Abstract:
Tunnel washing machines ( 10 ) are equipped with a rotary driven drum ( 12 ), through which the laundry to be subjected to wet treatment is conveyed longitudinally. For achieving the greatest possible performance in treatment, the goal is to drive the drum ( 12 ) at the highest possible circumferential speed. However, the result of this is that the laundry is not (completely) thrown off the paddle blades ( 21 ) in the drum ( 12 ). This, has a negative effect on the results of treatment. 
     The method according to the invention proposes that the drum ( 12 ) be driven with different circumferential speeds. When the laundry is thrown off the paddle blades ( 21 ) the drum ( 12 ) and its circumferential speed is thereby considerably reduced, thus causing the laundry to drop from the paddle blades ( 21 ) in a complete and reliable manner.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates to a method for the wet treatment of laundry items with the laundry being at least washed in a rotary driven drum. 
     2. Prior Art 
     Employed for the wet treatment of laundry items, particularly in commercial laundries, are so-called continuous tunnel washing machines which have a rotary driven drum which revolves about a preferably horizontal center axis. In the elongate drum, laundry items are, in a continuous pass, washed, rinsed and if necessary subjected to other treatment, in particular aftertreatment. The drum is driven in a preferably rotating, circulatory manner, thus executing complete circular movements during the wet treatment of the laundry. Arranged in the drum are built-in elements, in particular paddle blades. Permanently fixed in the drum, the paddle blades turn in the circumferential direction of the drum, thus serving to carry along the laundry within the drum and, according to need, to transport the laundry through the drum in its longitudinal direction. 
     During part of each revolution of the drum, the laundry lies in front of the paddle blades as well as upon the inner side of the drum. When, during the rotational actuation of the drum, the off-center paddle blades within the drum reach or pass through an upper cusp point (apex), the laundry drops into the interior of the drum due to gravity. This results in the laundry being thrown off the paddle blades and the inner side of the drum shell. 
     In order to increase the handling performance of tunnel washing machines, one aims at propelling the drum at the highest possible frequency of rotation, thus causing the drum to rotate at a correspondingly high speed. With increasing speed or rotational frequency, the laundry, particularly due to centrifugal forces, tends to adhere to the paddle blades and to the surfaces of the drum shell. This means that the laundry does not completely drop off when the paddle blades pass through the apex point in the drum. Having the laundry thrown off and drop down is essential for an effective washing and/or rinse cycle. Therefore, even incomplete throwing off and dropping down of the laundry results in a reduced intensity of the treatment; in particular, there is a drop in performance in washing and/or rinsing. The greater rotational frequency or driving speed of the drum thus becomes practically ineffective. 
     BRIEF SUMMARY OF THE INVENTION 
     Proceeding from the above, the invention is based on the problem of creating a method for a more effective and efficient wet treatment of laundry. 
     A method for solving this problem is characterized in that the drum is driven with different rotational frequencies. By having the drum driven at different rotational frequencies (in other words: different rotary frequencies or different number of revolutions), its rotational speed can be varied to meet these requirements. The disadvantages posed by driving the drum at a higher rotational frequency can be eliminated by a temporary or intermittent reduction of the rotational frequency. The faster drum drive speed at all other times can thus fully exploit the advantages of the drum action. 
     The drum is driven preferably in rotation, with the drum being driven at different rotational frequencies during at least some, preferably during all, of its revolutions. The drum is thereby driven with a different velocity profile during at least some of its revolutions, with slower drive speeds being selected when disadvantages arising from too rapid drive speeds may be encountered. The drum is driven more rapidly in those circumferential areas of the drum in which higher drive speeds do not have a disadvantageous effect on the performance of treatment, in particular concerning washing and/or rinsing efficiency, which on the whole makes it possible to achieve a greater efficiency in treatment using tunnel washers. 
     Pursuant to a preferred method, the drum is driven at a plurality of, preferably two, different rotational frequencies during a respective revolution, with each frequency being held essentially constant during its segment of the drum revolution. Accordingly, the drum runs at the same speed in the respective area, which results in an even wet treatment of the laundry. 
     It is also provided that the drum is to be braked or accelerated between the drive phases of the drum by means of applying a lower or higher rotational frequency, respectively. This gives a stepped velocity profile, with the phases of drum acceleration or braking serving to attain a higher or lower rotational frequency and/or circumferential speed (in other words: rotational speed) of the drum. In particular, braking the drum from the higher circumferential frequency to the lower circumferential frequency applies a impetus force on the laundry, which facilitates the loosening of the laundry from the drum and the paddle blades, and in particular ensures a more effective and above all more complete throwing off of the laundry. 
     According to a further proposal of the invention, the drum is driven with the higher rotational frequency over a greater segment of its circumference that with the lower rotational frequency. This keeps the reduction of the drum drive speed to a minimum but at the same time retains to the maximum possible degree the performance advantage offered by the higher circumferential speed of the drum. 
