Abstract:
A method and apparatus for washing items of laundry that makes provision to continuously filter the treatment liquid during the washing operation. As a result, interfering attendant materials in and on the treatment liquid are successively removed during the washing operation, which increases the efficacy of the washing operation. Provision is preferably made to remove both lighter constituents, such as foam and lint, from the treatment liquid and also to filter heavier constituents, such as impurities washed out of the items of laundry, from the treatment liquid using the same filter. The same filter can also be used, after the end of the washing operation, to filter the treatment liquid to be let out and to temporarily store the treatment liquid in a collecting tank before the filtered treatment liquid is reused. The invention thus permits multiple functions of the filter.

Description:
STATEMENT OF RELATED APPLICATIONS 
       [0001]    This patent application claims priority on and the benefit of German Patent Application No. 10 2011 013 806.4 having a filing date of 14 Mar. 2011. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The invention relates to a method for washing in particular items of laundry, the items of laundry being at least washed with a treatment liquid in a rotationally drivable drum and the treatment liquid being removed from the drum as required by means of at least one outer drum assigned at least to part of the drum. Furthermore, the invention relates to an apparatus for washing in particular items of laundry, with a rotationally drivable drum and at least one stationary outer drum which extends at least over part of the length of the drum. 
         [0004]    2. Prior Art 
         [0005]    The washing, namely the actual laundering and the rinsing, of all types of objects, in particular items of laundry, is undertaken in washing machines which have a rotationally driveable drum which is assigned at least one stationary and liquid-tight outer drum. The at least one outer drum extends over at least part of the drum, in particular part of the length of the rotationally driveable drum. The washing is undertaken using a treatment liquid, which optionally has treatment additives, in the drum. The treatment liquid takes up only a lower part of the drum. The level, i.e. the surface of the treatment liquid, preferably lies somewhat below the axis of rotation of the drum. Where the drum is assigned an outer drum, the treatment liquid is also located in the liquid-tight outer drum. By means of a perforation in the rotationally driveable drum in the region of the respective outer drum, the treatment liquid in the outer drum can enter the lower region of the rotating drum where the treatment liquid comes into contact with the objects to be washed, in particular items of laundry, which are located in the rotating drum. 
         [0006]    As a consequence of the drum executing full circle rotations or opposed part circle rotations (pivoting movements) during the washing, foaming occurs, caused especially by the treatment additives in the treatment liquid. The foam accumulates with lint at least partially combined therewith from the laundry to be washed on the surface of the treatment liquid. In addition, the treatment liquid absorbs dirt washed out of the laundry and possibly foreign materials which, for the most part, are heavier than the treatment liquid and therefore collect in the bottom region of the outer drum. The foam and the dirt impair the efficacy of the washing operation. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The invention is based on the object of providing a method and an apparatus for more effectively washing and/or rinsing items of laundry and other objects. 
         [0008]    A method for achieving this object is a method for washing in particular items of laundry, the items of laundry being at least washed with a treatment liquid in a rotationally drivable drum and the treatment liquid being removed from the drum as required by means of at least one outer drum assigned at least to part of the drum, wherein, during at least the washing, the treatment liquid is filtered outside the drum and the at least one outer drum. According thereto, the treatment liquid, preferably always only some of the treatment liquid, is filtered during the treatment, i.e. in particular the washing and rinsing of the items of laundry or other objects, outside the drum and the at least one outer drum assigned thereto. Since the filtering is undertaken during the washing operation, attendant materials which impair the washing operation are successively removed from the treatment liquid. The washing can then be undertaken more effectively because of the lower loading of the treatment liquid by the attendant materials. The washing operation is not impaired by the filtering outside the washing machine. 
         [0009]    The filtering of the treatment liquid is preferably undertaken continuously during the washing. As a result, attendant materials, in particular foam, lint, dirt residues and the like, which are newly collected in the treatment liquid as the washing operation proceeds are gradually filtered out, preferably continuously, in particular during the entire washing operation. 
         [0010]    Provision is preferably made for the continuous filtering of the treatment liquid to be undertaken in a manner such that the treatment liquid is successively circulated by being pumped through or via the filter. As a result, some of the treatment liquid is always subjected to filtering while the rest, especially a large part, of the treatment liquid remains in the outer drum of the rotationally driveable drum and therefore, despite the successive and/or continuous filtering of some of the treatment liquid being undertaken at the same time, the washing operation is maintained without a loss in performance. 
