Note: Descriptions are shown in the official language in which they were submitted.
131~
ENCAP8ULATED 8PRING A88EMBLY FOR RECLININ~ FURNITURE
This invention relates to springs and, more particularly,
to an improved encapsulated spring that contracts under
axial compression and is reinforced with a rigid dowel
member to prevent buckling of the spring when the spring
is in a compressed state.
Springs are classified by their shape into six major
categories. These are flat or leaf springs, helical,
spiral, torsion bar, disk and constant force springs.
Helical springs are essentially a bar or wire of
uniform cross section which has been wound into a helix.
When a helical spring is intended for use as a resistance
against compression-type forces, the helix is loosely
wound so that there is space between each coil, and the
last turn or two at each end of the spring is modified
to a plane surface which is perpendicular to the axis
of the spring. When the helical spring is intended for
use as a resistance against extension-type force, the
helix is tightly wound so that there are no spaces between
coils and, generally, the spring has hooks at each end.
An encapsulated spring is a hybrid of the compression-
type, helical spring and the constant force spring. The
encapsulated spring is a compression-type, helical spring
that has been encapsulated with a polymeric material,
typically polyurethane. An encapsulated spring provides
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~ constant force during periods of compression and expansion
of the compression-type, helical spring.
Encapsulated springs are especially useful in furniture
where it i6 desirable to have a ~ force during ~8/87
periods of movement of the various parts of the furniture
piece such as arms and backs.
Ideally, when a compression-type, helical spring
is fully compressed, each of the coils is in contact with
its immediately adjacent coils so that the spring forms,
essentially, a continuous cylinder from one end of the
spring to the other without any of the coils overlapping
any othex coil in the axial direction of the spring.
Typically, these compression-type springs have an
effective length. The term "effective length" as used
in the instant specification and claims means the axial
length of the spring when the spring has been compressed
to the minimum length at which the spring was intended
to operate. Such an effective length is generally greater
than the length of the spring when fully compressed and
shorter than the length of the spring without a compression
force acting thereon, i.e. at rest.
A problem associated with these compression-type
helical springs is that, during periods of compression,
and especially when the compression force is such that
2S the spring is near its effective length or when the spring
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is near the point of being fully compressed, the spring
tends to buckle or bulge so that the spring is no longer
compressed along its helical axis. When these compression-
type, helical springs buckle, the compression force of
the spring is greatly reduced and the spring no longer
functions properly.
To alleviate the buckling problem, it has been suggested
to replace the buckling spring with one that has a lower
aspect ratio, i.e. height to outer diameter width. A
drawback to such a solution is that more space is required
for the wider spring. Where space is at a premium, and
especially in the manufacture of reclining furniture where
the trend has been to make slimmer, more compact reclining
mechanisms in the furniture, using a wider spring is not
an acceptable solution.
Applicant has now discovered an improved compression-type,
helical spring that resists buckling during periods of
compression. In fact, applicant has learned quite surprisingly
that by using the spring of the present invention, larger
outer diameter, conventional, compression-type, helical
springs can be replaced with smaller outer diameter springs
of the present invention, and that the smaller outer diameter
springs of the present invention function substantially
equivalently to the larger conventional springs.
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Generally speaking the present invention may be
considered as providing in reclining furniture having a
reclining mechanism for providing resistance during periods
of movement of the reclining furniture wherein a spring
assembly is used in the reclining mechanism to provide the
resistance, the improvement in the spring assembly
comprising: an encapsulated helical spring, encapsulated in
a polymeric material to provide constant force during
periods of compression and expansion of the helical spring
in the reclining mechanism of the reclining furniture, the
encapsulated helical spring having a hollow internal area,
the hollow internal area having an inner diameter, the
encapsulated spring having an effective length; and a rigid
dowel member inserted in the hollow internal area, the rigid
dowel member having an outer diameter substantially equal to
the inner diameter of the hollow internal area, the rigid
dowel member having a length no greater than the effective
length of the encapsulated spring.
Preferably, the dowel member is a rigid dowel that is
rounded on at least one end and more preferably at both ends
to allow the spring to ride smoothly over the dowel member
as the spring is compressed. The rounded edges aid in
preventing the spring from becoming "hung-up" on the rigid
dowel member.
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The outer diameter width of the rigid dowel member is
substantially equal to the internal diameter of the spring
so that there is a slight interference between the rigid
dowel member and the spring. This slight interference
allows the rigid dowel member to be securely held in the
spring and helps prevent slippage of the dowel.
Also preferably, the length of the rigid dowel member
is substantially equal to the maximum compression length of
the spring when the spring is fully compressed.
