WO2005100792A1

WO2005100792A1 - Pressure and flow controller for a pump

Info

Publication number: WO2005100792A1
Application number: PCT/BR2005/000055
Authority: WO
Inventors: Gilberto Tadeu Pires De Paula
Original assignee: Gilberto Tadeu Pires De Paula
Priority date: 2004-04-14
Filing date: 2005-04-14
Publication date: 2005-10-27

Abstract

An automatic pressure and flow controller for a pump (10) is described. The device contains a relief-valve (20-30) and hydraulic pressure-switch (40) to turn the pump on/off depending on the pressure in pipe 1. The relief-valve (20-30) is constructed as a sliding piston with sections (21`,21``) with different diameters. A sensor (23) in the housing of the device cooperates with a magnetic element (22) in section (21`) of the piston. An upstream seat (66) cooperates with an O-ring (24) carried by section (21`) of the piston. Pressure-switch (40) contains a membrane (41) which acts on a piston (42) which can close and open electrical contacts to turn the pump (10) on or off. Pressure-switch (40) can be adjusted by srewing-in element (49) to a certain extent .

Description

"AUTOMATIC PRESSURE AND FLOW CONTROLLER AND CHA-RGE

CELL FORMING PART OF IT"

The present description refers to a patent of

invention for an automatic pressure and flow controller and charge cell

forming part of it, pertaining to the field of hydraulic installations, and

which have been designed to perform the same functions as similar

conventional equipment, but more efficiently, as well as introduce a, more

simplified construction being sensibly smaller in volume than the mentioned

conventional equipment, and provide further advantages. It is already known in the art, equipment intended

to keep a water pipeline under pressure by driving a water pump every time

the pressure drops below a given value, as well as intended to monitor the

liquid flow in the pipeline in order to secure the pump will not work dry for

a long time. Such conventional device comprises: a casing

through which the water runs; a relief valve; a flow detecting set

comprising: a special piston provided with a magnetic element, and which

moves along with the water flow; and a magnetic sensor suitably arranged

outside the body, and which is sensitized by the magnetic element of the

piston, when such moves, thus detecting the water flow; such device further

comprises: a diaphragm, which separates the inner part from the oxiter part of the device casing; a spring supporting the diaphragm; a magnetic element

which moves upon the movement of the spring diaphragm set; an external

sensor, which sets the pressure by detecting the movement of the magnetic

element; and an analog circuit that processes the originated flow and

pressure information, upon which it turns the water pipeline pressurization

pump either on or off.

Although such device is useful for the purpose

which it is intended to, it shows the inconvenient of having a relatively

complex construction comprising several sets, and as a result a similarly

complex manufacturing process.

Another drawback consists of the fact such usual

device is extremely bulky, what causes it to require a complicated

installation to receive it for use, and poses a limiting factor to its field of

application. Another drawback consists of the fact such

constructive complexity results in a relatively high cost device.

Therefore, the objective of the invention, object of

the present patent is to provide a pressure and flow controller, which

performs the same functions as the usual device, but overcomes the

drawbacks shown by the conventional device, further to providing other

advantages. Therefore, having the above-mentioned drawbacks

in mind, with the purpose of overcoming them, and aiming at meeting the

mentioned objectives, the automatic pressure and flow controller designed

according to the present patent of invention, essentially comprises: a piston

featuring a magnetic element associated with an external sensor, and a

casing chamber where the piston works, arranged to perform the functions

of flow detector and relief valve; a pressure sensible charge cell, which

features and subjects a power switch connected to the pipeline pressurization

pump, and either turns the switch on when the pressure in the pipeline drops

below the working pressure, or turns it or keeps it off, when the pressure

either reaches up to or is at the working pressure; said controller of the

present invention further comprises a microprocessed digital circuit

associated with the mentioned sensor and power switch, which controls the

on/off function of the pump and provides other functions. The piston and the chamber where it works are

arranged to perform functions such as flow detection and relief valve, as

provided in the present controller, thus the use of the relief valve provided in

the conventional device is not required, and as a consequence, the present

controller results to be simpler in construction than the conventional one. The charge cell essentially comprises: a cushion-

type elastic diaphragm, whose surface is subject to the pressure to be monitored; said cell is further formed: by a fixed external tubular body

provided with external means for setting it at the place of use, and at one end

of which the diaphragm is placed; a movable internal tubular body provided

with an end diaphragm path limiting stop; an outer thread screwed in the

inner thread of the fixed body, said movable body can then be turned at the

fixed body either to get closer to or move away from the diaphragm, and so

adjust its path, and consequently the charge cell driving pressure; said

charge cell further comprises a power microswitch placed at the movable

body end opposite to the stop, and whose button is driven by the diaphragm;

and a cover for fastening the microswitch to the movable body.

