Air powered dispensing pen for viscous fluids

A pneumatic dispenser for viscous fluids including a tubular pen barrel, a dispensing nozzle on one end of the pen barrel, and a pen cap constructed to sealingly receive the pen barrel. The pen cap also includes an air line connection and venturi arrangement so that when supplied with compressed air, air flow through the venturi reduces pressure in the pen and holds fluid in the pen. Interrupting air flow through the venturi causes pressure to increase in pen and fluid to be extruded through pen nozzle.

BACKGROUND 
1. Field of Invention 
This invention relates to dispensers for viscous fluids and more 
particularly to a dispensing pen which is operative for effectively and 
accurately dispensing controlled amounts of a viscous fluid. 
2. Description of Prior Art 
Currently, the most common type of dispenser for viscous fluids is the 
plastic squeeze bottle. While they are economical to produce, they are 
limited in the length of continuous line they can extrude before they must 
be allowed to return to their original shape. This introduces air bubbles 
into the fluid which can be extruded in subsequent use. Start and stop 
blobs and occasional bubbles are common problems. Also, many people with 
arthritis, carpal tunnel syndrome, or other wrist or hand problems find it 
difficult and tiresome to exert the constant pressure necessary to extrude 
a nice even line. 
Also on the market are miniature caulk guns. These use medical type 
syringes for barrels and a ratchet trigger assembly to advance a piston 
for extruding a fluid. From the hand's position on the trigger these 
devices lack precise control over the tip. Like the squeeze bottle they 
are limited in the length of continuous line they can produce. Also, 
constant pressure must be maintained to produce an even line and hand 
fatigue is again a problem. 
Another approach, used mainly in industry, is a dispensing pen that has a 
separate reservoir containing the fluid which is pressurized with air. The 
fluid is forced through a tube to a hand-held instrument containing a 
control valve. While working effectively, this dispenser requires a 
regulated air supply and is difficult to clean between fluid changes. To 
accomplish cleaning, the valve body must be disassembled and the reservoir 
and supply tube must be emptied and flushed. 
A fourth, and the most expensive approach, is another air powered device. 
Basically, this is a syringe for holding the fluid fitted with a cap and 
an air line. This air line is connected to a control box hooked to a 
regulated air supply. The control box contains a venturi apparatus, so by 
means of a foot switch the operator can pressurize the syringe and extrude 
fluid through the tip, or release the switch and create a partial vacuum 
in the syringe and stop all flow of material. These units work well, but 
are expensive by themselves, and in addition require a regulated air 
supply. This amount of equipment can be cumbersome as well if weight or 
space is a consideration. 
OBJECTS AND ADVANTAGES 
Accordingly, several objects and advantages of my dispenser are its ability 
to produce long, continuous lines, without start and stop blobs or 
bubbles, and without having to squeeze a bottle or trigger. My dispenser 
has further been designed to allow fingertip control of both the movement 
of the pen and the flow of fluid. The pen barrel and nozzle are the only 
elements that come in contact with the fluid and they are readily 
changeable and easy to clean. My dispenser also limits post extrusion 
using a partial vacuum as in the most expensive industrial dispensers. 
However, my dispenser accomplishes this by a venturi incorporated in the 
pen cap and controlled by fingertip. Also, where other dispensers require 
a regulated air supply, my dispenser operates with a conventional, 
inexpensive aquarium pump. 
Thus, my dispenser produces lines that are far superior to squeeze bottles 
and caulking gun type dispensers. And, being air powered, it causes little 
or no hand fatigue. Compared to other pneumatic dispensers, my dispenser 
is lighter, more compact, simpler to operate, easier to clean, and much 
more economical. And it produces lines comparable to any dispenser 
available. Further objects and advantages will become apparent from a 
consideration of the drawings and ensuing description.

