U.S. patent application number 13/633529 was filed with the patent office on 2013-04-18 for grinding apparatus with a slot nozzle.
This patent application is currently assigned to ROLLS-ROYCE PLC. The applicant listed for this patent is ROLLS-ROYCE PLC. Invention is credited to Christopher Knotts, Zdenek Zaruba.
Application Number | 20130095734 13/633529 |
Document ID | / |
Family ID | 45035244 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130095734 |
Kind Code |
A1 |
Zaruba; Zdenek ; et
al. |
April 18, 2013 |
GRINDING APPARATUS WITH A SLOT NOZZLE
Abstract
Apparatus for high speed grinding comprises a grinding wheel
having a circumferential grinding surface, a machine for mounting
and rotating the grinding wheel about the axis, a coolant supply
system including a slot nozzle arranged to direct coolant fluid
secantly to the grinding surface, the slot nozzle having an exit
with an elongate axis and a short axis wherein the elongate axis is
tilted relative to the axis of the grinding wheel.
Inventors: |
Zaruba; Zdenek; (Kent,
GB) ; Knotts; Christopher; (Glasgow, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROLLS-ROYCE PLC; |
London |
|
GB |
|
|
Assignee: |
ROLLS-ROYCE PLC
London
GB
|
Family ID: |
45035244 |
Appl. No.: |
13/633529 |
Filed: |
October 2, 2012 |
Current U.S.
Class: |
451/449 |
Current CPC
Class: |
B24B 55/03 20130101;
B24B 55/02 20130101 |
Class at
Publication: |
451/449 |
International
Class: |
B24B 55/03 20060101
B24B055/03 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2011 |
GB |
1117243.4 |
Claims
1. Apparatus for high speed grinding comprises a grinding wheel on
an axle having a circumferential grinding surface, a machine for
mounting and rotating the grinding wheel about the axle, a coolant
supply system including a slot nozzle arranged to direct coolant
fluid secantly to the grinding surface, the slot nozzle having an
exit with an elongate axis and a short axis wherein elongate axis
is parallel to a chord through the grinding wheel and tilted
relative to the axis of the grinding wheel.
2. Apparatus according to claim 1, wherein the elongate axis is
tilted between 5 and 20 degrees to the axis of the grinding
wheel.
3. Apparatus according to claim 1, wherein the slot nozzle has a
length along the elongate axis that is longer than the width of the
circumferential grinding surface.
4. Apparatus according to claim 3, wherein the length of the
elongate axis is more than 5% longer than the width of the
circumferential grinding surface.
5. Apparatus according to claim 1, wherein the machine for mounting
and rotating the grinding wheel rotates the wheel at peripheral
speeds between 10 metres per second and about 80 metres per
second.
6. Apparatus according to claim 1, wherein the coolant supply
system delivers a jet of liquid from the nozzle at a pressure of
between 40 and 70 Bar (4000 and 7000 kPa).
7. Apparatus according to claim 1 further comprising an alignment
tool having a first edge for alignment with a side of the grinding
wheel, a second edge for alignment with the grinding surface and a
third edge for alignment with an edge of the nozzle.
8. Apparatus according to claim 7, wherein the tool is provided by
a sheet of material.
9. Apparatus for high speed grinding comprises a grinding wheel on
an axle having a circumferential grinding surface, a machine for
mounting and rotating the grinding wheel about the axle, a coolant
supply system including a slot nozzle arranged to direct coolant
fluid secantly to the grinding surface, the slot nozzle having an
exit with an elongate axis and a short axis wherein elongate axis
is parallel to a chord through the grinding wheel and tilted
relative to the axis of the grinding wheel, wherein the slot nozzle
has a length along the elongate axis that is longer than the width
of the circumferential grinding surface.
10. Apparatus according to claim 9, wherein the elongate axis is
tilted between 5 and 20 degrees to the axis of the grinding
wheel.
11. Apparatus according to claim 3, wherein the length of the
elongate axis is more than 5% longer than the width of the
circumferential grinding surface.
12. Apparatus according to claim 9, wherein the machine for
mounting and rotating the grinding wheel rotates the wheel at
peripheral speeds between 10 metres per second and about 80 metres
per second.
13. Apparatus according to claim 9, wherein the coolant supply
system delivers a jet of liquid from the nozzle at a pressure of
between 40 and 70 Bar (4000 and 7000 kPa).
Description
[0001] The invention relates to a method and apparatus for
grinding.
[0002] The present invention seeks to provide an improved method
and apparatus for grinding. Grinding apparatus is described in U.S.
Pat. No. 6,123,606.
[0003] According to a first aspect of the invention there is
provided apparatus for high speed grinding comprises a grinding
wheel on an axle having a circumferential grinding surface, a
machine for mounting and rotating the grinding wheel about the
axle, a coolant supply system including a slot nozzle arranged to
direct coolant fluid secantly to the grinding surface, the slot
nozzle having an elongate axis and a short axis wherein the
elongate axis is parallel to a chord through the grinding wheel and
tilted relative to the axis of the grinding wheel.
