US20050246839A1

US20050246839A1 - Bed foundation having a structural foam perimeter utilizing mechanical interlocking

Info

Publication number: US20050246839A1
Application number: US10/842,226
Authority: US
Inventors: Alan Niswonger
Original assignee: Individual
Current assignee: Flexible Foam Products LLC
Priority date: 2004-05-10
Filing date: 2004-05-10
Publication date: 2005-11-10

Abstract

A bed foundation includes, in an advantageous form, a sidewall frame, a box-spring array, at least one spring interconnect, and at least a first structural foam layer. The sidewall frame includes a plurality of interlocking frame members. The sidewall frame has a frame interior, a frame top, and a frame bottom. The box-spring array is received within the frame interior and includes a plurality of springs. The at least one spring interconnect extends from the sidewall frame and into the frame interior. At least one spring interconnect interacts with at least one spring to thereby aid in retaining that at least one spring in place relative to the sidewall frame. The first structural foam layer is attached to one of the frame top and the frame bottom and extends thereacross. Advantageously, this first structural foam layer forms a mechanical interlock with the sidewall frame at the given one of frame top and the frame bottom to which it is attached.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a bed support or foundation having a perimeter formed of structural foam, and more particularly to a structural foam perimeter which utilizes mechanical interlocking to attach the various structural foam portions to each other and/or to a box spring set carried therewithin.
2. Description of the Related Art
Most beds available today employ a form of a bed support. With the use of a standard mattress, this bed support typically comes in the form of a set of box springs. In the case of a waterbed, this bed support is generally designed to enclose a waterbed bladder carried therewithin. Other bed supports may incorporate another type of interior support member such as an air bladder or a foam insert.
When the bed support is a standard set of box springs, there are certain associated drawbacks therewith. Such drawbacks include, but are not limited to, the “edge roll” that occurs as consumers sit or lay on or very near the edge of the bed. This edge roll effect is the tendency of the consumer to feel as though he/she is rolling/leaning off of the edge of the bed. This edge roll effect occurs due to springs along the perimeter of the box spring becoming loosened from the interior springs within the box-spring array and actually leaning outward toward the edges of the box springs. While there have been some attempts in the art to correct this “edge roll” the results have been less than ideal and have been generally labor intensive (as an example, the use of twist ties to attempt to attach the perimeter springs with adjacent interior springs within the box-spring array).
Other shortcomings are generally associated with the standard set of box springs. One drawback is the spring noise which can be associated therewith. Additionally, the standard set of box springs generally requires the employment of a significant amount of wood and carpentry expertise, thereby contributing to the expense thereof.
In an attempt to counteract some of the problems associated with bed supports and especially box spring sets, polyurethane foam products have been developed as bed support perimeters. However, such polyurethane perimeters have generally required a gluing step for their attachment to one another. There are several problems associated with such gluing. Gluing is a labor intensive process; gluing creates emissions of gas that may potentially be noxious to those working with and around them; and such glue requires a certain period in which to set, thereby necessitating a large number of premade supports taking up a large area of factory space and thereby decreasing the potential throughput of bed supports created during a production cycle.
What is needed in the art is a bed support unit incorporating a structural foam perimeter which avoids the need for gluing to attach the portions thereof together and which, even more ideally, provides a means to decrease “edge roll” associated with standard bed foundation units.

