Note: Descriptions are shown in the official language in which they were submitted.
CA 02221832 1997-11-21
SYRINGE FOR DISPENSING VISCOUS MATERIAL
Background of the Invention
The present invention relates to a syringe for dispensing
viscous materials, comprising an outlet member and a plunger
means for dispensing the material from the syringe whereby the
dispensing means can be at least partly inserted into the outlet
member.
Such a syringe is, for example, known from US Patent
3,900,954.
This syringe is characterized by an especially good
utilization of the dental material to be applied. The syringe
comprises a dispensing body at the forward end of the plunger of
the syringe. the dispensing body has a sonically tapering tip which
can be introduced into the outlet member so as to displace the
dental material as completely as possible.
With such a dispensing body it is possible to reduce the
amount of dental material that would otherwise remain within the
syringe. However, some material is always retained within the
outlet member so that the dental material within the syringe which
is, in general, an expensive product, cannot be completely utilized.
For example, when a light-curing dental material is used, the
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dental material over time will cure within the syringe and will plug
the outlet member.
In order to prevent such losses of dental material, it has
been suggested to shorten the dispensing body and to make it
more compact. Since such a syringe is used for applying the
filling material in the mouth of a patient, such a construction,
however, leads to the problem that not all teeth can be easily
reached with the syringe.
For example, from British Patent 298 292 it is known to use
a very short and thin outlet member into which a special end piece
of the plunger which is comprised of rubber can be introduced.
This solution, however, allows only for a comparatively minimal
dispensing velocity and the pressure applied onto the viscous
material increases with reduction of the flow cross-section of the
outlet member. Furthermore, the actuating force due to the
friction of the rubber plunger is relatively great, since the plunger
is slightly larger than the inner diameter of the housing in order to
provide the necessary sealing action. It is not surprising that such
rubber plungers have not found acceptance in practice.
Especially when the outlet member is positioned at an angle
relative to the axis of the syringe, the guiding of the dispensing
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body within the outlet member is unsatisfactory. The
forward end is relatively freely moveable and has the
tendency to cling to a wall when pressure is applied by the
plunger. Due to the asymmetric guiding of the dispensing
body there is the risk that the dental material can exit
laterally relative to the dispensing body. This can result
in a soiling of the syringe.
It is therefore an object of the present invention
to provide a syringe for viscous materials according to the
aforementioned kind and/or a method for manufacturing such a
syringe that allows for a reliable anc~t complete dispensing
of the used viscous material, especially a dental material.
Summary of the Tnvention
The present invention provides a syringe for
dispensing a viscous material, said syringe comprising: a
cylindrical housing having a first and a second end, and a
large diameter cylindrical opening at the second end; an
outlet member connected to said first end of said
cylindrical housing, said outlet member having a small
diameter cylindrical outlet opening; a de:Formable dispensing
body slidable in said cylindrical housing from said second
end to said first end for dispensing viscous material in a
dispensing direction of said syringe, said deformable
dispensing body capable of being deformed to such an extent
that it may be inserted at least partly into said small
diameter cylindrical outlet member when dispensing the
viscous material so that viscous materials may be
substantially completely dispensed from the syringe, said
dispensing body having a dimensionally stable trailing end
portion remote from said outlet member.
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Advantageously, the syringe further comprises a
plunger connected to the trailing end for moving the
deformable dispensing body within the cylindrical housing.
The deformable dispensing body is a plunger and
has an outer diameter matching the inner diameter of the
cylindrical housing. The deformable dispensing body
preferably has a leading end for deformable insertion into
the outlet member.
The outlet member preferably has a tapering cross-
section relative to the cylindrical housing.
Preferably, the syringe further comprises a guide
cone, connected between the cylindrical housing and the
outlet member, for guiding the deformable dispensing body
into the outlet
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member.
The deformable dispensing body preferably has a volume
matching the inner volume of the outlet member and of the guide
cone.
