Note: Descriptions are shown in the official language in which they were submitted.
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PREFORM CARRIER
Field Of The Invention:
This invention relates to a earner for tubular articles, and more particularly
to a cazrier
for gripping and transporting tubular preforms of thermoplastic material from
which
bottles are formed by a blow molding process. The preform earner of the
present
invention is adapted to carry heated bottle preforms to a heating station and
then to a
bottle blowing station.
Background Of The Invention:
Blow-molding thermo-plastic organic resins to form hollow container such as
bottles
for beer, carbonated beverages, and the like, is a known art and is the
preferred use of
the present invention. Suitable thermo-plastic resins include resins that are
biaxially
orientable such as polyethylene, terephthalate, and polypropylene. Preferred
resins
are linear polyesters such as polyethyleneteraphthalate (PETE) or
polybutyleneteraphthalate (PBTE). The biaxial orientation property requires
delivering the resin to the blow-mold at a temperature where it can so orient,
which is
generally within the range between the resin softening point and the resin
melting
point. The resin should also be heated evenly over the portions to be blown in
order to
produce an evenly expanded final product.
In apparatus for making bottles by the reheat and blow molding technique, the
preform is injection molded to provide a tubular structure that is open at one
end and
closed at the other end, similar to a test tube. The neck portion, sometimes
referred to
as the finish, is completely formed during the injection molding process, and
the
preforms can be cooled and stored for later use. When a bottle is to be
formed, the
body of the preform is reheated in a suitable heating station, and the heated
preform is
thereafter earned to and placed in a bottle mold with the neck or finish
extending
outwardly of the mold. Pressurized air is then introduced into the preform
through the
neck to expand the prefonn body against the mold walls to form the desired
bottle.
In the reheat and blow molding process, performs are transported from one
station to
another and possibly also within the stations. Thus, disposed upstream of the
working
station at which the blow molding operation is carried out is a heating
station where
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the preform is heated to a temperature which is as high as possible while
however still
being below the vitreous transition temperature of the resin. Although the
temperatures reached are below the vitreous transition temperature of the
plastic
material used, the preform is deformable.
Transportation of preforms to the heated station, and then of the heated
preforms to
the blow mold, is often carried out by employing a pallet or other conveyor
means
that includes several preform carriers to hold the preforms at their neck or
finish area.
Some pallets are arranged to carry the preforms in an inverted condition, with
the
open end of the preform facing in a downward direction. Other machines carry
the
preforms in an upright condition, with the open end facing upwardly.
6 When handling upright preforms, it is easier to grip the preforms
internally, at the
interior of the neck, rather than exteriorly, because the threads make it
difficult to
securely grip the outer portion of the neck without thread damage, and they
also make
it difficult to obtain a tight seal between the carrying device and the
threads, to
prevent loss of blowing pressure during the blowing operation.
One form of preform Garner for transporting tubular preforms in an upright
condition
by supporting the preform at the interior surface of the neck is shown in U.S.
Pat. No.
4,678,425. The preform carrier disclosed in that patent is referred to as a
spindle
nose, and is in the form of an annular sleeve of plastic material that is
flexible to
provide a seal between it and the preform.
Another form of preform carrier is disclosed in U.S. Pat. No. 4,763,778. This
carrier
is a collet, meaning that the preform is gripped and held on the outside of
the neck
portion. Fig. 1 shows prior art illustrated in U.S. Pat. No. 4,763,778, namely
an
assembly that includes a gripping member 16 that is inserted into the neck of
a
preform 14. The diameter of the gripping member 16 can be altered using a
shaft and
garter assembly. The diameter is decreased to allow the gripping member 16 to
be
inserted into the open end of the preform 14, and then allowed to increase
thereby
gripping and holding the preform.
One significant disadvantage with the preform carriers of the prior art is
that the
preforms may not always be carried in a very vertical orientation, but rather
may
sometimes become tilted off the vertical axis. This is of concern when the
preform
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enters the heating station for two reasons. First, the preform would not be
uniformly
heated, but instead one part of it would be heated more than other parts,
resulting in a
poorly formed bottle. Second, and perhaps more importantly, the preform may be
sufficiently tilted off the vertical axis that it comes into contact with a
heating element
in the heating station. Typically, such an element is a relatively expensive
heating
lamp, requiring that production be interrupted and the expensive lamp
replaced.
to Therefore, there is a need for a preform carrier that overcomes the
shortcomings of
the prior art and ensures that the preforms are held in a vertical
orientation.