         [0011]    In an advantageous development of the invention, a continuous stream of the treatment liquid is let out of the outer drum at at least one outlet and, after filtering, said treatment liquid is returned again to the outer drum. As a result, a small part of the treatment liquid is constantly circulated past the filter and the filter is continuously subjected to treatment liquid to be filtered. The volumetric stream of treatment liquid which is conducted via the filter is selected so as to correspond to the efficiency of the filter and the amount of treatment liquid remaining in the outer drum and in the drum containing the laundry to be treated is not significantly reduced, and therefore the level of the treatment liquid in the drum does not fall below the desired level. 
         [0012]    According to a preferred development of the method, lighter and heavier constituents are optionally, in particular alternately, filtered out of the treatment liquid. Therefore, constituents, such as foam, lint or the like, collecting on the surface of the treatment liquid and heavier constituents, such as dirt particles, foreign materials or the like, dropping onto the bottom of the outer drum can be gradually filtered out from the treatment liquid. It is alternatively also conceivable simultaneously to remove a mixture of treatment liquid containing lighter constituents and heavier constituents from the outer drum and to filter said constituents together. 
         [0013]    Preferably, in order to filter out lighter constituents from the treatment liquid, the treatment liquid, with the lighter constituents in the region of the surface thereof, specifically on the surface or just below the surface, is removed from the outer drum while the treatment liquid, with the heavier constituents below the surface of the treatment liquid, especially on the bottom or in the region of the bottom of the outer drum, is removed from same. By means of the various options for removing the treatment liquid to be filtered from the outer drum, the filter has a plurality of functions by being able to filter out lighter and heavier constituents, in each case separately or else together, from the treatment liquid. 
         [0014]    Provision is preferably made also to use the at least one filter in order to filter treatment liquid to be let out of the outer drum at the end of the washing operation. This provides a further option for using the same filter. The treatment liquid to be let out of the outer drum can also be completely filtered by filtering outside the outer drum. The filtered treatment liquid is preferably conducted into a storage tank. The filtered and used treatment liquid can be supplied from the collecting or storage tank for suitable reuse. 
         [0015]    According to a further preferred refinement of the method, the treatment liquid is filtered by a gravity filter. The treatment liquid can thus flow freely through the filter, wherein the filtered treatment liquid is separated from the filtered-out constituents by gravity. As an alternative or in addition, provision may be made to allow the liquid to flow in a freely flowing manner by means of gravity to the filter. The filter is thereby uniformly subjected to the treatment liquid following the gravity action and the filtering is likewise undertaken. In this case, however, it is conceivable for the flow rate or the amount of treatment liquid supplied to the filter per unit of time to be able to be set or changed by, for example, an adjustable throttle valve in a feed line to the filter. The treatment liquid supplied to the filter per unit of time can thus be matched to the efficiency of the filter and optimum filtering thus brought about. 
         [0016]    An apparatus for achieving the object referred to at the beginning, the apparatus preferably being a washing machine, is an apparatus for washing in particular items of laundry, with a rotationally drivable drum and at least one stationary outer drum which extends at least over part of the length of the drum, wherein a circulating line having at least one filter is assigned to at least one outer drum. Owing to the fact that a circulating line having a filter is assigned to at least one outer drum, the treatment liquid can be filtered, specifically in particular continuously, during the washing operation, namely the pre-washing, clear washing and/or rinsing. As a result, treatment liquid which is at least partially freed from constituents impairing the washing operation, especially foam, is always available for the washing operation. 
         [0017]    The circulating line is preferably provided with a plurality of outflows, in particular outflows which can be shut off individually, from the respective outer drum. In this case, an upper outflow is in particular arranged in the region of the level of the treatment liquid in the drum and in the outer drum while another outflow is preferably provided in the region of the bottom or in the bottom of the outer drum. This enables both treatment liquid with attendant materials swimming thereon in the region of the surface of the treatment liquid and also treatment liquid with dropping attendant materials to be removed from the outer drum. The capability of shutting off at least one outflow makes it possible to remove treatment liquid from the outer drum selectively from the top or from the bottom or, if desired, also to remove treatment liquid with floating and dropped attendant materials at the same time from the outer drum. 
