Note: Descriptions are shown in the official language in which they were submitted.
CA 02208771 1997-06-24
A Process and an Apparatus for Supplying the Interface between
an Abrasive Tool and a Workpiece with Cooling Lubrlcant
The present lnventlon relates to a process for
supplylng the interface between an abraslve tool and a work
plece with coollng lubrlcants.
In addltion, the lnventlon relates to an apparatus
for supplylng the lnterface between an abraslve tool and a
work plece with coollng lubrlcant.
In flnishlng processes that remove metal, whlch
include, in particular, grinding and similar processes, the
quallty and servlce llfe of the work plece that ls to be
flnlshed depends to a considerable extent on how good the
coollng and lubricatlon of the lnterface between the tool and
the work plece can be made durlng the productlon process.
DE 31 15 959 C2 descrlbes a devlce on a
gear-grlndlng machlne that ls used to supply coollng
lubrlcants to the partlcular area when the grlnding tool acts
on the work plece. Thls proceeds from the known process of
grlndlng wlthln a bath of coollng lubricant, ln whlch the
lnterface between the tool and the work plece ls submerged ln
the coolant that ls accommodated ln a coollng-lubrlcant
chamber.
It ls also part of the prior art that cooling
lubricant can be sprayed onto the lnterface, e.g., onto the
area ln whlch the grlndlng wheel and the work piece interact.
~ecause of the hlgh grlnding speeds that are used, in
particular, when grinding, there are extremely large
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centrifugal forces on the perlphery of the grlndlng tool and
these throw off the coollng lubrlcant, even lf it ls dellvered
under hlgh pressure, wlth the result that lt does not get to
the lnterface. Thls can result ln grlndlng damage, ln
partlcular grlndlng burns.
Grlnding that ls performed ln a bath of cooling
lubrlcant ls known ln prlnclple from US 3,047,987 and the
German perlodlcal Industr~e-Anzeiger [Industry Gazette], 97,
19.10.83.
Proceedlng from thls prlor art, DE 31 16 959 C 2 is
lntended to so lmprove a process of this klnd that it ls stlll
possible to perform grinding operatlons in a bath of cooling
lubrlcant. To thls end, provlsion ls made such that the
coollng-lubrlcant chamber or parts of the wall of the
coollng-lubrlcant chamber are conflgured so as to plvot and
lock or change shape, e.g., are flexlble, or that a grlndlng
wheel and a chamber that ls assoclated wlth the work wheel
together form a chamber, and that they allow the movement that
ls requ1red to lnstall and remove the grlndlng wheel and/or
the work plece, and to carry out the grlndlng process.
The use of thls and other processes for supplylng
the lnterface between work tool and work plece resulted ln
further lmprovements: lt has been shown that lncreaslng the
quantlty of oll that ls supplled to the lnterface per unlt
tlme has a posltlve effect. Subsequently, coollng-lubrlcant
supply systems were deslgned to dellver up to 500, and ln some
cases even up to 800 lltres of coollng lubrlcant to the
lnterface per mlnute. The pressure at whlch the oll or the
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emulsion is delivered was also increased, pressures of up to
20 bar and more belng used.
When such a plant ls used, a partlcular dlsadvantage
that ls encountered ls that lt causes large quantltles of
waste and thus hlgh costs. These lnclude not only the cost of
the plant ltself, but also costs incurred for the plant slte,
lncludlng oll tanks and tanks for preparlng and storing large
volumes of oll. In order to make lt possible to supply
foam-free oil at hlgh oil-lltre rates per unlt tlme, the oll
tanks must be able to contain up to 3000 lltres of oll. Thls,
in lts turn, causes higher costs because speclal securlty
measures must be put ln place ln order to prevent
envlronmental damage.
A further dlsadvantage ls the fact that desplte the
use of hlgh quantltles of oll belng dellvered per unit time,
lt ls not always posslble to achieve a satisfactory feed of
coollng lubrlcant to the work place. Thls ls based on the
knowledge that when an abraslve tool rotates at hlgh speed, a
cushlon or fllm of alr spreads around thls and thls cushlon or
fllm of alr prevents the cooling lubrlcant reachlng the work
place ln an optlmal way.
