WO2003096847A1

WO2003096847A1 - A coil spring assembly

Info

Publication number: WO2003096847A1
Application number: PCT/GB2002/002330
Authority: WO
Inventors: Ian Whitworth
Original assignee: Springform Technology Limited
Priority date: 2002-05-17
Filing date: 2002-05-17
Publication date: 2003-11-27
Also published as: AU2002302754A1

Abstract

A pocket coil spring assembly is disclosed, in which a plurality of springs are contained within a plurality of pockets, wherein the springs are aligned end to end in a string, the string comprising a plurality of rows (400, 401) of pocketed springs, the rows being positioned side by side to each other and each row extending substantially along a same direction. Springs of different types may be inserted into adjacent pockets, so that in use, under compression, a relatively firmer and relatively less firm spring may bear a same load, with force being transmitted between the relatively firm and the relatively less firm springs. The strings of springs may be arranged into a mattress (800), wherein firmer and less firm regions of the mattress are provided, and the mattress has first (801) and second (802) layers of pocketed springs.

Description

A COIL SPRING ASSEMBLY

Field of the Invention

The present invention relates to pocketed coil spring assemblies, and items manufactured therefrom.

Background to the Invention

Prior art mattresses for beds typically contain a layer of springs. The layer of springs comprises a plurality of "strings" of springs, each string comprising a plurality of pockets, each containing a spring. The pockets link together such that in use, under no load conditions, the springs are located such that a main length of each spring is substantially parallel to a main length of every other spring.

Referring to Fig. 1 herein, there is illustrated schematically part of a prior art string of springs. The string comprises a web of sheet material folded over into first and second layers 101 , 102 the first and second layers being positioned opposing each other, and joined along first and second edges 103, 104 respectively, and along a plurality of joins 105, each running transversely to the first and second joins 103, 104, to form a plurality of pockets, within each of which is contained a respective coil spring.

The sheet material may be any suitable material having flexibility enough to allow compression and expansion of the springs within the pockets, and the joins 103, 104 along the edges and transverse joins 105, may be formed by any process which provides mechanical strength at the joins and edges, enough to contain the enclosed springs during flexing and compression of the springs. In typical prior art mattresses, the sheet material comprises a material which is capable of being ultrasonically welded, or heat welded, for example a non-woven polypropylene fabric. Referring to Fig. 2 herein, there is illustrated schematically in cutaway view, a single pocket and spring of a string. The spring 200 is enclosed in the fabric pocket 201. The fabric pocket is sealed at one edge 202, and along a join 203. Within the pocket, the spring, under conditions of no load, expands to its natural uncompressed length. The pocket dimensions and amount of sheet material may be selected such that the pocket fits closely around the spring when the spring is in an uncompressed state. The fit of the spring within the pocket is such that the spring is held in the pocket such that its lateral movement within the pocket is restrained.

Prior art strings of springs allow for a single type of spring to be enclosed in each pocket. However, for modern prior art mattresses, comprising rows of strings glued together to form an array of upstanding pocketed springs, different areas of the mattress may be designed to give different "firmness". Differing areas of firmness are achieved by substituting different springs having a different elastic modulus in different areas of the mattress. The elastic modulus of a spring is a measure of the force required to effect a given deflection of a spring. The elastic modulus may be thought of as a measure of the "firmness" of a spring. Where pocketed coil spring assemblies are used in mattresses, the firmness of the individual springs affects the firmness of the mattress as a whole, and for individual regions of the mattress, the firmness of the springs underlying that region effects the firmness of that region. Different springs having different elastic modulae can be sealed in strings, providing firm and soft regions of the mattress. In general, because the springs extend through a whole thickness of the mattress, if the mattress is turned upside down, the firmness of the mattress is substantially the same on both sides of the mattress for equivalent regions.

Referring to Fig. 3 herein, there is illustrated schematically in a side cutaway view, an outline of a human person lying on a prior art mattress. Particular parts of the human body, for example the hips, shoulders, and head, exert more force on local regions of the mattress, than other areas for example the small of the back, or the back of the neck. Prior art mattress may be designed such that some areas where more support is needed have firmer springs whereas areas which generally require less support, may have slightly less firm springs. In the prior art mattress along a string of springs, each individual string may have a first set of springs A of a first elastic modulus, followed by a second set of springs B of a second elastic modulus, and in the general case, may have a plurality of different types of spring each of a different elastic modulus, positioned along the spring in a variety of sequences, in order to provide mattress having a required firmness profile.

