U.S. patent application number 10/838739 was filed with the patent office on 2004-10-21 for compression spring rod.
This patent application is currently assigned to Barnes Group Inc., a Delaware corporation. Invention is credited to Adoline, Jack W., Fischer, Thomas J..
Application Number | 20040207136 10/838739 |
Document ID | / |
Family ID | 27609349 |
Filed Date | 2004-10-21 |
United States Patent
Application |
20040207136 |
Kind Code |
A1 |
Adoline, Jack W. ; et
al. |
October 21, 2004 |
Compression spring rod
Abstract
A compression spring rod for relatively displacing elements
attached to end mounts of the rod assembly comprises a housing
having a rod member moveable between extended and retracted
positions relative thereto, and a first compression spring in the
housing surrounded by a second compression spring for biasing the
rod member to one of an extended or retracted position relative to
the housing. The two springs are oppositely wound, of different
length, of different outside diameter, and of different wire
diameter whereby, from a compressed condition, the spring rod
exerts an expansion force which increases at a linear rate. Two
sets of the springs can be arranged for biasing the rod member to a
central position relative to the housing.
Inventors: |
Adoline, Jack W.; (Toledo,
OH) ; Fischer, Thomas J.; (Whitehouse, OH) |
Correspondence
Address: |
FAY, SHARPE, FAGAN, MINNICH & McKEE
Seventh Floor
1100 Superior Avenue
Cleveland
OH
44114-2579
US
|
Assignee: |
Barnes Group Inc., a Delaware
corporation
|
Family ID: |
27609349 |
Appl. No.: |
10/838739 |
Filed: |
May 4, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10838739 |
May 4, 2004 |
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10056941 |
Jan 28, 2002 |
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6773002 |
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Current U.S.
Class: |
267/168 |
Current CPC
Class: |
F16F 3/04 20130101 |
Class at
Publication: |
267/168 |
International
Class: |
F16F 005/00 |
Claims
1-27 (Canceled).
28. A compression spring rod comprising a housing having an axis
and axially opposite ends, a rod member coaxial with said axis and
having an inner end in said housing and an outer end axially
outwardly of one of said opposite ends, means including a guide
member on said inner end of said rod member and a bushing at said
one of said opposite ends supporting said rod for reciprocation
axially of said housing between retracted and extended positions
relative thereto, and first and second compression springs each
extending between said guide member and said rod bushing coaxial
with said axis for biasing said rod toward the retracted position
thereof.
29. The compression spring rod of claim 28, wherein the direction
of winding of said first compression spring is opposite to the
direction of winding of said at least second compression
spring.
30. The compression spring rod of claim 28, wherein the length of
said first compression spring is unequal to the length of said
second compression spring.
31. The compression spring rod of claim 28, wherein the outside
diameter of said first compression spring is less than the outside
diameter of said second compression spring.
32. The compression spring rod of claim 28, wherein the wire
diameter of said first compression spring is less than the wire
diameter of said second compression spring.
33. The compression spring rod of claim 28, wherein the outside
diameter and wire diameter of said first compression spring are
respectively less than the outside diameter and wire diameter of
said second compression spring.
34. The compression spring rod of claim 28, wherein a guide rod
extends from said guide member toward the other of said opposite
ends coaxial with said axis and a cushioning spring surrounding
said guide rod and extending between said guide member and said
other of said opposite ends of said housing for cushioning
retracting movement of said rod member.
35. A compression spring rod comprising a housing having an axis
and axially opposite ends, first and second rods coaxial with said
axis and having an inner end in said housing and an outer end
axially outwardly of a different one of said opposite ends, means
including a guide member interconnecting said inner ends of said
rods and supporting said rods for reciprocation axially of said
housing between retracted and extended positions relative thereto,
first and second compression springs each extending between said
guide member and one of said opposite ends of said housing coaxial
with said axis, third and fourth compression springs each extending
between said guide member and the other of said opposite ends of
said housing coaxial with said axis, said compression springs
biasing said rods toward a central position thereof relative to
said housing.
36. The compression spring rod of claim 35, wherein the direction
of winding of said first and third compression springs is opposite
to the direction of winding of said second and fourth compression
springs.
37. The compression spring rod of claim 35, wherein the length of
said first and third compression springs are the same, and the
lengths of said second and fourth compression springs are the same
and different than the lengths of said first and third compression
springs.
