Patent Publication Number: US-3877842-A

Title: Air pumps

Description:
United States Patent [1 1 Greene et al.  
 l llApr. 15, 1975 1 1 AIR PUMPS [75] Inventors: Robert Raymond-Greene, Chicago;  
 Hans Oscar Jacob, Morton Grove; Meredith Wayne Meece, Niles, all of 111.  
 [73] Assignee: International Telephone and Telegraph Corp., New York, NY.  
 [ Notice: The portion of the term of this patent subsequent to Mar. 21, 1989, has been disclaimed.  
 [22] Filed: Dec. 27, 1971 [21] Appl. No.: 212,387  
  Related U.S. Application Data [62] Division of Ser. No. 4,615, Jan. 21, 1970.  
 [52] U.S. Cl 417/312; 417/368 [51] Int. Cl. F04b 21/00; F04b 17/00 [58] Field of Search 417/312, 480, 368;  
 [56] References Cited UNITED STATES PATENTS Owen 181/36 R 2,230,595 2/1941 Horton 417/480 2,588,112 3/1952 Hanson 181/36 R 2,735,366 2/1956 Hunter 417/313 X 2,943,699 7/1960 Thornburgh 181/36 R 3,049,284 8/1962 Alampresc 417/480 X 3,650,639 3/1972 Greene et al. 417/368 FORElGN PATENTS OR APPLICATIONS 806,072 12/1958 United Kingdom 418/101 Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. Gluck Attorney, Agent, or Firm-William J. Michals; James B. Raden [57] ABSTRACT Air pumps are provided having channels therein to allow cool air to circulate throughout the interior of the pump to promote efficient and effective cooling of the pump. Additionally, a dampening or muffling arrangement is provided which substantially reduces the air borne operational noise of the pumps.  
 4 Claims, 12 Drawing Figures PATENTEDAPRI 5 I975 sum 1 95 5 PATENTEDAPR 1 51975 snznaurg FIG. 2  
 PATENTEDAPR 1 5197s saw 3 o 5 PATENTEDAPR 1 5197s sum u g 5 FIG. 4 (1) AIR PUMPS This is a division of application Ser. No. 4,615. filed Jan. 21, I970.  
  This invention relates in general to air pumps and in particular to new and improved air cooled vacuum pumps and compressors.  
  A common type of pump for pumping a compressible gas such as air to a captive system is a diaphragm and piston pump. In this type of pump, a reciprocating diaphragm and piston positively displace the gas from a cylinder during the discharge stroke of the piston. Normally, these pumps are of small capacity and are generally single acting and air cooled. The diaphragms and pistons are usually moved reciprocatingly by a cam, crankshaft and cam follower connecting rod mechanism, or the equivalent, deriving motion from a driving source such as an electric motor. On being compressed, the gas is expelled through valves which open readily upon slight differential pressures. The term air pump&#34; is used generically hereinafter to describe these and other gas compressors, vacuum pumps, and the like.  
  The compression of a gas, such as air into a smaller volume gives rise to problems in designing such pumps. For example, a major problem in the design of air pumps is the need to remove the heat of compression from the pumping element. Disposal of this heat of compression generated during the compression cycle has always been a problem effecting the reliability, longevity and efficiency of air pumps. This heat disposal problem is especially severe in pumps or compressors of the flexible diaphragm type since the heat generated causes excessive embrittlement of the diaphragm and, consequently, a substantially reduced cycle life thereof.  
  Heretofore, air-cooled fluid pumps have employed heat-radiating fins cast integral with the pump body to furnish additional radiating surface to carry off the heat of compression. The use of these cooling fins has been successful only to a degree in providing a solution to the heat disposal problem. For example, these fins have not provided sufficient cooling of the units to adequately extend the cycle life of the diaphragms in the pumps. Consequently, the diaphragms have worn out too quickly resulting in costly maintenance problems and substantially reduced efficiency of the pump units.  
  An additional long standing problem in designing air pumps, and particularly air compressors is the reduction of noise level caused by the valve operation during compression of the gas. No completely adequate and economical solution has been suggested heretofore to reduce the air borne noise level caused by the compression and discharge of gas in an air compressor unit. Therefore, it would be advantageous to provide air compressors having means for muffling or dampening this working noise.  
