U.S. patent application number 11/794493 was filed with the patent office on 2008-12-04 for cooling device.
This patent application is currently assigned to HYDAC SYSTEM GMBH. Invention is credited to Winfried Klein, Rudolf Kunz.
Application Number | 20080295540 11/794493 |
Document ID | / |
Family ID | 35511136 |
Filed Date | 2008-12-04 |
United States Patent
Application |
20080295540 |
Kind Code |
A1 |
Kunz; Rudolf ; et
al. |
December 4, 2008 |
Cooling Device
Abstract
The invention relates to a cooling device for a machine tool
(10) for cooling a heated fluid, for example a cooling lubricants,
comprising at least one refrigerating unit (48) for a fluid which
is filtered by a filtering unit (40) and is received form at least
one storage tank (38) by means of a pumping unit provided with at
least one hydraulic pump (P2), separated clean (22) and waste (36)
tanks, wherein the refrigerating unit (48) returns the circulating
cooled fluid to the clean tank (22). Since the hydraulic pump (P2)
of the pumping unit supplies the fluid only filtered by the
filtering unit (40) from the waste tank (36) to the clean tank (22)
and another independent hydraulic pump (P5) continues to supply the
fluid from the clean tank to the refrigerating unit (48) for a
subsequent circulation, the base structure of a known refrigerating
device can be preserved and possible pressure losses caused by the
blinding of the filter of the filtering unit have no negative
effects on the constantly maintained flow rates for the
refrigerating unit.
Inventors: |
Kunz; Rudolf; (Zweibrucken,
DE) ; Klein; Winfried; (Wallerfangen, DE) |
Correspondence
Address: |
ROYLANCE, ABRAMS, BERDO & GOODMAN, L.L.P.
1300 19TH STREET, N.W., SUITE 600
WASHINGTON,
DC
20036
US
|
Assignee: |
HYDAC SYSTEM GMBH
Sulzbach/Saar
DE
|
Family ID: |
35511136 |
Appl. No.: |
11/794493 |
Filed: |
November 16, 2005 |
PCT Filed: |
November 16, 2005 |
PCT NO: |
PCT/EP05/12278 |
371 Date: |
June 29, 2007 |
Current U.S.
Class: |
62/475 ;
62/515 |
Current CPC
Class: |
B23Q 11/1069 20130101;
Y02P 70/171 20151101; B23Q 11/146 20130101; B23Q 11/122 20130101;
Y02P 70/10 20151101; B23Q 11/0057 20130101 |
Class at
Publication: |
62/475 ;
62/515 |
International
Class: |
F25B 43/00 20060101
F25B043/00; F25B 39/02 20060101 F25B039/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 2005 |
DE |
10 2005 004 673.8 |
Claims
1. Cooling device for a machine tool (10) for cooling a heated
fluid, such as cooling lubricant, with at least one refrigerating
unit (48) which receives filtered fluid from a filter means (40) by
a pumping means with at least one hydraulic pump (P2), and which
originates from at least one storage tank (38), with a subdivision
into a clean tank (22) and a dirty tank (36), the refrigerating
unit (48) returning the fluid which has been cooled in circulation
to the clean tank (22), characterized in that the hydraulic pump
(P2) of the pump means conveys fluid filtered exclusively with the
filter means (40) from the dirty tank (36) into the clean tank (22)
and that another independent hydraulic pump (P5) continues to
convey the fluid which has been delivered into the clean tank (22)
to the refrigerating unit (48) for circulation.
2. The cooling device according to claim 1, wherein the
refrigerating unit (48) is a compressor-refrigerating unit with a
heat exchanger (50), a compressor means (52) and an evaporator
means.
3. The cooling device according to claim 2, wherein the evaporator
means is formed from the heat exchanger (50).
4. The cooling device according to claim 1, wherein the machine
tool (10) has parts which are to be supplied with fluid, such as
drives (12, 14, 16) which are supplied by means of at least one
other third hydraulic pump (P4) to a feed line (20) from the
respective clean tank (22) and which return the fluid distributed
to them heated to the clean tank (22) via the return (28).
5. The cooling device according to claim 1, wherein fluid from the
clean tank (22) can be transported to a cleaning or flushing means
(30, 32) of the machine tool (10) by means of at least one
additional fourth hydraulic pump (P3).
