US3540521A - Sand blowing nozzle - Google Patents

Description

United States Patent 11 1 3,540,521

[72] Inventors Ronald R. Buck, Jr. [56] I References Cited l UNITED STATES PATENTS g' f 823,530 6/1906 Hewlett 164/202 PP 34,1 2,665,461 1/1954 Rodgers 164/202 [22] PM FOREIGN PATENTS [45] Patented Nov: 17, 1970 [73] Assignee Eaton, Yale& Towne Inc. 831,135 2/1952 Germany 164/201 ck'ehldi Ohio Primary Examiner-J. Spencer Overholser m of Ohio Assistant Examiner-John E. Roethel Attorney-Harness, Dickey & Pierce ABSTRACT: A blowing head assembly for making shell-type [$4] SAND BLOWING NOZZLE molds including a nozzle through which a substantially freelClai-a,5 Drawing Figs. flowing particulated molding material is discharged and directed against a pattern, and wherein a' diffuser wire is 521' 0,5,0! 164/202, disposed in .said nozzle and is adapted to vibrate, etfecting 164/37, 239/ 102 lateral deflection of some of the'pa'rticles, whereby improved 15]] In, (L B22c 15/24 distribution of the molding material is achieved with cor- [50] 'I'ield of Search 169/200, responding improvements in the accuracy and uniformity of the shell-type molds produced.

Patented Nov. 17, 1970 3,540,521

Sheet L of 3 SAND BLOWING NOZZLE BACKGROUND OF THE INVENTION Shell molding techniques are in widespread commercial use in foundries for producing precision metal castings which, due to their accuracy and superior surface finish, require only minimal final machining operations. Shell-type molding practices which are well known in the art employ sand or other particulated refractory materials in combination with suitable binder materials which conventionally are composed of thermosetting resins for forming a substantially free-flowing molding material, which is applied to the surface of a pattern and thereafter cured, forming a rigid thin-walled or shell mold. Shell molds of this type are dispensable and are characterized as having good gas permeability, dimensional stability and sur face smoothness to enable the casting of a variety of different metals.

In recent years, shell molding techniques have been extended to the formation of composite molds consisting of a reusable backup mold or support having a thin lining of a sand or other bonded refractory material applied to one face thereof defining the cavity in which the molten metal is cast. The use of such composite molds provides certain advantages over conventional unitary molds composed entirely of sand or refractory material, particularly in regard to the accuracy and the improved surface finish obtainable on castings produced therefrom. There has, however, been a continuing problem in both unitary shell molds and composite shell molds in being able to consistently produce molds and cores at commercial production rates which are consistently of high quality and uniform density and surface finish, whereby the castings produced therefrom are also of consistent metallurgical and physical characteristics. This problem is particularly aggravated when intricate patterns are employed in the formation of the molds and cores, wherein the particulated molding mixture has a tendency to shade or bridge at localized points of the pattern surface producing corresponding defects in the surface of the casting produced therefrom. The use of relatively shallow permanently-backed composite molds also has contributed toward the problem of nonuniformity in the density and porosity of shell linings which creates difficultyduring the pouring of molten metal, as well as affecting the properties of the castings produced.

Various techniques have heretoforebeen used or proposed for use to overcome the aforementioned problems, but have not been entirely successful for any ofa number of reasons. In accordance with the present invention, a substantial improvement in the uniformity of the density of shell molds and shell liners, as well as in the consistency of obtaining accurate aligning devices are provided for facilitating registration of the blowing head assembly and the backup mold. The blowing head assembly is further provided with an improved control device for regulating the rate of discharge of the particulated molding material which consists of a gate slidably mounted on the body and disposed between two layers of an embeddable flexible material having perforations therethrough which are adapted to align with corresponding perforations in the gate when the gate is in an open position, whereby the molding material is discharged through the nozzle openings. Accurate control of the amount and duration of molding material discharged is thereby achieved assuring a proper thickness of molding material on the pattern surface.

Other advantages and benefits of the present invention will become apparent upon a reading of the description of the preferred embodiments taken in conjunction with the accom panying drawings.

replicas of intricate pattern surfaces, are now attainable by virtue of an improved sand blowing nozzle assembly, which facilitates distribution of the particulated molding material adjacent to the pattern surface during the blowing of a mold or COI'B.

