US3237247A

US3237247A - Rotational casting apparatus

Info

Publication number: US3237247A
Application number: US322287A
Authority: US
Inventors: Jr Walter S Eggert; Harry M Russell-French
Original assignee: Budd Co
Current assignee: ThyssenKrupp Budd Co
Priority date: 1963-11-08
Filing date: 1963-11-08
Publication date: 1966-03-01
Anticipated expiration: 1983-03-01
Also published as: DE1454975B1

Description

March '1966 w. s. EGGERT, JR., ETAL 3,237,247

ROTATIONAL CASTING APPARATUS Filed Nov. 8, 1963 2 Sheets-Sheet 1 Fig.2

62 CENTRIFUGAL FAN INVENTORS WALTER S. EGGERT, JR. HARRY M. RUSSEL-FRENCH I6 60 M Qh UQLJK March 1, 1966 w. s. EGGERT, JR., ETAL 3,237,247

ROTATIONAL CASTING APPARATUS Filed Nov. 8, 1965 2 Sheets-Sheet 2 INVENTORS WALTER S.EGGERT,JR. BY HARRY M. RUSSE L- FRENCH ATTORNEY United States Patent 3,237,247 ROTATIONAL CASTING APPARATUS Walter S. Eggert, Jr., and Harry M. Russell-French, Philadelphia, Pa., assignors to The Budd Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Nov. 8, 1963, Ser. No. 322,287 Claims. (Cl. 18-26) This invention relates to apparatus for rotationally casting hollow objects of moldable materials such as synthetic resins.

A conventional way of making hollow plastic objects is by rotational molding or casting techniques wherein a charge of a moldable material is placed in a hollow mold that is simultaneously rotated about a plurality of axes and heated to set the material in a relatively uniform coating deposited inside the mold. The present invention is directed to rotational casting apparatus that is designed to carry out such a process, the apparatus comprising a rotary casting machine for rotating the mold and an oven for heating the mold, and one of the objects of the invention is to provide a novel rotary casting machine and oven that is easy to use, versatile, and can be operated to mold materials of diiferent molding characteristics.

Another object of the invention is to provide rotational casting apparatus wherein a mold is loaded and unloaded outside of an oven yet it can be readily placed in the oven and rotated to carry out steps of the molding process.

Still another object of the invention is to provide a novel rotary casting machine for rotating a mold within an oven wherein the casting machine comprises electric motors that are disposed outside of the oven for operation at room temperature.

A further object is to provide a novel forced circulation oven which provides rapid temperature changes within the oven.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of rotational casting apparatus embodying the invention;

FIG. 2 is a vertical elevational view, generally along lines 22 of FIG. 3, partly in section, looking towards the inside of the front of the oven and;

FIG. 3 is an enlarged vertical, longitudinal, sectional view, with portions removed, taken generally on lines 33 of FIG. 2.

Referring now to the drawings, the illustrated rotational casting apparatus comprises a hollow, sectional mold 10, a rotary casting machine 11, and an oven 12. The shape of mold 10 and the manner in which it is mounted and rotated is dependent, obviously, 0n the shape of the article being formed. For simplicity of illustration, mold 10 is shown as a cylindrical mold formed in two detachable section-s having a longitudinal parting line. Such a mold is designed to form a hollow cylinder.

The purpose of rotary casting machine 11 is to support and rotate mold 10 about a plurality of mutually perpendicular axes that intersect within the mold. To accomplish this, machine 11 comprises a rotary head 13 mounted on a base or carriage 14 having a plurality of Wheels 15 that roll on guiding rails 16 which extend perpendicularly to and in front of oven 12. Carriage 14 further comprises a base plate 17 on which is mounted, in addition to wheels 15, a vertical pin 18 having its lower end welded into a hole in the center of plate 17. The lower end of pin 18 extends through an annular, upwardly facing thrust bearing 19 that engages and supports the lower end of a rotatable, vertical sleeve 20 fitted over pin 18 for rotation about the axis thereof. The upper end of sleeve 20 carries a pair of

cylindrical arms

21 and 22 whose axes are coplanar with the axis of sleeve 20 and pin 18. Using the front of the oven as a reference, that is, the face of the oven facing to the left as viewed in FIG. 1, it will be seen that arm 21 extends rearwardly of sleeve 20 and arm 22 extends forwardly, the free ends of these arms carrying a yoke 23 and an adjustable socket or gripper 24, respectively.

