US2450468A - Motor-driven compressor - Google Patents

Description

Oct. 5, 1948. R.-T. CORNELIUS MOTOR muvm: COMPRESSOR 5 Sheets-Sheet 1 Filed Oct. 1, 1943 1 Q S n 4 v .m m w .m o M A. T w d w r 4 m u .m R 0 6 m .1 4 m: 3 B w B.

176 fig-1 R. 1'. CORNELIUS 2,450,468 v UOTOR DRIVEN COMPRESSOR s sheets-sheet 2 f/i'li 4H 177 Oct.'5, 1948.

Filed Oct. 1, 1943 Richard T. Cornelius \&F

ttpr neg:

Oct. 5, 1948. R. T. CORNELIUS MOTOR DRIVEN COMPRESSOR 5 Sheets-Sheet 3 Filed Oct. 1, 1943 lqveqtor Richard T. Cornelius 7 Am omega Oct. 5, 1948. R. 'r. CORNELIUS MOTOR DRIVEN COMPRESSOR 5 Sheets-Sheet 4 Filed Oct. 1, 1943 a. as 5 $13 5 I Inventor Richard T. Cornelius gt or megs Oct. 5,1948. R. T. CORNELIUS 2,450,468

MOTOR DRIVEN COMPRESSCR Filed Oct. 1, 1943 5 Sheets-Sheetfi Inveqbpry Richard Qbrneliu v Amer-neg:

Patented Oct. 5, 1948 UNITED STATES PATENT OFFICE MOTOR-DRIVEN COMPRESSOR Richard T. Cornelius, Minneapolis, Minn.

Application October 1, 1943, Serial No. 504,556

11 Claims. 1

My invention relates to motor driven compressors and has for an object to produce an extremely practical and efilcient compressor for compressing air and other fluids to relatively high pressures.

Another object of the invention resides in providing a relatively light and compact construction.

An object of the invention resides in providing a multiple step compressor in which the disadvantages due to freezing of condensation are overcome.

A still further object of the invention resides in the specific arrangement of the compressor, the reservoir and connecting conduits by means of which flow of air to the reservoir is maintained at all operating temperatures.

A still further object of the invention resides in providing a multiple step compressor in which the air or other fluid compressed is successively cleliver'ed from one stage to the other and to a reservoir through conduitsarranged so as to cool the fluid and to cause condensation in the fluid to drain toward the following compressor unit or reservoir.

Another object of my invention resides in providing a construction by means of which the operating parts may all be readily lubricated, whereby the compressor can be'run at a high rate of speed.

A still further object of the invention resides in providing mechanism for controlling the final pressure of the compressor.

Further objects of the invention reside in the novel combination and arrangement. of parts and in the details of construction hereinafter illustrated and/or described.

In the drawings:

Fig. 1 is a plan view of a motor driven compressor illustrating an embodiment of my invention.

Fig. 2 is a vertical sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a fragmentary vertical sectional view taken on line 3-3 of Fig. 1.

Fig. 4 is a fragmentary vertical sectional view taken on line 44 of Fig. 1.

Fig. 5 is a detailed sectional view taken on line 55 of Fig. 2.

Fig. 6 is an elevational view showing the compressor and reservoir in position.

My invention comprises an electric motor I which operates three compressor units I I, I2 and I3. The compressor unit I I is a low pressure unit, the compressor I2 is an intermediate pressure unit, while the compressor I3 is a high pressure unit. These various parts are carried by a case which is indicated in its entirety by the reference numeral I4. The high pressure unit I3 discharges into a reservoir 20. These parts will now :be described in detaill The motor I 0 consists of a housing I which supports a stator core IS. The core I6 is constructed in the usual manner and carries coils I! which form the field of the motor. Within the core I6 is rotatably mounted an armature l8 which has the usual winding I9 thereon connected to the bars of a commutator 2|. The armature I8 is mounted onan armature shaft 22 which is journaled at its upper end in a bearing 23 mounted in an end bell 24 which is secured to the upper end of the housing I5. The end bell 24 carries brush holders 25 in which brushes 26 are slidably mounted for engagement with the commutator 2|. The other'end of the armature shaft 22 is rotatably mounted in a bearing 21 carried by a seal 29 encircling the shaft 22 and mounted in partment 35.

the partition 28 prevents the passage of air or lubricant from the crank case 36 to the motor com- For the purpose of cooling the motor Ill, air holes 2I3 are formed in the motor housing I5 below the armature I8 and other air holes 2M in the end bell 24 above said armature. The lower end of the armature shaft 22 is threaded as indicated at 3i to receive a crank 32 which is rigidly screwed thereon. This crank is provided with a crank pin 30 to which is attached a ball bearing 33 which serves to operate the various compressor units. The crank 32 is provided with a counterweight 34 which counterbalances the weight of the crank 32, the bearing 33 and the other parts connected therewith.

