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 a 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.

2. A 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. A 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 layers have a different composition and different rigidity, characterised in that the two stacked layers are mechanically interconnected by an intermediate layer of the adhesive.

4. A method according to claim 2, wherein a second layer of the two stacked layers is an upholstery layer.

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

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

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

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

9. A method according to claim 1, wherein 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.

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

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

12. A method of manufacturing a mattress suitable for use in a method according to claim 1, wherein the method comprises: providing a first layer of contiguous pocketed springs, wherein the pockets are interconnected by adhering the pockets together using 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, connecting an overlaying upholstery layer to the first layer by adhering the upholstery layer to the first layer using the said adhesive or another 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.

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

14. A method according to claim 12, wherein the adhesive has a first-order transition temperature between 100° C. and 160° C., preferably between 120° C. and 150° C.

15. A method according to claim 12, wherein 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.

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

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

18. A mattress obtainable with a method according to claim 11.

Description

EXAMPLES AND FIGURES

[0028] Example 1 provides various adhesives for use in the present invention.

[0029] Example 2 describes a method to manufacture a mattress for use in the present invention.

[0030] Example 3 describes the monitoring the quality of a mattress during its lifetime, including replacing a worn part.

[0031] FIG. 1 is a DSC curve of an adhesive for use in the present invention.

[0032] FIG. 2 is a view on a partly cross-sectioned mattress.

[0033] FIG. 3 is a cross section of a pocketed spring.

EXAMPLE 1

[0034] 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.

[0035] The DSC measurement was done by following the following path at a speed of 5° C. per minute as follows:

[0036] 1. Start at −50° C.

[0037] 2. Increase to 250° C.

[0038] 3. Cool down to 25° C.

[0039] 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 (2nd 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.

[0040] 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.

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

[0041] 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.

[0042] 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

[0043] 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. 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.

[0044] 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.