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Патент USA US3055065

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Sept. 25, 1962
_
P. A. cooK ETAL
3,055,055
RUNNER HEATER FOR INJECTION MOLDING MACHINES
Filed Oct. 15, 1959
2 Sheets-Sheet 1
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PERCY ALBERT COOK
ARTHUR JACK JAMES
BERT TAYLOR
am?yé ,élé/uz
ATTORNEY
SePt- 25, 1962
P. A. cooK ETAL
3,055,055
RUNNER HEATER FOR INJECTION MOLDING MACHINES
Filed Oct. 15, 1959
2 Sheets-Sheet 2
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INVENTORS
PERCY ALBERT COOK
ARTHUR JACK JAMES
BERT TAYLOR
United States Patent O?ice
1
3,055,055
RUNNER HEATER FOR INJECTION
MOLDING MACHINES
Percy Albert (look, Toronto, Ontario, and Arthur Jack
James and Bert Taylor, Downsview, Ontario, Canada,
assignors, by mesne assignments, to Cardinal Enter
prises Limited, Toronto, Ontario, Canada
Filed Oct. 15, 1959, Ser. No. 846,589
6 Claims. (Cl. 18-30)
Conventional cold-runner molding techniques require
the use of at least a three~part mold when molding hollow
articles :such as cups from thermo-plastic materials, the
three parts being comprised by a front plate carrying the
male members of the mold, an intermediate plate formed
with the female cavities de?ning the outer surface of the
article to be molded, and a runner plate having runner
cavities connected to a common supply aperture and to
which plasticized molding material is supplied under a
considerable pressure so that the material will ?ow along
the runner cavities and into the respective cavities of the
intermediate plate when the mold is in an assembled con
dition.
The disadvantage of molds of this form is that in addi
3,055,055
Patented Sept. 25, 1962
2
ing elments and to selectively control determined ones of
those elements. This, however, renders the structural
design of the runner plates even more complex, for, due
to the varied mechanical cross-sections due to the accom
modation of the heating elements it is found very dii?cult
to control distortion of the runner plate.
The object of the present invention is to provide ex
tremely simple and inexpensive heating means for the
runner cavities of such a runner plate, and by means of
10 which the above outlined disadvantages are mitigated or
eliminated.
According to the invention a heater for a runner cavity
of a runner plate of an injection molding machine com
prises a tubular heat-producing electrical element which
is positioned directly within the runner cavity and which
is of suf?cient length for the element to extend substan
tially throughout the length of the runner cavity, the
element being of a major transverse cross-section which
is less than the complementary transverse cross-section
of the runner cavity for the outer surface of the element
to be spaced from the cavity de?ning walls to provide
for the passage of plasticized molding material along the
surface of said element.
The invention also contemplates a heated runner plate
tion to molding articles within the cavities de?ned by
assembly for an injection molding machine, which run
the female cavities and male mold members a runner and
sprue is also molded within the runner cavities. It is
therefore necessary to open each of the three parts of
plurality of runner cavities through which plasticized
the mold after each molding “shot” to enable the molded
articles to be removed and also to enable the solidi?ed
runner and sprue to be removed.
This disadvantage seriously militates against automa
tion, and to overcome the problem it has been proposed
to heat the runner plate so that the plasticized molding
material contained within the runner cavities is always
maintained at its plastic temperature, thus obviating the
necessity of separating the runner plate from the inter
mediate plate after each molding operation. Also, as
the articles molded are not attached to a solidi?ed run
ner or sprue they can be easily removed from the mold
by automatic devices without separating the intermediate
ner plate assembly includes a runner plate having a
molding material is to be forced under pressure from a
common supply aperture of the runner cavities to dis
charge apertures thereof, and a tubular heat-producing
electrical element within each runner cavity and of suf
?cient length for the element to extend substantially
throughout the length of the associated runner cavity,
the element being of a major transverse cross-section less
than the complementary transverse cross-section of the
associated runner cavity for the outer surface of the
element to be spaced from the cavity de?ning walls to
provide for the passage of plasticized molding material
along the surface of said element between said supply
and discharge apertures.