The low pressure compressor unit II is best shown in Fig. 2 and consists of a cylinder 31. Cylinder 31 is formed with a bore 38 which extends through the same and is closed at its outer end by means of a cylinder head 39; The inner end of the cylinder 31 which is indicated by the reference numeral 4|. extends through an opening 42 in the case I4. Screws 63 pass through a clamp 44 mounted on the end of the cylinder head 39 and are threaded into the housing I4. These screws hold the parts in proper assembled relationship. Within the bore 38 of cylinder 31 is slidably mounted a piston 45 which is operated by a connecting rod 46. Connecting rod 46 is pivotally connected at one end to the piston 45 by means of a wrist pin 41 and is formed at its other end with a boss 48 in which the bearing 33 is mounted. As the armature shaft 22 of motor I rotates, the connecting rod 45 and the piston 45 are reciprocated.

The cylinder head 39 is formed hollow to pro vide a compartment within the same opening at its outer end and closed at its inner end by a wall 52 forming part of said cylinder head. The wall '52 is provided with a valve seat 53 which encircles the same near the outer periphery thereof. Extending throughthis valve seat are a number of openings '54 which bring the bore 38 of cylinder 31 into communication with the chamber 5I. A disk valve 55 seated on the valve seat 53 serves to close the valve and obstruct passage through the openings 54. The disk valve 55 is normally held seated against the valve seat 53 by means of compression coil spring 58, which at one end engages said valve disk and at its other end engages a flange 51 formed on a tubular stop 58. The flange 5i is clamped in posi-- tion in a rabbet 59 formed in the end of the cylinder head 39. Said flange is held in position by means of a cap 6| which bears against said flange and is also received within the rabbet 59. The cap 6| is urged into position by means of the clamp 44 and the screws 43 previously referred to. The stop 58 serves to hold the spring 55 in proper position'and the end thereof terminates short of the valve disk 55 and limits the movement of said disk away from the valve seat 53. In this manner, the distance that the valve disk raises is limited so that a short travel for the valve disk is provided and a minimum loss of the fluid compressed is produced when the piston reaches the end of its stroke.

Air is introduced into the cylinder 31 through a crescent-shaped port 62 which is formed in the cylinder 31 at the proper locality. The air entering the bore 38 of cylinder 3'I'passes through an air filter 63 which is constructed with a case 64 having a chamber 65 within the same open to the exterior. A pad of filter material 56 extends across the opening in chamber 65 and is held in position by means of two reticulated plates 61 and 88. The case 53 has a pipe fitting 69 formed on it which is screwed into a threaded hole II formed in the cylinder 31 which communicates with the port 62.

The fluid compressed is conducted from the chamber 5| through a pipe fitting 12 which is threaded into the cylinder head 39 and communicates with said chamber. This pipe fitting has a tube 13 connected to it which, in turn, delivers the compressed fluid to the compressor unit I2 as will be presently described.

For a purpose to be presently described, the low pressure cylinder 31 is of ample proportions to-furnish the fluid utilized by the other two cylinders. Under certain conditions, its capacity exceeds that required and for this purpose,

a pressure relief valve indicated in its entirety by the reference numeral 14 is employed. This relief valve is shown in Fig. 2 and is constructed as follows: In the center of the cap BI is formed a discharge opening 15 which is encircled by a valve seat 16. This opening communicates with a chamber 8| formed in the clamp 44 which, in turn, communicates with the exterior through openings 19 in said clamp. A disk valve 11 seats against this seat and is urged into engagement therewith by means of a compression coil spring 80 which at one end engages said disk valve and at its other end engages the clamp 44. When the pressure within the chamber 5| becomes too great, the valve 14 is opened and the excess fluid escapes through the opening I5 in the cap BI and through the openings I9 in the clamp 44 to the exterior.