For thls reason, lt ls the task of the present
lnventlon to create a process and an apparatus wlth whlch lt
ls posslble to brlng coollng lubrlcant lnto lntlmate contact
wlth the lnterface zone between an abraslve tool and a work
plece, l.e., to supply the work plece wlth cooling lubricant
ln an optlmal manner. In partlcular, thls is to be posslble
lf the abrasive tool ls used at high worklng speed, whlch also
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means that maior peripheral acceleratlon forces are present on
the tool and a cushlon of alr forms around sald tool. In
addltlon, lt ls also lntended to brlng about a slgnlflcant
reductlon ln the volume of the flow of oll that ls requlred,
so that slgnlflcantly smaller coollng lubrlcant supply systems
can be used.
Accordlng to the present lnventlon, thls task has
been solved by a process to supply the lnterface zone between
an abraslve tool and a work plece wlth coollng lubrlcant uslng
the followlng steps:
a) provlslon of an annular gap (4) around the outslde
contour (5) of the abraslve tool (1), sald annular gap
(4) extendlng around the ma~or portlon of the perlphery
of the abraslve tool (l);
b) lnterruptlon of the annular gap (4) in a flrst area (6)
ln whlch the lnterface zone (3) between the abraslve tool
(1) and the work plece (2) ls located;
c) lnterruptlon of the annular gap (4) ln a second area (7)
that ls located ln an area of the perlphery of the
abraslve tool (1) that ls remote from the flrst area (6);
d) dellvery of coollng lubrlcant to the second area (7).
Provlslon ls also made such that the annular gap (4)
extends transversely to the perlpheral dlrectlon of the
abraslve tool (1) essentlally equldlstantly around the outslde
contour (5) of the abraslve tool (1). It ls advantageous that
the annular gap (4) extend ln the perlpheral dlrectlon of the
abraslve tool (1) at least in some sectlons essentlally
equldlstantly around the outslde contour (5) of the abraslve
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tool (1). In thls case, the width of the annular gap (4~ can
lncrease or decrease contlnuously at least ln some sectlons
around the perlphery of the abraslve tool (l). The wldth of
the annular gap (4) ls thus advantageously smaller than or
equal to 10 milllmetres, and in partlcular is smaller than or
equal to 1 mlllimetre.
Provision ls also made such that the lnterruptlon of
the annular gap (4) in the second area (7) ls made wlthin a
very small azimuthal area in the peripheral direction of the
abrasive tool (1).
The present invention is based on the fact that even
a llttle coollng lubrlcant is sufflcient to supply the
interface between the tool and the work place efficiently if
it can be ensured that the coollng lubrlcant actually reaches
the interface. The underlying thought ln the present
lnventlon ls thus to break up the film or cushion of air that
is forming, or to interrupt it, and deliver coollng lubrlcant
to the perlpheral area of the abraslve tool. To thls end-as
has been dlscussed-provlslon ls made for the followlng
indlvldual features that work ln con~unctlon wlth each other.
- a narrow annular gap that extends over a large area of
the perlphery of the abraslve tool ls provlded. The
abraslve tool ls surrounded by a houslng, the lnner slde
of whlch flts snugly around the tool and leaves only a
narrow essentlally equldlstant gap that, lf requlred,
gradually wldens out around the perlphery and ls thus
"conlcally" formed, through whlch the coollng lubrlcant
can be passed.
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- the annular gap is lnterrupted flrst at the polnt at
whlch the lnterface zone between the tool and the
workplace is located, i.e., the tool emerges from the
houslng ln a flrst area that ls close to or at the
working polnt.
- there ls a second lnterruptlon ln the annular gap that
lles at another polnt than the interface between the tool
and the work piece. At this point, the cooling
lubrlcants ls introduced lnto the annular gap; because of
the rotatlon of the tool, this coollng lubricant is
gulded through the annular gap and reaches the lnterface.
- the annular gap is optionally matched to the requlrements
of fluid mechanlcs in that, ln the areas to whlch no
coollng lubricant is to be delivered, it ls narrower than
in other areas; thus, lt ls not necessarily of equal slze
around the perlphery.
