US3700372A

US3700372A - Pump impeller molding apparatus

Info

Publication number: US3700372A
Application number: US887494A
Authority: US
Inventors: Donald P Lalley
Original assignee: March Manufacturing Co
Current assignee: March Manufacturing Co
Priority date: 1969-12-23
Filing date: 1969-12-23
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24

Abstract

Apparatus for molding a plastic pump impeller having an annular coupling magnet totally enclosed and sealed within a hub formation traversed by a shaft bore. The plastic melt is injected into a special mold having movable core and magnet-supporting parts and means for actuating the same in a time sequence such that the melt forms the impeller configurations at one end of the magnet while the shaft bore is temporarily blocked off. The melt is caused to flow about the external aspects of the magnet toward the distal end thereof and then to resume the flow with timed opening up of the shaft bore to line the latter and complete the total envelopment of the magnet in unitary joinder with the impeller.

Description

United States Patent Lalley PUMP IMPELLER MOLDING APPARATUS [72] Inventor: Donald P. Lalley, Elgin, Ill.

[73] Assignee: March Manufacturing Company,

Glenview, Ill.

[22] Filed: Dec. 23, 1969 [21] Appl. No.: 887,494

[52] [1.8. Cl. ..425/ 159, 425/249, 264/328 [51] Int. Cl. ..B29f 1/06 [58] Field of Search .1 8/30 WM, 30 WC, 30 UM, 36,

18/5 E, DIG. 10, DIG. 38; 249/142, 144

[56] References Cited UNITED STATES PATENTS 3,543,349 12/1970 Marocco 1 8/30 WC 2,469,l30 5/1949 Rodman Jr. 18/30 WM 51 Oct. 24, 1972 Primary Examiner--R. Spencer Annear Attorney-Canard Livingston [57] ABSTRACT Apparatus for molding a plastic pump impeller having an annular coupling magnet totally enclosed and sealed within a hub formation traversed by a shaft bore. The plastic melt is injected into a special mold having movable core and magnet-supporting parts and means for actuating the same in a time sequence such that the melt forms the impeller configurations at one end of the magnet while the shaft bore is temporarily blocked off. The melt is caused to flow about the external aspects of the magnet toward the distal end thereof and then to resume the flow with timed opening up of the shaft bore to line the latter and complete the total envelopment of the magnet in unitary joinder with the impeller.

14 Claims, 6 Drawing Figures PATENTEDucI 241912 SHEEI 1 OF 3 .INVEN'II'OR .D /7 hPLaZ/ y PATENTEDHIIT24 m2 3.700.372 sum 2 OF 3 f 4 INVENTDRA Z3404 v PUMP IMPELLER MOLDING APPARATUS Various methods have been proposed forprotecting internal pump-coupling magnets from corrosive action of circulated chemically active liquids, and conversely protecting the pumped liquids insensitive chemical and processing systems against even minute contamination by the pump body, and magnet materials.

According to one commercial construction an impeller is formed of molded plastic with shallow hub to which a separately encased coupling magnet is attached by cementing or suitable fusion of the material of the plastic envelope which encloses the magnet either partially or totally with a lined shaft bore. Such methods do not readily admit of the use of newly developed plastic materials which are so. highly acid and alkali proof at high temperatures that they are also immune to the solvent actions needed to bond a separately encased magnet to a separately formed impeller body.

In accordancewith another construction an impeller is unitized with the magnet by conformation of the impeller configuration with hub portions in which the magnet is simultaneously totally encased, inclusive of the shaft bore through the magnet. Such impellers have been especially made for corrosive and chemically sensitive environments by hand casting with subsequent machining ofthe cylindrical surfaces of the material which encloses the magnet in order to procure a very thin plastic wall section at the peripheral boundary of the annular magnet so that maximum magnetic coupling efficiency can be achieved. I

In accordance with the present disclosures, a production method and apparatus is afforded which permits use of the highly chemically resistant plastic materials and produces a very thin and uniform plastic section or skin-about the cylindrical aspects of the magnet, including a relatively thin section lining the shaft bore with no openings or leaks. l

Such a construction is achieved by use of the dis- .Closed mold means including movable parts in the mold cavities which are actuated in accordance with the methods and apparatus disclosed to cause the plastic melt to follow a certain path in a one-shot injection in a .way to leave the finished impeller free for automatic ejection when the mold opens.

