Control And Measure Instrument For Underwater Diving

Abstract

A measure and control instrument for divers comprising a time counter, a bathometer, and means actuated by said time counter and bathometer for automatically and continuously indicating the duration of the decompression stage to be observed by a diver. Such means comprises a mechanism driving at least one indicating member in an intermittent movement the frequency of which is constant and the amplitude of which varies with the depth of submersion.

Description

The exceptional development of underwater diving has accentuated the urgent need to provide divers, both sportsmen and professionals, with measuring and control instruments adapted to the rigorous requirements of the diving medecine.

It is known that the nitrogen of the air breathed by divers is absorbed by the organism, notably by the blood, in proportions increasing with the ambient pressure and the duration of submersion. A certain percentage of this nitrogen must imperatively be eliminated by the organism before the diver can return to the surface. Failing this elimination, the diver is liable to extremely grave physiological disorders, known as "the bends" , upon surfacing, these disorders capable of causing paralysis or even death.

The problem of the elimination of this nitrogen has been solved by making the diver rise very slowly towards the surface (with a speed of the order of 20 meters/min) and above all the observation of stops at certain depths (- 3m, - 6m, - 9m, - 12m), called decompression stages, during which the disequilibrium existing between the ambient pressure and the blood pressure generates the passage of the nitrogen dissolved in the blood to the exterior of the organism. Medical specialists in the field have sought to determine with a maximum precision the duration of these stages as a function of the depth of submersion. Evidently, it is practically impossible to determine, in this case, an exact mathematical relationship between the three values concerned. In these circumstances there have been established, by methods more or less scientific and more or less empirical, approximate values that have been arranged into tables indicating, for successive depths varying by intervals of 2 meters or 3 meters, the duration of the decompression stages to be observed as a function of the time interval of submersion.

To date, the known diving equipment included a watch to measure the duration of submersion, a pressure gauge or bathometer to measure the depth of submersion, and a chart or a table to be used by the diver underwater after having taken the readings from his watch and pressure gauge or bathometer. Some attempts have been made to simplify this clumsy equipment; for example, the use of watches provided with special glasses or dials having indications corresponding to the diving tables. However, these indications are complicated to interpret or to use, especially because they often necessitate manipulations underwater which are rendered difficult for many reasons, for example the obscurity, the difficulty of carrying out certain gests, and so on. In summary, the known equipment and procedure are totally unsuitable to the essential requirements of freedom of movement and safety.

There does not actually exist, up to now a single instrument enabling the diver to conveniently read the two measurements necessary for the constant control of a dive, that is depth and duration of submersion, and simultaneously have a permanent indication of the duration of the decompression stage or stages to be observed.

An object of this invention, which sets out to remedy this situation, is to provide a control and measuring instrument for divers comprising a time counter and a bathometer.

A further object of this invention is to provide such an instrument which comprises means which automatically and continuously transmit to at least one indicating member, the duration of the stage or stages of compression from data provided by the time counter and the pressure gauge or bathymeter.

The means in question can be mechanical, electronic or otherwise. The instrument too can be entirely mechanical, partly mechanical, partly electronic, or entirely electronic. These means must simply be capable of computing automatically and continuously the duration of the decompression stage or stages from information transmitted by the time counter and the pressure gauge or bathometer.

Various solutions can be envisaged ranging from a special mechanism -- as it will be particularly described later by way of example -- to a miniature computer.

It is to be understood that it is possible to provide an instrument with a wide range of use capable of being used both for sports or professional purposes, i.e. usable for depths from 0 to 350 m. and durations of submersion extending over several days; or covering special limited uses, such as that of sports diving with depths down to 40 meters and submersion times lasting 1 hour.

To provide such an instrument it is naturally necessary to know the function determining the duration of the decompression stage or stages from the depth of submersion. It has already been mentioned above that this function could not be exactly formulated. However, from an examination of the diving decompression tables available on the market and notably the one which is authoritavely accepted by diving experts, namely the air-diving table of the Underwater Study and Research Group of the French Navy (G.E.R.S.) and which incidentably coincides, down to depths of 60 meters, with that used by the U.S. Navy, the following facts, for sports diving (maximum depth 40 meters and 1 hour submersion), are observed:

1. It is sufficient to observe a single decompression stage at the - 3 meter level.

2. For each depth of submersion the relation between the duration of submersion t and the duration of the decompression stage T at - 3 meters can be approximated to a linear function, i.e. it can be graphically represented by a straight line.