In the case where the runner plate is provided by a
backing plate and a facing plate arranged in intimate
and runner plate.
face to face contact, the runner cavity is preferably pro
In molds at present in use and embodying heated run
ner plates it is necessary to heat the whole of the runner 45 vided by a groove in one or both of the juxtaposed sur
faces of the facing and backing plates and by a bore in
plate to an even temperature, and this gives rise to prob
the facing plate, the heater of the invention being posi
lems. The runner plate adequately must be insulated
tioned within the said groove.
from its supporting structure and from the inter-mediate
plate comprising the female mold to avoid excessive
heat loss from the runner plate; difficulties are encoun
tered in sealing the runners to avoid seepage of the plasti
cized molding material and consequential wastage; elab—
Further objects and advantages of the present invention
will become apparent from a study of the following
speci?cation when taken in conjunction with the ac
companying drawings in which:
FIGURE 1 is an exploded fragmentary perspective
view showing a very simple form of mold incorporating
spots can result in burning of the plasticized material; the 55 a heater and runner plate assembly according to the in
vention.
heat gradient across the runner plate very closely must
FIGURE 2 is a fragmentary perspective View showing
be kept at a constant to avoid the possibility of certain
the construction of the heater of the invention to a larger
ones of the runners reaching a temperature higher than
orate precautions have to be taken to ensure that no
localized hot spots occur in the runner plate, which hot
that of others of the runners, with a consequential un
scale; and,
evenness of ?ow rate of the plasticized molding material
FIGURE 3 is a diagrammatic cross-section through a
into the mold cavities; the heat loss from the runner
runner plate assembly formed by a facing and backing
plate depends to a great extent on atmospheric tempera
plate and incorporating the heater of the invention.
ture and humidity, and therefore the heat applied to the
Referring ?rst to FIGURE 1, the mold is shown as
runner plate must be very carefully controlled in de
being a three-part mold comprised by a front plate 10
pendence on ambient conditions; and, very careful struc 65 carrying a plurality of male members 11 of the mold,
tural design is required to ensure that the runner plate
which male members are to be inserted within female cavi
does not become thermally or mechanically distorted.
ties 12 of an intermediate plate 13 to provide the necessary
A major problem in the construction of such hot run
ner molds has been the maintenance of a constant tem
article de?ning cavities. The ingress of plasticized mold
perature gradient across the runner plate, and, in order 70 ing material to the interior of the female cavities 12 is per
mitted by apertures 14 which communicate with runner
to provide the necessary constant heat gradient it has been
cavities 15 of a runner plate 16, the plasticized molding
found necessary to provide intricate lattice works of heat
3
3,055,055
material being supplied to the runner cavities 15 through
a central common supply aperture 17.
Positioned :within the runner cavities 15 and within a
central aperture 17*L providing an extension of the supply
aperture 17 is the heater of the invention indicated gen
erally at 20.
The heater 20 includes a connection box 21 which lies
within the aperture 17a and which has a pair of electrical
connections 22, which, when the heater is positioned with
4
power requirements of the assembly are very greatly re
duced.
What we claim as our invention is:
1. The combination of a runner plate assembly and a
heating element for an injection molding machine, includ
ing a runner plate having a plurality of runner cavities
through which plasticized molding material is to be forced
under pressure from a common supply aperture of the
runner cavities to discharge apertures thereof, and a
in the runner cavities, extend through grooves 23 ma 1O tubular heat-producing electrical element within each run
chined in the face of the runner plate 16.
ner cavity and of su?icient length for the element to
Radiating from the junction box 21 is a plurality of
extend substantially throughout the length of the asso
arms 24, each comprising a heating element constructed
ciated runner cavity, the element being of a major trans
as shown more clearly in FIGURE 2. The heating ele
verse cross-section less than the complementary trans
ments are each provided by a tubular metal sheathing 25 15 verse cross~section of the associated runner cavity for the
which houses an electrical resistance Wire 26, the neces
outer surface of the element to be spaced from the cavity
sary electrical isolation between the resistance wire and
de?ning walls to provide for the passage of plasticized
the metal sheathing being provided by a ?ller 27 of cer
molding material ‘along the outer surface of said element.
amic, asbestos wool, or other suitable material. The
2. The combination of a runner plate assembly ‘and a
electrical resistance wire may be connected to the metal
heating element ‘for ‘an injection molding machine, in
sheathing at its end remote from the junction box for the
cluding a runner plate having a plurality of runner cavi
metal sheathing to provide the necessary return circuit.
