Rotary atomizing head type coater

Details Rotary atomizing head type coater Rotary atomizing head type coater

2002-08-19

2004-11-02

Mar, Michael (Department: 3752)

Fluid sprinkling, spraying, and diffusing

Slinger or splasher; or deflector rotated relative to effluent

Disc impeller type or bowl-like slinger or deflector

C239S224000, C239S296000

Reexamination Certificate

active

06811094

ABSTRACT:

TECHNICAL FIELD
This invention relates to a rotary atomizing head type coating machine which is suitable for use, for example, for coating vehicle bodies or the like.
BACKGROUND ART
Generally, rotary atomizing head type coating machines have been widely resorted to for coating vehicle bodies or similar work pieces. Shown by way of example in
FIGS. 16 and 17
is a prior art rotary atomizing head type coating machine of this sort.
In these figures, indicated at
100
is a rotary atomizing head type coating machine as a whole. The rotary atomizing head type coating machine
100
is largely constituted by a machine cover
101
which is formed in a tubular shape, an air motor
102
which is accommodated in the cover machine
101
, a rotational shaft
103
which is passed axially through the air motor
102
and rotationally driven by the latter, and a rotary atomizing head
104
which is mounted on the rotational shaft
103
on the front side of the machine cover
101
and thereby rotated at a high speed, for example, at a speed of 3,000 to 100,000 rpm to atomize and spray paint.
More specifically, as shown in
FIG. 17
, the rotational shaft
103
is provided with a male screw portion
103
A around the circumference of a front end portion which is projected forward of the air motor
102
. The rear side of the rotary atomizing head
104
is formed into a rotational shaft mount portion
104
A of a tubular shape to receive therein a fore end portion of the rotational shaft
103
. The rotational shaft mount portion
104
A is provided with a female screw portion
104
B on a deep inner peripheral portion for threaded engagement with the male screw portion
103
A of the rotational shaft
103
. The rotational shaft
103
and the rotary atomizing head
104
are integrally fixed to each other by tightly threading the male screw portion
103
A into the female screw portion
104
B.
A feed tube
105
is passed through the rotational shaft
103
, and the fore end of the feed tube
105
is projected from the rotational shaft
103
and extended into the rotary atomizing head
104
. A paint passage
105
A and a thinner passage
105
B are provided internally of the feed tube
105
.
Further, an annular shaping air ring
106
is detachably attached to the front side of the machine cover
101
, on the outer peripheral side of the rotary atomizing head
104
. In order to control the spray pattern of paint which is sprayed by the rotary atomizing head
104
, a large number of air outlet holes
106
A are formed in this shaping air ring
106
at intervals in a circumferential direction for spurting shaping air toward sprayed paint particles.
In the case of the rotary atomizing head type coating machine
100
which is constructed in the manner as described above, while the rotary atomizing head
104
is put in high speed rotation by the air motor
102
, paint is supplied to the rotary atomizing head
104
through the feed tube
105
. Since the rotary atomizing head
104
is in high speed rotation, the supplied paint is atomized into fine particles under the influence of centrifugal force and sprayed forward. The spray pattern of paint particles is controlled by shaping air which is spurted from the shaping air ring
106
while paint particles are sprayed forward for deposition on a work piece.
By the way, according to the above-described prior art rotary atomizing head type coating machine
100
, the rotational shaft
103
and the rotary atomizing head
104
are fixed to each other by threaded engagement of the male and female screw portions
103
A and
104
B. The screw threads of these screw portions
103
A and
104
B are tapped in the opposite direction with respect to the direction of rotation of the rotary atomizing head
103
, more specifically, are tapped as right-turn screws in a case where the rotary atomizing head
103
is put in rotation in a counterclockwise direction as seen arrow a in
FIG. 16
(turning leftward when seen from the front side of the rotary atomizing head
104
). Therefore, when the rotational speed of the air motor
102
is on the increase, the rotational shaft
103
is tightened relative to the rotary atomizing head
104
. On the other hand, when the rotational speed of the air motor
102
is on the decrease, the rotational shaft
103
is loosened relative to the atomizing head
104
.
Nevertheless, should a trouble occur to a drive portion of the air motor
102
when it is in high speed rotation, the rotational speed of the air motor
102
could drop abruptly and the rotation itself could be totally stopped. Besides, for the purpose of changing the paint feed rate to the rotary atomizing head
104
or for the purpose of washing the rotary atomizing head
104
prior to a color change, there may often arise a necessity for dropping the rotational speed of the air motor
102
abruptly from about 30,000 rpm to about 10,000 rpm.
In such a case, despite an abrupt drop in rotational speed of the rotational shaft
103
, the rotary atomizing head
104
tends to maintain a current rotational speed under the influence of inertial force, as a result acting to loosen the screw portions
103
A and
104
A, that is to say, to loosen the rotary atomizing head
104
relative to the rotational shaft
103
. Therefore, while the air motor
102
is in high speed rotation, an abrupt drop of the air motor speed can lead to loosening and fall-off of the rotary atomizing head
104
from the rotational shaft
103
.
Further, the rotary atomizing head
104
is subjected to large centrifugal force while in high speed rotation, and as a result the atomizing head mount portion
104
A is spread in radially outward directions, lowering the gripping force of the male and female screw portions
103
A and
104
B of the rotational shaft
103
and the rotary atomizing head
104
. Thus, upon a conspicuous drop in operating speed of the rotational shaft
103
or a sudden stop of the rotational shaft
103
, the male and female screw portions
103
A and
104
B can be loosened until the rotary atomizing head
104
falls off the rotational shaft
103
.
If the rotary atomizing head
104
should fall off the rotational shaft
103
during high speed rotation, it would be thrown away and hit against nearby equipments and work pieces, resulting in serious damages not only to the rotary atomizing head
104
itself but also to the nearby equipments and work pieces.
On the other hand, according to another prior art rotary atomizing head type coating machine, an O-ring is fitted on the outer periphery of a fore end portion of the rotational shaft or in the inner periphery of the rotary atomizing head mount portion to mount the rotary atomizing head on the rotational shaft through resilient force of the O-ring (e.g., as disclosed in Japanese Patent Laid-Open No. H11-28391).
However, in the case of the another prior art just mentioned, there is a problem of abrasive damages to the O-ring because the surface of the O-ring is abraded every time the rotary atomizing head is mounted on or dismantled from the rotational shaft. If an O-ring is used in a damaged state, it may no longer be able to stop the rotary atomizing head from falling off the rotational shaft because its force of fixing the rotary atomizing head to the rotational shaft is weakened considerably in the abrasive damage.
DISCLOSURE OF THE INVENTION
In view of the above-discussed problems with the prior art, it is an object of the present invention to provide a rotary atomizing head type coating machine which is, for the sake of higher reliability of operation and higher productivity, so arranged as to prevent a rotary atomizing head from coming off or from being thrown away from a rotational shaft when it is loosened relative to the latter while in operation.
The present invention is directed to a rotary atomizing head type coating machine of the sort which includes a high speed rotational drive source, a rotational shaft rotatably supported at a base end thereof by the rotational drive source and having a fore end portion projected on the front side of the rotational dr

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