US3316606A - Control of charge for ceramic extrusion - Google Patents

Description

May 2, 1967 c. J. KELLEHER CONTROL OF CHARGE FOR CERAMIC EXTRUSION 4 Sheets-Sheet 1 Filed Aug. 13, 1964 y 2, 1967 c. J. KELLEHER 3,316,606

CONTROL OF CHARGE FOR CERAMIC EX'I'RUSION Filed Aug. 13, 1964 4 Sheets-Sheet a V LO V X FIG. 2

May 2, 1967 c. J. KELLEHER CONTROL OF CHARGE FOR CERAMIC EXTRUSION 4 Sheets-Sheet 3 Filed Aug. 13, 1964 FIG. 4

FIG. 5

May 2, 1967 c. J. KELLEHER CONTROL OF CHARGE FOR CERAMIC EXTRUSION 4 Sheets-Sheet 4 Filed Aug. 13, 1964 j 1 H M m 6 :fM A A m m 4 M nu n I w Il ul 1| w M w H C l' ll' l V b Ill m x I il m 1 w m a z m m m \L 6 G W x \A F V m N I 4 k #8. Z AP o B w \M United States Patent Texas Filed Aug. 13, 1964, Ser. No. 390,264 Claims. (Cl. 25-22) This invention relates to pressure forming of ceramic bodies and more particularly, to preforming and vacuum pretreating of a charge of ceramic material preparatory to extrusion thereof.

This application is a continuation-in-part of application Ser. No. 312,700, now abandoned, filed Sept. 30, 1963.

The production of ceramic ware such as pottery, dishes and the like has been accomplished by several methods including slip casting and plastic forming, as well as pressure forming. Machines have been developed which are automated or semi-automated with the result that substantial uniformity of product may be achieved. However, many articles such as large plumbing fixtures, lavatories, water closets and the like, generally formed by slip casting, require long curing periods. This results in relatively low production rates and a somewhat non-uniform product because multiple molds are required to accommodate the long curing periods.

The present invention is directed primarily to production of bodies such as ceramic products whereby uniformity is assured and at the same time a substantial increase in production rates may accrue. A relatively thin mold liner serves as a container for a, charge to be formed and may be moved from one treating station to another. At each such station, the liner nests in a rigid mold to provide support to the liner and thereby primarily control the product configuration. At each such station, a forming die is forced under pressure into the mold and its nesting liner to distribute the charge into a cavity formed between the die and the mold liner.

The present invention is directed to the pretreatment of a charge of workable material placed in the liner preparatory to the actual extrusion thereof to the final shape. It has been found in high-pressure forming of ceramic materials which are in a substantially dry state, that it is highly desirable in order to provide a product of the finish desired that the charge be preformed as in the liner and that more importantly it be depleted to a substantial degree of air confined therein. This avoids the presence of pockets or bubbles in the finished product which cannot be tolerated when the unit is fired.

More particularly, in accordance with the present invention, there is provided a system for de-airing and preforming a flocculated charge in a mold preparatory to extruding the same to the shape of the mold as a ceramic body which includes a punch having a forming plate at the lower end thereof of configuration conforming with the configuration of said mold and mounted for reciprocation into and out of the mold with a traverse limit at a predetermined point spaced above the bottom of the mold. Resilient means carried with the punch above the forming plate engages the perimeter of the mold in sealing relation. A vacuum is then applied to the-zone below the sealing means during at least the terminal portion of the stroke of the punch for air removal during compacting of the charge at the bottom of the mold.

For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

3,316,606 Patented May 2, 1967 FIGURE 1 is a front view of an extrusion press for employing the present invention;

FIGURE 2 is a view of a preformed punch and mold for vacuum control embodying the present invention;

FIGURE 3 is a sectional view taken along the line 33 of FIGURE 2;

FIGURE 4 is a view taken along the line 44 of FIGURE 3;

FIGURE 5 illustrates another embodiment of the invention; and FIGURE 6 illustrates a preferred embodiment of the invention.

Referring now to the drawings, FIGURE 1 illustrates a hydraulic press system for forming a water closet tank and a lid therefor.