6. The cooling device according to claim 1, wherein on the machine
tool (10) fluid emerging into the exterior is collected in a
collecting station (34) and can be removed by means of at least
another fifth hydraulic pump (P1) to the respective dirty tank.
7. The cooling device according to claim 5, wherein a flow monitor
which has been inserted into the feed line (20) triggers the
respective fourth hydraulic pump (P3) and turns it off especially
when the feed line (20) is free of fluid.
8. The cooling device according to claim 1, wherein matching of the
current cooling power demand of the entire machine tool (10) takes
place by a control means which turns the refrigerating unit (48) on
or off when the upper or the lower boundary of the definable
setpoint temperature is reached.
9. The cooling device according to claim 4, wherein removal of the
fluid for the refrigerating unit (48) takes place in the hot region
of the clean tank (22) which is located in the vicinity of the
junction site of the return (26) into the clean tank (22) and
accepts the heated fluid from the parts of the machine tool (10) to
be supplied, within the clean tank (22).
10. The cooling device according to claim 1, wherein the machine
tool (10) is a grinding machine, especially a five-axle grinding
machine.
Description
[0001] The invention relates to a cooling device for a machine tool
for cooling a heated fluid, such as cooling lubricant, with at
least one refrigerating unit which receives filtered fluid from a
filter means by means of a pumping means with at least one
hydraulic pump, which fluid originates from at least one storage
tank, with a subdivision into a clean tank and a dirty tank, the
refrigerating unit returning the fluid which has been cooled in
circulation to the clean tank.
[0002] In a known generic cooling device as used in practical
applications, on a machine tool, for example a grinding machine,
fluid emerging in the exterior in the form of a cooling lubricant
is collected in a machine bed trough as a collecting station and is
conveyed by means of a hydraulic pump to the dirty tank as part of
a cooling lubricant storage tank. The fouled and possibly heated
fluid which has been delivered to the dirty tank in this way is
supplied to a filter means by another hydraulic pump, the fluid
which has been filtered in this way and therefore after passing
through the filter means is partially delivered to the clean tank
of the storage tank via a secondary branch, and in the main branch
a part of the filtered fluid travels to a refrigerating unit which
returns the filtered and cooled fluid to the clean tank in
circulation. From there the cleaned and cooled fluid in the form of
a cooling lubricant can be transported via another hydraulic pump
in the feed line of the machine tool to its parts to be cooled,
such as drives, then after passing through the drives the heated
cooling lubricant returning directly in backflow to the clean
tank.
[0003] In the known solution, in the supply or in the main branch
to the refrigerating unit there is a ball cock for adjusting the
division of quantities following the indicated filter means. The
purpose of this is that at a constant cooling power of the
refrigerating unit it always obtains the same flow amount of liquid
to be cooled from the dirty tank, in order if possible to create
constant temperature conditions in the clean tank, from which via
the feed line the drives of the grinding machine which are to be
cooled are supplied. Since grinding machines must work very exactly
and must ensure grinding-workpiece machining to within microns,
even the smallest temperature deviations in the cooling circuit
(feed line and return) for the drives to be supplied can entail
clear and undesirable machining inaccuracies.
[0004] If at this point in the known solution the counterpressure
in the filter means due to captured dirt (grinding dust, abraded
particles, etc.) in the cooling lubricant is increased by the
filter material used at the time, in this way the flow amount which
as described should be kept constant is reduced. This change of the
flow amount for the desired constant cooling power of the
refrigerating unit leads to temperature changes in the clean tank;
this has adverse effects on the machining accuracy of the grinder
as a machine tool. Even if thorough mixing in the clean tank with
the cooled fluid already located there occurs, the temperature
changes resulting therefrom are still relevant such that the
machining inaccuracies must be watched. Also, based on the altered
mixing in the clean tank due to the changed temperatures on the
discharge side of the refrigerating unit, temperature control for
the machine tool is adversely affected.
[0005] On the basis of this prior art, the object of the invention
is to further improve the known solution while retaining its
advantages such that for a machine tool such as a grinder, fluid
supply, especially with cooling lubricant, of constant temperature
is ensured which enables high-precision machining with the machine
tool. This object is achieved by a cooling device with the features
of claim 1 in its entirety.
