WO2023080787A1

WO2023080787A1 - A method to produce a mattress, a mattress obtainable with this method and a system for applying this method

Info

Publication number: WO2023080787A1
Application number: PCT/NL2022/050626
Authority: WO
Inventors: Dennis NIJLAND; Martijn PAF; Ronald Adriaan VAN DER AA
Original assignee: Koninklijke Auping B.V.
Priority date: 2021-11-08
Filing date: 2022-11-07
Publication date: 2023-05-11
Also published as: NL2029662B1; EP4429998A1

Abstract

The present invention pertains to a method to produce a mattress (1) having a predetermined length, width and height, the method comprising providing an in essence rectangular assembly of contiguous pocketed springs (8), the rectangular assembly having a length, width and height corresponding to the said predetermined length, width and height of the mattress (1), wherein the springs extend in the height direction; laterally compressing the assembly of pocketed springs (8) in both the length and width direction using a compression means; positioning two pairs of two resilient side walls (3,4,5,6) at opposing lateral sides of the compressed assembly of pocketed springs (8), thereby forming in essence a rectangular enclosure for the assembly of pocketed springs (8), wherein the sidewalls (3,4,5,6) have a height that corresponds to the height of the assembly of pocketed springs (8), and wherein in each pair of opposing side walls (3,4,5,6), these sidewalls are mutually positioned at a predetermined distance that corresponds to the predetermined length and width dimensions of the mattress (1) respectively; removing the compression means such that the assembly of pocketed springs (8) partially expands laterally towards the opposing resilient sidewalls (3,4,5,6) which are maintained at the said predetermined distance; wherein preceding the removal of the compression means, a reversible adhesive is provided in between the sides of the assembly (8) and each of the opposing sidewalls (3,4,5,6), in order to reversibly connect the assembly of the pocketed springs (8) with the side walls (3,4,5,6) while maintaining the predetermined distance between these side walls (3,4,5,6).

Description

A METHOD TO PRODUCE A MATTRESS, A MATTRESS OBTAINABLE WITH THIS METHOD AND A SYSTEM FOR APPLYING THIS METHOD

GENERAL FIELD OF THE INVENTION

The invention in general pertains to a method to produce a mattress having a predetermined length, width and height, the method comprising providing an in essence rectangular assembly of contiguous pocketed springs having a length, width and height corresponding to the said predetermined length, width and height of the mattress, wherein the springs extend in the height direction, and enclosing the assembly of pocketed springs by resilient side walls. This way, the assembly of pocketed springs is spatially limited and maintained at stable dimensions. Typically, a separate bottom and top layer, also referred to as a deck, are provided for additional stability and comfort, whereafter the complete package of pocketed springs, sidewalls and optional bottom and top layers is packed in a closely woven ticking or other upholstery cover to define a sleeping surface of the mattress. The invention also pertains to a mattress obtainable with this method, and a system that is devised for applying the novel method of production.

BACKGROUND OF THE INVENTION

As indicated, the present invention relates to mattress construction methods, which methods typically aim at facilitating placement of the various mattress components before the mattress is closed by providing the outer mattress cover. Generally, mattresses are formed with a mattress central portion, surrounded by a resilient mattress border construction, typically consisting of a foam material. The mattress central portion typically includes an assembly of coil springs connected together, enclosed in fabric pocket. Such pocketed springs are also referred to as Marshall springs. The mattress central portion may additionally comprise polyurethane or latex foam layers, or synthetic or natural fibres. To make the mattress robust and to provide sufficient support, mattress manufacturers thus have introduced mattresses with an encased inner core that gives greater edge support. The side wall or edge, e.g. a polymer foam, is also able to conform easily to various small size differences of the core that come about by slight (lateral) dimensional variations of individual springs. The edge is typically glued to a support layer and the coil unit may also be joined to the support layer, such as by a border wire and hog rings. The sleeping surface of the mattress is typically covered with a quilted fabric.

