DE1058702B - Method and device for the mechanical production of foundry molds from molding sand - Google Patents

Description

GERMAN

INTERNAT. KL.

PATENT OFFICE

B 27532 VI / 31b

A N M E L D E T A G: SEPTEMBER 18, 1953

NOTICE
THE REGISTRATION
AND ISSUE OF THE
EDITORIAL:

June 4, 1959

It is known that molding sand, which is filled in via a pattern device, is deposited on a molding box is put on, when it is pressed with a plate for the purpose of compaction, over the high model parts very strongly compressed, but that the compression drops considerably over the other parts. In practice, this phenomenon is intensified by the fact that the molding sand is poured in mostly from higher-lying silos in a strong jet impinges directly on the model equipment and therefore especially above the higher model sections, but also preferably in the middle of the molding box already at the Filling is strongly pre-compressed. Neither by shaking nor by placing filling frames the resulting compaction unevenness during the final compaction by pressing completely eliminated will. Also the application of horizontal or spatial vibrations or other means, which have been used in practice give imperfect results. With higher models you are therefore forced to either use profiled blocks or between precompaction by shaking and re-compacting by pressing the molding sand by hand over the middle sections and to be removed from the tall models and placed along the edge of the molding box to reduce the unevenness of compaction, which results after the final compaction by pressing, to reduce at least to a tolerable level. But it can also because it does not succeed when filling, always in a successful way in terms of quantity Apart from placing the same heavy filling with molding sand over the model equipment from the horizontal distribution, no uniform compression can be achieved.

It has also been suggested to put more sand over the molding box than for making the mold needs to be filled up and this excess sand to be removed again after the pre-compaction. This suggestion solves the task of achieving uniform molding sand compaction, but not because the sand only accumulates in excess in the middle of the flask and in the places that must be subjected to particularly careful compaction, no excess sand can fix. This is especially true for the edge area, where the loosely filled molding sand slides off when filling.

The purpose of the method according to the invention is to at least for the most part to delay the various disadvantages, thereby increasing the accuracy and surface finish to improve theforrrt and make a significant contribution to create the requirements for an automatic molding machine.

Method and device

for machine production

of foundry molds made from molding sand

Applicant: Erwin Bührer, Schaffhausen (Switzerland)

Representative: Dr.-Ing. E. Hoffmann, patent attorney, Munich 22, Widenmayerstr. 34

Claimed priority: Switzerland of October 22, 1952

Erwin Bührer, Schaffhausen (Switzerland), has been named as the inventor

The process for the mechanical production of foundry molds from foundry sand, in which this precompacted by shaking using a filling frame that can be placed on the molding box and is then subjected to a post-compression, characterized in that first of all over the Pattern equipment more molding sand is poured in than the finished form needs, and this excess is supported by the molding box height increasing means so that it over the entire surface of the Pattern equipment can be refilled, so that the excess molding sand is evened out when vibrating the pre-compression causes, whereupon the excess between pre-compression and post-compression is separated.

The molding sand is preferably poured in by sprinkling. The process arises after the pre-compression and after the removal of the excess molding sand, a pre-compressed Form in which the molding sand protrudes above the upper edge of the molding box by the height required for recompaction, d. i.e., it is weight-wise ü1) cr the raised model parts less, on the other hand over the other parts of the model equipment more molding sand than is available from the previous methods. This better horizontal distribution of the molding sand over the pattern equipment before recompaction - at least partially has to be done by pressing - allows to dispense with a compression acting transversely to the pressing direction. This is all the more important as experiments

909 529/112

have found that when pressing molding sand, the compaction effect transversely to the pressing direction is insignificant is small and also due to the highest compression pressures because of the internal self-locking of the molding sand cannot be increased. But this process also has the consequence that the pre-compressed In terms of weight, the amount of molding sand lying above the model is a certain, largely regular Has size.

The method according to the invention also provides that the pre-compression is preferably carried out vertically to the model level in the molding sand itself takes place inertial forces, and in the further that these through Shaking can be generated. This increases the pre-compaction in the deep parts of the sand and decreases towards the top. Both measures improve the pre-compressed form as a starting point for recompaction. In order to get as evenly compacted form as possible in the end, see this Procedure before that the vibration is elastically damped so strongly that when pre-compacting in the lower In part of higher sand layers, an intentional greater compaction is created than in the lower part of the lower part Sand layers, further that the pre-compaction intensity is chosen so strong that in the lowest Part of the highest sand layers has already achieved the desired full compaction. Through this As the calculation and the tests show, the compaction uniformity is further improved. It are probably suggestions to connect soft substrates between the vibrating mass and anvil or membrane-like, Made to use springy steel plates; however, the effect of these documents is too small to produce the above-described height-dependent compaction difference. The well-known suggestions made the sense of the pressure that the vibrating blow on the anvil produces, to zoom out. It should be emphasized here that the damping of the vibrating impact to generate various Compaction intensities at different sand heights only make sense when used of the present proceedings. The proposed bedding increases the malleability of the sand and This means that, for example, fonts can be reproduced on model equipment, etc. smaller when filling and the sand is distributed more evenly over the entire surface of the box.

