GB2094897A

GB2094897A - Impellers and processes for producing them by moulding

Info

Publication number: GB2094897A
Application number: GB8207477A
Authority: GB
Original assignee: GUINARD POMPES; POMPES GUINARD ETS
Current assignee: GUINARD POMPES; POMPES GUINARD ETS
Priority date: 1981-03-13
Filing date: 1982-03-15
Publication date: 1982-09-22
Also published as: IT8212447A0; BE892410A; IT1157637B; EP0061375A1; FR2501801A1

Description

SPECIFICATION Vane wheels, and equipment and processes for producing them by moulding The present invention relates to vane wheels and to equipment and processes for making them by moulding. There are three distinct types of vane wheels: those called centrifugal (or centripetal) radial vane wheels, where the paths of the fluid particles are contained in planes perpendicular to the axis of rotation, except in the immediate vicinity of the latter; those called axial vane wheels, in which the fluid particles remain substantially at a constant distance from the axis of rotation; and those called helico-centrifugal (or helico-centripetal) vane wheels, which come between the two preceding cases, and in which the vanes are shaped so that the fluid particles follow a path which has both a radial component and an axial component. It is this last type of wheel which the invention improves. The outline of the vanes of these wheels is governed by hydraulic factors which define, in particular, their angle of entry, angle of exit, length, height, leading edge and profile. The vane which results from this has a complicated skew shape. It cannot be removed from a mould. To produce it in a foundry, sand cores are made by assembling sectors which are held together by bonding and by tying. These assemblies give a casting which has many burrs, thus making it necessary to remove these burrs subsequently, and its dimensions are neither exact nor reproducible and its surface state is very mediocre. When the curves of the vanes are slight, a onepiece core is used, and the core maker loosens the fins of the core case to move them from the core during preparation of the latter.Consequently, not only do the cores no longer comply with the dimensions fixed by the hydraulic engineer and differ from one another, but also the hydraulic engineer does not know this difference in dimension, and it varies in an unforseen manner from one vane to another on one and the same wheel, according as the movement of the caster is more or less abrupt. The manufacturer of helicocentrifugal vane wheels does not know the actual profile of the vanes, although he has determined the theoretical profile with a great degreee of accuracy, and because of this uncertainty in production he is prompted to adopt larger tolerances. The invention overcomes these disadvantages by means of a helico-centrifugal vane wheel, the surface state of which, when obtained from casting or moulding, is flawless, the dimensions of which are accurate and can correspond exactly to the plans given to the caster, without insuperable difficulties facing him, and the production of which is quicker than in the past and can be automated. Experience has shown that this vane wheel gives at least the same performances as conventional helico-centrifugal wheels and often performances higher than these. The subject of the invention is a vane wheel comprising a web, forming a hub, which is in revolution about an axis and from which project helico-centrifugal vanes adopting the axis of the hub as an axis of repetition, characterised in that the imaginary prolongation of the generating line of the web intersects the axis of the hub, and the lower face and upper faces of the vanes extend over portions of surfaces of cylinders, the axes of which are inclined relative to that of the hub. Preferably, the cross-section of the cylinders is a circle and the web is substantially in the form of a truncated cone. The invention is also directed at a core case which comprises helico-centrifugal vanes with an axis of repetition, the lower face and upper face of each vane extending respectively over surface portions of cylinders, the axes of revolution of which are inclined relative to the axis of repetition. The process for moulding metallic vane wheels according to the invention consists in producing a sand core in which cavities are made with the shape of the vanes of the wheel to be moulded, filling these cavities with liquid metal, leaving the metal to solidify into a piece, and destroying the same core to release the piece, and it is characterised in that it consists in filling the core case according to the invention with sand, hardening the sand in it into a core, and removing the core from the case, taking the vanes of the case out of the core by giving them a translational movement along their axis of revolution. In the attached drawings given solely by way of example: Figure 1 is a partial perspective view of a vane wheel according to the invention. Figure 2 is a sectional view of a mould for moulding the wheel of Figure 1. Figure 3 is an exploded view, with a partial. cutaway, of a core case making it possible to obtain the core used in the mould of Figure 2; and Figure 4 is a sectional view of a vane of the core case. The wheel of Figure 1 comprises six helicocentrifugal vanes 1 (only one of these being shown), the lower face 2 and the upper face 3 of which extend respectively over portions of surfaces of cylinders, having a circular crosssection, the axes Y, Y' of which are inclined relative to the axis of repetition X, X' of the vanes 1. The wheel possesses a web 4 in revolution about the axis X, X'. The web is substantially in the form of a truncated cone. The vanes 1 project from the web 4. The wheel is produced, in casting, by means of two frames 9, 10, one lower and one upper, filled with sand and matching the outer shapes of the wheel, and, between the two frames, a sand core 8 reproducing the inner shape of the wheel (Figure 2). After the metal has been cast and cooled, the sand is destroyed, and the rough-cast wheel is obtained. To produce the two frames and the core, it is necessary to have: - two model plates reproducing the front face and the rear face of the wheel; a core case (Figure 3) for making the core. The model plates are obtained in the conventional way without difficulty. The core case consists essentially of a case bottom 11, an assembly of vanes 12 and a cap 13. Each vane 12 has a lower face and an upper face which extend over portions of surfaces of a cylinder, the axis of which is inclined relative to the axis X, X" of the bottom 11. It is appropriate to add to the actual vane a portion called a locating stud 14 (Figure 4). This "locating stud" is embedded in the case bottom 11 1 like a tenon in a mortice and will make it possible to put the vane 12 in place on the case bottom 11 and to remove it from this. Each vane 12 is withdrawn from the sand core as a result of a translational movement along the axis of the cylinder over which the vane extends. The core case makes it possible to produce as many sand cores 11 as it is desired to make vane wheels. Each core 11 is located between the two frames 9, 10. The metal is cast. The cast wheel is released by removing the sand.

Claims

1. Vane wheel comprising a web (4), forming a hub, which is in revolution about an axis (X, X') and from which project helico-centrifugal vanes (1) adopting the axis (X, X') of the hub as an axis of repetition, characterised in that the imaginary prolongation of the generating line of the web (4) intersects the axis of the hub, and the lower faces and upper faces of the vanes (1) extend over portions of surfaces of cylinders, the axes (Y, Y') of which are inclined relative to the axis (X, X') of the hub.

2. Wheel according to Claim 1, characterised in that the cross-section of the cylinders is a circle.

3. Wheel according to Claim 1 or 2, characterised in that the web is substantially in the form of a truncated cone.

4. Core case, used for producing wheels with helico-centrifugal vanes according to Claim 1, 2 or 3, characterised in that it comprises helicocentrifugal vanes with an axis of repetition, the lower face and upper face of each vane extending respectively over the portions of surfaces of cylinders, the axes of revolution of which are inclined relative to the axis of repetition.

5. Process for moulding a wheel with metallic helico-centrifugal vanes according to Claim 1, 2 or 3, which consists in producing a sand core in which cavities are made with the shape of the vanes of the wheel to be moulded, filling these cavities with liquid metal, leaving the metal to solidify into a piece, and destroying the sand core to release the piece, characterised in that it involves producing a core case according to Claim 4, filling the core case with sand, hardening the sand in it into a core, and removing the core from the case, taking the vanes of the case out of the core by giving them a translational movement along their axis of revolution.