Patent Publication Number: US-10315207-B2

Title: Pneumatic spraying assembly, restrictor for such an assembly and installation for projecting a coating product comprising such an assembly or such a restrictor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 USC § 119 of French Patent Application No. 16 606899 filed on Nov. 4, 2016. 
     FIELD OF THE INVENTION 
     The invention relates to a pneumatic spraying assembly for spraying a coating product intended to be used in a coating product spraying installation, as well as a restrictor forming a spare part for such an assembly and a coating product spraying installation comprising such a sprayer and/or such a restrictor. 
     BACKGROUND OF THE INVENTION 
     In an installation for spraying a coating product, it is known to supply one or several manual or automatic sprayers with a pressurized coating product, as well as with air for spraying this coating product. To that end, it is known to use a pump capable of delivering both pressurized air and pressurized coating product. In some cases, there may be several sprayers. In this case, each sprayer can be supplied by a hose with a different length and/or diameter. In this type of installation, in order to have the same flow rate for each sprayer, pressure regulators are mounted on the pump or the part of the pump that delivers the pressurized coating product. The regulators are used to avoid or limit pressure fluctuations in a hose supplying the sprayer with coating product and to adjust the pressures in each hose independently, in order to obtain an iso-pressure at each sprayer. 
     Some coating products, like those used to apply a color on wood, are very liquid, i.e., have a particularly low viscosity, close to that of water. To apply such coating products, the supply pressure of the spraying area of a sprayer must be low, in particular below 0.5 bars. Under these conditions, a volume provided inside the body of a sprayer to supply this spraying area most in turn be at a low pressure. This involves supplying the sprayer with a low-pressure coating product, which causes the regulator to operate outside its nominal pressure range, to the point that it is no longer effective and no longer makes it possible to hide travel inversions of the pump. This results in pressure fluctuations in the supply hose of the sprayer, which leads to an irregular application of the coating product. 
     SUMMARY OF THE DESCRIPTION 
     The invention more particularly aims to resolve these drawbacks by proposing a new pneumatic spraying assembly for a coating product that makes it possible to supply a spraying area with a low-pressure coating product, without any risk of causing a pressure limiter to operate outside its operating range. 
     To that end, the invention relates to a pneumatic spraying assembly for a coating product, comprising a pneumatic sprayer for spraying the coating product and a supply line for supplying this pneumatic sprayer from a pressurized coating product source to which the supply line is connected by its upstream end, the pneumatic sprayer comprising a sprayer body and a control valve for controlling flow of the coating product toward a spraying area for this product, this valve comprising a needle selectively closing off an outlet orifice of an inner volume of the sprayer body and the spraying assembly defining a flow path for the coating product, from the upstream end of the supply line to the outlet of the inner volume. According to the invention, a restrictor for restricting flow of the coating product is mounted on the flow path to create a pressure loss upstream from the outlet orifice. 
     Owing to the invention, the pressure loss created by the restrictor upstream from the sprayer makes it possible to keep a relatively high pressure in the upstream part of the supply line of the coating product sprayer, while the pressure in the inner volume of the body of the sprayer can be low enough, in particular below 0.7 bars, to allow a low-pressure supply of the spraying area. Thus, a pressure regulator arranged at the outlet of a supply pump of the sprayer can be implemented in its nominal operating pressure range, such that it remains effective, even when the pressure of the sprayed coating product is low. 
     In the present description and in the attached claims, the pressures indicated are relative and dynamic pressures, i.e., measured when the coating product circulates in the supply pipes and volume of the spraying area. 
     According to advantageous but optional aspects of the invention, such an assembly may incorporate one or more of the following features, considered in any technically allowable combination:
         The restrictor is mounted in the inner volume of the body of the sprayer.   The restrictor divides the inner volume into two chambers and connects these two chambers by at least one calibrated pipe.   The flow path includes a connecting member for connecting the supply line on the sprayer body and the restrictor is mounted in the connecting member.   The connecting member is configured so as, in the absence of the restrictor, to cooperate with a mechanism arranged at an outlet of the supply line in order to connect the pneumatic sprayer to the supply line, while the connecting member is configured also to cooperate with this mechanism when the restrictor is mounted in an intake coupling for the coating product.   The restrictor has a mouth with the same geometry as the geometry of a mouth of the connecting member.   The restrictor is made from a material more flexible than the material of the connecting member, in particular a synthetic material, which favors sealing.   The restrictor is mounted reversibly in the inner volume of the body of the sprayer or in the connecting member.       

