U.S. patent application number 10/819485 was filed with the patent office on 2004-09-30 for alloy for battery grids.
This patent application is currently assigned to Johnson Controls Technology Company. Invention is credited to Schaeffer, Charles J..
Application Number | 20040187986 10/819485 |
Document ID | / |
Family ID | 31714465 |
Filed Date | 2004-09-30 |
United States Patent
Application |
20040187986 |
Kind Code |
A1 |
Schaeffer, Charles J. |
September 30, 2004 |
Alloy for battery grids
Abstract
A grid for a battery having a current collection lug and a
plurality of wires is made by a method that includes forming the
grid utilizing a punching operation. The grid is formed of an alloy
including calcium in an amount of about 0.05 percent by weight to
about 0.08 percent by weight, tin in an amount of about 1.2 percent
by weight to about 1.8 percent by weight, and bismuth in an amount
of less than about 0.04 percent by weight. The balance of the alloy
comprises lead.
Inventors: |
Schaeffer, Charles J.;
(Wauwatosa, WI) |
Correspondence
Address: |
FOLEY & LARDNER
777 EAST WISCONSIN AVENUE
SUITE 3800
MILWAUKEE
WI
53202-5308
US
|
Assignee: |
Johnson Controls Technology
Company
|
Family ID: |
31714465 |
Appl. No.: |
10/819485 |
Filed: |
April 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10819485 |
Apr 7, 2004 |
|
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|
10217949 |
Aug 13, 2002 |
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Current U.S.
Class: |
148/706 ;
420/565 |
Current CPC
Class: |
H01M 4/72 20130101; Y02E
60/10 20130101; C22C 11/06 20130101; H01M 4/685 20130101 |
Class at
Publication: |
148/706 ;
420/565 |
International
Class: |
C22C 011/06 |
Claims
What is claimed is:
1. A grid for a battery having a current collection lug and a
plurality of wires, the grid made by a method comprising: forming
the grid utilizing a punching operation; wherein the grid is formed
of an alloy comprising: calcium in an amount of about 0.05 percent
by weight to about 0.08 percent by weight; tin in an amount of
about 1.2 percent by weight to about 1.8 percent by weight; and
bismuth in an amount of less than about 0.04 percent by weight;
wherein the balance of the alloy comprises lead; whereby the
bismuth is provided in an amount sufficient to enhance the hardness
stability of the alloy.
2. The grid of claim 1 wherein the calcium is in an amount of about
0.05 percent by weight to about 0.0725 percent by weight.
3. The grid of claim 1 wherein the calcium is in an amount of about
0.055 percent by weight to about 0.07 percent by weight.
4. The grid of claim 3 wherein the calcium is in an amount of about
0.06 percent by weight to about 0.07 percent by weight.
5. The grid of claim 1 wherein the tin is in an amount of about 1.2
percent by weight to about 1.65 percent by weight.
6. The grid of claim 1 wherein the ratio of the calcium to the tin
is greater than about 12 to 1.
7. The grid of claim 1 wherein the alloy further comprises silver
as an impurity element.
8. The grid of claim 1 wherein the alloy further comprises silver
in an amount of about 0.0005 percent by weight to about 0.02
percent by weight.
9. The grid of claim 1 wherein the alloy further comprises silver
in an amount of about 0.001 percent by weight to about 0.005
percent by weight.
10. The grid of claim 1 wherein the bismuth is in an amount of
about 0.0005 percent by weight to about 0.0225 percent by
weight.
11. The grid of claim 10 wherein the bismuth is in an amount of
about 0.001 percent by weight to about 0.0190 percent by
weight.
12. The grid of claim 11 wherein the bismuth is in an amount of
greater than about 0.0115 percent by weight.
13. The grid of claim 1 wherein the bismuth is in an amount of
about 0.0115 percent by weight to about 0.0165 percent by
weight.
14. The grid of claim 1 further comprising forming a slab from the
alloy prior to the step of forming the grid.
15. The grid of claim 14 further comprising rolling the slab to
decrease its thickness before the step of forming the grid
utilizing a punching operation.
16. The grid of claim 15 wherein the step of rolling the slab to
decrease its thickness comprises decreasing the thickness of the
slab to about 10 percent of the original thickness of the slab.
