U.S. patent number 3,765,416 [Application Number 05/168,851] was granted by the patent office on 1973-10-16 for locking arrangement for plastic telescoping tubes used to insert tampons and the like.
This patent grant is currently assigned to Kimberly-Clark Corporation. Invention is credited to Edward E. Werner, Edward G. Wollangk.
United States Patent |
3,765,416 |
Werner , et al. |
October 16, 1973 |
LOCKING ARRANGEMENT FOR PLASTIC TELESCOPING TUBES USED TO INSERT
TAMPONS AND THE LIKE
Abstract
A smoothly releasable temporary locking arrangement for a pair
of telescoping plastic tubes such as are employed for inserting
tampons or the like into body orifices. The locking arrangement
assures against premature bidirectional longitudinal movement
between the tubes. Backward movement of the inner tube is prevented
by a circumferential raised shoulder portion near the front end of
the inner tube which cooperates with a portion of reduced internal
diameter at the trailing end of the outer tube. Forward movement of
the interior tube is inhibited by the frictional relationship
between the tubes provided by a particularly defined degree of
interference between a circumferential portion of the inner tube
adjacent the raised shoulder portion and the reduced diameter
terminal portion of the outer tube.
Inventors: |
Werner; Edward E. (Oshkosh,
WI), Wollangk; Edward G. (Oshkosh, WI) |
Assignee: |
Kimberly-Clark Corporation
(Neenah, WI)
|
Family
ID: |
22613191 |
Appl.
No.: |
05/168,851 |
Filed: |
August 4, 1971 |
Current U.S.
Class: |
604/18;
604/14 |
Current CPC
Class: |
A61F
13/26 (20130101) |
Current International
Class: |
A61F
13/26 (20060101); A61F 13/20 (20060101); A61f
016/00 () |
Field of
Search: |
;128/260-265,270,269,235,237,341,285 ;221/154,268 ;222/385 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: McGowan; J. C.
Claims
What is claimed is:
1. An applicator consisting of a pair of telescopically associated
plastic tubes and comprising: an outer tube of right cylinder
configuration with a substantially uniform internal diameter A
throughout the major portion thereof and having a small area
adjacent the trailing end gradually tapered down to a rear opening
of predetermined smaller diameter B; and an inner tube with a
stepped exterior cylindrical configuration comprising a front right
cylinder shoulder portion C of substantial length with an exterior
diameter C' slightly smaller than the uniform internal diameter A
of said outer tube, an intermediate right cylinder barrel portion D
of substantial length adjacent said shoulder portion C with an
exterior diameter D' less than said shoulder portion C, and a back
portion E of substantial length adjacent said barrel portion D, the
outer diameter of said back portion E being gradually tapered
rearwardly to a smaller exterior diameter than said barrel portion
D and terminating at the back end of said inner tube; the exterior
diameter of said barrel portion D being slightly larger by a
predetermined amount than the internal diameter B of said rear
opening in said outer tube; said inner tube being disposed within
said outer tube with said barrel portion D in circumferential
frictional engagement with the edges of said rear opening B in said
outer tube.
2. The applicator of claim 1 wherein the axial force required to
overcome the resistance of the frictional engagement between said
barrel portion of said inner tube and said rear opening of said
outer tube is from about 200 to about 650 grams.
3. The applicator of claim 2 wherein the exterior diameter of said
barrel portion of said inner tube is from about 0.003 inch to about
0.0165 inch larger than the internal diameter of said rear opening
of said outer tube.
4. The applicator of claim 1 wherein the outer tube has an open
front end and a compressed tampon is disposed therein in frictional
engagement with the interior wall thereof.
5. The applicator of claim 1 wherein the outer tube has a tapered
front end and in which said front end is comprised of flexible
segments.
6. The applicator of claim 5 wherein a loose fitting bullet shaped
tampon is disposed within said outer tube.
Description
BACKGROUND OF THE INVENTION
Telescoping tube inserters for tampons and the like have been a
part of the patented art for many years. The most common type
comprises a pair of spirally wound paper tubes slidably engaged
with each other in telescopic association. As is well known, tube
inserts of this type require a temporary interlocking means to
prevent premature axial movement between the tubes prior to use.
