Abstract: A modular device for holding a workpiece or a bar of a material to be machined in a gripping chuck of a rotating spindle of a machine tool. A gripping chuck is actuated by a thrust tube coaxial with the spindle. To tighten the chuck, various forces are exerted including: a spring applying a first axial force on a thrust tube and applying a first air pressure force introduced through a duct into at least one tightening-pressure chamber. The tightening-pressure chamber is defined between at least a first wall fastened axially to the thrust tube and at least a second wall fastened axially to a regulating tube. Loosening of the chuck is obtained by a second air pressure introduced through another duct into at least one loosening-pressure chamber made between and on the other faces of the first walls fastened axially to the thrust tube and the other faces of the second walls fastened axially to a regulating tube.

Abstract: A slide (4) made up of a table (8) and a base (11) is actuated radially relative to a workpiece (M) to be machined via a stud (17) adjustable in a slot (16). The position of the stud can be regulated by means of a screw and a motor. A roller (24) borne by the stud then moves along another slot (25) in an arm (26) integral with a shaft (7f). The oscillations of the shaft are controlled by a control cam. Displacement of the stud relative to the pivot point of the arm permits the transmission ratio, hence the course of travel of the slide, to be varied. The angle .alpha. between the directions of the slots is other than zero at the end of the travel, so that the final position of a tool (29) can be adjusted by means of the control motor.

Abstract: The control device comprises a computer program. The machining of a workpiece comprises the writing of a program, the essential element of which is a step table. Starting from a predetermined profile of the workpiece, the movements of the X- and Y-axes are plotted in successive steps, and the cumulated intervals of time for obtaining the required movements, as a function of the characteristics of the machine tool and of the workpiece, are stored in the form of a table containing the movements .DELTA.t.sub.xi and the movements .DELTA.t.sub.yi. The reading of the steps, carried out as a function of an appropriate clock signal generator, brings about the successive transmission of the pulses which cause the X- and Y-axes to take their successive steps.

Abstract: The instantaneous position of a carriage (1) is made explicit in the form of data transmitted via a connection (10) to a circuit (9) by a signal converter (11) and a sensor (12) reading marks (13) on a rule (14). One of the marks (15) acts as a preselected reference mark. During a referencing sequence, the carriage is moved in one direction until it reaches a stop (18). The circuit then causes the appearance of a position error which attains a critical value, causing reversal of the direction of movement of the carriage and activation of detection of the preselected reference.

Abstract: Cheeks (2, 3) in the form of a solid rim are made integral with a pulley body (1) in that their cylindrical inside surfaces (6) are fitted under tension against cylindrical surfaces forming the bottoms of grooves (7, 8). Their positioning is carried out either by hot-collaring or by driving onto conical surfaces (9, 10). The bottoms of channels contrived between teeth (4) communicate with the outer sides of the pulley, thus permitting the movement of air during operation with a notched belt (5) and, consequently, a reduction of operating noise.

Abstract: On a processing machine having a tool-holding frame (13) facing a mutli-spindle barrel (3), one of the work stations is equipped with a support (23) bearing a spindle (38) capable of being driven axially (22) and rotatingly (C). During the cycle of operations, an auxiliary chuck mounted in a body (39) can move to grasp the end of a bar or a workpiece (57) and guide it into the field of a milling cutter (60). An AZ2C-axis control makes it possible, for example, to machine a helical groove in the cylindrical flank of the workpiece.

Abstract: The body (2) of the tool-holder (1) is equipped with spherical caps (14, 15, 16) which come to rest against the flat inside faces (6, 7, 8) of a trirectangular trihedron in the tool-mounting base. Flanges (17, 18) guide conical-tipped retaining pins (21, 22) in apertures (20, 21). These tips fit into conical recesses (23, 24). The rod (13) of a jack mounted on the base spreads the pins apart, and while entering the recesses, the pins exert on the tool-holder a force capable of immobilizing it and acting along a predetermined line of action.

Abstract: A primary piston (19) slides axially on a spindle body (5). Together with two cylindrical bearing surfaces of different diameters (D1 and D2) of the spindle body, the primary piston bounds a primary hydraulic chamber 22) which communicates via a conduit (25) with a secondary hydraulic chamber (24). The active face (33) of a secondary piston (20) bounds the secondary hydraulic chamber (24), so that the secondary piston (20) is displaced in response to a displacement of the primary piston (19) which is reduced in the same ratio as the cross-sections of the two chambers. The secondary piston (20) acts upon a chucking sleeve (15) which actuates the chuck (12) against the bias of a spring member (17) which, in the absence of pressure, holds the chuck (12) grippingly on a workpiece.

Abstract: An electric motor can drive a workpiece and a tool simultaneously at speeds in a ratio adjustable at will. The workpiece is driven via two pulleys and a belt, while the tool is driven via further pulleys and a belt from a hydraulic circuit comprising a pump coupled to the electric motor and a hydraulic motor. The pump is preferably of the variable-capacity type so that its flow can be modified independently of the speed of the electric motor.