U.S. patent number RE30,215 [Application Number 05/918,447] was granted by the patent office on 1980-02-19 for sealing and shearing member in a plastic resin blow molding machine.
This patent grant is currently assigned to Forest Mechanical Products Corp.. Invention is credited to Ernest O. Kuenzig, Frank L. Pennino.
United States Patent |
RE30,215 |
Kuenzig , et al. |
February 19, 1980 |
Sealing and shearing member in a plastic resin blow molding
machine
Abstract
In a blow molding machine a tubular parison is extruded around a
blow pin, a two-part mold is closed and the parison is expanded by
air pressure against the internal wall of the mold. Each mold half
at its top neck carries a sealing member comprising a first insert,
which is a shear insert, in the form of an approximately flat
one-half ring to sever the parison against the blow pin; a second
insert, which is a seal insert, in the form of a flat approximately
one-half ring, to seal the parison against the blow pin; and a base
member, in the form of an approximately one-half ring, having an
inverted shelf to locate and support the shear and seal
inserts.
Inventors: |
Kuenzig; Ernest O. (Glen Head,
NY), Pennino; Frank L. (Farmingdale, NY) |
Assignee: |
Forest Mechanical Products
Corp. (Kew Gardens, NY)
|
Family
ID: |
27098678 |
Appl.
No.: |
05/918,447 |
Filed: |
June 23, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
663124 |
Mar 2, 1976 |
04032278 |
Jun 28, 1977 |
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Current U.S.
Class: |
425/525; 425/527;
425/531; 425/532; 425/535 |
Current CPC
Class: |
B29C
49/48 (20130101); B29C 49/50 (20130101); B29C
49/76 (20130101) |
Current International
Class: |
B29C
49/50 (20060101); B29C 49/48 (20060101); B29C
49/76 (20060101); B29C 49/42 (20060101); B29C
017/07 () |
Field of
Search: |
;425/292,525,527,531,532,535 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Silbaugh; Jan H.
Attorney, Agent or Firm: Gerber; Eliot S.
Claims
We claim:
1. In a blow molding machine in which a plastic resin parison is
extruded in tubular form along an axis from an extruder around a
vertically aligned blow tube and in which said blow tube delivers
compressed air to expand the parison to form against the internal
walls of a two-part separable mold when the separable mold is in
its closed position, said mold being positioned beneath said
extruder along the axis of the blow tube and having open and closed
positions, the mold having a separable two-part top neck portion,
said blow tube carrying a cylindrical blow pin having a cylindrical
shoulder portion and a cylindrical shear portion, said blow pin
being movable vertically upwards to aid in severing the parison
after the mold parts are closed;
a plastic resin severing and closure device removably affixed at
said top neck portion of each of said two mold parts and separable
along with said mold parts, said device in cooperation with the
blow pin severing the parison and providing an air-tight seal
between the mold and the parison when the separable mold is in its
closed position;
said severing and closure device comprising two base members, each
base member being fixed to a top neck portion of one mold part and
being operable to hold a top seal insert and a bottom shear insert
fixedly in respect to the mold part, each base member being in
approximate form of a one-half ring and having a flat surface
generally perpendicular to said axis and having a flange portion
extending generally perpendicularly from said flat portion, said
flange portion being operable to align said top seal insert and
said shear insert with respect to said axis, said base members
being of a heat conductive metal alloy;
two top seal inserts each removably fixed to a base member and each
in the form of a generally flat member and being approximately a
one-half ring, each of said seal inserts being mounted such that an
inner edge is close to but not touching said shoulder of said blow
pin when the mold parts are closed in order to compress but not
shear said parison and thereby to seal and permit blow pressure
within said parison, said seal inserts being of heat hardened
steel;
means removably affixing each of said seal inserts on one of said
base members so that they are separable along with said mold
parts;
two bottom shear inserts separable along with said mold parts, each
bottom shear insert being in the form of a generally flat member
and being approximately a one-half ring member, each of said shear
inserts having an inner face which meets in a shearing action
against said shear portion of said blow pin to shear the parison
when the blow pin is moved vertically upwards, each of said shear
inserts having an inner edge with an inner diameter which is less
than the inner diameter of said inner edge of said seal inserts;
each of said shear inserts being of heat-hardened steel; and
means removably affixing each of said shear inserts on one of said
seal inserts and touching the flange portion of one of said base
members.