The interlock for paper tubes has commonly been provided by
simultaneously puncturing the walls of both tubes in a manner to
permit a tab or flap portion of the outer tube to extend through
the wall of the inner tube (U.S. Pat. No. 2,587,717). This tab
portion serves as a temporary lock which is easily displaced and
allows the tubes to be telescoped by merely applying longitudinal
pressure on the free end of the inner tube.
While this type of interlock is satisfactory for paper tubes, it
was found impractical for use with the telescoping plastic tubes
which are beginning to appear in the market place. For such tubes,
puncture-type locks do not function well because of the inherent
flexibility and memory of the plastic which tends to return to its
original shape if deformed. Accordingly it has been necessary to
design interlocking arrangements which are molded into the tubes as
they are fabricated. One such arrangement comprises at least one
circumferential groove or raised ring in the interior wall of the
outer tube and a mating raised ring or groove in the exterior wall
of the inner tube. This arrangement provides a good temporary
interlock, but in order to disengage the cooperating ring and
groove structure, it was found necessary to apply a comparatively
large amount of initial longitudinal force to the back end inner
tube. Because of this, disengagement of the two tubes results in a
rather precipitous release, and an abrupt and sudden initial
movement. Such precipitous release is undesirable for the insertion
purposes intended. The user is unable to reliably predict how much
force is required to break the interlock so there is an absence of
positive control in the ejection operation.
In another interlocking arrangement for plastic tubes, the front
edge of the inner tube has a built up circumferential flange while
the outer tube has near its trailing end at least one interior ring
portion of a diameter less than the flange to block rearward
movement of the inner tube (U.S. Pat. No. 3,148,680). However in
this arrangement no provision is made to prevent forward movement
of the inner tube other than that provided by the presence of a
tampon or other body in the forward end of the outer tube. In
addition, with this arrangement difficulties are encountered in
keeping the tubes together during assembly operations, especially
before the tampon or other body is put into place and frictionally
held in the outer tube.
In still another arrangement for plastic tubes, the outer tube has
a number of longitudinal ribs around its internal periphery with
the bearing surfaces defining an internal opening of a diameter
substantially the same as the external diameter of an inner tube
with an enlarged flange on the leading end. The inner tube is
designed to have a snug slidable association with the internal ribs
of the outer tube (U.S. Pat. No. 3,015,332). However, in such
construction extremely close tolerances are required in order to
retain a suitably snug fit.
In yet another construction, small hinged flaps on either the inner
or outer tube are bent back to provide a spring-like frictional
impedance in a circumferential gap between the tubes (U.S. Pat. No.
3,534,737). This, of course, necessitates punching out the flaps
and holding them in bent, folded back configuration until the tubes
are assembled.
The present invention provides a positive locking arrangement which
depends primarily on friction between cooperating portions of the
tubes to provide a positive forward lock. No fabricating operations
are necessary other than the forming of the tubes to dimensions
having tolerances within a predetermined range. Easier handling of
the tube combination prior to adding the tampon to complete the
assembly is thereby achieved. In addition, the disengagement of
this interlock by the user may be done with a smooth rather than
abrupt motion as is true in some prior constructions.
SUMMARY OF THE INVENTION
As indicated above, the applicator of this invention comprises a
pair of telescoping plastic tubes. The outer tube is of right
cylinder construction with a substantially uniform internal
diameter except for a small portion of the interior adjacent the
trailing end. At the trailing end the internal diameter is
gradually decreased to provide a rear opening of a predetermined
smaller diameter. The inner tube is of a stepped design. At the
front end there is a portion with an external diameter slightly
less than the internal diameter of the major portion of the outer
tube to provide a snug sliding fit. A small portion near the front
end may also have a slight conical taper for non-binding
association with the tube contents. Adjoining and to the rear of
this large diameter front end of the inner tube there is a stepped
down intermediate barrel portion with an external diameter less
than the diameter of the front end portion but slightly larger by a
predetermined amount than the internal diameter of the rear opening
in the outer tube. The remaining back portion of inner tube tapers
slightly to a still smaller external diameter at its back end. The
small difference in diameter between the internal dimension of rear
opening in the outer tube and the external dimension of barrel
portion of the inner tube provides an interference fit which
retains the two tubes in firm frictional association. Nevertheless,
the two tubes may be easily telescoped by applying a small amount
of force to the back end of the inner tube, i.e., in the range of
from about 200 to about 650 grams. The degree of force required is
readily adjusted by varying the amount of interference between the
tube diameters at the friction point and by the selection of
plastic used.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal section of a tampon and tube applicator
assembly in accordance with the invention;
FIG. 2 is a partial longitudinal section of the outer tube of FIG.