In a typical prior art bed, the mattress may either rest on a plurality of wooden slats, for example in a futon type arrangement, or may rest on a sprung base. The same mattress on a sprung base, may appear softer to a user than that mattress on a firm rigid base.

Summary of the Invention

One objective of specific implementations according to the present invention is to provide an improved mattress, having a firmness profile which is not necessarily the same as between an upper surface and a lower surface of the mattress. In one orientation, having a first side facing upwards, a mattress may have a different firmness profile compared to the inverted mattress having a second, opposite side facing upwardly.

Specific implementations of the present invention provide a pocketed coil spring assembly comprising a plurality of springs inserted into a plurality of pockets linked together to form a string, whereby in a direction transverse to a main length of the string, a plurality of pockets are provided, each pocket containing a spring. Springs having different elastic modulae may be contained in the plurality of pockets in any combination.

In one embodiment, a string of springs comprises a first plurality of pockets extending in a first row along a first side of the string, and a second plurality of pockets extending in a second row along a second side of the string. Each pocket of the first plurality is aligned with a corresponding respective pocket of the second plurality. The two sets of pockets are joined together by a substantially central join, extending along the main length of the string.

According to a first aspect of the present invention there is provide a coil spring assembly comprising:

a plurality of coil springs;

at least one sheet material, said sheet material forming a plurality of individual pockets for containing said plurality of coil springs;

said plurality of pockets being arranged in first and second rows, wherein in each of said first and second rows are arranged a plurality of springs, wherein said springs of said first row are arranged end to end with said springs of said second row; and

and at least one said spring of said first row is of a different type to at least one said spring of a said second row.

According to a second aspect of the present invention is provided a string of coil springs, said string comprising:

a first web of sheet material, said first web of sheet material forming a first skin of said string;

a second web of sheet material, said second web of sheet material forming a second skin of said string; and

a plurality of coil springs, said plurality of coil springs positioned between said first and second webs of sheet material, wherein said plurality of coil springs are arranged in a plurality of rows extending along a length of said string and a plurality of columns extending along a height of said string;

said first and second webs are joined such as to enclose each said coil spring in an individual pocket formed between said first and second webs of sheet material; and

said plurality of coil springs comprise at least one coil spring of a first type and at least one coil spring of a second type.

Said first and second webs may be formed from a same sheet of material or from two individual separate sheets of material

According to a third aspect of the present invention there is provided pocketed coil spring assembly in which a plurality of substantially co-axially aligned coil springs are enclosed in a plurality of pockets, wherein said pockets are sealed between said coil springs, and in which at least two of said coil springs are of different types to each other.

According to a fourth aspect of the present invention there is provided a mattress comprising a plurality of pocketed coil springs, said mattress comprising:

a first plurality of said pocketed coil springs arranged in a first layer;

a second plurality of said pocketed coil springs arranged in a second layer, wherein said first layer overlays said second layer;

wherein said mattress is designed such that said plurality of coil springs of said first layer comprise at least one coil spring of a substantially different type to at least one coil spring of said second layer. Other features of the invention are as recited in the claims herein

Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Fig. 1 illustrates schematically a prior art string comprising a plurality of pocketed coil springs;

Fig. 2 illustrates schematically a cutaway view of a single pocketed coil spring of the prior art string of Fig. 1 ;

Fig. 3 illustrates schematically in cutaway view a prior art mattress fabricated from a plurality of prior art strings and having first and second firmness regions, showing different pressure regions applied to the mattress and to individual springs in the mattress, in use;

Fig. 4 illustrates schematically a string of coil springs according to a first specific implementation of the present invention, having first and second rows of pockets containing first and second rows of coil springs respectively;

Fig. 5 illustrates schematically a section across a width of the string of Fig. 4, showing first and second pockets, containing first and second coil springs respectively;

Fig. 6 illustrates schematically in cutaway view, the first and second pockets of Fig. 5, viewed in a direction along a main length of the string; Fig. 7 illustrates schematically in cutaway plan view, first and second pockets of the string of Fig. 4, illustrating differing sized springs, and welds between first and second layers of sheet material comprising the string;

Fig. 8 illustrates schematically in cutaway side view, a second mattress according to a second specific embodiment of the present invention, the second mattress comprising a plurality of strings of springs according to the first specific embodiment, illustrating pressure regions applied to the mattress in use;

