Projectile syringe for blowpipe

An improved, projectible syringe is provided for the introduction of a fluid medicament or the like into an animal from a position remote from the animal. The syringe assembly includes a tubular syringe body having an internal, axially shiftable plunger and an elongated rod coupled with the latter; the plunger rod is used to withdraw the plunger and fill the syringe body with an injectible fluid. Structure is also provided for creating a biasing force against the plunger urging the same forwardly for injection purposes, along with apparatus for selectively restraining such forward plunger movement until the syringe assembly is used. In practice, a specialized injection needle having a transverse fluid outlet is provided, together with a shiftable fluid flow-blocking needle sleeve. When the syringe assembly is projected towards and through an animal's skin, the blocking sleeve is shifted, thereby exposing the needle aperture. The biasing force acting against the syringe plunger thereupon moves the plunger forwardly, injecting the fluid substance into the animal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is broadly concerned with an improved projectible 
syringe designed to facilitate the injection of sedatives or other 
medicaments into animals from a position remote from the animal. More 
particularly, it is concerned with such a projectible syringe which can be 
readily filled and manipulated by the user, whereupon, through the use of 
a blow gun or similar device, the device can be projected toward and into 
the skin of a subject animal, with the dose of medicaments thereupon being 
injected, all without the necessity of the user coming into close 
proximity to the animal. 
2. Description of the Prior Art 
Those involved in the care of large animals (e.g., zoo keepers and 
livestock handlers) often find it convenient to sedate such animals. This 
allows the user to approach and care for the animal without fear that the 
animal will become aroused and perhaps dangerous. By the same token, it is 
sometimes desired to directly inject medicament into animals from a remote 
position. 
It has been known in the past to provide a system including an elongated 
blow pipe together with a projectible syringe for such purposes. The 
syringe in this prior system is designed so that the injection needle 
thereof will pierce the skin of the animal and medicament will be 
thereupon injected by virtue of a charge of pressurized air established in 
the syringe prior to fixing thereof. Such a system is commercialized as 
the "Maxi-ject Veterinary Blowpipe System", and the overall structure of 
the blowpipe and syringe is described in an instruction manual distributed 
by Addison Biological Laboratory, Inc. of Fayette, Missouri. This 
instruction manual is incorporated by reference herein. 
Basically speaking, the Maxi-ject apparatus includes an elongated syringe 
body having a pair of shiftable plungers therein. An injection needle is 
also provided which is adapted to fit onto one end of the syringe body. 
This needle is of specialized construction in that it includes a 
transverse aperture spaced from the sharpened skin-piercing needle end 
thereof which is in communication with an axial fluid passageway. A 
shiftable silicon sleeve is positionable over this transverse aperture, so 
that, when the syringe is projected into the animal's skin, the sleeve is 
shifted away from the aperture. This in turn permits the dose to be 
injected from the syringe by virtue of a previously established 
pressurized charge of air behind the injection plunger. 
In practice however, the "Maxi-ject" apparatus requires the use of a 
conventional syringe in order to withdraw sedative or other medicament 
from a vial thereof, whereupon this conventional syringe is connected via 
a specialized coupler to the projectible syringe body. The fluid in the 
conventional syringe is then injected into the projectible syringe. The 
next step involves attachment of the specialized needle and flow-blocking 
sleeve onto the projectible syringe, followed by connection of a 
conventional air-filled syringe to the remote end of the projectible 
syringe body and filling the latter with a charge of compressed air 
between the two plungers. A guidance tail is then placed on the rear end 
of the projectible syringe remote from the needle, so as to complete the 
assembly and make it ready for use with the blowpipe. As can be 
appreciated, this procedure is rather complicated and unwieldly, 
particularly inasmuch as it is often necessary to carry out the make ready 
steps in the field. Accordingly, there is a real need in the art for an 
improved projectible syringe which can be readily filled and used without 
complicated procedures or extraneous equipment. 
SUMMARY OF THE INVENTION 
The present invention overcomes the problems noted above and provides an 
improved projectible syringe designed for use with a blowpipe or similar 
device. The syringe includes a tubular syringe body for holding a dose of 
an injectible fluid substance, together with means for drawing a dose into 
the syringe body, maintaining the dose within the body during projection 
and flight of the syringe toward a subject animal, and for injection of 
the dose into the subject once the injection needle is lodged with the 
animal's skin. 
