Blasting apparatus using mixture gas and powder

A blasting apparatus for blasting a predetermined portion of a work by spraying a powder to the work in a blasting chamber. The blasting apparatus includes a work bed for placing the work thereon, a spray nozzle for spraying the powder onto the work, a first driving section for linearly moving the work bed in a first direction, and a second driving section for linearly moving the spray nozzle in a second direction perpendicular to the first direction. Accordingly, the blasting apparatus can be reduced in size.

BACKGROUND OF THE INVENTION 
The present invention relates to a blasting apparatus for blasting a 
predetermined portion of an object or workpiece (hereinafter referred to 
as a work) by spraying a powder thereagainst. 
A blasting apparatus is known as an apparatus for blasting a work by 
spraying or fusillading a powder of metal or inorganic material 
(particulate matter) against the work using high-pressure air. This 
technique is used to form minute blind holes or through holes in a circuit 
board, for example. 
Such a blasting apparatus includes a work bed which receives a work 
thereon, a spray nozzle for spraying a powder against the work which is 
placed on the work bed, and means for moving the work bed. The work is 
previously masked so as to expose only those portions which are to be 
blasted. The work is moved in X and Y directions while the powder is 
sprayed against the work by the spray nozzle, thus effecting the blasting 
of the predetermined portion of the work. 
However, in this type of conventional blasting apparatus, the spray nozzle 
is fixed and the work bed is moved in the X and Y directions. Therefore, 
the blasting apparatus is required to have an area in plan almost four 
times that of the work placed on the work bed, thus causing an enlargement 
in size of the blasting apparatus. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a compact blasting 
apparatus. 
According to the present invention, there is provided a blasting apparatus 
for blasting a predetermined portion of a work by spraying a powder 
against the work while it is disposed in a blasting chamber. The blasting 
apparatus comprises a work bed for supporting the work thereon, a spray 
nozzle for spraying the powder onto the work, first means for linearly 
moving the work bed in a first direction, and second means for linearly 
moving the spray nozzle in a second direction perpendicular to the first 
direction. 
With this arrangement, the work bed is moved in the first direction (X 
direction) only by a distance corresponding to the length of the work. 
Accordingly, the area of the blasting apparatus in plan can be reduced, 
and the blasting apparatus can be rendered compact. 
It is preferable that the blasting apparatus further comprises a supply 
system for supplying the powder to the spray nozzle which includes a 
flexible tube connected to the spray nozzle. This is to enable the 
movement of the spray nozzle in the second direction (Y direction) to be 
easily effected. 
It is preferable that the blasting apparatus further comprises a nozzle 
height adjusting mechanism for adjusting a height of the spray nozzle 
relative to the work. This is required so that, the distance between the 
spray nozzle and the work can be suitably set, and the degree blasting can 
be properly adjusted. 
It is preferable that the blasting apparatus further comprises a sliding 
shaft for slidably supporting the work bed and a bellows-like cylindrical 
member for covering the sliding shaft. With this provision the deposition 
or penetration of the powder into a sliding mechanism consisting of the 
sliding shaft and a linear guide, can be prevented by the bellows-like 
cylindrical member. Meaning of a sliding surface between the sliding shaft 
and the linear guide can thus be prevented and accordingly prevent a 
reduction in accuracy due to looseness (play) in the sliding mechanism. 
It is preferable that the first means and the second means are provided 
outside the blasting chamber. With this disposition, possible deposition 
or penetration of the powder into the first and second means can be 
prevented, and a reduction in durability of the first and second means can 
be prevented. This of cause promotes stable movement of the work bed and 
the spray nozzle. 
It is preferable that the blasting apparatus further comprises a wire for 
connecting the work bed to the first means. With this arrangement, it is 
only necessary to form wire insert holes and insert a wire through a 
housing which defines the blasting chamber. The shieldability of the 
blasting chamber is therefore facilitated. 
Other objects and features of the invention will be more fully understood 
from the following detailed description and appended claims when taken 
with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
There will now be described a preferred embodiment of the blasting 
apparatus according to the present invention with reference to the 
accompanying drawings. 
