FR2623780A1 - Automatic and programmable device for the diffusion of a fluid contained in a container - Google Patents

Abstract

The invention relates to fluid diffusers. The invention is characterised in that the bottle 5 containing the fluid to be diffused is provided with an electrovalve 35 whose opening and closing are controlled by an electronic control circuit carried by a printed circuit 34. The control circuit can be programmed by the user by means of keys 31 in such a way as to select a diffusion time and a cycle time. The invention is applicable to diffusers of fluids, particularly of perfumes.

Description

AUTOMATIC BROADCASTING APPARATUS
AND PROGRAMMABLE OF A FLUID
CONTAINED IN A CONTAINER
The invention relates to apparatuses which make it possible to spread, diffuse or vaporize a fluid automatically for a determined duration and at instants separated by time intervals also of determined duration, the different durations being programmable by the user of the apparatus. It relates more particularly to devices of this type which are used for diffusing fluids contained in containers of the aerosol type.

 In many fields, it is necessary to diffuse or vaporize at precise times a determined quantity of a fluid in a volume or on a surface.

This is for example the case when it is desired to diffuse a deodorant, perfumed or not, in a room to eliminate certain odors, for example of tobacco. This is also the case when it is desired to lubricate certain rotating elements of a machine at regular intervals of adjustable duration.

 For rooms reserved for toilets, it is known to use an aerosol can containing a deodorizing fluid and to cause the opening of the valve of the bottle by a device with levers and rods connected to the entrance door of the room. Such a device has the disadvantage of operating each time the front door opens, which means that the aerosol can can be emptied in a very short period of time if the frequency of opening of the door is large. In addition, the quantity of fluid which is diffused is not proportional to the real needs.

 The system which has just been described succinctly requires human intervention to function and therefore cannot be considered to be entirely automatic and autonomous. In addition, the frequency of broadcasts and their durations are not adjustable and programmable.

 An object of the present invention is therefore to provide an apparatus for diffusing a fluid contained in a container, in particular an aerosol can, the operation of which is entirely automatic and autonomous.

 Another object of the present invention is also to provide a device for diffusing a fluid, the frequency of the diffusions and their duration are adjustable and programmable by the user.

The invention relates to an apparatus for diffusing a fluid contained in a pressure vessel, the outlet orifice of which is provided with a shut-off valve normally closed in the idle state, characterized in that it comprises - means for opening said closing valve and
put the container in communication with a
fluid outlet, - means for closing the fluid outlet conduit
to close said duct in the rest state, - means for opening said shutter means for said
outlet duct and thus allow said flow to flow
fluid, and - means for controlling the shutter means and
means for opening said outlet conduit so
to open said conduit at determined times and
for at least a fixed period.

 The means for closing and opening the outlet duct are advantageously made by a solenoid valve which is fixed to the container by an assembly and holding device. This assembly and holding device can be of the socket and bayonet type so as to open the valve of the container.

 In a particular embodiment, the container and the solenoid valve are each arranged in a cylindrical tube and the cylindrical tubes have facing partitions which provide the assembly and holding device mentioned above.

 The control means of the solenoid valve includes an electronic circuit for calculating the duration of a diffusion and the duration of the time interval separating two instants of diffusion.

 This electronic circuit is also provided for programming different durations, the values of which are displayed by a display device, for example with light-emitting diodes.

Other characteristics and advantages of the present invention will appear on reading the following description of a particular embodiment, said description being made in relation to the accompanying drawings in which - FIG. 1 is a view in longitudinal section along
line II of figure 2 of a particular example of
production of a fluid diffusion device
according to the invention, - Figure 2 is a top view of the device,
cover 4 removed, - Figure 3 is a cross-sectional view along the
lines III-III and of Figure 1, - Figure 4 is a longitudinal sectional view of a
solenoid valve which can be used, - Figure 5 is a longitudinal sectional view of a
another embodiment of the assembly device
and holding, - Figure 6 is a sectional view showing the function
nement of the assembly and holding device, and - Figure 7 is a block diagram of an example
particular realization of a control circuit of
the solenoid valve of figure 1.

