Abstract:
A pneumatic compressor is provided and includes a cylinder head having a first muffler cavity for drawing an intake air. Also included in the compressor is a compressor shroud including an inertial filter having a filter slot, and an integral muffler, wherein the inertial filter and the integral muffler are integrally formed within the compressor shroud.

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority of U.S. Provisional Application Ser. No. 61/986,138, filed Apr. 30, 2014 under 35 U.S.C. §119(e), which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    The present disclosure generally relates to pneumatic compressors, and more particularly relates to an air compressor used for supplying compressed air to a pneumatic tool. 
         [0003]    Conventional pneumatic compressors use an inertial filter configured to be disposed within a cylinder head using an inlet port tube(s). U.S. Pat. No. 5,137,434 discloses, for example, an air compressor assembly for providing ambient air flows at a predetermined velocity using one or more intake or inlet ports to the compressor, where some portions of the ambient air flows are diverted into the intake port. Specifically, the portions of the air flowing over a valve plate assembly and over the cylinder head are diverted into an air intake for the compressor. 
         [0004]    The diverted air abruptly changes flow directions from the remainder of the air by positioning baffles in the air compressor assembly. Any dust and other particles dispersed in the flow of cooling air have sufficient inertia that they tend to continue moving with the cooling air rather than change direction and enter the inlet ports. As a result, the inlet air is filtered through inertia, and the compressor and an associated motor are cooled by the air flows. Further, the cooling air increases the life of motor and compressor components, such as an air hose and reduces the burn risk for a user of the compressor. However, while this type of inertial filter can be an effective air filter, an inlet muffler size and its effectiveness is limited by a size of the cylinder head. 
         [0005]    Other conventional compressors use a portion of a compressor shroud and an additional partial muffler enclosure having the inlet tube for forming an enclosed inlet muffler cavity. Although this type of compressor shroud provides an effective inlet tube and muffler cavity at a cost of only a partial muffler cavity, the muffler cavity is divided into two different regions in the compressor assembly. Specifically, one half of the muffler cavity is located in the cylinder head, and the other half of the muffler cavity is located in a separate housing piece for forming the enclosed inlet muffler cavity. This type of two-stage muffler is also limited by the size of the cylinder head. 
         [0006]    Thus, there is a need for developing an improved compressor shroud having both the inertial filter and the muffler cavity that are not limited by the size of the cylinder head. 
       SUMMARY 
       [0007]    The present disclosure is directed to a compressor shroud having an inertial filter and an integral muffler, both of which are fully enclosed within the compressor shroud. The present compressor shroud provides both the inertial filter and the integral muffler without having to include additional, separate parts in the compressor shroud. One aspect of the present compressor shroud is that, as described in further detail below, the inertial filter can be positioned either upstream or downstream of a motor fan. This shroud configuration also provides support and sealing features for an additional second muffler tube connecting an enclosed muffler cavity in the shroud to an inlet port of a cylinder head. 
         [0008]    Another important aspect is that the muffler is integral with the compressor shroud, and includes a cavity barrier configured for accommodating at least one muffler cavity within the compressor shroud. Each muffler cavity is defined by at least one baffle, the shroud, and the cavity barrier. This muffler configuration generates about ten times larger muffler cavity at a significantly lower cost, and thus provides more efficient and compact muffling than conventional compressor shrouds. 
         [0009]    In one embodiment, a pneumatic compressor is provided and includes a cylinder head having a first muffler cavity for drawing an intake air. Also included in the compressor is a compressor shroud including an inertial filter having a filter slot, and an integral muffler, wherein the inertial filter and the integral muffler are integrally formed within the compressor shroud. 
         [0010]    In another embodiment, a pneumatic compressor is provided and includes a cylinder head having a first muffler cavity for drawing an intake air. Also included in the compressor is a compressor shroud including an inertial filter having a filter slot, and an integral muffler, wherein the inertial filter and the integral muffler are integrally formed within the compressor shroud. A cooling fan is positioned downstream of the filter slot relative to a flow of the intake air. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a partial vertical cut-away view showing a first embodiment of the present compressor shroud featuring an internal filter and an integral muffler; and 
           [0012]      FIG. 2  is a partial vertical cut-away view showing a second embodiment of the present compressor shroud of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Referring now to  FIG. 1 , the present compressor shroud is designated  10  and is configured for accommodating an inertial filter, generally designated  12 , having a filter slot  14 , and an integral muffler, generally designated  16 . Both the inertial filter  12  and the integral muffler  16  are fully enclosed within the present compressor shroud  10 , and are an integral part of the shroud. It is preferred that an electric motor  18  is provided for operation of a cooling or motor fan  20  for drawing an ambient air from outside of the compressor shroud  10 . However, other power sources, such as gasoline engines, are contemplated. An exemplary flow of the ambient air through the shroud  10  is indicated by a graphic arrow A. 
         [0014]    Powered by the motor  18 , the fan  20  draws the ambient air A into the compressor shroud  10  such that the ambient air cools compressor components. During an intake process initiated by a piston  22  reciprocating within a cylinder  23  under the action of the motor  18 , air is drawn into a first muffler cavity  24  (shown hidden) of a cylinder head  26  as the piston approaches its bottom dead center position. The present integral muffler  16  is designed to reduce the magnitude of pressure wave pulsations entering muffler cavities via a first muffler tube, and also the noise caused by the pulsations. 
         [0015]    This goal is achieved by including in the integral muffler  16  a cavity barrier  30  configured for defining and accommodating at least one second muffler cavity  32   a,    32   b  within the compressor shroud  10 . In a preferred embodiment, at least one second muffler cavity  32   a  is in fluid communication with the adjacent second muffler cavity  32   b  so that the intake air can travel from one cavity to the other. 
