U.S. patent number 3,747,284 [Application Number 05/125,580] was granted by the patent office on 1973-07-24 for cooling apparatus.
This patent grant is currently assigned to Inter-Probe, Inc.. Invention is credited to Felix J. Lyczko.
United States Patent |
3,747,284 |
Lyczko |
July 24, 1973 |
COOLING APPARATUS
Abstract
Cooling apparatus for removing heat from metal removal
operations or shaft bearings by the use of a jet of liquid coolant
and an electrostatic field set up in the coolant, which includes a
high voltage DC or AC supply connected to a probe associated with a
liquid coolant nozzle.
Inventors: |
Lyczko; Felix J. (Lake Forest,
IL) |
Assignee: |
Inter-Probe, Inc. (Chicago,
IL)
|
Family
ID: |
22420403 |
Appl.
No.: |
05/125,580 |
Filed: |
March 18, 1971 |
Current U.S.
Class: |
451/450; 451/53;
62/3.1; 409/136 |
Current CPC
Class: |
B24B
55/02 (20130101); Y10T 409/304032 (20150115) |
Current International
Class: |
B24B
55/02 (20060101); B24B 55/00 (20060101); B24b
055/02 () |
Field of
Search: |
;51/267,266,322
;83/169,170 ;408/56,57,61 ;90/11R ;204/140,143R,143G ;165/2 ;62/3
;239/15 ;310/6 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Kelly; Donald G.
Claims
The invention is hereby claimed as follows:
1. In combination with a machine for cutting metal from a workpiece
having a supply of liquid coolant applied to the cutting area,
wherein the metal removal rate is such as to cause film boiling of
the coolant at the surface of the workpiece, aparatus for
eliminating the film boiling, thereby increasing the heat transfer
coefficient between the workpiece and coolant, said apparatus
comprising means for generating an electrostatic field in the
coolant at the cutting area, said means including means setting up
a ground potential adjacent the cutting area, a probe mounted
adjacent to the cutting area, and a high voltage low amperage DC or
AC power supply of about 10 to 60 kv connected to the probe to
supply a potential just less than that which would cause
arcing.
2. The combination as defined in claim 1, wherein the coolant is an
electrolyte and said probe is covered with electrical
insulation.
3. The combination as defined in claim 1, wherein the coolant is a
dielectric and said probe is uninsulated.
4. The combination as defined in claim 1, wherein the machine is a
grinder and the workpiece is a metal part.
5. The combination as defined in claim 1, wherein said ground
potential setting means includes connecting the workpiece to ground
potential.
6. Apparatus for removing heat from a workpiece and a metal cutting
tool in a metal cutting machine comprising means directing a stream
of liquid coolant onto the workpiece and metal cutting tool at the
metal cutting area, and means generating an electrostatic field in
the coolant, said means including means mounting a probe in the
stream and terminating adjacent the metal cutting area, means
connecting the probe to a source of high voltage low amperage DC or
AC potential of about 10-60 kv such as to be slightly less than
that which would cause arcing, and means connecting the workpiece
to ground potential.
Description
This invention relates in general to cooling apparatus, and more
particularly to means for removing heat from workpieces and/or
tools engaged in metal removal operations, or shaft bearings under
load, and still more particularly to a combination liquid coolant
nozzle and high voltage DC or AC probe for effecting cooling of a
workpiece or mass.
Heretofore, it has been usual to cool workpieces being machined and
other masses by use of jets or streams of a liquid coolant which
absorbs the heat and carries it away. It has also been known to
remove heat from a mass of material by the application of a high
voltage, low amperage electrostatic field thereto, such as
disclosed in U.S. Pat. No. 3,224,497. It is also known that a
liquid coolant is sometimes employed for purposes of lubrication
between a workpiece and a cutting tool. Similarly, shaft bearings
under load have been lubricated and cooled by immersion in a liquid
lubricant.
The present invention involves the combining of liquid cooling and
electrostatic cooling in order to answer the cooling need in
production machining where metal is removed on a production basis
and in shaft bearings or the like under a high heat load.
It is known that metal removal rates, where only liquid cooling is
employed, can be limited by the incipient local melting of the
workpiece. Where such incipient local melting is present, it
follows that "film boiling" of the liquid coolant is also present,
this occurring where the heat flux at a solid surface in contact
with the liquid coolant is at such a temperature level that the
liquid coolant flashes into a continuous film of vapor. This vapor
film acts as an insulating barrier to the solid surface, thereby
driving the surface temperature up and possibly causing
catastrophic failure, severe damage, or inferior surface finish to
the part being machined.
By setting up an electrostatic field in the liquid coolant,
according to the present invention, the film is destroyed thereby
dramatically increasing the heat transfer coefficient between the
workpiece and the liquid coolant by a factor of 5-20. Accordingly,
the surface temperature of the workpiece is substantially reduced.
All of this allows an increase in the metal removal rate, thereby
decreasing production costs, and also allows obtaining a better
microfinish.
While "film boiling" may not occur where friction is created
between working surfaces, such as in a bearing structure, the
combination liquid coolant and electrostatic field, according to
the present invention, may be employed for cooling of the mass, in
this case the bearing structure, which would obviously reduce the
chance of failure, and enhance the working life or allow the
bearing to be continuously operated at conditions heretofore too
severe for extended life. It should be appreciated the liquid
coolant here would be of a type that would also lubricate.
It is therefore an object of the present invention to provide a
cooling apparatus especially useful for removing heat from parts
involved in a machining operation and other masses experiencing a
heat problem.
Another object of this invention is in the provision of a cooling
apparatus including a liquid coolant stream or jet, and means for
setting up an electrostatic field in the stream or jet.