17. The grid of claim 14 wherein the step of forming the slab
comprises casting the slab.
18. A grid for a battery having a lug for collecting current and a
plurality of wires, the grid manufactured by a method comprising:
providing a slab of grid alloy; rolling the slab to decrease the
thickness of the slab; and punching the slab after the rolling step
to form the grid; wherein the grid alloy comprises: calcium in an
amount of about 0.05 percent by weight to about 0.08 percent by
weight; tin in an amount of about 1.2 percent by weight to about
1.8 percent by weight; and bismuth in an amount of greater than
about 0.0115 percent by weight; wherein the balance of the alloy
comprises lead.
19. The grid of claim 18 wherein the tin is in an amount less than
about 1.5 percent by weight.
20. The grid of claim 18 wherein the grid alloy comprises silver in
an amount of about 0.0005 percent by weight to about 0.02 percent
by weight.
21. The grid of claim 18 wherein the grid alloy comprises silver in
an amount of about 0.001 percent by weight to about 0.015 percent
by weight.
22. The grid of claim 18 wherein the grid alloy comprises silver in
an amount of about 0.001 percent by weight to about 0.005 percent
by weight.
23. The grid of claim 18 wherein the grid alloy comprises silver as
an impurity element.
24. The grid of claim 18 wherein the bismuth is in an amount of
less than about 0.0275 percent by weight.
25. The grid of claim 21 wherein the bismuth is in an amount of
less than about 0.0225 percent by weight.
26. The grid of claim 25 wherein the bismuth is in an amount of
less than about 0.019 percent by weight.
27. The grid of claim 26 wherein the bismuth is in an amount of
about 0.015 percent by weight to about 0.0165 percent by
weight.
28. The grid of claim 18 wherein the bismuth is in an amount of
less than about 0.04 percent by weight.
29. The grid of claim 18 wherein the step of providing a slab of
grid alloy comprises casting the slab from the grid alloy.
30. A method of producing a grid for a battery having a lug for
collecting current and a plurality of wires, the method comprising:
providing a slab of grid alloy; decreasing the thickness of the
slab; and punching the slab to form the grid after the step of
decreasing the thickness of the slab; wherein the grid alloy
consists essentially of: calcium in an amount of about 0.05 percent
by weight to about 0.08 percent by weight; tin in an amount of
about 1.2 percent by weight to about 1.8 percent by weight; and
bismuth in an amount of less than about 0.04 percent by weight;
wherein the balance of the grid alloy comprises lead.
31. The method of claim 30 wherein the calcium is in an amount of
about 0.055 percent by weight to about 0.07 percent by weight.
32. The method of claim 31 wherein the calcium is in an amount of
about 0.06 percent by weight to about 0.07 percent by weight.
33. The method of claim 30 wherein the tin is in an amount of about
1.2 percent by weight to about 1.65 percent by weight.
34. The method of claim 30 wherein the ratio of calcium to tin is
greater than about 12 to 1.
35. The method of claim 30 wherein the grid alloy includes silver
as an impurity.
36. The method of claim 30 wherein the bismuth is in an amount of
about 0.0005 percent by weight to about 0.0225 percent by
weight.
37. The method of claim 36 wherein the bismuth is in an amount of
about 0.001 percent by weight to about 0.0190 percent by
weight.
38. The method of claim 30 wherein the step of forming the slab
comprises casting the slab.
39. The method of claim 38 further comprising rolling the slab to
decrease its thickness before the step of forming the grid
utilizing a punching operation.
40. The method of claim 39 wherein the step of rolling the slab to
decrease its thickness comprises decreasing the thickness of the
slab to about 10 percent of the original thickness of the slab.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation under 35 U.S.C. .sctn.
120 of U.S. patent application Ser. No. 10/217,949 titled "Alloy
for Battery Grids" filed on Aug. 13, 2002.
[0002] The disclosure of the following patent application is hereby
incorporated by reference in its entirety: U.S. patent application
Ser. No. 10/217,949 titled "Alloy for Battery Grids" filed on Aug.
13, 2002.
FIELD
[0003] The present invention relates generally to the field of lead
alloys. The present invention relates more specifically to a lead
alloy for a battery grid having calcium, tin and bismuth.