3. Up to a certain submersion time decreasing with the depth of submersion considered as a parameter, it is not necessary to observe a decompression stage. These values of maximum submersion without a compression stage are graphically given by the points of intersection of the straight lines, each corresponding to a certain depth on the abcissa ( t axis ).

4. The various straight lines which correspond to depths increasing by intervals of 2 meters converge substantially to a point on the ordinate ( T axis ).

In the case of sports diving, this implies that the referred-to-means, which must continuously compute the duration of the decompression stage from the measure of the time and the measure of the depth of submersion may achieve this object if they comprise a first element moving at a constant speed, a second element moving at a variable speed greater than that of the first element, a device for regulating the speed of this second element as a function of the depth of submersion, and an indicating member showing a value which is proportional at any instant to the difference of position of the two elements. If the parameters are correctly determined, this value gives a permanent measure of the length of the decompression stage.

While the invention is in no way limited to the field of sports diving, there will now be described, by way of example, an embodiment of the invention intended for amateur divers. This instrument is shown in the accompanying drawings, in which:

FIG. 1 is a plan view of the instrument, showing the dial side;

FIG. 2 is schematic plan view, similar to FIG. 1, the glass, hands, dial, and exterior control members having been removed;

FIG. 3 is a cross-section taken along line III--III of FIG. 2; but with the hands, dial and glass shown;

FIG. 4 is a cross-section of a detail taken along line IV--IV of FIG. 2;

FIG. 5 is a graph showing the duration of the decompression stage of - 3 meters indicated by the instrument for a diving depth of 30 meters;

FIGS. 6 to 11 schematically show the indications of the instrument corresponding to the diagram of FIG. 5 for submersion times of 0, 15, 30, 45, 60 and 75 minutes.

The instrument shown indicates the date, hour, minutes and seconds in the manner of a conventional watch and, during a dive, the duration of submersion, the depth of the diver and, continuously, the duration of the decompression stage to be observed at - 3 meters.

The instrument additionally indicates at any time to the diver, while he is carrying out a decompression stage, the remaining time that he must stay at that stage. Naturally, the instrument can be used for successive dives.

The instrument shown, worn on the diver' s wrist, comprises a monobloc watertight casing 10, a glass 11 fitted on a bezel 12 itself fixed on the bezel-snap with interpositioned joints ensuring an absolute watertightness down to a depth of at least 100 meters. In this casing are placed a watch movement 13 of which the barrel is substantially dimensionned in a manner to possess an energy reserve greater than average, this movement being placed on a cage ring 14, a first plate 15 taking support on the movement, and a second plate 16 embedded in the casing at the level of the bezel. Between these two plates is a mechanism 17 intended to drive, from the movement, on the one hand a graduated crown 18 and on the other hand, an indicating hand 19. This crown 18 and the hand 19 constitute the two elements mentioned above.

At the level of the crown 18, respectively positioned at the center and at the exterior thereof, are located an hour dial 20 and an annular dial 21 carrying a graduation 0 through 60. These two dials are fixed; the first rests on the plate 16 and the second is pinched between the bezel and the bezel-snap of the casing.

Above dial 20 turn three hands, hour hand 22, minute hand 23, and second hand 24, driven in a conventional manner by the watch movement through plates 16 and 17. Hand 19 is mounted on a fourth bush 25, exterior to and coaxial with the three others. The turning crown 18 is divided into a quarter-turn sector 26 colored white, and three-quarter turn sector 27 colored red. This second sector is graduated 0 through 45 minutes and has an index 30 indicating on the dial 21 the submersion time in minutes; reference numeral 29 designates the winding crown which also serves for setting the hour and date of the watch.

Crown 18 is intended to be driven at a rate of 1 revolution per 60 minutes by the watch movement through the intermediary of a pinion 39, a runner 41 pivoted between plates 15 and 16 and a toothed wheel 43 which meshes with an interior toothing of the crown 18.

