Rod centering device for an automatic lathe feeder

A centering device for rods fed to a lathe is designed to be arranged between a rod feeder outlet and a lathe inlet and comprises at least one centering unit (11) having a passage port therein to be run through by a rod to which it supplies lateral containment. The centering unit (11) comprises a first (14) and a second (15) sectors superimposed with each sector having a passage (16 or 17) therein. Linkage actuators (18,19) operable to move the superimposed sectors to change the superimposed quantity of the passages (16,17) therein and thereby the rod passage port.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for centering rods fed to a 
lathe. 
In automatic rod feeders centering units are arranged along the rod path 
towards the lathe chuck to hold the rod well centered with respect to the 
chuck and support it during rapid rotation. Clearly, in automatic feeders 
it is of primary importance to reduce to a minimum the vibrations which 
could be produced because of misalignment of the rod during rotation, 
vibrations which would increase machine noise and would reduce machining 
accuracy. 
Centering devices arranged immediately upstream of the chuck confine the 
rod laterally to bring it back to satisfactory linearity near the chuck. 
The centering action must be effective but at the same time the rod must 
not be excessively constrained in order not to prevent discharge of 
vibrations within the magazine guides. Lateral confinement must therefore 
have a predetermined play which must be adjustable depending on the 
changing rod diameter. The centering unit must also have sufficiently 
expandable passage to permit transit of the rear grasping collet of the 
magazine which has greater diameter than the rod. 
It is clear that providing a satisfactory centering unit is difficult and 
especially in the case of multichuck lathe magazines the solutions thus 
far found are very costly and complicated as they call for numerous moving 
parts. 
The general purpose of the present invention is to obviate the above 
mentioned shortcomings by supplying a centering device which would permit 
perfect centering of rods fed to a lathe without obstructing magazine 
operation and which would have a simple robust structure even in case of 
multiple embodiment for use in a multichuck lathe magazine. 
SUMMARY OF THE INVENTION 
In view of this purpose it was sought to provide in accordance with the 
present invention a centering device for rods fed to a lathe and designed 
to be arranged between the outlet of a rod feeder and the inlet of a lathe 
and comprising at least one centering unit with a passage port in it to be 
traversed in a sliding manner by a rod while affording it lateral 
containment and characterized in that the centering unit comprises a first 
and a second superimposed sectors with each sector having a passage in it 
with running means offsetting on command between a first and a second 
positions the superimposed sectors to change the superimposed amount of 
the passages in the sectors and therewith the clearance of the passage 
port formed thereby for the rod.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the figures in FIG. 1 there is shown a front view (i.e. 
viewed from the side where the rods emerge from the outlet of a rod feeder 
towards the inlet of a lathe) of a centering device which comprises as 
many centering units 11 as there are rods simultaneously feedable to the 
lathe. For example, in FIG. 1 is shown a centering device suited for a 
3-position multichuck lathe (the lathe chuck is shown schematically by 
reference number 12 in FIG. 2). The centering device comprises a circular 
supporting frame 13 to support the various centering units 11. Each 
centering unit 11 comprises two arcuate sections or sectors 14, 15 
arranged in spaced, parallel planes in circular recesses formed on the two 
opposing faces of the frame to be coaxially of the circumference of the 
frame. Each of the sectors 14, 15 has therethrough a circular passage 16, 
17 (formed advantageously of a roller bearing). The circular passage is 
sufficiently ample to allow passage of the magazine collet. The supporting 
frame 13 is drilled opposite the passages so that a rod to be fed can 
traverse the centering unit via the passage port formed by the registering 
portions of the passages 16 and 17 of the mutually aligned sectors. Each 
sector is operated to pivot circumferentially around a central axis of the 
frame by means of a linkage 18 moved by an actuator 19. FIG. 1 shows 
linkages and actuators of the sectors on the visible face of the device. 
The opposite face is equivalent to the one shown. 
By operating the actuators of the two aligned sectors of a centering unit 
11 the centerlines of the passages 16, 17 thereof may be offset 
symmetrically relative to the center of the rod passage port thereby to 
reduce the operative size of the passage port as seen for the upper 
centering unit in FIG. 1. The contact between the fed rod 20 and the inner 
peripheral surfaces of passages 16, 17 of the centering units takes place 
only on opposing surfaces of the rod depending on the intersection of 
cylinders. It has been found that this allows perfect guidance of the rod 
with minimal vibrations and friction. In the prior art there was a 
tendency to grip the rod with the greatest possible number of contact 
points along the circumference of the rod. 
Advantageously the actuators 19 are supported on each side of the frame 13 
by the interposition of an external ring 21 which can be partially rotated 
around the frame thanks to its guide grooves 22 guided on pins 23 in the 
frame. The ring can be locked by means of a screw (not shown). In this 
manner it is possible to regulate the position of the actuators with 
respect to the associated pivot pins 24 of the linkages 18 so as to allow 
adjustment of the offset of the passages 16, 17 with the actuators in the 
rest position. 
To define the closing position of the centering units there are provided 
adjustable stops 25 which interfere with the edge of the moving sectors 
when in the predetermined passage port closing position. To allow 
adjustment of this position the stops are supported at each side of frame 
13 on a central ring 26 rotating by means of grooves 27 in it and pins 28 
in the frame. The central ring can be locked once adjusted by means of a 
setscrew (not shown). 
As may be seen also in FIG. 2 the centering unit can be fixed in position 
on the magazine by means of a central collar 29 which can be clamped with 
a screw on a shaft 30 of the magazine. 
It is now clear that the preset purposes have been reached to supply a 
centering device with a simple and stout but at the same time reliable 
structure with excellent characteristics of guidance and elimination of 
vibrations. Naturally the above description of an embodiment applying the 
innovative principles of the present invention is given merely by way of 
example and therefore is not to be taken as a limitation of the patent 
right claimed here. For example, the drilled sectors could be offset by 
means of a noncircular movement.