U.S. patent application number 12/846889 was filed with the patent office on 2011-10-13 for laundry treating appliance with force damping feet.
This patent application is currently assigned to WHIRLPOOL CORPORATION. Invention is credited to DONALD R. MILLER, BRENNER M. SHARP.
Application Number | 20110247374 12/846889 |
Document ID | / |
Family ID | 43896895 |
Filed Date | 2011-10-13 |
United States Patent
Application |
20110247374 |
Kind Code |
A1 |
MILLER; DONALD R. ; et
al. |
October 13, 2011 |
LAUNDRY TREATING APPLIANCE WITH FORCE DAMPING FEET
Abstract
A laundry treating appliance having a cabinet, a rotatable drum,
and at least one foot extending from and supporting the cabinet,
with the foot being configured to dampen the vibrations of the
laundry treating appliance.
Inventors: |
MILLER; DONALD R.; (SAINT
JOSEPH, MI) ; SHARP; BRENNER M.; (BRIDGMAN,
MI) |
Assignee: |
WHIRLPOOL CORPORATION
BENTON HARBOR
MI
|
Family ID: |
43896895 |
Appl. No.: |
12/846889 |
Filed: |
July 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61323684 |
Apr 13, 2010 |
|
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Current U.S.
Class: |
68/139 |
Current CPC
Class: |
D06F 39/125
20130101 |
Class at
Publication: |
68/139 |
International
Class: |
D06F 25/00 20060101
D06F025/00 |
Claims
1. A laundry treating appliance comprising: a cabinet defining an
interior; a rotatable drum suspended within the interior defining a
laundry treating chamber; at least one relatively non-compliant
foot extending from the cabinet and supporting the cabinet on the
floor; at least one relatively compliant foot extending from the
cabinet and supporting the cabinet on the floor; wherein the at
least one relatively non-compliant foot has a first
weight-per-foot-normalized stiffness value greater than or equal to
about 1.0 (1/mm) and the at least one relatively compliant feet has
a second weight-per-foot-normalized stiffness value of less than or
equal to about 0.7 (1/mm).
2. The laundry treating appliance according to claim 1 wherein the
weight-per-foot-normalized stiffness of the at least one relatively
non-compliant foot is further less than or equal to about 1.6
(1/mm).
3. The laundry treating appliance according to claim 2 wherein the
weight-per-foot-normalized stiffness of the at least one relatively
compliant foot is greater than or equal to about 0.1 (1/mm).
4. The laundry treating appliance according to claim 1 wherein the
cabinet defines a front portion and a rear portion and the at least
one relatively non-compliant foot is located at the front portion
of the cabinet and the at least one relatively compliant foot is
located at the rear portion of the cabinet.
5. The laundry treating appliance according to claim 1 wherein the
at least one relatively non-compliant foot comprises a first pair
of relatively non-compliant feet and the at least one relatively
compliant foot comprises a second pair of relatively compliant
feet.
6. The laundry treating appliance according to claim 5 wherein the
cabinet defines a front portion and a rear portion and the first
pair of feet are located at the front portion of the cabinet and
the second pair of feet are located at the rear portion of the
cabinet.
7. The laundry treating appliance according to claim 5 wherein the
cabinet further defines four corners, with a first pair of the
corners located at the front portion and a second pair of the
corners located at the rear portion, and the first pair of feet
being mounted to the first pair of corners and the second pair of
feet being mounted to the second pair of corners.
8. The laundry treating appliance according to claim 1 wherein each
foot comprises a resilient pad having a predetermined
stiffness.
9. The laundry treating appliance according to claim 1 wherein the
at least one relatively non-compliant foot has the
weight-per-foot-normalized stiffness at least about 2.0 times
greater than the weight-per-foot-normalized stiffness of the at
least one relatively compliant foot.
10. The laundry treating appliance according to claim 1 wherein the
cabinet comprises a frame and the feet are mounted to the
frame.
11. The laundry treating appliance according to claim 1 wherein at
least one of the feet comprises a damping system providing the
corresponding stiffness.
12. The laundry treating appliance according to claim 11 wherein
the damping system comprises a damper and a spring.
13. The laundry treating appliance according to claim 11 wherein
the at least one of the feet comprises a pad coupled to the cabinet
by the damping system.
