Patent Description:
The furniture industry is influenced by the environmental requirements that consumers demand in different areas. In addition, financial requirements are always imposed on the end products, which means there is a need for reduced costs. These requirements that are desired to be met must not be at the expense of something else, such as safety, strength, workplace environment or the like. Wooden planks and ribs are frequently used as support members in furniture support frames. A problem with wooden planks and ribs is that they have a tendency to crack, especially near end portions in connection with attachment, e.g. by means of nails. This leads to disruptions in production and increased costs.

From, <CIT>, it is known that plank like members can be made of materials other than conventional wood and steel, in this case of composite. From SE <NUM>-<NUM> it is known to make plank like members by combining wood and plastic materials. Composite/plastic is a significantly worse alternative from an environmental point of view than wood and it may not compete from a price point of view. In case of fire, such a plank like member will contain much more energy that will lead to heavy heat generation and harmful flue gases from the plastic, not just carbon dioxide.

Plank like members and ribs made from cellulose fibers, e.g. paper, would bring about many benefits in relation to the above disadvantages related to plank like members in alternate materials. Many solutions are known, but none that may fulfil required needs for a plank like member in a successful manner. From <CIT> there is known a modular system using building elements that are built by layers of fiber material, e.g. paper, wherein the focus is to use the paper building elements as a concrete shed to enable in situ building with concrete, i.e. providing a significantly less heavy structural element to be shipped than in conventional concrete building.

From <CIT> and <CIT> there are known foldable construction elements made up of corrugated board walls, which is rather complex and therefore relatively expensive.

Further, from <CIT> and <CIT> there are known corrugated board elements in the form of supporting beams, i.e. large structural elements that are to carry heavy loads. Other examples of known support frames comprising paper ribs are disclosed in <CIT> and <CIT>.

The object of the present invention is to reduce environmental impact and price compared with current wooden ribs, which is achieved by a furniture support frame, comprising paper ribs, according to claim <NUM>, a rib for furniture support frame of claim <NUM> and a use of a paper rib for supporting a furniture frame of claim <NUM>. Preferred features of the invention are set out in the dependent claims. Further, the ribs are less prone to catch fire than wooden ribs, which is of essence regarding furniture.

Thanks to the invention, a rib is obtained for use in furniture and other support structures where demands from consumers regarding the environment, fire risk and price can be more easily met, while at the same time strength requirements can be met. A rib in paper has significant environmental benefits, both in relation to composite, wood and steel. None of the previously known materials can achieve the economic benefits that a rib in paper can. Moreover, a rib according to the invention has no tendency to crack and therefore the problems mentioned above associated with wooden ribs may be eliminated, or at least minimized.

Thanks to the invention, a rib is obtained which provides an easy-to-use product with high environmental and cost advantages, which meets needed durability requirements. The invention relates to a structural element which is primarily intended for use in furniture. Thanks to the invention, the working environment for furniture builders will also be improved since a rib according to the invention of paper is non-sticky, less risk of splinters, and substantially less heavy than wooden ribs and hence better from a handling point of view, as well as possible to cut off without chip formation and with substantially noiseless methods, such as cutting. For example, working environment and/or conditions may be improved due to the substantially noiseless methods.

According to the invention, there is provided a rib for furniture support frame, which rib comprises walls about a hollow core, said walls being made up of a plurality of joined layers of paper surrounding said hollow core, said walls having a homogeneous thickness in the range of <NUM>-<NUM> and comprising pairs of parallel walls, with a first pair of shorter walls having a width substantially less than the corresponding cross-sectional length of a second pair of parallel longer walls, wherein said walls comprise <NUM>-<NUM> layers of a paper layer bonded with glue, each paper layer having a grammage of <NUM>-<NUM> grams/m2, wherein said shorter walls having a width less than <NUM> and by arranging said shorter walls to be curved.

According to the invention, said curved shorter walls present a curvature having a radius within the range of <NUM>-<NUM>.

In some embodiments, the relation between said width and corresponding cross-sectional length is such that 2B> L> <NUM>.

According to the invention, said walls have a homogeneous thickness in the range of <NUM>-<NUM>.

According to the invention, said walls comprise <NUM>-<NUM>, preferably <NUM>-<NUM> layers of a paper layer with a grammage of <NUM>-<NUM> grams / m2.

In some embodiments, said paper layer is made by semi-chemical fluting.