SUMMARY OF THE INVENTION

The present invention generally relates to a perimeter for a bed support that is made of structural foam and provides for mechanical interlocking portions as part of the sections of the perimeter. Such interlocking members are structured and arranged to selectively facilitate the interconnection of the perimeter members to one another, to couple the perimeter members with the outlying perimeter springs within the array of box springs to reduce “edge roll”, and/or to ease the joinder between the perimeter members and a top and/or bottom structural foam piece, (e.g., the topper or bottom, respectively).
The present invention, in one particular form thereof, relates to a bed foundation including a first bed frame member and a second bed frame member. The first bed frame member is composed of a structural foam and has a pair of first frame member ends. At least one first frame member end has a first mechanical interconnect portion associated therewith. The second frame member is composed of a structural foam and has a pair of second frame member ends. At least one second frame member end has a second mechanical interconnect portion associated therewith. One of the first mechanical interconnect portion and the second mechanical interconnect portion is preferably one of slidably received and snap-fit within the other of the first mechanical interconnect portion and the second mechanical interconnect portion. The first mechanical interconnect portion and the second mechanical interconnect portion thereby form an interlocking connection.
The present invention, in another form thereof, sets forth a bed foundation including a sidewall frame, a box-spring array, and at least one spring interconnect mechanism. The sidewall frame defines a frame interior, and the box-spring array is received with such a frame interior. The box-spring array includes a plurality of perimeter springs, each being adjacent the sidewall frame. The at least one frame interconnect mechanism extends from the sidewall frame and into the frame interior. At least one spring interconnect mechanism interacts with at least one perimeter spring to thereby aid in retaining the at least one perimeter spring in place relative to the sidewall frame.
The present invention, in another form thereof, sets forth a bed foundation including a sidewall frame and a first structural foam layer. The sidewall frame has a frame top and a frame bottom. The first structural foam layer is mechanically interlocked with the sidewall frame and extends across one of the frame top and the frame bottom.
The present invention, in still another form thereof, sets forth a bed foundation including a sidewall frame, a box-spring array, at least one spring interconnection mechanism, and at least a first structural foam layer. The first sidewall frame is made up of a plurality of mechanically interlocking frame members. The sidewall frame has a frame interior, a frame top, and a frame bottom. The box-spring array is received within the frame interior, and such an array includes a plurality of springs. The at least one spring interconnect mechanism extends from the sidewall frame and into the frame interior. At least one spring interconnect mechanism interacts with at least one spring to thereby aid in retaining the at least one spring in place relative to the sidewall frame. The at least first structural foam layer is mechanically interlocked with the sidewall frame at one of the frame top and the frame bottom and correspondingly extends thereacross.
An advantage of the present invention is that the cost of manufacturing such a bed foundation, utilizing the mechanically interconnecting members of the present invention, is reduced over the cost associated with supports using standard box springs and with those using structural foam members attached via a resin, glue, or other adhesive, due to cost savings related to both assembly and parts.
Another advantage of the present invention is that the ability of the foam perimeter to interlock at least with a portion of the perimeter springs within the box-spring array helps to reduce the occurrence of “edge roll”.
Yet another advantage of the present invention is that it permits the creation of a tub/box that is capable of supporting/containing any one of a foam support insert, a box-spring array, an air bladder, a water bed bladder, or other interior support mechanism/system.
A series of advantages are associated with the use of a foam tub/box is that such a tub or box has an inherently cushiony feeling and is reasonably durable, sufficiently supportive, and inexpensive to produce.
An even further advantage of the present invention is that structural foam pieces can be cut to shape using computer controlled machinery (e.g., die cutting machines), thereby increasing the efficiency and accuracy possible with their production.
An additional advantage of the present invention is that the foam members will aid in dampening spring noise associated with a standard set of box springs.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of various embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
FIGS. 1A-H are schematic, top views of sidewall frames according to the first aspect of the present invention, incorporating various types of mechanical interlocks for attaching adjoining frame member ends;
FIG. 2 is a top, schematic view of a bed foundation according to a second aspect of the present invention, providing spring interconnect mechanisms for attaching the sidewall frame to at least a portion of the perimeter springs associated with a box-spring array;
FIG. 3 is a perspective view of a frame subassembly incorporating elements of both the first and second aspects of the present invention;
FIG. 4 is a perspective view of another embodiment of a frame member within the scope of the second aspect of the present invention;
FIG. 5 is a schematic, side sectional view of a bed foundation according to a third aspect of the present invention, the bed foundation incorporating both a topper and a bottom along with a sidewall frame to thereby house an inner-foundation component; and
FIG. 6 is a side, perspective view of an alternative embodiment of a spring interconnect mechanism of the present invention.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