 A particular embodiment 10 of the device for diffusing a fluid contained in a container according to the invention comprises an envelope or shell 1 essentially comprising two distinct parts 2 and 3 which are held in relation to each other by assembly and holding means described below. This shell, and therefore the parts which compose it, has for example the general shape of a cylinder of revolution. The lower part 2 is designed to receive a container 5 of the fluid to be diffused and it may be an aerosol can of cylindrical shape of revolution which is filled, as is known, with a fluid to be diffused and a vaporizing gas to a determined pressure. For the establishment of the bottle 5 inside the lower part 2, the latter has at its upper end a fixed transverse partition 6 and; at its lower end, a removable bottom 7 so that the upper part of the bottle abuts against said wall and is held there by the bottom 7 which is screwed onto a corresponding thread 12 of part 2 and by a spring 7a secured from the bottom 7. The bottom 7 serves as a rest base for the device and can be conformed so that the device is inclined relative to the vertical when it rests on this base.

 So that the axis of the bottle 5 coincides with that of the lower part 2, the partition 6 has, for example, a circular rim 8 which cooperates with a flange 9 of the bottle 5 so as to obtain centering of the bottle when it comes in abutment against the partition 6.

This centering can be facilitated and improved by the presence of one or more flexible rings of appropriate thickness and shape 50 and 51 carried by the wall 11 of the lower part 2 and spaced apart according to the height of the bottle.

 The partition 6 is fixed to the wall 11 and has a circular central opening 13 to allow, on the one hand, access from the top to an outlet orifice 14 of the bottle 5 and, on the other hand, the assembly, centering and maintaining the two parts 2 and 3.

 It should be noted that the flange 9 is of the type that is encountered in most aerosol bottles and is part of the device for closing the bottle after filling, a device which is crimped onto the opening of the bottle. This closing device, known moreover, comprises a central part 15 which has the outlet orifice 14 and which supports a closing valve 16 of said opening 14. This valve 16, when it is moved downwards opens the opening , which lets escape a mixture of gas coming directly from the top of the bottle and of fluid coming from the bottom of the bottle via a conduit 17.

 The upper part 3 is, like the lower part 2 to which it fits, of cylindrical shape of revolution and is designed to contain and support the various elements for controlling the diffusion of the fluid contained in the bottle 5. It is also provided for supporting on the lower side a part of the assembly and holding device with the lower part 2 and on the upper side a removable cover 4.

 From the point of view of its structure, this upper part 3 comprises a lower partition 18 and an upper partition 19 which are both integral with the wall 20 of the part 3. The lower partition 18 has a central opening 21 to allow the access to the orifice 14 of the bottle 5. The edges of this opening, side of the bottle 5, are provided with lugs or bayonets 22 (FIG. 3) which come to cooperate with notches 23, cut in the entire thickness of the edge of the 'opening 13 of the partition 6, which allow passage to said pins.

In addition to these notches 23, the edge of the opening 13 comprises, on the bottle side 5, three circular grooves 24 which each end in a notch 25 of shallow depth in which the lug 22 is fitted so as to snap the type of that used for fixing bayonet electric bulbs in the socket of the support.

 The upper partition 19 also has a circular opening 26 for the passage of a diffuser 43 and serves to support two groups of light-emitting diodes 28 and 29, control buttons 30 and 31, a switch 32 and at one end d 'a vertical partition 33, the other end of which is integral with the lower partition 18. The partition 33 is arranged eccentrically in the cylindrical volume of part 3 and serves as a support on one side for a printed circuit 34 and on the other side , that of the axis of revolution, to a solenoid valve 35. A battery 36 for the electrical supply of the solenoid valve 35 and of the electronic circuits 37 soldered on the printed circuit 34 is maintained between the partitions 18 and 19 and is accessible, on the cover side 4, through an orifice closed by a plug 52.

 The solenoid valve 35 is placed on the support partition 33 so that its lower duct 37 is disposed on the axis of revolution of the parts 2 and 3 and more precisely is aligned with the outlet orifice 14 of the bottle 5. This electro valve 35 is of a type known elsewhere but is preferably of the miniature magnetic control valve type such as that sold by the company "IMI Norgren Enots Ltd" under the name Reedex.

This solenoid valve essentially comprises (FIG. 4) a valve 38 disposed at the end of a movable contact 59 and a coil 39 surrounding the valve and the movable contact so as to move the movable contact to open or close the valve when a current flows or not in said coil. In the exemplary embodiment according to the invention, the solenoid valve 35 must be of the type closed at rest when no current is applied to the coil 39.

