Patent Publication Number: US-9422928-B2

Title: Electric motor thermal energy isolation

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the priority benefit under 35 U.S.C. §371 of international patent application no. PCT/IB2011/053679, filed Aug. 22, 2011, which claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/377,607 filed on Aug. 27, 2010, the contents of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a compressor, and, in particular, to a compressor having improved thermal handling characteristics. 
     2. Description of the Related Art 
     A compressor receives a supply of fluid, such as a liquid or gas, at a first pressure and increases the pressure of the fluid by forcing a given quantity of the received fluid from a first volume into a smaller second volume using a piston assembly. Some compressors have a reciprocating piston that reciprocates within the cylinder to compress the fluid. The pistons may be connected to a crank shaft housed in a crankcase. The crankshaft may be operated by a motor housed in a motor housing. A typical piston assembly includes a cup seal to provide a seal between the pressurized and non-pressurized sides of the piston. The cup seal flexes during movement of the piston within the cylinder and the frictional engagement creates wear along the cup seal. The pressurization of gas on the pressurized side of the piston, the frictional engagement of the cup seal with the cylinder, and/or other operating conditions generate heat to which the cup seal is exposed. This heat further hastens failure of the flexible cup seal, thus limiting the life of the compressor. 
     In some compressors, heat may be dissipated from the cup seal using a crankcase that is directly coupled to the cylinder. Because of its mass, the crankcase may be intended to function as a heat sink to conduct the heat from the cylinder and the cup seal. Subsequently, a fan may provide air convection to dissipate the heat away from the crankcase. 
     However, in compressors where the motor housing is directly coupled to the crankcase, heat may be simultaneously conducted from the motor to the crankcase when heat is conducted from the cup seal and the cylinder to the crankcase. This is problematic when the thermal heat from the motor exceeds the heat being generated at or within the cylinder. In such situations, the heat from the motor may be indirectly conducted to the cylinder and the cup seal, thus ultimately increasing the heat on the cylinder and cup seal rather than decreasing it. Accordingly, further steps must be taken to remove heat from the cylinder/crankcase/motor housing system. For example, a larger fan may be used to provide higher CFM (cubic feet per minute) of air to convect the heat However, this may cause the device that includes such compressor and fan to be larger and bulkier. Alternatively or additionally, a larger crankcase may be used. However, this may cause the compressor to be bulkier, more expensive to manufacture, and inefficient. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a compressor assembly that overcomes the shortcomings of conventional compressor assembly. This object is achieved according to one embodiment of the present invention by providing a compressor assembly configured to increase pressure of a fluid that includes a cylinder forming a space for compressing the fluid and a piston configured to reciprocate in the cylinder so as to compress the fluid. The compressor assembly also includes a crank shaft configured to drive the piston and a crank shaft housing that is operatively connected to the cylinder and configured to house the crank shaft. A motor operatively is connected to the crank shaft and is configured to drive the crank shaft. The compressor assembly further includes a motor housing operatively connected to the crank shaft housing and configured to house the motor. A thermal insulator is disposed between the motor housing and the crank shaft housing to enhance thermal insulation between the motor housing and the crank shaft housing. 
     Another aspect of the invention relates to a method of assembling a compressor assembly that is configured to increase pressure of a fluid. The method includes obtaining a compressor assembly. The compressor assembly includes a cylinder having space for compressing the fluid. The compressor assembly also includes a piston, wherein the piston is configured to reciprocate in the cylinder so as to compress the fluid. The compressor assembly further includes a crank shaft that is configured to drive the piston and a crank shaft housing. The crank shaft housing houses the crank shaft and is connected to the cylinder. The compressor assembly further includes a motor that is configured to drive the crank shaft and a motor housing configured to house the motor in the motor housing. The method further includes coupling the motor housing to the crank shaft housing with a thermal insulator disposed therebetween to enhance thermal insulation between the motor housing and the crank shaft housing. 
