Adjustable plug seal mechanism for heat transfer zone separation in hollow screws for extrusion machines

• US 4,355,905 A
• Filed: 03/24/1980
• Issued: 10/26/1982
• Est. Priority Date: 03/24/1980
• Status: Expired due to Term

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Trumbull, Walter A., St. Louis, Harold E.
• Primary Examiner(s): Coe, Philip R.
• Assistant Examiner(s): Simone, Timothy F.
• Application Number:
  US06/133,087
• Time in Patent Office: 946 Days
• Field of Search: 366/79, 366/83, 366/144, 366/147, 366/318, 425/378 R, 425/379 R, 425/131.1, 425/143, 425/144, 425/376 B, 277/12, 277/152, 277/3, 277/27
• US Class Current: 366/79
• CPC Class Codes: B29C 48/03 characterised by the shape of the extruded material at extrusion
• CPC Class Codes: B29C 48/515 for auxiliary fluids, e.g. foaming agents
• CPC Class Codes: B29C 48/84 by heating or cooling the feeding screws for hollow screws B29C48/515
• CPC Class Codes: B29C 48/845 Heating
• CPC Class Codes: B29C 48/85 Cooling
• CPC Class Codes: B29C 48/875 for achieving a non-uniform temperature distribution, e.g. using barrels having both cooling and heating zones

Abstract

An easily-movable plug seal that is susceptible to quick and ready longitudinal adjustment in the central, lengthwise bore of an internally differentially heated (or cooled) extruder screw for sequentially diverse and distinct heat controlled zones within the extruder barrel is comprised of at least a single, cup-like member that is adequately flexible and supple to be flared laterally outwardly and urged into tight wall contact to make a sealing engagement against the internal screw bore wall upon pressurization of the interior of the plug seal member by the heat transfer fluid being passed into and applied within the screw.

Claims

1. A cooperative assembly combination for ameliorated extrusion processing of resinous thermoplastic material comprising in a screw extruder apparatus:

(i) a barrel;

(ii) said barrel (i) having a first rearward end (A) and a second forward end (B);

(iii) means to provide a feed supply of thermoplastic resinous material to be processed to said first end (A) of said barrel (i);

(iv) means to discharge heat plastified thermoplastic resinous material from said second end (B) of said barrel (i);

(v) a hollow screw disposed within said barrel (i) and adapted to forward heat-plastified thermoplastic resinous material from said first end (A) to said second end (B) of said barrel (i), said screw containing and defining

(vi) a longitudinally-extending internal cavity having a generally cylindrical configuration;

(vii) a plug within the internal cavity (vi) adapted to divide said cavity in confined, separated fashion into

(viii) at least one heat-exchanging zone;

with

said heat-exchanging zone (viii) being disposed between said first end (A) and said second end (B) of said barrel (i) and having heat-exchanging fluid inlet and outlet conduits in operative connection with said heat-exchanging zone (viii) within said screw (E);

(ix) means for supplying and shutting off the supply of and venting a desired heat-exchanging fluid under pressure and at a selected wanted temperature into and out of said first heat-exchanging zone (h);

plus

the combined cooperative improvement comprised of;

(x) an expansible plug seal mechanism adapted to be fit and moved within said cavity (vi) of said screw (v),

said plug seal (x) having therein included at least one incompletely-enclosed and at least relatively cup-like member (xi) that is of a form and configuration which is so constructed and arranged with a centrally-contained interior void space therein as to be characterized in being;

resiliently deformable and flarable laterally outwardly activated when subject to and spreadingly urged by heat-exchange fluid under pressure when same is present centrally within said cup-like member (xi);

whereby the outer circumferential exterior surface(s) of each of said cup-like members (xi) are pressed against and in conforming sealing engagement with the internal wall surfaces of said cavity (vi) within the screw (v);

thus preventing substantial passage of heat-exchange fluid under pressure past or about the so-engaged and activated plug seal (x).

2. The assembly combination apparatus of claim 1 wherein there is only a single heat-exchanging zone (viii) therein;

and said heat-exchanging zone (viii) is situate in the internal cavity (vi) of said hollow screw (v) in the rearward portion of the screw which is disposed towards said rearward end (A) of said barrel (i);

with the forward portion of said screw which is disposed towards said forward end (B) of said barrel (i) being neutral and ambient with respect to its lack of heat-exchanging capability.

3. The assembly combination apparatus of claim 1 wherein there is only a single heat-exchanging zone (viii) therein;

and said heat-exchanging zone (viii) is situate in the internal cavity (vi) of said hollow screw (v) in the forward portion of the screw which is disposed towards the forward end (B) of said barrel (i);

with the rearward portion of said screw which is disposed towards said forward end (B) of said barrel (i) being neutral and ambient with respect to its lack of heat-exchanging capability.