In the preferred embodiment illustrated, reference numeral 1 generally 
designates a blasting apparatus for blasting a substrate to form a fine 
through hole or blind hole in the substrate. 
Reference numeral 2 designates a housing in which a work bed and a spray 
nozzle to be hereinafter described are movably provided. The housing 2 is 
formed of a sheet metal material. The internal space 3 of the housing 2 is 
substantially isolated from the outside. 
In the following description, the terms of "right" and "left" represent the 
right and left sides as viewed in FIG. 1, respectively, and the terms of 
"front" and "rear" represent the opposite sides before and behind the 
sheet of FIG. 1, respectively. Further, the term of "lateral" represents 
the right and left direction of the housing 2, and the term of 
"transverse" represents the front and rear direction of the housing 2. 
The housing 2 is elongated in the lateral direction. The housing 2 is 
generally comprised of a main portion 4 having a lower opening and a 
bottom portion 5 closing the lower opening of the main portion 4. 
An upper half of a front side wall 6 of the main portion 4 is inclined 
frontwardly, and a lower half of the front side wall 6 is vertical. The 
lower half is formed with a work window 6a having a size just smaller than 
that of the lower half. The work window 6a is normally closed by a door 7. 
The bottom portion 5 of the housing 2 is relatively flat such that it is 
formed like a funnel of an inverted quadrangular pyramid having an upper 
opening. The bottom portion 5 is formed at its bottom apex with a 
cylindrical hose connecting projection 5a. The upper opening of the bottom 
portion 5 is substantially registered with the lower opening of the main 
portion 4. 
A left side wall 8 of the main portion 4 is formed at its lower end (as 
viewed from the front side) in such a manner as to be indented inwardly. 
Reference numeral 9 designates a body frame of the blasting apparatus 1. 
The housing 2 is supported to a front portion of the body frame 9. 
Reference numeral 10 designates a pair of guide shafts for movably 
supporting a work bed to be hereinafter described. The guide shafts 10 are 
arranged just above the bottom portion 5 in the housing 2 so as to extend 
in parallel to each other in the lateral direction. Four shaft fixing 
members 12 are mounted at the lower end portions of the left side wall 8 
and the right side wall 11 of the housing 2. The opposite ends of the two 
guide shafts 10 are supported through the four shaft fixing members 12 to 
the opposite side walls 8 and 11 of the housing 2. 
Reference numeral 13 designates a work bed on which a substrate 14 is to be 
detachably placed. The work bed 13 includes a moving base movably 
supported to the guide shafts 10 and a work table to be detachably 
supported to the moving base. 
The lateral length of the main portion 4 of the housing 2 is about 2.5 
times the lateral length of the work bed 13, while the transverse width of 
the main portion 4 is larger than the transverse width of the work bed 13 
by a given amount. 
Reference numeral 15 designates a moving base of the work bed 13. The 
moving base 15 is rectangular as viewed in plan so as to be elongated in 
the lateral direction. The moving base 15 is formed in a relatively thin 
box-shape having an upper opening. A bottom plate 16 of the moving base 15 
is comprised of two horizontal portions 16a at the right and left end 
portions thereof and a relatively flat funnel portion 16b shaped like an 
inverted quadrangular pyramid. The funnel portion 16b is formed at its 
bottom apex with a cylindrical hose connecting projection 16c. 
Four positioning pins 17 project vertically upwardly from the horizontal 
portions 16a at the front and rear ends thereof. Each positioning pin 17 
is constituted by a small-diameter upper portion 17a and a large-diameter 
lower portion 17b having a diameter larger than that of the upper portion 
17a. 
Reference numerals 18 designate a pair of linear guides, e.g., linear ball 
bearings fixed to the front and rear end portions of a lower surface of 
the bottom plate 16 at a substantially laterally central position thereof. 
The two guide shafts 10 are respectively inserted through the two linear 
guides 18. Thus, the moving base 15 is supported on the guide shafts 10 so 
as to be movable in the axial direction of the guide shafts 10, that is, 
in the lateral direction. 