     Another aspect of the invention relates to a compressor assembly configured to increase pressure of a fluid. The compressor assembly includes a cylinder coated with anodized metal material, the cylindrical cylinder having a mating portion and a main portion. The compressor assembly also includes a piston configured to reciprocate in the cylinder so as to compress the fluid and a crank shaft configured to drive the piston. A crank shaft housing is operatively connected to the cylinder and is configured to house the crank shaft. The compressor assembly also includes a motor operatively connected to the crank shaft and configured to drive the crank shaft. The mating portion of the cylindrical cylinder contacts the crank shaft housing. The anodized metal material of the mating portion is decreased or removed to facilitate thermal conduction between the cylinder and the crank shaft housing at the mating portion. 
     These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. In one embodiment of the invention, the structural components illustrated herein are drawn to scale. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not a limitation of the invention. In addition, it should be appreciated that structural features shown or described in any one embodiment herein can be used in other embodiments as well. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a compressor in accordance with an embodiment; 
         FIG. 2  is a cross sectional view of the compressor in accordance with an embodiment; 
         FIG. 3  is a detailed cross sectional view of a piston and a cylinder of the compressor in accordance with an embodiment; 
         FIG. 4  is a perspective view of a thermal insulator of the compressor in accordance with an embodiment; 
         FIG. 5 a    is a cross sectional detailed view of the insulator ring disposed between a crankcase and a motor housing of the compressor in accordance with an embodiment; 
         FIG. 5 b    is a cross sectional detailed view of the insulator ring disposed between a crankcase and a motor housing of the compressor in accordance with another embodiment; 
         FIG. 6  is a cross sectional detailed view of the cylinder and the crankcase of the compressor in accordance with an embodiment; 
         FIG. 7 a    is a cross sectional view of the insulator ring in accordance with an embodiment; and 
         FIG. 7 b    is a cross sectional view of the insulator ring in accordance with another embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     As used herein, the singular form of “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. As used herein, the statement that two or more parts or components are “coupled” shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, “directly coupled” means that two elements are directly in contact with each other. As used herein, “fixedly coupled” or “fixed” means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. 
     As used herein, the word “unitary” means a component is created as a single piece or unit. That is, a component that includes pieces that are created separately and then coupled together as a unit is not a “unitary” component or body. As employed herein, the statement that two or more parts or components “engage” one another shall mean that the parts exert a force against one another either directly or through one or more intermediate parts or components. As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality). 
     Directional phrases used herein, such as, for example and without limitation, top, bottom, left, right, upper, lower, front, back, and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein. 
       FIG. 1  illustrates a compressor assembly  10  having cylinders  12   a ,  12   b  (two are shown in this embodiment) for compressing a fluid, such as a liquid or gas. As shown in  FIG. 2 , pistons  14   a ,  14   b  are configured to reciprocate in cylinders  12   a ,  12   b , respectively, so as to compress the fluid. Crank shafts  72  are configured to drive the pistons  14   a ,  14   b  within cylinders  12   a ,  12   b . In this embodiment, pistons  14   a ,  14   b  are wobble (or WOB-L) pistons. However it is contemplated that other types of piston may be used in other embodiments. Crank shafts  72  are housed in crankcases or crank shaft housings  18   a ,  18   b  that are operatively connected to cylinders  12   a ,  12   b . In this embodiment, two crankcases  18   a ,  18   b  are provided, each being associated with one of the cylinders  12   a ,  12   b . A motor  20  is operatively connected to the crank shafts  72  and is configured to drive the crank shafts  72 . The motor is housed in a motor housing  22  that is operatively connected to crankcases  18   a ,  18   b . The thermal contact between motor housing  22  and crankcases  18   a ,  18   b  are minimized by thermal insulators  24   a ,  24   b  that are disposed between motor housing  22  and crankcases  18   a ,  18   b.    
     In one embodiment, compressor assembly  10  has a tandem arrangement with two cylinders  12   a ,  12   b , each having a piston  14   a ,  14   b  received therein. A motor shaft  16  connects the motor  20  to crankshafts  72 , which are each connected to one of the two pistons  14   a ,  14   b , so that the movement of the pistons  14   a ,  14   b  oppose each other. However, this embodiment is not intended to be limiting, and it is contemplated that the compressor assembly  10  may have other arrangements and numbers of cylinders  12   a ,  12   b . For example, compressor assembly  10  may be of single or dual acting designs. Compressor assembly  10  may also include more than two cylinders. 
