FR2738911A1 - IMPROVED FLUID METER COMPRISING A MAGNETIC DRIVE OF THE REPELLENT TYPE - Google Patents

Abstract

A fluid meter (10) including a unit (12) for measuring the fluid volume passing through said meter and a repulsive magnetic drive consisting of a driving portion (26) connected to said measuring unit, and a driven portion (44), both of said portions being located opposite one another and rotatable about an axis XX'. During normal operation, the motion of the driving portion (26) rotates the driven portion (44). The driven portion (44) is movable along said axis, and when said driven portion does not follow the motion of the driving portion (26), it is subjected to variable axial magnetic repulsion forces from said driving portion, which forces act to space it apart therefrom. In the spaced-apart position, the driven portion (44) is acted upon by a resilient member (60) that, when bent, urges said driven portion towards the driving portion, whereby the driven portion is alternately subjected to opposite forces until it reaches the same rotation speed as the driving portion.

Description

The invention relates to a fluid meter comprising a member for measuring the volume of fluid passing through said meter and a magnetic drive of the repulsion type consisting of a so-called driving part linked to said measuring member and a so-called driven part, both being located opposite one another and movable in rotation about an axis, and during normal operation1 the movement of the driving part causing the driven part to rotate.

Fluid meters with magnetic drive generally consist of a measuring chamber to which are connected a supply and an evacuation of fluid and in which is installed a device for measuring the volume of fluid which is set in rotational movement around an axis when the fluid circulates in said measurement chamber.

The measuring member transmits its rotational movement to a totalizer which is separated from the latter by a sealed wall, by means of a magnetic drive consisting, on the one hand, of a so-called driving part linked to said measuring member and, on the other hand, a so-called driven part placed on the other side of said sealed wall with respect to the driving part.

The driven part of the magnetic drive is linked to one (or more) gear train (s) of the totalizer and is set in motion under the action of magnetic forces generated by the driving and driven parts and the rotational movement of the measuring device.

In some meters such as the one described in the document
DE 1 423 884 the magnetic drive is of the face to face and repulsion type, that is to say that the driving and driven parts are axially aligned along an axis and mobile in rotation around this axis.

These parts are opposite one another, and operate according to the principle of magnetic repulsion, a north pole or a south pole of a magnet of one of the parts cooperating with a pole of the same kind of a magnet from the other party.

Among these counters, some of them are characterized by a totalizer which has a resistant mechanical torque of low value compared to the stresses due to accelerations of the driving part.

When such meters are installed on site, for example at a user's home, these are not always placed in a position such that the axis of the driving and driven parts is arranged vertically.

The Applicant has thus been able to observe on installed water meters whose axis of the driving and driven parts is not vertical, that sometimes the acceleration of the measuring member, due for example to instantaneous water consumption very important, and therefore the acceleration of the driving part of the magnetic drive is such that the driven part of said magnetic drive cannot follow the movement of the driving part.

We are then witnessing a phenomenon known as stall, that is to say that the driven part of the magnetic drive is no longer rotated and therefore the totalizer no longer displays the volume of water passing through the counter.

The Applicant has also been able to observe this dropout phenomenon on counters in which the weight of the driven part is less than the magnetic repulsion force developed by the driving and driven parts, when the torque transmitted by the magnetic drive is zero and for which the axis of said driving and driven parts of the magnetic drive occupies a vertical position.

Document DE 32 32 649 discloses a water meter with magnetic drive comprising a turbine equipped with the driving part of the magnetic drive, the driven part of said magnetic drive being carried by a shaft aligned with the axis of the turbine and positioned on the other side of a sealed wall.

The driving part of the magnetic drive is connected to the axis of the turbine by means of a spring wound around said axis and which has the function of delaying the acceleration of the turbine in response to a rapid increase in the flow rate. of water, by absorbing the acceleration energy of said turbine before its transmission to the driving part.

This spring thus prevents the dropout phenomenon mentioned above.

 It is also mentioned in this document that the spring can alternatively be placed between the driven part of the magnetic drive and the shaft.

According to this document, the acceleration energy of the turbine is absorbed by the spring.