More detailed aspects of novelty and utility characteristic of the invention relate to the process, construction and operation of the apparatus and utilized in its practice set out in the following description in view of the annexed drawings in which:

FIG. 1 is a vertical section through a centrifugal pumpof the magnetically coupled type utilizing a unitary plastic impeller and coupling magnet of the type produced by the present disclosures;

FIG. 2 is an enlarged sectional detail of the impeller of FIG. 1;

FIG. 3 is a front view of the impeller with its cover plate removed, looking from left to right at FIG. 2;

FIG. 4 is a plan view of the cover plate for the impeller of FIG. 3;

modified to coact with the special mold means and processing apparatus described.

FIG. 1 depicts a pump wherein the. pump body is formed entirelyof plastic material and comprises a housing section --A- and a separable closure section -B-. secured to the housing by bolt means --C-.

The housing section includes an inlet port 10 opening into an impeller chamber 11 from which leads an outlet port 12. The closure section has a flange portion 13 fitting in sealed relation to the housing to close off the impeller chamber, and a cylindrical well formation 14 extends integrally away from the chamber in coaxial alignment with the inlet bore.

The impeller proper, generallyindicated at 15, is situated to rotate in the impeller chamber and has a long hub portion 16 extending into the well, a large, annular coupling magnetl7 being sealed within the hub formation so that its outer cylindrical periphery can rotate free of, but in closest possible proximity to the inner periphery of the well in order to procure maximum magnetic couplingcoaction with an outer annular driving magnet 18 seated in a carrier 19 rotated about the well by motor means 20 i As seen inFIG. 3, the impeller configurations may take the form of approximately radially arcuate vanes 22 spaced about acentral shaft bore 23, and each vane v has on its upper edge spaced integral plastic studs 24 FIG. 5 is a fragmentary sectional view of molding apparatus employed in the fabrication of the impeller unit and its cover plate;

FIG. 6 is a schematic illustrative of a process by which the impellers can be molded in a one-shot operation in a known type of molding machine only slightly Inn:

which fitinto holes 25 in a matching cover plate 26 such as shown in FIG. 4. This cover plate is manually fitted onto the vanes withthe studs in corresponding holes and the heads of the studs are heat pressed and flared, as at 27 in FIG. 2, to secure the cover plate in position, said plate having a large central opening 28 to admit the pumped fluid from the port 10 in the assembly depicted in FIG. 1.

When the impeller comes from the mold it has no cover plate in position, and the vanes 22 will have the appearance seen in FIG. 3. However, the process admits of the simultaneous formation of a cover plate with each impeller, such cover plate being affixed in a later operation.

As seen in FIG. 2, the finished impeller has another added component in the form of an insert sleeve bearing 30 formed largely of graphite and having an end flange 31 serving as a thrust bearing in the assembled condition of the impeller with a fixed spindle 32, FIG. 1

The pump illustrated is of the larger type requiring a proportionately large composite coupling magnet actually formed by cementing two

annular magnet rings

34 and 35 together along the line 37, it being not presently commercially feasible to manufacture such large magnets as a monolithic body.

It is desirable in some instances to balance the impellers dynamically, and in the case of relatively large impellers of the type shown and weighing, for example, as much as 2 pounds, it becomes necessary to eliminate a large concentration of plastic in the region between the impeller proper and the proximate end of the magnet in order to prevent warpage and stresses in the hub due to unequal cooling, and accordingly a metallic filler body 36, which may be an annulus of aluminum, for example, is cemented to theaxial end of the magnet which will be proximate to the impeller itself. Before the impeller is completed by application of the insert bearing In FIG. 2 it will be observed that, apart from the in-:

serted graphite sleeve bearing 30, the bore through the annular magnet and filler bodies is fully lined with plastic material as at 33, so that the magnet and filler are totally shielded from any corrosive exposure, it being further observed that the shaft 32 in this type of pump is formed of inert ceramic material and will preferably be supported at both axial ends, one in a bearing seat 40 formed in the end wall of the magnet well 14, and the other shaft end in an insert bearing 41 which may be of plastic or ceramic material in the corrosion proof pumps, and is fitted into a web across the inlet duct or port 10.

