Indexed operating head for automatic machine tools

An operating head for automatic machine tools, which includes a fork fitted on a support having various degrees of freedom; a mechanism for the numerical control of rotation of the fork around its axis; a support for a chuck, being fitted up on said fork and rotatably relative to it 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 the use 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.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an operating head for automatic machine 
tools, of the kind comprising: 
a fork fitted up on a support having several degrees of freedom; 
means for the numerical control of the rotations of the fork around its 
axis; 
a support for a chuck, being fitted up on said fork and rotatable around it 
under a numerical control as well, in which devices are provided for 
allowing the head to be reconfigurated by changing the angular position of 
both the fork and the support for the chuck, while keeping the tool in 
contact with the piece to be machined. 
This allows to achieve various advantages, especially when machining the 
outer part of the piece in by removing material for example in making 
contours or the like, since it is possible to reconfigurate the head 
without taking off the tool from the piece, preventing the signs of 
restarting machining from being visible. 
2. Discussion of the Background 
Various kinds of machine tools are known having an operating head, on which 
a chuck is fitted up with a connection for the tool, and the shifts of 
which are numerically controlled to perform even complex machining. 
In particular, machines are known comprising a support arm which is movable 
along a set of three Cartesian axes whereto a fork is hinged which, being 
numerically controlled, can rotate around the axis of the arm (axis C) and 
to which the support for a chuck is hinged, which, being numerically 
controlled as well, can in turn rotate around an axis which is orthogonal 
to the former (axis A). 
An operating head of this kind is described, e.g., in the U.S. Pat. No. 4 
904 131. 
In some cases these heads are indexed, i.e. they are provided with means 
permitting both the fork and the support of the chuck to be locked in a 
discrete number of angular positions around their axes, in order to enable 
the head to be configured according to the shape of the piece to be 
machined. 
For this purpose the connection between the support for the chuck and the 
fork or between the fork and its support takes place by means of pairs of 
mutually engaging racks, thus locking the various components in the 
desired configuration. 
The present invention relates in particular, although not exclusively, to 
such an operating head. 
In the known operating heads, in order to disengage either pair of racks 
and achieve a new configuration by rotating either the fork or the support 
of the chuck or both, we always intervene by moving the rack connected 
with the movable component, i.e. when adjusting the angular position of 
the chuck, the rack connected thereto is moved, leaving at the same time 
fixed the rack connected to the fork, whereas, in order to rotate the 
fork, the rack connected thereto is moved, leaving fixed the rack 
connected to the supporting arm. 
Up to now this solution has been universally adopted, since the shift of 
the rack fitted up on the fixed portion of the head turned out to be 
extremely complicated. 
However, this solution presents the disadvantage of the need to lift the 
tool from the piece in order to reconfigurate the head, with the drawback 
that, when the tool is lowered again to resume machining, on the piece the 
sign of restarting remains. 
SUMMARY OF THE INVENTION 
The object of the present invention is to overcome the above-mentioned 
drawback and, for this purpose, an operating head of the above-described 
kind is provided, in which, however, the racks forming each pair of racks 
disengage by moving the rack connected to the fixed portion of the head. 
With this system it is possible to reconfigure the machine without removing 
the tool from the piece, thus avoiding any sign of restarting machining.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the figure the reference numeral 1 designates the supporting arm or 
metal tube, on which a fork 2 is fitted up, to the arms of which the 
support 3 for a chuck 4 is hinged, said chuck 4 being provided with a 
conical connection 5 for the tool. 
The fork 2 is fitted up on the metal tube 1 by means of a thrust-bearing 
34, whereby the fork can rotate around the axis of the metal tube (axis 
C). 
The support for the chuck is fastened to a hub 6 and is fitted up on the 
arms of the fork by means of bearings 7 which allow them to be rotated 
around an axis which is orthogonal to the former (axis A). 
A motor 8, placed in the metal tube 1, makes a shaft 9 rotate directly, 
said shaft 9 transmitting motion, by means of bevel gears 10, to an 
inclined shaft 11, which, in turn, by means of bevel gears designated by 
the reference numeral 12, makes a shaft 13 rotate, said shaft 13 being 
coaxial with the hub of the support for the chuck. 
At its opposite end the shaft 13 is connected with the chuck by means of a 
final drive 14. 
