FR2473711A1 - IMPROVEMENTS IN FLUID PRESSURE DETECTORS AND IN CIRCUITS THAT CAN BE CONTROLLED BY SUCH DETECTORS - Google Patents

Abstract

A detector comprises a body 1 in two parts, the first having a hollow cylindrical appendage 2. The second comprises a bell 12 provided with a hollow rod 13. The two elements are conductive and separated by an insulator. A conductive movable bowl 22 slides in the body from which it is separated by an insulating ring 25. The bowl is movable between an electrical contact position determined by a stop and an isolation position. A conductive spring 20 pushes the cup back to its first position. (CF DRAWING IN BOPI)

Description

Improvements to fluid pressure detectors and circuits that can be controlled by such detectors.

 The present invention relates to a fluid pressure detector and to electronic circuits that can be controlled by this detector.

 Argentinean Patent No. 206,755 discloses a detection of an arrangement of such a control circuit, as well as its basic features and advantages.

 The device described and claimed in this Argentine patent achieves the goals it proposes and is an improvement over the state of the art at the time of submission of the application. The object of the invention is to prove that it is possible to realize an even more advantageous device, especially with regard to the economics of manufacture with regard to the detector, for operation of the same efficiency, and the precision of action. in the case of the electronic circuit associated with the detector.

If the detector and the control circuit allow to perform the same functions as the detector and the circuit of the Argentinean patent cited, the construction and the structural configuration in the case of the detector, as well as the circuit characteristics in the case of the circuits, are entirely different.-
This can be fully appreciated by comparing the embodiment described in the present application with that of the patent cited. One can see immediately the considerable differences in structure between the two detectors which not only allow a more economical realization in the case of the present application. because of the smaller amount of parts used, but which also allows a considerably simplified mounting requiring less manpower and ultimately to achieve a considerably more secure detector and more uniform construction when it comes to a mass production.

One of the differences immediately apparent is that in the case of the present invention it is not necessary to use the diaphragm of the cited patent, and is an element susceptible to rupture. pre, to perforate or to be damaged, and whose implementation is difficult. Another important difference comes from the considerable simplification of the many annular elements used in the cited patent. Because some of these elements are insulators and other conductors, they must be arranged in the structure with a high mechanical precision, which makes it more expensive. the product, whereas in the detector of the present application, only two insulating annular elements are used; in addition, the upper bell member of the sensor of the present invention allows mounting, in conjunction with the annular elements mentioned, in a considerably less difficult manner than in the case of the cited patent. This bell is also manufactured in a very simple manner because it does not require the axial rod as an integral part which complicates and increases the cost of making the bell. Another advantage of the constructional form of the present invention that the internal chamber of the bell discharges the air towards the atmosphere when the stop moves upwards, whereas in the case of the stem of the cited patent, the air contained in the chamber above the diaphragm and inside the bell had to be compressed and not be discharged to the outside, thus restricting the sensitivity of the detector a little.

 As for the electronic control circuits, they have been perfected so that they can operate more sare and more efficiently.

 One of the aims of the present invention is therefore to propose a new fluid detector and new electronic circuit arrangements that can be controlled by this detector.

The invention also aims to provide a construction detector significantly cheaper than those
known for this use in the prior art, both in
as regards the smaller quantity of parts used
that the greatest ease of manufacture and
mounting.

Another object of the invention is to propose a detec
of the type mentioned which is more
and more sustainable than those of the tech% uean-
pool.

Another object of the invention is to propose a detec
mentioned type of sensitivity greater than those
of the prior art.

Another goal is to propose a layout of the circuit
control electronics usable with this detector which
be safer than those known so far
in the art.

These goals, and others, are achieved through a detec
fluid pressure sensor characterized in that
comprises a body consisting of two elements, the first
comprising a cylindrical appendage-shaped part
hollow and a rounded portion of larger diameter
be the first part, the second element comprising
a bell-shaped part ending in one
rod provided with an axially traversing bore;
said two elements are of electrically conductive metal
mechanically coupled to each other with interposi
electrically insulating elements, an element of
movable cup-shaped contact of electrical material
conductive element, is slidably arranged in the shaped part
of bell with interposition of an element electrically
insulation between the inner wall of said shaped portion
rounded and the outer wall of the mobi contact element
the, which is able to adopt a first position in
which this movable contact element makes contact
electric by means of a stop associated with the inner wall
of the second part, of rounded form, and a second
position in which the movable contact element is out
electrical contact with the rounded portion;
an electrically conductive elastic element
orients the movable contact element towards the first position, the elastic element being in electrical contact with both this movable contact element and with said bell-shaped portion.

The present invention will be better understood on reading the detailed description of some possible embodiments of the invention which are currently considered preferred, and with reference to the accompanying drawings, in which:
Figure 1 is a vertical diametral section in elevation of a constructional form of a pressure sensor according to the invention;
FIG. 2 is a diagram of a first possible embodiment of an electric control circuit that can be used with the pressure sensor of the invention;
FIG. 3 represents another arrangement of a circuit, of an electronic character, usable with the pressure detector of the invention;
Figure 4 shows the layout of an electronic circuit simpler than that of Figure 3;
Figure 5 shows the arrangement of a more complete electronic circuit than that of Figures 3 and 4;
Figure 6 is a vertical diametral section in elevation of another embodiment of a pressure sensor according to the invention;
Figure 7 shows the arrangement of an electronic circuit constituting an improved embodiment of the arrangement shown in Figure 3, and incorporating a multivibrator device for controlling the yellow light indicator.

