Springs are efficient in storing and returning elastic potential energy but are unable to hold the energy they store in the absence of an external load. Lockable springs use clutches to hold elastic potential energy in the absence of an external load, but have not yet been widely adopted in applications, partly because clutches introduce design complexity, reduce energy efficiency, and typically do not afford high fidelity control over the energy stored by the spring. Here, we present the design of a novel lockable compression spring that uses a small capstan clutch to passively lock a mechanical spring. The capstan clutch can lock over 1000 N force at any arbitrary deflection, unlock the spring in less than 10 ms with a control force less than 1 % of the maximal spring force, and provide an 80 % energy storage and return efficiency (comparable to a highly efficient electric motor operated at constant nominal speed). By retaining the form factor of a regular spring while providing high-fidelity locking capability even under large spring forces, the proposed design could facilitate the development of energy-efficient spring-based actuators and robots.

翻译：弹簧在储存和释放弹性势能方面效率较高，但在无外部负载时无法保持所储存的能量。可锁定弹簧利用离合器在无外部负载时保持弹性势能，但尚未广泛应用于实际应用，部分原因在于离合器增加了设计复杂度、降低了能量效率，且通常无法对弹簧储存的能量实现高精度控制。本文提出一种新型可锁定压缩弹簧的设计，该弹簧利用小型绞盘离合器实现机械弹簧的被动锁定。该绞盘离合器可在任意挠度下锁定超过1000牛顿的力，在小于10毫秒内以低于最大弹簧力1%的控制力解锁弹簧，并提供80%的能量储存与回馈效率（与恒定额定转速下运行的高效电机相当）。该设计在保持常规弹簧外形的的同时，即使在较大弹簧力作用下也能实现高精度锁定能力，有望促进基于弹簧的高效驱动器与机器人技术的发展。