Industrial syringe

A syringe as disclosed having an elongated cylindrical tube open at both a first and second end. The first open end of the tube provides both a filling and dispensing opening for the contents of the tube. A cylindrical piston is slidably mounted within the tube and has a first axial end facing the fill and dispensing opening and a second axial end facing the opposite or second opening. The piston has an outside diameter slightly smaller than the inside diameter of the tube so that an annular clearance space is formed between the tube and the piston. A wiper extends radially outwardly from the second end of the piston and frictionally engages the cylindrical internal surface of the tube. In practice, when the syringe is filled, air is compressed through the annular opening and deflects the wiper such that the air escapes out of the syringe tube. The fill material, however, is sufficiently viscous such that, after air has been expelled from the tube, the viscous material slidably displaces the piston within the interior of the tube. A novel tamper evident cap is also disclosed for closing the second end of the tube.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
The present invention relates to syringes and, in particular, industrial 
syringes utilized to dispense adhesives, sealants and other industrial 
compounds. 
II. Description of the Prior Art 
Industrial syringes of the type utilized to dispense adhesives, sealants 
and the like are used in many different types of industrial applications. 
Such syringes, for example, are used by automated machines to dispense 
adhesives on printed circuit boards for the securing the electronic 
components to the board itself. Such automated machinery oftentimes 
dispenses the adhesive at a high repetition rate, typically in excess of 
300 adhesive dots per minute. 
The previously known industrial syringes typically comprise an elongated 
tube having a piston slidably mounted within the interior of the tube. The 
tube is open at both ends and one end of the tube forms a dispensing 
opening for the syringe. In order to fill the syringe with the industrial 
liquid, the piston is usually slid through the tube until it is adjacent 
the dispensing end of the tube. Thereafter, the industrial liquid is 
injected into the interior of the tube through its dispensing opening. In 
doing so, the piston actually slides towards the opposite end of the tube 
until it is filled. This common filling method is known as "neck filled." 
A cap is then conventionally placed across the end of the tube opposite 
from its dispensing end in order to protect the contents of the syringe 
from contamination as well as sealing the tube against leakage. 
Alternatively, the tube can be filled from its end opposite from the 
dispensing end. 
These previously known industrial syringes, however, suffer from a number 
of disadvantages. One disadvantage is that air is entrapped within the 
interior of the tube during the filling operation by the from wiper on the 
piston. Any air entrapped within the interior of the tube can cause the 
syringe to "misfire" and fail to eject an application of its contents, 
e.g. an adhesive dot, during an automated application operation. This, in 
turn, can lead to electronic components improperly attached, or not 
attached at all, to printed circuit boards as well as other problems. 
A still further disadvantage of these previously known industrial syringes 
is that a friction fit was typically used to secure the closure cap across 
the end of the syringe opposite from its dispensing end. These caps, 
however, would frequently become dislodged from the tube, especially when 
the syringe was subjected to high temperature variations. Once the cap has 
been dislodged, contaminants may enter into the contents of the syringe 
and/or permit leakage of the syringe material from the tube. 
Another disadvantage of these previously known closure caps is that they 
did not provide any means for easy removal. Using a thin, sharp object or 
fingernail to pry the closure cap off is a potential cause of injury. 
A still further disadvantage of these previously known industrial syringes 
is that the closure cap opposite from the dispensing opening can be 
removed and replaced without detection. When this occurs, undesirable 
contaminants can enter into the interior of the tube. 
SUMMARY OF THE PRESENT INVENTION 
The present invention provides an industrial syringe which overcomes all of 
the above-mentioned disadvantages of the previously known devices. 
In brief, the syringe of the present invention comprises an elongated 
cylindrical tube having a first opening at one end and a second opening at 
the opposite end. The first opening forms both an optional fill opening 
and a dispensing opening for the contents of the tube. 
A cylindrical piston is slidably inserted within the tube and has a first 
axial end which faces the first opening and a second axial end which faces 
the second opening. Axial movement of the piston within the tube towards 
the first opening of the tube accordingly dispenses the contents of the 
tube through the dispensing opening. 
