Abstract:
A compressor including a valve plate held between the body and the head with the interposition of a first and a second flat sealing gasket. The compressor further includes a thin-sheet aspiration valve associated with an aspiration hole provided on the valve plate. The entire valve is accommodated within a recessed area provided on a surface of the valve plate that is turned toward the body of the compressor.

Description:
FIELD OF THE INVENTION 
     The present invention generally concerns compressors of the type employed in airtight refrigerating units in household and similar apparatus, and particularly valve systems used therein. 
     BACKGROUND OF THE INVENTION 
     The numerous governmental regulations, such as the Directives of the European Union, which impose increasingly strict limits on the efficiency of household appliances, have become a ever more critical factor in refrigeration design. Energy consumption by refrigeration appliances is largely dependent upon the overall yield of the refrigerating unit, which in turn depends not only on the efficiency of the electric motor that operates it and the mechanical yield of the compressor itself, but also on the volumetric yield of the compressor. The valve system of the compressor plays a significant part in this determination. 
     With regard to aspiration type valves, which are of the thin-plate or reed type, it is well known how to fabricate them, using a process involving shearing steel ribbon and successive machining, so as to provide valves that are flush with a compressor&#39;s valve plate. The anchoring portion of the valve is permanently sealed, by at least one flat sealing gasket, between the plate and the cylinder body. This method is, however, less cost efficient than traditional valve systems due to the high tolerance requirements for the aspiration valve resulting in a less reliable valve and a higher cost of manufacture. 
     Another known method is fabricating an aspiration valve such that its anchoring portion includes creased tabs, whose edges are anchored in corresponding indentations in the valve plate, such as is disclosed in patent application WO 99/30037. While the sensitivity of the valve to tolerance is less important, this method instead requires a very precise machining of the body of the compressor to accommodate the anchoring portion of the valve (excluding the edges of the tabs) and of the head of the piston to accommodate the main portion of the valve in such a way as to minimize the wasted volume of the compressor. 
     It would therefore be desirable to devise an improved aspiration valve system for such refrigeration compressors, so as to increase the volumetric yield of the compressor, and consequently the overall yield of the airtight unit, while also simplifying the manufacturing process. 
     SUMMARY OF THE INVENTION 
     Provided according to one aspect of the present invention is a compressor for an airtight refrigerating unit comprising a cylinder body, a compressor head, a valve plate held between the cylinder body and the compressor head with the interposition of a first flat sealing gasket and a second flat sealing gasket, and a thin-sheet aspiration valve associated with an aspiration hole provided on the valve plate. The entire aspiration valve is substantially accommodated within a recessed area provided on a surface of the valve plate that is directed toward the cylinder body. 
     According to another aspect of the present invention, the recessed area comprises a main area which accommodates a main portion of the aspiration valve, and at least one other area of indentation having a depth greater than the depth of the main area. This other indentation is capable of accommodating an anchoring portion of the aspiration valve. 
     According to yet another aspect of the present invention, the aspiration valve does not substantially protrude into the cylinder, thus potentially providing an increase in usable cylinder volume and in turn an increase in overall compressor efficiency. 
     According to still another aspect of the present invention, the aspiration valve is a generally T-shaped flat tongue. This flat tongue comprises an elongated main portion having a free rounded end that is capable of sealing the aspiration hole of the valve plate, and a transverse anchoring portion that comprises at least one creased tab. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial section of a compressor of an airtight refrigerating unit according to the present invention; 
     FIG. 2 is a front view of a valve plate and an aspiration valve of the compressor of FIG. 1; 
     FIG. 3 is a transverse section of the valve plate taken along section line  3 — 3  of FIG. 2; 
     FIG. 4 is a transverse section of the valve plate taken along section line  4 — 4  of FIG. 2; 
     FIG. 5 is a front view of an aspiration valve positioned on a valve plate of the compressor of FIG. 1; and 
     FIG. 6 is a transverse section of the valve plate taken along section line  6 — 6  of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-6 illustrate a partial structure of a single cylinder compressor of an airtight refrigerating unit that comprises an electric motor (not shown), a cylinder body  10 , a cylinder  20  adapted to accommodate a piston  25 , a first flat sealing gasket  30 , a valve plate  40 , an aspiration valve  50 , a compressor head  60  and a second flat sealing gasket  70 . 
