Pocket Spring Mattress With Edge Support

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This application claims the benefit and priority to European Patent Application No. EP24223517.4 filed Dec. 27, 2024, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

[0002]The present invention relates to a pocket spring mattress.

BACKGROUND OF THE INVENTION

[0003]A well-known type of bedding or seating product comprises a spring assembly which includes a number of discrete coil springs, each of which is enclosed in a fabric pocket in a length of folded fabric material. Longitudinal axes of the coil springs are generally parallel with one another so that the top and bottom end turns of the coil springs define top and bottom faces of the spring assembly. A row of such pocketed springs is known in the industry as a string of pocketed springs. A bedding or seating product can be produced from such strings of pocketed springs by assembling and connecting the individual rows or strings of pocketed springs together.

[0004]This type of spring assembly is commonly referred to as a pocket spring mattress or pocketed spring unit due to the fact that each spring is contained within an individual pocket of fabric material.

[0005]There has been a general desire to provide zones or sections of different firmness in pocket spring mattresses, e.g. to provide an edge support in the form of firmer pockets around the whole or part of the perimeter of the pocket spring mattress, or to provide zones of varying firmness along the length of the mattress, to improve comfort and suit the needs of different users. Such attempts have e.g. been disclosed in U.S. Pat. No. 6,684,435, which proposes to use springs with double springs in some of the pockets, EP 2123197, which proposes to arrange one or more edge strings displaced in relation to the inner strings, EP 3535212 and U.S. Pat. No. 10,104,970, which both disclose arrangement of strings with smaller coil springs around the perimeter, WO 10/060202, disclosing springs with different height or bias arranged in the edge pockets, etc.

[0006]The provision of springs and pocket units with varying properties in a pocket spring mattress may be referred to as posturization or zoning. Posturization or zoning may provide multiple zones or sections of differing firmnesses within the mattress. For example, the middle regions of the mattress, which typically support a person's torso, often require a firmer more resilient support while other areas of the mattress which support the feet and head of a person require a softer feel.

[0007]However, a general problem related to the known mattresses is that they are relatively complicated and costly to produce. In particular, provision of different springs, different types of strings, etc., makes the production more cumbersome and tedious, and also difficult to make fully automated, thereby requiring much manual performed operations.

[0008]Other well-known drawbacks related to pocket spring mattresses, which also makes the mattresses complicated and costly to produce and handle, are e.g. the general need to arrange foam material, padding, or the like around the sides of the mattress, in order to make the sides smooth, planar and visually attractive. There is also a general need to provide a steel frame or the like around the upper or lower edge of the mattress, in order to improve stability. However, such added parts to the mattress make it difficult to compact the mattress for shipping and handling, such as by rolling or vacuum pressing of the mattress. A vacuum pressed and/or rolled mattress leads to further reduced cost, since each mattress will require much less space during transport and storage before it reaches the customers. However, especially when producing mattresses with the above-mentioned steel frame, the mattress cannot be vacuum pressed and rolled up for storage and transport without damaging the frame.

[0009]There is therefore a need for pocket spring mattresses, and associated methods and apparatuses for manufacture, which address the above-discussed shortcomings of the prior art. In particular, there is a need for pocket spring mattresses with varying firmness properties, i.e. a posturized or zoned pocket spring mattress, which can be produced and handled easier and more cost-effectively. which allows for vacuum and roll packaging, which reduces manual labor, which reduces the need for additional padding, layers, and/or the like. Thus, there is a need for a posturized or zoned pocketed spring mattress, and associated method and apparatus of manufacture, which offer the advantages of posturization or zoning of the spring assembly without the higher manufacturing costs, production difficulties and inefficiencies associated with known posturized/zoned pocketed spring mattresses.

SUMMARY OF THE INVENTION

[0010]It is therefore an object of the present invention to at least partly overcome these problems, and to provide an improved pocket spring mattress. These, and other objects that will be apparent from the following, are achieved by a pocket spring mattress according to the appended claims.

[0015]Since the strings of the second type have a greater linear density of springs than the strings of the first type, the strings of the second type are generally firmer than the strings of the first type. As will be discussed in the following, the firmer strings of the second type may be used in various ways, such as for providing an edge support around part of, or the whole, mattress, to provide zones having various firmness in the mattress, to provide separation between different parts or sections of the mattress, etc.

[0016]It has now been found that increasing the linear density of springs in a string is a very cost-efficient and effective way of increasing the firmness of the string. Hereby, the same springs may be used in both the two types of strings, making production simpler, faster and less costly.

[0017]All strings preferably have the same linear density of springs over its entire extension, so that some strings have uniform distribution of springs to provide the first linear density of springs, and some strings have a uniform distribution of springs to provide the second linear density of springs. However, it is also feasible to have sections with different linear density of springs within a string, such as sections having the first linear density of springs in one or more sections and sections having the second linear density of springs in one or more other sections.

[0018]Further, the provision of at least one stabilizing fabric strip connected to the fabric of the strings of the second type, over at least a part of the extension of the string, ensures that the compactness, i.e. the high linear density of springs, is maintained and secured over time. The stabilizing fabric strip(s) also contributes to an overall increased stability and firmness of the string. The increased stability also alleviates the need for other stabilizing measures, such as steel frames and the like.

