Abstract:
A warming mattress and mattress pad incorporating channeled areas for accepting heat and sensor wires. The inventive mattress and mattress pad includes an arrangement of seam structures defining channels housing substantially discrete elongate heating and sensing elements arranged in a substantially similar pattern within the mattress or mattress pad interior.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of and priority from U.S. Provisional Application 60/643,354, filed on Jan. 12, 2005 and Co-pending application Ser. No. 11/131,626, the contents of which are hereby incorporated by reference in their entirety as if fully set forth herein. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates generally to warming mattresses and mattress pads. More particularly, the invention relates to warming mattresses and mattress pads including channeled areas for accepting elongate heating and sensor elements. The heating and sensor elements are discrete from one another such that the sensor elements measure the bulk mattress and mattress pad temperature for regulated feedback control of the heating elements. Methods for forming the warming mattress and mattress pad and arranging the heating and sensor elements are also provided.  
       BACKGROUND  
       [0003]     This invention generally relates to mattress and mattress pads that generate heat from electricity. During the winter in cold climates, an unoccupied bed becomes relatively cold. Thus a person entering the bed is exposed to bedding surfaces which are considerably colder than human body temperature. It takes some time for the person&#39;s body heat to warm the bed. In addition, the elderly or people with poor circulation may rely upon electric blankets or other similar equipment to warm them during the wintertime.  
         [0004]     Various devices have been created to take the chill off of bedding so that a person upon entering the bed is not be exposed to cold surfaces in the winter. One common approach is to turn-on an electric blanket prior to entry into the bed to warm the region in which the person will sleep. Other devices supplied heated air into a space between the bed coverings. It would be desirable to have a warming mattress and mattress pad with heating and temperature sensing and control.  
       SUMMARY  
       [0005]     The present invention provides advantages and/or alternatives over the prior art by providing warming mattresses and mattress pads incorporating substantially discrete elongate heating and sensing elements arranged in a substantially similar pattern within the mattress or mattress pad interior.  
         [0006]     According to one contemplated practice the heating elements and sensing elements each incorporate one or more conductive metallic wires such as copper wire, copper alloy wire or the like in wrapped relation around a core of polymeric fiber or the like with an insulating jacket surrounding the core and wrapped wire. The discrete elongate heating elements and sensing elements are threaded through common channels at the interior of the mattress or mattress pad in a common pattern such that the heating elements and sensing elements run in substantially parallel relation to one another.  
         [0007]     According to another contemplated practice the heating elements and sensing elements each incorporate one or more conductive metallic wires such as insulated copper wire or the like in wrapped relation around a core of polymeric fiber or the like with an insulating jacket surrounding the core and wrapped wire. The discrete elongate heating elements and sensing elements are threaded through parallel channels at the interior of the mattress or mattress pad in a pattern such that channel walls separate the heating elements and sensing elements over at least a portion of the pattern. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention will now be described by way of example only, with reference to the accompanying drawings which constitute a part of the specification herein and in which:  
         [0009]      FIG. 1  is an overhead view of an exemplary warming mattress or mattress pad composite showing a channel pattern;  
         [0010]      FIG. 2  is a schematic view illustrating an exemplary formation line for applying a channel pattern to a multi-layer mattress or mattress pad;  
         [0011]      FIG. 3  is a cross-sectional view of one embodiment of the mattress.  
         [0012]      FIG. 4  is an exemplary pattern for threading heating and sensing elements through common channels within a warming mattress or mattress pad;  
         [0013]      FIG. 5  is an exemplary pattern for threading heating and sensing elements through discrete channels within a warming mattress or mattress pad;  
         [0014]      FIG. 6  is a cut-away view of a wrapped wire construction for use as a heating or sensing element utilizing a single wire wrapped around a fiber core;  
         [0015]      FIG. 7  is a cut-away view of a wrapped wire construction for use as a heating or sensing element utilizing two wires wrapped around a fiber core;  
         [0016]      FIG. 8  is a diagram representing operation of the warming mattress or mattress pad; and  
         [0017]      FIG. 9  is a bar chart illustrating comparative performance of various mattress or mattress pad constructions in holding a steady temperature during variations of room temperature.  
         [0018]      FIG. 10  is a cross-sectional view of one embodiment of the mattress pad. 