14. A laundry treating appliance comprising: a cabinet defining an
interior; a rotatable drum suspended within the interior defining a
laundry treating chamber; at least one relatively non-compliant
foot extending from the cabinet and supporting the cabinet on the
floor; at least one relatively compliant foot extending from the
cabinet and supporting the cabinet on the floor; wherein the at
least one relatively non-compliant foot has a
weight-per-foot-normalized stiffness at least about 2.0 times
greater than the stiffness of the relatively compliant feet.
15. The laundry treating appliance according to claim 14 wherein
the cabinet defines a front portion and a rear portion and the at
least one relatively non-compliant foot is located at the front
portion of the cabinet and the at least one relatively compliant
foot is located at the rear portion of the cabinet.
16. The laundry treating appliance according to claim 15 wherein
the at least one relatively non-compliant foot comprises a first
pair of relatively non-compliant feet and the at least one
relatively compliant foot comprises a second pair of relatively
compliant feet.
17. The laundry treating appliance according to claim 16 wherein
the cabinet defines a front portion and a rear portion and the
first pair of feet are located at the front portion of the cabinet
and the second pair of feet are located at the rear portion of the
cabinet.
18. The laundry treating appliance according to claim 17 wherein
the cabinet further defines four corners, with a first pair of the
corners located at the front portion and a second pair of the
corners located at the rear portion, and the first pair of feet
being mounted to the first pair of corners and the second pair of
feet being mounted to the second pair of corners.
19. The laundry treating appliance according to claim 14 wherein
each foot comprises a resilient pad having a predetermined
stiffness.
20. The laundry treating appliance according to claim 14 wherein
the cabinet comprises a frame and the feet are mounted to the
frame.
21. The laundry treating appliance according to claim 14 wherein at
least one of the feet comprises a damping system providing the
corresponding stiffness.
22. The laundry treating appliance according to claim 21 wherein
the damping system comprises a damper and a spring.
23. The laundry treating appliance according to claim 21 wherein
the at least one of the feet comprises a pad coupled to the cabinet
by the damping system.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 61/323,684 filed Apr. 13, 2010, which is
incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] A laundry treating appliance may be used to treat laundry
according to a pre-determined cycle of operation. In one
implementation, a laundry treating appliance may include a drum
defining a treating chamber and mounted for rotation inside a
cabinet. The drum of the laundry treating appliance may generate
vibrations during rotation, especially when the laundry creates an
imbalance within the drum, which may be caused by unevenly
distributed laundry inside the drum.
[0003] Feet are provided on the cabinet to provide for leveling the
cabinet relative to the surface on which the cabinet rests. The
feet provide a path for the vibrations to pass from the laundry
treating appliance to the surface. A foot is normally placed at
each corner of the cabinet.
BRIEF DESCRIPTION OF THE INVENTION
[0004] In one aspect, the invention, relates to a laundry treating
appliance having a cabinet; a rotatable drum that may be suspended
within the interior defining the laundry treating chamber; a first
pair of relatively non-compliant feet extending from the cabinet
and supporting the cabinet on the floor; and a second pair of
relatively compliant feet extending from the cabinet and supporting
the cabinet on the floor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] In the drawings:
[0006] FIG. 1 is a perspective view of a laundry treating appliance
in the form of a laundry washing machine according to a first
embodiment of the invention.
[0007] FIG. 2 is a bottom partial perspective view of the laundry
treating appliance of FIG. 1.
[0008] FIG. 3 is a front perspective view of the laundry treating
appliance of FIG. 1 and illustrating an alternative position
showing one possible motion of the laundry treating appliance in
response to the vibrations generated from an out-of-balance
condition during the operation of the laundry treating appliance
having laundry inside the drum.
[0009] FIG. 4 is a front view of a representative foot of FIG.
1.
[0010] FIG. 5 is front view of a first pair of relatively
non-compliant feet of FIG. 1 according to one embodiment of the
invention.
[0011] FIG. 6 is a front view of a second pair of relatively
compliant feet of FIG. 1 according to one embodiment of the
invention
[0012] FIG. 7 is a plot of the acceleration forces in g's versus
spin speed of the laundry treating appliance incorporating the feet
of FIGS. 5 and 6, with a comparison of a laundry treating appliance
with two pairs of non-compliant feet.
