Abstract:
A fluid-dispensing valve for dispensing pressurized fluid from a chamber employs a spring plate adjacent to the aperture. The spring plate includes a peripheral rim extending about the aperture, a sealing member abutting the aperture, and a plurality of springs extending from the peripheral rim to the sealing member. These springs bias the sealing member to close the aperture when the fluid pressure is less than a predetermined limit and allow the sealing member to open the aperture when the fluid pressure exceeds the limit.

Description:
RELATED APPLICATION 
       [0001]    The present application is based on and claims priority to the Applicants&#39; U.S. Provisional Patent Application 61/095,873, entitled “Fluid Dispensing Valve With A Spring Plate,” filed on Sep. 10, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to the field of valves for dispensing fluids. More specifically, the present invention discloses a fluid dispensing valve having a spring plate to prevent drips. 
         [0004]    2. Background of the Invention 
         [0005]    The present invention addresses the problem of dispensing fluid materials at a high rate of speed accurately and without drips. Current dispensing technologies for fluid materials have an inherent problem of dripping when not in use unless some means is used to stop material flow. Conventional methods to stop fluid dripping involve mechanical means that are operated by pneumatics or electronics to open and close a material pathway. This method when activated imparts a delay at the beginning of the dispense process due to the retraction of the pathway sealing device as it pulls material into the dispense nozzle or material pathway. Additional dispense time is required to replenish the material that moved with the sealing device. 
         [0006]    Subsequently, when conventional methods are employed to stop material flow, an extra quantity of material equivalent to the gap the sealing device must occupy is ejected, which can result in an undesirable bubble in the dispense path. To control the range of movement (i.e., stroke) in such conventional methods, a mechanical adjustment and setup are required that should be done with care and periodically checked to ensure dispense quantity. 
         [0007]    Other conventional methods to control fluid material flow involve the induction of vacuum or ensuring the dispense pathway is a sealed environment. These methods are not quick to react as they require a pressurization and depressurization of the material pathway or reservoir that may change in volume over the life of the material reservoir. This pressurization step takes valuable dispense time and also can yield inconsistent results when the controlling volume increases as the level in the material reservoir decreases. 
         [0008]    In contrast, the present invention substantially eliminates adjustment issues as it is a self-contained, consumable device requiring no adjustment. Dispense delay and excess material at the finish are all but eliminated. 
       SUMMARY OF THE INVENTION 
       [0009]    This invention provides a valve for dispensing a fluid material having a spring plate to prevent drips. The spring plate has a sealing member suspended by springs that bias the sealing member to close the aperture when the fluid pressure is less than a predetermined limit, but allow the sealing member to move away from the aperture and permit fluid flow when this pressure limit is exceeded. 
         [0010]    These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present invention can be more readily understood in conjunction with the accompanying drawings, in which: 
           [0012]      FIG. 1  is an exploded perspective view of the aperture plate  20  and spring plate  30 . 
           [0013]      FIG. 2  is a side elevational view of the valve assembly. 
           [0014]      FIG. 3  is a cross-sectional view of the valve assembly. 
           [0015]      FIG. 4  is a detail cross-sectional view of the lower portion of the valve assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Turning to  FIG. 1 , an exploded perspective view is provided showing one embodiment of an aperture plate  20  and spring plate  30  employed in the present invention.  FIGS. 2 and 3  are side elevational and cross-sectional views, respectively, of a valve assembly  10  incorporating the aperture plate  20  and spring plate  30 . A detail cross-sectional view of the lower portion of the valve assembly  10  is illustrated in  FIG. 4 . 
         [0017]    The other major components of the valve assembly  10  are discussed below. A feed tube  12  receives fluid from a reservoir and transmits fluid into the chamber  15  of the valve assembly  10 . The fluid in the chamber  15  is pressurized by rotation of an auger screw  14  in the embodiment shown in the accompanying drawings. However, other types of pumps or pressure sources could be readily substituted. For example, the fluid in the chamber  15  could be pressurized by pneumatically-generated or motor-generated motion of a piston, or other mechanically or pneumatically-generated means. The pressurized fluid can be delivered from the chamber  15  via a needle  18 . 
         [0018]    As shown in  FIG. 1 , the aperture plate  20  can be a flat, rigid disk with an aperture  22  extending through the plate  20  for dispensing fluid from the chamber  15 . The size of the aperture  22  can vary depending on the viscosity of the fluid. 
