This invention relates to an apparatus for cutting or melting shapes in synthetic and other materials. It is common practice to apply sufficient electrical power to a wire so that the wire heats up, provided that the temperature so generated exceeds the melting point of the material. The wire will enter the material, leaving a void in its wake, thus parting the material. Many other materials can be made to part by the use of a saw which removes particles of material, thus making a void in its wake. A synthetic material, expanded polystryrene, is ideally suited to be parted with hot wire and can also be parted with a saw. Where the correct temperature of a hot wire is used, that material melts, leaving the molten material bonded to either or both sides of the ensuing void and thus parting the material.

It is an object of the present invention to provide an improved cutting machine.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing, in which:-

Fig. 1 is a perspective view of a flail used in the embodiment;

Fig. 2 is a perspective view of an alternative cutting member; and

Fig. 3 illustrates a modified cutting member.

Referring to Fig 1, a flail, as described is one of a spaced pair facing each other across a table, both flails being electrically isolated one from the other and fully rotatable. A wire C, which may be only one of a number of similar spaced wires, is placed on a piece of studding G preventing any wire from departing from

its given position relative to the axis of rotation of the flail and extends across the table to the opposite flail, where it is secured either at the same distance from the axis of rotation or, as need be, some other distance, as required, for the desired shape(s) to be produced .

Any desired number of pairs of flails may be provided along the length of the table.

The wires are held under tension by a spring B secured to the side of the flail former H by a retaining hook A. One terminal of an electric power source is attached to one flail and the other terminal to the other flail, the electric current being sufficient to heat the wire to a temperature to melt such as expanded polystyrene. The flails are linked by mechanical linkage or similar, or individually by motors which are driven to produce precise, similar axial inclination. The flails are also linked in such a manner that they can be raised or lowered in unison.

The flails are mounted on staunchions located at the side of the table and exceeding the height of the table. On each staunchion facing the table is a flail, the axis point of both flails being set to correspond accurately to a similar height above the table. Motors are provided to rotate the set flails at precisely the same speed, the flails also being provided with another motor(s) that can raise or lower the flails in unison. On the table is a box with sprocket wheels engaging a chain extending the length of each side of the table. In the box is a motor and an electrical pulse generating wheel directly linked to the table top via its own independent wheel. The motor in this box and the pulse wheel output are electrically linked to a control panel where setting of a given number of pulses will allow

the motor to inch forward until coincidence of the set number of pulses is achieved and the motor will then stop.

As required, for our example, a slab of expanded polystyrene is placed on the table. Depending on the greatest circumference to be turned, the flails are taken up to avoid any wire fouling the table top when the flails revolve, ie., a bottom limit. The distance that the box is set to move forward, the distance of the longest diameter set on the flail wires, is then set. The flails are then given a top limit of movement to avoid the height of the chosen piece of expanded polystyrene. The sequence of operations now follows.

The leading edge of the expanded polystyrene slab moves forward as set and stops. The flails drop vertically so that the hot wires enter the slab. As this assembly engages the bottom limit, so the flails start to turn. On completing 360 degrees, the flails cease to turn and the flail assembly motor raises the flails vertically out and above the slab. As the flails reach the top limit, the process continues until the slab is fully utilised; thus, a cylinder or a number of different sized tubes have been produced by this operation, whilst holes with a similar diameters will have been formed in the slab.

Alternatively, rotating the flail assembly 90 degrees, then dropping the flails so that the wires are level with the top of the material block, heating the wires and allowing the flails to complete 360 degrees, advancing the block and repeating 360 degree revolution of the flails, produces a series of semi-circular forms, referred to as lagging.

When the flail rotation is held static, and a narrow gap is cut in the width of the table, the wire stretched between the flails can be made to descend below the table top and into the gap provided, the apparatus thus acting as a guillotine which can be used on both up and down strokes, the polystyrene workpiece being advanced the desired distance between strokes. Provision of suitable top and bottom sensors to initiate a cutting stroke enables a workpiece to be parted accurately into pieces of desired length.

In Fig. 2 the heated wire is replaced by a motorised oscillatory movement attachment and a saw or similar type tool.

In Fig. 3 further shapes such as balls can be formed by suitably attaching a tool holder to each flail and having shaped wire attached between these two holders, the operation of the apparatus then being substantially as described previously.

In a modified embodiment the one memory so far described can be replaced by a multi-memory system. This then allows shapes of a circular interpolation to be formed.

It is also clear that placing wires on the flails and keeping the flails in a vertical fixed position, or placing a separate frame across the table and by allowing the box to inch forward without interruption, a slab or sheets of expanded polystyrene can be produced.

More complicated shapes can be formed by suitably controlling relative movement of the wires and the workpiece by combining movement of the workpiece with raising and lowering the wires and rotating the wire about the flail axes.

In a further modified embodiment, instead of the block being inched over the table by a box, as earlier described, this can be a moving belt(s) controlled as earlier described by a pulse generating wheel. The belt(s) may also be provided with spikes.

These spikes may also be used to locate a board or similar abutment against which small pieces of polystyrene may be stacked for cutting.