Abstract:
A pin valve assembly includes a spring biasing a piston against a seal to seal an opening of a gas cylinder. The spring compresses a length determined by a distance between the insert and the plunger. The insert is pressed into an opening opposite the plunger and held in place by at least one barb extending inward from an inner diameter of a body of the insert. The insert includes an opening to allow communication of gas pressure to a rear portion of the piston. The inner diameter of the pin valve assembly includes at least one barb to secure and prevent removal of the insert.

Description:
This application claims priority to U.S. provisional application Ser. No. 60/435,210 filed Dec. 19, 2002. 

   BACKGROUND OF THE INVENTION 
   This application relates to a gas pin valve for a gas cylinder and specifically to a gas pin valve for a gas cylinder including tamper resistance and tamper evident features. 
   Typically, a gas cylinder is filled with a liquid or gas under a desired pressure. The gas cylinder is designed to withstand specific pressures and to deliver the gas and liquid at pressure to specific devices. Commonly, devices such as paintball guns or fire extinguishers use the pressurized gas within the cylinder to propel a paintball in the case of the paintball gun, or a fire suppression chemical in the case of a fire extinguisher. In any device, it is desired to maintain the gas or liquid within the cylinder at a given pressure until use. It is known to use a pin-type valve threaded into the outlet of the gas cylinder to control the outlet of gas pressure from the cylinder. 
   Typically, a pin valve includes a piston held against a seal by a spring. The spring is trapped between the piston and a threaded screw and provides a sufficient force within the gas cylinder to prevent unwanted expulsion of gas from the gas cylinder. Typically, gas pressure within the cylinder acts in concert with the spring to bias the piston against the seal. Gas is only expelled from the gas cylinder by overcoming the force of the spring and pressure exerted by gas within the cylinder. 
   The pin valve is threaded into the outlet of the gas cylinder and includes a threaded member having an inlet hole. When it is desired to release pressure from the cylinder, a pin extending from the piston through the opening is pushed downward. By pushing downward on the pin, the piston is lifted off the seal and gas pressure is allowed to escape through the inlet. The pin portion of the piston extends through the opening and is of a diameter smaller than the opening to allow gas pressure to be released from the gas cylinder. 
   As is appreciated, the spring force exerted by the spring onto the piston contributes a substantial portion of the biasing force used to maintain gas within the cylinder. The spring force exerted against the piston is determined by a distance between a rear end of the piston and a threaded member threaded into the body of the pin valve. Currently, the threaded member is machined with outer threads that are mated to internal threads that are fabricated within the body of the pin valve. The threaded member is then machined with an allen-type tool interface for assembly within the pin valve body against the force of the spring. As appreciated, machining of internal and external threads require expensive and time consuming machining operations. Further, such pin valves are commonly assembled to gas cylinders used in recreational devices where cost is a great factor determining commercial success. As appreciated, it is always desirable to decrease the cost of producing consumer goods. 
   Further, in some applications it is desirable to inhibit or evidence tampering of preset conditions. As appreciated, the preset spring force of the pin valve determines the amount of and point at which gas is exhausted from the gas cylinder. In some instances, tampering with this pin valve and the point and pressure required to release gas from within the gas cylinder can cause harm or injury. In such instances, it is desirable to evidence tampering by an operator in order to limit liability. Further, it is also desirable to prevent tampering by designing a mechanism that is destroyed upon modification and rendered unusable. 
   Accordingly, it is desirable to develop and design a pin valve that reduces production costs while also preventing and evidencing tampering. 
   SUMMARY OF THE INVENTION 
   An embodiment of this invention is a pin valve assembly including a plastic insert for holding a piston spring and piston against a seal. 
   A pin valve assembly includes a spring biasing a piston against a seal to seal a gas cylinder. The spring compresses a length determined by a distance between the insert and the plunger. The insert is pressed into an opening opposite the plunger and held in place by at least one barb extending inward from an inner diameter of a body of the insert. 
   The insert includes an opening to allow communication of gas pressure to a rear portion of the piston. The insert includes an outer diameter sized to correspond with an inner diameter of the body of the pin valve assembly. The inner diameter of the pin valve assembly includes at least one barb disposed to secure and prevent and evidence removal of the insert. The inset is pushed and pressed in opposite the piston to compress the spring and hold the piston against a seal. The insert is held in place by one or a series of barbs machined within the inner diameter of the pin valve body. 
   Accordingly, the pin valve assembly of this invention prevents and evidences tampering while reducing manufacturing costs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
       FIG. 1  is a cross-sectional view of a gas cylinder and valve assembly according to this invention; 
       FIG. 2  is a cross-sectional view of the pin valve assembly of this invention; 
       FIG. 3  is an enlarged cross-sectional view of the pin valve assembly and delron insert; and 
       FIG. 4  is another embodiment of the pin valve assembly. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a gas cylinder assembly  11  is shown in cross section and includes a cylinder  13  and a pin valve assembly  10 . The pin valve assembly  10  is received within a threaded interface with the cylinder  13 . The pin valve assembly  10  includes a piston  28  with a pin portion  58  extending from an opening. The piston  28  is movable within the valve assembly  10  to control the flow of gas from the cylinder  13 . 
   Referring to  FIG. 2 , the pin valve assembly  10  includes a body  12  that defines a first bore  14  and a second bore  16 . The outer features of the body  12  include a first threaded section  22  and a second threaded section  24 . Each of the sections are designed to accommodate either the specific gas cylinder or the specific device to which this pin valve  10  is attached. Preferably, the threads  22  are adapted and configured for mating to a gas cylinder (not shown). The threads  24  are adapted and configured to mate to the device to which the gas pressure held within the gas cylinder (not shown) is used. The body portion  12  also includes a hex nut portion  26 . 
