Abstract:
The invention relates to a valve ( 1 ), comprising a body ( 2 ), within which a needle ( 3 ) moves, which can rest with sealing against a seat ( 23 ), fixed to the body ( 2 ). The needle ( 3 ) is magnetically coupled to an actuator body ( 5 ), across a closed and a magnetic chamber ( 4 ) provided with several magnets ( 52 ) between which magnetic bodies ( 53 ) are interspersed. The needle ( 3 ) has no magnets and is provided with ribs ( 36 ) made from a magnetic material. According to the invention, an improved magnetic coupling may be achieved, whereby the thickness and the relative separation of the ribs ( 36 ) are largely equal to the thickness (e 53 ) and the relative separation (l 52 ) of the magnetic bodies ( 53 ).

Description:
FIELD OF THE INVENTION 
   The invention relates to a magnetic valve and to an installation for projecting coating product, which comprises, inter alia, such a valve. 
   BACKGROUND OF THE INVENTION 
   It is known, for example, from EP-A-0-997-676 or from U.S. Pat. No. 4,940,207, to produce a valve whose needle is actuated by magnetic coupling through a sealed partition, which enables the product passing through the valve to be separated physically from the control means without using a seal susceptible to degradation, in particular owing to wear by abrasion and/or corrosion. In known valves, the needle is equipped with permanent magnets which are to cooperate with permanent magnets carried by an actuating device in order together to constitute magnetic coupling means. The mounting of permanent magnets on the needle is a tricky operation which requires particular care of a kind which substantially increases the cost price of such a valve. The manufacturing and fitting tolerances of permanent magnets are such that the air gap between the needle and the associated actuating device must be relatively large in order to avoid frictional forces incompatible with the correct operation of the valve. This large air gap reduces the efficiency of the magnetic coupling sought. In addition, the magnets mounted on the needle are susceptible to attack by the fluid passing through the valve, and hence there is a risk of deterioration by abrasion and/or corrosion which may result in a decrease in the performance of such a valve. 
   It is those disadvantages which the invention more particularly aims to remedy by proposing a magnetic valve which is more economical and more reliable than the known valves, while its operation is entirely dependable. 
   SUMMARY OF THE INVENTION 
   To that end, the invention relates to a valve comprising a body inside which a needle capable of resting in a sealed manner against a seat fixedly joined to that body is mobile, the needle being coupled magnetically, through a sealed and non-magnetic partition, to an actuating device equipped with several magnets between which magnetic bodies are interposed, characterized in that the needle does not have magnets. 
   Owing to the invention, the material of the needle constitutes the induced poles of a magnetic coupling device whose magnetic bodies form the inducing poles. The manufacturing tolerances of the needle enable a narrower air gap to be used than when magnets are mounted on the needle. Advantageously, the needle is equipped with ribs formed from a magnetic material. The positioning and the geometry of those ribs are preferably adapted as a function of the positioning and the geometry of the polar masses constituted by the magnetic bodies. In particular, the thickness of the ribs may be substantially equal to the thickness of the magnetic bodies. Likewise, the relative spacing of the ribs may be substantially equal or correspond substantially to a multiple or a sub-multiple of the relative spacing of the magnetic bodies. The distribution and the geometry of the ribs of the needle permit a concentration of the magnetic flux at their location, and hence improved magnetic coupling between the needle and the actuating device. 
   According to advantageous aspects, a magnetic valve may comprise one or more of the following features taken in any technically possible combination:
         the needle is covered with a layer of anti-corrosion material;   the ribs are unitary with the body of the needle, which is particularly economical and enables them to be manufactured by machining, with a high degree of precision;   the volume between two adjacent ribs is packed with a non-magnetic filling material, which prevents the accumulation of product passing through the valve, for example a coating product, between two ribs;   the movements of the actuating device can be controlled pneumatically or mechanically;   the sealed partition is cylindrical, the needle being located inside it, while the actuating device is arranged around the partition. By way of variation, the partition may be flat overall while the ribs of the needle and the magnetic bodies or polar mass of the actuating device are provided with means for guiding the needle in translation. Those guide means may include magnetic field concentration regions which are formed opposite one another on the needle and on the actuating device, respectively, by the creation of cavities in the opposing surfaces of those ribs and those bodies;   an element coupled magnetically to the actuating device is located outside the body of the valve and is mobile between two positions in which it indicates the open state and the closed state, respectively, of the valve. In that case, the body may be provided with two marks corresponding to the closed state and to the open state, respectively, of the valve, while the above-mentioned element is capable of masking selectively one of those marks while leaving the other mark visible, or vice versa, as a function of its position as controlled by the movements of the actuating device. It may also be provided that a sensor located outside or inside the valve is capable of detecting the movements of that element and of supplying to a monitoring system a signal representative of the open or closed state of the valve.       

