Abstract:
A compressor assembly including a motor having a rotatable shaft, and a bracket attached to the motor. The bracket has fingers extending substantially perpendicular to the shaft. The fingers having ends with engagement surfaces. A connecting rod has a connecting end eccentrically connected to the shaft, and a piston end received in a cylinder sleeve. The cylinder sleeve is supported by shelves projecting from the fingers and is interposed between the fingers. A valve head member disposed above and in sealed engagement with the cylinder sleeve is interposed between the fingers, and the finger engagement surfaces retain the valve head member in sealed engagement with said cylinder sleeve.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     This invention relates to piston pumps and compressors, and more particularly to a method of assembling the unit as a reliable and robust package, maintaining a low cost and easily assembled configuration. 
     Small-scale air compressors are often used to power nebulizers. A typical type of compressor for that purpose uses a wobble piston. Examples of such compressors are found in U.S. Pat. No. 3,961,868, issued Jun. 8, 1976 to Arthur J. Droege, Sr. et al, for “Air Compressor” and U.S. Pat. No. 4,842,498, issued Jun. 27, 1989 to Roy J. Rozek, for “Diaphragm Compressor”. 
     In a typical compressor, a piston reciprocates in a cylinder sleeve to compress air. The piston is a plastic connecting rod having a piston end disposed in the cylinder sleeve, and a connecting end connected to an eccentric metal pin mounted to a shaft. As the shaft rotates, the connecting rod having a piston head disposed in a cylinder sleeve reciprocates to compress air. A valve head member in fluid communication with the cylinder sleeve feeds air into the cylinder through an intake port, and provides an escape for compressed air through an exhaust port, and ultimately to an outlet in the valve head member. 
     Typical compressor assemblies include a compressor housing fastened securely to the motor. A cylinder sleeve rests on the housing to accurately position the cylinder sleeve and corresponding valve plate at a fixed position relative to the motor shaft. The valve head member is routinely positioned on top of the cylinder sleeve, with a sealing gasket squeezed between the valve head member and cylinder sleeve. The valve head member is typically fastened in the position above the cylinder sleeve by screw type fasteners that project down into the housing. This type of configuration is normally complicated to assemble, and the gasket between the valve head member and cylinder sleeve is sometimes unreliable due to component tolerances and variations in the fasteners assembly. Therefore a need exists for a robust compressor that provides a reliable seal between component pales, yet is economical to produce and assemble. 
     SUMMARY OF THE INVENTION 
     The present invention provides a compressor assembly including a motor having a rotatable shaft, and a bracket attached to the motor. The bracket has fingers extending substantially perpendicular to the shaft, the fingers having ends with engagement surfaces. A connecting rod has a connecting end eccentrically connected to the shaft, and a piston end received in a cylinder sleeve supported by shelves projecting from the fingers and interposed between the fingers. A valve head member disposed above and in sealed engagement with the cylinder sleeve is interposed between the fingers, and the finger engagement surfaces retain the valve head member in sealed engagement with the cylinder sleeve. 
     The general objective of providing a compressor assembly which is easily assembled is accomplished by the bracket in which the cylinder sleeve and valve head member are positioned and retained without the use of tools. 
     The present invention also positions the cylinder in the correct position relative to the shaft by means of flexible support shelves under the cylinder sleeve. These shelves provide a constant force against the mating surface of the cylinder sleeve, forcing the valve plate surface against the adjacent head surface. The head is restrained by the finger engagement surfaces to prevent movement by any of the component parts. The force provided by the shelves provide a consistent force to squeeze the seal gasket and provide a leak free joint. The flexibility of the shelves provides a means to accommodate a greater tolerance in the appropriate components, thereby allowing those components to be economically produced. 
