Pocket mattress with integrated foam material

Abstract

A spring mattress comprises a plurality of interconnected coils enclosed in a casing, the springs having a first end and a second end, and for at least one of the springs, casing portions disposed at the first and second ends of the spring connect to one another by a joint through the spring. The jointed casing portions include openings through the spring. Pieces of foam material are disposed in the openings such that a first portion of each piece of foam material extends toward the first end of the spring and a second portion of each piece of foam material extends toward the second end of the spring. Machines and methods for manufacturing such mattresses are also disclosed.

Description

[[TECHNICAL FIELD]]

[0001] The present invention relates to a spring mattress provided with springs enclosed in casings, that is, a so-called pocket mattress in which donut-shaped enclosures / pockets are formed by connecting end portions of casing material to each other via springs. The present invention also relates to a method and an apparatus for manufacturing such a mattress. [[BACKGROUND ART]]

[0002] A common method for producing spring mattresses is the so-called pocket technique. This means that the springs are enclosed in pockets, that is, the springs are individually enclosed by casing material. In this configuration, since the springs have elasticity relatively independently, they can deflect individually without affecting adjacent springs. This improves user comfort because weight is more evenly distributed over the load-bearing surface.

[0003] However, a drawback of this type of mattress is that it is difficult to provide a thin mattress. If the length of the spring is shortened but the width is not reduced accordingly, particularly when the length approaches the diameter of the spring, the spring tends to rotate inside the casing, which dramatically degrades the comfort of the mattress. When manufacturing such mattresses, existing techniques require the use of a far greater number of springs. As a result, manufacturing becomes considerably more expensive and complex. Additionally, since an excessively thin wire cannot be used, it is difficult to prevent such mattresses from becoming stiff.

[0004] For these reasons, spring mattresses could not be used in many applications requiring thinner mattresses, such as overlay mattresses and seat cushions. Even so, spring mattresses have several properties that make them desirable for use even in such situations, including excellent comfort, individual flexibility, long service life, and easy and inexpensive manufacturability.

[0005] Solutions to this problem are presented in US6591438, US7748065, and US8087114 by the same applicant. Here, by moving the ends of the casing toward each other and connecting them via springs, a spring bias is created, resulting in a very compact and useful mattress. This makes it possible to produce a very thin pocket spring mattress. A similar type of mattress is disclosed in WO2019 / 096793, also by the same applicant. Such mattresses are very useful as an additional mattress placed on top of another mattress, such as a comfort layer or topper.

[0006] However, lying directly on a pocket mattress is generally not comfortable, and to provide good sleep and rest, an additional padding layer is usually needed on top of the mattress. Such padding layers are often incorporated into the pocket mattress to form an enclosed upholstered mattress. Alternatively, a separate padding mattress may be loosely placed on top of the pocket spring mattress. However, the drawback of such an additional top layer is that it does not provide optimal pressure distribution because it reduces the individual elasticity of the pocket units.

[0007] There are also attempts to incorporate foam material into individual pocket units of pocket spring mattresses. Such attempts are disclosed, for example, in US9936815. However, these mattresses are relatively complex and have high production costs. Furthermore, it is difficult to adequately attach the foam material to the pocket units, and there is a high risk that the foam material will separate from the pocket units over time.

[0008] Therefore, the drawbacks of this mattress and similar mattresses previously proposed are that the connection of the foam / pad to the coil springs and pockets is relatively complex and costly to implement. Furthermore, there is a serious risk that the foam / pad may deform or detach and become, for example, pushed into the rotation of the coil springs. This significantly impairs both the appearance and comfort of the mattress.

[0009] Therefore, there is a need for coil springs and pocket spring mattresses with individual pockets that are easier and / or cheaper to manufacture than other prior art pocket mattresses, while still providing at least equivalent comfort. There is also a need for such coil springs and pocket spring mattresses with individual pockets that provide good elasticity and responsiveness, and that can reduce the amount of cushioning and padding material used on bedding and seating products after the spring assembly is completed. Furthermore, such coil springs and pocket spring mattresses with individual pockets need to be more robust and maintain their properties even with longer-term use. In particular, there is a need for toppers and comfort layers with such properties.

[0010] Therefore, there is still room for improvement in pocket mattresses in terms of comfort and sleep quality. Furthermore, extending the lifespan of mattresses is also generally considered necessary. [Overview of the project]

[0011] The object of the present invention is to provide a pocket spring mattress that at least partially overcomes or mitigates the above-mentioned problems, as well as a method and apparatus for manufacturing the same.

[0012] This objective is achieved by the spring mattress described in the claims, as well as a method and apparatus for manufacturing the same.

[0013] This and other objectives are achieved by a spring mattress comprising a plurality of interconnected coils enclosed in a casing, wherein the springs have a first end and a second end, and for at least one of the springs, the casing portions located at the first and second ends of the spring comprise an opening through the spring and a piece of foam material located at the opening, wherein a first portion of each piece of foam material extends toward the first end of the spring and a second portion of each piece of foam material extends toward the second end of the spring.

[0014] The casing portions located at the first and second ends of the spring may be spaced apart and may be located at or near the first and second ends of the spring. Preferably, however, the casing portions located at the first and second ends of the spring are connected to each other by a joint via the spring, and the openings are located close to each other in the joined casing portions.

[0015] Since this mattress is of a general type, as disclosed in WO2019 / 096793 (incorporated herein by reference) by the same applicant, it inherently possesses all the advantages associated with this type of mattress, such as the ability to make the mattress thin and the favorable bias of the springs. However, the mattress of the present invention offers even more advantages.

[0016] By providing openings in the interconnection sections of the casing that penetrate the pockets and springs, it has been found that a highly efficient and convenient method can be obtained for fixing the foam material to the pocket units. The openings form constrictions in the foam material, so the foam material is mechanically held in place. Furthermore, since pre-formed pieces of foam material can be inserted and assembled into predetermined positions in an already prepared mattress, very rapid and cost-effective manufacturing is possible. The pieces of foam material can only be introduced from one side of the mattress, but they spread out toward both sides of the assembled mattress. This allows the use of conventional manufacturing processes for making pocket mattresses, with only the addition of foam material as a subsequent step. For this reason, the present invention is very suitable for automated and cost-effective manufacturing, and it is relatively easy to incorporate the additional step of assembling pieces of foam material into pocket units produced using previously known and used manufacturing processes.

[0017] Furthermore, the foam material pieces do not need to be directly connected to the coil springs. Instead, the foam material is positioned at a distance from the coil springs by the casing fabric.

[0018] The foam material provides high stability and elasticity within the coil spring. Furthermore, the foam material extending from the ends of the coil spring forms the top and / or bottom surface of the foam. This makes the top and / or bottom surface and layers of the mattress flexible and comfortable, reducing the need for additional padding layers.

