CA2358187A1

CA2358187A1 - Nozzle seal

Info

Publication number: CA2358187A1
Application number: CA002358187A
Authority: CA
Inventors: George Olaru; Denis Babin
Original assignee: Mold Masters 2007 Ltd
Current assignee: Mold Masters 2007 Ltd
Priority date: 2001-10-03
Filing date: 2001-10-03
Publication date: 2003-04-03
Also published as: US6945768B2; US6869276B2; US20040191355A1; US20030082264A1; US20050003039A1; US6988883B2

Abstract

A nozzle having a viscosity sealing surface which, when mounted to a mold cavity plate, makes a small gap with the mold cavity plate. Melt enters the gap and may solidify. Due to the viscosity of the melt, the melt in the gad seals against melt from passing through the gap.

Description

. 1 .
Title: Nozzte $eal FIELp OF THE INVENTION
This invention relates to an injection molding machine, and more particularly to a nozzle seal for an injection molding machine.
DESCRIPTION OF THE DRAWINGS
Far a better understanding of the present invention and to show mare clearly how it may be carried intfl effect, reference will now be made by way of example to the accompanying drawings, showing articles made according to a preferred embodiment of the present invention, in which:
Figure 1 is a sectional view of a portion of a nozzle in accordance with a first embodiment of the present invention;
Figure 2 is a magnified view of a sealing portion of the nozzle shown in Figure 1;
Figure 3a is a sectional view of a portion of a nozzle in accordance with a second embodiment of the present invention;
Figure 3b is a magnified view of a sealing portion of the nozzle shown in Figure 2;
Figure ~c is a sectional view of a portion of a nozzle in accordance with a third embodiment of the present invention;
Figure 4 is a sectional view of a portion of a nozzle in accordance With a fourth embodiment of the present invention;
Figure 5 is a sectional view of a portion of a nozzle in accordance with a fifth embodiment of the present invention; and Figure B is a sectional view of a portion of a nozzle in accordance with a sixth embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
3D Reference is made to Figures 1 and 2, which shows a nozzle 10, in accordance with a first embodiment of the present invention. Nozzle 10 is for transferring melt from a manifold in a hot runner injection molding machine to a mold cavity 11 in a mold cavity plate 12. Moid cavity cooling channels 13 may optionally be included in mold cavity plate 12. Naz~le 10 has a body 14, a tip 16, a nozzle seal piece 1$ and a nozzle guide 18. Th$ b4dy 14 has an inner layer 20, a heater 22, and an outer layer 24. Body 1fi may also include a thermocouple 26. ~'he body '14 has a melt passage 28 that passes therethrough that ends at the end of the tip 16.
6 ' The tip 16 may be removable from the body 14, or alternatively may be fixed to body 14. The tip 16 may be made of a thermally conductive material, such as Be-Cu, Tungsten Carbide WR (wear resistant). The tip 16 has a melt pa$cage 30 therethrough that communicates with the body melt passage 28.
The melt passage 30 may exit from tip 1fi into a chamber $2 that surrounds nozzle tip 16. The chamber 32 ends at a gate 34, which opens into the mold cavity 11.
Melt passes from a melt source, through one or more manifold runners, through the nozzle body melfi passage 2B, through the tip melt passage 30, through the chamber 32, through the gate 34 and fnally into mold cavity 11.
The centre of the gate 34 defines an axis 36, which is generally parallel to the direction of flow of melt through gate 34, into the mold cavity 11.
The tip melt passage exit into the Chamber 3~ is shown at 38. Exit 38 may be concentric with respect to axis 36, as shown, or alternatively exit 38 may be positioned off-centre from axis 36_ The seal piece 1 S may be removable from the tip 1B, or alternatively, may be integral with the tip 16. The seal piece 18 may be made of a less-thermally conductive material such as titanium, H13, stainless steel, mold steel or chrome steel, for example. The seal piece 18 may, for example, include a threaded portion 40 for mating with a corresponding threaded portion on the nozzle body 14. Alternatively the seal piece 18 may include an internal thread to mate with an external thread on the nozzle body 14. Seal piece 18 may also include a hexagonal gripping portion 42, for receiving a removal tool, so that seal piece 18 may be removed from nozzle body '14.
The seal piece 18 has an annular sealing portion 44 at the junction between the seal piece 18 and the mold cavity plate 12. The inside surface of sealing portion 44 makes up one of the surfaces that define chamber 32.