Fig. 9 illustrates schematically in side view, a first arrangement of coil springs within the string of Fig. 4 according to a third specific implementation of the present invention;

Fig. 10 illustrates schematically in side view, a second arrangement of coil springs in the first and second rows of pockets of the string of Fig. 4, according to a fourth specific implementation of the present invention;

Fig. 11 illustrates schematically a third mattress according to a fifth specific implementation of the present invention, the third mattress having first and second layers of springs, wherein a first layer of springs has regions of springs of differing firmness, to provide a first firmness profile of a mattress;

Fig. 12 illustrates schematically a fourth mattress according to a sixth specific implementation of the present invention, the fourth mattress having upper and lower layers of springs, wherein an upper layer of springs has first, second and third regions of firmness achieved by substitution of first, second and third spring types in the upper layer of springs; and

Fig. 13 illustrates schematically a fifth mattress according to a seventh specific implementation of the present invention, the fifth mattress having upper and lower layers of springs, wherein the mattress has a firmness profile comprising different bands of firmness extending across a width of the mattress, the different bands of firmness achieved by substituting spring types of a first, second, third and fourth resilience within individual strings of the mattress during manufacture, to achieve firmness regions of first, second, third and fourth firmnesses.

Detailed Description of the Best Mode for Carrying Out the Invention

There will now be described by way of example the best mode contemplated by the inventor for carrying out the invention. In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the present invention.

In this specification, the term "pocket" is used to mean an enclosure of sheet material capable of fully or partially containing a spring. The pocket may be formed of a substantially continuous sheet material, or the sheet material may have apertures or holes therein. For example the sheet material may comprise a sheet of material having a substantially continuous unbroken surface, or a netting type sheet material, having a plurality of apertures. An individual pocket is capable of containing at least one coil spring, and divides that coil spring from coil springs in other individual pockets.

In this specification, the term "web" is used to mean a length of material which has width and thickness and which forms one side of a string of springs.

In this specification, the term "string " means an assembly comprising a plurality of springs and a plurality of webs of sheet material.

Referring to Fig. 4 herein, there is illustrated schematically a "string" of springs comprising a plurality of springs contained within a plurality of corresponding respective pockets according to a first specific implementation of the present invention. A first row of pockets 400 contains a first plurality of springs. A second row of pockets 401 contains a second plurality of springs. The pockets are arranged in rows and columns, such that a first pocket of said first row aligns with a first pocket of said second row, and, in use under compression, a force applied to the first row of springs will be transmitted to the second row of springs, in a direction substantially transverse to a main length of the string.

The string is constructed as a first web of sheet material 403 and a second web of sheet material 404, the first and second webs forming the plurality of pockets, wherein each said pocket is formed from an area of said first web of said sheet material and from a second area of said second web of sheet material, the first area of sheet material and the second area of sheet material being welded together around a said spring, to form a pocket which encloses the spring. The first and second webs of sheet material are, in a best mode implementation formed from a single continuous sheet, which is folded over at a mid line along the sheet to form the first and second webs. The pockets are separated from each other by a plurality of joins between the first and second sheets of material. The sheet material may be any material which is easily fabricated into a string, and in the best mode comprises a single polypropylene sheet material which is folded over to form the first and second webs, and is ultrasonically weldable or heat weldable, thereby allowing efficient forming of the pockets, efficient insertion of the coil springs into the pockets, and sealing of the pockets once the coil springs are inserted.

Referring to Fig. 5 herein, there is illustrated schematically a first pocket 500 of a first row, and a second pocket 501 of a second row of a string. Other pockets of the string, to which the two pockets are attached, are not shown to aid clarity. In the best mode, the first and second pockets are made from a same upper web of sheet material 503 and same lower web of sheet material 504, wherein the sheet material has a central weld join 505 positioned between the two pockets, and separating a first coil spring in the first pocket from a second coil spring in the second pocket.

Around each pocket are a plurality of welded joins between the first and second webs of the sheet material. The welds may be substantially continuous welds, or may comprise a series of spot welds. Lines of welded join extend between adjacent pockets in the first row and between adjacent pockets in the second row. A plurality of individual welds in a direction transverse to a main length of the rows extend across the string, between first and second edges of the string 506, 507 respectively. A first edge join 508 extends along an edge of the entire first row, and a second edge join 509 extends along an edge of the entire second row. The central weld join 505 extends between the first and second rows of pockets, along substantially an entire length of the string.