 The same reference numerals have been used throughout the drawings to denote the same components or corresponding components.

 As can be seen in FIG. 1 of the drawings, the detector of the present invention comprises a mounting body indicated as a whole by the reference numeral 1 and provided with a projection in the form of a threaded appendage 2 through which an axial bore 3 passes. and provided externally with a thread indicated at 4. This projection 2 is intended to be introduced by screwing into an opening communicating with a space in which the fluid is to be detected whose pressure must be detected. The upper part 5 of the body 1 which is opposed to the projection 2 has a cup shape. The inner surface of this portion 5 is provided with a step-shaped shoulder 6 followed higher by a second step 7 and finally with a relatively thin collar 8.On the second step 7 is disposed a washer 9 made of electrically insulator whose outer diameter is substantially equal to the inner diameter of the flange 8 and whose inner diameter is slightly larger than that of the second step 7. On this washer 9 rests a cheek 10 of a superior bell-shaped element indicated by the general reference 11 and which, from this cheek directs outwards 10 is in the form of a dome 12 which comprises at its upper part a rod 13 which constitutes, as will be seen later one of the contacts detector, while the other is represented by the lower projection 2. The rod 13 is provided with an axial bore 14.On the cheek 10 is disposed a second washer 9 'of electrically iso material the relatively thin flange 8 is forcibly flexed inwards and downwards so as to grip all the washers 9 and 9 'and the cheek 10 of the bell 11, so as to firmly hold the bell 11 and in the same time the body 1 electrically isolated. This contributes to the fact that the flange 10 has an outside diameter smaller than the internal diameter of the flange 8, so that it has no direct electrical contact between this flange 8 and the bell 11.

 The inside of the axial bore 3 of the projection 2 has a threaded portion indicated at 15. Inside the axial bore 3 is introduced an adjusting abutment 16, threaded externally at 17 and provided with an axial bore 18. At its upper part, the regulating stopper 16 is provided with a projection 19 of smaller diameter than that of the abutment proper 16 and serving as a seat for one of the ends of a helicoidal spring of compression 20.

The movable element of the detector, designated 21, comprises a flat horizontal portion 22 constituting the bottom and a circular peripheral portion 23 facing upwards. The peripheral portion 23 comprises a channel-shaped throat 24 in which is disposed an annular seal of electrically insulating material 25. The bottom 22 comprises nn thrust member 26 of electrically insulating material and provided with a base 27, from which extends downwardly a projection 28, serving as a seat for the other end of the spring 20.

 Finally, the detector comprises a second helical pressure spring 29 disposed inside the chamber formed by the internal cavity of the bell 11 and the internal cavity of the movable element 21, so as to urge the latter permanently towards the bottom.

 We will now give an explanation on the operation of this detector.

 The detector can adopt two control positions, the first one now closing the electrical circuit and the second opening it. The first condition is that of abnormal operation corresponding to the case where the pressure of the fluid that one wishes to control is below a predetermined minimum value, while the second condition corresponds to the case of normal operation where the fluid pressure exceeds this predetermined minimum value.

 The electrical circuit controlled by the detector is as follows: the projection 2 of the body 1, which is electrically connected via the thread 4 with, for example, the block of an internal combustion engine; the upper part 5 of the body 1; the step 6 of the latter and the movable element; the spring 29; In the second condition, this electrical circuit remains interrupted because the movable element is pushed upwards because the fluid pressure exceeds the predetermined minimum value mentioned, and cuts off its contact with the step. 6 of the body 1.

 At first glance, in this second condition, it appears that a circuit is established between the projection 2 and the bell 11 via the regulating stopper 16, the spring 20, the movable element 21 and the spring 29; in fact this is not possible because there is no electrical contact between the spring 20 and the movable member 21 since the thrust member 26 is made of an electrically insulating material.

 Be that as it may, in the first position, the establishment of a continuous electrical contact between the projection 2 and the rod 13 constitutes an alarm which is detected by the control circuit which will be described later.

 The predetermined minimum value of the pressure of the fluid for which the operation of the detector is regulated, or even the sensitivity of the operation thereof, depends on the equilibrium between the force of the spring 29 on the one hand, and the force exerted by the combination of the force of the spring 20 and the pressure of the fluid on the other hand. In any case, by adjusting the force of the spring 20, the sensitivity of the detector can be adjusted within established limits. This result is obtained by rotating the regulator stop 16 in the axial bore 3 of the projection 2 so as to move it longitudinally in the latter by means of the threads 15 and 17, thereby varying the pressure of the spring 20 and this makes his strength.

However, it should be noted that this sensitivity adjustment device is not a specific part of the invention, since it is substantially similar to that described in the cited patent No. 206,755 in the name of
Applicants, and therefore not claimed. In addition, although this sensitivity adjustment is advantageous, it is not essential and can in fact remove the elements 16, 20 and 26, the sensitivity of the detector then being pre-established and fixed, and determined only by the strength of the sensor. spring 29.