2. A closure device as in claim 1 wherein the inner edges of each
of said seal inserts and said shear inserts are flat, and wherein
each of said inner edges of each insert meets a cut-back portion
and the said cut-back portions are assembled in facing
relationship.
3. A closure device as in claim 1 wherein each of said base member
is an aluminum alloy.
4. A closure device as in claim 1 wherein upon closure of said two
mold parts the two ends of one of said shear inserts contact the
two ends of the other of said shear inserts but the two ends of one
of said base members do not contact the two ends of the other base
member.
5. A closure device as in claim 1 wherein each end of each of said
base members has three raised portions connected in the form of an
unverted "U" and forming a pocket.
6. In a blow molding machine in which a plastic resin parison is
extruded in tubular form along an axis from an extruder around a
vertically aligned blow tube and in which said blow tube delivers
compressed air to expand the parison to form against the internal
walls of a two-part separable mold when the separable mold is in
its closed position, said mold being positioned beneath said
extruder along the axis of the blow tube and having open and closed
positions, the mold having a separable two-part top neck portion,
said blow tube carrying a cylindrical blow pin having a cylindrical
shoulder portion and a cylindrical shear portion, said blow pin
being movable vertically upwards to aid in severing the parison
after the mold parts are closed;
a plastic resin severing and closure device removably affixed at
said top neck portion of each of said two mold parts and separable
along with said mold parts, said device in cooperation with the
blow pin severing the parison and providing an air-tight seal
between the mold and the parison when the separable mold is in its
closed position,
said severing and closure device comprising two base members, each
base member being fixed to a top neck portion of one mold part and
being operable to hold a top seal insert and a bottom shear insert
fixedly in respect to the mold part, each base member being in the
approximate form of a one-half ring and having a flat surface
generally perpendicular to said axis and having a flange portion
extending generally perpendicularly from said flat portion, said
flange portion being operable to align said top seal insert and
said shear insert with respect to said axis, said base members
being of an aluminum alloy; each end of said base member being in a
plane parallel to said axis and having three raised portions
connected to form an inverted U;
two top seal inserts each removably fixed to a base member and each
in the form of a generally flat member and being approximately a
one-half ring, each of said seal inserts having a flat inner edge
perpendicular to said axis and being mounted such that an inner
edge is close to but not touching said shoulder of said blow pin
when the mold parts are closed in order to compress but not shear
said parison and thereby to seal and permit blow pressure within
said parison, said seal inserts being of heat hardened steel;
means removably affixing each of said inserts on one of said base
members so that they are separable along with said mold parts;
two bottom shear inserts separable along with said mold parts, each
bottom shear insert being in the form of a generally flat member
and being approximately a one-half ring member, each of said shear
inserts having an inner face which meets in a shearing action
against said shear portion of said blow pin to shear the parison
when the blow pin is moved vertically upwards, each of said shear
inserts having an inner edge which is flat and perpendicular to
said axis and with an inner diameter which is less than the inner
diameter of said inner edge of said seal inserts; each of said
shear inserts being of heat-hardened steel; and
means removably affixing each of said shear inserts on one of said
seal inserts and touching the flange portion of one of said base
members. .Iadd. 7. In a blow molding machine in which a plastic
resin parison is extruded in tubular form along an axis from an
extruder around a vertically aligned blow tube and in which said
blow tube delivers compressed air to expand the parison to form
against the internal walls of a two-part separable mold when the
separable mold is in its closed position, said mold being
positioned beneath said extruder along the axis of the blow tube
and having open and closed positions, the mold having a separable
two-part top neck portion, said blow tube carrying a cylindrical
blow pin having a cylindrical shoulder portion and a cylindrical
shear portion spaced axially from said shoulder portion, said blow
pin being movable axially vertically upwards to aid in severing the
parison after the mold parts are closed;
