Patent Application
20210244192
This patent application claims benefit to and priority of Luxembourg Patent Application No. LU100834 filed on 12 Jun. 2018 entitled “A Padding having Hollow Volumes and a Flexible Band”.
The invention relates to a foam padding having hollow volumes and a flexible band with an electrically conducting layer and to the use of such a padding as a mattress. The flexible band with an electrically conducting layer is capable of transporting excess thermal energy from the hollow volumes in the foam padding and its surrounding material, thereby allowing e.g. to reduce temperature in certain sections of a body resting on said padding.
Various types of paddings are known. In the state of the art, paddings are known that comprise hollow volumes, usually provided for giving comfort to the padding. On example of a known padding is a so called innerspring mattresses. These innerspring mattresses have a very open air-filled space within and around the springs. In any event the spring does not have any real thermal benefit and at least does not extent from one hollow volume or space to another. In foam-based paddings the hollow volumes will be much smaller and indeed one section of the padding will cover many of such hollow spaces.
Some mattresses have been proposed in the art which use cooling or heating fluid or propelled air. However, those approaches have proven to be unpractical.
Another example of a padding is known from US Patent Publication No. US2015/034528 (Tempur-Pedic) which describes a cushion for prolonged cooling that includes a region with a phase change material and an underlying copper layer connected to another region of phase change material. The phase change materials are filled with paraffin wax melting at certain predetermined temperature and thereby absorbing thermal energy. At the moment of melting, this phase change material feels ‘cool’. Naturally after melting the phase change is no longer able to absorb thermal energy. The patent application teaches an attempt to extend the duration of the melting phase by transporting thermal energy away from the phase change material by connecting this phase change material with a copper band located under the bottom of this phase change material, whereas the body heat is absorbed into the phase change material from the top of the phase change material.
Considering the temperature alone, the concept described in this '528 patent application appears plausible, as the phase change material feels ‘cool’ and a copper band can transport thermal energy. However, the deficiencies in the patent application are revealed when the flow of thermal energy is analyzed. The body heat emits thermal energy which cross into the phase change material. It is known that there will be a certain resistance for thermal energy to cross into the phase change material. Then this thermal energy must pass through the phase change material to reach the copper band. However, the paraffin wax used in the phase change material has an extremely low thermal conductivity (between 0.2-0.8 Wm−1 K−1), whereas the copper of the metal band has a thermal conductivity of 401 Wm−1 K−1. Due to the low thermal connectivity of the paraffin wax, the thermal energy will not reach this copper band at all or only to a very low extent. The document teaches that this copper band should be connected to another area to which the thermal energy has to flow. The phase change material is also located in that area, and the thermal energy needs to cross more of the phase change material again.
Analyzing this setup leads to the conclusion that the flow of thermal energy will be extremely small, much of the thermal energy will only be absorbed by the first phase change material by itself until that phase change material melts. The phase change material can absorb only up to 9 KJ/KG.
Furthermore, the phase change material has no flexibility so the phase change material can only be used in small quantities without diminishing comfort of the mattress.
It is known that the body emits about 230 KJ of thermal energy during an eight-hour period. Therefore, it can be calculated that the phase change material will have melted after approximately 20 to 30 minutes. After the phase change material has completely melted, then the construction of the mattress is more or less insulating with a thermal conductivity of 0.2-0.8 Wm−1 K−1
Another example is U.S. Pat. No. 4,043,544 (Ismer) which discloses a pad for seats or mattresses comprising a pad body of plastic material with recess means therein and a covering layer overlaying the pad body, strips of reinforcing material sandwiched between the pad body and the covering layer and at least selected ones of the stripes being in alignment with the recess means. Heat is dissipated from the covering layer through the recess means and the pad is reinforced by said stripes.
This document solves the problem that recesses cut into foams may be completely closed under body pressure, so the air inside the recesses is unable to move and will heat up. The document describes a method to prevent the recesses from collapsing under body pressure by reinforcing the recesses with steel bands. The thermal energy load is still described as flowing through the recesses and not through the steel bands. The flow of thermal energy is activated by ‘pumping’ behavior of the air within the recesses by movement of the body. There is no flow of thermal energy without movement of the body. As there is no definition of the positioning of the metal bands, the metal bands will only by chance transport thermal energy by itself. Furthermore, the patent teaches that plastic plates should be integrated into each crossing point of the steel bands, thereby reducing any chance flow of thermal energy to almost nothing.