~hese and other features of the present invention may
be more fully understood with reference to the drawings
wherein:
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Figure 1 illustrates a preferred embodiment of the
present invention wherein a rigid dowel member is inserted
inside an encapsulated spring;
~igure 2 illustrates the reinforced spring of Figure 1
partially compressed;
Figure 3 illustrates the rigid dowel member of Figure l;
Figure 4 illustrates a top view of the rigid dowel
member of Figure 3; and
Figure 5 illustrates yet another preferred embodiment
of the present invention wherein the dowel member is a
telescoping dowel member;
Figure 6 is still yet another embodiment of the present
invention where a spring means is contained within the
dowel member; and
Figure 7 illustrates a preferred embodiment of the
present invention where the length of the rigid dowel
member is no greater than the effective length of the
spring.
Figure 1 illustrates encapsulated spring 10 having
metal, compression-type, helical spring 12 encapsulated
by polyurethane 14. Inside of encapsulated spring 10
a hollow area 16 exists having an internal diameter 18,
and outer diameter 19. A rigid dowel member 20 is inserted
in hollow area 16. Rigid dowel member 20 is tapered at
both ends 22 and 24. The main body 26 of rigid dowel
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member 20 is hexagonal in cross-section. The overall
length 28 of rigid dowel member 20 is substantially equal
to the length of encapsulated spring 10 when fully compressed.
Figure 2 illustrates encapsulated spring 10 partially
compressed and illustrates how spring 10 rides down over
rigid dowel member 20 and how rigid dowel member 20 prevents
spring ln from buckling. Also illustrated are plates 30
and 32 which seal the ends of the encapsulated spring 10
and help to prevent dowel member 20 from working itself
free during repeated cycles of compression and expansion.
Typically, when the improved spring of the present invention
is used in furniture, it will have a plate at each end
of the spring such as plates 30 and 32 at each end of
encapsulated spring lO in Figure 2.
Figure 3 illustrates a rigid dowel member 20 apart
from encapsulated spring 10. Rigid dowel member 20 has
tapered ends 22 and 24 and a main body 26 which is hexagonally
shaped.
Figure 4 illustrates a top view of rigid dowel member 20
of Figure 3. The overall diameter 34 of rigid dowel member 20
is shown. The hexagonal shape of main body 26 is also
apparent. Tapered section 22 is also apparent. It is
preferred that overall diameter 34 of rigid dowel member 20
be substantially equal to internal diameter 26 of encapsulated
spring 10 as shown in Figures 1 and 2.
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It is evident that rigid dowel member 20 shown in
Figures 1~4 resists the force placed on it when spring 10
buckles and thereby maintains spring 10 in a proper posture.
Figure 5 illustrates another embodiment of the present
invention with encapsulated spring 10 having compression-
type, helical spring 12 encapsulated in polyurethane 14.
Dowel member 40 is telescoping so that upper member 42
,slides into housing 44. Housing 4q is attached to encapsulated
spring 10 by means of shoulders 46. Upper member 42 is
attached to encapsulated spring 10 by means of plate 48
which is attached to upper member 42.
It is apparant that as spring 10 moves up and down
upper member 42 slides into and out of lower member 44.
Lower member 44 has a tapered top 50 and main body 52 of
lower member 44 is hexagonal in shape. T~pered head 50
allows spring 10 to ride smoothly over lower member 4g
during periods of compression. The shoulders 46 ensure
that lower member 44 remains in the lower part of spring 10.
The plate 48 ensures that upper member 42 follows the
spring movements. It can be seen that dowel member 40
resists the force placed on it when spring 10 buckles
and thereby maintains spring 10 in a proper posture.
Figure 6 illustrates yet another embodiment of the
present invention wherein spring 10 has telescoping dowel
member 70 consisting of upper member 72 and lower member 74.
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Spring 10 is sealed at both ends by plates 76 and 78.
Inner spring means 80 is housed inside lower dowel member
74. Inner spring means 80 is shown as a conventional
compression-type, helical spring. Upper dowel member 42
rests on inner spring 80.
As spring 10 moves along its helical axis during
periods of compression and expansion, upper dowel member
72 moves into and out of lower dowel member 74. Inner
spring means 80 forces upper dowel member 72 to abut against
upper plate 76.
Inner spring means 80 can be of such a strength that
it merely causes upper dowel member 72 to follow spring 10
or it can be such that inner spring means 80 actually assists
in preventing compression and thereby aids in resisting
the force provided to compress and expand spring 10.
Spring means 80 can be any conventional spring such
as a compression-type, helical coil spring or an encapsulated
spring. It is readily apparent to one of skill in the
art that inner spring means 80 could be a conventional
hydraulic type arrangement with upper and lower dowel
members 72 and 74 making a conventional hydraulic cylinder.
It can be seen that dowel member 70 resists the force
placed on it when spring 10 buckles and thereby maintains
spring 10 in a proper posture.