Where a common spring wire having a same thickness and elastic modulus is used for first and second springs, but the firmness of the first and second springs are engineered to be different, the difference in firmness can be created by making the springs different dimensions. Variations in pitch, length, and diameter can be made to vary the firmness of the spring.

Known different shapes and heights include "barrel" springs, which have a shape in which first and second ends have a smaller diameter than a central portion; Bonnell type springs which are similar to an hour glass shape, having a diameter at first and second ends, which is larger than a diameter of the spring in a central region; and parallel springs which comprise a coil which is wound substantially within the confines of a cylinder, and having a same diameter or radius of turn along the whole of its length. Different coil springs may have difference dimensions, that is height, diameter and variation of diameter along a length of the spring, made of different material types, e.g. different grades of steel having different tensile strengths; have different resilience's, different pitches, different number of turns, and different thickness of wire from which they are formed, and have different elastic moduli. In the example shown, the first coil spring has a different dimension from the second coil spring. The first coil spring has a relatively larger diameter and relatively shorter length than the second coil spring which has a relatively smaller diameter and a relatively longer length. In the example shown, the volume enclosed by the pockets is substantially the same for each pocket, with the pocket adopting external dimensions dictated by the size of spring inserted inside the pocket. However, in the general case this is not essential that the first and second pockets have the same dimensions or volume, and the size of each individual pocket can be tailored to suit the size of the spring intended to be inserted into that pocket.

Alternatively, springs of a same pitch, diameter and length may be made, but using a different wire material, having a different resilience or elastic modulus, thereby providing similarly or identical sized springs, but the springs having different firmness to each other.

Referring to Fig. 6 herein, there is illustrated schematically in cutaway view a first pocket of the first row and a second pocket of the second row of a string of pockets as shown in Fig. 4 herein, as viewed in a direction along a main length of the string. First pocket 600 contains a relatively larger diameter first coil spring, and second pocket 601 contains a relatively smaller diameter second coil spring. The first and second coil springs behave differently to each other under compression, having different resilience to compression. First coil spring 602 is contained within first pocket 600, the first pocket 600 comprising a portion of a first web material 603, and a portion of a second web material 604, the first and second web materials being bonded to each other to form a plurality of joins or folds extending circumferentially around the first pocket, and the first coil spring being positioned there between, the bonding joins between the first and second web materials extending around the first coil spring substantially diametrically, across a lower end of the first coil spring to form a central join 606, a bond or fold across an upper end of the first coil spring, the bond or fold extending diametrically across said coil spring, to form a first edge join 607 and between the first edge join bond and the central join, the bonded joins extending in a direction parallel to a main axis of the first coil spring, on each of two sides of the coil spring, with the first coil spring positioned there between.

Similarly, second pocket 601 comprises a second portion 608 of the first web material and a second portion 609 of the second web material, the first and second portions of web material being bonded to each other so as to enclose the second coil spring there between, joins extending between the central join 606 at an upper end of the second spring, and a second edge join or fold 610 at a lower end of the second coil spring.

The first and second coil springs are aligned substantially along a same common central axis. In the embodiments shown, the second coil spring is offset and concentric with respect to the first coil spring. Under compression, folds 611 , 612 of the first and second web material in an area immediately surrounding central seam 606 prevent the smaller diameter second coil from sliding inside the larger diameter first coil. The folds of the sheet material between the first and second coils acts to transmit force between a lower end of the first coil spring and an upper end of the second coil spring.

Referring to Fig. 7 herein, there is illustrated schematically in cutaway view first and second pockets 700, 701 containing first and second coil springs 702,

703 respectively. The view of Fig. 7 is in a direction transverse to a main length of the string, and transverse to a main central axis of the first and/or second springs.

