BACKGROUND 
   1. Field 
   One or more embodiments described herein relate to compressors. 
   2. Background 
   Scroll compressors have been used in air conditioners, refrigerators, and other appliances. In a scroll compressor, two scrolls rotate relative to one another to form a plurality of pressure chambers. As the pressure chambers continuously move in a central direction, suction is created to discharge refrigerant gas. However, in related-art scroll compressors, foam builds up inside the compressor to degrade performance. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The embodiments will be described in detail with reference to the following drawings, in which like reference numerals refer to like elements: 
       FIG. 1  is a diagram showing a sectional view of one type of scroll compressor; 
       FIG. 2  is a diagram showing a cut away of the compressor of  FIG. 1 ; 
       FIG. 3  is a diagram showing a sectional view of another type of scroll compressor; 
       FIG. 4  is a diagram showing a cut away of the scroll compressor of  FIG. 3 ; 
       FIG. 5  is a diagram showing an example of a foam reduction device that may be included in the scroll compressor of  FIG. 3 ; 
       FIGS. 6 and 7  are diagrams showing sectional views of an interval maintaining member that be included in the foam reduction device of  FIG. 5 ; 
       FIG. 8  is a diagram showing a sectional view of another embodiment of a foam shut-off plate that may be included in the scroll compressor of  FIG. 3 ; and 
       FIGS. 9 ,  10 , and  11  are diagrams showing exemplary installations of a compressor which may include any of the embodiments of the foam reduction device embodied and broadly described herein. 
       FIG. 12  is a diagram showing an auxiliary fixing member that may be included in one or more embodiments discloses herein 
   


   DETAILED DESCRIPTION 
     FIG. 1  shows one type of scroll compressor which includes a casing  1 , a main frame  2 , a sub-frame  3 , a motor (M), a shaft  4 , a rotating scroll  5 , a fixing scroll  6 , a high/low pressure partition plate  7 , and a check valve  8 . An airtight internal space of the casing is divided into a suction area (S 1 ) and a discharge area (S 2 ). A gas suction pipe (SP) is installed in the suction area and a gas discharge pipe (DP) is installed in the discharge area. 
   The main frame  2  and sub-frame  3  are fixed to upper and lower circumferential surfaces of the casing. The motor is mounted between the main frame and sub-frame and shaft  4  transmits rotational force to the rotor of the motor. 
   The rotating scroll is mounted on the main frame and is fastened to the shaft. The fixing scroll has a fixing lap  6   a  of a spiral shape fixed to an upper surface of the main frame, such that the fixing lap engages rotating lap  5   a  of the rotating scroll to form a plurality of pressure chambers (P). The high/low pressure partition plate  7  is fastened to a rear surface of the fixing scroll to partition an internal space of the casing into the suction area and discharge area. The check valve  8  is connected to a rear surface of a light plate configured in fixing scroll  6  to prevent gas discharged into outlet space (S 2 ) from back flowing. 
   The sub-frame  3  is welded to an inner circumferential surface of the casing in a circular plate shape. The sub-frame has a hole  3   a  to support a lower portion of the shaft in a radial direction, or to support an oil inlet pipe  4   b  inserted in an oil path  4   a  of the shaft in a radial direction. 
   Also, a plurality of oil through-holes  3   b  are formed on the sub-frame in a circular arc shape with respect to oil drawn through oil path  4   a  of the shaft. The through-holes drop the oil drawn through oil path  4   a  of the shaft to a bottom reservoir of the casing. 
   In operation, once power is applied to the motor, shaft  4  rotates with the rotor of the motor to transmit rotational force to the rotating scroll  5 . The rotating scroll rotates to form pressure chambers (P), which continuously move, between rotating lap  5   a  and fixing lap  6   a . The pressure chambers are moved to a center by the continuous rotational movement of the rotating scroll to thereby reduce volume and compress refrigerant gas. 
