GB2446490A - Operating head for automatic machine tools - Google Patents

Abstract

The operating head for automatic machine tools includes a first support 3 mounted to rotate around a first axis C, on a support that moves along a set of three Cartesian axes. A body 7 is mounted on the support 3 such that it can rotate around a second axis A inclined by 45 degrees to the first axis C. An interchangeable chuck unit 11 is removeably mounted on the body 7 with the axis of rotation inclined at a 45 degree angle to the second axis A. The chuck unit is either a mechanical power chuck or a motorized chuck. A power train 12, 13, 14 transmits motion from a motor to a bevel gear 15 which engages a corresponding toothed bevel gear 16 on the chuck spindle. A pair of rings with front toothing 18 is mounted on the body 7 and the chuck unit 11 for precise positioning. Hydraulic and electrical connections (22, 23, figure 2) are on the facing surfaces of the body and the chuck unit. The tool may be used for machining very strong materials such as titanium and steel or to perform medium-speed roughing operations with high chip generation.

Description

OPERATING HEAD FOR AUTOMATIC MACHINE TOOLS WITH ROTATION

OF THE SECOND AXIS INCLINED AT A 45 ANGLE TO THE FIRST AXIS,

AND A MECHANICAL CHUCK UNIT INTERCHANGEABLE WITH A HIGH-

SPEED MOTORISED CHUCK UNIT

This invention relates to an operating head for automatic machine tools which consists of a first part that rotates around an axis parallel to the main support of the machine tool, while the second part rotates around the first, on a plane inclined by 450* The rotation of said second unit is controlled by a direct-current motor combined with a gear drive and devices of known type for the elimination of mechanical play.

The terminal part of said second unit has a plane parallel or normal to the axis of the main support, which is fitted with connectors for the transmission of electrical and hydraulic signals, rings with front reference toothing and locking systems so that a mechanical chuck which rece!ves motion via a power train with high torque at the chuck, or a chuck incorporating a motor consisting of a rotor integral with the chuck and astator integral with the interchangeable chuck holder, can be fitted according to operational requirements. This characteristic allows the automatic machine tool to be used for machining very strong materials such as titanium and steel or to perform medium-speed roughing operations with high chip generation.

e.g. mould machining (mechanical chuck), or for high-speed machining on light alloys or high-speed finishing operations on any type of material (motorised chuck).

This invention allows a dual use of the machine, with no need to replace the entire head complete with first axis, second axis and chuck, as in the case of many known devices, in which the changeover from power machining to high-speed machining requires replacement of the entire head unit.

The advantage of this invention is that operating times and costs are 80% tower than with known systems.

The automatic machine tools used for chip-generating milling comprise a support which moves along a set of three orthogonal axes, an operating head with two degrees of freedom that incorporates a chuck unit being fitted to said support. The chuck unit can consist of a mechanical chuck or a motorised chuck, to which the tools needed for machining are fitted as required.

The structure and characteristics of said operating heads vary substantially, depending on whether they are designed to perform power machining with a high chip-generating tool on hard materials, such as steel or titanium, which performs relatively slow rotations for this reason, ranging from to 1000 rpm with a maximum of 3000 rpm, removing large quantities of very hard material and consequently discharging high reaction forces and vibrations onto the structure of the machine tool.

Conversely, when finishing work is to be performed on the same pieces, or simple or complex machining on light alloys, the tool must rotate at high speeds, ranging from 4-5000 to 20-30,000 rpm, with low or medium chip generation and very low reaction forces Said motorised chucks are also used for roughing operations and high-speed finishing operations on light materials, mainly aluminium.

The stresses to which the tool is subjected during these different types of machining, 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.

Basically, according to the present state of the art, the changeover from power machining to high-speed machining can only be effected by replacing the entire operating head, at very high cost.

All this means an increase in overall costs, due to longer manufacturing times, the need for two or more operating heads complete with the associated linkages, or even two or more separate machines, to be used for power machining with high torque at low/medium speed for roughing, and at high speed for finishing and/or machining of light alloys and other complementary operations.

Said problem is now solved by the present invention, which relates to an operating head for automatic machine tools wherein the chuck unit is separate from and interchangeable with the second unit, which can rotate through 3600 at a 450 angle to the main unit, which in turn can rotate through 3600 in relation to the main support.

This particular architecture, in which the second unit that holds the various interchangeable chucks is mounted at a 450 angle to the first unit, allows the machining stresses to be discharged directly onto the main support, with the further advantage that it is possible to change over from horizontal-axis machining to vertical-axis machining merely by rotating the second axis through 180 , without the interference and loss of travel presented by units in which the chuck-holding head is mounted in the centre of a fork, or the chuck is mounted in a projecting configuration as in the case of heads with 2 axes and a single shoulder.

