US2793409A - Machine for the production of foundry cores and foundry moulds using compressed air - Google Patents

Description

May 28, 1957 F. HANSBERG 2,793,409

MACHINE FOR THE PRODUCTION OF FOUNDRY CORES AND FOUNDRY MOULDS USING COMPRESSED AIR Filed Sept. 15, 1954 INVEN TOR. FR/T'Z fi /vsazke' BY Mi Hwy.

United States Patent MACHINE FOR THE PRODUCTION OF FOUNDRY CORES AND FOUNDRY lVlOULDS USING COM- PRESSED AIR Fritz Hansberg, Milan, Italy Application September 15, 1954, Serial No. 456,265

Claims priority, application Germany February 16, 1954 Claims. (Cl. 22-40) The invention relates to a foundry machine, in which the core-sand or moulding sand is introduced into the core-box or moulding box by means of compressed air or other pressure medium.

The most varied embodiments of pneumatically operated moulding machines are known for filling moulding and core boxes with moulding sand. There are two fundamentally different types of machine and methods of operation, namely, on the one hand the pure blowing machines which work on the blast principle with a mixture of air and sand, and on the other hand the sand-shooting ma chines in which the moulding sand is injected abruptly into the moulding box without any admixture of air.

It is characteristic of the blowing machines working on the blast principle that the moulding sand with which a sand container is filled, should be mixed as thoroughly as possible with air so as to achieve a completely pneu-' matic loosening up of the sand before blowing, and to ensure that during the blowing operation each grain of sand is first surrounded with and enveloped by the compressed air and only then blown into the core-box or moulding box.

It is characteristic of the fundamentally difierent type of sand-shooting machine working on the shooting principle that the moulding sand is simply injected abruptly into the core-box or moulding box as a compact mass Without any admixture of air. The necessary acceleration is imparted to the moulding sand by resilient pressure, for example by compressed air acting as a resilient piston on an end-face of a column of sand, and forcing it. abruptly through a nozzle into the core box or moulding box.

While the compressed air enters from one side and presses on the end-face of the column of sand, the sand passes in the form of a compact jet, through the nozzle on r the other side into the box, which it fills partially or wholly according to the amount of sand subjected to pressure. As a result of the high acceleration impa'rte'clby the pneumatic pressure to the column of sand emerging from the nozzle, the sand, in the form of a compact, coherent body, is enabled to fill absolutely all the hollow spaces in the moulding or core box.

A fundamental difliculty withthis method of operation lies in the fact that the compact mass of moulding sand, which also remains compact when injected into the mould-- ing or core box, experiences a high surface friction, for which reason formerly only small amounts of sand could be shot.

Attempts have already been made to work with large amounts of sand by increasing the ramming eifect of the air acting on the end-face of the column of sand. For 65 this purpose there was provided on the machine, immediately before the intermediate sand container, a special pressure tank the contents of which were at least ten times as great as the largest core to be produced, and the total amount of compressed air stored in which could pass 70 abruptly, via a compressed air valve which could be opened suddenly, into the intermediate sand container 2,793,409 Patented May 28, 1957 ice , sand, so that even these machines only permitted operation with comparatively small amounts of sand, and then only with a comparatively large consumption of compressed air.

The inventor has therefore already suggested a machine working with a pressure chamber, by means of which,

0 while retaining the basic method of operation of a sandshooting machine,cores and moulds of any desired size and shape can be produced at a stroke with a minimum amount of compressed air, the surface friction of the compact column of sand being completely overcome in the sand storage container asa result of the fact that, simultaneously with the rammingefi'ect of the compressed air from the compression chamber, on the head of the compact col- I umn of sand, the'latter is somewhat compressed by a lateral pressure so that the compact column of sand, during its abrupt acceleration, as it were swims in the storage cont ainer, being lubricated all round with air, and can thus be accelerated by means of a comparatively small amount of compressed air, in such a manner that even the amount of moulding sand necessary to fill a large core-box or moulding box can be injected into the box at one stroke. This is achieved by introducing the com pact supply of sand, which remains compact even during its injection into the box, into a perforated insert. Perforated inserts were already known in the blowing machines working on the sand-air mixture system but in these machines they served a completely diiferent purpose and worked quite diiferently. In contrast to the perforated inserts in blowing machines, the perforations in the insert as required by the shooting principle with its ramlike method of operation which takes place without any admixture of air, are made so small and are so spaced that the compact column of sand is merely loosened from the side of the insert and no particular turbulence occurs between the supply of sand and the air, when the surrounding annular air-chamber is likewise suddenly placed under pressureduring the abrupt acceleration procedure.

