(Member of the Society.)
Moulding machines may be classed under three heads. First, machines
which only ram the moulds, and, when the ramming is done by means of a
side lever, by hand, are generally called "squeezers." Second,
machines which only draw the patterns, the ramming being accomplished
by the usual hand methods. Third, machines which both ram the moulds
and draw the patterns, ramming either by a hand-pulled lever or by
fluid pressure on piston or plunger and drawing the patterns through a
plate called a "stripping plate" or "drop plate"--till recently the
usual method--or without the use of this plate fitting everywhere to
pattern outline at the parting surface, the patterns being effectively
machine guided in either case.
It is to the third class that the machine which is used to illustrate
the subject of this paper belongs, and which would seem to have enough
that is novel in the application of machinery to the foundry to merit
the attention of the society.
[Illustration: FIG. 1.--ORDINARY METHOD OF DRAWING PATTERN SPIKE AND
RAPPER.]
At the risk of appearing pedantic, but with a view to developing an
appreciation of the true function of the method of pattern drawing
used in this machine, attention is called to the following sectional
views of moulds and ways of drawing patterns occurring in machine
moulding. Fig. 1 shows an ordinary "gate" of fitting patterns being
drawn from the drag or nowel part of the mould by means of a spike and
rapper wielded by the moulder's hand after cope and drag have been
rammed together on a "squeezer" and cope has been removed. Frequently
the pernicious "swab" is used to soak and so strengthen joint outlines
of the sand before drawing patterns, in such cases as this. In this
case, before cope is lifted, these patterns must be vigorously rapped
through the cope; an amount depending (and so does the size of the
casting) upon the mood and strength of the moulder.
Fig. 2 shows the stripping or drop plate method of drawing patterns.
[Illustration: FIG. 2.--STRIPPING PLATE METHOD OF DRAWING PATTERNS.]
In this method the patterns are not rapped at all and are drawn in a
practically straight line so that the mould is absolutely pattern
size.
The stripping plate is fitted accurately to every outline at the joint
surface of the patterns, obviously at considerable expense, and, of
course, at the instant of drawing the patterns, supports the joint
surface of the mould entirely. This is, at first sight, an ideal
method of drawing patterns, and it has for years been the only method
practiced on machines. It has two disadvantages. The patterns are
separated from the stripping plate by the necessary joint fissure
between the two. Fine sand continually falls into this and, adhering
to the joint surfaces more or less, grinds the fissure wider. This
leads to a gradual reduction of size of patterns on vertical surfaces
and a widening of the joint fissure often to such an extent that wire
edges are formed on the mould, causing, on fine work, "crushing" and
consequently dirty joints. A nicely fitted but worn plate of
twenty-four pieces which had cost, at shop expense only, $250, was
recently replaced by a plate of twenty-eight pieces, fitted ready for
the machine under the new system about to be described, for not more
than $25.
The stripping plate method has another drawback, not always
appreciated, probably because accepted as inevitable. Stripping plate
patterns are not rapped, and there frequently occur on surface of
patterns, remote from the action of the stripping plate, rectangular
corners just as important to mould sharply as those at the parting
line. Such corners have either to be filleted or "stooled" in
stripping plate work, and neither method often is practicable. When
the entire pattern and plate are vibrated so that the corners where
the pattern joins the plate draw perfectly, as they do in the machine
to be described, it is obvious that similar corners anywhere on
pattern surface will draw equally well.
The vibrating of patterns, or rather of moulds, during the operation
of drawing the patterns possesses little of novelty. Ever since a
bench moulder's neighbor first rapped the bench while he lifted a cope
or drew a pattern, the thing has been done in one way or another. In
fact, machines are now and then found on the market in which a device
like a ratchet or other mechanical means for jarring the machine
structure during pattern drawing renders the working of easy patterns
without stripping plates possible.
The idea of applying a power driven vibrator directly to the plate
carrying the patterns to thus vibrate them independently of other
parts of the machine and the flask and sand has been the subject of
the issue of patents to Mr. Harris Tabor, and the various figures
shown will serve to illustrate the mechanism.
