Machine tools abstract
The invention relates to a position drive for a tool head for use
in machine tools. The tool head comprises a base body (12), a tool
shank (16) which protrudes axially over the base body (12) and is
coupleable to a rotating machine spindle (14), and a thrust member
(18) which is movable with respect to the base body (12) and which
serves to move at least one tip holder or cutting tool (76). Further,
an electric motor arrangement (24), which is coupleable to the thrust
member (18), and a power supply device (26) for the motor arrangement
(24) are positioned on the base body (12). In order to ensure a
compact construction having an efficient motor arrangement, a hollow
shaft (50) is borne rotatable about an axis of the base body (12),
which is concentric with respect to a displacement axis (52) of
the thrust member (18), and the hollow shaft (50) has an internal
thread which engages in an external thread (42) of the thrust member
(18). The hollow shaft (50) has a toothed ring (62) which is positioned
concentric with respect to the external thread (42), for the engagement
of at least one gear (70) which is positioned on a driven shaft
(68) of the motor arrangement (24).
Machine tools claims
I claim:
1. A tool head having a position drive for use in machine tools,
comprising at least one transmission element movable with respect
to a base body, the transmission element being provided for the
displacement of a cutting tool or of a cutting tip carrier, the
tool head further comprising an electric motor arrangement positioned
in the base body and coupled to the transmission element, and further
comprising a power supply device for the motor arrangement, wherein
a hollow shaft, which is drivable by means of the motor arrangement
and which is coupled to the transmission element, is borne rotatably
and axially unmovably on the base body, the transmission element
comprising a thrust member which is movable with respect to the
base body in parallel to the axis of the hollow shaft, and the hollow
shaft is borne rotatably about an axis of the base body which is
concentric with respect to a displacement axis of the thrust member,
and the hollow shaft has an internal thread which engages in an
external thread of the thrust member, wherein an exchangeable cutting
head carrying at least one cutting tip is positioned removably at
the front face of the base body and has a central opening at its
front side for the insertion of the cutting tool which is connectable
to the thrust member.
2. A tool head having a position drive according to claim 1 wherein
the thrust member carries a coupling element, which is positioned
at the front side of and within the base body, for the insertion
of the cutting tool which extends through the central opening at
the front side of the base body or of the exchangeable cutting head
and which is retractable into a hollow space of the base body or
of the exchangeable cutting head.
3. A tool head having a position drive according to claim 1 wherein
the power supply device has an inductive current and data transfer
path which has a primary coil positioned in a first coil housing
at a machine side and a secondary coil which is positioned at a
tool head side in a second coil housing which surrounds a tool shank
in a ring-like manner, wherein the first and second coil housings
are separated from each other by an air gap when the tool shank
is coupled to a machine spindle, the cutting tool comprising a reaming
or drilling tool.
4. The tool head of claim 3 wherein primary or secondary electronics
for power conditioning are connected to the primary and secondary
coils, respectively, and are positioned in the first and second
coil housings at the machine side or tool head side.
5. A tool head for use in machine tools, comprising a base body,
a tool shank which protrudes axially over the base body and is coupled
to a rotating machine spindle, a thrust member movable with respect
to the base body and which serves to move a cutting tool, an electric
motor arrangement positioned in the base body and coupled to the
thrust member, a power supply device for the motor arrangement,
an exchangeable cutting head positioned at the front side of the
base body and which carries at least one cutting tip, and a coupling
element positioned within the base body, which is axially movable
with the aid of the motor arrangement, and which serves to accept
the cutting tool which penetrates a central opening at the front
of the exchangeable cutting head and which is retractable into the
inside of the exchangeable cutting head.
6. The tool head of claim 5 wherein the coupling element is a
clamping chuck.
7. The tool head of claim 5 wherein the coupling element has an
internal thread for receiving the tool shank which has a complementary
external thread.
8. The tool head of claim 7 wherein the coupling element is borne
non-rotatably and unmovably in a head piece of the thrust member
and has free play therein.