The charge cell constructed as described above

advantageously replaces the traditional devices which are pressure,

pressostat driven, based upon a membrane and spring, since it has all the

functions as the traditional devices added by the fact it is perfectly

adjustable, occupies a too much smaller space, and does not require the use

of a spring, and all the structure required to support it.

The constructive simplicity of the present charge

cell further results in an extremely simple manufacturing process required to

manufacture it in respect of the similar conventional devices. Further, the constructive and manufacturing

simplicity of the present charge cell results in costs dramatically lower than those required for manufacturing usual similar devices.

The microprocessed digital circuit of the present

controller, besides the pump on/off function, further provides conditions to

perform a number of other operations, such as: to set how many attempts the

circuit will allow to be made prior to entering into the error module; the time

between an attempt and the other; how low the pump must be kept on after a

lack of flow is detected; how long the circuit must wait for prior to turning

the pump on, when a pressure drop in the pipeline is detected, and other

operations according to the programming desired, which are only possible to

be performed and/or implemented by the digital circuit in a way simpler

than that of the analog circuit of the usual device.

Another advantage provided by the present

equipment over the conventional similar is a simpler construction and

manufacturing than those of the usual device and a volume extremely

smaller than that of the conventional device, what expands the choice of

application possibilities available to the present controller.

Such simplicity, and smaller volume result in a

final cost for the present controller that is lower than that for the usual

device. The accompanying drawings show the automatic

pressure and flow controller and the charge cell, object of the present patent, in which:

Figure 1 shows a lateral section of the controller at

the position where the flow is allowed to pass, and its pressure detected;

Figure 2 shows the same figure as above, but at the

position where it works as a relief valve to prevent the backflow, when lacks

inlet flow;

Figure 3 shows a cross-sectional view of the

controller;

Figure 4 shows an enlarged detail of the charge

cell, which is part to the controller;

Figure 5 shows the charge cell with its parts taken

separately; and

Figure 6 shows it mounted, and the working

indication. According to what is illustrated by the above-

mentioned figures, the purpose of the pressure and flow controller, object of

the present patent of invention is to keep a suitable pressure at a water

pipeline 1, upon monitoring the pressure and driving a pump 10, whenever

the pressure drops below a predetermined pressure value, and secure the

pump 10 will not work dry when flow is lacking, and it is of the type

essentially comprising: a flow detecting device 20, primarily consisting of: a piston 21 subject to flow "F"; a magnetic element 22 mounted over the

piston; a sensor 23 outside the flow circulation passage, sensible to the

movement of the magnetic element 22, and as a consequence, the movement

of the piston 21; a relief valve 30; a device 40 for setting the pump driving

pressure, essentially consisting of: elastic means 41 subject to pressure "P"

of the flow "F"; and power switch means 42 subject to the elastic means 41;

an electric circuit 80 associated with the sensor 23, and the power switch

means 42, and having the function to turn the pump 10 on/off; and a casing

60, where devices 20, 40; the relief valve 30 and the electric circuit 80 are

properly mounted; such casing being inserted into the water pipeline 1.

According to the present construction, a device 20-

30 with the functions to operate as a flow detector and relief valve is

provided, essentially comprising: a piston 21 being formed by: broader 21'

and narrower 21" sections, the broader section 21 ' being provided with the

magnetic element 22 and an 'O' ring 24 mounted on the face of said section

21 ' turned to the inlet 61 of casing 60, and the narrower piston section 21"

also turned to the inlet 61 having a diameter slightly smaller than the

passage 62 of the casing, and being guided by such casing.

Such device 20-30 with the functions to operate as

a flow detector and relief valve is further formed by: the casing 60 provided

by a chamber 63 broader than the passage 62, and slightly broader than the broader piston section 21', where it is arranged and ready to move; opposite

lateral recessed stripes extending into said chamber 63 and passage 62 (fig.