 The inlet conduit 37 of the solenoid valve is capped with an adapter 40 whose lower end cooperates with the valve 16 which is provided with the bottle 5. The outlet conduit 41 of the solenoid valve is also capped with an adapter 42 on which the diffuser 43 is fitted.

 The upper part 3 is capped with the cover 4 which has an opening 44 to allow passage to the diffuser 43 or at least the jet of vaporized fluid which it diffuses if the cover is provided with a chimney 46.

 The switch 32 has a movable contact 45, a part of which is flush with the outside of the wall 20 via a hole 47, cooperates with the side wall of the cover 4 so that the contact is in a certain position when the cover is removed and it is in another position when the cover covers the part 4. The function of this contact 45 will be explained below in relation to the description of the electronic circuit of FIG. 7.

 In order to limit the downward movement of the cover 4, the upper part 3 is provided with a stop which can have the form of a circular protuberance 48.

 Likewise, the lower part 2 is provided with a stop, which may have the form of a diametrical widening 49, for the lower circular edge of the upper part 3, when the latter comes to fit on the lower part in order to carry out their assembly.

 The functional diagram of FIG. 7 gives a particular example of nonlimiting embodiment of a control circuit for the solenoid valve 35, this control circuit making it possible for example to program four diffusion durations: one, two, four and five seconds and five time intervals: zero, three, six, twelve and twenty-four hours.

 This control circuit comprises a clock circuit 61 which supplies for example pulses at the frequency of four hertz, a first set 62 of circuits which is assigned to the measurement of the opening times of the solenoid valve, a second set 63 of circuits which is assigned to the measurement of the durations between two successive diffusions, a bistable circuit 64 common to the assemblies 62 and 63, a power stage 65, for controlling the winding 39 of the electro-valve 35, and the switch 32 with its contact 45.

 Each set of circuits 62 and 63 comprises a certain number of identical elements which are: a divider circuit 66 or 76, a multiplexer circuit 67 or 77, a decimal counter 68 or 78 and a display device 69 or 79 corresponding respectively to groups of light-emitting diodes 28 or 29 and the control keys 30 and 31. The assembly 63 additionally comprises a divider circuit 80 and a NOR circuit 81.

 The division ratios of the divider circuit 66 is four, sixteen and twenty so that it respectively supplies signals of periods one second, two seconds, four seconds and five seconds on the outputs 66a, 66b, 66c and 66d. Similarly, the division ratios of the divider circuit 76 are such that, when it receives signals at the frequency of four hertz from the clock circuit, it respectively provides signals of periods 1.25 seconds, 2.5 seconds, seconds and ten seconds on outputs 76a, 76b, 76c and 76d.

 The signals at the frequency four hertz supplied by the clock 61 are applied not only to the dividing circuits 66 and 76 but also to the decimal counters 68 and 78 by means of the push button button 30 for the counter 68 and the button with push button 31 for the counter 78. It is these two counters 68 and 78 which make it possible to select, according to their position, one of the four outputs of the dividing circuits 66 and 76 by means of the multiplexer circuits 67 and 77. A this effect, by pressing the key 30 or 31, the decimal counter 68 or 78 advances to the rhythm of the signals applied to it and its decimal outputs 68a, 68b, 68c and 68d or 78a, 78b, 78c, 78d and 78e are activated successively in a cycle of ten pulses.

 The outputs 68a, 68b, 68c and 68d are each connected, on the one hand, to the display device 69 to select one of the light-emitting diodes 28 and, on the other hand, to the multiplexer circuit 67 to select one of the outputs 66a, 66b, 66c and 66d of the divider circuit 66. Similarly, the outputs 78a, 78b, 78c, 78d and 78e are each connected, on the one hand, to the display device 79 to select one of the electro-diodes. luminescent 29 and, on the other hand, to the multiplexer circuit, except for the output 78e, to select one of the outputs 76a, 76b, 76c and 76d of the divider circuit 76. The output 78e is used to block the counting , for example by inhibiting the operation of counter 80.

 Each decimal counter 68 and 78 has a decimal output, not shown, corresponding to the digit 9 which is activated after nine pulses and which is used to reset the counter for a new count when the key 30 or 31 remains pressed.

