US2876510A - Apparatus for curing a moldable object with carbon dioxide - Google Patents

Description

March 10, 1959 L. R. ZIFFERER APPARATUS FOR A MOLDABLE OBJECT WITH CARBON DIOXIDE FilOd ll) 6, 1957 4 Sheets-Sheet 1 PMJ- Paul A TTORNEYS March 10, 1959 L. R. ZIFFERER- 2,876,510 APPARATUS FOR CURING A MOLDABLE OBJECT WITH CARBON DIOXIDE Filed May 6, 1957 4 Sheets-Sheet 2 PM d- Paul A TTORNEYS APPARATUS FOR CURING A MOLDABLE OBJECT WITH CARBON DIOXIDE Filed May 6, 1957 March 10,1959 L. R; ZIFFERER 4 Sheets-Sheet 3 2,876,510 APPARATUS FOR CURING A MOLDABLE OBJECT WITH CARBON DIOXIDE Filed May 6, 1957 March 10, 1959 R. ZIFFERER 4 Sheets-Sheet 4 Haw.

,1 ENERG/ZED ENEEG/ZED A TTORNEYS APPARATUS FOR CURING A MOLDABLE OBJECT.

This invention relates to an apparatus and method for curing or setting a molded granular object, and particularly relates to the curing of a mold, core, ladle lining or the like, used in founding operations and hereinafter referred to collectively as a sand form.

This application is a continuation-in-part of my copending application Serial No. 608,096, filed September 5, 1956, now Patent No. 2,824,345, issued Feb. 25, 1958.

In the aforementioned co-pending application I have pointed out that it is important to cure a'sand form, which has been mixed with water glass, by evacuating, forcing carbon dioxide under pressure into the sand form, re-evacuating, and again forcing carbon dioxide under pressure into the sand form. It is an object of this invention to provide an improved apparatus for carrying into elfect the method of the aforementioned patent, and it is a further object to provide an improved method wherein the applicable pressures during the individual stages of treatment of the sand mold are controlled within predetermined and critical limits.

Other objects and advantages of this invention, including the simplicity and economy of the same, will further become apparent hereinafter and in the drawings, whereof: i

Fig. 1 is a side elevation view showing one specific form of apparatus having features of construction in accordance with this invention, the apparatus being shown in an open position preparatory to placing the sand form into the curing chamber;

Fig. 2 is a view similar to 'Fig. 1, showing the upper portion of the apparatus, and .showing'the apparatus in position for curing the sand form;

Fig. 3 is a sectional view taken as indicated by the lines and arrows III-III which appear in Fig. 2;

Fig. 4 is a. sectional view taken as indicated by the lines and arrows IVIV which appear in Fig. 3;

Fig. 5 is a perspective view, broken away, showing an upper corner of the curing chamber which constitutes a portion of the apparatus;

Fig. 6 is a perspective view, broken away, showingthe cage in which the sand forms are placed in accordance with the practice of this invention;

Fig. 7 is a view in elevation showing the interior of the cage, with sand forms occupying a portion of the space therein and with blanks occupying another portion of said space;

Fig. 8 is a diagram showing the operative connections of the control elements which operate in accordance with the method of this invention; and

Figs. 9 and 10 are two detailed diagrams showing the raising and lowering of a cover plate in the operation of the apparatus.

Turning now to the particular form of the invention selected for illustration in Figs. l-3 of the drawings, the number It designates a chamber having a closed bottom and sides, which is open at the top. The chamber 10 is supported in a fixed posit-ion on a pair of opposed, upright slide members 11, 11. Also mounted on the slide members 11, 11 is a pair of carriage members 12 mounted on slides 13 which are slideable up and down the upright slide members 11. Each of the carriage members 12 is secured to the top of a cover plate or lid 14 which carries along its lower surface a gasket 15,

which may be a rubber O-ring or the like. The cover plate 14 is reciprocable up and down toward and away from the chamber 10.

