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The present invention relates to a device for signalling the presence of pressure inside a plant, duct or space in general.

The easiest but not always the most cost-effective and practical method to indicate the presence of pressure is to apply an analog gauge which, however, must have a dedicated connection or a digital pressure indicator which is not however capable of performing its function without electricity.

There are other devices for indicating the presence of pressure but they are usually impractical, cumbersome, sometimes even complicated from the constructional point of view and not very cost-effective.

It is the object of the present invention to provide the user/installer with a device for signalling the presence of pressure inside any space, duct, plant, etc. which is simple, practical, easy to be installed, and especially capable of providing pressure signals which are well identifiable and measurable.

Such an object is achieved with the device defined in claim 1, which also works without electricity and can also be an integral part of an electromechanical pressure switch or pressure sensor, for example. This is simply because the part indicating the presence of pressure can be incorporated within the pressure socket.

Moreover, the device is characterized in that it always indicates the presence of pressure with reference to the value at which the device has been previously adjusted/calibrated, and it suffers no damage also in case of overpressure.

Furthermore, its constructional simplicity makes it suitable for use in productions with high scale volumes and, no less important feature, the same constructional simplicity makes it reliable and constant over time. The fact that it can be integrated into any hydraulic connection makes it highly cost-effective since two products are installed with one operation and no special connection needs to be provided for its connection.

For a better understanding, an example of the device according to the present invention is shown in the accompanying drawings, in which:

figure 1 shows an axial section of the device for signalling the presence of pressure in rest position (pressure of 0 bar);

figure 2 shows an axial section of the device for signalling the presence of pressure in working position (pressure higher than the calibration value);

figure 3 shows a cross-section of the anti-rotation coupling system of the device according to line III- III in figure 1.

The exemplary device shown in the drawings mainly consists of three parts:

• a first hydraulic connection part (1), hereafter referred to as "lower part" with reference to figures 1 and 2

• a second part (2), hereafter referred to as "upper part", intended to support a measuring device

• a central pierced pin (3) axially inserted into parts (1) and (2). The lower part (1), provided with an outer thread (51), is used to connect the pressure signalling device to the plant or duct under control and may be manufactured in any shape required by the application, provided that it allows the central pin (3) and a helical spring (4), interposed between the shoulders (53) and (54) of pin (3) and of the lower part (1), to be accommodated therein along its axis.

The upper part (2) is manufactured so as to be axially sliding in the lower part (1) and at the top has any suitable shape to be coupled to a measuring device (400), such as for example a pressure switch or a pressure sensor.

The three main parts, lower part (1) for the hydraulic connection, upper part (2) and central pin (3), are kept connected to one another by means of an elastic ring (5) placed in a dedicated seat at the upper end of the central pin (3). In order to make the coupling between the upper part (2) and the central pin (3) stable, a dedicated seat (11) is obtained on the central pin (3) to serve as a shoulder against a neck (303) of the upper part (2). This coupling prevents the central pin (3) from sliding upwards within a chamber (200) of the upper part (2), thus damaging the measuring device (400) applied thereon.

The pressure of the fluid present inside the plant or duct under control, through an inlet bore (100), reaches and runs along its entire length an axial bore (52) of the central pin (3) up to an outlet bore (100a) of the central pin (3) to finally reach the chamber (200) obtained within the upper part (2). Thereby, for example, a pressure sensor (400) constructed above the upper part (2) directly receives the pressure and is free to independently perform its function.

When the inner passageway of the central pin (3) reaches the pressure value present inside the plant or duct under control, one or more lateral bores (6) on the central pin (3) allow the pressure to reach an upper chamber (300a) and then, through an annular cavity (300c), an enlarged lower chamber (300b) obtained between the inner part of the lower part (1) and the inner part of the upper part (2).

The main function of chamber (300b) is to increase the section on which the pressure acts to raise the upper part (2) and the measuring device (400) applied thereon.

Since the formula for obtaining the Force having a Pressure and a Surface is: F = PxS, having a small section on which the pressure presses, the detection and accuracy of operation at low pressures would be problematic. The increase in surface obtained by means of chamber (300b) allows this problem to be overcome because the total pressure surface is the sum of the surfaces (301, 302) of the chambers (300a, 300b) communicating with each other through the cavity (300c).

This increase in surface, and as a result in the force acting on the device, allows the parts not to be manufactured with high accuracy because any friction or rubbing due to the sliding parts has a proportionally much lower value than the force generated by the pressure.

Also in the rest position (fig. 1), both the upper chamber (300a) and the lower chamber (300b) with their surfaces (301, 302) are always in communication with each other and any pressure variation occurring in the plant or duct to which the device is connected, by means of the bore (6) of the central pin (3), acts immediately.

The hydraulic sealing between the lower part (1) and the upper part (2) is ensured by an O-ring (7) applied in a dedicated seat (7a) directly obtained in the upper part (2).

Moreover, in order to give a visual signal of the presence of pressure, in a dedicated seat (8) directly obtained in the upper part (2) there is a coloured ring (9) made of heat-shrinkable material or any other elastic material which allows the ring itself to always remain clamped. As the pressure and thus the force acting on the surfaces (3001, 302) increase, the upper part (2) exits from the housing obtained in the lower part (1) thus also lifting the measuring device (400) placed thereon, which is a pressure sensor (400) in this example.

In order to prevent the upper part (2) from exiting from the lower part (1) with a consequent fluid leak, a spring (4) of appropriate size and strength is provided which, when reaching a fully locked position without compressed air between the turns (fig. 2), limits this movement, thus ensuring the sealing even in case of overpressure. Spring (4) further ensures the return of the upper part (2) to the rest position when the pressure decreases.

By changing the features of spring (4), the pressures at which the signalling device must carry out its maximum displacement may be determined, thus fully displaying the coloured ring (9). The application of a graduated scale into the seat (8) obtained in the upper part (2), suitably manufactured, would also give an indication of the pressure.

In addition, in order to more finely calibrate spring (4), one or more rings (10) can be applied on the central pin (3) above or below the spring (4) itself.

On the upper part (2) there are also two or more projections (12) sliding inside two or more recesses (13) obtained in the lower part (1) (fig. 3). This movable coupling allows the device to be easily screwed on the plant or duct under control without the aid of tools, because by rotating the upper part (2), the lower part (1) is in turn pulled. Moreover, the projections (12) and recesses (13) are obtained so that, both in the presence of pressure and with pressure at 0 bar, they are always one inside the other, thus preventing the rotation of the upper part when the device is signalling the pressure.

If the projections (12) and recesses (13) were not always coupled, the upper part (2) would be rotated, thus making the pins (12) to be no longer in correspondence of guide (13), thus affecting the return of the upper part (2) to the position of no pressure and generating a visual signal which would not correspond to reality.