[0019] The present invention provides individual pocket spring units, each of which comprises a piece of foam material placed within a coil spring, preferably a piece of foam material sized to extend toward the end of the coil spring. By providing a piece of foam material within each individual pocket unit, each coil spring functions independently, resulting in a more comfortable bedding or seating product. This maintains the individual elasticity of the pockets, thus providing superior comfort and pressure distribution. In the case of such pocket units, no additional padding layer is required, because each pocket unit incorporates a cushioning pad that preferably extends beyond the end of the coil spring into the cavity formed by at least each coil spring.

[0020] Furthermore, the fact that the coil springs and foam pieces within each pocket unit are separated from each other by the casing fabric ensures that the foam material always remains in place. The casing material of the pocket units housing the coil springs prevents the foam material from shifting during use. As a result, the appearance and comfort of the mattress can be maintained even after prolonged use.

[0021] Furthermore, because the foam material is porous and air-permeable, ventilation and airflow are possible within the mattress through openings, even with the foam material present. During sleep, a large amount of moisture is lost from the body. High ventilation / airflow allows this moisture to be processed more efficiently without wetting the mattress. Moisture can be more efficiently removed from the user's body and away from the mattress. In addition, comfort and sleep quality can be improved, and a more stable sleep temperature and humidity can be ensured for the user. It also makes it easier for the user to regulate their body temperature. Moreover, by reducing moisture and humidity within the mattress, the growth and proliferation of mites, mold, bacteria, etc. are suppressed, and the mattress can be kept in a hygienic state for a longer period of time. This also reduces the risk of developing allergies. The risk of unpleasant odors is also reduced. Overall, high ventilation and airflow allow the mattress to be kept clean and hygienic for a longer period of time, thereby extending the lifespan of the mattress.

[0022] Additionally, a second opening may be provided between the springs. Such an opening could be located, for example, between four adjacent springs. Preferably, one such opening is provided in all groups of adjacent springs, or essentially in all groups. Such an additional second opening also improves the ventilation and breathability of the mattress.

[0023] The present invention is based on the recognition that, in this particular type of mattress, namely a pocket spring mattress in which casing portions located at the ends of the springs are joined to each other via the springs and have openings that penetrate the joints, the openings provide access to the entire internal cavity and both ends of the pocket unit, and the mechanical fixing of the foam elements is provided, making the arrangement of pieces of foam material very easy and efficient.

[0024] The foamed elements can be maintained in place by mechanical fastening alone. However, alternative methods of additional fastening, such as welding or bonding, may also be provided.

[0025] According to the present invention, each pocket, i.e., the casing that encloses each spring, is formed as a toroid having a donut shape that forms a circular compartment in which the spring is enclosed. Furthermore, the foam material may be formed as an hourglass having a central constriction and two inflated mushroom-shaped portions extending in opposite directions from the constriction. Due to the elasticity and flexibility of the foam material, the two shapes, i.e., the toroid shape of the casing and the hourglass shape of the foam material, can be complementary to each other to a high degree, so that the overall cross-sectional shape of the pocket unit can be circular, rectangular with rounded corners, or an intermediate shape.

[0026] At least one of the first and second portions of the foam material piece preferably extends beyond the first and second ends of the spring, respectively. In a preferred embodiment, the foam material bulges on each side of each spring. This allows the foam to provide the outermost layer of the mattress. However, it is also conceivable that the foam material extends beyond the spring end on only one side. Alternatively, the foam material may not extend beyond either end. In such embodiments, the foam material may be flush with the plane of the coil spring end rotation, or it may be located below such a plane.

[0027] The protruding pieces of the foam material may form a rounded convex upper surface and / or a rounded convex lower surface. Alternatively, the protruding pieces of the foam material may form an overall flat surface, thereby creating an overall flat and uniform mattress surface. In yet another alternative embodiment, the protruding pieces of the foam material may have a cup-shaped or concave upper surface and / or a cup-shaped or concave lower surface by having a low central portion surrounded by a periphery.

[0028] In the embodiment, each foam material piece is compressed at a portion arranged inside the opening, whereby a constricted portion on the foam material piece can be formed at said opening. The first portion and the second portion of the foam material piece expand to gradually larger cross-sectional shapes in a direction away from the opening.

[0029] A portion of the foam material that extends beyond the first end or the second end of the spring may have a cross-sectional dimension equal to or larger than the diameter of the upper end convolution or the lower end convolution of the spring that it extends through. Thereby, the extended foam material forms a relatively continuous layer above the spring.

[0030] The foam material may be composed of various materials. In a preferred embodiment, the foam is composed of urethane, latex, or a viscoelastic foam.

[0031] The foam material piece may be composed of a homogeneous material. However, the foam material piece may also be composed of a combination of different materials. Such different materials may be arranged in different layers, for example, to form a laminated structure. The layers are preferably arranged in a plane parallel to the mattress plane, that is, arranged one above the other in a direction parallel to the axial direction of the spring.

[0032] For example, a foam material piece may have a higher-priced material, such as latex or a viscoelastic material, facing one or both sides and therefore positioned as the top and / or bottom layer. The middle layer may then consist of a less expensive material, such as polyurethane. This allows the top and / or bottom layer to have different properties from the middle layer, for example, being softer, denser, or having higher viscoelasticity. Additionally or alternatively, a foam material piece may also have a thin additional layer made of a non-foam material, such as cloth, padding, or a woven piece. Such an additional thin layer may be positioned to provide, for example, a more durable top and / or bottom surface, a smoother top and / or flat surface, a denser top and / or bottom surface, etc. Such an additional thin layer may also be positioned between different layers made of foam material.

[0033] In one embodiment, the foam material piece comprises at least two layers, preferably at least three layers, more preferably at least four layers, and most preferably at least five layers.

[0034] Pieces of foam material may have a flared shape of a rectangular parallelepiped or cylindrical shape. The flared shape is the shape of the foam material when it is not constrained within a spring, i.e., the unbiased shape. Pieces of foam material may have a flared shape with essentially uniform cross-sectional shape and dimensions when viewed perpendicular to the longitudinal direction.

[0035] However, alternatively, the foam material may have a relaxed shape that forms a constricted portion, and a shape that generally corresponds to the shape envisioned when it is placed, for example, in a spring unit.

[0036] The foam material can be pre-formed, compressed, and inserted into the spring unit. Alternatively, the foam material may be formed directly within the spring unit, for example, by injecting it into the desired position in a liquid state.

[0037] Preferably, the connections in the casing section are sized and shaped such that the connections provide sufficient strength and stability. Furthermore, by changing the shape and size of the connections, the degree of spring bias can be varied. In this way, the bias can be easily changed between different mattresses, and between different springs in the same mattress. Preferably, the connections form contrasting joining areas.

[0038] The opening is preferably located within the outer circumference of the joint between the casing portions. The joint may be formed, for example, by welding, and may also be formed by continuous connection lines, or by spaced-out connection points or connection areas arranged, for example, as dashed or dotted lines. The opening may be substantially circular. However, alternatively, the opening may take the shape of a polygon, such as a rectangle, square, or hexagon. Other shapes, such as an ellipse, are also possible. Preferably, the opening has a symmetrical shape, and most preferably, the opening is substantially circular.

