Abstract:
An improved injection dart is disclosed. A flow restrictor positioned at a forward end of a dart body is provided. The flow restrictor has a generally cylindrical restrictor body portion and a radially outward extending flange portion at a forward end thereof. The flange is securely held in position. The restrictor body also having a recess in a rearward end. The flange portion holds said restrictor in a position where an inner bore of a cannula is precisely aligned with the restrictor bore. The restrictor acts to diminish a variable flow rate so that all flow rates above a maximum flow rate are restricted to be less than the maximum flow rate. The flange also keeps a forward end of the flow channel bore open but allows for radially inward deformation of the restrictor at a rear end of said flow channel bore.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an improved injection dart. More specifically, it relates to an improved injection dart which employs a flow restrictor which limits and controls the rate of flow of an injection administered by the dart. 
         [0003]    2. Description of the Prior Art 
         [0004]    Dart-type projectiles carrying a self-contained actuating means whereby detonate upon rapid deceleration are generally well known in delivering drugs, medicines and the like to animals from a distance. Studies have concluded the rate of injection can and will disturb living tissue and in some instances result in partial injection due to the dart propelled away from its intended target as a result of the injection rate. The use of hypodermic darts to administer anesthesia or other medications to animals is well known in the art. An early example is described and shown in Harris, U.S. Pat. No. 1,815,300. A number of injecting projectiles have been proposed by Crockford et al. including U.S. Pat. Nos. 2,854,925; 2,923,243; 3,022,785; and 3,209,695. Still other dart-like projectiles are described in Murdock, U.S. Pat. No. 3,207,157 and in Warren et al., U.S. Pat. No. 3,266,806. At the present time, injection darts are typically shot as projectiles from dart-projectors into the animal. 
         [0005]    Publication No. WO 1988010129 A1, by Allan Kenneth Wallace teaches that a large number of drug reactions are due to the rate of injection, not the species of drug and that “[i]deally, the contents of a syringe need to be delivered over a number of minutes.” 
         [0006]    Fischer, U.S. Pat. No. 5,944,698, discloses an adjustable flow syringe. In one embodiment of the invention described in column 8, lines 24-36, Fischer teaches the provision of an adjustable flow syringe  90  which includes a porous inset  94  which is capable of performing the function of a flow restrictor means for restricting the flow rate of a fluid in the syringe such that any force within a range of forces that can be manually applied to plunger  14  delivers fluid at a substantially constant flow rate 
         [0007]    Rosenblum, U.S. Pat. No. 2,444,677, teaches a flow control device wherein fluid flowing through the casing must flow through the fixed orifice direct to the hollow shank or through the compensating orifice and ports into the hollow shank before it is discharged from the casing. The rubber ring deflects downstream in accordance with the pressure of the fluid to vary the capacity of the compensating orifice. 
         [0008]    Kempton, U.S. Pat. No. 2,454,929, teaches a flow control which, as shown in  FIG. 5 , has a resilient annular member  11  which is deformed in the region of the orifice  17  when fluid under pressure is introduced in the bore  25  and is delivered through the bore  31  in the lower coupling member  26 . The extent of deformation of the resilient annular member  11  depends upon the pressure drop across the orifice, the greater the pressure drop the greater the deformation. Such deformation causes a reduction in the diameter of the orifice. 
         [0009]    Dahl et al., U.S. Pat. No. 2,936,788, teach a flow control system wherein disposed within the hollow interior of the housing  10  is a resilient, annular flow control washer  13  composed of rubber, chlorinated rubber, or similar elastic material. The flow control washer  13  is said to effective to maintain a substantially constant flow over a wide range of pressure variations by its automatic reduction in the cross-sectional area of its orifice  13   a  upon increases in pressure thereon. Dahl et al. teach the provision of a flow control washer  13  which includes a frusto-conical face  13   b.    
         [0010]    Diggs, U.S. Pat. No. 3,833,019, teaches an irrigation system which employs a flow control device. A resilient compressible orifice member  34  is provided which has a conically shaped orifice  37  in its center. When the fitting is compressed, the compressible member to be deformed radially inwardly to decrease the size of the orifice  37  and thus restrict the rate of flow. 
         [0011]    Taguri et al., U.S. Pat. No. 5,209,265, is yet another example of a flow control with a restrictor which includes an elastic valve  30  molded from a rubber or the like elastic material to have a small diameter section  31  and a large diameter section  32  with tapered periphery, as shown in  FIG. 3 . An aperture  33  is formed to extend through an axial center of the valve  30  for fluid communication between pipe  15  and passage  24 . The valve  30  is capable of elastically deforming so as to vary the diameter of the aperture  33  in proportion to the pressure applied thereto, thereby allowing the water to flow through the aperture  33  at a controlled rate of keeping the flow volume at a constant level irrespective of the variation of pressure of the water being supplied. 