The invention relates generally to pressure forming operations. For the purpose of describing the invention, an example will be employed in which a relatively deep thin-walled container and a shallow lid are formed from a semi-dry clay body into unitary thin-walled containers. The containers thus formed may then be fired or otherwise cured, it being understood that provision is made in die shapes and dimensions to accommodate for shrinkage.

In FIGURE 1 a hydraulic press includes a base frame 10 in a floor 10a. Corner posts 11 are supported by frame 10. The posts 11 support a crown 14 which in turn supports a platen 15 by means of a hydraulic cylinder 16. Posts 11 serve as guides for the platen 15. The floor 10a serves as the bed of the unit. The platen 15 moves toward and away from the bed under the control of timer unit 14a which controls a hydraulic system such as is well-known to those skilled in the art. Suitable systems are disclosed in the catalog H52, 1952, of the Verson All Steel Press Company, of Chicago, III.

A plurality of molds are positioned beneath platen 15 to form relatively thin-walled bodies of the type above described from a pliable matrix. A stepwise forming operation is carried out. While a variety of different products may be formed by use of suitable dies in the unit of FIGURE 1, the system shown is an embodiment of the invention for producing water closet tanks and lids from a semi-dry clay mixture.

A series of operating stations A-F are shown. The mix is loaded in measured amounts into a thin-walled mold liner at station A. The liner is then moved progressively from station A to station F. The clay charge is progressively molded into the form of the product desired. As illustrated in FIGURE 1 the liners and dies are fully retracted and ready to be transported to a next succeeding station.

Station A is a loading station having a holder into which a mold liner 21 is placed. The liner 21 is loaded while at station A. A clay mix issues from a preparing and storage unit 22 by way of a suitable pump 23, the output line of which, the line 24, leads by way of valve 25 to a pair of output spouts 26 and 27.

The liner 21 has a relatively deep pocket 21a. and a shallow pocket 21b to form a tank and lid respectively. The pocket 21a has an inner surface configuration corresponding with the outer surface of the tank to be formed. The inner surface of the pocket 21b corresponds to the outer surface of the tank lid. The liner 21 is a thinwalled shell, preferably formed of metal with an inner surface the character of which corresponds with the finish desired on the final product.

The station B is a de-airing station. While at station B the liner is vibrated to reduce the air content in the charge therein.

The station C is a molding and de-airing station in which the charge in each of the pockets 21a and 21b is preshaped so that the final shaping operations will be relatively free from entrapment of air within the clay body as it is formed.

Stations D and E are forming stations in which the clay bodies are given their final form.

At station F the liners are unloaded and placed on a product conveyor belt 30.

The present invention is directed particularly to the molding and de-airing operation taking place at station C. As illustrated in FIGURES 24, the punch and the mold have a configuration which permits the simultaneous preforming and de-airing of the charge.

The mold 60 of FIGURE 1 has been shown in simplified form.

In FIGURES 2-4, it is shown in detail. The punch 60 is secured to a base plate 110 which is to be bolted to the platen 15 of FIGURE 1. A mounting plate 111 is secured to the base plate 110 and has a plurality of legs or struts 112-116 extending downwardly therefrom. The struts 112-116 preferably are welded at the upper ends thereof to the plate 111 and similarly are welded at the lower ends thereof to a plate 117. Structure below the plate 117 includes resilient sealing ring 120, a rigid mounting ring 121, a rigid perforated ring 122, and a rigid molding plate 123. The sealing ring 120 is a relatively thick-walled rubber gasket having dimensions such that during the lower portion of its travel downward into the mold 32, it will engage the walls of the mold 32 to provide an air-tight seal. The forming plate 123 is of dimensions slightly smaller than the inner dimensions of the mold 32 so that air may escape around the edges thereof. The perforated ring 122 has inwardly directed passages extending along the length thereof at the upper face of the molding plate 123, so that air forced from the charge below the molding plate 123 may escape through the holes such as holes 124. As best seen in FIGURES 3 and 4 the holes, or, marginal passages, 124 are provided along the entire periphery of the ring 122. A central aperture 126 extends upwardly through the plate 117 and through the strut 114, the plate 111, and the mounting plate 110. The later port 126 communicates with a vacuum reservoir so that as the punch 60 is forced down into the mold 32, the flocculated charge 127 is compressed. At the same time, entrained air is forced therefrom to fiow upward along the perimeter of the molding plate 123 and through the holes 124 into the chamber 136 and then through the port 126 to the vacuum system.