   An oil feeder (not shown) or oil suction pipe  4   b  may be provided at a lower end of shaft  4 , and the oil remaining in the lower end of the casing is drawn through the oil feeder or oil suction pipe  4   b  to lubricate each sliding part before returning to the casing through the oil through-hole  3   b . During that process, the oil feeder or oil suction pipe  4   b  may stir the oil within the casing to generate foam. 
     FIG. 3  shows another type of scroll compressor,  FIG. 4  shows a sub-bearing and foam shut-off plate that may be included in the scroll compressor of  FIG. 3 , and  FIG. 5  shows an example of a foam reduction device that may be included in the scroll compressor of  FIG. 3 . 
   As shown in  FIGS. 3 to 5 , a scroll compressor having a foam reduction device includes a casing  10 , a motor  20 , a compression part  30  and an oil supply part  40 . The casing is formed airtight to hold a predetermined amount of oil. The motor is mounted within the casing to generate rotational force. The compression part receives the rotational force from the motor to form one or more pressure chambers (P) between two scrolls. And, oil supply part  40  pumps the oil from a reservoir of the casing to supply it to the compression part. 
   The airtight internal space of the casing is divided into a suction area (S 1 ) and a discharge area (S 2 ) by a high/low pressure partition plate  34 . A refrigerant suction pipe (SP) is installed in the suction space (S 1 ) and a refrigerant discharge pipe (DP) is installed in the discharge space (S 2 ). Main frame  11  and sub-frame  12  are fixed to opposite sides of the motor mounted within the suction area of the casing. 
   The motor includes a stator  21  and a rotor  22 , the latter of which is coupled to a shaft  23 . The stator is fixed within the casing and the rotor is provided within the stator in a predetermined air gap to rotate due to mutual action with the stator. The shaft is fastened to the rotor to transmit rotational force of the motor to the compression part. 
   The compression part includes a fixing scroll  31 , a rotating scroll  32 , an Oldham&#39;s ring  33 , high/low pressure partition plate  34 , and a check valve  35 . The fixing scroll is fixed to an upper surface of main frame  11  and forms a fixing lap  31   a  of a spiral shape on a down surface of its light plate. The rotating scroll is rotatably mounted on an upper surface of the main frame to form a rotating lap  32   a  of a spiral shape and the rotating scroll engages the fixing scroll to form a plurality of pressure chambers (P). The Oldham&#39;s ring is installed between the rotating scroll and main frame to rotate the rotating scroll, to thereby prevent the rotating scroll from rotating on its own axis. The high/low pressure partition plate  34  is installed on a rear surface of the light plate provided in the fixing scroll  31 . The check valve closes an outlet  31   c  of the fixing scroll  31  to prevent the discharged gas from back flowing. 
   The oil supply part  40  includes an oil feeder  41 , a foam shut-off plate  42 , and an interval maintenance member  43 . The oil feeder is installed at a low end of the shaft  23  to rotate together with the shaft so that the oil feeder pumps the oil of the casing. The foam shut-off plate is fixed to a side of the sub-frame  12  to shut-off oil of the casing from foamingly rising to the surface of oil. The interval maintenance member  43  is disposed between the sub-frame and foam shut-off plate  42  to vary the height of the foam shut-off plate based on the variation of the oil amount collected within the casing, and/or one or more environmental conditions, and/or a type of oil or refrigerant in the compressor. 
   The foam shut-off plate may be formed in a circular shape having a through-hole  42   a  through which shaft  23  of the motor passes. Oil through-holes  42   b  are formed adjacent through-hole  42   a  so that the lubricated oil or the oil drawn/separated through the gas suction pipe (SP) may flow through oil through-holes  42   b . Also, a plurality of fastening holes  42   c , corresponding to fastening recesses  12   b  of sub-frame  12 , are formed near oil through-holes  42   b  to be fastened by bolts (B). 
