	May 1985	Yoshida
4557685	December 1985	Gellert
4583284	April 1986	Gellert
4588367	May 1986	Schad
4621251	November 1986	Keefe
4635851	January 1987	Zecman
4641423	February 1987	Crandell
4643664	February 1987	Yoshida
4644140	February 1987	Hillinger
4652230	March 1987	Osuna-Diaz
4704516	November 1987	Tsutsumi
4711625	December 1987	Knauer et al.
4740674	April 1988	Tsutsumi
4768283	September 1988	Gellert
4771164	September 1988	Gellert
4795126	January 1989	Crandell
4837925	June 1989	Gellert
4865535	September 1989	Gellert
4882469	November 1989	Trakas
4894197	January 1990	Tsutsumi
4911636	March 1990	Gellert
4945630	August 1990	Gellert
4981431	January 1991	Schmidt
4988848	January 1991	Trakas
5051086	September 1991	Gellert
5055028	October 1991	Trakas
5136141	August 1992	Trakas
5136143	August 1992	Kutner et al.
5147663	September 1992	Trakas
5225211	July 1993	Imaida et al.
5226596	July 1993	Okamura
5235737	August 1993	Gellert
5266023	November 1993	Renwick
5282735	February 1994	Gellert
5326251	July 1994	Gellert
5360333	November 1994	Schmidt
5411393	May 1995	Askin et al.
5456592	October 1995	Shindo
5504304	April 1996	Noguchi et al.
5518389	May 1996	Nonomura et al.
5527177	June 1996	Potter
5614233	March 1997	Gellert
5704113	January 1998	Mak
5820900	October 1998	McGrevy
5871786	February 1999	Hume et al.
5955120	September 1999	Deissler
5973296	October 1999	Juliano et al.
6040528	March 2000	Kitamura et al.
6305923	October 2001	Godwin et al.
6394784	May 2002	Gellert et al.
6561789	May 2003	Gellert et al.
6638053	October 2003	Gellert et al.
6649095	November 2003	Buja
6761557	July 2004	Gellert et al.
6780003	August 2004	Sicilia et al.
6805549	October 2004	Gunther
6854971	February 2005	Pilavdzic et al.
7108502	September 2006	Gellert et al.
7131831	November 2006	Bazzo et al.
7147458	December 2006	Schmidt
2006/0292256	December 2006	Gellert et al.

Foreign Patent Documents


3324901	Jan., 1985	DE
8620956	Nov., 1986	DE
9201797.5	May., 1992	DE
4242505	Jun., 1994	DE
19522716	Sep., 1996	DE
19941038	Mar., 2001	DE
444748	Sep., 1991	EP
590621	Apr., 1994	EP
748678	Dec., 1996	EP
765728	Apr., 1997	EP
963829	Dec., 1999	EP
1252998	Apr., 2003	EP
1302295	Apr., 2003	EP
1302296	Apr., 2003	EP
64-58518	Mar., 1989	JP
WO-01/15884	Mar., 2001	WO

Other References

Husky, "1250 Series Hot Runner Manual; Operation and Maintenance", (Mar. 2001), p. 52, 55-57. cited by other .
Husky, "1250 Series Nozzles", (2000). cited by other .
Husky, "Hot Runner Systems", (Oct. 1998). cited by other .
Husky, "Husky 1250 JP Pamphlet", (Oct. 1998). cited by other.

Primary Examiner: Heitbrink; Tim
Attorney, Agent or Firm: Medler Ferro PLLC

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 11/510,994 filed Aug. 28, 2006 which is a continuation of U.S. application Ser. No. 10/601,190 filed Jun. 23, 2003 that issued as U.S. Pat. No. 7,108,502 on Sep. 19, 2006, which is a divisional of U.S. application Ser. No. 10/025,767 filed Dec. 26, 2001 that issued as U.S. Pat. No. 6,638,053 on Oct. 28, 2003, which is a continuation of U.S. application Ser. No. 09/520,843 filed Mar. 8, 2000 that issued as U.S. Pat. No. 6,394,784 on May 28, 2002, the entire disclosures of which are hereby incorporated by reference.

