GB1375294A - - Google Patents

Abstract

1375294 Sphygmomanometers N PANZER 16 March 1972 [4 May 1971] 12266/72 Heading A5K A sphygmomanometer comprises an inflatable cuff 12, an air line 20 leading to the inflatable cuff, a pressure gauge 18 communicating with the cuff via an air line 16, a bulb 24 having a bleed valve 22, a tube 26 secured between the bulb and an air line 20 and provided with a channel 28 which has a constructed throat 30, and a secondary tube 32 providing communication between the throat 30 and the surrounding atmosphere. In use when air is propelled from the bulb through the channel to inflate the cuff, the acceleration and consequent pressure drop caused by the throat, e.g. a venturi throat, causes entrainment of additional air from outside the tube 26 through. the tube 32 so that inflation of the cuff requires fewer compressions of the bulb. The secondary tube may be provided with bores 34 which can be closed by a slidably mounted sleeve valve 38. The angle of convergence of the channel in a section 60 is greater than that in a section 62, and the inside diameter at the ends of the tube is at least equal to that of the air line. Typical values are for the angles of convergence to be respectively 25‹-30‹ and 5‹-8‹, for the inside diameter of the ends of the throat to be 3mm, and for this diameter to be 3-4 times that of the throat. This results in entrainment of approximately three times as much air through the tube 32 as is propelled through the throat by the bulb. When the bleed vavle 22 is opened to allow air to pass from the inflatable cuff, air is entrained through the tube 32 so that air loss from the cuff is slowed down and a more accurate reading obtained from the gauge. The material of the tube 28 may be either plastics or aluminium.