The first and second springs 702, 703 respectively under conditions of no loading, are aligned substantially parallel to each other, end to end. A central axis of the first spring 702 aligns approximately with a central axis of the second spring 703. A first web of material 704 is shown cutaway, revealing the first and second springs inside the respective first and second pockets, and a second web of material 705 can be seen lying underneath the first and second springs. A first edge join 706 is positioned at an upper end of first spring 702, and a second edge join or fold 707 is positioned at a lower end of second spring 703, the first and second edge joins or folds lying on opposite edges of the string. A central welded join 708 lies between an upper end of the first spring and a lower end of the second spring, separating the two springs. Along a first side of the first and second springs is welded a cross join 709 which extends between the first and second edges of the string and separates the first and second pockets from adjacent pockets, and joins the first and second web materials to form the first and second pockets. Similarly, to a second side of the first and second pockets lies a second cross join 710 which joins the first and second sheets of web material, thereby closing the first and second pockets, and dividing the first and second pockets from a next set of adjacent pockets along the string. As mentioned herein before, the welded joins may be formed using any suitable welding process. In the best mode implementation, where the sheet material comprises polypropylene, the joins are formed as welded seams using ultrasonic welding or heat welding, the seams joining the first and second sheets of web material.

Referring to Fig. 8 herein, there is illustrated schematically in cutaway side view, a second mattress 800 according to a second specific embodiment of the present invention, the mattress comprising a plurality of strings of springs, wherein each string of springs comprises a first row of pockets 801, and resting upon the first row of pockets, a second row of pockets 802.

The first row of pockets 801 contain a first plurality of springs and the second row of pockets 802 contains a second plurality of springs. The mattress comprises a plurality of strings of springs arranged in parallel, the strings bonded together using a hot melt glue process.

The pockets are arranged in an upper layer and a lower layer, where the upper and lower layers are formed from the plurality of strings bonded together in side by side relationship such that, in use, each spring under no load conditions extends with its main central axis positioned upright.

Referring to Fig. 9 herein, there is illustrated schematically a section of a string of springs shown in side view according to a third implementation of the present invention, in which a plurality of coil springs are positioned with their main axes of compression in a vertical orientation. The string comprises a first, lower row of springs 900, and second, upper row of springs 901. Illustrated is a first arrangement of springs within the two rows, wherein a first row of pockets contains a first set of springs, each spring having a first resilience A, and a second row of pockets contains a second row of springs each spring of the second row having a second resilience B, where the first resilience is different to the second resilience. Welded joins separating the individual pockets are shown as dotted lines.

The arrangement of springs shown in Fig. 9 is one possible arrangement of springs. Many such combinations are possible, and other embodiments are not restricted to springs having two types of resilience, but may have a number N of different types of spring each having a different resilience.

Referring to Fig. 10 herein, there is illustrated schematically a portion of a further string, comprising first and second rows of pockets loop 1000, 1001 respectively, wherein two different spring types having resilience A and B respectively are arranged within the plurality of pockets such that at least one spring of a first type sits on top of at least one spring of a second type, the springs separated by seam joins of the pockets, shown as dotted lines.

Referring to Fig. 11 herein, there is illustrated schematically in cutaway plan view one example of a third mattress according to a fifth specific implementation of the present invention, in which the mattress comprises first and second layers of springs, wherein said first layer of springs lies on top of said second layer of springs, the first layer of springs being shown uppermost in Fig. 11. The springs are arranged as one or a plurality of strings, each string having an upper row and a lower row of pockets containing upper and lower rows of springs respectively, wherein individual springs within the strings are varied and selected, such as to have differing resilience properties under compression. In the example shown, a first region of the mattress 1101 comprises upper layer springs of a first resilience type, and a second region of the mattress 1102 comprises a second set of springs of second resilience type on the upper layer. In the example shown, the springs of the lower layer are all of the first resilience type. Consequently, the mattress has first and second regions of firmness 1101 , 1102 respectively, where the firmness of the first region is different to the firmness of the second region.

By varying the spring type inserted into the pockets of the upper layer and/or lower layer, it is possible to fabricate a wide range of firmness profiles for different mattress.

Referring to Fig. 12 herein, there is illustrated a fourth mattress, according to a sixth specific implementation of the present invention, comprising a plurality of strings of springs, wherein each string has upper and lower rows of pockets containing upper and lower springs respectively, wherein the upper springs are varied in resilience, such that in the fabricated mattress, there exists a region of first firmness 1201, a region of second firmness 1202 corresponding to a position where a first person may lay on the mattress, and a region of third firmness 1203, corresponding to a position where a second person may lay on the mattress. In this example, it is possible to fabricate a mattress having two different firmness regions, to suit two different individuals sharing the same mattress.