[0013] FIG. 8 is a schematic view of a laundry treating appliance
according to a second embodiment of the invention.
DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
[0014] FIG. 1 is a perspective view of a laundry treating appliance
10 according to a first embodiment of the invention. As
illustrated, the laundry treating appliance 10 may be a vertical
axis laundry washing machine 12, although the laundry treating
appliance 10 may be other machines, non-limiting examples of which
include a horizontal axis laundry washing machine, a laundry dryer,
a fabric freshener, and a non-aqueous laundry system.
[0015] As used herein, the "vertical axis" washing machine refers
to a laundry washing machine having a rotatable drum that rotates
about a generally vertical axis relative to a surface that supports
the washing machine. However, the rotational axis need not be
perfectly vertical to the surface. The drum may rotate about an
axis inclined relative to the vertical axis, with fifteen degrees
of inclination being one example of the inclination. Similar to the
vertical axis laundry washing machine, the horizontal axis washing
machine refers to a washing machine having a rotatable drum that
rotates about a generally horizontal axis relative to a surface
that supports the washing machine. The drum may rotate about the
axis inclined relative to the horizontal axis, with fifteen degrees
of inclination being one example of the inclination. The washing
machine described herein may share many features of a traditional
automatic laundry washing machine, which will not be described in
detail except as necessary for a complete understanding of the
invention.
[0016] As illustrated, the laundry treating appliance 10 in the
form of a vertical axis washing machine 12 may include a cabinet
14, a door 16, a first pair of relatively non-compliant feet 18, a
second pair of relatively compliant feet 20, a suspension system
22, and a user interface 24. The cabinet 14 may define an interior
26 and may include a top wall 28, a front wall 30, a pair of side
walls 32, and a rear wall 34. A chassis 38 or frame may be provided
on which the various walls may be mounted to define four corners of
the machine 40. The front wall 30 may help define a front 29 of the
laundry treating appliance 10. The front 29 is the side where a
user may be typically positioned to operate the laundry treating
appliance 10. The rear wall 34 may help define a back 35 of the
laundry treating appliance 10. The back 33 is the side where tubing
for a water inlet and a drain (not shown) are located. The door 16
may be hingedly mounted to the top wall 28 and may be configured to
be selectively movable to provide access to the interior 26.
[0017] A tub 35 may be located within the interior 26 and a
rotatable drum 36 may be mounted within and rotatable relative to
the tub 35. The suspension system 22 may operably couple the tub 35
and the cabinet 14 such that some of the vibrations generated from
the rotatable drum 36 are dampened. The drum 36 may define a
treating chamber 42 for receiving laundry items to be treated. The
drum 36 may include a plurality of perforations (not shown), such
that liquid may flow between the tub 35 and the drum 36 through the
perforations.
[0018] An agitator 43 may be mounted within and rotatable relative
to and/or with the drum 36. The agitator 43 may have a lower
circular base or skirt portion 44, a central shaft 45 extending
upwardly from the base 44, and at least one vane or blade 48 spaced
around and extending radially from the central shaft 45. The
central shaft 45 may be operably coupled with a bottom 46 of the
drum 36. A variety of other designs for the agitator 43 may also be
used without affecting the scope of the invention. The drum 36
and/or the agitator 43 may be driven by an electrical motor 47
operably connected to the drum 36 and/or the agitator 43.
[0019] The user interface 24 may include a parameter selector 54
that may be one or more knobs, switches, displays, and the like,
which a user may select to operate the laundry treating appliance
10. A controller 56 may be operably coupled with the parameter
selector 54 to selectively operate a pre-determined cycle of
operations set by the user through the parameter selector 54.
[0020] The first pair of relatively non-compliant feet 18 and the
second pair of relatively compliant feet 20 may be extended from
the cabinet 14 to support the cabinet 14 on a floor 50. FIG. 2
illustrates that a first pair of corners 58 may be located near the
front 60 of the cabinet 14 and that a second pair of corners 62 may
be located near the back 64 of the cabinet 14. The first pair of
relatively non-compliant feet 18 and the second pair of relatively
compliant feet 20 may be coupled with the first pair of corners 58
and the second pair of corners 62 of the cabinet 14 respectively.
