Machine tools abstract
Method and device for support control in machine tools where it
is controlled whether an object is arranged correctly on a support
surface in the machine tool, where a duct system is used which ends
in the support surface, and conducts a medium, and can be pressurised,
the final opening of the duct system is covered by the object, and
in the duct system the pressure of the medium is reduced at a choke
point, the differential pressure is determined before and after
the choke point, and is evaluated for support control.
Machine tools claims
1. Method for the support control in machine tools, where either
it is controlled whether an object is placed correctly on a support
surface, or clamped by a clamping device comprising a first and
a second clamping means, whether the object is placed correctly
as well as is clamped by means of the clamping device, where a duct
system is used which ends in the support surface, respectively in
the first clamping means, conducts a medium and can be pressurised,
the final opening, respectively openings, of the duct system is
or are covered either by the object or the second clamping means,
or by the object as well as the second clamping means, and in the
duct system the pressure of the medium is reduced at a choke point,
the differential pressure is determined before and after the choke
point, and is evaluated for the support control, respectively clamping
control, characterised in that as a medium the coolant/lubricant,
an air coolant mixture or the air coolant rinsing of a machine tool
is used.
2. Method according to claim 1 characterised in that as duct system
the existing coolant/lubricant system or air/coolant rinsing system
of the machine tool is used.
3. Method according to claim 1 characterised in that at least
one final opening of the duct system is provided in, respectively
on, at least one clamping means for clamping the object, and is
impinged for support control or clamping control with the medium.
4. Method according to claim 1 characterised in that the final
opening of the duct system, the support surface, respectively clamping
surface, is cleaned by the medium for a support process, respectively
clamping process.
5. Method according to claim 1 characterised in that at least
one final opening of the duct system is provided in, respectively
on, at least one clamping means, for example, in openings for the
engagement of clamping bolts, and they are rinsed before or during
the clamping process with the medium.
6. Method according to claim 1 characterised in that the object
is, if necessary, one more time lifted for the positioning process,
respectively the clamping process, if either an inaccurate positioning
or clamping has been determined, or an inaccurate positioning as
well as clamping has been determined, in order to clean either the
support surface or the final opening, or support surface and end
opening together, or each of the support surface, final opening
and the clamping means independently from each other, or support
surface, final opening and clamping means simultaneously, or one
after the other by the medium, and that, after that, the positioning
process, respectively the clamping process, is repeated.
7. Method according to claim 1 characterised in that the differential
pressure is permanently collected, processed and used as signal
for the control of a machine tool.
8. Method according to claim 1 characterised in that the processing
of the differential pressure is carried out in a control, preferably
in a machine control of the machine tool.
9. Method according to claim 1 characterised in that the processing
of the differential pressure is carried out in at least one of the
pressure sensors.
10. Method according to claim 1 characterised in that the differential
pressure is permanently collected, processed and used as signal
for controlling the machine tool, and the pressure, respectively
the differential pressure, is set to a set point, and, when it is
reached, respectively the pressure falls below it, the control carries
out a switch operation, for example a change of signals.
11. Method according to claim 1 characterised in that the differential
pressure is permanently collected, processed and used as signal
for controlling a machine tool, and the supply pressure before the
choke point is also evaluated.
12. Method according to claim 1 characterised in that the differential
pressure is permanently collected, processed and used as signal
for controlling a machine tool, and the processing of the differential
pressure is carried out in a control, preferably in the machine
control of the machine tool, and it is evaluated depending on the
supply pressure and the differential pressure by the control, whether
an object rests or not at the support surface, or at least at one
of the clamping means, or at support surface and clamping means
together.
13. Method according to claim 1 characterised in that the differential
pressure in the duct system is used additionally or exclusively
for determining the flow volume of coolant/lubricant.
14. Method according to claim 1 characterised in that the processing
of the differential pressure is carried out in a control, preferably
in the machine control of the machine tool, and, depending on the
supply pressure and the differential pressure, the flow volume of
the coolant/lubricant is determined and evaluated by the control,
whether or not there is either a sufficient volume flow for cooling
or lubricating, or for cooling and lubricating together of the work
piece, the spindle, respectively the tool.
15. Method according to claim 1 characterised in that the processing
of the differential pressure is carried out in a control, preferably
in the machine control of the machine tool, and the control, respectively
the machine control of the machine tool, evaluates the value(s)
of the pressure difference for determining the flow volume of coolant/lubricant,
and, if it falls below a defined set point, transmits resulting
control commands to the machine tool.
16. Method according to claim 1 characterized in that the processing
of the differential pressure is carried out in a control, preferably
in the machine control of the machine tool, and, depending on the
supply pressure and the differential pressure, the flow volume of
coolant/lubricant is determined and evaluated by the control, whether
or not there is either a sufficient volume flow for cooling or lubricating,
or cooling and lubricating together of the work piece, the spindle,
respectively the tool, and the flow rate of the coolant/lubricant
is evaluated either through the work piece or the tool or the spindle,
or through work piece, tool and spindle together, or through work
piece and spindle, or through tool and spindle.
17. Support control device for the support control, respectively
the control of clamping objects (5) on a support surface (10), respectively
in or on clamping means (150) of a clamping device (130) of the
machine tool, in particular for carrying out the method according
to claim 1 where in the support surface (10), respectively in,
respectively on, at least one first clamping means (150), a duct
system (11) which can be pressurised and conducts medium ends in
at least one final opening (4), the final opening (4) being covered
either by the object (5), or by a second clamping means, or either
by the object as well as the second clamping means, characterised
in that the duct system (11) is the coolant/lubricant duct system
of the machine tool, and in the duct system (11) a choke point (3)
is provided, before and after the choke point one respective pressure
sensor (1 2) is provided, and the differential pressure of the
pressures collected by the pressure sensors (1 2) is determined.
18. Support control device according to claim 17 characterised
in that in order to generate the pressure difference as choke point
(3) at least one choke, orifice, nozzle, tube section, or the like
is provided.
