Pellet implanter for animal treatment

A pellet implanter for the subcutaneous implantation of one or more spherical or cylindrical pellets of a total size of up to about 1/8 inch by 1 inch (3 mm .times. 25 mm) through a hypodermic needle uses a transparent compact flat cartridge having parallel feed chambers permitting visual observation of the feed and 360.degree. rotation of the cartridge holder with respect to the pistol grip and plunger assembly. A collet holds a replaceable injection needle which permits injection of therapeutic agents in repository form beneath the skin of animals for therapeutic and/or growth control purposes.

BACKGROUND OF THE INVENTION 
It has long been known that various substances affect the health and/or 
rate of growth of mammals. In the animal husbandry industry it is 
desirable that various substances be implanted beneath the skin of an 
animal to affect the rate of growth of the animal or to control other 
characteristics. For instance, antibiotics can be injected to control 
diseases, or hormones may be injected to increase the weight or enhance 
the characteristics of the meat. It has been considered desirable that any 
substances injected be injected in the ear or neck or other portion of the 
subject animal at such location as to minimize effects on useful meat and 
minimize the likelihood that a person eating meat from the animal would 
ingest whatever material had been implanted. Various growth influencing 
substance may be used depending upon the animal or the effect desired. 
Hormones such as diethyl stilbestrol have been implanted in chickens for 
instance where the material has the effect of caponizing a rooster, with 
improved production of tender meat. 
The present implantation device is designed for use with any solid pellets, 
or materials which may be incorporated with a carrier as a solid pellet, 
for injection beneath the skin of the subject domestic animal. 
PRIOR ART 
U.S. Pat. No. 2,620,796 -- Eriksen and White -- Dec. 9, 1952 -- PELLET 
INJECTOR -- shows a clip fed hypodermic type injector, with provisions for 
the control of the depth of penetration, in which a loop type handle at 
the end of the plunger is used for the control of the plunger, which as it 
slides forward picks up pellets from a clip of channel shaped 
configuration having an open slot through which the pellet may be viewed. 
U.S. Pat. No. 2,883,984 -- Candido and Miskel -- Apr. 28, 1959 -- PELLET 
IMPLANTER -- shows a piston grip type implanter with a hollow hypodermic 
needle in which an elongated plunger slides through a card to pick up 
pellets which are carried through the hypodermic needle into a subject. 
This patent discloses the implantation of pellets into beef cattle at the 
base of the ear and certain advantages of a piston grip hypodermic 
injector. The disclosure of this patent is hereby herein incorporated by 
this reference thereto. 
U.S. Pat. No. 3,402,712 -- Eisenhand -- Sept. 24, 1968 -- PELLET IMPLANTER 
-- shows a piston grip type implanter with a hypodermic needle and a 
plunger, which upon actuation by a trigger member causes pellets from a 
vertical pellet conduit to be fed into the path of the plunger and forced 
through the hypodermic needle into the subject. The plunger of this 
implanter releases only when there is a pellet in the chamber ready for 
implanting, so that the user is certain there is a pellet present to be 
implanted if the trigger operates. There is also a sight hole to permit 
visual inspection of the pellet in the load position. 
U.S. Pat. No. 3,538,916 -- Wiles & Groff -- Nov. 10, 1970 -- INJECTION 
PISTOL -- shows a sear released spring loaded plunger with adjustable 
depth control means, in which the pellet is loaded into the front of the 
needle at the time of use. 
U.S. Pat. No. 3,774,607 -- Schmitz -- Nov. 27, 1973 -- PELLET IMPLANT GUN 
-- shows a pistol type implant gun using a long throw plunger which 
operates through pellet cylinders in a circular magazine. The line of 
travel of the plunger through the magazine is opened to observation so 
that the user can check that the cylinder of the cartridge is aligned and 
that the cylinder actually contains pellets. Flexible fingers retain the 
pellets within the cylinders until time of use. 
Australian Pat. No. 228,022 -- Needham and Thorne -- accepted Apr. 12, 1960 
-- HYPODERMIC IMPLANTER, shows a circular magazine having chambers for the 
implantation of pellets through a hypodermic needle but uses a pair of 
circular finger grips and a operating knob at the back end of the plunger 
in alignment with the plunger for forcing of the plunger through the 
magazine and the hypodermic needle at the time of implantation of the 
pellet. 
SUMMARY OF THE INVENTION 
It has now been found that pellets may be implanted under the skin of 
domestic animals with a particularly convenient lightweight economical 
type of injection gun. 
