US 3048994 A
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Aug. 14, 1962 o. WELTER 3,048,994
WASHING MACHINES Filed Jan. 16, 1959 5 Sheets-Sheet 1 Inventor,-
ttorrzey 5 Aug. 14, 1962 Filed Jan.
O. WELTER WASHING MACHINES 3 Sheets-Sheet 2 Inventor.
Attomeyg Aug. 14, 1962 0. WELTER 3,048,994
WASHING MACHINES Filed Jan. 16, 1959 3 Sheets-Sheet 3 Inventor:
nited States Patent Gfihce 3,048,994 Patented Aug. 14, 1962 3,048,994 WASHING MACHiNES Otto Welter, Casa Montebello, flrselina, Ticino, Switzerland Filed Jan. 16, 1959, Ser. No. 787,172 Claims priority, application Great Britain Jan. 20, 1958 12 Ciaims. (Cl. 68184) This invention relates to machines which are described for convenience herein as washing machines but which are of more general application inasmuch as in addition to the domestic or industrial cleaning of clothing, fabrics and the like, crockery, dishes, glasses and the like, they may be used for example for the cleaning of fruit and vegetables, the cleaning and washing of the human body and animals, in industrial processes for example for the degreasing and cleaning of articles and parts, for a process equivalent to sand blasting in which finely divided abrasive material is included in the liquid in which the articles to be treated are immersed, the technical cleaning of watch stones and watch and similar precision parts and mechanisms, various forms of chemical treatment, for example the dyeing and bleaching of clothes, fabrics, yarns, and the like, the washing of material such as films and prints in photographic processing, and so on.
Machines are known in which washing or cleaning is effected by impressing ultrasonic vibrations on a body of liquid containing the articles to be treated. In such machines the ultrasonic vibrations are normally generated by means of piezoelectric or magnetostrictive vibratory systems which usually require electronic control gear and the machines are therefore expensive to construct and use. Moreover such vibration generators are also not very efficient if the temperature of the liquid is raised.
When machines of this kind are used for washing clothing and the like they are found to be less effective than might be expected and this is believed to be due to the fact that the ultrasonic vibrations are so attenuated in their passage through the washing liquid, which will normally be associated or will contain a large quantity of air bubbles, that in parts of the container remote from the vibration generator there will be little or no ultrasonic vibrations present.
Attempts to improve the operation of ultrasonic washing machines by increasing the amplitude of the vibrations generated fail since clothing or other textile articles being washed is likely to be damaged when it is acted upon by high energy vibrations in the vicinity of the generator. Moreover in the case of domestic washing ma chines the biological effects of high energy ultrasonic vibrations have also to be taken into account since the user of such a washing machine may be endangered.
In the improved machine of this invention washing or cleaning is effected by means of a liquid stream on which is superimposed vibrations of at least one relatively low frequency and of at least one relatively high frequency. Conveniently the vibrations of relatively low frequency lie in the sonic range while the vibrations of relatively high frequency lie in the ultrasonic range.
It has been found that the improved machine of this invention provides a better washing or cleaning effect than can be obtained with machines at present available and this is believed to be due at least in part to the observed fact that the amplitude of the higher frequency vibrations at points in the liquid remote from the source of vibrations is much greater than can be obtained if such higher frequency vibrations are used alone as has previously been proposed.
This result is believed to be due to the fact that when superimposed on a low frequency vibration which itself can penetrate the washing liquid more readily, the
higher frequency vibrations are not so rapidly attenuated as they would be if they were used alone. This accordingly enables a much greater efficiency of washing to be obtained since clothing or other articles being washed or cleaned will be affected by the higher frequency vibrations in all parts of the container even though the amplitude of these vibrations is held at a comparatively low and therefore safe value. Furthermore, and particularly in the case of machines for the treatment of textile articles, clothing, and the like, the stream of liquid may be arranged to cause the articles being treated to circulate and turn over in the container.
