Abstract: A multiple stage centrifugal compressor has baffle rings attached at the inlet to each of the impellers, between a shroud side curvature and a hub side curvature. The dimensions and spacings of the baffle rings are selected as a function of the shroud side radius of curvature R.sub.S and the hub side radius of curvature R.sub.H. For two baffle rings, the radii areR.sub.C1 =(R.sub.c.sup.2 .times.R.sub.H).sup.1/3 and R.sub.C2 =(R.sub.S .times.R.sub.H.sup.2).sup.1/3.

Abstract: A regenerative centrifugal compressor has an impeller disk with axial impeller blades on either side of the impeller disk rim, and a support housing for rotationally supporting a drive shaft for the impeller disk, and also defining annular compression chambers that respectively surround one or the other of the rows of impeller blades. The annular compression chambers extend in the rotation direction of the impeller from an inlet to an outlet, with a stripper section extending from the outlet to the inlet in the rotation direction. Stripper seal inserts formed of a low-friction material softer than the impeller blades are fastened into stripper receptacles on either side of the housing at the stripper section. A baffle at the inlet conducts inlet air around the impeller to a radially inward side thereof. Annular running seals are provided between the rim of the impeller disk and the housing. The blades of the impeller are shaped for optimal efficiency and compression.

Abstract: A pneumatic tube send/receive terminal has a dispatch carrier that is movable between a load position and a send position. A sprocket chain fits on two sprockets and rotates under motor power, and a cam is mounted on the chain. A clapper valve or cover is hinged to a trolley or carriage that also rotatably holds the dispatch holder. A block or cog attached to the chain connects to the dispatch holder, and this rotates the same 180 degrees and then moves the trolley and the dispatch holder laterally to the send position. The cam rides a camway on the valve, and normally holds it shut, but when the chain is moved, the cam rotates over the camway and releases the valve so that it opens, and any received pneumatic carrier drops out. Rotation of the dispatch holder 180 degrees prevents inadvertent accessing the pneumatic tube with a second carrier in a single send operation.