[0006] In that, as specified in the characterizing part of claim 1,
the hydraulic pump of the pump means conveys fluid which has been
filtered exclusively with the filter means from the dirty tank into
the clean tank and because another independent hydraulic pump
conveys the fluid which has been delivered into the clean tank to
the refrigerating unit for circulation, the basic structure of the
known cooling device can be maintained. The division of functions
according to the invention, on the one hand filtration from the
dirty tank into the clean tank, and on the other the transport of
fluid from the clean tank to the refrigerating unit and back into
the clean tank ensures that possible pressure losses, due to
clogging of the filter of the filter means, they can no longer
adversely affect the flow amounts which are to be kept constant for
the refrigerating unit, with the result that altogether the
temperatures on the clean tank side remain largely constant. This
in turn benefits the machining accuracy of the machine tool, its
parts to be supplied, such as drives, should receive a fluid of
constant temperature so that the temperature control which
interacts with the machine control can ensue uniform, exact
machining accuracy.
[0007] The solution according to the invention is economical to
produce and reliable in use. For one with average skill in the art
in the field of cooling devices, it is surprising that with only a
few measures and using existing components it acquires a much
improved machining accuracy for a machine tool to the extent it
separates the functions of filtration and cooling relative to the
dirty tank and the clean tank within the sketched framework. The
cooling device according to the invention need not be limited to
use of cooling lubricant cooling in grinding machines, but can be
used anywhere, also in hydraulic circuits, in machine tools, where
a constant temperature of the supply fluid is desirable to achieve
high positioning accuracies of drives or the like.
[0008] It has proven especially advantageous to undertake removal
for the refrigerating unit in the so-called hot region of the clean
tank, i.e., in the vicinity of the fluid return from the individual
fluid consumers of the machine tool.
[0009] In another preferred embodiment of the cooling device
according to the invention, provision is made such that by means of
at least one other hydraulic pump fluid can be transported from the
clean tank for cleaning or flushing of the machine tool. In this
way for example the grinding wheel of the machine tool can be
cleaned; this can also take place under high pressure. Furthermore
it is preferably provided that a flow monitor inserted into the
feed line triggers the pertinent hydraulic pump for the cleaning or
flushing means and turns it off especially when the feed line is
free of fluid. Because at this point the hydraulic pump is turned
off for the cleaning and flushing means, when the machine tool is
not in operation, the heat energy otherwise converted by the
permanently driven hydraulic pump can no longer reach the workpiece
when the cleaning or flushing nozzles are opened for the grinding
wheel via the fluid; this also helps increase machining
precision.
[0010] Other advantageous embodiments of the cooling device
according to the invention are the subject matter of the other
dependent claims.
[0011] The cooling device according to the invention will be
explained below for one embodiment with reference to the drawings.
In this connection, the figures are schematic and not to scale,
drawn in the manner of hydraulic diagrams.
[0012] FIG. 1 shows a solution as in the prior art and
[0013] FIG. 2 shows a representation corresponding to FIG. 1 with
the inclusion of the cooling device according to the invention.
[0014] Before the cooling device according to the invention is
explained using FIG. 2, the known structure as shown in FIG. 1 will
be detailed first.
[0015] FIG. 1 shows the known cooling device for a machine tool
designated as a whole as 10 in the form of a grinding machine. The
grinding machine 10 has three linear motors 12 and two axial motors
14 and a grinding spindle motor 16 for driving a grinding wheel
which is not shown. The other indicated motors 12 and 14 allow
five-axle grinding operation with which turbine blades or the like
can also be ground with high precision. Via a distributor 18 the
indicated motors 12, 14 and 16 are supplied with a fluid in the
form of a cooling lubricant via a feed line 20 in the form of a
fluid line by means of the hydraulic pump P4 from the clean tank
22. The possible level of the cooling lubricant in the clean tank
22 is symbolized with a level display 24. The cooling lubricant
supplied to the distributor 18 by means of the hydraulic pump P4
via the feed line 20 is supplied for cooling the motors 12, 14 and
16 accordingly to them via fluid lines and the heated cooling
lubricant is in turn discharged on fluid lines and supplied to a
collecting site 26 which returns the fluid which has then been
heated in the operation of the machine tool via a fluid line in the
form of a return 28 to the clean tank 22. In this way an inherently
closed cooling lubricant circuit for the motors of the machine tool
10 is implemented. The level displays used in each case can also be
used for triggering of the fluid level in the pertinent containers
(tanks).
