MOVABLE VACUUM FEEDTHROUGHS*)

For technological reasons it is often necessary to use movable feedthroughs in vacuum systems. The most widely used seal employed for this purpose is apparently the rubber seal.

The article being abstracted describes a device that makes it possible to use this seal for moving an object of interest to the researcher inside a vacuum chamber over a rather wide range of angles and distances. This device, shown in Fig. 1, consists of a ball \(B\), rotating in a ball socket. Along the opening of the ball slides the rod \(A\); the axis of the opening is a diameter of the ball. Both the rod and the ball are sealed by means of rubber rings \(O\). In the device described, the ball had a diameter of 25.4 mm. The ball and the socket in which it rotates were machined to an accuracy of hundredths of a millimeter.

The socket consists of two parts \(C\) and \(C_1\). The part of the socket \(C_1\), adjacent to the vacuum chamber, is vacuum-tight with it. The methods of connection may be different. On the left side of the drawing, a connection is shown by means of a row of bolts (one of which is visible in the figure) compressing a rubber ring. On the right side of the drawing, a soldered connection is shown. The part of the socket \(C\) is screwed onto part \(C_1\) and sealed by means of the rubber ring \(O\). This design makes it possible to move the part introduced into the chamber in any direction within limits of \(30^\circ\), measured from the central position of the rod.

The author of the article states that, in testing the device described above, a vacuum better than \(10^{-4}\) mm Hg was obtained. No deterioration of the vacuum was observed during translational motion of the rod, during rotation of the ball in the socket, or during rotation of the rod about its own axis.

V. V. Fedorov

*) O. Reitzloff, Rev. Sci. Instr. 20, 4 (1949).