US 7,200,884 discloses a method of manufacturing a mattress including the steps of providing a mattress core consisting of an assembly of pocketed springs, side walls surrounding the core, and an upholstery mattress cover, placing adhesive patches on surfaces of the side walls and the mattress core, and at least temporarily attaching with the adhesive patches the side walls to lateral surfaces of the mattress core to hold the side walls in place relative to the mattress core during assembly of the mattress. The method further includes at least temporarily attaching with the adhesive patches the upholstery cover to a major surface of the mattress core to hold the upholstery cover in place relative to the mattress core during assembly of the mattress, and thereafter permanently attaching an edge portion of the mattress cover to an edge portion of one por more of the side walls.

US 8,464,381 likewise discloses a core made from an assembly of pocketed springs, enclosed by side walls. The fabric pocketing material within which the springs are contained is semi-impermeable to air flow through the fabric material, which means that the fabric material, while permitting some air flow through the material, does so at a rate which retards or slows the rate at which a spring maintained in a pocket of the fabric may compress under load or return to its original height when a load is removed from the pocketed spring. In other words, air may pass through such a semi-impermeable material, but at a very reduced rate compared to the rate at which air usually flows freely through a fabric material. This increased the sleeping comfort of the mattress, although the system is expensive and the rate of semi-permeability of the fabric not constant over time.

US 10,881 ,217 discloses a mattress assembly that includes a dimensionally stable base layer and an inner pocketed spring core located over the base core layer. The mattress also includes a side wall assembly located around the perimeter of the inner core. The side wall assembly may include a spacer fabric located over and extending transverse to the base layer. The spacer fabric can include a first knit layer, a second knit layer, and an inner fibrous material located therebetween. The disclosed method of forming the mattress assembly includes providing the dimensionally stable base layer as a substrate for the mattress and disposing a plurality of coil springs positioned within individual pockets in an inner core located over the base core layer. The method includes thereafter disposing a spacer fabric around a perimeter of the inner core. The spacer fabric may define at least a portion of a side wall assembly of the mattress and the spacer fabric may be positioned over the base core layer. As taught here above, the spacer fabric may include a first knit layer, a second knit layer, and an inner fibrous material located therebetween.

US 2016/0066702 and US 2016/0214219 (both assigned to Dreamwell ltd) disclose a method of manufacturing a mattress, including a process for inserting an innercore unit of a mattress into a bucket during manufacture of a mattress, and includes feeding an innercore unit onto a support surface. Thereafter innercore unit is mechanically lifted in a vertical motion from the support surface. Then a bucket having a base layer and a side rail assembly about a perimeter of the base layer is fed to define a cavity onto the support surface and underneath the innercore unit, wherein the innercore unit is dimensioned to precisely fit within the cavity. An adhesive is applied to one or more surfaces of the cavity. Then the innercore unit is mechanically lowered into the cavity of the bucket to form an assembled innercore unit and bucket.

OBJECT OF THE INVENTION

Although the known methods of manufacturing a mattress are adequate, a need remains for a method that can be performed in a very small amount of time, yet producing a robust and precisely dimensioned mattress, which is comfortable to sleep on, even without a very thick deck layer. Also circularity, i.e. the possibility of deassembling the various parts after the mattress is worn, is an important object to meet.

SUMMARY OF THE INVENTION

In order to meet the object of the invention, a method to produce a mattress as introduced here above in the section title GENERAL FIELD OF THE INVENTION has been devised, the method comprising providing an in essence rectangular assembly of contiguous pocketed springs, the rectangular assembly having a length, width and height corresponding to (thus being similar, or at least being in agreement with, but not necessarily be the same as) the said predetermined length, width and height of the mattress, wherein the springs extend in the height direction (i.e. the compression and decompression direction of the springs is in the height direction of the mattress); laterally compressing the assembly of pocketed springs in both the length and width direction using a compression means; positioning two pairs of two resilient side walls at opposing lateral sides of the compressed assembly of pocketed springs, thereby forming in essence a rectangular enclosure for the assembly of pocketed springs (thus four walls together forming one enclosure for the assembly of pocketed springs), wherein the sidewalls have a height that corresponds to the height of the assembly of pocketed springs, and wherein in each pair of opposing side walls, these sidewalls are mutually positioned at a predetermined distance that corresponds to the predetermined length and width dimensions of the mattress respectively; removing the compression means such that the assembly of pocketed springs partially expands laterally (thus not leading to a laterally totally uncompressed state) towards the opposing resilient sidewalls which are maintained at the said predetermined distance (in order to meet predetermined dimensions of the mattress); wherein preceding the removal of the compression means, a reversible adhesive is provided in between the sides of the assembly and each of the opposing sidewalls, in order to reversibly connect the assembly of the pocketed springs with the side walls while maintaining the predetermined distance between these side walls.

