Flat type fan, particularly for electronic circuits

A flat type fan is provided having an axial dimension very much less than its radial dimension, comprising a casing forming a cylindrical duct for a fan blade unit. Two webs carry bosses having fixing bores therethrough. The length of the bosses is equal to the length of the casing, which allows the fan to be fixed on a wall by any one of its faces, for blowing or for suction.

BACKGROUND OF THE INVENTION 
The present invention relates to a fan of the flat type, intended more 
especially for ventilating electronic circuits. 
Fans of this kind, whose axial dimension is very much less than the radial 
dimension, generally comprise a casing forming a cylindrical duct and 
carrying in its central part, by means of arms, a support for a motor 
stator. Fan blades are integral with a rotor rotatably mounted on a shaft 
integral with the casing. Fixing to a wall is achieved by means of a 
square flange having holes at the corners for passing a screw there 
through. 
It is important for the same type of fan to be able to be used for suction 
or blowing. To this end, it is provided with two flanges, one on each 
side. But such a construction leads to complication and a high 
manufacturing cost, requiring removal from the mould both in the radial 
and in the axial directions. There also results high material consumption, 
relatively high weight and large dimensions. 
Efforts have been made to reduce these disadvantages by securing by means 
of two diamentrically opposite lugs situated in the facial planes of the 
casing. Thus economy in material is achieved, and at the same time 
manufacture is simplified, since removal from the mould is purely in the 
axial direction. But the same fan cannot be used both for suction and for 
blowing. 
The present invention aims at providing a fan whose manufacture remains 
particularly economical both from the amount of material used and the 
operating simplicity and which, furthermore, may be used equally for 
blowing or for suction, while presenting a relatively reduced weight and 
taking up relatively less space. 
SUMMARY OF THE INVENTION 
According to the invention, the flat type fan, particularly for ventilating 
electronic circuits, comprises a casing forming a cylindrical duct and 
carrying in its central part a support for a motor stator, and this 
support is connected by arms to the periphery of the duct. This fan 
further comprises fan blades integral with a rotor rotatably mounted on a 
shaft integral with the casing, and the casing comprises means for fixing 
to a wall. The fan is characterised in that it comprises, on the periphery 
of the casing, two diametrically opposite fixing bosses each having there 
through at least one fixing passage parallel to the axis of the fan, the 
length of the bosses along the axis of the fan being substantially equal 
to the length of the box in the same direction. 
With this construction, the flanges are suppressed which results in an 
appreciable gain in material and weight, and which reduces the radial 
dimension. Furthermore, manufacture is simplified since removal from the 
mould is purely in the axial direction. Finally, because of their length, 
the fixing bosses play the same role irrespective of the face of the fan 
which is applied against the wall. Thus the same fan may be used equally 
for blowing or for suction. 
To ensure interchangeability of the fan with those of an older type, it is 
sufficient to give to the passages the same distance between axis as that 
of two diagonal holes of the square flanges. 
According to an advantageous embodiment of the invention, each fixing boss 
has provided therethrough two parallel passages whose axis are in the same 
plane with the axis of the fan, which provides a possibility for adapting 
to boring standards. 
According to a preferred embodiment of the invention, the fixing bosses are 
made integral with the case by means of a web disposed transversally to 
the axis of the fan, which forms a particularly light and economical 
fixing means. 
One of the fixing webs of the bosses then carries advantageously an 
additional boss having a passage there through for receiving a ground 
connection. 
The ground connection boss has preferably a length less than the axial 
length of the casing, so as to leave room for a screw head. 
The web carrying the ground connection boss advantageously comprises a hole 
for fixing a collar for clamping supply wires, so that all the wiring 
relative to the fan ends in the same region. 
The collar for clamping the wires advantageously comprises a flexible 
projection having a retaining notch for securing same by clipping into the 
hole of the web. One of the arms connecting the stator support to the 
cylindrical duct is hollowed out to form a gutter for housing the supply 
wires, and leading them up to the stator. 
The fan preferably comprises a support block moulded on the supply wires, 
and the stator has a cavity for receiving this support block. 
This support block comprises, at one of its ends, a stop for co-operating 
with the stator and limiting its distance of insertion in the cavity of 
the stator and, at its other end, a projection made from a flexible 
material having a retaining notch for preventing extraction of the support 
block introduced into the cavity of the stator. 