In more detail, the projectible syringe of the invention includes an 
elongated injection needle affixable to the open end of the tubular body. 
This injection needle is of the known variety and presents a sharpened 
skin-piercing end and a tranversely extending projection aperture spaced 
from the sharpened end which communicates with an axial fluid passageway. 
The overall syringe assembly further includes a plunger within the tubular 
body which is axially shiftable along the latter and presents peripheral 
sealing means and a pair of opposed faces. An elongated plunger rod is 
operatively coupled with the plunger and extends out of the rear end of 
the syringe body for permitting selective withdrawal of the plunger in 
order to withdraw a dose of the injectible substance into the syringe 
body. 
Means is also provides for selectively restraining forward plunger movement 
to thereby maintain the fluid dose within the syringe body during fixing 
of the syringe. This restraining means includes a fluid flow-blocking 
member (such as a shiftable silicon sleeve) positionable in covering 
relationship over the transverse needle aperture and being shiftable away 
from the needle aperture upon encountering the skin of an animal. 
Finally, the complete syringe assembly of the invention includes means for 
creating a biasing force against the face of the plunger remoted from the 
injection needle in order to impart forward movement of the plunger 
towards the needle to inject the dose. Such a biasing force can be created 
by a number of different structural arrangements, including a spring 
positioned within the syringe body and engageable with the face of the 
plunger remote from the injection needle. In this fashion, as a dose is 
drawn into the syringe body the spring is compressed. In order to prevent 
premature injection of the dose, temporary plunger locking means is 
provided. This advantageously comprises mechanical latching structure 
engageable with the plunger rod in order to hold the plunger rod in a 
retracted position until the injectible needle and its associated 
flow-blocking member are in place. At this point the flow-blocking member 
serves to restrain forward plunger movement, and the temporary latching 
structure is released. In alternative forms, the force-creating structure 
may comprise one or more secondary rods coupled and shiftable with the 
main plunger rod and received within corresponding vacuum chamber(s). The 
secondary rod carries sealing means engaging the walls of the secondary 
chamber so that, upon retraction of the secondary rods a partial vacuum is 
created within the secondary chamber. Here again, mechanical latching 
structure is employed to maintain the plunger and secondary rods in their 
retracted position until the specialized needle and flow-blocking member 
are in place. This latching structure is then released so that upon use of 
the projectible syringe when the flow-blocking member is shifted from the 
needle aperture, atmospheric air serves to push the plunger forwardly for 
injection purposes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning now to the drawings, a projectible syringe assembly 20 is 
illustrated in FIGS. 1 and 2. Broadly speaking, the assembly 20 includes a 
tubular syringe body 22 adapted to hold a dose of fluid medicament or the 
like, a specialized injection needle 24 affixed to one end of the body 22, 
a shiftable plunger 26 situated within the body 22 and having a elongated 
plunger rod 28 affixed thereto and extending out of the rearward end of 
the body. Means is also provided for selectively restraining forward 
plunger movement, such including a shiftable flow-blocking sleeve 30 
mounted on needle 24. Finally, means 32 is provided for creating a biasing 
force against the plunger serving to move the latter forwardly to thereby 
inject a fluid substance into an animal. 
In more detail, the syringe body 20 is in the form of an elongated, 
circular in cross section tube presenting a reduced diameter open 
injection end 34 together with an opposed plunger end 36. The body is 
conventionally marked with appropriate volume indicators and is typically 
formed of a synthetic resin material. 
The needle 24 is adapted to be affixed to injection end 34 of syringe body 
22. The needle 24 includes an elongated metallic shank 38 having a 
sharpened skin-piercing end 40 and a radially enlarged, tubular, cup-like 
member 42 designed to fit over and mate with open injection end 34 of body 
22. In addition, the shank 38 is provided with an elongated, axially 
extending fluid flow passageway 44 which terminates in a transversely 
extending injection aperture 46. It will be noted in this regard that, as 
contrasted with conventional syringe needles, the aperture 46 is spaced 
from the sharpened end 40 of the needle 24. The importance of this feature 
will be explained hereinafter. 