19. Support control device according to claim 17 characterised
in that at least one of the pressure sensors (1 2) is designed
as intelligent pressure sensor in such a way that it processes the
values of the pressure collected by the pressure sensors into values
of the pressure difference, changes them into signals, and transmits
them to the control.
20. Support control device according to claim 17 characterised
in that the pressure of the process of the device is set in the
low pressure region up to 10 bars, preferably up to 2.5 bars.
21. Support control device according to claim 17 characterised
in that a clamping device (130) is provided with clamping means
(150) by means of which the object (5) or a pallet (140) carrying
the object (5) can be clamped, and at least one clamping means (150)
is connected with the duct system (11).
22. Support control system according to claim 17 characterised
in that a clamping device (130) is provided with clamping means
(150) by means of which the object (5) or a pallet (140) carrying
the object (5) can be clamped, and at least one clamping means (150)
is connected with the duct system (11), and at least one of the
clamping means (150) is provided on the object (5).
23. Support control device according to claim 17 characterised
in that a clamping device (130) is provided with clamping means
(150) by means of which the object(5) or a pallet (140) carrying
the object (5) can be clamped, and at least one clamping means (150)
is connected with the duct system (11), and at least one of the
clamping means (150) is provided on the pallet (140) carrying the
object.
24. Support control device according to claim 17 characterised
in that a clamping device (130) is provided with clamping means
(150) by means of which the object(5) or a pallet (140) carrying
the object (5) can be clamped, and at least one clamping means (150)
is connected with the duct system (11), and the final opening (4)
is provided in at least one of the clamping means (150) for clamping
the object (5).
25. Support control device according to claim 17 characterised
in that a clamping device (130) is provided with clamping means
(150) by means of which the object (5) or a pallet (140) carrying
the object (5) can be clamped, and at least one clamping means (150)
is connected with the duct system (11), and the final opening (4)
of the duct system is provided in at least one clamping indentation
(151) as clamping means of the pallet (140) carrying the object.
26. Support control device according to claim 17 characterised
in that a clamping device (130) is provided with clamping means
(150) by means of which the object (5) or a pallet (140) carrying
the object (5) can be clamped, and at least one clamping means (150)
is connected with the duct system (11), and the final opening (4)
of the duct system is provided in at least one clamping bolt (152)
as clamping means of the clamping device (130).
27. Support control device according to claim 17 characterised
in that a clamping device (130) is provided with clamping means
(150) by means of which the object (5) or a pallet (140) carrying
the object (5) can be clamped, and at least one clamping means (150)
is connected with the duct system (11), and between the machine
tool and the pallet (140), respectively work piece, a sealing, sealing
surface or a coupling, preferably an in-line quick coupling (160),
is provided in the duct system (11).
28. Support control device according to claim 17 characterised
in that the final opening (4) is designed nozzle-like.
29. Support control device according to claim 17 characterised
in that a control (6) is provided which collects and evaluates the
values of the pressure, which are determined, respectively transmitted,
by the pressure sensors (1 2), as switch signal.
30. Support control device according to claim 17 characterised
in that both pressure sensors (1 2) are designed as simple pressure
sensors, and the control processes, respectively evaluates, the
values of the pressure difference.
31. Support control device according to claim 17 characterised
in that a control (6) is provided which collects and evaluates the
values of the pressure which are determined, respectively transmitted,
by the pressure sensors (1 2) as switch signal, and the machine
control of the machine tool is provided as control (6) of the support
control device in such a way that it collects, evaluates and, if
necessary, transmits resulting control commands to the machine tool
the values of the pressure sensors (1 2).
32. Support control device according to claim 17 characterised
in that the choke point (3), respectively the means for reducing
the pressure and the pressure sensors (1 2), are arranged in the
coolant/lubricant circuit of the machine tool.
33. Support control device according to claim 17 characterised
in that a control (6) is provided which collects and evaluates the
values of the pressure which are determined, respectively transmitted,
by the pressure sensors (1 2) as switch signal, and a shut-off
valve (12) is arranged in the duct system (11), in particular after
the second pressure sensor (2), on which the control (6) for the
medium acts which is preferably connected with the machine door
of the machine tool in such a way that the shut-off valve (12) shuts
off the duct system (11) when the door is opened.
34. Support control device according to claim 17 characterised
in that as object (5) the support of which is controlled either
a work piece which has to be machined, or the tool, or a stopper
independently from each other, or the work piece which has to be
machined, the machining tool and the stopper simultaneously, or
a combination of the means defined as object is provided.
35. Support control device according to claim 17 characterised
in that the support surface (10) is arranged on a work piece carrier
of a work piece receiver or a tool receiver, in particular on the
spindle head of the machining spindle of a machine tool.
36. Support control device according to claim 17 characterised
in that a leakage gap (7) is provided through which a part of the
medium for cooling and lubricating purposes escapes permanently.
37. Support control device according to claim 17 characterised
in that a leakage gap (7) is provided through which a part of the
medium for cooling and lubricating purposes escapes permanently,
and the leakage gap (7) is provided on the junction point (170),
respectively the support point of the pallet (140) carrying the
object (5) to the machine tool.
38. Support control device according to claim 17 characterized
in that the duct system (11) serves simultaneously for the support
control device as well as for the conduction of coolant and lubricant
as medium.
39. Support control device according to claim 17 characterized
in that the duct system (11) is connected with either the tool spindle,
or the work piece, or the tool, respectively the tool support, single
and independently from each other, or simultaneously, or in different
combination with tool spindle, work piece, tool or tool support
for determining the flow volume of coolant/lubricant.
40. Support control device according to claim 17 characterised
in that either the control (6), or one of the pressure sensors (1
2), or control and one of the pressure sensors are designed in such
a way that they determine the flow volume of coolant/lubricant from
the pressure difference in the duct system.
41. Machine tool, in particular cutting machine tool, with a support
control device according to claim 17.