The intermediate pressure compressor unit I2 is best shown in Fig. 4 and comprises a cylinder 92 having a bore 83 therein of smaller dimensions than the bore 38 of cylinder 31. The end III 01 the cylinder 82 is received in an opening II2 formed in the case I4. Said cylinder has a flange II3 extending outwardly therefrom, which is secured to the said case by means of screws Hi4 passing through said flange and screwed into the case. In the bore 83 is slidably mounted a piston 84, which is connected by means of a wrist pin 85 to a connecting rod 85. Connecting rod 86 is pivotally connected to the boss 48 of connecting rod 96 by means of another wrist pin 91. As the crank 32 operates, piston 80 is reciprocated within the bore 83 of the cylinder 82. At the outermost end of the cylinder 82 is formed a tubular extension 88 which has a bore therein providing a chamber 89 of dimensions somewhat greater than the diameter of the cylinder bore 83. Disposed within said chamber and encircling bore 83 is a valve seat 9i. A valve disk 92 seats on said seat and controls the flow of fluid from the cylinder 83. A compression coil spring 93 acts between said valve disk and a flange formed on a tubular stop 95 similar to the stop 58 of the compressor unit II. This stop has an annular portion 96 which flts within the bore of the tubular-extension 80 and which is held in place therein by means of a ring 91 seated in a groove 98 in the wall of said tubular extension. A number of openings 99 in the flange 94 bring the chamber 89 into communication with a passageway m formed in a tube fitting m. The tube fitting I02 is attached to the end of the tubular extension 88 by means of a clamp nut I03 which is screwed upon threads I04 formed upon the exterior of the tubular extension 88. The fitting I02 has a tube I05 brazed or otherwise secured to it and conducts the fluid entering the passageway IN to the high pressure compressor unit I3.

The fluid to'be compressed enters the cylinder bore 83 through a crescent shaped port I01' which is formed in the wall of the cylinder 82. This port communicates with a passageway I03, which, in turn, communicates with a tube fltting I09 screwed into the cylinder 82. The tube I3 previously referred to, is connected to this fltting.

The high pressure compressor unit I3 is shown in detail in Fig. 4 and is similar to the unit II. This unit comprises a cylinder II5 having a bore II6 therein extending completely through the same. Said cylinder is constructed with an extension II! which is received in a hole I I8 in the case I4 opposite the hole 2. The cylinder III has a. flange II9 extending outwardly therefrom which is secured to said case by means of screws I2I. In the cylinder H5 is slidably mounted a piston I22 which is formed with an enlarged end I23. A connecting rod I24 is connected to the end I23 of piston I22 by means of a wrist pin I25. 4

bore H6 is a valve seat I29 similar to the valve seat 9| which is closed by means of a disk valve I'3I. Valve I9I is normally held seated by means of a compression coil spring I32 whi'dh at one end bears against saidvalve disk and at its other end against a stop I33. The stop I33 is similar to the stop 95 and is attached to the tubular extension I21 in the same manner. Secured to the outer end of said tubular extension is a tube fitting I34 which has a tube connector I35 formed thereon. This fitting is held in place by means of a clamp nut I36 similar to the clamp nut I63. The fiuid to be compressed is delivered into the cylinder II6 through a port I31 formed in the cylinder II5. A tube fitting I38 is screwed into the cylinder I I5 and communicates with this port. This tube fitting has connected to it the tube I66 leading from the intermediate pressure compressor unit I2.

The various compressor units are lubricated by means of a lubricating oil pump I4I illustrated in detail in Fig. 2. Beneath the case I5 is mounted an oil sump I42. This oil sump is in the form of a tubular receptacle with a bottom I49 and 2. cylindrical wall I44. The wall I44 is constructed at its upper end with an offset I45 which extends about a lip I46 formed on the lower end of the case I5. A gasket I41 carried by this lip engages the inner surface 'of the offset I45 and forms a fluid-tight connection therebetween. The sump I42 is detachably held secured to the case I4 by spring clips I48 best shown in Fig. 3, which snap under the ofiset I45. These clips have finger pieces I49 by means of which the same can be disengaged from the oiiset. Screws I5I hold said clips attached to the case I4.

