IL22622A - Washing machines particularly for dishes - Google Patents

Description

C O H E *"z E D E & S P I S B A C H R EG D. PAT E T ATTOR N E YS 24, LEVONTIN STR., P. O. B. l 16 12795/64 P A T E N T S &' D E S I G N S O R D I N A N C E SPECIFICATION IMPROVEMENTS IN AND RELATING TO WASHING MACHINBS PARTICULARLY FOR DISHES •trrnna ,ns"»rn m an t ^go V™* piyii WW? nip CHARLES COLSTON LIMITED, a Company incorporated tinder the laws of the United Kingdon, of Wellington Road, High Wycombe, Buckinghamshire, ENGLAND, BY DECLARE the nature of this invention and in what manner the same is to be performed to be particularly described and ascertained in and by the following statement : This invention relates to dishwashing machines having liquid filtering systems for cleaning a washing liquid contaminated with particulate soil or debris removed from the articles being washed.

It is customary in domestic dishwashing machines for the washing liquid to be passed through a mesh type strainer before bein recirculated to a spray device in the washing chamber. In practice it has been found undesirable to use a strainer having apertures less than about 1/32" to 1/16n in size due to the tendency for smaller apertures to become clogged with soil particles.

It is well known that there is a tendency for fine soil particles, which can pass through the strainer mesh, to deposit on and adhere to surfaces of articles in the machine whioh are not directly exposed to the full force of the washing spray, caueing a gritty feel on such surfaces when dry. This effect, which is commonly known as redeposit, is one of the more prevalent causes of imperfect results fom a domestic,dishwasher. In many modern machines this tendency for redeposit to occur is only kept within acceptable limits by the use of multiple washes and rinses, often in combination with a pre-rinse; eve so, objectionable Jfedeposit can still occur with a heavily soiled load unless the user takes the trouble to scrape the bulk of the soil off the dishes before loading them into the machine.

A known means by which an improvement can be obtained is the use of a by-pass filter utilizing mesh of finer size than is practicable in a full-flow filter; in this way soil particles as fine as .005" to .01" can be filtered out, bringing abou a substantial reduction of redeposit. Such a system is described in the specification of British Letters Patent No. 894,310· However, whilst giving good results, If this system is to operate efficiently it is essential for the user to clean the fine mesh filter at frequent intervals, and failure to do so can lead to ah indifferent result.

According to the present invention, a dishwashing machine comprises a washing chamber, and means for recirculating washing liquid and spraying it in said chamber, in which passages are provided whereby part of the recirculating liquid is diverted from the spraying means and delivered instead to the washing chamber via tangential inlet and vortex finding tube of a email end of the separator being connected to a eettling tank whereby a controlled soil rich fraction of the liquid may be passed thereto.

The invention is illustrated in the accompanying drawings as applied to a dishwashing machine, in which: Figure 1 is a sectional view of a dishwasher having a filtration system in accordance with the invention; Figure 2 is a detail section on an enlarged scale of one type of settling tank.

Figure 3 is a view of the rear of a dishwasher, showing a modified arrangement.

Figure 4 is a longitudinal sectional view of the cyclone used in the dishwashers of Figures 1 and 3.

Figure 5 is another cross sectional view of the cyclone on the line Α-Δ shown in Figure 4.

Figure 6 is a vertioal cross section of the settling tank for use in the modified arrange* ment of Figure 5« Figures 7 and 8 show two sections in perpendicular planes of a flow restrictor valve for use in the arrangement of Figure 3.

Referring to Figure 1 of the drawing, C indicates a washing chamber provided with racks R chamber and racks being through a door D. Circulation of the washing liquid is by means of a pump P which draws liquid from a sump S in the base of the washing chamber and delivers it through duc¾ M to a spray member T om which it issues in the form of a spray directed ove the articles in the racks* A removable filte screen P of mesh sufficiently coarse to avoid any tendency to clog, may be located in the mouth of the sump.

In the system of this invention a cyclone separator 7, has its tangential inlet 8 connected by a pipe 9 to the discharge duct M of the pump P.

The cyclone 7 (Figures 4 and 5) comprises an elongated conical body portion 40 tapering to a discharge passage 12 at its small end* the cone merging at its open end with one end of a cylindrical chamber 41 provided in its circumferential wall with a semivolute entry recess -4 HP" through which the liquid passes tangen ially from the inlet Θ into the cyclone. The other end of the cylindrical chamber is provided with a closure member 43 through which passes the vortex inding tube 10 of the cyclone, the entrance 44 to the vortex finding tube lying on the axis of the cyclone at the open end of the cone.

