GB2257646A

GB2257646A - Riser sleeves

Info

Publication number: GB2257646A
Application number: GB9115183A
Authority: GB
Inventors: Stuart Thorpe
Original assignee: FOSECO; Hepworth Minerals and Chemicals Ltd; Foseco International Ltd
Current assignee: FOSECO; Hepworth Minerals and Chemicals Ltd; Foseco International Ltd
Priority date: 1991-07-12
Filing date: 1991-07-12
Publication date: 1993-01-20
Also published as: DE9209400U1; GB9115183D0

Abstract

A riser sleeve is provided for use in metal casting moulds, particularly for insertion into the inverted cope mould of an automatic moulding plant equipped with a mould cope line synchronised with a drag line where cores are set in the drag, where it is important that the sleeves remain securely in place. Accordingly, an insert sleeve (2) has fastening means for securing the sleeve within a riser cavity of a metal casting mould, the fastening means being constructed of material different to that forming the riser sleeve and being secured to the riser sleeve. The fastening means may take the form of compressible means, such as rubber or polystyrene wedges 10, or silicon sealant (20, Fig 2), or spring clips (40, Fig 4), projecting mechanical means, such as pins or screws (50, 60, Figs 5, 6), or adhesive means, such as double-sided tapes or pads 70, 80 Figs 7 and 8. The riser sleeve may be of exothermic and/or heat-insulating material and may be associated with a breaker core (8).

Description

RISER SLEEVES This invention relates to riser sleeves for use in metal casting moulds.

The use of riser sleeves in metal casting moulds is well known. Riser sleeves have been incorporated either by moulding directly on the pattern used to make the mould or subsequently by insertion into the top or cope part of the mould into a cavity formed by a loose pattern piece which has been removed from the top of the mould.

Because of the increasing automation of methods used for the production of casting moulds from moulding material such as sand, there is less access to the pattern plates at the moulding station, especially in the production of repetition castings. As a result, it is often not possible to apply riser sleeves directly on the pattern plats, nor is it possible to locate a loose piece on the pattern plate to form a cavity into which is later inserted a riser sleeve.

When access to the pattern plate cannot be attained an alternative procedure may be possible with automatic moulding plants which are equipped with a cope mould line which is synchronised with a drag line where cores are set into the drag. On the moving cope line, inverted cope moulds are accessible for additional work, so riser sleeves may be inserted in the inverted cope mould.

With conventional riser sleeves such a technique has not been completely successful. Conventional riser sleeves have a cylindrical or substantially cylindrical outer surface for reasons partly concerned with their production technique and partly concerned with their function. Dimensional variations inherent in their method of production such riser sleeves mean they cannot be inserted into a preformed cavity with sufficient confidence that they will remain securely in place.

Known riser sleeves, particularly those which are closed by means of a cap at one end, have a positive taper from their base going up towards the cap, i.e. the outside diameter becomes larger from bottom to top and therefore they cannot be used for the subsequent insertion into the inverted cope mould.

British Patent No. 2065008B discloses a method for the production of a metal casting mould having a riser, in which method a riser sleeve is inserted in a cavity in the mould, the cavity being formed by locating a cavity former in a body of particulate moulding material, compacting the material about the former, and removing the former, characterised in that the former is made oversize relative to the sleeve to be received in the cavity and has one or more recesses therein whereby the cavity is formed with at least one inwardly projecting rib-like formation of moulded material for gripping the sleeve when received therein, and the former has a negative taper from bottom to top.

When riser sleeves are made in quantity to a predetermined nominal size i.e. heights and diameter, in practice the sleeves deviate from that nominal size.

Such sleeves can still be used provided that they can be inserted in the mould cavities which are to receive them and that once inserted they will remain in place.

By checking and recording the actual height and diameter of a particular nominal size of sleeve during the course of production it is possible to calculate the standard deviation in height and diameter from the mean values for those parameters for that sleeve.

British Patent No. 2124527B discloses a cavity former for use in the production of a metal casting mould having a riser characterised in that the exterior of the former has one or more recesses extending between the top and towards the bottom of the former and the former has a negative taper from bottom to top. The former is suitable for making riser cavities to suit sleeves whose mean outside diameters plus three times the standard deviation are smaller than the corresponding outside diameters of the former. In this way the outside diameter of the former is larger than the outside diameter of the riser sleeves which are to be inserted in the cavities. Retention of the sleeves in the cavities results from the grip on the outside of the riser sleeve of the sand ribs which are moulded from the recesses in the former.This results in a clamping effect because circles which can be geometrically inscribed inside the base of the recesses have diameters which are smaller than the corresponding mean outside diameters less three times the standard deviation of the riser sleeves which are to be used.