[0019]By adjusting the distance between the springs within the strings, i.e. adjusting the linear density, the firmness of the strings can be varied. Generally, the higher the linear density of springs in a string, the greater the firmness of the string.

[0020]In a preferred embodiment, the sum of the largest diameters for all the springs in the string exceeds a total length of the string for each string of the second type. In such an embodiment, the distance between adjacent springs in the strings is negative, so that at least the largest turns or convolutions of the adjacent springs overlap each other, when seen in a length direction or axial direction of the springs. Preferably, the overlap, corresponding to the negative separation distance, is relatively pronounced, such as being in the range of 5 mm or more, and preferably 1 cm or more, and even more preferably 2 cm or more. Differently put, the overlap is preferably in the range of 3-15% of the largest diameter of the springs, and most preferably in the range of 5-10% of the largest diameter of the springs.

[0021]In an embodiment, the first linear density may be in the range of 12-16 springs/m, and preferably 13-15 springs/m, such as about 15 spring/m. Correspondingly, the second linear density may be in the range of 17-25 springs/m, and preferably 18-23 springs/m, and most preferably 19-22 springs/m.

[0022]In an embodiment, the second linear density is at least 10% greater than the first linear density, and more preferably at least 15%, and most preferably at least 20%.

[0023]Due to the pronounced overlap of the turns/convolutions of the adjacent springs in the second type strings, the turns/convolutions will not change places in the length direction of the springs even upon compression. Hereby, any clicking sound etc., which may otherwise arise as the turns/convolutions change places, is avoided. Further, the overlapping turns/convolutions will also limit the independent resilience of the springs, so that compression of a single spring will also lead to at least some compression also of neighboring, adjacent springs. Generally, independent resilience is one of the great advantages of mattresses of pocket type and leads to a better load distribution over the mattress surface. However, when used e.g. along edges of the mattress etc., the need for independent resilience is limited, and the reduced independent resiliency instead in an advantageous manner adds to the increased firmness of the string.

[0024]The new pocket spring mattress can be produced very cost-efficiently, and e.g. lends itself for fully automatic or semi-automatic production. Further, since the new mattress can be produced with only one type of springs, or with only a few different types of springs, and with strings of the same or similar type, but later modified to obtain the difference in linear spring density, production becomes relatively simple and cost-effective.

[0025]As will be discussed more thoroughly in the following, the strings of the second type may provide stabilization and smoother sides to the mattress, thereby making the sides smooth, planar and visually attractive. This makes the addition of foam material, padding and the like redundant and unnecessary. This simplifies production of the new mattress even further and makes the new mattress even more cost-effective.

[0026]The increased stabilization provided by the second type strings also makes additional stabilization elements, such as steel frames, unnecessary. This also makes production simpler and more cost-effective, and also makes the mattress suitable for vacuum pressing and rolling, which simplifies handling and transportation of the mattress.

[0027]The new mattress is also more sustainable and environmentally friendly than previously known mattresses. In particular, it may be produced with a very limited amount of different materials, making the mattresses easy to recycle. In their simplest forms, the mattress may contain only coil springs of e.g. metal and fabric forming the pockets and the strips, made of e.g. nonwoven fabric.

[0028]In an embodiment, at least one spring is positioned in each of said pockets in each of the strings of the second type. In a preferred embodiment, each pocket of said second type strings contains one and only one spring. However, alternatively, some or all pockets may contain two or more springs. It is also feasible to provide some empty pockets in a string, e.g. for enabling curving of the string at corners of the mattress. In such an embodiment, a string may be arranged in a first direction, such as a length direction of the mattress, and continue in a second direction, such as a width direction of the mattress, and with the transition formed by an empty pocket.

[0029]Additionally, or alternatively, at least one spring may be positioned in each of said pockets in each of the strings of the first type. In a preferred embodiment, each pocket of said first type strings contains one and only one spring. However, alternatively, some or all pockets may contain two or more springs.

[0030]In an embodiment, all springs in the strings of the first type and strings of the second type are substantially identical. This means that only one type of spring may be used for the entire mattress, which greatly facilitates production. By substantially identical is here meant that the springs are identical, apart from possible small deviations due to manufacturing tolerances, etc.

[0031]In an embodiment, at least some, and preferably all, of the springs are barrel-shaped. In an embodiment, all springs in the strings of the second type are barrel-shaped. In barrel-shaped springs, each spring has upper and lower end turns and a plurality of central convolutions between said end turns, at least one of the central convolutions having a barrel diameter greater than the diameters of the other convolutions of the spring. It has been found that such a shape makes it easier to densify the strings, and also provides a smoother and flatter upper and lower surface, and also lowers the risk of sound from the contacting springs. However, alternative spring shapes are also feasible, such as an hourglass shape, with a waist, or cylindrical shapes.

[0032]In an embodiment, all springs of the second type strings have the same wire thickness, i.e. the same gauge wire, and preferably, all springs in both the first and second type strings have the same thickness.

[0033]The second type of strings, i.e. strings having a higher linear density, may be arranged in various ways within the mattress, to provide various desired properties to the mattress. For example, the second type strings may be arranged and used to provide zones or sections of different firmness in the pocket spring mattresses, e.g. to provide an edge support in the form of firmer pockets around the whole or part of the perimeter of the pocket spring mattress, or to provide zones of varying firmness along the length of the mattress, to improve comfort and suit the needs of different users.

