Method of monitoring the quality of a mattress

Abstract

The invention pertains to a method of monitoring the quality of a mattress during its lifetime, wherein the mattress is an assembly of multiple separate parts, wherein the parts are mechanically interconnected, the method comprising during its lifetime, assessing at least one property of the mattress, determining whether or not the property meets a predetermined specification, and when the property does not meet the predetermined specification, identifying a part of the said multiple separate parts that corresponds to the property, removing the identified part from the assembly and optionally replacing the removed part with a replacement part, wherein the mattress that is monitored is manufactured by forming the mechanical interconnection with an adhesive, which adhesive has a first order phase-transition temperature between 80° C. and 180° C., at which temperature the adhesive undergoes a solid-liquid transition, and wherein before the said removing of the identified part, the adhesive with which this part is interconnected with other parts in the assembly is heated to a temperature above its phase-transition temperature, whereafter the identified part is grasped and pulled out of the assembly. The invention also pertains to a method of manufacturing a mattress suitable for use in this monitoring method.

Claims

1. A method of monitoring quality of a mattress during a lifetime of the mattress, the method comprising: (a) providing a mattress comprised of an assembly of multiple separate parts which are mechanically interconnected with an adhesive having a first order phase-transition temperature at which the adhesive undergoes solid-liquid transition of between 80° C. and 180° C., (b) assessing during the lifetime of the mattress at least one property of the mattress, (c) determining whether or not the property assessed according to step (b) meets a predetermined specification, and when the property does not meet the predetermined specification, identifying a part of the multiple separate parts that corresponds to the property as a defective part to be removed from the mattress, (d) heating the adhesive interconnecting the identified defective part with any other parts of the assembly above the first order phase-transition thereof so as to disconnect the identified defective part from any other parts of the assembly, and thereafter (e) removing the disconnected identified defective part from the assembly by grasping and pulling the disconnected identified defective part out of the assembly.

2. The method according to claim 1, wherein the assembly comprises a first layer having length and width dimensions that correspond to length and width dimensions of the mattress, and wherein the first layer is a support layer comprising a collection of contiguous pocketed springs, wherein each pair of two contiguous pocketed springs are mechanically interconnected by the adhesive.

3. The method according to claim 1, wherein the assembly comprises two stacked layers having length and width dimensions that correspond to length and width dimensions of the mattress, and wherein the two stacked layers have a different composition and different rigidity, and wherein the two stacked layers are mechanically interconnected by an intermediate layer of the adhesive.

4. The method according to claim 3, wherein a second layer of the two stacked layers is an upholstery layer.

5. The method according to claim 4, wherein the upholstery layer comprises a three-dimensional reticulated material.

6. The method according to claim 5, wherein the reticulated material is connected directly to the first layer with the adhesive.

7. The method according to claim 1, wherein the adhesive has a first-order transition temperature between 100° C. and 160° C.

8. The method according to claim 1, wherein the adhesive has a first-order transition temperature between 130° C. and 150° C.

9. The method according to claim 1, wherein the adhesive comprises at least 50% by weight of a polymer selected from the group consisting of polyurethane, polycarbonate, polyester, mixtures thereof and copolymers thereof.

10. The method according to claim 1, wherein the adhesive comprises at least 50% by weight of a polyester.

11. The method according to claim 1, wherein the assembly of multiple separate parts comprises two or more parts that are made of a polyester polymer.

12. The method according to claim 1, wherein step (a) comprises: (a1) providing a first layer of contiguous pocketed springs, wherein pockets of the pocketed springs are interconnected by adhering the pockets together with the adhesive having the first order phase-transition temperature between 80° C. and 180° C., and (a2) connecting an overlaying upholstery layer to the first layer by adhering the upholstery layer to the first layer with the adhesive applied in step (a1) or with another adhesive that has a first order phase-transition temperature between 80° C. and 180° C. at which temperature the another adhesive undergoes a solid-liquid transition.

13. The method according to claim 12, wherein the upholstery layer comprises a three-dimensional reticulated material.

14. The method according to claim 12, wherein the adhesive has a first-order transition temperature between 100° C. and 160° C.

