DD239981B1 - METHOD AND DEVICE FOR THE INJECTION OF THIN-WALLED METAL PARTS - Google Patents

Description

GERMAN DEMOCRATIC REPUBLIC

(12) Business patent

Partially confirmed in accordance with § 18 (1) Patent Act

PATENT CERTIFICATE DD "ι) 239 981 B1

4 (51) B 29 C 45/14

OFFICE FOR INVENTING AND PATENTING

WP B 29 C / 279 368 2

(22) 05.08.85 (45) (44)

26.10.88 15.10.86

(71) VEB Combined Rolling Bearings and Standard Parts, Reichenhainer Straße 31/33, Karl-Marx-Stadt, 9022, DD

(72) Junghans, Werner, Dipl.-Ök. Pitzing, Günter; Braun, Dieter; Rule, Reinhard, Dipl.-Ing .; Cancer, Joachim; Schaudienst, Horst; Hildebrand, Christian, Dr.-Ing .; Samsel, Reinhold; Hendel, Reinhard, Dipl.-Ing., DD

(54) Method and apparatus for overmolding thin-walled metal parts

(57) The invention relates to methods and apparatus for overmolding of thin-walled metal parts with thermoplastic, which is applicable in the production of Radiai shaft seals, preferably seals on rolling and sliding bearings. The aim of the invention is to produce gaskets, in particular made of polyurethane elastomer, with internal metallic support body in various geometric designs cost and material economy. The object of the invention is to fix an unstable thin-walled, in particular ring-shaped metallic insert to be encapsulated with thermoplastic material within a mold cavity and to geometrically design a device required for this purpose so that the insert is completely surrounded by injection molding compound. The invention is achieved by a geometrically diverse designed metallic insert is clamped by device halves such that this is in the midst of a mold cavity, which corresponds to the profile of the molded part to be produced, in a floating position during injection molding and coated on all sides. Fig. 2

ISSN 0433-6461

pages

Claims (3)

