Solenoid switch for a coaxial engine starter

A solenoid switch for a coaxial engine starter comprises within a cylindrical case 31 a solenoid coil 33 wound around a hollow bobbin 34. The case supports stationary contact assemblies 42, 43 each composed of an electrical conductor 44 including a stationary contact element 45 and an electrically insulating member 46 disposed around the conductor so that the stationary contact element is within a cylindrical space 36 of the bobbin. A movable contact 39 is mounted on a plunger 37 which is magnetically actuatable by the solenoid coil for separably engaging with the stationary contact elements. The outer surface 50 of a tubular wall 47 of the bobbin is oval in cross-section so that thicker-wall portions 47a are defined between the inner and the outer surfaces 49, 50. The thicker-wall portions have recesses 51 for partially receiving the insulating members, which are sufficiently thick to provide the necessary electrical insulation for the conductors 44, and a sufficient radial spacing is provided for accommodating through bolts 24 for securing the solenoid switch to the starter motor 1.