The invention relates primarily to such a shooting machine, but it can also be applied in suitable cases to blowing machines working on the sand-air mixture system, for example with those havingan annular head for admitting the blowing air.

Particularly in the sand-shooters working on the shoot ing system, it is of the greatest importance that the compressed air should enter the sand storage container not slowly but suddenly, and in a shooting machine having a pressure chamber particular efforts are made to ensure that the amount of compressed air stored in the pressure chamber enters the sand 'storage container as quickly 'as possible and as .a Whole,-and hence exerts as strong an impact as possible on the head of the column of sand. For this purpose the pressure chamber is arranged-immediately before the inlet of the. sand storage container, and a valve is interposed which uncovers as large a ,passage aspo'ssible and can be controlled as quickly as possible, for which reason the inventor has already suggested that for ab'rup't control such a high speed valve should be fitted with a pneumatic piston.

then through the annular chamber, through holes provided at the upper end of the inner sand storage chamber into the inner sand storage chamber. As a result of this, the upper end of the sand storage chamber is free for charging with sand, an adjustable slide valve being provided there for charging the sand.

Apart from its obstructive and bulky overhang, the horizontal mounting of the high-speed valve has the disadvantage that the compressed air, which only enters the annular chamber at one point, is not evenly distributed therein simultaneously, which is important in such a sandshooting machine which operates in a matter of seconds, because, as a result, ramming air no longer enters the insert simultaneously from all sides as intended, and its ramming eliect is not such as could be achieved with an even small amount of compressed air, given simultaneous equal entry from all sides.

It is the object of the present invention to overcome the disadvantages associated with the unequal entry of the compressed air, and it provides a valve construction which ensures an equal concentric entry of the compressed air simultaneously from all sides, which, in a sand-shooting machine, means that the impact on the head of the column of sand by the ramming air takes place one hundred percent from the top and as a result of this and of the shortening of the path of the air which is made possible, the energy of the ramming air is utilized to the est possible advantage. At the same time the annoying wide overhang of the former bulky highspeed valve is removed.

According to the invention this is achieved by making the air inlet valve in the form of an annular slide valve which surrounds the sand storage container and is arranged parallel to its axis and preferably concentric therewith, the annular slide valve working either in the manner of a rotary slide valve with rotary displacement, or in the manner of a sleeve valve with axial displacement.

The use of such an annular slide valve is not, however, restricted to sand shooting machines working on the shooting principle, and such an annular slide valve can also be used, in suitable cases, in blowing machines working on the sand-air mixture principle.

Its preferred use is for a machine Working on the shooting principle and having an annular chamber mounted at the'top of the sand storage container for the supply of compressed air. The compressed air enters explosively through a high-speed valve with a large aperture and acts on the head of the column of sand introduced into an insert which is provided with only narrow slots or the like. of an upper-sand-charging slide. The compressed air simultaneously compresses said column of sand by means of its lateral pressure in such a manner that no particular turbulence or mixing of the moulding sand with air takes place and, solely by abrupt acceleration of the whole column of sand, a smaller amount of sand necessary for filling the core or moulding box, is shot into the core box without any particular air-sand blowing action. It is particularly advantageous to mount the annular slide valve acting as a wide-aperture high-speed valve, at the upper end of the sand storage container, inside the annular chamber or immediately adjacent thereto, in such a manner that the compressed air stored in the annular chamber end of a compressed air chamber which may be connected thereto, can suddenly emerge from the annular chamber and enter the upper portion of the sand storage container radially from all sides when the annular slide valve is actuated.