9. A tool head having a position drive for use in machine tools,
comprising at least one transmission element movable with respect
to a base body, the transmission element being provided for the
displacement of a cutting tool or of a cutting tip carrier, the
tool head further comprising an electric motor arrangement positioned
in the base body and coupled to the transmission element, and further
comprising a power supply device for the motor arrangement, wherein
a hollow shaft, which is drivable by means of the motor arrangement
and which is coupled to the transmission element, is borne rotatable
and axially unmovably on the base body, the transmission element
comprising a thrust member which is movable with respect to the
base body in parallel to the axis of the hollow shaft, and the hollow
shaft is borne rotatable about an axis of the base body which is
concentric with respect to a displacement axis of the thrust member,
and the hollow shaft has an internal thread which engages in an
external thread of the thrust member, wherein an exchangeable cutting
head carrying at least one cutting tip is positioned removably at
the front face of the base body and has a central opening at its
front side for the insertion of the cutting tool which is connectable
to the thrust member, the cutting tool comprising a reaming or drilling
tool, wherein the coupling element has-an internal thread for receiving
a tool shank which has a complementary external thread, wherein
the coupling element is borne non-rotatably and unmovably in a head
piece of the thrust member and has free play therein, and wherein
the coupling element has a polygonal driver portion and two spherical
calottes which adjoin the driver portion in opposite directions.
10. The tool head of claim 5 wherein the cutting tool comprises
a reamer for working on a tappet guide bushing of a cylinder head
that is connectable to the coupling element.
11. The tool head of claim 10 wherein the exchangeable cutting
head carries the cutting tip having an adjustable work angle for
precision turning of a valve seat ring which is coaxial to the tappet
guide bushing.
12. The tool head of claim 11 wherein the exchangeable cutting
head carries at least one further cutting tip for creating a bevel
delimiting the valve seat ring.
13. A tool head for use in machine tools, comprising at least one
transmission element movable with respect to a base body, the transmission
element being provided for the displacement of a cutting tool, the
tool head further comprising an electric motor arrangement positioned
in the base body and coupled to the transmission element, and further
comprising a power supply device for the motor arrangement, wherein
a hollow shaft, which is drivable by means of the motor arrangement
and which is coupled to the transmission element, is borne rotatably
and axially unmovably on the base body, the transmission element
comprising a thrust member which is movable with respect to the
base body in parallel to the axis of the hollow shaft, and the hollow
shaft is borne rotatable about an axis of the base body which is
concentric with respect to a displacement axis of the thrust member,
and the hollow shaft has an internal thread which engages in an
external thread of the thrust member, wherein a cutting tip holder
which is borne on the base body rotates about an axis which is perpendicular
to the direction of displacement of the thrust member, and transmission
means which translate the thrust movement of the thrust member into
a rotary movement of the cutting tip holder.
14. The tool head of claim 13 wherein the cutting tip holder,
the thrust member, and the transmission means form a thrust crank.
15. The tool head of claim 13 wherein the cutting tip holder carries
at least one cutting tip which functions as a ball turning tip.
16. The tool head of claim 15 wherein the cutting tip holder carries
two diametrically opposed cutting tips which function as ball turning
tips.
17. A tool head having a position drive for use in machine tools,
comprising at least one transmission element movable with respect
to a base body, the transmission element being provided for the
displacement of a cutting tool or of a cutting tip carrier, the
tool head further comprising an electric motor arrangement positioned
in the base body and coupled to the transmission element, and further
comprising a power supply device for the motor arrangement, wherein
a hollow shaft, which is drivable by means of the motor arrangement
and which is coupled to the transmission element, is borne rotatably
and axially unmovable on the base body, the transmission element
comprising a thrust member which is movable with respect to the
base body in parallel to the axis of the hollow shaft, and the hollow
shaft is borne rotatably about an axis of the base body which is
concentric with respect to a displacement axis of the thrust member,
and the hollow shaft has an internal thread which engages in an
external thread of the thrust member, wherein two sliders are displaceable
on the base body in opposite directions transverse or slanted with
respect to the direction of displacement of the thrust member, of
which at least one slider has a tool reception, and transmission
means which translate the thrust movement of the thrust member into
a displacement movement of the at least one slider.
Machine tools description
FIELD OF THE INVENTION
The invention relates to a position drive, in particular for use
in machine tools, comprising at least one transmission element which
is movable with respect to a base body, the transmission element
being provided especially for the displacement of a cutting tool
or of a cutting tip carrier, an electric motor arrangement which
is positioned on the base body and can be coupled to the transmission
element, and a power supply device for the motor arrangement.
BACKGROUND OF THE INVENTION
A tool head for use in machine tools is known (U.S. Pat. No. 3710659),
the position drive of which has a centrally positioned electric
drive motor with an axially aligned drive shaft for driving sliders
which are movable perpendicular to the axis of rotation of the tool
head. A transfer of the drive principle to other applications is
not easily possible. Moreover, the efficiency of the known drive
principle with its centrally positioned drive motor is not sufficient
for many applications.
Based on this, it is the object of the invention, to develop a
position drive of the type described above, which has a broad field
of applications and which is suited to be used in machine tools
for machining centers.