ties through which plasticized molding material is to be
At the ends of each of the heating elements 24 remote
forced under pressure from a common supply aperture of
from junction box 21 the sheathing 25 is turned substan
the runner cavities to discharge apertures thereof, and a
tially through a right angle for it to be axially aligned 25 tubular heat-producing electrical element Within each
with the associated discharge aperture 14, and is formed
runner cavity ‘and of sufficient length for the element to
with a hemispherical end surface 28. Each of the end
extend substantially throughout the length of the associ
surfaces 28 is provided with a pair of grooves 28a which
ated runner cavity, the element being of a major trans
intersect at the longitudinal axis of the sheathing and along
verse cross-seotion less than the complementary trans
which the plasticized molding material can ?ow into the
verse cross-section of the associated runner cavity for the
associated aperture 14.
outer surface of the element to be spaced from the cavity
FIGURE 3 shows more completely a hot runner plate
de?ning walls to provide for the passage of plasticized
constructed according to the invention and incorporating
the heating element of the invention. That construction
molding material along the outer surface of said element,
one end of each heater terminating at the discharge aper
includes a runner plate 30‘ in the form of a manifold 35 ture of the associated runner cavity in a hemispherical
comprised by backing plate 31 and a facing plate 32, the
runner cavities 15 being provided by grooves 15a ma
chined directly into the backing plate 31 and closed by the
juxtaposed face of the facing plate 32, and by bores 15b
machined in the facing plate 32. The backing and fac
ing plates are held together by bolts 33, and conveniently
the supply aperture 17 is provided with a wear resistant
insert 17‘D for coaction with a supply nipple of a conven~
tional plasticizing unit.
end surface overlying said discharge aperture, the hemi
spherical end surface including at least one groove which
pass through the longitudinal axis of the heater and which
extends over a minor portion of the length of ‘the heater.
3. The combination of a runner plate assembly and a
heating element for an injection molding machine, includ
ing a runner plate having a plurality of runner cavities
through which plasticized molding material is to be forced
under pressure from a common supply aperture of the
The female mold members in FIGURE 3 are comprised 45 runner cavities to discharge apertures thereof, and a
by a plurality of cup-shaped members 34 which are
tubular heat~producing electrical element Within each
clamped directly onto the facing plate 32 by a clamping
runner cavity and of su?icient length for the element to
plate 35, the female mold member receiving male mold
extend substantially throughout the length of the associ
members 36 carried by a plate 37. The annular members
ated runner cavity, the element ‘being of a major trans—
38 surrounding the male mold members are for the pur 50 verse cross-section less than the complementary trans
pose of stripping molded ‘articles from the male mold
verse cross~section of the runner cavity for the outer sur
members and are carried by a plate 39.
face of the element to be spaced from the cavity de?ning
The heater is indicated at 20, the arms each extending
walls to provide for the passage of plasticized molding
from the supply aperture 17 along the grooves 15a and
material along the outer surface of said element, one end
through the bores 15b for their spherical ends to lie close 55 of each heater terminating 'at the discharge aperture of
ly adjacent the nozzles 40, which nozzles are for charging
the associated runner cavity in a hemispherical end sur~
plasticized molding material into the mold cavities.
face overlying said discharge aperture, the hemispherical
As will be apparent, the heat loss from the runner plate
end surface including at least one groove which passes
assembly of the invention is far less than that with con
through the longitudinal ‘axis of the heater and which ex
ventional heated runner plate structures, for the heat is 60 tends over a minor portion of the length of the heater, and
supplied directly to the plasticized molding material which
?ows along the surface of the heating elements 24, which
posite end thereof and positioned within the supply aper
material acts to a degree as a thermo-insulation material.
The runner plate may thus be at a temperature which is
ture of the runner cavity.