[0016] Cooling lubricant can be supplied via another hydraulic pump
P3 from the clean tank 22 to a flushing gun which is not detailed
and which can be connected to a triggerable 2/2-way valve 30. The
working grinding wheel can on the one hand be cooled and on the
other cleaned by way of this flushing gun as part of a cleaning and
flushing means. Optionally there can also be a high pressure
cleaning means 32 which has a pressure booster in order to be able
to clean the indicated grinding wheel with high pressure. The
individual cleaning nozzles are then blocked via solenoid valves or
supplied with the cooling lubricant.
[0017] As FIG. 1 furthermore shows, in the region of the machine
tool 10 fluid emerging into the exterior in the form of a cooling
lubricant which occurs especially when the grinding wheel is
supplied from the outside, is collected in a collecting station 34,
which can constitute a type of machine bed trough for the machine
tool 10, the fluid level in the collecting station 34 being shown
symbolically with a level display 24'. A hydraulic pump P1
transports the fluid which has been fouled in this respect and
possibly heated into the dirty tank 36, an overflow from the dirty
tank 36 which is not shown to the machine bed trough as the
collecting station 34 ensuring that the dirty tank 36 is not
unintentionally overfilled. The possible fill level in the dirty
tank 36 is shown by way of example with the level display symbol
24''. Both the clean tank 22 and also the dirty tank 36 are a
common component of a storage tank 38; but it would also be
conceivable here to locate the clean tank 22 and the dirty tank 36
spatially separate from one another on the machine tool 10. In
addition, several tank units (not shown) could form the respective
individual tank. Furthermore, all hydraulic pumps are driven by
conventional electric motors M which release heat in operation.
[0018] The dirty tank 36 which is separated from the clean tank 22
via a partition has another hydraulic pump P2 which supplies the
dirty fluid from the dirty tank to a filter means 40. Following the
filter means 40, the pertinent fluid line is divided into a main
branch 42 and a secondary branch 44. The indication main branch and
secondary branch is arbitrarily chosen and need not necessarily be
related to the respective main flow amount of fluid following the
filter means 40. An adjustable ball cock 46 with pressure gauge
monitoring is connected to the main branch 42. The main branch 42
on the input side discharges into a refrigerating unit designated
as a whole 48, conversely the secondary branch 44 discharges into
the clean tank 22. On the input side, the refrigerating unit 48 has
a heat exchanger 50 which made for example as a plate heat
exchanger acts as an evaporator. The refrigerating unit 48
furthermore has a compressor 52 and a condenser 54. The
refrigerating unit 48 is therefore made as a
compressor-refrigerating unit and consists in this respect of a
closed refrigerating circuit 56 with a sealed compressor 52. A
conventional refrigerant is added to the refrigerating circuit.
Furthermore a drain line 58 which discharges into the clean tank 22
and which is a component of a cooling circuit which is open in this
respect is connected to the evaporator or heat exchanger 50, in
addition to the main branch 42.
[0019] In order to be able to ensure the desired setpoint
temperature by means of the refrigerating unit 48 which has an
almost constant cooling power, a definable flow amount is tapped by
means of the ball cock 46 via the main branch 42 following the
filter means 40 and is supplied to the refrigerating unit 48 with
its heat exchanger 50. The cooling power of the refrigerating unit
is controlled within certain limits by an expansion valve,
depending on the cooling power which prevails via the cooling
circuit 60 on the evaporator 50. The required cooling power, viewed
over a shorter time interval, is then almost constant due to the
operating mode of the machine tool. An excess partial amount which
may be present following the filter means 40 in the secondary
branch 44 is delivered directly to the clean tank 22 as an excess
amount. As fouling of the filter means 40 increases however, a
counterpressure builds up and the desired flow amount of cooling
lubricant which is to be kept constant in the main branch 42 is
reduced. This change of the flow amount at the indicated constant
cooling power leads to a change of temperatures in the return to
the clean tank 22 via the drain line 58. At the same time this
leads to altered mixing of the cooled fluid which has been
delivered via the drain line 58 and of the fluid which remained in
the clean tank 22.
