Tangential ventilating device

Abstract: There is provided a tangential ventilating device (1) wherein the fan (2; 2a) is defined by one (6) or more (6a, 6b) ventilating units; each unit in turn being defined by a one-piece body molded from plastic material and having two opposite longitudinal end portions (7, 8; 7a, 8a, 7b, 8b) substantially perpendicular to the axis of rotation (R) of the fan, and a number of longitudinal blades (10; 10a, 10b) spaced circumferentially apart and substantially parallel to one another and to the axis of rotation.

Description: The present invention relates to an improved tangential ventilating device, particularly suitable for household ovens, refrigerators, air-conditioning appliances, and electric household appliances in general. As is known, in the ventilation of ovens and refrigeration and air-conditioning systems in general, the trend is increasingly towards tangential power ventilators, the characteristics of which (e.g. low noise level, good pressure/airflow ratio, and compactness) represent an excellent cost/performance trade-off. Generally speaking, known ventilators of this type comprise a motor, normally a shaded-pole motor; and a tangential fan inside a screw. The motor substantially comprises a pack of laminations; and a rotor, the shaft of which rotates on bushings supported by two supports made of nonmagnetic material (normally die-cut or die-cast aluminium). At least one bushing is spherical for self-alignment and is held in position by a metal spring which comes in various forms and can be fitted to the support in various ways The tangential fan (i.e. which operates with flow substantially tangent to its outside diameter and is normally longer than its diameter) is normally defined by a number of longitudinal blades retained or at any rate inserted inside respective seats formed in a number of transverse disks; and both the blades and disks are made of die-cut metal (typically aluminium). Fans of this sort obviously have the drawback of involving the manufacture and assembly of a large number of component parts. The screw also comprises a number of die-cut metal components riveted or welded to one another, and which invariably pose problems of axial alignment, squareness and parallelism; high reject rate; sharp surface edges; poor appearance; compulsory painting of the parts; and frequent servicing of die-cutting and assembly equipment. GB-A-1421795 discloses a plastic fan incorporating one or more fan wheels connected to one another by riveting. i.e. by a permament connection which cannot be released. It is therefore an object of the present invention to eliminate the aforementioned drawbacks of the known state of the art by providing, in particular, a tangential ventilating device which is practical, provides for a high degree of performance and long-term reliability, and is also cheap and easy to produce. According to the present invention, there is provided a tangential ventilating device as claimed in the accompanying Claim 1. The device according to the invention therefore comprises a fan which, unlike the known state of the art, does not involve the manufacture and assembly of a large number of separate component parts, and therefore provides for considerable saving in terms of production cost and time. The fan can also be produced by axially connecting two or more modular ventilating units, so that, besides simplifying pressing of the individual units without complicating assembly (which, in fact, is extremely straightforward and fast), the blades of the various units may be offset to cut the resonance frequency of the rotating fan and so achieve optimum airflow and air pressure and reduce the noise level. The screw is also formed in one piece molded from appropriate plastic material, so that it is cheap, of desired appearance (color, finish, no flash) and dimensions, and within specified tolerances in terms of axial alignment and parallelism. According to a further aspect of the invention, the fan and motor supports are also made of plastic (and therefore nonmagnetic) material, and, unlike known self-aligning supports, require no springs. The spring, in fact, is replaced by elastic appendixes defining the seat of the spherical bushing, so that the support is still fully functional, including being self-aligning, but at the same time provides for significant saving in terms of the number of component parts and assembly time. A non-limiting embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a plan view of a tangential ventilating device in accordance with the invention; Figure 2 shows a partially-sectioned side view of the Figure 1 device; Figure 3, shows an exploded view in perspective of a fan applicable to the Figure 1 device; Figures 4a, 4b show side and front views respectively of a first component part of the Figure 3 fan; Figures 5a, 5b show side and front views respectively of a second component part of the Figures 3 fan; Figure 6 shows a larger-scale detail of the Figure 3 fan; Figure 7 shows a view in perspective of a screw forming part of the Figure 1 device; Figure 8 shows a view in perspective of a rotary member support applicable to the Figure 1 device. With reference to Figures 1 and 2, number 1 indicates as a whole a tangential ventilating device, e.g. for a known household oven (not shown). Device 1 comprises a tangential fan 2a housed in rotary manner inside a screw 3; a conveyor 4; and a motor 5 connected mechanically to fan 2a. With reference to Figures 3 to 6 a fan 2a comprises two modular ventilating units 6a, 6b having axial connecting means 26 for axial assembly end to end. Unit 6a is defined by a one-piece body of molded plastic material (e.g. polyamide) and has two opposite longitudinal end portions 7a, 8a substantially perpendicular to the axis of rotation R of fan 2a, and a number of longitudinal blades 10a spaced circumferentially and which are substantially parallel to one another and to axis of rotation R and extend longitudinally between end portions 