The latest type of this machine used a vertical needle bar and a straight needle.
As the follower moves in and out, the needle bar is moved from side to side.
Joseph Brown believed that the shaft and needle bars of the sewing machine must be crafted from hardened tool steel.
As the cam rotates, a fingerlike follower, connected to the needle bar, rides along the cam and tracks its indentations.
As the double cam rotates, the first follower rides along one track to move the needle bar from side to side, while the second follower rides along a different track to move the feed dogs forward and reverse.
Driven by the up and down stitching motion of the needle bar via the fork arm straddling the needle clamp, it executes the series of movements to complete a buttonhole by moving the " material " rather than by moving the " needle " position.
The lion ( sculpted to look like the work of J . Vasteugh Gyorgy ) stands on rocks that are hinged to allow the needle bar, presser foot and shuttle race to be seen whilst the head of the lion is also hinged to allow the user to insert the top reel and alter tension.