38. The compression spring rod of claim 35, wherein the outside
diameters of said first and third compression springs are less
respectively than the outside diameter of said second and fourth
compression springs.
39. The compression spring rod of claim 35, wherein the wire
diameters of said first and third compression springs are the same,
and the wire diameters of said second and fourth compression
springs are the same and greater than that of the first and third
compression springs.
40. The compression spring rod of claim 35, wherein the outside
diameters and wire diameters of said first and third compression
springs are less respectively than the outside diameters and wire
diameters of said second and fourth compression springs.
41. The compression spring rod of claim 40, wherein said outside
diameters of said first and third compression springs are the same,
the outside diameters of said second and fourth compression springs
are the same, the wire diameters of said first and third
compression springs are the same, and the wire diameters of said
second and fourth compression springs are the same.
42. A compression spring rod comprising a housing having an axis
and axially opposite ends, a first rod member coaxial with said
axis and having an inner end in said housing and an outer end
axially outwardly of one of said opposite ends, a guide member on
said inner end of said first rod member to support said first rod
member for reciprocation axially of said housing between retracted
and extended positions relative thereto, first and second
compression springs each extending between said guide member and
said one of said opposite ends coaxial with said axis for biasing
said first rod member toward the retracted position thereof; and a
second rod member extending from said guide member toward the other
of said opposite ends coaxial with said axis and a third spring
surrounding said second rod member and extending between said guide
member and the other of said opposite ends of said housing for
biasing retracting movement of said first rod member.
43. The compression spring rod of claim 42, wherein the direction
of winding of said first compression spring is opposite to the
direction of winding of said at least second compression
spring.
44. The compression spring rod of claim 42, wherein the length of
said first compression spring is unequal to the length of said
second compression spring.
45. The compression spring rod of claim 42, wherein the outside
diameter of said first compression spring is less than the outside
diameter of said second compression spring.
46. The compression spring rod of claim 42, wherein the wire
diameter of said first compression spring is less than the wire
diameter of said second compression spring.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to compression spring rods,
and more particularly, to a spring and rod assembly that exerts an
expansional force which increases at a linear rate.
[0002] The invention relates to a mechanism for biasing hoods,
tops, doors, hinged covers, and other elements from a closed to an
open position. The invention involves the use of springs in
conjunction with a rod member to exert the driving force on the
elements to be displaced. The following patents are incorporated
herein by reference as background information with regard to spring
mechanisms: U.S. Pat. No. 6,199,843 to DeGrace; U.S. Pat. No.
5,810,339 to Kuspert, et al.; and U.S. Pat. No. 4,962,916 to
Palinkas.
[0003] Compression spring rods are used in various applications,
for example, to assist in lifting, opening, and damping. Typical
applications include lifting a lid hinged to a stationary base.
Other applications include lifting and/or balancing elements for
the trunk or hatchback of an automobile. Still another application
includes a damping spring for closing a door hinged to a stationary
frame. Most applications involve the use of a pneumatic or gas
spring to assist the opening motion. Many of these types of
compression spring assemblies contain either gas or hydraulic fluid
to control forces and piston speeds. Consequently, because these
products contain a gas and/or fluid, they are subject to premature
failure, due to the leakage of the gas or fluid over time. The
leakage results in a loss of control forces and a subsequent loss
of spring life.
SUMMARY OF THE INVENTION
[0004] The present invention provides an improved compression
spring rod which overcomes the above referred-to difficulties and
others with regard to such rods heretofore available. More
particularly in this respect, a compression spring rod in
accordance with the invention is particularly adapted for lifting
or pivoting one component relative to another component at a
controlled rate. In accordance with one aspect, the invention
provides a lift mechanism for hinged covers and the like that
operates automatically upon release of the cover, or a lift
mechanism for a loaded platform wherein the platform is elevated,
progressively, as the load thereon is reduced. Advantageously, the
compression spring assembly applies a constant and controlled force
to open the cover or lift the platform. The mechanism is able to
support significant loads while maintaining strength over a greater
number of operating cycles than existing pneumatic or gas spring
designs. Further, the invention provides a purely mechanical
compression rod assembly that can yield controllable forces over a
long period of use and control the spring forces during both
extension and compression.
