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
2000-10-11
2002-06-25
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
C264S328150
Reexamination Certificate
active
06409497
ABSTRACT:
BACKGROUND
This invention pertains to a hot runner nozzle for injection-molding forms with a nozzle body having a throughput channel with a nozzle outlet opening for melts. On the outer perimeter of this nozzle is at least one jacket-heating unit to heat the nozzle body. The heating unit is enclosed at its outer perimeter by a sleeve, and the sleeve and the heating unit are flexible in the radial direction.
This type of hot runner nozzle is known from patent No. U.S. Pat. No. 5,411,392. It has a sleeve-shaped heating unit that has a continuous slit in the axial direction and whose inside lies adjacent to the outer perimeter of the nozzle body and encloses it. A sleeve that has a continuous slit in the axial direction and that is made of an elastic spring material encloses the heating unit. In its un-tensioned rest position, the sleeve has a smaller inside diameter than the outer diameter of the heating unit. In the operational position, the heating unit is pressed from the outside by a clamping force created by the restoration force of the elastic spring material of the sleeve. This clamping force presses the heating unit against the nozzle body. By pressing the heating unit against the nozzle body, a lower thermal resistivity, and thus a good thermal coupling between the heating unit and the nozzle body is attained. Also, the heating unit is fastened to the nozzle body. However, the known prior art hot runner nozzle has the disadvantage in that the clamping force of the slit retainer relaxes when it is heated. Also, due to the high temperatures occurring when heating the hot runner nozzle, the clamping force of the sleeve can relax after a long period of standing so that the nozzle body then is no longer sufficiently heated. It is also not beneficial that the sleeve has to be widened against the restoration force of its spring material when it is installed or removed from the heating unit using a suitable stretching device so that it can be pushed onto the heating unit or removed from it. The installation and removal of the hot runner nozzle as is required, for example for maintenance work on the heating unit, is thus relatively complicated.
From DE 30 46 471 A1, there is already known a hot runner nozzle of the type mentioned above that has a sleeve that is closed around the perimeter and has a somewhat smaller inner diameter than the outer diameter of the heating unit and that is pressed onto the heating unit. The heating unit has an electrical heating coil with a multitude of windings that are placed in a helical notch incorporated into the outer jacket of the nozzle body. In this way, the transfer of the heat generated by the heating unit to the nozzle body is improved. The hot runner nozzle has, however, the disadvantage in that the heating coil placed in the helical notch cannot be removed from the nozzle body in a practical manner. The contamination accumulated during operation of the hot runner nozzle between the sleeve and the nozzle body can thus not be removed, which reduces the lifespan of the hot runner nozzle accordingly.
From DE 195 14 487 A1, there is a hot runner nozzle of the above-mentioned type with a heating unit designed as a heating coil. Here, the heating coil is located on the inside of the sleeve and is welded to it. The inside diameter of the heating coil is somewhat larger than the outside diameter of the nozzle body. The sleeve has a threaded penetration in the radial direction in which a locking screw is located. With this locking screw, the sleeve can be fastened against the nozzle body. However, the disadvantage is that in the clamped position the heating coil located on the inside of the sleeve only sits against the side of the nozzle body opposite the locking screw, whereas a gap is formed between the nozzle body and the heating coil on the other side of the nozzle body. The heat generated by the heating coil is thus introduced to the nozzle body unevenly at its perimeter.
From U.S. Pat. No. 4,968,247, another hot runner nozzle of the above-mentioned type is known in which the sleeve is designed as a pipe strap with a sheet-metal strip extending around the perimeter of the heating unit. The opposite ends of this sheet-metal strip are connected to a stretching device that has an eccentric locking element located alongside the nozzle body that is used to fasten the sheet metal strip to the heating unit and thus to press the heating unit against the nozzle body. The stretching device also enables a largely even pressing of the heating unit against the nozzle body around the perimeter of the heating unit, but also has the disadvantage in that it requires a relatively large amount of space such that in the injection mold form, an open area must be provided for the stretching device. Due to the limited space relationship in the area of the injection molding form, this is frequently not possible, or is only possible at great expense. Also, the bending stiffness of the injection mold form parts is reduced due to the open space such that they can deform by bending due to the injection molding pressure.
SUMMARY
Therefore, the object is to create a hot runner nozzle of the type mentioned above that is designed compact, enables simple installation and has good thermal coupling between the heating unit and the nozzle body.
This object is met in that the sleeve is enclosed on its outer perimeter by at least one circular lock that can rotate about its longitudinal axis relative to the sleeve between a released position and a clamped position, that the surfaces of the sleeve and the lock that are facing one another each have a profile that deviates from that of a cylindrical shell that is concentric to this longitudinal axis, and that at least one of these surfaces facing one another is designed in areas as a wedge lock surface that has an abutting slant in the clamped position in a plane orthogonal to the longitudinal axis, the surface of the other part lying in this plane with a seating area.
Thus, the lock can be rotated in a simple manner about its longitudinal centerline from the released into the clamped position relative to the retainer, and can be locked to this retainer. Here, when the lock is in the clamped position it can be released from the retainer by rotating it in the reverse direction again and can be pulled off axially to remove the hot runner nozzle from the nozzle body. In an advantageous manner, the locking device formed by the lock and the locking sleeve enables a compact designed hot runner nozzle in which all parts of the locking device are arranged tightly against the nozzle body in the radial direction, which saves space. Thus, the hot runner nozzle can also be installed where there are limited spaces in an injection mold form. In the process, the parts of the locking device located on the outside perimeter of the nozzle body are nonetheless still accessible. Based on the compact dimensions of the hot runner nozzle, only relatively small recesses need to be provided in the injection mold form to insert the hot runner nozzle. This keeps the bending resistance of the injection mold form high. The hot runner nozzle also enables a simple installation and removal, which is especially advantageous in performing maintenance work on the hot runner nozzle and/or the injection mold form.
In the clamped position, the abutting slant of one of the two parts (lock, sleeve) lies against the seating area of the other part (sleeve, lock), so that the two parts are locked against one another. Here, the angle between the abutting slant against the seating area or the seating position and the cylindrical shell of a cylinder arranged concentric to the longitudinal axis of the retainer and extending through the seating position is designed such that the lock in the clamped position is fastened self-locking at the perimeter of the sleeve. Between this cylindrical shell and the abutting slant, a wedge gap is formed in the seating area that transfers the rotating moment, which acts between the lock and the sleeve when rotating the lock from the released po
Heitbrink Tim
Otto Manner Heisskanalsysteme GmbH & Co. KG
Volpe and Koenig P.C.
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