Reference numerals 19 designate a plurality of bellows (corrugated) hoses 
(shown in FIGS. 1 and 6 only) provided so as to cover the guide shafts 10. 
One end of each bellows hose 19 is fixedly engaged with an outer 
circumference of a cylindrical outer case of each shaft fixing member 12 
supporting the respective guide shaft 10, and the other end of each 
bellows hose 19 is fixedly engaged with an outer circumference of a 
cylindrical outer case of each linear guide 18 fixed to the bottom plate 
16 of the moving base 15. Accordingly, an outer circumference of each 
guide shaft 10 and a guide shaft insert hole of each linear guide 18 are 
shielded by each bellows hose 19 to be protected from powder deposition. 
Reference numeral 20 designates a work table of the work bed 13. The work 
table 20 is a rectangular flat member having an external form (as viewed 
in plan) which is just smaller than that of the moving base 15. A lower 
surface of the work table 20 is formed at its four corners with four 
positioning holes 20a. 
In positioning the work table 20 to the working base 15, the upper portions 
17b of the positioning pins 17 of the moving base 15 are inserted into the 
positioning holes 20a of the work table 20, and the lower opening edge 
portions of the positioning holes 20a are placed on the lower portions 17a 
of the positioning pins 17. Thus, the work table 20 is supported inside 
the moving base 15 so as to be positioned in the horizontal direction and 
the vertical direction. 
Reference numerals 21a and 21b designate two substrate pressers or 
restraints located on an upper surface of the work table 20 at a front end 
portion and a left end portion thereof, respectively. The substrate 
restraints 21a and 21b are rotatably supported to respective supporting 
shafts 22 (see FIG. 6) provided in the work table 20 in such a manner that 
the inside edge portions of the substrate restraints 21a and 21b are 
movable in the vertical direction and that they are normally biased by 
respective torsion springs (not shown) mounted on the supporting shafts 22 
to resiliently contact the upper surface of the work table 20. 
Reference numeral 21c designates another substrate restraint provided on 
the upper surface of the work table 20 so as to be movable in the 
transverse direction. The substrate restraint 21c is formed at its front 
edge with an elongated recess 21d opening to the front side and the lower 
side and extending over the lateral width of the substrate restraint 21c. 
The substrate 14 is held to the work table 20 by engaging a rear edge of 
the substrate 14 with the elongated recess 21d of the rear substrate 
restraint 21c and nipping a left edge and a front edge of the substrate 14 
between the inside edge portion of the left substrate restraint 21b and 
the upper surface of the work table 20 and between the inside edge portion 
of the front substrate restraint 21a and the upper surface of the work 
table 20, respectively. 
Various substrates having different sizes may be held by moving the rear 
substrate presser 21c in the transverse direction. 
Further, mounting and demounting of the substrate 14 with respect to the 
work table 20 are effected under the condition that the work table 20 is 
removed from the moving base 15 with the door 7 opened. 
Reference numerals 23 designate a pair of wire fixing members fixed to the 
lower surfaces of the horizontal portions 16a of the bottom plate 16 of 
the moving base 15 at the substantially central position in the transverse 
direction. Each wire fixing member 23 is formed with a wire insert hole 
23a extending in the lateral direction, and it is further formed with a 
tapped hole 23b extending between a lower surface of the member 23 and the 
wire insert hole 23a. 
Reference numerals 24 designate a pair of holes formed through the lower 
end portions of the left and right side walls 8 and 11 of the housing 2 at 
the positions opposed to the wire fixing members 23. Each hole 24 is 
closed by a sealing member 26 having a wire insert hole 25. 
Reference numeral 27 designates a pulley mounting plate fixed to an outer 
surface of the right side wall 11 of the housing 2. A guide pulley 28 is 
rotatably supported to an upper surface of the pulley mounting plate 27 at 
a left front position thereof. A geared motor 29 is fixed to a lower 
surface of the pulley mounting plate 27 at a right rear position thereof, 
and a drive pulley 30 is fixed to an outer shaft of the motor 29. The 
drive pulley 30 is located at the same level as that of the guide pulley 
28 over the upper surface of the pulley mounting plate 27. 