Machine tools description
[0001] The invention refers to a method for support control in
machine tools, where it is controlled whether or not an object is
arranged and/or clamped correctly on the support surface in a machine
tool. The invention also refers to a device for support control
to control the support of objects on a support surface, respectively
on or in the clamping means of a clamping device of a machine tool,
in particular in order to carry out the method.
BACKGROUND OF THE INVENTION
[0002] Methods, respectively devices, of this type are known. They
are methods which are carried out by means of pneumatics according
to the principle of impact pressure. An example for that is presented
in FIG. 3. For that purpose in the machine tool a pneumatic duct
system which can be pressurised is installed at the support spots,
respectively rest spots. This pneumatic system has to be installed
in addition to the, if necessary, present, coolant/lubricant duct
systems. In the duct system a constant supply pressure is generated.
This is done, for example, by means of a pressure control valve.
A downstream orifice or choke generates a pressure drop in the duct
system. The pressure is measured between orifice or choke, and the
measuring surface where air outlet openings are provided through
which the air can escape, if no work piece, tool, or the like is
positioned there. The pressure between the orifice or choke, and
the measuring surface, respectively measuring point, depends on
the relation between the orifice or adjustment of the choke, and
air gap between the support spots of the work pieces, respectively
the rest pieces. The change of pressure resulting from that is collected
electrically either directly or indirectly over a pneumatic limit
value switch, and processed in the machine control. Depending on
the volume of the duct and the required accuracy the indexing time
changes.
[0003] As the support points, respectively rest points, for the
work piece have to be clean all the time it is necessary to clean
the rest surfaces continuously from chips which might be there.
For that purpose additionally coolant or blast air is used. Therefore
the duct system has always to be pressurised in order to prevent
also the liquid from penetrating the measuring channels. The secure
recognition of the support of an object on the support surface could
reasonably, according to the required accuracy, only be realised
with pneumatic duct systems which had to be provided, as already
mentioned, additionally in support surfaces.
[0004] Because of the variable supply pressure in the systems working
with the coolant/lubricant, the required accuracy could not be reached
in the same way as it could be reached in pneumatically charged
systems. In this respect there are no hydraulic systems for support
control according to the prior art which work with sufficient accuracy
and reliability.
[0005] In the prior art also a device for pneumatic position control
is known where, via a pneumatic duct system, the pressure is measured
on a choke device in flow direction before and after this choke,
and a difference pressure sensor collects the respective differential
pressure. However, this is also a support control system already
described before, which is equipped for measuring, respectively
the support control itself, with an additional pneumatic duct system,
and thus becomes very expensive.
[0006] Another pneumatic support control installation with a differential
pressure sensor is known. This also works by means of a differential
pressure, and the evaluation via a differential pressure sensor.
For this pneumatic support control system also an additional pneumatic
duct system is necessary in addition to the coolant, respectively
flushing agent, system of the machine tool.
[0007] Another support control system is known from the state of
the art which already works with a liquid medium. Here, however,
the position of the work piece on a reference surface is determined
by a position detector. It determines the position of the work piece
because of the counterpressure and the distance. The production
of this measurement is also extremely complicated. Additionally
the detectors are quite prone to malfunctions because of the effects
of humidity.
BRIEF ABSTRACT OF THE INVENTION
[0008] Departing from the state of the art described before it
is an object of the invention to provide a method and a device by
means of which a support control in machine tools should be improved
in this a way that it works reliably, in particular if the pressure
varies.
[0009] The invention departs from the state of the art described
before, and suggests, in order to solve the problem, a method for
support control in machine tools where it is controlled whether
an object on a support surface in a machine tool is arranged correctly
and/or clamped by means of a clamping device comprising a first
and a second clamping means, where a duct system is used which ends
in the support surface, respectively in the first clamping means,
conducts a medium, and can be pressurised, the final opening of
the duct system is covered by the object and/or the second clamping
means, and in the duct system the pressure of the medium is reduced
at a choke point, the differential pressure is determined before
and after the choke point and is evaluated for the support control,
which is characterised in that as medium the coolant/lubricant flushing
of a machine tool is used. The solution according to the invention
can even be carried out with varying and non-constant supply pressure.
By determining the pressure difference the invention is independent
from pressure variations. This is obtained by collecting the pressure
before and after the choke point. This means, that the differential
pressure is relevant and not the impact pressure principle. In the
new method permanently the supply pressure, respectively the exit
pressure, and thus the differential pressure is collected, processed
and, according to the set parameters, transmitted, for example,
to the machine control as an electric signal.
[0010] Existing coolant/lubricant duct systems may be used simultaneously
also for the support control. This is independent from additional
pneumatic components. The arrangement can be easily retrofitted
into present hydraulic or even pneumatic cooling/flushing systems
without additional pinning effort.
[0011] According to an advantageous development of the invention
it is therefore provided that as a medium the filtered coolant/lubricant
of a machine tool is used. This makes it possible now to use the
hydraulic systems existing in most of the machines, like coolant
or lubricant systems, for the support control. This reduces the
effort for the support control altogether significantly. The installation
of pressure sensors which permanently collect the pressure difference
is easily possible, and also the permanent processing, respectively
evaluation, by the sensors or a control can now be carried without
any problems. Because of the incompressibility of liquids the arrangement
of the sensors is even possible in some distance from the final
opening, which is, in particular, an advantage compared with pneumatic
support controls.
[0012] The method according to the invention for support control
secures not only the control of the proper support of the object
on the provided spot of the machine tool. Simultaneously, by means
of this method, the clamping control may be carried out. That means,
if a clamping device is provided on the machine tool, which has
a first and a second clamping means which interact with each other
for clamping the object, it is provided according to the invention
to carry out the clamping control on at least one clamping means
in such a way that the pressurised duct system, respectively the
coolant/lubricant system ends in one of the clamping means. By means
of that simultaneously a control of the proper positioning of the
clamping device is possible. If, for example, one of the interacting
clamping means is soiled, a gap will form between the object and
the second clamping means, indicating that the clamping device is
not positioned exactly as there is a gap between the object which
has to be clamped, respectively the first clamping means, and the
second clamping means, allowing coolant, respectively lubricant,
to escape there which leads to a pressure drop. This changes the
differential pressure, and it is either indicated or the control
recognises that the clamping process has not been carried out exactly.
