JP2024521206A - Pocket mattress with integral foam material - Google Patents

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 located at the first and second ends of the spring connect to one another by a joint through the spring. The jointed casing portions have openings through the spring. Pieces of foam material are placed in the openings such that a first portion of each piece of foam material extends towards the first end of the spring and a second portion of each piece of foam material extends towards the second end of the spring. Machines and methods for manufacturing such mattresses are also disclosed.

Description

The present invention relates to a spring mattress comprising a spring enclosed in a casing, the end casing materials being connected to each other via the springs to form a doughnut-shaped enclosure/pocket, a so-called pocket mattress. The present invention also relates to a method and apparatus for manufacturing such a mattress.

A common method of making spring mattresses is the so-called pocket technique. This means that the springs are enclosed in pockets, i.e. individually enclosed in a casing material. In this way, the springs are relatively individually elastic and can flex individually without affecting the adjacent springs. This increases the comfort of the user, as the weight is distributed more evenly over the load-bearing surface.

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 without a corresponding shortening of the width, especially when this length approaches the length of the spring's diameter, the spring tends to rotate in the casing, dramatically reducing the comfort of the mattress. To produce such a mattress, existing techniques require the use of a much larger number of springs, which makes production considerably more expensive and complicated. Also, it is difficult to prevent such mattresses from becoming stiff, since wires that are too thin cannot be used.

For these reasons, spring mattresses cannot be used in many applications where a thinner mattress is required, such as overlay mattresses or seat cushions. Nevertheless, spring mattresses have several properties that make them desirable for use in these situations, such as excellent comfort, individual flexibility, long life, and easy and inexpensive manufacture.

Solutions to this problem are presented in US6591438, US7748065 and US8087114 by the same applicant. Here, the end parts of the casing are moved towards each other and connected to each other via springs, resulting in a bias of the springs, which results in a very compact and useful mattress. This allows a very thin pocket spring mattress to be produced. A similar type of mattress is disclosed in WO2019/096793, also by the same applicant. Such a mattress is very useful as an additional mattress to be placed on top of another mattress, such as a comfort layer or topper.

However, lying directly on a pocket mattress is generally not comfortable and to provide good sleep and rest it is usually necessary to add an additional padding layer on top of the mattress. Such a padding layer is often assembled to the pocket mattress to form an enclosed upholstered mattress. Alternatively, a separate padding mattress may be placed loosely on top of the pocket spring mattress. However, a drawback of such an additional top layer is that it reduces the individual elasticity of the pocket units and therefore does not provide optimal pressure distribution.

There have also been attempts to incorporate foam material into the individual pocket units of a pocket spring mattress. Such attempts are disclosed, for example, in US9936815. However, such mattresses are relatively complex and expensive to produce. 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.

Thus, a drawback of this mattress and similar mattresses proposed previously is that the connection of the foam/pad to the coil springs and pockets is relatively complicated and costly to implement. Furthermore, there is a significant risk that the foam/pad will deform or become dislodged and, for example, get wedged into the convolutions of the coil springs. This significantly detracts from both the appearance and comfort of the mattress.

Thus, there is a need for individual pocketed coil springs and pocket spring mattresses that are easier and/or less expensive to manufacture, yet provide at least the same level of comfort, as other prior art pocket mattresses. There is also a need for such individual pocketed coil springs and pocket spring mattresses that provide good resilience and responsiveness, and that may reduce the amount of cushioning or padding material used on bedding or seating products after the spring assembly is completed. There is also a need for such individual pocketed coil springs and pocket spring mattresses that are more durable and retain their properties over longer periods of use. In particular, there is a need for toppers, comfort layers, and the like that have such properties.

Therefore, there is still room for improvement in pocket mattresses with regard to comfort and sleep quality. There is also a general need to extend the lifespan of mattresses.

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

This object is achieved by the spring mattress and the method and apparatus for producing it described in the claims.

This and other objects are achieved by a spring mattress comprising 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, a casing portion disposed at the first end and the second end of the spring comprises an opening through the spring and a piece of foam material disposed 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.

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. However, preferably, 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.

The mattress is of the general type as disclosed in the applicant's WO 2019/096793 (hereby incorporated by reference) and therefore essentially has all the advantages associated with mattresses of this type, such as the ability to make the mattress thin, the advantageous biasing of the springs, etc. However, the mattress of the present invention offers many more advantages.

It has been found that by providing openings through the pocket and the spring at the interconnection of the casing parts, such openings provide a very efficient and convenient way of fixing the foam material to the pocket unit. The openings form waists in the foam material, which mechanically hold the foam material in a fixed position. Also, preformed pieces of foam material can be inserted and assembled in place in an already prepared mattress, allowing for very rapid and cost-effective manufacturing. The pieces of foam material can only be introduced from one side of the mattress, but extend towards both sides of the assembled mattress. This allows conventional manufacturing processes for making pocket mattresses to be used, with the foam material only being added as a subsequent step. The invention is therefore very suitable for automated and cost-efficient manufacturing, and it is relatively easy to incorporate the additional step of assembling pieces of foam material into pocket units produced by previously known and used manufacturing processes.

Furthermore, the piece of foam material does not need to be directly connected to the coil spring. Instead, the foam material is spaced from the coil spring by the casing fabric.

The foam material provides increased stability and resilience to the interior of the coil spring. Also, the foam material extending from the ends of the coil spring forms the upper and/or lower surface of the foam material. This allows the upper and/or lower surfaces and layers of the mattress to be soft and comfortable, reducing the need for additional padding layers, etc.

The present invention provides individual pocket spring units, each of which comprises a piece of foam material disposed within a coil spring, preferably dimensioned 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 provides superior comfort and pressure distribution, as the individual resiliency of the pockets is maintained. With such pocket units, no additional padding layer is required, since each pocket unit incorporates a cushion pad that extends into at least the cavity formed by each coil spring, preferably beyond the end of the coil spring.