   The hex nut portion  26  is adaptable for use by a tool to tighten and affix the pin valve assembly  10  either to the gas cylinder or to a device using the pressure within the gas cylinder. Further, other features on the body  12  include an o-ring land  44  adapted to fit a specific o-ring that would seal the device against the pin valve  10 . As appreciated, the external feature of the pin valve  10  can be of any type adapted for fitting to either the gas cylinder or the device using pressure within the gas cylinder. Note that it is within the contemplation of this invention that the external features of the pin valve  10  may be of any type and configuration known to one skilled in the art adapted to fit to either a gas cylinder or a device using pressure within the gas cylinder. 
   The piston  28  is of a length  52  that corresponds with a spring  30  and the insert  40 . The piston  28  includes a pin section  36 . The pin section  36  extends through an opening  58  in the body  12 . In this embodiment, the body  12  includes a concave portion  42  disposed in the opening area  58 . The concave portion  42  cooperates with the device using the pressure within the gas cylinder. The piston  28  is forced downward against a seal  32 . The seal  32  prevents the escape of gas pressure. The piston  28  is held against the seal  32  in part by the spring  30 . The piston  28  is also held against the seal  32  by gas pressure indicated by arrows  60  exerted on a rear portion of the piston  28 . 
   Threading a device onto the pin valve assembly  10  causes the pin portion  36  to engage a feature of the device that will push the piston  28  upward off of the seal  32  against the force of the gas pressure indicated at  60  and force of the spring  30 . This action opens gas pressure to be released into the device using pressure stored within the gas cylinder  13 . 
   The length between the upper portion of the piston  28  and the bottom portion of the insert indicated at  50  sets the amount of spring force exerted on the piston  28  against the seal  32 . 
   Holding the spring  30  downward against the piston  28  is the insert  40 . The insert  40  is pressed within an inner diameter  14  of the body  12 . Disposed on the inner diameter  14  of the body  12  are barbs  46 . At least one barb  46  disposed within this diameter to prevent and hold the insert  40  within the body  12 . 
   The insert  40  also includes an opening or inner diameter  38  to which gas pressure is communicated to a rear portion of the piston  28 . As appreciated, the insert  40  is held in place by the barbs  46  and does not require a plurality of threads either disposed on the exterior of the insert or interior of the insert. The insert  40  is simply pressed to a stop. The stop is a shoulder  62  that is disposed between inner diameters  14  and  16 . 
   Referring to  FIG. 3 , the body  12  is shown in an enlarged view highlighting the diameter  14  into which the insert  40  is pressed. The insert  40  includes an outer diameter  48  that corresponds to the inner diameter  14  of the body  12 . The inner diameter  14  includes at least two barbs  46 . As appreciated, two barbs  46  are used, however, it is within the contemplation of this invention that only one barb may be used, or several barbs may be used as is required by the specific application and configuration. A worker skilled in the art would understand that the number of barbs is determinative only in regard to the specific application and that several barbs may be required in order to prevent removal of the insert  40 . However, in some applications only one barb  46  may be required to prevent and evidence removal of the insert  40 . 
   The insert  40  is preferably fabricated from a plastic material. Delron is preferred because it has specific properties that prevent the plastic deformation or creep over time. Other materials that exhibit similar characteristics may also be used for fabrication of the insert such as plastic material. The insert  40  includes chamfers  56  on each side to allow the inserts to be fully seated on the shoulder  60 . Preferably, similar chamfers  56  are disposed on each end of the insert  40  to allow for assembly of the insert  40  in any direction. The inner diameter  38  of the insert  40  is sized to correspond to the desired amount of gas pressure exerted on the back of the piston  28 . The inner diameter of the body  12 , 16  corresponds with the piston  28  and pressure exerted by gas within the gas cylinder as indicated by  60 . 
   In operation, the delron insert  40  is machined to the proper dimensions with a desired outer diameter  48  that corresponds to the inner diameter  14 . The insert  40  is then pressed within the body  12  to the stops  62 . The insert is pressed into the pin valve  12  after the seal  32 ; piston  28  and spring  30  have been installed within the insert body  12 . Pressing of the insert  40  into the inner diameter  14  engages the barbs  46  with the insert  40 . The barbs  46  are positioned and configured such that as the insert  40  is pushed within the diameter  14 , rearward movement or movement to remove the insert  40  is substantially prevented and not possible without completely destroying the insert  40 . 
   Referring to  FIG. 4 , another embodiment of this invention is illustrated where the barbs  66  are disposed on the insert  40 . In this embodiment, the barbs  66  correspond with undercuts  64  within the inner diameter  14  of the body  12 . The insert  40  is pressed within the body  12  and the inner diameter  14  where the barbs  66  engage the undercut  64  to prevent removal of the insert  40 . An undercut  64  is all that is required on the inner diameter  14  of the body  12  and the barbs  66  are machined on the outer diameter  48  of the insert  40 . This embodiment, however, does require that the insert  40  be inserted into the inner diameter  14  in a specific direction in order for the barbs  66  to properly engage and prevent removal of the insert  40 . 
   As appreciated, many different configurations of barbs and undercuts are within the contemplation of this invention and a worker skilled in the art would understand that the specific configuration of the barbs relative to the body and insert are application specific and are within the scope of this invention. 
   The foregoing description is exemplary and not just a material specification. The invention has been described in an illustrative manner, and should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications are within the scope of this invention.