3), which set the flow passages laterally to the broader section 21' of the

piston; set between said passage 62 and the chamber 63, the downstream

stop 65, and upstream seat 66; said piston 21 moving between two positions:

one corresponding to the existence of flow "F", where the piston 21 is

pushed by the flow and bumps against the downstream stop 65, thus

positioning the magnetic element 22 adjacent to the sensor 23, and arranging

the sensor at the logic position at which the pump 10 can be turned on by

the device 40, in the event the pressure falls below the nominal working

pressure, and another corresponding position when flow "F" is lacking, at

which the piston 21 is pushed by the backflow "F' ", and its 'O' ring 24

closes against the seat 66, thus actuating as a relief valve, and the magnetic

element 22 of the piston simultaneously moves away from the sensor 23,

taking it to a logic position at which the pump 10 is either turned off, or

prevented from being turned on by the device 40.

The device for setting the pump driving pressure

40 has its elastic means 41 and power switch means 42 comprising a charge

cell (figs. 4 a 6) primarily consisting of: a cushion-type elastic diaphragm

43, one of its surfaces being kept subject to a pressure "P" to be monitored;

said cell is further formed by: a fixed external body 44 provided with external means 45 for setting in the place of use, in the event the casing 60 is

in the housing; an internal passage 46; an end 47, where the diaphragm 43 is

placed, and inner thread 48; an internal movable body 49 provided with an

internal passage 50; an end stop 51, which is adjacent to the diaphragm 43,

and its path limiter; outer thread 52 screwed in an inner thread 48 of the

fixed body 44, and which enables said movable body 49 to be turned and

axially displaced at the fixed body 44 either to get closer to or move away

from the diaphragm 43, and then adjust the diaphragm path, and

consequently the charge cell driving pressure; said charge cell further

comprises a power microswitch 42 placed at the end of the movable body 49

opposite to the stop 51, and whose button 42' is driven by the diaphragm 43;

and a cover 53 for fastening the microswitch 42 to the movable body 49.

The cushion-type diaphragm 43 is ring-shaped and

essentially comprises: an outer frame 54, which is placed at the end 47 of

the fixed body 44; an intermediate, elastic, circular crown-shaped membrane

55 whose periphery is incorporated into the frame, and which bends upon

receiving the monitored pressure "P", and whose bending path is limited by

the stop 51 of the movable body 49, according to the driving pressure

intended for the charge cell; and a rigid, central core 56 with the periphery

incorporated into the membrane 55, which is kept aligned with the button

42' of the microswitch 42, and which presses the button when the membrane is bent.

Mounting the diaphragm 43 at the end 47 of the

fixed external body 44 provides sealing means 57, which together with the

diaphragm 43 provide further sealing between the room where the

monitored pressure "P" occurs and the environment.

The stop 51 comprises a tapered recess-shaped

surface provided at the end of the movable body 49 adjacent to the

diaphragm 43, and at whose bottom the end of the internal passage 50 of the

body is located, where the button 42' of the microswitch 42 is arranged and

slightly projecting.

The electric circuit 80 is digitally micro-processed

and arranged to receive information from the sensor 23 and/or power switch

42, process such information, and then turn the electric pump 10 either on or

off through the triac 81; said circuit is further arranged to perform other

operations, such as: to set how many attempts the circuit will allow to be

made before entering into the error module; the time between an attempt and

the other; how long the pump must remain turned on after lack of flow is

detected; how long the circuit must wait for prior to turning the pump on,

when a drop in the pipeline pressure is detected, and other operations,

according to the desired programming.

The triac 81 is associated with a cooling system comprising a heat exchanging plate 82, one end of which keeps a physical

contact with the triac, and the opposite end dips into the water flow "F"

which circulates through the passage 62.

Preferably, the casing 60 is made of thermoplastic

material or similar one, and its diameter is slightly larger than that of the

pipeline 1 where it is set up, said pipeline being essentially formed by a

tubular body 68 and a connection 69.

The body end 68 is opposite to the connection 69,

which forms the water outlet 67, features a male screw, which connects to

the water pipeline 1, and a staggered passage extends along said body and

from said outlet 67, said passage being formed by: a longer, smaller

diameter section forming part of passage 62; radial surface forming the stop

65; an intermediate section, whose diameter is larger than the passage 62,

and forming part of the chamber 63, where laterally recessed passages 64

are provided; a female screwed section; a radial surface forming the sealing

stop, the end section being larger in diameter but having a short axial length,

these three latter elements receiving the connection 69; said body 68 further

features a upper vessel 70, which provides a chamber 71 communicating

with the passage 62, and receiving the charge cell, a means for placing the

electric circuit board 80, and means for fastening a cover 72.