 Having thus described in detail the construction and operation of the novel pressure sensor of the invention, certain electrical circuit arrangements which can be controlled by the new detector will now be described.

 In Figure 2 is shown that the provisions of the circuit of the present invention which is the most detailed.

 It comprises a power supply source 30 which can be constituted by a battery of 12 or 24 V and which comprises a positive terminal 31 and a negative terminal 32, the latter being connected to ground 33. The positive terminal 31 is connected to one of the two fixed contacts 34 of a single electrical switch provided with a movable contact 35. The second fixed contact 36 is connected to one of the fixed contacts 37 of a button switch, normally closed, comprising a movable contact 38 and a second stationary contact 39 which is connected to one of the terminals 40 of an electromagnetic valve or valve 41 which controls a fuel passage valve.This valve is of the solenoid type and may be of any known type suitable for to this purpose. The other terminal 42 of the valve 41 is connected to one of the fixed contacts 43 of a conventional temperature detector comprising a movable contact 44 and the other fixed contact 45 is connected to the ground 33 and also to the negative terminal 32 of the source 30. The same terminal 42 of the valve 41 is also connected to the rod 13 of the fluid pressure detector of the invention (Figure 1) which comprises the movable member 21 and the projection 2 of the body 1 is connected to ground 33.

The terminal 42 of the electromagnetic valve 41 is connected to one end 46 of a resistor 47 whose other end 48 is connected to one end S49 of an indicator lamp (for example blue) 50 whose other terminal 51 is connected to the ground 33. Finally, one of the ends 52 of a resistor 53 is connected to the fixed contact 39 of the button switch 38, while the other end 54 of the resistor is connected to one ends 55 of an indicator lamp (for example red) 56 whose other end is connected both to the end 46 of the resistor 47 and to the terminal 42 of the electromagnetic valve 41.The button switch 38, the lamps 50 and 56 and the resistors 47 and 53 can be mounted on a panel indicated generally by the dashed line 57, and this indicator panel can be mounted on the dashboard of a vehicle, visible and brought from the driver.

 The operation of this circuit is as follows.

 When the engine to be controlled operates under normal conditions of temperature and pressure, the sensors 21 and 44 remain normally open. In this case, the electromagnetic valve 41 keeps the fuel passage open because it receives no excitation current, since its terminal 40 is connected to the positive terminal 31 of the source 30 (the main switch 35 being closed), while its other terminal 42 is not brought to ground because the detectors are in the open position.

Under these conditions, the blue lamp 50 remains lit via the second circuit; the positive terminal 31 of the source 30, the main switch 35, the normally closed button switch 38, the exciter winding of the electromagnetic valve 41, the conductor 58, the resistor 47, the lamp 50 and (by the intermediate of the mass) the negative terminal 32 of the source 30. The red lamp 56 remains off because in these conditions its two ends 46 and 55 are both connected to the positive battery.Supposant now that any one of the two detectors 44 or 21 detects an abnormal temperature and / or pressure condition of the engine lubricating fluid, one or both, as the case may be, will close, which will produce a second effect: the blue lamp 50 is extinguished by the fact that the closing detector or sensors short circuit the lamp 50 and its resistor 47. At the same time, the red lamp 56 lights up (thus indicating an abnormal condition) by the second circuit: the pos terminal itive 31 of the source 30, the general switch 35, the switch button 38, the resistor 53, the lamp 56, the conductor 58, one or both detectors 44 and / or 21 which are closed, and the negative terminal 32 of the source 30 through the mass 33. At the same time, the solenoid valve 41, because it is energized, keeps interrupted the flow of fuel.

 Assuming that the user desires, despite the possibility of danger, continue walking, he can open the fuel valve by momentarily pressing the button 38 with which it will cut off the excitation of the solenoid valve 41. This may depending on the circumstances be justified if the driver believes he can continue for a few kilometers to reach a service station or a nearby workshop. However, to avoid the temptation to continue for too long under these conditions, a button switch 38 is used so that to continue driving, the driver is obliged to keep the button pressed permanently. When released, the fuel valve 41-turns off, resulting in the engine stopping by default fuel supply.

 If due to any eventuality the continuity of the electrical circuit which couples the elements of the table 57 to the solenoid valve 41 and the detectors 21 and 44 is interrupted, or if the solenoid valve burns or disconnects, the two blue lights 50 and red 56 will light together, but with attenuated light intensity for both, by the circuit formed by: the positive terminal 31 of the source 30, the general switch 35 (closed), the button switch 38, the resistor 53, the lamp 56, the resistor 47, the lamp 50, the ground 33 and the negative terminal 32 of the source 30. In this case, the driver will know that the protective equipment is out of order and that he must be careful itself to the systems (instruments and / or lights) conventional indicators of the vehicle.

 FIG. 3 represents another embodiment of a substantially similar circuit for its operation to that of FIG. 2, but which is of an electronic nature.

