The present invention relates to a waterbed mattress as described in the preamble of the first claim.
Most waterbed mattress are made of an envelope having a top wall, a bottom wall and side walls formed of a polymeric material, for example polyvinylchloride or polyethylene, which enclose a central storage volume for receiving water. The thickness of a waterbed mattress is often about 21 cm. Mostly, virtually the entire central volume is filled with water, the filling degree affecting the firmness of the mattress.
From US-A-5.210.892 a waterbed mattress is known, the envelope of which is made of a polymeric material. In the top wall of the waterbed mattress a plurality of expandable folds are formed to allow for a stretching of the top wall when a person lies on it. The folds are oriented such that the stretch in width direction of the mattress is larger than the stretch in longitudinal direction. To vary the amount of stretch provided by the folds in different regions of the top wall, the spacing between the folds and the size of the folds is varied. This is done to provide optimum accommodation of heavier as well as of lighter parts of the human body. This is also done to optimise comfort when the mattress is occupied by a lighter and a heavier person.
In particular in US-A-5.210.892 the folds are chosen such that the ratio of the surface area of the top wall when pulled taut, to the surface area when not charged, is between 1.03 and 1.3. The folds are spaced apart from each other by a distance L from about 0.25 to 4 inch. The ratio of the height of the folds to the distance between adjacent folds is between 1/16 and 1. It is alleged that the controlling of these parameters provides an improved lying comfort. According to an embodiment of US-A-5.210.892, the folds are arranged in a regular pattern and may have the shape of circular bumps or raised portions. Other suitable shapes are curled looped, swirled, curlique, quilted, box, rectangular and triangular.
However, the waterbed mattress disclosed in US-A-5.210.892 presents the disadvantage that the lying comfort provided by it is still insufficient, in particular it does not provide optimum lying comfort to all body parts. There is thus a need to a waterbed mattress which provides for an optimum lying comfort for all body parts, in particular the wider head and shoulder portion, the heavier, but narrower back and hip portion and the leg portion.
It is therefore the object of this invention to provide a waterbed mattress with a still improved lying comfort.
This is achieved according to the present invention with the characterising features of the first claim.
The waterbed mattress of the present invention comprises a top wall providing a laying surface, a bottom wall providing a support surface and a plurality of side walls, which together enclose a central storage volume for receiving the water.
The top wall is made of an elastic material. In the top wall a plurality of expandable folds is formed, such that several parts are created showing a different elasticity. The top wall is divided in at least three parts:
- 1. the first part (16) corresponding to a surface part having an elasticity of between 5 and 40 % for receiving the head and shoulder portion of a person occupying the mattress. The shoulder portion is given the highest elasticity to provide a maximum comfort when laying sideways. As the shoulders mostly form the widest part of the human body, the shoulders should be capable of being in a countersunk position if a virtually straight position of the vertebral column is aimed at.
- 2. the second part (17) being provided for receiving the back zone,
- 3. the third part (18) corresponding to a surface part for receiving the hip or bottom and leg zone having an elasticity of between 5-25 %. At this position an intermediate elasticity is desired as this forms the heaviest part of the body.
The inventor has now found that by adapting the mattress as described above, the upward pressure sensed by a person occupying the mattress, will generally be between 10-24 mm Hg pressure. Apparently within this range an optimum blood flow of human tissue and body parts is obtained, the risk to obstructions occurring in the blood flow being reduced to a minimum, which is sensed as an optimum lying comfort.
As the length of the head and shoulder portion of a human being occupying the first or head part of the mattress is mostly smaller than the length of the legs occupying the third or bottom part of the mattress, and as the length of the back and hip portion is usually in between these two, the length of the different parts of the mattress is chosen such that the first part has a length L1, the second part has a length L2 and the third part has a length L3, L1 being smaller than L2, which in turn is smaller than or equal to L3.
The elasticity of the top wall, or in other words, the ability of the top wall to stretch is in the mattress of this invention provided by the presence of a plurality of protrusions having an elongated, preferably a substantially oval shape.
To provide optimum contact pressure towards a body occupying the mattress, the head zone or first part of the top face of the mattress preferably comprises a plurality of first and second protrusions, the first protrusions extending in longitudinal direction of the mattress, the second protrusions extending in cross direction. The inventor has observed that the mutual co-operation of the longitudinally and transversally extending protrusions provide the desired elasticity to the mattress and maximum comfort for the head and shoulders.