     It is furthermore provided that when built-in elements of the drum, in particular paddle blades for carrying along the laundry, reach an upper region of reversed direction (apex) of the drum, the drum is driven at a slower circumferential speed or rotational frequency. Accordingly, the drum is driven more slowly as the laundry is thrown off and this reduces the centrifugal forces which might otherwise hold the laundry to the paddle blades and inner side of the drum shell. This results in an effective and in particular complete throwing off of the laundry in that it can loosen more easily from the inner walls of the drum and the paddle blades due to the lower circumferential speed of the drum. 
     Pursuant to a preferred embodiment of the method, when the paddle blades reach the upper reverse area of the drum—or even shortly before that—the drive of the drum is braked enough for the drum to shift from the higher rotational frequency to the lower rotational frequency. This braking action gives the laundry a dynamic impetus which favors its loosening from the paddle blades and the inner side of the drum wall, thus ensuring a reliable throwing off of the entire laundry at the apex of the drum. This not only represents an improvement in the efficiency of throwing off laundry at the apex region of blade motion by reducing the circumferential speed of the drum. This also favors and enhances the reliable throwing off of laundry by the braking of the drum required for reducing its rotational speed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention will be described in more detail below on the basis of the drawings, which show: 
     FIG. 1 a schematic side view of a tunnel washing machine for carrying out the method according to the invention, 
     FIG. 2 a cross-sectional view of a drum of the tunnel washing machine, and 
     FIG. 3 a cross-sectional view analogous to FIG. 2 with a schematic velocity profile of a revolution of the drum of the tunnel washing machine. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The shown tunnel washing machine  10  is employed preferably for the wet treatment of laundry items in commercial laundries. In the tunnel washing machine  10  the laundry items  11 , schematically represented in FIGS. 2 and 3, are washed, rinsed and, if necessary, subjected to aftertreatment, such as a finishing. The tunnel washing machine  10  has a elongate drum  12  with a cylindrical drum shell. The drum can be driven rotationally about a horizontal longitudinal center axis  13 . In the drum washing machine  10  shown here, the drum is driven completely or to a great extent in rotation. The drum  12  thus executes complete circular revolutions in succession. 
     The drum  12  of the tunnel washing machine  10  shown here is divided into different zones, namely a washing zone, which may comprise a pre-wash zone and a clear-wash zone, a rinsing zone and, if necessary, a finishing zone. The washing zone, the rinsing zone and any finishing zone are arranged in the successive direction of treatment  14  in the drum  12  of the tunnel washing machine  10 . The washing zone, the rinsing zone and also any finishing zone are formed from a plurality of successive chambers  15  in the longitudinal direction of the drum  12 , with any number of chambers being possible, i.e. not limited to the number of those in the exemplary embodiment shown in FIG.  1 . In particular, the chambers  15  can have various built-in elements. 
     Arranged before a feed end  16  of the drum  12  of the tunnel washing machine  10  (at the left in FIG. 1) is a hopper feeder  17 . The laundry items  11  to be washed are introduced at the feed end  16  through the hopper feeder  17  into the drum  12  of the tunnel washing machine  10 . In the shown exemplary embodiment, a discharge slide  19  is arranged at the rear (right-hand side in FIG. 1) discharge end  18  of the drum  12  of the tunnel washing machine  10 . Washed laundry items  11 , which exit the drum at the discharge end  18 , are transported out of the tunnel washing machine  10  on the discharge slide  19 , if necessary to a following hydroextraction machine (not shown), such as a drainage press. 
     The individual chambers  15  of the drum  12  are separated from one another by vertical partitions  20  running perpendicular to the longitudinal center axis  13  of the drum  12 . The individual chambers  15  are connected to the single-piece drum  12 , which runs continuously over the entire longitudinal center axis  13 , in the regions of the partitions  20 . The partitions  20  between the chambers  15  exhibit openings. Built-in elements, specifically paddle blades  21 , are provided between each two adjacent partitions  20  in preferably every chamber  15 . In particular a paddle blade  21  is provided in each chamber  15 , and the paddle blades  21  of all chambers  15  can be of the same or different configuration. 
     The drum  12  is movable by means of the bearing  22 , shown symbolically in FIG. 1, namely supported rotationally on a frame (not shown) of the tunnel washing machine  10 . The bearing  22  is configured as running wheels on which the shell of the drum rests such that during the rotational drive of the drum  12 , the shell moves about the longitudinal center axis  13  by rolling contact on the running wheels. 