   The invention relates also to an installation for projecting coating product, comprising at least one projector and at least one source of coating product, characterized in that it comprises at least one valve such as described above which is located in the line for supplying coating product or cleaning product to the discharge opening of the above-mentioned projector. 
   Such an installation permits efficient and reliable control over time of the amounts of coating product(s) and/or cleaning product(s) supplied to a projector. In such an installation, a valve according to the invention may also be used as a pressure regulator. 
   According to one advantageous aspect of the invention, the above-mentioned valve may be integrated in the projector with which it is associated, which can be linked with its particularly compact character. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and other advantages thereof will emerge more clearly in the light of the following description of seven embodiments of a magnetic valve according to the principle thereof and of coating product projecting installations comprising such valves, the description being given purely by way of example and with reference to the appended drawings in which: 
       FIG. 1  is a schematic longitudinal section through a valve in the closed configuration, according to a first embodiment of the invention; 
       FIG. 1A  is a view on a larger scale of the detail A in  FIG. 1  when the needle of the valve is in the course of displacement between its closed and open positions; 
       FIG. 2  is an outside view on a smaller scale of the valve of  FIG. 1  on which the sectional plane of  FIG. 1  is marked by the line I-I; 
       FIG. 3  is a partially cut-away perspective view of the valve of  FIGS. 1 ,  1 A and  2 ; 
       FIG. 4  is a section analogous to  FIG. 1  when the valve is in the open configuration; 
       FIG. 5  is an outside view similar to  FIG. 2 , the valve being in the configuration of  FIG. 4 ; 
       FIG. 6  is a schematic longitudinal section through a valve according to a second embodiment of the invention; 
       FIG. 7  is a section taken on the line VII-VII in  FIG. 6 ; 
       FIG. 8  is a schematic diagrammatic representation of a manual gun which projects coating product and which is equipped with a valve according to the invention; 
       FIG. 9  is a view similar to  FIG. 8  for a gun equipped with a valve according to another embodiment of the invention; 
       FIG. 10  is a schematic diagrammatic section through a valve according to the invention used as a connection having a controlled needle; 
       FIG. 11  is a schematic diagrammatic section through a valve according to the invention used as a tap; 
       FIG. 12  is a section similar to  FIG. 11  for another valve also used as a tap; 
       FIG. 13  is a schematic diagrammatic representation of an installation for projecting coating product incorporating a valve according to the invention and 
       FIG. 14  is a view similar to  FIG. 13  for another installation according to the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The valve  1  shown in  FIGS. 1 to 5  comprises a two-part body  2  formed by a base  21  and a cover  22  which are screwed one to the other. The base  21  defines the seat  23  of the valve  1 , against which seat rests a head  31  supported by the main body  32  of a mobile needle  3 . In practice, the head  31  is screwed to the end of an axial rod  33  which is unitary with the body  32 . 
   The body  32  is provided with a central drilled bore  34  from which diverge four ducts  35  which connect the drilled bore  34  to a volume V located around the rod  33  and the head  31  inside the cylindrical volume which has a circular base and which is defined by a sealed and non-magnetic partition  4 . 
   The cross-section of the needle  3  is such that it can slide in the volume defined by the partition  4 , being guided in translation. The central axis which is common to the elements  3  and  4  and which corresponds to the sliding direction of the needle  3  is marked X-X′. 
