GB2136717A - Casting chain - Google Patents

Abstract

Chain is cast in a mould comprising identical upper and lower halves each including a sequence of cavities (30, 31) fitted with identical core-pieces (C1, C2) which abut when the two parts of the mould are assembled. Each cavity is formed with a space (V1) co-operating with a corresponding space (V2) in the respective core-piece to define half of a vertical link, of which the other half is defined by corresponding spaces in the other half of the mould. The abutting faces of corresponding core pieces (C1, C2) are formed with spaces (H1, H3) defining the end portions of adjacent horizontal links, of which the central portions are defined by pairs of spaces (H2) in mating surfaces of the two parts of the mould and the opposite end portions are defined by similar spaces in the next adjacent pair of core pieces. A runner (20) extends along the junction of the two parts of the mould and communicates with the lower part of each space and a riser (24) communicates with the upper part of each space. <IMAGE>

Description

SPECIFICATION Casting chain The production of chain by a casting process has various advantages from the point of view of the properties of the chain itself, but previous proposals have involved such complicated moulds and procedures that the process as a whole has not proved economic. It is an object of the present invention to provide a simplified and economic process for this purpose.

In describing the present invention it will be assumed that alternate links are cast in a generally horizontal plane (referred to as horizontal links) and that the intervening connecting links are cast in a generally vertical plane (vertical links). In practice neither the absolute nor the relative dispositions of the two sets of links are critical and the terms "horizontal" and "vertical" are used merelyforthe sake of convenience.

According to the invention, chain is cast by means of a mould comprising effectively identical upper and lower halves each including a sequence of cavities fitted with identical core-pieces which are held in position in abutting relationship when the two parts of the mould are assembled together, and in which each cavity is formed with a space cooperating with a corresponding space in the respective core-piece, the two spaces together being shaped to define a respective half of a vertical link, of which the other half is defined by corresponding co-operating spaces in the cavity and core piece of the other half of the mould and the abutting faces of the corresponding core pieces are formed with co-operating pairs of spaces defining the end portions of adjacent horizontal links, of which the central portions are defined by co-operating pairs of spaces defined in mating surfaces of the two parts of the mould in the interval between adjacent cavities and the opposite end portions are defined by similar spaces in the abutting faces of the next adjacent pair of core pieces, a runner extending along the junction of the two parts of the mould to one side of the line of the chain, communicating with the lower part of each space and a riser extending along the other side of the chain, communicating with the upper part of each space.

As a result of this construction of mould, although all the links in the resultant chain will communicate with both the runner and the riser, they are otherwise independent of one another. Consequently, when the mould and core pieces are removed and the links are separated from the runner bar and the riser bar, it is only necessary to clean up the various links to give a finished chain. In other words, the casting procedure itself represents a major simplification over any previous proposals.

While the two halves of the mould may be formed by means of pattern boards from bonded sand and resin in the usual way, the operation of forming the parts of the mould may be simplified by use of the so-called V-process, as described for example in British patent specification 1,397,821. Accordingly, in a preferred method of casting in accordance with the invention, prior to pouring the metal, the two halves of the mould are first formed by the use of respective patterns, from sand which is bonded by the application of vacuum and the two halves of the mould and the core pieces are then assembled together.

An example of a mould in accordance with the invention which is particularly suitable for use in the method just referred to, will now be described in more detail, with reference to the accompanying drawings, in which: Figure 1 is an elevation of a short length of chain as cast, showing divisions between parts of the mould and core pieces in dotted lines; Figure 2 is a plan view corresponding to Figure 1; Figure 3 is a sectional view on the line Ill - Ill in Figure 1 showing the communication between a runner bar and a riser bar and a mould space; Figure 4 is a corresponding sectional view on the line IV - IV in Figure 1; and Figure 5 is an exploded perspective view showing the lower or drag half of the mould and including two cavities together with a core piece for location in one of the cavities and a co-operating core piece fitting in to a corresponding cavity in the upper or cope half of the mould (not shown).