It will be seen that the plate 121 is secured to plate 117 by means of bolts 130. Bolts 131 are then provided to extend through the latter plates to secure the forming plate 123 to the superstructure. As best seen in FIGURE 4, the bolts 131 extend through the perforated ring 122. Further, the bolts 130 bear against the lower surface of the plate. During the downward traverse of the punch 60, the edges of the resilient washer 120 wipe the walls of the mold liner 32. To the extent that the washer 120 is deformed with the edges being forced upwardly, the seal is enhanced as the vacuum is applied below the washer 120. A wedging action is thus formed as vacuum is applied.

As shown in FIGURE 1, a storage tank or vacuum reservoir 140 is coupled by way of a flexible line 141 to the passage 126 which extends upwardly through the punch 60 and into the platen 15. A valve 142 is actuated in timed relation with the stroke of the platen 15 to apply a vacuum at the point in the stroke of the punch 60 when the seal has been established by the washer 120. The linkage 143 is shown coupling the valve 142 to the superstructure 14 so that the valve 142 will be opened at a predetermined point in the downward stroke of the platen 15. The reservoir 140 may be operated with a suitable vacuum pump of Well-known character to maintain low pressure within the tank and to provide for the abrupt removal of substantially all of the air in the charge 127. As air is removed and as the forming plate 123 moves 4 downwardly, the charge is compacted into a uniform body in the bottom of the liner 32. Thus, when the punch 60 is retracted and the loaded liner 32 is moved to the stations D and E, the extrusion thereof by punches 100 and/ or 101, may provide a finished product of the desirable characteristics free from voids that would otherwise be present if the air was not substantially removed from the charge prior to the forming and extruding operation.

It will be noted that in FIGURE 1 the mold liners 21 and 31-35 are suspended on a transport unit which includes a pair of elongated cylindrical rods 40, only one rod being shown. The rods 40 are supported for slide movement in troughs such as trough 42. The trough 42 is secured as by suitable bolts or other means to the lower surface of the platen 15. The guides 42 span the distance between the posts 11 and 12. A plurality of hangers depend from the rods 40. A first pair of hangers including the hanger 46 is secured to the front rod 40 and supports a bar 47. Bar 47 includes hooks for engaging the lip of the mold liner 21. Similarly, a pair of hangers 48 and 49 support a bar 50. The bar 50 includes hooks engaging the lip of the liner 31. Similarly, bars 5154 are provided for movement with the rod 40. Similarly, six pairs of hanger bars and six pairs of bars such as the bar 50 are provided as appendages to the rods 40.

Arms 56 extend downwardly from the right-hand ends of the rods 40, respectively, and are coupled together by a spring 58 which serves to maintain the opposed bars 54- in contact with opposite sides of the molds to engage the lips of the mold liners.

Above stations D and E dies 62 and 63 and dies 64 and 65, respectively, are secured to the lower surface of the platen 15. Dies 64 and 65 have outer surface configurations which conform precisely to the inner surface configurations of the tank and lid, respectively, to be formed.

The platen 15 is driven to follow the liners 21 and 31-35 downward and then to force dies 60-65 therein.

The transfer rods 40 are moved in synchronism with the platen 15 by means of a hydraulic cylinder 70. The cylinder 70 is actuated under the control of a valve 71 which applies pressure from a supply line 72 to the control lines 73 and 74. The valve 71 is actuated in synchronism with movement of the platen 15 under control of timer 14a. The piston 75 is coupled to a member 76 which in turn is secured to the bars 40. By this means the bars 40 will be reciprocated longitudinally of the press of FIGURE 1. The bars 40 will travel vertically with the platen so that the trajectory moves the liners stepwise through the forming zone.

In a tank mold of the type illustrated in FIGURE 1, dimensions were of the order of 22 inches wide, 12 inches high and 8 inches deep. In order to form such structures with wall thickness of the order of one-half inch, it has been found preferable to pretreat the clay mix by sizing the clay particles. As prepared, the clay is a semi-dry body with water content within the limits of from 12% to 18%. Such a mixture is relatively dry compared to the slips that are employed in the usual methods of casting vitreous ware. Such pretreatment may include production of a slip and then spray-drying the same in spray dryers of the type well-known in the art.