  Accordingly, an object of the present invention is to provide new and improved air pumps. In particular, an object is to provide air cooled vacuum pumps and compressors which overcome the problem of disposal of the heat of compression.  
  A related object is to provide air cooled air pumps of the diaphragm type which are more efficient in operation, require less time consuming and costly maintenance and wherein the diaphragm component thereof has a substantially extended cycle life.  
  Another object is to provide air compressors which are substantially quieter in operation. More specifically, an object is to provide air compressors having noise dampening or muffler means to reduce the air borne noise level of the unit.  
  In accordance with one embodiment of the invention, a motor operated, air cooled pump is provided having a movable pump member comprising a piston and diaphram assembly. The pump member is arranged to move in an undulating reciprocal motion within a pumping chamber to produce compressed air. Ducts are provided to allow cool air to enter the pump body and cool the pumping chamber. After cooling the pumping chamber and, correspondingly, the piston and diaphragm therein, this air is drawn, by a fan operatively connected to the motor, through channels in the pump body over the motor, thus providing a cooling effect for the motor. The air is then expelled from the pump through outlet vents provided in the pump body. This arrangement promotes more efficient and effective cooling of the entire pump unit and, particularly, of the pumping chamber, piston and diaphragm resulting in higher compression efficiency, lower discharge air temperature and longer diaphragm life.  
  The abovementioned and other features and objects of this invention and the manner of obtaining them will become more apparent, and the invention will be best understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings in which:  
  FIG. 1 is a pictorial representation of the inventive air pump in the form of an air compressor;  
  FIG. 2 is a cross-sectional side view of the air compressor taken along line 2-2 of FIG. 1;  
  FIG. 3 is a sectional view of the piston and connector rod assembly in the air compressor of FIG. 1 showing the cavity in the body of the piston with the cellular material therein;  
  FIG. 4 is a schematic stop action representation showing the operation of the air compressor of FIG. 1 during the suction stroke and discharge stroke of the pumping member;  
  FIG. 5 is a sectional view ofa vacuum pump head assembly replacing the air compressor cylinder head assembly shown in the encircled area 5 of FIG. 2; and  
  FIG. 6 is a schematic stop action representation showing the operation of a vacuum pump, employing the vacuum pump head assembly of FIG. 5, during the suction stroke and discharge stroke of the pumping member.  
  In the FIG. 1 pictorial representation of a preferred embodiment of the invention, an air compressor assembly 10 is shown. The assembly includes a housing or casing 12, a front cover plate 14, a rear rotor housing 16 and a cylinder head 18. These constituent parts are securably fastened together to form the assembly 10 by any suitable arrangement such as screws, bolts and the like. The assembly 10 of the present embodiment is constructed for use as a portable unit. A mounting position 20 is provided for an adjustable handle (not shown) so that the assembly 10 can be easily transported. However, the assembly 10 can also be mounted in a stationary positioned, if desired. Fins 21 are provided about the outer surface of the assembly 10.  
  Means are provided for cooling a cylinder or pumping chamber 22 in the housing 12 by providing a flow of cool air about the outer surface thereof whereby the heat of compression generated within the cylinder 22 is effectively and efficiently dissipated. More specifically, a plurality of ducts or ports, such as duct 24, are positioned about the surface of the head 18 to provide inlets for entry of cool air into the housing 12. The ducts 24 in head 18 communicate with channels or passageways 26 in housing 12 and form continuous paths with these channels or passageways 26. Thus, as shown generally by arrows a, b and c in H6. 1, air flows into the assembly through ducts 24. The cool air then circulates about the outer surface of the cylinder 22 in the housing 12 through the channels or passageways 26. Corresponding paths are further provided through the fan scroll cavity 17 in the motor end cover plate 16 so that a continuous flow path is provided from the inlet ducts 24 through the entire pump body including housing 12 and rotor housing 16 to outletvents 28.  
