Patent GB-295621-A (GB)
Abstract: 295,621. Short & Mason, Ltd., (Taylor Instrument Cos.). May 14, 1927. Elastic-diaphragm pressure gauges; with recording-apparatus.-In apparatus for measuring and recording pulsating pressures, particularly the pressure of the blood, and comprising a casing 11, Fig. 4, divided by a diaphragm 12 into two parts in communication with the sources the pressure difference between which is to be measured, the diaphragm is connected with a recording pen by a rod 13, fixed to the diaphragm and having pivoted to its free end a cranked spindle 14 to which the pen arm 16 is frictionally secured. The bearings for the spindle 14 comprise a boss on the lower side of an extension 11<a> of the casing 11 and an external boss 14<c> bored to receive the spindle, the bore being enlarged at its upper end to form a deep cup which is filled with a viscous lubricating and sealing medium such as petroleum jelly. The cup is closed by a cap 18. Penadjusting means are provided comprising a depressible squared slide 30 having a depending fork 34 adapted to engage a pin or projection 35 on the spindle 14 and a rotatable spindle 31 cranked and forked at its lower end to engage the pen arm 16 and rotate it relative to the spindle. In an alternative construction the spindle 14 passes completely through the member 11<a> and is provided with upper and lower cupped bearings. The lower end of the spindle is cranked and engages a crank on a vertical shaft carrying the pen-arm. The pen-arm shaft may be locked when required by a lever actuated forked slide engaging a squared portion of the shaft. As applied to the measurement of the pressure of blood the pressure is transmitted through pneumatic cuffs to the pen-controlling diaphragm and the apparatus comprises besides the diaphragm and its casing 11, Fig. 1, a pneumatic reservoir 1, a recording disc 3 rotatable in strict conformity with the changes in pressure in the reservoir 1, a regulator 42 ensuring the transmission of the pressure pulse to one side only of the recording diaphragm, and a regulable leak device 49 permitting uniform fall of pressure in the apparatus. Pipes 69, 62 connected respectively to upper and lower cuffs strapped to the arm or the like, communicate direct and through a pipe 61 respectively with a valve 43 which also communicates with the reservoir 1. The, valve 43 also connects all parts of the apparatus with the leak device 49. With one setting of the valve the cuffs and the reservoir 1 are filled with air, at a pressure above blood pressure, delivered through a pipe 60, with the other setting air is allowed to leak out slowly and the pressure to fall until pulsations are recorded. The pipe 61 communicates, through an extension 61<a> and a manifold 63, with pipes 64, 40 leading to one side of the members 42, 11 and through a vertical narrow bore pipe 65<a> and a pipe 65 with the other side of the member 42. A pipe 41 and a branch pipe 67 establish connection between the members 11, 42 and the tank 1. The pipes 40, 41 communicate with the casing 11 through a valve 39 which is closed when desired by rotation of the casing 11 about it thereby avoiding damage to the pen mechanism. The casing 42 contains a diaphragm having a ball valve closing the pipe 65, which, in conjunction with the constricted pipe 65<a> serves to prevent pressure impulses propagated through the pipe 62 from reaching the remote side of the recording diaphragm. The pen-arm 16 carries a pen 16<a> which rests on a chart upon the disc 3. The connection between the disc 3 and the reservoir 1 comprises a diaphragm 2 in communication with the reservoir, a bell-crank lever in contact therewith and a wire 9 fastened to the lever and wound around a pulley on the disc spindle 3<a>. The wire 9 is tensioned by a leaf spring 10. The leak mechanism, Fig. 7, comprises an expansible chamber 50 the base of which supports the stem 53 of a spring pressed valve 52. The outflow of air through a pipe 45 is controlled by a manually adjustable valve 46. The valve 52 maintains the pressure of the issuing gas substantially constant. The diaphragms employed are formed of celluloid preferably with thin alum-tanned colon leather or the like.