Abstract:
A water pad is disclosed to include a closed fluid impervious flexible envelope, which defines therein a closed chamber and has a pressure inside within the range from a negative to balance with the atmospheric pressure, a soft, elastic inner pad, which is accommodated in the closed chamber inside the closed fluid impervious flexible envelope, said inner pad has open cells, a fluid filled in the open cells in the inner pad, and a buffering space defined within the closed chamber inside the closed fluid impervious flexible envelope around the inner pad for receiving the fluid when the fluid is forced out of the inner pad upon a force of the external pressure. The water pad can be made in different forms for use as hot/cold compress pad, seat cushion, water mattress, medical mattress, warm-keeping pad, mouse pad, etc.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to a pad and more particularly, to water pad, which does not expand or become hard when compressed.  
         [0003]     2. Description of the Related Art  
         [0004]     People may use different pads, such as bed pad, seat pad, pillow pad, hot compress pad, cold compress pad, eye pad, brassiere pad, etc. in different places for different purposes.  
         [0005]     A pad may be simply formed of a foamed material, or filled up with a fluid or stuffing material. Basically, a pad has a pad body and an outer covering or bag covering the pad body. For containing a fluid, the bag must be waterproof and well sealed to prevent leakage.  
         [0006]     Actually, water is the cheapest environment protective natural cooling agent of high specific heat. Therefore, water is intensively used in cold compress, hot compress, or fluid pad for cold/hot compress. However, due to the force of the gravity, the fluid in a conventional fluid pad always flows toward the bottom, causing uneven distribution of the fluid in the fluid pad. When used for cold/hot compress, it is difficult to retain the fluid to the desired place. When a conventional fluid pad is used for sitting, the fluid works as a means to transmit pressure, causing the fluid pad to expand and to become hard. Thus, the contact pressure is increased and unstably floating. Further, in order to eliminate the problem of vertical flow, the conventional fluid pad may be divided into multiple independent chambers, or thickener may be added to slow down the fluidity of the fluid, or silicon rubber may be used for the substitution.  
         [0007]     However, dividing the fluid pad into multiple independent chambers can only partially control the problem of vertical flow of the fluid, the fluid in every independent chamber still cannot against the gravity and will flow to the bottom of each chamber respectively. The use of the thickener cannot change the characteristic of the fluid but simply detain the time in which the fluid flows toward the bottom, providing no help in support. Further, the use of silicon rubber greatly increases the cost. The enthalpy (specific heat) of silicon rubber is below one half of the enthalpy (specific heat) of water. Therefore, it is not an efficient design, i.e., twice the work with half of results.  
         [0008]     U.S. Pat. No. 3,611,455, issued on Oct. 12, 1971, discloses a water pad designed to have a low contact pressure and stable support. However, in column 2 lines 17˜18 of the specification, the resilient solid and the fluid both work as support means. This is the common problem of the conventional fluid pads. When the fluid works as (a) support means, the pressure can be evenly transmitted. Which causes an unstable support and high contact pressure.  
         [0009]     According to Pascal&#39;s law, the fluid pressure at all points in a connected body of an incompressible fluid at rest, which are at the same absolute height, is the same, even if additional pressure is applied on the fluid at some place. Simply speaking, the heavier the weight of the body is the expanding extent and hardness of the fluid pad will be.  
         [0010]     Why the internal fluid becomes a pressure medium and a support means when compressed by an external pressure? The answer is “insufficient buffering space in the fluid pad”. Because the internal fluid of the fluid pad transmit the pressure of the body weight of the user, thereby causing the fluid pad to expand and to become hard, and therefore the contact area between the user and the fluid pad is relatively reduced, and the contact pressure is relatively increased. According to the equation P=W/A, wherein P: pressure; W: weight; A: area. This series of reaction produces a result against what U.S. Pat. No. 3,611,455 expected.  