Solid pellets containing antibiotics, hormones, anabolic growth regulants 
or other therapeutic agents may be implanted under the skin of domestic 
animals to control the growth rate or other characteristics. Such 
materials are well known. Some materials may be injected as a liquid or 
suspended in a liquid but the rate of dissolution or reaction is apt to be 
undesirably fast. Some materials may be implanted as a pellet, but 
conveniently many materials are incorporated in a carrier such as castor 
wax, beeswax or a delayed release matrix such as a polyester resin 
containing glycolic acid ester linkages which are subject to hydrolytic 
degradation to tissue compatible components, or other types of matrices in 
which the medicament is released at a desired rate. For injection in 
animals it is frequently desired that the material be injected in the neck 
or in an ear so that the site of the injection is not subject to human 
consumption, if the animal is used as a food product. 
The present gun is lightweight, and thin, so that a magazine having a 
series of chambers therein may be flat and of relatively small size, and 
fed into a C-shaped magazine receiver which may be rotated through 
360.degree. with respect to the main frame having a pistol grip so that 
either a right or a left handed person may rotate the magazine in its 
receiver to such a position that the feeding of the magazine through the 
magazine receiver is in a direction most convenient for the particular 
operator, having reference to the animal being treated, and the 
restraining system used to restrain the animal at the time of injection. 
Obviously, the animal is apt to express displeasure in being stuck and 
suitable restraints are required so that the operator may most accurately 
inject the pellet at a desired location, with a minimum of risk of 
misplacement, or injury to the operator or the animal during the 
procedure. The present pellet implanter is particularly small and 
convenient with respect to its capacity, so that comparatively large 
implants may be injected with a minimum of effort. Additionally, the 
implanter is relatively simple and readily cleaned so that even if it 
dropped to the ground at the scene of operations or covered with hair or 
blood from the injected animal it may be readily cleaned for subsequent 
use. 
While not limited thereto, it is convenient for the gun to handle one or 
more pellets and a total size of up to about 1/8th of an inch by 1 inch 
through a hypodermic needle. 
The pellets may be cylindrical, with a sufficient number of cylinders to 
completely fill the magazine pellet chambers, or partially fill the 
magazine pellet chambers for a smaller dose; the pellets may be spherical 
with as many spherical pellets in each magazine pellet chamber as are 
needed for a desired dose, up to the capacity of the magazine pellet 
chamber. 
It is desirable that the needle and the size of the pellet or pellets be as 
small as is consistent with the desired dosage. The present implanter is 
particularly convenient because smaller lengths of pellets for smaller 
dosage may be implanted using the same magazine containers and gun. A 
sleeve may be placed around the plunger in the gun, with a shorter needle 
for smaller implants. These and other advantages of the present pellet 
implanter are obvious from the following description of one embodiment 
thereof.

The pellet implanter has a main frame 11 conveniently consisting of a back 
case 12 and face case 13. Conveniently these are essentially symmetrical 
and each of one piece. If desired the back case can be deeper and the face 
case in effect merely a plate on top. Whereas described as of one piece 
each, as are many of the other items in the present assembly, it is to be 
understood that if because of manufacturing convenience in a particular 
machine shop it may be desirable to make the parts of two or more pieces 
which are welded, riveted or otherwise assembled to each other. These are 
spoken of as functionally integral. 
In the main frame, both in the front and back case, is a plunger slide 
groove 14 in which is mounted for reciprocating motion a plunger slide 15. 
The plunger slide has a T-shaped configuration with the head sliding in 
the plunger slide groove 14 and controlled as to orientation and direction 
that by this groove, and with a pair of operating bars 16 extended 
downward between which bars is an operating pin 17. 
Extending downward on the main frame is a pistol grip 18 near the front 
part of which is hinged an operating trigger 19. Conveniently the 
operating trigger 19 is full length for full hand motion control. Near its 
lower end is a trigger pin 20. As shown the operating trigger 19 is of 
U-shaped configuration so that the trigger pin 20 is internal thereof. A 
connecting link 21 is pivoted on a link pin 22 and extends between the 
operating pin 17 and the trigger pin 20, with a link slot 23 at each end 
of the link so that as the operating trigger 19 is depressed it rotates 
and in turn rotates the connecting link 21 with a mechanical 
multiplication causing the plunger slide 15 to move forward a greater 
distance, than the stroke length of the operating trigger 19. A clearance 
slot 24 in the operating trigger permits rearward motion of the operating 
trigger so that a full stroke of the connecting link 21 moves the plunger 
slide 15 forward for substantially the length of the main frame in the 
plunger slide groove 14. 
A biasing spring 25 extends between the connecting link 21 and a spring pin 
26 in the pistol grip, to retract the connecting link, and with it reset 
the operating trigger and the plunger slide when the operating trigger is 
released. 