   An actuating device  5  is located inside the body  2  and around the partition  4 . This device  5  comprises a body  51  in which are mounted several permanent magnets  52 , between which magnetic bodies  53  constituting the polar masses of the magnets  52  are located. The magnets  52  are annular and are arranged around the partition  4  which they therefore surround, their respective polarities being reversed in pairs as can be seen from the marking of their South and North poles on the right in  FIG. 1 . The bodies  53  are also annular. In practice, they may be steel washers. 
   Polar masses  53  are also provided on each side of the stack of magnets carried by the device  5 . 
   Protective packings  54  are located between the magnets  52  and the partition  4  in order to protect the magnets against the risk of wear by abrasion. 
   The width of a magnet  52  taken parallel with the axis X-X′ is marked l 52 . The thickness of a body  53  measured parallel with the axis X-X′ is marked e 53 . 
   The device  5  is also provided with a lip seal  56  configured to rest against the external surface  41  of the partition  4 . A second lip seal  57  is also mounted on the body  51  of the device  5  and rests against the internal surface  24  of the cover  22 . 
   In addition, the body  51  is provided with an external radial collar  58  on which rests a spring  6  which exerts on the collar  58  a resilient force F 1  directed towards the base  21 . 
   This base is provided with two openings  25  which may each be connected to a duct  7  for the admission of control air, as shown by the arrows F 2 . The air penetrating into the body  2  through the openings  25  enables the device  5  to be pushed back against the force F 1 . In other words, the position of the device  5  along the axis X-X′ can be controlled pneumatically by the supply of air from the duct  7 . 
   This controlled displacement of the device  5  is used to control the displacement of the needle  3  and, more particularly, of its head  31  relative to the seat  23  of the body  2 . 
   In order to do this, the body  32  of the needle  3  is provided with ribs  36  which are unitary with the body  32  and which are advantageously produced by machining its external radial surface. The ribs  36  are separated from one another by a distance d which is substantially equal to the width l 52  of the magnets  52 . Furthermore, each rib  36  has a thickness e 36 , taken parallel with the axis X-X′, which is substantially equal to the thickness e 53  of the bodies  53 . 
   Thus, and as shown partially in  FIG. 1A , the ribs  36  can be simultaneously aligned with the bodies  53  of the device  5 . They constitute the induced poles of the polar masses  53 . 
   As shown in  FIG. 1A  which corresponds to the configuration when the needle  3  follows a displacement imposed by the device  5  and when the alignment of the elements  36  and  53  is not prevented by the head  31  resting on the seat  23 , the magnetic field lines L created by the magnets  52  pass through the elements  53  and  36 , which corresponds to a position of equilibrium of the magnetic forces. 
   When the device  5  is moved away from the base  21  under the effect of a supply of air to the body  2  through the openings  25 , the bodies  53  move upwards in  FIG. 1 , so that the magnetic force generated on the ribs  36  displaces the body  32  in the same direction to reach the position represented in  FIG. 4  where the needle  3  rests against a portion  26  of the cover  22  which penetrates into the interior volume defined by the partition  4 . Thus, in that position, the needle is stable because it abuts the portion  26 , unlike the needle of the valve known from EP-A-0 997 676. 
   In the configuration of  FIG. 4 , the bodies  53  and the ribs  36  are not aligned because the device  5  has travelled further relative to the displacement of the needle  3 . 
   Likewise, in the configuration of  FIG. 1 , the travel of the needle  3  is limited by the head  31  resting against the seat  23 , while the travel of the device  5  can continue under the effect of the resilient force F 1 , in which case the elements  53  and  36  are not aligned. 
   Packing rings  37  are arranged around the body  32  in the grooves separating two adjacent ribs  36 , these rings being produced from a non-magnetic material which may be selected as a function of its coefficient of friction on the internal surface  42  of the partition  4 . 
   Since the ribs  36  are formed by machining, their geometry may be defined with a very high degree of precision, so that the manufacturing tolerances of the needle  3  may be low, which means that it is possible for there to be a narrow air gap between the elements  53  and  36  and hence efficient magnetic coupling between the device  5  and the needle  3 . 