     
    
     DETAILED DESCRIPTION  
       [0019]     Exemplary embodiments of the invention will now by described by reference to the drawings wherein like elements are designated by corresponding reference number throughout the various views. All referenced patent documents are hereby incorporated by reference as if fully set forth herein. Referring now to the figures, in  FIG. 1 , a warming mattress or mattress pad heating element  10  (shell structure) is shown incorporating a pattern of channels  12  defined between elongate seam structures  14 . The elongate seam structures  14  preferably connect together layers within the heating element  10  so as to define a pattern of barrier walls between the channels  12 . The seam structures  14  may be of any suitable construction including woven seams, sewn seams, adhesive seams, welded seams and the like. Adhesives such as curable urethane or the like may potentially be preferred.  
         [0020]     While this invention is directed towards warming mattresses and mattress pads, it may also be used in warming blankets, comforters, duvets, pillows, or the like.  
         [0021]     One practice for forming a potentially desirable mattress pad shell structure incorporating woven seams is illustrated in  FIG. 2  for one embodiment of a mattress pad. In the illustrated arrangement, let-off rolls are arranged such that two needle punch batting layers  16  and  16 ′ are brought together in adjacent opposing relation to one another. The batting layers  16  and  16 ′ are preferably needle punch fabric layers, but may be other layers such as non-woven fibrous layers or other batting layers depending on the construction of the mattress pad. In a potentially preferred practice the layers  16 ,  16 ′ may be formed of fibers including polyester, polypropylene, or other natural or synthetic batting materials. Although the weight of the inner layers can vary greatly, the layers should be of sufficient strength to provide a stable channel for wiring without increasing the composite stiffness significantly. The layers  16  and  16 ′ may have a weight of approximately 1.0 and 5.0 ounces per yard. This provides a low stretch, low friction channel and batting through which to insert the wire.  
         [0022]     In other embodiment, an optional additional high loft batting layer may be used in place of one or both of the needle punch batting layers. If a high loft batting layer is used, it is preferred to use a spunlace or spunbond nonwoven fabric between the high loft batting layer(s) and the heating element to have easier threading of the wires. It is contemplated that the shell fabrics are preferably warp knit, circular knit, nap knit micro-denier, woven, non-woven or needle punch construction formed from suitable fibrous materials including polyester, polypropylene or the like. It is also contemplated that the needle punch batting layers  16 ,  16 ′ and/or the optional high loft batting layer may be eliminated or replaced with other suitable materials if desired. The preferable mass per unit area for the decorative shell fabric layer is in the range from about 2.5 oz/yd 2  to about 6.0 oz/ yd 2 . The optional high loft batting layer is preferably a relatively high loft material for thermal insulation. For a mattress or mattress pad, the outer shell fabric layer  20 ′ defines the bottom of the of the mattress or mattress pad so that the batting traps the heat generated and radiates such heat upwards towards the user laying on the mattress or mattress pad. Furthermore, the batting is particularly useful in creating both a three-dimensional structure to the final composite and in masking the tactile perception of the heating wires by the user. The high loft batting is preferably a polyester resin-bond with a loft of between 0.125 inches and 0.50 inches. It should have adequate wash stability, and should not contribute to the overall flammability of the composite. The channels are sewn by sewing needle  24 . The mattress pad also includes an extendable elastic around at least a portion of the outer edge of the mattress pad (not shown) to keep the mattress pad on the mattress. Preferably, the conductive wires in the heating element substantially cover the enter surface of mattress when the mattress pad is applied to the mattress.  FIG. 10  shows the cross-section of a mattress pad made according to the process in  FIG. 2  after the heating element is inserted.  
         [0023]      FIG. 3  shows a cross-section of one embodiment of the warming mattress. It comprises a support layer  62 , a cushioning layer  64 , a heating element  10  and a ticking layer  68 . The support layer  62  may be any known support layer for a mattress such as metal springs, air, or foam. The cushioning layer  64  is typically made up of foam or fiber batting. The heating element  10  is described in greater detail below. There may be an additional batting layer between the heating element and the ticking layer (not shown). The ticking layer  68  is typically the outside fabric covering the mattress and may be a decorative fabric. The preferable mass per unit area for the ticking layer  68  is in the range from about 2.5 oz/yd 2  to about 6.0 oz/ yd 2 . In another embodiment of the invention, the heating element has an outer surface that can be the outer surface of the mattress, performing the same function as a ticking layer, eliminating the need for a separate ticking layer.  
