Abstract:
A clothes dryer which comprises a housing, a rotatable drum for receiving the clothes and a bearing for rotatably receiving the drum in the housing. In order to protect the bearing from overheating, a cooling air device for cooling the bearing is provided.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a dryer with a rotary drum for receiving laundry and a bearing for rotary mounting of the drum. 
     Dryers are known in which a drum is arranged horizontally for receiving laundry, and is pivoted by pivot bearings. The pivot bearings are subject to high thermal loads which negatively influence the reliability and life of the bearings, particularly when they are arranged adjacent to ducts conveying hot process air. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to make available a dryer that operates reliably, with a drum that is swivelled by means of a bearing. 
     This object is achieved by the characteristics in claim  1 . Advantageous embodiments and further developments of the invention are described in the dependent claims. 
     A dryer has a housing in which a drum for receiving laundry is swivelled by means of a bearing. To ensure that the bearing operates reliably at all times, a cooling device is provided for cooling the bearing. This enables the maximum thermal expansion of the drum bearing components to be reduced and hence also the mechanical load. Furthermore, the lubricant provided for the bearing is subjected to lower loads because of the cooling of the bearing if the bearing is operated at lower temperatures. Moreover, there is reduced risk of the lubricant in the bearing becoming fluid at low temperatures and escaping. This increases the life and reliability of the bearing, and hence of the dryer. 
     In an advantageous embodiment the cooling device comprises means for improving the radiation and/or convection of heat from the bearing or adjacent to the bearing. In particular, cooling faces may be provided which are connected thermally and conductively to the bearing. Such cooling faces may be formed by a suitably large surface design of the bearing bracket or by providing cooling ribs. 
     In an advantageous embodiment the cooling device has a device for conveying cooling air, preferably ambient air, to the bearing. This makes available active cooling with which defined thermal conditions can be created on the bearing. 
     In an advantageous embodiment a fan is provided for conveying process air through the drum and/or for conveying cooling air for a condenser, wherein the fan serves as a device for conveying cooling air to the bearing. This also makes it possible to make use of fans that are already installed in the dryer, either a fan for conveying process air or a fan for conveying cooling air to a condenser, as a cooling device for cooling the bearing. 
     In an advantageous embodiment a process air conduit is provided, wherein a section of the process air conduit and/or the drum is loaded with a vacuum due to the conveying action of the fan, and forms a vacuum space. Furthermore, a cooling conduit is provided between the vacuum space and the bearing so that air is sucked in adjacent to the bearing in the form of ambient air and conveyed by the cooling conduit as spent air to the process air. 
     In an advantageous embodiment the bearing has a bearing bracket which is secured to the housing, and a process air duct has an air distribution hood adjacent to the bearing which covers the process air inlet holes into the drum, wherein a cooling air conduit is formed between the air distribution hood and the bearing bracket, in the form of an annular gap, so that a cooling air flow is able to flow through the annular gap into the process air duct in the form of ambient air. The bearing is flushed on all sides with cooling air through the annular gap and is therefore effectively cooled. 
     In an advantageous embodiment a process air conduit is provided, wherein a section of the process air conduit and/or the drum is loaded with excess pressure by the conveying action of the fan, and forms an excess pressure space. Furthermore, a cooling conduit is provided between the excess pressure space and the bearing, so that some of the conveyed air is fed to the bearing in order to cool the bearing. 
     In an advantageous embodiment the process air conduit is provided as a circuit with a condenser which is cooled by a cooling air flow. Some of the cooling air flow is branched and fed via a cooling air conduit to the bearing in order to cool the bearing. 
     In an advantageous embodiment the cooling conduit is dimensioned so that the quantity of cooling air can be predetermined. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details, characteristics and advantages of the invention are evident from the following description of a preferred exemplary embodiment of a dryer according to the invention, with reference to the drawings, 
       in which: 
         FIG. 1  shows a sectional view of a dryer with a bearing for the drum according to a first exemplary embodiment; 
         FIG. 2  shows a detailed view of the bearing according to the dryer in  FIG. 1 ; 
         FIG. 3  shows a sectional view of a dryer with a bearing for the drum according to a second exemplary embodiment; 
         FIG. 4  shows a detailed view of the bearing according to the dryer in  FIG. 3 ; 
         FIG. 5  shows a sectional view of a dryer with a bearing for the drum 
     
    
    
     as a modified first or second exemplary embodiment. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to  FIGS. 1 and 2  a first exemplary embodiment of a dryer is represented in the form of an exhaust dryer. The dryer has a housing  1 , a drum  2  mounted in housing  1 , a front end plate  3 , a feed door  4  arranged in the front end plate  3  and a lint screen  5  fitted in the lower section of front end plate  3 . Drum  2  is mounted in the front section above rollers  6  arranged on the front end plate  3  and in the rear section above a central bearing  9  arranged on rear wall  8  of drum  2 , which bearing is in turn secured by a bracket  10  to rear wall  11  of housing  1 . Drum  2  is rotated about horizontal axis  14  by a motor  12  and a belt  13 . The dryer has a process air conduit  15  which, in this exemplary embodiment, comprises an inlet opening  16 , an inlet duct  17 , an air distribution hood  18  connected to it, which covers process air inlet holes  19  arranged on rear wall  8  of drum  2 , a process air outlet grid  20 , lint screen  5  and an outlet duct  21 , with a fan  22 . A heater  23  is also arranged in inlet duct  17 . The process air flows in arrow direction  24  from the ambient atmosphere into inlet opening  16  via inlet duct  17 , heater  23 , air distribution hood  18 , drum  2 , process air outlet grid  20 , lint screen  5 , outlet duct  21  and fan  22  back into the ambient atmosphere. Air distribution hood  18  is sealed against rear wall  8  of drum  2  by means of a rear seal  25 . Upstream from fan  22 , a vacuum space is formed, in particular in drum  2  and air distribution hood  18 . 
