F or the purpose ofenergizing the'magnets 20 from the point c'to the-point (Z, I have shown an arcuate conducting strip 29 (Fig. 3) mounted upon the frame of thefma-- chine to one side of the drum and extending Y from the point 0 to the point d. Thisconducting strip is connected to a source 'of-cur rent, as for instance to the positive pole of a battery 30 or any other'suitab'le source. The opposite end of,ballast crusher machine each coil 28 may be. grounded. Each coil is engaged at one end with an outwardly projecting pin or contact 31 which engages the strip 29 and-keeps its engagement 'with this strip while this pin istraveling from the point'c to the point (Z. During this period therefore the current is traveling through the coil 28 and the-elec tro-magnet is energized. WVhemhowever,
the'pin 31 passes the contact strip 29, the magnet becomes denergized. Some residualmagnetism, however, will remain in the magnet which might be suflicient to cause the particles to adherethereto and,-therefore, it is best to momentarily cause current to pass through the electro-magnets inan opposite direction to the direction of passage of the current while the pins were in contact with the strip 29, and to this end I mount in the path of travel of the pins and just forward of the end of the strip 29 a contact 32 with which each pin will momentarily contact, this contact 32, however, being connected to the negative pole of the battery so as to cause a momentary reversal of the current through the coils. This reverse current is merely momentary and acts to de-magnetize the magnets.
Another construction which might be used for forming the magnets is illustrated in Fig. 6, where the strips 23 are connected at their ends to cores 33 and surrounded by coils 34, these coils 34 being in turn connected to a common ground at one end and to pins 35 at the opposite end which are adapted to engage the strips 29. Here also the strips 23 will be rendered magnetic as the pins 35 come in...