Furthermore, the fact that the coil springs and pieces of foam material in each pocket unit are spaced apart from each other by the casing fabric ensures that the foam material is always in place. The casing material of the pocket units that house 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 over long periods of use.

In addition, the foam material is porous and air permeable, so that ventilation and aeration in the mattress are possible through the openings, even when the foam material is present in the mattress. During sleep, a large amount of moisture leaves the human body. With high ventilation/breathability, this moisture can be more efficiently handled without wetting the mattress. The moisture can be more efficiently removed from the user's body and away from the mattress. Furthermore, comfort and sleep quality can be improved, and a more stable sleeping temperature and humidity of the user can be guaranteed. In addition, the user's body temperature can be easily regulated. And, by reducing the moisture and moisture in the mattress, the occurrence and proliferation of mites, mold, bacteria, etc. can be 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 bad odors is also reduced. Overall, high ventilation and breathability allows the mattress to be kept clean and hygienic for a longer period of time, which extends the life of the mattress.

Additional second openings may also be provided at locations between the springs. Such openings may be located, for example, at locations between four adjacent springs. Preferably, one such opening is provided in every group of adjacent springs, or essentially every group. Such additional second openings also improve ventilation and breathability of the mattress.

The invention is based on the realization that in this particular type of mattress, i.e. a pocket spring mattress in which the casing parts located at the ends of the springs are joined together via the springs and have openings through the joints, the placement of the pieces of foam material is very easy and efficient, since the openings provide access to the entire internal cavity of the pocket unit and to both ends, and because mechanical fixation of the foam elements is provided.

The foam element may be held in place by mechanical fixation alone. However, alternatively, additional fixation by welding, gluing, etc. may be provided.

According to the invention, each pocket, i.e., the casing enclosing each spring, is formed as a toroid having a doughnut shape forming a circular compartment in which the spring is enclosed. Furthermore, the foam material can be formed as an hourglass with a central waist and two inflated mushroom-shaped portions extending in opposite directions from the waist. Due to the elasticity and flexibility of the foam material, the two shapes, i.e., the toroidal shape of the casing and the hourglass shape of the foam material, can be to a high degree complementary to each other, so that the overall cross-sectional shape of the pocket unit can be in the form of a circle, a rectangle with rounded corners, or a shape in between.

At least one of the first and second portions of the piece of foam material preferably extends beyond the first and second ends of the springs, respectively. In a preferred embodiment, the foam material bulges on each side of each spring, such that the foam provides the outermost layer of the mattress. However, it is contemplated that the foam material extends beyond the spring ends on only one side. It is also contemplated that the foam material does not extend beyond either end. In such an embodiment, the foam material may be flush with the plane of the end convolutions of the coil springs, or may be below such plane.

The protruding pieces of foam material may form a rounded convex upper surface and/or a rounded convex lower surface. Alternatively, however, the protruding pieces of foam may form a generally flat surface, thereby providing a generally flat and uniform mattress surface. In yet another alternative embodiment, the protruding pieces of foam material may have a lowered central portion surrounded by a peripheral edge, thereby providing a cup-shaped or concave upper surface and/or a cup-shaped or concave lower surface.

In an embodiment, each piece of foam material may be compressed at a portion disposed within an opening to form a waist in the piece of foam material at the opening. The first and second portions of the piece of foam material expand to a gradually larger cross-sectional shape in a direction away from the opening.

The portion of the foam material that extends beyond the first or second end of the spring may have a cross-sectional dimension that is equal to or greater than the diameter of the top or bottom end convolution of the spring through which it extends, so that the extended foam material forms a relatively continuous layer above the spring.

The foam material can be composed of a variety of materials. In a preferred embodiment, the foam is composed of urethane, latex, or viscoelastic foam.

The pieces of foam material may consist of a homogenous material. However, the pieces of foam material may also consist of a combination of different materials. Such different materials may for example be arranged in different layers to form, for example, a laminated structure. The layers are preferably arranged in a plane parallel to the mattress plane, i.e. one above the other in a direction parallel to the axial direction of the springs.

For example, the piece of foam material may have a more expensive material, such as latex or a viscoelastic material, facing one or both sides and thus arranged as a top and/or bottom layer, and a central layer made of a less expensive material, such as polyurethane. This allows the top and/or bottom layers to have different properties than the central layer, e.g., softer, denser, more viscoelastic. Additionally or alternatively, the piece of foam material may also comprise thin additional layers of non-foam material, e.g., cloth, padding, textile pieces, etc. Such additional thin layers may be arranged to provide, for example, a more durable top and/or bottom surface, a smoother top and/or flatter top and/or bottom surface, a denser top and/or bottom surface, etc. Such additional thin layers may also be arranged between different layers of foam material.

In an embodiment, the piece of foam material comprises at least two layers, preferably at least three layers, more preferably at least four layers, and most preferably at least five layers.

The piece of foam material may have a relaxed shape that is a rectangular or cylindrical shape. The relaxed shape is the shape of the foam material when not constrained within the spring, i.e., the unbiased shape. The piece of foam material may have a relaxed shape of essentially uniform cross-sectional shape and cross-sectional dimensions when viewed perpendicular to the longitudinal direction.

However, alternatively, the foam material may have a relaxed shape that defines a waisted portion and a shape that generally corresponds to the shape that it will assume when placed in, for example, a spring unit.

The foam material may be preformed and compressed before being inserted into the spring unit. Alternatively, however, the foam material may be formed directly within the spring unit, for example by injecting it in liquid form at the desired location.

The connections of the casing portions are preferably sized and shaped to provide sufficient strength and stability to the connections. Furthermore, the shape and size of the connections can be varied to provide different degrees of bias in the springs. In this way, bias can be easily varied between different mattresses and between different springs in the same mattress. Preferably, the connections provide symmetrical joining areas.

