CA2013950C - Integrally heated torpedo - Google Patents
Integrally heated torpedoInfo
- Publication number
- CA2013950C CA2013950C CA002013950A CA2013950A CA2013950C CA 2013950 C CA2013950 C CA 2013950C CA 002013950 A CA002013950 A CA 002013950A CA 2013950 A CA2013950 A CA 2013950A CA 2013950 C CA2013950 C CA 2013950C
- Authority
- CA
- Canada
- Prior art keywords
- torpedo
- melt
- body portion
- end portion
- heated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- Injection Moulding Of Plastics Or The Like (AREA)
Abstract
Abstract of the Disclosure An integral heated torpedo is provided for use in injection molding. The torpedo is formed from a single piece of metal and has an elongate body portion which extends axially from an enlarged end portion and which terminates in tip. The center of the torpedo body portion contains an axial cavity extending between the torpedo tip and the enlarged end portion.
The bore is adapted to receive a heating element which includes a coil of resistance wire and a thermocouple which are surrounded by heat insulative material. A plurality of melt flow passages extend axially through the enlarged end portion and are disposed generally around the torpedo bore to provide a series of melt flow paths through the enlarged end portion onto the heated exterior surface of the torpedo body.
The bore is adapted to receive a heating element which includes a coil of resistance wire and a thermocouple which are surrounded by heat insulative material. A plurality of melt flow passages extend axially through the enlarged end portion and are disposed generally around the torpedo bore to provide a series of melt flow paths through the enlarged end portion onto the heated exterior surface of the torpedo body.
Description
3 ~
PATENT
CaRe 890348 INTERNALLY HE~TED TORPEDO
Panos Trakas Back~ound_&_Summary of the Inventlon The present invention relate~ generally to injection molding sy~tems which use~ a heated torpedo disposed in a cavity plate to heat melt flowing from a ~elt injection nozzle ;~
through the cavity plate into ~ mold c~vi~y, and more particularly, to an improved heated torpedo having an integral ~onstruction. ~:
~: -Injection molding is widely used for the manufacture :;
of a variety of items. Injection molding i8 typically ~ performed by injecting heated, liquid melt into either a single ~;
I ~old cavity or into one or more mold bores, each of which feeds a number of mold cavities~ In either application, a heated flowpath must be provided to convey the injected, liquid melt ~rom the injection machine to the ~old cavities without ~:
interruption. It i8 therefore desirable to provide a cons ant -~
application of suff~cient h~at to the melt ~low to keep it ;
llquid while it pa~8e8 through the mold bore under pressure and into the mold cavities. Heated torpedoes are comDonly used for 1: thi~ purpose. ~-¦ ~eated torpedoes of two-piece cons~ruction typically : ,~. ~
use a separate torpedo body having an internal heater and a ~eparate torpedo end which welded together to ~orm the ~inal !
. heated torpedo. In this type o~ two-piece construction, the .
.~
~ 3~
weld which joins the 'corpedo body to the torpedo end i8 .
po6itioned on the exterior heated ~urface of the torpedo body, . .:
in the flow path of the pre6~urized liquid melt. Such welds mu~t be caref ully examined to ensure that no porosity i8 pre~ent which would allow entrance of the 1 iquid, pressurized melt into the internal heater leading to pos~ible contamination and burnout of the same. This problem described is a typical one for two-piece heated torpedo constructions which utilize separate torpedo bodies and end~
Additionally, in two-piece torpedo constructions, ~he heating element may not extend f or any 6ignif icant length into the torpedo end. Such torpedos are likely to have ~cold ~pots~', that i8 areas on the torpedo surface~ over which the melt passes which have different and lower temperature~. The pr~vious 601ution to a torpedo end which exhibited ~cold spots~
was to apply an external band heater. This Rolution adds to the cost and complexity of the molding operation.
~he presen~ invention is.directed to an internally heated torpedo o~ integral construction which avoid~ the above shortcoming~
In an internally heated torpedo constructed in ~coord~nce w$th ~he present invention, an elongate torpædo body :~
axially extends from a torpedo end disposed at the mel~ inlet end of the torpedo and termina~es in a tip at the ~orpedo bo~y melt outlet end. The torpedo body has a central cavity extending a~ially ~ro~ near the torpedo body tip to well inside the enlarged end portion which i8 adapted to receive a heating I element and position that heating element in close pro~imity ~o ¦ the outer surface of the torpedo body. The torpedo enlarged -2~
end contains a series of ~xial melt flow pa~sages di~posed around the tcrpedo body which passage ~erve to define the extent of the ~orpedo body within the enlarged end portion. ~n .
end cap i8 provided on the enlarged end portlon and def ines a melt flow entrance chamber or flow F~th to the melt flow ;~ .
passages.
Accordingly, it i~ a general object of the present invention to provide an in ernally heated torpedo of improved integral construction for use in injection molding ~yste~s.
Another object of the present invention i~ to provide ~n internally heated torpedo having a torpedo body terminating at one end in a tip and terminating at the other end in a torpedo enlarged ~nd, wherein the torpedo body has an internal electrical heating element which extend~ axially within the torpedo body between the tip and within the torpedo enlarged end to provide a uni~orm and effective heated surface the length of the torpedo for melt to flow. :
It is another object o~ the present invention to provide an internally heated torpedo of integral con~truction for use in injection molding sy~tems wherein the torpedo has ~n enlarged end portion at its melt inlet end and an elongate ~ :
torpedo body portion which axially extends from the enlarged end portion and t~rminates in a tip at the torpedo melt outle~
end ~nd wher~in the enlarged end portion include~ a plurality of melt ~low passzlges axially extending therethrough in close proxinity to the internal hea~er.
It is ~l:ill another object of the present invention :~ ;
to provide a heated torpedo having a torpedo body which i~
integral with a torpedo inlet end and haYing a heater di~posed ' ~'' -3~
~ . . . . . . . . .
jJr~ '' within the toepedo body which extends for substantially the entire length of the torpedo. :
It is still another object of the present invention to provide an in~ernally heated torpedo of integral S cons~ruction for us~ in injection molding wherein the torpedo has an enlarged torpedo inlet end having means to receive the melt flow from an injection ~olding nozzle and means to distribute the melt flo~ over the heated exterior urface of an elongate torpedo body portion to the torpedo outlet end wherein the torpedo body contains ~n internal electrical heating element which extends axially between the torpedo inlet and outlet ends.