A process suitable for forming the described impeller (less the sleeve bearing and an attached cover plate) may utilize a mold structure such as depicted in FIG. 5, which comprises rightand left-hand separable mold sections or components I and II adapted to meet in closure along a parting line III in the known construction of injection molds.

Within mold section I is a large mold cavity 50 defining most of the hub configuration of the impeller and opening at the right-hand side into the smaller cavity configurations 51 defining the head and impeller blades.

At the left-hand axial or distal end of the hub cavity is a mold wall portion 52 from which projects centrally and axially through the hub cavity into the impeller cavity, when the mold is closed, an elongated core and sleeve guide 53 over which telescopes a companion magnet-supporting sleeve element 54 attached at its remote end to the piston rod 55 of a hydraulic piston means 56 having inlet and outlet control-fluid ports 57 and 58.

When the mold is closed the free (left-hand) end of the hydraulically driven sleeve 54 will abut a shoulder 59 on the core and guide sleeve and complete, with the latter, a magnet-supporting rod structure of uniform diameter fitting into the bore of the annular magnet and

filler body assembly

34, 35, 36, which will be manually impaled upon the core guide before the mold At the upper region of both mold sections and very a close to the parting line, are further mold cavity configurations v70 defining a cover plate 26 for the impeller {of the type described in view of FIG. 4. The mold apparatus includes the usual knockout pins 71 and 72,

respectively, for the impeller and cover plates, which serve to eject these pieces when the knockout bar 73 is closes, the complementary supporting sleeve member 54 telescoping over the guide for the purposes aforesaid.

The left-handmold section I further includes a pin carrying member 60 attached to a plunger 61 actuated by a lever 62 connecting at 63 to the piston rod 64 of another hydraulic driving means 65 having inlet and outlet ducts 66, 67 for the hydraulic operating fluid.

The pin carrying member 60 is provided with a plurality of registry pins 68, of which there may be as many as eight arranged in a circle concentric with the bore axis of the impeller (only one being illustrated for clarity) and these pins are movable through the end wall 52 of the hub cavity to engage the distal axial end of the magnet to space the same slightly (for example, about 55' o'ne-thousandths of an inch) from the cavity wall so that the plastic melt can flow over this end of the magnet. At a certain time in the operation of the process, these registry pins will be withdrawn so that the melt can fill into the resulting spaces and holes.

automatically actuated in the known manner ing of the mold.

on open- The described mold blocks 1 and II are adapted to seat in a known type of molding machine caused to operate in accordance with the methods hereinafter described, and accordingly include the usual internal channeling and connections for circulation of coolant within the blocks, which will also include an injection or sprue bushing 74 surrounded by heating elements 75, together with an external injection nozzle seat 76 adapted to receive the molding machine injection nozzle 77.

The injected melt will pass from the injection duct 74A and fill into the impeller and cover cavities, respectively, via runner passages 74X and 74Z, it being observed that this melt will fill into the entire impeller configuration first, and then work around the outer periphery 69 of the inserted magnet assembly and thence around the distal axial end thereof, filling around the advanced registry pins 68 into the thin space between the end of the magnet and the cavity wall 52 determined by the slight projection of said pins.

At this juncture-in the process, the registry pins will be automatically withdrawn so that the melt can then complete coverage of the end of the magnet and work into the shaft bore, from which it will have been theretofore substantially blocked owing to the presence of the retractable supporting sleeve element 54. Shortly following withdrawal of the registry pins-68, the supporting and filler sleeve means 54 will be retracted by actuation of the hydraulic cylinder 56, the timing here being such, in conjunction with the temperature maintained in the mold blocks, that the very thin wall section of plastic surrounding the magnet periphery at 69 can harden sufficiently to support the magnet notwithstanding withdrawal of the sleeve 54, the mold being opened upon conclusion of a curing cycle, determined by the usual machine clocks for a duration of about 1% minutes, with the sleeve fully withdrawn so that ejection of the completed impeller body and cover can be started in the known manner by advance of the machine knockout pins 71, 72, before the mold is fully open.

As will appear more fully from the following description of the operation of the process, the registry pins and supporting sleeve will be automatically reset to their respectively advanced positions as a function of the conclusion of the molding cycle.

