Abstract:
A method and apparatus for pressurizing a fillable-structure, wherein a space defined by the pump, an untraversed plunger, and a closure is a volume, V t , and a stop to limit the travel of the plunger along the pump so a volume, V b , remains within the space defined by the pump, the fully traversed plunger, and the closure. Traversal or manipulation of the plunger expresses gas from the pump to the Tillable-structure wherein the pressurization of the fillable-structure is limited by the ratio of V t  to V b  whereby the fillable-structure can not be pressurized beyond a pressure P max .

Description:
FIELD 
       [0001]    The present invention relates to a gas pump comprising a stop mechanism wherein the stop mechanism limits the amount of pressure that can be inserted into a volume to be filled by a predetermined value. The present invention may be used to pump air, or other gasses, into structures such as inflatable toys, balloons, mattresses, rafts, and toys or other structures of fixed volume finable by a gas. 
       BACKGROUND 
       [0002]    The embodiments of the present invention described herein are directed towards a need that has not been addressed by previous implementations of air or gas pumps. Previous types of pumps do not adequately address scenarios where over-pumping can occur by an operator of a gas pump. Over-pumping may occur where the operator is unaware of the pressure at which a structure being filled with a gas will reach the upper limit of its structural integrity and rupture. Further, each relevant structure having a compartment fellable by a gas will vary in its tensile strength and ability to withstand pressure without rupturing. Alternatively, even where a structure does not rupture, its structural integrity may become so degraded by the pressure forces exerted upon it that it is no longer safe to use or may no longer have the ability to effectively serve its intended purpose. 
         [0003]    Alternatively, it may be desirable to only have a specified limited pressurization in a fillable volume for a given purpose, in excess of which would be undesirable. 
         [0004]    Accordingly, it is desirable to have a gas pump which will not allow the pump operator, or actuator, to cause over-pumping of a fillable structure. The present invention, disclosed herein, provides an efficient, cost-effective means for limiting the pressure that can be inserted into a volume to be filled by a predetermined value. Inflatable structures contemplated by this invention include, but are not limited to, inflatable toys, balloons, mattresses, rafts, and toys or other structures of fixed volume. 
       SUMMARY OF THE INVENTION 
       [0005]    A method and apparatus for pumping gas into a fillable structure is provided featuring a pressure limiting feature, wherein the pump, a closure sealing a first opening of the pump at a first end having a one-way valve allowing only the egress of gas from the pump into a volume to be filled, a second opening on the pump at the opposite end, a plunger sealing the second opening and configured to slide along or traverse the pump and thereby express gas from the pump through the one-way valve, wherein a space defined by the pump, the fully traversed plunger, and the closure is a volume, V t , and a stop to limit the travel of the plunger along the container so a volume, V b , remains within the space defined by the container, the plunger, and the closure and the pressurization of the volume to be filled is limited by the ratio of V t  to V b  and the volume to be filled can not be pressurized beyond a pressure, P max . 
     
    
     