Because of the fact that the lnterruptlon of the
annular gap ln thls second area, where the coollng lubricant
ls lntroduced, follows within a very small azimuthal area of
the perlphery, whlch ls to say abruptly or suddenly, and
because of the fluid-dynamic condltions, a partlal vacuum
results ln the second area and thls sucks the coollng
lubricant into the annular gap. Thls ensures that the annular
gap can functlon as a rellable path for the coollng lubrlcant
to move along. This also means that the oll ls transported
automatically to the lnterface wlthout the need to use larger
quantltles. Tests have shown that, uslng the process
accordlng to the present lnventlon, the quantltles of coollng
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lubricant required per unit time can be reduced by a factor of
10 or more relative to the quantities that are normally used.
Desplte the relatlvely small volumetric flow of cooling
lubricant, it is nevertheless ensured that no grinding burns
can result and that the amount of material removed in the
grinding wheel llmitlng tlme is not reduced.
In known processes and with known apparatuses, the
oil is transported constantly to the interface by a separate
dellvery system. In contrast to thls, accordlng to the
present lnvention the oll moves to the lnterface through the
tool ltself.
The apparatus that ls used to supply the lnterface
between the abrasive tool and the work piece wlth coollng
lubricant comprises
- a rotatlng abrasive tool (1) that at times is in contact
with the work piece ~2);
- a cover (8) for the abrasive tool (1);
- a dellvery system (9) for the coollng lubrlcant.
Accordlng to the present invention, this apparatus
ls characterlzed in that:
- the abrasive tool (1) and the cover (8) form an annular
gap (4) that extends around the outslde contour (5) of
the abraslve tool (1) and extends over a ma~or part of
the perlphery of the abrasive tool (l);
- the annular gap (4) is interrupted in a first area (5),
ln whlch the lnterface (3) between the abrasive tool (1)
and the work piece ~2) ls located, and
- the annular gap (4) ls lnterrupted ln a second area (6)
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that is located ln an area of the perlphery of the
abrasive tool (1) that ls spaced apart from the flrst
area (1), the coollng lubrlcant belng lntroduced lnto the
second area (6).
Here, too, provlslon ls also made such that the
annular gap (4) extends transversely to the perlpheral
dlrectlon of the abraslve tool (1), essentlally equldlstantly
around the outslde contour (5) of the abraslve tool (1). The
annular gap (4) extends ln the peripheral dlrectlon of the
abraslve tool (1) at least ln some sections essentially
equldistantly around the outslde contour (5) of the abraslve
tool (1). In this case, the width of the annular gap (4) can
increase or decrease contlnuously, at least ln some sectlons
around the periphery of the abrasive tool (1). The wldth of
the annular gap (4) ls thus advantageously smaller than or
equal to 10 millimetres, and in particular is smaller than or
equal to 1 millimetre.
It ls also advantageous if the interruptlon of the
annular gap (4) ln the second area (7) ls made ln a very small
azlmuthal area ln the perlpheral dlrectlon of the abraslve
tool (1), whlch ls to say beyond the perlphery, elther
suddenly or abruptly.
The followlng are advantageous developments of the
present invention:
The grlndlng tool (1) ls a grlndlng tool, ln
partlcular, a shaplng grlnder. The proflle of the shaplng
grlnder corresponds, essentlally, to the shape of the proflle
of the work piece that is to be ground. Advantageously, the
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grinding tool is a gear grlnder, the proflle of the gear
grinding tool correspondlng essentially to the shape of the
gaps ln a gear wheel that ls to be ground. The shaped
grlndlng dlsk generates a tooth campalgn of the deslred shape
and slze when lt ls ground.
The abraslve tool (1) can be a steel body that has a
an abraslve coating, or lt can be a dressable grindlng tool.
Alternatlvely, the abraslve tool can be a flexlble
dlsk.
Oll, emulslon, or compressed alr can be used as the
coollng lubrlcant.