That is, the first pair of relatively non-compliant feet 18 may be
extended from the first pair of corners 58 and the second pair of
relatively compliant feet 20 may be extended from the second pair
of corners 62 to support the cabinet 14 on the floor 50.
[0021] FIG. 3 illustrates the laundry treating appliance of FIG. 1
and as well as an alternative position (shown in phantom) showing
one possible motion of the laundry treating appliance in response
to the vibrations generated from an out-of-balance condition during
an operation of the laundry treating appliance, such as during a
spin or extraction phase of the cycle of operation, having laundry
inside the drum.
[0022] In a typical cycle of operation, multiple fabric items 68,
which collectively form a laundry load, are placed in the drum 36.
Some of the fabric items 68 will be in direct contact with the
agitator 43 and some will not. A washing fluid 66 may also be
introduced into the drum 36. As the agitator 43 moves, the
individual fabric items 68 will be moved directly or indirectly by
the agitator 43 to impart mechanical energy to the items, which
will move the fabric items 68 about the treating chamber 42. More
specifically, during a pre-programmed cycle of operation, the
central shaft 45 inside drum 36 may continuously oscillate about
its own vertical axis in clockwise and counterclockwise directions
for a pre-determined time to impart mechanical energy to the
laundry 68 to wash out soil and stain on the laundry 68.
[0023] During the cycle of operation, the laundry 68 may become
unevenly distributed within the drum 36 and may pile up in some
regions inside the drum 36. Particularly, in the spinning phase
where the drum 36 is being rotated at very high speeds, the effect
of an unevenly distributed load may be noticeable, and may generate
severe vibrations. The unevenly distributed load may cause an out
of balanced condition so great that the drum 36 may bottom out its
suspension and/or contact a portion of the cabinet 14, which may be
very undesirable as the severe vibrations may from time to time
make a loud noise.
[0024] The out-of-balanced load or unevenly distributed load in the
drum 36 may generate an oscillating force in the form of
vibrations, which act on the cabinet 14, the first and the second
pairs of feet 18 and 20 (FIG. 2), and ultimately the floor 50. If
the magnitude of the oscillating force is great enough, the cabinet
14 may pivot about a pivot line 70 in the laundry treating
appliance 10. This may result in a side-to-side rocking motion as
illustrated in phantom in FIG. 3. The higher the rotational speed
of the drum 36 inside the cabinet 14, the greater the magnitude of
the oscillating force may result. Thus, the higher rotational speed
of the drum 36 results is an increased likelihood that the laundry
treating appliance 10 will begin a side-to-side rocking motion. The
cabinet vibrations (A) may be measured using an accelerometer that
may be attached to the upper part of the laundry treating appliance
10 while the drum 36 rotates at a pre-determined spin speed for a
pre-determined time, and may be represented by g's of
acceleration.
[0025] Both the first pair of relatively non-compliant feet 18 and
the second pair of relatively compliant feet 20 may include a
representative foot 72 as illustrated in FIG. 4. As illustrated,
the foot 72 may comprise a stem 74 and a pad 76. The stem 74 may be
coupled with the cabinet 14 by connecting members 78. The pad 76
may be operably coupled with the stem 74 to support the cabinet 14
on the floor 50. The connecting members 78 may include at least one
of a washer 80 and a nut 82. The stem 74 may be threaded such that
when it is coupled with one of the mating connecting members 78 the
levelness and the height of the laundry treating appliance 10 may
be adjusted relative to the floor 50 on which the laundry treating
appliance 10 is positioned.
[0026] When the laundry treating appliance 10 weighing M (Kg) is
supported by N number of feet extending from the corners of the
cabinet 14, a weight-per-foot-normalized stiffness NK (1/mm) of
each foot comprising material with a stiffness K (N/mm) may be
represented according to equation (1):
NK ( 1 / mm ) = K ( N / mm ) M ( Kg ) .times. g ( m / s 2 ) N ( 1 )
##EQU00001##
[0027] The acceleration due to gravity g (m/s.sup.2) in equation
(1) is defined to be 9.807 m/.sup.2. The stiffness K (N/mm) is an
inherent mechanical property of the foot that measures the
resistance offered by an elastic body to any deformation such as
bending, stretching or compression. The physical meaning of the
weight-per-foot-normalized stiffness NK (1/mm) is the reciprocal of
the amount of deformation that each foot would experience if the
total weight M (Kg) of the laundry treating appliance 10 is
supported by the foot. For instance, the weight-per-foot-normalized
stiffness of 0.2 (1/mm) may be construed to mean that one foot may
deform by 5 mm if one foot supports the entire weight of the
laundry treating appliance 10. In case the laundry treating
appliance 10 has four feet on which the weight of laundry treating
appliance 10 is evenly distributed, the foot may deflect by 1.25
mm. Therefore, the weight-per-foot-normalized stiffness would be
the value that is normalized with respect to the weight and the
number of feet of the laundry treating appliance 10.