         [0012]    Despite the many known examples of projectile darts and the many known methods of providing flow control, there remains a need for an improved injection dart which can address the difficult and complex problem of reliably and consistently injecting an animal with various medications at a rate which does not cause damage or injury to the tissue of the animal and does not cause the dart to eject from the animal&#39;s skin because of excessive backward pressure from a too rapid injection. 
       SUMMARY OF THE INVENTION 
       [0013]    This invention relates to improvements in means for administering liquid drugs, medications and the like to animals and more particularly to a means for administering drugs, medicines and the like to an animal which are remotely situated or are unapproachable by a person desiring to administer the drugs, medicines and the like to such animal when using a medium to rapid injection rate dart for intramuscular or subcutaneous injections. 
         [0014]    The present invention solves this problem by utilizing the general known principal of deforming an opening in an annular compressible rubber member to form a flow control function but provides a flow control member with unique geometries and features which provide reliable and consistent results in a very specialized environment where rapidly changing pressures may result because of the nature of the injection methods employed in injection darts. 
         [0015]    It is the objective of this present invention to provide an improved means for administering drugs, medicines and the like to animals, by reducing the rate of injection for any medium to rapid rate injection dart manufactured to deploy drugs, medicines and the alike to an animal with minimum trauma to body tissues. 
         [0016]    It is a further objective of this present invention whereby the improved means for administering drugs, medicines and the like is such that the device insures the dart is easily fillable or loadable with the drug or medicine to he administered. 
         [0017]    Yet another objective of this present invention is to provide adaptability to a variety of nosecone and dart body designs at relatively low cost, simple construction, and which is easily operated. 
         [0018]    In its simplest form, the present invention provides an improved injection dart of the type having a dart body, a ferrule at a forward end of said body to which a cannula is attached, a drug containment chamber located in said dart body, a plunger initially positioned at a rear end of said drug containment chamber, mechanical or chemical means to provide pressure to and exert force on a rear end of said plunger causing the plunger to move forwardly toward said cannula whereby a drug fluid within the drug containment chamber is discharged through said cannula at a variable flow rate, the improvement comprising: a flow restrictor positioned at a forward end of said dart body immediately juxtaposed against a rear end surface of said cannula, said flow restrictor having a generally cylindrical restrictor body portion, said flow restrictor having a radially outward extending flange portion at a forward end thereof, said flange securely held in position between a forward end of said dart body and said ferrule, said flow restrictor having a flow channel bore extending through a centerline of said cylindrical restrictor body from a forward end of said restrictor body to a rearward end thereof, said restrictor body also having a recess in a rearward end thereof said recess being symmetrically aligned along said centerline, whereby said flange portion holds said restrictor in a position where an inner bore of said cannula is precisely aligned with said restrictor bore and whereby said variable flow rate is altered such that all flow rates above a maximum flow rate are restricted to be less than said maximum flow rate. 
         [0019]    Preferably, the holding of said flange in place also restricts radially inward deformation of the restrictor at a forward end of said flow channel bore keeping said forward end of said flow channel bore open but allowing for radially inward deformation of the restrictor at a rear end of said flow channel bore reducing the cross sectional area of said flow channel bore at such rear end thereby reducing the rate of flow which passes to the cannula. 
         [0020]    Preferably, the holding of said flange in place also restricts radially inward deformation of the restrictor at a forward end of said flow channel bore keeping said forward end of said flow channel bore open but increasingly allowing for radially inward deformation of the restrictor at locations more distant from said forward end of said flow channel bore reducing the cross-sectional area of said flow channel bore at such locations thereby reducing the rate of flow which passes to the cannula. 
         [0021]    Preferably, said recess in the rearward end of said restrictor body is frustoconical in configuration. 
         [0022]    Preferably, said frustoconical recess has a diameter at said rearward end of said restrictor body portion which is about 0.6 times the diameter of said restrictor body leaving a flat rim portion around an outer circumference of the rear end of said restrictor body. 
         [0023]    Preferably, said frustoconical recess has a diameter at a most forward end thereof of about 0.5 times the diameter of said restrictor body leaving a flat internal rim portion around an outer circumference of said flow channel bore. 
         [0024]    Preferably, said frustoconical recess has a depth as measured from the rear end of said restrictor body to a most forward end thereof of between 0.25 times and 0.5 times the length of said flow restrictor. 
         [0025]    Preferably, said variable flow rate is altered such that the flow rate is always above zero during discharge until all said drug fluid is discharged. 
         [0026]    Preferably, said flow restrictor is formed from a compressible rubber material. 