The invention also includes improved apparatus for generating in a body of liquid vibrations of at least two different frequencies, the apparatus comprising a centrifugal impeller arranged for rotation within an annular housing having at least one aperture therein adjacent the periphery of the impeller such that the liquid stream expelled through the aperture by the action of the impeller has superimposed thereon vibrations of the one frequency, and in which the impeller is so constructed and arranged that in operation at least a part vibrates at the other frequency whereby to superimpose vibrations at the other frequency on the liquid stream.
Conveniently the impeller is constructed as a disc-like member having on one face vanes which extend from the disc in an axial and radial direction and is arranged for rotation with the radially extending edges of the vanes closely adjacent a relatively rigid member so that vibration of the impeller in an axial direction causes the liquid moving between the impeller and the rigid member to be modulated at the frequency of vibration of the impeller.
It has been found that the impeller can be arranged to produce powerful vibratory components in the ultrasonic range if it is made of a hard elastic material, for example hard bronze, chromium-steel, glass, or a suitable ceramic. Such an impeller can be excited to vibrate with several degrees of freedom according to its geometrical shape and the characteristic coefficients of the material of which it is made, and by suitable selection of these quantities the frequency of vibration can be controlled over a wide range according to requirements.
It will be appreciated this method of producing the relatively high frequency or ultrasonic vibrations will in general provide vibrations at several different frequencies; this is, however, not a disadvantage but the invention does not exclude the possibility of using vibrations of only one relatively high frequency. The frequency of these vibrations is not in general critical and it has been found in practice that good results are obtained by using frequencies in the range of up to 40,000 c.p.s.
As regards the relatively low frequency vibrations, it has been found that a frequency or frequencies within the range 50 to 2,000 c.p.s. is suitable. Such frequencies may be achieved with a very simple form of impeller driven at a speed of, say, 1,500 rpm. which is a convenient speed for the electric motor which normally will be used to drive the impeller.
It will be appreciated that the actual frequency of the lower and the higher frequency vibrations will be selected according to the intended use of the machine.
In order that the invention may be clearly understood some forms thereof will now be described with reference to the accompanying drawings, in which:
FIGURES 1 and 2 are a central vertical section and a plan respectively of one form of washing machine,
FIGURES 3 and 4 are a part section and a plan respectively of another form of washing machine,
FIGURE 5 is a part-secti0nal view of a modification of the machine of FIGURES 1 and 2,
FIGURE 6 is a development of a detail of FIGURE 5, and
FIGURES 7, 8 and 9 are a part-sectional view and plans respectively illustrating a further modification of the machine of FIGURES l and 2.
Referring now to FIGURES l and 2, there is shown a washing machine suitable for use in the domestic washing of clothing. The machine comprises a casing 1 within which is housed a tub 2 generally of square cross-section. An apparatus for producing a liquid stream on which is superimposed at least two vibrations of different frequency, and which will be called for convenience the vibration generator, is mounted centrally on the floor of the tub.
The vibration generator 3 comprises an impeller 4 which is mounted for rotation on the upper end of a spindle 5 of an electric motor 6. As shown, the motor is of the axial air gap type comprising a rotor 7 and a stator 8 but any other type of motor may be used if desired.- The motor frame 9 is formed with a flanged boss 10 and is secured on the floor 11 of the tub 2 by bolting the flange 12 to the floor or otherwise. The central portion of the boss 10 is formed with a threaded spigot 13 which projects into the tub and on to which is screwed an annular member 14 which has holes 14 therein through which liquid may pass to the eye of the impeller 4. This impeller in the form shown consists of a disc 15 provided on its lower face with a plurality, for example eight, of axially and radially extending vanes 16 and it is arranged with the radially extending edges 17 of the vanes in close proximity to the surface of a rigid annular member 18. This member is secured on the frame member 14 and carries in turn a dome shaped cowl or housing 19 for the impeller. The inner periphery of the housing is closely spaced from the axially extending edges 20 of the vanes 16 and is formed with a plurality of slots 21 through which liquid is ejected by the action of the impeller into the interior of the tub.
