Information
-
Patent Grant
-
6261702
-
Patent Number
6,261,702
-
Date Filed
Friday, May 21, 199925 years ago
-
Date Issued
Tuesday, July 17, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Webb Ziesenheim Logsdon Orkin & Hanson, P.C.
-
CPC
-
US Classifications
Field of Search
-
International Classifications
-
Abstract
A steel sheet having an embossed pattern of straight parallel grooves along the longitudinal axis of the sheet which replicate an abrasively polished surface. Furthermore, a working roll with the embossing pattern comprised of matching channels is disclosed along with methods for imparting the embossed pattern to the steel sheet. Finally, a method for fabricating the channels within the working roll is disclosed utilizing an abrasive element against the periphery of the roll.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to embossed rolled steel sheet. More specifically, the invention relates to embossed rolled steel sheet with a surface pattern that replicates an abrasively polished surface along with a method and apparatus for producing the same.
2. Description of the Prior Art
A significant portion of the flat rolled stainless steel sheet used commercially has a polished finish. The finish is generally produced by abrading the surface to produce a sanded appearance. This sanded appearance may also be produced by embossing on the steel sheet a similar pattern. While embossing generally provides the visual equivalent of the abraded surface, a relatively small percentage of steel sheet is processed in this fashion to produce such a surface.
However, abrasive finishing is costly and time-consuming and may produce an inconsistent surface that is prone to defects, such as polishing chatter, pits, and abrasive belt marks.
FIG. 1
illustrates a section of steel sheet
10
having a surface
15
with a sanded appearance. The surface
15
includes a multiplicity of slits
20
oriented about a longitudinal axis
25
generally in a random fashion.
As seen in
FIG. 2
, the slits (not shown) on the surface
15
of the sheet
10
are produced by moving the sheet
10
in a direction
30
from a payoff reel
32
past an abrasive roller
35
which has abrasive tape
40
about the periphery of the roller
35
to a take-up reel
37
. A relatively rigid roller
45
opposes the roller
35
, thereby permitting the abrasive tape
40
of the roller
35
to be applied against the sheet
10
with a predetermined pressure. Furthermore, the roller
35
rotates as indicated by arrow
47
against the direction
30
of travel of the sheet
10
by a motor
50
and a connecting belt
55
.
The surface
15
of the sheet
10
contacts the roller
35
only tangentially such that rotation of the roller
35
against the surface
15
produces the short slits
20
found in FIG.
1
. In general, the length of these slits along the longitudinal axis
25
is between 5 to 10 millimeters and these slits are unevenly spaced since they correspond with the locations of the individual pieces of grit on the abrasive tape
40
.
While this surface finish is aesthetically pleasing, in the event a portion of the surface becomes damaged, once repaired the sanded appearance must be reproduced. It is extremely difficult to reproduce this appearance because of the randomly spaced longitudinal slots
20
and it is equally difficult to provide a seamless transition between the repaired surface and the original surface. For that reason, a different type of surface finish was sought that would be more amenable to being repaired.
FIG. 3
illustrates a portion of a steel sheet
110
having a surface
115
with a plurality of grooves
120
extending parallel to a longitudinal axis
125
.
As illustrated in
FIG. 4
, the grooves
120
in the surface
115
of the sheet
110
are produced by moving the sheet
110
in the direction of arrow
130
from a payoff reel
132
between an element
135
having an abrasive surface
140
and a rigid roller
145
opposing the element
135
to a take-up reel
147
. The abrasive surface
140
extends across the entire width of the sheet
110
such that when the sheet
110
is moved in the direction
130
, the plurality of grooves
120
is produced over the surface
115
of the sheet
110
.
This surface finish is more amenable to being repaired; however, as previously mentioned, abrasive finishing is costly and time-consuming and may produce an inconsistent surface with defects. As an example,
FIG. 5
, which is an optical microscopy image of a steel sheet of stainless steel type
304
having an AISI number
3
polished finish to give the appearance of a brushed finish, illustrates typical surface tears and pits, not uncommon when abrasive polishing is used.
