Test bar for a vacuum chamber

#This invention relates to a device for introducing an article into and withdrawing the same from the interior of a chamber sealed from the surrounding environment. More particularly, the invention relates to a test bar movably supported in a gastight manner in a housing coupled with a vacuum chamber. The test bar is adapted to support a sample, for example, in a recess, and has a length so dimensioned that the bar, whether the recess is internally or externally of the chamber, performs its function regarding the sealing of the chamber with respect to its environment.

#It is a common characteristic of a great number of manufacturing or testing methods involving vacuumized environment that the articles, substances, substrates or specimens (hereinafter simply referred to as "specimen") have to be brought into a closed vacuum vessel from the ambient, atmospheric environment. In the simplest case, the vacuum device is de-vacuumized, opened and the specimens are introduced. Thereafter the device is again closed and evacuated. Particularly when the specimen is to be exposed to high vacuum or ultra high vacuum, the above-outlined mode of introducing the specimen inherently involves significant loss of time. For this purpose, various types of vacuum locks have been designed.

#The locks in general comprise a vacuumizable pre-chamber which is closed by two sealing systems or valves. This pre-chamber is coupled through one sealing system or valve with the principal vacuum chamber and through a further sealing system or valve with the atmospheric air. The specimen is first brought from the atmosphere into the pre-chamber. Thereafter the pre-chamber is vacuumized, whereupon the specimen is moved into the principal vacuum chamber. According to a particularly advantageous known solution of a vacuum lock, the specimen is positioned in a recess of an otherwise linear, smooth and polished cylindrical bar. The bar which serves for transporting the specimen from the atmospheric outer environment into the principal vacuum chamber is guided in a housing coupled to the vacuum chamber. In the housing, there are provided O-rings or O-ring systems surrounding the rod for providing a packing system for sealing the chamber from the surrounding environment. Since the bar should perform its sealing function in any geometric position of the specimen, the bar has to extend on either side of the specimen to such a distance that the bar, in any position, fully cooperates with the O-ring system. Instead of O-rings, other sealing arrangements may be used, such as magneto-fluid or labyrinth seal. It is a disadvantage of this arrangement that in case the test bar is to be replaced, the entire vacuum system has to be de-vacuumized if no additional valve is provided. Such a replacement is necessary, for example, if a specimen or several specimens are to be handled under different conditions. Thus, different test bars are used for different temperature ranges (for example, for ranges of -180.degree. to +350.degree. C, 20.degree. to 600.degree. C and 20.degree. to 1500.degree. C) and for different specimen configurations.

#FIG. 1 is a sectional side elevational view of a vacuum chamber incorporating the invention, wherein the test bar is shown in a fully advanced position.

#FIG. 2 is a sectional side elevational view of a slightly modified vacuum chamber, wherein the test bar is shown in a withdrawn position.

#FIG. 3 is a longitudinal sectional view of a preferred embodiment of the invention.

#Turning now to FIG. 1, there is shown a vacuum chamber 1 which slidably receives a test bar generally indicated at 2. The test bar 2 is formed of length portions 3 and 4 which, according to the invention, are detachably secured to one another by a releasable coupling device (not illustrated in FIG. 1) and have a parting zone 5. The test bar portion 4 is provided with a specimen-receiving recess or depression 6 which, in FIG. 1, is shown in its operational position, since the test bar 2 is illustrated in its fully advanced (pushed-in) state. The vacuum chamber 1 has a flange 7 by means of which the vacuum chamber 1 is coupled with a housing 8 having an opening through which the test bar 2 passes in a vacuumtight manner. For this purpose, in the housing 8 there are provided, in circumferential grooves of the housing wall, O-rings 9 and 10 which surround and sealingly engage the test bar 2 about its circumference. The vacuum chamber 1 further has a coupling nipple 11 which is connected with a vacuum pump, not shown.

#Turning now to FIG. 2, it is seen that the test bar 2 is withdrawn to such an extent that the specimen-receiving recess 6 and the parting zone 5 are situated externally of the vacuum chamber 1 and more particularly, externally of the sealing assembly 9, 10. In this position, the test bar portion 3 of the test bar 2 is immobilized by means of a locking pin 12 supported at the outer rim of the housing 8' and movable normal to the path of motion of the test bar 2. In the immobilizing position, the locking pin 12 projects into an aperture 13 in the test bar portion 3. In this position of the test bar 2, the test bar portion 4 can be detached from the test bar portion 3 and thus another test bar portion which, for example, has a differently shaped specimen-receiving recess can be inserted. It is noted that in FIG. 2 the housing 8' is formed as a one-piece, integral member with the vacuum chamber 1.

#Turning now to FIG. 3, the test bar 2a is shown in section to illustrate a preferred embodiment of a releasable coupling device connecting the test bar portions to one another. The test bar 2a is formed of separable test bar portions 3a and 4a being in engagement along the parting zone 5a. The test bar portion 4a has a central opening 6a adapted to receive a specimen. For purposes of a light-weight construction, both test bar portions 3a and 4a are, at least partially, of hollow, tubular shape. The test bar portion 4a has, in the parting zone 5a, an axial bore 14 into which fits a stub portion 15 which is integral with the test bar portion 3a which is oriented in the length dimension of the test bar. The test bar portions 3a and 4a are secured to one another by means of a pin or screw member 16 which passes transversely through the bore 14 and the stub portion 15 positioned therein. The test bar portion 3a is further provided, adjacent the stub portion 15, with a blind bore 13a which, similarly to the aperture 13 of FIGS. 1 and 2, serves for receiving an immobilizing pin for temporarily fixedly holding the test bar portion 3a while the test bar portion 4a is removed or attached. The required venting of the bore 14 is effected by longitudinal grooves (not shown) provided on the stub portion 15 and the pin 16.