     In the embodiment shown in  FIG. 2 , cylinders  12   a ,  12   b  are coupled to the crankcases  18   a ,  18   b  and motor housing  22  is disposed between crankcases  18   a ,  18   b . Each generally cylindrical crankcase  18   a ,  18   b  has an annular horizontally extending cylindrical flange  30  formed as a lateral extension that joins with the generally cylindrical motor housing  22 . Cylindrical flange  30  extends from a side portion  31  of each crankcase  18   a ,  18   b . Thermal insulators  24   a ,  24   b , taking the form of rings in this embodiment, are disposed between motor housing  22  and the crank shaft housings  18   a ,  18   b  at an upper portion and a lower portion, respectively. In such configurations, at least portions of thermal insulators  24   a ,  24   b  may contact flanges  30  of crankcases  18   a ,  18   b . For example, thermal insulators  24   a ,  24   b  may surround at least a portion of flanges  30 . Thermal insulators  24   a ,  24   b  will be described in more detail later. 
     In the illustrated embodiment, cylinders  12   a ,  12   b  are directly coupled to crankcases  18   a ,  18   b . Each cylinder  12   a ,  12   b  may include a main portion  15  (see  FIG. 6 ) and a mating portion  17  (see  FIG. 6 ). Mating portion  17  may be an annular portion of the cylinders  12   a ,  12   b  that contacts at least portions of crankcases  18   a ,  18   b  when cylinders  12   a ,  12   b  are coupled thereto. 
     Referring back to  FIG. 1 , a threaded member  26  (such as an elongated screw) may be used to hold cylinders  12   a ,  12   b  together, with motor housing  22  therebetween. Threaded member  26  may be received in receiving structures  28  extending from crankcases  18   a ,  18   b . It is contemplated that bolts, pins, or other attachment mechanisms may be used in other embodiments. 
     As shown in  FIG. 1 , each cylinder  12   a ,  12   b  has a compressor head  32  operatively connected thereto. Each compressor head  32  has an extension  41  with an opening (not shown) formed therein. A screw  45  is configured to be inserted through the opening of each compressor head  32  and into an opening (not shown) formed in an extension  43  in each crankcase  18   a ,  18   b . Accordingly, screws  32  secure the connection among compression heads  32 , cylinders  12   a ,  12   b , and crankcases  18   a ,  18   b.    
     As shown in  FIG. 3 , compressor head  32  has a gas intake port  34  formed therein. In the illustrated embodiment, a plate  49  is provided between compressor head  32  and the cylinder  12   a . Above an upper portion  40  of the plate  49 , compressor head  32  includes an internal chamber  36  that communicates with gas intake port  34  and an internal exhaust chamber  38  that communicates with an exhaust port  42 . As shown in  FIG. 1 , exhaust port  42  is connected to both compression heads  32  and provides a common outlet  44  for fluids from both compressor heads  32 . Referring back to  FIG. 3 , a lower portion  46  of plate  49  is provided below the upper portion  40  so as to define a middle portion  48  between lower portion  46  and upper portion  40 . Valves may be provided such that fluids may travel between chambers  36 ,  38  in compressor head  32  and a first interior space  50  in cylinder  12 . 
     In this embodiment, an input valve  52  enables fluid to be drawn through intake port  34  to the first interior space  50  when pistons  14   a ,  14   b  tilt within the cylinders  12   a ,  12   b . An output valve  51  may be provided in the middle portion  48  to enable fluids to travel through first interior space  50  to exhaust port  42 . Input valve  52  may be constructed and arranged such that input valve  52  allows air through only when pistons  14   a ,  14   b  are moving downwards. Output valve  51  may be constructed and arranged such that output valve  51  allows air through only when pistons  14   a ,  14   b  are moving upwards. Cylinder  12   b  may have a similar configuration as cylinder  12   a.    