Steel sheet surfaces with these defects have associated disadvantages. First of all, the exposed steel sheet with surface tears and pits is more prone to corrosion than a surface without these. Furthermore, polished steel sheet is used on equipment in contact with food, chemicals and pharmaceuticals because of its resistance to corrosion and oxidation. It is important for the surface finish to be aesthetically pleasing, cleanable and resistant to corrosion. The cleanability of the sheet is significantly reduced by the introduction of such defects. Furthermore, as highlighted in the discussion of
FIG. 4
, the abrasive surface
140
is urged against the surface
115
of the sheet
110
and therefore a typical abrasive element
135
must be replaced approximately every 5,000 feet of surface that is abraded. Finally, the speed at which the sheet
110
travels past the abrasive element
140
is generally approximately 50 feet per minute. This produces a bottleneck since, for the most part, all of the other processes associated with finishing the sheet run at much higher speeds.
For that reason, a sheet is desired with a surface pattern that provides the same relative ease of repair to damage on the brushed surface but does not have the disadvantages associated with the damage caused by abrasion, relatively short life of the abrasive element and relatively slow speed associated with the abrasion process.
BRIEF SUMMARY OF THE INVENTION
One embodiment of the invention is an embossed steel sheet having a longitudinal axis comprising a plurality of straight grooves in the steel sheet which are continuous and parallel to one another defining an embossed pattern of straight grooves along a groove axis with each groove having associated with it one valley and two peaks. Each groove also has a wall connecting the peak of the groove to the valley of the groove with the vertical distance between the peak and valley of the groove defining the depth of the groove.
In a second embodiment of the invention, a steel sheet is embossed with a pattern using a method comprising the steps of providing a steel sheet having a sheet longitudinal axis and embossing the steel sheet by rolling the steel sheet with a working roll having a plurality of straight channels in the roll periphery along a channel axis which are continuous and parallel to one another defining an embossing pattern of straight channels along the channel axis. Each groove also has a wall connecting the peak of the channel to the valley of the channel with the vertical distance between the peak and valley of the channel defining the depth of the channel.
A third embodiment of the invention is a method of making an embossed steel sheet having surface characteristics optimized to improve repairability, corrosion resistance and cleanability of the sheet surface, the method comprising the steps of providing a steel sheet having a sheet longitudinal axis and embossing the steel sheet by rolling it using a textured working roll so that the resulting embossed steel sheet has a plurality of straight grooves which are continuous and parallel to one another defining an embossed pattern of straight grooves along a groove axis. Each groove also has a wall connecting the peak of the groove to the valley of the groove with the vertical distance between the peak and valley of the groove defining the depth of the groove.
A fourth embodiment of the invention is a roll on a temper mill used to emboss a surface pattern onto steel sheet, wherein the roll has a roll longitudinal axis and a roll radial axis and wherein the surface of the roll is comprised of a plurality of straight channels along the roll periphery which are continuous and parallel to one another defining a roll surface pattern, and wherein each channel also has a wall connecting the peak of the channel to the valley of the channel with the vertical distance between the peak and valley of the channel defining the depth of the channel.
A fifth embodiment of the invention is a method for fabricating a roll on a working mill used to emboss a surface pattern onto steel sheet comprising the steps of rotating the roll about a roll longitudinal axis, pressing an abrasive element against one end of the roll at the periphery of the roll, and traversing the abrasive element across the roll to impart a pattern to the periphery defined by a plurality of straight channels along a channel axis which are continuous and parallel to one another.