Claims

What is claimed is:

1. An injection molding apparatus, comprising: an injection molding manifold heated by a manifold heater; a mold plate having a well, wherein the mold plate is separated from the manifold by an air space; a mold gate communicating with a mold cavity; an injection nozzle seated in the well and located between the manifold and the mold gate, the injection nozzle having a nozzle body with a nozzle melt bore having a longitudinal axis; a first electrical resistive heater fixed to the nozzle body and having a first wire element wrapped around the nozzle body, the first wire element being electrically insulated from the nozzle body; and a second electrical resistive heater fixed to the nozzle body and having a second wire element wrapped around the nozzle body, the second wire element being electrically insulated from the nozzle body, wherein the first electrical resistive heater and the second electrical resistive heater are positioned from substantially one end of the nozzle body to another end of the nozzle body and wherein the second electrical resistive heater provides redundancy in operation for the first electrical resistive heater.

2. The injection molding apparatus according to claim 1, wherein the first electrical resistive heater and the second first electrical resistive heater have successive windings that are closer together at an end of the nozzle.

3. The injection molding apparatus according to claim 2, wherein the successive windings that are closer together of the first electrical resistive heater are adjacent the successive windings that are closer together of the second electrical resistive heater.

4. The injection molding apparatus according to claim 1, wherein the first and second wire elements are coiled.

5. The injection molding apparatus according to claim 1, wherein the first and second wire elements are folded.

6. The injection molding apparatus according to claim 1, wherein the nozzle is secured to the manifold at one end by a threaded portion and is secured near the mold gate at the other end.

7. The injection molding apparatus according to claim 1, wherein the first and second wire elements are simultaneously operable.

8. The injection molding apparatus according to claim 1, wherein operation of the first and second wire elements permits a higher wattage heater to be obtained.

9. An injection molding apparatus, comprising: an injection molding manifold heated by a manifold heater; a mold plate having a well, wherein the mold plate is separated from the manifold by an air space; a mold gate communicating with a mold cavity; an injection nozzle seated in the well and located between the manifold and the mold gate, the injection nozzle having a nozzle body with a nozzle melt bore having a longitudinal axis; a first electrical resistive heater fixed to the nozzle body and having a first folded wire element wrapped around the nozzle body, the first wire element being electrically insulated from the nozzle body; and a second electrical resistive heater fixed to the nozzle body and having a second folded wire element wrapped around the nozzle body, the second wire element being electrically insulated from the nozzle body, wherein the first electrical resistive heater and the second electrical resistive heater are positioned from substantially one end of the nozzle body to another end of the nozzle body and where the first and the second electrical resistive heaters have successive windings that are closer together at an end of the nozzle.

10. The injection molding apparatus according to claim 9, wherein the first and second wire elements are coiled.

11. The injection molding apparatus according to claim 9, wherein the successive windings that are closer together of the first electrical resistive heater are adjacent the successive windings that are closer together of the second electrical resistive heater.

12. The injection molding apparatus according to claim 9, wherein the nozzle is secured to the manifold at one end by a threaded portion and is secured near the mold gate at the other end.

13. The injection molding apparatus according to claim 9, wherein the second electrical resistive heater provides redundancy in operation for the first electrical resistive heater.

14. The injection molding apparatus according to claim 9, wherein the first and second wire elements are simultaneously operable.

15. The injection molding apparatus according to claim 9, wherein operation of the first and second wire elements permits a higher wattage heater to be obtained.

16. An injection molding hot runner nozzle operable with an injection molding manifold, comprising: a nozzle having a nozzle body and a melt bore therein for delivering melt to a mold cavity, the nozzle having a length defined between an end near the manifold and another end near a mold gate; a first electrical resistive heater fixed to the nozzle body and having a first wire element electrically insulated from the nozzle body, wherein the first electrical resistive heater is spirally wound around the nozzle and traverses substantially the entire length of the nozzle with varying distribution of windings, the first electrical resistive heater to provide heat to the melt bore; and a second electrical resistive heater fixed to the nozzle body and having a second wire element electrically insulated from the nozzle body, wherein the second electrical resistive heater is spirally wound around the nozzle and traverses substantially the entire length of the nozzle with varying distribution of windings, the second electrical resistive heater for redundancy if the first electrical resistive heater fails.

17. The injection molding hot runner nozzle of claim 16, wherein the distribution of windings of the first electrical resistive heater and the distribution of windings of the second electrical resistive heater are substantially the same along the entire length of the nozzle.

18. The injection molding hot runner nozzle of claim 16, wherein the first and second wire elements are coiled.

19. The injection molding hot runner nozzle of claim 16, wherein the first and second wire elements are folded.

20. The injection molding apparatus according to claim 16, wherein the first and second wire elements are simultaneously operable.