Within the sump I42 is mounted a cylindrical housing I52. This housing has three ears I53 formed thereon, which are secured by means of screws I 55 to bosses I54 extending inwardly from the lip I46 of case I4. The housing I52 has an upper end wall I56 and a partition I51 spaced from the extreme lower end thereof. In the end wall I56 and in the partition I51 are provided bearings I58 and I59 which rotatably support a vertical extending shaft NH. The shaft I6I extends upwardly into the crank case compartment 36 and has attached to its protruding end a driving member I62. The driving member I62 has a flange I63 through which an extension I64 of the crank pin 36 of the crank 32 extends. The shaft I6I is coaxial with the armature shaft 22 so that as the armature I8 rotates, shaft I6I is driven in unison with it. Within the cylindrical housing I52 and by means of the partition I51 is formed at the lower end of said housing a downwardly opening compartment I65. Shaft I5I extends into this compartment. Attached to the lowermost end of the shaft I6I and disposed within the compartment I65 is the rotor I66 of a centrifugal pump, indicated in its entirety by the reference numeral I61. A discharge passageway I63 is formed in the housing I52 and communicates with the compartment I65. This passageway extends into the crank case compartment 36 and is adapted to discharge the oil from the sump I44 into the crank case, where the same lubricates the various pistons, connecting rods, crank and wrist pin bearings. The surplus oil drains back into the sump I42 between the ears I53. In this manner, all of the operating parts of the device except the motor bearings, are lubricated.

- I2 and I3, respectively, are also formed with radiating fins I12. At the top of the device and attached to the protruding end I13 of the armature shaft 22 is a fan I14. This fan is of a' I greater diameter than the diameter of the crank der side of the diaphragm case I4 and the motor housing I5 and serves to force air downwardly along the same. Part of the air so conducted passes through the fins of the various compressor units II, I2 and I3, and cools the same. Another portion of the air is forced by said fan through the holes 2I4 in end bell '24 and is directed into the motor compartment 35. The air leaves this compartment through the holes 2I3 formed in the case I4. A guard I15, secured to the end bell 24, protects the fan I14.

In order to control the operation of the device, an automatic switch mechanism is employed which is mounted in a switch box I11 which is attached to the motor housing I5. This switch box has side walls I18 and I19, upper and lower walls I86 and I82 and a rear wall I63. The wall I83 has ears I84 projecting outwardly therefrom through which cap screws I85 extend. These cap screws are threaded into the housing I5 and serve to attach the switch box to the device. Mounted Within the box I11 is an electric switch I6I, which is connected in the circuit operating the motor I6. A plug I96, carried by the wall I19 or box I11 permits it connecting the motor to a source of electric energy. .Inasmuch as the switch I 8! forms no particular feature of the instant invention, the construction thereon has not been shown in detail. This switch, however, has a button I66 projecting outwardly therefrom, which is normally urged outwardly through suitable spring means and which, upon depression, is adapted to open the switch. When pressure is relieved on this button, the switch automatically closes.

The switch IIII is operated by means of the following construction: Formed on the wall I18 of box I11 is a boss I81, which is threaded to receive a bushing I88. A tube connector I89 is screwed into this bushing and has connected to it a tube I9I. Tube MI is connected to the fitting I34 of the compressor unit I3 and brings the chamber I92 within the bushing I88 into communication with the high pressure side of the compressor unit I3. Extending across the end of the bushing is a diaphragm I93 which is clamped by means of said bushing against a seat I94. A follower I95 bears against the un- I93. Mounted for swinging movement within the box I11 is a lever I96, which is pivoted on a fulcrum I'91 which is attached to a boss 266 on the rear The entire compressor is cooled in the following wall I63 ofbox I11. Alink I96 extends between the lever I66 and the follower I and I93 to The extreme end of lever I96 transmits motion of the diaphragm said lever I95. is engaged by a spindle I99 which has a conical head 2! at the extreme end thereof which'is seated in a suitable socket 262 in said lever. Spindle I99 is slidably mounted in a guide 262 screwed into a boss 264 issuing inwardly into the box I11 from thewall I19 thereof. A compression coil spring 265 encircles the spindle I99 and urges the same into engagement with the lever I96. Movement of the lever I96 in a counter-clockwise direction is terminated by means of an adjustable stop 266 which is carried by the wall I18 of box I11. The lever I96 carries an adjustable stud 261 which engages the button I36. As the diaphragm I 93 moves, lever I36 is oscillated and operation of the switch I8I occurs. When the pressure produced by the high pressure unit I3 reaches the desired amount which can be adjusted by means of thestud 201, switch I8I is opened and compressor stops.