The schematic diagram of FIG. 6 depicts part of a form of conventional molding machine and its control equipment adapted to receive the mold means l-II of FIG. 5, together with a process control system working in conjunction with certain timed operations of such a machine to effectuate the method of making the impeller, reference characters heretofore introduced being repeated where appropriate, and it being assumed that the two mold sections l and II, described in view of FIG. 5, have been bedded in such machine in the known manner.

A molding cycle may be started after one of the mag- .net assemblies has been placed by the attendant over the combination core and sleeve rod 53 while the mold stands open, following which the attendant will shut the usual glass safety door 78 to initiate the machine cycle by closure of the usual door safety switch 80, thereby causing actuation of the machine injection control means 81 to operate the closing ram 82 and move the mold section 1 into closure with the companion section II, which in turn will cause closure of the usual forward limit switch means 83 to actuate a master machine relay means 84 permitting the melt to be injected through the machine nozzle 77.

As previously mentioned, the registry pins 68 and the magnet supporting sleeve 54 are respectively standing in advanced condition before the mold closes, and when the forward limit switch 83 is actuated by closure of the mold to pull in the master relay 84, the latter also operates a reset relay means 85 forming part of the process control system and the reset relay causes a holding relay means 86 to operate and lock itself in.

Reset relay 85 starts a timing means including two conventional clock switches 87 (T-l) and 88 (T-2), the timing of T-l being such as to allow an interval in which the melt can work entirely into the space about the distal end of the magnet determined by the advanced condition of the registry pins 68; and at the conclusion of this interval, timer T-l will start the hydraulic pump means P-l to activate piston means 65, and cause retraction of the registry pins 68 so that the melt can fill the holes left thereby. A pressure limit switch 90 will automatically stop pump P-l when the pins are fully withdrawn.

A few tenths of a second following withdrawal of the registry pins, clock switch T-2 will start the second hydraulic control pump means P-2 and activate the sleeve hydraulic piston means 56 to retract the magnet supporting sleeve 54, this pump being automatically stopped by another pressure limit switch means 91.

At the time the registry pins are withdrawn, as aforesaid, the plastic skin or sheath about the outer cylindrical periphery of the magnet assembly will be sufiiciently hard, owing to the very thin section thereof and the maintained temperature of the mold, to support the magnet while the sleeve means 54 retracts its support, and about the time the pressure limit switch means 91 for pump P-Z stops this pump, the usual machine clock system will, in known manner, have .completed the curing and cooling phase of the conventional machine cycle (as distinguished from the process cycle)'and cause the ram thereby to reverse and open the mold, the forward injection switch 83 thereby dropping out the Master Machine Relay 84 and the Reset Relay 85 and causing timer T-l to reset automatically and close normal contacts which will start pump P-l again in reverse, so that the registry pins are once again advanced into the mold cavity as a function of the opening of the mold, this pump P-l being stopped again by another pressure limit switch means 90X.

Movement of the mold into fully open position causes operation of a special Process Reset Switch'92, provided for control of the process, and actuated by the mold on full opening thereof, to drop out the hold relay means 86 and thereby reset the second timer T-2, which in turn will reverse (through normal contacts,

part thereof) the second pump P-2 causing the magnet supporting sleeve to be restored to advanced position, this pump being automatically stopped by its pressure limit switch means 91X, thereby terminating the process cycle with the mold standing open in readiness for application of another magnet assembly and initiation of a new molding cycle, the molded impeller and its cover plate being automatically ejected into a suitable receptacle in known manner by action of the knockout pins 71, 72 attendant upon the terminal operations of the machine, beginning with the opening of the mold.

Thus the process provides for actuation of certain movable mold components in a certain timed coaction with the basic machine molding cycle to effect the steps of a method in which the melt is flowed progressively or in stages to form certain initial configurations, and the melt is then caused to flow outwardly over external aspects of the conjoined magnet and subsequently into and through internal aspects thereof defining the shaft bore, in timed dependence upon the timed movements of the movable mold elements and pre-hardening of thin-walled sections of the envelope about the magnet.

