Note: Descriptions are shown in the official language in which they were submitted.
736
The present invention relates to a spring unit for
use in a mattress or a box spring.
A conventional spring unit used in a mattress or a
box spring comprises a plurality of main springs~ Each
main spring is made of a single wire and has a straight
rod portion and two spring protions. The upper ends of
these spring portions are coupled to the ends of the rod
portion. The main springs are disposed on a rectangular
base plate. They are divided into a first group of long
main springs and a second group of short main springs.
The long main springs are arranged parallel to the long
sides of the base plate and the short main springs are
arranged parallel to the short sides of the base plate.
Hence, the main springs of both groups form a lattice.
The lower ends of the spring portions are secured to the
four edges of the base plate. The rod portions are
reinforced by in-termediate support springs~ Like the
main spring, each intermediate support spring has a
straight rod portion and two spring portions. The upper
ends of the spring portions are coupled to the ends of
the rod portion, and the lower ends of -the spring
portions are secured to the base plate.
In the conventional spring unit, the spring
portions of the main springs and intermediate support
springs are torstion bar springs. A torsion bar spring
deforms very slightly when a compressive load is applied
on it. However, it will be permanently deformed if a
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compressive load is applied on it many times. The known
spring unit, which comprises torsion bar springs, may
lose its elasticity in a relatively short time.
Therefore, the object of the present invention is
to provide a spring unit which retains a high elasticity
over a long period of time.
According to the invention, there is provided a
spring unit a rectangular base plate; a plurality of
main springs each having a first straight rod portion
and two first coil portions which are connected at one
end to the ends of the first straight rod portion, said
main springs being disposed on said rectangular base
plate with the first straight rod portions arranged at
right angles to one another; first fastening means
fastening the other end of each first coil protion to
said rectangular base plate; a rectangular frame; first
coupling means coupling said rectangular frame to said
one end of each first coil portion; a plurality of
intermediate support springs disposed on said
rectangular base plate; second coupling means coupling
one end of each intermediate support spring to the
corresponding first straight rod portion; and second
fastening means fastening the other end of each
intermediate support spring to said rectangular base
plate.
The accompanying drawings show an embodiment of the
present invention, in which:
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Fig. 1 is a plan view schematically showing the
structure of a spring unit;
Fig. 2 is a side view showing the structure of the
spring unit;
Fig. 3 is a plan view of a main spring;
Fig. 4 is a side view of the main spring;
Fig. 5 is a plan view of an intermediate support
sprlng;
Fig. 6 is an enlarged sectional view showing the
state of connection of a pair of wire rods;
Fig. 7 is a side view showing a partial section of
a coil spring and a base plate which are fixed to each
other;
Figs. 8A to 8D are side view of the main spring of
1, another type respectively;
Fig. 9 is a plan view of the intermediate support
spring of another type;
Fig. 10 is a perspective view of the intermediate
support spring shown in Fig. 9;
Fig. 11 is a side view of a single coil spring; and
Fig. 12 is a perspective view of a single torsion
spring.
As shown in Figs. 1 and 2, a spring unit, an
embodiment of the invention, has a base plate 1. The
plate 1 comprises a rectangular base frame la and a
plurality of parallel crosspieces lb fixed to the base
frame la. The crosspieces lb are parallel to the short
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sides of the base frame la and spaced apart from one
another at equal intervals. The spring unit further
comprises a plurality of main springs 3, a plurarity of
intermediate support springs 4, four corner springs 5
and a rectangular wire frame 6. The springs 3 and --
springs 5 are disposed in a specific manner, as will be
described later.
The rectanular wire frame 6 is made of a steel wire
having a circular section profile. Its size is
substantially the same as that of the base plate lr
As shown in Figs. 3 and 4, each main spring 3 is
made of a steel wire having a circular sectional profile
and has a straight rod portion 8, and two coil portions
7 which are provided with two straight segments 9
respectively. The straight segments ~ are continuous to
at one end to the ends of -the rod portion 8 respectively
and the two coil portions 7 are continuous at one ends
to the other ends of the straight segments 9
respectively. The axis Ll of one of the coil portions 7
and the axis L2 of the other coil portion 7 are parallel
as illustrated in Fig. 4. The straight segments 9 are
substantially at right angles to the rod portions 8, as
shown in Fig. 3.