[0034]The provision of springs and pocket units with varying properties in a pocket spring mattress may be referred to as posturization or zoning. Posturization/zoning may provide multiple zones or sections of differing firmnesses within the mattress. For example, the middle regions of the mattress, which typically support a person's torso, often require a firmer more resilient support while other areas of the mattress which support the feet and head of a person require a softer feel.

[0035]In an embodiment, at least one string of the second type is arranged along one or more perimeter sections of the mattress. For example, in one embodiment, the strings of the first type are arranged in parallel and connected together to form a core of the mattress, and one to three strings of the second type are arranged in parallel with and connected to the strings of the first type on opposing side of said core. Hereby, a firm perimeter is formed along the sides of the mattress. Such firm sides are of advantage when e.g. using the sides for sitting, and also provides a boarder preventing the user from falling out of the bed when lying and moving on the mattress. The pocket spring mattress may further comprise one to three strings of the second type of strings arranged perpendicular to the strings of the first type, located on opposing end sides of the strings of the first type.

[0036]Additionally, or alternatively, the strings of the second type may be arranged in between strings of the first type, thereby forming zones with different resiliency properties in the mattress. Hereby, firmer zones, with strings of the second type, may e.g. be arranged underneath the user's buttocks and shoulders, whereas other zones, such as underlying the user's legs, feet, back and head, may contain softer strings of the first type. The strings of the second types may also have various firmness, e.g. by having higher and lower linear density, thereby e.g. providing different firmness to the firmer zones.

[0037]The stabilizing fabric strips ensure that the strings maintain the springs in the compacted, dense state of the second linear density. Each strip generally extends over and along only one string. However, strips of various shapes, dimensions and material could be contemplated.

[0038]The strips are preferably made of the same material as the fabric forming the strings, such as a nonwoven fabric. The fabric is preferably weldable. However, different fabrics may also be used, as well as strips made of plastic, etc.

[0039]In an embodiment, each stabilizing fabric strip has a length extension corresponding to the length of the string to which it is connected. Here, the stabilizing fabric strip may extend over the entire string, providing maximum stabilization. In such an embodiment, the strip may also be connected and attached, e.g. by welding or adhesion, to each pocket along the string.

[0040]In an embodiment, each stabilizing fabric strip is connected to all pockets in the string to which it is connected.

[0041]However, in alternative embodiments, the strip may have a shorter length extension, e.g. extending only over a number of pockets. In such an embodiment, the linear density of springs may vary along the length of the string, providing some sections with the first linear density of springs and other sections with the second linear density of springs. This may e.g. be useful in creation of zones with varying firmness in the mattress. The sections with the second density of springs may also be arranged close to one or both ends of the strings, e.g. for creating a firmer perimeter along the end sides of the mattress.

[0042]In an embodiment, the one or more stabilizing fabric strip is connected to the fabric of the string overlying the top and bottom of the pockets in the string. Hereby, stabilization is provided along both an upper and lower side of the string. However, alternatively, a strip(s) may be arranged only on one side, such as only on a top side or bottom side of the string.

[0043]Embodiments where strips are arranged on both a top and bottom side of the string may be realized by separate strips being arranged on the top and bottom side, respectively. Thus, a first strip may be arranged extending over the top side of the string, and a second strip may be arranged extending over the bottom side of the string. The first and second strips may be parallel to each other and may have the same length and width extensions. However, it is also possible to use strips with different properties on top and bottom side, such as using wider strips on one side and more narrow strips on the other.

[0044]It is also feasible to use a wider strip which is folded over the string, thereby extending over both the top and bottom side. In such an embodiment, the stabilizing fabric strip may comprise a first part extending along a top of the string, a second part extending along a bottom of the string, and an intermediate part extending along a side of the string. Attachment of a single strip is generally easier than attachment of several strips, which facilitates production. Further, this single strip provides further enhanced stability, in particular in other directions than in the length direction of the string, such as in lateral directions. Still further, the intermediate part extending along the side of the string provides a smooth and flat surface, which is visually appealing and further alleviates the need for additional padding and the like.

[0045]In an embodiment, the pocket spring mattress may comprise a pair of strings of the second type being arranged in parallel and attached to each other, whereby the stabilizing fabric strips on the pair of strings are arranged so that the intermediate parts extending along the sides of the strings are arranged along the sides of the strings facing away from each other. In such an arrangement, the two strings of the second type together form a very stable beam-like structure, which has great stability in essentially all directions.

[0046]In any of the embodiments described above, the strings may be oriented transversely or longitudinally. A longitudinal orientation is generally preferred for mattresses where the strings of the second type are arranged as edge supports along the perimeter of the mattress, whereas a transversal orientation is generally preferred for mattresses where the strings of the second type are arranged to provide longitudinally separated zones of varying firmness.

[0051]According to this embodiment, similar specific features and advantages as discussed in relation to the foregoing are obtainable.

[0052]The provision of strings may comprise manufacturing of an endless string of pocketed coil springs, which is subsequently, or during manufacturing, cut into suitable lengths. The strings of the second type may be formed of strings of the first type, which are compacted and stabilized in the compacted state with the stabilizing fabric.