As shown there are four of these slots 21 and they occupy each about A of the periphery of the housing. In consequence the liquid flow between each of the eight vanes 16 produced by the rotation of the impeller 4 will be periodically interrupted and accordingly the stream of liquid through each slot will have superimposed thereon vibrations having a frequency of 200 c.p.s. assuming a motor speed of 1500 rpm.
The impeller 4 is formed of a suitable hard elastic material such as bronze, gun metal, glass or ceramic and is so designed that it has a natural frequency of vibration lying preferably in the ultrasonic region, for example at 18,000 c.p.s. or thereabouts. The principal mode of vibration is preferably in the axial direction and relative to the centre of the impeller which may be a node. Such vibration, which may be excited merely by the flow of liquid when the impeller rotates, will cause the periphery of the impeller to move in an axial direction and this movement will act to produce alternate compression and rarefication of the liquid flowing between the impeller 4 and the annular member 18 and between each vane. In consequence the liquid stream will be modulated at the frequency of vibration of the impeller and accordingly the liquid stream through the slots 21 will have superimposed thereon vibrations of a relatively low frequency namely 200 c.p.s. and also a relatively high frequency, namely 18,000 c.p.s.
The slots 21 in the housing 19 are preferably shaped as shown so as to impose a rotary component on the liquid in the tub 2 and so as to direct the liquid stream in an upwards direction. These measures cause the articles being washed to circulate in the tub and to be held up from the floor.
In order to allow circulation of the liquid in the tub back to the impeller, one wall, the left-hand wall 23 as shown, is formed as a perforated false wall which is spaced from the real wall 24 to provide a passage for the return circulation. For the same reason the tub is provided with a false floor 25 which is spaced above the real floor 11.
For convenience in assembly the housing 19 is detachably mounted as by means of a bayonet joint on to the annular member 18 and is formed with a flange 26 which seats on the upper face of the false floor 25 to form therewith a seal.
The machine illustrated is provided with an electric heater 27 and with a pump 28 driven by a small electric motor 29 so that the tub can be emptied when required.
FIGURES 3 and 4 illustrate certain modifications of the machine shown in FIGURES l and 2. The arrangement of the generator is essentially the same, like parts will be denoted by the same reference numerals and only the differences in the two constructions will be described in detail.
FIGURE 3 illustrates an alternative means for mounting the generator on the floor 11 of the tub. In this case the base or frame 14 of the generator is provided with a threaded spigot 34 which is passed through an aperture in the floor 11 and is secured therewith by means of a nut 35. The illustrated arrangement also shows a very simple means for mounting the motor 6, the body of which is screwed on to the spigot 34 and secured therewith by means of the nut 36.
In the case of a washing machine, reversal of the direction of rotation of the motor may be used to change the strength of the washing action. In the arrangement of FIGURES 3 and 4 this is achieved by arranging that the slot 22 formed in the periphery of the housing 19 extends round only part of the periphery, for example through an angle of about as shown by the arrows, apart from the provision of a few narrow webs provided for mechanical reasons. If the generator is then mounted non-symmetrically in the tub 2 which may be of oval section as shown in FIGURE 4, the position of the slot 22 relative to the Wall of the tub may then be selected so that for one direction of rotation the liquid stream emitted from the generator will mainly impinge on the nearest part of the wall While for the other direction of rotation the liquid stream will be directed along the wall and towards the interior of the tub. For example, if in FIGURE 4 the centre of the slot 22 is in the upper and left-hand part of the generator housing 19, for clockwise rotation of the impeller the stream will be towards the right and more or less along the upper wall of the tub 2, whereas for anti-clockwise rotation the stream will mainly impinge on the part of the wall nearest to the generator. In both cases, however, it is desired that there shall be a generally circulatory current of liquid in the tub but in the one case this can be made much more powerful.
The same result may be obtained in the case of the machine of FIGURES 1 and 2 since owing to the shape of the slots 21 in the housing 19 the liquid stream will be directed more nearly towards the wall of the tub 2 for one direction of rotation of the impeller than for the other direction of rotation.