The opening is preferably within the periphery of the joint between the casing parts. The joint may be formed, for example, by welding, and may be formed by a continuous connection line or by spaced connection points or areas, for example arranged as dashed or dotted lines. The opening may be substantially circular. However, alternatively, the opening may have a polygonal shape, such as a rectangle, a square, a hexagon, etc. Other shapes, such as an elliptical shape, are also contemplated. Preferably, the opening has a symmetrical shape, and most preferably, the opening is substantially circular.

The bond is preferably formed by a surface bond such as adhesive bonding, welding, etc. In a preferred embodiment, the surface bond is formed by welding.

The diameter of the opening is preferably much smaller than the diameter of the spring, i.e. the diameter of the largest turn of the spring. In particular, the diameter of the opening may be about half the diameter of the largest turn of the corresponding string. In an embodiment, the average diameter of the opening is in the range of 30-70% of the average diameter of the spring, preferably in the range of 40-60%, and most preferably in the range of 45-55%.

The casing portions may be connected by a continuous weld around the periphery of the opening, or by multiple weld points distributed around the periphery of the opening.

The casing portions may be connected by multiple weld points distributed around the opening. For example, the joint may include 2, 3, 4, 6 or 8 weld points. Alternatively, the casing portions 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. The weld points may be symmetrically positioned around the opening to ensure sufficient strength at the interconnection.

In an embodiment, the casing preferably forms a plurality of interconnected parallel strings, 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 strings and a plurality of transverse connection lines extending transversely to the longitudinal direction of the strings, and coil springs are disposed in the casing and in pockets of the strings, the connection lines preferably being disposed laterally of the springs and therefore between adjacent springs.

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 plane is preferably substantially perpendicular to the longitudinal axis of the spring.

It has been found to be very advantageous to connect the strings to one another via longitudinal connection lines, which typically consist of welds and which often protrude from the strings, automatically providing an advantageous spacing between the strings. Furthermore, the strings are thus attached to one another only along a line, preferably only at a number of points along this line. It has been found that this results in a very flexible mattress, in which the springs have a very high degree of mobility relative to their neighbours.

In another embodiment, the casing is formed by an upper fabric sheet and a lower fabric sheet, which are connected to each other between the springs to form pockets. For example, the casing may be formed by 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, thereby forming individual pockets for the springs. Thus, in such an embodiment, the pockets are integral 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 the length dimension and the width dimension.

The connections of the sheets may be provided, for example, in the form of connecting lines. For example, the connecting 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. Thereby, the connecting lines may form a grid between which the springs are enclosed. Alternatively, however, the connecting lines may be arranged as a circle or polygon surrounding each spring. In yet another alternative embodiment, the connections may be formed as point connections arranged between the springs, preferably in each group of two springs, i.e. in each "four-leaf clover" formed by the springs, or connections formed as x's, o's, etc.

The casing is preferably constructed from a weldable textile material.

In an embodiment, the connection of the casing portions at the ends of each spring is such that the spring is biased, preferably such that the length of the spring in the biased state 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 that is less than the width of the spring, preferably less than 2/3, most preferably less than about 1/2. The casing material portions located at the ends of the springs move relative to each other via the springs.

According to another aspect of the present invention,
a device for encapsulating the spring in a casing material;
a device for forming openings in casing portions located at the first and second ends of the spring and selectively connecting the casing portions to one another by means of a joint through the spring;
a device for inserting pieces of foam material into 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;
A machine for manufacturing a pocket spring mattress is provided, comprising:

By means of this apparatus, mattresses of the type described above can be manufactured and the corresponding advantages associated with this novel mattress can be achieved.

The device for connecting the casing parts through the springs may comprise an insertion device and a counter device arranged at a distance therefrom adapted to perform relative displacements towards and away from each other to bring the casing material at the spring ends of the springs arranged between the casing materials closer to each other through the springs so that the springs are in a biased state, an interconnection device for forming a joint connecting the casing material thus integrated from the two spring ends, and a drilling device for drilling an opening in the interconnection between the casing material from the two spring ends.

In one embodiment, the insertion device and the counter device may be positioned to both provide a connection, e.g., by welding, and to form an opening, e.g., by drilling.

The device for inserting the pieces of foam material may comprise 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. However, alternatively, the foam may be formed directly at the desired location, for example by an injector providing the foam material in liquid form.

According to another aspect of the invention, a method for manufacturing a spring mattress comprising a plurality of interconnected coil springs enclosed in a casing, comprising the steps of: encapsulating the springs in a casing material; biasing at least one of the springs; and interconnecting the springs, the step of biasing the springs comprising the partial steps of moving casing parts located against the ends of the springs towards each other through the springs and interconnecting them by joints; forming openings through the springs at the joints; and placing pieces of foam material in the openings such that a first portion of each piece of foam material extends towards the first end of the spring and a second portion of each piece of foam material extends towards the second end of the spring.
A method is provided.

By this method, a mattress of the type described above can be manufactured and the corresponding advantages associated with this novel mattress are achieved.

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

These and other advantages of the present invention will become apparent from the detailed description of specific embodiments below.

The present invention will be described in detail below with reference to the accompanying drawings showing an embodiment of the present invention.