The annular slide valve may conveniently be constructed from a hollow cylinder in such a manner that it can slide axially on the outer surface of the sand storage container.

For its control, the annular slide valve in the shape of a hollow cylinder may be fitted with an annular control The insert can preferably be closed by means piston, which is preferably mounted at the lower end of the hollow cylinder.

The annular control piston may be spring-loaded on one side, but it is advantageously constructed as a double-acting piston, whereby the one annular side of the piston may be in direct communication with the annular chamber in such a manner that the pressure from the ramming air stored in the annular chamber permanently loads it. This has the advantage that, when the other annular side of the piston is relieved of pressure by means of a control valve, the opening of the annular slide valve takes place abruptly and automatically as a result of the ramming air stored in the annular chamber. In order that the same compressed air supply may be used to control the annular slide valve as is used to produce the ramming effect on the head of the column of sand, and that no compressed air at an increased pressure may be needed, the compressed air for control simply being taken from the annular chamber, that face of the double-piston which is permanently loaded by the pressure of the compressed air stored in the annular chamber, is provided with a smaller area on which the pressure acts than the other face of the piston. In addition, springs may be provided which tend to restore the annular slide valve to its closed position.

When an axially movable annular slide valve is used, the sealing in the closed position may take place in such a manner that the upper edge of the annular slide valve in the shape of a hollow cylinder is pressed against a seal. As a result of this it is also possible, instead of providing the sand storage container with upper perforations, simply to leave its upper end open in the form of a ring. By this means, when the annular slide valve is actuated, the compressed air which emerges suddenly from the annular chamber into the sand storage container, does not meet any obstacle but can simply enter the sand storage container radially from all sides at the top end.

In order to protect the sliding surfaces of the slide valve from sand, the slide valve may conveniently be provided at its upper end with a seal which engages round the upper end of the sand storage container and passes into the inner chamber.

The sand storage container may conveniently have a flange with which it can be withdrawn from the machine frame, and the sand storage container and the annular slide valve construction surrounding it may be constructed as a complete unit which can be removed as a whole from the head of the machine frame when the flange bolts have been undone.

In order to use the annular chamber not only for distributing the compressed air flowing out of the compressed-air chamber attached directly thereto, but also at the same time directly as a compressed air chamber, it is a particular advantage to surround substantially the whole of the sand storage container and the annular slide construction surrounding it, with a hollow chamber which serves to store the ramming air which causes the ramming effect, which air can then enter the sand storage container directly through the annular slide valve. This hollow chamber may then simultaneously act as a holder in that it may be constructed as the headpiece of the machine frame carrying the sand storage container.

As the inventor has already proposed in principle for sand shooting machines, a second compressed air chamber maybe provided upstream of said hollow chamber serving to store the ramming air causing the actual ramming effect, from which second chamber the compressed air can flow through a small regulating valve, the setting of which prolongs or shortens the shot, thus adapting it to the size of grain or other factors making desirable such variation. This second compressed air chamber may, for example, be housed in the machine upright, or said upright itself may be constructed to form the compressed air chamber.

The insert for the sand container, which is provided With narrow slots or the like, may, like the sand storage greases;

container itself, simply open in the form of a ring at its upper end, though it is advisable to provide the insert with a large number of perforations for example horizontal slots, arranged all round it, immediately opposite the valve aperture uncovered by the actuation of the annular slide valve, through which perforations the compressed air suddenly emerging from the annular chamber can enter the insert and act as ramming air on the head of the column of sand.

By way of example, the accompanying drawing shows diagrammatically, in vertical section, a preferred embodiment of the machine according to the invention, using the annular slide valve construction, in a sand-shooting machine fitted with a slotted insert, the parts which are not absolutely necessary for an understanding of the invention being merely indicated or omitted altogether, while the drawing shows only the upper part of the machine without the working table and the core box or moulding box.

Referring to the drawing, upright 1 carries atits upper endra headpiece 2, which, at the same time, is constructed as a hollow chamber 3, in which sand storage container 4, with the annular slide valve construction surrounding it, is inserted like a stopper from below, the inserted unit being held by a flange 5 provided on the sand storage container 4 near its lower end, by means of flange bolts 6.

