Machine tools abstract
A workpiece holding means for machine tools and more particularly
for milling and/or drilling machines, comprising a pivoting bridge
supported between two bearing walls. The bearing walls respectively
laterally delimit a working area. At least one drive motor serves
for pivoting the pivoting bridge, such motor being arranged outside
the working area on at least one outer side of the bearing walls.
The pivoting bridge is provided with a gear ring adjacent to one
or both of the inner sides of the bearing walls, such gear ring
being drivingly connected with the drive gear wheel driven by at
least one drive motor. The bearing points or bearing pins of the
pivoting bridge accordingly do not have to transmit any drive torque
and are not subjected to any torque load so that more precise running
and more precise positioning is possible.
Machine tools claims
1. A workpiece holding means for machine tools and more particularly
for milling and/or drilling machines, comprising a pivoting bridge
supported between two bearing walls delimiting between them a working
area laterally and furthermore at least one drive motor for pivoting
the pivoting bridge, such drive motor being arranged clear of the
working area on a at least one outer side of the bearing walls,
wherein the pivoting bridge is provided with a gear ring at one
or both of the inner sides of the bearing walls, such gear ring
being drivingly connected with a drive gear wheel itself driven
by the at least one drive motor.
2. The workpiece holding means as set forth in claim 1 wherein
the drive motor and/or a drive shaft driven by it and provided with
the drive gear wheel extends at least partially from the outer side
into the bearing wall or through the bearing wall.
3. The workpiece holding means as set forth in claim 1 wherein
the gear ring and the drive gear wheel are in mesh with each other
or are connected together by the a drive sprocket chain or a drive
belt.
4. The workpiece holding means as set forth in claim 1 wherein
the drive gear ring fits at least partly into an annular or disk-like
recess in the inner side of the bearing wall.
5. The workpiece holding means as set forth in claim 1 wherein
the drive gear ring is attached to or formed on a disk-like region
of the pivoting bridge and more especially on the flat side thereof
facing the bearing wall.
6. The workpiece holding means as set forth in claim 5 comprising
a sealing ring for sealing the drive gear ring and/or the drive
gear wheel between the disk-like region and the inner side of the
corresponding bearing wall, the engagement face between the sealing
ring and the disk-like region or the inner face of the bearing wall
being preferably in the form of a plain seal face and/or a labyrinth
seal face.
7. The workpiece holding means as set forth in claim 1 wherein
the pivoting bridge possesses two bearing pins, which are more particularly
mounted in bearing sleeves, for pivotally supporting same in the
two bearing walls.
8. The workpiece holding means as set forth in claim 7 wherein
at least one of the bearing pins possesses a concentric motor-driven
drive shaft, which drives at least one workpiece table, which is
rotatably supported on the pivoting bridge, by a power transmission
train running in or on the pivoting bridge.
9. The workpiece holding means as set forth in claim 8 wherein
the drive motor for the drive shaft in the bearing pin is fixed
in the same in a manner preventing relative rotation.
10. The workpiece holding means as set forth in claim 1 wherein
the pivoting bridge possesses two gear rings adjacent to the inner
faces of the two bearing walls and two drive motors are provided
for synchronously driving the twos gear rings.
11. The workpiece holding means as set forth in claim 1 wherein
the diameter of the gear ring is larger than the diameter of the
drive gear wheel.
Machine tools description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a workpiece holding means for machine
tools and more particularly for milling and/or drilling machines,
comprising a pivoting bridge more particularly possessing two bearing
pins for the pivotal support between two bearing walls respectively
laterally delimiting a working area, and furthermore at least one
drive motor for pivoting the pivoting bridge, such motor being arranged
outside the said working area on at least one outer side of the
bearing walls.
THE PRIOR ART
[0002] The use of such pivoting bridges as workpiece holding means
for machine tools is for example disclosed in the European patent
publication 0712682 or in the German patent publication 3624284
C2. The drive motor is in each case arranged externally on one of
the two bearing walls, i. e. clear of the working area in order
to protect same from shavings produced in the course of machining
and from lubricating substances and coolants. This externally mounted
drive motor drive drives, at this position, one of the bearing pins
so that same must transmit the entire driving torque from the bearing
pin to the pivoting bridge. More particularly in the case of high
precision machining the torque on the bearing pin has turned out
to be disadvantageous, since effects are produced on the accuracy
of positioning and the running behavior.
SHORT SUMMARY OF THE INVENTION
[0003] One object of the invention is to so improve a workpiece
holding means of the type initially mentioned that if the drive
motor is externally mounted torque forces on the bearing pins may
be prevented.
