Axial thread rolling head

Axial thread rolling head which comprises a bearing unit including the thread rollers and rotatably supporting said thread rollers by means of eccentric shafts, an axial shank being axially movable with respect to said bearing unit and, in a first axial relative position, cooperating with a claw clutch portion of said bearing unit by means of a claw clutch portion to connect both portions so as to be resistant to torsional strength, a first gear between said shank and said eccentric shafts, a helical spring between said shank and said bearing unit being so provided that in a second axial relative position, in which said claw clutch portions are out of mesh, said helical spring, on the occasion of a displacement of said bearing unit into a first direction of rotation with respect to said shank, is tensioned or, respectively, said tensioned helical spring displaces said bearing unit into the second direction of rotation relative to said shank, spring means which tension said shank and said bearing unit into the first relative position towards each other, and mechanical switching means which, when getting into touch with a workpiece, cause said shank and said bearing unit to move into the second relative position, a power operated drive being arranged on said shank and connected to said bearing unit (LE) via a second gear for displacing said bearing unit into the first direction of rotation by a preset angle of rotation, with said shank and said bearing unit (LE) being in the second axial relative position.

SUMMARY OF THE INVENTION 
The invention relates to an axial thread rolling head. 
For reasons of saving time and a higher strength of the thread, many 
standard threads are rolled by means of rolling systems or rolling heads. 
There is distinguished between an axial, radial and tangential rolling 
head. The present invention relates to an axial rolling head. 
BACKGROUND OF THE INVENTION 
Conventional axial rolling heads comprise three profile rollers arranged 
offset by 120.degree. which are rotatably supported within a bearing unit. 
The bearing unit is supported by a shank which is clamped into a machine 
tool. The rolling head is kept in the direction of rotation, however, can 
move axially. The rolling head is forced on the rotating workpiece, with 
the feed being made by the axially freely movable rolling head while 
milling the thread. 
Upon completion of the thread milling it is necessary to disengage the 
profile rollers with the workpiece. It is known to arrange the profile 
rollers on eccentric shafts, the rotation of which results in a change of 
the distance between the profile rollers. It is also known to secure to 
the eccentric shafts small gear wheels meshing with a central gear wheel 
which is arranged on the shank in a fixed position and cannot rotate. A 
helical spring with the one end is secured to the bearing unit and with 
the other end it is secured to the shank. The helical spring is biased, 
with the profile rollers being, in the operating position. As soon as the 
feed has reached a preset value the workpiece abuts against a rod axially 
provided within the shank of the rolling head. As a result, the bearing 
unit and the shank are axially moved apart and thus a claw clutch is 
divided between said parts. Now the spring can displace the bearing, unit 
by a given angle by twisting. In this way, the gear wheels are caused to 
also roll on the central gear wheel and twist the eccentric shafts for 
displacing the profile rollers. Thereafter, the workpiece can be removed 
from the thread rolling head. 
Before starting a new working cycle it is necessary to "lock" the rolling 
head again. This usually is done by hand. A so-called spring housing with 
the helical spring contained therein is turned in reverse direction by 
hand or by corresponding means. As the helical spring is axially extended 
during the described releasing procedure the shank and the bearing unit 
are caused to be tensioned. As soon as the moving back of the spring 
housing has reached a preset value the claw clutch mentioned before locks 
into place again and the thread rolling head is locked. 
It is the object of the invention to provide an axial thread rolling head 
where the thread rolling head can be locked automatically. 
The axial thread rolling head according to the invention comprises a drive, 
preferably an electrical motor, arranged on the shank and connected to the 
bearing unit by means of a second gear for relatively twisting the bearing 
unit into the first direction of rotation by a preset angle of rotation as 
soon as the shank and the bearing unit have reached the second axial 
relative position. With other words the motor provided on the shank twists 
the bearing unit into the locking position of the rolling head by means of 
a suitable gear, with the claw clutch, as already mentioned before, being 
locked automatically again. 
It goes without saying that there also can be used a hydraulic, pneumatic 
or another drive, especially a so-called direct drive which does not need 
a gear. 
