Note: Descriptions are shown in the official language in which they were submitted.
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Pattern withdrawing device in foundry plants.
The present invention relates to a pattern withdrawing
device in plants and molding machines for use in foundries
and, in particular, in those types of plants in which the
molding boxes are automakically conveyed to the molding
stations and hence to the following working stations. In
the relevant molding station the model plate pushes, from
beneath, the molding box upwards, which box on reaching a
certain height, is locked and filled up with sand, which
will then be tamped by the usual means.
The molding being thus carried out, the model plate
goes down together with the molding box, stopping when
reaching the height of the transport plane.
The model plate keeps on going down, thus starting the
real pattern withdrawing operation; at the end of which
the molding box resumes its travel away from the molding
station, which will be subsequently occupied by a new
molding box.
The operations described so far are characteristic
of equipment already known in the art. However, the con-
2~ tinuous use of the molding boxes causes their deformation,due in particular to the high temperatures they are
submitted to during the casting operations.
Thus it happens often enough that after a certain
number of utilizations, owing to said deformations, the
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lower surface of the molding bow does no longer fit itself
perfectly to the bearing plane consisting of the pattern
withdrawing rollers (or push rods~ of the transport plane
of the molding station.
Owing to this uncertain bearing condition, when the
pattern withdrawing operation starts, the molding box is
impelled to take a different bearing position on the
rollers. This relative displacement between molded box
and model exerts a certain stress on the tamped sand
causing, on certain occasions, the breakage (tearing) of
the less resistant parts and of those parts the pattern
withdrawing of which arises some problems. So as to avoid
this inconvenience, the bearing surface oE the molding
boxes was periodically submitted to grinding operations
aiming at restoring their coplanar conditions. These
operations, besides the cost involved, reduced, in the
long run, and in an unacceptable way, the height dimen-
sions of the molding boxes, which were consequently
rejected and substituted.
On account of the high unit cost of the molding
boxes and of the consequent production losses, it became
necessary to study a different solution of the problem.
This constitutes the purpose of the present invention.
The technical problem to solve in order to attain the
purpose stated above was to create a new uniform bearing
plane for the strained molding boxes, i.e. a plane capable
to fit by itself, whenever necessary, to any possible
deforrnation suffered by the bearing plane of the molding
boxes~
~he solution of the technical problem is characterized
by the introduction of four hydraulic cylinders with
pistons so operated as to constitute self~aligning bearing
elements so as to adapt thernselves to the molding boxes
during their pattern withdrawing operation, together with
a simultaneous locking system of said pistons to stop the
motion of the molding boxes in connection with the model
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holding table which, while pursuing its travel downwards,
carries out the pattern withdrawing operation correctly.
Further features and advantages will become evident from
the description of a preferred realization of the invention
and from the drawings attached hereto, in which:
Fig. 1 is a schematic and perspective view of the
equipment including the device constituting the object
of the present invention;
Fig. 2 is a plane view of the equipment of Fig. l;
Figs. 3 and 4 show a deta,il of Fig. 1 and
Fig. 5 shows the pneumatic plan referring to the
operation of the equipment being the object of the
invention.
In Fig. 1 we have denoted with the number 10 a molding
box consisting of four vertical walls 12 and of two frames,
an upper one 14 and a lower one 15 delimiting the lateral
walls. By sectioning the molding box into vertical planes
in parallel with the transversal and longitudinal axes of
the molding box, the contouring walls would appear in the
shape of a "C".
This configuration depends on the transfer s~stem of
the molding boxes, which transfer takes place on roller
guides 16.
During its travel towards the molding station, the box
rests on said rollers with the lowe'r surface of the upper
frame 14 and it is pushed on same conveying rollers by
some special arms operated pneumaticall~. Nearhy the
rnolding s-tation the roller walls are shaped with the
rollers arranged according to a lower line in such a way
as to impel the molding box to rest on them with the lower
surface of the lower Erame ]5 (Fig. 2) and to be able to
make the vertical translations recluirecl by the molding
ancl pattern withdrawing operations, as illustrated on the
following pages.
In the molding station there is the model bearing table
1~, which is provicled with two vertical pins 20 to Eit into
the corresponding holes 22 provided on the frames 14 and 15
of the molding box 10.
The part bearing table 18 is rigidly connected with the
shank 24 of a piston 26 sliding in a simple effect pneuma-
tic cylinder (Fig. 5) and it follows the motions of the
shank, being guided and supported by the body 29. Connec-
ted with the internal walls of plates 30 (Fig. 2) there are
four small cylinders 32 provided with the relevant small
pistons 34l the function of which will be illustrated in
detail on the following pages (Figs. 1 and 5).