The dellvery of the coollng lubrlcant to the
interface by way of the annular gap ls of partlcular
lmportance. In one development, provlslon ls made such that
ln the flrst area (6) of the lnterface zone between the
abrasive tool (1) and the work plece (2) at the place where
the annular gap (4) ls lnterrupted, there are means (10) that
conduct the coollng lubrlcants onto the lnterface zone (3).
Most advantageously, ln the case of proflle grlndlng, thls ls
achleved in that the means (10) to conduct the coollng
lubrlcant when gear wheels or workpieces wlth other proflles
(e.g., compressor rotors) that belng ground, are matched to
the shape of the proflle of the workplece that ls to be
ground.
The drawlngs that are appended hereto show one
embodlment of the present lnventlon. These drawlngs are as
follows:
Flgure 1 A diagrammatlc cross section through the
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apparatus according to the present inventlon for supplying
coollng lubrlcant;
Figure 2: A diagrammatic partial cross section of
an abrasive tool and the surrounding cover as shown on the
section line A-B;
Flgure 3: A partlal cross sectlon through the
abraslve tool and the work place on the sectlon line C-D;
Figure 4 The same cross section as in Figure 3,
but with the tool removed;
Figure 5: A diagram showing the speed curve in the
annular gap for the outermost area of the abrasive tool.
Figure l is a diagrammatic side view of an abrasive
tool 1 that rotates about its axis as indicated by the arrow.
This abraslve tool 1 ls a grlnding wheel that is used to grind
a gear wheel 2. This is done by full-shape grinding ~or the
single or two-flank grind), i.e., the shape of the grindlng
wheel 1 corresponds to the shape of the tooth gap so that,
preferably, two ad~acent sides and, optionally, the tooth foot
that lies between them are ground. The abrasive tool l
generates the desired shape of the tooth gap during the
machining process. It should be noted that the process
according to the present invention is not, however, restricted
to thls type of machining, but that any machinlng with
geometrically lndeterminate cuts as well as many processes
with geometrically determined cuts can be carried out using
the teachings of the present invention.
During the machining process, the grlndlng wheel 1
and work plece 2 are in contact with each other in the
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lnterface zone 3. There must be a sufflclently large quantlty
of coollng lubrlcant avallable at thls polnt ln order to
ensure proper machlnlng, and so as to conduct the heat
generated durlng the machlnlng process away from the lnterface
and also to clear mlcroparticles that have been removed from
the workplece out of the lnterface zone.
In the present case, the coollng lubrlcant, for
example in the form of oll, ls introduced lnto a dellvery
system for dellverlng the coollng lubrlcant 9 ~see arrow
marked "oll"). The dellvery system 9 ls connected to the
cover 8. The oll passes through a bore 11 ln the cover 8 to
an annular gap 4 that ls formed between the abraslve tool 1
and the houslng 8.
The lnterface 3 (flrst areas 6) between the tool and
the work plece, whlch ls to say the locatlon at whlch the
coollng lubrlcant ls requlred, ls located at some dlstance
from the place at whlch the coollng lubrlcant ls lntroduced
(second area 7). Thls distlngulshes the conflguratlon
accordlng to be present lnventlon from other, usual
apparatuses.
In the present case, there ls approximately 270~ of
the perlphery of the grlndlng wheel between the lntroductlon
polnt for the oll and the grlndlng polnt. The present
lnventlon makes provlslon such that the oll flows ln the
annular groove 4 ln the dlrectlon of movement of the grlndlng
wheel untll lt reaches the work polnt. The angular path along
whlch the oll ls passed wlthln the annular gap 4 ls best
greater than 90~. Thls ensures that there ls lntlmate contact
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between the cooling lubrlcant and the worklng surface of the
grlnding wheel. The fllm of alr ~cushlon of alr) that ls
normally formed on the grlndlng wheel is thus broken down.
The apparatus that has been described works
partlcularly advantageously lf the polnt of lntroduction 7 for
the oll ls so conflgured as to brlng about a ma~or change ln
the cross sectlon ("abrupt" or sudden lnterruptlon of the
annular gap 4). Thls can be achieved, e.g., ln that the oll
supply bore 11 enters the annular gap as far as possible
radlally, l.e., at a large angle. Because of the laws of
hydrodynamlcs, at a relatlvely hlgh speed of the grlndlng
wheel and thus at a hlgh oll flow rate ln the annular gap and
glven a relatlvely low flow speed ln the bore 11 (at a
sufflclently large dlameter of the bore) there wlll be a
~suction effect~ in the annular gap 4, so that the oil is
accelerated on to the worklng surface of the grlndlng wheel
wlth the result that there ls lntlmate contact wlth the oll ln
thls area.