Other objects and advantages of the present invention will become apparent and obvious from the study of the following description and accompanying drawings which are merely illustrative of such invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is prior art and represents a sketch of the surface of an abraded steel sheet with a multiplicity of longitudinally oriented short slits;
FIG. 2
is prior art and illustrates a sketch of the apparatus utilized to produce the surface finish in
FIG. 1
;
FIG. 3
is prior art and shows the surface of an abraded steel sheet with a plurality of longitudinally oriented, parallel grooves;
FIG. 4
is prior art and illustrates a sketch of the apparatus utilized to produce the surface finish in
FIG. 3
;
FIG. 5
is prior art and shows an optical microscopy image at 1,000× showing the surface of a sheet of stainless steel type
304
with the abraded surface sketched in
FIG. 3
;
FIG. 6
shows a portion of steel sheet in accordance with the present invention having an embossed surface made up of a plurality of parallel grooves angled relative to the longitudinal axis;
FIG. 7
illustrates a perspective view of a section of the steel sheet in accordance with the subject invention;
FIG. 8
illustrates an optical microscopy image at 1,000× showing the surface of the steel sheet in accordance with the subject invention;
FIG. 9
illustrates a sketch of an apparatus utilized to emboss the surface finish of the subject invention onto the steel sheet;
FIG. 10
illustrates a method and apparatus utilized to impart the embossing pattern onto a temper roll;
FIG. 11
is an enlarged view of the portion labeled “T” in
FIG. 10
; and
FIG. 12
illustrates another method and apparatus for imparting the embossing pattern onto a temper roll.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 6
illustrates a top view of a section of sheet
210
having embossed upon its surface
215
a plurality of grooves
220
which are straight, continuous and parallel to one another defining an embossed pattern of straight grooves
220
along a groove axis
222
. A separate longitudinal axis
225
extends along the length of the sheet
210
. As illustrated in the perspective view in
FIG. 7
of this same sheet, groove
220
has associated with it one valley
230
and a first peak
235
and second peak
240
. It should be appreciated that each groove
220
has a common peak with an adjacent groove.
Each groove
220
also has a first wall
245
and a second wall
250
connecting the peak
235
, for example, to the valley
230
of the groove
220
. The vertical distance d between the peak
235
and a valley
230
of a groove
220
defines the depth of the groove
220
. In a preferred embodiment, the arithmetic average surface roughness (RA) of the grooves
220
in the sheet
210
in a direction transverse to the longitudinal axis
225
is from about 5 to 50 micro inches. Furthermore, the average peak count across a transverse section of the sheet
210
is approximately between
325
to
500
peaks per inch. These parameters, which, as will be explained, are imparted to the sheet
210
utilizing an embossing process which provides a surface generally equivalent to an AISI number 3 polished finish.
However, unlike the relatively rough surface illustrated in
FIG. 5
caused by abrasion polishing, the relatively inclusion-free finish is imparted to the surface utilizing the embossing process.
FIG. 8
is an optical microscopy image at 1,000× showing the surface
215
of the sheet
210
of stainless steel type
304
subsequent to the embossing process. This process as shown provides a much smoother finish. As an example, the arithmetic average surface roughness of the surface illustrated in
FIG. 5
in a direction transverse to the longitudinal axis is approximately 25-45 micro inches compared to the values of 5 to 50 micro inches associated with the embossed surface of FIG.
8
.
It should be noted that both FIG.
6
and
FIG. 7
illustrate a groove angle (a) measured between the longitudinal axis
225
and the groove axis
222
. Since it is desirable for the orientation of the grooves
220
relative to the longitudinal axis
225
to be as close to parallel with the longitudinal axis
225
as possible, it is desired to make the groove angle (a) as low as possible. Therefore, the groove angle (a) may have a value of between 0° and 5° and, as will be seen, is entirely a function of the embossing process.
While the average depth d of a groove
220
is approximately 196 micro inches, the maximum depth of a groove
220
is approximately 283 micro inches.
The sheet
210
may be any bright annealed strip and may include steel selected from cold rolled steel, hot rolled steel, coated sheet steel or other metals such as aluminum, copper or bronze which have a bright shiny surface. The preferred sheet is a bright annealed stainless steel sheet having a bright shiny surface requirement.
