IMPROVEMENTS IN LOOMS FOR WEAVING
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by William Lawrence Mitchell at
the Office of the Commissioners of Patents, with his Petition, on
the 19th May 1870.
I, WILLIAM LAWRENCE MITCHELL, of Kirkcaldy, in the County of
Fife, North Britain, do hereby declare the nature of the said Invention
of "IMPROVEMENTS IN LOOMS FOR WEAVING," to be as follows, that is to
say:
This Invention; which relates to certain improvements in looms for
weaving textile fabrics, consists as follows:-
First. In obtaining or producing two beats of the lay by means of
one revolution of the driving shaft. This part of the Invention is carried
into effect by placing eccentrics on the driving shaft, and in coupling
the lay by toggle jointed rods to the gable of the loom framing. The
toggle jointed rods are again coupled to the eccentrics by means of straps
and connecting rods, so that during a revolution of the eccentrics' the
lay is drawn back to its extreme position. When the major radius of
the eccentrics is uppermost and the lay is thrown into the extreme
forward position for beating up the weft when the major radius of the
eccentrics is in a horizontal or nearly horizontal position, having passed

page_text: through the first quarter of a revolution and when the major radius of
.the eccentrics is passing through the second quarter of a revolution, the
toggle jointed rods are further depressed, thus again bringing back the
lay, and this is again thrown forward to beat up the weft as the major
radius passes through the third quarter of a revolution. In this manner
two shots of weft or two runs of the shuttle are made during one
revolution of the driving shaft. In place of using eccentrics as herein-
before described for driving the toggle jointed rods, cranks may be
employed. By means of this part of the Invention the employment of
the usual spur gearing is dispensed with.
Second. In obtaining or producing one entire beat of the lay and a
succeeding short beat of the lay for closing up the weft by a second
action, the result of the succeeding short beat. Under this part of the
Invention the shuttle is run through the warp during the entire or long
beat of the lay, which allows time for the shot to take place when the
lay is in its extreme or nearly extreme backward position and at the
wide part of the shed, and as the lay returns from that position it beats
up the weft, but in practice it is found that in weaving certain classes
of fabrics, such, for example, as bed ticking, the single beat of the lay
does not sufficiently close the weft. In order, then, the better to effect
the closing the second or short beat of the lay is used, not, however, to
beat a second time on the weft itself, but to beat on the portion of the
warp which encloses the weft.
Under this part of the Invention the lay is also driven by toggle
jointed rods, as under the former part, but as one throw of the shuttle
only is required to the two beats of the lay, or to the whole and part
of such beats, the eccentrics or cranks which drive the lay are actuated
from the first motion shaft of the loom by spur gearing arranged in such
proportion that two revolutions of the eccentrics or cranks are made
during one revolution of the driving shaft. The variation in the lengths
of the two beats is effected by placing the toggle jointed rods in such
position that they are thrown to a greater distance on one side of their
mean or straight position than they are on the opposite side of that
position.
•
Third. This part of the Invention relates to an arrangement of
mechanism for driving the lay in broad looms so that the lay is stationary,
or nearly so, during the time the shuttle is run through the warp; this
being a necessity for allowing time for the shot in very broad looms to

page_text: take place, and the same mechanism also produces a rapid movement of
the lay during the time the weft is being beaten up in place of the slow
motion produced by the crank. This part of the Invention is carried
into effect by driving the lay by elliptical or eccentric tooth wheels.
The picking motion or motions for driving the shuttle consist of a cam
on the driving shaft, which as it revolves lifts a weighted lever. The
lever is provided with a curved guide plate that acts upon the tappets
of the rod which carries the picking arm, and as soon as the step of
the cam passes over or beyond the part of the lever on which it acts the
lever falls rapidly, on account of the weights with which it is provided,
and striking on the picking tappets produces the necessary motion for
striking the shuttle. In place of using weights one or more springs may
be used for actuating the lever. In order to produce variations in the
length of the stroke of the lay this is effected by means of cranks or
crank discs provided with slots in which the crank pins are adjustable.