 The divider circuit 80 comprises fourteen binary stages Q1 to Q14 and receives the signal from one of the outputs 76a, 76b, 76c or 76d of the divider circuit 76 via the multiplexer circuit 77. A judicious choice of the outputs of a certain number of stages makes it possible to measure a time interval. Thus, by choosing the outputs of stages Q6, Q7, Q8 and Q13, we obtain a cycle of 86,400 seconds = 24 hours (table 1) if the signals applied to the counter 80 have a period of ten seconds (output 76d) .

TABLE 1
Duration output in seconds
Q1 20
Q2 40
Q3 80
Q4 160
Q5 320
Q6 640
Q7 1280
Q8 2560
Q9 5120
Q10 10240
Qll 20480
Q12 40960
Q13 81920
Q14 163840
For this purpose, the outputs of stages Q6, Q7, Q8 and
Q13 are connected to the NOR 81 circuit which provides an end of cycle signal. This signal is used to set the bistable circuit 64 to state 1 so that it opens the solenoid valve 35 but also to reset the divider circuits 66, 7,6 and 80. Thus, the divider circuit 66 begins a new division cycle so that the multiplexer circuit 67 supplies a signal at its output after a time equal to the duration selected by the decimal counter 68 at one, two, four or five seconds. It is this signal which resets at state 0 the bistable circuit 64, which closes the solenoid valve 35.

 The switch 32 has two fixed contacts 32a and 32b and a movable contact 45. The movable contact 45 has one end connected to ground potential and the other end which can take one of the two positions 32a and 32b. The contact 32a is connected to the light-emitting diodes and the contact 32b is connected to the divider circuits 66 and 76. When the movable contact 45 is in position 32a, which corresponds to the cover 4 removed, the light-emitting diodes 28 and 29 are connected at ground potential and can light up; on the other hand, the stages of the dividing circuits 66 and 76 are at a floating potential and cannot function. In this position, the decimal counters 68 and 78 operate and the broadcasting time and cycle selections can be made.

 When the movable contact is in position 32b, which corresponds to the cover 4 in place, the light-emitting diodes 28 and 29 are at a floating potential and do not light, hence an energy saving; on the other hand, the stages of the dividing circuits 66 and 76 are at ground potential and can therefore operate.

 The operation of the circuit of FIG. 7 is then as follows, starting with the selection of the durations, the cover 4 being removed to actuate the keys 30 and 31. By pressing the key 30, the four light-emitting diodes of group 28, of red color for example, light up successively, each corresponding diode has a certain diffusion duration which is indicated in clear in the immediate vicinity by etching. Releasing the key 30 stops the decimal counting over a certain period, for example four seconds, and the corresponding diode remains on.

 Then, by pressing the key 31, the five light-emitting diodes of group 29, of green color for example, light up successively, each diode corresponding to a certain cycle time between two broadcasts, which time is indicated in clear å proximity of each diode. Releasing the key 31 stops the decimal counting over a certain period, for example 24 hours, and the corresponding diode remains on. If you want the device not to work, you choose the duration zero, which prevents counting and no broadcast can take place.

 These selections being made, the cover 4 is put in place, which turns off the two lit diodes and activates the dividers 66 and 76. By choosing a cycle time of 24 hours, we actually selected output 76d which provides a signal with a period equal to ten seconds, this signal being applied to the divider 80. After 86,400 seconds, the NOR circuit 81 provides a signal, which as explained above, sets the bistable circuit 64 to being 1 and opens the solenoid valve. The bistable circuit 64 is reset to the state o four seconds later by the signal which is supplied by the output 66c of the divider 66. The signal on the output 66c also serves, after a certain delay, to reset the divider circuit to zero 66. Furthermore, the signal which is supplied by the NOR circuit 81 also serves, after a certain delay, to reset the dividing circuits 66, 76 and 80 to zero. A new cycle can then begin.

 When the user chooses a cycle of zero duration, the output 78e of the counter 78 is activated and its signal blocks the counter 80 so that no signal comes to set the bistable circuit 64 to state 1: the device is a the stop.

The embodiment of the control circuit which has just been described in relation to FIG. 7 has certain advantages - it makes it possible to measure two successive durations of
very different periods, one of several hours and
the other by a few seconds - the basic electronic circuits (dividers,
multiplexers, decimal counters, display) are
practically identical no matter how long
is measured - programming of time intervals can be
made over twenty four hours or values
lower; - the programming of the durations is simple to carry out - finally, the number of elementary electronic circuits
used to perform the different functions is
relatively small.