The first aspect of the present invention is illustrated in FIGS. 1 a-1 h, illustrating the concept of interlocking frame members for creating a frame/perimeter of a bed foundation according to the present invention. Frame assemblies 10 a-10 h each include, respectively, a first spring member 12 a-12 h and a second frame member 14 a-14 h. First spring member 12 a-12 h is in turn supplied with a male connecting portion 16 a-16 h, respectively, while second frame member 14 a-14 h is supplied with a female connector portion 18 a-18 h, respectively. Such connector portions 16 a-16 h are able to snap fit and/or slideably connect with respective female member 18 a-18 h.
As illustrated, any of a variety of connection configurations may be employed with respect to the interconnecting portions, so long as a sufficient interlocking is achieved between the two portions. By creating interlocking portions, it is possible to avoid the need to further glue such portions together in order to maintain a connection therebetween. However, it is conceivable that some sort of adhesive may be used in connection with such a mechanical interlock to achieve even further stability. Frame members 12 a-12 h and 14 a-14 h are advantageously made of a structural foam material such as polyurethane. For optimal performance the foam type should be high ILD 40-200 <<units??>> and have a density in the range of 1.5 to 6.0 <<units??>>. It is further contemplated that the interconnect provided between the portions 16 a-16 h and corresponding portions 18 a-18 h will preferably resist disconnection upon joining thereof.
Advantageously, male connection members 16 a-16 h can be integrally formed as part of first frame members 12 a-12 h, and likewise female connector portions 18 a-18 h can be integrally formed as a portion of second frame members 14 a-14 h, respectively. Such formation of structural foam is highly suitable to die cut operations and/or computer control for the formation thereof. It is, however, contemplated that male members 16 a-16 h could be co-formed or otherwise attached to respective members 12 a-12 h. Any such co-forming or attachment step would ideally lend itself to an automated process which would take an amount of time similar to that offered by die cutting and which would create a similar connective strength between male members 16 a-16 h and respective first members 12 a-12 h, as is possible when such male members 16 a-16 h are formed integrally therewith.
It is to be understood that third and fourth frame members (not shown in FIGS. 1A-1H) are to be able to be connected to the frame using similar mechanical interlocks as proposed to connect first frame member 12 a-12 h with respective second frame member 14 a-14 h. It is also to be understood that it is possible for the first frame members 12 a-12 h to have a female connecting portion and instead for the second frame member 14 a-14 h to carry the male connecting portions. Any such combination of female-to-male connection points are possible so long as the appropriate mechanical interlock can be achieved therebetween.
A second aspect of the present invention is illustrated in FIGS. 2-4. The second inventive aspect of the present invention provides a means for suppressing edge roll or spring roll proximate the edge of the bed or the bed foundation. Illustrated in FIG. 2 is a bed foundation 30 composed of a sidewall frame 32, a box-spring array 34, and a series of spring interconnect mechanisms 36.
Sidewall frame 32 defines a frame interior 38 for a receiving box-spring array 34. Ideally, sidewall frame 32 is divided into multiple sections or members to allow for frame assembly at the end of the production cycle to minimize the storage space needed for the bed frame 32 until the full frame is required. Such frame members are ideally made of a structural foam such as polyurethane. Additionally, such frame members are advantageously provided with the interlock system illustrated in FIGS. 1A-1H to allow for a mechanical interlocking of the four frame members. Alternatively or additionally, such members can be connected via the use of an adhesive or a mechanical fastener.
Box-spring array 34 includes perimeter springs 42 and interior springs 44. It is the perimeter springs 42 that are the primary subject of the second aspect of the invention, as such perimeter springs are prone to rollover and/or exhibit edge roll. Interior springs 44 are not as prone to rollover problems as they have springs on each side thereof to help support and maintain the positioning of these individual springs. However, perimeter springs 42 each have one side, i.e., the side they are facing toward sidewall frame 32, thereby making them prone to rollover problems.
To counteract and minimize such rollover/edge roll, spring interconnect mechanisms 36 are provided in this second aspect of the invention. Such spring interconnect mechanisms 36 promote the positional stability of sidewall frame 32 with respect to at least select perimeter springs 42. Spring interconnect mechanisms 36 are able to at least partially surround such chosen perimeter springs 42 to help maintain the positioning thereof relative both to the other springs within the box-spring array 34 and with respect to sidewall frame 32.
Each spring interconnect mechanism 36 extends from sidewall frame 32 and, more specifically, from a given frame member 40. Such spring interconnect mechanisms 36 are preferably integrally formed as part of a sidewall frame or co-formed therewith. The integral formation of interconnect spring mechanisms 36 can be achieved by die cutting a given frame member so as to include one or a series of spring interconnect mechanism 36 as part of the finally formed frame member 40.