The sand storage container 4 carries at its lower end a detachable shooting head 9 constructed in the form of a hollow chamber and equipped with a nozzle 7 and a perforated plate 8. Inside the sand storage container 4 there is mounted, with a slight clearance gap 12, an insert or inner container 19, which has small perforations in the form of slots 11 at suitable points, through which the air present in the gap 12 acts on the column of sand with which the insert is filled, and during the acceleration procedure said air compresses said column of sand laterally to some extent, when the annular gap 12 is likewise placed under pressure, during the ramming effect of the compressed air stored in the hollow chamber 3. In order that most of the compressed air stored up in the hollow chamber 3 may conveniently enter the space inside the top of the slotted inner container 10, the latter is provided all round the upper end with a large number of horizontal slots 13. The upper end of the slotted inner container 16 is centred in two cover plates 14 and 15, between which a sand-charging shutter 16, which may conveniently be pneumatically controlled, slides on seals, said shutter being shown in the drawing in its open position, and permitting convenient refilling with moulding or core sand from a sand-charging tray 17.

Round the sand storage container 4 is mounted the air inlet valve in the form of an annular slide valve 18, which is constructed as an elongated hollow cylinder 19, which embraces the part of the sand-storage container 4 which projects into the hollow chamber 3, and is slidable axially on the outside surface of the sand storage container 4 or on projecting slideways provided on said outer surface.

The sand storage container projecting into the hollow chamber 3 isopen in the form of a ring at its upper end 20 and in order to protect the sliding parts of the slide valve from sand, the hollow cylinder 19 of the slide valve 18 is provided at its upper end 21 with a seal 22 which engages round the upper end 24 of the sand storage container 4 and passes inside the sand storage container 4. In order to leave sufiicient room for the compressed air emerging from the hollow chamber 3 to enter the annular gap 12 when the slide-valve 18 is opened, the inner surface of the sand-storage container 4 is somewhat set back at the upper end 20 where the embracing seal 22 slides on it, so that an adequate clearance remains out ward of'the insert 10 in the region of the seal 22.

The hollow cylinder 19 of the slide valve 18 is fitted at its lower end with an annular control valve 23 which is constructed as a double-acting piston having two annular faces 25, 26 and slidable in a cylinder 24 formed by the hollow chamber 3. The face 25 of the piston is in direct communication with the annular chamber 3 so that the pressureof the compressed air stored in the annular chamber 3 constantly loads it and tends to urge the piston23 and with it the annular slide valve 18 into its lower dead position. The other face 26 of the piston is in communication by a duct 31 with a control valve 27, and the pressure acting on the face 26 of the piston tends to urge the piston 23 into the upper dead position, as a result of which the annular slide valve 18 is pressed'with its upper edge 28 against a seal 29 and thus the annular hollow chamber 3 is sealed off from the sand storage container 4.

The control valve 27 is mounted for easy access on the front of the machine and is covered by a housing 30. In order that the control valve 27 may be supplied with the same compressed air, e. g. simply from the hollow chamber 3, the area of the face 26 of the piston, on which acts the air pressure regulated by control valve 27 to close the slide valve 18, has an area greater than the area of the other face 25 of the piston on which the pressure in chamber 3 acts, so that in spite of the pressure of the ramming air stored in the annular chamber 3 loadingthe face 25 of the piston, the slide valve 18 is reliably pressed in an airtight manner against the seal 29 when .in the positionof rest.

The machine works as follows:

First of all the slotted insert 10 is filled from the top with moulding sand from the sand-charging tray 17, and then the sand-charging shutter 16 is pushed into its closed position, for example by pneumatic operation by the control valve 27 arrangedto perform this function also. The inner chamber of the sand storage container 4 or of the insert 10 is thereby closed at the top in an airtight manner. Next, also by pneumatic operation by the control valve 27, the machine table (not shown) is raised and the core-box (not shown) which is placed thereon, is pressed against the perforated plate 8 and the nozzle '7. Meanwhile, the chamber 3 has been filled with compressed air from an ordinary compressed air line for example via an intermediate chamber and a regulating valve, while the compressed air acting on the face 26 of the piston holds the annular slide valve 18 with its upper edge 23 against the upper seal 29, against the action of the compressed air acting on the face 25 of the piston.