None of the foam paddings described in the art have been practical and there is therefore a need for an improved foam padding that can improve the comfort of a user of such a foam padding
The invention provides for an improved padding as defined in the independent claim, preferred embodiments are defined in the dependent claims. According to one aspect of the invention a padding is provided with a band which if positioned as claimed, allows to at least locally reduce temperature in a padding, such as a mattress so that the user feels more comfortable. Unlike state of the art invention to solve the problem of overheating of a user of mattresses (being most likely made from at least some Polyurethane foam) this invention is not using air as the medium to move thermal energy. Using air (i.e. with ventilators or air channels cut into foam) will mostly trigger the air to move upwards, towards the user. Also, this invention is not using material to absorb thermal energy (i.e. PCM's, Gel) as a typical use situation of a mattress is sleeping on a mattress for an extended time, typically several hours. Any material just absorbing thermal energy would be thermally exhausted long before finishing use, as the body heat is emitting consistently a high amount of thermal energy during use.
This invention is based on research and many tests performed to invent a solution where the thermal energy load is in fact transported and not just stored, this solution being mechanically flexible as not to impact the comfort parameters of the mattress negatively, furthermore taking into account the existence of hollow volumes and this transportation of thermal energy being consistent over an extended period of time.
It was found that paddings generally incorporate hollow volumes. These might be large hollow volumes as created by springs or small hollow volumes as found in all polyurethane foams. These hollow volumes store excessive thermal energy and only release them slowly over time, as they contain air, which releases excessive thermal energy slowly. The invention describes a method to remove that excessive thermal energy in those hollow volumes.
To achieve this, a material with a high thermal conductivity is used in a complete different way than previously. Instead of blending material with high thermal conductivity into the whole padding it is proposed to manufacture a band with high thermal conductivity, this band having a good mechanical flexibility. This band being able to transport thermal energy is placed in a very specific way into the mattress. It should be noted that only by placing the band as claimed and described in this document a consistent flow of thermal energy is achieved. Just placing the band any different into a mattress will not work. It had been observed that the placement of this band has to be done carefully, knowing very well the distribution of thermal energy within the hollow volumes of a padding to achieve satisfying results. It should be noted that the distribution of thermal energy in the hollow sections within a padding (for example a padding for a mattress) must be analyzed during use (during impact of body heat) and for an extended period of time. The band must be placed so that it touches sections with hollow volumes within the mattress with higher thermal energy (most likely just below the body of the user) and running uninterrupted to a section of the mattress with hollow volumes without higher thermal energy. The band described in this invention incorporates a layer of electrically conducting material, this layer itself also being uninterrupted or in other words continuous. Any interruption of the electrically conducting layer or the band itself will prohibit the band to work thermally. The only exception to this rule would be puncturing or perforating the band carefully, this is not reducing the thermal effect as has been found. This invention describes further variation of use, especially meaningful combination of the invention with other thermally effective methods previously known.
In the following aspects of the invention will be described in more detail referring to preferred embodiments as illustrated in the figures. The following description is for illustrative purposes, only and is not intended to restrict the scope of protection as defined by the appended claims. Features shown in one embodiment may be combined with features of other embodiments and the person skilled in the art will appreciate, that the illustrated embodiments are merely provided for a better understanding of the inventive concept.
In the following a mattress as an embodiment of the padding according to the present invention will be described in more detail. The thermal comfort of a mattress is critical to obtaining a comfortable experience. There is a growing trend in the mattress industry to employ new materials which create a cooling effect for users with the use of innovative phase change materials (PCMs) or cooling gels included in the near-surface foam of a product. These materials seek to alleviate overheating during use or provide a more comfortable environment for those who may suffer from medical conditions which cause excess heat production.
The comfortable temperature window during sleep is relatively narrow as the body must try to maintain its core body temperature of 98.6° F. (or 37° C.). Haex reports that the optimal insulating sleep system should ensure a bed temperature between 28 V and 32° C. which should allow the contact temperature between the body and bed to stabilize between 30° C. and 35° C. Too high of a bed insulation will result in temperature rise which leads to excessive sweating and an increase in relative humidity. On the other hand, if insulation is too low, the body will cool off which may cause shivering and similar issues with sleep disturbance. These insulating properties are mainly dependent on the core materials and design. Cores made out of latex or PU for instance, will carry higher insulation values than a spring mattress. Aside from the core, the contact temperature itself is mainly dependent on the top layer and its ability to hold air.
There are not many solutions to this challenge for designing a mattress. Since ‘feeling hot’ is a feel of temperature, designers are looking for methods to reduce temperature. They are looking for ‘cooling’—may it be active or passive. This leads to solutions with an air conditioner combined with a mattress, with ventilators, materials with high thermal connectivity blended into foam or with channels cut into foam materials running along the mattress. These methods are either expensive (air conditioner), noisy (ventilator) or not working at all (blending thermal conductive materials into foam, channels).