 The positive terminal 31 of the positive source 30 is connected to one of the fixed contacts 34 of a general switch 35 whose other contact 36 is connected to a first fixed contact 37 of a button switch 38 whose second contact fixed is ~ connected to one of the terminals 40 of the exciter winding of a solenoid valve 41 for controlling the passage of fuel. The other terminal 42 of the solenoid valve is simultaneously connected to one of the terminals 43 of the temperature detector which comprises a movable contact 44 and to one of the terminals 13 of the pressure sensor of the present invention which comprises the movable contact 21. The other terminals 45 and 2 of the detectors are connected to the negative terminal 32 of the source 30 (advantageously via the ground 33). At the same time, the positive terminal 31 is connected (via the switches 35). and 38) at one end of a resistor 59 whose other end is connected to the base 60 of a transistor 61. This base 60 is also connected to the emitter 62 via a resistor 63 and this transmitter is also connected the terminal 42 of the solenoid valve 41 and the terminals 43 and 13 of the detectors. On the other hand, the transmitter 62 already mentioned is also connected to the ground 33 (and therefore to the negative terminal 32 of the source 30) via two series resistors 64 and 65. The collector 66 The transistor 61 is connected to the positive terminal of the source 30 via an indicator lamp 56 (eg red), a resistor 53 and switches 38 and 35 (closed).

A second transistor 67 comprises a base 68 connected to the collector 66 of the transistor 61 via a resistor 69 and to the negative terminal 32 of the source 30 via a resistor 68 ', while its emitter 70 is connected to the negative terminal 32 of the source 30
(advantageously via the mass 33) and that its collector 71 is connected to the positive terminal 31 of the source 30 by means of an indicator lamp 72
(eg yellow), a resistor 73 and switches 35 and 38 (closed).

Finally, a third transistor 74 has its base connected to the junction point of the resistors 64 and 65, its emitter 76 being connected to the negative terminal 32 of the source 30
(advantageously via the mass 33). The collector 77 of the transistor 74 is connected on the one hand to the base 68 of the transistor 67 via a resistor 78 and on the other hand to the positive terminal 31 of the source 30 via a lamp indicator 50
(for example blue), a resistor 47 and switches 35 and 38 (closed).

 The operation of the circuit of FIG. 3 is as follows.

 When the engine is running under normal conditions of temperature and lubricant pressure, the indicator lamp 50 (for example blue) remains connected while the main switch 35 is closed and the engine is running. The base 75 of the transistor 74 is positively biased through the resistor 64, the movable contacts 21 and 44 of the detectors being open. The emitter 76 of the transistor 74 is connected to the negative terminal 32 of the source 30 and its collector 77 to the positive terminal 31 by means of the indicator lamp 50 and the resistor 47.

In any case, as long as the movable contacts 21 and 44 of the detectors do not close, the solenoid valve 41 remains de-energized and the indicator lamp 50 (for example blue) remains lit, which indicates a normal operating condition. On the contrary, the indicator lamp 56 (for example red) remains off because the transistor 61 is not conductive because its emitter 62 is positively polarized. Similarly, the indicator lamp 72 (for example yellow) remains off because the base 68 of the transistor 67 receives through the resistor 69 only half of the positive polarization that is necessary for its activation. In the assumed normal condition, the other half of the necessary bias does not pass through the resistor 78 because the transistor 74 is conducting while the lamp 50 is on.

 Now assuming that either or both of the detectors detect an abnormal condition (upper temperature and / or lower pressure than a predefined value), the movable contact 21 and / or 44 will close, the direct circuit of excitation of the solenoid valve 41 will remain closed, the emitter 62 of the transistor 61 will negatively bias through the resistor 59 and the transistor 61 will begin to be conducting by producing the ignition of the indicator lamp 56 (for example red), thus providing a warning on an abnormal operating condition. As long as this condition persists, the indicator lamp 50 (for example blue) will remain off because the transistor 74 will not be conducting, its base 75 then being negatively biased. In this condition, the indicator lamp 72 (for example yellow) remains also off because the transistor 67 is polarized in the same way as in normal condition, in accordance with the explanation given above, except that now the missing half of the bias is due to the fact that it is the transistor 61 which is conductive while the transistor 74 is not.

 In the case of a fortuitous interruption of the circuit which connects the solenoid valve and the detectors to the elements of the indicator board (which is indicated as a whole inside the dashed line 57), the transistors 61 and 74 will not be conducting. for the obvious reasons shown in the diagram of FIG. 3. On the other hand, the transistor 67 becomes conductive because it receives the polarization required by the resistors 69 and 78. The indicator lamp 72 (for example yellow ) will illuminate and indicate that the protective equipment is out of order. It is possible in the context of the invention to make the lamp 72 flash instead of being constantly lit.This is fully within the knowledge of those skilled in the art. One way to obtain this result is for example to use a two-transistor, low-frequency, multivibrator device which excites the lamp 72 and which is controlled by the transistor 67.

 FIG. 4 schematically shows another embodiment of a circuit, also of electronic nature but simpler than that of FIG. 3.