The connection 69 is formed by a staggered passage consisting of: an end, larger diameter section, which forms another

part of the chamber 63, and arranged as a continuation of part of body 68; a

radial surface forming the seat 66, and the end, opposite, smaller diameter

section, which constitutes part of the passage 62, forming the inlet 61, and

provided with a male screw connecting to the water pipeline 1, and at the

end of said part of the passage 62 next to the seat 66 a retaining rod 73 is

placed, where a longitudinal rip 74 is guided and made along the piston

section having a smaller width 21"; externally, said connection provides an

intermediate flange 75, which fits inside the end section of the body 68,

whose section is larger in diameter and has a small axial length, and an 'O'

ring 76 is arranged around said connection and adjacent to said flange 75,

and seals against the body sealing stop 68, the end of said connection

connecting to the body 68 further features a male screw.

Thus, the automatic pressure and flow controller of

the present invention works as follows: when there is a flow "F" at a

nominal pressure level "P", the diaphragm 43 of the charge cell bends, and

presses the button 42' of the normally closed switch 42 towards reaching the

open position at which the water pump 10 is not turned on. Simultaneously,

flow "F" pushes the piston 21 against the stop 65, and its magnetic element

22 is adjacent to the sensor 23, and thus the sensor is arranged at the logic

position at which the pump is allowed to be turned on, in case of pressure drop. When there is a flow "F", but the pressure drops below the nominal

value, the diaphragm 43 takes over the non-bent position, releasing the

button 42' of the normally closed switch 42, which is automatically

switched to the position that turns on the pump 10, and then the nominal

pressure conditions are restored in the pipeline 1 (fig. 1).

When flow "F" is disrupted, the backflow "F"'

pushes the piston 21 towards a position at which the 'O' ring 24 of said

piston seals against the seat 66, thus acting as a relief valve. Simultaneously,

the magnetic element 22 moves away from the sensor 23, and the sensor

takes over another logic position at which the pump 10 is either turned off,

in case it is on, or the pump 10 is prevented from being turned on, in case it

is off, in order to avoid the pump from working dry (fig. 2).

The charge cell is used with any equipment, such

as for instance, the present flow and pressure controller, whose internal

pressure "P" is to be monitored, so that when a predetermined limit is

reached, some procedure will be started. The pressure limit value is

determined and the monitoring and driving are carried out by the charge

cell. Therefore, said charge cell is mounted at the equipment so the outer

face of its diaphragm 43 will be subject to pressure "P", and previously, by

means of a suitable screw to the fixed external body 44, the movable internal

body 49 is arranged at a desired distance in respect of the diaphragm 43, which sets the diaphragm bending path, and as a result, the cell driving

pressure. This way, when the monitored pressure "P" reaches the pre¬

programmed limit by means of the positioning of the movable body 49, and

its stop 51 inside the fixed body 44, the diaphragm 43 bends along the preset

path and turns on the microswitch 42, which starts some procedure

associated therewith, as for instance, driving the controller pump, or relief

valve, or other operations.

Under this condition, the movable body 49 and its

stop 51 can be arranged at several positions in respect of the diaphragm 43,

causing the microswitch 42 to be turned on at a number of corresponding

pressure levels, in order to meet the application to which the cell is intended.

In addition to such function, once adjusted in respect of the diaphragm 43,

the movable body 49 and its stop 51 also act in order to keep a constant

distance between the diaphragm core 56 and the button 42' in order to avoid

pressure overload over the button.

According to the above described primary

construction, the controller and charge cell object of the present patent of

invention can have changes relating to materials, dimensions, constructive

details and/or functional and/or ornamental configuration, without departing

from the scope of the protection required.