     According to another aspect, the invention relates to a restrictor forming a spare part for an assembly as described above. This restrictor is formed by a part that defines at least one calibrated pipe for flow of a coating product, having a length comprised between 1 and 25 mm, preferably between 8 and 15 mm, still more preferably about 10 mm, and having a maximum transverse dimension less than 2 mm, preferably comprised between 0.5 and 1.8 mm. 
     It is possible to provide that an end of the restrictor, which defines a mouth thereof, has frustoconical outer and inner shapes with apical angles having the same value. This allows the restrictor to be placed in a traditional coupling member of the sprayer with the supply line. 
     According to still another aspect, the invention relates to an installation for spraying coating product, that comprises at least one reservoir for the coating product, at least one pneumatic sprayer for the coating product, a supply pump for supplying the at least one sprayer with the coating product from the at least one reservoir, as well as a supply line for supplying the at least one pneumatic sprayer from the supply pump. According to the invention, the pneumatic sprayer and the supply line form an assembly as described above and/or comprise a restrictor as described above. 
     Owing to the invention, the restrictor makes it possible to create a controlled pressure loss and to obtain, within the installation, the same pressure in each sprayer, while using a single pressure regulator, even in the case where there are several sprayers connected on the same outlet of the regulator. 
     Advantageously, the supply pump is equipped, at its outlet, with a pressure regulator adjusted to deliver the coating product to a supply line of the coating product sprayer, under a pressure comprised between 0.5 and 3 bars, while the restrictor is configured to deliver the coating product to the outlet orifice of the inner volume of the body of the sprayer under a pressure below 1 bar, preferably between 0.3 and 0.7 bars. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood, and other advantages thereof will appear more clearly, in light of the following description of two embodiments of a spraying assembly, a restrictor and an installation for spraying coating product according to its principle, provided solely as an example and done in reference to the appended drawings, in which: 
         FIG. 1  is a schematic perspective illustration of an installation for spraying coating product according to the invention; 
         FIG. 2  is a longitudinal sectional view of the front part of a sprayer belonging to a spraying assembly according to the invention belonging to the installation of  FIG. 1 ; 
         FIG. 3  is a side view of a restrictor intended to be used with the sprayer of  FIG. 2 ; 
         FIG. 4  is a sectional view along line IV-IV in  FIG. 3 ; 
         FIG. 5  is a sectional view similar to  FIG. 2 , when the sprayer is equipped with the restrictor of  FIGS. 3 and 4 ; 
         FIG. 6  is a sectional view similar to  FIGS. 2 and 5 , when the sprayer equipped with the restrictor is connected to a coating product supply hose; and 
         FIG. 7  is a sectional view similar to  FIG. 2  for a sprayer belonging to a spraying assembly according to a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The installation  2  shown in  FIG. 1  is intended to coat objects O, such as wood panels transported by a conveyor  4 , with a liquid coating product stored in a reservoir  6 . 
     To that end, the installation  2  comprises a sprayer  8 , which here is formed by a pneumatic gun, of the “Airspray” type, intended to be manipulated by an operator. 
     In an alternative that is not shown, the sprayer  8  is a sprayer of the automatic pneumatic Airspray type intended to be mounted on a support, optionally mobile, and controlled by an automaton. 
     The installation  2  also comprises a pump  10  connected to the reservoir  6  by a suction tube  12 . The pump  10  is also connected to the sprayer  8  by a supply line  14  supplying the sprayer with pressurized coating product. A pressure regulator  16  is mounted at the outlet of the pump  10 , on the side of the line  14 , and makes it possible to regulate the pressure of the coating product circulating in this line, based on a setpoint value adjusted using a button  18 . Reference  141  denotes the upstream end of the line  14  by which this line is connected on the regulator  16 . 
     The pump  10  delivers the coating product under a pressure comprised between 2 and 40 bars. The pressure regulator is built such that the setpoint value is comprised between 0.5 and 3 bars. In other words, the pressure regulated in the hose  14  may normally be adjusted between 0.3 and 3 bars. 
     Furthermore, the pump  10  is connected to an air source  20  that may be a compressed air source. An air suction tube  22  connects the source  20  to the pump  10 . 
     A supply line  24  supplying the sprayer  8  with air connects the pump  10  to the sprayer  8 . A regulator  26  is mounted at the outlet of the pump  10 , at the beginning of the line  24 , and makes it possible to adjust the air pressure in this hose  24  using a control button  28 . 
     In practice, in the illustrated case of the gun-type sprayer  8 , the lines  14  and  24  can be formed by flexible hoses. 