         [0018]    Another advantageous refinement of the apparatus makes provision to provide at least one pump in the circulating or circulation line downstream of the at least one filter, preferably as seen in the direction of flow of the treatment liquid. By means of the pump, the filtered liquid can be pumped back into preferably the same outer drum from which the treatment liquid was removed, optionally also a different outer drum, even if the position of the introduction of the filtered liquid into the outer drum is located higher than the filter. 
         [0019]    Provision may be made for the circulating line to be connected, preferably downstream of the pump, to an inflow, which can be preferably shut off, to the outer drum. The capability of shutting off the inflow makes it possible to pump filtered treatment liquid to a different location. For example, the circulating line can have an outflow, to which at least one collecting tank is preferably assigned. The outflow may be located upstream of the pump, as seen in the direction of flow, if the filtered treatment liquid can be conducted away by gravity. By contrast, it is expedient to arrange the outflow downstream of the pump in the direction of flow if the filtered treatment liquid has to be pumped to the outflow located higher. 
         [0020]    In a preferred apparatus, the at least one filter is designed as a gravity filter. This filter operates automatically. Above all, the treatment liquid to be filtered does not need to be pumped through the gravity filter by a pump. On the contrary, the treatment liquid can flow automatically on account of the potential energy thereof out of the outer drum to the filter and through or via the latter. A filter of this type may be designed as a sieve, through the opening in which the treatment liquid to be filtered flows, but heavier and lighter attendant materials are retained, and therefore said attendant materials can be removed on the filtering surface which is formed by the sieve and can have a rectilinear, oblique and/or curved profile. 
         [0021]    In order to clean the filtering surface, in particular the filter sieve, said filtering surface can be subjected to a flowing fluid, for example by means of spray nozzles under the preferably sieve-like filtering surface. 
         [0022]    The invention is suitable particularly for apparatuses designed in the manner of commercial washing machines, namely what are referred to as continuous process washing machines. A washing machine of this type has an elongate, overall rotationally driveable drum with a plurality of consecutive chambers, at least one of the chambers being assigned an outer drum. An outer drum is customarily located where treatment liquid, such as pre-washing liquid, clear washing liquid and/or rinsing liquid, can be conducted out of the drum or liquids can be supplied to the drum. By means of the assignment of the outer drum to at least one chamber, the invention makes it possible, in a chamber-related manner in a continuous process washing machine, always preferably to continuously filter only the treatment liquid present in the relevant chamber during the washing operation, specifically in particular to at least partially remove both lighter constituents and also heavy constituents successively, but constantly, especially continuously, from the treatment liquid in the relevant chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    A preferred exemplary embodiment of the invention is explained in more detail below with reference to the drawing, in which: 
           [0024]      FIG. 1  shows a schematic side view of an apparatus according to the invention in the form of a continuous process washing machine. 
           [0025]      FIG. 2  shows a cross section through a chamber, which is provided with an outer drum, of the continuous process washing machine from  FIG. 1  in a schematic illustration. 
           [0026]      FIG. 3  shows a cross section analogously to  FIG. 2  in a different manner of operation. 
           [0027]      FIG. 4  shows a cross section analogously to  FIG. 2  in yet another manner of operation. 
           [0028]      FIG. 5  shows a longitudinal section through a filter merely illustrated schematically in  FIGS. 1 to 4 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    The invention is described below with reference to an apparatus, in the form of a continuous process washing machine  10 , for washing and rinsing items of laundry. However, the invention is not restricted thereto. 
         [0030]    The continuous process washing machine  10  shown schematically in  FIG. 1  has a cylindrical drum  12  which is rotationally driveable about a preferably horizontal axis of rotation  11 . The axis of rotation  11  lies on the longitudinal center axis of the drum  12 . The laundry to be washed is transported from the left to the right (with respect to  FIG. 1 ) in the treatment direction  13  through the rotationally driven drum  12 . 
         [0031]    A plurality of chambers  15  which are consecutive in the treatment direction  13  are formed by transversely directed partitions  14  in the drum  12 . One laundry batch is treated, in particular washed and rinsed, in each chamber  15 . The chambers  15  may be identical in size, but may also differ in size. The partitions  14  have central or eccentric openings (located at the edge) which are not shown in the figure. Through the openings, the laundry can be transferred batchwise in the treatment direction  13  from one chamber  15  into the following chamber  15 . The continuous process washing machine  10  shown in  FIG. 1  has twelve chambers  15 . However, the invention is not restricted thereto. The continuous process washing machine  10  may have a larger or smaller number of chambers  15 . 
