| 摘要 |
A distance measuring device for attachment to the hub of a vehicle wheel includes a pendulum, which remains generally stationary, as the hub rotates. A counting mechanism rotates with the hub, and is coupled through a worm wheel and lost-motion mechanism to the pendulum. The lost-motion mechanism reciprocates a feeding arm against the bias of a spring, which shifts periodically back and forth over center, as the lost-motion mechanism periodically transmits motion. A feed spring, mounted on the feeding arm, acts as a pawl to intermittently advance a ratchet wheel, coaxially disposed on the counting mechanism, to thereby index the counting mechanism as the vehicle wheel turns. If the counting mechanism, by any means, becomes jammed then the feed spring will deform, preventing further operation of the counting mechanism.
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