1. A method for overmolding of thin-walled metal parts with thermoplastic, in particular polyurethane elastomer, in which a thermoplastic injection molding compound to be joined metal insert, for example, supporting body for rolling bearing, is coated with thermoplastic in the sealing effective range, characterized in that the geometrically diverse designed metallic Insert (3) is clamped by device halves so that it is in the middle of a mold cavity, which corresponds to the profile of the molded part (11) to be produced during the injection molding in a floating position and coated on all sides, without prior special treatment, such as degreasing,. Sandblasting or applying adhesion promoters. 2. A device for encapsulating thin-walled metal parts with thermoplastic, consisting of a mold cavity enclosing device parts, characterized in that a plurality of dimensionally and geometrically coordinated positioning pins (2,4) in the device upper part (T) and device lower part (5) are arranged, with the insert (3) in the closed state in connection, wherein the insert part (3) between the positioning pins (2,4) is not rigidly fixed. 3. A device according to claim 2, characterized in that the molded part of the upper side (8) facing positioning pins (2) conical, spherical or prismatic and the molding lower side (9) facing positioning pins (4) are formed flat. For this 1 page drawings Field of application of the invention The invention is mainly used in the production of radial shaft seals, in particular of seals on rolling and sliding bearings, which consist of thermoplastic, in particular polyurethane elastomer, overmolded thin-walled metallic support bodies. Characteristic of the known state of the art The known solutions for the production of sealing discs are characterized mainly by the fact that a more or less closed, partially profiled layer of modified rubber or synthetic rubber is applied by vulcanization to a thin-walled metal part {hereinafter support body). Processes and devices for the production of such gaskets require not only a high capital investment technologically conditioned preparations of the metallic support body to enter into a mechanically strong connection between metal and rubber or rubber. A particular disadvantage of the known methods is the removal of the rubber cake on molded Funktionsstelten. In this case, a tear may occur primarily in the region of the sealing lips, which could lead to leaks in the rolling bearing in the subsequent application. Other disadvantages of the known methods and devices are characterized by the fact that by inexact adjustment of the support body, eccentricities between the outer inner edge of the support body and the outer inner edge of the sealing disc can occur. The adverse consequences for the application of the sealing discs made of thermoplastic in bearings by previous methods and devices are possible leaks and increased, one-sided frictional resistance of the sealing lips. In a werteren known method for injection molding of plastic parts with embedded core of the core is currency end of the injection process by means of movable, spring-loaded positioning held (DD-PS 146696). In the phase of pressure increase, the positioning elements are forced back by the injection molding compound to achieve the intended effect of completely enclosing the metal core by the injection molding compound. Thin-walled parts as a metal core are not to be encapsulated with the described method, since such may not have a rigid fixation because of instability. A part of the known methods and devices also require a high workload. The disclosures disclosed according to AT-PS 290225 and AT-PS 309919 show for the process and product an unsatisfactory solution in accordance with today's requirements and expectations. Object of the invention The aim of the invention is to provide methods and devices that make it possible to produce sealing disks, in particular made of polyurethane elastomer, with inlying metallic support body in various geometric designs cost-effective, the application requirements and material economically appropriate. Explanation of the essence of the invention It is the object of the invention to fix an unstable thin-walled, in particular annular metallic insert to be encapsulated with thermoplastic material within a mold cavity in such a way and geometrically to design a device required for this purpose so that the insert is completely surrounded by injection molding compound. The essence of the invention is that a geometrically diverse designed metallic insert is clamped by device halves such that this is in the middle of a Fbrmhohlraumes, which corresponds to the profile of the molded part, during the injection molding in a floating position. The insert is coated on all sides, without prior special treatment, such as degreasing, sandblasting or application of bonding agents. By introducing adapted to the size of the insert flow openings in the insert a positive stable sheath of the insert is guaranteed. To realize the method according to the invention, a plurality of dimensionally and geometrically coordinated positioning pins are arranged in the upper and lower device part in the injection molding tool (device). The positioning pins are in the closed state in connection with the insert, wherein the insert is not rigidly fixed between the positioning pins. The injected into the mold cavity plastic compound is mainly located between positioning pins in the upper part of the device and insert. The positioning of the top part facing pins are conical, spherical or prismatic and the mold bottom facing positioning pins are flat. embodiment The invention will be explained in more detail below with reference to an exemplary embodiment, the use case for producing sealing disks for radial ball bearings being described specifically.
In the accompanying drawings show Figure 1: device upper part and lower part with einzulegendem metallic insert (support body) in the open state Figure 2: device in the closed state after completion of the injection process with completely coated metal support body, still connected to the runner To explain the embodiment, the opened device is installed in a horizontal position in the injection molding machine and described in accordance with Figure 1. An insert 3 to be encapsulated, for example support body, is placed on positioning pins 4 in the device lower part 5 in such a way that circular flow openings 6 are located in the insert part 3 between the positioning pins 4. Thereafter, both halves of the device are closed. The arranged in a device upper part 1 positioning pins 2 are tuned in the protruding in a mold cavity of the device height so that in the closed state of the device halves a distance of 0.02 mm to 0.05 mm between positioning pins 2 and insert 3 is met. With this described device design and the associated technological setting values on the injection molding machine, a closed polyurethane elastomer surface is guaranteed around the insert 3, in particular around the positioning pins 2 in the device upper part 1 and thus on the visible surface of the molded part 11 (corrosion attack surface). When used as radial shaft seals for rolling bearings, the special requirements for a homogeneous surface, a geometrically complete and burr-free formed sealing lip by the particular selection of the gate system 7 and the course of the device parting plane 10 are met. The selected runner system 7, which surrounds the molded parts on the circumference, is removed by mechanical cutting by means of a cutting device in the subsequent operation. The polyurethane elastomers used require pretreatment in the following parameters: - Crushing the splinter granules to a particle size <4mm - Adding liquid lubricant of 0.25Vol .-% to 0.3 vol .-% under the condition of the utilization of residual heat from the predrying process for better wetting of the splinter granules in the temperature range <353 ⁰ K > 333 ⁰ K. The invention achieves the following advantages: - longer life of the molded parts, in particular sealing washers, - Process and device can be realized with any suitable injection molding machine, which guarantees compliance with the technological parameters, without special adaptation, - Realization of simultaneously several moldings, also of different types, in one operation, - Ensuring the production of elastomer moldings in the mass production process.