US3111058A

US3111058A - Apparatus for casting thixotropic material

Info

Publication number: US3111058A
Application number: US823153A
Authority: US
Inventors: Herschel Q Holley; Marsh Erwin
Original assignee: Thiokol Corp
Current assignee: ATK Launch Systems LLC
Priority date: 1959-06-26
Filing date: 1959-06-26
Publication date: 1963-11-19
Anticipated expiration: 1980-11-19

Description

United States Patent 3,111,058 APPARATUS FUR CASTENG THEXGTROPIC MATERIAL Herschel Q. Holley and Erwin Marsh, Marshall, Tex.,

assignors to 'lliiolrol llmi3l Corp, Trenton, N.J., a

corporation of Delaware Filed June 26, 1959, Ser. No. 823,153 11 laims. (Cl. 86--20) The present invention relates to apparatus for producing flow of thixotropic material, and more particularly to casting solid fuel propellants in the casings of rocket engines. The term thixotropic material as used in the specification and claims is intended to include those viscous materials in which the rate of flow can be increased by mechanical treatment as well as those materials which can only be made to flow by mechanical treatment.

Solid fuel propellants used in rocket engines have a thick dough-like consistency which sets-up into a substantially rigid mass. lt is the usual practice to cast the material to form a particular shape by pouring the material into a mold or directly into the casings of the rocket engines. Such solid fuels are usually mixed in batches and delivered from a mixer to a casting can for intermediate storage or for direct use in a casting apparatus. When the material is to be cast, a casting can is mounted on the casting apparatus from which the material is poured into a mold. The material is rendered fluent by the application of heat and pressure, but the casting of the material has always presented a problem because of its resistence to flow. Recently developed types of solid fuel propellants have further accentuated the problem because they are so viscous that they will not readily flow by the application of heat and pressure within the limits which can be safely used in production.

One of the objects of the present invention is to provide an apparatus for improving the flow characteristics of thixotropic materials to and from containers to facilita-te casting the materials in molds.

Another object is to provide an apparatus for casting thixotropic material of the type indicated which subject the entire mass of material to mechanical treatment for enhancing flow from a casting can and into a mold.

Another object is to provide a casting can which renders thixotropic material fluent when vibrated and acts as a pump for propelling the material through a feed line.

Still another object is to provide a casting can which is of a relatively simple and compact construction, economical to manufacture and reliable in its operation to render the thixotropic material fluent.

These and other objects will become more apparent from the following description and drawing in which like reference characters denote like parts throughout the several views. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not a definition of the limits of the invention, reference being bad for this purpose to the appended claims.

In the drawing:

FIGURE 1 is a side elevational view showing the thixotropic material being dumped from a mixer into a casting can;

FIGURE 2 is a sectional view of a casting apparatus in side elevation and showing the vibrating platform on which the casting can is mounted;

FIGURE 3 is a top plan view of a casting can showing the fin plates attached to the sides of the can and extending inwardly toward the center thereof;

FIGURE 4 is a sectional view taken on line 4-4 of FIGURE 3 and showing the tin plates attached to the side of the can through only a portion of their length adjacent the top and extending inwardly and downwardly toward the center and bottom of the can;

ii i lfi-Sd Patented Nov. 19,1963

FIGURE 5 is a perspective view of the open top of the can and showing the dough-like consistency of the thixotropic material delivered to a can; and

FIGURE 6 is a view similar to FIGURE 5 showing the fluid consistency of the material after treatment in the apparatus of the present invention.

In an endeavor to develop a way of casting certain types of solid fuel propellants which would not flow by the methods of casting previously used, it was discovered that the material would become fluid, at least to some degree, when vibrated. However, a conventional vibrating device when attached to the side of a casting can did not render the material fluent as the vibrations were absorbed by the material within two or three inches of the external wall of the can. The casting can was then mounted on a vibrating device of sufficient size to bodily vibrate the cm and material. This vibration also was found to be ineffective to cause the material to flow to the degree required for casting. It was then discovered that bailles or fin plates attached to the inside of the can and extending inwardly into the interior of the mass were effective to cause the material to flow until the level of the material in the can fell below the fin plates at which time the flow again became slow. The bafiles were then extended throughout the height of the can and only the upper portion of the battle fins attached to the sides of the can. Baille plates of this type were found to be very effective in producing flow when the entire can and contents was vibrated and the tin plates acted as propellers for pushing the thixotropic material through the feed line in the manner of the pump. Also, it was found that the apparatus was very useful in improving the flow characteristics and decreasing the time required for casting less viscous types of solid fuel propellants.