These and other object~, features and advantages of the present invention will be clearly under~tood through a consideration of the following detailed de~cription.
Brief DescriPtion of the Drawinqs : -:
: ' In the course of this description, reference will be frequently made to the attache~ drawings, in which: -FIG. 1 is a sectional view o~ an in~ernally heated torpedo in~orporating ~he principles o~ the pre~nt invention;
FIG. 2 i~ an el~vational view o~ the heated torpedo of FIG. 1 ,n place within a mold bore in a ~old block, ~he latter being shown in sectionS
~ 25 FIG. 3 i8 a bottom plan view of the heated torpedo of I FIG. 2 FIG. 4 is a top plan view of the heated torpedo of FIG. 2;
FIG. S i~ a ~ectional plan view taken along lin~ 5-5 of FIG. 2.
i~s ;~
FIG. 6 i~ a pærspective view of the heated torpedo of FIG. 2. ;
Detailed Description of ~he Invention A heated torpedo 10 which incorpora~es the principles of the present invention is shown in its operational environment in FIG. 20 The heated torpædo 10 ha a melt inlet end 22 located in æn enlarged end 16 thereof and a melt outlet end 20 terminating in a solid tip 14, which may be shaped by machining to achieve the proper tip profile necessa~y. ~ :
generally cylindrical ~orpedo body 12 axially extend~ a preselected di~tance from the generally cylindrical torpedo enlarged end 16. In operation, the torpedo 10 i8 eated in the ~old bore 72 of a cavity plate 74 of a mold block 70 in alignment with the ~old gate 77 tbrough the cavity plate ~4 whlch leads to a mold cavity 76.
As best seen in FIG. 1, the torpedo 10 is fabricated from a solid metal torpedo cylindrical member (not shown) which `::~
i8 hollo~ed out when an axial heater cavi~y 18 i~ ~ormed in the center of the torpedo member. The heater cavity 18 may be formed by any conventiona} and suitable ~eans such a~ drilling or electric di~charge machin,ing (~DMa). The heater cavi~y 18 extends for ~ubstantially ~he entire length of the ~orpedo 10 through the torpe,do enlarged end lC and the torpedo bo~y 12 and terminates shortl~y before the ~orpedo outlet end 20 proximate .
to the torpedo tip 14. The heater cavity 18 is spaced a preselected di~tance from the exterior surface 36 of the holl~w torpedo body 12 to provide the ~ost beneficial heat transfer characteri~tics.
' -~, ', ~,'' - ,', ~ - .
'.
2~i!3~5~
The torpædo inlet end 22 ha~ a generally cylindrical enlarged end 16 which has a diameter greater than that of the torpedo body 12. ~uring ~abricatiOn~ the differ2nce in the diameter~ of the torE~edo body 12 and torpedo end 16 may be S achieved by any suitable machining method. As will be described in greater detail below, because the toLpedo i 8 fabricated fro~ a solid metal torpedo cylindrica~ member, the resulting torpedo is essentially o~ one piece constr wtion. No separation between the torpedo hollow enlarged end 16 and the torpedo hollow body portion 12 i~ present on the exterior ~ -.
~urface 36 of the hollow torpedo body 120 The hollow torpedo ~;
body 12 extends a significant distance up into the hollow torpedo end portion 16 along the centerline of the torpedo heater cavity 18. The extent to which the torpedo hollow body 12 is present within the torpedo hollow enlarged end 16 i~
defined by the axial ~elt flow pas~ages 44 passing through the enl~rged end 16 and abutting the exterior surface 36 of the torpedo bollow body portion 12.
The torpedo 10 i8 provided with means for heating the exterior surface 36 of the torpedo body 12, illustrated as a co~led heating element 26, which i8 disposed in the internal heater cavity 18. The heating element 26 is formed by winding a preselected length of resi~tance wire 28 around a ceramic rod or core member 30. The heating element 26 has a preselected I 25 outer dia~eter that 15 le88 than the torpedo body heater cavity ¦ inner diameter to allow easy in~ertion of the heater into the -~
¦ cavity 18.
¦ The dif;Eerence in diameter~ between ~he heating ¦ ele~ent 26 and the heater cavity 18 defines an annular ~pace therebetween. This annular space~ and the space which :'.
-6~
~ay occur at the tip end 19 of the heater cavity 18 i8 filled with a particula~e ceramic refractory material 34, ~uch as magnesium oxide. This ceramic material 34 facilitates the transfer of heat between the internal heating element 26 and the torpedo body exterior surface 36 and al~o insulates the re~istance wire 28 from contact with the inner wall 38 of the ~orpedo body heater cavity 18. Magne~ium oxide i6 the preferred ceramic refractory màterial of choice ~ince it has excellent heat transfer capabilitie~ a~ high temperatures when 0 it i8 compacted. The powdered magne~ium oxide i8 al80 preferably finely ground 80 that it fills the air voids present in the torpedo bore heater cavity annular space.
The heating element rod 30 may have an axial opening 31 passing through its center to receive one end 32 of the ~, 15 resistance wire 28 to convey that wire end 32 toward the enl~rged end 16 and to insulate it from contact with the heating element wire coils 29 and the surrounding metal wall 13 of the torpedo body 12. The heat~ng element resistance wire :~
i end~ 32, 33 exit out of the torpedo 10 through the enl~rged end ¦ 20 16 by way of a radial 810t 80 which is cut through the ~idew~
¦ 82 of the torpedo enlarged end 16.
¦ For purposes of ~onitoring and con~rolling the amount ;`
of heat transferred by the heating element 26 to the exterior ~urface 36 of the ~orpedo hollow body 12, a ~hermowell 40 i~
placed in the heater cavity ~nnular space. The ther~owell 40 extends the entir~ length o~ th~ heater cavity 18, and i~
adapted to receive a thermocouple (not shown). The ~` thermocouple allow~ the temperature of the exterior ~urface 36 -of the torpedo to b~ monitored and controlled. After 7 ;. ~ ;
-- 2~3~
insertion into the heater cavi~y 18,, the ceramic material 34 and the heating elemen~ 26 are co~ cted by subj ecting the torpedo body to a swaging process. Aft~r swaging, the ultimate diameter of the torpedo body 12 i8 def ined.