7a and 8a. End portion 7a is substantially disk-shaped, and comprises a central disk 31 coaxial with axis of rotation R; end portion 8a is defined by a ring 32 radially outwards with respect to disk 31; blades 10a, at one end, project radially from a radially outer peripheral edge 33 of disk 31, and, at the opposite end, are butt connected and substantially inscribed in a face 34 of ring 32; and, besides being connected to peripheral edge 33 of disk 31, blades 10a have respective reinforcing portions 35 connected to a face 36 of disk 31 facing end portion 8a. Similarly, unit 6b is defined by a one-piece body of molded plastic material (e.g. polyamide) and has two opposite longitudinal end portions 7b, 8b substantially perpendicular to the axis of rotation R of fan 2a, and a number of longitudinal blades 10b spaced circumferentially and which are substantially parallel to one another and to axis of rotation R and extend longitudinally between end portions 7b and 8b. End portion 7b is substantially disk-shaped, and comprises a disk 41 coaxial with axis of rotation R; and end portion 8b is defined by a ring 42 radially outwards with respect to disk 41. In this embodiment, too, end portions 7a, 8a and 7b, 8b of each unit 6a, 6b therefore have respective solid portions and hollow portions, the solid portions of one end portion being superimposable over the hollow portions of the opposite end portion. Blades 10b, at one end, project radially from a radially outer peripheral edge 43 of disk 41, and, at the opposite end, are butt connected and substantially inscribed in a face 44 of ring 42. Blades 10b also have respective reinforcing portions 45 connected to a face 46 of disk 41 facing end portion 8b. To support fan 2a in rotary manner, disk 31 is provided integrally with a hollow shaft 50; and disk 41 has a central through seat 51 for housing a known drive member, e.g. a disk of elastomeric material as described previously. Axial connecting means 26 comprises a number of (e.g. four) connecting pins 52 carried by ring 32 of unit 6a and insertable frontwards and interferentially - or bayonet-fashion, as in the non-limiting example shown - inside respective through seats 53 in ring 42 of unit 6b. As shown in detail in Figure 6, each pin 52 is substantially L-shaped and comprises a root portion 54 projecting axially from a face 55, opposite face 34, of ring 32; and a head 56 substantially perpendicular to root portion 54 and for engaging ring 42. Each seat 53 comprises a circumferential slide portion 57 having a narrow or tight portion 58 for click-on connection to a respective pin 52; and blades 10b adjacent to seats 53 have respective recesses 59 to permit insertion of heads 56. Two aligning notches 60 are formed on respective outer edges of rings 32, 42 to position units 6a, 6b correctly at assembly. Ring 32 has a locating collar 61, which projects axially from a radially inner peripheral edge 62 of ring 32 and is insertable inside ring 42. Advantageously, units 6a, 6b are so connected that respective blades 10a, 10b, as opposed to being aligned axially, are offset circumferentially to cut the resonance frequency of rotating fan 2a and so achieve optimum airflow and air pressure and reduce the operating noise level. More specifically, blades 10a, 10b of units 6a, 6b are offset half a space (i.e. each blade 10a of unit 6a is located halfway between two blades 10b of unit 6b). With reference to Figure 7, screw 3 is molded in one piece from plastic material, e.g. polyamide, and comprises two parallel, longitudinally opposite sides 70, 71 connected by a curved air-conveying wall 72, and by a front longitudinal member 73 facing curved wall 72 and defining an air outlet 74. Sides 70, 71 also have respective lateral flanges 75 in which holes 76 are formed for attachment to a supporting surface. Conveyor 4 (not shown in Figure 7 for the sake of clarity; see Figures 1 and 2) is fixed to longitudinal member 73 : advantageously, conveyor 4 is molded in one piece with screw 3, so that device 1 constitutes an integrated unit ready for assembly to the user appliance. Sides 70, 71 have respective self-aligning supports 100, 101 (shown in Figure 7 and Figure 8 respectively) for supporting fan 2 or 2a and motor 5 in rotary manner. Each support 100, 101 comprises a base member 102 having a seat 103 for a known spherical bushing 104. Base member 102 comprises a circular collar 105 projecting axially from a surface 106 of base member 102; and three elastic appendixes 107, which project from base member 102, are spaced circumferentially (e.g. 120° apart) about collar 105, define seat 103, and are block-shaped to cooperate elastically with bushing 104 and so support and retain bushing 104 inside seat 103. More specifically, the respective free ends of appendixes 107 have respective contact portions 108 shaped to cooperate with a curved outer lateral surface 109 of bushing 104, to prevent any axial or rotary movement of bushing 104, and to only allow a substantially transverse alignment movement of bushing 104, which clicks axially inside seat 103 by virtue of the elasticity of appendixes 107. Appendixes 107 and collar 105 are formed integrally in one piece with base member 102, e.g. molded from the same plastic material as screw 3. In the non-limiting example shown in Figures 7, support 100 is formed integrally in one piece with side 70 of screw 3, so that respective base member 102 is defined by a portion of screw 3 itself. It is to be understood, however, that support 100 may be a separate component fitted to screw 3, e.g. inserted inside a seat formed in side 70, as shown by the dash line in Figure 7. Support 101, on the other hand, comprises a substantially known disk-shaped body 110 connected to side 71 by bayonet fasteners 111 inserted inside respective seats 112 formed about a central hole 113 in side 71; in which case, base member 102 is defined by a portion of disk-shaped body 110, which is molded in one piece with base member 102, collar 105 and appendixes 107.