Rotary head 13 comprises a tubular cylindrical housing 26 that is pivotally attached by trunnions 27 at the rear end of the housing to yoke 23 for pivotal movement about a horizontal axis extending through trunnions 27. The other end of housing 26 has a pair of dependent lugs 28 pivotally connected to the upper end of a downwardly extending rod 29 that passes through and is detachably secured to gripper 24. By loosening and tightening gripper 24, arm 29 can be moved vertically to rotate or pivot housing 26 and rotary head 13 to the desired angular position. In the illustrated embodiment, the range of angular adjustment is approximately thirty-five degrees from a horizontal position and an inclined position. Obviously, this range can be varied to suit the particular application desired.

Rotary head 13 further comprises a main tubular cylindrical drive shaft 30 rotatably supported, by suitable bearings, in housing 26 in coaxial relationship thereto. The length of shaft 30 is greater than the length of housing 26 and the ends of shaft 30 extend beyond the ends of housing 26. The front end of shaft 30 carries a sprocket driven by a chain 32, that in turn, is driven by a sprocket connected to the output shaft of a variable speed, integral gear box and electric motor 33 mounted on a support plate 34 Welded to the upper front end of housing 26, the gear box having an overriding clutch permitting manual rotation in the direction opposite to the driven direction.

The rear end of shaft 30 is connected to a transversely extending arm 35 of rectangular tubing, having a counterweight 36 attached to one of its ends and a tubular, rearwardly extending arm 37 attached to its other end. Arm 37 supports, at its rear end, a yoke 38 that rotatably supports a rotary shaft 39 having a mold mounting plate 40 attached to its radially inner end. Mold 10 comprises a U-shaped mounting member 41 that is mounted on plate 40 by suitable releasable fasteners, e.g., bolts, and supports mold 10 so that the axes of rotation of

shafts

30 and 39 pass through the center of the mold and intersect each other at right angles.

Shaft 39 is rotated about its own axis by a bevel gear 43 mounted thereon, the bevel gear being engaged with another bevel gear 44 mounted on a shaft 45 that is rotatably mounted coaxially to and within arm 37. At its front end shaft 45 carries a sprocket driven by a chain 46 which, in turn, is driven by a sprocket carried on the rear end of a drive shaft 47 rotatably mounted within and coaxial to shaft 30. Drive shaft 47 is longer than shaft 30 and its ends project beyond the ends of shaft 30. The front end of shaft 47 carries a sprocket driven by a chain 49 connected to a sprocket carried by the output shaft of a variable speed gear box and electric motor 49 mounted on plate 34 alongside motor 33, the gear box having a manual override. C-

hains

32 and 49 and the sprockets can be covered by a protective cover 50.

Motors

33 and 49 can be separately or simultaneously operated to rotate mold 10 about the axis of shaft 30 and about the axis of shaft 39, respectively.

Carriage 14 further supports a flat, vertical enclosure member or oven panel 52 by means of a support plate 53 and an angle plate 54 mounted on sleeve 20 and bolted to a pair of vertically-spaced, angle members 55 attached to the panel. Panel 52 has a first opening 56 through which arm 21 passes, the opening being shaped to seal as much as possible the space around the arm where it passes through the panel. The panel also has a second opening 57 vertically spaced above opening 56 through which housing 26 passes, this opening being shaped to permit angular adjustment of head 13. Opening 57 is partially sealed by an adjustable seal comprising two, vertically sli-

d'able plates

58 and 59 mounted in tracks on opposite sides of the panel and adjustable vertically so that their adjacent edges, cut out to conform to the exterior of housing 26 as much as possible, abut housing 26.

