Patent Publication Number: US-7901192-B2

Title: Two stage reciprocating compressor and refrigerator having the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present disclosure relates to subject matter contained in priority Korean Patent Application No. 10-2007-0033410, filed Apr. 4, 2007, and 10-2007-0057883, filed Jun. 13, 2007, which are herein expressly incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a reciprocating compressor, and more particularly, to a two stage reciprocating compressor which may be provided in a refrigerator having two evaporators for minimizing vibration and noise generated from the compressor resulting from the vibration generated from two compressing units by implementing one compressor having the two compressing units, and a refrigerator having the same. 
     2. Description of the Related Art 
     Generally, compressors convert electric energy into kinetic energy so as to compress a refrigerant by using the kinetic energy. The compressor is a core element of a freezing cycle system, and there are various types of compressors that compress the refrigerant, such as a rotary compressor, a scroll compressor, a reciprocating compressor, and so on. 
       FIG. 1  is a cross-sectional view of a conventional reciprocating compressor. As shown, the reciprocating compressor includes a casing  100  having a gas suction pipe  110  and a discharge pipe  120 , a frame unit  200  disposed in the casing  100 , a reciprocating motor  300  mounted at the frame unit  200  so as to generate a linear reciprocating driving force, a compressing unit  400  compressing gas by receiving the driving force from the reciprocating motor  300 , and a resonance spring unit  500  for generating resonance by using the driving force of the reciprocating motor  300 . 
     The frame unit  200  includes a front frame  210  supporting one side of the reciprocating motor  300 , a middle frame  220  supporting another side of the reciprocating motor  300 , and a rear frame  230  coupled to the middle frame  220  so as to form a space with the middle frame  220 . 
     The reciprocating motor  300  includes an outer stator  310  fixed between the middle frame  220  and the rear frame  230 , an inner stator  320  inserted into the outer stator  310  so as to be fixedly-coupled to a side of the front frame  210 , a mover  330  movably inserted between the outer stator  310  and the inner stator  320 , and a winding coil  340  coupled to the inside of the outer stator  310 . The mover  330  includes a magnet  331  and a magnet holder  332  supporting the magnet  331 . 
     The compressing unit  400  includes a cylinder  410  fixedly-coupled to the front frame  210 , a piston  420  having one side movably inserted into the cylinder  410  and another side fixedly-coupled to the mover  330 , a discharge valve assembly  430  mounted at one side of the cylinder  410  so as to control the discharge of the refrigerant, and a suction valve  440  mounted at an end portion of the piston  420  so as to control a flow of the refrigerant that is sucked into an inner space of the cylinder  410 . 
     The piston  420  includes a cylindrical body  421  which has specific length and outer diameter, a flange  422  extended from the end of the cylindrical body in a vertical direction so as to be coupled to the magnet holder  332  of the mover, and a suction passage  423  penetratingly formed in the cylindrical body  421 . 
     The discharge valve assembly  430  includes a discharge cover  431  for covering the inner space of the cylinder  410 , a discharge valve  432  inserted into the discharge cover  431  so as to open/close the inner space of the cylinder  410 , and a discharge spring  433  inserted into the discharge cover  431  so as to elastically support the discharge valve  432 . 
     The resonance spring unit  500  includes a spring support  510  fixedly-coupled with the piston  420  and the mover  330 , a front coil spring  520  coupled between the spring support  510  and the middle frame  220 , and a rear coil spring  530  coupled between the spring support  510  and the rear frame  230 . 
     Reference numeral  10  denotes a support spring, and  411  denotes the inner space of the cylinder. 
     An operation of the reciprocating compressor will be described as follows. 
     When power is supplied to the reciprocating compressor, the linear reciprocating driving force is generated by an electromagnetic interaction of the reciprocating motor  300 , and the linear reciprocating driving force is transferred to the piston  420  through the mover  330 . 
     The piston  420  is linearly reciprocated in the inner space  411  of the cylinder by receiving the linear reciprocating driving force of the mover  330 . By the linear reciprocating motion of the piston  420 , the suction valve  440  and the discharge valve  432  are operated by a difference between a pressure of the inner space  411  and an external pressure of the cylinder. The refrigerant is sucked and compressed so as to be discharged into the inner space  411  of the cylinder. The discharged refrigerant flows outside of the compressor through the discharge cover  431  and the discharge pipe  120 . This procedure is repeated so that the refrigerant is compressed. 