   In order to avoid the risk of the ribs  36  being oxidized, the needle  3  is coated, at least at its ribs, with a layer of anti-corrosion material, such as electrolytically deposited chromium. 
   Since the needle  3  does not have a magnet, the magnets of the valve  1  are not at risk of being soiled by the product passing through the valve, even if this product were to spread into the gap between the external radial surface of the needle  3  and the surface  42 . The magnets  52  are protected from the products passing through the valve  1  owing to the partition  4 . 
   It will be appreciated that it is not necessary to provide a spring in a region susceptible to attack by the product passing through the valve, such a product possibly being corrosive or chemically aggressive. 
   A control ring  8  produced from a magnetic material is mounted outside the cover  22 , being able to slide around the cover parallel with the axis X-X′. Magnetic coupling is obtained, through the cover  22  which is non-magnetic, between the device  5  and the ring  8 . The geometry of the collar  58  associated with a second collar  59  may be selected to promote this coupling. Thus, the ring  8  can slide around the body  2  as a function of the position of the device  5 . Two inscriptions  81  and  82  are provided respectively on the outside of the cover  22  and are provided in order to be selectively masked by the ring  8 . To be more precise, the ring  8  masks the inscription  82  which signifies “open” when the valve is closed, as shown in  FIG. 2 . The inscription  81  which signifies “closed” is then visible. A person looking at the valve  1  can thus read the inscription  81  and know that this valve is closed. 
   Conversely, in the configuration of  FIGS. 4 and 5 , the ring  8  masks the inscription  81  and leaves the inscription  82  visible, in which case a person looking at the valve  1  knows that it is in an open configuration. 
   According to a variant of the invention which is not shown, the movements of the ring  8  can be detected by a sensor of any known type, the sensor enabling a signal which is a function of the open or closed state of the valve to be delivered to a monitor. The sensor may be, for example, inductive, electrical, optical or pneumatic. 
   The partition  4  may have a base other than a circular base, in which case the geometry of the moving parts is adapted. 
   In the configuration of  FIGS. 4 and 5 , the arrows E represent the flow of a product such as a coating product through the valve  1 . 
   In the second embodiment of the invention shown in  FIGS. 6 and 7 , the elements analogous to those of the first embodiment bear identical references increased by  100 . The valve  101  of this embodiment comprises a body  102  whose internal volume is separated into two portions by a sealed partition  104  which is flat overall and non-magnetic. A needle  103  is located in the body  102 , on one side of the partition  104 , inside a volume V connected by an opening  127  to a coating product supply. The needle  103  carries a head  131  which is to rest selectively against a seat  123  formed by the body  102 . 
   An actuating device  105  is provided in the body  102 , on the other side of the partition  104  relative to the needle  103 , and is subjected to the action of a spring  106  and a source of control air  107 . The arrow E in  FIG. 6  represents the flow path of a coating product when the valve is open. 
   As above, the device  105  carries magnets  152  between which magnetic bodies  153  are located. The main body  132  of the needle  103  is for its part provided with ribs  136  which are unitary with the body and have a thickness and spacing substantially equal to the thickness and spacing of the magnetic bodies  153 . 
   Packing strips  137  are provided between the ribs  136 , and likewise packing strips  154  are provided between the bodies  53 , the strips  154  covering magnets  152 . 
   As emerges more especially from  FIG. 7 , cavities  136   c  are provided in the ribs  136 , while cavities  153   c  of a corresponding shape are provided in the bodies  153 . These cavities enable the magnetic field lines L to be concentrated around them, which enables the needle  103  to be brought back into alignment relative to the device  105 . In other words, the edge effects of the magnetic field are used to guide the needle  103  in translation. 
   By way of variation, the guiding of the needle  103  in translation can be obtained by relief portions, in particular grooves or ribs provided longitudinally on the partition  104  and/or on the internal surface of the body  102 . 
   As can be seen from  FIG. 8 , a valve  201  according to the invention can be integrated in a gun P for projecting coating product. In that case, it is a valve whose needle  203  is substantially circular and located inside a volume defined by a sealed and non-magnetic partition  204  around which an actuating device  205  is arranged. 