         [0024]     A fire retardant layer may be incorporated into the mattress and/or mattress pad. For the mattress, the flame retardant layer may be above or below the heating element  10 . In the case that the heating element is the outer layer of the mattress, the fire retardant layer will be below the heating element. Fire retardant chemistries are well known and may be used as the flame retardant layer in the invention. A preferred fire barrier material is an aramid fiber which is made by E.I. DuPont de Nemours &amp; Co. and sold as KEVLAR. Other known fire barrier materials which are known are preoxidized acrylic and fiberglass.  
         [0025]     Regardless of the formation technique or layer pattern utilized, the resulting heating element  10  (a shell structure) is preferably characterized by a predefined pattern of channels through which elongate heating and sensor elements may be threaded. A first exemplary arrangement of channels containing a patterned arrangement of elongate heating and sensor elements is illustrated in  FIG. 4 . As shown, in this construction the seam structures  14  run in parallel relation to one another in the length direction of the mattress or mattress pad. The seam structures  14  define boundaries for interior channels through which a discrete elongate heating element  30  and a discrete elongate sensing element  32  are threaded in a desired pattern such as the illustrated arrangement. In the illustrated construction the elongate heating element  30  and the elongate sensing element  32  follow a common pattern thereby remaining substantially parallel to one another while extending through common channels. If desired, the elongate heating element  30  and the elongate sensing element  32  may cross at localized points such as where they reverse direction at the top and bottom of the pattern while nonetheless maintaining a common pattern.  
         [0026]     A second exemplary arrangement of channels containing a patterned arrangement of elongate heating and sensor elements is illustrated in  FIG. 5  wherein elements corresponding to those previously described are designated by like reference numerals increased by  100 . As shown, in this construction a higher concentration of seam structures  114  is utilized with the elongate heating element  130  and the elongate sensing element  132  running through separate channels separated by the seam structures  114 . Thus, while the elongate heating element  130  and the elongate sensing element  132  utilize the same pattern running from end to end of the mattress or mattress pad, there is a slight phase shift between the two patterns. Physical separation between the elongate heating element  130  and the elongate sensing element  132  is maintained by the seam structures  114 . Thus, as with the embodiment of  FIG. 4 , the elongate heating element  130  and the elongate sensing element  132  are disposed in substantially parallel relation to one another with the channels. As shown, the elongate heating element  130  and the elongate sensing element  132  may cross at localized points such as where they reverse direction at the top and bottom of the pattern while nonetheless maintaining the desired common pattern.  
         [0027]     Although they perform different functions, the elongate heating element and the elongate sensing element may be of substantially similar construction. By way of example only, and not limitation, constructions for such elongate elements are illustrated in  FIGS. 6 and 7 . In the construction illustrated in  FIG. 6 , a single conductive metallic wire  40  such as copper or the like extends in wrapped relation around a flexible core  42  such as a polymeric fiber or the like. The metallic wire  40  may be formed of any suitable material including copper, copper alloys, and other ferrous and nonferrous metals including nickel, steel, and the like. According to one contemplated practice, the metallic wire  40  may be a copper alloy wire such as is available from Fisk Alloy having a thickness of about 33 to about 42 American wire gauge (awg). The metallic wire  40  may be wrapped around a PET textile core having a linear density of about 500 to about 1000 denier. An insulating layer  44  such as PVC or the like extends in surrounding relation to the wrapped structure. It has been found that elongate structures of such construction exhibit substantial flexibility without undue levels of strain hardening so as to permit their insertion in a desired pattern without undue strain hardening and embrittlement. If desired, the metallic wire  40  may also include a nonconductive coating such as enamel or the like. However, metallic wires without such coating may also be utilized if desired.  