The bottom 32 of the casing, which has openings 33 and an aneroid membrane 31 welded on a ledge of this bottom, defines a chamber 34 in which water can enter. The deformations undergone by this membrane under the action of the water pressure are transmitted to a needle 35 through a lever 36, a rack 37 and a pinion 38 freely turning on a runner 58 pivoted between the plates 15 and 16. The link between the pinion 38 and the needle 35 is through a pinion 60 secured to a fifth bush 61 positioned between the bush upon which is secured the hour hand 22 and the bush upon which is secured the indicating hand 19.

An arm 50, at the end of which is mounted a finger 49 provided with a ball, is solid in rotation with the pinion 38. Consequently this finger is angularly displaced in the clockwise direction upon increase in the pressure on the membrane and in the opposite direction upon decrease of this pressure. Arm 50 is positionned approximately at 12 o' clock when the instrument is only submitted to atmospheric pressure, and approximately at 3 o' clock when the pressure on the membrane reaches 7 atmospheres (60 meters).

The precise role of finger 49 will be explained in detail farther on.

The assembly formed by the membrane 31, lever 36, rack 37, pinion 38 and hand 35 constitutes a bathometer the depth indications of which are given by needle 35 and dial 21. A shock-absorber 54 mounted on the bottom of the movement absorbs the deformations of the membrane caused by movements of the diver.

It is seen that dial 21 cooperates not only with index 30 to indicate the time of submersion, but also with hand 35 to indicate the pressure, or correctly speaking, the depth; the 0 through 60 graduation is thus read in minutes or in meters, depending whether index 30 or hand 35 is under consideration. Hand 19 is normally caused to rotate by the watch movement through pinion 39, two toothed wheels 28 and 40 both belonging to the runner 41 and by a crank-shaft comprising a toothed wheel 42 pivoted in plate 16 (FIG. 4). On the disk of the wheel 42 is mounted a rod 44 carrying at its end a click 45 intended to cooperate with a ratchet wheel 46.

The click 45 and wheel 46 form a click and ratchet wheel of which the stop click is indicated by reference numeral 47. Wheel 46 is keyed on the previously-mentioned runner 58 and its displacements are transmitted by a toothed wheel 57 of this runner to a toothed wheel 56 solid with a bush 25 and by this bush to hand 19.

Rod 44 is submitted to the action of a spring blade 48 which tends to urge the click 45 against the ratched wheel 46.

It is however remarked that the end of rod 44 located at the level of finger 49 abuts against this latter for a certain time during its movement before the click 45 can actuate wheel 46. In fact, the angular position of finger 49 is capable of varying about 90.degree. between the two above-mentioned extreme positions, and it is seen that the first tooth with which the click meshes upon the driving alternation of the rod thus varies according to the angular position of arm 50. It follows that the angular displacement imposed to the ratchet wheel 46 and consequently to the hand 19, upon each rotation of the wheel 42, corresponds to a variable number of teeth of the ratchet wheel.

In fact, when the pressure reaches and exceeds 5 atmospheres (40 meters), finger 49 is completely retracted, i.e. it does not obstruct the movement of the rod and the displacement of the ratchet wheel is maximum. In the second of the above-considered extreme positions, finger 49 permanently maintains the rod and the click away from the ratchet wheel.

The number of teeth of the wheel 46, the dimensions and speeds of the various members of the mechanism, and the shape of the rod are determined in a manner such that this latter situation is maintained until the angular position of the arm 50 corresponds to a depth of 16 meters inclusive. Only from a depth of 18 meters does the click 45 come into engagement with the wheel 46 and cause an angular displacement which regularly increases each time that the depth increases by 2 meters, from 18 meters down to 40 meters.

Precise calculations, confirmed by laboratory tests have shown that in these conditions it is possible with a 60-tooth ratchet wheel to obtain a displacement of eight teeth at a depth of 18 meters and to increase this displacement by one tooth for every interval of 2 meters down to a depth of 40 meters. That is, to bring this displacement to 19 teeth at 40 meters depth.