Claims

1)- "AUTOMATIC PRESSURE AND FLOW CONTROLLER", of the type

comprising a flow detecting device (20), primarily formed by: a piston (21)

subject to flow "F"; a magnetic element (22) mounted over the piston; a

sensor (23) set up outside the flow circulation passage, and which

cooperates with the magnetic element (22); a relief valve (30); a device (40)

for setting the pump (10) driving pressure to k-eep the pipeline (1) pressure;

said device (40) essentially fonned by: elastic means (41) subject to pressure

"P" of flow "F" in the pipeline (1); and a power switch means (42) subject

to the elastic means (41); an electric circuit (SO) associated with the sensor

(23) and the power switch means (42), and with a function to turn the pump

(10) on/off; and a casing (60), where the devices (20), (40); the relief valve

(30) and the electric circuit (80) are mounted, and said casing is inserted into

the water pipeline (1), characterized in that a device (20)-(30) having the

function to act as flow detector and relief valve is provided, essentially

comprising: a piston (21) formed by: broader (21)' and narrower (21)"

sections, the broader section being provided with the magnetic element (22),

and an 'O' ring (24) mounted tumed to the inlet (61) of the casing (60), and

the narrower piston section (21)" is also turned to the inlet (61) and has a

diameter slightly smaller than the casing passage (62), and is guided therein;

said device (20)-(30) is further formed by: a casing (60) provided with a chamber (63) broader than the passage (62), and slightly broader than the broader piston section (21)', and where the piston is arranged and ready to move; lateral, opposite recessed stripes (64) are provided to extend over said chamber (63) and at the passage (62), and such stripes set the flow passages

₅ laterally to the broader piston section (21)'; a downstream stop (65), and a upstream seat (66) are set between said passage (62) and the chamber (63); the downstream stop limits the path of the piston (21) when it is moved by flow "F", and places its magnetic element (22) adjacent to the sensor (23), which is taken to the logic position at which an eventual driving of the pump

L_Q (10) by the device (40) is allowed, and the upstream seat (66) limits the path of the piston (21), when there is no flow "F", and the piston is moved by the backflow "F"', simultaneously the O' ring (24) of the piston (21) seals the upstream seat (66), acting as a relief valve and the magnetic element (22) is located away from the sensor (23), and takes such sensor (23) to the logic

_{l 5} position at which the pump (10) is turned off and prevented from being turned on by the device (40).

2)- "AUTOMATIC PRESSURE AND FLOW CONTROLLER", as claimed in claim 1, characterized in that the device (40) which sets the pressure for driving the pump features its elastic means (41) and power switch means 0 (42), comprising a charge cell primarily formed by: a diaphragm (43), which is subject to pressure "P" and formed by: a frame (54) mounted over the fixed body (44), mounted in the casing (60) housing; an intermediate elastic

membrane (55), which is bent or not in view of the nominal pressure "P"

and nominal pressure of flow "F", respectively, in the pipeline (1); and an

aligned central core (56), which presses the button (42)' of the power switch

means (42), under the nominal pressure condition "P"; said power switch

means (42) comprising a normally closed switch, and the charge cell further

comprises a driving pressure adjusting means featuring a movable, tubular,

internal body (49), which is screwed inside the fixed body (44), whose end

turned to the diaphragm (43) features a recessed stop (51), which limits the

diaphragm path, and the opposite end houses the power switch means (42),

whose button (42)' is slightly projecting in respect of the body passage at

the stop (51).

3)- "AUTOMATIC PRESSURE AND FLOW CONTROLLER", as claimed

in claim 1 , characterized in that the electric circuit (80) is digitally micro-

processed, and arranged to receive information from the sensor (23), and

power switch (42), process such information, and then either turn the

electric pump (10) on or off through the triac (81).

4)- "AUTOMATIC PRESSURE AND FLOW CONTROLLER", as claimed

in claim 3, characterized in that the electric circuit (80) is further arranged

to perform other operations, such as: to set how many attempts the circuit

will allow to be made prior to entering into the error module; the time between an attempt and the other; how long the pump must be kept on after

a lack of flow is detected; how long the circuit must wait for prior to turning

the pump on, when detecting a pressure drop in the pipeline, and other

operations according to the programming.

5)- "AUTOMATIC PRESSURE AND FLOW CONTROLLER", as claimed

in claim 3, characterized in that the triac (81) is associated with a cooling

system comprising a heat exchanging plate (82), one end of which keeps a

physical contact with the triac, and the opposite end dips into the water flow

"F", which circulates through the passage (62).

