Field of the Invention:

This invention concerns improvements relating to mechanical manipulators of the kind which comprise a platform connected by first universal joints at three positions triangularly disposed thereon to six legs which are longitudinally movably supported in hexagonally-disposed bearings carried by second universal joints that the position and attitude of the platform in space relative to the bearings is fully defined by the lengths of the legs between the respective joints and bearings.

Background of the Invention:

A mechanical manipulator of the abovementioned kind is disclosed in WO 92/17313 and promises to revolutionize the machine tool industry. A platform is suspended by three pairs of supportive legs which are coupled to the platform at triangularly spaced-apart locations by means of three universal joints each of which couples to one end of each of the two legs of a respective pair, the two legs of each pair extending from their respective universal joint

in divergent directions to spaced-apart locations in an overhead mounting whereat each leg is drivingly engaged by a respective universal joint mounted electric motor arranged to move the leg in its own longitudinal direction. The platform position and orientation can thus be precisely controlled by appropriate operation of the six leg drive motors.

The platform can serve for the mounting of a power tool such as a powered gripper mechanism or a rotary cutting tool, for example. In the specific embodiment described in WO 92/17313 a rotary indexing stage is mounted on the platform for rotation in the plane of the platform, and this indexing stage serves as a mounting for a pivotal stage providing for pivotal movement in a plane perpendicular to the plane of rotation of the indexing stage. Mounted on the pivotal stage is a rotary tool holder. By control of the leg drive motors and of further motors controlling the indexing stage and the pivotal stage, a tool held in the tool holder can be arranged to access a workpiece from substantially any direction and to move in substantially any direction for machining the workpiece. Configured thus as a machine tool, the machine of WO 92/17313 is free from all of the movement constraints and limitations which afflict conventional 3-axis machine tools.

Object and Summary of the Invention:

The object of the present invention is to improve the mechanical manipulator that is described in WO 92/17313. According to the present invention, the mounting whereat the legs are drivingly engaged by respective universal joint mounted leg drive motors is domed for enhanced rigidity.

Further features of the present invention are set forth in the appended claims and will be well understood from consideration of the following description given with reference to the accompanying drawings.

Brief Description of the Drawings: Figure 1 is a perspective view from one aspect of an exemplary embodiment of the present invention; and Figure 2 is a perspective view of the embodiment of Figure 1 from a different aspect and with the machine partly cut away to show its internal configuration.

Detailed -Description of the Embodiment:

Referring to the drawings, the machine illustrated has overall dimensions of the order of 2.80m length, 2.10m width and 3.0m height and has a

worktable which is 960ram square. The machine provides for the design of a component on a CAD system and the automatic machining of the component in accordance with the CAD data. The machine has a rigid triangulated framework 1 formed of welded rectangular steel tubing and, secured with a rectangular opening in the upper surface of this framework, there is a domed mounting plate 2 which supports universal joint mounted leg drive motors 3 generally as described in WO 92/17313 with reference to Figs. 26A-D thereof. Each leg drive motor 3 incorporates a motor driven ball screw which interacts with a respective one of the six legs 4 of the machine to determine the longitudinal position of the leg with respect to the mounting plate 2. At their other ends, the six legs 4 connect in pairs to respective ones of three ball-and-socket universal joints 5 secured in an equilateral triangular array on a platform 6. A spindle motor 7 is mounted on the other side of the platform 6 and serves to mount a rotary cutting tool.

A workpiece 8 is shown affixed to the worktable

9 of the jnachine and is being machined by the cutting tool driven by spindle motor 7. A swarf collection system is incorporated into the machine and a removable swarf tray 10 is shown in Fig 2.

The machine advantageously incorporates its own computer 11 with display and keyboard/touch-screen facilities. An umbilical to a separate computer work-station may, if desired, be provided, though it is preferred that the machine be fully self-contained. Controls for the leg drive motors and for other parts of the machine are conveniently housed in a compartment 12 at the rear of the machine.

The domed mounting plate 2 preferably has a part-spherical configuration and may be formed of cast metal, cast iron or cast steel for example, and may incorporate channels for the supply of coolant for example to the leg drive motors 3. The domed shape of the mounting plate 2, oriented with its convex side outermost, enhances the rigidity of the mountings of the leg drive motors 3 and provides the legs 4 with the maximum range of useful movement.

It is to be well understood that the embodiment illustrated is exemplary only and that modifications and variations are possible without departure from the scope of the invention as set forth in the appended claims. For example, the use of ball screws to drive the legs- is not obligatory and other arrangements could be employed and similarly the universal joints mounting the leg drive means with respect to the domed mounting plate need not be of the preferred

ball-and-socket type. The leg drive means need not be mounted at the universal joints coupling the legs to the domed mounting, and could alternatively be mounted on the legs themselves which might for example be telescopic.