4. The combination of a runner plate assembly and a
a connection 'box secured to the element adjacent an op
far lower than the plasticizing temperature of the plas 65 heating element for an injection molding machine, in
ticized molding material, and it is therefore unnecessary
cluding a runner plate comprised by a backing plate and a
to provide any sealing devices for the electrical connec
facing plate arranged in intimate face contact, the run
tions 22, or for the juxtaposed ‘faces of the intermediate
ner plate having a plurality of runner cavities provided
member 13 and runner plate 16, or for the juxtaposed
by grooves between the juxtaposed faces of the backing
faces of the backing and facing plates 31, 32, for any 70 and facing plates, and having a common supply aperture
seepage of the plasticized molding material will “freeze”
in the backing plate through which plasticized molding
to form a very effective seal between those members.
material under pressure may be forced through the
Other problems such as distortion of the backing plate
runner cavities and out through discharge apertures
and insulation of the backing plate from its supporting
of the facing plate, and a tubular heat-producing
structure are ‘also greatly mitigated, and the electrical 75 electrical element Within each runner cavity and
3,055,055
5
of suf?cient length for the element to extend sub
stantially throughout the length of the associated runner
cavity, the element being of a major transverse cross-sec
tion less than the complementary transverse cross-section
of the associated runner cavity for the outer surface of the
6
plate having a plurality of runner cavities provided by
grooves between the juxtaposed faces of the backing and
facing plates and bores in the facing plate connecting
with said grooves, the runner cavities having a common
supply aperture in the back plate through which plas
ticized molding material under pressure may be forced
through the runner cavities and out through a discharge
apenture of the facing plate, and :a tubular heat-produc~
ing electrical element within each runner cavity and of suf
supply and discharge apertures.
5. The combination of a runner plate assembly and a 10 ?cient length for the element to extend substantially
throughout the length of the associated runner cavity,
heating element for an injection molding machine, includ
the element being of ‘a major transverse cross-section less
ing a runner plate comprised by a backing and a facing
than the complementary transverse cross-section of the
plate arranged in intimate face contact, the runner plate
associated runner cavity for the outer surface of the ele
having a plurality of runner cavities provided by grooves
between the juxtaposed faces of the backing and facing 15 ment to be spaced from the cavity de?ning walls to pro
vide vfor the passage of plasticized molding material
plates and bores in the facing plate connecting with said
along the outer surface of said element between said
grooves, the runner cavities having a common supply
supply and discharge apertures, one end of each heater
aperture in the backing plate through which plasticized
terminating at the ‘discharge aperture of the associated
molding material under pressure may be forced through
the runner cavities and out through discharge apertures 20 runner cavity in a hemispherical end surface overlying
said discharge aperture, the hemispherical end surface
of the facing plate, and a tubular heat-producing electri
including at least one groove which passes through the
cal element within each runner cavity and of suf?cient
longitudinal axis of the heater and which extends over a
length for the element to extend substantially throughout
minor portion of the length of the heater, and a connec
the length of the associated runner cavity, ‘the element
being of a major transverse cross-section less than the 25 tion box secured to the element adjacent an opposite end
thereof and positioned within the supply aperture of the
complementary transverse cross-section of the associated
runner.
runner cavity for the outer surface of the element to be
spaced from the cavity de?ning walls to provide for the
References Cited in the ?le of this patent
passage of plasticized molding material along the outer
UNITED STATES PATENTS
surface of said element between said supply and discharge 30
element to be spaced from the cavity de?ning walls and
to provide for the passage of plasticized molding material
along the outer surface of said element between said
apertures, one end of each heater terminating at the dis
charge aperture of the associated runner cavity in a
hemispherical end surface overlying said discharge aper
ture, the hemispherical end surface including at least one
groove which passes through ‘the longitudinal axis of the 35
heater and which extends over a minor portion of the
length of the heater.
6. The combination of a runner plate assembly and a
heating element for an injection molding machine, includ
959,233‘
1,920,629
1,927,570
2,118,415
2,735,922
2,770,011
2,864,929
2,871,515
1910
1933
1933
1938
1956
1956
1958
1959
FOREIGN PATENTS
ing a runner plate comprised by a backing plate and a fac
ing plate arranged in intimate face contact, the runner
Lanum ______________ .. May 24,
Chevassus ___________ __ Aug. 1,
Lofthouse __________ __ Sept. 19,
Pesark _____________ __ May 24,
Johnson ______________ .._ Feb. 21,
Kelly ______________ __ Nov. 13,
Schwing ____________ __ Dec. 16,
Loew _________________ __ Feb. 3,
586,125
Germany ____________ __ Oct. 17, 1933
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