FIG. 1 is a perspective view of a portion of a mattress according to an embodiment of the invention prior to placement of pieces of foam element. FIG. 2 is a cross-sectional side view of a portion of the mattress of FIG. 1 looking in the string direction. FIG. 3 is a schematic perspective view from obliquely above of an apparatus for manufacturing the mattress according to FIGS. 1 and 2, according to one embodiment of the present invention. FIG. 4 is a view of a portion of the mattress of FIG. 1 from above. FIG. 5 is a schematic top perspective view of a hole drilling step in the manufacture of a mattress according to an alternative embodiment of the present invention. FIG. 6a is a schematic cross-sectional side view showing an alternative step and apparatus for inserting pieces of foam element into a spring. FIG. 6b is a schematic cross-sectional side view showing an alternative step and apparatus for inserting the foam element pieces into the spring. FIG. 7 is a schematic diagram of the foam element of FIGS. 6a and 6b in various cross-sectional views. FIG. 8 is a schematic top view of a mattress according to an embodiment of the present invention. FIG. 9 is a schematic top view of a mattress according to another embodiment of the present invention. FIG. 10 is a schematic top view of a mattress according to yet another embodiment of the present invention. FIG. 11 is a schematic top view of a mattress according to yet another embodiment of the present invention. FIG. 12a is a schematic cross-sectional view of the top or bottom of a firing element according to an embodiment of the present invention. FIG. 12b is a schematic cross-sectional view of the upper or lower portion of a firing element according to an embodiment of the present invention. FIG. 12c is a schematic cross-sectional view of the top or bottom of a firing element according to an embodiment of the present invention. FIG. 13a is a schematic cross-sectional view of an alternative foam element disposed in a spring unit according to another embodiment of the present invention. FIG. 13b is a schematic cross-sectional view of an alternative foam element disposed in a spring unit according to another embodiment of the present invention. FIG. 13c is a schematic cross-sectional view of an alternative foam element disposed in a spring unit according to another embodiment of the present invention. FIG. 14a is a schematic side view of a piece of foam material having various relaxed shapes, according to an embodiment of the present invention. FIG. 14b is a schematic side view of a piece of foam material having various relaxed shapes, according to an embodiment of the present invention. FIG. 14c is a schematic side view of a piece of foam material having various relaxed shapes, according to an embodiment of the present invention. FIG. 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. FIG. 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. FIG. 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. FIG. 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. FIG. 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. FIG. 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. FIG. 16 is a schematic cross-sectional side view of a mattress according to another embodiment of the present invention.

As illustrated, sizes of layers and regions may be exaggerated for illustrative purposes and, therefore, may be provided to illustrate the overall configuration of embodiments of the present invention. Like reference numbers refer to like elements throughout.

The present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:

As shown in Figures 1 and 2, a 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 suitably constructed from a preferably weldable textile material, although other materials such as different types of plastic materials may also be used. It is also possible to use non-weldable textile materials such as cotton cloth.

In this embodiment, the mattress comprises a string 3 of casing material 2 in which a number of pockets 4 are arranged. Here, the pockets are defined by at least one longitudinal connection line 5 extending parallel to the longitudinal direction of the string and a number of transverse connection lines 6 extending transversely to the longitudinal direction of the string. Preferably, the string comprises a casing material made of a folded piece material. In the folded piece material, the fold lines extend in the longitudinal direction of the string. A closed longitudinal connection line 5 is arranged on the opposite side of the string. The transverse connection lines extend between the fold lines and the longitudinal connection lines. Alternatively, it is also possible to use more than one piece material to construct each string. In this case, additional connection lines may be required.

In the mattress, the springs are oriented in the pockets so that the connection lines are located laterally of the springs and therefore between adjacent springs. Preferably, the casing material portions at the ends of the springs are therefore essentially free of other connections. However, it is also possible to arrange the longitudinal connection lines so that they overlap the spring ends above the strings.

In at least one of the springs, and preferably in all springs, the casing parts arranged at the ends of the springs are arranged to move towards each other via the springs and to connect with each other by a connecting device 7, preferably providing at least some bias. Preferably, the casing parts move towards each other so as to make 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 comprise a mechanical connecting element, such as a clamp or a rivet, or a surface joint, such as glueing or welding. However, other fixing elements are also conceivable. The load on the fixing element is usually small, since it is only loaded when the mattress is not loaded and is not loaded at all when the mattress is loaded. In a preferred embodiment, the joint is formed by one or more welds.

Furthermore, the end portion is provided with an opening 9 passing through the joint and through the spring. The opening 9 is preferably substantially circular, but other shapes can be used. Openings 9 running the length of the spring can help provide proper breathability of the mattress. The openings are also used to stabilize and secure the foam element, as will be further explained below. As shown in FIG. 4, the openings are here substantially circular, but openings of other shapes can be used. The diameter of the openings is, for example, 5 mm to 50 mm, preferably 10 mm to 30 mm, more preferably 15 mm to 25 mm. The diameter of the openings is preferably much smaller than the diameter of the largest turn of the coil spring, and preferably much smaller than the diameter of the smallest turn of the coil spring.

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

Many sizes of coil springs can be used in connection with the present invention, and essentially any size spring can be used. However, it is preferred to use springs with a diameter of 2-10 cm, more preferably 3-7 cm, and most preferably 4-5 cm. Preferably, the spring comprises at least 3 turns, and preferably less than 10 turns. Furthermore, the spring is advantageously made from a helical wire with a thickness in the range of 0.5-3 mm, preferably a wire thickness of 1.0-2.5 mm. Preferably, the spring is slightly spool-like, i.e. with smaller turns at the top and bottom.

In the mattress described above, the strings with springs are preferably arranged side by side and fixed to each other, as shown in Figures 1 and 2. The rows are preferably connected to each other by means of fastening points 8, which advantageously connect the longitudinal connection line 5 of one string to the side of the adjacent string. Of course, a smaller or larger number of fastening points than shown are conceivable. It is also possible to arrange long fastening lines instead of several short fastening points. The connection between the strings can be made by welding or gluing. Preferably, the welded or glued surfaces are distributed around the opening so that the interconnection is provided with good strength. This can be achieved, for example, by points distributed symmetrically around the opening or by a continuous line surface around the opening. However, alternatively, the connection can be made by clamps, Velcro tapes or in any other suitable manner.

By arranging the interconnection of the strings via longitudinal connection lines, the strings are automatically spaced apart without the need for additional casing material. This allows the mattress to have fewer springs, which is very advantageous from the standpoint of comfort on the one hand and makes the mattress more cost-effective on the other hand.