[0039] The joint is preferably formed by surface bonding such as adhesion or welding. In a preferred embodiment, the surface joint is formed by welding.

[0040] The diameter of the opening is preferably much smaller than the diameter of the spring, i.e., the diameter of the spring's maximum turn. In particular, the diameter of the opening may be about half the diameter of the corresponding string's maximum turn. In embodiments, the average diameter of the opening is in the range of 30-70%, preferably 40-60%, and most preferably 45-55% of the average diameter of the spring.

[0041] The casing portion can be connected by a continuous weld around the opening, or by a plurality of welding points dispersed around the opening.

[0042] The casing portion may be connected by multiple welding points distributed around the opening. For example, the joint may have two, three, four, six, or eight welding points. Alternatively, the casing portion may be connected by a continuous weld around the opening. By providing a weld around the opening, adequate strength is maintained at the interconnection even with the opening present. The welding points can be arranged symmetrically around the opening to ensure sufficient strength at the interconnection.

[0043] In the embodiment, the casing forms a plurality of strings which are interconnected, preferably arranged parallel to one another, each string comprising a continuous casing material, the casing being defined by at least one longitudinal connection line extending parallel to the longitudinal direction of the string, and a plurality of transverse connection lines extending across the longitudinal direction of the string, the coil springs being arranged in the casing and pockets of the string, and the connection lines being preferably located laterally to the springs and therefore between adjacent springs.

[0044] The longitudinal and transverse connection lines of the string preferably extend substantially perpendicular to the longitudinal axis of the spring. Furthermore, the longitudinal and transverse connection lines of the string preferably extend in essentially the same plane, which is preferably substantially perpendicular to the longitudinal axis of the spring.

[0045] Connecting strings to each other via longitudinal connecting lines has proven to be highly advantageous. These longitudinal connecting lines, typically welded and often protruding from the strings, automatically provide advantageous spacing between the strings. Furthermore, the strings are thus attached to each other only along the line, preferably at multiple points along this line. This has been found to result in a highly flexible mattress in which the springs have extremely high mobility relative to their neighbors.

[0046] In another embodiment, the casing is formed from an upper woven sheet and a lower woven sheet, the sheets connected to each other between the springs to form pockets. For example, the casing may be formed from a relatively large upper sheet and a relatively large lower sheet. The sheets are connected to each other along longitudinal and transverse connection lines to form, for example, a grid pattern. This forms individual pockets for the springs. Thus, in such embodiments, the pockets are integrated with each other from the same material not only in one direction as in the string embodiment described above, but in two directions, i.e., in length and width dimensions.

[0047] The connection of the sheets may be provided, for example, in the form of connection lines. For example, the connection lines may be arranged as a first set of parallel lines extending in a first direction and a second set of parallel lines extending in a second direction, the second direction being, for example, perpendicular to the first direction. This may cause the connection lines to form a grid in which the springs are enclosed. Alternatively, however, the connection lines may be arranged as circles or polygons surrounding each spring. In yet another alternative embodiment, the connection may be formed as point connections, or connections formed as ×, ○, etc., arranged between the springs, preferably in each group of two springs, i.e., in each “four-leaf clover” formed by the springs.

[0048] The casing is preferably made of a weldable fibrous material.

[0049] In the embodiment, the connection of the casing portion at the end of each spring is such that the spring is biased, preferably such that the length of the biased spring is less than 2 / 3, preferably less than 1 / 2, of the length of the same spring in its original unbiased state, or preferably such that the spring has a height less than the width of the spring, preferably less than 2 / 3 of the width, most preferably less than about 1 / 2 of the width. The casing material portions located at the ends of the springs move relative to each other via the springs.

[0050] According to another aspect of the present invention, A device for sealing a spring in a casing material, A device for forming openings in the casing portions located at the first and second ends of the spring, and for selectively connecting the casing portions to each other by joining them via the spring, A device for inserting pieces of foam material into the opening such that a first portion of each piece of foam material extends toward the first end of the spring, and a second portion of each piece of foam material extends toward the second end of the spring, A machine for manufacturing pocket spring mattresses, equipped with the necessary components, is provided.

[0051] This device enables the manufacture of the aforementioned type of mattress, and achieves the corresponding advantages associated with this novel mattress.

[0052] The apparatus for connecting the casing portions via the spring may include an insertion device and a counter device positioned at a distance therefrom, the insertion device and the counter device being adapted to bring the casing materials at the spring ends of the springs positioned between the casing materials closer together via the springs, by performing relative displacement toward and away from each other so that the springs are biased; an interconnecting device for forming a joint connecting the casing materials thus integrally formed from the two spring ends; and a drilling device for drilling an opening in the interconnecting portion between the casing materials from the two spring ends.

[0053] In one embodiment, the insertion device and the opposing device may be arranged for the purpose of both providing a connection by, for example, welding, and forming an opening by, for example, drilling.

[0054] An apparatus for inserting pieces of foam material may include a compression body, such as a funnel, for compressing the foam material to a size that can be inserted into the opening inside the spring. Alternatively, the foam may be formed directly at the desired position, for example, by an injector that provides the foam material in liquid form.

[0055] According to another aspect of the present invention, a method for manufacturing a spring mattress comprising a plurality of interconnected coil springs enclosed in a casing, comprising the steps of: enclosing the springs in a casing material; biasing at least one of the springs; and interconnecting the springs, wherein the step of biasing the springs comprises a sub-step of moving casing portions positioned relative to the ends of the springs toward each other via the springs and interconnecting them by joining; a sub-step of forming an opening in the joining through which the springs pass; and a sub-step of positioning pieces of foam material in the opening such that a first portion of each piece of foam material extends toward the first end of the spring and a second portion of each piece of foam material extends toward the second end of the spring. A method is provided.

[0056] This method allows for the manufacture of the aforementioned type of mattress, and achieves the corresponding advantages associated with this novel mattress.

[0057] The step of forming an opening in the joint may be performed before the joint is formed, after the joint is formed, or simultaneously with the joint formation. If the opening is formed before the joint is formed, the opening may be formed before inserting the spring into the casing / pocket, or after inserting the spring.

[0058] These and other advantages of the present invention will become apparent from the detailed description of the following specific embodiments.

