GB2123327A - Production of sand moulds - Google Patents

Abstract

A mould box for small castings such as items of jewellery comprises a base plate 2, for carrying a pattern 14, 14a, and a movable wall member 18 adapted to seat on said base plate and to be pressed by releasable taper means 20 into engagement with an upstanding plate 16 located on said base plate, the wall member and the upstanding plate forming an enclosure for receiving mould material, one or more upstanding spigots 20, or the like, being provided to form register means in the formed mould. The taper means may be in the form of a tapered sleeve located on a bolt 6 used to secure the base plate to supporting plate 4. <IMAGE>

Description

SPECIFICATION Production of moulds This invention relates to the production of moulds and is particularly concerned with the production of moulds for use in the manufacture of small castings such as items of jewellery and similar size articles.

Conventionally it is the practice to produce such moulds in mould boxes which have to be very accurately machined and from which it is relatively difficult to release the formed mould, it being necessary in many instances to support the mould box and formed mould in suitable supports and to strike the support so as to obtain release of the mould from the box. Such striking of the support in many cases tends to cause damage to the mould box and to the mould itself, and the present invention seeks to obviate these and other disadvantages by providing an improved form of mould box.

According to the present invention, there is provided a mould box comprising a base plate carrying or for carrying a pattern, and a movable member adapted to seat on said base plate and to be pressed by releasable taper means into engagement with an upstanding plate located at one end of said base plate so as to enclose said pattern, said member and said upstanding plate constituting an enclosure for receiving the mould material, said base plate carrying one or more upstanding spigots or the like so as to provide register means in the formed mould.

Preferably, said base plate will be composed of brass ad will be carried by and secured to a supporting plate, the upstanding plate being secured to said supporting plate and abutting against the end of the base plate.

The movable member will preferably be a threesided member having an open end and will be pressed into engagement with the upstanding plate by means of a tapered sleeve located on a bolt or nut used to secure the base plate to the supporting plate.

The pattern carried by the base plate will prefer ably be silver soldered to the base plate to prevent the moulding sand from getting beneath the pattern, which would thus make it difficult to release the formed mould from the mould box.

There will preferably be two upstanding spigots or the like on the base plate, such spigots being arranged symmetrically relative to the pattern and being in the form of nuts carried by threaded bolts or screws which pass upwardly through the supporting plate and base plate, the nuts thus performing the dual function of securing the base plate to the supporting plate and providing the register holes in the formed mould.

In orderthatthe invention may be more readily understood, an embodiment thereof will now be described, by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a plan view of apparatus according to the invention; and Figure 2 is a cross-section along the line ll-ll in Figure 1.

Referring to the drawing, the apparatus comprises a base plate 2 supported by and secured to a supporting plate 4.-The base plate 2 is secured to the supporting plate4 by means of a centrally located threaded bolt 6 having a nut 8 and by two threaded screws 10 each having a nut 12, the screws 10 and nuts 12' beinglocate'd sym symmetrically relative to the longitudinal axis of the apparatus. As will be seen, the bolt 6 and screws 10 are counter-s.unkinto the supporting plate 4.

Located on the base plate 2-and secured thereto preferably by means of a screw 13 is a sprue former 14, at the end of which is a pattern 14A which jnthe illustrated embodiment is representative of one half of a signet ring - the former 14 and pattern 14A being located symmetrieally about the Ipngitudinal axis of the apparatus, the pattern 14A being secured to the base plate preferably by silver soldering.

The supporting plate 4 has secured thereto, for example by welding, an upstanding back p!at.e 16 against which the base plate 2, preferably composed of brass, and the former 14 abut.

In order to form a mould box in which a mould can be produced, the base plate 2 is adapted to receive an enclosing member 18 which as will best be seen from Figure 1 is a three-sided, open-ended,- i.e. a generally U-shaped member. The free extremities of the legs of the member 18 are intended to bear against the back plate 16 and the member 18 is biassed towards said'back plate 16 by the location of a tapered sleeve 20 on the threaded bolt 6. The sleeve 20 is not threaded and is intended to be a sliding fit on the bolt 6 such that it can be readily and easily freed therefrom as will be later explained.

In use, the member 18 is located relative to the base plate 2 and is pressed into engagement with the back plate 16 by the application of the tapered sleeve 20 to the bolt 6. Thereafter, the moulding material, for example moulding sand, is poured into the area bounded by the member 18, the base plate 2 and the back plate 16 at least until the former 14 and the nuts 12 are completely covered - in practice the said area will be completely filled with the .moulding sand. The sand is then bonded in the mould box, whereaftertheformed mould may be released simply by removing the tapered sleeva20,soas to release the member 18. The formed.mould may then be removed from the base plate without impacting the mould box.

By producing two moulds from the mould box, the two moulds will be exact replicas of each other, and the two moulds may be placed tpgether to form a single mould. In order to achieve accurate location of the two moulds, i.e. the twotalves of the fez complete mould, sleeves may be located in the holes in one half - these holes having been formed by the nuts 12 -which sieeves will locate in the corresponding holes in the other mould half. Thus a perfect register of the two mould halves is simply and effectively achieved.

With a mould box according to the invention, there is provided a simple but easily produced unit which can be used repeatedly without detracting from the accuracy of the moulds produced. In addition, the screws 10 and bolt 6 serve dual purposes in that they provide the means for securing the base plate 2 to the supporting plate 4 and also provide locations respectively for the tapered sleeve and the nuts 12.

It will be appreciated that dissimilar mould halves may be produced and that they may be accurately located together to produce assymmetricai castings.

It will be appreciated that the pattern may be of other configuration and that the shape of the member 18 may be varied, the main criterion of the member 18 being that it encloses the former and that is removable from the base plate 2.

Claims (8)

1. According to the present invention, there is provided a mould box comprising a base plate carrying or for carrying a pattern, and a movable member adapted to seat on said base plate and to be pressed by ieleasable taper means into engagement with an upstanding plate located at one end of said base plate so as to enclose said pattern, said member and said upstanding plate constituting an enclosure for receivihg the mould material, said base plate carrying one or more upstanding spigots or the like so as to provide register means in the foamed mould.

2. A mould box according to Claim 1, wherein said base plate is composed of brass and is carried by and secured to å supporting plate.

3. A mould box according to Claim 1 or Claim 2, wherein said upstanding plate is secured to said supporting plate and abuts against the end of the bese plate.

4. A mould box according to any of Claims 1 to 3, viherain said movable member is a three-sided member having an open end, said movable member being pressed into engagement with the upstanding plate by means of a tapered sleeve.

5. A mould box according to Claim 4, wherein said tapered sleeve is located on a bolt or nut used to secure the base plate to the supporting plate.

6. A mould box according to any of Claims 1 to 5, wherein the pattern carried by the base plate is silver soldered to said bee plate.

7. A mould box according to any of the preced Claims, inr,luding two upstanding spigots or the like on said base plate, said spigots being arranged symmetrically relative to the pattern and being in the form of nuts carried by threaded bolts or screws which pass upvvardlythrough the supporting plate and base plate.

8. A mould box substantially as herein described with reference to and as illustrated in the accompanying drawings.