GB2232630A

GB2232630A - Improvements in or relating to the production of anatomical replicas

Info

Publication number: GB2232630A
Application number: GB8913993A
Authority: GB
Inventors: Peter Edwards
Original assignee: Osteon Ltd; OSTEON Ltd
Current assignee: Osteon Ltd; OSTEON Ltd
Priority date: 1989-06-17
Filing date: 1989-06-17
Publication date: 1990-12-19
Also published as: GB8913993D0

Abstract

A mould for forming an anatomical replica, such as of a skull, comprises moulding each of a plurality of mould parts on an anatomical original e.g. a skull mandible. Each mould part is built up from successively applied layers 3 and 4 of silicone rubber and strips of strengthening material to form, after curing a flexible inner skin 7, onto which is then applied successive layers of resin, woven tissue glass and chopped glass strands, to form a rigid outer casing 6 which is detachable from the skin 7, to enable release of a subsequently moulded replica from the mould part, by peeling away of the flexible inner skin 7. The replica is moulded by applying resin and glass fibre reinforced resin coatings 12, 13 to the inner skin surfaces of opposed mould parts 6, 7 and 6', 7' and curing the skins together between the clamped mould parts, to form a hollow walled replica. The mould parts may include separately cast rubber inserts 8. <IMAGE>

Description

"Improvements in or relating to the production of anatomical replicas" This invention relates to methods of producing anatomical replicas and to methods of producing moulds for forming anatomical replicas.

It has long been the practice in hospitals and medical teaching establishments for actual human skeletons and bones to be used as aids for teaching human anatomy and for carrying out demonstrations on the human anatomy.

However actual human bones are very often not easily obtainable, and it has become the practice to make use of replicas of actual bones. Such replicas as are at present available, however, are not of particularly good quality and therefore do not meet with general acceptance. More particularly these replicas do not include much of the detail of the originals and do not have the same surface appearance as the originals.

It is an object of the invention to provide anatomical replicas which closely resemble the originals.

According to one aspect of the present invention there is provided a method of producing a mould for forming an anatomical replica, which method comprises applying a plurality of moulding parts to an anatomical original to be replicated, allowing the moulding parts to cure so that each of the moulding parts comprises a flexible inner skin and a detachable rigid outer casing, detaching the rigid outer casings from the flexible inner skins, and subsequently peeling the flexible inner skins from the original, whereby the flexible inner skins and the rigid outer casings may subsequently be used as mould parts for moulding a replica of the original.

The application of the moulding parts to the original preferably includes the application of successive layers of a liquid substance to the original, the layers subsequently being cured to form the flexible inner skins.

The liquid substance may be a silicone rubber.

Furthermore the flexible inner skins may be strengthened by the application to the layers of strengthening material, such as flexible woven mesh.

In certain circumstances it may also be desirable to apply additional insets, made for example from rubber, after application of the layers to fill recesses in the original. Preferably the layers are treated, for example with paraffin wax, so that the insets do not adhere to the layers.

The application of the moulding parts to the original preferably also includes the application of successive layers of material to form the rigid outer casings. The material may include a resin and a catalyst.

Furthermore the application of the layers of material may include the application of layers of woven material, such as so-called tissue glass, and optionally also the application of chopped glass strands.

Conveniently the application of each moulding part is carried out in a separate operation from the application of the other moulding part or parts, the area of the original to which the moulding part is to be applied being defined by a boundary wall, made for example of plasticene, which is temporarily applied to the original during the operation.

According to another aspect of the present invention there is provided a method of producing an anatomical replica, which method comprises applying moulding material to a plurality of mould parts which have been formed from an anatomical original to be replicated, each of the mould parts comprising a flexible inner skin and a detachable rigid outer casing, clamping the mould parts together, allowing the moulding material to cure, detaching the rigid outer casings from the flexible inner skins of the mould parts, and subsequently peeling the flexible inner skins from the moulding material which will have cured to form the anatomical replica.

It is particularly advantageous if the moulding material is applied to the mould parts in such a manner as to form a replica having moulded walls separated by hollow spaces. Such a hollow structure reproduces the structure of the anatomical original.

The application of moulding material to the mould parts preferably includes application of a pigmented gel coat to the flexible inner skins, for instance a coat comprising a thixotropic resin, a catalyst and dispersed pigments.

