US2933785A

US2933785A - Process and devices for the production of blanks, cores, and moulds for casting purposes

Info

Publication number: US2933785A
Application number: US647325A
Authority: US
Inventors: Hansberg Fritz
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-03-23
Filing date: 1957-03-20
Publication date: 1960-04-26
Anticipated expiration: 1977-04-26
Also published as: DE1097621B; CH364587A; GB823301A

Description

Apnl 26, 1960 F. HANSBERG 2,933,785

PROCESS AND DEVICES FOR THE PRODUCTION OF BLANKS, CORES AND MOULDS FOR CASTING PURPOSES Filed March 20, 1957 7 Sheets-Sheet 1 INVENIUP FQ/rZ ///9A/J8R G 7 Sheets-Sheet 2 April 26, 1960 F. HANSBERG PROCESS AND DEVICES'FOR THE PRODUCTION OF BLANKS, CORES AND MOULDS FOR CASTING PURPOSES Filed March 20, 1957 Hllil Apnl 26, 1960 F. HANSBERG 2,

PROCESS AND DEVICES FOR THE PRODUCTION OF BLANKS, CORES AND MOULDS FOR CASTING PURPOSES Filed March 20. 1957 7 Sheets-Sheet 3 Hrrokmsfi April 26, 1960 F. HANSBERG 2,933,785

PROCESS AND DEVICES FOR THE'PRODUCTION 0F BLANKS, CORES AND MOULDS FOR CASTING PURPOSES Filed March 20, 1957 7 Sheets-Sheet 4 FIG. 6

F767 l/ld a 81 HOW We Quad firromvsrs April 26, 1960 F. HANSBERG CORES 7 Sheets-Sheet 5 PROCESS AND DEVICES FOR THE PRODUCTION OF BLANKS AND MOULDS FOR CASTING PURPOSES Filed March 20, 1957 gzy /z l v v mm ::ti.

r g llllll fiwz-wrop FR/rz A /weave 2,933,785 CORES April 26, 1960 F. HANSBERG PROCESS AND DEVICES FOR THE. PRODUCTION OF BLANKS AND MOULDS FOR CASTING PURPOSES 7 Sheets-Sheet 6 Filed March 20, 1957 HH ll! Hrromws/s April 25, 1960 F. HANSBERG 2,933,785

PROCESS AND DEVICES FOR THE. PRODUCTION OF BLANKS, CORES AND MOULDS FOR CASTING PURPOSES Filed March 20, 1957 i 7 Sheets-Sheet 7 F76. If

PROCESS AND DEVICES FOR THE PRODUCTION OF BLANKS, CORES, AND MOULDS FOR CAST- ING PURPOSES Fritz Hansberg, Modena, Italy Application March 20, 1957, Serial No. 647,325

Claims priority, application Germany March 23, 1956 25 Claims. (Cl. 22 -10,)

This invention relates to a process and 'a moulding machine of use for instance in foundries where core sand or moulding sand or other shapeable substance has to be charged into a core box or moulding box. The invention also relates to a box therefor and can be used in other fields where similar problems arise, for instance, for the production of shaped members made up of sands andv of air and sand, and sand shooting machines in which the moulding sand is simply displaced by impact into the box to be charged without any special eddying and mixing. The characteristic features are explained in the introduction to the United States Patent No. 2,793,409, Serial No. 456,205, filed September 15, 1954.

In one very simple method of mixing, compressed air is used to create a suction acting upon the moulding sand at the exit from a sand chamber, and the sand, mixed with the compressed air in a kind of suspension, is carried into the core box or moulding box. When the compressed air is introduced into the sand chamber, machines operating on the blowing principle produce a very intimate mixing of the sand in the chamber with air. By this means, the sand is loosened by fully pneumatic means before being blown from the sandchamber, each grain of sand being surrounded by compressed air and only then being blown into the core box or moulding box after the fashion of a suspension. As a rule, an agitator for agitating the supply of sand is provided in the sand chamber to improve the mixing of the supply of sand to be loosened with the mixing air which is introduced into the supply of sand downwardly and, as a rule, laterally too. It is also known to combine these several separate steps in such manner thatcompressed air is also used to produce a downward-acting pressure upon a shapeable substance which is disposed in a closed pressure vessel and which may or may not be agitated therein, compressed air also being used to apply suction to the said substance at the exit thereof from the vessel. To this end, at least one delivery nozzle of the pressure vessel is formed as an injector, for instance, by providing in the vessel an injector-like casing, which is rigidly secured to the base of the vessel and to which compressed air is ciple, the moulding sand being urged into the core box or moulding box to be charged, abruptly as a compactv mass without any special mixing with air. The necessary acceleration is imparted to the moulding sand by resilient pressure, for instance, by compressed air acting, after the fashion of a resilient piston, upon one end surface of the column of sand and urging the same abruptly through a nozzle into the core box or moulding box. The compressed air enters from one side and acts upon the end face of the sand column, and the sand issues on the other side through the nozzle in the form of a compact stream into the box which is wholly or partly charged depending upon the quantity of sand to-which pressure has been applied. The considerable acceleration imparted by the air pressure to the sand issuing from the nozzle enables the sand to fill all the interstices of the core box or moulding box completely as a compact and cohesive substance.