21. The injection molding apparatus according to claim 16, wherein operation of the first and second wire elements permits a higher wattage heater to be obtained.

22. An injection molding hot runner nozzle operable with an injection molding manifold, comprising: a nozzle body having a melt bore; a primary heater wire element having cold pin connections for connecting the primary heater wire element to a power supply, wherein the primary heater wire element is wrapped around the nozzle body over the entire length of the nozzle body to heat melt within the melt bore and includes successive windings closer together proximate at least one end of the nozzle; and a redundant heater wire element, wherein the redundant heater wire element is wrapped around the same length of the nozzle body as the primary heater wire element to heat the melt within the melt bore upon failure of the primary heater wire element.

23. The injection molding hot runner nozzle of claim 22, wherein the redundant heater wire element may be operated with the primary heater wire element to obtain a higher wattage heater.

24. The injection molding hot runner nozzle of claim 22, wherein the primary heater wire element and the redundant heater wire element are electrically insulated from the nozzle body.

25. The injection molding hot runner nozzle of claim 22, wherein the primary heater wire element and the redundant heater wire element are fixed to the nozzle body.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to injection molding and more particularly to an injection molding nozzle having an integral electrical heating element surrounded by layered dielectric insulation.

2. Related Art

Heaters for injection molding and hot runner applications are known in the prior art, as demonstrated amply by the following U.S. Pat. Nos.: 2,991,423, 2,522,365, 2,769,201, 2,814,070, 2,875,312, 2,987,300, 3,062,940, 3,550,267, 3,849,630, 3,911,251, 4,032,046, 4,403,405, 4,386, 262, 4,557,685, 4,635,851, 4,644,140, 4,652,230, 4,771,164, 4,795,126, 4,837,925, 4,865,535, 4,945,630, and 4,981,431.

Heaters are of course also amply known in non-injection molding applications, as shown for example in U.S. Pat. Nos. 2,088,586, 2,378,530, 2,794,504, 4,438,322 and 4,621,251.

There are in general three types of heaters known for use in the hot runner nozzles. The first is so-called "integral heaters" which are embedded or cast in the nozzle body. Examples of such nozzles are disclosed in the following patents: U.S. Pat. No. 4,238,671, U.S. Pat. No. 4,386,262, U.S. Pat. No. 4,403,405 and EP 765728. The second is so-called "independent external heaters" which have their own support and that can be removed and replaced. Essentially, in such a design, shown in FIG. 1a, the heating element H is external to the nozzle body N. Heating element H comprises a resistance wire W surrounded by electrical insulating material E and is encased in a steel casing C. Examples of such nozzles are disclosed in the following patents: U.S. Pat. No. 3,553,788, U.S. Pat. No. 3,677,682, U.S. Pat. No. 3,831,004, U.S. Pat. No. 3,912,907, U.S. Pat. No. 4,588,367, U.S. Pat. No. 5,360,333, U.S. Pat. No. 5,411,393, U.S. Pat. No. 5,820,900, EP 748678, EP 963829 and EP 444748. The third is so-called "attached external heaters" which are positioned spirally around the exterior of the nozzle or the nozzle tip but cannot be removed therefrom by reason of being brazed or embedded in the nozzle surface. Referring to FIG. 1b, heating element H' is embedded in a groove G' in nozzle body N'. Examples of such nozzles are disclosed in the following patents: U.S. Pat. No. 4,557,685, U.S. Pat. No. 4,583,284, U.S. Pat. No. 4,652,230, U.S. Pat. No. 5,226,596, U.S. Pat. No. 5,235,737, U.S. Pat. No. 5,266,023, U.S. Pat. No. 5,282,735, U.S. Pat. No. 5,614,233, U.S. Pat. No. 5,704,113 and U.S. Pat. No. 5,871,786.

Electrical heaters have been also used in the design of the so-called hot runner probes. Unlike the hot runner nozzles, the hot runner probes do not comprise the melt channel. The probes are located inside the melt channel of the nozzle and thus create an annular flow. The melt is heated from the inside and this heating approach is not applicable to all materials and applications. Examples of such nozzles are disclosed in the following U.S. Pat. Nos. 3,800,027 3,970,821, 4,120,086, 4,373,132, 4,304,544, 4,376,244, 4,438,064, 4,492,556, 4,516,927, 4,641,423, 4,643,664, 4,704,516, 4,711,625, 4,740,674, 4,795,126, 4,894,197, 5,055,028, 5,225,211, 5,456,592, 5,527,177 and 5,504,304.