[0053]Compacting of the string into the compacted state, with the second linear spring density, can e.g. be made by pushing a non-compacted string, e.g. having the first linear spring density, into a channel or the like, where the friction between the channel walls and the string provides compacting of the string. The stabilizing fabric may at the same time be feed into the channel, from openings in one or more of the walls of the channel, such as from the bottom. Adhesive may be applied to the stabilizing before entering the channel, on one or more sides of the stabilizing fabric arranged to be in contact with the string.

[0054]Other ways of compacting the string are also feasible, such as manually, or in other automated ways. For example, a non-compacted string may be feed through one or more conveyor belts exerting compacting forces to the pockets of the strings.

[0055]For assembling the mattress, each string is connected to at least one adjacent string, e.g. with adhesive. In the assembling, parallel strings may first be connected to each other in a side-by-side arrangement, as in conventional production of pocket spring mattresses. However, in this process, strings of the first and second type may be used interchangeably, thereby e.g. arranging 1-3 strings of the second type towards one or both of the sides, to form a mattress perimeter of increased firmness and stability. In such a case, additional strings of the second type may subsequently be arranged in a transverse direction and connected to the end sides of the mattress.

[0056]These and other features and advantages of the present invention will in the following be further clarified with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0057]The present invention will be described in more detail with reference to the appended drawings, showing currently preferred embodiments of the invention.

[0058]FIG. 1 is a schematic top view of a part of a mattress in accordance with an embodiment.

[0059]FIG. 2 is a schematic top view of a part of a string having sections with different linear densities of springs.

[0060]FIGS. 3a-c are schematic cross-sectional side views of strings of the second type, seen in the length direction of the strings.

[0061]FIGS. 4a-c are schematic cross-sectional side views of pocket spring mattresses having strings of the first and second type, seen in the length direction of the strings.

[0062]FIG. 5 is a schematic cross-sectional side view of a string of the second type, seen in the width direction of the string.

[0063]FIGS. 6a-c are schematic top views of pocket spring mattresses having strings of the first and second types, in accordance with various embodiments.

[0064]FIG. 7 is a schematic top view of pocket spring mattresses having strings of the first and second types arranged in lateral directions, in accordance with an embodiment.

[0065]FIG. 8 is a schematic top view of a double pocket spring mattress in accordance with an embodiment.

[0066]FIGS. 9a-c are views in perspective and from the side of strings of the first type, in accordance with an embodiment.

[0067]FIG. 10 is a perspective view of strings of the first type, in accordance with another embodiment.

[0068]FIGS. 11a-b are views in cross-section and perspective of strings of the first type, in accordance with another embodiment.

[0069]FIGS. 12a-b are views in perspective and in cross-section of strings of the first type in accordance with yet another embodiment.

[0070]FIGS. 13 and 14 are cross-sectional views of strings of the first type in accordance with a further embodiment.

[0071]FIG. 15 is a schematic side view of an apparatus for compacting strings and production of strings of the second type, in accordance with an embodiment.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

[0072]In the following detailed description, preferred embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention.

[0073]FIG. 1 shows a portion of a pocket spring mattress 1 in accordance with an embodiment of the present invention in an exemplifying manner.

[0074]The mattress 1 comprises a plurality of strings 2a, 2b interconnected side by side, and each string 2a, 2b comprises a plurality of continuous casings 3. Within each casing 3, i.e. pocket, there is an enclosed coil spring 4 (see e.g. FIG. 3a), the springs 4 having spiral turns with a diameter of approximately 2 to 10 cm, and preferably 6 cm.

[0075]Each of the strings comprise first and second opposed plies of fabric and a plurality of pockets formed along a length of the string by a longitudinal seam and transverse seams joining said first and second plies. At least some of the pockets, and preferably all pockets, within each string accommodate a coil spring

[0076]The mattress comprises a plurality of strings of springs, each string joined to at least one adjacent string. The strings can be connected by adhesive, arranged in lines, dots, or in other ways. Other ways of connecting the strings are also feasible, such as by welding, etc.

[0077]At least some of the strings may be arranged parallel to each other, extending e.g. in the length direction of the mattress. Alternatively, as will be exemplified further below, the strings may instead be arranged in the width direction of the mattress, or be arranged both in a length and width direction.

[0078]The strings include strings of a first type and strings of a second type, i.e. first type strings 2a and second type strings 2b. The strings 2a of the first type have a first linear density of springs and the strings 2b of the second type have at least in a section thereof and preferably over their entire length, a second linear density of springs. The second density of springs is greater than the first linear density of springs, thereby making the strings 2b of second type more compact than the strings 2a of the first type.

[0079]In the illustrative example of FIG. 1, two strings 2b of the second, compact type are arranged at the upper end. These strings may be exterior strings, forming a boarder or perimeter of the mattress. Connected to these are a number of strings 2a of the first, non-compacted type. These strings may be interior strings, forming an inner core of the mattress.

[0080]All strings preferably have the same linear density of springs over their entire extension, so that some strings 2a have uniform distribution of springs to provide the first linear density of springs, and some strings 2b have a uniform distribution of springs to provide the second linear density of springs.