One embodiment of the method and apparatus for embossing the pattern upon the sheet
210
is illustrated in FIG.
9
. The sheet
210
is drawn from a payoff reel
255
in a direction illustrated by arrow
260
to a take-up reel
257
. The strip
210
is fed between working rolls
265
and
267
which rotate in clockwise directions as illustrated by arrows
270
and
272
, respectively. Each roll
265
,
267
is supported by a backup roll
275
,
277
. As an example, the sheet
210
is passed between the working rolls
265
and
267
on a standard temper mill wherein at least one of the working rolls
265
,
267
has specially designed grooves which will be discussed. The sheet
210
passes through the rolls with standard roll force, roll crown and tension and at an elongation on the order of 1% and less. While the same sheet
210
would move through an abrasive grinding operation at a speed of approximately 50 feet per minute, a speed of 1,000 feet per minute is typical when the working rolls
265
,
267
are utilized to impart a pattern onto the surface
215
of the sheet
210
.
FIG. 10
illustrates a sketch of an apparatus utilized to impart embossing channels into the working roll. In one embodiment, an unfinished working roll
265
is mounted within a lathe
310
on two centers
315
and
320
and rotated in a direction indicated by arrow
325
. An abrasive element
330
is supported on a block
335
which moves linearly along rails
340
and
345
in a direction indicated by arrow
350
. Mounted upon the abrasive element
330
is an abrasive tape
355
comprised of, for example, grit having a size of approximately 170 microns. Such a tape is standard in the grinding industry and available from 3M and generally identified as Scotch Brite® tape.
Because the width of the tape
355
is not as wide as the length of the roller
265
, to grind the working roll embossing channels
268
, it is necessary to traverse the belt
355
over the surface of the working roll
265
, thereby producing a helical pattern on the periphery of the working roll
265
.
In actuality, there is a single helical embossing channel on the working roll, but for purposes of this discussion it will be referred to as a series of channels. This helical pattern, when embossed onto the steel sheet
210
, will manifest itself on the sheet
210
(
FIG. 7
) as the series of parallel grooves
220
oriented relative to the longitudinal axis
225
of the sheet
210
at a groove axis angle (a). For that reason, the feed rate of the abrasive tape
355
over the face of the working roll
265
will be very low in an effort to produce the smallest channel axis angle (b) (
FIG. 11
) possible within a reasonable amount of time. As previously mentioned, ideally, the groove axis angle (a) should be 0°. However, utilizing the technique described with
FIG. 10
, it is impossible. Therefore, with the understanding some angle is required, the channel axis angle (b), and therefore the groove axis angle (a), will be so small that the perception of an observer will be that the grooves are parallel to the longitudinal axis
225
.
FIG. 11
illustrates an enlarged portion of the working roll
265
portion circled and identified as item T. The pattern on the working roll
265
is imparted directly to the surface
215
(
FIG. 7
) of the sheet
210
. The peripheral surface
360
of the working roll
265
, which is about a central axis
365
, has a plurality of channels
268
, each with a valley
375
and a first peak
380
and second peak
385
, which define within the channel
268
a first wall
390
and a second wall
395
. However, unlike with the sheet
210
, the depth d
2
between a peak
380
and valley
375
is greater than the depth d
1
in FIG.
7
. Furthermore, the average surface roughness RA on the periphery of the working roll
265
is approximately between 75 micro inches and 105 micro inches. The average peak count across the width of the working roll
265
is between approximately
325
and
500
peaks per inch. It should be noted the average peak count of the working roll periphery is also different from the average peak count imparted to the sheet
210
. Since the depth of each valley of the working roll
265
is different, there may be some valleys that are relatively deep and, as a result, the surface
215
of the sheet
210
will never contact them to conform to their shape. As a result, the sheet
210
will have fewer peaks than the working roll
265
.