Suspended from the cover plate 14 is a cage member 16 having a pair of sides and a bottom but which is open at the other two sides. The cage member constitutes a supporting member for one or more sand forms 8 which are to be treated in accordance with the process of this invention.

The number 20. designates a cylinder which is vertically arrangedalong a line co-extensive with the path of reciprocation of the cage 16 up and down. The cylinder 20 is stationary, and has a piston member 21 which has capacity to reciprocate up and down, conforming with the aforementioned movement of the cover plate 14 and cage member 16.

Means are provided for subjecting the sand mold S alternately to the action of vacuum and the action of carbon dioxide. It will be observed that the chamber 10 has a vacuum gauge 19 and a vacuum line 22 leading to a vacuum pump or accumulator tank, as will further appear. The number 23 designates a vacuum valve solenoid which is connected to control the vacuum valve 24. Similarly, the number 25 designates a pipe extending to a source of carbon dioxide, and the carbon dioxide valve 26 is controlled by a valve solenoid 27.

Means are provided for regulating the movement of the cage 16 up and down with respect to the chamber 10. The number 30 designates a two-way bleed valve carried on the upper end of the cylinder 20, which admits air above the piston, permitting the gradual. descent of the cage 16 into the chamber 10. It will be observed that one of the slides 13 carries a switch trip 31 which is arranged to contact a microswitch 29 when the cover plate 14 is about to contact the upper surface or rim of the chamber 10. The microswitch 29 is connected to actuate the cylinder 20 in response to the closure of the chamber 10 as heretofore described, thereby applying pressure downwardly upon the cover 14, maintaining the lid '14 tightly secured against the opening of the chamber 10, thereby sealing said chamber. Means are also provided for opening the chamber after the completion of the curing operation, as will be further explained hereinafter.

Referring further to Figs. 1 and 2, the number 32 desi nates a timer which is connected to cause the automatic operation of the apparatus. The timer is connected to a solenoid 33 operating a valve 34 causing air to lift the piston 21, and the timer 32 is also connected to a solenoid 35 which operates a valve 36 connected to the cylinder 20 to cause said cylinder to press downwardly on the cover plate 14. The timer 32 is also automatically con nected to actuate other portions of the apparatus, as will further appear in detail hereinafter.

Means are provided for presenting a clean surface at the upper rim of the chamber 10, when the lid or cover plate 14 is descending and the apparatus is being closed. It will be observed that, at the upper corners of the chamber 10 a plurality of air tubes are provided, such tubes being actuated through an air line 1. 0 controlled from a valve 41 and connected to air nozzles 42. The air nozzles 42, which are more clearly shown in Fig. 5 of the drawings, are directed along the upper surfaces of the four side walls of the chamber 10. They serve to blow any sand or other loose material off the upper surface of the rim, thereby permitting the formation of a sound air-tight connection between the cover plate 14 and the close again when the limit of downward movement is reached. The rod 44 isspring-urged toward its closed position, and when the cover plate 14 moves upwardly, the

actuating rod 43 also moves upwardly, permitting the rod 44 to spring upward and into its normal closed position.

It is an important and advantageous feature of this invention that the chamber is upright and is closed at the bottom and all sides but open at the top. Carbondioxide is heavier than the air and the chamber 10 accordingly holds over carbon dioxide from one treating cycle to the next. This results in improved curing and makes possible an equal cure using a lesser vacuum. Referring to Fig. 6, it will be appreciated that the cage member 16 has a multiplicity of perforations 45, which permit the free flow of the carbon dioxide or any other gas which may be present, through the cage member 16 itself. This not only facilitates the application of vacuum to the sand form, but has the particular advantage that when the cage member 16 is moved upwardly at the completion of a cycle, the heavier carbon dioxide is not agitated to any appreciable extent and remains in the chamber 10 for further use.

Fig. 7 shows another factor which results in a considerable saving of carbon dioxide. It will be observed that, when only a small percentage of the total volume of the cage 16 is filled with sand forms S, a large percentage of the remaining volume can be filled with blank cubes 3, such blanks being ordinary blocks made of wood or any other suitable substance. The blanks B not only result in the saving of carbon dioxide but also decrease the cost and time necessary for each vacuum treatment.