[0059] The present invention will be described in detail below with reference to the accompanying drawings illustrating embodiments of the present invention. [Brief explanation of the drawing]

[0060] [Figure 1] Figure 1 is a perspective view of a portion of a mattress according to an embodiment of the present invention, before the placement of the foam element pieces. [Figure 2] Figure 2 is a cross-sectional side view of a portion of the mattress shown in Figure 1, viewed in the string direction. [Figure 3] Figure 3 is a schematic perspective view from above and to the side of an apparatus for manufacturing the mattresses shown in Figures 1 and 2, according to one embodiment of the present invention. [Figure 4] Figure 4 is a view of a portion of the mattress shown in Figure 1, seen from above. [Figure 5] Figure 5 is a schematic perspective view from diagonally above of the hole-punching step in the manufacturing of a mattress according to an alternative embodiment of the present invention. [Figure 6a] Figure 6a is a schematic cross-sectional view from the side showing an alternative step and apparatus for inserting a piece of foam element into a spring. [Figure 6b] Figure 6b is a schematic cross-sectional view from the side showing an alternative step and apparatus for inserting a piece of foam element into a spring. [Figure 7] Figure 7 is a schematic diagram showing various cross-sectional views of the foam element shown in Figures 6a and 6b. [Figure 8] Figure 8 is a schematic top view of a mattress according to an embodiment of the present invention. [Figure 9] Figure 9 is a schematic top view of a mattress according to another embodiment of the present invention. [Figure 10] Figure 10 is a schematic top view of a mattress according to yet another embodiment of the present invention. [Figure 11] Figure 11 is a schematic top view of a mattress according to yet another embodiment of the present invention. [Figure 12a] Figure 12a is a schematic cross-sectional view of the upper or lower part of a foaming element according to an embodiment of the present invention. [Figure 12b] Figure 12b is a schematic cross-sectional view of the upper or lower part of a foaming element according to an embodiment of the present invention. [Figure 12c] Figure 12c is a schematic cross-sectional view of the upper or lower part of a foaming element according to an embodiment of the present invention. [Figure 13a]Figure 13a is a schematic cross-sectional view of an alternative foam element arranged in a spring unit according to another embodiment of the present invention. [Figure 13b] Figure 13b is a schematic cross-sectional view of an alternative foam element arranged in a spring unit according to another embodiment of the present invention. [Figure 13c] Figure 13c is a schematic cross-sectional view of an alternative foam element arranged in a spring unit according to another embodiment of the present invention. [Figure 14a] Figure 14a is a schematic side view of pieces of foam material having various relaxed shapes according to embodiments of the present invention. [Figure 14b] Figure 14b is a schematic side view of pieces of foam material having various relaxed shapes according to embodiments of the present invention. [Figure 14c] Figure 14c is a schematic side view of pieces of foam material having various relaxed shapes according to embodiments of the present invention. [Figure 15a] Figure 15a is a schematic side view of a piece of foam material having various types of layered structures according to an embodiment of the present invention. [Figure 15b] Figure 15b is a schematic side view of a piece of foam material having various types of layered structures according to an embodiment of the present invention. [Figure 15c] Figure 15c is a schematic side view of a piece of foam material having various types of layered structures according to an embodiment of the present invention. [Figure 15d] Figure 15d is a schematic side view of a piece of foam material having various types of layered structures according to an embodiment of the present invention. [Figure 15e] Figure 15e is a schematic side view of a piece of foam material having various types of layered structures according to an embodiment of the present invention. [Figure 15f] Figure 15f is a schematic side view of a piece of foam material having various types of layered structures according to an embodiment of the present invention. [Figure 16] Figure 16 is a schematic cross-sectional view from the side of a mattress according to another embodiment of the present invention. [Modes for carrying out the invention]

[0061] As shown in the figures, the sizes of layers and regions may be exaggerated for illustrative purposes and are therefore provided to illustrate the overall configuration of embodiments of the present invention. Similar reference numerals refer to elements that are similar throughout.

[0062] Now, for illustrative purposes, the present invention will be described in detail using embodiments with reference to the accompanying drawings.

[0063] As shown in Figures 1 and 2, the spring mattress according to an embodiment of the present invention comprises a plurality of interconnected coil springs 1 enclosed in a casing / pocket 2. The casing is preferably appropriately constructed from a weldable fibrous material, but other materials such as different types of plastic materials can also be used. It is also possible to use non-weldable fibrous materials such as cotton cloth.

[0064] In this embodiment, the mattress comprises a string 3 of a casing material 2 on which a plurality of pockets 4 are arranged. Here, each pocket is defined by at least one longitudinal connection line 5 extending parallel to the longitudinal direction of the string, and a plurality of transverse connection lines 6 extending across the longitudinal direction of the string. Preferably, the string comprises a casing material made of a bent piece material. In the bent piece material, the bend line extends in the longitudinal direction of the string. A closed longitudinal connection line 5 is located on the opposite side of the string. The transverse connection lines extend between the bend line and the longitudinal connection line. Alternatively, it is also possible to use two or more piece materials to constitute each string. In this case, additional connection lines may be required.

[0065] In a mattress, the springs are oriented into pockets such that the connecting lines are positioned laterally to the springs, and therefore between adjacent springs. Preferably, the casing material portion at the end of the spring is thus essentially free of other connections. However, it is also possible to position the longitudinal connecting lines so as to overlap the spring ends above the strings.

[0066] In at least one, preferably all, of the springs, casing portions located at the ends of the springs move toward each other via the springs and are connected to each other by the connecting device 7, preferably arranged to provide at least some degree of bias. Preferably, the casing portions move toward each other so as to be in contact with each other, but it is of course possible to interconnect them in other ways, such as by wires or long clamps. The connecting device 7 may consist of mechanical connecting elements such as clamps or rivets, or surface joining such as adhesive or welding. However, other fixing elements are also conceivable. The load on the fixing elements is usually small. This is because the fixing elements are only loaded when there is no load on the mattress, and are not loaded at all when there is a load on the mattress. In a preferred embodiment, the joint is formed by one or more welds.

[0067] Furthermore, the end portion is provided with an opening 9 that penetrates the joint and the spring. The opening 9 is preferably substantially circular, but other shapes are also available. An opening 9 that extends along the length of the spring can help provide proper ventilation for the mattress. The opening is also used to stabilize and secure the foam element, as will be further described below. As shown in Figure 4, the opening is substantially circular here, but other shapes of openings are also available. The diameter of the opening is, for example, 5 mm to 50 mm, preferably 10 mm to 30 mm, and more preferably 15 mm to 25 mm. The diameter of the opening is preferably much smaller than the diameter of the maximum turn of the coil spring, and preferably much smaller than the diameter of the minimum turn of the coil spring.

[0068] The end sections are connected here by welding points 10 distributed around a substantially circular opening 9, as shown in Figure 4. Here, four welding points are distributed around the opening, but any number of welding points, e.g., three, six, or eight, can be used. Alternatively, a continuous weld around the opening can be used. The end sections are preferably connected to each other by welding. In this case, the welding surfaces are positioned to connect the end sections to each other. The size and / or location of the welds can be advantageously controllable and selected to obtain the desired height of the mattress and bias for the springs.

[0069] In connection with the present invention, many sizes of coil springs can be used, and basically any size of spring can be used. However, it is preferable to use a spring having a diameter of 2 to 10 cm, more preferably 3 to 7 cm, and most preferably 4 to 5 cm. Preferably, the spring has at least 3 turns, preferably fewer than 10 turns. Furthermore, the spring is advantageously made from a helical wire having a thickness in the range of 0.5 to 3 mm, preferably 1.0 to 2.5 mm. Preferably, the spring is slightly spool-like, that is, the turns are smaller at the top and bottom.