Each spring interconnect mechanism 36 includes an extension portion 46 and a retainer portion 48. The extension portion 46 is connected to a respective frame member 40, while retainer portion 48 resides at a distal end of the extension portion 46, opposite the given frame member 40. The length of the extension portion 46 needs to be chosen so as to permit the spring interconnect mechanism 36 to be able to extend at least slightly beyond the first perimeter springs 42 and into the interior of box-spring array 34 upon assembly of bed foundation 30. Meanwhile, retainer portion 48, upon assembly, must be configured to help maintain at least one perimeter spring 42 in position relative to extension portion 36 and a given frame member 40. In one advantageous embodiment for extension portion 46, as shown in FIG. 2, the extension portion 46 has an arrow shape. This arrow shape allows it to be easily inserted between a given pair of perimeter springs 42 yet inhibit retraction from therebetween, upon assembly.
It is to be understood that extension portion 36 could have a length which would allow spring interconnect mechanism 36 to extend beyond the row of perimeter springs 42 and into one or more rows of interior springs 44 for greater holding power and stability. The only limitation on the distance of insertion is that the spring interconnect mechanism 36 must still be able to satisfy its function of reducing rollover. As such, the mechanism must be able to help maintain the perimeter spring or springs 42 with which it is associated in place relative to box-spring array 34 and sidewall frame 32.
When two or more such spring interconnect mechanisms 36 are positioned adjacent one another (as per FIGS. 2 and 4), they together define a spring receiving zone 50 therebetween. In such a spring receiving zone 50, at least one spring may be received. Due to the nature of such a spring receiving zone 50, it is possible to even more stably retain given perimeter spring(s) 42.
The frame subassembly 60, as shown in FIG. 3, employs elements of both the first and second aspect of the present invention. Frame subassembly 60 includes first frame member 62 and second frame member 64. First frame member 62 employs male frame member interconnect 66 at opposing ends thereof, while second frame member 64 employs female interconnects 68 at opposite ends thereof. FIG. 3 offers an exploded or unassembled view of a set of mating interconnects 66 and 68. Additionally, Frame subassembly 60 incorporates at least one spring interconnect mechanism 70, as illustrated. It is to be understood that the use of any number of spring interconnect mechanisms 70 is expected to improve the rollover situation with a given set of perimeter springs 42. Thus, while it is acknowledged that the use of a plurality of mechanisms 70 would likely gain further improvements in performance with respect to edge roll, it is to be understood that the present invention contemplates the scenario in which a single interconnect mechanism 70 is employed on a given frame member 40.
Frame member 80 (FIG. 4) has a plurality of T-shaped spring interconnect mechanisms extending therefrom for the purpose of stabilizing the position of perimeter springs 84 (schematically indicated). As shown, such spring interconnect mechanisms 82 extend the foundation height 86 and are repeated along the foundation length 88 (or width as appropriate). Each pair of adjacent T-spring interconnect mechanisms 82 together define a spring receiving zone 90 for a given perimeter spring 84 and further define a spring insertion gap 92 through which a particular spring 84 may be snap fit into zone 90. Like other structural foam members of the present invention, frame member 80 with T-shaped spring interconnect mechanisms 82 is advantageously formed of a structural foam such as polyurethane. Furthermore, it preferably has a material density in a range of about 1.5 to 6.0 <unit??> and an associated ILD of 30 to 100<unit?>.
Bed foundation 100 displayed in FIG. 5 includes a sidewall frame 102, a topper 104, and a bottom 106, which together house an inner-foundation component 108. Each of sidewall frame 102, topper 104, and bottom 106 are advantageously made of a structural foam material. It is further to be understood that one of topper and bottom could potentially not be provided, thereby creating a tub formation for housing a particular inner-foundation component 108. Inner-foundation component 108 may be, for example, any one of a structural polyurethane foam insert, an air bladder, a water bed bladder, or a box-spring array. It is further to be understood that any foundation component which would provide the user of the bed an appropriate degree of support and comfort is also within the scope of the present invention.
As further indicated in FIG. 5, a mechanical interlock may be provided between frame top 112 and topper 104 and/or between frame bottom 114 and bottom piece 106. Mechanical interlock 110 offers similar advantages as discussed with respect to an mechanical interlock between adjoining foam member ends. Further, it is understood that, additionally or alternatively, another type of joining means may be employed between frame 102 and topper 104 and/or bottom 106. These joining means may include, but are not necessarily limited to, other types of mechanical connectors and/or adhesives. It is to be further understood that sidewall frame 102 can further employ the frame-member interlock concept, as per the first aspect of the invention, and/or the spring interconnect mechanism associated with the second aspect of the invention.
Spring interconnect mechanism 120 represents a further alternate embodiment of the present invention. This spring interconnect mechanism 120 for stabilizing the position of a particular perimeter edge coil or spring 122 includes a cylinder insert 124, a hook member 172, and an extension portion 174. Cylinder insert 124 is configured for insertion into a particular edge coil 122. This cylinder insert can be then held in place upon the attaching of hook member 172 around a bed foundation and frame portion (not shown). While this particular spring interconnect mechanism 120 can be potentially incorporated with other embodiments of the present invention, a potential particular use as such a spring interconnect mechanism 120 is that it would allow for retrofitting of current box-spring bed foundations with such a mechanism 120 to thereby help reduce edge rollover that occurs in such foundations.
It is to be understood that any of the components of the three various aspects described herein can be used in conjunction with one another and be within the scope of the present invention.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

