FIELD OF THE INVENTION This invention relates to an accessory for use with a grinding tool. In particular, though not exclusively, this invention relates to an accessory for use with a grinding tool of the type used to shape prosthetics such as dental prosthetics.

10 BACKGROUND OF THE INVENTION Prosthetics, such as dental prosthetics, are usually fabricated of a material that can be harmful if comminuted and inhaled. Comminution of the material takes place when such prosthetics are shaped and/or trimmed with a grinding tool.

At present, in many cases, trimming and sometimes shaping of prosthetics is carried out in an open setting. Resulting prosthetic dust can then be circulated by, for example, being drawn into air conditioning units. It will be appreciated that this is undesirable.

Respiratory symptoms from inhalation of such dust range from sinus or 20 nasal irritation to more serious conditions such as pulmonary fibrosis or silicosis.

Acrylic resin material causes pulmonary fibrosis if comminuted and inhaled over a period of time. Dentures are fabricated of this material. In many cases the dentures are trimmed and adjusted to fit in a dental clinic without any means for removal of the dust. As a result, both the patient and the dental personnel or staff are at risk. It will be appreciated that there are a number of other materials used in the fabrication of prosthetics that are also dangerous if comminuted and inhaled.

A number of different types of trimming boxes are available. These are 30 relatively complex devices that incorporate a suction motor or a vacuum motor or an exhaust fan that is positioned on a receptacle to extract air from the receptacle. These devices have a substantial weight and can be prohibitively expensive.

The suction or vacuum motors are positioned beneath the receptacle, rendering them bulky and difficult to manoeuvre. A number of receptacles also cannot be connected to a single vacuum or suction pump since these devices already incorporate such suction or vacuum motors.

As a result of these disadvantages, many clinics do not own such a device.

It is an object of this invention to provide an accessory for a grinding tool 10 that addresses these disadvantages and facilitates a healthier working environment for dental personnel or staff and patients.

SUMMARY OF THE INVENTION According to the invention, there is provided an accessory for use with a grinding tool, the accessory comprising a receptacle that defines a working volume in which a grinding tool can be received and at least one exhaust opening in fluid communication with the working volume ; and an extraction pump connector that is mounted on the receptacle in fluid 20 communication with the, or each, exhaust opening to permit an inlet conduit of an extraction pump to be connected to the receptacle in fluid communication with the working volume.

A channelling member may be positioned in the receptacle to span the working volume. The channelling member may be shaped so that an operatively lowest region of the channelling member is positioned proximate the exhaust opening. Thus, comminuted material that falls on the channelling member is channelled towards the exhaust opening.

The receptacle may include a floor, a front wall, a rear wall and a pair of opposed sidewalls. The exhaust opening may be defined in the rear wall and 30 the channelling member may be positioned operatively above the floor.

A lid may be attached to the receptacle to allow a user to open or close the receptacle.

An access opening may be defined in each sidewall so that a user can gain access to the working area by inserting his or her arms through the respective access openings.

A mounting member may be positioned on the receptacle to permit the receptacle to be mounted on a stand.

The invention is now described, by way of example, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS 10 In the drawings: Figure 1 shows a three dimensional view of an accessory, in accordance with the invention, for a grinding tool.

Figure 2 shows a front view of the accessory.

Figure 3 shows a side view of the accessory.

Figure 4 shows a rear view of the accessory.

Figure 5 shows a top plan view of the accessory.

Figure 6 shows a bottom plan view of the accessory.

Figure 7 shows a schematic layout of a number of the accessories connected to a single vacuum source.

20 DETAILED DESCRIPTION OF THE DRAWINGS In the drawings, reference numeral 10 generally indicates an accessory, in accordance with the invention for a grinding tool (not shown). The grinding tool is of the type that is used for shaping or trimming prosthetics, in particular dental prosthetics such as dentures.

The accessory 10 includes a receptacle 12. The receptacle 12 has a floor 14, a front wall 16, a rear wall 18 and a pair of opposed sidewalls 20.

An exhaust opening 22 is defined in the rear wall 18, proximate the floor 14. Netting 24 is positioned in the exhaust opening 22 to inhibit a prosthetic 30 from being sucked out of the receptacle 12.