BACKGROUND
[0004] Batteries (e.g. lead-acid electric storage batteries)
typically include cell elements having positive and negative grids
or plates and separators between the grids. The grids are typically
made of a lead alloy that includes various alloying elements
intended to improve performance, life and/or manufacturability of
the grids and battery.
[0005] It is generally known to provide any of a variety of
alloying elements to improve performance, life, and/or
manufacturability of battery grids. For example, it is known to add
calcium to the alloy to increase hardness, which may improve grid
manufacturability. Calcium in certain amounts, however, may result
in increased corrosion of the grid due to formation of precipitated
Pb.sub.3Ca, or may result in increased grid growth due to premature
overaging.
[0006] It is also known to add silver to the alloy to increase
mechanical strength (e.g. creep resistance) and hardening rate. It
is also known to add bismuth to the alloy. However, relatively high
amounts of silver and/or bismuth may cause drossing or unfavorable
grain structure. Further, relatively high amounts of bismuth may
result in isolated regions of discontinuous precipitate in the grid
(e.g. substantially non-hardening precipitates formed from the
reaction of bismuth with lead and/or tin), which may negatively
impact the life of such grid due to accelerated corrosion
penetration and grid growth.
[0007] Accordingly, it would be advantageous to provide a lead
alloy for use in a battery grid that has an acceptable corrosion
rate and life. It would also be advantageous to provide a lead
alloy for a battery grid that includes bismuth. It would also be
advantageous to provide a lead alloy for a battery grid that has a
relatively high hardness stability (i.e. resistance to overaging).
It would be desirable to provide for an alloy for a battery grid
having one or more of these advantageous features.
DESCRIPTION OF THE FIGURES
[0008] FIG. 1 shows a battery grid according to an exemplary
embodiment.
[0009] FIG. 2A shows a bar graph of the hardness stability integral
of an alloy for a battery grid according to an exemplary
embodiment.
[0010] FIG. 2B shows a line graph of the hardness stability
integral versus the amount of bismuth for of an alloy for a battery
grid according to an exemplary embodiment.
[0011] FIG. 3A shows a photograph of an alloy for a battery grid
having bands of untransformed material according to an exemplary
embodiment.
[0012] FIG. 3B shows a photograph of the alloy of FIG. 3A having
bands of untransformed material according to an exemplary
embodiment.
SUMMARY
[0013] The present invention relates to a grid for a battery having
a current collection lug and a plurality of wires is made by a
method that includes forming the grid utilizing a punching
operation. The grid is formed of an alloy including calcium in an
amount of about 0.05 percent by weight to about 0.08 percent by
weight, tin in an amount of about 1.2 percent by weight to about
1.8 percent by weight, and bismuth in an amount of less than about
0.04 percent by weight. The balance of the alloy comprises
lead.
[0014] The present invention also relates to a grid for a battery
having a lug for collecting current and a plurality of wires. The
grid is manufactured by a method that includes providing a slab of
grid alloy, rolling the slab to decrease the thickness of the slab,
and punching the slab after the rolling step to form the grid. The
grid alloy includes calcium in an amount of about 0.05 percent by
weight to about 0.08 percent by weight, tin in an amount of about
1.2 percent by weight to about 1.8 percent by weight, and bismuth
in an amount of greater than about 0.0115 percent by weight. The
balance of the alloy comprises lead.
[0015] The present invention also relates to a method of producing
a grid for a battery having a lug for collecting current and a
plurality of wires. The method includes providing a slab of grid
alloy, decreasing the thickness of the slab, and punching the slab
to form the grid after the step of decreasing the thickness of the
slab. The grid alloy consists essentially of calcium in an amount
of about 0.05 percent by weight to about 0.08 percent by weight,
tin in an amount of about 1.2 percent by weight to about 1.8
percent by weight, and bismuth in an amount of less than about 0.04
percent by weight. The balance of the grid alloy comprises
lead.