Summary of the Invention:
1 t According to one aspect of the present invention, there is provided a
preform carrier
for carrying a preform having an open end defining a neck, the preform Garner
comprising:
(a) a preform Garner base having retaining means for retaining the preform
carrier to a pallet used for transporting a plurality of preforms from one
location to another;
(b) a plurality of resilient gripping fingers extending from the preform
carrier base and adapted to be received through the open end and to
extend into the neck of the preform;
whereby the gripping fingers carry securely and releasably the preform.
Brief Description Of The Drawings:
t2 The preferred embodiments of the present invention will be described with
reference
to the accompanying drawings in which like numerals refer to the same parts in
the
several views and in which:
t3 FIG. 1 is a simplified, partially cutaway drawing of prior art apparatus
employed for releasably holding a preform.
14 Fig. 2 is a perspective view of one embodiment of the preform carrier of
the
present invention.
15 Fig. 3 is a top view of the preform carrier of Fig. 2.
3
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16 Fig. 4 is a cutaway side view of the preform Garner of Fig. 3 taken along
lines
A-A.
17 Fig. 5 is a perspective view of a further embodiment of the preform Garner
of
the present invention.
Detailed Description Of The Preferred Embodiments:
~ s The present invention will be described with reference to its preferred
embodiments.
19 Refernng now to the drawings, and particularly to Fig. 1, there is shown
schematically a pallet assembly 10 including a pair of prior art preform
carriers 12
that are carried in the pallet. The pallet assembly may hold up to from 200 to
400
preforms and is suitably supported for movement along a machine frame (not
shown)
that carnes and supports the preform carriers 12. The pallets are adapted to
be carned
along suitable frame members so that the preforms 14 traverse a path that may
include
preform loading, reheating, blowing and ejecting work stations.
2o Preforms 14 are preferably injection molded at another location and then
loaded onto
the pallet and releasably held by the preform Garner 20 as the preform 14
moves from
the loading station, through the heating and blow molding stations, until the
formed
bottle is ejected.
21 Fig. 2 shows in a perspective view a preferred embodiment of the preform
Garner 20
of the present invention. The preform carrier 20 includes a preform base 22,
which in
this embodiment, a circular plate of diameter greater than the diameter of the
neck of
the preform to be releasably carried and held. Extending from one face 24 of
the base
22 are a plurality of resilient gripping fingers 26. In the preferred
embodiment shown
in Fig. 2, there are twelve such gripping fingers 26, however, any suitable
number
may be used, preferably from 3 to 24, and most preferably from 8 to 16.
22 The gripping fingers 26 are disposed on the face 24 in a generally circular
configuration, as is best seen in Fig. 3, to form a generally cylindrical
shape. The
outer most outside edges 28 of the gripping forgers 26 when seen from the top
plan
view of Fig. 3, generally define a circle having a diameter substantially the
same as,
or slightly greater than the inside diameter of the neck of a preform 14.
4
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23 Each gripping finger 26 is spaced from an adjacent gripping finger 26 by a
space 30.
Spaces 30 between the gripping fingers 26 assist in cooling the gripping
fingers 26
and preform carrier 20, thereby keeping the preform carrier 20 of the present
invention at a temperature cooler than other preform Garners. Gripping fingers
26 are
resilient and capable of flexing so that the diameter of the circle defined by
the
outside edges 28 can be decreased to fit into the open end of a preform 14.
24 Preform Garner 20 further includes a retaining means for releasable
engagement of the
preform carrier 20 to the pallet. In the preform carrier 20, the retaining
means is a
centrally located hole 32 in base 22. Hole 32 is used to releasably secure the
preform
carrier 20 to a pallet by means of a suitable nut, bolt or other retainer.
25 As best seen in Fig. 4, gripping fingers 26 have a length defined by the
distance from
the face 24 of base 22 to the end 34. When viewed in side elevation, gripping
fingers
26 each have an outside face generally denoted by numeral 36 and an inside
face 38.
