Pumps – With condition responsive pumped fluid control – Expansible chamber pump distributor operation modified
Patent
1996-02-26
1997-10-21
McAndrews, Jr., Roland G.
Pumps
With condition responsive pumped fluid control
Expansible chamber pump distributor operation modified
417569, 137855, F04B 5310
Patent
active
056789831
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention refers to a discharge valve actuating system for reciprocating hermetic compressors such as are used in small refrigerating appliances and which are provided with a discharge valve having an impelling means.
BACKGROUND OF THE INVENTION
Reciprocating hermetic compressors for refrigeration are provided with a block, which is mounted inside a hermetically sealed shell. In said block, there is a cylinder, in which reciprocates a piston, which is driven by the shaft of an electric motor through a connecting rod, in order to effect the suction and compression of a refrigerant gas.
The cylinder presents an end, which is opposite to that end by which the piston is articulated to the connecting rod, and which is opened to a valve plate, which separates the internal cavity of said cylinder from a cylinder head, where the discharge and suction chambers of the compressor are defined. The communication between the internal cavity of the cylinder and each of said chambers is made through discharge and suction orifices provided on said valve plate, which are periodically and selectively closed by respective discharge and suction valves mounted on said valve plate.
For reasons of constructive simplicity, these compressors use suction and discharge valves of the reed type which, together with the piston, produce an intermittent flow of refrigerant gas. These systems further have muffler assemblies or acoustic filters, mounted at the suction and discharge lines of the compressor in order to attenuate the noises caused by said intermittent flow of refrigerant gas.
Such muffler assemblies include at least one discharge muffler, where the compressed gas coming from the compressor is expanded, reducing its pressure and, consequently, reducing the noise intensity.
The known discharge mufflers are usually defined by a chamber, which is formed in the cast block of the cylinder and which has a first channel, communicating with the discharge chamber, and a second channel, communicating with the discharge tube or, in some constructions, with a second discharge muffler chamber.
It is known that during the discharge of the refrigerant gas to the discharge chamber, the hermetic compressors present yield loss, resulting from the late opening of the discharge valve. This means that the discharge valve is opened at an instant of time after the instant at which the discharge pressure is achieved, i.e., the pressure inside the cylinder at the compression end has surpassed that minimum pressure needed to cause the opening of the discharge valve. This late opening results from inertial problems of the valve movement, due to its construction characteristics, or from a gluing effect of the contact surface of said discharge valve with an oil film existing on the valve seat.
A solution to eliminate the problem of opening delay of the discharge valve during compression is by using a valve impelling means, which actuates together with said discharge valve, as described in the Brazilian patent document PI 9002967.
Nevertheless, as in this solution the valve impelling means is constantly actuating together with the discharge valve, forcing the latter to open, the closing of said valve is impaired. This constant actuation of the impelling means allows a gas backflow to the cylinder inside, with a consequent volumetric loss for the compressor.
OBJECTS OF THE INVENTION
Thus, it is a general object of the present invention to provide a discharge valve actuating system for reciprocating hermetic compressors, which minimizes the effect of the forces acting on the discharge valve that delay its opening during compression, thereby increasing the compressor yield, without impairing the closing of said discharge valve.
It is another object of the present invention to provide a discharge valve actuating system for reciprocating hermetic compressors of the above type, which minimizes the effect of the forces that delay the opening of said valve by using the power available in the compressor.
BRIEF DESCRIPTION
Empresa Brasileira de Compressores S/A - Embraco
McAndrews, Jr. Roland G.
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