[0005] A compression spring rod according to the invention is
comprised of multiple compression springs. The compression spring
rod assembly includes a rod which is adapted to extend and retract
relative to a housing. In one application, for example, the
compression springs will build potential force as the springs are
compressed, and release that force once the springs are allowed to
expand. This extension of the springs imparts a force to the parts
connected to the ends of the rod and housing and, advantageously,
multiple end configurations can be used to adapt the spring rod to
a variety of mounting applications. The compression springs of a
spring rod according to the invention are interrelated to produce a
linear load versus deflection curve. The encased springs minimize
load losses over time, and the mechanism does not contain any fluid
or gases within the lift body. This advantageously eliminates the
inevitable problem of leakage and subsequent loss of utility.
[0006] It is accordingly an outstanding object of the present
invention to provide an improved compression spring rod for
exerting an operating force on a displaceable member at a
controlled rate.
[0007] Another object of the invention is the provision of a
compression spring rod that supplies a consistent force over an
extended period of time and maintains strength over a greater
number of cycles compared to compression spring rods heretofore
available.
[0008] Yet another object of the invention is the provision of a
compression spring rod having at least two compression springs
interrelated to produce a linear load versus deflection curve.
[0009] Yet another object of the invention is the provision of a
compression spring rod having at least two compression springs
interrelated to minimize load losses over time.
[0010] A further object of the invention is the provision of a
mechanical compression spring rod assembly that provides an
operating force that increases at a linear rate.
[0011] Yet a further object of the invention is to provide a
mechanical compression spring assembly that can accommodate,
selectively, multiple end configurations, thus adapting the
assembly for mounting in a wide variety of use applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The foregoing and other objects and advantages will in part
be obvious and in part pointed out in the following description
taken together with the accompanying drawings in which:
[0013] FIG. 1 is a side elevation view, partially in section, of a
compression spring rod according to the invention in the extended
position;
[0014] FIG. 2 is a longitudinal cross section view of the
compression spring rod in the compressed position;
[0015] FIG. 3 is a cross sectional view taken along line 3-3 of
FIG. 2;
[0016] FIG. 4 is an exploded perspective view of the component
parts of the compression spring rod shown in FIGS. 1-3;
[0017] FIG. 5 is a side elevation view of the compression springs
of the compression spring rod;
[0018] FIG. 6 is a graph illustrating the relationship between
spring force and compression of the compression spring rod
assembly;
[0019] FIG. 7 is a perspective view of a box with a lid pivotable
about a horizontal axis and compression spring rod elements shown
in FIGS. 1-3 between the box and lid;
[0020] FIG. 8 is a side elevation view, in section, of a spring rod
in accordance with a second embodiment of the invention;
[0021] FIG. 9 is an exploded perspective view of the component
parts of the compression spring rod shown in FIG. 8;
[0022] FIG. 10 is a perspective view illustrating a use of the
compression spring rod of FIGS. 8 and 9;
[0023] FIG. 11 is a side elevation view, in section, of a spring
rod in accordance with another embodiment of the invention;
[0024] FIG. 12 is an exploded perspective view of the component
parts of the compression spring rod shown in FIG. 11; and,
[0025] FIG. 13 is an illustration of an application of the
compression spring rod of FIGS. 11 and 12.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0026] Referring now in greater detail to the drawings, wherein the
showings are for the purpose of illustrating preferred embodiments
of the invention only, and not for the purpose of limiting the
invention, a compression spring rod 10, in accordance with the
invention, as shown in FIGS. 1-6, has an axis 11 and includes a rod
member 22 which is axially extendable and retractable relative to a
one-piece tubular housing 24. Rod 22 has an outer end 22a and an
inner end 22b connected to a guide rod 26 as set forth more fully
hereinafter. Guide rod 26 extends axially inwardly of inner end 22b
of rod 22 and is surrounded by a first compression spring 28 which
is supported by the exterior surface 46 of guide rod 26 against
buckling. First compression spring 28 is surrounded by a second
compression spring 30 which is supported against buckling by the
interior surface 48 of housing 24. Alignment of compression springs
28 and 30 relative to one another and axis 11 is maintained by the
exterior surface 46 of guide rod 26 in conjunction with the
interior surface 48 of housing 24. Housing 24 has a mounting end 23
and an outer or opposite end 25, and compression springs 28 and 30
are axially captured between a tail bushing 38 at mounting end 23
and a guide member 34 mounted between guide rod 26 and the inner
end 22b of rod 22 as set forth hereinafter. Tail bushing 38 is
supported in housing 24 by bending the endmost portion of the
housing radially inwardly to define a retaining flange 39.
