Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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2193300
REMOVAL OF INJECTION-MOLDED TIE FROM MOLD BY TEMPORARILY
RETAINING CORE BETWEEN PAWL AND ABUTMENT SURFACE OF TIE
The present invention generally pertains to injection molding of a tie that is
useful
for forming a loop for retaining a bundle of elongated articles, such as
cables. Such a tie is
s commonly known as a cable tie. The present invention is particularly
directed to removal
from the mold of a tie having at least one tooth on an abutment surface in the
locking head
of the tie.
One type of tie includes an elongated tongue with two ends and two broad
sides, a
locking head at one end of the tongue, a tip at the other end of the tongue, a
first set of
to ratchet teeth extending along one broad side of the tongue and a second set
of ratchet
teeth extending along the other broad side of the tongue, wherein the locking
head has
sides defining an opening for receiving the tip of the tongue, the sides
including a movable
pawl that is hinged at one side of the opening and an abutment surface that is
across the
opening from the pawl, wherein the pawl has at least one pawl tooth disposed
for
15 engaging the first set of ratchet teeth when the tip of the tongue has been
inserted through
the opening with the first set of ratchet teeth facing the pawl, wherein the
pawl, when the
at least one pawl tooth is so engaged, is movable toward the abutment surface
in response
to pressure applied to the tongue in a direction opposite to the direction of
insertion in
order to force the second set of ratchet teeth against the abutment surface;
and wherein at
20 least one tooth is disposed on the abutment surface for engaging the second
set of ratchet
teeth when the tip of the tongue has been inserted through the opening with
the second set
of ratchet teeth facing the abutment surface and the side of the tongue
including the
second set of ratchet teeth is forced against the abutment surface by movement
of the
pawl. Such a tie is described in U.S. Patent No. 4,473,524 to Paradis.
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A prior art method of injection molding such a tie includes the steps of ~ "
(a) providing a mold that includes mold parts for defining a cavity between
the
mold parts in the general shape of the tie;
(b) injecting molten plastic material into the mold cavity;
s (c) solidifying the plastic material in the mold cavity to form the tie;
(d) separating the mold parts to enable removal of the tie from the mold; and
(e) removing the tie from the mold.
When such a tie is formed by injection molding, it is difficult to remove the
tie
from the mold without significantly damaging the at least one tooth on the
abutment
to surface unless the apex of the tooth is defined at a parting line between
mold parts because
the portion of the mold part that defines the abutment surface has a lateral
dimension that .
is broader than the space between such tooth and the pawl, whereby withdrawal
of such
mold part from a parting line between mold parts compresses and thereby
distorts such
tooth.
15 SUMMARY OF TIIE INVENTION
The present invention provides a method of injection molding a tie, wherein
the tie
is removed from the mold without significantly damaging the at least one tooth
on the
abutment surface.
The present invention is a method of injection molding a tie that includes an
2o elongated tongue with two ends and two broad sides, a locking head at one
end of the
tongue, a first set of ratchet teeth extending along one broad side of the
tongue and a
second set of ratchet teeth extending along the other broad side of the
tongue, wherein the
locking head has sides defining an opening for receiving the tongue, the sides
include a
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movable pawl that is hinged at one side of said opening and an abutment wall
that is
across the opening from the pawl, and the pawl has at least one pawl tooth
disposed for
engaging the set of first ratchet teeth when the tongue has been inserted
through said
opening with the first set of ratchet teeth facing the pawl, wherein the pawl,
when the at
least one pawl tooth is so engaged, is movable toward an abutment surface of
the
abutment wall in response to pressure applied to the tongue in a direction
opposite to the
direction of said insertion in order to force the second set of ratchet teeth
against the
abutment surface; and wherein the abutment surface includes at least one tooth
for
locking engagement with the second set of ratchet teeth when the tongue has
been
inserted through the opening with the second set of ratchet teeth facing the
abutment
surface and the side of the tongue including the second set of ratchet teeth
is forced
against the abutment surface by movement of the pawl; the method comprising
the steps
of
(a) providing a mold that includes first and second mold parts and a core that
is
movable within the first mold part for defining a cavity between the mold
parts in the
general shape of the tie when the core is not retracted;
(b) injecting molten plastic material into the mold cavity;
(c) solidifying the plastic material in the mold cavity to form the tie;
(d) separating the mold parts to enable removal of the tie from the mold; and
(e) removing the tie from the mold;
wherein step (a) comprises providing a said core that defines at least a
portion of
the abutment surface that includes the at least one abutment surface tooth and
at least a
portion of the pawl that includes the at least one pawl tooth; and providing a
said first
mold part that defines at least a portion of the opposite side of the abutment
wall from the
abutment surface and at least a portion of the opposite side of the pawl from
the at least
one pawl tooth; and
wherein step (d) comprises the step of
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(f) separating the core from the second mold part after the first mold part is
separated from the second mold part to thereby enable both the abutment wall
and the
pawl to flex into space vacated by movement of the first mold part during
separation of
the first mold part from the second mold part so that the tie can be removed
from the
mold pursuant to step (e) without significantly damaging either the at least
one abutment
surface tooth or the at least one pawl tooth.
Additional features of the present invention are described with reference to
the
detailed description of the preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is sectional view illustrating formation of the abutment wall and the
pawl
portions of a tie in a mold utilized in a preferred embodiment of the
injection molding
method of the present invention.
i5 FIG. 2 is sectional view illustrating relative separation of the mold parts
shown in
FIG. 1 at one stage of a preferred embodiment of the method of the present
invention.