     The front coil spring  520  and the rear coil spring  530  are contracted/relaxed together with the reciprocating motion of the mover  330  and the piston  420 , thereby elastically supporting the mover  330  and the piston  420  and causing the resonance. 
     The reciprocating compressor may be provided in a freezing cycle apparatus and the freezing cycle apparatus may be provided in a refrigerator. 
     Refrigerators may be categorized as a type having one evaporator (cooling unit) or another type having two evaporators. 
     In a refrigerator having two evaporators, i.e., a freezing chamber evaporator and a refrigerating chamber evaporator, the temperature of the freezing chamber and the refrigerating chamber is accurately controlled so that it is possible to store foods in fresh state for a long time. However, in a refrigerator having two evaporators and one compressor, the freezing chamber and the refrigerating chamber should be alternately operated. Further, in a refrigerator having two evaporators and two compressors, a large space for a machine chamber for installing the compressors is required, such that the space for storing the foods is smaller. 
     Meanwhile, when the reciprocating compressor having one compressing unit is applied to a refrigerator having two evaporators, two reciprocating compressors must be mounted in the refrigerator. Accordingly, the space for the machine chamber where the compressor is installed is enlarged, and the storing space of the refrigerator is smaller. 
     SUMMARY OF THE INVENTION 
     Therefore, the present invention is directed to a two stage reciprocating compressor which is capable of being applied to a refrigerator having two evaporators for minimizing vibration and noise generated from the compressor resulting from the vibration generated from two compressing units by implementing one compressor having the two compressing units, and a refrigerator having the same. 
     According to an aspect of the invention, a two stage reciprocating compressor includes a casing; a first compressing unit disposed in the casing and including a first piston and a first cylinder, the first compressing unit being driven by a reciprocating motor to linearly reciprocate the first piston in the first cylinder to suck in and compress gas; a second compressing unit disposed in the casing and including a second piston and a second cylinder, the second compressing unit being driven by vibration of the first compressing unit to linearly reciprocate the second piston in the second cylinder to suck in and compress gas; and a vibration transfer member that transfers the vibration from the first compressing unit to the second compressing unit. The first and second compressing units extend in parallel and face toward each other. 
     The first compressing unit and the second compressing unit may be configured such that the first piston of the first compressing unit and the second piston of the second compressing unit are moved in opposite directions. The first compressing unit and the second compressing unit may have opposite sucked gas flowing directions. The first piston of the first compressing unit and the second piston of the second compressing unit may be aligned. The second piston of the second compressing unit may be fixedly-coupled to the vibration transfer member, and a support frame may be coupled with the second cylinder. 
     The vibration transfer member may be connected to the first compressing unit, and a connection frame may be connected to the vibration transfer member and have the second compressing unit mounted thereat. The vibration transfer member may include a connection plate portion provided with a through hole, and a plurality of connecting portions extending from one surface of the connection plate portion. The connection frame may include a base portion provided with a coupling hole therein, and a connection support portion extending from a plurality of interval maintaining portions which extend from one surface of the base portion so as to be connected to the vibration transfer member. 
     According to another aspect of the invention, a refrigerator includes a refrigerator body; a refrigerating chamber evaporator disposed in the refrigerator body to generate and supply cool air to a refrigerating chamber; a freezing chamber evaporator disposed in the refrigerator body to generate and supply cool air to a freezing chamber; and a two stage reciprocating compressor connected to the refrigerating chamber evaporator and the freezing chamber evaporator. The two stage reciprocating compressor includes a casing; a first compressing unit disposed in the casing and including a first piston and a first cylinder, the first compressing unit being driven by a reciprocating motor to linearly reciprocate the first piston in the first cylinder to suck in and compress gas; a second compressing unit disposed in the casing and including a second piston and a second cylinder, the second compressing unit being driven by vibration of the first compressing unit to linearly reciprocate the second piston in the second cylinder to suck in and compress gas; and a vibration transfer member that transfers the vibration from the first compressing unit to the second compressing unit. The first and second compressing units extend in parallel and face toward each other. 