         [0028]     In the construction illustrated in  FIG. 7 , a pair of conductive metallic wires  40 ′,  41 ′ such as previously described extends in wrapped relation around a flexible core  42 ′ such as a polymeric fiber or the like. In all other respects the structure is substantially identical to that of  FIG. 6 . Such structures exhibit substantial flexibility with sufficient structural stability to be threaded through channels within the mattress or mattress pad. A potential benefit is that the two wires may be connected together at one end of the structure as shown thereby completing a circuit so that only one end of the elongate structure needs to be available to the heating or sensing circuit.  
         [0029]     As illustrated in  FIG. 8 , according to one contemplated practice, a user will connect the system to a power source and select a desired user setting  50  such as a dial setting of 1 to 10 or specific desired temperature to activate the system. A signal is sent from the user setting  50  to a heating power controller  52  for delivery of current to the heating element  30 ,  130 . In conjunction with activation of the system, a sensing current output  54  is delivered to the elongate sensing element  32 ,  132 . During application of the sensing current a voltage sensor measures the voltage across the sensing element and transmits that data to the heating power controller. Based on the known sensing current output and the measured voltage across the sensing element, the heating power controller calculates the temperature of the sensing element based on a comparison circuit and transfer function  60  and/or a look-up table programmed into the controller. Based on the measured temperature of the sensing element, the heating power controller then adjusts the current flow to the heating element as necessary to achieve the selected user setting. This process is performed continuously to achieve and maintain a desired steady state temperature.  
         [0030]     As previously indicated, in the present invention the elongate heating element  30 , 130  and elongate sensing element  32 ,  132  are substantially discrete from one another rather than being contained within a common elongate structure. However, they are nonetheless arranged in a common pattern in substantially parallel relation to one another within the mattress or mattress pad. The use of such discrete heating and sensing elements arranged in common patterns with one another has been shown to provide a dramatically improved ability to maintain a steady state temperature within the blanket as the room temperature changes.  
         [0031]     In order to demonstrate the benefits of the present mattress and mattress pad invention, temperature data was collected on warming blankets with different wiring arrangements within a temperature controlled room. These test blankets have the same wire configurations and electronics that would be used for the corresponding warming mattress or mattress pad. The test blankets were identical to one another in all respects except for the wiring. The test blankets were set at an initial setting and left at that setting throughout the test. The room temperature was cycled from an initial set point of 75 degrees Fahrenheit. The first hour was at 75 degrees Fahrenheit, the next hour the room temperature was reduced to 65 degrees Fahrenheit, then increased back to 75 degrees Fahrenheit, and finally increased to 85 degrees Fahrenheit. Blanket temperature was measured throughout the test to see how well the blanket sensed the room temperature and then responded. The test samples were: (1) a commercial warming blanket having a heating and sensor wire arranged in a common sleeve running in a sinusoidal pattern, (2) a warming blanket that is believed to be formed according to the teachings in U.S. Pat. No. 6,686,561, (3) a warming blanket incorporating separate discrete elongate heating and sensing elements arranged through common interior channels in a pattern as shown in  FIG. 4 , a warming mattress or mattress pad incorporating separate discrete elongate heating and sensing elements arranged through separate interior channels in a pattern as shown in  FIG. 5 .  
         [0032]     Performance was evaluated based on the deviation of the blanket temperature from the initial set point of 75 degrees Fahrenheit. A perfect blanket would have the same temperature regardless of what the room temperature was resulting in a value of zero deviation. A blanket with poor temperature control would substantially follow room temperature and have approximately the same value of deviation as the room.  FIG. 9  is a bar chart showing the average deviation values for the room and for each blanket relative to the initial 75 degree Fahrenheit at the different time points, and a final summation of the deviations. The summation of the deviations is believed to be the clearest identifier of the blanket performance. As demonstrated, blankets  3  and  4  provided superior performance in maintaining a steady temperature when subjected to changes in room temperature with blanket  4  providing the best results of any blanket tested. These learnings can be applied to mattresses and mattress pads.  
         [0033]     While the present invention has been illustrated and described in relation to certain potentially preferred embodiments and practices, it is to be understood that the illustrated and described embodiments and practices are illustrative only and that the present invention is in no event to be limited thereto. Rather, it is fully contemplated that modifications and variations to the present invention will no doubt occur to those of skill in the art upon reading the above description and/or through practice of the invention. It is therefore intended that the present invention shall extend to all such modifications and variations as may incorporate the broad aspects of the present invention within the full spirit and scope of the invention.