Dishwasher wherein liquid is circulated with granules and separation device for separating granules from the liquid

A dishwasher for washing with granules heavier than liquid, comprises a washing chamber (1), a device (7) for spraying washing liquid with or without granules against dishes in the washing chamber, a tank (10) which is connected to an outlet (11) from the washing chamber, and a circulation pump (5), the suction side of which is joined to an outlet (4) from the tank, and the pressure side of which is joined to a manifold (6) for conducting liquid sucked in from the tank, with or without granules, to the spray device (7). According to the invention, the dishwasher comprises a dividing wall (8), defining an upwardly open tank chamber (12) in the tank. The upper edge of the wall is disposed beneath the upper limit of the tank. Furthermore, the outlet opening (11) of the washing chamber is disposed above the tank chamber (12) defined by the dividing wall.

FIELD OF THE INVENTION 
The present invention relates to a heavy-duty dishwasher for washing with 
granules heavier than liquid, comprising a washing chamber, a spray device 
for spraying washing liquid, with or without granules, against articles to 
be washed in the washing chamber, a tank which is Joined to an outlet from 
the washing chamber, and a circulation pump, the suction side of which is 
joined to an outlet from the tank and the pressure side of which is Joined 
to means for conducting liquid sucked into the tank, with or without 
granules, to the spray device. 
A number of heavy-duty dishwashers are previously known in which blast 
particles or granules together with the washing liquid are thrown or 
sprayed against the articles to be washed. 
BACKGROUND OF THE INVENTION 
EP-A1-0 016 895 reveals a heavy-duty dishwasher of this type, which 
contains in its tank a granule collecting sieve container with its inlet 
connected to the washing chamber and its outlet connected to the suction 
chamber of the pump. A gate closes in one end position the outlet of the 
sieve container and thereby opens a connection between the suction chamber 
and portions of the tank lying outside the sieve container, so that only 
liquid is sucked up by the pump: In the other end position of the gate, 
said connection is closed and the pump sucks liquid from the tank via the 
sieve container, whereby the liquid sucked in has granules from the sieve 
container. In addition to the fact that such a dishwasher has relatively 
complicated construction, it requires time consuming maintenance in order 
to prevent the sieve container from being clogged by food particles 
carried by the circulating liquid. 
EP-A2-0 195 959 and EP-A1-0 169 847 show dishwashers of the above-mentioned 
type for granules heavier than the washing liquid. In such machines, a 
vertically moveable cylinder is disposed at the bottom outlet of the tank. 
In the upper position of the cylinder, liquid and granules flow from the 
tank through the annular gap between the lower end of the cylinder and the 
bottom outlet of the tank. This gap is closed when the cylinder is in its 
lower position, where liquid from the tank is sucked in through a gap 
between the upper end of the cylinder and a conical plate which prevents 
granules from flowing from above into the upper open end of the cylinder. 
The dishwasher according to EP-A2-0 195 959 also contains an annular sieve 
plate in the last mentioned gap in order to prevent granules from 
accompanying liquid sucked into the upper end of the cylinder. In EP-A1-0 
169 847, it is assumed that the granules will sink by their own weight to 
the bottom of the tank, and that only liquid will be sucked into the upper 
end of the cylinder when the cylinder assumes its lower end position. 
However, granules which pass by the upper end of the cylinder when it 
serves as a pump inlet will be sucked into the inlet, and therefore it 
takes a relatively long time for such a machine to assume a state where 
only liquid is circulated and all the granules have sunk to the bottom of 
the tank. 
SUMMARY OF THE INVENTION 
The present invention is intended to achieve a heavy-duty dishwasher using 
granules, said dishwasher not containing any sieve element to prevent 
granules from accompanying liquid sucked into the pump; and which can be 
immediately switched from a state where liquid with granules is sucked up 
by the pump to a state where only liquid is sucked into the pump, and 
which also has a simple and sturdy design with few components. 