' The invention provides a third process and a third category of machines not involving a positive application of artificial force to the supply of sand, the charging of the core box being effected through the agency of an abruptly created static pressure difference between the supply of sand and the inside of the core box. This has the special advantage that the supply of sand need not be charged into a pressure-tightclosable container, but can be contained in a simple sheet metal trough orthe like which is open at the top and which can be refilled in any desired manner without the need of a charging slide or other devices such as are essential for the sand chambers of machines operating on the blowing or shooting principle. The need to raise and lower a machine table before and after the charging of the box is eliminated; on the contrary, the novel machine can simply be formed as a table support. Thereis no wear on core boxes such as is disadvantageous with the dynamic processes and more particularly with a blowing machine having an air-supply injector nozzle. Furthermore since there is a large degree of independence from the need to carefully arrange the flow of sand into the box to be charged, complicated cores can be produced.

The process according to the invention for producing shaped objects from a shapeable. substance, more particularly for the production of foundry cores and foundry moulds, which might be called the vacuum moulding process, is distinguished in that a compactsupply of sand is initially placedimmediately before the one or more charging apertures of the core box or moulding box, whereafter a negative pressure is produced very rapidly and abruptly in the box interior to be charged, the pressure drop being so great that enough of the compact supply of sand to charge the box penetrates correspondingly rapidly and abruptly, into the box interior. which is thus filled completely. 7 v

Expediently, the abrupt pressure drop in 'the box interior is produced at one or more stations therein which are opposite the sand entry. In order that eventhe furthest regions of the box interior may be filled compactlywith the moulding sand or the like, the pressure drop is expediently produced also or only by one or more station's inside the box, such station or stations being furthest from the sand entry in respect of the distance which the sand has to travel inside the box when the box is charged. To ensure that cut-back parts of the box interior are filled compactly, the pressure drop is produced also or only from such cut-back regions.

The core-box or moulding box according to the invention and serving for the carrying out of the vacuum moulding process according to the invention, which box can be called a vacuum box, is first distinguished in that it has suction channels for theproduction 'ofya negative pressure or vacuum in the interior to be charged.

Conveniently, in accordance with the process, the inner apertures of the said suction channels are disposed at those regions of the box interior which are opposite the sand entry .of the box and also or only at those regions of the box interior which are furthest from the sand entry in respect to the distance which the sand has to travel in the box. If the box interior has cut-back regions, inner apertures of the box suction channels are provided also or .only at the cut-back regions.

Advantageously, the negative pressure channels which serve to produce thevacuum in the box interior and which are disposed in the box walls extend to one or more central suction stations of the box, the central suction stations conveniently being dished recesses in the 'outer walls of the box. Where the vacuum box is to be fitted to a table plate or the like having'suction nozzles for the production of the negative pressure in its interior, a particularly'good suction efl'ect is produced if ajse'aling means, for instance, of. rubber or other sealing resilient material, is provided around the possibly dish-shaped suction stations in the outer walls of the box.

-The suction channelscan simply be'drilled in the walls of the box and their inner apertures provided with conventional fine-slotted nozzles otherwise known as evacuating nozzles. If the various suction stations inside the box cannot be connected to the dish-shaped outer suction station by rectilinear direct bores, the required connection can be effected through the agency of trans- Verse channels blanked off at the inoperative end.

The moulding machine according to the invention for carrying the vacuum process according to the invention finto effect, which can be called a vacuum moulding machine, is initially distinguished by a suction nozzle for producing a negative pressure in the interior of the core box or moulding box to be charged, and also by an open sand supply container, that is, a container subject to atmospheric pressure, having oneor possibly more sand outlet nozzles for the arrangement of a .compact supply of sand immediately before'the one or more charging apertures of the core box or moulding box to be charged.

The sand supply container can consist merely of a thin .walled, funnel-shaped or trough-like container made of .sheet metal or the like, the base possibly being thicker and being formed with one or more sand outlet nozzles.

While the process and apparatus according to the invention allow of horizontal and inclined operation, it is very advantageous if the charging operation is performed vertically and downwards. To this end, the open sand :container is disposed above the box to be. charged and is so mounted as to be pivotable laterally and/or adjust- "able in height. In one advantageous embodiment, the mounting of the open container comprises a hollow column in which a piston is axially displaceable, the top piston rod end carrying the open container and therefore .being adapted to project out of the top of the bearing column. The operation of the piston, and therefore the adjustment of the height of the sand container for engagement with the box to be charged and for subsequent raising, can be effected hydraulically but is conveniently performed pneumatically by compressed air, which is always available in foundries and is used generally as a driving medium. For a coarse adjustment to the height of the core box, the hollow bearing column can be mounted for vertical displacement on the machine frame, the said column having, for such adjustment, an externally screw-threaded spindle and a handwheel. A special construction of the sand container relates to the use of one -or more slotted nozzle ends of resilient material in one or more of the sand delivery nozzles of the sand container. Preferably, such a nozzle end has the shape of a hollow cone which is retained at the top in the sand delivery nozzle by a retaining collar and which can be made of rubber. The advantage of a nozzle end of the kind specified is that there is no need to adapt the-size of th sand delivery nozzle to the core sand used, since the nozzle end prevents very fine-grain dry mixtures of sand and synthetic resin, such as are used, for instance, for the Croning process, from running out unwantedly. By virtue of the slotted arrangement, the nozzle end can open after the fashion of resilient jaws for the moulding sand to flow through into the box to be charged. 7