By way of example, a suitable body composition may include the following ingredients in the following proportions:

Percent Kona F-4 Feldspar 1 32.5 Konafiint 1 15.0 Putnam Clay 2 12.5 Monarch Clay 2 12.5 Weldon Clay 3 13.75 Black Charm Clay 3 13.75

Prepared and sold by International Minerals and Chemical Corporation, Old Orchard Road, :Skokie, I11.

Prepared and sold by United Clay Mines Corporation Trenton, NJ

T 3 Prepared and sold by H. C. 'Splnks Clay Company, Paris,

enn.

The above mixture has the following approximate body chemical analysis:

The above mixture has a particle distribution such that 62.82% of the particles are less than microns; 49.15% are less than 5 microns; 36.20% are less than 2 microns; 27.37% are less than 1 micron; 19.62% are less than 0.5 micron; and 9.99% are less than 0.2 micron. The mixture, carefully controlled in size and water content, is introduced into the traveling mold liners as indicated in FIGURE 1.

In order successfully to extract the dies such as dies 64 and 65 from the product without damage thereto, it has been found that two conditions must be established. A lubricant must be present and the temperature of the die must be substantially elevated relative to that of the product. Thus, before each stroke of the platen 15, the die members 60-65 are coated, as by spraying, with a suitable material which will aid retraction of the die without tearing the thin clay wall from the liner.

A suitable coating material or lubricant for permitting extraction of the die has been found to be an aqueous solution of a material marketed by Oakite Products, Inc., 19 Rector St., New York, N.Y., as Special Drawing Compound. Such material mixed in proportions of one part to five parts water may be applied to dies 60-65 either by brush or by spray in the manner disclosed in Patent No. 2,793,070.

In FIGURE 1, heating elements 100 and 101 are provided in the dies 62 and 64, respectively. Heating may be introduced through such electrical heaters or the temperature of the dies may be maintained elevated by other heating means. Similarly, dies 63 and 65 will be provided with suitable heating means so that the temperature of the large die, such as die 64, will be maintained at a temperature of the order of 250. The shallow die 65 for forming the lid, having much smaller area of contact with the clay body, can be operated successfully at lower temperatures, such as of the order of 150.

The foregoing description has dealt with a system in which a semi-dry pulverized clay body is introduced into each liner placed in the system. It will be found satisfactory, however, to carry out the present invention through the use of clay pugs of the type illustrated and described in Patent No. 2,450,437. In that system a clay body is worked into a unified mass from which measured amounts are severed and placed in a mold. In this event, the pug employed will have physical characteristics generally represented by the body composition above described for the pulverized case. The pug will be preformed and de-aired in the deep liner pocket as by a die 60, following which it will be fully shaped as by a die 64 with the mold line serving to transport the preformed body from the preform station to the molding station and from there to the extracting station.

Mold liners from station E are delivered to a curing station where the product formed therein is removed and/or cured. The liner may then be re-used in the system of FIGURE 1. The invention provides substantial advantage over prior art methods in the use of the liner, thus requiring only one, two or three rigid force-opposing molds with relatively resilient liners adapted to nest therein and thus be supported by the rigid molds. The liners, though preferably of a thin-walled metal, may be formed from other materials such as plastics and the like. However, in general, liners will be preferred in which the surface quality can be controlled and wear minimized. In any event, a multiplicity of liners can be provided at substantially lower cost than molds ordinarily found necessary in order to accommodate curing processes. The use of liners with semi-dry clay mixes with high pressure dies permits production of vitreous ware with high efliciency and desirable finish and minimizes variations in the product. Body materials other than clay may be employed in such system with the same beneficial results.

