Neck-down feeder

Abstract

The invention provides a neck-down feeder of unitary construction for use in metal casting. The feeder comprises a body portion integrally formed at a first end thereof with a tapered base portion for mounting on a mold pattern. The body portion and the base portion are defined by a continuous sidewall having one or more regions of weakness arranged such that the feeder is breakable in use whereby at least a part of the base portion detaches from the body portion and is received therein.

Claims

1. A neck-down feeder of unitary construction for use in metal casting, comprising a body portion integrally formed at a first end thereof with a tapered base portion for mounting on a mould pattern, the body portion and the base portion being defined by a continuous sidewall having one or more regions of reduced thickness arranged such that, under the application of force in the direction of the mould pattern, the feeder is breakable whereby at least a part of the base portion detaches from the body portion and is received therein, and wherein the force required to initiate breakage in the one or more regions of reduced thickness is no more than 5 kN.

2. The feeder according to claim 1, wherein the one or more regions of reduced thickness in the sidewall are situated at least partially in the base portion of the feeder.

3. The feeder according to claim 2, wherein the one or more regions of reduced thickness in the sidewall are situated entirely in the base portion of the feeder.

4. The feeder according to claim 1, wherein the force required to initiate breakage in the one or more regions of reduced thickness is no more than 3 kN.

5. The feeder according to claim 1, wherein the or each region of reduced thickness is constituted by a continuous band of reduced thickness that extends around the entire circumference of the sidewall.

6. The feeder according to claim 1, wherein the thickness of the sidewall in the or each region of reduced thickness is less than 70% of the thickness of the remainder of the sidewall of the body portion and/or the base portion.

7. The feeder according to claim 6, wherein the thickness of the sidewall in the or each region of weakness is less than 50% of the thickness of the remainder of the sidewall of the body portion and/or the base portion.

8. The feeder according to claim 1, wherein the region of reduced thickness is provided by a groove, channel or one or more cut-outs in the sidewall.

9. The feeder according to claim 1, wherein the one or more regions of reduced thickness are arranged such that, in use, the feeder is breakable into substantially two pieces.

10. The feeder according to claim 1, further comprising a lid.

11. The feeder according to claim 10, further comprising a moulding pin, an end of which is received within a central bore that extends partially or entirely through the lid.

12. The feeder according to claim 1, wherein the feeder has a density of from 0.8 to 1.0 g cm.sup.−3.

13. The feeder according to claim 1, wherein the feeder comprises an exothermic composition.

14. A feeder system comprising the feeder of claim 1 and a breaker core.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described, by way of example, with reference to the accompanying drawings in which:

(2) FIG. 1 shows, schematically, a cross-section of a feeder in accordance with an embodiment of the present invention;

(3) FIG. 2 shows, schematically, a cross-section of the feeder of FIG. 1 after the application of pressure and fracture of the feeder;

(4) FIG. 3 shows, schematically, a cross-section of a feeder in accordance with another embodiment of the present invention;

(5) FIG. 4 shows, schematically, a cross-section of the feeder of FIG. 1 as used in conjunction with a lid and a moulding pin; and

(6) FIG. 5 shows, schematically, a cross-section of feeder prior to modification to provide a feeder in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 shows a feeder 10 mounted on a moulding pattern plate 28 and comprising a continuous sidewall 12 which defines a cavity 14 for receiving molten metal. Although the sidewall 12 is continuous it may be considered to comprise two parts; a generally tubular upper sidewall 12a of circular cross section, which defines a body portion 10a, and a generally frustoconical lower sidewall 12b, which defines the base portion 10b. In the embodiment shown the thickness of the lower sidewall 12b is generally greater than of the thickness of the upper sidewall 12a.

(8) The sidewall 12 has an outer surface 16 which extends parallel to the longitudinal axis A of the feeder 10 from the top of the body portion 10a along most of its length and then tapers inwardly from a region close to the bottom end of the body portion 10a towards the longitudinal axis A of the feeder 10 to the bottom end of the base portion 10b.

(9) The upper sidewall 12a has an inner surface 18 which is parallel to the longitudinal axis A of the sleeve 10 thereby defining a cylindrical cavity region 14a. It will be understood therefore that most of the upper sidewall 12a is of constant thickness with a (external) taper at its bottom end.

(10) The lower sidewall 12b has an inner surface 20 which is mostly parallel to the tapered portion of the outer surface 16, thereby defining a frustoconical cavity region 14b, but is flared at the bottom of the base portion to define a restriction in the lower cavity region 14b. In the embodiment shown, the interior angle α between the inner surface 20 and the longitudinal axis A of the feeder is 27°. After casting, this region results in a notch being formed in the residual metal in the feeder and facilitates knock-off.

(11) The upper extent of the base portion 10b is defined by an annular surface 22 which interconnects the lower end of the inner surface 18 of the upper sidewall region 12a and the upper end of the inner surface 20 of the base portion 10b. A right angle is defined between the annular surface 22 and the inner surface 18.

(12) It will be understood that the above configuration results in the sidewall 12 having a region or band of significantly reduced thickness 24. This region 24 extends around the entire circumference of the feeder 10. In the embodiment shown, the thickness of this region 24, at its narrowest point, is reduced to approximately 40% of the thickness of the upper sidewall 12a. The region of reduced thickness 24 provides an area of weakness such that when a force is applied to the feeder 10 in the direction of the arrow F, the sidewall 12 breaks and severs the base portion 10b from the body portion 10a. The configuration of the sidewall 12 around the region of weakness 24 results in the formation of a substantially vertical fracture which is approximately parallel to the direction of the applied force, as indicated by the section defined by dotted lines B1 and B2. Vertical breakage of the feeder 10 results in detachment of a substantial part of the base portion 10b which has an external diameter no greater than the internal diameter of the upper cylindrical cavity 14a of the body portion 10a. Therefore, upon the application of further pressure to the feeder 10, that part of the base portion 10b is received within the cylindrical cavity 14a of the body portion 10a, as the latter moves towards the mould plate, as shown in FIG. 2. As the body portion 10a moves down in the direction of the force applied, the mixed sand 30 in the area under the taper and above the mould pattern 28 is further compressed and compacted.

