JP5294122B2 - Tube painting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the efficiency of coating work of a part having ruggedness such as an inner surface of a socket or an outer surface of an inserting opening of a tubular body. <P>SOLUTION: In the method of coating the tubular body p having the socket 3 in one end and the inserting opening 2 in the other end, powder electrostatic coating is applied onto the inner surface 3a of the socket 3 by arranging a nozzle 10 for coating in the socket 3, moving the nozzle 10 back and forth from a tube end part 3b of the socket 3 side to the deep part 3c of the socket 3 while rotating the tubular body p around the tube axis and discharging electrified powder paint from the nozzle 10 during the back and forth movement from the tube end part 3b to the deep part 3c. In the powder coating, the so-called electrostatic powder coating is applied and a coating surface having a uniform film thick free from unevenness is formed by moving the nozzle 10 back and forth from the tube end part 3b of the socket 3 side to the deep part 3c of the socket 3. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a coating method performed on a pipe used for forming various pipes such as water pipes.

  In general, pipes forming pipes for water supply, gas, and other uses are coated and coated with various materials and various methods for the purpose of corrosion prevention.

For example, in the case of a ductile cast iron pipe for water supply buried in the ground, an anticorrosion coating is applied to the outer surface of the pipe body in order to prevent corrosion due to surrounding soil and moisture.
In addition, mortar lining or powder coating (for example, epoxy resin powder coating) may be applied to the inner surface of the tube body in order to prevent corrosion caused by water passing through the tube. Many.

  As shown in FIG. 3, a duct body of a ductile cast iron pipe generally has a straight pipe portion 4 having a constant pipe diameter in the pipe axis direction, one end in the pipe axis direction being the insertion port 2, and the other end being adjacent to the tube section p. It is the receiving port 3 which can receive the insertion port 2 of the other tubular body p which fits inside.

  In this tubular body p, the tube inner surface 3a has a lot of irregularities in the portion of the coating area on the tube inner surface close to the receiving port 3. This unevenness corresponds to the shape of the packing, lock ring or the like used when receiving the insertion opening 2 of the adjacent tubular body p, or the outer shape of the insertion opening 2 itself.

  The inner surface of the receiving port 3 is generally coated with a solvent-based paint (hereinafter referred to as “synthetic resin coating”). That is, at least the pipe inner surface 4a of the straight pipe portion 4 is subjected to powder coating as a primary coating (range indicated by the symbol A in FIG. 3), and then the pipe inner surface 3a in the vicinity of the receptacle 3 with many irregularities is Synthetic resin coating is performed as the secondary coating (range indicated by symbol B in FIG. 3).

JP 2003-53220 A

  Performing synthetic resin coating on the inner surface of the receiving port 3 having a complicated inner surface shape is a very complicated operation. That is, the inner surface of the receiving port 3 is not flat and the orientation of the surface to be painted varies, so it is often performed manually (by hand), not by so-called automatic painting in which the painting process is controlled. Currently.

  Such manual painting (synthetic resin coating) is a particularly troublesome work especially for small-diameter pipes.

  In addition, the synthetic resin coating has a problem that it takes a long time to apply and dry the coating process because the coating process needs to be repeated three times. In order to meet the recent demand for cost reduction, it is an urgent task to improve the lead time.

  Further, the outer surface of the tubular body p having a relatively flat surface can be normally coated with a synthetic resin by automatic coating. In particular, a protrusion (ring welded portion) 6 is provided on the outer surface of the insertion slot 2. In the case of having, it is necessary to paint from the upper direction and from the oblique direction, for example, while appropriately changing the direction of the coating gun according to the outer surface shape of the protrusion 6.

  In painting while changing the direction of the painting gun, the above-mentioned three times of recoating are required in each direction of painting. For this reason, work efficiency is also desired in the coating of the outer surface 2b of the insertion slot 2.

  Therefore, an object of the present invention is to increase the efficiency of the painting work in the coating of the portions having irregularities such as the inner surface of the receiving opening of the tubular body and the outer surface of the insertion opening.