The present invention provides an alternative system for securing riser sleeves within a riser cavity.

According to the present invention there is provided a riser sleeve having fastening means for securing the riser sleeve within a riser cavity of a metal casting mould in which the fastening means is constructed of material different to that forming the riser sleeve and is secured to the riser sleeve.

The invention provides riser sleeves having fastening means which allows the sleeves to be securely located within riser cavities of metal casting moulds.

The fastening means is readily able to compensate for dimensional variations in the riser cavity or riser sleeve ensuring the riser sleeves remain securely in place. Thus, there is no risk of the riser sleeves being displaced when the parts of the mould are assembled for metal casting.

The riser sleeves may be formed of any suitable material e.g. exothermic, exothermic and heat-insulating or heat-insulating material. The riser sleeves may be cured to provide a rigid non-deformable structure or may be made of a material providing a degree of deformability or friability.

The shape and configuration of the riser sleeve may vary depending upon the casting mould. In general, riser sleeves will have a cylindrical or substantially cylindrical outer surface or may be tapered e.g. the outer surface forming an angle of up to 20 with the vertical. The ratio of height to diameter may have any value that is generally within the range 1 : 1 to 2 : 1.

The riser sleeve may comprise a breaker core.

The fastening means may be selected from a wide range of options. The fastening means will generally be selected from three types. Compressible fastening means which are positioned on the exterior or the riser sleeve and are compressed when the sleeve is inserted into the cavity and thereafter provide radial forces between the exterior surface of the sleeve and the interior surface of the cavity sufficient to maintain the riser sleeve securely in place. Adhesive fastening means which provide an adhesive bond between the riser sleeve and surface of the cavity. Mechanical fastening means which provide a mechanical interlock with the material forming the mould. The fastening means may comprise a combination of such types.

Suitable compressible fastening means may comprise rubber, foam, polymeric materials such as polystyrene, and elastomeric materials e.g. silicon sealants. The compressible materials may be in the form of pads or strips secured to the exterior of the cylindrical surface of the sleeve, or may be in the form of a circumferential ring. The compressible material may be configured to provide a wedge to facilitate insertion of the riser sleeve. Other examples of compressible material include the use of spring clips which may be formed from metal or plastics material.

Suitable mechanical fastening means include the provision of a screw projecting from the cap of the riser sleeve or metal pins extending radially beyond the cylindrical surface of the riser sleeve which may be forced into the material forming the mould.

Adhesive fastening means include the use of doublesided adhesive coated pads and tapes. The pads or tape may be secured to the cylindrical surface of the riser sleeve in the form of strips extending circumferentially or longitudinal. Alternatively, the tape or pads may be applied to the cap of the riser sleeve. The outer surface of the tape or pads will generally be protected by a release liner which is removed prior to insertion of the riser sleeve. When the riser sleeve is inserted into the riser cavity the exposed adhesive contacts and bonds to the wall of the cavity. The use of pads having a degree of compressibility allows the combination of pressure and adhesion to secure the riser sleeve in place. Similarly compressible materials such as silicone sealents may possess a degree of tack or adhesion.

The invention will now be described with reference to the accompanying drawings in which: Figures 1 to 8 represent cross-sections of riser sleeves in accordance with the invention.

Figures 1 to 8 illustrate riser sleeves generally shown at (2) having a closed top (4) and tapered walls (6). The sleeve may optionally have a breaker core (8) as shown in Figure 1. It is not essential that the sleeves have a closed top. In accordance with the invention the riser sleeve is provided with fastening means.

The fastening means shown in Figure 1 comprises one or more wedges of compressible material e.g. polystyrene, resilient foam etc. The fastening means may comprise a plurality of wedges (10) spaced circumferentially around the outer wall or may be in the form of an annulus extending completely around the outermost wall of the riser sleeve. The wedges may be secured to the riser sleeve by suitable adhesive. When the riser sleeve is inserted into the riser cavity the wedge(s) are compressed and the riser sleeve and associated fastening means are force fixed into the cavity thereby securing the riser sleeve in place.

The fastening means of Figure 2 comprises an annulus (20) of compressible material e.g. a flexible sealant material such as silicon rubber which may be tacky. The annulus may be positioned at any suitable point around the wall. When the riser sleeve is inserted into the cavity the annulus is compressed between the cavity wall and the wall of the riser. The riser may be held in place under the pressure material of the compressed annulus and by any adherent property of the material.