     According to another aspect of the invention, a two stage reciprocating compressor includes a casing; a first compressing unit disposed in the casing and including a first piston and a first cylinder, the first compressing unit being driven by a reciprocating motor to linearly reciprocate the first piston in the first cylinder to suck in and compress gas; a second compressing unit disposed in the casing and including a second piston and a second cylinder, the second compressing unit being driven by vibration of the first compressing unit to linearly reciprocate the second piston in the second cylinder to suck in and compress gas; and a vibration transfer member that transfers the vibration from the first compressing unit to the second compressing unit. The vibration of the first compressing unit and vibration of the second compressing unit at least partially offset or attenuate each other. 
     The first compressing unit and the second compressing unit may be configured such that the first piston of the first compressing unit and the second piston of the second compressing unit are moved in opposite directions. The first compressing unit and the second compressing unit may have opposite sucked gas flowing directions. The first piston of the first compressing unit and the second piston of the second compressing unit may be aligned. The second piston of the second compressing unit may be fixedly-coupled to the vibration transfer member, and a support frame may be coupled with the second cylinder. 
     The vibration transfer member may be connected to the first compressing unit, and a connection frame may be connected to the vibration transfer member and have the second compressing unit mounted thereat. The vibration transfer member may include a connection plate portion provided with a through hole, and a plurality of connecting portions extending from one surface of the connection plate portion. The connection frame may include a base portion provided with a coupling hole therein, and a connection support portion extending from a plurality of interval maintaining portions which extend from one surface of the base portion so as to be connected to the vibration transfer member. 
     According to another aspect of the invention, a refrigerator includes a refrigerator body; a refrigerating chamber evaporator disposed in the refrigerator body to generate and supply cool air to a refrigerating chamber; a freezing chamber evaporator disposed in the refrigerator body to generate and supply cool air to a freezing chamber; and a two stage reciprocating compressor connected to the refrigerating chamber evaporator and the freezing chamber evaporator. The two stage reciprocating compressor includes a casing; a first compressing unit disposed in the casing and including a first piston and a first cylinder, the first compressing unit being driven by a reciprocating motor to linearly reciprocate the first piston in the first cylinder to suck in and compress gas; a second compressing unit disposed in the casing and including a second piston and a second cylinder, the second compressing unit being driven by vibration of the first compressing unit to linearly reciprocate the second piston in the second cylinder to suck in and compress gas; and a vibration transfer member that transfers the vibration from the first compressing unit to the second compressing unit. The vibration of the first compressing unit and vibration of the second compressing unit at least partially offset or attenuate each other. 
     According to another aspect of the invention, a method of compressing gas with a compressor having a first compressing unit with a first piston and a first cylinder, and a second compressing unit with a second piston and a second cylinder, includes driving the first compressing unit to linearly reciprocate the first piston in the first cylinder to suck in and compress gas; transferring vibration from the first compressing unit to the second compressing unit; driving the second compressing unit by vibration of the first compressing unit to linearly reciprocate the second piston in the second cylinder to suck in and compress gas; and at least partially offsetting or attenuating vibration of the first compressing unit and vibration of the second compressing unit with each other. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a cross-sectional view of a conventional reciprocating compressor; 
         FIG. 2  is a cross-sectional view of one embodiment of a two stage reciprocating compressor in accordance with the present invention; 
         FIG. 3  is a perspective view of one embodiment of a refrigerator in accordance with the present invention; 
         FIG. 4  is a cross-sectional view showing an operation state of the two stage reciprocating compressor of  FIG. 2 ; and 
         FIG. 5  is a cross-sectional view showing gas suction in the two stage reciprocating compressor of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given in detail of the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
       FIG. 2  is a cross-sectional view showing one embodiment of the two stage reciprocating compressor in accordance with the present invention. 
     As shown in the drawing, a first compressing unit may be disposed in the casing  100  having a certain inner space so as to suck gas and compress same by receiving a reciprocating driving force from a reciprocating motor M. 
     The first compressing unit may include a main frame  710  having a certain shape, a middle frame  720  spaced from the main frame  710  with a constant interval, the reciprocating motor M coupled between the main frame  710  and the middle frame  720 , a first cylinder  730  penetratingly coupled to the main frame  710 , a first piston  740  inserted into the first cylinder  730  to be reciprocated, a first discharge valve assembly  770  mounted at one side of the first cylinder  730  so as to control discharging of a refrigerant, and a first suction valve  750  mounted at an end portion of the first piston  740  so as to control a flow of the refrigerant sucked into an inner space of the first cylinder  730 . 