In FIGURE 5, there is illustrated a modification of the sealing means for vacuum control in the preforming step. In this embodiment, the upper plate 110 supports plate 111 which in turn has a bellows structure 150 secured thereto. The bellows 150 includes a plurality of resilient foldable rings 151-154. Stilfeners, such a rigid rings 155 and 156, are provided at the outer periphery of the resilient members 151-154. In addition, rigid rings 157-159 are positioned intermediate the adjacent ones of the resilient members 151-154. The foregoing elements are secured together and support a lower washer 160 which carries an O-ring 161 in the lower surface thereof. The O-ring 161 when lowered contacts the upper surface of the mold liner 32 to seal the same. The

bellows permits the piston, including struts 112 and 113, to be driven into the mold liner 32 to compact and preform the charge therein. At the same time, the zone inside the bellows 150 may be evacuated to remove air from the charge. It will 'be appreciated that other forms of sealing means may be provided as alternatives or modifications of the systems shown in FIGURES 2-5. However, in each case, the seal will be established to at least a portion of the interior of the mold in timed relation with the movement of a punch therein 50 that as the charge is preformed, it is also subject to vacuum so that air will be more efliciently removed therefrom.

In FIGURE 6 a preferred embodiment of the invention is illustrated, in which a de-airing punch is provided with a floating follower which serves to seal the mold cavity to permit evacuation thereof. As in FIGURE 2, the base plate 110 mounted on the platen of the hydraulic press is adapted to move toward and away from the mold liner 32 which is supported in the mold body C. A pair of cylinders and 172 extend downwardly from the base plate 110, being secured thereto by a template 174. The cylinders 170 and 172 are both provided with enlarged heads such as the head 176 on cylinder 170. Cylinders 170 and 172 extend through an adapter plate 178 which is secured to template 176 (by means not shown). The cylinders 170 and 172 support a foot 180 at the lower end thereof. The foot 180 is adapted to mate closely with the wall surface of liner 32 near the lower portion of the punch.

The foot 180 includes a lower plate 182 which is secured to an upper plate 184. The plate 184is secured to the ends of the shoulders 170 and 172. The lower plate 182 extends inwardly to form a recess 186 along the edge thereof and above the zone 188 at which a close fit is effected between the foot 180 and the liner 32. The lower surface of the upper plate 184 has a peripheral groove 190 in the bottom surface thereof. A plurality of ports 192 extend upwardly from the zone 186 through the upper flange on the lower plate 182 for communication with the peripheral groove 190. The groove 190 is connected to the center 'bore 194 and the cylinder 170. This bore communicates with a flow channel 196 in the upper plate 178. By this means a vacuum may be applied through a line 200 (shown dotted) which is coupled to the center bore 194. Thus, low pressure may be produced inside the mold liner 32 when the top of the mold is sealed.

The sealing of the top of mold liner 32 is accomplished in a preferred embodiment of the invention by a floating plate 202. The floating plate 202 is adapted to slide along the cylinders 170 and 172. The floating plate includes a main body -having a pair of apertures therethroug-h which are provided with a pressure seal 204 in the form of a gasket maintained under pressure by a ring 205. Thus, the floating plate 202 may slide along the cylinders 170 and 172 and yet be maintained in gas-tight relation with respect thereto.

As gasket 206 is mounted in a peripheral groove in the lower surface of the plate 202. The gasket has an outwardly curved groove therein adapted to mate with the mold liner 32 at the mouth thereof. A plate 208 is secured to the bottom of the floating plate 202 to secure the gasket 206 in position. A port 210 extends upwardly from the lower surface of the plate 208 and into the floating plate 202. A channel 212 extends laterally through the floating plate communicating with the port 210. Thus, a vacuum may be applied by way of channel 214 to draw the floating plate 202 tightly onto the mouth of the liner 32.

In operation, a charge is placed in the mold liner 32 located in the support C. The platen 15 of the press is then lowered, forcing the de-airing punch down into the mold 32. The floating plate 202, normally resting on the top of the foot 180, comes to rest in its downward travel as the gasket 206 engages the lip of the mold 32. At this point, the pressure inside the mold is reduced by way of the channel 214. As the piston moves downward and engages the clay charge in the bottom of the mold, a relatively high vacuum is abruptly applied to the zone 186 to accelerate the removal of air entrained or entrapped in the clay charge. Valve 142, FIGURE 1, located in line 200, and a similar valve (not shown) located in channel 214 are actuated in dependence upon movement of platen 15 to control the evacuation of the molds.

