Fan stage configuration

The invention comprehends an inter or after stage of a fan system in which the stage has curvilinear spiralling guidance blades and integral blade tips angled in an axial direction to provide guidance for air flow to the spiralling guidance blades.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to fans and, more specifically, relates to a 
centrifugal fan having an inter stage and/or an after or discharge stage. 
2. Summary of the Prior Art 
Inter stage and after stage devices for centrifugal fan systems are known 
and have been utilized with fans and fan systems for many years. It is 
also known to provide blading or shrouds for these devices which tend to 
turn the flow of the centrifugal fan stage discharge. An attempt has been 
made, in many instances, in the design of the blading or shrouding, to 
obtain a smooth transition at the discharge from the centrifugal fan. This 
has taken, generally, the form of a separate structure to define the 
desired air flow channel, leaving an intermittent or discontinuous guided 
flow path for the centrifugal fan discharge. This causes losses and 
inefficiencies of some magnitude for the discharge flow from the fan 
system. 
Accordingly, it is an object of the invention to provide a guidance 
arrangement for the flow of discharge air from a fan having improved 
static recovery and efficiency. 
It is a further object of the invention to provide guidance blading 
operative to smoothly guide air axially towards a discharge port or a 
centrifugal fan eye. 
It is an additional object of the invention to provide continuous blading 
for an inter stage or after stage which turns the fan discharge from an 
outward tangential direction to an axial, radial direction. 
It is a still further object of the invention to incline the outer ends of 
stage blades in an axial direction to provide guidance for the fan 
discharge as it moves to a fan eye or central discharge point. 
It is an even further object of the invention to angle the blade tip ends 
of continuous blades axially to accommodate a streamlined flow for a 
motor-fan system. 
It is also an object of the invention to angle the blade tips end, at an 
angle axially to accommodate the operating point of the motor-fan system. 
SUMMARY OF THE INVENTION 
The invention contemplates a motor-fan having one or more centrifugal fans 
and a possible stator inter stage and/or a stator after stage. The 
centrifugal fan or fans, conventionally, takes the form of a series of 
curvilinear blades mounted between two end plates and centered with the 
center of rotation of the fan. These fans are driven to rotate at high 
speed by being mounted on a shaft rotatably driven by an electric motor or 
the like. Disposed downstream or behind each fan is a stator stage also 
including curvilinear blades which tend to lead the peripherally, 
tangentially discharged fan air radially inwardly for a central, axial 
discharge to the next stage fan or to discharge from the fan system. 
In order to smoothly accomplish this function, the stator stage blades are 
inwardly, curvilinear, leading to a central discharge point while, at 
their tips, they are angled curvilinearly in an axial direction to help 
turn the air, tangentially discharged from the fan tips. These differently 
angled blade sections also merge smoothly with each other so as to form a 
continuous generally non turbulent guidance arrangement for the air flow 
from the fan. The blade tips may be advantageously specifically angled to 
accommodate the operating point of the motor fan system.

DETAILED DESCRIPTION OF THE INVENTION 
There is shown in FIG. 1, a motor fan system 10 including an electric motor 
12 an a staged fan system 14. The motor 12 includes a stator 16 and an 
armature 18 attached to a driving shaft 20. Shaft 20 is mounted to rotate 
in bearings 22 and 24 so as to rotatably drive the staged fan system 14. 
This fan system includes a pair of fans 26, 28. 
The fans 26, 28 are clampingly held on drive shaft 20 in compression 
between a balancing ring 32 and a washer 34, disposed on opposite sides of 
the fan 26, an elongated fan space 36 disposed generally between the fans 
26 and 28 on shaft 20, a pair of washers 38, 40, disposed on opposite 
sides of fan 28, and a bearing spacer 42, disposed between the washer 40 
and the bearing 22. A fan assemblage 44 is thereby formed fast with the 
shaft 20 so as to rotate with it as it is driven by the electric motor 12, 
with this assemblage captivated between compression nut 30 and bearing 22. 
Mounted non-rotatably also, as a part of the staged fan system 14 are an 
inter stage 46 and an after stage or discharge 48. The inter stage 46 is 
mounted fast to a fan cover 50 while the after stage 48 is mounted to a 
motor bearing retainer plate 52. This is accomplished in the following 
manner. 
The bearing retainer plate 52 is provided with a pair of threaded bores 54, 
54 through which bolts 56, 56 are threaded, with the heads of the bolts 
56, 56 engaging with a housing 58 or the electric motor 12. 
After or discharge stage 48 is then mounted by rivets 60, 60 (only one 
shown) to the bearing retainer plate 52, these rivets passing through 
bores 55, 55 in the bearing retainer plate 52. This connection prevents 
the after stage 48 from rotating relative to the fans 26 and 28. The inter 
stage 46 is also prevented from rotating by being mounted with a second 
fan cover 62 through the aegis of struck over tabs, like the integral tab 
64, which mount the inter stage 46 to this fan cover. Fan cover 62, in 
turn, is force fit at its innermost portion 64 over an outer wall 66 of 
bearing retainer plate 52. 