The main problem is that product designers see temperature as the parameter to be changed, so they end up with ‘cooling’ materials or methods. But temperature is only the result of the change of other parameters and not an elemental parameter by its own. The temperature of any material is the result of
T
(Mat@t)
=T
(Mat@t-1)
+E
(therm-inflow)
−E
(therm-outflow)
With T(Mat@t) being the Temperature of a given material at a given time, T(Mat@t-1) being the Temperature of this material before this given time, E(therm-inflow) being the thermal energy reaching the material between t−1 and t and E(therm-outflow) being the thermal energy leaving the material between t−1 and t. Based on this assumption a change of the temperature is not done by changing the temperature of the material itself but rather analyzing and optimizing the thermal energy flows effecting the materials.
In analyzing the thermal energy flows within a mattress, most product designers assume that thermal energy moves upward, like warm air, which rises if within cooler air. But as this invention teaches this assumption is not helping to design a mattress having superior thermal properties. It is true that warmer air rises within cooler air, but this only effect air. It is not directly the thermal energy itself which rises, but the physical effect that air with a higher level of thermal energy is lighter than air with a lower level of thermal energy. As air molecules can slide past each other easily, as the density of air is gaseous, the lighter air will have the tendency and capability to rise above the heavier air. But thermal energy itself has no weight and there is no gravity involved in moving thermal energy. Also helping warmer air to move upwards would only get the elevated thermal energy closer to the user instead of further away, as the user will in most cases lie on top of the mattress. But any method to reduce temperature should move thermal energy away from the user—not towards him.
Taking above mentioned formula, in order to lower the temperature in a material you either have to lower the inflow of thermal energy or raise the outflow. In a typical mattress, most inflow of thermal energy is from the impact of body heat. The body during sleep emits a heat flux of 40 W/qm skin, approx. 70-80 W/person which translates to an influx of 230 kJ per night. Additional influx of thermal energy can be heating devices used, or thermal energy used in conjunction with dynamic foams. There is no realistic method to reduce the inflow of thermal energy into a mattress, and the quantity of this inflow is obviously high.
The invention raises the outflow of thermal energy within a mattress. It uses materials itself flexible, so they can be incorporated in a mattress without reducing the comfort feeling. The invention is not using energy and is not transporting the excessive thermal energy upwards as warmer air would do. Therefore, the invention can be used to transport excessive thermal energy to the side or bottom of a mattress or to any section not felt by the user.
The invention utilizes a property of modern—mostly foam based—mattresses that thermal energy is not distributed evenly within the product. Old innerspring mattresses had a very open air-filled space within and around the springs. Thermal energy could move freely within the mattress therefore distributing excessive thermal energy from the body heat to sections of the body with less impact of body heat and therefore, the excessive thermal energy could not be felt by the user. But modern foam-based mattresses are very different in this respect. Polyurethane foam typically has many hollow volumes (usually called cells), which are either open (connected to each other) or closed (not connected to each other). These hollow volumes contain air, which gradually is becoming warmer with use. Even with open cell foams the movement of this air is very restricted and also air would move upwards towards the user, but not away from him. Besides the air as a transport medium for thermal energy within the mattress the foam material itself could be a transport medium for thermal energy. But foam has a low thermal conductivity. Foam material cannot transport thermal energy very well or rather not at all. There are solutions to blend material with a higher thermal conductivity with foam, so that the material can transport thermal energy away from the body. But these blended materials cannot transport thermal energy as the molecule chains with higher thermal conductivity are usually interrupted by molecule chains of Polyurethane stopping thermal energy flow. So, the molecule chains blended into foam can absorb some but not transport the excessive thermal energy. As mattresses are used for long periods up to 10 hours thermal energy must be transported away and not only absorbed.
This is also the reason why PCM's (Phase Change Material) are not effective in mattresses. The PCM will absorb some thermal energy (i.e. 9 KJ/m2) but by far not the 230 kJ emitted during a typical night.
Therefore, this invention is not absorbing thermal energy from the air within the hollow volumes but effectively transporting it to sections with hollow volumes where it is not felt by the user or to the outside air. The form factor of the invention is a band, as this is a form which is flexible in both dimension. Even though an electrically conducting layer is used in the invention a band is usually bended only in one direction (along the length) as the width is too short to bend the material. A band can also affect larger sections within a mattress, as several bands can be used with distance between it, so that moisture or humidity can pass easily between the bands.
The band has an electrically conducting layer and has therefore a high thermal conductivity. This parameter is not enough to really transport thermal energy, but it is necessary for function. Usually materials with carbon content are preferred, like graphite, but also other material, such as but not limited to copper or aluminum, could be used. To achieve some kind of flexibility the thickness of the electrically conducting layer needs to be reduced to below 0.5 mm, but higher thickness is also allowed in this invention as long as a certain flexibility is achieved.