  Means are further provided for cooling a motor 30 in the assembly 10 by the passage of cooling air thereover. More particularly, additional cool air inlet ports 32 are provided through the base of the housing 12. These ports 32 connect with channels 26 in the housing 12. The air entering these ports 32 combines with the air flowing in channels 26 which entered through ducts 24. This combined air flow enchances cooling of the motor bearings and windings of the motor 30 as the air passes over the motor 30 and through the motor end cover plate 16 before being expelled through outlet vents 28. This cooling of the motor 30 and the motor bearings promotes extended bearing life and substantially increases the motor efficiency.  
  Means, such as fan 34 best seen in FIG. 2, positioned in the motor end cover plate 16 adjacent to outlet vents 28 are employed to achieve the desired air flow into and through the assembly 10. In greater detail, the fan 34 is operatively connected to the motor 30 and acts to draw air into the assembly 10 through ducts 24 and ports 32 and causes this, air to circulate through the channels or passageway 26 provided in the assembly 10. Additionally, the fan 34 forces the air out of the assembly 10 through outlet vents 28 after the, air has completed its flow path through the pump body- As best illustrated in FIG. 2,, it is seen that the air compressor 10 is operated by a motor 30 such as an electrically driven motor mounted in a space provided in the housing 12 and motor end cover plate 16. The motor 30 is operatively attached to the fan 34 in the motor end cover plate 16 by a shaft 36 and bearings 38.  
  A shaft 40 extends from the opposite end of the motor 30 and is connected to a connecting rod assembly 42 which extendsin a vertical plane perpendicular to the axis of the shaft 40. This connection is made in any suitable manner such as by bearings 43 and 44 and a cam or eccentric 46 to impart motion to the rod 42. The motion thus attained can be characterized generally as reciprocal motion in a plane parallel to the axis of the shaft 40 and as a slight rocking or undulating motion in a plane perpendicular to this axis.  
  The upper end of the rod 42 is flared outwardly to form a piston-line member 48&#39;which is disposed within a pump cylinder or chamber 50 in the housing 12. A  
 cavity or chamber 52 defined by shell 54 is provided within the piston body 48 as shown in FIG. 3. The cav- 58, such as a feather valve. a reed valve and the like. Holes 60 are provided through the base of the shell 54, to allow air to enter therein.  
 Means such as cellular material 62 are provided for I reducing the noise caused by the operation of the valves during the compression and exhaust cycles of the compressor 10. More specifically, the cavity 52 through the cellular material 62 having the high inter nal loss properties before it is expelled from the cavity 52 through outlet opening 57 and valve 58. Consequently, the sound waves are dampened or muffledto a high degree due to the acoustical impedance by the cellular material 62 having inefficient vibration trans,-  
 mission characteristics. This dampening or muffling effect on the sound waves results in substantially reduced air borne noise level and, thus, quieter valve operation. Accordingly, the cavity 52 with material 62 forms a noise dampening chamber or muffler which reduces the air borne valve noise and thus provides a quieter operating pump.  
 An annular shaped flexible diaphragm 64, of suitable elastic material such as rubber, is secured to the upper face of the piston 48 by the cover plate or retainer 56 and screws 55. The outer periphery of the diaphragm 64 is clamped in sealing engagement between the outer end of the cylinder 50 and the cylinder head 18. The  
 cylinderhead 18 isbolted to the outer end of the cylinder 50. I  
  The cylinder head 18 includes an inverted cup-like body 68 closed on the inner end by an exhaust or valve plate 70. A compression chamber 72 is thus formed be-&#39; tween the cover plate 56 and the exhaust plate A central outlet opening or port 74 extends through, exhaust plate 70 and terminates in communication with 1 the compression chamber 72. The outlet opening 74 is enclosed at the top by a suitable valve mechanism 76 such as a feather valve, a reed valve and the like to interconnect chamber 72 with a highpressure chamber 78. A discharge port 80 interconnects the high pressure chamber 78 to a suitable outlet conduit 82 for transfer of the compressed air directly to a compressed air load.  
 The front cover plate 14 is provided with an inlet port a 84 to allow air to enter the compressor assembly 10. The port 84 is abutted by a removable filter material 85 such as porous felt and the like. The perforated metal plate 86 retains filter material 85. This filter material 85 filters the air entering the unit through port 84 to eliminate any undesirable contaminants before the air enters the cavity 52 of piston 48 through the holes 60 in the shell 54 and, subsequently, the compression chamber 72.  