If using an electrical motor it is certainly thinkable to feed it front 
outside as it is stationarily arranged on the shank being axially movable 
only. However, a battery supply is to be preferred. Correspondingly, 
according to an embodiment of the invention, the shank comprises means for 
receiving a battery. 
According to another embodiment of the invention, there is arranged on the 
shank at least one sensor for receiving a contactlessly transmitted 
control signal for the driving motor. Preferably, the sensor is an 
infrared sensor. If the rolling head according to the invention is 
arranged within a N/C machine the control for the driving motor may be 
part of the program. For this purpose, the N/C machine can also receive a 
signal when the thread rolling head has been released and/or the workpiece 
has left the rolling head so as to be aide to start the locking procedure. 
It goes without saying that besides the sensor a control circuit is also 
to be associated to the motor which causes the motor to be turned on and 
off as a result of the transmitted signal. Turning off, however, may be 
easily performed by a limit switch which turns off the motor as soon as a 
given angle of rotation has been reached. 
There may be used various ways to form the gear so as to displace the 
bearing unit by twisting. According to an embodiment of the invention, 
there is arranged on the motor shaft a small pinion meshing with a toothed 
segment of a rotatably supported switch ring which transfers a rotational 
movement to the bearing unit. For this purpose, the switch ring may 
comprise an engaging portion which cooperates with an engaging portion of 
the bearing unit. 
According to another embodiment of the invention, the motor is arranged 
within an annular casing provided on the shank. If using a battery box, 
it, preferably, also is annularly arranged on the shank and, preferably, 
is provided adjacent to the annular motor casing. 
According to a further embodiment of the invention, the bearing unit 
comprises a spring housing rotatably supported on the shank and forming 
the claw clutch together with the shank. It goes without saying that the 
relative rotation of the spring housing and the shaft is only possible if 
the claw clutch is out of mesh. The spring housing and the switch ring are 
surrounded by a common covering. The covering causes the switch ring to be 
also engaged in case of an axial displacement of the spring housing as a 
result of the before described abutment against the workpiece. 
The invention will be more detailedly explained hereinafter with the aid of 
drawings.

DETAILED DESCRIPTION OF THE INVENTION 
First of all, reference is made to FIG. 1 where a conventional axial thread 
rolling head is shown. It comprises one bearing unit LE and one shank 1. 
As appears therefrom, the shank 1 which, for example, may be clamped into 
a numerically controlled machine tool, comprises a coupling portion 30 as 
well as a cylindrical bearing portion 32 and a spline connection portion 
34. 
The bearing unit comprises three profile rollers 18, each of which being 
supported on eccentric shafts 5. The ends of the eccentric shafts 5 are 
arranged in corresponding bores of a front plate 4 and a distance plate 3. 
Both plates 3, 4 are spaced from each other by bolts 6. The thread portion 
of bolt 6 extends through corresponding bores provided in the distance 
plate 3. The profile rollers 18 are rotatably supported on the eccentric 
shafts 5 which, at the rear end, are flattened, said flattened end 
cooperating with correspondingly formed bores of gear wheels 8 meshing 
with a central gear wheel 7. The central gear wheel is arranged on the 
spline connection portion 34 of the shank 1. Rotation of the central gear 
wheel 7 causes the gear wheels 8 and, thus, the eccentric shafts to 
rotate, too. A displacement of the eccentric shafts 5 by means of twisting 
results in a change of the distance between the profile rollers 18. The 
thread milling makes a preset distance between the profile rollers 
necessary. This distance must be increased for removing the workpiece 
between the rollers 18. 
A spring housing 2 with a central bore is arranged on a bearing portion 32 
and comprises a claw clutch portion (not shown) which cooperates with the 
claw clutch portion 30 of the shank 1. In the spring housing 2 a helical 
spring 10 is arranged, the outer end of which cooperates with a slot 
within the spring housing 2. The inner end of the helical spring 10 is 
connected to the portion 32 of the shank 1 (not shown). In a bore 24 of 
the spring housing 2 a shank 9 is provided which can be twisted with the 
spring housing 2 if the claw clutch portions are out of mesh. 