A channelling member 26 is positioned in the receptacle to extend between the front and rear walls 16,18 and the sidewalls 20. The channelling member 26 has a generally V-shaped, 45 degree profile with a vertex 28 that slopes downwardly, also at about 45 degrees, from the front wall 16 to a position immediately below the exhaust opening 22. Thus, the walls 16,18 and 20 and the channelling member 26 define a work area 30 above the channelling member 26. It will be appreciated that any grindings that precipitate on to the channelling member 26 are directed towards the exhaust opening 22 as a result of the shape of the channelling member 26.

A suction pipe connector 32 is attached to the rear wall 18 in fluid communication with the exhaust opening 22 and thus the work area 30. The 10 suction pipe connector 32 has an outlet conduit 34 that can be connected to an inlet pipe of a vacuum or suction device. In one embodiment, the outlet conduit 34 can be connected to suction tubing of a dental chair. In this case, the outlet conduit 34 is in the form of an adaptor that is configured to suit the suction tubing of the dental chair in question.

The connecter 32 has a coupling member 56 that is fast with the rear wall 18. The outlet conduit 34 is rotatably attached to the connector 32 to permit the conduit 34 to swivel with respect to the coupling member 56.

Where necessary, a number of the accessories 10 can be connected to a single vacuum source in the form of a suction pump 36, as shown in Figure 7. In 20 this embodiment, an inlet manifold 38 can be connected between the outlet conduits 34 and the suction pump 36 to direct exhaust from the respective receptacles 12 to and out of the suction pump 36 at 40.

A lid 42 is pivotally mounted on the rear wall 18 with hinges 44 to allow the work area 30 to be opened and closed. A handle 46 is positioned on the lid 42 to facilitate opening and closing of the lid 42. It should be noted that in Figure 1, the accessory 10 is shown without the lid 42 so that the work area 30 can be seen.

Each sidewall 20 defines an access opening 48 that is dimensioned to receive an operator's arm. An expandable shielding member 50 is positioned in 30 each opening 48 to accommodate the operator's arm and to inhibit the escape of dust from the openings 48.

The receptacle 12 and the lid 42 are of a transparent material. An example of a suitable material is a clear plastics material such as clear acrylic or Perspex.

A mounting plate 52 is positioned in the floor 14 of the receptacle 12. The mounting plate 52 has a threaded opening 54 to permit the receptacle to be fastened to a support. An example of a suitable support is a tripod of the type used to support a camera. It will be appreciated that such tripods incorporate a fastener that is threadedly received in a base of the camera. It follows that the mounting plate 52 may be configured to permit such a fastener to be threadedly 10 received in the opening 54.

It will be appreciated that the receptacle 12 can be of any suitable size depending on the application. For example, for medical and dental use, the receptacle 12 can have a length of 500 mm, a width of 250 mm and a height of 300 mm at the rear wall 18.

As can be seen in the drawings, the rear wall 18 has a greater height than the front wall 16. As a result, the lid 42 slopes downwardly towards the operator, in use, for ergonomic reasons.

In use, the receptacle 12 is mounted on a tripod or placed on any other suitable support, such as a workbench. The operator holds a work piece in the 20 form of a prosthetic to be shaped or trimmed in the work area 30 with one hand received through one of the access openings 48. The other hand is received through the other access opening 48 and grips the grinding tool. Thus, while the prosthetic is shaped or trimmed, the comminuted material is extracted by the suction pump 36 via the exhaust opening 22.

Applicant submits that the accessory 10 provides a simple and cost- effective device that can be used in a wide range of clinics, laboratories and industries. The accessory 10 is readily portable without the bulk and weight of an incorporated fan or vacuum pump by simply detaching the inlet conduit of a vacuum or suction device. When not in use, the accessory 10 can be stored in a 30 drawer or cupboard so as to save working space. The mounting plate 52 allows the accessory 10 to be simply attached to a camera tripod, thereby allowing the accessory 10 to be used in a wide range of locations.

In the arrangement of figure 7, it is clear that a number of the accessories 10 can be used in series in, for example, a laboratory or industrial setting where a number of operators may be required to carry out similar tasks, such as shaping or trimming prosthetics. In such an environment, Applicant envisages substantial cost saving through the use of a single pump 36 to extract grindings from a number of receptacles 12.

Generally, the Applicant believes that the invention provides a means whereby a cleaner and healthier working environment for prosthetic technicians, medical and dental personnel, customers and patients can be achieved.