For this purpose, a heavy-duty dishwasher of the type described by way of 
introduction is characterized in that it comprises a dividing wall, 
defining an upwardly open chamber in the tank, the upper edge of said wall 
being disposed beneath the upper limit of the tank and that the outlet 
opening of the washing chamber is disposed above the chamber defined by 
the dividing wall. In this dishwasher, the upper edge of the dividing 
walls serves as a spillway and it allows liquid supplied to the chamber 
defined in the tank to overflow to the portion of the tank lying outside 
said chamber, while granules will sink due to gravity to the bottom of the 
chamber. Due to the fact that the overflow from this chamber to the 
portion of the tank lying outside the chamber occurs essentially at the 
surface of the liquid held in the chamber, the granules sinking in the 
chamber will only be given a small horizontal component of movement due to 
surface flow, and this means that all of the granules falling down from 
the washing chamber will sink to the bottom of the tank chamber. 
In a preferred embodiment of the invention, the dividing wall at its lower 
end comprises a portion which can be pivoted between the first position in 
which the tank chamber defined by the wall is closed at its lower end, and 
a second position in which the lover portion of the tank chamber is in 
communication with the rest of the tank. Furthermore, the lower portion of 
the tank is preferably tapered to a bottom outlet and the lower end of the 
dividing wall is disposed to one side of and above the bottom outlet of 
the tank. By this design, the dishwasher can easily switch between washing 
with and without granules in the circulating washing liquid, at the same 
time as the positioning of the dividing wall away from the bottom outlet 
means that the flow about the bottom outlet will not, or only minimally, 
be effected by the operation of the pivoting portion of the dividing wall.

The heavy-duty dishwasher shown in FIGS. 1 and 2 comprises a washing 
chamber 1, in which the dishes to be washed can be placed in a suitably 
manner and held in place. An outlet from the washing chamber is defined by 
two bottom plates 2 and 3. In the present case, the washing chamber is 
rectangular and the bottom plates extend between the walls of the tank 
leaving a rectangular outlet opening 11. The bottom plates 2, 3 are also 
somewhat inclined in order to make sure that liquid and granules falling 
thereon will be led to the outlet opening 11. 
Beneath the washing chamber there is a tank 10 with a bottom outlet 4. 
Preferably, the tank tapers at its bottom towards the bottom outlet. 
The dishwasher also comprises a circulation pump 5, which is connection on 
its suction side to the bottom outlet 4 of the tank. The pressure side of 
the pump 5 is Joined to manifolds 6, of which only one is shown in the 
figures, from which manifolds the nozzles 7 extend. In order to understand 
the present invention, it is sufficient to know that the nozzles are 
arranged to direct and spray liquid sucked up by the pump against the 
dishes in the washing chamber, and therefore the description will not deal 
in detail with the arrangement of the pipes and nozzles. 
The tank 10 has a dividing wall 8 which defines an upwardly open tank 
chamber 12. The outlet opening 11 from the washing chamber is located 
above the tank chamber 12. The dividing wall 8 extends parallel to the 
longitudinal sides of the rectangular outlet opening 11, i.e. 
perpendicular to the cross-sectional plane of the figures, and is 
laterally spaced from said opening. 
At its lower portion, the dividing wall 8 has a pivoting portion, which in 
the embodiment shown consists of a gate 9 pivotable above a central axis. 
This gate can extend between the tank walls and thus constitute the entire 
lower portion of the dividing wall or can be an integrated portion of the 
lower portion of the dividing wall and be hinged thereto. The gate 9 can 
also be hinged about its upper or lower end, but the embodiment shown in 
FIGS. 1 and 2 is preferable since the gate 9 can be rotated between its 
closed and open positions by always rotating the gate in the same 
direction. In other words, no reversable pivot mechanism is required. The 
pivot mechanism for the gate 9 is of suitable type and is designed so that 
the gate will either assume the position shown in FIG. 1, in which the 
lower end of the tank chamber 12 is closed by the gate, or the position 
shown in FIG. 2, in which the lower end of the chamber 12 is open and 
connects the tank chamber 12 to the rest of the tank. Suitably, actuation 
of the pivot mechanism for the gate results in the gate being turned a 
quarter revolution, for example with the aid of a stepping motor. 