However, when the turbine is subjected to an acceleration for too long, the acceleration energy stored by the spring is released and is superimposed on the acceleration of said turbine, thus favoring the stall phenomenon which it was sought to avoid. .

In addition, the incorporation of such a spring into the counter makes it more difficult to assemble said counter.

Document DE 24 55 266 also discloses a fluid meter equipped with a spring which aims to ensure exact magnetic drive during sudden acceleration of the turbine in order to avoid the stall phenomenon.

Analogously to what was mentioned above with reference to document DE 32 32 649, the spring has the function of absorbing the acceleration energy of the turbine before its transmission to the driving part.

The counter described in this document has the same drawbacks as that described in the first document.

In addition, the presence of these springs in the counters described in these documents can cause vibration phenomena which affect the proper functioning of the counters.

The present invention therefore aims to solve simply and effectively the problem associated with the phenomenon of the stall of the magnetic drive of the fluid meters, when this phenomenon appears.

The present invention thus relates to a fluid meter comprising a member for measuring the volume of fluid passing through said meter and a magnetic drive of the repulsion type consisting of a so-called driving part linked to said measuring member and a so-called driven part. , both being located opposite one another and movable in rotation about an axis, and during normal operation, the movement of the driving part causing the driven part to rotate, characterized in that the driven part can move along the axis and, when said driven part does not follow the movement of the driving part, it is subjected to the action of variable axial repulsive magnetic forces on the part of this latter which tend to move it away, the driven part being, in this remote position, subjected to the action of an elastic part which, when it deforms, tends to bring said driven part closer to the driving part, the p driven part thus being alternately subjected to efforts in the opposite direction until said driven part acquires the same speed of rotation as that of the driving part.

When the driven part of the magnetic drive is subjected to the action of variable magnetic repulsion forces directed in a direction opposite to the driving part, said driven part deforms the elastic part.

When the magnetic repulsion forces decrease, the driven part is then directed towards the driving part under the action of the deformation force of the elastic part then is again subjected to the action of the variable repulsion forces directed towards the part elastic.

These axial back-and-forth movements which can be likened to rebounds, allow a transfer of kinetic energy of rotation between the driving and driven parts and, after a few rebounds, the driven part acquires the speed of rotation which allows him to follow the movement of the leading part again.

Contrary to the invention described above, none of the counters of the prior art described above makes it possible to effectively solve the problem linked to the stall phenomenon when this phenomenon occurs in a magnetic drive.

 It has also been mentioned above that the fluid meters cited in documents DE 32 32 649 and DE 24 55 266 do not always avoid the phenomenon of dropout and, when it occurs, do not offer any solution for remediate.

Preferably, the driven part is connected to a shaft aligned with the axis and one end of which, opposite to that near which said driven part is located, comes into contact with the elastic part.

In order not to create excessively high friction during contact between the end of the axis and the elastic piece, said end of the axis forms a point.

To reduce this friction, it is also preferable that the tip is in contact with a flat surface of the elastic piece.

où M représente la masse de la partie menée, Nd représente la vitesse de rotation minimale de la partie menante à partir de laquelle la partie menée ne suit plus le mouvement de ladite partie menante dans le cas où la partie menante est soumise à une forte accélération et lorsque la pièce élastique n'est pas présente, N1 et N2 représentent respectivement le nombre d'aimants dipolaires des parties menante et menée et max(N1,N2) désigne le plus grand des deux nombres N1 et
N2.According to a preferred characteristic of the invention, the elastic part has a stiffness K verifying the relationship

where M represents the mass of the driven part, Nd represents the minimum speed of rotation of the driving part from which the driven part no longer follows the movement of said driving part in the case where the driving part is subjected to a strong acceleration and when the elastic part is not present, N1 and N2 respectively represent the number of dipole magnets of the driving and driven parts and max (N1, N2) denotes the larger of the two numbers N1 and
N2.

According to another preferred characteristic of the invention, the calibration of the elastic part is included in the field
Fm + FM
+ 30%, where Fm and FM respectively designate the
2 minimum and maximum magnetic repulsion forces when the driven part no longer follows the movement of the driving part.