  In order to solve the above problems, the present invention provides a tube coating method for a tube body having a receiving port at one end and an opening at the other end, wherein a coating nozzle is disposed in the receiving port, Reciprocating the nozzle from the tube end on the receiving side to the back of the receiving port by moving the nozzle and the tube relative to each other in the tube axis direction while rotating the tube around the tube axis; Electrostatic powder coating is applied to the inner surface of the receiving port by discharging charged powder coating from the nozzle until the nozzle reciprocates from the tube end to the back. The tube painting method was adopted.

In the pipe inner surface coating applied to the pipe body, conventionally, powder coating has been adopted in the straight pipe part constituted by a relatively flat surface, but in the portion of the receiving inner surface where there are many irregularities. Has not been adopted.
This is because if there are many irregularities on the painted surface, there is a concern that the powder coating will not spread over the entire surface.

However, when performing the powder coating, so-called electrostatic powder coating is adopted, and a powder coating gun (nozzle) is reciprocated from the tube end on the receiving side to the back of the receiving port. With that
It was confirmed that a coated surface having a uniform film thickness with little unevenness was formed.

  Further, in a tube coating method performed on a tube body having a receiving port at one end and an insertion port at the other end, and having a protrusion for retaining on the outer surface of the tube on the insertion port side, on the outer surface side of the insertion port. A nozzle for painting is disposed, and the nozzle is moved from the tube end on the insertion port side by moving the nozzle and the tube relative to each other in the tube axis direction while rotating the tube around the tube axis. A range of a predetermined distance is reciprocated toward the mouth side, and the charged powder coating material is discharged from the nozzle until the nozzle reciprocates the range of the predetermined distance from the tube end toward the port side. Thus, a tube coating method characterized in that electrostatic powder coating is applied to the outer surface of the insertion opening.

Even in the configuration in which the outer surface of the insertion opening is provided with a retaining protrusion, electrostatic powder coating is employed in the same manner as described above, and a powder coating gun (nozzle) is connected to the insertion opening side tube. It was confirmed that a coated surface having a uniform film thickness with little unevenness was formed by reciprocating from the end to the range of a predetermined distance toward the receiving port.
The predetermined distance is at least a range including all the protrusions on the outer surface of the insertion port, and preferably includes all parts that enter the reception port when the insertion port is inserted into the reception port. It is desirable.

  According to each of these configurations, it is possible to form a coating surface with a uniform thickness with little unevenness. It is possible to form a uniform coating film with a film thickness of the same, and it is possible to avoid a situation in which the joint performance is impaired due to the formation of the uniform coating film, such that the rubber ring of the joint portion cannot be inserted.

The present invention employs so-called electrostatic powder coating for performing powder coating, and reciprocates a gun (nozzle) for powder coating within the coating range, thereby achieving uniform film thickness with less unevenness. A painted surface can be formed. For this reason, the efficiency of the painting work can be increased in the coating of the uneven portions such as the inner surface of the receiving opening of the tubular body and the outer surface of the insertion opening.
In addition, it is possible to form a uniform coating film with an arbitrary film thickness even if it is powder coating on the inner surface of the receptacle and the part where the irregularities such as the outer surface of the insertion slot are present. Thus, it is possible to avoid a situation in which the joint performance is impaired, such as the rubber ring of the joint portion cannot be inserted.

Sectional drawing which shows the coating method of the pipe inner surface of one Embodiment Sectional drawing which shows the coating method of the pipe outer surface of one Embodiment Explanatory drawing showing the painting range of the pipe

  An embodiment of the present invention will be described with reference to the drawings. The pipe body p to be painted is a ductile cast iron pipe shown in FIG.

  The pipe body p is provided with a receiving port 3 at one end in the tube axis direction and an insertion port 2 at the other end, sandwiching a straight pipe portion 4 having a constant tube diameter. The insertion opening 2 is fitted into the receiving port 3 via a rubber ring, a lock ring or the like (not shown), thereby constituting a seismic resistant joint. On the outer surface of the insertion slot 2, a protrusion 6 for preventing the seismic pipe joint from being detached is provided on the entire circumference.

Since this embodiment corresponds to the rubber ring and the lock ring, the inner surface 3a of the receptacle 3 having a relatively large number of irregularities and the outer surface 2b of the insertion slot 2 having irregularities by providing the projections 6 Powder coating is performed.
Hereinafter, a method of coating the inner surface 3a of the receiving port 3 and the outer surface 2b of the insertion port 2 will be described.