Injection molding nozzles having integral heaters typically have electrical heating elements, wound spirally around the nozzle, which offer an efficient response to the many critical process conditions required by modem injection molding operations. There has been a continuous effort in the prior art, however, to improve the temperature profile, the heating efficiency and durability of such nozzles and achieve an overall reduction in size. Most of these efforts have been aimed at improving the means of heating the nozzle.

For example, U.S. Pat. No. 5,051,086 to Gellert discloses a heater element brazed onto the nozzle housing and then embedded in multiple layers of plasma-sprayed stainless steel and alumina oxide. To avoid cracking of the ceramic layers caused by excessive thickness and the differing thermal properties of the ceramic and the stainless steel, Gellert employs alternating thin layers of stainless steel and alumina oxide. The heating element of Gellert is a nickel-chrome resistance wire (i.e. see W in FIGS. 1a and 1b herein) extending centrally through a refractory powder electrical insulating material (i.e. see E in FIGS. 1a and 1b), such as magnesium oxide, inside a steel casing (i.e. see C in FIGS. 1a and 1b). The heating element is integrally cast in a nickel alloy by a first brazing step in a vacuum furnace, which causes the nickel alloy to flow by capillary action into the spaces around the heater element to metallurgically bond the steel casing of the element to the nozzle body. This bonding produces very efficient and uniform heat transfer from the element to the nozzle body.

Nozzles with this type of electrical heaters, however, are often too big to be used in small pitch gating due to the size of the insulated heater required. These heaters are also generally expensive to make because of complex machining required. Also, the manufacturing methods to make these nozzle heaters are complex and therefore production is time consuming.

U.S. Pat. No. 5,955,120 to Deissler which discloses a hot runner nozzle with high thermal insulation achieved by coating the electrical heater with layers of a thermally insulation materials (mica or ceramic) and high wear resistance material (titanium). Like Gellert, the heater element of Deissler has its own electrical insulation protection and thus can be placed in direct contact with the metallic nozzle body (see FIG. 2 of Deissler). Also the heater element of Deissler is attached to the nozzle by casting (brazing) a metal such as brass. Deissler is thus similar to Gellert in that it discloses an insulated and brazed heater element. Again, as with Gellert, such a device requires many additional steps to braze and insulate the heater and is therefore time consuming. Also, as with Gellert, the use of an insulated element makes the size of the heated nozzle not well suited for small pitch applications.

In an attempt to reduce nozzle size, U.S. Pat. No. 5,973,296 to Juliano shows a thick film heater applied to the outside surface of an injection nozzle. The nozzle heater comprises a dielectric film layer and a resistive thick film layer applied directly to the exterior cylindrical surface of the nozzle by means of precision thick film printing. The thick film is applied directly to the nozzle body, which increases the nozzle's diameter by only a minimal amount. Flexibility of heat distribution is also obtained through the ability to apply the heater in various patterns and is, thus, less limited than spiral designs.

There are limitations to the thick film heater, however. Thermal expansion of the steel nozzle body during heating can cause unwanted cracking in the film layers due to the lower thermal expansion of the film material. This effect is particularly acute after a large number of injection cycles. The cracks could affect the resistive film heater because it is not a continuous and homogeneous material (as is a wire), but rather the fine dried powder of the conductive ink, as disclosed in Juliano '296.

Another heated nozzle design is disclosed in U.S. Pat. No. 4,120,086 to Crandell. In one embodiment, Crandell '086 discloses an electrically heated nozzle having an integral heater comprising a resistance wire heater disposed between two ceramic insulating layers. The Crandell '086 nozzle is made by wrapping a metal nozzle body with flexible strips of green (i.e. unsintered) ceramic particles impregnated in heat dissipatable material, subsequently winding a resistance wire heating element around the wrapped green layer, wrapping a second layer of the flexible strips of green ceramic particles thereover, heat treating the assembly to bake out the heat dissipatable material and sinter the ceramic particles together, and then compacting the assembly to eliminate air voids in the assembly. In U.S. Pat. No. 4,304,544, also to Crandell, the inventor further describes the flexible green ceramic strips as comprising a body of green ceramic insulator particles which are impregnated in a heat dissipatable binder material. In the green state, such strips are pliable and bendable, permitting them to be wrapped around the metal nozzle core, but when baked, the strips become hard and the particles agglomerate into a mass.

