Abstract:
Clothes dryers that distribute air through one or more lifters are disclosed. An example domestic clothes dryer includes a rotating drum defining a drying chamber, an air inlet upstream the drum, and lifter mounted in the drum, wherein said lifter is in communication with the air inlet for distributing air inside the drum through a plurality of openings. An example air inlet includes a shaped air plenum chamber facing a lower portion of a rear perforated wall of the drum and capable of delivering air to said lifter and/or directly to the drum through said rear perforated wall.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority from European Patent Application 13154316.7 filed on Feb. 7, 2013, the entirety of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to clothes dryers and, more particularly, to clothes dryers that distribute air through one or more lifters. 
       BACKGROUND 
       [0003]    JP-A-9056991 describes a lifter fixed at the periphery part of a rotary drum and cylindrical seals are fixed at the outer periphery of an air intake plenum and of an air exhaust plenum, so that a circulation passage is formed on the back of the rear wall of the drum. The use of two concentric air plenum chambers and related seals makes the above known solution quite complex and not easy to be implemented. Moreover in the above known solution the process hot air is flowing always and entirely through the lifters, even if the lifters are in an upper position during drum rotation. In this condition, i.e. when the lifters are not in contact with clothes, the effectiveness of having air flowing in the lifter is substantially reduced. Another disadvantage of the above known solution is that it cannot be adapted to traditional dryers where air flow enters the drum from a perforated rear wall and leaves the drum from an aperture placed adjacent the front opening of the drum. 
       SUMMARY 
       [0004]    It is an object of this disclosure to provide a tumble clothes dryer that does not present the above disadvantages and which can provider higher drying performances, better fabric care and reduced wrinkles. 
         [0005]    The above object is reached thanks to the features listed in the appended claims. 
         [0006]    One of the most relevant technical features of a dryer according to this disclosure is the use of a distribution device in the air inlet plenum chamber capable of delivering air to the drum either indirectly, i.e. through one or more lifters, or directly, i.e. though a rear perforated wall of the drum. 
         [0007]    According to this disclosure, the distribution device is a shaped air plenum chamber which faces only a lower portion of the rear perforated wall, from its side opposite to the drum, so that air is delivered to the drum only though the lower portion of the rear perforated wall. Therefore, when the position of the lifter during rotation of the drum corresponds to the shaped air plenum chamber, air is flowing entirely or partially through the lifter, and when the position of the lifter does not correspond to said air plenum chamber, air is flowing through the plurality of holes of the rear wall of the drum facing the shaped air plenum chamber. The shape of said plenum chamber, together with the shape of an air conveying base portion of the lifter orthogonal to the active portion of the lifter on the drum side wall (such base portion covering, at a predetermined distance, a part of the perforated rear wall of the drum in order to create a sort of inner chamber) will be responsible on the amplitude of arc during which air is delivered through the lifter. 
         [0008]    In one example, the shape of the base portion of the lifter covers substantially a circular sector covering from 60° to 100° of arc of the perforated rear wall of the drum, while the air plenum chamber covers an area a bit wider than said base portion of the lifter, so that at least a percentage of process air flows always through the perforated wall also when the lifter, during its rotation with the drum, it is in a lower portion of the drying chamber. This has been found beneficial in terms of drying efficiency and energy saving. 
         [0009]    The use of lifters for blowing air into the drum as described herein can be implemented without significant modification of existing machines. Moreover, as described herein the air is flowing through the lifter only if this latter is aligned with the distribution device (i.e. inlet air plenum chamber). In this way air flows in the lifter only when this latter is in contact with clothes, i.e. in the lower part of its circular trajectory. 
         [0010]    Another advantage derives from use of a dedicated cycle and the use of separate actuation for drum tumbling and air blowing that enables energy saving and reduced fabric shrinkage. For instance, the use of “blowing lifters” (i.e. use of lifters though which process air can be fed to the drum) increases significantly the drying evenness with respect to traditional dryers, particularly because air flows where it is needed, towards clothes placed in the bottom of the drum, on the lifter, where in the above known solution most of the air would flow through the upper lifter and only a limited part would flow through clothes therefore reducing significantly the efficiency of the overall drying process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Further advantages and features of this disclosure will be clear from the following detailed description, with reference to the attached drawings, in which: 
           [0012]      FIG. 1  is an isometric view of an example clothes tumble dryer; 
           [0013]      FIG. 2  is an isometric enlarged view of the inside of the drum of  FIG. 1 ; 
           [0014]      FIG. 3  is an isometric view of the rear of the drum of  FIGS. 1 and 2 ; 
           [0015]      FIG. 4  is a partial cross-sectional view of a detail of  FIG. 2 ; 
           [0016]      FIG. 5  is a front view of the perforated rear wall of the drum where the shape of the distributor is shown in solid and dotted line; and 
           [0017]      FIG. 6  is a schematic view of how a clothes dryer according to this disclosure works. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    With reference to  FIG. 1 , an example tumble dryer  10  includes a cabinet  12  having an upper wall  12   a,  a front wall  12   b  provided with a hingedly mounted door  14 , side walls  12   c  and a rear wall  12   d.  Inside the cabinet  12  a rotating drum  16  is mounted which is actuated by an electric motor (not shown) and which defines a drying chamber  17 . The drum  16  includes at least one lifter  18  having a plurality of holes  20  for air passage. The lifter  18  may be hollow. The lifter  18  includes a rear base portion  18   a  covers a portion of a rear perforated wall  16   a  of the drum in order to convey air entering through the perforated wall  17   a  towards the holes  20  of the lifter  18 . The rear base portion  18  may have a triangular or circular sector shape. The base portion  18   a  defines with the facing portion of the rear wall  16   a  of the drum  16  a sort of inner chamber  19  (see  FIG. 4 ) which covers an arc ranging preferably from 60 to 100° and which communicates with the portion of the lifter  18  fixed to the side wall of the drum  16 . The clothes dryer  10  may also have a dispensing system for dispensing treating chemistries into the drum  16 , and including a reservoir  22  that is closed by a cover  24 . The clothes dryer  10  is also provided with a controller  26  that may receive input from a user through a user interface  28  for selecting a cycle of operation. 