 It comprises a source of electrical energy 30 whose negative terminal 32 is connected to ground 33, while its positive terminal 31 is connected to one of the fixed contacts 34 of the main switch 35 whose other contact 36 is connected to one of the fixed contacts 37 of a button interrupter 38 whose other fixed contact 39 is connected to the emitter 79 of a transistor 80. The base 81 is connected on the one hand to the transmitter 79 via a resistor 82 and is further connected via another resistor 83 to the terminals 13 and 43 of the pressure and temperature detectors 21 and 44 respectively. terminals 2 and 45 of the detectors are connected to the negative terminal 32 of the source 30 (advantageously via the mass 33). One of the terminals 42 of the excitation winding of the solenoid valve 41 for controlling the supply of fuel is connected to the negative terminal 32 of the source 30, while the other terminal 40 is connected to the collector 84 of the transistor 80. An indicator lamp 50 (for example blue) is connected on the one hand to the positive terminal 31 of the source 30 via the switches 35 and 38 (closed), and on the other hand to the collector 84 of the transistor 80 and the terminal 40 of the solenoid valve 41 via a resistor 85.A second indicator lamp (for example red) 56 is connected firstly to the collector 84 of the transistor 80 and secondly to the negative terminal 32 of the source 30 (advantageously via the mass 33) via a resistor 86.

 The operation of the circuit of FIG. 4 is as follows.

When the engine is running in normal condition of lubricant temperature and pressure, the indicator lamp 50
(eg blue) is lit continuously, indicating that the conditions are normal, that the main switch 35 is closed and the engine is running; the indicator lamp 56 (for example red) remains off. Under these conditions, the transistor 80 is not conducting and the lamp 50 is connected on the one hand directly to the positive 31 and on the other hand to the negative 32 via the resistor 85 and the solenoid valve 41.

If the detectors detect an abnormal condition of insufficient pressure or excessive temperature and if the movable contact 21 and / or 44 closes, the bias change of the transistor 80 (which was not conductive until then) makes it conductive and produces an excitation of the solenoid valve 41 which interrupts the supply of fuel. At the same time, the conductivity of the transistor 80 closes the circuit of the lamp 56 which turns on and off.
bypasses the circuit of the lamp 50 which goes out.

The indicator lamp 56 (for example red) warns that the conditions are abnormal.

 In the case where the continuity of the connection circuit between the elements mounted on the board (indicated by the dashed line 57) and the solenoid valve is interrupted, the lamps 50 and 56 light up both, but with a lower brightness intensity, because they are excited through the circuit constituted by the positive terminal 31 of the source 30, the switches 35 and 38, the lamp 50, the resistance 85, the lamp 56 and the resistance 86, and the negative terminal 32 of the source 30. The simultaneous ignition of the lamps 50 and 56 is a warning that the protective equipment is out of service.

 FIG. 5 represents a fourth embodiment of the control circuit, in principle retaining a certain similarity with that of FIG. 3.

It comprises an electric power source 30 comprising a positive terminal 31 and a negative terminal 32, the latter being connected to the ground 33. The positive terminal 31 is connected to one of the fixed contacts 34 of a general switch 35 of which the other fixed contact 36 is connected to one of the fixed contacts 37 of a push-button interrupter 38
The other fixed contact 39 is connected to the base 87 of a transistor 88 via a resistor 89. The collector 90 is connected to the fixed contact 39 of the button switch 38 via a indicator lamp 50 (for example blue) and a resistor 47.The base 87 is also connected via a resistor 91 to one of the terminals 42 of the exciter winding of a solenoid valve 41 interruptible fuel and at the negative terminal 32 of the source 30 (advantageously via the mass 33). The other terminal 40 of the solenoid valve 41 is connected to the emitter 92 of the transistor 88.

On the other hand, the base 87 is connected via a resistor 93 and a resistor 94 to the base 95 of a transistor 96, the base 95 being connected to the emitter 97 of the same transistor by via a resistor 98, and the collector 99 is connected to the emitter 92 of the transistor 88. In addition, the emitter 97 is connected to the positive terminal 31 of the source 30 via the switches 38 and 35.

 At the junction point (represented by the conductor 100 between the resistors 93 and 94) are connected the respective terminals 13 and 43 of the pressure and temperature detectors respectively; in case of closure of one or both of their respective movable contacts 21 and 44, they connect the conductor 100 directly to the negative terminal 32 of the source 30 (advantageously via the mass 33).

 The junction point 101 between the emitter 92 of the transistor 88 and the collector 99 of the transistor 96 is connected to the base 102 of the transistor 103 via a resistor 104 and the emitter 105 is connected to the base 102 via via a resistor 106 and directly to the negative terminal 32 of the source 30. The collector 107 is connected to the positive terminal 31 of the source 30 via an indicator lamp 56 (for example red), a resistor 53 and switches 38 and 35.

A transistor 108 is mounted with its base 109 connected to the collector 90 of the transistor 88 via a resistor 110, to the negative terminal 32 of the source 30
(advantageously via the mass 33) via a resistor 111 and to the collector 107 of the transistor 103 via a resistor 112.

The transmitter 113 is connected directly to the negative terminal 32 of the source 30 (advantageously via the ground 33), while the collector 114 is connected to the positive terminal 31 of the source 30 via a lamp 72 (for example yellow), a resistor 73 and two switches 38 and 35.

 The operation of the embodiment of FIG. 5 is as follows.