While the depth does not reach 18 meters, a finger 55 carried by the dial 18 drives the hand 19 at the speed of this latter, i.e. at a rate of 1 revolution per 60 minutes.

The starting and the resetting to zero of the disk 18 and hand 19 are controlled simultaneously by the push-piece 52. The mechanisms used for this purpose, well known to watch makers, have not been shown. The knurled crown 53 enables the needle to be started from an arbitrarily chosen angular position. The importance of this feature will appear further on.

By way of example, the graph of FIG. 5, shows readings taken with the described instrument for a dive carried out to a depth of 30 meters and a duration of submersion from 0 to 75 minutes. These readings are compared with the corresponding values shown in tables, in this case by the GERS table (blacked in coordinates) and the SEEMANN table (circular coordinates). In FIGS. 6 to 11, are shown the positions respectively occupied by the dial 18 and hand 19 of the described instrument for durations of submersion equal to 0, 15, 30, 45, 60 and 75 minutes. The good agreement between the readings of the instrument and the tabular values will be noted. The small divergences noted fall within the safety margin for the instrument.

The agreement is also good for all other depths. So as not to needlessly lengthen this description, the readings given by the instrument and those given in the tables for other depths have not been shown. However, it is noted that the straight lines corresponding to depths of 18, 20, 22..... 40 meters, converge substantially to the point - 15 minutes on the ordinate (T axis). The submersion times for which decompression stages are not necessary can be read on the t axis and decrease regularly with depth. They are practically always found to coincide with the tabular values.

Returning to the graph of FIG. 5, it is seen that the maximum submersion time without a decompression stage for a depth of 30 meters given by the instrument is 19 minutes, whilst the GERS table gives 20 minutes. For a submersion time of 60 minutes, the instrument indicates a decompression stage of 33 minutes, the SEEMANN table 30 minutes and the GERS table 37 minutes. For a submersion time of 75 minutes, the instrument indicates 45 minutes, the GERS table 46 minutes.

In the case considered in FIGS. 5 to 11 (depth 30 meters), to give the observed readings the hand 19 must carry out 2 1/4 revolutions in 75 minutes, i.e. 9/5 revolution in 60 minutes.

Returning to the above-indicated numerical values given by way of example, (60 tooth ratchet wheel), it is shown that the angular displacement of this wheel by the alternating drive of the rod will be, for a depth of 30 meters, 14 teeth. If, to give a precise example, it is supposed that the wheel 42 turns at a rate of 1 revolution per minute, hand 19 will advance at an angular speed of 9/5 that of the dial; i.e. in 1 minute it will turn through an angle corresponding to 1 minute and 48 seconds. This advance will be intermittent because the click 45 performs a forward movement in 30 seconds and a return movement in 30 seconds, and because click 45 rotates the wheel 46 during its forward movement only. This angle will be swept through in 30 seconds, then the hand will remain immobile for the 30 following seconds. However, this intermittent displacement is not in practice perceptible to the eye especially underwater and once more falls within the previewed safety margin.

It is however clear that this drawback if it is considered as a drawback could be easily eliminated by replacing the described mechanism by a double effect system, or by another mechanism, but such a solution would normally only be adopted for an instrument where extreme precision is required, for professional purposes.

The use of the instrument is extremely simple; at the moment of diving, the wearer presses the chronometric push-piece 52 once to set the index 30 and hand 19 at zero (i.e. at 12 o' clock), and again to start the disk 18 and hand 19 which, at that moment, is driven by the finger 55. Whilst the diver is at or below the 16 meter limit, the crank-shaft mechanism turns but is inoperative, as has been previously explained, because the position of the finger 49 prevents the click 45 from reaching the teeth of the ratchet wheel; on the contrary, the hand 19 turns with the crown 18 at a rate of 1 revolution per 60 minutes.

At the depth of 18 meters the finger 49 reaches an angular position such that the click 45 can engage the wheel 46 and advance it eight teeth by alternating movement; the hand 19 thus turns faster than the dial 18 and penetrates in the white zone of the crown; if the diver continues to descend the finger 49 retracts more and more and the click 45 can engage increasingly earlier with the ratchet wheel; this results in a regular increase in the angular speed of the hand 19 of 1/60 revolution per hour each time that the diver descends 2 more meters.