This electrically conducting layer within the band has to be uninterrupted, meaning thickness, composition and width need to be above the minimum values along the whole length of the band. This condition is most important. Only by connecting the electrically conducting layer based on this principle a consistent flow of thermal energy can be observed in case also the following condition is met.
The last condition is the positioning of the band in a way that it touches the hollow volumes in section with excessive thermal energy i.e. direct under the body or any heating device and at the same time also touches uninterrupted at least one hollow volume in a section with normal or reduced thermal energy. These sections can be found in any mattress.
The sections of lower thermal energy are the left and right side of the mattress, or the feet portion. If the mattress is placed on a surface allowing air to reach the lower side of a mattress (i.e. slated frame, spring box) also this lower side can be used. There are two principles governing this invention.
The effects of this invention can be clearly measured.
The band itself is small and therefore not a blockade to humidity passing through the mattress. But if the humidity should pass through the band this can be punctured well with holes in regular patterns. The thermal energy flow will pass around these holes and not be interrupted. The puncture can be so dense that it is similar to a perforation which is also allowed within this invention. It is recommended to keep the holes as small as possible.
A band being flexible and consisting purely from electrically conducting material will typically be sensitive to punctual impact and react with break. The break should be especially avoided as this creates an interruption of thermal energy flow. It has been found that a laminating of a very thin PE layer (<0.18 mm thickness) is enough to prevent a break of the band. This lamination can of course also be applied on both sides but usually this is not necessary. Also, other material adding stability can be applied as long as it is flexible i.e. Polyurethane.
The band connecting the two sections with excessive and lower thermal energy can pass through or end in a section of the mattress filled with gel infused foam. Gel infused foam (“Gelfoam”) is usually used to prevent the user from feeling too hot, so it answers a similar question. But typically, the invention described in this document creates a much higher thermal energy flow than gel infused foam. This combination adds up the thermal capabilities of the gel infused foam and of the band described in this document.
A further variation is based on the observation that the thermal energy level in the section with lower thermal energy should be as low as possible. It might be that based on the specific shape of the mattress even this section is penetrated by thermal energy from the body. So, any thermal shield (insulating layer) between said section and the body would lower the thermal energy level in that section, increases the thermal energy difference between said section and the section of excessive thermal energy and therefore increases flow of thermal energy within the band.
The band can be positioned purely within the mattress, but it can also be positioned that the band runs from the section of excessive thermal energy outside the body, i.e. along a side or the lower side of the mattress or completely outside (i.e. from the mattress into a spring box below). Typically, the outside thermal energy level is determined by room temperature this temperature being much lower than the temperature of sections of excessive thermal energy. It could be observed that this difference in thermal energy level is large enough to create a superior flow of thermal energy through the band. A section of the band of 20% outside the mattress or along the side of the mattress is more than enough to increase the flow of thermal energy to an optimal value.
The band described should have a thickness between 0.1 mm to 0.5 mm. A thin band is more flexible but also more sensitive to break whereas a thicker band is the opposite. Also, the capacity of the band to absorb and transport thermal energy can be affected by the thickness of the band.
The band was observed to fit well into a mattress if the width is between 4 cm to 10 cm, though also smaller or wider dimensions are allowed. In case wider dimensions are used the puncturing or perforating variation is preferred as not to reduce humidity flow within the mattress.
Most superior thermal effect of the band was observed when using graphite as the electrically conducting layer of choice. As graphite comes in very different variations good results were achieved using graphite with a carbon content greater than 99% and/or a content of ash lower than 1% and/or a density of greater than 1 g/qcm and/or a content of Sulphur lower than 1.800 ppm.
Also, there are very different types of graphite available. The type called highly oriented pyrolytic graphite (HOCG) is very capable to transport thermal energy based on the special molecular structure. Highly oriented pyrolytic graphite (HOPG) is a highly pure and ordered form of synthetic graphite. It is characterized by a low mosaic spread angle, meaning that the individual graphite crystallites are well aligned with each other. The best HOPG samples have mosaic spreads of less than 1 degree. It had been found that this graphite type is generating very good results in transporting thermal energy.
In another version of the invention the electrically conducting layer is made from graphene. This material has an allotrope of carbon in the form of a two-dimensional, atomic-scale, hexagonal lattice in which one atom forms each vertex. It is the basic structural element of other allotropes, including graphite, charcoal, carbon nanotubes and fullerenes. It can also be considered as an indefinitely large aromatic molecule, the ultimate case of the family of flat polycyclic aromatic hydrocarbons. As graphene has a thermal conductivity of greater than 1.000 W/mK it can be much smaller than a flexible band with an electrically conducting layer of normal graphite having with the same thermal performance.
| Number | Date | Country | Kind |
|---|---|---|---|
| LU100834 | Jun 2018 | LU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/063898 | 5/29/2019 | WO | 00 |