DETAILED DESCRIPTION OF PREFERRED AND OTHER EXEMPLARY
EMBODIMENTS
[0016] A battery plate or grid 10 is shown in FIG. 1. The grid is a
"stamped" or punched grid made from a wrought alloy according to a
preferred embodiment, and may be made from a cast alloy according
to an alternative embodiment. The grid is a "positive" grid for a
lead-acid battery according to a preferred embodiment, and may be a
"negative" grid according to an alternative embodiment. Grid 10
includes an electric current collection lug 12. Generally vertical
wires 14 extend from lug 12. Generally horizontal wires 16
intersect vertical wires 14. The grid includes a lead alloy having
calcium, tin and bismuth according to a preferred embodiment. The
lead alloy may include silver according to an alternative
embodiment.
[0017] The amount of calcium in the alloy is selected to provide
suitable hardness of the alloy, which can aid in manufacturability
of the alloy according to a preferred embodiment. Such suitable
hardness of the alloy may eliminate the need for heat treatment of
the alloy. The amount of calcium in the alloy should not be so
great as to cause an unacceptable increase in corrosion rate or
reduction in hardness stability. Aluminum may be included in the
alloy (or in the melt pot of the alloy) to reduce the loss of
calcium according to a preferred embodiment.
[0018] The alloy includes calcium in an amount greater than about
0.05 percent by weight according to a preferred embodiment. The
alloy includes calcium in an amount of about 0.05 percent by weight
to about 0.08 percent by weight according to an alternative
embodiment. The alloy includes calcium in an amount of 0.055
percent by weight to about 0.075 percent by weight according to
another alternative embodiment. The alloy includes calcium in an
amount of about 0.05 percent by weight to about 0.07 percent by
weight according to an alternative embodiment. The alloy includes
calcium in an amount of 0.055 percent by weight to about 0.07
percent by weight according to an alternative embodiment. The alloy
includes calcium in an amount of 0.06 percent by weight to about
0.07 percent by weight according to an alternative embodiment.
[0019] The amount of tin in the alloy is selected to reduce
corrosion according to a preferred embodiment. Without intending to
be limited to any particular theory, it is believed that tin will
react with calcium to form Sn.sub.3Ca (which provides corrosion
resistance), and that the tin will inhibit the reaction of lead
with calcium, thereby reducing the formation of discontinuous
Pb.sub.3Ca precipitate (which may promote grid growth).
[0020] The alloy includes tin in an amount of greater than about
1.2 percent by weight according to a preferred embodiment. The
alloy includes tin in an amount of about 1.2 percent by weight to
about 1.65 percent by weight according to an alternative
embodiment. The alloy includes tin in an amount of about 1.2
percent by weight to about 1.5 percent by weight according to an
alternative embodiment.
[0021] The ratio of tin to calcium is selected to minimize the
formation of Pb3Ca precipitate according to a preferred embodiment.
The ratio of tin to calcium is greater than about 10 to 1 according
to a preferred embodiment. The ratio of tin to calcium is greater
than about 12 to 1 according to other preferred or alternative
embodiments. The ratio of tin to calcium is greater than about 20
to 1 according to other preferred or alternative embodiments. For
example, where the alloy has a calcium content of about 0.07
percent by weight, it is preferred that the tin content exceed
about 0.84 percent by weight. Increasing the ratio of tin to lead
may reduce "coarsening" of the precipitates in the grid by
suppressing formation of precipitated Pb.sub.3Ca, which in turn
decreases grid growth and increases the life of the grids.
[0022] According to an alternative embodiment, silver may be
included in "trace" amounts or as an impurity that is present in
"secondary" or recycled lead.
[0023] The alloy includes silver in an amount of about 0.0005
percent by weight to about 0.02 percent by weight according to a
preferred embodiment. The alloy includes silver in an amount of
about 0.001 percent by weight to about 0.015 percent by weight
according to an alternative embodiment. The alloy includes silver
in an amount of about 0.001 percent by weight to about 0.01 percent
by weight according to an alternative embodiment. The alloy
includes silver in an amount of about 0.001 percent by weight to
about 0.005 percent by weight according to an alternative
embodiment.
[0024] The amount of bismuth in the alloy is selected to provide an
acceptable hardness stability (i.e. "microhardness") of the alloy.
