GB2215058A - Low pressure indicator - Google Patents

Abstract

A low pressure indicator in which a flexible diaphragm (9) contained within a housing and forming a seal to prevent fluid loss is deformed by pressure to operate a free sliding indicator member (10) urged against the diaphragm by a spring. <IMAGE>

Description

LOW ASSURE INDICATOR.

Pressure indicators are in common use in which the pressure to be indicated is caused to bear upon one side of a piston that will, in consequence, cause the said piston to move co-axially within a cylinder against a spring. That side of the piston not facing the pressure to be indicated is open to atmosphere.Thus it will be seen that a force must exist between the peripheral surface of the piston and cylinder wall that will prevent any leakage of the pressure median to be indicated1from by-passing the piston to the side that is open to atmosphere. inhere the pressure to be indicated is high, the said force exerted by the piston to the cylinder wall may be relatively small in relation to -the force applied to that surface of the piston upon which the pressure to be indicated is acting.It will be ualderstood that the ratio of the force acting upon the piston by pressure to be indicated, and that force required to overcome the static resistance of the said piston due to peripheral contact is not constant for varying piston and cylinder diameters. This is because the peripheral dimension of pistons of different diameters are a direct and linear fraction of the ratio of diameters, but the area of that side of the piston upon which the pressure to be indicated is acting will be a fvnction of the square of the ratio of diameters, hence to indicate low pressures a large diameter piston and bore would be necessary for the static resistance of the piston within the bore to be insi;nificant and old not be practicable for many applications.

The object of the present invention is to completely eliminate any resistance of the sliding member within a cylinder that may be calibrated to indicate values of lov pressure, whilst ensuring that the pressure medium camlot escape to that side of the cylinder that is open to atmospheric pressure. The said pressure to be indicated is made to bear against one side of a flexible membrane or diaphragm that is effectively sealed from atmosphere, That side of the membrane or diaphragm not facing the said pressure will be exposed to atmospheric pressure, thus the pressure to be indicated (when above atmosptieric) will cause the said membrane or diaphragm to concave by an amount dependant on the said pressure.The said membrane or diaphragm when thus concaved will exert force and cause axial rnovement to an indicating member which has been caused to bear against -the convex surface of the said membrane or diaphrag-ll by a spring or other means as the membrane or diaphragm deforms in consequence to the applied pressure to be indicated.It will be understood that the resilience of the membrane or diaphragm will be such as to cause hiiil axial Inovement to -the indicating member, which said member may be graduated to indicate varying values of pressure that may be acting on the concave side of the membrane or diaphragm, and for mairy applications magnifica-tions Or movement by further means would be unnecessary but could be utilised. The resilience to applied pressure of the membrane or diaphragm and rate of spring that causes the indicating member to be in contact with the convex side of the said membrane or diaphragm may be varied to suit desirable ranges of pressure.

The present invention is particularly suitable as a pressure indicator referred to in previous latent Application No. 8728544 in rliich it is required to indicate the low internal pressure of a keg of brew, but the said pressure must be retained and be shown to be retained for prolonged periods of time, and is described as a specific embodiment of the invention by way of example with reference to Figs. 1 and 2 in which, Pig.1, indicating member (1) is a free sliding fit inside cylindrical body (2) and held in contact with flexible diaphragm (3) by return spring (4). End member (5), flexible diaphragm (3) and end member (6) are fixed members.

en pressure to be indicated, Fig.2, is applied at inlet (7) the flexible diaphragm (3) will concave (8), so that the convex surface (9) of the said flexible diaphragm (3) will cause the indicating member (1) to extend from the end member (5) and expose calibration (10) to indicate degrees of pressure tha-t is being exerted upon it by the flexible diaphragm (), in consequence to the pressure being indicated.

Claims (1)

1. tOW PRESSURE IN OR.

   CLAIMS.

   1. A low pressure indicator in which fluid under pressure is communicated to within a housing and thereby to one surface of the said housing which is a flexible diaphragm and which flexible diapijragm isealed to the said housing so that the said fluid when under pressure cannot by-pass the said flexible diaphragm but will cause the said flexible diaphragm to de-form outwards from they'said pressure to bear upon a sliding member contained within the said housing and which sliding member can slide freely within the housing without the need to form an effective seal by outward pressure to the housing wall and which sliding member is made to bear on the flexible diaphragm at all times by a spring or other means, and which sliding member will slide axially as a result of the pressure being applied to it by the deformation of the flexible membrane, and the protusion of the sliding member from the said housing will indicate the degree of force of the pressure that is being exerted upon the flexible diaphragm by the fluid.

   2). A low pressure indicator as in Claim 1 in which the the flexible diaphragm material and diameter and the spring tension may be selected to suit the operation pressures to be indicated.

   3). A low pressure indicator as in Claims 1 and 2 in which the deformation of the flexible diaphragm is magnified by mechanical or other means for indirect pressure readings.