This application is a continuation of patent application
Ser. No. 09/092,757 filed on Jun. 5, 1998. The subject invention
relates to medical syringes and, more specifically, to the lubrication
of syringe barrels and stoppers.
BACKGROUND OF THE INVENTION
 By way of background, syringes typically include a tubular
barrel portion and a plunger having a stopper disposed at one end.
The plunger and stopper are inserted into the tubular barrel of
the syringe. The stopper portion is typically made of an elastomeric
material such as natural or synthetic rubber, which engages an inner
surface of the syringe tubular barrel to create a seal that facilitates
ejecting a fluid from the syringe when pressure is applied to the
 Traditionally, the inside of the syringe tubular barrels,
whether constructed of plastic or glass, and the outside of the
stoppers have been lubricated with a silicone oil to reduce the
friction between the two parts. By selecting the viscosity and the
amount of silicone applied to the inside of the tubular barrel and
to the stopper, the friction between them is reduced or adjusted
to a desired level.
 In conventional syringe fabrication, silicone is applied
to the syringe tubular barrels by spraying the silicone oil downwardly
into the tubular barrel. This generally results in the entire inside
surface of the tubular barrel being covered with silicone. Likewise,
the entire stopper typically is coated with silicone oil in a batch
process in which a number of stoppers are tumbled together with
silicone oil. In both of these processes, the entire inside surface
of the syringe barrel and the entire stopper is covered with silicone.
In this case, the resultant amount of silicone applied to the syringe
barrel and the stopper exceeds what is required to sufficiently
reduce the friction between the two parts to a suitable level.
 While medical grade silicone oils are not typically harmful,
it is desirable to have a medical syringe and method for making
the medical syringe that minimizes the amount of silicone used and
more effectively and strategically places silicone on the syringe
components to reduce the friction between the moving parts of the
syringe while eliminating excess lubricant. The advantages of minimizing
the amount of silicone which is injected into the body of a patient
or subject along with the drug, preventing the leakage of silicone
to the outside of the syringe thereby reducing the likelihood that
the syringe will slip in the hands of a medical practitioner, and
minimizing the interaction between the lubricant (silicone) and
the contents of the syringe. Minimizing the interaction between
the lubricant and the contents of the syringe is particularly important
where syringes are pre-loaded with a particular injectable drug,
which may be stored for some time before being administered to a
 Accordingly, it is desirable and advantageous to have a
medical syringe assembly and method for making a medical syringe
assembly in which lubricant is only disposed over a limited area
of the syringe in a sufficient amount to provide adequate reduction
of friction between the syringe barrel and the stopper.
SUMMARY OF THE INVENTION
 A medical syringe assembly for administering an injectable
drug includes a tubular barrel having an inner wall. A plunger includes
a stopper having an engagement surface in slidable engagement with
the surface of the inner wall of the tubular barrel. A lubricant
is disposed over a limited area of at least one portion of the inner
wall of the tubular barrel and the engagement surface of the stopper
whereby a sufficient amount of the lubricant is available to adequately
reduce friction between the surface of the inner wall of the tubular
barrel and the engagement surface of the stopper.
 The method of this invention is useful for applying a lubricant
on a surface of the inner wall of a tubular barrel of a medical
syringe assembly over an area extending completely circumferentially
around the tubular barrel and extending axially from a first opening
of the tubular barrel along a distance less than the entire length
of the inner wall of the tubular barrel. The method includes providing
an applicator including a container for holding the lubricant. The
container preferably has a sidewall with at least one aperture.
One end of the applicator is disposed into the first opening of
the tubular barrel and the applicator is rotated while depositing
the lubricant against the inner wall of the tubular barrel. The
applicator moves axially into the tubular barrel as the applicator
is rotating for a distance less than the axial length of the inner
wall of the tubular barrel. The applicator is removed when the desired
amount of the tubular barrel has been coated with the lubricant.
 A method for coating a stopper of a medical syringe assembly
with a lubricant over a circumferential area less than the total
circumferential area of the stopper is also disclosed which includes
providing the stopper with annular ribs, each rib including an outer
surface, and pattern coating the outer surface of each rib with
a lubricant. The conical area at the leading end of the stopper
also should not have lubricant.
 Also there is disclosed a method for coating a stopper of
a medical syringe assembly with a lubricant over a circumferential
area less that the total circumferential area of the stopper which
includes pattern coating the outer surface of the stopper having
one or more annular rings with lubricant wherein the combined axial
length of the annular rings is less than the axial length of the
outer surface of the stopper.
BRIEF DESCRIPTION OF THE DRAWINGS
 Other advantages of the present invention will be readily
appreciated as the same becomes better understood by reference to
the following detailed description when considered in connection
with the accompanying drawings wherein:
 FIG. 1 is a cross-sectional view of a syringe barrel and
coating apparatus of the subject invention; and
 FIG. 2 is a side view of a portion of a plunger including
a stopper of the subject invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to the Figures, wherein like numerals indicate
like and corresponding parts throughout the several views, a medical
syringe assembly is shown generally at 10. The syringe assembly
10 is of the type to be utilized for the administration and injection
of injectable drugs.
 The syringe assembly 10 includes a generally cylindrical
or tubular barrel 12 having a mouth opening 14 disposed at one end
and an outlet 16 disposed at the opposite end. A continuous circumferential
wall 18 defines the tubular barrel 12. A lubricant 34 is disposed
on a portion of an inner surface 20 of the wall 18. The lubricant
34 is preferably only disposed over a limited area of the inner
surface 20 of the tubular barrel 12.