[0004] By tilting the exit of the slot nozzle an improved flow
distribution to the grinding surface is achieved.
[0005] Preferably the elongate axis is tilted between 5 and 20
degrees to the axis of the grinding wheel.
[0006] The slot nozzle may have a length along the elongate axis
that is longer than the width of the circumferential grinding
surface.
[0007] The extended length provides a flow of coolant over the
edges of the grinding surface to further improve cooling of the
grinding wheel. Preferably the length of the elongate axis is more
than 5% longer than the width of the circumferential grinding
surface.
[0008] The machine for mounting and rotating the grinding wheel may
be capable of rotating the wheel at peripheral speeds between 10
metres per second and about 80 metres per second.
[0009] The coolant supply system may deliver a jet of liquid from
the nozzle at a pressure of between 40 and 70 Bar (4000 kPa-7000
kPa).
[0010] Preferably the apparatus further comprises an alignment tool
having a first edge for alignment with a side of the grinding
wheel, a second edge for alignment with the grinding surface and a
third edge for alignment with an edge of the nozzle.
[0011] The tool may be provided by a sheet of material.
[0012] The invention will now be described by way of example only
and with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic diagram illustrating an embodiment of
the invention;
[0014] FIG. 2A depicts a perspective view of a nozzle for use in
the system of FIG. 1,
[0015] FIG. 2B depicts a top view of the nozzle, and FIG. 2C
depicts a side view of the nozzle;
[0016] FIG. 3 is a schematic depicting the nozzle of FIG. 2
presented to a grinding wheel
[0017] FIG. 3A is a side view of the nozzle and grinding wheel, and
FIG. 3B is a schematic view of the nozzle relative to the grinding
wheel circumferential face;
[0018] FIG. 4 is a diagram of a nozzle, alignment tool and grinding
wheel;
[0019] FIG. 5 is a diagram of a nozzle, further alignment tool and
grinding wheel;
[0020] FIG. 6 depicts a supply pipe for supplying coolant fluid to
the nozzle.
DETAILED DESCRIPTION
[0021] For the purposes of illustrating the principles of a
grinding process incorporating the invention, FIG. 1 shows a
grinding set-up which comprises a grinding wheel 2 rotating in the
direction of arrow 4 while a workpiece 6 is fed past the wheel 2 in
the relative direction of arrow 8. In the illustrated example this
produces an operation known in the art as "down" grinding in a
contact region generally indicated at 9. The invention is found to
work just as well with "up" grinding. Essentially the process of
the invention is a developed form of the process known as
creep-feed grinding, although this may be regarded as something of
a misnomer since the enhancement results is very much faster
removal of workpiece material.
[0022] The grinding wheel 2 is mounted on a rotary spindle 10
carried by a tool head or chuck 12 which is part of a standard
multi-axis machine. The workpiece 6 is held by means of a mounting
fixture 14 on a surface mounting table 16. Since, in this
embodiment, a "one-pass" grinding process is shown the width of the
grinding wheel can be determined by the corresponding width of the
ground surface required. We have found no significant variation of
results using grinding wheels in a width range of 10 mm to 45 mm
providing the surface speed is maintained constant. On the other
hand we have found no indication of a width limit and the invention
may be expected to be useful regardless of the width of the
grinding wheel, other considerations aside.
[0023] The range of values of surface speed for the type of
grinding wheel employed is from about 10 metres per second up to
about 80 metres per second. Wheels of various diameters gave
consistent results providing surface speed was matched with all
other parameters. The maximum diameter of grinding wheel used to
date is around 220 mm, but this upper limit was imposed by physical
clearance in the operative region of the machine, rather than by
the inherent stability of the wheel construction. Obviously
grinding wheels by the nature of their composition and construction
possess limitations in terms of maximum rotational speed, depth of
cut achievable to name but two, but in this example these did not
curtail the operational parameters of the process. Thus, where the
machine permits in respect of size, and speed higher figures may be
expected to be achieved e.g. up to 400 mm or more.
[0024] A jet 18 of liquid coolant, comprising a water soluble oil,
is directed through nozzle means 20 at an aiming point 19 on the
periphery of wheel 2. The nozzle 20 is the outlet of a closed-loop
coolant delivery, collection and filtration system. Spent coolant
ejected from the wheel is collected in a sump 22, in the lower part
of the machine, and drawn-off through an efficient filtration
system 24 to remove debris down to a particle size, typically of at
least, about 10 micron.
[0025] Integral with the filtration system 24 is a very high
pressure pump system 26 which delivers coolant under pressure
through outlet 28 to the delivery nozzle 20. In the illustrated
embodiment the coolant supply is delivered via the outlet 28 at a
pressure of up to 100 bar (10000kPa), typically between 40 bar and
70 bar (4000 to 7000 kPa), at a flow rate of up to about 130 litres
per minute.