The flow of fan driven air 68 is generally from leftward to rightward in 
FIG. 1, passing through an aperture 70 in fan cover 50, fan 26, inter 
stage 46, fan 28, after stage 48 and bearing retainer plate 52, through 
openings 72, 72, to thereby pass into the electric motor 12 to cool it. It 
is discharged from the end of the motor through conventional slots (not 
shown). It is to be noted that the staged fan system 14 is not provided 
primarily for motor cooling but is operative to move a substantial flow of 
air such as necessitated by its use in a clean air system canister cleaner 
or the like. Its use is not limited, however, to this function since it 
would find general utilizity in the motor driven fan art. The fans and the 
inter and after stages 46 and 48 will now be described. 
The inter stage 46 is shown more specifically in FIGS. 5-9. As can be seen, 
it is of molded configuration and includes a back plate 74 with a central 
hub 76 for shaft 70 through mounting, as previously described. Mounted on 
an interior side 78 of the inter stage 46 are a series of conventional 
concentric equally spaced curvilinear integral, spiralling blade portions 
80, 80 (eight in number) which extend in an inward axial direction for a 
limited amount to give them depth. These blade portions terminate at an 
outer circumference 82 of inter stage 46. A circumferentially and axially 
extending strengthening rim 84 is also present at this circumference on 
the exterior side 86 of the back plate 74 of inter stage 44. 
The spiralling blades 80, 80, at the outer ends, terminate angularly (in an 
axial direction) to accommodate integral axially angled, curvilinear tips 
88, 88 that are curvilinear, in plan, relative to the interior side 78 of 
inter stage 46. Each merges smoothly with an angled end 90 of the 
spiralling blades 80 and each is a continuation of the spiral of its blade 
80. The lending edge of these blade tips includes a bevel 89 for smooth 
transition for air flow from the fan 26. The curvilinear tips 88, 88 do 
not overlap, one with the other, in the horizontal direction so that the 
leading edge (bevel 89) of one is offset at an angle 95 from a trailing 
edge 91 of the next blade 80. This angle is set at at least 5.degree. to 
permit a relatively easy molding of the inter stage 46. The trailing edge 
91 of each of the blades 80 is also beveled to provide a smooth merging of 
a tip 88 with a terminating flat edge 93 of its respective spiralling 
blade 80. The tip of the blades 88 is also angled relative to the axial 
direction of the inter stage 46 by an angle 97, the tangent of this angle 
selected to be as close to the ratio of the average axial velocity over 
the average tangential velocity of the operating range of air flow through 
the system. This provides a higher efficiency for the air flow system than 
would otherwise be obtainable. 
Each of the blades 80, 80 have a tab 92 spaced along their spiral which 
extends axially and is inserted through slots (unnumbered) in second fan 
cover 62 and the tabs then struck over to non-rotationally mount the inter 
stage 46 to the motor fan system 10. First fan cover 50 is then located 
over it, and inserted over the end of second fan cover 62 to place it also 
in a non-rotational condition. 
After stage 48 is quite similar to inter stage 46 in that it has a series 
of spiralling blades 94, 94 (six in number) a back plate 96, a rim (not 
seen) and axially angled spiralling tips 98, 98 each integral with blade 
94. However the tips 98, 98 are extended and not truncated (to prevent 
overlap in inter stage 46) so they slowly narrow and merge smoothly in a 
spiralling fashion with a circumference 100 of the after stage 48. This 
increases static pressure recovery after that occasioned by inter stage 46 
without acting as much of a limiting choke. This also reduces noise 
greatly over that generated by the inter stage 46 which is important 
because of the location of it in the system. A beveled portion 102 between 
the terminations of the tips 98 aids in this noise reduction. The 
nontruncated extension of the tips 98, 98 reduces the number of blades 
with tips that may be molded into the after stage thereby increasing the 
width of the air channels between. Thus, in order to insure more directed 
streamlined flow of air, splitter blades 104, 104 (six in number) are 
interposed between the blades 94, 94. Each of the blades 104 is 
curvilinear and spirals in a uniform manner relative to the blades 94, 94 
but it includes no angularly angled tip and extends in its spiral, to 
substantially the circumference 100 of the after stage 48. At its outward 
end it includes a spiralling angled portion 106 which somewhat mirrors in 
its axial projection the surface 102 to limit noise. 
All of the blades 94, 104 are stepped downwardly at their inner ends to 
provide inward portions 108 on blades 94 and inward portions 110 on blades 
104. This advantageously, provides clearance for the interfitting of 
bearing retainer plate 52 with after stage 48. 
Each of the fans 26, 28 includes inner and outer flanges 112, 114, with 
flange 112 including a fan eye 116 for the passage of air inwardly to a 
series of blades 118. The blades 118, include fangs 120 for attachment to 
the flanges 112, 114. No further description will be given relating to the 
fans 26, 28 since they are entirely conventional. 
The description of the invention being generally completed, it should be 
obvious that a fan system has been provided which includes at least one 
stator stage in which the blading is continuous for the guidance of air in 
both an axial and a radial direction and that blades and blade tips of 
curvilinear and spiralling character have been adapted for this purpose 
and that such an arrangement would streamline air passing through it, 
increasing efficiency while at the same time reducing noise. It should be 
obvious that modifications to this description might occur to one skilled 
in the art which would still fall within its spirit and purview.