     Bearing  9  is shown in more detail in  FIG. 2 . Bearing  9  has a shaft  26  which is secured to rear wall  8  of drum  2 , and a spherical bearing member  27 , which is preferably manufactured from oil saturated sinter material. Bearing member  27  has a hole  28  in which shaft  26  is able to rotate. Furthermore, bearing  9  has two seals  29 . Bracket  10  has an outer half-shell  30  and an inner half-shell  31 , between which the spherical bearing member  27  is retained. Between outer half-shell  30  and inner half-shell  31  is arranged a conical spring element  32 , which restricts the bearing member  27  from also rotating. Spherical bearing member  27  is able to perform swivel movements transversely to the horizontal center line  14 , to compensate for an angular displacement of drum  2 . The central section of air distribution hood  18  is secured on the inside of bracket  10 , parallel with bracket  10 , forming an annular gap  33 . Annular gap  33  is formed by spacer members  34 , which are formed on air distribution hood  18 . 
     Outer half-shell  30  and inner half-shell  31  are each manufactured from a steel sheet which is capable of transferring heat away from the bearing and discharging heat by thermal radiation and convection. However, since there is hot process air between rear wall  8  of the drum and air distribution hood  18 , bearing  9  is subjected to considerable heating. Due to the provision of annular gap  33  between bracket  10  and air distribution hood  18 , a cooling conduit is formed between the vacuum space in the drum  2  and bearing  9 , wherein cool ambient air is sucked into the process air as so-called spent air passing through annular gap  33  on bearing  9 . In particular, fan  22 , which is responsible for building up the vacuum in drum  2 , therefore serves as a conveying device. Because of the formation of the relatively long, parallel annular gap  33 , a large surface is made available for heat transfer from the hot bearing to the cooling ambient air flowing through annular gap  33 . A very simple device is therefore made available for cooling bearing  9  using the other devices, such as fan  22  of the dryer. 
       FIGS. 3 and 4  show a second exemplary embodiment of the dryer in the form of a condensation dryer. Only the differences relative to the dryer designed as an exhaust dryer are shown below in  FIGS. 1 and 2 . Process air conduit  15  is designed as a closed circuit in which a condenser  35  is also inserted, which condenser is normally designed as a cross flow or counterflow condenser, and is cooled by means of a condenser cooling air flow  36 . Condenser cooling air flow  36  is produced in a condenser cooling air conduit  38  by an additional fan  37 , which can be mounted on the same drive shaft as fan  22 . A cooling air conduit  41 , which opens into a space  39  between rear wall  11  of housing  1  and bracket  10 , is branched off from the section of condenser cooling air conduit  38  on the pressure side. As shown in more detail in  FIG. 4 , the cooling air flows into space  39 , and through openings  40  formed in the bracket into annular gap  33  between bracket  10  and air distribution hood  18 . 
       FIG. 5  shows a modification both for the exemplary embodiment according to  FIGS. 1 and 2  and for the exemplary embodiment in  FIGS. 3 and 4 . In this modification the direction of the cooling air flow according to  FIG. 4  is reversed, and cooling air is sucked off through cooling air conduit  41  from space  39  through annular gap  33 . Here the suction may take place on cooling air conduit  41  either via the suction side of condenser cooling air conduit  38  ( FIG. 3 ) or via the suction side of process air conduit  15 , upstream from heater  23  shown in  FIG. 1 . 
     Alternatively to the embodiment shown in  FIG. 1 , fan  22  may be arranged upstream from drum  2 , so that an excess pressure prevails in the process air conduit before drum  2 , and also in drum  2 . Some of this air upstream from drum  2 , and also upstream from heater  23 , may be fed through a branch conduit to bearing  9  in order to cool bearing  9 .