   As shown in  FIG. 9 , a gun P may also comprise a valve  301  of the same type as that described with reference to  FIGS. 6 and 7 , with a sealed, non-magnetic and flat partition  304 . 
   In the two cases of  FIGS. 8 and 9 , the trigger G of the gun P is connected mechanically to the actuating device  205  or  305  of the valve  201  or  301 , which enables the associated movements of the needle  203  or  303 , and the supply to the discharge openings O of the guns P to be controlled. As above, the needles  203  and  303  do not have magnets and are provided with ribs  236  and  336  whose geometry and position enable them to constitute the induced poles of a set of magnets  252  and  352  and of polar masses  253  and  353 . 
   As shown in  FIG. 10 , a valve  401  according to the invention can be used as a connection having a needle controlled by an external source  407 . 
     FIG. 11  shows a valve  501  according to the invention which is to be supplied by way of an opening  527  which is formed in its casing  502  and the outlet of which forms a seat  523  acting as a rest for a head  531  carried by a needle  503  provided with ribs  536  which are to participate in the magnetic coupling of the needle  503 , through a sealed and non-magnetic partition  504 , to an actuating device  505  provided with magnets  552  between which magnetic bodies  553  forming polar masses for the magnets  552  are located. 
   The position of the device  505  is controlled by screwing in or unscrewing the device  505  inside the casing  502 , which is shown by the arrow R. This screwing-in or unscrewing movement enables the device  505  to be displaced parallel with a central axis X-X′ of the valve  501  and the needle  503  and its head  531  to be displaced in corresponding translation. It is thus possible to free the passage for the flow of coating product between the opening  527  and a discharge opening  528  of the valve. 
   The valve  501  may here be regarded as a tap. 
   A ring  508  of the same-type as the ring  8  of the first embodiment can be mounted outside the casing  502  and coupled magnetically to the device  505  in order to indicate the position of the device  505  and the needle  503 . The ring  508  is mobile between two end positions and can take up various intermediate positions as a function of the degree of opening of the valve  501 . A graduation may be provided on the casing  502  in order to facilitate the noting of the position of the ring  508 . 
   The valve  601  represented in  FIG. 12  may also be regarded as a tap, of which the needle  603 , the sealed partition  604  and the actuating device  605  are similar to those shown in  FIGS. 6 and 7 . In this embodiment, the device  605  is fixedly joined to a push-button  609  on which a user can exert a force F 3  which permits the displacement of the push-button  605  and the needle  603  against a return force generated by a spring  606 . The valve  605  is a tap which can be operated simply by pressing. 
   As shown in  FIG. 13 , a valve  701  according to the second embodiment described above may be integrated in a line  1001  for the supply of coating product to a coating product projector P which may be of any known type, electrostatic or non-electrostatic, manual or automatic. A flow or pressure sensor  1002  is connected to a regulating unit  1003  which controls a source  1007  for the supply of compressed air to the valve  701 . 
   As shown in  FIG. 14 , a valve  801  according to the first embodiment may also be used in an installation comprising a line  1001 , a sensor  1002 , a regulating unit  1003  and a source  1007  of pressurized air. 
   The invention has been represented with magnetic valves of the two-way type. It is, however, applicable to three-way valves by making modifications that are within the competence of the person skilled in the art. 
   The invention is independent of the exact number of magnets carried by the actuating device. In fact, that number is chosen as a function of the intensity of the coupling force sought. 
   In addition, according to a variant of the invention which is not shown, the relative spacing d of the ribs  36  and the like may be selected to be equal to a sub-multiple of the width l 52  of the magnets  52 . In that case, alignment of some ribs  36  or the like with the other bodies  53  and the like remains possible, some other ribs  36  then being opposite the magnets  52 . These other ribs  36  are then not functional for the magnetic coupling sought. This applies to all of the embodiments envisaged. 
   According to another variant of the invention which is not shown, the spacing d may be equal to a multiple of the width l 52 , that is to say, of the spacing between the bodies  53 . In that case, some bodies  53  are opposite a ring  37 . This may be applied to all of the embodiments envisaged. 
   The technical features of the various embodiments described above may be combined with one another within the scope of the present invention.