In this method, the manufacture does not start off with the assembly of the pocketed springs, around which an enclosure of side wall is made, but with an enclosure of sidewalls that meets predetermined dimensions by positioning an maintain the opposing sidewalls at a predetermined distance, and only thereafter fill the enclosure with the mattress core. This is because the inventors recognized that the pocketed springs inherently have small lateral size variations, which may ultimately lead to variations of more than 1-2 cm in the width and length of a complete assembly of (laterally) uncompressed pocketed spring, which on its turns leads to unwanted size variations in the width and length of a mattress. This problem can be overcome by starting with the positioning of the side walls at predetermined mutual distances, this way forming an outer casing for the spring core with exact predetermined dimensions, and then compressing a slightly oversized pocketed spring assembly to be able and fit into the outer side wall casing, after which the compression means can be removed and the assembly is at least partly decompressed. This way, the inner pocketed spring core stably fits the side wall casing and every mattress produced this way, despite variations in lateral size of the pocketed spring has the same approximate size (small variations may still arise from variations other than that of the pocketed springs). This is where the present concept deviates for example from US 2016/0066702 where the inner cores assembly is dimensioned to slidingly fit into the outer wall casing. Multiple additional advantages of the lateral compression and partly decompression to fit into the casing occur when using this concept. The first advantage is that the mattress is more comfortable to sleep on. Because the assembly of pocketed springs is inherently slightly compressed (the compression ratio of the spring assembly in the ultimate mattress is for example around 5-10%), lateral stress due to a person lying on the mattress is precompensated. Thus, the situation where a mattress is elongated to a value such that the pocketed springs come under lateral tension and thus feel “hard”, is only arrived at when applying very high loads (for example when the person sleeping on the mattress is very heavy, or when applying high pressure locally). The consequence is that for a person of a particular weight, the mattress feels more comfortable. Another advantage is that automation of the production method is easier to accomplish. Positioning a compressed assembly of fixed dimensions in an encasing of fixed dimensions is easier to automate than making a casing around an assembly of pocketed springs that has significant variable dimensions. Yet another advantage is that a reversible adhesive can be used (i.e. an adhesive which can be treated to deconnect easily) even when desiring a robust connection. Normally such adhesives are regarded as less strong, but since there is an inherent push of the pocketed spring assembly against the side walls, the strength of a reversible adhesive was found to be sufficient. This means that the parts can be de-assembled for recycling relatively easily.

The invention also pertains to a mattress obtainable with the novel method. Due to the inherent presence some lateral compression in the pocketed spring core, the mattress feels more comfortable, in particular under high (local) loads. Also, the use of a reversible adhesive makes the mattress more easy to recycle.

The invention also pertains to a system for the production of a mattress having a predetermined length, width and height, the system comprising a support for receiving a dimensionally stable mattress base layer, a forming means for automatically (thus without the need of any operator intervention, not excluding that the action is operated initiated or terminated) forming an in essence rectangular enclosure consisting of two pairs of two opposing side walls that are connected to the mattress base layer and extend vertically therefrom, thereby forming a rectangular open space having predetermined length and width dimensions for receiving a mattress core, a means for providing an in essence rectangular assembly of pocketed springs, which assembly has length and/or width dimensions that exceed the length and/or width dimensions of the rectangular space, a compression means for laterally compressing the assembly of pocketed springs automatically, to provide that the assembly in its compressed state has length and width dimensions that subceed the length and width dimensions of the rectangular space, means for automatically providing a reversible adhesive on the sides of the side walls facing the rectangular space, and optionally on the mattress base layer, positioning means for automatically positioning the compressed assembly of pocketed springs into the rectangular space onto the mattress base layer to serve as the mattress core, and means to automatically remove the compression means after positioning the assembly of pocketed springs into the rectangular space onto the mattress base layer.