SUMMARY OF THE INVENTION The foregoing and other benefits and advantages of the present invention are achieved by an improved blowing head assembly which is comprised of a body having one or more nozzle openings therein, through which a particulated freeflowing molding material is adapted to be discharged against a pattern surface. A diffuser wire is tautly stretched across each nozzle opening and is adapted to vibrate during the discharge of the particulated molding material, effecting a lateral deflection of some of the particles relative to the axis of the nozzle opening, achieving thereby a more uniform distribution of the molding material. In the blowing of composite permanentlybacked shell-lined molds, the blowing head assembly is preferably provided with seals encircling the periphery of each of the nozzle openings, which are adapted to be disposed in aligned registration with ports formed in the backing mold, through which the molding material is discharged. Suitable BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the blowing headassembly constructed in accordance with the preferred embodiments of the present invention;

FIG. 2 is a longitudinal vertical sectional view through the blowing head assembly shown in FIG. 1, and taken substan- DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in detail to the drawings, and as may be best seen in FIGS. 1 and 2, a blowing head assembly constructed in accordance with the preferred embodiments of the present invention consists of a body or framework including a base plate 6 to the upper surface along two opposed edges of which a pair of spacer guides 8 are securely fastened. An adapter plate 10 is secured to the upper surface of the spacer guides 8 and is disposed in substantialparallelism with the base plate 6. A circular tubular member 12 is affixed to the upper surface of the adapter plate 10 and is provided with a flanged closure member 14 at the upper end thereof provided with a circular lar member 12.

The blowing head assembly is adapted to be mounted in a suitable, press or other suitable movable support for positioning the lower face of base plate 6 adjacent to a pattern to be blown. The circular port 16 is adapted to be disposed in communication with a supply of a pressurized gas, such as air, for example, for pressurizing a particulated molding material, indicated at 20 in FIG. 2; within the chamber 18, effecting a discharge thereof out through the ports provided in the adapter plate and base plate. The introduction of pressurized air through the port 16 exerts a ram effect against the upper surfaceof the molding material 20 without any appreciable intermixing therebetween, effecting the discharge of the moldingmaterial through the ports and nozzle arrangements as herein. subsequently described. The supply of compressed air or gas is achieved in a manner well known in the art and the magnitude of the pressure may conventionally range from about 50 p.s.i. up to about 200 p.s.i. consistent with the nature of the molding material, the size and configuration of the discharge ports and nozzles, and the size and depth to which the pattern is to be blown.

The molding material 20 may comprise any suitable freeflowing particulated material, of which silica sand is most common. The sand may include portions of other refractory oxides in admixture therewith, such as alumina and the like. The particular size of the particles is varied so as to provide the desired degree of surface finish and permeability of the mold produced. The binding agents employed in the molding material conventionally consist of therr'nosetting resins, of which phenol formaldehyde, urea formaldehyde and furfural resins are the most common. The plastic binder is conventionally introduced as a liquid, a powder or as a coating on the individual sand particles which, upon subsequent subjection to elevated temperatures, initiates a curing reaction, effecting a tenacious bonding of the particles to each other. Such thermosetting binders or other binders of the types well known in the art are usually employed in amounts of from 1 percent up to l percent by weight of the molding composition and, more conventionally, from about 2 percent to about 4 percent by weight.

The exemplary embodiment of the blowing head assembly, as best seen in FIGS. 2 and 3, is one which is adapted for blowing the particulated molding material into a cavity ofa backup mold 22, which in turn is mounted in registered relationship on a pattern 24. The lower edges of the backup mold 22 are keyed or otherwise removably fixed in accurate registration on the upper surface ofthe pattern 24, defining therebetween a cavity 26, which is adapted to be filled with the particulated molding material, forming an accurate replica of the pattern surfaces 28 integrally formed on the upper surface of the pattern plate. Entry of the molding material into the cavity 26 is achieved through three elongated inwardly tapered ports 30 formed in the upper surface of the backup mold, which are adapted to be disposed in registered alignment with elongated nozzle openings 32 formed in the base plate 6. In accordance with this particular arrangement, upon the completion of blowing of the preheated backup mold and pattern assembly, the blowing head assembly is retracted and the blown mold is permitted to stand for a sufficient time to effect substantially complete curing of the molding material. Thereafter, the pattern 24 is stripped from the backup mold and is reused for the formation of a similar lined backup mold. The backup mold incorporating the cured or bonded molding material as a liner therein is placed in mating relationship with another lined backup mold in which the mating refractory linings define cavities into which molten metal is cast. Upon subsequent solidification of the castings, the paired backup molds are separated, the castings are removed and the sand linings are stripped from the backing molds which are again reused in forming similar composite molds.

It will be understood the term mold" as employed herein is used in its broad sense to encompass both molds and cores which may be unitary in which they are composed entirely of the molding material or of a composite construction in which the molding material is applied as a lining to a rigid backup member. In addition, the blowing operation is intended to encompass the discharge of the particulated molding material against a cold or cool pattern, which subsequently is heated to effect a curing of the molding material or, alternatively, against a heated pattern wherein curing of the molding material is initiated upon contact with the pattern. Particular advantages and benefits are achieved by the blowing head assembly comprising the present invention when employed for blowing composite molds which are relatively shallow and of considerable. width, as typified by the backup mold 22 and pattern 24 shown in FIGS. 2 and 3, using a molding material which is not entirely free-flowing or a preheated pattern which renders the material nonfree-flowing due to activation of the binder on coming in contact with the pattern.