FIGURES 3 and 4 illustrate a further modification of the machine of FIGURES l and 2 inasmuch as the return circulation of the liquid is effected through the floor of the tub instead of through one side. As shown, the tub 2 is provided with a false floor 33 which is perforated as at 39 to allow liquid within the main body of the tub to flow towards the impeller. In some cases this floor 38 may be covered with a filtering medium, for example an appropriate grade of paper or fabric or a metal mesh, in order that fibres and other foreign matter loosened from the material being treated may be prevented from passing into the generator.
A further constructional feature of the arrangement illustrated in FIGURE 3 includes the provision of an opening to the interior of the generator so that air or gas or a liquid may be supplied to the generator through a pipe 41 which extends from above the liquid level in the tub to the inlet to the impeller, and a valve may be included to control the quantity of air, gas or liquid supplied if desired. As shown, this opening takes the form of a tubular bushing 40 secured with the body 14 of the generator and extending through the floor 11 of the tub, the bushing also serving to locate the generator when it is mounted in position.
The supply of air to the generator tends to reduce the damping of the oscillatory impeller and hence a greater amplitude of vibration can be obtained. Moreover the action of the impeller on the air causes a large quantity of small bubbles to be produced and distributed in the Washing liquid and these bubbles when they collapse cause local shocks or vibrations which have a favourable infiuence on the washing operation.
This arrangement may also be used for the supply of a gas such as ozone which acts to bleach and sterilise the materials being washed and an ozone generator may be arranged in a suitable position on the machine and connected with the pipe.
The arrangement may also be used for the supply of a special liquid to the machine such as may be required when the machine is used for bleaching or dyeing, the operation of the impeller causing such special liquid to be rapidly and intimately mixed with the liquid in the tub.
The machine shown in FIGURES 1 and 2 may be adapted for the washing of crockery and the like by means of the modification shown in FIGURES 5 and 6. For this purpose the housing 19 is removed and in its place is arranged an annular member 42 while the periphery of the impeller 4 is surrounded by a band or sleeve 43 formed with a series of staggered slots 44. When the impeller is rotated the arrangement will provide a series of liquid jets at different levels which strike and are reflected from the curved surface 45 of the annular member 42 such that strong jets of liquid will be directed into all pa1ts of the interior of the tub in which the crockery is held in a suitably designed cage. It will be appreciated that when used for this purpose only a small quantity of liquid will be provided in the tub.
In the arrangements so far described the impeller is designed to vibrate at its natural frequency of vibration and will normally execute such vibrations without the provision of special means. While such an arrangement is found to produce higher frequency vibrations of an energy adequate for domestic purposes, it is in some cases desirable to provide means which operate positively to produce forced vibration of the impeller and the increased energy which can thereby be produced is of value in many industrial applications of the machine. One arrangement for this purpose is illustrated in FIGURES 7 to 9. As shown, a ring 49 of rigid material is secured inside the housing '19 with its lower face parallel with and closely adjacent to the upper face of the impeller 4. The adjacent faces of the ring 49 and impeller 4 are formed with a pattern 59 of crests and troughs extending radially and when the impeller is rotated the relative movement of the two patterns will cause the liquid in the space between the ring 49 and impeller 4 to be alternately compressed and rarefied. Owing to the incompressibility of liquid, the impeller 4, and the ring 49, will be subjected to an oscillatory force and the impeller 4 will thus be caused to vibrate at a frequency determined by the number of crests and troughs on the impeller and the ring and the speed of rotation of the impeller. In practice it has been found possible to provide, say, 650 crests and troughs which at a motor speed of 1,500 rpm. gives a frequency of vibration of about 16,500 c.p.s. The amplitude of the crests and troughs can be very small and they may be formed by machining or during the manufacture of the impeller and ring by a moulding or die casting operation.
