May 1954 ET-314
United States Department of Agriculture
Agricultural Research Service
Entomology Research Branch
HAND INJECTOR FOR LIQUID SOIL INSECTICIDES"
By W. C. Fest
A hand injector has been developed for the injection of small volumes
of liquid insecticides into balled and burlaped nursery stock to destroy
the immature stages of the Japanese beetle (Popillia japonica Newm.) in
the soil about the roots of the plants. This paper describes the general
construction and operation of this injector, which is a modification of a
commercial caulking gun with a lever action-cocked plate.
The assembled injector is shown in figure 1, and the nozzle, as-
sembled and disassembled, in figure 2.
The protective sleeve (A) is of brass 3 1/4 inches long and 5/16 inch
in diameter, with a bore 2/1-000 inch larger than 1/4 inch to within 1/4
inch of the tip, where it is 3/16 inch. The lower 1/4 inch of the outside
of the sleeve is tapered from 5/16 inch to 3/16 inch. At the top of the
sleeve is a collar 5/8 inch long with an outside diameter of 7/16 inch to
within 1/16 inch of the end, where it is 5/8 inch.
The injector tube (B), of brass with a pointed steel tip, is 4 1/4
inches long. The outside diameter is 1/4 inch to within 1/2 inch of the
lower end, and then 3/16 inch to within 1/16 inch of the steel tip, where
it tapers to 1/8 inch. The inside bore is 3/32 iribh. Four 1/16-inch
holes are drilled in the tube immediately below the point where the out-
side diameter is decreased to 3/16 inch; only one of these holes is shown
in figure 2. The steel tip, 1/2 inch long, having a shank 3/32 inch in
diameter and 3/8 inch in length and a-head 1/8 inch in diameter beveled
to a point, is forced into the lower end of the injector tube so that the
head is in close contact with it. There is a 1/4-20 thread 1/2 inch long
at the upper end of the tube.
The sliding top (C) for the protective sleeve (A) is made of 1/8-inch
steel 3/4 inch wide and 2 1/2 inches long, bent into a U-shape with arms
1/ L. B. Parker, of the Japanese beetle laboratory, took the
3/4 inch long. The hole in the center of the upper arm is 3/8 inch in
diameter and that in the lower arm 29/64 inch. The release (D) for the
protective sleeve (A) is made of 16-gage steel 1 1/4 inches long and 1/2
inch wide, with a hole 9/32 inch in diameter in the center. E is a 1/4-20
hexagonal nut, and F is a flare nut of brass having the lower end bored
with a 1/4-20 thread.
The liquid-pressure valve (G), with an inside bore of 9/32 inch, is
threaded on each end for connecting to the flare nut (F) and the 1/4-inch
iron pipe tee (H). A ball seat of brass 9/32 inch in diameter and 1/8 inch
long with a 3/16-inch bore is pressed into the upper end, and a spring
stop of the same dimensions into the lower end of the pressure valve.
I is a steel spring 1/4 inch in diameter and 1 1/4 inches long and J a steel
check ball 7/32 inch in diameter, both functioning within the pressure
valve. There is a brass petcock (K) on the tee to which flexible tubing
is connected for loading the injector.
A wing-nut adjustment (L) on the injector handle regulates the dis-
tance the trigger (R) can be moved and thus the volume of liquid dis-
charged. M is the piston rod and N the latch for the recoil plate (0).
When the recoil plate is inserted under the latch, the piston rod can be
moved without engaging the trigger (R).
The lower cap (P) of the barrel (Q) is threaded and screws onto the
barrel. The original washer in this cap did not have enough bearing
surface on the end of the barrel to make the union sufficiently tight to
confine liquids. This difficulty was remedied by fitting a sleeve 1/4 inch
long, made from 2-inch copper tubing, into the lower end of the barrel.
To load the injector with a liquid insecticide, the petcock (K) is
opened, the end of the recoil plate (0) is inserted under the latch (N),
and the piston rod (M) is pushed into the barrel (Q) for the full distance
to expel the air. A piece of flexible tubing is put on the petcock. With
the lower end of the flexible tubing in the liquid insecticide, the injector
is held with the nozzle downward and the piston rod (M) is slowly with-
drawn; thus the liquid insecticide is pulled into the barrel (Q). The
petcock (K) is then closed, the flexible tubing removed, and the recoil
plate (0) released from the latch (N). The recoil plate should always
be released when the injector is operated to engage the trigger mech-
anism. The injector is held with the nozzle pointing upward. The
trigger (R) is then pressed two or three times until the liquid insecti-
cide is discharged from the nozzle tip. This operation expels any air
and fills the injector tube with liquid. When filled completely, the in-
jec'tor holds 380 ml. of liquid insecticide.
The amount of liquid discharged is regulated by the distance the
trigger is moved. The injector can be set to deliver 2 to 8 ml. of
liquid per discharge. The setting of the wing-nut adjustment (L) on the
injector handle to discharge a definite amount of liquid is a trial-and-
error process. For example, if approximately 4 ml. per discharge is
desired, the injector should be discharged 10 times into a graduated
cylinder and the volume determined. If the volume of discharge is not
between 40 and 45 ml., the wing-nut adjustment (L) should be reset and
the process repeated until this volume is obtained in three successive
trials. After the desired setting of the wing-nut adjustment has been
obtained, the amount delivered by the injector should be rechecked from
time to time, preferably each day.
To inject the liquid insecticide into balled and burlaped nursery stock,
the injector tube is first inserted into the soil to a depth of approximately
3 inches, then withdrawn about 1/2 inch until the lower side of the collar
on the protective sleeve (A) strikes the lower arm of the sliding stop (C).
In this way the protective sleeve remains stationary in thte soil, and the
injector tube (B) is withdrawn into it, leaving a space for the discharge
of the liquid. The trigger is then pressed to discharge the liquid, and
the injector is withdrawn from the soil.
UNIVERSITY OF FLORIDA
III6 092 2 Il9491I1I1I11 Il6i I11I1Illill
3 1262 09242 9496
Figure l.--Assembled hand injector for liquid soil insecticides.
Figure 2.--Details of the nozzle. Top, assembled; bottom, disassembled.