The solution with a string of continuous casing material with individual casings for the springs is only one of many ways to implement the invention. The invention can involve, for example, individual casings for the springs that are then attached to each other, a continuous sheet of casing material for the entire mattress with casings for the individual springs, or any other solution regarding the casing material.

A mattress according to the above-mentioned embodiment may be manufactured by enclosing the springs in pockets of strings of casing material. The pockets are made of a continuous casing material with at least one longitudinal connection line running parallel to the longitudinal direction of the strings and a number of transverse connection lines running transverse to the longitudinal direction of the strings. The method further comprises the steps of moving the casing parts located against the ends of the springs towards each other, connecting them to each other, and drilling or forming by any other means openings in the casing parts at the ends of the springs. There may also be a step of interconnecting the strings side-by-side.

For example, the strings may be manufactured by folding the casing material in half and placing transverse welds to form an open pocket. Compressed springs are then inserted into the pockets, which are then sealed with welds running along the strings. Additional welds are then placed through each spring to connect the end sections together, preferably without rotating the springs. Openings are drilled through the casing sections at the ends, preferably at the center of the weld points or continuous welds. The springs are then joined side-by-side with the longitudinal welds between the strings to form the mattress.

The steps can be performed in a different order. The connecting lines are then placed on the sides of the springs, and thus between adjacent springs. The step of moving the end portions towards each other usually involves biasing the springs by connection with a connecting element, so that the springs in the biased state have a shorter longitudinal extent than in the original unbiased state. Such biasing can be done immediately after the springs are enclosed 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 biasing is done before the springs are enclosed in the string pockets. In this case, a significantly smaller amount of casing material can be used. 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.

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

Furthermore, the strings with springs are preferably interconnected side-by-side, for example as shown in FIG. 2. As mentioned above, this can be done by locating the fixing points on the longitudinal connection lines for fixing on the sides of adjacent strings.

An apparatus for carrying out the above-mentioned method comprises means for enclosing the coil springs in a pocket of the string. The pocket is made of 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 transversely to the longitudinal direction of the string. As shown diagrammatically in FIG. 3, the means may comprise a device for folding the casing material around the row of springs and a facility 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 over the springs, it is alternatively possible to compress the springs separately and insert them in a compressed state into the folded casing.

The welding fixture preferably comprises welding dies 11, 12 movable towards the casing material and corresponding anvils 13, 14 on the opposite side. Separate welding fixtures are preferably arranged to produce the longitudinal and transverse connection lines, respectively. The means for encapsulating the coil springs are adapted to place the connection lines on the sides of the springs, such that the connection lines are located between adjacent springs in the finished mattress.

The device further includes means for moving the casing portions disposed relative to the ends of the spring toward each other to connect them together, and means for interconnecting the strings side-by-side.

The means for moving the casing parts arranged against the ends of the spring towards each other to connect them to each other preferably comprises an insertion device 15 and a counter device 16, such as an anvil arranged at a distance therefrom. In use, the spring is arranged with one end facing the insertion device and the other end facing the anvil. The insertion device is movable towards and away from the anvil, moving the casing material at one spring end past the spring towards the casing material on the other side. The insertion device 15 is preferably a welding die for producing the connecting weld. However, alternatively, other fastening means can be provided instead. It is also possible to use a movable anvil. In this case, both sides of the spring are pressed towards each other, after which a stitching, welding or similar connection can be made.

The device also comprises means for drilling holes in the casing portion at the end of the spring. The perforator here comprises a perforator piece 17 and an abutment or anvil 18. The perforator 17 here is driven through the spring against the abutment 18, so that a substantially circular opening is drilled 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 opening may also be formed by pre-drilling the casing prior to the other steps.

The interconnection of the casing parts can be done in a step simultaneous with the formation of the openings, for example by performing a drilling step and forming weld points around the drilled holes, as shown in FIG. 5. Here, a circular insertion device 15 is attached to a circular counter device 16, while a perforator 17 moves through the tubular insertion device to form holes through the springs in the casing parts. The connector here comprises four projections 19 in the profile of the parts to be connected to the insertion device. The projections define the weld points to be formed between the casing parts.

A system according to the invention may advantageously comprise multiple parallel devices, for example two devices operating in parallel.

Furthermore, means are included for interconnecting the strings with the springs, preferably side-by-side, as shown, for example, in FIG. 2. As mentioned above, this may be accomplished by locating fastening points on the longitudinal connection lines for fastening the sides of adjacent strings together.

The biasing of the spring is preferably performed so that the length of the spring in the biased state is less than 2/3, preferably less than 1/2, of the length of the same spring in the original unbiased state. Also, the ratio of the length of the spring to its diameter in the biased state is preferably less than 2, preferably less than 1, and most preferably less than 1/2.

The string's longitudinal connection lines may be located on the spring. However, preferably, the longitudinal connection lines are located along the sides of the spring, rather than on the ends.

Furthermore, the smooth end parts are moved towards each other and attached, for example by welding. Thus, in this way, very thin mattresses can be provided, in fact one or a few centimeters. For example, a mattress having a thickness of 25 mm can be provided. It can therefore be said that the invention is well suited for seat cushions, overlay mattresses to be placed on other mattresses, and similar applications where a thin mattress is required. For this reason, it is very advantageous to be able to make overlay or topper mattresses made of pocket springs. This is not only because they can be made softer, which increases comfort, but also because springs usually do not fatigue over time, as materials such as polyethylene do. The mattress according to the invention is very light, soft and comfortable, and can, if desired, be very sturdy and firm due to the bias. The openings through the springs also ensure good ventilation of the mattress, which provides better dryness, cold and/or warmth, reduced growth of bacteria, etc., and increased comfort.

