IMPROVEMENTS IN 'SILENT' MINCING MACHINES
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by John Marshall at the Office of the
Commissioners of Patents on the 24th November 1880.
JOHN MARSHALL, of Glasgow, in the County of Lanark, North Britain.
"IMPROVEMENTS IN 'SILENT' MINCING MACHINES."
This Invention relates to certain improvements in the construction of "silent"
meat mincing machines of the kind in which the meat is carried in a revolving bowl
to be minced or cut by rotating knives, and the improvements are specially designed
to render such machines more efficient in action and capable of being operated with
less expenditure of power than as hitherto constructed.
Under one modification of the improvements the revolving bowl or basin con-
taining the meat is carried on a central vertical shaft, pivot, or stud, supported in
bearings in the machine frames, but instead of revolving in a continuous manner
as usual it is fed forward or round intermittently. The cutting knives or blades,
which are preferably of "sickle" form, are fitted in a horizontal revolving shaft
supported in bearing brackets secured to the upper side of a board or table immi-
diately over the meat bowl and binged or otherwise fixed to the side frames of the
machine. The knives, which may be two, three, or more in number, are preferably
secured by their socks in a slot formed in an enlarged part of the shaft, and they
are ranged in a row all on one side of the shaft and fitted so as to be capable of
adjustment to or from each other. The knife shaft is fitted about mid-way between
the centre and the outer edge of the meet bowl, which is hollowed to correspond
in cross section with the path of the cutting knives or blades during their revolu-
tion, and the shaft is driven either by a hand crank direct or through spur gearing
or by a belt and pulley from a motive power shaft. The same shaft is also used to
communicate the intermittent motion to the meat bowl and in such a manner that
it moves only when the knives are in that part of their revolution in which they
are out of contact with the meat and remains stationary whilst the knives are.
cutting the meat. To effect this object an eccentric or cam is fitted on the knife
shaft to bear against an arm on a ratchet pawl carried by and centred on a sliding
guide piece held in a slot in the table above, and this pawl engages in ratchet teeth
fitted or formed round the rim of the bowl and is reciprocated, pushed, or drawn by
means of the eccentric or cam to move the bowl round to the extent of one or more
of the ratchet teeth for each revolution of the knife shaft, the return of the pawl
being effected by a spring which may also keep the pawl in action. The action of
the pawl and ratchet is rendered noiseless by interposing a soft pad or cushion on

page_text: either side of its centre, which prevents the pawl when it leaves one tooth from
stricking on the succeeding tooth. Or the eccentric may be connected by a strap or
rod to the spring pawl to reciprocate it longitudinally, whilst it would also be
moved transversely to cause it to take into the ratchet teeth on the rim of the
pawl by means of a cam on the eccentric shaft against the outward spring action
of the pawl.
This intermittent motion of the bowl may be obtained by other means, as by a
jointed shoe on a reciprocating bar actuated from the knife shaft by cams or
eccentrics, or other well known mechanical means may be employed to operate the
bowl with this regular noiseless intermittent motion.
The covering board or table over the meat bowl is slotted for the
passage and
cleaning of the knife blades in their rotation, and has also openings formed in it
for the insertion and withdrawal of the meat from the bowl, these openings being
quite clear of the knives so that the meat can be removed and the bowl refilled
without danger while the machine is in motion.
The usual curved plate is provided for turning over the meat so as to expose a
new surface to the action of the knives at each revolution. This turning over of
the meat from the outer edge to the middle of the bowl commonly has the effect of
forcing the meat up against the table or board, causing great friction and consequent
loss of power in driving the machine. To overcome this objection a tapered or
conical roller is fitted horizontally and radially over the bowl to dip slightly into
it. This roller is carried in bearings at each end, and may either revolve simply
by the action of the meat on its surface or be driven through intermediate gearing
from the knife shaft.
Under another modification of the improvements the meat bowl is made to
revolve continuously in the usual way, but the cutting knives are in this case made
in the form of screw blades to cut through the meat as it advances with the bowl
and also tend to press the meat forward. The cleansing or cleaning of the knives
when so made is effected by spring combs pressing against their sides.
This form of screw cutting blade minces or slices the meat most effectually and
obviates or prevents undue pressure and friction of meat against the blades, which
is common with the knives or discs hitherto employed.
Under a modification of this mode of forming the blades a similar result is
obtained by setting the cutting blades askew on the knife shaft the action of the
cutting blades on the meat being practically equivalent to that of the screw
blades.
By a further modification of the improvements the cutting knives or blades are
arranged to revolve in opposite directions and near each other. For this purpose
two knife shafts are provided, the one solid and fitted within the other, which is
tubular.
The one knife or set of knives are fixed as before described to the inner shaft, and
the knife or knives of the tubular shaft are made with eyes to pass over the inner
and be secured to the tubular shaft. These shafts are geared at their outer ends,
preferably to revolve at the same speed but in the opposite direction and from the
same motive power shaft.