15. The method according to claim 12, wherein the adhesive comprises at least 50% by weight of a polymer selected from the group consisting of polyurethane, polycarbonate, polyester, mixtures thereof and copolymers thereof.

16. The method according to claim 12, wherein the adhesive comprises at least 50% by weight of a polyester.

17. The method according to claim 12, wherein the pockets, the overlaying upholstery layer and the adhesive are made of a polyester polymer.

18. A mattress obtained by the method according to claim 12.

19. The method according to claim 12, wherein the adhesive has a first-order transition temperature between 120° C. and 150° C.

20. The method according to claim 1, further comprising the step of: (f) replacing the removed defective part with a replacement part.

Description

BRIEF DESCRIPTION OF DRAWING FIGURES

(1) FIG. 1 is a DSC curve of an adhesive for use in the present invention;

(2) FIG. 2 is a view on a partly cross-sectioned mattress;

(3) FIG. 3 is a cross section of a pocketed spring; and

(4) FIG. 3A is a schematic view of a monitoring system that may be used to monitor the quality of a mattress.

EMBODIMENTS OF THE INVENTION

(5) In a first embodiment of the invention the assembly comprises a first layer having length and width dimensions that correspond to length and width dimensions of the mattress (i.e. having dimensions in the same range, i.e. less than ten times smaller or less than ten times larger, particularly maximally 5 times smaller or larger, more particularly 1-2 times smaller or larger, or even having the same dimensions), wherein the first layer is a support layer comprising a collection of contiguous pocketed springs, and each pair of two contiguous pocketed springs are mechanically interconnected by the adhesive. Although the nature of the adhesive for use in the present invention is intrinsically brittle, it was found that it can still be used to durably connect neighbouring springs by gluing their respective pockets together. Even a thin layer of the brittle adhesive is able to durably connect these (textile) pockets. This is not straightforward since the springs can individually be compressed, causing high tearing loads between the pockets.

(6) In a second embodiment of the invention the assembly comprises two stacked layers having length and width dimensions that correspond to length and width dimensions of the mattress, wherein the layers have a different composition and different rigidity and wherein the two stacked layers are mechanically interconnected by an intermediate layer of the adhesive. Many mattresses consist essentially of a rectangular piece of foam (which may comprise different layers of a varying foam type), provided with a ticking. The foam layer(s) provide the support as well as the comfort. Another concept is to use two stacked layers of very different composition and rigidity, one layer to provide the needed support, the other layer to provide the comfort. A downside of the latter constitution is that these two different materials of different composition and different rigidity, deform completely differently when the mattress is in use and still, have to be mechanically interconnected to provide for a durable mattress. To achieve this, it was beforehand expected that the particular brittle adhesives of the presently claimed type would not be suitable for creating the durable connection. Surprisingly however, these adhesives appeared to be suitable, even in this arrangement of layers.

(7) In a further embodiment the first layer of the two stacked layers is a support layer comprising a collection of contiguous pocketed springs. The second layer of the two stacked layers may be an upholstery layer. Even in such a case, where the deformation between the two layers is markedly different (not only because of the two very different compositions, but also of the presence of separate springs), the adhesives as used in the present invention may provide for a strong durable bond between neighbouring pockets and the upholstery layer, and at the same time allow for easy de-connection of individual parts. Preferably, the upholstery layer comprises a three-dimensional reticulated material (such as for example ZenXit® of Gabriel, Aalborg Denmark; AirSkin® spacer fabric of Springs Creative Products Group, Rock Hill, S.C., USA; Labyrinth® of Enkev, Volendam, The Netherlands; Arnitel® of DSM, Heerlen, The Netherlands; Enkair® of Low&Bonar, Arnhem, The Netherlands) or (such or other) comfort layers as available from Müller Textiles, Wiehl, Germany or TWE Meulebeke BVBA, Meulebeke, Belgium) which may be connected directly to the first layer with the adhesive. It was found that a reticulated layer has an advantage over a foam layer as basic part of a comfort layer since in a reticulated layer air can move freely through the layer which increases the breathability of the mattress.

(8) In another embodiment the adhesive has a first-order transition temperature between 100° C. and 160° C. Preferably the adhesive has a first-order transition temperature between 120° C. and 150° C.