FURTHER EMBODIMENTS OF THE INVENTION

In a further embodiment of the method according to the invention, the assembly of pocketed springs is laterally compressed for 5-20% during the method of manufacturing. This means that in the ultimate produced mattress the inherent compression of the assembly as present between the side walls may be typically around 1-15%, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13 or 14%. The value of 5-20% appears to be suitable to deal with inherent variations in dimensions of individual pocketed springs and at the same time provide a comfortable and easy to assemble mattress. A compression of at least 5% also provides sufficient open space (and thus room to maneuver) between the sides of the assembly and the side walls to enable automatic positioning of the assembly to fit the encasing, i.e. the outer side wall enclosure. In particular, in the production method the assembly of pocketed springs is laterally compressed for 8-12%.

In yet a further embodiment the opposing resilient side walls are maintained at the said predetermined distance by connecting the sidewalls to a dimensionally stable mattress base layer, for example a non-woven base layer such as a felt base as commonly known. It was found that a relatively easy way to maintain the predetermined distance is to fix the side walls to the base layer. Although for example a mould or other way could be used, since the base layer has to be fixed to the rest of the mattress anyway, it is advantageous to simply fix the side walls at the beginning of the process to the base, this way forming the enclosure/casing for the pocketed spring core. In this embodiment, the said positioning of the resilient side walls at opposing lateral sides of the compressed assembly of pocketed springs may take place by placing the compressed assembly of pocketed springs in between the sidewalls connected to the dimensionally stable mattress base layer, and onto this base layer. So instead of actually moving the side wall towards the compressed assembly of pocketed springs, the side walls can be kept at their predetermined position (simply by being firmly connected at their base to the mattress base layer) while the assembly of pocketed springs is actually moved and placed in the open space that the side walls enclose. The assembly of pocketed springs can be simply placed onto the same base layer.

In a preferred embodiment, before placing the compressed assembly of pocketed springs onto the base layer, the base layer is provided with an adhesive to connect the assembly of pocketed springs to the base layer. Yet further preferred is that the sidewalls and assembly of pocketed springs are connected to the dimensionally stable mattress base layer using the said reversible adhesive. This way, all major parts of the mattress are connected using the same reversible adhesive which not only makes production easier but also disassembly.

In still a further embodiment, the two pairs of opposing side walls are provided as four separate parts that are each cut of a length of wall material. The advantage of this embodiment is that the material for the sidewall can be provided to the manufacturing machine in the form of a roll. It was recognised that it is easier to automatically feed material from a roll and to cut off a required length of that material, than to feed separate pieces of material that have the required predetermined length dimensions. In a particular embodiment, before connecting the side walls to the base layer, each separate side wall as cut off from the roll of side wall material is positioned on a frame that serves as a mould to meet the predetermined distance between each pair of sidewalls, whereafter the connection of the sidewalls to the stable base layer comprises moving the frame towards this base layer, and removal of this frame after the sidewall are connected to the base layer. The use of such an inner frame is easy to automate and may lead to very precise predetermined dimensions. Next to this, the side wall material can in fact be wound around the frame when leaving the roll, and only once secured to the inner frame, be cut at the ends of each side. This appeared to be far more easy to automate then to position pre-cut pieces at exact positions. In a particular further embodiment, after removal of the (inner) frame, each side wall is at its surface directed away from a centre of the mattress, mechanically gripped by a needle gripper. This way, the free lateral end (top end) of each side all can be moved for some distance while controlling its exact position. In particular this can be used when desiring to dose the adhesive to the inner sides of the side walls: before the reversible adhesive is provided, each needle gripper can be used to bend each corresponding side wall while being connected to the base layer, such that each free top side of each side wall is moved away from the centre of the mattress towards the base layer (and thus takes a more horizontal configuration), whereafter the adhesive is provided on the inner side of each side wall. It appeared to be easier to dose adhesive on a more horizontal surface than on a vertical surface.