Other mechanical movements may be used to transmit trigger movement to the 
plunger slide. 
Extending from the front of the plunger slide 15 is a plunger 27. The 
plunger extends towards the front of the main frame 11 and is of such a 
length that on full retraction of the plunger slide, the front of the 
plunger is behind the magazine feed slot 29 in the magazine 30, as 
described below. 
On full extension the plunger slides forward far enough to eject the one or 
more solid pellets 52 in the chamber 45 in the magazine. 
At the front of the main frame is a C-shaped magazine receiver 28. The 
magazine receiver is of generally C-configuration and has therein a 
magazine feed slot 29. The magazine feed slot 29 is of generally 
rectangular configuration to receive a magazine 30. 
The magazine receiver 28 has at its rear end a cylindrical boss 31 having 
therein a retaining groove 32. 
In the front of the main frame is a hollow cylindrical magazine receiver 
clamping sleeve 33 having therein a retaining ring 34. The retaining ring 
34 fits into the retaining groove 32 on the cylindrical boss 31 so that 
the cylindrical boss is free to rotate on slight loosening of the hollow 
cylindrical magazine receiver clamping sleeve 33. On additional loosening 
the boss will slide out of the sleeve permitting disassembly. Assembly 
screws 35 hold the two cases of the main frame together; and a sleeve 
clamping screw 36 permits clamping of the hollow cylindrical magazine 
receiver clamping sleeve 33. By slightly loosening the screws adjacent to 
the boss, the magazine receiver may be rotated for 360.degree. around the 
front end of the main frame to permit alignment of the magazine receiver, 
for the convenience of the operator. 
The magazine receiver 28 is of generally rectangular configuration with two 
lips adjacent to an open face 37 of the magazine feed slot 29. A rear lip 
38 extends over and holds the back part of the magazine 30. The front lip 
39 holds the front part of the magazine 30 and has a slighter greater 
spacing so that the magazine can be designed to be slightly thicker at the 
front thereby controlling orientation. The front lip 39 may extend over 
the front of the magazines and have a slight locking lip 40 to further aid 
in controlling orientation. 
By having the magazine of such shape that the magazine can be inserted into 
the magazine feed slot in only one orientation, the risk of the user 
putting the magazine in backwards or upside down is minimized. 
At the back of the magazine feed slot 29 is a positioning detent slot 41 in 
which is a detent spring 42, as shown in FIG. 4, which is held by a detent 
spring screw 43. The detent spring 42 locks into a groove 44 in the 
magazine when the magazine is in proper position. The detent spring 42 
serves to control linear positioning of the magazine 30 and insure that 
the chamber 45 is coaxial with the plunger 27 at the time of operation of 
the trigger. 
At the front face of the magazine receiver 28 is a hypodermic needle 
holding collet 46 consisting of the usual collet fingers 47 which are 
clamped by the usual collet ring 48 against the hypodermic needle 49. 
The collet fingers 47 may be integral with the magazine receiver 28, but 
conveniently are on separate collet sleeve 50--as too often the collet 
ring is accidentally clamped against the collet fingers without a needle 
being in place, which bends and mutilates the fingers. A separate 
replaceable collet sleeve permits convenient replacement, and also 
different size sleeves permit using different size hypodermic needles. 
The magazine 30 itself is a flat multichambered insert, preferably 
transparent and having therein a series of uniformly spaced parallel 
chambers 45 for the pellets 52. At the rear end of each chamber is a 
concentric restriction 51. This constriction is large enough to admit the 
plunger 27 but it is small enough to retain a pellet 52 in the chamber. 
Each chamber may hold one or more pellets 52. The number and size of 
pellets is controlled by the optimum size for injection of a particular 
material into a particular subject animal and depends upon the 
characteristics of the injected material. Those dose may be molded into 
one or more pellets for consecutive injection into the subject animal. It 
may be convenient, for instance, to have four pellets each about 1/8th of 
an inch diameter by 1/4 inch long for a maximum load; with 1, 2 or 3 
pellets being used for smaller dosage in otherwise identical magazines. 
Smaller pellets may be used in smaller animals. 
At the other end of the chambers is a cover clip 53 which is a snap or 
friction fit for easy assembly over the front of the magazine. 
The cover clip 53 has a thickened corner 54 which fits into the front lip 
39 in the magazine receiver 28 and may be held by the locking lip 40 so 
that the magazine having a cover clip thereon can only be inserted with 
one orientation into the magazine receiver. 
Additionally, the cover clip has molded therein a series of discharge 
apertures 55, each generally large enough for the discharge of the pellets 
in the chamber, but having formed therein flexible pellet-retaining leaves 
56. These leaves 56 are sufficiently thin and flexible that they may be 
easily displaced on injection of a pellet but are sufficiently rigid to 
retain the pellets in position during shipment and storage and until the 
time of injection. 