Having described the invention in connection with certain specific embodiments thereof, it is to be understood that further modifications may now suggest themselves to those skilled in the art and it is intended to cover such modifications as fall within the scope of the appended claims.

What is claimed is:

1. In a system for de-airing a fiocculated charge in a mold preparatory to extruding the same to the shape of said mold, the combination which comprises:

(a) a preforming punch having a foot which closely mates with the inside of said mold at a near bottom point therein,

(b) reciprocating means including a pair of cylindrical members supporting said punch at the lower ends thereof for moving said punch in and out of said mold with travel limited to said near bottom point,

(c) a vacuum source,

(d) a plate above said foot having downward opening ports flow-connected through at least one of said cylindrical members to said vacuum source,

(e) a plate slidable on said cylinders in sealed relation having resilient means for engaging the mouth of said mold in a sealing relation, and

(f) valve means operable during the portion of the stroke of said punch after said resilient means seals said mold for evacuating air from said mold.

2. In a system for de-airing a fiocculated charge in a mold having upwardly and outwardly sloping walls preparatory to extruding the charge to the shape of said mold, the combination which cmprises:

(a) a rigid preforming punch having a foot portion closely approaching in configuration the configuration of said mold at a predetermined level above the bottom of said mold,

(b) drive means for mounting said punch for reciprocation in and out of said mold with travel limited to said predetermined level to compress said charge,

(c) a sealing plate movable with said punch and supported therewith from said drive means and having resilient means for engaging the perimeter of said mold in a sealing relation,

(d) structure movable with said punch located above said punch and below said sealing plate having marginal passages opening into said mold cavity at a plurality of points spaced around and adjacent to the periphery of said punch, and

(e) evacuating means including valve means operable as said punch approaches said predetermined level and after said resilient means seals said mold for evacuating air through said passages from the portion of said mold below said resilient means.

3. The combination set forth in claim 2 wherein said sealing plate is secured to said punch as to move therewith, and wherein said resilient means is a rubber ring the edges of which extend beyond the edges of said punch to engage the walls of said mold in sliding sealing relation above said punch.

4. The combination set forth in claim 2 wherein said sealing plate is movable relative to said punch and follows said punch as said punch moves with said mold and engages the mouth of said mold in sealing relation after which said punch moves to said point.

5. The combination set forth in claim 2 wherein structure supporting said punch has a flow channel therethrough coupled to said valve means at one end and to said marginal passages at the lower end for evacuation of the zone below said resilient means.

References Cited by the Examiner UNITED STATES PATENTS 59,475 ll/ 1866 Stevens -90 1,703,783 2/1929 Schmidt 10090 XR 1,868,425 7/1932 Miller 25-22 2,770,025 1 1/ 1956 Mollers 25--27 2,959,900 11/ 1960 Wollett l00-90 I. SPENCER OVERHOLSER, Primary Examiner. R.- SPEN ER N E R, A i a t Ex mi r.

Claims (1)

1. IN A SYSTEM FOR DE-AIRING A FLOCCULATED CHARGE IN A MOLD PREPARATORY TO EXTRUDING THE SAME TO THE SHAPE OF SAID MOLD, THE COMBINATION WHICH COMPRISES: (A) A PREFORMING PUNCH HAVING A FOOT WHICH CLOSELY MATES WITH THE INSIDE OF SAID MOLD AT A NEAR BOTTOM POINT THERIN, (B) RECIPROCATING MEANS INCLUDING A PAIR OF CYLINDRICAL MEMBERS SUPPORTING SAID PUCH AT THE LOWER ENDS THEREOF FOR MOVING SAID PUNCH IN AND OUT OF SAID MOLD WITH TRAVEL LIMITED TO SAID NEAR BOTTOM POINT, (C) A VACUUM SOURCE, (D) A PLATE ABOVE SAID FOOT HAVING DOWNWARD OPENING PORTS FLOW-CONNECTED THROUGH AT LEAST ONE OF SAID CYLINDRICAL MEMBERS TO SAID VACUUM SOURCE, (E) A PLATE SLIDABLE ON SAID CYLINDERS IN SEALED RELATION HAVING RESILIENT MEANS FOR ENGAGING THE MOUTH OF SAID MOLD IN A SEALING RELATION, AND

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