Therefore this results in two other advantages of the method according
to the invention, namely first, it is recognised whether the object
is positioned properly, respectively exactly, on the machine tool
on the provided spot, and secondly, at the same time whether the
object is properly clamped. The object may be, according to the
invention, a work piece or good which has to be machined. Of course,
the object may be also a pallet carrying a work piece on which the
work pieces are fixed in the usual way.
[0013] Furthermore it is a characteristic of the invention that
it may be used in existing machine tools with suitable duct systems
for coolant, respectively lubricant, or air/coolant-flushing systems,
and this is even subsequently. This makes it only necessary to retrofit
certain connecting drillings, if possibly, and then to install a
measuring system for differential pressure before and after a choke
point which may be retrofitted also, if necessary. Such a retrofitting
can actually be done very economically, and can, in particular,
be combined with an existing machine control in such a way that
a relatively small expense is necessary for the measuring of the
differential pressure.
[0014] According to an advantageous development of the invention
it is provided that at least one final opening of the duct system
is provided in, respectively on, at least one clamping means for
clamping the object, and is pressurised with the medium for support
or clamping control.
[0015] According to another modification of the invention it has
been found to be an advantage if the final opening of the duct system,
the support surface, respectively clamping surface, is cleaned by
the medium for a support, respectively clamping process. This may
be controlled, for example, in such a way that a pressure impact
is initiated before putting on, respectively clamping, in order
to remove, if necessary, existing soils. Of course, a simple pump
may be provided which then is activated one more time shortly before
positioning, respectively clamping, in order to let coolant/flushing
agent pass again on the support surface, respectively clamping surface,
and thus remove existing soilings.
[0016] A method as described above is characterised, according
to a development, in that at least one final opening of the duct
system is provided in, respectively on, a clamping means, for example
in openings for the engagement of clamping bolts, and they are flushed
with the medium before or during the clamping process. By means
of that also an improved positioning, an improved clamping, and,
in particular, the control of both processes may be obtained.
[0017] According to the invention it has also been found that to
be an advantage, if the object is lifted, id necessary, one more
time for the positioning, respectively clamping, process if an inaccurate
positioning and/or clamping has been stated in order to clean the
support surface and/or the final opening and/or the clamping means
with the medium, and that the positioning process, respectively
the clamping process, is repeated after that. This is no problem
in view of the control and the installation technique. The existing
clamping devices in machine tools have, as a rule, suitable positioning
means, respectively lifting means, in order to carry out the necessary
movements. Via the machine control movements of this type can be
controlled very easily.
[0018] Furthermore a development of the method according to the
invention suggests that the differential pressure is collected,
processed and used as signal for controlling a machine tool permanently.
[0019] Here it has turned out to be an advantage if the processing
of the differential pressure is carried out in a control, preferably
in the machine control of the machine tool. This modification according
to the invention is always chosen if there is already a sufficiently
capable machine control of the machine tool. Relatively simple pressure
sensors may be used which transmit the corresponding values as signals,
for example electric signals, to the machine control or the control.
[0020] Of course, it is also provided according to the invention
that the processing of the differential pressure is carried out
in at least one of the pressure sensors. Here an already intelligent
pressure sensor is used which collects and processes both values
of the pressure sensors. The result is that the determined value
then does not have to be processed in a control or in the machine
control, if there is one, or if there is no control, that the corresponding
values are then, for example, indicated. However, this requires
that at least one high quality pressure sensor is used as so-called
master sensor in order to be able to realise this task.
[0021] Another aspect of the method according to the invention
is given by the fact that the pressure, respectively the differential
pressure, is set to a set point, and if it is reached, respectively
fallen below, the control carries out a switch process, for example
a change of signal. This makes an accurate determination possible
whether or not an object rests on the support points, respectively
the clamping means, respectively their correspondingly interacting
surfaces, or whether or not the object is clamped exactly.
[0022] The method according to the invention is, according to a
development, also characterised in that the supply pressure before
the choke point is also evaluated. This permits, that it is permanently
evaluated, because of the differential pressure which is between
the first pressure sensor before the choke point, and the second
pressure sensor after the choke point, which leads to a very high
accuracy even with varying pressures, as they, for example exist,
in a coolant duct system.
[0023] The method according to the invention is also characterised
in that depending on the supply pressure and the differential pressure
the control evaluates whether or not an object rests on the support
surface, respectively clamping surface. This is, if necessary, then
indicated also by corresponding switch processes or signal changes.
[0024] The method is, for example, carried out in such a way that
the supply pressure is set as make contact to certain value, and,
if this value is reached, the control carries out a change of signal
from "0" to "1", and the differential pressure
as break contact is set to a certain lower value, and the control,
if this value is not reached, carries out a second change of signal
from "0" to "1". The control may be designed
here as electric control so that the generated electric signals
can be, for example, processed easily by a machine control. This
circuit, respectively adjustment, leads to the following logic:
1 signal 2 differential signal 1 pressure Logic supply pressure
>0.08 bars No coolant/lubricant "0" "0" no
work piece coolant/lubricant > 2.5 bars "1" "0"
No work piece coolant/lubricant > 2.5 bars "1" "1"
work piece accurate
[0025] The circuit may be, for example, designed in such a way
that in the coolant circuit a first sensor is arranged as master
sensor. In the sequence of the coolant duct system further on then
the arrangement of a orifice is following for reducing pressure.
Subsequently then the second pressure sensor follows as simple pressure
sensor. The duct system is then lead to the support system, comprising
one or more support spots, or the clamping system, comprising one
or more clamping spots, respectively clamping means. The support
spots may not only be provided as direct support spot for a work
piece. According to several preferred modifications it is, of course,
also possible to provide the outlet openings at tool receivers,
in particular at the spindle head of the machining spindle of a
machine tool, indicating whether the tool itself or the spindle
is positioned properly. If there is no such signal transmitted to
the control, for example, it is deposited in the control that then
the machine cannot carry out the machining process. Rather the positioning
process has to be carried out anew, if necessary, after a flushing
cleaning on the tool receiver. Only after the tool has been positioned
properly the start of the machining process by the machine tool
is carried out. Therefore the support surfaces or spots may also
be seen as rest surfaces.