FIG. 3 is sectional view illustrating further relative separation of the mold
parts
shown in 1FIG. 1 at a stage in the preferred embodiment of the method of the
present
invention subsequent to the stage shown in FIG. 2.
2o FIC'T. 4 is sectional view illustrating ejection of the tie from the second
mold part
subsequent to the stage in the preferred embodiment of the method shown in
FIG. 3.
DETAILED DESCRIPTION
25 Referring to FIG. 1, in a preferred embodiment of the method of the present
invention, a tie of the type described above is injection molded in a mold
including a first
mold part 10, a second mold part 12 and a core mold part 14. When the mold is
closed,
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as shown in FIG. 1, the first mold part 10, the second mold part 12 and the
core'riiold part
' 14 define a cavity therebetween in the general shape of the tie, which
includes an abutment
wall 16 having an abutment surface 20 and a pawl 18. An abutment surface 20 of
the
abutment wall 16 includes at least one tooth 22 facing the pawl 18; and the
pawl 18
s includes at least one tooth 24 facing the abutment wall 16. The first mold
part 10 defines
at least a portion of a surface 26 of the abutment wall 16 that is on the
opposite side of the
abutment wall 16 from the portion of the abutment surface 20 that includes the
at least one
abutment surface tooth 22 and at least a portion of the side 28 of the pawl 18
that is
opposite the side of the pawl 18 that includes the at least one pawl tooth 24.
The first
to mold part 10 and the core mold part 14 are movable in relation to each
other. When the
mold is closed, the first mold part 10 joins the second mold part 12 at a
parting line P.L.
and the core mold part 14 also joins the second mold part 12 at the parting
line P.L.
The core mold part 14 is disposed when the mold is closed for defining at
least a
portion of the abutment surface 20 that includes the at least one abutment
surface tooth 22
15 and at least a portion of the pawl 18 that includes the at least one pawl
tooth 24.
Molten plastic material is injected, into the mold cavity and solidified
therein to
form the tie.
Referring to FIG. 2, the core mold part 14 is separated from the second mold
part
12 not sooner than the first mold part 10 is separated from the second mold
part 12 to
2o thereby enable (a) the pawl 18 to flex into a space 30 vacated by movement
of the first
mold part 10 and (b) the abutment wall 16 to flex into a space 31 also vacated
by such
movement of the first mold part 10 during separation of the first mold part 10
from the
second mold part 12 so that the tie can be removed from the mold without
significantly
damaging either the at least one pawl tooth 24 or the at least one abutment
surface tooth
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22. The first mold part 10 is separated from the second mold part 12 in a
direction Normal
to at least a portion of the parting line P.L. Preferably, the core mold part
14 remains in
contact with the second other mold part until the first other mold part has
moved to vacate
both the space 30 into which the pawl 18 thereby is able to flex. and the
space 31 into
s which the abutment wall 16 thereby is able to flex. The core mold part 14 is
retained in
contact with the second mold part 12 by a spring 32 while the first mold part
10 is initially
separated from the second mold part 12. In alternative embodiments (not shown)
compressed air, hydraulic pressure or the mere grip of the core mold part 14
between the
at least one abutment surface tooth 22 and the at least one pawl tooth 24 is
used to retain
to the core mold part 14 in contact with the second mold part 12 while the
first mold part 10
is being separated from the second mold part 12.
Referring to FIG. 3, as the first mold part 10 is further separated from the
second
mold part 12, the core mold part 14 is separated from the second mold part 12
while the
tie is retained in the second mold part 12, whereupon the pawl flexes into the
space 30 and
15 the abutment wall flexes into the space 31 and the tie is removed from the
core mold part
12 without significantly damaging either the at least one pawl tooth 24 or the
at least one
abutment surface tooth 22.
Referring to FIG. 4, the tie is ejected from the second mold part 12 by
protraction
of a pair of ejector pins 34.
2o In an alternative embodiment (not shown), the tie is retained on the core
mold part
14 when the core mold part 14 is separated from the second mold part 12; and
the tie is
then ejected from the core mold part 14 by protraction of a pair of ejector
pins.
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When hydraulic pressure or compressed air is used to retain the core mold part
14
' in contact with the second mold part 12 during separation of the first mold
part 10 from
the second mold part 12, variation of such hydraulic pressure or compressed
air can be
used to retract the core mold part 14 before or during ejection of the tie so
that the tie
does not become caught by or entangled with the protracted core mold part 14.
The method described herein enables injection molding of a tie in which the
free
end of the pawl 18 is relatively thick between the side of the pawl 18 that
includes the at
least one pawl tooth 24 and the side 28 of the pawl 18 that is opposite the
side of the pawl
that includes the at least one pawl tooth 24, as shown in the Drawing. As a
result one is
1o able to injection mold a tie in which the free end of the pawl is of such
thickness that the
pawl is strong enough to resist bending when a high pulling force is applied
to the pawl in ,
a direction opposite to the direction of insertion while the pawl is engaged
with the first
set of ratchet teeth so that the pawl may not be bent to such an extent that
the pawl
becomes disengaged from the first set of ratchet teeth and enables the tongue
to become
unlocked from the locking head. This aspect of the method described herein is
the subject
of a separate patent application being filed on even date herewith.
The advantages specifically stated herein do not necessarily apply to every
conceivable embodiment of the present invention. Further, such stated
advantages of the
present invention are only examples and should not be construed as the only
advantages of
2o the present invention. While the above description contains many
specificities, these
should not be construed as limitations on the scope of the present invention,
but rather as
exemplifications of the preferred embodiments described herein. Other
variations are
possible and the scope of the present invention should be determined not by
the
embodiments described herein but rather by the claims and their legal
equivalents.
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