DE2048704A1 - Method for connecting a metal part with a molded plastic part - Google Patents

Description

TOE NATIONAL CASH REGISTER CX) MPANY 4 U 4 Q / U H Dayton, Ohio (V.St.A.)

Patent application no .:
Our reference: 1228 / Germany

PROCESS FOR BONDING A METAL PART WITH A CAST PLASTIC STUFF

The invention relates to a method for connecting a metal part with a plastic part produced by a casting process.

In known methods for connecting metal parts with plastic parts the metal part is partially cast into the plastic, the cast piece of the metal part preferably being shaped so that this is mechanically anchored in the plastic. However, the metal-plastic connections produced in this way have the disadvantage that they break or loosen easily when subjected to shock loads. These difficulties occur in particular when using plastic as a carrier for the print hammers of high-speed printers. These hammers will carried by one or more feathers. Metal trelves are preferred as springs used, one end of which is embedded in the hammer body and are attached at their other end to the frame of the printing device. Attempts to make the known metallic hammer body by such However, replacing plastics, which are easier and cheaper to manufacture, have not given satisfactory results because the Metal! -Plastic connection are not able to cope with the strong and rapidly successive shock loads.

The invention now relates to an improved method of joining a metal part with a body made of castable plastic.

9th 1970

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Accordingly, the invention relates to a method for producing a partially embedded in a molded plastic body Metal part, which is characterized in that the metal part is provided with an adhesive layer at its end to be cast and then embedded in the molten plastic, after which it is listened to, and that the adhesive is elastomeric or during or after the hardening of the plastic in an elastoraeren Condition is hardened.

With this method it is possible to create a metal1-plastic connection produce by a single casting process, in which the molded plastic body, for example a Print hammer, can be made. The elastomeric adhesive or the adhesive that is thermally and / or chemically converted into an elastomeric Cured state is used to create an elastic adhesive bond that attaches to the metal! -Plastic connection able to absorb impact loads. The contact established by the method according to the invention between the adhesive and the material of the hammer body is much more intense and uniform through the well-known Einkfcben a metal part can be achieved in a prefabricated plastic body.

For the person skilled in the art, there are no difficulties in finding adhesives or mixtures of suitable for the process according to the invention Select adhesives. If a heat-curable adhesive is used, the curing can be partial or complete due to the heat acting on the adhesive during the casting process. However, it is also possible to harden the adhesive after the plastic body has hardened through a special heat treatment to effect. However, it must be ensured that the adhesive used can withstand the temperatures occurring during the casting process.

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^ 204870A

d. H. that no decomposition or any adverse affect on it Adhesive properties occurs.

The adhesive coating can be applied to the metal part in any way be applied. Preferably, the metal part is first coated with trichlorethylene or another cleaning agent degreased and then applied a solution of the adhesive and the solvent evaporates.

For the casting of the pressure hammer body, a person skilled in the art offers itself Variety of castable plastics. Glass fiber reinforced materials are preferred Nylon used. Epoxy resin modified with nitrile polymer is particularly suitable as an adhesive for this. Polyurethane adhesives however, they have also been used successfully. The invention is described below with reference to drawings which relate to a preferred one Embodiment referring to in addition to that described Adhesive bonding uses a mechanical anchor to attach a spring to a pressure hammer body. This double anchorage is extremely difficult to achieve using conventional methods.

In the drawings shows:

Fig. 1 is a schematic representation of a printing mechanism with a print hammer and retaining or return springs; Figure 2 is a sectional view of the hammer and springs; 2A is an enlarged sectional view of a junction between a spring and the cast print hammer.

From Fig. 1 it can be seen that the hammer carried by two springs 31 is moved by a lever 17 when the electromagnet 5 ^ is energized.

As a result, the impact insert 4l is moved against a type located, for example, on a moving type chain or another type carrier. A stop control element kh limits the hammer movement j and the springs J> \ bring it back to the rest position. The electromagnet was de-energized before the pressure contact was reached. Supporting spring stops 33 and 39! E Limitation of the spring movement. The ends of the springs are fastened to the frame of the printing device by fasteners y 1 and 35. The fasteners may contain an adhesive to absorb shock loads between the spring and the frame.

Fig. 2 shows the hammer 28 with attached by the novel process on it springs 31. The striking head kl can also be a

JBl 9. WO 209R19 / 0111

Type element can be replaced if a direct print is to be followed by a print haramerjeif intended for each type.

- In Fig. 2A, the embedded in the hammer 28 end of the spring Jtt is shown. This end is bent into a ring, so that the stresses that occur are distributed more evenly over the entire connection point and better mechanical anchoring of the spring in the material of the hammer body is achieved. The adhesive 60 bt the spring and binds it to the material of the hammer body. Due to the elastomeric properties of the adhesive, there is a certain elasticity within the connection point. The pin JQ, which can consist of the same material as the hammer body, results from the manufacturing process preferably used for this connection, which is described in more detail below. The groove 69 is achieved by the design of the casting mold and serves to distribute the stresses more evenly.