[0026] The simple pressure sensor and the master sensor are connected
with each other, so that the master sensor can determine the pressure
difference and transmit it as electric signal to the control. By
means of that a very simple and, nevertheless, effective support
control, respectively clamping control, is provided which can be
used independent from pressure variations of the supply pressure,
as it occurs regularly in flushing or coolant circuits. It is guaranteed
that the effort which results from the construction of an additional
pneumatic duct system according to the state of the art, is completely
unnecessary by the invention.
[0027] The method also permits a very high accuracy, and works
without additional blowing air, for example for cleaning the support
surfaces. If the pneumatic technique was used, it had to be adjusted
exactly, which needed accordingly expensive adjustments. As the
pneumatic systems were often prone to malfunctions, and frequently
were even switched off unintended, further disadvantages of the
system occurred. The availability of a support control system according
to the state of the art was therefore limited.
[0028] The solution suggested now therefore permits a very simple
and reliable method for carrying out a support and clamping control.
The invention is also suitable for retrofitting a support control
system in machine tools which have a coolant circuit, respectively
a flushing agent circuit. It is not necessary there to drill additional
channels for air.
[0029] Another advantage of the invention is also the fact that
the measurements are now independent from the lengths of the ducts
as the pressure existing in the liquid is eventually available for
the liquid altogether to the same extent, because of the incompressibility
of liquids in contrast to the compressibility of air. This is also
the reason why the hydraulic support control in the hydraulic circuit
can even be installed far away from the actual support surface,
as the conditions after the support control do not change dramatically,
as a rule. Such a procedure is almost impossible with pneumatic
systems as in a relatively long channel, of course, air is compressed
which leads to corresponding indexing times or inaccuracies.
[0030] The invention also provides a method, as described above,
which is, according to a development, characterised in that the
differential pressure in the duct system is used additionally or
exclusively for determining the flow volume of coolant/lubricant.
Departing from the knowledge that in particular in a system with
strong variations of pressure as in a coolant/lubricant system,
a measurement of the flow volume is very difficult to realise, here
the pressure difference which is measured on the two sensors before
and after the choke point, is used for determining whether sufficient
coolant/lubricant reaches the tool, the tool spindle, respectively
the work piece. By means of this it may, for example, be recognised
whether there are malfunctions in the system. These may be, for
example, soiling with chips at the outlet spots of the coolant/lubricant.
Also malfunctions within the coolant system in the work piece, respectively
the spindle, may now be recognised reliably by the method according
to the invention.
[0031] A method as described before is, according to a development,
characterised in that depending on the supply pressure and the differential
pressure the flow volume of coolant/lubricant is determined and
evaluated by the control, in the way whether or not a sufficient
volume flow exists for cooling and/or lubricating the work piece,
the spindle, respectively the tool.
[0032] A development of the method described in this way is characterised
in that the control, respectively the machine control of the machine
tool, evaluates the value(s) of the pressure difference in order
to determine the flow volume of coolant/lubricant, and transmits,
if a determined set point is fallen below, the resulting control
commands to the machine tool.
[0033] A method aimed in particular to the measurement, respectively
the determination, of the flow volume of coolant/lubricant is characterised,
according to a development of the method described before, in that
the work piece and/or the tool and/or the spindle are controlled
and evaluated with reference to the flow volume of the coolant/lubricant,
and corresponding control commands then are triggered by the control
when a certain predefined set point is fallen below. These may be,
for example, commands for stopping the spindle, respectively for
flushing certain duct sections.
[0034] The methods for support control and for measuring the flow,
respectively control the flow, may also be applied on their own
and independently from each other, so that an independent protection
can be claimed.
[0035] The problem of the invention is also solved by a support
control device for the support control of objects on a support surface,
respectively in or on clamping means of a clamping device of a machine
tool, in particular for carrying out the method as described before,
where in the support surface, respectively on at least one clamping
means, a duct system, which can be pressurised and which ducts a
medium, ends in at least one final opening, the final opening being
covered by the object and/or a second clamping means interacting
with the first clamping means, which is characterised in that the
duct system is the coolant/lubricant duct system of the machine
tool, and in the duct system a choke point, one pressure sensor
before and one after the choke point is provided, and the differential
pressure of the pressures determined by the pressure sensors is
stated. Differing from the practice used so far, namely to determine
an absolute pressure, it is now possible to measure the pressure
difference of a first and a second pressure, and to use the resulting
value for determining the support control, as well as the control
of clamping. With a large drop of pressure in the duct system it
is clear that the liquid can escape on the support opening. The
pressure difference is then accordingly large. If the object the
support of which is supposed to be controlled is positioned accurately,
the pressure difference will be adjusted to a smaller value.
[0036] In this case it may be defined via the control that certain
set points, for example the supply pressure and the differential
pressure are predefined in order to be able to conclude the correct
position, respectively clamping, of the object, for example work
piece or tool.
[0037] In this connection it is in particular be pointed out that
all features and characteristics described with regard to the device,
but also methods in the sense also with regard to the formulation
of the method according to the invention can be transferred and,
in the sense of the invention, also be used and are considered to
be disclosed together with them. This goes also vice versa, which
means that constructive, that means device, features only cited
with regard to the method may also be taken into consideration in
the frame of the device claims, and be claimed, and also count to
the invention and disclosure.
[0038] For generating the pressure difference, according to a development
of the support control device of the invention, at least one choke,
orifice, nozzle, tube section, or the like is provided as choke
point.