Figure 7 illustrates yet another preferred embodiment
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of the presen~ invention wherein spring 10 has rigid dowel
member 90 inserted therein. Rigid dowel member 90 has
an overall length 92 equal to the effective length of
spring 10. The rigid dowel member in Figure 7 acts not
only as a means to prevent the spring from buckling but
also as a means to limit the compression of the spring
and, with respect to reclining furniture, acts as a means
to limit the movement of $he specific part of the furniture
that utilizes the improved spring of the present invention.
It can be seen that the dowel member 90 resists the
force placed on it when spring 10 buckles and thereby
maintains spring 10 in a proper posture.
The compression-type, helical spring of the pxesent
invention includes: metal, compression-type, helical springs;
elastomeric, compression-type, tube springs; and encapsulated
springs. The preferred spring is an encapsulated, metal,
helical spring as shown in Figures 1-2, and 5-7. Preferably,
the encapsulated spring of the present invention is encapsulated
in polyurethane.
The spring used in the present invention must have
a hollow area inside of itself for the placement of the
dowel member of the present invention. Such a hollow
area, as is typical of metal, compression-type, helical
springs and encapsulated springs, may extend throughout
the interior of the spring. Preferably, the hollow area
extends throughout the interior of the spring.
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The dowel member of the present invention is inserted
into the hollow area inside the ~pring.
- The outer diameter of the dowel member is no greater
than the internal diameter of the spring. Preferably,
the outer diameter of the rigid dowel member is substantially
equal to the internal diameter of the spring. When the
outer diameter of the rigid dowel member is substantially
equal to the internal diameter of the spring, the rigid
dowel member is securely held in the inside hollow area
of the spring.
The external cross-sectional shape of the dowel can
be hexagonal, s~uare, circular, or any shape which fits
inside said hollow area. Preferably a hexagonal shape
is used with the rigid dowel member. The hexagonal shape
when used in an encapsulated spring has been found not
to cut the encapsulating polyurethane when it is compressed
and to allow some expansion of the polyurethane.
Preferably, at least one end of the rigid dowel member
is rounded and more preferably both ends of the rigid
dowel member are rounded. Good results have been obtained
by tapering both ends of the dowel member as shown in
Figures 1-4 and 7. The rounding of the edges of the rigid
dowel member alleviates the possibility of catching by
the spring during periods of compression.
The axial length of the rigid dowel member is preferably
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no greater than the effective length of the spring and
more preferably substantially equal to the axial length
of the spring when fully compressed. The rigid dowel
member can be longer than the length of the spring when
the spring is at rest, however, a longer rigid dowel member
will protrude from the spring. Such a situation is generally
unacceptable in furniture.
The rigid dowel member may be made from any rigid
material such as plastic, metal or wood. A metal material
is preferred.
The rigid dowel member may be hollow or a solid mass.
A solid mass is preferred.
In order to avoid the rigid dowel member from working
itself free of the spring, it is preferred that both ends
of the spring be sealed. This can be done by merely ensuring
that both ends of the spring are against solid stops such
as are shown in Figure 2. Alternatively, the ends may
be sealed by other means such as tape.
These and other aspects of the present invention
may be more fully understood with r~ference to the following
example.
EXAM__PLE 1
This examples illustrates the synergistic results
obtained when using the improved spring made in accordance
with the present invention. Table 1 below shows the dimensions
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of the three springs tested and the results obtained therefrom.
TABLE 1
Spring Compression Force Results
Encapsulated, 1" O.D.* 3/4 compressed No buckle
Fully compressed No buckle
Encapsulated, 5/8" O.D. 3/4 compressed Buckled
Fully compressed Buckle worsened
Encapsulated, S/8" O.D. 3/4 compressed No buckle
with rigid dowel Fully compressed No buckle
member therein
(Present Invention)
* O.D. is outside diameter
Each encapsulated spring had an overall length of 2-1/2
inches when uncompressed. The metal dowel insert in the
5/8 inch spring of the present invention had an overall
length of about 1 inch and a width across its main body
of about 5/16 inch. The dowel used in this example was
hexagonal in cross section with both ends tapered as shown
in Figure 3. Wire used to make the 1 inch spring was
a flat wire with a total of 8 coils, 6 colls being active
coils. The wire was about 0.06 inches thick and about
0.21 inches wide. The 5/8 inch spring was a standard
5/8 inch spring sold by Dieco Company and labelled M-123.
The 5/8 inch springs had a total of 15 coils, 13 of which
were active coils.
The material used to encapsulate the wire springs
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in this example was polyurethane.
It will be understood that the claims are intended
to cover all changes and modifications of the preferred
embodiments of the invention herein chosen for the purpose
of illustration which do not constitute a departure from
the spirit and scope of the invention.