4. An assembly combination apparatus in accordance with that of either claim 2 or claim 3, wherein each of said cup-like members (xi) is so oriented in said plug seal mechanism (x) so as to open in a direction that is facing and against the heat-exchanging zone (viii) within said internal cavity (vi) of the hollow screw (v).

5. A cooperative assembly combination which is in general accordance with that of claim 1 for ameliorated extrusion processing of resinous thermoplastic material comprising in a screw extender apparatus:

(a) a barrel;

(b) said barrel (a) having a first rearward end (b1) and a second forward end (b2);

(c) means to provide a feed supply of thermoplastic resinous material to be processed to said first end (b1) of said barrel (a);

(d) means to discharge heat plastified thermoplastic resinous material from said second end (b2) of said barrel (a);

(e) a hollow screw disposed within said barrel (a) and adapted to forward heat-plastified thermoplastic resinous material from said first end (b1) to said second end (b2) of said barrel (a), said screw containing and defining

(f) a longitudinally-extending internal cavity having a generally cylindrical configuration;

(g) a plug within the internal cavity (f) adapted to divide said cavity in confined, separated fashion into at least

(h) a first heat-exchanging zone; and

(i) a subsequent, minimally second heat-exchanging zone;

with said first heat-exchanging zone (h) being disposed towards said first end (b1) of said barrel (a); and

said second heat-exchanging zone (i) being disposed towards said second end (b2) of said barrel (a);

(j) heat-exchanging fluid inlet and outlet conduits in operative connection with said first heat-exchanging zone (h) within said screw (e);

(k) means for supplying and shutting off the supply of and venting a desired heat-exchanging fluid under pressure and at a selected wanted temperature into and out of said first heat-exchanging zone (h);

(l) heat-exchanging fluid inlet and outlet conduits in operative connection with said second heat-exchanging zone (i) within said screw (e);

(m) means for supplying and shutting off the supply of and venting a desired heat-exchanging fluid under pressure and at a selected wanted temperature into and out of second heat-exchanging zone (i);

plus

the combined cooperative improvement comprised of;

(n) an expansible plug seal mechanism adapted to be fit and moved with said cavity (f) of said screw (e),

said plug seal (n) having therein included at least one incompletely-enclosed and at least relatively cup-like member (o) that is of a form and configuration which is so constructed and arranged with a centrally-contained interior void space therein as to be characterizable in being;

resiliently deformable and flarable laterally outwardly activated when subject to and spreadingly urged by heat-exchange fluid under pressure when same is present centrally within said cup-like member (o);

whereby the outer circumferential exterior surface(s) of each of said cup-like members (o) are pressed tightly against and in conforming sealing engagement with the internal wall surfaces of said cavity (f) within the screw (e);

thus preventing substantial passage of heat-exchange fluid under pressure past or about the so-engaged and activated plug seal (n).

6. The assembly combination apparatus of claim 5, wherein said plug seal mechanism (n) contains at least a pair of oppositely-oriented cup-like members (o);

with each of the diversely oriented cup-like members (o) being respectively open in opposite directions that are individually correspondingly in separate directions that are facing and against the said respective heat-exchanging zones (h) and (i) within said internal cavity (f) of said hollow screw (e).

7. An assembly combination apparatus in accordance with that of either claim 1 or claim 5 and including, in addition thereto and in further combination therewith a

(p) slidable adjuster rod means extending longitudinally and reciprocally moveable within the defined longitudinally-extending hollow cavity (vi) or (f) of said hollow screw (v) or (e) for supporting said plug seal mechanism (x) or (n) at the internal end of said rod (p);

and moving said plug seal mechanism (x) or (n) to desired position location within the cavity upon reciprocating adjustment movement of said rod (p).

8. An assembly combination apparatus in accordance with that of claim 7, a conduit means formed and provided integral in and as part of said adjuster rod means for passing heat-exchange fluid therethrough into and out of a therewith connected heat exchange zone within the hollow screw of said extruder apparatus.

9. An assembly combination apparatus in accordance with that of either claim 1 or claim 5, wherein each cup-like member (xi) or (o) is a substantially unitary structure having a circumferential wall for engaging the internal cavity wall surfaces of the hollow screw.

10. An assembly combination in accordance with that of either claim 1 or claim 5, wherein each cup-like member (xi) or (o) is a two-piece structure having a piston-like substructure support of flexible metal about which there is circumferentially positioned a resilient washer ring band for engaging the internal cavity wall surfaces of the hollow screw.

11. An assembly combination in accordance with that of claim 10 wherein there is disposed a longitudinally splined construction in the piston-like substructure support of each cup-like member.

12. An assembly combination in accordance with that of either claim 1 or claim 5, wherein each of said plug seal mechanisms (x) or (n) is further characterizable in being free-floating and easily movable within the confines of the cavity void space of the hollow screw when not subject to fluid under pressure within the cavity.