S The heating element 26 ha~ a preferred pre~elected length ~uch that it extends in the heater cavity 18 between the ~ ~ .
torpedo tip 14 and up into ~he torpedo enlarged end portion 16. :
The lcwer end of the heating element 26 terminates close to the torpedo tip 14, while the upper end ter~inates within the torpedo enlarged end 16 clo~e to the electrical wire exit area a~ deflned by the radial slot 80. Thi6 distance is typi.cally will be one-quarter and three quarters of the length, L, o~ the enlarged end 16 starting ~rom the torpedo enlarged end ~old bore seat 93 . (FIG. 2 . 3 After ~waging, the resistance wire ends 32, 33 and the ther~owell 40 are bent 80 tha~ they exit the torpedo hollow enlarged end 16 by way of the radial slot 80. The remaining spaces in the torpedo end 16 and radial 810t 80, re~pectively, 84 and 86, are ~illed with either addi~ional powdered ceramic 34 or a conventional high-tempærature resistance ce~ent 62.
~he protruding ends of the re~istance wires 32 and 33 and the thermowell 40 ~ay be connected in any conventional ~anner to exterior power and control wires (not ~hown) which lead to an appropriat~ power source via cable 66.
The heater cavity 18 in the torpedo enl~rged end 16 i8 sealed by a ~e~al cover plate 87 which overlieæ the high-te~perature cement 62 and ex~ends through the ~idewall 59 o~ the enlarged end 16 over the heater cavity 18. The co~er : : `
plate 87 i8 ~elded to the enlarged end 16 by an appropriate method to properly ~eal the heater cavity 18 and e~larg~d end :
radial ~ot 80. Tha remainder of the radial ~lot 80 in the t~ 3 ;~
sidewall 59 of the torpes~o enlarged end 16 ~ filled ~ way of a plug weld 88, the outee surfacle of whieh i~ machined to match the conf iguration of the torpedo end 16. The balance of the heater cavity 18 in the hollow enlarged end 16 is al80 similarly sealed, which seal is ~ho~wn as a metal end plug 52 welded to the enlarged end 16. The rear of the end plug 52 preferably includes an enlarged portion 96 o~ generally hemispherical ~haped configuration~ This enlarged portion ~ise~ above the floor 92 of the ~elt distribution chamber 58.
The end plug 52 completes ~he e~tent of the torpedo body portion 12 within the enlarged end 16.
After the insertion of the heating element 26 into the heater cavi~y 18 and the subsequent swaging of the torpedo body 12, the rear surface 90 of the enlarged end portion 16 i8 . ~ `
hollowed out to form the floor 92 and the endwall 57 of the enlarged end 16, which together define the melt inlet chamber :
58. A~ter forming the melt inlet chamber 58, a plurality of I axial melt flow pa88age8 44 are drilled through the torpedo hollow enlarged end 16.` As 6hown in FIG. 1, these a~ial I 20 passages 44 extend completely through the hollow enlarged end 1 16 and abut the torpedo hollow body exterior surface 36a 80 that the wall 45 of each a~ial pa~sage ~4 includes a portion 35a of the torpedo hollow body e~terior surface 36. (FIGS. 1 &
3). As an altern~tive to drilling the axial pa88aqe8 44 may be ~ade in the enlarged end 16 by way of ED~o The a~i~l melt flow pa88age8 4~ define the torpedo body exterior sucfaces 36a within the torpedo enlarged end 16. ::~
The torpedo hollow body exterior surface portion~ 36a ! o~ these axial pa~age~ 44 are ~paced the same distance from the hea~ing eleMent 26 a~ ~he torpedo hollow body ex~erior _9_ sur~ace 36 and thus the injected melt pa~sing from the mel~
inlet chamber 58 through the axial pas~ages 44 i5 heated to the same temperature a~ ~he lnjected m~ exiting the axial pa~sages 44 and passing over the torpædo hollow body exterior S surface 36. Therefore, the injected melt i8 virtually always in contact with the torpedo body heated exterior surface 36 as it ~lows between the inlet end 22 and the outlet end 20 of the torpedo into the mold cavity 76. The heating element 26 ` extends into the torpedo end 16 up to the radial 810t 80, ~sr a : 10 di~tance of between one-quarter ~nd three-guarters of the enlarged end length, L, ~rom the torpedo mold bore seat 93 80 that the torpedo body portion integrally ~ormed within the enlarged end 16 i8 heated when the torpedo is energizedO '!
Thu~, the likelihood of ~cold 8pot3~ on the torpedo hollow enlarged end 16 is greatly minimized and the need for an ::
¦ external band heater applied to the enlarged end 16 i8 ~:
el iminated.
- .
The torpedo enlarged end 16 i~ co~pleted by the insertion of an inlet endcap 54 which fits within the enlarged end endwall 57 and sits on a rim 60 thereof. The inlet endcap 1 5~ is joined to the endwall 59 in an appropriate manner ~uch as 3 by welding. The endcap 54 has ~ circular melt inlet opening 56 di~posed in its center and the interior surface 57 thereof i8 finished to d~fine a melt inlet chamber 58 in the enclo~ed portion 59 of th~! torpedo enlarged end 16. The bottom of the torpedo hollow er~arged end 16 includes a mold bore seat 93 which is separated from the torpedo hollow body exterior ., ~, ` . surface 36 by ~eans of an annular channel 98 which e~tends up into the enlarged ~nd 16. The mold bore seat 93 seat~ on a ;;
ledge 71 of ~he ~old 70 and, by Yirtue of its separa~ion fro~
2~3r~0 he torpedo body, minimizes the tr~nsfer of heat between the torpedo hollow body exterior ~urfa~e 36 and the mold cavity plates 74.
Importantly, the torpedo 10, and in particular, the exterior surface 36 of the torpedo body 12 i8 formed fro~ a ~ingle piece of metal, ~uch that no weld junctions are located on the torpedo body exterior l:urface 3S ~etween the 'corpedo inlet end 22 and the torpedo outlet end 20. Becau~e of the one-piece cons~ruction of the enlarged end portion 16 such that he torpedo body portion 12 and enlargeâ end portion 16 are in~egral with each other, the heating element 26 tran~fers heat ;~
to the axial pas~ageæ 4~ oP the enlarged end portion 16 and ~aintainE a heat level therein conducive to the fIow of liquid ~ :
melt therethrough.