The stripped ends of the wires are thus held perfectly immovable with 
respect to the fan, which facilitates connection thereof to the windings 
of the stator. 
According to a preferred embodiment of the invention, the fan comprises a 
number of connecting arms between the stator support and the cylindrical 
duct sufficient to form a protection grid. 
Since the number of arms is thus appreciably increased with respect to 
known constructions, it is possible to reduce their section, more 
especially in the axial direction, which allows the axial dimension of the 
fan to be reduced. 
For further reducing the axial dimension of the fan, the fan blades have a 
single bearing comprising two bearing surfaces axially offset and 
separated by a cavity, the outer diameter of the bearing being reduced at 
the level of these bearing surfaces. 
Thus an axial dimension is obtained very much less than that obtained by 
conventional mounting with two bearings separated by an oil felt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 to 3, the fan comprises a casing 1 which forms a 
cylindrical duct 2 and carries, in its central part, a support 3 for the 
stator 4 of an electric motor. Support 3 is connected to the cylindrical 
duct 2 by arms 5 which are sufficient in number to form a protection grid. 
Distance pieces 6 connect these arms while forming a ring which serves 
both for strengthening and as an additional protection. 
A shaft 7 housed in the centre of support 3 carries fan blades 8 through 
the bearing 9 housed in the hub 11 of the fan blade unit which contains 
the rotor 12 of the motor. 
Two webs 13, 14 integrally formed with casing 1 are substantially 
diametrically opposite outside duct 2, the position of their plane 
relative to the faces 15, 16 of the case (FIG. 3) being dictated by 
moulding requirements. 
A boss 17 is integral with these webs and the securing thereof to duct 2 is 
strengthened by a rib 18. The length of this boss is substantially equal 
to the axial length of case 1 (FIG. 4), and it has there through two 
parallel passages 19, 21 whose axis are substantially in the same plane 
with the axis of rotation of fan blade unit. At each of their ends, these 
passages open into a common chamber 22. 
Web 14 carries an additional boss 23, the securing of which to duct 2 is 
strengthened by rib 24, and which is pierced with two symmetrical blind 
bores 25 in the extension of each other (FIG. 5), so as to form a closed 
passaged having an axis parallel to the axis of rotation of the fan. 
The length of boss 23 is less than the distance separating the faces 15 and 
16 of casing 1, so as to leave a space between it and the wall to which 
any one of these faces might be applied. 
Web 14 further comprises, in a thicker portion 26, a bore 27 (FIG. 6) for 
receiving a collar 28 (FIGS. 2 and 3) in which are clamped the supply 
wires 29 for the motor. 
Collar 28 (FIG. 12) comprises a projection made from a flexible material 
formed of three points 31 each having a retaining catch 32, so that it is 
efficient to push the points into bore 27 until the catches 32 come out on 
the other side of web 14 for the collar to be clipped into the web. 
At about 90.degree. on the bosses 17, casing 1 comprises two symmetrical 
lands 33 which facilitate handling thereof and lend themselves to 
inscriptions. 
One of the connecting arms 5, reference 5a in FIGS. 2 and 6, is wider than 
the others and is formed with a gutter section (FIG. 10) for containing 
the supply wires 29 coming from collar 28. At the end of this arm, the 
stator support 3 has a bore there through 34 for allowing the wires 
through to the stator. 
At the end of wires 29 going into the stator there is moulded a support 
block 35 (FIG. 1) which is housed in a cavity 36 of the stator, the ends 
37 of the wires which come out from this block being stripped. 
Support block 35 comprises, on the sides of ends 37, a top 38 (FIGS. 13 and 
14) for co-operating with a face of the stator and limiting its insertion 
into cavity 36. At its other end, it comprises a projection 39 made from a 
flexible material (FIG. 1) having a retaining catch 41 for co-operation 
with the other face of the stator and for preventing the support block 35 
from being removed once introduced into cavity 36. 
Bearing 9 integral with the fan blade unit 8 and rotatively mounted on 
shaft 7 comprises two bearing surfaces 42 (FIG. 1) separated by a central 
cavity 43 serving as an oil reserve. The ends 44 of the bearing situated 
at right angle to bearing surfaces 42 have reduced outer diameters. Thus, 
during force fitting of the bearing into the fan blade unit, deformation 
of the metal is not applied to the zone of the bearing surfaces and their 
coaxiallity is not affected. 