SUMMARY OF THE INVENTION
The solution according to the invention is based on the use of
a hollow shaft which is borne rotatably in the base body and drivable
by means of the motor arrangement. There is a drive unit available
which is compactly built yet efficient, which can be used for different
applications with different objects, and which is especially well
suited to be used in machine tools for machining centers.
A first variant of the invention provides that the transmission
element is formed to be a thrust member which is movable with respect
to the base body, while the hollow shaft is borne rotatable about
an axis of the base body, which is concentric with respect to a
displacement axis of the thrust member, and that the hollow shaft
has an internal thread which engages in an external thread of the
thrust member.
In an advantageous or alternative embodiment of the invention,
the hollow shaft has a toothed ring which is positioned concentric
with respect to the external thread, for the engagement of at least
one gear which is positioned on a driven shaft of the motor arrangement.
In order to increase the efficiency of the motor, the motor arrangement
has a plurality of electric motors which are distributed over the
circumference of the hollow shaft, and the drive shafts of which
each carry a gear which meshes with a toothed ring of the hollow
shaft, and which are drivable in unision by the control electronics.
The electric motors are positioned at equal circumferential distances
in a base-body-fixed motor block with their driven shafts in parallel
with respect to the axis of the hollow shaft. They are formed to
be e.g. stepper motors or servo motors which are driveable by means
of a common NC-control.
Between the hollow shaft and a base-body-fixed part, for instance
the motor block, there is advantageously positioned a sensor for
monitoring the speed and direction of rotation of the hollow shaft,
which is preferably formed to be an incremental transmitter. Instead
of the sensor, an encoder which is positioned on one of the electric
motors may be provided for monitoring the speed and direction of
rotation of the hollow shaft.
In order to ensure an optimal force transfer between the electric
motors and the hollow shaft, the toothed ring is formed to be an
internal gear ring, the diameter of which is larger than that of
the internal thread.
In a preferred application of the position drive according to the
invention, an exchangeable cutting head is positioned removably
on the base body, which has a central opening and/or a guide bushing
at its front side for the insertion of a reaming or drilling tool
which is connectable to the thrust member. To this end, the thrust
member carries a coupling element, which is positioned at the front
side of and within the base body, for the insertion of a reaming
or drilling tool which extends through a central opening at the
front side of the base body or of the exchangeable cutting head
and which is retractable into a hollow space of the base body or
of the exchangeable cutting head. The coupling element is advantageously
formed to be a collet chuck sleeve.
In a preferred embodiment of the invention, the coupling element
has an internal thread for receiving the tool shank which has a
complementary external thread. The coupling element is advantageously
borne non-rotatably and unmovably in a head piece of the thrust
member and has free play there, and preferably has a polygonal driver
portion and two spherical calottes which adjoin the driver portion
in opposite directions. Due to the degrees of freedom of play, it
ensures that no constraining forces act on the tool.
A reamer for working on a tappet guide bushing of a cylinder head
may be clamped or screwed into the coupling element, while the exchangeable
cutting head carries a cutting tip preferably having an adjustable
work angle for spot facing a valve seat ring which is coaxial to
the tappet guide bushing. The exchangeable cutting head may additionally
carry at least one further cutting tip for creating an inner and/or
outer bevel delimiting the valve seat.
In a further preferred application of the invention, there are
provided a cutting tip holder which is borne on the base body rotatable
about an axis which is perpendicular to the direction of displacement
of the thrust member, and transmission means which translate the
thrust movement of the thrust member into a rotary movement of the
cutting tip holder, wherein the cutting tip holder, the thrust member,
and the transmission means may form a thrust crank. The tool head
may in this case be used as a ball turning head, in which the cutting
tip holder carries at least one cutting tip which has a cutting
edge for ball turning.
In order to be able to use the position drive in a plane or slanted
slider head, two sliders which are displaceable on the base body
in opposite directions transverse or slanted with respect to the
direction of displacement of the thrust member are provided, of
which at least one slider has a tool reception. Furthermore, transmission
means which translate the thrust movement of the thrust member into
a displacement movement of the slider are provided. In this, the
transmission means can be formed by helical gearings which mesh
in pairs and are fixed to the thrust guide and to the slider.