Liquid entering the cyclone is given a rotary movement by the tangential arrangement the entry recess 42, and soil particles in the liquid, if of greater densit than the latter are thus subjected to a resultant centrifugal orce tending to move them towards the walls of the cyclone along which they pass with a spiral motion towards the discharge passage 12 at the small end of the separator. The relatively soil-free liquid left towards the axis of the cyclone is discharged through the vortex finding tube 10.

The vortex finding tube 10 of the cyclone is connected by a pipe 11 to discharge into the chamber C, and the discharge passage 12 at the small end discharges into a container 13, hereinafter called the "settling tank*. This settling tank has connected to its outlet 14» a shor length of rubber tubing 15» which is surrounded by and sealed into a jacket 16, connected by tube 17 to the discharge line of pump P.

The other end of valve tube 15 is connected by a tube 18 to the drai line of the machine.

Operatio of the system is as followsi- The washing liquid is continually recirculated by pump P, and a proportion of the tota circulatory flow (conveniently in the region of 5$» to 15 ) 1B by-passed through line 9 to cyclone 7» from whioh most of said by÷passed liquid is discharged through the vortex inding tube 10 back into the main circulatory flow* As is well known in cyclone technology, the centrifugal forces acting on the liquid passing through the cyclone* cause any solid particles having a specific gravity greater than that of the liquid to move towards the apex of the cone and to discharge from the passage at the small end of the cyclone, whilst oonversely the liquid discharged from the vortex finding tube is relatively free from such particles i.e. it is returned as relatively soil-free liquid to the washing chamber* B returning it direct to the washing chamber ae in the embodiment illustrated, it may be used as an auxiliary spray to wash surfaces of articles not direot-ly exposed to the main liquid spray.

The soil-rich liquid discharged from the small end falls into the settling tank, being restrained therein by virtue of the pump pressure in jacket 16, which causes the valve tube 15 to collapse (as shown in Figure 1) and close the outlet from the settling tank.

As the liquid level in the settling tank builds up, the pressure developed in the entrapped air acts to retard the ingress of further liqid from the cyclone underflow.

In practice it is ound that the underflow The underflow discharge then commences to slow down considerably, and eventually becomes so slow that it takes several minutes or the settling tank to fill with the result that, b the time the settling tank is completely full, the great bulk of the soil has been removed from circulation.

When the washing operation is completed and the liquid circulating in the machine has been d rained away, the pumping pressure alls to csero; consequently the rubber valve tube 15» being freed from external pressure, will expand and on opening out, allows the soil and liquid collected in the settling tank to fall into the drain line and be discharged together with the bulk of the liquid drained from the machine* It will b e understood that the valve tube 15» closed by pumping pressure, is shown by way of example only, and ny other type of valve may be utilized to provide the same general effect, i.e. to close the settling tank outlet while the washing liquid Is being circulated, and open it when the washing liquid is drained away. In such an alternative construction (not illustrated) the tube 15 paeses between an anvil member and a plunger urged war e a l membe b a i to diaphragm exposed to liquid from the discharge line of pump P, the plunger being spring biased to move away from the anvil when the liquid pressure in the discharge line falls to zero as the pump stops. As a further alternative, the settling tank outlet could be left open during the early part of the washing cycle in order to ensure a maximum rate of iltration, and be closed in the latter par of the washing cycle to reduce loss of liquid.

In a further variation, the liquid collected in the settling tank may be allowed to overflow back into the washing chamber, and a fine-mesh filter screen may be inserted in the overflow path to ensure that none of the soil particles collected in the settling tank are entrained in s aid overflow return* For this purpose, as shown in Figure 2, a bottle of settling tank 21, attached to the small end of a liquid cyclone 22, as a flne-mesh filter screen 23» which screen acts as a partition to divide the bottle into two parts, the lowe part has an outle 24 connected to the drain line of the machine via a suitable discharge valve, indicated diagrammatically /ta 26, and the upper par has an outlet 25 communicating with the washing chamber* In operation soil-rich liquid discharged from the small end of the cyclone collects in the lower part of bottle 21, being retained therein by the valve 26 in outlet 24· Liquid trapped in the lower part of the bottle can pass upwardl through filter screen 23 and out of top outlet 25 into the washing chamber. At the end of the ashi g period, outlet valve 26 is opened* thus allowing the co tents of bottle 21 to drain away. During this draining process, the filtered liquid in the upper part of bottle 21 will flow back through filter 25» i.e. in the reverse direction, thus flushing away any particles of soil that may have tended to adhere to the underside of the filter screen during the washing operation* Figure 3 shove a furthe modification. She cyclone 7 has Its tangential inlet 8 connected by a by-pass pipe 9' leading out of the return flo duet M which delivers washing liquid from pump J? to the spra member (not shown), all as previously described. The vortex finding tube 10* is connected by pipe 11* to discharge into the washing chamber* and may conveniently be arranged to discharge the liquid against directly exposed to the main spray.