     The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a compressor assembly incorporating the present invention; 
     FIG. 2 is an exploded front perspective view of the compressor assembly of FIG. 1; 
     FIG. 2A is an exploded perspective view of the cylinder sleeve and valve head member of FIG. 2; 
     FIG. 3 is a front view of the compressor of the compressor assembly of FIG. 1; 
     FIG. 4 is a sectional view along line  4 — 4  of the compressor assembly of FIG. 3; 
     FIG. 5 is a front view of the wobble piston of FIG. 1; 
     FIG. 5A is a sectional view along line  5 A— 5 A of the wobble piston of FIG. 5; 
     FIG. 6 is a sectional view along line  6 — 6  of the wobble piston of FIG. 5A; 
     FIG. 7 is a top perspective view of the cylinder sleeve of FIG. 1; 
     FIG. 8 is a bottom plan view of head valve member of FIG. 7; 
     FIG. 9 is a sectional view along line  9 — 9  of the head valve member of FIG. 4; and 
     FIG. 10 is a detailed view along line  10 — 10  of the relief valve knob of FIG.  2 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A compressor assembly  10 , shown in FIGS. 1-5, includes an electric motor  12  having a laminated core  14  surrounded by a coil winding  16 . Front and rear brackets  20  and  18 , respectively, are attached to each other and to the laminated core  14 . The brackets  20  and  18  mount bearings  60  and  61  that support a motor shaft  22 . The motor shaft  22  mounts a fan  24  at one end, and an eccentric assembly  25 , having an eccentric pin  28 , located at the other end of the shaft. The eccentric pin  28  is journalled in a bore  30  formed in a connecting block  32  of a connecting rod  34  which forms a lower end of a wobble piston  36 . Rotation of the shaft  22  drives the eccentric assembly  25 , and thus the connecting rod  34 , in an upwardly and downwardly reciprocating motion. The piston  36  operates in a cylinder sleeve  38  with a valve head member  40  mounted on the top of the sleeve  38 . The piston  36  may be of the style and form disclosed in U.S. Pat. No. 5,213,025 issued May 25, 1993 to Roy J. Rozek, for “Conical Rod Piston”. 
     Looking particularly at FIG. 2, the motor  12  is interposed between the front and rear brackets  20 ,  18  which are mounted thereto. The front bracket  20  has a rectangular base  42  with a top  44  and bottom  46  joined by opposing sides  48  and a face  50 . Screw bosses  52  formed on each base side  48  abut the motor laminated core  14 . Screws  54  inserted through rear bracket screw bosses  56  and holes  58  formed in the motor laminated core  14  threadably engage the front bracket screw bosses  52  to mount the brackets  20 ,  18  to the motor  12 . A bearing  61  disposed in an aperture  62  formed in the base face  50  supports the motor shaft  22  extending therethrough. 
     Substantially parallel fingers  64  extend from the base sides  48  upwardly past the base top  44  to align and support the cylinder sleeve  38  and retain the valve head member  40 . Shelves  66  extending inwardly from the fingers  64  above the base top  44  support and locate the cylinder sleeve  38 . The connecting rod  34  extends through a notch  68  formed in the base top  44  and a gap  70  between the shelves  66  when connected to the eccentric pin  28  and disposed in the cylinder sleeve  38 . 
     Wedges  72  formed at each upper end of the fingers  64  have engagement surfaces  74  which engage a catch  76  formed as an integral part of the valve head member  40 . The wedges  72  guide the valve head member  40  between the fingers  64 , and the engagement surfaces  74  retain the valve head member  40  in position above the cylinder sleeve  38 . Advantageously, the wedge engagement surfaces  74  maintain the valve head member  40  in a sealed engagement with the cylinder sleeve  38 . Shelves  66  are flexible members that provide a sustained force to the bottom surface  90  of sleeve  96 , pushing the sleeve  96  against the valve head member  40 , and subsequently against the engagement surfaces  74 . 
     Referring now to FIGS. 5-6, the connecting rod  34  is preferably formed from a plastic material, such as nylon, and includes a generally vertically oriented rod section  78  having a connecting end  82 . The connecting block  32  is formed as an integral part of the connecting end  82 , and has the bore  30  formed partially through the block  32  for journalling the eccentrically mounted pin  28 . Importantly, an axial groove  84  formed in the bore  30  provides an escape path for grease and air trapped in the bore  30  during assembly. Advantageously, the groove  84  also retains grease  85 , or other lubricant media, to provide lubrication for the pin  28  by wiping lubricant around the pin during compressor operation. 