The function of the heavy-duty dishwasher shown is quite simple. The pump 5 
sucks liquid from the lower portion of the tank 10 and the liquid sucked 
in is sprayed through the nozzles 7 against the dishes in the washing 
chamber. The liquid then falls down to the bottom of the washing chamber 
and flows through the outlet opening 11 down into the chamber 12 of the 
tank 10. If the lower end of the tank chamber is closed and if the liquid 
level in the tank chamber lies below the upper edge of the dividing wall 
8, this chamber will be filled to the upper edge of the wall and then 
overflow over said edge and into the rest of the tank 10. This circulation 
pattern is shown in FIG. 1. 
FIG. 2 shows the circulation pattern when the lower end of the tank chamber 
12 is open, i.e. when the gate 9 has been turned a quarter turn relative 
to the position shown in FIG. 1. Due to the fact that the tank chamber now 
communicates with the rest of the tank, the liquid levels in the tank 
chamber 12 and the rest of the tank will be evened out, and this means 
that a liquid flow corresponding to the liquid flow supplied to the tank 
chamber 12 via the outlet opening 11 will flow through the open lower end 
of the dividing wall 8 into the rest of the tank 10. Thus, essentially 
only the liquid in the tank chamber 12 and in the lower portion of the 
tank 10 will participate in the liquid circulation shown in FIG. 2. 
In FIGS. 1 and 2, the round rings symbolize the blast particles or granules 
which are mixed into the washing liquid and which are heavier than said 
liquid, for example plastic granulate. In normal washing in the dishwasher 
shown, the granules are mixed into the liquid sucked in by the pump 5 and 
sprayed together with the liquid against the dishes so that the blasting 
effect will knock off burned-on or dried-on food residue from the dishes. 
The heavy-duty dishwasher is then in the above-described mode shown in 
FIG. 2. 
After finished washing with the granules, the dishes must be rinsed with 
liquid alone in order to wash off the granules which may have stuck to the 
dishes or to the walls of the washing chamber. To do this it is sufficient 
to close the lower end of the tank chamber 12 by turning the gate 9 a 
quarter turn from the position shown in FIG. 2. The granules mixed with 
the liquid at the lower portion of the tank will accompany the liquid 
sucked into the pump, while the granules, which are mixed with the liquid 
in the chamber 12, will sink by gravity to the bottom of said chamber. By 
closing the tank chamber 12, initially no liquid will be supplied to the 
portion of the tank outside the tank chamber 12, and the liquid level 
there will drop until the tank chamber 12 is filled. Thereafter, there 
will be a flow as large as the flow sucked through the bottom outlet of 
the tank, which will flow over the upper edge of the dividing wall 8. 
By dimensioning the dividing wall and placing it in such a manner that the 
volume of the tank chamber 12, which in the circulation mode shown in FIG. 
2 extends above the liquid surface in the tank chamber and must thus be 
filled before liquid overflows the upper portion of the dividing wall, is 
at least as great as the sum of the volume of the lower portion of the 
tank outside the tank chamber, containing liquid mixed with granules, and 
the volume of the pipe system between the tank and the washing chamber, it 
is possible to assure that all of the granules have been returned to the 
tank chamber 12 before the liquid begins to overflow the upper edge of the 
dividing wall. 
For such an arrangement it is, however, not necessary to assure that 
granules accompanying the liquid flowing out from the outlet opening 11 
are not drawn with liquid overflowing the upper edge of the dividing wall. 
Due to their kinetic energy, the granules will quickly pass through a 
surface layer of the liquid in which the lateral flow takes place without 
being imparted in any appreciable horizontal component of movement and 
then sink by gravity to the bottom of the chamber 12 where they are 
collected as shown in FIG. 1. Near the upper edge of the dividing wall 8, 
the lateral flow is however sufficiently strong to pull granules with it, 
and therefore the dividing wall should be laterally spaced from the outlet 
opening 11. 