The invention allows the height of the spring elements to be easily adjusted by changing the position and size of the fastening devices when connecting the end portions to each other. In this way, it is easy to provide different thicknesses in different parts of the mattress or to provide mattresses of different thicknesses without having to make any changes in the manufacturing process apart from this connection. This makes the manufacturing very flexible and controllable. In particular, it is possible to provide mattresses with a cup shape or the like, to be used as seat cushions or other mattresses intended for sitting. Similar height variations can also be utilized to control the position of the user on the mattress.

The mattress described above is of the type including a plurality of interconnected coil springs enclosed in a casing, the springs having a first end and a second end. For at least one of the springs, casing portions disposed at the first and second ends of the spring are connected to one another via the spring by a joint. The jointed casing portions include an opening extending through the spring. Also, a piece of foam material is disposed in the opening, as described in more detail below.

In one embodiment shown in Figures 6a and 6b, such a piece of foam material 20 is shown inserted, and a process and apparatus for the insertion of the foam piece is also shown.

The foam piece 20 extends toward the first end of the spring in a first portion 20a and toward the second end of the spring in a second portion 20b.

The foam piece 20 is inserted through an opening 9 in the casing/pocket around the spring to form a waist in the opening. This mechanically holds the foam piece in place in a fixed position. This creates a strong mechanical connection, so it is not necessary to connect the foam piece directly to the coil spring. Instead, the foam is spaced from the coil spring by the casing fabric. Optionally, further connection elements such as gluing, welding, etc. may be used to increase the fixing force. In most cases, however, a mechanical connection is sufficient.

Thus, each pocket or casing enclosing each spring is formed as a toroid having a doughnut shape forming a circular compartment in which the spring is enclosed. Furthermore, the foam may be formed as an hourglass having a central waist and two inflated mushroom-shaped portions extending in opposite directions from the waist. Due to the elasticity and flexibility of the foam, the two shapes, the toroidal shape of the casing and the hourglass shape of the foam, may be highly complementary to each other, so that the overall cross-sectional shape of the pocket unit may be in the form of a circle, a rectangle with rounded corners, or a shape in between.

At least one of the first and second portions 20a and 20b of the foam piece preferably extends beyond the first and second ends of the springs, respectively. In the illustrated example of Figures 6a and 6b, both the first and second portions 20a and 20b extend beyond the first and second ends of the springs, such that the foam provides the outermost layer of the mattress on both sides.

For example, as shown in FIG. 7, the piece of foam material 20, when placed in the spring, may have a generally circular waist or other shape that corresponds to the shape of the opening. Towards both ends, the piece of foam material expands from the waist to the top and bottom. The portions 20a, 20b that protrude 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 contemplated.

The portion of the foam material that extends beyond the first or second end of the spring may have a cross-sectional dimension that is equal to or greater than the diameter of the top or bottom end convolution of the spring through which it extends, so that the extended foam material forms a relatively continuous layer above the spring.

In embodiments, the maximum cross-sectional dimension of the portion of the foam material extending from the spring may be equal to or greater than the diameter of the largest turn of the spring, such that the foam material essentially covers the spring when viewed parallel to the axial direction of the spring.

The upper and lower surfaces formed by portions 20a and 20b, respectively, may be slightly curved and convex, as shown diagrammatically in FIG. 12a. However, other shapes are contemplated. For example, as shown in FIG. 12b, the upper and/or lower surfaces may have an inwardly directed depression to form a concave or cup shape. As shown in FIG. 12c, the upper and/or lower surfaces may be generally flat.

In the illustrated examples of Figures 6a and 6b, the piece of foam extends beyond the spring in both an upward and downward direction. However, it is contemplated that the piece of foam extends from the spring in only one direction.

It is also contemplated to provide a piece of foam material that generally extends into the plane formed by the upper and/or lower turns of the spring, such that the upper and/or lower surfaces of the piece of foam material are generally flush with the upper and/or lower sides of the pocket unit. An example of such is shown in FIG. 13a, where the upper portion 20a' essentially terminates in the plane formed by the upper turns of the spring, and the lower portion 20b' substantially terminates in the plane formed by the lower turns of the spring.

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

In yet another embodiment shown in FIG. 13c, the piece of foam material having portions 20a''' and 20b''' does not extend beyond the upper and lower turns of the spring, and as a result terminates at a position completely inside the spring.

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

In an embodiment, as shown in Figures 6a and 6b, the piece of foam material may be compressed at the portion disposed within the opening to form a waist in the piece of foam material at the opening. The first and second portions of the piece of foam material expand to progressively larger cross-sectional shapes in a direction away from the opening. Thus, the foam material may have a relaxed shape prior to insertion into the spring, and once in place within the spring, may assume one of the shapes described above, for example an hourglass shape that forms a waist in the middle of the piece of foam material. The relaxed shape is the shape of the foam material when unconstrained within the spring, i.e., the unbiased shape.

The piece of foam material may have a relaxed shape with essentially uniform cross-sectional shape and cross-sectional dimensions when viewed perpendicular to the longitudinal direction. The relaxed shape may be, for example, a rectangular parallelepiped shape, such as a square cube or a square prism, as shown in the illustrated examples of Figs. 6a and 6b, and as shown in Fig. 14a. However, other relaxed shapes are also contemplated, such as a cylindrical shape, as shown diagrammatically in Fig. 14b. In the illustrated example, the cylinder has a circular cross-section. However, other cross-sectional shapes are also contemplated, such as ellipses, polygons, etc. Other shapes are also possible, such as shapes with dimensions that vary over their height. For example, the relaxed shape may have a smaller cross-sectional dimension in the middle and a larger cross-sectional dimension at the top and bottom, forming a waist in the material, as shown in 14c, for example. In one embodiment, the foam material may have a relaxed shape that generally corresponds to the shape it will assume when placed in the spring unit.

The foam material can be composed of a variety of materials. In a preferred embodiment, the foam is composed of urethane, latex, or viscoelastic foam.