Furthermore the application of the moulding material to the mould parts may also include application of a subsequent support coating comprising, for example, a resin, a catalyst, a filler and a strengthening material.

The resin may be an onyx polyester resin and the filler may be a fine marble filler. The strengthening material may be chopped glass strands.

In order that the invention may be more fully understood, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a diagrammatic section through the main body of a skull illustrating the manner in which a moulding part is produced from the original; and Figure 2 is a diagrammatic section through two mould parts used in producing a replica of the main body of the skull.

Tho following description will be given with respect to the production of a mould, and use of the mould, for forming a replica of the main body of a skull.

It should be understood that a replica of a complete skull is produced from three components, that is the skull cap, the main body of the skull and the lower mandible. Since the production of all three components, and the production of the moulds for forming the components, is very similar only the production of the main body and the mould therefor will be discussed below. It should be understood that similar principles will also apply to production of replicas of other bones in the human body, and moulds therefor, as well as the production of other anatomical replicas.

The production of the mould for a replica main body from an original main body of a skull comprises the production of three separate mould parts, and will first be described with reference to Figure 1. The part of the main body 1 to which the first moulding part is to be applied is first defined by application of a plasticene wall 2 to the mandible 1 so that only the area to be moulded from is exposed. A first layer 3 of liquid is then applied to the original with a brush, using a stippling motion to eliminate air bubbles and penetrate every crevice. The liquid comprises a mixture of a cold cured RTV silicone rubber and a catalyst.

Six more layers 4 of the liquid are then applied, with the addition to each layer 4 of strips of strengthening material in the form of pieces of semielastic, woven nylon mesh tights. A drying time of about three hours is allowed between the application of each layer, leaving sufficient tackiness to achieve bonding between successive layers.

The object is then again built up with plasticene walls, such as 5, for the casting of keys for the accurate location of the outer casing 6 with the rubber inner skin 7, and additional rubber insets, such as 8, to be cast separately. A layer of paraffin wax 9 is applied to the existing rubber surface so that it does not adhere to the rubber insets being cast adjacent to it.

Once the rubber has cured, the plasticene is removed.

In order to produce the rigid outer casing 6 of the moulding part the following procedures are followed.

Firstly 20% thixotropic flexible polyester gel coat is floated onto the object with a brush. Then a layer of a rigid polyester laminating resin and a MEK organic peroxide catalyst is applied with a brush, again using stippling technique. This is backed with a layer of socalled woven tissue glass which is then stippled all over with resin. A layer of chopped glass strands comprising a mixture of 225 gm. and 300 gm. chopped strand mat, is added and a rigid polyester laminating resin is applied.

The lamination of tissue glass, resin and chopped glass is repeated six times. A 4 cm wide rim 10 is built up around the perimeter of the casing 6 to provide extra strength, using four layers of the same combination of materials.

The casing 6 is then cured for a week at room temperature.

After curing the plasticene is removed to expose another area of the main body 1 to be moulded. Extraneous rubber around the edges is trimmed off with a sharp blade, and all the surfaces are cleaned (to remove plasticene detritus) with acetone and white spirit. The rim 10 is pcslished with wax to provide a smooth surface.

New plasticene walls are constructed around the next area to be encased in rubber and resin. The rubber is applied as before, and the insets are made after the area has been re-structured with plasticene. All the plasticene is then removed and the surfaces are chemically cleaned with acetone and white spirit. Any surface of the moulding part which is to be in contact with a surface of another moulding part is sprayed with a release agent to make eventual separation easier. The laminated fibreglass casing for the area is then constructed as before.

This process is repeated for all three parts of the mould.

The moulding parts are removed from the original by first ut:ning the outer casings 6 and then subsequently peeling away the rubber inner skins 7. Thus the three-part mould for forming replicas of the main body is formed. A two part mould for the skull cap and a two part mould for the lower mandible of the skull are formed in similar manner, except that it is not necessary to provide rubber inset for these moulds.

The manner in which the mould is used for forming a replica of the main body will now be described with reference to Figure 2. Firstly the mould is disassembled into its constituent mould parts such as 11 and 11', each of which comprises a rigid outer casing 6, 6' and a rubber inner skin 7, 7'.