The Crandell '086 and '544 nozzle has relatively thick ceramic layers, employs an awkward process for applying the ceramic layers and requires additional heat treatment steps in fabrication. Crandell '086 concedes that the baking step is time consuming (see column 5, lines 20-25) and therefore admits that the design is less preferable than other embodiments disclosed in the patent which do not utilize this method. Also, as mentioned above, it is desirable to reduce nozzle size, which is not possible with the thick ceramic strips of Crandell '086 and '544.

The use of ceramic heaters for both hot runner nozzle heaters and hot runner probe heaters is also disclosed in U.S. Pat. No. 5,504,304 to Noguchi. Noguchi, like Juliano, uses a printing method to form an electrical resistive wire pattern of a various pitch from a metal or a composite paste. A ceramic heater embodiment for a nozzle probe (shown in FIG. 1 of Noguchi) is made by printing various electrical resistive patterns shown in FIGS. 3-4 of Noguchi. Noguchi discloses a method whereby a mixture of insulating ceramic powder such as silicon carbide (SiC), molybdenum silicide (MoSi.sub.2) or alumina (Al.sub.2O.sub.3) and silicon nitride (SiN), and electrically conductive ceramic powder such as titanium nitride (TiN) and titanium carbide (TiC) is sintered and kneaded into a paste, which is then printed in a snaking manner on the external surface of a cylindrical insulating ceramic body, as shown in FIG. 3 of Noguchi. The printing state is made denser in certain areas and, by so controlling the magnitude of the so-called "wire density," a temperature gradient is given to the heater. The heater pattern can be formed using metals such as tungsten, molybdenum, gold and platinum. A ceramic heater embodiment for a hot runner nozzle is also disclosed in Noguchi (see FIG. 9 of Noguchi). This self-sustained ceramic heater is also made by wire-printing using the same paste or metals. The heater is placed over the nozzle body and is then sintered and kneaded into a paste comprising a mixture of insulation ceramic powder such as silicon carbide, molybdenum silicide or alumina and conductive ceramic powder such as titanium nitride and titanium carbide. The paste is printed in a single snaking line on the part where, again, the heater pattern is formed by applying temperature gradients by varying the magnitude of wire density across the part.

Although Noguchi introduces a wire-printing method to achieve a certain heat profile along the nozzle it does not teach or show how this wire-printing method is actually implemented. More detailed information about this wire-printing method is provided by the patentee's (Seiki Spear System America. Inc.) catalogue entitled "SH-1 Hot Runner Probe" (undated). According to the catalogue, the circuit pattern, which provides the resistance for heating, is screen printed direction onto a "green" or uncured ceramic substrate. The flexible "green" substrate with the printed circuit is wrapped around an existing ceramic tube and the complete unit is fired and cured to produce a tubular heater. The resistive circuit pattern is encased within the ceramic between the tube and the substrate and has no exposure to the outside atmosphere. The thermocouple is inserted through the centre of the tubular heater and positioned in the tip area. Thermocouple placement in the probe tip gives direct heat control at the gate. The ceramic heater unit is then fixed outside the probe body. Thus, this Seiki Spear method of making a ceramic heater body according to Noguchi including a printed-wire is similar to the method disclosed in Crandell '086, with the exception that Crandell uses a self-sustained resistance wire wound spirally around the nozzle between two "green" ceramic layers. As with Crandell, as well, an additional sintering step is required to sinter the green ceramic layers.

Accordingly, there is a need for a heated nozzle which overcomes these and other difficulties associated with the prior art. Specifically, there is a need for a heated nozzle which is simpler to produce and yields a more compact design.

SUMMARY OF THE INVENTION

The present invention provides an injection molding nozzle which is smaller in diameter than most prior art nozzles but which does not sacrifice durability or have the increased manufacturing costs of previous small diameter nozzles. Further the nozzle of the present invention is simpler, quicker and less costly to produce than prior art nozzles and minimizes the number of overall steps required in production. In particular, the need for heat treating the dielectric materials of the heater is removed entirely, saving time, money and hassle in fabrication. Further, the apparatus of the present invention provides a removable and/or replaceable cartridge heater design which offers the advantage of low-cost repair or replacement of a low cost heater component, rather than wholesale replacement of an intricately and precisely machined nozzle. The methods of the present invention similarly provide reduced and simplified steps in manufacturing, as well as permitting precise temperature patterns to be achieved in a nozzle more simply than with the prior art.