The mattress can be produced by first enclosing the springs in pockets, connecting the casing material to each other at the ends via the springs and forming openings in the connection areas, as described above with respect to FIG. 2. The foam piece can then be inserted into the spring unit. For example, a foam piece having a relaxed shape larger than the restrained shape assumed at the insertion position can be compressed for insertion. For example, the foam piece can be forced into an open ended cone 21, such as a funnel, as shown in FIG. 6a. However, other methods of compressing the foam piece to a smaller dimension are also conceivable. For example, a temporary outer envelope layer can be formed around the foam material, which can be removed once the foam material has reached its intended position.

In another embodiment shown in FIG. 6b, the piece of foam material is instead pulled through an opening in the spring. This can be done, for example, by a gripping tool 21'. The gripping tool 21' is configured to be inserted through the opening 9, grip the piece of foam material 20 on the opposite side, and pull the piece of foam element into an insertion position by retracting the gripping tool 21'. The gripping tool 21' can be provided with a pick-up claw or pick-up jaw at its end, for example with two or more arms/claws that can be separated before gripping and that can move towards each other to grip the piece of foam material. The gripping tool 21' can function as tweezers by having only two arms/claws. However, more than two arms/claws may be provided, for example three, four or five arms/claws. In such an embodiment, where the gripping tool 21' has at least three arms/claws spaced around the circumference, the gripping tool can also be used to compress the piece of foam material when it is gripped to facilitate insertion through the opening 9.

However, alternatively, the foam material may be formed directly within the spring unit, for example by injecting it in liquid form at the desired location.

In the embodiment shown in FIG. 3 and described above, the casing preferably defines a plurality of interconnected parallel strings, each string comprising 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 transversely to the longitudinal direction of the strings. Springs are then disposed in pockets of the casing and the strings. The connection lines are preferably disposed laterally of the springs and therefore between adjacent springs.

However, the mattress can also be formed in other ways. In one embodiment, shown diagrammatically in FIG. 8, the casing is formed by an upper textile sheet and a lower textile sheet, which are connected to each other between the springs to form pockets. For example, the casing can be formed by a relatively large upper sheet and a relatively large lower sheet. The sheets are connected to each other along the longitudinal connection lines 6' and the transverse connection lines 6, for example forming a grid pattern. This forms individual pockets for the springs. In such an embodiment, the pockets are therefore 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 the length dimension and in the width dimension.

The connections 10 of casing material placed above and below the spring and passing through the spring, forming openings 9 through the spring, can be achieved in the same manner as in the embodiment described above with reference to FIG. 3. Furthermore, the insertion of the pieces of foam material through the strings and openings can also be done in the same manner as described above with reference to FIG. 6, for example.

In the embodiment of FIG. 8, the connections 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. The connecting lines may thereby form a grid between which the springs are enclosed.

However, alternatively, the connection lines 6" may be arranged, for example, as a circle or polygon surrounding each spring, as shown in FIG. 9.

In yet another alternative, as shown diagrammatically in FIG. 10, the connections 6" may be formed as point connections between the springs, preferably located in each group of four springs, i.e. in each "four-leaf clover" formed by the springs, or connections formed as an X, an O, etc.

9 and 10, the connections 10 of the casing material above and below the spring and passing through the spring, forming the openings 9 through the spring, can be achieved in the same manner as in the embodiment described above with reference to FIG. 3. Furthermore, the insertion of the pieces of foam material through the strings and openings can be done in the same manner as described above with reference to FIG. 6, for example.

11, a schematic diagram of the mattress of FIG. 8 is shown with a piece of foam material 20 inserted. Here, the foam material is arranged to extend from the springs and form a covering portion having a generally rectangular cross section as also shown in FIG. 7. The foam material is now dimensioned such that, when viewed in a direction parallel to the axial direction of the springs, the foam material essentially covers the springs. This results in a relatively uniform upper layer formed from the foam material.

To improve ventilation and breathability, additional secondary openings may be provided at locations outside the springs. Such additional secondary openings 9' are shown in FIG. 9. The additional secondary openings may be located, for example, at locations between four adjacent springs, and may be located in all such groups of four adjacent springs, as shown in the example, i.e. in the center of each "four-leaf clover" formed by the springs.

The pieces of foam material may consist of a homogenous material. However, the pieces of foam material may also consist of a combination of different materials. Such different materials may for example be arranged in different layers to form, for example, a laminated structure. The layers are preferably arranged in a plane parallel to the mattress plane, i.e. one above the other in a direction parallel to the axial direction of the springs.

Some exemplary embodiments comprising such laminated foam pieces are described with reference to Figures 15a-15f.

In the exemplary embodiment of FIG. 15a, the piece of foam material includes a central layer 202 that is disposed through an opening in the spring, a separate top layer 201, and a separate bottom layer 203. In such an embodiment, the top and/or bottom layers may have different properties than the central layer, e.g., softer, denser, more viscoelastic. 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 top layer 201 and/or bottom layer 203.

In the exemplary embodiment of FIG. 15b, a similar structure is shown as described with respect to FIG. 15a, except that here, the separate layer 201 is only disposed on one side of the central layer 202'. Here, the separate layer 201 is disposed as the top layer, but it could also be disposed as the bottom layer.

In the exemplary embodiment of FIG. 15a, the top layer 201 and the bottom layer 203 may be made of the same material and have essentially the same properties to provide the same properties on both sides of the mattress. However, it is also possible to use different materials for the top layer 201 and the bottom layer 203', as shown diagrammatically in FIG. 15c.

In the embodiment of FIG. 15b, the piece of foam material comprises two layers, whereas the embodiments shown in FIGS. 15a and 15c comprise three layers. However, it is contemplated that there may be more than three layers, for example four layers, five layers, or even more layers.