         [0027]    Preferably, said flow restrictor body portion has an outer diameter which is greater than an inner diameter of said drug containment chamber whereby even when said flow restrictor compressed to fit within said drug containment chamber said flow channel bore is not compressed beyond acceptable limits. 
         [0028]    Preferably, said flow restrictor body portion has an outer diameter which is greater than an inner diameter of said drug containment chamber whereby even when said flow restrictor is compressed to fit within said drug containment chamber said flow channel bore has an inner diameter dimension of about 0.0575 inches. 
         [0029]    Preferably, said flow restrictor body portion has an outer diameter which is greater than an inner diameter of said drug containment chamber whereby even when said flow restrictor is compressed to fit within said drug containment chamber said flow channel bore has an inner diameter dimension between 0.0560 inches and 0.0590 inches. 
         [0030]    According to this invention, medium to rapid injection rate darts are facilitated through the means of a flow rate restrictor positioned within and at the end of the forward or anterior portion of the body between the end cap/nosecone of the dart. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0031]      FIG. 1  is a side elevational view of the flow restrictor of the present invention. 
           [0032]      FIG. 2  is a cross-sectional view of the flow restrictor of the present invention. 
           [0033]      FIG. 3  is a cross-sectional view of the flow restrictor of the present invention as positioned within one form of an injection dart. 
           [0034]      FIG. 4  is an exploded perspective view showing the various components of one form of injection dart including a flow restrictor according to the present invention. 
           [0035]      FIG. 5  is a side elevational view of the injection dart of  FIG. 4  in fully assembled form. 
           [0036]      FIG. 6  is a cross-sectional view of the flow restrictor of the present invention showing additional details. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]      FIGS. 1 ,  2  and  6  show the details regarding the flow restrictor  30  of the present invention. An injection dart  5  into which the flow restrictor may be placed is shown in  FIGS. 3 ,  4  and  5 . 
         [0038]    Referring to  FIGS. 3 ,  4  and  5 , the injection dart  5  (preferably approximately 4¾ inches long), includes a cannula (or injection needle)  10  at the dart&#39;s anterior or forward end. The cannula includes an inner bore  11  through which medications are injected into an animal. The cannula may also have an opening (not shown) along its cylindrical wall to allow for the passage of medications not only through the forward end of the inner bore  11  but also at a point along its length. The cannula  10  is aligned along and defines a centerline of the dart  5 . The cannula  10  is firmly attached to the center of a ferrule  20 . The ferrule  20  is a generally cylindrical cup shaped and has a closed forward end through with the cannula  10  extends and is preferably formed of aluminum or other light metal. The closed forward end may have a slightly sloping conical shape or may be flat. The conical shape, if utilized, allows for a more complete insertion of the entire exposed cannula  10  into the animal without interference from the ferrule. The rear portion of the ferrule is open and is sized to receive a forward end of a dart body  50 . The dart body  50  may be formed from any suitable material such a polycarbonate, which is presently preferred, or from any other resin suitable composition or from aluminum or other metal, for example. As best shown in  FIG. 3 , the inside of the cup portion of the ferrule  20  has a flat inner surface against which a flat forward surface  43  ( FIG. 6 ) of the flow restrictor  30  is juxtaposed. 
         [0039]    Referring to  FIGS. 3 and 6 , the flow restrictor  30  has a flange portion  48  at a forward end and has a generally cylindrical body portion  40  at a rear end. The flow restrictor  30  has a length  33  (preferably approximately 5/32 inch), has a body portion  40  with a diameter of  31  (preferably approximately 11/32 inch) and has a flange portion  42  which extends radially around the body portion  40  a distance  33  (preferably approximately 1/32 inch) and having a flange length or thickness (preferably approximately 1/32 inch). It will be understood that the flange portion  48  has two distinct and important functions. First, the flange portion  48  keeps the flow channel bore  34  which extends through a centerline of the flow restrictor body  40  precisely aligned with the inner bore  11  of the cannula  10 . Second, because the flange portion  48  of the flow restrictor  30  is tightly held in position around the entire circumference at the forward end  43  of the flow restrictor  30 , the flow channel bore  34  is deterred from inward deformation at such forward end  43  of the flow channel bore. The rear end of the bore  34  (that end closest to the internal annular flat surface portion  36 ) is not so deterred and when sufficient pressure is applied to the rear end  44  of the flow restrictor, the rear portion and to a lesser extent the intermediate portions of the flow channel bore  34  do expand radially inward causing a reduction in the flow rate to the cannula inner bore  11 . A forward end of the dart body  50  is juxtaposed against the rear surface  47  of the flange  48 . As mentioned, the forward surface  43  of the flange  48  is juxtaposed against a flat inner surface of the ferrule  20 . The length of the flange portion  48  is not considered critical but should be long (thick) enough so that the high pressure forces to which it will be exposed will not cause the flange  48  to rip or tear away from the restrictor body portion  40 . In this regard, upon activation of a rapid delivery dart, internal pressures encroach 2,000 PSI as the plunger is deployed and the pressure subsides. This is why the design of a suitable flow restrictor for this type of dart is so difficult and so necessary. The length of surface  47  or the flange  48  is preferably equal to or slightly less that the thickness of the sidewall portions of the dart body  50 . 