a plastic resin severing and closure device removably affixed at
said top neck portion of each of said two mold parts and separable
along with said mold parts, said device in cooperation with the
blow pin severing the parison and providing an air-tight seal
between the mold and the parison when the separable mold is in its
closed position;
said severing and closure device comprising two base members, each
base member being fixed to a top neck portion of a respective mold
part and being operable to hold a top seal means and a bottom shear
means fixed with respect to the mold part, each base member being
in the approximate form of a one-half ring and having a flat
surface generally perpendicular to the axis of said blow pin and
having a flange portion extending generally perpendicularly from
said flat portion, said flange portion being operable to align said
top seal means and said shear means with respect to said blow pin
axis, said base members being of a heat conductive metal alloy;
two top seal means for compressing but not shearing and thereby
sealing and permitting blow pressure within said parison, each of
said seal means being associated with a respective base member and
each being generally flat and being approximately a one-half ring,
each of said seal means being mounted such that an inner edge
thereof is close to but not touching said shoulder portion of said
blow pin when the mold parts are closed, said seal means being of
heat hardened steel;
two bottom shear means for shearing the parison when the blow pin
is moved vertically upwards, each of said bottom shear means being
separable along with said mold parts, each bottom shear means being
generally flat and being approximately a one-half ring, each of
said shear means having an inner face which meets in a shearing
action against said shear portion of said blow pin, each of said
shear means having an inner edge with an inner diameter which is
less than the inner diameter of said inner edge of said seal means;
each of said shear means being of heat-hardened steel; and
means removably affixing said shear means and said seal means so
that they touch the flange portion of one of said base members and
so that they are separable along with said mold parts. .Iaddend.
.Iadd. 8. A closure device as in claim 7 wherein the inner edges of
each of said seal means and said shear means are flat, and wherein
each of said inner edges meets a cut-back portion and the said
cut-back portions are assembled in facing relationship.
.Iaddend..Iadd. 9. A closure device as in claim 7 wherein each of
said members is an aluminum alloy. .Iaddend..Iadd. 10. A closure
device as in claim 7 wherein upon closure of said two mold parts
the two ends of one of said shear means contact the two ends of the
other of said shear means but the two ends of one of said base
members do not contact the two ends of the other base member.
.Iaddend..Iadd. 11. A closure member as in claim 7 wherein each end
of each of said base members has three raised portions connected in
the form of an inverted "U" and forming a pocket. .Iaddend..Iadd.
12. A closure device as in claim 7 wherein said shear means and
said seal means of the same base member are associated integrally
with one another. .Iaddend.
Description
BACKGROUND OF THE INVENTION
A number of machines have been proposed for producing bottles from
plastic resin materials. One of the methods presently widely used
to produce containers, such as bottles, from a thermoplastic resin,
such as polyethylene, is called "blow molding."
In the blow molding process the plastic resin, generally in the
form of pellets, is placed in a hopper. The hopper leads to an
extrusion screw which, by means of pressure or heat and pressure,
causes the solid pellets to flow into a viscous semi-fluid mass.
The semi-fluid resin is forced by pressure to flow around a mandrel
and through an extrusion die orifice which shapes it into a
thin-walled elongated tube called a "parison."
At this stage in the blow molding process the parison, having just
been forced from the extruder, is hot; for example, it may be about
350.degree. F. The parison is then positioned over a blow tube and
within an opened two-part mold. The mold is then closed and its
sealing members seal the top and the bottom of the parison to form
an air-tight unit. Air is then blown through the blow tube and into
the inside of the parison, causing it to expand against the inner
walls of the mold. The air is under high pressure, for example, 80
pounds per square inch, and is injected into the parison in a quick
burst of pressure. The walls of the mold are cooled by circulating
cold water, or a mixture of water and anti-freeze, in a constant
stream through an outer jacket surrounding the mold face. The cold
walls of the mold cool the resin and form the parison into a
bottle. The air is then exhausted and the two mold halves are
opened.
