The subject-matter of the present disclosure relates to a lock spring (18) for securing a battery frame (16) to a housing (14) in a personal care apparatus assembly (10). The lock spring (18) comprises: a plurality of anchor points (36) for engaging a respective plurality of anchor formations on each of the battery frame and the housing, in-use; a plurality of pinching tabs (38), each pinching tab of the plurality of pinching tabs configured for engaging a finger digit of a user, in-use; a resilient structure linking together the plurality of anchor points and extending in a plane (P), the resilient structure configured to deform in response to an external force applied to the plurality of pinching tabs by the fingers to reduce a separation distance (D) between first and second anchor points of the plurality of anchor points, in-use, wherein each pinching tab of the plurality of pinching tabs extends substantially orthogonally from the plane.