Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
(1) Field of the Invention:
This invention relates to blow molding devices in which thermo-
plastic materials such as resins are shaped into various hollow
articles.
(2) Description of the Prior Art:
Typical patents illustrating the prîor art comprise United
States Patents 3,325,860 of June 20, 1967 to G. Hansen; 3,640,672 of
February 8, 1972 to Starr; 3,806,587 of April 23, 1974 to Turner;
3,399,279 of Aug. 12, 1975 to Hudson~ et al; 3,910,746 of Oct. 7, 1975
to Mrusek, et al and 3,969,060 of duly 13, 1976 to Rosenkranz, et al.
In Patent 3,325,860 the improvement related to providing the
mold sections with suction nozzles for applying suction to the outside
of the upper end of the parison within the mold.
In Patent 3,640,672 the improvement provides the formation of the
blow pin with openings arranged so that air blown through one of the
openings blows the container body and the aTr directed through the other
opening blows the handle of the particular article disclosed in the
patent.
In Patent 3,806,587 a principal point of novelty relates to the arrange-
ment of the apparatus for stretching a pinched portion of the parison
while the latter is in a closed mold prior to or during the inflation of
the pinched parison portion which has been chilled to partially reduce
the ternperature thereof.
In Patent 3,899,279 the novelty comprises the formation of a blow
mold with neck forming jaws with spaced apart choke rings which restrict
the movement of the thermoplastic material from the neck area of the
28 container during the formation of the same.
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Patent 3 910 746;a b1OW molding apparatus is disclosed which includes
an improved cooling system to rapidly reduce the temperature of the thermo-
plastic material by introducing a coolant directly into the blown article.
In Patent 3 969 060 blow molding apparatus is disclosed in which the
parison of thermoplastic material is preheated and then gripped so as to
reduce the cross section of the gripped portion which results in the
deformation of the gripped portion to provide a desired profile formation.
None of the prior art of the aforesaid patents disclose blow molding
devices wherein blow molds and more particulariy the neck ring or shear
insert thereof is provided with notches in the engaging portions thereof
which define the pinch~off of the thermoplastic material on the so called
pinch~off line of the article being formed so that additional quantities
of the thermoplastic material are present in indicated critical areas
which can then be smoothed by the withdrawing blow pin and mandrel to
form a smooth inner annular surface completely eliminating the pinch off
groove heretofore -formed on the inner surface of a hollow ar-ticle formed
in accordance with the prior art techniques.
Summary of the Invention
A blow molding device is disclosed which comprises a blow mold
the half portions of which are provided with shear inserts for pinching
off the upper and lower ends of the parison of thermoplastic material
positioned in the mold halves. Notches are formed in the edyes of the
shear inserts defining the pinch~off line of the parison and the article
blow molded therefrom to retain additional amounts of thermoplastic
material in the areas of the pinch-off line where it crosses critical
areas of the surface defining the inner configuration of the blow
molded article such as the neck or finish portion thereof.
8 Description of the Drawings
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Figure 1 is a plan view oF one half portion of a blow mold positioned
below an extruding head and a blow pin;
Figure 2 is an enlarged detailed elevation of a portion of the blow
mold and blow pin of Figure l with broken lines illustrating the blown
thermoplastic material being formed therein;
Figure 3 is a view similar to Figure 2 showing the blow pin and mandrel
being removed outwardly with broken lines illustrating the sheared flash
of the parison;
Figure 4 is a portion of a bottle with parts broken away and parts
in cross section showing the neck finish and the elimination of the
groove defining the pinch-off line on the inner surface thereof;and
Figure 5 is a hori~ontal section on line 5-5 of Figure 4 illustrating
the smooth inner annular surface oF the critical area of the neck finish
at the pinch-off line.
Description of the Preferred Embodiment
....
In Figures l,2 and 3 oF the drawings, a half portion lO of a blow
mold may be seen to include a neck ring ll and a first shear insert 12
at one end thereof and a second shear insert 13 at the other end thereof.
The half mo1d 10 and another half thereof, not shown, when moved together
will define a mold.cavity 14. An extruder head 15 is arranged in relation
to the mold lO so that a tubular parison may be delivered through a passage-
way 16 in the extruder head and positioned longitudinally of the mold
cavity 14~ A mandrel 18 is positioned on a blow pin 17!
Those skilled in the art will observe that the two half mold portions,
one of which is illustrated herein, will when arranged in a blow molding
rnachine define the mold cavity 14 so that a tubular parison of thermoplastic
28 resin or the like delivered through the passageway 16 in the extruder head
15 and around the mandrel 18 may be shaped by the introduction of air
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through the blow pin 17 which extends through the mandrel 18.
By referring to Figure 2 of the drawings, it will be seen that a
tubular parison of thermoplastic material is indicated by the letter P
and that the blow pin 17 and its mandrel 18 have been moved into a posi
tion within the first shear insert 12 and neck ring 11 and wherein an
annular groove 19 in the mandrel 18 is located in oppositely disposed rela~ion
to an inner annular shoulder 20 on the shear insert 12. The mandrel 18 has annular
portions 21 and 22 immediately adjacent the annular groove 19. The
annular portion 22 being of larger diameter than the annular portion
10 21. The arrangement is such that the annular portions 21 and 22 form closures
with respect to the adjacent portions of the shear inserts 12 when the
thermoplastic material P of the parison is positioned therebetween as
shown by the broken lines in Figure 2.
