Operating head for automatic machine tools, with projecting interchangeable chuck unit

Abstract: Operating head for automatic machine tools of the type comprising a structure (2) which moves along a set of three Cartesian axes, a first support (3), fitted to the said structure in such a way that it can rotate around a first axis (C), and a chuck unit (5) fitted to the said support, wherein the said chuck unit (5) is interchangeable and projects from the said first support (3), and is designed to allow angular positioning around a second axis (A) orthogonal to the said first axis (C). Said first support (3) incorporates a power transmission system and means designed to connect the said power transmission system to the said chuck unit (5). This feature allows to change over from roughing to finishing tasks without replacing the entire head, as is necessary with known equipment in which the chuck assembly is mounted on a fork support, merely by replacing the chuck unit, a much quicker and cheaper operation.

Description: This invention relates to an operating head for automatic machine tools according to the preamble of claim 1. In particular, the head in accordance with the invention comprises a support that rotates around a first axis, which said support incorporates a power transmission system, and a kinematic mechanism for angular positioning of the chuck unit around a second axis, usually orthogonal to the axis of rotation of the support. A plate integral with the chuck assembly is fitted with couplings designed for the connection of the said support. The chuck assembly can incorporate a power unit or motorised chuck suitable to perform high-speed finishing tasks. This characteristic allows the operator to change over from roughing to finishing tasks without replacing the entire head (as is necessary with known equipment in which the chuck assembly is mounted on a fork support), merely by replacing the chuck unit, a much quicker and cheaper operation. The automatic machine tools used to perform chip-forming tasks such as milling, contouring, etc., comprise a support that moves along three orthogonal axes on which an operating head with two degrees of freedom is mounted; the said operating head carries a tool unit consisting, for example, of a chuck or motorised chuck, on which the tool required for each task is mounted. The structure and characteristics of these operating heads vary considerably, depending on whether the job in hand is a high-power task, performed with a roughing tool which rotates at a relatively low speed (max. 3000-5000 rpm) and removes large amounts of material, consequently discharging considerable reactive forces onto the structure, or a finishing/milling task, performed with a tool which rotates at high speed (up to 15,000-30,000 rpm). The stresses to which the tool is subjected during these various types of work, which are discharged onto the structure and the upstream devices, require the use of chucks with different characteristics and dimensions, which means that different operating heads have to be manufactured. In accordance with the present state of the art, when the operator wishes to change over from a high-power task to a finishing task, the entire operating head must be replaced, involving very high costs. These factors lead to an increase in overall costs, due not only to the longer production times but also to the need to have two or more operating heads complete with the corresponding kinematic mechanisms, if not two or more separate machines used for roughing, finishing or other complementary tasks. US-A-5.584.621, representing the closest prior art according to the preamble of claim 1, discloses a multiple axes rotary head for a machine tool in which linear motors are provided, for angular positioning of the spindle. The assembly includes a fork mounted for rotation about a first axis and a spindle mounted between the fork arms for rotation about a second axis orthogonal to the previous one. The fork is mounted on a support arm which includes a housing for the motor. The spindle is not quickly interchangeable, in the sense that there is no rapid connection that allows to easily remove and mount the spindle without the need of disassembling the head. US-A-5.385.436 discloses an operating head for automatic machine tools, which includes a fork fitted on a support having various degrees of freedom, means for the rotation of the fork around its axis, a support for a chuck, which can rotate around an axis which is orthogonal to the former, under a numerical control, a shaft coaxial with the axis of rotation of the support for the chuck and connected, by means of bevel gears, at one end to devices for the transmission of motion and, at its other end, to the shaft of the chuck wherein devices are provided for allowing change of the angular position of both the fork and support for the chuck, keeping the tool in contact with the piece to be machined. The chuck is not interchangeable, because it can be removed only after having removed the support bearings, and this requires the disassembling at least of part of the head. The above problems can be solved by the present invention, as defined in claim 1. For example, as the power transmission system and angular positioning devices of the chuck are built into the support to which the chuck unit is fitted, the operator can switch from a power chuck to a medium- or high-speed motorised finishing chuck very quickly, with no need to replace the entire head. This invention will now be described in detail, by way of example but not of limitation, by reference to the annexed figures in which: figure 1 shows a cross-section of the operating head in accordance with the invention figure two is a side view in partial cross-section of the operating head illustrated in figure 1, showing the arrangement of the couplings which lock the various chuck assemblies and the corresponding hydraulic and electrical power supplies which drive the automatic operating devices figure 3 schematically illustrates the interchangeable chuck unit, on which a motorised chuck is fitted figure 4 shows the plate fitted to the chuck unit for connection to the corresponding support. In figure 1, no. 1 indicates an operating head in accordance with the invention, fitted to a sleeve 2 in such a way that it can rotate around a first axis identified as "C". The head comprises a support 3, fitted to the sleeve via bearings 4, a chuck unit 5 being mounted on the said sleeve. Interchangeable chuck unit 5 may be a chuck, as illustrated in figure 1, or a motorised chuck, as illustrated in figure 3. A shaft 6, connected to motor systems not illustrated in the figure, transmits motion via a bevel gear pair 7 to a second, inclined shaft 8, which, via another bevel gear pair 9, rotates a shaft 10. A coupling of known type is fitted at the end of shaft 10 to transmit motion to shaft 11 of another bevel gear pair 12, fitted to the chuck unit and connected to power chuck 5. The invention is not limited to the configuration illustrated, but also covers all equivalent solutions. For example, in the case of power transmission systems, the invention will not be limited to the solution with an inclined shaft, but also extends to heads with other types of transmission, such as those with parallel and/or orthogonal shafts and the like. The chuck unit is shaped in such a way as to form a coupling for connection to a body or support 16 with a set of pins or shanks 14, which are gripped by gripper elements 15 of known type fitted to support 16, to lock chuck 5. Support 16 is fitted with toothing 17 which is engaged by corresponding toothing 17 present on the body of the chuck, and acts as a location plate for the correct positioning of the chuck. Alternatively, in order to position the chuck unit precisely in relation to support 16, different devices can be fitted instead of the reference toothing, such as pins inserted into corresponding seatings in the adjacent piece or other systems. A set of rapid couplings of known type 25 and 26 is fitted to the plate which constitutes the interface between the chuck unit and its support; the said couplings 25 and 26 are designed to connect the unit to electrical power supply devices and fluid supply devices, such as lubricants or coolants, respectively (fig. 2). A motor 18, schematically illustrated in figure 2, causes corresponding toothing 20 on support 16 to rotate via a cogwheel drive 19 with take-up system of known type. Motor 18, controlled by a transducer, controls the angular positioning of the chuck unit around an axis identified as "A". As will clearly appear from the description and the annexed drawings, chuck unit 5 can easily be removed, as it is only connected to the transmission devices via a coupling which requires the two parts to be brought into contact with one another and clamped with a simple, straight approach movement; it can therefore be detached with no need to remove any part of the head, merely by activating grippers 15 to release shanks or pins 14 and disconnect the electric and hydraulic couplings. Chuck 5 can therefore be quickly and easily replaced with a different chuck unit which has the same coupling, such as a motorised chuck designed to perform high-speed finishing or milling tasks. Subsequently, during operation, motor 18 will cause support 16 to rotate in order to position the chuck around axis "A", whereupon, in the case of machining performed with three machine axes (3+2 mode), support 16 will lock in the position reached. For this purpose, a ring-shaped chamber shown as no. 30 in figure 1, with walls made of a deformable material, is fitted around support 16. Chamber 30 is connected to means designed to convey pressurised fluid into the chamber so as to deform the walls, dilating them outwards in order to lock support 16 by friction. Machining can be commenced by rotating the chuck tool via the transmission system constituted by shafts 6, 8, 10 and 11. In the case of machining with 5 simultaneous axes, motor 18 will continuously vary the angle of the chuck unit under numerical control. Chip-exhausting devices are also fitted, comprising a ring-shaped chamber 21 which surrounds the base of the head and contains one or more slits fitted with a rapid coupling 22 of known type for connection of an arm 23; another arm 24, which terminates close to the tool, is connected to the end of the said arm 23. During machining, chips and/or dust are exhausted through ducts 24, 23 and 21 by devices of known type; if the chuck needs to be replaced, it is sufficient to disconnect ducts 23 and 24, which are removed together with the chuck and replaced by new ducts associated with the chuck to be fitted to the head, the said new ducts being connected via rapid coupling 22.