Reference numerals 31 and 32 designate two guide pulleys rotatably 
supported to a pulley mounting plate 27' (shown in FIG. 3 only) fixed to 
the left side wall 8 of the housing 2. The two guide pulleys 31 and 32 are 
located somewhat apart from each other in the transverse direction. 
These guide pulleys 28, 31 and 32 and the drive pulley 30 are located at 
the same level as that of the wire insert holes 25 of the sealing members 
26. 
Reference numeral 33 designates a wire fixed at its opposite ends to the 
wire fixing members 23 fixed to the work bed 13. Thus, the wire 33 is made 
endless through the work bed 13. A substantially half portion of the wire 
33 is drawn out of the housing 2 through the wire insert holes 25 of the 
sealing members 26, and is wound around the guide pulleys 28, 31 and 32 
and the drive pulley 30. 
The opposite ends of the wire 33 are inserted into the wire insert holes 
23a of the wire fixing members 23, and are fixed to the wire fixing 
members 23 by means of two set screws 34 threadedly engaged with the 
respective tapped holes 23b. 
When the motor 29 is rotated, the drive pulley 30 is rotated in the same 
direction to move the wire 33 in a direction according to the rotational 
direction of the motor 29, thereby moving the work bed 13 in the lateral 
direction. 
The work bed 13 is movable between an initial position shown by a solid 
line in FIG. 1 and a terminal position shown by a phantom line in FIG. 1. 
A suitable tension is normally applied to the wire 33 by a tensioner (not 
shown). 
Each sealing member 26 is comprised of a housing 35 and a packing 40 
located in the housing 35 (see FIG. 5). 
While FIG. 5 shows the left sealing member 26 only, the right sealing 
member 25 also has the same form and structure as those of the left 
sealing member 26. Accordingly, the explanation for the right sealing 
member 26 will be omitted hereinafter. 
The housing 35 is comprised of a substantially disk-shaped outside half 36 
projecting at its central portion inwardly of the housing 2 and a 
substantially disk-shaped inside half 37 somewhat smaller in size than the 
outside half 36 has an outer diameter substantially equal to a diameter of 
the hole 24 formed through the left side wall 8. The outside half 36 is 
formed at its central portion with a through hole 39 extending in the 
axial direction. 
The through hole 39 of the outside half 36 is comprised of a large diameter 
portion 39a extending from the inside surface of the outside half 36 to 
the axially half portion thereof and a small diameter portion 39b 
extending from the large diameter portion 39a to the outside surface of 
the outside half 36. 
The inside half 37 has an outer diameter equal to that of the projecting 
portion 38 of the outside half 36. The inside half 37 is formed at its 
central portion with a through hole 37a extending in the axial direction. 
The through hole 37a of the inside half 37 has a diameter somewhat smaller 
than that of the large diameter portion 39a of the through hole 39 of the 
outside half 36. 
The packing 40 is formed in a substantially ring-like shape having a 
through hole 40a. The packing 40 has an outer diameter substantially equal 
to the diameter of the large diameter portion 39a of the through hole 39 
and an inner diameter somewhat smaller than a diameter of the wire 33. The 
packing 40 is set into the housing 35 in the following order. First, the 
packing 40 is fitted into the large diameter portion 39a of the outside 
half 36. Secondly, the inside half 37 is mounted on the projecting portion 
38 of the outside half 36 so as to cover the large diameter portion 39a. 
Finally, the inside half 37 is fixed to the outside half 36 by means of 
screws. Thus, the wire insert hole 25 of the sealing member 26 is formed 
by the through hole 39 of the outside half 36, the through hole 40a of the 
packing 40, and the through hole 37a of the inside half 37. 