In the embodiment of FIG. 15d, the configuration of the foamed material pieces is essentially similar to that of FIG. 15a, except that here a thin additional layer 204 is disposed above the top layer 201 and a thin additional layer 205 is disposed below the bottom layer 203. The thin additional layer may be, for example, a foamed material, but may be other types of materials. One or both of the additional layers 204 and 205 may be comprised of a cloth, a pad, a woven piece, etc. The additional thin layers 204 and 205 may be arranged to provide, for example, a more durable upper and/or lower surface, a smoother upper and/or flat surface, a denser upper and/or lower surface, etc.

As shown diagrammatically in FIG. 15e, such a thin additional layer 204 may be disposed on only one side of the piece of foam material.

Additionally or alternatively, such additional thin layers 204' and 205' may be disposed between layers of foam material, such as between top layer 204 and middle layer 202 and/or between middle layer 202 and bottom layer 203, as in the illustrative example of FIG. 15f. Such additional thin layers 204' and 205' may be used for purposes such as providing a stronger connection between different foam materials to facilitate manufacturing.

In the above-described embodiment, the pocket unit is configured such that the casing parts located at the first and second ends of the spring are connected to each other by a joint via the spring, with the openings being located close to each other in the joined casing parts. However, in certain applications, particularly in the case of relatively thin mattresses, it is also conceivable that the casing parts remain spaced apart and are not joined inside the spring, and pieces of foam material are placed through the openings located at the first and second ends of the pocket.

Figure 16 shows such an embodiment diagrammatically. Here, the casing parts arranged 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. The openings 9a, 9b formed in the casing parts are thus spaced apart from each other by a distance that essentially corresponds to the height of the spring. The foam element 20 is arranged through both the first and second openings 9a, 9b, with its top 20a extending from the first opening 9a and its bottom 20b extending from the second opening 9b. The central part extending through the spring is shown here as a relatively thin section with a cross section that essentially corresponds to the size of the openings. However, alternatively, the central part may be wider and thicker and extend towards both sides of the spring. In such an embodiment, the piece of foam material may form two waists at the two openings with a wider section between them.

The present invention has been described above by means of embodiments. However, several variations of the present invention may be envisaged. For example, as mentioned above, other types of fixing elements may be used, as well as other solutions regarding casing materials, spring sizes. Also, the pieces of foam material may have other relaxed and/or restrained shapes. Furthermore, the device and method may be designed in other ways. Such obvious variations must be considered as constituting the present invention as defined by the appended claims.

Claims (16)

1. A spring mattress comprising a plurality of interconnected coils enclosed in a casing,
The spring has a first end and a second end.
a spring mattress, wherein for at least one of the springs, casing portions disposed at the first and second ends of the spring include an opening through the spring and a piece of foam material disposed 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. The spring mattress of claim 1, wherein at least one of the first and second portions of the piece of foam material extends beyond the first and second ends of the springs, respectively. the casing portions disposed at the first end and the second end of the spring are connected to each other by a joint via the spring;
3. The spring mattress according to claim 1 or 2, wherein the openings are arranged in the joined casing parts. each piece of foam material is compressed at the portion located at the opening to form a waist in the piece of foam material at the opening;
4. The spring mattress of claim 3, wherein the first and second portions of the piece of foam material gradually expand to a larger cross-sectional shape in a direction away from the opening. The spring mattress of any one of claims 1 to 4, wherein the portion of the foam material that extends beyond the first or second ends of the springs has a cross-sectional dimension that is equal to or greater than the diameter of the bottom or top end convolution of the spring through which the foam material extends. The pocket spring mattress of any one of claims 1 to 5, wherein the piece of foam material has a relaxed shape of a rectangular parallelepiped or cylindrical. The pocket spring mattress of any one of claims 1 to 6, wherein the piece of foam material has a relaxed shape with an essentially uniform cross-sectional shape and cross-sectional dimensions when viewed perpendicular to the longitudinal direction. A pocket spring mattress according to any one of claims 1 to 7, wherein the average diameter of the openings is in the range of 30-70% of the average diameter of the springs, preferably in the range of 40-60%, and most preferably in the range of 45-55%. A pocket spring mattress according to any one of claims 1 to 8 dependent on claim 3, wherein the casing portions are connected by a continuous weld around the periphery of the opening or by a plurality of weld points distributed around the periphery of the opening. the casing defines a plurality of interconnected strings in a side-by-side arrangement;
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 transversely to the longitudinal direction of the strings;
A coil spring is disposed in the casing of the string;
A pocket spring mattress as claimed in any one of the preceding claims, wherein the connecting lines are preferably located laterally of the springs and therefore between adjacent springs. The casing is formed by an upper fabric sheet and a lower fabric sheet,
A pocket spring mattress as claimed in any preceding claim, wherein the sheets connect to each other between the springs to form the pockets. The pocket spring mattress of any one of claims 1 to 11, wherein the piece of foam material comprises at least two layers of different materials. The pocket spring mattress of any one of claims 1 to 12, wherein the mattress further comprises additional second openings disposed between the springs. a device for encapsulating the spring in a casing material;
a device for forming openings in casing portions located at the first and second ends of the spring and selectively connecting the casing portions to one another by means of a joint through the spring;
and a device for inserting pieces of foam material into the openings so 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 device for connecting the casing parts via said spring,
15. The machine according to claim 14, wherein the apparatus comprises an insertion device and an opposing device arranged at a distance therefrom, adapted to effect relative displacement towards and away from each other to bring casing material at the spring ends of a spring arranged between casing materials closer to each other via the springs so that the springs are in a biased state, an interconnection device for forming a joint connecting the casing material thus integrated from the two spring ends, and a perforation device for perforating an opening in the interconnection between the casing material from the two spring ends. 1. A method for manufacturing a spring mattress comprising a plurality of interconnected coil springs enclosed in a casing, comprising the steps of:
encapsulating the spring in a casing material;
biasing at least one of the springs;
and interconnecting the springs.
the step of biasing the springs comprises the partial steps of moving casing portions positioned against the ends of the springs toward each other through the springs and interconnecting them with joints; forming openings through the springs at the joints; and placing pieces of foam material 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.

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