To facilitate the penetration of the compact sand from the sand container into the box to be charged, an electric or pneumatic vibration motor known per se can be provided on the container wall, such motor being operated at least during the charging of the box.

In a particularly advantageous embodiment of the vacuum moulding machine according to the invention, the suction nozzle for producing the negative pressure in the interior of the core box to be charged is disposed in the machine table upon which the core box merely needs tobe placed and, after positioningof .the sand container, charged. The suction nozzle can consist of a conventional slotted nozzle of the kind used for removing air from core boxes. If the cores or core boxes are relatively large in extent, more than one suction nozzle can be provided in the machine table, the nozzles being sealed off by plugs or cocks when not in use.

Expediently, the vacuum pump serving to produce the negative pressure in the boxinterior is enclosed in the frame of the vacuum moulding machine. In one advantageous embodiment of the invention, the frame of the vacuum moulding machine is itself formed as a vacuum pump, for instance, if the machine frame forms one or more cylinders in which, for instance, a double piston operates to produce the-vacuum. In one very advantageous embodiment of the vacuum moulding machine according to the invention, the base of the machine table is formed as a vacuum pump. Preferably, the said base comprises two cylinders which are disposed one upon another and. in which a double piston moves vertically to produce the vacuum. Expediently, the bottom piston and the corresponding bottom cylinder are larger in diameter than the top piston and corresponding top cylinder, with the result that the vacuum is produced more abruptly and impactwise. Intermediate the two cylinders disposed one on top of another there can be provided a separate intermediate plate which can have the channels for the supply and delivery of the operating compressed air to and from the cylinders and which can also have quick-acting 'air valves.

A suitable form of quick-acting valve for the purpose air is admitted, that its end face, which has sealing means, is pressed against a smaller-diameter valve seating in the outlet channel. The control piston releases a lateral air admission channel comprising a non-return valve, for instance, in needle form, which non-return valve, when the compressed air ceases to be applied, restricts the flow of air returning into the lateral channel to such an extent that the air pressure upon the two sides of the control piston is different and the excess pressure acting upon the sealing end face of the control piston lifts the same off the seating, with the result that the lateral channel is sealed by the wall of the control piston and one or more air outlet apertures are released. The supply of compressed air to the quick-acting compressed air valves of the cylinders can be governed by a central control valve which can also, if required, serve. to actuate the piston associated with adjustment of the height of the sand supply container. 1 1 Conveniently, to protect the vacuum pump against the entry of fine particles of sand, the suction pipe extending from the core box or moulding box to the vacuum pump inlet'comprises an air filter and/or air washer. In the embodiment having a table nozzle, the machine table plate can have suction channels extending from the table D 2 0 e air filterand/or air washer and thenceto '5 the suction 'chambe'r of "the top cylinder of the machine table base. Preferably, the machine table plate is formed 'with at least one other outlet channel extending from the suction chamber of the top cylinder to a non-return valve which is, for instance, spring-loaded and which, after the charging of the box, serves to re-eject air sucked out of the box interior. Conveniently, a number of such airejecting non-return valves can be distributed around the bottom of the machine table. If an air filter is used, this can be rod-shaped and so introduced laterally into the machine table plate that the actual filter element extends into the suction channel in the table plate and filters the air sucked through. Like the air ejection valves, the air washer can be borne by the machine table plate.

It has been found that the filtering of the air evacuated abruptly by the vacuum pump from the core box or moulding box to be charged can be performed more simply and with considerably reduced suction losses if the air filter is disposed directly in the machine table between the table suction nozzle and the inlet side of the vacuum pump, the air filter taking in this case the form of a wide-surface filter layer preferably of the same diameter as the suction piston of the vacuum pump.

The filter layer can consist,-for instance, of granular metal swarf or of, for instance, granular plastic or any other suitable filter material. To facilitate air filter'replacement, it is very advantageous if the air filter takes the form of a finely perforated, box-like filter capsule releasably introduced into the machine table and charged with the filter material. A preferably plate-like ceramic filter member releasably introduced into the machine table can also serve as the filter layer.

Conveniently, the machine table plate is formed as a number of parts, one of the component plates being formed with a recess to receive the preferably capsulelike or plate-like filter layer. Conveniently, where the same is disposed in the bottom plate, it is retained by means of the top plate which has the suction nozzles. More advantageously, however, the filter layer is disposed in the top plate and retained through the agency of 'a cover plate fitted with the suction nozzles, for then the underplate can have a substantially plane surface and the filter layer can be replaced more readily, merely by releasing the cover plate.