The small end of the cyclone 12· is connected to discharge into a settling tank 13r (Pig.6), through a diffusing cone 30, which delivers the soil-rich liquid to the lower par of the settling tank. She cone continuously increases in cross-section towards its lower end 31 to ensure that the velocity of the incoming liquid is gradually reduced so as to encourage the soil to settle gently without turbulence or eddying* whilst the discharge of the soil-rich liquid into . the lower part of the tank avoids contamination of the relatively soil-free liquid in the upper part of the tank 13'. A vent 32 permits the escape of an air trapped in the cone 30 into the upper part of the tank.

The settling tank, which is in the form of a cylindrical tube, having end portions 33,34 provided with top and bottom outlets 28*, 14* , has its axis inclined to the vertical to further assist in suppressing unwanted internal circulation of soil-rich liquid, Ihe diffusing cone 30 is supported axially in the settling tank by radially extending ribs 35» an inlet 36 passing f om the top of the cone throug the wall of the tank being connected to the cyclone underflow 12* · The lower outlet 14' of the settling tank is connected by pipe 15* to a drain valve 27f and thence by pipe 18* to the drain line of the machine. The outlet 28* at the top of the settlin tank 13* i connected to <$te» charge into the washing chamber, through a flow restrictor 28 (Pig. 3) . Referring to Figures 7 and 8, this flow restrictor comprises a cylindrical chamber 50, closed at one end by a cap 51» a tangential inlet passage 52 from the settlin tank and an axial diecharge passage 53 to the interior of the washing chamber. In use, the mass of rotating liquid set up in the chamber by the tangential position of the passage 2 produces centrifugal head which acts as a back pressure in the inlet passage thus reducing, the ratefcf flow in this passage. This arrangement is pre erable to restricting the bore of the top outlet pipe from the settling tank as suc p restricted bore is liable to become blocked as a result of furring in the pipe. In operation* the soil i the soil-rich discharge from the small end 12* of the cyclone settles by gravity in the lower end of the settling tank 13*, from whence it is discharged to the machine drain liiie via the drain valve 27 which ie synchronised to operate in unison with the machine drain valve» The relatively soil* free liquid i the upper part of the settling tank overflows through flow reetriotor 28 into the washing chamber where it re-combines with the main circulatory flow. The characteristics of flow reetriotor 28 are made such that the rate of flow is sufficient to allow the cyclone to operate efficiently throughout the whole washing time, without being so high as to interfere with free settling of soil in the settling tank} in practice it is found that the low through 28 can conveniently be of the order of 5$ of the flow through feed pipe 9* .

It is not, of course, essential that the cyclone should have the specific conical shape and configuration of the orthodox liquid cyclone, and any like form of liquid-operated centrifuging vortex chamber capable of separating the feed thereto into soil-rich and soil-free fractions* may be used. If desired, two or more cyclones could be used in series, i.e. the small end of the first one discharges into the inlet of the next one, in order more heavily to concentrate the proportion of soil in the last discharge at the small end of the final cyclone.

By arranging for the soil-free liquid discharged from the vortex finding tube of the cyclone to flow bade into the washing chamber, there is the further advantage# as indicated above, that by directing it to fall o spray over those surfaces of the soiled articles which are not directly exposed to the main washing spray, it will still further reduce redeposit by increasing the volume of liquid (and simultaneously reducing the amount of soil) reaching these relatively blind or shielded surfaces.

The iltering system of this invention has the advantage over existing systems that there is virtually no limit to the smallness of particle size dealt with, and no need for cleaning or other attention by the user.

Moreover, the efficiency of the system as applied to a dishwasher is such as to eliminate the occurrence of redeposlt without requiring the user to pre^scrape the dishes and without needing an undue multiplicity of washes and rinses.

Claims (1)

WHAT WE CLAIM IS:- 1. A dishwashing machine comprising a washing chamber, and means for recirculating washing liquid and spraying it in said chamber* in which passages are provided whereby part of the recirculating liquid is diverted rom the spraying meane and delivered instead to the washin chamber via the tangential inlet and vortex finding tube of a cyclone separator, the discharge passage at the small end of the separator being connected to a settling tank whereby a controlled soil rich fraction of the liquid may be passed thereto, 2. A dishwashing machine as claimed in

1. Claim 1, in which the circulating and spraying means comprise a circulation pump withdrawing liquid from the chamber and supplying i under pressure to spray means in the chamber, a m