US 2096891 A
Description (OCR text may contain errors)
Oct. 26, 1937.l E. F. G. FREDLUNYD VACUUM CLEANER Filed DeC. 18, 1934 Patented Oct. 26, 1937 UNITED STATES PATENT oFFlcE* VACUUM CLEAN EB Application December 1s, 1934., serial No. 757,993 In Germany December 21, 1933 6 Claims. (Cl. 23o-232) My invention relates to vacuum cleaners and more particularly to means for reducing the noise emitted from a vacuum cleaner due to the operation of the motor-fan unit.
According to the invention this reduction in noise is mainly effected Aby constructing and arranging the outer and inner parts of the cleaner, especially those parts placed behind the fan counted in the direction of flow of air, in such manner that at least one of the air channels defined by said parts is equivalent to an air cylinder the diameter of which is preferably less than-its length and at the most less than twice its length and which begins andv ends with sudden changes in area. The arranging of the air passage in this manner causes sudden contractions and expansions of the air passing therethrough which has the effect of reducing the noise of the motor fan unit which is emitted from the cleaner.
Further objects and advantages of my invention will be apparent from the following description considered in connection with the following drawing which forms a part of this specification and of which:
Fig. 1 is a diagrammatic view illustrating the principle of my invention; and
Fig. 2 is a. cross-sectional view of my invention embodied in a preferred form of vacuum cleaner.
In Fig. 1 there is shown diagrammatically an air passage comprising sections a, b and c. The diameters of these sections are represented by y and z, respectively, and it will be noted that adjacent sections are of diierent diameter and 35 that the change in diameter between adjacent sections is abrupt. The length of the respective sections are represented by o, p and q and it will be noted that in each`case the lengthA is greater than the diameter of the respective section.
40 When air is passed through a passage of the type shown diagrammatically in Fig. 1, sound waves which may be present in the air at the entrance end of the passage are reduced to a great 45 extent by the time the air 4leaves the passage.
'I'his is due to the sudden compression and expansion of the air as it passes from a section of one diameter to a section having a different diameter.
In Fig. '2 there is shown a vacuum cleaner so constructed that the passage for the ow of. air from the fan to the outlet contains portions or sections having' free ow areas arranged in accordance with the principle illustrated in Fig. 1. 55 Reference character I0 designates a preferably cylindrical casing. To one end of casing ID a cap` Il may be secured in any suitable manner, as by spring clips I2. Cap I I is formed with a centrally threaded aperture into which a co'upling member I3 may be screwed. Coupling I3 has a central aperture adapted to receive a flexible hose I4 which may be connected to any suitable suction nozzle or other cleaning implement. A ring I5 is adapted to be clamped between cap II and the end of casing I0 and serves to support the open. end of a. dust bag I6.
'I'he other end of vcasing I0 is provided with a ring Il to which may be secured, in any suitable manner, a motor supporting ring I8. Ring I8 is provided with a plurality of lugs I9 which carry pins 20. These pins support the inner ends of coil springs 2|, the other ends of which are secured to a motor housing 22. Housing 22 is provided With a forward bearing shield 23 and a rear bearing shield 24. These shields are formed with openings 25 and 26, respectively, which communicate with air passages 21 extending through the eld of the electric motor. An armature 28 is rotatably supported in the bearing shields and the forward end of armature shaft 29 supports fan rotors 30 and 3|.
An inner fan housing 32 is formed with a cylindrical portion surrounding rotor 3| and with a forward wall having a central opening 33 therethrough. An outer fan housing 34 surrounds rotor 30 and has a forward wall with a central opening 35 therethrough. The rear ends of both the fan housings are formed with outwardly extending i'langes which are clamped with a packing ring between rings I 'l and I8, whereby the fan housings are secured in place. Forward bearing shield 23 supports a circular plate 36 disposed immediately behind rotor 3|. Plate 36 is formed with a. cylindrical ange portion 3l which is concentric with the cylindrical portion 4of inner fan housing 32 and forms an air flow channel 38 therebetween. Radially extending guide vanes 39 may be supported by forward bearing shield 23 and serve to reduce the rotational movement of air passing from the rotors toward the motor. A sealing ring 40 carried by the forward bearing shield 23 serves to cause all of the air discharged from the fan to pass through the air passages 2l in the motor in order to obtain maximum cooling of the latter.
A hood member 4I surrounds the rear end of the motor and is supported fromA motor ring I8 by means of bolts 42. Hood member 4I has a cylindrical portion 43 which is spaced inwardly from the cylindrical portion of an end cap 44 so as to form an annular channel 45 therebetween. A plurality of openings' 46are formed in the cylindrical portion 4I.
Cap member 44 is formed with an end wall 41 provided with a centrally located outlet opening 48. Inclined vanes 49 extend across the outlet opening and the more central vanes are formed integral with a sleeve 5e. A bolt 5I extends within sleeve |50 and has threaded engagement with the end of hood member 4I, thus serving to hold the cap 44 in piace. A illter member 52 may be located between the end of hood 4| and the outlet ll.
A circular disc Il is disposed within cap member 44 adjacent t outlet 4I and may be supported by vanes I4, which-also serve to reduce whirling oi' air. Plate ll and the end 41 of cap 44 form between them a discharge channel Il leading to the outlet". As is shown in Fig. 2, the end wall 41 is formed as a hyperbolic surface, whereby the cross-sectional area oi' discharge channel Il is constant throughout its length.