The assembly of the outside half 36, the inside half 37 and the packing 40 
is fixed to the left side wall 8 of the housing 2 by inserting the inside 
half 37 and the projecting portion 38 of the outside half 36 into the 
through hole 24 of the left side wall 8 and fixing the outside portion of 
the outside half 36 other than the projecting portion 38 to the left side 
wall 8 by means of screws. Similarly, the right sealing member 26 is also 
fixed to the right side wall 11 of the housing 2. 
Reference numeral 41 designates a powder supply tank (partially shown in 
FIG. 1) for storing the powder, and reference numeral 42 designates a 
mixing tank. The powder supply tank 41 and the mixing tank 42 are fixed to 
an upper surface of an upper wall 43 of the housing 2. The and the mixing 
tank 42 is located at a substantially laterally central position of the 
upper wall 43. 
A flexible feed tube 44 extends from the mixing tank 42 so as to be 
inserted through a hole of a cylindrical sealing member 45 fixedly engaged 
with a hole 43a formed through the upper wall 43 and be introduced into 
the housing 2. A lower end of the feed tube 44 is connected to a nozzle 
portion 47 of a spray nozzle 46. 
The powder is supplied on occasion from the powder supply tank 41 to the 
mixing tank 42, so that a suitable amount of the powder is always stored 
in the mixing tank 42. On the other hand, a high-pressure air is supplied 
from an air compressor (not shown) to the mixing tank 42, and is mixed 
with the powder in the mixing tank 42. The mixture of the powder and the 
high-pressure air is fed under pressure to the spray nozzle 46. 
The spray nozzle 46 includes the nozzle portion 47 mentioned above, a 
nozzle cover 51 covering the nozzle portion 47, and two connecting members 
53 fixed to the nozzle cover 51. 
The nozzle portion 47 is formed in a vertically elongated box-shape having 
a lower opening 47a. A transverse width of the nozzle portion 47 is 
relatively small. A lateral width of the nozzle portion 47 at its lower 
half is somewhat larger than that at its upper half. A laterally elongated 
nozzle tip 48 is fixedly mounted to the lower opening 47a of the nozzle 
portion 47. A lower end 48a of the nozzle tip 48 is formed as a spray hole 
having a narrowed transverse width. 
A cylindrical tube connector 49 communicating with the inside of the nozzle 
portion 47 projects upwardly from an upper wall of the nozzle portion 47, 
and the lower end of the feed tube 44 is connected to the tube connector 
49. Accordingly, the powder fed through feed tube 44 is introduced into 
the nozzle portion 47, and is sprayed downwardly from the spray hole 48a 
of the nozzle tip 48. The spray of the powder is in the form of a band 
having a suitable lateral length. 
Reference numerals 50 designate two nut members fixed to a front side wall 
of the nozzle portion 47. The nut members 50 are located apart from each 
other in the lateral direction so that the axes of the nut members 50 are 
oriented in the transverse direction. 
The nozzle cover 51 is larger in size than the nozzle portion 47, and it is 
formed in a box-shape having a lower opening. A front side wall of the 
nozzle cover 51 is formed with two vertically elongated holes 51a 
extending in parallel to each other. The nozzle portion 47 is located in 
the nozzle cover 51, and threaded portions of two screws 52 are inserted 
through the respective elongated holes 51a from the outside of the nozzle 
cover 51. The threaded portions of the two screws 52 are threadedly 
engaged with the respective nut members 50. Thus, by tightening each screw 
52, the side edge portion of each elongated hole 51a is firmly nipped 
between the corresponding nut member 50 and a head portion of the 
corresponding screw 52, thus firmly supporting the nozzle portion 47 to 
the nozzle cover 51. 
A vertical position of the nozzle portion 47 with respect to the nozzle 
cover 51 can be adjusted by loosening the screws 52. 
An upper side wall of the nozzle cover 51 is formed with a hole 51b, and 
the tube connector 49 of the nozzle portion 47 is inserted through the 
hole 51b of the nozzle cover 51 to project upwardly. 