         [0016]    A first muffler tube  34  is connected to the cylinder head  26  at a first end  36 , and an opposite, second end  38  is inserted into an opening  40  of the cavity barrier  30  in fluid communication with the cylinder head. As a result, inlet air generated by the intake stroke of the compressor is drawn into the cylinder head  26 . As shown, the tube  34  is preferably corrugated. 
         [0017]    In a preferred embodiment, a tube holder  42  is provided in one of the second muffler cavities  32   a,    32   b  for securely holding the second end  38  of the first muffler tube  34  such as by clamping action by complementary upper and lower members, or by a friction fit. Each second muffler cavity  32   a  can be defined by an inner surface of the compressor shroud  10 , an inner surface of the cavity barrier  30 , and at least one divider wall or baffle  44 . However, it is also contemplated that the second muffler cavity  32   b  can be defined by the inner surface of the cavity barrier  30 , and at least one baffle  44 . Each divider wall or baffle  44  is an integral part of the shroud  10 , and extends either from the inner surface of the compressor shroud or from the inner surface of the cavity barrier  30  for forming an expansion chamber for reducing the pulsation noise of the intake air. 
         [0018]    Although two second muffler cavities  32   a,    32   b  are shown for illustration purposes, any number of second muffler cavities is contemplated to suit the situation. Further, any suitable shape and arrangement of the baffles  44  is also contemplated for different applications. A second muffler tube or channel  46  having the filter slot  14  is provided in one of the second muffler cavities  32   b  such that the first muffler tube  34  and the second muffler tube  46  occupy different second muffler cavities  32   a,    32   b.  For example, the first muffler tube  34  can occupy the upper second muffler cavity  32   a,  and the second muffler tube  46  can occupy the lower second muffler cavity  32   b.    
         [0019]    The second muffler tube  46  is defined by the inner surface of the compressor shroud  10 , the inner surface of the cavity barrier  30 , and the at least one baffle  44 . In one embodiment, the intake air travels sequentially from the inertial filter slot  14  through the second muffler tube  46  to the lower second muffler cavity  32   b,  to the upper second muffler cavity  32   a  through the first muffler tube  34  and into the head  26 . As discussed above, this type of muffler configuration generates about ten times larger muffler cavity at a significantly lower cost, and thus provides more efficient and compact muffling than conventional compressor shrouds. 
         [0020]    In operation, the inertial filter  14  requires high speed air, provided by the motor fan  20 , to pass by the slot. As the compressor enters its intake mode, and air is drawn into the slot  14 , the more dense dust and particulate contaminants cannot turn quickly enough to enter the narrow slot. However, the less dense air is able to make the turn into the slot  14  and provides clean air for the compressor. 
         [0021]    Another important aspect of the present compressor shroud  10  is that the cooling fan  20  is positioned upstream of the filter slot  14  relative to the flow of the ambient air A. In this configuration, both the inertial filter  12  and the muffler  16  are seamlessly integrated together in the compressor shroud  10  without having to introduce any additional components for the filter or the muffler. 
         [0022]    Referring now to  FIG. 2 , another embodiment of the present compressor shroud  10  is designated  50 . Components shared with the shroud  10  are designated with identical reference numbers. A major difference featured in the shroud  50  is that the cooling fan  20  is positioned downstream of the filter slot  14  relative to the flow of the ambient air A. Also, the shroud  50  has three second muffler cavities, such as an upper second muffler cavity  52   a,  a middle second muffler cavity  52   b,  and a lower second muffler cavity  52   c.    
         [0023]    In this embodiment, the second end  38  of the first muffler tube  34  is disposed in the lower second muffler cavity  52   c.  Thus, a longitudinal length of the first muffler tube  34  is longer than the length of the first muffler tube in the  FIG. 1  embodiment. Another difference is that the tube holder  42  is disposed between the middle second muffler cavity  52   b  and the lower second muffler cavity  52   c  such that the inlet air travels sequentially from the inertial filter slot  14  through the second muffler tube  46  to the upper second muffler cavity  52   a,  to the middle second muffler cavity  52   b,  to the lower second muffler cavity  52   c,  through the first muffler tube  34  and into the compressor head  26 . 
         [0024]    Yet another important difference of the present compressor shroud  50  is that the second muffler tube  46  is substantially horizontally disposed relative to a longitudinal axis of the cooling fan  20 , whereas the second muffler tube in the  FIG. 1  embodiment is substantially vertically disposed relative to the longitudinal axis of the cooling fan. As is the case with the first muffler tube  34 , a longitudinal length of the second muffler tube  46  is also longer than the length of the second muffler tube in the  FIG. 1  embodiment. It is preferred that the second muffler tube  46  is connected at one end to the divider wall or baffle  44 , and at an opposite end to an inner surface of the compressor shroud  50 . 
         [0025]    In both of the embodiments described above, intake noise and low pressure pulsations travel at the speed of sound in the opposite direction from the cylinder head  26  back through the first muffler tube  34  and the muffler cavities. A feature of the present integral muffler  16  is that the relatively larger muffler cavity ( 32   a,    32   b ) increases the frontal area of the pressure pulse and lowers the pulse pressure. Also, the second muffler tube  46  intercepts the relatively high surface area low pressure wave and transmits that lower and quieter pulse to the ears of those individuals near the compressor. 
         [0026]    While a particular embodiment of the present invention has been described herein, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the present disclosure in its broader aspects.