     As shown in  FIG. 2 , each piston  14   a ,  14   b  includes a head portion  54  and a rod portion  56 . First interior space  50  of cylinders  12   a ,  12   b  may be defined by an inner surface  11  of the cylinders and head portion  54  of the pistons. In this embodiment, head portion  54  and rod portion  56  are integral, although they may be separate in other embodiments. Head portion  54  and rod portion  56  may be cast from a strong light weight material such as aluminum alloy. A cap  53  may be operatively connected to the head portion  54 . Head portion  54  has a generally flat circular configuration with an annular groove  58  defined by a top edge  66  of the head portion  54  and a radially outer bottom portion  64  of the cap  53  for receiving a cup seal  60 . 
     As mentioned above, cup seal  60  is configured to provide a seal between the pressurized and non-pressurized sides of the pistons  14   a ,  14   b . That is, cup seal  60  may have an outward bias relative to head portion  54  such that it compressively engages inner walls  13   a ,  13   b  of cylinders  12   a ,  12   b , respectively, throughout the pistons&#39;  14   a ,  14   b  strokes, thereby preventing fluid from escaping from the upper interior space  50 . Cup seal  60  may adopt an upwardly flexed position with respect to inner surface  11  of cylinders  12   a ,  12   b . A screw  62  may be used to secure cap  53  to head portion  54  of piston  14   a ,  14   b , thereby also retaining cup seal  60  within groove  58 . 
     In the illustrated embodiment, rod portion  56  of pistons  14   a ,  14   b  has a lower end  68  with a bearing  70 . Each bearing  70  has a center  71  that is configured to receive a portion of the crank shaft  72 . Eccentric crank shafts  72  are connected to motor shaft  16  such that the axis defined by the motor shaft is offset from the axis defined by center  71  of bearings  70 . Thus, motor shaft  16  and pistons  14   a ,  14   b  are configured to be eccentric. As such, as the motor shaft rotates crankshafts  72 , pistons  14   a ,  14   b , which ride on the bearings  70 , reciprocates upwardly and downwardly within the cylinders  12   a ,  12   b . This configuration enables pistons  14   a ,  14   b  to tilt relative to cylinders  12   a ,  12   b  at all positions (except when pistons  14   a ,  14   b  are at the top most and bottom most positions) due to the eccentricity of crank shafts  72 . It is contemplated the crank shafts do not need to be eccentric and may have other configurations or arrangements. As an exemplary reference, piston  14   a  shown in  FIG. 2  is in the bottom most position and piston  14   b  shown in  FIG. 2  is in the top most position. This configuration of pistons  14   a ,  14   b  and crankshafts  72  converts the rotary energy from motor  20  into linear motion of pistons  14   a ,  14   b  within cylinders  12   a ,  12   b.    
     As mentioned above, the movement of pistons  14   a ,  14   b  within cylinders  12   a ,  12   b  causes heat to increase on cup seals  60  and cylinders  12   a ,  12   b  due to the frictional engagement between the cup seals  60  and inner surface  11  of cylinders  12   a ,  12   b , and/or due to the compression of fluid. Crankcases  18   a ,  18   b  may be used as a heat sink to conduct the heat from cylinders  12   a ,  12   b  and cup seals  60 . A cooling fan (not shown) may be provided to generate cooling current for convecting heat away from compressor assembly  10 . 
     In the embodiment shown in  FIG. 2 , instead of directly coupling motor housing  22  to crankcases  18   a ,  18   b , upper and lower thermal insulators  24   a ,  24   b  are provided between motor housing  22  and crankcases  18   a ,  18   b  to enhance the thermal isolation between them. In the embodiment shown in  FIG. 4 , thermal insulator  24   a  takes the shape of a ring having an inner surface  21  and an outer surface  25 . Thermal insulator  24   b  may have a similar size and configuration as thermal insulator  24   a . Thermal insulators  24   a ,  24   b  may have various cross sections. For example, in one embodiment, thermal insulators  24   a ,  24   b  may have a U-shaped cross section as shown in  FIG. 7 a   . In such embodiment, the U-shaped cross section may be defined by a top surface  29  (see  FIG. 5 a   ), a middle surface  33  (see  FIG. 5 a   ), and a bottom surface  35  (see  FIG. 5 a   ). Alternatively, thermal insulators  24   a ,  24   b  may have an L-shaped cross section as shown in  FIG. 7 b   . In such embodiment, L-shaped cross section may be defined by the middle surface  33  (see  FIG. 5 b   ) and the bottom surface  35  (see  FIG. 5 b   ). However, it is contemplated that thermal insulators  24   a ,  24   b  may have any cross-section and are not limited to the examples shown in these Figures. 