[0070] In the mattress described above, as shown in Figures 1 and 2, the strings having springs are preferably arranged side by side and fixed to one another. Preferably, the strings are connected to each other by fixing points 8, which are advantageously fixed by connecting the longitudinal connection line 5 of one string to the side of the adjacent string. Naturally, fewer or more fixing points than those shown are conceivable. It is also possible to arrange long fixing lines instead of multiple short fixing points. The strings may be connected by welding or bonding. Preferably, the welding or bonding surfaces are distributed around the opening so that good strength is provided at the interconnection. This can be achieved, for example, by point surfaces symmetrically distributed around the opening, or by a continuous line surface around the opening. However, alternatively, this connection may be made by clamps, Velcro tape, or in any other suitable manner.

[0071] By arranging the interconnections of the strings via vertical connecting lines, the strings automatically separate from each other without requiring additional casing material. This reduces the number of springs in the mattress, which is highly advantageous from a comfort standpoint, and also makes the mattress more cost-effective.

[0072] A solution consisting of strings made of a continuous casing material with individual casings for springs is just one of many embodiments for carrying out the present invention. The present invention may also involve, for example, individual casings for springs that are later attached to one another, or a continuous sheet made of casing material for an entire mattress with individual spring casings, or any other solution relating to the casing material.

[0073] The mattress according to the above embodiment may be manufactured by enclosing springs in pockets of strings made of casing material. The pockets are made of a continuous casing material having at least one longitudinal connection line extending parallel to the longitudinal direction of the strings and a plurality of transverse connection lines extending across the longitudinal direction of the strings. Furthermore, the method comprises the steps of moving casing portions positioned relative to the ends of the springs toward each other, connecting them toward each other, and forming openings by perforating or otherwise forming openings in the casing portions at the ends of the springs. There may also be a step of interconnecting the strings in a parallel manner.

[0074] For example, a string can be manufactured by folding a casing material in half and arranging transverse welds to form an open pocket. A compressed spring is then inserted into the pocket, and the pocket is then sealed by welds extending along the string. Preferably, additional welds are arranged through each spring without rotating the spring to connect the end portions to each other. An opening is drilled through the casing portion at the end, preferably in the center of multiple weld points or a continuous weld. The multiple springs are then joined together so that longitudinal welds are between the strings to form a mattress.

[0075] The steps can be carried out in different orders. The connecting lines are positioned to the sides of the springs, and therefore between adjacent springs. The step of moving the end portions toward each other typically involves creating a bias by connecting the connecting elements such that the biased springs have a shorter longitudinal range than their original unbiased state. Such a bias can be created immediately after the springs are sealed in the casing material, i.e., before the springs are assembled to form the mattress, or after the mattress has been assembled. However, preferably the bias is created before the springs are sealed in the string pockets. In this case, the amount of casing material used can be significantly reduced. In particular, the greater the bias and the thinner the mattress, the less casing material can be used. In this way, all the springs in the mattress layer are appropriately biased.

[0076] In the manufacture of the mattress, as described above, it may also be ensured that at least two adjacent strings are connected to each other such that there is an intermediate spacing between them.

[0077] Furthermore, as shown in Figure 2, for example, the strings having springs are preferably interconnected in an adjacent arrangement. As described above, this can be achieved by placing fixing points on the longitudinal connection lines for fixing on the sides of adjacent strings.

[0078] An apparatus for carrying out the above-described method comprises means for enclosing coil springs in pockets of strings. The pockets are made from a continuous casing material having at least one longitudinal connection line extending parallel to the longitudinal direction of the string and a plurality of transverse connection lines extending across the longitudinal direction of the string. As schematically shown in Figure 3, the apparatus may comprise an apparatus for folding the casing material around a row of springs and equipment for welding the connection lines to the folded casing material. Instead of placing the springs in the casing and compressing them in a folded state with the casing covering the springs, it is alternatively possible to compress the springs separately and insert them into the folded casing in a compressed state.

[0079] The welding equipment preferably comprises welding dies 11, 12 movable toward the casing material and corresponding anvils 13, 14 on the opposite side. Preferably, separate welding equipment is arranged to produce longitudinal and transverse connection lines, respectively. The means for enclosing the coil springs is adapted to position the connection lines laterally to the springs so that the connection lines are located between adjacent springs in the finished mattress.

[0080] Furthermore, the device includes means for moving casing portions positioned relative to the ends of the springs toward each other and connecting them, and means for interconnecting the strings in a aligned state.

[0081] Means for moving casing portions positioned relative to the ends of a spring toward each other and connecting them preferably comprise an insertion device 15 and a counter device 16, such as an anvil, positioned at a distance from the insertion device. In use, the spring is positioned so that one end faces the insertion device and the other end faces the anvil. The insertion device is movable toward and away from the anvil, moving the casing material at one end of the spring through the spring toward the casing material on the other side. The insertion device 15 is preferably a welding die for creating a connecting weld. However, alternatively, other fixing means may be provided instead. It is also possible to use a movable anvil. In this case, both sides of the spring are pressed toward each other, after which suturing, welding, or similar connection may be performed.

[0082] The apparatus also includes means for drilling a hole in the casing portion at the end of the spring. The driller here comprises a drilling piece 17 and a contact portion, or an anvil, 18. The driller 17 here is driven through the spring toward the contact portion 18, thereby drilling a substantially circular opening in the casing portion at the end of the spring. Alternatively, the opening may be formed, for example, by cutting. In one embodiment, the opening may be formed by rotating a cutting tool such as a drill. The casing may be pre-drilled to form the opening before other steps.

[0083] The interconnection of the casing portions can be achieved in a step simultaneous with the formation of the opening, for example, by performing a drilling step and simultaneously forming welding points around the drilling, as shown in Figure 5. Here, a circular inserting device 15 is attached to a circular opposing device 16 as the drilling device 17 moves through a tubular inserting device to form a hole in the casing portion through the spring. The connector here has four protrusions 19 on the profile of the portion to be connected to the inserting device. The protrusions define the welding points to be formed between the casing portions.

[0084] The system according to the present invention may, advantageously, comprise a plurality of parallel devices, for example, two devices operating in parallel.

[0085] Furthermore, as shown in Figure 2, for example, means for interconnecting strings having springs, preferably in an aligned state. As described above, this can be accomplished by placing fixing points on longitudinal connection lines for fixing the sides of adjacent strings together.

[0086] It is preferable that the spring biasing is performed such that the length of the biased spring is less than 2 / 3, preferably less than 1 / 2, of the original unbiased length of the same spring. Furthermore, the ratio of the spring length to its diameter in the biased state is preferably less than 2, preferably less than 1, and most preferably less than 1 / 2.

[0087] The longitudinal connecting lines of the string may be positioned on the spring. However, preferably, the longitudinal connecting lines are positioned along the sides of the spring rather than on the ends of the spring.