     The first cylinder  730  may have a cylindrical shape and be provided with a cylinder hole  731  into which the first piston  740  is inserted. The first cylinder  730  may be coupled to the main frame  710  so as to be perpendicular with the main frame  710 . 
     The first piston  740  may include a body portion  741  having a certain length and outer diameter, a flange portion  742  curvedly extended from one side of the body portion  741 , and a suction passage  743  penetratingly formed in the body portion  741 . The body portion  741  of the first piston  740  may be inserted into the cylinder hole  731  of the first cylinder  730 . 
     The reciprocating motor M may include an outer stator  761  coupled between the main frame  710  and the middle frame  720 , an inner stator  762  coupled to an outer circumferential surface of the first cylinder  730  spaced from the outer stator  761  with a constant interval therebetween, and a magnet  763  located between the outer stator  761  and the inner stator  762 . The magnet  763  may be coupled to a magnet holder  764 , and the magnet holder  764  may be coupled to the flange portion  742  of the first piston  740 . A winding coil  765  may be provided at the outer stator  761 . The magnet holder  764  and the magnet  763  may be referred to as a mover. 
     The first discharge valve assembly  770  may include a first discharge cover  771  covering one side of the first cylinder  730 , a first discharge valve  772  located in the first discharge cover  771  so as to open/close the first cylinder  730 , and a first valve spring  773  elastically supporting the first discharge valve  772 . 
     A discharge pipe  774  for discharging gas may be connected to one side of the first discharge cover  771 , and be penetratingly coupled to the casing  100 . 
     A first resonance spring unit  780  may be provided to elastically support the first piston  740 . The first resonance spring unit  780  may include a rear frame  781  coupled to the middle frame  720 , a spring holder  782  coupled to the flange portion  742  of the first piston  740 , a front resonance spring  783  disposed between the spring holder  782  and the rear frame  781 , and a rear resonance spring  784  disposed between one side of the spring holder  782  and the middle frame  720 . Preferably, the front and rear resonance springs  783 ,  784  may be formed of a plurality of coil springs. 
     A vibration transfer member  800  may be coupled to the main frame  710 . 
     The vibration transfer member  800  may include a connection plate portion  801  having a certain area and provided with a through hole having a certain inner diameter therein, and a plurality of connecting portions  802  extended from one surface of the connection plate portion  801  with a certain interval therebetween so as to be connected to the main frame  720 , respectively. 
     A connection frame  810  may be coupled to the vibration transfer member  800 . The connection frame  810  may include a base portion  811  having a certain area and provided with a coupling hole therein, and a connection support portion  813  curvedly extended from end portions of a plurality of interval maintaining portions  812  extended from one surface of the base portion  811  by a certain length. The connection support portion  813  of the connection frame  810  may be coupled to the plate portion  801  of the vibration transfer member  800 . 
     A second compressing unit may be provided at the connection frame  810 . 
     The vibration transfer unit may include the vibration transfer member  800  and the connection frame  810 . The vibration generated by compressing gas at the first compressing unit may be transferred to the second compressing unit through the vibration transfer member  800  and the connection frame  810 . The vibration generated from the first compressing unit may be transferred to the second compressing unit through the vibration transfer unit, thereby compressing gas at the second compressing unit by using the vibration. 
     The second compressing unit may include a second piston  820  fixedly-coupled to the base portion  811  of the connection frame  810 , a second cylinder  830  into which the second piston  820  is inserted, a support frame  840  coupled to the second cylinder  830 , a second discharge valve assembly  850  mounted at one side of the second cylinder  830  so as to control discharging of the refrigerant, and a second suction valve  860  mounted at the end portion of the second piston  820  so as to control the flow of the refrigerant sucked into the inner space of the second cylinder  830 . 
     The second piston  820  may include a body portion  821  having a certain outer diameter and length, a suction passage  822  penetratingly formed in the body portion  821 , and a ring-shaped flange portion  823  curvedly extended from the outer circumferential surface of one side of the body portion  821  in a certain thickness and length. 
     The second piston  820  may be penetratingly inserted into a base portion coupling hole of the connection frame  810  so that the flange portion  823  may be coupled to the base portion  811 . The portion to which the second suction valve  860  is coupled may be located to face the first discharge valve assembly  770  of the first compressing unit. 