Briefly, the operation of the machine is as follows: The ramming head
shown thrown back at the top of the machine is drawn into a vertical
position after flask has been placed and filled with sand. The 3-way
cock shown at the extreme left is then quickly opened, admitting
compressed air of 70 to 80 pounds pressure to the inverted cylinder
shown at the center of the cut. The cylinder, with the entire upper
portion of the machine, is thus driven forcibly up against the ramming
head, flask, sand and all. Often a single blow suffices to rain the
mould--often the blow is quickly repeated, according to the demands of
the particular mould in hand. Gravity returns the machine to its
original position, as the 3-way cock opens to exhaust. After pushing
the ramming head back and cutting sprue, if the half mould is cope,
the operator seizes the lever shown just inside the 3-way cock at the
right, and, drawing it forward and down, raises the outer frame of the
top of machine containing the flask pins, with flask and sand thereon,
away from the patterns, thus drawing them from the sand. Just as he
seizes the pattern drawing lever with his right hand, he presses with
his left on the head of a compression valve shown at the left side of
top of machine, thus admitting air to the pneumatic vibrator already
referred to.
[Illustration: FIG. 3.--POWER DRIVEN VIBRATOR MACHINE.]
Fig. 3, a rear view of the machine, shows at the top center, with its
inlet hose hanging to it, this vibrator, which is shown in section in
Fig. 4. It consists simply of a double acting elongated piston having
a stroke of about 5/16 inch in a valveless cylinder and impacting upon
hardened anvils at either end at the estimated rate of 5,000 blows per
minute.
[Illustration: FIG. 4.--SECTION THROUGH VIBRATOR.]
The method of communicating the rapid yet small oscillations of the
vibrator to the patterns and yet keeping them from being transmitted
to the rest of the mechanism is this:
A frame, called a vibrator frame, to which the pneumatic vibrator is
bolted and keyed, is shown in Fig. 5. To this frame the plate carrying
the patterns, often, in cases of patterns having irregular parting
lines, forming one and the same casting with the patterns, is fastened
by the four machine screws, the small tapped holes for which are shown
in the corners. In fact, in changing patterns, the process consists of
simply removing these four machine screws, taking up the pattern
plate and screwing to the vibrator frame the new pattern plate. The
vibrator frame itself is secured to the machine structure by the four
larger bolts, the holes for which are shown in the inner corners.
These bolts are, as shown in Fig. 7, surrounded by thick bushings.
These bushings are elastic to such a degree as to absorb the sharp
vibrations of vibrator frame and patterns, while so firm and well
fitted as to hold patterns accurately to their position.
[Illustration: FIG. 5.--VIBRATOR FRAME.]
The action of the vibrator is such as to give to the entire pattern
surface an exceedingly violent shiver, making it impossible that any
sand should adhere to this surface, while the magnitude of the actual
movement of the pattern is so slight that it is found to fill the
mould so completely that it is impracticable to draw it a second time
without rapping. Yet, so truly are the patterns held and so little
disturbed from their original position, that it is perfectly
practicable to return patterns to a mould having the finest ornamental
surface in the ordinary practice of "printing back."
In cases where deep pockets of hanging sand occur, which cannot be
held during lifting off and rolling over, machines are arranged to
roll the flask over in their operation and draw the patterns up under
the influence of the pneumatic vibrator, though, owing to the time
consumed in the rolling over process (and each operation counts in
seconds on a moulding machine) this style of machine is not usually as
rapid in its working as the simpler type, in which the flasks come off
in the same way they go on.
[Illustration: FIG. 6. SET OF PATTERNS FITTED TO PLATES.]
Fig. 6 shows a set of patterns as they are ordinarily fitted to plates
for this machine. Round holes will be noticed at places in the plate
surface. These are openings for the insertion of what are called
"stools."
When it is found necessary to support the sand surface at any point,
or generally, round holes are drilled through either plate or pattern
surface and loose cylindrical pieces are dropped into these holes,
their upper end surfaces being flush with the plate or pattern surface
and their lower ends resting on the plate called, from this use, a
stool plate. This plate appears in Fig. 7 at A and is hung solidly by
the brackets shown at B from the frame which carries the flasks, so
that it has the same upward motion as the flasks, and the upper ends
of the stools remain in contact with the sand of the mould until same
is lifted from machine. Fig. 7, showing a vertical section through a
machine, will make perfectly clear the position and action of these
stools.
[Illustration: FIG. 7. VERTICAL SECTIONS FITTED TO PLATES.]
As illustrating the importance of being able to work without stripping
plates on a line of work which is much more extended than that
possible with them, we may say that a machinist with a drill press
supplied with split patterns and planed pattern plates has matched and
fixed five sets of from four to eight pieces in a day: and wooden
patterns fitted for temporary use in the same way are of frequent
occurrence when it is not thought wise to go to the expense of metal
patterns on account of the relatively small number of castings to be
made from them.
It is not perhaps too much to say that pattern expense is not the
final evil of the costly and not durable stripping plate patterns.
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