Referring to the drawings, a batch of the thixotropic material, such as a liquid polymer used as a rocket fuel, is processed in a mixer 10 shown in FIGURE 1. After a batch of the material has been processed, the mixer 10 is tilted to dump the dough-like mass of material into the open top of a casting can 11. The material falls into the can 11 in separated masses or chunks and takes a form 'n the can generally like that illustrated in FIGURE 5. referably, the casting can 11 is mechanically vibrated while the material is being delivered to the can from mixer 19 to cause the material to flow into and fill the can, as illustrated in FIGURE 6. To this end, the casting can may be mounted on the vibrating table of the casting apparatus 12, later to be described, during a filling operation, or may be mounted on a separate but similar vibrating apparatus during filling. Thus, the thixotropic material may be delivered alternately from the mixer 10' to casting can 11 and from the casting can to a mold M while mounted on the casting apparatus 12, or the material may be placed in a can at the mixer for temporary storage or for transfer to a casting apparatus located remotely from the mixer It).

In accordance with the present invention, the casting can 11 has fin plates 13 projecting inwardly from the side walls 14 toward the center and downwardly toward the bottom wall 15 of the can. Casting can 11 may have any desired shape and any required number of fin plates 13 projecting inwardly from its side walls 14. In the illustrated embodiment the casting can 11 is of generally cylindrical shape, see FIGURES 3 and 4, having a vertical side wall 14, a curved bottom wall 15 with an axial outlet opening 16 and an open top 17. An outer jacket wall 18 surrounds the inner wall 14 to provide a space 19 therebetween through which a heating medium is circu lated to heat the thixotropic material in the can. As illustrated in FIGURE 4, a nipple 20 depends from the outlet opening 16 in bottom wall 15. Nipples 21 and 22 also are provided at the side of the outer jacket wall 18 and have

fittings

23 and 24 for detachable connection to conduits for conducting a heating medium, such as hot water, into a jacketed space The open top 17 of the casting can Ill is adapted to be closed and sealed by a cover 25; see FIGURE 2, which is held on the can by clamps 2.5. Cover 25 has a nipple 2'7 projecting therefrom and a fitting 28 for connection to a line for supplying a fluid under pressure, such as air, to the closed casting can. Casting can 11 is mounted on legs 29 which depend from the skirt 34 welded or otherwise attached to the outer wall 18.

Pin plates 13 transmit motion from the walls of the casting can ll to the interior of the mass of thixotropic material therein and mechanically work the material in shear transverse to the direction of flow. While the fin plates 13 may take other forms, the particular construction illustrated in this construction, four of the tin plates 13 are provided and are of generally rectangular form and positioned vertically in the casting can with the upper edges below the top or" the can and the outer edges adjacent the side wall 14- of the can. The upper portions 36 of the outer edges project laterally beyond the lower edge portions 31 for a distance of from one third to one half the height of the fin plates, for example, to 6 inches, and the laterally projecting portions 36 are attached to the wall as by weldin The lower edge portion 31 of each fin plate 13 is off-set inwardly from the side wall 14, but positioned closely adjacent thereto, and the lower edge 32 overlies the bottom wall in closely adjacent relationship. For example, the side and

bottom edges

31 and 32 of the fin plates 13 may be spaced from the side wall 14 and bottom 15 about one-quarter of an inch. The rectangular fin plates 13 project radially inwardly from the cylindrical wall 14 with the inner edges 33 adjacent the axis of the casting can 11 and closely adjacent each other. Thus, each of the fin plates 13 is attached to casting can 11 at the upper portion 39 of its outer edge only and is free to vibrate transversely in the casting can H and mechanically work the thixotropic material therein.