     A covering member  870  having a certain area may be fixedly-coupled to the base portion  811  of the connection frame  810  so as to cover one side of the suction passage  822  of the second piston  820 . A through hole may be formed in the covering member  870  to be communicated with the suction passage  822  of the second piston  820 . A first suction pipe  880  may be connected to the through hole and penetratingly coupled to the casing  100 . 
     The second cylinder  830  may have a cylindrical shape having a certain length and include a cylinder body  832  in which a cylinder hole  831  is penetratingly formed, and a flange portion  833  formed at the outer circumferential surface of one side of the cylinder body  832 . 
     The body portion  821  of the second piston  820  may be inserted into the cylinder hole  831  of the second cylinder  830 . 
     Since the second piston  820  is fixed to the connection frame  810 , the second cylinder  830  can be reciprocated thereon. Preferably, the second piston  820  and the second cylinder  830  may be on the same line with the first piston  740  of the first compressing unit. 
     The support frame  840  may include a body portion  841  having a coupling hole therein and a support portion  842  extended from the body portion  841 . The second cylinder  830  may be coupled to the coupling hole of the support frame  840 . 
     The second discharge valve assembly  850  may include a second discharge cover  851  covering one side of the second cylinder  830 , a second discharge valve  852  disposed in the second discharge cover  851  so as to open/close the second cylinder  830 , and a second valve spring  853  elastically supporting the second discharge valve  852 . Discharge holes H may be formed at one side of the second discharge cover  851  to discharge gas. 
     The second discharge valve assembly  850  covering the second cylinder  830  may be located laterally of the first discharge valve assembly  770  to face the first discharge valve assembly  770  of the first compressing unit. 
     Further, a second resonance spring unit  890  may be provided to elastically support the second cylinder  830  and the support frame  840 . 
     The second resonance spring unit  890  may include a front resonance spring  891  disposed between the connection support portion  813  of the connection frame  810  and one surface of the support portion  842  of the support frame  840  so as to elastically support the motion of the support frame  840 , and a rear resonance spring  892  disposed between another surface of the support portion  842  of the support frame  840  and one surface of the base portion  811  of the connection frame  810  so as to elastically support the support frame  840 . 
     Preferably, the front and rear resonance springs  891 ,  892  may be formed of a plurality of coil springs which are disposed with a constant interval therebetween. 
     The first and second compressing units may be supported at a lower surface of the casing  100  by an elastic support unit, such as by springs. 
     The lower surface of the inside of the casing  100  may be filled with a certain amount of oil. A second suction pipe  910  may be coupled to one side of the casing  100  so as to suck the refrigerant into the casing  100 . 
       FIG. 3  is a perspective view showing a refrigerator in accordance with the present invention. 
     As shown in the drawing, the refrigerator in accordance with the present invention may include a refrigerator body  200  provided with a refrigerating chamber R and a freezing chamber F, a refrigerating chamber evaporator E 1  mounted at the refrigerating body  200  so as to generate cool air to be supplied to the refrigerating chamber R, and a freezing chamber evaporator E 2  mounted at the refrigerator body  200  so as to generate cool air to be supplied to the freezing chamber F, the two stage reciprocating compressor connected to the refrigerating chamber evaporator E 1  and the freezing chamber evaporator E 2 , a condenser D connected to the two state reciprocating compressor so that the refrigerant discharged therefrom may be condensed and supplied to the refrigerating chamber evaporator E 1  and the freezing chamber evaporator E 2 , a first expanding unit G 1  for expanding the refrigerant flown into the refrigerating chamber evaporator E 1 , and a second expanding unit G 2  for expanding the refrigerant flown into the freezing chamber evaporator E 2 . 
     The two stage reciprocating compressor is as described above. 
     The discharge pipe  774  of the two stage reciprocating compressor may be connected to the condenser D. And, the first suction pipe  880  may be connected to the freezing chamber evaporator E 2  disposed at the side of the freezing chamber and the second suction pipe  910  may be connected to the refrigerating chamber evaporator E 1  disposed at the side of the refrigerating chamber. 
     Reference numeral  210  denotes a machine chamber, and  300  denotes a door. 
     Hereafter, the operations of the two stage reciprocating compressor and the refrigerator having the same will be described. 
     First, when a power supplied to the two stage reciprocating compressor is applied to the reciprocating motor M, the mover may be linearly reciprocated by an interaction between flux formed by an electric current flowing the winding coil  765  and the flux of the magnet  763 . By the linear reciprocating motion of the mover, as shown in  FIG. 4 , the first piston  740  connected to the mover may be linearly reciprocated in the first cylinder  730 . 