One or more drilled passageways 23 establish communication between
the blow pin 17 and the annular groove 19 and air blown through the blow
pin 17 is thus delivered to the area between the closures formed by the
annular portions 21 and 22 and therefore shapes the parison in this area
of the blow mold.
Still referring to Figure 2 of the drawings-, it will be seen that a
notch 24 is formed in the first shear inser-t 12 and in the area of an
annular rib 25 which forms the desired inner annular configuration of
the finish or neck portion of the bottle being blown in the blow molding
device. The notch 24 illustrated in Figure 2 of the drawings is on the
pinch-off line of the parison and by réferring again to Figure 1 of the
drawings it will be seen that a comparable notch 24 is formed on the other
side of the shear insert 12 so that it is also located on the pinch-off
line of the parison whsre it crosses the annular rib conFiguration 25.
28 The closing off of the area between the annular portions 20 and 21 of
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the mandrel and directing air thereinto by way of the passageways 23
and the annular groove 19 desirably shapes the parison in this area and
moves a small extra amount of the thermoplastic material of the parison P
into the areas of the notches 24 so that when the blow pin 17 and the
mandrel 18 move outwardly of the blow mold, upwardly in Figures 1 and
2 and 3 of the drawings, the annular portion 22 imparts a smooth annular
inner surface to the annular portion of the blown bottle shape which
correSponds with the annular rib 25, by pulling the extra material from
the notches 24 over the rib 25.
By referring to Figures 4 and 5 of the drawings, the resultant smooth
annular surface may be seen. In Figure 4 a portion of a blow molded
bottle 26 has a neck portion or finish 27 which tapers upwardly and in-
wardly and an annular groove 28 in the exterior thereof forms an inwardly
disposed annular rib 29 which is spaced inwardly from the upper open end
of the neck or finish of the bottle 26. The inner annular rib 29 is
provided to Form a smooth annular area of uniform diameter against which
a depending flange on a bottle cap, not shown, may be engaged when the
bottle cap is positioned on the finish of the bottle and held thereon
by snap-in relation with respect to the annular groove 28. The smooth
surface of the inner annular rib 29 forms a liquid tight seal when so
engaged by a depending annular flange on a bottle cap.
Bottles with neck finishes as heretofore formed in blow molds have
always had objectionable pinch-off line ribs on the exterior of the
neck finish and pinch-ofF line grooves on the interior of the neck finish.
Caps as heretofore applied to blow molded bottles were not liquid
tight due to the pinch-off line ribs and grooves and the prior art bottles
frequently had mechanical smoothing performed on the exterior and upper
28 surfaces of the neck finish to eliminate the pinch off line ribs so
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that the caps when applied would be liquid tight. Frequently even such
mechanical smoothing failed and many bottle caps have been provided
with foam inserts to insure a liquid tight seal between the cap and
the finish of the bottle. Such bottles are widely used for the packaging
of milk and other liquids and it is therefore essential that a liquid
tight closure between the cap and the bottle finish of the neck portion
be achieved.
The present invention produces a blow molded bottle with an inner
smooth annular rib against which a flange on a bottle cap will form a
liquid tight seal when engaged therewith.
In Figures 4 and 5 of the drawings, the pinch-off rib on the exterior
of the bottle is indicated by the numeral 30 and the pinch off line
groove on the interior of the bottle is indicated by the numeral 31 and
it will be observed that the inner surface of the annular rib 29 is
uniformly smooth as the pinch-off line groove has been completely
eliminated by the extra material that had been positioned in the notches
2L~ in the shear inserts 12 and which extra material was smoothed by the
movement of the annular portion 22 of the mandrel l8 thereagainst when
the blow pin 17 and the mandrel 18 were withdrawn from the bottle being
blown.
By referring now to Figure 3 o-F the drawings, it will be seen that
the blow pin 17 is illustrated moving outwardly of the mold 10 and the
shear inserts 12 with respect to the position illustrated in Figure 2 of
the drawings and heretofore described. In Figure 3 of the drawings, the
larger annular portion 22 of the mandrell8 has moved upwardly so as to
smooth and move the extra thermoplastic material in the notches 24 to
form the smooth inner annular surface of the annular rib 29 as hereinbefore
2~ described and hasshearingly engaged the parison P with respect to the inner
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annular shou1der 20 so as -to separate the same and cause it to roll upwardly
as shown ;n broken lines and indicated by the numeral 33 The shearing
of the parison P forms the uppermost inturned edge 34 of the neck or
finish portion of the bottle being blown~
It will thus be seen that blow molding devices have been disclosed
which act to form a blow molded article, such as a bottle, and more
particularly the neck or finish portion thereof with a smooth continuous
inner annular rib against which a flange on a closure cap can form a
liquid tight seal and that the formation of the smooth surface on the
inner annular rib is caused by the relative action of the desirably
shaped mandrel, introduction of air through the mandrel into areas of the
tubular parison between closures defined by the mandrel and the mold,
and the positioning of extra quantjties of the thermoplastic material on
the pinch-off lines of the parison through the expediency of the notches
formed in the shear inserts of the mold which provide the extra material
for filling and smooth;ng the pinch-off line grooves in the article
being blown.
The blow molded bottle or other article formed in the novel blow
molding device requires no further mechanical finishing or smoothing
operations and therefore considerably improves production rate and
reduces production costs while at the same time forming a perfect finish
on a bottle or similar article which will receive and retain a cap in
liquid tight relation.
Although but one embodiment of the present invention has been
illustrated and described, it will be apparent to those skilled in the
art that variouS changes and modifications may be made therein without
27 departing from the spirit of the invention.