  The operation of the compressor 10 is depicted in the schematic stop action illustrations, FIGS. 4(a), 4(b), 4(c), and 4(d). During the suction stroke (FIG. 4a) of the piston 48 when the piston 48 and diaphragm 64 move downwardly, air from filter 85 enters the housing 12 and is drawn into cavity 52 through holes 60. The air then passes through cellular material 62. The valve 58 is open due to the differential pressure between cavity 52 and compression chamber 72. This allows, air to flow through outlet port 57 and into compression chamber 72.  
  As the downward suction stroke ends and the discharge or exhaust stroke begins, the piston 48 and diaphragm 64 reverse direction and begin to travel upward. At some point in this upward discharge stroke (FIG. 4b), the pressure in the cavity 52 and the pressure in the compression chamber 72 approximately equalize and the valve 58 closes. The air in the compression chamber 72 is thus trapped therein. The air cannot escape into the cavity 52 since valve 58 is closed; nor can the air pass into the high pressure chamber 78 since the differential pressure between the compression chamber 72 and the high pressure chamber 78 is such that valve 76 is closed.  
  The piston 48 continues its upward discharge stroke (FIG. 40) and the pressure of the air trapped in the compression chamber 72 increases due to the compressive action of piston 48 thereon. The pressure of the air in chamber 72 continues to mount until a point is reached at which the pressure differential between the compression chamber 72 and the high pressure chamber 78 is such that the valve 76 opens. Then the compressed air passes through outlet opening 74 from the compression chamber 72 into the high pressure chamber 78 and hence through discharge port 80 into the outlet conduit 82.  
  Subsequently. the piston 48 begins its downward suction stroke again. At some point in this downward suction stroke (FIG. 4d). the pressure differential between the high pressure chamber 78 and the compression chamber 72 becomes such that valve 76 closes thus returning the unit to its approximate starting condition wherein valves 58 and 76 are closed. Thereafter, as the compressor continues to operate. the above described operation is repeated continuously.  
  In a further embodiment of the present invention, the inventive air pumps are vacuum pumps. The structure and operation of the vacuum pumps generally is similar to that heretofore described with reference to air compressors in FIGS. 1-4. The housing 12, the front cover plate 14 and the rear rotor housing 16 and the constituent elements therein are the same as above described. However, the encircled area 5 in FIG. 2 comprising cylinder head 18 of compressor is replaced by a vacuum pump head 88 shown in FIG. 5.  
  The vacuum pump head 88 includes an inverted cuplike body 90 with a centrally positioned ridge 92. The body 90 is closed on the inner end by a valve plate 94. In assembly, the bottom end of ridge 92 is sealed with plate 94 forming two discrete chambers 96 and 98 in body 90. Chamber 96 is an inlet chamber and chamber 98 is a discharge chamber.  
  A compression chamber similar to chamber 72 of compressor 10 is formed between the valve plate 94 and a cover plate such as cover plate 56 in housing 12 shown in FIGS. 2-3. An inlet opening or port 100 and an exhaust opening or port 102 are provided in plate 94. The inlet opening 100 interconnects inlet chamber 96 with compression chamber 72 and, likewise, exhaust opening 102 interconnects compression chamber 72 with discharge chamber 98. Inlet opening 100 is enclosed at the bottom within chamber 72 by a suitable valve mechanism 104 and exhaust opening 102 is enclosed at the top within discharge chamber 98 by a similar type valve mechanism 106. Suitable valve mechanisms 104 and 106 include feather valves, reed valves and the like. The valves 104 and 106 are held in position by valve screws 108 and valve keepers 110.  
  An inlet port 112 interconnects a suitable inlet conduit 114 to the inlet chamber 96 for introduction of air into the head 88. This air subsequently passes through opening in plate 94 into compression chamber 72. After compression, the compressed air is expelled from the pump head 88 through opening 102 in plate 94 and discharge chamber 98 into a discharge port 116. The discharge port 116 interconnects the discharge chamber 98 to a suitable outlet conduit 118 and the compressed air is thereby transferred directly to a compressed air load.  