For the purpose of supporting the compressor, the box II'l is constructed with ears 2 which project outwardly therefrom. These ears have holes 212 therein through which suitable fasteners may extend to attach the compressor to a vertical support. The compressor is preferably mounted above fioor level, so that the oil sump M2 may be easily removed therefrom for the purpose of filling and inspection.

In conjunction with my motor-driven compressor, I employ a reservoir such as designated at 215 in Fig. 6 and into which the compressed air or gas is directed. This reservoir is tubular in form, having a cylindrical wall 23I, a lower end 232 and an upper end 233. This reservoir is constructed in two halves, 236 and 28'! welded or soldered together at the center, as indicated at M8. The reservoir 2I5 is arranged in verti-' cal position and is mounted on the support to which the compressor is attached. For the purpose of illustration, a channel frame member 2 l 9 has been shown for this purpose. This frame member may be a portion of the aeroplane or other structure in which the compressor is to be used. Bolts 22E extend through the ears 2II f the compressor switch box I'll and through the web 222 of the channel 2'I9. Spacers 223 between said ears and web hold the compressor in proper position.

The reservoir 2I5 has attached to it a mounting plate 223. This mounting plate has secured to it bands 225 which encircle the reservoir proper and clamp the mounting plate in position. The plate 224 overlies the web 222 of channel 2I9 and the bolts 22I pass through the same. In this manner, the reservoir 2I6 is mounted in proximity to the compressor and is supported by the same support.

The tube connector I35 which is formed on i the tube fitting I34 associated with the compressor unit I3 has connected to it a tube 226. This tube is connected to a tube fitting 221 which is screwed into a boss 228 secured to the reservoir 2I5. The inlet through the fitting tube 221 is disposed above the lower end 232 of the reservoir 2I5 and below the outlet in the tube fitting 234. It will thus be seen that the tube 226 inclines throughout its extent from the cylinder II! to the reservoir 2I5 and that the discharge is located above the lower end of the reservoir to form the space 229 above said inlet in which water may collect. The tube 226 is covered with an insulating jacket 230.

Opposite the tube fitting 221 is a relief valve 234 which is threaded into a bushing 235 secured to the wall 23I of said reservoir. At the bottom of the reservoir is a drain I which is secured to the wall 232.

Airis led from the reservoir to a. tube fitting 236 which is screwed into a bushing 231 secured to the upper end 233 of said reservoir. For the purpose of preventing water and foreign material from entering the fitting 236, a filter 238 is employed which is supported by a pervious plate 239 secured to the wall 23I of the reservoir '2I5 below the upper end 233 thereof.

The operation of my invention is as follows: When the pressure produced by the high pressure unit I3 drops below a certain value, or when the device is being first started, pressure on the diaphragm I93 is released and the lever I96 urged against the stop 206 by means of the spring 205. This causes the switch I8I to close and energize the motor Ill. The operation of motor Ill causes simultaneous operation of the pistons within the various compressor units II, I2 and I3, and the compression of the fiuids within the cylinder thereof. When the motor-driven compressor comprising the instant invention is used at high altitudes, all of the air compressed in cylinder 37 is required to furnish the necessary amount of air at the desired pressure to be successively compressed in the cylinders 32 and H5. When, however, the compressor is used at low altitudes, an excess of air would be drawn into the cylinder 31. For the purpose of disposing of the excess air, the relief valve M is employed. Spring Bil operating this valve is so designed as to relieve the pressure in cylinder 31 when the amount of air pumped by the compressorunit H reaches the desired volume. It will be noted that the tube fitting I2 connected to the discharge end of the compressor unit Il extends upwardly and that the tube I3 which is connected to it slopes downwardly from this fitting to the inlet fitting N9 of cylinder 82, which inlet fitting is disposed at the lowermost portion of the cylinder 32. By means of this construction, the condensation occurring in tube 13 fiows downwardly from the unit II to the unit I2. To produce the same condition in the tube I06 which is connected to the high pressure side of the compressor unit i2, said tube extends upwardly from the fitting I02 and is then caused to travel downwardly toward its point of connection with thehigh pressure cylinder II5. Since the upstanding portion of tube I06 is short, condensation does not occur until the air reaches the inclined portion of the tube from which it drains into the cylinder H5 of unit 53. In this manner,