The power supply device for the electric motors and the measuring
and control electronics advantageously have an inductive current
and data transfer path which has a primary coil positioned in a
coil housing at the machine side and a secondary coil which is positioned
at the tool head side in a coil housing which surrounds the tool
shank in a ring-like manner, wherein the coil housings are separated
from each other by an air gap when the tool shank is coupled to
the machine spindle. Primary or secondary electronics for power
conditioning and/or stabilization, which are connected to the primary
and secondary coils, respectively, are advantageously positioned
in the coil housing at the machine side and/or tool head side.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the invention is further described with the aid
of some embodiments schematically shown in the drawing, in which
FIG. 1 shows an axial section through a tool head for finishing
valve seat rings and tappet guide bushings in cylinder heads;
FIG. 2 shows a section through the position drive of the tool head
according to FIG. 1 in an enlarged representation;
FIG. 3 shows a top view of the position drive according to FIG.
2;
FIGS. 4a and 4b show the thrust member with collet chuck sleeve
in a partially cut side view and in a top view;
FIGS. 5a and 5b show the thrust member with a coupling element
which has an internal thread in a partially cut side view and in
a top view;
FIG. 6 shows a tool head which is formed to be a ball turning head
in a partially cut side view;
FIG. 7 shows a tool head which is formed to be a plane turning
head in a partially cut side view.
DETAILED DESCRIPTION
The tool heads 10 shown in the drawing mainly consist of a base
body 12 a tool shank which protrudes axially over the base body
12 and is coupleable to a motor-drivable, rotating machine spindle
14 of a machine tool, an axially movable thrust member 18 which
is positioned axial centrally in the base body 12 for displacing
at least one tip carrier or cutting tool, an electric motor arrangement
24 which is positioned in the base body 12 and which is coupleable
to the thrust member 18 and a power supply device 26 for the motor
arrangement 24 and measuring and control electronics 28 which are
positioned in the base body.
The power supply device 26 consists of a coil housing 30 in which
there is a secondary coil 32 which is embedded in a mechanically
resilient synthetic or resin material, with accompanying stabilizing
electronics. The secondary coil 32 is part of an inductive transfer
path. The primary coil of the inductive transfer path and the affiliated
current conditioning electronics are positioned in a housing 34
at the machine side, which engages radially outside of the tool
shank 16 into the free axial space between the front face of the
machine spindle 14 and the free front face of the coil housing 30
at the tool head side. The electronics on the primary side are connected
to a power supply (not shown) by means of a cable 36. The coil housing
34 on the machine side extends in a segment-like manner only by
approximately 70.degree. over the circumference of the tool shank
16 and leaves free the major part of the circumference of the shank,
forming a free space 38 for the access of a tool gripper for an
automatic changing of tools. The tool head 10 is gripped during
the tool changing at the driver groove 40 and displaced axially
with respect to the machine spindle 14 when the tool couple is loosened.
The thrust member 18 has a threaded body 44 with an external thread
42 which is axially guided in a non-rotatable manner in a thrust
guide 48 which is conected to the base body. A hollow shaft 50
which has a complementary internal thread 54 engaged in the external
thread 42 of the threaded body 44 is borne in the base body 12
rotatably about a rotation axis which is concentric with respect
to the displacement axis 52 of the thrust member 18. The hollow
shaft 50 is borne rotatable and unmovable in axial and radial plain
bearings 58 and has at its front end a ring flange 60 with an internal
gear ring 62 which is positioned radially outside of the internal
thread 54 on the side of the motor block 56. The toothed ring forming
the internal gear ring 62 is connected to the ring flange 60 by
means of screws 64.
A plurality, in the embodiment of FIG. 3 five, of numerically controlled
electric motors, preferably stepper motors, are positioned axially
parallely aligned in the motor block 56 so that their gears 70
which are positioned on the corresponding driven shaft 68 together
mesh with the internal gear ring 62 which is fixed on the hollow
shaft. The control of the individual stepper motors is effected
NC-controlled by way of the inductive transfer path 32 34. A sensor
72 which is formed to be an incremental transducer, for monitoring
the speed and direction of rotation is positioned in the region
between the motor block 56 and the hollow shaft 50. Alternatively,
an encoder 72' which is connected to one of the motors 66 may be
provided for monitoring the speed and direction of rotation.
In the embodiment shown in FIG. 1 4a, and 4b the tool head is
intended to be used for finishing valve seat rings 92 and tappet
guide bushings 90 of a cylinder head 94. To this end, the thrust
member 18 is rigidly connected to a clamping chuck 74 which is positioned
at the face side within the base body 12 and which is formed to
be a collet chuck sleeve, and which is to be fitted with a reamer
76. As can be seen especially in FIGS. 4a and b, the reamer 76 is
inserted into the chuck 74 and it is held there in a non-rotatable
manner with its key surface 78 in the polygonal bushing 80 and clamped
there with its shank 82. The clamping and loosening is advantageously
performed from the outside with a mechanically actuated tension
jack or an air actuated impulse tensioner 83', 83".
