Note: Descriptions are shown in the official language in which they were submitted.
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ORTH 310
This invention relates to an improved vaginal
diaphragm and to a method of making it. In particular,
the present invention relates to diaphragms prepared from
thermoplastic elastomers.
A vaginal diaphragm commonly comprises an
imperforate cup-shaped member made of a thin rubber-like
material having a round, somewhat stiff kut resilient rim.
A spring iq generally incorporated therein to maintain the
shape of the diaphragm. Opposite sides of the rim can be
folded together to form a compact diaphragm unit to
facilitate insertion of the diaphragm into the vagina.
The presence of the spring causes the diaphragm to assume
a "bow" shape when folded. Without the spring the
diaphragm would not be rigid enough to form the "bow"
shape and would, therefore, be difficult to insert. When
the folded diaphragm is fully inserted within the vagina,
release of the diaphragm establishes the round shape of
the diaphragm rim which then makes the sealing engagement
with the inner walls of the diaphragm around the cervix,
which fits within the diaphragm. The seal formed by the
rim prevents ingress of sperm cells into the cervical region.
Present day diaphragms generally consist of a latex
membrane and a metal spring encapsulated in latex. They
are generally prepared by compression molding. Generally
speaking, the latex membrane comprises a molded rim and
dome both of which are molded separately from the spring.
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ORTH 310
Latex has certain properties which make it less
than ideal as a material from which to make diaphragms.
It has been shown that latex because of its polyisoprenic
structure will undergo some decomposition by autooxidation.
It has also been shown that some of the stabilizers,
emulsifiers and decomposition by-products associated with
the use of latex are potential cytotoxicological agents.
Rubber or rubber-like materials and certain thermoplastic
substances such as plasticized polyvinyl chloride and
polyethylene, for example, have also been employed in the
making of diaphragms but these too have certain dis-
advantages connected with their use. There is a need,
therefore, for a material which can be made into films for
use in the fabrication of diaphragms which has the
resiliency and flexibility of the prior art materials but
does not have the disadvantages inherent in the prior art
materials.
One object of the present invention is to provide
a vaginal diaphragm comprised of a thermoplas~ic elastomer
which has sufficient resiliency and flexibility to allow
easy insertion of the diaphragm by the user without the aid
of an instrument.
A second object of the invention is to provide a
method of making a diaphragm by means of which the several
parts of a diaphragm are molded from a thermoplastic
elastomer.
, ` .~8B
ORTH 310
These and other objects of the invention will be
better understood upon reference to the following
description and the accompanying drawings in which:
Figure 1 is a perspective view of one embodiment of
S the invention;
Figure 2 is a perspective view of the diaphragm of
Figure 1 wherein the opposite peripheral portions are
squeezed together in preparation for insertion and use;
Figure 3 i8 a top-plan view of the diaphragm of
Figure 1 with a spring ring embedded within the rim;
Figure 4 is a sectional view taken at line 4 of
the diaphragm of Figure 1.
Figure 5 is a top-plan view of the spring ring
which is embedded within the rim of the diaphragm of
Figure 3.
-
Referring now specifically to the drawings, there
i9 shown in Figure 1 a diaphragm 2 having a cup portion
3 and a rim 4. Figure 4 shows a rim and film formed by
injection molding. As shown in-Figure 2, when the rim is
thus squeezed together, the cup takes on something of a
draped condition between the two ends of the bow formed
by the rim. This facilitates insertion and proper place-
ment of the diaphragm.
ORTH 310
In accordance with the present invention, there is
provided a vaginal diaphragm comprising a film and rim
made from a thermoplastic elastomer. Both the film and
the rim may be made from the ~ame or different elastomers.
The film and rim can be formed individually or they can
be made and formed in one piece employing the appropriate
molding techniques. In the former method, the rim is
formed individually by means of injection molding and
sealed to a film of the thermoplastic material. The two parts
can be ~oined together by various means such as radio
frequency technique~, heat sealing or solvent or adhesive
bonding, for example. Alternatively, the film and rim can
be formed simultaneously by injection molding. The
properties of thermopla tic elastomers are such that the
rim once formed has the required rigidity but remains
freely flexible. When the diaphragm 2 is in position, the
rim 4 lie~ flat against adjacent organ surfaces and its
flexibility permits it to accommodate itself to the
contour of the ~urfaces. However, the rim 4 is rigid enough
to hold the cup portion 3 of the diaphragm 2 in its
extended position and is completely flexible throughout.
This not only adds to the comfort, but ensures the proper
fitting of the diaphragm.
Thermoplastic elastomers are known in the art to
be biocompatible and their long-term tissue compatibility
is well known. Prior to the present invention, however,
thermoplastic elastomers have not been employed in the
preparation of diaphragms.