         [0019]    The clothes dryer  10  also includes an air inlet channel  30  (see  FIG. 6 ) and an outlet channel  32 , a heating system (not shown) that heats air entering the drum (e.g. by means of resistors, heat exchangers, etc.), and a blower (not shown) that makes air flowing across the drum  16 . 
         [0020]    The drum outlet  32 , where a removable filter  33  for removing fluff or lint is placed, can be eventually connected to the drum inlet  30  thus realizing a closed loop system in which heat exchangers, resistors, heat pump, etc. control the condensation and heating process. As an alternative the drum outlet  32  can be connected to an air vent. 
         [0021]    The lifter  18  functions not only to increase the heat exchange efficiency between air and clothes and improve the evenness of the drying result by means of clothes redistribution during the whole cycle, but also to improve the efficiency of hot air distribution. 
         [0022]    A common drawback of known dryers is that when the load size increases to almost fill the drum volume, the efficiency of the lifter in redistributing the load within the drum is decreased thus leading to the risk of damaging the clothes that are positioned in the rear end of the dryer (where temperatures are higher) and reducing the evenness of drying results. 
         [0023]    With a lifter design that allows not only the hot air to flow through the lifter  18  but also by means of a distribution of air through the lifter  18  only during a certain degree of rotation of the drum  16 , the temperature gradient in the drum  16  is reduced and the evenness of drying is increased, reducing also the risk of clothes damaging. 
         [0024]    The above controlled distribution is carried out by means of a shaped fixed distributor  34  which forms an air inlet plenum chamber upstream the drum  16 . The shape of the distributor  34  ( FIG. 5 ) does not corresponds necessarily to the circular sector shape of the base portion  18   a  of the lifter  18 , but need not extend higher than the lower half of the drum  16 . In  FIG. 5 , two shapes are shown (in dotted and solid lines) which have worked well in tests carried out by the applicants. Such shapes maximize the air flow either though the lifter  18  (when this latter is in the lower positions during rotation) and through clothes adjacent the lifter. 
         [0025]    In other examples, the enhanced lifter design can be combined with a dedicated cycle design, able to stop tumbling when the lifter  18  is located in a position that minimizes the temperature gradient. This approach can furthermore increase the above mentioned advantages and can provide also energy saving benefits due to reduced motor usage. One or more lifters of the type disclosed above can also be used together with one or more typical lifters that do not match the above description. Due to the fact that the lifter  18  is physically connected to the drum  16 , during tumbling it changes its position with respect to the air inlet  34  thus leading to a variable air mass flow rate in the lifter  18  and in the drum  16 . This is clearly shown in  FIG. 6  where arrows A show the air flow through the lifter  18  (when this latter is placed in the lower position inside the drum  16 ), and arrows B show the air flow through the rear wall  16   a  of the drum  16  when the lifter  18  is in a position not matching the air distributor  34 . This alternating air flow path in the drum  16  creates the conditions for a variable heat flux as well that improves the evenness of drying and fabric care. 
         [0026]    The examples disclosed herein can improve significantly also the drying and fabric care performances with delicate cycles. As described above, aiming to reduce the mechanical action on this type of loads, the tumbling is often reduced or even avoided; this solution has the negative result of increasing the temperature gradient thus leading to the already discussed drawbacks. If the proposed lifter design is used, the machine can be designed to stop tumbling (for the whole cycle or only for part of it, also e.g., using a PWM approach) in a way that the air can flow through the lifter  18  to provide a means to optimize heat flux for these type of loads using appropriate design of the lifter. In some examples, the drum  16  is in a position where the lifter  18  lays on the bottom of the drum  16 , thus having the clothes laying on it. The method used to stop the drum  16  in the correct position is well known in the art and it can be easily transferred from the known solutions for top loader washer for having the door in upwards location to facilitate loading and unloading of the drum. 
         [0027]    Moreover, since air can flow through the lifter  18 , the latter can be designed to host a cartridge containing a fragrance or some other chemical additives to improve quality of drying that can be released in the drum  16 . 
         [0028]    In some examples, the lifter  18  is used with a drum  16  having an air inlet and outlet port on opposite sides thus enabling fine optimization of heat fluxes. Nevertheless the examples disclosed herein can be applied to those drums in which inlet and outlet air connections are located on the same side (with a dedicated air collector similar to air distributor  34 ). In these examples the lifter  18  can be used to convey hot inlet air towards the opposite side of the drum  16 , therefore improving significantly the heat flux distribution in the longitudinal direction. 
         [0029]      FIG. 4  shows a detail of the air distributor  34  which is made preferably by a shaped metal or plastic sheet  35 . In order to increase the efficiency, a sealing means (not shown) can be interposed between the edge of the shaped sheet  35  forming the distributor  34  and the rear wall  16   a  of the drum  16 .