[0027] Compression spring rod 10 involves the use of a one-piece
housing 24 which facilitates smooth movement of lift rod 22 and
compression springs 28 and 30 during operation of the spring rod.
As shown in the exploded view of FIG. 4, tail bushing 38 includes a
neck portion 42 having a diameter sized to be received in the
interior of compression spring 28. Tail bushing 38 also has a
threaded stud 44 distal to the neck portion 42 which is received in
a threaded recess 17 in a mounting element 18. Guide rod 26
includes a threaded stud 52 at the outer end thereof which passes
through an opening 58 in guide member 34 and into a threaded bore
54 provided therefor in rod 22. Lift rod 22 passes through an
opening 72 through a rod bushing 32 at outer end 25 of housing 24,
and has a threaded stud 70 on outer end 22a thereof which is
received in a threaded recess 27 provided therefor in a mounting
element 20. Mounting elements 18 and 20 have openings 19 and 21
therethrough, respectively, for receiving a variety of different
mounting components common in the industry including, for example,
pins, bolts, swivels, and the like. Advantageously, the threaded
studs 44 and 70 at opposite ends of the spring rod assembly provide
for accommodating the use of different mounting elements than those
shown so as to modify the assembly for use in a variety of
structural environments.
[0028] Guide member 34 is slidable in housing 24 and includes a
guide ring 35 of suitable material to facilitate such sliding
movement. Rod 22 is slidably supported at end 25 of housing 24 by
rod bushing 32 which is secured to the housing by a pair of set
screws 40 having inner ends received in an annular recess 41 in the
rod bushing. Rod bushing 32 is further axially retained in housing
24 by bending the outermost part of end 25 radially inwardly to
provide a retaining flange 33. At full extension, rod 22 is
cushioned by rod bushing 32 and an impact absorbing metal spring
ring 36 received in a recess 55 at inner end 22b of rod 22 adjacent
the axially outer face of guide member 34. When rod 22 is fully
extended, spring ring 36 engages in a recess 51 in the axially
inner end of rod bushing 32. Lubrication can be provided in housing
24 to facilitate the sliding movement of guide member 34 therein.
As will be appreciated from the foregoing description, guide member
34 and rod bushing 32 support rod 22 for reciprocation in housing
24 such as to maintain minimal breakaway forces for rod 22.
Additionally, guide member 34 and rod bushing 32 keep rod 22
coaxial with axis 11 and decrease the effect of side loading on the
assembly.
[0029] Compression spring rod 10, through the multiple spring rate
characteristics of compression springs 28 and 30, serves to provide
smooth extension forces to the movement of lift rod 22 from the
retracted to the extended position thereof relative to housing 24.
Depending upon the application, the appropriate load versus
deflection can be determined and the corresponding physical and
elastic properties of the combination of compression springs 28 and
30 can then be ascertained. The compression springs 28 and 30 can
each be fabricated from spring material, such as music wire, and,
for example, ASTM A228 or 302 stainless steel.
[0030] Each compression spring 28 and 30 has a different stress and
strain characteristic. If the spring is considered to be a
one-dimensional object, the only stress will be extensional (or
compressional, which will be the negative of extensional) and the
units of stress will be force per unit of extension. Within a range
of compression, each spring obeys "Hook's Law", which states that
for forces in a defined range, the stretch of a material is
proportional to the applied force:
F=-k.DELTA.L
[0031] The proportionality constant, k, is known as the spring
constant with dimensions of force over length, and .DELTA.L is the
amount of compression. The negative sign indicates that the force
is in the opposite direction of extension: if the spring is
extended, the force tries to restore it to its original length.
Likewise, if the spring is compressed (.DELTA.L<0), the force
attempts to expand the spring, again to its original length. The
spring constant depends on both physical and elastic properties of
the material being stretched. Hook's Law is fairly intuitive at a
basic level, and can be illustrated by everyday experience in which
it is known that a thin wire will stretch more than a thick wire or
rod of the same material when the same stretching force is applied
to both. The formula U=1/2k(.DELTA.L).sup.2, gives the work of
extension (U) or alternatively, the amount of potential energy
stored in the spring.