     Thermal insulators  24   a ,  24   b  may have any configuration that enables thermal insulators  24   a ,  24   b  to enhance thermal isolation between crankcases  18   a  and motor housing  22 . The size and thickness of thermal insulators  24   a ,  24   b  may depend on the configuration and arrangement of crankcases  18   a ,  18   b  and motor housing  22 . For example, as mentioned above and as shown in  FIG. 2 , each generally cylindrical crankcase  18   a ,  18   b  has the annular horizontally extending cylindrical flange  30  formed as a lateral extension that joins with motor housing  22 . Alternatively or additionally, cylindrical crankcases  18   a ,  18   b  may have other structures configured to join crankcases  18   b  with motor housing  22 . 
     Referring back to the embodiment shown in  FIG. 2 , flange  30  has a smaller circumference than side portion  31  of each crankcase  18   a ,  18   b , and thus, at least portions of flange  30  are disposed within motor housing  22 . Thermal insulators  24   a ,  24   b  may be configured to be disposed on flanges  30  such that the thermal insulators form a periphery around flanges  30  of crankcases  18   a ,  18   b , respectively.  FIGS. 5 a -5 b    show the arrangement of thermal insulator  24   b  positioned on crankcase  18   b . Thermal insulator  24   a  may be positioned on the crankcase  18   a  as a mirror image of thermal insulator  24   b.    
     As shown in  FIG. 5 a   , flange  30  and side portion  31  of crankcase  18   b  define an annular ledge  74  formed on an outer surface of the flange  30 . The difference in circumference between flange  30  and side portion  31  also defines a vertical peripheral surface  23 . In the illustrated embodiment, at least portions of inner surface  21  of thermal insulator  24   b  are constructed and arranged to be disposed on ledge  74 . In this embodiment, thermal insulator  24   b  is configured such that when the thermal insulator is disposed on the ledge, the thermal insulator extends above side portions  31  of crankcase  18   b  and at least portion of thermal insulator  24   b  may be configured to contact the vertical peripheral surface  23  of crankcase  18   b . In this embodiment, at least portions of motor housing  22  is received in the U-shaped portion of thermal insulator  24   b  that is defined by top surface  29 , middle surface  33 , and bottom surface  35  of the thermal insulator  24   b . Thus, in this embodiment, motor housing  22  contacts top surface  29 , middle surface  33 , and bottom surface  35  of thermal insulator  24   b.    
     In the embodiment shown in  FIG. 5 b   , thermal insulator  24   b  is arranged on crankcase  18   b  in a similar manner as the embodiment shown in  FIG. 5 a   . However, in this embodiment, motor housing  22  is received on the L-shaped portion of the thermal insulator  24   b  defined by middle surface  33  and bottom surface  35  of thermal insulator  24   b . Thus, in this embodiment, motor housing  22  contacts both middle surface  33  and bottom surface  35  of thermal insulator  24   b . It is contemplated that motor housing  22  may contact any combination or all of surfaces  29 ,  33 ,  35  of the various embodiments of thermal insulators  24   a ,  24   b . Accordingly, thermal insulator  24   b  prevents the motor housing  22  from contacting ledge  74  or other parts of crankcase  18   b  directly. 