The time cycle of the illustrative arrangement and operation is substantially the cycle of the molding machine from the time the safety door is closed to initiate the cycle until the mold again stands open. A typical cycle may be of 2 minutes or 120 seconds duration, in which the first second is utilized for the fill, which is very rapid under the high pressures usually employed in such machines, and of this 1 second, about 0.4 second is used to retract the registry pins and normally 0.6 second for retracting the sleeve, although different runs may extend this latter interval to as much as 0.8 to 1 second. As much as seconds may be allotted to curing and cooling, and 3 seconds allowed for ejection of the object by the knockout pins, with a final 6 seconds for hydraulic resetting of the registry pins and sleeve.

The process may employ either thermoplastic or therrnosetting materials, a very satisfactory material for fabrication of the described pump impellers being a thermoplastic of the class of polypropylenesuch, for example, as the proprietary material known as Penton (Hercules Powder Co.).

In general, the apparatus and method are not limited to the fabrication of pump impellers, but may be employed for production molding of a variety of other items required to have totally included therein some other object having a melting point unaffected by the temperature and pressure conditions required for the principal item or form, where the included object has a perforation, bore, or other configuration compatible with support thereof by the compound core means disclosed; and accordingly no limitations are intended or implied in the foregoing illustrative description except as may attend the appended claims.

Iclaim:

1. Mold means adapted to receive an injected plastic melt for forming as a unitary body a pump impeller having a through bore for a shaft, together with an annular magnet totally sealed therein concentrically with said bore, said mold means comprising a mold structure including separable mold sections having respective cavity configurations defining said body in the closed condition thereof; compound core means for the shaft bore comprising elongated and respectively fixed and movable core members the movable one of which is adapted to telescope with the fixed member in said closed condition, the fixed core member projecting from a particular wall portion of the cavity configurations in one of said sections, and the movable core member being carried at one supported end thereof in the other section by movable means operative to advance and retract such core member axially into and from telescoped interfit with the fixed member, said core members being spaced apart in the separated open condition of the mold sections to admit placement of a magnet annulus upon the fixed member, said movable core member in the advanced condition thereof being moved into interfit with the fixed'member by closure of the mold sections to complete a core structure defining said shaft bore and blocking off entry of the melt therein; the supported magnet having an axial end proximate to the impeller configurations of said body and a distal end remote therefrom and confronting said particular wall portion of the mold cavity, said particular wall portion communicating with adjoining cavity portions surrounding the outer cylindrical aspect of the magnet such that the melt can progress from said aspect to fill over said distal end; duct means for admitting and guiding injected plastic melt into the mold structure in a general direction to fill into the impeller configurations at the proximate end of the magnet and progress over said cylindrical aspect and thence over said distal end thereof with a tendency to move finally into the bore from which it is blocked, however, by the presence of the interfitted movable core member until the latter is withdrawn; registry means including at least one registry member movable for advance into and retraction from a registry position between said particular mold wall portion and the distant end of the magnet to space the latter for filling of the melt thereover as aforesaid; and actuating means operable to move said movable core member and said registry means independently to and from the respective advanced and retracted positions thereof.

2. Apparatus according to claim 1 wherein the advanced position of said registry member and direction of progress of the melt is such as to have a tendency to force the magnet and the distal end thereof in an axial direction against said member whereby to afford a uniform cavity space thereat and consequent uniform wall thickness of the plastic over said distal end of the magnet.

3. Apparatus according to claim 1 further characterized in that there are a plurality of said registry members arranged about the axial center of the shaft bore at said distal end of the magnet and said members are jointly movable by the appertaining actuating means in approximate parallelism with the axis of the shaft bore in moving into and from said advanced and retracted registry position thereof.

4. Apparatus according to claim 1 wherein said elongated fixed core member is mounted at one end upon said particular wall portion concentrically with the center of the axis of the shaft bore and said registry .member is a pin reciprocable in said particular wall portion at a location disposed radially of said center for movement as aforesaid.

5. Apparatus according to claim 1 wherein said actuating means comprises separate reversible hydraulic piston devices respectively having driving connection with one of said registry members and movable core members and respectively operative to move the same in the manner and for the purposes aforesaid.

6. Apparatus according to claim 5 wherein the hydraulic piston devices respectively driving the re gistry means and movable core member are contained within the appertaining mold sections.