Oven 12 is an electrically-heated, forced-air oven and is suported by a plurality of legs 60 above the floor whereby rails 16 and carriage 14 extend beneath, in the manner illustrated in the drawings, when the panel is in place. As best seen in FIG. 2, oven 12 has a main heating chamber 61 in which mold is rotated and heated and through which forced air is circulated by means of a centrifugal fan 62. The circulated air is heated by an electric resistance heater 63 placed at the outlet of fan 62 and the inlet into chamber 61, and an electric resistance heater 64 mounted at the outlet of the chamber 61. Mounted above heater 64 are a plurality of arcuate deflectors 65 that aid circulation of the air through the oven.

Oven 12 further comprises a fresh air inlet 66 and an exhaust outlet 67 connected to a suitable exhaust stack 68. The flow of air through the inlet and outlet is controlled by a movable valve member or damper 69 that is movable, upon actuation of a handle 71, between the positions shown in full lines and dotted lines in FIG. 2 to recirculate air through or dump air from the heating chamber. The controls for the centrifugal fan and heaters can be contained in suitable control boxes 70 mounted on the outside of the oven.

Mounted on the front of the oven are two

doors

72 and 73 hinged for rotation about vertical axes. The doors are laterally spaced to define an opening which panel 52 is adapted to cover when it is in the position illustrated in the drawings.

Doors

72 and 73 support a pair of hooks 74 that cooperate with a latch bar 75 to allow

doors

72 and 73 and panel 52 to be locked to close the front of chamber 61,

Operation At the start of a molding cycle, carriage 14 is rolled away from oven 12 to a position where the rotary head 13 can be pivoted to a loading station at one side of the tracks where mold is attached to the casting machine. The mold can be either charged prior to attaching or after it has been attached with a charge of a moldable plastic material. Thereafter, the sleeve 20/ is rotated back to the position where panel 52 extends parallel to the front of the oven. Then, carriage 14, is rolled along rails 16 until panel 52 abuts the oven,

doors

72 and 73 are shut, and latch bar 75 is placed in position to lock the doors and panel. Next,

motors

33 and 49 are actuated to rotate mold 10 in the desired manner and the centrifugal fan 62 and

heaters

63 and 64 are energized to circulate heated air through chamber 61. During the heating cycle, valve member 69 is located in the position shown by full lines in FIG. 2 so that air is merely recirculated through the oven. As the material is heated and as it passes over the inner surfaces of mold 10, it sets, in a manner dependent on the particular material. After the material initially sets, the rotation can be stopped and the mold kept in the oven until the material fully sets such as by polymerizing. Thereupon,

heaters

63 and 64 can be deenergized and valve member 69 is rotated to the position shown in the dotted lines whereupon cool air is sucked into the oven through inlet 66 and is blown through chamber 61,.outlet 67 and stack 68. When the oven and mold have been cooled sufiiciently, the centrifugal fan is stopped, latch bar is removed, and the carriage is withdrawn or moved away from the oven. Thereupon, the mold along with the formed object, are removed.

Although it will be apparent that the apparatus can be used to rotationally cast a wide variety of materials and synthetic resins, such as the vinyl polymers, polyethylene, etc. the particular apparatus disclosed was designed for rotationally casting caprolactum which upon polymeriza tion produces nylon-6. With this particular material, the oven was designed to circulate air at a maximum rate of 5,000 cu. ft. per minute, at a pressure head of p.s.i. and at a maximum temperature of 500 F. To achieve such temperatures, heaters were provided having capacities of 15.3 kw. and 25.5 kw.

While only a single embodiment has been illustrated, it will be apparent to those skilled in the art that many changes can be made in the details and arrangement of parts without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. In apparatus for rotationally casting a hollow plastic object in a hollow sectional mold, the combination comprising: an oven provided with a heating chamber and an opening communicating with the said chamber; a base disposed adjacent to said oven; an enclosure member mounted on said base and adapted to close said opening; and a rotary casting machine mounted on said base and extending through said enclosure member, said machine comprising rotatable support means located on one side of said enclosure member and adapted to support and rotate the mold in said chamber about a plurality of axes, and motor means mounted on the other side of enclosure member and operatively connected for rotating said support means.

2. The combination of claim 1 wherein said base comprises a wheled carriage moveable toward and away from said oven, and said oven comprises means for locking said enclosure member in place so as to prevent movement of said carriage and enclosure member away from said opening.