In again a further embodiment wherein the springs are of a magnetisable metal, the assembly of pocketed springs is compressed using two pairs of two opposing compression plates that compress the assembly laterally while maintaining the compressed state by gripping the top surface of the compressed assembly with a magnetic gripper adjacent its outer circumference. It was found that a needle gripper is not ideal for grasping the pockets. Although it could be done (textile can be easily gripped with such needle grippers), there is a risk that the needles hit the metal springs and get damaged. Therefore, a magnetic gripper is advantageously used instead. By magnetically gripping the compressed assembly adjacent its outer circumference, the compressed state can be maintained to a considerable level even when the compression plates are removed. This opens the option to remove in a first step the two pairs of two compression plates while maintaining the compressed state at least partly with the magnetic gripper and in a consecutive second step by removing the magnetic gripper. This makes it easier to fit the compressed assembly of pocketed springs into the open space of the side walls, in particular when the compressed assembly has hardly any smaller lateral dimensions than the open space in between the side walls. The risk of adhesive sticking to the compression plate, or even removed by a plate rubbing along the adhesive is therewith minimised or even prevented.

The present method also allows the common practice of providing a top side of the assembly of pocketed springs, after it is connected to the side walls, with a top layer of a resilient material to further increase comfort.

Advantageously, the reversible adhesive is a hot melt adhesive. This makes it very easy to disassemble the various parts. By simply heating the adhesive to a temperature above its melting temperature, the adherent properties vanish almost completely, and the parts can be easily taken apart. It is noted that not all hot melt are reversible adhesives. On the contrary, the majority of hot melt adhesives are reactive adhesives (in particular polyurethane adhesives) that once hardened provide for a durable and irreversible connection.

In an embodiment, the reversible (hot melt) adhesive, the side walls and the pockets of the pocketed springs are all made of a (compatible) polyester. This means the mattress can be recycled by simply melting the mattress and picking up the metal springs from the melt.

All of the above described (and hereunder further exemplified) particular embodiments have corresponding embodiments in the system according to the invention.

The invention will now be further illustrated using the following specific examples.

EXAMPLES

Figure 1 is a schematic view of the main components of a pocketed spring mattress.

Figure 2 is a side view of variants of a mattress according to figure 1, provided with a deck layer.

Figure 3 is a schematic overview of the main components of a system according to the invention.

Figure 4 is a schematic view of a robot to pick of various layers for use in a system according to the invention.

Figure 5 is a schematic view of a robot to provide adhesive to various surfaces, for use in a system according to the invention.

Figure 6 is a schematic view of a forming means to produce a mattress core enclosure for a mattress according to the invention. Figure 1

Figure 1 is a schematic view of the main components of a pocketed spring mattress 1. The mattress has as a base a dimensionally stable felt layer 2, having a length (X direction) and width (Y direction) that are virtually the same as the dimensions of the ultimate mattress. Adhered to the base layer 2 with a polyester hot melt adhesive are two pairs of two opposing side walls (3,4 and 5,6 respectively), which side walls are made of a polyester foam and together form an enclosure for the mattress core. The core consists of an assembly of pocketed metal springs 8 (of which only a part is shown in figure 1) that fill up the open space 7 of the enclosure. The height of the side walls and pocketed springs (direction Z) correspond to the height of the mattress (see also figure 2A and 2B). In this embodiment, the contiguous pockets are made of a polyester fabric. The pockets are adhered to each other using a polyester hot melt adhesive. The same adhesive is used to adhere the pockets to the base layer 2. Also, the pocket assembly is adhered to the sidewall using the same polyester hot melt adhesive. So apart from the felt base layer and the metal springs, all materials of the mattress 1 are made of polyester.