It is evident from the above that the heavy-duty dishwasher described here 
can be operated with a higher level of filling than that shown in FIGS. 1 
and 2, in other words with a liquid level lying above the upper edge of 
the dividing wall 8. With such a level of filling, when washing with 
liquid without granules, only surface flow will arise in the liquid 
surface and the stronger flow in the vicinity of the upper edge of the 
dividing wall is eliminated. When washing with liquid containing granules 
there arises, in addition to flow through the open lower end of the 
dividing wall as was described previously with refence to FIG. 2, a 
surface flow as well. For reasons mentioned previously, this surface flow 
will not appreciably effect the movement of the granules. 
In order to give the granules sufficient kinetic energy to achieve the 
required blast effect when the granules are sprayed against the dishes, 
the pump 5 must have large capacity, and this means that the suction in 
the bottom outlet 4 of the tank 10 must be quite powerful. This creates a 
powerful turbulent flow in the vicinity of the bottom outlet. This 
turbulent flow means that the granules, which when the gate 9 is turned 
from the closed to the open position, flow in high concentration out of 
the lower end of the tank chamber, will very quickly be distributed more 
or less evenly in the liquid above the bottom outlet, and the steady state 
shown in FIG. 2 when washing with granules, in which the granules are 
relatively evenly distributed in the circulating liquid, will be achieved 
shortly after the gate is opened. As can be seen in FIGS. 1 and 2, the 
volume of the tank chamber 12 is less than the volume of the rest of the 
tank 10. This means that the liquid flow between the tank chamber 12 and 
the rest of the tank which occurs to replace the liquid sucked up by the 
pump will be sufficiently strong to provide the granules with the 
significant horizontal component of movement, and this also contributes to 
achieving an even granular distribution relatively quickly. 
FIGS. 3-5 show variants of the dividing wall 8. FIG. 3 shows a dividing 
wall 8.sub.1 which can be pivoted between a vertical position and a 
position in which the lower edge of the dividing wall is in contact with 
the tank wall and closes off a chamber 12 in the tank. The pivotability of 
the dividing wall 8.sub.1 is indicated by an arrow in FIG. 3. This variant 
functions in principle in the same manner as the embodiment according to 
FIGS. 1 and 2. 
FIG. 4 shows a dividing wall 8.sub.2 which is pivotable between a lower 
position in which it closes off a tank chamber 12 and an upper position in 
which it is in contact with one edge of the outlet opening 11. 
Functionally this variant differs from that in FIGS. 1 and 2 by virtue of 
the fact that when washing with granules, the granules are supplied from 
above to the portion of the tank 10 containing the bottom outlet, and that 
the granules are imparted a horizontal component of movement by rolling 
down an inclined plane instead of being acted on by a liquid flow. 
In FIG. 5, a dividing wall 8.sub.3 is shown, comprising a bottom portion 
9.sub.3 which is vertically moveable between a lower and an upper 
position. Functionally, this variant functions in principle in the same 
manner as that shown in FIG. 4. 
In a variant not shown, the entire dividing wall or a lower portion thereof 
is vertically moveable to open the lower portion of the chamber in the 
tank which said wall defines. This variant functions in the same manner as 
the embodiment according to FIGS. 1 and 2. 
By making the washing chamber with bottom plates which define an outlet 
opening, it is possible to empty the dishwasher of granules in an elegant 
manner prior to cleaning thereof by placing a straining cloth sack in the 
outlet opening. 
The dishwasher embodiments described can of course be modified in a number 
of ways within the scope of the invention. For example, the washing 
chamber and the tank can have other cross-sectional shapes than those 
described and shown, and the outlet of the tank could be arranged in a 
lateral wall of the tank. Furthermore, the outlet opening need not extend 
between the walls of the washing chamber but can be completely defined by 
the bottom plates and also be non-rectangular, which permits a 
corresponding modification of the horizontal cross-section of the tank 
chamber defining dividing wall. The invention will therefore only be 
limited by the scope of the attached patent claims.