The mold is constructed in two halves which must be brought
together quickly and in exact alignment in order to prevent escape
of air. The top of the mold is sometimes called a "neck ring." The
mold will form the body of the bottle and "flashing," usually at
the top and bottom of the bottle. Since the opposite walls of the
parison are hot and collapse together under pressure, they may
coalesce to form the sheet-like flashing. The flashing consists of
the collapsed opposite walls of the parison tube which have been
brought together and which must subsequently be trimmed off from
the bottle.
After the bottle is formed, the mold halves are opened and the
bottom flashing may be used to pull the bottle out of the mold.
This action of pulling the bottle will also remove the formed
bottle from around the blow pipe. The bottles may be removed by
fingers, i.e., metal snap members, which reach up and grab the
bottom flashing, sometimes called a "tail." The fingers pull the
bottle down onto a conveyor belt which conveys the bottles from the
blow molding machine to subsequent machines in which the flashing
is removed. The flashing material, which is generally at the neck
of the bottle and at its bottom, may be re-used to form additional
bottles.
This type of blow molding machine is generally described in U.S.
Pat. No. 3,369,272; and U.S. Pat. No. 3,470,582 describes a
somewhat similar machine. Both of these patents are assigned on
their faces to Hoover Ball and Bearing Company. In U.S. Pat. No.
3,369,272 an "annular shearing edge 70" of "portions 68 of the mold
sections 60" is used for sealing and shearing the neck of the
formed plastic resin bottle. In U.S. Pat. No. 3,470,582 the "mold
cavity neck portion 68" is used for separation of the parison.
From time to time there have been certain problems with this type
of blow molding machine if a "pre-finish" neck is utilized, i.e., a
neck formed by a shearing action in the mold. Upon closure of the
mold parts, a sealing and shearing member is moved into a
cylindrical hollow on the blow pin, leaving a gap filled by the
resin parison, to form a seal using the parison. Then the sealing
neck member attached to the blow pipe, called a "blow pin," is
moved axially upwards; and the rising blow pin shears the plastic
resin of the neck by forcing it against the shearing and sealing
member which remains level.
One problem may arise because the blow pipe is not supported at its
bottom end. The blow pin is supported only by the blow pipe, which
is a thin and lengthy tube and which must carry the compressed air
and so is necessarily hollow. The blow pipe is under considerable
thermal stress as it is surrounded by a fast-moving hot tube of
formed plastic resin and intermittently receives blasts of
compressed air. Due to all these factors, and due to human error
and inexperience in both the axial and lateral adjustment of the
blow pin, it may happen that the blow pin is not exactly centered
or it is too high or too low. Not being centered means that an
imaginary axis drawn through the center of the hollow and
cylindrical blow pin would not be aligned with, or coincide with,
the imaginary central axes of the two halves of the mold.
The non-centering or non-exact alignment of the blow pin may cause
difficulties because the mold is closed under great pressure. If
the blow pin has been misaligned, the sealing and shearing member,
sometimes called "shear steels" or "shear rings," which meet the
blow pin, may strike it with great force. This may damage the blow
pin or, more frequently, may damage or cause undue wear or stress
on those members.
These problems may be either aggravated or lessened by the presence
of the plastic resin parison. The plastic resin parison acts as a
lubricant and prevents wear which might otherwise occur between the
metal members. On the other hand, the parison may present
considerable difficulty in the event of non-exact alignment between
the shearing member and the blow pin. If there is a misalignment of
mis-matching, the plastic may become too thin, causing holes. If
there is a hole, it will permit escape of the compressed air upon
the compressed air stroke, resulting in a deformed or nonformed
bottle.
One feature of the present invention provides a plastic resin
severing and mold closure device to be utilized in a two-part mold
blow molding machine. In such a blow molding machine a plastic
resin parison is extruded in tubular form around a blow tube, and
the blow tube delivers compressed air to expand the parison to form
against the internal walls of a two-part separable mold having a
top neck portion. The blow tube carries a cylindrical blow pin
having a cylindrical shoulder portion and a cylindrical shear
portion. The severing and mold closure device is removably affixed
at the top neck portion of each of the two mold parts.