         [0011]     Actually, the buffering space defined in the bag according to U.S. Pat. No. 3,611,455 is insufficient. This can be known from the statement in column 2, lines 29˜31 of the specification. The bag expanding and rise only when the inside buffering space is insufficient to receive the fluid that flows out of the inner pad. Because this design allows the fluid to work as support means, the bag expands and becomes hard when receives an external pressure. At this time, the fluid supports the major part of the user&#39;s weight, therefore, it is unstable to sit the body on the fluid.  
         [0012]     Further, column 3, lines 43˜47 of the specification and FIG. 3 of the annexed drawings also indicate the problem of insufficient buffering space. The fluid is compressed to expand the pad, and the bottom side of the fluid pad is highly stretched like a ball fully filled up with water. This indication is in conformity with the requisite condition that the fluid participates in supporting the pressure. When the user moves the body slightly at this time, the fluid will be forced to deform the fluid pad, and the body becomes unstably supported on the fluid pad. So, the problems of high contact pressure and unstable support are all caused by the insufficiency of the inside buffering space.  
         [0013]     Except the aforesaid drawbacks, U.S. Pat. No. 3,611,455 still has other problems. PU (Polyurethane) foam is a hydrophilic porous material that can contain water more than 90%. However, according to U.S. Pat. No. 3,611,455, the inner pad contains water only 80%. This means 20% of the inner pad is occupied by air. This arrangement reduces the enthalpy and lowers the support stability. These problems can be seen in column 4, lines 7˜9 of the specification.  
         [0014]     Therefore, it is desirable to provide a fluid pad that eliminates the aforesaid various problems of the conventional designs.  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention has been accomplished under the circumstances in view. According to one aspect of the present invention, the water pad comprises a closed fluid impervious flexible envelope, said closed fluid impervious flexible envelope defining therein a closed chamber and having a pressure inside within the range from a negative to balance with the atmospheric pressure, an inner pad made out of a soft and elastic material and accommodated in the closed chamber inside said closed fluid impervious flexible envelope, said inner pad having a plurality of open cells; a fluid filled in the open cells in said inner pad; and a buffering space defined within said closed chamber inside said closed fluid impervious flexible envelop for receiving said fluid when said fluid is forced out of said inner pad upon a force of the external pressure.  
         [0016]     According to another aspect of the present invention, the closed fluid impervious flexible envelope is made out of polymers; inner pad is made out of sponge or a foamed material; the fluid is water containing an anti-freezing agent.  
         [0017]     According to still another aspect of the present invention, the buffering space is below the topmost elevation of the inner pad when a negative pressure design, and the fluid has a fluid level within 0.5 cm above the elevation of the topmost side of the inner pad.  
         [0018]     According to still another aspect of the present invention, the buffering space is sufficient to receive the fluid that flows out of the inner pad without causing the water pad to expand or to become hard when the water pad supports an external pressure. Further, the buffering space is defined within the closed fluid impervious flexible envelope around the inner pad. Alternatively, the buffering space can be formed of holes and grooves on the inner pad, or the inner pad can be made having a plurality of holes and grooves that form the buffering space.  
         [0019]     According to still another aspect of the present invention, the closed fluid impervious flexible envelope is made out of TPU (Thermoplastic Polyurethane), SBR (Styrene-butadiene rubber), PU (Polyurethane) foam, or SB (Styrene-butadiene) foamed rubber; the inner pad is made out of PU (Polyurethane) foam or SB (Styrene-butadiene) foamed rubber.  
         [0020]     According to still another aspect of the present invention, the amount of the fluid is within 85%˜120% relative to the volume of the inner pad. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is an elevational view of a water pad according to the present invention.  
         [0022]      FIG. 2  is a schematic drawing, showing the water pad deformed upon an external pressure.  
         [0023]      FIG. 3  is a schematic drawing showing the status of the water pad in a hanging position.  
         [0024]      FIG. 4  is an elevational view of an alternate form of the inner pad for the water pad according to the present invention.  