Since the moulding machine is particularly suited for carrying outthe mould mask process, where the moulding sand is mixed with liquid or powdered synthetic resin and the box serving to produce the moulding masks must be 'heated, the top plate is conveniently formed as a hollow chamber through which a cooling liquid can fiow, so that the filter layer in the machine table plate and the associated suction nozzles can be cooled and are not caked bythe. synthetic resin. Sealing means are provided between the top and bottom plates in the boundary gap; they surround the suction channels or the filter layer and protect them from the cooling liquid.

Preferred embodiments of the vacuum moulding machine according to the invention and of the vacuum box according to the invention are diagrammatically illustrated,'with details, in the accompany drawings in which:

Figure 1 is a side elevation of the vacuum moulding machine, the sand container lifting device and the fitted vacuum box being shown in section;

Figure 2 is a front elevation, in vertical section, of the vacuum moulding machine with the vacuum box of Figure 1 fitted;

Figure 3 is a view in section on an enlarged scale of the nozzle end of thesand supply container shown in Fig- Hire "Figure. 4 illustrates, in vertical section and on an enlarged scale,'another embodiment of the nozzle plate of the sand container and of a vacuum box;

Figure 5 is a view, in vertical section and on an en larged scale, of the air-ejecting non-return valve shown in Figure 2;

entrees Figure 6 is a view, invertical'sectic'm andori *an' en.- larged scale, of the table suction nozzle shown in Figure 2;

Figure 7 is a view, in vertical section and on an enlarged scale, of one of the two identical quick-acting compressed air valves shown in Figure 2;

Figure 8 is a view, in vertical section and on an enlarged scale, through the air washer shown in Figure 2;

Figure 9 corresponds to the top of the moulding machine illustrated in vertical section in Figure 2, but with the difference that, instead of the lateral air'washer, a filter capsule is disposed in the machine table;

Figure 10 shows the filter capsule of Figure 9 separately and to an enlarged scale, and

Figure 11 is a constructional variant of Figure 9 and shows how the filter layer can be arranged in the bottom plate of the machine table.

Referring to Figures 1 and 2, the vacuum moulding machine comprises a pedestal-like frame '1 which bears a machine table 2 at the top and has at the rear a swing arm 3 for holding a sand supply container 4. The mounting of the sand supply container 4 comprises a hollow bearing column 5 rigidly secured in the swing arm} and having, for vertical height adjustment, 'an externally screwthreaded spindle and, resting upon the swing arm 3, a'spindle hand wheel 6. A piston 7 can move vertically in the hollow inside of the column 5 and can be. controlled pneumatically or hydraulically by way of a control supply pipe 8. The free top piston rod end 9 bears on an arm 10 a relatively thick baseplate 11 of the container 4. In the example illustrated, only one sand outlet nozzle 12 is provided in the baseplate 11 and receives a resilient, slotted nozzle end 13. The container 4, which is a truncated conical funnel in the example illustrated, is made of thin sheet metal and is open at the top. Disposed on the wall of the container 4 is a vibration motor 14 which is operated at least during the filling of the vacuum box 15 fitted to the machine table 2 and which facilitates the passage of the compact supply of sand 16 from the container 4 through the

nozzle

12, 13 into the interior 17 of the vacuum box 15. The height H of the core box can be adjusted by means of the handwheel 6, while by means of the hollow bearing column 5 and the piston 7 therein, the, container 4 can be raised and lowered through the reduced distance h or swung out laterally.

Referring to Figure 2, the base 1 is formed as a vac} uum pumpand to this end comprises two

cylinders

18 and 19 which are disposed one on top of another and in which a double piston 20 moves vertically to produce a vacuum. The bottom cylinder 18 is larger in diameter than the top cylinder 19 'andbears the latter with the interposition of an intermediate plate 21. Corresponding: ly, the bottom piston 22 has a larger operative area than the top piston 23. Formed in the plate 21 are

ducts

24 and 25; the duct 24 serves tosupply and remove com pressed air to and from the bottom cylinder 18 and the duct 25 serves to supply and remove compressed air to and from the top cylinder 19. Also'fitted to the plate 21 are two quick-acting compressed air valves 26 and 27 connected, by way of

air lines

28 and 29, to a central control valve 30 to which compressed air is supplied through a supply pipe 31. The top cylinder 19 bears the machine table plate 32 of the machine table" 2. The machine table 2 has, in the embodiment illustrated, only one suction nozzle 33 over which the vacuum box 15 tobe charged is placed. A suction pipe 34 extends from: the nozzle 33 to a'disc-shaped channel 35 and thence, by way of a suction duct 36, to an air filter introduced laterally into the machinetable 'plate'32, and thence toan air washer 38 borne'by'the plate 32, and thence, by

way of another suction duct 39, to the suction chamber 40 of the top cylinder 19. The plate 32 also has outlet ducts 41 which are disposed in radial direction and which. extend from the suction chamber of the top cylinder 19 to aireiecting nonreturn valves 42-distributed around the bottom of the plate 32. The disc-shaped outlet Channel 35 is separated from the suction chamber 40 by a sealed disc 43.

