Permanent magnetic suspension with roller guides

#1. Field of the Invention

#The present invention generally relates to a lens which is movably positioned along a guide rod, and in particular relates to a movably positioned lens having magnetic means for holding it in place on the guide rod.

#2. Description of the Prior Art

#FIG. 1, not drawn to scale, shows a movable lens arranged on guide rods according to the present invention; and

#FIG. 2, not drawn to scale, shows a cross-sectional view of the guide rod and the permanent magnetic assembly along lines 2--2 in FIG. 1.

#FIG. 1 shows a movable lens assembly 2 arranged on guide rods 4 and 6. In one embodiment, the guide rods 4 and 6 are two hardened steel rods.

#The movable lens assembly 2 includes a lens cell 10 having a perimeter 10a with a permanent magnet assembly 12 arranged thereon at the top of the lens cell 10 as shown. A pre-load bearing 14 and guide beating 16 are also arranged on the perimeter 10a of the lens cell 10 at a 90.degree. angle with respect to the permanent magnetic assembly 12. The pre-load beating 14 and guide beating 16 cooperate with the guide rod 6 to further support and position the lens cell 10 along the guide rod 4.

#The permanent magnet assembly 12 has a permanent magnet 20 which provides a closed-coupled attractive magnetic force to support the lens assembly 2 to the guide rod 4. Magnetic force lines f1 and f2 illustrate the magnetic force applied to the guide rod 4 as a close-coupled attractive magnetic force. The permanent magnet 20, in the embodiment, is U-shaped, having a north pole 40 and a south pole 42, and having a V-shaped recessed longitudinal channel 44 placed in close proximity to the guide rod 4 on the permanent magnet assembly 12 to attract the guide rod and hold it against the ball bearings. The north pole 40 and south pole 42 are disposed parallel to and spaced apart from each other and also parallel to a lengthwise axis (not shown) of guide rod 4. As shown in FIG. 2, the north pole 40 and south pole 42 are disposed about the guide rod 4 with a small air gap or clearance 41, at an arc segment of .alpha.. In a preferred embodiment, .alpha. equals 60.degree..