[0081]In order to maintain the compactness and provide stability to the strings 2b of the second type, each string 2b of the second type comprises at least one stabilizing fabric strip 5 connected to the fabric of said string over at least a part of the extension of the string, the stabilizing fabric strip(s) being arranged to extend solely along a surface of the string.

[0082]The provision of at least one stabilizing fabric strip 5 connected to the fabric 3 of the strings 2b of the second type, over at least a part of the extension of the string, ensures that the compactness, i.e. the high linear density of springs, is maintained and secured over time. The stabilizing fabric strip(s) 5 also contributes to an overall increased stability and firmness of the string. The increased stability also alleviates the need for other stabilizing measures, such as steel frames and the like.

[0083]The strips 5 are preferably made of the same material as the fabric forming the strings 2a, 2b, such as a nonwoven fabric. The fabric is preferably weldable. However, different fabrics may also be used, as well as strips made of plastic, etc.

[0084]Each stabilizing fabric strip may have a length extension corresponding to the length of the string to which it is connected. Hereby, the stabilizing fabric strip may extend over the entire string, providing maximum stabilization. In such an embodiment, the strip may also be connected and attached, e.g. by welding or adhesion, to each pocket along the string.

[0085]However, as schematically illustrated in FIG. 2, it is also feasible to have sections with different linear density of springs within a string 2b of the second type, such as sections 2a′ having the first linear density of springs in one or more sections and sections 2b′ having the second linear density of springs in one or more other sections. Thus, in such embodiments, the strip 5 may have a shorter length extension, e.g. extending only over a number of pockets. Such different sections may e.g. be useful in creation of zones with varying firmness in the mattress. The sections with the second density of springs may also be arranged close to one or both ends of the strings, as e.g. in the illustrative example of FIG. 2, e.g. for creating a firmer perimeter along the end sides of the mattress.

[0086]Each strip 5 generally extends over and along only one string. However, strips of various shapes, dimensions and material could be contemplated. Such embodiments will now be discussed with reference to FIGS. 3a-c.

[0087]In an embodiment, as illustrated in FIG. 3a, stabilizing fabric strips 5 are connected to the fabric of the string 2b overlying the top and bottom of the pockets in the string. Hereby, stabilization is provided along both an upper and lower side of the string 2b. However, alternatively, stabilizing strips 5 may be arranged only on one side, such as only on a top side or only on a bottom side of the strings.

[0088]In the embodiment of FIG. 3a, strips are arranged on both a top and bottom side of the string 2b, and this is realized by separate strips 5 being arranged on the top and bottom side, respectively. Thus, a first strip 5 may be arranged extending over the top side of the string, and connected to all the pockets on the upper side, and a second strip 5 may be arranged extending over the bottom side of the string, and connected to all the bottom side of the pockets. The first and second strips 5 may be parallel to each other and may have the same length and width extensions. However, it is also possible to use strips with different properties on top and bottom side, such as using wider strips on one side and more narrow strips on the other.

[0089]It is also feasible to use a wider strip 5′, as illustrated in FIG. 3b, which is folded over the string 2b, thereby extending over both the top and bottom side. In such an embodiment, the stabilizing fabric strip may comprise a first part 5′a extending along a top of the string, a second part 5′b extending along a bottom of the string, and an intermediate part 5′c extending along a side of the string. Thus, the strip hereby encloses 3 out of 4 sides of the string, when seen in cross-section, in a shape similar to a C or a bracket. Attachment of a single strip is generally easier than attachment of several strips, which facilitates production. Further, this single strip 5′ provides further enhanced stability compared to the embodiment of FIG. 3a, in particular in other directions than in the length direction of the string, such as in lateral directions. Still further, the intermediate part 5′c extending along the side of the string 2b provides a smooth and flat surface, which is visually appealing and further alleviates the need for additional padding and the like.

[0090]It is also feasible, as illustrated in FIG. 3c, to provide an even wider strip 5″, which may be arranged to encircle the entire string 2b. In such an embodiment, the stabilizing fabric strip may comprise a first part 5″a extending along a top of the string, a second part 5″b extending along a bottom of the string, an intermediate part 5″c extending along a side of the string and a second intermediate part 5″d, extending along the opposite side of the string 2b. Such a fully enclosing single strip 5″ provides further enhanced stability compared to the previously discussed embodiments, in particular in other directions than in the length direction of the string, such as in lateral directions.

[0091]For all the previously discussed embodiments, the compacted string 2b of the second type have a non-compacted length prior to compacting and prior to attachment of the stabilizing strips. Thus, even in situations where the stabilizing strip has a length corresponding to the length of the compacted string, this length of the stabilizing strip is shorter, and preferably much shorter, than the initial non-compacted length of the same string.

[0092]The strings of the second type may be arranged at the perimeter of the mattress, as exterior strings, to provide enhanced firmness and stability to the boarder of the mattress.

[0093]In one embodiment, as illustrated in FIG. 4a, one string 2b of the second type is arranged at the perimeter of a core formed by strings 2a of the first type. In this embodiment, the string 2b has a strip of the bracket type, as discussed in the foregoing in relation to FIG. 3b. The intermediate part 5′c is preferably arranged to be facing away from the interior strings 2a of the first type, thereby forming a flat and smooth outer surface of the mattress side.