     According to the invention, the drum  12  is driven in a special manner. This drive action occurs at different rotational frequencies. In the shown exemplary embodiment, the drum is driven at two different rotational frequencies. Each of the two rotational frequencies is constant over a segment of the revolution of the drum  12 . The velocity profile for one revolution of the drum  12  is represented schematically in FIG. 3 around the circumference of the drum  12 . Accordingly, the drum is driven over a greater segment  23  of its circumference or of a revolution at a higher rotational frequency of up to fourteen revolutions per minute. This rotational frequency is constant over the greater segment  23  of the revolution of the drum  12 . The drum  12  is driven at a smaller, constant rotational frequency over a smaller segment  24  of its circumference. The smaller rotational frequency has a maximum rate of 5 revolutions per minute, thus being a third less than the larger rotational frequency. Seen in the direction of revolution  25 , the segment  23  with the higher rotational frequency is followed by a braking phase  25 , which in turn extends over a small segment of the circumference of the drum  12 . During the braking phase  26 , the drum  12  is steadily braked from the higher rotational frequency (segment  23 ) to the lower rotational frequency (segment  24 ). Seen in the direction of revolution  25 , the lower rotational frequency is followed by an acceleration phase  27 . This too extends over a small segment of the circumference of the drum  12  and serves to accelerate the drum from the lower rotational frequency (segment  24 ) to the higher rotational frequency (part  23 ). 
     The segment  24  of the circumference of the drum  12  where it is driven with lower rotational frequency is located at the upper reversal area of the paddle blades  21  in the respective chamber  15  of the drum  12 , i.e. where the laundry items  11  reach the apex of the drum  12  and are here thrown off the paddle blades  21  by dropping down in the chamber  15  (FIG.  3 ). The segment  24  of the circumference of the drum  12  in which it is driven with the lower rotation frequency, begins approximately at that point where the middle of the paddle blade  21  reaches the highest point in the drum  12 , i.e. where it intersects a vertical longitudinal center axis of the drum  12 . The segment  24 , where the drum  12  is driven with the lower rotational frequency, ends at the point where one end of the paddle blade  21  meets the inner side of the shell of the drum  12 . This ensures that the drum  12  is driven at the constant lower rotational frequency when the laundry items  11  are thrown off the paddle blade  21  of the respective chamber  15 . This smaller segment  24  of the drum  12 , which revolves at a constant lower speed, extends in the shown exemplary embodiment along approximately 32° of the circumference of the drum  12 . In contrast, segment  23 , where the drum  12  is driven at the higher circumferential speed, is considerably larger, occupying in the shown exemplary embodiments approximately 305° of the circumference of the drum  12 . The braking phase  26  in the shown exemplary embodiment extends about 13° of the circumference of the drum  12 . By comparison, the acceleration phase is somewhat smaller, extending namely in the exemplary embodiment only over approximately 10° of the circumference of the drum  12 . Depending on the configuration of the paddle blades  21 , the segments  23  and  24  for driving the drum  12  at a constant higher or lower circumferential speed can be either larger or smaller than those of the exemplary embodiment shown in FIG.  3 . Likewise, the braking phase  26  and the acceleration phase  27  can be greater or smaller than those of the shown exemplary embodiment. The braking phase  26  and the acceleration phase  27  can also be of the same magnitude if necessary, or the acceleration phase  27  can be greater than the braking phase  26 . The exact lengths of these phases depends no only on the configuration of the paddle blades  21  and other built-in elements, but also on the ratio of the different speeds. They can therefore be varied to meet actual requirements so that the invention is not limited to the circumferential speed profile of the drum  12  as shown in FIG.  3 . 
     By driving the drum  12  at different rotational frequencies, in particular with the speed profile shown in FIG. 3, during a revolution of the drum  12 , it is possible to drive it at a relatively high circumferential speed in such a phase where the laundry items  11  can and should lie on the inner side of the wall of the drum  12  and temporarily also on the paddle blades  21  of the respective chamber  15  for being lifted out of the liquid bath  28 . On the other hand, for throwing the laundry items  11  off the paddle blades  21 , the drive of the drum  12  is braked during the braking phase  26  at constant deceleration to the lower circumferential speed. This lower circumferential speed is attained at the latest when the laundry items  11  start to be thrown off the paddle blades  21 , preferably somewhat later, with the deceleration occurring during the braking phase  26  favoring a loosening of the laundry items  11  from the paddle blades  21  and inner shell of the wall of the drum  12 , in particular by generating an additional throw-off impetus. As soon as the rear end of the paddle blade  21  bordering the shell of the drum  12  reaches the highest point in the chamber  15 , namely the apex of the drum  12 , and the process of throwing the laundry items  11  off the paddle blade  21  is completed, the drum  12  is put under constant acceleration along the acceleration phase  27  in order to attain the higher circumferential speed for lifting once again the laundry items  11  out of the liquid bath  28 . This operation can extend over singular, but also multiple complete revolutions of the drum  12 . It is also conceivable to drive the drum  12  constantly with alternating rotational frequencies of various magnitudes, in particular with a circumferential speed profiles as shown for example in FIG.  3 . 
     List of Designations 
       10  tunnel washing machine 
       11  laundry item 
       12  drum 
       13  longitudinal center axis 
       14  direction of treatment 
       15  chamber 
       16  feed end 
       17  hopper feeder 
       18  discharge end 
       19  discharge slide 
       20  partition 
       21  paddle blade 
       22  bearing 
       23  segment (greater) 
       24  segment (smaller) 
       25  direction of revolution 
       26  braking phase 
       27  acceleration phase 
       28  liquid bath