Referring now to Figure 3, the sand outlet nozzle 12 in the baseplate 11 of the container 4 is provided with a nozzle end 13 which consists of resilient material and is in the form of a hollow cone having at its upper and widened end a retaining collar 44 serving for the mounting of the nozzle end 13 in the nozzle 12, in which it is retained by a snap ring 45. By virtue of one or more vertical slots 46 which extend from the cone apex to the collar 44, the nozzle end 13 can open after the fashion saute ends 13 of rubber.

In the vacuum box illustrated in Figure 2; filter-like apertures 48 of the box suction ducts 49 are contrived .in the base of the box interior 17 only opposite the sand entry 47. The ducts 49 extend to a central suction station 50 which comprises a dish-shaped recess in the box outer wall and is disposed above the suction nozzle 33 of the machine table 2. The ducts 49 act as negative pressure ducts for the production of the vacuum in the box interior 17. On the other hand, in the vacuum box 15 illustrated in Figure 4, internal filter-like slotted apertures 51 are also provided at undercut regions 52 of the box interior 17. Also provided are inner filter apertures 53 which: are furthest from the box entry 47 or sand outlet nozzle 12 in respect of the distance which the sand has to travel from the said entry 47 in the interior 17. The lateral

negative pressure apertures

51 and 54 communicate, by way of negative pressure ducts 49a extending transversely in the box wall, with the dish-shaped central suction station 50, their inoperative ends being blanked off by plugs 55. To produce a very powerful suction and charging effect, the topand bottom of the vacuum box illustrated in Figure 4 are provided with sealing means 56 around the sand entry 47 and the dish-shaped suction recess 50, the sealing means consisting in this case of rubber.

Referring to Figure 5. the air-ejecting valve 42 of the top cylinder 19 comprises a casing which has a number of circumferentially spaced outlet apertures 57 and which is screwed to the bottom of the plate 32. Mounted in the casing is a tappet valve 58 acted upon by a closure spring 59 which urges the resilient valve head 60 against the seating 61 of the air outlet duct 41. When the top piston 23 rises, the air expelled through the duct 41 lifts the valve head 60 from the seating 61 and flows through the apertures 57 to atmosphere.

The table nozzle or suction nozzle 33 shown in Figure 6 comprises a slotted nozzle screwed into the table 2 by means of a screwthreaded tube 62. Disposed below the nozzle 33 is a close-meshed filter 63 which filters the air sucked from the box 15 before such air enters the suction pipe 34 of the plate 32. The nozzle 33 can be screwed out together with the tube 62 and replaced by a screwthread plug or a set screw, for instance, if a number of such nozzles 33 are provided in the table 2 and some of them' are not required. Referring to Figure-7, the quick-acting compressed air valve 26 and 27 serves to supply and remove the working compressed air toand from the

cylinders

18 and 19 respectively. Thevalve 26.and 27 has a screwthreaded eonneetion 64, the free end of which is screwed into the aperture-of the ducts 24and respectively in the interirlediate plate.21. 'A control piston 66 can be freely displaced horizoritallyin the'valve casing 65. ,The piston 66Ihas. 'on its end'face'6'l'fsealing means 68' which, when thepis'toii- 66 .is in'thef left-hand end position, bears ggar s iavawe 'seating'i69l of air outlet'ehannel .70,

The seating 69 is smaller in diameter than the piston 66, so that the left-hand pressure surface of the piston 66 is smaller than the right-hand pressure surface thereof when the piston 66 has its sealing means 68 urged against the seating 69. In this position the piston wall uncovers the aperture 71 of a lateral air intake channel 72 through which the compressed air supplied by way of the air connection 73 can flow. Such air lifts, in the inner outlet aperture of the lateral channel 72, a releasably fitted conical pin 74 which acts under its own weight as a nonreturn valve. When the piston 66 is in its right-hand end position, its wall seals off the entry aperture 71 of the lateral channel 72, while its end face 69, which is then raised clear of the valve seating 69, opens a passage from the air exit channel to a number of circumferentially spaced air exit apertures 75 arrangedin stellate form. e The air cleaner illustrated in Figure 8 comprises an air filter 37, which is introduced laterally into the plate 32, and an air washer 38 which is screwed on to the bottom of the plate 32. The filter 37 is fitted to a rodlike bearer 76 and extends into the widened end of the suction duct 36 so that the air sucked through the duct 35 must pass through the filter 37, whence it passes through another close-mesh filter '78 and through circumferentially spaced apertures 79 in the member 76 to the air washer 38. The entry tube 80 of the air washer 38 is screwed into the bottom of the plate 32 and extends deeply into a liquid vessel 81 screwed on to the bottom of the plate 32 and forces the air to pass through the washing liquid which, in the example illustrated, is oil. The compressed air which rises in the vessel 81 passes through two close-mesh filters 82, reaches the return suction duct 39 and passes therethrough to the suction chamber 40 of the vacuum pump. In the embodiment illustrated in Figure 9, the top plate 2 is formed with a recess 83 on its bottom surface and the filter layer 84 is introduced into the recess 83, the filter layer 84 taking the form of the box-like perforated filter capsule 85 shown to an enlarged scale in Figure 10. The capsule 85 is retained at the top by means of a cover disc 86 which in this embodiment contains the suction nozzles 33 and which is formed with a disc-like distributing duct 87 on its bottom surface. A matching disc-like distributing duct 88 is formed below the filter capsule 85 in the plate 32, and three ducts 89 extend from the duct 88 to the suction chamber 40 of the cylin= der 19. The top plate 2 is formed as a hollow chamber so that cooling liquid supplied and removed by way of the connection 90 can flow through the top plate 2. An annular packing 91 which screens the filter layer 84 from the cooling liquid is provided around the filter layer 84 131;: the gap between the top plate 2 and the bottom plate In the machine according to Fig. 11, the lower plate 32 is formed with a recess 83 to receive the filter layer 84 which is encased in the box-like perforated filter capsule 85 retained by cover disc 86. The suction nozzles 33 are disposed in suction ducts 92 formed in upper table plate 2. This table plate also includes channels and the ducts 92 are sealed by sealing rings 91 against thecoolant flowing through the machine.

