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Full text of "Modern Mechanical Engineering Vol-I"

i66

FOUNDRY WORK

the machines afford great economies, since they will " press " or will
" jar-ram " the largest moulds within their capacity in a few minutes, the
time spent depending chiefly on the rapidity with which the sand is thrown

into the box part. The amount
required for compression is mea-
sured within a sand " frame " of
wood or metal (fig. 70). Except
in the deeper moulds, and under
loose, projecting pieces, no pre-
liminary peg-ramming is required,
but two or three squeezings with
the presser head suffices. In the
jar - ramming machines a few
bumps consolidate the sand in the



Fig. 71.—Radiators and Flanges of Motor Cylinder
drawn through Stripping Plate in a Fixed Table A

deepest moulds. These there-
fore, after the plating, afford the
chief economies of machine work.
Delivery of patterns by hand
is only the work of a minute or
two. The advantage of using a
machine is therefore that it sub-
stitutes an accurate mechanical
lift for the unsteady action of
the hands, and that in very many
instances the employment of

stripping plates prevents breaking down of the sand, and consequent
mending-up, with inaccurate results. Some machines do not include this,
but their utilities are confined to the shallower patterns, and those whose
shapes favour delivery. The mechanical withdrawal is furnished by means

Fig. 72.—Boxes Pressed and Delivered in Unison on a
Non-turn-over Table A