According to the invention, there is provided a use of a paper rib for supporting a furniture frame, which paper rib comprises walls about a hollow core, said walls being made up of a plurality of joined layers of paper surrounding said hollow core, said walls having a homogeneous thickness and comprising pairs of parallel walls, with a first pair of shorter walls having a width substantially less than the corresponding cross-sectional length of a second pair of parallel longer walls, wherein said walls comprise <NUM>-<NUM> layers of a paper layer bonded with glue.

In the following, the invention will be described in more detail, with reference to the accompanying figures wherein;.

In <FIG>, a perspective view of a rib <NUM> is shown as an example, presenting a hollow rectangular cross-section with a short wall <NUM> and a long wall <NUM>. The rib <NUM> is made up of a plurality of joined layers <NUM> of paper. Sometimes, the rib is referred to as "paper rib", "tube" or the like.

The rib is according to the invention, designed so that its short wall <NUM> has a width B1 that is substantially less than the corresponding cross-sectional length L1 of the longer wall <NUM>, preferably the ratio is such that <NUM>*B1< L1. In a most preferred embodiment, the width B1 is <NUM>-<NUM> and the cross-sectional length L1 <NUM>-<NUM>. According to the invention, the short walls <NUM> are curved which may improve strength, such that the paper layers <NUM> at the short walls generally extend along a radius R, preferably the radius R is between <NUM>-<NUM>. According to the invention, the. thickness of the wall is chosen to be about <NUM>-<NUM>, preferably <NUM>-<NUM>.

According to the invention, the walls <NUM>,<NUM> comprise <NUM>-<NUM> layers of paper layers <NUM> (see <FIG>) with a grammage of <NUM>-<NUM> grams / m2, more preferred of <NUM>-<NUM> layers of paper layers <NUM> with a grammage of <NUM>- <NUM> grams / m2. Preferably, paper is used mainly made of short-fiber pulp, more preferred semi-chemical fluting, which is an advantageous choice because the short-fiber composition results in the paper having a tight structure that provides good strength. In some examples, it may be preferred to have <NUM>-<NUM> layers of paper layers <NUM>.

The paper layers <NUM> are joined with adhesive <NUM>. The adhesive <NUM> is preferably polyvinyl acetate, which is an advantageous choice because it is water-soluble and cost-effective.

The example relates to a rib <NUM> as a structural element primarily for use in furniture, such as furniture support frames, upholstery furniture support frames, bed support frames, sofas support frames, or the like. This means that requirements from consumers regarding the environment and price can be met without impairing other requirements. Today, for the most part, ribs are made of wood for building furniture, which, from several viewpoints, present disadvantages. With the inventive rib <NUM>, there is provided an easier-to-use product with great environmental and cost advantages that may meet all the requirements in terms of durability, etc., as competing, typically more expensive, materials have.

The rib preferably has outer dimensions B1 = <NUM> and L1 = <NUM> and a hollow core <NUM>, see <FIG>. The construction of it has been made by winding several layers of paper layer <NUM> glued with, e.g. polyvinyl acetate, adhesive around a core (not shown) so that the total thickness the several paper layers is <NUM>-<NUM>. The paper layers are suitably made from short-fiber pulp, preferably manufactured by semi-chemical fluting.

In <FIG> there is shown an exemplary furniture frame <NUM>, e.g. to be used as a bottom support for a bed, including a plurality of cross-wise extending ribs <NUM>, in accordance with the invention. It is shown an outer rectangular frame <NUM> that may be constructed by means of two different frame members <NUM>, <NUM>. Both of these frame members <NUM>, <NUM> may be made in accordance with the same principles as the rib <NUM>. Alternatively, the frame members <NUM>,<NUM> may be manufactured as a beam having a cross-section as the unified frame members <NUM>,<NUM>. However, preferably more layers of paper <NUM> are used in at least the outer frame members <NUM>, and/or suitably a paper of higher grammage, than for the ribs <NUM>, due to having larger dimensions B4 and H4 and intended to carry more load than a rib <NUM>. Further, due to having a larger width B there will normally not be a desired to have curved short sides. In some applications it may be an advantage to have radius r in the corners of the frame members <NUM>, <NUM>, which radius preferably then is smaller than radius R of the curved short sides <NUM> of the rib <NUM>. For example, curved corners may reduce wear on any fabric at least partially enclosing the frame <NUM>.