The main springs 3 are divided into, i.e., a first
group of long springs 3 and a second group of short
springs 3. On the base plate 1, the long main springs 3
are arranged parallel to the long sides of the frame la
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-- 5 --
and the short springs 3 are arranged parallel to the
short sides of the frame la. Hence, the rod portions 8
of the main springs 3 of both groups form a lattice.
The coil portions 7 of every main spring 3 are secured
at the other ends to the frame la by staples 20, as
illustrated in Fig. 7.
Each intermediate support srping 4 is made of a
single steel wire having a circular sectional profile,
like each main spring 3. As shown in Fig. 5, it has a
straight rod portion 10a, first straight segments 11, a
second straight segment 12, and coil portions 10. One
of the first straight segments 11 is continuous at one
end to one end of the second straight segment 12 whose
other end is continuous to one end of the rod portion
10a. The other first straight segment 11 is continuous
at one end to the other end oE the rod portion 10a. The
upper end of the first coil portion 10 is con-tinuous to
the other end of the first straight segment 11, and the
other coil portion 10 is continuous to the other end of
the straight segment 11. One of the straight segment
and straight portion 11 and 12 are at right angles to
each other, forming an L-shaped portion.
The straight rod portion 10a of each intermediate
support spring 4 is much shorter than the straight rod
portion 8 of each main spring 3. More specifically, the
length of the rod portion 10a is substantially equal to
the diagonal length of each box of the lattice formed by
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-- 6
the rod portions 8 of the main springs 3.
As shown in Fig~ 1~ each corner spring 5 is made of
a single steel wire having a circular sectional profile.
It has a coil portion 15, a straight portion 16, and a
straight segment 17. The straight segment 17 is
continuous to one end of the straigt portion 16 and
inclined at a particular angle thereto. The upper end
of the coil portion 15 is continuous to the other end of
the straight portion 16.
As shown in Figs. 1 and 6, the rectangular wire
frame 5 is fastented to the straight segments 9 of each
main spring 3 by c'ips 13. Likewise, the upper ends of
the coil portions of each intermediate support spring 4
are fastened by clips 13 to the xod portion 8 of one
short main spring 3, respectively. The straight
segments 11 thereof are fastened by clips 13 to the rod
portions 8 of one long main spring 3 and the straight
segment 12 thereof is also fastened by clip5 13 to the
rod portion 8 of one short main spring 3, respectively.
Similarly, the upper end of the coil portion 15 of each
corner spring 5 is fastend at two points by clips 19 to
the corresponding corner portion of the frame 6. The
straight segment 17 of each corner spring 5 is fastened
by a clip 18 to the straight rod portion 8 of one main
springs 3.
The clips 13, 14, 18 and 19 are metal strips having
a predetermined width. Each clip is bent around two
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-- 7 -
steel wires, thus bundling them together.
In the spring unit having the above-mentioned
structure, both ends of the portion ~ of each main
spriny 3 and those of the portion lOa of each
intermediate support spring 4 are integrally formed with
the coil spring portions 7 and 10, respectively. The
deformation in each of the coil spring portions 7 and 10
due to a compressive load is greater than that in each
torsion bar spring. However, even if the compressive
load is repeatedly applied to the coil spring portions 7
and 10, there is no tendency for a permanent set to
occur. Therefore, the spring unit will not lose its
high elasticity at an early stage of use, unlike the
conventional spring unit.
The wire frame 6 is fastened by the clip 14 to each
straight segment 9 formed at one end of the coil spring
portions 7 of each main spring 3 such that the straight
segment 9 and straight portion of the wire frame 9 are
in contact with each other. As a result, the contact
~ length between each main spring 3 and the frame 6 is
greatly increased compared with the case where coil
spring portions 7 do not have straight segments 9.