     The first flat sealing gasket  30  has top and bottom surfaces  30 A,  30 B. The gasket  30  is generally circular in shape and has an interior diameter that is the approximately equal to the outside diameter of the cylinder  20 . 
     The valve plate  40  has top and bottom surfaces  40 A,  40 B. The plate  40  is provided with exhaust holes  41  and  42  forming part of the exhaust route of the compressor, an aspiration hole  43 , and a recessed area  44 . The area  44  is recessed with respect to the bottom surface  4 B of the valve plate  40 , as better explained below. The plate  40  is also provided with four holes  49  to accommodate bolts (not shown) that anchor the various parts of the compressor. 
     The aspiration valve  50  in the present embodiment is a flat tongue having in design a shape substantially like a “T”, as best shown in FIG.  2 . The valve  50  comprises an elongated main portion  51  having a central narrow part  52  to expose exhaust hole  41 , a free rounded end  53  that is capable of sealing the aspiration hole  43  (see FIG.  5 ), and a transverse anchoring portion  54  including two creased tabs  55  and  56  (see FIG.  6 ). 
     The compressor head  60  is joined to the cylinder body  10  by means of the previously mentioned four bolts which pass through the holes  49  of the valve plate  40 . 
     The second flat sealing gasket  70  has top and bottom surfaces  70 A,  70 B. The gasket  70  has several openings, including an opening  71  corresponding to the aspiration hole  43  of the valve plate (see FIG.  1 ). Further, the gasket  70  provides an adequate seal between the valve plate  40  and the compressor head  60 . 
     As previously mentioned, and illustrated in FIGS. 2-6, the recessed area  44  on the surface  4 B of the valve body  40  is capable of accommodating the entire aspiration valve  50 . As a result, the aspiration valve  50  does not substantially protrude into the cylinder  20  and the piston  25  may elevate to a position within the cylinder  20  such that a top surface  25 A of the piston  25  is substantially level with a top surface  10 A of the cylinder housing  10 . This results in the potential for an increased volumetric yield of the compressor. 
     Specifically, as best shown in FIGS. 2 and 3, the recessed area  44  includes two indentations  45  and  46  in such a form and disposition to be able to accommodate with a calibrated interference the creased tabs  55  and  56  of the anchoring portion  54  of the valve  50  (see FIG.  6 ). Further, as best shown in FIGS. 2 and 4, the recessed area  44  includes a main indentation  47  that accommodates the elongated main portion  51  of the valve  50  (see FIG.  2 ). The depth P 1  of the indentations  45  and  46  (see FIG. 3) is greater than the depth P 2  of the main indentation  47  within the same recessed area  44  (see FIG.  4 ). This feature provides self-centering and minimal play between the aspiration valve  50  and the valve plate  40 . As a result, the risk of loss of refrigerant gas from the perimeter of the valve is minimized. 
     The free end  53  of the aspiration valve  50  is designed to have a shape and size sufficient to completely seal the aspiration hole  43  on the valve plate  40  (see FIG.  5 ). This seal is the only critical fit in the assembly of the compressor. Thus, the circular rim that surrounds the aspiration hole  43  is the only portion that must be machined after casting, thereby simplifying the manufacturing process. 
     Although a particular embodiment of the invention have been described in detail, it is understood that the invention is not limited correspondingly in scope, but includes all changes and modifications coming within the spirit and terms of the claims appended hereto, including aspiration valves having a different shape and valve plates having aspiration holes with a different disposition and/or orientation.