Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Reexamination Certificate
2002-07-29
2004-10-19
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
C425S572000
Reexamination Certificate
active
06805549
ABSTRACT:
The invention relates to a nozzle for injection molds and to a nozzle assembly.
BACKGROUND ART
Nozzles for hot runners or cold runners are generally known. They are used in injection molds for feeding a melt flow at a predefined temperature under high pressure to a separable tool block (mold cavity). For example, in order to prevent a hot plastics flow from premature cooling within the nozzle, electric heating means are provided—as described in DE-U1-295 01 450—which concentrically surround the nozzle body or a duct located therein in order to keep the plastics melt at the desired temperature. However, if for example reactive polymers are processed, it is necessary to cool the nozzle body for ensuring that the mass to be processed will not exceed a specific temperature as it enters the mold cavity. A thermosensor is normally used to probe the temperature.
In the case of hot runner nozzles, the nozzle body and the heating element are usually separate component parts, the heating element being integrated with the thermosensor in a jacket to be pushed onto the nozzle body periphery. As disclosed in DE-U1-89 15 318, DE-U1-295 07 848 or U.S. Pat. No. 4,558,210, the surrounding element may be a rigid unit fixed onto the nozzle body in an axial direction by holding or clamping means. Alternatively, flexible heating strips or mats are used which are attached to the perimeter of the nozzle body (see e.g. EP-B-0 028 153 or WO 97/03540).
SUMMARY OF THE INVENTION
An essential drawback of these generally detachable heating devices is their usually inefficient heat transfer from the heating element to the nozzle body. Now in order to protect the heating means from overheating, it is necessary to increase their dimensions whereby the overall assembly size and thus the space required in the mold will also increase. Furthermore, there are problems with the linear temperature distribution in the duct walls. Rarely will these have a constant temperature over the entire length of the duct. By reason of the increased heat dissipation at the tip of the nozzle, an adequate power density and thus constant temperature at this point can only be achieved with relatively high expenditures.
In numerous fields of applications, it will irrespectively thereof be necessary to inject into separate cavities in order to manufacture a number of articles simultaneously or more complex components. To this end, nozzles for hot runners or cold runners are mounted at defined distances parallel to each other in a manifold or manifold block. However, due to the concentric arrangement of the heating or cooling means on the nozzles and to the fact that their electric terminals usually project laterally from the nozzle casings, the nozzles cannot be positioned closely to each other, which will be problematic where cavity spacings are small or gating points are directly adjacent.
For remedy, it was attempted to attain reduced cavity spacings by positioning the nozzle duct and the heating means laterally, e.g. in a hot runner nozzle as described in DE-U1-296 10 268. However, this reduces the width of the nozzle in a preferred direction only, irrespective of the width of the heating means which still is rather voluminous. Another drawback is the fact that heat will dissipate to only one side of the flow melt, thus possibly causing unbalanced temperature distributions in the duct. Adaptation and control of the power input required is only possible within limits since the power density of the heating means, often a heater cartridge, can be tuned to only one particular application at a time. Pluralities of plug connectors and elaborate cable lines not only require additional space but also extra fitting work, in particular where the terminals of the heating means used are in the interior of the nozzle assembly.
It is an object of the present invention to overcome these and other drawbacks of the prior art and to provide a nozzle for an injection mold permitting uniform heat transfer and temperature distribution characteristics within the nozzle body and requiring little space when mounted to a mold. In an economical manner, a structure is to be obtained which can be manufactured and installed with a minimum of expenditures and which ensures long-term operational reliability.
Another important object of the invention is to provide a nozzle assembly containing an arbitrary number of closely packed hot runner nozzles or cold runner nozzles, which assembly is suited to be cheaply produced with simple means and to be quickly installed. Furthermore, the nozzle interior is to provide uniform heat transfer and temperature distribution characteristics.
In a nozzle for an injection mold comprising a nozzle body adapted to be mounted onto a mold or manifold, the nozzle body having at least one duct for a melt flow which duct opens at or in a nozzle tip, and comprising a heating and/or cooling means for the melt flow, the invention provides that the nozzle body has at least one substantially plane lateral face which supports or accommodates said heating and/or cooling means in a full-faced engaging and/or joining arrangement.
This integral connection between the heating or cooling means and said lateral face in the hot runner nozzle guarantees constant optimal heat transfer from the heating unit to the nozzle body, which will be heated extremely uniformly and precisely. Due to the full surface engagement or joining of the heating means with the plane or slightly curved lateral surface of the nozzle body, the hot runner nozzle has extremely small overall dimensions compared with conventional designs, whilst exhibiting almost identical performance. The same applies to a cooling means integrated with the nozzle body, which cooling means is according to a preferred embodiment directly enclosed in the nozzle body and is flush therewith. Heat transfer from the hot medium to the cooling means is always optimal.
Since the heat is generated and dissipated directly at the lateral surface of the nozzle body to be heated, the power density of such a heating unit can be raised considerably and overheating of the usually sensitive heating elements is reliably avoided. Furthermore, there is no need for elaborate control means to regulate delays caused by thermal inertia of the flow melt. The plastics composition in the flow duct is rapidly and precisely heated, which has a favorable effect on the overall production process. Particularly uniform heating or cooling is achieved where two opposing lateral faces are provided with at least one heating and/or cooling means.
Another substantial advantage of the invention consists in that the hot runner or cold runner nozzle has extremely small dimensions due to the heating or cooling means being located directly against or in the nozzle body. This applies particularly if the heating means positioned at the plane and/or at least partially curved lateral surfaces of the nozzle body is designed as a thin lamina heating unit.
According to another embodiment of the invention, temperature sensing is carried out preferably in the same plane where heating or cooling is effected so that no additional space is required. Heating or cooling means and the thermosensor can be provided on the nozzle body in like manner and in a single manufacturing operation whereby production is simplified considerably.
In a nozzle assembly for injection molds comprising at least two nozzles, each having a nozzle body capable of being mounted on a mold or manifold, the nozzle body including at least one melt flow duct that opens at or in a nozzle tip, and comprising a heating and/or cooling means for the melt flow, the invention provides that the nozzles form a nozzle row within which they are disposed closely and parallel to each other, said nozzle row having at least one substantially plane lateral surface for full-faced engagement or joining to said heating and/or cooling means.
Owing to this extremely compact and space-saving design, the tips of the individual nozzles are very closely packed. Such a row of nozzles allows effortless inject
Clark & Brody
Gunther Heisskanal Technik GmbH
Heitbrink Tim
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