Outside face 36 is of varying contour along the length of the gripping forgers
26.
Adjacent the face 24 of base 22, each gripping finger 26 has a first segment
40 having
a thickness (defined as the distance from the inside face 38 to the outside
face 36 of
the gripping fingers 26) smaller than the thickness of the second segment 42.
In
second segment 42, the outside face 28' is the outer most edge of the gripping
fingers
26.
26 A third main segment 44 is located after second segment 42, with the
thickness of
third segment 44 being substantially the same as that of first segment 40. An
intermediate portion 46 is located between second arid third segments 42 and
44; the
thickness of intermediate portion 46 decreases gradually. A second
intermediate
portion 48, having a gradually increasing thickness, is located between third
segment
44 and fourth segment 50. Fourth segment 50 has a thickness equal to that of
second
segment 42, so that outside faces 28 and 28', when viewed in top plan view,
generally
define a circle having a diameter substantially the same as, or slightly
greater than the
inside diameter of the neck of a preform 14.
2'7 Between fourth segment 50 and end 34 is a slanted portion 52 that has a
slanted
outside face 54. Slanted face 54 assists in guiding preform Garner 20 into the
open
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end of the neck of a preform 14 when the preform 14 is loaded onto the preform
Garner 20.
28 First segment 40 of reduced thickness provides some resiliency to the
gripping fingers
26, allowing them to bend inwardly (towards the center of the preform Garner
20)
when preform Garner 20 is inserted into the neck of a preform 14. Once
inserted into
the neck, the resiliency of the gripping fingers 26 causes the latter to
spring back and
grip the interior walls of the neck of the preform 14. The gripping fingers 26
thus act
as a mandrel for the loading and unloading of the preform 14. Once a bottle
has been
blown from the preform 14 is allowed to cool if necessary, the bottle can be
''ejected"
from the preform carrier 20 by causing the bottle to slide off the preform
carrier 20.
29 The preform Garner 20 may be made of stainless steel, or other suitably
equivalent
material. Preferably, there are no plastic or rubber parts in the preform
Garner 20,
except for plastics and rubbers that can withstand the temperatures
encountered in the
heating stations (about 270°C). Stainless steel provides the preform
Garner 20 with
adequate resiliency and stability for repeated heating and cooling throughout
the
entire reheat and blow molding process. If necessary, the preform Garner 20
may be
heat treated in known ways to provide the gripping fingers 26 with the desired
resiliency. A preferred stainless steel is SS 420 grade heat treated to 52 to
54
Rockwell hardness.
30 The particular design of the preform carrier 20, and in particular the
gripping forgers
26, allows a preform 14 to be held in a very vertical orientation, without
undue tilting
or wobbling as the pallet carnes the preform 14 from station to station. This
prevents
the preform 14 from tilting to an off vertical position, thereby reducing the
risk of
inconsistent heating of the preform and/or damage to the heating lamps.
31 In a further embodiment as shown in Fig. 5, the preform carrier 20 may also
include a
cylindrically shaped plug 60 that fits within the space 62 defined by the
inside faces
38 of the gripping fingers 26. The outer diameter of the plug 60 is less than
the
diameter defined by the inside faces 38. The plug 60 prevents the gripping
fingers 26
from bending too much towards the inside of the preform Garner 20 when being
inserted into the neck of a preform 14, thereby breaking the gripping fingers
26. The
plug 60 may be held in place by suitable retaining means such as a bolt, etc.,
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32 It will be understood by those skilled in the art that the specific shape
of the gripping
fingers 26, and in particular the contour of the outside face 36 may vary. For
example, the shapes of some of the segments and intermediate portions shown
and
described herein may be changed, so long as the gripping fingers 26 retain
sufficient
resiliency to allow them to bend when being inserted into the neck of a
preform 14
and then grip the preform and releasably hold it as it is carried from station
to station..
33 Although the present invention has been shown and described with respect to
its
preferred embodiments, it will be understood by those skilled in the art that
other
changes, modifications, additions and omissions may be made without departing
from
the substance and the scope of the present invention as defined by the
attached claims.
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