Figure 2

Figure 2 is a side view of variants of a mattress according to figure 1 , provided with a deck layer. The components 2, 5 and 6 are also depicted in figure 1. In figure 2A a variant is shown wherein the pocketed springs 8 and the side walls 5,6 have the same height, which height corresponds to the height (thickness) of the ultimate mattress, but is slightly less than that height. This is because the deck 10 covers the assembly of pocketed springs as well as the top end of the sidewalls. In figure 2B a variant is shown wherein the deck 10 covers only the assembly of pocketed springs but is laterally enclosed by the sidewalls. In this embodiment the side walls have a height that is virtually the same as that of the ultimate mattress, differing only in the thickness of the upholstery cover (as such not shown in figure 2) and the felt base layer.

Figure 3

Figure 3 is a schematic overview of the main components of a system 100 according to the invention. The system comprises two feed lines 20 and 20’ (duplicates of each other to increase production capacity), which are transfer supports for receiving and thereafter automatically feeding various layers of material and components for manufacturing a mattress, in particular for receiving and supporting the mattress base layer and the assembly of pocketed springs. These components are put onto the supports manually, and when properly aligned, further transported towards manufacturing supports 22 and 22’ respectively, where the mattresses are formed. At these supports 22 and 22’, so called “layer-pick-up” (LPA) robots 21 and 2T are present (identical robots), which pick up the fed components from the transport supports and place them on manufacturing supports 22 and 22’ (see figure 4 for more details of these LPA robots). In between the manufacturing supports 22 and 22’, there is a so-called glue robot (see figure 5 for more details) that is able to provide a hot melt adhesive onto several surfaces of components present on supports 22 and 22’.

In the area opposite from the LPA robots, a robot 24 is provided, the so called sidewall robot, or SW robot (see figure 6 for more details). These SW Robot together with feeding means 25, which means is able to feed sidewall material form a length of this material wound up on a roll, constitutes a forming means for automatically forming the enclosure of side walls.

Once manufactured (to an extent basically as shown in figure 1 or 2, the mattress is picked up by the respective robot from the manufacturing support and put on exit lane 30 to leave the system 100. For safety reasons, the robot work area is fenced with a fence 31.

In operation, firstly a human operator puts a felt base layer of the required length and width dimensions on support 20. After proper alignment, the operator initiates transport of these layer towards LPA robot 21. The layer is picked up by this LPA robot using needle-grippers and laid on support 22. In the meantime, the rectangular enclosure of side walls is formed by forming means 24, 25 (see figure 6 for more details). Although made from one length of side wall material (a polyester foam), the enclosure is formed to consist of four separate pieces of material that are not interconnected (they are cut at the corners). When completed, the base layer is provided with a string of hot melt adhesive using glue robot 23, at the part of the surface of the base layer to which the side walls need to be connected. Immediately thereafter, since the hot melt adhesive solidifies very quickly (within 25-35 seconds), the SW robot positions the side walls to their predetermined position on the base layer which leads to the automatic connection of the side walls to the base layer (upon solidification of the hot melt adhesive), thereby forming the enclosure for the mattress core, at predetermined length and width dimensions. In the mean time the operator has put an assembly of pocketed springs on the transport support 20. This assembly (which typically contains 2-3 sub-assemblies as known form the art) has slightly wider dimensions, at least in one direction, preferably in two directions, than the open space of the side wall enclosure. After transport to the LPA robot 21 , the robot picks up the assembly by using lateral compression plates at all four sides of the assembly, and a top magnetic gripper plate (see figure 4). The compression is to a percentage such that the assembly has smaller length and width dimensions than the open space of the side wall enclosure. Just before the assembly of compressed pocketed springs is positioned into the rectangular space onto the mattress base layer to serve as the mattress core, the glue robot is used to provide on the top of the mattress base a layer of hot melt adhesive, as well as on the inside surfaces of each of the four sidewalls. To obviate the latter, each side wall is gripped adjacent its (free) top end with a needle gripper, and bend away from the centre of the mattress to extend at least partly in horizontal direction. This way, providing a layer of hot melt adhesive using the glue robot is easier. After the hot melt adhesive is provided, the compressed assembly of pocketed springs is positioned into the open space of the side wall into the base layer, whereafter the lateral compression plates are removed, maintaining the magnetic gripper plate on the assembly, and the sidewall are pushed back in vertical position towards the assembly of pocketed springs. After that, the magnetic gripper is also released. This way, the heart of the mattress as shown in figure 1 is formed, wherein the parts are interconnected using a (reversible) hot melt adhesive. Optionally, the deck layer 10 is also put on the mattress using the system (via manually placing the deck on support 20 and following the above procedure correspondingly). Ultimately, the mattress is picked up by the LPA robot and put on exit lane 30. This way, in about 70 seconds a mattress (without its ticking) can be manufactured.