[0004] In order to achieve these and/or other objects appearing
from the present specification, claims and drawings, in the present
invention the pivoting bridge is provided with a gear ring at one
or both of the two inner sides of the bearing walls, such gear ring
being drivingly connected with a drive gear wheel itself driven
by the at least one drive motor.
[0005] There is the advantage that not only a bearing pin but also
the pivoting bridge is driven directly by way of its gear ring so
that there is a short power transmission path and no torque load
on the bearing pins. This leads to improved running properties and
to a greater accuracy of positioning. As regards precise bearing
means the bearing pins may be optimized without paying heed to the
drive means.
[0006] The measures recited in the claims represent advantageous
further developments and improvements of the invention.
[0007] The drive motor and/or a drive shaft driven by it and provided
with a drive gear wheel extend at least partially from the outside
through the bearing wall. This means that simple dismounting of
the drive for the pivoting bridge is possible, for example by detaching
the drive motor from the bearing wall and drawing it outward together
with the drive gear wheel.
[0008] The gear ring and the drive gear wheel are preferably in
mesh with each other or connected together by way of a drive train
such as a sprocket chain or a toothed belt.
[0009] In an advantageous form of the invention the drive gear
ring extends into an annular or disk-like recess in the inner side
of the bearing wall at least partially so that it is substantially
protected against matter produced in the course of machining such
as shavings or the like.
[0010] In accordance with an advantageous design of the invention
the drive gear ring is attached to of formed on a disk-like area
of the pivoting bridge and more particularly on a flat side thereof
facing the bearing wall. The disk-like area accordingly serves not
only as a holding socket for the gear ring but also additionally
for screening off from the working area, more especially in the
case of an arrangement of the gear ring let into the bearing wall.
[0011] In order to achieve an even better sealing effect for the
gear wheel drive to shut it off from the working area it is an advantage
to arrange a seal ring for sealing the drive gear ring and/or the
drive gear wheel between the disk-like area of the pivoting bridge
and the inner side of the corresponding bearing wall, the face of
engagement between the sealing ring and the disk-like area or the
inner side of the bearing wall preferably being in the form of a
plain bearing means and/or a labyrinth seal face. Accordingly it
is possible for the gear ring or, respectively, the drive gear wheel
to be reliably protected or sealed from liquids and lubricants required
for machining.
[0012] In accordance with an advantageous development of the invention
at least one of the bearing pins, which are more especially supported
in bearing sleeves, contains a concentric, motor-driven drive shaft,
which drives, by way of an power transmission train, running in
or on the pivoting bridge, at least one workpiece table supported
in a rotatable manner on the pivoting bridge. Such a drive, which
in principle is disclosed in the initially mentioned prior art,
for a workpiece table through the bearing pin can be designed for
substantially more simply, if in accordance with the invention the
bearing pin is not required from the pivotal drive of the pivoting
bridge.
[0013] The drive motor for the drive shaft in the bearing pin is
secured to the latter in a manner preventing relative rotation so
that the pivotal motion of the pivoting bridge is decoupled for
the rotary movement of the workpiece table.
[0014] The torsion force acting on the pivoting bridge may be further
reduced if the pivoting bridge has two gear rings at the inner sides
of the two bearing walls and if two drive motors are provided for
a synchronous drive of such two gear rings.
[0015] The diameter of the gear ring is preferably substantially
larger than the diameter of the drive gear wheel, something which
contributes to increasing precision of positioning of the pivoting
bridge. Furthermore, for the drive motor a transmission with an
extremely low step-down transmission ratio may be selected, or it
is even possible to completely do without such a step-down transmission.
[0016] Further advantageous developments and convenient forms of
the invention will be understood from the following detailed descriptive
disclosure of one embodiment thereof in conjunction with the accompanying
drawings.
LIST OF THE SEVERAL VIEWS OF THE FIGURES
[0017] FIG. 1 shows a diagrammatic overall elevation of a pivoting
bridge pivotally supported between two bearing walls as an embodiment
of the invention.
[0018] FIG. 2 shows a more detailed representation of the drive
placed on the left hand bearing wall.
DETAILED ACCOUNT OF WORKING EMBODIMENT OF THE INVENTION
[0019] The workpiece holding means illustrated in FIGS. 1 and 2
for machine tools such as milling machines, or drilling machines,
essentially comprises a pivoting bridge 10 which at its two opposite
terminal regions possesses two bearing pins 11 and 12 turned in
opposite directions. The pivoting bridge 10 is supported in a pivotal
manner by means of such bearing pins 11 and 12 on two spaced apart
bearing walls 13 and 14. In the case of such bearing walls 13 and
14 it may be a question of side walls of the machine tool or of
side walls of a customized holding means for the pivoting bridge
10.