     Thermal insulator  24   a  may be configured to be disposed between crankcase  18   a  and motor housing  22  in a similar manner. Thermal insulator  24   a  may also be configured to contact motor housing  22  in a similar manner as either of the two embodiments of thermal insulator  24   b  shown in  FIGS. 5 a -5 b   . Thermal insulator  24   a  may be constructed and arranged in a similar manner as thermal insulator  24   b . However, the size and configuration of thermal insulators  24   a ,  24   b  may be varied in other embodiments to achieve the optimal performance for thermal isolation. In the embodiment of  FIG. 2 , thermal insulator  24   a  is arranged between crankcase  18   a  and motor housing  22  such that thermal insulator  24   a  is a mirror image of thermal insulator  24   b  arranged between crankcase  18   b  and motor housing  22 . 
     Thermal insulators  24   a ,  24   b  may be manufactured and/or assembled with compressor assembly  10 . In some embodiments, thermal insulators  24   a ,  24   b  may be retrofit into existing compressor assemblies  10 . That is, compressor assemblies  10  may already be manufactured and assembled without thermal insulators  24   a ,  24   b . In such embodiments, thermal insulators  24   a ,  24   b  may be added to compressor assemblies  10  at the points of contact between crankcases  18   a ,  18   b  and motor housing  22  to enhance thermal isolation therebetween. 
     Thermal insulators  24   a ,  24   b  may be made of stainless steel, such as those having a conductivity of about 15 W/(m*K) (Watts per meter-Kelvin). The stainless steel may have wear resistant properties, low creep, and may be constructed at a low cost. Other materials may also be used, such as, just for example, glass filed nylon (e.g., 30% glass filled Nylon 66 having a conductivity of 0.27 W/(m*K)), Telfon®, ceramics having properties of low creep and low conductivity, plastics having low thermal conductivity and low creep, and/or other materials with low thermal conductivity and low creep. Crankcases  18   a ,  18   b  may be made of aluminum, such as those having a conductivity between 100 and 200 W/(m*K)) or other materials. Motor housing  22  may be made of aluminum or other materials. Cylinders  12   a ,  12   b  may also be made of aluminum, or may be made of other materials. In one embodiment, cylinders  12   a ,  12   b  are made of aluminum having a grade of AL6061 with a conductivity of about 170 W/(m*K). The cylinders may have an anodized coating to improve the properties thereof, such as to increase its corrosion resistance and wear resistance. However, the anodized coating in such embodiments may cause the conductivity of cylinders  12   a ,  12   b  to decrease. In some embodiments, the conductivity may be decreased to, just for example, 30-35 W/(m*K). As such, the effectiveness of the heat dissipation from the cylinders  12   a ,  12   b  to crankcases  18   a ,  18   b  are also decreased. 
     The lowered conductivity may be problematic when crankcases  18   a ,  18   b  function as heat sinks for cylinders  12   a ,  12   b . That is, lowered conductivity due to anodized coatings may impede the flow to crankcases  18   a ,  18   b  of heat generated in cylinders  12   a ,  12   b  by the frictional engagement between cup seal  60  and inner surface  11  of cylinders  12   a ,  12   b  and/or by the compression of fluids. 
     The following description of crankcase  18   a  and cylinder  12   a  may also be applicable to crankcase  18   b  and cylinder  12   b . In the embodiment shown in  FIG. 6 , crankcase  18   a  has a vertically extending flange  76  formed as a vertical extension extending from an outer portion  78  of the crankcase. Flange  76  is offset from the outer portion  78 . Thus, flange  76  and outer portion  78  define a ledge  80  located on a top surface of outer portion  78  of crankcase  18   a . In the illustrated embodiment, mating portion  17  of cylinder  12   a  is constructed and arranged to be disposed on ledge  80 . Mating portion  17  may also be constructed and arranged to contact the flange  76  at an outer surface  82  of flange  76 . Thus, the contact between mating portion  17  of cylinder  12   a  and outer surface  82  of flange  76  and the contact between mating portion  17  of cylinder  12   a  and ledge  80  of crankcase  18   a  dissipates the heat from cylinder  12   a  to crankcase  18   a . However, as mentioned above, the anodized coating of cylinders  12   a  may impede the conduction of the heat from cylinder  12   a  to crankcase  18   a.    
