A centrifugal ventilator

Abstract: The invention relates to a centrifugal ventilator (10) comprising an impeller (2) rotating internally of a volute (3) afforded as an impression made in a parallelepiped single block (1) made of a plastic material. The single block (1) is provided with an external shape which is different to a shape of the volute (3) and exhibits, in a zone thereof not occupied by the volute (3), impressions (5) and/or through-holes (6) of various shapes and dimensions; a cover (4) also being provided for closing the impression forming the volute (3).

Description: The invention relates in particular to the field of centrifugal ventilators for industrial use, which are destined to generate considerable, generally low-pressure, air flows, and which are called upon to function continuously in work areas containing several personnel. These ventilators are provided with an impeller, normally set in rotation by a motor, and rotating internally of a volute usually realized by means of a shell which can be made by casting, though since construction of this type of ventilator is especially economical, more frequently the shell is made of specially fashioned sheet metal. The main drawback exhibited by such ventilators is that they are noisy enough to irritate personnel, as during functioning vibrations are created both by the rotations of the impeller and by the flow of air produced. To obviate this drawback, such ventilators are located, if possible, in areas not frequented by personnel; also, construction quality thereof has been improved, especially with regard to the shell, and by covering the shell itself with sound-absorbent material. The prior art also comprises centrifugal ventilators as described in the preamble of claim 1. DE 1503610 discloses such a centrifugal ventilator, wherein an involute or scroll-shaped surface of the airflow passage is formed substantially wholly from a self-coherent, air permeable sound absorbing medium, such as expanded polyurethane. The air-permeable medium is contained in an enclosure having airimpermeable walls provided with inlet and outlet openings. In EP 0083704 a fan casing is provided with guide ducts for the medium to be conveyed. The fan casing consists of a casing block made of sound absorbing material, such as a porous plastic of a predetermined hardness, and of two cover plates at the end faces which accommodate the casing block between them and of which at least one can likewise consist of sound absorbing material. FR 2469770 discloses an impeller which rotates internally of a volute made as an impression in a single block of plastic material having a right parallelepipedic shape. All of these solutions, however, only partially reduce the noise level generated by such ventilators. The main aim of the present invention is to obviate the above-described limits and drawbacks in the prior art, by providing a centrifugal ventilator which is constructionally simple and economical and which generates, during functioning, only limited noise. Some of the advantages of the invention are its compactness, its simplicity of manufacture and installation, and the fact of being able to vary the external geometry of the ventilator in such a way as to eliminate possible noise determined by special installation and functioning conditions. The above aims and objectives are all attained by more the centrifugal ventilator of the invention, as it is characterized in the claims that follow. Further characteristics and advantages of the present invention will better emerge from the detailed description that follows, of an embodiment of the invention, illustrated in the form of a non-limiting example in the accompanying drawings, in which: figure 1 is a lateral view of the ventilator, with some parts removed better to evidence others; figure 2 is a section according to line II-II of figure 1; figure 3 is a lateral view from the right of figure 1. With reference to the figures of the drawings, 10 denotes in its entirety a centrifugal ventilator provided with an impeller 2 which rotates internally of a volute 3. In the present invention the volute 3 is afforded is a single block 1 of plastic material (preferably polyeurethane), provided with an external shape which is different to the shape of the volute 3. It has been demonstrated that the combination of the above-mentioned characteristics (especially the use of a plastic material and the adoption of an external shape which does not follow the shape of the volute 3) produces a reduction in the number of vibrations and noises created by the ventilator 10 during use, and, at the same time, enables the ventilator 10 to be made extremely simply and economically. The single block 1 preferably has a parallelepiped shape, with a flat inferior surface that enables it to be placed on a support plane, for which reason the ventilator 10 is self-standing. A cover 4 for closing the volute 3 is also provided (not shown in figure 1 for reasons of clarity of illustration). The volute 3 afforded in the single block 1 exhibits on one side an aperture 9, coaxial to the impeller 2, through which a shaft 8 (for driving the impeller 2) of a motor 7 can pass. The aperture 9 can be conformed in such a way as to house therein a support for the shaft 8. In a further embodiment (not illustrated) of the invention, a recess complete with ventilation apertures is made internally of the single block 1, which recess can house a motor for the impeller 2, thus reducing ventilator vibrations and noise levels even further. The cover 4 exhibits a mouth 11, coaxial to the impeller 2, for the inlet of air into the ventilator 10. 12 denotes an outlet mouth of the ventilator 10. The breadth of the single block 1, measured in the various radial directions with respect to the impeller 2 starting from the outline of the volute 3 and going externalwise, is of the same order as the diameter of the impeller 2. This characteristic improves sound absorption during ventilator 10 functioning. In the part of the single block 1 which is not occupied by the volute 3, one or more impressions 5 are made, variously-shaped and of various dimensions and depths; also present are one or more through-holes 6, also of various shapes and dimensions. Tests have shown that the presence of cavities (impressions, niches, lowered parts, through-holes etc.) on the walls of the single block 1 further reduces the noise levels of the ventilator during its functioning. The single block 1 can be manufactured in known ways and with relatively contained costs, by pressing or by moulding molten plastic material. The above-indicated cavities are indicated by 5 and 6 and can be made directly during the single block 1 hot-pressing process, for example by inserting cores into the die, or after manufacture by removing material, for example after the installation of the ventilator 10 once excessive noise levels and vibrations are noted. The single block 1 can also be provided with projections, recesses, grips, feet and the like, all directed at simplifying, for example, the setting up of the ventilator, its mounting on an external frame, the application on the single block 1 of the cover 4 to close the volute 3, and so on. It is further possible to provide holes 13 in the single block 1 around the outlet mouth 12, to allow fixture thereto of a connection flange to an external outlet. Thanks to the considerable breadth of the single block 1, it is possible to create chambers therein which can be used, for example, for storing tools and other objects.

Claims: A centrifugal ventilator, comprising an impeller (2) which rotates internally of a volute (3), said volute (3) being made as an impression in a single block (1) of plastic material provided with an external shape which is different from a shape of said volute (3); a cover (4) being provided for closing said volute (3); characterized in that in a part of said single block (1) not occupied by said volute (3) one or more through-holes (6) are afforded. A centrifugal ventilator as in claim 1, characterized in that a breadth of said single block (1), measured in various radial directions with respect to said impeller (2) and starting from the shape of said volute (3) and moving in an externalwise direction, is of a same order of size as a diameter of said impeller (2). A centrifugal ventilator as in claim 1 or 2, characterized in that in a part of said single block (1) which is not occupied by said volute (3) one or more impressions (5) are provided. A centrifugal ventilator as in any one of the preceding claims, characterized in that said single block (1) has a parallelepiped shape. A centrifugal ventilator as in any one of the preceding claims, characterized in that said single block (1) is made of polyeurethane.

Inventors: MARCHI GERMANO, MARCHI, GERMANO
Applicants: IDR HOLDING S A, IDR HOLDING S.A.
Application year: 1996
Main classification: F04D29
IPC codes: F04D29