Figure 4

Figure 4 is a schematic view of the LPA robot 21 as introduced in figure 3, to pick of various layers for use in a system according to the invention. The robot has a main body 210 and support 211 , as well as movable are 212. This set-up is common in the art. Connected to the arm are individually movable compression plate pairs 213, 214 and 215, 216. Also depicted is magnetic gripper plate 218 which can move independently of the compression plates, and which is able to grip almost the entire surface of an assembly of pocketed springs when compressed by the compression plates. The LPA robot is also provided with needle-grippers around its circumference, of which grippers only the front gripper row 217 is shown in figure 4. These needle grippers can be used to pick up the felt base layer and the deck layer.

Figure 5

Figure 5 is a schematic view of the glue robot 23 to provide the hot melt adhesive to various surfaces, for use in a system according to the invention. The robot 23 basically has the same set-up as LPA robot 21 , viz. a main body 230 and support 231 , as well as movable arm 232. At the end of the arm a glue head 233 is provided with which head a string of hot melt adhesive, or multiple parallel strings at the same time can be provided on any surface.

Figure 6

Figure 6 is a schematic view of the forming means to produce mattress core enclosure for a mattress according to the invention. These means comprise SW robot 24 and side wall feeder 25. To start with the latter, the side wall feeder comprise a cassette 248 in which a length of side wall material 245 is present in wound up form. The material can be fed out of the cassette as a strip of material 246 onto a table 244 with guiders 249. In practice, multiple cassettes can be present next to each other to hold side wall material of different heights, only one of which is shown in figure 6.

The SW robot 24 basically has the same set-up as LPA robot 21 and glue robot 23, viz. a main body 240 and support 241 , as well as movable arm 242. At the end of the arm a frame 243 is provide which frame has adjustable length and width dimensions, corresponding to the dimensions of mattresses to be produced. A length 246 of the side wall material 245 is fed onto the table 244 and guided by guider 249. The length is than gripped by one side of the frame 243 using needle-grippers, and cut off of the length of material 246 at the corner of the frame 243. Then, the frame is rotated over 90°, to form the next side wall of the enclosure around the frame. This process continues until an enclosure consisting of four separate pieces of side wall material is formed around frame 243. Thereafter the enclosure is moved over to the manufacturing table 22 as described here above with reference to figure 3.

Claims

1. A method to produce a mattress having a predetermined length, width and height, the method comprising:

- providing an in essence rectangular assembly of contiguous pocketed springs, the rectangular assembly having a length, width and height corresponding to the said predetermined length, width and height of the mattress, wherein the springs extend in the height direction;

- laterally compressing the assembly of pocketed springs in both the length and width direction using a compression means;

- positioning two pairs of two resilient side walls at opposing lateral sides of the compressed assembly of pocketed springs, thereby forming in essence a rectangular enclosure for the assembly of pocketed springs, wherein the sidewalls have a height that corresponds to the height of the assembly of pocketed springs, and wherein in each pair of opposing side walls, these sidewalls are mutually positioned at a predetermined distance that corresponds to the predetermined length and width dimensions of the mattress respectively;

- removing the compression means such that the assembly of pocketed springs partially expands laterally towards the opposing resilient sidewalls which are maintained at the said predetermined distance;

- wherein preceding the removal of the compression means, a reversible adhesive is provided in between the sides of the assembly and each of the opposing sidewalls, in order to reversibly connect the assembly of the pocketed springs with the side walls while maintaining the predetermined distance between these side walls.