 Assuming that the engine or other device desired to be monitored operates under normal pressure and temperature conditions (the movable elements 21 and 44 now open the respective detectors), the base 87 of the transistor 88 receives a positive bias at the same time. intermediate of two circuits: the elements 31, 35, 38, 39, 91 and 32; and the elements 31, 35, 38, 98, 94, 93, 91 and 32. Under these conditions, the transistor 88 is conductive and the indicator lamp 50 (for example blue) remains lit.On the other hand, the indicator lamp 56 (eg red) remains off because the transistor 103 has its base 102 negatively biased through the solenoid valve 41. Similarly, the indicator lamp 72 (eg yellow) remains off because the base 109 of the transistor 108 receives only half of the total positive polarization (necessary for it to be conductive) through the resistor 112, while it does not receive the other half through the resistor 110 of the Transistor 88 is conductive.

 If it is now assumed that one or both of the detectors detect an abnormal pressure and / or temperature condition, the movable elements 21 and / or 44 of said detectors close the circuit connecting the conductor 100 to the negative terminal (ground 32) of the source 30. Under these conditions, the transistor 96 is conductive since its base 95 receives a negative bias through the resistor 94. It follows that the base 102 of the transistor 103 is positively polarized via of the resistor 104 so that the transistor is conducting and the indicator lamp 56 (eg red) lights up and indicates an abnormal condition. At the same time, the transistor 96 being conductive, the solenoid valve 41 is energized and interrupts the fuel supply. Under these conditions, the indicator lamp 50 (for example blue) remains off because the transistor 88 is not conducting. because its emitter 92 is then at a positive polarity. The lamp 72 (yellow) also remains off since the base 109 of the transistor 108 receives through the resistor 110 only half of the necessary positive polarization, and that it does not receive the other half via the resistor 112 because the transistor 103 is then conductive.

Finally, if we suppose an interruption of the electrical continuity between the elements installed on the board 57
(indicated by the dashed line) - and the detectors and solenoid external to this table (21, 41 and 44), for an accidental reason, the transistor 88 ceases to be conductive, so that the base 109 of the transistor 108 receives a total positive bias, half by the resistor 110 and the other half by the resistor 112. Under these conditions, the transistor 108 is conductive and causes the illumination of the lamp 72 (yellow) which indicates that the equi - protection is out of order.

 To summarize, it is suggested four circuits, two of these (Figures 2 and 4) containing two indicator lamps, for example one blue and one red respectively indicating normal and abnormal conditions, both having a mean light intensity when there is a disconnection of the control elements; the other two (Figures 3 and 5) use the same two lamps (blue and red) that perform the same functions, and a third (yellow) indicating a disconnection or an equivalent fault. If desired, it can also be done so that the third lamp flashes (intermittently) instead of being lit continuously by adding for example in the circuit a transistor multivibrator.

 Instead of small incandescent lamps, light emitting diodes (so-called LED diodes) can be used as light indicators.

 In all four embodiments, the button switch 38 has the same function as that explained with reference to the first embodiment (Fig. 2). The main switch 35 may advantageously be the general key for starting up the vehicle, so that the protective equipment is automatically put into service when the general ignition is connected.

 By way of example only, and without limiting the scope of the invention in any way whatsoever, a list of the electrical characteristics of the components of each of the circuits of FIGS. 2 to 5 will now be given.