(13) FIG. 3 shows another embodiment of a feeder 100 comprising a continuous sidewall 112 which defines a cavity 114. As in the embodiment shown in FIG. 1, the sidewall 112 comprises a generally tubular upper sidewall 112a of circular cross section, which defines a body portion 100a, and a generally frustoconical lower sidewall 112b, which defines a base portion 100b.

(14) The sidewall 112 has an inner surface 118 which extends parallel to the longitudinal axis A of the feeder 100 from the top of the body portion 100a to the top end of the base portion 100b, thereby defining a cylindrical cavity region 114a. From the top end of the base portion 100b, the inner surface 118 tapers inwardly towards the longitudinal axis A of the feeder 100 to almost the bottom end of the base portion 100b, thereby defining a frustoconical cavity region 114b. The inner surface 118 is flared at the bottom of the base portion 100b to define a restriction in the lower cavity region 114b. After casting, this region results in a notch being formed in the residual metal in the feeder and facilitates knock-off.

(15) The sidewall 112 has an outer surface 116 which extends parallel to the longitudinal axis A of the feeder 100 from the top end of the body portion 100a and partly into the base portion 110b. It will be therefore understood that the upper sidewall 112a is of constant thickness. From close to the top end of the base portion 100b, the outer surface 116 tapers inwardly towards the longitudinal axis A of the feeder 100 to the bottom end of the base portion 100b. The tapered portion of the outer surface 116 is intersected by an annular surface 122a and a cylindrical surface 122b, which together define a right-angled groove or step in the lower sidewall 112b.

(16) The groove in the outer surface 116 of the lower sidewall 112b results in a region or band of significantly reduced thickness 124 in the base portion, near to the junction with the body portion. This band of reduced thickness 124 extends around the entire circumference of the feeder 100. As in the embodiment of FIG. 1, this region of reduced thickness 124 provides an area of weakness such that when a force is applied to the feeder 100 in the direction of the arrow F, the lower sidewall 112b breaks and severs across the section bordered between the dotted lines B1 and B2. Once again, the vertical breakage of the feeder 100 results in detachment of a substantial part of the base portion 100b which is then received within the cylindrical cavity 114a of the body portion 100a, as the latter moves in the direction of the applied force F. The body portion 100a, by having an annular surface 122a at its base allows for good compression and compaction of the mixed sand 30 above the mould pattern 28.

(17) FIG. 4 shows a feeder 10 having a lid 40. The lid 40 has a recess or blind bore 42 that accommodates a support pin 50, which is used to hold the feeder 40 in position on the moulding pattern 28 before and during the moulding operation. The provision of the recess 42 in the lid 40 results in the lid having a thin section 44.

(18) The support pin has a body 52a and a narrower top portion 52b, both of which are generally cylindrical. The body 52a has a screw thread (not shown) at its base which secures the body 52a in position on a boss 55, which in turn is positioned on the pattern plate 28. When pressure is applied to the top of the feeder 10 and the lid 40 in the direction of the arrow F, the feeder body 10a and the lid 40 move downwardly in the direction of the mould pattern 28, parallel to and without deviation from the longitudinal axis A. This movement causes the top portion 52b of the pin 52 to travel through the recess 42 and pierce the thin section 44 of the lid 40. In addition to preventing moulding sand from falling into the feeder and casting cavity during moulding, the piercing of the lid 40 creates a vent that allows mould gasses generated on casting to be readily released.

EXAMPLE

(19) Feeders 60 (designated “ZTA1”), as shown in FIG. 5, having a tubular body portion 62 integrally formed with a frustoconical base portion 64 were prepared from KALMINEX exothermic slurry using conventional vacuum forming techniques. The dimensions of the feeders are shown in Table 1. At the junction between the base and the body portions, the interior sidewall was ground down by 6 or 12 mm to provide regions of reduced thickness,

(20) TABLE-US-00001 TABLE 1 Nominal dimensions (mm) Vol. Feeder A B C D E F (dm.sup.3) ZTA1 69 38 100 78 100 27 0.41

(21) A standard compression test of the modified ZTA1 feeders was carried out. The results are shown in Table 2. For comparison, the fracture strengths of different types of feeders supplied by the Applicant for use in high pressure moulding lines are also shown.

(22) TABLE-US-00002 TABLE 2 Feeder Average strength (kN) ZTA1 (6 mm) 1.87.sup.1 ZTA1 (12 mm) 0.93.sup.1 Comparative feeder X 23-34 Comparative feeder Y 33-40 Comparative feeder Z >50 .sup.1The value shown for the ZTA1 feeders is the fracture strength, i.e. the force required for the feeder to break into two predetermined portions, one portion being received inside the other. It will be appreciated that the comparative feeders do not have a ‘fracture’ strength since these feeders do not fracture into two defined portions but instead are broken into many fragments when sufficient force is applied. The strengths of the comparative feeders are therefore the ‘crush’ strengths.

(23) When placed under compression, the ZTA1 feeders collapsed such that the base portion of the feeder was detached from and received within the body of the feeder. In each test carried out the feeder fractured around its circumference in the region of reduced thickness, as expected. A clean break was achieved in each case, releasing only a few small particles of feeder material. The fracture strength of the ZTA1 feeders was found to be less than 3 kN. As shown in Table 2, the crush strengths of the comparative feeders for use in high pressure moulding lines were found to be significantly higher.