1;
FIG. 3 is a partial longitudinal section of the inner tube of FIG.
1;
FIG. 4 is a side view of another form of applicator in accordance
with the invention;
FIG. 5 is a longitudinal section of FIG. 4;
FIG. 6 is a graph indicating axial force required to telescope the
tubes in one embodiment of the invention where both tubes are made
of low density polyethylene, and
FIG. 7 is a graph indicating axial force required to telescope the
tubes in another embodiment of the invention where the outer tube
is low density polyethylene and the inner tube is
polypropylene.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the FIG. 1 longitudinal section there is shown a tube tampon
structure comprising an outer plastic tube 10 and an inner plastic
tube 12. Disposed in the forward end of outer tube 10 is a tampon
body 14 in light frictional contact with the interior wall 16 of
outer tube 10. Attached to the rear end of the tampon body 14 is
the usual withdrawal string 17 which extends completely through the
inside of inner tube 12. Outer tube 10 also has a ring-like
projection 15 at its rear end to provide finger gripping means.
As will be seen later, the dimensions of the inner diameter B at
the rear end of outer tube 10 and the dimensions of the outer
diameter D' of a mid-portion D of inner tube 12 with respect to
each other are critical to this invention. The partial sectional
views of these tubes in FIGS. 2 and 3 have these particular
dimensions separately identified to more clearly illustrate these
relationships.
In one particular embodiment, the inner diameter A of outer tube 10
throughout a major part of its length is about 0.579 inch, and the
thickness of outer wall 18 is about 0.020 inch. The rear opening 19
of outer tube 10 has an inner diameter B of about 0.556 inch.
For inner tube 12, the outer diameter C' of shoulder section C is
about 0.565 inch, the outer diameter D' of barrel section D is
about 0.563 inch, and the trailing section E tapers to an outer
diameter of about 0.525 inch at trailing end 20.
Thus, at numeral 21, where rear opening 19 of outer tube 10 has an
inner diameter of 0.556 inch, the outer tube is in circumferential
frictional engagement with barrel portion D of inner tube 12 which
has an outer diameter of 0.563 inch and there is an interference
between the tubes of about 0.007 inch, i.e., the inner tube in this
area is 0.007 inch greater in outer diameter than the inner
diameter of the outer tube with which it is in contact. Throughout
this specification the word "interference" will mean the difference
in dimensions between the smaller interior diameter of the rear
opening 19 of the outer tube and the larger exterior diameter of
the barrel portion D of the inner tube.
Now referring to the graph of FIG. 6 it will be noted that at 0.007
inch interference, and when both tubes are made of low density
polyethylene, about 425 grams of axial force are required to
overcome the frictional resistance between the two tubes, in order
to telescope the tubes for ejection of the tampon.
Referring to the graph of FIG. 7 it will be noted that when the
outer tube is low density polyethylene and the inner tube is
polypropylene the axial force required to overcome frictional
resistance between the tubes at 0.007 inch interference is about
370 grams.
It should also be noted from these graphs that as the amount of
interference between tubes is increased the degree of frictional
resistance to movement between the tubes does not increase linearly
as might be expected, but forms a hyperbolic curve. That is, for
each increment of interference there is not a proportionate
increase in the amount of force required to break the frictional
interlock. This indicates that the increased force required to
break the interlock is asymptotic, almost approaching zero as the
higher levels of interference shown are reached.
It is well known in the molding of plastics that the degree of
shrinkage varies from time to time even though the base material is
supposedly of a standard molecular weight, so taht where close
tolerances between fitted pieces are called for, difficulties in
fittings are often encountered. The discovery that the frictional
resistance between the tubes in this instance is asymptotic as the
degree of interference increases indicates that a wider range in
tolerance for diameter dimensions can be used and still assure that
in the finished product there is sufficient interference between
tubes to provide a satisfactory frictional fit.
It will thus be seen that a range of inner and outer dimensions for
the tubes can be established within normal fabricating tolerances
for plastics to provide a suitable interference between the tubes
and to assure frictional resistance sufficient to give a good lock
without increasing the required breaking force of the interlock to
undesirable levels.