         [0032]    The first four chambers  15 , as seen in the treatment direction  13 , form a pre-washing zone  16  in the continuous process washing machine  10  shown. The following five chambers  15  form a clear washing zone  17 . A rinsing zone  18  having three consecutive chambers  15  follows the clear washing zone  17 , as seen in the treatment direction  13 . The pre-washing zone  16 , clear washing zone  17  and rinsing zone  18  may have a number of chambers  15  differing from the exemplary embodiment (shown in  FIG. 1 ) of the continuous process washing machine  10 . It is also conceivable for at least one further chamber (not illustrated in  FIG. 1 ) to follow the rinsing zone  18  in order to form a finishing zone. The rinsing zone  18  may also be omitted. 
         [0033]    In the continuous process washing machine  10  shown here, the final chamber  15  of the pre-washing zone  16 , the clear washing zone  17  and the rinsing zone  18  has in each case an outer drum  19 . In addition, an outer drum  19  is assigned to the first chamber  15  of the clear washing zone  17  and the rinsing zone  18 . All of the outer drums  19  are designed to be equally impermeable to liquid. So that treatment liquid for the laundry in the outer drum  19  can communicate with that section of the drum  12  which extends over the relevant chamber  15  with an outer drum  19 , the drum  12  is designed to be at least partially permeable for treatment liquid, in particular is perforated, in regions of those chambers  15  which are assigned an outer drum  19 . As a result, treatment liquid can enter the liquid-permeable section of the drum  12 , which section is assigned to the chamber  15 , from the respective outer drum  19 , and vice versa. The treatment liquid in the respective chamber  15  has a desired level. The level is preferably somewhat below the axis of rotation  11  ( FIGS. 2 and 3 ). Consequently, the surface of the treatment liquid in the relevant chamber  15  is also located somewhat below the axis of rotation  11 . 
         [0034]    The lower region of each of the outer drums  19  of identical design preferably has an expanded portion preferably designed in the manner of a terminal box. Said expanded portion accommodates a stock of treatment liquid below the drum  12 . 
         [0035]    Constituents which are lighter than the treatment liquid, for example foam, lint and the like, collect on the surface of the treatment liquid. The lint is preferably at least for the most part combined in the foam. Solid constituents of the treatment liquid that are heavier than the treatment liquid can collect on a bottom  20  of the outer drum  19 , which is expanded at the bottom in order to form the terminal box. The heavier constituents are dirt and other solids washed out of the laundry, for example small foreign bodies which can pass through the perforation in the drum  12  in the region of the respective chamber  15  with the outer drum  19 . 
         [0036]    In the case of the continuous process washing machine  10  shown here, the outer drum of the final chamber of the clear washing zone  17  and the outer drum  19  of the final chamber  15  of the rinsing zone  18  are each assigned a circulating line  21  with a filter  22 . The latter are of identical design at the end of the clear washing zone  17  and at the end of the rinsing zone  18 . Both the circulating line  21  and the respective filter  22  are located outside the drum  12  and the outer drum  19 . The respective filter  22  and the circulating line  21  assigned thereto are preferably assigned, in particular fastened, to a rack  23  of the continuous process washing machine  10 . However, the filters  22  may also be located at a different location in the laundry away from the continuous process washing machine  10 . A pump  24  is provided downstream of the or each filter  22 , as seen in the direction of flow of the treatment liquid through the circulating line  21 , in order to pump the filtered treatment liquid back into the respective outer drum  19 . 
         [0037]      FIGS. 2 to 5  show in more detail the circulating line  21  and the filter  22  assigned thereto in the region of the final chamber  15  of the clear washing zone  17 . The circulating line  21  and the filter  22  in the region of the outer drum  19  of the final chamber  15  of the rinsing zone  18  are designed in the same manner. 
