Apparatus for compacting granular molding materials by pressurized gaseous mediums

The apparatus has a plurality of tubular hollow members arranged between the pressure chamber and the molding units, in the pressure surge flow direction, for conducting the gaseous medium to the top of the molding material. With distribution of the pressure medium flow through a plurality of independent and different cross sections, the lifting force required to open the packing element is greatly reduced and the packing element can be opened rapidly.

FIELD OF THE INVENTION 
The present invention relates to an apparatus for compacting granular 
molding materials, particularly foundry molding sand, by applying a surge 
of gaseous pressure to the surface of a mass of molding material poured 
loosely over a mold pattern unit. 
BACKGROUND OF THE INVENTION 
Conventional apparatus for compacting granular molding materials with 
pressurized gases, particularly compressed air, have a passage opening 
between its pressure chamber and mold unit covered by a diaphragm or a 
plate-like shut-off element. The diaphragm or element closes and opens the 
passage opening to permit the air pressure to contact and compress the 
molding material. 
When the full passage opening is in use in the conventional apparatus, the 
transverse cross-sectional area of the passage opening determines the 
force required to lift the packing element. Such packing element can be a 
diaphragm, a valve disk or some other device. The larger the 
cross-sectional area of the passage opening, the greater is the required 
lifting force to open the passage opening. 
The greater lifting forces, required for conventional apparatus with large 
transverse cross-sectional area passage openings, are difficult to attain. 
This is especially the situation with rapid-opening devices because of the 
short time available to move the packing element. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an apparatus for 
compacting granular molding material by a surge of pressure of a gaseous 
medium wherein the lifting forces for moving the packing element to open 
the passage opening, even for relatively large cross-sectional area 
passage openings, are minimized, and wherein complete flowthrough is 
attained in a very short reaction time. 
The foregoing object is obtained by an apparatus for compacting granular 
molding materials, particularly foundry molding sand, comprising a 
pressure chamber which can form a closed system with a molding material 
filled molding unit at the pressure chamber outlet, a passage providing 
fluid communication between the pressure chamber and the outlet, and a 
common packing element. The passage includes a plurality of hollow members 
extending within the pressure chamber and separated from each other in the 
pressure chamber. Each hollow member has a first open end within the 
pressure chamber and a second open end opening at the outlet. The common 
packing element releasably covers and closes each of the first open ends 
to control fluid pressure flow from the pressure chamber to the molding 
unit. 
By forming the apparatus in this manner, the hollow members, extending 
through the pressure chamber, separate the total cross-sectional area of 
the passage and expose the packing element to the fluid pressure in the 
pressure chamber so that such fluid pressure exerts an upward force on the 
packing element tending to move the packing element upwardly to an open 
position. The cross-sectional areas of the individual hollow members 
determine the lifting force required for the packing element. Thus, the 
required lifting force is relatively small and the time required to open 
the passage is minimized. 
Other objects, advantages and salient features of the present invention 
will become apparent from the following detailed description, which, taken 
in conjunction with the annexed drawings, discloses preferred embodiments 
of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
FIGS. 1 to 4 illustrate embodiments of the present invention having similar 
features. A packing plane 1 is formed by first open ends 5 of a plurality 
of tubular hollow members or bodies 2. Hollow members 2 are mounted in a 
pressure chamber housing 3 separately and spaced from each other, forming 
spaces 4 between the hollow members. Spaces 4 and the inside 15 of the 
housing 3 provide an undivided or continuous space. The second open ends 6 
of the hollow members opposite packing plane 1 open to the outside of 
housing 3 and in a molding unit over a mass of molding material. Hollow 
members 2 can be arranged so that their longitudinal axes extend parallel 
to each other. Alternatively, the axes can extend somewhat radially 
relative to each other. The second open ends 6 of hollow members 2 
opposite packing plane 1 are tightly connected with a part of housing 3 
forming part of the housing wall. The lengths and the spacing of hollow 
members 2 projecting into the pressure space and spaces 4 between the 
hollow members 2 can be arranged in any cross-sectional alignment 
depending on the plurality of hollow member cross-sectional configurations 
provided. Additionally, the required quantitative low-loss flowthrough of 
pressure medium can be met. 
FIG. 1 shows a packing element 7 in the form of a plate-like piston. 
Element 7 is constructed with one or more aperture-like cutouts 8 to save 
weight, and is coated closely with an elastomer. 
This piston packing element is inserted in an air-tight packing housing 9 
with the packing element guided loosely with little lateral play within 
the periphery of packing housing inside surface 10. About 0.1-0.3 mm 
lateral play is required. 
Such piston can also be concave so that it can be guided properly. 
The packing housing 9 is connected by reinforcements 11 with housing 3. 
Compressed gas, e.g. compressed air, is conducted through control line 12 
in the housing cover 14 and into packing housing 9 for actuation of piston 
packing element 7. Control line 12 can be attached through a valve 13 to a 
suitable control device. Valve 13 can be operated pneumatically, 
hydraulically or electrically. 
Open ends 6 of hollow members 2 opposite packing plane 1 open in a 
discharge part or outlet 16 of housing 3. Ends 6 are tightly attached to 
their peripheries with a base part 17 of housing 3. This discharge part 16 
has a flange connection 18, in the present embodiment, which is configured 
for connection with a molding unit. Other types of connections can be 
used. An air pressure feed line 19 is mounted on the side of the housing 
to supply pressure medium to the housing inside 15. The valve 20 can be 
provided in line 19. 