- condensation is caused to travel through the compressor from one cylinder to the other. When the air leaves the compressor I3, the same flows through the tube 226 and into the lower end of the reservoir 2I5. Due to the insulating jacket 230, freezing of the water is prevented'during its passage through tube 226, Any water which may have been condensed from the liquid, flows into the bottom of said reservoir and is confined within the space 229. The air travels upwardly and passes through filter 238 prior to its discharge from the reservoir, through the tube fitting 233. By arranging the conduits between the compressor units and the reservoir as disclosed, pocketing of the condensation is eliminated and the condensation discharged through the compressor with the compressed air and into the reservoir, where separation occurs. When the pressure in the high pressure compress-or unit I3 reaches the desired amount, switch I8I is automatically closed as previously described. Whereupon the compressor ceases to function.

My invention is highly advantageous in that an extremely simple and practical device is produced which will positively and effectively function to produce the desired results. With my invention, air can be compressed at difierent altitudes without adjustment of the apparatus. My i improved motor-driven compressor can beconstructed relatively light in weight, so that the same may be installed, on the aeroplanes or wherever a light weight construction is desired. By means of the lubricating system employed with my invention, all of the parts are thoroughly lubricated, so that the compressor can be driven at a higher rate of speed. With the automatic switch m "chanlsm, the pressure is maintained any desirable value. Adjustment of the pressure can be readily made by adjusting the guide forming the spring seat for the pressure regulating device. Cooling of the compressor is procured by the motor operating the compressor :units. The sump for lubricating oilis readily removed and inspectionof the interior of the compressor is readily had upon removal of the same.

Changes in the specific form of myinvention as hereindisclosed may be made within the scope of what is claimed without departing from the spirit of my invention. 1

Having described my invention, what I claim as new and desire to protect by Letters Patent is.

1. A compressor comprising a case, a motor mounted on the upper portion of said case and of diametral dimensions substantially the same as those of the case said motor including an armature shaft, a plurality of compressor units pro- Electing outwardly from said caseand extending beyond the confines of said motor and case, means for operating said compressor units from the armature shaft of said motor, said case and motor having ventilating openings for conducting air through the motor, the armature shaftof said motor extending upwardly beyond the-same, and

a fan mounted on said armature shaft and proof said compressor units from said crank, a conduit having a reach extending upwardly from the.

discharge of a lower pressure compressor unit and anotherreach inclining downwardly toward the intake of a higher pressure compressor unit,

the intake ,of said higher pressure compressor unit being disposed at the uppermost portion thereof to cause condensation collected in said last-named reach to how by gravity into the higher pressure compressor unit.

3. In combination, a compressor having a high pressure cylinder, a piston in said cylinder, means for operating said piston, an inlet and an outlet for said cylinder, a reservoir, a conduit extending between the outlet of said cylinder and reservoir and serving to discharge into the reservoir,'said conduit inclining downwardly throughout its extent, the inlet from said conduit beingabove the bottom of said reservoir, an outlet at the uppermost portion of the reservoir, and adrain at the lowermost portion of said reservoir.

4. In combination, a compressor having a high pressure cylinder, a piston in said cylinder, means for operating said piston, an inlet and an outlet for said cylinder, a, reservoir, a conduit extending between the outlet of said cylinder and reservoir and serving to discharge into the reservoir, said conduit inclining downwardly throughout its extent, an insulating jacket surrounding said conduit, the, inlet from said conduit being disposed intermediate the upper and lower ends of the reservoir, an outlet at the uppermost portion of the reservoir and a drain in the' reservoir at a locality below said inlet.

5. A compressor comprising acase, a motor mounted on the upper end of the case and having an armature shaft extending into said case, a crank attached to said armature shaft and disposed within said case, said crank including a crank pin, a plurality of compressor units carried by said case and disposed radially with reference *to the moving parts within said case.