In these cases, there will always be a loss of working clearance equal to the distance between the second axis of rotation and the front part of the chuck, generally called the pivot-point", which forces the manufacturer of the machine to increase the travel relative to the linear axes of the automatic machine tool by twice the value of the pivot-point, to ensure that the chuck covers the entire operating field. All this further increases costs.

Another very important factor is that the combined rotation of the first and second units in accordance with known trigonometrical formulae enables the chuck axis to be oriented continuously in space, thus allowing machining with 5 simultaneous axes on parts of any shape or size, without interference and with the possibility of performing power machining at low rpm and high torque, and switching to high-speed machining merely by changing the chuck unit.

A further advantage of this invention is that in the event of maintenance on one of the chuck units there is no need for the entire machine to shut down because, with the automatic change of the chuck units, the automatic machine tool can continue operating without the down time (sometimes as long as 15 days) considered normal by end users of the machine.

This invention will now be described in detail, by way of example but not of limitation, by reference to the annexed figures wherein: * Figure 1 illustrates in cross-section a 450 head according to the invention, with the mechanical chuck unit positioned vertically; * Figure 2 shows the front view of the same 450 operating head as in figure 1, illustrating the arrangement of the connectors for locking the various chuck units and the associated hydraulic and electrical connectors that control the automatic operating mechanisms; * Figure 3 shows a partial cross-section of the 450 head according to the invention, to which a motorised chuck is fitted, after automatic change, with the second unit rotated through 180 and the chuck axis positioned horizontally; * Figure 4 shows a cross-section of the motorised chuck; * Figure 5 is a front view of the motorised chuck showing the arrangement of the locking connectors and the corresponding hydraulic and electrical power connectors arranged in the same position as on the mechanical chuck.

In Figure 1, no. I indicates an operating head assembly according to the invention, mounted on sleeve 2, in such a way that a first unit 3 can rotate around a first axis identified by the letter "C", which controls the rotation of first unit 3 via a torque motor 4, the stator of which is mounted integrally with sleeve 2, while rotor 5 controls the rotation of first unit 3 on a bearing 6.

A second unit 7 rotates around a second axis inclined at a 45 angle to the first, identified by the letter "A", on a bearing 8. The rotation is controlled by a power train consisting of a direct-current motor, reducer and gears that form an assembly 9, and mesh with a crown 10 integral with unit 7.

Mechanical chuck unit 11, which is interchangeable with the motorised chuck illustrated in figure 4, is fitted to unit 7.

A shaft 12, connected to a power motor with a torque multiplier not illustrated in the figure, transmits motion via a bevel gear pair 13 to a second shaft 14, inclined by 45 , which rotates around axis "A".

The terminal part of shaft 14 is fitted with a second pair of bevel gears and 16, the first of which (15) is mounted on second unit 7, while the second (16) is integral with chuck unit 11 and directly causes chuck 17 to rotate.

The reference and precision meshing of gears 15 and 16 is ensured by a pair of rings with front toothing 18, which also ensure the precise, repeatable angular positioning of the entire chuck unit 11.

Figure 2 shows the window 19 through which gear 15 connects to gear 16 when mechanical chuck 11 is fitted, and remains free when motorised chuck 20 is fitted, as shown in figure 3.

The two or more chuck units 11 and 20 are therefore fitted and referred to second unit 7 via the double front toothing 18, and locked with a series of reverse-taper pins 21, positioned as required by their physical dimensions.

Moreover, on the two corresponding surfaces of the coupling of chuck units 11 and 20 there is a set of hydraulic connectors 22 and electrical connectors 23 of known type (figures 2 and 5) for the connection of the various hydraulic utilities for locking, and the supply of fluids and electricity for the power connections of the motorised chuck, and for the various safety and angular positioning systems.

As clearly appears from the description and the annexed drawings, chuck unit 11 is easily removable, because it is only connected to the drive devices via a coupling which allows the two parts to be brought into contact with one another and clamped with a simple rectilinear approach motion, which allows it to be detached from unit 7, with no need to remove any part of the head, merely by operating grippers 24 to release pins or shanks 21, and disconnecting the electrical and hydraulic connectors with a simple linear retraction movement.

Chuck unit 11 can therefore be replaced easily and quickly with one or more motorised chucks which have the same connectors and perform different and/or complementary types of machining to those performed with the mechanical power chuck.

Axes of rotation "C" and "A" are also equipped with measurement systems (not illustrated) which allow continuous positioning with a precision of a thousandth of a degree and angular locking systems (not illustrated) which allow the chuck axis to be locked precisely in each spatial position in order to operate in "3+2" mode, namely with three free linear axes, identified by the ISO standards as X, Y, and Z, whereas the two polar axes, identified as C and A, are locked on predefined inclinations.

In the case of machining with five simultaneous axes, motor units 4 and 9 will continuously vary the angle of the chuck unit axis by means of combined rotation of axes "C" and "A", and by controlling the three linear axes of the machine tool, normally defined by the ISO standards as "X", "Y" and "Z", with numerical control.