[0020] But the altered mixing then again adversely affects the
temperature control and it is not possible to supply cooling
lubricant with a constantly given temperature (setpoint
temperature) via the feed line 20 of the machine tool 10 with its
parts to be cooled. Since in this regard especially an altered
temperature situation which deviates from the setpoints arises on
the motors 12, 14, and 16, in this respect high-precision machining
with the machine tool 10, especially with its grinding wheel, is
not possible. This is further supported in that via the hydraulic
pump P3, whether with normal pressure or whether with high
pressure, cooling lubricant with an altered temperature is supplied
to the grinding wheel (not shown) and therefore to the workpiece
via a cleaning or flushing means. Furthermore, matching of the
current cooling power demand of the entire machine tool 10 takes
place by the compressor-refrigerating unit 48 being turned on or
off. Turning on takes place when the upper boundary of a setpoint
temperature is reached, and turning off takes place when the lower
boundary of the setpoint temperature is reached. As a result of the
unwanted temperature changes in the clean tank 22, switching
hysteresis then occurs which likewise causes a temperature
fluctuation in the feed line 20 of the parts of the machine tool 10
to be cooled; this in turn has an adverse effect on accuracy in
machining.
[0021] To avoid the aforementioned disadvantages in a known cooling
device for a conventional machine tool 10 in the form of a grinding
machine, the solution according to the invention with an altered
cooling device is used, as follows in detail from FIG. 2. With
respect to the representation of the machine tool 10, it has the
same structure as the known solution and likewise a
compressor-refrigerating unit 48. Furthermore, the clean tank 22
has been preserved, likewise the dirty tank 36 and the collection
station 34 in the form of a machine bed trough. Furthermore, as
before, a hydraulic pump P4 supplies the machine tool components to
be cooled and by means of a hydraulic pump P1 fouled fluid in the
form of cooling lubricants travels from the collecting station 34
into the dirty tank 36. Likewise the hydraulic pump P3, as already
described, supplies the cleaning and flushing means for the
grinding wheel of the machine tool 10. In this regard reference is
made to the aforementioned statements for the known solution as
shown in FIG. 1.
[0022] The cooling device according to the invention at this point
has an independent filter circuit 62 in which by means of the
hydraulic pump P the fouled and possibly heated fluid from the
filter means 40 travels cleaned to the clean side with the clean
tank 22. From there, then by means of a further independent
hydraulic pump P5 in the closed cooling circuit 60, the fluid is
relayed to the evaporator or heat exchanger 50 of the refrigerating
unit 48 and the fluid which has been cooled in this way
(lubricating coolant) then travels via the drain line 58 back into
the clean tank 22 for recirculation by means of the hydraulic pump
P5. In this way a very uniform temperature distribution within the
clean tank 22 at a constant level relative to the given setpoint
temperature can be achieved. Preferably removal of the fluid takes
place via the hydraulic pump P5 in the hot region of the clean tank
22 which faces away from the drain line 58 with the cooled cooling
lubricant and in the vicinity has the input of the return 28 via
which the heated cooling lubricant coming from the machine tool 10
is returned to the clean tank 22. An internal, closed cooling
circuit 60 thus is obtained via the clean tank 22, even if the
clean tank 22 can be made open to the exterior.
[0023] By decoupling of the filter circuit 62 to the cooling
circuit 60, in any case the pressure losses in the cooling circuit
60 are kept constant; this in turn leads to the flow amounts and
thus the temperature being able to be kept constant. A special
controller function of the refrigerating circuit 56 in the
compressor-refrigerating unit (continuous running with bypass
control) additionally enables an improvement of the constancy of
the feed line temperature, i.e., hysteresis of 1 K, that is,
.+-.0.5 K in the feed line 20 to the parts of the machine tool 10
which are to be supplied is achieved. With the cooling device
according to the invention therefore the temperature of the fluid
in the clean tank 22 can be kept constant and thus supply of the
machine tool 10 with fluid of a definable setpoint temperature
which is not changed by the supply of fluid from the filter circuit
62 is possible; this leads to high-precision machining with the
machine tool 10. The cooling device according to the invention need
not be limited to the use of cooling lubricants, but can be used
wherever fluids, also hydraulic media, are to have a temperature as
constant as possible in machine tools and from which particle dirt
has been removed via a filter means 40. When reference is made to
hydraulic pumps in the application, their use is not limited to oil
hydraulics, but designed as a fluid or media pump also other
fluids, such as cooling lubricants or the like, can be
transported.
* * * * *