In operation, either a ~ingle inj~ction molding ~achine nozzle or a hot manifold tnot shown) i8 moved up against the torpedo inlet endcap 54 in an abutting injection r~lationship with the ~orpedo melt inlet opening 56. The -~
injected melt flows under pressure through the inlet op~ning 56 and into the ~elt flow chamber 58 ~here it i8 distribu~ed to :
the melt flow axial pa~ages 44 by the heating cav~ty e~d plug 52. The injected m~lt travels through the a~ial pa58age8 44 and out of the hollow torpedo enlarged end 16 at the annular channel 98 onto the torpedo body e~terior surace 36 such that . ~
its t~mperature i8 maintained b~ the torpedo internal heating . :;
element 2~ for the full extent of the torpedo body 12.
Th~ torpedo 10 may also further include means for posi'cioning the torpedo 10 within the mold block bore 72 located on the torpedo body 12 near the tip 14, which are ~hown . .
~11--`~
3~J
in the drawing6 as radially extending ~in~ 75 which extend out a preselected di6tance from the torlpedo body to contact the mold bore wall ~9 and properly po~ition the torpedo tip 1~ with respect to the mold cavity gate 77. (FIG. 2) The fins 75 may ~eparate parts which are attached to the torpedo body 12 by any suitable conventional means, such as ~elding, or they may be machined down from an enlarged diameter pOEtiOn of the torpedo body at this location.
It will be understood that the embodiment of the prezent invention which bas been described i8 merely illu~trative of one application of the principles of the pre6ent invention. Numerous modification~ may be ~ade 1~ those skilled in the ar without departing from the true spirit of scope o~ the invention. .
`
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," ~.. , . . . , , , , ~ ~ , . ,
PATENT
CaRe 890348 INTERNALLY HE~TED TORPEDO
Panos Trakas Back~ound_&_Summary of the Inventlon The present invention relate~ generally to injection molding sy~tems which use~ a heated torpedo disposed in a cavity plate to heat melt flowing from a ~elt injection nozzle ;~
through the cavity plate into ~ mold c~vi~y, and more particularly, to an improved heated torpedo having an integral ~onstruction. ~:
~: -Injection molding is widely used for the manufacture :;
of a variety of items. Injection molding i8 typically ~ performed by injecting heated, liquid melt into either a single ~;
I ~old cavity or into one or more mold bores, each of which feeds a number of mold cavities~ In either application, a heated flowpath must be provided to convey the injected, liquid melt ~rom the injection machine to the ~old cavities without ~:
interruption. It i8 therefore desirable to provide a cons ant -~
application of suff~cient h~at to the melt ~low to keep it ;
llquid while it pa~8e8 through the mold bore under pressure and into the mold cavities. Heated torpedoes are comDonly used for 1: thi~ purpose. ~-¦ ~eated torpedoes of two-piece cons~ruction typically : ,~. ~
use a separate torpedo body having an internal heater and a ~eparate torpedo end which welded together to ~orm the ~inal !
. heated torpedo. In this type o~ two-piece construction, the .
.~
~ 3~
weld which joins the 'corpedo body to the torpedo end i8 .
po6itioned on the exterior heated ~urface of the torpedo body, . .:
in the flow path of the pre6~urized liquid melt. Such welds mu~t be caref ully examined to ensure that no porosity i8 pre~ent which would allow entrance of the 1 iquid, pressurized melt into the internal heater leading to pos~ible contamination and burnout of the same. This problem described is a typical one for two-piece heated torpedo constructions which utilize separate torpedo bodies and end~
Additionally, in two-piece torpedo constructions, ~he heating element may not extend f or any 6ignif icant length into the torpedo end. Such torpedos are likely to have ~cold ~pots~', that i8 areas on the torpedo surface~ over which the melt passes which have different and lower temperature~. The pr~vious 601ution to a torpedo end which exhibited ~cold spots~
was to apply an external band heater. This Rolution adds to the cost and complexity of the molding operation.
~he presen~ invention is.directed to an internally heated torpedo o~ integral construction which avoid~ the above shortcoming~
In an internally heated torpedo constructed in ~coord~nce w$th ~he present invention, an elongate torpædo body :~
axially extends from a torpedo end disposed at the mel~ inlet end of the torpedo and termina~es in a tip at the ~orpedo bo~y melt outlet end. The torpedo body has a central cavity extending a~ially ~ro~ near the torpedo body tip to well inside the enlarged end portion which i8 adapted to receive a heating I element and position that heating element in close pro~imity ~o ¦ the outer surface of the torpedo body. The torpedo enlarged -2~
end contains a series of ~xial melt flow pa~sages di~posed around the tcrpedo body which passage ~erve to define the extent of the ~orpedo body within the enlarged end portion. ~n .
end cap i8 provided on the enlarged end portlon and def ines a melt flow entrance chamber or flow F~th to the melt flow ;~ .
passages.
Accordingly, it i~ a general object of the present invention to provide an in ernally heated torpedo of improved integral construction for use in injection molding ~yste~s.
Another object of the present invention i~ to provide ~n internally heated torpedo having a torpedo body terminating at one end in a tip and terminating at the other end in a torpedo enlarged ~nd, wherein the torpedo body has an internal electrical heating element which extend~ axially within the torpedo body between the tip and within the torpedo enlarged end to provide a uni~orm and effective heated surface the length of the torpedo for melt to flow. :
It is another object o~ the present invention to provide an internally heated torpedo of integral con~truction for use in injection molding sy~tems wherein the torpedo has ~n enlarged end portion at its melt inlet end and an elongate ~ :
torpedo body portion which axially extends from the enlarged end portion and t~rminates in a tip at the torpedo melt outle~
end ~nd wher~in the enlarged end portion include~ a plurality of melt ~low passzlges axially extending therethrough in close proxinity to the internal hea~er.