The transfer of the particulated molding material from the storage chamber 18 to the nozzle openings 32 for discharge against a pattern is achieved through elongated ports 34 formed in the adapter plate 10, which are disposed in axial alignment with the nozzle openings 32 in the base plate 6. The elongated ports 34 are formed with upwardly tapered walls 36 to facilitate downward and inward flow of the pressurized molding material into the elongated ports 34. The control of the flow of molding material downwardly for discharge from the blowing head assembly is achieved by a slidably mounted gate valve or slide 38, which is positioned with its face surfaces in sliding bearing contact between two resilient pads 40, which are of a material possessing embeddability characteristics for the particulated molding mixture. Pads composed of a suitable compacted fibrous material, such as felt, for example, have been found particularly suitable for this purpose. The upper pad 40 is adhesively secured or otherwise affixed to the underside of the adapter plate 10, while the lower pad 40 is similarly adhesively secured or affixed to the upper surface of the base plate 6, maintaining them in ap propriate stationary relationship.

The slide 38 is formed with a plurality of apertures therethrough which are formed in aligned rows of a length and lateral spacing consistent with the length and lateral spacing of the nozzle openings 32 and elongated ports 34. Similarly, each of the pads 40 is formed with corresponding apertures 44 of substantially the same size and disposition as the apertures 42. in the slide, whereby when the slide is in the open position, as shown in solid lines in FIGS. 2 and 3, the apertures 42 and id are in axial alignment with each other and with the nozzle openings and elongated port 34. In the exemplary embodiment as illustrated, three laterally spaced, substantially parallel nozzle openings are provided with a corresponding number of elongated ports 34- and aligned rows of apertures 42 and 44. The number, length and disposition of the nozzle openings, elongated ports and apertures can be varied consistent with the nature of the'molding material being blown, the size and depth of the cavity being filled and the particular contour of the pattern surface against. which the molding material is discharged. The arrangement selected in each such instance provides for optimum blowing characteristics to achieve rapid and uniform filling ofthe mold cavity with the molding material.

Regulation of the flow of molding material is controlled by the position of the slide, which is movable to and from an open position, as shown in solid lines in FIGS. 1, 2 and 3, to a closed position, as shown in phantom in FIG. 1, in which the apertures 42 therethrough are disposed out of alignment with the apertures 44 in the pads. Guided movement of the slide between the two positions is achieved by the bearing contact of the two pads 40 on the opposed surfaces thereof, as well as the sliding coaction of the inner surfaces of the spacer guides 8 with'the side edges of the slide. The movement of the slide can be achieved manually or, preferably, as shown in the drawings, by a double-acting fluid-actuated cylinder 46, which can be automatically or. remotely actuated to achieve a desired blowing sequence. to provide the requisite quantity of molding material.

As best. seen in FIGS. 1 and 3, the cylinder 46 is pivotally connected at its blank end to a pivot pin 48, which is supported by a bracket 50 securely fastened to the base plate and spacerguide. A clevis-type fitting 52 is affixed to the end portion of a piston rod 54 which in turn is pivotally connected by a pin 56 to the end of a lever arm 58 pivotally mounted on a pin 60 affixed to the base plate 6. The other end of the lever arm 58 is formed with an elongated aperture 62 which is disposed in encircling relationship about a stud 64 affixed to an arm 66 integrally formed and projecting longitudinally and centrally of the slide 38. In accordance with this arrangement, actuation of the cylinder 46 effects corresponding oscillation of the lever arm 58, effecting longitudinal movement of the slide between the open and the closed position.

Accurate positioning of the slide in the open and in the closed positions, respectively, is achieved by suitable coasting stop means such as a stop' screw 68 adjustably mounted on a bracket 70 and a stop screw 72 adjustably mounted on a bracket 74. The brackets 70 and 74 are securely fastened to the base plate such as by means of socket head screws 76. The shank end of the stop screw 68 isadjusted so as to abut against the forward edge of the slide plate when it attains the closed 2' position, preventing any'overtravel' or drift of the 'slide'plate from the closed position. Similarly, the stop screw72 is adjusted such that the end of its shank engages the rearward the blowing head as may be-desi'red.