  The operation of the vacuum pump is depicted in the schematic stop action illustrations, FIG. 6(a), 6(b), 6(0), and 6(d). During the suction stroke (FIG. 6a) of the piston 48, when the piston 48 and diaphragm 64 move downwardly, air from inlet conduit 114 enters inlet chamber 96 through inlet port 112. the valve 104 enclosing opening 100 in valve plate 94 opens due to the differential pressure between inlet chamber 96 and compression chamber 72. This allows the air to flow into compression chamber 72.  
  As the downward suction stroke ends and the discharge or exhaust stroke begins, the piston 48 and diaphragm reverse direction and begin to travel upward. At some point in this upward discharge stroke (FIG. 6b), the pressure in the inlet chamber 96 and the pressure in the compression chamber 72 approximately equalize and valve 104 closes. The air in the compression chamber 72 is thus trapped therein. The air cannot escape into the inlet chamber 96 since valve 104 is closed; nor can the air pass into the discharge chamber 98 since the differential pressure between the compression chamber 72 and the discharge chamber 98 is such that valve 106 is closed.  
  The piston 48 continues its upward discharge stroke (FIG. 60) and the pressure of the air trapped in the compression chamber 72 increases due to the compressive action of piston 48 thereon. The pressure of the air in chamber 72 continues to mount until a point is reached at which the pressure differential between the compression chamber 72 and the discharge chamber 98 is such that the valve 106 opens. Then the compressed air passes through exhaust opening 102 from the compression chamber 72 into the discharge chamber 98 and hence through discharge port 116 into outlet conduit 118.  
  Subsequently, the piston 48 begins its downward suction stroke again. At some point in this downward suction stroke (FIG. 6d), the pressure differential between the discharge chamber 98 and the compression chamber 72 becomes such that valve 106 closes thus returning the unit to its approximate starting condition wherein valves 104 and 106 are closed. Thereafter, as the vacuum pump continues to operate, the above described operation is repeated continuously.  
  From the above description, it should now be clear that air pumps have been provided which effectively and efficiently dispose of the heat of compression generated by the compression of gases in the pump. This disposal of heat or cooling feature of the invention is highly advantageous in promoting higher compression efficiency of the pumps, lower discharge air temperature and longer diaphragm life. Additionally, the unique and superior cooling feature of the inventive pumps provides excellent cooling of the motor and motor bearings and windings which promotes increased motor life and materially increases motor efficiency. A further advantageous feature of the present invention is the provision of a muffler or damper means resulting in quieter operating pumps.  
  While the principles of the invention have been described above in connection with specific apparatus and applications, it is to be understood that this description is made only by way of example and not as a limitation on the scope of the invention.  
 We claim:  
  1. A motor operated air cooled pump including a pump body having disposed therein a pumping chamher, said pumping chamber having a movable pump member disposed therein, valve means for controlling the flow of air in said pumping chamber, said pump member operating with a suction stroke to draw air from a first air inlet means through a first air duct channel means into said pumping chamber and a discharge stroke to compress said air and to expel the compressed air from said pump chamber through a first air outlet means, second air inlet and outlet means separate from said first air inlet and outlet means, said second air inlet and outlet means being positioned about the surface of said pump body, said second air inlet means being connected to said second air outlet means by second air duct channel means separate from said first air duct channel means, said second air duct channel means extending through said pump body in a manner such that said second channel means extend in sequence from said second air inlet means around the outer surface of said pumping chamber over the surface of said motor and then to said second air outlet means, means for:  
 drawing cool air into said pump body through said second air inlet means and for drawingsaid air through said second channel means and for expelling said air from said pump body through said second air outlet motor surface, and dampening means positioned within said pump member for reducing noise caused by the operation of the valve during said suction stroke and said discharge stroke.  
  2. The air cooled pump of claim 1 wherein said pump member comprises a piston and diaphragm assembly.  
  3. The air cooled pump of claim 2 wherein said pump is an air compressor.  
 4. The air cooled pump of claim 2 wherein said pump is a vacuum pump.