[0094]In another embodiment, as illustrated in FIG. 4b, two strings 2b of the second type are arranged at the perimeter of a core formed by strings 2a of the first type. In this embodiment, both the strings 2b have a strip of the bracket type, as discussed in the foregoing in relation to FIG. 3b. The intermediate parts 5′c are here arranged to be facing away from the interior strings 2a of the first type, thereby forming a flat and smooth outer surface of the mattress side, and the two strings 2b together forming increased firmness and stability to the mattress boarder.

[0095]In yet another embodiment, as illustrated in FIG. 4c, two strings 2b of the second type are again arranged at the perimeter of a core formed by strings 2a of the first type. Also in this embodiment the strings 2b have a strip of the bracket type, as discussed in the foregoing in relation to FIG. 3b. In this embodiment, the outermost string has the intermediate part 5′c arranged to be facing away from the interior strings 2a of the first type, thereby forming a flat and smooth outer surface of the mattress side. The innermost string 2b has the intermediate part 5′c facing in the opposite direction, i.e. away from the outermost string 2b, and towards the core of the strings 2a of the first type. Thus, the intermediate parts 5′c of the two strings 2b are here arranged at opposite sides, and facing away from each other. In such an arrangement, the two strings of the second type together form a very stable beam-like structure, which has great stability in essentially all directions.

[0096]Since the strings of the second type have a greater linear density of springs than the strings of the first type, the strings of the second type are generally firmer than the strings of the first type. Due to the difference in linear density of the springs, this effect can be accomplished with the same springs, and/or with strings formed in the same way.

[0097]By adjusting the distance between the springs within the strings, i.e. adjusting the linear density, the firmness of the strings can be varied. Generally, the higher the linear density of springs in a string, the greater the firmness of the string. Thus, the strings of the second type may have different linear spring density, and consequently different firmness. The strings of the second type may have the same linear spring density in each mattress, but may differ between mattresses. However, it is also feasible to use strings of the second type having different linear spring density and firmness within the same mattress. For example, strings with a greater linear spring density may be used around the boarder of the mattress, whereas strings of lower linear spring density, but still exceeding the first linear spring density, may be used in specific zones and the like.

[0098]In a preferred embodiment, the sum of the largest diameters for all the springs in the string exceeds a total length of the string for each string of the second type. In such an embodiment, the distance between adjacent springs in the strings is negative, so that at least the largest turns or convolutions of the adjacent springs overlap each other, when seen in a length direction or axial direction of the springs.

[0099]Such an embodiment is illustrated in FIG. 5. Here, the string 2b comprises a longitudinal seam 6 and transversal seams 7, separating individual pockets. All, or at least most, of the pockets are accommodating coil springs 4. In the illustrative example, the string has been compacted, thereby forcing the convolutions of adjacent springs into each other, in a nested arrangement. As a consequence, the originally straight transversal seams 7 will in the compacted state occur along a curved, meandering path.

[0100]Preferably, the overlap, corresponding to the negative separation distance, is relatively pronounced, such as being in the range of 5 mm or more, and preferably 1 cm or more, and even more preferably 2 cm or more. Differently put, the overlap is preferably in the range of 3-25% of the largest diameter of the springs, and most preferably in the range of 10-20% of the largest diameter of the springs.

[0101]In an embodiment, the first linear density may be in the range of 12-16 springs/m, and preferably 13-15 springs/m, such as about 15 spring/m. Correspondingly, the second linear density may be in the range of 17-25 springs/m, and preferably 18-23 springs/m, and most preferably 18-22 springs/m.

[0102]In an embodiment, the second linear density is at least 10% greater than the first linear density, and more preferably at least 15%, and most preferably at least 20%.

[0103]Due to the pronounced overlap of the turns/convolutions of the adjacent springs in the second type strings, the turns/convolutions will not change places in the length direction of the springs even upon compression. Hereby, any clicking sound etc., which may otherwise arise as the turns/convolutions change places, is avoided. Further, the overlapping turns/convolutions will also limit the independent resilience of the springs, so that compression of a single spring will also lead to at least some compression also of neighboring, adjacent springs.

[0104]As will be discussed in the following, the firmer strings of the second type may be used in various ways, such as for providing an edge support around part of, or the whole, mattress, to provide zones having various firmness in the mattress, to provide separation between different parts or sections of the mattress, etc. Thus, the second type of strings, i.e. strings having a higher linear density, may be arranged in various ways within the mattress, to provide various desired properties to the mattress.

[0105]For example, the second type strings may be arranged and used to provide zones or sections of different firmness in the pocket spring mattresses, e.g. to provide an edge support in the form of firmer pockets around the whole or part of the perimeter of the pocket spring mattress. Such embodiments are illustrated in FIGS. 6a-c.

[0106]In the embodiment of FIG. 6a, an inner core is formed by strings 2a of the first type, arranged parallel to each other in a side-by-side arrangement, and with firmer strings 2b of the second type arranged at the outer sides of the core. In the illustrative example, a single string 2b of the second type is arranged on each side of the core. However, alternatively, 2 or 3, or even more strings 2b of the second type may be arranged at each side. Further, the mattress may also have different numbers of strings of the second type at the opposite sides, e.g. when the mattress is intended for use together with another mattress in a double bed. In such embodiments, string(s) 2b of the second type may also be arranged only on one side of the mattress.