[0032] As shown in FIGS. 3 and 5, compression spring 28 has a free
length L1 which is greater than the free length L2 of spring 30,
and spring 28 has an outer diameter greater than that of
compression spring 30. Also, the wire diameter of spring 28 is less
than that of spring 30, and the spring rate of spring 28 is less
than that of spring 30. As an example of one particular
application, the specific physical characteristics of compression
spring 28 are: wire diameter 0.055", inside diameter 0.5444",
outside diameter 0.6544", free length 17.2", and a spring rate of
0.95 lbs./inch; and the physical characteristics of compression
spring 30 are: wire diameter 0.081", inside diameter 0.675",
outside diameter 0.837", free length 13.8", and a spring rate of
3.37 lbs./inch. FIG. 6 displays the load versus deflection curve
for compression springs 28 and 30 having the foregoing
specifications, and for the combined springs in the assembly shown
in FIGS. 1 and 2. It is to be noted that springs 28 and 30 are
oppositely wound and that this interrelationship together with the
dimensional characteristics of the springs produces the combined
linear load versus deflection graph depicted in FIG. 6. The
different free lengths, as shown in FIG. 5, of springs 28 and 30 is
one component that helps to control the forces and stabilize the
guide member 34 and rod 22 during initial displacement thereof from
the position shown in FIG. 1 to the position shown in FIG. 2 and
during the termination of the movement from the position shown in
FIG. 2 to the position shown in FIG. 1. In this respect, the longer
spring 28 is, in the free state of the spring 30 shown in FIG. 1,
slightly compressed to the length of the latter spring and,
therefore, exerts a stabilizing force on the components which
eliminates any free play during initial and terminal displacement
thereof during use.
[0033] FIG. 7 illustrates two compression spring rods 10 according
to the invention connected between a box 12 and a lid 14 therefor.
While not shown in detail, lid 14 is suitably mounted on box 12,
such as by hinges, to be pivotable about an axis A relative
thereto. The mounting elements 18 and 20 of compression spring rods
10 are suitably secured to box 12 and lid 14, respectively. A latch
15 is shown on lid 14 for engagement with a keeper 16 on box 12 to
releasably hold the lid closed relative to box 12. Latch 15 may be
of various types common in the industry, and the method for
releasing latch 15 may be by hand, foot, key, remote, etc.
Subsequent to releasing the latch 15, compression spring rods 10
automatically extend from the position shown in FIG. 2 to the
position as shown in FIG. 1, during which the spring rods 10
expand, releasing the stored compressive force in compression
springs 28 and 30 to displace lid 14 from the closed to the open
position thereof.
[0034] FIGS. 8 and 9 illustrate another embodiment of a compression
spring assembly according to the invention. In this embodiment,
compression spring rod 100 has an axis 101 and includes a rod 102
which is axially extendable and retractable relative to a one-piece
tubular housing 104. Rod 102 has an outer end 102a and an inner end
102b connected to a guide rod 106 as set forth more fully
hereinafter. Guide rod 106 extends axially inwardly of inner end
102b of rod 102. A first compression spring 108 is supported
against buckling by the exterior surface 103 of rod 102. Spring 108
is surrounded by a second compression spring 110 which is supported
against buckling by the interior surface 105 of housing 104.
Coaxial alignment of compression springs 108 and 110 relative to
one another and axis 101 is maintained by the exterior surface 103
of rod 102 in conjunction with the interior surface 105 of housing
104. When assembled, compression springs 108 and 110 are axially
captured between a rod bushing 112 at end 114 of housing 104 and a
guide member 116 secured to inner end 102b of the rod between the
latter and guide rod 106. Guide rod 106 includes a threaded stud
107 at the outer end thereof which passes through an opening 115 in
guide member 116 and into a threaded bore 137 provided therefor in
rod 102. A tail bushing 120 is supported in end 124 of housing 104
by set screws 122 received in an annular recess 126 in the tail
bushing 120. For the purpose set forth hereinafter, the component
parts of spring rod 100 are cushioned during operation of the
compression spring assembly by a cushioning spring 130 which
surrounds guide rod 106. Spring 130 is axially captured between the
tail bushing 120 at end 124 and the guide member 116. Tail bushing
120 includes a neck portion 123 having a diameter sized to be
received in the interior of cushioning spring 130. Tail bushing 120
also has a threaded stud 125 distal to neck portion 123 which is
received in a threaded recess 127 in a mounting element 132. Guide
member 116 is slidable in housing 104 and includes a guide ring 117
of suitable material to facilitate such sliding movement. Rod 102
is slidably supported at end 114 of housing 104 by rod bushing 112
which is secured to housing 104 by a pair of set screws 122 having
inner ends received in an annular recess 113 in bushing 112. Rod
102 passes through an opening 111 in bushing 112 at outer end 114
of housing 104, and has a threaded stud 139 on outer end 102a
thereof which is received in a threaded recess 140 provided
therefor in a mounting element 134. As will be appreciated from the
foregoing description, guide member 116 and rod bushing 112 support
rod 102 for reciprocation in housing 104 such as to maintain
minimal breakaway forces for rod 102. Mounting elements 132 and 134
have openings 133 and 135 therethrough, respectively, for receiving
a variety of different mounting components common in the industry
including, for example, pins, bolts, swivels, and the like.