The third part comprises a plurality of third and fourth protrusions, the third protrusions having a larger length as compared the fourth protrusions and extending in width direction of the mattress, the fourth protrusions having a smaller length and preferably also a smaller width and extending in height direction of the mattress. In that way a reduced elasticity as compared to the first part of the mattress is obtained.
To provide optimum body support, the central volume of the waterbed mattress preferably comprises at least at the position of the second part of the top face, an elastic insert comprising a plurality of side by side disposed collapsible elastic bodies, which extend and are collapsible in height direction of the mattress. By the presence of the collapsible bodies, an upward pressure is generated at the position of back and hip part, as a consequence of which the hips receive an upward pressure and the vertebral column is supported so as to extend substantially horizontally in a sideways position of the human body.
The invention is further elucidated in the appending figures and description of the figures.
- Figure 1 is a perspective of a waterbed mattress in general.
- Figure 2 is a perspective view of a preferred embodiment of the waterbed mattress of this invention, one of the side walls being left out.
- Figure 3 is a perspective view of another preferred embodiment of the waterbed mattress of this invention, one of the side walls again being left out.
- Figure 4 is a detailed view to a part of the top wall of the waterbed mattress of this invention.
- Figure 5 shows a detail of a spring insert for the waterbed mattress of this invention.
The waterbed mattress shown in figure 1 comprises an envelope of a polymeric material, having
- a top wall 10 providing a sleeping or laying surface,
- a bottom wall 11 providing a support surface to the mattress
- and four side walls 12-15
which together enclose a central storage volume 2 for receiving water.
The waterbed mattress 1 shown in figure 2 comprises an elastic top wall 10. The elasticity is at least partly provided by the presence of a plurality of expandable folds in the top wall 10.
As can be seen from figure 1, the top wall 10 is divided in at least three parts 16, 17, 18 which run parallel to the transverse direction of the mattress, the three parts having a different elasticity. An optimum comfort is provided when the vertebral column, in each laying position of the body, takes a substantially horizontal orientation.
A first part 16 of the top wall 10 corresponds to the surface part accommodating the head and shoulders of a person occupying the mattress. This first part 16 is made of a material having the highest elasticity as the shoulders are the part which extends the most from the body when occupying the mattress in a sideways position. In the sideways position, the pressure exerted by the shoulders per surface area unit will be higher as compared to the position when the body is laying on the back or front side. A larger stretching of the first part 16 will occur, as compared to the back lay position. Because of the elasticity, the top wall will adapt itself automatically to laying position and the weight of the body occupying it.
The second part 17 corresponds to the surface part accommodating the back part of a person. As it is important that the vertebral column is supported in a substantially horizontal position when sleeping and supported over the entire length, this second part of the mattress is given a limited elasticity, which is substantially less than the elasticity of the first part 16.
The third part 18 corresponds to the foot-end of the mattress which is provided for accommodating the hips and legs of a body. The elasticity of this part 18 is limited as compared to the elasticity of the first part 16. Some elasticity is required so as to keep the vertebral column in the correct, preferably substantially horizontal position, on the other hand the elasticity needs to be limited as the hip and leg part of the body have the largest weight.
Preferably, the first part 16 has an elasticity of between 5-40 % preferably 10-40 %, more preferably 15-30 %, most preferably 20-30 %, which means that the length and width of the first part of the top wall can be increased with a maximum of 40 % when occupied by a body. The third part 18preferably has an elasticity of between 5-25 %, more preferably 10-20%.
The first part 16 of the waterbed mattress has a length L1, the second part 17 has a length L2 and the third part 18 has a length L3, L1 < L2 ≤ L3. In a practical situation L1 mostly varies from 40-55 cm, preferably 45-50 cm, L2 varies from 45-55 cm, preferably from 50-55 cm, and L3 varies from 50-100 cm.
At least part of the elasticity of the top wall 10 is provided by the presence of a plurality of expandable folds 3-6 (see figure 4) in the top wall. Expandable folds can take any shape known to the man skilled in the art, but preferably have the shape of a rounded protrusion so as to provide uniform material strength along the folds combined with optimum elasticity. The protrusions 3-6 may however also have an irregular shape if this contributes to providing the envisaged elasticity to the surface part involved. However, to achieve optimum support for a body combined with a nice aesthetic effect the top wall 10 comprises a plurality of protrusions 3-6.