[0107]In the embodiment of FIG. 6a, the strings 2b of the second type are only arranged along the long sides, i.e. the major sides, of the mattress. Generally, this is where there is the greatest need for increased boarder stability. However, it is also feasible to arrange strings 2b of the second type also at the end sides, as in the embodiment illustrated in FIG. 6b. Here, strings 2b are attached to a mattress similar to the one discussed in relation to FIG. 6a, but in a transverse direction, covering the end sides of the mattress.

[0108]In this embodiment, the strings 2b of the second type surround the entire perimeter of the mattress. On each side, the number of strings 2b of the second type may be 1, 2, 3 or even more, depending on how large a firm perimeter that is needed, and the number of strings 2b of the second type on each side need not necessarily be the same on all sides.

[0109]For example, as illustrated in FIG. 6c, a greater firm perimeter may be arranged along the major side of the mattress, whereas a narrower firm perimeter may be arranged at the end sides. In the embodiment of FIG. 6c, two strings 2b of the second type are arranged along the major sides of the mattress, whereas a single string 2b of the second type is arranged at each end side.

[0110]Alternatively, a firmer boarder at the end sections may be provided by arranging sections of firmer, more compacted springs at the ends of the strings forming the inner core, as in the embodiment of FIG. 2.

[0111]Additionally, or alternatively, the strings 2b of the second type may be used to form various zones with different firmness in the mattress. Such an embodiment will now be discussed in relation to FIG. 7. Here, the strings are mainly arranged in a lateral direction, i.e. in the width direction of the mattress. In this embodiment, a first zone is provided by strings 2b′ of the second type, followed by a zone of strings 2a of the first type, a second zone of strings 2b″ of the second type, followed by a zone of strings 2a of the first type, and a third zone of strings 2′″ of the second type. The zones of increased firmness may be arranged at different positions, and more or fewer zones of increased firmness may be provided.

[0112]In the illustrative example, strings 2b of the second type are also arranged around the perimeter of the mattress, in accordance with previously discussed embodiments. However, a zoned mattress may also be provided without such a firm perimeter.

[0113]The strings of increased firmness may be the same throughout the mattress. However, the strings of the second type may also be different, providing varying degree of firmness. Thus, the strings 2b, 2b′, 2b″ and 2b′″ may be identical, similar, or different, as long as they still have a linear spring density exceeding the first linear spring density of the strings 2a of the first type. In one embodiment, all of the strings 2b, 2b′, 2b″ and 2b′″ have the same linear spring density, and the same firmness. In another embodiment, the strings 2b have a greater linear spring density than the strings 2b′, 2b″ and 2b′″. In yet another embodiment, at least some of the strings 2b′, 2b″ and 2b′″ may have different linear spring densities, and consequently different firmness.

[0114]The strings 2b of second type may also be used to form a separation between two sleeping areas in a double mattress, as in the illustrative example of FIG. 8. In this embodiment, the mattress comprises two sleeping areas, formed by strings 2a of the first type. Strings 2b of the second type are arranged as a frame around the mattress, in the same way as e.g. in the embodiment of FIG. 6b. In addition, one or more strings 2b of the second type may be arranged between the sleeping areas, thereby forming a firmer area between these areas. The strings 2b of the second type consequently provide an individual firmer frame or boarder around each of the sleeping areas.

[0115]In any of the embodiments described above, the strings may be oriented transversely or longitudinally. A longitudinal orientation, i.e. an orientation where at least most of the strings are arranged in the length direction of the mattress, is generally preferred for mattresses where the strings of the second type are arranged as edge supports along the perimeter of the mattress, whereas a transversal orientation, i.e. where at least most of the strings are arranged in a width direction of the mattress, is generally preferred for mattresses where the strings of the second type are arranged to provide longitudinally separated zones of varying firmness.

[0116]In an embodiment, all springs in the strings of the first type and strings of the second type are substantially identical. This means that only one type of spring may be used for the entire mattress, which greatly facilitates production.

[0117]In an embodiment, at least some, and preferably all, of the springs are barrel-shaped. In an embodiment, all springs in the strings of the second type are barrel-shaped. In barrel-shaped springs, each spring has upper and lower end turns and a plurality of central convolutions between said end turns, at least one of the central convolutions having a barrel diameter greater than the diameters of the other convolutions of the spring. It has been found that such a shape makes it easier to densify the strings, and also provides a smoother and flatter upper and lower surface, and also lowers the risk of sound from the contacting springs. However, alternative spring shapes are also feasible, such as an hourglass shape, with a waist, or cylindrical shapes.

[0118]In an embodiment, all springs of the second type strings have the same wire thickness, i.e. the same gauge wire, and preferably, all springs in both the first and second type strings have the same thickness.

[0119]The strings 2a of the first type may be of any known type of pocket strings used in pocket spring mattresses.

[0120]For example, the strings 2a of the first type may be of the type disclosed in U.S. Pat. No. 9,314,110 by the same applicant, said document hereby being incorporated in its entirety by reference. This pocket string type is illustrated in FIGS. 9a-c. The pocket strings comprise strings made of folded fabric, connected by a longitudinal seam 6, arranged either at the top or bottom, as in FIG. 9b, or at the side, as in FIG. 9c. Pockets in the strings are defined by transversal seams 7, and each pocket contains a coil spring 4. In order to provide a flat, smooth and uniform top surface, the fabric between the springs is folded down and connected through the lateral seams 7.