     As in particular shown in  FIG. 2 , the sprayer  8  comprises a body  82  on which a head or cap  84  immobilized by a nut  86  is mounted, with interposed sealing gaskets  88  and  90 . 
     In the example, the head  84  is intended to deliver a flat jet and to that end comprises two horns, only one of which is visible in  FIG. 2  with references  842 . The head is provided with air circulation channels coming from the hose  24 . Some of these channels are visible in  FIG. 2  with reference  844 . 
     The body  82  is in turn provided with air circulation channels  824  from a connecting zone of the hose  24  on the body  82  and up to the inside of the head  84 . Only one of these channels is visible in  FIG. 2 , having specified that the number and depiction of the channels  824  and  844  are not limiting, nor is their number. 
     Furthermore, the sprayer  8  comprises a valve  92  that makes it possible to control the coating product outlet using a trigger  94 . The valve comprises a needle  96  and a nozzle  98  that defines a seat  981  on which the needle  96  bears in the closed configuration of the valve  92  shown in  FIGS. 2, 5 and 6 . 
     The nozzle  98  cooperates with a sleeve  100  arranged inside the body  2  to define an inner volume V 82  of the body  82 , which is intended to receive the coating product flowing toward an outlet orifice  982  of the nozzle  98 . Downstream from this outlet orifice  982 , a spraying area Z 8  of the sprayer  8  is formed in which the coating product leaving the volume V 82  through the orifice  982  is sprayed by air coming from the channels  844  and shaped by the air coming from the channels arranged in the horns  842 . 
     A connecting member  102  is mounted on the body  82  such that its inner volume V 102  is in communication with the volume  82 . In the example, the member  102  is screwed on the body  82 . This connecting member  102  is intended to be coupled to the downstream end  142  of the supply pipe  14 . It thus constitutes part of an intake coupling for the coating product in the body  82 , more particularly in the volume V 82 . The member  102  is sometimes called “intake coupling”. 
     The connecting member  102  is equipped with an outer thread  104  intended to cooperate with a nut  106  mounted freely rotating around a coupling element  108  provided with a crenulated rod introduced and immobilized by shape cooperation in the downstream end  142  of the supply pipe  14 . The elements  108  and  110  are visible in  FIG. 6 . 
     The connecting member  102  is provided with a frustoconical mouth  112  converging toward the body  82 . Furthermore, the coupling element  108  is provided with a front surface  114 , also frustoconical and with a geometry complementary to that of the mouth  112 . 
     It is thus possible to fluidly connect the member  102  and the element  108  by causing the surface  114  to bear on the mouth  112  and by screwing the nut  106  on the thread  104 . This configuration is not shown in the figures, but can be deduced from the geometry of the parts  102 ,  106  and  108 . The member  102  and the element  108  therefore form two parts of a supply coupling supplying the sprayer  8  with coating product. 
     A flow path C for pressurized coating product is defined between the end  141  of the line  14  and the orifice  982 . This flow path C comprises the inner volume of the hose forming the supply line  14 , the inner volume V 102  of the member  102  and the inner volume V 82 . 
     According to the invention, a restrictor  120  is mounted in the volume V 102 , i.e., within the flow path C, in order to create a pressure loss on the path of the coating product, upstream from the volume V 82 . 
     The restrictor  120  is in a single piece and has a circular section. Its outer surface  122  is complementary to the inner surface  103  of the member  102 , which also has a circular section. References X 102  and X 120  respectively denote longitudinal and central axes of the parts  102  and  120 . The outer surface  122  comprises a frustoconical section  122   a  with a shape complementary to the mouth  112 . In particular, the apical angle a 122  of the section  122   a  is the same as the apical angle a 112  of the mouth  112 . This allows surface bearing of the section  122   a  on the mouth  112 . 
     The restrictor  120  comprises a downstream end  124  that has the smallest outer diameter of the restrictor  120  and that is intended to be engaged up to the bottom of the volume V 102  toward the volume V 82 . The end surface  124   a  of the end  124  is in the form of an annular disc centered on the axis X 120  of the restrictor  120  and pierced with an orifice  126  that constitutes the outlet of a calibrated pipe  128  with a circular section arranged in the restrictor  120  and centered on the axis X 120 . The surface  124   a  participates in limiting the volume V 82 . 
