EP1579797B1

EP1579797B1 - Powered low-noise suction generating unit for a cleaning apparatus and apparatus with same

Info

Publication number: EP1579797B1
Application number: EP05005762A
Authority: EP
Inventors: Luigi Simonetti
Original assignee: Ametek Italia SRL
Current assignee: Ametek Italia SRL
Priority date: 2004-03-24
Filing date: 2005-03-16
Publication date: 2012-05-09
Anticipated expiration: 2025-03-16
Also published as: EP1579797A1; ITMI20040577A1

Description

This invention relates to a suction unit of the type including an impeller or turbine keyed axially on an electric motor to suck a stream of air axially. The motor is traversed by a cooling-air stream expelled rearward therefrom.
This type of suction unit is generally fitted into a body of a cleaning apparatus such as a vacuum cleaner to have the suction inlet of the rotor facing into a suction chamber of the apparatus while the outgoing air stream is started out of the apparatus through purposeful slits.
In cleaning apparatuses the suction unit is the greater source of noise and therefore manufacturers of apparatuses adopt soundproofing coverings that are applied in layers on the inner walls of the apparatus. This results in various problems such as greater manufacturing complexity and the need for larger dimensions of the apparatus compared with what would be needed for housing of the suction unit only. In addition, the effectiveness of soundproofed coverings is often unsatisfactory and the apparatuses remain excessively noisy anyway.
Even attempts to supply a soundproofed casing inside for the whole motor unit did not give fully satisfactory results because of the excessive size that the unit attains and the difficulty given by the need to supply in any case outlet for the air streams and cooling for the motor.
It must also be allowed for that the openings necessary for passage of the air stream toward the outlet of the apparatus create an outlet for the noise toward the exterior. On the other hand, reduction of the passage would unacceptably reduce the efficiency of the apparatus and cooling of the motor.
DE-A-3402603 discloses a suction unit with a motor surrounded by a soundproof casing, wherein the motor cooling air is evacuated through openings of the soundproof casing immediately after having been extracted from the motor.
US4733429 discloses a suction unit with a motor surrounded by a soundproof casing.
In the evolution of apparatuses the operating speed of the motor has always increased over the years and motors with even very high operating speeds are used ever more, typically well over 30,000 rpm. For this reason, the noise produced has not only always increased in intensity but has also increased in frequency to cause a considerable increase in subjective bother.
The general purpose of this invention is to remedy the above mentioned shortcomings by making available a powered low-noise suction unit.
In view of this purpose it was sought to provide in accordance with this invention a suction unit for cleaning apparatuses according to claim 1. An apparatus with said unit is also claimed.
To clarify the explanation of the innovative principles of this invention and its advantages compared with the prior art there is described below with the aid of the annexed drawings a possible embodiment thereof by way of non-limiting example applying said principles. In the drawings:

FIG 1 shows a partially cross-sectioned side view of a suction unit in accordance with this invention,
FIG 2 shows a plan view of a part of the unit of FIG 1,
FIG 3 shows a partially cross-sectioned diagrammatic view of an apparatus fitted with the unit of FIG 1, and
FIG 4 shows a graph of the effectiveness of the solution in accordance with this invention.