Molded in the backside of the magazine 30 are a series of grooves 44. Each 
groove is of a size and shape to engage the detent spring 42 when the 
magazine is in a properly aligned position. 
The alignment is such that the plunger 27, the funnel shaped plunger 
orifice 57 in cylindrical boss, and the hypodermic needle 49 in the collet 
46 are coaxial and in alignment with the chamber 45 in a magazine 30 in 
the magazine receiver 28 at the time of injection of a pellet into a 
domestic animal. 
As indicated above, one or more pellets, not necessarily of the same size 
may be conveniently stored in each of the chambers 45 until time of 
injection. The number of chambers and the size of chambers in a magazine 
may be varied depending upon therapeutic requirements. A smaller size 
chamber may be used. A smaller size plunger may conveniently be used with 
a smaller size hypodermic needle, if the subject and the therapeutic 
requirements so indicate. A slightly conical entrance to the magazine and 
a smaller plunger can be adapted readily to the assembly without having to 
modify other parts. 
If it is desired to use a shorter stroke with a shorter hypodermic needle, 
a short section of tube may be placed over the plunger 27 to restrict and 
control the length of its stroke. 
Usually it is desirable that the plunger upon operation of the trigger 19 
extend far enough that the end of the plunger is very close to the bevel 
58 on the hypodermic needle 49. 
It is also convenient to put a shield on the front of the hypodermic needle 
to control the depth of injection, if it cannot be readily controlled by 
eye or if the subject animal is unruly. 
FIG. 6 shows a modification having a compact magazine 59 in a compact 
magazine receiver 60. This compact magazine is interchangeable in the 
hollow cylindrical magazine receiver clamping sleeve 33; and has short 
chambers 61 for one or two spherical pellets 62. A short hypodermic needle 
63 may be used. The shorter needle and spherical pellets are convenient 
for smaller doses of medicament, and smaller animals. The choice of needle 
size and lengths, and site and amount of material injected may vary over a 
wide range depending upon the desires of the user, for a specific 
situation. 
The magazine can be designed with grooves in both faces, and a symmetrical 
clip, so that the magazine can be introduced from the top or bottom of the 
magazine feed slot 29, and with an interchangeable top and bottom of the 
magazine. Using one axis and two planes of symmetry is convenient for 
insertion. With such construction both faces of the magazine should be 
transparent to permit visual inspections of chamber contents. The top and 
bottom of the magazine are convenient areas for product designation with 
this construction. 
At the time of use, the individual operator selects one or more magazines 
containing pellets, depending upon the number of animals to be injected, 
and makes arrangements for the animals to be confined on their movement 
restricted, as for example by an animal chute or a tie-down, then adjusts 
the angle of the magazine receiver to the main frame to that most 
convenient, tightens the assembly screws 35 and sleeve clamping screw 36, 
then proceeds to insert a hypodermic needle and inject one or more pellets 
from the magazine into the subject domestic animal. 
It is convenient, but not necessary, that either the magazine itself 30 or 
the cover clip 53 by color coded as to dosage and material so that the 
user can immediately spot by color magazines having interchangeable 
contents. Similarly, the magazines may have a label attached thereto or 
may have embossed on one face such information as may be of value to the 
user. Usually a group of magazines will be packaged in a protective box 
giving suitable protection for storage, and complete instructions. For 
some materials it will be necessary that the contents of the box be merely 
clean, others clean and sterile, and for some protection may be required 
against ambient moisture or oxygen. 
Theoretically, at least, if the cover clip fits on by a snap fit, it can be 
unsnapped and the magazine reloaded however it is usually preferable to 
use new magazines of a disposable type, to permit the advantages of 
factory loading by the manufacturer and to guarantee that maximum 
standardization of dosage levels be obtained. 
FIG. 7 shows an alternative magazine construction in which a magazine face 
64 is molded with U-shaped chambers 65, and the open U-shaped chambers 
closed by a magazine cover 66, which has detent grooves 67 therein. 
Retaining leaves 68 are molded in the magazine cover 66. The magazine is 
the functional equivalent of the magazine having a cylindrical chamber 45, 
but easier to mold of plastic. Even if the chambers 45 have a slight 
taper, drilling or molding may be more expensive than using U-shaped 
chambers. 
The choice depends upon available molding equipment, and loading 
convenience. 
The magazine cover may be either a friction fit, or adhesively united. 
Usually adhesively uniting is preferred as it prevents reloading with the 
wrong pellets. 
Other modifications and changes within the scope of the following claims 
suggest themselves to those skilled in the art.