         [0038]    In particular,  FIG. 2  shows that the circulating line  21  is divided, namely consists of a starting part, as seen in the direction of flow to the filter  22 , and a return part emerging from the filter  22 . As a result, the circulating line  21  is interrupted in the region of the filter  22 , but the starting part and the return part of the circulating line  21  are connected in terms of flow by the filter  22 . In addition, the starting part of the circulating line  21  is designed in two strands, namely has a first starting part  25  and a second starting part  26 . The first starting part  25  of the circulating line  21  is connected to an outflow  27  of the outer drum  19 , the outflow being located in the region of the level or the surface of the treatment liquid in the chamber  15  to which the outer drum  19  is assigned. The second starting part  26  of the circulating line  21  is connected to a second outflow  28  in the bottom region, in particular in the vicinity of the bottom  20 , of the outer drum  19  of the final chamber  15  of the clear washing zone  17 . The outflow  28  may also be provided in the bottom  20  of the outer drum  19 . Both starting parts  25  and  26  end upstream of the filter  22 . The return part of the circulating line  21  is assigned to that side of the filter  22  on which the filtered treatment liquid is obtained. The filtered liquid is pumped back into the outer drum  19  by the pump  24  in the return part of the circulating line  21 . For this purpose, an inlet  29  is provided for connecting a rear end of the return part of the circulating line  21  to the outer drum  19  below the surface of the treatment liquid. 
         [0039]    A discharge line  30  branches off from the return part of the circulating line  21  downstream of the pump  24 , the discharge line leading to a collecting tank  31  or opening into the collecting tank  31 . 
         [0040]    The second starting part  26  of the circulating line  21  is assigned a valve  32 . This is preferably an adjustable throttle valve with which the flow rate of the treatment liquid through the second starting part  26  can be changed, but the second starting part  26  may also be closed. In this way, the inflow of treatment liquid from the bottom region of the outer drum  19  to the filter  22  can be entirely prevented or changed in respect of the volumetric stream of the treatment liquid to the filter  22  per unit of time, for example for adaptation to the capacity of the filter  22 . Similarly, if required, a simple shut-off valve or an adjustable throttle valve may be arranged in the first starting part  25  of the circulating line  21 . It is then possible for partial streams from the surface of the treatment liquid and from the bottom of the outer drum  19  to be conducted in a directed manner to the filter  22  at the same time and for the flow rate of the treatment liquid through the first starting part  25  to be changed and optionally for the first starting part  25  of the circulating line  21  also to be completely closed. A further valve  33  is located in the return part of the circulating line  21 , specifically downstream of the branching off of the discharge line  30  form the circulating line  21 , as seen in the direction of flow of the treatment liquid. A valve  34  is also assigned to the discharge line  30 . By means of the valves  33  and  34 , the outflow of the filtered treatment liquid can be controlled in a directed manner, specifically either back to the outer drum  19  or into the collecting tank  31 . 
         [0041]    The filter  22  is illustrated in detail in  FIG. 5 . This involves what is referred to as a gravity filter, in which the treatment liquid to be filtered is caused by gravity to flow through a filter sieve  31 , specifically from the upper side of the filter sieve  48  to the lower side thereof. This may also be undertaken during the flow of the treatment liquid to be filtered along on the filter sieve  48 . The filter sieve  48  is arranged in a preferably completely closed housing  35 . The upper side of the housing  35  may optionally be open. The housing  35  has (as seen from the side) an oblique profile with an oblique bottom  36 . From above, the ends of the two starting parts  25  and  26  of the circulating line  21  are guided at the highest point into the oblique housing  35 . The filter sieve  48  is likewise fastened in an obliquely directed manner in the housing  35  at a distance from the bottom  36 . As a result, the filter sieve  48  divides the housing  35  into an upper part  37  located above the surface of the filter sieve  34  and a lower part  38  located below the filter sieve  48 . The filter sieve  48  may be formed from a perforated sheet with a uniform grid of passage holes of corresponding size or from a wire cloth with a corresponding mesh width. 
         [0042]    The filter sieve  48  is preferably designed in two layers. Said filter sieve  48  consists of a lower, stable and large-meshed supporting lattice and a fine-meshed sieve which is arranged above the latter and is designed in the manner of a lattice or is braided. The optionally flexible sieve is then supported by the supporting lattice. 