1. A bed foundation, comprising:

a first bed frame member, said first frame member being composed of a structural foam, said first frame member having a pair of first frame member ends, at least one said first frame member end having a first mechanical interconnect portion associated therewith; and

a second bed frame member, said second frame member being composed of a structural foam, said second frame member having a pair of second frame member ends, at least one said second frame member end having a second mechanical interconnect portion associated therewith, said first mechanical interconnect portion and said second mechanical interconnect portion forming an interlocking connection.

2. The bed foundation of claim 1, wherein said first bed frame member and said second bed frame member define a first side wall and a second side wall, respectively, of said bed foundation.

3. The bed foundation of claim 1, wherein at least one of said first mechanical interconnect portion and said second mechanical interconnect portion is one of integral and co-formed with a respective one of said first bed frame member and said second bed frame member.

4. The bed foundation of claim 1, wherein said first mechanical interconnect portion and said second mechanical interconnect portion together define a male/female interconnection.

5. The bed foundation of claim 4, wherein said first mechanical interconnect portion and said second mechanical interconnect portion together define a notched interconnection.

6. The bed foundation of claim 1, further comprising a third bed frame member and a fourth bed frame member, said third bed frame member being mechanically connected to said first bed frame member and said fourth bed frame member, said fourth bed frame member being further mechanically connected to said second bed frame member.

7. The bed foundation of claim 6, wherein said third bed frame member is interlocked with said first bed frame member and said fourth bed frame member, said fourth bed frame member being further interlocked with said second bed frame member.

8. The bed foundation of claim 6, wherein said first bed frame member, said second bed frame member, third bed frame member, and a fourth bed frame member together define a side wall frame of said bed foundation.

9. The bed foundation of claim 8, wherein said side wall frame has a frame top, a frame bottom, and a frame interior, said bed foundation further including at least one of a box-spring array received within said frame interior; a foam topper mechanically interlocked with said frame top; and a foam bottom mechanically interlocked with said frame bottom.

10. The bed foundation of claim 8, including said box-spring array received within said frame interior, said box-spring array including a plurality of perimeter springs, each said perimeter spring being adjacent said side wall frame, said side wall frame having at least one spring interconnect mechanism extending therefrom into said frame interior, at least one said spring interconnect mechanism interacting with at least one said perimeter spring to thereby aid in retaining said at least one said perimeter spring in place relative to said side wall frame.

