The invention concerns a machine, particularly a machine-tool, driven by motive means through a gear device, the transmission of the movement of the gear device to the machine being effected by meshing of an output pinion of the device with a fixed axis ring gear of the machine, this gear device being housed in a casing independant of the machine and fixed thereon by resilient means. These resilient means, on the one hand, comprise at least one spring fixed to the casing to cancel out that component of the weight of the casing which is not borne by the meshing axis of the output pinion of the casing with the ring gear of the machine and, on the other hand, are arranged so that the forces (actions and reactions) exerted on the casing are either borne by the meshing axis of the output pinion of the casing with the ring gear of the machine, or else are situated in the mean plane (P) of the output pinion of the casing perpendicular to the axis of said pinion, with which arrangement it is possible to maintain as accurately as possible an equipollence between the axis of the output pinion of the device and the fixed axis of the ring gear of the machine.

An apparatus for use in machining and statically balancing a large and heavy workpiece such as the runner of a hydraulic turbine. The apparatus includes a vertical center support column on the upper end of which is mounted a rotatable turntable. The workpiece which is to be machined and statically balanced is suitably clamped to and rotates with the turntable, the workpiece extending radially beyond the turntable so that as the turntable is rotated the workpiece is moved past a machining tool which is suitably supported along the path of rotary movement of the workpiece. The turntable is detachably secured to a composite member which comprises a bearing, such as a roller bearing, integral with a gear, such as an internal ring gear, the composite member being in underlying relation to the turntable. A pair of diametrically opposed rotary hydraulic motors are housed within the center support column, each hydraulic motor rotatably driving a pinion gear which meshes with the internal ring gear of the composite member secured to the underside of the turntable, whereby to rotatably drive the turntable. A hydraulic cylinder is carried by the center column, and a piston movable within the hydraulic cylinder is rigidly connected to the turntable. The hydraulic cylinder may be continuously pressurized while the turntable is rotating during the machining operation whereby to exert an upward force on the turntable sufficiently to relieve a predetermined amount of thrust load on the bearing and thus whereby to make a greater part of the rotative power applied to the turntable available for the machining operation. Upon the completion of the machining operation, when it is desired to statically balance the workpiece, the composite member comprising the bearing integral with the gear is detached from the turntable, although the composite member remains in underlying relation to the turntable. For the static balancing operation, the turntable with the workpiece, such as the runner of the hydraulic turbine, still secured thereto, is then elevated by means of the attached hydraulic piston sufficiently to clear the centering joint with which it normally engages the composite bearing and gear. Any improper weight distribution of the workpiece will cause a tilting of the piston in the hydraulic cylinder together with a tilting of the attached turntable and of the workpiece mounted on the turntable, such tilting being sensed by machinist's levels or the like temporarily positioned on the workpiece. An appropriate compensating weight or weights is/are then permanently added to a circumferentially-extending weight pocket on the workpiece whereby to correct the detected improper weight distribution of the workpiece.