It will thus be seen that the passage through which the air must pass from the rear rotor si to the outlet 4I comprises a plurality of sections. The ilrst is the air ilow channel 3l between the inner fan housing It and cylindrical flange I1. 'I'he second is made up of the air passages 21 through the motor. The third is the annular channel-4l between hood 4I and cap 44. The fourth .is the discharge channel il between plate I3 and end wall 41. The free ilow cross-sectional area of each of these sections is substantially constant throughout the length of the section and the free iiow cross-sectional areas of adjacent sections are diilerent. Moreover, the changes in oros-sectional area between adjacent sections are abrupt. Also, the length of each of the last three sections, that is, passage 21 and channels 4I and is greater than the diameter oi' a circle having an area equal to the free ilow area of the respective sections, in accordance with the principle tically shown in each oi' the sections'illustrated in Fig. i, while the diameter oi' a circle having an area equal to the area oi' the ilrst section, namely channel 3l, is not greater than twice the length oi this section, as is permissible.
In operation, the rotation oi' the rotors I. and ll bymeansofamotorcausesairtobedrawn through hose I4 into dust bag I0. Here any entrained dust is deposited and the air throughthematerial oithedustbag. Thisair passes through opening All to the center o! rotor il and is discharged from the periphery of this rotor and passes through opening u to the center oi.' rotor Il. 'I'he air discharged from the peripheryoi' rotor Il passes through air ilow channelllandthencethroughairpassages 21 inthe motor. There is an abrupt change in crosssectional area between air ilow channel ll and passages l1. From these passages the air passes through openings 46 into annular channel 45, there again being an abrupt change in the crosssectional area. From channel 4l the air passes through illter Il and into discharge channel Il, there being an abrupt change in cross-sectional area between channels 4l and Il. Prom heretheairpassesthroughoutlet 4l to the atmosphere The sound produced by the rotation of the armature and the rotors il and ll, which would otherwise be carried out ci the cleaner by the air stream, is to a great extent muiiied by forcing the air to suddenly expand and contract during its passage from the rotors to the outlet, as has been previously described. 'I'his results in a much quieter operation oi the device.
While I have shown and described a preferred embodiment of my invention, it is to be understood that the scope thereof is to be limited only by the appended claims viewed in the light of the prior art.
What I claim is:
1. In a vacuum cleaner, a casing having an inlet opening and an outlet opening, a motor ian unit in said casing, the motor being between the ian and said outlet opening, and means providing an air ilow channel between said fan and said motor, said channel having a substantially constant tree ilow cross-sectional area throughout its entire length, the cross-sectional area of said channel being equal to the area of a circle, the
diameter of which is less than twice the length o! said channel, said motor being formed with air passages therethrough in communication with said channel, the free ilow cross-.sectional area ot said passages being substantially constant and di!- ierent from that oi.' said channel.
2. In a vacuum cleaner, a casing having an inlet opening and an outlet opening, a motor fan unit in said casing, the motor being between. the fan and said outlet opening, said motor being formed with air passages therethrough having a substantially constant free ilow cross-sectional area, the length of said passages being greater than the diameter of a circle having an area equal to the aggregate cross-sectional area of said passages, means for conveying air from said fan to the ends oi said passages adjacent to said Ian and a hood member between said motor and said outlet and forming with said casing an annular channel therebetween, said channel being in communication with the other ends o! said passages, the crm-sectional area o! said annular channel being substantially constant and dinerent from that of said passages.
3. In a vacuum cleaner, a casing having an inlet opening and an outlet opening, a ian in said casing, a hood member between said i'an and said outlet and forming with said casing an annular channel therebetween oi substantially constantl cross-sectional area, and a plate between said hood and said outlet forming with said casing a discharge channel havingl a substantially constant cross-sectional new area which is diilerent from the cross-sectional area of said annular channel.
4. In avacuum cleaner,a casing having an inlet opening and an outlet opening, a motor-Ian unit in said casing, the motor being between the ian and said outlet opening, means between said fan and said motor providing an air now channel having a substantially constant free flow cross-sectional area, said motor being f ormed with air passages therethrough in communication with said channel, the free ilow cross-sectional area of said passages being substantially constant and diilerent from that ci said channel, a hood member between said motor and said outlet and spaced inwardly from said casing to form an annular channel therebetween, said hood member being -formed with openings for establishing communication between said passages and said annular channel, the cross-sectional area of said annular channel being substantially constant and diilerentl from that oi said passages,and aplate between said hood and said outlet forming with said casingadischargechannelleadingtosaidoutlet and having a substantially constant cross-sectional area being different from the cross-sectional area of said annular channel.
5. In a vacuum cleaner, a cylindrical casing having an inlet opening and an end formed with an outlet opening therein, the diameter of said casing being greater than that of said outlet opening, means for producing ow of air through caid casing, and a circular plate within said casing adjacent to said outlet and forming with the end of said casing a discharge channel, the end of said casing being a hyperbolic surface whereby the cross-sectional flow area through said channel is substantially constant.
6. In a vacuum cleaner, a casing having an inlet opening and an outlet opening. a. motor fan unit in said casing, the motor being between the fan and the outlet opening, and means providing a passageway for ow of air from said fan to said outlet opening, said passageway including a plurality of sections, each section being of substantially constant free flow cross-sectional area and adjacent sections being of diierent area with abrupt transitions therebetween, the cross-sectional area of each of said sections being equal to the area of a circle the diameter of which is less than twice the length of the respective section.
ERNST FREDRIK GEORG FREDLUND.