Figure 3 shows a fastening means comprising an annulus (30) of compressible material positioned in a circumferential recess (32) moulded at the end of the riser sleeve. The annulus (30) may be constructed of compressible material such as rubber, foam etc. which may optionally possess adhesive properties.

Figure 4 illustrates a fastening means comprising spring clips (40) projected from arms (42). There are preferably three or more arms (42) extending from a central portion (44), each bearing an associated spring clip (40). The arms (42) may be configured to grip tightly around the wall of the riser sleeve holding the fastening means in place, alternatively, the fastening means may be secured in place by adhesive, nail, screw etc. The fastening means may be constructed of resilient plastics or metal. When the riser sleeve is inserted in the riser cavity the spring clips (40) are compressed and exert sufficient force against the wall of the cavity to maintain the riser sleeve securely in place.

Figure 5 of the accompanying drawings shows a metal pin (50) having ends (52) extending radially beyond the wall of the riser. The pin may be embedded in the riser sleeve during its fabrication or may be secured to the riser sleeve with adhesive or other fixing means such as a staple. In use the riser sleeve is inserted in the riser cavity during which the ends (52) of the pin gouge a groove in the wall of the cavity. When the riser sleeve has been inserted to the required degree, it is rotated slightly to lock it into position.

Figure 6 illustrates a fastening means comprising a screw (60) which is embedded in the end of'the riser sleeve dtlring manufacture. The threaded end (62) of the screw (60) projects through the end of the riser sleeve and the riser sleeve may be fitted in the riser cavity to rotate to secure the sleeve in position.

The fastening means shown in Figure 8 comprises a double-sided adhesive coated strip (70). The strip is adhered to the outside wall of the riser sleeve and initially its adhesive layer (72) is protected with a release liner (74). The release liner is removed prior to insertion of the riser sleeve within the riser cavity.

The adhesive layer (72) bonds to the wall of the cavity and the strip (70) may be subject to compression during insertion if it is composed of compressible material.

The fastening means may comprise three or more strips or pads spaced circumferentially around the wall of the riser sleeve or may be in the form of a strip or annulus extending completely around the wall.

The fastening means of Figure 8 is similar to that of Figure 7 comprising pads (80) having an adhesive layer (82) positioned at the top or bottom of the wall of the riser sleeve. The pads may be in the form of a circumferential strip extending around the wall or three or more individual pads spaced circumferentially around the wall.

Claims

1. A riser sleeve having fastening means for securing the riser sleeve within a riser cavity of a metal casting mould in which the fastening means is constructed of material different to that forming the riser sleeve and is secured to the riser sleeve.

2. A riser sleeve as claimed in Claim 1 in which the fastening means comprises compressible material.

3. A riser sleeve as claimed in Claim 2 in which the compressible material comprises a foam, rubber, or an elastomer.

4. A riser sleeve as claimed in Claims 2 or 3 in which the compressible material is in the form of three or more strips spaced circumferentially around the outer wall of the riser sleeve or in the form of an annulus extending around said outer wall.

5. A riser sleeve as claimed in Claim 4 in which the strips are wedge-shaped.

6. A riser sleeve as claimed in Claim 1 in which the fastening means comprises a plurality of compressible clips spaced circumferentially around the outer wall of the riser sleeve.

7. A riser sleeve as claimed in Claim 1 in which the fastening means comprises a screw, the head of which is embedded in the end of the riser sleeve, the threaded end of the screw extending outwardly of the riser sleeve.

8. A riser sleeve as claimed in Claim 1 in which the fastening means comprises one or more pins having an end extending radially outwardly of the exterior wall of the riser sleeve.

9. A riser sleeve as claimed in Claim 1 in which the fastening means comprises a double-sided adhesive strip secured to the outer wall of the riser sleeve.

10. A riser sleeve as claimed in Claim 9 in which there are three or more adhesive strips spaced circumferentially around the outer wall.

11. A riser sleeve as claimed in Claim 9 in which the adhesive strip extends circumferentially around the outer walls.

12. A riser sleeve as claimed in any one of Claims 9 to 11 in which the strip is in the form of a pad.

13. A riser sleeve as claimed in Claim 12 in which the pad comprises compressible material.

14. A riser sleeve as claimed in any one of Claims 9 to 13 in which the outer adhesive layer is covered by a release liner.

15. A riser sleeve as claimed in Claim 1 substantially as herein described with reference to any one of the drawings.