Accordingly, the coil spring portions 7 and the frame 6
will not become loose at an early stage of use and the
frame 6 and the coil spring portions 7 do not strike
each other, thereby no mechanical noi.se occurs since
they are firmly fastened by the clips 14. The coil
spring portions 7 of the main springs 3 are properly
reinforced by the frame 6 over a long period of time.
Each straight segment 11 of each intermediate
support spring 4 is fastened by a clip 13 to the
corresponding portion 8 of a main spring 3 such that the
straight portion 8 and segment 11 contact each other,
thus ensuring the reinforcement of the portions 8 of the
main springs 3.
Furthermore, the second straight segment 17
integrally formed with the portion 16 of each corner
spring 5 is brought into tight contact with the portion
8 of the corresponding main spring 3 and is firmly
fastened thereto by a clip 18. As a result, the second
straight segment 17 and the portion 8 are firmly
fastened to each other.
In the above-described embodiment, the spring unit
is assembled by the main spring 3, intermediate spring 4
and corner spring 5 having the cylindrical coil portions
7, 10, 15.
However, the coil portions 7 of each main spring 3
may be shaped like an inverted cone as shown in Fig. 8B.
In other words, their diameter may decrease along their
axes toward their lower ends. Their diameter is not so
large that they touch each other. The coil protions 10
of each intermediate support spring 4 and the coil
portions 15 of each corner spring 5 also may be
identical with these coil portions 7 in shape and
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g
diameter. The coil portions 7, 10 and 15 are indeed
more liable to elastically deform than torsion bar
springs when a compressive load is applied on them, but
they are less liable to permanent deformation than
torsion bar springs. Hence, their elasticity is
preserved over a long period of time, unlike that of
torstion bar springs.
As mentioned above, in the modified embodiment, the
coil portions 7, 10, 15 are shaped like an inverted
cone. Hence, when a load acts on each coil portion 7,
10, 15 the turn of the greatest diameter is first
elastically deformed, the turn of the second greatest
diameter is then deformed, and so forth. When the spring
unit is used as bed spring unit, it can comfortably
support the user lying on the bed, regardless of his
weightu In other words, the bed is neither too soft nor
too hard to the user. Since the diameter of the coil
portion 7, 10, 15 of each main spring 3 decreases toward
the lower end, the turns do not contact one another when
the coil portion 7 is compressed, thus generating no
noise.
According to -the present invention, the shape of
the coil portions of each main spring 3, intermediate
spring 4 or each corner spring 5 is not limited to the
cylindrical shape or the inverted cone shape. The coil
portion may take any other non-cylinderical shape. For
example, it may be shaped like a hourglass as shown in
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-- 10 --
Fig. 8A. Alternatively, it may have such a conical
shape as illustrated in Fig. 8C. Further, it may be
shaped like a barrel as depicted in Fig. 8D.
In the embodiment described above, each main spring
3 is made o~ a single steel wire. Instead, it may be
formed of two sections each of which is made of a steel
wire. In this case, each section may have a straight
rod element portion and a coil spring portion. The
straight rod element portion o the sections may be
coupled to that of the other section, thus forming a
main spring 3 which has one straight rod portion
consisting of the two coupled rod element portions.
In the above-described embodiment, moreover, each
intermediate support spring 4 is provided with a coil
spring portion 10. Alternatively, however, the coil
spring portion 10 may be replaced with a torsion spring
portion 20, as shown in Figs. 9 and 10. The torsion
spring portion 20 is formed of a plurality of torsion
rods 21 arranged parallel to one another; and a
plurality of connecting rods 22, each of which is
continuous to the corresponding two adjacent torsion
rods 21. A straight rod portion lOa is continuous at
both ends to the uppermost torsion rods 21 of the
torsion spring portions 20. These torsion spring
portions 20 can support the rod portions 8 of the main
springs 3 with sufficient elasticity.
Furthermore, each intermediate support spring 4 may
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be replaced by a single coil spring 30, as shown in
Fig. 11, or a single torsion spring 31, as shown in
Fig. 12, which is not provided with the connecting rod
portion lOa.