[0039] It is an advantage here, if at least one of the pressure
sensors is designed as intelligent pressure sensor, respectively
as so-called master pressure sensor, in such a way that it processes
the values of the pressure collected by the two pressure sensors
into values of the pressure difference, turns them into signals,
and transmits them to the control of the machine tool or to a separate
control. Such a support control device is always a possibility if
the control has not enough capacity for processing the values, or
if the control is not designed for turning the signals provided
by the pressure sensors.
[0040] Of course, it is also possible to provided only two simple
pressure sensors, one before and one after the choke point, which
transfer their values of the determined pressure to the control,
and the control carries out the processing and evaluation. This
possibility exists always if there is a sufficiently dimensioned
machine control which can process, without any problems, values
provided by the support control system and/or clamping control system,
respectively the support control device.
[0041] According to an advantageous development of the invention
it is provided that the process pressure of the device is set in
the low-pressure region up to 10 bars, preferably up to 2.5 bars.
Thus expensive devices, respectively systems, for providing pressure
are not necessary.
[0042] It is, in particular, possible to use the flushing systems,
respectively coolant systems, working in the low-pressure region.
[0043] A support control device as described before is, according
to a development, characterised in that a clamping device is provided
with clamping means by means of which the object or a pallet carrying
the object can be clamped, and at least one clamping means is connected
with the duct system. By the connection of at least one clamping
means with the duct system now, besides the support control, even
a control of the proper clamping is possible. Besides the control
whether the clamping process has been carried out correctly, of
course, a control of a proper position of the corresponding clamping
means of the clamping device is possible beforehand. This may, for
example, be indicated by the fact that there still may be a certain
drop in pressure during the positioning, which, however, may not
exceed certain set points. If this is not the case the control of
the machine tool may be designed in such a way that the clamping
device is lifted once again, and the clamping means are, if necessary,
cleaned again by a flushing shot. If the positioning is correct,
and there is a soiling at the clamping surfaces of the clamping
means it may nevertheless happen that the clamping device does not
clamp the object correctly. This will be recognised also by the
thus still existing gap because through this gap liquid may escape,
and a drop in pressure, respectively another differential pressure,
is determined. In this respect, by means of the support control
according to the invention, not only a control of the proper support
of the object, but also simultaneously a clamping control device,
respectively support control device for the clamping means is provided.
According to that a development of the invention is characterised
in that at least one of the clamping means is provided on the object,
respectively on the pallet carrying the object.
[0044] The final opening of the coolant duct system, respectively
the flushing agent duct system, is provided, according to a development,
at least in one of the clamping means for clamping the object.
[0045] The final opening may here either be provided in at least
one clamping indentation as clamping means of the pallet carrying
the object. In the same way it is, according to the invention, also
provided to arrange the final openings of the duct system in at
least one of the clamping bolts as clamping means of the clamping
device.
[0046] For a proper connection of the duct system with the clamping
system, respectively the clamping means, for example a sealing,
sealing surfaces or a coupling, preferably an in-line quick coupling
is provided in the duct system between the machine tool and the
pallet, respectively the work piece. The sealing, respectively the
sealing surfaces, are here possible in different embodiments. Thus,
for example, a metal sealing by ground-in or polished surfaces are
possible as well as a solution where a sealing is provided for one
side or both sides of the surfaces which have to be sealed. Of course
also a known coupling for such a duct system may be used for that
purpose, preferably an in-line quick coupling. The invention is
not restricted to such a sealing type. Rather all possible types
of sealings are comprised by the invention.
[0047] The final opening is, according to a modification of the
invention, designed like a nozzle. This has the effect that the
coolant, respectively lubricant, can escape with corresponding pressure
or correspondingly distributed, depending on the design of the supports,
respectively the clamping surfaces.
[0048] Another aspect of the support control device according to
the invention is given by the fact that a control is provided which
collects the values of the pressure collected, respectively transmitted,
by the pressure sensors as switch signal, and evaluates them. For
example, the switch signals, as described above, can be given in
a corresponding logic so that during the adjustment of the respective
pressure the support control device indicates the corresponding
values, and, if necessary, executes the commands belonging to that.
As already mentioned, at least two modifications of the invention
are possible, namely in such a way that two pressure sensors are
designed as simple pressure sensors, and the control processes the
values of the pressure difference, respectively evaluates them.
It is also possible here to provide the machine control of the machine
tool as control of the support control device, in such a way that
it collects the values of the pressure sensors, evaluates them and,
if necessary, transfers resulting control commands to the machine
tool. The second modification is given by the use of a so-called
master sensor, which is already able to carry out calculations,
respectively evaluations, and to transmit them to the control or
indication means.
[0049] Another aspect of the support control device according to
the invention is given by the fact that the choke point, respectively
means for reducing the pressure, respectively for changing the pressure,
and the pressure sensors are arranged in the coolant circuit of
the machine tool. This has the advantage that no additional systems
for support control, respectively clamping control, have to be provided
but existing systems can be used. For retrofitting, if necessary,
only a support outlet opening on the support surface, respectively
rest surface, has to be provided. This can be realised even for
retrofitting relatively simple.
[0050] A development of the support control device, as described
before, is characterised in that a shut-off valve is provided in
the duct system on which the medium control acts, which is connected
preferably with the machine door of the machine tool in such a way
that the shut-off valve shuts off the duct system when the door
is opened. This prevents coolant, respectively flushing liquid,
from further escaping, or, if necessary, from splashing out of the
machine tool, when the machine door is opened, or an entering user
or maintenance person from being soiled, respectively injured. The
shut-off valve is arranged preferably in the duct system after the
second pressure sensor. This may prevent a larger loss of coolant,
respectively flushing liquid.
[0051] The objects the support of which is supposed to be controlled
are, according to the invention, a work piece which has to be machined,
and/or the machining tool itself, and/or a dead stop because it
always has to reach the same position.
[0052] Furthermore it is convenient if the support surface is arranged
on a work piece receiver, a work piece carrier, or a tool receiver,
in particular the spindle head of the machining spindle of a machine
tool. For that purpose, if necessary, also the support surface has
to be defined as rest surface. This depends on the location of the
surface, and on the location of the outlet openings for the liquid.
