DE2904415A1 - METHOD OF CASTING A HOLLOW BODY AND A CORE THAT CAN BE USED IN CONNECTION WITH IT - Google Patents

Description

Patontanwälte D i ρ '.- 1 r · g. C U Γι W a I f a c h

Dipl.-ing. Günther Koch

3 · Dipl.-Phys. Dr Tino Haibach

Dipl.-Ing. Rainer Feldkamp

D-8000 Munich 2 Kaufingerstraße 8 Telephone (0 89) 24 02 75 Telex 5 29 513 waKai d

Date: February 6, 1979

Our symbol: l6 5 ^ 2 - Κ / Αρ

Applicant: Lydmet Limited

Tutnalls

Lydney, Gloucestershire GL15 5PX
England

Name: method of casting a

Hollow body and core that can be used in connection with it

909832/0760

• I »·

The invention relates to a method of casting long hollow iron objects, for example for making a camshaft and on a core for making this hollow body.

As is known, the outer shape of a hollow cast body is created by a mold, and the inner cavity can through a core can be generated, which is defined in the shape. Then molten iron is poured in to the space between to fill in the core and the form.

When casting long hollow bodies, for example when casting a camshaft with a length of about 300 mm to 500 mm and an outer diameter (from which the cams protrude) of about 40 mm with a cylindrical central channel of about 7 to 12 mm in diameter, it has proven to be Proven to be inexpedient to use a core made of the material conventionally used for this purpose, for example solidified sand. Such cores are used when the ratio of the core length to the diameter is significantly smaller, as is the case with the casting of typical hollow bodies. The reason why these cores are unsuitable is, on the one hand, their poor strength and, on the other hand, the problem of evacuating the gas generated during casting. These difficulties were found when iron alloys that melt ^{in a temperature range between 1000 °} C. and 1700 ^{° C. were cast.}

Attempts have been made to use ceramic material as the core material. However, it has been shown that the ceramic cores in Use to make an internal cavity that is long compared to the transverse dimension for distortion tend. In the manufacture of camshafts, this means that the passage channel is not concentric to the outer

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. S-

diameter of the shaft over the entire length and as a result such a wave represents a scrap.

The only method previously considered possible for creating a hole of this size and length is this Drilling method is currently used for this purpose only is used. This is costly and time consuming because the shaft must be precisely aligned, and especially with regard to the difficult-to-machine material that has to be drilled, especially with regard to on the carbide build-up that is created by permanent mold casting (cementite).

According to a feature of the invention, the method for casting a hollow body made of iron, the inner cavity of which is long compared to its transverse dimension, is carried out in that a carbon core is inserted into the mold before molten metal in the temperature range between 1000 ⁰ C and 1700 ⁰ C is poured in, wherein the carbon core is designed so that it defines the inner cavity.

According to a further feature of the invention, the core, which is used during the casting of the hollow body made of iron at a temperature of 1000 ° C to 1700 ⁰ C, of carbon. Here, the inner cavity is long compared to the transverse dimension.

The term "iron" as used in the description should be understood according to the common usage, ie it refers not only to pure elemental iron, but also to iron alloys.

In the context of this description, carbon shall mean a

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preselected mixture of graphite and amorphous carbon are understood that are mixed together and to which a suitable binder has been added so that the core is produced in the desired shape under pressure and the core is then heated to a high temperature to form a solid coherent structure create that is suitable for the stated purpose. Such a material is used for arc lamp coals and such cylindrical rods are sold under the name "Morganite CY 9", which are made from extruded carbon exist.

The invention is particularly applicable to the production of camshafts by die casting from iron, that is, of camshafts that are manufactured in that. molten iron is poured into sand molds, the metallic quenching parts that locally accelerate the cooling of the molten metal to foresee the desired Carbic structure (instead of gray cast iron). However, the process can also be used in casting processes, that do not use cooling-accelerating metal inserts.

An exemplary embodiment of the invention is described below with reference to the drawing. In the drawing show:

Fig. 1 is a schematic perspective view of a part of a cam shaft manufactured according to the invention,

Fig. 2 is a perspective view of the for making the

Camshaft according to FIG. 1 used a core made of carbon.

The camshaft (lo) shown in the drawing has a cylindrical shaft (11) with an outer diameter of 4omm, from which the cams (12) protrude in a known manner. Such camshafts are used on a large scale for actuating intake and exhaust valves of internal combustion engines which operate with reciprocating pistons. the

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BATH ORIGINAL

Camshaft has a cylindrical central channel that runs from one end to the other and one Has a diameter of 7mm. This channel should be concentric to the shaft (11) lie within specified tolerances. The total length of such a camshaft, only part of which is shown, can for example be 500mm.

When creating the camshaft x ^ ground two sand molds manufactured using a model, as is customary, to define the external shape of the finished item. The sand molds contain the usual sprue and riser, and they can also be made of ketallic molds from those above have the reasons described.

In order to generate (13) the central passageway, a core is required, which is required to have in this embodiment, 7- ^r rm Au3endurchmesser, and must be of long a genügendos piece are supported as the cam shaft so that parts of the end sections in suitable recesses of the two Pormhälften can. In this case the core is cylindrical and in the form of a hollow rod made of carbon (as defined above).

The ends of the core are inserted into the recesses of the mold before the two halves of the mold are in the usual position Way to form the mold cavity.

Then geschmolzenens eingegoßen metal is in the mold cavity under a temperature in the range between 1000 ⁰ C to 1700 ⁰ C and this flows around the core and solidifies.

It has been found that while ceramic cores are distorted under these circumstances, this distortion is avoided if a core made of carbon (as defined above) is used.

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BATH ORIGINAL

Although a hollow core is preferred because it improves the quality of the cast, probably because it is absorbed Gases are discharged, it is also possible to use a solid core.

The carbon core is removed from the interior of the casting after solidification, either by vibration - impact method or by a rotating grinding device, so that a through hole (I3) is obtained, that from one end of the camshaft to the other cylindrical and concentric within the required tolerances goes through.

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BATH ORIGINAL

Claims (7)

Patent attorneys D i ρ '.- 1 ί <g. Curt Wallach Dipl.-Ing. Günther Koch Dipl.-Phys. Dr Tino Haibach Dipl.-Ing. Rainer Feldkamp D-8000 Munich 2 · Kaufingerstraße 8 · Telephone (0 89) 24 02 75 · Telex 5 29 513 wakai d Date: February 6, 1979 Our reference: 16 502 - K / Ap patent claims 1. Method of casting a hollow iron body, the inner cavity of which is long in relation to Transverse dimension is characterized in that a carbon core is introduced into the mold before molten iron is ^{filled in a temperature range between 1000 0} C to 170 ⁰ C, and in that the carbon core is designed so that it forms the inner cavity. 2. The method according to claim 1,
characterized in that the carbon core is removed from the interior of the cast body after casting. 3. The method according to claim 2,
characterized in that the core is removed by a vibratory impact method or by a rotary grinding method. 4. The method according to claims 1 or 2 or 3, characterized in that the carbon core is cylindrical. 909832/0760 5. The method according to any one of claims 1 to 4, characterized in that that the hollow body is a camshaft. 6. core for performing the casting process according to claims 1 to 5, characterized in that it consists of carbon. 7. core according to claim 6, characterized in that it is designed as a hollow cylinder and consists of a compressed mixture of graphite and amorphous carbon. 909832/0760