GB2067673A - Centrifugal blower impeller - Google Patents

Abstract

The curved part of the front plate 5 of the impeller is replaced by a conical supporting ring 6, the upper edge or which is attached to the blades 2 and the lower edge to the cylindrical suction ring 7. A guide ring 8 made of thin plate is mounted inwards from the supporting ring. <IMAGE>

Description

SPECIFICATION Impeller in a centrifugal blower, especially a high-pressure blower The present invention relates to an impeller in a centrifugal blower, especially a high-pressure blower.

In order to achieve high efficiency, the impeller of a centrifugal blower must have rounded, aerodynamically correct forms. However, especially the rounding of the front plate of the impeller causes problems in manufacturing techniques, since the thicknesses of material are rather great. The rounding of the front plate is therefore considerably expensive.

The curving part of the front plate can, according to the present invention, be replaced by a conical supporting ring, by means of which loads are transferred to the blades and the cylinder ring of the impeller. The aerodynamically correct form for the supporting ring is achieved by means of a guide ring made of thin plate; the manufacturing cost of this guide ring is low. The characteristics of the invention are given in the accompanying

claim.

The strength of the combined structure according to the invention is higher than the strength of a rounded, i.e. curved, front plate, since the invention eliminates the bending stresses produced in the curved part and the stress peak produced in the curved front plate and the curved part of the blades.

Owing to its flexibility, the guide ring does not receive stresses, but stresses are transferred from the front plate to the suction ring via the supporting cone, which can be manufactured at low cost in, for example, a rounding machine. This eliminates the stress peak otherwise inevitably produced in the center point of the rounding in both the blades and in the suction ring, and a stress level approx. 2030% lower is achieved than by prior known structures. This stress peak is crucial for the dimensioning of the entire impeller.

Thus the essential point is that in the structure according to the invention the aerodynamical design and the strengths design have been carried out separately, whereby a structure is obtained which is optimal both in strength and aerodynamically and less expensive to manufacture than known structures.

The aerodynamically correct form is achieved by means of a guide plate which is made from thin plate and is easy to produce at low cost by compression tools, pressure turning, etc. The radius of curvature is not iimited as is the case in structures produced by turning, and in certain cases this is very important considering the performance of the blower.

The invention can be applied to conventional impellers, but it is especially significant in high-pressure blowers, in which the blades of the impeller extend as far as the hub of the impeller and in which that part of the blades which faces the suction opening has been designed in:an aerodynamically appropriate way.

One embodiment of the invention is described below with reference to the accompanying drawing, but without limiting the invention to this embodiment.

In the embodiment depicted in the drawing the impeller 1 of a high-pressure blower has a structure in which the blades 2 extend as far as the hub 3 of the impeller and in which that part of the blades 2 facing the suction opening 4 has been designed appropriately. The rounded part of the front plate 5 has been replaced by a conical support ring 6; the upper edge of this ring has been attached to the blades 2 and its lower edge to the cylindrical suction ring 7 of the impeller. A guide plate 8 made of thin plate has been mounted inwards from the supporting ring 6; the stress peak of the guide ring 8 is indicated by 9.

CLAIMS 1. An impeller in a centrifugal blower, especially a high-pressure blower, characterized in that the curved part of the front plate (5) of the impeller (1) has been replaced by a conical supporting ring (6) the upper edge of which has been attached to the blades (2) of the impeller (1 ) and the lower edge to the cylindrical suction ring (7) of the impeller, and that a guide ring (8) made of thin plate has been mounted inwards from the supporting ring (6).

2. An impeller in a centrifugal blower, especially a high-pressure blower, constructed and adapted to operate substantially as hereinbefore described, with reference to, and as shown in, the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Impeller in a centrifugal blower, especially a high-pressure blower The present invention relates to an impeller in a centrifugal blower, especially a high-pressure blower. In order to achieve high efficiency, the impeller of a centrifugal blower must have rounded, aerodynamically correct forms. However, especially the rounding of the front plate of the impeller causes problems in manufacturing techniques, since the thicknesses of material are rather great. The rounding of the front plate is therefore considerably expensive. The curving part of the front plate can, according to the present invention, be replaced by a conical supporting ring, by means of which loads are transferred to the blades and the cylinder ring of the impeller. The aerodynamically correct form for the supporting ring is achieved by means of a guide ring made of thin plate; the manufacturing cost of this guide ring is low. The characteristics of the invention are given in the accompanying claim. The strength of the combined structure according to the invention is higher than the strength of a rounded, i.e. curved, front plate, since the invention eliminates the bending stresses produced in the curved part and the stress peak produced in the curved front plate and the curved part of the blades. Owing to its flexibility, the guide ring does not receive stresses, but stresses are transferred from the front plate to the suction ring via the supporting cone, which can be manufactured at low cost in, for example, a rounding machine. This eliminates the stress peak otherwise inevitably produced in the center point of the rounding in both the blades and in the suction ring, and a stress level approx. 2030% lower is achieved than by prior known structures. This stress peak is crucial for the dimensioning of the entire impeller. Thus the essential point is that in the structure according to the invention the aerodynamical design and the strengths design have been carried out separately, whereby a structure is obtained which is optimal both in strength and aerodynamically and less expensive to manufacture than known structures. The aerodynamically correct form is achieved by means of a guide plate which is made from thin plate and is easy to produce at low cost by compression tools, pressure turning, etc. The radius of curvature is not iimited as is the case in structures produced by turning, and in certain cases this is very important considering the performance of the blower. The invention can be applied to conventional impellers, but it is especially significant in high-pressure blowers, in which the blades of the impeller extend as far as the hub of the impeller and in which that part of the blades which faces the suction opening has been designed in:an aerodynamically appropriate way. One embodiment of the invention is described below with reference to the accompanying drawing, but without limiting the invention to this embodiment. In the embodiment depicted in the drawing the impeller 1 of a high-pressure blower has a structure in which the blades 2 extend as far as the hub 3 of the impeller and in which that part of the blades 2 facing the suction opening 4 has been designed appropriately. The rounded part of the front plate 5 has been replaced by a conical support ring 6; the upper edge of this ring has been attached to the blades 2 and its lower edge to the cylindrical suction ring 7 of the impeller. A guide plate 8 made of thin plate has been mounted inwards from the supporting ring 6; the stress peak of the guide ring 8 is indicated by 9. CLAIMS

1. An impeller in a centrifugal blower, especially a high-pressure blower, characterized in that the curved part of the front plate (5) of the impeller (1) has been replaced by a conical supporting ring (6) the upper edge of which has been attached to the blades (2) of the impeller (1 ) and the lower edge to the cylindrical suction ring (7) of the impeller, and that a guide ring (8) made of thin plate has been mounted inwards from the supporting ring (6).

2. An impeller in a centrifugal blower, especially a high-pressure blower, constructed and adapted to operate substantially as hereinbefore described, with reference to, and as shown in, the accompanying drawing.