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Description  |
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BACKGROUND OF THE INVENTION
This invention relates generally to mattress foundation structures and more
particularly to a box spring assembly of a type which utilizes non-coil
springs. Box spring assemblies of this general type have been known since
1964, the first such spring assembly being disclosed in U.S. Pat. No.
3,286,281. Subsequently issued patents disclosing the same general type of
box spring assembly are: U.S. Pat. Nos. 3,487,480; 3,506,987; 3,574,240;
3,574,241; 3,665,529; 3,680,157; 3,755,833; 3,824,639; 3,852,838;
4,060,862; 4,120,058; 4,131,961; 4,195,376; 4,218,790; 4,238,861;
4,251,892; 4,253,208 and 4,470,584. Box spring assemblies of the general
type shown in the above list of patents, all of which are assigned to the
assignee of this application, are advantageous with respect to the
conventional box spring assemblies using coil springs because they provide
a desired stiffer foundation for the mattress and contain a reduced amount
of wire. These box spring assemblies are also advantageous from the
standpoints of prolonged service life, ease of assembly, and cost of
manufacture.
Additional box spring assemblies of this general type are shown in U.S.
Pat. Nos. 3,546,723; 3,596,299; 3,722,013; 3,825,960; 3,833,948;
3,835,485; 3,869,740; 3,990,121; 4,000,531 and 4,559,654.
The present invention provides a box spring assembly which utilizes a wire
mattress support deck or platform and a supporting spring that is
different from the formed wire springs utilized in the patented box spring
assemblies discussed above. The spring in the present box spring assembly
is improved from the standpoint of providing desired qualities of
firmness, internal strength, and edge support to the wire deck.
SUMMARY OF THE INVENTION
The box spring assembly of this invention consists of a rectangular frame
having side rails, end rails, and a plurality of cross rails that are
generally parallel to each other and to the end rails and are
substantially perpendicular to the side rails. The box spring assembly
also includes a rectangular wire mattress support deck positioned above
the frame and a plurality of limited deflection wire springs that are
mounted on the cross rails and end rails and connected to the deck so as
to yieldably resist downwardly directed bedding loads.
Each of the springs is formed of spring steel wire and includes a pair of
vertically collapsible column sections which are connected at their lower
ends to a lower mounting portion and at their upper ends to an upper
attaching platform portion. The lower mounting portion includes a pair of
horizontal mounting feet having transverse torsion bars located between
the mounting feet and column sections. The upper attaching platform
includes a straight wire for attaching to the grid, a pair of transverse
torsion bars on opposite sides of the straight wire and parallel to the
straight wire and joined to opposite ends of the straight wire by cross
wires. The column sections include a torsion bar spaced vertically and
horizontally from the torsion bars of the lower mounting portion and upper
attaching platform. Upper and lower connecting bars connect the torsion
bars of the column sections with the torsion bars of the upper attaching
platform and lower mounting portion. The upper connecting bars diverge in
an upward direction while the lower connecting bars diverge in a downward
direction.
During loading, the spring deflects vertically downward as the torsion bars
in the column sections move inward until the torsion bars engage one
another to limit the spring deflection. This occurs while the upper
attaching portion is still vertically spaced from the engaged torsion
bars. The use of three torsion bars, one in each portion of the spring,
results in a lower peak torsional stress in the spring, producing a longer
life spring and permitting the use of smaller diameter wire. In addition,
the platform is allowed to rotate about the engaged torsion bars, allowing
the wire platform to conform to the bedding load, increasing comfort.
Further objects, features and advantages of the invention will become
apparent from a consideration of the following description and the
appended claims when taken in connection with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a fragmentary perspective view of the box spring assembly of this
invention, showing a representative intermediate support spring supported
at its lower end on an end rail and one cross wire spring mounted at one
end on a cross rail, both being in supporting relation at their upper ends
with the box spring wire deck;
FIG. 2 is a diagrammatic plan view of a box spring assembly of this
invention illustrating one arrangement of the supporting springs on the
frame to support the wire deck;
FIG. 3 is an isolated elevational view of one of the intermediate support
springs of this invention in an unloaded position;
FIG. 4 is a plan view of the support spring of FIG. 3;
FIG. 5 is an elevation view of the intermediate support spring of this
invention in a loaded position showing engagement of the torsion bars of
the column sections to limit deflection of the spring;
FIG. 6 is a perspective view of the intermediate support spring of this
invention shown in FIG. 3; and
FIG. 7 is an end view of the loaded spring shown in FIG. 5 taken in the
direction of the arrow 7.