A plurality, suitably four, of outer frame members <NUM>, or beams, form the outer part of the frame <NUM>, which outer frame members <NUM> has the largest dimensions, at least regarding height H4. In the exemplary embodiment the upper surfaces <NUM> of the outer frame members <NUM> carries a major part of the load, applied from above via a second frame part (not shown). The upper surfaces <NUM> faces outwardly from the frame, i.e. away from the interior of the frame <NUM>. The ribs <NUM> has as a main object to reinforce the frame <NUM>, e.g. to fixate the desired positions of the outer frame members and provide added strength.

Further, there is an inner frame member <NUM> having a height H3 that is smaller than the height H4 of the outer frame member. The inner frame member <NUM> is fixedly attached to the inside surface <NUM> of the outer frame member <NUM> and will provide a support surface <NUM> for the ribs <NUM>, such that the rib <NUM> may be securely attached onto the upper surfaces <NUM> of the inner frame member <NUM> and thereby. The upper surfaces <NUM> faces outwardly from the frame <NUM>, i.e. away from the interior of the frame <NUM>. Thanks to this design it is easily achieved to attach a plurality of ribs <NUM> parallelly within the frame <NUM>. Thanks to having a plurality of ribs <NUM>, the stability and strength of the frame <NUM> may be sufficiently high to meet highest demands.

In the shown preferred embodiment there are four frame members <NUM>, <NUM>, <NUM>, <NUM> forming the outer frame part, such that a rectangular frame may be achieved. The outer frame members <NUM>-<NUM> are preferably attached to each other at the frame corners by means of use of corner attachment device, such that a stable and strong joint between the outer frame members <NUM>-<NUM> is achieved. As an example, the corner attachment device may comprise be one or more wooden blocks that fits in the interior of the frame members. Thanks to the wooden blocks screws for fixating the joint may get good grip in the otherwise empty interior.

Preferably there are only two inner frame members <NUM>, <NUM>, which frame members may be attached to a pair of the outer frame members <NUM>, <NUM>, preferably the longest outer frame members in appropriate manner, e.g. by gluing, riveting or screwing, or a combination of one or more of said manners.

In regard to attachment with screws it has been noted that preferably the frame members <NUM>, <NUM> should be coated by means of resin, which will increase strength and provide stronger/safer grip of screws.

The dimensions of the frame members are preferably such that the outer frame members <NUM> have a height H4 in the range of <NUM> to <NUM> and a width <NUM> to <NUM> and the inner frame members <NUM> preferably have a height H4 in the range of <NUM> to <NUM> and a width <NUM> in the range of <NUM> to <NUM>.

It is evident for the skilled person that the frame <NUM> described above may be used in various furniture to provide a support frame which may be both very strong and light weight and also less fire prone than traditional furniture frames. Furthermore, it is evident for the skilled person that the frame <NUM>, as described above, may also be constructed by means of using traditional wood planks in place of the preferred frame members <NUM>, <NUM>, either both of them or one of them. Furthermore, it is evident that not all ribs <NUM> must be made in accordance with e.g. the example of <FIG>, but that a combination may be used with traditional wooden planks, despite the fact that some of the advantages may then be minimized.

Preferably the inner frame member <NUM> is positioned to have its bottom short side in level with the bottom short side of the outer frame member <NUM> such that both frame members <NUM>, <NUM> jointly form a lower support surface <NUM> of the frame. Further, preferably the height H3 of the inner frame member is such that the difference in height H4 of the outer frame member <NUM> is substantially the same as the width W1 of the rib <NUM>, whereby the upper surface <NUM> of the frame <NUM>, and the outer frame members <NUM>, will be substantially in level with the upper surface of the ribs.

In the shown example the frame <NUM> is intended to be used for beds and may advantageously be provided with varied height, since it is often required by customers, e.g. a desire need for having a relatively high furniture frame <NUM> for a bed. In that connection it is foreseen that the outer frame member <NUM> may be constructed by using two or more frame members on top of each other, i.e. not producing the outer high frame member <NUM> in one piece, on each side, but using a plurality of frame members (not shown) to obtain the desired total height of the frame. According to a preferred embodiment this latter principle may be applied in connection with having a plurality of outer frame members <NUM> of different heights, such that a variety of heights may be achieved by combining different frame members <NUM> of different heights, thereby providing a modular system to easily adapt furniture frames to different needs.

In case of fire, the paper rib <NUM>, and also paper frame members <NUM>,<NUM>, will contain no more than a fraction of the energy contained in a wood rib, whereby no significant amount of heat will develop by the rib in a fire. There is also only an insignificant amount of harmful flue gases in the event of fire.