It is ~l:ill another object of the present invention :~ ;
to provide a heated torpedo having a torpedo body which i~
integral with a torpedo inlet end and haYing a heater di~posed ' ~'' -3~
~ . . . . . . . . .
jJr~ '' within the toepedo body which extends for substantially the entire length of the torpedo. :
It is still another object of the present invention to provide an in~ernally heated torpedo of integral S cons~ruction for us~ in injection molding wherein the torpedo has an enlarged torpedo inlet end having means to receive the melt flow from an injection ~olding nozzle and means to distribute the melt flo~ over the heated exterior urface of an elongate torpedo body portion to the torpedo outlet end wherein the torpedo body contains ~n internal electrical heating element which extends axially between the torpedo inlet and outlet ends.
These and other object~, features and advantages of the present invention will be clearly under~tood through a consideration of the following detailed de~cription.
Brief DescriPtion of the Drawinqs : -:
: ' In the course of this description, reference will be frequently made to the attache~ drawings, in which: -FIG. 1 is a sectional view o~ an in~ernally heated torpedo in~orporating ~he principles o~ the pre~nt invention;
FIG. 2 i~ an el~vational view o~ the heated torpedo of FIG. 1 ,n place within a mold bore in a ~old block, ~he latter being shown in sectionS
~ 25 FIG. 3 i8 a bottom plan view of the heated torpedo of I FIG. 2 FIG. 4 is a top plan view of the heated torpedo of FIG. 2;
FIG. S i~ a ~ectional plan view taken along lin~ 5-5 of FIG. 2.
i~s ;~
FIG. 6 i~ a pærspective view of the heated torpedo of FIG. 2. ;
Detailed Description of ~he Invention A heated torpedo 10 which incorpora~es the principles of the present invention is shown in its operational environment in FIG. 20 The heated torpædo 10 ha a melt inlet end 22 located in æn enlarged end 16 thereof and a melt outlet end 20 terminating in a solid tip 14, which may be shaped by machining to achieve the proper tip profile necessa~y. ~ :
generally cylindrical ~orpedo body 12 axially extend~ a preselected di~tance from the generally cylindrical torpedo enlarged end 16. In operation, the torpedo 10 i8 eated in the ~old bore 72 of a cavity plate 74 of a mold block 70 in alignment with the ~old gate 77 tbrough the cavity plate ~4 whlch leads to a mold cavity 76.
As best seen in FIG. 1, the torpedo 10 is fabricated from a solid metal torpedo cylindrical member (not shown) which `::~
i8 hollo~ed out when an axial heater cavi~y 18 i~ ~ormed in the center of the torpedo member. The heater cavity 18 may be formed by any conventiona} and suitable ~eans such a~ drilling or electric di~charge machin,ing (~DMa). The heater cavi~y 18 extends for ~ubstantially ~he entire length of the ~orpedo 10 through the torpe,do enlarged end lC and the torpedo bo~y 12 and terminates shortl~y before the ~orpedo outlet end 20 proximate .
to the torpedo tip 14. The heater cavity 18 is spaced a preselected di~tance from the exterior surface 36 of the holl~w torpedo body 12 to provide the ~ost beneficial heat transfer characteri~tics.
' -~, ', ~,'' - ,', ~ - .
'.
2~i!3~5~
The torpædo inlet end 22 ha~ a generally cylindrical enlarged end 16 which has a diameter greater than that of the torpedo body 12. ~uring ~abricatiOn~ the differ2nce in the diameter~ of the torE~edo body 12 and torpedo end 16 may be S achieved by any suitable machining method. As will be described in greater detail below, because the toLpedo i 8 fabricated fro~ a solid metal torpedo cylindrica~ member, the resulting torpedo is essentially o~ one piece constr wtion. No separation between the torpedo hollow enlarged end 16 and the torpedo hollow body portion 12 i~ present on the exterior ~ -.
~urface 36 of the hollow torpedo body 120 The hollow torpedo ~;
body 12 extends a significant distance up into the hollow torpedo end portion 16 along the centerline of the torpedo heater cavity 18. The extent to which the torpedo hollow body 12 is present within the torpedo hollow enlarged end 16 i~
defined by the axial ~elt flow pas~ages 44 passing through the enl~rged end 16 and abutting the exterior surface 36 of the torpedo bollow body portion 12.
The torpedo 10 i8 provided with means for heating the exterior surface 36 of the torpedo body 12, illustrated as a co~led heating element 26, which i8 disposed in the internal heater cavity 18. The heating element 26 is formed by winding a preselected length of resi~tance wire 28 around a ceramic rod or core member 30. The heating element 26 has a preselected I 25 outer dia~eter that 15 le88 than the torpedo body heater cavity ¦ inner diameter to allow easy in~ertion of the heater into the -~
¦ cavity 18.
¦ The dif;Eerence in diameter~ between ~he heating ¦ ele~ent 26 and the heater cavity 18 defines an annular ~pace therebetween. This annular space~ and the space which :'.
-6~
~ay occur at the tip end 19 of the heater cavity 18 i8 filled with a particula~e ceramic refractory material 34, ~uch as magnesium oxide. This ceramic material 34 facilitates the transfer of heat between the internal heating element 26 and the torpedo body exterior surface 36 and al~o insulates the re~istance wire 28 from contact with the inner wall 38 of the ~orpedo body heater cavity 18. Magne~ium oxide i6 the preferred ceramic refractory màterial of choice ~ince it has excellent heat transfer capabilitie~ a~ high temperatures when 0 it i8 compacted. The powdered magne~ium oxide i8 al80 preferably finely ground 80 that it fills the air voids present in the torpedo bore heater cavity annular space.
The heating element rod 30 may have an axial opening 31 passing through its center to receive one end 32 of the ~, 15 resistance wire 28 to convey that wire end 32 toward the enl~rged end 16 and to insulate it from contact with the heating element wire coils 29 and the surrounding metal wall 13 of the torpedo body 12. The heat~ng element resistance wire :~
i end~ 32, 33 exit out of the torpedo 10 through the enl~rged end ¦ 20 16 by way of a radial 810t 80 which is cut through the ~idew~
¦ 82 of the torpedo enlarged end 16.
¦ For purposes of ~onitoring and con~rolling the amount ;`
of heat transferred by the heating element 26 to the exterior ~urface 36 of the ~orpedo hollow body 12, a ~hermowell 40 i~
placed in the heater cavity ~nnular space. The ther~owell 40 extends the entir~ length o~ th~ heater cavity 18, and i~
adapted to receive a thermocouple (not shown). The ~` thermocouple allow~ the temperature of the exterior ~urface 36 -of the torpedo to b~ monitored and controlled. After 7 ;. ~ ;
-- 2~3~
insertion into the heater cavi~y 18,, the ceramic material 34 and the heating elemen~ 26 are co~ cted by subj ecting the torpedo body to a swaging process. Aft~r swaging, the ultimate diameter of the torpedo body 12 i8 def ined.