Claims: An operating head for automatic machine tools comprising: a first support (3) adapted for rotation about a first axis (C), mounted on a structure (2) movable along three Cartesian axes; a second support (16) rotatably mounted to the first support (3) for rotation about a second axis (A) orthogonal to the first axis (C); an interchangeable chuck unit (5), mounted on said second support (16); means for controlling rotation of the second support about the second axis; locking means for locking the second support against rotation about the second axis; a power transmission system (6, 8, 10, 11) having a coupling connectable to a drive of a chuck of said chuck unit; characterized in that : said second support (16) has a coupling (14, 15) for quick connection of the chuck unit; said chuck unit is connectable to said power transmission system via a coupling comprising parts (10, 11) to be brought into contact with one another and clamped with a straight approach movement. An operating head for automatic machine tools according to claim 1, characterized in that said power transmission system comprises a drive having shafts (6, 8, 10) and bevel gear pairs (7, 9), connected on one side to a motor system mounted in the structure (2), and having a coupling on the other side, for connection to kinematic devices (12) provided on the chuck unit. An operating head for automatic machine tools according to claim 2, characterized by the fact of providing a coupling fitted to a shaft (10) of said transmission system to transmit motion to a shaft (11) of a bevel gear pair (12), fitted to the chuck unit and connected to power chuck (5). An operating head for automatic machine tools according to claim 1, characterized in that said second support (16) has a rapid coupling (25, 26) for connection to electrical power supply devices and fluid supply devices, such as lubricants or coolants, respectively. An operating head according to any of the preceding claims, wherein the interchangeable chuck unit (5) is one of a motorized chuck and a power chuck. An operating head according to one of the preceding claims, wherein the said locking means comprises a chamber (30) having walls made of a deformable material and fluid means for introducing a pressurized fluid into the chamber to deform the walls and frictionally lock the second support in the rotated position. Operating head as claimed in claim 1, characterised in that the said coupling for quick connection of the chuck unit consists of grippers (15) designed to engage shanks (14) which are integral with the support of the said chuck unit (5). Operating head as claimed in one of the preceding claims, characterised by the fact of providing a ring-shaped chamber (21), connected on one side to exhausting devices and on the other to ducts (23, 24) which terminate close to the coupling of the tool, is fitted to the said structure 2.

Inventors: COLOMBO MAURO, COLOMBO, MAURO
Applicants: TECNICHE IND SRL, TECNICHE INDUSTRIALI S.R.L.
Application year: 2001
Main classification: B23Q1
IPC codes: B23Q11, B23Q37, B23Q1, B23Q5