Mounting element 132 is fixedly attached to tail bushing 120 for
mounting the compression spring assembly to a work supporting
surface.
[0035] FIG. 10 illustrates four compression spring rods 100 each
connected between a corresponding fixed support 142 and a platform
or work supporting table 140. The spring rods 100, as shown in FIG.
10, are designed to expand in the direction of arrow z in response
to a load applied to platform 140, thus compressing springs 108 and
110. Compression springs 108 and 110 then expand and retract the
spring rods in the direction of arrow y as the load is
progressively removed from platform 140. Compression springs 108
and 110 have the same physical characteristics as compression
springs 28 and 30 described in the first embodiment. The
arrangement of spring rods 100 and platform 140 as shown in FIG. 10
is suitable, for example, as a progressive load lifter, such as for
metal plates. As plates are progressively stacked on platform 140,
the spring rods 100 extend in the direction of arrow z, whereby the
compression springs 108 and 110 are progressively compressed. As
stated, when the springs are compressed (.DELTA.L<0) the
resultant force attempts to expand the spring rod to its original
length. Thus, as the plates are progressively removed from the
platform, the compression springs 108 and 110 expand thereby
causing the platform 140 to move in the direction of arrow y. In
this manner, the springs provide controlled forces by which the top
plate in the stack on the platform remains at a given level as the
platform moves first in the z direction and then in the y
direction. If the entire load is suddenly removed from the
platform, the spring rods retract rapidly and cushioning spring 130
cushions the retracting movement to protect the spring rods against
damage. Additionally, it will be appreciated that this embodiment
is particularly well suited as a counterbalance system, conveyor
chain tensioner, door lift assist, and dampener.
[0036] FIGS. 11 and 12 illustrate another embodiment of a
compression spring assembly according to the invention. In this
embodiment, compression spring rod 180 has an axis 181 and includes
two rods 182 and 184 which are alternately axially extendable and
retractable together relative to a one-piece tubular housing 186.
Rod 182 has an outer end 182a and an inner end 182b and rod 184 has
an outer end 184a and an inner end 184b connected to inner end 182b
of rod 182 together with a guide member 200 as set forth more fully
hereinafter. Rod 182 extends axially inwardly of end 186a of
housing 186 and is surrounded by a first compression spring 188
which is supported by the exterior surface 183 of rod 182 against
buckling. First compression spring 188 is surrounded by a second
compression spring 190 which is supported against buckling by the
interior surface 187 of housing 186. Rod 184 extends axially
inwardly of opposite end 186b of housing 186 and is surrounded by a
third compression spring 192 which is supported by the exterior
surface 185 of rod 184 against buckling. Third compression spring
192 is surrounded by a fourth compression spring 194 which is
supported against buckling by the interior surface 187 of housing
186. Alignment of compression springs 188, 190, 192, and 194
relative to one another and axis 181 is maintained by the exterior
surfaces 183 and 185 of rods 182 and 184, respectively, in
conjunction with the interior surface 187 of housing 186.
Compression springs 188 and 190 are axially captured between a rod
bushing 196 at end 186a and the guide member 200, and compression
springs 192 and 194 are axially captured between a rod bushing 202
at end 186b of the housing and the guide member. Rod bushing 196 is
supported in housing 186 by set screws 206 at end 186a thereof
which extend into an annular recess 197 in bushing 196. Similarly,
rod bushing 202 is supported in housing 186 by set screws 206 at
end 186b thereof which extend into an annular recess 203 in the
bushing. Axial retention of bushings 196 and 202 is further
enhanced by bending the corresponding end of housing 186 radially
inwardly of the bushings.
