Machinery and processes of the industrial arts, and apparatus of the exact sciences (1869) (14597486647)

Identifier: machineryprocess00barn (find matches)
Title: Machinery and processes of the industrial arts, and apparatus of the exact sciences
Year: 1869 (1860s)
Authors: Barnard, Frederick A. P. (Frederick Augustus Porter), 1809-1889
Subjects: Machinery Scientific apparatus and instruments
Publisher: Washington, Govt. print. off.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress



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vedand united with the cylinder at both extremities. At the middle pointof this tube, a branch leading from it may be connected with a con-densing apparatus; so that the pump may be used for compression aswell as for rarefaction. When used for the ordinary purposes of an air-pump, however, this branch is open to the atmosphere. On the otherside, the two inward opening valves are similarly connected, and thebranch tube on that side establishes communication with the receiver tobe exhausted. But when the pump is employed to compress air, this32 i A 498 PARIS UNIVERSAL EXPOSITION. branch is open in its turn to the atmosphere. The valves as drawn inthe figure are operated by the elasticity of the air. But in the con-struction now given to this part of the apparatus, they are opened andshut mechanically by the piston itself. For this purpose, there areintroduced two cylindrical rods passing through the piston and reachingfrom end to end of the cylinder, but capable of a slight longitudinal
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Deleuils Free-piston Air-pump. movement as the piston changes its direction. This movement opens avalve at one end and simultaneously closes the corresponding one atthe opposite end; but this change having been effected, the rod remainsstationary, the piston sliding on it as it continues its movement. The deleuils free-piston air-pump—acoustics. 491) particular contrivance here described is not peculiar to Mr. Deleuilspumps, however, as it has been often employed before. The interior bore of the barrel must, of course, be very truly cylin-drical and well polished. The piston is, in length, more than equal toits diameter. When the pump is used for compression, a greater lengthof piston is employed than is necessary for exhaustion. In point offact, in this case, the difference of pressure on opposite sides of thepiston becomes several times greater than it can be when the machineis employed only to produce a vacuum. There is no difficulty in carry-ing the condensation, in the course o