[0020] The two bearing pins 10 and 11 are arranged at two disk-like
terminal regions 15 and 16 of the pivoting bridge 10 which are
respectively positioned directly adjacent to and parallel to the
bearing walls 13 and 14. As shown in the more detailed representation
of FIG. 2 the bearing pins 11 and 12 are supported in anti-friction
bearings 17 in bearing sleeves 18 and 19 which are respectively
inserted in corresponding recesses in the bearing walls 13 and 14.
The bearing pins 11 and 12 respectively fit into the disk-like terminal
regions 15 and 16 and are held in same by means of flanges 20.
[0021] A gear ring 21 is mounted on the outer side, facing the
bearing wall 13 of the left hand disk-like terminal region 15
the ring being screwed or pinned in place in some manner not illustrated
in detail. These gear ring 21 fits in a corresponding annular recess
22 in the left hand bearing wall 13. A first drive motor 23 for
pivoting the pivoting bridge 10 is inserted from the outside i a
corresponding holding recess 24 in the left hand bearing wall 13
and locked in place by means of a holding flange 25. A drive gear
wheel 27 driven by a drive shaft 26 of the drive motor 23 is in
mesh with the radially outwardly directed teeth 28 of the gear ring
21. The drive gear wheel 27 is located in the extension of the holding
recess 24 into which the first drive motor 23 is partly fitted.
After detachment of the holding flange 25 the first drive motor
23 may be drawn out together with the drive gear wheel 27 outward
from the left bearing wall 13.
[0022] Instead of toothed engagement between the drive gear wheel
27 and the gear ring 21 it is possible for the transmission of power
to be by way of a drive chain, a toothed belt or the like.
[0023] For the protection of the drive device essentially comprising
the gear ring 21 and the drive gear wheel 27 against shavings and
against lubricants and coolants and the like during machining, which
are present in the working area 29 between the two bearing walls
13 and 14 a sealing ring 30 is provided, which is fixed on the
left hand bearing wall 13 and is so fitted about the disk-like terminal
region 15 of the pivoting bridge 10 that the drive gear wheel 27
is enclosed. This sealing ring 30 is in contact by way of plain
sealing face 31 or, respectively, a labyrinth seal face with the
radially outwardly turned peripheral face of the terminal region
15. As an alternative to this the sealing ring 30 could also be
fixed on the terminal region 15 the plain sealing face 31 being
formed between the sealing ring 30 and the inner face, facing the
working area 29 of the left hand bearing wall 13.
[0024] A workpiece table 32 is rotatably mounted on the pivoting
bridge 10 and onto it workpieces may be clamped, the axis of rotation
extending perpendicularly to the pivot axis of the pivoting bridge
10. The drive of such workpiece table 32 is in a known manner by
way of a second drive motor 33 which is flange-mounted by means
of a flanged cup 34 on the free terminal side of the bearing pin
11. In the interior of such bearing pin 11 a drive shaft 35 is rotatably
mounted by means of anti-friction bearings 36 and at one end is
connected by way of a connection member 37 with the drive shaft
38 of the second drive motor 33. The other end of the direction
shaft 35 bears a gear wheel 39 driving the workpiece table 32 by
way of a power transmission train 40 not illustrated in detail.
Such transmission train can include drive sprocket chains, toothed
belts, drive shafts or the like in a known manner.
[0025] Instead of a workpiece table 32 the pivoting bridge 10 may
also possess several such workpiece tables, which are either driven
by way of the same drive or by way of separate drives. For instance,
for this purpose the second bearing pin 12 may be provided with
a further corresponding drive device. The simplest possible design
would have one pivoting bridge 10 without rotary workpiece tables
32.
[0026] The diameter of the gear ring 21 is substantially larger
than that of the drive gear wheel 27 so that for this reason the
speed of rotation of the first drive motor 23 would be stepped down.
In case of need the first drive motor 23 may further possess a step-down
transmission. This also applies from the second drive motor 33.
[0027] As a modification of the illustrated working example the
drive of the pivoting bridge 10 may also be from both sides in order
to reduce the torque acting of the pivoting bridge owing to the
drive forces as far as possible. For this purpose the right disk-like
terminal region 16 is provided with a gear ring corresponding to
the gear ring 21 and in the right hand bearing wall 14 a drive motor
corresponding to the first drive motor 23 is provided. The two drive
motors are operated synchronously. |