GB2143758A - Detecting wear in foundry patterns or core boxes - Google Patents

Abstract

There is disclosed foundry pattern equipment which is constructed as a pattern 1 or core die (box) of plastics material. In order to detect permissible wear of the plastics surface of the pattern or core box in time, there is provided a wear-indicator marking. The marking, which erodes with wear, can comprise adjacent or superimposed differently coloured and different thickness sections (3,4), or a single wedge shaped section (34, Fig. 2a). Alternatively, the section may comprise a harder wearing metal pin (7) inserted into a conical bore (6) of the pattern, originally flush with the pattern surface, so that it protrudes after wear of the adjacent pattern surface. The advantage of the disclosed embodiments consists in the simplified form of the marking, combined with optimum achievement of an early warning function. <IMAGE>

Description

SPECIFICATION Foundry pattern This invention relates to a pattern for use in metalcasting, the pattern having a wear-indicator for detecting permissible wear of the surface of the pattern.

It is known to make a pattern from a body of plastics material (particularly reinforced synthetic resin plastic), onto which is applied a first layer of copper. A second layer of nickel is then applied over the entire surface of the pattern. The purpose of the copper layer, apart from functioning as an adhesive layer, is to serve as a wear-indicator in that it provides a marking for detecting wear (through the nickel surface layer). If the copper becomes visible in certain places, then this indicates that the limit of permissible wear has been reached.

Further working with the pattern is also excluded from this moment on, because after the exposure of the copper layer (which is softer than nickel), further use is impossible because of the abbrasive wear that then occurs. This known solution to the problem of wear-indication is also relatively expensive, but nevertheless does not guarantee any warning signal for an operator so that he knows that the pattern eqipment will shortly have to be changed because the permissible wear limit has been reached.

The present invention has been developed with a view to provide a pattern having a simplified type of construction of wear-indicator so that an appropriate early warning function can be achieved, as in contrast to the previously known nickel layers it does not carry out any function that is purely of the casting art.

According to one aspect the invention provides a pattern for use in metal-casting which has a surface which is made of a material which is substantially uniform with regard to wear characteristics, and which is provided with a wear-indicator for detecting permissible wear of the surface, in which: the surface of the pattern is made of plastics material; and the wear-indicator forms a part of said surface and has a distinctive appearance.

A preferred arrangement of wear-indicator comprises the provision of adjacent portions on the pattern surface which are of different thickness.

This may be achieved by the different thickness of adjacent areas being made by a wedge-shape.

Another possibility in this respect is that two differently coloured sections are superposed.

Because of this construction there is produced for the detection of wear an embodiment of pattern arrangement that is simple with regard to construction and which is best as regards use. Wear does not expose the wear-indicator (marking) as the final limit but rather in the opposite sense the section carrying out the marking function is worn away. Thus the invention proceeds from the knowledge that each corresponding pattern, core box or the like has specific places which are most sensitive to wear that are known to the expert in moulding, and that it is sufficient to restrict the wear indicator sections to these places only. They are thus marked and recognisable to the operator.

Unlike, with the previously known solutions, there are no doubts and no corresponding examination to see whether in fact there is a corresponding marking or if it is already exposed. Since the marking sections otherwise have no casting functions at all, they can directly carry out merely this early warning function with respect to the wear that has occurred. If they are completely or partialiy worn away, then there is still a completely functional surface; the corresponding early warning function may be still further optimised by adjacent, differently coloured areas being provided, one of which is thicker than the other, or by the corresponding wedge-shape or by the superposition of differently coloured sections. The wedge-shape thus even guarantess a continuous detection and if necessary measurement of the wear that has taken place.The corresponding possibilities also take into account the fact that in many cases it is not the actual pattern contours that are subject to the great wear which necessitates renewal of the pattern device, but rather e.g. the core marks. If the core marks wear away unnoticed on a pattern, then this is first manifested in the fact that the clearance between the pattern and the core is reduced and that as the wear continues it leads to sand scratches and pressure points on the pattern and then spoilage gradually increases. In an embodiment according to the invention, there is the advantage that the (wear indicator) sections can also be inserted where they have the greatest monitoring function.The layer thickness or the increase in the wedge in connection with its surface extension can thus be adapted to the examination frequency that is normal in operations, or to the time for preparation and removal of a replacement device. The sections can also be produced with the simplest means since they can be attached in the negative as small coloured plates of the same plastics material before insertion of the surface resin; after the pattern or the core die (box) has been released they are completely visible. When they have worn completely, only the marking is lost; the entire surface retains its uniformity as regards material as before.

According to a further aspect of the invention there is provided a pattern for use in metal-casting and having a surface wear-indicator, in which the wear-indicator is incorporated in said surface and is substantially flush with the surface before the latter becomes worn, the exposed surface of the wear-indicator having substantially greater wearresistance than that of at least the region of said surface which surrounds the wear-indicator.

One advantageous embodiment of the further aspect provides a wear-indicator in the form of a hard metal pin which is inserted in formfit manner into a conical bore in the pattern surface.

With this embodiment the marking function is such that the material surrounding the hard metal pin erodes through wear, and the resultant projection of the wear resistant hard metal pin from its surrounding surface is the basis of measurement for the wear. If this projection exceeds a specific value, then one can easily determine to what extent castings will still be in the region of permissible accuracy. The hard metal pins are thus so attached that their direction coincides with the forming-out direction. The attachment of hard metal pins of this type is particularly recommended with core dies. The projection of the hard metal pins resulting through wear does not least to waste as it lies within the tolerance as regards measurement.

