A dripless syringe for dispensing a material such as glue, caulking, cement, foods, cosmetics, paint, oil, pharmaceuticals; etc., and any other materials suitable for dispensing thereby. The syringe plunger includes a generally hemispherically-shaped piston portion for pushing the material out of the syringe. Except for the piston portion, the plunger slides easily within a barrel of the syringe. In operation, the hemispherical piston portion is deformed during dispensing, but returns to its original shape after dispensing is finished. Upon returning to its original shape, the piston portion stops further dispensing of the material from the syringe.

BACKGROUND OF THE INVENTION 
This invention relates to a no-drip syringe adapted for dispensing one or 
more materials. For example, the syringe can be used to dispense glue, 
caulking, cement, foods, cosmetics, paint, oil, pharmaceuticals; etc., and 
any other materials suitable for dispensing thereby comprising a single 
material or multiple materials as desired. In accordance with this 
invention, the direction in which the material being dispensed flows 
during the dispensing operation is reversed when the dispensing operation 
ends. This reversal of the direction of material flow stops the flow of 
material from the syringe when it is no longer desired to dispense 
material from the syringe. 
In most prior art syringes, one has to pull back on the plunger in order to 
stop the flow of material out of the syringe spout. It is also known to 
utilize a spring which acts on the plunger to automatically pull it back 
when the pressure on the plunger is released. However, such an approach is 
unduly complicated and expensive. 
Accordingly, the invention disclosed herein provides an infrared no-drip 
syringe. It has a configuration which can include a minimum of parts and 
is easy to operate. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a no-drip syringe is provided 
which overcomes the deficiencies in the prior art approaches. The syringe 
comprises a dispensing body for supporting at least one column of the 
material to be dispensed. At least one plunger comprising an elongate 
member is provided with an actuating pad at one end of the member and a 
piston portion at the opposing end thereof. The piston portion is adapted 
to act upon the at least one column of material to dispense it from the 
syringe dispensing body. 
In accordance with this invention, a no-drip system is provided for 
substantially stopping the dispensing of the material being dispensed when 
the at least one plunger is not being actuated. The no-drip system 
comprises the piston portion itself which is configured to have a 
preferred generally hemispherical shape with a concave hollow face for 
acting on the material being dispensed. The piston portion is resilient. 
Means are provided for deforming the piston portion from the preferred 
shape during a dispensing operation while allowing the piston portion to 
return to its preferred shape after the dispensing operation is stopped. 
The deforming means preferably comprises a portion of the plunger 
connecting the piston portion to the elongate member. Preferably, the 
syringe body includes at least one chamber for supporting therein at least 
one column of material. The chamber itself comprises a barrel portion 
having a longitudinally extending internal wall surrounding the material. 
Preferably, the elongate member is arranged to slide loosely within the 
barrel portion and the piston portion is arranged to move within the 
barrel portion with generally sealing engagement with the internal wall. 
The elongated member, preferably, comprises a central 
longitudinally-extending core having a plurality of longitudinal flanges 
extending radially outwardly from the core with the radial extent of the 
flanges being selected so that the member is adapted to loosely slide 
within the barrel portion. The connecting portion, preferably, has a 
radial extent which is substantially smaller than the radial extent of the 
flanges. The piston portion, preferably, includes a convex face opposing 
the concave face and the connecting portion is, preferably, connected to a 
central portion of the convex face. 
If desired, the syringe, in accordance with this invention, can include 
means resistant to chemical attack by the material being dispensed 
supported by the piston portion. One such means comprises a grommet 
supported by the piston portion which is adapted to cooperate with the 
hemispheric face of the piston portion so as not to interfere with the 
no-drip operation of the syringe. Preferably, the elongate member, the pad 
portion, the connecting portion and the piston portion comprise a unitary 
member which may be formed or molded of a material such as plastic.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, a no drip or dripless syringe is shown. The syringe 10 
is comprised of a dispensing body 11 for supporting at least one column of 
the material to be dispensed. The syringe 10 also includes at least one 
plunger 12 for acting upon the column of material to be dispensed to 
dispense it from the syringe 10 via spout 13. 
Referring now to FIG. 2, the plunger 12 is shown in greater detail. The 
plunger 12 comprises an elongated member 14 having an actuating pad 
portion 15 at one end and a piston portion 16 at the opposing end of the 
member 14. The piston portion 16 is adapted to act upon the column of 
material to be dispensed from the syringe 10 to push the material through 
the spout 13 as in FIG. 1 so that it can be applied by the operator as 
desired. The pad portion 15 is adapted to be engaged, for example, by the 
operator's thumb, in order to apply pressure to the plunger 12 so as to 
dispense the material from the syringe 10. Referring to FIG. 1, the 
dispensing body 11 includes a finger support flange 17 at its end opposing 
the spout 13. Therefore, in operation, a person supports the dispensing 
body 11 by two fingers disposed under the flange 17 on either side of the 
body 11 and presses with the thumb against the pad portion 15 of the 
plunger 12. 