Suppose that the diver stops at a depth of 30 meters to carry out observations or any work whatsoever. The angular speed of the hand 19 remains constant, greater than that of the dial 18; as long as the hand 19 is in the white zone 26, the diver knows that it is not necessary to carry out a decompression stage. From the moment when this hand penetrates in the red zone, he knows that he must carry out a decompression stage the duration of which is indicated at any moment by the position of the hand 19 facing the graduation carried by the red zone 37. Additionally, the index 30 read on dial 18 also gives him at any moment his submersion time. Finally, his depth is indicated on the same dial 18 by needle 35. Supposing that he remains a total of 45 minutes at the depth of 30 meters, he can immediately see at that moment by looking at the relative position of the hand 19 and dial 18 (FIG. 9) that he must carry out a decompression stage of 21 minutes. In fact, it will later be seen that the exact measurement of the duration of this stage is not indispensable. He also immediately knows by reading the index 30 on dial 18 that he has remained 45 minutes underwater.

Having completed his dive, he rises at the prescribed speed of 20m/minutes until the - 3 meter level. During this rise the speed of the hand 19 diminishes and stops when he passes the - 16 meter level; on the contrary, the dial 18 still continues rotation at the same speed of 1 revolution per 60 minutes in such a manner that after the passage of 21 minutes the limit of the two sectors 25 and 27 rejoins hand 19. At this moment the diver knows that he can surface without danger. The nitrogen content in his organism is eliminated to a safe level and the proportion of nitrogen remaining in the blood can be calculated by the diver, when he surfaces, from special tables indicating this proportion as a coefficient "C" , or "C-factor" .

According to controls and tests carried out by diving medical experts, approximately 6 hours in the fresh air is required to completely eliminate the residual nitrogen. If the diver waits for this period before undertaking a further dive, he need take no special measure, i.e. he simply re-sets his instrument to zero before re-entering the water.

On the contrary, if the diver wishes to carry out another dive before this 6 hours period has expired, he must adjust his instrument to take into account of the residual amount of nitrogen still in his blood. The value of the C-factor can be calculated from tables according to the time that has elapsed between these two dives. From this C-factor (for example 1.8), the diving time is increased by a calculated amount upon rediving.

Practically, it is sufficient to simply displace hand 19 by means of the crown 53 and to bring it into a starting position, with respect to the disk 18, corresponding to the calculated increase.

The data from the above-mentionned table can additionally be carried by a bezel, possibly turning, on the instrument casing so that the diver does not need to consult separate tables.

It is also clear that the invention is not limited to the embodiment which has been described and shown by way of example. In particular, it is possible to provide means automatically indicating the duration of the decompression stage that the diver must carry out at - 6 meters when the submersion time exceeds certain limits. For example, there could be provided a further hand driven by the hand 19 by interpositionning a demultiplicator gear and for which the starting point would be situated at a determined point in the white sector. This hand would only reach the red sector at the moment where the hand 19 reaches the angular position at which it is necessary to carry out a decompression stage at - 6 meters.

Claims

I claim:

1. A measure and control instrument for use by divers, comprising a time counter for measuring the time of submersion, a bathometer for measuring the depth of submersion, and means actuated by said time counter and said bathometer for determining and indicating the duration of the decompression stage to be observed by a diver in function of the time and depth of submersion, said means comprising a mechanism driving at least one indicating member in an intermittent movement the frequency of which is constant and the amplitude of which varies with the depth of submersion.

2. A measure and control instrument as defined in claim 1, wherein said mechanism comprises a ratchet wheel, a rod driven by the time counter in a back and forth movement, a click articulated on said rod and cooperating with the ratchet wheel to cause it to rotate, and an element the position of which depends on the pressure measured by the bathometer and which increases the active path of said click upon increase in pressure, thereby increasing the rotational speed of said ratchet wheel.

3. A measure and control instrument as defined in claim 1, wherein said indicating member indicates the duration of the decompression stage at a depth of 3 meters.

4. A measure and control instrument as defined in claim 1, wherein said indicating member cooperates with a second indicating member driven by said time counter.