   As shown in  FIG. 4 , the foam shut-off plate may be installed on an upper surface of the sub-frame  12  because the amount of oil can vary, for example, based on the type of oil or kind of refrigerant drawn into the casing or based on environmental changes of an air conditioner having the scroll compressor. Although not shown in the drawings, foam shut-off plate  42  may alternatively be installed on a lower surface of the sub-frame. 
   Interval maintenance member  43  may be formed in one piece as shown in  FIG. 5 , or may be formed from a plurality of layered metal sheets as shown in  FIG. 6  to adjust the height of the foam shut-off plate more precisely. In the latter case, each metal sheet of the interval maintenance member may be separately arranged or formed in a circular shape. 
   Further, as shown in  FIG. 7 , the interval maintenance member may be an elastic member, e.g., a compression coil spring. If so, fastening protrusions  12   a  and  42   d  may be formed between and in contact with sub-frame  12  and foam shut-off plate  42  to allow for insertion of the compression coil spring. 
   Also, the interval maintenance member may be made of metal to be welded or fixed by a bolt. Alternatively, the interval maintenance member may be made from molded plastic to be fixed to the sub-frame by a bolt. Considering production costs, it may be preferable in some instances to make the interval maintenance member from plastic. 
   As shown in  FIG. 8 , the appropriate height of the foam shut-off plate may be adjusted and the foam shut-off plate may be fastened to an inner circumferential surface of casing  10 , separate from sub-frame  12 . In this case, the foam shut-off plate may be made of metal so that it can be welded to the casing. Alternatively, an auxiliary fixing member  44  may be welded to the casing and the foam shut-off plate may be made of non-metal material such as plastic to be fastened to fixing member  44 . 
   In the case where the foam shut-off plate is assembled to fixing member  44 , interval maintenance member  43  may be formed in one piece (e.g., to have a unitary construction) and a plurality of metal sheets or an elastic member may be provided between the foam shut-off plate and the fixing member. In addition to these features, it is noted that reference numeral  12   a  corresponds to a bearing hole, reference numeral  23   a  identifies an oil path, and reference numeral  31   b  identifies an inlet. 
   The scroll compressor described herein may therefore include a foam reduction device which can vary the height of a foam shut-off plate based on the variable amount of oil within a casing according, for example, to surrounding changes of air conditions and/or the type of oil or refrigerant used. Structurally, in accordance with one embodiment, the foam reduction device may include a casing that holds a predetermined amount of oil, a plurality of frames fixed to opposite sides of the casing, a shaft supported by the frame in a radial direction to transmit rotational force of a motor to a rotating scroll such that the rotating scroll is engaged with a fixing scroll to form one or more pressure chambers, and with the shaft suctioning oil to be supplied to sliding parts, and a foam shut-off plate installed on an upper or lower portion one frame installed in a lower half portion of the casing to shut-off foams generated when the shaft rotates. 
   Descriptions of scroll compressors and the operation thereof may be found, for example, in U.S. Pat. Nos. 6,695,600, 6,685,441, 6,659,735, and 6,287,099, the contents of which are incorporated herein by reference and which are subject to an obligation of assignment to the same entity. 
   Although the embodiments described herein relate to scroll compressors for ease of discussion, it is understood that an oil pump as embodied and broadly described herein may be applied to other types of compressors and/or other applications which require fluid pumping. These other types of compressors include but are not limited to different types of scroll compressors, reciprocating compressors, centrifugal compressors, and vane-type compressors. 
   Moreover, a compressor containing the foam reduction device described herein may have numerous applications in which compression of fluids is required. Such applications may include, for example, air conditioning or refrigeration applications. One such exemplary application is shown in  FIG. 9 , in which a compressor  710  having an oil pump as described herein is installed in a refrigerator/freezer  700 . The installation and functionality of a compressor when embodied within a refrigerator is discussed in detail in U.S. Pat. Nos. 7,082,776, 6,955,064, 7,114,345, 7,055,338, and 6,772,601, the entirety of which are incorporated herein by reference. 