S The heating element 26 ha~ a preferred pre~elected length ~uch that it extends in the heater cavity 18 between the ~ ~ .
torpedo tip 14 and up into ~he torpedo enlarged end portion 16. :
The lcwer end of the heating element 26 terminates close to the torpedo tip 14, while the upper end ter~inates within the torpedo enlarged end 16 clo~e to the electrical wire exit area a~ deflned by the radial slot 80. Thi6 distance is typi.cally will be one-quarter and three quarters of the length, L, o~ the enlarged end 16 starting ~rom the torpedo enlarged end ~old bore seat 93 . (FIG. 2 . 3 After ~waging, the resistance wire ends 32, 33 and the ther~owell 40 are bent 80 tha~ they exit the torpedo hollow enlarged end 16 by way of the radial slot 80. The remaining spaces in the torpedo end 16 and radial 810t 80, re~pectively, 84 and 86, are ~illed with either addi~ional powdered ceramic 34 or a conventional high-tempærature resistance ce~ent 62.
~he protruding ends of the re~istance wires 32 and 33 and the thermowell 40 ~ay be connected in any conventional ~anner to exterior power and control wires (not ~hown) which lead to an appropriat~ power source via cable 66.
The heater cavity 18 in the torpedo enl~rged end 16 i8 sealed by a ~e~al cover plate 87 which overlieæ the high-te~perature cement 62 and ex~ends through the ~idewall 59 o~ the enlarged end 16 over the heater cavity 18. The co~er : : `
plate 87 i8 ~elded to the enlarged end 16 by an appropriate method to properly ~eal the heater cavity 18 and e~larg~d end :
radial ~ot 80. Tha remainder of the radial ~lot 80 in the t~ 3 ;~
sidewall 59 of the torpes~o enlarged end 16 ~ filled ~ way of a plug weld 88, the outee surfacle of whieh i~ machined to match the conf iguration of the torpedo end 16. The balance of the heater cavity 18 in the hollow enlarged end 16 is al80 similarly sealed, which seal is ~ho~wn as a metal end plug 52 welded to the enlarged end 16. The rear of the end plug 52 preferably includes an enlarged portion 96 o~ generally hemispherical ~haped configuration~ This enlarged portion ~ise~ above the floor 92 of the ~elt distribution chamber 58.
The end plug 52 completes ~he e~tent of the torpedo body portion 12 within the enlarged end 16.
After the insertion of the heating element 26 into the heater cavi~y 18 and the subsequent swaging of the torpedo body 12, the rear surface 90 of the enlarged end portion 16 i8 . ~ `
hollowed out to form the floor 92 and the endwall 57 of the enlarged end 16, which together define the melt inlet chamber :
58. A~ter forming the melt inlet chamber 58, a plurality of I axial melt flow pa88age8 44 are drilled through the torpedo hollow enlarged end 16.` As 6hown in FIG. 1, these a~ial I 20 passages 44 extend completely through the hollow enlarged end 1 16 and abut the torpedo hollow body exterior surface 36a 80 that the wall 45 of each a~ial pa~sage ~4 includes a portion 35a of the torpedo hollow body e~terior surface 36. (FIGS. 1 &
3). As an altern~tive to drilling the axial pa88aqe8 44 may be ~ade in the enlarged end 16 by way of ED~o The a~i~l melt flow pa88age8 4~ define the torpedo body exterior sucfaces 36a within the torpedo enlarged end 16. ::~
The torpedo hollow body exterior surface portion~ 36a ! o~ these axial pa~age~ 44 are ~paced the same distance from the hea~ing eleMent 26 a~ ~he torpedo hollow body ex~erior _9_ sur~ace 36 and thus the injected melt pa~sing from the mel~
inlet chamber 58 through the axial pas~ages 44 i5 heated to the same temperature a~ ~he lnjected m~ exiting the axial pa~sages 44 and passing over the torpædo hollow body exterior S surface 36. Therefore, the injected melt i8 virtually always in contact with the torpedo body heated exterior surface 36 as it ~lows between the inlet end 22 and the outlet end 20 of the torpedo into the mold cavity 76. The heating element 26 ` extends into the torpedo end 16 up to the radial 810t 80, ~sr a : 10 di~tance of between one-quarter ~nd three-guarters of the enlarged end length, L, ~rom the torpedo mold bore seat 93 80 that the torpedo body portion integrally ~ormed within the enlarged end 16 i8 heated when the torpedo is energizedO '!
Thu~, the likelihood of ~cold 8pot3~ on the torpedo hollow enlarged end 16 is greatly minimized and the need for an ::
¦ external band heater applied to the enlarged end 16 i8 ~:
el iminated.
- .
The torpedo enlarged end 16 i~ co~pleted by the insertion of an inlet endcap 54 which fits within the enlarged end endwall 57 and sits on a rim 60 thereof. The inlet endcap 1 5~ is joined to the endwall 59 in an appropriate manner ~uch as 3 by welding. The endcap 54 has ~ circular melt inlet opening 56 di~posed in its center and the interior surface 57 thereof i8 finished to d~fine a melt inlet chamber 58 in the enclo~ed portion 59 of th~! torpedo enlarged end 16. The bottom of the torpedo hollow er~arged end 16 includes a mold bore seat 93 which is separated from the torpedo hollow body exterior ., ~, ` . surface 36 by ~eans of an annular channel 98 which e~tends up into the enlarged ~nd 16. The mold bore seat 93 seat~ on a ;;
ledge 71 of ~he ~old 70 and, by Yirtue of its separa~ion fro~
2~3r~0 he torpedo body, minimizes the tr~nsfer of heat between the torpedo hollow body exterior ~urfa~e 36 and the mold cavity plates 74.