[0028] The pad 76 may be formed of a resilient material such as
rubber, polymer, or a rubber-polymer composite. Further, the pad 76
may be made of two or more resilient materials in the form of a
stacked or a randomly mixed composite. Depending on the
weight-per-foot-normalized foot stiffness required for the foot 72,
materials other than a resilient material may be used for pad
76.
[0029] FIG. 5 illustrates the first pair of relatively
non-compliant feet 18 including non-compliant feet 84. The first
pair of relatively non-compliant feet 18 may be defined as feet
having a weigh-per-foot-normalized stiffness value greater than or
equal to 1.04 (1/mm). More specifically, the relatively
non-compliant feet 84 may be defined as feet having the
weight-per-foot-normalized stiffness values ranging from 1.04 to
1.56 (1/mm). FIG. 5 includes arrows 85; the length of the arrow 85
represents the magnitude of the deformation of non-compliant feet
84 in the vertical direction.
[0030] It should be noted that for purposes of this description,
while the weight-per-foot-normalized stiffness values are being
described in terms relative to the second decimal place, that this
should not be construed as indicating that there is substantive
relevance at the second decimal place. For purposes of the
invention, the range of 1.04 to 1.56 (1/mm) could be rounded to the
range 1.0 to 1.60 without impacting the practical results of the
range. The similar is true of the other values in this
description.
[0031] FIG. 6 illustrates the second pair of relatively compliant
feet 20 including compliant feet 86. The second pair of relatively
compliant feet 20 may be defined as feet having a
weight-per-foot-normalized stiffness value less than or equal to
0.71 (1/mm). More specifically, the relatively compliant feet 86
may be defined as feet having the weight-per-foot-normalized
stiffness values ranging from 0.16 to 0.71 (1/mm), with a round
range of 0.10 to 0.70. FIG. 6 includes arrows 87; the length of the
arrow 87 represents the magnitude of the deformation of the
compliant feet 86 in the vertical direction. Thus, as illustrated,
the magnitude of the deformation in the vertical direction for the
non-compliant foot 84 is smaller than the vertical deformation for
the compliant foot 86. The first pair of relatively non-compliant
feet 18 located near front 60 of the cabinet 14 may have a
weight-per-foot-normalized stiffness at least 2.0 times greater
than the weight-per-foot-normalized stiffness of the second pair of
relatively compliant feet 20 located near back 64 of the cabinet
14. This may effectively suppress the vibrations and possible
corresponding side-to-side rocking movement of the laundry treating
appliance 10.
[0032] In operation, when oscillating forces in the form of the
vibrations are ultimately transferred to the stem 74 and the pad 76
of each of the first pair of relatively non-compliant feet 18 and
the second pair of relatively compliant feet 20, the second pair of
relatively compliant feet 20 located near the back 64 of the
cabinet 14 may isolate the laundry treating appliance 10 from the
floor 50 to suppress the vibrations during high speed spinning
phase (for example, above 700 rpm). At the same time, the first
pair of relatively non-compliant feet 18 located near the front 60
of the cabinet 14 may control the side-to-side rocking movement of
the laundry treating appliance 10 during any intermediate rinse
spins speeds (for example, 350-550 rpm).
[0033] FIG. 7 is a plot of the acceleration forces in g's versus
spin speed of the laundry treating appliance 10 incorporating the
first pair of relatively non-compliant feet 18 and the second pair
of relatively compliant feet 20 during a spinning cycle in the
laundry treating appliance 10. Further, a comparison of a laundry
treating appliance with two pairs of non-compliant feet is also
presented for comparison purposes. In the plot, the spin speed
(i.e., the x-axis) may be the spin speed of the drum during a water
extraction phase. The g's of acceleration (i.e., the y-axis) may be
the amount of the vibration in the side-to-side rocking motion
(such as that shown in phantom in FIG. 3).