         [0040]    Referring to  FIG. 6 , the flow restrictor  30  has forward end  43  and rear end  44 . The outer diameter of the body  40  (i.e. the distance between an upper end  45  and lower end  46  of the cylindrical body portion  40 ) is preferably greater than an inner diameter of said drug containment chamber. Even when said flow restrictor body  40  is compressed to fit within said drug containment chamber  50 , said flow channel bore  34  is not compressed beyond acceptable limits. Preferably, even when said flow restrictor is compressed to fit within said drug containment chamber said flow channel bore  34  has an inner diameter dimension (i.e. the distance between upper surface  35  and lower surface  33 ) of about 0.0575 inches or between 0.0560 inches and 0.0590 inches. 
         [0041]    The rear end  44  of the flow restrictor  30  has a recess  31  therein. Preferably, the recess  31  is frustoconical in configuration. Preferably, the frustoconical recess is provided such that a flat annular surface or rim portion  38  remains at the rear end  44  of the flow restrictor body  40  and such that a second inner flat annular surface or rim portion  36  remains at the rear opening of the flow channel bore  34 . Which the forces and areas of deformation under varying pressures are complex and depend on a number of variables, when the durometer or compressibility of the rubber material out of which the flow restrictor is made is held constant, it has been found that reliable, consistent and repeatable results can be achieved with the configuration of a flow restrictor as described herein. Clearly, the length of the flow control channel  34  is critical. Since the forward end is essentially held open by the flange portion  48 , if the length of the channel  34  is too short there will be insufficient flow reduction. If the length of the channel is too long, there is a possibility that it will completely close off under high pressure. Various shapes and configurations of the flow restrictor have been contemplated and tested but none have provide acceptable results for this type of use except where a forward flange is utilized in combination with a rear recess. The shape of the recess is not believed to be absolutely critical but it is highly recommended that the shape be symmetrical around a center line of the flow control channel  34  and cannula  10 . The recess might be dish shaped rather than purely frustoconical or may be frustoconical with slightly convex or concave surfaces. The preferred shape, however, is shown in  FIG. 6 . It is believed that the forward pressure of fluid against the flat rim portion  38 , the second flat rim portion  36  and frustoconical surface  37  causes sufficient deformation at rear and mid-portions of the flow control channel  34  to provide superior and repeatable results with multiple darts having the same flow control  34  configuration. Preferably, said frustoconical recess has a diameter at said rearward end of said restrictor body portion which is about 0.6 times the diameter of said restrictor body leaving a flat rim portion  38  around an outer circumference of the rear end  44  of said restrictor body. Preferably, said frustoconical recess has a diameter at a most forward end thereof of about 0.5 times the diameter of said restrictor body leaving a flat internal rim portion  36  around an outer circumference of said flow channel bore. 
         [0042]    Referring back to  FIGS. 3 ,  4  and  5 , the dart  5  also contains a P type plunger  60 , a percussion cap  70 , a P type spring  72 , a firing pin  74 , a P type slip fit tail  90  which is held in place by melted stem  92  ( FIG. 5 ). As is well known, when this type of dart  5  is fired from a suitable dart projector, the cannula  10  is shot into the animal&#39;s body until the ferrule  20  hits the animals skin and immediately stops the forward momentum of the dart  5 . However, the forward momentum of the firing pin  74  is sufficient to overcome the force of spring  72  causing the firing pin to strike the percussion cap  70  causing a controlled explosion within the dart body rearward the plunger  60 . The percussion cap is typically a small cylinder of copper or brass with one closed end. Inside the closed end is a small amount of a shock-sensitive explosive material such as fulminate of mercury. The force of the explosion causes a rapid increase in pressure and causes the plunger  60  to move forwardly injecting the medication through the cannula into the animal. However, without the flow restrictor, damage to animal tissue may occur or the dart might fall out or be pushed out of the animal because of a too rapid injection flow rate. The flow restrictor  30  of the present invention may be utilized on both disposable darts or on darts which are designed to be reused. 
         [0043]    It is to be understood that while certain forms of the present invention have been illustrated and described herein, the present invention is not to be limited to the specific forms or arrangements of parts described and shown.