         [0043]    The filter sieve  48  ends at a distance upstream of a transverse wall  39  at the lower end of the housing  35 . A height-adjustable, transversely directed weir  40  is located upstream of the end of the filter sieve  37 . By appropriate height adjustment of the plate-like weir  40  a gap of corresponding width for conducting away the constituents filtered out of the treatment liquid is produced above the end of the lint sieve  34 . A pivotable flap may also be provided instead of the height-adjustable weir  40 . A chamber  42  for collecting the constituents filtered out of the treatment liquid is located between that end of the filter sieve  48  which is spaced apart from the transverse wall  39  and is formed by a lower transverse edge  41  of same. A collecting container  43  for filtered-out constituents can be provided in the chamber  42 . The collecting container  43  can preferably be removed from the chamber  42  or can be withdrawn from the chamber  42  in the manner of a drawer. 
         [0044]    At the bottom end region upstream of the transverse wall  39 , the bottom  36  of the housing  35  has a depression which forms a sump  44 . During the emptying of the filter  22 , the remaining filtered treatment liquid collects in the sump  44  as the lowermost point of the housing  35 . In addition, the sump  44  forms a pump reservoir which ensures that, during operation of the filter  22 , the pump  24  is constantly supplied with sufficiently filtered treatment liquid. In addition, a float switch  45  serving to prevent dry operation of the pump  24  is provided in the sump  44 . Furthermore, a closable outflow  46  is located at the lowermost point of the sump  44 . When the outflow  46  is opened, the treatment liquid can be completely let out of the housing  35  of the filter  22 . 
         [0045]    A plurality of cleaning nozzles  47  directed toward the lower side of the filter sieve  48  are provided in the lower part  38  of the housing  35 . The cleaning nozzles  47  are distributed in the lower part  38  in such a manner that they can subject the entire lower side of the filter sieve  48 , or at least a large part thereof, to cleaning liquid. The cleaning liquid is preferably fresh water. However, filtered treatment liquid from the collecting tank  31  may also be used. The used cleaning liquid is then pumped back again into the collecting tank  31  through the return part of the circulating line  21  and the discharge line  30  or conducted into an outflow. 
         [0046]    The method according to the invention is described in more detail below with reference to the previously described apparatus, namely the continuous process washing machine  10 . 
         [0047]    The method according to the invention makes provision, on the basis of the respective chamber  15  with an outer drum  19 , to preferably continuously filter the treatment liquid outside the outer drum  19  during the washing operation. The treatment liquid from each outer drum  19  or else only selected outer drums  19  or from only one outer drum  19  can be filtered. The filtration can be undertaken periodically during the washing operation, but also continuously during the entire washing operation. With the filtration during the washing operation, a small amount of the treatment liquid, which is continuously removed from the treatment liquid, is pumped through the circulating line  21  by the pump  24  and, in the process, is filtered by the filter  22 , which is designed as a gravity filter, in accordance with the principle of gravity. Only such a small part of the treatment liquid at a time is subjected to the filtering that the provided treatment liquid level in the drum  12  receiving the items of laundry to be washed and in the outer drum  19  is maintained. In the exemplary embodiment shown, the level of the treatment liquid in the drum  12  is selected such that the surface  49  of the treatment liquid lies somewhat below the axis of rotation  11  of the drum  12  ( FIGS. 2 to 4 ). 
         [0048]    The flow rate of the treatment liquid through the circulating line  21  is selected or set at the throttleable valve  32  in such a manner that, over the course of a treatment operation of the batch of laundry in the relevant chamber  15 , the treatment liquid in said chamber  15  is completely circulated at least once and filtered by the filter  22 . 
         [0049]    The method according to the invention is designed in such a manner that it permits a multiple function of the filter  22 . Accordingly, the filter  22  is used in order to carry out different filtering tasks which are illustrated schematically in  FIGS. 2 to 4 . 
         [0050]      FIG. 2  shows the use of the filter  22  for removing those constituents from the treatment liquid that are lighter than the treatment liquid, for example foam, in particular foam together with entrained lint. The possibly lint-containing foam collects on the surface  49  of the treatment liquid in the drum  12 . Via the outflow  27 , which is located in the region of the surface  49  of the treatment liquid, the foam containing lint and other lighter constituents is removed together with the treatment liquid located on the surface  49  from the drum  12  and the outer drum  19  and fed to the filter  22  via the first starting part  25  of the circulating line  21 . In the process, the treatment liquid with the lighter components passes into the upper part  37  of the housing  35  of the filter  22 . As a result of the oblique position of the filter sieve  48 , the treatment liquid to be filtered flows together with the lighter constituents to be filtered out along the filter sieve  48 . By means of gravity, only the treatment liquid passes through the filter sieve  48 , and said treatment liquid thus passes filtered into the lower part  38  of the housing  35  of the filter  22 . The filtered treatment liquid is then pumped by the pump  24  through the circulating line  21 , with the valve  33  open, to the inlet  29  in the outer drum  19  and therefore the filtered treatment liquid is supplied again to the washing process, namely to the outer drum  19  and the drum  12 . 
