Multiple Needle Sewing Machines
There are Singer Machines for making from two to twelve parallel rows of stitching at one operation [Singer Class 41].
On machines carrying from three to twelve needles the spacing may be arranged as desired within a limit of 2 13/32 inches, the extreme distance between outside shuttles. ...These machines are capable of changes in distance between the rows of stitching without other adjustment than a simple change of needle.
The least distance between the points of two shuttles is 3/16 inch and, for obvious reasons, it is essential that the shuttles on these machines shall be as thin as possible. They cannot, therefore, contain a bobbin for the under thread, and this thread is carried in ready-wound cops that fit tightly into the shuttles.
These cops unwind from their outer edge and deliver thread through center of shuttle, thus securing central delivery of thread until the cops are entirely unwound and used.