The two connecting members 53 are fixed to the upper surface of the nozzle 
cover 51 at the right and left ends thereof. The connecting members 53 are 
respectively formed with mounting holes 53a extending in the transverse 
direction, and two sliding shafts 61 of a nozzle driving section 54 to be 
hereinafter described are fixedly engaged with the mounting holes 53a of 
the connecting members 53, respectively. 
Referring to FIGS. 4 and 10, the nozzle driving section 54 is provided to 
support the spray nozzle 46 and move the same in the transverse direction. 
Reference numeral 55 designates a supporting base for the nozzle driving 
section 54. The supporting base 55 is mounted on the body frame 9 at a 
portion thereof behind the housing 2. The supporting base 55 is comprised 
of a horizontal bottom portion 56 and a vertical wall portion 57 standing 
from a front end of the bottom portion 56. 
A rear side wall 58 of the housing 2 is formed at its substantially central 
portion with two holes 58a (one of which being shown in FIG. 10) spaced a 
suitable distance from each other in the lateral direction. Each hole 58a 
is closed by a sealing member 59 having a through hole 59a. 
The vertical wall portion 57 of the supporting base 55 is formed with two 
through holes 57a (one of which being shown in FIG. 10) opposed to the 
respective holes 58a of the rear side wall 58. 
Two linear guides 60 (one of which is shown in FIG. 10) each having a 
sliding shaft insert hole 60a are mounted on a rear surface of the 
vertical wall portion 57 in such a manner that the sliding shaft insert 
hole 60a is aligned with the corresponding through hole 57a of the 
vertical wall portion 57. 
The two column like sliding shafts 61 each are slidably inserted through 
the respective sliding shaft insert holes 60a of the linear guides 60, the 
respective through holes 57a of the vertical wall portion 57, and the 
respective through holes 59a of the sealing members 59. The front end 
portions of the sliding shafts 61 are fixedly engaged with the respective 
mounting holes 53a formed through the connecting members 53 of the spray 
nozzle 46. 
Thus, the spray nozzle 46 is supported through the sliding shafts 61 to the 
linear guides 60 at a position just over a locus of movement of the work 
bed 13 in such a manner as to be movable in the transverse direction, that 
is, in the direction perpendicular to the moving direction of the work bed 
13. 
Reference numerals 62 and 62' denote two counter pulleys rotatably 
supported to supporting members 63 and 63' projecting from a rear end 
portion of the bottom portion 56 and an intermediate portion of the 
vertical wall portion 57 of the supporting base 55, respectively. An 
endless timing belt 64 is wrapped between the two counter pulleys 62 and 
62'. 
One of the two counter pulleys 62 and 62' is driven by a motor (not shown) 
to thereby drive the timing belt 64. 
Reference numeral 65 designates a connecting member fixed to the timing 
belt 64. The rear end portions of the sliding shafts 61 are fixed to the 
connecting member 65. Accordingly, when the timing belt 64 is driven, the 
connecting member 65 is moved together with the sliding shafts 61 in the 
transverse direction. 
The spray nozzle 46 is allowed to be moved between a retracted position 
shown by a solid line in FIG. 4 and an advanced position shown by a 
phantom line in FIG. 4. 
Reference numeral 66 designates an auxiliary guide shaft supported to the 
supporting base 55 and extending in the transverse direction. The upper 
end portion of the connecting member 65 is slidably supported to the 
auxiliary guide shaft 66, thereby stably maintaining the attitude of the 
sliding shafts 61 and the spray nozzle 46 fixed thereto. 
The blasting operation of the blasting apparatus 1 with respect to the 
substrate 14 is carried out in the following exemplary. 
First, the substrate 14 is set on the work bed 13 as mentioned above. 
As previously mentioned, the setting of the substrate 14 is carried out by 
first removing the work table 20 of the work bed 13 from the moving base 
15, then placing the substrate 14 on the work table 20, and then mounting 
the work table 20 onto the moving base 15. Thereafter, the work window 6a 
is closed by the door 7 to substantially isolate the interior of the 
housing 2. 