The elastic piece is for example a flexible strip.

The elastic piece can also be a spring.

According to yet other preferred characteristics of the invention - an abutment limits the axial displacement of the driven part, - the axial displacement of the driven part is greater than 8% of the axial distance between the driving and driven parts when these have the same speed of rotation, - the stop is integral with the shaft of the driven part and cooperates with a fixed part of said counter, - the stop is arranged diametrically opposite the driven part with respect to the elastic part in order to limit the deformation of said elastic piece.

The measuring member is for example a turbine whose axis of rotation coincides with the axis of rotation of the driving and driven parts.

The fluid meter may be of the single jet or multiple jet type.

The measuring member can, for example, move inside a measuring chamber in a cyclic movement by trapping a volume of fluid determined during each cycle.

Other characteristics and advantages will appear during the description which follows, given solely by way of example and made with reference to the appended drawings in which - FIG. 1 is a schematic view in longitudinal section of a fluid meter according to a embodiment of the invention, - Figure la is an enlarged schematic view of part of the fluid meter of Figure 1 on which are shown the end 52b of the shaft 52 and the elastic part 60, - the Figure 2 is a schematic view in longitudinal section of a fluid meter according to another embodiment of the invention.

As shown in FIG. 1 and designated as a whole by the general reference noted 10, a single jet water meter comprises a measuring member 12 which is in the form of a turbine disposed inside a measuring chamber 14 and which is rotated about a longitudinal axis XX 'under the action of a flow of water in said chamber.

The water meter of Figure 1 is installed in a position such that the longitudinal axis XX 'is horizontal.

The measurement chamber 14 is connected to a water supply 16 and to a water discharge 18 which are offset with respect to the section plane of FIG. 1.

The turbine 12 is formed by a central hub 20 to which are attached several blades 22 regularly distributed around its periphery.

The central hub 20 is extended at one of its so-called lower ends by a collar 20a. The function of this flange is to promote the lifting of the turbine 12 at high flow rates, that is to say for example greater than 200 Uh, so as not to degrade the tip of the pivot 24 on which the said turbine rests and which contributes to give the meter its sensitivity to low flow rates.

The central hub 20 is extended at its opposite end called the upper end by a shaft 20b which is equipped with a magnet support 26 constituting the driving part of the magnetic drive of the counter.

The measurement chamber 14 is delimited by two opposite end walls 28, 30 of which one of these walls 28 receives, in its central part, the magnet support 26.

The shaft 20b is guided in rotation around a pivot 31 secured to the wall 28.

Radial ribs 32 are fixed to the wall 28 by means of a wall element 34 drilled in the middle to receive the shaft 20b of the hub of the turbine 12.

The other opposite end wall 30 receives a wall element 36 on which the pivot 24 is mounted and to which radial ribs 38 are fixed.

The water meter 10 also includes a totalizer 40 disposed above the measurement chamber 14, when the axis XX 'of said meter is vertical, and delimited at its lower part by a partition 42.

For the sake of clarity, only a few elements of the totalizer 40 are shown in FIG. 1.

A mobile magnet holder 44 is disposed inside the totalizer 40 and constitutes the driven part of the magnetic drive of the counter.

The driving part and the driven part are arranged opposite one another and are movable in rotation around the axis of rotation XX ′ of the turbine 12.

The partition 42 and the end wall 28 provide between them a space 46 of generally annular shape surrounding the driving part 26 of the magnetic drive.

A piece of magnetic material 48 having the shape of a half-cup hollowed out in its central part to let through the driving part 26 and the deformed central part of the end wall 28 is disposed inside the annular space 46 of so as to surround said driving part.

Another part made of magnetic material 50 of the same shape but inverted with respect to the part 48 is placed around the driven part 44.

The two half-cups 48, 50 thus form a protection of the driving and led parts vis-à-vis a magnetic field external to the meter.

The driving and driven parts are respectively each made up of an even number N1, N2 of dipole magnets, for example equal to two.

