GB2061782A

GB2061782A - A core assembly for producing castings provided with thin passages

Info

Publication number: GB2061782A
Application number: GB8028225A
Authority: GB
Original assignee: KLOTH SENKING METALLGIESSEREI
Current assignee: KLOTH SENKING METALLGIESSEREI
Priority date: 1979-09-15
Filing date: 1980-09-02
Publication date: 1981-05-20
Also published as: IT8024618A0; FR2464767A1; JPS5674350A; IT1132820B; SE8006353L; NL8004918A; ATA454480A

Abstract

The assembly comprises a plurality of core sections (1, 2), each core section comprising an external wire coil (1a, 2a) formed from juxtaposed successive convolutions of a wire and an internal structure formed from at least one further wire (16, 26) so as to act as a support for the external coil, the core sections (1, 2) being soldered (3) together. A covering (4) is provided in the region of the interconnection of the core sections. <IMAGE>

Description

SPECIFICATION Core assembly for producing castings The present invention relates to a core assembly for use in casting. In casting technology, it is often desired to provide a casting with cavities. Cores are therefore inserted into the mould to hollow out such opening. Such cores usually comprise core sand bonded with a bonding agent and the cores are removed after the casting has cooled.

Recently, it has become desirable to provide long thin passages in the castings which, in use, form conduits for hydraulic or pneumatic fluids. Such passages cannot usually be formed long enough and/or of small enough bore utilising sand cores, because sand cores which are long and of small diameter are prone to collapse both during their manufacture and during further processing such as their finishing and insertion into the mould.

Moreover, such cores are often unable to stand up adequately to the forces which occur during casting, so that even if it proves possible to insert the cores in an undamaged manner into the mould, a relatively large percentage of faulty castings are produced.

To remedy this, cores have been proposed which comprise external wire coil formed by closely juxtaposing successive convolutions of a wire and an internal structure made from at least one further wire which acts as a support for the external coil. To enable branched passages to be produced in castings, a core made of a plurality of interconnected core sections is required.

Such cores are already known. In one type of such a core, the core sections are interconnected in that the central wire of one core section projects beyond the end of the section into a bore provided in the central wire or a second core section. However, to achieve this, the first central wire must either have a smaller diameter than the second central wire or must be provided with a pin machined thereon. Apart from the fact that a plug-type connection of this type in which a pin has to be machined onto the end of a wire, is expensive to produce, the plug and sockettype connection weakens the core structure, particularly those core sections provided with a socket-type bore.

In a second known type of core the core sections are interconnected by extending the external wire coil of one core section so that it envelops a further core section. Such a core assembly has the advantage that the core sections are not weakened. On the other hand, due to the absence of a closing shape, it is more difficult to prevent the outer core section from sliding along the inner core section, particularly under the effect of the forces which occur during casting. Moreover, although free wire coiled section of the inner core section is securely retained in that its end is anchored between the convolutions of the external wire coil of the other core section, a problem arises in that the core sections cannot be separated from one another when they are to be removed from the casting.

The present invention seeks to provide a core assembly for producing castings having thin passages which core comprises a plurality of core sections having an external wire coil formed of closely juxtaposed successive convolutions of a wire and an internal structure formed from a further wire which acts as a support for the external coil.

The invention further seeks to provide a core assembly in which the core sections are interconnected in a simple and reliable manner but which, nevertheless, on completion of the casting operation, may be readily disengaged from one another and removed from the casting.

According to the present invention, there is provided a core assembly for producing castings provided with thin passages comprising a plurality of core sections, each core section comprising an external wire coil formed from juxtaposed successive convolutions of a wire and an internal structure formed from at least one further wire so as to act as a support for the external coil, the core sections being soldered together.

It has been found particularly favourable if the soldering agent comprises a soft solder. It is desirable if the solder comprises a solder paste.

In a preferred embodiment of the invention, the core sections have a covering in their regions of interconnection. This further increases their secure connection before the completion of the casting. At the same time, it is ensured that the casting particularly in the regions of the branched passages has satisfactory transitions and substantially radiused edges. It is advantageous if the covering comprises a foil strip woven from glass fibres.

The invention will be further described, by way of example, with reference to the accompanying drawings, the single Figure of which shows a partially schematic view of a core assembly in accordance with the present invention.

In the Figure there is shown a core assembly comprising two core sections 1 and 2.

Each section comprises an external wire coil 1 a, 2a formed of closely juxtaposed successive convolutions of a wire. The core section 1 has a central wire 1 b acting as a support for the wire coil 1 a. Similarly, the core section 2 has a central wire 2b acting as a support for the wire coil 2a. The central wire 2b of the core section 2 projects from the wire coil 2a to the extent of the width of one convolution of the coil 2a, the end thereof protruding between convolutions of the wire coil 1 a and being soldered, in the region 3, to the central wire 1 b of the core section 1. As the solder, a solder paste comprising a soft solder is employed. In the connecting region of the core sections 1 and 2, a covering 4 is provided which comprises a foil strip woven from glass fibres.

The removal of the core from the completed casting can be effected without problems. The heat of the casting material, during the casting process, causes the foil strip to weaken and the solder connection to become undone, or at least weakened so that the removal of the core sections causes substantially no difficulties. Firstly the central wires 2b, l b are drawn or pulled. Subsequently thereto, the wire coils 2a, 1 a may be pulled out so as to form an elongate wire. In other words, by so doing, successive convolutions lose contact with the casting.

Claims

1. A core assembly for producing castings provided with thin passages comprising a plurality of core sections, each core section comprising an external wire coil formed from juxtaposed successive convolutions of a wire and an internal structure formed from at least one further wire so as to act as a support for the external coil, the core sections being soldered together.

2. A core assembly as claimed in claim 1 wherein the solder comprises a soft solder.

3. A core assembly as claimed in claim 1 or 2, wherein a solder paste is used as the soldering agent.

4. A core assembly as claimed in any preceding claim- wherein the core sections, in their connecting region are provided with a covering.

5. A core assembly as claimed in claim 4 wherein the covering comprises a foil strip woven from glass fibres.

6. A core assembly constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.