A washer 45 forming an oil seal is disposed about shaft 7 on the side of 
its embedded end. This washer comprises a peripheral flange 46 coming to 
bear on bearing 9. Radial indentations 47 are formed in this flange so as 
to cause the periphery of shaft 7 to communicate with cavity 48 formed 
between the fan blade unit 8 and part 44 of the bearing whose outer 
diameter is reduced (FIG. 15). 
According to a further embodiment, casing 1 comprises securing bosses 117 
(FIG. 7) where only a single passage 121 is formed. Fixing is then 
achieved by means of a threaded rod 49 associated with a knot 51, with a 
block of resilient material 52 occupying one of the chambers 122 (FIG. 11) 
and bearing on the shoulder formed at the end of this chamber. 
In the above described embodiment, the presence of two passages 19,21 
allows immediate adaptation to two standard distances between axes, and 
more especially allows this fan to be used as a replacement for a 
conventional fan having four securing points, by disposing the line of the 
bosses diagonally across the existing securing points. 
According to a further embodiment, bosses 217 have a lateral opening 253 
(FIGS. 6 to 9), so as to allow insertion of resilient protruding sleeve 
254 (FIG. 8), into which is then inserted a rigid tube 255 for limiting 
crushing of sleeve 254 during tightening of the securing screw. 
In this case, boss 217 properly speaking is of a length a little less than 
the axial length of casing 1, compensation being obtained by the 
protruding flange of sleeve 254. 
In all cases, it is apparent, considering the symmetry of the securing 
bosses, that the fan may be fixed to a wall by any of its faces 15 or 16, 
i.e. either for blowing or for suction. 
A ground wire 57 may also be fixed, by means of a screw 56 (FIG. 3), to 
boss 23, on any side, the head of the screw having room to be accomodated 
within the axial dimension of casing 1. 
To fit the fan, with stator 4 installed, wires 29 are passed through cavity 
36 of the stator until the support block 35 moulded thereover is 
introduced therein. This block is then pushed well in until it is clipped 
in place by projection 39. Then the stripped ends 37, thus held fixed, are 
soldered to the stator wires. Then wires 29 are brought back into the 
gutter of arm 5a and collar 28 is clipped into bore 27. 
Then the fan blade unit 8 is engaged, by means of bearing 9, on shaft 2 
after oil has been introduced into the central cavity 43 of the bearing. 
In operation, the oil which leaves the end of the bearing is projected by 
centrifugal force and, passing through the indentations 47 of washer 45, 
accumulates in cavity 48 where it is in contact with the bearing. 
It is apparent that, by doing away with the conventional square flanges, 
considerable economy in material, a reduction in weight and a reduction in 
the radial dimension are achieved. And these advantages are in no way 
obtained to the detriment of the performances of the fan, which result 
essentially from the peripheral feed of the fan blade unit, so from the 
diameter thereof, which has in no ways been modified. 
Besides these advantages in material, weight and radial size of this fan, 
with respect to conventional flange construtions, a reduction in the axial 
dimension is obtained more especially by increasing the number of 
connecting arms, which allows their section to be reduced, particularly in 
the axial direction. This advantage of the arms is added to that by which 
these arms dispense with the need, at least on one side of the apparatus, 
for the addition of a projection grid. 
Although the dimension of arms 5 is reduced in the axial direction, the 
dimension of their section in the tangential direction is still further 
reduced, as shown in the cut-back 5b (FIG. 2), which confers on this arm 
an axial fin shape which serves as a honeycomb rectifier and improves the 
efficiency. The arms are in fact situated in the air output face. This 
role is completed by a similar shape for the distance pieces 6 (FIG. 1). 
This reduction in the axial dimension is further the result of using a 
single bearing, which allows the length of the hub of the fan blade unit 
to be reduced. In all, the axial dimension may thus be reduced from 38 mm 
(11/2") to 25.4 mm (1"). 
The fan according to the invention thus forms a novel industrial product 
forming a functional unit which complies with a single finality of 
economy, manufacture and use. 
Of course, the invention is not limited to the examples described but 
covers any technological variation within the scope of a man skilled in 
the art.