   Another exemplary application is shown in  FIG. 10 , in which a compressor  810  having an oil pumping assembly as described herein is installed in an outdoor unit of an air conditioner  800 . The installation and functionality of a compressor when embodied within an outdoor unit of air conditioner is discussed in detail in U.S. Pat. Nos. 7,121,106, 6,868,681, 5,775,120, 6,374,492, 6,962,058, 6,951,628, and 5,947,373, the entirety of which are incorporated herein by reference. 
   Another application of the compressor containing an oil pump as described herein relates to an integrated air conditioning unit. As shown in  FIG. 11 , this application includes a compressor  910  having an oil pump as described herein is installed in a single, integrated air conditioning unit  900 . The installation and functionality of a compressor when embodied within an outdoor unit of air conditioner is discussed in detail in U.S. Pat. Nos. 7,036,331, 7,032,404, 6,588,228, 6,412,298, 6,182,460, and 5,775,123, the entirety of which are incorporated herein by reference. 
   The foam reduction device of the compressor described herein may therefore have one or more of the following advantageous effects. 
   First, as shaft  23  rotates by power applied to motor  20 , rotating scroll  32  rotates an eccentric distance. Hence, pressure chambers (P) formed between rotating lap  32   a  of rotating scroll  32  and fixing lap  31   a  of fixing scroll  31  continuously move. The pressure chambers (P) move to a center position by the continuous rotation of rotating scroll  32 . As a result, the volumes of the pressure chambers (P) are reduced to compress refrigerant gas. 
   When shaft  23  sunk into the oil rotates, the oil held in a lower portion of the casing  10  is sucked up along oil path  23   a  of the shaft to lubricate one or more moving or sliding parts. Hence, the oil passing through the oil through-holes  42   b  is dropped to a bottom (reservoir) of the casing. The shaft, or alternatively an oil feeder or an oil suction pipe, stirs the oil to generate foam. The foam tries to rise up toward compression parts  30  but is stopped from rising by the foam shut-off plate  42 . 
   Thus, safety of an oil surface is enhanced and oil is prevented from being sucked into the pressure chambers and being mixed with refrigerant. Also, since the surface of oil remains calm to thereby maintain the amount of oil suction and to prevent alternation with the rotor, the efficiency of the compressor may be enhanced. 
   Next, when the scroll compressor is adapted to an air conditioner or other appliance, the surroundings of the air conditioner may be changed or the amount of oil may be changed by the kind of refrigerant or oil. Thus, although the sub-frame is installed in an optimal position to support the shaft, the position of the foam shut-off plate may be adjustable according to the oil suction amount. Thus, there is another advantageous effect of foam shut-off. 
   Also, the foam shut-off plate is fixed to the casing, separate from the sub-frame and the foam shut-off plate is installed at an optimal position based on the oil amount of the sub-frame. This results in another advantageous effect of shutting off the foam completely. 
   Also, since the foam shut-off plate can be made of various materials, the foam shut-off plate is not difficult to fabricate and production costs can therefore be lowered. Since the elastic member is installed between the foam shut-off plate and the sub-frame, or alternatively the auxiliary fixing member, noise generated by vibration transmitted from foam can be reduced. 
   Any reference in this specification to “one embodiment,” “an exemplary,” “example embodiment,” “certain embodiment,” “alternative embodiment,” and the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment as broadly described herein. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to affect such feature, structure, or characteristic in connection with other ones of the embodiments. 
   Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, numerous variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.
A foam control device includes a first member coupled to an oil reservoir of a compressor and a second member to prevent foam from flowing into an interior section of the compressor. When a shaft of the compressor rotates. The second member controls a position of the first member based on at least one condition which, for example, may include an amount of oil in the reservoir, an environmental condition, or the type of oil or refrigerant used. According to one embodiment, the first member includes a plate containing one or more apertures that allow oil, suctioned from the reservoir, to pass back into the reservoir when the compressor shaft rotates.