When pressure is thus applied to the pad portion 15, the material in the 
syringe is dispensed therefrom by flowing in a first direction out of the 
spout 13. In accordance with this invention, a no-drip system is provided 
for substantially stopping the dispensing of the material when the 
pressure is removed from the plunger so that it is not being actuated to 
dispense the material. 
Referring now to FIGS. 2-5, the no-drip system to provide the no-drip 
operation is described in greater detail. The piston portion 16 is 
configured to have a preferred generally hemispherical shape with a 
concave hollow face 18 for acting on the material being dispensed. The 
piston portion 16 is resilient so that if it is deformed it springs back 
to its preferred generally hemispherical shape. The term "hemispheric 
shape" as used herein is not intended to be limited to a full hemisphere 
since it can comprise a portion of the hemisphere as shown. Further, it 
does not have to be exactly hemispheric, but rather it should have a 
generally arcuate shape as shown comprising a hollow face 18 facing the 
material being dispensed and a convex opposing face 19 which is, 
preferably, of a correspondingly arcuate nature. 
The piston portion 16 having the generally hemispheric shape acts in a 
manner analagous to the bottom of an oil can. When not in use, the plunger 
12 and the hemispheric concave face 18 sit on top of a column of the 
material to be dispensed. At this point, the hemispheric face 18 has its 
desired preferred profile. When pressure is applied to the thumb pad 15, 
the hemispheric face 18 is generally flattened out by the action of the 
central connecting portion 20. This action changes the shape of the 
hemispherical face 18 from its natural preferred shape, as shown in FIG. 
3, into a more flattened out shape. The more flattened out shape generally 
has an effective radius of larger dimension than the radius of the face 18 
in its preferred preformed profile. As the face 18 is flattened out, the 
column of material being dispensed (not shown) is pushed downwards through 
the spout 13 as in FIG. 1. 
When the proper amount of material has been dispensed, the operator removes 
his thumb from the pad 15 thereby releasing the pressure on the plunger 
12. The piston portion 16 is formed of a resilient material having 
sufficient springiness so that when the pressure on the plunger is 
released, the piston portion tends to return to its preferred shape. This 
automatically pushes the plunger 12 upwardly away from the material being 
dispensed. The tendency of the hemispherical piston portion 16 to return 
to its preferred shape causes the shape of any void between the concave 
face 18 and the top of the column of the material being dispensed to 
change. This, in turn, causes a reduced pressure which further causes the 
material being dispensed to be drawn up into the barrel 21 of the syringe 
10 from the spout 13 thereby immediately stopping the flow of the material 
and holding it there until pressure is again applied to the plunger 12. 
The elongated member portion 14 of the plunger 12 is arranged to slide 
easily within the barrel 21 of the dispensing body 11. In contrast, the 
piston portion 16 is arranged to move within the barrel portion 21 in a 
generally sealing engagement with the internal wall 22 of the barrel 
portion. 
The plunger 12 can comprise a hollow member as in the embodiment of FIG. 3 
or a solid member as in the embodiment of FIG. 6. Referring to FIGS. 3-5, 
the plunger 12 elongated member 14 comprises a cylindrical body extending 
from the actuating pad portion 15 at one end and has a bottom portion 23 
closing off the opposing end of the elongated member 14. The piston 
portion 16 is connected to the bottom portion 23 of the elongated member 
14 by connecting portion 20. 
The connecting portion 20 includes radially extending support ribs 24. The 
support ribs 24 extend radially outwardly from a central axis 25 of the 
plunger 12 to a greater extent for the section adjacent the bottom portion 
23 and to a much lesser extent for the section adjacent the piston portion 
16. This is important since the portion of the connecting portion 20 
adjacent the piston portion 16 acts as a means for deforming the piston 
portion from its preferred generally hemispherical shape to flatten it out 
during a dispensing operation. It also allows it to return to its 
preferred shape after the dispensing operation is over. 
In order to guide plunger 12 within the barrel 21, a plurality of flanges 
26 are arranged about the barrel 21 so as to extend radially outwardly 
therefrom. The radial extent of the flanges 26 is selected so as to just 
engage the internal wall 22 of the barrel 21 to permit easy sliding of the 
plunger 12 within the dispensing body 11. The longitudinal extent of the 
flanges 26 is limited to only a small portion of the elongated member 14 
adjacent the end thereof to which the piston portion 16 is attached. The 
flanges 26 are so limited in order to permit the plunger 12 to slide 
easily within the barrel 21. 