The drawing shows an example of a device for carrying out the method, it shows:

Fig. 1 is an elevational section of the device along section line I-I in Fig. 2,

Fig. 2 is a plan view of the same according to Fig. 1,

Fig. 3 is a side elevation of Fig. 1, partly along the section line H-II in Fig. 2,

4 shows a view of the filling frame, seen in the direction of arrow A in FIG.

The drawing shows a molding machine with a machine stand 1, a plunger 2 and a vibrating piston 3, which is lifted by a pressure medium in a known manner and, after draining, this pressure medium falls back by its own weight on the plunger 2, which during the vibrating process on the bottom of the Machine stand 1 rests. All control elements and lines are not shown in the figures for the sake of clarity. The vibrating flask 3 carries the vibrating table 3ö, on which a model plate 4 with a model 5 rests. The molding box 6 is supported on the pattern plate 4, and the filling space 7 rests on its upper edge. This has on its lower side a reinforced edge 7 a, which has on its inner sides obliquely downward and outward surfaces 7 &, which serve to form S a truncated pyramid shape of the sand, facilitate the lifting of the filling frame 7 from the molding box 6 and when Recompaction prevent molding sand from falling over the edge of the molding box. Under molding sand it becomes more clay-bound

ίο Quartz, chamotte, zircon sand or the like understood.

Sit on the reinforced edge 7 a , with this one

connected, opposite the parallel walls "ic, whereas on an edge portion of the blade 8 lies and on the other edge portion of the flap 9. The two walls 7 are c egg through the wall 7 and the piece of tube 7e connected to each other (Fig. 1, 3) . the sand container of the filling frame 7 is accordingly c through the side walls 7, the blade 8 and the flap 9 is limited. the blade 8 is located with the ends of its lower edge 8a on the c over the walls 7 inwardly projecting edge 7a, while the ends of their upper edge 8b are connected to two endless chains 10. These chains are guided over chain wheels 12 and 13 which sit on shafts 14 and 15 which are mounted in walls 7c , which engages in the piston rod 18 designed as a rack, the piston 18a of which is moved in both directions by compressed air in the cylinder 19 (Fig. 4). The piston rod 18 slides in the guide piece 20. Outside the chains are on bolts 22 Sekto Ren 23 pivotally mounted on which the flap 9 is attached. In the chain wheels 13, arranged like crank pins, are seated bolts 24, which at times reach under the ribs 25 of the sectors 23. In one direction, the shovel 8 is moved in the direction of the flap 9, which is simultaneously lifted by the bolts 24 so that the sand pushed by the shovel 8 can fall from the filling frame 7 into the sand return channel 27 covered with a grate 7 6.

The frame 7 is lowered onto the molding box by means of a pneumatic lifting device and after it has been filled and the molding sand has been precompacted, it is lifted so high from the molding box that the pressing plate 30, which is attached to the pivot arm 45 and is used for recompaction, can be pivoted over the mold. The lifting device is arranged on a stand 31, on which the press plate 30 can also be pivoted about the axis 32. There are two eyes 33 and 34 on the edge 7 a of the filling frame 7 and an eye 35 on the upper edge of the associated frame wall 7 c . These eyes are provided with conical bores into which the conical centering bolts 37 attached to the head 36 engage. The head 36 is fastened to the piston rod 38, the piston 39 of which is seated in the cylinder 40 which is fastened to the stand 31. The piston rod 38, which is secured against twisting by a wedge 41, moves so far down that the conical bolts 37 protrude from the bores when the filling frame 7 rests on the molding box, so that this unhindered the vibrating movements of the molding box 6 during precompression can participate. Above the uppermost position of the filling frame 7, a vibrating screen 42 is arranged at the lower end of a molding sand silo 43, the vibrating movement of which is generated by an electromagnet 44 and whose vibrating time can be controlled by a timer. Switching on the

1 UOO I \ J

Electromagnet can be done by hand or by an unspecified contact that is closed is after the frame rests on the molding box. This contact is useful actuated by the piston rod 38, which is still seated further down.

The device works as follows: It is assumed that a finished shape, just finished compacted by pressing, as shown in FIG. 3, is on the machine. Now by actuation a control member, not shown, drained the pressure medium under the plunger 2, the Plunger 2 and thus the vibrating table 3 a with the pattern set 4 or 5 and the finished form descend. The pressing plate 30 is moved into the pivoted position, as shown in FIG. 2, and the finished form lifted off in a known way. After placing a new molding box 6 is by actuating another, also not shown control member, 'which with the already mentioned can be combined, drained the pressure medium under the piston 39, this lowers and thus also lowers the filling frame 7 until it rests on the molding box 6, where it is supported by stops 7 /, as Fig. 1 shows, is performed on the molding box 6 in the horizontal direction, whereupon by further Lowering the piston 39 to the bottom of the cylinder 40 keeps the conical bolt 37 out of sight 33, 34, 35 are pulled out, so that the filling frame 7 without physical connection with the Bolt 37 and thus with the piston rod 38 etc. is. At the same time, by pressing a contact The electromagnet 44 is supplied with current and thus the vibrating screen 42 is actuated.