Advantageously, the syringe further comprises a plunger for
moving the deformable dispensing body within the cylindrical
housing. The plunger is preferably fastened to the trailing end of
the deformable dispensing body.
The plunger and the deformable dispensing body
expediently are in the form of a unitary plastic part, wherein the
plunger is formed by curing or cross-linking a portion of the unitary
plastic part.
The plunger is preferably glued to the trailing end.
The trailing end comprises a guide disk forming a plunger
of the syringe and providing a seal relative to the cylindrical
housing.
Expediently, the deformable dispensing body consist of a
silicone elastomer or a non-silicone elastomer having a shore
hardness of 10 to 90. The shore hardness is preferably 20 to 60.
The deformable dispensing body comprises a pointed tip in
a relaxed state thereof, wherein the tapering angle of the pointed
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tip is greater than the tapering angle of the outlet member.
Preferably, the deformable dispensing body comprises a
substantially non-deformable plunger and an elastic part
connected to the plunger, wherein the elastic part is insertable into
the outlet member for completely dispensing the viscous material
from the outlet member.
The elastic part has a radial projection forming a sealing lip
relative to the inner diameter of the cylindrical housing.
The outlet member is angularly positioned relative to the
cylindrical housing and the deformable dispensing body extends
into the outlet member when the syringe is completely emptied.
The outlet member is positioned at an angle of 45° relative
to the cylindrical housing.
The deformable dispensing body is a fluid-filled body,
preferably filled with a hydrogel.
Advantageously, the syringe further comprises a plunger for
moving the deformable dispensing body within the cylindrical
housing. The deformable dispensing body is inserted into the
cylindrical housing before inserting the plunger.
The present invention also relates to a syringe according to
the inventive embodiment in combination with a viscous material
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contained in the cylindrical housing.
The present invention further provides a method
for manufacturing a syringe for dispensing viscous material,
said syringe comprising a cylindrical housing and an outlet
member connected thereto, said syringe fi..irther comprising a
plunger slidable in said cylindrical housing and a
deformable dispensing body positioned in front of said
plunger in a dispensing direction of said syringe, wherein
said deformable dispensing body is prc>vided for displacing
the viscous material from said syringe and is at least
partly insertable into said outlet, said method comprising
the steps of: injection molding in tw~;~ steps a first layer
and a second layer so as t.o form said deforrnable dispensing
body, wherein said second layer is more elastic than said
first layer; positioning said deformable dispensing body in
said cylindrical housing such that said second elastic layer
faces said outlet member.
Advantageously, the method further comprises the
step of cross-linking the deformable dispensing body at one
end for hardening the first layer.
The inventive solution allows with surprisingly
simple means the complete dispensing of dental material from
the outlet member without encountering canting of the
plunger, even when the outlet member i.s slanted, and without
impairing the sealing function of
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the plunger. This holds also true for very narrow outlet members.
It is especially favorable that, in essence, the plunger and the
dispensing body are combined to form one component whereby
the dispensing body due to its elastic deformability can be shaped
to any shape of the tip of the outlet member and practically
automatically changes its shape upon moving the plunger in the
dispensing direction.
Even though a certain dimensional stability of the
dispensing body is desirable and aids in completely dispensing the
viscous material that sometimes has a very high flexibility, in
principal, it is also possible to provide instead of the elastic
deformability a plastic deformability as long as it is ensured that
the dispensing action, by introduction of the dispensing body into
the tip (outlet member), results in the complete removal of the
material, especially the dental material.
It is especially favorable when between the cylindrical
housing of the syringe and the outlet member a guide cone for the
deformation of the dispensing body is provided. This guide cone
initiates the deformation of the dispensing body upon moving the
plunger into the dispensing direction whereby the abrupt change
of the cross-section between the cylindrical part of the syringe and
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the outlet member is reduced by the guide cone.
It is also advantageous when the dispensing body is
deformable such that a forward (leading end) is suitable for at
least a partial introduction into the outlet member. Due to its
elasticity, a portion of the dispensing body can remain within the
cylindrical housing of the syringe in order to fill the space therein
while a continuous transition into the outlet member is ensured
because of the elasticity of the plastic material used.