Referring to Fig. 13 herein, there is illustrated a fifth mattress, according to a seventh specific implementation of the present invention, the fifth mattress having a firmness profile, achieved by variation of substitution of springs of different firmness profiles within an upper layer of springs, where the mattress has a lower layer of springs of first resilience and an upper layer of springs having individual springs of differing resilience. The mattress comprises a first region 1301 of first firmness, extending across a width of the mattress, a second region of second firmness 1302, extending across the width of the mattress at a position midway along a length of the mattress, a third region 1303 having a third firmness and extending across the width of the mattress; at a position near a lower end of the length of the mattress; and a fourth region 1304 of fourth firmness achieved by a fourth set of springs in the upper layer.

Since individual springs within individual pockets of the upper and/or lower layers of springs may be inserted in any order, there are a wide variety of firmness profiles for a mattress having upper and lower layers of springs as shown, and Figs. 11 to 13 illustrate only three possible examples.

In Figs. 4 to 13 herein there has been described strings and mattresses comprising one or a plurality of such strings, where the string has first and second rows of pockets, containing first and second rows of springs. However, there are other possible strings according to other specific implementations of the invention, having three, four or more rows of pockets running in parallel comprising a single string, where the pockets are arranged such that the springs are aligned such that a compressive force across a width of the string loads all springs in the string at a position across the string at which a compressive force is applied. In string embodiments having three rows of pockets containing three rows of strings respectively, wherein each pocket contains a single spring, a further level of complexity of firmness profile of mattress is possible compared to a two row string, by varying the type of spring enclosed in the pockets, in a wide variety of orders. Further, whist in this specification, many of the embodiments refer to two types of spring only, having first and second resilience respectively, types of spring inserted in the pocket may be varied over a wide range of spring type, provided the spring has physical dimensions suitable to fit the spring into the pocket. Variations of spring diameter, length, pitch, and material elastic modulus may be made, such that there a large variety of different spring types which may be incorporated in any one string, giving rise to a wide range of possible firmness profiles for a mattress.

Claims

Claims:

1. A coil spring assembly comprising:

a plurality of coil springs;

5 at least one sheet material, said sheet material forming a plurality of individual pockets for containing said plurality of coil springs;

said plurality of pockets being arranged in first and second rows, wherein in 10 each of said first and second rows are arranged a plurality of springs, wherein said springs of said first row are arranged end to end with said springs of said second row; and

and at least one said spring of said first row is of a different type to at least 15 one said spring of a said second row.

2. The coil spring assembly as claimed in claim 1 , wherein said first and second rows are arranged substantially side by side to each other in a direction of a said row.

20

3. The coil spring assembly as claimed in claim 1 or 2, wherein:

said first and second rows of pockets lie substantially parallel to each other, and are separated from each other by an elongate join extending between said 25 first and second rows of pockets.

4. The coil spring assembly as claimed in any one of the preceding

!) claims, comprising:

30 a first web of material and a second web of material; said first and second webs of material being arranged substantially over laying each other, forming a plurality of voids there between, said plurality of voids being separated by a plurality of joins between said first and second webs, wherein said plurality of voids comprise said individual pockets.

5. The coil spring assembly as claimed in any one of the preceding claims, wherein:

a first set of said coil springs having of a first type are located within a first set of said pockets, and a second set of said coil springs of a second type are located within a second set of said pockets.

6. The coil spring assembly as claimed in any one of the preceding claims, wherein:

a first set of coil springs and said first set of pockets are located along a first side of said assembly; and

a second set of coil springs and said second set of pockets are located adjacent said first set of coil springs and said first set of pockets, on a second side of said assembly.

7. The coil spring assembly as claimed in claim 6, wherein:

each said coil spring of said first set is aligned with a corresponding respective coil spring of said second set.

8. The coil spring assembly as claimed in any one of the preceding claims, wherein;

said first set of pockets containing a first set of coil springs are arranged in a first row; and said second set of pockets containing a second set of coil springs are arranged in a second row,

wherein said first row of pockets is aligned substantially parallel to said second row of pockets, said first and second rows of pockets being joined such that ends of said first set of coil springs are positioned opposite ends of said second set of coil springs, and in use, individual pockets of said first set align with individual pockets of said second set, such that a compression force applied across a width of said coil spring assembly is transmitted through a coil spring of said first set and through a coil spring of said second set.