In one aspect, the present invention provides an injection molding nozzle comprising a nozzle body having an outer surface and at least one melt channel through the body, a first insulating layer having a chemical composition, the first insulating layer disposed on the nozzle body outer surface so as to substantially cover at least a portion of the nozzle body, at least one wire element disposed exterior to and in contact with the first insulating layer, the at least one wire element being connectable to a power supply capable of heating the wire element, a second insulating layer having a chemical composition, the second insulating layer disposed over the first insulating layer and the at least one wire element, the second insulating layer substantially covering the at least one wire element and at least a portion of the first insulating layer, and wherein the chemical compositions of the first and second insulating layers remain substantially unchanged once the layers are disposed on the nozzle body.

In a second aspect, the present invention provides an injection molding nozzle comprising a nozzle body assembly having an outer surface and at least one melt channel through the assembly, the assembly having a core and a surface layer disposed around the core, the surface layer forming at least a portion of the nozzle body assembly outer surface, the core being composed of a first metal and the surface layer being composed of a second metal, the second metal having a higher thermal conductivity than the first metal, a first insulating layer disposed on the nozzle body assembly outer surface so as to substantially cover at least a portion of the outer surface, at least one wire element disposed exterior to and in contact with the first insulating layer, the at least one wire element being connectable to a power supply capable of heating the wire element and a second insulating layer disposed over the first insulating layer and the at least one wire element, the second insulating layer substantially covering the at least one wire element and at least a portion of the first insulating layer.

In a third aspect, the present invention provides an injection molding nozzle comprising a nozzle body having an outer surface and at least one melt channel through the body, a first insulating layer disposed on the nozzle body outer surface so as to substantially cover at least a portion of the nozzle body, at least one wire element disposed exterior to and in contact with the first insulating layer, the at least one wire element being connectable to a power supply capable of heating the wire element, a second insulating layer disposed over the first insulating layer and the at least one wire element, the second insulating layer substantially covering the at least one wire element and at least a portion of the first insulating layer, and wherein the first insulating layer is between 0.1 mm and 0.5 mm in thickness.

In a fourth aspect, the present invention provides an injection machine for forming a molded article, the machine comprising a mold cavity, the mold cavity formed between a movable mold platen and a stationary mold platen, at least one injection molding nozzle connectable to a source of molten material and capable of feeding molten material from the source to the mold cavity through at least one melt channel therethrough, the at least one nozzle injection molding having a nozzle body having an outer surface and the at least one melt channel through the body, a first insulating layer having a chemical composition, the first insulating layer disposed on the nozzle body outer surface so as to substantially cover at least a portion of the nozzle body, at least one wire element disposed exterior to and in contact with the first insulating layer, the at least one wire element being connectable to a power supply capable of heating the wire element, a second insulating layer having a chemical composition, the second insulating layer disposed over the first insulating layer and the at least one wire element, the second insulating layer substantially covering the at least one wire element and at least a portion of the first insulating layer, and wherein the chemical compositions of the first and second insulating layers remain substantially unchanged once the layers are disposed on the nozzle body.

In a fifth aspect, the present invention provides an injection mold to form an article, the mold comprising a mold half capable of communication with a mold manifold, at least one injection molding nozzle in flow communication with the mold half through at least one melt channel, the at least one nozzle injection molding having a nozzle body having an outer surface and the at least one melt channel through the body, a first insulating layer having a chemical composition, the first insulating layer disposed on the nozzle body outer surface so as to substantially cover at least a portion of the nozzle body, at least one wire element disposed exterior to and in contact with the first insulating layer, the at least one wire element being connectable to a power supply capable of heating the wire element, a second insulating layer having a chemical composition, the second insulating layer disposed over the first insulating layer and the at least one wire element, the second insulating layer substantially covering the at least one wire element and at least a portion of the first insulating layer, and wherein the chemical compositions of the first and second insulating layers remain substantially unchanged once the layers are disposed on the nozzle body.

In a sixth aspect, the present invention provides an injection molding nozzle comprising the steps of providing a nozzle body, the nozzle body having an outer surface and at least one melt channel through the body providing a first insulating layer on the outer surface of the nozzle body, the first insulating layer having a chemical composition, the first insulating layer substantially covering at least a portion of the nozzle body outer surface, positioning at least one wire element exterior to and in contact with the first insulating layer, the at least one wire element being connectable to a power supply capable of heating the at least one wire element, providing a second insulating layer on the first insulating layer and the at least one wire element, the second insulating layer having a chemical composition, the second insulating layer substantially covering the at least one wire element and at least a portion of the first insulating layer, and wherein the chemical compositions of the first and second insulating layers remain substantially unchanged once the layers are provided on the nozzle body.

