IMPROVE- MENTS IN THE CONSTRUCTION OF SEWING MACHINES
Year: 1862

page_text: PROVISIONAL SPECIFICATION left by Silas Covell Salisbury at the Office
of the Commissioners of Patents, with his Petition, on the 25th April
1862.
I, SILAS COVELL SALISBURY, of Coventry, in the County of Warwick,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN THE CONSTRUCTION OF SEWING MACHINES," to be as follows:-
The object of this Invention is to manufacture sewing machines that
shall be equal to heavy work, such as boot sewing and the sewing of coarse
clothing. To avoid the vibration which attends the working of machines with
a rocking lever or levers for operating the vertical needle and presser foot,
I propose to employ a novel combination of parts, which enables me to work
the needle and presser and also the shuttle cams on the driving.shaft, which
shaft is mounted above the table of the machine. The cam shaft is mounted
in a hollow bracket arm, and carries at its extremity a compound cam.
A groove in this cam receives a bowl from the pendent arm of a crank lever
which has its fulcrum on the bracket arm. The other arm of this lever is
connected by a link to the vertical needle bar, and through this arrangement
the vertical movements of the needle are obtained. A second crank lever
mounted on the bracket arm and set at right angles to the first-mentioned
lever is operated by the inner face of the cam, and while reciprocating it
strikes on the under side of a pin projecting from the stem of the presser, and
lifts the same from the work. A spring (as usual) serves to return the presser

page_text: to its depressed position. The feed motion is effected by a cam projection on
the outer end of the cam acting upon one end of a rock lever, the other end
of which carries a pin that bears upon the inner edge of the presser foot stem.
Every rotation therefore of the cam shaft will impart a rocking motion to the
presser foot, and thereby effect the feed of the cloth up to the vertical nee:lle.
For taking up the slack thread I employ a swinging arm, pendent from the
vertical needle guide box; through the end of which the thread is passed on its
way to the eye of the needle. A crank pin on the end of the crank shaft
gives this arm a movement outwards at the moment the slack is made, and
thus the slack thread is drawn on one side. This arrangement applies to the
improved spool knot stitch machine for which I obtained Letters Patent,
dated 26th of April 1861, No. 1059, and also to the ordinary class of shuttle
machines. The fly wheel and driving pulley are mounted at the other end of
the driving shaft, and so also is the cam for working the rotary spool or the
shuttle, as the case may be. The movements of the spool require a compound
cam, which operates two rock levers that convey to it the axial and recipro-
cating motions. When, however, the ordinary shuttle is used a single grooved
cam is employed for communicating the reciprocating motion to the shuttle.
Instead of forming the shuttle race as heretofore I propose to support the
shuttle carriage on guide rods, which form an open bottom to the race and
effectually prevent the accumulation of dust and dirt in the shuttle race. The
shuttle carriage is secured to the guide rods by means of a clamping piece,
which yet allows the carriage to move freely. In order to maintain the
proper tension of the vertical needle thread I propose to give the bobbin which
carries that thread an intermittent axial motion by means of a cam on the
driving shaft actuating a pawl, which takes into the teeth of a ratchet wheel
on the bobbin axle.