9. A string of coil springs, said string comprising:

a plurality of coil springs, said plurality of coil springs positioned between said first and second webs of sheet material, wherein

said plurality of coil springs are arranged in a plurality of rows extending along a length of said string and a plurality of columns extending along a height of said string;

said first and second webs are joined such as to enclose each said coil spring in an individual pocket formed between said first and second webs of sheet material; and said plurality of coil springs comprise at least one coil spring of a first type and at least one coil spring of a second type.

10. The string as claimed in claim 9, wherein said first type of coil spring has a different compression characteristic to said second type of coil spring.

11. The string as claimed in claim 9 or 10, wherein said first coil spring type has a different elastic modulus to said second coil spring type.

12. The string as claimed in any one of claims 9 to 11, wherein said first coil spring type has a different diameter to said second coil spring type.

13. The string as claimed in any one of claims 9 to 12, wherein said first coil spring type has a different pitch to said second coil spring type.

14. The string as claimed in any one of claims 9 to 13, wherein said first coil spring type has a different length to said second coil spring type

15. The string as claimed in any one of claims 9 to 14, wherein said first coil spring type has a first resilience, and said second coil spring type has a second resilience, said first and second resiliences being substantially different to each other.

16. The string as claimed in any one of claims 9 to 15, wherein said first coil spring type is formed of a first material and said second coil spring type are formed of a second material.

17. The string as claimed in any one of claims 9 to 16, wherein said first coil spring type is formed of a first wire type of a first thickness, and said second coil spring type is formed of a second wire type of a second thickness wherein said first wire type is of a different thickness to said second wire type.

18. A pocketed coil spring assembly in which a plurality of substantially coaxially aligned coil springs are enclosed in a plurality of pockets, wherein said pockets are sealed between said coil springs, and in which at least two of said coil springs are of different types to each other.

19. A pocketed coil spring assembly as claimed in claim 18, in which at least two of the coil springs have different elastic moduli to each other.

20. A pocketed coil spring assembly as claimed in claim 18 or 19, in which at least two of the coil springs are of different types to each other.

21. A pocketed coil spring assembly as claimed in any of claims 18 to 20, in which at least two of said coil springs have different diameters to each other.

22. A pocketed coil spring assembly as claimed in any one of claims 18 to 21 , in which at least two of said coil springs have different pitches.

23. A pocketed coil spring assembly as claimed in any one of claims 18 to 22, in which at least two of said coil springs have different wire thicknesses to each other.

24. A pocketed coil spring assembly as claimed in any one of claims 18 to 23, in which at least two of the coil springs comprise different tensile strengths to each other.

25. A pocketed coil spring assembly as claimed in any of claims 18 to 24, comprising a plurality of said pockets joined together.

26. A pocketed coil spring assembly as claimed in any one of claims

18 to 25, wherein the function of the seal is to separate the coil springs.

27. A pocketed coil spring assembly as claimed in any one of claims 18 to 26 in which said coil spring assembly is suitable for use in a mattress.

28. An extended coil spring assembly comprising a plurality of pocketed spring assemblies as claimed in anyone of claims 18 to 27, wherein said fabric pockets are juxtaposed and fixed on an axis parallel to an axial plane of the coil spring.

29. An extended coil spring assembly as claimed in claim 28 in which the coil springs are arranged in a pattern within said extended coil spring assembly according to the properties of said coil springs.

30. An extended coil spring assembly as claimed claim 28 or 29, in which a set of coil springs with a first set of properties is positioned above a further set of coil springs comprising coil springs with a second set of properties, wherein first and second sets of the properties of the coil springs are different.

31. A mattress comprising a plurality of pocketed coil springs, said mattress comprising:

a first plurality of said pocketed coil springs arranged in a first layer;

wherein said mattress is designed such that said plurality of coil springs of said first layer comprise at least one coil spring of a substantially different type to at least one coil spring of said second layer.

32. The mattress as claimed in claim 31, wherein, said first layer of pocketed springs comprises at least one spring having a different firmness to at least one other spring of said first layer.

33. The mattress as claimed in claim 31 or 32, wherein said plurality of springs of said second layer comprise at least one spring having a different firmness to at least one other spring of said second layer.

34. The mattress as claimed in any one of claims 31 to 33, wherein said plurality of springs are arranged to give an effect of differing firmness across a length and width of said mattress.

35. The mattress as claimed in any one of claims 31 to 34, wherein individual said coil springs of said first layer overlay individual said coil springs of said second layer.