Spring rings 11, 12 guarantee the axial support of the bearing unit LE on 
the shank 1 and the thread portions of bolts 6 extend through bow-shaped 
elongated holes of the spring housing 2 and bores through a disk 16. The 
spring housing 2 is permanently screwed on the distance plate 3 by means 
of screw nuts 15, with the relative position of rotation being exactly 
adjustable before. For this purpose, a scale is provided on the spring 
housing 2. 
A bolt 21 is secured in shank 1 with the aid of two screw nuts 20, 22, said 
bolt 21 being adjustable on account of its thread portion in its relative 
position within the shank 1. 
The function of the shown rolling head is as follows. The rollers 18 are 
spaced apart from each other at a preset distance while the claw clutch 
portions are in meshing engagement with each other. Thereat the helical 
spring 10 is under tension. To mill a thread into a workpiece which is 
guided between rollers 18 (not shown) the workpiece moves into the rolling 
head or respectively, the bearing unit LE until it abuts against bolt 21. 
In this way, the feed of shank 1 is terminated together with the bearing 
unit LE and the bearing unit LE itself continues moving as a result of the 
described feed. This causes the claws of the claw clutch to get out of 
mesh and the spring housing 2 and, consequently, the bearing unit LE 
performs a turn in consequence of the spring action of helical spring 10, 
said turn only being performed over a preset angle of rotation as a result 
of the out-of-mesh-portion of the claw clutch. This relative turn of the 
shaft 1 and the bearing unit LE, as described before, cause the eccentric 
shafts 5 to be displaced by twisting so that the rolling head is released. 
The workpiece thus can be removed from the rolling head. To lock the 
rolling head again the spring housing 2 must be displaced by twisting in 
the opposite direction via shaft 9 until the claw clutch can lock into 
place again. As during the described releasing procedure the bearing unit 
LE has been axially removed from shank 1, a tension force was also exerted 
on the helical spring 10. With the aid of this tension force the claw 
clutch portions are caused to return into their locking position. Thus the 
rolling head is again locked for a new working cycle. 
As far as FIGS. 2 to 16 show parts which are identical to those according 
to FIG. 1, there are used the same reference numbers by adding an "a". 
It appears from FIG. 2 that behind the claw clutch portion 30a of the shank 
la an annular motor casing 40 is arranged on shank 1a. Adjacent to the 
motor casing 40 an annular battery housing 42 is arranged on shank 1a. An 
electrical motor 44 is received by an eccentric bore of the casing 40 and 
extends into a bore 46 of the battery housing 42. There is still entered 
into further details later on. The reference to an electrical motor is 
made by way of example only and must not be interpreted as any limitation. 
A bearing unit 48 connected to the motor casing 40 carries a motor shaft 50 
which comprises a pinion 52. The pinion meshes with a toothed segment of a 
switch ring 54 which strikes against the right side of the spring housing 
2a. A covering 58 surrounds the spring housing 2a as well as the switch 
ring 54, said covering 58 abutting against a projection of the spring 
housing 2a while forming an axial limitation for the switch ring 54 
together with a projection 60. In this way, the switch ring 60 can rotate 
whenever there is a rotation of the pinion 52 but an axial movement can 
only be performed together with the spring housing 2a. The covering 58 is 
surrounded by a protective covering 62. 
FIG. 4 shows the bearing component 48 where only two bores 64, 66 are 
demonstrated, the first one of which receiving a screw bolt and the second 
one of which receiving a pin for the purpose of connecting to the motor 
casing 40 (see FIG. 3 and also FIG. 13) which still will be more 
detailedly explained later on. 
In FIGS. 11 and 12 the switch ring, 54 is demonstrated more clearly. It 
shows a toothing 68 arranged in segments inside and meshing with the 
pinion 52. The toothing extends over an angle of about 120.degree.. The 
switch ring 54 comprises a finger 70 radially pointing inwardly. As can be 
seen from FIG. 3, the finger 70 cooperates with a stop element 72 which is 
arranged on the right or rear side of the spring housing 2a. The locked 
position is demonstrated at 70'. Between the locked and the released 
position an angle of rotation of about 60.degree. is contained. 