FIGURE 2
References Components Characteristics (1)
21 Pressure sensor (according to
the present invention Simple, unipolar
30 24 V (12 V) Electric Power Source
35 General Ignition Key Single, Unipolar
38 Single button switch, unipolar
41 Solenoid valve (depending on the valve
fuel)
44 Simple, unipolar temperature detector
(classic) 47 Resistance 330 # - LED 1200 #
(100A) - (LED 680 #)
50 Lamp (blue) 24V, 2W - LED 20 mA
53 Resistance 100fl - LED 1200
(none) (LED 680 #)
56 Lamp (red) 12V, 29; - LED 20 mA
FIGURE 3
References Components Characteristics (1)
21 Pressure sensor (according to
the present invention Simple, unipolar
30 24 V (12 V) Electric Power Source
35 General Ignition Key Single, Unipolar
38 Single button switch, unipolar
41 Solenoid valve (depending on the valve
fuel)
44 Simple, unipolar temperature detector
(Classical)
47 Resistance 270 # - 1 ;; ED 1200 #
(none) (LED 680Q)
50 Lamp (blue) 24V, 2W - LED 20 mA
53 Resistance 270 # - LED 1200 n
(none) (LED 680 #)
56 Lamp (red) 12V, 2W - LED 20 mA
59 2200-LED resistance 2200
(680 #) (LED 680 #)
61 Transistor Texas 2A3726
63 Resistance 68 # (47R
64 Resistance 2200 #
65 Resistance 68n. (47n)
67 Texas Transistor 2A-3726
68 'resistance 56
69 Resistance 2700 # (1200 #)
72 Lamp (yellow) 24V, 2W - LED20 mA
73 Resistance 270 R - LED 1200 #
(LED 680 #
74 Transistor Texas 2A3726
78 Resistance 2700 # (1200 #)
FIGURE 4
References Components Characteristics (1)
21 Pressure sensor (according to
the present invention Simple, unipolar
30 24 V (12 V) Electric Power Source
35 General Ignition Key Single, Unipolar
38 Single button switch, unipolar
41 Solenoid valve (depending on the valve
fuel)
44 Simple, unipolar temperature detector
(Classical)
50 Lamp (blue) 24V, 2w - LED 20 mA
56 Lamp (red) 12V, 2w - LED 20 mA
80 Transistor Texas TIP 34 82 Resistance 8 # # (3.9 #)
83 Resistance 47 # (22 #
85 Resistance 270 # - LED 1200 n
(100 #) - (LED 680R
86 Resistance 100 # - LED 1200 #
(LED 680 #)
FIGURE 5
References Components Characteristics (1)
21 Pressure sensor (according to
the present invention Simple, unipolar
30 Saurce electric power 24 V (12 V)
35 General Ignition Key Single, Unipolar
38 Single button switch, unipolar
41 Solenoid valve (depending on the valve
fuel)
44 Simple, unipolar temperature detector
(classic) 47 Resistance 270 Q - LED 1200fil
(LED 680 #
50 Lamp (blue) 24V, 2W - LED 20 mA
53 Resistor 270R - LED 1200 #
(LED 680 #)
56 Lamp (red) 12V, 2w- LED 20 mA
88 Transistor Texas 2A3726
89 Resistance 2700 # (1200 #)
91 Resistance 56 #
93 Resistance 2700 #. (1200 (1)
94 Resistance 47 # (22n)
96 Texas TIP Transistor 34
98 Resistance 8 (1 (3.6 #)
103 Transistor Texas 2A3726
104 Resistance 2200 # 1680a)
106 Resistance 68 # (47 #)
108 Texas transistor 2A3726 110 Resistance 2700 # (1200n)
111 Resistance 56 n
112 Resistance 2700 n (1200fi)
(1) The values in parentheses correspond to the case where a source of 12 V is used. The absence of a value in parentheses means that the same value is used for both 24 V and 12 V.

 Although only a few embodiments of the invention have been described, it will be understood that those skilled in the art can easily imagine various modifications and changes of detail without departing from the scope of the invention. of the invention.

 Figure 6 shows an improved form of the construction of the pressure sensor. This embodiment offers construction, mounting and operational safety advantages over the first embodiment.

 As can be seen in FIG. 6, the appendix 2 'comprises, in this improved form, a filter 115 intended to prevent the entry of foreign matter into the hollow interior 116 of the appendix 2', the filter 115 which can be introduced simply by pressure within the appendage, or can be threaded outside and fixed by means of a corresponding thread provided on the inner face of the appendix 2 '. Within the appendix 2 'there is provided an element 117 comprising a tubular portion 118 and a funnel portion 119 whose interior is tapered, as indicated at 120, its outer portion having a vertical straight wall being attached to the inside the upper end of Appendix 2 '. The movable element 22 'extends at its lower part into a projection 121 whose cross-section may be circular but which, with a view to a better effectiveness of the electrical contact, will preferably be polygonal, for example hexagonal, with three alternate faces of less magnitude than the other three.

 In addition, the lower flange 122 of the bell-shaped dome 123 is acute to provide a safer electrical contact, and is provided at the same time with at least one channel directed diametrically (not shown) and which communicates with each other. the lower part of the dome 123 with the space 124 in order to avoid the compression of the air in the latter when the element 22 'is in the raised position.

 This embodiment provides greater sensitivity, safety of operation, and easier mounting because the spring 20 of the first-described embodiment, or the delicate adjustment, is not used. its pressure relative to the force of the main spring 125 (29 in Figure 1).

FIG. 7 shows an arrangement of the electrical control circuit which is very similar to that of FIGS. 3 and 5. The differences lie in the fact that a multivibrator device is added comprising two transistors 126 and 127 arranged according to a conventional multivibrator circuit. which in this embodiment controls the yellow light indicator (for example a
LED) shown at 128, instead it is directly controlled by transistor 67 of FIG. 3 or by transistor 108 of FIG. 5. The function of the multivibrator is to make the luminous indication 128 intermittent (flashing) instead of continuous . Another difference between the arrangements of FIGS. 3 and 5 on the one hand and of FIG. 7 on the other hand is that the input of the control electronic part itself is taken in the case of FIG. 7, before the switch button 38 with additionally a fuse 129, instead of this input being derived from the switch 38. In this way, the illumination of the yellow indicator light occurs both in the event of a failure of operation of the switch 38 only when the fuse 129 does not make contact or is burned.

 Although several forms have been described for implementing the invention, it will be understood that one skilled in the art can imagine various modifications and changes in detail that will remain within the scope of the invention.