The vacuum moulding machine shown in Figures 1 to 8 operates as follows: l The core box 15 to be charged is so fitted to the machine table 2 that its dish-like central suction station 50 is disposed above the suction nozzle 33 of the machine table 2. The sand container 4, which may have been swung out laterally and which may be in the raised position; is brought over the charging aperture 47 of thecore box'15 and lowered on to said aperture by removing air from ,thepiston supply pipe 8. When the control valve lever 30 is moved intothe position I, compressed airis supplied from the air line 31 byway of thelipej 29 '9 -'to the quick-acting air valve 27, moves the =c'ontrol piston '66 into its left-hand end position and thus seals the air exit duct 70. By way of the lateral channel 72, the compressed air, lifting the non-return valve 74, passes through the tubular connection 64 and the duct 25 in the intermediate plate into the top cylinder 19 below the top piston 23 which thus moves into its uppermost position and, in so doing, expels to atmosphere any air in the suction chamber 40 by Way of the outlet duct 41 and the outlet perforations 57 of the air-ejecting non-return valve 42.

When the lever of-the control valve 30 is pivoted into its position II so that the air line 29 has the air removed from it, the compressed air in the cylinder 19 reacts upon the control piston 66. The needle valve 74 restricts the pressure in the lateral duct 72 to such an extent that the compressed air acting upon the piston end face 67 in the air outlet duct 70 abruptly urges the control piston 66 into its right-hand end position, with simultaneous sealing of the entry aperture 71 of the lateral duct 72. Hence the compressed air in the cylinder 19 can flow without restriction to atmosphere by way of the air outlet aperture 75. Simultaneously, compressed air is supplied, by way of the central control valve 30, from the air line 31 through the air line 28 to the quick-acting air valve 26 of the bottom cylinder 18 and urges the bottom piston 22 into its bottom end position. Since the operative area of the bottom piston 22 is greater than the operative area of the top piston 23, the double piston 20 is moved downwards abruptly.

As the top piston 23 descends, a vacuum is produced in the suction chamber 40 and acts, by way of the suction duct 39, air washer 38, air filter 37, and suction ducts 34 to 36, upon the core box 15 to be charged. As a result, the air in the interior 17 of-the core box 15 is removed through the nozzle apertures 48, box suction duct 49, the dish-shaped central suction station 50, and the suction nozzle 33 of the machine table 2. It is filtered on the way to the vacuum piston 23 in the air filter 37 and freed from the last particles of sand in the air washer 38.

As a result of the production of an abrupt and considerable pressure ,drop in the box interior 17, the co'mpact sand 16, under the eifect of the static pressure difference between the sand 16 and the box interior 17, urges apart the slotted resilient nozzle end 1'3, rushes out of the container 4 through the outlet nozzle 12 and penetrates into the box interior 17 which is thus charged completely and compactly.

The piston 7 is again supplied with pressure medium by way of the pipe 8 and the container 4 is again raised by the distance h and, if required, swung out to one side. The charged box 15 can then be-removed from the rnachine table 2 and released from the finished core,

an operation which can, if required, be performed on the machine table 2.

- The vacuum moulding machine further charging operation.