3. Rotational casting apparatus, comprising: an oven provided with a heating chamber, an opening extending into said chamber, means for circulating air through said chamber, and means for heating air circulated through said chamber; guide rail means disposed adjacent to said oven and aligned with said opening; a carriage mounted on said guide rails means for movement relative to said oven between a first position spaced from said oven and a second position adjacent to said oven; an oven panel mounted on said carriage and adapted to close said opening when said carriage is in said second position; and a rotary casting machine mounted on said carriage and adapted to support a mold on one side of said panel for rotation about a plurality of axes, said rotary machine extending through said panel and comprising motor means located on the other side of said panel and operatively connected for rotating said mold.

4. Rotational casting apparatus comprising: an oven provided with a main heating chamber and an opening communicating with said chamber; a carriage mounted for movement towards and away from said opening; an

oven panel mounted on said carriage and adapted to close said opening on movement of said carriage theretowards; and a rotary machine mounted on said carriage and adapted to support and rotate a mold in said heating chamber, said machine comprising mounting means for the mold disposed on one side of said panel, motor means disposed on other side of said panel, a housing extending through said panel, and means driven by said motor means for driving said mounting means and extending through said housing.

5. In an apparatus for rotationally casting, the combination comprising: a forced air, electric resistance oven having a main heating chamber and an opening communicating directly with said chamber; a rotary casting machine adapted to support and rotate a mold about a plurality of mutually perpendicular axes in said chamber, said rotary casting machine having a housing extending through said panel, motor means mounted on one end of said housing, a mold mount, and means connected to said motor means and said mold mount for rotating said mold mount in response to operation of said motor means; support means disposed outside of said oven supporting said rotary casting machine and including means for adjusting the inclination of said housing; and an oven panel mounted on said support means and adapted to close said opening.

6. The combination of claim 5 wherein said panel comprises an adjustable seal for sealing the space where said housing passes through said panel.

7. The combination of claim 5 wherein said support means comprises a wheeled carriage movable towards and away from said oven, and the combination further includes releasable lock means engageable with said panel for preventing movement of said carriage away from said oven.

8. The combination of claim 7 and further including guide rail means aligned with said opening and supporting said carriage for movement therealong.

9. The combination of claim 8 wherein said support means comprises a support member rotatable about a vertical axis and supporting said panel and said rotary casting machine.

10. The combination of claim 5 wherein said oven comprises a flow passage having an inlet and outlet communicating with said main heating chamber, an exhaust outlet and a fresh air inlet; said oven further comprising a valve member movable between first and second positions wherein air is recirculated through said heating chamber and is dumped from said chamber, respectively.

References Cited by the Examiner UNITED STATES PATENTS 2,629,130 2/1953 Remble l826 2,681,472 1/ 1954 Remble l826 2,958,907 11/1960 Mumford et a1 l826 3,072,965 1/1963 Miller l826 WILLIAM J. STEPHENSON, Primary Examiner.

Claims

1. IN APPARATUS FOR ROTATIONALLY CASTING A HOLLOW PLASTIC OBJECT IN A HOLLOW SECTIONAL MOLD, THE COMBINATION COMPRISING: AN OVEN PROVIDED WITH A HEATING CHAMBER AND AN OPENING COMMUNICATING WITH THE SAID CHAMBER; A BASE DISPOSED ADJACENT TO SAID OVER; AN ENCLOSURE MEMBER MOUNTED ON SAID BASE AND ADAPTED TO CLOSE SAID OPENING; AND A ROTARY CASTING MACHINE MOUNTED ON SAID BASE AND EXTENDING THROUGH SAID ENCLOSURE MEMBER, SAID MACHINE COMPRISING ROTATABLE SUPPORT MEANS LOCATED ON ONE SIDE OF SAID ENCLOSURE MEMBER AND ADAPTED TO SUPPORT AND ROTATE THE MOLD IN SAID CHAMBER ABOUT A PLURALITY OF AXES, AND MOTOR MEANS MOUNTED ON THE OTHER SIDE OF ENCLOSURE MEMBER AND OPERATIVELY CONNECTED TOF ROTATING SAID SUPPORT MEANS.