It is preferred that the dispensing body extends, when the
plunger abuts the forward end of the syringe, into the forward end
of the outlet member in order to completely dispense or remove
the dental material from the outlet member, especially when a
light-curing dental material is contained in the syringe.
Such a complete removal of the dental material is
advantageous in regard to the disposal of the syringe since the
inventive syringe is then especially suitable for the application of
hazardous materials because the expensive disposal of the used
syringes as contaminated or hazardous waste can be avoided.
It is understood that the plunger, in a manner known per se,
can be activated with a push rod or a threaded spindle and that
the design in other respects can be selected as needed. The
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inventive syringe can be especially applied when a design with an
angularly positioned outlet member is required, as is needed for
the so-called Cavifils, because the inventive dispensing body is
easily laterally deformable.
It is furthermore favorable that the partially higher pressure
stress, observed during removal of remaining material from
conventional syringes and possibly detrimental to the employed
material, can be inventively avoided so that a gentle removal of
the material by the elastic plunger is possible and dead volume
can be completely avoided.
In conjunction with conventional filling devices, there is also
the advantage that an air bubble free frlling of the syringe can be
accomplished since, after return of the plunger, a deformation of
the dispensing body in the reverse direction takes place without
leading to hollow spaces within the syringe.
In order to prevent that dental material can be retained
laterally relative to the deformable dispensing body, it is preferred
to provide the dispensing body in the relaxed state with a
dispensing surface at its front end that is as large as possible.
However, it is also possible to provide the front end with a conical
shape.
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However, it is preferred that the dispensing body be
conically deformed only within the guide cone whereby it is
preferred in this context that the end of the guide cone at the
cylindrical housing is the end stop for the movement of the plunger
so that an abutment for the plunger is provided. In this context it
is favorable when the inner volume of the outlet member and the
guide cone is substantially identical to the volume of the
dispensing body. Additionally, the volume of the dispensing body
should take into consideration the spring travel of the dispensing
body when comprised of a compressible material.
The invention thus provides a syringe that can be
completely emptied of dental material so that, in principle, such
syringes can be reused without running the risk that the newly
introduced dental material could be contaminated by remains of
old dental material. This holds true especially for the
comparatively expensive, high-quality threaded syringes whereby
it is understood that, if necessary, only refurbishing with the
dispensing body and optionally the plunger can be performed
while the syringe housing and the drive are completely reusable.
Thus, the complete removal of dental material contributes to cost
reduction in dental labs, respectively, dental practices.
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Brief Description of the Drawings
The object and advantages of the present invention will
appear more clearly from the following specification in conjunction
with the accompanying drawings, in which:
Fig. 1 is a section of the inventive syringe with the
outlet member being filled, i.e., before
dispensing occurs;
Fig. 2 shows the syringe of Fig. 1 after completion
of the dispensing process;
Fig. 3 shows another embodiment of the inventive
syringe in the state before dispensing; and
Fig. 4 shows the syringe according to Fig. 3 after
dispensing.
Description of Preferred Embodiments
The present invention will now be described in detail with
the aid of several specific embodiments utilizing Figures 1 through
4.
The syringe represented in Fig. 1 comprises a cylindrical
housing 12 having connected thereto an outlet member 14 which,
relative to the cylindrical housing 12, has a smaller inner cross-
section. The transition between the cylindrical housing 12 and the
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outlet member 14 is provided in the form of a guide cone 16.
The syringe 10 also includes a plunger 18 which consists
of a dimensionally stable material. Connected to the plunger 18
is a dispensing body 20 consisting of a deformable material.
Furthermore, a filling chamber 22 for the dental material is
provided within the syringe whereby the syringe in the rest position
is not yet filled. In order to provide for an improved accessability
of tooth cavities and for improving manipulation, the outlet member
14 is positioned at an angle relative to the axes of the plunger 18
and the cylindrical housing 12.