6)- "AUTOMATIC PRESSURE AND FLOW CONTROLLER", as claimed

in claim 1, characterized in that the casing (60) diameter is slightly larger

than that of the pipeline (1) where it is set up, and the casing is essentially

formed by: a tubular body (68); and a connection (69); said body (68)

having an end opposite to that receiving the connection (69), which

constitutes the water outlet (67), featuring a male screw connecting to the

water pipeline (1), a staggered passage extending along said body and from

said outlet (67), said staggered passage being formed by: a longer, smaller

diameter section, which forms part of the passage (62); a radial surface

constituting the stop (65); an intermediate section, whose diameter is larger

than the passage (62), and forming part of the chamber (63), where lateral

recessed passages (64) are provided; a section with female screw; a radial surface constitutes the sealing stop, and an end section being larger in

diameter and having a short axial length, these three latter elements

receiving the connection (69); said body (68) further features a upper vessel

(70), which provides a chamber (71) communicating with the passage (62),

and receiving the charge cell, a means for placing the electric circuit board

(50), and means for fastening a cover (72).

7)- "AUTOMATIC PRESSURE AND FLOW CONTROLLER", as claimed

in claim 6, characterized in that the connection (69) is formed by a

staggered passage consisting of: an end, larger diameter section, which

forms the other part of the chamber (63), and arranged as a continuation of

the part of the body (68); a radial surface constitutes the seat (66) and

opposite, end, smaller diameter section forming part of the passage (62),

which forms the inlet (61), and provided with a male screw, which connects

to the water pipeline (1), and at the end of said part of the passage (62) next

to the seat (66) a retaining rod (73) is arranged, in which a longitudinal rip

(74) is guided and made along the smaller width section (21)" of the piston;

externally, said connection provides an intermediate flange (75), which fits

inside the end section of the body (68) being larger in diameter and having a

small axial length, and an 'O' ring (76) is arranged around said connection

and adjacent to the mentioned flange (75), and seals against the body sealing

stop (68), the end of said connection further connecting to the body (68) featuring a male screw.

8)- "CHARGE CELL", which forms part of the pressure and flow controller

of claims 1 to 7 and comprising: elastic means (41), one face of which being

subject to a pressure "P" to be monitored; a fixed body (44), where the

elastic means (41) is set, and which is located at the receiving equipment;

and means (49) for adjusting the cell driving pressure, set up in the fixed

body (44), and which subjects the elastic means (41), characterized in that

the elastic means consists of a cushion-type elastic diaphragm (43), one

surface of which being subject to pressure "P" to be monitored; a fixed,

external body (44) provided with external means (45) for setting at the

place of use; an internal passage (46); an end (47), where the diaphragm (43)

is located, and an inner screw (48); the means for adjusting the pressure

comprising a movable, internal body (49) provided with an internal passage

(50); an end stop (51), which is adjacent to the diaphragm (43) and a

diaphragm path limiter; an outer thread (52) screwed to the inner thread (48)

of the fixed, external body (44) in order to displace axially the movable,

internal body (49) in the fixed, external body (44) to have the diaphragm

(43) to get close to or move away from the end stop (51), and adjust the

diaphragm path, and as a result the charge cell driving pressure; said charge

cell further comprising a power microswitch (42) set up at the end of the

movable body (49) opposite to the stop (51), and whose button (42') is driven by the diaphragm (43); and a cover (53) for fastening the microswitch

(42) to the movable body (49).

9)- "CHARGE CELL", as claimed in claim 8, characterized in that the

cushion-type diaphragm (43) essentially comprises: an outer frame (54),

which is located at the end (47) of the fixed, extemal body (44); an

intermediate, elastic, circular crown-shaped membrane (55), whose

periphery is incorporated into the frame, and which bends as a result of the

monitored pressure "P" along a bending path limited by the stop (51), and

with a length according to the driving pressure intended for the charge cell;

and a rigid, central core (56) with the periphery incorporated into the

membrane (55) aligned with the button (42') of the microswitch (42), and

which presses this button when the membrane is bent.

10)- "CHARGE CELL", as claimed in claim 8, characterized in that

mounting the diaphragm (43) at the end (47) of the fixed, external body (44)

provides the sealing means (57).

11)- "CHARGE CELL", as claimed in claim 8, characterized in that the

stop (51) comprises a tapered recess-shaped surface provided at the end of

the movable body (49) adjacent to the diaphragm (43), and at whose bottom

part the end of the internal passage (50) of the body is located, where the

button (42') of the microswitch (42) is located and slightly projecting.