When the thixotropic material is to be cast a casting can 11 with the material therein is mounted on a vibrating platform 35 of the casting apparatus 12. To this end, feet 3d at the lower ends of the legs 29 are clamped to pads 37 on the platform 35 by means of clamps or bolts 38, as shown in FIGURE 2. The platform 35 may be vibrated by any suitable mechanism, but the one illustrated in FIGURE 2 has been found to be especially effective. The vibrating mechanism illustrated comprises a circular base 4-0 and a plurality of springs 41 positioned between the base and platform 35 in equally s aced relation around the periphery of the base. Springs 41 extend at an angle to the vertical, for example, 45 and the ends of the springs bear against

angular abutments

42 and 43 on the base and platform, respectively. A link 44 for each spring 41 extends between the base it? and platform 35 and across the spring at an angle equal and opposite the angle of the spring 41. The ends 45 and 4-6 of each link 4-4 are pivotally connected to the base and platform 35, respectively. Base 4% is anchored to the floor by bolts 39 and the platform 35 is mounted on the anchored base for a combined vertical reciprocation and lateral oscillation.

Vibrating platform 35 is excited by a shaft 47 mounted in

bearings

43 and 49 on the base .0 and driven'by a pulley 5i? and driving belt 51. Eccentrics 52 and 53 on said shaft 47 operate in

eccentric straps

54 and 55 having their upper ends pivotally connected to

lugs

56 and 57 depending from the opposite sides of the table 35 through pins 59. Angularly extending links 69 are pivotally connected between the pin 59 and the base 49 to control the motion of the platform 35 from the eccentrics 52 and 53. The shaft and eccentrics 52 and mounted thereon are rotated at a speed to produce a combined vertical reciprocating and lateral oscillating vibratory motion having a frequency corresponding to the natural frequency of the weight loaded springs 41. In a particular application, a casting can ill of 20 gallons capacity is used and the total load to be vibrated is 1092 pounds of which 810 pounds is the casting can lll filled with propellant. The springs are so designed as to produce a natural frequency of 385 cycles per minute for this particular spring load. Thus, the shaft is initially rotated at 385 rpm. and the speed is gradually increased as the load decreases to maintain the vibration at the natural frequency of the spring-load. This vibration of platform 35 and casting can 511 is transmitted by the fin plates 13 to the thixotropic material in the can and mechanically work the material which renders it fluid.

he thixotropic material flows from the elevated casting can 11 to mold M through a delivery conduit 61. Delivery conduit 61 in the illustrated embodiment is in the form of a flexible hose having its upper end attached to the nipple 28 depending from the casting can 11 by of a hose clamp s2. Hose 61 extends downwardly from the nipple 29 and then laterally between the legs 29 with its lower end overlying the mold M to be filled. A suitable elongated nozzle 63 may be used, which detachably connects to the lower end of hose 61, to reach down into the mold and deliver the material close to the bottom and adapt the nozzle to be raised as the level of the material rises in the mold. When required, additional vibrating devices 65' are provided at spaced positions along the hose 61 which will produce vibrations in a direction transverse to the direction of flow of the thixotropic material therethrough. A flex valve also may be provided for controlling flow through hose 61 and comprises opposed clamping elements 66 and 6'7 for pinching a portion of the flexible hose therebetween.

As shown in FlGURE 2, mold M is mounted in chocks 6 3 on a platform 6% also mounted on springs 70 for vibration to cause the thixotropic material to flow into and completely fill the mold. Platform 69 may be vibrated by a mechanism like that used for vibrating the casting can 11 or by other suitable vibrating mechanism. ()ne form of the invention having now been described, the mode of operation of the apparatus to cast the thixotropic material is now described.

A batch of the thixotropic material in the form of a liquid polymer is discharged from mixer 10 into the open top of casing can 11. The casting can 11 may or may not be vibrated during a filling operation and if vibrated it may be mounted on the vibrating platform 35 of the casting apparatus 12., or may be vibrated by a separate vibrating mechanism. For purposes of description let it be presumed that the casting can is mounted on the casting apparatus 12 while the can 11 is being filled. During the filling operation, the clamping

elements

66 and 67 of the flex valve are actuated to pinch the flexible delivery conduit 61 to prevent flow therethrough. If the casting can 11 is not vibrated during a filling operation the material will have a consistency like that illustrated in FIGURE 5. Preferably, the casting can 11 is vibrated during a filling operation and the material flows into the can as illustrated in FIGURE 6.

After the casting can 11 has been filled, cover 25 is applied to the open top 17 and sealed thereto by the clamps 26. Lines are then attached to the

fittings

23 and 24 on can 11 to deliver hot water to the jacketed space 19 to maintain the material in the can at a desired temperature of, for example, F. A fluid pressure line also is connected to the fitting 28 in the cover 25 to apply pressure to the top of the thixotropic material in the can 11.