     The piston  36  is formed by providing a piston end  80  on the rod section end opposite the connecting end  82 . Referring back to FIGS. 2 and 4, the frustoconical connecting rod piston end  80  reciprocates in the cylinder sleeve  38  to draw air into the cylinder sleeve  38  when moving in a downwardly direction, and to force the air out of the cylinder sleeve  38  when moving in an upwardly direction. A sliding seal  86  secured to the piston end  80  by a retainer plate  88  sealingly engages a cylindrical cylinder sleeve wall  94  as the piston end  80  reciprocates in the cylinder sleeve interior. The retainer plate  88  is secured to the piston end  80  by methods known in the art, such as ultrasonic welding, adhesives, screws, and the like. Preferably, a screw  89  threadably engaging the connecting rod  34  secures the retainer plate  88 , and thus the sliding seal  86 , to the piston end  80  to provide a quick and easy assembly. 
     Looking at FIGS. 2,  2 A, and  7 , the cylinder sleeve  38  has an open bottom  90  and a closed top  92  connected by the cylindrical wall  94  having an axis to define the cylinder sleeve interior. A bottom plate  96  extends radially proximal the open bottom  90 . The plate  96  engages the front bracket fingers  64 , and in cooperation with stops  98  extending downwardly from the bottom plate  96  which engage the shelves  66 , to position the cylinder sleeve  38  beneath the valve head member  40 . 
     The cylinder sleeve top  92  has an inlet aperture  100  and an outlet aperture  102  formed therein. A curb  104  surrounding each aperture  100 ,  102  positions a flapper  106  with an integral gasket  108  on the cylinder sleeve top  92 . The gasket  108  is received in a groove  110  formed in the cylinder sleeve top  92  surrounding the curbs  104  and apertures  100 ,  102 . Alignment posts  112  extending upwardly from the cylinder sleeve top  92  engage alignment holes  114  (shown best in FIG. 8) formed on the valve head member  40  to properly align the valve head member  40  with the inlet and outlet apertures  100 ,  102 . 
     As shown in FIGS. 2A and 4, the flexible flapper  106  is disposed between the cylinder sleeve  38  and the valve head member  40  to maintain fluid flow in the proper direction through the compressor  10 . In particular, the flapper  106  prevents fluid compressed in the cylinder sleeve  38  from exiting the cylinder sleeve  38  through the inlet aperture  100 , and prevents fluid from being drawn into the cylinder sleeve  38  through the cylinder sleeve outlet aperture  102 . The flapper  106  has a pair of joined wings  116 ,  118  surrounded by the gasket  108 . When the compressor  10  is assembled, each wing  116 ,  118  is surrounded by one of the curbs  104 , and the groove  110  surrounding the apertures  100 ,  102  and curbs  104  receives the gasket  108 . 
     When fluid is being drawn into the cylinder sleeve  38 , the wing  116  disposed over the outlet aperture  102  is drawn against the outlet aperture  102  preventing air from passing therethrough. When fluid is forced out of the cylinder sleeve  38 , the wing  118  disposed over the inlet aperture  100  is forced against an inlet port  120  in the valve head member  40  preventing fluid from passing into the valve head member inlet port  120 . The gasket  108  provides a seal between the cylinder sleeve  38  and the valve head member  40  to prevent fluid from escaping from between the cylinder sleeve  38  and valve head member  40 . 
     The valve head member  40  directs fluid flow to and from the cylinder sleeve  38 . Preferably, the valve head member  40  is formed from plastic, such as glass reinforced polyethylene teraphthalate, and includes a rectangular base  122  having a top  124 , bottom  126 , front  128 , back  130 , and sides  140 . Front, back and side walls  144 ,  146 ,  148  extend upwardly from the base top  124  along the base periphery defining a cavity  150 . Handles  142  formed on opposing base sides  140  wrap around the front bracket fingers  64  to hold it in place. Guide extensions extending from the base sides  140  toward the handles  142  properly align the fingers  64  in the handles  142 . The alignment holes  114  are formed in the base bottom  126  and receive the cylinder sleeve alignment posts  112  when assembling the compressor  10 . 
     The inlet port  120  and an outlet port  154  formed in the valve head member  40  guide the fluid through the base  122 . The inlet port  120  extends through the base front wall  144 , and is in fluid communication with the inlet aperture  100  formed in the cylinder sleeve  38 . The outlet port  154  also extends through the base front wall  144 , and is in fluid communication with the outlet aperture  102  formed in the cylinder sleeve  38 . 