Claims: A tangential ventilating device (1) comprising a fan (2a) of the type having longitudinal blades substantially parallel to an axis of rotation (R) of the fan; said fan (2a) comprising two or more modular ventilating units (6a, 6b) having axial connecting means (26) for axial assembly end to end; each unit being defined by a one-piece body molded from plastic material and having two opposite longitudinal end portions (7a, 8a, 7b, 8b) substantially perpendicular to said axis of rotation (R), and a number of longitudinal blades (10a, 10b) spaced circumferentially apart, substantially parallel to one another and to said axis of rotation, and extending longitudinally between said end portions; the device being characterized in that said axial connecting means (26) comprise a number of connecting pins (52) carried by a first unit (6a) and insertable frontwards and interferentially or bayonet-fashion inside respective seats (53) on a second unit (6b) for click-on connection of each seat (53) to a respective pin (52). A device as claimed in Claim 1, characterized in that said end portions (7a, 8a, 7b, 8b) of each unit (6a, 6b) are so formed as to comprise respective solid portions and hollow portions; the solid portions of one end portion being superimposable over the hollow portions of the opposite end portion. A device as claimed in Claim 2, characterized in that said blades (10a, 10b) of each unit (6a, 6b) project radially, at one end, from a peripheral edge (33, 43) of a first end portion (7a, 7b) of the unit, and, at the opposite end, are butt connected and substantially inscribed in a ring (32, 42) of a second end portion (8a, 8b) of the unit. A device as claimed in any one of the foregoing Claims, characterized in that said units (6a, 6b) are so connected that the respective numbers of blades (10a, 10b) are offset. A device as claimed in any one of the foregoing Claims, characterized in that each pin (52) is substantially L-shaped and comprises a root portion (54) and a head (56) substantially perpendicular to said root portion (54); each seat (53) comprising a circumferential slide portion (57) having a narrow or tight portion (58) for click-on connection to a respective pin (52). A device as claimed in Claim 5, characterized in that blades (10b) adjacent to seats (53) have respective recesses (59) to permit insertion of said heads (56). A device as claimed in any one of the foregoing Claims, characterized in that said units (6a, 6b) have respective first end portions (7a, 7b) comprising respective disks (31, 41), and respective second end portions (8a, 8b) defined by respective rings (32, 42) radially outwards with respect to the respective disks; the blades (10a, 10b) of said units extending from respective radially outer peripheral edges (33, 43) of said disks (31, 41), and being substantially inscribed in respective faces (34, 44) of said rings (32, 42). A device as claimed in any one of the foregoing Claims, and comprising a screw (3) housing said fan (2a) in rotary manner and having two parallel, longitudinally opposite sides (70, 71) connected by a curved air-conveying wall (72) and by a front longitudinal member (73) facing the curved wall and defining an air outlet (74); the device being characterized in that said screw (3) is molded in one piece from plastic material. A device as claimed in the foregoing Claim, characterized by comprising at least one self-aligning support (100, 101) carried by a side (70, 71) of said screw (3) and for supporting said fan (2a) in rotary manner; said support (100, 101) comprising a base member (102) having a seat (103) for a spherical bushing (104); and said seat (103) being defined by a number of elastic appendixes (107), which project from said base member (102), are spaced apart circumferentially, and are block-shaped to cooperate elastically with said bushing (104) and so support and retain said bushing (104) inside said seat (103). A device as claimed in the foregoing Claim, characterized in that the respective free ends of said appendixes (107) have respective contact portions (108) shaped to cooperate with a curved outer lateral surface (109) of the bushing (104), to prevent any axial or rotary movement of the bushing, and to only allow a substantially transverse alignment movement of the bushing. A device as claimed in the foregoing Claim, characterized in that said appendixes (107) are formed integrally in one piece with said base member (102), and are preferably molded from plastic material. A device as claimed in the foregoing Claim, characterized in that said base member (102) comprises a circular collar (105) projecting axially from the base member (102); and three appendixes (107) spaced 120° apart about said collar (105). A device as claimed in one of Claims 9 to 12, characterized in that said base member (102) is formed integrally in one piece with a side (70) of said screw (3).

Inventors: PAGANO GAETANO, PAGANO, GAETANO
Applicants: MEDYS S P A, MEDYS S.P.A.
Application year: 2001
Main classification: F04D17
IPC codes: F04D17, F04D29