In FIGS. 5 and 6 the shank 1a is more detailedly demonstrated. One can see 
that the coupling portion 30a comprises three pairs of claw portions, 
namely high, middle and deep, which in FIG. 6 are marked by H, M and T. As 
shown in FIGS. 7, 9 and 10, they cooperate with corresponding claws of the 
claw clutch portion 74 of the spring housing 2a. FIGS. 9 and 10 show the 
deep, mid and high portions (H, M, T). Furthermore, three claws 76 are 
provided more outside at the rear side of the spring housing 2a being 
spaced 120.degree. apart and engaging the switch ring 54. Besides, in the 
10 o'clock position according to FIG. 9, those bores are shown above which 
said stop element 72 is secured together with the spring housing 2a. 
Moreover, FIGS. 7, 8 and 9 show the bow-shaped elongated holes 78 through 
which the bolts do extend according to bolts 6 of FIG. 1 for connecting 
the parts as to form a bearing unit. 
In FIGS. 13 and 14 the motor casing 40 is demonstrated more detailedly. It 
comprises an eccentrically provided bore 80 which receives the motor 44. 
The bore 80 ends in an annular recess 82 of the casing 40 into which 
recess the right portion of the covering 58 with its shoulder 60 extends. 
At the rear side the casing 40 comprises cylindrical recesses 84 parallel 
to the axis which are aligned with corresponding recesses in the battery 
box still to be described for receiving batteries. 
FIG. 13 thread bores are shown at 86 which are intended to connect the 
bearing portion 48 (FIGS. 3 and 4) to the motor casing 40. 
The battery box 42 arranged adjacent to the motor casing 40 comprises 
cylindrical recesses 90 which are aligned with the recesses 84 of the 
motor casing 40 for receiving batteries. Besides, it also comprises recess 
46 for receiving the rear portion of the motor 44. 
As indicated in FIG. 2, two infrared sensors 92 are arranged in the battery 
box 46 which receive infrared signals, for instance from the N/C machine, 
for driving the motor 44 via a suitable control circuit (not shown). The 
control circuit may be provided in the motor casing 40 or in the battery 
box 42. 
The function of the thread rolling head according to FIGS. 7 to 16, with 
respect to the working cycle and the release after performing thread 
milling, corresponds to that of the rolling head according to FIG. 1. It, 
therefore, is not necessary to detailedly explain it again. However, it is 
important to mention that during the reversed rotation of the spring 
housing 2a the engaging portion or stop element 72 via the finger 70 
displaces the switch ring into a position as it is shown in FIG. 3 at 
about 8 o'clock. During this procedure the high or, respectively, deep 
portions of the claw clutch are out of mesh while the mid portions have 
been brought into engagement so that during the described releasing 
procedure a rotation over the corresponding deep and high portions is 
restricted after 60.degree.. As soon as the workpiece has been removed 
from the rolling head the motor can receive a corresponding signal in the 
form of an infrared signal from the N/C machine. The sensors 92 drive the 
motor via the control circuit (not shown) and start it. It starts 
rotational movement, with its pinion 52 displacing the switch ring 54 by 
twisting. During the described releasing movement where shank 1a and the 
spring housing 2a have moved apart by a few millimeters to cause the 
spring housing 2a to be displaced by twisting, the spring housing 2a has 
axially engaged the switch ring 54 via covering 58. The meshing between 
the pinion 52 and the toothed segment 68, however, remains unaffected. 
Thus, the rotation of the motor results in a rotation of the switch ring 
54 which moves the spring housing 2 back via finger 70 and the engaging 
portion 72 until the corresponding high and deep portions of the claw 
clutch are facing each other and can lock in position as a result of the 
axial function of the helical spring (not shown). The helical spring 
arranged in connection with the rolling head according to FIG. 2 is 
arranged within the spring housing in the same way as this has been 
described in connection with FIG. 1. As soon as the angle of rotation has 
been reached, a limit switch causes the motor to cut off. The cut-off 
signal or, respectively, another signal indicating the termination of the 
locking procedure of the rolling head, in turn, can be transmitted to the 
N/C machine in a contactless way so as to initiate another working cycle.