EP2205394A2

EP2205394A2 - Direct drive two rotary axis spindle head

Info

Publication number: EP2205394A2
Application number: EP08803741A
Authority: EP
Inventors: Roberto Colombo
Original assignee: Technai Team Srl
Current assignee: Technai Team Srl
Priority date: 2007-09-14
Filing date: 2008-09-05
Publication date: 2010-07-14
Also published as: WO2009034030A2; WO2009034030A3; ITMI20071773A1

Abstract

It is described a direct drive two rotary axis spindle head (1) comprising a fork (5), rotatable around a first axis (B), with two arms (3, 4) accommodating between them an electric spindle (2). The electric spindle (2) is rotatable around a second axis (A) perpendicular to said first axis (B). A first direct drive electric motor (6) for the rotation of the fork (5) around said first axis (B), and at least a second direct drive electric motor (9) for the rotation of the electric spindle (2) around said second axis (A). The second motor (9) comprises a rotor (10) and a stator (11), where the stator (11) is housed in a casing (12) fixed to the outer faces (13, 14) of the fork (5), in such a way that the casing (12) and part of the rotor (10) remain on the outside of the fork (5).

Description

"Direct drive two rotary axis spindle head". DESCRIPTION

The present invention relates to a direct drive two rotary axis spindle head.

Means for driving electric spindle heads to follow the contour of parts requiring complex machining processes that involve abrupt changes in the surface being machined and thus require rapid changes in the tilt angle of the tool, as is the case, for example, of machining processes in the aeronautics industry, are known. Such heads are preferably equipped with direct drive motors, which provide a faster response compared to a transmission of motion in which a servo motor transmits rotational motion by means of a gear reduction unit.

An example of this type is provided by document EP-B 1-885081, which illustrates a spindle head with a first motor that rotates a fork around its longitudinal axis, and a second motor on the fork that rotates an electric spindle, coupled to said fork, around an axis perpendicular to the first, the electric spindle being equipped with a motor of its own for driving the tools. The second motor comprises two units that define the second axis and are mounted in two cylindrical cavities of the fork, which enclose said units, which, due to the type of fork, are substantially inaccessible once they have been mounted on it.

This solution has an evident disadvantage in terms of the overall dimensions of the fork, which must be increased in order to accommodate the units of the second motor, with the drawback, as compared to more agile solutions, of precluding access to narrower recesses. One may moreover assume that there will be some problems in actuating and verifying the centring of the electric spindle in relation to the second axis of rotation in this type of solution. The object of the present invention is thus to provide a direct drive two rotary axis spindle head without any of the aforesaid drawbacks.

According to the invention this object is achieved with a direct drive two rotary axis spindle head comprising a fork, rotatable around a first axis, with two arms pivotably accommodated between which is an electric spindle rotatable around a second axis perpendicular to said first axis, a first direct drive electric motor for the rotation of the fork around said first axis and at least a second direct drive electric motor for the rotation of the electric spindle around said second axis, characterised in that the second motor comprises a rotor and a stator, where the stator is housed in a casing fixed to the outer faces of the fork so that the casing and part of the rotor remain on the outside of the fork.

These and other characteristics of the present invention will become more apparent from the following detailed description of two embodiments thereof, illustrated by way of a non-restrictive example in the appended drawings, in which: figure 1 shows a partially exploded axonometric view of a spindle head according to the invention; figure 2 shows an axonometric view of the fork of said spindle head; figure 3 shows a front view of the fork with the motor mounted; figure 4 shows a vertical section view taken along the line IV-IV of figure 3; figure 5 shows a vertical section view according to a plane passing through axes A and B of figure 1 ; figure 6 shows an enlarged detail of figure 5. With reference to the appended drawings, and in particular figures 1 and 5, one may note a spindle head 1 with an electric spindle 2 mounted between two arms 3 and 4 of a fork 5. The head 1 is equipped with a first direct drive electric motor 6, comprising a rotor 7 and a stator 8, for the rotation of the fork 5 around a first axis B longitudinal to the head 1. Two units of a second direct drive electric motor 9 are disposed on two arms 3 and 4 of the fork 5, and drive the rotation of the electric spindle 2 around a second axis A, perpendicular to the first axis B. The electric spindle 2 is equipped with its own motor (not illustrated), which drives the tools. It should be noted, with reference to figure 5, that the rotor 7 of the first motor 6 is directly flanged to the fork 5 for direct transmission of the rotational motion around the first axis B.