7. Mold means in accordance with claim 1 wherein said mold sections meet along a parting line which intercepts the cavity configurations defining the impeller configurations of said body, and said melt-admitting and guiding duct meanshas an injection entry in the mold section having the movable core member communication through duct passages along said parting line into said impeller defining cavity configurations, such that in the closed condition of the sections the melt first enters said last-mentioned configurations to fill the same and then progresses therefrom over the cylindrical aspects to the distal end of the magnet supported on the core means as aforesaid.

8. Molding apparatus for forming a principal plastic object by injection of a melt into a mold cavity, said object having totally included therein a second and previously formed object of a character which will not be materially affected by the temperature required for the melt, said apparatus comprising relatively separable mold members cooperatively defining a cavity formation for the configuration of the principal object in closed condition of the mold members; and an elongated compound core structure comprising relatively fixed and movable elongated core members, one of which is fixed at one end in one of said mold members and projects axially into a part of said cavity formation, and the other of which is carried by the remaining mold member in axial alignment with the fixed core member, one said core member telescoping with the other; drive means operatively associated with the mold member having the movable core member and operative to move said movable core member into and withdraw it from telescoped relation with the fixed core member in the closedcondition of said mold members, at least; said movable core member being adapted to support said second object in withdrawn condition and carry the same with it in telescoping with the fixed core member to dispose the second object in a predetermined position in said cavity formation in the closed condition of the mold members; and means for guiding melt in said closed mold members into said cavity formation along a predetermined path to form the principal object and partly envelope the second object while the core members are in telescoped relation, and thereafter permit completion of the flow of the melt responsive to withdrawal of the movable core member from telescoped relation with the fixed member by actuation of said drive means while the mold members are still in closed condition, whereby to complete the principal object with total envelopment thereby of the second object.

9. Apparatus according to claim 8 further characterized in that said drive means is hydraulically actuated and contained within that one of the mold members which has the movable core member.

10. Apparatus according to claim 8 further characterized in that a movable registry member is included as apart of the particular mold member having the fixed core member, together with second drive means operatively associated with said particular mold member and operative to move said registry member to and from engagement with said second object in the telescoped relation of said core members to space said second object a predetermined distance from a part of said cavity formation and thereby determine a portion of said predetermined flow path.

11. Apparatus according to claim 10 wherein the respective drive means comprises reversible hydraulically driven piston means having connection with said movable core member and registry member for respectively actuating the same in the manner and for the purposes set forth.

12. In a mold for forming a principal object from a plastic melt injected therein under pressure and having a secondary object wholly contained therein, separable mold members defining a forming cavity for the principal object in their closed relation; a first elongated core member affixed at one end to one of said mold members and projecting with a free end into said cavity; a second core member having one end mounted in the other said mold member and a tubular portion extending to a free end thereof and movable axially onto and from closing telescoped engagement with the first core member over the free end thereof to block flow about said first core member, said movable core member being adapted to support said secondary object by placement of the latter thereon in the open condition of said mold members, said supported secondary object being disposed in a predetermined position in said cavity in closing telescoped relationship of the movable core member as aforesaid in the closed condition of the mold members; and means in one of said mold members, at least, directing injected plastic melt along a predetermined flow path into said cavity to form said principal object and cover outer portions of the supported secondary object not blocked by said telescoped core members; and reversely operable actuating means cooperable with the supporting means for the movable core member and operative to move the latter to and from telescoped relation with the fixed core member such that said melt can fiow about the fixed core member responsive to withdrawal of the movable core member from closing telescoped engagement as aforesaid to complete the formation of the principal object with total envelopment of the secondary object.

13. Apparatus for molding a plastic pump impeller having a shaft bore and an annular coupling magnet sealed within its confines in concentricity with said bore, which comprises supporting means for the magnet including a core means in the cavity of a mold having a fixed elongated core rod and a coaxially movable core rod with hollow portions telescoping onto the fixed rod, said magnet being supported upon the hollow one of said rods in the separated condition thereof, means operative to bring said rods into telescoped relationship to afford support along the bore of the magnet annulus and to define a shaft bore for the impeller; means guiding flow of injected plastic melt into said c avit in a raegion thereof defining im ller configuratrons ocate at a proximate axial end 0 the magnet to flow progressively along the outer cylindrical aspects thereof and onto the opposite distal end of the magnet; means spacing said distal end of the magnet temporarily from a wall of the cavity to permit the melt to cover said distal end, means operative in timed relation to said melt flow to withdraw the movable core member from telescoped engagement with the fixed core member to permit further flow of the melt into the shaft bore about the fixed core member as the movable core member retreats whereby -to line said bore and complete the total envelopment of the magnet as a wholly contained part of the impeller.