[0121]As another example, the strings 2a of the first type may be of the type disclosed in U.S. Pat. No. 7,048,263 by the same applicant, said document hereby being incorporated in its entirety by reference. This pocket string type is illustrated in FIG. 10. The pocket strings comprise strings made of folded fabric and with pockets in the strings defined by transversal seams 7, similar to the embodiment of FIGS. 9a-c. Here, however, the lateral seams are provided as double seams, with a separation distance between them, thereby providing a separation between the pockets and the coil springs 4.

[0122]As yet another example, the strings 2a of the first type may be of the type disclosed in U.S. Pat. Nos. 10,098,474 and 11,793,320 by the same applicant, said documents hereby being incorporated in their entirety by reference. This pocket string type is illustrated in FIGS. 11a and 11b. The pocket strings comprise strings made of folded fabric and with pockets in the strings defined by transversal seams 7, similar to the previously discussed embodiments. Here, however, a piece of foam material 81 or padding is arranged on top of springs 4, i.e. above the uppermost turn 41. The piece of foam material 81 is arranged within a cavity 82 formed by an additional piece of fabric 83, which may be connected to the rest of the string via the lateral seams 7.

[0123]As a further example, the strings 2a of the first type may be of the type disclosed in U.S. Pat. Nos. 6,591,438, 7,748,065, 8,087,114 and 10,973,340 by the same applicant, said documents hereby being incorporated in their entirety by reference. Such a pocket string type is illustrated in FIGS. 12a and 12b. The pocket strings comprise strings made of folded fabric and with pockets in the strings defined by longitudinal seams 6 and transversal seams 7, similar to the previously discussed embodiments. Here, however, the fabric arranged overlying the top and bottom turns of the springs 4 have been brought into contact with each other, through the springs, and connected together, e.g. by a weld spot 9, thereby forming a pocket shaped as a toroid or doughnut.

[0124]As still another example, the strings 2a of the first type may be of the types disclosed in U.S. Pat. No. 12,064,036 by the same applicant, said document hereby being incorporated in its entirety by reference. Such pocket string types are illustrated in FIGS. 13 and 14. The pocket strings comprise strings made of folded fabric and with pockets in the strings defined by longitudinal seams and transversal seams, similar to the previously discussed embodiments. Here, however, a piece of foam material 91 is arranged through each pocket and through each spring, and extending out at the top and bottom side. The protruding parts form foam layers at the top and bottom of the strings. In the embodiment of FIG. 13, the strings are generally of the type discussed in relation to FIGS. 12a and 12b, but with an opening provided through the pieces of fabric being connected inside the springs. In the embodiment of FIG. 14, the fabric overlying the top and bottom turns of the springs are not brought together, but are still provided with openings 92 to allow the piece of foam material 91 to extend through the springs.

[0125]The above-discussed embodiments of pocket strings are useable as pocket strings of the first type, but other pocket string types may also be used.

[0126]The pocket strings of the second type may be of the same type as the pocket strings of the first type, but compacted to have a greater linear spring density. However, it is also feasible to use different pocket string types for the strings of the first type and the strings of the second type.

[0131]The provision of strings may comprise manufacturing of an endless string of pocketed coil springs, which is subsequently, or during manufacturing, cut into suitable lengths.

[0132]The strings 2b of the second type may be formed of strings 2a of the first type, which are compacted and stabilized in the compacted state with the stabilizing fabric 5, e.g. in an apparatus as illustrated in FIG. 15. Compacting of the string into the compacted state, with the second linear spring density, can e.g. be made by pushing a non-compacted string 2a, e.g. having the first linear spring density, into a channel 100 or the like, where the friction between the channel walls and the string provides compacting of the string. The stabilizing fabric 5 may at the same time be feed into the channel, from openings in one or more of the walls of the channel, such as from the bottom. Adhesive may be applied to the stabilizing before entering the channel, e.g. by an adhesive spraying device 102, on one or more sides of the stabilizing fabric arranged to be in contact with the string.

[0133]Other ways of compacting the string are also feasible, such as manually, or in other automated ways. For example, a non-compacted string may be feed through one or more conveyor belts exerting compacting forces to the pockets of the strings.

[0134]For assembling the mattress, each string is connected to at least one adjacent string, e.g. with adhesive. In the assembling, parallel strings may first be connected to each other in a side-by-side arrangement, as in conventional production of pocket spring mattresses. However, in this process, strings of the first and second type may be used interchangeably, thereby e.g. arranging 1-3 strings of the second type towards one or both of the sides, to form a mattress perimeter of increased firmness and stability. In such a case, additional strings of the second type may subsequently be arranged in a transverse direction and connected to the end sides of the mattress.

[0135]The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the number of strings of the first and second type may be varied, and many other string arrangements are feasible, to provide other zone arrangements etc. Such and other obvious modifications must be considered to be within the scope of the present invention, as it is defined by the appended claims. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting to the claim. The word “comprising” does not exclude the presence of other elements or steps than those listed in the claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.