In assembling the embodiment of the applicator shown in FIG. 1 the
small trailing end of inner tube 12 can be inserted into the front
end of outer tube 10 until shoulder portion 13 abuts the inner
tapered rear portion of the outer tube. Frictional resistance
between the tubes at circumferential area of interference provided
at 21 then holds this assembly together while tampon 14 can be
inserted and string 17 drawn through the inner tube. In this
structure, the outside diameter of compressed tampon 14 is slightly
greater than the internal diameter of outer tube 10 so that a small
frictional force is generated to hold tampon 14 within outer tube
10. In a modified embodiment of the invention as shown in FIGS. 4
and 5 a compressed, bullet-shaped tampon 24 is loosely encased in a
plastic tube 26 having flexible triangular segments 28 forming a
tapered tip. In this example tampon 24 is designed with a smaller
outside diameter than the inner diameter of tube 26 so that it is
not frictionally engaged with the walls of tube 26 and therefore
requires a closed or semi-closed front end for inner tube 22 as
provided by flexible triangular segments 28. When the inner
diameters of the portions of outer tube 26 from the base of the
tapered tip rearward are dimensioned similarly to those of outer
tube 10 as shown in FIGS. 1-2 and described above, and when
dimensions G and H of inner tube 22 are similar to dimensions C and
D of inner tube 12, the tubes comprising the applicator of FIGS. 4
and 5 are flexible enough to permit the complete device to be
assembled by first pushing tampon through the reduced diameter rear
opening 29 of outer tube 26, drawing string 27 through inner tube
22 and then forcing leading end 30 of tube 22 through opening 29
until its shoulder 31 is within the edge of opening 29. After such
assembly, the amount of breaking force required will be
substantially the same as for the FIG. 1 embodiment described
above.
By referring to the graphical representations of axial force needed
to overcome the frictional lock at various amounts of interference
between tubes as shown in FIGS. 6 and 7, it will be seen that a
comparatively wide range of diameter dimensions for the two tubes
may be used as long as the interference between the rear opening of
the outer tube and the central barrel portion of the inner tube is
maintained within predetermined limits.
The preferred range of interference, as indicated in FIGS. 6 and 7,
is between about 0.005 inch to about 0.016 inch. In such range the
axial force required is from about 350 grams to about 600 grams
when low density polyethylene is used for both tubes as shown in
FIG. 6, or from about 200 grams to about 600 grams when low density
polyethylene is used for the outer tube and low density
polypropylene is used for the inner tube.
In setting up a typical engineering specification for injection
molding dies needed to fabricate the applicator, the following
range of dimensions were found useful in obtaining suitable
tubes.
For the outer tube: Wall thickness 0.020" Outer diameter 0.618" to
0.620" Inner diameter 0.578" to 0.580" Rear opening inner diameter
0.554" to 0.558" For the inner tube: Wall thickness 0.020" Outer
diameter at C 0.563" to 0.566" Outer diameter at D 0.562" to 0.564"
Outer diameter at end of E 0.525"
thus it will be seen that when tubes are fabricated within the
limits of such specifications the interference between barrel
portion D of the inner tube and the rear opening diameter 19 of the
outer tube can vary between 0.010 inch and 0.004 inch and the axial
force needed to break the lock by overcoming friction still will
not exceed about 600 grams. The axial force for such range of
interference varying from between about 250 to about 600 grams.
While the above defined engineering specifications provide a
preferred range of tolerances, it is evident that a much wider
range is possible without exceeding a desirable breaking force.
This is especially true with respect to the upper limits where as
indicated on the graphs of FIGS. 6 and 7 an interference of as much
as 0.0165 inch is within a reasonable release force. Accordingly,
while the preferred range of interference is between about 0.005
inch and about 0.016 inch the device will still function
satisfactorily with a range of interference between about 0.003
inch and 0.0165 inch. With such range, the amount of force required
to overcome the frictional resistance between the two tubes at the
point of contact is from about 200 to about 650 grams.
While reference has been made only to low density polyethylene and
polypropylene in the specific examples, it is understood that the
invention defined herein is applicable to other plastic materials
such as nylon, polyesters polystyrene and the like as long as they
have sufficient flexibility and resilience to perform as
indicated.
In addition to use with tampons, the applicator is also useful as
well for inserting suppositories and medicaments into body
cavities.
* * * * *