| 摘要 |
A borehole instrument having four arm pad members utilizes four independent bow springs, each of the bow springs being anchored to the instrument at one of their ends and being individually slidably mounted at their other ends to the instrument. A push-pull rod activated by a solenoid within the instrument causes each of the slidable collars connected to the bow springs, respectively, to move down and thus close the instrument for easy passage through the borehole when not logging. When the push-pull rod is pulled up, each of the bow springs acts independently to cause the individual pads to make contact with the borehole wall. In an alternative embodiment, spring-driven pad linkage assemblies are likewise closed by pushing on the push-pull rod and are allowed to open and move out against the borehole wall when the rod is pulled up by action of the solenoid.
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