EP1434245B1

EP1434245B1 - Differential pressure switch

Info

Publication number: EP1434245B1
Application number: EP03079064A
Authority: EP
Inventors: Marco Gerolamo Omati; Ennio Omati
Original assignee: Ma-Ter Srl
Current assignee: Ma-Ter Srl
Priority date: 2002-12-24
Filing date: 2003-12-16
Publication date: 2005-10-12
Anticipated expiration: 2023-12-16
Also published as: ES2247483T3; ITMI20022761A1; CN1510707A; HK1065887A1; DE60301846T2; CN1327464C; DE60301846D1; ATE306717T1; EP1434245A1

Abstract

A differential pressure switch is described comprising a first (1) and a second (2) inlet for first and second fluids operating respectively on opposite faces of a deformable membrane (3) in such a way so as to determine opposite movements of the membrane (3) for the activation or the disactivation of a sensor (8, 13) as a function of the difference in pressure between the first and the second fluid. Lever means (9) are interposed between the membrane (3) and the sensor (8, 13) so as to amplify the movements being commanded to the membrane (3) in the direction of the sensor (8, 13). <IMAGE>

Description

The present invention concerns a differential pressure switch.
There are known differential pressure switches comprising two distinct inlets for two different fluids which exert on opposite faces of a deformable membrane, respectively, a first and a second pressure. The pressure switch is sensitive to the difference in said pressures, in that the membrane moves in one sense or in the other one, thus activating or disactivating a sensing member (for instance the push-button of an electric switch), depending on whether the first pressure is greater or smaller than the second one.
In order to increase the sensitivity of the differential pressure switch it is necessary to increase the surface of the membrane with consequent increase in the dimensions of the pressure switch.
US-A-3 207 868 discloses an electric switch mechanism according to the preamble of claim 1.
In view of this state of the art, object of the present invention is to provide a differential pressure switch that is more sensitive than the known pressure switches with equal conditions and dimensions.
According to the present invention, such object is attained by means of a differential pressure switch as defined in claim 1.
The characteristics and the advantages of the present invention will become evident from the following detailed description of an embodiment thereof, illustrated as a non-limiting example in the enclosed drawings, in which:
Figure 1 is a front view of a pressure switch according to the invention;
Figure 2 is a section view according to the line II-II of the pressure switch in Figure 1;
Figure 3 is a vertically sectioned view, according to the line III-III of Figure 2, of the pressure switch with the membrane in a first position;
Figure 4 is a vertically partially sectioned back view of the pressure switch with the membrane moved to said first position;
Figure 5 is a section view similar to the one in Figure 4 with the membrane moved in a second position;
Figure 6 is a section view of a pressure switch according to the line VI-VI in Figure 4.
In the Figures 1-6 a differential pressure switch 4 according to the invention is shown. The pressure switch comprises a base 30, a cap 31, a cover or lid 32 put onto the cap 31 and a clamp 33 suitable to keep the base 30 and the cover 32 united to each other with the cap 31 interposed between the two. An internal partition 40 of the cap 31 separates the internal space of the pressure switch in a first chamber 41 and a second chamber 42 that are watertight with respect to the other one (Figure 6).
A deformable round membrane 3 is located inside the chamber 41 and is peripherally fastened between the base 30 and the cap 31. The base 30 is provided with a first inlet 1 for a first fluid destined to operate at a pressure P1 on a face of the membrane 3 and a second inlet 2 communicating with a passage 20 is provided in the cover 32 and cap 31 for a second fluid destined to operate at a pressure P2 on the opposite face of the membrane 3 (Figures 1-3).
The membrane 3 supports a rigid plate 5 fastened to the membrane 3 by means of a "RESCA" system, that is fastened at the center and at an intermediate point 34 of the membrane 3. On the plate 5 a central projection 6 is obtained that is suitable to house a reaction spring 7 arranged between the plate 5 and the cap 31.
In the chamber 42 a sensor for the position of the membrane is housed, that in the example being considered is made up of a microswitch 8 which operates on an external electric circuit not visible in the figures. The microswitch 8 is provided with an activation push-button 13, visible in Figure 4.
In addition the pressure switch comprises a lever 10 made up of a first lever arm 9 housed in the chamber 41 and engaged with the plate 5 and a second lever arm or actuator 11 housed in the chamber 42 (Figures 4-6). The lever arm 10 and the actuator 11 are made integral with a revolving shaft or fulcrum 12 with watertight packings 43, arranged parallel to the plate 5 and fastened to the cap 31.
When the pressure P2 of the fluid at the inlet 2 is greater or equal to the pressure P1 at the inlet 1, the membrane 3 is withheld by the spring 7 against the base 30 and the actuator 11 is distant from the activation push-button 13 of the microswitch 8 (Figure 4). When the pressure P1 of the fluid at the inlet 1 is greater than the pressure P2 of the fluid at the inlet 2, the difference in pressure determines an upward movement of the membrane 3 (Figure 5) with consequent upward movement of the lever arm 10 that is transmitted to the actuator 11 by the shaft 12.
The actuator 11 can thus operate on the push-button 13 so as to cause switching of the microswitch 8. The lever 9 formed by the arm 10 and the actuator 11 amplifies the upward movement of the membrane 3 and therefore increases the sensitivity of the pressure switch with equal dimensions and conditions.
A calibration dowel 14 located inside the inlet 1 (Figures 4 and 5) allows the adjustment of the position of the actuator 11 with respect to the push-button 13 of the microswitch 8.
It should be noticed that due to the effect of the partition 40 the microswitch 8 is in a completely separate chamber 42, which is watertight with respect to the chamber 41 in which there is the fluid entered through the inlet 2. This allows to use the above described pressure switch both for gas and for liquids, possibly even in the presence of an electric sensor as the microswitch 8.

Claims

Differential pressure switch comprising a first (1) and a second (2) inlet for first and second fluids operating respectively on opposite faces of a deformable membrane (3) so as to determine opposite movements of said membrane (3) for the activation or the disactivation of a sensor (8, 13) as a function of the difference in pressure between the first and the second fluid, lever means (9) interposed between said membrane (3) and said sensor (8, 13) so as to amplify the movements being commanded by said membrane (3) in the direction of said sensor (8, 13), a rigid plate (5) fastened to said membrane (3) in the zone of operation of said membrane (3) on said lever means (9), said lever means (9) comprising a first lever arm (10) engaged with said plate (5) and a second lever arm or actuator (11) capable to operate on said sensor (8, 13), characterised in that said membrane (3) and said first lever arm (10) are housed in a first chamber (41) and said second lever arm or actuator (12) and said sensor (8, 13) are housed in a second chamber (42) separate and watertight with respect to said first chamber (41).
Pressure switch according to claim 1, characterised in that said lever arms (10, 11) are connected with each other by a shaft or fulcrum (12) revolving around a fixed axis substantially parallel to the plane of said plate (5).