In addition, separate powder coating is performed on the inner surface 4a of the straight pipe portion 4 (including the inner surface 2a of the insertion opening 2) within the range indicated by the symbol A in FIG. For powder coating of the straight pipe portion 4, electrostatic powder coating is not used as in the prior art.
Moreover, synthetic resin coating is performed on the outer surface of the tube body p except for the outer surface 2b of the insertion slot 2. Since these are the same as those in the prior art, description thereof is omitted.

  For painting on the inner surface 3 a of the receiving port 3, first, as shown in FIG. 1, a coating nozzle 10 is arranged in the receiving port 3. At this time, the nozzle 10 is directed downward, and the position where the discharged powder coating is sprayed onto the tube end 3b of the inner surface 3a (the position in the tube axis direction) is the starting point of the nozzle 10. In this embodiment, the starting point is generally such that the center position q of the opening 10a of the nozzle 10 coincides with the position of the tube end 3b in the tube axis direction.

  The nozzle 10 is moved from the tube end 3b on the receiving port 3 side to the back 3c of the receiving port 3 while rotating the tube body p around the tube axis by the driving force of a rotating device (not shown). It is moved at a constant speed in the direction of the arrow D (first pass). The back portion 3 c of the receiving port 3 is a step portion 5 at the boundary between the receiving port 3 and the straight pipe portion 4.

  At this time, the position where the discharged powder coating is sprayed onto the stepped portion 5 (the position in the tube axis direction) is the end point of the nozzle 10. In this embodiment, the end point is generally such that the center position q of the opening 10a of the nozzle 10 matches the position of the stepped portion 5 in the tube axis direction.

  In addition, the powder coating material discharged from the nozzle 10 is in a charged state by passing between the electrodes provided in the coating gun. The voltage applied between the electrodes is appropriately determined depending on the material of the powder coating, the material of the tube, the temperature, the temperature, the humidity, and the like. When charging the powder coating material, other methods such as friction charging may be employed.

  Further, the tube axis positions of the start point and end point may be changed as long as good electrostatic powder coating can be applied to the inner surface 3a of the receiving port 3, and the positions of the start point and end point are slightly different from each other at the end of the tube. It may be on the 3b side or the insertion port 2 side.

  When the nozzle 10 reaches the end point, it immediately starts moving in the reverse direction. That is, the nozzle 10 moves in the direction of the arrow E in the drawing (second pass).

  Thus, by discharging the charged powder coating from the nozzle 10 until the nozzle 10 reciprocates from the tube end 3b to the back 3c and from the back 3c to the tube end 3b, Electrostatic powder coating is applied to the inner surface 3 a of the receptacle 3.

  In addition, before apply | coating a powder coating material, since the pipe p is heated by the furnace, a coating film is hardened by the preheating.

  Next, the coating on the outer surface 2b of the insertion slot 2 will be described. As shown in FIG. 2, a coating nozzle 10 is disposed on the outer surface side of the insertion opening 2. At this time, the nozzle 10 is directed downward, and the position where the discharged powder coating is sprayed onto the tube end 2c of the outer surface 2b (the position in the tube axis direction) is the starting point of the nozzle 10. In this embodiment, the starting point is generally such that the center position q of the opening 10a of the nozzle 10 coincides with the position of the tube end 2c in the tube axis direction. The shape of the nozzle is not particularly limited.

  The nozzle 10 is inserted into the receiving port 3 side by a predetermined distance from the tube end 2c on the insertion port 2 side while rotating the tube body p around the tube axis by the driving force of a rotating device (not shown). Move to the back of the mouth 2d at a constant speed in the direction of arrow F in the figure (first pass).

  At this time, a position (pipe axis direction position) at which the discharged powder coating material is sprayed to the insertion opening back portion 2d is set as the end point of the nozzle 10. In this embodiment, the end point is generally such that the center position q of the opening 10a of the nozzle 10 coincides with the position of the insertion opening back portion 2d in the tube axis direction.

  The powder coating material discharged from the nozzle 10 is in a charged state by passing between the electrodes provided in the coating gun, as in the case of tube inner surface coating. Similarly, the voltage applied between the electrodes is appropriately determined depending on the material of the powder coating material, the temperature of the tube, the temperature, and the like.