Preferably, the plunger 12 as shown comprises a unitary body including the 
elongated member 14, the actuating pad portion 15, the piston portion 16 
and the connecting portion 20. The plunger 12 may be formed of any desired 
material, but, preferably, is molded of an inexpensive material such as 
plastic. 
Since only the piston portion 16 has a substantial frictional engagement 
with the internal wall 22 of the barrel 21, the piston portion 16 can 
easily return to its preferred shape after a dispensing operation by 
moving the plunger 12 in a direction away from the material being 
dispensed. 
Referring now to FIGS. 6 and 7, a particularly preferred plunger design is 
shown. The plunger 27 shown in FIGS. 6 and 7 also, preferably, comprises a 
unitary body, including an actuating pad portion 28, an elongated member 
29, a connecting portion 30 and a piston portion 31. The piston portion 31 
is essentially the same as described in reference to the embodiment of 
FIGS. 2-5. 
The plunger 27 differs from the plunger 12 principally in the use of a 
solid elongated member 29. The elongated member 29 comprises a central 
longitudinally extending core 32 having a plurality of longitudinally 
extending flanges 33 extending radially outwardly from the core 32. The 
radial extent of the flanges can be selected so that the elongated member 
is adapted to loosely sit within the barrel 21. The connecting portion 30 
comprises a portion of a flange 33 wherein the radial extent of the flange 
33 has been substantially reduced as compared to the remainder of the 
elongate body 29. As in the previous embodiment, it is important that the 
radial extent of the connecting portions 30 be relatively small and that 
the portion 30 be centrally located so as to act on the generally 
hemispherically-shaped piston portion 31 to flatten it out during a 
dispensing operation. The connecting portion 30 is connected to a central 
portion of the convex face 34 of the piston portion 31. 
Referring now to FIGS. 1, 3, and 6, it should be apparent that the 
dispensing body 11, and barrel 21 in combination with the spout 13 define 
a chamber for supporting the at least one column of the material to be 
dispensed. The syringes have been illustrated thus far, as including a 
single barrel 20. If desired, they could include plural barrels and a 
corresponding plurality of plunges 12 or 27. Further, if desired and in 
accordance with known prior art techniques, the plungers 12 can be joined 
together so that they are actuated in common. In such a plural barrel 
syringe arrangement, there can be separate multiple chambers for 
supporting separate and, if desired, distinct materials to be dispensed. A 
syringe can employ common spout 13 communicating with each of the chambers 
or it can comprise a separate spout for each chamber. 
On occasion, the material selected to form the plunger 12 or 27 may react 
chemically with the material being dispensed. In prior art approaches, 
this problem has been overcome by the use of a grommet which is chemically 
resistant to the material being dispensed. The grommet is supported by the 
plunger 12, if desired. In accordance with this invention, a grommet 35 as 
shown in FIG. 8 can be similarly employed. In this embodiment, the radial 
extent of the piston portion 31 has been reduced to allow the grommet to 
be flipped over the piston portion. The grommet 35 shown has a concave 
portion 36 generally conforming to the concave face 37 of the piston 
portions 31. 
It is not necessary for the grommet 35 to be springy or resilient as in the 
case of the previously described piston portions 31. However, it can be 
formed of a relatively flexible material so that it conforms to the shape 
of the concave face 37 in operation. The edge portions 30 of the grommet 
include a plurality of ridges 39 for sealingly engaging the internal wall 
22 of the barrel 21. In operation, the concave portion 36 of the grommet 
35 conforms to the shape of the piston portion 31. Therefore, the 
operation of the plunger 12 or 27 including a grommet 35 is essentially 
the same as previously described in reference to FIGS. 2-7. Accordingly, 
the grommet 35 acts to insulate the material being dispensed from the 
piston portion 31 while not interfering with the intended action of the 
hemispherically shaped piston portion. 
The syringe, in accordance with this invention, can be used to dispense 
thin as well as thick materials; namely, materials having any desired 
viscosity. It can be used to dispense any suitable material and is not 
limited in application to the materials specifically mentioned herein. 
It should be understood that the foregoing description is only illustrative 
of the invention. Various alternatives and modifications can be devised by 
those skilled in the art without departing from the invention. 
Accordingly, the present invention is intended to embrace all such 
alternatives, modifications and variances which fall within the scope of 
the appended claims.