         [0025]      FIG. 5  is a sectional view of the present invention showing the inner pad of  FIG. 4  used. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]     Referring to FIGS.  1 ˜ 3 , a water pad in accordance with the present invention is shown comprised of a envelope  1 , an inner pad  2 , and a fluid  3 .  
         [0027]     The envelope  1  has a size greater than the inner pad  2  so that the inner pad  2  can be accommodated in the envelope  1 . To prevent leakage, the envelope  1  is made out of a waterproof material, for example, polymers. After accommodation of the inner pad  2  in the envelope  1 , an enclosed buffering space  11  exists in the envelope  1  around the inner pad  2 . Under a normal use of the water pad, the buffering space  11  is sufficient to receive the fluid  3  that is squeezed out of the inner pad  2  so that force of the external pressure can only be applied to the inner pad  2  without causing the fluid  3  to transmit the pressure. Therefore, the fluid  3  does not work as support means, and the envelope  1  is maintained in a soft manner. The aforesaid buffering space  11  is defined to be sufficient to receive the fluid  3  that flows out of the inner pad  2  without causing the water pad to expand or to become hard when the water pad supports a pressure. Therefore, a negative pressure design, the buffering space  11  is defined within the envelope  1  around the inner pad  2 . Alternatively, this buffering space can be formed of holes  22  or grooves  23  on the inner pad  2  (see  FIG. 4 ). Further, as shown in  FIG. 5 , the amount of the fluid  3  can be increased to such an extent that the fluid lever of the fluid  3  is equal to or slightly higher than the top surface of the inner pad  2  for the atmospheric pressure design, and the buffering space  11  is sufficient to maintain the water pad in a soft condition without causing the water pad to expand or to become hard when the water pad receives a force of the external pressure.  
         [0028]     The inner pad  2  is made out of a soft, elastic material, for example, sponge or foamed material that has a plurality of open cells  21  in it. When compressed, the inner pad  2  is forced to deform and to expand the contact area, thereby lowering the contact pressure.  
         [0029]     As a matter of fact, the contact pressure can be known by means of defining the shape, size, and hardness of the inner pad  2 . When the support pressure on the inner pad  2  is defined, the amount  3  and the size of the buffering space  11  can be figured out. Further, the size of the buffering space  11  can be modified subject to different applications. For example, for the purpose of hot/cold compresses, the buffering space  11  can be relatively reduced; for the purpose of sitting or sleeping, the buffering space  11  should be relatively increased. Further, if the inner pad  2  is relatively smaller and harder, the buffering space  11  can be relatively reduced. In another word, the amount of the fluid  3  can be relatively increased when the requirement of the buffering space  11  is relatively smaller. However, the buffering space  11  must be greater than the volume of the fluid  3  that moves out of the inner pad  2  so that the water pad does not expand or become hard.  
         [0030]     The fluid  3  can be clean water added with an anti-freezing agent to prevent freezing. Further, the inner pad  2  is compressed to expel internal air before filling the fluid  3  into the open cells  21 . At this time, the internal pressure of the water pad is a negative pressure. Following the filling of the fluid  3  into the inner pad  2  to expand the inner pad  2 , the level of the negative pressure in the water pad is gradually balanced to the level of the atmospheric pressure.  
         [0031]     Simply speaking, under the condition of having a proper buffering space  11 , it is easy to set different combinations of pressure and fluid content to fit different requirements for different products by means of controlling the filling of the fluid  3 . For example, a product that does not allow vertical flow adopts the design of negative pressure. A product that maintains a long temperature regulating time adopts the design of the balanced-pressure with the amount of the fluid  3  approximately equal or slightly greater than the volume of the inner pad  2 .  
         [0032]     For a negative pressure design to maintain a stable support, low contact pressure, and distribution uniformly of the fluid and to prohibit vertical flow of the fluid  3  in the inner pad  2 , the fluid level of the fluid  3  must not surpass the top surface of the inner pad  2 . For a balanced-pressure design to have the inside pressure and the outside pressure in balance, the fluid level of the fluid  3  can be equal or slightly higher than the top surface of the inner pad  2 , and the amount of the fluid  3  is kept within 85%˜120% relative to the volume of the inner pad  2 , i.e., the fluid level of the fluid  3  surpasses the topmost point of the inner pad  2  but not over 0.5 cm.  