The magnetic drive is of the repulsive type, that is to say when the north pole of one of the magnets of the driving part 26 is located opposite a north pole of one of the magnets of the driven part 44 as a result of a rotational movement of the turbine 12, the poles of the same type repel each other which imposes a rotational movement on said driven part, thus ensuring the transmission of the movement of the turbine.

The driven part 44 of the magnetic drive is integral with a shaft 52 aligned with the longitudinal axis XX '.

The shaft 52 is rotatably mounted by one of its ends 52a in a housing 54 of the partition 42 acting as a bearing.

The driven part 44 also has a degree of freedom in axial translation and can therefore move along the longitudinal axis.
XX '.

However, the axial displacement of the driven part 44 is limited by the presence of a so-called axial stop 56 which is integral with the shaft 52 and which comes into contact, after a predetermined stroke of said driven part, with a plate 58. This stop is for example formed by a sleeve molded onto the shaft 52.

More specifically, the plate 58 has in alignment with the longitudinal axis XX 'an element 58a projecting in the direction of the axial stop 56 and which forms a seat for said stop when the latter is in contact with said element 58a.

When the turbine 12 is driven in a regular rotational movement, the driving part 26 of the magnetic drive rotates the driven part 44, the driving and driven parts have the same speed of rotation and are spaced apart from the another, for an average axial position of the turbine between the pivots 24 and 31, of an average axial distance also called mean air gap.

According to a variant of the invention not shown in the figures, the stop can also be placed behind the elastic piece 60 in order to further limit the deformation of this piece.

The plate 58 has at the center of the projecting element 58a an orifice 58b allowing the passage of the end 52b of the shaft 52.

An elastically deformable part 60 of stiffness K having the form of a strip is disposed on the other side of the plate 58 relative to the driven part 44. The flexible strip 60 of substantially constant thickness is in the form of a flat central portion 60c which connects two end portions 60a and 60b which are also flat and parallel to one another.

The central portion 60c forms with each end portion 60a, 60b an angle which varies during the compression of the strip.

The strip 60 is fixed for example by gluing by its end 60a to a support 62 integral with the totalizer 40.

The part 60 could also be a spring or any other elastically deformable means.

The strip 60 rests by its opposite end 60b against the plate 58 in line with the orifice 58b so as to be in contact with the end 52b of the shaft 52 when the driven part 44 of the magnetic drive moves axially .

During normal operation of the magnetic drive, when the axis XX 'of the counter is horizontal (fig la), the end 52b of the shaft 52 is in contact with the elastic part 60. There is a residual play between the end 52a of the shaft 52 and the bottom of the housing 54.

The end 52b of the shaft 52 which is in contact with the elastic part 60 preferably forms a point thus making it possible to minimize the mechanical contact and therefore not to introduce friction which would adversely affect the sensitivity of the counter and
The effectiveness of the invention. It is also preferable that the end 52b is in contact with a flat surface of the elastic part.

In this counter, the resistive torque offered by the totalizer is considered to be relatively low compared to the stresses due to the accelerations of the driving part.

For example, such a resistant torque is of the order of one fifth to one tenth of the torque transmissible by the magnetic drive when the turbine 12 rotates at high speed and this regardless of the position of the longitudinal axis XX 'of said turbine.

When the turbine is subjected to sudden acceleration due for example to the opening of a valve, the movement acquired by the driving part 26 of the magnetic drive cannot be transmitted to the driven part 44 and the phenomenon known as dropout occurs. The minimum speed of rotation of the driving part from which the driven part no longer follows the rotational movement of said driving part is denoted Nd, in the absence of the elastic part.

This stalling phenomenon results in a relative movement of rotation of the driving part with respect to the driven part, which results in a variable repulsion force F between said parts.

This effort varies substantially sinusoidally between two minimum values Fm and maximum FM as a function of the relative angular position of the driving and driven parts. These fixed values Fm and FM are a function of the geometry of the driving and driven parts of the magnetic drive and of the materials which compose them and have an axial direction.

The value Fm corresponds to the magnetic repulsion force generated by the magnetic drive when the latter does not transmit torque.