The closure device comprises a base member, preferably of an
aluminum alloy, in the approximate form of a one-half ring seen in
top view; and the base member has a flat top portion and a
descending flange portion. The flange portion forms an inverted
shelf seen in side view, and the base member is of a heat
conductive metal alloy. The closure device further comprises a top
insert, which is a seal insert in the form of a generally flat
member and is approximately a one-half ring. The seal insert has an
inner edge with an inner diameter which is close to, but not
touching, the shoulder of the blow pin in order to compress, but
not shear, the parison and thereby permit blow pressure with the
parison upon closure of the mold.
A bottom insert, which is a shear insert, is in the form of a
generally flat member and is approximately a one-half ring member.
The shear insert has an inner edge which meets in a shearing action
against the shear portion of the blow pin to shear the parison.
Both the seal insert and the shear insert are made of heat
tempered, i.e., heat hardened, steel. The inner edge of the shear
insert has an inner diameter which is less than the inner diameter
of the inner edge of the seal insert. The closure device also
provides means to removably fasten the shear insert to the seal
insert and to the base member.
OBJECTIVES OF THE INVENTION
It is consequently an objective of the present invention to provide
a sealing member which is attachable to each half of the mold at
its upper portion, specifically at its neck ring, and which may be
readily detached from those mold members by relatively
inexperienced personnel.
It is a further objective of the present invention to provide such
a sealing member which will be an excellent thermal conductor, and
specifically will conduct the cold from the mold to the plastic
resin when the resin is between the sealing member and the blow pin
of the blow pipe.
It is a further objective of the present invention to provide such
a sealing member which will have a half-ring seal insert which, if
it should become worn or damaged, may readily be replaced in exact
alignment by relatively inexperienced personnel.
It is a further objective of the present invention to provide such
a sealing member which will have a pinch-off shear insert which is
of hard heat-tempered material and which may be readily replaced by
inexperienced personnel.
Other objectives of the present invention will be apparent from the
following description providing the inventors' best mode of
practicing the invention. The description set forth below should be
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is an exploded view of one-half of the sealing member of the
present invention;
FIG. 2 is a one-half sectional side view showing the sealing member
of the present invention located in the position when the blow pin
is down and the mold is closed, but without the parison;
FIG. 3 is a sectional view similar to FIG. 2 but with the blow pin
halfway up;
FIG. 4 is a top plan view of the sealing member of the present
invention shown in its position when the mold is closed;
FIG. 5 is a bottom plan view of the sealing member of the present
invention shown in its position when the mold is closed;
FIG. 6 is an enlarged view of one end of a bottom shear steel;
FIG. 7 is an enlarged perspective view showing the parison and the
blow pin and the seal insert in the position in which the mold
would be sealed air-tight as the parison is squeezed between the
blow pin and the seal insert; and
FIG. 8 is an enlarged perspective view showing the parison as it is
being severed by being pressed between the upwardly moved blow pin
and the shear insert.
As shown in FIG. 1, the sealing member 10 of the present invention
consists of six parts, not including the bolts which connect those
parts. FIG. 1 is an exploded view which illustrates the three parts
which make up one-half of the complete sealing assembly. The
symmetrical opposite half of the sealing assembly is also
illustrated and will be explained subsequently.
As shown in FIG. 1, one-half of the sealing assembly includes a
base ring 11. The base ring 11 is constructed of a hard metal which
has excellent thermal conductive properties. The base ring 11 is
preferably of high tensile strength aluminum alloy. The base ring
11 has as integral portions thereof a top platform portion 12 and
flange portion 13. The platform portion 12 and flange portion 13
form a shelf 15 which is directed downward. The base 11 is
generally in the form of one-half of a ring. However, it is
carefully constructed so that it never fully closes with its
opposite member, i.e., it never forms a complete closed ring. Each
of the two ends of the base ring 11 has an open pocket or cavity.
Each cavity is formed by an inside beveled shoulder 15, a top
beveled shoulder 16, and an outside beveled shoulder 17.
The base ring 11 has, in its half-ring form, four holes through it
which are holes 20, 21, 22 and 23. These holes are utilized to
fasten the base ring 11 to neck ring 30. Additionally, there are
three inner holes which extend through the top portion of the base
ring 11. These holes 24, 25 and 26 are used to fasten the inserts
31 and 32 to the base ring 11.