[0037] The compression spring rod 180 involves the use of a
one-piece housing 186 which facilitates smooth movement of rods 182
and 184 and compression springs 188, 190, 192, and 194 during
operation of the spring rod. As shown in the exploded view of FIG.
12, rod 184 includes threads 230 and 231 at opposite ends of the
rod. Threads 230 are received in a threaded recess 232 in a
mounting element 220. Threads 231 pass through an opening in spring
ring 210, an opening through guide member 200, and an opening in
spring ring 208 and are received in a threaded recess 235 in rod
182. Rod 182 includes threads 234 distal to recess 235, which are
received in a threaded recess 233 in a mounting element 222. As
will be appreciated from the foregoing description, guide member
200 and rod bushings 196 and 202 support rods 182 and 184,
respectively, for reciprocation in housing 186 such as to maintain
minimal breakaway forces for rods 182 and 184 in use of the spring
assembly.
[0038] Spring rod assembly 180 is adapted to apply an extension
force, alternately, in axially opposite directions at a
controllable rate. At full extension from housing 186, rods 182 and
184 are cushioned by rod bushings 196 and 202, respectively. In
addition, impact in the direction of extension is absorbed by metal
spring rings 208 and 210 which are received in recesses 212 and
214, respectively, at inner end 182b of rod 182 and inner end 184b
of rod 184. Spring rings 208 and 210 are adjacent the axially outer
faces of guide member 200 and respectively engage rod bushings 196
and 202 upon full extension of the rods in the respective direction
of extension. Lubrication can be provided in housing 186 to
facilitate the sliding movement of guide member 200 therein.
[0039] As shown in FIG. 13, spring rod assembly 180 is capable of
self-centering a load which, as illustrated by way of example only,
is in the form of two workpieces 230 and 232 having ends 230a and
232a pivotally attached to a fixed support member 231. Spring rod
180 has the outer ends of rods 182 and 184 thereof respectively
pivotally connected to ends 232b and 230a of the workpieces. Spring
rod 180 is supported centrally between workpieces 230 and 232 by a
bracket 224 rigidly secured to support member 231 by a support arm
225. The springs of each pair of compression springs 188 and 190
and 192 and 194 have the same physical characteristics as
compression springs 28 and 30 described in the first embodiment. In
the arrangement shown in FIG. 13, spring rod 180 is a load
centering assembly. In this respect, it will be appreciated that if
either workpiece 230 or 232 is displaced in the direction of arrow
c, rod 184 extends relative to housing 186 and the springs 192 and
194 are compressed. The resultant force of springs 192 and 194 in
the direction of arrow e attempts to expand the springs to their
original length. It will be appreciated that the opposite is true
when either workpiece is displaced in the direction of arrow d. In
this respect, springs 188 and 190 are compressed and springs 192
and 194 are totally relaxed. The resultant force in the direction
of arrow e attempts to expand springs 188 and 190 to their original
length. During return movement of workpieces 230 and 232 to the
central position thereof, the relaxed pair of springs cushion the
return movement. As with the earlier embodiments, the springs 188
and 190 and 192 and 194 provide controlled forces to self-center
workpieces 230 and 232 when either is deflected from the neutral
position. It will be appreciated that this embodiment is
particularly well suited as a centering device in a steering
mechanism, linkage mechanism, gating mechanism, and dampener.
[0040] While considerable emphasis has been placed herein on the
structures and configurations of the preferred embodiments of the
invention, it will be appreciated that other embodiments, as well
as modifications of the embodiments disclosed herein, can be made
without departing from the principles of the invention. In this
respect, it will be appreciated that the spring rod can be used in
applications other than those disclosed herein. Similarly, multiple
combinations of coaxial and surrounding springs (i.e. three, four,
etc.) may be configured to meet the desired load versus deflection
for a particular application. Likewise, it will be appreciated that
a spring rod according to the invention can be secured to
relatively displaceable components in any number of different ways.
These and other modifications of the preferred embodiments, as well
as other embodiments of the invention, will be obvious and
suggested to those skilled in the art from the disclosure herein,
whereby it is to be distinctly understood that the foregoing
descriptive matter is to be interpreted merely as illustrative of
the present invention and not as a limitation thereof.
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