To pour a casting, the

clamps

66 and 67 of the flex valve are released and the platform 35 of the casting apparatus is vibrated by rotating shaft 47. Eccentrics 52 and 53 on shaft 45 acting through the

links

54 and 55 produce a combined reciprocation and oscillation of the platform at the natural frequency of the mounting springs 41. Casting can Ill vibrates bodily with the platform and the vibration is transmitted by the fin plates 13 from the Wall 14 of the can into the interior of the thixotropic material therein. Due to the connection of the fin plates 13 through a short length of the upper portion 30 of the side edges only, the fin plates vibrate independently of the can and work the material which transforms it from a thick dough-like mass as illustrated in FIGURE 5 to a fluid which fills the can at a fixed liquid level as illustrated in FIGURE 6. In addition, the vibrating fin plates 13 act to propel the now fluent material through the outlet opening 16' in the bottom of the can. The fluent material then flows downwardly through the delivery conduit 61 and nozzle 63 into the bottom of the mold M. The additional vibration produced by the vibrating rings as on the hose and the platform 69 supporting the mold M insures the continuous flow of the material to completely fill the mold. As the level of the material rises in the mold M, the nozzle 63 may be raised to maintain the outlet end of the nozzle adjacent the surface of the material to prevent entrapment of air therein.

When the pouring of a casting has been completed, the clamping

elements

66 and 67 of the flex valve are actuated to pinch the flexible delivery conduit and stop the flow. The mold M with the material therein is then removed from the platform 69, a new mold mounted in the chocks 68, the clamping

elements

66 and 67 of the flex valve withdrawn and the pouring in the new mold initiated. When all of the material in the casting can 11 has been poured, the rotation of the shaft 47 is stopped, the cover 25 removed from the casting can 11 and another batch of material is delivered to the can through its open top 17, preferably while vibrated by the platform 35 of the casting apparatus.

It will be understood that the material to be cast may be delivered from the mixer into a casting can 11 either with or Without vibration and temporarily stored, or the filled casting can may be used to transport the material from the mixer 10 to a remotely located casting apparatus 12.. When the latter is the case, the casting can llll is mounted on the platform 35 of the casting apparatus 12 and connected thereto by the fastening means 38.

In one application where the polymer containing an oxidizer and additives had a consistency almost like wet sand and would not flow when heated to 138 F. with an applied pressure of 30 pounds per square inch, the material was rendered fluent enough in the apparatus of the present invention to cast 215 pounds of the material in 15.5 minutes. When the vibration was stopped the material could not be cast. Various other compositions of liquid polymers used as solid fuel propellants were tested and the flow characteristics of all of the compositions were greatly improved by use of the apparatus of the present invention as well as producing an improvement in the casting.

It will now be observed that the present invention provides an apparatus for rendering thixotropic material fluent for flow into and from containers to adapt the material to be cast. It also will be observed that the present invention provides an apparatus for casting thixotropic material which affects the entire mass of material to cause it to flow from a casting can and fill the mold into which it is poured. It will further be observed that the present invention provides a casting can which renders the thixotropic material fluid when vibrated and acts as a pump for propelling the material through a delivery conduit. It will still further be observed that the present invention provides a casting can of the type indicated which is of relatively simple and compact construction, reliable in rendering the thixotropic material fluid, and is economical to manufacture.

While a single embodiment of the invention is herein illustrated and described, it will be understood that changes may be made in the construction and arrangement of elements without departing from the spirit or scope of the invention. Therefore, Without limitation in this respect the invention is defined by the following claims.

We claim:

1. Apparatus for casting thixotropic material comprising a mold to be filled, a vibrating platform, a container for the thixotropic material having an outlet opening and rigidly mounted on the vibrating platform, a conduit from the outlet opening in the container to the mold, means for vibrating the platform and container mounted thereon, and fin plates projecting inwardly from the wall of the container to transmit vibrations from the wall into the interior of the thixotropic material therein whereby to render the thixotropic material in the container fluid.

2. Apparatus for casting liquid polymers having a thick Viscous consistency comprising a mold to be filled, a vibrating platform, a container for the polymer having an outlet opening and rigidly mounted on the vibrating platform, a conduit from the outlet opening in the container to the mold, means for vibrating the platform and container mounted thereon, and fin plates projecting inwardly from the wall of the container to transmit vibration from the wall into the interior of the polymer therein whereby to render the polymer in the container fluid.