6. In. combination, a multiple stage compressor comprising a plurality 'of cylinders arranged horizontal ly and at substantially the same plane, pistons in'said cylinders, means for operating said pistons, inlets and outlets for said cylinders, a conduit extending between the outlet of a cylinder of lower pressure to the inlet of a. cylinder of higher pressure, said conduit at the locality of the first named cylinder having a substantially upwardly extending vertical reach, and a reach run ning between said vertical reach and the other cylinder and inclined substantially throughout its extent toward the second named cylinder.

'7. In combination, a compressor having a hlgh pressure cylinder arranged in a horizontal posi-- tion, a piston in said cylinder, means for operating said piston, an inlet for said cylinder, an outlet for said cylinder comprising a discharge chamber atthe end of the cylinder, a vertically extending reservoir disposed adjacent said cylinder, a conduit connected to the under side of said discharge chamber and to said reservoir and serving to discharge into the reservoir, said conduit inclining downwardly throughout its extent, the inlet from said conduit to said reservoir being disposed intermediate the upper and lower ends of the reservoir, an outlet at the'uppermost portion of the'reservoir and a drain in the reservoir at a locality below said inlet.

8. A compressor comprising a case, a motor mounted on the upper end of the case and having a vertically extending armature shaft disposed withln the case, a crank attached to said armature shaft and disposed within said case, a plurality of compressor units carried by the case and extending radially with reference thereto, means for operating all of said compressor units from said crank, an oil sump disposed below said case, means for detachably securing said sump to the lower end of the case, a pump housing disposed within said sump, means for detachably securing said pump to the lower end of the case, said pump having a rotor at the lowermost por- 7 tion thereof, a shaft for driving said rotor, said shaft being substantially coaxial with said armature shaft, said pump shaft having an eccentric part disposed adjacent a corresponding part on the crank, a pin on one of said parts and a hole in the other of said parts for the reception of said pin for restraining relative movement between 5 said shafts and forming a driving connection beprojecting outwardly from said case and extendassociated with said ing beyond the confines of said motor and case, an oil sump disposed below said case and being of substantially the same diametral dimensions as said case, means for operating said compressor units from the armature shaft of said motor, said case and motor having ventilating openings for conducting air through the motor, the armature shaft of said motor extending upwardly beyond the same, and a fan mounted on said armature shaft and projecting radially outwardly beyond said motor and case, said fan serving to force air past said compressor unit and sump and through said motor.

10. A multiple stage compressor comprising a plurality of cylinders arranged in coplanar horizontal relation, pistons therein, means for simultaneously operating said pistons at predetermined relative speeds, said cylinders being proportioned to procure different pressures therein, a lower pressure cylinder having an inlet and a discharge outlet and the cylinder of the next higher pressure having an inlet and a discharge outlet, a conduit extending between saidcylinders and having a vertical reach extending upwardly from the outlet of said lower pressure cylinder and a downwardly inclining reach extending from the uppermost portion of the vertical reach to the inlet of said higher pressure cylinder to cause most of the condensation collected in said conduit to flow by gravity into said higher pressure cylinden- 11. A multiple stage compressor comprising a plurality of cylinders arranged in coplanar horizontal relation, pistons therein, means for simultaneouslyoperating said pistons at pre-determined relative speeds, said cylinders being proportioned to procure different pressures therein, a lower pressure cylinder having an inlet and having a discharge outlet at the uppermost portion of the same and the cylinder of the next higher pressure having an outlet and having an inlet at the uppermost portion of the same, a conduit between said cylinders having a vertical reach extending up- I REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 740,133 Heldenbraud Sept. 29, 1903 918,194 Pocock et al. Apr. 13, 1909 1,408,942 Holdsworth Mar. 7, 1922 1,410,125 Rhoads Mar. 21, 1922 1,683,182 Heisler Sept. 4, 1928 1,846,655 Rayfield' Feb. 23, 1932 1,860,193 Loranger May 24, 1932 1,969,076 Hirsch Aug. 7, 1934 2,046,477 Omhart July 7, 1936 2,065,350 Steenstrup Dec. 22, 1936 2,066,177 Johnson Dec. 29,1936 2,073,547 Berry Mar. 9, 1937 2,096,297 Goldner et al. Oct. 19, 193': 2,186,492 Paget Jan. 9, 1940 2,274,942 Touborg Mar. 3, 1942 2,286,272 Highham June 16, 1942 2,312,335- Halleck -11-- Mar} 2, 1943

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