     Reference  130  denotes the upstream end of the restrictor  120 , opposite the downstream end  124  and which defines a mouth  132  of this restrictor. This mouth has a frustoconical shape. Reference a 132  denotes its apical angle. The angles a 122  and a 132  have the same value. In other words, the upstream end  130  of the restrictor  120  has frustoconical outer and inner shapes, with a constant thickness over its length except at an end collar  134  that protrudes from the volume V 102  in the configuration of the restrictor  120  mounted in the connecting body  102 , as shown in  FIG. 5 . 
     In practice, the angles a 112 , a 122  and a 130  can have a value comprised between 45° and 70°, preferably equal to 60°. 
     Between the mouth  132  and the pipe  128 , along the axis X 120 , the restrictor  120  defines an inner volume V 120 , the diameter of which is denoted d 120 . This volume V 120  forms a passage chamber for the coating product between the mouth  132  and the calibrated pipe  128 . 
     Reference L 128  denotes the length of the pipe  128  measured parallel to the axis X 120 . Reference d 128  denotes the diameter of this pipe. 
     These dimensions L 128  and d 128  are selected so as to create a significant pressure loss during the passage of the coating product from the volume V 120  toward the volume V 82 . 
     In practice, the length L 128  is chosen between 1 and 25 mm, preferably between 8 and 15 mm, still more preferably about 10 mm, while the diameter d 128  is chosen to be less than 2 mm, preferably between 0.5 and 1.8 mm. The diameter d 128  is strictly smaller than the diameter d 120  and the inner surface  123  of the restrictor  120  comprises a frustoconical section  123   b  converging toward the mouth  127  of the calibrated pipe  128 . 
     In the example, the frustoconical section  123 B results in the cross-section of the flow path gradually decreasing between that of the hose forming the line  14 , which is substantially equal to that of the inner volume V 120 , and that of the calibrated pipe  128 . This avoids creating nooks where the coating product may become blocked. 
     Alternatively, the pipe  128  does not have a circular section. In this case, its maximum transverse dimension is selected as being smaller than 2 mm, preferably comprised between 0.5 and 1.8 mm. In the case of a pipe with a circular section, its maximum transverse dimension is equal to the diameter d 128  of this pipe  128 . 
     To install the restrictor  120  in the intake coupling  102 , it suffices to align the axes X 120  and X 102  of the volume V 102  and to push the restrictor  120  toward the volume V 82  in a direction pushing into the inside of the coupling  102 , shown by arrow F 1  in  FIG. 5 , until causing a second frustoconical section  122   b  of the surface  122  and the section  122   a  respectively to engage in surface bearing on a frustoconical section  102   b  of the inner surface of the coupling  102  and against the mouth  112 . 
     The apical half angles β 102  and β 122  of the surfaces  102   b  and  122   b  are equal, with a value comprised between 15° and 30°, preferably equal to 20°. 
     In practice, the restrictor  120  is done by molding, machining or 3D printing of a synthetic material more flexible than the material making up the coupling  102 . For example, the coupling  102  can be made from steel or brass, while the restrictor  102  is made from elastomer. This allows the restrictor  120  to adapt to the inner shape of the connecting member  102  and to ensure the sealing between the parts  102  and  120 . 
     Alternatively, the restrictor  120  can be made from a metal, for example bronze. 
     At the end of the insertion of the restrictor  120  into the connecting member  102 , the sprayer is in the configuration of  FIG. 5 , where the outer surface  122  of the restrictor substantially marries the inner shape of the coupling  102 , while the collar  134  protrudes from the volume V 102 . 
     It is then possible to connect the hose  14  on the sprayer  8  by introducing the front surface  114  of the coupling element  108  into the mouth  132  of the restrictor  120 , then screwing the nut  106  on the thread  104  of the connecting member  102 . This results in compressing the upstream end  130  of the restrictor  120  between the mouth  112  and the surface  114 , which ensures good sealing at the interface between the member  102  and the element  108 . In this case, the engagement length between the inner tapping of the nut  106  and the thread  104  is shorter than the engagement length between this tapping and this thread without the restrictor  120 . 
     Thus, the member  102  is configured to cooperate with the elements  106  and  108  both with the restrictor  120  being absent, and with the restrictor  120  being present in the volume V 102 . 
     In the configuration of  FIG. 6 , the pressure in the hose  14  and up to inside the volume V 120  is substantially equal to the pressure P 16  regulated by the regulator  16 , while considering the pressure losses in the supply line  14  to be negligible. 
     The pressure P 82  in the volume  82  can be significantly lower than the pressure P 16  because a significant pressure loss is created by the restriction formed by the calibrated pipe  128 . 