FIG. 2 shows a cross-sectional view through the hollow member arrangement 
of FIG. 1, along line A--A. The hollow members are formed as pipes with 
partially the same and partially different, circular cross-sectional 
configurations. However, the hollow members can also have polygonal 
cross-sectional configurations and/or be conical in length. The 
longitudinal axes of hollow members 2 in FIGS. 1-2 are parallel to each 
other. The horizontal cross section of hollow members 2 and the 
corresponding cross section of the intermediate spaces 4 between hollow 
members 2 are aligned generally for the flow of the pressure medium. Thus, 
it can be advantageous, from a flow technology consideration, to vary the 
hollow member cross sections from the outside inward, relative to a bundle 
of hollow members. Larger hollow member cross sections 21 are 
advantageously subdivided by transverse rods 22, to distribute the 
pressure of packing element 7. 
FIG. 3 shows an apparatus similar to that of FIG. 1, but with a closed 
packing element. Hollow members 2a are in a radiating configuration, and 
can be cylindrical or conical. The hollow members are separated and spaced 
from each other in the pressure chamber, forming spaces 4a between the 
hollow members. Packing element 7a, engaging hollow member open ends 5a in 
packing plane 1, is configured as a one-piece, unitary, integral unit. The 
side of the element 7a facing packing plane 1 is provided with a 
reinforcement plate 23 to receive the packing pressure. The reinforcement 
plate 23 is of light metal to avoid creating large forces. Plate 23 can 
also be plastic, and is of suitable configuration. To guarantee stability 
of the shape of the plate in a pressure-less state, a material is selected 
for use on this side of packing element 7a which has a sufficient inherent 
rigidity, but is nonetheless flexible. Reinforced elastomers are suitable. 
The hollow space 24 of packing element 7a can be filled with a pasty 
substance, a suitable liquid or the like, to improve the rigidity when it 
is in a pressureless state, and to keep the hollow space as small as 
possible. 
Pressure chamber housing 3a has a packing housing 9a on the top 25 for 
packing element 7a. Housing 9a is detachably connected with housing 3a. On 
the side of housing 3a, a feed line 26 is provided for the pressure 
medium, e.g. compressed air. A valve 27 is provided to close or open the 
feed line 26. The discharge ends 28 of hollow members 2a open into a 
cylindrical discharge part 29 which is provided with a connection flange 
30. Ends 28 are connected tightly with a base 31 of discharge part 29. 
However, it is also possible to connect ends 28 of hollow members 2a 
directly with pressure chamber housing base 32, without connection to 
discharge part 29. The requirement that the sum of the intermediate spaces 
4a between hollow members 2a is at least as great as the total 
cross-sectional area of the plurality of hollow member cross sections must 
be fulfilled. This guarantees a direct flowthrough of the pressure medium. 
FIG. 4 shows an embodiment with a molding apparatus for the manufacture of 
foundry molds and with a diaphragm-like packing element. 
The top of pressure chamber housing 3b is closed with a cover 37 in which 
packing plane 1 is located. Packing plane 1 is similar to that in FIG. 1, 
i.e., made from a plurality of ends 5b of hollow members 2b. The hollow 
members are aligned in the flow direction of the pressure medium and are 
separated from each other. Ends 5b of hollow members define packing 
surfaces. 
The discharge ends 33 of hollow members 2b are connected tightly at their 
outside peripheries with a base part 34 of a discharge part 35. Discharge 
part 35 is incorporated into the base part 36 of housing 3b and thus, 
together with the cover 37 and packing element 7b, limit the inside space 
41 of the pressure chamber housing. 
A plate, provided as a diaphragm, forms packing element 7b. Element 7b is 
held at its periphery both by housing cover 37 and by packing cover 38. A 
control line 39 extends through the cover 38 for actuating diaphragm 7b 
with air. Line 39 can be operated through a valve 40 which can be operated 
pneumatically, hydraulically, or electrically. A feed line 42 for a 
conveyor or pressure medium, e.g. compressed air, is provided on the side 
of the pressure chamber housing wall. A valve 43 inserted in line 42, as 
needed, allows constant or interrupted feed of compressed gas to the 
inside 41 of housing 3b. 
The apparatus of FIG. 4 is illustrated in combination with a molding unit 
(shown in phantom lines). Housing 3b is configured with its bottom end 
having means for coupling it to the molding unit. 
The molding unit comprises a loading chamber 44 in a molding box 45 and a 
pattern assembly 46. A cylindrical elevator arrangement 47 lifts and 
lowers this unit. Molding material 48 is provided in the proper amount in 
box 45 via an aerating line 49 with a valve 50. Thus, the compressed gas 
remaining after the in-flow can be expanded through the molding material 
before lowering the molding unit. The unit is then subsequently separated. 
The apparatus according to the present invention operates as follows. 
Assuming that a gaseous medium must be conveyed, a control pressure medium 
is passed through the control line at a predetermined pressure to the 
packing element which is thereby brought into the packing or closed 
position on the packing surface. A conveyor or pressure medium is then 
brought through the feed line into the pressure chamber housing, i.e. into 
the pressure space, and readies the apparatus to conduct the pressure 
medium or to produce a surge of pressure. 
It is easy to provide the pressure for the control medium in the same 
manner as for the conveyor or pressure medium. The mediums can be of the 
same type. 
Thereafter, the pressure in the control line is lowered by operation of the 
control valve so that the pressure, which had been greater until this 
time, on the control side of the packing element is reduced below the 
pressure on the pressure chamber side. The force working on the pressure 
space side of the packing element raises the element when equilibrium has 
been passed. In this manner, the packing element is raised suddenly and 
the conveyor medium can be discharged as a surge of pressure. 
While various embodiments have been chosen to illustrate the invention, it 
will be understood by those skilled in the art that various changes and 
modifications can be made therein without departing from the scope of the 
invention as defined in the appended claims.