Turning now to Fig. 8 of the drawings, the operative connections of the controlling elements for the apparatus will be observed in further detail. The number 50 designates a source of carbon dioxide under pressure and the number 51 designates a heat exchanger which is adapted to heat the carbon dioxide as it passes through the pipe 25. The number 52 designates a carbon dioxide pressure control, which is connected for operation by the timer 32 in a manner further to be described hereinafter.

The number 53 designates an accumulator tank having appropriate valve fittings, and a vacuum pump 54 is connected into the circuit with the accumulator tank 53.

In the operation of the apparatus, it is to be assumed that the cover plate 14 is elevated as shown in Fig. 8, and that the air, vacuum and carbon dioxide valves are closed. The operator places one or more sand forms S into the cage member 16, and closes the main switch to the timer 32. The push button 63 on timer 32 is pressed which closes solenoid valve 34 (see Fig. 9) which normally operates to lift the piston of the cylinder 20. Air then flows in through the bleed 30 on valve 36, through pipe 55 into the top of cylinder 20 and out through the pipe 56 and bleed 57 on valve 34, permitting the gradual descent by gravity of the cage member 16. Just when the cover plate 14 closes, the switch trip 31 contacts the microswitch 29, which, through a cam 60 of the timer .32, energizes the solenoid 35 and opens the valve 36, see also Fig. 10, admitting air under pressure on top of the plstomforcing the cover plate 14 downwardly upon the upper rim of the chamber 10. Concurrently, while the cover plate 14 is descending, the members 43, 44 coact with one another to operate the air nozzles 42 to provide a short burst of air to clean off the upper surfaces of the chamber rim. With the revolution of the timer, the cam 61 operates the vacuum control valve 24, evacuating the chamber. Due to the action of cam 61, the valve 24 closes after a predetermined time. The cam 62 then opcrates the carbon dioxide control valve 26 U? admit cari 4 bon dioxide to the chamber. When the carbon dioxide pressure reaches a predeterminedvalue, the pressure control 52 is actuated, thereby closing the carbon dioxide control valve, limiting the-maximum carbon dioxide pressure. After a predetermined time, the cam 62 closes the valve 26. The cam 61 then again opens and then closes the vacuum control valve 24. With further revolution of the timer, under the influence of cam 62 the carbon dioxide control valve 26 is opened, again admitting carbon dioxide into the chamber 10, and later closing the valve 26. At the completion of this series of steps, the timer has shut the vacuum and carbon dioxide control valves and cam 60 closes the valve 36 and push button 63 is released to open valve 34, applying pressure underneath the piston of cylinder 20, as seen in Fig. 8, lifting the cover plate 14 to facilitate the removal of the finished sand forms S. Such lifting action is gradual, and is controlled by air bleeding out through bleed 30 on valve 36. It is an important safety factor that the cage descends by gravity, and without pressure from the cylinder 20. Should the operator inadvertently place his hand between the cover plate and the upper rim of the chamber 10, no harm will be done since the forces acting on his hand are simply due. to weight of the apparatus, without air pressure. Air pressure can be applied only when the lid is substantially completely closed, at which time it would be impossible for an operator to expose himself to danger. The relative values of the pressure and degrees of vacuum in accordance with this invention are important and critical. It is important that this apparatus be so governed that the chamber is exhausted to a vacuum of about 25 to 29.9 inches of mercury, carbon dioxide is then introduced at a pressure of about minus 3 to plus 3 pounds per square inch gauge, a vacuum of about 25 to 29.9 inches of mercury is again applied, carbon dioxide is again introduced to a pressure of about minus 3 to plus 3 pounds per square inch, and the chamber door is opened. It has been found that, when the processing steps are practiced in the apparatus as described herein, the critical limitations just expressed enable an operator to produce excellent mold curing on sand forms comprising particles of material which are previously mixed with sodium silicate.