The embodiment shown in FIGS. 5a and b differs from the embodiment
of FIGS. 4a and b in that instead of the chuck 74 a coupling element
132 which has an internal thread 130 is provided, into whose internal
thread 130 the reamer 76 can be screwed with its shank 82 which
has a complementary external thread 134. The coupling element 132
is positioned non-rotatably and unmovably in a bushing 136 of a
broadened head piece 138 which is formed onto the thrust member
18. To this end, the coupling element has a driver portion with
a hexagonal outline and two spherical calottes 142 which adjoin
the driver portion at opposite ends, while the bushing 136 in the
thrust member 18 has an inner contour which is complementary to
the coupling element 132. By a floating bearing of the coupling
element 132 in the bushing 136 it is attained that no unwanted constraining
forces act on the reamer 76 during the work. The tool head shown
in FIG. 1 additionally carries an exchangeable cutter head 84 which
is removably connected to the front face of the base body 12 and
which has a central opening 86 and a guide bushing 88 at its front
side for the insertion of a reamer 76 which is connected to the
chuck 74. The reamer is intended to be used for working on a tappet
guide bushing 90 of a cylinder head 94 which is shown by the dash-dotted
line in FIG. 1. For spot facing the valve seat ring 92 of the cylinder
head 94 an angularly adjustable cutting tip is positioned on the
exchangeable cutter head 84. Moreover, the exchangeable cutter head
84 carries two further cutting tips 98 100 for creating outer and
inner bevels which delimit the valve seat. The tappet guide bushing
is reamed out by the reamer 76 which is clamped in the chuck 74
and axially movable with the thrust member 18 after the valve seat
in the valve seat ring 92 and the protecting bevels of the valve
seat are precision machined in the same mounting of the tool 10.
The order of machining may also be reversed. The important thing
is, that the cutting tips have no contact with the valve seat during
the reaming operation, and that the reamer does not intrude into
the tappet guide bushing during the work on the valve seat.
The tool head 10 shown in FIG. 6 is formed to be a ball turning
head. To this end, it has a cutting tip holder 106 which is borne
on a base body top 104 and is rotatabe about an axis of rotation
102 which is aligned perpendicularly with respect to the displacement
axis 52 of the thrust member 18. The cutting tip holder 106 is rotated
by means of the thrust member 18 and the connecting rod 108. The
cutting tip holder 106 carries two diametrically opposed cutting
tips 110 which have cutting edges for spherical turning, with which
concentric spherical calottes can be turned into the work piece
113.
In the embodiment shown in FIG. 7 the tool head 10 is formed to
be a plane turning head. To this end, it has a top 114 with two
sliders 118 which are displaceable against each other perpendicularly
with respect to the displacement direction 52 of the thrust member
18 in the direction of the double arrow 116. One of the sliders
118 carries a tip holder 120 and the other a counterweight 122 for
balancing purposes. Between the thrust member 18 and the sliders
118 transmission means (not shown) are positioned, which translate
the thrust movement of the thrust member into the displacement movements
of the sliders. These transmission means may for instance be formed
by helical gearings which mesh in pairs and are fixed to the thrust
member and the sliders, as shown and descibed for instance in DE-OS
27 28 975.
A substantial advantage of the position drives described above
is that they are fitted with an efficient motor arrangement 24
which makes the actuating mechanisms on the machine side superfluous
and therefore enables an automatic changing of tools and a use in
machines with a rotating machine spindle.
In summary the following is to be stated: The invention relates
to a position drive for a tool head for use in machine tools. The
tool head comprises a base body 12 a tool shank 16 which protrudes
axially over the base body 12 and is coupleable to a rotating machine
spindle 14 and a thrust member 18 which is movable with respect
to the base body 12 and which serves to move at least one tip holder
or cutting tool 76. Furthermore, an electric motor arrangement 24
which is coupleable to the thrust member 18 a power supply device
26 for the motor arrangement 24 and measuring and control electronics
are positioned on the base body 12. In order to ensure a compact
construction having an efficient motor arrangement, a hollow shaft
50 is provided, which is borne rotatable about an axis of the base
body 12 which is concentric with respect to a displacement axis
52 of the thrust member 18 and which is driven by the motor arrangement,
and the hollow shaft 50 has an internal thread which engages in
an external thread 42 of the thrust member 18 as well as a toothed
ring 62 which is positioned concentric with respect to the external
thread 42 for the engagement of at least one gear 70 which is positioned
on a driven shaft 68 of the motor arrangement 24.
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