If, as a result of a suitable setting of the control valve, the face 26 of the piston 23 is now relieved of pressure, then as a result of the pressure of the-compressed air stored in the annular chamber 3 on the side 25 of the piston, the piston 23 and with it the hollow cylinder 19 will be rammed suddenly into its lower dead position and the annular slide valve 18 will thus be abruptly opened, as a result of which the compressed air stored in the annular hollow chamber 3 rushes explosively into the interior of the sand storage container 4 radially from all sides simultaneously and equally. A small proportion of the compressed air reaches the annular gap 12 and, through the vertical slots 11, exerts a slight lateral compression on the compact column of sand (not shown) which is in the insert 10 and thus reduces its surface friction while the greater part of the compressed air stored in the chamber 3 passes through the horizontal slots 13 into the upper space in the insert 10 and acts as ramming air on the head of the compact column of sand inside the insert 10, accelerating it abruptly in such a manner that moulding sand is forced, in the form of a compact plastic jet of sand, through the nozzle 7 into the core-box which it fills until the injected sand comes into forced contact with the filter-like perforated plate 8, while at the same time the atmospheric air forced out of the core-box by the incomingpjet of sand passes through the perforated plate 8 into the hollow chamber in the shooting head 9 from which it escapes to the atmosphere through suitable apertures (not shown) or through holes in the perforated plate 8 which are not covered by the core-box or moulding box.

After this shot, by means of yet another suitable setting of the control valve 27, the side 26 of the piston again has compressed air admitted to it and the annular slide valve 18 is thus restored to its closed position and is thus pressed against the seal 29 so that the compressed air flowing into the annular chamber 3 from the air-line or intermediate chamber can again attain its maximum pressure. At the same time, by the setting of the control valve 27, the space above the column of sand which has come to rest, is relieved of pressure by means of a relief valve, so that no more sand passes out through the nozzle 7 when the core-box subsequently sinks, while the sand supply is automatically loosed up somewhat by the suction or backwash of the air in the gap 12 during the relief of pressure.

The machine is then again ready for another shot.

In practice, the individual manipulations of the control valve 27 supplement and overlap each other so that the operator controls the machine with only a few manipulations and the machine is again ready for a new shot after a few seconds.

What I claim is:

l. A foundry machine employing compressed air for ramming cores and filling molding boxes with molding sand, said machine comprising a container for the sand to be rammed, said container having in its bottom a sand outlet and at its top an air inlet, a structure forming a storage chamber for pressure air surrounding said container for supplying pressure air thereto, an air control valve means for controlling the admission of pressure air through said air inlet, said valve means including a tubular valve member surrounding the top portion of the container having said air inlet and being movable between a closing position covering said air inlet and an open position uncovering said inlet, and actuating means for moving the valve member from one position into the other.

2. A foundry machine employing compressed air for ramming cores and filling molding boxes with molding sand, said machine comprising a container for the sand to be rammed, said container having in its bottom a sand outlet and at its top an air inlet, a perforated lining member disposed within said container spaced apart from the wall thereof and open ended at its edge adjacent to said air inlet, said air inlet communicating with the inner space in the container as defined by said lining member and also with the space between the container wall and the lining member for directing air into said inner space of the container from the top thereof and also laterally into the inner space through the perforations in said lining member, a structure forming a storage chamber for pressure air surrounding said container for supplying pressure air thereto, an air control valve means for controlling the i admission of pressure air through said air inlet, said valve means including a tubular valve member surrounding the top portion of the container having said air inlet and being movable between a closing position covering said air inlet and an open position uncovering said inlet, and actuating means for moving the valve member from one position into the other.