With reference to figures 1 and 6, it should be noted that each of the second electric motors 9 is formed by a rotor 10 and a stator 11, where the stator 11 is fixed to the fork 5 by means of a casing 12 of the second motor

9, and the casing 12, upon assembly, comes to rest against an outer vertical face 13 or 14 (the latter not illustrated) of the fork 5. The casing 12 and part of the stator 11 of the second motor 9 remain on the outside of the fork 5, also after assembly, and do not require a cylindrical structure of the fork 5 to enclose them, which is wholly advantageous in that it allows more compact dimensions, greater ease of construction and better manoeuvrability of the head 1.

It is useful to point out the advantages during the assembly and above all centring phases of such a configuration of the fork. Before and after assembly, the fork 5 maintains a degree of positive circumferential play in relation to the second motor 9, which permits it to be easily inserted into the arm 3 through a seat 15 of the fork 5, visible in figure 2, with the casing 12 resting against the outer face 13. The second motor 9 is fixed here without any particular attention to the position. The additional unit of the second motor 9 is inserted in the other arm 4 through an additional seat 16, left free, so that the additional casing 12 is resting against the outer face 14. Before being fixed definitively into place, the additional second motor 9, resting against the outer face 14, is adjusted in position until the desired centring is achieved between the two second motors 9. It appears evident that the centring operation is facilitated by this mode of assembly, which makes it possible to have ample clearance around each arm.

With reference in particular to figures 3 and 4, in order to favour the assembly and centring between the second motor 9 and the fork 5, the fork 5 is provided, on the arms 3 and 4, with seats 15 and 16 for accommodating the two units of the second motor 9. Each seat 15 and 16 has been shaped in such a way that the second motor 9 can be mounted with a predefined direction, which permits the coupling, with play, between a flaring 17, provided in each of the seats 15 and 16, and a projecting member 18 of complementary volume, with which each unit of the second motor 9 is provided.

The electric spindle 2 is assembled as follows: to a fastening shaft 19, integral with the electric spindle, a centring hub 20 is assembled; it is fixed to the rotor 10 of the second motor 9 and rests elsewhere upon bearings 21. As a further guarantee of correct functioning and centring, the head 1 may make use of a position retroaction device 22 to adjust the speed of the rotor 10 and effectively position the electric spindle 2 in relation to the second axis A.

With particular reference to figure 6, one may also note the presence of a duct in the casting of the stator 11 of the second motor 9: it is a stainless steel cooling coil 23. The cooling fluid thus flows in proximity, to the extent possible given the presence of the stator windings and rotor magnets, of the rotor 10 of the second motor 9, so as to improve the functioning thereof.

Claims

1. Direct drive two rotary axis spindle head (1) comprising a fork (5), rotatable around a first axis (B), with two arms (3, 4) accommodated between which is an electric spindle (2) rotatable around a second axis (A) perpendicular to said first axis (B), a first direct drive electric motor (6) for the rotation of the fork (5) around said first axis (B), and at least a second direct drive electric motor (9) for the rotation of the electric spindle (2) around said second axis (A), characterised in that the second motor (9) comprises a rotor (10) and a stator (11), where the stator (11) is housed in a casing (12) fixed to the outer faces (13, 14) of the fork (5), in such a way that the casing (12) and part of the rotor (10) remain on the outside of the fork (5).

2. Head according to claim 1, characterised in that the first motor (6) comprises a stator (8) and a rotor (7), where said rotor (7) is directly flanged to the fork (5) and directly transmits to it the motion of rotation around the axis (B).

3. Head according to claim 1 or 2, characterised in that the structure of the stator (11) of the second motor (9) comprises a cooling system located in proximity to the rotor (10) of the second motor (9).

4. Head according to claim 3, characterised in that the cooling system consists in a cooling duct.

5. Head according to claim 4, characterised in that the cooling duct is a stainless steel coil (23) embedded in the casting of the stator (11) of the second motor (9).

6. Head according to any of the claims 3 to 5, characterised in that cooling is achieved by means of a fluid.

7. Head according to any of the previous claims, characterised in that it is equipped with a position retroaction device (22) to adjust the speed of the rotor (10) of the second motor (9) and effectively position the second axis (A).