. Although very satisfactory operation can be obtained without using the accumulator tank 53, its use has considerable advantage. When molds are being treated which require an exceptionally hard cure, an advantage is gained in employing the terminal vacuum of the pump 54 which is higher than can be obtained in the chamber by use of the accumulator tank 53. When the pump 54 is used directly, the settings on the automatic timer 32 are changed to provide a longer time for the vacuum stages of the machine cycle. When less critical work is being treated, the use of the vacuum accumulator tank 53 greatly shortens the machine cycle time.

Although this invention has been described with particular reference to specific forms of the apparatus, it will be appreciated that various changes may be made in the apparatus and method without departing from the scope of this invention. For example, equivalent elements may be substituted for those specifically shown and described, certain features of the invention may be used independently of other features, and parts of the apparatus may be reversed, all within the spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, I claim:

1. Apparatus for curing a sand form with carbon dioxide comprising a support, a chamber fixed on said support having closed bottom and sides but open at the top, a cover plate carried by said support, actuating means connected to cause relative movement of said chamber and cover plate to open and close said chamber, and a cage depending from said cover plate and extendable into said chamber below the top thereof, said cage having a plurality of openings therein, means for evacuating said chamber, and means for introducing carbon dioxide into said chamber.

2. The apparatus defined in claim 1, wherein said cover plate is supported by a fluid actuated cylinder disposed above said cover plate, and wherein means are provided for inactivating said cylinder causing said cover plate to descend by gravity to close said chamber.

3. The apparatus defined in claim 2, wherein an automatic means responsive to movement of said cover plate is connected for actuating said cylinder as said cover plate reaches the top of said chamber.

4. The apparatus defined in claim 1, wherein an air jet means is located at the upper edge of said chamber, and directed to blast any loose particles off said edge to provide a tight seal.

5. The apparatus defined in claim 4, wherein an automatic actuating means is connected to actuate said air jet means, said automatic actuating means being located in the path of descent of said cover plate.

6. Apparatus for curing a sand form with carbon dioxide comprising a chamber open at the top, a cover plate, actuating means connected to cause relative movement of said chamber and cover plate to open and close said chamber, and a cage depending from said cover plate and extendable into said chamber below the top thereof, said cage having a plurality of openings therein, means for evacuating said chamber, means for introducing carbon dioxide into said chamber, and a plurality of removable blocks carried by said cage and occupying surplus space in said chamber.

7. Apparatus for curing a sand form with carbon dioxide comprising a chamber open at the top, a cover plate, actuating means connected to cause relative movement of said chamber and cover plate to open and close said chamber, and a cage depending from said cover plate and extendable into said chamber below the top thereof, said cage having a plurality of openings therein, means for evacuating said chamber, means for introducing carbon dioxide into said chamber, and means connected to cause the automatic actuation of said evacuating means and said carbon dioxide introducing means.

8. Apparatus for curing a sand form with carbon dioxide comprising a,support, a chamber fixed on said support having a closed bottom and sides but open at the top, a cover plate carried by said support, a pneumatic cylinder connected to cause movement of said cover plate up and down to open and close said chamher, and a cage depending from said cover plate and extendable into said chamber below the top thereof, said cage having a plurality of openings therein, means for evacuating said chamber, means for introducing carbon dioxide into said chamber, automatic valves and actuators connected to said evacuating means and to said carbon dioxide introducing means, and means for actuating said pressurizing means when the carbon dioxide pressure in the chamber reaches a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 591,168 Hernzerling Oct. 5, 1897 825,088 Thom July 3, 1906 876,783 Dresler Jan. 14, 1908 1,165,306 Allen et al Dec. 21, 1915 1,335,222 Davis Mar. 30, 1920 1,421,791 Lemoine July 4, 1922 2,205,650 Hagemeyer June 25, 1940 2,294,530 Wiese Sept. 1, 1942 2,367,648 Nichols Jan. 16, 1945 2,463,218 Travis Mar. 1, 1949 2,547,323 Hener Apr. 3, 1951

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