The alloy includes bismuth in an amount of less than about 0.04
percent by weight according to a preferred embodiment. The alloy
includes bismuth in an amount of about 0.0005 percent by weight to
about 0.0275 percent by weight according to an alternative
embodiment. The alloy includes bismuth in an amount of about 0.0005
percent by weight to about 0.025 percent by weight according to an
alternative embodiment. The alloy includes bismuth in an amount of
about 0.001 percent by weight to about 0.0225 percent by weight
according to an alternative embodiment. The alloy includes bismuth
in an amount of about 0.001 percent by weight to about 0.0190
percent by weight according to an alternative embodiment. The alloy
includes bismuth in an amount of about 0.0115 percent by weight to
about 0.0165 percent by weight according to an alternative
embodiment. The alloy includes bismuth in an amount of about 0.0150
percent by weight according to a particularly preferred
embodiment.
[0025] The alloy may include relatively low amounts of other
materials according to any preferred or alternative embodiments.
For example, the alloy may include background "impurities" or trace
materials that are present in a commercially recycled lead stream.
Impurities in the alloy in the following amounts may be acceptable:
(1) zinc in an amount of less than about 0.005 percent by weight
according to an alternative embodiment, zinc in an amount of less
than about 0.0025 percent by weight according to a preferred
embodiment; (2) antimony in an amount of less than about 0.005
percent by weight according to an alternative embodiment, antimony
in an amount of less than about 0.0025 percent by weight according
to a preferred embodiment; (3) arsenic in an amount of less than
about 0.0025 percent by weight according to a preferred embodiment;
(4) copper in an amount of less than about 0.005 percent by weight
according to an alternative embodiment, cooper in an amount of less
than about 0.0025 percent by weight according to a preferred
embodiment.
[0026] The alloy includes calcium in an amount of about 0.05
percent by weight and about 0.07 percent by weight, tin in an
amount of about 1.2 percent by weight and about 1.5 percent by
weight, and bismuth in an amount of 0.0005 to 0.0275 percent by
weight according to an exemplary embodiment, with the balance being
lead. Silver may optionally be included in the alloy in an amount
less than about 0.015 percent by weight according to an alternative
embodiment. The balance may also include additional elements that
are present in recycled lead (e.g. bismuth, arsenic, copper,
silver, tellurium, etc.) in limited amounts (e.g. less than
approximately 0.0025 percent by weight for each impurity).
[0027] The alloy includes calcium in the amount of about 0.065
percent by weight, tin in an amount of about 1.35 percent by
weight, silver in an about of about 0.0035 percent by weight, and
bismuth in an amount of about 0.0005 percent by weight to about
0.0275 percent by weight, with the balance being lead and other
additional elements that are present in recycled lead, according to
a preferred embodiment.
[0028] The alloy may include calcium in the amount of about 0.0652
percent by weight, tin in an amount of about 1.35 percent by
weight, silver in an about of about 0.0036 percent by weight, and
bismuth in an amount of about 0.0005 percent by weight to about
0.0236 percent by weight, with the balance being lead and other
additional elements that are present in recycled lead, according to
a preferred embodiment.
[0029] The percent by weight of the various alloy elements (e.g.
calcium, tin, silver, bismuth) may vary according to alternative
embodiments. For example, according to an alternative embodiment,
silver may be present in an amount between approximately 0.005 and
0.015 percent by weight. According to another alternative
embodiment, tin may be present in an amount between approximately
1.2 percent by weight and about 1.8 percent by weight.
EXAMPLES
[0030] Alloys A, B, C, D, E and F were prepared having calcium,
tin, silver and bismuth (the balance being lead) in the amounts
listed in TABLE 1 through TABLE 6.
1 TABLE 1 Alloy A Calcium 0.0645 percent by weight Tin 1.39 percent
by weight Silver 0.0021 percent by weight Bismuth 0.0005 percent by
weight
[0031]
2 TABLE 2 Alloy B1 Alloy B2 Calcium 0.0652 percent by weight 0.0672
percent by weight Tin 1.4 percent by weight 1.38 percent by weight
Silver 0.0038 percent by weight 0.0038 percent by weight Bismuth
0.0005 percent by weight 0.0005 percent by weight
[0032] Alloys B1 and B2 are collectively referred to as Alloy B.
The average amount of silver in Alloy B was 0.0021 percent by
weight. The average amount of bismuth in Alloy B was 0.005 percent
by weight.