The plunger 26 is in the form of a disc-like elastomeric body presenting a 
plurality of peripheral sealing ribs 48 designed to engage the inner 
surface of the sidewall of body 22. In addition, the plunger has a 
somewhat conical forward face 50 together with an opposed rearward face 
52. Plunger rod 26 in this embodiment comprises an elongated, central rod 
54 permanently affixed to plunger 26 and extending out end 36 of the body 
22. The outermost end of rod 54 is in the form of a transversely extending 
cap 56 which also supports a pair of laterally spaced apart elongated 
secondary rods 58, 60, the importance of which will be explained 
hereinafter. It should further be noted that the rod 54 is provided with a 
plurality of axially spaced apart detents 62 along the upper end thereof, 
and here again the importance of this feature will be explained below. 
The overall syringe body 22 is further provided with a pair of elongated, 
axially extending secondary chambers 62, 64 respectively within the 
defining sidewall of the syringe body. These secondary chambers in turn 
receive the corresponding secondary rods 58, 60 as will be readily 
apparent from a study of FIG. 2. Each of the rods 58, 60 further is 
provided with terminal seals 64, 65 serving to establish a fluid tight 
seal between the rods and the defining surfaces of the secondary chambers 
during reciprocation of the rods. 
The rods 58, 60 carry a latching plate 66 situated between end 36 of body 
22 and cap 56. This plate 66 is provided with a central aperture 68 which 
slidably receives plunger rod 54. In addition, the plate 68 includes a 
somewhat T-shaped stop 70 having an inner locking end 72. The shank of 
stop 70 is shiftable within a U-shaped guide 74. It will be noted in this 
respect that the locking end 72 is designed for insertion into the 
respective detents 62 provided in rod 54. 
In the use of assembly 20, a conventional hypodermic needle (not shown) is 
temporarily affixed to end 34 of syringe body 22. This temporary needle is 
used to fill the body 22 with a dose of fluid medicament or the like, 
through the simple expedient of inserting the needle into a vial of 
medicament and withdrawing plunger rod 54 so as to draw the dose into the 
syringe body. At this point the stop 70 is manipulated so as to engage end 
72 with one of the detents 62, thereby locking the plunger in its 
retracted position and preventing forward movement thereof which would 
serve to prematurely expel the fluid from the syringe body. It will 
further be noted that during this filling step, the secondary rods 58, 60 
are simultaneously withdrawn within their corresponding chambers 62, 64. 
This serves to establish partial vacuum conditions within these chambers 
which, absent the aforementioned locking structure, would cause the 
plunger 54 to move forwardly upon release of the plunger rod. 
The next step involves removal of the temporary hypodermic needle from end 
34, and placing thereon the specialized injection needle 24. Sleeve 30 is 
moved to the position shown in phantom in FIG. 5, i.e., in covering 
relationship to aperture 46, so as to prevent flow of medicament out of 
syringe body 22. At this point the stop 70 can be withdrawn from the 
associated rod detent 62. 
In this condition the assembly 20 is ready to be used as a projectible 
syringe. This typically involves placement of the loaded syringe assembly 
into a blowpipe which can be used in the known fashion to project the 
entire syringe assembly toward a subject animal. As the sharpened end 40 
of needle 24 enters the animal's skin, sleeve 30 is encountered and moved 
upwardly as viewed in FIG. 5 to a point where aperture 46 is no longer 
covered. By virtue of the partial vacuum conditions created within the 
chambers 62, 64 as explained above, atmospheric pressure acting on cap 56 
shifts plunger 54 forwardly thereby injecting the charge of fluid 
medicament into the animal. 
FIGS. 6-10 illustrate another syringe assembly 76 in accordance with the 
invention. Here again, the assembly 76 includes a tubular syringe body 78 
presenting an open injection end 80 and an opposed plunger end 82. In this 
instance, however, an end cap 84 is affixed as by threading to end 82 of 
the syringe body. The cap 84 is provided with a non-circular opening 
therethrough, in this instance a cross-shaped opening 86. 
A plunger 88 is situated within body 78 as illustrated, and includes 
peripheral sealing ribs 90. An elongated plunger rod 91 is permanently 
affixed to plunger 88 and extends out end 82 of the body 78. In this 
respect, it will be noted that the plunger rod includes a plurality of 
elongated sections 92, 94 and 96 each having a cross sectional 
configuration mated to that of opening 86, i.e., in this instance 
cross-shaped. The remainder of the plunger rod between plunger 88 and 
lowermost section 92, and the zones 98, 100, separating the 3 zones 92, 
96, are of circular configuration and have a diameter permitting passage 
thereof through the non-circular opening 86. Finally, it will be seen that 
each of the zones 98, 100, has an axial length slightly greater than the 
thickness of the top wall of cap 84. 
