| 摘要 |
A push-rod (12) extends through a support (11, 16) and is longitudinally slidable relative to the support. A first stop means (11) defines a rest position of an operating component (13) secured to the push-rod. A drive collar (14) is engaged as an interference fit with the push-rod. A spring (15) acting between the push-rod and the support urges the push-rod (12) to said rest position. The spring (15) limits movement of the drive collar (14). A knob (15, 19) is slidably engaged with said drive collar (14) and abutment means (17, 22) on the knob and the drive collar limit movement of the knob relative to the collar in a direction opposite that in which the push-rod is urged by the spring (15). A second spring (23) acting between the support and the knob biasses the knob in the same direction as the push-rod (12) is biassed by the spring (15) and a member (24) on the support (11) limits movement of the knob (18, 19) relative to the support (11, 16).
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