3 TABLE 3 Alloy C Calcium 0.07 percent by weight Tin 1.38 percent
by weight Silver 0.0035 percent by weight Bismuth 0.0005 percent by
weight
[0033]
4 TABLE 4 Alloy D Calcium 0.069 percent by weight percent Tin 1.35
percent by weight Silver 0.0036 percent by weight Bismuth 0.0126
percent by weight
[0034]
5 TABLE 5 Alloy E1 Alloy E2 Calcium 0.0684 percent by weight 0.0645
percent by weight Tin 1.37 percent by weight 1.33 percent by weight
Silver 0.0037 percent by weight 0.0032 percent by weight Bismuth
0.0199 percent by weight 0.0207 percent by weight Alloy E2 Alloy E4
Calcium 0.0654 percent by weight 0.644 percent by weight Tin 1.33
percent by weight 1.31 percent by weight Silver 0.0036 percent by
weight 0.0034 percent by weight Bismuth 0.0208 percent by weight
0.0194 percent by weight
[0035] Alloys E1, E2, E3 and E4 are collectively referred to as
Alloy E. The average amount of silver in Alloy E was 0.0035 percent
by weight. The average amount of bismuth in Alloy E was 0.0202
percent by weight.
6 TABLE 6 Alloy F Calcium 0.0654 percent by weight Tin 1.37 percent
by weight Silver 0.0037 percent by weight Bismuth 0.0236 percent by
weight
[0036] The alloys were cast as a slab and flattened (e.g. by a
roller) to about 10 percent the original thickness of the slab.
Grids for batteries each having a thickness of about 42
one-thousands of an inch were formed from the slab and stamped in a
grid pattern. The grids were held at 85 degrees Celsius for 3
weeks, and then tested for hardness stability (i.e. diamond pyramid
hardness or "DPH") using a diamond pyramid indentor. The load was
200 grams for 15 seconds for the hardness stability test. The
hardness stability integral for each of Alloy A, B, C, D, E and F
is shown in TABLE 7.
7 TABLE 7 Bismuth Silver percent by percent by weight weight
Hardness Stability Integral Alloy (average) (average) (DPH * number
weeks) A 0.0005 0.0021 52.4 B 0.0005 0.0035 52.4 C 0.0005 0.0040 55
D 0.0126 0.0035 60.4 E 0.0202 0.0035 55.1 F 0.0236 0.0035 58.5
[0037] The hardness stability integral for each of Alloy A, B, C,
D, E and F is shown in FIG. 2A. FIG. 2A shows that grids having
bismuth in the amount of 0.0005 percent to 0.0236 percent by weight
had a relatively acceptable hardness stability. FIG. 2B shows the
data of TABLE 7 fit to a curve according to a preferred
embodiment.
[0038] Alloy E2 was cast as a slab and flattened to about 10
percent the original thickness of the slab. Grids for batteries
each having a thickness of about 42 one-thousandths of an inch were
formed from the slab and stamped in a grid pattern. The grids were
held at 85 degrees Celsius for 5 weeks. FIG. 3A shows 75.times.
magnification of a section of the grid. FIG. 3B shows a detailed
view of the section of the grid of FIG. 3A. FIG. 3B shows bands of
untransformed material having a relatively high hardness (shown in
rectangles 22a and 22b) and some bands of recrystalized material
(shown in ovals 24a and 24b).
[0039] It is important to note that the construction and
arrangement of the elements of the alloy for a battery grid as
shown in the preferred and other exemplary embodiments is
illustrative only. Although only a few embodiments of the present
inventions have been described in detail in this disclosure, those
skilled in the art who review this disclosure will readily
appreciate that many modifications are possible (e.g. variations in
combinations and subcombinations of the amounts of the alloy
elements) without materially departing from the novel teachings and
advantages of the subject matter recited in the claims. For
example, elements may be substituted and added, and the amounts of
the elements may vary. Accordingly, all such modifications are
intended to be included within the scope of the present invention
as defined in the appended claims. The order or sequence of any
process or method steps may be varied or re-sequenced according to
alternative embodiments. In the claims, any means-plus-function
clause is intended to cover the structures described herein as
performing the recited function and not only structural equivalents
but also equivalent structures. Other substitutions, modifications,
changes and omissions may be made in the design, operating
conditions and arrangement of the preferred and other exemplary
embodiments without departing from the spirit of the present
inventions as expressed in the appended claims.
* * * * *