1. Field of the Invention
The present invention relates to a moving mechanism, for example, a moving mechanism that moves a form measurer.
2. Description of Related Art
An apparatus shown in FIG. 13 is known, for example, as a form measuring apparatus 20 measuring a profile shape of a measured object W (Japanese Patent No. 2539998). A support pillar 2 stands on a base 1. A moving screw is rotatably provided inside the support pillar 2. An operation handle 2A is provided at an upper end of the moving screw (the moving screw is hidden inside the support pillar and thus invisible in FIG. 13). A lift member 3 is provided to the support pillar 2 so as to be movable upward and downward. A nut fixated to the lift member 3 is threaded together with the moving screw. Thus, rotation of the moving screw raises and lowers the nut and the lift member 3 (the nut is hidden inside the lift member 3 and thus invisible in FIG. 13).
A form measurer 11 is provided to the lift member 3 via a swing member 4. The swing member 4 is angle-adjustable with reference to a swing axis, which is an axis orthogonal to an axis of the support pillar 2. The form measurer 11 swingably supports a measuring arm 12 and electrically detects a swing amount of the measuring arm 12. A stylus 13 projects from a fore end of the measuring arm 12, the stylus 13 moving along a surface profile of the measured object W.
For measurement, the measured object W is placed on the base 1 and the stylus 13 is positioned at a measurement start point of the measured object W. At this time, the form measurer 11 needs to be adjusted to be positioned such that the stylus 13 is positioned slightly higher than a height of a measured surface of the measured object W. Then, a user rotates the operation handle 2A to raise and lower the lift member 3 by way of screw movement.
Since fine positioning is required for the form measuring apparatus 20, a screw lead of the moving screw is designed to be fine. This is beneficial to enable fine positioning; however, a circumstance concurrently arises where a movement amount per rotation of the operation handle 2A is extremely limited. Given that the form measurer 11 needs to be moved substantially every time the measured object W is replaced, positioning of the form measurer 11 requires a substantial amount of time.
In view of the above, the inventors of the present application have already devised a moving mechanism using twist rollers, instead of screw movement (Japanese Patent Nos. 5049514 and 5235039).
The moving mechanism disclosed in Japanese Patent Nos. 5049514 and 5235039 has a plurality of twist rollers capable of making contact with and separating from a drive shaft. A collet holding and releasing the drive shaft is provided to pivotally support the twist rollers. When the collet holds the drive shaft, the twist rollers come into contact with the drive shaft. When the collet releases the drive shaft, the twist rollers separate from the drive shaft. Expansion and contraction of the collet is controlled by a cam. Specifically, a cam having an elliptical shape in cross section is inserted to the collet. Rotating the cam changes a gap of the collet. Rotating the drive shaft in a state where the twist rollers are in contact with the drive shaft allows advancement and retraction by an amount of a twist angle of the twist rollers. In other words, fine movement is achieved. Meanwhile, in a state where the twist rollers are separated from the drive shaft, the collet is free and thus high-speed movement (rough movement) is enabled. With a moving body, such as a form measurer, provided to the collet, for example, switching between fine movement and rough movement of the form measurer (moving body) is enabled.
The configurations of Japanese Patent Nos. 5049514 and 5235039 reliably allow high-speed movement (rough movement) and fine positioning (fine movement). However, the configurations slightly lack in operability. In the configurations of Japanese Patent Nos. 5049514 and 5235039, for example, the cam needs to be rotated every time the fine movement and the rough movement are switched. When the fine movement and the rough movement are switched repeatedly to adjust positioning of the form measurer (moving body), it is cumbersome to operate the cam every time.
In addition, a practical circumstance as below arises. For example, the cam is rotated to separate the twist rollers from the drive shaft. At this time, the collet is free and thus the high-speed movement (rough movement) is enabled. However, when the user's hand is removed, the collet may operate in a manner not intended by the user. This circumstance is not notable in horizontal movement as described in Japanese Patent Nos. 5049514 and 5235039. In a vertically moving mechanism, however, in which a drive shaft is provided vertically, a collet may drop together with a form measurer (moving body). Thus, the user needs to support the form measurer (moving body) with one hand and then rotate the cam with the other hand to bring the twist rollers into contact with the drive shaft. Such an operation is very cumbersome and requires the user to perform in an unnatural manner.
Such a circumstance is not limited to the form measurer and is common to a moving mechanism that requires fine positioning and is sometimes required to make a large movement as well.