 The control circuit which has just been described can be replaced, without departing from the scope of the invention, by any other circuits which would allow programming of the cycle and diffusion durations.

Of course, such a control circuit can be produced in the form of an integrated circuit.

 The invention has been described in relation "with a particular example of embodiment and arrangement of the various elements, but it is clear that its field is not limited to this example. In particular, the assembly of the two parts 2 and 3 can be done differently without making a work of invention.

 This is how FIGS. 5 and 6 show another embodiment of the device for assembling and holding the lower 2 and upper 3 parts.

In these figures, the elements identical to those of Figures 1, 2 and 3 have the same references. The embodiment of Figures 5 and 6 differs from that of Figures 1, 2 and 3 in that, on the one hand, the outer walls of parts 2 and 3 do not serve as a centering guide during assembly and, on the other hand, that the parts which serve for assembly and maintenance are attached parts which are integral with the returns in the radial direction of the walls 11 and 20.

 Indeed, the walls 11 and 20 no longer fit into each other but close inward by a circular border referenced 90 for the lower part 2 and 91 for the upper part 3, border whose width is variable. These edges 90 and 91 each respectively serve as a support for parts 92 and 93 which are complementary to one another to carry out the centering, the assembly and the maintenance of parts 2 and 3.

 The part 92 has on the lower side a circular groove 94 which cooperates with the flange 9 of the bottle 5. This part 92 extends towards the axis or its inner edge 95 acts as a centering and guiding of the upper part 3 by l intermediary of the adapter 40. The part 92 has, on its upper part, three notches for example, such as that referenced 96 (FIG. 6) for the passage each of one of the three lugs 97 carried by the part 93. When the lug 97 reaches the bottom of the notch 96, a position which corresponds to the opening of the valve 16, a groove 98 cut in the part 92 allows the pivoting of the part 3 around its axis until each lug 97 comes to lock in a corresponding notch 99.

 In the two embodiments of the device for assembling and holding parts 2 and 3 which have been described, the two elements of the device are integral with parts 2 and 3. Such an arrangement is not always necessary and provision can be made that the bottle 5 itself carries a part of the assembly device which would, for example, be fixed on the flange 9 of said bottle.

 Finally, instead of having a device comprising two parts 2 and 3 which couple, one can make a monocoque device separated into two parts by a partition, a lower part for the bottle and an upper part for the solenoid valve. and its control and programming circuit.

 In the same vein, the invention applies to the case where the bottle 5 and the solenoid valve 35 are not axially aligned and are for example side-by-side.

 The two exemplary embodiments of the assembly and holding device which have been described are of the bayonet type, but it is clear that other types of assemblies and amintian can be used without departing from the scope of the invention.

Claims (21)