These values are for example obtained by digital simulation on a computer by modeling the magnetic drive but can also be obtained by means of force sensors placed on the driving and driven parts.

In this counter, the mass M of the driven part is such that the weight of said driven part is greater than the minimum magnetic repulsion force Fm generated by the magnetic drive.

It will be noted that the invention also applies to a fluid meter whose weight of the driven part of the magnetic drive is less than the minimum magnetic repulsion force Fm and for which the longitudinal axis XX 'of the turbine can occupy any position.

When the phenomenon of stalling has occurred, the driving part 26 of the magnetic drive rotates at high speed and, due to the force F of magnetic repulsion, the driven part 44 moves away from said driving part.

In a counter of the prior art in which the longitudinal axis is horizontal, the driven part of the magnetic drive remains held in abutment in a position remote from the driving part under the action of the magnetic repulsion force.

On the contrary, in the counter according to the present invention, due to the presence of the flexible strip 60, when the driven part 44 moves away from the driving part 26 under the action of the repulsion force F, the latter elastically deforms said strip when the repulsion force is greater than the setting value of the strip until the deformation force of the latter is greater than the force F.

The driven part 44 then undergoes an action on the part of the compressed strip which tends to bring the driven part towards the driving part.

This back-and-forth movement allows a transfer of kinetic energy of rotation between the driving and driven parts.

The driven part is pushed back again towards the strip 60 under the action of the repulsion force and, in a similar manner to what has just been described, the deformation force of the strip pushes the said driven part again. towards the leading part. A new transfer of energy occurs between said driving and driven parts and the driven part thus acquires an increasing kinetic energy of rotation.

After a few axial 1bounces1 of the driven part, it acquires the speed of rotation of the driving part and then succeeds in following its rotational movement.

The axial displacement of the driven part 44 is at least equal to 8% of the mean air gap previously defined so that the axial rebounds have a sufficient amplitude to allow a good transfer of energy.

For example, the possible axial displacement is equal to 30% of the average air gap.

où

représente la fréquence propre de la partie menée et de la pièce élastique et Nd x max (N1, N2) représente la fréquence de la sollicitation axiale après le phénomène de décrochage, max (N1,N2) désignant le plus grand des deux nombres N1 et N2.In order to allow the elastic part 60 to be more efficient and therefore to speed up the re-hooking phase, the setting T of said part is preferably between the values 0.7 x (Fm + Fi) / 2 and 1, 3 (Fm +
FM) / 2 It is also preferable that the stiffness K of the elastic part 60 satisfies the following relationship:

or

represents the natural frequency of the driven part and the elastic part and Nd x max (N1, N2) represents the frequency of the axial stress after the dropout phenomenon, max (N1, N2) designating the larger of the two numbers N1 and N2.

With this value of stiffness, there is better stability and better repeatability of the performance of the invention.

As a numerical example, K = 6.5 N / m M = 0.8g
Nd = 12 turns / s
Fm = 0.2.10-2N
FM = 2.2.10-2N T = 1.1.10-2N
The flexible strip 60 is for example made of beryllium copper.

 It should be noted that the invention is particularly simple in design and implementation with respect to the water meters of the prior art cited in documents DE 32 32 649 and DE 24 55 266.

In addition, the presence of the elastic part in the meter does not generate any vibration phenomenon capable of adversely affecting the proper functioning of the meter.

The water meter can also be of the multiple jet type.

FIG. 2 represents another well-known type of water meter in which the measuring member is a piston referenced 70 which moves inside a measuring chamber 72 in a rotary movement around the pivot 74.

The pivot 74 is arranged in the part forming the bottom of the measurement chamber 72 and is aligned along a longitudinal axis XX '.

A magnetic drive 76 of the repulsion type comprises, on the one hand, a driving part 78 which is subject to the piston 70 by
The intermediary of a so-called central portion of the piston of generally cylindrical shape and called the piston tail 80, and, on the other hand, of a driven part 82 which is connected to a shaft 84.

The driving parts 78 and led 82 of the magnetic drive are located opposite one another and are aligned along the axis
XX '.

The water flow symbolized by the arrow F enters the water meter by the water supply 86, is introduced into the measurement chamber 72 by a first passage 87 and sets in motion the piston 70.