3. A foundry machine employing compressed air for ramming core and filling molding boxes with molding sand, said machine comprising a generally cylindrical container for the sand to be rammed, said container having on one end a sand outlet and at the other end an air inlet, a structure forming a storage chamber for pressure air surrounding said container for supplying pressure air thereto, an air control valve means for controlling the admission of pressure air through said air inlet, said valve means including a generally cylindrical valve member surrounding at least the part of the container having said air inlet and disposed coaxially with the container, said valve cylinder being mounted axially 8 movable between an open position uncovering said air inlet and a closed position covering said inlet, and actuating means for moving the Valve cylinder from one position into the other.

4. A machine according to claim 3, wherein said container has at its end opposite said sand outlet end a plurality of circumferentially spaced openings to form said air inlet.

5. A machine according to claim 3, wherein said actuating means comprise a control cylinder, a piston slidable in said cylinder and connected to the valve cylinder for movement in unison therewith, said piston having faces of different area, said air pressure chamber being in communication with cylinder spaces on both sides of the piston, and control means for rendering selectively effective the pressure air on one side of the piston to move the valve cylinder from one position into the other.

6. A machine according to claim 5, wherein the space of the control cylinder on the side of the small piston face is in direct communication with said pressure air chamber and a conduit connects the space of the cylinder on the side of the large piston face with said chamber for normally urging the valve cylinder into its closing position, and wherein check valve means are included in said conduit for controlling the flow of pressure air through the same, opening of the conduit effecting movement of the valve cylinder into its open position.

7. A machine according to claim 6, wherein said control cylinder encompasses said container coaxially therewith and said piston is an annular piston.

8. A foundry machine employing compressed air for ramming cores and filling molding boxes with molding sand, said machine comprising a frame structure including a generally cylindrical open ended space, a perforated cylindrical insert for receiving a charge of ramming sand fitted in said space coaxially therewith and having a diameter smaller than said cylindrical space to form an annular chamber defined by said insert and the respective wall portion of said frame structure, a sand outlet nozzle mounted adjacent to one end of said insert in alignment therewith, the opposite end of the insert having an air inlet, said air inlet communicating with said annular chamber and the interior of said insert, said frame structure further including a chamber for pressure air surrounding the part of the insert having said air inlet to supply pressure air to the interior of said insert and said annular chamber, an air control valve means for controlling the admission of pressure air through said air inlet, said valve means including a generally cylindrical valve member surrounding at least the part of the insert having said inlet and disposed coaxially therewith, said valve cylinder being mounted axially movable between an open position uncovering said inlet and a closed position covering said inlet, and actuating means for moving the valve cylinder from one position into the other.

9. A machine according to claim 8, wherein the part of the insert having said inlet protrudes from the wall portion of the frame structure defining said cylindrical .space, and wherein a further wall portion of the frame structure in conjunction with the wall portion forming the cylindrical space defines a ring space juxtaposed to said air inlet and communicating with said air pressure chamber, said valve cylinder respectively opening and closing the communication between said ring space and said air pressure chamber in response to an axial displacement of said valve cylinder.

10. A machine according to claim 9, wherein sealing means are provided on said further Wall portion, said valve cylinder engaging said sealing means in its closed position to seal the interior of said insert from said pressure chamber.

11. A machine according to claim 10, wherein the end of the valve cylinder coacting with said sealing means is bent back into slidable engagement with the inside of the wall portion defining said cylindrical space to prevent the ingress of sand into the air pressure chamber.

12. A machine according to claim 11, wherein the respective part of the said wall portion is widened to maintain said annular chamber between the insert and the wall portion of the frame structure in which the insert is fitted.

13. A machine according to claim 12, wherein said protruding part of the insert has a plurality of circumferentially spaced apertures to form said air inlet, the total area occupied by said apertures being large in comparison with the total area occupied by the perforations of the inlet.

14. A machine according to claim 13 wherein said perforations in the insert are in the form of narrow axial slots.

References Cited in the file of this patent UNITED STATES PATENTS 2,611,938 Hansberg Sept. 30, 1952 2,654,924 Wood et al Oct. 13, 1953 FOREIGN PATENTS 557,503 Germany Aug. 24, 1932 471,174 Italy May 7, 1952

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