14. Apparatus for molding a plastic pump impeller of the type comprising a body having impeller configurations situated at one axial end of a hub configuration and an annular coupling magnet totally contained and sealed within said hub configuration and a shaft bore extending through a distal axial end of the hub configuration and the magnet annulus and through the opposite axial end of the magnet annulus which is proximate to the impeller configurations and which opens through the latter configurations, said apparatus comprising an elongated core member in the impeller-forming molding cavity formed by complementary separable and closable mold sections, the core member comprising separable coaxial relatively telescoping portions concentric with the required shaft bore and axially separable by movement of the movable one of the core members and also by opening movement of the appertaining mold section on separation from the companion section, means guiding injected plastic melt along a predetermined path within said mold sections in closed condition, said path leading first into impeller forming configurations of said cavity and thence about the outer cylindrical aspects of the magnet annulus to the distal end thereof; means spacing said distal end of the magnet from a wall portion of the cavity to form a plastic coating over said distal end; and means operative to separate the movable core member from the fixed core member to admit movement of the melt for full flow about the fixed core member thereby coating the inner the magnet annulus and defining a fully plastic lined shaft bore passage through the entire impeller.

UNITED swi'ss ?A'IE'NT ewes CERTIFICATE 6F CGBREC'I'ION Patent No, 3,700,372 Dated October 2a, 1972 Donald P, Leliey 1-2; is certified that errer appears in the above- Mentified Letters Patent and that said Letters Petewt are hereby corrected as shown below:

(301mm 10 line 53 (Claim 111), after "inner", insert Me-periphery of,

Signed and sealed this 29th day of May 1973.

(SEAL) Attes't:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer v v Commissioner of Patents

Claims

1. Mold means adapted to receive an injected plastic melt for forming as a unitary body a pump impeller having a through bore for a shaft, together with an annular magnet totally sealed therein concentrically with said bore, said mold means comprising a mold structure including separable mold sections having respective cavity configurations defining said body in the closed condition thereof; compound core means for the shaft bore comprising elongated and respectively fixed and movable core members the movable one of which is adapted to telescope with the fixed member in said closed condition, the fixed core member projecting from a particular wall portion of the cavity configurations in one of said sections, and the movable core member being carried at one supported end thereof in the other section by movable means operative to advance and retract such core member axially into and from telescoped interfit with the fixed member, said core members being spaced apart in the separated open condition of the mold sections to admit placement of a magnet annulus upon the fixed member, said movable core member in the advanced condition thereof being moved into interfit with the fixed member by closure of the mold sections to complete a core structure defining said shaft bore and blocking off entry of the melt therein; the supported magnet having an axial end proximate to the impeller configurations of said body and a distal end remote therefrom and confronting said particular wall portion of the mold cavity, said particular wall portion communicating with adjoining cavity portions surrounding the outer cylindrical aspect of the magnet such that the melt can progress from said aspect to fill over said distal end; duct means for admitting and guiding injected plastic melt into the mold structure in a general direction to fill into the impeller configurations at the proximate end of the magnet and progress over said cylindrical aspect and thence over said distal end thereof with a tendency to move finally into the bore from which it is blocked, however, by the presence of the interfitted movable core member until the latter is withdrawn; registry means including at least one registry member movable for advance into and retraction from a registry position between said particular mold wall portion and the distant end of the magnet to space the latter for filling of the melt thereover as aforesaid; and actuating means operable to move said movable core member and said registry means independently to and from the respective advanced and retracted positions thereof.

4. Apparatus according to claim 1 wherein said elongated fixed core member is mounted at one end upon said particular wall portion concentrically with the center of the axis of the shaft bore and said registry member is a pin reciprocable in said particular wall portion at a location disposed radially of said center for movement as aforesaid.

6. Apparatus according to claim 5 wherein the hydraulic piston devices respectively driving the registry means and movable core member are contained within the appertaining mold sections.