[0088] Furthermore, the smooth end portions are moved toward each other and joined, for example, by welding. Thus, a very thin mattress, actually one centimeter or a few centimeters thick, can be provided. For example, a mattress with a thickness of 25 mm can be provided. Therefore, it can be said that the present invention is well suited to seat cushions, overlay mattresses placed on top of other mattresses, and similar applications where a thin mattress is required. For this reason, it is very advantageous that an overlay mattress or topper mattress can be made from pocket springs. This is not only because it can be made softer to increase comfort, but also because springs do not typically experience fatigue over time like materials such as polyethylene. The mattress according to the present invention is very light, soft, and comfortable, and can also be biased to have very high sturdiness and rigidity if desired. In addition, the openings that pass through the springs ensure good ventilation of the mattress, thus providing better drying, coolness and / or warmth, reduced growth of bacteria, etc., and improved comfort.

[0089] This invention allows for easy adjustment of the height of the spring elements by changing the position and size of the fixing devices used to connect the end portions to each other. In this way, it becomes easy to provide mattresses with different thicknesses in different sections, or mattresses of different thicknesses, without requiring any other changes in the manufacturing process beyond this connection. Therefore, manufacturing can become highly flexible and controllable. In particular, it is possible to provide mattresses with cup shapes, etc., that can be used as seat cushions or other mattresses intended for sitting. Similar height adjustments can also be used to control the user's position on the mattress.

[0090] The mattress described above is of a type that comprises multiple interconnected coil springs enclosed in a casing, each having a first end and a second end. For at least one of the springs, casing portions located at the first and second ends of the spring are connected to each other via the spring by joining. The joined casing portions have openings through which the springs pass. Furthermore, as will be described in more detail below, pieces of foam material are placed in the openings.

[0091] In one embodiment shown in Figures 6a and 6b, an inserted piece 20 of such foam material is shown, and a process and apparatus for inserting the foam piece are also shown.

[0092] The foam material piece 20 extends toward the first end of the spring in the first part 20a and toward the second end of the spring in the second part 20b.

[0093] The foam material piece 20 is inserted through an opening 9 formed in the casing / pocket around the spring, forming a constriction within the opening. This mechanically holds the foam material piece in place in a fixed position. This creates a strong mechanical connection, eliminating the need to directly connect the foam material piece to the coil spring. Instead, the foam material is positioned away from the coil spring by the casing fabric. Further connecting elements such as adhesive or welding may be selectively used to increase the fixing force. However, in most cases, a mechanical connection is sufficient.

[0094] Therefore, each pocket containing each spring, i.e., the casing, is formed as a toroid having a donut shape that forms a circular compartment in which the spring is enclosed. Furthermore, the foam material can be formed as an hourglass having a central constriction and two inflated mushroom-shaped portions extending in opposite directions from the constriction. Due to the elasticity and flexibility of the foam material, the two shapes, namely the toroidal shape of the casing and the hourglass shape of the foam material, can be complementary to each other to a high degree, so that the overall cross-sectional shape of the pocket unit can be circular, rectangular with rounded corners, or an intermediate shape.

[0095] At least one of the first portion 20a and the second portion 20b of the foam material piece preferably extends beyond the first and second ends of the spring, respectively. In the illustrated examples of Figures 6a and 6b, both the first portion 20a and the second portion 20b extend beyond the first and second ends of the spring. This allows the foam to provide the outermost layer of the mattress on both sides.

[0096] For example, as shown in Figure 7, when placed in the spring, the foam material piece 20 may have a generally circular constriction or other shape corresponding to an opening. Towards both ends, the foam material piece expands from the constriction towards the top and bottom. The portions 20a and 20b protruding from the spring may have a generally rectangular cross-section, such as a square cross-section. However, other shapes, such as a circular cross-section, are also possible.

[0097] A portion of the foam material extending beyond the first or second end of the spring may have a cross-sectional dimension greater than or equal to the diameter of the upper or lower end of the spring through which it extends. This causes the extended foam material to form a relatively continuous layer above the spring.

[0098] In this embodiment, the maximum cross-sectional dimension of a portion of the foam material extending from the spring may be greater than or equal to the diameter of the spring's maximum turn. This allows the foam material to essentially cover the spring when viewed from a direction parallel to the spring's axial direction.

[0099] The upper and lower surfaces formed by portions 20a and 20b, respectively, may be slightly curved and convex, as schematically shown in Figure 12a. However, other shapes are also possible. For example, as shown in Figure 12b, the upper and / or lower surfaces may form a concave or cup shape by having inwardly curved depressions. As shown in Figure 12c, the upper and / or lower surfaces may be generally flat.

[0100] In the illustrations in Figures 6a and 6b, the foam material piece extends beyond the spring in both the upward and downward directions. However, it is also possible for the foam material piece to extend from the spring in only one direction.

[0101] It is also conceivable to provide a piece of foam material that extends generally to the plane formed by the upper and / or lower turns of the spring, so that the upper and / or lower surfaces of the foam material piece are generally flush with the upper and / or lower surfaces of the pocket unit. An example of this is shown in Figure 13a, where the upper part 20a' essentially terminates in the plane formed by the upper turn of the spring, and the lower part 20b' substantially terminates in the plane formed by the lower turn of the spring.

[0102] In a similar embodiment shown in Figure 13c, the upper and lower surfaces of the foam material piece formed by the upper 20a'' and lower 20b'' are generally cup-shaped and have peripheral portions that extend somewhat beyond the upper and lower turns of the spring, respectively, and a central portion that is located slightly below the upper and lower turns of the spring.

[0103] In yet another embodiment shown in Figure 13c, the foam material piece having portion 20a''' and portion 20b''' does not extend beyond the upper and lower turns of the spring and consequently terminates in a position entirely inside the spring.

[0104] Such embodiments may be combined in various ways. For example, a piece of foam material may extend beyond the spring on one side but not on the other, or one side of the foam piece may be convex and the other concave, etc. Thus, it is conceivable that the foam material extends beyond the spring on only one side. It is also conceivable that the foam material does not extend beyond either end. In such embodiments, the foam material may be flush with the plane of the coil spring's end rotation, or it may be located inside the spring at a distance from such a plane.

[0105] In embodiments, as shown in Figures 6a and 6b, the foam material piece is compressed in the portion placed within the opening, thereby forming a constriction in the foam material piece at the opening. The first and second portions of the foam material piece gradually expand to a larger cross-sectional shape in the direction away from the opening. Thus, the foam material may have a relaxed shape before being inserted into the spring, and when placed in a predetermined position inside the spring, it may take on one of the shapes described above, for example, an hourglass shape that forms a constriction in the center of the foam material piece. The relaxed shape is the shape of the foam material when it is not constrained within the spring, i.e., the unbiased shape.

[0106] Pieces of foam material may have a relaxed shape with essentially uniform cross-sectional shape and dimensions when viewed perpendicular to the longitudinal direction. The relaxed shape may be a rectangular parallelepiped, such as a cuboid or a square prism, as illustrated in Figures 6a and 6b, and as shown in Figure 14a. However, other relaxed shapes, such as a cylindrical shape, are also possible, as schematically shown in Figure 14b. In the illustrated example, the cylinder has a circular cross-section. However, other cross-sectional shapes such as elliptical or polygonal shapes are also possible. Other shapes, such as shapes with dimensions that vary over height, are also possible. For example, the relaxed shape may have a smaller cross-sectional dimension in the center and larger cross-sectional dimensions at the top and bottom, forming a constriction in the material, as shown in 14c, for example. In one embodiment, the foam material may have a relaxed shape that roughly corresponds to the shape envisioned when placed in a spring unit.