       DRAWINGS 
         [0006]    While the accompanying claims set forth features of an apparatus and method for limiting pressure as disclosed herein with particularity, embodiments of the device and method may be best understood from the following detailed description taken in conjunction with the accompanying drawings, of which: 
           [0007]      FIG. 1  illustrates a sectional view of a gas pump as exists in the prior art. 
           [0008]      FIG. 2  illustrates a sectional view of a pump with a limited pressure feature, as disclosed herein. 
           [0009]      FIG. 3  illustrates a sectional view of a pump with a limited pressure feature, as disclosed herein, wherein the stop is comprised of a separation between two chambers of the pump. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    The present invention claims priority from United States Provisional Patent Application Ser. No. 61/183,811, filed Jun. 3, 2009, the contents of which are incorporated herein in their entirety by reference thereto. 
         [0011]      FIG. 1  is a sectional view of a gas pump  100  as existing in the prior art. The apparatus comprises a pump  101  having a long axis and enclosing a volume of gas, V t . A first opening  102  on said pump  101  is located at the first end of the long axis wherein said first opening  102  includes a one-way valve for the egress of gas from said pump  101  into a volume to be inflated. A second opening  103  is located on the opposite end of said pump  101 . A plunger  104  sealing said second opening  103  is configured to slide along the long axis of the pump  101 . The gas having volume V t  may be expressed from the pump through the one-way valve located at the first opening  102 . Upon full traversal of the plunger  104  along the long axis of the pump  101 , all the gas in volume V t  is expressed through the one-way valve located at the first opening  102 . The target fillable structure substantially receives all of the gas expressed from the pump  101 . 
         [0012]    In instances where the gas pump  100  has a third opening located on the long axis of the pump  101 , the third opening may have a one-way valve which allows the ingress of gas to said pump  101 . As the operator, or actuator, retracts the plunger  104 , the pump  101  having volume V t  fills again with gas. The source of the gas may be atmospheric, an external gas container, a compressor, or any other relevant means of providing gas thereto. The plunger  104  may then be manipulated again to express the entirety of the gas into the target finable structure. 
         [0013]    All possible target fillable structures have a maximum pressure value, P max . P max  may be a function of the tensile strength of the materials comprising the Tillable structure. If a fillable structure attains an internal pressure beyond P max , then the structure may rupture. Even where the structure does not rupture, its structural integrity may become so degraded by the pressure forces exerted upon it that it no longer is either safe to use or may no longer have the ability to effectively serve its intended purpose. Alternatively, it may be desirable to have a limited amount of pressure in a fillable structure, where pressure in excess of the stated amount is undesirable. 
         [0014]    Accordingly, over repeated manipulations of the plunger  104 , or even a single manipulation, the target fillable structure may attain an internal pressure which is in excess of the ideal pressure, P max , recommended for that particular structure. Theoretically, through over-pumping, the internal pressure of the gas inside the finable structure can approach infinity. As stated, over-pumping may lead to rupturing of the fillable structure or, alternatively, conditions which are dangerous or negatively impact the utility of the fillable structure. This result is undesirable. 
         [0015]    As disclosed in  FIG. 2 , the present invention improves upon the prior art and solves the problems caused by over-pumping by implementing a stop  205  to create a buffer zone having a volume V b . In a preferred embodiment, the stop  205  is a ribbing or molding extruding from a fixed location on the interior of the pump  201 . However, the stop  205  may be comprised of any suitable means capable of limiting the travel distance of the plunger  204 . In a first alternative embodiment, the stop  205  is a post. In a second alternative embodiment, the stop  205  comprises a separation of two chambers of the pump  201 . In a further alternative embodiment, the stop  205  may be slidable along the long axis of the pump  201  through an adjustment means accessible to the operator, or actuator, to achieve an ideal allocation of volume V b . 
         [0016]    The stop  205  operates to limit the distance along the long axis of the pump  201  that the plunger  204  can travel. The buffer zone is the volume of gas present in between the location of the stop  205 , across which the plunger  204  cannot travel, and the first opening  202 . Whereupon the plunger  204  has fully traversed the long axis of the pump  201 , the gas comprising volume V t , less volume V b , may be expressed into the target finable structure. 
         [0017]    The stop  205  must be located at an ideal position within the pump  201  in view of P max . The ideal location of the stop  205  (i.e. the necessary volume of the buffer zone, V b ) may be determined by the following equation: 
         [0000]        V   b =( V   t   P   0 )/ P   max    
         [0018]    The above equation assumes an ideal system, wherein no heat transfers to or from the environment of the pump and its components occurs. In the above equation, V b  is the desired volume of the buffer zone to be determined; V t  is the total volume of the pump  201 ; P 0  is the initial pressure of the gas within volume V t ; and P max  is the maximum pressure, or ideal pressure, of the target fillable structure, dependent upon the specifications and intended use of the structure. Accordingly, the stop  205  is positioned along the long axis, adjacent to the first opening as offset by volume V b  of the pump  201 . If, however, it is desirable to have an operator, or actuator, perform multiple manipulations of the plunger  204 , then the position of stop  205  may be adjusted accordingly, preserving the ratio between V t  and V b . Furthermore, where practical considerations of scale between the pump  201  and the target fillable structure require, the ratio between V t  and V b  may be adjusted accordingly. 
         [0019]    Manipulation of the plunger  204  may cause several different scenarios. The first instance is the “initial state,” the target fillable structure having a maximum pressure value of P max , contains no gas and the plunger  204  has not yet been manipulated. Manipulation of the plunger  204  will result in the entirety of the gas comprising volume V t , less the volume comprising volume V b , to be expressed to the target finable structure. However, if the pressure of the gas within the target fillable structure is equal to or greater than P max  during manipulation or traversal of the plunger  204 , or upon full manipulation or traversal of the plunger  204 , then the pressure within volume V b  will equal P max  and no further gas will be expressed into the fillable structure. Accordingly, the present invention limits the pressure of the gas in the fillable structure to not exceed maximum compressed air pressure, or P max , by the ratio of the total volume of the pump, V t , to the volume of the buffering zone, V b . 
         [0020]    In a second instance, a gas is already present in the target fillable structure and the pressure of the gas within the structure has not yet exceeded P max . Here, the operator, or actuator, may continue to pump until the pressure of the target fillable structure equals P max , whereupon further pumping will not be possible, as described above. Accordingly, the problem in the prior art of possible over-pumping is addressed by the present invention. 
         [0021]    It should be appreciated by those of skill in the art that the configuration and shape of the pump  201  may take several forms, including, but not limited to, a hand-pump, a foot-pump, a box-pump, a circular pump, or an oval pump. Accordingly, pumps envisioned by the present invention may not have a long axis. Further, a pump may be constructed of any suitable rigid or flexible material. In instances where a flexible material is used, the plunger may be the actual structure of the pump being compressed or traversed. Accordingly, it is to be appreciated that the embodiments discussed are exemplary and not limiting in the construction of the invention disclosed herein.