     Referring to FIGS. 2A and 9, a pressure relief valve  156  is formed as an integral part of the valve head member  40 , and regulates the pressure of the air exiting the cylinder sleeve  38 . The pressure relief valve  156  includes a boss which is integral with and extends upwardly from the base top  124 . The boss includes an axial bore  162  which is in fluid communication with the outlet port  154  to provide a fluid path from the outlet port  154  to the atmosphere where the valve  156  opens. A poppet  164  disposed in the bore  162  is urged against the fluid pressure in the outlet port  154  by a spring  166 . The spring  166  is compressed by relief valve knob  168  disposed in the bore  162 . 
     Looking particularly at FIG. 9, the metal relief valve knob  168  (e.g. steel, aluminum, or brass) compresses the spring  166  to urge the poppet  164  against the fluid and into a valve seat  158  extending into the outlet port  154 . The poppet  164  and spring  166  prevents fluid having a pressure below a predetermined level from passing from the outlet port  154  through the bore  162 . Adjusting the spring compression by moving the relief valve knob  168  closer to or further away from the poppet  164  determines the fluid pressure level which will force the poppet  164  out of the seat  158 , and allow fluid to escape through the boss  160  and into the atmosphere. 
     Referring back to FIG. 2A, the substantially cylindrical relief valve knob  168  has a top  170 , a bottom  172 , an outer surface  174 , and an axial through bore  176  extending from the top  170  to the bottom  172 . The through bore  176  provides a path for the fluid through the pressure relief valve  156  to the atmosphere. Preferably, the knob top  170  is formed as a hex head for engagement with an Allen wrench, and the knob bottom  172  has an annular groove  178  (shown in FIG. 9) coaxial with the through bore  176  for receiving one end of the spring  166 . 
     Referring to FIG. 10, assembly of the pressure relief valve  156  is simplified by external buttress threads  180  formed on the knob outer surface  174 . The buttress threads  180  have an outer diameter slightly larger than the boss bore internal diameter to provide an interference between the threads  180  with the boss bore  162 . The threads  180  are wedge shaped having an upwardly ramped surface  182  which assists in the insertion of the knob  168  into the boss bore  162  when pressed therein without threadably engaging the threads  180  with the boss  160 . 
     Referring again to FIG. 2A, preferably, the cylindrical valve knob  168  has opposing flat areas  184  on the knob outer surface  174  which allows the boss  160  to flex during assembly while maintaining a tight interference between the threads  180  and boss  160 . The flat areas  184  allow a greater latitude in the dimensional tolerances for the interfering diameters of the threads  180  and boss bore  162 . The interference between the threads  180  and the boss bore  162  and the flexing of the boss provide sufficient restraining force on the knob  168  to retain the spring  166  and poppet at the desired position. The upwardly ramped surface on knob  168  provides additional retention by aggressively pressing into the walls of boss  160  when an outward force is supplied by the poppet and spring. Further adjustment of the desire pressure setting can be achieved when the knob  168  is rotated about its axis in the bore  162 . Rotating the knob  168  cuts threads into the boss  160  thus providing adjustment of the knob height in the boss bore  162 , and thereby controls the spring compression and desired pressure setting. 
     Looking at FIGS. 1-5, when assembling the compressor  10 , the front and rear brackets  20 ,  18  are mounted to the motor  12  with the motor shaft  22  extending through the bearing  61  mounted in the front bracket base face  50 . The eccentric assembly  24  with the eccentric pin  28  is press fit on the end of the motor shaft  22  extending through the bearing  61 . The connecting rod connecting end bore  30  is filled with grease, or other lubricant known in the art, and then the pin  28  is slipped into the bore  30 . The connecting rod piston end  80  is slipped into the cylinder sleeve  38 , and the cylinder sleeve  38  with the flapper  106  mounted thereon is slipped between the front bracket fingers  64 , and onto the shelves  66 . The pressure relief knob  168  is pressed into the bore  162  formed in the pressure relief valve boss  160 , and the front bracket fingers  64  are then inserted into the handles  142  of the valve head member  40 . The valve head member  40  is urged toward the cylinder sleeve  38  until the wedge engagement surfaces  74  engage the valve head member top  76  to hold the valve head member  40  in sealed engagement with the cylinder sleeve  38 . 
     While there has been shown and described what are at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention defined by the appended claims.