Turning first to Figure 1, the length of chain illustrated includes two vertical links V connected by a horizontal link H and parts of two further horizontal links H. The division between the upper and lower halves of the mould is indicated by a dotted line 11, which divides the chain into two symmetrical halves.

The lower half of each vertical link V is formed by a correspondingly shaped space of which the lower half V1 of its cross section is formed in the lower half of the mould and the upper half V2 of its cross section is formed in a core piece C1 which has a flat upper surface defined by the dotted line 11 and a curved lower surface defined by a dotted line 12 which also defines the boundary between the spaces V1 and V2. Similarly, the upper half of each vertical link V is formed by a space of which the upper half V3 of the cross section is formed in the upper half of the mould and the lower half V4 of the cross section is formed in a core piece C2 having a flat lower surface mating with the upper surface of the core piece C1 and a curved upper surface defined by a dotted line 13 forming the boundary between the spaces V3 and V4.

The spaces V1, V2 and V3, V4 are seen in cross section in the view of Figure 4 which shows the core pieces C1 and C2 in solid outline and also shows parts of the drag half MD of the mould and the cope half MC of the mould, these portions of the mould being bounded buy a chain dotted line 15. Figure 4 also illustrates a runner bar 20 which communicates with the space V1, V2 by way of a sprue 21 formed in the lower core piece C1. Similarly, the upper space V3, V4 communicates with a riser bar 24 by way of a sprue 25 formed in the upper core part C2. It will be understood that the runner bar 21 extends along the whole length of the chain being cast and communicates with one or more pouring openings through which metal is poured so as to flow along the length of the bar 20 and thence into each space V1, V2.As is clearfrom Figure 1,the spaces, V2 is merely the lower half of the space V3, V4so that the molten metal progressively fills up the whole space defining each vertical link V, expelling air into the riser bar 24 from which it eventually escapes to atmosphere by way of one or more risers extending from the bar 24.

The shape of the different components and spaces so far described can be better envisaged from the perspective view of Figure 5. This shows firstly a short length of the drag half MD of the mould, this length containing two cavities indicated generally as 30 and 31,the outline of which when seen in transverse section corresponds to the dotted line 12 in Figure 1. A single lower core piece C1 is shown for fitting into the cavity 30 and it will be seen that this has a flat upper surface formed with spaces H1 and H3 for the casting of parts of adjacent horizontal links as will be described later. The lower surface of the core piece C1 is formed with a curvature corresponding to that of the dotted line 12 in Figure 1 so as to form an exact fit with the surface of the cavity 30.

The mating surfaces of the core piece C1 and the cavity 30 are formed with the spaces V1 and V2 already described which, between them, define the lower half of each vertical link.

The upper core piece C2, as already described, is identical to the core piece C1 and has a flat lower surface mating with the upper surface of the core piece Ci and formed with two curved spaces H4 and H6 which co-operatewith the spaces H1 and H3.

Although omitted from Figure 5 for purposes of simplicity, the two core pieces C1 and C2 are located in exact register with one another by corresponding projections and recesses 35 and 36 seen in Figure 4.

The upper core piece C2 fits into a cavity in the cope half of the mould (not shown) which is identical with the cavity 30 in the drag half of the mould. The space V4 in the core piece C2 co-operates with the space V3 in the cope half of the mould to define the upper half of each vertical link as previously described. Figure 5 also shows the lower half of the runner bar 20 and of the riser bar 24 together with various sprues, as will be described later.

The formation of the horizontal links H is best described in relation to Figures 2 and 3. Each of these links is formed by a space comprising three longitudinal portions. Thus the left hand portion of each of the two complete horizontal links seen in Figure 2 is designated H1 and is formed by a correspondingly shaped space defined at the right hand side of the two corresponding core pieces C1 and C2, this space being seen in section in Figure 1.