At the initiation of a blowing operation, the cylinder 46 is actuated wherein the slide is moved to the open position and the molding material is forced downwardly by the compressed air or gas in the chamber 18 through the elongated ports 34 in v the adapterplate and through the apertures 44 and 42 in the pads and slides, respectively, and thence downwardly and outwardly of the nozzle openings 32. It will be appreciated from the arrangement as illustrated in FIG. 2 that the width of the cavity 26 to be filled with material occasions difficulty due to the confined streams of molding material passing downwardly through the communicating ports in the base of the blowing head assembly. In accordance with the present invention, a dispersion and lateral deflection of at least some of the particles of the molding material is achieved, whereby substantially uniform filling of the cavity is attained. This lateral deflection and dispersion of the molding material is achieved by a diffuser wire 78 extending longitudinally and substantially centrally of the outlet portion of each of the nozzle openings 32 which are tensioned so as to vibrate within a frequency range of about up to about 20,000 cycles per second. Vibration of the diffuser wire occurs as a result of the impingement of some of the molding material particles thereagainst which in turn are deflected and which impact or collide with other particles, effecting diversions of the molding material discharged from the nozzle opening.

in order to maintain the diffuser wires in appropriate position relative to the nozzle opening, the lower surface of the base plate 6 is provided with notches or grooves 80, as best seen in FIG 4, which extend longitudinally from each endof the nozzle opening to the edge of the base plate in which the diffuser wire is seated. The lower portion of the nozzle opening itself, as best seen in FIG. 2, is recessed, as indicated at 82, and is of enlarged width corresponding substantially to the width of the ports in the upper portion of the backup mold. In accordance with a preferred construction, suitable resilient seals 84, as best seen in FIG. 5, are provided which are affixed to and extend around the periphery of the recessed portion 82 of the nozzle openings and are adapted to be-compressed against the upper surface of the backup mold during a blowing operation, preventing inadvertent escape of the particulated molding material therebetween.

The diffuser wire 78, as shown in the drawings, is ofa circu-' lar cross section and may be composed of any abrasion-resistant material, such as steel, for example. Particularly satisfactory results have been obtained by employing music wire of about ZO-gauge, which is tensioned to vibrate in the audible range. One of the ends of each of the diffuser wires 78 is secured to a locking screw 86, as shown in FIG. 4, threadably secured in the side of one of the spacer guides '8. The other end of each of the diffuser wire 78 is affixed to a locking screw 88 threadably engaged in a block 90, which is slidably adjustable in a vertical direction within a stepped bracket 92, as best seen in FlGS. l and 3. Appropriate vertical adjustment of each of the blocks 90 is achieved by socket head screw 94, whereby appropriate tensioning of each of the dif- .fuserwires can be achieved independently. in accordance witha preferred form of the present invention, each of the brackets 50,70 and 74 is preferably formed with a depending charnfered cam extension 96, which is adapted to coact with and overlie the side faces of the backup mold 22, assuring accurate lateral and longitudinal positioning of the blowing head relative to the backup mold and pattern assembly wherein the nozzle openings and the inlet ports are in registeredalignment. I

W ile it Wlll e apparent that the invention herein disclosed is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification,

' variation and change without departing from the proper scope or'fair meaning of the subjoined claims.

. We claim;

1. A blowing head assembly foi' blowing a particulatcd substantially free-flowing molding material against a pattern comprising a body formed with at least one nozzle opening therein through which a particulated molding material is adapted to be discharged, a diffuser wire tautly stretched across said nozzle opening and disposed in the path of discharge of the particulatedmolding material, means for tensioning said wire so that said wire can vibrate at a frequency of from about 20 to about 20,000 cycles per second during discharge of a particulated molding material effecting lateral deflection of some of the particles relative to the axis of said nozzle opening, and control means for regulating the flow of a molding material through said nozzle opening.

'2. The blowing head assembly as defined in claim 1, wherein said nozzle opening is of an elongated configuration and said diffuser wire extends substantially longitudinally and centrally thereof.

3. The blowing head assembly as defined in claim 1, further including a backup mold formedwitli a port therethrough, said nozzle opening disposed in registered aligripi en't with said port during a blowing operation.

4. The blowing head assembly as defined in claim 13, wherein said control means includes a slide plate incorporating a plurality of apertures therethrough rnovably mounted on said body for movement between a first position wherein said apertures are disposed in communication with said nozzle opening and a second position wherein said apertures are disposed out of communication with said nozzle opening.

5. The blowing head assembly as defined in claim 3, further including sealing means around the outer periphery of said nozzle opening for 'sealingly engaging the opposed face of said backup mold around the periphery of said port therethrough to prevent inadvertent escape of molding material therebetween during a blowing operation.

6. The blowing head assembly as defined in claim 4, wherein said slide plate is 'slidably disposed between two resilient pads possessing embeddability characteristics of the particulated molding material, said pads formed with a plurality of aligned apertures therethrough disposed in alignment with said nozzle opening and oriented so as to become aligned with said apertures in said slide plate when in said first position.

7. The blowing head assembly as defined in claim 4, further including actuating means for moving said slide plate between said first and said second position, and stop means for limiting travel of said slide plate when it attains said first and said second position.

8. The blowing head assembly as defined in claim 3, further including coacting means on said body and said backup mold for guiding said blowing head assembly into proper registration with said backup mold.

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