If, for example, the correspondingly correct position of a machining
spindle of a machine tool is checked this will be carried out on
the rest surfaces of the spindle in the direction, for example,
to the drive. If, in contrast to that, a tool receiver is equipped
with a support control device, the outlet openings have to be arranged
at the rest surfaces of the tool receiver for the tool. In the same
way it is, of course, provided that the support surfaces, respectively
the rest surfaces, are arranged on a work piece carrier, respectively
on the corresponding surfaces of a work piece receiver for support,
respectively resting. The combination of several modifications is
also subject of the invention.
[0053] For permanent cleaning and/or cooling of the support surfaces
it is provided that a leakage gap is arranged on the support surface.
This leakage gap makes a continuous escape of a part of the medium
for cooling and flushing purposes possible. By means of this, if
necessary, also the support surfaces, respectively the rest surfaces,
may be cleaned.
[0054] A modification of the support control device according to
the invention is characterised in that the leakage gap is provided
at the junction point, respectively the support point, of the pallet
carrying the work piece to the machine tool. This makes a support
control device with leakage gap possible and also is the simultaneous
conduction of the coolant, respectively the flushing liquid, respectively
the lubricant, given.
[0055] According to the invention the duct system of the support
control device serves at the same time as control device for support,
respectively clamping, as well as the duct of coolant/flushing liquid
as medium.
[0056] A support control device as described before, is, according
to a development, characterised in that the duct system is connected
with the tool spindle, and/or the work piece, and/or the tool, respectively
the tool receiver, for determining the flow volume of coolant/lubricant.
This ensures that besides the support control simultaneously also
the sufficient flow volume of coolant/lubricant is controlled and
monitored.
[0057] At the same time it is, however, also possible to realise
the measurement of volume flow, respectively the control, and the
support control independently from each other, for example by means
of independently working devices, by means of which also may be
reached an independent protection.
[0058] It is furthermore an advantage here if the control and/or
at least one of the pressure sensors are designed in such a way
that the flow volume of coolant/lubricant can be determined by means
of the pressure difference and/or the supply pressure in the duct
system by these.
[0059] The invention provides also a machine tool, in particular
cutting machine tool, with a support control device, as described
before.
BRIEF DESCRIPTION OF THE DIFFERENT VIEWS OF THE DRAWINGS
[0060] The invention is described in detail in the following by
means of examples and drawings. In the figures:
[0061] FIG. 1 schematic view of an embodiment of the invention
as modular mimic diagram;
[0062] FIG. 2 an embodiment of the invention;
[0063] FIG. 3 a view of an example of the state of the art and
[0064] FIG. 4 a detail of another embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0065] FIG. 1 shows a schematic view of an embodiment of the invention
as modular mimic diagram. In the duct system 11 a choke point 3
is arranged which causes two pressures P1 and P2 in the duct system
11. In the duct system furthermore a shut-off valve 12 is arranged
which is connected via a connection with the control. At the end
of the duct system 11 in the support surface 10 the outlet opening
for the liquid is positioned next to, respectively corresponding
with, the object 5 the position of which has to be controlled. Reference
number 9 indicates the generation of pressure for the duct system
schematically. This may be, for example, a pump. In the duct system
11 before the choke point 3 the first pressure sensor 1 and,
after the choke point 3 the second pressure sensor 2 is arranged.
Both pressure sensors 1 and 1 are connected to each other via a
connecting duct. One of either pressure sensors is here designed
intelligently as so-called master sensor which enables it to turn
the collected values of the pressure into electric signals, and
simultaneously to determine the pressure difference between the
pressure sensor 1 and the pressure sensor 2 and to transmit it to
the control 6.
[0066] The control 6 is, as already mentioned, connected with the
shut-off valve 12. The shut-off valve 12 is activated, for example,
when the machine door is opened. This is schematically shown with
the switch symbol. This is supposed to prevent coolant/lubricant
from escaping when the machine door is opened. Another connection
is provided from the control to the tool spindle. This is selected
if, for example, the pressure sensors, respectively the control,
recognises that the object 5 respectively the work piece, is not
positioned properly. The tool spindle is then not released for the
machining movement, but only when the object 5 is in the exactly
predetermined position, and thus the final opening 4 is, at least
partly, closed.
[0067] In the shown example a leakage gap 7 is provided on the
support surface. However, this is not really necessary in the invention,
only then when permanently a part of the coolant/lubricant shall
escape from the duct system. This may happen, for example, for cooling
and lubricating purposes, but also for cleaning purposes. The object
5 however, may be positioned accurately on the support surface
10 if this leakage gap 7 is not provided. It can be seen clearly
that the duct system 11 may be here at the same time the coolant/lubricant
system of the machine tool. No additional duct, respectively no
additional duct system, is needed for a support control. It is only
necessary to arrange the pressure sensors before, respectively after
the choke point, and, if necessary, to connect a final opening 4
in an existing support system with the coolant/lubricant system.
Therefore also a retrofitting of a machine tool with a coolant/flushing
liquid circuit may be realised quite simply.
[0068] The connection to the control of the machine tool is a preferred
modification of the invention. However, it is, in the same way,
also possible to provide a separate control which carries out only
the function of the control indicated here of the tool spindle of
the machine door, respectively of the shut-off valve, and provides,
if necessary, the generating of pressure.
[0069] FIG. 2 shows another embodiment of the invention. The significant
difference to the modification shown in FIG. 1 is given by the fact
that both pressure sensors 1 and 2 are designed similarly as simple
sensors. The signals of the values of the pressure transmitted by
the sensors are processed in control 6. This is the only significant
difference compared with the embodiment according to FIG. 1. All
other features may also be provided in the same way also in the
embodiment according to FIG. 2. This goes, for example, for the
shut-off valve, and the connection to the control, respectively
the machine door, or the connection to the control of the tool spindle.
In the same way also positioning of an object, for example of the
work piece 5 is described. The final opening 4 is also located
in the support surface 10 and it may be provided in another embodiment
of the invention that a leakage gap 7 is provided between support
surface 10 and one of the sides of the object which has to be positioned.