 Referring specifically to FIG. 2, a plunger 22 includes
a shaft portion 24 having a stopper 26 disposed at its distal end.
The stopper 26 is preferably constructed of an elastomeric material
such as a synthetic rubber which conforms to the dimensions of the
barrel 12, defined by the wall 18, to provide a seal therebetween.
The stopper 26 includes a conical portion 28 disposed at the most
distal end of the stopper 26. The stopper 26 also includes at least
one annular rib 30 that includes an engagement surface 32 for engaging
the inner surface 20 of the wall 18 of the tubular barrel 12. The
engagement surface 32 of each rib 30 preferably is coated with the
lubricant 34 to aid in the reduction of friction between the stopper
and the inner surface 20 of the tubular barrel 12.
 The tubular barrel 12 and plunger shaft 24 can be constructed
of any suitable material. For example, the tubular barrel 12 and
the plunger shaft 24 can each be constructed of a suitable material
such as glass or plastic. Plastics are the preferred materials as
they are more easily manufactured and can be easily disposed.
 The inner surface 20 of the tubular barrel 12 extends completely
circumferentially around the inner wall 18 and extends axially from
the mouth 14 of the tubular barrel 12 to the outlet 16.
 Referring specifically to FIG. 1, a coating head assembly
50 for applying the lubricant 34 to the inner surface 20 of the
tubular barrel 12 is shown schematically. The coating head assembly
50 includes a spindle 52 which includes a proximal end 53 and a
distal end 55. The proximal end 53 can be attached to a mechanism
(not shown) for rotating the spindle 52 and moving it axially (i.e.,
up and down according to the drawing). A coating head 54 is attached
to the distal end 55 of the spindle 52. The coating head 54 includes
a lubricant reservoir 56 for supplying lubricant 34 for coating
the inner surface 20 of the tubular barrel 12. A passageway 58 is
disposed in communication with the reservoir 56 and at least one
aperture 60 disposed in the coating head 54 for permitting the lubricant
34 to exit the reservoir and be applied to the inner surface 20
of the tubular barrel 12.
 In operation, the coating head assembly 50 is placed into
the mouth 14 of the tubular barrel 12 and is then axially displaced
downwardly from the mouth 14 of the tubular barrel 12. The assembly
50 only moves a distance sufficient to coat a preselected portion
of the inner surface 20 of the wall 18. Following the coating of
the selected portion of the inner surface 20 of the tubular barrel
12, the coating head 54 is withdrawn from the tubular barrel 12.
 The amount of lubricant 34 applied to the inner surface
20 of the tubular barrel 20 can be adjusted by selecting a predetermined
pattern for the apertures 60 disposed in the rotating coating head
54, by varying the size of the apertures 60, the speed of rotation
of the coating head 54, the depth of travel of the coating head
54, and controlling the amount of lubricant which is initially deposited
into reservoir 56 and the amount which is radially dispensed against
the inner surface 20 of the tubular barrel 12.
 The application of the lubricant 34 preferably extends completely
circumferentially around the inner surface 20 but extends axially
only from near the mouth 14 of the tubular barrel 12 along a distance
less than the entire length of the wall 18 of the tubular barrel
12. That is, the lubricant 34 preferably is disposed only on the
inner surface 20 of the tubular barrel 12 at an area extending completely
circumferentially around the tubular barrel 12 but extending axially
only from near the mouth 14 of the tubular barrel 12 along a distance
which is only a portion of the length of the wall 18 of the tubular
barrel 12. In the preferred embodiment, the lubricant 34 extends
axially from near the mouth 14 of the tubular barrel 12 along a
distance that is only slightly greater than the length of the stopper
26 of the plunger 22. Since the stopper 26 will typically be maintained
near the mouth 14 in a prefilled syringe assembly, the lubricant
34 need only coat the corresponding area of the inner wall 20 to
achieve the desired lubrication.
 Also in order to minimize the amount of lubricant 34 utilized
in the syringe assembly 10, the lubricant preferably is disposed
on the outer surface 27 of the stopper 26 in an annular pattern
having an axial length smaller than the axial length of the stopper
26. That is, the lubricant 34 preferably is disposed only on discrete
annular portions of the stopper 26. Preferably, as described above,
the stopper 26 includes at least one annular rib 30 with the lubricant
34 disposed only on the outer or engagement surface 32 of each of
the annular ribs 30. Since the engagement surface 32 of each rib
30 is the only portion of the stopper 26 in contact with the inner
surface 20 of the wall 18 of the tubular barrel 12, by applying
the lubricant 34 to only the engagement surface 32 of each rib 30,
the total amount of lubricant utilized can be greatly reduced while
reducing friction between the stopper 26 and the tubular barrel
 The application of the lubricant to the selected areas of
the stopper 26 can be accomplished by adapting known methodologies
from the printing arts such as pattern coating or by transferring
a thin layer of lubricant to selected areas of the stopper 26 by
rolling and pressing. Additionally, lubricant 34 can be applied
to the selected areas of the stopper 26 by masking or covering those
portions of the stopper 26 to which no lubricant 34 is to be applied,
while applying, preferably by spraying, the lubricant 34 onto the
remaining, unmasked portions of the stopper 26.
 The lubricant 34 is preferably a medical grade silicone
oil. Other suitable medical lubricants, such as glycerin, may be
utilized without departing from the spirit of the invention.
 The invention has been described in an illustrative manner,
and it is to be understood that the terminology which has been used
is intended to be in the nature of words of description rather than
 Modifications and variations of the present invention are
possible in light of the above teachings. It is, therefore, to be
understood that within the scope of the following claims, the invention
may be practiced otherwise than as specifically described above.