A roller channel axis
397
is aligned with each channel
268
and oriented relative to a radial axis
399
extending perpendicular to the longitudinal axis
365
of the roller
265
to form a channel axis angle (b) which is identical to the groove axis angle (a) associated with the sheet
210
illustrated in FIG.
7
. For that reason, the pattern imparted to the sheet
210
is the projection of the pattern on the face of the working roller
265
as the roller
265
is rotated across the sheet
210
.
What has been described so far is a sheet
210
in which grooves
220
are imparted at an angle (a) relative to the longitudinal axis
225
as illustrated in FIG.
7
. What has also been described is an apparatus for imparting this pattern to the sheet
210
. As mentioned, the angled pattern on the sheet
210
and the helical pattern on the roller
265
to impart this pattern are caused entirely by the mechanism used to impart channels
268
to the roller
265
. The apparatus described in
FIG. 10
by its operation will impart such a pattern.
It is possible, however, using the same principles of the subject invention to impart to a roller a pattern without such an angle.
FIG. 12
illustrates an arrangement by which two centers
415
and
420
support a roller
422
which rotates in a direction indicated by
425
about the centers. An abrasive element
430
supported by a block
435
is urged against the periphery
440
of the roller
465
until channels
450
are imparted to the sheet
210
.
While the arrangement discussed in
FIG. 10
includes an abrasive element
330
having a relatively small width, it is entirely possible to place a series of such abrasive elements side by side as illustrated by elements
445
which may be placed side by side to create one unitary abrasive element as indicated by
430
. Such an arrangement may be utilized not only to provide grooves which are parallel to the longitudinal axis of the sheet
210
but furthermore may do so utilizing an operation which takes less time since the entire roll
465
is being acted upon by the abrasive elements
330
at one time.
The abrasive elements
330
and
430
illustrated in
FIGS. 10 and 12
, respectively, may be slowly indexed to refresh the grit contacting the rollers but not to avoid imparting any geometry to the face of the roller
265
. As an example, recall in the discussion of the prior art displayed in
FIGS. 1 and 2
that the rotation of the roller
35
imparted a plurality of slits
20
to the sheet
10
. Since the intention of indexing the abrasive elements
430
is only to refresh the grit and not to impart any shape, then the abrasive elements
330
and
430
may be mounted to a wheel which may slowly rotate at a rotational speed of, for example, between 10 and 20 revolutions per minute.
The subject invention imparts an embossed pattern to steel sheet which improves corrosion resistance and furthermore improves cleanability of the sheet surface. As an example, Table 1 shows the results of a corrosion test utilizing sheet finished in accordance with the subject invention versus sheet abrasively polished to a standard AISI #4 polished finishy using as specimens a sheet of Type 304 stainless steel and Type 201 stainless steel. The data in this table indicates the time for a known quantity of material to be corroded from the sheet when a voltage is applied to the sheet while submerged in a 3.5% solution of sodium chloride.
TABLE 1
|
|
Breakdown Potential in 3.5% NaCl (V vs. SCE)
|
#4 Polish
Long Grain
|
|
304
0.346
1.194
|
201
0.061
0.494
|
|
As illustrated, the corrosion resistance of the sheet fabricated in accordance with the subject invention is significantly greater than the corrosion resistance of a similar sheet with an abrasion polish.
Furthermore, because the sheet fabricated in accordance with the subject invention has fewer occlusions and pits, the cleanability is much greater, which is extremely important in commercial uses of the sheet where cleanliness is important.
Table 2 illustrates the results of cleanability tests using Type 304 stainless steel sheet subject to an AISI #4 polished finish, the embossing procedure of the subject invention, and a sheet finished with a standard AISI 2B finish. Standard stains were used.