Inside the hub 6 a cylinder is provided in which a piston 15 slides, the 
movements of which cause the end of a stem 16 to engage a corresponding 
seat 17 in the body of the chuck, in order to block its rotation around 
axis C. The piston 15 and its stem 16 are coaxial with axis A, to allow 
anyway the support 3 for the chuck to rotate around axis A, even when the 
stem 16 engages the seat 17. 
A circular rack 18 is integral with the body of the fork, said circular 
rack 18 engaging with a corresponding rack 19 slidingly fitted up on the 
shaft of the fork, to perform limited axial shifts being parallel to axis 
C in contrast with the force exerted by springs 20 or the like, which tend 
to keep mutually engaged the teeth of the racks 18 and 19. 
One or more keys 21 engage the rack 19 and the body of the metal tube, thus 
enabling the rack 19 to slide, but not to rotate relative to the body of 
the metal tube itself. 
In its interior the rack 19 is stepped and it is connected with a 
corresponding step, designated by the reference numeral 22, obtained in 
the shaft of the fork. 
Near the vertical walls of the rack 19, which look onto the corresponding 
walls of the fork, there are seals 23 and 24. 
This way between the horizontal walls of the rack 19 and of the body of the 
fork, near the step 22, a sort of annular chamber is formed which is 
connected, by means of ducts not shown in the figure, to devices capable 
of pumping a fluid under-pressure into the chamber via the pump shown in 
FIG. 1, in order to actuate the shift of the rack 19 in contrast with the 
force exerted by the springs 20 and to disengage it from the rack 18. 
In FIGS. 2a and 2b the detail now described is shown, in the positions of 
engagement and disengagement of the racks. 
Similarly, a circular rack 25 is fastened to the hub 6 supporting the 
chuck, the teeth 26 of said rack 25 engaging corresponding teeth 27 of a 
circular rack 28, which is also fitted up on the hub 6 but can slide 
axially in contrast with the force exerted by springs 29. A key 30 
prevents angular shifts between the rack 28 and the arm of the fork, 
allowing, however, their mutual sliding. 
The conjugate surfaces of the racks 25 and 28 are also shaped to define a 
chamber 31, which is delimited by seals 32 and 33 and is connected to 
means making it possible to pump under-pressure fluid. 
This detail is shown enlarged in FIG. 3. 
Operation of the invention takes place as follows. 
The pairs of racks 18-19 and 25-28 being mutually engaged, the motion 
imposed by the motor 8 on the shaft 9 is transmitted, by means of the 
final drives 10 and 12, to the shafts 11 and 13 respectively. 
From here, by means of the final drive 14, the motion is transmitted to the 
chuck, setting it into rotation around its axis, in order to machine the 
piece. 
When it is necessary to change the configuration of the machine, once the 
motor 8 has been stopped, the piston 15 is driven, said piston 15 leading 
the pin 16 to become positioned in the seat 17 of the chuck, preventing it 
from rotating around its axis. 
At this point, in order to rotate the fork around axis C, fluid 
under-pressure fluid is pumped into the chamber located between the shaft 
of the fork and the rack 19, causing its axial shift and leading it, by 
overcoming the force of the springs 20, into the opening position shown in 
FIG. 2b. 
Thus, the teeth of the racks 18 and 19 being disengaged, on imposing a 
rotation to the shaft 9 by means of the motor 8, since the whole kinematic 
chain has been locked from the beginning as a consequence of locking the 
chuck, the whole fork rotates around axis C. 
The amplitude of the rotation is controlled by means of the motor 8, 
whereas the positioning precision results from the engagement between the 
teeth of the circular racks 18 and 19. 
In the same way, in order to change the angular position of the support for 
the chuck around axis A the pin 16 is led to engage the seat 17, and fluid 
is pumped into the chamber 31, this time thus realizing the axial shifting 
of the circular rack 25. 
By proceeding as mentioned before, by means of the rotation of the shaft 9 
this time the positioning of the support for the chuck relative to axis A 
may be controlled. 
Therefore, with the described solution it is possible to change at will the 
configuration of the head, by adjusting its angular positions relative 
both to axis A and to axis C, without any need to lift the tool, which can 
always keep in contact with the piece to be machined and avoid, in such a 
way, that thereon remains the sign of restarting when machining is 
resumed. An expert of the field will then be able to provide for several 
modifications and variations, which, however, shall all be considered 
included in the range of the present invention.