It is preferred that the protrusions 3-6 have an elongated shape as this allows gradually increasing the elasticity from the edge of the protrusion towards the centre, which contributes to providing an optimum elasticity to the top wall 10. The elongated shape also allows achieving an overlapping elasticity between adjacent protrusions 3-6. The dimensions of the protrusions 3-6are not critical to the invention and will generally adapted by the man skilled in the art taking account of the envisaged elasticity of the part involved.
As can be seen from figure 4, it is preferred that the shape of the protrusions 3-6 is substantially oval as this provides optimum elasticity. The protrusions may however have any other suitable elongated, rounded shape known to the man skilled in the art.
To provide a different elasticity in the first or head part 16 and the third or foot part 18 of the mattress, the first part 16 comprises a plurality of first 3 and second 4 protrusions having approximately the same dimensions. The first protrusions 3 extend in longitudinal direction of the mattress 1, the second protrusions 4 extend in a different direction, preferably in cross direction so as to provide uniform elasticity in longitudinal and transversal direction of the mattress 1. However, the shape and dimension of both the first and second protrusions 3, 4 may be adapted taking into account the envisaged elasticity of the first part 16.
The third part or foot part 18 of the mattress comprises a plurality of third and fourth protrusions 5, 6, the third protrusions 5 extending in width direction of the mattress, the fourth protrusions 6 extending in longitudinal direction of the mattress 1, the third protrusions 5 having a larger length and width as compared to the fourth protrusions 6. In the embodiment shown in figure 4 two fourth protrusions 6 correspond to one single third protrusion 5. This arrangement assists in limiting the elasticity of the third part 16.
In practise the length of the first and second protrusions 3,4 will mostly vary from 30-40 mm, preferably 35-37 mm, at a width of 25-35 mm, preferably 30-33 mm. The length of the fourth protrusions 6 will mostly be from 25-35 m, preferably 30-33 mm, at a with of 10-20 mm, preferably 15-17 mm.
The distance between adjacent protrusions 3-6 is not critical to the invention and will be adapted by the man skilled in the art depending on the required elasticity. In general however, the distance between adjacent protrusions will mostly be between 2-10 mm, preferably 5-7 mm.
A further control of the elasticity of the top wall 10 can be achieved by providing in the central volume 2 of the mattress 1 a spring insert as is shown in figure 5, the presence of which adds to increasing control of the local elasticity and improving the support provided by that specific part of the mattress 1. A spring insert may be provided exclusively at the position of the second part 17 of the top wall 10, but also at the position of the first and third part 16, 18. By the presence of the spring insert, the elasticity of the mattress may be adapted so as to allow accommodating bodies with large weight difference, or bodies preferring a different firmness of the mattress.
As can be seen from figure 5, the spring insert comprising a plurality of side by side disposed elastic bodies 7, 8, which are collapsible in height direction of the mattress 1. In particular the collapsible elastic body 7, 8 comprises a coil of polymeric material enclosing a central space 21 and having a plurality of superposed interconnected bulges 9, at least one of the bulges comprising a vent 19 through which the water contained in the mattress can be displaced, in view of facilitating collapse and stretching of the bodies. In case the bodies 7, 8 should provide limited elasticity, most often the material thickness will be increased. Simultaneously however also the height of the coils may be increased.
Within the part of the mattress 1 corresponding to the first, second or third part 16, 17, 18 of the top wall 10, either one single type of elastic bodies 7, 8 may be mounted having the same height, width, material thickness and elasticity. It is however also possible to insert two or more types of elastic bodies of which these properties take different values, or to have a superposition of two or more different types as shown in figure 6a and 6b. Furthermore, also the diameter of the coils may be varied in view of varying the elasticity.
For example, in order to provide maximum support in the hip zone, in the third part 18 of the mattress plastic coils may be provided having a material thickness of 0.04-0.08 inch, a height of 1.3-5 inch, an outer diameter of 3.05 inch, and a central hole with a diameter of 1.25 inch, the bulges having a height of 6.25 inch, the vent holes having a diameter of 0.25 inch which may however be smaller or larger. In the first part 16 for example coils may be provided having a height of between 0.75-2.5 inch, the other parameters remaining the same.
Usually the coils 7, 8 will be interconnected or received in corresponding recess in the internal volume 2 of the mattress to prevent them from floating.
The waterbed mattress of this invention may further comprise one or more sheets or layers of a fibrous material 20, which further assist in controlling the elasticity. The fibrous material sheets 20 further function as a stabiliser to control water flow within the mattress.