The piston has an outside diameter slightly less than the inside diameter 
of the tube so that an annular clearance space is formed between the 
piston and the tube. An annular wiper extends radially outwardly from the 
piston only at the second end of the piston and this wiper frictionally 
contacts the interior walls of the tube. The elimination of the previously 
known front wiper on the piston also prevents air entrapment within the 
syringe during the filling operation. 
In practice, the syringe is usually filled from this dispensing opening. As 
the fill material or liquid, typically a sealant or an adhesive, enters 
into the interior of the tube, the liquid fills the annular space between 
the piston and the tube. In doing so, the liquid expels air outwardly from 
the interior of the tube by compressing the wiper radially inwardly and 
allowing the air to escape. 
After the air has been expelled from the interior of the tube, the 
relatively viscous liquid causes the piston to move axially from the first 
end of the tube and towards the second end of the tube. This completes the 
filling operation. 
In order to protect the contents of the tube from contaminants, as well as 
to protect against leakage of the contents of the syringe, a closure cap 
is removably disposed across the second end of the tube after the filling 
operation. This closure cap includes a radially outwardly extending rib 
which is received within a like shaped channel formed on the interior of 
the tube thus forming an interlock between the cap and the tube. This 
interlock prevents displacement of the cap from the tube which might 
otherwise be caused by differential thermal expansion of the tube and cap. 
In order to remove the cap from the tube, a ring is provided exteriorly of 
the tube around the cap so that one portion of the ring is integrally 
joined with the cap. The ring is then pulled to remove the cap from the 
tube. 
In order to provide an indication that the cap has been removed from the 
tube, at least one, and preferably four, frangible links are provided 
between the ring and the cap. These frangible links are broken whenever 
the cap is removed from the tube, thus providing a tamper evident 
indication of the cap removal. These links also help to keep the ring in 
place.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
With reference first to FIGS. 1 and 2, a preferred embodiment of the 
industrial syringe 10 is there shown and comprises an elongated 
cylindrical tube 12 having a preset internal diameter which forms a 
cylindrical internal surface 14. The tube 12 is preferably made out of any 
conventional plastic material, such as polypropylene. 
As best shown in FIG. 2, a first opening 16 is formed at a first end 18 of 
the tube while, similarly, a second opening 20 is formed at the opposite 
end 22 of the tube 12. The opening 16, however, is much smaller in 
diameter than the diameter of the interior of the tube. Furthermore, a 
curvilinear internal surface 24 joins the opening 16 to the cylindrical 
internal surface 14 of the tube 12. 
A piston 26, also preferably made of a plastic material, is axially 
slidably mounted within the interior 28 of the tube 12 so that one end 30 
of the piston 26 faces the opening 16 while the opposite end 32 faces the 
opening 20. Furthermore, the end 30 of the piston 26 is complementary to 
the tube internal surface 24 and, as such, is curvilinear in shape. 
Still referring to FIG. 2, the tube opening 16 is utilized both as an 
opening to fill the interior 28 of the tube 12 with an industrial liquid, 
as well as to dispense the liquid from the tube 12. In order to fill the 
tube 12 with the industrial liquid, a fill unit 34, illustrated only 
diagrammatically, is fluidly connected to the tube opening 16. Thus, with 
the piston adjacent the fill opening 16 as illustrated in the phantom 
line, industrial liquid from the fill unit 34 is injected into the 
interior of the tube thus moving the piston to the position shown in solid 
line in FIG. 2. As more industrial liquid is injected into the interior 28 
of the tube 12, the piston 26 is further axially displaced within the 
interior of the tube to the position shown in phantom line adjacent the 
second end 22 of the tube 12. 
With reference now especially to FIG. 3, the outside diameter of the piston 
26 is slightly less than the inside diameter of the tube 12 thus forming a 
small annular clearance space 36 between the piston 26 and tube 12 along 
the length of the piston 26. However, in order to seal the piston 26 to 
the tube 12, a thin wailed annular wiper 38 extends radially outwardly 
from the piston 26 adjacent its rear or second end 32. This wiper 38 
contacts the interior cylindrical wall 14 of the tube 12 thus sealing the 
piston 26 to the tube 12. Preferably the wiper 38 and piston 26 are of a 
one piece plastic construction. 