The vacuum moulding machine illustrated in Figures 9 to 11 operates on the same basic principle as the machine illustrated in Figures 1 to 8, as follows:

The core box 15 to be charged is sofitted to the machine table 2, 32 that its dish-shaped central suction station 50 is disposed above the suction nozzles 33. The sand supply container 4, which may have been swung out to one side and which maybe in the raised-position, is brought over the charging aperture 47 of the core box 15 and lowered on to said aperture. By appropriate operis then ready for a ation of the control valve (not shown), the top piston 23 isdriven into its uppermost position and,. in so doing, expels to atmosphere any air in thesuct-ion chamber by W y of the outlet duct 41 and outlet perforations in the air-ejecting non-return valve 42. g vI f the control valve {not shown) is again operated,'t-h'e top piston 23 is driven downwards impactwise into its bottom en'dpositiomwith the result that 'a v'ac'uum is 15rd duced in the suction chamber 40 and extends, by way of the suction ducts 89, wide-surface filter layer 84 and suction nozzles 33, to the box 15 to be charged. As a result, the air in the interior 17 of the box 15 is removed, by way of the nozzle apertures 48, box suction duct 49, the dish-shaped central suction station 50, and the suction nozzle 33 of the machine table 2. It is filtered on the way to the vacuum piston 23 in the wide-surface filter layer 84 and thus freed from sand particles. As a result of the considerable and abrupt pressure drop in the box interior 17, the compact sand 16, under the effect of the static pressure difiference between the sand 16 and the box interior 17, widens the slotted resilient nozzle end 13, rushes from the sand container 4 through the sand outlet nozzle 12, penetrates impactwise into the box interior 17 which is thus charged completely and compactly.

If the sand container 4 is then raised again and, if'required, swung aside, the charged box 15 can be removed from the machine table 2 and released from the finished core, an operation which, can, if required, be performed 'on the machine table 2.

The vacuum moulding machine is then ready for a further charging operation.

I claim:

l. A machine for producing casting blanks, casting cores and casting molds, comprising a support structure for supporting a box to be charged with molding sand and quick acting vacuum pump means including a suction chamber of comparatively large reception volume for abruptly creating a comparatively high vacuum in the interior of said box, said support structure forming at least one cylinder constituting said suction chamber of comparatively large reception volume, a piston displaceable in said cylinder to produce the vacuum, and a suction nozzle connected to said suction chamber and communicating with said box supported on said support struc- 'ture.

2. A machine for producing casting blanks, casting cores and casting molds, comprising a support structure for supporting a box to be charged with molding sand and quick acting vacuum pump means including a suction chamber of comparatively large reception volume for abruptly creating a comparatively high vacuum in the interior of said box, said support structure forming two cylinders in tandem, one of said cylinders constituting said suction chamber of comparatively large reception volume, a twin piston displaceable in said cylinders to produce the vacuum, and a suction nozzle connected to said suction chamber and communicating with said box supported on said support structure.

3. Machine according to claim 2, wherein said two cylinders in tandem are disposed upright and form a machine table base including a machine table for placing a box thereupon with at least one suction nozzle formed therein, said nozzle being connected to said suction chamher and communicating with the box supported on said table.

' 4. Machine according to claim 3 characterized in that the bottom piston and cylinder are of larger diameter than the top piston and cylinder.

- 5. A machine for producing casting blanks, casting cores and casting molds, comprising a support structure for supporting a box to be charged with molding sandand quick acting vacuum pump means including a suction chamber of comparatively large reception volume for abruptly creating a comparatively high vacuum in the interior of said box, said support structure forming two cylinders in tandem, one of said cylinders constituting said suction chamber of comparatively large reception volume, a twin piston displaceable in said cylinders to produce the vacuum, and a suction nozzle connected to said suction chamber and communicating with said box supported on said support structure, a conduit for supplying pressure air and discharging the air from said cylinders to effect displacement of the twin piston, and quick acting air valves to control the fiow of air through said conduit means.

6. A machine for producing casting blanks, casting cores and casting molds, comprising a support structure for supporting a box to be charged with molding sand, said sup port structure forming quick acting vacuum pump means including a suction chamber of comparatively large reception volume, a nozzle connected to said suction chamber, said suction nozzle communicating with a box supported on said support structure for producing an abrupt pressure drop in said box upon activation of said pump means, said vacuum pump means including two cylinders formed in said support structure, a piston slidable in each of said cylinders to produce said pressure drop by displacement of the pistons, said pistons being coupled for joint movement, a conduit means for supplying pressure air to and discharging from saidcylinders to effect displacement of the pistons therein, and quick acting air valves to control the flow of air through said conduit means, said conduit means including an air inlet conduit and an air outlet conduit, said quick acting air valves each including a housing, a control piston having sealing means on one of its faces and slidable in said housing, said piston being movable by compressed air into a position in which said piston face presses against a valve of smaller diameter seating in the air outlet conduit, said movement of the control piston uncovering the air inlet conduit laterally issuing into the housing, said inlet conduit including a non-return valve which upon discontinuation of the flow of pressure air limits the fiow of air into the lateral conduit to such an extent that the resultant excess pressure acting upon the face of the control piston having said sealing means lifts said face off its seating whereby said lateral conduit is sealed and at least one air outlet aperture is uncovered.

