Abstract:
The invention relates to a unit comprising an accessory fixed to a heat exchanger comprising fins made of aluminum, this accessory being equipped with bearing surfaces designed to come to rest on the fins. 
     The bearing surfaces are formed on an accessory support made of steel integral with the accessory, and an electrically insulating material is placed between the bearing surfaces and the fins of the exchanger.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a device for attaching an accessory to a heat exchanger. 
     BACKGROUND OF THE INVENTION 
     The mounting of an accessory directly on the core of a heat exchanger is known. For example French Patent Application 2730009 describes the attachment of the motor of a motor fan unit to the radiator for cooling the engine of a motor vehicle. 
     In this document, the cooling unit of the exchanger is clamped between two groups of bearing elements by screws which pass through said unit through recesses provided in the fins between the tubes. Distance sleeves also pass through the unit in these same recesses to avoid a crushing of the fins, and raised shapes slightly deform these fins during the tightening of the screws to avoid any sliding of the motor in relation to the unit of the exchanger. 
     On the side of the exchanger where the motor is situated, the bearing elements are formed in a flange made of plastic material which is integral with the body of the motor. The raised shapes are produced in this flange in particular. 
     This arrangement is generally satisfactory. However, it cannot be used when the operating temperature exceeds a certain limit allowable by the plastic material of the flange. In such a case one is induced to produce a motor support made of steel. But in this case it is no longer possible to fix the support directly onto the aluminium fins because the risk of corrosion and deterioration of the mechanical connection. 
     The present invention aims to reduce these difficulties. 
     SUMMARY OF THE INVENTION 
     According certain embodiments to the present invention there is provided a unit comprising an accessory fixed to a heat exchanger comprising fins made of metal, especially aluminium, the said accessory being equipped with bearing surfaces designed to come to rest on the said fins, wherein the said bearing surfaces are formed on a steel accessory support integral with the said accessory, and wherein an electrically insulating material is placed between the bearing surfaces and the fins of the exchanger. 
     As the accessory support is made from steel it withstands any desired operating temperature. Furthermore, the risk of corrosion is averted by the presence of the electrically insulating material placed between the bearing surfaces made of steel and the fins made of metal, especially aluminium. 
     In a first embodiment of the invention, the said material is made in the form of an electrically insulating coating, covering the said bearing surfaces. 
     This electrically insulating coating may be of the paint or varnish type, which is applied in the liquid state. It may also occur in the form of an adhesive bonded onto the bearing surfaces. In these two cases, gripping protrusions may be provided, for example by stamping, in the portion of the accessory support forming the bearing surfaces. 
     In another embodiment, the electrically insulating material is in the form of blocks made of plastic material fixed to the said bearing surfaces. 
     The attachment of the blocks to the bearing surfaces may be performed by latching means cooperating on the block and on the accessory support. 
     The blocks advantageously comprise gripping protrusions on their face facing the fins of the exchanger. 
     The blocks may also comprise a sleeve designed to engage in a recess provided in the fins of the exchanger between the tubes, so as to form at least one distance sleeve portion. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     Two preferred embodiments of the invention will now be described, as a non-restrictive example, with reference to the attached diagrammatical drawings in which: 
     FIG. 1 is a front view of a motor of a motor fan unit fixed to a heat exchanger in accordance with a first embodiment of the invention; 
     FIG. 2 is a side view of this motor turned towards the heat exchanger, said heat exchanger not being represented; 
     FIG. 3 is a front view of a motor of a motor fan unit fixed to a heat exchanger in accordance with a second embodiment of the invention; 
     FIG. 4 is a view of this motor similar to FIG. 2; 
     FIG. 5 is a perspective view on a larger scale of one of the blocks represented in FIGS. 3 and 4; and 
     FIG. 6 is a sectional view along line VI—VI of FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     On FIGS. 1 and 2 can be seen the electric motor  1  of a motor fan unit in which the fan, not represented, is designed to be mounted on the shaft  2  of the motor. 
     A motor support  3  is fixed to the motor  1  by any suitable means. 
     The support  3  comprises fastening lugs  4  forming bearing surfaces  5  for its mounting on a heat exchanger  6 , for example the radiator of an engine of a motor vehicle. The support  3  is made from sheet steel, whereas the fins of the exchanger  6 , alone in contact with the support  3 , are made of aluminium. 
     The lugs  4  are drilled with holes  7  for the passage of screws (not represented) . These screws allow the mounting of the motor  1  on the exchanger in a known manner, by means of distance sleeves. 
     Moreover, the sheet metal of the lugs  4  is stamped to form ribs  8  having a substantially triangular section. The ribs  8  protrude from the lugs  4  on the side of the bearing surfaces  5 , facing the heat exchanger  6 . Thus, when the motor support  3  is pressed onto the exchanger by the fixing screws, the ribs  8  penetrate whilst slightly deforming the fins of the exchanger, preventing any subsequent slipping of the motor in relation to the exchanger. 
     The bearing surfaces  5  in contact with the exchanger  6  are here covered with an electrically insulating coating  9 . The coating  9  may be of any known type capable of being applied onto the steel, such as a paint or a varnish. Its application may more particularly be performed by spraying or by immersion. 
     The coating, by virtue of its electrical insulating nature, decreases the risks of corrosion, which otherwise would be associated with the contact between the steel of the motor support  3  and the aluminium of the fins of the exchanger  6 , to be averted. 
     In the embodiments of FIGS. 3 to  6 , the ends of the fastening lugs  4 , which rest on the fins of the heat exchanger  6 , are equipped with blocks  10  made from insulating plastic material, placed between the support  3  and the exchanger  6 . 
     The blocks  10  may comprise a roughly flat base  11  having a shape corresponding to that of the end of the fastening lugs  4  of the support  3 . It is this base  11  which is placed between the support  3  and the heat exchanger  6 . The edge of the base  11  is provided with a rim  12  turned in the opposite direction to the fins and surrounding the end of the lug  4  along the section thereof. 
     Tongues  13 , designed to return on the face of the lug  4  opposite that which is facing the exchanger  6  rise from the rim  12 . The tongues  13  therefore ensure the immoblization, of the block  10  on the lug  4 . Mounting is performed by causing the sheet of the lug  4  to slide between the base  11  on the one hand and the tongues  13  on the other hand. 
     The block  10  is locked onto the lug  4  by means of another tongue  14  stamped in the base  11  and projecting therefrom on the side of the rim  12  and of the tongues  13 . This tongue  14  cooperates with a tongue  15  stamped in the lug  4  and projecting therefrom towards the base  11  of the block  10 . When the block  10  is slid on the lug  4 , the tongue  14  has sufficient elasticity to retract during the passage of the protruding tongue  15 . Then, when this tongue  15  has passed, the tongue  14  springs back and latches behind the tongue  15 , ensuring the locking of the block on the fastening lug. 
     The base  11  of the block  10  also comprises, on its side facing the heat exchanger  6 , a protruding rib  16  having the same hooking function as the rib  8  of the first embodiment. 
     Finally, on the same side as the rib  16 , the base  11  forms a protruding sleeve  17 . The sleeve  17  is provided with a hole  18  passing through the base  11  in the alignment of the hole  7  of the lug  4 , for the passage of screws for fastening the motor  1  onto the exchanger  6 , The sleeve  17  is engaged in a recess provided in the fins of the exchanger  6  and forms a distance sleeve to prevent crushing of the latter during the tightening of the attachment screws. 
     Just like the coating  9 , the base  11  of the blocks  10  prevents corrosion which would be caused by direct contact between the motor support  3  and the heat exchanger  6 .