1. Apparatus for diffusing a fluid contained in a  pressure vessel (5) including the outlet (14)  is fitted with a normally closed shut-off valve (16)  in a state of rest, characterized in that it comprises  - Means (37, 6, 8) for opening said valve  closing (16) and communicating the container  with a fluid outlet duct (37),  - sealing means (38) of the outlet conduit (37)  fluid to close said duct in the rest state,  - means (39) for opening said shutter means  (38) of said outlet conduit (37) and thus leave  flow said fluid, and  - control means (34, 36, 37) of the shutter means  ration and means for opening said conduit  exit so as to open said conduit at instants  and for at least a fixed period. 2. Diffusion apparatus according to claim 1, charac  terized in that the closure means (38) -and  opening means (39) of said outlet conduit are  constituted by a solenoid valve (35) which has a  inlet conduit (37) and an outlet conduit (41), the  inlet conduit (37) cooperating with the means  opening the container closing flap and the  outlet duct (41) being provided with a diffuser (43). 3. Diffusion apparatus according to claim 2, charac  terrified in that the means for opening the flap of  container closure include device  hooking and holding (6, 8, 13) of the solenoid valve  (35) on the container (5). 4. Apparatus according to claim 3, characterized in that  the device for hanging and holding the electro  valve on the container comprises means integral with  the solenoid valve (18, 33) which are provided to cooperate  together so that the closing flap (16) of the  container opens during assembly of said means and  the solenoid valve (35) is held in place on the  container while keeping the valve open  container. 5. Apparatus according to claim 4, characterized in that  the means secured to the container and the means  integral with the solenoid valve are constituted by  socket and bayonet type fasteners  (22, 97). 6. Apparatus according to claim 4 or 5, characterized in that  that the means integral with the container comprise a  cylindrical tube (2) in which is held in place  said container (5), the cylindrical tube (2) being provided,  on the assembly side with the solenoid valve (35), of a  partition (6) which conforms to cooperate with  assembly means integral with the electro-valve. 7. Apparatus according to claim 4, 5 or 6, characterized in  what the means integral with the solenoid valve include  a cylindrical tube (3) in which is held in  places the electro-valve, said tube being provided on the side of  assembly with the container of a partition (18) which  is shaped to cooperate with the assembly means  secured to the container.  8. Apparatus according to claim 6 or 7, characterized in that  that the cylindrical tube (2) for holding the container and  the cylindrical tube (3) for holding the solenoid valve  partially fit into each other at the level of the  partitions opposite.  9. Apparatus according to claim 6, 7 or 8, characterized in  what the cylindrical tube (2) holding the container  is closed, on the side opposite to the assembly partition (6),  by a removable bottom (7) which cooperates in maintaining  place the container (5) in the tube (2) and against the  partition (6). 10. Apparatus according to claim 9, characterized in that  the bottom (7) of the cylindrical container holding tube  (6) serves as a rest base for the device and is shaped  so that the device is tilted relative to the  vertical when it rests on this base. 11. Apparatus according to any one of the claims  previous 1 to 10, characterized in that the means of  control (60) mainly include a circuit  measurement electronics (61, 62, 63, 64) of at least two  durations, that of opening of the shutter means (35)  and that of the time interval between two instants  opening the sealing means. 12. Apparatus according to claim 11, characterized in that  the control means (60) further comprises a  electronic programming circuit (30, 31, 68, 78)  which allows you to program several opening times  shutter means (35) and several durations  time intervals between the opening times  sealing means. 13. Apparatus according to claim 11 or 12, characterized in  which the control means (60) further comprises  a display device (28, 29, 69, 79) of the  different durations. 14. Apparatus according to claim 12 or 13, characterized in  which the control means (60) further comprises  a switch which, in the programming position, activates  the display device (28, 29, 69, 79) and stops the  measure durations and which, in operating position  off the display, and  authorizes the measurement of durations. 15. Apparatus according to claim 13 or 14, characterized in  that the display device (69, 79) includes  light-emitting diodes (28, 29). 16. Apparatus according to any of claims 2 to 14,  characterized in that the control means (60) are  integral with the solenoid valve (35). 17. Apparatus according to claim 11, 12, 13 or 14, charac  characterized in that the electronic circuit for measuring at  minus two durations includes  - a first divider circuit (76, 80) which measures the  duration of the time interval between two instants  opening the sealing means,  - a second divider circuit (66) which measures the duration  shutter opening and which is activated  by the first circuit at the end of the interval  time, and  - a clock circuit (61) which supplies pulses  to said first and second dividing circuits (76,  80, 66). 18. Apparatus according to claim 17, characterized in that  the first divider circuit includes  - a first part (76) which is intended to provide  on these outputs signals of different periods and  pre-determined, and  - a second part (80) which is intended to measure a  determined number of signals provided by the first  part and that provides a signal when that number  determined is reached. 19. Apparatus according to claim 17 in its attachment  to claims 12, 13, 14, characterized in that the  electronic programming circuit includes  - a first counter (78) which receives the pulses from the  clock circuit (61) via a button  control (31) and whose output signals  control a multiplexer circuit (77) connected to å  some exits from the first part (76) of the first  divider circuit (76, 80) so as to direct the  signals of different periods provided by said  outputs, and  - a second counter (68) which receives the pulses from the  clock circuit (61) and whose output signals  control a connected multiplexer circuit (67) 9  some outputs of the second divider circuit (66) of  so as to route the signals of different periods  supplied by said outputs. 20. Apparatus according to claim 19, characterized in that  that it further comprises a bistable circuit (64) which is  connected, on the one hand, to the second part (80) of the  first divider circuit so as to change state  when said determined number is reached and, on the other  share, to the divider circuit (66) via the  multiplexer circuit (67) so as to return to being  initial after a fixed period corresponding to the  duration of opening of said shutter means. 21. Apparatus according to one of claims 17 to 20, charac  characterized in that said circuits are made under the  form of a single integrated circuit.