In Flgure 1, the annular gap 4 extends around almost
the whole perlphery of the abraslve tool 1 ln a constant
manner, l.e., the annular gap 4 ls formed equidlstantly across
the perlphery of the tool 1. For reasons of clarlty, thls ls
as shown but lt does not necessarlly have to be so. It may be
more useful that the annular gap 4 between the second area
(entry polnt for the coollng lubricant) 7 and the right-hand
lower end of the cover 8 ls smaller than ln the remalnlng area
of the cover 8, slnce ln no coollng lubrlcant has to be
dellvered to thls area. In the flgure, thls area ls shown to
12
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be exactly as large as in the remaining part of the annular
gap 4. In addition, it can also be useful that-although this
case is not shown-the annular gap 4 even though it runs
essentially equldlstantly around the perlphery of the abrasive
tool 1, grows gradually larger or smaller which is to say that
it is configured so as to be "conical." The annular gap 4
thus does not necessarily have to be equally large around the
whole of the cover.
Figure 2 is a cross section of the line A-B in
Figure 1. It can be seen that the grinding tool 1 is enclosed
by the cover or the housing 8. As can also be seen, the cover
is such that an annular gap 4 is formed and this is of equal
thickness across the effective profile of the tool 1, l.e.,
the annular gap ls equldlstant, the vertlcal dlstance between
the outer contour 5 of the grindlng wheel and the lnside llne
of the cover 8 ls ldentical across a desired area. It has
been shown to be advantageous if an equal distance, thus a
width of the annular gap 4, of one millimetres is used.
Flgure 3a is a cross section along the line C-D in
Figure 1, and shows the process of profile gear-wheel
grinding. In this example, as viewed from its working
profile, the grlnding tool 1 is so preclsely conflgured that a
gear wheel gap, which is to say two ad~acent sides and
possibly the tooth foot that is located between them are
ground. This results in the interface zone 3 between work
tool 1 and gear wheel 2.
Also important is the provision and configuration of
a conductor 10 for the cooling lubricant in order to guide lt
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ln optlmal manner to the lnterface zone, see Flgure 4. Thls
ls the same cross sectlon as ls shown ln Flgure 3, although
the tool 1 has been removed. Provision is made such that the
conductor 10 matches the shape or the outllne of the grlndlng
wheel or that of the tooth gap that ls to be ground. The
shape of the tooth gap of the gear wheel 2 that results ln
thls case ls provlded wlth coollng lubrlcant in an optimal
manner ln thls way.
Finally, Flgure 5 shows the speed curve within the
annular gap 4 for the outermost reglon of the abraslve tool.
Correspondlng speed curves results for the whole of the
annular gap area for the outer contour 5 of the tool 1. The
grlndlng speed Vs, whlch is normally about 14 m/s is that of
the grindlng wheel ltself and thus determlnes the speed at one
end of the annular gap 4. In contrast to thls, the speed at
the houslng ls zero, and thls results ln the speed proflle
shown for the annular gap.
Not shown but ~ust as appllcable are the teachlngs
of the present lnventlon lf no lndlvldual dlsk but rather,
e.g., grlndlng dlsk sets are used. To a certain extent, the
apparatus descrlbed hereln can be used for worm hobs. In
prlnclple, the technology descrlbed hereln can be used for all
abraslve processes such as grlndlng, honlng, and the llke.
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Reference numbers used in drawings:
1 Abraslve tool
2 Workpiece
3 Interface zone
4 Annular gap
Outer shape of the abraslve tool
6 First area (interface zone)
7 Second area (entry point for cooling lubricant)
8 Cover of the abrasive tool
9 Delivery system for the cooling lubricant
Conductor for the cooling lubricant
11 Bore
Vs Speed of grinding wheel
lS
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