The seal insert 31, which is the upper insert, is a generally flat
one-half ring member. It has a flat inner edge 29 and a and portion
33. It also has a screw-threaded hole 35 and clearance holes 34 and
36, which align with the holes 25, 24 and 26, respectively. Each of
the symmetrical ends of the seal insert 31 has a protruding portion
37 having two bevels and a flat outer face 38.
The shear insert 32 is similar in many respects to the construction
of the seal insert 31. However, the shear insert 32 has a slightly
smaller inner diameter at its flat inner edge than the edge 29 of
the seal insert 31. The flat inner edge 40 is between the flat top
face 41 and the inward slanting cut-back 42.
The outer two ends of the shear insert 32 each have a flat portion
43 and a raised portion 44, which is raised above the flat portion
43. As shown in the enlarged drawing of FIG. 6, the raised portion
44 has a channel 45 which has two inwardly slanting bevels,
respectively 46 and 47, which meet a three-sided outer edge
consisting of top slanted side 48, inner vertical side 49, and
bottom flat edge 50. The shear insert 32 has two screw-threaded
holes 51 and 52 which align with holes 34 and 36, respectively, and
also with holes 24 and 26 respectively. These holes 51 and 52 are
screw-threaded and enable the shear insert 32 to be exactly aligned
on the seal insert 31. It will be noted that both inserts
consequently may be readily exactly aligned by placing them one on
top of the other and placing them both on the shelf 14. The inward
hexagonal screws are then inserted and, when tightened, will
exactly align each of the inserts on the base 11.
As shown in FIG. 2, the base 11 is attached by means of screws
through the holes 20, 21, 22 and 23 to the neck ring 30 of the
half-mold. When the blow pin 61 is down, as shown in FIG. 2, the
bottom shear insert 32 has its edge 40 aligned opposite the groove
60 of the blow pin 61. The hollow and tubular blow pin 61 is
cylindrical, centered about an imaginary central axis, and attached
at the bottom of the blow tube 62. When the blow pin 62 is down, as
shown in FIG. 2, the plastic resin material of the parison is
sealed against the internal air pressure because the parison fills
the space between the inner edge 29 of the seal insert 31 and the
straight upper rim 63 of the blow pin 61. The compressed air is
then expelled through a bottom tube 64 attached at the bottom end
of the blow pin 61. That compressed air causes the parison to
expand and fit closely to the cooled walls of the mold. The parison
at its upper end will expand against the inner wall 65 of the neck
ring 30.
The blow pin 61 is then raised to the position shown in FIG. 3 in
order to shear the neck of the formed parison. When the blow pin 61
is so raised, the inner edge 40 of the bottom shear insert 32
contacts the rim 66 of the blow pin 61 below its groove 60. That
contact of the edge 40 with the blow pin 61 shears (severs) the
parison.
The blow pin 61 is then raised, i.e., pulled further upwards (not
shown) and the portion of the parison above the shear steel 32 is
bent back on itself between the seal insert 32 and the bottom ring
portion of the blow pin 61, that bottom ring portion being below
circular rim line 66. As this is generally waste material, a
separate drawing of that operation is not shown. The mold is then
opened and the bottle is removed by its tail flashing (not shown).
The cycle is then repeated and the blow pin is then again lowered
to the position shown in FIG. 2 and the parison again flows over
the blow pin. The mold is then closed, the sealing member closes
and seals the parison at the top, and the remainder of the cycle is
repeated.
As shown in FIG. 4, the two base rings do not meet when the mold is
closed. There is a small space 70 (for example, 0.025 inch) between
their ends. If they did meet, upon closure of the mold the ends may
soon become worn or damaged due to the large force with which the
mold is closed. However, as shown in FIG. 5, the two bottom shear
inserts 32, i.e., both parts of the complete ring, do touch and
meet at the lines 71, 72 when the mold is closed. The two upper
seal inserts 31 do not touch at the ends upon closure of the
mold.
* * * * *