[0026] The nozzle 20 is positioned close to the periphery of wheel
2 to deliver the very high pressure jet 18 of coolant at the wheel
at a point approximately 45 degrees in advance of the cutting
region on workpiece 6. The nozzle is a slot nozzle 20 constructed
and arranged to direct a jet 18 of coolant fluid to the periphery
of the wheel with the impact point across the full width of the
wheel. In the embodiment the nozzle 20 has a jet orifice which is
approximately rectangular having a length approximately equal to
the width of the wheel 2, but preferably slightly longer, and which
is 0.5 mm to 1 mm in depth. This orifice, therefore, directs a jet
18 of coolant in the shape of a sheet or fan at the periphery of
the wheel.
[0027] Also, in FIG. 1, a pair of radii 30,32 are shown (in
chain-line) centred on the wheel spindle 10. A first radius 30 is
drawn through the impingement region of the jet 18 on the periphery
of the wheel 2, while the second radius 32 is drawn through the
contact point between the wheel 2 and the workpiece 6. The included
angle between these two radii 30,32 defines the circumferential
position of the impact point of jet 18. It will be apparent from
the illustration of the present embodiment, which used a wheel
diameter of approximately 80 mm at the smaller end of the range,
that this included angle is approximately 45 degrees and the jet 18
is in advance of the grinding wheel contact point. Other included
angles may be appropriate.
[0028] A more detailed view of the nozzle is shown in FIG. 2. As
may be observed the nozzle body has an inlet portion 40, a tapering
portion 42 and a flow forming portion 44 before the nozzle outlet
46 which offers a consistent laminar flow from the nozzle and helps
to reduce the amount of air in the coolant flow and can reduce,
where the substrate suffers, tarnishing and oxidation at the
grinding point. FIG. 2 depicts a perspective view (FIG. 2a) a top
view (FIG. 2b) and a side view (FIG. 2c). In an alternative
arrangement the inlet portion has a nut or other connecting feature
for connecting the nozzle to pipework which supplies the cooling
fluid to the nozzle.
[0029] The nozzle may be formed from stainless steel pipe
manufactured on customised jaws and aperture former to produce the
elongate nozzle shape.
[0030] FIG. 3 depicts the preferred alignment of the nozzle 20 to
the grinding wheel 2. The nozzle 20 directs the coolant fluid as a
jet 18 secantly to the wheel such that it impacts the grinding
surface from an angle that is leant relative to the true radius of
the wheel. In the most extreme case the jet is directed
tangentially to the wheel but normally angle of the nozzle is
between 5 and 20 degrees from the tangent. The tem secantly
includes the arrangement where the fluid is directed
tangentially.
[0031] As shown in FIG. 3b the nozzle is presented to grinding
wheel to supply coolant to the grinding face which is the
circumferential face. It has been found that the orientation of the
nozzle relative to the circumferential face is important; not just
the secant angle onto the circumferential face but also the angle
.theta. of the elongate axis of the nozzle to the axis of the
grinding wheel. By arranging the elongate axis of the nozzle at an
angle .theta. between 5.degree. and 15.degree., and preferably at
around 10 .degree. to the axis of the grinding wheel an improved
cooling distribution is achieved.
[0032] Where a particularly wide grinding face is used it may be
necessary to use more than one elongate coolant nozzle which may be
at different angles relative to each other and to the axis of the
grinding wheel. The nozzles may overlap to provide extra coolant to
particular regions of the grind face. One or more of the nozzles
may be parallel to the axis of the grinding wheel.
[0033] The tip (exit orifice) of the nozzle 20a,20b in use is
preferably positioned very close to the peripheral, circumferential
surface of the grinding wheel 2. To aid simple alignment of the
nozzle a tool may be used as show in FIG. 4. The tool 102 has a
first datum face 104 to align with a side of the grinding wheel, a
second datum face 106 to align with the grinding face of the
grinding wheel, a third datum face 107 to locate the axial position
of the end of the nozzle relative to the grinding face to ensure
overlap and a fourth datum face 108 to align the angle of the
elongate nozzle to the axis of the grinding wheel. The tool may be
formed from readily available sheet metal offering a simple and
elegant solution to what could be a complex and costly set up
process.
[0034] A further alignment tool an example of which is shown in
FIG. 5 may be used which locates the nozzle in its correct
secantial or tangential position relative to the edge of the
grinding wheel. The tool has an elongate member 110 which is long
enough to span the distance between the nozzle 20 and the edge of
the grinding wheel 2 and a notched portion 112 which engages with
the nozzle. To align the nozzle the notched portion is placed into
engagement with the nozzle and the elongate member then the axis of
the wheel or the entry to pipework supplying fluid to the nozzle
moved till the elongate member is at the desired secantal or
tangential angle to the grinding wheel.
[0035] FIG. 6 shows top view (FIG. 6a) and a side view (FIG. 6b)
for an option of pipework which may be used to supply the cooling
fluid to the nozzle. The pipework is made of three separate
sections which are joined together, preferably by welding, to avoid
significant bending of a full length pipe and fluctuations in bore
size at the bending points and weakness in the material. The bends
are all kept below 90 degrees so that fluctuations in flow are
minimised.
* * * * *