         [0033]     Both the inner pad  2  and the contained fluid  3  are constrained by the atmospheric pressure against gravity. In the former negative pressure design, the amount of the fluid  3  is kept over 85% relative to the volume of the inner pad  2 . For a balanced-pressure design, the amount of the fluid  3  does not surpass 120% relative to the volume of the inner pad  2 . Further, in a balanced-pressure design, the amount of the fluid that flows in vertical direction is limited to the part that surpasses the volume of the inner pad  2 . In case the water pad is set vertical, the maximum amount of the fluid that flows to the bottom does not exceed by 20%.  
         [0034]     Referring to  FIG. 2  again, if the water pad adopts a negative pressure design in actual practice, the atmospheric pressure will compress the closed envelope  1  to constrain the fluid  3  to keep in the open cells  21  in the inner pad  2 . Normally, the fluid  3  does not flow vertically downwardly to the bottom when the water pad is moved or turned. When the water pad receives a force of the external pressure, the inner pad  2  is forced to deform. Increasing the applied force to the water pad may expel the fluid  3  out of the inner pad  2  into the buffering space  11  inside the envelope  1 . However, when the force of the external pressure disappeared, the fluid  3  is forced by the atmospheric pressure to flow into the open cells  21  in the inner pad  2  again. Further, because the inner pad  2  is filled up with the fluid  3 , the residual air in the inner pad  2  is insignificant, and therefore the fluid  3  does not move in the inner pad  2 .  
         [0035]     Referring to  FIG. 5 , if the water pad is of the balanced-pressure design with the inside pressure and the outside pressure in balance, the fluid  3  in the inner pad  2  will do not move in vertical direction and only the small part of the fluid  3  outside the inner pad  2  can flow in vertical direction, thereby achieving the same effects as the aforesaid negative pressure design. Therefore, this design allows filling of an amount of the fluid  3  greater than the volume of the inner pad  2  without occupying the designed buffering space  11 . For example, the amount of the fluid  3  according to this design can be as great as 120% relative to the volume of the inner pad  2 .  
         [0036]     Further, the envelope  1  and the inner pad  2  can be made extensible. In this case, the envelope  1  can be made out of TPU (Thermoplastic Polyurethane), SBR (Styrene-butadiene rubber), PU (Polyurethane) foam, SB (Styrene-butadiene) foamed rubber, or the like; the inner pad  2  can be made out of PU (Polyurethane) foam, SB (Styrene-butadiene) foamed rubber, or the like. The water pad can be made in the shape of a narrow elongated strip that can be directly tied to a part of the body of a human for hot/cold compress. Therefore, the invention can be used as a first-aid product. Further, the invention can also be made for use as a seat cushion, water mattress, medical mattress, warm-keeping pad, mouse pad, etc. that shows functions and quality superior to similar conventional products.  
         [0037]     As indicated above, the invention utilizes the atmospheric pressure and re-sets the relationship among component parts to produce many new functions, eliminating the drawbacks of the conventional products of unstable support, high contact pressure, easy breaking of sealing edges, vertical flow of fluid, and etc. Basically, the fluid according to the present invention distributes in the water pad subject to the shape of the inner pad. By means of the shape design of the inner pad, the water pad fits the curvature of any part of the body perfectly, providing an optimal hot/cold compress effect. Further, because of the advantages of stable support, no vertical flow, and maximum fluid content, the invention can also be designed for use as a cooling mattress in the hot season so that the user doesn&#39;t need to switch on the air conditioner when sleeping on the water pad.  
         [0038]     A prototype of water pad has been constructed with the features of FIGS. 1 ˜ 5 . The water pad functions smoothly to provide all of the features discussed earlier.  
         [0039]     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.