With reference to the figures, FIG 1 shows a suction unit designated as a whole by reference number 10 for cleaning apparatuses.
The unit includes a suction turbine 11 arranged coaxially with an electric rotation motor 12. The turbine is a known type with axial suction mouth 13 and therefore not further shown in detail. The turbine includes known air-stream paths not shown here.
In accordance with the prior art the motor is traversed by a stream of its cooling air that is evacuated from the end 14 of the motor opposite the turbine. Advantageously, the motor has more than 15,000 rpm and advantageously at least around 20,000 rpm to 30,000 rpm.
The electric motor part of the unit is enclosed in a soundproofing casing 15 shaped generally like a tumbler with axis 16 coinciding virtually with the axis of the motor and with the tumbler edge 17 closed on the turbine casing or body. The tumbler-like casing has its inner surface spaced from the motor walls and is provided with openings 18 arranged near said edge closed on the rotor. The openings 18 on the edge are advantageously formed of rectangular notches in the edge.
The casing shape found particularly advantageous was found to be the one shown with cylindrical side wall and bottom joined without edges to the walls.
Again advantageously, as may be seen well in FIG 2 showing the tumbler from the mouth to the bottom, the openings 18 are arranged at regular distances along the edge and in particular are three in number arranged at 120° from each other.
It was found particularly advantageous that the total of the extensions of the openings along the edge be between 1/3 and 1/2 of the total perimeter of the edge. As shown in FIG 2, with a cylindrical-shaped tumbler each opening can advantageously have an angular extension α between 45° and 60° and preferably around 50°. Again advantageously, the area of the openings on the casing is at least equal to the area of the air extraction openings on the motor.
The rearward air flow out of the motor is forced into an S-shaped path that runs parallel to the motor wall and toward the impeller in the air space between the motor and the outer shell 15.
As may be seen in FIGS 1 and 2, the tumbler has a wall formed by an external casing 19 of rigid plastic material and an internal layer 20 of fibrous or porous sound absorbent material. Polypropylene was found to be a particularly advantageous material for the rigid external shell. The thickness of the shell is between 1.5 mm and 5 mm and advantageously around 3 mm while the internal layer has a thickness between 10 mm and 20 mm and advantageously around 15 mm.
As may be seen again in FIGS 1 and 2, the casing has a bottom with members 21 projecting towards the motor to constitute supports on the motor, for example between or in radial spokes of the motor. In the preferred embodiment the projecting members are two in number arranged symmetrically around the motor axis and extending towards the motor in a direction parallel to said axis.
FIG 3 shows partially a cleaning apparatus 22, for example a vacuum cleaner, otherwise of prior art and therefore not shown in detail being easily imaginable to those skilled in the art,. The apparatus 22 has a shell 23 containing the suction unit of FIG 1 so as to identify a suction chamber 24 into which faces the suction mouth 13 of the suction unit and a chamber 25 at the back insulated from the first and receiving the suction unit body and that has slots 26 for evacuation outward of the air sucked by the turbine.
Advantageously, the tumbler-shaped casing 15 of the suction unit has a bottom with external engagement seats 27 designed to at least partially support the cleaning apparatus unit. For this support, the apparatus has internal fastening members 28 inserted with their end in the seats 27. The members 28 can possibly be made of material such as for example rubber suitable for not transmitting operating vibrations.
With a suction unit in accordance with this invention it was surprisingly found that the soundproofed casing arranged only on the motor with outlet openings as mentioned above avoids resonance and reverberations and allows a more than adequate air stream outlet from the motor while preventing outlet of noise with very high efficiency. Stopping the noise near its origin avoids its diffusion and, despite the dimensions kept reduced, provides high silence of the apparatus in which the unit is fitted even without equipping the apparatus with soundproofing systems of relatively high space occupied and costly. It was also found that the faster the motor's speed of rotation (more than 15,000 rpm and in particular more than 30,000 rpm, for example around 40,000 rpm to 50,000 rpm) the more the noise is generated in the motor part of the unit and not in the turbine. Surprisingly, it was found thus that the effectiveness of the above-mentioned solution increases with increase in motor speed and that it is not necessary to provide soundproofing protection for the rest of the suction unit.
FIG 4 shows a graph of the undeniable advantages of a suction unit realized in accordance with this invention. A broken line shows the course of the noise of a prior art unit with a 15,000 rpm motor. Note the high noise peak around 5,000 Hz. From the comparison with the solid line showing the noise of a similar unit realized however in accordance with the principles of this invention the noise reduction is evident with a flattening toward the lower part of the noise curve at higher frequencies. The residual noise is truly much reduced. Entirely without increasing the transversal dimensions of the unit compared with prior art units of equal power (the transversal dimension is given by the turbine that remains unchanged). It should be noted that the transverse dimensions of a suction unit are the most important for the final dimensions of the apparatus.
Naturally the above description of an embodiment applying the innovative principles of this invention is given by way of non-limiting example of said principles within the scope of the exclusive right claimed here. For example, small soundproofing internal covering panels can be used anyway in the apertures if desired to further reduce the small residual noise possibly still heard. In addition, the members 21 can be of a number different from that shown. It can also be thought to use a single tube-shaped member to blend the rear hub part of the motor.