11. A bed foundation, comprising:

a side wall frame defining a frame interior;

a box-spring array received within said frame interior, said box-spring array including a plurality of perimeter springs, each said perimeter spring being adjacent said side wall frame; and

at least one spring interconnect extending from said side wall frame and into said frame interior, at least one said spring interconnect interacting with at least one said perimeter spring to thereby aid in retaining said at least one said perimeter spring in place relative to said side wall frame.

12. The bed foundation of claim 11, including a plurality of spring interconnects, at least one pair of said spring interconnects being positioned adjacent one another in a manner so as to thereby define a spring receiving zone therebetween, at least one said perimeter spring being received within said spring receiving zone.

13. The bed foundation of claim 12, wherein said at least one pair of said spring interconnects is configured for at least one of slidably fitting around said at least one said perimeter spring and forming a snap-fit therewith.

14. The bed foundation of claim 13, wherein each said spring interconnect is T-shaped, each said spring interconnect being separate from each adjacent said spring interconnect, said at least one pair of said spring interconnects being configured for snap fitting around at least one said perimeter spring.

15. The bed foundation of claim 11, wherein each said spring interconnect is one of integral and co-formed with at least a portion of said side wall frame.

16. The bed foundation of claim 11, wherein at least said spring interconnect has an arrow shape configured for easy insertion between two adjacent said perimeter springs and for subsequent difficult removal from therebetween.

17. The bed foundation of claim 11, wherein each said spring interconnect is composed of a structural foam material.

18. A bed foundation, comprising:

a side wall frame having a frame top and a frame bottom; and

a first structural foam layer mechanically interlocked with said side wall frame and extending across one of said frame top and said frame bottom.

19. The bed foundation of claim 18, wherein said first structural foam layer mechanically interlocks with said side wall frame at at least one wall location on said one of said frame top and said frame bottom.

20. The bed foundation of claim 18, wherein said first structural foam layer is attached to said frame top, said first structural foam layer thereby being a foam topper.

21. The bed foundation of claim 18, wherein said first structural foam layer is attached to said frame bottom, said first structural foam layer thereby being a foam bottom.

22. The bed foundation of claim 21, wherein said side wall frame and said foam bottom together define a foundation tub configured for selectably receiving one of a structural foam support insert, an air bladder, a water containment unit for a waterbed, and a box-spring set.

23. The bed foundation of claim 21, further comprising a second structural foam layer attached to said frame top, said second structural layer being a foam topper, said side wall frame, said foam bottom, and said foam topper together defining a foundation box configured for selectably receiving one of a structural foam support insert, an air bladder, a water containment unit for a waterbed, and a box-spring set.

24. A bed foundation, comprising:

a side wall frame comprised of a plurality of mechanically interlocking frame members, said side wall frame having a frame interior, a frame top, and a frame bottom;

a box-spring array received within said frame interior, said box-spring array including a plurality of springs;

at least one spring interconnect extending from said side wall frame and into said frame interior, at least one said spring interconnect interacting with at least one said spring to thereby aid in retaining said at least one said spring in place relative to said side wall frame; and

at least a first structural foam layer mechanically interlocked with said side wall frame at one of said frame top and said frame bottom and extending across said one thereof.

25. A bed foundation, comprising:

a side wall frame comprised of a plurality of frame members, at least two said frame members mechanically interlocking at adjoining ends thereof.

26. The bed foundation of claim 25, wherein said mechanical interlocking is in the form of one of a slide connection and a snap-fit.

27. The bed foundation of claim 25, wherein said side wall frame defines a frame interior, said bed foundation further comprising:

a box-spring array received within said frame interior, said box-spring array including a plurality of springs; and

at least one spring interconnect extending from said side wall frame and into said frame interior, at least one said spring interconnect interacting with at least one said spring to thereby aid in retaining said at least one said spring in place relative to said side wall frame.

28. The bed foundation of claim 25, wherein said side wall frame defines a frame top and a frame bottom, said bed foundation further comprising:

at least a first structural foam layer attached to said side wall frame at one of said frame top and said frame bottom and extending across said one thereof.

29. The bed foundation of claim 27, wherein said first structural foam layer is mechanically interlocked with said side wall frame.