[0107] The foam material can be composed of various materials. In a preferred embodiment, the foam is made of urethane, latex, or viscoelastic foam.

[0108] A mattress can be produced, for example, as described above with respect to Figure 2, by first enclosing springs in pockets, connecting casing materials to each other at the ends via the springs, and forming openings in the connection areas. Subsequently, pieces of foam material can be inserted into the spring units. For example, pieces of foam material having a relaxed shape larger than the constrained shape intended at the insertion position can be compressed for insertion. For example, a piece of foam material can be pushed into an open-ended cone 21, such as a funnel, as shown in Figure 6a. However, other methods of compressing pieces of foam material to smaller dimensions are also possible. For example, a temporary outer covering layer may be formed around the foam material, which can be removed once the foam material reaches its intended position.

[0109] In another embodiment shown in Figure 6b, the foam material piece is pulled through an opening in the spring instead of being pulled upwards. This can be done, for example, by a gripping tool 21'. The gripping tool 21' is inserted so as to pass through the opening 9, grips the foam material piece 20 on the opposite side, and is configured to pull the foam element piece into insertion position by retracting the gripping tool 21'. The gripping tool 21' may have, for example, two or more arms / claws that can be separated before gripping and have pickup claws or pickup jaws at its ends that are movable toward each other to grip the foam material piece. The gripping tool 21' can function as tweezers by having only two arms / claws. However, it may have more than two arms / claws, for example, three, four, or five arms / claws. In such embodiments where the gripping tool 21' has at least three arms / claws that are separated around its periphery, the gripping tool may also be used to compress the foam material piece when it is gripped to facilitate insertion through the opening 9.

[0110] However, alternatively, the foam material may be formed directly within the spring unit by, for example, injecting it into the desired position in a liquid state.

[0111] In the embodiment shown in Figure 3, the casing forms a plurality of interconnected strings, preferably arranged in parallel to one another, and each string comprises a continuous casing material. The casing is defined by at least one longitudinal connection line extending parallel to the longitudinal direction of the strings and a plurality of transverse connection lines extending across the longitudinal direction of the strings. The springs are then positioned in pockets of the casing and strings. The connection lines are preferably located laterally to the springs and therefore between adjacent springs.

[0112] However, mattresses can also be formed in other ways. In one embodiment schematically shown in Figure 8, the casing is formed of an upper woven sheet and a lower woven sheet, the sheets connected to each other between the springs to form pockets. For example, the casing may be formed of a relatively large upper sheet and a relatively large lower sheet. The sheets are connected to each other along longitudinal connection lines 6' and transverse connection lines 6' to form, for example, a grid pattern. This forms individual pockets for the springs. Thus, in such embodiments, the pockets are integrated with each other from the same material not only in one direction as in the string embodiment described above, but in two directions, i.e., in length and width dimensions.

[0113] A connection 10 of casing material positioned above and below the spring and passing through the spring, forming an opening 9 through the spring, can be achieved in the same manner as described above with reference to Figure 3. Furthermore, inserting a piece of foam material through the string and the opening can also be done in the same manner as described above with reference to Figure 6, for example.

[0114] In the embodiment shown in Figure 8, the connection of the sheets may be provided, for example, in the form of connecting lines. For example, the connecting lines are arranged as a first set of parallel lines 6' extending in a first direction and a second set of parallel lines 6' extending in a second direction, the second direction being, for example, perpendicular to the first direction. This allows the connecting lines to form a grid in which springs are enclosed between them.

[0115] However, alternatively, the connecting line 6" can be arranged, for example, as a circle or polygon surrounding each spring, as shown in Figure 9.

[0116] In yet another alternative example, as schematically shown in Figure 10, the connection 6" may be formed between the springs, preferably in each group of four springs, i.e., in each "four-leaf clover" formed by the springs, as point connections or connections formed as ×, ○, etc.

[0117] In the embodiments described with reference to Figures 9 and 10, the connection 10 of the casing material positioned above and below the spring and passing through the spring, which forms the opening 9 through the spring, can be achieved in the same manner as in the embodiments described above with reference to Figure 3. Furthermore, inserting the foam material piece through the string and the opening can also be done in the same manner as described above, for example with reference to Figure 6.

[0118] Figure 11 shows a schematic diagram of the mattress from Figure 8 with the foam material piece 20 inserted. Here, the foam material is positioned to extend from the springs and forms a covering portion having a roughly rectangular cross-section, as also shown in Figure 7. The foam material is sized such that, when viewed from a direction parallel to the axial direction of the springs, it essentially covers the springs. This creates a relatively uniform upper layer formed from the foam material.

[0119] To improve ventilation and airflow, additional second openings may be provided on the outside of the spring. Such additional second openings 9' are shown in Figure 9. The additional second openings may be located, for example, between four adjacent springs, and may also be located in all such groups of four adjacent springs, i.e., in the center of each "four-leaf clover" formed by the springs, as shown in the illustrated example.

[0120] The foam material pieces may be composed of a homogeneous material. However, the foam material pieces may be composed of a combination of different materials. Such different materials may be arranged, for example, in different layers to form a laminated structure. Preferably, the layers are arranged in a plane parallel to the mattress plane, that is, arranged vertically relative to each other in a direction parallel to the axial direction of the spring.

[0121] Several exemplary embodiments comprising such stacked foam material pieces will be described with reference to Figures 15a to 15f.

[0122] In the exemplary embodiment shown in Figure 15a, the foam material piece comprises a central layer 202 positioned through an opening in the spring, a separate uppermost layer 201, and a separate lowermost layer 203. In such embodiments, the uppermost and / or lowermost layers may have different properties from the central layer. For example, they may be softer, denser, or have higher viscoelasticity. For example, a less expensive material such as polyurethane may be used for the central layer 202, and a somewhat more expensive material such as latex or a viscoelastic material may be used for the uppermost and / or lowermost layer 201 and / or lowermost layer 203.

[0123] In an exemplary embodiment shown in Figure 15b, a structure similar to that described with respect to Figure 15a is shown, except that a separate layer 201 is located on one side of the central layer 202'. Here, the separate layer 201 is located as the uppermost layer, but it may also be located as the lowermost layer.

[0124] In the exemplary embodiment shown in Figure 15a, the top layer 201 and the bottom layer 203 may be made of the same material and have essentially the same properties, thereby providing the same properties to both sides of the mattress. However, as schematically shown in Figure 15c, it is also possible to use different materials for the top layer 201 and the bottom layer 203'.

[0125] In the embodiment shown in Figure 15b, the foam material piece comprises two layers. On the other hand, the embodiments shown in Figures 15a and 15c comprise three layers. However, it is also conceivable to have more than three layers, for example, four layers, five layers, or even more layers.