During a complete rotational movement of the piston 70, a predetermined volume of water taken from the flow coming from the inlet 86 is trapped between said piston and the inner wall 72a of the measurement chamber 72 and is discharged towards the water evacuation 88 via a second passage 89.

During this movement, the driving part 78 rotates the driven part 82 of the magnetic drive.

The counter is placed in a position such that the axis XX 'is horizontal.

The inlet 86 and the water outlet 88 have been shown vertically but they could also be horizontal.

In this position, the shaft 84 is moved to the right of the figure and comes into contact with an elastic piece 90 having for example the shape of a flexible strip and which performs the same function as that of the piece 60 described with reference in Figures 1 and la.

Consequently, all that has already been described in relation to these figures and which relates to the problem of detaching the magnetic drive from the counter remains valid and will not be repeated.
The invention also applies to other types of fluid meters and in particular to gas meters.

Claims (15)

1. Fluid meter (10) comprising a measuring member (12) of  volume of fluid passing through said meter and a drive  magnetic repulsion type consisting of a so-called part  lead (26) linked to said measuring member and a so-called part  led (44), both being located opposite one another  and mobile in rotation around an axis XX ', and during a  normal operation, movement of the driving part (26)  driving in rotation the driven part (44), characterized in that  the driven part (44) can move along the axis and, when  said led part does not follow the movement of the part  driving (26), it is subjected to the action of magnetic forces of  variable axial repulsion on the part of the latter which tend  away from it, the driven part (44) being, in this position  distant, subjected to the action of an elastic piece (60) which,  when it deforms, tends to bring said driven part closer to  the driving part, the led part being thus alternately  subjected to efforts of opposite direction until said part  driven acquires the same rotational speed as that of the game  leading. 2. Counter according to claim 1, in which the driven part  (44) is connected to a shaft (52) aligned with the axis XX 'and one of which  end (52b), opposite to that (52a) near which is  locates said driven part, comes into contact with the elastic part  (60). 3. Counter according to claim 2, wherein the end (52b)  in contact with the elastic piece (60) forms a point. 4. Counter according to one of claims 1 to 3, wherein the  taring T of the elastic part (60) is included in the field  Fm + FM  + 30%, where Fm and FM respectively designate the  2  minimum and maximum magnetic repulsion forces. 5. Counter according to one of claims 1 to 4, wherein the  elastic piece (60) has a stiffness K verifying the relationship

 of the two numbers N1 and N2.  leading and led parts and max (N1, N2) denotes the largest  respectively represent the number of dipole magnets  leading part in the absence of elastic part, N1 and N2  which the driven part (44) no longer follows the movement of said  minimum rotation speed of the driving part (26) from  where M represents the mass of the led part, Nd represents the 6. Counter according to one of claims 1 to 5, wherein the  elastic piece (60) is a flexible strip. 7. Counter according to one of claims 1 to 5, wherein the  elastic piece (60) is a spring. 8. Counter according to one of claims 1 to 7, in which a  stop limits the axial movement of the driven part (44). 9. Counter according to claim 8, wherein the displacement  axial of the driven part (44) is greater than 8% of the distance  axial between the driving (26) and driven (44) parts when those  these have the same rotation speed. 10. Counter according to claims 2 and 8, wherein the stop  (56) is integral with the shaft (52) of the driven part (44) and  cooperates with a fixed part (58a) of said counter. 11. Counter according to claim 8, in which the stop is  diametrically opposite to the driven part  (44) relative to the elastic piece (60) in order to limit the  deformation of said elastic piece. 12. Counter according to one of claims 1 to 11, wherein  the measuring member is a turbine (12) whose axis of rotation XX '  coincides with the axis of rotation of the driving parts (26) and  conducted (44). 13. A meter according to claim 12, being of the single jet type. 14. Meter according to claim 12, being of the multiple jet type. 15. Counter according to one of claims 1 to 11, wherein  the measuring member (70) moves inside a  measure (72) following a cyclic movement by trapping a  volume of fluid determined at each cycle.