TABLE 2
|
|
#4 Polish
Invention
2B
|
|
|
Sakura
Faint
Very Faint
Dark
|
SG-7 Blue
|
Magnum
Faint
Very Faint
Dark
|
44-Red
|
Marks A Lot
Faint
None
Dark
|
Black
|
Video Jet
Dark
None
Dark
|
Blue
|
|
As illustrated, the sheet surface in accordance with the subject invention provided greater cleanability than either of the other two sheet treatments.
What has been described is a steel sheet having a unique embossed surface which is corrosion resistance and easily cleaned. Furthermore, the roller for imparting this embossed surface to the sheet has also been described along with associated methods for imparting this surface pattern and for fabricating the embossing roller.
The present invention may, of course, be carried out in other specific ways other than those herein set forth without departing from the spirit and the essential characteristics of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
Claims
- 1. An embossed steel sheet having a sheet longitudinal axis comprising:a) a plurality of straight grooves in the steel sheet which are continuous and parallel to one another defining an embossed pattern of straight grooves along a groove axis with each groove having associated with it one valley and two peaks, b) wherein each groove also has a wall connecting the peak of the groove to the valley of the groove with the vertical distance between the peak and valley of the groove defining the depth of the groove, and c) wherein the sheet is a bright annealed stainless steel sheet having a bright shiny surface requirement with a finish of at least an AISI number 3 polished finish.
- 2. The steel sheet according to claim 1 wherein the arithmetic average surface roughness of the grooves in a direction transverse to the longitudinal axis is from about 5 to 50 micro inches.
- 3. The steel sheet according to claim 1 wherein the maximum depth of a groove is about 283 micro inches.
- 4. The steel sheet according to claim 1 wherein the average peak count is 220 to 380 per inch.
- 5. The steel sheet according to claim 1 wherein the groove axis is parallel to the longitudinal axis.
- 6. The steel sheet according to claim 1 wherein the groove axis forms a groove angle with the longitudinal axis of greater than zero and less than 5 degrees.
- 7. The steel sheet according to claim 6 wherein the groove angle is 1 degree.
- 8. A steel sheet embossed with a pattern using a method comprising the steps of:a) providing a steel sheet having a sheet longitudinal axis, and b) embossing the steel sheet by rolling the steel sheet with a working roll having a plurality of straight channels in the roll periphery along a channel axis which are continuous and parallel to one another defining an embossing pattern of straight channels along the channel axis, c) wherein each channel also has a wall connecting the peak of the channel to the valley of the channel with the vertical distance between the peak and valley of the channel defining the depth of the channel, and d) wherein the sheet is a bright annealed stainless steel sheet having a bright shiny surface requirement with a finish of at least an AISI number 3 polished finish.
- 9. The steel sheet according to claim 8 wherein the method further includes the step of rolling the steel sheet with the working roll so that the arithmetic average surface roughness of the grooves in a direction transverse to the longitudinal axis is from about 5 to 50 micro inches.
- 10. The steel sheet according to claim 8 wherein the method further includes the step of rolling the steel sheet with the roll so that the maximum depth of a groove is about 283 micro inches.
- 11. The steel sheet according to claim 8 wherein the method further includes rolling the steel sheet to produce an average peak count between 220 to 380 per inch.
- 12. The steel sheet according to claim 8 wherein the method further includes rolling the steel sheet to produce a groove axis on the sheet parallel to the longitudinal axis.
- 13. The steel sheet according to claim 8 wherein the method further includes rolling the steel sheet to produce a groove having a groove axis and having a groove angle between the groove axis and the sheet longitudinal axis of greater than 0 and less than 5 degrees.
- 14. The steel sheet according to claim 13 wherein the groove angle is 1 degree.
US Referenced Citations (25)
Foreign Referenced Citations (4)
Number |
Date |
Country |
0251759 |
Jan 1988 |
EP |
0712954A1 |
May 1996 |
EP |
50-24699 |
Aug 1975 |
JP |
1592068 |
Sep 1990 |
SU |