In a seventh aspect, the present invention provides an injection molding nozzle comprising the steps of providing a nozzle body, the nozzle body having an outer surface and at least one melt channel through the body positioning a self-supporting insulating sleeve around the nozzle body, the sleeve substantially covering at least a portion of the nozzle body outer surface positioning at least one wire element exterior to and in contact with the insulating sleeve, the at least one wire element being connectable to a power supply capable of heating the at least one wire element, providing a second insulating layer on the insulating sleeve and the at least one wire element, the second insulating layer substantially covering the at least one wire element and at least a portion of the insulating sleeve.

BRIEF DESCRIPTION OF THE FIGURES

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example to the accompanying drawings.

The drawings show articles made according to embodiments of the present invention.

FIGS. 1a and 1b are partial sectional views of heated nozzle configurations according to the prior art.

FIG. 2 is a sectional view of a portion of an injection molding system showing a heated nozzle according to a preferred embodiment of the present invention.

FIG. 3 is an enlarged sectional view of the nozzle of FIG. 2.

FIG. 4 is a further enlarged and rotated (90.degree. counter-clockwise) sectional view of the heater assembly of the nozzle of FIG. 2.

FIG. 5 is an enlarged sectional view, similar to FIG. 4, of an alternate embodiment of a nozzle heater assembly according to the present invention.

FIG. 6 is an enlarged sectional view, similar to FIG. 4, of another alternate embodiment of a nozzle heater assembly according to the present invention.

FIG. 7 is an enlarged sectional view, similar to FIG. 4, of a further alternate embodiment of a nozzle heater assembly according to the present invention.

FIG. 8 is an enlarged sectional view, similar to FIG. 4, of a yet further alternate embodiment of a nozzle heater assembly according to the present invention.

FIG. 9 is an exploded isometric view of an alternate embodiment of the nozzle heater of the present invention.

FIG. 10 is a sectional view of a further embodiment of the nozzle heater of the present invention.

FIG. 11 is an enlarged sectional view of another nozzle embodiment employing a heater according to the present invention.

FIG. 12a is an isometric view of a straight wire element for use as a heater element of the present invention.

FIG. 12b is an isometric view of a coiled wire element for use as a heater element of the present invention.

FIG. 13a is an isometric view of a doubled and twisted straight wire element for use as a heater element of the present invention.

FIG. 13b is an isometric view of a doubled, coiled wire element for use as a heater element of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A multi-cavity injection molding system made in accordance with the present invention is shown in the Figures generally at M. Referring to FIG. 2, a portion of injection molding system M is shown. A melt passage 10 extends from a common recessed inlet 12 in a manifold extension 14 to an elongated manifold 16 where it branches out to a number of outlets 18. As can be seen, each branch 20 of melt passage 10 extends through a steel nozzle 22, having a central melt bore 24 in communication with melt passage outlet 18 from manifold 16 to a gate 26 leading to each cavity 28. Nozzle 22 is a heated nozzle having a heater 30 according to a preferred embodiment of the invention, as described in greater detail below.

Manifold 16 is heated by a heating element 32 which may be integrally brazed into it. Manifold 16 is held in place by a central locating ring 34 and insulating pressure pads 36. Locating ring 34 bridges an insulative air space 38 between manifold 16 and a cooled spacer plate 40. Pressure pads 36 provide another insulative air space 42 between manifold 16 and a cooled clamp plate 44. Spacer plate 40, clamp plate 44 and cavity plate 46 are cooled by pumping cooling water through a plurality of cooling conduits 48. Clamp plate 44 and spacer plate 40 are secured in place by bolts 50 which extend into cavity plate 46. Manifold extension 14 is held in place by screws 52 and a locating collar 54 which is secured to the clamp plate 44 by screws 56.

Each nozzle 22 is seated in a well 58 in spacer plate 40. An insulative air space 64 is provided between heated nozzle 22 and the surrounding cooled spacer plate 40.

Referring to FIGS. 2 and 3, nozzle 22 has a body 68 having a steel central core portion 70, an outer surface 72, and a tip 74, which is seated in gate 26. Tip