Claims (14)

 1. Fluid pressure detector characterized in that it comprises a body consisting of two elements, the first comprising a cylindrical shaped portion drive appendix hollow and a rounded portion of larger diameter than the first part, the second element comprising a generally bell-shaped portion terminating in a rod provided with an axially traversing bore, said two elements being made of electrically conductive metal and mechanically coupled to each other with the interposition of electrically insulating elements, an element of movable cup-shaped contact of electrically conductive material slidably disposed in the bell-shaped portion with the interposition of an electrically insulating member between the inner wall of said rounded portion and the outer wall of the movable contact element which is able to adopt a first position in which this mobile contact element establishes an electrical contact by means of an abutment associated with the inner wall of the second part, of rounded shape, and a second position in which the movable contact element is out of electrical contact with the rounded part, and an element an electrically conductive elastic capable of orienting the movable contact element to the first position, the elastic member being in electrical contact with both said movable contact member and said bell-shaped portion.  2. Detector according to claim 1, characterized in that the peripheral edge of the rounded portion extends into a collar of greater internal diameter than that of said rounded portion defining an internal step between the latter and the rim. , a first electrically insulating washer being disposed on the upper face of this step, the portion of the bell having a cheek directed radially outwards and whose outer diameter is substantially smaller than the internal diameter of the collar and substantially larger than the inner diameter of the rounded portion, the cheek being applied to the first insulating washer, while a second insulating washer is disposed on the top of the cheek of the bell-shaped portion, the flange of the shaped portion; curved being bent radially inward and pressed downwardly so as to maintain associated with each other p ar compression rounded and bell-shaped parts and washers.  3. Detector according to any one of claims 1 or 2, characterized in that the elastic element is constituted by a helical spring.  4. Detector according to any one of the preceding claims, characterized in that it comprises a device for regulating the operating threshold of the detector by pressure.  An electrical control circuit comprising a fluid pressure sensor according to any one of the preceding claims, characterized in that it further comprises a source of electrical energy provided with first and second terminals, a first indicator element and a second indicator element electrically connected to one another in series, a first end of the electrically connected series being connected to the first terminal of the source via a first main switch and a second button switch, the other end of the series being electrically connected to the second terminal of the source and a fuel supply solenoid valve one of whose terminals is connected to the first end of the slag and the other at the point of junction between the indicating elements, the detector pressure being electrically coupled between the junction point of the two indicators and the second terminal of the a source.  An electronic control circuit comprising a fluid pressure sensor according to any one of claims 1 to 4, characterized in that it further comprises a source of electrical energy provided with a first and a second terminal, a first, second and third indicator elements provided with first ends electrically connected in parallel with each other and in turn electrically connected to the first terminal of the source via a first main switch and a second button switch each element having its other end electrically connected to a first, a second and a third control transistor, a fuel supply solenoid valve one of whose terminals is electrically connected to the first terminal of the source via the main switch and the button switch and the other terminal is electrically connected in control relationship to said first and third transistors, and to the second terminal of the source via the pressure detector, the second transistor being electrically connected in control relation with the first and third transistors, the pressure detector being electrically connected by one of its terminals to the other terminal of the solenoid valve and electrically connected by its other terminal to the second terminal of the source.  7. An electronic control circuit comprising a fluid pressure sensor according to any one of claims 1 to 4, characterized in that it further comprises a source of electrical energy provided with a first and a second terminals, a first indicator element and a second indicator element electrically connected in series with each other, a first end of the series being electrically connected to the first terminal of the source via a first main switch and a second button switch and the other end of the series being electrically connected to the second terminal of the source, a fuel supply solenoid valve being electrically connected in parallel with the first indicator element, the connection point between the indicators being connected in control relation with a first transistor, while the pressure detector is electrically connected between the second terminal of the source and said transistor.  An electronic control circuit comprising a fluid pressure sensor according to any one of claims 1 to 4, characterized in that it further comprises a source of electrical energy provided with a first and a second terminal, a first, second and third indicator elements having their first ends electrically connected in parallel with each other and electrically connected to the first terminal of the source via a first main switch and a second switch each having their second end electrically connected to a first, second and third control transistor, a fuel supply solenoid valve one of whose terminals is electrically connected to the second terminal of the source and the other of which terminal is electrically connected in control relation to said first and third transistors and to a fourth transistor, the second transistor nsistor being electrically connected in control relation to said first and third transistors and the fourth transistor being electrically connected in control relation to said first and third transistors, the pressure detector being electrically connected by one of its terminals in control relation to the first transistor and to the fourth transistor while it is connected by its other terminal to the second terminal of the source.  9. Circuit according to any one of claims 5 to 8, characterized in that the temperature detector is electrically connected in parallel with the pressure sensor.  10. Circuit according to any one of claims 5 to 9, characterized in that the first and second indicator elements are constituted by a light indicator selected from the group consisting of incandescent lamps and light-emitting diodes.  11. Circuit according to any one of claims 6 or 8, characterized in that the third indicator element is constituted by a light source selected from the group consisting of incandescent lamps and light emitting diodes.  12. Circuit according to any one of claims 6 or 8 to 11, characterized in that it comprises a flashing device associated with the third indicator element, which may comprise an electronic multivibrator.  13. fluid pressure sensor according to claim 1, characterized in that it comprises in the appendix a filter element and a contact element provided with a tubular projection directed downwards forming at the same time the collecting chamber of foreign materials and a tapered funnel-shaped top portion constituting an electrical contact seat, the movable member including a downwardly projecting projection capable of making contact with said seat in the lowered position of the movable member.  14. A pressure sensor according to claim 13, characterized in that the cross section of said projection of the movable member is polygonal, preferably hexagonal three alternating faces greater than the other three.