Still another object of this invention resides in the provision of
a cooling apparatus capable of destroying the film boiling effect
of a coolant, thereby dramatically increasing the heat transfer
coefficient.
A further object of the present invention is to provide a
combination liquid coolant and electrostatic field arrangement for
materially increasing the heat transfer coefficient of a part being
machined so that the metal removal rate can be materially increased
thereby reducing production costs, and so that a smoother finish
can be produced.
Other objects, features and advantages of the invention will be
apparent from the following detailed disclosure, taken in
conjunction with the accompanying sheet of drawing, wherein like
reference numerals refer to like parts, in which:
FIG. 1 is an elevational view, partly diagrammatic, of a grinding
machine with the cooling apparatus of the invention applied thereto
to illustrate its application in the machining of metal;
FIG. 2 is a diagrammatic, top plan view of the arrangement in FIG.
1 with some parts omitted;
FIG. 3 is an enlarged cross sectional view taken substantially
along line 3--3 of FIG. 1; and
FIG. 4 is a diagrammatic, elevational view illustrating another
application of the cooling apparatus according to the invention,
and in particular for cooling a shaft bearing.
The cooling apparatus of the invention includes generally a nozzle
or the like for discharging a stream or jet of liquid coolant, and
a probe or conductor associated with the nozzle to impart an
electrostatic field of high intensity in the coolant in order to
materially increase the rate of heat transfer from the surface to
be cooled. The cooling apparatus is applicable for removing heat
from any mass, and especially for removing heat from a metal
machining operation in order to permit the increase of metal
removal rates to thereby lower production costs. For example, the
cooling apparatus may be applied to a grinding machine set up to
remove metal by grinding from a workpiece, such as a bearing part.
It should be appreciated that the cooling apparatus can likewise be
applied in any production machining operation where metal removal
at a high rate is required.
An example of applying the cooling apparatus to other than a metal
removal operation would include the operation of a shaft bearing or
the drawing of metal through drawing dies. Thus, wherever cooling
has heretofore been required in the form of a liquid coolant, the
present invention is applicable to enhance the cooling rate, and
the coolant may have lubricating properties if desired.
The problem encountered in the machining of metal in the presence
of a liquid coolant which limits the metal removal rate, such as in
a grinding operation, can result in damage to the workpiece caused
by incipient local melting. The incipient local melting occurs
during "film boiling" of the coolant which constitutes the
generation of a film of vapor at the workpiece surface acting as an
insulating barrier which limits the rate of heat transfer and the
maximum amount of heat that can be carried away by the coolant.
Thus, the vapor barrier will cause the temperature of the workpiece
surface to rise beyond that which it can tolerate and cause failure
or damage to the workpiece. Application of an electrostatic field
in the liquid coolant, in accordance with the present invention,
destroys the vapor barrier thereby allowing a material increase in
the rate of heat transfer and the amount of heat that can be
removed by the liquid coolant, and also greatly improves the finish
attainable.
The invention as applied to a machining operation, is illustrated
in FIGS. 1 and 2, wherein a workpiece 10 is supported by jaws 11 of
a chuck 12 adjacent a grinding wheel 13 carried on a shaft 14 of a
motor 15. The chuck 12 may be rotatable or nonrotatable as the
situation requires, and additionally movable toward and away from
the grinding wheel 13. The details of the grinding machine are not
a part of the invention and it may take any suitable form.
Normally, wherein the workpiece 10 may be a hardened bearing part,
or a part where it is necessary to apply a liquid coolant in the
areas of metal removal, and the rate of metal removal is limited by
the "film boiling" phenomena.
According to the present invention, the liquid coolant is applied
by means of a nozzle or pipe 16 for directing the liquid coolant at
the point of engagement between the grinding wheel and the
workpiece. An electrostatic field is generated in the liquid
coolant by means of a probe or conductor 17 that may be mounted
within the nozzle, as illustrated, or therwise mounted adjacent
thereto, and connected to a high voltage DC or AC supply 18. Where
the liquid coolant is an electrolyte, as most coolants are, the
probe or conductor 17 would be completely electrically insulated in
order to prevent current movement through the electrolyte which
would create an electrical short, as shown in FIG. 3 where the
conductor 17 includes a wire 17a covered by insulation 17b. Where
the coolant may be a dielectric, it may be necessary to have the
probe or conductor bare in order to produce ions for establishing
the electrostatic field. However, it should be appreciated that
ions are already present in an electrolyte, and therefore none need
be produced where the coolant is an electrolyte. In order to set up
the electrostatic field, it is also necessary to provide a path for
same by way of either connecting the workpiece and/or grinding
wheel to ground potential such as indicated by the ground line
19.
In FIG. 4, the invention is illustrated in connection with the
cooling of a mass where the "film boiling" phenomena is not
experienced. A shaft 25 having a bearing 26 is illustrated in
connection with the liquid coolant nozzle 16, the electrical probe
or conductor 17 is connected to the high voltage DC or AC supply 18
wherein the coolant of a lubricating type is directed toward the
bearing, and an electrostatic field is generated in the coolant. In
this arrangement, a ground wire 27 is illustrated for connecting
the shaft and bearing to the ground potential. Again, the
electrostatic field will serve to bombard the surfaces of the
bearing with ions to enhance the rate of heat transfer. With
respect to this embodiment, and the illustration of FIGS. 1 and 2,
a voltage level of between 10 and 60 KV would be applied, the level
being slightly less than that which would cause arcing.
It will be understood that modifications and variations may be
effected without departing from the scope of the novel concepts of
the present invention, but it is understood that this application
is to be limited only by the scope of the appended claims.
* * * * *