         [0051]    The filtered-out lighter constituents of the treatment liquid flow along the oblique filter sieve  48 . Through the gap below the transverse edge  41  of the weir  40 , said filtered-out lighter constituents, in particular foam and lint, enter the collecting container  43  of the filter  22 . The collecting container  43  collects lint, in particular, which can be disposed of from time to time by the collecting container  43  being withdrawn or removed from the chamber  42  of the housing  35  of the filter  22 . Other constituents can be collected at another point of the chamber  42  and removed from there, for example into an outflow. 
         [0052]    The valves  32  and  34  are closed during the previously described filtering off of lighter constituents from or out of the treatment liquid. Only light constituents are then separated from the treatment liquid, and the filtered treatment liquid is continuously pumped back circulating through the circulating line  21  into the continuous process washing machine  10 . As a result, cleaned treatment liquid is continuously supplied again to the treatment liquid, and therefore the quantity of treatment liquid in the relevant chamber  15  always remains substantially the same and is reduced only by the treatment liquid located in the circulating line  21  and in the region of the filter  22 . By means of the filtering off of foam, which is undertaken during the washing operation, with light constituents combined thereon or therein, the foam carpet on the treatment liquid is reduced and the washing action thereby increased, as a result of which stains especially can be more effectively removed from the laundry. It is also conceivable to temporarily close the weir  40  or the pivotable flap for certain time intervals during the filtering out of the foam with the light constituents combined therein and to subject the foam in the region of the filter  22  to water, preferably fresh water. As a result, the foam is destroyed, as it were, and the quantity of foam reduced. 
         [0053]      FIG. 3  schematically illustrates a second intended use of the filter  22 . Here, the valve  32  in the second starting part  26  of the circulating line  21  is opened or adjusted to such an extent that the treatment liquid can be supplied continuously to the filter  22  during the washing of the laundry. In this case, the valve  32 , which is preferably designed as a throttle valve, is adjusted in such a manner that only a desired volumetric stream of the treatment liquid flows through the circulating line  21 . The treatment liquid enters the second starting part  26  through the outflow  28  arranged in the vicinity of the bottom  20  of the outer drum  19 . In this case, with the treatment liquid, heavier constituents thereof, for example dirt particles removed form the laundry, but also other small solid particles and possibly foreign bodies, pass via the outflow  28  and the second starting part  26  of the circulating line  21  to the filter  22 . The solid constituents are filtered out here from the treatment liquid by gravity by the solid constituents being retained by the filter sieve  48  and only the treatment liquid flowing through the filter sieve  48  and, in the process, being filtered. The filtered treatment liquid is pumped back again via the circulating line  21  through the inlet  29  into the outer drum  19 . Filtered-out solid constituents are removed laterally above the filter sieve  48  as a result of the oblique arrangement of same and are collected in the chamber  42  of the housing  35  of the filter  22 . Like lint, the solid constituents can also be collected in the collecting container  43 . 
         [0054]    In the exemplary embodiment shown, the first starting part  25  of the circulating line  21  cannot be shut off by a valve. Constituents floating on the surface  49  of the treatment liquid are therefore continuously conducted through the first starting part  25  of the circulating line  21  to the filter  22 . By contrast, only treatment liquid with heavier constituents contained therein, if this is desired, flows through the second starting part  26  of the circulating line  21  as a result of the valve  32  which is assigned to said circulating line and can be shut off and throttled. For example, the valve  32  may be opened only periodically during the washing. However, the valve  32  may also be opened continuously, the throttle allowing only as much treatment liquid to be guided through the second starting part  26  to the filter  22  as the filter capacity permits. However, it is also conceivable likewise to assign a valve to the first starting part  25  of the circulating line  21 . If said valve is closed, with the valve  25  in the second starting part  26  open, only treatment liquid with heavier constituents contained therein can be supplied to the filter  22  and the treatment liquid freed from heavier constituents by said filter. 
