Title:
MIXER IMPELLER BLADE
United States Patent 3816024


Abstract:
A light weight but strong blade for a mixer impeller is formed of relatively thin steel having a hat cross-section with a thin steel plate covering the outer portion of the cavity formed by the crown portion of the hat section and spot welded to the brim portion. At the inward end of the blade, a barrier closes the crown cavity to prevent fluid flow and pumping action. The outer edges of the crown section are scarfed to prevent eddy currents.



Inventors:
QUINN J
Application Number:
05/359421
Publication Date:
06/11/1974
Filing Date:
05/11/1973
Assignee:
PHILADELPHIA GEAR CORP,US
Primary Class:
Other Classes:
416/223R
International Classes:
B01F7/00; B01F15/00; (IPC1-7): B01F7/24
Field of Search:
416/210,223
View Patent Images:
US Patent References:
3628888LIGHT WEIGHT FAN ASSEMBLY1971-12-21Wooden
2388464Airplane propeller1945-11-06Bergen
1246086N/A1917-11-13Glantzberg
0686211N/A1901-11-05



Foreign References:
BE520709A
GB152416A1920-10-12
GB450992A1936-07-28
Other References:

Chemical Engineering; Oct. 4, 1971; Vol. 78; No. 22; Page 23.
Primary Examiner:
Powell Jr., Everette A.
Attorney, Agent or Firm:
Paul & Paul
Claims:
What is claimed is

1. A blade for a mixer impeller, said blade comprising:

2. A blade according to claim 1 wherein an inner portion of the crown portion of the hat-section, inward of said cover plate and barrier plate, is adapted to receive the ear of the hub member of an impeller shaft.

3. A blade according to claim 1 wherein the outer edges of the crown portion of the hat-section are scarfed.

4. A blade according to claim 3 wherein said scarfing is of an angle of the order of 45°.

5. A mixer blade according to claim 2 wherein the sides of the crown portion of the hat section are disposed at an angle of the order of 45° relative to the plane of the brim portions.

6. A mixer blade according to claim 1 wherein said cover plate is spot welded to the brim portions.

7. A mixer blade according to claim 1 wherein the blade is rectangular in plan view.

Description:
BACKGROUND OF THE INVENTION

Mixer-impeller blades of the prior art have ordinarily been made of relatively heavy steel plate having a longitudinal reinforcing rib welded to the back surface thereof.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a mixer blade of lighter weight but substantially equal strength to that of the prior art and so constructed as to reduce the amount of welding and the distortion which it generates.

The foregoing object is achieved, in accordance with the present invention, by providing a hat-section of relatively thin steel and covering the forward portion of the cavity of the crown portion with a thin plate spot welded to the brim portion, and by providing a closure plate or barrier at the inward end of the cover plate to prevent pumping action by preventing fluid flow through the crown cavity. Preferably, the outer edges of the crown portion of the hat-section are scarfed to reduce eddy currents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a four-bladed mixer impeller, the blades of which are constructed in accordance with the present invention;

FIG. 2 is a plan view of the impeller of FIG. 1;

FIG. 3 is an exploded schematic view showing the hat section and the cover plate having a depending closure element or barrier which closes the inward end of the crown cavity of the hat-section;

FIG. 4 is a plan view of one of the mixer blades;

FIG. 5 is a view, in section, looking along the line 5--5 of FIG. 4;

FIG. 6 is a view, in section, looking along the line 6--6 of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1, which is a perspective view of a four-bladed mixer impeller, shows blades 10 constructed in accordance with the present invention. Each blade 10 consists of a hat-section of relatively thin stainless steel, having a crown portion 12 and brim portions 14. The inclined side walls of the crown portion 12 are identified as 13. These side portions 13 may preferably be inclined at an angle of the order of 45° relative to the plane of the brim portions 14. The cavity 15 formed by the crown portion of the hat section is covered by a thin flat plate 16, also of stainless steel, which as indicated in FIG. 4, may preferably be spot-welded as at 18 to the brim portions 14.

The cover plate 16 only covers the outer three-quarters (approx.) portion of the cavity 15. The inner one-quarter (approx.) portion of the crown cavity is left uncovered to allow a bracket plate 21 to be bolted thereat. The inward edge of the cover plate 16 has secured thereto, as by welding, a closure or barrier plate 17 which depends from the inward edge of the cover plate 16 and is shaped to close the cavity 15 formed by the crown of the hat section.

As seen in FIGS. 1, 2 and 4, the four blades are angularly secured to a hub 20 which is adapted to be keyed to the impeller shaft. The four blades are secured by four ears or bracket plates 21, each of which is secured to hub 20 as by welding. The ears or bracket plates 21 are received within the inner uncovered portion of the crown cavity 15 and bolted to the crown 12, as by four bolts, with a washer plate 22 being placed on the opposite surface of the crown 12.

The forward edge of the crown portion of the hat section is preferably beveled or scarfed to avoid the generation of eddy currents.

The closure barrier 17 at the inner edge of the cover plate 16 provides an important function in that it prevents fluid flow through the hat cavity 15, thereby avoiding the pumping action which would otherwise occur. The provision of barrier 17 improves the efficiency very substantially. The reduction in power resulting from the use of barrier 17, in comparison with a similar blade having no barrier element, is of the order of 25 percent.

The construction shown and described provides a mixer blade of adequate strength which is considerably lighter in weight than those which have been provided by the prior art. Also, welding of a reinforcing rib to the back of the blade is avoided.

A typical prior art blade for a mixer impeller may, for example, be formed of a rectangular plate of 5/16 inch stainless steel, Nos. 304L or 316L, 38 inches long and of the order of 24 inches wide having welded to the rearward surface thereof a rib which extends the full length of the blade.

In contrast to the above prior-art blade, and without intending to be limited to the values given, a blade according to the present invention may be formed of a rectangular sheet (32 inches × 24 inches) of 11-gauge (0.120 inches) stainless steel Nos. 304L or 316L. The cover plate 16 may be 12-gauge (0.1054 inches). No reinforcing rib is necessary, and the welding thereof is avoided. Only the spot welding of the cover plate 16 to the brim 14 is required, plus the welding of the barrier plate 17 to the inner edge of the cover plate.

The depth of the crown portion of the hat section may, for example, be 13/4 inches. The sides 13 of the hat section may preferably be inclined at an angle of 45° relative to the plane of the brim 14. The outer edges of the crown of the hat section may preferably be scarfed at an angle of the order of 45° to prevent the establishment of eddy currents. The blades may be disposed, relative to the axis of hub 20, at various angles according to the particular mixer needs. In the illustrated embodiment, an angle of the order of 32° is indicated.

The new mixer blade is of the order of 50-60 percent lighter in weight than prior-art blades of equal strength.