The method of manufacturing the pressure hammer according to the invention consists essentially in embedding the metal part coated with the adhesive in the molten plastic, which is then hardened to form the hammer body. This can expediently take place in that the end of the adhesive-coated metal part is placed in a casting mold which is then filled with the molten plastic in the usual manner. The metal part can be fixed in any way in the mold before the plastic is poured in. Preferably, this can be done by a pin whose Druchmesser coincides with the inner diameter of the annular part JII of the spring, is inserted into this ring and removed after casting. The resulting hole is then filled by inserting the aforementioned pin 350. This can in turn take place in that a rod made of the material of the hammer body, which is coated with the adhesive 60, is pushed into the hole and then cut to the appropriate length.

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The pin J5O can, however, also be formed by the hole is filled with a curable polymeric substance that is the same can be like the polymeric substance used as an adhesive, if it is curable. This polymer is then mapped Substance. The latter method is more economical than the former and is therefore preferred. However, it is Care should be taken during the hardening process that no shrinkage occurs which would reduce the diameter of the pin.

From Pig. 2A, it can be seen that the adhesive 60 completely surrounds the pen using the former method. If a pen is not used to position the spring during the casting process, the adhesive in area 4o and that is omitted The inside of the annular end of the spring is filled with the material of the heart body and forms a unit with it. The shape of the hammer and the metal part can be varied as desired without deviating from the principle of the invention. aside from that Metal parts other than the springs mentioned can also be connected to the hammer by means of the method according to the invention. For the impact insert 41 and the arrangement 63 (see Fig. 2) has however, the application of the method according to the invention has not been found necessary, since these elements do not have such strong stresses are exposed like feathers.

For the manufacture of the hammer body, glass fiber reinforced is preferred Nylon with 40 wt. # Glass used. The adhesive known as WE 4O3O-D is preferably used as the epoxy-nitrile adhesive, containing an acrylonitrile butadiene modifier and manufactured by American Cyanamid Company. Another suitable one Adhesive is EC-2290 manufactured by Minnesota Mining and Manufacturing Company.

The following is a specific example of the invention Procedure described in more detail.

The annularly bent ends of the springs 31 are several times

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one after the other degreased in tri-steam, after which they are in trichlorethylene, then in methyl ethyl ketone and then in a sodium dichromate solution can be immersed at 65 C. They are then deionized with Rinsed off with water. The sodium dichromate solution consists of 450 g of sodium dichromate, 4o8 ecm sulfuric acid with a specific gravity of 1.8354 and 2 250 ecm distilled water. The immersion time everyone Liquid takes several minutes each and the feathers are dried after each immersion process and after the final rinse.

The cleaned ends of the springs are now provided with a layer of the adhesive WE 4030-D. This should be done within an hour happen after the regeneration process and can be done in that a solution of the glue in 44 ". Dichloromethane on the surface the spring is sprayed on. The coating is first for one hour at room temperature and then for 20 minutes at 70 C in one Oven dried. The adhesive-coated springs are now used for the production of the print hammer by means of fixing pins Casting mold attached. The impact inserts 41 and other elements 62 are also after a cleaning process in trichlorethylene fixed in the mold.

Now the glass fiber reinforced nylon is poured into the mold.

spritzt./Temperature of the mold is 70 C and the temperature of the Spray nozzle 300 ° C. The injection pressure is 32 to 39 kg / cm.

The finished hammers are removed after cooling, from the mold and the remaining by the locating pins, holes are closed by inserting adhesive-coated nylon _w rods, the holes may also be coated with adhesive before. The nylon rods are then cut to the required length. The hammers are now left at room temperature for about an hour and the adhesive is then cured at 168 ° C. within 40 minutes.

In the case of several hammers used as test samples, a force of It takes more than .19 kg to pull a spring out of the hammer body.

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Claims (10)

—Υ— claims 1. A method for producing a metal part partially embedded in a cast plastic body, characterized in that the metal part is provided with an adhesive layer at its end to be poured in and is then embedded in the molten plastic, after which it is hardened, and that the adhesive is or is elastomeric is cured during or after the curing of the plastic in an elastomeric state. 2. The method according to claim 1, characterized in that the metal part is curved or shaped in some other way to achieve mechanical anchoring in the molded plastic. 3. Process according to claims 1 or 2, characterized in that said end of the metal part is placed in a casting mold which is then filled with the molten plastic. 4. The method according to claims 1 to 3 » characterized in that the adhesive is cured after curing of the cast body by heating and / or a chemical reaction in an elastomeric state. Method according to claims 1 to 4, characterized in that the metal part and the plastic part form a cast pressure hammer body with metal springs firmly connected to it, on which the hammer can move during the printing operation in the printing device. 6. The method according to claims 1 to 5 » characterized in that the plastic is glass fiber reinforced nylon. 7. Method according to claim 6, characterized in that the proportion of glass fibers is approximately 40 % of the total weight. 9/30/1970 209 819/0111 8. The method according to claims 1 to 7, characterized in that the adhesive is or contains a mixture of epoxy resin and Ni tr Llpolymer. 9. The method according to any one of claims 1 to 7, characterized in that the adhesive is or contains polyurethane. 10. A component consisting of a metal part partially cast in a plastic body, characterized in that an intermediate layer of elastomeric adhesive is arranged between the metal and the cast plastic. 1970 ? 0 9 M 9 / Π 1 1 1