Still referring to FIG. 3, in practice, the construction of the piston 26 
with its wiper 38 enables air to be expelled from the interior 28 of the 
tube 12 during the filling process. More specifically, during the filling 
process, the liquid industrial material displaces the air contained 
between the piston 26 and the fill opening 16 into the annular space 36 
between the piston 26 and tube 12. In doing so, the air in the annular 
space 36 compresses and flexes the wiper 38 radially inwardly so that the 
air is expelled around the wiper 38 as indicated by arrow 40. Thus, the 
provision of the single wiper 38 at the rear of the piston 26, together 
with the elimination of sharp comers; i.e. corners found at very small 
radii of curvature in both the tube 12 and piston 26, prevents entrapment 
of air in the syringe 10 during a filling operation. 
The viscous industrial liquid, however, after filling the annular space 36 
axially displaces the piston 26 so that the piston 26 moves towards the 
second end 22 of the tube 12 after the air has been expelled from between 
the piston 26 and the fill opening 16. This axial displacement of the 
piston 26, furthermore, occurs since the viscous industrial liquid axially 
displaces the piston 26 before leakage past the wiper 38 occurs. As such, 
the construction of the piston 26 insures that the air is substantially 
entirely displaced from the interior of the tube followed by axial 
displacement of the piston 26. 
With reference again to FIGS. 1 and 2, after the tube 12 has been filled 
with the industrial liquid, a cap 42, preferably constructed of a plastic 
material such as polyethylene, is inserted into the second end 22 of the 
tube 12 to both protect the contents of the tube 12 from contaminants as 
well as prevent leakage from the tube 12 of the contents of the syringe. 
With reference now to FIG. 4, the end 22 of the tube 12 preferably has a 
radially outwardly extending annular channel 44 formed around its interior 
surface 14. The cap 42, similarly, includes a radially outwardly extending 
annular ridge 46 which is complementary in shape to the channel 44 so 
that, with the cap 42 inserted to its closed position into the end 22 of 
the tube 12, the ridge 46 and channel 44 interlock with each other. This 
interlock thus prevents dislodgement of the cap 42 from the tube 12 which 
might otherwise result from differential thermal expansion of the cap 42 
and tube 12. 
With reference now to FIGS. 5 and 6, the cap 42 preferably includes a 
cylindrical main body 50 and a pull ring 52. The main body 50 is partially 
inserted within the end 22 of the tube 12 (FIG. 4) when the cap 42 is 
moved to its closed position thus sealing the end 22 of the tube 12. 
Conversely, the pull ring 52 is positioned exteriorly of the tube 12 and 
preferably coaxially around the cap main body 50. The main body 50 and 
pull ring 52 are preferably of a one piece plastic construction and are 
joined together by a connecting portion 56. Consequently, in order to 
remove the cap from the housing 12, the pull ring 52 is simply pulled away 
from the tube 12 thus removing the main body 50 from the tube 12 via the 
connecting portion 56. 
As best shown in FIG. 5, at least one, and preferably severable, frangible 
links 58 extend between the ring 52 and main body 50 of the cap 42 at a 
position annularly spaced from the connecting portion 56. These frangible 
links 58 are broken whenever the pull ring 52 is used to remove the cap 42 
from the housing thus providing a tamper evident indication that the cap 
has been removed. 
From the foregoing, it can be seen that the present invention provides an 
industrial syringe which is greatly advantageous over the previously known 
devices. In particular, the provision of a single wiper on the rear of the 
piston together with the elimination of sharp corners in both the tube and 
piston insures that air is expelled from the interior of the syringe 
during the filling process. Additionally, the present invention provides a 
novel closure cap for the syringe, once filled, that interlocks with the 
syringe until its removal is desired and also provides a tamper evident 
indicating means that the closure cap has been removed. 
Having described my invention, however, many modifications thereto will 
become apparent to those skilled in the art to which it pertains without 
deviation from the spirit of the invention as defined by the scope of the 
appended claims.