The molding sand is then sprinkled onto the models 5 and the mold plate 4, with it flowing continuously from the silo 43. After the necessary amount, which can be set at a time switch, has been sifted out, the current is interrupted, the electromagnet 44 stands still and the sifting of the molding sand stops. The pre-compaction by shaking, which now begins, is carried out in a known manner by actuating the control element already mentioned. After the molding sand has been pre-compressed, a pressure medium is fed to the cylinder 19 via the opening 19 a by actuating another control element, which can also be combined with those already mentioned, while the pressure medium on the opposite side can flow out via the opening 19 b. The shovel 8 is thus pushed by the movement of the piston 18 a via the piston rod 18, gear 17, chain wheels 12 and chains 10 from the position shown in FIG. 1 into the position shown in FIG. 4, while at the same time the flap 9 is pushed by the bolts 24 is raised into the position shown in FIG. As a result, the excess molding sand located above the molding box 6 is peeled off to the level of the inwardly protruding edge 7 a of the filling frame 7 and falls through the grating 26 into the sand return channel 27 Pressure medium is supplied, while the pressure medium on the opposite side can flow out through the opening 19a, whereby the blade 8 is withdrawn into the position shown in FIG. 1 and the flap 9 is lowered into the position shown in FIG. 1 in the opposite direction to the process already mentioned . At the same time, the cylinder 40 receives pressure, lifts the piston 39, so that the piston rod 38, the head 36 with the centering pins 37 fastened therein, whereby after covering a partial stroke via the conical bores in the eyes 33, 34 and 35 the filling frame 7 in the position shown in Fig. 3 is raised, which is set by the ■ stroke limitation of the piston 39 in the offset bore of the cylinder 40, after pivoting the pressure plate 30 from the position shown in FIG. 2 to the position shown in FIG under the press -

ίο piston 2 by actuating a control element Pressure medium supplied, whereupon this and thus the vibrating table 3 α, the mold plate 4, the model 5 and raise the molding box 6 and press the precompacted form against the press plate 30 that the in the pre-compressed state, the molding box in the shape of a truncated pyramid towering over Molding sand is compressed up to the upper edge of the molding box. After the completion of compaction, the Work sequence all over again.

The idea of the invention is not tied to the device described, nor is it exclusive to the work sequence described. It can e.g. B. the pre-compression by shaking already during the filling of the molding sand are initiated. It should also be pointed out in particular that the process is not tied to the drawn silo shape or to the spreading. The procedure can used on all types of molding machines, both on "lifting machines" and on "turning machines" will; it is only a matter of the presence of appropriate means for pre-compression and post-compression. tight bound. Instead of using straight, flat shovels to remove the excess granular mass To be separated evenly above the molding box, the section surface can also be uneven in two or three dimensions be generated. Furthermore, it is not necessary to use the blades to separate the excess granular Combine mass with the filling frame. The latter can be constructed in several parts, see above that the separating agents can be stored separately on their own.

Claims (6)

Claims ·. I. Process for the mechanical production of foundry molds from molding sand, in which this precompacted by shaking using a filling frame that can be placed on the molding box and then subjected to post-compression, characterized in that first of all over the Pattern equipment filled in more molding sand than the finished form needed, and this excess is supported by the molding box height enlarging means that it over the whole Surface of the pattern device can be filled, so that the excess molding sand when vibrating a Uniformity of the pre-compression causes, whereupon the excess between pre-compression and post-compression is separated. 2. The method according to claim 1, characterized in that the vibrating impact during precompression is elastically damped so much that the molding sand in the lower part of higher filling layers is more pre-compressed than in the lower part of lower strata. 3. The method according to claims 1 and 2, characterized in that the pre-compression intensity is chosen so strongly that in the lowest part of the highest filling layers of the molding sand the desired final compaction degree is reached. 4. Apparatus for performing the method according to claim 1, characterized by a the molding box attachable filling frame (7) with a device such. B. with a shovel (8), is provided for separating off the excess of the molding sand. 5. Apparatus according to claim 4, characterized in that the filling frame (7) has a downwardly projecting edge (7 b) which is suitably beveled pyramid-shaped and whose height corresponds to the volume reduction during recompaction. 6. Apparatus according to claim 4, characterized in that the on the piston rod (38) attached head (36) has conical bolts (37) which in conical holes (33 to 35) of the filling frame grab and step out of this as soon as the filling frame rests on the molding box. Considered publications:
German Patent No. 741,383;
Austrian Patent Nos. 57 020, 169 105; British Patent No. 394,667;
U.S. Patent No. 1,554,402. 1 sheet of drawings