         [0019]    The spring plate  30  is mounted immediately downstream from the aperture plate  20 . Preferably, the spring plate  30  is directly below and abutting the aperture plate  20 , as shown in  FIGS. 3 and 4 . In this embodiment, the spring plate  30  has a peripheral rim  32 , a sealing member  36  that is aligned to seal the aperture  22  in the aperture plate  20 , and a plurality of springs  34  suspending the sealing member  36  from the peripheral rim  32 . As depicted in  FIG. 1 , the sealing member  36  can be a flat disk having a diameter large enough to seal the aperture  22  in the aperture disk  20 . In this embodiment, the springs  34  and peripheral rim  32  are also substantially flat or planar. The peripheral rim  32  can be a flat ring that extends about the aperture  22 . 
         [0020]    The springs  34  serve to suspend the sealing member  36  from the peripheral rim  32  of the spring plate  30 , but also to bias the sealing member  36  against the aperture  22  in the aperture plate  20 . Preferably, the springs  34  extend in a radial pattern between the sealing member  36  and the peripheral rim  32 . For example, the springs  34  can be a web of flat, U-shaped members allowing a range of elastic deformation in response to fluid pressure on the sealing member  36  exerted through the aperture  22  in the aperture disk  20 . As shown, the entire spring plate  30  can be formed as a single, flat piece of material, such as sheet metal or plastic. Other types and configurations of elastically-deformable materials could be used as springs. For example, the springs  34  could be S-shaped, curved or a zig-zag shape. Coil springs could also be used. 
         [0021]    In operation, the springs  34  bias the sealing member  36  upward against the aperture  22  in the plane of the spring plate  30 . As long as the fluid pressure within the chamber  15  remains below a predetermined limit (i.e., a threshold value), the springs  34  exert sufficient force to hold the sealing member  36  against the aperture  22 , and thereby seal the aperture  22  to prevent fluid flow through the aperture  22 . However, if fluid pressure increases beyond this limit, the pressure exerted on the sealing member  36  is sufficient to elastically deform the springs  34  downward out of the plane of the spring plate  30  and push the sealing member  36  downward and away from the aperture  22  in the aperture plate  20 . This unseals the aperture  22  and allows fluid flow through the aperture  22 . 
         [0022]    In other words, by using a combination of a stiff, non-flexing aperture plate  20  and a flexible, spring plate  30 , a dynamic membrane is created that allows a fluid to pass when sufficient pressure is applied on the inlet side of the aperture  22 . Pressure exceeding some threshold value will separate the plates  20 ,  30  allowing the fluid to pass. As long as the pressure is maintained fluid will continue to flow. Reducing the fluid pressure causes the plates  20 ,  30  to return to their normally closed state which stops fluid flow. The opening and closing action follows the pressure curve generated by the pressure source for the valve assembly  10  and has a specific pressure required to open and close. This specific pressure results in an even flow of material that eliminates excess or insufficient material. 
         [0023]    The size of the aperture  22  should be specifically selected for physical properties of the fluid being dispensed and the operating parameters of the valve assembly, such as the range of fluid pressures. The aperture  22  size controls the fluid pressure exerted on the spring plate  30 . If the aperture  22  is too large the fluid column will have enough pressure to overcome the spring plate sealing force and the system may drip. Similarly, the thickness and physical properties of the springs  34  and the dimensions of the sealing member  36  should also be specifically selected in light of the fluid properties and operating parameters. These design parameters can accommodate various levels of fluid fillers, viscosities and the pressure of the fluid column. 
         [0024]    In the embodiment shown in  FIGS. 2-4 , the lower portion of the valve assembly  10  can be removed by unthreading a nut  16 . This provides ready access to the chamber  15  and internal components of the valve assembly. The aperture plate  20  and spring plate  30  are also readily removable and can be quickly replaced. As shown most clearly in  FIG. 4 , the aperture plate  20  and spring plate  30  can be dropped into this lower portion of the valve assembly housing, which is then threaded with the nut  16  onto the upper portion of the valve assembly  10 . 
         [0025]    It should be noted that the aperture and spring plates  20 ,  30  are positioned between the chamber  15  of the valve assembly  10  and the outlet (i.e., needle  18 . This configuration minimizes the distance from the fluid to travel from the pressure generator to the exit at the needle  18  orifice, which serves to minimize dispense time and increase the accuracy of the quantity of fluid dispensed. 
         [0026]    The previous discussion and the drawings involve an embodiment of the present invention in which the aperture and spring plates  20 ,  30  are completely separate components. It should be understood that these components could be combined into one piece to simplify assembly and replacement. For example, the peripheral rim  32  of the spring plate  30  could be bonded or attached to the underside of the aperture plate  20 . 
         [0027]    The above disclosure sets forth a number of embodiments of the present invention described in detail with respect to the accompanying drawings. Those skilled in this art will appreciate that various changes, modifications, other structural arrangements, and other embodiments could be practiced under the teachings of the present invention without departing from the scope of this invention as set forth in the following claims.