Fluid sprinkling – spraying – and diffusing – Electrostatic type – With impeller
Reexamination Certificate
2001-09-28
2003-06-24
Freay, Charles G. (Department: 3746)
Fluid sprinkling, spraying, and diffusing
Electrostatic type
With impeller
C239S690000
Reexamination Certificate
active
06581857
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an externally pressurized gas bearing spindle mounted in a rotary atomizing head type electrostatic painting machine to support a main spindle carrying a paint spray head in a non-contact manner by means of an externally pressurized gas bearing.
Heretofore, for painting of automotive parts, electric parts, etc., various kinds of electrostatic painting machines have been used in which paint is atomized and electrostatically charged with a negative charge to cause it to adhere to surfaces to be painted using electrical attraction.
With such an electrostatic painting machine, in order to obtain a uniform painted surface by reducing the particle diameter of the atomized paint as much as possible, it is required to rotate the atomizing head for paint at high speed. In order to cope with this requirement, a structure is usually employed in which a rotary shaft of a spindle on which is mounted the atomizing head is supported by an externally pressurized gas bearing in a non-contact manner.
FIG. 9
shows a first example of a conventional spindle for a rotary atomizing head type electrostatic painting machine. In this spindle, a high voltage generator
2
for generating a negative high voltage is electrically connected to a housing
1
. Inside of the housing, an air passage
3
with an air inlet
3
a
connected to a compressed air supply source (not shown) is formed. In an internal hole
1
a
in the housing
1
, a plurality of air supply nozzles
4
,
5
,
5
′ communicating with the air passage
3
are formed.
In the internal hole
1
a
in the housing
1
, a main spindle
7
and a rotor
8
of a turning force generator (e.g. air turbine) provided at the rear end of the main spindle for rotating the main spindle
7
are inserted so as to form bearing gaps
6
,
6
′. Between the periphery of the main spindle
7
and the air supply nozzles
4
, a journal air bearing portion
9
is formed. Between the rotor
8
and the air supply nozzles
5
,
5
′, thrust air bearing portions
10
,
10
′ are formed. When compressed air is supplied from the air supply nozzles
4
,
5
and
5
′ into the bearing gap
6
,
6
′, due to the pressure of the air, the main spindle
7
and the rotor
8
are supported in a floating state and out of contact with the housing
1
, so that the externally pressurized gas bearing comprising the journal air bearing portion
9
and the thrust air bearing portion
10
,
10
′ reveals its function.
At the front end of the main spindle
7
, a paint atomizing head
13
for atomizing and spraying paint to the surroundings by the rotation of the main spindle
7
is fixed by suitable means such as screws. A conduit
11
having an injection nozzle
17
at its tip to feed paint to the spray head
13
is inserted into the main spindle
7
out of contact with the main spindle.
With this spray head
13
, paint injected from the injection nozzle
17
into a paint introducing space
15
defined by a partitioning wall
16
passes through a flow-out hole
18
and is introduced to an inner peripheral surface
14
of the spray head
13
by high-speed rotation of the spray head
13
, and scattered in a mist to the surroundings by centrifugal force. If the spray head
13
is in a negatively charged state, the paint flowing along the inner peripheral surface
14
is electrostatically charged with a negative charge.
Around the rotor
8
at the rear end of the main spindle
7
, a plurality of turbine blades
19
are arranged. In the housing
1
, compressed air blow-out nozzles
20
for blowing compressed air against the turbine blades
19
is formed. Also, a compressor
21
is coupled to the blow-out nozzle
20
. With this structure, when compressed air is blown against the turbine blades
19
through the blow-out nozzle
20
, turning force is given to the turbine blades
19
. Thus, the main spindle
7
, which is supported in a floating state, rotates at a high speed.
FIG. 10
shows a second example of a prior art spindle for an electrostatic painting machine using an air turbine as a driving means. It has a main spindle
7
and a rotor
8
provided at the rear end of the main spindle. The rotor
8
is formed with a plurality of recesses
19
′ in its outer periphery and a housing
1
is formed with an air blow-out nozzle
20
at a position opposite to the rotor
8
. Compressed air is blown from the nozzle
20
to rotate the main spindle
7
. A paint spray head (not shown) is mounted to the front end of the main spindle
7
.
The main spindle
7
and the rotor
8
integral with the main spindle are rotatably supported in a non-contact manner by bearing sleeves
51
,
52
and first and second housings
53
,
54
by a journal bearing portion
9
and thrust bearing portions
10
,
10
′ formed by the bearing sleeves
51
,
52
and the first and second housings
53
,
54
.
The journal bearing portion
9
and the thrust bearing portion
10
are formed by mounting the bearing sleeve
51
in the first housing
53
by shrinkage fitting, press fitting or bonding. Similarly the thrust bearing portion
10
′ is formed by mounting the bearing sleeve
52
in the second housing
54
by shrinkage fitting, press fitting or bonding.
The bearing sleeves
51
and
52
are made of a copper alloy which is an ordinary air bearing material. They are formed with air supply nozzles
4
,
4
′ for the journal bearing and air supply nozzles
5
,
5
′ for the thrust bearing.
Between the first and second housings
53
,
54
is mounted a third housing
55
. The first to third housings
53
-
55
are secured together by bolts or the like. The first to third housings (forming the entire housing
1
) are arranged in a painting machine casing
56
made of a resin through elastic members
57
. The housing
1
is normally made of a light metal such as aluminum alloy for lighter weight.
The first and second housings
53
,
54
are formed with annular grooves
58
-
60
which communicate with air supply nozzles
4
,
4
′ and
5
,
5
′ formed in the bearing sleeves
51
,
52
. Also, air passages
3
,
3
′,
62
,
61
communicating with these annular grooves
58
-
60
are formed in the housings
53
,
54
and
55
.
The air passage
63
communicating with an air supply port
3
a
is formed in the painting machine casing
56
. Also, the third housing
55
is formed with the compressed air blow-out nozzles
20
opening opposite to the recesses
19
′ of the rotor
8
in a tangential direction.
Compressed air supplied from the air passage
63
in the painting machine casing
56
is supplied from the air supply port
3
a
of the first housing
53
through the annular groove
59
and the air passage
3
to the annular grooves
58
,
59
and blown out to the bearing surface through the air supply nozzles
4
,
4
′ of the bearing sleeve
51
so that the journal bearing portion
9
supports the main spindle
7
in a radial direction.
Also, compressed air is blown out through the annular groove
59
of the first housing
53
from the air supply nozzle
5
to the bearing surface of the thrust bearing portion
10
′. The compressed air is also supplied through the air passages
3
′,
62
and
61
of the first, third and second housings
53
,
55
and
54
, respectively, to the annular groove
60
and blown from the air supply nozzle
5
′ to the bearing surface of the thrust bearing portion
10
′. Thus the thrust bearing portions
10
,
10
′ support the main spindle
7
in an axial direction.
On the other hand, compressed air supplied from an air passage
64
of the painting machine casing
56
is blown from the air blow-out nozzles
20
of the third housing
55
toward the recesses
19
′ of the rotor
8
of the main spindle
7
in a tangential direction. After applying a turning force to the main spindle
7
, compressed air is discharged through an exhaust port (not shown) out of the housing
1
. At one end (right-hand end in
FIG. 10
) of the main spindle
7
, a paint
Fujii Shoji
Fujikawa Yoshio
LandOfFree
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