The plunger 18 is actuatable by a non-represented push rod
which is part of a syringe securing device that is also not
represented.
The syringe securing device engages projections 24 at the
cylindrical housing 12 of the syringe 10 while the push rod acts
onto a pressure surface 27 of the plunger 18.
In the shown embodiment, the plunger 18 is a
comparatively long plunger which is favorable with regard to
dimensional stability. However, with respect to material savings,
the plunger can be embodied so as to be substantially shorter,
respectively, can have a length of only a third of its diameter. Due
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to the elasticity of the dispensing body 20, it acts as a sealing
element so that the plunger 18 provides essentially a uniform
pressure distribution at the back side of the dispensing body 20.
When needed, the plunger 18 can also be realized by coating the
dispensing body 20 with a dimentionally stable material.
In order to facilitate introduction, an insertion cone 28 is
provided at the rearward end of the syringe 10. This insertion
cone 28 allows the introduction of the dispensing body 20 and of
the plunger 18, preferably formed as a unitary part, even when the
dispensing body 20 in the relaxed state has a larger diameter than
the inner diameter of the cylindrical housing 12.
The dispensing body 20 in the relaxed state is preferably
cylindrical. If desired, in the relaxed state it can be provided so as
to have a mantle surface in the shape of a flat cone. With such
an embodiment the inner pressure within the area neighboring the
plunger 18 is increased which improves the sealing action.
Furthermore, it is possible to provide the tip of the dispensing
body 20 with a rather flat cone which should have a cone angle
greater than the cone angle of the guide cone 16.
As can be seen in Fig. 2, the dispensing body 20 is
deformable to such an extent that it allows the complete removal
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of the dental material 22 from the syringe 20 by completely filling
the entire interior space (inner volume) of the guide cone 16 and
of the outlet member 14. In the shown embodiment, the outlet
member 14 has a cylindrical inner shape whereby it is understood
that the diameter of the outlet member 14 in a modified
embodiment can also be slightly tapered.
As can be seen in Fig. 2, the plunger 18 contacts the guide
cone 16 in the position in which the dispensing body 20
completely fills the outlet socket 14. Thus, the guide cone 16
provides an abutment for the plunger 18 and a signal for the
operator that a further dispensing action is not possible and the
dental material contained in the syringe has been completely
dispensed. As can been seen in Fig. 2, no dental material
remains within the area of the guide cone 16 and of the outlet
member 14. The syringe is thus completely emptied and can be
disposed of as a disposable syringe.
Fig. 3 shows a further embodiment of an inventive syringe.
In this embodiment, the outlet member 14 extends coaxially within
the cylindrical part 12. Furthermore, the diameter difference
between the outlet member 14 and the cylindrical housing 12 is
less pronounced than in the embodiment represented in Figures
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1 and 2 of the inventive syringe 10. In the embodiment of Fig. 3,
the guide cone 16 extends at a flatter cone angle than in Fig. 1 so
that only a reduced deformation of the dispensing body 20 is
required. The syringe 10, represented in Fig. 3 in the filled state
and in Fig. 4 in the empty state, is designed for a screw actuation
the elements of which are known per se and are not represented
in detail in the drawings. The plunger 18 comprises a pressure
surface 26 and abuts directly the dispensing body 20. The
dispensing body 20 is elastically deformable and, upon
introduction into the guide cone 16, compressed automatically to
the diameter of the outlet member 14 as shown in Fig. 4.
Since a relatively large diameter of the outlet member 14 is
provided, it is possible, if desired, to return the plunger 18 and the
dispensing body 20 connected thereto, after loosening the screw
acutuation rod for the plunger, in order to refill the syringe with
new dental material. Thus, a reuse of the threaded drive is
possible. It is understood that it is preferred to exchange, if
needed, the component comprised of the plunger and the
dispensing body.
The present invention is, of course, in no way restricted to
the specific disclosure of the specification and drawings, but also
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encompasses any modifications within the scope of the appended
claims.
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