In practice the arrangement provides very powerful vibrations while the energy may be controlled by adjusting the spacing of the ring 49 from the impeller 4. It will be appreciated that the arrangement described with reference to FIGURES 7 to 9 may be modified in many ways, for example the ring 49 could be replaced by a suitable projecting surface formed on the interior of the housing 19 itself, while substantially the same result might be obtained by forming the radially extending crests and troughs on the surface of the rigid member 18 and on the radially extending edges 17 of the vanes 16 of the impeller.
In the machine of this invention, particularly when used for washing clothing and the like, the slots or apertures in the housing are preferably so arranged as to impose a component of rotation on the liquid stream issuing from them so that the articles being washed are caused to circulate in the tub or container and to turn over and over as they move. It will, however, be appreciated that in such machines the liquid stream is not intended to have the scouring effect which it has in many known types of clothes washing machines and since the movement of the articles is not nearly so vigorous as in these known types of machines, the articles being washed will be subjected to a much gentler treatment.
For industrial purposes, however, both the energy of the vibrations and the velocity of the liquid stream may be increased. Moreover in such cases more than one vibration generator may be used and they may be positioned on the walls as well as on the floor of the liquid container or may even be suspended from above so as to lie submerged in the liquid. It is also possible to arrange the generator outside the container to which it supplies a stream of liquid on which is superimposed vibrations both at the lower and at the higher frequencies.
It will also be appreciated that the vibration generator may be used with a liquid container which is closed and adapted to be operated under pressure as may be required if the apparatus is to be used for certain dyeing operations, or, for example, for sterilising purposes with the liquid held at temperatures above C.
The improved generator may be used for many purposes where it is required to set up vibrations in a liquid, the cleaning of filter screens and the treatment of liquid/ liquid or liquid/solid mixtures to produce emulsions or suspensions may be mentioned by way of example.
The generator has also been found useful for therapeutic purposes since the vibrations will act to provide a form of massage for any part of a living body which is immersed in a liquid in which the vibrations are set up.
1. A washing machine comprising a liquid container, a centrifugal impeller mounted for rotation in said container and designed to vibrate at at least one ultrasonic frequency at the normal impeller speed and an annular housing surrounding said impeller and formed with at least one aperture in its periphery closely adjacent the periphery of said impeller.
2. A Washing machine comprising a liquid container, a centrifugal impeller mounted for rotation in said container and so designed as to have a natural frequency of vibration in the supersonic range at an amplitude sufficient to impose vibrations on the stream of liquid pumped by said impeller and at normal impeller speed, and a housing surrounding said impeller and having a plurality of apertures in its periphery closely adjacent the periphery of said impeller.
3. A washing machine comprising a liquid container, a centrifugal impeller mounted for rotation in said container, a housing surrounding said impeller and for-med with a plurality of apertures in its periphery closely adjacent the periphery of the impeller, and means for causing said impeller to execute forced vibrations at a frequency in the ultrasonic range and at an amplitude sutficient to impose vibrations on the stream of liquid pumped by said impeller and at normal impeller speed.
4. A washing machine comprising a liquid container, a centrifugal impeller mounted for rotation in said container, said im eller comprising a disc-shaped member having on one face thereof a plurality of axially and radially extending vanes, a rigid annular member disposed adjacent the radially extending edges of said vanes and defining with said disc-shaped member and said vanes a plurality of radially extending channels, means for causing said impeller to vibrate in an axial direction at an ultrasonic frequency at normal impeller speed whereby periodically to compress liquid in said radially extending channels, and a stationary housing enclosing the axially extending edges of said vanes and the other said face of said disc-shaped member, said housing being formed with a plurality of apertures closely adjacent the axially extending edges of said vanes.
5. A washing machine as claimed in claim 4, in which said impeller is constructed of a hard elastic material and is so dimensioned as to have a natural frequency of vibration in an axial mode lying within the ultrasonic range.
6. A Washing machine as claimed in claim 4 including means for causing said impeller to execute forced vibrations in an axial mode at said ultrasonic frequency.
7. A washing machine as claimed in claim 6, said means for producing forced vibrations comprising a rigid member mounted adjacent the other said face of said discshaped member, the adjacent faces of said rigid member and said disc-like member each being formed with a pattern of alternate crests and troughs extending in a radial direction thereof.