[0034] In the graph, it is shown that the g's of acceleration for
the laundry treating appliance 10 having the first pair of
relatively non-compliant feet and the second pair of relatively
compliant feet is substantially suppressed compared to the laundry
treating appliance having two first pairs of relatively
non-compliant feet at a full spin speed region
(approximately>700 rpm). The g's of acceleration for the laundry
treating appliance 10 having the first pair and the second pair of
feet at the intermediate spin phase range was further suppressed by
adapting a newly proposed intermediate spin speed around 400 rpm,
instead of using a previous intermediate spin speed of 450 rpm.
FIG. 7 clearly illustrates that the first pair of relatively
non-compliant feet near the front of the cabinet and the second
pair of relatively compliant feet near the back of the cabinet may
significantly suppress the vibrations and the side-to-side rocking
movements.
[0035] FIG. 8 is a schematic view of a laundry treating appliance
90 according to a second embodiment of the invention. While the
first embodiment was described in terms of compliant feet, the
embodiment of FIG. 8 illustrates that this concept may be thought
of in terms as the feet having a damping system that provides the
compliance.
[0036] As illustrated in FIG. 8, first and second pairs of feet 94,
96 extend from a cabinet 92 of an appliance 90. Each of the first
and second pairs of feet 94, 96 comprise a first and second damping
systems 95, 97, respectively, on which are provided pads 99.
[0037] The feet 94, 96 may have different degrees of damping, which
may be quantified by a damping coefficient and a spring
coefficient, to achieve the desired functionality. Therefore, the
feet are illustrated as a damper and spring supporting the pad 99
to the cabinet 92. More specifically, each foot 94 of the first
damping system 95 may include a first damper 100 having a damping
coefficient C.sub.f and a first spring 102 having a stiffness
K.sub.f, where the first damper 100 and the first spring 102 may be
arranged in parallel to each other. The first pair of feet 94 may
be provided along a front side 104 of the laundry treating
appliance 90 at opposite corners of the cabinet 92. Likewise, each
foot 96 of the second damping system 97 may include a second damper
106 having a damping coefficient C.sub.r and a second spring 108
having a stiffness K.sub.r, where the second damper 106 and the
second spring 108 may be arranged in parallel to each other. The
second pair of feet 96 may be provided along a rear side 110 of the
laundry treating appliance 90 at opposite corners of the cabinet
92.
[0038] In order to provide the desired stiffness to effectively
suppress the vibrations from the laundry treating appliance 90 to
the floor 98, the relationship of the damping coefficients C.sub.f
and C.sub.r (Nsec/mm) of the dampers 100, 106 and the stiffnesses
K.sub.f and K.sub.r (N/mm) of the springs 102, 108 may be expressed
as follows:
C f C r = K f K r ( 2 ) ##EQU00002##
[0039] The second embodiment of the invention may be thought of as
a broader or more generalized form of the first embodiment of the
invention, in which the non-compliant and compliant feet of the
first embodiment are modeled as the first and second damping
systems, respectively. As such, the first dampening system may have
similar properties as those disclosed above the non-compliant feet
and the second dampening system may have similar properties as
those disclosed above for the compliant feet.
[0040] It is noted that other configurations in terms of the
number, location of damping systems are possible. For example,
instead of having pairs of feet forming the first and second
dampening systems, the dampening systems may be formed by single
elongated feet that extend, partially or fully, along opposite
sides of the cabinet 92 of the laundry treating appliance 90. In
such a configuration, the relationship of the dampening
coefficients and stiffnesses of each dampening system may follow
equation (2).
[0041] While the invention has been specifically described in
connection with certain specific embodiments thereof, it is to be
understood that this is by way of illustration and not of
limitation. For example, the number of relatively non-compliant
feet may not be two, non-limiting examples may include one, three,
or any number. Similarly the number of relatively compliant feet
may vary. Reasonable variation and modification are possible within
the scope of the forgoing disclosure and drawings without departing
from the spirit of the invention which is defined in the appended
claims.
* * * * *