[0126] In the embodiment shown in Figure 15d, the configuration of the foam material pieces is essentially similar to that in Figure 15a, except that a thin additional layer 204 is placed above the top layer 201, and a thin additional layer 205 is placed below the bottom layer 203. The thin additional layers may consist of, for example, foam material, but may also be other types of material. One or both of the additional layers 204 and 205 may consist of cloth, pads, woven pieces, etc. The additional thin layers 204 and 205 may be arranged to provide, for example, a more durable top and / or bottom surface, a smoother top and / or flat surface, a denser top and / or bottom surface, etc.

[0127] As schematically shown in Figure 15e, such a thin additional layer 204 may be placed on only one side of the piece of foam material.

[0128] Additionally or alternatively, such additional thin layers 204' and 205' may be placed between layers of foam material, for example, between the top layer 204 and the middle layer 202, and / or between the middle layer 202 and the bottom layer 203, as illustrated in Figure 15f. Such additional thin layers 204' and 205' may be used for purposes such as providing stronger connections between different foam materials to facilitate manufacturing.

[0129] In the embodiments described above, the pocket unit is configured such that casing portions located at the first and second ends of the spring are joined together via the spring. Here, the openings are located close to each other in the joined casing portions. However, in certain applications, particularly with relatively thin mattresses, if these casing portions remain spaced apart and not joined inside the spring, it is also conceivable to place pieces of foam material through the openings located at the first and second ends of the pocket.

[0130] Figure 16 schematically illustrates such an embodiment. Here, the casing portions positioned at the first and second ends of the spring are spaced apart and located at or near the first and second ends of the spring. Thus, the openings 9a and 9b formed in the casing portions are spaced apart from each other by a distance essentially corresponding to the height of the spring. The foam element 20 is positioned to penetrate both the first and second openings 9b, with its top portion 20a extending from the first opening 9a and its bottom portion 20b extending from the second opening 9b. The central portion extending through the spring is shown here as a relatively narrow section having a cross-section essentially corresponding to the size of the opening. However, alternatively, the central portion may be wider and thicker and extend toward both sides of the spring. In such an embodiment, the piece of foam material may form two constrictions at the two openings, with a wider section between them.

[0131] The present invention has been described above with reference to embodiments. However, several modifications of the present invention can be envisioned. For example, as described above, other types of fixing elements, as well as other solutions relating to casing materials and spring sizes, are available. Also, the foam material pieces may have other relaxed and / or constrained shapes. Furthermore, the apparatus and methods can be designed in other embodiments. Such obvious modifications should be considered to constitute the present invention as defined by the appended claims.

Claims

1. A spring mattress comprising multiple interconnected coil springs enclosed in a casing, The coil spring has a first end and a second end, In at least one of the coil springs, the casing portion located at the first and second ends of the coil spring comprises an opening that penetrates the coil spring, and a foam material piece located at the opening, wherein a first portion of each foam material piece extends toward the first end of the coil spring, and a second portion of each foam material piece extends toward the second end of the coil spring. A spring mattress in which the first or second portion of the foam material piece extending beyond the first or second end of the coil spring has a cross-sectional dimension that is greater than or equal to the diameter of the curvature at the first end or the curvature at the second end of the coil spring through which the foam material piece extends.

2. The spring mattress according to claim 1, wherein at least one of the first portion and the second portion of the foam material piece extends beyond the first end and the second end of the coil spring, respectively.

3. The casing portions, which are positioned at the first and second ends of the coil spring, are connected to each other by joining via the coil spring. The spring mattress according to claim 1 or 2, wherein the opening is located in the joined casing portion.

4. Each piece of foam material is compressed in the portion placed in the opening, thereby forming a constricted portion in the piece of foam material at the opening. The spring mattress according to claim 3, wherein the first and second portions of the foam material piece gradually expand in the direction away from the opening to form a larger cross-sectional shape.

5. The spring mattress according to claim 1, wherein the pieces of the foam material have a relaxed shape of a rectangular parallelepiped or a cylindrical shape.

6. The spring mattress according to claim 1, wherein the pieces of foam material have a relaxed shape having essentially uniform cross-sectional shape and cross-sectional dimensions when viewed perpendicular to the longitudinal direction.

7. The spring mattress according to claim 1, wherein the average diameter of the opening is within the range of 30 to 70% of the average diameter of the coil springs.

8. The spring mattress according to claim 3, wherein the casing portion is connected by a continuous weld around the opening, or by a plurality of welding points dispersed around the opening.

9. The casings form multiple strings that are interconnected in a line-up configuration. Each string is provided with a continuous casing material, The casing is defined by at least one longitudinal connection line extending parallel to the longitudinal direction of the string, and a plurality of transverse connection lines extending across the longitudinal direction of the string. The coil spring is placed in the casing of the string, The spring mattress according to claim 1, wherein the longitudinal connecting line and the transverse connecting line are arranged to the side of the coil spring and therefore between adjacent coil springs.

10. The casing is formed from an upper woven sheet and a lower woven sheet. The spring mattress according to claim 1, wherein the upper fabric sheet and the lower fabric sheet are connected to each other between the coil springs to form a pocket.

11. The spring mattress according to claim 1, wherein the foam material piece comprises at least two layers of different materials.

12. The spring mattress according to claim 1, further comprising an additional second opening positioned between the coil springs.

13. A machine for manufacturing the spring mattress described in Claim 1, A device for enclosing a coil spring in casing material, A device for forming openings in the casing portions located at the first and second ends of the coil spring, and for selectively connecting the casing portions to each other by joining them via the coil spring, A machine for manufacturing a spring mattress, comprising: a device for inserting pieces of foam material into an opening such that a first portion of each piece of foam material extends toward the first end of the coil spring, and a second portion of each piece of foam material extends toward the second end of the coil spring.

14. The device includes a mechanism for connecting the casing portion via the coil spring, The apparatus comprises an insertion device and a counter device positioned at a distance therefrom, the insertion device and the counter device being adapted to bring the casing materials at the spring ends of the coil springs positioned between the casing materials closer together via the coil springs by performing relative displacement toward and away from each other so that the coil springs are in a biased state; an interconnecting device for forming a joint connecting the casing materials thus integrally formed from the two spring ends; and a drilling device for drilling an opening in the interconnecting portion between the casing materials from the two spring ends, according to claim 13.

15. A method for manufacturing the spring mattress described in Claim 1, The steps include: sealing the coil spring in the casing material; The steps include: putting at least one of the coil springs into a biased state; The step of interconnecting the coil springs is included, The step of biasing the coil spring comprises a sub-step of moving casing portions positioned relative to the ends of the coil spring toward each other via the coil spring and connecting them together by joining; a sub-step of forming an opening in the joining through which the coil spring passes; and a sub-step of positioning pieces of foam material in the opening such that a first portion of each piece of foam material extends toward the first end of the coil spring and a second portion of each piece of foam material extends toward the second end of the coil spring.

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