7. Mold means in accordance with claim 1 wherein said mold sections meet along a parting line which intercepts the cavity configurations defining the impeller configurations of said body, and said melt-admitting and guiding duct means has an injection entry in the mold section having the movable core member communication through duct passages along said parting line into said impeller defining cavity configurations, such that in the closed condition of the sections the melt first enters said last-mentioned configurations to fill the same and then progresses therefrom over the cylindrical aspects to the distal end of the magnet supported on the core means as aforesaid.

8. Molding apparatus for forming a principal plastic object by injection of a melt into a mold cavity, said object having totally included therein a second and previously formed object of a character which will not be materially affected by the temperature required for the melt, said apparatus comprising relatively separable mold members cooperatively defining a cavity formation for the configuration of the principal object in closed condition of the mold members; and an elongated compound core structure comprising relatively fixed and movable elongated core members, one of which is fixed at one end in one of said mold members and projects axially into a part of said cavity formation, and the other of which is carried by the remaining mold member in axial alignment with the fixed core member, one said core member telescoping with the other; drive means operatively associated with the mold member having the movable core member and operative to move said movable core member into and withdraw it from telescoped relation with the fixed core member in the closed condition of said mold members, at least; said movable core member being adapted to support said second object in withdrawn condition and carry the same with it in telescoping with the fixed core member to dispose the second object in a predetermined position in said cavity formation in the closed condition of the mold members; and means for guiding melt in said closed mold members into said cavity formation along a predetermined path to form the principal object and partly envelope the second object while the core members are in telescoped relation, and thereafter permit completion of the flow of the melt responsive to withdrawal of the movable core member from telescoped relation with the fixed member by actuation of said drive means while the mold members are still in closed condition, whereby to complete the principal object with total envelopment thereby of the second object.

10. Apparatus according to claim 8 further characterized in that a movable registry member is included as a part of the particular mold member having the fixed core member, together with second drive means operativelY associated with said particular mold member and operative to move said registry member to and from engagement with said second object in the telescoped relation of said core members to space said second object a predetermined distance from a part of said cavity formation and thereby determine a portion of said predetermined flow path.

12. In a mold for forming a principal object from a plastic melt injected therein under pressure and having a secondary object wholly contained therein, separable mold members defining a forming cavity for the principal object in their closed relation; a first elongated core member affixed at one end to one of said mold members and projecting with a free end into said cavity; a second core member having one end mounted in the other said mold member and a tubular portion extending to a free end thereof and movable axially onto and from closing telescoped engagement with the first core member over the free end thereof to block flow about said first core member, said movable core member being adapted to support said secondary object by placement of the latter thereon in the open condition of said mold members, said supported secondary object being disposed in a predetermined position in said cavity in closing telescoped relationship of the movable core member as aforesaid in the closed condition of the mold members; and means in one of said mold members, at least, directing injected plastic melt along a predetermined flow path into said cavity to form said principal object and cover outer portions of the supported secondary object not blocked by said telescoped core members; and reversely operable actuating means cooperable with the supporting means for the movable core member and operative to move the latter to and from telescoped relation with the fixed core member such that said melt can flow about the fixed core member responsive to withdrawal of the movable core member from closing telescoped engagement as aforesaid to complete the formation of the principal object with total envelopment of the secondary object.

13. Apparatus for molding a plastic pump impeller having a shaft bore and an annular coupling magnet sealed within its confines in concentricity with said bore, which comprises supporting means for the magnet including a core means in the cavity of a mold having a fixed elongated core rod and a coaxially movable core rod with hollow portions telescoping onto the fixed rod, said magnet being supported upon the hollow one of said rods in the separated condition thereof, means operative to bring said rods into telescoped relationship to afford support along the bore of the magnet annulus and to define a shaft bore for the impeller; means guiding flow of injected plastic melt into said cavity in a region thereof defining impeller configurations located at a proximate axial end of the magnet to flow progressively along the outer cylindrical aspects thereof and onto the opposite distal end of the magnet; means spacing said distal end of the magnet temporarily from a wall of the cavity to permit the melt to cover said distal end, means operative in timed relation to said melt flow to withdraw the movable core member from telescoped engagement with the fixed core member to permit further flow of the melt into the shaft bore about the fixed core member as the movable core member retreats whereby to line said bore and complete the total envelopment of the magnet as a wholly contained part of the impeller.