Specification of Robert Mann Lowne : spirometers.

  • Lowne, Robert Mann.
Date:
1871
Catalogue details

Licence: Public Domain Mark

Credit: Specification of Robert Mann Lowne : spirometers. Source: Wellcome Collection.

    5/16 (page 3)
    5 10 15 20 25 30 35 Provisional Specification. A.D. 1870.—N“ 3343. 3 Loione’s Improvements in Spirometers. thi’ougli a tube which enters the fan wheel box, the axis of this tube is in a line with the tangent of a circle described through the centres of the fans, so that the air which passes through it may strike directly upon the flat surfaces of the fans. The air when passing through this tube causes the fans and wheel to revolve, the rate at which they revolve depending upon the velocity, consequently the force with which the air strikes them. Now if it is apparent that a given quantity of air striking the fans at a given velocity will always cause them to revolve at the same rate and the same number of revolutions, other contingencies being the same, it will likewise he seen that when the moving air has ceased to drive the fans they will still revolve from the momentum they have acquired, this momentum would cause the fans to revolve con¬ siderably more after they had acquired a high velocity than it would at a low velocity; this revolving of the fans from their momentum after the air had ceased to act on them I found a cause of inaccuracy, for before the fans would stop their motion became very slow, and small causes arising from friction and imperfect workmanship caused them sometimes to stop suddenly and before they otherwise would. To obviate this defect I employ a small piston of glass or other suitable material which is acted upon by the internal pressure of the air from the receiving box; this piston is fitted loosely in a tube, one end of which communicates with the interior of the receiver, and the other enters the fan box; this tube is pei’pendicular so as to allow the piston to fall by its own weight, the piston is so arranged that its weight is borne by one end of a lever, the other end of which has a stop or pin on it which catches and fixes the wheelwork connected with the hands. On blowing into the instrument the piston rises and allows the end of the lever which has the stop to fall, thereby releasing the wheelwork. Directly the velocity and consequently the pressure of the air have ceased the piston falls to its original position thereby pressing on the lever and raising the end, which again catches the wheelwork. The piston is fitted loosely in the tube; I avoid making it air-tight in order that it may act with the slightest pressure from beneath; thus it will be seen that there will be a considerable escape of air between the piston and cylinder, this escape I conduct through a small pipe placed so that the air which passes through it strikes upon the fans in a direction to make them revolve. All the air might be sent between the piston and cylinder, or the air might be allowed to pass