A rib <NUM> or frame members <NUM>,<NUM> in hollow-core paper also has the advantage of enabling processing/handling with simple means, for example by use of a regular knife to make holes in it for water and/or electricity pipes and/or to cut off it into desired lengths. In addition, it is very light weight which is a great advantage from the working environment point of view.

As described herein, there is provided a novel and inventive use of a paper rib for supporting a furniture frame, which paper rib comprises walls about a hollow core, said walls being made up of a plurality of joined layers of paper surrounding said hollow core, said walls having a homogeneous thickness and comprising pairs of parallel walls, with a first pair of shorter walls having a width substantially less than the corresponding cross-sectional length of a second pair of parallel longer walls, wherein said walls comprise <NUM>-<NUM> layers of a paper layer bonded with glue. This exemplifying use of the paper rib may be combined with any one or more of the embodiments of the paper rib disclosed herein.

An advantage, with this and other embodiments herein, is that fastening of the paper rib is considerably improved as compared to fastening of wood ribs to the frame member <NUM>, or e.g. at least one of the frame members <NUM>,<NUM>. A problem with wood ribs may be that the ends of the wood rib may crack, splinter or become damaged when clamped to the frame member <NUM>. In contrast thereto, the paper rib according to various embodiments herein is not prone to crack or splinter when clamped, e.g. with a nail, a staple or the like. As a result, the manufacturing process becomes quicker and fewer, if any, ribs need to be disposed due to cracks or splinter. Yield of rib is accordingly improved, where yield is a ratio of mounted installed ribs to total number of ribs (i.e. mounted and wasted ribs).

Below, there are shown test results produced at the test lab in BillerudKorsnäs Gruvön, wherein the tensile strength of a rib according to e.g. the example of <FIG> is evaluated. The ribs are about <NUM> long and are fixated in at the ends. Then a force is applied at the middle, i.e. about <NUM> from each end of the paper rib.

<FIG> illustrate schematically average results of a number of samples of the paper rib. Bending force is along the y-axis and the displacement in mm is along the x-axis. The results show that the paper ribs have consistent properties in the range shown, i.e. up to about <NUM>. Normally, the paper ribs need not be displaced more than <NUM>, since the ribs need only to support the furniture frame and to hold any interior parts, such as seating, madras, springs, etc., in place within the frame. Objects or persons occupying a piece for furniture having the furniture frame do not put weight on the ribs, at least not to any larger extent.

The heat test is conducted by that the paper rib and the wood rib are placed on an electrical heating plate, e.g. a cooking plate or the like. Next, it is observed how the ribs are affected by the heating. Heat is turned on to max and left on max until no or very little change may be observed in a time frame, such as <NUM>-<NUM>.

It may be concluded that the paper rib is less prone to burn, which may cause a fire, when exposed to heat.

The fire test is conducted by that the paper rib and the wood rib are placed metal grid over an open fire. Next, it is observed how the ribs are affected by the fire. The fire is large enough to have about the same heating and size during the experiment. When no or very little change may be observed in a time frame, such as <NUM>-<NUM>, the experiment is considered to be ended.

It may be concluded that the paper rib has better fire protection properties due to less flames and less material to be consumed by the fire (or less material to fed the fire).

In view of the above, the ribs according to at least some embodiments herein are advantageous in one or more of the following aspects: light weight and fire safe.

Claim 1:
A furniture support frame (<NUM>), comprising at least one rib (<NUM>), which rib (<NUM>) comprises walls (<NUM>, <NUM>) about a hollow core (<NUM>), said walls (<NUM>, <NUM>) being made up of a plurality of joined layers of paper (<NUM>) surrounding said hollow core (<NUM>), said walls (<NUM>, <NUM>) having a homogeneous thickness (T) in the range of <NUM>-<NUM> and comprising pairs of parallel walls (<NUM>, <NUM>), with a first pair of shorter walls (<NUM>) having a width (B1) substantially less than the corresponding cross-sectional length (L1) of a second pair of parallel longer walls (<NUM>), wherein said walls (<NUM>, <NUM>) comprise <NUM>-<NUM> layers of a paper layer (<NUM>) bonded with glue (<NUM>), each paper layer (<NUM>) having a grammage of <NUM>-<NUM> grams/m2, wherein said support frame (<NUM>) comprises at least one pair of opposing frame members (<NUM>,<NUM>), said rib (<NUM>) having its ends fixedly connected onto a support surface (<NUM>) connected to each one of said pair of opposing frame members (<NUM>,<NUM>), characterized by said shorter walls (<NUM>) having a width (B) less than <NUM> and by arranging said shorter walls (<NUM>) to be curved.