DETAILED DESCRIPTION OF THE INVENTION
With reference to the drawing, a fragmentary portion of a box spring
assembly of this invention indicated generally at 10 is ilustrated in FIG.
1. The box spring assembly 10 includes a generally rectangular,
horizontally disposed frame 12, a plurality of wire intermediate support
springs 14 mounted to the top of the frame 12 and a horizontally disposed
wire mattress support deck 16 mounted on the springs 14.
The frame 12, generally constructed of wood, has side rails 18 and end
rails 20. The end rails 20 include a lower member 22, each end of which is
connected to the side rail 18 and an upper member 24 which overlies the
lower member 22 and overlaps the end of side rail 18. Horizontally spaced
from and parallel to the end rails are a plurality of cross rails (not
shown) which overlap the side rails 18 and are coplaner with the upper
members 24 of end rails 20. The cross rails are not shown as the
arrangement of springs 14 mounted thereon is identical to that illustrated
in FIG. 1.
The wire mattress support deck 16 forms a platform disposed in a horizontal
plane at a predetermined distance above the frame 12. The mattress support
deck 16 includes border wire 26, long wires 28 and a portion of cross wire
springs 30. Each of the cross wire springs 30 has an elongated load
bearing portion 32 and a vertically yieldable portion 34. The long wires
28 and the load bearing portions 32 of the cross wire springs 30 are
arranged in a criss-cross fashion with the load bearing portions 32 of
cross wire springs 30 intersecting the long wires 28. The ends of the long
wire 28 are fastened to border wire 26 with clips 33.
Each long wire has a plurality of spaced apart notches 34 along its length.
Likewise, each load bearing portion 32 of each of the cross wire springs
30 has a plurality of spaced apart notches 36. Each of the notches 36 is
an upwardly arched deflection in the wire member. Notches 34 saddle
notches 36 at intersections 38 between the long wires 28 and cross wire
springs 30. The engagement of notches 34 and 36 of long wires 28 and load
bearing portions 32 of cross wire springs 30 respectively prevents side
ways movement of the wire members at the notched intersections 38. The
ends of the load bearing portions 32 of the cross wire springs 30 are
attached to border wire 26 by clips 42.
A plurality of limited deflection intermediate support springs 14, arranged
in a predetermined pattern on frame 12, yieldably support the deck 16 in
position above the frame 12 for resilient movement toward the frame to
accommodate bedding loads. The pattern and number of springs 14 may vary
depending upon the size of the springs, number of cross rails, and other
manufacturing and support characteristic considerations for the deck 16.
One preferred pattern of spring placement is illustrated schematically in
FIG. 2.
As best appears in FIGS. 1, 3, 4 and 6, each spring 14 comprises an
intermediate upright yieldable portion 44 formed integrally at its upper
end with a horizontal upper attaching platform 46 and formed integrally at
its lower end to a horizontal lower mounting portion 48.
The upper attaching platform 46, which serves as a generally horizontal
support platform for the wire deck 16, consists of an intermediate
straight wire section 50, a pair of upper transverse torsion bars 52 which
are disposed on opposite sides of section 50 in a spaced relation with the
section 50 and in positions generally parallel to each other and to the
straight section 50, and crosswise sections 54 which integrally connect
the torsion bars 52 to opposite ends of the intermediate section 50.
The lower mounting portion 48 comprises a pair of substantially
horizontally disposed mounting feet 56 having lower transverse torsion
bars 58 located between the mounting feet 56 and the intermediate upright
yieldable portion 44. Springs 14 are mounted to the cross rails and end
rails 20 of the frame 12 by staples 60 over the lower torsion bars 58.
The intermediate yieldable portion 44 comprises a pair of vertically
collapsible column sections to support the upper attaching platform 46
resiliently on the lower mounting portion 48. The column sections each
include a middle transverse torsion bar 62 spaced vertically and
horizontally inward from the upper torsion bar 52 in the upper attaching
platform 46 and lower torsion bar 58 in the lower mounting portions 48. An
upper connecting bar 64 connects one end of the middle transverse torsion
bar 62 to one end of the upper transverse torsion bar 52 in the upper
attaching platform 46. A lower connecting bar 66 connects the opposite end
of middle torsion bar 62 with one end of the lower transverse torsion bar
58 in the lower mounting portion 48. As shown in FIG. 3 the torsion bars
are located such that the upper connecting bars 64 diverge in an upward
direction and the lower connecting bars 66 diverge in a downward
direction.
