Combination lock

A combination lock to control opening of a closure member, and comprising a bolt movable from a locking position to a release position and including a bolt actuator part, the combination lock being characterised by

• a plurality of carrier plates mounted rotatably upon a spindle such as to shield the bolt actuator part from an exterior face of the closure member, the spindle being on an axis non-aligned with said bolt actuator part,
• each rotatable carrier plate having an arcuate array of openings centred on the spindle axis,
• each of said openings being selectively engageable by a selector pin that is rotatable by depressible dial means, the progressive depression and rotation of which effects engagement of the selector pin with a said opening in progressively each of the rotatable carrier plates,
• and characterized in that
• each carrier plate has an aperture therethrough, said apertures being equi-spaced radially from the spindle axis,
• an insert in each said aperture is slidable laterally of the associated carrier plate and, with carrier plate rotation, is rotatable into alignment with the bolt actuator part, each insert being expressible laterally from its associated carrier plate when and only when all the inserts are in said alignment with the bolt actuator part whereby the insert nearest to the bolt actuator part can engage it and cause movement of the bolt to its said release position.