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~ ORTH 310
Any thermoplastic elastomer may be employe~ to form
the films used to prepare the diaphragm of the present
- invention. However, in order to achieve a certain degree
of softness for the dome and flexibility for the rim, it
is preferred to use thermoplastic elastomers having an
aver~ge Shore A hardness of about 50 to about 90. The most
preferred range is from about 75 to 90. However, softer
or harder thermoplastic elastomers can be employed; they
can be compounded with compatible polymers such as ethylene
1~ propylene ela~tomers, plasticized polyvinyl chloride, or
acrylonitrile-butadiene-styrene terpolymer, for example,
to introduce the desired modulus. Suitable thermoplastic
elastomers which may be employed in preparing the diaphragms
include styrene-butadiene block copolymer, styrene-isoprene
block copolymer, ethylene vinylacetate, ethylene propylene
copolymer and ethylene propylene terpolymer. The preferred
thermoplastic elastomers are the thermoplastic polyurethanes
having a polyester or polyether linkage. Suitable
thermopl~stic polyurethanes which can be employed include
Pellathane (an Upjohn polyether based urethane
elastoplastic polymer), Cyanoprene (an American Cyanamid
Company fully-reacted polyester or polyether type urethane
thermoplastic elastomer), Estane (a B. F. Goodrich Company
thermoplastic polyurethane made from polyester or polyether
based urethanes), Roylar (a Uniroyal Company thermoplastic
polyurethane elastomer), Rucothane (a Hooker Chemical
Company polyurethane thermoplastic elastomer), Q-Thane (a
Quinn Company polyurethane thermoplastic elastomer) and
*
Texin (a Mobay Chemical Company polyurethane thermoplastic
elastomer).
* Trademark
_~_
Z8
ORTH 310
Thermoplastic elastomers and the thermoplastic
polyurethanes in particular have been found to be superior
to the priox art materials in physical strength. Films
made from thermoplastic elastomers exhibit superior
abrasion resistance and tear resistance properties and
have greater tensile strength than the prior art materials.
In addition, the thermoplastic elastomers generally do not
show a significant amount of absorption of materials like
body enzymes or other proteins; these are properties which
make them more desirable materials for the preparation of
vaginal diaphragms.
In a preferred embodiment of the invention, the
diaphragm consists of a dome-shaped thermoplastic polymeric
film and a thermoplastic polymeric rim. The dome-shaped
film and the rim can be made from the same or from
different types of thermoplastic elastomers. In another
embodiment of the invention, a spring comprising a
flexible polymeric ring or metal coil may be embedded in
~he rim to give it added rigidity. One suitable form of
metal coil comprises a helical spring which is bent into an
annulus. The ends of the spring can be joined by any
suitable means. They may be intermeshed, welded, or
otherwise secured together so that the spring is annular.
The spring itself may be made from any material from which
~5 a spring of suitable characteristics may be formed. The
spring, however, is an optional feature of this invention
since the physical properties of the thermoplastic elastomers
are sufficient to give the rim and diaphragm the rigidity
required to assure proper fitting of the diaphragm after
insertion.
ORT~ 310
When using a diaphragm of this type, it is common
practice to place within the cup a quantity of spermacidal
cream or jelly or other spermacide and the diaphragm is
then inserted into the vagina. One end of the bow formed
when the rims are squeezed together is then easily
inserted rearwardly into the vagina, and the diaphragm is
readily moved into position. Once the diaphragm has been
moved into its proper position, the rim is released and
the diaphragm is allowed to return to its original shape.
As previou~ly indicated, the flexible rim readily
accommodates itself to the contour of the adjacent organ
surfaces.
A~ indicated above, the vaginal contraceptive
diaphragms in use today are made of rubber or rubber-like
materials and are generally manufactured by compression
molding. Flexible springs, where employed, are placed in
the mold so that during compression in combination with
heat, the molten rubber encaseY the spring and the dome and
rim become fused.
The diaphragm of the present invention can be
produced by injection molding. The method consists of
melting the thermoplastic elastomer and injecting it into
a split diaphragm mold containing one or more cavities
each consisting of a ring and a thin dome-shaped area. The
softened polymeric material is injected into the ring
portion of the cavity and then forced into the dome area.
The amount of each shot injected is proportional to cavity
size. The cycle time from injection to separation of the
ORTH 310
diaphragm from the mold can vary according to the speed of
injection, temperatures used and efficiency of cooling the
mold. In a typical process, the thermoplastic polyurethane
i~ heated prior to injection to a temperature high enough
to soften the polymer but low enough to prevent chemical
breakdown. ThiS is generally accomplished at a temperature
between about 400-450F. The mold temperature is generally
maintained at about 70-120F during the operation. For a
single cavity mold, a cycle time of about 5-10 seconds
for filling, 5-10 seconds for holding and about 30 seconds
for setup time prior to ejection of the diaphragm from the
mold may generally be employed. The temperature and time
employed in the molding step are not critical. The
particular temperature range and cycle time employed in
the molding step, however, will depend upon the particular
thermoplastic elastomer employed and the time allowed for
the elastomer to set.
Although preferred embodiments of this invention are
illustrated, it is to be understood that various modifica-
tions may be resorted to without departing from the scope
of the invention disclosed and claimed herein.