3. Apparatus for casting a thixotropic propellant material into the casing of a rocket engine comprising the rocket engine casing, a casting can containing the thixotropic material and having an outlet opening in the bottom, a platform on which the casting can is mounted, a conduit extending from the outlet opening in the casting can to the casing of the rocket engine to be filled, means for vibrating the platform and casting can mounted thereon about a vertical axis through the casting can, and fin plates projecting inwardly from the sides of the casting can into the interior of the thixotropic material and having edges terminating adjacent each other at the interior of the material to render it fluent and cause it to flow from the casting can into the conduit.

4. Apparatus for casting thixotropic propellant material in accordance with claim 3 in which the upper portions of the outer edges of the fin plates are attached to the sides of the casting can, the fin plates extending radially inwardly with the inner edgm closely adjacent each other, and the free portions of the fin plates below the attached edges extending downwardly closely adjacent the sides and bottom of the casting can and acting as vibrating paddles.

5. Apparatus for casting a thixotropic propellant material in accordance with claim 3 in which the casting can has an inner wall to which the fin plates are attached, a jacket wall surrounding the inner wall to provide a space therebetween, and inlet and outlet connections to the jacket wall for circulating a fluid heating medium in the space between the walls.

6. Apparatus for casting a thixotropic propellant material in accordance with claim 3 in which a cover is provided for closing the open top of the casting can, means for clamping the cover to the casting can to provide a pressure vessel, and a fitting on the cover for supplying fluid thereto under pressure.

7. Apparatus for casting a thixotr-opic propellant material in accordance with claim 3 in which vibrating means are mounted on the conduit extending from the outlet opening of the casting can to the casing to be filled for vibrating the conduit to insure flow of the thixotropic material therethrough.

8. Apparatus for casting a thixotropic propellant material in accordance with claim 3 in which the means for vibrating the platform comprises a base, springs extending between the base and platform at an angle to the planes thereof, links extending between the base and platform at an angle opposite to the angle of the springs, the ends of the links being pivotally connected to the base and platform, respectively, eccentric means mounted on the base and connected to vibrate the platform, and means for driving the eccentric means at the natural frequency of the springs to vibrate the platform with a combined oscillating and reciprocating motion.

9. A container for thixotropic material which may be bodily vibrated to render the material fluent for ilow into or from the container, said container being cylindrical and having a longitudinal axis and enclosing wa ls including a side Wall parallel to the longitudinal axis and a bottom Wall transverse thereto with an outlet opening at the axis, vibrating fin plates having a portion of their side edges only attached to the side Wall of the container and extending inwardly toward the center of the container with their inner edges adjacent each other and the outlet opening, and the unattached edges of the free portions of said fin plates adjacent the side and bottom Walls of the container being positioned closely adjacent thereto for relative movement.

10. A container for thixotropic material in accordance with claim 9 having an open top, a cover for closing the open top of the container, means for clamping the cover to the container to provide a pressure vessel, and a connection on the cover for supplying fluid under pressure to the top of the closed pressure vessel.

11. A container for thixotropic material in accordance UNITED STATES PATENTS 988,798 Maxim Apr. 4, 1911 988,886 Maxim Apr. 4, 1911 1,835,937 Ellis Dec. 8, 1931 2,156,541 Misenhirner et a1 May 2, 1939 2,414,273 Richman Jan. 14, 1947 2,426,619 Knight Sept. 2, 1947 2,435,610 Schneider Feb. 10, 1948 2,956,711 Mortara et a1. Oct. 18, 1960 3,004,462 Cook et a1. Oct. 17, 1961 FORElGN PATENTS 126,427 Great Britain May 15, 1919

Claims

1. APPARATUS FOR CASTING THIXOTROPIC MATERIAL COMPRISING A MOLD TO BE FILLED, A VIBRATING PLATFORM, A CONTAINER FOR THE THIXOTROPIC MATERIAL HAVING AN OUTLET OPENING AND RIGIDLY MOUNTED ON THE VIBRATING PLATFORM, A CONDUIT FROM THE OUTLET OPENING IN THE CONTAINER TO THE MOLD, MEANS FOR VIBRATING THE PLATFORM AND CONTAINER MOUNTED THEREON, AND FIN PLATES PROJECTING INWARDLY FROM THE WALL OF THE CONTAINER TO TRANSMIT VIBRATIONS FROM THE WALL INTO THE INTERIOR OF THE THIXOTROPIC MATERIAL THEREIN