Importantly, the torpedo 10, and in particular, the exterior surface 36 of the torpedo body 12 i8 formed fro~ a ~ingle piece of metal, ~uch that no weld junctions are located on the torpedo body exterior l:urface 3S ~etween the 'corpedo inlet end 22 and the torpedo outlet end 20. Becau~e of the one-piece cons~ruction of the enlarged end portion 16 such that he torpedo body portion 12 and enlargeâ end portion 16 are in~egral with each other, the heating element 26 tran~fers heat ;~
to the axial pas~ageæ 4~ oP the enlarged end portion 16 and ~aintainE a heat level therein conducive to the fIow of liquid ~ :
melt therethrough.
In operation, either a ~ingle inj~ction molding ~achine nozzle or a hot manifold tnot shown) i8 moved up against the torpedo inlet endcap 54 in an abutting injection r~lationship with the ~orpedo melt inlet opening 56. The -~
injected melt flows under pressure through the inlet op~ning 56 and into the ~elt flow chamber 58 ~here it i8 distribu~ed to :
the melt flow axial pa~ages 44 by the heating cav~ty e~d plug 52. The injected m~lt travels through the a~ial pa58age8 44 and out of the hollow torpedo enlarged end 16 at the annular channel 98 onto the torpedo body e~terior surace 36 such that . ~
its t~mperature i8 maintained b~ the torpedo internal heating . :;
element 2~ for the full extent of the torpedo body 12.
Th~ torpedo 10 may also further include means for posi'cioning the torpedo 10 within the mold block bore 72 located on the torpedo body 12 near the tip 14, which are ~hown . .
~11--`~
3~J
in the drawing6 as radially extending ~in~ 75 which extend out a preselected di6tance from the torlpedo body to contact the mold bore wall ~9 and properly po~ition the torpedo tip 1~ with respect to the mold cavity gate 77. (FIG. 2) The fins 75 may ~eparate parts which are attached to the torpedo body 12 by any suitable conventional means, such as ~elding, or they may be machined down from an enlarged diameter pOEtiOn of the torpedo body at this location.
It will be understood that the embodiment of the prezent invention which bas been described i8 merely illu~trative of one application of the principles of the pre6ent invention. Numerous modification~ may be ~ade 1~ those skilled in the ar without departing from the true spirit of scope o~ the invention. .
`
.. . .
," ~.. , . . . , , , , ~ ~ , . ,
Claims (16)
1. An integral heated torpedo for use in injection molding and for maintaining liquid melt at a temperature conducive to melt flow while the melt is passing over an exterior surface thereof, the torpedo comprising: an elongated heated member having a melt inlet end and a melt outlet end, said elongated heated member having a torpedo body portion extending axially outwardly from a torpedo enlarged end portion thereof, the torpedo body portion having a first diameter and the torpedo enlarged end portion having a second diameter which is greater than the torpedo body portion first diameter, said torpedo enlarged end portion being disposed at the melt inlet end of said elongated heated member, said torpedo body portion being disposed proximate to the melt outlet end of said elongated heated member, said torpedo body portion having an integral sidewall, end tip portion and an inner cavity, the integral sidewall of said torpedo body portion having an exterior surface heated by a heating element, said enlarged end portion being integrally joined to said torpedo body portion, said torpedo body portion further extending within said enlarged end portion, said enlarged end portion including a plurality of melt flow axial passages passing through said torpedo enlarged end portion and opening onto said torpedo body portion, each of the melt flow axial passages being in a heat transfer relationship to the exterior heated surface of said torpedo body portion integral sidewall, said melt flow axial passages further defining an extent of said torpedo body portion integral sidewall exterior heated surface within said enlarged end portion, said torpedo body portion further including an inner axial cavity extending through a central portion of said torpedo body portion and enlarged end portion, the inner axial cavity extending from a first end of the torpedo body portion to a second end of said torpedo body portion and terminating within said torpedo body portion inwardly of the second end of said torpedo body portion, said axial cavity having the heating element disposed therein in a heat transfer relationship with the exterior surface of said torpedo body portion integral sidewall, whereby heat is transferred from said heating element to said torpedo body portion integral sidewall exterior surface to maintain the melt passing over said torpedo body portion integral sidewall exterior surface in a liquid melt flow condition said plurality of melt flow passages defining a flow path for injected melt through said melt inlet end and said torpedo enlarged end portion over said integral sidewall exterior surface of said torpedo body portion, said elongated heated member further including means disposed within said torpedo enlarged end portion for distributing melt injected into said melt inlet end of said elongated heated member over said torpedo body portion integral sidewall exterior surface, the melt distribution means including a generally annular melt distribution chamber, said melt distribution chamber having means for directing liquid melt entering said torpedo melt flow inlet end into said plurality of melt flow axial passages, the melt distribution chamber having a general inner annular diameter which is equal or less than said torpedo body portion first diameter and a general outer annular diameter which is greater than said torpedo body portion first diameter.
2. The integral heated torpedo of claim 1, wherein said heating element includes a resistance wire heater and temperature sensing and controlling means including a thermocouple, said heating element and the temperature sensing and controlling means being embedded in a particulate ceramic refractory material in said axial cavity.
3. The integral heated torpedo of claim 1, wherein said heated member includes mold positioning means extending radially outwardly from and integral with said torpedo body portion sidewall.
4. The integral heated torpedo of claim 1, wherein said heating element extends between said melt inlet and outlet ends within said elongated heated member inner axial cavity, one end of said heating element being proximate to said melt outlet end and an opposite end of said heating element extending a preselected distance into said enlarged end portion of between one-quarter and three-quarters of an axial length of said enlarged end portion defined by top and bottom surfaces of said enlarged end portion.
5. The integral heated torpedo of claim 1, wherein said torpedo enlarged end portion includes a mold cavity plate seat, the mold cavity plate seat being separated from said torpedo body portion by an annular channel, said axial passages opening into the annular channel, said annular channel providing a space between said exterior surface of said torpedo body portion and said mold cavity plate seat.
6. The integral heated torpedo of claim 1 wherein each of said melt flow axial passage torpedo body portion integral sidewall exterior surface portions extends completely through said torpedo enlarged end within said melt flow axial passages and into said melt distributing means, thereby providing a heated surface of said elongate heated member within said melt flow axial passages, said melt flow axial passages being arranged in a generally semi-circular pattern within said melt distribution chamber.