A helical spring 102 is located within body 78 between the plunger 88 and 
cap 84. The spring is sized so that upon withdrawal of the plunger rod 91 
the spring will be compressed. 
The injection needle forming a part of assembly 76 is identical to that 
described in connection with the first embodiment and accordingly like 
reference numerals have been applied thereto. 
The use of syringe assembly 76 is in most respects identical to that 
described with reference to assembly 20. That is to say, in the first 
place a conventional hypodermic needle is applied to end 80, whereupon the 
needle is inserted into a vial of fluid medicament. The plunger rod 91 is 
then withdrawn, which draws medicament into chamber 78. Simultaneously, 
this rod movement causes spring 102 to compress. At an appropriate point 
corresponding to the desired dosage to be injected, one of the reduced 
diameter zones 98, 100 aligns with the top wall of end cap 84. In order to 
temporarily lock the rod 91 in its retracted position against the bias of 
spring 102, the rod is axially rotated so that the adjacent cross-shaped 
section 94 or 96 is moved out of alignment with the cross-shaped opening 
86. This condition is illustrated in FIG. 10. 
The next step in the procedure involves replacement of the conventional 
hypodermic needle with the needle 34, the latter having sleeve 30 in 
flow-blocking position. Plunger rod 91 is then rotated so that the 
adjacent cross-shaped section 94 or 96 is aligned with the opening 86. The 
entire assembly 76 is then ready for use in the manner described above. 
Upon projection of the syringe the sharpened end 40 of needle 24 enters 
the animal's skin, shifting sleeve 30 rearwardly. This opens the aperture 
46, causing plunger 88 to be shifted forwardly under the influence of 
compressed spring 102, in order to thereby inject the dose into the 
animal. 
Another embodiment of the invention is illustrated in FIGS. 11-17, in the 
form of syringe assembly 104. The latter includes a tubular syringe body 
106 having a reduced diameter open injection end 108 together with an 
opposed plunger end 110. A plunger 112 is located within body 106 and 
presents peripheral sealing ribs 114, a forward injection face 116, and a 
rearmost face 118. The face 118 is provided with an upstanding, hollow 
housing 120 whose upper wall 122 has a somewhat T-shaped opening 124 
therethrough. 
A plunger rod 126 also forms a part of the assembly 104, with rod 26 
including an uppermost cap 128. The inner or lower end of the rod 126 is 
in the form of a T-shaped locking element 130 which is sized to pass 
through opening 124 and be situated within the confines of housing 120. 
The assembly 104 further includes end cap 132 having a threaded shank 134 
adapted to mate with corresponding threading provided adjacent end 110 of 
syringe body 106. Cap 132 has a bore 136 therethrough terminating in a 
resilient valve 138 of the type typically used for the filling of 
footballs or basketballs. 
Finally, the syringe assembly 104 has the specialized injection needle 24 
described in detail above, together with the slidable elastomeric sleeve 
30. 
The use of syringe assembly 104 proceeds as follows. First, a hypodermic 
needle of conventional construction is placed on end 108 of body 106, and 
this needle is inserted into a vial 140 of medicament. The rod 126, having 
locking element 130 within housing 120 and out of alignment with opening 
124, is used to withdraw plunger 112, thereby drawing liquid medicament 
into body 106. At this point the filled syringe body is placed in an 
inverted position, and the hypodermic needle removed. The specialized 
needle 24 is then placed on end 108, with the sleeve 30 in its 
flow-blocking position. The rod 126 is then rotated so that element 130 
aligns with opening 124 whereupon the rod is completely removed from 
housing 120 and withdrawn from the open rearward end of body 106. The end 
cap 132 is then threaded into the rearward end 110 of the body 106, in 
order to achieve a fluid tight connection. The needle 142 of a 
conventional air filled syringe is then pushed through the flexible valve 
138 in order to inject pressurized air into the region of body 106 between 
face 118 of plunger 112 and cap 134. Inasmuch as the sleeve 30 is in place 
over the opening 46, however, such pressurized air does not move plunger 
112 towards end 108. 
The use of assembly 104 in its filled condition is identical with the 
embodiments described previously. Here again, when the specialized needle 
24 penetrates an animal's skin the sleeve 30 is shifted rearwardly, 
opening aperture 46. Plunger 112 is then shifted toward injection end 108 
under the influence of the biasing force created by the pressurized air 
above the plunger as described. This of course serves to inject the dose 
into the animal.