Brush holder which can lock brushes in place

An apparatus for holding a brush 1 in contact with a moving conductive surface (16, Fig 1) includes a rotatable member 9 disposed adjacent to the brush and a spring 6 coupled to the brush and to the member and configured to bias the brush towards the surface. When the rotatable member in a first position it makes contact with the brush to secure the brush from movement and when in a second position it releases the brush from the contact to allow the spring to hold the brush in contact with the surface. The rotatable member may be moved by a linkage 8 which is in tune moved by a detachable handle 2. The brush holder may hold two brushes and allow them to be replaced using only one hand while the machine is operating. It may incorporate a brush wear indicator 4 and may mount the brushes outside supporting pins 5 for improved cooling.