(9) In yet another embodiment the adhesive comprises at least 50% by weight of a polymer chosen from the group consisting of polyurethane, polycarbonate, polyester, mixtures thereof and/or copolymers thereof. Preferably the adhesive comprises at least 50% by weight of a polyester.

(10) In again another embodiment, wherein the assembly of multiple separate parts comprises two or more parts that are made of a polymer, each of the said two or more parts are made of polyester polymer. In other words, all parts that are made of polymer material in the said matrass are made of polyester polymer (not excluding that different parts are made of different kinds of polyester, e.g. different kinds of PET or even a combination of PET and PBT). This embodiment is in particular advantageous since it is easier to assemble and recycle a one-polymer-type mattress given the fact that the pockets as well as the other materials such as the overlaying upholstery material can be manufactured from polyester. So, apart from removing the optional metal springs, no disassembly is needed for complete recycling of the mattress. This method will in particular be useful for mattresses which are manufactured by using polymer pockets and polymer overlaying upholstery. Indeed, when adding other polymer parts to manufacture the mattress such as for example the ticking, or additional foam elements, these are advantageously also made of polyester polymer in this embodiment.

(11) The invention will now be further explained using the following examples.

EXAMPLES

(12) Example 1 provides various adhesives for use in the present invention.

(13) Example 2 describes a method to manufacture a mattress for use in the present invention.

(14) Example 3 describes the monitoring the quality of a mattress during its lifetime, including replacing a worn part.

EXAMPLE 1

(15) In this example various adhesives that are useful in the present invention are described, viz. adhesives that have a first order phase-transition temperature between 80° C. and 180° C., at which temperature the adhesive undergoes a solid-liquid transition. In FIG. 1 a differential scanning calorimetry (DSC) curve of a first adhesive is provided. This adhesive is a polyester made by reacting a mixture of 10 moles terephthalic acid with 8.7 moles 1,6-hexanediol and 1.5 moles ethylene glycol, an elevated temperature (above 220° C.) under the removal of water until adequate conversion.

(16) The DSC measurement was done by following the following path at a speed of 5° C. per minute as follows:

(17) 1. Start at −50° C.

(18) 2. Increase to 250° C.

(19) 3. Cool down to 25° C.

(20) What is shown in the curve of FIG. 1 is the following. The heating from −50° C. to 250° C. (lower line) shows the glass transition (2.sup.nd order transition) around 40° C. Also, around 110° C. the solid adhesive starts to melt. Above 140° C. the adhesive is completely molten and transformed into a liquid. The upper line shows the cooling of the adhesive from 250° C. to 25° C. Between 110° C. and 60° C. the crystallization of the molten adhesive is seen with the crystallization point around 80° C. The melting temperature (peak temperature) of this adhesive is 130.7° C. The DSC curve shows that this adhesive undergoes a first order transition at 130.7° C., at which temperature the adhesive undergoes a solid-liquid transition.

(21) Here below in Table 1, several useful adhesives are mentioned (by providing the constituting monomers in the correct mole ratio), together with the temperature at which these adhesives undergo a first order solid-liquid transition.

(22) TABLE-US-00001 TABLE 1 Adhesives and their melting temperature Adhesive Tm [° C.] 6.04 mole Terephthalic acid/3.96 mole Fumaric acid/ 91° C. 10.7 mole 1,6-Hexanediol 7.5 mole Terephthalic acid/2.5 mole Adipic acid/ 108° C./118° C. 10.7 mole 1,6-Hexanediol 10.0 mole Terephthalic acid/9.31 mole 121° C./133° C. 1,6-Hexanediol/1.49 mole Ethyleneglycol 10.0 mole Terephthalic acid/4.0 mole 171.6° C. Diethyleneglycol/4.0 mole Ethyleneglycol 10.0 mole Terephthalic acid/8.7 mole 130.7° C. 1,6-Hexanediol/1.5 mole Ethyleneglycol 7.5 mole Terephthalic acid/2.5 mole Adipic acid/ 91.6° C. 8.7 mole 1,6-Hexanediol/2.8 mole Ethyleneglycol

EXAMPLE 2

(23) This example describes in general the constitution and manufacturing of a common type of mattress, the so called pocket spring mattress. What most pocket coil mattresses have in common is that the coil spring, contained in an individual fabric pocket, lies under a sheet or multiple sheets (i.a. a layer), of padding and cushioning material that provide initial loading softness, a softer sleeper feel, help in reducing localized high pressure interface points, reduce the sensation of lying directly on a metal spring, and help conform to body contours.