A weighed quantity of paste is then prepared from 20% thixotropic flexible polyester gel coat resin, an MEKP organic peroxide catalyst and dispersed polyester pigments. A coating 12 of the paste is applied to the inner surfaces of the mould parts, keeping clear of the edges which will butt onto each other and thereby avoiding the formation of flash lines on the cast. Care is taken to eliminate any air bubbles trapped within the coating.

When the coating has gelled to a tacky consistency, a coating 13 of a mixture of translucent onyx polyester resin, chopped strands of 6 mm. glass, polyester pigment, an MEKP organic peroxide catalyst and fine marble filler is applied with a stippling brush action, avoiding the edges as before. The inside edges of the rims 10 are beaded with the pigmented gel coat.

The mould parts such as 11, 11' are assembled together whilst the mixture within is still wet, and clamps 14 are applied to hold the mould parts together.

The clamped mould is left to cure for about two hours, after which the clamps 14 are removed. The replica is separated from the mould by the removal of the outer casings 6, 6' and subsequent peeling away of the rubber inner skins 7, 7'.

Flash lines on the replica are eliminated with files, and the foramena (holes in the skull for nerves, etc.) are drilled out.

In the complete skull the cranium and mandible are assembled using two springs, locating pins and hooks.

The above-described methods are particularly advantageous as they produce replicas which are hollow and made of materials which simulate the weight, texture and colour of the original. The use of rubber inner skins in the mould parts enables the separation of the replica cast from the mould without damage or distortion of delicate features and important detail. Furthermore production of replicas from the mould parts can be achieved in considerably less time than with more conventional methods.

Claims

CLAIMS.

1. A method of producing a mould for forming an anatomical replica, which method comprises applying a plurality of moulding parts to an anatomical original to be replicated, allowing the moulding parts to cure so that each of the moulding parts comprises a flexible inner skin and a detachable rigid outer casing, detaching the rigid outer casings from the flexible inner skins, and subsequently peeling the flexible inner skins from the original, whereby the flexible inner skins and the rigid outer casings may subsequently be used as mould parts for moulding a replica of the original.

2. A method according to claim 1, wherein the application of the moulding parts to the original includes the application of successive layers of a liquid substance to the original, the layers subsequently being cured to form the flexible inner skins.

3. A method according to claim 2, wherein the flexible inner skins are strengthened by the application to the layers of strengthening material.

4. A method according to claim 1, 2 or 3, which includes the application of additional insets to fill recesses in the original.

5. A method according to any preceding claim, wherein the application of the moulding parts to the original includes the application of successive layers of material to form the rigid outer casings.

6. A method according to claim 5, wherein the application of the layers of material to form the rigid outer casings includes the application of layers of woven material.

7. A method according to claim 5 or 6, wherein the application of the layers of material to form the rigid outer casings includes the application of chopped glass strands.

8. A method according to any preceding claim, werein the application of the rigid outer casings includes the application of each moulding part is carried out in a separate operation from the application of the other moulding part or parts, the area of the original to which the moulding part is to be applied being defined by a boundary wall which is temporarily applied to the original during the operation.

9. A method of producing an anatomical replica, which method comprises applying moulding material to a plurality of mould parts which have been formed from an anatomical original to be replicated, each of the mould parts comprising a flexible inner skin and a detachable rigid outer casing, clamping the mould parts together, allowing the moulding material to cure, detaching the rigid outer casings from the flexible inner skins of the mould parts, and subsequently peeling the flexible inner skins from the moulding material which will have cured to form the anatomical replica.

10. A method according to claim 9, wherein the moulding material is applied to the mould parts in such a manner as to form a replica having moulded walls separated by hollow spaces.

11. A method according to claim 9 or 10, wherein the application of moulding material to the mould parts includes application of a pigmented gel coat to the flexible inner skins.

12. A method according to claim 9, 10, or 11, wherein the application of moulding material to the mould parts includes application of a subsequent support coating comprising a resin, a catalyst, a filler and a strengthening material.

13. A method of producing a mould for an anatomical replica, the method being substantially as hereinbefore described with reference to the accompanying drawing.

14. A method of producing an anatomical replica, the method being substantially as hereinbefore described with reference to the accompanying drawing.

15. A mould for forming an anatomical replica, the mould having been produced by a method according to any one of claims 1 to 8 and 13.

16. An anatomical replica which has been produced by a method according to any one of claims 9 to 12 and 14.