7. In a machine for producing casting blanks, casting cores and casting molds by charging of a box with molding sand, a machine base including a table plate for placing thereon the box to be charged with sand, said base being in the form of a quick acting pump having a suction chamber of comparatively large reception volume, said pump comprising two cylinders disposed upright in tandem and a twin piston reciprocatory in said cylinders, one of said cylinders constituting said suction chamber, a suction nozzle included in said table plate for'coacting with the box placed thereupon, a suction pipe connecting said nozzle with said suction chamber to effect an abrupt pressure drop in the box in response to a displacement of said pistons in a direction for creating a vacuum in said chamber, and an air filter means included in said suction pipe.

8. A machine for producing casting blanks, casting cores and casting molds, said machine comprising a holder for molding sand, said holder being open at the top to the atmosphere and having a discharge opening; a suction chamber with high air capacity and comparatively large reception volume having a suction duct, a box to be charged with molding sand mounted so as to be movable into a charging position in communication with the suction duct of said chamber and in communication with the discharge opening of said holder, said communications constituting the only access to the box in said charging position, and means for creating in said chamber a comparatively high vacuum to remove abruptly the atmospheric air from the interior of said box into said chamber thereby causing a quantity of sand to penetrate abruptly and substantially free of admixture of air through the discharge opening of the holder into the box for filling the latter with compacted sand, said box having suction apertures provided at undercut regions of the box interior and suction conduits extending in the box walls from said suction apertures to at least one central suction station positioned immediately before a suction nozzle of said suction chamber for abruptly producing a pressure drop in the-interior of said box.

f9. A. machine for producing casting blanks, casting cores and casting molds, said machine comprising a holder for molding sand, said holder being open at the top to the atmosphere and having a discharge opening, a suction duct,

a box having a hollow interior space for charging the same with molding sand and being movable into a charging position in communication with the discharge opening of said holder and with said suction duct, said communications constituting the only access to the box in said charging position, a suction chamber with high air capacity and comparatively large air reception volume arranged near said box, said suction chamber being in the form of a large suction cylinder having a suction end, said suction end being connected to said suction duct, and means for creating in said suction chamber a comparatively high vacuum and abruptly airwise, enlarging said interior box space by said air reception volume to remove abruptly the atmospheric air from the interior space of said box into said reception chamber thereby causing a substantially compacted quantity of sand to penetrate abruptly and substantially free of admixture of air through the discharge opening of the holder into the box filling the latter with compacted sand, said means for creating said comparatively high vacuum and abruptly enlarging said interior box space including a suction piston displaceable in said cylinder from said suction end to a limit position.

10. Machine according to claim 4, wherein a partition plate is interposed between the top and the bottom cylinder, said plate including ducts for supplying pressure air to and discharging from said cylinders to displace said twin piston therein.

11. Machine according to claim 6, characterized by a central control valve controlling the supply of compressed air to the quick-acting air valves of the cylinders.

12. Machine according to claim 7, wherein the air filter means is in the form of a filter layer which is disposed directly in the machine table between said suction nozzle and said suction cylinder of said vacuum pump. 13. Machine according to claim 12, wherein said air filter means is a wide-surface filter layer of substantially the same diameter as the suction piston of said vacuum pump.

14. Machine according to claim 12, wherein said filter layer comprises a granular metal swarf.

15. Machine according to claim 12, wherein said air filter means comprises a finely perforated capsule releasably fitted into said machine table and filled with filter material.

16. Machine according to claim 12, wherein said filter layer is a plate-like ceramic filter member releasably fitted into said machine table. t

17. Machine according to claim 12, wherein said machine table comprises a number of stacked plates and one of the plates is fo'rmed with a recess to receive said filter layer. 1

18. Machine according to claim 17, wherein said filter layer is disposed in the bottom plate of the machine table and is retained by the top plate, said top plate including at least one suction nozzle.

19. Machine according to claim 17, wherein said filter layer is disposed in the top plate of the machine table and is retained by means of a cover disc, said cover disc including at least one suction nozzle.

20. Machine according to claim 17, wherein the top plate includes spaces forthe passage of a coolant to cool said filter layer and said suction nozzle.

' 21. Machine according toclaim 20, wherein at least one sealingmean's is provided around the suction ducts and around said filter layer in the gap between the top plate and the bottom plate of said stack of plates.

22. Machine according to claim 7, wherein an air washer is included in said suction pipe between said air filter means and said suction cylinder of said vacuum Pl P- 23:.' Ma'chine according to claim 22, wherein said machine table plate comprises suction ducts which extend from said suction nozzle to said air filter means and to said air washer and also to the suction cylinder of said vacuum pump, said machine table plate also including at least one air removal channel extending from said suction cylinder of said vacuum pump to at least one springloaded air-ejecting non-return valve.

24. Machine according to claim 23, wherein said air filter means is fitted in said plate and said air washer and said non-return valve are supported by said plate.

25. Machine according to claim 8 in which said box has sealing means provided around said suction station and said charging aperture in the outer walls of said box.

References Cited in the file of this patent UNITED STATES PATENTS Peterson June 25, Lougheed Nov. 4, Vest Feb. 25, Mariette Aug. 2, De Ranek Aug. 7, Taccone May 27, Daniel et al. Aug. 7, Magnuson et al. Aug. 21, Peterson Sept. 4, Buhrer May 21,