Each upper transverse torsion bar 52 is arranged in a side-by-side relation
with a straight wire 28 under an intersection 38 of the wires in the deck
16 as shown in FIG. 1. The side-by-side transverse torsion bars 52 and
wires 28 are then secured together by wrap around clips 42 on either side
of the intersection 38. This clamps wire 28, cross wire spring 30 and
spring 14 together.
The portions of the wires 28 that are clipped to the springs 14 may be
provided with a coating of a yieldable plastic material prior to the
application of the clips 42, as disclosed in U.S. Pat. No. 4,186,223, also
assigned to the assignee of this application. The plastic coating may be a
vinyl coating, a polyurethane coating or of some other soft plastic
coating that facilitates the application of the clips 42 to the springs 14
and the straight wires 28 of wire deck 16.
Alternatively, the upper transverse torsion bars 52 of the springs 14 can
be provided with the coating or the entire deck 16 can be coated.
Preferably, at least the areas of the deck 16 which engage the springs 14
are coated. This not only facilitates the application of the clips 42 but
also eliminates any unwanted noise caused by relative movement of the deck
16 and the springs 14 which may occur when the assembly 10 is loaded and
unloaded.
When a downward load is applied to the box spring assembly 10, the springs
14 and the cross wire springs 30 will yield in a vertical direction to
accommodate the bedding loads and provide the occupant of a mattress
supported on the deck 16 with the desired feel that is associated with
comfort. The springs 14 will only permit a limited vertical deflection.
During deflection, the middle transverse torsion bars 62 of the column
sections twist, rotating vertically, and move inwardly until the middle
torsion bars 62 engage one another as shown in FIG. 5. This engagement
limits the vertical deflection of the horizontal platform 46 to a fully
deflected position in which the platform 46 is spaced a predetermined
distance above the engaged torsion bars 62.
In the fully deflected position, lower connecting bars 66, as viewed from
the side in FIG. 5, form a generally fixed triangular support which also
limits further vertical deflection of the spring. The engaged torsion bars
62 form a fulcrum about which the platform 46 may pivot in the direction
shown by arrows 70. This allows portions of the wire deck 16 to deviate
from a generally horizontal plane to conform to applied bedding loads
thereby increasing the comfort provided by the box spring assembly.
Middle torsion bars 62 twist and rotate in a generally vertical plane as
they move toward each other during deflection of springs 14. Ends 74 of
torsion bars 62, shown in the perspective view of the spring 14 in FIG. 6,
tend to rotate downward relative to ends 76 of torsion bars 62 which tend
to rotate upward. When the bars 62 engage thus limiting any further
deflection of the spring 14, the bars 62 are no longer parallel to one
another. Bars 62 engage in a cross bucking pattern as shown in FIG. 7.
FIG. 7 is a side view as viewed in the direction of arrow 7 of FIG. 6.
This cross bucking engagement pattern assures that bars 62 will firmly
engage one another to limit the spring deflection.
The spring disclosed in U.S. Pat. No. 4,559,654 also is of a limited
deflection design. However, this design differs significantly from
Applicant's invention. The deflection of the platform in U.S. Pat. No.
4,559,654 is limited by the cross bars of the platform itself contacting
the torsion bars of the intermediate column section.
The spring 14 in Applicant's invention limits deflection by the engagement
of the middle torsion bars 62 while the platform 46 is spaced above the
middle torsion bars 62. This reduces the angular rotation and twist in the
middle torsion bars 62 to less than the twist experienced by the
corresponding bars of the spring shown in U.S. Pat. No. 4,559,654.
Accordingly, the torsional stresses produced in Applicant's springs are
less for springs of the same width.
With a reduced peak stress in spring 14, it is more difficult to stress the
springs 14 during use of the assembly 10 to the point where they take a
"set", thus providing the assembly 10 with a longer service life and
allowing smaller diameter spring wire to be used to achieve a comparable
service life. Smaller diameter spring wire is more ecomonical to produce
thus reducing the overall cost of the assembly.
It is to be understood that the present invention is not limited to the
exact construction or method illustrated and described above, but that
various changes and modifications may be made without departing from the
spirit and scope of the invention as defined in the following claims.
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