The operating head according to the invention therefore offers the considerable advantage that one type of chuck can be replaced in less than a minute with a completely different one: in particular, a power chuck can be replaced with a motorised finishing chuck, or vice versa.

For power machining, the mechanical chuck is brought into contact with body 7 with a rectilinear movement; the rings with front toothing ensure its precise positioning and the cogs of bevel gear pair 15 and 16 mesh together, through the corresponding windows which are positioned opposite to one another.

From an electric motor with a speed reduction unit and torque multiplier (not illustrated in the figure) the motion is transmitted to shaft 12 and from there, via bevel gear pair 13 and shaft 14, to cogwheels 15 and 16 and then to the spindle of chuck 11.

When the time comes to change over to finishing work, it is sufficient to release grippers 24 and remove the mechanical chuck, which can easily be replaced with a motorised chuck of suitable type, again fitted with a ring with front toothing 18 and shanks 21 which are engaged by grippers 24.

The motorised chuck receives electrical power via contacts 23 on body 7, while fluids, such as cooling fluids, pressurised oils for clamping in position and so on, are supplied via contacts 22, also on body 7.

Claims (11)

1) Operating head for automatic machine tools, characterised in that it comprises: * a first support (3) mounted, in such as way that it can rotate around a first axis (C), on a support that moves along a set of three Cartesian axes; * a body (7) mounted on support (3) in such a way that it can rotate around a second axis (A) indlined at a 45 angIe to said first axis (C): * an interchangeable chuck unit (11), mounted removably on said body (7), with the axis of rotation inclined at a 450 angle to said second axis (A).

2) Operating head as claimed in claim 1, characterised in that said chuck unit (11) can be either a mechanical power chuck or a motorised chuck.

3) Operating head as claimed in claim 2, characterised in that it includes, located inside said first body (3) and second body (7), mechanical means (12, 13, 14, 15-16) that transmit power to said chuck unit (11), and means (23) designed to transmit electrical power to said motorised chuck.

4) Operating head as claimed in claim 3, characterised in that it includes quick-coupling means (21, 24) to secure said chuck unit to said body (7).

5) Operating head as claimed in claim 4, characterised in that said quick-coupling means are constituted by a plurality of hydraulic grippers (24) mounted on said body 7, which are designed to clamp shanks (21) of said chuck unit.

6) Operating head as claimed in any of the preceding claims, characterised in that it comprises: * a shaft (12), mounted on said first body (3), which receives motion from a power motor located upstream of the operating head; * a bevel gear pair (13) that transmits motion to a shaft (14) which is inclined at a 450 angle to said first shaft (12), and runs from said first body (3) to said second body (7); * a second bevel gear pair formed by a first cogwheel (15) mounted on said shaft (14) and a second cogwheel (16) mounted on the spindle of chuck (11); * windows being formed in the structure of said body (7) and said chuck (11) in correspondence with said cogwheels (15, 16), so that at least one of them partly projects from said window in such a way that said cogwheels (15 and 16) are engaged when chuck (11) is brought into contact with said body (7).

7) Operating head as claimed in any of the preceding claims, characterised in that it includes, on the wall of said body (7) which comes into contact with said chuck (11), a plurality of hydraulic connectors (22) and electrical connectors (23), corresponding connectors being fitted on chuck (11).

8) Operating head as claimed in any of the preceding claims, characterised in that it includes, on said body (7) and on said chuck (11), pairs of rings with front toothing (18) for the positioning of the various chuck units (11) in relation to said body (7).

9) Operating head as claimed in any of the preceding claims, characterised in that the first rotation unit (3) is fitted with a power train consisting of an electric motor, with reducer and corresponding drive to control the rotation of second rotation unit (7) in a controlled way around axis (A), inclined at a 450 angle to said first axis (C).

10) Operating head for automatic machine tools, characterised in that it comprises: * a first support (3) mounted, in such as way that it can rotate around a first axis (C), on a support which moves along a set of three Cartesian axes; * a second rotation unit (7) mounted on said first unit (3) in such a way that it can rotate around a second axis (A) inclined at a 450 angle to said first axis (C); * a mechanical chuck unit (1 1), interchangeable with a motorised chuck, mounted on said second rotation unit (7); * a power train (12, 13, 14 and 15) which, via said bodies (3) and (4), transmits motion from a motor located upstream of the head to a bevel gear (15) which, through an opening, engages a corresponding toothed bevel gear (16) mounted on the chuck spindle; * a pair of rings with front toothing (18) mounted on said body (7) and on said chuck unit (11) to ensure the precise positioning thereof; * hydraulic and electrical connections (22, 23) on the facing surfaces of said body (7) and said chuck unit (11).

11) An operating head for automatic machine tools substantially as herein described with reference to the accompanying drawings.