[0070] FIG. 3 shows an example of the state of the art. It is clear
here that, besides the duct system for coolant, respectively flushing
liquid 11 another duct system 17 is provided for the support control.
This is, according to the state of the art, designed as purely pneumatic
system. Reference number 19 indicates a pressure reducing valve
which provides the necessary pressure for the system. It is here
a task of the valve to keep the pressure P1 constant. In the pneumatic
duct system 17 a choke point 13 is provided in the same way as according
to the embodiment of the invention. However, there is only one pressure
sensor 14 here which measures the absolute pressure in the duct
system 17 as impact pressure, and transmits it, if necessary, to
a control which is not shown in the example according to the FIG.
3. Parallel to the duct system 17 the duct system 11 is shown which
concerns the coolant and lubricant system. The final opening 20
of this duct system is located in the support plane, respectively
on the support surface 10 as well as the final opening 16 of the
support pressure control in this drawing. The reference number 15
indicates the leakage gap through which permanently compressed air
has to escape in order to prevent flushing liquid or coolant from
penetrating into the duct system 17 and which, at the same time,
serves for cleaning the support surface, respectively the rest surface
10.
[0071] FIG. 4 shows a detail of another embodiment of the invention.
It is provided here to arrange the object 5 respectively a pallet
140 carrying the object 5 on the support surface 10. The duct system
11 is located in the machine tool, for example in the support table.
The machine tool, according to the embodiment of FIG. 4 has a clamping
device 130. This is indicated schematically by an arrow. The clamping
device 130 comprises, among others, clamping indentations 151 provided
in the pallet 140 into which a clamping bolt 152 engages for clamping.
If the clamping bolt 152 is arranged correctly in the clamping opening
151 (as shown), the clamping bolt is clamped, and thus the work
piece, respectively the object, pressed onto the pallet. The duct
system 11 runs into the clamping indentation 151 below the pallet.
The final opening 4 of the duct system 11 is provided there. According
to a modification of the invention it is furthermore provided that
the final opening 4 is designed nozzle-like. At the junction point,
where the clamping indentation 151 is arranged, which is arranged
in the pallet 140 which is positioned corresponding to the duct
system, an in-line quick coupling 160 is provided. It may be given,
for example, by grounded, self-sealing surfaces. Of course, it is
also possible to provide there suitable sealing means, like O-rings,
lip sealings, or the like. The leakage gap 7 is located at the junction
point 170 respectively the support spot of the pallet 140 carrying
the object 5. The support control device now uses the clamping device
simultaneously as support control and control of the clamping process.
The advantage of this modification is that by means of the flushing
liquid, respectively coolant, if the positioning is not correct,
in particular during the clamping, respectively positioning process,
the rest surfaces for the clamping bolt are cleaned. By means of
that escaping flushing liquid, respectively coolant, can be conducted,
for example, via the leakage gap 7. If the clamping device, respectively
the pallet, is positioned correctly, this is, of course, indicated
by the support control, respectively it is signalised to the control
accordingly. If this is not the case, the clamping, respectively
positioning process, is stopped, the clamping device in the upper
part with the clamping bolt 152 is lifted again, and, if necessary,
again the pressure of the flushing system, respectively coolant
system, is raised, in order to remove soilings which may be in the
clamping opening 151 by flushing, respectively to remove them from
the clamping bolt 152. Of course, also a reversion of the system
is possible, in such a way that the coolant, respectively the flushing
liquid, is ducted to or through the clamping bolt 152 in order to
clean then from there the clamping bolt 152 and the clamping opening
151. The advantage of this modification is that, besides a support
control, at the same time the clamping can be controlled. Only if
the clamping bolt is positioned correctly in the clamping opening
151 and the clamping has been carried out, for example, the duct
system 11 is locked off, so that, if necessary, this may possibly
be indicated by the indication device, respectively collected by
the control and signalised. In this respect this modification is
in particular suitable to provide, besides measurements saving expenses
by saving an additional support control duct system, a considerable
safety of the positioning and clamping process for the work piece
which has to be machined, respectively the object, which has to
be clamped.
[0072] From the explanations above the disadvantages of the state
of the art in contrast to the modifications described in the embodiments
of the invention can be discerned clearly. Summed up, there are
the following advantages:
[0073] The support control according to the invention operates
with the same coolant/lubricant which is also used for flushing
the support and is therefore present.
[0074] Support control according to the invention may also operate
with oil as coolant/lubricant.
[0075] The support control according to the invention does not
cause nebulising of coolant or oil.
[0076] The device for support and clamping control provided by
the new method and device has high availability and interrogation
reliability.
[0077] The support control device according to the invention can
be retrofitted, if requested, even in older machines, which do not
yet have a support or clamping control system.
[0078] The new method and the new support control device are independent
from duct lengths as the coolant is incompressible.
[0079] By means of the incompressibility the new support control
system is significantly faster than previous pneumatic support control
systems.
[0080] According to the invention individual work piece supports
with particular pinnings are not necessary, resulting in less modifications
of supports. Altogether, by means of this, production is simplified,
the supply with spare parts and storing is rationalised.
[0081] The new support and clamping control is not sensitive to
coolant, therefore it is, for example, not necessary to provide
"permanent blasting air" which has to prevent coolant
from penetration into the pneumatic duct system according to the
state of the art.
[0082] Additionally no or small amounts of compressed air are necessary
so that the use of compressed air can be reduced altogether. Furthermore
the new support and clamping control makes considerably less noise
than the previous one. This is caused by avoiding blowing noises.
A lower sound level (dB(a) value) is obtained.
[0083] Although the invention has been described by exact examples
which are illustrated in the most extensive detail, it is pointed
out that this serves only for illustration, and that the invention
is not necessarily limited to it because alternative embodiments
and methods become clear for experts in view of the disclosure.
Accordingly changes can be considered which can be made without
departing from the contents of the described invention.
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