Sealing portion 44 includes a viscosity sealing portion 46. The viscosity sealing portion 46 is made up of a conical surface 47a and a vertical surface 47b, which make up a sealing surfaces 4? that is positionecJ so that a small gap G exists between the sealing surface 47 and the mold cavity plate 12. Melt from chamber 32 eventually Ells in the gap G betwaell the viscosity sealing surface 47 and the mold cavity plate 12. Because of the viscosity of the melt in a typical Gljeetidn molding application, once the melt flows into the S gap G to fill a portion or more of the gap G, the sealing portion 48 pr~vents melt from traversing therethrough. The narrow gap G in conjunction with the viscosity of the melt acts as a seal. The melt that eaters the gap G may solidify, due to the narrowness of the gap and the class contact of the melt with the nozzle seal piece 18, which may be less thermally conductive than the tip 16. An advantage to including a viscosity sealing portion 46 is that the manufacturing tolerances for this portion of the seal piece 18 are reduced, relative to a typical mechanical sealing portion. Gap G is preferably between approximately .02 and approximately .07 mm if it the sole seal and is not combined with a mechanical seal.
Because of the relatively generous tolerances in the sealing surface 47, nozzle guide 'i8 is included to provide an alignment means for the nozzle 10 with respect to the gate 34. The nozzle guide 19 has an outer rim 50 that provides a alone flt with the bare 52 of the mold cavity plate 12.
Reference is made to Figure 3a and 3b, which show a nozzle 60 in accordance with a second embodiment of the present invention. Nozzle 6Q is similar to nozzle 10, except as follows. NQZZIe 54 does not include a nozzle guide 19. Nozzle fi0 includes nozzle body 14, tip 16 and a nozzle seal piece 61. Nozzle seal piece 61 is similar to seal piece 18, but has a sealing portion 62, which includes viscosity sealing portion 4B and a mechanical sealing portion B4. The mechanical sealing portion 64 may act as a backup seal to the viscosity sealing portion 46, or may work in conjunction with the viscosity sealing portion 46 so that the tolerances on the viscosity sealing portion 48 may be loosened further. In this embodiment gap G may be approximately .15 mm with a range of approximately .05 to .35 mm in combination with a mechanical seal. Furthermore, the mechanical sealing portion fi4 can be any suitable mechanical seal for injection molding applications. For example, the mechanical sealing portion 64 may consist of an interference fit between the seal piece 18 and the bore 50 on the mold cavity plate 12. The mechanical eealin~ portion G~ ~hQwn in this embodiment may act both as a acel end as . I~ .
an alignment means fur the nuzzle 10 with respect to the gate 34 ort the mold cavity plate 92. Alternatively, the mechanical sealing portion 64 be any other type of seal and a separate alignment means may be located elsewhere on the nozzle B0.
Reference is made to Figure 3c. The tip melt passage 30 may alternatively exit off-centre from the axis 30 of the gate 3A.. Far example, the tip 18 may include a melt passage having one of more exits (ie. the melt passage 3a may divide near its end) that are off centre from gate axis 3fi.
Reference is made to figure 4. The tip melt passage 30 is offset, similar to the embodiment in Figure 3c. An alternative viscosity sealing portion 80 is shown, having a conical sealing surface 82 with no accompanying vertical surface. A meahanioal sealing portion 84 may be included, as shown, and optionally a separate alignment means.
Reference is made to Figure 5, which shows an alternative viscosity sealing portion 90, which has a vertical sealing surface 92. A mechanical sealing portion 94 may be included, as shown, and optionally a separate alignment means As shown in Figure 6, an alternative viscosity seating portion 100 is shown, having a horizontal sealing surface 102. In this embodiment, a mechanical sealing portion 104 may be included, and provides a aont2~Ct surface between the nozzle and the mold cavity plate, so that the gap G
exists. In this embodiment, a separate alignment means is required, because the mechanical sealing portion 104 is horizontal and does not help to position the nozzle.
It will be ,appreciated that the particular configuration ~f the vi$eosity sealing portion can be selected depending on the specific molding application.
While the above description constitutes the preferred embodiments, it will be appreciated that the present invention is susceptible to modification and change without departing from the fair meaning of the accompanying claims.

Claims

1. An injection molding machine comprising:
an injection manifold having a plurality of melt channels an injection nozzle in communication with the manifold having a nozzle body, a melt channel and a nozzle tip a nozzle seal element located adjacent said nozzle tip, said nozzle seal element having an outer sealing surface []
a mold gate opening area having a substantially cylindrical wall portion surrounding a mold gate orifice and located adjacent said nozzle seal element, a viscous seal located between the outer surface of the nozzle seal and the wall portion], whereby the viscous seat retains a small quantity of molten material during the first injection cycle.

2. An injection molding machine having a nozzle seal as described in claim 1, in Combination with a mechanical seal.