     The mover and the first piston  740  may be supported by an elastic force of the first resonance spring unit  780  so as to generate the resonance. 
     As the first piston  740  is linearly reciprocated in the first cylinder  730 , the first suction valve  750  and the first discharge valve  772  may be operated by a difference between internal pressure and external pressure of the first cylinder  730 . Accordingly the refrigerant filled in the casing  100  may be sucked into the first cylinder  730  through the suction passage  743  of the first piston  740  and the sucked refrigerant may be compressed, thereby being discharged in a pre-set pressurized state. 
     The refrigerant having high temperature and pressure which has been discharged from the first cylinder  730  may be flowed outside of the casing  100  through the first discharge cover  771  and the discharge pipe  774 . 
     At the same time, the mover of the first compressing unit and the first piston  740  may be reciprocated, accordingly sucking the refrigerant and compressing same. The refrigerant may be discharged, and accordingly vibration may be generated. The vibration may be transferred to the second compressing unit through the vibration transfer member  800  and the connection frame  810 . 
     As the vibration generated from the first compressing unit is transferred to the second compressing unit through the vibration transfer member  800 , the second cylinder  830  elastically supported by the second resonance spring unit  890  and the support frame  840  may be reciprocated by the vibration transferred to the second compressing unit. The second cylinder  830  may be reciprocated along the second piston  820 , and the second resonance spring unit  890  may cause the resonance of the second cylinder  830  and the support frame  840 . 
     By the reciprocating motion of the second cylinder  830 , the second suction valve  860  and the second discharge valve  852  may be operated by the difference between the internal pressure and the external pressure of the second cylinder  830 . Accordingly the refrigerant may be sucked into the second cylinder  830  through the first suction pipe  880  and the suction passage  822  of the second piston  820 , and the sucked refrigerant may be compressed, thereby being discharged in the pre-set pressurized state. The discharged refrigerant may be flowed into the casing  100  through the discharge holes H of the second discharge cover  851 . 
     Meanwhile, when the first suction pipe  880  is connected to the evaporator disposed at the side of the freezing chamber of the refrigerator, and the second suction pipe  910  is connected to the evaporator disposed at the side of the refrigerating chamber of the refrigerator, the refrigerant having passed through the freezing chamber evaporator may be compressed at the second compressing unit through the first suction pipe  880  so that the refrigerant may be discharged into the casing  100 , and the refrigerant having passed through the refrigerating chamber may be sucked into the casing  100  through the second suction pipe  910 . 
     The refrigerants which are discharged from the second compressing unit and sucked into the casing  100  through the second suction pipe  910 , respectively, may be sucked into the first compressing unit so as to be compressed and discharged. The discharged refrigerant which has high temperature and pressure may be flowed toward the evaporator through the discharge pipe  774 . 
     A compressing ratio of the first compressing unit and the second compressing unit can be variable according to an operation voltage and an operation frequency. And, as shown in  FIG. 5 , the first piston  740  of the first compressing unit and the second cylinder  830  of the second compressing unit may be reciprocated facing toward each other, thereby reducing the vibration generated from the first and second compressing units due to compressing gas. In this manner, the first and second compressing units extend in parallel and face toward each other, such that vibrations of the first and second compressing units may offset or attenuate each other. 
     Further, the first discharge valve assembly  770  of the first compressing unit and the second discharge valve assembly  850  of the second compressing unit may be disposed to face each other. Accordingly heat exchange may be generated in the procedure since the gas discharged from the second compressing unit is sucked into the compressing portion of the first compressing unit, thereby enhancing efficiency of the cycle. 
     In accordance with the present invention, the first and second compressing units are disposed in the casing, enabling application in a refrigerator having evaporators disposed in the freezing chamber and the refrigerating chamber, respectively, and enabling the freezing chamber and the refrigerating chamber to be consecutively or simultaneously operated. 
     The two stage reciprocating compressor in accordance with the present invention, is capable of being applied to a refrigerator having two evaporators by implementing one compressor having two compressing units. Accordingly, when applied to the refrigerator, the space for the machine chamber can be minimized so that the space for storing foods can be relatively enlarged. Also, the vibration generated by compressing of gas can be reduced so that the generation of noise due to the vibration can be minimized, thereby enhancing a reliability of the product. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. 
     As the present inventive features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.