  Further, the tube axis direction positions of the start point and end point may be appropriately changed as long as good electrostatic powder coating can be applied to the outer surface 2b of the insertion slot 2, and the positions of the start point and end point are slightly different from each other at the tube end portion. The point which may be in the 2c side or the receptacle 3 side is also the same.

  When the nozzle 10 reaches the end point, it immediately starts moving in the reverse direction. That is, the nozzle 10 moves in the direction of the arrow G in the drawing (second pass).

  In this manner, the nozzle 10 is charged from the nozzle end 2c until it reciprocates within a predetermined distance range from the tube end 2c to the insertion port back portion 2d and from the insertion port back portion 2d to the tube end portion 2c. By discharging the powder coating material, electrostatic powder coating is applied to the entire outer surface 2b of the insertion opening 2 including the outer surface of the protrusion 6.

(Experimental example)
Using a ductile cast iron pipe having a nominal diameter of φ150 (NS-1 pipe), a powder coating experiment was performed on the inner surface 3a of the receiving port 3. The results are shown in Table 1.

  Similarly, a powder coating experiment was performed on the outer surface 2b of the insertion opening 2 using a ductile cast iron pipe having a nominal diameter of φ150 (NS-1 pipe). The results are shown in Table 2.

  In any of the experiments shown in Tables 1 and 2, the powder coating is charged, and the reciprocating two passes (the above-mentioned arrow D (first pass) and arrow E (second pass), or arrow F (one pass) Eye) and arrow G (corresponding to the second pass)), a good result was confirmed.

  On the other hand, when the powder coating material was not charged, the unpainted portion remained in both experiments shown in Tables 1 and 2.

  Furthermore, even if the powder coating is charged, if it is not a reciprocating two-pass but a one-way one-pass (a method in which the above-described second-pass coating is not performed), a pinhole or the like is generated.

  Further, by adopting so-called electrostatic powder coating on the uneven portions of the inner surface 3a of the receiving port 3 and the outer surface 2b of the insertion port 2, as shown in Tables 1 and 2, 100 to 300 μm. The formation of a uniform coating film could be confirmed at any film thickness.

2 Insert 2b Outer surface 3 Receiving port 3a Inner surface 4 Straight tube portion 4a Inner surface 5 Step portion 6 Projection p Tube

Claims (2)

In the tube coating method for the tube (p) having the receiving port (3) at one end and the opening (2) at the other end,
A coating nozzle (10) is disposed in the receiving port (3), and the nozzle (10) and the tube (p) are moved in the tube axis direction while rotating the tube (p) around the tube axis. Packing used when receiving the insertion port (2) of the adjacent tube (p) from the tube end (3b ) on the receiving port ( 3) side by moving the nozzle (10) relative to The boundary between the concave and convex receptacle (3) corresponding to the shape of the lock ring or the outer shape of the insertion slot (2) itself and the straight pipe portion (4) located at the back of the receptacle (3) The powder paint charged from the nozzle (10) is reciprocated up to the step (5) until the nozzle (10) reciprocates from the tube end (3b) to the step (5). by discharging the pipe the stepped portion from the end portion (3b) (5) electrostatic powder until the inner face (3a) of the receptacle (3) Tube coating method characterized by applying a coating. A tube body (p) having a receiving port (3) at one end and an insertion port (2) at the other end and having a projection (6) for retaining the tube on the outer surface (2b) on the insertion port (2) side. In the pipe coating method to be performed on
A coating nozzle (10) is disposed on the outer surface side of the insertion opening (2), and the nozzle (10) and the tube (p) are connected to each other while rotating the tube (p) around the tube axis. By reciprocally moving in the axial direction, the nozzle (10) is reciprocated within a predetermined distance from the tube end (2c) on the insertion port (2) side toward the receiving port (3), and the nozzle ( The powder charged from the nozzle (10) until 10) reciprocates in a predetermined distance range including the outer surface of the protrusion (6 ) from the tube end (2c) toward the receiving port (3). A tube coating method, wherein electrostatic powder coating is applied to the outer surface (2b) of the insertion opening (2) including the protrusion (6) by discharging body paint.

Images