Claims

Suction unit (10) for a cleaning apparatus, including an electric rotation motor (12) and a suction turbine (11) comprising a turbine body, which is keyed coaxially to the electric rotation motor (12), with the motor (12) being traversed by a stream of air for its cooling and the electric motor (12) being also enclosed in a soundproof casing (15) shaped generally like a tumbler with the tumbler edge (17) closed by the turbine body, characterized in that the motor (12) being provide with an end (14) opposed to the turbine, through which the cooling air is evacuated, the tumbler-like casing (15) has openings (18) arranged near said edge (17) closed by the turbine body, the tumbler-like casing (15) having its internal surface spaced from the motor casing walls to form an air space between the tumbler-like casing internal surface and the motor casing walls identifying an S-shaped path for evacuated cooling air which is directed from said motor end (14), running along said air space towards the turbine (11), to the openings (18) arranged near said edge (17) closed by the turbine body.
Suction unit in accordance with claim 1 characterized in that the openings (18) on the tumbler edge (17) are formed from rectangular notches on said edge (17).
Suction unit in accordance with claim 1 characterized in that the openings (18) are arranged at regular distances along the tumbler edge (17).
Suction unit in accordance with claim 3 characterized in that the openings (18) are three in number, arranged at 120° from each other.
Suction unit in accordance with claim 1 characterized in that the sum of the extensions of the openings (18) along the tumbler edge (17) is between 1/3 and 1/2 of the total edge perimeter.
Suction unit in accordance with claim 1 characterized in that the area of the openings (18) on the casing is at least equal to the area of openings present on the motor (12) for extraction of said air stream.
Suction unit in accordance with claim 6 characterized in that said extraction openings are placed in the end (14) of the motor (12) near the bottom of the tumbler (15).
Suction unit in accordance with claim 1 characterized in that the tumbler-like casing (15) has a bottom connected without edges to the walls.
Suction unit in accordance with claim 1 characterized in that the tumbler (15) has a wall formed by an external shell (19) of rigid plastic material and an internal layer (20) of fibrous or porous soundproof material.
Suction unit in accordance with claim 9 characterized in that the external shell (19) is of polypropylene.
Suction unit in accordance with claim 9 characterized in that the thickness of the shell (19) is between 1.5 mm and 5 mm and advantageously around 3 mm.
Suction unit in accordance with claim 9 characterized in that the internal layer (20) has a thickness between 10 mm and 20 mm and advantageously around 15 mm.
Suction unit in accordance with claim 1 characterized in that the tumbler-like casing (15) has a cylindrical side wall.
Suction unit in accordance with claim 1 characterized in that the tumbler-like casing (15) has a bottom with members (21) projecting toward the motor (12) to constitute supports on the motor.
Suction unit in accordance with claim 1 characterized in that the projecting members (21) are arranged symmetrically to the motor axis (16) and extend toward the motor (12) in a direction parallel to its axis.
Suction unit in accordance with claim 1 characterized in that the tumbler-like casing (15) has a bottom with engagement seats (27) on the outside, designed as at least partial support of the unit (10) in a cleaning apparatus (22).
Suction unit in accordance with claim 1 characterized in that the motor (12) has a number of revolutions greater than 15,000 rpm.
Cleaning apparatus (22) with a suction unit (10) in accordance with any one of the above claims.