(24) Referring now to FIGS. 2 and 3, a pocket spring mattress 1 generally has a layer of pocket coil springs 6 (the encasing textile pockets for each spring have not been depicted in FIG. 2), alternatively know as Marshall Type Springs, engaged with a base 3. Mattress 1 further has an upholstery layer comprising a basic padding layer 4 and an upper cushioning layer 5 disposed above pocket coil springs 6. The mattress is enclosed by a mattress ticking cover 2. First described in U.S. Pat. No. 685,160, a Marshall Type Spring is a coil spring 8 encased in a material pocket 7, closed by stitches 9. The pocket coil assemblies are made by inserting coil springs 8 into respective fabric coil pockets 7 that are usually connected in the form of a continuous pocket coil strip. These strips are often made at a specialized production facility and thereafter cut into length and assembled in a 2-dimensional structure to form the support layer of the mattress as depicted in FIG. 2. Layers 4 and 5 are connected to this support layer. To manufacture a mattress that is suitable for use in the present invention, the individual pockets are mechanically connected to each other by using an adhesive that has a first order phase-transition temperature between 80° C. and 180° C., at which temperature the adhesive undergoes a solid-liquid transition. By heating the adhesive to above its phase transition temperature, it can be easily applied to the individual pockets, for example by using a method as known from WO 02/44076 (assigned to Calino S.A). After cooling down to below its crystallisation temperature, the adhesive provides for a strong interconnection of the pockets. Using the same adhesive, or another adhesive (as long as it has a first order phase-transition temperature between 80° C. and 180° C., at which temperature the adhesive undergoes a solid-liquid transition), the layers 4 and 5 can also be connected into the assembly.

EXAMPLE 3

(25) This example describes the monitoring of a quality of a mattress (for example the mattress of example 2) during its lifetime, including replacing a worn part. The mattress can be monitored for various properties such as local elasticity of the springs, local elasticity of the upholstery layer, integrity of the various parts, local (lasting) deformation, contamination etc. One or more of these properties is monitored. This can be done by human inspection, or by using a dedicated monitoring apparatus. In case of human inspection for example, the mattress can be inspected for integrity of the comfort layer by applying friction over the ticking to search for irregularities. Elasticity of the springs can also be monitored by hand, by simply pressing and releasing each spring, but it can also be checked automatically in a dedicated testing device such as shown in FIG. 3A whereby an upper cushioning layer 5 is placed over the pocket coil springs 6 and a property such as a local elasticity may be checked using a testing device 20. When it is determined that the property which is monitored for does not meet a predetermined specification (for example: “upholstery layer may not be torn or locally deformed”, or “each spring must have at least 95% of its original spring stiffness”), the part in the mattress assembly that correspond to that property is identified. In case of not meeting the “upholstery layer may not be torn”, this is the upholstery layer and in case of not meeting the “each spring must have at least 95% of its original spring stiffness” for an individual spring, this is the spring.

(26) The method of the invention now enables relatively easy removal of the part that provides the lack of meeting the predetermined property. Of course, the ticking layer 2 needs to be removed in any case. If the upholstery layer was identified as the “out of spec” part, the adhesive between the upholstery layer and the pocket springs needs to be heated to above its first order transition temperature (its melting point). This can be done for example by using microwaves, heat radiation, light radiation or other form of heating that is able to locally heat a layer in a mattress assembly. As soon as the adhesive is heated and turned into a liquid, the upholstery layer can be easily removed since it is no longer mechanically interconnected with the other parts in the assembly. After that the upholstery layer can be replaced with a new layer. Also, if upon inspection it appears that many sprigs are for example broken, it can also be decided to de-connect all of the pocket springs to completely dismantle the mattress for complete recycling.