FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
' &
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
An Impeller and a method of joining the Shrouds thereof
APPLICANTS
Crompton Greaves Limited, CG House, Dr. Annie Besant Road, Worli, Mumbai -400 030, Maharashtra, India, an Indian Company
INVENTOR
Sukhadia Rajnikant Ishwarlal and Rajgor Divyesh Amrutbhai of Crompton Greaves
Limited, Pump Division (M5), A-28, MIDC, Ahmednagar - 414111, Maharashtra, India, both Indian nationals
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:


FIELD OF INVENTION
This invention relates to an impeller and a method of joining the shrouds thereof. BACKGROUND OF THE INVENTION
Impellers are rotating devices that force liquids, gases and vapors in a desired direction. They are widely used in pumping, blowing, and mixing applications. An impeller of a centrifugal pump usually comprises of two shrouds joined to each other and mounted on a hub portion connected to a shaft. A motor drives the shaft thereby rotating the shrouds. It is of critical importance that the shrouds remain binded to each other during the operation of the impeller. Conventionally, the shrouds are joined by either welding or riveting. Owing to the requirement of a very narrow spacing between the shrouds, an accurate and strong welding there between requires a lot of precision. Such a welding is also time consuming and costly. Alternatively, the shrouds are joined by means of a rivet. The rivets are first pushed through the holes punched in each disc such that the rivet lug protrudes from the hole of one of the shrouds joined together. The protruding lug is then riveted against the disc. Using rivets to bind/join two shrouds together adds extra weight to the impeller which in turn either limits the rotational speed of the impeller or requires more power to rotate thereof thereby resulting in low efficiency of the impeller. Also, due to the presence of rivets, both the surfaces of the shroud are rendered having a rough finish thereby leading to a high frictional loss during the operation of the impeller further reducing its efficiency.
OBJECTS OF THE INVENTION
An object of the invention is to provide a method of binding/joining the shrouds of an impeller wherein no external material is required to join the shrouds.
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Another object of the invention is to provide a method of binding/joining the shrouds of an impeller by which the bind between the shrouds is of superior mechanical strength.
Another object of the invention is to provide a method of binding/joining the shrouds of an impeller which is simple, inexpensive and consumes less time.
Another object of the invention is to provide a method of binding/joining the shrouds of an impeller which renders the impeller efficient.
Another object of the invention is to provide a method of binding/joining the shrouds of an impeller by which at least one of surface of the binded/joined shrouds is smooth.
Another object of the invention is to provide an impeller whose shrouds are binded/joined together without any use of an external material.
Another object of the invention is to provide an impeller wherein the bind between the shrouds is of superior mechanical strength.
Another object of the invention is to provide an impeller which is efficient and has a smooth finish on at least one of surface of the binded/joined shrouds.
DETAILED DESCRIPTION OF THE INVENTION
In order to achieve the aforesaid and other objectives, according to the invention, a method is provided for joining the two shrouds of an impeller. The method comprises the steps of piercing a hole in one of the said shrouds, projecting the periphery of the hole or a portion thereof axially outwardly from said one shroud, punching a hole in the other shroud for receiving said projection, inserting the projection into the hole of the other
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shroud and folding back the projection from the hole of the other shroud onto a surface of the other shroud thereby joining said shrouds.
In order to achieve the aforesaid and other objectives, according to the invention, there is also provided an impeller comprising of two shrouds being joined by means of a projection of a hole or a part thereof of one shroud wherein said projection is inserted into a hole of the other shroud and folded back onto a surface thereof.
These and other aspects, features and advantages of the invention will be better understood with reference to the following detailed description, accompanying drawings and appended claims, in which,
Fig la illustrates an exploded view of the impeller.
Fig lb illustrates an isometric view of the impeller.
Fig 2a to Fig 2c illustrates a step by step method of joining of the two shrouds.
Fig la and lb illustrates an exploded and isometric view of the impeller respectively. The impeller comprises of a back shroud 1, a front shroud 2, a hub 3 and a hub disc 4. The hub 3 and the hub disc 4 comprises of a coaxial bore at its centre. The diameter of the bore of the hub disc 4 is larger than the diameter of the bore of the hub 3 so as to be mounted thereupon. The bore of the hub 3 receives the shaft (not shown in the fig) connected to a motor (not shown in the fig) which drives the impeller. The back shroud 1 comprises of a bore for receiving the hub 3 so as to be fitted on it and be rotated when the shaft rotates. A plurality of guide vanes 7 are provided on the surface of the back shroud 1 for enabling the circulation of the fluid there through. A plurality of holes 8 are also punched on the surface of the back shroud 1. The front shroud 2 is essentially a flat circular disc with a plurality of holes 9 and a large bore at its centre for receiving the fluid to be pumped out. A plurality of holes 9 are pierced on the surface of the front
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shroud 2. Further, the periphery of the holes 9 are projected outwards axially to be inserted through the holes 8 of the back shroud 1 and folded back onto surface of the back shroud 1 by fullering process thereby joining both the shrouds.
Fig 2a to Fig 2c shows a cross section of the front and the back shrouds illustrating a step by step method of joining of the two shrouds. Fig 2a shows a cross section of the front and the back shrouds in close proximity. The back and front shrouds 1 & 2 are provided with a plurality of holes 8 & 9 respectively on its surfaces. The holes 8 are punched while the holes are 9 are pierced onto the respective surfaces of the shrouds 1 & 2. The periphery of each hole 9 of the front shroud 2. is projected axially outwardly from its surface thereof. Subsequently, as shown in Fig 2b.t the projections 11 of the front shroud 2 are inserted through the corresponding holes 8 of the back shroud 1. Finally, the projections 11 protruding outside the holes 8 of the back shroud 1 are folded back onto the surface of the back shroud 1 so as to bind the shrouds 1 & 2 together. The folding back of the projections 11 is carried out by fullering process.
Different ways of executing the above method are possible. For example, instead of projection the periphery of the holes of the front shrouci, holes of the back shroud can be projected. Instead of projecting the periphery of the entire hole, only a part of the periphery can be projected. The thickness of projection Across the periphery may vary upon the design parameters of the impeller.
According to the invention, the simple and less time consuming method of joining the two shrouds of an impeller obviates the need of an external material such a welding material or a rivet thereby rendering the impeller devoid of any extra weight and a rough surface and hence increasing the efficiency in its operation as well as cost effectiveness in its manufacturing.
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Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the invention as defined.
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We claim:
1. A method of joining the two shrouds of an impeller, said method comprising the
steps of:
o piercing a hole in one of the said shrouds;
o projecting the periphery of the hole or a portion thereof axially outwardly
from said one shroud; o punching a hole in the other shroud for receiving said projection; o inserting said projection into the hole of the other shroud; and o folding back the projection from the hole of the other shroud onto a
surface of the other shroud thereby joining said shrouds.
2. The method as claimed in claim 1, wherein said projection is folded onto the surface of the other shroud by fullering process.
3. The impeller comprising of two shrouds being joined by means of a projection of a hole or a part thereof of one shroud wherein said projection is inserted into a hole of the other shroud and folded back onto a surface thereof.
4. The impeller as claimed in claim 3, wherein said hole is pierced in said one shroud.
5. The impeller as claimed in claim 3, wherein said hole is punched in said hole of the other shroud.
6. The impeller as claimed in claim 3, wherein said projection is folded onto the surface of the other shroud by fullering process.