     To combat this, in the embodiment of  FIG. 6 , mating portion  17  is ground or polished to decrease the anodized coating thereon such that the conductivity of the mating portion may be increased. By grounding/polishing mating portion  17 , the thickness of the anodized coating on the mating portion is decreased such that the anodized coating on the mating portion is thinner than the anodized coating on main portion  15 . Mating portion  17  may be beveled due to the grounding thereof. Any tools or methods may be used to grind the anodized coating from mating portion  17 . It is also contemplated that any abrasive material may be used to remove the anodized coating on mating portion  17 . In some embodiments, main portion  15  may have anodized coating having a thickness of 0.001 inches. In some embodiments, the anodized coating may be completely removed from mating portion  17 . In one embodiment, rather than grinding down an existing anodized coating, a coating of a lesser thickness (or no coating at all) may be formed on mating portion  17  separate from the coating formed on main portion  15 . 
     Mating portion  17  may be configured to include any portion of cylinder  12   a  that contacts crankcase  18   a . Mating portion  17  may be the portion of cylinder  12   a  that contacts or mates with crankcase  18   a , or may optionally be larger such that only a portion of mating portion  17  contacts crankcase  18   a . Main portion  15  of cylinder  12   a  may be the rest of cylinder  12   a  (or any portion of cylinder  12   a  that is not mating portion  17 ). Cylinder  12   b  may have a similar configuration as cylinder  12   a.    
     Compressor assembly  10  may operate as follows in accordance with an embodiment. In one embodiment, motor  20  rotates crankshaft  72  via motor shaft  16  to operate piston  14   a . As piston  14   a  travels from the top most position to the tilted position (not shown), the suction created within its associated cylinder  12   a  causes fluid to travel from the chamber  36  into its associated cylinder  12   a  through input valve  52 . Cup seal  60  may adopt an upwardly flexed position where it engages interior surface  11  of cylinder  12   a  when piston  14   a  is moving downwards towards the bottom most position. 
     After piston  14   a  has reached the bottom most position, the piston then moves upwards to a tilted position, thereby compressing the fluid in its associated cylinder  12   a . Cup seal  60  may optionally adopt a downwardly flexed position where it engages with inner surface  11  of cylinder  12   a  when piston  14   a  is moving upwards. The upward motion of piston  14   a ,  14   b  causes output valve  51  to open, thereby allowing the fluid to travel to internal exhaust chamber  38  and to exhaust port  42 . The other piston  14   b  functions in an opposing way. Thus, when piston  14   a  moves from the down most position towards the top most position, piston  14   b  moves from the top most position to the down most position. During the movement of pistons  14   a ,  14   b  within cylinders  12   a ,  12   b , the heat generated by the frictional engagement between cup seals  60  and inner surfaces  11  of cylinders  12   a ,  12   b  and/or by the compression of fluid is conducted from cylinders  12   a ,  12   b  to crankcases  18   a ,  18   b . Heat is conducted from cylinders  12   a ,  12   b  to crankcases  18   a ,  18   b  via mating portions  17  of the cylinders that have been ground to decrease the anodized coatings thereon. In addition, as motor  20  rotates crankshaft  72  to move pistons  14   a ,  14   b , heat is generated by motor  20 . Thermal insulators  24   a ,  24   b  thermally isolate motor housing  22  to decrease the amount of heat conducted from motor housing  22  to crankcases  18   a ,  18   b . Thus, heat dissipation may be enhanced in compressor assembly  10  by the use of thermal insulators  24   a ,  24   b  and/or by grounding portions of cylinders  12   a ,  12   b  (i.e., mating portion  17 ) to decrease or remove the anodized coating thereon. 
     Although a compressor assembly  10  is described above, it is contemplated thermal insulator  60  may be used with other devices such as, just for example, gear motors, pumps, and blowers, or any device that has a motor that is mechanically coupled to other components. By thermally isolating the motor from other components, the performance and efficiency of the devices would be improved. Furthermore, the thermal insulators may also help reduce the size of the fan required to cool the device, thus reducing the costs associated with the device. 
     Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.