The middle portion of each of the two links, shown as H2 is formed by a space defined in the mating surfaces of the two halves of the mould in the interval between adjacent cavities. The lower halves of the spaces H2, i.e. those in the drag half of the mould, are seen quite clearly in Figure 5 as semicircular channels in the surface of the mould between the two cavities 30 and 31. Similar channels in the cope half of the mould form the upper half of the cross section of this central portion of each horizontal link.The right hand portion of each horizontal link, shown as H3, had the lower half of its cross section defined at the left hand end of the next adjacent lower core piece C1 and the upper half of its cross section formed at the corresponding end of the co-operating core piece C2, these spaces being seen quite clearly in Figure 5.

During the casting operation, metal flows from the runner bar 20, along a sprue 40 and into the right hand part of the central portion H2 of each horizontal length as seen in Figure 3. From there, the metal flows around the curved parts H1 and H3, pushing the air from the space before it until it reaches the opposite portion H2 where the air is expelled along a sprue 41 and into the riser bar 24. It will thus be understood that although both the vertical and horizontal links all communicate with the runner bar 20 and the riser bar 24, they are otherwise independent of one another so that when the mould and core pieces are removed, it is only necessary to separate the runner bar 20 and the riser bar 24 together with the respective connections from the various links to yield a finished chain.The two halves of the mould may be lifted clear without damage, but the core pieces are trapped by the interfitting of the various links and have to be smashed before they can be removed. Forthis purpose, they need to be made from the normal combination of sand and resin which can be shaped by an injection moulding process and then hardened to give the shape of each core piece shown in Figure 5.

The two halves of the mould itself are effectively identical and may be of considerable length. In order to increase the length of chain cast in a single operation without making the mould unduly long, the chain may be caused to follow a sinuous path so that two or more runs of the chain are parallel with one another. Each half of the mould may be formed by means of a pattern board in the usual way and, as mentioned above, the channels forming the runner bar 20 and the riser bar 24 form an integral part of the mould.

As mentioned previously, it is quite possible to form the two halves of the mould by means of pattern boards, from bonded sand and resin in the usual way. Preferably, however, the operation of forming the parts of the mould is simplified by use of the V-process, referred to above. No detailed description of this process is necessary in the present specification, but broadly speaking,the sand is bonded by the application of vacuum after the pattern board has been pressed into place. The moulding surface is lined with a thin sheet of polyethylene which forms a seal so that when vacuum is applied in the presence of the pattern, the sand is forced against the surface of the pattern and is solidified. The presence of the seal causes the sand to remain in its solid condition after removal of the pattern board and during the subsequent assembly of the complete mould including the core pieces and the pouring of the metal. Subsequent release of the vacuum allows the sand to return to its normal fluent condition so that the mould coliapses and the cast chain, together with the enclosed core pieces can then be removed without difficulty.

Claims (3)

1. A mould for casting chain comprising effec tively identical upper and lower halves each including a sequence of cavities fitted with identical core-pieces which are held in position in abutting relationship when the two parts of the mould are assembled together, and in which each cavity is formed with a space co-operating with a corresponding space in the respective core-piece, the two spaces together being shaped to define a respective half of a vertical link, of which the other half is defined by corresponding co-operating spaces in the cavity and core piece of the other half of the mould and the abutting faces of corresponding core pieces are formed with co-operating pairs of spaces defining the end portions of adjacent horizontal links, of which the central portions are defined by cooperating pairs of spaces defined in mating surfaces of the two parts of the mould in the interval between adjacent cavities and the opposite end portions are defined by similar spaces in the abutting faces of the next adjacent pair of core pieces, a runner extending along the junction of the two parts of the mould to one side of the line of the chain, communicating with the lower part of each space and a riser extending along the other side of the chain, communicating with the upper part of each space.

2. A mould according to claim 1 in which the sequence of cavities defining the length of the chain follows a sinuous path of which two or more runs are substantially parallel with one another.

3. A method of casting chain using a mould according to claim 1 or claim 2, in which, prior to pouring the metal, the two halves of the mould are first formed by the use of respective patterns, from sand which is bonded by the application of vacuum and the two halves and the core pieces are then assembled together.