DESCRIPTION FIGS. 1-3 
FIG. 1 shows a perspective view of my dispensing pen 18. A nozzle 10 is a 
disposable hypodermic needle where the stainless steel canula tubing has 
been square cut leaving 1 c.m. of the tubing and the remaining end 
deburred and chamfered. A luer lock connector 12 connects nozzle 10 to a 
12 c.c. syringe or a pen barrel 16. Pen barrel 16 has been machined with a 
male thread 26--1.9 c.m. dia., 6.3 threads/c.m. (3/4"NF16). A pen cap 28 
has been machined with a female thread 30--1.9 c.m. dia., 6.3 threads/c.m. 
(3/4"NF16). Male thread 26 and female thread 30 allow connection of pen 
barrel 16 and pen cap 28. A vinyl seal 14 is a 2 c.m. long section of 
vinyl tubing, 1.9 c.m. O.D., 1.6 c.m. I.D. Vinyl seal 14 is situated 
around bottom end of pen barrel 16 to effect an airtight seal with pen cap 
28. 
FIG. 2-B shows an air line connector 20 which is a 1.6 c.m. long brass tube 
0.16 c.m. O.D., 0.08 c.m. I.D. This air line connector 20 is reduced on 
one end to 0.05 c.m. I.D. by an orifice 36. Air line connector 20 is glued 
into one end of a control tube 22 with the addition of a vinyl bushing 34. 
Control tube 22 is a 9.4 c.m. long polystyrene tube, 0.64 c.m. O.D., 0.32 
c.m. I.D. Vinyl bushing 34 is a 0.64 c.m. long vinyl tube, 0.32 c.m. O.D., 
0.16 c.m. I.D. A pressure transfer hole 38, 0.16 c.m. diameter is located 
in control tube 22 with its edge adjacent to orifice 36. Adjacent to 
opposite edge of pressure transfer hole 38 is a movable venturi element 
40. Movable venturi element 40 is a 0.8 c.m. long vinyl tube 0.32 c.m. 
O.D., 0.16 c.m. I.D. A vein 23, 0.64 c.m. radius, is routed. 0.12 c.m. 
deep, longitudinally, the entire length of pen cap 28. This is best shown 
in FIG. 2A. Pen cap 28 is constructed of a 10 c.m. section of PVC tube; 21 
m.m. O.D., 18 m.m. I.D. (1/2" SDR 13.5 PVC pipe). 
FIG. 2B shows a hole 39, 0.16 c.m. diameter, drilled in the center of vein 
23 at a distance from the end so that when hole 38 and hole 39 are lined 
up, a flow control port 24 will be flush with bottom edge of pen cap 28. 
Control tube 22 is glued in this position with special attention to 
forming an airtight seal around hole 38 and hole 39. Control tube 22 has 
been reamed to 0.48 c.m. I.D. and cut at a 22 degree angle to form control 
port 24. A pen cap end plug 32 is glued in threaded end of pen cap 28. All 
glue used is waterproof epoxy. The open end of pen cap 28 has been drilled 
to a diameter to slidably receive pen barrel 16 shown in FIG. 3. 
Operation FIGS. 1-3 
The manner of operation of dispensing pen 18 is to connect a 0.32 c.m. 
O.D., 0.16 c.m. I.D. vinyl tubing (not shown) from air connector 20 to a 
conventional aquarium pump (not shown), supplying air at a rate of 3-4 
liters per minute at a pressure of 0.18 KG-0.3 KG per cm.sup.2. Next, 
remove pen barrel 16 and fill with up to 12 c.c. of desired fluid (glue, 
paint, fabric paint, dye resist, etc.). Reinsert pen barrel 16 into pen 
cap 28 and screw until vinyl seal 14 seats against pen cap 28 forming an 
airtight seal. Dispensing pen 18 should be held with point down when 
loaded to keep fluid in pen barrel 16. Air flow through orifice 36 and 
movable venturi element 40 will create a partial vacuum in pen cap 28 and 
prevent extrusion of fluid through nozzle 10. Movable venturi element 40 
is slidable in control tube 22 for adjusting vacuum to accommodate 
variations in aquarium pump outputs. Pen should be held so forefinger 
rests near flow control port 24. This port has been reamed and cut on an 
angle to facilitate its use. Covering port 24 will cause pressure to rise 
in pen cap 28 via pressure transfer hole 38 and pressure transfer hole 39 
and fluid will be extruded through nozzle 10. Uncovering flow control port 
24 will stop flow of fluid. Pen barrel 16 and nozzle 10 are easily cleaned 
with a 12 c.c. syringe plunger (not shown). 
Thus the reader will see that the dispensing pen 18 of the invention 
provides a simple, reliable, and economical device that can be used by 
almost anyone. While my above description contains many specificities, 
these should not be construed as limitations on the scope of the 
invention, but rather as an exemplification of one preferred embodiment 
thereof. Many other variations are possible. For example, pen cap 28 and 
control tube 22 could be molded as one piece. Control tube 22 could even 
be contained entirely in the side wall of pen cap 28. 
Accordingly, the scope of the invention should be determined not by the 
embodiment illustrated, but by the appended claims and their legal 
equivalents.