2. A method according to claim 1, characterised in that the assembly of pocketed springs is laterally compressed for 5-20%.

3. A method according to any of the preceding claims, characterised in that the assembly of pocketed springs is laterally compressed for 8-12%.

4. A method according to any of the preceding claims, characterised in that the opposing resilient side walls are maintained at the said predetermined distance by connecting the sidewalls to a dimensionally stable mattress base layer.

5. A method according to claim 4, characterised in that the said positioning of the resilient side walls at opposing lateral sides of the compressed assembly of pocketed springs takes place by placing the compressed assembly of pocketed springs in between the sidewalls connected to the dimensionally stable mattress base layer, and onto this base layer.

6. A method according to claim 5, characterised in that before placing the compressed assembly of pocketed springs onto the base layer, the base layer is provided with an adhesive to connect the assembly of pocketed springs to the base layer.

7. A method according to any of the preceding claims 4-6, characterised in that the sidewalls and assembly of pocketed springs are connected to the dimensionally stable mattress base layer using the said reversible adhesive.

8. A method according to any of the preceding claims 4-7, characterised in that the two pairs of opposing side walls are provided as four separate parts that are each cut of a length of wall material.

9. A method according to claim 8, characterised in that each separate side wall is positioned on a frame that serves as a mould to meet the predetermined distance between each pair of sidewalls, and wherein the connection of the sidewalls to the stable base layer comprises moving the frame towards this base layer, and removal of this frame after the sidewalls are connected to the base layer.

10. A method according to claim 9, characterised in that after removal of the frame, each side wall is at its surface directed away from a centre of the mattress, mechanically gripped by a needle gripper.

11. A method according to claim 10, characterised in that before the reversible adhesive is provided, each needle gripper is used to bend each corresponding side wall while being connected to the base layer, such that each free top side of each side wall is moved away from the centre of the mattress towards the base layer, whereafter the adhesive is provided on the inner side of each side wall.

12. A method according to any of the preceding claims, wherein the springs are of a 16 magnetisable metal, characterised in that the assembly of pocketed springs is compressed using two pairs of two opposing compression plates that compress the assembly laterally while maintaining the compressed state by gripping the top surface of the compressed assembly with a magnetic gripper adjacent its outer circumference.

13. A method according to claim 12, characterised in that the compression means are removed by removing in a first step the two pairs of two compression plates while maintaining the compressed state at least partly with the magnetic gripper and in a consecutive second step by removing the magnetic gripper.

14. A method according to any of the preceding claims, characterised in that a top side of the assembly of pocketed springs, after it is connected to the side walls, is provided with a top layer of a resilient material.

15. A method according to any of the preceding claims, characterised in that the reversible adhesive is a hot melt adhesive.

16. A method according to any of the preceding claims, characterised in that the reversible adhesive, the side wall and the pockets of the pocketed springs are made of a polyester.

17. A mattress obtainable according to any of the preceding claims.

18. A system for the production of a mattress having a predetermined length, width and height, the system comprising:

- a support for receiving a dimensionally stable mattress base layer;

- a forming means for automatically forming an in essence rectangular enclosure consisting of two pairs of two opposing side walls that are connected to the mattress base layer and extend vertically therefrom, thereby forming a rectangular open space having predetermined length and width dimensions for receiving a mattress core;

- a means for providing an in essence rectangular assembly of pocketed springs, which assembly has length and/or width dimensions that exceed the length and/or width dimensions of the rectangular space;

- a compression means for laterally compressing the assembly of pocketed springs automatically, to provide that the assembly in its compressed state has length and width 17 dimensions that subceed the length and width dimensions of the rectangular space;

- means for automatically providing a reversible adhesive on the sides of the side walls facing the rectangular space, and optionally on the mattress base layer;

- positioning means for automatically positioning the compressed assembly of pocketed springs into the rectangular space onto the mattress base layer to serve as the mattress core;

- and means to automatically remove the compression means after positioning the assembly of pocketed springs into the rectangular space onto the mattress base layer.