Connectecl hy means of the rod 36 with the model bearing
table 18 there is a cam 38 operating, by its very motion,
some special valves controlling the subsequent phases of
the molding and pattern withdrawing cycles, as is specif-
ied more in detail in the description of the pneumatic
operating plan. With reference to Figs. 3 and 4, we give
now the description of one of the four cylinders 32.
In the upper part of it there is piston 34, which is
hydraulically operated. The operating oil, gathered in
the tanks 102 and 108 (Fig. 5), reaches the cylinder from
below through hole 42 (Fig. 3), a circular chamber 44,
ducts 46, hole 48, and hole 50 (Fig. 4). In the lower
part the cylinder is provided with a shutter device to
prevent the flowing of the oil and, lastly, the piston 34
in a given position.
This device consists of a small piston 52 sliding
inside a bushing 54 and ending up as a truncated cone
~itting into an opening 56, which connects duct 46 with
hole 48. The opposite side of the small piston 52 is
connected with air intake 60 connected, in its t~lrn, with
the pneumatic equipment operating the whole pattern with-
drawing equipment.
In cylinder 32 (Fig. 3) there is also a duc-t 62 to
convey the oil in the upper part of the cylinder throuqh
hole 64 to move the piston downwards.
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We illustrate hereunder the working of the device
which is the object of the invention with reference to
Fig. 5 in which, for simplicity's sake, we have shown only
the elements directly involved in the working of said
device. To understand said working it is sufficient to
bear in mind that lines 153 and 153' represent the general
air feeding whereas lines 149 and 151 are connected with
the remaining pneumatic circuit; line 151 is under pres-
sure in the lifting phase of the model bearing table 18
and in relief in the lowering phase of same, whereas line
149 is in relief in the lifting phase and under pressure
in the lowering phase. When molding box 10 reaches the
molding station, it is enabled to send a pneumatic signal
of comrnunication to a pre-working valve 150 through way
151. This valve 150 by communicating itself links the
general air feed network 153 with the pilot of a valve
154, which commutes itself and sends to cylinder 25 the
air which pushes piston 26, the model bearing table 18 and
molding box 10 positioned above it upwards.
When table 18, in its travel upwards, reaches a height
at which its cam 38 commutes valve 166, a pneumatic signal
of commutation is sent to valve 100, which is connected
with the main feed network 153'; consequently the compres-
sed air reaches tank 102 compelling the oil in 102, in duct
104 and in cylinder 32 to push the pattern withdrawing
pistons 34 upwards.
Having reached the upper end position of its travel,
the model bearing 18 operates, by means of cam 38, the
valve 168. This commutes itself and sends the air coming
from line 151 to the pilot valve 170, commuting it.
The air arrives at double-acting cylinder 173 thus
pushing piston 175 to the left and operating the mechanical
block 177 of shaft 2~ of piston 26. The molding box 10 is
thus secured to its sand loading and tamping position for
the molding operation.
At the end of this operation there is the starting of
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the descent phase: valve 168 gets discharged through way
151, which enters into its discharging phase, and valve
170 gets commuted through line 149, which gets activated
to send the air to cylinder 173, in order to urge piston
175 to the right and release piston 26. At the end of its
travel, piston 175 commutes valve 1~4 and, consequently,
the air reaches, from line 149, the pilot of valve 150
which, getting itself commuted, puts valve 154 in a dis-
charge condition. In the absence of the feed to piston
26, this along with molding box 10 and the model bearing
table 18, starts its descent pulled down by the force of
gravity. At the beginning of its descent travel, the
model bearing table 18, with cam 38, leaves valve 166,
which gets commuted and removes the air from tank 102.
The molding box 10 lies down, in its descent, on pat-
tern withdrawing pistons 34, which get self-aligned and
build up a safe support for the molding box.
At the end of a travel of about 100 mm, cam 38 operates
valve 180, which sends a pneumatic signal to commutation
valve 182. The air reaches connection 60 ~Fig. 4) through
feed line 106, thus operating the oil stopping device 51.
Piston 52 (Fig. 4) is pushed against surface 56 and it
closes the oil duct. The molding box is thus locked and
supported by four pads of the oil contained between locking
piston 52 and piston 34 (Fig. 4).
The model bearing table 18 continues going down, thus
carrying out the pattern withdrawing operation in the most
favourable conditions without any danger of provoking tears
in the weaker spots of the mold.
When reaching its lowest position, cam 38 leaves the
pilot lever oE valve 180, so that valve 182 gets commuted
again on the discharge phase, thus bringing again the oil
stopping device 51 in a non operating condition.
In this condition valve 164 is commuted, which valve
commutes in its turn valve 110, which sends air from line
153' to tank 108.