When an operation start command is generated, the work bed 13 is moved from 
the initial position toward the terminal position. In the course of the 
movement of the work bed 13, when the right end portion of the substrate 
14 on the work bed 13 comes to a position opposed to a locus of movement 
of the spray nozzle 46, the movement of the work bed 13 is stopped. 
Then, the spray nozzle 46 is advanced to a position opposed to the 
substrate 14. From this advanced position, the spray nozzle 46 starts to 
spray the powder and is further advanced, thereby effecting the blasting 
to the substrate 14 in a predetermined band-shaped region which extends in 
the transverse direction. 
When the spray nozzle 46 comes to the final advanced position, the work bed 
13 starts to be moved again toward the terminal position by a 
predetermined pitch, that is, the same distance as the lateral width of 
the spray hole 48a of the spray nozzle 46. 
The spray nozzle 46 then is moved to the retracted position as spraying the 
powder, thereby effecting the blasting of another band-shaped region of 
the substrate 14. 
Such pitch feed of the work bed 13 and movement of the spray nozzle 46 are 
repeated to thereby expose the entire surface of the substrate 14 to the 
spray. Accordingly, those portions of the substrate 14 other than those 
previously masked are eroded by the spray of the powder. 
When the work bed 13 comes to the terminal position, it is returned to the 
initial position. Further, the spray of the powder from the spray nozzle 
46 is stopped, and the spray nozzle 46 is returned to the retracted 
position to wait at this position. 
Reference numerals 67 designate two hose connecting pipes projecting 
obliquely upwardly from the right and left side walls of the nozzle cover 
51. The hose connecting pipes 67 are communicated with the inside of the 
nozzle cover 51. Two bellows-like recovery hoses 68 are connected at their 
lower ends to the hose connecting pipes 67, respectively, and the upper 
ends of the recovery hoses 68 are connected to the lower ends of two hose 
couplings 69 inserted through the upper side wall 43 of the housing 2, 
respectively. Further, two suction hoses (not shown) extending from a 
powder recovery section (not shown) are connected to the upper ends of the 
hose couplings 69, thereby evacuating the inside of the nozzle cover 51. 
Accordingly, the powder sprayed from the spray nozzle 46 and which is 
reflected back off the substrate 14 is sucked from the space inside the 
nozzle cover 51 through the hose connecting pipes 67, the recover hose 68, 
the hose couplings 69 and the suction hoses to the powder recovery 
section. 
Reference numeral 70 designates a valve block located behind the housing 2. 
The valve block 70 is connected to the powder recovery section, and it is 
provided with a plurality of powder valves 70a. 
Reference numerals 71 and 72 designate recovery hoses similar to the 
above-mentioned recovery hoses 68. One end of the recovery hose 71 is 
connected to the hose connecting projection 5a formed at the bottom apex 
of the housing 2, and the other end is connected to one of the powder 
valves 70a of the valve block 70. On the other hand, one end of the 
recovery hose 72 is connected to the hose connecting projection 16c of the 
moving base 15 of the work bed 13, and the other end is connected to a 
hose coupling 73 inserted through the bottom portion 5 of the housing 2. 
The hose coupling 73 is connected through a connecting hose (not shown) to 
another one of the powder valves 70a. 
Accordingly, the inside of the moving base 15 of the work bed 13 and the 
inside of the housing 2 are evacuated, so that a part of the powder 
sprayed from the spray nozzle 46 onto the substrate 14 other than the part 
sucked through the recovery hoses 68 is almost entirely sucked from the 
inside of the moving base 15 through the recovery hose 72 to the powder 
recovery section. Further, the powder which has scattered outside the work 
bed 13 and the nozzle cover 51, is sucked through the recovery hose 71 to 
the powder recovery section. Thus, all the powder sprayed from the spray 
nozzle 46 onto the substrate 14 is returned to the powder recovery 
section. 
While the invention has been described with reference to a specific 
embodiment, the description is illustrative and is not to be construed as 
limiting the scope of the invention. Various modifications and changes may 
occur to those skilled in the art without departing from the spirit and 
scope of the invention as defined by the appended claims.