         [0055]      FIG. 4  shows the method according to a third manner of operation of the filter  22 . The treatment liquid is filtered here when the treatment liquid is completely let out of the chamber  15 . This is the case when a bath change, i.e. an exchange of the treatment liquid, is undertaken in the relevant chamber  15 . Such a bath change is preferably undertaken after the washing of the items of laundry in the relevant chamber  15  when the laundry batch is transferred from the chamber  15  into the next chamber  15  in the treatment direction  13 , for example the first chamber  15  of the rinsing zone  18 , or in order to unload the completely washed and rinsed laundry batch from the continuous process washing machine  10 . 
         [0056]    When the treatment liquid is let out, the valve  32  in the second starting part  26  of the circulating line  21  and a possible valve in the first starting part  25  are preferably fully open. The treatment liquid can then be entirely let out of the drum  12  and out of the outer drum  19  assigned to the latter. The treatment liquid to be let out is filtered by the filter  22  and the filtered treatment liquid is subsequently conducted by the pump  24  through the circulating line  21 , with the valve  34  in the discharge line  30  open, into the collecting tank  31 . The following valve  33  in the circulating line  21  in the direction of flow of the treatment liquid through the circulating line  21  to the discharge line  30  is then preferably closed. 
         [0057]    The lower sump  44  in the housing  35  of the filter  22  makes it possible to conduct the treatment liquid out of the filter  22  through the outflow  46  without leaving a residue. However, only the remaining treatment liquid collecting at the bottom in the sump  44  and being unable to be pumped by the pump  24  into the collecting tank  31  leaves the outflow  46 . As a consequence of the complete emptying not only of the outer drum  19  but also of the filter  22 , mixing of the treatment liquid of the washing operation which has taken place last with possibly different treatment liquid for the next washing operation is avoided. 
         [0058]    If the treatment liquid is completely let out of the drum  12  and the outer drum  19 , cleaning of the filter sieve  48  preferably takes place with the filter  22  currently not carrying out any filtering. This is undertaken from the lower side of the filter sieve  48  by means of the cleaning nozzles  47  which are directed at said lower side. For this purpose, the cleaning nozzles  47  can be supplied with fresh water or cleaned treatment liquid from the collecting tank  31  as the cleaning liquid. The soiled cleaning liquid obtained during the cleaning of the filter sieve  48  is conducted away below the filter sieve  48 , i.e. in the lower part  38 . The cleaning liquid collects in the sump  44  at the lowermost point of the housing  35  of the filter  22  and is completely conducted away therefrom through the outflow  46  and subsequently disposed of. The filter  22  may also be cleaned in order to destroy the foam or reduce the quantity thereof during the manner of operation of the filter  22  according to  FIG. 2 . 
         [0059]    The method operates in the above-described manner both in the region of the final chamber  15  of the clear washing zone  17  and of the final chamber  15  of the rinsing zone  18 . It is optionally also possible for the method to be carried out at the final chamber  15  of the pre-washing zone  16 . The above-described method is also suitable for continuous process washing machines which only have a pre-washing zone  16  and a clear washing zone  17 , but not a rinsing zone  18 . 
         [0060]    The invention is suitable not only for all types of continuous process washing machines but also for other washing machines and washing machines for washing and cleaning any other objects, i.e. not only items of laundry. 
       LIST OF REFERENCE NUMBERS 
       [0000]    
       
           10  Continuous process washing machine 
           11  Axis of rotation 
           12  Drum 
           13  Treatment direction 
           14  Partition 
           15  Chamber 
           16  Pre-washing zone 
           17  Clear washing zone 
           18  Rinsing zone 
           19  Outer drum 
           20  Bottom 
           21  Circulating line 
           22  Filter 
           23  Rack 
           24  Pump 
           25  First starting part 
           26  Second starting part 
           27  Outflow 
           28  Outflow 
           29  Inlet 
           30  Discharge line 
           31  Collecting tank 
           32  Valve 
           33  Valve 
           34  Valve 
           35  Housing 
           36  Bottom 
           37  Upper part 
           38  Lower part 
           39  Transverse wall 
           40  Weir 
           41  Transverse edge 
           42  Chamber 
           43  Collecting container 
           44  Sump 
           45  Float switch 
           46  Outflow 
           47  Cleaning nozzle 
           48  Filter sieve 
           49  Surface