     In practice, the diameter d 128  of the pipe  128  can be chosen to be equal to 0.8 mm, 0.9 mm, 1 mm, 1.2 mm, 1.4 mm or 1.8 mm, which makes it possible to adapt the pressure P 82  to the nature of the coating product that must be sprayed, in particular to its viscosity. 
     The use of the restrictor  120  makes it possible for the pressure P 82  to be less than 1 bar, for example between 0.3 and 0.7 bars, while the pressure P 16  is comprised between 0.5 and 3 bars. 
     In practice, the restrictor  120  makes up a wearing part that can be mounted reversibly and without tools inside the connecting member  102  and that avoids retention areas for coating product contained in its inner shape, in particular due to the gradual decrease in the passage section due to the frustoconical surface  123   b . No tool is necessary to install the restrictor  120  in the coupling  102  by pushing it in the direction of the arrow F 1 . A traditional key is sufficient to tighten the nut  106  on the connecting member  102 . When the restrictor  120  must be disassembled, it suffices to loosen the nut  106  with a key, then to pull on the collar  134  parallel to the axis X 102 , in a separating direction relative to the body  82  opposite that of the arrow F 1 . It is therefore easy to adapt the pressure loss created by the restrictor  120 , i.e., the pressure P 82  within the volume V 82 , by installing a restrictor  120  in the volume V 102 , the pipe  128  of said restrictor having a suitable length and maximum transverse direction. 
     According to one alternative of the invention that is not shown, the connecting member  102  can form a single piece with the body  82  or be fastened thereon in a manner other than by screwing. 
     In the second embodiment of the invention shown in  FIG. 7 , the elements similar to those of the first embodiment bear the same references. Hereinafter, we only describe what distinguishes this embodiment from the previous one. 
     In this embodiment, the restrictor  120  is mounted not in the connecting member  102 , but inside the volume V 82 , i.e., within the body  82 . More specifically, the restrictor  120  divides the volume V 82  into an upstream chamber C 82   a  and a downstream chamber C 82   b . The needle  96  traverses a central bore  121  of the restrictor  120 , most of the volume of which it occupies. More specifically, the diameter d 121  of the bore  120  is slightly larger than the diameter d 96  of the needle  96 , for example by 5 to 10%, such that a calibrated annular pipe  128 , the thickness of which measured radially to a longitudinal axis X 96  of the needle  96  is denoted e 128 , is formed around the needle  96  and inside the restrictor  120 . 
     Reference L 128  also denotes the length of this calibrated pipe  128 . 
     As before, the length L 128  and the radial thickness e 128  are chosen to create a pressure loss on the flow path C of the coating product. This flow path C extends from the upstream end of a supply line  14 , defined as in the first embodiment, to the outlet orifice  982  of the nozzle  98 , this flow path comprising a hose making up the line  14 , the inner volume V 102  of the member  102 , the chamber C 82   a , the pipe  128  and the chamber C 82   b.    
     In practice, the length L 128  is chosen between 1 and 25 mm, preferably between 8 and 15 mm, still more preferably about 10 mm, while the radial thickness e 128  is chosen to be less than 2 mm, preferably between 0.5 and 1.8 mm. 
     According to one alternative of the invention that is not shown, one or several longitudinal pipes parallel to the axis X 96  can be pierced in the material of the restrictor  120 , to increase the passage section between the chambers C 82   a  and C 82   b . These pipes can be used in addition to or in place of the pipe  128  that surrounds the needle  96 . 
     According to another embodiment of the invention that is not shown, the restrictor  120  can be integrated within the hose making up the supply line  14 . 
     However, this restrictor is preferably integrated into the flow path for the coating product in an area close to the outlet orifice  982 , i.e., as close as possible to the downstream end  142  of the line  14  or within the sprayer  8 , as in the two embodiments shown in the figures. 
     Irrespective of the embodiment, the installation of the restrictor  120  in the connecting member  102 , in the body  82  or elsewhere in the flow path C of the sprayer  8  therefore makes it possible to maintain a relatively high pressure P 16  in an upstream part of the hose that forms the pipe  14 , while the pressure P 82  of the coating product at the outlet of the volume V 82  and the pressure of this product in the spraying area Z 8  are low and adapted to the viscosity of the sprayed coating product. 
     This allows the supply of several sprayers  8  from a same pump  10  and under a same pressure, which proves quite advantageous in practice, simultaneously in terms of bulk, cost and maintenance. 
     According to one alternative of the invention that is not shown, the latter may be implemented with an electrostatic sprayer. 
     The embodiments and alternatives considered above can be combined to provide new embodiments of the invention.