7. An electrically heated torpedo having a melt inlet end and a melt outlet end, the torpedo having an elongated metal body portion having a first torpedo diameter and disposed between an enlarged end portion thereof and the melt outlet end, the enlarged end portion having a second torpedo diameter which is greater than the first torpedo diameter portion, said enlarged end portion being disposed at the melt inlet end thereof, said metal body portion having a heated exterior surface of said torpedo defined by said first torpedo diameter, said enlarged end portion having a plurality of melt flow passages disposed therein, said plurality of melt flow passages axially extending through said enlarged end portion and opening onto at least one-half of a circumference of the body portion heated exterior surface, said body portion heated exterior surface extending into said torpedo enlarged end for a predetermined length of said melt flow axial passages, said metal body having a central axial cavity disposed therein which is adapted to receive an elongated heating element therein for providing heat to said torpedo exterior surface, the central axial cavity extending within said body portion from a first end thereof and terminating inwardly of a tip portion of said body portion, said central axial cavity defining an integral sidewall and tip portion of said body portion, said integral sidewall and tip portions of said body portion being integral with said enlarged end portion, said enlarged end portion including means for internally distributing melt from said metal inlet end through said plurality of melt flow axial passages, the melt distributing means including a general annular distribution passage disposed generally centrally within said enlarged end portion, said distribution passage interconnecting said melt inlet end and all of said plurality of melt flow axial passages, said distribution passage having a general outer diameter which is greater than said torpedo first diameter, said melt distributing means further including a raised portion which defines a general inner diameter of said annular passage.
8. The electrically heated torpedo of claim 7, wherein said plurality of melt flow axial passages are disposed in said body enlarged end around the periphery of said exterior heated surface in a generally semi-circular pattern, and wherein said melt distribution means distribution passage raised portion includes an enlarged generally hemispherical protrusion.
9. The electrically heated torpedo of claim 7 wherein said torpedo body portion includes a means for positioning said torpedo body portion in a mold bore, said torpedo body portion positioning means including a fin member formed integrally with an extending outwardly from said torpedo body portion.
10. The electrically heated torpedo of claim 7 wherein said torpedo body enlarged end portion includes a mold cavity plate seat disposed opposite said metal body melt inlet end, the mold cavity plate seat having an annular depression separating said mold cavity plate seat from said metal body heated exterior surface, said melt flow axial passages opening into the annular depression.
11. The electrically heated torpedo of claim 7 wherein said elongated heating element extends into said enlarged end portion for between one-quarter and three quarters of a length of said enlarged end portion.
12. An internally heated integral torpedo for use in injection molding and for insertion into a mold bore during injection molding for providing a heated surface for injected melt to flow over as the injected melt passes through the mold bore into a mold cavity, the torpedo comprising: a generally cylindrical elongated member formed from a single piece of metal, the elongated member having a torpedo hollow body portion of a first diameter formed integral with a torpedo hollow end portion of a second diameter, the torpedo hollow end portion second diameter being greater than the torpedo hollow body portion first diameter, said torpedo hollow body portion including a central cavity extending a preselected distance within said torpedo hollow body portion and defining an integral sidewall and tip portion of said torpedo hollow body portion, the torpedo hollow body portion central cavity having a heating element disposed in said torpedo hollow body portion central cavity a predetermined distance from an exterior surface of said torpedo hollow body portion in a heat transfer relationship therewith, such that said heating element heats the torpedo hollow body portion exterior surface when energized, said hollow body portion central cavity also extending a preselected distance into said torpedo hollow end portion, said torpedo hollow end portion including a plurality of melt transfer passages axially extending therethrough and disposed longitudinally in said torpedo hollow end portion in a region between said torpedo hollow body portion first diameter and said torpedo hollow end portion second diameter and means for distributing the melt injected into said melt transfer passages, the melt distribution means including an internal melt distribution chamber located in said torpedo body end portion, the internal melt distribution chamber having a general annular configuration, said annular chamber having a general inner annular diameter and a general outer annular diameter, the distribution chamber general outer diameter being greater than the torpedo hollow portion first diameter, the annular chamber general inner diameter being equal to or less than said torpedo hollow end portion second diameter, whereby said melt distribution chamber opens into said plurality of melt transfer passages, said plurality of melt transfer passages being arranged in a generally semi-circular pattern within said torpedo hollow end portion, said torpedo hollow body portion exterior surface extending axially within each of said melt transfer passages and further defining an end position of said torpedo hollow body portion within said torpedo hollow end portion, said torpedo hollow end portion having a melt inlet opening therein in melt flow communication with said internal melt distribution chamber thereof, thereby providing a path for transfer of heated melt injected into said torpedo end portion to said mold cavity through said torpedo hollow end portion melt transfer passages over substantially all of the exterior surface of said torpedo hollow body portion, said torpedo hollow end portion further including means for exiting said torpedo hollow end portion including an opening which is adapted to receive power and control wires for energizing said heating element and controlling any heat generated thereby.
13. The internally heated torpedo of claim 12, wherein said torpedo hollow end portion further includes a torpedo mold bore seat, said torpedo hollow end portion including an annular groove therein, the annular groove separating said torpedo mold bore seat from said torpedo hollow body portion, said melt transfer passages opening into said torpedo hollow end portion annular groove.
14. The internally heated torpedo of claim 12, wherein said heating element extends into the central cavity portion of said torpedo hollow end portion.
15. The internally heated torpedo of claim 12, further including means for positioning said torpedo within said mold bore, said positioning means including a fin member extending outwardly from said torpedo hollow body portion.
16. The internally heated torpedo of claim 12, wherein said melt distribution means further includes an enlarged central portion having a general hemispherical configuration.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US335,113 | 1981-12-28 | ||
| US33511389A | 1989-04-07 | 1989-04-07 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2013950A1 CA2013950A1 (en) | 1990-10-07 |
| CA2013950C true CA2013950C (en) | 1994-08-16 |
Family
ID=23310316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002013950A Expired - Fee Related CA2013950C (en) | 1989-04-07 | 1990-04-05 | Integrally heated torpedo |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2013950C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2679112A1 (en) | 2012-06-26 | 2014-01-01 | 3M Innovative Properties Company | Method for manufacturing fasteners and precursor webs, a fastener and a precursor web |
-
1990
- 1990-04-05 CA CA002013950A patent/CA2013950C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2013950A1 (en) | 1990-10-07 |
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