Embodiments of foundry pattern according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure i is a view of a pattern provided with a surface wear-indicator section; Figure 2 is a partial section along the line ll-ll in Figure 1; Figure 2a is a partial section, similar to Figure 2, of an alternative, wedge-shaped wear-indicator section; Figure 3 is a representation, corresponding to Figure 2, wherein one (of two) marked sections of lesser thickness has disappeared through wear; Figure 3a is a representation, corresponding to Figure 2a, wherein part of the wedge of the marked section has disappeared through wear; Figure 4 illustrates a further adapted embodiment in which two indicator sections are arranged superposed;; Figure 5 is a partial longitudinal section through a pattern, which has a wear-indicator in the form of a hard metal pin which is received by a conical bore in the pattern surface; and Figure 6 is a representation, corresponding to Figure 5, after a certain amount of wear.

A pattern 1 of plastics material, shown in Figure 1, has at wear-sensitive points 2 differently marked sections 3, 4 (forming a wear-indicator of distinctive appearance) inset into the pattern surface, the material wear resistivity of which sections corresponds to that of the pattern material. Moreover the sections 3, 4 plane-sealing with the pattern surface are so marked that they stand out in easily recognisable manner with respect to the pattern material because of their different colouring.

The section 3 has a thickness x which more or less corresponds to the amount of permissible wear of the pattern. The thickness y of the other section 4, on the other hand, is thinner.

After a corresponding wear of the pattern 1 there can occur the situation of Fig. 3. Due to wear y' which is equal to or greater than the amount y, the marked partial surface 4 of lesser thickness has disappeared. On examination of the pattern this is clearly visible. The absence of the marked area 4 of lesser thickness indicates that the pattern 1 has to be replaced, but is still within the range of permissible tolerance.

In the solution according to Figure 2a, the section 34 is wedge-shaped, running from the thickness x to the thickness y. The section 34 which acts as marking becomes smaller according to the amount of wear. For example, if it has reached the amount according to Figure 3a, then it is evident that the pattern has to be replaced soon.

Fig. 4 shows that two sections 3', 4' can be ar ranged directly on top of one another. The thick ness of both sections together corresponds to the permissible tolerance. As long as the outer marked section 4' can be recognised, the pattern does not yet have to be renewed.

This is not necessary until, due to the wear of section 4', the other section 3' can be seen.

With the embodiment shown in Figures 5 and 6, there is inserted into a part 5 (of plastics material) shown partially in section, e.g. a core die (or core box), a conical hard metal pin 7 into a conical bore 6 of this core die, the surface 7' of which pin closes the bore 6 and lies flush with the adjacent pattern surface 5', before the latter becomes worn. The surface 7' thus forms the section disposed in the region of a wear-sensitive point 8. After wear of the surface 5' of the pattern in the region of the wear-sensitive point 8 there can occur the case according to Figure 6. Material has been eroded through wear so that the hard metal pin protrudes by the amount z beyond the adjacent surface 5'.

This amount can be determined by a simple measurement procedure.

It is recommended to construct the hard metal pin 7 forming the section, and the pattern material, of different colours so that the hard metal pin stands out from and is clearly visible relative to the pattern 5. The conical shape of the bore 6, and of the hard metal pin 7 correspondingly adapted to it prevents pressure stresses leading to a change in the length of the hard metal pin 7 after the hard metal pin has been driven-in position.

It should be understood that there may be novel features disclosed herein, even though they may not be expressly specified in the claims.

Claims (10)

1. A pattern for use in metal-casting which has a surface which is made of a material which is substantially uniform with regard to wear characteristics, and which is provided with a wear-indicator for detecting permissible wear of the surface, in which: the surface of the pattern is made of plastics material; and the wear-indicator forms a part of said surface and has a distinctive appearance.

2. A pattern according to claim 1, in which the distinctive appearace of the wear-indicator comprises the provision of a different colour for the wear-indicator to the colour of at least the surrounding portions of said surface.

3. A pattern according to claim 1 or 2, in which the wear-indicator comprises adjacent portions on said surface which are of different thicknesses.

4. A pattern according to claim 3, in which said adjacent portions of different thicknesses are provided by a wedge-shaped element on said surface.

5. A pattern according to claim 1 or 2, in which the wear-indicator comprises a pair of differently coloured portions arranged one on the other.

6. A pattern for use in metal-casting and having a surface wear-indicator, in which the wear-indicator is incorporated in said surface and is substantially flush with the surface before the latter becomes worn, the exposed surface of the wear-indicator having substantially greater wear-resistance than that of at least the region of said surface which surrounds the wear-indicator.

7. A pattern according to claim 6, in which the wear-indicator comprises a hard-metal pin which is pressed into a conical bore formed in said surface so that the head of the pin forms an uninterrupted part of said surface before the latter becomes worn.

8. A pattern according to claim 7, in which the head of the pin is differently coloured from the surrounding region of said surface.

9. A pattern according to claim 1 and substantially as hereinbefore described with reference to, and as shown in Figures 1 to 3, Figure 1, 2a and 3a, or Figure 1 and Figure 4 of the accompanying drawings.

10. A pattern according to claim 6 and substantially as hereinbefore described with reference to, and as shown in Figures 5 and 6 of the accompanying drawings.