8. A washing machine comprising a liquid container having a main floor and sidewalls and a false floor spaced above said main floor with the space between said main floor and said false floor opening into the space above said false floor, a centrifugal pump including a framework secured on said main floor, an electric motor mounted on said framework externally of said container and having a spindle projecting vertically upwards into said container, an impeller mounted on said spindle, said impeller comprising a disc-shaped member having axially and radially extending vanes formed on its lower face, a rigid annular member mounted on said framework in close proximity to the lower edges of said vanes so as to define therewith a plurality of radially extending channels, a housing mounted on said framework and projecting through an aperture in said false floor, said housing closely surrounding the periphery of said impeller and the upper face of said discshaped member and being formed with a plurality of openings through which liquid streams are projected into the interior of the container with a component of rotation by the operation of said pump, the said impeller being formed of a hard elastic material and so dimensioned as to have a natural frequency of vibration in the ultrasonic range at an amplitude suflicient to impose vibrations on the stream of liquid pumped by said impeller and at normal impeller speed.
9. A washing machine comprising a liquid container having a main floor and side walls and a false floor spaced above said main floor, a centrifugal pump including a framework secured on said main floor, an electric motor mounted on said framework externally of said container and having a spindle projecting vertically upwards into said container, an impeller mounted on said spindle, said impeller comprising a disc-like member having axially and radially extending vanes formed on its lower face, a rigid annular member mounted on said framework in close proximity to the lower edges of said vanes so as to define therewith a plurality of radially extending channels, a housing mounted on said framework and projecting through an aperture in said false floor, said housing closely surrounding the periphery of said impeller and the upper face of said disc-shaped member and being formed with a plurality of openings through which liquid streams are projected into the interior of the container with a con1- ponent of rotation by the operation of said pump, and means for producing forced vibrations of said impeller at a relatively high frequency, said means comprising a rigid member mounted closely adjacent the upper face of 8,.- said disc-shaped member, the facing surfaces of the two members being each formed with a pattern of alternate crests and troughs extending radially thereof.
10. Apparatus for producing a liquid stream having simultaneously superimposed thereon vibrations of at least one lower sonic frequency and one higher ultrasonic frequency comprising a centrifugal pump including a rotor having a plurality of vanes defining radially extending liquid channels, and a stationary member having at least one aperture therein positioned closely adjacent to said rotor to obstruct intermittently the flow of liquid through said channels when said rotor is rotated whereby to superimpose on the liquid stream through said aperture vibrations of the said lower frequency, said rotor being adapted to vibrate at said higher frequency at normal impeller speed whereby to superimpose vibrations of said higher frequency on said liquid stream.
11. Apparatus for producing a liquid stream having simultaneously superimposed thereon vibrations of at least one lower sonic frequency and one higher ultrasonic frequency comprising a centrifugal pump including a discsh-aped rotor having on one face thereof a plurality of axially and radially extending vanes, a rigid stationary member adjacent the radially extending edges of said vanes and defining with said rotor and said vanes a p1urality of radially extending liquid channels, means for setting said rotor into vibration at said higher frequency in an axial direction at normal impeller speed whereby to modulate the liquid stream through said channels, said means including a second rigid member arranged adjacent the other said face of said rotor and a pattern of radially extending crests and troughs formed on the facing surfaces of said second rigid member and said rotor, and a housing closely surrounding the periphery of said rotor and formed with at least one aperture therein whereby to interrupt at said lower frequency the flow of liquid in said channels.
12. A washing machine including a liquid container, rotary pump means for injecting a unidirectional stream of liquid into liquid in said container, means for periodically interrupting the liquid stream from said pump, means for superimposing on said stream vibrations of a lower frequency in the sonic range, and said pump means having a vibratable rotor which is adapted to vibrate at a higher frequency in the ultrasonic range at normal rotor speed for simultaneously superimposing on said stream higher frequency vibrations in the ultra-sonic range.
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